U.S. patent application number 12/140438 was filed with the patent office on 2008-10-09 for deposition apparatuses.
Invention is credited to Ronald A. Weimer.
Application Number | 20080245301 12/140438 |
Document ID | / |
Family ID | 37198715 |
Filed Date | 2008-10-09 |
United States Patent
Application |
20080245301 |
Kind Code |
A1 |
Weimer; Ronald A. |
October 9, 2008 |
Deposition Apparatuses
Abstract
The invention includes deposition methods and apparatuses which
can be utilized during atomic layer deposition or chemical vapor
deposition. A heated surface is provided between a stack of
semiconductor substrates and a precursor inlet, and configured so
that problematic side reactions occur proximate the heated surface
rather than proximate the semiconductor substrates. The precursor
inlet can be one of a plurality of precursor inlets, and the heated
surface can be one of a plurality of heated surfaces.
Inventors: |
Weimer; Ronald A.; (Boise,
ID) |
Correspondence
Address: |
WELLS ST. JOHN P.S.
601 W. FIRST AVENUE, SUITE 1300
SPOKANE
WA
99201
US
|
Family ID: |
37198715 |
Appl. No.: |
12/140438 |
Filed: |
June 17, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11127945 |
May 11, 2005 |
7407892 |
|
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12140438 |
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Current U.S.
Class: |
118/724 |
Current CPC
Class: |
C23C 16/45546 20130101;
C23C 16/45578 20130101; C23C 16/4557 20130101 |
Class at
Publication: |
118/724 |
International
Class: |
C23C 16/00 20060101
C23C016/00 |
Claims
1-28. (canceled)
29. A deposition apparatus comprising: a reaction chamber; a
substrate holder configured for retaining at least one
semiconductor substrate within the chamber; an inlet port
configured for injecting fluid into the reaction chamber, the inlet
port being a last port along a path of the injected fluid; a heated
surface within the reaction chamber and proximate the inlet port;
wherein the inlet port, the heated surface and the substrate holder
are configured such that the bulk flow of one or more precursors
into the reaction chamber is through the inlet port and directed by
the inlet port to interact with the heated surface prior to
reaching any substrate retained by the substrate holder; and
wherein the heated surface is a surface of a plate provided in the
reaction chamber between the inlet port and the substrate
holder.
30. The apparatus of claim 29 wherein the heated surface of the
plate curves at least partially around the inlet port.
31. (canceled)
32. A deposition apparatus comprising: a reaction chamber; a
substrate holder configured for retaining at least one
semiconductor substrate within the chamber; an inlet port
configured for injecting fluid into the reaction chamber, the inlet
port being a last port along a path of the injected fluid; a heated
surface within the reaction chamber and proximate the inlet port;
wherein the inlet port, the heated surface and the substrate holder
are configured such that the bulk flow of one or more precursors
into the reaction chamber is through the inlet port and directed by
the inlet port to interact with the heated surface prior to
reaching any substrate retained by the substrate holder; and
wherein: the inlet port is an orifice in sidewall of an inlet
nozzle; a tube substantially entirely surrounds the inlet nozzle
such that the inlet port directs the bulk flow of the one or more
precursors into a wall of the tube; the tube has at least one
opening extending therethrough into the chamber; and the wall of
the tube is the heated surface.
33. The apparatus of claim 29 wherein the substrate holder is
configured to retain a batch of two or more semiconductor wafers
within the reaction chamber.
34. A deposition apparatus, comprising: a reaction chamber; a
substrate holder configured for retaining a plurality of
semiconductor substrates within the chamber; a plurality of inlet
ports configured for injecting fluid into the reaction chamber, the
inlet ports each being a last port along a path of the injected
fluid that passes therethrough into the chamber; a plurality of
heated surfaces within the reaction chamber and proximate the inlet
ports; wherein the inlet ports, the heated surfaces and the
substrate holder are configured such that the bulk flow of one or
more precursors into the reaction chamber is through the inlet
ports and directed by the inlet ports to interact with the heated
surfaces prior to reaching substrates retained by the substrate
holder; and wherein the heated surfaces are surfaces of plates
provided in the reaction chamber between the inlet ports and the
substrate holder, the plates being in one-to-one correspondence
with the inlet ports.
35. A deposition apparatus, comprising: a reaction chamber; a
substrate holder configured for retaining at least one
semiconductor substrate within the chamber; an inlet port
configured for injecting fluid into the reaction chamber, the inlet
port being a last port along a path of the injected fluid; a heated
surface within the reaction chamber and proximate the inlet port;
wherein the inlet port, the heated surface and the substrate holder
are configured such that the bulk flow of one or more precursors
into the reaction chamber is through the inlet port and directed by
the inlet port to interact with the heated surface prior to
reaching any substrate retained by the substrate holder; and
wherein the heated surface is a surface of a plate provided in the
reaction chamber between the inlet port and the substrate holder,
the plate having a curved surface that extends only partially
around the inlet port.
Description
TECHNICAL FIELD
[0001] The invention pertains to deposition methods and to
deposition apparatuses. In particular aspects, the invention
pertains to atomic layer deposition methods and apparatuses, and/or
to chemical vapor deposition methods and apparatuses.
