U.S. patent application number 09/916234 was filed with the patent office on 2003-02-13 for an apparatus for annealing substrates in physical vapor deposition systems.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Cha, Yonghwa Chris, Yoon, Ki Hwan, Yu, Sang-Ho.
Application Number | 20030029715 09/916234 |
Document ID | / |
Family ID | 25436918 |
Filed Date | 2003-02-13 |
United States Patent
Application |
20030029715 |
Kind Code |
A1 |
Yu, Sang-Ho ; et
al. |
February 13, 2003 |
An Apparatus For Annealing Substrates In Physical Vapor Deposition
Systems
Abstract
Methods and apparatus are provided for annealing of materials
deposited in a processing chamber to form silicide layers. In one
aspect, a method is provided for treating a substrate surface
including positioning a substrate having silicon material disposed
thereon on a substrate support in a chamber, forming a metal layer
on at least the silicon material, and annealing the substrate in
situ to form a metal silicide layer. In another aspect, the method
is performed in an apparatus including a load lock chamber, an
intermediate substrate transfer region connected to the load lock
chamber, the intermediate substrate transfer region comprising a
first substrate transfer chamber and a second substrate transfer
chamber, a physical vapor deposition processing chamber disposed on
the first substrate transfer chamber and an annealing chamber
disposed on the second substrate transfer chamber.
Inventors: |
Yu, Sang-Ho; (Sunnyvalve,
CA) ; Cha, Yonghwa Chris; (San Jose, CA) ;
Yoon, Ki Hwan; (Sunnyvale, CA) |
Correspondence
Address: |
APPLIED MATERIALS, INC.
2881 SCOTT BLVD. M/S 2061
SANTA CLARA
CA
95050
US
|
Assignee: |
APPLIED MATERIALS, INC.
|
Family ID: |
25436918 |
Appl. No.: |
09/916234 |
Filed: |
July 25, 2001 |
Current U.S.
Class: |
204/192.2 ;
257/E21.165; 257/E21.169; 257/E21.17 |
Current CPC
Class: |
H01L 21/28518 20130101;
H01L 21/28556 20130101; C23C 16/54 20130101; C23C 16/06 20130101;
H01L 21/76864 20130101; H01L 21/76876 20130101; C23C 14/566
20130101; H01L 21/76843 20130101; H01L 21/76855 20130101; H01L
21/76846 20130101; H01L 21/2855 20130101 |
Class at
Publication: |
204/192.2 |
International
Class: |
C23C 014/00 |
Claims
1. A system for processing a substrate, comprising: a load lock
chamber; an intermediate substrate transfer region connected to the
load lock chamber, the intermediate substrate transfer region
comprising a first substrate transfer chamber and a second
substrate transfer chamber, wherein the first substrate transfer
chamber is coupled to the load lock chamber and the second
substrate transfer chamber is coupled to the first substrate
transfer chamber; a physical vapor deposition (PVD) processing
chamber disposed on the first substrate transfer chamber; and an
annealing chamber disposed on the second substrate transfer
chamber.
2. The apparatus of claim 1, further comprising plurality of vacuum
pumps communicating with the intermediate substrate transfer region
and each of the processing chambers, wherein the plurality of pumps
establish a vacuum gradient of increasing pressure across the
apparatus from the load lock chamber to the processing
chambers.
3. The apparatus of claim 1, wherein the second transfer chamber
has a higher chamber pressure than the first substrate transfer
chamber.
4. The apparatus of claim 1, wherein the PVD processing chamber has
an annealing pedestal disposed therein.
5. The apparatus of claim 1, wherein the PVD processing chamber has
a target of material selected from the group of cobalt, titanium,
tantalum, tungsten, molybdenum, platinum, nickel, iron, niobium,
palladium, and combinations thereof.
6. The apparatus of claim 1, wherein the PVD processing chamber
comprises a cobalt target and an annealing pedestal disposed
therein.
7. The apparatus of claim 1, wherein the annealing chamber
comprises a rapid thermal annealing chamber.
8. The apparatus of claim 1, further comprising a chemical vapor
deposition chamber disposed on the first substrate transfer
chamber, the second substrate transfer chamber, or combinations
thereof.
9. The apparatus of claim 1, wherein the apparatus comprises two
PVD processing chambers comprising a cobalt target and an annealing
pedestal disposed therein are disposed on the first transfer region
and two annealing processing chambers are disposed on the second
transfer chamber, wherein the second transfer chamber has a higher
operating temperature than the first transfer chamber.
10. The apparatus of claim 1, wherein the physical vapor deposition
(PVD) processing chamber comprises: a chamber enclosing a
sputtering source; a substrate support member disposed generally
parallel to the sputtering surface of the sputtering source, the
substrate support member comprising: a generally planar substrate
receiving surface configured to receive a substrate thereon; an
electrically resistive heating element disposed in the substrate
support member; and a fluid channel connected to a fluid supply and
regulated by a controller; and a collimator mounted between the
sputtering source and the substrate support member.
11. The apparatus of claim 10, wherein the substrate support member
comprises: an electrostatic chuck having an electrode, an
electrical insulator having a generally planar substrate receiving
surface disposed on the electrode and configured to receive a
substrate thereon; an electrically resistive heating element
disposed in the electrostatic chuck; and a fluid channel connected
to a fluid supply and regulated by a controller.
12. The apparatus of claim 10, further comprising an electrically
conductive lead for coupling the electrically resistive heating
elements to a voltage source.
13. The apparatus of claim 12, further comprising at least one
temperature sensor connected to the substrate support member.
14. The apparatus of claim 12, further comprising a source of gas
connected to a channel disposed in the support pedestal, the
channel connecting the source of gas to the planar substrate
receiving surface.
15. The apparatus of claim 11, wherein the collimator has upper and
lower surfaces and at least one of the surfaces being a convex
surface.
16. A method for forming a silicide layer on a substrate,
comprising: positioning a substrate having silicon material
disposed thereon on a substrate support disposed in a deposition
chamber having a metal target disposed therein; applying a current
to the substrate support to heat the substrate to a first
temperature; introducing an inert gas into the deposition chamber;
generating a plasma by applying a bias between a metal target and
the substrate support in the inert gas environment to sputter
material from the metal target; depositing the sputtered material
on at least the silicon material; providing a backside gas between
the substrate pedestal and the substrate; and annealing the
substrate in situ at a second temperature greater than the first
temperature to form a metal silicide layer.
