U.S. patent application number 11/385484 was filed with the patent office on 2006-11-09 for in-situ silicidation metallization process.
Invention is credited to Srinivas Gandikota, Avgerinos V. (Jerry) Gelatos, Arulkumar Shanmugasundram, Michael P. Stewart, Timothy W. Weidman.
Application Number | 20060251801 11/385484 |
Document ID | / |
Family ID | 37024461 |
Filed Date | 2006-11-09 |
United States Patent
Application |
20060251801 |
Kind Code |
A1 |
Weidman; Timothy W. ; et
al. |
November 9, 2006 |
In-situ silicidation metallization process
Abstract
Embodiments of the invention provide a simplified method of
filling contact level features formed in a semiconductor device. In
general the method includes a novel method of forming a contact
level feature that contains a silicide interface and a tungsten CVD
deposited layer. The processes discussed below are less complex and
less time consuming than other conventional contact level
interconnect formation processes and thus will have an improved
device yield.
Inventors: |
Weidman; Timothy W.;
(Sunnyvale, CA) ; Gandikota; Srinivas; (Santa
Clara, CA) ; Stewart; Michael P.; (Mountain View,
CA) ; Gelatos; Avgerinos V. (Jerry); (Redwood City,
CA) ; Shanmugasundram; Arulkumar; (Sunnyvale,
CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
37024461 |
Appl. No.: |
11/385484 |
Filed: |
March 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60663493 |
Mar 18, 2005 |
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60683599 |
May 23, 2005 |
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60703538 |
Jul 29, 2005 |
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60703633 |
Jul 29, 2005 |
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60709564 |
Aug 19, 2005 |
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60754230 |
Dec 27, 2005 |
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Current U.S.
Class: |
427/99.5 ;
257/E21.165; 257/E21.174; 427/250 |
Current CPC
Class: |
C23C 16/14 20130101;
C23C 18/31 20130101; C23C 18/48 20130101; H01L 2924/0002 20130101;
H01L 21/76844 20130101; C23C 18/1651 20130101; C23C 18/38 20130101;
H01L 21/02074 20130101; C23C 18/1678 20130101; H01L 21/76855
20130101; C23C 18/1653 20130101; C23C 18/1608 20130101; H01L
21/76862 20130101; C23C 18/34 20130101; H01L 21/28518 20130101;
H01L 21/02063 20130101; C25D 5/34 20130101; H01L 2924/00 20130101;
B82Y 30/00 20130101; H01L 21/2885 20130101; H01L 23/53238 20130101;
H01L 21/76847 20130101; H01L 21/288 20130101; H01L 21/76846
20130101; H01L 2924/0002 20130101; C23C 18/32 20130101; C23C 18/40
20130101; H01L 21/76843 20130101; H01L 21/76879 20130101; H01L
21/76856 20130101; C23C 16/045 20130101; C23C 16/0227 20130101;
H01L 21/76877 20130101; H01L 21/28556 20130101; C23C 16/0281
20130101; H01L 21/76814 20130101; H01L 21/76849 20130101; H01L
21/76861 20130101; H01L 21/76874 20130101 |
Class at
Publication: |
427/099.5 ;
427/250 |
International
Class: |
B05D 5/12 20060101
B05D005/12 |
Claims
1. A method for depositing a material on a substrate, comprising:
providing a substrate that has one or more contact level features
that have an exposed doped silicon containing region; selectively
depositing a metal containing layer over a surface of the exposed
doped silicon containing regions; and depositing a tungsten layer
on the metal layer at a temperature between about 300.degree. C.
and about 450.degree. C., wherein during the process of depositing
tungsten layer a metal silicide is formed at the surface of the
exposed doped silicon containing region.
2. The method of claim 1, wherein the metal containing layer
contains an element selected from a group consisting of cobalt and
nickel.
3. The method of claim 1, wherein the tungsten layer is deposited
using a tungsten hexafluoride (WF.sub.6) containing gas.
4. The method of claim 1, wherein the process of selectively
depositing a metal containing layer comprises electrolessly
depositing a nickel-containing layer having a thickness between
about 10 angstroms and about 100 angstroms.
5. A method for depositing a material on a substrate, comprising:
providing a silicon containing substrate that has one or more
contact level features that have an exposed doped silicon
containing region; pretreating the exposed doped silicon containing
region, wherein the pretreating process is adapted to remove an
oxide layer from the exposed doped silicon containing region;
depositing a metal containing layer over a surface of the exposed
doped silicon containing regions; and depositing a tungsten layer
over the metal containing layer at a temperature between about
300.degree. C. and about 450.degree. C., wherein during the
tungsten layer deposition process a metal silicide is formed.
6. The method of claim 5, wherein the metal containing layer
contains an element selected from a group consisting of cobalt and
nickel.
7. The method of claim 5, wherein the tungsten layer is deposited
using a tungsten hexafluoride (WF.sub.6) containing gas.
8. The method of claim 5, further comprises depositing a cobalt
containing layer on the nickel containing layer prior to depositing
the tungsten layer.
9. The method of claim 5, wherein the process of depositing a metal
containing layer comprises electrolessly depositing a
nickel-containing layer having a thickness between about 10
angstroms and about 100 angstroms.
10. A method for depositing a material on a substrate, comprising:
providing a silicon containing substrate that has one or more
contact level features that have an exposed doped silicon
containing region; pretreating the exposed doped silicon containing
region, wherein the pretreating process is adapted to remove an
oxide layer from the exposed doped silicon containing region;
depositing a nickel containing layer over the bottom surface of the
one or more contact level features; forming a nickel silicide layer
by exposing the deposited nickel containing layer and silicon
containing substrate to temperatures greater the 250.degree. C.;
depositing a cobalt containing layer over the nickel silicide
layer; and depositing a tungsten layer on the cobalt containing
layer.
11. The method of claim 10, wherein the tungsten layer is deposited
using a tungsten hexafluoride (WF.sub.6) containing gas.
12. The method of claim 10, wherein the cobalt containing layer is
a cobalt-tungsten alloy.
13. The method of claim 10, wherein the process of depositing a
nickel containing layer comprises electrolessly depositing a
nickel-containing layer having a thickness between about 10
angstroms and about 100 angstroms.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of U.S. Provisional Patent
Application Ser. No. 60/663,493, filed Mar. 18, 2005 [APPM 9916L],
U.S. Provisional Patent Application Ser. No. 60/683,599, filed May
23, 2005 [APPM 9916L02], U.S. Provisional Patent Application Ser.
No. 60/703,538, filed Jul. 29, 2005 [APPM 9916L03], U.S.
Provisional Patent Application Ser. No. 60/703,633, filed Jul. 29,
2005 [APPM 9916L04], U.S. Provisional Patent Application Ser. No.
60/709,564, filed Aug. 19, 2005 [APPM 9916L05], and U.S.
Provisional Patent Application Ser. No. 60/754,230, filed Dec. 27,
2005 [APPM 9916L06], which are all herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to methods for
depositing materials on substrates, and more specifically to
methods for filling apertures within a high aspect ratio
contact.
[0004] 2. Description of the Related Art
[0005] Multilevel, 45 nm node metallization is one of the key
technologies for the next generation of very large scale
integration (VLSI). The multilevel interconnects that lie at the
heart of this technology possess features with small CD's and high
Aspect Ratios including contacts, vias, lines and other apertures.
