U.S. patent application number 11/115053 was filed with the patent office on 2005-12-22 for massively parallel atomic layer deposition/chemical vapor deposition system.
Invention is credited to Doering, Ken, Jansz, Adrian, Puchacz, Jurek, Seidel, Thomas E..
Application Number | 20050281949 11/115053 |
Document ID | / |
Family ID | 23357523 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050281949 |
Kind Code |
A1 |
Seidel, Thomas E. ; et
al. |
December 22, 2005 |
Massively parallel atomic layer deposition/chemical vapor
deposition system
Abstract
A method and apparatus for the use of individual vertically
stacked ALD or CVD reactors. Individual reactors are independently
operable and maintainable. The gas inlet and output are vertically
configured with respect to the reactor chamber for generally
axi-symmetric process control. The chamber design is modular in
which cover and base plates forming the reactor have improved flow
design.
Inventors: |
Seidel, Thomas E.;
(Sunnyvale, CA) ; Jansz, Adrian; (Albuquerque,
NM) ; Puchacz, Jurek; (Pleasanton, CA) ;
Doering, Ken; (San Jose, CA) |
Correspondence
Address: |
BLAKELY SOKOLOFF TAYLOR & ZAFMAN
12400 WILSHIRE BOULEVARD
SEVENTH FLOOR
LOS ANGELES
CA
90025-1030
US
|
Family ID: |
23357523 |
Appl. No.: |
11/115053 |
Filed: |
April 25, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11115053 |
Apr 25, 2005 |
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10282609 |
Oct 29, 2002 |
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6902624 |
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60346005 |
Oct 29, 2001 |
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Current U.S.
Class: |
427/248.1 ;
118/719 |
Current CPC
Class: |
C23C 16/45546 20130101;
C23C 16/45544 20130101; C23C 16/4412 20130101; C23C 16/54
20130101 |
Class at
Publication: |
427/248.1 ;
118/719 |
International
Class: |
C23C 016/00 |
Claims
What is claimed is:
1. A method to perform atomic layer deposition or chemical vapor
deposition comprising: placing a plurality of substrates separately
into processing chambers of a plurality of vertically stacked
deposition reactors having a low vertical profile relative to
length and width dimensions, but in which the reactors have
separate internal gas inlet at a top of the processing chamber and
separate internal exhaust at a bottom of the processing chamber to
provide, a generally axi-symmetric vertical gas flow across the
substrates when the substrates are placed in the processing
chambers of individual reactors; and introducing a processing gas
through horizontally disposed passages to the internal gas inlet
and exhausting through horizontally disposed passages from the
internal exhaust, the horizontal passages being integrated within
the reactor, to deposit a film layer on the substrates.
2. The method of claim 1 further comprising loading the substrates
into the processing chambers by retrieving the substrates from a
load lock unit, but in which the substrates are already placed at
corresponding vertical position as the reactors so that further
vertical translation to load the substrates into the reactors is
not needed.
3. The method of claim 1 further comprising sourcing in a
processing gas at different time intervals for the stacked reactors
to stagger processing phases for the substrates to be processed in
the stacked reactors.
Description
RELATED APPLICATIONS
[0001] The present application is a Divisional of U.S. patent
application Ser. No. 10/282,609, filed Oct. 29, 2002, entitled
"Massively Parallel Atomic Layer Deposition/Chemical Vapor
Deposition System", which claims priority to U.S. Provisional
Application No. 60/346,005, filed on Oct. 29, 2001. This patent
application is hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to semiconductor processing
and, more particularly, to an apparatus and method for providing a
massively parallel ALD/CVD system.
BACKGROUND OF THE RELATED ART
[0003] Chemical Vapor Deposition (CVD) is a widely used deposition
process for the growth of thin films on various substrates,
including semiconductor wafers. As microelectronics device
dimensions are reduced, or scaled down, CVD is an attractive method
for the deposition of conformal films over complex device
topography. In the field of atomic/molecular level film deposition,
a process known as Atomic Layer Deposition (ALD) has emerged as a
promising candidate to extend the abilities of CVD techniques.