17. The method of claim 16, wherein the substrate is positioned
between about 90 mm and about 400 mm from the target.
18. The method of claim 16, wherein the metal material is selected
from the group of cobalt, titanium, tantalum, tungsten, molybdenum,
platinum, nickel, iron, niobium, palladium, and combinations
thereof.
19. The method of claim 16, further comprising collimating the
sputtered material.
20. The method of claim 16, wherein the first temperature is about
200.degree. C. or less.
21. The method of claim 16, wherein annealing the substrate in situ
at a second temperature comprises annealing the substrate at a
temperature between about 300.degree. C. and about 900.degree. C.
on the substrate support.
22. The method of claim 21, wherein the substrate is annealed for
between about 10 seconds and about 600 seconds.
23. The method of claim 22, wherein annealing the substrate in situ
comprises annealing the substrate at a second temperature for a
first period of time in the deposition chamber, transferring the
substrate to an annealing chamber, and annealing the substrate at a
third temperature greater than the second temperature for a second
period of time without breaking vacuum in a processing system.
24. The method of claim 23, wherein the second temperature is
between about 300.degree. C. and about 500.degree. C. and the third
temperature is between about 400.degree. C. and about 900.degree.
C.
25. The method of claim 23, wherein the first period of time is
between about 5 second and about 300 seconds and the second period
of time is between about 5 seconds and about 300 seconds.
26. The method of claim 23, wherein annealing the substrate in situ
comprises annealing the substrate at a second temperature higher
than the first temperature in a first annealing chamber,
transferring the substrate to a second annealing chamber, and then
annealing the substrate at a third temperature higher than the
second temperature for the second period of time without breaking
vacuum in a processing system.
27. The method of claim 23, wherein the substrate surface is
treated by annealing the substrate in the deposition chamber at a
first temperature for a first period of time, transferring the
substrate to the thermal annealing chamber, and annealing the
substrate at a second temperature for a second period of time
without breaking vacuum in the processing system.
28. A method of processing a substrate, comprising: introducing a
substrate having silicon material disposed thereon into a load
lock; transferring the substrate to a first transfer chamber in
vacuum tight communication with the loadlock; positioning the
substrate on a heating pedestal in a physical vapor deposition
chamber in vacuum tight communication with the first transfer
chamber; depositing a metal layer on the silicon material;
annealing the substrate prior to transferring the substrate to a
second transfer chamber having an annealing chamber disposed
thereon, wherein the second transfer chamber is in vacuum tight
communication with the first transfer chamber; and annealing the
substrate in the annealing chamber to form a metal silicide
layer.
29. The method of claim 28, wherein annealing the substrate prior
to transferring the substrate comprises annealing the substrate in
the physical vapor deposition processing chamber.
30. The method of claim 28, further comprising a vacuum annealing
chamber in vacuum tight communication with the first transfer
chamber.
31. The method of claim 30, wherein annealing the substrate in the
annealing chamber comprises annealing the substrate in the vacuum
annealing chamber.
32. The method of claim 28, wherein annealing the substrate
comprises annealing the substrate at a temperature between about
300.degree. C. and about 900.degree. C. without breaking
vacuum.
33. The method of claim 28, wherein depositing a metal layer
comprises sputtering the metal target at a substrate temperature of
about 200.degree. C. or less.
34. The method of claim 28, wherein the second transfer chamber has
a higher chamber pressure than the first substrate transfer
chamber.
35. The method of claim 28, wherein the metal target comprises a
material selected from the group of cobalt, titanium, tantalum,
tungsten, molybdenum, platinum, nickel, iron, niobium, palladium,
and combinations thereof.
36. The apparatus of claim 28, wherein the physical vapor
deposition processing chamber comprises a cobalt target and an
annealing pedestal disposed therein.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the fabrication of
semiconductor devices and to the deposition and annealing of
materials on a semiconductor substrate.
[0003] 2. Description of the Related Art
[0004] Recent improvements in circuitry of ultra-large scale
integration (ULSI) on semiconductor substrates indicate that future
generations of semiconductor devices will require sub-quarter
micron multi-level metallization. The multilevel interconnects that
lie at the heart of this technology require planarization of
interconnect features formed in high aspect ratio apertures,
including contacts, vias, lines and other features. Reliable
formation of these interconnect features is very important to the
success of ULSI and to the continued effort to increase circuit
density and quality on individual substrates and die.
[0005] ULSI circuits include metal oxide semiconductor (MOS)
devices, such as complementary metal oxide semiconductor (CMOS)
field effect transistors (FETs). The transistors can include
semiconductor gates disposed between source and drain regions. In
the formation of integrated circuit structures, and particularly in
the formation of MOS devices using polysilicon gate electrodes, it
has become the practice to provide a metal silicide layer over the
polysilicon gate electrode, and over the source and drain regions
of the silicon substrate, to facilitate lower resistance and
improve device performance by electrically connecting the source
and drain regions to metal interconnects.
[0006] One important processing technique currently used in CMOS
processing technology is the Self-Aligned Silicidation (salicide)
of refractory metals such as titanium and cobalt. In a salicide
process using cobalt (Co), for example, the source and drain and
polysilicon gate resistances are reduced by forming a high
conductivity overlayer and the contact resistance is reduced by
increasing the effective contact area of the source and drain with
subsequently formed metal interconnects. Salicide processing
technology seeks to exploit the principle that a refractory metal
such as cobalt deposited on a patterned silicon substrate will
selectively react with exposed silicon under specific processing
conditions, and will not react with silicon oxide material.
[0007] For example, a layer of cobalt is sputtered onto silicon,
typically patterned on a substrate surface, and then subjected to a
thermal annealing process to form cobalt silicide (CoSi.sub.2).
Unreacted cobalt, such as cobalt deposited outside the patterned
silicon or on a protective layer of silicon oxide, can thereafter
be selectively etched away. The selective reaction of cobalt
silicide will result in maskless, self-aligned formation of a
low-resistivity refractory metal silicide in source, drain, and
polysilicon gate regions formed on the substrate surface and in
interconnecting conductors of the semiconductor device. After the
etch process, further processing of the substrate may occur, such
as additional thermal annealing, which may be used to further
reduce the sheet resistance of the silicide material.
[0008] However, it has been difficult in integrating cobalt
silicide processes into conventional manufacturing equipment.
