U.S. patent application number 14/108286 was filed with the patent office on 2015-06-18 for probe-based data collection system with adaptive mode of probing.
This patent application is currently assigned to DCG Systems, Inc.. The applicant listed for this patent is DCG Systems, Inc.. Invention is credited to Mike Berkmyre, Sergiy Pryadkin, John Sanders, Richard Stallcup, Vladimir A. Ukraintsev.
Application Number | 20150168444 14/108286 |
Document ID | / |
Family ID | 53192832 |
Filed Date | 2015-06-18 |
United States Patent
Application |
20150168444 |
Kind Code |
A1 |
Ukraintsev; Vladimir A. ; et
al. |
June 18, 2015 |
PROBE-BASED DATA COLLECTION SYSTEM WITH ADAPTIVE MODE OF
PROBING
Abstract
A system for analyzing a sample is described. The system for
analyzing a sample includes a probe and a controller circuit. The
controller circuit configured to control a movement of the probe to
at least a first position and a second position on the sample based
on navigation data. In response to the movement of the probe, the
controller circuit is configured to adjust a force of the probe on
the sample at the first position from a first force value to a
second force value and the force of the probe on the sample from a
third force value to a fourth force value at said second position
on the sample. And, the controller circuit is configured to acquire
sample data with the probe at the first position on the sample.
Inventors: |
Ukraintsev; Vladimir A.;
(Allen, TX) ; Stallcup; Richard; (Frisco, TX)
; Pryadkin; Sergiy; (Plano, TX) ; Berkmyre;
Mike; (Allen, TX) ; Sanders; John; (Coppell,
TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DCG Systems, Inc. |
Fremont |
CA |
US |
|
|
Assignee: |
DCG Systems, Inc.
Fremont
CA
|
Family ID: |
53192832 |
Appl. No.: |
14/108286 |
Filed: |
December 16, 2013 |
Current U.S.
Class: |
850/3 |
Current CPC
Class: |
H01J 2237/2583 20130101;
G01Q 10/06 20130101 |
International
Class: |
G01Q 10/04 20060101
G01Q010/04; G01Q 30/02 20060101 G01Q030/02 |
Claims
1. A system for analyzing a sample comprising: a probe; and a
controller circuit configured to: control a movement of said probe
to at least a first position and a second position on the sample
based on navigation data; in response to said movement of said
probe, adjust a force of said probe on the sample at said first
position from a first force value to a second force value and said
force of said probe on the sample from a third force value to a
fourth force value at said second position on the sample; and
acquire sample data with said probe at said first position on the
sample.
2. The system of claim 1, wherein said controller circuit is
configured to register said probe at a registration position on the
sample.
3. The system of claim 1, wherein said controller circuit is
configured to adjust said force of said probe based on navigation
data.
4. The system of claim 1, wherein said navigation data is
computer-aided design data.
5. The system of claim 1, wherein said controller circuit is
configured to adjust said force of said probe based on acquired
sample data.
6. The system of claim 1, wherein said controller circuit is
configured to acquire sample data with said probe at said position
until a signal-to-noise ratio is achieved.
7. The system of claim 1, wherein said controller circuit is
configured to adjust said force of said probe during said movement
to said first position and said second position.
8. The system of claim 1, wherein said controller circuit is
configured to adjust a speed of said movement of said probe.
9. The system of claim 7, wherein said controller circuit is
configured to control said movement of said probe based on sample
data acquired during said movement of said probe.
10. The system of claim 9, wherein said sample data acquired is
based on capacitance.
11. The system of claim 1, wherein said first force value is equal
to said third force value and said second force value is equal to
said fourth force value.
12. A method to analyze a sample comprising: moving said probe to a
position based on navigation data; in response to moving said probe
to said position based on navigation data, adjusting a force of
said probe on said sample from a first force value to a second
force value at said position; and acquiring sample data with said
probe at said position.
13. The method of claim 12 further comprising: registering said
probe at a registration position.
14. The method of claim 12 further comprising: moving said probe to
a second position based on said navigation data; and adjusting said
force of said probe at said second position.
15. The method of claim 14, wherein moving said probe to said
second position based on said navigation data includes registering
said probe at said registration position after moving said probe to
said position.
16. The method of claim 12 further comprising: determining a second
position to acquire sample data based on data acquired with said
probe; and adjusting said force of said probe at said second
position.
17. The method of claim 12, wherein said moving said probe to said
position based on navigation data includes adjusting a speed of
moving said probe.
