U.S. patent application number 12/326521 was filed with the patent office on 2009-06-04 for apparatuses and methods for cleaning test probes.
This patent application is currently assigned to FormFactor, Inc.. Invention is credited to Gary W. Grube.
Application Number | 20090139040 12/326521 |
Document ID | / |
Family ID | 25532704 |
Filed Date | 2009-06-04 |
United States Patent
Application |
20090139040 |
Kind Code |
A1 |
Grube; Gary W. |
June 4, 2009 |
APPARATUSES AND METHODS FOR CLEANING TEST PROBES
Abstract
Apparatuses and methods for cleaning test probes used in a
semiconductor testing machine of the type having a plurality of
test probes configured to contact the surface of a semiconductor
wafer to test one or more dies formed thereon. In one embodiment,
the apparatus includes a roller-support arm and a cylindrical
roller supported by the roller-support arm. The roller has an outer
surface comprising a sticky material. Debris on the probes will
adhere to the sticky material as roller is rolled across tips of
the probes. The probes are thereby cleaned.
Inventors: |
Grube; Gary W.; (Pleasanton,
CA) |
Correspondence
Address: |
N. KENNETH BURRASTON;KIRTON & MCCONKIE
P.O. BOX 45120
SALT LAKE CITY
UT
84145-0120
US
|
Assignee: |
FormFactor, Inc.
|
Family ID: |
25532704 |
Appl. No.: |
12/326521 |
Filed: |
December 2, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11742960 |
May 1, 2007 |
7458123 |
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12326521 |
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10990640 |
Nov 16, 2004 |
7211155 |
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11742960 |
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09986751 |
Nov 9, 2001 |
6817052 |
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10990640 |
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Current U.S.
Class: |
15/3 |
Current CPC
Class: |
G01R 3/00 20130101; H01L
21/67028 20130101; B08B 7/0028 20130101 |
Class at
Publication: |
15/3 |
International
Class: |
B08B 7/00 20060101
B08B007/00 |
Claims
1-18. (canceled)
19. An apparatus for cleaning tips of probes used for testing dies
of a semiconductor wafer, comprising: a roller having a sticky
outer surface; and an arm for supporting the roller and for
engaging the roller against the tips of the probes, wherein debris
adhering to the tips of the probes is transferred to the sticky
outer surface of the roller as it is rolled along the tips of the
probes.
20. An apparatus for cleaning tips of probes used for testing dies
of a semiconductor wafer, comprising: a roller having an
electrostatic outer surface; and an arm for supporting the roller
and for engaging the roller against the tips of the probes, wherein
debris adhering to the tips of the probes is transferred to the
electrostatic outer surface of the roller as it is rolled along the
tips of the probes.
21. An apparatus for cleaning tips of probes used for testing dies
of a semiconductor wafer, comprising: a roller having an outer
surface including micro-pores, said micro-pores containing a
cleaning agent; and an arm for supporting the roller and for
engaging the roller against the tips of the probes, wherein the
tips of the probes are cleaned by said cleaning agent as the outer
surface of the roller is rolled along the tips of the probes.
22-33. (canceled)
34. An apparatus for cleaning tips of probes used for testing dies
of a semiconductor wafer, comprising: a roller having an outer
surface; and an arm for supporting the roller and for engaging the
roller against the tips of the probes, wherein the tips of the
probes are cleaned when the outer surface of the roller as is
rolled along the tips of the probes.
35. (canceled)
36. An apparatus for cleaning tips of probes used for testing dies
of a semiconductor wafer, comprising: first and second rollers for
supporting a sheet of material there-between, wherein the sheet of
material has a sticky outer surface; and a maneuvering mechanism to
maneuver the first and second rollers such that the sticky outer
surface faces the tips of the probes, whereby debris is transferred
from the tips of the probes to the sticky surface of the sheet of
material when the maneuvering mechanism moves the sheet of material
toward and against the tips of the probes, and whereby a previously
unexposed portion of the sheet of material is rolled from one of
the first and second rollers when a previously exposed portion of
the sheet of material is rolled about the other one of the first
and second rollers.
37-38. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to probe cards that
are used to perform tests on semiconductor devices. The present
invention more particularly relates to the cleaning of probe
elements that extend from such probe cards.
[0003] 2. Background Art
[0004] Individual semiconductor (integrated circuit) devices (dies)
are typically produced by creating several identical dies on a
semiconductor wafer, using known techniques of photolithography,
deposition, and the like. Generally, these processes are intended
to create a plurality of fully-functional integrated circuit
devices, prior to singulating (severing) the individual dies from
the semiconductor wafer. In practice, however, certain physical
defects in the wafer itself and certain defects in the processing
of the wafer inevitably lead to some of the dies being "good"
(fully-functional) and some of the dies being "bad"
(non-functional). It is generally desirable to be able to identify
which of the plurality of dies on a wafer are good dies prior to
their packaging, and preferably prior to their being singulated
from the wafer. To this end, a wafer "tester" or "prober" may
advantageously be employed to make a plurality of discrete pressure
connections to a like plurality of discrete connection pads (bond
or contact pads) on the dies. In this manner, the semiconductor
dies can be tested and exercised, prior to singulating the dies
from the wafer. A conventional component of a wafer tester is a
"probe card" to which a plurality of probe elements are
connected--tips of the probe elements effecting the pressure
connections to the respective pads of the semiconductor dies.
