U.S. patent application number 13/073585 was filed with the patent office on 2011-07-14 for segmented contactor.
This patent application is currently assigned to FORMFACTOR, INC.. Invention is credited to Harry D. Cobb, Mohammad Eslamy, David V. Pedersen.
Application Number | 20110171838 13/073585 |
Document ID | / |
Family ID | 23275229 |
Filed Date | 2011-07-14 |
United States Patent
Application |
20110171838 |
Kind Code |
A1 |
Eslamy; Mohammad ; et
al. |
July 14, 2011 |
SEGMENTED CONTACTOR
Abstract
A method of fabricating a large area, multi-element contactor. A
segmented contactor is provided for testing semiconductor devices
on a wafer that comprises a plurality of contactor units mounted to
a substrate. The contactor units are formed, tested, and assembled
to a backing substrate. The contactor units may include leads
extending laterally for connection to an external instrument such
as a burn-in board. The contactor units include conductive areas
such as pads that are placed into contact with conductive terminals
on devices under test.
Inventors: |
Eslamy; Mohammad; (San Jose,
CA) ; Pedersen; David V.; (Scotts Valley, CA)
; Cobb; Harry D.; (Ripon, CA) |
Assignee: |
FORMFACTOR, INC.
Livermore
CA
|
Family ID: |
23275229 |
Appl. No.: |
13/073585 |
Filed: |
March 28, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12546924 |
Aug 25, 2009 |
|
|
|
13073585 |
|
|
|
|
11426621 |
Jun 27, 2006 |
7578057 |
|
|
12546924 |
|
|
|
|
10667689 |
Sep 22, 2003 |
7065870 |
|
|
11426621 |
|
|
|
|
10202971 |
Jul 25, 2002 |
6640415 |
|
|
10667689 |
|
|
|
|
09327116 |
Jun 7, 1999 |
7215131 |
|
|
10202971 |
|
|
|
|
Current U.S.
Class: |
439/55 |
Current CPC
Class: |
Y10T 29/49149 20150115;
Y10T 29/49204 20150115; Y10T 29/49178 20150115; Y10T 29/49211
20150115; Y10T 29/49117 20150115; Y10T 29/49171 20150115; Y10T
29/49147 20150115; G01R 3/00 20130101; Y10T 29/4921 20150115; Y10T
29/49004 20150115; G01R 31/2886 20130101 |
Class at
Publication: |
439/55 |
International
Class: |
H05K 1/11 20060101
H05K001/11 |
Claims
1-86. (canceled)
87. A segmented contactor assembly comprising: a backing substrate
comprising a surface; and contactor units each comprising
electrically conductive resilient contact elements extending from a
first side of said contactor unit and having contact tips disposed
in a sub-pattern, wherein second sides opposite said first sides of
said contactor units are coupled to said surface of said backing
substrate in particular positions such that said sub-patterns of
said contact tips form an overall pattern that corresponds to
terminals of integrated circuits to be contacted by said contact
tips.
88. The segmented contactor assembly of claim 87, wherein said
backing substrate comprises alignment structures that define said
particular positions.
89. The segmented contactor assembly of claim 88, wherein said
alignment structures extend from said surface and are disposed
between adjacent ones of said contactor units.
90. The segmented contactor assembly of claim 87 further comprising
adhesive material disposed between and adhering said second sides
of said contactor units to said surface of said backing
substrate.
91. The segmented contactor assembly of claim 87 further comprising
electrical connectors coupled to said first sides of said contactor
units.
92. The segmented contactor assembly of claim 91, wherein each of
said segmented contactor units comprises electrical connections
between said electrical connector coupled to said first side of
said contactor unit and said contact elements extending from said
first side of said contactor unit.
93. The segmented contactor assembly of claim 92, wherein said
electrical connectors are flex strip connectors.
94. The segmented contactor assembly of claim 87 further comprising
electrical connections electrically connecting adjacent ones of
said contactor units.
95. The segmented contactor assembly of claim 94, wherein said
electrical connections comprise flex strip connections.
96. The segmented contactor assembly of claim 94, wherein said
electrical connections comprise wires bonded to terminals on said
first sides of said adjacent contactor units.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to a method of
fabricating a large area multi-element contactor and, more
particularly, to a segmented contactor fabricated by mounting
multiple contactor units on a substrate.
BACKGROUND OF THE INVENTION
[0002] Semiconductor devices (such as integrated circuits) are
generally fabricated on a substrate of silicon known as a wafer. A
single wafer typically includes a large number of devices (such as
integrated circuits) that are grouped into units called dies. A
single wafer typically has a plurality of dies formed thereon. Each
die is later singulated from the wafer and further processed and
packaged. Modern technology typically uses 8-inch (200-mm) diameter
wafers, and is moving to 12-inch (300-mm) wafers. Essentially every
single device fabricated on a wafer needs to be electrically tested
by probing. Probing more than one device at a time is particularly
advantageous. Modern probing equipment can probe 32 or more
semiconductor devices at the same time. However, this is often only
a small fraction of the total number of devices on a wafer. There
has been great interest in developing a probing system that can
contact more, preferably all devices on a wafer at the same
time.
[0003] It is generally desirable to identify which of the plurality
of dies on a wafer are good prior to their packaging, and
preferably prior to their, being singulated from the wafer. To this
end, a wafer "tester" or "prober" may be employed to make a
plurality of discrete pressure connections to a like plurality of
discrete connection pads (bond pads) on the dies. In this manner,
the semiconductor dies can be tested, prior to singulating the dies
from the wafer.