Generally, ALD is a process wherein conventional CVD processes are
divided into separate deposition steps that theoretically go to
saturation at a single molecular or atomic monolayer thickness and
self-terminate. For ALD applications, the molecular precursors are
introduced into the reactor separately. Typically, an ALD precursor
reaction is followed by inert gas purging of the reactor to remove
the precursor from the reactor prior to the introduction of the
next precursor.
[0004] Commercial ALD systems today include those with a precursor
inject flow with respect to the substrate, such as a semiconductor
wafer, of "horizontal" or a "vertical" flow design. In the
horizontal flow design, the flow is directed across (parallel to)
the surface of the wafer. In the vertical inject design, a
purge-pump configuration requires that the gas flow actually have
both vertical and horizontal components near to and with respect to
the wafer plane.
[0005] Horizontal flow reactors generally require, as a minimum,
the transport of the exposure pulses of the precursor chemical over
the diameter of the wafer, whereas vertical flow reactors allow for
axi-symmetric injection of the precursor chemical, so that the
transport of the exposure pulses is over the radius of the wafer.
This means the trailing edge of the precursors for vertical inject
is sharper and may be placed closer to the initial edge of
sequential reacting precursors, thus minimizing gas phase
reactions. These considerations are important in the design of a
practical and efficient commercial ALD reactor.
[0006] In order to improve throughput of wafers, the semiconductor
industry has employed batch processing. However, as wafer diameters
increase (e.g. 200 mm and 300 mm wafer diameters or larger),
industry preference is for single wafer processing in a reactor
chamber. In reference to ALD processes, batch ALD reactors are
believed to be difficult to maintain relative to single wafer
reactors, which historically have had the capability for in-situ
cleans, at least films made by CVD. Films made by single wafer ALD
reactors may also be in-situ cleaned if or when appropriate
cleaning chemistry(s) are developed. Accordingly, vertical flow
designs may be more preferable for practical ALD systems.
[0007] The use of single wafer reactors is also more likely to be
accepted by the semiconductor industry, since single wafer reactors
allow for improved uniformity and high throughput for wafer
processing over batch reactors. However, one critical limitation
for wider acceptance of ALD is the fact that high throughput
processes are difficult to realize with single reactor systems.
[0008] It would be advantageous to have a single wafer vertical
flow reactor that is also compact and low in profile in its form
factor, so that the reactors may be stacked one atop another.
Multiple stacked reactors would allow higher throughput per system
and improve a given unit area of factory floor space per wafer
processed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Embodiments of the present invention are illustrated by way
of example and are not for the purpose of limitation. In the
figures of the accompanying drawings, similar references are
utilized to indicate similar elements.
[0010] FIG. 1 is a perspective view of one embodiment of a
massively parallel ALD/CVD deposition system of the present
invention.
[0011] FIG. 2 is a top-plan view of the system of FIG. 1.
[0012] FIG. 3 is a side-plan view of the system of FIG. 1, but
showing only one process module.
[0013] FIG. 4 is an exploded view of an embodiment of a compact ALD
reactor for the system shown in FIG. 1.
[0014] FIG. 5 is an exploded sectional-view of the embodiment of
the compact ALD reactor shown in FIG. 4.
[0015] FIG. 6 is a cross-sectional view of an assembled compact ALD
reactor having a cone-like shape near the gas inlet and exhaust to
improve gas flow in the chamber.
[0016] FIG. 7 is a cross-sectional view of an assembled compact ALD
reactor having a horn-like shape near the gas inlet and exhaust to
improve gas flow in the chamber.
[0017] FIG. 8 is a timing diagram showing a time phased control of
chemical pulses and purges for a three-stack reactor module for the
system of FIG. 1.
SUMMARY
[0018] A massively parallel ALD/CVD system is described. A
plurality of ALD/CVD reactors have a compact, low vertical profile
so that the reactors may be vertically stacked. The stacked
deposition reactors are coupled to receive a material, such as a
semiconductor wafer, from a load lock unit to place in one of the
reactors. In one embodiment, separate load lock units corresponding
to the reactors are used, so that the wafer may be vertically
positioned to the respective height of the vertically stacked
reactors when the wafers are to be located in the load lock.
