U.S. patent application number 11/336527 was filed with the patent office on 2006-07-13 for ruthenium layer formation for copper film deposition.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Mei Chang, Seshadri Ganguli, Nirmalya Maity.
Application Number | 20060153973 11/336527 |
Document ID | / |
Family ID | 34216303 |
Filed Date | 2006-07-13 |
United States Patent
Application |
20060153973 |
Kind Code |
A1 |
Chang; Mei ; et al. |
July 13, 2006 |
Ruthenium layer formation for copper film deposition
Abstract
In one embodiment, a method for forming a material on a
substrate is provided which includes positioning a substrate
containing a dielectric material having vias formed therein within
a process chamber, forming a barrier layer within the vias and on
the dielectric material during a barrier deposition process,
forming a ruthenium layer on the barrier layer during a ruthenium
deposition process, and filling the vias with a copper material
during a copper deposition process. The copper material may be
formed by depositing a copper bulk layer over a copper seed layer.
The method further provides that the ruthenium layer may be formed
by an atomic layer deposition process (ALD) or a physical vapor
deposition (PVD) process and the copper material may be formed by
an electroless chemical plating process, an electroplating process,
a chemical vapor deposition process, an ALD process and/or a PVD
process.
Inventors: |
Chang; Mei; (Saratoga,
CA) ; Ganguli; Seshadri; (Sunnyvale, CA) ;
Maity; Nirmalya; (Los Altos, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
34216303 |
Appl. No.: |
11/336527 |
Filed: |
January 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10634662 |
Aug 4, 2003 |
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11336527 |
Jan 20, 2006 |
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10443648 |
May 22, 2003 |
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10634662 |
Aug 4, 2003 |
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60385499 |
Jun 4, 2002 |
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Current U.S.
Class: |
427/96.8 ;
205/184; 257/E21.171; 427/124; 427/301; 427/97.7 |
Current CPC
Class: |
B82Y 30/00 20130101;
H01L 21/76873 20130101; H01L 21/28562 20130101; H01L 21/76843
20130101; H01L 21/76874 20130101; C23C 16/18 20130101; C23C
16/45553 20130101; H01L 21/76871 20130101 |
Class at
Publication: |
427/096.8 ;
427/097.7; 427/301; 427/124; 205/184 |
International
Class: |
B05D 5/12 20060101
B05D005/12; C23C 28/00 20060101 C23C028/00; H05K 3/00 20060101
H05K003/00; C23C 28/02 20060101 C23C028/02; B05D 3/10 20060101
B05D003/10 |
Claims
1. A method for forming a material on a substrate, comprising:
positioning a substrate containing a dielectric material within a
process chamber, wherein vias are contained within the dielectric
material and each via has a bottom surface and sidewalls; forming a
barrier layer within the vias and on the dielectric material during
a barrier layer deposition process; forming a ruthenium layer on
the barrier layer during a ruthenium deposition process; exposing a
contact layer within the vias by removing material from the bottom
surface during a punch-through step; and filling the vias with a
copper material during a copper deposition process.
2. The method of claim 1, wherein the barrier layer contains at
least one material selected from the group consisting of titanium,
titanium nitride, tantalum, tantalum nitride, tungsten, tungsten
nitride, a derivative thereof, and a combination thereof.
3. The method of claim 2, wherein the barrier layer contains a
tantalum layer and a tantalum nitride layer.
4. The method of claim 1, wherein the copper material contains a
copper seed layer and a copper bulk layer.
5. The method of claim 4, wherein the copper seed layer is
deposited by an electroless chemical plating process and the copper
bulk layer is deposited by an electrochemical plating process.
6. The method of claim 4, wherein the copper seed layer and the
copper bulk layer are deposited by electroless chemical plating
processes.
7. The method of claim 4, wherein the copper seed layer is
deposited by a chemical vapor deposition process and the copper
bulk layer is deposited by an electrochemical plating process.
8. The method of claim 4, wherein the copper seed layer is
deposited by a physical vapor deposition process and the copper
bulk layer is deposited by an electrochemical plating process.
9. The method of claim 1, wherein the ruthenium layer is deposited
by exposing the substrate to a ruthenium precursor during an atomic
layer deposition process.
10. The method of claim 9, wherein the ruthenium precursor contains
a 2,4-dimethylpentadienyl ligand.
11. The method of claim 9, wherein the ruthenium precursor is
selected from the group consisting of bis(2,4-dimethylpentadienyl)
ruthenium, (2,4-dimethylpentadienyl) ruthenium (cyclopentadienyl),
(2,4-dimethylpentadienyl) ruthenium (methylcyclopentadienyl),
(2,4-dimethylpentadienyl) ruthenium (ethylcyclopentadienyl),
(2,4-dimethylpentadienyl) ruthenium (isopropylcyclopentadienyl),
derivatives thereof, and combinations thereof.
12. The method of claim 1, wherein the ruthenium layer is deposited
by sequentially exposing the substrate to a ruthenium precursor and
a reagent during an atomic layer deposition process.
13. The method of claim 12, wherein the ruthenium precursor is
selected from the group consisting of
bis(2,4-dimethylpentadienyl)ruthenium,
(2,4-dimethylpentadienyl)ruthenium(cyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(methylcyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(ethylcyclopentadienyl),
(2,4-dimethylpentadienyl) ruthenium (isopropylcyclopentadienyl),
derivatives thereof, and combinations thereof.
14. The method of claim 13, wherein the reagent is selected from
the group consisting of hydrogen, atomic hydrogen, ammonia,
derivatives thereof, and combinations thereof.
15. The method of claim 12, wherein the ruthenium-containing
compound is selected from the group consisting of
tris(2,2,6,6-tetramethyl-3,5-heptanedionato) ruthenium,
bis(2,4-dimethylpentadienyl)ruthenium, dicarbonyl pentadienyl
ruthenium, ruthenium acetyl acetonate, (2,4-dimethylpentadienyl)
ruthenium(cyclopentadienyl),
bis(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(1,5-cyclooctadiene),
(2,4-dimethylpentadienyl)ruthenium(methylcyclopentadienyl),
(1,5-cyclooctadiene)ruthenium(cyclopentadienyl),
(1,5-cyclooctadiene)ruthenium(methylcyclopentadienyl),
(1,5-cyclooctadiene)ruthenium(ethylcyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(ethylcyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(isopropylcyclopentadienyl),
bis(N,N-dimethyl 1,3-tetramethyl
diiminato)ruthenium(1,5-cyclooctadiene), bis(N,N-dimethyl
1,3-dimethyl diiminato)ruthenium(1,5-cyclooctadiene),
bis(allyl)ruthenium(1,5-cyclooctadiene),
((6-C.sub.6H.sub.6)ruthenium(1,3-cyclohexadiene),
bis(1,1-dimethyl-2-aminoethoxylato)ruthenium(1,5-cyclooctadiene),
bis(1,1-dimethyl-2-aminoethylaminato)ruthenium(1,5-cyclooctadiene),
derivatives thereof, and combinations thereof.
16. The method of claim 15, wherein the reagent is selected from
the group consisting of hydrogen, atomic hydrogen, ammonia,
nitrogen, silane, disilane, dimethylsilane, methylsilane, borane,
diborane, triethylborane, derivatives thereof, and combinations
thereof.
17. The method of claim 12, wherein the ruthenium layer has a
thickness within a range from about 10 .ANG. to about 60 .ANG..
18. The method of claim 9, wherein the ruthenium layer has a
thickness of about 30 .ANG. or less.
