U.S. patent application number 15/050728 was filed with the patent office on 2016-06-16 for gas injection system for chemical vapor deposition using sequenced valves.
This patent application is currently assigned to Veeco Instruments, Inc.. The applicant listed for this patent is Veeco Instruments, Inc.. Invention is credited to Eric A. Armour, William E. Quinn.
Application Number | 20160168710 15/050728 |
Document ID | / |
Family ID | 46234763 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160168710 |
Kind Code |
A1 |
Quinn; William E. ; et
al. |
June 16, 2016 |
Gas Injection System For Chemical Vapor Deposition Using Sequenced
Valves
Abstract
A gas injection system for a chemical vapor deposition system
includes a gas manifold comprising a plurality of valves where each
of the plurality of valves has an input that is coupled to a
process gas source and an output for providing process gas. Each of
a plurality of gas injectors has an input that is coupled to the
output of one of the plurality of valves and an output that is
positioned in one of a plurality of zones in a chemical vapor
deposition reactor. A controller having a plurality of outputs
where each of the plurality of outputs is coupled to a control
input of one of the plurality of valves. The controller instructs
at least some of the plurality of valves to open at predetermined
times to provide a desired gas flow to each of the plurality of
zones in the chemical vapor deposition reactor.
Inventors: |
Quinn; William E.;
(Whitehouse Station, NJ) ; Armour; Eric A.;
(Pennington, NJ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Veeco Instruments, Inc. |
Plainview |
NY |
US |
|
|
Assignee: |
Veeco Instruments, Inc.
Plainview
NY
|
Family ID: |
46234763 |
Appl. No.: |
15/050728 |
Filed: |
February 23, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12972270 |
Dec 17, 2010 |
9303319 |
|
|
15050728 |
|
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Current U.S.
Class: |
427/9 ;
427/255.28; 427/8 |
Current CPC
Class: |
C23C 16/18 20130101;
C23C 16/52 20130101; C23C 16/45561 20130101; C23C 16/45574
20130101 |
International
Class: |
C23C 16/52 20060101
C23C016/52; C23C 16/18 20060101 C23C016/18; C23C 16/455 20060101
C23C016/455 |
Claims
1-19. (canceled)
20. A method of gas injection into a chemical vapor deposition
system, the method comprising: a) providing a process gas to inputs
of a plurality of valves; b) providing the process gas from outputs
of the plurality of valves to a plurality of gas injectors
positioned in a plurality of zones in a chemical vapor deposition
reactor; c) determining desired duty cycles for opening each of the
plurality of valves that provide a desired amount of process gas to
each of the plurality of zones in the chemical vapor deposition
reactor; and d) opening each of the plurality of valves for their
desired duty cycle, thereby providing the desired amount of process
gas to each of the plurality of zones in the chemical vapor
deposition reactor for deposition.
21. The method of claim 20 wherein the process gas comprises an
alkyl gas.
22. The method of claim 20 further comprising measuring at least
one of growth rate and deposited film thickness during
deposition.
23. The method of claim 22 wherein the measurements comprise
in-situ reflection measurements.
24. The method of claim 20 further comprising measuring at least
one of growth rate and deposited film thickness in at least two of
the plurality of zones during deposition and adjusting a duty cycle
for opening at least one of the plurality of valves in response to
the measurements.
25. The method of claim 24 wherein the duty cycle is adjusted to
improve the uniformity of the deposited film across at least two of
the plurality of zones.
26. The method of claim 24 wherein at least one of the growth rate
and the deposited film thickness is measured across the plurality
of zones in a radial direction.
27. The method of claim 20 wherein the duty cycle for opening at
least one of the plurality of valves is inversely proportional to a
radius of the corresponding one of the plurality of zones.
28. The method of claim 20 wherein at least one of the plurality of
valves is opened sequentially and at least one of the plurality of
valves is continuously open during deposition.
29. The method of claim 20 wherein all of the plurality of valves
are opened sequentially.