[0019] The vertically stacked ALD/CVD reactors have a low height
profile, but allow separate gas inlet at the top of a chamber and
separate exhaust at the bottom of the chamber to provide a
generally axi-symmetric vertical gas flow across the wafer when the
wafer is processed in the reactor chambers. The vertical
arrangement allows multiple wafers to be processed separately in
module housing the multiple reactors.
[0020] In one embodiment, the reactor chamber is formed by placing
a top plate and a bottom plate onto a frame. The top plate and the
bottom may have a particularly shaped recessed regions to form the
top and bottom of the chamber conforming to the particular shape.
In one embodiment, the top and bottom of the chamber has a
cone-shape to improve the generally axi-symmetric gas flow in the
chamber. In another embodiment, horn-shaped chamber is used to
provide an option to further improve the gas flow. The low profile
reactors are individually constructed with a cover plate integrated
with and containing a horizontal input conduit and a base plate
integrated with and containing a horizontal conduit for exhaust to
minimize the total vertical height of the assembled low profile
reactors.
DETAILED DESCRIPTION OF THE INVENTION
[0021] In the description below, the present invention is described
in reference to various embodiments. The example embodiments are
described in terms of depositing film material on a substrate by
Atomic Layer Deposition (ALD). Although ALD is described, the
method and apparatus may be readily adapted for the practice of
Chemical Vapor Deposition (CVD) or variants thereof. However, the
practice of the invention is not limited to these processes.
Furthermore, the substrate may be of a variety of base materials
for depositing subsequent material layers and need not be limited
to the deposition of film layers on a semiconductor substrate
(wafer). For example, substrates used for manufacture of flat panel
displays may readily be the base substrate.
[0022] Referring to FIG. 1, an example embodiment of a Massively
Parallel ALD System (MPAS) 100 is shown. A top plan view and a side
plan view of the MPAS 100 are respectively shown in FIGS. 2 and 3
(in FIG. 3, only one process module is shown). MPAS 100 is a
complete equipment (tool) manufactured for the purpose of providing
deposition of thin film material on to a substrate (either the base
substrate or a material layer formed on the substrate). A common
substrate is a semiconductor substrate, such as a silicon wafer.
Again, as noted above, the MPAS 100 is not limited to ALD or CVD
(including plasma assisted ALD or plasma assisted CVD), although
the description below pertains to the practice of ALD. The MPAS 100
comprises a number of main assemblies. The MPAS 100 is also
illustrated as a cluster tool having a number of assemblies around
a common hub. The MPAS 100 may be readily designed to operate in a
non-cluster environment, but generally, MPAS 100 is designed as a
cluster tool to improve throughput of wafers.
[0023] The core architecture of the example MPAS 100 shown includes
a central vacuum chamber/platform 101, four process modules 102,
load locks 103 and associated connections between the various
components and assemblies. As will be described below, the process
modules includes three low profile Compact ALD Reactors (CARs) 110,
so that a total of twelve such CARs (3.times.4) are present in the
example MPAS 100. The actual number of CARs 110 per process module
may vary and may be less than or more than three. Similarly, the
number of process modules 102 may vary, so that the total number of
CARs 110 for a given MPAS 100 may be less than or greater than
twelve.
[0024] With the noted design of the MPAS 100 having twelve CARs
110, more wafers may be processed in a smaller footprint area when
compared to existing ALD equipment tools. Where productivity is
defined as a throughput per unit area of factory floor space, MPAS
100 allows for improved productivity due to the compact design of
the CARs 110 and the cluster tool environment. Furthermore, the
process capability within a processing chamber of an individual
vertical flow compact reactor of the CARs 110 may be made
compatible with current thermal and plasma assisted ALD (or CVD)
processes, thus, permitting the use of a suitable in-situ clean for
continuous operation, as well as plasma assisted CVD or ALD. Other
economy of scale features apply, such as common chemical source and
pump usage for the stacked reactors in a common process module,
which reduces the cost to produce, while still allowing the
operation of the independent process modules for high availability
of the system operation.
[0025] For a standard semiconductor wafer processing, such as for a
300 mm wafer implementation, a Front Opening Unified Pod (FOUP)
allows for a standard mechanical wafer interface to a factory. The
FOUP typically resides opposite a wall 121 (or some other
partition) and is placed onto a FOUP support 119. The wall 121
separates two environments, one environment for handling/storing
the wafer and the other environment where the MPAS 100 is located.
