U.S. patent application number 11/011420 was filed with the patent office on 2005-05-05 for method of forming an electrical contact.
Invention is credited to Akram, Salman.
Application Number | 20050093557 11/011420 |
Document ID | / |
Family ID | 23532149 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050093557 |
Kind Code |
A1 |
Akram, Salman |
May 5, 2005 |
Method of forming an electrical contact
Abstract
In a test system, a silicon interconnect is provided that can
accommodate a packaged part, such as a Land Grid Array (LGA)
package. The interconnect can be made by etching a silicon
substrate to form projections therefrom; forming an insulation or
passivation layer through deposition or growth; depositing a seed
layer over the insulation layer; depositing a metal layer over the
seed layer; and etching contact members from the seed and metal
layers using a single mask step. In a preferred embodiment, the
metal layer is coated with another metal layer that matches the
metal of the packaged part's electrical communication nodes. In one
embodiment, the contact surfaces of the silicon contact are plated
in gold and are planar. Included within the scope of the current
invention are at least one method of testing an LGA package and at
least one method of allowing electrical communication with a
packaged part.
Inventors: |
Akram, Salman; (Boise,
ID) |
Correspondence
Address: |
JAMES R. DUZAN
TRASKBRITT, PC
P. O. Box 2550
Salt Lake City
UT
84110
US
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Family ID: |
23532149 |
Appl. No.: |
11/011420 |
Filed: |
December 13, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11011420 |
Dec 13, 2004 |
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10423239 |
Apr 25, 2003 |
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6831472 |
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10423239 |
Apr 25, 2003 |
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09387987 |
Sep 1, 1999 |
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6556030 |
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Current U.S.
Class: |
438/14 |
Current CPC
Class: |
H01L 2924/01079
20130101; H01L 2224/45015 20130101; H01L 2224/48091 20130101; H01L
2924/00 20130101; H01L 2224/45099 20130101; H01L 2924/00 20130101;
H01L 2924/00014 20130101; H01L 2924/00014 20130101; H01L 2924/207
20130101; H01L 2224/45099 20130101; H01L 2924/00014 20130101; H01L
2224/85399 20130101; H01L 2924/30107 20130101; H01L 2224/48091
20130101; G01R 3/00 20130101; H01L 2224/49433 20130101; H01L 24/48
20130101; H01L 2924/00014 20130101; H01L 2924/00014 20130101; H01L
2924/14 20130101; H01L 2224/05644 20130101; H01L 2924/09701
20130101; H01L 2224/05644 20130101; H01L 2224/49431 20130101; H01L
23/13 20130101; H01L 2924/00014 20130101; H01L 2224/48465 20130101;
H01L 2924/04941 20130101; H01L 2924/01029 20130101; H01L 2924/01046
20130101; H01L 2224/48465 20130101; H01L 24/49 20130101; H01L
21/4846 20130101; H01L 2924/01078 20130101; G01R 1/0483 20130101;
H01L 2224/48091 20130101; G01R 1/0466 20130101; H01L 2924/14
20130101; H01L 2224/85399 20130101 |
Class at
Publication: |
324/754 |
International
Class: |
G01R 031/26 |
Claims
What is claimed is:
1. A method of processing a substrate comprising: masking at least
portions of the substrate using a first mask patterned after a
configuration of electrical communication nodes of an LGA package;
etching a plurality of projections from the substrate; forming at
least two metal layers over the plurality of projections; forming a
plurality of contact members, corresponding to the plurality of
projections from the at least two metal layers using solely one
additional patterned mask; and etching an unmasked portion of the
at least two metal layers.
2. The method in claim 1, wherein: the method further comprises
forming an insulation/passivation layer over at least portions of
the substrate including the plurality of projections; the forming
of at least two metal layers over the plurality of projections
comprising forming the at least two metal layers over at least
portions of the insulation/passivation layer; and the etching an
unmasked portion of the at least two metal layers further
comprising etching the at least two metal layers without etching
the insulation/passivation layer.
3. The method in claim 2, wherein the forming an
insulation/passivation layer comprises including the first mask as
at least a portion of the insulation/passivation layer.