30. The method of claim 20 further comprising moving at least some
of the plurality of gas injectors.
31. The method of claim 20 further comprising changing a dimension
of an orifice of one of the plurality of gas injectors.
32. The method of claim 20 wherein a dimension of the orifice of
one of the plurality of gas injectors is changed in response to at
least one of a growth rate and a deposited film thickness
measurement in at least one of the plurality of zones in the
chemical vapor deposition reactor.
33. A method of improving deposition rate uniformity in a chemical
vapor deposition system, the method comprising: a) providing an
alkyl process gas to inputs of a plurality of valves; b) providing
the alkyl process gas from outputs of the plurality of valves to a
plurality of alkyl gas injectors positioned in a plurality of zones
in a chemical vapor deposition reactor; c) determining a duty cycle
for opening at least one of the plurality of valves that provides
an amount of alkyl process gas to a corresponding one of the
plurality of alkyl gas injectors that improves deposition rate
uniformity; and a) opening at least one of the plurality of valves
for the determined duty cycle, thereby providing an amount of alkyl
process gas to at least one of the plurality of zones in the
chemical vapor deposition reactor that improves deposition rate
uniformity.
34. The method of claim 33 further comprising measuring at least
one of growth rate and deposited film thickness in at least two of
the plurality of zones during deposition and adjusting a duty cycle
for opening at least one of the plurality of valves in response to
the measurements to further improve the uniformity of the deposited
film across at least two of the plurality of zones.
35. The method of claim 34 wherein the at least one of the growth
rate and the deposited film thickness is measured across the
plurality of zones in the radial direction.
36. The method of claim 33 wherein at least one of the plurality of
valves is opened sequentially and at least one of the plurality of
valves is continuously open during deposition.
37. The method of claim 33 wherein all of the plurality of valves
are opened sequentially.
38. The method of claim 33 further comprising moving at least some
of the plurality of gas injectors.
39. The method of claim 33 further comprising changing a dimension
of an orifice of at least one of the plurality of gas injectors to
improve uniformity.
Description
[0001] The section headings used herein are for organizational
purposes only and should not to be construed as limiting the
subject matter described in the present application in any way.
INTRODUCTION
[0002] Chemical vapor deposition involves directing one or more
gases containing chemical species onto a surface of a substrate so
that the reactive species react and form a film on the surface of
the substrate. For example, CVD can be used to grow compound
semiconductor material on a crystalline semiconductor substrate.
Compound semiconductors, such as III-V semiconductors, are commonly
formed by growing various layers of semiconductor materials on a
substrate using a source of a Group III metal and a source of a
Group V element. In one CVD process, sometimes referred to as a
chloride process, the Group III metal is provided as a volatile
halide of the metal, which is most commonly a chloride, such as
GaCl.sub.3, and the Group V element is provided as a hydride of the
Group V element.
[0003] One type of CVD is known as metal organic chemical vapor
deposition (MOCVD), which is sometimes called organometallic
vapor-phase epitaxy (OMVPE). MOCVD uses chemical species that
include one or more metal-organic compounds, such as alkyls of the
Group III metals, such as gallium, indium, and aluminum. MOCVD also
uses chemical species that include hydrides of one or more of the
Group V elements, such as NH.sub.3, AsH.sub.3, PH.sub.3 and
hydrides of antimony. In these processes, the gases are reacted
with one another at the surface of a substrate, such as a substrate
of sapphire, Si, GaAs, InP, InAs or GaP, to form a III-V compound
of the general formula
In.sub.XGa.sub.YAl.sub.ZN.sub.AAs.sub.BP.sub.CSb.sub.D, where X+Y+Z
equals approximately one, and A+B+C+D equals approximately one, and
each of X, Y, Z, A, B, and C can be between zero and one. In some
instances, bismuth may be used in place of some or all of the other
Group III metals.
