U.S. patent application number 10/680656 was filed with the patent office on 2008-05-08 for tandem process chamber.
This patent application is currently assigned to APPLIED MATERIALS, INC.. Invention is credited to Jessica Barzilai, Kevin Fairbairn, Hari K. Ponnekanti, W.N. (Nick) Taylor.
Application Number | 20080105202 10/680656 |
Document ID | / |
Family ID | 25022385 |
Filed Date | 2008-05-08 |
United States Patent
Application |
20080105202 |
Kind Code |
A9 |
Fairbairn; Kevin ; et
al. |
May 8, 2008 |
Tandem process chamber
Abstract
The present invention provides an apparatus for vacuum
processing generally comprising an enclosure having a plurality of
isolated chambers formed therein, a gas distribution assembly
disposed in each processing chamber, a gas source connected to the
plurality of isolated chambers, and a power supply connected to
each gas distribution assembly.
Inventors: |
Fairbairn; Kevin; (Saratoga,
CA) ; Barzilai; Jessica; (Mountain View, CA) ;
Ponnekanti; Hari K.; (Santa Clara, CA) ; Taylor; W.N.
(Nick); (Dublin, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP - - APPM/TX
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
APPLIED MATERIALS, INC.
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20040069225 A1 |
April 15, 2004 |
|
|
Family ID: |
25022385 |
Appl. No.: |
10/680656 |
Filed: |
October 6, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09575025 |
May 19, 2000 |
6635115 |
|
|
10680656 |
Oct 6, 2003 |
|
|
|
08751524 |
Nov 18, 1996 |
6152070 |
|
|
09575025 |
May 19, 2000 |
|
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Current U.S.
Class: |
118/715 ;
156/345.31 |
Current CPC
Class: |
C23C 16/4412 20130101;
H01L 21/67173 20130101; H01L 21/67201 20130101; H01L 21/67196
20130101; H01L 21/67167 20130101; H01L 21/67017 20130101; C23C
16/54 20130101; H01L 21/6719 20130101 |
Class at
Publication: |
118/715 ;
156/345.31 |
International
Class: |
C23C 16/00 20060101
C23C016/00; H01L 21/306 20060101 H01L021/306 |
Claims
1. A tandem vacuum processing chamber, comprising a chamber body
defining a first and a second processing regions, the first and
second processing regions comprising: a bottom wall; an annular
sidewall positioned in communication with the bottom wall and
configured to separate the first processing region from the second
processing region; a substrate support assembly centrally
positioned in each of the first and second processing regions, the
substrate support assembly having an outer perimeter that is
symmetric about the annular sidewall; a first gas distribution
assembly positioned above the first processing region; and a second
gas distribution assembly position above the second processing
region.
2. The processing chamber of claim 1, wherein the first and second
gas distribution assemblies each comprise: a gas distribution
manifold in fluid communication with a gas supply; and a showerhead
positioned between the gas distribution manifold and the substrate
support assembly.
3. The processing chamber of claim 2, wherein the showerhead is
manufactured from a material that conducts radio frequency
energy.
4. The processing chamber of claim 1, further comprising an annular
pumping channel positioned in the annular sidewall of the first and
second processing regions.
5. The processing chamber of claim 4, wherein the annular pumping
channel is vertically positioned above an upper surface of the
substrate support assembly and below a lower surface of a gas
distribution assembly.
6. The processing chamber of claim 4, further comprising a vacuum
source in fluid communication with the annular pumping channel of
the first and second processing regions, the vacuum source being
configured to cooperatively control the pressure in the first and
second processing regions.
7. The processing chamber of claim 4, wherein the annular pumping
channel of the first processing region is in fluid communication
with the annular pumping channel of the second processing
region.
8. The processing chamber of claim 1, further comprising an
interior wall positioned between the first and second processing
regions.
9. The processing chamber of claim 1, further comprising a
cylindrically shaped removable liner positioned in each of the
first and second processing regions adjacent the annular
sidewall.
10. The processing chamber of claim 1, wherein the first processing
region is in fluid communication with the second processing region
through a conduit.
11. The processing chamber of claim 10, wherein the conduit
provides the same pressure in each of the processing regions.