19. A method for forming a material on a substrate, comprising:
positioning a substrate containing a dielectric material within a
process chamber, wherein vias are contained within the dielectric
material and each via has a bottom surface and sidewalls; forming a
barrier layer within the vias and on the dielectric material during
a barrier layer deposition process; exposing a contact layer within
the vias by removing material from the bottom surface during a
punch-through step; forming a ruthenium layer on the barrier layer
and the contact layer during a ruthenium deposition process; and
filling the vias with a copper material during a copper deposition
process.
20. The method of claim 19, wherein the barrier layer contains at
least one material selected from the group consisting of titanium,
titanium nitride, tantalum, tantalum nitride, tungsten, tungsten
nitride, a derivative thereof, and a combination thereof.
21. The method of claim 20, wherein the barrier layer contains a
tantalum layer and a tantalum nitride layer.
22. The method of claim 19, wherein the copper material contains a
copper seed layer and a copper bulk layer.
23. The method of claim 22, wherein the copper seed layer is
deposited by an electroless chemical plating process and the copper
bulk layer is deposited by an electrochemical plating process.
24. The method of claim 22, wherein the copper seed layer and the
copper bulk layer are deposited by electroless chemical plating
processes.
25. The method of claim 22, wherein the copper seed layer is
deposited by a chemical vapor deposition process and the copper
bulk layer is deposited by an electrochemical plating process.
26. The method of claim 22, wherein the copper seed layer is
deposited by a physical vapor deposition process and the copper
bulk layer is deposited by an electrochemical plating process.
27. The method of claim 19, wherein the ruthenium layer is
deposited by exposing the substrate to a ruthenium precursor during
an atomic layer deposition process.
28. The method of claim 27, wherein the ruthenium precursor
contains a 2,4-dimethylpentadienyl ligand.
29. The method of claim 27, wherein the ruthenium precursor is
selected from the group consisting of
bis(2,4-dimethylpentadienyl)ruthenium,
(2,4-dimethylpentadienyl)ruthenium(cyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(methylcyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(ethylcyclopentadienyl),
(2,4-dimethyl pentadienyl)ruthenium(isopropylcyclopentadienyl),
derivatives thereof, and combinations thereof.
30. The method of claim 19, wherein the ruthenium layer is
deposited by sequentially exposing the substrate to a ruthenium
precursor and a reagent during an atomic layer deposition
process.
31. The method of claim 30, wherein the ruthenium precursor is
selected from the group consisting of bis(2,4-dimethylpentadienyl)
ruthenium, (2,4 -dimethylpentadienyl)ruthenium(cyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(methylcyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(ethylcyclopentadienyl),
(2,4-dimethylpentadienyl) ruthenium(isopropylcyclopentadienyl),
derivatives thereof, and combinations thereof.
32. The method of claim 31, wherein the reagent is selected from
the group consisting of hydrogen, atomic hydrogen, ammonia,
derivatives thereof, and combinations thereof.
33. The method of claim 19, wherein the ruthenium layer has a
thickness within a range from about 10 .ANG. to about 60 .ANG..
34. The method of claim 27, wherein the ruthenium layer has a
thickness of about 30 .ANG. or less.
35. A method for forming a material on a substrate, comprising:
positioning a substrate containing a dielectric material having
vias formed therein within a process chamber; forming a barrier
layer within the vias and on the dielectric material during a
barrier deposition process; forming a ruthenium layer on the
barrier layer during an atomic layer deposition process; and
filling the vias with a copper material during an electroless
chemical plating process.
36. A method for forming a material on a substrate, comprising:
exposing a substrate to a pre-clean process, wherein the substrate
contains a dielectric layer having vias formed therein; forming a
barrier layer on the dielectric layer and within the vias during a
barrier layer deposition process; forming a ruthenium layer on the
barrier layer during an atomic layer deposition process or a
physical vapor deposition process; and filling the vias with a
copper material during an electroless chemical plating process or
an electrochemical plating process.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. Ser. No.
10/634,662 (APPM/005975.P1), filed Aug. 4, 2003, which is a
continuation-in-part of U.S. Ser. No. 10/443,648 (APPM/005975),
filed May 22, 2003, which claims benefit of U.S. Ser. No.
60/385,499 (APPM/005975L), filed Jun. 4, 2002, which are herein
incorporated by reference in their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to a method
for forming noble metal layers, and more particularly to methods
for forming ruthenium layers used in copper integration.
[0004] 2. Description of the Related Art
[0005] Sub-quarter micron, multi-level metallization is one of the
key technologies for the next generation of very large scale
integration (VLSI) and ultra large scale integration (ULSI)
semiconductor devices. The multilevel interconnects that lie at the
heart of this technology require the filling of contacts, vias,
lines, and other features formed in high aspect ratio apertures.
Reliable formation of these features is very important to the
success of both VLSI and ULSI as well as to the continued effort to
increase client density and quality on individual substrates and
die.
[0006] As circuit densities increase, the widths of contacts, vias,
lines and other features, as well as the dielectric materials
between them may decrease to less than about 250 nm, whereas the
thickness of the dielectric layers remains substantially constant
with the result that the aspect ratios for the features, i.e.,
their height divided by width, increases. Many conventional
deposition processes have difficulty filling structures where the
aspect ratio exceeds 6:1, and particularly where the aspect ratio
exceeds 10:1. As such, there is a great amount of ongoing effort
being directed at the formation of void-free, nanometer-sized
structures having aspect ratios wherein the ratio of feature height
to feature width can be 6:1 or higher.
[0007] Additionally, as the feature widths decrease, the device
current typically remains constant or increases, which results in
an increased current density for such feature. Elemental aluminum
and aluminum alloys have been the traditional metals used to form
vias and lines in semiconductor devices because aluminum has a
perceived low electrical resistivity, superior adhesion to most
dielectric materials, ease of patterning, and the ability to obtain
aluminum in a highly pure form. However, aluminum has a higher
electrical resistivity than other more conductive metals such as
copper. Aluminum can also suffer from electromigration leading to
the formation of voids in the conductor.
[0008] Copper and copper alloys have lower resistivities than
aluminum, as well as a significantly higher electromigration
resistance compared to aluminum. These characteristics are
important for supporting the higher current densities experienced
at high levels of integration and increased device speed. Copper
also has good thermal conductivity. Therefore, copper is becoming a
choice metal for filling sub-quarter micron, high aspect ratio
interconnect features on semiconductor substrates.
[0009] A thin film of a noble metal such as, for example,
palladium, platinum, cobalt, nickel and rhodium, among others may
be used as an underlayer for the copper vias and lines. Such noble
metals, which are resistant to corrosion and oxidation, may provide
a smooth surface upon which a copper seed layer is subsequently
deposited using for example, an electrochemical plating (ECP)
process.
[0010] The noble metal is typically deposited using a chemical
vapor deposition (CVD) process or a physical vapor deposition (PVD)
process. Unfortunately, noble metals deposited on high aspect ratio
interconnect features using CVD and/or PVD processes generally have
poor step coverage (e.g., deposition of a non-continuous material
layer). The poor step coverage for the noble metal material layer
may cause the subsequent copper seed layer deposition using an ECP
process to be non-uniform.
[0011] Therefore, a need exists for a method to deposit a noble
metal, such as ruthenium, within a high aspect ratio interconnect
feature while maintaining good step coverage.
SUMMARY OF THE INVENTION
[0012] A method of noble metal layer formation for high aspect
ratio interconnect features is described herein. The noble metal
layer is formed using a cyclical deposition process, such as atomic
layer deposition (ALD). The cyclical deposition process includes
alternately adsorbing a noble metal-containing precursor and a
reducing gas on a substrate structure. The adsorbed noble
metal-containing precursor reacts with the reducing gas to form the
noble metal layer on the substrate. Suitable noble metals may
include, for example, ruthenium, palladium, platinum, cobalt,
nickel, or rhodium.