4. A method of coating an interconnect projection on a substrate
comprising: forming a seed layer over the interconnect projection
on the substrate; forming a copper layer over the seed layer; and
forming a gold layer directly over the copper layer, the gold layer
including a flat top.
5. The method in claim 4, wherein the forming a copper layer
comprises electroplating copper onto the seed layer.
6. The method in claim 4, wherein the forming a copper layer
comprises sputtering copper onto the seed layer.
7. The method in claim 6, wherein the forming a seed layer further
comprises sputtering tungsten over the interconnect projection.
8. A process method for an electrical contact for a die having an
electrical communication node, the electrical communication node
having a known shape formed from a known material, the method
comprising: forming a support structure for forming a contact for
the known shape of the electrical communication node of the die;
forming a portion of the support structure to have a shape for
contacting a portion of the electrical communication node of the
die; forming an aluminum layer over a portion of the support
structure formed to have a shape for contacting a portion of the
electrical communication node of the die; forming a zinc layer; and
forming a contact surface, the contact surface of the same material
as the material of the electrical communication node of the
die.
9. The method in claim 8, further comprising forming the zinc layer
after forming an aluminum layer and before forming a contact
surface.
10. The method in claim 9, further comprising forming a nickel
layer after forming a zinc layer and before the forming a contact
surface.
11. The method in claim 10, wherein forming an aluminum layer
comprises sputtering aluminum over the support structure.
12. The method in claim 11, wherein forming a zinc layer comprises
exposing the aluminum layer to a zincate solution.
13. The method in claim 12, wherein forming a nickel layer
comprises exposing the zinc layer to a nickel solution.
14. The method in claim 13, wherein the forming a contact surface
comprises providing a selection of one of a gold surface and a
palladium surface.
15. The method in claim 13, wherein the forming a contact surface
comprises forming a contact surface essentially matching the shape
of the electrical communication node of the die.
16. The method in claim 15, wherein forming a contact surface
comprises forming an essentially flat contact surface.
17. A substrate processing method comprising: masking at least
portions of a substrate using a first mask having a pattern for
forming electrical communication nodes for an LGA package; etching
a plurality of projections from the substrate; forming at least two
metal layers over the plurality of projections; forming a plurality
of contact members corresponding to the plurality of projections
from the at least two metal layers using a second mask; and etching
an unmasked portion of the at least two metal layers.
18. The method in claim 17, wherein: the method further comprises
forming an insulation/passivation layer over at least portions of
the substrate including the plurality of projections; the forming
of at least two metal layers over the plurality of projections
comprising forming the at least two metal layers over at least
portions of the insulation/passivation layer; and the etching an
unmasked portion of the at least two metal layers further
comprising etching the at least two metal layers without etching
the insulation/passivation layer.
19. The method in claim 18, wherein the forming an
insulation/passivation layer comprises including the first mask as
at least a portion of the insulation/passivation layer.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/423,239, filed Apr. 25, 2003, now U.S. Pat. No. 6,831,472,
issued Dec. 14, 2004, which is a divisional of application Ser. No.
09/387,987, filed Sep. 1, 1999, now U.S. Pat. No. 6,556,030, issued
Apr. 29, 2003.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates generally to a device and
method for providing electrical communication with a packaged
integrated circuit device. More specifically, the present invention
concerns a silicon interconnect and a method for fabricating a
silicon interconnect for a Land Grid Array package.
[0004] 2. State of the Art
[0005] In testing a semiconductor die, it is often useful to
establish an electrical connection between the test equipment and
the circuitry of a die. Testing may be performed on an unpackaged
die that has been singulated from a semiconductor wafer, on a
section of dice that is still part of the wafer, or on all of the
dice on a wafer. In order to test a singular die, a partial wafer,
or a full wafer, it may be beneficial to house the die structure in
a temporary package such as a socket. The socket is configured to
attach to a board which, in turn, is coupled to the test circuitry.
