U.S. patent application number 11/048969 was filed with the patent office on 2005-06-23 for methods of fabricating contact interfaces.
Invention is credited to Akram, Salman, Hu, Y. Jeff.
Application Number | 20050136647 11/048969 |
Document ID | / |
Family ID | 22472622 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050136647 |
Kind Code |
A1 |
Akram, Salman ; et
al. |
June 23, 2005 |
Methods of fabricating contact interfaces
Abstract
A contact used in testing semiconductor devices components
includes a protrusion that is configured to be received by a
semiconductor device component and a silicide layer, or interface,
over at least a portion of the protrusion. The silicide layer may
be formed with a barrier layer, such as titanium nitride, and an
underlying thin dielectric layer between a silicon-containing
substrate and a silicidable material or a silicide. The barrier
layer prevents the formation of electrical passages, formed by the
silicidable material or a silicide thereof, within imperfections or
voids through the thin dielectric layer.
Inventors: |
Akram, Salman; (Boise,
ID) ; Hu, Y. Jeff; (Boise, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
22472622 |
Appl. No.: |
11/048969 |
Filed: |
February 2, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11048969 |
Feb 2, 2005 |
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10620003 |
Jul 14, 2003 |
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6881663 |
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10620003 |
Jul 14, 2003 |
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10174164 |
Jun 17, 2002 |
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6599832 |
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10174164 |
Jun 17, 2002 |
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09795882 |
Feb 28, 2001 |
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6410420 |
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09795882 |
Feb 28, 2001 |
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09136384 |
Aug 19, 1998 |
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6235630 |
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Current U.S.
Class: |
438/630 ;
257/E21.165; 257/E21.296; 257/E21.584; 257/E21.649;
257/E21.658 |
Current CPC
Class: |
H01L 21/76841 20130101;
H01L 21/76814 20130101; H01L 21/76855 20130101; G01R 1/07314
20130101; H01L 21/76843 20130101; H01L 21/32053 20130101; H01L
21/28518 20130101; Y10S 438/952 20130101; H01L 27/10855 20130101;
H01L 27/10888 20130101 |
Class at
Publication: |
438/630 |
International
Class: |
H01L 021/4763 |
Claims
What is claimed is:
1. A method for forming a contact interface, comprising: forming at
least one protruding contact structure on a substrate, the at least
one protruding contact structure being configured to be received by
a recess of a contact pad of a semiconductor device component; and
forming a silicide contact over at least a portion of the at least
one protruding contact structure.
2. The method of claim 1, wherein forming the silicide contact
comprises forming the silicide contact so as to be electrically
isolated from the substrate.
3. The method of claim 2, further comprising: forming a layer
comprising dielectric material over at least a portion of the at
least one protruding contact structure prior to forming the
silicide contact.
4. The method of claim 3, wherein forming the layer comprising
dielectric material comprises forming silicon dioxide.
5. The method of claim 3, wherein forming the layer comprising
dielectric material comprises depositing TEOS.
6. The method of claim 3, wherein forming the at least one
protruding contact structure comprises forming the at least one
protruding contact structure from a semiconductor substrate.
7. The method of claim 3, wherein forming the silicide contact
comprises: forming a layer comprising silicon over the layer
comprising dielectric material; forming a layer comprising
electrically conductive silicidable material over the layer
comprising silicon; and annealing the silicon and the electrically
conductive silicidable material.
8. The method of claim 7, wherein forming the layer comprising
electrically conductive silicidable material comprises forming a
layer comprising cobalt.
9. The method of claim 7, wherein annealing is effected by heating
at least the silicon to a temperature of about 400.degree. C. to
about 800.degree. C.
10. The method of claim 7, wherein annealing is effected by heating
at least the silicon to a temperature of about 450.degree. C. to
about 600.degree. C.
11. The method of claim 7, further comprising: removing an
unreacted portion of the electrically conductive silicidable
material.
12. The method of claim 11, wherein removing the unreacted portion
is effected without substantially removing reacted electrically
conductive silicidable material.