[0005] More specifically, in the typical wafer testing process, the
probe card is mounted to the prober, and probe elements (simply
referred to as "probes") extending from the probe card are brought
into contact with pads formed on the dies of the wafer. In one
process, electrical connection of the prober and the pads is
achieved by applying a predetermined pressure to the probes after
the probes have been brought into contact with the pads so that the
probes penetrate the material forming the surface of the pads and
come into low-resistance contact with the portions forming the
bodies of the pads. Such penetration of the pad surfaces produces
debris (e.g., aluminum oxide chips). In a more preferred process,
used with probes that are elastic or springy, electrical connection
of the prober and the pads can be achieved by applying a
predetermined pressure to the springy probes after the probes have
been brought in contact with the pads so that the probes are
compressed, making a solid electrical connection. When the probes
are compressed, a slight X and/or Y swipe is affected to the probes
causing a portion of the material (e.g., an aluminum oxide film)
forming the surface of the pads to be scraped off. The scraping of
the pad surfaces produces debris (e.g., aluminum oxide chips).
[0006] Foreign matter including aluminum oxide chips (i.e., debris)
adhering to the dies and/or the probes may obstruct proper
electrical connection. Various measures have been taken to prevent
problems in achieving satisfactory electrical contact.
[0007] In one conventional probe cleaning process, an abrading pad
is used to remove foreign materials adhering to end portions (e.g.,
tips) of the probes. The abrading pad can be composed of a mixture
of an elastic base material and abrasive particles. Alternatively,
the abrading pad can be composed of tungsten carbide. Foreign
materials adhering to the tips of the probes are scraped off the
tips by repeating a cleaning cycle of pressing-and-extracting the
tips of the probes against (and possibly into) the pad. The
pressing-and-extracting cleaning cycle includes moving the abrading
pad vertically (e.g., in the Z direction) against the probes, and
then vertically away from the probes.
[0008] A disadvantage of the above described conventional cleaning
process is that the portions of the base material (e.g., silicon
rubber) and/or abrasive particles (e.g., abrasive grains) may fall
or chip off the abrading pad during the pressing-and-extracting
process, thereby producing additional foreign material that may
stick to the probe tips. Further, foreign matter (previously
removed from probe) that has fallen onto the abrading pad may later
stick to the probes being cleaned. Accordingly, additional cleaning
steps may be necessary to acceptably clean the probes.
[0009] These additional steps may include blowing an organic
solvent against the probes, and then blowing dry air against the
probes. The use of such solvents is undesirable for many reasons.
For example, the blowing of an organic solvent is time consuming
and potentially messy. Additionally, blowing of dry air is time
consuming. Further, special equipment is required to blow the
solvents and the dry air.
[0010] One attempt to improve upon the conventional process
includes attaching a dust removing film to the top surface of the
abrading pad. The purpose of the dust removing film is to confine
foreign material, such as fine particles of worn base material and
fallen abrasive particles produced by the repetition of the
pressing-and-extracting cleaning cycle, so that those foreign
materials may not be discharged outside the dust removing film. For
example, this process may not be useful for cleaning elastic or
springy contact probes (often referred to as "spring contacts" or
"contact springs"), such as those disclosed in U.S. Pat. No.
6,184,053, entitled "Method of Making Microelectronic Spring
Contact Elements," U.S. Pat. No. 5,476,211, entitled "Method for
Manufacturing Electrical Contacts, Using a Sacrificial Member,"
U.S. Pat. No. 5,917,707, entitled "Flexible contact structure with
an electrically conductive shell," U.S. Pat. No. 6,110,823,
entitled "Method of modifying the thickness of a plating on a
member by creating a temperature gradient on the member,
applications for employing such a method, and structures resulting
from such a method," U.S. Pat. No. 6,255,126, entitled
"Lithographic contact elements", and PCT Publication No. WO
00/33089, entitled "Lithographic contact elements," all of which
are incorporated herein by reference.
[0011] Another attempt to improve upon the conventional probe
cleaning process includes using a polymeric covered wafer to remove
foreign materials following the pressing-and-extracting cleaning
cycle described above. More specifically, the gel pad is positioned
under the probes and then brought into contact with the probes (in
a similar manner as the pressing-and-extracting using the abrading
pad). The debris that has been loosened by the abrading pad, or
produced by the abrading pad, sticks to the gel pad and is thereby
removed from the probes. A disadvantage of this cleaning process is
that an operator must typically swap the abrading pad with the gel
pad during the cleaning process, because testing systems typically
include only one auxiliary tray for holding such pads. This is
undesirable because it prevents wafer testing from being a
completely automated process, thereby significantly reducing wafer
testing throughput. Accordingly, there is a need for improved
methods and apparatuses for cleaning probes.
BRIEF SUMMARY OF THE INVENTION
[0012] The present invention is directed to apparatuses and methods
for cleaning test probes used in a semiconductor testing machine of
the type having a plurality of test probes configured to contact
the surface of a semiconductor wafer to test one or more dies
formed thereon. The test probes being cleaned can be any type of
probe, such as tungsten needles, vertical probes, cobra probes,
L-type probes, plunger probes, spring probes, contact bump probes
formed on a membrane, etc.
[0013] In one embodiment, the apparatus of the present invention
includes a roller-support arm, and a cylindrical roller supported
by the roller-support arm. An outer surface of the roller comprises
a sticky material. Debris on the probes will adhere to the sticky
material as roller is rolled across tips of the probes.
