U.S. patent application number 16/947286 was filed with the patent office on 2020-11-19 for low resistivity films containing molybdenum.
The applicant listed for this patent is Lam Research Corporation. Invention is credited to Hanna Bamnolker, Gorun Butail, Joshua Collins, Michal Danek, Raashina Humayun, Griffin John Kennedy, Chiukin Steven Lai, Shruti Vivek Thombare, Patrick van Cleemput.
Application Number | 20200365456 16/947286 |
Document ID | / |
Family ID | 1000004993530 |
Filed Date | 2020-11-19 |
United States Patent
Application |
20200365456 |
Kind Code |
A1 |
Thombare; Shruti Vivek ; et
al. |
November 19, 2020 |
LOW RESISTIVITY FILMS CONTAINING MOLYBDENUM
Abstract
Provided herein are low resistance metallization stack
structures for logic and memory applications and related methods of
fabrication. In some implementations, the methods involve providing
a tungsten (W)-containing layer on a substrate; and depositing a
molybdenum (Mo)-containing layer on the W-containing layer. In some
implementations, the methods involve depositing a Mo-containing
layer directly on a dielectric or titanium nitride (TiN) substrate
without an intervening W-containing layer.
Inventors: |
Thombare; Shruti Vivek;
(Sunnyvale, CA) ; Humayun; Raashina; (Los Altos,
CA) ; Danek; Michal; (Cupertino, CA) ; Lai;
Chiukin Steven; (Sunnyvale, CA) ; Collins;
Joshua; (Sunnyvale, CA) ; Bamnolker; Hanna;
(Cupertino, CA) ; Kennedy; Griffin John; (San
Leandro, CA) ; Butail; Gorun; (Fremont, CA) ;
van Cleemput; Patrick; (San Jose, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lam Research Corporation |
Fremont |
CA |
US |
|
|
Family ID: |
1000004993530 |
Appl. No.: |
16/947286 |
Filed: |
July 27, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16676169 |
Nov 6, 2019 |
10777453 |
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16947286 |
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15948143 |
Apr 9, 2018 |
10510590 |
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16676169 |
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62483857 |
Apr 10, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/53266 20130101;
H01L 23/5226 20130101; H01L 21/76877 20130101; H01L 27/11556
20130101; H01L 21/76843 20130101; H01L 27/11582 20130101; H01L
21/76864 20130101; H01L 21/28568 20130101; H01L 21/28562 20130101;
H01L 27/10891 20130101; H01L 21/76879 20130101; H01L 21/76876
20130101 |
International
Class: |
H01L 21/768 20060101
H01L021/768; H01L 21/285 20060101 H01L021/285; H01L 23/522 20060101
H01L023/522 |
Claims
1.-17. (canceled)
18. A method comprising: providing a substrate comprising a feature
having a dielectric surface; forming a molybdenum layer directly on
the dielectric surface without an intervening diffusion barrier
layer.
19. The method of claim 18, wherein forming the molybdenum layer
comprises forming a reducing agent layer on the dielectric
surface.
20. The method of claim 19, wherein forming the molybdenum layer
further comprises exposing the reducing agent layer to a
molybdenum-containing precursor.
21. The method of claim 20, wherein the reducing agent layer is
converted to molybdenum by the exposure.
22. The method of claim 19, wherein the reducing agent layer is
conformal to the feature.
23. The method of claim 2, wherein the reducing agent layer is
between 10 Angstroms and 50 Angstroms thick.
24. The method of claim 18, wherein the dielectric surface is a
silicon oxide surface.
25. The method of claim 18, wherein the dielectric surface is a
silicon nitride surface
26. The method of claim 18, wherein the dielectric surface is an
aluminum oxide surface.
27. The method of claim 18, wherein the feature further comprises a
conductive surface.
28. The method of claim 18, wherein molybdenum layer has less than
1 (atomic) % impurities.
29. The method of claim 18, wherein molybdenum layer is formed from
one of: molybdenum hexafluoride (MoF.sub.6), molybdenum
pentachloride (MoCl.sub.5), molybdenum dichloride dioxide
(MoO.sub.2Cl.sub.2), molybdenum tetrachloride oxide (MoOCl.sub.4),
and molybdenum hexacarbonyl (Mo(CO).sub.6).
30. The method of claim 18, wherein molybdenum layer is formed from
an organometallic precursor.
31. A method comprising: providing a substrate comprising a feature
having a dielectric surface; forming a conformal reducing agent
layer in the feature including directly on the dielectric surface;
and exposing the reducing agent layer to a molybdenum-containing
precursor to form a conformal molybdenum layer including directly
on the dielectric surface.
32. The method of claim 31, wherein the reducing agent layer is
between 10 Angstroms and 50 Angstroms thick.
33. The method of claim 31, wherein the dielectric surface is a
silicon oxide surface, a silicon nitride surface, or an aluminum
oxide surface.
34. The method of claim 31, wherein the molybdenum precursor is one
of molybdenum hexafluoride (MoF.sub.6), molybdenum pentachloride
(MoCl.sub.5), molybdenum dichloride dioxide (MoO.sub.2Cl.sub.2),
molybdenum tetrachloride oxide (MoOCl.sub.4), and molybdenum
hexacarbonyl (Mo(CO).sub.6).
35. The method of claim 31, wherein molybdenum precursor is an
organometallic precursor.
36. A method comprising: depositing a molybdenum-containing
nucleation layer on a substrate using a first reducing agent; and
depositing by chemical vapor deposition (CVD) a molybdenum bulk
layer on the molybdenum nucleation layer using a second reducing
agent, wherein the second reducing agent is different from the
first reducing agent.
37. The method of claim 36, wherein the molybdenum bulk layer is
deposited by a reducing a molybdenum compound selected from:
molybdenum hexafluoride (MoF.sub.6), molybdenum pentachloride
(MoCl.sub.5), molybdenum dichloride dioxide (MoO.sub.2Cl.sub.2),
molybdenum tetrachloride oxide (MoOCl.sub.4), and molybdenum
hexacarbonyl (Mo(CO).sub.6).
Description
INCORPORATION BY REFERENCE
[0001] An Application Data Sheet is filed concurrently with this
specification as part of the present application. Each application
that the present application claims benefit of or priority to as
identified in the concurrently filed Application Data Sheet is
incorporated by reference herein in its entirety and for all
purposes.
BACKGROUND
[0002] The background description provided herein is for the
purposes of generally presenting the context of the disclosure.
Work of the presently named inventors, to the extent it is
described in this background section, as well as aspects of the
description that may not otherwise qualify as prior art at the time
of filing, are neither expressly nor impliedly admitted as prior
art against the present disclosure.
[0003] Tungsten (W) film deposition using chemical vapor deposition
(CVD) techniques is an integral part of semiconductor fabrication
processes. For example, tungsten films may be used as low
resistivity electrical connections in the form of horizontal
interconnects, vias between adjacent metal layers, and contacts
between a first metal layer and the devices on a silicon substrate.
Tungsten films may also be used in various memory applications,
including in formation of buried wordline (bWL) architectures for
dynamic random access memory (DRAM), and logic applications. In an
example of bWL deposition, a tungsten layer may be deposited on a
titanium nitride (TiN) barrier layer to form a TiN/W bilayer by a
CVD process using WF.sub.6. However, the continued decrease in
feature size and film thickness bring various challenges to TiN/W
film stacks. These include high resistivity for thinner films and
deterioration of TiN barrier properties.
SUMMARY
[0004] One aspect of the disclosure relates to methods including
providing a tungsten (W)-containing layer on a substrate; and
depositing a molybdenum (Mo)-containing layer on the W-containing
layer. In some embodiments, the W-containing layer is a WCN layer.