13. The method of claim 11, wherein removing the unreacted portion
is effected with a hydrochloric/peroxide mixture solution.
14. The method of claim 7, wherein forming the silicide contact
further comprises: forming another layer comprising dielectric
material over the layer comprising silicon, prior to forming the
layer comprising electrically conductive silicidable material.
15. The method of claim 14, wherein forming the another layer
comprising dielectric material comprises depositing silicon
dioxide.
16. The method of claim 14, wherein forming the silicide contact
further comprises: exposing a portion of the layer comprising
silicon through the another layer comprising dielectric
material.
17. The method of claim 14, wherein forming the silicide contact
further comprises: forming a layer comprising barrier material over
the another layer comprising dielectric material, prior to forming
the layer comprising electrically conductive silicidable
material.
18. The method of claim 17, wherein forming the layer comprising
barrier material comprises forming a layer comprising at least one
of titanium nitride, tungsten nitride, tungsten silicon nitride,
and titanium silicon nitride.
19. The method of claim 17, wherein forming the silicide contact
further comprises: exposing a portion of the layer comprising
silicon through the layer comprising barrier material and the
another layer comprising dielectric material.
20. The method of claim 19, wherein annealing is effected through
the barrier layer and the another layer comprising dielectric
material.
21. The method of claim 20, further comprising: removing an
unreacted portion of the electrically conductive silicidable
material.
22. The method of claim 21, wherein removing the unreacted portion
is effected without substantially removing the barrier
material.
23. The method of claim 17, wherein forming the layer comprising
barrier material comprises preventing the electrically conductive
silicidable material from reacting with the silicon through at
least one of a void and an imperfection in the another layer
comprising dielectric material.
24. The method of claim 17, further comprising: removing the layer
comprising barrier material after forming the silicide contact.
25. The method of claim 24, wherein removing the layer comprising
barrier material is effected without substantially removing the
silicide contact.
26. The method of claim 24, wherein removing the layer comprising
barrier material is effected without substantially removing the
layer comprising dielectric material.
27. The method of claim 24, wherein removing the layer comprising
barrier material comprises substantially completely removing the
barrier material.
28. The method of claim 24, wherein removing is effected with an
ammonia/perioxide mixture solution.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/620,003, filed Jul. 14, 2003, pending, which is a continuation
of application Ser. No. 10/174,164, filed Jun. 17, 2002, now U.S.
Pat. No. 6,599,832, issued Jul. 29, 2003, which is a divisional of
application Ser. No. 09/795,882, filed Feb. 28, 2001, now U.S. Pat.
No. 6,410,420, issued Jun. 25, 2002, which is a continuation of
application Ser. No. 09/136,384, filed Aug. 19, 1998, now U.S. Pat.
No. 6,235,630, issued May 22, 2001.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to contact interfaces on the
surface of semiconductor substrates and methods of forming the
same. More particularly, the present invention relates to forming
silicide interfaces for use with thin film devices and backend
integrated circuit ("IC") testing devices.
[0004] 2. Background of Related Art
[0005] In the processing of integrated circuits, electrical contact
must be made to isolated active-device regions formed within a
semiconductor substrate, such as a silicon wafer. Such
active-device regions may include p-type and n-type source and
drain regions used in the production of NMOS, PMOS, and CMOS
structures for production of DRAM chips and the like. The
active-device regions are connected by conductive paths or lines
which are fabricated above an insulative or dielectric material
covering a surface of the semiconductor substrate. To provide
electrical connection between the conductive path and the
active-device regions, openings in the insulative material are
generally provided to enable a conductive material to contact the
desired regions, thereby forming a "contact." The openings in the
insulative material are typically referred to as "contact
openings."
[0006] Higher performance, lower cost, increased miniaturization of
components, and greater packaging density of integrated circuits
are goals of the computer industry. However, as components become
smaller and smaller, tolerances for all semiconductor structures
(such as circuitry traces, contacts, dielectric thickness, and the
like) become more and more stringent. In fact, each new generation
of semiconductor device technology has seen a reduction in contact
size of, on average, about 0.7 times. Further, the reduction in
size of integrated circuits also results in a reduction in the
height of the integrated circuits.
