U.S. patent application number 10/465776 was filed with the patent office on 2004-12-23 for focused ion beam microlathe.
Invention is credited to Stevens, Mary B., Zwigl, Peter.
Application Number | 20040256577 10/465776 |
Document ID | / |
Family ID | 33517587 |
Filed Date | 2004-12-23 |
United States Patent
Application |
20040256577 |
Kind Code |
A1 |
Stevens, Mary B. ; et
al. |
December 23, 2004 |
FOCUSED ION BEAM MICROLATHE
Abstract
An apparatus for customizing focused ion beam (FIB) probes is
described. Prior to taking probe measurements, the probe tips are
milled with a beam of gallium ions on a microlathe platform. A
motor rotates the probes such that the probe tips are uniformly
milled.
Inventors: |
Stevens, Mary B.;
(Sacramento, CA) ; Zwigl, Peter; (Citrus Heights,
CA) |
Correspondence
Address: |
Edwin H. Taylor
Blakely, Sokoloff, Taylor & Zafman LLP
Seventh Floor
12400 Wilshire Boulevard
Los Angeles
CA
90025-1030
US
|
Family ID: |
33517587 |
Appl. No.: |
10/465776 |
Filed: |
June 18, 2003 |
Current U.S.
Class: |
250/492.21 |
Current CPC
Class: |
H01J 37/20 20130101;
H01J 2237/20214 20130101; H01J 2237/31749 20130101; H01J 37/3056
20130101 |
Class at
Publication: |
250/492.21 |
International
Class: |
H01J 037/31 |
Claims
What is claimed is:
1. A focused ion beam (FIB) system, comprising: a probe platform
that mounts a microelectronic chip sample to be modified on the FIB
system; a focused ion beam base coupled to the probe platform,
wherein the focused ion beam base comprises circuitry to store
photographic images of the microelectronic chip sample; and a
microlathe platform coupled to the probe platform, wherein the
microlathe platform is coupled to a first microlathe rotational
device that is positioned on the microlathe platform to position a
first probe to come into contact with a beam of ions, wherein the
beam of ions mills the tip of the first probe.
2. The FIB system of claim 1, wherein the first microlathe
rotational device rotates the first probe as the beam of ions mills
the first probe tip.
3. The FIB system of claim 1, wherein the beam of ions is
approximately 500-1000 picoamperes.
4. The FIB system of claim 3, further comprising: a second
microlathe rotational device coupled to the microlathe platform,
wherein the second microlathe rotational device positions a second
probe to sharpen the tip of the second probe by the beam of
ions.
5. The FIB system of claim 1, wherein the microlathe platform is
removed from the probe platform prior to mounting a chip sample to
the probe platform.
6. The FIB system of claim 1, further comprising: a
microelectromechanical system (MEMS) device coupled to the first
microlathe rotational device that positions the MEMS device to come
into contact with a beam of ions, wherein the beam of ions mills
the MEMS device.
7. The FIB system of claim 1, further comprising: a
micromanipulator coupled to the first microlathe rotational device
that positions the micromanipulator to come into contact with a
beam of ions, wherein the beam of ions mills the
micromanipulator.
8. A system, comprising: an ion source that generates a gallium ion
beam; a plurality of tungsten probes positioned to be in contact
with the ion beam, wherein each of the plurality of probes is
coupled to a device that rotates the probes, wherein the gallium
ion beam reduces the surface area of the tips of each of the
plurality of probes; and a platform for coupling a microelectronic
sample to the system, wherein the ion beam modifies a circuit of
the sample.
9. The system of claim 8, wherein the intensity of the ion beam for
reducing the surface area of the tips of the plurality of probes is
greater than the intensity of the ion beam for modifying the
sample.
10. An apparatus, comprising: means for improving positioning of a
probe tip on a metal line; and means for removing oxidation from
the probe tip.
11. The apparatus of claim 10, further comprising: means for
reducing cross talk of signals measured by the probe tip.
