U.S. patent application number 11/327022 was filed with the patent office on 2006-07-20 for system and method of planar positioning.
Invention is credited to Gary M. Gunderson.
Application Number | 20060156569 11/327022 |
Document ID | / |
Family ID | 33029892 |
Filed Date | 2006-07-20 |
United States Patent
Application |
20060156569 |
Kind Code |
A1 |
Gunderson; Gary M. |
July 20, 2006 |
System and method of planar positioning
Abstract
A system and method of controlling the relationship between two
surfaces (such as a primary surface and a reference surface) and
correcting any deviation from the desired or ideal relationship
generally employ a plurality of actuators and flexural assemblies.
The actuators may be driven in unison to translate the primary
surface in one-dimension; the actuators may also be driven
independently, accommodating fine adjustment in pitch, roll, or
both, of the primary surface. Flexural assemblies may be
implemented to minimize lateral cross-coupling between the linear
actuators.
Inventors: |
Gunderson; Gary M.;
(Issaquah, WA) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN LLP
ATTENTION: DOCKETING DEPARTMENT
P.O BOX 10500
McLean
VA
22102
US
|
Family ID: |
33029892 |
Appl. No.: |
11/327022 |
Filed: |
January 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10801925 |
Mar 15, 2004 |
6986211 |
|
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11327022 |
Jan 6, 2006 |
|
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60454559 |
Mar 14, 2003 |
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Current U.S.
Class: |
33/645 |
Current CPC
Class: |
G01B 21/24 20130101 |
Class at
Publication: |
033/645 |
International
Class: |
G01D 21/00 20060101
G01D021/00 |
Claims
1-17. (canceled)
18. A method of controlling the relationship between surfaces in a
probe card analysis system; said method comprising: defining a
reference surface a primary surface coupling said reference surface
to a primary surface by a plurality of actuators; and, controlling
the relationship between said primary surface and said reference
surface; wherein controlling comprises driving selected ones of
said plurality of actuators, and receiving feedback from at least
three of said plurality of actuators.
19. The method of claim 18 wherein said driving includes driving
each of said plurality of actuators in unison to obtain linear
motion.
20. The method of claim 18 wherein said driving includes driving at
least one of said plurality of actuators independently to control
pitch and roll.
21. A system comprising: a platform having a primary surface
attached thereto; a frame, and a plurality of actuators attaching
said platform to said frame, said plurality of actuators operable
to provide feedback from at least three of said plurality of
actuators.
22. A metrology system comprising: a metrology frame having one or
more vertically-aligned structural members; a plurality of linear
actuators attached to said vertically-aligned structural members;
and a platform supporting a primary surface and coupled to each of
said plurality of linear actuators; wherein said plurality of
linear actuators is operative to stabilize the primary surface
relative to a reference surface.
23. The metrology system of claim 22 and further comprising a
respective flexural assembly attached to each of said plurality of
linear actuators and coupling a respective linear actuator to said
platform.
24. The metrology system of claim 23 wherein each respective
flexural assembly is operative to minimize lateral cross-coupling
between said plurality of linear actuators.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation and claims the
benefit of priority from copending U.S. Non-Provisional application
Ser. No. 10/801,925, filed Mar. 15, 2004, which is incorporated
herein by reference, in its entirety and for all purposes. U.S.
application Ser. No. 10/801,925 benefits from the priority of
now-expired U.S. Provisional Application Ser. No. 60/454,559, filed
Mar. 14, 2003, entitled "METHOD OF PLANAR POSITIONING," the
disclosure of which is also hereby incorporated herein by reference
in its entirety.
FIELD OF THE INVENTION
[0002] Aspects of the present invention relate generally to the
field of accurately placing one surface with respect to another,
and more particularly to a system and method of determining angular
deviation from parallel between two surfaces and correcting such
deviation.
BACKGROUND OF THE INVENTION
[0003] In probe card metrology applications, it is often necessary
or desirable to know the distance between a flat surface (a
"primary" or "principal" surface) and another surface to which a
probe card is attached ("reference" surface). A common approach
employed by many systems is illustrated in FIG. 1. Specifically,
FIG. 1 is a simplified diagram illustrating three views of the
structural components employed in a typical probe card metrology
system. Platforms A and B are connected or rigidly affixed by three
or more legs or vertical structural members; the platforms and the
legs form a metrology frame to which other components of the
metrology system may be attached during use. A z-stage, such as the
exemplary wedge driven z-stage, for example, is attached to
platform A. The primary surface is typically attached to the top of
this stage, while a reference ring or other structural reference
component is attached to the bottom side of platform B. Where a
ring is used, the top surface of the reference ring is typically
designated as the reference plane, and ordinarily supports a probe
card to be analyzed. Through linear horizontal translation of wedge
C, wedge D may be driven vertically, thereby translating the
primary surface relative to the reference surface. In that regard,
a linear scale or encoder (labeled "linear encoder" in FIG. 1) may
measure displacement of wedge D relative to platform A.