[0013] The noble metal layer formation is compatible with
integrated circuit fabrication processes. In one integrated circuit
fabrication process, the noble metal layer may be used as an
underlayer for a copper seed layer within a copper interconnect.
For such an embodiment, a preferred process sequence includes
providing a substrate having an interconnect pattern defined in one
or more dielectric layers formed thereon. The interconnect pattern
includes a barrier layer conformably deposited thereon. A noble
metal layer (e.g., ruthenium) is conformably deposited on the
barrier layer. The noble metal layer is deposited using a cyclical
deposition process by alternately exposing the substrate to a noble
metal-containing gas and a reducing gas. Thereafter, the copper
interconnects are completed by depositing a copper seed layer on
the noble metal layer and filling the vias with bulk copper
metal.
[0014] In one embodiment, a method for forming a film on a
substrate is provided which includes positioning the substrate
within a process chamber and forming a ruthenium layer on at least
a portion of the substrate by sequentially chemisorbing monolayers
of a ruthenium-containing compound and a reducing gas on the
substrate to form the ruthenium layer.
[0015] In another embodiment, a method for forming a ruthenium
layer on a substrate for use in integrated circuit fabrication is
provided which includes positioning the substrate within a process
chamber, wherein the process chamber is in fluid communication with
a gas delivery system, delivering a ruthenium-containing compound
from the gas delivery system to the process chamber, chemisorbing a
ruthenium-containing layer on the substrate, delivering a reducing
gas from the gas delivery system to the process chamber and
reacting the reducing gas with the ruthenium-containing layer to
form the ruthenium layer on the substrate.
[0016] In another embodiment, a method for forming a layer
containing ruthenium material on a substrate surface is provided
which includes exposing the substrate surface to a
ruthenium-containing compound to form a ruthenium-containing layer
on the substrate surface, purging the chamber with a purge gas,
reacting a reducing gas with the ruthenium-containing layer, and
purging the chamber with the purge gas.
[0017] In another embodiment, a method for forming a ruthenium
layer on a substrate is provided which includes positioning the
substrate within a process chamber and forming the ruthenium layer
on at least a portion of the substrate by sequentially chemisorbing
monolayers of a ruthenium-containing compound and a reducing gas.
The method further includes that the process chamber contains a
substrate support, a chamber lid with a passageway at a central
portion of the chamber lid and having a bottom surface extending
from the passageway to a peripheral portion of the chamber lid. The
bottom surface is shaped and sized to substantially cover the
substrate. The process chamber further contains one or more valves
coupled to the passageway, one or more gas sources coupled to each
valve and a reaction zone. The reaction zone is defined between the
chamber lid and the substrate and occupies a small volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] 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.
[0019] FIG. 1 depicts a schematic cross-sectional view of a process
chamber that may be used to perform a cyclical deposition process
described herein;
[0020] FIG. 2 depicts a schematic cross-sectional view of another
process chamber that may be used to perform a cyclical deposition
process described herein;
[0021] FIG. 3 illustrates a process sequence for noble metal layer
formation using cyclical deposition techniques according to one
embodiment described herein;
[0022] FIG. 4 illustrates a process sequence for noble metal layer
formation using cyclical deposition techniques according to an
alternate embodiment described herein; and
[0023] FIGS. 5A-5C illustrate schematic cross-sectional views of an
integrated circuit fabrication sequence.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0024] FIG. 1 depicts a schematic cross-sectional view of a process
chamber 10 that can be used to perform integrated circuit
fabrication in accordance with embodiments described herein. The
process chamber 10 generally houses a substrate support pedestal
48, which is used to support a substrate (not shown). The substrate
support pedestal 48 is movable in a vertical direction inside the
process chamber 10 using a displacement mechanism 48A.
[0025] Depending on the specific process, the substrate can be
heated to some desired temperature prior to or during deposition.
For example, the substrate support pedestal 48 may be heated using
an embedded heating element 52A. The substrate support pedestal 48
may be resistively heated by applying an electric current from an
AC power supply 52 to the heating element 52A. The substrate (not
shown) is, in turn, heated by the pedestal 48. Alternatively, the
substrate support pedestal 48 may be heated using radiant heaters
such as, for example, lamps (not shown).
[0026] A temperature sensor 50A, such as a thermocouple, is also
embedded in the substrate support pedestal 48 to monitor the
temperature of the pedestal 48 in a conventional manner. The
measured temperature is used in a feedback loop to control the AC
power supply 52 for the heating element 52A, such that the
substrate temperature can be maintained or controlled at a desired
temperature which is suitable for the particular process
application.
[0027] A vacuum pump 18 and the conduit system 46A are used to
evacuate the process chamber 10 and to maintain the pressure inside
the process chamber 10. A gas manifold 34, through which process
gases are introduced into the process chamber 10, is located above
the substrate support pedestal 48. The gas manifold 34 is connected
to a gas panel (not shown), which controls and supplies various
process gases to the process chamber 10.
[0028] Proper control and regulation of the gas flows to the gas
manifold 34 are performed by mass flow controllers (not shown) and
a microprocessor controller 70. The gas manifold 34 allows process
gases to be introduced and uniformly distributed in the process
chamber 10. Additionally, the gas manifold 34 may optionally be
heated to prevent condensation of any reactive gases within the
manifold.
[0029] The gas manifold 34 includes a plurality of electronic
control valves (not shown). The electronic control valves as used
herein refer to any control valve capable of providing rapid and
precise gas flow to the process chamber 10 with valve open and
close cycles within a range from about 0.01 seconds to about 10
seconds, preferably, from about 0.05 seconds to about 2 seconds,
and more preferably, from about 0.1 seconds to about 1 second.
[0030] The microprocessor controller 70 may be one of any form of
general purpose computer processor (CPU) that can be used in an
industrial setting for controlling various chambers and
sub-processors. The computer may use any suitable memory, such as
random access memory, read only memory, floppy disk drive, compact
disc drive, hard disk, or any other form of digital storage, local
or remote. Various support circuits may be coupled to the CPU for
supporting the processor in a conventional manner. Software
routines as required, may be stored in the memory or executed by a
second, remotely located CPU.
[0031] The software routines are executed to initiate process
recipes or sequences. The software routines, when executed,
transform the general purpose computer into a specific process
computer that controls the chamber operation so that a chamber
process is performed. For example, software routines may be used to
precisely control the activation of the electronic control valves
for the execution of process sequences according to the present
invention. Alternatively, the software routines may be performed in
hardware, as an application specific integrated circuit or other
type of hardware implementation, or a combination of software or
hardware.
[0032] FIG. 2 is a schematic cross-sectional view of one embodiment
of a chamber 80 including a gas delivery apparatus 130 adapted for
cyclic deposition, such as atomic layer deposition or rapid
chemical vapor deposition. A detailed description for a chamber 80
is described in commonly assigned U.S. Pat. No. 6,916,398, and
commonly assigned and co-pending U.S. Ser. No. 10/281,079, entitled
"Gas Delivery Apparatus for Atomic Layer Deposition," filed Oct.
25, 2002, and published as US 2003-0121608, which are both
incorporated herein by reference in their entirety. The terms
"atomic layer deposition" (ALD) and "rapid chemical vapor
deposition," as used herein, refer to the sequential introduction
of reactants to deposit a thin layer over a substrate structure.
The sequential introduction of reactants may be repeated to deposit
a plurality of thin layers to form a conformal layer to a desired
thickness. The chamber 80 may also be adapted for other deposition
techniques.
[0033] The chamber 80 contains a chamber body 82 having sidewalls
84 and a bottom 86. A slit valve 88 in the chamber 80 provides
access for a robot (not shown) to deliver and retrieve a substrate
90, such as a 200 mm or 300 mm semiconductor wafer or a glass
substrate, from the chamber 80.