Current processing systems performing cobalt silicide processes
require transfer of the substrate between separate chambers for the
deposition and annealing process steps. Transfer between chambers
may expose the substrate to contamination and potential oxidation
of silicon or cobalt deposited on the substrate surface
[0009] Oxide formation on the surface of the substrate can result
in increasing the resistance of silicide layers as well reducing
the reliability of the overall circuit. For example, oxidation of
the deposited cobalt material may result in cobalt agglomeration
and irregular growth of the silicide layer. The agglomeration and
irregular growth of the cobalt layer may result in device
malformation, such as source and drain electrodes having different
thicknesses and surface areas. Additionally, excess cobalt silicide
growth on substrate surface may form conductive paths between
devices, which may result in short circuits and device failure.
[0010] One solution to limiting cobalt and silicon contamination is
to sputter a capping film of titanium or titanium nitride on the
cobalt and silicon film prior to transferring the substrate between
chambers. The capping film is then removed after annealing the
substrate and prior to further processing of the substrate.
However, the addition of titanium nitride deposition and removal
processes increase the number of processing steps required for
silicide formation, thereby reducing process efficiency, increasing
processing complexity, and reducing substrate through-put.
[0011] Therefore, there is a need for a method and apparatus for
forming suicide materials on a substrate while reducing processing
complexity and improving processing efficiency and throughput.
SUMMARY OF THE INVENTION
[0012] Embodiments of the invention described herein generally
provide methods and apparatus for forming a metal suicide layer
using a deposition and annealing process. In one aspect, a system
is provided for processing a substrate including a load lock
chamber, an intermediate substrate transfer region connected to the
load lock chamber, the intermediate substrate transfer region
comprising a first substrate transfer chamber and a second
substrate transfer chamber, wherein the first substrate transfer
chamber is coupled to the load lock chamber and the second
substrate transfer chamber is coupled to the first substrate
transfer chamber, a physical vapor deposition (PVD) processing
chamber disposed on the first substrate transfer chamber and an
annealing chamber disposed on the second substrate transfer
chamber.
[0013] In another aspect, a method is provided for forming a
silicide layer on a substrate including positioning a substrate
having silicon material disposed thereon on a substrate support
disposed in a deposition chamber having a metal target disposed
therein, applying a current to the substrate support to heat the
substrate to a first temperature, introducing an inert gas into the
deposition chamber, generating a plasma by applying a bias between
a metal target and the substrate support in the inert gas
environment to sputter material from the metal target, depositing
the sputtered material on at least the silicon material, providing
a backside gas between the substrate pedestal and the substrate,
and annealing the substrate in situ at a second temperature greater
than the first temperature to form a metal silicide layer.
[0014] In another aspect, a method is provided for processing a
substrate including introducing a substrate having silicon material
disposed thereon into a load lock, transferring the substrate to a
first transfer chamber having a physical vapor deposition
processing chamber disposed thereon, the first transfer chamber is
connected to the loadlock and the depositing chamber has a metal
target and heating pedestal disposed therein, positioning the
substrate into the physical vapor deposition chamber, depositing a
metal layer on the silicon material, annealing the substrate prior
to transferring the substrate to a second transfer chamber having
an annealing chamber disposed thereon, wherein the second transfer
chamber is connected to the first transfer chamber, and annealing
the substrate in the annealing chamber to form a metal silicide
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] So that the manner in which the above recited aspects 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.
[0016] 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.
[0017] FIG. 1 is schematic top view of one embodiment of an
integrated multi-chamber apparatus suitable for depositing a
conformal PVD layer on a semiconductor substrate and suitable for
annealing the deposited layer;
[0018] FIG. 2 is schematic top view of another embodiment of an
integrated multi-chamber apparatus suitable for depositing a
conformal PVD layer on a semiconductor substrate and suitable for
annealing the deposited layer
[0019] FIG. 3 is a cross-sectional view of one embodiment of a
sputtering chamber included within the invention;
[0020] FIG. 4 is an expanded view of FIG. 3 including upper area of
the shields near the target;
[0021] FIG. 5 is a plan view of one embodiment of a ring
collimator;
[0022] FIG. 6 is a partial plan view of one embodiment of a
honeycomb collimator;
[0023] FIG. 7A is a cross-sectional view of one embodiment of a
pedestal for annealing a substrate;
[0024] FIG. 7B is a cross-sectional view of another embodiment of a
pedestal for annealing a substrate; and
[0025] FIG. 8 is a simplified sectional view of a silicide material
used as a contact with a transistor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Embodiments of the invention described herein provide
methods and apparatus for forming a metal silicide layer in a
deposition chamber or substrate processing system. One embodiment
described below in reference to a physical vapor deposition (PVD)
process is provided to illustrate the invention, and should not be
construed or interpreted as limiting the scope of the invention.
Aspects of the invention may be used to advantage in other
processes, such as chemical vapor deposition, in which an anneal is
desired for forming metal silicide layers.
[0027] FIG. 1 is schematic top view of one embodiment of an
integrated multi-chamber substrate processing system suitable for
performing at least one embodiment the metal deposition and
annealing processes described herein. The deposition and annealing
processes may be performed in a multi-chamber processing system or
cluster tool having a PVD chamber disposed thereon. One processing
platform that may be used to advantage is an Endura.TM. processing
platform commercially available from Applied Materials, Inc.,
located in Santa Clara, Calif.
[0028] The processing platform 35 typically includes a cluster of
process chambers including two transfer chambers 48, 50 and at
least one long throw physical vapor deposition (PVD) chamber 36,
additional processing chambers 38 and 40, and an annealing chamber
41. Generally, the annealing chambers 41 and the PVD chambers 36
are disposed in separate transfer chambers, which are operated at
different vacuum pressures. Chambers 38 and 40 may include PVD
chambers or chemical vapor deposition (CVD) chambers for depositing
other materials as desired by the operator. Rapid thermal annealing
(RTA) chambers that can anneal substrates at vacuum pressures may
be used for the annealing chamber 41 on transfer chamber 48 or 50
based upon the configuration desired by the operator.
[0029] The processing platform 35 may further comprise one or more
pre-clean chambers 42, such as PreClean II chambers available from
Applied Materials, for removing contaminants, two degas chambers
44, and two load lock chambers 46. The processing platform 35
typically includes transfer robots 49, 51, disposed in transfer
chambers 48, 50 respectfully, and two cooldown or pre-heating
chambers 52 separating the transfer chambers 48, 50. The processing
platform 35 is automated by programming a microprocessor controller
54. RTA chambers (not shown) may also be disposed on the first
transfer chamber 48 of the processing platform 35 to provide post
deposition annealing processes prior to substrate removal from the
platform 35. While not shown, a plurality of vacuum pumps are
disposed in fluid communication with each transfer chamber and each
of the processing chambers to independently regulate pressures in
the respective chambers. The pumps may establish a vacuum gradient
of increasing pressure across the apparatus from the load lock
chamber to the processing chambers.
