U.S. patent application number 11/711922 was filed with the patent office on 2007-06-28 for systems and methods of forming refractory metal nitride layers using disilazanes.
This patent application is currently assigned to MICRON TECHNOLOGY, INC.. Invention is credited to Brian A. Vaartstra.
Application Number | 20070144438 11/711922 |
Document ID | / |
Family ID | 31976321 |
Filed Date | 2007-06-28 |
United States Patent
Application |
20070144438 |
Kind Code |
A1 |
Vaartstra; Brian A. |
June 28, 2007 |
Systems and methods of forming refractory metal nitride layers
using disilazanes
Abstract
A method of forming (and apparatus for forming) refractory metal
nitride layers (including silicon nitride layers), such as a
tantalum (silicon) nitride barrier layer, on a substrate by using a
vapor deposition process with a refractory metal precursor
compound, a disilazane, and an optional silicon precursor
compound.
Inventors: |
Vaartstra; Brian A.; (Nampa,
ID) |
Correspondence
Address: |
MUETING, RAASCH & GEBHARDT, P.A.
P.O. BOX 581415
MINNEAPOLIS
MN
55458
US
|
Assignee: |
MICRON TECHNOLOGY, INC.
Boise
ID
|
Family ID: |
31976321 |
Appl. No.: |
11/711922 |
Filed: |
February 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10929827 |
Aug 30, 2004 |
7196007 |
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11711922 |
Feb 28, 2007 |
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10229802 |
Aug 28, 2002 |
6794284 |
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10929827 |
Aug 30, 2004 |
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Current U.S.
Class: |
118/715 ;
118/723E; 118/723MP |
Current CPC
Class: |
H01L 21/28556 20130101;
H01L 21/76841 20130101; H01L 28/55 20130101; C23C 16/34 20130101;
C23C 16/45531 20130101; H01L 21/76864 20130101; C23C 16/45523
20130101; C23C 16/45553 20130101; H01L 21/28562 20130101; H01L
28/60 20130101 |
Class at
Publication: |
118/715 ;
118/723.0MP; 118/723.00E |
International
Class: |
C23C 16/00 20060101
C23C016/00 |
Claims
1. A vapor deposition system comprising: a first vessel; one or
more refractory metal precursor compounds in the first vessel,
wherein the one or more refractory metal precursor compounds are of
the formula MY.sub.n (Formula I), wherein M is a refractory metal,
each Y is independently a halogen atom, and n is an integer
selected to match the valence of the metal M; a second vessel; and
one or more disilazanes in the second vessel, wherein the one or
more disilazanes are of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3.
2. The system of claim 1 further comprising: a third vessel; and
one or more silicon precursor compounds in the third vessel.
3. The system of claim 2 further comprising: a fourth vessel; and
one or more reaction gases in the fourth vessel, wherein the one or
more reaction gases are other than the one or more disilazanes and
the one or more silicon precursor compounds.
4. A vapor deposition system comprising: a vapor deposition
chamber; a first vessel; one or more refractory metal precursor
compounds in the first vessel, wherein the one or more refractory
metal precursor compounds are of the formula MY.sub.n (Formula I),
wherein M is a refractory metal, each Y is independently a halogen
atom, and n is an integer selected to match the valence of the
metal M; a second vessel; and one or more disilazanes in the second
vessel, wherein the one or more disilazanes are of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3.
5. The system of claim 4 wherein the vapor deposition chamber is a
chemical vapor deposition chamber.
6. The system of claim 4 wherein the vapor deposition chamber is an
atomic layer vapor deposition chamber.
7. A vapor deposition system comprising: a vapor deposition
chamber; a substrate positioned in the depostion chamber; a first
vessel; one or more refractory metal precursor compounds in the
first vessel, wherein the one or more refractory metal precursor
compounds are of the formula MY.sub.n (Formula I), wherein M is a
refractory metal, each Y is independently a halogen atom, and n is
an integer selected to match the valence of the metal M; a second
vessel; and one or more disilazanes in the second vessel, wherein
the one or more disilazanes are of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3.
8. The system of claim 7 wherein the substrate comprises a
semiconductor substrate.
9. The system of claim 7 wherein the substrate comprises a
silicon-containing surface.
10. The system of claim 7 wherein the substrate comprises a silicon
wafer.
11. A vapor deposition system comprising: one or more vessels
comprising one or more refractory metal precursor compounds of the
formula MY.sub.n (Formula I), wherein M is a refractory metal, each
Y is independently a halogen atom, and n is an integer selected to
match the valence of the metal M; and one or more vessels
comprising one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3.
12. The system of claim 11 wherein Y is independently selected from
the group consisting of F, Cl, I, and combinations thereof.
13. The system of claim 11 wherein each Y is a fluorine atom.
14. The system of claim 11 wherein M is selected from the group
consisting of Ti, Nb, Ta, Mo, and W.
15. The system of claim 11 wherein M is tantalum and n is 5.
16. The system of claim 11 wherein each R is independently selected
from the group consisting of a (C1-C6) organic group.
17. The system of claim 16 wherein each R is independently ethyl or
methyl.
18. The system of claim 17 wherein the disilazane is
tetramethyldisilazane (TMDS),
(CH.sub.3).sub.2HSiNHSiH(CH.sub.3).sub.2, or
hexamethyldisilazane.
19. The system of claim 18 wherein the disilazane is
tetramethyldisilazane.
20. A vapor deposition system comprising: one or more vessels
comprising one or more refractory metal precursor compounds of the
formula MY.sub.n (Formula I), wherein M is a refractory metal, each
Y is independently a halogen atom, and n is an integer selected to
match the valence of the metal M; one or more vessels comprising
one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3; and one or more
vessels comprising one or more silicon precursor compounds.
21. The system of claim 20 wherein the one or more silicon
precursor compounds comprises silane (SiH.sub.4), disilane
(Si.sub.2H.sub.6), halogenated silanes, and organic silanes of the
formula SiH.sub.pR.sup.1.sub.q wherein p=1-4, q=4-p, and each
R.sup.1 is independently an organic group having up to six carbon
atoms.
22. The system of claim 21 wherein each R.sup.1 is independently an
organic group having up to two carbon atoms.
23. The system of claim 22 wherein each R.sup.1 is independently an
organic moiety.
24. The system of claim 20 wherein the one or more silicon
precursor compounds are selected from the group consisting of
silane (SiH.sub.4), disilane (Si.sub.2H.sub.6), dichlorosilane
(SiH.sub.2Cl.sub.2), trichlorosilane (SiHCl.sub.3), and
trimethylsilane (SiH(CH.sub.3).sub.3).
25. A vapor deposition system comprising: one or more vessels
comprising one or more refractory metal precursor compounds of the
formula MY.sub.n (Formula I), wherein M is a refractory metal, each
Y is independently a halogen atom, and n is an integer selected to
match the valence of the metal M; one or more vessels comprising
one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3; and one or more
vessels comprising one or more reaction gases other than the one or
more disilazanes.