In some embodiments, the W-containing layer is a W nucleation
layer. In some embodiments, the W-containing layer is deposited
from one or more tungsten chloride precursors. In some embodiments,
the Mo-containing layer is a Mo layer having less than 1 (atomic) %
impurities. In some embodiments, the method includes thermally
annealing the Mo-containing layer. In some embodiments, the
Mo-containing layer is deposited by exposing the W-containing layer
to a reducing agent and a Mo-containing precursor selected from:
molybdenum hexafluoride (MoF.sub.6), molybdenum pentachloride
(MoCl.sub.5), molybdenum dichloride dioxide (MoO.sub.2Cl.sub.2),
molybdenum tetrachloride oxide (MoOCl.sub.4), and molybdenum
hexacarbonyl (Mo(CO).sub.6). In some embodiments, a substrate
temperature during exposure to the Mo-containing precursor is less
than 550.degree. C. In some embodiments, the substrate is exposed
to the reducing agent at first substrate temperature and is exposed
to the Mo-containing precursor at a second substrate temperature,
wherein the first substrate temperature is less than the second
substrate temperature. In some embodiments, the reducing agent is a
mixture of a boron-containing reducing agent and a
silicon-containing reducing agent.
[0005] Another aspect of the disclosure relates to method including
flowing a reducing agent gas to a process chamber housing a
substrate, at a first substrate temperature to form a conformal
reducing agent layer on the substrate; and exposing the conformal
reducing agent layer to a molybdenum (Mo)-containing precursor at a
second substrate temperature to convert the reducing agent layer to
molybdenum. In some embodiments, the first substrate temperature is
less than the second substrate temperature. In some embodiments,
the reducing agent is a mixture of a boron-containing reducing
agent and a silicon-containing reducing agent. In some embodiments,
the first substrate temperature is no more than 400.degree. C. and
the second substrate temperature is at least 500.degree. C. In some
embodiments, the methods further include annealing the
molybdenum.
[0006] Another aspect of the disclosure relates to a method
including pulsing a reducing agent, wherein the reducing agent is
boron (B)-containing, silicon (Si)-containing or germanium
(Ge)-containing; and pulsing a Mo-containing precursor, wherein the
Mo-containing precursor is reduced by the reducing agent or a
product thereof to form a multi-component tungsten-containing film
containing one or more of B, Si, and Ge on the substrate. In some
embodiments, the multi-component tungsten-containing film contains
between 5% and 60% (atomic) B, Si, or Ge. In some embodiments, the
between 5% and 60% (atomic) B, Si, or Ge is provided by the
reducing agent.
[0007] Another aspect of the disclosure are apparatuses for
performing the methods disclosed herein. These and other features
are discussed further with respect to the drawings.
BRIEF DESCRIPTIONS OF DRAWINGS
[0008] FIGS. 1A and 1B are schematic examples of material stacks
that include molybdenum (Mo) according to various embodiments.
[0009] FIG. 2 depicts a schematic example of a DRAM architecture
including a Mo buried wordline (bWL).
[0010] FIG. 3A depicts a schematic example of a Mo wordline in a 3D
NAND structure.
[0011] FIG. 3B depicts a 2-D rendering of 3-D features of a
partially-fabricated 3D NAND structure after Mo fill including a Mo
wordline and a conformal barrier layer.
[0012] FIGS. 4A and 4B provide process flow diagrams for methods
performed in accordance with disclosed embodiments.
[0013] FIGS. 5 and 6 are graphs showing Mo thickness (Angstroms)
vs. CVD Duration (seconds) and Mo Resistivity (.mu..OMEGA.-cm) vs
Mo thickness (Angstroms), respectively, for various substrate
temperatures and chamber pressures for CVD deposition of Mo on
tungsten (W) nucleation layers.
[0014] FIGS. 7 and 8 are graphs showing Mo growth rate and
resistivity vs Mo film thickness, respectively, for CVD deposition
of Mo on WCN at various substrate temperatures and chamber
pressures.
[0015] FIG. 9 is a graph showing thickness and resistivity of a CVD
deposited Mo layer as a function of WCN underlayer thickness.
[0016] FIG. 10 is a graph showing the reduction in stack
resistivity for Mo stacks of various thicknesses deposited on 2 nm
WCN after anneal at 800.degree. C.
[0017] FIG. 11 is a block diagram of a processing system suitable
for conducting deposition processes in accordance with embodiments
described herein.
DETAILED DESCRIPTION
[0018] In the following description, numerous specific details are
set forth to provide a thorough understanding of the presented
embodiments. The disclosed embodiments may be practiced without
some or all of these specific details. In other instances,
well-known process operations have not been described in detail to
not unnecessarily obscure the disclosed embodiments. While the
disclosed embodiments will be described in conjunction with the
specific embodiments, it will be understood that it is not intended
to limit the disclosed embodiments.
[0019] Provided herein are low resistance metallization stack
structures for logic and memory applications. FIGS. 1A and 1B are
schematic examples of material stacks that include molybdenum (Mo)
according to various embodiments. FIGS. 1A and 1B illustrate the
order of materials in a particular stack and may be used with any
appropriate architecture and application, as described further
below with respect to FIGS. 2 and 3. In the example of FIG. 1A, a
substrate 102 has a Mo layer 108 is deposited thereon. The
substrate 102 may be a silicon or other semiconductor wafer, e.g.,
a 200-mm wafer, a 300-mm wafer, or a 450-mm wafer, including wafers
having one or more layers of material, such as dielectric,
conducting, or semi-conducting material deposited thereon. The
methods may also be applied to form metallization stack structures
on other substrates, such as glass, plastic, and the like.
[0020] In FIG. 1A, a dielectric layer 104 is on the substrate 102.
The dielectric layer 104 may be deposited directly on a
semiconductor (e.g., Si) surface of the substrate 102, or there may
be any number of intervening layers. Examples of dielectric layers
include doped and undoped silicon oxide, silicon nitride, and
aluminum oxide layers, with specific examples including doped or
undoped layers SiO.sub.2 and Al.sub.2O.sub.3. Also, in FIG. 1A, a
diffusion barrier layer 106 is disposed between the Mo layer 108
and the dielectric layer 104. Examples of diffusion barrier layers
including titanium nitride (TiN), titanium/titanium nitride
(Ti/TiN), tungsten nitride (WN), and tungsten carbon nitride (WCN).
Further examples diffusion barriers are multi-component
Mo-containing films as described further below. The Mo layer 108 is
the main conductor of the structure. As discussed further below,
the Mo layer 108 may include a Mo nucleation layer and a bulk Mo
layer. Further, in some embodiments, the Mo layer 108 may be
deposited on a tungsten (W) or W-containing growth initiation
layer.
[0021] FIG. 1B shows another example of a material stack. In this
example, the stack includes the substrate 102, dielectric layer
104, with Mo layer 108 deposited on the dielectric layer 104,
without an intervening diffusion barrier layer. As in the example
of FIG. 1A, the Mo layer 108 may include a Mo nucleation layer and
a bulk Mo layer, and, in some embodiments, the Mo layer 108 may be
deposited on a tungsten (W) or W-containing growth initiation
layer. By using Mo, which has a lower electron mean free path than
W, as the main conductor, lower resistivity thin films can be
obtained.
[0022] While FIGS. 1A and 1B show examples of metallization stacks,
the methods and resulting stacks are not so limited. For example,
in some embodiments, Mo may be deposited directly on a Si or other
semiconductor substrate, with or without a W initiation layer.
[0023] The material stacks described above and further below may be
employed in a variety of embodiments. FIGS. 2, 3A, and 3B provide
examples of structures in which the Mo-containing stacks may be
employed. FIG. 2 depicts a schematic example of a DRAM architecture
including a Mo buried wordline (bWL) 208 in a silicon substrate
202. The Mo bWL is formed in a trench etched in the silicon
substrate 202. Lining the trench is a conformal barrier layer 206
and an insulating layer 204 that is disposed between the conformal
barrier layer 206 and the silicon substrate 202. In the example of
FIG. 2, the insulating layer 204 may be a gate oxide layer, formed
from a high-k dielectric material such as a silicon oxide or
silicon nitride material. In some embodiments disclosed herein the
conformal barrier layer is TiN or tungsten-containing layer. In
some embodiments, it TiN is used as a barrier, a conformal
tungsten-containing growth initiation layer may be present between
the conformal barrier layer 206 and the Mo bWL 208. Alternatively,
the Mo bWL 208 may be deposited directly on a TiN or other
diffusion barrier.