BACKGROUND OF THE INVENTION
[0002] Some background on ALD and CVD may assist the reader in
understanding the present disclosure. ALD is generally considered
to include processes in which precursors alternately react at an
exposed surface in a self-limiting manner with no direct
interaction except for the exposed surface. CVD is generally
considered to include processes in which one or more precursors
react above a surface to form a material that ultimately deposits
over the surface in a continuous deposition or not self-limiting
manner. However, the distinction between ALD and CVD processes
often blurs in actual applications so that processes that primarily
proceed by ALD may still have some CVD-type contribution.
[0003] Typically, ALD includes exposing an initial substrate to a
first chemical species 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, as further described below, chemisorption
might not occur on all portions of the substrate. Nevertheless,
such an imperfect monolayer is still a monolayer in the context of
this document. 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.
[0004] The first species is purged from over the substrate and a
second chemical species is provided to chemisorb onto 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. Also, a third species or more may be
successively chemisorbed and purged just as described for the first
and second species. It is noted that one or more of the first,
second and third species can be mixed with inert gas to speed up
pressure saturation within a reaction chamber.
[0005] 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, Ne, Kr, Xe, etc. Purging may instead
include contacting the substrate and/or monolayer with any
substance that allows chemisorption byproducts to desorb and
reduces the concentration of a species preparatory to introducing
another species. A suitable amount of purging can be determined
experimentally as known to those skilled in the art. Purging time
may be successively reduced to a purge time that yields an increase
in film growth rate. The increase in film growth rate might be an
indication of a change to a non-ALD process regime and may be used
to establish a purge time limit.
[0006] 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. The
various aspects of the present invention described herein are
applicable to any circumstance where ALD may be desired. It is
further noted that local chemical reactions can occur during ALD
(for instance, an incoming reactant molecule can displace a
molecule from an existing surface rather than forming a monolayer
over the surface). To the extent that such chemical reactions
occur, they are generally confined within the uppermost monolayer
of a surface.
[0007] Traditional ALD can occur within frequently-used ranges of
temperature and pressure and according to established purging
criteria to achieve the desired formation of an overall ALD layer
one monolayer at a time. Even so, ALD conditions can vary greatly
depending on the particular precursors, layer composition,
deposition equipment, and other factors according to criteria known
by those skilled in the art. Maintaining the traditional conditions
of temperature, pressure, and purging minimizes unwanted reactions
that may impact monolayer formation and quality of the resulting
overall ALD layer. Accordingly, operating outside the traditional
temperature and pressure ranges may risk formation of defective
monolayers.
[0008] The general technology of chemical vapor deposition (CVD)
includes a variety of more specific processes, including, but not
limited to, plasma enhanced CVD and others. CVD is commonly used to
form non-selectively a complete, deposited material on a substrate.
One characteristic of CVD is the simultaneous presence of multiple
species in the deposition chamber that react to form the deposited
material. Such condition is contrasted with the purging criteria
for traditional ALD wherein a substrate is contacted with a single
deposition species that chemisorbs to a substrate or previously
deposited species. An ALD process regime may provide a
simultaneously contacted plurality of species of a type or under
conditions such that ALD chemisorption, rather than CVD reaction
occurs. Instead of reacting together, the species may chemisorb to
a substrate or previously deposited species, providing a surface
onto which subsequent species may next chemisorb to form a complete
layer of desired material.
[0009] Deposition methods, such as, for example, atomic layer
deposition (ALD) and chemical vapor deposition (CVD) methods are
commonly utilized to form materials during semiconductor device
fabrication. The deposition methods can be conducted to process a
single semiconductor wafer at a time, or to process multiple
semiconductor wafers at one time. It can be desired to process a
batch of multiple semiconductor wafers in order to increase
throughput of a fabrication process, however, such can also lead to
difficulties in forming uniform thicknesses of material across the
semiconductor wafers.
[0010] FIGS. 1 and 2 illustrate an exemplary deposition apparatus
10 which can be utilized for either an ALD process or a CVD
process. Although FIGS. 1 and 2 are illustrating the same
apparatus, the method of illustration is different so that the
apparatus is shown in a more generalized manner in FIG. 2 than in
FIG. 1. For instance, FIG. 1 shows that the apparatus comprises a
cylindrical shape with a liner 17 contained within an outer wall
15; whereas FIG. 2 does not provide specific detail about the shape
of the apparatus or the presence of the liner. Although FIG. 1 has
more detail than FIG. 2, it is to be understood that FIG. 1 is
still a generalized diagram and that other features can be included
in addition to those shown in FIG. 1. For instance, heating coils
can be included in the apparatus.
[0011] The apparatus 10 comprises a reaction chamber 12 having a
plurality of semiconductor wafer substrates 14,16,18, 20 and 22
retained therein. Such substrates would be retained within a
substrate support structure which is not shown in the diagrammatic
views of FIGS. 1 and 2.
[0012] An inlet 24 and outlet 28 extend into the chamber 12. In
operation, precursor is flowed into the reaction chamber through
the inlet, and substances (for instance, reaction by-products,
unreacted precursor, etc.) are exhausted out of the reaction
chamber through the outlet. The precursor can be considered to flow
in a stream 30 (such stream can also be referred to as a bulk flow
of the precursor). Valves (not shown) can be provided to control
flow of matter into and out of the reaction chamber. Also, there
can be various pumps and other fluid-flow control devices (not
shown) associated with apparatus 10 for assisting in flowing matter
into and out of the reaction chamber.