The number of FOUP supports 119 utilized will depend on the
particular system and, thus, the actual number of FOUPs present
will vary. Three such FOUP supports 119 are shown in FIG. 2. A
variety of FOUPs known in the art may be readily adapted for use
with MPAS 100. It is also to be noted that other wafer loading
interfaces may also be utilized to allow the transfer of the wafers
from one environment to the environment of MPAS 100. In some
instances, a FOUP may not be desired because of its appreciable
cost. For example, in certain cases where small piece parts and
non-semiconductor materials are employed for processing, other
simpler interfaces may be used.
[0026] On the other side of the wall 121, a mini-environment
interface (referred to as mini-environment 130) is present. The
mini-environment 130 is a "clean" entry space (for example, Class
1) between the wafer handling environment and the vertical process
module 101. Thus, the FOUPs are linked to the mini-environment 130,
so that the loaded wafers are transferred to the mini-environment
130. The mini-environment is used to interface between the
atmospheric environment located to the left of the wall 121 (where
the FOUPs are located) and the clean environment where the central
robotic vacuum chamber 101 and the processing modules 102 are
located. Mini-environments of various schemes may be implemented
for the mini-environment 130, including mini-environments known in
the art.
[0027] In the particular embodiment shown, an atmospheric robot 135
is employed in the mini-environment to move the wafers through the
mini-environment 130. In one embodiment the robot 135 is specified
with a suitable vertical motion (e.g. approximately 24-36 inches)
to accommodate the design for efficient transfer of wafers to the
load locks and then to the stacked reactors of the processing
modules.
[0028] Wafers from the FOUP(s) are loaded into the load locks 103
by the atmospheric robot 135 in the mini-environment 130 using
appropriate vertical motion. The load locks 103 have vertical
positions that at least at one time in the wafer transfer operation
nominally match the vertical positions of the vertically stacked
CARs 110. Thus, load locks 103 shown are vertically stacked to
correspond to the vertically stacked CARs 110. However, common load
lock chambers (not vertically stacked) may also be used in other
designs, wherein the load lock is provided with a vertical vacuum
movement mechanism for the wafers in the load lock, so that wafers
may be placed approximately to match the vertical positions of the
center-line position of the stacked reactors. The number of load
locks 103 to be used may vary from system to system.
[0029] A central robot (not shown) is located within the central
vacuum chamber 101 and directly above a robot(s) control housing
142. The vacuum robot may or may not be an industry standard
component known in the art, however, it may be modified so that it
uses multiple end effectors so as to pick and place more than one
wafer at a time from the load lock position to transfer wafers to
the CARs 110. The central vacuum robot may take one or more wafers
at a time from load lock chambers (less than or of the order of
1.5.times. the diameter of the wafer and a height defined by the
number of wafers to be accommodated by the load lock). For example,
if there are 24 wafers in each FOUP, and there are 2 load locks,
there may be 36 wafers placed in each load lock 103. The load locks
are generally placed about the same horizontal plane or level as
the center line of the CARs 110. Options for robotic transfer for
one or more wafers under one loading motion are possible. For
example, 3 wafers may be removed from the load lock 103 and placed
into 3 stacked CARs 110 of one process module 102 in one transfer
loading motion or operation. This operation may be sequentially
repeated for supplying wafers to the other process modules. During
the time of transfer of wafers to the CARs 110 of the second (and
other) process module(s), ALD deposition process may take place in
the previously wafer loaded process module(s).
[0030] Thus, the central vacuum chamber 101 includes vacuum robots
to transfer wafers from the load locks 103 to the CARs 110. A
central vacuum robot control unit 142 may be attached to the bottom
of the central vacuum chamber 101 and a second central robot may be
attached to the top of the central vacuum robotic chamber 101 for
increased flexibility.