Reliable formation of these features is very important for the
success of VLSI and the continued effort to increase quality and
circuit density on individual substrates. Therefore, there is a
great amount of ongoing effort being directed to the formation of
void-free features with low contact resistance having high aspect
ratios of 10:1 (height: width) or greater.
[0006] Tungsten is a metal of choice for filling contact level VLSI
features, such as for example a sub-micron high aspect ratio
contact (HARC) on a substrate. Contacts are formed by depositing a
conductive interconnect material, such as tungsten into an aperture
on the surface of insulating material disposed between two
spaced-apart conductive layers. A high aspect ratio of such an
opening may inhibit deposition of a conformal conductive
interconnect material to fill an aperture. One simplified example
of a conductive interconnect is typical MOS device shown in FIG. 1.
In the illustrated MOS structure, the conductive N+source and drain
regions 102 and 104 are formed in a P-type silicon substrate 100,
which are adjacent to the field oxide portions 106. A gate oxide
layer 108 and a polysilicon gate electrode 110 are formed over
silicon substrate 100 in between source and drain regions 102 and
104 with oxide spacers 112 formed on the sidewalls of polysilicon
gate electrode 110. A dielectric material 122 may be deposited over
the formed structure and etched to provide a contact level aperture
120. The contact level apertures 120 are then filled with a thin
barrier layer 105 and a contact material 107. The barrier layer 105
may be tungsten, cobalt or titanium and titanium nitride stack that
is typically deposited using a physical vapor deposition (PVD)
process. The contact material 107, which is typically a tungsten
containing layer, is formed using a chemical vapor deposition (CVD)
or atomic layer deposition (ALD) techniques. After depositing the
barrier layer 105 a silicide layer 103 is formed at the interface
of the source and drain regions 102 and 104 by allowing the
deposited barrier layer 105 metal to form a silicide during a high
temperature thermal anneal step (e.g., .about.800-1000.degree. C.).
The contact level apertures 120 thus provide a low resistance
interconnect between various parts of the device (e.g., source
region, drain region) and the layers above (not shown).
[0007] Contact level metallization processes require the formation
of a silicide at the doped silicon source or drain interface to
reduce the contact resistance and thus improve the speed of the
formed device(s). Typically, conventional contact level
metallization process(es) require the time consuming and complex
process steps of depositing a metal layer that will form a silicide
at the doped silicon interface (e.g., source or drain interface),
removing the excess metal layer from the "Yield" (e.g., top surface
of the substrate in which the features are formed) by use of a
chemical mechanical polishing (CMP) type process, performing a high
temperature anneal process to form a metal silicide layer,
depositing a liner/barrier layer (e.g., titanium nitride (TiN),
titanium (Ti), tantalum (Ta), tantalum nitride (TaN)) over the
formed metal/metal silicide layer, and then filling the contact
feature formed in the dielectric layer with tungsten (W) using a
tungsten hexafluoride (WF.sub.6) chemical vapor deposition (CVD)
process. Since the contact level metallization process is
relatively complex and requires a number of process steps, the
chance of misprocessing the substrate or the chance that
contamination will affect the device yield is very high.
[0008] A need exists for a less time consuming and less complex
method of forming a contact level interconnect that has a silicide
formed at the doped silicon interface. There is also a need for a
process of forming a contact level interconnect that is less likely
to be misprocessed and has improved device yield due to reduced
chance of contamination during processing.
SUMMARY OF THE INVENTION
[0009] The present invention generally provide a method for
depositing a material on a substrate, comprising providing a
substrate that has one or more contact level features that have an
exposed doped silicon containing region, selectively depositing a
metal containing layer over a surface of the exposed doped silicon
containing regions, and depositing a tungsten layer on the metal
layer at a temperature between about 300 .degree. C. and about
450.degree. C., wherein during the process of depositing tungsten
layer a metal silicide is formed at the surface of the exposed
doped silicon containing region.
[0010] Embodiments of the invention further provide a method for
depositing a material on a substrate, comprising positioning a
silicon containing substrate that has one or more contact level
features that have an exposed doped silicon containing region,
pretreating the exposed doped silicon containing region, wherein
the pretreating process is adapted to remove an oxide layer from
the exposed doped silicon containing region, depositing a metal
containing layer over a surface of the exposed doped silicon
containing regions, and depositing a tungsten layer over the metal
containing layer at a temperature between about 300.degree. C. and
about 450.degree. C., wherein during the tungsten layer deposition
process a metal suicide is formed.
[0011] Embodiments of the invention further provide a method for
depositing a material on a substrate, comprising positioning a
silicon containing substrate that has one or more contact level
features that have an exposed doped silicon containing region,
pretreating the exposed doped silicon containing region, wherein
the pretreating process is adapted to remove an oxide layer from
the exposed doped silicon containing region, depositing a nickel
containing layer over the bottom surface of the one or more contact
level features, forming a nickel silicide layer by exposing the
deposited nickel containing layer and silicon containing substrate
to temperatures greater the 250.degree. C., depositing a cobalt
containing layer over the nickel silicide layer, and depositing a
tungsten layer on the cobalt containing layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] So that the manner in which the above recited features of
the invention are attained and can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to the embodiments thereof which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0013] FIG. 1 illustrate schematic cross-sectional view of a MOS
type integrated circuit formed by a process described in the
art;
[0014] FIG. 2 illustrates a flow chart depicting an electroless
deposition process as described within an embodiment herein;
[0015] FIG. 3A-G illustrate schematic cross-sectional views of an
integrated circuit formed by a process to cap a defect within a
contact plug described within an embodiment herein;
[0016] FIG. 4 illustrates a flow chart depicting an electroless
deposition process as described within an embodiment herein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0017] Embodiments of the invention provide a simplified method of
filling contact level features formed in a semiconductor device. In
general the method includes a novel method of forming a contact
level feature that contains a silicide interface and a tungsten CVD
deposited layer. The processes discussed below are less complex and
less time consuming than other conventional contact level
interconnect formation processes and thus will have an improved
device yield.
1. Silicidation During Tungsten Deposition Process
[0018] FIG. 2 illustrates a series of method steps 1000 that may be
used to fill a contact level feature. FIG. 3A illustrates a
cross-sectional view of substrate 1500 having a contact level
aperture 1510 formed into dielectric layer 1504. The dielectric
layer 1504 contains an insulating material that includes silicon
dioxide, silicon nitride, SOI, BPSG, silicon oxynitride and/or
carbon-doped silicon oxides, such as SiOxCy, for example, BLACK
DIAMOND.TM. low-k dielectric, available from Applied Materials,
Inc., located in Santa Clara, Calif. Contact level aperture 1510
may be formed in dielectric layer 1504 using conventional
lithography and etching techniques to expose the silicon junction
1502, such as a MOS type source or drain interface. Silicon
junction 1502 is generally a doped silicon region, such as a N+or
P+doped silicon region.