[0024] FIG. 3A depicts a schematic example of a Mo wordline 308 in
a 3D NAND structure 323. In FIG. 3B, a 2-D rendering of 3-D
features of a partially-fabricated 3D NAND structure after Mo fill,
is shown including the wordline 308 and a conformal barrier layer
306. FIG. 3B is a cross-sectional depiction of a filled area with
the pillar constrictions 324 shown in the figure representing
constrictions that would be seen in a plan rather than
cross-sectional view. The conformal barrier layer 306 may be a TiN
or tungsten-containing layer as described above with respect to the
conformal barrier layer 206 in FIG. 2. In some embodiments, a
tungsten-containing film may serve as a barrier layer and a
nucleation layer for subsequent CVD Mo deposition as discussed
below. If TiN is used as a barrier, a conformal tungsten-containing
growth initiation layer may be present between the barrier and the
wordline. Alternatively, the Mo wordline 308 may be deposited
directly on a TiN or other diffusion barrier.
[0025] The methods of forming Mo-containing stacks include vapor
deposition techniques such as CVD and pulsed nucleation layer (PNL)
deposition. In a PNL technique, pulses of a co-reactant, optional
purge gases, and Mo-containing precursor are sequentially injected
into and purged from the reaction chamber. The process is repeated
in a cyclical fashion until the desired thickness is achieved. PNL
broadly embodies any cyclical process of sequentially adding
reactants for reaction on a semiconductor substrate, including
atomic layer deposition (ALD) techniques. PNL may be used for
deposition of Mo nucleation layers and/or W-based growth initiation
layers in the methods described herein. A nucleation layer is
typically a thin conformal layer that facilitates subsequent
deposition of bulk material thereon. According to various
implementations, a nucleation layer may be deposited prior to any
fill of the feature and/or at subsequent points during fill of the
feature.
[0026] PNL techniques for depositing tungsten nucleation layers are
described in U.S. Pat. Nos. 6,635,965; 7,005,372; 7,141,494;
7,589,017, 7,772,114, 7,955,972 and 8,058,170. Nucleation layer
thickness can depend on the nucleation layer deposition method as
well as the desired quality of bulk deposition. In general,
nucleation layer thickness is sufficient to support high quality,
uniform bulk deposition. Examples may range from 10 .ANG.-100
.ANG..
[0027] In many implementations, deposition of the Mo bulk layer can
occur by a CVD process in which a reducing agent and a
Mo-containing precursor are flowed into a deposition chamber to
deposit a bulk layer in the feature. An inert carrier gas may be
used to deliver one or more of the reactant streams, which may or
may not be pre-mixed. Unlike PNL or ALD processes, this operation
generally involves flowing the reactants continuously until the
desired amount is deposited. In certain implementations, the CVD
operation may take place in multiple stages, with multiple periods
of continuous and simultaneous flow of reactants separated by
periods of one or more reactant flows diverted.
[0028] Mo-containing precursors include molybdenum hexafluoride
(MoF.sub.6), molybdenum pentachloride (MoCl.sub.5), molybdenum
dichloride dioxide (MoO.sub.2Cl.sub.2), molybdenum tetrachloride
oxide (MoOCl.sub.4), and molybdenum hexacarbonyl (Mo(CO).sub.6).
Organometallic precurors such as molybdenum silylcyclopentadienyl
and molybdenum silylallyl complexes may be used. Mo-containing
precursors may be halide precursors, which include MoF.sub.6 and
MoCl.sub.5 as well as mixed halide precursors that have two or more
halogens that can form a stable molecule. An example of a mixed
halide precursor is MoCl.sub.xBr.sub.y with x and y being any
number greater than 0 that can form a stable molecule.
Mo-Containing Layer on a W-Based Growth Initiation Layer
[0029] In certain embodiments, structures including a molybdenum
(Mo)-containing layer on a tungsten (W)-based growth initiation
layer are provided. Also provided are methods of forming
Mo-containing films.
[0030] The W-based growth initiation layer may be any W-containing
layer. In some embodiments, it is a nucleation layer, i.e., a thin
conformal layer that serves to facilitate the subsequent formation
of a bulk material thereon. In some embodiments, the W-based growth
initiation layer is a bulk W-containing layer, which itself may be
deposited on a nucleation layer. When used for feature fill, a
nucleation layer may be deposited to conformally coat the sidewalls
and bottom of the feature. Conforming to the underlying feature
bottom and sidewalls can be critical to support high quality
deposition. According to various embodiments, the W-based growth
initiation layer may be deposited by one or both of PNL and CVD.
For example, a CVD layer may be deposited on a PNL layer.
[0031] In some embodiments, the W-containing layer is an elemental
W layer. Such layers may be deposited by any appropriate methods
include PNL or CVD methods. Elemental W is distinguished from
binary films such as WC or WN and ternary films like WCN, though it
may include some amount of impurities. It may be referred to as a W
layer or W film.
[0032] In some embodiments, the W-based growth layer is a low
resistivity W (LRW) film. Deposition of low resistivity tungsten
according to certain embodiments is described in U.S. Pat. No.
7,772,114. In particular, the '114 patent describes exposing a PNL
W nucleation layer to a reducing agent prior to CVD deposition of W
on the PNL W layer. LRW films have large grain sizes that provide
good templates for large Mo grain growth.
[0033] In some embodiments, the W-based growth layer is a PNL W
nucleation layer deposited using one or more of a boron-containing
reducing agent (e.g., B.sub.2H.sub.6) or a silicon-containing
reducing agent (e.g., SiH.sub.4) as a co-reactant. For example, one
or more S/W cycles, where S/W refers to a pulse of silane followed
by a pulse of tungsten hexafluoride (WF.sub.6) or other
tungsten-containing precursor, may be employed to deposit a PNL W
nucleation layer on which a Mo layer is deposited. In another
example, one or more B/W cycles, where B/W refers to a pulse of
diborane followed by a pulse of WF.sub.6 or other
tungsten-containing precursor, may be employed to deposit a PNL W
nucleation layer on which a Mo layer is deposited. B/W and S/W
cycles may both be used to deposit a PNL W nucleation layer.
Examples of PNL processes using one or both of a boron-containing
reducing agent and a silicon-containing reducing agent are
described in U.S. Pat. Nos. 7,262,125; 7,589,017; 7,772,114;
7,955,972; 8,058,170; 9,236,297 and 9,583,385.
[0034] In some embodiments, the W-based growth layer is a W layer
or other W-containing layer deposited using a tungsten chloride
(WCl.sub.x) precursor such as tungsten hexachloride (WCl.sub.6) or
tungsten pentachloride (WCl.sub.5). Deposition of W-containing
layers using tungsten chlorides is described in U.S. Pat. No.
9,595,470; U.S. Patent Publication No. 20150348840; and U.S. patent
application Ser. No. 15/398,462.
[0035] In some embodiments, the W-based growth layer is a low
fluorine W layer. U.S. Pat. No. 9,613,818, describes sequential CVD
methods of depositing a low-fluorine W layer. U.S. Patent
Publication No. 2016/0351444 describes PNL methods of depositing
low fluorine W layers.
[0036] In some embodiments, the W-based growth layer is a WN, WC,
or WCN film. Methods of depositing one or more of WN, WC, or WCN
are described in each of U.S. Pat. Nos. 7,005,372; 8,053,365;
8,278,216; and U.S. patent application Ser. No. 15/474,383.