12. A tandem substrate processing chamber, comprising: a first
annular processing region having a first bottom member and a first
interior sidewall; a first substrate support member positioned in
the first annular processing region, the first substrate support
member being symmetric about the first interior sidewall; a second
annular processing region having a second bottom member and a
second annular sidewall, the second annular processing region being
positioned adjacent to the first processing region such that the
second sidewall joins the first sidewall; a second substrate
support member positioned in the second annular processing region,
the second substrate support member being symmetric about the
second interior sidewall; and a pumping assembly in fluid
communication with the first and second processing regions.
13. The processing chamber of claim 12, wherein the pumping
assembly comprises: a first annular pumping channel positioned in
the first interior sidewall; a second annular pumping channel
positioned in the second interior sidewall; and a vacuum source in
fluid communication with the first annular pumping channel and the
second annular pumping channel.
14. The processing chamber of claim 12, wherein the first and
second interior sidewalls are annular.
15. The processing chamber of claim 12, wherein the first and
second substrate support members each comprise an annular upper
substrate support surface that is symmetric about the respective
interior sidewall.
16. The processing chamber of claim 12, wherein the first and
second processing regions are in fluid communication with each
other via an exhaust conduit.
17. The processing chamber of claim 12, further comprising an
individual gas distribution assembly positioned in each of the
first and second processing regions above each of the fist and
second substrate support members.
18. The processing chamber of claim 17, wherein the gas
distribution assembly comprises: a gas distribution manifold in
fluid communication with a gas source; and a showerhead assembly
positioned between the gas distribution manifold and the respective
substrate support member.
19. The processing chamber of claim 18, wherein the gas
distribution assembly is configured to conduct radio frequency
energy.
20. The processing chamber of claim 12, wherein the first and
second substrate support members further comprise a heating element
positioned in communication therewith.
21. A tandem vacuum processing chamber, comprising: a chamber body
having a bottom member; a first gas distribution assembly
positioned above the bottom member and defining an upper boundary
of a first annular processing region; a second gas distribution
assembly positioned above the bottom member and defining an upper
boundary of a second annular processing region; and a substrate
support member positioned in each of the first and second
processing regions, an outer portion of the substrate support
member being parallel to an annular sidewall defining a lateral
boundary of each of the processing regions.
22. The processing chamber of claim 21, wherein the first and
second gas distribution assemblies comprise a gas showerhead
assembly.
23. The processing chamber of claim 22, wherein the gas showerhead
assembly comprises: a perforated plate positioned to dispense a
processing gas into the respective processing volumes from a front
side and a gas distribution manifold positioned to supply a
processing gas to a backside of the perforated plate.
24. The processing chamber of claim 21, further comprising an
annular pumping channel positioned in the annular sidewalls of each
of the processing regions at a vertical position that is equal to
or above an upper surface of the respective substrate support
member.
25. The processing chamber of claim 24, further comprising a vacuum
source in fluid communication with the annular pumping channel, the
vacuum source being configured to cooperatively control the
pressure in the first and second processing volumes.
26. The processing chamber of claim 21, wherein the substrate
support member comprises a heating element positioned in
communication therewith.
27. The processing chamber of claim 21, wherein the first and
second annular sidewalls share a common interior wall.
28. The processing chamber of claim 21, further comprising a fluid
conduit positioned in communication with the first and second
processing volumes and a vacuum source, the fluid conduit being
configured to equalize the pressure between the respective
processing volumes.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 09/575,025, filed May 19, 2000. Each of the
aforementioned related patent applications is herein incorporated
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method and apparatus,
including a system and individual system components, for concurrent
processing of multiple wafers in the fabrication of integrated
circuits. More particularly, the present invention provides a
staged vacuum system having one or more process chambers which
share one or more utilities, one or more loadlock chambers and a
transfer chamber connected to both the loadlock chambers and the
process chambers.
[0004] 2. Description of the Related Art
[0005] The term "cluster tool" generally refers to a modular,
multichamber, integrated processing system having a central wafer
handling module and a number of peripheral process chambers.
Cluster tools have become generally accepted as effective and
efficient equipment for manufacturing advanced microelectronic
devices. Wafers are introduced into a cluster tool where they
undergo a series of process steps sequentially in various process
chambers to form integrated circuits. The transfer of the wafers
between the process chambers is typically managed by a wafer
handling module located in a central transfer region. Typically,
cluster tools are of two different types: single wafer processing
or batch wafer processing. Single wafer processing generally refers
to a chamber configuration in which a single wafer is located for
processing. Batch wafer processing generally refers to a chamber
configuration in which multiple wafers are positioned on a
turntable and are processed at various positions within the chamber
as the turntable rotates through 360.degree.. A cluster tool
configured for batch processing allows multiple wafers, typically
from four (4) to seven (7) wafers, to'be simultaneously processed
in a single chamber.