[0007] Of course, the reduction in contact size (i.e., diameter)
has resulted in a greatly reduced area of contact between the
active-device regions and the conductive material. Regardless of
the conductive material used to fill these small contact openings
to form the contacts (such as tungsten or aluminum), the interface
between the conductive material and active-device region must have
a low resistance.
[0008] Various methods have been employed to reduce the contact
resistance at the interface between the conductive material and
active-device region. One such method includes the formation of a
metal silicide contact interface atop the active-device region
within the contact opening prior to the application of the
conductive material into the contact opening. A common metal
silicide material formed is cobalt silicide (CoSi.sub.x, wherein x
is predominately equal to 2) generated from a deposited layer of
cobalt. Cobalt silicide is preferred for shallow junctions of thin
film structures because it forms very smooth, fine grained
silicide, and will not form tightly bonded compounds with arsenic
or boron atoms used in the doping of shallow junctions.
[0009] FIGS. 27-31 illustrate a common method of forming a cobalt
silicide layer on an active-device region of a thin film
semiconductor device. FIG. 27 illustrates an intermediate structure
400 comprising a semiconductor substrate 402 with a polysilicon
layer 404 thereon, wherein the polysilicon layer 404 has at least
one active-device region 406 formed therein with a thin dielectric
layer 408, such as tetraethyl orthosilicate--TEOS, disposed
thereover. The dielectric layer 408 must be as thin as possible to
reduce the height of the thin film semiconductor device. A contact
opening 412 is formed, by any known technique, such as patterning
and etching, in the dielectric layer 408 to expose a portion of the
active-device region 406, as shown in FIG. 28. A thin layer of
cobalt 414 is applied over the dielectric layer 408 and the exposed
portion of the active-device region 406, as shown in FIG. 29. A
high temperature anneal step is conducted in an inert atmosphere to
react the thin cobalt layer 414 with the active-device region 406
in contact therewith which forms a cobalt silicide layer 416, as
shown in FIG. 30. However, dielectric materials, such as
TEOS--tetraethyl orthosilicate, BPSG--borophosphosilicate glass,
PSG--phosphosilicate glass, and BSG--borosilicate glass, and the
like, are generally porous. Thus, the thin dielectric layer 408 has
imperfections or voids which form passages through the thin
dielectric layer 408. Therefore, when the high-temperature anneal
is conducted, cobalt silicide also forms in these passages. The
cobalt silicide structures in the passages are referred to as
patches 418, as also shown in FIG. 30. When the nonreacted cobalt
layer 414 is removed to result in a final structure 422 with a
cobalt silicide layer 416 formed therein, as shown in FIG. 31, the
patches 418 also form conductive paths between the upper surface of
the thin dielectric layer 408 which can cause shorting and current
leakage on IC backend testing devices which leads to poor
repeatability and, thus, poor reliability of the data from the
testing devices.
[0010] Although such voids can be eliminated by forming a thicker
dielectric layer 424, the thicker dielectric layer 424 leads to
poor step coverage of the cobalt material 426 in bottom corners 428
of the contact opening 412, as shown in FIG. 32. The poor step
coverage is caused by a build-up of cobalt material 426 on the
upper edges 432 of the contact opening 412 which causes shadowing
of bottom corners 428 of the contact openings 412. The result is
little or no cobalt material 426 deposited at the bottom corners
428 of the contact opening 412 and consequently an inefficient
silicide contact formed after annealing.