[0037] The W-based growth layers are not limited to the examples
given above, but may be any W or other W-containing film deposited
by any appropriate method including ALD, PNL, CVD, or physical
vapor deposition (PVD) methods. ALD, PNL, and CVD deposition
involves exposure to a W-containing precursor. In addition to the
WF.sub.6 and WCl.sub.x precursors, examples of W-containing
precursors include tungsten hexacarbonyl (W(CO).sub.6) and
organo-metallic precursors such as MDNOW (methyl
cyclopentadienyl-dicarbonylnitrosyl-tungsten) and EDNOW
(ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten). In many ALD,
PNL, and CVD deposition processes, a reducing agent is used to
reduce the W-containing precursor. Examples include hydrogen gas
(H.sub.2), silane (SiH.sub.4), disilane (Si.sub.2H.sub.6) hydrazine
(N.sub.2H.sub.4), diborane (B.sub.2H.sub.6) and germane
(GeH.sub.4).
[0038] Also as noted above, the W-containing films described herein
may include some amount of other compounds, dopants and/or
impurities such as nitrogen, carbon, oxygen, boron, phosphorous,
sulfur, silicon, germanium and the like, depending on the
particular precursors and processes used. The tungsten content in
the film may range from 20% to 100% (atomic) tungsten. In many
implementations, the films are tungsten-rich, having at least 50%
(atomic) tungsten, or even at least about 60%, 75%, 90%, or 99%
(atomic) tungsten. In some implementations, the films may be a
mixture of elemental tungsten (W) and other tungsten-containing
compounds such as WC, WN, etc.
[0039] The Mo-containing film may be deposited on the W-based
growth initiation layer by any appropriate method including ALD or
CVD. In some embodiments, sequential CVD processes may be used.
Sequential CVD processes are described in U.S. Pat. No. 9,613,818,
incorporated by reference herein.
[0040] Deposition of Mo-containing films may involve exposing the
W-based growth initiation layer to a Mo-containing precursor and a
reducing agent or other co-reactant, either simultaneously or
sequentially. Examples of Mo-containing precursors include
MoF.sub.6, MoCl.sub.5, MoOCl.sub.4, and Mo(CO).sub.6.
Organometallic precurors such as molybdenum silylcyclopentadienyl
and molybdenum silylallyl complexes may be used. Mo film purity
(e.g., as measured by O content) can be tuned by varying the
precursor and co-reactant partial pressures.
[0041] Substrate temperature during Mo deposition may be between
300.degree. C. to 750.degree. C., and in particular embodiments,
between 450.degree. C. and 550.degree. C. Substrate temperature
will depend on the thermal budget and the deposition chemistry.
Thermal budget depends on the applications, while high deposition
temperature may not be an issue for memory applications, it can
exceed the thermal budget for logic applications.
[0042] The presence of the W-containing growth initiation layer
allows the deposition to be performed at lower temperatures. For
example, Mo deposition from MoCl.sub.5 or MoOCl.sub.4 cannot be
performed at temperatures less than 550.degree. C. due to the
strength of the Mo--Cl bond. However, with a W-containing growth
initiation layer, the deposition can be performed at less than
550.degree. C. Chamber pressure during Mo deposition may be, for
example, 5 torr to 60 torr.
[0043] In some embodiments, H.sub.2 is used as reducing agent,
rather than a stronger reducing agent such SiH.sub.4 or
B.sub.2H.sub.6. These stronger reducing agents can result in an
undesirable oxygen rich interface when using an oxygen-containing
Mo-containing precursor. The Mo-containing film may an elemental Mo
film, although such films may include some amount of other
compounds, dopants and/or impurities depending on the particular
precursors and processes used.
Mo-Containing Layer on a PNL-Deposited Mo Nucleation Layer
[0044] In certain embodiments, a Mo-containing layer may be
deposited without the use of a W-based growth initiation layer. For
example, an elemental Mo layer may be deposited on a TiN or
dielectric layer. For certain precursors, deposition temperatures
may be relatively high (above 550.degree. C.) to obtain deposition.
CVD deposition using chlorine-containing precursors such as
MoOCl.sub.5, MoOCl.sub.4, and MoO.sub.2Cl.sub.2 may be performed at
temperatures of greater than 550.degree. C. on TiN and dielectric
surfaces. At lower temperatures, CVD deposition may be performed on
any surface using a W-based growth initiation layer as described
above. Further, in some embodiments, CVD deposition may be
performed on any surface using a Mo-containing nucleation layer
deposited by a PNL process.
[0045] As described above, in a PNL process, pulses of a
co-reactant, optional purge gases, and Mo-containing precursor are
sequentially injected into and purged from the reaction chamber. In
some embodiments, a Mo nucleation layer deposited using one or more
of a boron-containing reducing agent (e.g., B.sub.2H.sub.6) or a
silicon-containing reducing agent (e.g., SiH.sub.4) as a
co-reactant. For example, one or more S/Mo cycles, where S/Mo
refers to a pulse of silane followed by a pulse of a Mo-containing
precursor, may be employed to deposit a PNL Mo nucleation layer on
which a CVD Mo layer is deposited. In another example, one or more
B/Mo cycles, where B/Mo refers to a pulse of diborane followed by a
pulse of a Mo-containing precursor, may be employed to deposit a
PNL Mo nucleation layer on which a CVD Mo layer is deposited. B/Mo
and S/Mo cycles may both be used to deposit a PNL Mo nucleation
layer, e.g., x(B/Mo)+y(S/Mo), with x and y being integers. For PNL
deposition of a Mo nucleation layers, in some embodiments, the
Mo-containing precursor may be a non-oxygen containing precursor,
e.g., MoF.sub.6 or MoCl.sub.5. Oxygen in oxygen-containing
precursors may react with a silicon- or boron-containing reducing
agent to form MoSi.sub.xO.sub.y or MoB.sub.xO.sub.y, which are
impure, high resistivity films. Oxygen-containing precursors may be
used with oxygen incorporation minimized. In some embodiments,
H.sub.2 may be used as a reducing gas instead of a boron-containing
or silicon-containing reducing gas. Example thicknesses for
deposition of a Mo nucleation layer range from 5 .ANG. to 30 .ANG..
Films at the lower end of this range may not be continuous;
however, as long as they can help initiate continuous bulk Mo
growth, the thickness may be sufficient. In some embodiments, the
reducing agent pulses may be done at lower substrate temperatures
than the Mo precursor pulses. For example, or B.sub.2H.sub.6 or a
SiH.sub.4 (or other boron- or silicon-containing reducing agent)
pulse may be performed at a temperature below 300.degree. C., with
the Mo pulse at temperatures greater than 300.degree. C.
Mo Deposition Using a Reducing Agent Layer
[0046] Deposition at lower temperatures (below 550.degree. C.) may
also be performed directly on non-W surfaces such as dielectric and
TiN surfaces by a process as shown in FIG. 4A. It may also be used
on W-containing surfaces. FIG. 4A provides a process flow diagram
for a method performed in accordance with disclosed embodiments.
Operations 402-408 of FIG. 4A may be performed to form a conformal
Mo layer directly at least a dielectric surface or other
surface.
[0047] In operation 402, the substrate is exposed to a reducing
agent gas to form a reducing agent layer. In some embodiments, the
reducing agent gas may be a silane, a borane, or a mixture of a
silane and diborane. Examples of silanes including SiH.sub.4 and
Si.sub.2H.sub.6 and examples of boranes include diborane
(B.sub.2H.sub.6), as well as B.sub.nH.sub.n+4, B.sub.nH.sub.n+6,
B.sub.nH.sub.n+8, B.sub.nH.sub.m, where n is an integer from 1 to
10, and m is a different integer than m. Other boron-containing
compounds may also be used, e.g., alkyl boranes, alkyl boron,
aminoboranes (CH.sub.3).sub.2NB(CH.sub.2).sub.2, carboranes such as
C.sub.2B.sub.nH.sub.n+2. In some implementations, the reducing
agent layer may include silicon or silicon-containing material,
phosphorous or a phosphorous-containing material, germanium or a
germanium-containing material, boron or boron-containing material
that is capable of reducing a tungsten precursor and combinations
thereof. Further example reducing agent gases that can be used to
form such layers include PH.sub.3, SiH.sub.2Cl.sub.2, and
GeH.sub.4. According to various embodiments, hydrogen may or may
not be run in the background. (While hydrogen can reduce tungsten
precursors, it does not function as a reducing agent in a gas
mixture with a sufficient amount of stronger reducing agents such
as silane and diborane.)