[0013] In the exemplary apparatus of FIGS. 1 and 2, precursor flow
into the chamber is directed upwardly through the chamber along
lateral edges of the substrates 14, 16,18, 20 and 22. The precursor
then diffuses between the substrates (with such diffusion being
diagrammatically illustrated as flow of stream 30 over and between
the substrates in FIG. 2) and forms material (not shown in FIGS. 1
and 2) ultimately deposited over surfaces of the substrates
14,16,18, 20 and 22.
[0014] In CVD processes, it can be desired that a rate of reaction
of precursor to form deposited material be relatively slow so that
the material is relatively evenly distributed across surfaces of
substrates 14, 16, 18, 20 and 22 as the precursor mixture diffuses
over and between the substrates. In other words, it can be desired
that a rate of reaction of precursor to form deposited material be
optimal for the diffusion rate of the precursor over and between
the semiconductor wafer substrates. If the rate of reaction is too
fast, deposited material will build up much faster at the edges of
the substrates than at central locations of the substrates.
[0015] Due to the desire to have relatively slow formation of
deposited material, relatively slow reacting precursors will
typically be utilized in batch CVD processes. As an example, a
silicon nitride deposit can be formed utilizing dichlorosilane and
ammonia as precursors, or can be formed utilizing silane and
ammonia as precursors. If a single wafer is treated by a CVD
process, it will frequently be silane and ammonia utilized as
precursors, in that such are the fast-reacting precursors and
accordingly utilization of such precursors can increase throughput.
Alternatively, if a batch CVD process is utilized it will typically
be dichlorosilane and ammonia utilized as precursors in order to
enable a more uniform coating to be deposited across the multiple
substrates of the batch than could be achieved with the faster
reacting precursors.
[0016] Even if relatively slow reacting precursors are utilized,
there can be problems with the uniformity of deposition achieved
across a semiconductor wafer substrate surface during a batch CVD
process. For instance, FIG. 3 shows the semiconductor wafer
substrate 20 after a coating (in other words, deposited material)
50 has been formed across an upper surface of the substrate. The
substrate 20 can be considered to comprise a central region 21, and
an edge region 23 surrounding the central region. Dashed lines 25
are illustrated in FIG. 3 to diagrammatically represent boundaries
between the central region 21 and the edge region 23. The coating
50 is shown to be formed significantly thicker in the edge region
than in the central region. Such non-uniformity of deposition of
coating 50 can significantly complicate further processing.
[0017] FIGS. 4-7 describe a prior art method which has been
developed to address the problem illustrated in FIG. 3. Referring
initially to FIG. 4, such shows an assembly 63 comprising a
semiconductor wafer substrate 60 at a preliminary processing stage.
As will be known to persons of ordinary skill in the art, a
semiconductor wafer substrate can comprise any of numerous
semiconductor materials, and frequently will comprise, consist
essentially of, or consist of silicon. To aid in interpretation of
the claims that follow, the terms "semiconductive substrate" and
"semiconductor substrate" are defined to mean any construction
comprising semiconductive material, including, but not limited to,
bulk semiconductive materials such as a semiconductive wafer
(either alone or in assemblies comprising other materials thereon),
and semiconductive material layers (either alone or in assemblies
comprising other materials). The term "substrate" refers to any
supporting structure, including, but not limited to, the
semiconductive substrates described above.
[0018] The substrate 60 of assembly 63 is retained by support pins
61 joined to rails 59. The assembly 63 also includes a boat 62
(which can also be referred to as a ringboat) forming a physical
extension proximate the substrate, and supported by the pins 61.
The boat 62 will commonly comprise, consist essentially of, or
consist of quartz. The boat 62 and substrate 60 can be considered
to form a sub-assembly 58, which is shown in top view in FIG.
5.
[0019] A gap 65 is shown between the substrate 60 and boat 62 in
the views of FIGS. 4 and 5 to assist the reader in distinguishing
the boat from the substrate. In practice the boat can be provided
very close to the substrate, or even in contact with an edge of
substrate.
[0020] The top view of FIG. 5 shows that the semiconductor wafer
substrate 60 can comprise a circular configuration, and that the
boat 62 can be an annular ring provided around the substrate.
[0021] FIG. 6 shows the construction 58 after it has been subjected
to a batch CVD process of the type described with reference to FIG.
3. Such has formed the deposit 50 across an upper surface of
substrate 60, and across an upper surface of boat 62.
[0022] Referring next to FIG. 7, the boat 62 (FIG. 6) can be
removed to leave the substrate having a relatively uniform layer of
the deposit 50 thereon.
[0023] A problem with the processing of FIGS. 4-7 is that the boat
is an added expense and has a limited lifetime.
[0024] Problems similar to those discussed above with reference to
FIG. 3 occur in ALD processes. In theory, if processes were truly
entirely ALD such problems should not occur in that deposition
occurring during ALD should be self-limiting. Accordingly, deposits
should form as a single monolayer across a substrate surface, and
there should not be problems with build-up of deposit at edges of
the substrate. However, ALD processes frequently have a CVD-type
component, and such component can lead to the problematic edge
build-up comparable to the build-up discussed above with reference
to FIG. 3 for a CVD process.
[0025] Although the problems of FIG. 3 are discussed relative to
batch processes, it is to be understood that similar problems can
also occur in single wafer processes.