[0011] Step coverage can be improved by using filtering techniques,
such as physical collimated deposition and low-pressure long throw
techniques, which are used to increase the number of sputtered
particles contacting the bottom of the contact opening. However,
such filtering techniques are costly and the equipment is difficult
to clean. Furthermore, filtering techniques also reduce the
deposition rate of the cobalt material which reduces product
throughput and, in turn, increases the cost of the semiconductor
device. Moreover, using a thick dielectric layer is counter to the
goal of reducing semiconductor device size. Finally, a thick
dielectric layer eliminates the ability of the structure to be used
as a backend IC probing device since the contacts are too small and
too deep in the dielectric material. This is a result of dielectric
material not being scalable. As device geometries get smaller, the
thickness of the dielectric cannot be reduced without the potential
of shorting and/or formation of patches. Thus, contact size must be
increased to allow probe tips to fit in contacts, which is counter
to the goal of reducing semiconductor device size.
[0012] Thus, it can be appreciated that it would be advantageous to
develop a technique and a contact interface which is free from
patch formations, while using inexpensive, commercially available,
widely practiced semiconductor device fabrication techniques and
equipment without requiring complex processing steps.
SUMMARY OF THE INVENTION
[0013] The present invention relates to methods of forming silicide
interfaces for use with thin film devices and backend integrated
circuit testing devices and structures so formed. The present
invention is particularly useful when a porous dielectric layer is
disposed between a silicon-containing substrate and a silicidable
material deposited to form a silicide contact in a desired area. As
previously discussed, dielectric layers may have imperfections or
voids which form passages through the thin dielectric layer.
Therefore, when the high-temperature anneal is conducted to form
the silicide contact from the reaction of the silicidable material
and the silicon-containing substrate, a silicide material may also
form in these passages through the dielectric material. Such
silicide material extending through these passages can cause
shorting and current leakage. The present invention prevents the
formation of silicide material through passages in the dielectric
material by the application of a barrier layer between the
dielectric material and the silicidable material.
[0014] In an exemplary method of forming a contact according to the
present invention, a semiconductor substrate is provided with a
polysilicon layer disposed thereon, wherein at least one
active-device region is formed in a polysilicon layer. A thin
dielectric layer is deposited or grown (such as by a thermal
oxidation process) over the polysilicon layer and a layer of
barrier material, preferably titanium nitride, is deposited over
the thin dielectric layer.
[0015] A mask material is patterned on the barrier material layer
and a contact opening is then etched through the barrier material
layer and the thin dielectric layer, preferably by an anisotropic
etch, to expose a portion of the active-device region. Any
remaining mask material is removed and a thin layer of silicidable
material, such as cobalt, titanium, platinum, or palladium, is
deposited over the barrier material layer and into the contact
opening over the exposed portion of the active-device region. A
high temperature anneal is conducted to react the thin silicidable
material layer with the active-device region in contact therewith,
which forms a silicide contact. The barrier material prevents the
formation of silicide structures within voids and imperfections in
the thin dielectric layer. The nonreacted silicidable material
layer and remaining barrier material layer are then removed.
[0016] In an exemplary method of forming a testing contact used in
backend testing of semiconductor devices, a silicon-containing
substrate is provided having at least one contact projection
disposed thereon. A first dielectric layer is deposited or grown
over the substrate and the contact projection. A layer of
polysilicon is then deposited over the first dielectric layer. A
second dielectric layer is optionally deposited over the
polysilicon layer and a layer of barrier material is deposited over
the optional second dielectric layer, or over the polysilicon, if
the optional second dielectric layer is not used.
[0017] A mask material is patterned on the barrier material layer.