12. A method, comprising: loading m probes on a microlathe platform
that is coupled to a focused ion beam (FIB) system, wherein m is an
integer greater than or equal to one; and rotating the m probes and
milling the m probes using an ion beam.
13. The method of claim 12, wherein the ion beam is 500-1000
picamperes.
14. The method of claim 12, wherein the milling duration is a
function of the rotation speed of the m probes.
15. The method of claim 12, further comprising: unloading the m
probes and the microlathe platform from the FIB system.
16. The method of claim 15, further comprising: loading n probes in
a prober, wherein n is an integer less than or equal to m.
17. The method of claim 16, further comprising: loading a
microelectronic sample in the FIB system; and loading the prober in
the FIB system.
18. The method of claim 17, further comprising: making
modifications to the microelectronic sample; and taking
measurements of the microelectronic sample using the prober.
Description
FIELD OF THE INVENTION
[0001] The present invention pertains to the field of
microelectronic device testing. More particularly, the present
invention relates to an apparatus that reduces the tip diameter and
profile size of commercially available focused ion beam probes.
BACKGROUND OF THE INVENTION
[0002] Focused ion beam (FIB) technology is often used to make
precision circuit modifications in microelectronics. The FIB
typically utilizes a controlled beam of ions to drill holes through
passivation layers and to cut metal lines. In addition, the FIB has
been used to deposit metal and insulators.
[0003] A prober is often used to measure electric characteristics
of components of microelectronic chips. The probe is typically made
of tungsten and shaped like a spear. The pointed end of the probe
(the probe tip) may be 100 nanometers or less. Measurements of the
chip are taken by establishing a contact between a probe tip and
on-chip metal lines. A plurality of probes are usually coupled to
the prober. Each probe is coupled to a shaft that is positioned
over the chip surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a side view of an embodiment of a focused ion beam
system that mills probe tips;
[0005] FIG. 2 is a top view of an embodiment of a focused ion beam
system that mills probe tips; and
[0006] FIG. 3 is a flowchart of a process for milling probe tips
using a modified focused ion beam system.
DETAILED DESCRIPTION
[0007] In the following detailed description, numerous specific
details are set forth in order to provide a thorough understanding
of the invention. However, it will be understood by those skilled
in the art that the present invention may be practiced without
these specific details. In other instances, well-known methods,
procedures, components and circuits have not been described in
detail so as not to obscure the present invention.
[0008] In order to decrease chip dimensions and to reduce costs,
the trend in microelectronic design is towards smaller devices and
thinner metal lines. As the width of metal lines continue to
shrink, probe tip radii provided by manufacturers are becoming too
large to provide accurate measurements. For example, probe tips are
often too wide to allow precise positioning of the tips on metal
lines. This is especially a problem when multiple probes are used
to measure metal lines in close vicinity to one another. In
addition, the exact position of the probe tip that is used to
contact the metal line is often uncertain because the view of the
metal line is obstructed by the tip itself.
[0009] FIG. 1 shows a FIB system that allows the probe or just the
probe tip to be milled prior to probing. The system comprises a FIB
base 110 coupled to a probe platform 120. A microelectronic sample
is typically placed on the probe platform 120 to take measurements
of the sample. A microlathe platform 130 is coupled to the probe
platform 120. A microlathe rotational device 150 is coupled to the
microlathe platform 130. A probe 160 is coupled to the microlathe
rotational device 150. The probe 160 may be composed of tungsten.
An ion source 140 generates an ion beam for the system.
[0010] A beam of Gallium (Ga) ions may be focused on the probe 160.
The tip of the probe 160 is positioned below the ion source 140 by
the microlathe rotational device 150 and the microlathe platform
130. The ion beam for milling the tip of probe 160 may be more
intense than the ion beam used to make modifications to a
microelectronic sample. For one embodiment of the invention, the
ion beam for probe tip milling is approximately 500-1000
picoamperes.