[0004] Typically, semiconductor devices are exercised (burned-in
and tested) only after they have been singulated (separated) from
the wafer and have gone through another long series of "back-end"
process steps in which they are assembled into their final
"packaged" form. The added time and expense of singulating and
packaging the device goes to waste if the final "packaged" device
is found to be defective after packaging. Consequently, performing
testing or burn-in of semiconductor devices prior to their being
singulated from the wafer has been the object of prolonged
endeavor. Modern integrated circuits include many thousands of
transistor elements, for example, with many hundreds of bond pads
disposed in close proximity to one another; e.g., 4 mils (about
100.mu.) center-to-center. One common layout of the bond pads has
one or more rows of bond pads disposed close to the peripheral
edges of the die. Another common layout has is called "lead on
center" (LOC) with typically a single row of contacts along a
center line of a die. Other layouts, some irregular, are not
uncommon. The proximity and number of pads is a challenge to the
technology of probing devices.
[0005] Generally, probing devices for testing semiconductor devices
on a wafer have involved providing a single test substrate with a
plurality of contact elements for contacting corresponding pads on
the wafer being tested. To test a full wafer simultaneously
generally requires extremely complex interconnection substrates,
which may easily include tens of thousands of such contact
elements. As an example, an 8-inch wafer may contain 500 16 Mb
DRAMs, each having 60 bond pads, for a total of 30,000 connections
between the wafer under test (WUT) and the test electronics.
Earlier solutions included mating with some subset of these
connections to support limited or specialized testing. It would be
advantageous to fully connect an entire wafer.
[0006] Moreover, the fine pitch requirements of modern
semiconductor devices require extremely high tolerances to be
maintained when bringing the test substrate together with the wafer
being tested. During testing or burn-in processes, heat is produced
which causes thermal expansion of the underlying substrate
materials. Thermal expansion presents a further challenge to
connecting a test substrate to the WUT because of the extremely
tight tolerances and close spacing of pads.
[0007] To effect reliable pressure connections between contact
elements and, e.g., a semiconductor device, one must be concerned
with several parameters including, but not limited to: alignment,
probe force, overdrive, contact force, balanced contact force,
scrub, contact resistance, and planarization. A general discussion
of these parameters may be found in U.S. Pat. No. 4,837,622,
entitled "High Density Probe Card," incorporated by reference
herein, which discloses a high density epoxy ring probe card
including a unitary printed circuit board having a central opening
adapted to receive a preformed epoxy ring array of probe
elements.
[0008] A more sophisticated probe card uses resilient spring
elements to make contact with a device on a wafer. Commonly
assigned U.S. Pat. No. 5,806,181, entitled "Contact Carriers for
Populating Larger Substrates with Spring Contacts," issued Sep. 15,
1998, ('181 patent), incorporated by reference herein, discloses
such a probe card. The resilient spring elements of the '181 patent
are pre-fabricated on individual spring contact carriers
("tiles").
[0009] The resilient spring elements can alternatively be
prefabricated on the wafer itself. This configuration is known as
MOST Technology, using Microspring Contacts On Silicon. Such a
wafer is conveniently manufactured using techniques described in
commonly assigned, copending U.S. patent application Ser. No.
08/558,332, entitled "Method of Mounting Resilient Contact
Structures to Semiconductor Devices," filed Nov. 15, 1995,
incorporated by reference herein. A contactor or testing substrate
that can perform a wafer-level test or burn-in procedure on a MOST
wafer must provide corresponding conductive areas that can
precisely align with the thousands of microsprings disposed on the
wafer.
[0010] Providing a contactor that can be precisely aligned with
each of the resilient spring elements or bond pads is challenging
because of tolerances and the expansion of the underlying substrate
materials due to heat produced during the testing or burn-in
processes. Also, providing a large size contactor that has
corresponding conductive areas for each spring element on the wafer
under test can be problematic because if one of the thousands of
conductive areas is defective, the entire contactor will be deemed
defective.
[0011] Thus, what is needed is a segmented contactor that provides
separate contactor units for performing wafer-level testing or
burn-in procedures and that minimizes problems related to
tolerances and thermal expansion.
SUMMARY OF THE INVENTION
[0012] In one example of the present invention, a segmented
contactor comprises a relatively large backing substrate and at
least one relatively small contactor unit ("tile") mounted to the
backing substrate. Preferably, a plurality of contactor units is
provided. The contactor units are disposed on the front (facing the
WUT or other device) surface of the backing (support) substrate. It
is also possible (and may be preferable) that one contactor unit is
bigger than an individual device under test (DUT) and "mates" with
two or more DUTs.
[0013] The contactor units can include active semiconductor
devices, such as application-specific integrated circuits (ASICs).
For example, the ASIC can enable the number of signals being
provided to the test substrate from an outside source (e.g., a host
controller) to be minimized.
[0014] In one example of the invention, resilient contact elements
that provide the conductive pressure connections are preferably
mounted by their bases directly to the WUT (i.e., to the DUTs on
the WUT) so as to have free ends extending to a common plane above
the surface of the WUT. The segmented contactor of the present
invention preferably has a coefficient of thermal expansion which
is well-matched with that of the WUT. Alternatively, the resilient
(or spring) contact elements are mounted to the contactor units of
the segmented contactor.
