U.S. patent application number 11/676142 was filed with the patent office on 2007-12-20 for high resolution analytical probe station.
This patent application is currently assigned to THE MICROMANIPULATOR COMPANY, INC.. Invention is credited to Kenneth F. Hollman.
Application Number | 20070290703 11/676142 |
Document ID | / |
Family ID | 28453984 |
Filed Date | 2007-12-20 |
United States Patent
Application |
20070290703 |
Kind Code |
A1 |
Hollman; Kenneth F. |
December 20, 2007 |
High Resolution Analytical Probe Station
Abstract
A method and system for probing with electrical test signals on
an integrated circuit specimen using a high resolution microscope
positioned for observing a surface of the specimen exposing
electrically conductive terminals thereon. A housing is provided
with a carrier therein for supporting the specimen in relation to
the microscope and a probe assembly is positionable on the surface
of the specimen for conveying and acquiring electrical test signals
to and from the specimen. A drive system is provided for shifting
at least one of the probe and the carrier to a predetermined test
position. In one form the system has a heat shield for protecting
one of the probe assembly and the carrier from heat energy
generated upon operation of the drive system, and in another form,
the system has an environmental control for maintaining a desired
temperature within the housing so that accurate measurements may be
taken from the specimen.
Inventors: |
Hollman; Kenneth F.; (Carson
City, NV) |
Correspondence
Address: |
FITCH EVEN TABIN AND FLANNERY
120 SOUTH LA SALLE STREET
SUITE 1600
CHICAGO
IL
60603-3406
US
|
Assignee: |
THE MICROMANIPULATOR COMPANY,
INC.
1555 Forrest Way
Carson City
NV
89706
|
Family ID: |
28453984 |
Appl. No.: |
11/676142 |
Filed: |
February 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10816114 |
Apr 1, 2004 |
7180317 |
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|
11676142 |
Feb 16, 2007 |
|
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|
10119346 |
Apr 8, 2002 |
6744268 |
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|
10816114 |
Apr 1, 2004 |
|
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|
09774249 |
Jan 30, 2001 |
6621282 |
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|
10119346 |
Apr 8, 2002 |
|
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|
09527874 |
Mar 17, 2000 |
6191598 |
|
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09774249 |
Jan 30, 2001 |
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09140910 |
Aug 27, 1998 |
6198299 |
|
|
09527874 |
Mar 17, 2000 |
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Current U.S.
Class: |
324/750.14 ;
324/750.25; 324/750.28; 324/756.02 |
Current CPC
Class: |
G01R 1/025 20130101;
G01R 31/2891 20130101; G01R 31/2887 20130101; G01R 31/307 20130101;
G01R 1/07392 20130101; G01R 31/2851 20130101 |
Class at
Publication: |
324/760 ;
324/754 |
International
Class: |
G01R 31/02 20060101
G01R031/02 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. A probe station for high resolution, low current probing of a
DUT, the probe station comprising: a vacuum housing having an
interior space in which a DUT is disposed with the interior space
under vacuum conditions during testing operations; a high
resolution microscope extending into the interior space for
acquiring images of the DUT; a probe assembly in the housing
interior space for taking low current measurements from the DUT; a
carrier in the housing space for supporting the DUT during testing
operations; a drive system for shifting at least one of the probe
assembly and the carrier to a predetermined test position; and
means for causing precision movements of the at least one of the
probe assembly and the carrier via operation of the drive system in
the vacuum housing despite generation of heat energy upon drive
system operation.
9. The probe station of claim 8 wherein the means for causing
precision movements comprises a heat insulating or heat shielding
device connected to the drive system to allow for precision
shifting of the at least one of the probe assembly and the carrier
by the drive system in the vacuum housing.
10. The probe station of claim 8 wherein the drive system includes
a motor and the means for causing precision movements comprises an
output shaft assembly of the motor of a predetermined heat
insulating material.
11. The probe station of claim 10 wherein the output shaft assembly
includes a lead screw that is of the predetermined heat insulating
material which comprises at least one of a ceramic material,
sapphire material and ruby material having a low coefficient of
thermal expansion.
12. The probe station of claim 8 wherein the drive system includes
a motor and a motor output shaft assembly and the means for causing
precision movements comprises a coupling made of a predetermined
heat insulating material which insulates portions of the output
shaft assembly from each other in order to minimize heat transfer
from one portion to another portion.
13. The probe station of claim 8 wherein the drive system includes
a motor and a drive shaft that is rotated upon operation of the
motor for shifting the one of the probe and the carrier by the
drive system in the vacuum housing; and the means for causing
precision movements comprises a shield disposed between the motor
and the drive shaft to deflect heat or energy from the operating
motor away from the drive shaft in the vacuum housing.
14. The probe station of claim 13 wherein the shield forms an
annular ring about the motor and extends out from the motor at an
angle sufficient to deflect radiated heat or energy from the
operating motor away from the drive shaft in the vacuum
housing.
15. The probe station of claim 8 further comprising an
environmental control system associated with the housing and
including a heat transfer fluid that substantially maintains a
desired temperature within the vacuum housing so that accurate
measurements may be taken from the DUT.
16. The probe station of claim 15 wherein the environmental control
system further includes a conduit disposed within the vacuum
housing for carrying the heat transfer fluid therein.
17. The probe station of claim 15 wherein the environmental control
system conduit comprises a group of lines positioned about the at
least one of the probe assembly, carrier and drive system, the
lines carrying the heat transfer fluid for transferring heat to
maintain a desired temperature within the vacuum housing.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of prior application Ser.
No. 10/816,114, filed Apr. 1, 2004, now U.S. Pat. No. 7,180,317,
which is a divisional of prior application Ser. No. 10/119,346,
filed Apr. 8, 2002, now U.S. Pat. No. 6,744,268, which is a
continuation-in-part of prior application Ser. No. 09/774,249,
filed Jan. 30, 2001, now U.S. Pat. No. 6,621,282, which is a
continuation of prior application Ser. No. 09/527,874, filed Mar.
17, 2000, now U.S. Pat. No. 6,191,598, which is a continuation of
prior application Ser. No. 09/140,910, filed Aug. 28, 1998, now
U.S. Pat. No. 6,198,299, which are hereby incorporated herein by
reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] The invention relates in general to the use of high
resolution microscopy probe stations, and particularly to methods
and system for probing with electrical test signals on integrated
circuit (IC) specimens using a scanning electron microscope (SEM)
positioned for observing the surface indicia of the specimen
identifying the electrically conductive terminals for the
positioning of the probes.
[0003] Presently, probe stations typically employ optical
microscopes. Although the diameters of wafers are getting larger,
the structures constructed on and in those wafers are getting
smaller. In the past several decades, the industry has driven the
size of these structures from large sizes on the order of
hundredths of an inch to small fractions of micrometers today.
Until recently, most structures could be observed by normal high
magnification light microscopes and probed. However, modern
structures have now achieved a size that no longer allows viewing
with standard light microscopes. With the industry integrated
circuit design rules driving towards 0.18 micron features and
smaller, most advanced optical light microscopes cannot be relied
upon to accurately identify the electrically conductive terminals
from the conductive path indicia of the surface of the integrated
circuit specimens under test. Additionally, when viewing very small
features on a specimen, the optical microscope lens often must be
positioned so close to the specimen that it may interfere with the
test probes.
[0004] Another approach is necessary in addition to optical
microscopy if the industry is to continue to probe these
structures, which is surely needed. It would be desirable therefore
to provide a probe station which can visualize and probe features
not typically visible under even the most advanced light
microscope, that can be used in conjunction with electron optics
while maintaining the features typically found on optical
microscope probe stations.
SUMMARY OF THE INVENTION
[0005] Briefly summarized, the present invention relates to a
method and system for probing with electrical test signals a
specimen using high resolution microscopy, such as a scanning
electron microscope (SEM) or a Focus Ion Beam (FIB) system,
positioned for observing a surface of the specimen to identify
locations of electrically conductive terminals on the specimen. In
a preferred form, a carrier is provided for supporting the specimen
in relation to the scanning electron microscope while a controller,
such as a computer, acquires an image identifying conductive path
indicia of the surface of the specimen from the scanning electron
microscope. The carrier may be anyone of a number of items known to
one of ordinary skill in the art, such as a chuck (e.g., ambient,
thermal, triaxial, etc.), a probe card adapter and probe card, a
socket stage adapter, etc.
[0006] Motorized manipulators can be automatically controlled by
the computer, or manually by the operator using a joystick or the
like, to precisely position associated probes on or near the
surface of the specimen for acquiring and conveying electrical test
signals inside a vacuum chamber inner enclosure which houses at
least a portion of the scanning electron microscope, the carrier,
the motorized manipulators and probes for analyzing the specimen in
a vacuum. A feedthrough or electrical connector mounted to the
vacuum chamber allows for the computer to be electrically
interconnected to the motorized manipulators and their associated
probes in the sealed enclosure and can provide access to the
internal vacuum chamber for additional wiring and conduits. The
computer communicates with the motorized manipulators for
positioning the probes thereof, and for acquiring and applying
electrical test signals from and/or to the terminals on the
specimen using the image acquired by the computer to identify the
electrically conductive terminals from the conductive path indicia
of the surface of the specimen observed with the scanning electron
microscope.
[0007] The computer includes a display which shows a viewer an
enlarged view of the surface of the specimen being probed. A cursor
indicates the selected location or test site on the specimen at
which test signals are transferred to and from the probe. In this
manner, an operator can change selected test locations via
on-screen manipulation of the cursor, as by a mouse or other
computer interface control. Moving the cursor causes the relative
position between the probe and the specimen surface to shift under
software control so that the probe is oriented at the selected test
site. To this end, the software is programmed to operate actuators
of the probe assemblies and/or the carrier on which the specimen is
affixed for precision shifting thereof to position the probe at the
selected test site. Accordingly, with a mouse, an operator can
click on the cursor, and drag it across the screen to the desired
conductive path indicia location or terminal they desire to
test.
[0008] To improve low current testing accuracy, the preferred
probing system is highly flexible in allowing for different
guarding and/or shielding schemes to be employed throughout
substantially every level of its operating components. For example,
the probe station housing can be separated into two electrically
isolated outer and inner portions each having conductive walls so
that the inner portion can be driven to the same potential as the
signal applied to the specimen to assist in isolating the testing
area from noise and other environmental interference and the outer
portion can be grounded to reduce the risk of electrical shock to
probe station users. The probes and chuck can be wired in a similar
configuration to further isolate the testing area from noise and
interference. Further, locations of the electrical interconnects
can be selected to minimize lengths of wiring runs from the chamber
walls to the operating components, e.g., probe and chuck and their
actuators or motors.
[0009] To compensate for the sources of heat and radiation of heat
within the vacuum chamber, the drive mechanisms of the system are
constructed of heat insulating materials having low coefficients of
thermal expansion to insulate components of the drive mechanisms
from heat and unwanted movement or drift caused by thermal
expansion, and have radiation shields for deflecting heat or energy
from the motors of the drive systems toward the housing walls which
are better equipped to handle the buildup of heat due to their
proximity to the outer atmosphere.
[0010] In other aspects, the probes can include extended cladding
to minimize the amount of unwanted insulator charging. A touchdown
sensing mechanism can be utilized to reduce the risk of damage to
the specimen caused by excessive force applied thereto by probe
engagement. The duty cycle of the high resolution microscope is
preferably reduced as by a shuttering system. In this way, damage
done to the DUT via the beam of the microscope is minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 shows a high resolution probe station embodying the
present invention;
[0012] FIG. 2 shows a vacuum chamber in cross-section housing at
least a portion of a scanning electron microscope (SEM), motorized
manipulators, and a plurality of probes positioned on an integrated
circuit specimen in accordance with the invention;
[0013] FIGS. 3A, 3B and 3C are perspective views of the vacuum
chamber in which electrical signals from a computer are coupled to
motorized manipulators and a plurality of probes allowing the
computer to communicate with the motorized manipulator for
positioning the probes for applying electrical test signals;
[0014] FIG. 4 is a SEM photograph showing probe positioning
providing electrical test signals to an integrated circuit specimen
showing the specimen surface indicia and plural probes;
[0015] FIGS. 5A-5K are views of another form of high resolution
probe station in accordance with the present invention showing a
vacuum chamber housing the probe assemblies and chuck with the
station generally set up in triaxial or coaxial configurations;
[0016] FIG. 5A is a perspective view of the high resolution
analytical probe station with its cover open;
[0017] FIG. 5B is a front elevational view of the high resolution
analytical probe station with its cover closed;
[0018] FIG. 5C is a right side elevational view of the high
resolution analytical probe station with its cover open;
[0019] FIG. 5D is a top plan view of the high resolution analytical
probe station with the cover open;
[0020] FIG. 5E is a perspective view of the housing of the high
resolution analytical probe station taken from below the
housing;
[0021] FIG. 5F is a right side elevational view of the high
resolution analytical probe station with the cover closed;
[0022] FIG. 5G is a rear view of the high resolution analytical
probe station with its cover closed;
[0023] FIG. 5H is a cross sectional view of the high resolution
analytical probe station with its cover closed;
[0024] FIG. 5I is an enlarged view of the upper left side of the
high resolution analytical probe station with its cover closed;
[0025] FIG. 5J is an enlarged view of the upper right side of the
high resolution analytical probe station with its cover closed;
[0026] FIG. 5K is a cross sectional view of the housing of the high
resolution analytical probe station with its cover closed;
[0027] FIG. 6 is an elevational view, in partial cross-section, of
a triaxial electrical connector which may be used for the
feedthroughs mounted to the vacuum chamber;
[0028] FIGS. 7A and 7B are elevational views of other connector
which may be used for the feedthroughs mounted to the vacuum
chamber;
[0029] FIG. 8 is a schematic diagram of the scanning electron
microscope of FIG. 5;
[0030] FIGS. 9A and 9B are elevational and plan views, in cross
section, of a thermal chuck;
[0031] FIGS. 10A-10E are elevational, plan, exploded and enlarged
views of the triaxial chuck of FIG. 5;
[0032] FIGS. 11A-11B are perspective and side elevational views of
a socket stage adapter used in place of a chuck for testing
packaged specimens;
[0033] FIGS. 12A-12C are perspective, enlarged and cross sectional
views of a probe assembly used in the high resolution analytical
probe station;
[0034] FIGS. 13A-13C are perspective, enlarged and cross sectional
views of an alternate probe assembly showing a manipulator and a
probe with slide assemblies operable to shift the probe in X, Y and
Z directions;
[0035] FIG. 14 is an enlarged schematic view of the high resolution
probe assembly, showing the triaxial wiring configuration from one
of the feedthroughs to one of the probe assemblies and showing an
alternate chuck;
[0036] FIGS. 15A-15F are perspective, front elevational and
enlarged views of fixed probe card adapter which may be used in
place of the probe assemblies of FIGS. 12 and 13;
[0037] FIG. 16 is an enlarged view of an alternate probe, showing
extended cladding on the probe with the probe wired in a triaxial
configuration;
[0038] FIG. 17 is a side elevational view of an alternative probe
having a detachable probe tip portion and showing an extended guard
conductor keeping unguarded exposure of the signal conductor to a
minimum;
[0039] FIG. 18 is a schematic elevational view of the high
resolution probe station showing the probe station set up in a
coaxial configuration;
[0040] FIG. 19 is an enlarged schematic view of the high resolution
probe assembly of FIG. 18, showing the coaxial configuration from
one of the feedthroughs to one of the probe assemblies;
[0041] FIG. 20 is block diagram of an electronic touchdown sensing
mechanism for sensing engagement of the probes with the
specimen;
[0042] FIG. 21 is a schematic cross-sectional view of the high
resolution probe station of FIG. 5 including a temperature control
system and showing a bank of heat exchange tubes through which a
cooling or heating fluid is run to control the temperature within
the vacuum chamber;
[0043] FIGS. 22A and 22B are views of screen printouts showing
video images of the specimen and a wafer profile of the
specimen;
[0044] FIG. 23 is a drawing of the lift mechanism showing the
hydraulic cylinder, arm cam assembly and track which the system
uses to raise and lower the housing cover;
[0045] FIGS. 24A-24C are perspective, front elevational and right
side elevation views of the probe station located within the high
resolution analytical probe station housing, showing the housing
floor and the tilt/tip mechanisms;
[0046] FIGS. 25A and 25B are top plan and side elevational views,
shown in partial cross section, of the X and Y stage for the system
platform (the platform stage);
[0047] FIGS. 26A and 26B are top plan and side elevation views,
shown in partial cross section, of the X stage used for translating
the carrier in the X direction; and
[0048] FIG. 27 is a side elevational view, shown in partial cross
section, of a stage drive mechanism for a manipulator.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0049] Referring to the drawings and especially to FIGS. 1 and 2, a
system 10 is shown for high resolution analytical probing of an
integrated circuit specimen, (e.g., a semiconductor wafer 50). The
system 10 is capable of applying electrical test signals to an
integrated circuit specimen 50, which may include whole wafers,
packaged parts, or wafer fragments. Thus the system 10 may probe
entire wafers in addition to a large variety of similarly sized
specimens. A conventional scanning electron microscope (SEM), an
X-ray microscope for material analysis during probing functions, or
a Focus Ion Beam (FIB) system 12, may be employed for enhanced
capabilities. Thus, the prober may be integrated into FIB systems
as well as SEM systems. The embodiment described herein uses a SEM
provided by R.J. Lee Instruments Ltd. which is positioned for
observing a surface of the specimen 50 exposing electrically
conductive terminals on the specimen 50. See, e.g., FIG. 4,
discussed below. The system 10 may be provided with Electron Beam
Induced Current (EBIC) capabilities to allow for current path
tracing tests and the like as a form of non-contact probing.
[0050] As shown in FIG. 2, a carrier 14 is provided for supporting
the specimen 50 in relation to the scanning electron microscope 12.
The scanning electron microscope 12 is positioned sufficiently
above the specimen 50 so as to allow for the positioning of several
test probes on the specimen 50, which may not be possible using an
optical microscope for viewing very small circuit features. A
computer system 16, is coupled to the carrier/motion control 14 in
FIG. 1, and provides for acquisition of the high resolution images
of FIG. 4 which identify the conductive path indicia of the surface
of the specimen 50 with the scanning electron microscope 12. The
computer system 16 may be provided as a processor such as a
conventional microprocessor-based system, or an electronic
controller, or microcontroller suitable for the information
processing described below. Multiple motorized manipulators
identified by reference numerals 18, 19, 20, 21, 22 and 23
respectively are also remotely controlled by the computer system
16. A plurality of probes 24 are thus used for conveying electrical
test signals, and are positionable on the surface of the specimen
50 with motorized manipulators 18-23.
[0051] A vacuum chamber 26 shown in perspective views in FIGS. 3A,
3B and 3C illustrates system operation in which an inner enclosure
27 is adapted for housing the scanning electron microscope 12, the
carrier 14, multiple motorized manipulators 18-23, and the
plurality of probes 24 for analyzing the specimen 50 in a vacuum
generated by the vacuum chamber 26 for use with the scanning
electron microscope 12. An angle of incidence from
45.degree.-90.degree. with adjustment capability in the form of
different styles of replaceable probe tips, (e.g., with 45.degree.
and 90.degree. attack angles), facilitates probe positioning in
relation to the scanning electron microscope 12.
[0052] The chamber size of the inner enclosure 27 is dependent upon
the type of probing required. A relatively small chamber is needed
for small sample probing. Small samples are likely packaged parts
or wafer fragments. For wafer level probing, the chamber size has
to be much larger to accommodate wafer stage translations up to 300
mm and larger. The chamber is approximately 23'' inner
diameter.times.10'' deep. This allows for a 6'' wafer chuck having
less than an inch of travel in the X and Y directions. It also
allows for up to six (6) programmable manipulators having at least
50 nm resolution and 0.5 inches of travel in all axis. The
footprint of the system is approximately 3'.times.3'.times.5' which
includes all of the electronics and pumping facilities
required.
[0053] The system 10 is built upon a vibration isolation table
provided by Kinetics Systems, which may be supplied by a variety of
manufacturers. The design of this table system is customized to
accommodate the vacuum chamber, which resides above and below the
tabletop surface. This arrangement is made to allow easy access to
the prober without having to work much above normal tabletop
height. In the embodiment shown, a lift mechanism 29, which is
either pneumatically or hydraulically driven, is employed to raise
and lower the chamber top 28. Further, all of the hardware services
needed for the system to function are integrated into the table leg
area.
[0054] The chamber wall 27 has feedthroughs welded to it which
provide flanged access for the needed cabling to both operate the
programmable functions of the system as well as provide for signal
paths to the surface of chuck 14, individual probe contacts 24, and
probe card signals (not shown). A thermal chuck 14 may be employed
within the system chamber. The chamber floor 13 also has
feedthroughs welded to it with flanged access to attach a means for
pulling a vacuum in the chamber as well as additional feedthrough
ports for interconnection requirements, discussed below. Thus, the
system 10 is well suited for low noise and low current testing when
fitted with the described interconnection hardware and
instrumentation.