[0004] Another type of CVD is known as Halide Vapor Phase Epitaxy
(also known as HVPE). HVPE processes are used to deposit Group III
nitrides (e.g., GaN, AlN, AlN, and AlGaN) and other semiconductors
(e.g. GaAs, InP and their related compounds). These materials are
formed with Group III elements arranged as metals and supplied to a
substrate through a hydrogen halide. The hot gaseous metal
chlorides (e.g., GaCl or AlCl) are reacted with ammonia gas
(NH.sub.3) or hydrogen. The metal chlorides are generated by
passing hot HCl gas over the hot Group III metals. All reactions
are done in a temperature controlled quartz furnace. One feature of
HVPE is that it can have a very high growth rate, that is up to or
greater than 100 .mu.m per hour for some state-of-the-art
processes. Another feature of HVPE is that it can be used to
deposit relatively high quality films because films are grown in a
carbon-free environment and because the hot HCl gas provides a
self-cleaning effect.
[0005] Rotating disk reactors are commonly used for CVD processing.
Rotating disk reactors inject one or more gases onto the surface of
a rotating substrate to grow epitaxial layers thereon. One type of
rotating disk reactor is a vertical high-speed rotating disk
reactor. The gas or gases in these reactors are injected downwardly
onto a surface of a substrate that is rotating within the reactor.
Vertical high-speed rotating disk reactors are frequently used for
CVD and MOCVD growth. These reactors have been used for growing a
wide variety of epitaxial compounds, including various combinations
of semiconductor single films and multilayered structures such as
lasers and LED'S.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The present teaching, in accordance with preferred and
exemplary embodiments, together with further advantages thereof, is
more particularly described in the following detailed description,
taken in conjunction with the accompanying drawings. The skilled
person in the art will understand that the drawings, described
below, are for illustration purposes only. The drawings are not
necessarily to scale, emphasis instead generally being placed upon
illustrating principles of the teaching. The drawings are not
intended to limit the scope of the Applicants' teaching in any
way.
[0007] FIG. 1 illustrates a schematic diagram of a multi-zone
alkyls injection system for an MOCVD rotating disc reactor that
adjusts the reactant gas flow of each zone individually.
[0008] FIG. 2 illustrates a schematic diagram of a multi-zone
alkyls injection system according to the present invention for a
CVD rotating disc reactor that includes a single alkyls gas source
coupled to a gas manifold comprising a plurality of valves.
[0009] FIG. 3 illustrates a schematic diagram of another multi-zone
alkyls injection system 300 according to the present invention for
a CVD rotating disc reactor that is similar to the multi-zone
alkyls injection system that was described in connection with FIG.
2, but that also includes a second gas manifold comprising a
plurality of valves for controlling the flow of the push
gasses.
DESCRIPTION OF VARIOUS EMBODIMENTS
[0010] Reference in the specification to "one embodiment" or "an
embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment of the teaching. The
appearances of the phrase "in one embodiment" in various places in
the specification are not necessarily all referring to the same
embodiment.
[0011] It should be understood that the individual steps of the
methods of the present teachings may be performed in any order
and/or simultaneously as long as the teaching remains operable.
Furthermore, it should be understood that the apparatus and methods
of the present teachings can include any number or all of the
described embodiments as long as the teaching remains operable.
[0012] The present teaching will now be described in more detail
with reference to exemplary embodiments thereof as shown in the
accompanying drawings. While the present teaching is described in
conjunction with various embodiments and examples, it is not
intended that the present teaching be limited to such embodiments.
On the contrary, the present teaching encompasses various
alternatives, modifications and equivalents, as will be appreciated
by those of skill in the art. Those of ordinary skill in the art
having access to the teaching herein will recognize additional
implementations, modifications, and embodiments, as well as other
fields of use, which are within the scope of the present disclosure
as described herein.