[0031] It is to be noted that one or more of these robotic units
may be designed to have movement in the up-down direction
(z-direction). The atmospheric robot 135 in the mini-environment
130 may have z-direction movement, so that the wafers may be loaded
to the correct height in the load locks 103, and a control
mechanism 140 for vertical motion of wafers within the load lock
103 so as to align at the appropriate height for the corresponding
CAR 110. In general, there are options to transport wafers to the
CARs by the single motion or combined vertical motion of the
atmospheric robot in the mini-environment 130, load lock 103,
and/or the central vacuum robot(s) in the central vacuum chamber
101. It is also to be noted that with the embodiments described
above, the wafers when transported to or within the location of the
load lock(s) 103, may be vertically positioned already for entry
into the corresponding CAR 110, so that significant movement beyond
that for placement (or hand-off) within the reactor(s) (generally
in the order of approximately 1 cm) is not required of the robot(s)
in the central vacuum chamber 101.
[0032] The central vacuum chamber 101 is positioned as a hub for
the four process modules 102 arranged around the periphery. Again
the number of such process modules 102 may vary and the exact
layout will depend on the particular footprint. However, a typical
layout is the arrangement shown in FIG. 2. The wafers are then
moved from the central vacuum chamber 102 into individual CARs
110.
[0033] The process modules 102 houses the CARs 110 in a stacked
arrangement and typically disposed so that the CARs 110 are aligned
with the horizontal movement of the wafer from the load lock 103. A
chemical source 145 is shown located above the process modules 102
to source the various chemicals to the CARs 110. A delivery unit,
in form of a gas switching manifold 146 reside between the chemical
source 145 and the CARs 110 to control the switching in/out the
precursor chemicals being sourced to the CARs 110. Although
individual chemical sources 145 are shown for each process module
102 in the example embodiment, other embodiments may employ a
common chemical source for delivery of the chemical(s) to all of
the process modules 102. If a common chemical source is utilized,
the source may be placed in a variety of remote locations. If
placed semi-remotely (away from the overhead projection of a
process module 102, but still within or nearly within the overhead
projection of the cluster platform), the chemicals may be in a
common source "box" that contains all the individual chemical
sources for the process modules 102.
[0034] It is to be noted that a given process module 102 has the
chemical source 145, gas switching manifold 146 and the CARs 110
disposed in a vertical arrangement to provide a smaller footprint
on the factory floor. Likewise, much of the machinery (e.g. the
robotic units and control units) are placed below the load locks
103 and the central vacuum chamber 101, as well as with the module
102. Furthermore, shown in FIG. 2 (but not in FIGS. 1 and 3) are
electronic control racks 109, which may house various electronic
components, controls, etc. In some systems, these control racks 109
may be removable to allow access to the cluster hub, such as for
performing maintenance.
[0035] In the particular embodiment shown, the chemical source 145
is located in the elevated location above the level of the
uppermost reactor of a particular process module 102. The elevated
chemical source 145 operates as a common chemical source for the
corresponding CARs 110 of the same process module 102. The chemical
source 145 supplies precursors for the grouped of stacked CARs 110
of the respective process module 102, by using time phased control
sequence. One such control sequence is described below in reference
to FIG. 8 for an ALD process.
[0036] FIGS. 4 and 5 illustrate one example embodiment 200 of the
CAR unit 110 described above. The CAR unit 200 generally has a low
profile with regard to its height dimension, as compared to its
length and width dimensions. However, larger height reactors may be
employed, although such larger height profile reactor units may
limit the number that may be stacked and/or increase the overall
height of the process module 102. In one embodiment, the CAR unit's
lateral dimensions may be targeted for approximately 1.3.times. to
2.times. the wafer diameter to be processed. The height may
targeted for 0.5.times. to 1.1.times. the lateral dimensions,
however larger than 1.0.times. may also be useful for a limited
number of stacked reactors.