[0014] The roller can comprise an inner cylindrical portion or
core, and the sticky material can be disposed on a peripheral
surface of the inner cylindrical portion. The roller core spins
about its longitudinal axis. Different portions of the sticky
material engage against the tips of the probes as the roller core
spins. Friction between the sticky material and the tips of the
probes causes the roller core to spin as the arm moves in the
horizontal direction.
[0015] According to an embodiment of the present invention, the
roller-support arm is pivotally connected to a wafer chuck of the
testing machine. The wafer chuck is typically used for supporting
the semiconductor wafer to be tested. An outer circumference of the
roller is below a horizontal plane of the wafer when the
roller-support arm is in a first position. This enables the wafer
chuck to be maneuvered without the roller engaging the probe tips.
When the roller-support arm is moved to a second position, at least
a portion of the outer circumference of the roller is above the
horizontal plane of the wafer and aligned with a horizontal plane
of the probe tips. When the arm is in the second position, the
outer surface of the roller engages with and rolls across the
probes tips as the wafer chuck is moved in a horizontal
direction.
[0016] According to another embodiment of the present invention,
the roller-support arm is connected to some other maneuvering
mechanism. That is, in another embodiment, the roller is connected
in no way to a wafer chuck.
[0017] In another embodiment of the present invention, the
roller-support arm extends between a pair of tracks. The sticky
material engages the tips of the probes as the arm moves
horizontally along the tracks.
[0018] In an embodiment of the present invention, the apparatus for
cleaning probes also includes a loosening means for loosening
debris from the probes. The loosened debris can then be removed
using the cylindrical roller having the sticky outer surface. More
specifically, the loosened debris will adhere to the sticky outer
surface of the roller as it is rolled across tips of the
probes.
[0019] The loosening means can include a second cylindrical roller
having an abrasive outer surface. The debris is loosened from the
probes as the outer surface of the second roller is rolled across
the tips of the probes. The loosening means can alternatively
include a block having an abrasive top surface. The debris is
loosened from the probes as the abrasive top surface of the block
is moved in a horizontal direction along the tips of the
probes.
[0020] In another embodiment the loosening means includes an
abrading pad. Debris is loosened from the probes as the abrading
pad is repeatedly moved in a vertical direction against and away
from the tips of the probes. In an alternative embodiment, the
loosening means includes a second cylindrical roller having a
bristled outer surface. Debris is loosened from the probes as the
outer surface of the second roller is rolled across the tips of the
probes.
[0021] In still another embodiment, the loosening means comprises a
block having a bristled top surface. Debris is loosened from the
probes as the bristled top surface of the block is moved in a
horizontal direction along the tips of the probes.
[0022] In another embodiment, the apparatus for cleaning of probes
includes a roller having an electrostatic outer surface. An arm for
supports the roller and engages the roller against tips of the
probes. Debris adhering to the tips of the probes is transferred to
the electrostatic outer surface of the roller as it is rolled along
the tips of the probes.
[0023] A method for cleaning test probes, according to an
embodiment of the present invention, includes the step of
maneuvering a cylindrical roller having a sticky outer surface such
that the sticky outer surface is engaged against tips of the
probes. The sticky outer surface is then rolled along the tips of
the probes to thereby transfer debris adhering to the probes to the
sticky outer surface.
[0024] Prior to engaging the sticky outer surface of the roller
against the tips of the probes, it may be beneficial to first
loosen the debris. The debris can be loosened by scraping the tips
of the probes against an abrasive surface. This can be accomplished
by maneuvering a second cylindrical roller having an abrasive outer
surface such that the abrasive outer surface is engaged against the
tips of the probes. The abrasive outer surface is then rolled along
the tips of the probes to thereby loosen the debris from the
probes.
[0025] The debris can alternatively be loosened by repeatedly
moving an abrasive surface in a vertical direction against and away
from the tips of the probes to thereby loosen the debris from the
probes.
[0026] In another embodiment, the debris is loosened by maneuvering
a second cylindrical roller having a bristled outer surface such
that the bristled outer surface is engaged against the tips of the
probes. The bristled outer surface is then rolled along the tips of
the probes to thereby loosen the debris from the probes.
[0027] Alternatively, a bristled surface can be moved in a
horizontal direction along the tips of the probes to thereby loosen
the debris from the probes.
[0028] In another embodiment, the method for cleaning test probes
includes the step of maneuvering a cylindrical roller having a
electrostatic outer surface such that the electrostatic outer
surface is engaged or nearly engaged against tips of the probes.
The electrostatic outer surface is then rolled along the tips of
the probes to thereby transfer debris adhering to the probes to the
electrostatic outer surface.