[0030] FIG. 2 is a schematic top view of another embodiment of an
integrated multi-chamber substrate processing system suitable for
performing at least one embodiment the metal deposition and
annealing processes described herein. In this embodiment, two PVD
deposition chamber are disposed on the first transfer chamber 48
with two degas chambers 44, and two load lock chambers 46. One of
the PVD deposition chambers may be substitute with a vacuum
annealing chamber or a pre-clean chamber 42, such as the PreClean
II chamber. Two annealing chambers 41, are disposed on the second
transfer chamber 50. The operating pressure of the first transfer
chamber 48 is generally lower than that for the second transfer
chamber 50 since high vacuum PVD processes are performed on the
first transfer chamber 48 and high pressure processes, such as
atmosphere annealing processes, are performed on the second
transfer chamber 50.
[0031] FIG. 3 illustrates one embodiment of a long throw physical
vapor deposition chamber. Example of suitable long throw PVD
chambers are ALPS plus.TM. and SIP.TM. PVD processing chambers,
both commercially available from Applied Materials, Inc., Santa
Clara, Calif.
[0032] Generally, the long throw PVD chamber 36 contains a
sputtering source, such as a target 142, and a substrate support
pedestal 152 for receiving a semiconductor substrate 154 thereon
and located within a grounded enclosure wall 150, which may be a
chamber wall as shown or a grounded shield.
[0033] The chamber 36 includes a target 142 supported on and sealed
by O-rings to a grounded conductive aluminum adapter 144 through a
dielectric isolator 146. The target 142 may be a bonded composite
of a metallic cobalt surface layer and a backing plate of a more
workable metal. The target 142 comprises the material to be
deposited on the substrate surface during sputtering. The target
may include, for example, materials including cobalt, titanium,
tantalum, tungsten, molybdenum, platinum, nickel, iron, niobium,
palladium, and combinations thereof, which are used in forming
metal silicide layers. For example, targets comprising elemental
cobalt, nickel cobalt alloys, or nickel iron alloys may be used as
the target 142.
[0034] A controllable DC power source 148 applies a negative
voltage or bias to the target 142, typically between about between
about 0 V and about 2400 V to the target 142 to excite the gas into
a plasma state. The adapter 144 in turn is sealed and grounded to
an aluminum chamber sidewall 150. Ions from the plasma bombard the
target 142 to sputter atoms and larger particles onto the substrate
154 disposed below. While, the power supplied is expressed in
voltage, power may also be expressed as kilowatts or a power
density (W/cm.sup.2). The amount of power supplied to the chamber
may be varied depending upon the amount of sputtering and the size
of the substrate size being processed.
[0035] A pedestal 152 supports a substrate 154 to be sputter coated
in planar opposition to the principal face of the target 142. The
substrate support pedestal 152 has a planar substrate receiving
surface disposed generally parallel to the sputtering surface of
the target 142. In operation, the substrate 154 is positioned on
the substrate support pedestal 152 and plasma is generated in the
chamber 36. A long throw distance of at least about 90 mm separates
the target 142 and the substrate. The substrate support pedestal
152 and the target 142 may be separated by a distance between about
100 mm and about 300 mm for a 200 mm substrate. The substrate
support pedestal 152 and the target 142 may be separated by a
distance between about 150 mm and about 400 mm for a 300 mm
substrate. Any separation between the substrate and target that is
greater than 50% of the substrate diameter is considered a long
throw processing chamber.
[0036] A RF power supply 156 in some applications is connected to
the pedestal electrode 152 in order to induce a negative DC
self-bias on the substrate 154, but in other applications the
pedestal 152 is grounded or left electrically floating. The D.C.
power supply 148 or another power supply may be used to apply a
negative bias, for example, between about 0 V and about 500 V, to
the substrate support pedestal 152. The pedestal 152 is vertically
movable through a bellows 158 connected to a lower chamber wall 160
to allow the substrate 154 to be transferred onto the pedestal 152
through an load lock valve (not shown) in the lower portion of the
chamber and thereafter raised to a deposition position.
[0037] Processing working gas is supplied from a gas source 162
through a mass flow controller 164 into the lower part of the
chamber. A vacuum pumping system 166 connected through a pumping
port 168 in the lower chamber is capable of maintaining the chamber
at a base pressure of less than 10.sup.-6 Torr, but the processing
pressure within the chamber is typically maintained at between 0.2
and 2 milliTorr, preferably less than 1 milliTorr, for cobalt
sputtering. The processing gas includes non-reactive or inert
species such as argon (Ar), xenon (Xe), helium (He), or
combinations thereof.
[0038] A rotatable magnetron 170 is positioned in back of the
target 142 and includes a plurality of horseshoe magnets 172
supported by a base plate 174 connected to a rotation shaft 176
coincident with the central axis of the chamber 140 and the
substrate 154. The horseshoe magnets 172 are arranged in closed
pattern typically having a kidney shape. They produce a magnetic
field within the chamber, generally parallel and close to the front
face of the target 142 to trap electrons and thereby increase the
local plasma density, which in turn increases the sputtering rate.
The magnets 172 are rotated so as to more uniformly sputter the
target 142 and coat the substrate 154.
[0039] The chamber 36 of the invention includes a grounded bottom
shield 180 having, as is more clearly illustrated in the exploded
cross-sectional view of FIG. 4, an upper flange 182 supported on
and electrically connected to a ledge 184 of the adapter 144. A
dark space shield 186 is supported on the flange 182 of the bottom
shield 180, and screws (not shown) recessed in the upper surface of
the dark space shield 186 fix it and the flange 182 to the adapter
ledge 184 having tapped holes receiving the screws. This metallic
threaded connection grounds the two shields 180, 186 to the adapter
144. Both shields 180, 186 are typically formed from hard,
non-magnetic stainless steel. The dark space shield 186 has an
upper portion that closely fits an annular side recess of the
target 142 with a narrow gap 188 between the dark space shield 186
and the target 142 which is sufficiently narrow to prevent the
plasma to penetrate, hence protecting the ceramic isolator 146 from
being sputter coated with a metal layer, which would electrically
short the target 142. The dark space shield 186 also includes a
downwardly projecting tip 190, which prevents the interface between
the bottom shield 180 and dark space shield 186 from becoming
bonded by sputter deposited metal.