26. The system of claim 25 wherein the one or more reaction gases
are selected from the group consisting of NH.sub.3, N.sub.2H.sub.4,
B.sub.2H.sub.6, PH.sub.3, and combinations thereof.
27. A vapor deposition system comprising: one or more vessels
comprising one or more refractory metal precursor compounds of the
formula MY.sub.n (Formula I), wherein M is a refractory metal, each
Y is independently a halogen atom, and n is an integer selected to
match the valence of the metal M; one or more vessels comprising
one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3; and an inert
carrier gas.
28. The system of claim 27 wherein the inert carrier gas is
selected from the group consisting of nitrogen, helium, argon, and
mixtures thereof.
Description
FIELD OF THE INVENTION
[0001] This invention relates to methods of forming refractory
metal nitride layers (including silicon nitride layers) on
substrates using a vapor deposition process with a refractory metal
halide (preferably, fluoride) precursor compound, a disilazane, and
optionally a silicon precursor compound. The formed refractory
metal (silicon) nitride layers are particularly useful as diffusion
barriers for polysilicon substrates to reduce diffusion of oxygen,
copper, or silicon.
BACKGROUND OF THE INVENTION
[0002] In integrated circuit manufacturing, microelectronic devices
such as capacitors are the basic energy storage devices in random
access memory devices, such as dynamic random access memory (DRAM)
devices, static random access memory (SRAM) devices, and
ferroelectric memory (FERAM) devices. Capacitors typically consist
of two conductors acting as electrodes, such as parallel metal
(e.g., platinum) or polysilicon plates, that are insulated from
each other by a layer of dielectric material.
[0003] Historically, silicon dioxide has generally been the
dielectric material of choice for capacitors. However, the
continuous shrinkage of microelectronic devices over the years has
led to dielectric layers approaching only 10 .ANG. in thickness
(corresponding to 4 or 5 molecules). To reduce current tunneling
through thin dielectric layers, high dielectric metal-containing
layers, such as Al.sub.2O.sub.3, TiO.sub.2, ZrO.sub.2 HfO.sub.2,
Ta.sub.2O.sub.5, (Ba,Sr)TiO.sub.3 Pb(Zr,Ti)O.sub.3 and
SrBi.sub.2Ti.sub.2O.sub.9, have been developed lo replace SiO.sub.2
layers. However, these metal-containing layers can provide high
leakage paths and channels for oxygen diffusion, especially during
annealing. Also, an undesirable interfacial layer of SiO.sub.2 is
frequently created by oxidation of polysilicon during the annealing
of the dielectric layer.
[0004] One way to address these problems is to deposit a thin,
conductive, amorphous, metal nitride barrier layer on the substrate
prior to the deposition of the thin resistive metal oxide layer.
For example, reactive metal silicon nitride barrier metal layers
are used to protect polysilicon from oxygen diffusion prior to
applying very thin (i.e., less than 10 .ANG.) barium strontium
titanate dielectric films.
[0005] Refractory metal nitrides and refractory metal silicon
nitrides, such as titanium nitride (Ti--N), tantalum nitride
(Ta--N), tungsten nitride (W--N), molybdenum nitride (Mo--N),
titanium silicon nitride (Ti--Si--N), tantalum silicon nitride
(Ta--Si--N) and tungsten silicon nitride (W--Si--N), are also
useful as conductive barrier layers between silicon substrates and
copper interconnects to reduce copper diffusion. This copper
diffusion has led to degradation of device reliability, causing
semiconductor manufacturers to turn toward other less conductive
metals, such as aluminum and tungsten.
[0006] Further improvements in high temperature adhesion and
diffusion resistance can be realized when about 4 to about 30 atom
% silicon is incorporated to form a more amorphous metal silicon
nitride layer. Examples of refractory metal silicon nitrides that
are useful as barrier layers include tantalum silicon nitride
(Ta--Si--N), titanium silicon nitride (Ti--Si--N), and tungsten
silicon nitride (W--Si--N).
[0007] Methods for using physical vapor deposition (PVD) methods,
such as reactive sputtering, to form Ta--Si--N barrier layers are
known. Hara et al., "Barrier Properties for Oxygen Diffusion in a
TaSiN Layer," Jpn J. Appl. Phys., 36(7B), L893 (1997) describe
noncrystalline, low resistivity Ta--Si--N layers that acts as a
barrier to oxygen diffusion during high temperature annealing at
650.degree. C. in the presence of O.sub.2. The Ta--Si--N layers are
formed by using radio-frequency reactive sputtering with pure Ta
and Si targets on a 100 nm thick polysilicon layer. Layers having
relatively low silicon content, such as
Ta.sub.0.50Si.sub.0.16N.sub.0.34 are stated to have a desirable
combination of good diffusion barrier resistance along with low
sheet resistance. These Ta--Si--N barrier layers have improved peel
resistance over Ta--N barrier layers during annealing
conditions.
[0008] Lee et al., "Structural and chemical stability of Ta--Si--N
thin film between Si and Cu," Thin Solid Films, 320:141-146 (1998)
describe amorphous, ultra-thin (i.e., less than 100 .ANG.)
tantalum-silicon-nitrogen barrier films between silicon and copper
interconnection materials used in integrated circuits. These
barrier films suppress the diffusion of copper into silicon, thus
improving device reliability. Barrier films having compositions
ranging from Ta.sub.0.43Si.sub.0.04N.sub.0.53 to
Ta.sub.0.60Si.sub.0.11N.sub.0.29 were deposited on silicon by
reactive sputtering from Ta and Si targets in an Ar/N.sub.2
discharge, followed by sputter-depositing copper films.
[0009] However, when PVD methods are used, the stoichiometric
composition of the formed metal nitride and metal silicon nitride
barrier layers such as Ta--N and Ta--Si--N can be non-uniform
across the substrate surface due to different sputter yields of Ta,
Si, and N. Due to the resulting poor layer conformality, defects
such as pinholes often occur in such layers creating pathways to
diffusion. As a result, the effectiveness of a physically deposited
diffusion barrier layer is dependent on the layer being
sufficiently thick.
[0010] Vapor deposition processes such as chemical vapor deposition
(CVD) and atomic layer deposition (ALD) processes are preferable to
PVD processes in order to achieve the most efficient and uniform
barrier layer coverage of substrate surfaces. There remains a need
for a vapor deposition process to form refractory metal nitrides
and refractory metal silicon nitride barrier layers (especially
Ta--N and Ta--Si--N layers) on substrates, such as semiconductor
substrates or substrate assemblies.