18. The method of claim 12, wherein said moving said probe to a
second position based on navigation data includes adjusting a speed
of movement of said probe.
19. A system for scanning an integrated circuit comprising: a
probe; and one or more processing units configured to control:
moving said probe to a position based on navigation data; in
response to said movement of said probe, adjust a force of said
probe on the sample at said first position from a first force value
to a second force value and said force of said probe on the sample
from a third force value to a fourth force value at said second
position on the sample; and acquire sample data with said probe at
said first position on the sample.
20. The system of claim 19, wherein said one or more processing
units are further configured to control registering said probe at a
registration position.
Description
BACKGROUND
[0001] 1. Field
[0002] Embodiments of the invention relate to inspection of
nano-scale features of a sample. In particular, embodiments of the
invention relate to a system and method for inspection of
nano-scale features of a sample having regions of different
characteristics using adaptive electrical probing.
[0003] 2. Related Art
[0004] Scanning technologies are used to characterize and test
nano-scale features of a sample for measurement, topographical
mapping, testing etc., for example, for measuring features and
testing performance of integrated circuits. Scanning technology
instruments used to characterize and to test electrical performance
of integrated circuits include atomic force prober ("AFP") and
scanning electron microscopy ("SEM") based nanoprober. An AFP
system is usually used in contact mode to obtain a topographical
image of an integrated circuit. In contact mode, an AFP system uses
a probe that is scanned over the various features of the sample in
constant contact with the scanned area in order to obtain an
elevation or "relief" image of the features that make up the
sample, e.g., the integrated circuit. As the dimensions of the
devices are shrinking with technology progress and are reaching
nanometer scale, the constant force used by an AFP system to obtain
an image results in damage to the devices of the integrated circuit
that are scanned. Further, the force required to establish
sufficient electrical contact to test the performance of one or
more devices and/or components on an integrated circuit is such
that damage to the integrated circuit occurs.
[0005] SEM based nanoprobing employs an electron microscopy to
locate an area of interest. This approach may also damage devices
and components used in the integrated circuit because the
high-energy primary electrons generated by the SEM to obtain an
image of the integrated circuit penetrate into the integrated
circuit and generate undesired defects. This damage is especially
problematic for smaller devices and components that have nanometer
scale dimensions. Moreover, when the electron beam of the SEM is
scanned over a dielectric, it charges the scanned area, which may
interfere with the measurements. Thus, the use of an SEM at an area
of an integrated circuit may modify the devices of interest
obscuring the measurements and making the use of SEM based
technologies problematic.
SUMMARY
[0006] The following summary is included in order to provide a
basic understanding of some aspects and features of the invention.
This summary is not an extensive overview of the invention and as
such it is not intended to particularly identify key or critical
elements of the invention or to delineate the scope of the
invention. Its sole purpose is to present some concepts of the
invention in a simplified form as a prelude to the more detailed
description that is presented below.
[0007] According to described embodiments, adaptive (i.e.,
variable) mode of probe motion is performed during sample probing
(e.g., hopping, contact scanning, non-contact scanning, taping,
scanning with variable feedback type, speed, force, amplitude of
oscillation, etc.), which is controlled by local properties of the
sample known a priory (for example from CAD information) or/and are
assessed in real time (for example from robust high signal-to-noise
ratio of electrical or mechanical probe signal). One benefit of the
disclosed approach is data quality improvement achieved using an
optimized probe-sample interaction adjusted for and dependent on
(1) local properties of the sample and also (2) type of measurement
to be done at the particular location. Another benefit is
preventing or minimizing possible damage to the sample and probe(s)
for repeatable and precise measurements.
[0008] By utilizing disclosed embodiments, sample damage caused by
contact mode of scanning used in existing atomic force probers is
avoided. For example, if it is known a priori that a specific area
of the sample is softer, the pressure of the probe tip is reduced
when it is traversing that area. Additionally, data quality is
improved, for example, by placing the probe in full stop during
data acquisition. Also, disclosed embodiments lead to probe
lifetime improvement, for example, by having the probe fly at safe
height over areas of no-interest. Consequently, prober throughput
and data quality is optimized using high-speed non-contact motion
over areas of no-interest and slow contact (optimized) motion or
even a full stop at sites of interest (for the period of time
needed to achieve desired quality of data). In embodiment where
registration is utilized, device damage, conventionally caused by
primary electrons of SEM is avoided.