[0048] In some embodiments, the reducing agent gas is a mixture
including a small amount of a boron-containing gas, such as
diborane, with another reducing agent. The addition of a small
amount of a boron-containing gas can greatly affect the
decomposition and sticking coefficient of the other reducing agent.
It should be noted that exposing the substrate sequentially to two
reducing agents, e.g., silane and diborane may be performed.
However, flowing a mixture of gases can facilitate the addition of
very small amounts of a minority gas, e.g., at least a 100:1 ratio
of silane to diborane. In some embodiments, a carrier gas may be
flowed. In some embodiments, a carrier gas, such as nitrogen
(N.sub.2), argon (Ar), helium (He), or other inert gases, may be
flowed during operation 402.
[0049] In some embodiments, a reducing agent layer may include
elemental silicon (Si), elemental boron (B), elemental germanium
(Ge), or mixtures thereof. For example, as described below, a
reducing agent layer may include Si and B. The amount of B may be
tailored to achieve high deposition rate of the reducing agent
layer but with low resistivity. In some embodiments, a reducing
agent layer may have between 5% and 80% B for example, or between
5% and 50% B, between 5% and 30%, or between 5% and 20% B, with the
balance consisting essentially of Si and in some cases, H. Hydrogen
atoms be present, e.g., SiH.sub.x, BH.sub.y, GeH.sub.z, or mixtures
thereof where x, y, and z may independently be between 0 and a
number that is less than the stoichiometric equivalent of the
corresponding reducing agent compound.
[0050] In some embodiments, the composition may be varied through
the thickness of the reducing agent layer. For example, a reducing
agent layer may be 20% B at the bottom of the reducing agent layer
and 0% B the top of the layer. The total thickness of the reducing
agent layer may be between 10 .ANG. and 50 .ANG., and is some
embodiments, between 15 .ANG. and 40 .ANG., or 20 .ANG. and 30
.ANG.. The reducing agent layer conformally lines the feature.
[0051] Substrate temperature during operation 402 may be maintained
at a temperature T1 for the film to be conformal. If temperature is
too high, the film may not conform to the topography of the
underlying structure. In some embodiments, step coverage of greater
than 90% or 95% is achieved. For silane, diborane, and
silane/diborane mixtures, conformality is excellent at 300.degree.
C. and may be degraded at temperatures of 400.degree. C. or higher.
Thus, in some embodiments, temperature during operation 202 is at
most 350.degree. C., or even at most 325.degree. C., at most
315.degree. C., or at most 300.degree. C. In some embodiments,
temperatures of less than 300.degree. C. are used. For example,
temperatures may be as low as 200.degree. C.
[0052] Operation 402 may be performed for any suitable duration. In
some examples, Example durations include between about 0.25 seconds
and about 30 seconds, about 0.25 seconds and about 20 seconds,
about 0.25 seconds and about 5 seconds, or about 0.5 seconds and
about 3 seconds.
[0053] In operation 404, the chamber is optionally purged to remove
excess reducing agent that did not adsorb to the surface of the
substrate. A purge may be conducted by flowing an inert gas at a
fixed pressure thereby reducing the pressure of the chamber and
re-pressurizing the chamber before initiating another gas exposure.
Example inert gases include nitrogen (N.sub.2), argon (Ar), helium
(He), and mixtures thereof. The purge may be performed for a
duration between about 0.25 seconds and about 30 seconds, about
0.25 seconds and about 20 seconds, about 0.25 seconds and about 5
seconds, or about 0.5 seconds and about 3 seconds.
[0054] In operation 406, the substrate is exposed to a
Mo-containing precursor at a substrate temperature T2. Examples of
Mo-containing compounds are given above and include chlorides and
oxychlorides. Use of oxygen-containing precursors can lead to
impurity incorporation and higher resistivity. However, if oxygen
is incorporated, a very thin, possibly discontinuous reducing agent
layer may be used for an acceptable resistivity. In some
embodiments, a carrier gas, such as nitrogen (N.sub.2), argon (Ar),
helium (He), or other inert gases, may be flowed during operation
406. Examples of temperatures are 500.degree. C. to 700.degree.
C.
[0055] Operation 406 may be performed for any suitable duration. In
some embodiments, it may involve a soak of the Mo-containing
precursor and in some embodiments, a sequence of Mo-containing
precursor pulses. According to various embodiments, operation 406
may or may not be performed in the presence of H.sub.2. If H.sub.2
is used, in some embodiments, it and the Mo-containing precursor
may be applied in an ALD-type mode. For example:
[0056] Pulse of H.sub.2
[0057] Argon purge
[0058] Pulse of Mo-containing precursor with or without H.sub.2 in
background
[0059] Argon purge
[0060] Repeat
[0061] The substrate temperature T2 is high enough that the
Mo-containing precursor reacts with the reducing agent layer to
form elemental Mo. The entire reducing agent layer is converted to
Mo. In some embodiments, the temperature is at least 450.degree.
C., and may be at least 550.degree. C. to obtain conversion of at
or near 100%. The resulting feature is now lined with a conformal
film of Mo. It may be between 10 .ANG. and 50 .ANG., and is some
embodiments, between 15 .ANG. and 40 .ANG., or 20 .ANG. and 30
.ANG.. In general, it will be about the same thickness as the
reducing agent layer. In some embodiments, it may be may be up to
5% thicker than the reducing agent layer due to volumetric
expansion during the conversion. In some embodiments, a CVD Mo
layer may be deposited on the conformal Mo layer.
Multi-Component Mo Film
[0062] In some embodiments, a multi-component Mo-containing film is
provided. In some such embodiments, the multi-component
Mo-containing film may include one or more of boron (B), silicon
(Si), or germanium (Ge). FIG. 4B provides a process flow diagram
for a method performed in accordance with disclosed
embodiments.
[0063] First, a substrate is exposed to a reducing agent pulse
(452). In some embodiments, a surface that is exposed to the
reducing agent pulse on which the film is formed is a dielectric.
According to various embodiments, the film may be formed on other
types of surfaces including conducting and semiconducting
surfaces.
[0064] The reducing agent employed in block 452 will reduce a
Mo-containing precursor employed in a subsequent operation as well
as provide a compound to be incorporated into the resulting film.
Examples of such reducing agents include boron-containing,
silicon-containing, and germanium-containing reducing agents.
Examples of boron-containing reducing agents include boranes such
B.sub.nH.sub.n+4, B.sub.nH.sub.n+6, B.sub.nH.sub.n+8,
B.sub.nH.sub.m, where n is an integer from 1 to 10, and m is a
different integer than m. In particular examples, diborane may be
employed. Other boron-containing compounds may also be used, e.g.,
alkyl boranes, alkyl boron, aminoboranes
(CH.sub.3).sub.2NB(CH.sub.2).sub.2, and carboranes such as
C.sub.2B.sub.nH.sub.n+2. Examples of silicon-containing compounds
include silanes such as SiH.sub.4 and Si.sub.2H.sub.6. Examples of
germanium-containing compounds include germanes, such as
Ge.sub.nH.sub.n+4, Ge.sub.nH.sub.n+6, Ge.sub.nH.sub.n+8, and
Ge.sub.nH.sub.m, where n is an integer from 1 to 10, and n is a
different integer than m. Other germanium-containing compounds may
also be used, e.g., alkyl germanes, alkyl germanium, aminogermanes
and carbogermanes.
[0065] According to various embodiments, block 452 may involve
adsorption of a thin layer of thermally decomposed elemental boron,
silicon, or germanium onto the surface of the substrate. In some
embodiments, block 452 may involve adsorption of a precursor
molecule onto substrate surface.