[0019] An oxide surface 1512 is usually formed at the silicon
junction 1502 during previous etching and ashing processes used to
form contact level aperture 1510. Oxide surface 1512 may be a
continuous layer or a discontinuous layer across the surface of
silicon junction 1502 and include a surface terminated with oxygen,
hydrogen, hydroxides, a metal or combinations thereof. In examples
wherein silicon junction 1502 contains a silicon-containing
material, oxide surface 1512 is usually a silicon oxide surface.
Also, in examples wherein silicon junction 1502 contains a
metal-containing material, oxide surface 1512 is usually a metal
oxide surface.
[0020] The first step of the method steps 1000 includes a
pretreatment process step 1002, to remove the oxide layer so
subsequent processes can be preformed on the surface of the silicon
junction 1502. In this process step the substrate 1500 is exposed
to a pretreatment process to form a treated surface (not shown) on
the silicon junction 1502, which is substantially free of oxide
surface 1512. In one example, the silicon junction 1502 contains a
silicon-containing material and treated surface contains a
hydride-terminus surface, such as a silicon hydride layer. In
another example, the silicon junction 1502 contains a
metal-containing material and the treated surface contains a
reduced metal surface. The various processes that may be used to
perform the pretreatment process step 1002 on the surface of the
silicon junction 1502 are described below (see Pretreatment
Process).
[0021] The second step of the method steps 1000 includes a metal
deposition step 1004, that is used to form a metal layer 1514 over
the silicon junction 1502. In one aspect, the metal layer 1514 is a
nickel containing layer. The metal deposition step 1004 may be
performed by use of a PVD, CVD, plasma enhanced CVD, ALD, plasma
enhanced ALD or electroless deposition process to form the nickel
layer. In one aspect, when a non-selective deposition process is
used, such as a PVD, non-selective CVD, non-selective plasma
enhanced CVD, non-selective ALD, and/or non-selective plasma
enhanced ALD process(es), the method steps 1000 may include an
optional nickel removal step 1006. The optional metal removal step
includes the step of removing any deposited nickel from the field
region 1505 (FIGS. 3A-B) by use of a wet clean process, CMP
process, electrochemical process or other comparable material
removal processes.
[0022] In one aspect of method steps 1000, as shown in FIG. 3C, the
metal deposition step 1004 is performed using a selective nickel
deposition process to deposit the metal layer 1514 over the silicon
junction 1502. In this case the selectively deposited electroless
nickel layer is only formed over the silicon junction 1502. An
exemplary selective electroless deposition process is described
below. In this case there is generally no need to perform the
optional metal removal step 1006, since the metal layer 1514 will
be selectively deposited at the surface of the silicon junction
1502.
[0023] The last step of the method steps 1000 is the deposit a
tungsten containing layer to fill the contact level aperture 1510
using a CVD tungsten deposition process that is performed at a
temperature that will cause at least some portion of the metal
layer 1514 to form a metal silicide layer 1515 (e.g., NiSi,
Ni.sub.2Si). The tungsten CVD deposition process used in step 1010
is performed using conventional tungsten hexafluoride (WF.sub.6)
precursor chemistries at a temperature in the range between about
300.degree. C. and about 450.degree. C. Preferably, the CVD
tungsten deposition process temperature range is between about
300.degree. .degree. C. and about 400 .degree. C. Preferably, the
CVD tungsten deposition process temperature is about 350.degree. C.
A conventional CVD process generally involves the simultaneous
introduction of gas phase reactants, such as tungsten precursor
(typically tungsten hexafluoride) and a hydrogen containing gas
(e.g., H.sub.2), near a heated wafer surface while a vacuum is
applied to the system. The reaction is driven by the energy
provided by the heated wafer and the free energy change of the
chemical reaction. In this step a tungsten layer 1520 is directly
deposited on the metal layer 1514 formed on the silicon junction
1502 during step 1004. In one aspect, the metal layer 1514 is
deposited to a thickness between about 10 .ANG. and about 100
.ANG.. In one aspect of step 1010, at the end of the tungsten
deposition process a metal silicide layer 1515 (e.g., nickel
silicide (Ni.sub.xSi.sub.y)) is formed having sufficient thickness
to form a good electrical contact (e.g., ohmic contact) between the
tungsten layer 1520 and the silicon junction 1502. A metal silicide
layer is formed as the metal layer 1514 reacts with the silicon
atoms found at the silicon junction 1502 interface, thus consuming
at least a portion of the metal layer 1514 and some of the silicon
atoms at the silicon junction. Since tungsten hexafluoride tends to
attack the exposed metal layer 1514 during the early stages of the
deposition process, it is desirable to assure that the metal layer
1514 thickness is large enough to assure that enough material
remains at the silicon junction 1502 after the deposited tungsten
layer 1520 has covered the exposed metal layer 1514 to assure that
a good silicide contact can be formed.
2. Cobalt Containing Barrier Layer Fill Process
[0024] The second novel method, illustrated in FIG. 4, is a series
of method steps 1001 that are used to fill a contact level feature.
FIG. 3A illustrates a cross-sectional view of substrate 1500 having
a contact level aperture 1510 formed into dielectric layer 1504.
The dielectric layer 1504 contains an insulating material that
includes silicon dioxide, silicon nitride, SOI, BPSG, silicon
oxynitride and/or carbon-doped silicon oxides, such as
SiO.sub.xC.sub.y, for example, BLACK DIAMOND.TM. low-k dielectric,
available from Applied Materials, Inc., located in Santa Clara,
Calif. Contact level aperture 1510 may be formed in dielectric
layer 1504 using conventional lithography and etching techniques to
expose the silicon junction 1502, such as a source or drain
interface. Silicon junction 1502 is generally doped silicon region,
such as a N+ or P+ doped silicon region.
[0025] An oxide surface 1512 is usually formed at the silicon
junction 1502 during previous etching and ashing processes used to
form contact level aperture 1510. Oxide surface 1512 may be a
continuous layer or a discontinuous layer across the surface of
silicon junction 1502 and include a surface terminated with oxygen,
hydrogen, hydroxides, a metal or combinations thereof. In examples
wherein silicon junction 1502 contains a silicon-containing
material, oxide surface 1512 is usually a silicon oxide surface.
Also, in examples wherein silicon junction 1502 contains a
metal-containing material, oxide surface 1512 is usually a metal
oxide surface.
[0026] The first step of the method steps 1001 includes a
pretreatment process step 1002, to remove the oxide layer so
subsequent processes can be preformed on the surface of the silicon
junction 1502. In this process step the substrate 1500 is exposed
to a pretreatment process to form a treated surface (not shown) on
the silicon junction 1502, which is substantially free of oxide
surface 1512. In one example, the silicon junction 1502 contains a
silicon-containing material and treated surface contains a
hydride-terminus surface, such as a silicon hydride layer. In
another example, the silicon junction 1502 contains a
metal-containing material and the treated surface contains a
reduced metal surface. The various processes that may be used to
perform the pretreatment process step 1002 on the surface of the
silicon junction 1502 are described below.
[0027] The second step of the method steps 1001 includes a metal
deposition step 1004 (FIG. 3C), that is used to deposit a metal
layer 1514 over the silicon junction 1502. In one embodiment, the
metal layer is a cobalt containing or nickel containing layer. The
metal deposition step 1004 may be performed by use of a PVD, CVD,
plasma enhanced CVD, ALD, plasma enhanced ALD or electroless
deposition process to form a metal containing layer. In one aspect,
when a non-selective deposition process is used, such as a PVD,
non-selective CVD, non-selective plasma enhanced CVD, non-selective
ALD, and/or non-selective plasma enhanced ALD process(es), the
method steps 1001 may include an optional metal removal step 1006.