[0015] An example of a method of fabricating a segmented contactor
is provided wherein a plurality of contactor units is mounted on a
backing substrate such that resilient contact elements attached to
a device on a silicon wafer can be aligned with a plurality of
conductive contact areas on each contactor unit during testing.
[0016] An exemplary method includes forming a plurality of
contactor units on a single contactor substrate, testing
electrically each of the contactor units, separating each of the
contactor units from the single contactor substrate, and assembling
the contactor units which have passed the electrical testing to
form the segmented contactor.
[0017] Preferably, the contactor units are tested before being
separated from the single contactor substrate onto which they are
formed. Alternatively, the contactor units can be tested
individually after being separated.
[0018] Also, each contactor unit preferably includes a plurality of
electrically conductive leads extending horizontally beyond an edge
of each contactor unit. The plurality of leads is preferably in the
form of a flex strip which can have a connector attached to the
leads for connecting the contactor unit to an external testing
device.
[0019] Assembling the contactor units to form the segmented
contactor can include providing an assembly fixture for holding the
contactor units during the assembly. An example of an assembly
fixture is a plate that defines holding spaces. A contactor unit is
placed into a corresponding holding space on the plate. Each
contactor unit has a first side and a second side. An adhesive or
attachment means can be provided on the second side either before
or after the contactor unit is placed within its respective holding
space on the plate. After the contactor units are placed into
respective holding spaces, a backing substrate is pressed onto the
adhesive to mount the contactor units to the backing substrate. The
backing substrate is then lifted away from the plate. The contactor
units are thus properly aligned and mounted to the backing
substrate.
[0020] The assembly fixture provided for the assembly of the
segmented contactor is preferably a flat plate that includes
grooves into which guide blocks are placed to define the holding
spaces between the guide blocks. The guide blocks provide the
proper relative alignment of each contactor unit.
[0021] The method and apparatus of an example of the present
invention also provide that the first sides of the contactor units
are substantially coplanar when mounted onto the backing
substrate.
[0022] The contactor units can be removably mounted to the backing
substrate, such that each contactor unit can be removed and
replaced upon failure or discovery of a defect in any one
particular contactor unit, for example.
[0023] An example of the device of the present invention can be
readily used for partial to full wafer-level testing of devices
which have spring contact elements mounted thereto. In use, the
segmented contactor including the backing substrate with plurality
of contactor units mounted thereto and having conductive leads
extending therefrom (the leads being connected to external testing
equipment) is urged toward the wafer under test so that the
resilient contact elements extending from the devices on the wafer
make contact with corresponding conductive areas or pads on
corresponding contactor units of the segmented contactor. The
ability of all the resilient contacts to make contact with the
plurality of contactor units, all at once, can facilitate such
processes as wafer-level burn-in or testing. However, it is not
necessary that every die on the wafer contact a corresponding
contactor unit on the segmented contactor at once.
[0024] An alternative example of the present invention includes a
segmented contactor which includes spring contact elements mounted
to the contactor units of the segmented contactor.
[0025] It will also be appreciated that a segmented contactor of
the invention may be used, after assembly, to test devices other
than a semiconductor wafer, such as another contactor or a printed
circuit board.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The present invention is 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:
[0027] FIG. 1 is a flowchart of a method performed in accordance
with the present invention;
[0028] FIG. 2 is a flowchart of another method performed in
accordance with the present invention;
[0029] FIG. 3 is a flowchart of another method performed in
accordance with the present invention;
[0030] FIG. 4 is a flowchart of another method performed in
accordance with the present invention;
[0031] FIG. 5 is a flowchart of another method performed in
accordance with the present invention;
[0032] FIG. 6 is a top plan view of a segmented contactor in
accordance with the present invention;
[0033] FIG. 7 is a front elevational view of the segmented
contactor of FIG. 6;
[0034] FIG. 8 is a front elevational view of another embodiment of
the segmented contactor of the present invention;
[0035] FIG. 9 is a front elevational view of the segmented
contactor of the present invention with a wafer including resilient
contact elements mounted on the wafer;
[0036] FIG. 10 is a front elevational view of the segmented
contactor of the present invention including resilient contact
elements mounted on contactor units of the segmented contactor;
[0037] FIG. 11 is a top plan view of a substrate on which contactor
units are formed in accordance with the present invention;
[0038] FIG. 12 is a top plan view of a contactor unit showing a
plurality of conductive areas on the top side of the contactor
unit;
[0039] FIG. 13 is a cross sectional view of the contactor unit
taken along line 13-13 of FIG. 12;
[0040] FIG. 14 is a bottom plan view of the contactor unit of FIG.