[0034] A substrate support 92 supports the substrate 90 on a
substrate receiving surface 91 in the chamber 80. The substrate
support 92 is mounted to a lift motor 114 to raise and lower the
substrate support 92 and a substrate 90 disposed thereon. A lift
plate 116 connected to a lift motor 118 is mounted in the chamber
80 and raises and lowers pins 120 movably disposed through the
substrate support 92. The pins 120 raise and lower the substrate 90
over the surface of the substrate support 92. The substrate support
92 may include a vacuum chuck, an electrostatic chuck, or a clamp
ring for securing the substrate 90 to the substrate support 92
during processes.
[0035] The substrate support 92 may be heated to heat a substrate
90 disposed thereon. For example, the substrate support 92 may be
heated using an embedded heating element, such as a resistive
heater, or may be heated using radiant heat, such as heating lamps
disposed above the substrate support 92. A purge ring 122 may be
disposed on the substrate support 92 to define a purge channel 124
which provides a purge gas to a peripheral portion of the substrate
90 to prevent deposition thereon.
[0036] A gas delivery apparatus 130 is disposed at an upper portion
of the chamber body 82 to provide a gas, such as a process gas
and/or a purge gas, to the chamber 80. A vacuum system 178 is in
communication with a pumping channel 179 to evacuate any desired
gases from the chamber 80 and to help maintain a desired pressure
or a desired pressure range inside a pumping zone 166 of the
chamber 80.
[0037] In one embodiment, the chambers depicted by FIGS. 1 and 2
permit the process gas and/or purge gas to enter the chamber 80
normal (i.e., 900) with respect to the plane of the substrate 90
via the gas delivery apparatus 130. Therefore, the surface of
substrate 90 is symmetrically exposed to gases that allow uniform
film formation on substrates. In another embodiment, the process
gas may have a circular flow pattern, such as a "vortex," "helix,"
or "spiral" flow passing through the expanding channel 134 towards
the substrate. The circular flow may establish a more efficient
purge of the expanding channel 134 due to the sweeping action of
the vortex flow pattern across the inner surface of the expanding
channel 134 and a laminar flow efficiently purging the surface of
the chamber lid 132 and the substrate 90. The process gas includes
a ruthenium-containing precursor during one pulse and includes a
reducing gas in another pulse.
[0038] Chamber 80, depicted in FIG. 2, produces a more uniform film
than chamber 10, depicted in FIG. 1. Also, chamber 80 employs a
smaller cycle time than chamber 10, since chamber 80 takes less
time to purge and less time to dose the wafer to saturation with
precursor than chamber 10. The lesser dosing time is important
because many of the ruthenium-containing compounds have the
inherent characteristic of a low vapor pressure. The low vapor
pressure correlates to less precursor saturating the carrier gas
per time and temperature, therefore, more time is needed to
saturate the surface of the wafer with ruthenium-containing
compound (e.g., Cp.sub.2Ru) than a traditional precursor with a
higher vapor pressure (e.g., TiCl.sub.4). Therefore, chamber 10 may
dose a ruthenium-containing compound for about 1 second or less,
while chamber 80 may dose the same ruthenium-containing compound
for about 0.2 seconds or less.
[0039] In one embodiment, the gas delivery apparatus 130 comprises
a chamber lid 132. The chamber lid 132 includes an expanding
channel 134 extending from a central portion of the chamber lid 132
and a bottom surface 160 extending from the expanding channel 134
to a peripheral portion of the chamber lid 132. The bottom surface
160 is sized and shaped to substantially cover a substrate 90
disposed on the substrate support 92. The expanding channel 134 has
gas inlets 136A, 136B to provide gas flows from two similar pairs
of valves 142A/152A, 142B/152B, which may be provided together
and/or separately.
[0040] In one configuration, valve 142A and valve 142B are coupled
to separate reactant gas sources but are preferably coupled to the
same purge gas source. For example, valve 142A is coupled to
reactant gas source 138 and valve 142B is coupled to reactant gas
source 139, and both valves 142A, 142B are coupled to purge gas
source 140. Each valve 142A, 142B includes a delivery line 143A,
143B having a valve seat assembly 144A, 144B and each valves 152A,
152B includes a purge line 145A, 145B having a valve seat assembly
146A, 146B. The delivery line 143A, 143B is in communication with
the reactant gas source 138, 139 and is in communication with the
gas inlet 136A, 136B of the expanding channel 134. The valve seat
assembly 144A, 144B of the delivery line 143A, 143B controls the
flow of the reactant gas from the reactant gas source 138, 139 to
the expanding channel 134. The purge line 145A, 145B is in
communication with the purge gas source 140 and intersects the
delivery lines 143A, 143B downstream of the valve seat assembly
144A, 144B of the valves 142A, 142B. The valve seat assembly 146A,
146B of the purge line 145A, 145B controls the flow of the purge
gas from the purge gas source 140 to the delivery line 143A, 143B.
If a carrier gas is used to deliver reactant gases from the
reactant gas source 138, 139, preferably the same gas is used as a
carrier gas and a purge gas (i.e., an argon gas used as a carrier
gas and a purge gas).
[0041] Each valve seat assembly 144A, 144B, 146A, 146B may comprise
a diaphragm and a valve seat. The diaphragm may be biased open or
closed and may be actuated closed or open respectively. The
diaphragms may be pneumatically actuated or may be electrically
actuated. Examples of pneumatically actuated valves include
pneumatically actuated valves available from Fujiken and Veriflow.
Examples of electrically actuated valves include electrically
actuated valves available from Fujiken. Programmable logic
controllers 148A, 148B may be coupled to the valves 142A, 142B to
control actuation of the diaphragms of the valve seat assemblies
144A, 144B, 146A, 146B of the valves 142A, 142B. Pneumatically
actuated valves may provide pulses of gases in time periods as low
as about 0.020 seconds. Electrically actuated valves may provide
pulses of gases in time periods as low as about 0.005 seconds. An
electrically actuated valve typically requires the use of a driver
coupled between the valve and the programmable logic
controller.
[0042] Each valve 142A, 142B may be a zero dead volume valve to
enable flushing of a reactant gas from the delivery line 143A, 143B
when the valve seat assembly 144A, 144B of the valve is closed. For
example, the purge line 145A, 145B may be positioned adjacent the
valve seat assembly 144A, 144B of the delivery line 143A, 143B.
When the valve seat assembly 144A, 144B is closed, the purge line
145A, 145B may provide a purge gas to flush the delivery line 143A,
143B. In the embodiment shown, the purge line 145A, 145B is
positioned slightly spaced from the valve seat assembly 144A, 144B
of the delivery line 143A, 143B so that a purge gas is not directly
delivered into the valve seat assembly 144A, 144B when open. A zero
dead volume valve as used herein is defined as a valve which has
negligible dead volume (i.e., not necessary zero dead volume).
[0043] Each valve pair 142A/152A, 142B/152B may be adapted to
provide a combined gas flow and/or separate gas flows of the
reactant gas 138, 139 and the purge gas 140. In reference to valve
pair 142A/152A, one example of a combined gas flow of the reactant
gas 138 and the purge gas 140 provided by valve 142A comprises a
continuous flow of a purge gas from the purge gas source 140
through purge line 145A and pulses of a reactant gas from the
reactant gas source 138 through delivery line 143A. The continuous
flow of the purge gas may be provided by leaving diaphragm of the
valve seat assembly 146A of the purge line 145A open. The pulses of
the reactant gas from the reactant gas source 138 may be provided
by opening and closing the diaphragm of the valve seat 144A of the
delivery line 143A. In reference to valve pair 142A/152A, one
example of separate gas flows of the reactant gas 138 and the purge
gas 140 provided by valve 142A comprises pulses of a purge gas from
the purge gas source 140 through purge line 145A and pulses of a
reactant gas from the reactant gas source 138 through delivery line
143A. The pulses of the purge gas may be provided by opening and
closing the diaphragm of the valve seat assembly 146A of the purge
line 145A open. The pulses of the reactant gas from the reactant
gas source 138 may be provided by opening and closing the diaphragm
valve seat 144A of the delivery line 143A.