[0006] FIGS. 1 and 2 show examples of commercially available batch
processing systems 10. FIG. 1 is a top schematic view of a radial
cluster tool for batch processing that is available from Novellus
Corporation. This cluster tool includes two batch processing
chambers 12, 13 that each holds six wafers 14 for processing. A
single wafer handling robot 16 located in a transfer chamber 18 is
used to transfer wafers from a loadlock chamber 20 to a first batch
processing chamber 12 one by one, where the wafers are sequentially
received on a turntable 22 before receiving the same processing
steps. The wafers may then be transferred, one by one, to a second
batch processing chamber 13, where the wafers undergo additional
processing steps. Typically, wafers are loaded into the system one
at a time and moved into a chamber where they receive partial
processing at various positions as the wafers are rotated
360.degree. on the turntable.
[0007] FIGS. 2A and 2B are top and side schematic views of a
cluster tool 10 for batch processing that is available from Mattson
Technology. The loadlock chamber 20 and transfer chamber 18 have a
common wafer elevator 19 that allow the wafers to be staged within
the transfer chamber. A transfer robot 16 transports wafers to the
processing chamber, such as a chemical vapor deposition (CVD)
chamber, which holds up to four wafers. The wafers are then
returned to the wafer elevator and eventually withdrawn from the
tool.
[0008] One disadvantage of batch processing, including the
processing performed in the cluster tools described above, is that
batch processing frequently provides poor deposition uniformity
from the center of the wafer to the edge of the wafer. Process
uniformity is important in order to obtain uniformity of deposition
on the wafer. The poor uniformity of batch processing systems is a
direct result of having multiple wafers being partially processed
at multiple stations within a single chamber.
[0009] An alternative approach to improve process uniformity is the
use of single wafer processing chambers. Single wafer processing is
generally considered to provide a higher degree of control over
process uniformity, because a single wafer is positioned in a
process chamber where it undergoes a complete process step, such as
a deposition step or an etch step, without having to be moved to a
different position. Furthermore, the components of a single wafer
processing chamber can be positioned concentrically or otherwise
relative to the single wafer.
[0010] FIG. 3 shows a top schematic view of a cluster tool 10
having multiple single wafer processing chambers 12 mounted
thereon. A cluster tool similar to that shown in FIG. 3 is
available from Applied Materials, Inc. of Santa Clara, Calif. The
tool includes a loadlock chamber 20 and a transfer chamber 18
having a wafer handling module 16 for moving the wafers from
location to location within the system, in particular, between the
multiple single wafer processing chambers 12. This particular tool
is shown to accommodate up to four (4) single wafer processing
chambers 12 positioned radially about the transfer chamber.
[0011] There is a need for a vacuum processing system that provides
both uniform wafer processing and high throughput. More
particularly, there is a need for an integrated system and process
chambers that work in cooperation to incorporate single wafer
architecture with batch wafer handling techniques. It would be
desirable to have a system with a small footprint/faceprint and
which requires lower capital investments and operating costs than
typical cluster tools.
SUMMARY OF THE INVENTION
[0012] The present invention provides an apparatus for vacuum
processing generally comprising an enclosure having a plurality of
isolated chambers formed therein, a gas distribution assembly
disposed in each processing chamber, a gas source connected to the
isolated chambers, and a power supply connected to each gas
distribution assembly. The chambers also preferably include a
remote plasma system for generation of excited cleaning gases and
delivery of these gases into the chamber. The chambers within an
enclosure preferably share process gases and an exhaust system, but
includes separate power sources connected to each gas distribution
system.
[0013] In one aspect of the invention, the chambers are configured
to provide concurrent processing of multiple wafers having shared
gas supplies and a shared exhaust system. To facilitate chamber
cleaning, a remote plasma system is disposed adjacent to the
chambers to deliver reactive cleaning gases into the chambers.
[0014] In another aspect of the invention; the chambers provide
independent temperature and power control to facilitate plasma
process control within each chamber. Each gas distribution assembly
preferably includes its own power supply and related power control.