The barrier material layer and the optional second dielectric layer
(if used) are then etched to expose the polysilicon layer over the
contact projection, then any remaining mask material is removed. A
thin layer of silicidable material is deposited over the barrier
material layer and onto the exposed contact projection. A high
temperature anneal is conducted to react the thin silicidable
material layer with the exposed portion of the polysilicon layer
over the contact projection which forms a silicide layer. The
nonreacted silicidable material layer and the remaining barrier
material layer are then removed to form the testing contact.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] While the specification concludes with claims particularly
pointing out and distinctly claiming that which is regarded as the
present invention, the advantages of this invention can be more
readily ascertained from the following description of the invention
when read in conjunction with the accompanying drawings in
which:
[0019] FIGS. 1-8 are cross-sectional views of a method of forming a
contact interface in a thin semiconductor structure according to
the present invention;
[0020] FIG. 9 is a cross-sectional view of CMOS structures within a
memory array of a DRAM chip formed by a method according to the
present invention;
[0021] FIGS. 10-17 are cross-sectional views of a method of forming
a testing interface according to the present invention;
[0022] FIG. 18 is a cross-sectional view of a testing interface
according to the present invention with a chip-under-test disposed
therein;
[0023] FIGS. 19-26 are cross-sectional views of another method of
forming a testing interface according to the present invention;
[0024] FIGS. 27-31 are cross-sectional views of a method of forming
a contact interface in a thin semiconductor structure according to
a known technique; and
[0025] FIG. 32 is a cross-sectional view of the deposition of a
metal layer in an opening in a thick dielectric according to a
known technique.
DETAILED DESCRIPTION OF THE INVENTION
[0026] FIGS. 1-8 illustrate a method of forming a contact interface
of the present invention. It should be understood that the
illustrations are not meant to be actual views of any particular
semiconductor device, but are merely idealized representations
which are employed to more clearly and fully depict the formation
of contact interfaces in the present invention than would otherwise
be possible. Additionally, elements common between FIGS. 1-8 retain
the same numerical designation.
[0027] Although the examples presented are directed to the
formation of cobalt silicide contact interfaces, any metal or metal
alloy which is capable of forming a silicide may be employed,
including, but not limited to, titanium, platinum, or
palladium.
[0028] FIG. 1 illustrates a semiconductor substrate 100, such as a
silicon-containing substrate, having a polysilicon layer 102
thereon, wherein at least one active-device region 104 is formed in
a polysilicon layer 102, with a thin dielectric layer 106, such as
TEOS, of a thickness of approximately 1 kA disposed over the
polysilicon layer 102. A layer of barrier material 108, preferably
titanium nitride deposited to a thickness of between about 100-150
.ANG., is deposited over the thin dielectric layer 106, such as by
PVD, as shown in FIG. 2. Other potential barrier materials include
tungsten nitride, tungsten silicon nitride, titanium silicon
nitride, and the like.
[0029] A mask material 112 is patterned on the barrier material
layer 108, as shown in FIG. 3. A contact opening 114 is then etched
through the barrier material layer 108 and the thin dielectric
layer 106, preferably by a dry etch such as reactive ion etching or
the like, to expose a portion of the active-device region 104, then
any remaining mask material 112 is removed, as illustrated in FIG.
4. A thin layer of cobalt 116 is deposited, preferably by PVD, over
the barrier material layer 108 and into the contact opening 114
over the exposed portion of the active-device region 104, as shown
in FIG. 5. A high temperature anneal step, preferably between about
400 and 800.degree. C., most preferably between about 450 and
600.degree. C. for between about 5 seconds and 1 hour, is conducted
in an inert atmosphere, preferably nitrogen containing gas, to
react the thin cobalt layer 116 with the active-device region 104
in contact therewith which forms a cobalt silicide layer 118, as
shown in FIG. 6. The barrier material layer 108 prevents the
formation of cobalt silicide structures within voids and
imperfections in the thin dielectric layer 106. In particular, it
has been found that a thin titanium nitride film acts as a good
diffusion barrier for a thin TEOS dielectric layer. Further, it has
been found that titanium nitride does not react with cobalt. Thus,
cobalt silicide patch formations have been eliminated when titanium
nitride is used as a barrier layer over a thin TEOS dielectric
layer.
[0030] The nonreacted cobalt layer 116 is removed, preferably by a
wet etch such as hydrochloric acid/peroxide or sulfuric
acid/peroxide mixtures, wherein the barrier material layer 108
preferably acts as an etch stop, as shown in FIG. 7. Preferably,
the nonreacted cobalt layer 116 is etched in a dilute HPM
(Hydrochloric acid/Peroxide Mixture) solution (typically, 1 volume
of hydrochloric acid to 1 volume of peroxide to 5 volumes of water)
for about 30 seconds at about 30.degree. C. Such an HPM solution is
preferred because its selectivity is greater than 10.sup.4 for
cobalt against cobalt silicide and titanium nitride.