[0040] Returning to the overall view of FIG. 3, the bottom shield
180 extends downwardly in a upper generally tubular portion 194 of
a first diameter and a lower generally tubular portion 196 of a
smaller second diameter to extend generally along the walls of the
adapter 144 and the chamber body 150 to below the top surface of
the pedestal 152. It also has a bowl-shaped bottom including a
radially extending bottom portion 198 and an upwardly extending
inner portion 100 just outside of the pedestal 152. A cover ring
102 rests on the top of the upwardly extending inner portion 100 of
the bottom shield 180 when the pedestal 152 is in its lower,
loading position but rests on the outer periphery of the pedestal
152 when it is in its upper, deposition position to protect the
pedestal 152 from sputter deposition. An additional deposition ring
(not shown) may be used to shield the periphery of the substrate
154 from deposition.
[0041] The chamber 36 may also be adapted to provide a more
directional sputtering of material onto a substrate. In one aspect,
directional sputtering may be achieved by positioning a collimator
110 positioned between the target 142 and the substrate support
pedestal 152 to provide a more uniform and symmetrical flux of
deposition material on the substrate 154.
[0042] A metallic ring collimator 110 rests on the ledge portion
106 of the lower shield, thereby grounding the collimator 110. The
ring collimator 110 includes, as better illustrated in the plan
view of FIG. 5, three concentric tubular sections 112, 114, 116
linked by cross struts 118, 120. The outer tubular section 116
rests on the ledge portion 106 of the lower shield 180. The use of
the lower shield 180 to support the collimator 110 simplifies the
design and maintenance of the chamber. At least the two inner
tubular sections 112, 114 are sufficiently high to define high
aspect-ratio apertures that partially collimate the sputtered
particles. Further, the upper surface of the collimator 110 acts as
a ground plane in opposition to the biased target 142, particularly
keeping plasma electrons away from the substrate 154.
[0043] Another type of collimator usable with the invention is a
honeycomb collimator 124, partially illustrated in the plan view of
FIG. 6 having a mesh structure with hexagonal walls 126 separating
hexagonal apertures 128 in a close-packed arrangement. An advantage
of the honeycomb collimator 124 is, if desired, the thickness of
the collimator 124 can be varied from the center to the periphery
of the collimator, usually in a convex shape, so that the apertures
128 have aspect ratios that are likewise varying across the
collimator 124. The collimator may have one or more convex sides.
This allows the sputter flux density to be tailored across the
substrate, permitting increased uniformity of deposition.
Collimators that may be used in the PVD chamber are described in
U.S. Pat. No. 5,650,052, issued Jul. 22, 1997, which is hereby
incorporated by reference herein to the extent not inconsistent
with aspects of the invention and claims described herein.
[0044] Referring to FIGS. 7A and 7B, embodiments of the substrate
support pedestal 152 may be heated by resistive heaters
electrically coupled to a power source and may be cooled by a
thermal medium passing through fluid conductors connected fluid
source, i.e., a liquid heat exchanger. Embodiments of the substrate
support pedestal 152 are described below, and are provided for
illustrative purposes and should not be construed or interpreted as
limiting the scope of the invention.
[0045] One embodiment of a substrate support pedestal 152 is shown
in FIG. 7A. The substrate support pedestal 152 is suitable for use
in a high temperature high vacuum annealing process. Generally, the
substrate support pedestal 152 includes a heating portion 210
disposed on a base 240 coupled to a shaft 245.
[0046] The heating portion 210 generally includes heating elements
250 disposed in a thermally conducting material 220 and a substrate
support surface 275. The thermally conducting material 220 may be
any material that has sufficient thermal conductance at operating
temperatures for efficient heat transfer between the heating
elements 250 and a substrate support surface 275. An example of the
conducting material is steel. The substrate support surface 275 may
include a dielectric material and typically includes a
substantially planar receiving surface for a substrate 280 disposed
thereon.
[0047] The heating elements 250 may be resistive heating elements,
such as electrically conducting wires having leads embedded within
the conducting material 220, and are provided to complete an
electrical circuit by which electricity is passed through the
conducting material 220. An example of a heating element 250
includes a discrete heating coil disposed in the thermally
conducting material 220. Electrical wires connect a voltage source
(not shown) to the ends of the electrically resistive heating coil
to provide energy sufficient to heat the coil. The coil may take
any shape that covers the area of the substrate support pedestal
152. More than one coil may be used to provide additional heating
capability, if needed.
[0048] The body provides support for the heating portion and
includes fluid channels 290 disposed therein. The fluid channels
290 are generally coupled to a surface of the heating portion 210
and may provide for either heating or cooling of the substrate
support pedestal 152. The combination of heating elements 250 and
fluid channels 290 generally achieve temperature control of the
surface of the substrate support pedestal 152.
[0049] The fluid channels 290 may include a concentric ring or
series of rings, or other desired configuration, having fluid
inlets and outlets for circulating a liquid from a remotely located
source (not shown). The fluid channels 290 are connected to the
fluid source 294 by fluid passage 292 formed in the shaft 245 of
substrate support pedestal 152.
[0050] The heating elements 250 can heat the substrate on the
substrate support pedestal up to about 900.degree. C. and the fluid
channels may cool the substrate to a temperature of about 0.degree.
C. The combination of heating elements 250 and the fluid channels
290 are generally used to control the temperature of a substrate
280 between about 10.degree. C. and about 900.degree. C., subject
to properties of materials used in substrate support pedestal 152
and the process parameters used for processing a substrate in the
chamber 36.
[0051] Temperature sensors 260, such as a thermocouple, may be
attached to or embedded in the substrate support pedestal 152, such
as adjacent the heating portion 210, to monitor temperature in a
conventional manner. For example, measured temperature may be used
in a feedback loop to control electric current applied to the
resistive heaters from a power supply, such that substrate
temperature can be maintained or controlled at a desired
temperature or within a desired temperature range. A control unit
(not shown) may be used to receive a signal from temperature sensor
and control the heat power supply or a fluid source in
response.