Each pedestal also preferably including a temperature controlled
member and a temperature control.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0016] The above and other advantages of the present invention are
described in conjunction with the following drawing figures, in
which:
[0017] FIG. 1 is a top schematic view of a radial cluster tool for
batch processing that is available from Novellus Corporation;
[0018] FIGS. 2A and 2B are top and side schematic views of a linear
cluster tool for batch processing that is available from Mattson
Technology;
[0019] FIG. 3 is a top schematic view of a cluster tool having a
plurality of single wafer processing chambers;
[0020] FIG. 4 is a perspective view of one embodiment of the vacuum
processing system of the present invention;
[0021] FIG. 5 is a top schematic view of one embodiment of the
vacuum processing system of the present invention;
[0022] FIG. 6 is a front end view of one embodiment of the vacuum
processing system of the present invention;
[0023] FIG. 7 is a back end view of one embodiment of the vacuum
processing system of the present invention;
[0024] FIG. 8 is a perspective view of the front end loading system
of the present invention;
[0025] FIG. 9 is a substantially front perspective view of the
inside of a loadlock chamber of the present invention;
[0026] FIG. 10 is a cross sectional view of a loadlock chamber of
the present invention;
[0027] FIG. 11 is a perspective view of a loadlock chamber showing
a gate valve and actuating assembly mounted on the front of the
loadlock chamber;
[0028] FIG. 12 is a perspective view of another embodiment of a
loadlock chamber of the present invention;
[0029] FIG. 13 is a top view of the present invention showing a
transfer chamber having a transfer wafer handling member located
therein and a front end platform having two wafer cassettes and a
front end wafer handling member mounted thereon for wafer mapping
and centering;
[0030] FIG. 14 is a cross sectional side view of a transfer chamber
of the present invention;
[0031] FIG. 15 is a top view of a transfer chamber and a processing
chamber showing a wafer handling member of the present invention
mounted in the transfer chamber and in a retracted position ready
for rotation within the transfer chamber or extension into another
chamber;
[0032] FIG. 16 is a top view of a transfer chamber and a processing
chamber showing a wafer handling member of the present invention
mounted in the transfer chamber and in an extended position wherein
the blades are positioned in the processing chamber;
[0033] FIG. 17 is a cross sectional view of a magnetically coupled
actuating assembly of a wafer handling system of the present
invention;
[0034] FIG. 18 is a perspective view of one embodiment of a
processing chamber of the present invention;
[0035] FIG. 19 is a cross sectional view of one embodiment of a
processing chamber of the present invention;
[0036] FIG. 20 is an exploded-view of the gas distribution
assembly;
[0037] FIG. 21 is a top view of a processing chamber of the present
invention with the lid removed;
[0038] FIG. 22a is a schematic diagram of a vacuum system of the
present invention;
[0039] FIG. 22b is a schematic diagram of another vacuum system of
the present invention;
[0040] FIG. 23 is a perspective view of a remote plasma chamber
mounted on a processing chamber;
[0041] FIG. 24 is a cross sectional view of a remote plasma chamber
mounted on a processing chamber; and
[0042] FIG. 25 is an illustrative block diagram of the hierarchical
control structure of a computer program for process control;
[0043] FIG. 26 is a top view of a transfer chamber showing a time
optimal path for a robot of the present invention;
[0044] FIG. 27 is a graph showing the optimal velocity profile for
the path shown in FIG. 26;
[0045] FIG. 28 is a top view of a transfer chamber showing a time
optimal path for a robot of the present invention; and
[0046] FIG. 29 is a graph showing the optimal velocity profile for
the path shown in FIG. 28.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0047] The present invention generally provides a
cassette-to-cassette vacuum processing system which concurrently
processes multiple wafers and combines the advantages of single
wafer process chambers and multiple wafer handling for high quality
wafer processing, high wafer throughput and reduced system
footprint. In accordance with one aspect of the invention, the
system is preferably a staged vacuum system which generally
includes a loadlock chamber for introducing wafers into the system
and which also provides wafer cooling following processing, a
transfer chamber for housing a wafer handler, and one or more
processing chambers each having two or more processing regions
which are isolatable from each other and preferably share a common
gas supply and a common exhaust pump. Isolatable means that the
processing regions have a confined plasma zone separate from the
adjacent region which is selectively communicable with the adjacent
region via an exhaust system. The processing regions within each
chamber also preferably include separate gas distribution
assemblies and RF power sources to provide a uniform plasma density
over a wafer surface in each processing region. The processing
chambers are configured to allow multiple, isolated processes to be
performed concurrently in at least two regions so that at least two
wafers can be processed simultaneously in separate processing
regions with a high degree of process control provided by shared
gas sources, shared exhaust systems, separate gas distribution
assemblies, separate RF power sources, and separate temperature
control systems. For ease of description, the terms processing
regions a chamber may be used to designate the zone in which plasma
processing is carried out.