[0031] As shown in FIG. 8, the remaining barrier material layer 108
is then removed, preferably by etching in an APM solution
(Ammonia/Peroxide Mixture) solution (typically, 1 volume of ammonia
to 1 volume of peroxide to 5 volumes of water) for between about 1
and 2 minutes at about 65.degree. C. Such an APM solution is
preferred because of its selectivity for titanium nitride against
cobalt silicide and TEOS.
[0032] It is contemplated that the process of the present invention
may be utilized for production of DRAM chips, wherein the contact
interfaces are used in the MOS structures within a memory array of
a DRAM chip. Such a MOS structure 200 is illustrated in FIG. 9 as a
portion of a memory array in a DRAM chip. The MOS structure 200
comprises a semiconductor substrate 202, such as a lightly doped
P-type crystal silicon substrate, which has been oxidized to form
thick field oxide areas 204 and exposed to implantation processes
to form drain regions 206 and source regions 208. Transistor gate
members 212, including a wordline 214 bounded by insulative
material 216, are formed on the surface of the semiconductor
substrate 202 and thick field oxide areas 204. A barrier layer 218
is disposed over the semiconductor substrate 202, the thick field
oxide areas 204, and the transistor gate members 212. The barrier
layer 218 has bitline contacts 222 contacting the source regions
208 for electrical communication with a bitline 224 and, further,
has capacitor contacts 226 contacting the drain regions 206 for
electrical communication with memory cell capacitors 228. Each of
the bitline contacts 222 and capacitor contacts 226 may have
silicide layer interfaces 232, formed as described above, for
reducing resistance between the bitline contacts 222 and the source
regions 208, and between the capacitor contacts 226 and the drain
regions 206. The memory cell capacitors 228 are completed by
depositing a dielectric material layer 234, then depositing a cell
poly layer 236 over the dielectric material layer 234.
[0033] FIGS. 10-17 illustrate a method of forming a testing contact
used in backend testing of semiconductor devices. It should be
understood that the illustrations are not meant to be actual views
of any particular semiconductor device, but are merely idealized
representations which are employed to more clearly and fully depict
the formation of contact interfaces in the present invention than
would otherwise be possible. Additionally, elements common between
FIGS. 10-17 retain the same numerical designation.
[0034] FIG. 10 illustrates a substrate 302 having at least one
contact projection 304 disposed thereon, preferably with a height
of approximately 100 .mu.m, wherein the substrate 302 and the
contact projection 304 have a first dielectric layer 306,
preferably silicon dioxide, disposed thereover. The first
dielectric layer 306 may be deposited by any known technique or, if
silicon dioxide, may be grown on the surface of the substrate 302
by a thermal oxidation process. A layer of polysilicon 308 is
deposited by any known technique over the first dielectric layer
306. As shown in FIG. 11, a second dielectric layer 312, such as
TEOS or silicon dioxide, is deposited over the polysilicon layer
308 and a layer of barrier material 314, preferably titanium
nitride, is deposited over the second dielectric layer 312, such as
by PVD.
[0035] A mask material 316 is patterned on the barrier material
layer 314, as shown in FIG. 12. The barrier material layer 314 and
the second dielectric layer 312 are then etched, preferably by a
dry etch such as reactive ion etching or plasma etching, to expose
the polysilicon layer 308 over the contact projection 304, then any
remaining mask material 316 is removed, as illustrated in FIG. 13.
A thin layer of cobalt 318 is deposited, preferably by PVD, over
the barrier material layer 314 and onto the exposed contact
projection 304, as shown in FIG. 14. A high temperature anneal
step, preferably between about 400 and 800.degree. C., most
preferably between about 450 and 600.degree. C. for between about 5
seconds and 1 hour, is conducted in an inert atmosphere, preferably
nitrogen containing gas, to react the thin cobalt layer 318 with
the exposed portion of the polysilicon layer 308 over the contact
projection 304 which forms a cobalt silicide layer 322, as shown in
FIG. 15.