One way to establish electrical communication between the die's
bond pads and the socket is through the use of an interconnect. The
interconnect is often made of silicon or some other etchable
material, which may be coated with a conductive material to aid in
electrical communication. The use of etchable materials such as
silicon allows for the use of semiconductor fabrication techniques
to form electrical contact members from a silicon substrate. Such
techniques enable formation of electrical contact members at a
pitch matching that of the die's bond pads. Silicon interconnects
accommodate dice in other ways as well. For example, it is
noteworthy that a die's bond pads are often made of aluminum. Given
the temperatures associated with certain tests, it is important
that the outermost coating of the interconnect be of some material
other than aluminum; otherwise, the interconnect will permanently
weld to the die during testing. Thus, it is taught in the art to
coat a silicon interconnect with a material that is different from
the material it will temporarily contact. Moreover, aluminum
oxidizes relatively easily and, as a result, a die's aluminum bond
pads are often covered with a thin film of nonconductive aluminum
oxide. An interconnect must penetrate this oxide to reach the
conductive aluminum of the bond pad in order to establish good
electrical contact. To achieve this, it is taught to include
fabrication steps that provide penetrating elements, such as
blades, on the top of each interconnect contact. Steps that provide
such elements are addressed in more detail in U.S. Pat. Nos.
5,326,428 and 5,419,807. These elements, while considered to be an
improvement over flat contacts to a die's bond pads (see, for
example, U.S. Pat. No. 5,607,818), necessarily cause damage to the
bond pads and may shorten their useful life. Moreover, there is a
risk that the elements will break off of the interconnect's
contact.
[0006] These fabrication steps result in an interconnect that is
configured to be inserted into the socket, receive a die's bond
pads therein, and connect them to electrical terminals of the
socket. Given the material of the interconnect and its placement in
the package, such an interconnect is often referred to as a
"silicon insert." The die is placed in the socket so that the die's
bond pads are aligned with the interconnect's contact members; the
socket is attached to the board; the board is coupled to the test
circuitry; and testing commences.
[0007] After testing, the die may be removed from the socket. The
interconnect may be removed as well, perhaps to be replaced by
another interconnect having a different arrangement of contact
members for another die. Dice that do not pass testing may be
discarded, while those that do pass may undergo further processing,
such as a bum-in process, and packaging.
[0008] Concerning the packaging of a die, there are varying degrees
and types of packaging that a die may undergo. For example, a die
may be configured as a "flip chip," wherein conductive material
such as solder balls is attached directly to the bond pads or
electrical traces formed in the surface of the die; the die is then
"flipped," or mounted face down, so that the solder balls may
connect with contact members of another device, such as a carrier
substrate. Another example is a "chip scale package," which
includes a die along with one or more minimal package elements,
such as an encapsulating material in the form of a thin protective
coating formed of glass or other materials. Such a coating may be
bonded at least to the active surface of the die and edges thereof
and sometimes to the sides and back side of the die as well. In
addition, solder balls may be attached to electrical traces in the
surface of the die or directly to the die's bond pads through
openings in the encapsulating material in order to provide the
aforementioned "flip chip" configuration. A Ball Grid Array (BGA)
package serves as yet another example that involves even more
packaging: the die is wire bonded to a substrate and encapsulated,
and an array of solder balls on one side of the substrate is bonded
to electrical traces leading through the substrate to the die.
Alternatively, the package may comprise a Land Grid Array (LGA),
which is similar to a BGA, except that flat contact pads--or
lands--serve as external electrical communication nodes on the
substrate instead of solder balls. Similarly, if an array of pins
serves as the external electrical communication nodes for the
package, such a package is known as a Pin Grid Array (PGA).
[0009] Other types of packages known in the art include dual
in-line packages (DIP), wherein the leads extending from the
package define two lines. Zigzag in-line packages (ZIP) have a line
of leads, wherein every other lead extends into one of two planes
(see U.S. Pat. No. 4,790,779). Leadless chip carrier (LCC) packages
use sockets or conductive pads in place of leads and are configured
to directly connect to a circuit board (see U.S. Pat. No.
5,375,320). Small outline packages (SOP) and thin small outline
packages (TSOP) use a plastic ring around the package to contact
the far end of the leads extending straight from two opposing edges
of the package. The plastic ring can be removed after testing, and
the leads may then be bent as needed. Quad flat pack (QFP) packages
are similar to the SOPs in that a plastic ring surrounds the
package and contacts the far end of the leads. In the QFP, however,
the leads extend from four sides of the package (see also FIG. 6 of
U.S. Pat. No. 5,903,443). Small outline j-bend (SOJ) packages use
leads bent in a "j" shape, which allows for resiliency once the
packages are attached to a circuit board.