[0044] The delivery lines 143A, 143B of the valves 142A, 142B may
be coupled to the gas inlets 136A, 136B through gas conduits 150A,
150B. The gas conduits 150A, 150B may be integrated or may be
separate from the valves 142A, 142B. In one aspect, the valves
142A, 142B are coupled in close proximity to the expanding channel
134 to reduce any unnecessary volume of the delivery line 143A,
143B and the gas conduits 150A, 150B between the valves 142A, 142B
and the gas inlets 136A, 136B.
[0045] In FIG. 2, the expanding channel 134 comprises a channel
which has an inner diameter which increases from an upper portion
137 of cap 172 to a lower portion 135 of the expanding channel 134
adjacent the bottom surface 160 of the chamber lid 132.
[0046] In one specific embodiment, the inner diameter of the
expanding channel 134 for a chamber adapted to process 200 mm
diameter substrates is between about 0.2 inches (0.51 cm) and about
1.0 inch (2.54 cm), more preferably between about 0.3 inches (0.76
cm) and about 0.9 inches (2.29 cm) and more preferably between
about 0.3 inches (0.76 cm) and about 0.5 inches (1.27 cm) at the
upper portion 137 of the expanding channel 134 and between about
0.5 inches (1.27 cm) and about 3.0 inches (7.62 cm), preferably
between about 0.75 inches (1.91 cm) and about 2.5 inches (6.35 cm)
and more preferably between about 1.1 inches (2.79 cm) and about
2.0 inches (5.08 cm) at the lower portion 135 of the expanding
channel 134.
[0047] In another specific embodiment, the inner diameter of the
expanding channel 134 for a chamber adapted to process 300 mm
diameter substrates is between about 0.2 inches (0.51 cm) and about
1.0 inch (2.54 cm), more preferably between about 0.3 inches (0.76
cm) and about 0.9 inches (2.29 cm) and more preferably between
about 0.3 inches (0.76 cm) and about 0.5 inches (1.27 cm) at the
upper portion 137 of the expanding channel 134 and between about
0.5 inches (1.27 cm) and about 3.0 inches (7.62 cm), preferably
between about 0.75 inches (1.91 cm) and about 2.5 inches (6.35 cm)
and more preferably between about 1.2 inches (3.05 cm) and about
2.2 inches (5.59 cm) at the lower portion 135 of the expanding
channel 134 for a 300 mm substrate. In general, the above dimension
apply to an expanding channel adapted to provide a total gas flow
of between about 500 sccm and about 3,000 sccm.
[0048] In other specific embodiments, the dimension may be altered
to accommodate a certain gas flow therethrough. In general, a
larger gas flow will require a larger diameter expanding channel.
In one embodiment, the expanding channel 134 may be shaped as a
truncated cone (including shapes resembling a truncated cone).
Whether a gas is provided toward the walls of the expanding channel
134 or directly downward towards the substrate, the velocity of the
gas flow decreases as the gas flow travels through the expanding
channel 134 due to the expansion of the gas. The reduction of the
velocity of the gas flow helps reduce the likelihood the gas flow
will blow off reactants absorbed on the surface of the substrate
90.
[0049] Not wishing to be bound by theory, it is believed that the
diameter of the expanding channel 134, which is gradually
increasing from the upper portion 137 to the lower portion 135 of
the expanding channel, allows less of an adiabatic expansion of a
gas through the expanding channel 134 which helps to control the
temperature of the gas. For instance, a sudden adiabatic expansion
of a gas delivered through the gas inlet 136A, 136B into the
expanding channel 134 may result in a drop in the temperature of
the gas which may cause condensation of the gas and formation of
particles. On the other hand, a gradually expanding channel 134
according to embodiments of the present invention is believed to
provide less of an adiabatic expansion of a gas. Therefore, more
heat may be transferred to or from the gas, and, thus, the
temperature of the gas may be more easily controlled by controlling
the surrounding temperature of the gas (i.e., controlling the
temperature of the chamber lid 132). The gradually expanding
channel may contain one or more tapered inner surfaces, such as a
tapered straight surface, a concave surface, a convex surface, or a
combination thereof or may contain sections of one or more tapered
inner surfaces (i.e., a portion tapered, such as bottom surface 160
and a portion non-tapered, such as choke 162).
[0050] In one embodiment, the gas inlets 136A, 136B are located
adjacent the upper portion 137 of the expanding channel 134. In
other embodiments, one or more gas inlets may be located along the
length of the expanding channel 134 between the upper portion 137
and the lower portion 135.
[0051] In FIG. 2, a control unit 180, such as a programmed personal
computer, work station computer, or the like, may be coupled to the
chamber 80 to control processing conditions. For example, the
control unit 180 may be configured to control flow of various
process gases and purge gases from gas sources 138, 139, 140
through the valves 142A, 142B during different stages of a
substrate process sequence. Illustratively, the control unit 180
comprises a central processing unit (CPU) 182, support circuitry
184, and memory 186 containing associated control software 183.
[0052] The control unit 180 may be one of any form of general
purpose computer processor that can be used in an industrial
setting for controlling various chambers and sub-processors. The
CPU 182 may use any suitable memory 186, such as random access
memory, read only memory, floppy disk drive, compact disc drive,
hard disk, or any other form of digital storage, local or remote.
Various support circuits may be coupled to the CPU 182 for
supporting the chamber 80. The control unit 180 may be coupled to
another controller that is located adjacent individual chamber
components, such as the programmable logic controllers 148A, 148B
of the valves 142A, 142B. Bi-directional communications between the
control unit 180 and various other components of the chamber 80 are
handled through numerous signal cables collectively referred to as
signal buses 188, some of which are illustrated in FIG. 2. In
addition to control of process gases and purge gases from gas
sources 138, 139, 140 and from the programmable logic controllers
148A, 148B of the valves 142A, 142B, 152A, 152B the control unit
180 may be configured to be responsible for automated control of
other activities used in wafer processing--such as wafer transport,
temperature control, chamber evacuation, among other activities,
some of which are described elsewhere herein.
Noble Metal Layer Formation
[0053] A method of noble metal layer formation for high aspect
ratio interconnect features is described. The noble metal layer is
deposited using a cyclical deposition process. The cyclical
deposition process provides alternately adsorbing a noble
metal-containing precursor and a reducing gas on a substrate
structure. The noble metal-containing precursor and the reducing
gas undergo a reaction to form the noble metal layer on the
substrate. Suitable noble metals may include, for example,
ruthenium, palladium, platinum, cobalt, nickel, or rhodium,
preferably ruthenium. The ruthenium layer may have a thickness of
less than about 500 .ANG., preferably, within a range from about 10
.ANG. to about 100 .ANG., such as about 30 .ANG..