12 showing conductive areas on the bottom side of the contactor
unit;
[0041] FIG. 15 is an enlarged partial cross sectional view of the
contactor unit of FIG. 13;
[0042] FIG. 16 is a top plan view of a backing substrate of the
present invention;
[0043] FIG. 17 is a perspective view of an assembly fixture in
accordance with the present invention;
[0044] FIG. 18 is a top plan view of a plate defining grooves of
the assembly fixture;
[0045] FIG. 19 is an enlarged partial plan view of a portion of the
plate of FIG. 18;
[0046] FIG. 20 is a side elevational view of a guide block in
accordance with the present invention;
[0047] FIG. 21 is an end view of the guide block of FIG. 20;
[0048] FIG. 22 is an enlarged partial sectional view of the plate
of FIG. 18 taken along line 22-22 of FIG. 18 and showing a guide
block inserted in a groove defined in the plate of FIG. 18;
[0049] FIG. 23 is a cross sectional view taken along line 23-23 of
FIG. 18 of an assembly fixture holding contactor units and a
backing substrate in accordance with the present invention;
[0050] FIG. 24 is an enlarged partial cross sectional view of the
assembly fixture of FIG. 23; and
[0051] FIG. 25 is an enlarged partial cross sectional view of
another embodiment of an assembly fixture in accordance with the
present invention.
DETAILED DESCRIPTION
[0052] An improved large area multi-element contactor and method of
fabricating the contactor is described. In the following
description numerous specific details are set forth, such as
specific equipment and materials, etc., in order to provide a
thorough understanding of the present invention. It will be
obvious, however, to one skilled in the art that the present
invention may be practiced without these specific details. In other
instances, well-known machines and methods for making such machines
have not been described in particular detail in order to avoid
unnecessarily obscuring the present invention.
[0053] FIG. 1 illustrates a method of fabricating a segmented
contactor comprising forming a contactor unit (110), testing
electrically the contactor unit (112), and assembling the contactor
unit which has passed the electrical testing with a substrate to
form the segmented contactor (114). The method shown in FIG. 1 can
include forming a plurality of contactor units and assembling the
plurality of tested contactor units with a substrate to form the
segmented contactor. When a plurality of contactor units is formed,
each of the contactor units is preferably tested before assembling
to the substrate to form the segmented contactor. Alternatively,
the testing can be performed after assembling. In another example
of the method of fabricating a segmented contactor, the contactor
unit (or units) can be retested after assembling the contactor unit
with a substrate.
[0054] The method of FIG. 1 can include, as a precursor, forming
the contactor unit from a single contactor substrate. For example,
a tile can be formed on the single contactor substrate. The tile is
the body of the contactor unit and may include conductive areas on
at least one side. The tile may also include runners or conductive
pathways within the tile. The tile can be made from a layered
substrate, for example, with the runners disposed within or through
selected layers.
[0055] The tile can be tested electrically either before or after
being separated from the contactor substrate. Preferably, the
testing is performed before the tile is used in a testing assembly
such as a segmented contactor.
[0056] The method shown in FIG. 1 can further include testing a
device on a wafer with the segmented contactor. For example, a
wafer can include a plurality of semiconductor devices, such as
integrated circuits. The segmented contactor can be used to test
some or all of the devices on the wafer. Techniques for performing
wafer-level burn-in and test of semiconductor devices are described
in commonly assigned, copending, U.S. patent application Ser. No.
08/784,862, entitled "Wafer-Level Burn-In and Test," filed Jan. 15,
1997, incorporated by reference herein.
[0057] FIG. 2 illustrates another method of fabricating a segmented
contactor. An example of the method shown in FIG. 2 comprises
forming a plurality of contactor units on a single contactor
substrate (120), testing electrically each of the contactor units
(122), separating each of the contactor units from the single
contactor substrate (124), and assembling the contactor units which
have passed the testing to form the segmented contactor (126).
Forming the plurality of the contactor units (120), however, need
not be accomplished on a single contactor substrate. For example,
the contactor units can be formed individually.
[0058] The testing (122) of the contactor units can be performed
either before or after separating (124) each contactor unit from
the single contactor substrate. Another example of the method
includes testing (122) the contactor units after they are assembled
(126) to the substrate to form the segmented contactor. The method
can also include retesting of the contactor units once they are
assembled after having been previously tested before assembly to
form the segmented contactor.
[0059] The method of fabricating a segmented contactor for testing
multiple devices on a wafer can also include connecting at least
one of the contactor units that have been assembled on the
substrate with another one of the contactor units on the substrate.
This electrical connection can be accomplished with discrete wires
or through flexible strips which include a plurality of conductive
leads, for example. The wires or flexible strips can be soldered or
otherwise suitably connected between two or more contactor units.
The electrical connection between contactor units can also be
accomplished with connectors on corresponding edges of adjacent
contactor units. Alternatively, contactor units can be electrically
connected to each other through conductive pathways formed in the
backing substrate, which conductive pathways terminate at
conductive pads or vias on the surface of the substrate. The
conductive paths or vias can be aligned with corresponding
conductive areas on separate contactor units that are to be
electrically connected. The contactor units and the conductive
pathways of the backing substrate can thus be electrically
connected with a suitable means of connecting, such as wiring or
solder.
[0060] Connecting multiple contactor units together on a segmented
contactor can be advantageous when the segmented contactor is
designed for testing a plurality of semiconductor devices on a
single wafer. For example, although there can be a one to one
correspondence between contactor units of the segmented contactor
and devices on the wafer, each separate contactor unit can be sized
and designed to test a plurality of devices on the wafer. For
example, to test a wafer having 400 devices (DUTs), a segmented
contactor can be provided that has 8 contactor units, each of which
can accommodate 50 DUTs.
[0061] Another example of the method shown in FIG. 2 can further
include attaching a plurality of electrically conductive leads to
at least one of the plurality of contactor units. Preferably, the
leads extend beyond the edge of a corresponding contactor unit, and
a connector is provided on the leads for connecting the leads to an
external testing device, for example to a burn-in board, which in
turn may be connected to other test equipment.