[0010] As for testing these packaged dice, current methods of doing
so also have problems. For example, testing LGA packages involves
contacting the lands of the LGA with pins that have been stamped
from a metal sheet. Each pin is placed within a hole that is one of
an array of holes found within a plastic mold. This mold keeps an
array of pins aligned with the package's array of lands. Test
equipment may then access the lands through these pins.
Unfortunately, there are several problems with using such pins.
First, as the overall size of packages becomes smaller, the area of
the lands decreases, as does the space between the lands. It is
difficult for the stamped pins/plastic mold formation process to
match the rate at which die packages are shrinking. In addition,
using such pins often results in high inductance, thereby
interfering with testing. Moreover, as with the silicon
interconnects and the die bond pads, there exists the risk of a
scrubbing action of the pins against the lands, which could damage
both the pins and the lands.
[0011] Thus, there is a need in the art for improved testing
structures and methods, including a need for improved temporary
packaging for testing dice that have already undergone some degree
of packaging. Included within this need is the desire to establish
electrical communication between an interconnect and a related
packaged die. Further, there is a more general need for improved
electrical communication with a die, whether such communication is
with a die as part of a permanently packaged part or a temporarily
packaged part, or whether such communication is for test or
non-test purposes.
BRIEF SUMMARY OF THE INVENTION
[0012] Accordingly, the current invention provides an electrical
connector and a method of forming it. Many exemplary embodiments of
the current invention apply semiconductor fabrication techniques to
an interconnect for a packaged part while reducing if not
eliminating the problems attendant with prior silicon interconnects
and prior interconnects for packaged parts. Such embodiments
involve forming silicon interconnects having a contact surface that
is complementary to the electrical contact surface of the packaged
part to be tested. In some embodiments, such as those configured to
contact LGA packages, the interconnect's contact surface is planar
and parallel to the packaged part's contact surface. In more
general embodiments, the interconnect's contacts are non-invasive
or non-penetrating with respect to the electrical contacts of the
packaged part. Some of these embodiments may be described as
defining "male-female" configurations between the interconnect's
contact surface and that of the packaged part.
[0013] An exemplary method of fabricating interconnects such as the
ones described above involve defining a projection or protrusion
from a substrate; providing a passivation/insulation layer over the
substrate, including the projection; providing at least one seed
layer over the passivation/insulation layer; providing at least one
metal layer over the seed layer; and simultaneously patterning the
metal layer and seed layer. In a preferred embodiment, the metal
layer of the interconnect is the same metal as the packaged part's
contact points.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0014] FIG. 1 depicts two in-process electrical connectors having
undergone processes known in the prior art.
[0015] FIG. 2 illustrates two in-process electrical connectors
having undergone a step included within an exemplary embodiment of
the current invention.
[0016] FIG. 3 illustrates two in-process electrical connectors
having undergone another step included within an exemplary
embodiment of the current invention.
[0017] FIG. 4 illustrates two in-process electrical connectors
having undergone yet another step included within an exemplary
embodiment of the current invention, as well as a cross-sectional
view of a first exemplary apparatus embodiment of the current
invention.
[0018] FIG. 5 illustrates a top-down view of the first exemplary
apparatus embodiment of the current invention.
[0019] FIG. 6 illustrates a top-down view of a second exemplary
apparatus embodiment of the current invention.
[0020] FIG. 7 illustrates a top-down view of a third exemplary
apparatus embodiment of the current invention.
[0021] FIG. 8 illustrates a cross-sectional view of a fourth
exemplary apparatus embodiment of the current invention.
[0022] FIG. 9 illustrates a cross-sectional view of a fifth
exemplary apparatus embodiment of the current invention.
[0023] FIG. 10 illustrates a cross-sectional view of a sixth
exemplary apparatus embodiment of the current invention.
[0024] FIG. 11 shows an exemplary embodiment concerning the use of
an electrical connector.
[0025] FIGS. 12A-E disclose an exemplary embodiment of the current
invention.
[0026] FIGS. 13A-E disclose an alternative exemplary embodiment of
the current invention.