SUMMARY OF THE INVENTION
[0011] This invention is directed to methods of using vapor
deposition processes to deposit refractory metal (silicon) nitride
layers (i.e., refractory metal nitride and refractory metal silicon
nitride layers) on substrates. The process involves combining one
or more refractory metal halide precursor compounds, one or more
nitrogen precursor compounds (disilazanes), and optionally one or
more silicon precursor compounds.
[0012] In one embodiment, the present invention provides a method
of forming a layer on a substrate (preferably, in a process of
manufacturing a semiconductor structure). The method includes:
providing a substrate (preferably a semiconductor substrate or
substrate assembly such as a silicon wafer); providing a vapor that
includes one or more refractory metal precursor compounds of the
formula MY.sub.n (Formula I), wherein M is a refractory metal
(e.g., Ti, Nb, Ta, Mo, and W), each Y is independently a halogen
atom (preferably, F, Cl, I, or combinations thereof, and more
preferably, F), and n is an integer selected to match the valence
of the metal M (e.g., n=5 when M=Ta); providing a vapor that
includes one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3; and directing the
vapors that include the one or more refractory metal precursor
compounds and the one or more disilazanes to the substrate to form
a refractory metal nitride layer (e.g., tantalum nitride) on one or
more surfaces of the substrate. The resultant nitride layer (or
silicon nitride layer) is typically suitable for use as a diffusion
barrier layer, which is particularly advantageous when the
substrate includes a silicon-containing surface.
[0013] The present invention also provides a method of
manufacturing a memory device. The method includes: providing a
substrate (preferably a semiconductor substrate or substrate
assembly) that includes a silicon-containing surface; providing a
vapor that includes one or more refractory metal precursor
compounds of the formula MY.sub.n (Formula I), wherein M is a
refractory metal, each Y is independently a halogen atom, and n is
an integer selected to match the valence of the metal M; directing
the vapor that includes the one or more precursor compounds of the
Formula I to the substrate and allowing the one or more compounds
to chemisorb on the silicon-containing surface; providing a vapor
that includes one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3; directing the
vapor that includes the one or more disilazanes to the substrate
with the chemisorbed compounds thereon to form a refractory metal
nitride barrier layer on the silicon-conlaining surface; providing
a first electrode on the barrier layer; providing a high dielectric
material over at least a portion of the first electrode; and
providing a second electrode over the high dielectric material.
[0014] Preferred methods of the present invention also include
steps of providing a vapor that includes one or more silicon
precursor compounds and directing the vapor to the substrate to
form a refractory metal silicon nitride layer. Optionally, the
methods can also provide one or more reaction gases other than the
disilazanes and silicon precursor compounds and direct the one or
more reaction gases to the substrate. Also, in certain embodiments,
the methods can provide a vapor that includes one or more
metal-containing precursor compounds of a formula different from
Formula I and direct this vapor to the substrate.
[0015] The present invention also provides a vapor deposition
apparatus that includes: a vapor deposition chamber having a
substrate positioned therein; and one or more vessels that include
one or more refractory metal precursor compounds of the formula
MY.sub.n (Formula I), wherein M is a refractory metal, each Y is
independently a halogen atom, and n is an integer selected to match
the valence of the metal M; and one or more vessels that include
one or more disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group, and x is 1 to 3. Optionally, the
apparatus can include one or more vessels with one or more silicon
precursor compounds therein and/or one or more reaction gases other
than the disilazanes and silicon precursor compounds therein.
[0016] The methods of the present invention can utilize a chemical
vapor deposition (CVD) process, which can be pulsed, or an atomic
layer deposition (ALD) process (a self-limiting vapor deposition
process that includes a plurality of deposition cycles, typically
with purging between the cycles). Preferably, the methods of the
present invention use ALD. In one embodiment of an ALD process, the
refractory metal nitride layer is formed by alternately introducing
the one or more vaporized precursor compounds and one or more
vaporized disilazanes into a deposition chamber during each
deposition cycle.
[0017] "Substrate" as used herein refers to any base material or
construction upon which a metal-containing layer can be deposited.
The term "substrate" is meant to include semiconductor substrates
and also include non-semiconductor substrates such as films, molded
articles, fibers, wires, glass, ceramics, machined metal parts,
etc.
[0018] "Semiconductor substrate" or "substrate assembly" as used
herein refers to a semiconductor substrate such as a metal
electrode, base semiconductor layer or a semiconductor substrate
having one or more layers, structures, or regions formed thereon. A
base semiconductor layer is typically the lowest layer of silicon
material on a wafer or a silicon layer deposited on another
material, such as silicon on sapphire. When reference is made to a
substrate assembly, various process steps may have been previously
used to form or define regions, junctions, various structures or
features, and openings such as capacitor plates or barriers for
capacitors.
[0019] "Layer" as used herein refers to any metal-containing layer
that can be formed on a substrate from the precursor compounds of
this invention using a vapor deposition process. The term "layer"
is meant to include layers specific to the semiconductor industry,
such as "barrier layer," "dielectric layer," and "conductive
layer." (The term "layer" is synonymous with the term "film"
frequently used in the semiconductor industry.) The term "layer" is
also meant to include layers found in technology outside of
semiconductor technology, such as coatings on glass.
[0020] "Barrier layer" as used herein refers to a conductive,
interfacial layer that can reduce diffusion of ambient oxygen
through a dielectric layer into a semiconductor substrate
(typically a polysilicon substrate) or can reduce diffusion of one
layer into another, such as a copper conductive layer into a
semiconductor substrate (typically a polysilicon substrate). For
this invention, the barrier layer is a tantalum nitride or tantalum
silicon nitride layer.
[0021] "Refractory metal" as defined by Webster's New Universal
Unabridged Dictionary (1992) is a metal that is difficult to fuse,
reduce, or work. For the purposes of this invention, the term
"refractory metal" is meant to include the Group IVB metals (i.e.,
titanium (Ti), zirconium (Zr), hafnium (Hf)); the Group VB metals
(i.e., vanadium (V), niobium (Nb), tantalum (Ta)); and the Group
VIB metals (i.e., chromium (Cr), molybdenum (Mo) and tungsten
(W)).
[0022] "Precursor compound" as used herein refers to refractory
metal precursor compounds, nitrogen precursor compounds, silicon
precursor compounds, and other metal-containing precursor
compounds, for example. A suitable precursor compound is one that
is capable of forming, either alone or with other precursor
compounds, a refractory metal-containing layer on a substrate using
a vapor deposition process. The resulting refractory
metal-containing layers also typically include nitrogen and
optionally silicon. Such layers are often useful as diffusion
barrier layers (i.e., barrier layers).
[0023] "Deposition process" and "vapor deposition process" as used
herein refer to a process in which a metal-containing layer is
formed on one or more surfaces of a substrate (e.g., a doped
polysilicon wafer) from vaporized precursor compound(s).