[0013] The present teaching relates to a gas injection system for
CVD systems, such as rotating disc reactors. One skilled in the art
will appreciate that the methods and apparatus of the present
invention can be applied to any type of CVD system and are not
limited to only rotating disk reactors. In vertical high-speed
rotating disk reactors, one or more injectors are spaced above a
substrate or workpiece carrier to provide a predetermined gas flow,
which upon contact with the substrate, deposits layers of epitaxial
material on the surface of the substrate. Such, rotating disk
reactors for growing epitaxial material on larger wafers typically
include several injectors spaced above the substrate. The injectors
are usually spaced above the substrate in various positions along
one or more radial axes of the substrate, relative to the central
axis of the substrate carrier.
[0014] Growth uniformity is achieved only if growth parameters are
linearly distributed across the reactor. The gas injectors can be
designed to provide a uniform reactant gas distribution across the
reactor. In some rotating disk reactors, the rate of source
reactant material injected into the reactor varies from injector to
injector. Some reactant injectors may be designed and operated to
provide different gas flow velocities than other reactant injectors
in order to achieve a uniform molar quantity of reactant material
along the surface of the substrate. This variation in reactant flow
rate/velocity is necessary in order to achieve a uniform molar
quantity of reactant material along the entire surface of the
substrate. The variation in reactant flow rate/velocity is
necessary because of the relative placement of the reactant
injectors. In particular, the injectors near the outer edge of the
carrier inject gas over a larger surface area on the carrier than
the injectors closer to the center of the carrier in any given time
period. Consequently, the outer injectors typically are designed
and operated to have a greater reactant gas flow rate than the
inner injectors in order to maintain the desired uniformity. In
some rotating disk reactors, the reactant gas flow rates of the
outer most injectors are adjusted to be as much as a factor of
three to four higher than the reactant gas flow rates of the inner
most injectors.
[0015] In multi-zone alkyls injector systems, the deposition
uniformity is provided by adjusting the alkyls gas flow for each
zone individual flow. FIG. 1 illustrates a schematic diagram of a
multi-zone alkyls injection system 100 for an MOCVD rotating disc
reactor 102 that adjusts the reactant gas flow of each zone
individually. The injection system 100 is shown with three separate
zones 104, 106, and 108 positioned in a radial direction. Each of
the three separate zones 104, 106, and 108 includes separate
Alkyls, and two push flow gas mass flow controllers 110. In the
example shown, nitrogen and hydrogen push flow gases are used to
control the flow dynamics. The use of three separate mass flow
controllers for each zone significantly limits the number of zones
that can be employed in a practical system to a relatively small
number.
[0016] Optimizing the uniformity of the multi-zone alkyls injection
system 100 requires performing separate deposition runs for each of
the zones because the individual response from the each zone is
different and is strongly dependent on the process conditions.
Optimizing different process conditions typically requires having
different zone sizes. However, the zone sizes are typically fixed
and are not adjustable. Consequently, multi-zone Alkyls injectors
with a limited number of zones may not provide for the best
possible deposition uniformity under all process conditions.
[0017] The multi-zone alkyls injection system of the present
teaching uses an alkyls gas source including a mass flow controller
having an output that is coupled to a gas manifold comprising a
plurality of valves. Each of the plurality of valves has an output
that provides alkyls process gas to one of a plurality of gas
injectors that is positioned in one of a plurality of zones in a
CVD reactor. There are many possible configurations according to
the present teaching. In one configuration, a single mass flow
controller having an input coupled to an alkyls process gas source
is used to provide alkyls process gas to a gas manifold that
provides alkyls process gas to the entire CVD reactor. However, in
other embodiments, two or more mass flow controllers having inputs
coupled to one or more alkyls process gas sources have outputs that
are coupled to two or more gas manifolds that provides alkyls
process gas to the CVD reactor.
[0018] In addition, in some gas injection systems according to the
present teaching, a single mass flow controller is used to provide
a push flow gas to each of the plurality of zones in the CVD
reactor to control the gas flow dynamics. In some gas injection
systems, a gas manifold comprising a plurality of valves is coupled
to the output of the single mass flow controller. Each of the
plurality of valves has an output that provides push flow gas to
one of a plurality of gas injectors that is positioned in one of a
plurality of zones in a CVD reactor.