[0055] A Model 900VM manipulator, manufactured by The
Micromanipulator Company, Inc., Carson City, Nev., is designed to
meet the needs of "hands-off" operation and programmable probe
applications. The manipulators 18-23 are motorized in the X, Y and
Z axes. The Z axis positioning is aided by manual, coarse
positioning allowing compensation for various probe holders and
probe station systems, which may be operated in a fully
programmable or motorized-only (e.g., joystick control) mode
depending upon the choice of control system. The Model 900VM
manipulator accepts all standard probe holders in disposable tip or
integrated tip models.
[0056] At 0.05 microns, the Model 900VM manipulators offer very
high manipulator resolution. This resolution is attainable with
either motorized (e.g., joystick) or programmable control. The
900VM also features a wide range of probe holder "Z" positioning
settings, an indexed rotational nosepiece, fast manual "Z" lift for
fast probe tip changes and a stable vacuum base with quick release.
The model 900VM may be used with joystick only control (REM
version) or with external computer control using pcProbe.TM.
software discussed below.
[0057] A feedthrough is provided on the vacuum chamber 26 for
coupling electrical signals, (e.g., via a computer bus 28), from
the computer system 16 to the motorized manipulators 18-23, stage
14, and the plurality of probes 24. The feedthroughs used are
provided by PAVE Technology Co., Inc. and others that include
signal, positioner, and probe card connection interconnects which
fall into either of two categories. The first category includes
those interconnects provided for device under test (DUT) 50 test
signal handling capabilities. These can be, but are not limited to
single pin jack, coax, triax, SMA, and UMC connections. Further,
with fixed position probe card usage, all mentioned feedthroughs
may be used together plus many others meant to handle large
quantities of leads. The second category are those interconnects
which are dedicated to providing control signals to all of the
prober functions needed. A typical axis of control may require
seven leads for motor step and direction as well as limits controls
with respect to travel.
[0058] Further, additional leads may be used where position
feedback is employed. For example, Kelvin probes and probe holder
configurations can be adapted to this application. These would
require double the number of signal leads. The computer system 16
communicates with the motorized manipulators 18-23 for positioning
the plurality of probes 24 for applying the electrical test signals
to the terminals on the specimen 50 using the image acquired by the
computer system 16 to identify the electrically conductive
terminals from the conductive path indicia of the surface of the
specimen 50 observed with the scanning electron microscope 12.
[0059] As described, the probe station system 10 positions the
scanning electron microscope 12 for observing a surface of the
specimen 12 for positioning the probes 24. The system 10 provides
means for supporting the specimen 50 which include the
carrier/motion control 14 and a chuck for supporting the specimen
50. The fully configured prober with chuck, probe card adapter, six
or more programmable manipulators, stage and platen translation and
measurement signal paths could require one hundred and twenty-six
(126) or more feedthrough connections for the system requirements.
At least five signal paths are used for stage surface and probes,
and as many as are needed are used for probe card based
connections. Kelvin probes and probe holder configurations may
double the number of interconnections.
[0060] With reference to FIG. 2 and FIG. 3A, once the chamber top
28 is raised, it may be rotated out of the way such that optical
microscope 70 may be moved into position over the wafer chuck 14 by
sliding it on the microscope bridge 71 to facilitate the initial
positioning of probes over the DUT 50 in the area of interest to
the user. This is done to decrease the time spent locating areas to
be probed on the DUT 50 once the system is under vacuum. Having
completed this, the optical microscope 70 can be positioned out of
the way so that the chamber top 28 may be lowered into place. There
may be two tapered pins (not shown) that will drop into bushings
appropriately placed such that the chamber top 28 with SEM column
12 may properly align with the chamber wall 27 perfecting a seal.
Further, the chamber top 27, by means of the alignment pins, should
ensure that the SEM column 12 will be properly positioned amidst
the probes 24 and manipulators 18-23.
[0061] With the SEM embodiment of system 10 described above, hot
cathode electron emitter techniques may be used, however an
alternate embodiment of the system 10 may use field emission, as
discussed above. Field emission provides improved image quality
with much less potential for damaging the specimen 50.
[0062] Within the chamber 26, there is a motorized X-Y prober
platform 46 which will support all of the normal prober functions
as described below. The purpose of this platform 46 besides being a
support structure is that of translating all of the prober
functions in unison to simulate the typical microscope translation
found on most probing stations today. The X/Y translation provided
by the platform 46 facilitates large area DUT 50 viewing without
disturbing the probes 24. Since the microscope column 12 cannot
move easily independent of the stage, platen 25, and manipulators
18-23, moving the platform allows the user to scan the DUT 50 for
sites to probe or to check the position of each probe or all of the
probes provided by a probe card, which is an approach unique to
this function.
[0063] Below the platform 46 and between the platform and the
bottom of the chamber 26 is a mechanism used for tilting the
platform in the "Z" direction vertically with the motorized tilt
axis 15. This mechanism allows the platform 46 to be tipped or
tilted along either the "X" or "Y" axis to allow the user to
observe the probe 24 making contact with the DUT 50 from an angle
other than vertical. The motorized tip and tilt functions improve
the probe-viewing angle. This aids the user in "seeing" touchdown
of the probes 24 on the DUT 50 on very small DUT structures. Thus,
the tip/tilt functions provided by the motorized tilt axis 15 with
the platen 25 allows vertical movement for alternate views of the
probes 24 and probe positioning on the specimen 50.
[0064] Attached to the platform is an X-Y stage 17 with Theta
adjust provided for the stage 17 for the chuck 14. Also attached to
the platform 46 is the "Z" platen 25 which supports both fixed
probe cards and manipulators. The platen is motor driven in the "Z"
axis such that either fixed position probe cards and/or single
probes may be raised and lowered simultaneously. This controlled
motion provides for probe and probe card "Z" positioning. The
platen 25 may be used to simultaneously raise the manipulators and
move a fixed position probe card which may be used.
[0065] The method of DUT 50 attachment to the wafer chuck 14 is by
mechanical means because vacuum, as a method of hold down, will not
work in a vacuum chamber. Thus a spring clip arrangement which
secures the wafer to the chuck is used. The wafer 50 sets into a
slight depression with alignment pins for registration with the
notches or flats typically found on most wafers today.
[0066] The multiple motorized/programmable micromanipulators 18-23
sit on top of the platen 25. The supplied drawings indicate six of
these devices. While six is likely a practical limit, any number
may be used to direct probes into contact with the DUT as
required.
[0067] The scanning electron microscope 12 is coupled to the
computer system 16 with a scanning electron microscope interface
30, which may be used with CAD navigation software. The computer
system 16 thus communicates via the bus 28 to the scanning electron
microscope 12 through a SEM interface 30 which includes means for
acquiring the image.
[0068] The computer system 16 may include a first computer 32, such
as a general purpose personal computer (PC) configured as a digital
image processor for acquiring the images from the scanning electron
microscope 12. The computer system 16 may also include a second
computer 34 for remotely controlling the plurality of probes 24 via
the motorized manipulators 18-23 which are remotely controlled by
the computer 34. Alternatively, the computer system 16 may be a
single PC or server which performs control operations for both the
prober functions and the microscope functions. The computer system
16 may also include two computers and three monitors. In a
prototype version, all of this could be accomplished with a single
computer and monitor. It was found however that having two
monitors, one for high-resolution viewing and one for all of the
system control and navigation functions was advantageous in the
described embodiment.
[0069] Separate video display units (VDUs) 36 and 38, which may be
provided as conventional PC computer monitors, are used for
displaying high resolution microscope images and computer graphics
relating to the SEM 12 and probes 24, respectively. The VDUs 36 and
38 are used to visually assist a user in remotely controlling the
plurality of probes 24 for placement on the specimen 50 by
acquiring the images which convey information to the user relating
to particular integrated circuit surface indicia corresponding to
the exposed electrically conductive terminals of the specimen
50.
[0070] The Micromanipulator Company, Inc. pcProbeII.TM. software
(PCPII) is used with a Windows.TM. based personal computer and
provides functions such as auto planarity compensation, auto
alignment and setup which automatically guide the occasional user
through the process of getting ready to probe. Manual controls 40
(e.g., mouse and/or joystick), are also used by the user to control
the plurality of probes 24 being placed on the specimen 50. An
electrical test signal probe interface 42 is coupled to the probes
24 for applying the electrical test signals to the specimen 50.
Alternatively, the plurality of probes 24 may be provided as a
fixed position probe card for applying the electrical test signals
to the specimen 50.
[0071] The PCPII probe software used with the computer system 16
provides a probe positioning system having control capabilities in
the form of a simplified intuitive icon-based tool kit. The PCPII
probe software is designed in a modular format allowing for wafer
mapping, die and in-die stepping, multiple device navigation
options and probe touchdown sensing. The PCPII probe features
include on-screen video with an active navigation control, advanced
alignment and scaling functions and programming through wafer map,
interactive learning and matrix mode. The PCPII probe navigation
software supports Windows, DDE, RS-232 and GPIB interfaces. The
PCPII probe navigator module provides interactive device management
for controlling four or more manipulators 18-23, the platen 25, and
the microscope 12.
[0072] While analyzing the specimen 50 using the probes, the
navigator display shows the position and control information for
the active specimen device. The navigator module also provides
system operation data and probe touch-down parameters. The wafer
mapping module provides a continuous visual indication of the die
selected, and displays the exact coordinates of the die specimen.
The PCPII probe software also includes a video module for imaging
of the specimen 50 with the personal computer. Each PCPII module
uses a separate application window, which allows the user to tailor
the viewing screen by defining the placement of each module and
minimizing or maximizing each window individually.
[0073] Environmental controls 44 (FIG. 1) are provided for, among
other things, controlling the temperature and for generating the
vacuum in the inner enclosure 27 of the chamber prober housing, for
operating the scanning electron microscope 12, and for analyzing
the specimen 50 under controlled environmental conditions in a
vacuum. The environmental controls 44 may include, e.g., first as
with most E-beam optical systems, magnetic shielding without which,
the beam may not be properly collimated for proper resolution.
Second, as the wafer probing area is completely enclosed by metal,
the user will experience significant electromagnetic shielding
characteristics that are an improvement over current conventional
probe stations.
[0074] An additional layer of insulator with a metalized surface
may be employed for shielding the chuck surface 14 and provides a
low noise environment. Additionally, the use of isolated coax
connections will allow for triaxial measurements when the chamber
is connected to ground. Next, because the probing function occurs
in a vacuum, frost formation during low temperature probing
applications may be nonexistent. Since little air is present,
probes will not oxidize during ambient and elevated temperature
applications. Finally, a thermal chuck employed with system 10
provides that the DUT may be tested at temperatures above and below
ambient.
[0075] A bench style table was used for supporting the VDU
monitors, keyboards, mouse and joystick. The chamber for a 200 mm
system is on the order of about 2'.times.2'.times.1'+/- and
approximately 3'.times.5'.times.1' for a 300 mm system. The pumping
elements for the larger chambers may require additional space.
[0076] Turning now to FIG. 4, in which a SEM photograph is shown
with multiple views 52, 56 and 58 of probe 24 positioned on the
specimen 50 at an exposed electrically conductive circuit path 54
as a method of providing the electrical test signals at the
integrated circuit. The method of analyzing the integrated circuit
specimen 50 includes acquiring the image identifying conductive
path indicia of the surface of the specimen from the scanning
electron microscope 12, which is driven in a preferred embodiment
by the PCPII software interface. The PCPII navigation software
facilitates the process of positioning the probes 24 within the
high resolution image of the specimen 50. Thus, the image acquiring
step is used to identify the electrically conductive terminals from
the conductive path indicia 54 on the surface of the specimen 50
observed with the scanning electron microscope 12 for positioning
the plurality of probes with the step of remotely controlling the
plurality of probes, as discussed above. The lowest magnification
view is item 56, the intermediate magnification view is item 58,
and the highest magnification view is item 52. The reason for the
three views is to assist the operator in maintaining a good
viewpoint of where they are working.
[0077] Another form of the high resolution analytical probe station
or system is shown in FIGS. 5A-5K, and is generally designated with
reference numeral 100. As discussed above, the system 100 is
capable of being used in applications where traditional optical (or
light) microscopes cannot be used due to the size of the specimens
being examined, (e.g., applications which require resolutions that
are incapable of being reached by light microscopes). The need for
higher resolution probe stations, such as probe station 100, is a
result of the electronics industry's drive towards smaller and more
complex components, (e.g., the need to conduct low current/low
voltage probing at sub-micron levels). Unfortunately, high
resolution microscopes such as electron or ion microscopes 104
including SEMs and FIBs are typically much more costly, and are
heavy and inconvenient to move about. The high expense of these
microscopes makes it more desirable to minimize the amount of
movement and handling of the microscope. The probe station 100
herein minimizes the amount of movement of the microscope by
mounting the microscope to a portion of the probe station housing
102 that is fixed during probe positioning procedures and probing
itself and by primarily moving the specimen or device under test
(DUT) 118 instead of the microscope 104, (e.g., thereby simulating
movement of the microscope). It should be noted that while the
microscope 104 can be fixed, it is also possible to enable small or
fine movements thereof for positioning it properly relative to the
portion of the DUT to be probed. In this instance, it is still the
movement of the chuck probes that is primarily used to orient the
microscope 104 for viewing the portion of the DUT that is desired
to be probed.
[0078] More particularly, the probe station 100 minimizes the
handling of the microscope by having the high resolution microscope
mounted to the cover 194 of the probe station 100 and using a lift
mechanism 196 (FIG. 5B), such as a pneumatic or hydraulically
driven lift as described more fully hereinafter, to raise the cover
194 of the probe station 100 up and away from the inner probe
station chamber so that specimens can be adjusted, replaced, and/or
viewed without the high resolution microscope. Furthermore, with
the cover 194 open or retracted away from the inner chamber 190, a
system operator can conduct additional probing and/or setup, using
light microscope 105. More particularly, the light microscope 105
would be positioned above the DUT 118 by sliding the microscope 105
along the microscope bridge so that the system operator can use
this microscope to view the DUT 118. Thus, system 100 allows for
both light microscope probing and high resolution microscope
probing.
[0079] The probe station 100 also provides a highly integrated
approach to isolating the testing area from outside influences.
Guarding and/or shielding configurations are readily provided
depending on what is necessary for obtaining accurate results given
the low level current and voltage measurements that may need to
take place, such as those having sensitivities in the high
attoampere (10-18) and the low femtoampere (10-15) range. For
example the housing 102, microscope 104 and probe assembly 106 of
the probe station 100 can all be wired in a coaxial or triaxial
configuration in order to reduce noise and thereby allow the
accurate taking of such sensitive measurements, as will be
discussed in further detail below.
[0080] The probe station 100 generally includes a probe station
housing 102, high resolution microscope 104, and several probe
assemblies 106, such as the four assemblies shown in FIGS. 5A-5K.
The housing 102, as shown in the preferred form in FIG. 5H, has a
double-walled construction, or alternatively may have a single wall
construction with an insulated metallic coating applied thereon to
allow different guarding and/or shielding configurations to be
applied thereto. In the double-walled configuration, the system 100
has an outer housing 108 and an inner housing 182. The housing 102
provides a vacuum chamber 190 in which the probe assemblies 106,
carrier 250, platen 258, and specimen 118 are disposed.
Accordingly, by having two layers of conductive walls that enclose
the chamber 190, the testing area is further isolated from external
noise sources by the guarding/shielding configuration in which the
housing walls are arranged. To that end, the walls of the
respective outer and inner housing portions 108 and 182 of the
probe station housing 102 are electrically insulted from each other
as by a gap 191 therebetween which optionally can be filled with
insulative material to further insulate the housing portions 108
and 182 from each other. In the form shown, the gap 191 is
maintained via standoff insulators or housing isolators 192.
[0081] More specifically, the housing outer portion 108 has a base
wall 112 and an outer side wall 114 upstanding therefrom. At the
upper end of the side wall 114, a top cover wall 110 is attached to
complete the structure of the outer housing portion 108.
[0082] In many low current/low voltage probing applications, the
DUT 118 has an increased sensitivity to noise, such as light,
electrical interference, air contaminants and vibration. For
example, some of the wafers manufactured today for integrated
circuits are so small and sensitive that simple exposure to light
can induce a current in the circuitry of the wafer 118. Such noise
can distort low level test readings or probe readings taken from
the wafer unless the light/noise is substantially removed. Thus,
the outer housing portion 108 of housing 102 serves as a first
barrier for noise reduction by reducing, if not eliminating, many
of the traditional elements of noise such as the amount of light
that is allowed into the internal space 190 of the housing 102.
[0083] Inside the outer housing portion 108, walls of the inner
housing portion 182 corresponding to the walls 110-114 of the outer
housing portion 108 are provided. As mentioned, alternatively these
can be metallic layers applied to the inside surfaces of the walls
110-114 and insulated therefrom. The walled inner housing portion
182 includes a bottom wall 186 adjacent the base 112, top wall 184
adjacent the cover 110, and side wall 188 adjacent side wall 114
and extending between the top and bottom walls 184 and 186 with the
corresponding walls separated by gap 191, as previously mentioned.
Either the outer housing walls 110-114 or the inner housing walls
184-188, or both, cooperate to form the vacuum chamber 190 of the
housing 102 and thus either set of the walls 110-114 and 184-188
where formed as separate members may have a vacuum-type seal
therebetween such as between the top wall 184 and the upper end of
the side wall 188, as described further herein. The provision of
the vacuum enclosure 190 in which the test area is disposed is
desirable due to the preferred high resolution or electron
microscope 104 employed herein. In this manner, an environment
substantially free of gas particles or molecules that could affect
the path of electron beams from the electron microscope to and from
the target DUT is provided.
[0084] The housing 102 has through openings 142 to allow vacuum
pump 115 to be connected thereto for drawing down the pressure in
the chamber 190 to vacuum conditions. In FIG. 5H, it is shown that
the openings 142 extend through the bottom walls 112 and 186 of the
housing 102. In the embodiment shown, another vacuum pump 116 is
connected to the high resolution microscope 104. Such a
configuration allows the microscope 104 to be run at a different
vacuum pressure than the chamber which can reduce the amount of
surface charging that occurs within chamber 190 due to the presence
of an electron beam from microscope 104. For example, if the vacuum
within the microscope column is at a pressure of 10-6 Torr, and the
vacuum within chamber 190 is at a pressure of 10-5 Torr, a degree
of environmental conductivity is created which increases the amount
of time it takes to charge the various surfaces within chamber 190
and/or provides a means for dissipating surface charges by bleeding
the surface charges created by the beam off of the surfaces in the
chamber 190. This is beneficial for a variety of reasons, including
the fact that dissipation of surface changes and/or hindering
surface charges from occurring reduces the chance that such charged
surfaces will interfere with the probing as measurements are taken
by system 100. For example, by hindering a surface within the
environment from changing, that surface is less likely to generate
noise or interference within the chamber 190. This is particularly
important when low voltage/low current measurements are being taken
therein as they can be influenced or distorted by even the
slightest form of noise/interference. In practice, a vacuum state
can be reached in the illustrated probe station 100 in
approximately three minutes. As is apparent, this time period can
be changed by altering the size of the enclosure 190 and/or the
capacity of the vacuum pump.
[0085] In order to reduce if not elements the amount of noise such
as vibration experienced in chamber 190 due to the operation of
vacuum pumps 115 and 116, the vacuum pumps are mounted to the
housing a vibration coupler which absorbs noise generated by the
pumps 115 and 116 and allows the pumps to move freely so that they
may vibrate as needed. Additional steps for reducing the amount of
vibration noise experienced within chamber 190 instruct the use of
the vibration isolation table shown in FIGS. 5A-5C. This table
contains isolators 117 located between the table top and the leg.
Furthermore, the housing 102 is suspended from a circular opening
in the table top via additional vibration isolation arms not shown,
which acts as additional means or backup means of vibration
isolation.
[0086] Through openings are formed in sidewall 114 and aligned with
corresponding inner sidewall through openings to provide access
openings or feedthroughs 119, 121, 122, 123, 124, 125 and 127 in
the housing 102 from the housing exterior to the vacuum chamber
190. These through openings can be used for running leads 120 from
an external controller 576, such as a computer, into the housing
102. In this way, the probe assemblies 106, actuators for the
carrier 250, and other system utilities (e.g., environmental
controls, motor drives, etc.) can be remotely controlled externally
from outside the vacuum chamber 190 in which these components are
operable. The leads 120 can be in the form of electrical cable
(e.g., coaxial, triaxial, ribbon, etc.), wiring or conduit for
wiring, hydraulic fluid lines, or the like.
[0087] The feedthroughs can include flanged connector mounts 126
and 128 schematically shown in FIGS. 5H-5J that are secured in the
openings 122 and 124 and which include respective passages 126a and
128a extending outward from the sidewall 114 and into which
electrical connectors 138 and 140 are secured. The mounts 126 and
128 have radially enlarged flanges or end portions 130 and 132,
respectively, to which end caps 134 and 136 are mounted for sealing
each passage about the connectors 138 and 140. In this regard, the
end caps 134 and 136 can be drilled out to form central openings
134a centrally aligned with the respective passageways 126a and
128a to allow the connectors 138 and 140 to be inserted and mounted
therein. Accordingly, access from the exterior of the housing
through the passages 126a and 128a and to the interior vacuum
chamber 190 is provided via the connectors 138 and 140 which are
attached to the end caps 134 and 136. The connectors 138 and 140
allow leads to be passed from the exterior of the housing into the
inner enclosure 190 while maintaining a vacuum-tight seal so that
the vacuum state can be achieved within the housing 102.