[0066] Next, the chamber in which the substrate sits may be
optionally purged (454). A purge pulse or an evacuation can be
employed to remove any byproduct, if present, and unadsorbed
precursor. This is followed by a pulse of a Mo-containing precursor
(456). In some embodiments, the Mo-containing precursor is a
Cl-containing precursor such as MoOCl.sub.4, MoO.sub.2Cl.sub.2, and
MoCl.sub.5. An optional purge (457) may be performed after block
456 as well. The Mo-containing precursor is reduced by the reducing
agent (or a decomposition or reaction product thereof) to form the
multi-component film.
[0067] A deposition cycle will typically deposit a portion of the
Mo-containing layer. After block 457, a deposition cycle may be
complete in some implementations with the deposited film being a
tungsten-containing binary film such as MoB.sub.x, MoSi.sub.x, and
MoGe.sub.x, where x is greater than zero. In such embodiments, the
process may proceed to block 462 with repeating the cycle of blocks
452-457 until the desired thickness is deposited. Example growth
rates may be about 100 .ANG. per cycle.
[0068] In some embodiments, the process will proceed with
optionally introducing a third reactant (458). The third reactant
will generally contain an element to be introduced into the film,
such as carbon or nitrogen. Examples of nitrogen-containing
reactants include N.sub.2, NH.sub.3, and N.sub.2H.sub.4. Examples
of carbon-containing reactants include CH.sub.4 and C.sub.2H.sub.2.
An optional purge (459) may follow. The process may then proceed to
block 462 with repeating the deposition cycle.
[0069] Examples of ternary films including nitrogen or carbon are
given above. In some embodiments, a film may include both nitrogen
and carbon (e.g., MoSiCN).
[0070] According to various embodiments, the multi-component
tungsten film may have the following atomic percentages: Mo about
5% to 90%, B/Ge/Si about 5% to 60%, C/N about 5% to 80%. In some
embodiments, the multi-component films have the following atomic
percentages: Mo about 15% to about 80%; B/Ge/Si: about 15% to about
50%; and C/N about 20% to about 50%. According to various
embodiments, the multi-component Mo film is at least 50% Mo.
[0071] According to various embodiments, the deposition is
relatively high, e.g., between 500.degree. C. and 700.degree. C.,
including between 550.degree. C. and 650.degree. C., and in some
embodiments greater than about 500.degree. C. This facilitates
Mo-containing precursor reduction and also permits incorporation of
B, Si, or Ge into the binary film. The high end of the range may be
limited by thermal budget considerations. In some embodiments, any
one or more of blocks 452, 456, and 458 may be performed at a
different temperature than any of the other blocks. In certain
embodiments, transitioning from block 452 to block 456 and from
block 456 to block 458 involves moving the substrate from one
deposition station to another in a multi-station chamber. Still
further, each of block 452, block 456, and block 458 may be
performed in a different station of the same multi-station chamber.
In some embodiments, the order of blocks 452, 456, and 458 may be
changed.
[0072] In some embodiments, electrical properties such as work
function of the binary or ternary film may be tuned by introducing
nitrogen or carbon. Similarly, the amount of reducing agent may be
modulated (by modulating dosage amount and/or pulse time) to tune
the amount of B, Si, or Ge that is incorporated into the film.
Still further, any one or two of blocks 452, 456 and 458 may be
performed more than once per cycle to tune the relative amounts of
the tungsten and the other components of the binary or ternary
films and thus their physical, electrical, and chemical
characteristics. The multi-component layer may include Mo, one or
more of B, Si, and Ge, and, optionally, one or more of C and N.
Examples include MoB.sub.x, MoSi.sub.x, MoGe.sub.x,
MoB.sub.xN.sub.y, MoSi.sub.xN.sub.y, MoGe.sub.xN.sub.y,
MoSi.sub.xC.sub.y, MoB.sub.xC.sub.y, MoGe.sub.xC.sub.y, where x and
y are greater than zero.
[0073] It should be noted that in the process described with
reference to FIG. 4B, an element in the reducing agent (B, Si, or
Ge) is deliberately incorporated into the Mo-containing film. This
is in contrast to certain PNL and CVD deposition processes
described above and certain embodiments of the deposition process
described in FIG. 4B in which a B-containing, Si-containing, or
Ge-containing reducing agent may be used to form an element Mo film
that has none of or only trace amounts of these elements.
Incorporation of B, Ge, or Si can be controlled by the pulse
duration and dosage amount. Further, in some embodiments, higher
temperatures may be employed to increase incorporation. If the
temperature is too high, it can result in uncontrolled
decomposition of the reactant gas. In some embodiments, the
substrate temperature may be lower temperature for the reducing
agent gas and a higher temperature for the Mo precursor, as
described above with respect to FIG. 4A.
[0074] In some embodiments, the process in FIG. 4B may be modified
such that B, Si, or Ge is not incorporated into the film, but block
458 is performed to incorporate C and/N, e.g., to form MoC, MoN, or
MoCN films. A C- and/or N-containing reactant may be used in such
embodiments.
[0075] In some embodiments, the multi-component Mo-containing film
is a diffusion barrier, e.g., for a wordline. In some embodiments,
the multi-component tungsten-containing film is a work function
layer for a metal gate. In some embodiments, a bulk Mo layer may
deposited on the multi-component layer. The bulk layer may be
deposited directly on the multi-component Mo-containing film
without an intervening layer in some embodiments. In some
embodiments, it may be deposited by CVD.
Experimental
[0076] CVD Mo films were grown on tungsten nucleation layers
deposited by PNL using silane and diborane, respectively, to reduce
WF.sub.6. The silane-deposited tungsten nucleation layer is
referred to as a SW nucleation layer, and the diborane-deposited
tungsten nucleation layer is referred to as a BW nucleation layer.
Mo films were deposited from MoOCl.sub.4 and H.sub.2.
[0077] 30 Torr and 45 Torr process pressures were compared for each
deposition. No Mo deposition and some W loss was observed at 30
Torr, with more W loss observed for BW nucleation than SW
nucleation. Secondary ion mass spectrometry (SIMS) data showed O
content at less than 1 atomic %.
[0078] Mo was deposited by CVD on SW nucleation layers and BW
nucleation layers at different temperatures (500.degree. C. and
520.degree. C.), pressures (45 Torr and 60 Torr). The number of BW
or SW cycles use to deposit the nucleation layer was also varied
(1, 2, 3 or 4). FIGS. 5 and 6 show Mo thickness (Angstroms) vs. CVD
Duration (seconds) and Mo Resistivity (.mu..OMEGA.-cm) vs Mo
thickness (Angstroms), respectively.
[0079] Lower resistivity is observed at 60 Torr process pressure
than at 45 Torr. No significant difference between 500.degree. C.
and 520.degree. C. at 60 Torr was observed. For comparable BW
nucleation layer and SW nucleation layer thicknesses, lower
resistivity was observed on the SW nucleation layers. Higher
resistivity was observed on thinner (fewer cycles) SW nucleation
layers.
[0080] Mo was deposited by CVD on WCN at different temperatures
(500.degree. C. and 520.degree. C.) and pressures (45 Torr and 60
Torr). FIG. 7 shows Mo growth rate and FIG. 8 shows resistivity vs
Mo film thickness. FIG. 9 shows thickness and resistivity as a
function of WCN underlayer thickness. WCN etching was observed at
45 Torr whereas uniform Mo deposition was observed at 60 Torr. At
60 Torr, a higher growth rate at 520.degree. C. was observed, with
temperature not impacting resistivity. Mo was grown on WCN as thin
as 10 Angstroms, with thinner WCN resulting in lower resistivity.
SIMS data showed that CVD Mo on WCN was smooth with less than 0.5
(atomic) % total impurities (e.g., O, B, C) in the bulk.