The optional metal removal step includes the step of removing any
deposited metal(s) from the field region 1505 (FIG. 3A-B) by use of
a by use of a wet clean process, conventional CMP process,
electrochemical process and/or other comparable material removal
process.
[0028] In one aspect of method steps 1000, as shown in FIGS. 3C,
the metal deposition step 1004 is performed using a selective
deposition process to deposit the metal layer 1514 over the silicon
junction 1502. In this case the selectively deposited electroless
metal layer is only formed over the silicon junction 1502. An
exemplary selective electrochemical deposition of a nickel
containing layer is described below. In this case there is
generally no need to perform the optional metal removal step 1006,
since the metal layer 1514 will be selectively deposited at the
surface of the silicon junction 1502.
[0029] In one aspect, the metal layer 1514 is a nickel containing
layer. For example, a nickel film is formed on the Si surface using
a galvanic plating bath. To perform this process the films are
created from a plating bath which contains a nickel(II) salt, such
as nickel sulfate, an electrolyte such as tetramethylammonium
sulfate, and a wetting agent such as diethanolamine, adjusted to
basic pH with tetramethylammonium hydroxide (TMAH) and maintained
at temperatures above 60.degree. C. The wetting agent may be part
of the electrolyte. No reducing agent is required to be added.
During the galvanic deposition of Ni on silicon (Si), the surface
of the Si acts as a reducing agent. In other embodiments, a
sacrificial element or structure attached to the silicon may act as
a reducing agent. The addition of a wetting agent to the galvanic
system eliminates the need for galvanic displacement plating
schemes on Si (see attached PDFs). Therefore, a superficial
oxidation of the Si surface with a hydrochloric acid/peroxide
mixture (HPM), ethanol, or other pre-treatments which allow the
galvanic solution to wet the oxide free Si surface (the Si-H
surface is very hydrophobic) is not needed. The formation of a
nickel film on Si by this method is self-limiting, which allows a
mechanism of film thickness control.
[0030] The next process step in the method steps 1001, is a step
that uses a conventional thermal processing techniques to cause the
deposited metal layer 1514 to form a metal silicide layer 1515 at
the silicon junction 1502 (see step 1007). Typically, the
conventional thermal processing techniques include performing an
RTP or furnace anneal step at temperatures greater than about
250.degree. C. for a desired period of time to cause a desired
thickness of the metal silicide to form at the silicon junction
1502. An RTP system that may useful for completing aspects of this
invention described herein may be purchased from Applied Materials
Inc. of Santa Clara, Calif.
[0031] The next process step in the method steps 1001 is a
selective barrier layer deposition step 1008 (FIG. 3F), which
generally causes a metal containing layer 1518 to be deposited over
the metal silicide layer 1515 formed on the silicon junction 1502.
The barrier layer provides for protection of the silicide layer
during the tungsten deposition process. In one aspect, the barrier
layer is selectively deposited using an electroless deposition
process. The barrier layer could also be a PVD tungsten layer
followed by a CVD tungsten. The barrier layer deposition step 1008
may be performed by use of a PVD, CVD, plasma enhanced CVD, ALD,
plasma enhanced ALD or electroless deposition process to form a
cobalt containing layer in the contact level aperture 1510. In one
aspect, the metal containing layer 1518 is a cobalt containing
layer. In one aspect, as shown in FIG. 3F, cobalt containing layer
deposition step 1008 is adapted to selectively deposit the metal
containing layer 1518 on the metal silicide layer 1515. In one
aspect, the selective barrier layer deposition step 1008 is
performed using an electroless deposition process to selectively
deposit a layer that contains, for example, a cobalt-tungsten alloy
(e.g., CoW, COWP, CoWB, COWPB). An example of an electroless
solution used to deposit a cobalt-tungsten alloy may contain a
cobalt source, a tungsten source, a citrate source, a hypophosphite
source, a borane reductant and other additives. Other electroless
deposition solutions that may be used to deposit a cobalt-tungsten
alloy are further described in the commonly assigned U.S. patent
application Ser. No. 10/967,919, entitled, "Selective
Self-initiating Electroless Capping of Copper with
Cobalt-containing Alloys," filed on Oct. 18, 2004, which is
incorporated by reference to the extent not inconsistent with the
claimed aspects and description herein. Exemplary electroless
deposition process cell may be the same process cells/chambers as
described in the capping processes described herein.
[0032] The final step in the method steps 1001 is a CVD tungsten
deposition process that is used to fill the contact level aperture
1510. The tungsten CVD deposition process used in step 1010 is
generally performed using conventional tungsten hexafluoride
(WF.sub.6) precursor chemistries to fill the contact level aperture
1510. In this step a tungsten layer 1520 is directly deposited on
the metal containing layer 1518. A selective tungsten CVD process
can also be used.
Exemplary Pretreatment Process
[0033] FIG. 3A illustrates a cross-sectional view of substrate 1500
having a via or aperture 1510 formed into dielectric layer 1504.
Aperture 1510 may be formed in dielectric layer 1504 using
conventional lithography and etching techniques to expose the
silicon containing layer 1502, such as a source region, drain
region or gate region of a MOS device. The silicon containing layer
1502 may be a silicon-containing material or a metal-containing
material.
[0034] In some examples, silicon containing layer 1502 is a
silicon-containing material that may also contain germanium,
carbon, boron, phosphorous, arsenic or combinations thereof. For
example, silicon containing layer 1502 may contain silicon, silicon
carbide, silicon germanium, silicon germanium carbide, combinations
thereof or doped variants thereof. In another embodiment, silicon
containing layer 1502 contains a metal silicide or silicon dopant
material (e.g., N-type or P-type dopants).
[0035] Substrate 1500 is exposed to a pretreatment process to form
treated surface 1514 of silicon containing layer 1502,
substantially free of oxide surface 1512 (not shown). In one
example, silicon containing layer 1502 contains a
silicon-containing material and treated surface 1514 contains a
hydride-terminus surface, such as a silicon hydride layer.
[0036] In one embodiment, substrate 1500 is exposed to a wet clean
process to remove oxide surface 1512 and to form treated surface
1514. In one example, oxide surface 1512 is removed by a HF-last
solution to form treated surface 1514 as a substantially
oxide-free, silicon hydride surface. In another example, oxide
surface 1512 is removed during a liquid reduction process to form
treated surface 1514 as a substantially oxide-free, metallic
surface. In another example, oxide surface 1512 is exposed to a
hydrogen plasma to form treated surface 1514 as a substantially
oxide-free, silicon hydride surface.
[0037] During one embodiment of a pretreatment process, substrate
1500 is exposed to a wet-clean process for a predetermined time to
remove oxide surface 1512 and form treated surface 1514. A wet
clean process may include dispensing a wet clean solution across or
sprayed on the surface of substrate 1500. The wet clean process may
be an in situ process performed in the same processing cell as a
subsequent electroless deposition process. Alternatively, substrate
1500 may be wet cleaned in a separate processing cell from the
subsequent electroless deposition processing cell. An example of an
exemplary electroless deposition processing cell is further
described in the U.S. patent application Ser. No. 10/996,342 [APPM
9032], filed 11/22/2004, and U.S. patent application Ser. No.