[0026] The problem of FIG. 3 is but one of several problems that
can occur during utilization of a deposition apparatus, such as the
exemplary apparatus of FIGS. 1 and 2. Another problem that can
occur is that precursor can become depleted within the flow 30 as
the flow migrates through the reaction chamber of the
apparatus.
[0027] It would be desirable to develop methods and apparatuses
which can alleviate, and preferably prevent, the edge build-up
problems discussed above with reference to FIG. 3 for CVD and ALD
processes. It would be further desirable to develop methods and
apparatuses which can address some of the other problems associate
with deposition processes, such as, for example, the problem of
precursor depletion that can occur in batch processes.
SUMMARY OF THE INVENTION
[0028] In one aspect, the invention includes a deposition method.
At least one semiconductor wafer substrate is provided within a
reaction chamber of a deposition apparatus. The semiconductor wafer
substrate is heated to a first temperature within the reaction
chamber. A surface is provided within the reaction chamber that is
heated to at least about the first temperature. The surface is
spaced from the semiconductor wafer substrate by a distance.
Deposition material is flowed toward the surface and thereafter
toward the semiconductor wafer substrate. The deposition material
interacts with the heated surface so that side reactions occur. The
side reactions generate one or more problematic products. The
distance between the heated surface and the semiconductor wafer
substrate is sufficient so that substantially none of the one or
more problematic products reaches the semiconductor wafer
substrate.
[0029] In one aspect, the invention encompasses another deposition
method. A deposition apparatus is provided which has one or more
semiconductor wafer substrates retained therein. The apparatus
includes a reaction chamber, an inlet port configured for injecting
fluid (specifically, a precursor-containing fluid) into the
reaction chamber, and a heated surface within the reaction chamber
and proximate the inlet port. The one or more semiconductor wafer
substrates are within the reaction chamber. The one or more
semiconductor wafer substrates are heated to a first temperature
within the apparatus. The heated surface is heated to a second
temperature which is at least about the same as the first
temperature. A bulk flow of one or more precursors is provided
through the inlet port and toward the heated surface, and
thereafter toward the one or more semiconductor wafer substrates.
The bulk flow of the one or more precursors interacts with the
heated surface for a sufficient time so that undesired side
reactions occur prior to the bulk flow migrating beyond the heated
surface toward the one or more semiconductor wafer substrates. In
some aspects, the inlet port is one of a plurality of inlet ports,
and the heated surface is one of a plurality of heated
surfaces.
[0030] In one aspect, the invention encompasses a deposition
apparatus. The apparatus includes a reaction chamber, a substrate
holder within the reaction chamber, an inlet port extending into
the reaction chamber, and a heated surface within the reaction
chamber and proximate the inlet port. The substrate holder is
configured for retaining at least one semiconductor substrate
within the chamber. The inlet port, the heated surface, and the
substrate holder are configured such that the bulk flow of one or
more precursors into the reaction chamber is through the inlet port
and directed by the inlet port to interact with the heated surface
prior to reaching any substrate retained by the substrate holder.
In some aspects, the inlet port is one of a plurality of inlet
ports, and the heated surface is one of a plurality of heated
surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Preferred embodiments of the invention are described below
with reference to the following accompanying drawings.
[0032] FIG. 1 is a diagrammatic, cross-sectional view of a prior
art deposition apparatus having a plurality of substrates retained
therein.
[0033] FIG. 2 is a more generalized, diagrammatic, cross-sectional
view of the prior art deposition apparatus of FIG. 1 having the
plurality of substrates retained therein.
[0034] FIG. 3 is a diagrammatic, cross-sectional view of a
semiconductor wafer substrate having a material deposited
thereover.
[0035] FIG. 4 is a diagrammatic, cross-sectional view of an
assembly comprising a semiconductor wafer substrate and a
ringboat.
[0036] FIG. 5 is a top view of a portion of the FIG. 4 assembly,
with a segment of the FIG. 4 cross-section being along the line 4-4
of FIG. 5.
[0037] FIG. 6 is a diagrammatic, cross-sectional view of a portion
of the FIG. 4 assembly shown at a processing stage after a deposit
has been formed over the substrate and ringboat.
[0038] FIG. 7 is a diagrammatic, cross-sectional view of the FIG. 6
assembly shown after removal of the ringboat.
[0039] FIG. 8 is a diagrammatic, cross-sectional view of a
deposition apparatus that can be utilized in accordance with an
aspect of the present invention, and which has a plurality of
semiconductor wafer substrates retained therein.
[0040] FIG. 9 is a diagrammatic, cross-sectional view of another
deposition apparatus that can be utilized in accordance with an
aspect of the present invention, and which has a semiconductor
wafer substrate retained therein.
[0041] FIG. 10 is a diagrammatic, cross-sectional view of another
deposition apparatus that can be utilized in accordance with an
aspect of the present invention, and which has a plurality of
semiconductor wafer substrates retained therein.
[0042] FIG. 11 is a diagrammatic, cross-sectional top view of
another exemplary deposition apparatus which can be utilized in
accordance with an aspect of the present invention, with the
apparatus being shown having a semiconductor substrate retained
therein.
[0043] FIG. 12 is a diagrammatic, cross-sectional top view of
another deposition apparatus which can be utilized in accordance
with another aspect of the present invention, with the apparatus
being shown having a semiconductor substrate retained therein.