[0054] FIG. 3 illustrates a process sequence 100 detailing the
various steps used for the deposition of the silicon layer. These
steps may be performed in a process chamber similar to that
described above with reference to FIGS. 1 and 2. As shown in step
102, a substrate is provided to the process chamber. The substrate
may be for example, a silicon substrate having an interconnect
pattern defined in one or more dielectric material layers formed
thereon. The process chamber conditions such as, for example, the
temperature and pressure are adjusted to enhance the adsorption of
the process gases on the substrate so as to facilitate the reaction
of the noble metal-containing precursor (e.g., ruthenium
metallocene) and the reducing gas. In general, for noble metal
layer deposition, the substrate should be maintained at a
temperature of less than about 500.degree. C., preferably, within a
range from about 200.degree. C. to about 400.degree. C., such as
about 350.degree. C. The process chamber pressure is maintained
within a range from about 0.1 Torr to about 80 Torr, preferably,
from about 1 Torr to about 10 Torr. The noble metal-containing
precursor may be provided having a flow rate within a range from
about 0.01 sccm to about 20 sccm, preferably, from about 0.1 sccm
to about 5 sccm, and more preferably, from about 0.1 sccm to about
1 sccm. The reducing gas may be provided having a flow rate within
a range from about 1 sccm to about 100 sccm, preferably, from about
10 sccm to about 50 sccm.
[0055] In one embodiment where a constant carrier gas flow is
desired, a carrier gas stream is established within the process
chamber as indicated in step 104. Carrier gases may be selected so
as to also act as a purge gas for the removal of volatile reactants
and/or by-products from the process chamber. A carrier gas or a
purge gas that may be used during processes described herein
include helium (He), argon (Ar), nitrogen (N.sub.2), hydrogen
(H.sub.2), or combinations thereof. The pulse of the purge gas
lasts for a predetermined time interval, such as, within a range
from about 0.01 seconds to about 10 seconds, preferably, from about
0.07 seconds to about 2 seconds, and more preferably, from about
0.1 seconds to about 1 second. The carrier gas and purge gases may
be provided having a flow rate within a range from about 500 sccm
to about 5,000 sccm, preferably, from about 500 sccm to about 2,500
sccm for 200 mm substrates and from about 1,000 sccm to about 5,000
sccm for 300 mm substrates.
[0056] Referring to step 106, after the carrier gas stream is
established within the process chamber, a pulse of a noble
metal-containing precursor is added to the carrier gas stream. The
term pulse as used herein refers to a dose of material injected
into the process chamber or into the carrier gas stream. The pulse
of the noble metal-containing precursor lasts for a predetermined
time interval, such as, within a range from about 0.01 seconds to
about 10 seconds, preferably, from about 0.05 seconds to about 1.5
seconds, and more preferably, from about 0.1 seconds to about 1
second.
[0057] The noble metal-containing precursors may contain noble
metals, such as ruthenium, palladium, platinum, cobalt, nickel, or
rhodium. Suitable ruthenium-containing precursors include
tris(2,2,6,6-tetramethyl-3,5-heptanedionato) ruthenium,
bis(2,4-dimethylpentadienyl) ruthenium, dicarbonyl pentadienyl
ruthenium, ruthenium acetyl acetonate, (2,4-dimethylpentadienyl)
ruthenium (cyclopentadienyl),
bis(2,2,6,6-tetramethyl-3,5-heptanedionato) ruthenium
(1,5-cyclooctadiene),
(2,4-dimethylpentadienyl)ruthenium(methylcyclopentadienyl),
(1,5-cyclooctadiene)ruthenium(cyclopentadienyl),
(1,5-cyclooctadiene)ruthenium(methylcyclopentadienyl),
(1,5-cyclooctadiene)ruthenium(ethylcyclopentadienyl),
(2,4-dimethylpentadienyl) ruthenium(ethylcyclopentadienyl),
(2,4-dimethylpentadienyl)ruthenium(isopropylcyclopentadienyl),
bis(N,N-dimethyl 1,3-tetramethyl
diiminato)ruthenium(1,5-cyclooctadiene), bis(N,N-dimethyl
1,3-dimethyl diiminato)ruthenium(1,5-cyclooctadiene),
bis(allyl)ruthenium(1,5-cyclooctadiene),
(.eta..sup.6-C.sub.6H.sub.6) ruthenium (1,3-cyclohexadiene),
bis(1,1-dimethyl-2-aminoethoxylato)ruthenium(1,5-cyclooctadiene),
or bis(1,1-dimethyl-2-aminoethylaminato)ruthenium
(1,5-cyclooctadiene). Suitable palladium-containing precursors
include bis(allyl)palladium, bis(2-methylallyl)palladium, or
(cyclopentadienyl)palladium(allyl). Suitable platinum-containing
precursors include dimethyl platinum (cyclooctadiene), trimethyl
platinum (cyclopentadienyl), trimethyl(methylcyclopentadienyl)
platinum, cyclopentadienyl(allyl) platinum, methyl(carbonyl)
platinum cyclopentadienyl, trimethyl platinum (acetylacetonato),
and bis(acetylacetonato) platinum. Suitable cobalt-containing
precursors include bis(cyclopentadienyl) cobalt, (cyclopentadienyl)
cobalt (cyclohexadienyl), cyclopentadienyl(1,3-hexadienyl) cobalt,
(cyclobutadienyl) cobalt (cyclopentadienyl),
bis(methylcyclopentadienyl) cobalt, (cyclopentadienyl) cobalt
(5-methylcyclopentadienyl), or bis(ethylene) cobalt
(pentamethylcyclopentadienyl). A suitable nickel-containing
precursor includes bis(methylcyclopentadienyl) nickel. Suitable
rhodium-containing precursors include bis(carbonyl) rhodium
(cyclopentadienyl), bis(propylene) rhodium, bis(carbonyl) rhodium
(ethylcyclopentadienyl), or bis(carbonyl) rhodium
(methylcyclopentadienyl).
[0058] The time interval for the pulse of the noble
metal-containing precursor is variable depending upon a number of
factors such as, for example, the volume capacity of the process
chamber employed, the vacuum system coupled thereto and the
volatility/reactivity of the reactants used. For example, (1) a
large-volume process chamber may lead to a longer time to stabilize
the process conditions such as, for example, carrier/purge gas flow
and temperature, requiring a longer pulse time; (2) a lower flow
rate for the process gas may also lead to a longer time to
stabilize the process conditions requiring a longer pulse time; and
(3) a lower chamber pressure means that the process gas is
evacuated from the process chamber more quickly requiring a longer
pulse time. In general, the process conditions are advantageously
selected so that a pulse of the noble metal-containing precursor
provides a sufficient amount of precursor so that at least a
monolayer of the noble metal-containing precursor is adsorbed on
the substrate. Thereafter, excess noble metal-containing precursor
remaining in the chamber may be removed from the process chamber by
the constant carrier gas stream in combination with the vacuum
system.
[0059] In step 108, after the excess noble metal-containing
precursor has been flushed from the process chamber by the carrier
gas stream, a pulse of a reducing gas is added to the carrier gas
stream. The pulse of the reducing gas also lasts for a
predetermined time interval. In general, the time interval for the
pulse of the reducing gas should be long enough for adsorption of
at least a monolayer of the reducing gas on the noble
metal-containing precursor. The pulse of reducing gas lasts for a
predetermined time interval, such as, within a range from about
0.01 seconds to about 10 seconds, preferably, from about 0.1
seconds to about 2 seconds, and more preferably, from about 0.1
seconds to about 1 second. Thereafter, excess reducing gas is
flushed from the process chamber by the carrier gas stream.
Suitable reducing gases may include, for example, hydrogen (e.g.,
H.sub.2 or atomic-H), ammonia (NH.sub.3), silane (SiH.sub.4),
disilane (Si.sub.2H.sub.6), trisilane (Si.sub.3H.sub.8),
tetrasilane (Si.sub.4H.sub.10), dimethylsilane (SiC.sub.2H.sub.8),
methyl silane (SiCH.sub.6), ethylsilane (SiC.sub.2H.sub.8),
chlorosilane (ClSiH.sub.3), dichlorosilane (Cl.sub.2SiH.sub.2),
hexachlorodisilane (Si.sub.2Cl.sub.6), borane, diborane, triborane,
tetraborane, pentaborane, triethylborane, or combinations
thereof.