[0037] FIGS. 4 and 5 show an exploded view, in which a main body
(or frame) 201 has a low profile. The low profile is defined by the
height being equal or less than the width and length (cross section
dimension) of the CAR unit 200, with a first side 202 using a wafer
slot 203 to define a reference side of the CAR frame. A heater
assembly piece 205 is shown opposite the first side 202. In other
embodiments, the heater assembly piece 205 may be adjacent the
first side 202. A heater 206 and a susceptor 207, upon which
surface where a wafer is placed, are coupled to the heater assembly
piece 205. Once in position with the frame 201, a wafer may be
inserted through the slot 203 and made to reside atop the susceptor
207 and heated by heater 206. Typically, with the described
embodiment, an end effector of the wafer handler vacuum robot lifts
and places the wafer on the susceptor 207. The other remaining
sides of the frame 201 are enclosed. The heater 206 is coupled to a
heating source, such as electrical power, so that when applied, a
wafer resident on the susceptor 207 is heated. A resistive heater
element may be used for example to provide wafer temperatures from
100-500 degrees C. CAR wall temperatures may be controlled to a
temperature approximately 80-140 degrees C. to minimize the
adsorption of sticky reactive species, such as water or
NH.sub.3.
[0038] The CAR unit 200 also includes a cover plate 210 and a base
plate 220. The cover plate 210 resides atop the frame 201 to
enclose the frame 201 from the top. Likewise, the base plate 220
encloses the frame 201 from the base (bottom). The frame 201 has a
cavity region, which when enclosed by the top and base plates 210,
220 operates as a processing chamber 230 for the wafer.
Accordingly, when a wafer is inserted through the wafer slot 203
and placed atop the susceptor 207, the wafer is in position in the
processing chamber 230 and may be heated by driving electrical
power to a resistive heater and allowing the wafer to reach
temperature by thermal conductive and/or radiative heat
transfer.
[0039] As detailed in FIG. 5, the base plate 220 includes a
recessed region 221, which has an exhaust opening 222 at or
proximal to the center of the recessed region 221. An exhaust
conduit 223 extends from the opening 222 to a side of the base
plate 220, where an exhaust port 224 is present. The exhaust
conduit 224 is shown in FIG. 5 to extend to a side perpendicular to
the wafer slot opening 203. As noted, the exhaust conduit 224 is
disposed horizontally and, in the example, integrated with the base
plate 220. In the particular embodiment, the conduit 223 is
axi-symmetric, although various other shapes and sizes may be
readily implemented.
[0040] The cover plate 210 also includes a recessed region 211,
which has a source opening 212 at or proximal to the center of the
recessed region 211. A source conduit 213 extends from the opening
212 to a side of the top plate 210, where an inlet port 214 is
present. In the particular example, the source conduit 213 extends
to the side opposite the exhaust conduit 224. As noted, the source
conduit is disposed horizontally and, in the example, integrated
with the cover plate 210. Also in the particular example, the
conduit 213 leading to the inlet port 214, couples to gas injection
lines to introduce precursors and inert gas. Although a single
source conduit 213 is shown, multiple conduit lines, openings
and/or ports may be used.
[0041] The heater assembly piece 205, base plate 220 and cover
plate 210 are shown assembled in a particular arrangement in FIGS.
4 and 5. That is, the heater assembly piece 205 is assembled and
placed opposite the wafer slot 203, the exhaust port 224 is to the
right of the wafer slot 203, and the inlet port 214 is to the left
of the wafer slot 203. However, the assembly and configuration may
be made in a variety of other any combinations. When completely
assembled, the various components form the CAR unit 200.
[0042] When assembled, the various components units 201, 202, 205,
207, 210 and 220 form the CAR unit 200. Cross-sections of the
assembled CAR unit 200 are detailed in FIGS. 6 and 7. FIGS. 6 and 7
differ in that the recessed regions 211 and 221 have different
shapes. In FIG. 6, the cover plate 210 and the base plate 220 have
a cone-shaped recessed regions 215, 216. In FIG. 7, the two plates
210, 220 have a shape which is convex near the source and exhaust
openings 212, 222 and concave near the near the side walls of the
chamber 230. This convex-concave shape is referenced as horn-shaped
and form horn-shaped regions 217, 218.
[0043] It is to be noted that a feature of the CARs illustrated in
FIGS. 6 and 7 for describing the low profile reactor is that it is
constructed with a cover plate integrated with or containing the
horizontal conduit 213 for input of reactants and purge gases and
with a base plate integrated with or containing the horizontal
conduit 223 for exhaust of chemical by-products, unused reactants
and purge gases. This integrated construction reduces the total
vertical dimension that would otherwise be obtained by the use of
separate input and exhaust lines that are not integrated within the
body of the CARs illustrated in FIG. 6 and 7. Separate horizontal
conduit input and exhaust lines that are not integrated within the
cover and base plates would most likely require additional hardware
and assembly distance(s) above and below the reactor upper and
lower surfaces. The novel design minimizes the total vertical
height of the assembled low profile reactors and allow the CARs to
be stacked more effectively.