[0027] FIG. 14 shows another exemplary embodiment of the current
invention.
[0028] FIG. 15 shows yet another exemplary embodiment of the
current invention.
[0029] FIG. 16 shows still another exemplary embodiment of the
current invention.
[0030] FIG. 17 depicts one more exemplary embodiment of the current
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0031] FIG. 1 depicts two in-process contact members--ones in the
process of being formed--having undergone steps known in the art.
For purposes of explanation, it is assumed that these contact
members are part of an in-process interconnect device 18, although
the current invention includes within its scope an electrical
contact and methods of forming an electrical contact in other
contexts. A substrate 20 has been provided. In the current
application, the term "substrate" or "semiconductor substrate" will
be understood to mean any construction comprising semiconductor
material, including but not limited to bulk semiconductive
materials such as a semiconductor wafer (either alone or in
assemblies comprising other materials thereon), and semiconductive
material layers (either alone or in assemblies comprising other
materials). Further, the term "substrate" also refers to any
supporting structure including, but not limited to, the
semiconductive substrates described above. Preferably, the
substrate 20 comprises an etchable material such as silicon,
germanium, silicon-on-glass or silicon-on-sapphire. The substrate
20 can also be formed of ceramic. In addition, the substrate 20 can
be formed of a photosensitive glass, or glass-ceramic material,
such as "FOTOFORM" manufactured by Coming.
[0032] FIG. 1 further indicates that a patterned mask layer, such
as a nitride layer, was provided over the substrate 20, and an
anisotropic etch was subsequently performed, thereby forming two
projections 22 from the remaining substrate 20. This etch can be a
wet etch, wherein the substrate is exposed to a mixture of
KOH:H.sub.2O (40% KOH by volume) at about 70 C. A representative
height of projections 22 can range from 25-100 microns, and a
representative width on each side can be from 40-100 microns.
Moreover, FIG. 1 illustrates that a passivation/insulation layer 24
is provided over the projections 22 and the remaining substrate 20.
This layer 24 can be an oxide, either grown or deposited, or some
other dielectric material, such as Si.sub.3N.sub.4 or polyimide.
Growing an oxide, for example, might involve exposing the
in-process interconnect device 18 to an O.sub.2/H.sub.2O
environment at a temperature of 900 C or greater. Depositing oxide
can be accomplished through chemical vapor deposition (CVD) using
tetraethylorthosilane (TEOS) at a temperature of about 400 C.
Alternatively, a layer of Si.sub.3N.sub.4 may be provided through
CVD. An exemplary thickness of this layer may range from 500
angstroms to 2 microns.
[0033] A subsequent exemplary step within the scope of the current
invention is illustrated in FIG. 2. That figure indicates that at
least one seed layer 26 is deposited over the
passivation/insulation layer 24. This seed layer 26 can be blanket
deposited so that it conforms to the substrate 20 including its
non-planar topography, thereby covering each projection 22,
including the sidewalls and top thereof. This seed layer 26
provides nucleation sites for any subsequently deposited layer (in
this exemplary embodiment, there will be a subsequently deposited
metal layer). Moreover, this layer may also serve to help the
subsequently deposited layer adhere to the in-process device as
well as act as a barrier layer--preventing material from migrating
from one side of the layer to the other. Exemplary materials for
this seed layer 26 include tungsten, aluminum, copper, titanium
nitride, and combinations thereof. General methods of depositing
these seed layers are known in the art. For example, a tungsten
layer may be sputtered onto the passivation/insulation layer 24
using a tungsten target and an argon source, and having a substrate
temperature of about 250.degree. C., an ambient temperature of
about 200.degree. C., and a low pressure, such as one ranging from
0.01 millitorr to 1.times.10.sup.-6 torr. Layers of the other
materials may be sputtered under similar conditions with the
appropriate target material. Sputtering titanium nitride may be
accomplished using a titanium target and introducing nitrogen gas
along with or after the argon source gas. As an exemplary range,
this seed layer 26 can be 200 to 1000 angstroms thick.