Accordingly, the preferred feedthroughs herein include the flanged
access ports 126 and 128 and attached electrical connectors 138 and
140, although it will be apparent that other feedthrough
constructions may be employed.
[0088] The end caps 134 and 136 form a vacuum-tight seal with the
flange portions 130 and 132 as by a sealing ring or rubber grommet
compressed therebetween for substantially preventing leakage from
the ports 126 and 128. The flanged end portions 130 and 132 may be
fastened to the end caps 134 and 136 via fasteners such as nuts and
bolts which, when tightened, draw the end caps and flanged ends
tightly against the rubber grommet and into compression to create a
vacuum-tight seal between these components of the housing 102.
[0089] As will be appreciated specific configurations of the
connectors 138 and 140 can vary significantly. In the preferred
form, BNC/coaxial, triaxial, conduit and piping connectors are used
as feedthrough connectors 138 and 140.
[0090] For example, in FIG. 6, a triaxial-type connector 146 is
shown for being fitted to the end caps 134 and 136 and respective
end caps 134 and 136 in sealed relation thereto. The connector 146
includes an inner elongate triaxial shank 147 having an outer
sleeve 148 adhered thereon as by epoxy. The sleeve 148 includes a
threaded portion 149 having external threads 151 formed thereon. A
stepped flange portion 154 of the sleeve 148 has a polygonal
driving surface 155 for turning of the sleeve 148 and shank 147. An
O-ring seal 156 is seated in a forwardly opening recess 157 formed
in the sleeve flange portion 154 so that with the shank 147
inserted into the passageways 126a and 128a, the ring seal 156 is
adjacent to or engaged with the outer sides of the respective end
caps 134 and 136. An internally threaded jam nut (not shown) is
screwed onto the external threads 151 of the threaded portion 149.
The jam nut can be advanced axially along the sleeve 148 toward the
flange portion 154 with appropriate turning of the nut. To compress
the ring 156, the jam nut is screwed into engagement with the inner
surface of the end caps for drawing the ring 156 into tight,
clamping engagement with the caps 134 and 136.
[0091] The triaxial shank 147 has bayonet-type detent couplings 158
with annular grooves 158a and biased balls 158b seated therein
provided at either lug end 147a and 147b thereof for being
releasably connected to mating triaxial male connectors (not shown
provided on external and internal leads 120a and 120b,
respectively). To this end, the shank 147 has an outer shield
conductor portion 152 and an intermediate guard conductor portion
159 spaced radially from shield portion 152 and insulated therefrom
for being electrically coupled to corresponding shield and guard
portions of lead connectors. A signal conductor portion 160 of the
triaxial shank 147 extends centrally and axially within the shield
and guard portions 152 and 159 and has a tubular construction for
forming a female socket into which a corresponding male signal
conductor of the lead connector is press fit. Once coupled, the
shield, guard and signal conductors of the mating leads are
electrically connected to form a triaxial connection
therebetween.
[0092] The flanged ports 126 and 128 and attached end caps 134 and
136 are preferably conductive like the outer sleeve 149 of the
connector 146. Further, the ports 126 and 128 are mounted to the
double-walled housing 102 so as to be electrically connected to the
housing outer portion 108. In this manner, the probe station 100
can be grounded via any of the electrically connected outer housing
108, ports 126 and 128, or the shield portions 152 of the
electrical connectors 138 and 140. Similarly, the guard portion 159
of the connector 146 can be electrically coupled to the inner
housing 182 so that the guard portion 159 and inner housing 182 can
be driven to substantially the same potential as the signal line
160 to further isolate the signal from noise and dissipation as
well as the vacuum chamber 190 from noise, thereby keeping the test
area substantially free from electrical interference for accurate
measurements at the low testing levels employed by the probe
station 100 herein. As is apparent, common grounding and shielding
can be employed for the housing 102 and the connectors 146. In the
housing 102 shown in FIGS. 5H and 51, the outer housing 108 is
grounded (or shielded) and the inner housing 182 is guarded.
[0093] In FIG. 7A, a coaxial-type connector 164 is shown having a
coaxial shank 166 for being connected to coaxial connectors (not
shown) on lead ends as by sockets 168 and 170 to create an
electrically conductive coaxial connection therebetween. The
remaining structure of the coaxial connector 164 is similar to the
above-described triaxial connector 146. More specifically, the
connector 164 has jam nut 180, threaded on a coaxial sleeve portion
172. The sleeve portion 172 further includes a radially enlarged
stepped flange 174 having an outer polygonal surface 176 for
screwing the sleeve 172 into tight sealing engagement against the
end cap 134 or 136 to which it is mounted.
[0094] When mounted to the probe station housing 102, the threaded
sleeve 172 is passed through the end cap opening 134a or 136a and
the jam nut 180 is threaded onto the sleeve 172 on the opposite
side of the end cap 134 or 136. The jam nut 180 is advanced axially
along the sleeve 172 toward the flange portion 174 with appropriate
turning of the nut 180 until a tight sealing engagement is made
between the connector 164 and one of the end caps 134 or 136. As
the sleeve 172 and nut 180 are tightened together, the sealing ring
178 is pressed between the flange 174 and the cap 134 or 136
thereby making a vacuum-tight seal therebetween. FIG. 7B is another
form of coaxial connector identified generally by reference numeral
181. This connector 181 has a similar configuration to the
above-described bayonet-type detent coupling of connector 146, with
the exception of having coaxial conductors instead of triaxial
conductors, (e.g., a coaxial shank versus a triaxial shank).
[0095] Other forms of connectors may be used for feedthroughs 138
and 140 so long as they are capable of providing a vacuum tight
seal capable of allowing chamber 108 to be pulled into a vacuum
state. For instance, flat cable such as ribbon cable 120 shown in
FIG. 5E may pass through a vacuum-tight connector such as the
PAVE-FLEX connector manufactured by Pave Technology Company, Inc.
of Dayton, Ohio, in order to connect circuitry from within the
vacuum chamber 190 to a controller located outside the housing 102.
In this regard, the feedthroughs 138 and 140 may consist of a
disc-shaped insert through which a bulkhead is formed for allowing
a flat cable to pass through the insert while maintaining a
vacuum-type seal about the cable. By way of example and not
limitation, the bulkhead may be s-shaped or z-shaped to assist in
maintaining the vacuum-type seal and support a variety of cable
types, (e.g., coplanar, microstrip, stripline, as well as
single-strand, stranded, twisted pair, coaxial, triaxial, ribbon
cable, and the like). Vacuum-tight, as used herein, does not
necessarily mean that a hermetic seal must be reached, but rather
means that the seal developed must be capable of allowing the
housing interior chamber 190 to be pulled into a vacuum state. By
way of example, but not limitation, the feedthrough electrical
connectors 138 and 140 may create a seal that has a helium leak
rate of less than 1.times.10.sup.-7 cc/sec at one atmosphere.
[0096] The probe station 100 may be set up so that a bank of
feedthrough connectors can be connected to openings 122 and 124, as
shown in FIGS. 5A, 5B, 5D, and 5E, with each connector being
generally aligned in side-by-side fashion. Alternatively, the probe
station 100 may be set up with multiple openings and passages, with
each opening/passage having its own connector or feedthrough.
[0097] Other types of connectors are shown connected to the system
100 in FIG. 5E. With respect to access opening 119, a bank of
integrated circuit headers 129 arranged in a three column/two row
format is shown, which may provide electrical connections for
various system utilities. With respect to access opening 125, a
bank of cable feedthroughs 131 is shown to provide cable access to
the vacuum chamber. By way of example, such as approximately one
hundred and four coaxial cables 120 can enter/leave the housing 102
via connector 131 without affecting the pressure of vacuum chamber
190.
[0098] As mentioned, in order for the housing inner portion 182 to
be driven as guard while the outer portion 108 is driven as shield,
the housing portions 108 and 182 must be electrically isolated from
one another. This electrical isolation can be achieved by using
nonconductive material to space the housing portions 108 and 182
apart from one another. In a preferred form, nonconductive
rod-shaped standoffs 192 are employed which maintain the housing
portions 108 and 182 spaced apart from each other by gap 191.
However in alternate forms of probe station 100, the nonconductive
material can be sandwiched between the housing portions 108 and 182
throughout the probe station 100, or the housing portions 108 and
182 can consist of conductive coatings on a wall of insulation such
as in the single walled construction discussed above.
[0099] Top wall portions 110 and 184 include aligned through
openings within which the high resolution microscope 104 is mounted
for observing and assisting in various probe applications. With
respect to top portion 110 of housing portion 108, a vacuum-tight
seal is made between it and the microscope 104, so that a vacuum
can be pulled in the vacuum chamber 190. In a preferred form of
probe station 100, an electrically insulative material, such as
rubber, is used to form an O-ring 195 (FIG. 5H) which creates a
vacuum-tight seal between the high resolution microscope 104 and
the top 110 and can also serve to isolate the microscope 104 from
the top 110. One reason for electrically isolating the microscope
104 from the top cover wall 110 is to allow the probe station 100
to be connected and/or wired in a variety of fashions. For example,
with the microscope 104 electrically isolated from the top 110,
either the microscope 104 or the top wall 110 may be connected to
ground while the other is connected to a guard signal. This type of
configuration may be desired for providing a guarded surface
directly above the DUT 118 for creating optimal low noise testing
conditions which will be discussed further below. Additional
O-rings 195a and 195b are provided for creating a vacuum-tight seal
between the portions 110, 112 and 114 of the outer housing portion
108.
[0100] Like the top wall 110, top wall 184 of the inner housing
portion 182 also has an opening within which the scanning electron
microscope 104 can be mounted so that the bottom portion 226 of the
microscope 104 extends into the vacuum chamber 190 of the housing
102. An electrically insulative material is preferably used to
isolate the metallic casing of the high resolution microscope 104
from the top wall 184. This material may also be used to perfect a
vacuum-tight seal between the microscope 104 and top 184, if
desired, or may simply be used to provide an additional or back up
means for blocking out noise such as light. With such a
configuration, the lower portion of the microscope 104 and the top
184 can be driven the same (e.g., both as guard or both as shield)
to offer additional noise/interference protection. If both the
microscope 104 and the top 184 are always to be driven to the same
potential, it is not necessary to electrically isolate these items;
however, a benefit to isolating the microscope 104 and the top 184
is that such a configuration allows maximum flexibility as to how
the entire probe station 100 can be set up. For example, the probe
station 100 may be set up so that neither the housing portions 108
and 182 nor the microscope 104 is driven as guard or shield.
Alternatively, the probe station 100 may be set up so that each of
the housing portions 108 and 182 and microscope 104 are used
differently, such as doing nothing with the outer housing portion
108, connecting the inner housing portion 182 as shield, and
driving the microscope 104 as guard. It also is not necessary to
make a vacuum-tight seal between the high resolution microscope 104
and top 184. This is because the seal between microscope 104 and
top 110 is sufficient to draw down the pressure in the interior of
housing 102, (the vacuum chamber 190), to vacuum conditions. It
may, however, be desirable to make the seal between top 184 and
microscope 104 vacuum-tight to allow for additional housing
configurations.
[0101] In a preferred form, the outer housing portion 108 is
connected to ground in order to reduce the chance of electrical
shock to a probe station user, and the inner housing portion 182
and the lower portion 226 of microscope 104 (located within chamber
190) are connected to a guard signal to minimize the amount of
parasitic capacitance and EMI by minimizing the number of available
conductors surrounding the DUT 118 and probe assembly 106 that can
be charged via leakage current and electromagnetic fields. Thus,
with this configuration the entire probe station 100 can be set up
in a triaxial configuration with the DUT completely surrounded by
guard and then shield which minimizes the amount and effect of
noise or interference as described above. In another form, the
system 100 is configured so that the outer housing 108 and
microscope 104 are shielded, and the inner housing 182 is guarded.
This setup avoids any problems that may be encountered when
connecting the microscope 104 to guard, (e.g., problems with the
electron beam encountered when applying a potential to the outer
surface of the microscope 104).
[0102] As described, the top wall portions 110 and 184 of the outer
and inner housing portions 108 and 182, respectively, collectively
form a cover 194 for the probe station 100 which carries the high
resolution microscope 104 therewith. As discussed previously, the
cover 194 may be raised via a lift mechanism 196 so that the top
portions 110 and 184 and microscope 104 can be lifted and retracted
away from the remainder of inner chambers 108 and 182 and/or the
remainder of housing 102. This shifting of the microscope 104 gives
a probe station user access to the internal operating components
including the probe assemblies 106 located within the chamber 190,
and the various leads passing through the housing 102. The lift
mechanism 196 may be powered by pneumatics or hydraulics to provide
the necessary power to lift and retract the heavy combined weight
of the cover 194 and high resolution microscope 104 that it
carries.
[0103] In the preferred and illustrated form (FIG. 5C and FIG. 23),
the lift mechanism 196 includes a power or hydraulic cylinder 197
having an arm or ram actuator 198. A cam member 199 is attached
between the arm and cover assembly so that operation of the arm 198
moves the cover 194. The cam member or coupling 199 has an arcuate
cam track 199a formed along the side thereof within which a cam
201a from an upstanding column portion 201 travels. The column 201
is fixed at one end to the surface of a support structure such as
table 144, and has cam 201a fixed near its upper end. The arcuate
track 199a is configured so that when the arm actuator 198 is
shifted to its extended position, the cover 194 is lifted and then
simultaneously lifted and pivoted away from the side walls 114 and
188 of the housing 102. In this manner, the microscope is
automatically moved from its high resolution viewing position
relative to the chucked specimen with the cover 194 seated on the
side walls 114 and 188, (preferably in sealed relation therewith as
previously described), to a retracted or non-viewing position so
that the specimen is no longer in the high resolution microscope's
field of view, and the interior of the housing 102 is accessible to
an operator for system set-up procedures, additional probing with
using the light microscope 105, additional testing, and/or
maintenance.
[0104] The track 199a can be configured with a short vertical
section at the beginning of the track so that the cover 194 travels
in a straight up and down (or vertical) direction for a
predetermined amount of time right after it starts opening (or just
before it finishes closing). Thus, the cover 194 will travel
vertically for a period of time prior to traveling in an angular
direction upon opening, or for a period of time after traveling in
an angular direction upon closing, to ensure that an adequate
clearance is provided between the microscope 104 and the remainder
of the probe station 100 and particularly the components located
within chamber 190 (e.g., probe assemblies 106). A manual override
mechanism may also be provided so that the cover 194 can be removed
in cases of emergency or in power loss. In a preferred form such an
override would consist of a removable crank handle which when
inserted and turned, moves the cover 194 to its open position.
[0105] In alternate forms of system 100, the track 199a may be
configured so that a period of vertical travel is provided for at
the other end of the track 199a as well. Furthermore, the angular
movement allows for the cover 194 to be opened/closed in a minimal
amount of time. In alternate forms, the track 199a of system 100
may be set up as an angled track, an L-shaped track, or in other
configurations providing various paths for the cover 194 to follow
during its opening/closing. FIG. 23 illustrates one way in which
the cam 201a and track 199a can be configured.
[0106] As shown in FIGS. 5A-5D, 5F and 5G, the housing 102 contains
locating members 192 including upstanding columns 192a connected,
at their bottom end, to the support structure 144 and having
tapered locating pins 193 projecting up from their upper end for
ensuring the proper position of the cover 194 before allowing it to
complete the last portion of travel required to close or seal the
system 100. Such a design is desirable in that the last portion of
travel, in which the cover perfects the vacuum seal and the
microscope 104 is lowered downward very near the surface of carrier
250, is critical because failure to have proper alignment could
damage the microscope 104, probe assemblies 106, and/or DUT 118.
For example, if the cover alignment is off, the microscope 104
could damage its lens or damage a probe assembly 106 by coming into
contact with one of the probe assemblies 106. Furthermore, such
contact could cause the probe assembly 106 to move and damage the
DUT 118. In the illustrated form, a properly aligned cover 194 is
allowed to complete the last portion of travel required to close
the system when the position orienting members 192 and pins 193 are
aligned with openings 189 in the cover. More particularly, during
the last portion of travel in the downward direction, the tapered
pins 193 are inserted into opening 189 so that cover 194 can be
completely closed.
[0107] Problems during the last portion of travel in which the
cover perfects the vacuum seal between cover 194 and housing 102
via O-ring 195b could also result in making the vacuum pumps 115
and 116 work harder than they need to thereby wasting energy and/or
prevent the vacuum chamber 190 from ever reaching its desired state
or pressure. Thus, by providing locating members 192, the system
100 further ensures that the proper vacuum tight seal will be made
when the cover 194 compresses the O-ring 195b against its lower
surface and the upper surface of housing 102.
[0108] The above-described automated shifting of the microscope 104
between its viewing and non-viewing positions, as well as the
position orienting features, are desired because high resolution
microscopes are typically very costly, heavy, and inconvenient to
move about. In FIG. 7, a schematic diagram of a typical scanning
electron microscope (SEM) is shown generally at reference numeral
200. During operation of the SEM, an electron gun 202 emits
electrons from a filament tip 204, such as a fine tungsten-wire
filament, or from a sharply pointed wire attached to the filament
tip 204. The emitted electron beam 206 is focused by lenses 208 and
210 and then deflected over the DUT 118 via upper and lower heavy
deflection coils 212 and 214 and lens 216. The image of the DUT 118
is formed by scattering the electrons from beam 206 over the DUT
118 and collecting the electrons via electron collector 220. The
denser or thicker portions of the DUT 118 in which the cover
perfects the vacuum seal scatter more electrons than the thinner
portions and will appear darker. Although the SEM is capable of
generating high resolution images of objects with depths of focus
that can produce an incredibly accurate three dimensional view of
the DUT 118, the intensity of the electron beam 206 can often cause
damage to the DUT 118 if left on for too long and/or affect or
distort the probe readings taken from the probe station 100 by
inducing noise into the system via the energy given off by
microscope 104. This fact, however, must be balanced with the fact
that longer SEM scanning periods result in higher resolution,
noise-free, images.
[0109] Ideally, the probe station user would simply shut off the
microscope during probing or testing of the DUT 118 in order to
avoid any interference generated by the microscope. Unfortunately,
however, high resolution microscopes such as microscope 104 can
take several minutes to power back up for operation and reacquire
(or focus on) the desired image. To improve cycle times and
minimize electrical interference that may be generated by a
constant "on" operation of the microscope 104 it is preferred that
the system include an apparatus for reducing the duty cycle of the
microscope 104, (e.g., reducing the ratio of operating time for the
microscope 104 to the total elapsed time for the testing of the
DUT). This apparatus provides a way in which unwanted irradiation
of the DUT 118 can be reduced without having to turn the microscope
104 off. In a preferred embodiment this apparatus may consist of an
optional shutter 218 which can block (or blank) the beam 206 of
microscope 104 during testing thereby limiting the DUT's exposure
while allowing the microscope 104 to continue to scan the DUT 118.
In this way, the electron beam 206 is not continuously focused on
the testing area during image acquisition procedures. The shutter
218 may be positioned within the microscope 104 or external to the
microscope 104, may take any shape or size, and may be made of any
material so long as it is capable of blocking at least a portion of
the electron beam 206 from damaging the specimen or DUT 118. For
example, the shutter may be a disc located within the microscope
that is capable of covering the entire lens 216 of microscope 104
so that none of the beam 206 reaches the DUT 118. Alternatively,
the shutter 218 may be a revolving disc, located below microscope
104, with holes or slits located about the disc that block varying
portions of the beam 206 as the disc revolves.
[0110] The shutter 218 may also be manual, semi-automatic or fully
automatic. For example, the probe station 100 may be configured
such that the probe station user must manually open the shutter 218
to receive a high resolution image of the DUT 118, or may require
the user to manually close the shutter 218 in order to block the
beam 206 to prevent damage to the DUT 118. However, due to the
frequency with which the shutter must be open and shut in a manual
shutter is not as desirable as a semi-automatic or fully automatic
shutter. Alternatively the probe station 100 may be configured with
a semi-automatic shutter 218 wherein the user has to activate a
switch (not shown) indicating that the high resolution image is no
longer needed, which in turn activates the shutter 218 to block at
least a portion of the beam 206.
[0111] The probe station 100 may also be configured with a fully
automatic shutter 218 which allows the DUT 118 to be exposed to the
beam 206 for a predetermined amount of time and then activates the
shutter 218 thereby blocking at least a portion of the beam 206.
Since the probe station user only needs to see the microscope image
while setting-up/positioning the probes, and does not need the
microscope to be imaging (or emitting beam 206) onto the DUT during
testing, a preferred form of probe station 100 uses the shutter to
blank the beam 206 during testing to reduce the risk of damaging
DUT 118 and/or reduce the chance of the microscope 104 affecting
the testing/probing results. Thus it is clear that an actual method
of operating the probe station 100 in such a way as to limit DUT
exposure to beam 206 may be used to further improve the operation
of the probe station 100. If desired, the probe station 100 may be
set up to caption the last image of the DUT 118 prior to the
shutter 218 being activated and/or set up to display the captured
image during the time the shutter 218 is activated.