[0029] Further features and advantages of the present invention, as
well as the structure and operation of various embodiments of the
present invention, are described in detail below with reference to
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES
[0030] The accompanying drawings, which are incorporated herein and
form part of the specification, illustrate various exemplary
embodiments of the present invention and, together with the
description, further serve to explain the principles of the
invention and to enable a person skilled in the pertinent art to
make and use the invention. In the accompanying drawings:
[0031] FIG. 1 is a side view of exemplary testing environment in
which the present invention is useful;
[0032] FIGS. 2A and 2B are side views of the exemplary testing
environment of FIG. 1, with a roller embodiment of the present
invention incorporated therewith;
[0033] FIG. 3 is a perspective view of the exemplary testing
environment of FIG. 1, with a roller embodiment of the present
invention incorporated therewith;
[0034] FIGS. 4A and 4B illustrate an embodiment of the present
invention that incorporates multiple rollers;
[0035] FIG. 5 illustrates an embodiment of the present invention
where rollers are attached to a maneuvering mechanism other than a
wafer chuck;
[0036] FIGS. 6A and 6B, respectively, illustrate an abrasive block
and a bristled block, that can be used to loosen debris from
probes, according to embodiments of the present invention;
[0037] FIG. 7 illustrates an alternative embodiment for maneuvering
the rollers of the present invention;
[0038] FIG. 8 is a flow diagram useful for describing the operation
of embodiments of the present invention; and
[0039] FIG. 9 illustrates an embodiment of the present invention in
which a sticky material, that can be used to clean tips of probes,
is exposed between a pair of rollers.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The following description is of the best modes presently
contemplated for practicing the invention. This description is not
to be taken in a limiting sense but is made merely for the purpose
of describing the general principles of the invention. The scope of
the invention should be ascertained with reference to the claims.
In the description of the invention that follows, like numerals or
reference designators will be used to refer to like parts or
elements throughout.
[0041] FIG. 1 is a side view of a portion of an exemplary
probing-test system 100 that includes a probe card 102, a test head
106 (also known as a probe head), a wafer chuck 112, and a
translation mechanism 114. One of ordinary skill in the art will
appreciate that these elements have not been drawn to scale. For
example, the pitch of probes elements 104 extending from probe card
102 may be such that hundreds or thousands probe elements 104 may
extend from probe card 102.
[0042] A semiconductor wafer 110 is supported by wafer chuck 112
(also know as a wafer stage, prober stage, or wafer holding table).
Translation mechanism 114 displaces (i.e., maneuvers) wafer chuck
112 in X, Y, Z and/or .theta. directions as required. Translation
mechanism 114 includes or is attached to an actuator type device
that imparts the displacement. Wafer 110 includes a plurality of
dies (not shown) formed by photolithography, deposition, diffusion,
and the like, on its top surface. Each die (e.g., chip or device
pattern) typically has a number of electrode contact areas, e.g.,
bond or contact pads (not shown), which may be disposed at any
location and in any pattern on the surface of the die. Note that
the terms "die" and "dice" are used throughout the specification to
refer to both unsingulated die and dice, that is, a die or dice in
wafer form, and individual, singulated die or dice. Typically,
these dies are fabricated to be identical to one another. However,
as is known, flaws in either wafer 110 itself or in any of the
processes to which wafer 110 is subjected to form the dies, can
result in certain dies being non-functional, according to well
established test criteria.
[0043] Probe card 102 is shown above wafer chuck 112. A plurality
of probe elements 104 (simply referred hereafter as "probes")
extend from probe card 102.
[0044] Examples of probes 104 include tungsten needles, vertical
probes, cobra probes, L-type probes, plunger probes, and elastic or
spring probes (such as those disclosed in the patents that were
incorporated by reference above). Probes 104 make contact with the
contact areas (e.g., bond or contact pads) of the dies when wafer
110 is appropriately maneuvered by wafer chuck 112. More
specifically, end portions (e.g., tips) of probes 104 make contact
with the contact areas on the dies so that an electrical connection
is made. Accordingly, the dies of wafer 110 and the test head 106
can be electrically connected through probes 104 by moving chuck
112 upward to cause the electrode pads on the dies to contact
probes 104.
[0045] Tests (e.g., burn-in tests) of the dies can then be
performed. Probes may also contact sacrificial pads of a scribe
sheet.
[0046] When pressure is applied to probes 104, bringing probes 104
into contact with electrode pads, foreign matter chips or particles
adhering to the dies and/or probes 104 can obstruct the electrical
connections. Additionally, such foreign matter chips or particles
(referred to collectively hereafter as "debris") originally located
on the die may be transferred to probes 104. Examples of debris
that may adhere to probes 104 include: aluminum, aluminum oxide,
copper, chrome, gold, polyamide, titanium metal, titanium nitride,
tungsten, silicon, silicon oxide, phosphor, boron and any other
materials from which the dies are produced.
[0047] Sometimes, even things such as dust, hair, skin, dirt and/or
clothing particles may adhere to probes 104. Indeed, any material
that is in a semiconductor fabrication area may become attached to
the probes.
[0048] The present invention relates to improved methods and
apparatuses for removing (i.e., cleaning) such debris from probes
104.
[0049] FIGS. 2A, 2B and 3 illustrate a first embodiment of the
present invention.
[0050] As shown in FIG. 2A, a first end of a support arm 202 is
pivotally attached to wafer chuck 112. At an opposite or second end
of arm 202, a roller 204 is supported. For example, roller 204 can
be pivotally attached to arm 202 at the second end of arm 202.
Alternatively, roller 204 can slide onto a shaft or bar (not shown)
extending perpendicularly (e.g., in the Y direction, shown in FIG.
3) from the second end of arm 202. These are just of few examples
of how arm 202 can support roller 204, and thus, are not meant to
be limiting. Ball bearings can optionally be used to enable roller
204 to smoothly spin or turn as an outer surface 302 (shown in FIG.
3) of roller is in contact with and moved along tips of probes 104,
as described below.