[0060] In one embodiment, a deposition cycle for forming a noble
metal layer is depicted by steps 104-108 in FIG. 3. A constant flow
of carrier gas is provided to the process chamber modulated by
alternating periods of pulsing and non-pulsing where the periods of
pulsing alternate between the noble metal-containing precursor and
the reducing gas along with the carrier gas stream, while the
periods of non-pulsing include only the carrier gas stream.
[0061] The time interval for each of the pulses of the noble
metal-containing precursor and the reducing gas may have the same
duration. That is, the duration of the pulse of the noble
metal-containing precursor may be identical to the duration of the
pulse of the reducing gas. For such an embodiment, a time interval
(T.sub.1) for the pulse of the noble metal-containing precursor is
equal to a time interval (T.sub.2) for the pulse of the reducing
gas.
[0062] Alternatively, the time interval for each of the pulses of
the noble metal-containing precursor and the reducing gas may have
different durations. That is, the duration of the pulse of the
noble metal-containing precursor may be shorter or longer than the
duration of the pulse of the reducing gas. For such an embodiment,
a time interval (T.sub.1) for the pulse of the noble
metal-containing precursor is different than the time interval
(T.sub.2) for the pulse of the reducing gas.
[0063] In addition, the periods of non-pulsing between each of the
pulses of the noble metal-containing precursor and the reducing gas
may have the same duration. That is, the duration of the period of
non-pulsing between each pulse of the noble metal-containing
precursor and each pulse of the reducing gas is identical. For such
an embodiment, a time interval (T.sub.3) of non-pulsing between the
pulse of the noble metal-containing precursor and the pulse of the
reducing gas is equal to a time interval (T.sub.4) of non-pulsing
between the pulse of the reducing gas and the pulse of the noble
metal-containing precursor. During the time periods of non-pulsing
only the constant carrier gas stream is provided to the process
chamber.
[0064] Alternatively, the periods of non-pulsing between each of
the pulses of the noble metal-containing precursor and the reducing
gas may have different duration. That is, the duration of the
period of non-pulsing between each pulse of the noble
metal-containing precursor and each pulse of the reducing gas may
be shorter or longer than the duration of the period of non-pulsing
between each pulse of the reducing gas and the noble
metal-containing precursor. For such an embodiment, a time interval
(T.sub.3) of non-pulsing between the pulse of the noble
metal-containing precursor and the pulse of the reducing gas is
different from a time interval (T.sub.4) of non-pulsing between the
pulse of the reducing gas and the pulse of noble metal-containing
precursor. During the time periods of non-pulsing only the constant
carrier gas stream is provided to the process chamber.
[0065] Additionally, the time intervals for each pulse of the noble
metal-containing precursor, the reducing gas and the periods of
non-pulsing therebetween for each deposition cycle may have the
same duration. For such an embodiment, a time interval (T.sub.1)
for the noble metal-containing precursor, a time interval (T.sub.2)
for the reducing gas, a time interval (T.sub.3) of non-pulsing
between the pulse of the noble metal-containing precursor and the
pulse of the reducing gas and a time interval (T.sub.4) of
non-pulsing between the pulse of the reducing gas and the pulse of
the noble metal-containing precursor each have the same value for
each deposition cycle. For example, in a first deposition cycle
(C.sub.1), a time interval (T.sub.1) for the pulse of the noble
metal-containing precursor has the same duration as the time
interval (T.sub.1) for the pulse of the noble metal-containing
precursor in subsequent deposition cycles (C.sub.2 . . . C.sub.n).
Similarly, the duration of each pulse of the reducing gas and the
periods of non-pulsing between the pulse of the noble
metal-containing precursor and the reducing gas in the first
deposition cycle (C.sub.1) is the same as the duration of each
pulse of the reducing gas and the periods of non-pulsing between
the pulse of the noble metal-containing precursor and the reducing
gas in subsequent deposition cycles (C.sub.2 . . . C.sub.n),
respectively.
[0066] Alternatively, the time intervals for at least one pulse of
the noble metal-containing precursor, the reducing gas and the
periods of non-pulsing therebetween for one or more of the
deposition cycles of the noble metal layer deposition process may
have different durations. For such an embodiment, one or more of
the time intervals (T.sub.1) for the pulses of the noble
metal-containing precursor, the time intervals (T.sub.2) for the
pulses of the reducing gas, the time intervals (T.sub.3) of
non-pulsing between the pulse of the noble metal-containing
precursor and the reducing gas and the time intervals (T.sub.4) of
non-pulsing between the pulses of the reducing gas and the noble
metal-containing precursor may have different values for one or
more deposition cycles of the cyclical deposition process. For
example, in a first deposition cycle (C.sub.1), the time interval
(T.sub.1) for the pulse of the noble metal-containing precursor may
be longer or shorter than one or more time interval (T.sub.1) for
the pulse of the noble metal-containing precursor in subsequent
deposition cycles (C.sub.2 . . . C.sub.n). Similarly, the durations
of the pulses of the reducing gas and the periods of non-pulsing
between the pulse of the noble metal-containing precursor and the
reducing gas in the first deposition cycle (C.sub.1) may be the
same or different than the duration of each pulse of the reducing
gas and the periods of non-pulsing between the pulse of the noble
metal-containing precursor and the reducing gas in subsequent
deposition cycles (C.sub.2 . . . C.sub.n).
[0067] Referring to step 110, after each deposition cycle (steps
104 through 108) a thickness of the noble metal will be formed on
the substrate. Depending on specific device requirements,
subsequent deposition cycles may be needed to achieve a desired
thickness. As such, steps 104 through 108 are repeated until the
desired thickness for the noble metal layer is achieved.
Thereafter, when the desired thickness for the noble metal layer is
achieved the process is stopped as indicated by step 112.
[0068] In an alternate process sequence described with respect to
FIG. 4, the noble metal layer deposition cycle comprises separate
pulses for each of the noble metal-containing precursor, the
reducing gas and a purge gas. For such an embodiment, the noble
metal layer deposition sequence 200 includes providing a substrate
to the process chamber (step 202), providing a first pulse of a
purge gas to the process chamber (step 204), providing a pulse of a
noble metal-containing precursor to the process chamber (step 206),
providing a second pulse of the purge gas to the process chamber
(step 208), providing a pulse of a reducing gas to the process
chamber (step 210), and then repeating steps 204 through 210, or
stopping the deposition process (step 214) depending on whether a
desired thickness for the noble metal layer has been achieved (step
212).
[0069] The time intervals for each of the pulses of the noble
metal-containing precursor, the reducing gas and the purge gas may
have the same or different durations as discussed above with
respect to FIG. 3. Alternatively, corresponding time intervals for
one or more pulses of the noble metal-containing precursor, the
reducing gas and the purge gas in one or more of the deposition
cycles of the noble metal layer deposition process may have
different durations.
[0070] In FIGS. 3-4, the noble metal layer deposition cycle is
depicted as beginning with a pulse of the noble metal-containing
precursor followed by a pulse of the reducing gas. Alternatively,
the noble metal layer deposition cycle may start with a pulse of
the reducing gas followed by a pulse of the noble metal-containing
precursor.