Specifically, one or more metal precursor compounds are vaporized
and directed to one or more surfaces of a heated. substrate (e.g.,
semiconductor substrate or substrate assembly) placed in a
deposition chamber. These precursor compounds form (e.g., by
reacting or decomposing) a non-volatile, thin, uniform,
metal-containing layer on the surface(s) of the substrate. For the
purposes of this invention, the term "vapor deposition process" is
meant to include both chemical vapor deposition processes
(including pulsed chemical vapor deposition processes) and atomic
layer deposition processes.
[0024] "Chemical vapor deposition" (CVD) as used herein refers to a
vapor deposition process wherein the desired layer is deposited on
the substrate from vaporized metal precursor compounds and any
reaction gases used within a deposition chamber with no effort made
to separate the reaction components. In contrast to a "simple" CVD
process that involves the substantial simultaneous use of the
precursor compounds and any reaction gases, "pulsed" CVD
alternately pulses these materials into the deposition chamber, but
does not rigorously avoid intermixing of the precursor and reaction
gas streams, as is typically done in atomic layer deposition or ALD
(discussed in greater detail below).
[0025] "Atomic layer deposition" (ALD) as used herein refers to a
vapor deposition process in which numerous consecutive deposition
cycles are conducted in a deposition chamber. Typically, during
each cycle the metal precursor is chemisorbed to the substrate
surface; excess precursor is purged out; a subsequent precursor
and/or reaction gas is introduced to react with the chemisorbed
layer; and excess reaction gas (if used) and by-products are
removed. As compared to the one cycle chemical vapor deposition
(CVD) process, the longer duration multi-cycle ALD process allows
for improved control of layer thickness by self-limiting layer
growth and minimizing detrimental gas phase reactions by separation
of the reaction components. The term "atomic layer deposition" as
used herein is also meant to include the related terms "atomic
layer epitaxy" (ALE) (see U.S. Pat. No. 5,256,244 (Ackerman)),
molecular beam epitaxy (MBE), gas source MBE, organometallic MBE,
and chemical beam epitaxy when performed with alternating pulses of
precursor compound(s), reaction gas and purge (i.e., inert carrier)
gas.
[0026] "Chemisorption" as used herein refers to the chemical
adsorption of vaporized reactive precursor compounds on the surface
of a substrate. The adsorbed species are irreversibly bound to the
substrate surface as a result of relatively strong binding forces
characterized by high adsorption energies (>30 kcal/mol),
comparable in strength to ordinary chemical bonds. The chemisorbed
species are limited to the formation of a monolayer on the
substrate surface. (See "The Condensed Chemical Dictionary", 10th
edition, revised by G. G. Hawley, published by Van Nostrand
Reinhold Co., New York, 225 (1981)). The technique of ALD is based
on the principle of the formation of a saturated monolayer of
reactive precursor molecules by chemisorption. In ALD one or more
appropriate reactive precursor compounds are alternately introduced
(e.g., pulsed) into a deposition chamber and chemisorbed onto the
surfaces of a substrate. Each sequential introduction of a reactive
precursor compound is typically separated by an inert carrier gas
purge. Each precursor compound co-reaction adds a new atomic layer
to previously deposited layers to form a cumulative solid layer.
The cycle is repealed, typically for several hundred times, to
gradually form the desired layer thickness. It should be
understood, however, that ALD can use one precursor compound and
one reaction gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows a device structure including a refractory metal
nitride diffusion barrier layer according to the present
invention.
[0028] FIG. 2 is a structure showing a high dielectric capacitor
including an electrode having a refractory metal nitride diffusion
barrier layer according to the present invention.
[0029] FIG. 3 is a perspective view of a vapor deposition coating
system suitable for use in the method of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
[0030] The present invention provides methods of forming a
metal-containing layer on a substrate using a vapor deposition
process with one or more refractory metal halide precursor
compounds, one or more nitrogen precursor compounds (disilazanes),
and optionally one or more silicon precursor compounds. For the
present invention, the metal-containing layer is a refractory metal
nitride layer, preferably, a refractory metal silicon nitride
layer. More preferably, the layer is a tantalum silicon nitride
barrier layer.
[0031] The layers or films formed can be in the form of refractory
metal nitride-containing films or refractory metal silicon
nitride-containing films, wherein the layer includes one or more
refractory metal nitrides or refractory metal silicon nitrides
optionally doped with other metals. Thus, the term "refractory
metal (silicon) nitride" films or layers encompass refractory metal
nitrides, refractory metal silicon nitrides (of all possible
proportions of refractory metal, Si, and N), as well as doped films
or layers thereof (e.g., mixed metal (silicon) nitrides). Such
mixed metal species can be formed using one or more
metal-containing precursor compounds of a formula different from
Formula I, which can be readily determined by one of skill in the
art.
[0032] The layers of the present invention are preferably
conductive. That is, they preferably display an electrical
resistivity of no more than about 10 m.OMEGA.-cm. The layers of the
present invention are typically useful as barrier layers,
particularly in the manufacture of semiconductor interconnects. For
example, tantalum silicon nitride is being considered as a copper
barrier, and is of great interest as a barrier between high
dielectric constant oxides and silicon. The addition of silicon to
tantalum nitride yields a material that is resistant to
crystallization and therefore to diffusion of silicon and metal
species via grain boundaries.
[0033] The substrate on which the metal-containing layer is formed
is preferably a semiconductor substrate or substrate assembly. Any
suitable semiconductor material is contemplated, such as for
example, conductively doped polysilicon (for this invention simply
referred to as "silicon"). A substrate assembly may also contain a
layer that includes platinum, iridium, rhodium, ruthenium,
ruthenium oxide, titanium nitride, silicon dioxide, aluminum,
gallium arsenide, glass, etc., and other existing or
to-be-developed materials used in semiconductor constructions, such
as dynamic random access memory (DRAM) devices and static random
access memory (SRAM) devices, for example. Preferred substrates
include a silicon-containing surface.
[0034] Substrates other than semiconductor substrates or substrate
assemblies can be used in methods of the present invention. These
include, for example, fibers, wires, etc. If the substrate is a
semiconductor substrate or substrate assembly, the layers can be
formed directly on the lowest semiconductor surface of the
substrate, or they can be formed on any of a variety of the layers
(i.e., surfaces) as in a patterned wafer, for example.
[0035] Refractory metal precursor compounds useful in the practice
of this invention are of the formula MY.sub.n (Formula I) wherein M
is a refractory metal, and each Y is independently a halogen atom.
More preferably, each Y is a fluorine atom. Preferably, M is a
Group IVB (Ti, Zr, Hf), VB (V, Nb, Ta), or VIB (Cr, Mo, W) metal
(also referred to as Groups 4, 5, and 6 of the Periodic Table).