[0051] When arm 202 is in a first position, as shown in FIG. 2A, an
outer most circumference 206 of roller 204 is below a horizontal
plane 210 of wafer 110. While arm 202 is in the first position,
translation mechanism 114 and wafer chuck 112 can be used to
maneuver wafer 110 such that wafer 110 is appropriately aligned
under probes 104 protruding from probe card 102. At that point,
translation mechanism 114 and wafer chuck 112 can maneuver wafer
110 in an upward vertical direction (e.g., the Z direction) until
probes 104 make contact with the contact areas on the dies of wafer
110 so that electrical connections are made, as shown in FIG. 2A.
Once the electrical connections are made, appropriate testing of
the dies of wafer 110 can be performed. Accordingly, neither arm
202 nor roller 204 interfere with the normal testing of the dies
when arm 202 is in the first position.
[0052] When arm 202 is moved to a second position, as shown in FIG.
2B, at least a portion of the outermost circumference 206 of roller
204 is above horizontal plane 210 of wafer 110. FIG. 3 shows a
perspective view of roller 204, when arm 202 is in the second
position. Additionally, when arm 202 is in the second position,
outermost circumference 206 of roller 204 should be aligned with a
horizontal plane 208 formed by the tips of probes 104. This will
cause an outer surface 302 (shown in FIG. 3) of roller 204 to make
contact with the tips of probes 104 when wafer chuck 112 moves in a
horizontal direction (e.g., the X direction), as is shown in FIGS.
2B and 3.
[0053] Outer surface 302 of roller 204 should be sticky enough to
remove debris from probes 104. Accordingly, roller 204 may also be
referred to herein as a "sticky roller". Preferably, outer surface
302 of roller 204 should also be stable enough that it does not
produce new debris that may stick to probes 104. In other words,
outer surface 302 of roller 204 should generally resist
transferring material to probes 104. The only material transfer
should be from probes 104 to outer surface 302 of roller 204. Outer
surface 302 of roller 204 can be made from any material or
combinations of materials that exhibit the above described desired
properties. Exemplary materials that can be used to produce outer
surface 302 include, but are not limited to: polymeric materials,
silicone, urethane and acrylic.
[0054] Outer surface 302 of roller 204 can have additional
desirable properties. For example, roller 204 is preferably
elastomeric so that it does not damage probes 104 when roller 204
is moved along the tips of probes 104.
[0055] In an alternative embodiment, rather than being sticky,
outer surface 302 of roller 204 is made from an electrostatic
material that can electrostatically remove debris from probes
104.
[0056] According to an embodiment of the present invention, rather
than being a sticky material, outer surface 302 includes a material
with micro-pores containing a cleaning agent (e.g., a basic or
acidic cleaner). Accordingly, the tips of the probes can be cleaned
by the cleaning agent as the outer surface of the roller as is
rolled along the tips of the probes.
[0057] When arm 202 is in the second position, and wafer chuck 112
moves in a horizontal direction (e.g., the X direction), outer
surface 302 of roller 204 engages (i.e., come into contact with)
the tips of probes 104, as shown in FIGS. 2B and 3. Loose debris
adhering to probes 104 (e.g., debris electrostatically stuck to
probes 104) thereby comes into contact with and sticks to outer
surface 302 of roller 204. Probes 104 are thereby cleaned. As wafer
chuck 112 continues to move in the horizontal direction, friction
between outer surface 302 of roller 204 and the tips of probes 104
causes roller 204 to turn about its pivotal connection to arm 202.
This friction between roller 204 and probes 104, which is much less
than it would be if a non-pivoting surface were scraped along the
tips of probes 104, is not enough to cause probes 102 to gouge into
the outer surface of roller 204. Thus, neither roller 204 nor
probes 104 are damaged by this cleaning procedure.
[0058] In an alternative embodiment, rather than being pivotally
connected, support arm 202 is in a fixed position that is offset
from the top of wafer chuck 112, for example, fixed in the position
shown in FIG. 2B.
[0059] A vertical (e.g., in the Z direction) contact force of, for
example, approximately 15 grams (including as little as 2 grams or
less and as much as 150 grams or more) may be desired between
roller 204 and probes 104 to ensure that debris sticks to roller
204.
[0060] Arm 202 can be maneuvered from the first position to the
second position (or from the second position to the first position)
in any appropriate manner. For example, arm 202 can be spring
loaded in the direction shown by arrow 212 to allow for cleaning
pressure control. In another example, an electric motor can be used
to maneuver arm 202. Alternatively, arm 202 can be pneumatically
driven. In still another example, hydraulics can be used to
maneuver arm 202. These examples are not meant to be limiting.
[0061] As shown in FIG. 3, more than one arm 202 can be used to
support roller 204. For example, roller 204 can be pivotally
connected at one of its longitudinal ends to first arm 202a and at
its other longitudinal end to second arm 202b. Alternatively, a bar
or shaft (not shown) can extend between arms 202a and 202b in a
perpendicular direction (e.g., the Y direction) from each of arms
202a and 202b. Roller 204 can rest about the bar or shaft.
[0062] As shown in FIG. 3, arms 202a and 202b are optionally gimbal
mounted to allow for accommodation of a non-planar relationship
between roller surface 302 and plane 208 of probe tips 104. An
arrow 306 illustrates a possible pivot direction if arms 202a and
202b were supported by an exemplary gimbal mount 304.
[0063] Roller 204 is preferably cylindrical, as can be seen in FIG.