[0048] FIGS. 4-7 illustrate the processing system 100 of the
present invention schematically. The system 100 is a self-contained
system having the necessary processing utilities supported on a
main frame structure 101 which can be easily installed and which
provides a quick start up for operation. The system 100 generally
includes four different regions, namely, a front end staging area
102 where wafer cassettes 109 (shown in FIG. 8) are supported and
wafers are loaded into and unloaded from a loadlock chamber 112, a
transfer chamber 104 housing a wafer handler, a series of tandem
process chambers 106 mounted on the transfer chamber 104 and a back
end 108 which houses the support utilities needed for operation of
the system 100, such as a gas panel 103, power distribution panel
105 and power generators 107. The system can be adapted to
accommodate various processes and supporting chamber hardware such
as CVD, PVD and etch. The embodiment described below will be
directed to a system employing a DCVD process, such as a silane
process, to deposit silicon oxide. However, it is to be understood
that these other processes are contemplated by the present
invention.
Front End Staging Area
[0049] FIG. 8 shows the front end staging area 102 of the system
100 which includes a staging platform 110 having one or more wafer
cassette turntables 111 rotationally mounted through the platform
110 to support one, or more wafer cassettes 109 for processing.
Wafers housed in the wafer cassettes 109 are loaded into the system
100 through one or more doors 137 disposed through a front cover
139 (both shown in FIG. 6). A front end wafer handler 113, such as
a robot, is mounted on the staging platform 110 adjacent to the
wafer cassette turntables 111 and the loadlock chamber door 209
(shown in FIG. 11). Preferably, the front end wafer handler 113
includes a wafer mapping system to index the wafers in each wafer
cassette 109 in preparation for loading the wafers into a loadlock
cassette disposed in the loadlock chamber 112. One wafer handler
used to advantage in the present system which includes a wafer
mapping system is available from Equippe Technologies, Sunnyvale,
Calif., as model nos. ATM 107 or 105. The wafer mapping sensor
verifies the number of wafers and orientation of the wafers in the
cassette 109 before positioning the wafers in the loadlock chamber
112 for processing. An exhaust system such as ULPA filter,
available from Enviroco Corporation located in Alburquerque, N.
Mex.; Flanders located in San Rafael, Calif., or Filtra located in
Santa Ana, Calif., is mounted to the, bottom of a, support shelf
115 above the platform 110 to provide particle control on the front
end of the system. A computer monitor 117 is supported on a monitor
shelf 119 above the support shelf 115 to provide touch control to
an operator.
Loadlock Chamber
[0050] FIG. 9 shows a substantially side perspective view of one
embodiment of a loadlock chamber 112 of the present invention. The
loadlock chamber 112 includes a sidewall 202, a bottom 204 and a
lid 206. The sidewall 202 defines a loadlock loading port 208 for
loading wafers into and unloading wafers out of the vacuum system
100. Passages 210 and 212 are disposed in the sidewall 202 opposite
the loading port 208 to allow wafers to be moved from the loadlock
chamber 112 into the transfer chamber 104 (not shown). Slit valves
and slit valve actuators are used to seal the passages 210 and 212
when isolation or staged vacuum is desired. A service port 214 and
service door or window 216 are disposed on one end of the loadlock
chamber 112 to provide service and visual access to the loadlock
chamber 112.
[0051] A loadlock cassette 218 is disposed within the loadlock
chamber 112 to support the wafers in a spaced relationship in the
loadlock chamber 112 so that a wafer handler can pass between the
wafers to place and remove wafers from the loadlock cassette 218.