[0112] As seen best in FIG. 5, the high resolution microscope 104
of probe station 100 has a generally cylindrical or column shaped
housing or casing including an upper portion 222 and intermediate
portion 224 projecting upwardly from the cover 194. An electron gun
is located in the upper portion 222, lenses and deflection coils in
an intermediate portion 224, and a final lens and aperture located
in a lower portion 226. As mentioned it is preferred that the
microscope 104 include a shutter 218 which contains holes or slits
such as every five degrees for reducing the duty cycle of the beam
206 of microscope 104 as discussed above. This configuration allows
the probe station user to continually update the microscope image
while minimizing the amount of damage to DUT 118. In addition, to
further assist in reducing noise within chamber 190 and/or
obtaining low current/low voltage readings, the shutter 218 may be
configured such that it can be connected to guard or shield in
keeping with the feasibility of the system configuration afforded
by the present invention and as has been discussed previously. For
example, the shutter 218 may be electrically isolated from the
microscope 104 so that it may be wired to guard while the
microscope 104 is shielded, or the microscope 104 and the shutter
218 may be electrically connected to one another in instances where
both items will be connected in a similar fashion.
[0113] The microscope 104 is positioned so that at least part of
the lower portion 226 extends below the tops 108 and 184 and into
the chambers 108 and 182. A power supply 227 is located atop the
cover 194 near the microscope 104 for supplying power to the same
during high resolution probing with system 100.
[0114] An electron collector 220 extends through the cover 194 near
the microscope 104 and is positioned at an oblique angle to the
plane of the cover 194 in order to collect the electrons from the
beam 206 deflected off of the DUT 118 to provide a high resolution
image of the target area. As shown in FIG. 5K, a column 228 is
located adjacent the microscope 104, containing a variable vacuum
pressure valve 230 which allows the vacuum pressure of the
microscope column to be adjusted independent from the vacuum
pressure of the chamber 190. The microscope vacuum pump 116 is
connected to the column 228 along with a microscope column
pressure/vacuum sensor 231. These components can be arranged in a
variety of positions about the system 100, however, in a preferred
form the electron collector 220 is positioned so that it will be
located at the front of the system 100 when the cover 194 is
closed. Such a configuration allows for additional probe assemblies
106 to be added along the rear side of the chamber 190 in clearance
from the front mounted collector 220. The front mounting of the
collector 220 also makes it easier for the system operator to
access the probe assemblies 106, carrier 250, stages and motor
drives, etc., as well as, determine where the probe assemblies
should be positioned so that they do not interfere with the
microscope 104, electron collector 220 and other components of the
cover 194. This configuration also leaves the removable portion of
the platen 258 free from components so that a system user can
quickly and easily get access to the carrier 250, stages 311, 312,
314, 316 and platform 544 through opening 258a.
[0115] The portions 220, 222, and 224 of microscope 104 may also be
electrically isolated from one another so that the probe station
100 can be configured in a variety of ways, (e.g., with some
portions connected to ground, others connected to guard, etc.), as
discussed above. For example, in one form the lower portion 226 is
electrically isolated from the upper and intermediate portions 222
and 224 so that the lower portion 226 can be connected to a guard
signal to further reduce noise/interference such as parasitic
capacitance and EMI as discussed above, and the upper and
intermediate portions 222 and 224 can be connected to ground to
reduce the risk of electrical shock to a probe station user. Again,
such a configuration allows the probe station to be connected in a
triaxial arrangement having the DUT 118 surrounded by a guard layer
formed by top 184, bottom 186, sidewall 188, and lower scope
portion 226, and further surrounded by a shield layer formed by top
110, bottom 112, sidewall 114 and upper and intermediate scope
portions 222 and 224. In a preferred form, however, the microscope
104 and outer housing 108 are shielded and the inner housing 182
and shutter 218 are connected to guard. Thus the DUT 118 will be
surrounded by a guard layer and a shield layer in order to reduce
noise and allow for optimal probing/measurement conditions.
[0116] Inside the housing 102 are the operating components of the
probe station 100 for probing of the specimen including a carrier
250, (e.g., a chuck, fixed probe card, socket stage adapter and its
respective socket cards, etc.), and a plurality of manipulators
252a, b, c, and d, each including conductive portions in the form
of probes 256 for testing DUTs such as electronic components or
specimens 118. In general, the carrier 250 is used to support the
specimen 118 in a rigid and fixed position during testing.
Preferably, the carrier 250 is capable of moving the specimen in
the X, Y and Z directions. The manipulators 252a-d are mounted on a
support or platen 258 which is located within the vacuum chamber
190 and includes a central opening which provides access for the
probes 256 to the carrier 250 located beneath the platen 258.
Although four programmable manipulators are shown, the system can
be set up to handle additional manipulators. For example, in one
form the system 100 may be set up using six manipulators having at
least 10 nm resolution and 0.5 inches of travel in all axes.
[0117] In a preferred form, the platen 258 has an access panel
which can be opened and/or removed in order to give the system
operator access through opening 258a to support portions of the
carrier 250, motor drive systems, and additional components located
within chamber 190. In the embodiments shown in FIG. 5D and FIG.
24, the access panel has been removed to show the opening 258a
covered thereby.
[0118] The manipulators 252a-d operate to position their associated
probes 256 about various conductive path indicia, or test points,
located on the surface of the specimen 118. Prior to discussing
further operation of the probe assembly 106, however, each
component of the probe assembly 106 will be discussed in further
detail below.
[0119] The carrier shown in FIGS. 5A-5K and 14 is a chuck 260 which
is generally circular in shape and is used for supporting the
specimen or DUT 118 which is to be probed. The chuck 260 may range
in complexity from simple single layer disk shapes to more complex
multi-layered shapes. An advantage of using a multi-layered
configuration is that the noise reduction principles associated
with the various shielding and guarding configurations discussed
above with respect to housing 102 can be applied to the carrier 250
as well. For example, the chuck 260 can be configured in a coaxial
or triaxial arrangement in order to minimize the effects of
parasitic capacitance and/or EMI by reducing the number of
available conductive surfaces which can be charged and protecting
the DUT 118 against interference from external electromagnetic
fields.
[0120] In FIG. 14, the chuck 260 is a triaxial chuck having a
multi-layered disk shape consisting of a first conductive element
261, a second conductive element 262, and a third conductive
element 264. The first conductive element 261 is generally circular
in shape and is electrically isolated from the second conductive
element 262 via a similarly shaped insulating plate 263. The second
conductive element 262 is also generally circular in shape and is
connected to the third conductive element 264 via insulative rods
265, which serve to electrically isolate the second conductive
element 262 from the third conductive element. The third conductive
element 264 is generally circular in shape, and has a bottom
portion 266 which extends laterally below the second conductive
element 262, and an annular side wall 267 which extends opposite
the outer periphery of the first and second conductive elements 261
and 262.
[0121] In a preferred form, the first conductive element 261 and
insulator 263 are combined into a ceramic puck having a platinum
sputtered conductive outer layer with the ceramic portion serving
as insulator 263 and the outer conductive layer serving as the
first conductive element 261. Alternatively, the insulating plate
263 may be made of a non-conducting material such as TEFLON. The
second conductive element 262 is made from a conductive metal such
as cast aluminum, and the third conductive element 264 is made from
a conductive metal such as stainless steel. The insulators 265 are
made from a non-conducting material such as sapphire and can take
any shape, such as a rod or a simple dielectric disc shape stacked
between the second and third conductive elements 262 and 264.
[0122] As mentioned above, the multilayered chuck configuration
assists the probe station 100 in conducting low noise probing by
allowing the chuck 260 to be connected in a variety of
configurations including those mentioned with respect to housing
102. For example, the chuck 260 can be connected in a triaxial
configuration similar to the probe's connection to triaxial cable
275, wherein the first conductive element 261 of chuck 260 is
connected to the center conductor or signal line, the second
conductive element 262 is connected to guard, and the third
conductive element 266 is connected to shield. Alternatively, the
chuck 260 can be connected in a coaxial configuration wherein the
first conductive element 261 is connected to the center conductor
or signal and the second conductive element 262 and/or third
conductive element 264 are connected to the outer shield line. Yet
another configuration may have the second conductor 262 connected
to shield and the third conductor 264 connected to guard. As should
be apparent to one of ordinary skill in the art, the electrically
isolated configuration of probe station 100, carrier 250 and probes
256 allows for a number of different wiring schemes to be
implemented. This flexibility allows the system 100 to be
configured in a fashion that best suits the type of testing to be
done.
[0123] In addition to the variety of chuck configurations that can
be used for carrier 250, the probe station 100 may also use chucks
having any number of chuck features such as thermal capabilities.
For example, the chuck 260 may be a thermal chuck which is capable
of raising and/or lowering the temperature of the chuck 260,
thereby allowing the DUT 118 to be tested at temperature. The
ability to test at temperature allows the DUT 118 to be tested in
simulated application conditions thereby allowing testing to more
accurately reflect use conditions of the DUT 118. As can be seen in
FIGS. 9A-9B, the temperature of a thermal chuck may be raised above
ambient temperatures via resistive wiring 276 which is placed
within a metal sheathing 278 that is cast into one of the layers of
the chuck 260. One of the benefits of conducting tests at
temperature in a vacuum environment is that the test measurements
will not be affected by environmental side effects from raising and
lowering the temperature. For example, when the thermal chuck is
lowered to temperatures well below ambient temperatures, frost will
not occur due to the vacuum environment. Similarly, when the
thermal chuck is raised to temperatures above ambient temperatures,
humidity will not occur due to the vacuum environment.
[0124] In order to heat the chuck using the heating elements shown
in FIGS. 9A-9B, electrical current is run through wire 276 causing
the wire 276 and sheathing 278 to heat up and radiate heat
throughout the conductive elements 261 and 262. The conductive
elements 261 and 262, in turn, radiate heat to the entire probe
station 100, including the chuck surface and DUT 118. The more
current that is run through the wiring 276, the more heat is
generated due to the resistive nature of the wiring. Therefore, in
order to increase the temperature of the probe station 100, the
probe station user need only increase the amount of current that is
being fed through the wire 276. In order to maintain the desired
temperature for testing the DUT 118 at temperature, the chuck 260
has temperature sensors (not shown) which are capable of detecting
the temperature of the probe station 100. In one form, the
temperature sensor can be a thermocouple attached to the chuck 260.
As the temperature of probe station 100 begins to fall below the
desired testing temperature, more electrical current is applied to
the wire 276, causing the wire to radiate more heat and increase
the temperature of the probe station 100. As the temperature begins
to rise above the desired temperature for testing, less current is
applied to wire 276 causing the wire to radiate less heat.
[0125] The temperature of the thermal chuck shown in FIGS. 9A and
9B is lowered below ambient temperatures by passing a coolant or
heat transfer fluid through conduit (or piping) 280 which is cast
in one of the layers of chuck 260. Typically the coolant is a
liquid or vapor and the conductive element within which the conduit
280 is cast is made of a good thermal conductor such as cast
aluminum so that heat transfer can readily take place throughout
the probe station 100 thereby allowing the vacuum chamber 190 to be
raised or lowered to the desired temperatures. In order to lower
the temperature of the probe station 100, the probe station user
need only increase the amount of fluid being sent through the
conduit 280 which in turn will lower the temperature of the probe
station 100 via heat transfer. As discussed above, the chuck 260
may contain a temperature sensor such as a thermocouple to monitor
and maintain the desired temperature of the chuck 260. As the
temperature begins to rise above the desired probing temperature,
more fluid is sent through the conduit 280 thereby lowering the
temperature of the system. As the temperature begins to fall below
the desired testing temperature, less fluid is sent through the
conduit 280. In alternate forms of the chuck 260, the heating of
system 100 may be accomplished in a similar manner to the cooling
described above (e.g., passing heating liquid or vapor through
tubes).
[0126] The thermal chuck may be configured so that the heating and
cooling elements 276 and 280 are cast into the second conductive
element 262 or into a combination of both the first conductor 261
and the insulator 263. For example, the heating and cooling
elements 276 and 280 may be cast into a cast aluminum disc serving
as the second conductor 262. Alternatively, the heating and cooling
elements 276 and 280 may be cast into a ceramic puck having a
platinum sputtered conductive layer as discussed above. In this
configuration the ceramic serves as the insulator 263 and the
platinum conductive layer serves as the conductor 261.
[0127] With the many alternatives and options discussed above
regarding chucks, it should be clear that the type of chuck used
with probe station 100 depends on what type of testing or probing
is to be completed and what type of information is to be gathered
(e.g., is probing being done at ambient conditions or at
temperature, is a triaxial chuck necessary or not, etc.). In
alternate forms, the probe station 100 may be set up using any one
of the chucks manufactured and sold by The Micromanipulator
Company, Inc. More particularly, the probe station 100 may be set
up using one of the chucks described in Micromanipulator's
co-pending U.S. patent application Ser. No. 09/815,952 filed on
Mar. 23, 2001, (the '952 application), which is hereby incorporated
herein by reference in its entirety. For example, in a preferred
form, the chuck 260 may be Micromanipulator's CHK 8000-A thermal
triaxial chuck, which is one of the chucks disclosed in the '952
application. The CHK 8000-A can be configured for either coaxial or
triaxial configurations, ambient or thermal applications, and
offers a high level of performance for low noise probing.
[0128] As can be seen in FIGS. 5H-5J and FIGS. 10A-10E, the CHK
8000-A chuck 260 includes central conductive element 268 deposited
on an electrical insulator element 270 of ceramic. The central
conductive element 268 is preferably of a metal material and may be
deposited on the insulative element 270 via plasma discharge
sputtering, electroplating or other suitable technique. An outer
conductive element 269 is deposited along the periphery of the
insulator 270 and is electrically isolated from the central
conductive element 268 via a spaced arrangement. As shown in the
plan view of FIG. 10B, the electrically isolated outer conductive
element 269 forms a concentric ring about the central conductive
element 268 with an insulative region therebetween. The outer
conductive element 269 is also a deposited metal which, as
illustrated, has a side portion that extends around the outer
periphery of insulator element 270. Preferably, the outer
conductive element 269 extends down along the entire periphery of
insulator element 270, as shown, but it is also possible to
terminate the conductive material at a location on the periphery
above the bottom edge of the insulator.
[0129] In a preferred form, the uppermost surfaces of conductors
268 and 269 share the same plane and a portion of the insulator 270
fills the space between the conductive elements 268 and 269 to
further isolate each element. The coatings of metal deposited on
conductive elements 268 and 269 may be as thin as one micron, or
thicker, without significant change in overall performance and in
order to accommodate thermal expansion associated with the thermal
chuck apparatus for operation over a temperature range of, e.g.,
-65 to +400.degree. C., or beyond.
[0130] The insulator element 270 itself is supported on an
intermediate conductive element 271, which consists of a
disk-shaped aluminum alloy with cast-in heating and cooling
elements and temperature sensors (not shown). As mentioned above,
the heating elements are provided as electric resistive heaters,
and the cooling elements comprise metal tubes connected to a source
of liquid or vapor coolant. The temperature sensors are thermal
couples which are connected to a temperature controller. The
temperature controller monitors and controls the temperature of
chuck 260 and/or probe station 100 by turning on and off the
heating and cooling elements. If the controller is located outside
of housing 102, the leads connecting the controller and the
heating/cooling elements and thermal couples may pass through the
feedthroughs 119, 121, 122, 123, 124, 125 and/or 126 as discussed
above in order to maintain the vacuum state in the interior of
housing 102.
[0131] In the thermal chuck 260 shown in FIGS. 10A-10E, the heating
and cooling elements are cast into the intermediate conductor 271,
therefore the insulator 270 should be a good thermal conductor to
transfer heat from the conductor 271 to the center conductor 268
and particularly to wafer 118. As discussed above, the central
conductive element 268 and insulator element 270 may alternatively
be replaced by a ceramic disk with cast in heating, and cooling
elements, a temperature sensor, and a metalized outer surface. The
ceramic portion of the disk serving as the insulator 266 and the
metalized outer surface serving as the central conductor 262.
[0132] In chuck 260 of FIGS. 10A-10E, the diameter of insulator
element 270 is larger than that of the intermediate conductive
element 271 to provide a greater insulative barrier between the
outer conductor element 269 and central conductive element 268 in
the radial or horizontal direction. Preferably, the amount of
insulation provided radially between the conductors 268 and 269 is
greater than or equal to the bulk thickness of the insulator 270.
In other words, the concentric gap between the central conductive
element 268 and the isolated outer conductive element 269 is
preferably greater than or equal to the thickness of the insulator
270 to minimize electrical leakage or conductance, such as the EMI
and parasitic capacitance discussed above, when testing at low
femtoampere and high attoampere ranges. The diameter of the central
conductive element 268 is typically that of the largest specimen
118 to be tested. For example, for an eight inch wafer and an outer
conductive element 269 that extends radially 0.025 inches on an
insulator and is 0.312 inches apart from the central conductive
element 268, the overall diameter of the chuck insulator 270 should
extend at least approximately 8.674 inches
(8''+2.times.0.312''+2.times.0.025''). The intermediate conductive
element 271 is preferably of larger diameter than the wafer
diameter so that the effects of thermal losses to the atmosphere at
the peripheral edge of the intermediate conductive element 271 are
moved away from, and therefore minimized at, the edge of wafer 118.
With such a configuration, improved temperature control and thermal
uniformity are achieved by reducing the chance that the peripheral
edges of wafer 118 will not be heated to the same temperature as
the rest of the wafer 118.
[0133] Accordingly, the chuck apparatus 260 of FIGS. 10A-10E
includes a central conductive element 268 for supporting the DUT
118, an intermediate conductive element 271, and an intervening
insulator 270 for positioning the central conductive element 268
above the intermediate conductive element 271. The chuck 160 also
has an electrically isolated outer (or peripheral) conductor 269
consisting of a horizontally extending ring concentric with the
central conductive element 268. The outer conductive element 269
may also extend vertically along the outer lateral edge of the
chuck insulator 270.
[0134] The chuck 260 further includes a lower conductive element
272 which has a bottom portion 273 that extends laterally below the
intermediate conductive element 271, and has an annular side wall
274 which extends opposite the outer periphery of the intermediate
conductive element 271. The lower conductive element 272 is located
below intermediate conductive element 271 and has a portion
extending vertically around the side periphery of the intermediate
conductive element 271. The lower conductive element 272 is
connected to a hub of probe station 100 via hub adapter 279 which
itself is connected to the lower conductive element 272 by
non-conductive standoffs 281. The hub and hub adapter will be
discussed in greater detail below.
[0135] As shown in FIGS. 10A-10E, central conductive element 268
and the insulator 270 are circular, and the insulator 270 has a
diameter greater than the diameter of the central conductive
element 268 and that of intermediate conductive element 271. In
this arrangement, the combination of the conductive elements 269
and 271 provide a line-of-sight barrier between the central
conductive element 268 and the lower conductive element 272. When
the chuck 260 is wired in a triaxial configuration with the central
conductor 268 connected to signal line, outer conductor 269 and
intermediate conductor 271 connected to guard, and the lower
conductor 272 coupled to ground, the guarded line-of-sight barrier
made up of conductors 269 and 271 serves to minimize the amount of
leakage current and parasitic capacitance affecting central
conductive element 268 and the DUT 118 which it supports. Thus, the
center conductor 268 (and DUT 118) are effectively protected by a
guarded layer (conductors 271 and 269) and then a shielded layer
(conductor 272).
[0136] The larger diameter of insulator 270 provides for proper
isolation between the center conductive element 268 and the outer
conductive element 269. The outer conductive element 269
facilitates additional guarding around the side periphery of the
test area made up of central conductive element 268 and/or DUT 118,
and provides an electrical barrier between the test area and
conductive components of the probe assembly located off to the side
of the test area. The vertical sidewall 274 of lower conductive
element 272 may extend further upward than shown in FIGS. 10A-10E
toward the test surface without negatively affecting the system's
operational abilities because the guard conductor 269 reduces the
risk of interfering capacitive effects between the test surface and
the side wall 274 of element 272.
[0137] The lower element 272 is provided with insulative supports
277 for supporting the intermediate conductive element 271 above
the laterally extending bottom portion 273 of lower element 272. In
a preferred form of probe station 100, the supports 277 consist of
sapphire rods 277 which extend into corresponding bores in the
conductive elements 271 and 272, as shown. The bores in element 271
preferably extend to within 0.020-0.060 inches from the top surface
of element 271. These measurements have been found to minimize the
amount of vertical expansion associated with temperature variations
of conductive element 271. Alternatively, or in addition to the
sapphire rods 277, a plate of dielectric material may be provided
in the space between conductive elements 271 and 272 in order to
electrically isolate the elements.
[0138] As stated above, the test area (or test surface) of chuck
260 is located on the centrally located conductive element 268 and
the DUT 118, when present. The diameter of the test surface is
typically dictated by the size of the specimen to be tested.