11/043,442 [APPM 8024.P1], filed 1/26/2005, which are all
incorporated by reference herein in their entirety. In one example,
the wet-clean process utilizes an HF-last solution containing
water, HF and optional additives including chelators, surfactants,
reductants, other acids or combinations thereof. The hydrogen
fluoride concentration of a wet-clean solution may be within a
range from about 10 ppm to about 5 wt %, preferably from about 50
ppm to about 2 wt %, and more preferably, from about 100 to about 1
wt %, for example, about 0.5 wt %.
[0038] A wet-clean pretreatment process may occur for about 10
minutes or less, such as within a range from about 15 seconds to
about 5 minutes, preferably from about 30 seconds to about 4
minutes, and more preferably from about 1 minute to about 3
minutes. During the pretreatment process, the substrate is
maintained at a temperature within a range from about 15.degree. C.
to about 50.degree. C., preferably about room temperature (e.g.,
20.degree. C.). The wet-clean process may be performed in a
TEMPEST.TM. wet-clean system, available from Applied Materials,
Inc., located in Santa Clara, Calif.
[0039] In another embodiment of a pretreatment process, substrate
1500 is exposed to a liquid reduction process containing a
metal-reductant to form treated surface 1514. The metal-reductant
may be a Ti.sup.3+ compound, such as titanium citrate. In an
alternative embodiment of a pretreatment process, substrate 1500 is
exposed to a plasma process for a predetermined time to reduce
oxide surface 1512 and form treated surface 1514.
Exemplary Nickel Electroless Solution and Deposition Process
[0040] Nickel-containing materials are deposited on the silicon
containing layer 1502 by an electroless deposition process. The
electroless deposition solution to form nickel-containing materials
is an aqueous solution that generally contains a nickel source, a
reductant, a complexing agent, a pH adjusting agent and optional
additives and surfactants. A nickel-containing material may be
deposited by an electroless process utilizing either a pre-mixed
electroless deposition solution or an in-line mixing process that
combines solution components to generate the electroless solution.
An example of an exemplary in-line mixing process and apparatus is
further described in the U.S. patent application Ser. No.
11/040,962 [APPM 8926], filed 1/22/2005, which is incorporated by
reference herein in their entirety.
[0041] The nickel source within the electroless deposition solution
may have a concentration in a range from about 20 mM to about 200
mM, preferably from about 40 mM to about 80 mM, and more preferably
from about 50 mM to about 70 mM, such as about 60 mM. Nickel
sources provide nickel ions (e.g., Ni.sup.2+) dissolved within the
electroless solution and later reduced out as the deposited
nickel-containing material. Useful nickel sources include nickel
sulfate, nickel chloride, nickel acetate, nickel phosphate,
derivatives thereof, hydrates thereof or combinations thereof. In a
preferred embodiment, nickel sulfate hexahydrate
(NiSO.sub.4.6H.sub.2O) is used in the electroless solution to
deposit nickel-containing materials.
[0042] The reductant within the electroless deposition solution may
have a concentration in a range from about 1 mM to about 100 mM,
preferably from about 2 mM to about 50 mM, and more preferably from
about 5 mM to about 20 mM, such as about 14 mM. Reductants provide
electrons to induce chemical reduction of the nickel ions that form
and deposit the nickel-containing material. Reductants may include
organic reductants (e.g., formaldehyde or glyoxylic acid),
hydrazine, organic hydrazines (e.g., methyl hydrazine),
hypophosphite sources (e.g., hypophosphorous acid
(H.sub.3PO.sub.2), ammonium hypophosphite
((NH.sub.4).sub.4-xH.sub.xPO.sub.2) and salts thereof), borane
sources (e.g., dimethylamine borane complex
((CH.sub.3).sub.2NH.BH.sub.3), DMAB), trimethylamine borane complex
((CH.sub.3).sub.3N.BH.sub.3), TMAB), tert-butylamine borane complex
(.sup.tBuNH.sub.2.BH.sub.3), tetrahydrofuran borane complex
(THF.BH.sub.3), pyridine borane complex (C.sub.5H.sub.5N.BH.sub.3),
ammonia borane complex (NH.sub.3.BH.sub.3), borane (BH.sub.3),
diborane (B.sub.2H.sub.6), derivatives thereof, complexes thereof
or combinations thereof. In a preferred embodiment, DMAB is used as
a reductant in the electroless solution for depositing
nickel-containing materials.
[0043] Chelators or complexing agents are in the electroless
solution to complex nickel ions thereby stabilizing the solubility
and reduction of nickel ions. The complexing agents may have a
concentration in a range from about 50 mM to about 2 M, preferably
from about 100 mM to about 1 M, and more preferably from about 200
mM to about 500 mM. Complexing agents generally may have functional
groups, such as carboxylic acids, dicarboxylic acids,
polycarboxylic acids, amino acids, amines, diamines, polyamines,
alkylamines, alkanolamines and alkoxyamines. Complexing agents may
include citric acid, citrates, glycolic acid, glycine, malonic
acid, maleic acid, lactic acid, ethylenediaminetetraacetic acid
(EDTA), ethylenediamine (EDA), triethylene tetramine (TETA),
diaminoethane, monoethanolamine, diethanolamine (DEA),
triethanolamine (TEA), hydroxylamine hydrochloride, ammonia,
ammonium chloride, derivatives thereof, salts thereof or
combinations thereof. Usually, the electroless solution contains
more than one complexing agent. Preferably, the electroless
solution contains at least citric acid or citrate salts, more
preferably, the electroless solution also contains DEA, glycine
and/or lactic acid. In one example, the electroless solution
contains about 60 mM of citric acid, 115 mM of DEA, 30 mM of
glycine and 120 mM of lactic acid.
[0044] A pH adjusting agent is added to adjust the electroless
solution to a pH value in a range from about 8 to about 11,
preferably from about 9 to about 10, and more preferably from about
9.2 to about 9.6, such as about 9.4. The pH adjusting agent may be
an acidic compound to decrease the pH value of the electroless
solution and include hydrochloric acid, sulfuric acid, phosphoric
acid, derivatives thereof or combinations thereof. Alternatively,
the pH adjusting agent may be a basic compound to increase the pH
value of the electroless solution and include metal hydroxides,
tetraalkylammonium hydroxides (e.g., tetramethylammonium hydroxide
((CH.sub.3).sub.4NOH, TMAH) or tetraethylammonium hydroxide
((CH.sub.3CH.sub.2).sub.4NOH, TEAH)), ammonium hydroxide, DEA, TEA,
derivatives thereof or combinations thereof. The pH adjusting agent
may be dissolved in water prior to adjusting the pH value of the
electroless solution. In one example, a 25 wt % aqueous solution of
TMAH is used as a pH adjusting agent. In another example, both TMAH
and DEA are used to adjust the pH value of an electroless
solution.