[0019] FIG. 2 illustrates a schematic diagram of a multi-zone
alkyls injection system 200 according to the present invention for
a CVD rotating disc reactor 202 that includes a single alkyls gas
source 204 coupled to a gas manifold 206 comprising a plurality of
valves 208. Many aspects of the present teaching are described in
connection with a rotating disk reactor. However, it should be
understood that the methods and apparatus of the present teachings
can be applied to any type of CVD reactor. A mass flow controller
210 is coupled between the alkyls gas source 204 and the gas
manifold 206 to provide precise control over the alkyls gas flow to
the gas manifold 206. In some embodiments of the present teaching,
mass flow controllers are also positioned at one or more of the
outputs of the gas manifold 206 to provide a precise flow of alkyls
and/or push flow gases to individual gas injectors 212.
[0020] In various embodiments, at least some of the plurality of
valves 208 in the gas manifold 206 are independently controllable.
For example, the plurality of valves 208 can be electrically
controllable or pneumatically controllable. However, in some
systems, at least one of the plurality of valves 208 is partially
or fully open during the entire duration of the process run. Using
electrically and/or pneumatically controllable valves that provide
gas to corresponding zones can significantly increase the number of
zones which can be practically used without increasing the overall
gas injection system cost and complexity. One skilled in the art
will appreciate that numerous types of valves can be used. For
example, at least some of the plurality of valves 208 in the gas
manifold 206 can be MEMS type valves. MEMS type valves can have
very fast response times that can result in very precise control of
the gas flow.
[0021] A plurality of gas injectors 212 are coupled to each of the
plurality of valves 208 comprising the gas manifold 206. Each of
the plurality of gas injectors 212 has an input that is coupled to
the output of a corresponding one of the plurality of valves 208.
In some CVD reactors, at least some of the plurality of the
injectors 212 are concentrically positioned in the CVD reactor. An
output of each of the plurality of gas injectors 212 is positioned
in one of a plurality of zones in the CVD reactor 202. In various
embodiments, the diameter of orifices comprising the output of each
of the plurality of gas injectors 212 can be the same or can be
different depending upon the position of the gas injector 212 in
the CVD reactor 202.
[0022] In some embodiments, at least one of the plurality of gas
injectors 212 is movable. For example, see U.S. patent application
Ser. No. 11/827,133, entitled "Movable Injectors in Rotating Disc
Gas Reactors." The entire disclosure of U.S. patent application
Ser. No. 11/827,133 is incorporated herein by reference. In these
embodiments, the gas injectors can be adjustable to configure the
reactor prior to processing so that the CVD reactor 202 has certain
predetermined gas flow dynamics during processing. In other
embodiments, at least some of the plurality of gas injectors can be
movable during processing.
[0023] A controller 214 or processor is used to electrically or
pneumatically open and close some or all of the plurality of valves
208 for a predetermined time period and with a predetermined duty
cycle. The controller 214 has a plurality of outputs where each of
the plurality of outputs is coupled to a control input of one of
the plurality of valves 208. The controller 214 generates control
signals that instruct at least some of the plurality of valves 208
to open at predetermined times and with a predetermined duty cycle
to provide a desired gas flow to each of the plurality of zones in
the rotating disc CVD reactor 202. In various embodiments, the
control signals can directly control the plurality of valves 208 or
can operate electronically controllable pneumatic valves that
control the operation of the plurality of valves 208.
[0024] There are numerous possible valve timing sequences that can
be used for controlling the opening of the plurality of valves 208.
For example, the plurality of valves 208 can be opened for a time
period and a duty cycle that is equivalent to an integer multiple
of the radial rotation rate of the rotating disc CVD reactor 202.