[0052] The power supply and the fluid supply of the heating and
cooling components are generally located external of the chamber
36. For example, each of the resistive heaters communicate via
voltage sources by wires disposed through utility passages (not
shown) formed in the base 240 and shaft 245 of the substrate
support pedestal 152 and are coupled to utility sources, such as
power, located externally to the chamber 36. The utility passages,
including the fluid passage 294, are disposed axially along the
base 240 and shaft 245 of the substrate support pedestal 152. A
protective, flexible sheath 295 is disposed around the shaft 245
and extends from the substrate support pedestal 152 to the chamber
wall (not shown) to prevent contamination between the substrate
support pedestal 152 and the inside of the chamber.
[0053] The substrate support pedestal 152 may further contain gas
channels (not shown) fluidly connecting with the substrate
receiving surface 275 of the heating portion 210 to a source of
backside gas (not shown). The fluid channels 270 define a backside
gas passage control passage of a heat transfer gas or masking gas
between the heating portion and the substrate 280.
[0054] A support pedestal disposed in the chamber may include an
electrostatic chuck for supporting a substrate during deposition.
Examples of suitable electrostatic chucks that may be used for the
support pedestal include MCA.TM. Electrostatic E-chuck or Pyrolytic
Boron Nitride Electrostatic E-Chuck, both available from Applied
Materials, Inc., of Santa Clara, Calif.
[0055] FIG. 7B illustrates another embodiment of the substrate
support pedestal 152 having an electrostatic chuck 210 mounted to
or forming the heating portion of the substrate support pedestal
152. The electrostatic chuck 210 includes an electrode 230 and a
substrate receiving surface 275 coated with a dielectric material
235. Electrically conducting wires (not shown) couple the
electrodes 230 to a voltage source (not shown). A substrate 280 may
be placed in contact with the dielectric material 235, and a direct
current voltage is placed on the electrode 230 to create the
electrostatic attractive force to grip the substrate.
[0056] Generally, the electrodes 230 are disposed in the thermally
conducting material 220 in a spaced relationship with the heating
elements 250 disposed therein. The heating elements 250 are
generally disposed in a vertically spaced and parallel manner from
the electrodes 230 in the thermally conducting material 220.
Typically, the electrodes are disposed between the heating elements
and the substrate receiving surface 275 though other configurations
may be used. Fluid channels 290 disposed on a bottom portion of the
electrostatic chuck 210 may also be used to achieve temperature
control of the substrate support pedestal 152 and are connected to
the fluid source by fluid passage 292 formed in the substrate
support pedestal base 240. Temperature sensors 260 are attached to
or embedded in the electrostatic chuck 210 to monitor
temperature.
[0057] The electrostatic chuck 210 may further contain channels 270
formed in the substrate support pedestal 152 fluidly connecting
with the substrate receiving surface 275 of the electrostatic chuck
210 to a source of backside gas (not shown). The fluid channels 270
define a backside gas passage control passage of a heat transfer
gas or masking gas between the electrostatic chuck 210 and the
substrate 280.
[0058] The embodiments of the substrate support pedestals 152
described above may be used to form a high vacuum anneal chamber.
The high vacuum anneal chamber may include substrate support
pedestals 152 disposed in a PVD chamber, such as the long throw
chamber 36 described herein, with a blank target disposed therein
or without a target and without bias coupled to either the target
or substrate support pedestal. In operation, a substrate is
disposed on the substrate support pedestal, and the substrate is
heated, with or without the presence of a backside gas, by the
heating elements 250 to the desired processing temperature,
processed for sufficient time to anneal the substrate for the
desired anneal results, and then removed from the chamber.
[0059] While the embodiments of substrate support pedestal 152
described herein may be used to anneal the substrate, commercially
available anneal chambers, such as rapid thermal anneal (RTA)
chambers may also be used to anneal the substrate to form the
silicide films. The invention contemplates utilizing a variety of
thermal anneal chamber designs, including hot plate designs and
heated lamp designs, to enhance the electroplating results. One
particular thermal anneal chamber useful for the present invention
is the WxZ.TM. chamber available from Applied materials, Inc.,
located in Santa Clara, Calif. One particular hot plate thermal
anneal chamber useful for the present invention is the RTP XEplus
Centura.RTM. thermal processing chamber available from Applied
Materials, Inc., located in Santa Clara, Calif. One particular lamp
anneal chamber is the Radiance.TM. thermal processing chamber
available from Applied Materials, Inc., located in Santa Clara,
Calif.
[0060] Anneal chambers capable of operating at vacuum pressures may
be disposed on the PVD transfer chamber 50, to allow post
deposition annealing without breaking vacuum. Anneal chamber that
are capable of operating at near atmosphere pressures may be
disposed on the first transfer chamber 48. In the embodiment shown
in FIG. 3, PVD deposition chambers with cobalt targets are disposed
on the first transfer chamber 48 and the anneal chambers 41 that
are capable of operating at near atmosphere pressures may be
disposed on the second transfer chamber 50.
[0061] Metal Silicide Process
[0062] The deposition and annealing step used in forming a metal
silicide layer may be formed in situ, such as in a deposition
chamber or in a processing system without breaking vacuum. In situ
is broadly defined herein as performing two or more processes in
the same chamber or in the same processing system without breaking
vacuum. For example, in situ annealing may be performed in the same
processing chamber as the metal deposition.
[0063] In another example, in situ annealing may performed in a
chamber adjacent to the deposition chamber, both of which are
coupled to a transfer chamber, and the vacuum on the transfer
chamber is not broken during processing. In a further example, in
situ annealing may be performed on the same processing system at
separate processing pressures, such as processing a substrate in
processing chambers and annealing chambers disposed on the first
and second transfer chambers 48, 50, respectfully, in system 35
without breaking the vacuum on the system 35 or tranfer of th
substrate to another processing system.
[0064] While the following material describes the deposition of a
cobalt film, the invention contemplates the use of other materials,
including titanium, tantalum, tungsten, molybdenum, platinum,
nickel, iron, niobium, palladium, and combinations thereof, to form
the metal silicide material as described herein.
[0065] Metal Deposition
[0066] In one embodiment, a metal layer may be deposited on a
silicon substrate disposed in chamber 36 and annealed on the
substrate pedestal 152 to form the metal silicide layer without
breaking vacuum. Metal for forming the metal silicide layer is
deposited using the PVD chamber 36 described above. The target 142
of material, such as cobalt, to be deposited is disposed in the
upper portion of the chamber 36. A substrate 154 is provided to the
chamber 36 and disposed on the substrate support pedestal 152. The
substrate 154 includes silicon material disposed thereon and is
generally patterned to define features into which metal silicide
films will be formed.