[0044] As noted in FIGS. 6 and 7, the inlet of the source gases
(precursor and/or inert gas) is at the top of the chamber 230 at
the source opening 212 and the exhaust is at the exhaust opening
222. The wafer resides centrally between the two openings 212, 222.
This vertical flow of gases allows generally axi-symmetric flow
across a radius of the wafer when ALD (or CVD) is performed on the
wafer. The generally axi-symmetric vertical gas flow achieves
generally axi-symmetric conditions for better uniformity control
via parasitic CVD control. This condition is desirable to minimize
the effect of etching of downstream exchange reaction ALD
by-products that may more adversely take place in a horizontal flow
arrangement, and to allow simultaneous provision for plasma
processes for initiation and plasma assisted ALD. It also provides
reduced broadening or dispersion of reactant pulse characteristic
allowing for minimal purge time for sequential reactant separation
and lack of gas phase reactions.
[0045] Furthermore, the vertical flow CAR unit 200 has internal
reactor configuration designed with a first generally axi-symmetric
homelike or cone-like inject surface shape to confine and
distribute the reactants and inert purge gases and a second
homelike or cone-like surface for obtaining generally axi-symmetric
pumping flow for exhaust. The selection of low aspect ratio
cylindrically symmetric generally axi-symmetric cone or horn like
surfaces are used to help reduce the height and eliminates dead
spaces from the comers of the reactor chamber 230. Below the heater
assembly, the reverse cone or horn shape surface provides high
conductance conduit pathway to the exhaust and limits the
desorbtion effects related to back-streaming from dead space to the
region above the wafer. The cone or horn like shape have very low
aspect rations (height much less than the diameter) to enable the
performance of the vertical flow, low profile compact reactor
concept. It is to be noted that other surface shapes may also be
implemented and the cover and base plate recessed shapes need not
be limited to cone or horn like shapes for achieving improved
flow.
[0046] Referring to FIG. 8, an example ALD gas switching sequencing
diagram 300 is shown for a stack of three CAR units 200. The
precursor chemicals are delivered to the CARs 200 from a gas
switching manifold (such as manifold 146 shown in FIG. 3). In such
an example ALD sequencing, the pulse sequence is: precursor A-purge
A-precursor B-Purge B. These four sequences comprise the "ALD
cycle."
[0047] For example, in a stack of three CAR units 200, the upper
reactor is pulsed with an A precursor first and the A pulse is
completed before the center reactor is A pulsed, and the lower
reactor is A pulsed after the center reactor has completed it's A
pulse. Each sequentially A exposure draws precursor from a common
chemical precursor source for its process module. Subsequently, the
sequence of pulses is repeated for the second precursor B. In
between the A and B precursor injection pulses, purge gas flows in
the chamber to remove the earlier precursor or any byproducts
before the new precursor is introduced.
[0048] Thus, a novel vertical flow CAR integrated with MPAS is
described with gas inlets and outputs vertically configured into
and out of the processing chamber. The low profile allows compact
stacking to place multiple reactors in parallel, allowing for dense
reactor packing and easy maintenance, but with separate gas
injection into and outflow from the reaction chamber, which flow is
generally axi-symmetric. The reactor has external geometry that is
low profile and substantially rectilinear in its envelope
surface.
[0049] Furthermore, CARs may be rack mounted, one over the other in
a process module to make a vertical stack of independent reactors,
so that each reactor may be designed to be removed in a horizontal
plane, while the other reactors may continue operation. Precursor
and inert purge gases are fed horizontally thru elements 214 and
213 and the exhaust pump flows are carried out horizontally through
elements 223 and 224 with respect to the exterior of the CAR to
facilitate integration. However, the interior reactor gas flows are
vertical with respect to the wafer surface. The exterior shape or
form factor of the CAR may be square, rectilinear, round or some
other shape. Thermal engineering may be utilized to compensate for
proximity effects of upper and lower reactors being in a different
thermal environment than the interior (such as the center reactor
unit of a three-reactor stack), such as to control the wall
temperatures and to assure reactor matching.