[0009] A system for analyzing a sample is described. The system for
analyzing a sample includes a probe and a controller circuit. The
controller circuit configured to control a movement of the probe to
at least a first position and a second position on the sample based
on navigation data. In response to the movement of the probe, the
controller circuit is configured to adjust a force of the probe on
the sample at the first position from a first force value to a
second force value and the force of the probe on the sample from a
third force value to a fourth force value at said second position
on the sample. And, the controller circuit is configured to acquire
sample data with the probe at the first position on the sample.
[0010] Other features and advantages of embodiments of the present
invention will be apparent from the accompanying drawings and from
the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings, which are incorporated in and
constitute a part of this specification, exemplify the embodiments
of the present invention and, together with the description, serve
to explain and illustrate principles of the invention. The drawings
are intended to illustrate major features of the exemplary
embodiments in a diagrammatic manner. The drawings are not intended
to depict every feature of actual embodiments nor relative
dimensions of the depicted elements, and are not drawn to
scale.
[0012] Embodiments of the present invention are illustrated by way
of example and not limitation in the figures of the accompanying
drawings, in which like references indicate similar elements and in
which:
[0013] FIG. 1 illustrates a block diagram of a probe-based data
collection system according to an embodiment;
[0014] FIG. 2 illustrates a flow diagram of a method for analyzing
a sample including adjusting a force of a probe according to an
embodiment;
[0015] FIG. 3 illustrates a flow diagram of a method for analyzing
a sample including registering a probe according to an
embodiment;
[0016] FIG. 4 illustrates a block diagram of a system for
controlling a probe according to an embodiment;
[0017] FIG. 5 illustrates an example of variable speed and probe
tip force during examination of a sample; and
[0018] FIG. 6 illustrates an example for navigating the probe tip
to a desired examination location without imaging the desired
location.
DETAILED DESCRIPTION
[0019] Embodiments of a probe-based data collection system with
adaptive mode of probing are described. In particular, a
probe-based data collection system is described that is configured
to have an adaptive mode of probe motion during sample probing.
Such an adaptive mode of probe motion includes varying the motion
of a probe during scanning a sample. According to embodiments, a
probe-based data collection system is configured to vary one or
more movements including, but not limited to, hopping, contact
scanning, non-contact scanning, tapping, scanning with variable
feedback, speed of movement, force of probe on sample, amplitude of
oscillation, and other types of movement. A probe-based data
collection system may be configured to vary one or more movements
based on a priori information related to local properties of the
sample, a type of measurement to be done at a particular location
of a sample and/or data acquired during sample probing.
[0020] A probe-based data collection system with adaptive mode of
probing improves quality of the data acquired because of the
ability to adjust or control the movement of a probe to optimize
probe-sample interaction. Further, according to some embodiments,
optimizing probe-sample interaction based on a priori information
related to local properties of the sample and/or a type of
measurement to be done at a particular location of a sample
achieves more reliable results more efficiently. In addition, the
adaptive mode of probing preserves a sample from damage and/or
minimizes damage of a sample and a probe because of the ability to
adjust and/or control the movement of a probe based on a prior
information related to local properties of the sample and/or a type
of measurement to be done at a particular location of a sample.
Embodiments of such a system provide repeatable and precise
measurements because of the ability to adapt the movement of a
probe to optimize for conditions of a sample.
[0021] FIG. 1 illustrates a block diagram of a probe-based data
collection system according to an embodiment. Specifically, FIG. 1
illustrates a probe-based collection system 100 including a
controller circuit 102 and a probe 104. A controller circuit 102 is
coupled with a probe 104. According to an embodiment, a controller
circuit 102 is coupled with a probe 104 through motors, actuators,
gears, sensors, and other mechanical and/or electronic devices used
to move or otherwise control a movement, a force of a probe 104,
and/or a speed of a movement using techniques including those known
in the art. A controller circuit 102 may include one or more
components that included, but are not limited to, one or more of
any of a microprocessor, a microcontroller, memory, a feedback
loop, a sensor, a detector, or other components to alone or with
other components control a movement of a probe 104 including
components such as those know in the art.
[0022] For an embodiment, a probe 104 may be a single tip or
multi-tip probe including probes such as those known in the art.
For a particular embodiment, a probe 104 is configured to scan and
sample an integrated circuit including components and/or devices
having dimensions on the order of a few nanometers or less. A probe
104 may be configured as one or more of an electrical probe, a
mechanical probe, an optical probe, a chemical probe, or other
types of probe including those known in the art. A probe 104 may be
a passive probe or an active probe. An active probe may include,
but is not limited to, a probe configured to stimulate a sample 106
using photons, electrons, and/or other particles.