[0067] A processing gas is introduced into the chamber 38 at a flow
rate of between about 5 sccm and about 30 sccm. The chamber
pressure is maintained below about 5 milliTorr to promote
deposition of conformal PVD metal layers. Preferably, a chamber
pressure between about 0.2 milliTorr and about 2 milliTorr may be
used during deposition. More preferably, a chamber pressure between
about 0.2 milliTorr and about 1.0 milliTorr has been observed to be
sufficient for sputtering cobalt onto a substrate.
[0068] A plasma is generated by applying a power level to the
target 142 between about 0 volts (V) and about 2400 V. For example,
a power level is delivered to the target 142 at between about 0 V
and about 1000 V to sputter material on a 200 mm substrate. A power
level between about 0 V and about 500 V may be applied to the
substrate support pedestal 152 to improve directionality of the
sputtered material to the substrate surface. The substrate is
maintained at a temperature between about 10.degree. C. and about
500.degree. C. during the deposition process.
[0069] An example of a deposition process includes introducing an
inert gas, such as argon, into the chamber at a flow rate between
about 5 sccm and about 30 sccm, maintaining a chamber pressure
between about 0.2 milliTorr and about 1.0 milliTorr, applying a
negative bias of between about 0 volts and about 1000 volts to the
target 142 to excite the gas into a plasma state, maintaining the
substrate at a temperature between about 10.degree. C. and about
500.degree. C., preferably about 50.degree. C. and about
300.degree. C., and most preferably, between about 50.degree. C.
and about 100.degree. C. during the sputtering process, and spacing
the target between about 100 mm and about 300 mm from the substrate
surface for a 200 mm substrate. Cobalt may be deposited on the
silicon material at a rate between about 300 .ANG./min and about
2000 .ANG./min using this process.
[0070] General In-Situ Annealing Process
[0071] The cobalt and silicon layer is then annealed in situ at a
temperature between about 300.degree. C. and about 900.degree. C.
for between about 10 seconds and about 600 seconds to form the
metal silicide layer. The annealing process may be performed under
an inert gas environment in the deposition chamber by first
introducing an inert gas into the chamber at a flow rate between
about 0 sccm (Le., no backside gas) and about 15 sccm, maintaining
a chamber pressure between of about 2 milliTorr or less, heating
the substrate to a temperature between about 300.degree. C. and
about 900.degree. C. for between about 5 seconds and about 600
seconds to form the metal silicide layer.
[0072] Deposition and Annealing Process with Backside Gases in the
Deposition Chamber.
[0073] The metal may be deposited at substrate temperature of
200.degree. C. or less, and then rapidly annealed on the substrate
support pedestal 152 at temperatures of about 400.degree. C. or
greater by introducing a backside gas flow. An example of a
deposition process includes introducing an inert gas, such as
argon, into the chamber at a flow rate between about 5 sccm and
about 30 sccm, maintaining a chamber pressure between about 0.2
milliTorr and about 1.0 milliTorr, applying a negative bias of
between about 0 volts and about 1000 volts to the target 142 to
excite the gas into a plasma state, maintaining the substrate at a
temperature of about 200.degree. C., and spacing the target between
about 100 mm and about 300 mm from the substrate surface for a 200
mm substrate.
[0074] The substrate temperature may be maintained at about
200.degree. C. by heating the substrate in the absence of a
backside gas at a heating level that would normally heat the
substrate to temperatures of 400.degree. C. or greater. This
reduced temperature control is achieved by inefficient heat
transfer between the pedestal surface and the backside of the
substrate at vacuum pressures. Cobalt may be deposited on the
silicon material at a rate between about 300 .ANG./min and about
2000 .ANG./min using this process.
[0075] The annealing process can then be performed in the
deposition chamber by ending the plasma and applying a backside gas
to the substrate support to enhance heating of the substrate to a
temperature between about 400.degree. C. and 600.degree. C. at the
same heating levels used for the deposition process. The annealing
process is performed at a temperature between about 400.degree. C.
and about 600.degree. C. for between about 5 seconds and about 300
seconds. Preferably, the substrate is annealed in the deposition
chamber at 500.degree. C. for between about 60 seconds and 120
seconds.
[0076] Low Temperature Deposition and Two-Step In-Situ Annealing
Process in Two Chambers
[0077] In another embodiment, the metal layer may be physical vapor
deposited on a silicon substrate in chamber 36, annealed for a
first temperature for a first period of time, transferred to a
second chamber, for example chamber 41, in the system 35, and
annealed at a second temperature for a second period of time to
form the metal suicide layer without breaking vacuum.
[0078] The physical vapor deposition of the metal is performed as
described above at a temperature of about 200.degree. C. or less,
preferably between about 0.degree. C. and about 100.degree. C. The
first step of the two step in situ annealing process described
above may be performed under an inert gas environment in the
deposition chamber by first introducing an inert gas into the
chamber at a flow rate between about 0 sccm and about 15 sccm,
maintaining a chamber pressure between about 0 milliTorr and about
2 milliTorr, heating the substrate to a temperature between about
400.degree. C. and about 600.degree. C. for between about 5 seconds
and about 300 seconds. Preferably, the substrate is annealed in the
deposition chamber at 500.degree. C. for between about 60 seconds
and 120 seconds.
[0079] The substrate is then removed from the deposition chamber
and transferred to a vacuum anneal chamber disposed on the same
transfer chamber, such as transfer chamber 48 described above in
FIG. 2. The high vacuum anneal chamber may include a PVD chamber
having a blank target and substrate support pedestal 152 described
above or a commercial high vacuum anneal pedestal, such as the High
Temperature High Uniformity, HTHU.TM. substrate support
commercially available from Applied Materials Inc., of Santa Clara
Calif.
[0080] The second annealing step may then be performed by
maintaining a chamber pressure between about 0 milliTorr and about
2 milliTorr and heating the substrate to a temperature between
about 600.degree. C. and about 900.degree. C. for a period of time
between about 5 seconds and about 300 seconds to form the metal
silicide layer. Preferably, the substrate is annealed in the anneal
chamber at 800.degree. C. for between about 60 seconds and 120
seconds.
[0081] Low Temperature Deposition and Two-Step Anneal Process in
Two Chambers
[0082] In an alternative embodiment of the two chamber deposition
and anneal process, the metal layer is deposited according to the
process described herein at about 200.degree. C. or less,
preferably between about 0.degree. C. and about 100.degree. C., in
the deposition chamber. The substrate is then annealed in the
deposition chamber according to the anneal process described above.