[0062] FIG. 3 shows a method of assembling a segmented contactor
comprising providing an assembly fixture including a plate that
defines a contactor position (130), placing a contactor unit into
the contactor position (132), and placing a backing substrate over
the contactor unit in order to mount the contactor unit to the
backing substrate (134).
[0063] An example of the plate preferably defines a plurality of
contactor positions that are holding spaces into which can be
placed corresponding ones of a plurality of contactor units. The
holding spaces are defined in the plate such that boundaries are
defined for the individual contactor units which are placed into
the holding spaces. The assembly fixture of the example of the
method of FIG. 3 can provide a selected configuration of contactor
positions so that the contactor units can be arranged to match
corresponding dies or devices as they are laid out on a
semiconductor wafer. The assembly fixture preferably holds the
contactor units in near final position as accurately as
possible.
[0064] In one preferred implementation following the method of FIG.
3, a plate is provided in which grooves are defined. The method can
further comprise inserting guide blocks into the grooves to define
the holding spaces or boundaries between the guide blocks. The
contactor unit has a first side and a second side. The first side
preferably faces the plate when the contactor unit is placed into
the holding space.
[0065] The method can also further include providing a securing
mechanism such as an adhesive on the second side of the contactor
unit for securing or mounting the contactor unit to the backing
substrate. The method can include affixing the adhesive to the
contactor unit before the contactor unit is placed into the
assembly fixture. Alternatively, the adhesive can be affixed to the
backing substrate before the backing substrate is placed over the
contactor unit that has been inserted into the holding space of the
assembly fixture. Another alternative is to place the adhesive onto
the contactor unit after the contactor unit has been placed into
the holding space of the assembly fixture.
[0066] The method shown in FIG. 3 can further include testing of
the contactor unit. The testing can be performed before or after
placing the contactor unit into the holding space of the assembly
fixture. The method can further include retesting the contactor
unit after placing the backing substrate onto the contactor
unit.
[0067] FIG. 4 shows a method of repairing a segmented contactor
assembly comprising removing a selected mounted contactor unit from
a backing substrate of the segmented contactor assembly (140),
testing electrically a replacement contactor unit (142), and
mounting the replacement contactor unit of the backing substrate
(144). The exemplary method of FIG. 4 can be implemented in a
variety of sequences. For example, the mounted contactor unit can
be tested (142) to determine whether it is defective, for example,
prior to being removed (140) from the backing substrate.
Alternatively, a known "bad" contactor unit can be removed from the
backing substrate and replaced with a new contactor unit without
testing the bad contactor unit. The new contactor unit can be
tested (142) either before or after being mounted (144) to the
backing substrate. Yet another alternative scenario can include
repair of the contactor unit which has been removed (140) from the
backing substrate. In this case, the bad contactor unit can be
removed (140) from the backing substrate, tested (142), repaired if
necessary, and then replaced (144) onto the backing substrate. The
method illustrated in FIG. 4 can also be implemented when it is
desired to change a contactor unit that may not necessarily be
defective. For example, it may be desirable to change a particular
configuration of contactor units to accommodate a change in the
semiconductor dies or devices being tested on the wafer.
[0068] FIG. 5 shows a method of testing a plurality of devices on a
wafer comprising providing a segmented contactor (150) as
previously described. The segmented contactor provided in the
example of FIG. 5 preferably includes a tile having a first side
and a second side wherein the tile has electrically conductive
areas on the first side for contacting corresponding electrically
conductive terminals on the device or devices of the wafer under
test. The tile further preferably has a plurality of electrically
conductive leads extending beyond edge of the tile. The method
further comprises connecting the plurality of leads extending from
the tile to an external testing instrument or device, bringing the
terminals on the devices under test into contact with corresponding
conductive areas on the tiles, energizing the contactor units, and
performing a test on the devices.
[0069] An electrical testing assembly 200 such as a segmented
contactor for testing a device on a semiconductor wafer, is shown
in FIG. 6. The electrical testing assembly includes a substrate
210, a plurality of contactor units 220 assembled with the
substrate 210, and a plurality of electrically conductive areas 222
arranged on each of the contactor units 220. For simplicity of
illustration, only a few of the plurality of conductive areas 222
on the contactor units 220 are shown in FIG. 6.
[0070] The contactor units 220 preferably have each been tested
electrically prior to being assembled with the substrate 210 to
form the segmented contactor 200. Also, the conductive areas 222 on
each of the contactor units 220 are configured to be electrically
connected to the device under test (not shown).
[0071] As shown in FIG. 6, the substrate 210 is a rectangular piece
on which is mounted a plurality of generally rectangular contactor
units 220 that are arranged in two columns 224 and multiple rows
226. The arrangement or configuration of the contactor units 220 on
the substrate 210 can, however, be any desired shape, size, or
arrangement as may be required for the particular devices and wafer
being tested by the segmented contactor 200.
[0072] The electrically conductive areas 222 on each contactor unit
220 can also be arranged or configured in any desired arrangement
as necessary to match corresponding electrically conductive
terminals on the wafer that will be tested with the segmented
contactor 200. The electrically conductive areas 222 of the
contactor units 220 are preferably conductive pads, but
alternatively can include other contact elements such as solder
balls, points, and the like. Particularly preferred are extended
freestanding resilient contact elements.