[0011] During probe tip milling, the microlathe rotational device
150 rotates the probe 160 such that the ion beam is uniformly
applied to the periphery of the probe tip. Milling the probe tip
using ion beams allows the user to customize the dimensions of the
tip of probe 160. By reducing the width of the probe tip, more
precise positioning of the tip on a metal line of a microelectronic
chip may be achieved. Moreover, reducing the width of the probe tip
allows for the position of the tip to be more readily attained.
[0012] The ion beam also helps to remove oxidation that may build
up on the probe tip. Removing oxidation helps to provide for a
better contact between the probe and metal lines. In addition, a
thinner probe tip may help to reduce cross talk. When multiple
probe tips are used to take measurements from adjacent metal lines
on a chip, the signals measured by the probe tips may generate
cross talk. Reducing the width of probe tips may reduce cross talk
by allowing more separation between probe tips during
measurements.
[0013] After probe tip milling is complete, the microlathe platform
130 and the microlathe rotational device 150 are removed from the
probe platform 120. A microelectronic sample is then mounted to the
probe platform 120 to modify or take measurements of the sample.
The focused ion beam base 110 may comprise a microscope and an
apparatus for recording images.
[0014] For another embodiment of the invention, an atomic force
microscopy (AFM) probe, a microelectromechanical system (MEMS)
device, a stylus, or a micromanipulator may be coupled to the
rotational device 150 for milling.
[0015] For yet another embodiment of the invention, the FIB system
may comprise a plurality of rotational devices for milling probes.
FIG. 2 shows an overhead view of a FIB system for milling probes.
Microlathe platform 130 is coupled to probe platform 120. The
microlathe platform 130 has an orifice that is the approximate
location of the ion beam target 235. Microlathe rotational devices
210, 211, 212, and 213 are coupled to the microlathe platform 130.
Probe 220 is coupled to the microlathe rotational device 210. Probe
221 is coupled to the microlathe rotational device 211. Probe 222
is coupled to the microlathe rotational device 212. Probe 223 is
coupled to the microlathe rotational device 213.
[0016] An ion beam is directed at the ion beam target 235. The
microlathe rotational devices 210-214 may each comprise a motor.
The rotational devices 210-214 rotate the probes 220-224 at
approximately the same time that the ion beam is milling the probes
220-224. The milling duration will depend on the speed that the
rotational devices 210-214 rotate the probes 220-224, the amount of
removal desired from the probes 220-224, and the magnitude of the
ion beam.
[0017] Even though FIG. 2 depicts four microlathe rotational
devices coupled to the microlathe platform 130, more than four
microlathe rotational devices may be coupled to the microlathe
platform 130. For example, a dozen microlathe rotational devices
may be coupled to the microlathe platform 130 around the ion beam
target 235 such that 12 probes may be milled at approximately the
same time. The microlathe rotational devices may be distributed
around the ion beam target 235 or the devices may be coupled to the
microlathe platform 130 in columns or rows.
[0018] FIG. 4 shows a flowchart of a process for milling probes
using a modified FIB system. The probes are loaded on a microlathe
platform in operation 310. The microlathe platform is coupled to a
FIB system. The probes are milled in operation 320 using a beam of
ions. The probes are rotated to help ensure uniform milling of each
probe surface. The probes are unloaded from the microlathe platform
in operation 330 after milling is complete. The microlathe platform
may also be removed from the FIB system.
[0019] The probes are then loaded in the prober in operation 340.
The microelectronic sample is loaded in the FIB system in operation
350. Finally, the prober is loaded in the FIB system in operation
360.
[0020] For another embodiment of the invention, the probes are
loaded on a microlathe platform in operation 310. The probes are
milled in operation 320 using a beam of ions. The probes are
unloaded from the microlathe platform in operation 330 after
milling is complete. The probes are then loaded in the prober in
operation 340. The prober is mounted in the FIB system in operation
350. The sampled is then loaded in operation 360.
[0021] In the foregoing specification the invention has been
described with reference to specific exemplary embodiments thereof.
It will, however, be evident that various modification and changes
may be made thereto without departure from the broader spirit and
scope of the invention as set forth in the appended claims. The
specification and drawings are, accordingly, to be regarded in an
illustrative rather than restrictive sense.
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