The substrate may then be transferred to a RTA chamber disposed on
transfer chamber 50 in FIG. 2 for a second anneal process.
[0083] Annealing in an RTA anneal chamber may be performed by
introducing a process gas including nitrogen (N.sub.2), argon (Ar),
helium (He), and combinations thereof, with less than about 4%
hydrogen (H.sub.2), at a process gas flow rate greater than 20
liters/min to control the oxygen content to less than 100 ppm,
maintaining a chamber pressure of about ambient, and heating the
substrate to a temperature between about 600.degree. C. and about
900.degree. C. for between about 5 seconds and about 300 seconds to
form the metal silicide layer. Preferably, the substrate is
annealed in the RTA anneal chamber at 800.degree. C. for about 30
seconds.
[0084] Low Temperature Deposition and Two-Step Annealing Process in
Three Chambers.
[0085] In another embodiment, the metal layer may be deposited on a
silicon substrate in chamber 36, transferred to a first anneal
chamber, such as a vacuum anneal chamber disposed on the same
transfer chamber 48 on the system 35, annealed for a first
temperature for a first period of time, transferred to a second
anneal chamber, for example chamber 41, in the system 35, and
annealed at a second temperature for a second period of time to
form the metal suicide layer without breaking vacuum.
[0086] The metal deposition is performed in the deposition chamber
according to the process described above at a substrate temperature
of about 200.degree. C. or less, preferably between about 0.degree.
C. and about 100.degree. C. The first step of this embodiment of
the annealing process may be performed in situ in a first high
vacuum anneal chamber disposed on a processing system by
introducing an inert gas into the anneal chamber at a flow rate
between about 0 sccm and about 15 sccm, maintaining a chamber
pressure between about 0 milliTorr and about 2 milliTorr, heating
the substrate to a temperature between about 400.degree. C. and
about 600.degree. C. for between about 5 seconds and about 300
seconds. Preferably, the substrate is annealed in the deposition
chamber at 500.degree. C. for between about 60 seconds and 120
seconds. The first annealing step is believed to form an oxygen
resistant film such as CoSi.
[0087] The substrate may be annealed in situ by transfer to a
second high vacuum annealing chamber in the processing system. The
second annealing step may then be performed by maintaining a
chamber pressure of about 2 milliTorr or less and heating the
substrate to a temperature between about 600.degree. C. and about
900.degree. C. for a period of time between about 5 seconds and
about 300 seconds to form the metal silicide layer. Preferably, the
substrate is annealed in the anneal chamber at 800.degree. C. for
between about 60 seconds and 120 seconds.
[0088] Alternatively, the substrate may be transferred to a second
annealing chamber located outside the transfer chamber or
processing system, such as an atmosphere pressure RTA chamber.
Annealing in an RTA anneal chamber may be performed by introducing
a process gas including nitrogen (N.sub.2), argon (Ar), helium
(He), and combinations thereof, with less than about 4% hydrogen
(H.sub.2), at a process gas flow rate greater than 20 liters/min to
control the oxygen content to less than 100 ppm, maintaining a
chamber pressure of about ambient, and heating the substrate to a
temperature between about 400.degree. C. and about 900.degree. C.
for between about 5 seconds and about 300 seconds to form the metal
suicide layer. Preferably, the substrate is annealed in the RTA
anneal chamber at 800.degree. C. for about 30 seconds.
[0089] High Temperature Deposition and Annealing Process.
[0090] The metal may be deposited at a high deposition temperature.
An example of a deposition process includes introducing an inert
gas, such as argon, into the chamber at a flow rate between about 5
sccm and about 30 sccm, maintaining a chamber pressure between
about 0.2 milliTorr and about 1.0 milliTorr, applying a negative
bias of between about 0 volts and about 1000 volts to the target
142 to excite the gas into a plasma state, maintaining the
substrate at about an annealing temperature, Le., between about
400.degree. C. and about 600.degree. C. by applying a backside gas,
and spacing the target between about 100 mm and about 300 mm from
the substrate surface for a 200 mm substrate. The temperature may
be maintained at about 200.degree. C. by heating the substrate in
the absence of a backside gas. Cobalt may be deposited on the
silicon material at a rate between about 300 .ANG./min and about
2000 .ANG./min using this process.
[0091] The annealing process can then be performed in the
deposition chamber by ending the plasma and heating of the
substrate to a temperature between about 400.degree. C. and
600.degree. C. at the same heating levels used for the deposition
process. The annealing process is performed at a temperature
between about 400.degree. C. and about 600.degree. C. for between
about 5 seconds and about 300 seconds. Preferably, the substrate is
annealed in the deposition chamber at 500.degree. C. for between
about 60 seconds and 120 seconds.
[0092] The second annealing step may then be formed in an annealing
chamber without breaking vacuum or in an annealing chamber located
on a separate transfer chamber or processing system. The second
annealing step includes heating the substrate to a temperature
between about 600.degree. C. and about 900.degree. C. for a period
of time between about 5 seconds and about 300 seconds to form the
metal silicide layer. Preferably, the substrate is annealed at
800.degree. C. for between about 60 seconds and 120 seconds.
[0093] The metal silicide material, including suicides of cobalt,
titanium, tantalum, tungsten, molybdenum, platinum, nickel, iron,
niobium, palladium, and combinations thereof, may be used in the
formation of a MOS device shown in FIG. 8. In the illustrated MOS
structure, N+ source and drain regions 402 and 404 are formed in a
P type silicon substrate 400 adjacent field oxide portions 406. A
gate oxide layer 408 and a polysilicon gate electrode 410 are
formed over silicon substrate 400 in between source and drain
regions 402 and 404 with oxide spacers 412 formed on the sidewalls
of polysilicon gate electrode 410.
[0094] A cobalt layer is deposited over the MOS structure, and in
particular over the exposed silicon surfaces of source and drain
regions 402 and 404 and the exposed top surface of polysilicon gate
electrode 410 by the process described herein. The cobalt material
is deposited to a thickness of at about 1000 .ANG. or less to
provide a sufficient amount of cobalt for the subsequent reaction
with the underlying silicon at 402 and 404. Cobalt may be deposited
to a thickness between about 50 .ANG. and about 500 .ANG. on the
silicon material. The cobalt layer is then annealed in situ as
described herein to form cobalt silicide.
[0095] The unreacted cobalt is removed from the substrate surface
and the cobalt
* * * * *