Typical specimens may include wafers that are approximately eight
inches in diameter, although the chuck may be sized to accommodate
any other wafer size, such as 25 mm-300 mm wafers or larger, and
semiconductor integrated circuits or packaged parts. Also, while
the invention is described with reference to a chuck, and chuck
layers having circular peripheral configurations, chucks and chuck
layers of other geometries, e.g., square, rectangular, oval, etc.,
may be constructed in accordance with the invention.
[0139] The chuck 260 of FIGS. 10A-10E is wired in a triaxial
configuration, in which the center conductor of a triaxial lead 275
is connected to the central conductive element 268 of chuck 260,
and the middle (or intermediate) conductor of the triaxial lead 275
is connected as a guard connection to elements 269 and 271, and the
outer conductor of the triaxial lead 275 is connected to element
272 and ground. In this arrangement, the conductive components of
the probe station 100 may provide shielding from noise sources
external and internal to the probe station 100. More particularly,
the intermediate conductive element 271 and the ring-shaped
conductive element 269 provide a line-of-sight barrier between the
test surface and the shield element 272, thereby minimizing leakage
currents and parasitic capacitances that may result between the
test surface and the lower conductor element 272, while the lower
conductor element 272 protects or shields the DUT from external
EMI. By removing these forms of interference, this configuration
increases the accuracy of probe readings taken by probe station
100. In addition, the intermediate conductive element 271 and the
ring-shaped conductive element 269 are connected via the middle
conductor of the triaxial lead 275 as a guard to provide a barrier
between the test surface and the shield elements and to minimize
leakage currents at the test surface. This wiring configuration can
be seen more clearly in FIGS. 10D and 10E, in which the center
conductor of triaxial cable 275 is connected to center conductor
element 268 via line 286a and the guard of cable 275 is connected
to outer conductor 269 via line 269a.
[0140] As should be apparent, the conductive elements 268 and 269
are fixed relative to each other such that the desired concentric
registration between these elements may be maintained. Proper
spacing of the conductive element 268 and the conductive element
269 is likewise maintained by the solid insulator 270 and portions
thereof which separate elements 268 and 269. Accordingly, the
desired isolation, capacitance and thermal characteristics designed
into the chuck apparatus by selection of materials and dimensions
are maintained throughout the life of the chuck.
[0141] Although the Model CHK 8000-A chuck is identified as a
preferred embodiment, the probe station 100 may use any number of
different chucks, including conventional ambient chucks, thermal
chucks, low noise chucks, and the like.
[0142] In other testing configurations, carrier 250 may be in the
form of a socket stage adapter and socket card instead of chuck 260
as shown in FIGS. 11A and 11B. For example, the probe station 100
may be set up to use a socket stage adapter 320 and socket card 330
to conduct tests on packaged components, (e.g., components packaged
in a dye). As shown in FIGS. 11A and 11B, socket stage adapter 320
has a generally thin base plate 321 having card retainer 322
extending therefrom. In the form illustrated the card retention
mechanisms 322 are generally rectangular in shape and have guide
channels 323 for guiding and retaining the socket card 330 in the
socket stage adapter 320. Associated with the retention mechanisms
322 are fasteners 324 such as thumb screws for securely fixing the
card 330 to the adapter 320 so that it can be probed.
[0143] The socket stage adapter 320 has a hub adapter similar to
hub adapter 279 shown in FIGS. 10A and 10C for chuck 260. The hub
adapter is used to securely connect the adapter 320 to hub 310,
thus making the adapter a carrier connected to system 100. In the
illustrated form, adapter 320 is fastened to the hub 310 via bolts.
The hub 310 is itself connected to the theta drive 311 of system
100, which allows the hub 310 and adapter 320 to be rotated about
vertical hub axis 310a as needed or desired. A variety of theta
drives are available offering different ranges of rotation (e.g.,
0.degree.-360.degree.) and different resolutions. In a preferred
form, the theta drive 311 is capable of rotating 100.degree. with a
resolution of 0.7 .mu.m. In alternate forms, however, a theta drive
capable of 360.degree. rotation and better resolution may be
desired. The theta drive 311 has a generally disk shaped driving
member 311a, a motor 311b, and an optional fine adjustment knob
311c. The driving member 311a engages the hub 310 and is used to
rotate the hub 310, and carrier attached thereto, as desired. The
theta may be automatically adjusted via the motor 311b or manually
adjusted via knob 311c. In a preferred form, both course and fine
adjustments of the theta drive may be made remotely using the
equipment controlling system 100 and additional fine adjustments
may also be made via the optional adjustment know 311c. In
alternate forms, the system 100 may be configured so that all theta
adjustments are made remotely via a controller located outside of
the chamber 190, or configured so that all theta adjustments are
made manually from within the chamber 190.
[0144] The socket card 330 is typically made up of a printed
circuit board (PCB) having an integrated circuit (IC) socket 329
electrically attached to the circuit located on the PCB. The leads
of the packaged component 327 are inserted into the corresponding
sockets of IC socket 329 and a securing bar 329a is adjusted to
lock the packaged part 327 into the socket 329. An edge connector
325 is connected to the end of the socket card having a plurality
of electrical contacts (or terminals) 330a from which an electrical
connecting can be made with the circuit of the PCB. The edge
connector 325 has a plurality of mating contacts or terminals 326
which the system operator can use to connect the packaged component
327 (once inserted into the socket 329) to various types of test
equipment, indicated in FIG. 11A by reference numeral 328. The test
equipment 328 may be located inside or outside of chamber 190;
however, it is preferred that this equipment remain outside of
chamber 190 particularly if the packaged part 327 is going to be
tested at temperature so that such changes in environment will not
effect the operation of the testing equipment and thereby taint the
measurements taken by system 100. As discussed above, the leads
connecting the test equipment 328 to the edge connector 326 may be
fed into the vacuum chamber 190 using any of the access openings
121, 122, 123, 124, 125 and 127, as well as any of the connectors
used therewith.
[0145] Once the socket stage and card have been connected to probe
station 100, the integrated circuit dye package 327 can be tested
and run as if it was installed in its actual end product. For
example, if the component is typically operated in a high
temperature environment, the environment of chamber 190 can be
raised to that temperature and then probed to ensure that it is
operating correctly and/or to determine why it is not operating as
it should. Typically the upper portion of packaging 327 is removed
via a process known as de-lidding in order to expose the conductive
path indicia of the integrated circuit 327 so that additional
testing/probing can be performed. More particularly, the upper
portion of package 327 may be removed by acid so that probes 256
can be positioned about the conductive path indicia located within
package 327 and the device can be probed.
[0146] In order to probe this device, the socket card adapter 320,
hub 310, and theta drive 311, are moved about via X, Y and Z stages
312, 314 and 316 so that probes 256 can test (e.g., acquire and/or
apply test signals) to desired portions of the IC 327. As will be
discussed in further detail below, the probes 256 can be positioned
onto the conductive path indicia by lowering the platen 258 via Z
stage 316 and/or lowering the probes via manipulators 252a, b, c
and d. If the system 100 is equipped with a theta drive 311, the
adapter 320 and card 330 can be rotated via the theta drive 311 in
order to assist the system operator in positioning the part 327
exactly where he or she wants it. Once the desired theta rotation
has been reached, the system operator can lock the theta position
via the theta lock knob 311d. The system 100 (or DUT 118) may also
be tipped or tilted as needed via tilt mechanisms which will also
be discussed further below in order to view the conductive path
indicia better via microscope 104 or 105.
[0147] The probe assemblies 106 of FIGS. 5A, 5D, 5H-5J, and 12A
include manipulators 252a-d which operate to position their
associated probes 256 about various conductive path indicia or test
points located on the surface of the specimen or DUT 118. Each
manipulator 252a-d is mounted on a base 350 which is in turn
attached to the platen 258. Some forms of manipulators utilize
magnetic mounting bases or vacuum/suction mounting bases to attach
the manipulators to the platen 258. For example, the mounting bases
350 may be made out of magnetic material which is capable of
securing the manipulators 252a-d to a platen 258 made out of
magnetically attractive material such as metal. In a preferred
form, the manipulators 252a-d are hard mounted (e.g., bolted) to
the platen 258 in order to provide maximum stability for precision
probing.
[0148] Slidingly coupled to the mounting bases 350 are the
manipulator block body assemblies 352 which include the control or
adjustment mechanisms that are used to position the probes 256. The
manipulators 252a-d utilize screw drive adjustment mechanisms
having threaded shafts driven by motors capable of precisely
positioning probes 256, such as by a stepping motor, servomotor or
the like. The position adjustments for manipulators 252a-d may be
made automatically via a controller, such as a computer, which
operates X, Y and Z position adjusting mechanisms 354, 356 and 358
in order to adjust the probes 256 in the X, Y and Z directions,
respectively. More particularly, the motors of position adjusting
mechanisms 354, 356 and 358 may be operated to rotate their
associated screws thereby causing blocks 354a, 356a and 358a to
slide back and forth in the X, Y and Z direction respectively. The
block portions 354a, 356a and 358a of the block body assembly 352
have slide bearing surfaces and guides which allow for relative
sliding movement of the block portions upon actuation of the
mechanisms 354, 356 and 358.
[0149] In FIG. 12A, actuation of the X-adjusting mechanism 354
causes the corresponding screw drive to be driven or rotated
thereby moving block 354a, along with the remaining portions of the
manipulator assembly that rest on block 354a (e.g., Y-adjusting
mechanism 356, Z-adjusting mechanism 358, manipulator arm support
plate 362, extension 363, arm assembly 364, and probe 256). This
movement translates into moving the face 360 of the manipulators
252a-d forward or backward in the direction identified by arrow
354b. A portion of the cavity within which the screw of the X
adjustment screw drive mechanism is rotated can be seen in block
354a of FIG. 12A. The Y-adjusting mechanism 356 causes its
corresponding screw drive to be rotated thereby moving block 356a,
along with everything resting thereon (e.g., the Z-adjusting
mechanism 358, manipulator arm support plate 362, extension 363,
arm assembly 364, and probe 256). This movement translates into
moving the face 360 left and right as identified by arrow 356b. The
Z-adjusting mechanism 358 causes its corresponding screw drive to
be rotated thereby moving block 358a, along with everything
connected thereto (e.g., manipulator arm support plate 362,
extension 363, arm assembly 364, and probe 256). This movement
translates into moving the face 360 up and down in the direction
identified by arrow 358b.
[0150] In FIGS. 12A-12C, the support plate 362 is attached to the
face 360 for mounting the arm assembly 364 to the manipulator. The
arm assembly has members 366 and 368 that project out forwardly
from the manipulator assembly and connect to the probe 256. In a
preferred form, the probe 256 is connected to lower member 368 via
a probe retaining mechanism such as spring clip 369, and the arm
assembly 364 includes an adjustment mechanism 370 positioned at the
joint connecting upper and lower members 366 and 368, respectively.
The adjustment mechanism 370 is used to pivotally adjust the lower
member 368 about vertical axis 370a with respect to the upper
member 366, which is fixed to support plate 362. In the form
illustrated in FIG. 12A, arm extension 363 is used to increase the
lower reach of the arm assembly 364. More particularly, the arm
extension (or collar) 363 is used to separate arm members 366 and
368 by a desired vertical distance. In the illustrated embodiment,
extension 363 does not alter the ability to pivotally adjust lower
member 368 with respect to upper member 366 and is attached to the
upper and lower members via a screw and/or bolt relationship.
[0151] Once the manipulators have positioned the probes 256 in the
desired locations, the probes 256 will be placed into contact with
the DUT 118 and testing/probing will begin. The actual placement of
the probes on the DUT 118 may involve the use of a variety of
motion control mechanisms and sensors, and will be discussed
further below with respect to the operation of probe station
100.
[0152] The manipulators 252a-d, shown in FIGS. 5A, 5D, 5H-5J, and
12A, are Micromanipulator Model 900VM manipulators. At 0.01
microns, the 900VM manipulators offer very high manipulator
resolution and features such as an indexed rotational nose piece,
probe arm with fast tip changing capacity, and stable mounting with
preset stable mountings. As mentioned above, however, a variety of
different probes and manipulators may be used with system 100. For
example, another form of manipulator is illustrated in FIG. 13A and
is identified generally by reference numeral 371. This manipulator
offers a low profile which may be desirable in a variety of
applications, including light microscope probing as well as high
resolution microscope probing. The low profile manipulator 371 has
X, Y and Z position adjusting mechanisms 372, 373 and 374, which
operate similar to those discussed above with respect to FIG. 12A.
Unlike the manipulator from FIG. 12A, however, manipulator 371 has
an extended block portion within which at least a portion of the
Z-adjustment mechanism 374 is recessed. This allows for a lower
clearance or profile and allows for the arm assembly 364 and probe
256 to be extended out further from the base of the
manipulator.
[0153] The arm assembly 364 of manipulator 371 is similar to that
described earlier in that in contains two members 366 and 368 that
project out from the manipulator. The probe 256 is also connected
to the lower member 368 in a similar fashion (e.g., probe retention
mechanism 369). Just as in FIG. 12A, the arm assembly 364 also
contains an adjustment mechanism 370 positioned at the joint
connecting upper and lower members 366 and 368. The adjustment
mechanism 370 is used to pivotally adjust the lower member 366
about vertical axis 370a with respect to the upper member 366 which
is fixed to the manipulator.
[0154] In addition to using a variety of manipulators, the system
100 may also use a variety of probes 256. For example, the
manipulators 252a-d may use one of the triaxial probes depicted in
FIG. 14, or may use any one of a variety of different probes, such
as the coaxial probes illustrated in FIGS. 5A, 5D, 5H-5J, 12A-12C,
and 13A-13C, RF/Microwave probes, etc. As mentioned above, the
probe assemblies 106 also include probes 256, which are used to
acquire and apply test signals to the DUT 118 during testing. The
probes 256 are mounted to the lower members 368 of the manipulator
arms 364 and are positioned according to the procedures discussed
above with respect to the manipulators 252a-d. For optimal probing,
triaxial probes which contain a center conductor surrounded by a
guard conductor and a shield (or ground) conductor can be employed.
The triaxial configuration of probe station 100, including its
components such as the carriers 250 and probes 256, minimizes noise
and allows for more accurate testing of the DUT 118 by shielding
the DUT 118 from external EMI and reducing the effects of parasitic
capacitance and other interferences via a blanketing guard layer.
The triaxial probes of FIG. 14 are schematically shown connected to
a triaxial lead or cable 275. The triaxial cable 275 of FIG. 14 has
a shield (or outer) line 382, a guard (or intermediate) line 384,
and a signal (or inner) line 386 which are electrically isolated
from one another via insulative material. The insulative layers or
sheathing of lead 380 have been removed in order to more clearly
show the three conductive lines 382, 384 and 386 in this schematic
view. The lead 275 is connected to probe 256 via a threaded stub
connector 388, which is generally cylindrical in shape and includes
three conductive portions, including outer portion 390,
intermediate portion 392, and inner portion 394, which are also
electrically isolated from one another via an insulative material.
With the triaxial lead 375 connected to connector 388, the
conductive portions 390, 392 and 294 are electrically connected to
shield, guard, and signal lines 382, 384 and 386.
[0155] The connector 388 is connected itself to the main body 396
of probe 256 at base 398. The main body 396 of the probe includes
an outer conductor 400, intermediate conductor 402 and inner
conductor 404, which correspond, and are electrically connected to,
the conductive portions 390, 392 and 394, respectively. Thus, when
the triaxial lead 375 is connected to connector 388, the outer
conductor 400 is connected to the shield line 382, the intermediate
conductor 402 is connected to the guard line 384, and the inner
conductor 404 is connected to the signal line 386.
[0156] As can be seen in FIG. 14, the first (or outer) insulator
406 electrically isolate the outer conductor 400 from the
intermediate conductor 402, and a second (or inner) insulator 408
electrically isolates the intermediate conductor 402 from the inner
conductor 404. The outer conductors 400 and first insulators 406
generally are rectangular in cross-sectional configuration and
taper in toward the exposed end of intermediate conductor 402,
(e.g., taper in towards the probe tip which is located on the side
opposite the manipulator arm 364). The intermediate conductor 402
and second insulator 408 are generally annular in cross-sectional
configuration and protrude out from the distal terminal ends of the
first insulator 406 and outer conductor 400.
[0157] The intermediate conductor 402 and second insulator 408
further include concentric apertures 410 which define a passageway
within which probe tip 412 may be substantially rigidly inserted.
The probe tip 412 is a needle-like conductor which, when inserted
into the aperture 410, makes electrical contact with inner
conductor 404 thereby electrically connecting the tip 412 to signal
line 386. In order to electrically isolate the probe tip 412 from
the intermediate conductor 402, the concentric aperture of the
intermediate conductor 402 is made larger in diameter than the
aperture in the second insulator 408, which results in separating
the probe tip conductor 412 from the intermediate conductor 402. In
a preferred form, inner insulator 408 has a threaded bore located
in its end. The bore intersects with the passageway defined by
aperture 410 of insulator 408 so that a set screw can be threaded
into the bore and tightened against the probe tip 412. This
configuration allows the probe tip 412 to be fastened to the probe,
but also offers the ability to release and replace the probe tip
412, when desired, without having to replace the entire probe 256.
In alternate systems, the probe tip 412 may be press fit or
friction fit into the passageway defined by aperture 410, and may
be equipped with a preloaded spring feature to assist in the
removal of the tip 412 when desired.
[0158] The apertures 410 may be angled in a variety of ways in
order to give the probe tip 412 the desired angle with respect to
the DUT 118, (or angle of attack). This configuration allows the
probe tip 412 to be angled so that it can be placed one right next
to the other without interfering with other probes and structures.
This configuration also allows for various hard to reach portions
of the specimen 118 to be probed. For example, the probe tips may
be angled at varying angles so that more probes can be positioned
near one another on the DUT.
[0159] In alternate forms of system 100, the probes 256 may be
wired or configured coaxially as shown in FIGS. 5I-5J, 12B-12C, and
13B-13C. In these illustrations, the outer conductor housing 400 of
probe 256 has a first end 420 designed to couple the probe 256 to
the manipulator arm 364, and a second end 422 from which the probe
tip 412 and needle extends. The first end 420 contains a dove-tail
flange portion 424 which engages a mating recess 426 in lower
member 368 of the manipulator arm 364. In order to provide for
quick and easy replacement of the probe 256, the manipulator arm
364 includes a release mechanism, such as a spring loaded latch in
the form of spring clip 369, which engages the dove-tail flange
portion 424 of the first end 420 when released, and disengages when
depressed or squeezed (e.g., causing the spring to be compressed).
More particularly, when probe 256 is to be inserted onto
manipulator arm 364, the user depresses the release mechanism 369
to provide clearance for sliding the dove-tail flange portion 424
down into the mating recess 426 until it is received fully within
the mating recess 426. Releasing the spring latch 428 allows it to
pivotably return to the spring loaded securing position with its
forward end pushing the rear flange portion 424 of the probe
tightly against the surfaces of the recess 426 so that the probe
housing 400 is tightly and securely frictionally held in the mating
recess 426.
[0160] A stop may be provided so that the user can more easily
determine when the probe 256 is fully inserted into the recess 428.
For example a lip may be provided on the bottom of recess 426 which
will prevent the dove-tailed flange portion 424 from sliding
completely through the mating recess 428 from top to bottom. In
another form, a detent mechanism such as a spring loaded ball and
socket may be used to assist the user in determining when the probe
256 has been fully attached to the arm 364. In the form shown, a
lug 425 is provided on the surface of the recess 426 which is
guided into rear channel 427 on the probe and prevents the probe
from being inserted further once the lug 425 engages lip 429.
[0161] In FIGS. 5I-5J, 12B-12C, and 13B-13C, threaded stub
connector 421 is provided for connecting the probe 256 to coaxial
lead 423, thus electrically coupling the outer conductor 400 to the
shield line of the lead 423 and the inner conductor 404 to the
signal line of lead 423. A schematic view of this coaxial
connection is illustrated in FIG. 13C. As shown in FIGS. 12C and
13C, the inner conductor 404 of probe 256 is connected to the
signal line of connector 423 and to the probe tip 412, and will
acquire and/or apply test signals from/to the DUT 118 via probe tip
412. In the embodiments illustrated, a probe holder 405 is inserted
into the probe and provides the electrical connection by which the
signal line of connector 423 and probe tip 412 are connected. A
clamp or set screw 407 is provided for securing the probe tip 412
into the probe holder 405.
[0162] Another form of probe, as shown in FIG. 16, may be used with
system 100 which can reduce the amount of surface charge and/or
delay its build-up by shielding the exposed insulative surfaces of
the probe. This probe 590 can be configured for either coaxial or
triaxial system configurations (or wiring schemes) and is similar
to the probe discussed above and illustrated in FIGS. 5I-5J,
12B-12C, 13B-13C, and 14, with the exception of having an extended
portion of conductor 600 (or cladding). More particularly, probe
tip 612 is inserted into the passageway defined by apertures 610 of
probe 600 in order to make an electrical connection between the
probe tip 612 and the inner conductor 594. As mentioned above, the
passageway defined by concentric apertures 610 passes through outer
and intermediate conductors 600 and 602 and the first and second
insulators 606 and 608, and determines the angle (or angle of
attack) with which the probe tip extends from the probe 590. The
probe tip 612 is electrically isolated from the conductors 600 and
602 and is preferably angled at a thirty degree angle of attack to
the left or right, or a ninety degree angle of attack in which the
probe tip extends straight down or vertically from the probe
590.