[0044] FIG. 13 is a diagrammatic, cross-sectional side view of the
deposition apparatus of FIG. 12.
[0045] FIG. 14 is a diagrammatic, cross-sectional top view of
another deposition apparatus which can be utilized in accordance
with an aspect of the present invention, with the apparatus being
shown having a semiconductor substrate retained therein.
[0046] FIG. 15 is a diagrammatic, cross-sectional top view of
another deposition apparatus which can be utilized in accordance
with an aspect of the present invention, with the apparatus being
shown having a semiconductor substrate retained therein.
[0047] FIG. 16 is a diagrammatic, cross-sectional side view of the
deposition apparatus of FIG. 15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0048] This disclosure of the invention is submitted in furtherance
of the constitutional purposes of the U.S. Patent Laws "to promote
the progress of science and useful arts" (Article 1, Section
8).
[0049] The invention includes incorporation of at least one heated
surface into a deposition chamber so that injected fluids interact
with the heated surface prior to reaching semiconductor wafer
substrates. The semiconductor wafer substrates are heated to
conventional temperatures for a deposition process, and the heated
surface is heated to at least about the temperature of the
semiconductor wafer substrates. Specifically, the heated surface is
heated to a sufficient temperature so that undesired thermal
reactions that would occur proximate the heated substrates instead
occur proximate the heated surface. Thus, the reference to the
heated surface being heated to "at least about the temperature of
the semiconductor substrates" (or alternatively, at least
approximately the temperature of the semiconductor substrates) is
used to indicate that the heated surface is heated to a sufficient
temperature to induce thermal reactions that would otherwise be
induced by the heated substrates.
[0050] The fluids injected into the reaction chamber would
typically be gases, and would typically include one or more
precursors mixed with carrier gas. The heated surface can be any
suitable material, and in particular aspects will comprise ceramic
material or metallic material. Although methods and apparatuses of
the present invention can be utilized with single wafer tools or
batch reactors, it can be particularly advantageous to incorporate
aspects of the present invention into applications utilizing batch
reactors. The invention can be utilized with either CVD processes
or ALD processes, and can be utilized to reduce or alleviate the
deposition non-uniformity discussed above with reference to FIG.
3.
[0051] In particular aspects, the invention is utilized with ALD
processes to improve uniformity of deposition. As discussed
previously, the non-uniformity of deposition of the type discussed
above with reference to FIG. 3 should theoretically not occur with
a pure ALD process. Instead, the process should be self-limiting so
that a monolayer is formed across all reactive surfaces exposed to
ALD precursor. In practice, however, it is found that many ALD
processes have a CVD component, and accordingly the thickness
variation discussed above with reference to FIG. 3 is found to
occur in ALD processes.
[0052] The CVD problem in the ALD processes can have numerous
causes, including, for example, insufficient pumps/purges, gas
decomposing prior to getting to a wafer, contaminants present
within ALD precursor gases, and/or by-products of the ALD
reaction.
[0053] In typical deposition processes, substrate surfaces are
heated to a temperature exceeding the average temperature within a
deposition apparatus. One aspect of the invention is a recognition
that the CVD aspects of ALD processes appear to be thermally
induced as precursor materials encounter heated substrate surfaces.
Exemplary aspects of the invention include provision of at least
one heated surface within the reaction chamber along the precursor
flow path and upstream of the substrate surfaces. The heated
surface is utilized to thermally induce problematic reactions
upstream of the semiconductor substrates, and to substantially or
entirely exhaust the precursor stream of problematic components
before the stream reaches the semiconductor substrates.
[0054] Aspects of the present invention can significantly reduce
CVD-type problems in particular types of ALD applications. For
instance, if the CVD-type problems result from precursor materials
decomposing when exposed to a heat associated with semiconductor
wafers, the methodologies of the present invention can
significantly reduce the CVD-type problems. Also, if the CVD-type
problems result from contaminants present in ALD precursor gases,
the methodologies of the present invention can significantly reduce
the CVD-type problems.
[0055] Exemplary ALD precursors which can have undesired CVD-type
side reactions leading to material build-up are
tetrakis(dimethylamido)hafnium (TDMAH),
tetrakis(ethylmethylamino)hafnium (TEMAH) and
tetrakis(methylethylamino)hafnium (TMEAH), which are commonly used
for deposition of hafnium. Such precursors can react with a heated
semiconductor wafer substrate to form a hafnium-containing
component, and to form one or more other components that may
undergo CVD-type reactions. The hafnium-containing component can
interact with the semiconductor wafer substrate surface to form a
desired ALD deposit on such surface, and simultaneously the other
components can undergo CVD-type reactions to form additional
deposit that accumulates over the surface. Such additional deposit
can accumulate faster over edges of the substrate than over a
central region of the substrate to lead to the problem discussed
above with reference to FIG. 3. In a particular aspect of the
present invention, a heated surface is provided proximate a
precursor inlet so that CVD-type side reactions occur at a suitable
distance from the semiconductor wafer substrates such that any
problematic products from the CVD-type side reactions do not reach
the semiconductor wafer substrates, or at least so that
substantially all of the problematic products do not reach the
semiconductor wafer substrates (with the term "substantially all"
meaning that the amount of problematic product is significantly
reduced, and in some aspects can mean that there is no detectable
problematic product reaching the semiconductor wafer
substrates).