The loadlock cassette 218 preferably supports two or more wafers in
a side-by-side arrangement on wafer seats 220. The wafer seats 220
are formed on cassette plates 222 which are supported in spaced
relation on a movable shaft 224. Preferably, the plates 222 are
made of anodized aluminum and can handle up to about 14 wafers
spaced vertically apart by about 0.6 inch. In the embodiment shown
in FIG. 9, six rows of wafer seats 220 are provided to support a
total of twelve (12) wafers.
[0052] Each wafer seat 220 defines at least two grooves 226 in
which a support rail 228 is disposed to support a wafer above the
wafer seat 220 to provide a cooling gas passage below the wafer. In
a preferred embodiment, at least two rails 228 made of a ceramic
are provided to support the wafer, but more rails may be used.
Wafers are supported about 1 to about 15 mils above the wafer seats
220 on the ceramic rails 228 to provide uniform cooling of the
wafers.
[0053] The shaft 224 is disposed through the bottom 204 of the
loadlock chamber 112 and supports the cassette plates 222 within
the loadlock chamber 112. A motor, such as a stepper motor or other
elevator system, is disposed below the bottom 204 of the loadlock
chamber 112 and moves the shaft 224 upwardly and downwardly within
the loadlock chamber 112 to locate a pair of wafers in alignment
with a wafer handler for loading or unloading wafers from the
loadlock chamber 112.
[0054] FIG. 10 shows a side view of the loadlock chamber 112 with
the front removed. The cassette plates 222 include a central
portion 230 through which the shaft 224 extends to support the
plates 222. The outer edges of the cassette plates 222 are
supported in a spaced relationship by spacers 232 which are secured
thereto with pins 234. Each plate 222 defines a central channel 236
formed into each plate to form a slot for the robot blade to pass
under the wafer when, the wafer is supported on the seat 220.
[0055] FIG. 11 shows a front perspective view of the loadlock
chamber 112. Loading door 209 and door actuator 238 are shown in a
closed and sealed position. The loading door 209 is connected to
the actuator 238 on movable shafts 240. To open the door 209, the
actuator 238 tilts away from the side wall 202 to unseal the door
209 and then the shafts 240 are lowered to provide clearance of the
door 209 and access to the port 208 (shown in FIG. 9). One door
actuator used to advantage with the present invention is available
from VAT, located in Switzerland.
[0056] An on-board vacuum pump 121 is mounted on the frame 101
adjacent the loadlock chamber 112 and the transfer chamber 104 to
pump down the loadlock chamber and the transfer chamber. An exhaust
port 280 is disposed through the bottom of the loadlock chamber 112
and is connected to the pump 121 via exhaust line 704. The pump is
preferably a high vacuum turbo pump capable of providing milliTorr
pressures with very low vibration. One vacuum used to advantage is
available from Edward High Vacuum.
[0057] The transfer chamber 104 is preferably pumped down through
the loadlock chamber 112 by opening a pair of slit valves sealing
passages 210, 212 and pumping gases out through the exhaust port
280 located in the loadlock chamber 112. Gas-bound particles are
kept from being swept into the transfer chamber 104 by continually
exhausting gases out of the system through the loadlock chamber
112. In addition, a gas diffuser 231 is disposed in the loadlock
chamber to facilitate venting up to atmosphere. The gas diffuser
231 is a preferably a conduit disposed in the loadlock chamber and
connected to a gas purge line such as an N.sub.2 purge gas line.
The gas diffuser 231 distributes the purge gas along a larger
surface area through a plurality of ports 233 disposed along the
length of the diffuser, thereby decreasing the time needed to vent
the chamber up to atmosphere. The vacuum system of the present
invention will be described in more detail below.
Dual Position Loadlock Chamber
[0058] FIG. 12 shows a cut-away perspective view of another
embodiment of a loadlock chamber 112 of the present invention. The
loadlock chamber 112 includes chamber walls 202, a bottom 204, and
a lid 206. The chamber 112 includes two separate environments or
compartments 242, 244 and a transfer region 246. Compartments 242,
244 include a wafer cassette in each compartment 242, 244 to
support the wafers therein. Each compartment 242, 244 includes a
support platform 248 and a top platform 250 to define the bottom
and top of the compartments 242, 244. A support wall 252 may be
disposed vertically within the compartments 242, 244 to support
platforms 248, 250 in a spaced relationship. Transfer region 246
includes one or more passages 192 for providing access from the
loadlock chamber 112 into the transfer chamber 104 (not shown).
Passages 192 are preferably opened and closed using slit valves and
slit valve actuators.