[0004] The lower travel limit of the z-stage may be measured
(relative to the reference surface) using a depth indicator, for
example, as illustrated in FIG. 2. Specifically, FIG. 2 is a
simplified diagram illustrating three views of the structural
components employed in a probe card metrology system adapted for
use with a depth indicator. Such a depth indicator is typically set
in a flat bar spanning the reference ring. By first zeroing or
calibrating the depth indicator flush with the flat bar, absolute
depth of the primary surface can be measured. Similarly, relocating
the depth indicator and taking measurements at three points on the
primary surface may allow parallelism to be determined. Any
non-parallelism may be removed, for example, by adjusting the
pitch, roll, or both, of either the z-stage base, platform A,
platform B, or some combination thereof. In the embodiment
illustrated in FIGS. 1 and 2, the linear encoder is attached
between wedge D and platform A; as noted briefly above, this linear
encoder may measure displacement of the wedge relative to the
platform. Since the starting height is known from the depth
indicator measurements, such measurement of the displacement may
allow the final height to be determined.
[0005] The Abbe principle dictates, however, that displacement at
points away from the linear encoder can only be inferred. Any
compression or deflection of components above the linear encoder
(such as platform B), for example, is not measured, nor is any
deflection or deformation of the reference or primary surfaces,
such as due to forces exerted by probes during overtravel.
Additionally, current technology can provide no information
regarding parallelism degradation. Since only one linear encoder is
provided, angular displacement cannot be measured absent
complicated and time-consuming relocation of the depth indicator
and recalibration. Any dimensional changes to the stiffness loop
due to temperature or strain, for example, are typically not
considered, and can influence measurement results.
[0006] In other words, a displacement of 10 .mu.m as measured by
the linear encoder in a conventional system does not guarantee
uniform, one-dimensional translation of the principal plane
relative to the probe card of that 10 .mu.m distance. In that
regard, measurement accuracy is a function of the rigidity of the
structural components of the system, the trueness of stage travel,
the stability of the metrology frame, and other factors which are
not taken into account by conventional metrology methods and
technologies.
SUMMARY
[0007] Aspects of the present invention overcome the foregoing and
other shortcomings of conventional technology, providing a system
and method of controlling the relationship between two surfaces and
correcting any deviation from the desired or ideal relationship.
Exemplary systems and methods may generally comprise a plurality of
linear actuators which may be driven in unison or
independently.
[0008] In accordance with one embodiment, for example, a method of
controlling the relationship between a primary surface and a
reference surface in a probe card analysis system may comprise:
defining the reference surface at a selected point on a metrology
frame; attaching a plurality of linear actuators to the metrology
frame; coupling a platform supporting the primary surface to each
of the plurality of linear actuators; and controlling the
relationship between the primary surface and the reference surface
utilizing the plurality of linear actuators. In some exemplary
embodiments, the coupling comprises utilizing a flexural assembly
between the platform and each of the plurality of linear
actuators.
[0009] For linear motion, the controlling comprises driving each of
the plurality of linear actuators in unison; for pitch and roll
control, for example, the controlling comprises driving one of the
plurality of linear actuators independently. In that regard,
methods are set forth herein wherein the controlling comprises
dynamically controlling an angular orientation between the primary
surface and the reference surface, and wherein the controlling
comprises dynamically compensating for changes in shape of
structural elements of the metrology system, such as a probe card
analysis system, for example. In accordance with the present
disclosure, the controlling generally comprises determining a
distance between the primary surface and the reference surface at
one or more selected locations on the platform supporting the
primary surface; such determining may comprise utilizing a linear
encoder at the one or more selected locations, and the controlling
may additionally comprise feeding distance information back to the
plurality of linear actuators.
[0010] In accordance with another exemplary embodiment, a metrology
system may comprise: a metrology frame having one or more vertical
structural members; a plurality of linear actuators attached to the
frame; and a platform supporting a primary surface; wherein the
platform is coupled to each of the plurality of linear actuators.
As with the method noted above, one system may comprise a
respective flexural assembly attached to each of the plurality of
linear actuators and coupling a respective linear actuator to the
platform. In particular, each respective flexural assembly may be
operative to minimize lateral cross-coupling between the plurality
of linear actuators.