[0034] As mentioned above and depicted in FIG. 3, at least one
metal layer 28 is subsequently deposited over the seed layer 26. As
with the seed layer 26, this metal layer 28 can be conformably
blanket deposited. The metal layer 28 can comprise a selection of
copper, gold, palladium, chromium, or alloys thereof, such as
chromium-copper. While exemplary embodiments of the current
invention include those having multiple metal layers, it is
preferred that the metal layer configured to contact the package to
be tested be of the same material used for the package's electrical
contact nodes. Assuming for example, that an LGA package is to be
tested using this interconnect device 18, it should be noted that
the lands of an LGA are often made of gold. Accordingly, in one
exemplary embodiment, the metal layer 28 should also be gold.
Depositing the metal layer 28 can be accomplished through
sputtering, electroplating, or other methods for depositing metals
known in the art. As an exemplary range, this layer 28 can be 500
angstroms to 4 microns thick.
[0035] A patterned mask layer is then provided over the metal layer
28. The metal layer 28 and seed layer 26 are etched according to
the patterned mask, and the result appears in FIG. 4. Specifically,
the contact members 30 are electrically isolated from one another.
The etch also defines a conductive trace 32 and a connection pad 34
for at least one if not all of the contact members 30.
[0036] The conductive traces 32 and connection pads 34 are more
easily distinguished in FIG. 5, illustrating a top-down view of an
interconnect device 18. This figure specifically depicts a silicon
insert 38 configured to be inserted into a socket and receive the
nodes or members establishing electrical contact or communication
with the packaged die for testing. Again, for purposes of
explanation, it will be assumed that the package being tested is an
LGA package. This view demonstrates that the contact members 30 are
formed in places on the silicon insert 38 that correspond to the
lands of the LGA package to be tested. The dashed line 36 defines
the site of the LGA package during testing. It should be further
noted that the lands of an LGA packaged die are not necessarily
limited to the periphery. An LGA packaged die may contain more
centrally located lands, and a silicon insert within the scope of
the current invention can have contact members arranged accordingly
and having a pitch or spacing matching that of the lands of the LGA
package. The conductive traces 32 lead from the contact members 30
to the connection pads 34 which, in this exemplary embodiment, are
located on the sides of the silicon insert 38. Returning to FIG. 4,
a connection pad 34 may then be electrically connected to a
conductive portion of a socket 40 using a bond wire 42. An LGA
package (not shown) may then be placed in the socket 40 in
communication with the contact members 30. Testing may then
commence as described above. The silicon insert 38 depicted in FIG.
5 has a rectangular periphery, with a size slightly larger than the
LGA to which it will connect. Those skilled in the art, however,
can now appreciate that the insert may have other configurations
accommodating another LGA or other packages to be tested as well as
accommodating the socket in which the insert will be placed.
[0037] FIGS. 6 and 7 illustrate other configurations for an
interconnect under the current invention. In FIG. 6, the
interconnect 118 is configured to accommodate a group of dice, such
as an array of dice that is on a semiconductor wafer. A pattern 44
of contact members 30 is provided for each die in the array to be
tested. As in the embodiment in FIG. 5, a conductive trace 32 in
FIG. 6 may lead from each contact member 30, although not all are
shown for purposes of clarity. In FIG. 7, the interconnect 218 is
configured to test all of the dice on a semiconductor wafer. Such
configurations are further detailed in copending application Ser.
No. 08/829,193.
[0038] One advantage of the method embodiment depicted in FIGS. 2
through 4 is that only one mask step is required--the one used to
pattern the metal layer 28 and the seed layer 26. This is in
addition to the mask step known in the art that is used to define
the projections 22. Thus, in terms of the entire contact
member-forming process, only two mask steps are used. This is
beneficial, as additional mask steps require additional process
time and expense.
[0039] Moreover, additional metal layers may be added without
adding mask steps. Assuming that it is desirable to have a gold
layer contact the packaged part being tested, it may not
necessarily be desirable to have gold serving as the only layer
over the seed layer. For instance, given the cost of gold, it may
be preferable to deposit a different metal layer over the seed
layer, wherein that layer serves as the main current-carrying
layer, with a thinner plate of gold deposited thereover. In one
such exemplary embodiment, the main current-carrying layer can be
500 angstroms to 4 microns thick, whereas the gold layer ranges
from 200 angstroms to 1 micron in thickness. Further, a different
metal layer may be able to adhere to the seed layer better than
gold. Accordingly, embodiments having additional metal layers are
exemplified in FIGS. 8-10. The contact member 830 achieved in FIG.