[0059] Compartments 242, 244 are each connected to an elevator
shaft 224, each of which is connected to a motor, such as a stepper
motor or the like, to move the compartments upwardly or downwardly
within the loadlock chamber 112. A sealing flange 256 is disposed
peripherally within the loadlock chamber 112 to provide a sealing
surface for support platform 248 of compartment 242. Sealing flange
258 is similarly disposed to provide a sealing surface for support
platform 250 of compartment 244. The compartments 242, 244 are
isolated from one another by sealing flanges 256, 258 to provide
independent staged vacuum of the compartments 242, 244 within the
loadlock chamber 112.
[0060] A back side pressure is maintained in spaces 260, 262
through a vacuum port disposed therein. A vacuum pump is connected
to the spaces 260, 262 via exhaust lines 264 so that a high vacuum
can be provided in the spaces 260, 262 to assist in sealing the
platforms 248, 250 against the sealing flanges 256, 258.
[0061] In operation, compartments 242, 244 can be loaded or
unloaded in the position shown in FIG. 12. Loading doors 209 and
actuators 238, such as those described above (shown in FIG. 11),
are provided through the front wall (not shown) at the upper and
lower limits of the loadlock chamber 112 corresponding with
compartments 242, 244. The pressure in a selected compartment is
pumped down after wafers have been, loaded into the compartment via
exhaust lines 287, 289 and the selected compartment is moved into
the transfer region 246. Compartments 242, 244 move independently
into the transfer region 246 by the stepper motor. The advantage of
having upper and lower compartments 242, 244 is that processing of
one set of wafers can occur while a second set of wafers is loaded
into the other compartment and that compartment is pumped down to
the appropriate pressure so that the compartment can be moved into
the transfer region 246 and in communication with the transfer
chamber 104.
Wafer Center-Finding
[0062] FIG. 8 shows the wafer handling robot 113 on the front end
102 of the system 100 which includes a wafer transfer blade for
transferring wafers from the wafer cassettes 109 into and out of
the loadlock chamber 112. The wafers do not always lie in precisely
the same position within each wafer cassette 109 and, therefore,
are not positioned identically on the blade when they are
transferred into the loadlock cassette 218. Thus, before the wafer
is loaded into the loadlock cassette, the precise location of the
wafer on the robot blade must be determined and provided to a
controlling computer. Knowing the exact center of the wafers allows
the computer to adjust for the variable position of each wafer on
the blade and deposit the wafer precisely in the desired position
in a loadlock cassette 218 so that, ultimately, the wafer handler
in the transfer chamber can precisely position the wafers in the
process chambers 106.
[0063] An optical sensing system 170 which provides wafer position
data (preferably the center coordinate of the wafer) to enable the
robot to precisely position the wafers in, the loadlock cassette
218 is provided adjacent to each cassette turntable 111 on the
front end 102. Each system comprises three optical sensors 172
mounted on the lower support 173 of a C clamp 174 adjacent the
cassette turntable 111 along a line perpendicular to the path of
the robot blade and three optical emitters 176 positioned on the
upper support 177 of the C clamp 174 aligned with the associated
sensors so that the sensors intercept the light beams from the
associated emitters. Typically, each pair comprises a conventional
infrared emitter and sensor.
[0064] The output of the sensors is converted by associated analog
to, digital converters into digital signals which are applied as
input to the system computer for use in computing the center
coordinate of the wafers as they enter the loadlock chamber 112,
and controlling the operation of the robot drive motors as required
to enable precise positioning of each wafer in the loadlock
cassette 218 by the robot 113. Details of the sensing and motor
control circuitry are described in more detail in U.S. Pat. No.
4,819,167, by Cheng et al., which is incorporated herein by
reference.