[0081] In some embodiments, Mo may be deposited selectively on a
metal or pure (no native oxide) Si surface with respect to
dielectric underlayers. For example, for metal contact or middle of
line (MOL) logic applications, Mo can be grown selectively on
metal, resulting in bottom-up, void free gap fill. In such
applications, the Mo may be deposited directly on a metal or Si
surface that is adjacent an exposed silicon dioxide or other
exposed dielectric surface. The nucleation delay on the dielectric
is such that the Mo is deposited preferentially on the metal
surface. For example, a feature having a metal bottom and silicon
dioxide sidewalls may be exposed to a Mo-containing precursor and a
co-reactant. Mo will grow from the bottom-up rather than from the
sidewalls.
Anneal
[0082] In some embodiments, a thermal anneal is performed after Mo
deposition. This can allow Mo grain growth and lower resistivity.
Because the melting point of Mo is lower than that of W, grain
growth and the accompanying decrease in resistivity occur at lower
temperatures for Mo films. Examples of anneal temperatures range
from 700.degree. C. to 1100.degree. C. The anneal may be performed
in a furnace or by rapid thermal annealing. According to various
embodiments, it may be performed in any appropriate ambient,
including a hydrogen (H.sub.2) ambient, a nitrogen (N.sub.2)
ambient, or vacuum.
[0083] According to various embodiments, the Mo film may or may not
be exposed to air between deposition and annealing. If it is
exposed to air or other oxidizing environment, a reducing
environment may be employed during or before anneal to remove
molybdenum dioxide (MoO.sub.2) or molybdenum trioxide (MoO.sub.3)
that has formed as a result of the exposure. MoO.sub.3 in
particular has a melting point of 795.degree. C. and could melt
during anneal if not removed.
[0084] Table 1, below, compares two W films (A and B) and two Mo
films (C and D)
TABLE-US-00001 A B C D Resistivity 20 .mu..OMEGA.-cm at 28
.mu..OMEGA.-cm at 25 .mu..OMEGA.-cm at 17 .mu..OMEGA.-cm at 20 nm
20 nm 10 nm 10 nm 40 .mu..OMEGA.-cm at (after 800 C. 10 nm anneal)
Composition <3E18 at/cm.sup.3 F <5E18 at/cm.sup.3 Cl, 95% Mo
+ 5% <1% O, <1E19 F below detection H, <1E19 at/
at/cm.sup.3 Cl limit cm.sup.3 Cl Stress <0.55 Gpa @ <0.2 Gpa
@ 0.4 GPa @ 0.6 GPa @ 30 nm 20 nm 20 nm 70 nm
[0085] Film A is a low fluorine tungsten (LFW) film deposited using
WF.sub.6. Film B is a tungsten film deposited using WCl.sub.5 and
WCl.sub.6. Film C is a molybdenum film deposited using MoCl.sub.5
and film D is a molybdenum film deposited using MoOCl.sub.4. Film D
was subject to a post-deposition anneal. Notably, the resistivity
is lower for Films C and D than films A and B. Resistivity
decreases with thickness, with the 25.mu..OMEGA.-cm (film C) and
17.mu..OMEGA.-cm (film D) directly comparable to the
40.mu..OMEGA.-cm (film A). Film D, deposited with an O-containing
precursor, shows low O. The stress of films C and D is comparable
to that of films A and B.
[0086] FIG. 10 is a graph showing the reduction in resistivity for
Mo films of various thicknesses deposited on WCN after anneal at
800.degree. C. Resistivity of a W film on WCN is also shown for
comparison. A significant decrease in resistivity is observed. The
decrease in resistivity is due to grain growth. Table 2, below,
shows phases and average grain size for Mo grains in as deposited
and post-anneal CVD Mo films.
TABLE-US-00002 Average Crystallite Sample Phase Size (nm) CVD
Mo/WCN Mo - Molybdenum Cubic 14.5 as deposited CVD Mo/WCN Mo -
Molybdenum Cubic 33.5 post-anneal
Furnace anneals of 1 hour and 5 mins at 800.degree. C. in H.sub.2
ambient showed comparable results.
Apparatus
[0087] Any suitable chamber may be used to implement the disclosed
embodiments. Example deposition apparatuses include various
systems, e.g., ALTUS.RTM. and ALTUS.RTM. Max, available from Lam
Research Corp., of Fremont, Calif., or any of a variety of other
commercially available processing systems. The process can be
performed on multiple deposition stations in parallel.
[0088] In some embodiments, a tungsten nucleation process is
performed at a first station that is one of two, five, or even more
deposition stations positioned within a single deposition chamber.
In some embodiments, various steps for the nucleation process are
performed at two different stations of a deposition chamber. For
example, the substrate may be exposed to diborane (B.sub.2H.sub.6)
in a first station using an individual gas supply system that
creates a localized atmosphere at the substrate surface, and then
the substrate may be transferred to a second station to be exposed
to a precursor such as tungsten hexachloride (WCl.sub.6) to deposit
the nucleation layer. In some embodiments, the substrate may then
be transferred back to the first station for a second exposure of
diborane or to a third station for a third reactant exposure. Then
the substrate may be transferred to the second station for exposure
to WCl.sub.6 (or other tungsten chloride) to complete tungsten
nucleation and proceed with bulk molybdenum deposition in the same
or different station. One or more stations can then be used to
perform Mo chemical vapor deposition (CVD) as described above.
[0089] FIG. 11 is a block diagram of a processing system suitable
for conducting deposition processes in accordance with embodiments
described herein. The system 1100 includes a transfer module 1103.
The transfer module 1103 provides a clean, pressurized environment
to minimize the risk of contamination of substrates being processed
as they are moved between the various reactor modules. Mounted on
the transfer module 1103 is a multi-station reactor 1109 capable of
performing nucleation layer deposition, which may be referred to as
pulsed nucleation layer (PNL) deposition, as well as CVD deposition
according to embodiments described herein. Chamber 1109 may include
multiple stations 1111, 1113, 1115, and 1117 that may sequentially
perform these operations. For example, chamber 1109 could be
configured such that stations 1111 and 1113 perform PNL deposition,
and stations 1113 and 1115 perform CVD. Each deposition station may
include a heated wafer pedestal and a showerhead, dispersion plate
or other gas inlet.
[0090] Also mounted on the transfer module 1103 may be one or more
single or multi-station modules 1107 capable of performing plasma
or chemical (non-plasma) pre-cleans. The module may also be used
for various other treatments, e.g., reducing agent soaking. The
system 1100 also includes one or more (in this case two) wafer
source modules 1101 where wafers are stored before and after
processing. An atmospheric robot (not shown) in the atmospheric
transfer chamber 1119 first removes wafers from the source modules
1101 to loadlocks 1121. A wafer transfer device (generally a robot
arm unit) in the transfer module 1103 moves the wafers from
loadlocks 1121 to and among the modules mounted on the transfer
module 1103.
[0091] In certain embodiments, a system controller 1129 is employed
to control process conditions during deposition. The controller
will typically include one or more memory devices and one or more
processors. The processor may include a CPU or computer, analog
and/or digital input/output connections, stepper motor controller
boards, etc.
[0092] The controller may control all of the activities of the
deposition apparatus. The system controller executes system control
software including sets of instructions for controlling the timing,
mixture of gases, chamber pressure, chamber temperature, wafer
temperature, radio frequency (RF) power levels if used, wafer chuck
or pedestal position, and other parameters of a particular process.
Other computer programs stored on memory devices associated with
the controller may be employed in some embodiments.
[0093] Typically there will be a user interface associated with the
controller. The user interface may include a display screen,
graphical software displays of the apparatus and/or process
conditions, and user input devices such as pointing devices,
keyboards, touch screens, microphones, etc.
[0094] System control logic may be configured in any suitable way.
In general, the logic can be designed or configured in hardware
and/or software. The instructions for controlling the drive
circuitry may be hard coded or provided as software. The
instructions may be provided by "programming." Such programming is
understood to include logic of any form, including hard coded logic
in digital signal processors, application-specific integrated
circuits, and other devices which have specific algorithms
implemented as hardware. Programming is also understood to include
software or firmware instructions that may be executed on a general
purpose processor. System control software may be coded in any
suitable computer readable programming language. Alternatively, the
control logic may be hard coded in the controller. Applications
Specific Integrated Circuits, Programmable Logic Devices (e.g.,
field-programmable gate arrays, or FPGAs) and the like may be used
for these purposes. In the following discussion, wherever
"software" or "code" is used, functionally comparable hard coded
logic may be used in its place.