[0073] As further shown in FIG. 6, the contactor units 220 can be
electrically connected to each other by wire bond connections 228
or by a flexible strip 230 that includes a plurality of conductive
leads 232.
[0074] The segmented contactor 200 shown in FIG. 6 can also include
a plurality of electrically conductive leads 240 extending from at
least one (shown in FIG. 6) and preferably from each of the
contactor units 220. The electrically conductive leads 240 are
preferably configured for connection to an external instrument (not
shown). For example, a connector 242 can be provided on the free
ends of the leads 240. The leads 240 are preferably attached to the
contactor unit 220 and correspond to selected ones of the plurality
of electrically conductive areas 222 on the contactor unit 220. The
leads 240 are preferably carried in a flexible strip 244. A
plurality of flexible strips 244 can be provided and attached to
one contactor unit 220. The flexible strip 244 can be secured to
the contactor unit 220 on either the first side 221 or the second
side (not shown) of the contactor unit 230.
[0075] FIG. 7 shows the contactor units 220 extending partially
over the edge 212 of the backing substrate 210. The extending
portion 234 of the contactor units 220 provides an area that is
available to secure a flexible strip 244 or a plurality of flexible
strips 244 to either the first 221 or second sides 223 or both
sides of the contactor unit 220.
[0076] As shown in FIG. 7, the contactor units 220 are secured to
the backing substrate 210 with a securing mechanism such as an
adhesive 250, for example. Any suitable securing means can be used
to accomplish the mounting of the contactor units 220 to the
backing substrate 210; however, an adhesive that is relatively
thin, durable and that can withstand high temperatures is
preferable. The adhesive 250 can be such that the contactor units
220 are either relatively securely or removably mounted to the
substrate 210. Alternatively, the contactor units 220 can be
mounted to the backing substrate 210 with a conductive material in
place of the adhesive 250. The conductive material can be
electrically conductive and/or thermally conductive.
[0077] FIG. 7 also shows that the first sides 221 of the contactor
units 220 are preferably coplanar with each other when mounted onto
the backing substrate 210. The coplanarity of the contactor units
220 of the segmented contactor 200 is desirable to provide a better
electrical connection between the resilient contact elements or
conductive terminals of the wafer under test over the entire
surface of the segmented contactor 200.
[0078] FIG. 8 shows a segmented contactor 200 that includes a
backing substrate 210 and contactor units 220 mounted to the
backing substrate 210. Also, an alignment mechanism 260 such as a
rail or block can be provided between contactor units 220.
Preferably, the alignment mechanism does not extend significantly
higher than the surface of the contactor units 220.
[0079] Preferably, the backing substrate 210 and the contactor
units 220 or tiles are made of silicon. It is preferable that the
backing substrate 210 and contactor units 220 have a similar
coefficient of thermal expansion relative to each other and to the
wafer under test. Providing materials having similar coefficient of
thermal expansion among all the pieces of the segmented contactor
and the wafer under test is advantageous because the heat generated
during testing procedures can cause thermal expansion of the parts.
Due to the enormous number of connections and extremely tight
tolerances that must be maintained between conductive areas and
between each terminal on the wafer, any amount of expansion due to
heat can potentially cause misalignment of the conductive areas 222
on the contactor units 220 and the conductive terminals of the
wafer under test. Therefore, if all the materials have a
substantially similar coefficient of thermal expansion, the effect
of thermal expansion on the dimensions of the parts can be
minimized. Also, because the segmented contactor 200 is preferably
comprised of a plurality of contactor units 220 rather than a
single contactor unit substrate, the effect of thermal expansion on
each contactor unit 220 is not as great as the same amount of
expansion over a longer span of material. Thus, the effect of
thermal expansion on the tolerance stack-up is minimized.
[0080] An example of a material that can be used to construct the
substrate of the contactor unit is silicon. An alternative material
that can be used is glass or a material including silicon dioxide
(SiO.sub.2). It is contemplated that the contactor units 220 can be
made of a flexible material such as UPILEX.TM. material. Also, the
contactor units 220 can potentially be made of an organic material
such as that which is commonly used as the base material of printed
circuit boards.
[0081] FIGS. 9 and 10 show examples of segmented contactors used
for testing wafers that include semiconductor devices such as
integrated circuits. Referring to FIG. 9, a segmented contactor 200
is shown attached to an external instrument 270 such as a testing
device or a burn-in board. The contactor units 220 of FIG. 9
include electrically conductive areas 222 on their top or first
sides 221. The electrically conductive areas 222 in the example of
FIG. 9 are configured as electrically conductive pads. Backing
substrate 210 is shown below the contactor units 220 in the
exemplary configuration of FIG. 9. Leads 240 are shown extending
from the contactor units 220 and connected to the external
instrument 270. As shown in FIG. 9, the leads 240 can extend from
either the first side 221 or the second side 223 of the contactor
units 220. Also, the leads 240 can be configured in groups such as
those carried in flexible strips 244. Such grouped leads 240 or
flexible strips 244 can extend from one side of the contactor units
220 but can be attached in a staggered fashion or an overlapping
fashion as shown in FIG. 9.