8 is the result of sputtering a tungsten layer 842 onto the
passivation/insulation layer 24 overlying substrate 20 and
projection 22, plating a copper layer 844 over the tungsten layer
842, and plating a gold layer 846 over the copper layer 844. One
mask and etch step can then be used on all three layers 842-846 to
define the contact member 830.
[0040] Yet another exemplary embodiment appears in FIG. 9, wherein
a titanium nitride layer 942 is sputtered onto the
passivation/insulation layer 24 overlying substrate 20 and
projection 22; a copper layer 944 is sputtered over the titanium
nitride layer 942; and a gold layer 946 is plated over the copper
layer 944. Once again, one mask and etch step can then be used on
all three layers 942-946 to define the contact member 930.
[0041] FIG. 10 depicts still another exemplary embodiment. As a
seed layer, an aluminum layer 1042 is sputtered onto the
passivation/insulation layer 24 overlying substrate 20 and
projection 22. This aluminum layer 1042, however, may have a
tendency to oxidize. Hence, it is preferred in this embodiment to
dip the in-process device into a zincate solution, which removes
aluminum oxide that may have formed on the aluminum layer 1042. In
addition, such a step results in an overlying zinc passivation
layer 1044. Subsequently, the in-process device may be subjected to
a nickel flash step, wherein the in-process device is briefly
dipped into an electrolytic solution containing nickel, thereby
creating a thin nickel layer 1046. A gold or palladium layer 1048
is then plated over the nickel layer 1046 to define contact member
1030.
[0042] Another mask-saving benefit of the exemplary embodiments
discussed above is that additional masks are not used to form
penetrating blades on the upper surfaces of the projections 22. In
addition to allowing for a simpler fabrication process, these
embodiments avoid the risk of a blade breaking off from one of the
projections 22 in response to contact with the land of an LGA
package. Moreover, these embodiments limit the damage done to the
testing and tested devices more so than the bond-pad-penetrating
blades of prior art silicon interconnects and the pins of prior
packaged part testing equipment.
[0043] One skilled in the art can appreciate that, although
specific embodiments of this invention have been described above
for purposes of illustration, various modifications may be made
without departing from the spirit and scope of the invention. For
example, it is possible in one exemplary embodiment to retain the
mask layer used to define the projections 22 seen in FIG. 1. That
patterned layer, which can be Si.sub.3N.sub.4, can serve in whole
or as part of the passivation/insulation layer 24. Retaining that
layer saves the time and effort of removing that mask material and
may quicken the process of providing a continuous
passivation/insulation layer 24, if such continuity is desired. In
addition, it is not required under the current invention to define
the projections with an anisotropic etch; other exemplary
embodiments include those wherein the projections result from an
isotropic etch.
[0044] Moreover, the configuration of contact members may vary from
the ones described above. FIG. 11 depicts the silicon interconnect
device 18 that can result from the process described in FIGS. 1
through 4 and the relevant text. (Further, FIG. 11 serves as a
simplified version of the other embodiments discussed above.) FIG.
11 illustrates the silicon interconnect device 18 contacting an LGA
package 1100 at its lands 1102. Each contact member 30 has a
generally planar contact surface 1104 configured to receive a land
1102. Further, in this embodiment, each contact surface 1104 is
coplanar and parallel to its corresponding land 1102. It is not
necessary, however, for all of the contact members 30 to extend to
the same height. As seen in FIG. 12A, a patterned mask 1200
deposited over substrate 20 can be used to define the site of a
first protrusion. A subsequent etching process known in the art can
then be used to partially form the first protrusion 1202 (FIG.
12B). A second mask 1204 can be subsequently deposited and
patterned to define at least one site for at least one additional
protrusion (FIG. 12C--showing two such sites). Further etching
forms protrusions 1206 and completes the formation of protrusion
1202 (FIG. 12D). Additional steps already discussed above can be
used to provide a passivation/insulation layer 24, a seed layer 26,
and at least one metal layer 28 (FIG. 12E). The result is an
interconnect device 18 having contact members 30 of varying height.