[0023] According to an embodiment, a controller circuit 102 is
configured to control a movement of a probe 104 to scan and/or test
a sample 106 based on local properties know a priori. Examples of
local properties known a priori included, but are not limited to,
material composition, topography, electrical properties, etc. For
an embodiment, control of a movement of a probe 104 is based on
navigation data. Navigation data may include, but is not limited
to, computer-aided design data, sample image, sample fabrication
data, and other data used to describe areas of interest on a sample
106 including, but not limited to, connections of and/or locations
of components or devices on a sample 106. For an embodiment,
navigation data may indicate a position of a component, a device, a
circuit, an area of interest, or portion thereof on a sample 106.
For an example, a system may use navigation data, which represents
a circuit layout and indicates how components and devices in a
circuit are connected, to locate a position of a component or
device on a sample 106, such as an integrated circuit. A position
determined by navigation data, for example, may be the location of
a component or a device on a sample 106 or a portion thereof.
[0024] For an embodiment, a control circuit 102 is configured to
adjust a force of a probe 104 at a position on a sample 106. A
controller may be configured to adjust the force of the probe 104
at a position on a sample 106 in response to the movement of the
probe 104 based on navigation data. Further, a controller circuit
102 may be configured to adjust a force of a probe 104 by
controlling a movement of the probe 104 in the direction of or away
from a sample 106 using techniques including those knowing in the
art. For an embodiment, a force of a probe 104 on a sample 106 may
be increased or decreased based on navigation data. A controller
circuit 102, according to an embodiment, may control a force of a
probe 104 based on sample data acquired by the probe 104. For
example, a controller circuit 102 may be configured to increase the
force of a probe 104 on a sample 106 at a position on the sample
106 until a signal-to-noise ratio of the sample data acquired by
the probe 104 reaches a level or is within a specified range.
Sample data includes but is not limited to, measurements based on
capacitance, resistance, inductance, a mechanical probe signal, or
other properties of a sample.
[0025] A controller circuit 102, according to an embodiment, may be
configured to adjust a force of a probe 104 on a sample 106 and a
movement of the probe 104 based on navigation data and/or acquired
sample data. For example, CAD database 120, which is not associated
with the prober, but which stores CAD data design for fabrication
of the sample to be tested, can be used to obtain topographical and
design data so as to derive navigation data for the prober. In one
example, the NEXS Software Suite, available from DCG Systems, of
Fremont, Calif., is used to provide navigation data for the prober
by directly reading and cross-mapping the physical and logical
design data from database 120. The NEXS suite reads the LEF
(Library Exchange Format) and DEF (Design Exchange Format) files of
the integrated circuit ("IC") design, e.g., GDS2 for the physical
layout and Netlist for the logical circuit, and cross correlate it
to generate navigation data. This navigation data is used to vary
the pressure and/or speed of the probe tip depending on its
location over the sample.
[0026] For an embodiment, a controller circuit 102 is configured to
control a probe 104 to perform adaptive scanning. To perform
adaptive scanning, a controller circuit 102 may be configured to
control a speed of a movement of a probe 104 and/or a force of the
probe 104 on a sample 106. The controller circuit 102 is configured
to control a speed of a movement of a probe 104 and/or a force of
scanning based on acquired sample data. According to an embodiment,
a controller circuit 102 is configured to control a speed of a
movement of a probe 104 and/or a force of scanning based on a probe
signal level of acquired sample data. Once a probe signal level of
sample data is detected to be with a range or is equal to a
prescribed threshold, a controller circuit 102 determines that
position on a sample 106 to be an area of interest to acquire
sample data. Upon determining a position to acquire sample data the
control unit 102 is configured to decrease the speed of the
movement of the probe 104, including stopping the movement of the
probe 104.
[0027] Further, the controller circuit 102 is configured to
increase the force of the probe 104 based sample data. The
controller circuit 102 is configured to stop the movement of the
probe 104 based a probing signal level of sample data and increase
the force of the probe 104 until the probing signal level reaches a
prescribed level or is within a prescribed threshold range. The
controller circuit 102 is configured to increase the speed of the
probe 104 and decrease the force of a probe 104 once the probing
signal level, for example the signal-to-noise ratio of the sample
data, reaches a prescribed level or is within a prescribed
threshold range. A controller circuit 102, according to an
embodiment, is configured determine a position to acquired sample
data based on a probe signal level.