[0095] The computer program code for controlling the deposition and
other processes in a process sequence can be written in any
conventional computer readable programming language: for example,
assembly language, C, C++, Pascal, Fortran or others. Compiled
object code or script is executed by the processor to perform the
tasks identified in the program.
[0096] The controller parameters relate to process conditions such
as, for example, process gas composition and flow rates,
temperature, pressure, plasma conditions such as RF power levels
and the low frequency RF frequency, cooling gas pressure, and
chamber wall temperature. These parameters are provided to the user
in the form of a recipe, and may be entered utilizing the user
interface.
[0097] Signals for monitoring the process may be provided by analog
and/or digital input connections of the system controller. The
signals for controlling the process are output on the analog and
digital output connections of the deposition apparatus.
[0098] The system software may be designed or configured in many
different ways. For example, various chamber component subroutines
or control objects may be written to control operation of the
chamber components necessary to carry out the inventive deposition
processes. Examples of programs or sections of programs for this
purpose include substrate positioning code, process gas control
code, pressure control code, heater control code, and plasma
control code.
[0099] In some implementations, a controller 1129 is part of a
system, which may be part of the above-described examples. Such
systems can include semiconductor processing equipment, including a
processing tool or tools, chamber or chambers, a platform or
platforms for processing, and/or specific processing components (a
wafer pedestal, a gas flow system, etc.). These systems may be
integrated with electronics for controlling their operation before,
during, and after processing of a semiconductor wafer or substrate.
The electronics may be referred to as the "controller," which may
control various components or subparts of the system or systems.
The controller 1129, depending on the processing requirements
and/or the type of system, may be programmed to control any of the
processes disclosed herein, including the delivery of processing
gases, temperature settings (e.g., heating and/or cooling),
pressure settings, vacuum settings, power settings, radio frequency
(RF) generator settings in some systems, RF matching circuit
settings, frequency settings, flow rate settings, fluid delivery
settings, positional and operation settings, wafer transfers into
and out of a tool and other transfer tools and/or load locks
connected to or interfaced with a specific system.
[0100] Broadly speaking, the controller may be defined as
electronics having various integrated circuits, logic, memory,
and/or software that receive instructions, issue instructions,
control operation, enable cleaning operations, enable endpoint
measurements, and the like. The integrated circuits may include
chips in the form of firmware that store program instructions,
digital signal processors (DSPs), chips defined as application
specific integrated circuits (ASICs), and/or one or more
microprocessors, or microcontrollers that execute program
instructions (e.g., software). Program instructions may be
instructions communicated to the controller in the form of various
individual settings (or program files), defining operational
parameters for carrying out a particular process on or for a
semiconductor wafer or to a system. The operational parameters may,
in some embodiments, be part of a recipe defined by process
engineers to accomplish one or more processing steps during the
fabrication of one or more layers, materials, metals, oxides,
silicon, silicon dioxide, surfaces, circuits, and/or dies of a
wafer.
[0101] The controller 1129, in some implementations, may be a part
of or coupled to a computer that is integrated with, coupled to the
system, otherwise networked to the system, or a combination
thereof. For example, the controller 1129 may be in the "cloud" or
all or a part of a fab host computer system, which can allow for
remote access of the wafer processing. The computer may enable
remote access to the system to monitor current progress of
fabrication operations, examine a history of past fabrication
operations, examine trends or performance metrics from a plurality
of fabrication operations, to change parameters of current
processing, to set processing steps to follow a current processing,
or to start a new process. In some examples, a remote computer
(e.g. a server) can provide process recipes to a system over a
network, which may include a local network or the Internet. The
remote computer may include a user interface that enables entry or
programming of parameters and/or settings, which are then
communicated to the system from the remote computer. In some
examples, the controller receives instructions in the form of data,
which specify parameters for each of the processing steps to be
performed during one or more operations. It should be understood
that the parameters may be specific to the type of process to be
performed and the type of tool that the controller is configured to
interface with or control. Thus as described above, the controller
may be distributed, such as by including one or more discrete
controllers that are networked together and working towards a
common purpose, such as the processes and controls described
herein. An example of a distributed controller for such purposes
would be one or more integrated circuits on a chamber in
communication with one or more integrated circuits located remotely
(such as at the platform level or as part of a remote computer)
that combine to control a process on the chamber.
[0102] Without limitation, example systems may include a plasma
etch chamber or module, a deposition chamber or module, a
spin-rinse chamber or module, a metal plating chamber or module, a
clean chamber or module, a bevel edge etch chamber or module, a
physical vapor deposition (PVD) chamber or module, a CVD chamber or
module, an ALD chamber or module, an atomic layer etch (ALE)
chamber or module, an ion implantation chamber or module, a track
chamber or module, and any other semiconductor processing systems
that may be associated or used in the fabrication and/or
manufacturing of semiconductor wafers.
[0103] As noted above, depending on the process step or steps to be
performed by the tool, the controller might communicate with one or
more of other tool circuits or modules, other tool components,
cluster tools, other tool interfaces, adjacent tools, neighboring
tools, tools located throughout a factory, a main computer, another
controller, or tools used in material transport that bring
containers of wafers to and from tool locations and/or load ports
in a semiconductor manufacturing factory.
[0104] The controller 1129 may include various programs. A
substrate positioning program may include program code for
controlling chamber components that are used to load the substrate
onto a pedestal or chuck and to control the spacing between the
substrate and other parts of the chamber such as a gas inlet and/or
target. A process gas control program may include code for
controlling gas composition and flow rates and optionally for
flowing gas into the chamber prior to deposition in order to
stabilize the pressure in the chamber. A pressure control program
may include code for controlling the pressure in the chamber by
regulating, e.g., a throttle valve in the exhaust system of the
chamber. A heater control program may include code for controlling
the current to a heating unit that is used to heat the substrate.
Alternatively, the heater control program may control delivery of a
heat transfer gas such as helium to the wafer chuck.
[0105] Examples of chamber sensors that may be monitored during
deposition include mass flow controllers, pressure sensors such as
manometers, and thermocouples located in pedestal or chuck.
Appropriately programmed feedback and control algorithms may be
used with data from these sensors to maintain desired process
conditions.
[0106] The foregoing describes implementation of embodiments of the
disclosure in a single or multi-chamber semiconductor processing
tool.
[0107] The foregoing describes implementation of disclosed
embodiments in a single or multi-chamber semiconductor processing
tool. The apparatus and process described herein may be used in
conjunction with lithographic patterning tools or processes, for
example, for the fabrication or manufacture of semiconductor
devices, displays, LEDs, photovoltaic panels, and the like.
Typically, though not necessarily, such tools/processes will be
used or conducted together in a common fabrication facility.
Lithographic patterning of a film typically comprises some or all
of the following steps, each step provided with a number of
possible tools: (1) application of photoresist on a workpiece,
i.e., substrate, using a spin-on or spray-on tool; (2) curing of
photoresist using a hot plate or furnace or UV curing tool; (3)
exposing the photoresist to visible or UV or x-ray light with a
tool such as a wafer stepper; (4) developing the resist so as to
selectively remove resist and thereby pattern it using a tool such
as a wet bench; (5) transferring the resist pattern into an
underlying film or workpiece by using a dry or plasma-assisted
etching tool; and (6) removing the resist using a tool such as an
RF or microwave plasma resist stripper.
CONCLUSION
[0108] Although the foregoing embodiments have been described in
some detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications may be practiced
within the scope of the appended claims. It should be noted that
there are many alternative ways of implementing the processes,
systems, and apparatus of the present embodiments. Accordingly, the
present embodiments are to be considered as illustrative and not
restrictive, and the embodiments are not to be limited to the
details given herein.
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