[0036] The nonreacted cobalt layer 318 is removed, preferably by a
wet etch, such as hydrochloric acid/peroxide or sulfuric
acid/peroxide mixtures, wherein the barrier material layer 314
preferably acts as an etch stop, as shown in FIG. 16. Preferably,
the nonreacted cobalt layer 318 is etched in a dilute HPM
(Hydrochloric acid/Peroxide Mixture) solution (typically, 1 volume
of hydrochloric acid to 1 volume of peroxide to 5 volumes of water)
for about 30 seconds at about 30.degree. C.
[0037] As shown in FIG. 17, the remaining barrier material layer
314 is then removed, preferably etching in an APM (Ammonia/Peroxide
Mixture) solution (typically, 1 volume of ammonia to 1 volume of
peroxide to 5 volumes of water) for between about 1 and 2 minutes
at about 65.degree. C., and the remaining second dielectric layer
312 and polysilicon layer 308 are also removed, by any known
technique. The cobalt silicide layer 322 is not disturbed by the
removal of the remaining barrier material layer 314 or the removal
of the second dielectric layer 312 and polysilicon layer 308, as
dry etches containing chlorine or fluorine will not etch cobalt
silicide (i.e., CoF.sub.x and CoCl.sub.x are nonvolatile).
[0038] Structures such as illustrated in FIG. 17 are generally used
for testing of flip-chips, wherein, as illustrated in FIG. 18,
solder bumps 332 of a flip-chip 330 electrically contact the cobalt
silicide layer 322. The cobalt silicide layer 322 conducts
electrical signals to and/or receives electrical signals from the
flip-chip 330 through the solder bumps 332.
[0039] FIGS. 19-26 illustrate another method of forming a testing
contact used in backend testing of semiconductor devices. Elements
common between FIGS. 10-17 and FIGS. 19-26 retain the same
numerical designation.
[0040] FIG. 19 illustrates a substrate 302 having at least one
contact projection 304 disposed thereon, wherein the substrate 302
and the contact projection 304 have a first dielectric layer 306,
preferably silicon dioxide, disposed thereover. A layer of
polysilicon 308 is deposited by any known technique over the first
dielectric layer 306. As shown in FIG. 20, a layer of barrier
material 314, preferably titanium nitride, is deposited over the
polysilicon layer 308.
[0041] A mask material 316 is patterned on the barrier material
layer 314, as shown in FIG. 21. The barrier material layer 314 is
then etched to expose the polysilicon layer 308 over the contact
projection 304, then any remaining mask material 316 is removed, as
illustrated in FIG. 22. A thin layer of cobalt 318 is deposited
over the barrier material layer 314 and onto the exposed contact
projection 304, as shown in FIG. 23. A high temperature anneal
step, preferably between about 400 and 800.degree. C., most
preferably between about 450 and 600.degree. C. for between about 5
seconds and 1 hour, is conducted in an inert atmosphere, preferably
nitrogen containing gas, to react the thin cobalt layer 318 with
the exposed portion of the polysilicon layer 308 over the contact
projection 304 which forms a cobalt silicide layer 322, as shown in
FIG. 24.
[0042] The nonreacted cobalt layer 318 is removed, preferably by a
wet etch, such as hydrochloric acid/peroxide or sulfuric
acid/peroxide mixtures, wherein the barrier material layer 314
preferably acts as an etch stop, as shown in FIG. 25. As shown in
FIG. 26, the remaining barrier material layer 314 and the remaining
polysilicon 308 are removed.
[0043] Having thus described in detail preferred embodiments of the
present invention, it is to be understood that the invention
defined by the appended claims is not to be limited by particular
details set forth in the above description as many apparent
variations thereof are possible without departing from the spirit
or scope thereof.
* * * * *