More preferably, M is Ti, Nb, Ta, Mo, or W. Most preferably, M is
Ti or Ta. In Formula I, n is an integer selected to match the
valence of the metal M. For example, when M is tantalum (or another
pentavalent metal), n is 5. For particularly preferred embodiments,
the refractory metal precursor compound is a tantalum precursor
compound of the formula TaF.sub.5.
[0036] Nitrogen precursor compounds useful in the practice of this
invention are volatile disilazanes of the formula
(R).sub.xH.sub.3-xSiNHSi(R).sub.xH.sub.3-x, wherein each R is
independently an organic group and x is 1 to 3. Preferably, each R
is independently a (C1-C6) organic group, and more preferably, a
(C1-C4) organic group. Preferably, the organic group is an organic
moiety such as ethyl and methyl. Particularly preferred examples of
the disilazane include tetramethyldisilazane (TMDS),
(CH.sub.3).sub.2HSiNHSiH(CH.sub.3).sub.2, and hexamethyldisilazane.
Most preferably, the disilazane is tetramethyldisilazane
(TMDS).
[0037] These nitrogen sources are significant relative to ammonia
because they provide conductive metal nitride films with tantalum
precursors, whereas ammonia does not. Further, processes using
ammonia often lead to solid by-products that can result in
detrimental particulates on the substrate or deposits on chamber
walls or downstream piping.
[0038] Optional silicon precursor compounds (other than the
disilazane) useful in the practice of this invention include silane
(SiH.sub.4), disilane (Si.sub.2H.sub.6), halogenated silanes
(preferably chlorinated silanes of the formula SiH.sub.rCl.sub.s
wherein r=1-4 and s=4-r), and organic silanes of the formula
SiH.sub.pR.sup.1.sub.q wherein p=1-4, q=4-p, and each R.sup.1 is
independently an organic group (preferably having up to six carbon
atoms, more preferably up to two carbon atoms, and most preferably,
being an organic moiety). Examples include silane (SiH.sub.4),
disilane (Si.sub.2H.sub.6), dichlorosilane (SiH.sub.2Cl.sub.2),
Irichlorosilane (SiHCl.sub.3), and trimethylsilane
(SiH(CH.sub.3).sub.3).
[0039] As used herein, the term "organic group" is used for the
purpose of this invention to mean a hydrocarbon group that is
classified as an aliphatic group, cyclic group, or combination of
aliphatic and cyclic groups (e.g., alkaryl and aralkyl groups). In
the context of the present invention, suitable organic groups for
precursor compounds of this invention are those that do not
interfere with the formation of a metal-containing layer using
vapor deposition techniques. In the context of the present
invention, the term "aliphatic group" means a saturated or
unsaturated linear or branched hydrocarbon group. This term is used
to encompass alkyl, alkenyl, and alkynyl groups, for example. The
term "alkyl group" means a saturated linear or branched monovalent
hydrocarbon group including, for example, methyl, ethyl, n-propyl,
isopropyl, t-butyl, amyl, heptyl, 2-ethylhexyl, dodecyl, octadecyl,
and the like. The term "alkenyl group" means an unsaturated, linear
or branched monovalent hydrocarbon group with one or more
olefinically unsaturated groups (i.e., carbon-carbon double bonds),
such as a vinyl group. The term "alkynyl group" means an
unsaturated, linear or branched monovalent hydrocarbon group with
one or more carbon-carbon triple bonds. The term "cyclic group"
means a closed ring hydrocarbon group that is classified as an
alicyclic group, aromatic group, or heterocyclic group. The term
"alicyclic group" means a cyclic hydrocarbon group having
properties resembling those of aliphatic groups. The term "aromatic
group" or "aryl group" means a mono- or polynuclear aromatic
hydrocarbon group. The term "heterocyclic group" means a closed
ring hydrocarbon in which one or more of the atoms in the ring is
an element other than carbon (e.g., nitrogen, oxygen, sulfur,
etc.).
[0040] As a means of simplifying the discussion and the recitation
of certain terminology used throughout this application, the terms
"group" and "moiety" are used to differentiate between chemical
species that allow for substitution or that may be substituted and
those that do not so allow for substitution or may not be so
substituted. Thus, when the term "group" is used to describe a
chemical substituent, the described chemical material includes the
unsubstituted group and that group with nonperoxidic O, N, or S
atoms, for example, in the chain as well as carbonyl groups or
other conventional substituents. Where the term "moiety" is used to
describe a chemical compound or substituent, only an unsubstituted
chemical material is intended to be included. For example, the
phrase "alkyl group" is intended to include not only pure open
chain saturated hydrocarbon alkyl substituents, such as methyl,
ethyl, propyl, t-butyl, and the like, but also alkyl substituents
bearing further substituents known in the art, such as hydroxy,
alkoxy, alkylsulfonyl, halogen atoms, cyano, nitro, amino,
carboxyl, etc. Thus, "alkyl group" includes ether groups,
haloalkyls, nitroalkyls, carboxyalkyls, hydroxyalkyls, sulfoalkyls,
etc. On the other hand, the phrase "alkyl moiety" is limited to the
inclusion of only pure open chain saturated hydrocarbon alkyl
substituents, such as methyl, ethyl, propyl, t-butyl, and the
like.
[0041] Various precursor compounds can be used in various
combinations, optionally with one or more organic solvents
(particularly for CVD processes), to form a precursor composition.
The precursor compounds may be liquids or solids at room
temperature (preferably, they are liquids at the vaporization
temperature). Typically, they are liquids sufficiently volatile to
be employed using known vapor deposition techniques. However, as
solids they may also be sufficiently volatile that they can be
vaporized or sublimed from the solid state using known vapor
deposition techniques. If they are less volatile solids, they are
preferably sufficiently soluble in an organic solvent or have
melting points below their decomposition temperatures such that
they can be used in flash vaporization, bubbling, microdroplet
formation techniques, etc. Herein, vaporized precursor compounds
may be used either alone or optionally with vaporized molecules of
other precursor compounds or optionally with vaporized solvent
molecules, if used. As used herein, "liquid" refers to a solution
or a neat liquid (a liquid at room temperature or a solid at room
temperature that melts at an elevated temperature). As used herein,
"solution" does not require complete solubility of the solid but
may allow for some undissolved solid, as long as there is a
sufficient amount of the solid delivered by the organic solvent
into the vapor phase for chemical vapor deposition processing. If
solvent dilution is used in deposition, the total molar
concentration of solvent vapor generated may also be considered as
a inert carrier gas.
[0042] Solvents can be used with the metal-containing precursors if
desired. The solvents that are suitable for this application
(particularly for a CVD process) can be one or more of the
following: aliphatic hydrocarbons or unsaturated hydrocarbons
(C3-C20, and preferably C5-C10, cyclic, branched, or linear),
aromatic hydrocarbons (C5-C20, and preferably C5-C10), halogenated
hydrocarbons, silylated hydrocarbons such as alkylsilanes,
alkylsilicates, ethers, polyethers, thioethers, esters, lactones,
ammonia, amides, amines (aliphatic or aromatic, primary, secondary,
or tertiary), polyamines, nitrites, cyanates, isocyanates,
thiocyanates, silicone oils, alcohols, or compounds containing
combinations of any of the above or mixtures of one or more of the
above. The compounds are also generally compatible with each other,
so that mixtures of variable quantities of the precursor compounds
will not interact to significantly change their physical
properties.