Also, the plurality of valves 208 can be opened for a time period
and a duty cycle which enables all wafers at a certain radial
position on the rotating disk CVD reactor 202 to have an equivalent
film thickness. In some embodiments, at least one of the time
period and the duty cycle that the plurality of valves 208 is open
is a function of the rotation rate of the rotating disk CVD reactor
202. In some systems, it has been determined that a rotation rate
of the rotating disk CVD reactor 202 that is greater than about 120
rpms enhances film uniformity.
[0025] For example, in some methods, the controller 214 generates
control signals having duty cycles for opening at least one of the
plurality of valves 208 that are proportional to the radius squared
of the aperture of the respective gas injector 212. In other
methods, the controller 214 generates control signals having duty
cycles for opening at least one of the plurality of valves 208 that
is longer than 1 radial rotation of the disc in the rotating disc
CVD reactor 202. In these methods, the duty cycle of the control
signals that open the valves 208 and the diameter of the aperture
of the gas injectors 212 are chosen to provide a predetermined
amount of gas to a particular zone in the rotating disc CVD reactor
202.
[0026] Some CVD systems according to the present teaching include
one or more in-situ deposition rate monitors that measure at least
one of deposition rate and deposited film thickness in at least one
of the plurality of zones in the rotating disc CVD reactor 202. In
many systems, an in-situ deposition rate monitor 220 measures at
least one of deposition rate and deposited film thickness in each
of the plurality of zones in the rotating disc CVD reactor 202. An
output of each of the in-situ deposition rate monitors 220 is
electrically connected to one of a plurality of sensor inputs of
the controller 214. The controller 214 processes the data from the
in-situ deposition rate monitors 220 and generates control signals
in response to the data that control the timing and duty cycle for
opening at least some of the plurality of valves 208 in response to
the in-situ growth deposition rate monitor measurements.
[0027] In addition, a nitrogen push gas source 222 is coupled to a
single mass flow controller 224. The output of the mass flow
controller 224 is coupled to the gas injectors 212 in each of the
plurality of zones. Similarly, a hydrogen push gas source 226 is
coupled to a single mass flow controller 228. The output of the
mass flow controller 228 is coupled to gas injectors 212 in each of
the plurality of zones. In various embodiments, one or both of the
nitrogen and hydrogen push gas sources 222, 226 can be coupled to
more than one mass flow controller so that different zones can
receive different volumes of push gas. Also, in various
embodiments, the outputs of one or both of the nitrogen and
hydrogen push gas mass flow controllers 224, 228 can be coupled to
a gas manifold comprising a plurality of valves. In these
embodiments, each of the plurality of valves of the gas manifold
has an output that provides push flow gas to one of a plurality of
gas injectors 212 positioned in one of a plurality of zones in the
rotating disc CVD reactor 202.
[0028] A method of gas injection into a CVD system according to the
present teaching includes providing a process gas to inputs of a
plurality of valves 208 and then providing the process gas from
outputs of the plurality of valves 208 to a plurality of gas
injectors 212 positioned in a plurality of zones in a CVD reactor
202. The method applies to all types of CVD reactors, such as
rotating disc-type CVD reactors. The method is particular useful
for alkyl gas injection because the method can be used to provide
precise amounts of alkyl gas to particular areas of a CVD reactor
while using only a single mass flow controller.
[0029] A controller 214 or processor determines the desired timing
and duty cycles for opening each of the plurality of valves 208 in
order to provide a desired amount of process gas to each of the
plurality of zones in the CVD reactor 202. Each of the plurality of
valves 208 is then opened for its desired duty cycle, which
provides the desired amount of process gas to each of the plurality
of zones in the CVD reactor 202 for deposition. In various
embodiments, some or all of the plurality of valves 208 are opened
sequentially. Also, in various embodiments, some of plurality of
valves are continuously open during deposition.