[0056] In other aspects of the invention, a precursor which
generally undergoes purely ALD-type reactions is contaminated with
another precursor which undergoes CVD-type reactions. The ALD-type
reactions and CVD-type reactions are enhanced when the precursor
mixture reaches the heated environment of the semiconductor wafer
substrate surfaces within a reaction chamber. Accordingly, the
CVD-type reactions occurring from the contaminant form deposits
proximate the semiconductor wafer substrates, and such deposits can
have the non-uniformity of deposition discussed above with
reference to FIG. 3. In such aspects, the present invention can
comprise provision of a heated surface proximate the precursor
inlet so that the CVD-type side reactions occur at the heated
surface and at a sufficient distance from the semiconductor wafer
substrates so that problematic products produced by such side
reactions do not reach the semiconductor wafer substrates.
[0057] Although the specific aspects of the invention have been
described thus far with reference to ALD processes, it is to be
understood that the invention can also have application to CVD
processes. For instance, a CVD reactant that undergoes a desired
slow reaction to form a deposit can be contaminated with another
reactant that undergoes a fast reaction to form the deposit, and
the contaminant can increase the problematic effect discussed above
with reference to FIG. 3.
[0058] An exemplary CVD process is discussed above in the
Background section of this disclosure as a process utilizing
dichlorosilane and ammonia to form silicon nitride in CVD processes
utilizing batch reactors. As also discussed above, it is frequently
not desired to utilize silane and ammonia to form silicon nitride
in batch reactors due to the silane reacting too fast with the
ammonia and thereby causing too much of the effect discussed with
reference to FIG. 3.
[0059] If the relatively slow reacting CVD material dichlorosilane
is contaminated with the relatively fast reacting material silane,
the problem of FIG. 3 will occur during the formation of silicon
nitride from the contaminated material. Accordingly, there will be
a large excess of silicon nitride formed at edges of treated
semiconductor substrates relative to the amount formed in central
regions of the semiconductor substrates.
[0060] The substrates within a chamber are typically heated, and
the temperature within the majority of the reaction chamber is low
enough so that CVD reactions occur primarily proximate the heated
substrates. The problematic CVD reactions are thus thermally
accelerated by the heated substrates.
[0061] In some aspects of the present invention, a heated surface
is provided proximate a precursor inlet in a CVD reactor so that
contaminating materials are thermally activated to react at the
heated surface to produce problematic products. The heated surface
is provided to be an appropriate distance from semiconductor wafer
substrates so that the problematic products do not reach the
semiconductor wafer substrates, or at least so that substantially
none of the problematic products reach the semiconductor wafer
substrates. If multiple precursor inlets are present in a
particular reaction chamber design, multiple heated surfaces can be
provided so that some, and in some aspects all, of the precursor
inlets have a heated surface paired therewith.
[0062] Specific reactor designs which can be utilized in accordance
with various exemplary aspects of the present invention are
described with reference to FIGS. 8-16.
[0063] Referring to FIG. 8, a deposition apparatus 100 configured
in accordance with an aspect of the present invention is
illustrated. Similar numbering will be utilized in describing the
apparatus 100 as was utilized in describing the prior art apparatus
of FIGS. 1 and 2, where appropriate.
[0064] The apparatus 100 comprises the reaction chamber 12
described previously, and comprises semiconductor wafer substrates
14, 16, 18, 20 and 22 retained therein. The substrates would be
retained with a substrate holder (not shown). The shown apparatus
is a batch reactor, and accordingly is configured for treating a
plurality of semiconductor wafer substrates simultaneously. It is
to be understood, however, that aspects of the invention can also
be applied to deposition methods utilizing apparatuses configured
for single wafer treatment rather than batch wafer treatment.
[0065] The inlet 24 and outlet 28 are shown extending through
sidewalls of the reaction chamber. The opening of the inlet from
which precursor enters the chamber can be referred to as an inlet
port. In operation, a stream 30 of deposition material (i.e., one
or more deposition precursors) is flowed into the reaction chamber
through the inlet, and reaction by-products as well as unreacted
precursor are exhausted from the chamber through outlet 28.
[0066] The apparatus 100 of FIG. 8 differs from the apparatus 10 of
FIGS. 1 and 2 in that a plate 102 is provided in front of the port
of inlet 24. Accordingly, the deposition material first flows into
contact with the plate, and then flows around the plate into the
reaction chamber.
[0067] In a typical operation, the semiconductor wafer substrates
14,16,18 20 and 22 would be heated to a first temperature during a
deposition process. The plate 102 would be heated to a temperature
which is at least about the first temperature. The plate 102 has a
surface 103 facing the inlet 24, and deposition material injected
from the inlet port would impact the heated surface 103. Upon
impact with the heated surface 103, various side reactions can
occur within the deposition material. For instance, if the
deposition material is an ALD precursor having contaminants therein
which undergo CVD-type side reactions at the temperature of the
substrates 14, 16, 18, 20 and 22, such side reactions can occur
when the precursor impacts surface 103. The side reactions will
generate one or more problematic products. However, the distance
from heated surface 103 to substrates 14, 16, 18, 20 and 22 is
preferably sufficient so that substantially none of the problematic
products reach the semiconductor substrates. Rather, the
problematic products either fall out of the deposition material and
onto a bottom of the reaction chamber, or form a deposit along the
surface 103 of the heated plate.