[0163] With the configuration shown in FIG. 16, the probe tip 612
can be easily replaced by simply withdrawing the tip 612 from the
passageway defined by aperture 610 and inserting a new probe tip in
its place. As mentioned above, such a configuration allows for
disposable probe tips 612 to be used and can save the probe station
user from having to buy entire probes when tips go bad, as by
excessive wear or breakage.
[0164] Another advantage to this configuration is that the triaxial
configuration of the probe, (e.g., inner conductor surrounded by
intermediate conductor, surrounded by outer conductor), is allowed
to remain present very near the DUT contact end 612a of the tip 612
of probe 590. This not only assists with minimizing the effects of
noise on probe readings for the reasons discussed above with
respect to the chuck 260 and housing 102, but also serves to
prevent the unwanted charging of insulators 606 and 608 by the beam
206 emitted from the high resolution microscope 104. For example,
the probe from FIG. 16, when compared to the probes of FIGS. 5, 14,
and 15, has an extended portion of the outer conductor (or
cladding) 600 which covers or shields the intermediate conductor
602 and inner conductor 604 closer to the probe tip end 612a. This
extension (or extended cladding) allows more of the
center/innermost conductor to be guarded and/or shielded, depending
on the wiring scheme used, (e.g., coaxial, triaxial, etc.).
[0165] More particularly, the emitted beam 106 of the high
resolution microscope 104 has the tendency to induce a charge on
all of the surfaces the electrons scatter over. When insulators or
dielectrics such as insulators 606 and 608 are exposed to the beam
106, they too may develop a charge which can distort the readings
taken from the DUT. The extended cladding of outer conductor 600
serves to reduce charge buildup on the insulators 604 and 606, and
thereby improves the system's measurement capabilities. For
example, if charge is allowed to buildup on the insulators 606 and
608, the readings taken from the signal line 386 or signals applied
to lines 386 could be affected by the added charge from the
insulators thereby distorting the test results taken during
probing. As such, the additional cladding can be used to block or
shield the insulators 604 and 606 and/or drain the built up charge
away from the signal line 386 via grounded outer conductor 600.
Thus the measurement capabilities are improved, and noise and other
interferences are reduced, by allowing a triaxial connection scheme
to remain present very near the tip of the probe.
[0166] In view of the probe tip replacement capabilities discussed
above, and in order to reduce the time necessary for replacement
and to increase the accuracy of the probes 256 and 590 once a new
tip 412 or 612 has been inserted, a probe presetting station may
also be used. In such cases, the probe 256 or 590 may be placed on
a fixed link similar to the manipulator arm 364, so that the
replacement probe tip 412 or 612 can be adjusted to ensure that it
is in the same relative position as the previous probe tip and to
ensure that it is the same relative length of the previous probe
tip, (a process referred to as probe tip refresh). Once the probe
tip refresh is complete, the probe 256 or 590 may be re-inserted
onto the manipulator 252a-d so that testing can commence. Since the
probe tip 412 or 612 is now very near the same position with
respect to the probe 256 or 590 as the previous probe tip, the
probe station user will spend significantly less time getting the
probe station 100 ready to test/probe.
[0167] Like the chuck 260 and housing 102, the probes 256 and/or
590 can be set up and wired in a variety of ways, preferably with
either a triaxial configuration or a coaxial configuration. In the
typical triaxial configuration, shown in FIGS. 14 and 16, a
triaxial lead (or cable) 275 is connected to the probe lead
connector 388 so that the outer, intermediate and inner lines 382,
384 and 386 are electrically connected to the outer, intermediate
and inner conductors 400, 402 and 404 of the probe 256. In the
typical triaxial configuration, the outermost conductor and line,
400 and 382, are coupled to ground (or grounded), the intermediate
conductor and line 402 and 384 are coupled to a guard signal, and
the innermost conductor and line 404 and 386 are coupled to the
center line signal. FIG. 14 further shows how this triaxial
configuration compliments the triaxial configuration of the entire
probe station 100 and assists in conducting low current/low voltage
probing with minimal amounts of noise by showing how the DUT 118 is
surrounded (e.g., above, below, and around) by a triaxial
arrangement. For example, below the DUT 118 is chuck 260 having
first conductive element 261 coupled to the signal line, second
conductive element 262 connected to the guard line, and third
conductive element 264 connected to ground. Above the DUT 118, are
probes 256, which have outer conductors 400 connected to ground,
intermediate conductors 402 connected to the guard line, and inner
conductors 404 connected to the signal line. Around the entire
probe assembly 106 is second chamber 182 and lower portion 226 of
microscope 104 (or alternatively shutter 218) which may be coupled
to the guard signal, and are themselves surrounded by first chamber
108 and upper and intermediate portions 222 and 224 of probe 104
which may be connected to ground.
[0168] In the coaxial configuration shown in FIGS. 5J, 12B-12C,
13B-13C, 18, and 19, a coaxial lead (or cable) 423 is connected to
the probe lead connector 421 so that the outer conductor 423a of
the lead 423 is connected to the outermost portion (or housing) 400
of probe 256 and the innermost conductor 423b of the lead 423 is
connected to the innermost line 404 of probe 256. More
particularly, the outermost conductor and line 400 and 423a are
coupled to ground (or are grounded), and the innermost conductor
and line 404 and 423b are coupled to the center line signal. In
alternate coaxial wiring schemes, where a triaxial probe is used,
both the outer conductor and the intermediate conductors 400 and
402 may be connected to ground. In yet other schemes, as shown in
FIG. 5I, a triaxial cable may be connected to internal coaxial
cables which are connected to various components within chamber
190. In such configurations the internal coaxial cables may be
connected such that the outer conductor is connected to the guard
conductor of the triaxial cable (as shown in FIG. 5I), or the outer
conductor may be connected to the outer conductor of the triaxial
cable.
[0169] FIG. 19 shows how coaxial configuration of probes 256 would
compliment a coaxially configured probe station 100 and how such
would assist in conducting low current/low voltage probing with
minimal amounts of noise by surrounding the DUT 118, (e.g., above,
below, and around), by a coaxial arrangement. For example, below
the DUT 118 is chuck 260 which, in a coaxial configuration, has
first conductive element 261 coupled to the signal line, and second
and third conductive elements 262 and 264 connected to ground.
Above the DUT 118, are probes 256, which could be configured
coaxially by having outer and intermediate conductors 400 and 402
connected to ground, and inner conductor 404 connected to the
signal line. Around the entire probe assembly 106 is first and
second chambers 108 and 182, and upper, intermediate and lower
portions 222, 224 and 226 of microscope 104 which may be coupled to
ground.
[0170] As mentioned previously, any number of wiring schemes could
be used for each of the components of probe station 100. For
example, the innermost conductor and line 404 and 386 could be
coupled to the signal line and the outermost conductor and line 400
and 382 could be coupled to the guard line. In a preferred form of
probe station 100, the system and all of its components are set up
in a triaxial configuration due to the added protection such
configurations offer with respect to shielding and preventing
interference such as noise and parasitic capacitance. In addition,
those conductors used for shielding, e.g., outer probe station
housing 108, third chuck conductor 264 and outer probe housing
portion 400, and those used for guarding, e.g., inner housing 182,
second chuck conductor 262, and intermediate probe conductor 402,
can be electrically connected together to provide an integrated
approach to the shielding/guarding configurations of the probe
station 100.
[0171] In other forms of probe station 100, other types of probes
may be used. For example, the probe station 100 may use a triaxial
probe similar to the one disclosed in U.S. patent application Ser.
No. 09/815,952, filed on Mar. 23, 2001, which is hereby
incorporated herein by reference in its entirety. FIG. 17 shows a
side view of one embodiment of such a probe, which is identified
generally at reference numeral 430. In the embodiment shown, the
probe 430 of the invention has a main horizontal section 432 that
extends along longitudinal axis 432a and a rear section 434 that
extends upward at an angle B to the axis 432a. By way of example
and not limitation, the angle B can be approximately 65.degree..
The angled section extends to an integral connector assembly 436
which provides an electrical connection to the female connector of
a triaxial lead (or cable) for electrically connecting the probe
430 to test instrumentation. Connector assembly 436 includes a
conductive outer body 438, which is made of a conductive metal such
as gold plated brass. The conductive outer body 438 includes
threads 440 on its outer surface at an end thereof adjacent
enlarged portion 442 for mating with the connector of the triaxial
cable. Shank 448 extends from the connector assembly 436 in a
direction approximately parallel to longitudinal axis 432a for
being attached to a connector of a manipulator to thereby permit
precise adjustment of the probe tip end 446 relative to conductive
path indicia on the DUT 118. The shank 444 includes shank portion
448 extending from base portion 450, and is welded to the outer
body 438 of connector assembly 436 at a beveled end of the base
portion 450. By way of example, and not limitation, the horizontal
section 432 of probe holder 430 can extend approximately 2.375
inches in length from the terminal end of insulator member 452 to
bend 454, and the rear section 434 of the probe holder 430 can
extend about 1.25 inches from the bend 454 to shoulder 442.
[0172] The probe tip 456 has a bent configuration so that the
projecting portion 458 may have a predetermined angle of attack
toward a specimen or DUT 118. The probe 430 has a main horizontal
section 432 that extends along longitudinal axis 432a of the probe
430 for positioning of the projecting portion 458 adjacent the DUT
118 remote from the manipulator the probe 430 is attached to. The
projecting portion 458 can define an attack angle A of
approximately 45.degree. with the axis 432a. The user may wish to
change the attack angle to accommodate the physical space
limitations of the probe station and spacial orientation of
integrated circuits present in a given test application. The
detachable connection with which probe tip 456 is connected to
probe 430 permits probe tips of different attack angles to be
quickly and conveniently interchanged by the user when a different
attack angle is desired. Probe tips having attack angles from
45.degree. to 70.degree. have been found to be suitable for many
test applications, although attack angles can be tailored to angles
outside this range as may be necessary in certain test setups.
[0173] The probe station 100 may also be equipped with a probe
touchdown sensing mechanism 460 so that the probes 256 do not
damage the DUT and/or conductive path indicia during testing. This
is particularly true when it comes to testing/probing expensive
DUTs such as 300 mm wafers. In order to prevent such damage from
occurring, the probe station 100 may use touchdown sensing
mechanisms that are capable of sensing when the probes 256 have
made sufficient contact with the conductive path indicia to conduct
the necessary testing or probing. This type of touchdown sensing
can be achieved by mechanical means or by electronic means. One
type of mechanical touchdown sensing mechanism that may be used is
disclosed in U.S. Pat. No. 4,956,923, issued to Pettingell on Sep.
18, 1990, which is hereby incorporated herein by reference in its
entirety. According to this touchdown sensing mechanism, when the
probe tip is lowered into engagement with the target circuitry 118,
a contact block is moved out of engagement with a lower terminal or
screw causing the normally closed set of contacts to open, and
eventually moving the contact block into engagement with another
contact causing the normally open set of contacts to be closed.
This touchdown sensing mechanism also serves as a force control
which allows the force with which the probe point touches the DUT
118 to be adjusted to either require less force for sensing or
require more force for sensing depending on what type of
sensitivity is desired for a particular application.
[0174] In another form, the touchdown sensing mechanism 460 of
probe station 100 may use an electrical signal sensing mechanism.
In a preferred form, this is accomplished by connecting the
touchdown sensing mechanism between the probes 256a-d and the
test/measurement equipment 464. The sensing mechanism 460 applies a
carrier signal to the specimen 118, and begins moving the probes
256 into contact with the specimen 118 until they make electrical
contact with the specimen 118 and begin sensing or detecting the
carrier signal applied to the specimen 118. To move the probes
256a-d and DUT 118 into contact, the system 100 may raise the
carrier 250, or lower the probes 256 via the platen 258 and/or the
z-stage 316. Once the touchdown sensing mechanism 460 senses the
carrier signal through one of the probes, it stops sensing for the
carrier signal with that probe because sufficient contact (or
touchdown) has been made between that probe and the conductive path
indicia (or target) of the DUT 118. In a preferred embodiment, as
shown in FIG. 20, the contact sense module 460 is connected to the
inputs 462 of probes 256a-d and associated manipulators 252a-d,
test/measurement equipment 464, and the DUT 118 (and/or chuck 260).
The probes 256a-d are themselves electrically connected to various
conductive path indicia on the DUT 118. The sense module 460
supplies a low frequency carrier signal 464 with a very low
amplitude (e.g., a 5 kHz sine wave at 15 mV) to the DUT 118 via a
probe. At this point, the sense module 460 begins monitoring the
remaining probe inputs looking for a rapid change in potential.
When the module 460 senses the sine wave through a measurement
probe, indicating sufficient contact or touchdown has been made,
the module 460 energizes a light emitting diode (LED) associated
with that probe, emits an audible alarm indicating the signal has
been detected, and switches the output of the probe that has
detected the signal from sensing to output. Once all of the probes
have made sufficient contact with the DUT 118, the module 460 stops
outputting the carrier signal.
[0175] In a preferred form of contact sense module 460, the system
operator will "reset" the module 460 causing it to reconnect/output
the carrier signal to the probes 256a-d in order to confirm that
touchdown has been made. If the carrier signal is sensed on all of
the probes again, the oscillator output signal will be disconnected
and probing may begin. If the module 460 does not sense contact on
any, or all, of the probes 256a-d, an inspection of the probes
256a-d should be conducted to determine if the probes 256a-d are no
longer capable of maintaining good contact with the DUT 118, (in
which case tip replacement should be performed), and/or to
determine what, if any, other problems may exist. Once sufficient
contact or touchdown has been detected, the contact sensing module
460 relinquishes control/monitoring of the probe inputs to the
test/measurement equipment 464 so the system operator can begin
probing the DUT 118.
[0176] The contact sensing module 460 may also include an optional
sensitivity control which allows the system operator to adjust the
module 460 from less sensitive settings to more sensitive settings
when desired. When adjusted to a less sensitive setting, the module
460 will take longer to detect probe touchdown. When adjusted to a
more sensitive setting, the module 460 will react quicker to probe
touchdown to ensure that only the lightest contact is made between
the probe and the DUT 118. Thus, a less sensitive setting is
appropriate when testing a more durable specimen, whereas a more
sensitive setting should be used when testing a fragile specimen.
When the module 460 is set for maximum sensitivity, however, it is
more susceptible to noise and may erroneously signal touchdown
prior to good contact being made with the DUT 118.
[0177] The contact sensing module 460 may be configured such that
it is a stand-alone device, or may be integrated into the control
systems of system 100. In addition, the contact sensing module 460
may be set up so that touchdown is achieved via a fully automated
process, a fully manual process, or a combination of the two.
[0178] The form of electrical touchdown sensing described above is
a combination of automated processes and manual processes in that
it allows the module 460 to automatically detect the initial
touchdown of the probes 256a-d, and thus relies on the system
operator to manually initiate a reset procedure in which the module
confirms proper touchdown. In alternate forms of sensing, the
manual confirmation step may be done automatically. In yet other
forms, the system operator may lower the probes 256a-d manually
until touchdown is detected by receipt of the carrier signal.
[0179] Depending on the type of testing needed to be done, the
probe station 100 may be set up using a very basic probe consisting
of a single conductor with which test signals can be applied or
acquired, while in other applications, the probe may consist of a
more complex probe, such as the low current/low voltage triaxial
probes discussed above, or high frequency probes capable of
applying and acquiring high frequency test signals. In other
instances the probe station 100 may be set up using probe cards and
their respective probe card holders or adapters. For example, the
probe station 100 may be set up to use a fixed probe card and a
fixed probe card adapter to conduct a final wafer test on an
integrated circuit prior to the circuit being packaged. Typically,
the fixed probe card includes a card made of ceramic or fiberglass,
which defines an opening (usually in the center of the card), and
has a plurality of probes positioned around, and extending into,
the opening so that the probes will make contact with bonding pads
located about the perimeter of each integrated circuit die located
on the wafer. The fixed probe card is placed in an adapter or
holder which positions the probe card over the DUT. Typically the
probe card adapter features easy load and unload controls,
planarization adjustment controls, and theta adjustment controls,
for making setup and use as easy as possible. Once positioned, the
plurality of probes extending from the probe card are used to
acquire and apply various test signals to the bonding pads located
on the wafer or DUT so that the device can be checked prior to
being broken out and packaged. Typically, the testing of the DUT
will involve a full diagnostic check to make sure the circuit will
operate as it is suppose to once it is packaged.
[0180] An example of a fixed probe card and a fixed probe card
adapter assembly is illustrated in FIGS. 15A-15F and is identified
generally by reference numeral 470. The assembly 470 includes a
probe card adapter 471 which has a generally circular shaped
framework consisting of an outer ring portion 471a and an inner
card holding portion 471b. The assembly 470 also includes probe
card 472, which is retained by card holding portion 471b and has a
plurality of probes 256 extending downward from a centrally located
opening in the card 472. The card holding portion 471b has two
rectangularly shaped supports 473 which form channels or side
guides 474 extending the length thereof and within which at least
an outer side edge portion of card 472 is held. In the form
illustrated, the supports 473 are connected to the lower surface of
ring portion 471a via fasteners such that they depend from the ring
471a toward the carrier 250, and the guides 474 are formed from a
lower T-shaped portion of the supports 473. With this
configuration, each support 473 contains two channels or guides 474
and can therefore by used universally on either side of the probe
card 472 and/or either side of the ring portion 471a.
[0181] Once the card 472 has been inserted into the guides 474, a
plurality of card retainers such as thumb screws 475 may be used to
secure the card fixed into the adapter 471. The adapter 471 is
itself secured to the platen 258 via additional securing mechanisms
or fasteners such as screws 476, and includes planarity adjustment
or screw mechanisms 477 which may be used to tilt, tip or level the
adapter 471 with respect to the DUT 118 and/or surface of chuck
260. In a preferred form, the planarity adjustment mechanisms 477
are used to make course adjustments to planarity.
[0182] The adapter 471 may also be configured such that rotation or
adjustment of the card 472 can be made while the card is secured by
the adapter, as shown in FIGS. 15A-15F. In a preferred form, this
rotation is achieved by the ring portion 471a by having a stable or
static outer rim from which the adapter is connected to the platen
258, and having a movable inner rim from which the card holding
portion 471b is connected. The rotation of the card 471 and inner
rim is controlled by theta adjustment mechanism 478, which causes
the inner rim of adapter 471 to rotate within its outer rim by
turning the knob 478a of theta adjustment mechanism 478. The knob
478a operates a geared transmission which translates the knob
rotations into movement of the inner rim of adapter 471.
[0183] When installed on system 100, the assembly 470 may be
connected to various test equipment in a similar fashion to that of
the socket stage adapter and socket card discussed above. More
particularly, leads from the various test equipment, and/or an edge
connector, can be connected to the plurality of terminals or
contacts 472a located on the edge of the card 472. Each contact
472a is connected to at least one of the plurality of probes 256
and can allow the system operator to apply the desired signals,
(e.g., current, voltage or data) and/or receive resultant
information to/from the DUT 118. In this way, a variety of
different testing or probing can be accomplished with system
100.
[0184] The components of the system 100 may be moved about and
operated in a variety of fashions. In a preferred form, the system
100 includes motion control mechanisms 540 (FIGS. 5H, 24A-24C,
25A-25B, 26A-26B, and 27) which may include X, Y and Z drives, as
well as tilt/tip mechanisms 542. The control mechanisms 540 and 542
shown in FIGS. 5H, 24A-24C, 25A-25B, 26A-26B, and 27, allow the DUT
118 to be moved about below the platen 258 so that the probes 256
can reach, and the microscope 204 can view, the various conductive
path indicia of the DUT. Similar to the motor control mechanisms
discussed above with respect to probe assemblies 106, mechanisms
540 include motor driven screw drives which are used to move the
platform 544 and/or the carrier 250 about below the microscopes 104
and/or 105 thereby simulating microscope movement 104 over the DUT
118.
[0185] The platform 544 is generally rectangular in shape and is
operably connected to the carrier 250 via the Theta, X and Y drive
stages 311, 312 and 314, and to the platen 258 via Z drive members
316 which extend upward from the platform 544 to the platen 258.
More particularly, the platform 544 is designed as a base or stage
to which the X, Y and Z drives 312, 314 and 316, the theta drive
311, the carrier 250, platen 258 and probe assemblies 106 are
supported or connected.
[0186] As shown in FIGS. 25A and 25B, the platform 544 can be
driven in the X and Y direction via motor and screw drive
assemblies 702 and 704, respectively. Operation of the X axis stage
drive 702 moves the bed 700 of the platform in the X-direction
indicated by arrows 702a. Operation of the Y axis stage drive 704
moves the bed 700 in the Y-direction indicated by arrows 704a. This
movement is achieved by using the motor to rotate a lead screw to a
nut attached to the bed 700 and threaded onto the screw. Rotation
of the motor in one direction causes the lead screw to move the
nut, along with the bed 700 attached thereto, towards the motor.