[0043] In the practice of this invention, one or more reaction
gases other than the nitrogen and silicon precursor compounds
described herein can be used if desired. These include, for
example, NH.sub.3, N.sub.2H.sub.4, B.sub.2H.sub.6, PH.sub.3, and
combinations thereof. Typically, the reaction gases referred to
herein do not include metal-containing compounds.
[0044] The precursor compounds can be vaporized in the presence of
an inert carrier gas if desired. Additionally, an inert carrier gas
can be used in purging steps in an ALD process. The inert carrier
gas is typically selected from the group consisting of nitrogen,
helium, argon, and mixtures thereof. In the context of the present
invention, an inert carrier gas is one that is generally unreactive
with the complexes described herein and does not interfere with the
formation of the desired metal-containing film (i.e., layer).
[0045] The deposition process for this invention is a vapor
deposition process. Vapor deposition processes are generally
favored in the semiconductor industry due to the process capability
to quickly provide highly conformal layers even within deep
contacts and other openings. Chemical vapor deposition (CVD) and
atomic layer deposition (ALD) are two vapor deposition processes
often employed to form thin, continuous, uniform, metal-containing
(preferably, barrier) layers onto semiconductor substrates. Using
either vapor deposition process, typically one or more precursor
compounds are vaporized in a deposition chamber and optionally
combined with one or more reaction gases to form a metal-containing
layer onto a substrate. It will be readily apparent to one skilled
in the art that the vapor deposition process may be enhanced by
employing various related techniques such as plasma assistance,
photo assistance, laser assistance, as well as other
techniques.
[0046] The final layer (preferably, a barrier layer) formed
preferably has a thickness in the range of about 10 .ANG. to about
500 .ANG.. More preferably, the thickness of the metal-containing
layer is in the range of about 30 .ANG. to about 80 .ANG..
[0047] Chemical vapor deposition (CVD) has been extensively used
for the preparation of metal-containing layers, such as barrier
layers, in semiconductor processing because of its ability to
provide highly conformal and high quality barrier layers at
relatively fast processing times. The desired precursor compounds
are vaporized and then introduced into a deposition chamber
containing a heated substrate with optional reaction gases and/or
inert carrier gases. In a typical CVD process, vaporized precursors
are contacted with reaction gas(es) at the substrate surface to
form a layer (e.g., barrier layer). The single deposition cycle is
allowed to continue until the desired thickness of the layer is
achieved.
[0048] Typical CVD processes generally employ precursor compounds
in vaporization chambers that are separated from the process
chamber wherein the deposition surface or wafer is located. For
example, liquid precursor compounds are typically placed in
bubblers and heated to a temperature at which they vaporize, and
the vaporized liquid precursor compound is then transported by an
inert carrier gas passing over the bubbler or through the liquid
precursor compound. The vapors are then swept through a gas line to
the deposition chamber for depositing a layer on substrate
surface(s) therein. Many techniques have been developed to
precisely control this process. For example, the amount of
precursor material transported to the deposition chamber can be
precisely controlled by the temperature of the reservoir containing
the precursor compounds and by the flow of an inert carrier gas
bubbled through or passed over the reservoir.
[0049] Preferred embodiments of the precursor compounds described
herein are particularly suitable for chemical vapor deposition
(CVD). The deposition temperature at the substrate surface is
preferably held at a temperature in a range of about 100.degree. C.
to about 600.degree. C., more preferably in the range of about
200.degree. C. to about 500.degree. C. The deposition chamber
pressure is preferably maintained at a deposition pressure of about
0.1 torr to about 10 torr. The partial pressure of precursor
compounds in the inert carrier gas is preferably about 0.001 torr
to about 10 torr.
[0050] Several modifications of the CVD process and chambers are
possible, for example, using atmospheric pressure chemical vapor
deposition, low pressure chemical vapor deposition (LPCVD), plasma
enhanced chemical vapor deposition (PECVD), hot wall or cold wall
reactors or any other chemical vapor deposition technique.
Furthermore, pulsed CVD can be used, which is similar to ALD
(discussed in greater detail below) but does not rigorously avoid
intermixing of precursor and reactant gas streams. Also, for pulsed
CVD, the deposition thickness is dependent on the exposure time, as
opposed to ALD, which is self-limiting (discussed in greater detail
below).
[0051] A typical CVD process may be carried out in a chemical vapor
deposition reactor, such as a deposition chamber available under
the trade designation of 7000 from Genus, Inc. (Sunnyvale, Calif.),
a deposition chamber available under the trade designation of 5000
from Applied Materials, Inc. (Santa Clara, Calif.), or a deposition
chamber available under the trade designation of Prism from
Novelus, Inc. (San Jose, Calif.). However, any deposition chamber
suitable for performing CVD may be used.
[0052] Alternatively, and preferably, the vapor deposition process
employed is a multi-cycle ALD process. Typically, this process
provides for optimum control of atomic-level thickness and
uniformity to the deposited layer (e.g., barrier layer) and to
expose the metal precursor compounds to lower volatilization and
reaction temperatures to minimize degradation. Typically, in an ALD
process, each reactant is pulsed sequentially onto a suitable
substrate, typically at deposition temperatures of about 25.degree.
C. to about 400.degree. C. (preferably about 150.degree. C. to
about 300.degree. C.), which is generally lower than presently used
in CVD processes. Under such conditions the film growth is
typically self-limiting (i.e., when the reactive sites on a surface
are used up in an ALD process, the deposition generally stops),
insuring not only excellent conformality but also good large area
uniformity plus simple and accurate thickness control. Due to
alternate dosing of the precursor compounds and/or reaction gases,
detrimental vapor-phase reactions are inherently eliminated, in
contrast to the CVD process that is carried out by continuous
coreaction of the precursors and/or reaction gases. (See Vehkamaki
et al, "Growth of SrTiO.sub.3 and BaTiO.sub.3 Thin Films by Atomic
Layer Deposition," Electrochemical and Solid-State Letters,
2(10):504-506 (1999)).
[0053] A typical ALD process includes exposing an initial substrate
to a first chemical species (e.g., refractory metal precursor
compound of the formula MY.sub.n) to accomplish chemisorption of
the species onto the substrate. Theoretically, the chemisorption
forms a monolayer that is uniformly one atom or molecule thick on
the entire exposed initial substrate. In other words, a saturated
monolayer. Practically, chemisorption might not occur on all
portions of the substrate. Nevertheless, such an imperfect
monolayer is still a monolayer in the context of the present
invention. In many applications, merely a substantially saturated
monolayer may be suitable. A substantially saturated monolayer is
one that will still yield a deposited layer exhibiting the quality
and/or properties desired for such layer.