[0082] The wafer under test 180 in the example of FIG. 9, includes
electrically conductive terminals 182 that are resilient contact
elements 184, for example. The wafer 180 is positioned above the
segmented contactor 200 such that the resilient contact elements
184 face the first side 221 of the contactor units 220 and are
aligned with the electrically conductive areas 222 on the contactor
units 220. The wafer 180 is securely held and accurately positioned
by any of a variety of techniques. See, for example, U.S. patent
application Ser. No. 08/784,862 (generally). To accomplish the
test, the wafer 180 and the segmented contactor 200 are urged
toward each other so that the resilient contact elements 184 come
into physical contact with the electrically conductive areas 222 on
the segmented contactor 220. Preferably, the resilient contact
elements 184 are configured such that when a force is applied
perpendicularly to the wafer 180, the resilient contact elements
184 exhibit slight movement laterally such that a scrubbing action
can occur on the electrically conductive areas 222. The scrubbing
(or siping) action serves to provide a better electrical contact by
scraping away oxidation or contamination that may be accumulated on
the electrically conductive areas 222.
[0083] Once the wafer under test 180 and the segmented contactor
200 are in contact, electrical power and signals can be provided
from the burn-in board or external instrument 270 through the leads
240 to test or exercise the devices such as the integrated circuits
on the wafer 180. This testing procedure can be accomplished within
a testing chamber (not shown) so that the atmosphere and
temperature can be controlled, for example.
[0084] FIG. 10 illustrates an alternative embodiment of the
segmented contactor 300 wherein resilient contact elements 384 are
mounted to the first side 321 of the contactor units 320. The wafer
under test 190 in the example of FIG. 10 includes conductive
terminals 192 such as pads 194 that are aligned with the resilient
contact elements 384 of the contactor units 320. The wafer 190 and
the segmented contactor 300 are urged toward each other, similarly
to the configuration of FIG. 9, to accomplish testing or wafer
exercise procedures.
[0085] It will be appreciated that a segmented contactor of the
invention may be used to test devices other than a semiconductor
wafer, such as another contactor or a printed circuit board.
[0086] FIGS. 11 through 15 show an example of a contactor unit 220.
As shown in FIG. 11, a contactor substrate 215 can be provided on
which a plurality of contactor units 220 can be formed. The
contactor substrate 215 can be monolithic. The contactor units 220
preferably comprise tiles 225 that are defined or formed on the
larger contactor substrate 215. It is not necessary, however, to
form a plurality of contactor units 220 on a large contactor
substrate 215. Alternatively, contactor units 220 can be formed
individually. The contactor substrate 215 can preferably be a
semiconductor wafer or similar substrate.
[0087] FIG. 12 shows an example of a contactor unit 220 that
comprises a tile 225 having electrically conductive areas 222 on
its first side 221. For simplicity of illustration, electrically
conductive areas 222 are only partially shown on FIG. 12. The
electrically conductive areas 222 are preferably disposed over most
of the first side 221, but can be arranged in any desirable
configuration for a particular contactor unit 220.
[0088] FIG. 13 shows the contactor unit 220 including leads 240
attached to electrically conductive areas 222 on the first side 221
and the second side 223 of the tile 225. The leads 240 are shown
overlapping and including connectors 242 on the free ends of the
leads 240. As previously described, leads 240 can be carried in
flexible strips 244 or can be discrete wires. Alternatively, an
edge connector (not shown) can be provided in place of leads 240.
The edge connector can be configured to accept a jumper wire or
cable for connection to the external instrument, or the edge
connector can be directly connected to an external instrument.
[0089] FIG. 14 shows a contactor unit 220 having electrically
conducive areas 222 on its second side 223. It is not necessary,
however, to provide electrically conductive areas 222 on the second
side 223 of the contactor unit 220.
[0090] FIG. 15 shows an example of a contactor unit 220 that has
electrically conductive areas 222 on both the first side 221 and
the second side 223 of the tile 225. An example of a contactor unit
220 having conductive areas 222 on both sides can be an interposer.
The electrically conductive areas 222 on both sides of the tile 225
can be connected by conductive pathways 227 through the tile 225.
The conductive pathways 227 need not be formed vertically or
directly through the tile 225, but can extend laterally along the
length of the tile 225 so as to connect electrically conductive
areas 222 on both sides or on the same side of the tile 225 that
are not directly opposed from each other.
[0091] FIG. 15 also shows the backing substrate 210 mounted to the
contactor unit 220 with an example of conductive material 252. As
shown in FIG. 15, the conductive material 252 can comprise
individual pieces that are associated with corresponding
electrically conductive areas 222 on the surface of the contactor
unit 220. For example, the conductive material 252 can be discrete
amounts of solder.
[0092] Also shown in FIG. 15 is the backing substrate 210 having
electrically conductive runners 217 such as those found in a
multi-layer printed circuit board (PCB). The conductive material
252 provides a connection between the conductive pathways 227 and
the electrically conductive areas 222 on the contactor unit 220 to
electrically conductive areas or pathways 217 on the backing
substrate 210.
[0093] FIG. 16 shows an example of a backing substrate 210 on which
a plurality of contactor units can be mounted. The backing
substrate 210 is preferably made of the same material as the tiles
of the contactor units, however, it can alternatively made of PCB
material or glass. The example of the backing substrate shown in
FIG. 16 is generally a square shaped piece, but any suitable shape
or size can be provided for a particular application. For example,
the backing substrate can be a rectangle 8 inches wide by 8.25
inches long.