[0068] In some aspects, the side reactions can occur not because of
contaminants, but rather because an ALD precursor breaks down upon
reaching surface 103 to form a first component which undergoes
CVD-type reactions and a second component which will undergo
ALD-type reactions. The component which undergoes ALD-type
reactions can flow around the heated plate and toward the
substrates 14, 16, 18, 20 and 22; whereas the component which
undergoes CVD-type reactions will undergo such reactions proximate
the plate to form problematic products which never reach the
substrates 14, 16, 18, 20 and 22.
[0069] In another aspect, the deposition material which enters the
reaction chamber in stream 30 can include a CVD precursor which
undergoes a relatively slow CVD-type reaction, and a contaminating
precursor which undergoes a relatively rapid CVD-type reaction. The
contaminant can react upon being heated by surface 103 to form a
problematic product which then falls out of the bulk stream 30 of
deposition material so that the remaining stream is relatively pure
in the CVD-precursor that undergoes relatively slow reaction by the
time the stream of deposition material reaches substrates 14, 16,
18, 20 and 22.
[0070] The distance between plate 102 and the port of inlet 24 can
be any suitable distance. In some aspects, it can be desired that
the material impacting the surface 103 and flowing around the plate
be traveling at about a diffusion rate of the material. Thus, the
rate of migration of the material across the heated surface 103
will approximately match the rate that the material will diffuse
across heated surfaces of substrates 14,16,18, 20 and 22. Any
problematic side reactions that would occur due to the deposition
material flowing across substrates 14,16,18, 20 and 22 will then
have already occurred due to the material flowing across the
surface 103.
[0071] If the amount of problematic reactant within the deposition
material is limited (such as, for example, if the reactant is a
contaminant, or is a thermally-generated breakdown by-product
resulting from the deposition material reaching a temperature of
the substrates) the problematic reactant will be removed from
stream 30 before the stream reaches substrates 14,16, 18, 20 and
22. Further, the distance between plate 102 and the substrates is
preferably sufficient so that any problematic products generated
near the plate do not reach the substrates. In some aspects, the
distance between the plate and substrates is sufficient so that any
reactant by-products generated by thermal breakdown of precursor
proximate the plate 102 have time to react with one another and
form products prior to reaching the substrates, and also so that
such products have time to fall out of the flow 30 of deposition
material prior to the flow reaching the substrates.
[0072] In some aspects, the flow of deposition material can be
considered to be a bulk flow 30 of one or more precursors. The
configuration of FIG. 8 can be considered to allow one or more
precursors within such bulk flow to interact with heated surface
103 so that undesired side reactions occur prior to the bulk flow
migrating beyond the heated surface toward the semiconductor wafer
substrates 14, 16,18,20 and 22.
[0073] The configuration of FIG. 8 is but one of numerous suitable
configurations for orienting a heated surface proximate an inlet
port within a deposition apparatus. Another exemplary aspect of the
invention is described with reference to FIG. 9.
[0074] FIG. 9 shows an apparatus 101 in cross-sectional side view,
and shows a semiconductor wafer substrate 22 retained within the
apparatus. Apparatus 101 comprises a pair of inlets 24 and 25, and
comprises an outlet 28. The apparatus also comprises a pair of
heated plates 102 and 105, with the heated plate 102 being in front
of a port of inlet 24, and the heated plate 105 being in front of a
port of inlet 25. The heated plates 102 and 105 can be considered
to be paired with inlets 24 and 25, respectively. The heated plates
102 and 105 can be the same size and composition as one another, or
can differ from one another in one or both of size and
composition.
[0075] The plates 102 and 105 of apparatus 101 can be used
identically to the plate 102 of the FIG. 8 apparatus 100.
Accordingly, plates 102 and 105 can be heated to temperatures at
least approximately that of substrate 22, and be spaced from
substrate 22 by a sufficient distance so that the plates can be
utilized to substantially prevent problematic by-products and
contaminants of deposition precursors from reaching substrate
22.
[0076] Yet another exemplary aspect of the invention is described
with reference to FIG. 10 which shows an apparatus 107 in
cross-sectional side view, and which shows semiconductor wafer
substrates 14, 16, 18, 20 and 22 retained within the apparatus.
[0077] Apparatus 107 comprises a plurality of inlets 24, 25, 27,
29, 31 and 33; and comprises a plurality of outlets 28, 111, 113,
115 and 117. The number of outlets can be the same as the number of
inlets, or different. In some aspects, multiple inlets can be
provided together with only one outlet.
[0078] A plurality of heated plates 102, 105, 119, 121, 123 and 125
are in front of the inlets; and a plurality of baffles 109 (which
can be dummy substrates having the size of the semiconductor wafers
but formed of a different composition) are between the substrates.
The heated plates 102, 105, 119, 121, 123 and 125 can be the same
size and composition as one another, or at least some of them can
differ from others in size and/or composition. Also, the baffles
109 can be the same size and composition as one another, or at
least some of them can differ from others in size and/or
composition.