[0054] The first species is purged from over the substrate and a
second chemical species (e.g., a different compound of the formula
MY.sub.n, a metal-containing precursor compound of a formula
different than MY.sub.n, or a disilazane compound) is provided to
react with the first monolayer of the first species. The second
species is then purged and the steps are repeated with exposure of
the second species monolayer to the first species. In some cases,
the two monolayers may be of the same species. As an option, the
second species can react with the first species, but not chemisorb
additional material thereto. That is, the second species can cleave
some portion of the chemisorbed first species, altering such
monolayer without forming another monolayer thereon. Also, a third
species or more may be successively chemisorbed (or reacted) and
purged just as described for the first and second species.
[0055] Purging may involve a variety of techniques including, but
not limited to, contacting the substrate and/or monolayer with a
carrier gas and/or lowering pressure to below the deposition
pressure to reduce the concentration of a species contacting the
substrate and/or chemisorbed species. Examples of carrier gases
include N.sub.2, Ar, He, etc. Purging may instead include
contacting the substrate and/or monolayer with any substance that
allows chemisorption by-products to desorb and reduces the
concentration of a contacting species preparatory to introducing
another species. The contacting species may be reduced to some
suitable concentration or partial pressure known to those skilled
in the art based on the specifications for the product of a
particular deposition process.
[0056] ALD is often described as a self-limiting process, in that a
finite number of sites exist on a substrate to which the first
species may form chemical bonds. The second species might only bond
to the first species and thus may also be self-limiting. Once all
of the finite number of sites on a substrate are bonded with a
first species, the first species will often not bond to other of
the first species already bonded with the substrate. However,
process conditions can be varied in ALD to promote such bonding and
render ALD not self-limiting. Accordingly, ALD may also encompass a
species forming other than one monolayer at a time by stacking of a
species, forming a layer more than one atom or molecule thick.
[0057] The described method indicates the "substantial absence" of
the second precursor (i.e., second species) during chemisorption of
the first precursor since insignificant amounts of the second
precursor might be present. According to the knowledge and the
preferences of those with ordinary skill in the art, a
determination can be made as to the tolerable amount of second
precursor and process conditions selected to achieve the
substantial absence of the second precursor.
[0058] Thus, during the ALD process, numerous consecutive
deposition cycles are conducted in the deposition chamber, each
cycle depositing a very thin metal-containing layer (usually less
than one monolayer such that the growth rate on average is from
about 0.2 to about 3.0 Angstroms per cycle), until a layer of the
desired thickness is built up on the substrate of interest. The
layer deposition is accomplished by alternately introducing (i.e.,
by pulsing) refractory metal precursor compound(s) and disilazane
compound(s) into the deposition chamber containing a semiconductor
substrate, chemisorbing the precursor compound(s) as a monolayer
onto the substrate surfaces, and then reacting the chemisorbed
precursor compound(s) with the other co-reactive precursor
compound(s). The pulse duration of precursor compound(s) and inert
carrier gas(es) is sufficient to saturate the substrate surface.
Typically, the pulse duration is from about 0.1 to about 5 seconds,
preferably from about 0.2 to about 1 second.
[0059] In comparison to the predominantly thermally driven CVD, ALD
is predominantly chemically driven. Accordingly, ALD is often
conducted at much lower temperatures than CVD. During the ALD
process, the substrate temperature is maintained at a temperature
sufficiently low to maintain intact bonds between the chemisorbed
precursor compound(s) and the underlying substrate surface and to
prevent decomposition of the precursor compound(s). The temperature
is also sufficiently high to avoid condensation of the precursor
compounds(s). Typically the substrate temperature is kept within
the range of about 25.degree. C. to about 400.degree. C.
(preferably about 150.degree. C. to about 300.degree. C.), which is
generally lower than presently used in CVD processes. Thus, the
first species or precursor compound is chemisorbed at this
temperature. Surface reaction of the second species or precursor
compound can occur at substantially the same temperature as
chemisorption of the first precursor or, less preferably, at a
substantially different temperature. Clearly, some small variation
in temperature, as judged by those of ordinary skill, can occur but
still be a substantially same temperature by providing a reaction
rate statistically the same as would occur at the temperature of
the first precursor chemisorption. Chemisorption and subsequent
reactions could instead occur at exactly the same temperature.
[0060] For a typical ALD process, the pressure inside the
deposition chamber is kept at about 10.sup.-4 torr to about 1 torr,
preferably about 10.sup.-4 torr to about 0.1 torr. Typically, the
deposition chamber is purged with an inert carrier gas after the
vaporized precursor compound(s) have been introduced into the
chamber and/or reacted for each cycle. The inert carrier gas(es)
can also be introduced with the vaporized precursor compound(s)
during each cycle.
[0061] The reactivity of a precursor compound can significantly
influence the process parameters in ALD. Under typical CVD process
conditions, a highly reactive compound may react in the gas phase
generating particulates, depositing prematurely on undesired
surfaces, producing poor films, and/or yielding poor step coverage
or otherwise yielding non-uniform deposition. For at least such
reason, a highly reactive compound might be considered not suitable
for CVD. However, some compounds not suitable for CVD are superior
ALD precursors. For example, if the first precursor is gas phase
reactive with the second precursor, such a combination of compounds
might not be suitable for CVD, although they could be used in ALD.
In the CVD context, concern might also exist regarding sticking
coefficients and surface mobility, as known to those skilled in the
art, when using highly gas-phase reactive precursors, however,
little or no such concern would exist in the ALD context.
[0062] After layer formation on the substrate, an annealing process
can be optionally performed in situ in the deposition chamber in a
nitrogen atmosphere or ammonia atmosphere. Preferably, the
annealing temperature is within the range of about 400.degree. C.
to about 1000.degree. C. Particularly after ALD, the annealing
temperature is more preferably about 400.degree. C. to about
750.degree. C., and most preferably about 600.degree. C. to about
700.degree. C. The annealing operation is preferably performed for
a time period of about 0.5 minute to about 60 minutes and more
preferably for a time period of about 1 minute to about 10 minutes.
One skilled in the art will recognize that such temperatures and
time periods may vary. For example, furnace anneals and rapid
thermal annealing may be used, and further, such anneals may be
performed in one or more annealing steps.
[0063] As stated above, the use of the complexes and methods of
forming films of the present invention are beneficial for a wide
variety of thin film applications in semiconductor structures. For
example, such applications include capacitors such as planar cells,
trench cells (e.g., double sidewall trench capacitors), stacked
cells (e.g., crown, V-cell, delta cell, multi-fingered, or
cylindrical container stacked capacitors), as well as field effect
transistor devices.