3. Inner portions of roller 204 can be made from any number of
materials, so long as outer surface 302 of roller 204 exhibits the
desired properties. For example, an inner or core portion of roller
204 can be made of an inexpensive hard plastic material, and a
sheet of material exhibiting some or all of the above described
desired properties can be adhesively disposed on a peripheral
surface of the core material.
[0064] In one embodiment of the present invention, a plurality of
sheets of material having the desired properties are disposed one
above the other such that each sheet sticks to a sheet of a
previous layer. After a top sheet has been sufficiently covered
with debris from cleaning probes, the top sheet can be pealed off
such that a clean sheet of the previous layer becomes the top
sheet.
[0065] In another embodiment, a cylindrical sleeve is used. The
sleeve is sized so that the sleeve can be removably inserted or
slid over a core of roller 204. The sleeve has disposed about its
outer surface one or more sheets of material having the sticky
property described herein. When the sleeve is about the core of
roller 204, outer surface 302 of roller 204 is the outer surface of
the sleeve.
[0066] When necessary, roller 204 can be replaced by an operator.
Alternatively, spare rollers 204 can be stored at a location that
allows arm 202 to automatically swipe out a used roller 204 and
load in a clean roller 204. For example, spare rollers can be
stored in a rack (not shown). Arm 202 can replace a roller with
another roller from the rack when appropriate. In such an
embodiment, it is beneficial that arm 202 be an articulating arm
that can further pivot about a mid portion of the arm. This would
provide arm 202 will an increased range of motion. The rollers in
the rack can all be identical to one another. Alternatively,
different types of rollers can be stored in the rack. For example,
some rollers 204 may have an abrasive outer surface that is used to
loosen debris from tips of probes 104. Other rollers 204 may have a
sticky outer surface that is used to remove loosened debris. An
articulating arm 202 can first obtain an abrasive roller 204 from
the rack to loosen debris. Arm 202 can then replace the abrasive
roller 204 with a sticky roller to remove the loosened debris.
[0067] Similarly, when a sleeve is used, the sleeve can be replaced
by an operator by sliding the sleeve off a core of roller 204, and
sliding a new sleeve onto the core. This operation of replacing the
sleeve can alternatively be automated as just discussed above
(e.g., a rack is used to store spare sleeves that can be obtained
by an articulating arm 202).
[0068] Roller 204 of the present invention can be used to improve
upon prior cleaning processes. For example, debris on probes 104
can first be loosened by pressing-and-extracting the tips of probes
104 against an abrading pad. The abrading pad can be made from a
mixture of an elastic base material and abrasive particles.
Alternatively, the abrading pad can be made from tungsten carbide
or any other appropriate material whose hardness is substantially
similar to the hardness of the probe tips. This will enable the
abrading pad to loosen debris from tips of probes 104, while
limiting any damage to probes 104. Debris adhering to the tips of
probes 104 are scraped off or loose by repeating a cleaning cycle
of pressing-and-extracting the tips of the probes against (and
possibly into) the abrading pad. After the debris has been loosened
by the pressing-and-extracting process, roller 204 of the present
invention can be used to remove the loosened debris from the tips
of probes 104, as described above. Accordingly, the present
invention enables automated removal (i.e., without operator
intervention) of the loosened debris from probes 104.
[0069] Use of roller 204 is very advantageous even if the tips of
probes 104 are not first scraped or scrubbed by an abrading pad.
For example, use of roller 204 without first scraping tips of
probes 104 will still remove a majority of the loose debris
adhering to probes 104. Accordingly, use of roller 204 will improve
electrical contact between probes 104 and electrodes on dies of
wafer 110 even when probes 104 are not first scraped. Further, the
use of roller 204 is very practical where optical recognition
sensors, e.g., cameras (not shown), are used to make sure probes
104 are appropriately aligned with electrodes on dies of wafer 110.
Depending on the lighting techniques employed, loose debris on the
tips of probes 104 may prevent the optical sensors from recognizing
probes 104. Even without first scraping or scrubbing probes 104,
roller 204 will remove enough loose debris from probes 104 so that
the optical recognition sensors can recognize probes 104 and
accurately perform their function.
[0070] Roller 204 of the present invention can also be used to
clean contact bumps of probe membranes that are used in some wafer
testers, such as those discussed in U.S. Pat. No. 5,422,574,
entitled "Large Scale Protrusion Membrane For Semiconductor Devices
Under Test With Very High Pin Counts," which is incorporated herein
by reference.
[0071] A longitudinal length (e.g., the Y directional length) of
roller 204 is preferably longer than the area of probe card 102
from which probes 104 protrude. Stated another way, roller 204 is
preferably wide enough to clean all probes 104 of probe card 102
with one directional roll of roller 204. Alternatively, if roller
204 is not wide enough to clean all probes 104 with one roll,
multiple rolls may be necessary.
[0072] In the above described embodiments, roller 204 is described
as being moved with respect to test head 106. Alternatively, test
head 106 can be moved with respect to roller 204 to thereby engage
roller 204 against probes 104. Further, movement of roller 204
relative to test head 106 during probe cleaning can be in an X
direction and/or a Y direction. One pass or multiple passes may be
made in any pattern.
[0073] In another embodiment, a motor connected to arm 202, or
within roller 204, causes roller 204 to spin even when roller 204
is not rolled along tips of probes 104. Thus, roller 204 can be
spun against a specific portion of probe card 102 even when the
roller is not moving in an X, Y or Z direction with respect to
probe card 102.