[0028] According to another embodiment, a probe-based data
collection system is configured to navigate the probe tip to the
area of interest without imaging the sample at the area of
interest. Instead, the controller circuit 102 is configured to
register the probe 104 at a registration position. The registration
position includes a position on a sample 106 outside an area of
interest for investigation with a probe 104. According to an
embodiment, a registration position may be determined using
navigation data and may be a target fabricated specifically for the
purpose of registration or simply a known feature. The controller
circuit 102 may be configured to determine a registration position
or verify a registration position using imaging tools. The imaging
tools include, but are not limited to, microscopy including SEM,
interferometry and other techniques to determine the registration
location on a sample 106. Once a controller circuit 102 moves a
probe 104 to a registration position, the controller circuit 102,
is configured to use navigation data to move a probe 104 to a
position that is an area of interest to acquire sample data on a
sample 106. That is, using navigation data, such as, e.g., the
NEXS, the relative position of the area of interest with respect to
the registration position is determined. The controller circuit 102
is configured to move the probe 104 from the registration point to
the position of interest using the relative position data. The
movement of the probe tip is performed without exerting a force on
the sample 106, but rather by keeping the probe tip at sufficient
elevation above the sample to avoid any obstacles. This eliminates
or minimizes damage to the sample 106 in the area of interest and
avoids potential collision of the probe tip with high topographical
features.
[0029] FIG. 2 illustrates a flow diagram for analyzing a sample
including adjusting a force of a probe according to an embodiment.
A first step includes moving the probe to a first position based on
navigation or imaging data as illustrated by block 202 in FIG. 2,
using techniques including those described herein. As illustrated
in block 204, the controller 102 adjusts the force of the probe at
the first position using techniques including those described
herein. Adjustment of the probe at a position may be responsive to
moving the probe to the position based on navigation data. The
method also includes acquiring sample data with the probe at the
first position using techniques including those described herein,
as illustrated in block 206.
[0030] According to one embodiment, the method may optionally
determine a second position to acquire sample data based on data
acquired with the probe, as illustrated by block 208, using
techniques including those described herein. As illustrated by
block 210, the method includes moving the probe to a second
position using techniques including those described herein. As
illustrated by block 212, the method optionally includes adjusting
the force of the probe at the second position using techniques
including those described herein.
[0031] For some embodiments, the method may adjust the force of the
probe on the sample before moving from the first position to the
second position. Other embodiments include adjusting the force of
the probe on the sample during moving the probe from the first
position to the second position using techniques including those
described herein. The method according to an embodiment optionally
includes adjusting a speed of the movement of the probe as
illustrated by block 214, using techniques including those
described herein. For some embodiments, the method includes
adjusting the speed of movement of the probe during movement from a
first position to a second position based on data acquired during
moving the probe. The method may also adjust the speed of movement
of the probe during movement from a first position to a second
position based on navigation data.
[0032] FIG. 3 illustrates a flow diagram for analyzing a sample,
including registering a probe according to an embodiment. The
method includes registering the probe at a registration position,
as illustrated by block 302, using techniques including those
described herein. Referring to block 304, the method includes
moving a probe to a first position based on navigation data using
techniques including those described herein. As illustrated by
block 306, the method adjusts the force of the probe at the first
position using techniques including those described herein.
Adjustment of the force of the probe may be in response to moving
the probe to a position based on navigation data. The method also
includes acquiring sample data with the probe at the first position
using techniques including those described herein, as illustrated
in block 308.
[0033] According to an embodiment, the method may optionally
register the probe, as illustrated by block 310, using techniques
including those described herein. The method may include
registering the probe at the same registration position as used
previously or at a new registration position after acquiring data
with the probe at a first position. Referring to block 312, the
method optionally includes adjusting the force of the probe using
techniques including those described herein. The force of the probe
may be adjusted after acquiring sample data at the first position
to decrease the force of the probe on the sample. The force of the
probe may be adjusted while the probe is moving to another
position. The force of the probe may be adjusted at a second
position, for example to acquire data at the second position.
[0034] Referring to block 314, the method according to an
embodiment includes moving the probe to the second position using
techniques including those described herein. For some embodiments,
the method may adjust the force of the probe on the sample before
moving from the first position to the second position. Embodiments
may include adjusting the force of the probe on the sample during
moving from the first position to the second position. As
illustrated by block 316 in FIG. 3, the method according to an
embodiment optionally includes adjusting a speed of the movement of
the probe using techniques including those described herein. The
method may include adjusting the speed of movement of the probe
during movement from a first position to a second position based on
data acquired during moving the probe. The method may also adjust
the speed of movement of the probe during movement from a first
position to a second position based on navigation data.