[0064] Use of the barrier layers of the present invention in
semiconductor constructions shall be described generally with
reference to FIGS. 1 and 2.
[0065] FIG. 1 illustrates a structure 10 including a substrate
assembly 11 and a refractory metal nitride diffusion barrier layer
13 according to the present invention formed on a surface 12 of the
substrate assembly 11, e.g., a silicon containing surface. The
structure 10 further includes a conductive layer 14 (e.g., a copper
layer). The structure 10 is illustrative of the use of a refractory
metal nitride diffusion barrier layer for any application requiring
an effective barrier layer, for example, to prevent diffusion from
a silicon containing surface. In other words, the refractory metal
nitride diffusion barrier layer 13 may be used in the fabrication
of semiconductor devices wherever it is necessary to prevent the
diffusion of one material to an adjacent material. For example, the
substrate assembly 11 may be representative of a contact structure
having an opening extending to a silicon containing surface. In
such a structure, diffusion barriers are commonly used in such
openings to prevent undesirable reactions, such as the reaction of
a conductive contact material, e.g, copper or aluminum, with the
silicon containing surface.
[0066] Further, for example, the refractory metal nitride diffusion
barrier layer 13 may be used in the formation of storage cell
capacitors for use in semiconductor devices, e.g., memory devices.
As further described herein, the refractory metal nitride diffusion
barrier layer is used within a stack of layers forming an electrode
of a capacitor, e.g., the other layers including layers formed of
materials such as platinum, ruthenium oxide, etc. One skilled in
the art will recognize that various semiconductor processes and
structures for various devices, e.g., CMOS devices, memory devices,
etc., would benefit from the barrier characteristics of the barrier
layers of the present invention and in no manner is the present
invention limited to the illustrative embodiments described
herein.
[0067] FIG. 2 shows a structure 50 including substrate assembly 52
(e.g., a silicon substrate) and capacitor structure 54 formed
relative thereto. Capacitor structure 54 includes a first electrode
56, a second electrode 60, and a high dielectric constant layer 58
interposed therebetween. For example, the dielectric layer may be
any suitable material having a desirable dielectric constant, such
as TiO.sub.2, ZrO.sub.2, HfO.sub.2, Ta.sub.2O.sub.5,
(Ba,Sr)TiO.sub.3, Pb(Zr,Ti)O.sub.3, or SrBi.sub.2Ti.sub.2O.sub.9.
With use of the high dielectric constant layer 58, diffusion
barrier properties of the electrodes is particularly important. For
example, to function well in a bottom electrode of a capacitor
structure, the electrode layer or electrode stack must act as an
effective barrier to the diffusion of silicon, particularly due to
the processes used to form the high dielectric constant materials.
Such diffusion barrier properties are required when the substrate
assembly 52 includes a silicon-containing surface 53 upon which the
capacitor is formed, e.g., polysilicon, silicon substrate material,
N-doped silicon, P-doped silicon, etc., since oxidation of the
diffused silicon to form silicon dioxide may result in degraded
capacitance, e.g., capacitance for a memory device. In addition,
the electrode stack must act as an oxygen barrier (e.g., diffusion
barrier layer 62) to protect the silicon-containing surface under
the slack from oxidizing. The formation of the refractory metal
nitride diffusion barrier layer enhances the barrier properties of
the stack.
[0068] A system that can be used to perform vapor deposition
processes (chemical vapor deposition or atomic layer deposition) of
the present invention is shown in FIG. 3. The system includes an
enclosed vapor deposition chamber 110, in which a vacuum may be
created using turbo pump 112 and backing pump 114. One or more
substrates 116 (e.g., semiconductor substrates or substrate
assemblies) are positioned in chamber 110. A constant nominal
temperature is established for substrate 116, which can vary
depending on the process used. Substrate 116 may be heated, for
example, by an electrical resistance heater 118 on which substrate
116 is mounted. Other known methods of heating the substrate may
also be utilized.
[0069] In this process, precursor compounds 160 (e.g., a refractory
metal precursor compound and a disilazane) are stored in vessels
162. The precursor compounds are vaporized and separately fed along
lines 164 and 166 to the deposition chamber 110 using, for example,
an inert carrier gas 168. A reaction gas 170 may be supplied along
line 172 as needed. Also, a purge gas 174, which is often the same
as the inert carrier gas 168, may be supplied along line 176 as
needed. As shown, a series of valves 180-185 are opened and closed
as required.
[0070] The following examples are offered to further illustrate the
various specific and preferred embodiments and techniques. It
should be understood, however, that many variations and
modifications may be made while remaining within the scope of the
present invention, so the scope of the invention is not intended to
be limited by the examples.
EXAMPLES
Example 1
Pulsed Chemical Vapor Deposition of Tantalum Silicon Nitride
[0071] Using a pulsed CVD method, the following precursor compounds
were pulsed for 200 cycles in a deposition chamber as described in
FIG. 3 containing a borophosphosilicate glass (BPSG) substrate,
each cycle consisting of pulses in the following order: (1)
tantalum pentafluoride (Alfa Aesar, Ward Hill, Mass.), (2)
tetramethyldisilazane (TMDS) (Sigma-Aldrich Chemical C., Milwaukee,
Wis.), (3) tantalum pentafluoride and (4) disilane (VOC Gases).
During each cycle, excess amounts of each precursor compound not
chemisorbed were purged from the chamber after chemisorplion and
prior to the introduction of the next precursor compound using an
argon sweep at 30 mL/min and a vacuum pump. The substrate
temperature was kept at approximately 320.degree. C. throughout the
entire deposition process.
[0072] At the end of the pulsed CVD process, a 1375 .ANG. thick
mirror-like layer of tantalum silicon nitride was formed. The layer
contained about 54 atom % tantalum, 24 atom % nitrogen, 10 atom %
silicon, 8 atom % carbon and 4 atom % oxygen as determined by x-ray
photoelectron spectroscopy (XPS) analysis after a sputter time of 1
minute. X-ray diffraction analysis (XDA) showed the layer to be
amorphous, as measured immediately after the pulsed CVD process was
completed and also after annealing in nitrogen for 1 minute at
750.degree. C. Resistivity of the layer was 300 .mu..OMEGA.-cm,
before and after annealing for 1 minute at 750.degree. C.
[0073] The complete disclosures of the patents, patent documents,
and publications cited herein are incorporated by reference in
their entirety as if each were individually incorporated. Various
modifications and alterations to this invention will become
apparent to those skilled in the art without departing from the
scope and spirit of this invention. It should be understood that
this invention is not intended to be unduly limited by the
illustrative embodiments and examples set forth herein and that
such examples and embodiments are presented by way of example only
with the scope of the invention intended to be limited only by the
claims set forth herein as follows.
* * * * *