Rotation of the motor in the other direction will cause the lead
screw to move the nut and bed 700 in a direction away from the
motor. This configuration allows for movement of the carrier 250,
manipulators 252a-d, and probes 256 by simply moving the platform
544, and allows the microscope 104 to remain primarily stationary
which, as discussed above, is advantageous due to the expense,
size, and difficulty in moving the microscope 104.
[0187] In FIG. 25B, which is a cross sectional view taken along
line A-A in FIG. 25A, the Y axis stage drive 704 is shown having
motor 706 connected to lead screw 708 via coupling 710. Nut 712,
which is connected to bed 700 via mounting bracket 712a is threaded
onto the screw 708. The bed 700 has a lower guide member 700a upon
which an upper slide member 700b is shifted. The mounting bracket
712a connects the nut 712 to upper member 700b so that linear
movement of the nut 712 along the rotating screw 708 will shift the
upper member 700b along the screw axis 708a extending in the
Y-direction. As motor 706 rotates its output shaft 706a, lead screw
708 is rotated causing the nut to travel along the screw 708 either
closer to, or farther from, motor 706.
[0188] In the present high resolution probing station 100, the
vacuum chamber 190 is desired for the preferred scanning electron
microscope 104 to minimize interference with the electron beam it
generates for obtaining high resolution images of the DUT 118. With
the low vacuum pressures, however, thermal expansion of the
materials of the components employed in the chamber 190 is
exacerbated due to the substantial absence of a heat conducting
medium, e.g. atmospheric air, for dissipating any heat that may be
generated therein. In particular, the aforedescribed drives for the
platform stages situated in the vacuum chamber generate heat upon
operation of their motors. This heat is conducted to the connected
screw drives, which can create imprecision in the movements to be
controlled thereby. Further, heat generated by motor operation can
radiate to metallic components in the chamber increasing their
temperature. Because of the often very small movements that are
usually desired in the chamber, any derivation such as due to
thermal expansion of the screws, nuts or brackets is to be avoided.
Thus, the preferred high resolution probing station 100 has stage
drive systems that are well-suited for use in the present vacuum
chamber 190 to provide high precision movements of these stages
therein.
[0189] Preferably the motion control mechanisms and drives of
system 100 are constructed of materials having low coefficients of
thermal expansion such as ceramic in order to insulate the
mechanisms/drives from the heat generated by operation of the
motors in the vacuum chamber 190 and particularly to minimize the
amount of material growth that is experienced by the positioning
equipment due to this heat. In the Y axis stage 704 shown in FIG.
25B, a ceramic coupling 710 is used to keep the heat generated by
motor 706 from conducting or transferring to the lead screw 708.
This insulates the lead screw 708 from heat conducted thereto by
the motor 706 which could cause the screw to expand resulting in
unwanted movement of the stage and components attached thereto,
(e.g., the platform 544).
[0190] In the form illustrated, the lead screw 708 is also
constructed of heat insulating material such as jewels like single
crystal sapphires or rubies, or ceramics having very low
coefficients of thermal expansion. This composition further keeps
the heat of the motor from causing thermal expansion in the lead
screw 708 and growth thereof and attendant unwanted platform
movement due to such thermal expansion. Additional components of
the drive mechanism, such as motor mounts, bearings and bearing
mounts, nuts, brackets, and the like, can be constructed of similar
heat insulating materials in order to further insulate the stage
and drive mechanism from heat and unwanted movement.
[0191] The drive mechanism of FIG. 25B also has a radiation shield
716 positioned between the heat generating motor and the lead screw
708 and other driven components for deflecting the radiated heat or
energy created by the operating motor back toward the housing
walls, which are better able to handle a buildup of heat due to
their exposure to the outer atmosphere. More particularly, the
radiation shield 716 is made from stainless steel and forms a
ringed collar about the motor which is angled for optimal
deflection of the unwanted heat or energy.
[0192] As shown in FIGS. 25A and 25B, the upper slide member 700b
of bed 700 has standoff columns 714 extending therefrom which are
connected to the lower surface of platform 544 and are used to
create clearance between the lower surface of the platform 544 and
the outer housing of motor 706. Thus, with such a configuration,
the platform drive assemblies can be positioned directly below the
platform 544 for space conservation in the chamber 190. Once
connected, the platform 544 and X and Y stage drive assemblies 702
and 704 allow the system operator to move the carrier 250,
manipulators 252a-d, and probes 256 by simply moving the platform
544 so that the desired specimen can be quickly positioned below
the microscope 104 or 105.
[0193] The lower guide member 700a of bed 700 is further connected
to the tip/tilt control mechanism 542, as best shown in FIGS.
24A-24C. This tilt/tip motion control mechanism allows the platform
544, along with the theta drive 311 and X, Y and Z drives 312, 314
and 316, and the platen 258 and probe assemblies 106, to be tilted
and/or tipped in desired directions so that optimal views of the
DUT 118 or placement of probes 256 may be had.
[0194] The tilt/tip motion control mechanisms 542 includes three
separate bearing pivots 722, 724 and 726 spaced about the bottom of
the housing 102 below the platform 544. In a preferred form, the
pivots 722 and 724 have motor driven support bars 722b and 724b for
raising or lowering their respective lower guide member portions
independent of one another. The third pivot, pivot 726, is a fixed
pivot or gimble which is not capable of raising and/or lowering its
respective lower guide member portion. Since pivots 722 and 724 are
motorized, pivot 726 does not need to be motorized in order to
tilt/tip the platform 544 and its connected components in the
desired manner. For example, if a system operator desires to tilt
the platform 544 shown in FIG. 24B down to the left, the operator
need only lower the support bars of the pivots 722 and 724.
Alternatively, if the system operator desires to tilt the platform
544 down to the right, they would raise the support bars of the
pivots 722 and 724 until the desired amount tilting has been
reached. The pivots 722, 724 and 726 are positioned in triangular
manner so that any desired tilting/tipping can be achieved. With
such a configuration, any two pivots can form an axis about which
tilting or tipping can be performed. The selected operator of
motors 722a and 724a determine about which axis the platform 544
will be tilted.
[0195] In order to provide the maximum amount of tilting, the
support bars of pivots 722 and 724 are preferably at mid travel
when the platform 544 is parallel to the floor or base walls 112
and 186 of housing 102. With such a configuration, the platform 544
can be tilted up or down in equal amounts by pivots 722 and 724.
The support bars preferably have rounded end portions for
connecting to the lower guide member 700a in a ball and socket type
fashion for smooth pivoting engagement therebetween.
[0196] The pivots 722, 724 and 726 are mounted to a lower support
plate 730 which in turn is mounted to the floor of housing 102.
Given the lower support plate's proximity to the floor of the
housing 102, and the vacuum pump openings 142 located therein, a
preferred form of the lower support plate 730 includes openings 732
which correspond to pump openings 142 and assist air flow in
chamber 190 and minimize the amount of time it takes for vacuum 115
to pump air out of chamber 190. The lower support plate 730 is
preferably of such a height to provide clearance for the pivot
motors 722a and 724a from the floor of the housing 102.
[0197] In alternate forms of system 100, the lower guide member
700a may be connected to an upper support plate for the tilt/tip
mechanism 542 in order to provide additional clearance for motors
and/or in order to provide a more compartmentalized system 100. For
example, an alternate form of system 100 is shown in FIG. 5H in
which tilt/tip mechanisms 542 have been removed to reduce the size
of housing 102 and system 100.
[0198] Positioned atop the platform 544 is the X drive (or stage)
312, which may be used to move the carrier 250 along its X axis.
Movement of this stage 312 also results in movement of the Y stage
314 and the theta drive 311 carried thereby. As shown in FIGS. 26A
and 26B, the X drive 312 is similar in construction to the platform
drive or stage discussed above (e.g., X and Y drives 702 and 704).
The X drive 312 has a stage (or bed) 740 upon which the Y drive 314
is mounted, and has a drive mechanism 742 for translating the stage
740 back and forth along the X axis. The stage 740 is comprised of
a lower guide member 740a upon which an upper slide member 740b
travels. The drive mechanism 742 consists of a motor 744 connected
to lead screw 746 via coupling 748. Operation of the motor 744
rotates its output shaft 744a, which rotates coupling 748 and lead
screw 746. Rotation of the lead screw 746 causes nut 750 to travel
along the screw shift closer to or farther from motor 744. The nut
750 is connected to the upper slide member 740b via nut mounting
bracket 750a. When the lead screw 746 is rotated in one direction
the nut 750 is moved toward the motor 744 thereby causing the upper
slide member 740b of x-stage 740 to travel in the same direction
and parallel to the lead screw 746. When the lead screw is rotated
in the opposite direction, the nut 750 is moved away from the motor
744 thereby causing the upper slide member 740b to travel in the
same direction as the nut and parallel to the lead screw 746.
[0199] In order to reduce or minimize the effect heat has on the X
drive 312, the drive has been constructed similar to the platform
drives 702 and 704 discussed above. More particularly, radiator
shield 752 is connected to motor 744 in order to block or hinder
the amount of heat or infrared energy generated by motor 744 from
radiating to other portions of the drive mechanism 742 and system
100. In a preferred form, the shield is angled at its radially
outer positions back toward the housing side wall 188. In this way,
radiation is directed generated by heating of the motor 744
operating in the vacuum chamber 190 to the side wall 188. The side
wall 188 has a great mass of metal material relative to other
system components in the housing 102 to better absorb and conduct
heat throughout its entire extent. Further, heat from the side wall
188 can be conducted to outer side wall 114 which can dissipate
external heat to the atmosphere.
[0200] To further assist in reducing or minimizing the effects of
heat on system 100, and particularly on drive mechanism 742, the
lead screw 746 is connected to the motor output shaft 744a via a
ceramic coupling 748. This removes the metal-to-metal contact
between screw 746 and shaft 744a and hinders the heat transfer from
the motor 744 to the screw 746. To further reduce heat transfer and
its effects on the motion control mechanism 312, the screw 746 may
be made from an insulating material such as a jewel like ruby or
sapphire, or a ceramic or other insulative material.
[0201] The bearing 754 used with screw 746 may also be made of an
insulative material in order to minimize the effect heat has on
drive 742. Likewise, bearing mount 756 and motor mount standoff 758
may also be constructed of such insulative materials. The use of
such materials for drive assembly 742 minimizes unwanted shifting
of the drive components affecting their precision movements of the
carrier 250. The low coefficient of thermal expansion of ceramic
ensures minimum of thermal expansion of these drive components.
Although ceramic motor mount standoff 758, bearing mount 756 and
bearing 754 were not mentioned above with respect to the platform
drive systems, such features can also be utilized in these drive
assemblies to achieve a similar beneficial result.
[0202] Coupled to the X-stage 312 is Y-stage 314, which rests atop
the X-stage and allows the carrier 250 to be translated back and
forth in the Y direction or axis. Movement of this stage also
results in the movement of theta drive 311. As can best be seen in
FIG. 24A, the Y stage 314 is very similar in construction to the
X-stage 312 discussed above, however, the Y-stage 314 is mounted
such that movement of the carrier 250 is in a direction
perpendicular to that of the direction traveled by the X-stage 312.
The Y stage 314 has a drive mechanism 760 which consists of a motor
operated screw drive identical to that of the X stage drive
mechanism 742. Heat protection similar to that mentioned above with
respect to the X-stage 312 can be implemented in the Y-stage 314
and is present in a preferred form of the high resolution vacuum
probing 100 herein.
[0203] In order to make system 100 more effective for probing large
specimen such as 300 mm wafers, the X and Y stages 312 and 314 may
be designed with enlarged beds or stages or support structures in
order to minimize the amount of Y-stage 312 overhang from the
X-stage 312. This prevents deflection that can occur if too large
of an overhang is created which results in shifting of the carrier
250 and specimen falling out of focus. For example, if system 100
is being used to view/probe a large specimen and the Y-stage 314 is
translated to an extreme end in the Y direction, the combined
weight of the carrier 250, theta drive 311 and specimen 118 may be
enough to cause the Y-stage to deflect down at the end furthest
from the X-stage 312 creating enough movement in the testing
surface to place the specimen out of focus with the microscope 104
or 105. In order to avoid this, the width of the X-stage 312 is
preferably increased to accommodate the full extent of y-axis
movement thereby avoiding overhang, and/or additional support
structures may be added off to the side of the X-stage 312 in order
to provide support to the Y-stage 314. An example of the latter
would be to configure the nut and nut mounting bracket shown in
FIG. 24A so that it also serves as support for the Y-stage 314 when
translated out beyond the side of the X-stage.
[0204] Before discussing the Z-stage 316, it should be noted that
the concepts of the motion control mechanisms discussed thus far
are generally applicable to any of the motion control mechanisms of
system 100, such as those used in conjunction with the manipulators
252a-d. For example, an adjustment mechanism for any of the X, Y
and Z stages of manipulators 252a-d is shown in FIG. 27. According
to this illustration, the adjustment mechanism (which is referred
to generally by reference numeral 500) includes a motor 502 which
is coupled to isolated lead screw 504 via insulative shaft coupling
506. As discussed previously any insulator may be used for coupling
506 so long as it contains the desirable thermal properties, i.e.,
low coefficient of thermal expansion, for handling the heat
generated and/or radiated within chamber 190. When the screw 504 is
rotated in a first direction, the nut 508 is moved farther away
from the motor 502 causing motion plate 510 which is attached to
nut 508 to also move away from motor 502 in the direction defined
by the axis of screw 504. When the screw 504 is rotated in the
opposite (or second) direction, the nut 508 and motion plate 510
are moved closer to the motor 502.
[0205] The manipulator adjustment mechanism 500 may also utilize
the thermal protection concepts discussed above with respect to
other motion control mechanisms. For example, in FIG. 27, radiator
shield 512 is used to deflect and/or hinder radiation of
heat/energy from motor 502. The motor 502 is also isolated from the
remainder of the drive mechanism 500 by isolating spacers 514. In
addition, a thermal bearing insulator 516 is used to isolate
bearing 518 from the rest of the mechanism 500. Alternatively, in
other forms of system 100, a ceramic bearing may be used with the
adjustment mechanism 500.
[0206] Turning now to FIGS. 24A-24C, the Z-stage 316 preferably
includes four column shaped members 316a, b, c and d that have
screw drives for raising and lowering the platen 258 with respect
to platform 544 therebelow. More particularly, each column 316a-d
has a sprocket 770 which is located below the platform 544 and is
connected to a lead screw 772. The lead screw 772 passes through an
opening in the platform 544 and supported by bearing 774
thereunder. A nut 776 is threaded onto the screw 772 and connected
to the sleeve portion that makes up the majority of column shaped
members 316a-d. When the motor operates to rotate sprocket 770 and
lead screw 772, the nut 776 and its attached sleeve or column are
moved closer to or farther from the sprocket 770. For example, when
the sprocket 770 and lead screw 772 are rotated in one direction,
the nut 776 and sleeve are moved away from the sprocket thereby
raising the platen 258. When the sprocket 770 and screw 772 are
rotated in the opposite direction, the nut 776 and sleeve are moved
closer to the sprocket thereby lowering the platen 258. Thus, the Z
drive 316 operates to raise and lower the platen in the Z direction
or axis.
[0207] The sprockets of the column members 316a-d are connected to
one another via a driven member such as a belt or chain 778 (FIG.
24C). The driven member 778 is connect to, and driven by, the
single motor 780 which can best be seen in FIG. 24A. In this way,
only one motor is needed to operate the Z-drive 316, and each
column member 316a-d will raise or lower the platen 258
simultaneously in equal amounts. In alternate forms of system 100,
however, each column 316a-d could be configured having its own
motor or drive mechanism and with each column member being operable
independent of the others. With such a configuration, the Z-drive
316 could be used not only to raise and lower the platen in the Z
direction, but also to perform tilt/tip functions similar to those
discussed above with respect to tilt/tip drive mechanisms 542.
[0208] A Z-shape guide and slide 781 is positioned near the back of
the chamber 190 and is attached to the platform 544. This
guide/slide 781 is similar in construction to the guide and slides
discussed with respect to X and Y drives 312 and 314 and operates
to guide the Z drive mechanisms 316a-d in a straight up and down
(or vertical) manner to ensure that no lateral movements are made
which might affect the positioning of the DUT 188.
[0209] The motion control mechanisms of system 100 may be operated
and configured in a variety of ways in order to provide any number
of desired movements. For example, the platform 544 may be used for
coarse adjustments of the carrier 250 and DUT 118, while more
precise (or fine) adjustments may be made via the X, Y, and Z
stages 312, 314 and 316 of the carrier 250. The motion control
mechanisms 540 of platform 544 may be used to generally position
the desired portion of the DUT 118 and carrier 250 under the
microscope 104 or 105, (e.g., general X and Y positioning), while
the X, Y and Z stages 312, 314 and 316 of carrier 250 may be used
to actually position the probes 256 on the desired conductive path
indicia of the DUT 118, (e.g., fine X, Y and Z positioning).
[0210] The fine positioning of the DUT and carrier typically
involves using the X and Y stages 312 and 314 of chuck 260 to
position the DUT 118 in the appropriate X and Y positions and then
using the Z stage 316 to raise the DUT 118 into contact with the
probes 256 and/or lower the probes 256 into contact with DUT 118
via the Z position adjustment mechanism 358 or 374 of manipulators
252a-d.
[0211] In alternate forms of probe station 100, the probes 256 may
be capable of positioning themselves, (e.g., probes with internal
motor driven joints), however, such a configuration is less
desirable than the configurations discussed above because it
introduces additional noise making components, which are very near
to the probes 256, thereby increasing the risk of noise or other
interference affecting the acquired and applied test signals. As
with the X, Y and Z stages 312, 314 and 316, the screw drive motion
control mechanisms 540 may use a variety of types of motors, such
as linear motors, stepper motors, servo-motors, or the like, as
long as they are capable of providing the desired translation of
the platform 544 (including platen 258, carrier 250, manipulators
252a-d, probes 256).
[0212] As mentioned above, the tilt/tip mechanisms 542 also
position the DUT 118 under the probes 256 and microscope 104. For
example, these mechanisms 542 may be used to position probes 256 on
the DUT in a desired fashion, to assist the user in "seeing"
probe-touchdown on the DUT, or simply to allow the user to observe
the probes 256 making contact with the DUT 118 from an angle other
than vertical.
[0213] The probe station 100 may also be set up with environmental
controls 550 which operate to control the temperature and
atmosphere within the housing 102. Such controls 550 may be used to
conduct "at temperature" testing or to obtain specified atmospheric
conditions in order to more accurately test how a DUT 118 will
operate in its actual application environment. The environmental
controls 550 may also be used to minimize the deleterious effect
any of the components within housing 102 may have on the
probing/testing of the DUT 118. For example, a temperature control
system 552 is shown in FIG. 21 which consists of a network of fluid
carrying tubes 554 that are used heat up or cool down the
temperature within housing 102 and/or the various components
therein.
[0214] In a preferred form of probe station 100, the tubes 554
carry a coolant, such as cold water, throughout the inner chambers
108 and 182 in order to cool down the probe station 100. The tubes
554 rely on heat transfer principals to remove unwanted or
excessive heat generated by the motion control mechanisms 540,
stages 312, 314, 316, manipulators 252a-d, and carrier 250. Such a
system 552 is particularly desired in vacuum environments because
vacuum environments are excellent thermal insulators in that there
is nowhere for the heat generated by the system to go. This
built-up heat can have deleterious effects on the probe station
and/or its components. For example, the probe station 100 may be
set up using a thermal chuck 260 which is used to test a wafer 118
at temperatures slightly above ambient temperatures. While testing
the wafer 118 at temperature, the motors used to move the chuck
260, the manipulators 252a-d, the platform 544 may begin to
generate heat due to their use. Without a temperature control 552,
this motor-generated heat may raise the temperature inside housing
102 to a level above that which the wafer 118 was to be tested at
and may cause inaccurate readings to be taken when conducting the
probing of the specimen 118. However, by providing a temperature
control system 552, the motor-generated heat may be accounted for
and removed from the probe station 100 so that the wafer 118 can be
tested at the appropriate temperature. Another negative effect of
component-generated heat is that it can affect the operation of the
probe station equipment. For example, excessive temperature within
housing 102 has been shown to cause the probes 256 to vibrate or
wobble. Such motion in the probes 256 not only makes it more
difficult to operate the probe station 100 because of difficulties
in placing the probes 256, but also may prevent the probe station
100 from being used to probe various specimens 118 such as very
small wafers having minute conductive path indicia because any type
of vibration may make it impossible to position and maintain the
probes 256 on the desired indicia.
[0215] The temperature control system 552 also allows the probe
station 100 to maintain a desired temperature within housing 102 by
accounting for the fact that components, other than those
specifically meant to supply heat such as a thermal chuck 260, may
end up generating heat over time themselves. Although the network
of fluid carrying tubes (or lines) 554 shown in FIG. 21 should be
sufficient to dissipate any unwanted heat, additional lines
carrying fluid about the carrier 250, manipulators 252a-d, probes
256 and motion control components may be employed to control the
temperature of each device and/or assist in controlling the
temperature within housing 102.