[0074] In another embodiment, a region of outer surface 302 is a
sticky material and another region is an abrasive material that is
used to loosen debris. For example, 180 degrees of outer surface
302 is sticky, and the remaining 180 degrees of outer surface 302
is an abrasive. Of course, this example is not meant to be
limiting. This embodiment is especially useful if roller 204 is
spun by a motor.
[0075] Referring now to FIGS. 4A and 4B, a plurality (i.e., two or
more) rollers 204a and 204b can be used to clean probes 104. In
FIG. 4A, arm 202 is in a first position such that the outer
circumferences of rollers 204a and 204b are below horizontal plane
210 of wafer 110. In FIG. 4B, arm 202 is in a second position such
that at least a portion of the outer circumferences of rollers 204a
and 204b are above plane 210 and can contact probes 104 when wafer
chuck 112 is moved in the horizontal direction (e.g., the X
direction).
[0076] In one embodiment, the two rollers 204a and 204b are
essentially identical in that they are both sticky rollers.
Accordingly, following roller 204b would remove any debris possibly
missed by leading roller 204a.
[0077] In another embodiment, leading roller 204a has an abrasive
outer surface, for example, a surface made from tungsten carbide.
Such a roller is thus also referred to herein as an "abrasive
roller". In this embodiment, the abrasive roller (e.g., roller
204a) is used to loosen debris from probes 104. The abrasive roller
can be made from any other appropriate material (e.g., tungsten
carbide) whose hardness is preferably substantially similar to the
hardness of the probe tips. This will enable the abrasive roller to
loosen debris from tips of probes 104 while limiting damage to
probes 104. The following roller (e.g., roller 204b), which is a
sticky roller, is then used to remove the loosened debris from
probes 104.
[0078] Both rollers 204a and 204b can be supported by a common arm
202, as shown in FIGS. 4A and 4B. Alternatively, rollers 204a and
204b can each be supported by its own dedicated arm (as shown in
FIG. 5).
[0079] Preferably, when arm 202 is in the second position, and the
abrasive roller (e.g., roller 204a) is engaged against (i.e., in
contact with) probes 104, the abrasive roller is vertically offset
from (i.e., not above) wafer 110, as shown in FIG. 4B. This will
prevent debris loosened by the abrasive roller from possibly
falling onto wafer 110.
[0080] In one embodiment, leading roller 204a has a bristled outer
surface rather than an abrasive outer surface. The bristles of the
roller are used to loosen debris from tips of probes 104.
[0081] In another embodiment, leading roller 204a is replaced by an
abrasive block 604 (e.g., as shown in FIG. 6A) that does not spin
or roll. A top surface 606 is preferably rounded, as shown in FIG.
6A. When arm 202 is in the second position, and top surface 606 of
abrasive block 604 is engaged against probes 104, the tips of
probes 104 will scrape against top surface 606 as wafer chuck 112
is moved in a horizontal direction (e.g., the X direction), thereby
loosening debris. In still another embodiment, leading roller 204a
is replaced by a block 614 having a bristled top surface 616, as
shown in FIG. 6B. When arm 202 is in the second position, and
bristled top surface 616 of block 614 is engaged against probes
104, the bristles loosen debris from tips of probes 104 as wafer
chuck 112 is moved in a horizontal direction (e.g., the X
direction). In either embodiment, a sticky following roller (e.g.,
roller 204b) is preferably used to remove the loosened debris from
probes 104. Each supporting arm 202a and 202b is optionally
independently suspended (e.g., using independent springs) to
provide independent suspension for blocks 604 or 614.
[0082] In the above described embodiments, roller 204(s) (and
possibly blocks, e.g., 604 or 614) is/are described as being
supported by one or more arms 202 that is/are pivotally attached to
wafer chuck 112. Arm(s) 202 can alternatively be attached to some
other maneuvering mechanism 502 (other than wafer chuck 112)
capable of appropriately maneuvering roller(s) 204 (and possibly
blocks, e.g., 604 or 614). In one embodiment, arm(s) 202 are
pivotally attached to maneuvering mechanism 502 and roller(s) 204
(and possibly blocks, e.g., 604 or 614) can be engaged against
probes 104 in a manner similar to that discussed above. In another
embodiment, arm(s) 202 and maneuvering mechanism 502 are integrally
formed, rather than pivotally connected. The point is, roller(s)
204 (and possibly blocks, e.g., 604 or 614) need not be attached in
any way to wafer chuck 112.
[0083] In one embodiment, roller 204 is supported by a bar 702
(which is an implementation of arm 202) that extends between a pair
of tracks 704, as shown in FIG. 7. Tracks 704 can be attached to
opposite sides of a test chamber of the wafer testing system such
that roller 204 is at the appropriate vertical (e.g., Y) height.
When bar 702 is moved along tracks 704 in the vertical direction
706 (e.g., the X direction) by an appropriate means, outer surface
302 of roller 204 engages with and rolls across the tips of probes
104, thereby cleaning probes 104. More than one bar 702, and thus,
more than one roller 204, can be supported by tracks 704. A first
roller can be an abrasive or bristled roller 204 that is followed
by a sticky roller 204. Similarly, a non rolling abrasive or
bristled block (such as those shown in FIGS. 6A and 6B,
respectively) can be followed by a sticky roller 204. Each of track
704 can be attached to a respective side of the test chamber in
such a way that independent suspension (e.g., in the Z direction)
is provided for each end of bar 702.