[0030] In one method according to the present teaching, the duty
cycle for opening the plurality of valves 208 in the gas manifold
206 of the rotating disk CVD reactor 202 is inversely proportional
to a radius of the corresponding one of the plurality of zones. In
this method, the gas provided by some or all of the plurality of
gas injectors 212 is determined by the radial position of the gas
injector 212 in the rotating disk reactor 202. Gas injectors 208
that are positioned closer to the outer diameter of the rotating
disk reactor 202 will provide a greater volume of gas compared with
gas injectors 212 closer to the center of the rotating disk reactor
202.
[0031] In some methods, at least one of growth rate and deposited
film thickness is measured during deposition. For example, growth
rate and/or deposited film thickness can be measured across the
plurality of zones in a radial direction. Numerous methods can be
used to measure growth rate and/or deposited film thickness. For
example, in-situ reflection measurements can be used to measure
both growth rate and overall deposited film thickness. These growth
rate and/or deposited film thickness measurements can be performed
in any number of locations across the CVD reactor 202 during
deposition. For example, the growth rate and/or deposited film
thickness measurements can be performed in at least two of a
plurality of zones of the CVD reactor 202 during deposition.
[0032] The resulting in-situ measurements can be used to adjust the
timing and/or duty cycle for opening at least one of the plurality
of valves 208 in response to the measurements. These methods of
in-situ growth rate and/or deposited film thickness can be used to
provide feedback to the mass flow controllers 210, 224, and 228 for
adjusting the gas flow dynamics in the CVD reactor 202 so as to
improve the uniformity of the deposited films. In addition, these
methods of in-situ growth rate and/or deposited film thickness can
be used to provide feedback to the mass flow controllers 210, 224,
and 228 to adjust the gas flow dynamics in the CVD reactor 202 so
that a precise deposited film thickness can be achieved.
[0033] These methods of in-situ growth rate and/or deposited film
thickness can also be used to change a dimension of an orifice of
one or more of the plurality of gas injectors 212 in one or more
zones of the CVD reactor 202 in response to at least one deposition
metric. Some deposition metrics include growth rate, deposited film
thickness, and deposited film uniformity. Furthermore, these
methods of in-situ growth rate and/or deposited film thickness can
be used to change the position of one or more movable gas injectors
in one or more of the plurality of zones of the CVD reactor 202 in
response to at least one deposition metric. In some methods, the
gas injectors 212 are moved to particular fixed locations. In other
methods, the gas injectors 212 are scanned at a constant speed or
at a variable speed during growth. Moving the alkyls injectors
provides for a simple and effective method to adjust
uniformity.
[0034] Also, in some methods, the volume of gas injected by the gas
injector 212 is variable during growth. In one particular method,
the alkyls gas flow varies to compensate for the "dead zone" that
occur during each linear movement where linear speed of the gas
injector 212 is equal to zero. In one method where the materials
being grown are sensitive to growth rate, the alkyls injectors are
moved in a pattern where the positions of some gas injectors are
phase shifted relatively other gas injectors.
[0035] The gas injection system of the present teaching has
numerous modes of operation. One mode of operation is the
simultaneous mode. In the simultaneous mode of operation, each of
the plurality of valves 208 is open during the entire deposition.
The position of the valve opening can be adjusted to change the
volume and fluid dynamics of gas injected from the associated gas
injector 212 in the CVD reactor 202. However, the adjustment of one
valve adjusts the flow available to the other valves. Consequently,
it is difficult to control deposition metrics in the simultaneous
mode of operation.
[0036] Another mode of operation is the sequential mode. In the
sequential mode of operation, only one of the plurality of valves
208 connected to the gas manifold 206 is open at each moment of
time. It is relatively easy to optimize deposition metrics in the
sequential mode of operation because there is no interaction of
gasses flowing from different valves in the gas manifold 206 that
are injected in the CVD reactor 202 with different gas injectors
212. Consequently, the response characteristics of each of the
plurality of valves 208 can be easily determined and used to
directly optimize one or more deposition metrics. However, if the
properties of the deposited material are a strong function of the
deposition rate, then each zone along the wafer carrier can have a
significantly different growth rate. Material deposited using the
sequential mode of operation generally has the same integrated
material properties across the CVD reactor 202, but there are
different gradients of the material thickness. In some CVD reactors
202, different alkyls sources with different flow characteristics
are used for each zone to compensate for these different gradients
of the material thickness.