Such a configuration would be useful in testing a packaged part
1208 having a topography that also defines varying heights. For
that matter, the interconnect device 18 in FIG. 12E would be useful
in testing non-packaged parts as well.
[0045] Furthermore, it is not necessary that the members have
planar contact surfaces. Exemplary embodiments of the current
invention also include those wherein the interconnect's contact
members, while non-planar, nevertheless have portions that are
configured to be parallel to corresponding portions of the packaged
part's contact. An exemplary method embodiment capable of achieving
such a configuration is illustrated beginning with FIG. 13A. That
figure indicates that a mask 1700 is deposited over substrate 20
and patterned. A subsequent etch creates the recess 1702 seen in
FIG. 13B. FIG. 13C illustrates that a second mask 1704 is deposited
into, above, and beyond the recess 1702 and patterned to define a
contact site. A protrusion 1706 is formed from substrate 20 by an
etch guided by the second mask 1704. The result of this etch is
pictured in FIG. 13D. Again as discussed above, a
passivation/insulation layer 24, a seed layer 26, and at least one
metal layer 28 can be subsequently provided. Such a contact
configuration accommodates the electrical communication node 1708
of packaged part 1710 by complementing the surfaces of that node
1708. For instance, a first portion 1712 of the contact member 30
defines a slope from a horizontal plane that matches the slope of a
first portion 1714 of node 1708. As a result, the two portions 1712
and 1714 are parallel. A second portion 1716 of contact member 30
complements a second portion 1718 of node 1708 in a similar manner.
Given this configuration, package part node 1708 could be
considered a "male" contact, while the accommodating interconnect
contact member 30 could be considered to be the "female"
counterpart.
[0046] Concerning the use of contact members, it should be noted
that contact members such as the ones described above may be used
in conjunction with packages other than an LGA package. For
example, as shown in FIG. 14, a BGA package 1300 is electrically
coupled to the interconnect device 18. It follows that embodiments
of the current invention can accommodate other packages as well,
including the packages mentioned above: dual in-line (DIP), zigzag
in-line (ZIP), leadless chip carrier (LCC), small outline package
(SOP), thin small outline package (TSOP), quad flat pack (QFP),
small outline j-bend (SOJ), and pin grid array (PGA) packages in
addition to bare die packages, chip scale packages, flip chip
packages, and combinations thereof.
[0047] Further, not only will the above-mentioned methods and
devices work for silicon inserts and interconnects in general, but
they have applications in other contexts as well. For example, FIG.
15 illustrates at least one electrical connector 1400, included
within the scope of the current invention, that forms a part of a
test head 1402. The test head 1402 is configured to allow
electrical communication between the sockets 1404 of a carrier 1406
and test equipment 1408 through the electrical connectors 1400. The
test equipment 1408 may include circuitry configured to transmit,
receive, and in general analyze the performance of the device being
tested. The electrical connectors 1400 can be formed by the methods
disclosed above and used to form the contact members of a silicon
insert. The electrical connectors 1400 can be dimensioned so that
there is one electrical connector 1400 corresponding to every
contact point on the carrier 1406. Under the methods disclosed
above, it is possible in certain embodiments to provide electrical
connectors 1400 having a contact surface made of the same material
as the connections of the carrier 1406.
[0048] As an alternative to or in addition to the electrical
connectors 1400 forming part of a test head, it may be desirable to
include at least one electrical connector 1500 as part of a chip
carrier 1506, as seen in FIG. 16. The chip carrier 1506 can be
configured to allow electrical communication between each contact
point of each socket 1504 to an electrical connector 1500. Once
again, the electrical connectors 1500 can terminate with a material
similar to the material to be contacted.
[0049] Yet another alternative embodiment appears in FIG. 17,
wherein the interconnect device 18 includes an elastomer 1800
deposited on the underside of the substrate 20. The elastomer 1800
allows for flexibility of movement of the interconnect device 18,
which will help ensure good electrical connection in the event
interconnect device 18 is subjected to an uneven biasing force.
[0050] Moreover, the methods and devices described above are not
limited to testing circumstances; rather, they could also be used
for interconnect devices in permanent or semipermanent packaging.
Accordingly, the invention is not limited except as stated in the
claims.
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