[0094] FIG. 17 shows an example of an assembly fixture 400 that can
be used to assemble a segmented contactor of the present invention.
Assembly fixture 400 includes a plate 410 that is a generally flat
piece of material having moderate thickness. The plate 410 can be
any suitable shape that will accommodate the desired or selected
configuration of contactor units 220. One example of a plate 410
defines grooves 420 that preferably have been cut into plate 410
using a wafer saw, for example. The grooves 420 are of a selected
depth and width such that they accommodate guide blocks 430. The
grooves 420 are cut into the plate 410 in a configuration such that
when the guide blocks 430 are placed into the grooves 420,
contactor positions 440 are defined within the boundaries defined
by the guide blocks 430. In the example shown in FIG. 17, contactor
positions 440 are the areas or spaces within the boundaries defined
by guide blocks 430. Contactor positions 440 can also be referred
to as holding spaces.
[0095] While FIG. 17 shows one example of a plate that defines
contactor positions, other examples can be contemplated. For
example, the plate can define holes or sockets into which a key or
protrusion on the tile or contactor unit can fit.
[0096] As further shown in FIG. 17, during assembly of the
segmented contactor, a contactor unit 220 is placed within a
corresponding contactor position 440 defined on the plate 410 of
the assembly fixture 400. The contactor unit 220 may already
include an adhesive 250 or other securing mechanism on the second
side 223 of the contactor unit 220. The contactor unit 220 is
placed into the contactor position 440 with the adhesive 250, if
applied, facing up. The backing substrate 210 can then be pressed
or placed onto the adhesive 250 in order to mount the contactor
unit 220 to the backing substrate 210.
[0097] Preferably, the adhesive is cured after the backing
substrate 210 is pressed onto the adhesive 250 of the contactor
unit 220. One way to accomplish curing is to expose the parts to
relatively higher temperatures. Also, pressure can be applied to
the backing substrate 210 in order to effect curing and proper
adhesion. An example of an adhesive is a thermal set epoxy such as,
for example, TORRAY.TM. T-61 epoxy. For example, the assembled
parts can be baked at approximately 150.degree. C. for
approximately 45 minutes while the backing substrate 210 is applied
to the contactor unit 220 under pressure of approximately 15 psi.
The pressure is then released, and the flatness of the contactor
units can be measured: This laminating assembly procedure results
in a high degree of coplanarity among the contactor units 220;
preferably less than about 0.3-0.4 mm.
[0098] FIG. 18 shows an example of a plate 410 that can be used for
an assembly fixture 400 including grooves 420 defined therein.
Grooves 420 are preferably about 4 to 5 mils wide, for example.
[0099] FIG. 19 shows an example of the grooves 420 that have been
cut into the plate 410.
[0100] FIGS. 20 and 21 show an example of a guide block 430 that
can be inserted into the grooves of the plate of FIGS. 18 and 19.
The guide blocks 430 are preferably dimensioned for a snug fit
within the grooves of the plate. The guide block 430 is preferably
made of a polyamide material such as, for example, KAPTON.TM. or
UPILEX.TM. materials.
[0101] FIG. 22 shows a guide block 430 inserted into a groove 420
of a plate 410 and extending upwardly beyond the surface 412 of the
plate 410.
[0102] FIG. 23 shows a cross section of a plate 410 having guide
blocks 430 inserted into grooves 420 that have been cut into the
plate 410. The guide blocks 430 define contactor positions 440
between adjacent guide blocks 430. The guide blocks and the
contactor positions are preferably dimensioned to take into account
tolerances and to allow a release of the contactor units from the
assembly fixture. A plurality of contactor units 220 is shown
placed between the guide blocks 430 and in the contactor positions
440. An adhesive 250 is shown placed on top of the contactor units
220. A backing substrate 210 is shown placed on top of the adhesive
250.
[0103] FIG. 24 also illustrates the plate 410 including a groove
420 into which a guide block 430 has been inserted. The guide block
430 extends above the surface 412 of the plate 410 so that
contactor units 220 can be placed between adjacent guide blocks
430. An adhesive 250 is shown placed on top of contactor units 220.
Preferably the adhesive 250 is placed on the second side 223 of the
contactor unit 220. The first side 221 of the contactor unit 220 is
preferably placed into the assembly fixture 400 facing the plate
410. A backing substrate 210 is shown on top of the adhesive
250.
[0104] FIG. 25 shows an alternate embodiment plate of an assembly
fixture 500 including a plate 510 that defines contactor positions
540. In the example of the assembly fixture 500 of FIG. 25, the
contactor positions 540 can be defined by removing material from
the plate 510 and leaving upwardly extending walls 530. In this
case, pockets 532 are formed into the plate 510 in which the
contactor units 210 are then placed. The first side 221 of the
contactor unit 220 is similarly placed facing downwardly toward the
plate 510, while the second side 223 of the contactor unit 220
faces up. An adhesive 250 can be applied to the contactor unit 220,
and a backing substrate 210 can then be pressed onto the adhesive
250 using the techniques previously described.
[0105] Thus, a segmented contactor has been described. Although the
present invention has been described with reference to specific
exemplary embodiments, it will be evident that various
modifications and changes may be made to these embodiments without
departing from the broader spirit and scope of the invention as set
forth in the claims. Accordingly, the specification and drawings
are to be regarded in an illustrative rather than a restrictive
sense.
* * * * *