[0045] The optional additives may include levelers, accelerators
and suppressors. Levelers within the electroless solution are used
to achieve different deposition thickness as a function of leveler
concentration and feature geometry while depositing
nickel-containing materials. The leveler within the electroless
deposition solution may have a concentration in a range from about
20 ppb to about 600 ppm, preferably from about 100 ppb to about 100
ppm. Examples of levelers that may be employed in an electroless
solution include, but are not limited to alkylpolyimines and
organic sulfonates, such as
1-(2-hydroxyethyl)-2-imidazolidinethione (HIT), 4-mercaptopyridine,
2-mercaptothiazoline, ethylene thiourea, thiourea or derivatives
thereof. The electroless deposition solution may contain
brighteners or accelerators and suppressors as alternative
additives to provide further control of the deposition process. The
role of accelerators is to achieve a smoothly deposited surface of
the nickel-containing material. The accelerator within the
electroless deposition solution has a concentration in a range from
about 20 ppb to about 600 ppm, preferably from about 100 ppb to
about 100 ppm. Accelerators that are useful in an electroless
solution for depositing nickel-containing materials may include
sulfur-based compounds such as bis(3-sulfopropyl) disulfide (SPS),
3-mercapto-1-propane sulfonic acid (MPSA), aminoethane sulfonic
acids, thiourea, derivatives thereof, combinations thereof.
Suppressors are used to suppress nickel deposition by initially
adsorbing onto underlying catalytic surfaces and therefore blocking
access to the catalyst of the reaction. Suppressors generally may
include polyethylene glycol (PEG), polypropylene glycol (PPG),
polyoxyethylene-polyoxypropylene copolymer (POCP), benzotriazole
(BTA), dipyridyl, dimethyl dipyridyl, derivatives thereof or
combinations thereof. The suppressor within the electroless
deposition solution has a concentration in a range from about 20
ppb to about 600 ppm, preferably from about 100 ppb to about 100
ppm.
[0046] The electroless solution may contain boric acid as an
additional additive. Boric acid is added to provide additional
buffering and to stabilize the composition of the solution. Boric
acid is an oxidation by-product from the chemical reactions of
borane reductants (e.g., DMAB). Therefore, an electroless solution
containing boric acid is more normalized at the start of the
deposition process since a less steep dissipation gradient exist as
additional boric acid is formed from the borane reductant. Boric
acid is preferably within the electroless deposition solution at
concentration in a range from about 1 mM to about 50 mM, preferably
from about 2 mM to about 20 M, and more preferably from about 5 mM
to about 15 mM, such as about 10 mM.
[0047] Also, an optional surfactant may be added to the electroless
solution. The surfactant is a wetting agent to reduce the surface
tension between the electroless solution and the substrate surface.
Surfactants are generally added to the electroless solution at a
concentration of about 1,000 ppm or less, preferably about 800 ppm
or less, such as from about 20 ppb to about 600 ppm. The surfactant
may have ionic or non-ionic characteristics. A preferred surfactant
includes dodecyl sulfates, such as sodium dodecyl sulfate (SDS).
Other surfactants that may be used in the electroless deposition
solution include glycol ether based surfactants (e.g., polyethylene
glycol). For example, a glycol ether based surfactants may contain
polyoxyethylene units, such as TRITON.RTM. 100, available from Dow
Chemical Company. A nonylphenol ethoxylate surfactant is useful in
the electroless deposition solution, such as TERGITOL.RTM.,
available from Dow Chemical Company or IGEPAL-630, available from
GAF Corporation. Other useful surfactants may contain phosphate
units, for example, sodium poly(oxyethylene) phenyl ether
phosphate, such as RHODAFAC.RTM. RE-610, available from Rhodia,
Inc. The surfactants may be single compounds or a mixture of
compounds of molecules containing varying length of hydrocarbon
chains.
[0048] An electroless process to deposit nickel-containing
materials may utilize an in-line mixing process to form the
electroless solution. The process may contain the addition of two,
three, four or more componential solutions to form the electroless
solution. In one example, the electroless solution is formed by
combining a buffered cleaning solution, a nickel-containing
solution, a reducing solution and water, where each solution is a
concentrate and water is added to reach a predetermined
concentration of the final solution. In another example, the
electroless solution is formed by combining a buffered cleaning
solution, a nickel-containing solution and a reducing solution,
where each of the solutions are pre-diluted and therefore do not
require additional water. In another example, the electroless
solution is formed by combining a buffered nickel-containing
solution, a reducing solution and water, where a buffered cleaning
solution and a nickel-containing solution are combined to form the
buffered nickel-containing solution. Further details of in-line
mixing processes and componential solutions are further described
in the commonly assigned U.S. patent application Ser. No.
10/967,919, entitled, "Selective Self-initiating Electroless
Capping of Copper with Cobalt-containing Alloys," filed on Oct. 18,
2004, and published as US 2005-0136193, which is incorporated by
reference to the extent not inconsistent with the claimed aspects
and description herein.
[0049] A buffered cleaning solution usually contains water, at
least one complexing agent, additives and a pH adjusting agent. The
complexing agent within the buffered cleaning solution is at a
concentration from about 0.2 M to about 3 M, preferably from about
0.5 M to about 2 M. The additive within the buffered cleaning
solution is at a concentration from about 10 mM to about 1 M,
preferably from about 50 mM to about 500 mM. The pH adjusting agent
is at a concentration to provide the buffered cleaning solution
with a pH value in a range from about 8 to about 11, preferably
from about 9 to about 10, and more preferably from about 9.2 to
about 9.6, such as about 9.4. In one example, a buffered cleaning
solution contains water, about 1.15 M of DEA, about 375 mM of
citric acid, about 300 mM of glycine, about 100 mM of boric acid
and a concentration of TMAH to adjust the pH value to about 9.4. In
another example, a buffered cleaning solution contains water, about
330 mM of DEA, about 300 mM of citric acid, about 150 mM of
glycine, about 50 mM of boric acid and a concentration of TMAH to
adjust the pH value to about 9.4.
[0050] A nickel-containing solution usually contains water, a
nickel source, at least one complexing agent and a pH adjusting
agent. The nickel source within the nickel-containing solution is
at a concentration from about 50 mM to about 1 M, preferably from
about 100 mM to about 500 mM, such as about 300 mM. The complexing
agent within the nickel-containing solution is at a concentration
from about 0.2 M to about 2 M, preferably from about 0.5 M to about
1 M. The pH adjusting agent is at a concentration to provide the
nickel-containing solution with a pH value in a range from about 8
to about 11, preferably from about 9 to about 10, and more
preferably from about 8.0 to about 8.5, such as about 8.5. In one
example, a nickel-containing solution contains water, about 100 mM
of citric acid, about 300 mM of nickel sulfate, about 600 mM of 85%
lactic acid and a concentration of TMAH to adjust the pH value to
about 9.4.
[0051] A reducing solution usually contains water, at least one
reductant, at least one complexing agent and a pH adjusting agent.
The reductant within the reducing solution is at a concentration
from about 10 mM to about 500 mM, preferably from about 50 mM to
about 100 mM, such as about 70 mM. The complexing agent within the
reducing solution is at a concentration from about 1 mM to about 50
mM, preferably from about 5 mM to about 15 mM, such as about 10 mM.