[0050] Stacked reactors in a given process module may be pumped by
being connected to a common or shared pump line. Various options
including the combination of dedicated connecting pump lines and
shared line (such as a shared manifold line 149 shown in FIG. 3)
defines the pump manifold. Individual pumps for individual reactors
may also be used. A pump line connecting to an individual CAR may
have a line with a shut-off valve and controlling throttle valve in
series to their dedicated CAR chamber; the throttle valve achieving
a desired set point value or range of values of pressure in each
reactor, which can be nominally the same.
[0051] A reactor is fed its reactant and purge gases by its own
dedicated manifold line or as an alternative, use a shared manifold
line. One embodiment has an arrangement with its last reactant and
inert gas switching valves "close" to each reactor for
implementation of rapid gas switching and to the extent possible a
similar distance from each inlet orifice leading to the CAR
reaction space to achieve matched process performance. Also,
individual CAR units may have remotely operable vacuum valves at
its wafer input side to be opened for wafer transport into or out
of the reactor and closed for process operation of the reactor.
[0052] Finally, the MPAS may be computer or processor controlled.
Individual stacks of CARs may share a common pump manifold with a
single mechanical pump. Individual CARs may be isolated from cross
talk with an independently controlled isolation valve for pressure
control and gas flow. The process pressure control is independently
controlled via hardware and software, such that closed loop
pressure control may be permissible from 0 to 10 Torr without
affecting the process (deposition or in-situ clean) on the other
CAR modules. Also, wafer temperature control from 100 degrees C. to
500 degrees C. and plasma deposition from 10 watts to IKW is
in-situ plasma clean is independently controlled without
significant crosstalk within the stacked or clustered CARs.
[0053] Applications In Alternative Low Cost Manufacturing
[0054] In the practical MPAS system described above, the work piece
may be a large silicon wafer, (such as a 200 mm or 300 mm wafer).
In such cases where robotic wafer transport is not rate limiting,
throughputs may be doubled or more compared with state-of-the-art
high productivity systems and are particularly well designed for
certain ALD applications. These applications would be led by
barrier films for interconnect applications, which may have to be
50-100 A, but with ALD deposition rates which are not as large as
certain dielectrics. TiN, for example using TiCl.sub.4 and NH.sub.3
has a deposition rate of about only 0.4 A/cycle, providing about 3
wafers/hr/module for the desired thickness. Thus, a 6 module system
may produce only about 18 wph/system, whereas the MPAS provides of
order 36 wph/system, that is more suitable for interconnect
manufacturing. Since interconnect designs may have 7+ levels of
metallization and a level may require the use of an ALD barrier
layer, the system cost is prohibitive with the lower ALD system
throughput. These MPAS implementations are well suited to
semiconductor manufacturing of large area, highly complex chips,
such as those of 1 to 2 cm.sup.2 and containing billion level
transistor component counts, and where the film is used many times
for the fabrication of each device and wafer.
[0055] The cost of a 300 mm starting wafer is more than nominal and
unlikely to be reduced using current silicon crystal pull, cut and
polish manufacturing methods. The cost of the wafer itself has been
rationalized for silicon semiconductor use against the high value
of large area chips using large wafer.
[0056] However, some applications may benefit from the use of small
wafers, which may cost much less. For example, a 100 mm (4 inch)
silicon or compound semiconductor substrate. If a device, such as a
system on a chip or a any small commodity part or component may
have a cost to produce of only a few dollars, then the MPAS might
be used without a FOUP arrangement or even individual 100 mm
wafers. One may use a collection of low cost 100 mm substrates or
other small work pieces, such as individual or grouped sets of
small parts, components or devices carried on a large area
(.about.300 mm diameter in size) carrier. If 9 such 100 mm wafers
were placed on a nominal 300+mm square carrier, then the
productivity is 36.times.9 or 324 w/hr/ MPAS system. This method
utilizing large area parallel carrier methods using MPAS and a
large number of small form-factor work pieces may be generalized to
multiple application.
[0057] Thus, massively parallel ALD/CVD deposition system is
described.
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