[0216] Given the various types of testing that may be performed and
various types of carriers 250, manipulators 252a-d, and probes 256
that may be used by probe station 100, it is foreseeable that these
components may be swapped in and out of the probe station 100 quite
frequently. As such, the probe station 100 may equip the components
and/or the leads connecting the components in such a way that they
can be quickly and easily removed and re-installed. For example, in
FIG. 21, the electrical leads 120 that run to each device may
include detachable interconnections 560 located proximate to the
device so that the operator does not need to spend time installing,
uninstalling and/or reinstalling corresponding leads 120 every time
he or she wishes to swap in and/or out a device. The detachable
interconnections 560 may be located at a variety of positions about
the leads and lines. Furthermore, the components of the probe
station 100, such as the carriers 250, manipulators 252a-d, probes
256, etc., may contain lead connections or ports that allow for
quick and easy installation, removal, and/or reinstallation of the
leads 120 connected to that component. In a preferred form,
detachable interconnections 560 are located on the leads 120
proximate to the carrier 250, manipulators 252a-d, and probes 256,
as well as proximate to the feedthroughs 138 and 140, and proximate
to the controllers used to operate the probe station 100. Ideally
the carrier 250, manipulators 252a-d, and probes 256 contain lead
connections or ports which further allow for quick and easy
installation, removal, and/or reinstallation of the leads 120.
[0217] While the above description of probe station 100 discussed
the basic structure of the probe station, including its housing
102, high resolution microscope 104 and probe assembly 106, the
following will discuss the setup and operation of the probe station
100 and provide additional details regarding the software used to
operate the probe station. The probe station 100 is a high
resolution analytical probe station that is capable of conducting
low voltage/low current testing in a low noise environment. More
particularly, the probe station 100 is connected to a controller,
such as a processor or network of processors, which operate,
monitor, and collect data from the probe station 100. Preferably
the controller consists of a personal computer, as mentioned above,
having a monitor 572 and video imaging capabilities. The controller
is connected to the various components of the probe station 100,
(e.g., theta drive 311, X, Y and Z drives 312, 314 and 316, carrier
250, probe assemblies 106, etc.), via leads (or lines) 120 passing
through feedthroughs 138 and 140. Feedthroughs 138 and 140 allow
vacuum tight seals to be made with the housing so that the housing
portions 108 and 182 can be pulled into a vacuum state. As
discussed above, the leads/lines may consist of triaxial cables
275, coaxial cables 423, thermocouples, and piping or conduit for
such things as wire, vacuum lines, air lines, and/or environmental
controls 550 such as fluid carrying tubes 554.
[0218] Additional leads 120 may be connected from the controller or
other supporting equipment, such as air tanks, vacuum pumps,
temperature controllers, etc., directly to other portions of the
probe station 100. For example, microscope operating leads may be
connected directly from the controller and the mains power supply
to the microscope 104. In addition, vacuum lines may be connected
directly from a vacuum pump to pump passages 142 and 144 of housing
102.
[0219] The probe station 100 tests the specimen 118 by positioning
probes 256, via the controller, over various conductive path
indicia located on the surface of the specimen 118 and uses the
probes 256 to either apply or acquire a variety of test signals to
or from the DUT 118. More particularly, the controller operates
motion control mechanisms 540 and tilt mechanisms 542 to position
the platform 544 and the associated carrier 250 so that probes 256
are generally above the desired conductive path indicia to be
probed (or target area). The controller further operates X and Y
position adjustment mechanisms of manipulators 252a-d, and X and Y
stages 312 and 314 of probe assemblies 106, to position the probes
256 above the target area. Then the controller raises the carrier
250 via Z stage 312 of probe assembly 106, and/or lowers probes 256
via Z position adjustment mechanism 358 of manipulators 252a-d,
until the probes 256 have made sufficient contact with DUT 118 to
conduct the desired testing. In a preferred form, the controller is
connected to a contact sense module 460 and stops the motion
control mechanisms when sufficient probe touchdown has occurred.
This prevents the DUT 118 from being inadvertently damaged by
probes touching down with excessive force.
[0220] The environmental control system 550 monitors and/or
controls the environment, including the temperature, humidity,
vacuum state, etc., within housing 102 so that it is set at, and
remains at, the desired setting for testing the DUT 118. The
various parts of the probe station, such as the environmental
control system 550, may be controlled by the controller and/or may
be controlled at least in part by additional controllers.
[0221] Once the probes 256 are positioned and the environment is
set, testing is ready to begin. At this point, the probe station
100 begins using the probes 256 to either apply or acquire test
signals. Typically, one probe will be used to apply a test signal
at a desired point in the circuit of specimen 118, and another
probe will be used to acquire the signal resulting from the
application of the test signal at another point on the circuit of
specimen 118. The probe station 100 may then be used to analyze the
acquired signal to determine if it is generally equal to the signal
that should have been acquired at that particular point in the
circuit of specimen 118. If it is equivalent, that portion of the
circuit is presumed to be operating correctly. If the acquired
signal is not equivalent to the signal that should have been
received at that particular point in the circuit, then the specimen
118 may be further analyzed to determine what is wrong, or may
simply be marked as a defective component.
[0222] After this target area has been probed, the probe station
100 may locate and begin testing another target area on DUT 118.
Depending on the location of the next target area, the probe
station 100 may simply need to raise and re-position the probes 256
via manipulators 252a-d to position the probes 256 above the new
target area, or the probe station may need to use additional motion
control components including manipulators 252a-d, X, Y and Z stages
312, 314 and 316, and motion control mechanisms 540 and tilt
mechanisms 542 in order to position the probes 256 above the new
target area. For example, if the new target area is very close to
the area that was just probed, fewer motion control mechanisms may
be needed in order to position the probes over the new target area.
However, if the new target area is farther away from the area that
was just probed, more or even all of the motion control mechanisms
may be needed in order to position the probes over the new target
area (e.g., if the manipulators 252a-d cannot move the probes 256
far enough to reach the new target area, the carrier X, Y and Z
stages 312, 314 and 316 may be needed; similarly, if the X, Y and Z
stages cannot move the probes 256 far enough, the motion control
mechanisms 540 may be needed).
[0223] Once the probes have been positioned over the new target
area of the DUT 118, the controller (or other actuator control)
will raise the carrier 250 via Z stage 312 and/or lower the probes
256 via manipulators 252a-d to move the probes 256 into sufficient
contact with DUT 118 to conduct the desired testing. As discussed
above, a probe touchdown sensing mechanism 450 may be used to
determine when sufficient probe touchdown has been made. Once
testing is ready to begin, the controller begins acquiring and/or
applying test signals about the target area via the probes and
analyzes the test results to determine if the DUT is operating
correctly. The probe station 100 may also be set up using a socket
stage adapter 320 and socket card 330, fixed probe card, and/or a
test head with which various types of DUTs can be tested. Although
the connections and setup for these devices may differ, the general
operation of probe station 100 is similar to that discussed above,
(e.g., applying probes to target areas, probing and analyzing data,
etc.).
[0224] The actual control and operation of probe station 100 may be
made via traditional input devices associated with the controllers,
such as a keyboard, mouse, joystick, touch sensitive screen, or the
like. The probe station 100 may also be programmed so that the
probe station 100 is capable of performing repetitive testing with
minimal user input. Additional controls may be provided on the
exterior of housing 102 and/or may be provided in a pendant control
which is commonly used in the industry and with the products sold
by The Micromanipulator Company, Inc.
[0225] In order to assist the user in probing the DUT 118 and
moving the DUT about so that multiple target areas can be probed,
the probe station 100 may be set up with the PCPII software
discussed above. Screen views of the PCPII software as they may
appear on a monitor 572 of a controller external from probe station
housing 102, such as computer system 16 mentioned above, can be
seen in FIGS. 22A and 22B. In FIG. 22A, the PCPII software
interface 580 allows the probe station user to make remote
adjustments to the microscope 104, and manipulators 252a-d and
probes 256 via user interface control panels 582 and 584
respectively. For example, the microscope control panel 582 allows
the probe station user to adjust the focus of microscope 104 via
control 586. In addition, speed may be adjusted by scrolling up or
down scroll bar 588 on the control panel 582.
[0226] The manipulators 252a-d, and probes 256 can be controlled
via control panel 584. For example, speed and direction of travel
in the X and Y directions can be adjusted via XY settings 590.
Similarly the speed and direction of travel in the Z direction can
be adjusted via Z settings 592. The control panel 584 also displays
the current position data below the XY settings 590 and Z settings
592, and allows the probe station user to select what units
measurements and/or movements are made in.
[0227] The PCPII software interface 580 also allows the probe
station user to set up and view a wafer profile via control panel
594. For example, when the DUT 118 consists of a wafer, the probe
station user can type in the diameter of the wafer and a grid of
dies present on the wafer can be generated, (e.g., columns and
rows). The probe station user can enter particular features
pertaining to the die via the die program tools 596 and can pick
which die is to be viewed by the microscope 104 by simply selecting
the die with cursor 598.
[0228] More particularly, cursor 598 can be used to indicate the
respective selected location or test site on the specimen being
probed, (e.g., the sites at which test signals are transferred to
and from the probe). In this manner, an operator can change
selected test locations via on-screen manipulation of the cursor,
as by a mouse or other computer interface control. Moving the
cursor 598 causes the relative position between the probe 256 and
the specimen surface to shift under software control so that the
probe 256 is oriented at the selected test site. To this end, the
software is programmed to operate actuators of the probe assemblies
106 and/or the carrier 250, (e.g., X, Y and Z stages 312-316 and/or
the motion control mechanisms 450), on which the specimen is
affixed for precision shifting thereof to position the probe 256 at
the selected test site. More particularly, the software is used to
interpret the cursor movement and determine the precise distance
with which the DUT needs to be moved. This analysis may not only
require the application of a scaling factor to calculate the
horizontal distance that must be traveled, but also may involve
determining which actuators are to be used (e.g., probe assembly
actuators, carrier actuators, etc.) in order to accomplish the
desired travel in the most efficient manner.
[0229] Accordingly, with a mouse, an operator can click and drag
the cursor 258 across the screen to the desired conductive path
indicia location or terminal they desire to test. This cursor
movement can result in a variety of different movements for the
probe station 100. For example, the user may click and drag the
cursor from one die to another, causing the probes 256 to move from
one die to another so that the new die may be probed or analyzed.
Alternatively, the user may click and drag the cursor from one
probe location to another, causing the selected probe to move from
one location on a particular die to another location on that same
die. In a preferred form, the operator or user is capable of
selecting what type of movement he or she wants via the software
prior to making the move. For example, if the user would like to
move a single probe from one location to another, he or she would
position the cursor 258 over the probe he or she wishes to move,
and then would click and hold the mouse input button down and drag
the mouse until the cursor 258 is at the desired new test location
for that probe. Once the mouse input is released, the software
would cause the selected probe to move to its new location.
Alternatively, the user could indicate that he or she wishes to
switch dies and he or she would position the cursor 258 over the
current die, and then click and drag the cursor to the desired die
to be probed. Once the mouse input is released, the software would
cause the desired die to be placed under the high resolution
microscope 104 for probing.
[0230] Although a click and drag type input process has been
described, alternate input processes may be used so long as the
desired movement is achieved. For example, movement from one die to
another could be achieved by simply positioning the cursor 258 over
the desired die to be tested and clicking or double-clicking the
mouse input causing the selected die to be positioned under the
high resolution microscope 104. Similarly, probe movement from one
location to another on the same die could be achieved by clicking
on the desired probe to move, or selecting via a menu which probe
is to be moved, moving the cursor 258 over the desired new location
for that probe, and then clicking or double-clicking the mouse
input at that cursor location causing the selected probe to move to
the desired new location.
[0231] The wafer profiles and settings entered into the probe
station 100 can be saved so that similar DUTs can be probed by
simply calling up the stored settings. For example, a wafer ID can
be assigned to certain types of wafers and the probe settings and
testing procedures for these types of wafers can be recalled by
simply entering the assigned wafer ID into the wafer ID field 593.
This allows the probe station user to test similar wafers more
rapidly and provides a way in which routine probing can be
programmed into the probe station 100 so that it can be accurately
repeated in the future.
[0232] Video images of the probes 256 and DUT 118 may be viewed
and/or adjusted via control panel 595. The video images 597 are
provided to help the probe station user identify where on the DUT
118 they are at, as well as to assist the user in positioning the
probes 256 and in probing the DUT 118. One of the notable features
of this control panel 595 is the ability to print images of the DUT
118 via the print icons located in the tool bar of the control
panel 595.
[0233] The screen view shown in FIG. 22B depicts another form of
software interface 620 which may be used to control system 100. In
this interface, power to system 100 is turned on/off via power
switch 622. The system user can perform an automatic start feature
by selecting AutoStart 624 which will start the high resolution
microscope 104 imaging. An active image of the probes 256 will be
displayed in field 626, and a "bird's eye" view of the probes and
specimen will be generated in field 628. The electron beam
characteristics can be monitored and controlled view field 630.
More particularly, the system user can adjust or monitor the beam's
voltage 630a, filament 630b and current 630c via field 630 so that
the desired testing can be performed. Similarly, the system user
can control the vacuum characteristics and stages of system 100 in
fields 632 and 634. The image displayed in field 626 can be
automatically adjusted via the brightness and contrast adjustment
switches of filed 636, and/or can be manually adjusted by selecting
the advance settings box and selecting AutoVideo button. The
optical controls of the SEM 104 can also be adjusted by selecting
any of the items in the optics field 638. For example, the
magnification of the image can be increased or decreased via the
control settings 638a. The spot size and focus characteristics can
also be adjusted in field 630 at 630b and 630c. Additional settings
for the microscope 104 can be adjusted in field 630 including the
astigmatism, beam scan rate, image size and image rotation.
[0234] According to this interface 600, the system operator moves
the desired probe 256 by selecting which probe assembly 106 he or
she wants from the icons identified by reference numeral 640. Once
selected an icon 640a identifying which assembly has been selected
appears in the top left corner of the active image viewing field
626. In the illustration shown in FIG. 22B, manipulator one has
been selected. Thus, the manipulator controls and monitoring
sections pertain to that of manipulator one. For example, the
manipulator X and Y controls 642 displayed in FIG. 22B are
currently set up to maneuver manipulator one and to display the
positioning data of this same manipulator. Similarly, the
manipulator Z controls 644 shown display the pertinent Z data for
manipulator one and control the Z drive mechanism for this
assembly. Some of the Z controls shown include probe up/down
selections, theta speed setting selections, and course adjustment
selections for the Z direction (or Z job selections).
[0235] Below the manipulator selection icons 640, are stage
selection, tilt selection, theta selection, live image selection
and freeze image selection icons which allow the system user to
perform the stated task and/or select from a variety of available
tasks for the stated feature. For example, the system operator
could select the stage select icon and then select from any of the
stage mechanisms discussed above including the theta drive 311, X,
Y and Z stage 312, 314 and 316, or microscope stage (or platform
stage) coupled to platform 544. An auto start feature may be
provided for the software interfaces which will provide the system
user with quick and easy images from which to start.
[0236] FIGS. 22A and 22B reflect how the PCPII software has been
created and/or modified to control both the SEM 104 and the probe
station components including probe assemblies 106, carrier 250 and
stages 311, 312, 314, 316, 702 and 704. In a preferred form of
system 100, the SEM imaging software supplied with SEM 104, was
only set up to be run with an ActiveX component having specific
names and interfaces. Since the ActiveX component is the only way
to interface other components with SEM 104, the PCPII software of
system 100 was redesigned to handle both the SEM imaging and
control, and the probe station navigation (pcNav) and video
(pcVideo). The pcNav and pcVideo are collectively referred to
herein as the probe station application.
[0237] A pcRouter Dynamic Data Exchange interface was created to
allow the 16 bit probe station application (probe station
navigation and video) to work in conjunction with the 32 bit SEM
control application. Since both applications are competing for
system resources, a preferred form of system 100 turns the SEM
imaging application off when navigation is desired, and turns the
navigation application off when SEM imaging is desired. Thus, when
the system user is done viewing a target with the SEM 104 and
desires to move to a new target on DUT 118, the SEM imaging
application is shut off and the pcNav application is operated. In
this way the user can move from conductive path indicia on one die
to other conductive path indicia on the same die or on other dies
located on the DUT 118. Conversely, when SEM imaging is again
desired, the pcNav application can be shut off and the SEM imaging
turned back on so that SEM 104 can begin scanning the target
specimen and system 100 can display a high resolution image. This
configuration ensures that all motion control functions will be
initiated from the ActiveX navigator in the SEM 104.
[0238] The optional joystick or pendant control discussed above
with respect to the operation of the system 100 can be used in
conjunction with the PCPII software interface and is implemented by
using an application such as pcLaunch to take over the operating
system of the controller, (e.g., to take over WINDOWS). More
particularly, when a movement in the joystick or input device is
made, pcLaunch is activated thereby taking control of the operating
system. Once this event occurs, the SEM imaging application is shut
off so that the desired navigation function can be performed. Once
navigation is complete, the navigation application (including the
joystick navigation controls) is shut off and the SEM imaging
application is turned back on.
[0239] Thus, PCPII provides an interface for allowing the system
user to both control the SEM 104 and the probe station including
its many components (e.g., the carrier 250, probe assemblies 106,
drives and stages 311, 312, 314, 316, 702 and 704, etc.). With the
interfaces described a system user can position individual probes,
as well as multiple probes, wafer (or carrier) stages 311, 312,
314, 316, 702 and 704, platen 258, and probe assemblies 106
including the various stages of manipulators 252a-d. More
particularly, the probe assembly controls and high resolution
microscope controls can be integrated together with auto scaling to
the SEM image in on the screen (the active image), which allows for
the click-n-drag navigation to be used. Furthermore, the
positioning controls of system 100 are kept from being effected by
the image update time of microscope 104. For example, the
click-n-drag navigation of the software interfaces described above
allows for precise placement of probes without concern for the
amount of time microscope 104 takes for image updating.
[0240] The system 100, as described above, is a fully functional
probe station incorporating high resolution microscopy in order to
allow a system user to probe 0.1 .mu.m. It is low current ready and
can pump down in less than five minutes. The system is further
capable of dual duty as a high resolution probe station on one
hand, and as a light microscope probe station on the other hand.
Such a dual capacity may be desired for a variety of reasons beyond
the obvious fact that two separate pieces of equipment can now be
replaced by one. For example, the light microscope 105 may be used
to set up the DUT for testing and for laser cutting. The light
microscope 105 may also be operated by the software interface and
can be adjusted manually or by motorized drives. The high
resolution SEM microscope 104 offers sufficient resolution to probe
100 nm features and offers a magnification range of 15.times. to
25kx. By offering probing capabilities, the system 100 can also
offer the ability to both inject signals and measure actual signal
amplitudes.
[0241] The drive mechanisms of system 100 provide heat radiators
for probe drift caused by thermal expansion as discussed above and
offer high precision lead screw drives which offer high resolutions
with large ranges of motion. In a preferred form, the platform
stage may be moved up to one inch (25 mm) and allow for X and Y
travels approximately equal to 0.25 inches. The manipulators
utilized offer the ability to stay on submicron devices for
extended periods of time without damaging the DUT or sliding off
the target. The preferred manipulators offer X, Y and Z travel of
approximately 12.5 mm with a position resolution of 50 nm. The X
and Y stages 312 and 314 have the ability to travel approximately
200 mm in the X and Y direction with a resolution of 0.1 .mu.m and
an accuracy or repeatability of .+-.1.5 .mu.m. In addition, the
preferred theta drive offers 100.degree. of travel with 0.7 .mu.m
of resolution and the ability to be controlled by the
joystick/pendant or software interface.
[0242] The probes are designed with probe link arms that are
capable of further dampening vibration and can give strong support
to the probes. The probes 256 can all be placed within one square
micron or less and four probes can be placed within one square
.mu.m area. A variety of different probe tips may be used with the
probes of system 100, including concave, convex and nipple tipped
configurations. For example, concave tips which are very sharp but
not very durable, can be used in applications where a low Z forces
are desired to be applied to the DUT. Convex tips which are durable
but have no point, can be used in applications where it is desired
to penetrate (or punch through) oxides or in applications where
probes that exert a large amount of force are desired. Nipple tips
are both durable and sharp and find uses in a variety of
applications.
[0243] The system can further image at low beam voltages and can
blank the beam to prevent damage to DUTs and allow for low current
measurements (e.g., sub-femto ampere measurements) to be taken. The
beam voltage can be varied from a preferred range of 1.5 kV to 20
kV.
[0244] The software of system 100 also allows for the system user
to interface with CAD navigation systems and equipment, and gives
the system operator the ability to combine control and microscope
images on one screen.
[0245] While there has been illustrated and described a preferred
embodiment of the present invention, it will be appreciated that
modifications may occur to those skilled in the art, and it is
intended in the appended claims to cover all those changes and
modifications which fall within the true spirit and scope of the
present invention.
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