The pH adjusting agent is at a concentration to provide the
reducing solution with a pH value in a range from about 8 to about
11, preferably from about 9 to about 10, and more preferably from
about 8.0 to about 8.5, such as about 8.5. In one example, a
reducing solution contains water, about 10 mM of citric acid, about
70 mM of DMAB and a concentration of TMAH to adjust the pH value to
about 9.4.
[0052] The electroless solution is preferably formed by in-line
mixing process that combines various volumetric ratios of the
buffered cleaning solution, the nickel-containing solution, the
reducing solution and water. In one example, one volumetric
equivalent of a buffered cleaning solution, two volumetric
equivalents of a nickel-containing solution, two volumetric
equivalents of a reducing solution and five volumetric equivalents
of deionized water are in-line mixed to form an electroless
solution. That is, the volumetric ratio of the buffered cleaning
solution, the nickel-containing solution, the reducing solution and
the deionized water is 1:2:2:5. In another example of an
electroless solution, a volumetric ratio of the buffered cleaning
solution, the nickel-containing solution, the reducing solution and
the water is 1:1:1:3.
[0053] In one embodiment, an electroless solution contains: nickel
sulfate with a concentration in a range from about 20 mM to about
200 mM, preferably from about 40 mM to about 80 mM, and more
preferably from about 50 mM to about 70 mM, such as about 60 mM;
DMAB with a concentration in a range from about 1 mM to about 100
mM, preferably from about 2 mM to about 50 mM, and more preferably
from about 5 mM to about 20 mM, such as about 14 mM; citric acid
with a concentration in a range from about 5 mM to about 500 mM,
preferably from about 10 mM to about 100 mM, and more preferably
from about 40 mM to about 80 mM, such as about 60 mM; DEA with a
concentration in a range from about 5 mM to about 500 mM,
preferably from about 10 mM to about 200 mM, such as about 33 mM or
about 115 mM; glycine with a concentration in a range from about 1
mM to about 150 mM, preferably from about 2 mM to about 80 mM, and
more preferably from about 5 mM to about 50 mM, such as about 15 mM
or about 30 mM; boric acid with a concentration in a range from
about 1 mM to about 100 mM, preferably from about 2 mM to about 50
mM, and more preferably from about 3 mM to about 20 mM, such as
about 5 mM or about 10 mM; lactic acid with a concentration in a
range from about 10 mM to about 500 mM, preferably from about 50 mM
to about 200 mM, and more preferably from about 100 mM to about 140
mM, such as about 120 mM; TMAH with a concentration to adjust the
electroless solution to a have pH value in a range from about 8 to
about 11, preferably from about 9 to about 10, and more preferably
from about 8.0 to about 8.5, such as about 8.5.
[0054] In one embodiment, citrate is a preferred complexing agent
and is present in each componential solution, such as the buffered
cleaning solution, the nickel-containing solution and the reducing
solution. Citrate may be added as citric acid and/or as a citrate
salt. Citrate plays an important role of buffering each of the
individual componential solutions while being combined to form the
plating solution. Citrates generally have poor solubility in water
at high concentrations, while the componential solutions may have
relatively concentrated solutions. If a substantial citrate
concentration of the final electroless solution is desired, a
single componential solution may not be capable of completely
containing all the dissolved citrate. Therefore, the citrate may be
dissolved in each componential solution to assure no formation of
citrate precipitate, and subsequently combined with water forming
the electroless solution at a final concentration.
[0055] The electroless deposition process may be conducted at a
temperature in a range from about 35.degree. C. to about
120.degree. C., preferably from about 60.degree. C. to about
100.degree. C., and more preferably from about 80.degree. C. to
about 85.degree. C. The water may be degassed, preheated and/or
deionized water. Degassing the water reduces the oxygen
concentration of the subsequently formed electroless solution. An
electroless solution with a low oxygen concentration (e.g., less
than about 100 ppm) may be used during the deposition process.
Preheated water allows forming the electroless solution at a
predetermined temperature just below the temperature used to
initiate the deposition process, thereby shortening the process
time.
[0056] A chamber useful to conduct an electroless deposition
process for depositing a cobalt-tungsten material, a cobalt-nickel
material or a nickel-containing material is the electroless
deposition process cell, further described in the commonly assigned
U.S. patent application Ser. No. 10/965,220, entitled "Apparatus
for Electroless Deposition," filed on Oct. 14, 2004, and published
as US 2005-0081785, U.S. patent application Ser. No. 10/996,342,
entitled, "Apparatus for Electroless Deposition of Metals on
Semiconductor Wafers," filed on Nov. 22, 2004, U.S. patent
application Ser. No. 11/043,442, entitled, "Apparatus for
Electroless Deposition of Metals onto Semiconductor Substrates,"
filed on Jan. 26, 2005, and U.S. patent application Ser. No.
11/040,962, entitled "Method and Apparatus for Selectively Changing
Thin Film Composition During Electroless Deposition in a Single
Chamber," filed on Jan. 22, 2005, which are each incorporated by
reference to the extent not inconsistent with the claimed aspects
and description herein.
Examples of Cobalt and Nickel Electroless Deposition
Chemistries
Cobalt
[0057] In one embodiment, an electroless solution for depositing
metallic cobalt contains: cobalt ions (CO.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; hydrazine hydrate
with a concentration in a range from about 100 mM to about 2 M,
preferably from about 200 mM to about 1 M, and more preferably from
about 300 mM to about 700 mM, such as about 500 mM; citric acid or
citrate salt with a citrate concentration in a range from about 5
mM to about 200 mM, preferably from about 10 mM to about 100 mM,
and more preferably from about 30 mM to about 70 mM, such as about
50 mM; and an optional pH adjusting agent (e.g., TMAH) with a
concentration to adjust the electroless solution to a have pH value
in a range from about 10 to about 14, preferably from about 11.5 to
about 13, and more preferably from about 12.2 to about 12.8, such
as about 12.5. In one example, a pH value is about 11.5 or higher,
preferably, about 12.0 or higher, and more preferably, about 12.5
or higher. The electroless deposition process to deposit metallic
cobalt may be conducted at a temperature within a range from about
35.degree. C. to about 100.degree. C., preferably from about
60.degree. C. to about 90.degree. C., and more preferably from
about 70.degree. C. to about 80.degree. C., such as about
75.degree. C.
Cobalt Boride
[0058] In one embodiment, an electroless solution for depositing
cobalt boride contains: cobalt ions (CO.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; DMAB with a
concentration in a range from about 1 mM to about 200 mM,
preferably from about 10 mM to about 100 mM, and more preferably
from about 30 mM to about 50 mM, such as about 40 mM; citric acid
or citrate salt with a citrate concentration in a range from about
5 mM to about 500 mM, preferably from about 30 mM to about 300 mM,
and more preferably from about 50 mM to about 150 mM, such as about
100 mM; and an optional pH adjusting agent (e.g., TMAH) with a
concentration to adjust the electroless solution to a have pH value
in a range from about 8 to about 11, preferably from about 8 to
about 10, and more preferably from about 8.5 to about 9.5, such as
about 8.9. The electroless deposition process to deposit cobalt
boride may be conducted at a temperature within a range from about
35.degree. C. to about 100.degree. C., preferably from about
60.degree. C. to about 80.degree. C., and more preferably from
about 65.degree. C. to about 75.degree. C., such as about
70.degree. C.