[0079] The plates 102, 105, 119, 121, 123 and 125 of apparatus 107
can be used identically to the plate 102 of the FIG. 8 apparatus
100. Accordingly, plates 102, 105, 119, 121, 123 and 125 can be
heated to temperatures at least approximately that of the
substrates, and be spaced from the substrates by sufficient
distances so that the plates can be utilized to substantially
prevent problematic by-products and contaminants of deposition
precursors in stream 30 from reaching the substrates. The use of
multiple inlets (i.e., injection ports) can alleviate or even
prevent prior art problems of precursor depletion that occur when
only single inlets are utilized in batch reactors. The baffles 109
are optional, but can assist in directing flow of precursor around
the substrates.
[0080] Yet another exemplary aspect of the invention is described
with reference to FIG. 11 which shows an apparatus 127 in
cross-sectional top view, and which shows a semiconductor wafer
substrate 22 retained within the apparatus.
[0081] Apparatus 127 comprises an inlet 24 and an outlet 28. The
apparatus also comprises a heated plate 102 in front of the inlet,
and comprises heating elements 129 around the substrate. The
heating elements heat the substrate to a temperature, and the
heated plate is preferably at a temperature equal to or greater
than the temperature of the substrates so that the plate can be
utilized for substantially preventing problematic by-products and
contaminants of deposition precursors in stream 30 from reaching
the substrate.
[0082] Yet another exemplary aspect of the invention is described
with reference to FIGS. 12 and 13, which show an apparatus 150 in
cross-sectional top view, and cross-sectional side view,
respectively. The apparatus includes a reaction chamber 12 having
an internal sidewall 151. A substrate holder 159 is within the
apparatus, and semiconductor substrates 14, 16, 18, 20 and 22 are
retained within the holder. An inlet 152 is within the reaction
chamber and has a plurality of ports 154 therein. The inlet is
configured so that a flow of one of more precursors in a stream 30
is directed toward the sidewall 151. The sidewall can be heated,
and accordingly can correspond to a heated surface having a
function analogous to the function discussed above with reference
to the surface 103 of plate 102.
[0083] FIG. 14 shows a cross-sectional top view of a deposition
apparatus 160 having a configuration similar to that of the
apparatus 150 of FIG. 12. The apparatus 160 comprises a reaction
chamber 12. A substrate holder 169 is within the apparatus, and a
semiconductor wafer substrate 22 is shown retained within the
holder. The apparatus 160 comprises an inlet tube 162 having a port
164 extending therein. Further, the apparatus 160 also comprises a
heated plate 166 in front of the port 164. The shown plate 166 is a
curved plate that extends partially around the inlet tube 162. In
other aspects (not shown) the plate 166 can extend entirely around
the inlet tube. If the plate 166 extends entirely around the inlet
tube, the plate can have an opening at the bottom and/or top so
that precursor can flow past the plate. Alternatively, or
additionally, the plate can have various openings formed therein so
that the precursor can penetrate the plate, and in some aspects,
the plate can comprise at least a portion which is a screen that
allows precursor to flow therethrough.
[0084] A stream 30 of precursor is shown being directed toward the
plate 166 from the inlet port 164. The stream then migrates around
the plate, and toward the semiconductor wafer substrate 22. Plate
166 can function analogously to the plate 102 of FIG. 8 to permit
undesired side reactions of materials within stream 30 to occur
prior to flow of the stream 30 to substrate 22.
[0085] FIGS. 15 and 16 show a deposition apparatus 170 illustrating
another aspect of the invention. The apparatus 170 comprises a
reaction chamber 12. A substrate holder 179 is within the
apparatus, and a semiconductor wafer substrate 22 is shown retained
within the holder. An inlet tube 172 is within the chamber, and the
inlet tube comprises ports 174. The inlet tube can be considered an
inlet nozzle, and the inlet ports are orifices in a sidewall of
such nozzle. A tube 176 entirely surrounds the inlet nozzle such
that the inlet nozzle directs deposition material within stream 30
to contact a wall of the tube 176. The tube 176 has at least one
orifice 178 extending therethrough. In operation, the stream 30 of
deposition material circulates within the inside of the tube 176,
and then exits from the tube through the orifices 178 to migrate
toward substrates 14, 16, 18, 20 and 22. Tube 176 can be heated,
and an interior surface of the tube can then function analogously
to the surface 103 of FIG. 8 to enable side reactions of materials
within stream 30 to occur prior to the stream migrating to the
substrates.
[0086] The tube 176 can extend entirely around the inlet nozzle, or
can extend substantially entirely around the inlet nozzle. Also,
the tube can have a single orifice 178 therethrough, a few orifices
extending therethrough, or in some aspects the tube can comprise at
least a portion which is a screen and accordingly can have many
orifices therethrough for exit of precursor stream 30.
[0087] Among the advantages of the apparatuses and methods of the
present invention relative to the prior art apparatuses and methods
discussed above with reference to FIGS. 4-7, are that the boats 62
tend to be expensive and are a consumed material. In contrast,
reaction chamber modification to accomplish the methods of the
present invention can be done economically. Also, the heated
surfaces utilized in methodologies of the present invention may
last much longer than the boats utilized in the prior art
methodologies.
[0088] In compliance with the statute, the invention has been
described in language more or less specific as to structural and
methodical features. It is to be understood, however, that the
invention is not limited to the specific features shown and
described, since the means herein disclosed comprise preferred
forms of putting the invention into effect. The invention is,
therefore, claimed in any of its forms or modifications within the
proper scope of the appended claims appropriately interpreted in
accordance with the doctrine of equivalents.
* * * * *