[0084] FIG. 8 is a flow diagram useful for describing operation of
the various embodiments of the present invention. More
specifically, FIG. 8 can be used to describe methods for cleaning
test probes 104 configured to contact the surface of a
semiconductor wafer 110 to test one or more dies formed thereon.
According to an embodiment of the present invention, the method
includes at a step 804, maneuvering a cylindrical roller 202 having
an outer surface 302 possessing desirable properties, such that the
outer surface 302 is engaged against the tips of the probes 104. At
a next step 806, the outer surface is rolled along the tips of the
probes to thereby transfer debris adhering to the probes to the
outer surface of the roller.
[0085] As described above, a desirable property of outer surface
302 of roller 202 is that it is sticky, such that debris adhering
to probes 104 will be transferred from probes 104 to sticky outer
surface 302 as it is rolled across the tips of probes 104. Another
desired property of outer surface 302 is that it is stable enough
that there is little to no material transfer of portions of outer
surface 302 (e.g., chips or particles of outer surface 302) to
probes 104. Preferably, material transfer is generally limited to
transfer from probes 104 to outer surface 302. Other desirable
properties of a sticky outer surface 302 are discussed above.
[0086] As described above, more than one sticky roller 202 can be
used to clean probes 104. Accordingly, steps 804 and 806 can be
repeated using, for example, a second sticky roller to thereby
remove any debris not removed by a first sticky roller 202.
[0087] In another embodiment, also mentioned above, the outer
surface 302 of roller 202 is made from a material that can
electrostatically remove debris from probes 104.
[0088] In another embodiment, debris is loosening from the probes
104 at a step 802 (shown in dashed line), which is performed prior
to step 804. As explained above, debris can be loosened in a number
of different ways. For example, a roller 202 having an abrasive
outer surface (i.e., an abrasive roller 202) can be engaged against
the tips of the probes and then rolled across the tips of the
probes to thereby loosen debris. In another embodiment, a bristled
roller 202 is used in place of the abrasive roller 202. In other
embodiments, both of which are described above, a non rolling
abrasive block, or bristled block, is moved in a horizontal
direction along the tips of probes 104. In still another
embodiment, also described above, an abrading pad is repeatedly
move vertically against and away from the tips of probes 104 to
thereby loosen debris from probes 104.
[0089] Embodiments of the present invention can also be used in
various other types of probing-test systems. For example,
embodiments of the present invention can be used in a probing-test
system that has an arrangement where probe card 102 and wafer 110
are vertically oriented. In this arrangement, wafer 110 (and/or
probe card 102) are moved in a horizontal direction (e.g., the X or
Y direction) until probes 104 make contact with the contact areas
on the dies of wafer 110 so that electrical connections are made.
In another type of probing-test system, the positions of wafer 110
and probe card 102 (as shown, for example, in FIGS. 1, 2A, 2B, 4A
and 4B) are reversed.
[0090] Another embodiment of the present invention is described
with reference to FIG. 9. At least a two rollers 904a and 904b
support a sheet of material 906 having a top surface that is
sticky. Accordingly, this sheet of material 906 is also referred to
as "sticky sheet" 906. Rollers 904a and 904b are attached to a
maneuvering mechanism 902 capable of appropriately maneuvering
rollers 904a and 904b and sheet 906 that extends there-between.
More specifically, maneuvering mechanism 902 can be used to move
sticky sheet 906 underneath probe card 102, and then toward probe
card 102 until tips of probes 104 engage against sticky sheet 906.
Alternatively, probe card 102 is moved against sticky sheet 906.
Debris adhering to tips of probes 104 is thereby transferred to
sticky sheet 906. When appropriate, roller 904a and/or roller 904b
is spun (in a clockwise or counterclockwise direction) manually or
automatically (e.g., by a motor). This causes a dirty portion of
sticky sheet 906 to be rolled up (e.g., about one of rollers 902a
and 902b) and a clean portion of sticky sheet 906 to be rolled out
(e.g., from the other one of rollers 902a and 902b) and thereby
exposed.
[0091] In many embodiments described above, a roller 204 having a
sticky outer surface 302 is used to clean debris from tips of
probes 104 of a probe card 102. Alternatively, a roller 204 having
a sticky outer surface 302 can be used to clean debris from a wafer
110. This can be especially useful for cleaning debris from the
type of wafer including dies having extending spring like contacts.
More specifically, this can be especially useful for removing
debris that adheres to spring like contacts that extend from dies
of a wafer. Additionally, debris adhering to such spring like
contacts can initially be loosened using various embodiments
discussed above. In wafer cleaning embodiments, an arm 202 that
supports a sticky roller 204 (and/or an abrasive roller or other
surface) can be connected to test head 106, or some other location,
so that roller 204 can be maneuvered such that its outer surface
302 is engaged against wafer 110 (or wafer 110 can be maneuvered so
that it is engaged against outer surface 302 of roller 204).
[0092] The previous description of the preferred embodiments is
provided to enable any person skilled in the art to make or use the
present invention. While the invention has been particularly shown
and described with reference to preferred embodiments thereof, it
will be understood by those skilled in the art that various changes
in form and details may be made therein without departing from the
spirit and scope of the invention.
* * * * *