Cobalt Tungsten Boride
[0059] In one embodiment, an electroless solution for depositing
cobalt tungsten boride contains: cobalt ions (CO.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; tungstic acid or
tungstate salt with a tungstate concentration in a range from about
0.1 mM to about 10 mM, preferably from about 0.5 mM to about 5 mM,
and more preferably from about 1 mM to about 3 mM, such as about 2
mM; DMAB with a concentration in a range from about 1 mM to about
200 mM, preferably from about 10 mM to about 100 mM, and more
preferably from about 30 mM to about 50 mM, such as about 40 mM;
citric acid or citrate salt with a citrate concentration in a range
from about 5 mM to about 500 mM, preferably from about 30 mM to
about 300 mM, and more preferably from about 50 mM to about 150 mM,
such as about 100 mM; and an optional pH adjusting agent (e.g.,
TMAH) with a concentration to adjust the electroless solution to a
have pH value in a range from about 8 to about 11, preferably from
about 8 to about 10, and more preferably from about 8.5 to about
9.5, such as about 8.9. The electroless deposition process to
deposit cobalt tungsten boride may be conducted at a temperature
within a range from about 35.degree. C. to about 100.degree. C.,
preferably from about 60.degree. C. to about 80.degree. C., and
more preferably from about 65.degree. C. to about 75.degree. C.,
such as about 70.degree. C.
Nickel Boride
[0060] In one embodiment, an electroless solution for depositing
nickel boride contains: nickel ions (Ni.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; DMAB with a
concentration in a range from about 1 mM to about 200 mM,
preferably from about 10 mM to about 100 mM, and more preferably
from about 30 mM to about 50 mM, such as about 40 mM; citric acid
or citrate salt with a citrate concentration in a range from about
5 mM to about 300 mM, preferably from about 10 mM to about 100 mM,
and more preferably from about 40 mM to about 60 mM, such as about
50 mM; lactic acid or lactate salt with a lactate concentration in
a range from about 5 mM to about 300 mM, preferably from about 10
mM to about 100 mM, and more preferably from about 40 mM to about
60 mM, such as about 50 mM; and an optional pH adjusting agent
(e.g., TMAH) with a concentration to adjust the electroless
solution to a have pH value in a range from about 8 to about 11,
preferably from about 8 to about 10, and more preferably from about
8.0 to about 8.5, such as about 8.5. The electroless deposition
process to deposit nickel boride may be conducted at a temperature
within a range from about 35.degree. C. to about 100.degree. C.,
preferably from about 60.degree. C. to about 80.degree. C., and
more preferably from about 65.degree. C. to about 75.degree. C.,
such as about 70.degree. C.
Nickel Tungsten Boride
[0061] In one embodiment, an electroless solution for depositing
nickel tungsten boride contains: nickel ions (Ni.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; tungstic acid or
tungstate salt with a tungstate concentration in a range from about
0.1 mM to about 10 mM, preferably from about 0.5 mM to about 5 mM,
and more preferably from about 1 mM to about 3 mM, such as about 2
mM; DMAB with a concentration in a range from about 1 mM to about
200 mM, preferably from about 10 mM to about 100 mM, and more
preferably from about 30 mM to about 50 mM, such as about 40 mM;
citric acid or citrate salt with a citrate concentration in a range
from about 5 mM to about 300 mM, preferably from about 10 mM to
about 100 mM, and more preferably from about 40 mM to about 60 mM,
such as about 50 mM; lactic acid or lactate salt with a lactate
concentration in a range from about 5 mM to about 300 mM,
preferably from about 10 mM to about 100 mM, and more preferably
from about 40 mM to about 60 mM, such as about 50 mM; and an
optional pH adjusting agent (e.g., TMAH) with a concentration to
adjust the electroless solution to a have pH value in a range from
about 8 to about 11, preferably from about 8 to about 10, and more
preferably from about 8.5 to about 9.5, such as about 8.9. The
electroless deposition process to deposit nickel tungsten boride
may be conducted at a temperature within a range from about
35.degree. C. to about 100.degree. C., preferably from about
60.degree. C. to about 80.degree. C., and more preferably from
about 65.degree. C. to about 75.degree. C., such as about
70.degree. C.
Cobalt Nickel Boride
[0062] In one embodiment, an electroless solution for depositing
cobalt nickel boride contains: cobalt ions (CO.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; nickel ions
(Ni.sup.2+) with a concentration in a range from about 1 mM to
about 100 mM, preferably from about 5 mM to about 50 mM, and more
preferably from about 10 mM to about 20 mM, such as about 15 mM;
DMAB with a concentration in a range from about 1 mM to about 200
mM, preferably from about 10 mM to about 100 mM, and more
preferably from about 30 mM to about 50 mM, such as about 40 mM;
citric acid or citrate salt with a citrate concentration in a range
from about 5 mM to about 500 mM, preferably from about 30 mM to
about 300 mM, and more preferably from about 50 mM to about 150 mM,
such as about 100 mM; and an optional pH adjusting agent (e.g.,
TMAH) with a concentration to adjust the electroless solution to a
have pH value in a range from about 8 to about 11, preferably from
about 8 to about 10, and more preferably from about 8.5 to about
9.5, such as about 8.9. The electroless deposition process to
deposit cobalt nickel boride may be conducted at a temperature
within a range from about 35.degree. C. to about 100.degree. C.,
preferably from about 60.degree. C. to about 80.degree. C., and
more preferably from about 65.degree. C. to about 75.degree. C.,
such as about 70.degree. C.
Cobalt Nickel
[0063] In one embodiment, an electroless solution for depositing
cobalt nickel contains: cobalt ions (CO.sup.2+) with a
concentration in a range from about 1 mM to about 100 mM,
preferably from about 5 mM to about 50 mM, and more preferably from
about 10 mM to about 20 mM, such as about 15 mM; nickel ions
(Ni.sup.2+) with a concentration in a range from about 1 mM to
about 100 mM, preferably from about 5 mM to about 50 mM, and more
preferably from about 10 mM to about 20 mM, such as about 15 mM;
hydrazine hydrate with a concentration in a range from about 100 mM
to about 2 M, preferably from about 200 mM to about 1 M, and more
preferably from about 300 mM to about 700 mM, such as about 500 mM;
citric acid or citrate salt with a citrate concentration in a range
from about 5 mM to about 500 mM, preferably from about 30 mM to
about 300 mM, and more preferably from about 50 mM to about 150 mM,
such as about 100 mM; and an optional pH adjusting agent (e.g.,
TMAH) with a concentration to adjust the electroless solution to a
have pH value in a range from about 10 to about 14, preferably from
about 11.5 to about 13, and more preferably from about 12.2 to
about 12.8, such as about 12.5. The electroless deposition process
to deposit cobalt nickel may be conducted at a temperature within a
range from about 35.degree. C. to about 100.degree. C., preferably
from about 60.degree. C. to about 90.degree. C., and more
preferably from about 70.degree. C. to about 80.degree. C., such as
about 75.degree. C.
[0064] While foregoing is directed to the preferred embodiment of
the invention, other and further embodiments of the invention may
be devised without departing from the basic scope thereof, and the
scope thereof is determined by the claims that follow.
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