[0011] A metrology system as set forth in detail below may further
comprise a respective linear encoder associated with each of the
plurality of linear actuators. Each respective linear encoder is
generally operative to acquire distance information representing a
distance between the primary surface and a reference surface. The
plurality of linear actuators may be driven in unison responsive to
the distance information; alternatively, one of the plurality of
linear actuators may be driven independently responsive to the
distance information.
[0012] In one embodiment, each of the plurality of linear actuators
is attached to a respective one of the one or more vertical
structural members of the frame.
[0013] The foregoing and other aspects of the disclosed embodiments
will be more fully understood through examination of the following
detailed description thereof in conjunction with the drawing
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a simplified diagram illustrating three views of
the structural components employed in a typical probe card
metrology system.
[0015] FIG. 2 is a simplified diagram illustrating three views of
the structural components employed in a probe card metrology system
adapted for use with a depth indicator.
[0016] FIG. 3 is a simplified diagram illustrating three views of
one embodiment of a metrology system constructed and operative in
accordance with the present disclosure.
[0017] FIG. 4 is a simplified diagram illustrating two views of a
flexural assembly constructed and operative in accordance with the
present disclosure.
DETAILED DESCRIPTION
[0018] As set forth in more detail below, a metrology system and
method are disclosed which enable the coplanarity of the primary
surface and the reference surface to be controlled by a plurality
of actuators; in some instances, flexural assemblies supporting the
reference surface (i.e., coupling the reference surface and the
actuators) may minimize lateral cross-coupling between the
plurality of actuators. In particular, the actuators may be used
dynamically to compensate for changes (e.g., in shape or
orientation) of the reference surface or of the metrology frame due
to environmental changes such as temperature; compensation in this
context may include compensating for relative pitch, roll, or both
between the reference surface and the primary surface. It will be
appreciated that a system and method configured and operative in
accordance with the present disclosure enable the actuators to
stabilize the positioning of the primary surface relative to the
reference surface even under dynamic loading conditions.
[0019] With specific reference now to FIGS. 3 and 4, it is noted
that FIG. 3 is a simplified diagram illustrating three views of one
embodiment of a metrology system, and FIG. 4 is a simplified
diagram illustrating two views of a flexural assembly, both of
which are constructed and operative in accordance with the present
disclosure. The system is generally indicated at reference numeral
100. In the exemplary FIG. 3 embodiment in which the metrology
frame 110 comprises three legs or vertical structural elements 111,
three linear actuators 120 may be employed; in that regard, a
respective linear actuator 120 may be mounted to, attached to,
associated with, or otherwise deployed with respect to each
respective vertical structural element 111 of a metrology frame
110.
[0020] It is noted that the following description of system 100
employing three vertical structural elements 111 is provided by way
of example only, and for the sake of clarity. While three vertical
structural elements 111 and respective actuators 120 may provide a
stable frame 110 and enable acceptable positioning characteristics
and functionality as set forth below, other embodiments of system
100 employing fewer or more vertical structural elements 111 are
also contemplated herein, and may have utility in various
applications.
[0021] Linear actuators 120 may be embodied in or comprise any of
various types of linear actuator mechanisms, including, but not
limited to, those employing or characterized by worm gears, racks
and pinions, bellows driven linear translation devices, and the
like. In the FIG. 3 embodiment, linear actuators 120 may be rigidly
attached to (or otherwise maintained in a fixed relationship with
respect to) the metrology framework in general, and vertical
structural elements 111, in particular. By way of example, and as
implemented in the FIG. 3 embodiment, linear actuators 120 may also
be supported at the top and bottom by platforms B and A,
respectively. Each respective linear actuator 120 may comprise,
incorporate, or be associated with a respective flexural assembly
121 (FIG. 4). In one exemplary implementation, a respective
flexural assembly 121 may be attached to, for example, or
incorporated into the structure of, the carriage or other
structural component of each respective linear actuator 120. A
third platform C may then be attached to, supported by, or
otherwise coupled to these flexural assemblies 121.
[0022] In that regard, and with specific reference to FIG. 4,
flexural assemblies 121 may be employed to couple linear actuators
120 to platform C on which primary surface 191 is disposed and to
minimize lateral cross-coupling between linear actuators 120. Each
respective flexural assembly 121 may generally comprise a fixed
portion 129 and a flexural portion 128. In the FIG. 4 embodiment,
fixed portion 129 may be fixedly or rigidly attached to a
respective actuator 120; alternatively, flexural assembly 121 may
be integrated into the structure of linear actuator 120 as set
forth above. Flexural portion 128 may be configured and operative
to couple platform C to linear actuator 120 through fixed portion
129, and may include one or more projections, knobs, protuberances,
or other platform attachment structures 127 for that purpose.