[0071] In one example, a method for depositing a ruthenium layer by
an ALD process includes positioning a substrate (e.g., 300 mm
diameter) into the process chamber 80 of FIG. 2. The method
includes providing pulses of a ruthenium-containing compound, such
as bis(2,4-dimethylpentadienyl) ruthenium, from gas source 138
through valve 142A, having a flow rate within a large from about
0.01 sccm to about 5 sccm, preferably, from about 0.1 sccm to about
1 sccm. A pulse time of about 1.5 seconds or less, such as about
0.1 seconds or less, and as low as about 0.05 seconds or less may
be used for the ruthenium-containing compound due to the smaller
volume of the reaction zone 164 (as compared to chamber 8 of FIG.
1). The process further includes providing pulses of a reducing
gas, such as diborane (B.sub.2H.sub.6), from gas source 139 through
valve 142B, having a flow rate within a range from about 1 sccm to
about 80 sccm, preferably, from about 10 sccm to about 50 sccm. A
pulse time of about 2 seconds or less, about 1 second or less, or
about 0.1 seconds or less may be used for the reducing gas due to a
smaller volume of the reaction zone 164. An argon purge gas having
a flow rate within a range from about 500 sccm to about 5,000 sccm,
preferably, from about 1,500 sccm to about 3,500 sccm, may be
continuously provided from gas source 140 through valves 142A,
142B. The time between pulses of bis(2,4-dimethylpentadienyl)
ruthenium and B.sub.2H.sub.6 may be about 0.5 seconds or less, such
as about 0.1 seconds or less, and as low as about 0.07 seconds or
less due to the smaller volume of the reaction zone 164. It is
believed to fill a reaction zone with a reactant gas and/or purge
gas, pulse times as low as about 0.016 seconds are sufficient, with
correspondingly shorter pulse times for a reaction zone 164 sized
for smaller wafers (e.g., 200 mm). The substrate may be heated to a
temperature within a range from about 200.degree. C. to about
400.degree. C., preferably, about 350.degree. C., and the chamber
may be pressurized at a pressure within a range from about 1.0 to
about 10 Torr, preferably, about 4 Torr. A process provides a
ruthenium layer having a thickness within a range from about 0.5
.ANG. to about 1.0 .ANG. per cycle. The alternating sequence of the
cycle may be repeated to obtain a desired thickness of the
ruthenium layer.
[0072] In one embodiment, the ruthenium layer is deposited on a
sidewall with a thickness coverage of about 50 .ANG. or less. In
another embodiment, the ruthenium layer is deposited on a sidewall
with a thickness coverage of about 20 .ANG. or less. In still
another embodiment, the ruthenium layer is deposited on a sidewall
with a thickness coverage of about 10 .ANG. or less. A ruthenium
layer having a thickness of about 10 .ANG. or less is believed to
be a sufficient thickness as an underlayer to adhere copper
deposition (i.e., seed layer) and to prevent copper diffusion
(i.e., barrier layer). In one aspect, a thin ruthenium underlayer
may be advantageously used prior to filling sub-micron (e.g., less
than 0.15 .mu.m) and smaller features having high aspect ratios
(e.g., greater than 5 to 1). Of course, a layer may also be used
that has a sidewall with a thickness coverage of greater than 50
.ANG.. In one embodiment, a ruthenium material is deposited as a
seed layer. In another embodiment, a ruthenium material is
deposited as a barrier layer.
Formation of Copper Interconnects
[0073] FIGS. 5A-5C illustrate cross-sectional views of different
stages of a copper interconnect being fabricated by sequences that
incorporate a noble metal layer formed during a process as
described herein. FIG. 5A, for example, illustrates a
cross-sectional view of a substrate 300 having metal contacts 304
and a dielectric layer 302 formed thereon. The substrate 300 may
contain a semiconductor material such as, for example, silicon,
germanium, or gallium arsenide. The dielectric layer 302 may
contain an insulating material such as, for example, silicon oxide
or silicon nitride. The metal contacts 304 may contain for example,
copper. Apertures 304H may be defined in the dielectric layer 302
to provide openings over the metal contacts 304. The apertures 304H
may be defined in the dielectric layer 302 using conventional
lithography and etching techniques.
[0074] A barrier layer 306 may be formed in the apertures 304H
defined in the dielectric layer 302. The barrier layer 306 may
include one or more refractory metal-containing layers such as, for
example, titanium, titanium nitride, tantalum, tantalum nitride,
tungsten, or tungsten nitride. The barrier layer 306 may be formed
using a suitable deposition process. For example, titanium nitride
may be deposited using a chemical vapor deposition (CVD) process or
ALD process wherein titanium tetrachloride and ammonia are
reacted.
[0075] Referring to FIG. 5B, a noble metal layer 308 (e.g.,
ruthenium) is formed on the barrier layer 306. The noble metal
layer is formed using the cyclical deposition techniques described
above with reference to FIGS. 3-4. The thickness for the noble
metal layer is variable depending on the device structure to be
fabricated. Typically, the thickness of the noble metal layer is
less than about 100 .ANG., preferably, within a range from about 10
.ANG. to about 60 .ANG.. In one embodiment, a ruthenium layer has a
thickness of about 30 .ANG..
[0076] Thereafter, referring to FIG. 5C, the apertures 304H may be
filled with copper 310 to complete the copper interconnect. The
copper 310 may be formed using one or more suitable deposition
processes. In one embodiment, for example, a copper seed layer may
be formed on the ruthenium layer by using a CVD process followed by
deposition of bulk copper to fill the interconnects using an
electrochemical plating (ECP) process. In another embodiment, a
copper seed layer is deposited to the ruthenium layer via physical
vapor deposition (PVD), thereafter an electroless copper plating is
utilized to deposit a copper bulk fill. In another embodiment, the
ruthenium layer serves as a seed layer to which a copper bulk fill
is directly deposited with ECP or electroless copper plating.
[0077] Several integration sequence are conducted in order to form
a ruthenium layer within the interconnect. In one embodiment, the
subsequent steps follow: a) pre-clean of the substrate; b)
deposition of a barrier layer (e.g., ALD of TaN); c) deposition of
ruthenium by ALD; and d) deposition of copper by ECP or Cu-PVD
followed by ECP. In another embodiment, the subsequent steps
follow: a) deposition of a barrier layer (e.g., ALD of TaN); b)
punch-through step; c) deposition of ruthenium by ALD; and d)
deposition of copper by ECP or Cu-PVD followed by ECP. In another
embodiment, the subsequent steps follow: a) deposition of ruthenium
by ALD; b) punch-through step; c) deposition of ruthenium by ALD;
and d) deposition of copper by ECP or Cu-PVD followed by ECP or
Cu-PVD. In another embodiment, the subsequent steps follow: a)
deposition of ruthenium by ALD; b) punch-through step; c)
deposition of ruthenium by ALD; and d) deposition of copper by ECP.
In another embodiment, the subsequent steps follow: a) pre-clean of
the substrate; b) deposition of ruthenium by ALD; and c) deposition
of copper by ECP or Cu-PVD followed by ECP.
[0078] The pre-clean steps include methods to clean or purify the
via, such as the removal of residue at the bottom of the via (e.g.,
carbon) or reduction of copper oxide to copper metal. Punch-through
steps include a sputtering method to remove material (e.g., barrier
layer) with a plasma from the bottom of the via to expose
conductive layer, such as copper. Further disclosure of
punch-through steps are described in more detail in the commonly
assigned, U.S. Pat. No. 6,498,091, and is herein incorporated by
reference. The punch-through steps may be conducted in a process
chamber, such as either a barrier chamber or a clean chamber. In
embodiments of the invention, clean steps and punch-through steps
are applied to ruthenium barrier layers. Further disclosure of
overall integrated methods are described in more detail in the
commonly assigned, U.S. Ser. No. 60/478,663, entitled "Integration
of ALD Tantalum Nitride for Copper Metallization", filed Jun. 13,
2003, and is herein incorporated by reference.
[0079] 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.
* * * * *