[0037] Another mode of operation is the combined mode of operation.
In the combined mode, a first group of alkyls injector operates in
the simultaneous mode of operation. In some methods using the
combined mode of operation, the bulk of the material growth is
performed using the simultaneous mode of operation. For example,
90% or an even higher percentage of the material grown can be
performed using the simultaneous mode of operation. Deposition
metrics, such as the deposited film uniformity, may be relatively
poor for material deposited using the simultaneous mode of
operation. A second group of alkyls injector then operates in the
sequential mode of operation and provides fine tuning of the
deposition thickness and/or other deposition metrics in desired
regions of the CVD reactor 202. In some method using this mode of
operation, only a small fraction of the material is grown in the
sequential mode of operation. For example, in some methods less
than 10% of the material is grown using the simultaneous mode of
operation.
[0038] FIG. 3 illustrates a schematic diagram of another multi-zone
alkyls injection system 300 according to the present invention for
a CVD rotating disc reactor that is similar to the multi-zone
alkyls injection system 200 that was described in connection with
FIG. 2, but that also includes a second gas manifold 302 comprising
a plurality of valves 304 for controlling the flow of the nitrogen
and hydrogen push gases. One skilled in the art will appreciate
that numerous types of valves can be used. For example, at least
some of the plurality of valves 304 in the second gas manifold 302
can be MEMS type valves as described herein. In various
embodiments, at least some of the plurality of valves 304 in the
second gas manifold 302 are independently controllable. For
example, the plurality of valves 304 can be electrically
controllable or pneumatically controllable. In some systems and
methods of operation, at least one of the plurality of valves 304
is partially or fully open during the entire duration of the
process run.
[0039] The plurality of gas injectors 212 are coupled to each of
the plurality of valves 208 comprising the first gas manifold 208
and also to each of the plurality of valves 304 comprising the
second gas manifold 302. In other embodiments, a first plurality of
gas injectors is coupled to each of the plurality of valves 208
comprising the first gas manifold 206 and a second plurality of gas
injectors is coupled to each of the plurality of valves 304
comprising the second gas manifold 302.
[0040] In various embodiments, the diameter of orifices comprising
the output of each of the plurality of gas injectors 212 is chosen
to correspond to a position of the corresponding valve opening in
the gas manifold 302 so that the desired amounts of alkyls and push
flow gasses are delivered to the CVD reactor 202.
[0041] In another embodiment of the present teaching, separate gas
manifolds are used for each push gas source. That is, a second gas
manifold comprising a second plurality of valves is coupled to the
output to the nitrogen mass flow controller 222 and a third gas
manifold comprising a third plurality of valves is coupled to
output to the hydrogen mass flow controller 222.
[0042] There are numerous possible valve timing sequences that can
be used for controlling the opening of the plurality of valves 304.
These timing sequences can be the same as or different than the
timing sequences used to control the opening of the plurality of
valves 208. For example, the timing sequences can be used to
provide gas flow velocity matching in some or all of the plurality
of zones. Flow velocity matching is important because the areas of
the various zones can be significantly different. Also, in some
methods according to the present teaching, the timing sequences for
opening the plurality of valves 304 are advanced or delayed in time
with respect to the timing sequences opening of the plurality of
valves 208.
EQUIVALENTS
[0043] While the Applicants' teaching are described in conjunction
with various embodiments, it is not intended that the Applicants'
teaching be limited to such embodiments. On the contrary, the
Applicants' teaching encompass various alternatives, modifications,
and equivalents, as will be appreciated by those of skill in the
art, which may be made therein without departing from the spirit
and scope of the teaching.
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