Platform attachment structure 127 may be inserted into or coupled
with a cooperating structure on platform C, enabling flexural
assembly 121 both to support platform C and to couple platform C to
linear actuator 120.
[0023] It will be appreciated that the structural characteristics
of flexural assembly 121 are susceptible of numerous variations
depending, for example, upon the degree of integration between
flexural assembly 121 and linear actuator 120, the structure of
platform C, the type of constraints and degrees of freedom desired
for platform C (which may be application specific), and other
factors.
[0024] As set forth above, an exemplary metrology system 100 for
use in probe card analysis operations and other applications may
generally comprise: a first platform A and a second platform B
rigidly attached by vertical structural members 111 to form a
metrology frame 110; a plurality of linear actuators 120, each of
which may be affixed or attached to (or incorporated or otherwise
integrated into the structure of) a respective vertical structural
member 111; a respective flexural assembly 121 affixed or attached
to (or incorporated or otherwise integrated into the structure of)
each respective linear actuator 120; and a third platform C coupled
to each respective linear actuator 120. In some instances, the
third platform may be supported by each respective flexural
assembly 121.
[0025] The primary surface 191 may be bonded or otherwise attached
to platform C. In some embodiments, one or more linear encoders 130
may be set into or disposed on platform C with tips protruding
upward, for example, accurately to determine a distance between
primary surface 191 and a reference surface 192 at one or more
selected locations on platform C. In the structural arrangement
depicted in FIG. 3, the bottom side of the platform B (i.e., the
surface proximal to platform C) may be designated as reference
plane 192; it will be appreciated that some other surface may be so
designated, depending upon the structural configuration of the
various components, the specific application for which system 100
may be employed, and other factors. It may be desirable to attach a
reference ring 195 or similar reference structural element to the
foregoing bottom side of platform B, since in this implementation,
the reference surface of the ring 195 (upon which a probe card may
be supported during metrology applications) may be coplanar with
reference surface 192 of platform B.
[0026] Each respective linear encoder 130 described above may be
zeroed to primary surface 191, for example, with a straightedge, a
laser, or other appropriate guide and calibration mechanism. When
platform C is translated toward platform B during operation,
encoders 130 may contact reference surface 192; accordingly, each
respective encoder 130 may read the exact distance between primary
surface 191 and reference surface 192. Feedback from encoders 130
to actuators 120 may allow for accurate positioning of primary
surface 191 with respect to reference surface 192.
[0027] Driving linear actuators 120 in unison generally causes
primary surface 191 to translate in one-dimension (i.e., the z
direction), while driving linear actuators 120 independently may
accommodate fine adjustment in pitch, roll, or both, of primary
surface 191. Flexural assemblies 121 may allow unconstrained
movement of actuators 120 over small angular displacements when
actuators 120 are driven independently, yet provide fully
constrained support of platform C and primary surface 191 disposed
or supported thereon.
[0028] Those of skill in the art will appreciate that the foregoing
structural arrangement and its equivalents may enable significant
reduction or elimination of the Abbe error. For example, since
encoders 130 directly measure the distance between primary surface
191 and reference surface 192, the only contributors to Abbe error
are those affecting the deflection of platforms B or C (or of
primary surface 191 disposed thereon) inbound of encoders 130. In
that regard, if the second platform B deforms (e.g., deflects
upward from the force of overtraveled probes), the foregoing
implementation may not account for such deformation. The same may
be true for deflections downward, or for other deformations, of
platform C or of primary surface 191. Such deflections may be
reduced or minimized, however, to an acceptable level by stiffening
those areas.
[0029] Conventional systems, even if designed to measure
parallelism shifts, cannot correct such shifts in real time. The
exemplary embodiment illustrated and described herein, however,
provides a rigid platform that is compliant for pitch and roll
shifts through the use of flexural assemblies 121. In the case of a
deflection or deformation of frame 110, for example, due to strain
or temperature effects, linear encoders 130 may identify the
effects of such a deformation and feed appropriate information back
to actuators 120; accordingly, the design allows for stable
positioning of primary surface 191 relative to reference surface
192 even under dynamic loading conditions.
[0030] Aspects of the present invention have been illustrated and
described in detail with reference to particular embodiments by way
of example only, and not by way of limitation. It will be
appreciated that various modifications and alterations may be made
to the exemplary embodiments without departing from the scope and
contemplation of the present disclosure. It is intended, therefore,
that the invention be considered as limited only by the scope of
the appended claims.
* * * * *