[0035] FIG. 4 illustrates an embodiment of a system 402 to control
a probe according to embodiments described. For an embodiment
system 402 may be included a controller circuit or be coupled to a
controller circuit and configured to generate one or more signals
that are used by the controller circuit to adjust the movement, the
force of a probe, and/or the speed of movement. The system 402
according to an embodiment includes one or more processing units
(CPU's) 404, one or more network or other communication interfaces
406, a memory 408, and one or more communication buses 410 for
interconnecting these components. The system 402 may optionally
include a user interface 426 comprising a display device 428 and a
keyboard 430. The system 402 may include a touchscreen 432 in
addition to or instead of a keyboard 430 and display 428. The
memory 408 may include high speed random access memory and may also
include non-volatile memory, such as one or more magnetic or
optical storage disks. The memory 408 may include mass storage that
is remotely located from CPU's 404. Moreover, memory 408, or
alternatively one or more storage devices (e.g., one or more
nonvolatile storage devices) within memory 408, includes a computer
readable storage medium. The memory 408 may store the following
elements, or a subset or superset of such elements: an operating
system 412 that includes procedures for handling various basic
system services and for performing hardware dependent tasks; a
network communication module (or instructions) 414 that is used for
connecting the system 402 to one or more circuits, such as a
controller circuit, components, or probe via the one or more
communications interfaces 406 (wired or wireless), such as a
communication port, a communication circuit, Internet, other wide
area networks, local area networks, metropolitan area networks, and
so on; a movement controller 416 for controlling a movement of a
probe; a force controller 418 for controlling a force of a probe; a
speed controller 420 for controlling a speed of a movement of a
probe; and navigation data 422.
[0036] FIG. 5 illustrates an example of variable speed and probe
tip force during examination of a sample. In FIG. 5, sample 500
consists of a substrate 505 and features 510 dispersed in substrate
505. For example, features 510 may be metal lines or vias
fabricated in silicon substrate 505. The features 510 may be fully
embedded inside the substrate 505, or may partially or fully extend
above the top surface of substrate 505. In this example, the probe
is scanned over the sample to obtain test readings from the
features 510. The scan starts at a given scan speed and tip force,
which are designed to traverse the sample relatively fast, while
exerting minimal, if any, force on the sample. As the probe starts
traversing over the first features 510, the speed of the scan is
reduced and the force is increased, so that a test signal having
good signal to noise is obtained. That is, once proper signal level
is detected, scanning speed of the probe tip is slowed down until
it reaches full stop. The force of the tip is increased and data
acquisition starts. Once proper probing signal-to-noise level is
achieved, data acquisition stops and scanning is continued at the
high speed and with low or zero force of contact. Specifically,
once the tip passes the feature 510, the speed is increased and the
force is reduced until the next feature 510 is reached and the
process repeats itself.
[0037] FIG. 6 illustrates an example for navigating the probe tip
to a desired examination location without imaging the desired
location. In FIG. 6 the device under test 600 is made out of a
substrate 605 with features 610. Assume, for example, the one
featured desired to obtain a test reading from is feature 610b.
According to one embodiment, the probe tip is navigated to a
specially prepared target 615 using any available imaging method,
e.g., using SEM. Then, using navigation database, such as, e.g.,
NEXS, the relative position of the desired feature 610b with
respect to the target is calculated and the probe tip is moved to
that location "blindly", i.e., without imaging. In other words,
according to an embodiment, the probe tip is moved to that location
such that there is no probe-sample interaction, the probe is
elevated above the sample, and an electron beam of a SEM is turned
off. According to another embodiment, if no target 615 is provided,
the probe tip can be navigated to an available feature, e.g.,
feature 610a. Then, using a navigation database, such as, e.g.,
NEXS, the relative position of the desired feature 610b with
respect to the acquired feature 610a is calculated, and the probe
tip is moved to that location "blindly," i.e., without imaging. As
in prior embodiments, the move to the calculated relative position
is performed at relatively high speed while the probe tip is
elevated above the sample, i.e., minimal or no probe tip force on
the sample 600 and minimal or no electron beam irradiation on the
sample 600. In either of the described cases, if after arriving at
the relative position no signal is obtained, small steps can be
made in various directions to attempt to acquire the desired
feature.
[0038] In the foregoing specification, specific exemplary
embodiments of the invention have been described. It will, however,
be evident that various modifications and changes may be made
thereto. The specification and drawings are, accordingly, to be
regarded in an illustrative rather than a restrictive sense.
* * * * *