Transfer Chamber
[0065] FIG. 13 shows a top view of the processing system 100 of the
present invention. The transfer chamber body includes sidewalls 302
and bottom 304 and is preferably machined or otherwise fabricated
from one piece of material, such as aluminum. A lid (not shown) is
supported on the sidewalls 302 during operation to form a vacuum
enclosure. The sidewall 302 of transfer chamber 104 supports
processing chambers 106 and loadlock chamber 112. The sidewall 302
defines at least two passages 310 on each side through which access
to the other chambers on the system is provided. Each of the
processing chambers 106 and loadlock chamber 112 include one or
more slit valve openings and slit valves which enable communication
between the processing chambers, the loadlock chamber and the
transfer chamber while also providing vacuum isolation of the
environments within each of these chambers to enable a staged
vacuum within the system. The bottom 304 of the transfer chamber
104 defines, a central passage 306 in which a wafer handler 500,
such as a robot assembly, extends and is mounted to the bottom of
the transfer chamber. In addition, the bottom 304 defines a
plurality of passages 308 through which one or more slit valve
actuators extend and are sealably mounted. A gas purge port 309 is
disposed through the bottom 304 of the transfer chamber 104 to
provide a purge gas during pump down.
[0066] FIG. 14 shows the transfer chamber 104 in partial
cross-section. The passages 310 disposed through the sidewalls 302
can be opened and closed using two individual slit valves or a
tandem slit valve assembly. The passages 310 mate with the wafer
passages 610 in process regions 618, 620 (shown in FIG. 15) to
allow entry of wafers 502 into the processing regions 618, 620 in
chambers 106 for positioning on the wafer heater pedestal 628.
[0067] Slit valves and methods of controlling slit valves are
disclosed by Tepman et al. in U.S. Pat. No. 5,226,632 and by
Lorimer in U.S. Pat. No. 5,363,872, both of which are incorporated
herein by reference.
Transfer Chamber Wafer Handler
[0068] FIG. 15 shows a top schematic view of a magnetically coupled
robot 500 of the present invention in a retracted position for
rotating freely within the transfer chamber 104. A robot having
dual wafer handling blades 520, 522 is located within the transfer
chamber 104 to transfer the wafers 502 from one chamber to another.
A "very high productivity" (VHP) type robot which can be modified
and used to advantage in the present invention is the subject of
U.S. Pat. No. 5,469,035 issued on Nov. 21, 1995, entitled "Two-axis
Magnetically Coupled Robot", and is incorporated herein by
reference. The magnetically coupled robot 500 comprises a frog-leg
type assembly connected between two vacuum side hubs (also referred
to as magnetic clamps) and dual wafer blades 520, 522 to provide
both radial and rotational movement of the robot blades within a
fixed plane. Radial and rotational movements can be coordinated or
combined in order to pickup, transfer and deliver two wafers from
one location within the system 100 to another, such as from one
processing chamber 106 to another chamber.
[0069] The robot includes a first strut 504 rigidly attached to a
first magnet clamp 524 at point 525 and a second strut 506 rigidly
attached to a second magnet clamp 526 (disposed concentrically
below the first magnet clamp 524) at point 527 (See also FIG. 17).
A third strut 508 is attached by a pivot 510 to strut 504 and by a
pivot 512 to the wafer blade assembly 540. A fourth strut 514 is
attached by a pivot 516 to strut 506 and by a pivot 518 to the
wafer blade assembly 540. The structure of struts 504, 508, 506,
514 and pivots 510, 512, 516, 518 form a "frog leg" type connection
between the wafer blade assembly 540 and the magnet clamps 524,
526.
[0070] When magnet clamps 524, 526 rotate in the same direction
with the same angular velocity, then robot 500 also rotates about
axis A in this same direction with the same velocity. When magnet
clamps 524, 526 rotate in opposite directions with the same
absolute angular velocity, then there is no rotation of assembly
500, but instead, there is linear radial movement of wafer blade
assembly 540 to a position illustrated in FIG. 16.
[0071] Two wafers 502 are shown loaded on the wafer blade assembly
540 to illustrate that the individual wafer blades 520, 522 can be
extended through individual wafer passages 310 in sidewall 302 of
the transfer chamber 104 to transfer the wafers 502 into or out of
the processing regions 618, 620 of the chambers 106. The
magnetically coupled robot 500 is controlled by the relative
rotational motion of the magnet clamps 524, 526 corresponding to
the relative speed of two motors. A first operational mode is
provided in which both motors cause the magnet clamps 524, 526 to
rotate in the same direction at the same speed. Because this mode
causes no relative motion of the magnet clamps, the robot will
merely rotate about a central axis A, typically from a position
suitable for wafer exchange with one pair of processing regions
618, 620 to a position suitable for wafer exchange with another
pair of processing regions. Furthermore, as the fully retracted
robot is rotated about the central axis A, the outermost radial
points 548 along the edge of the wafer define a minimum circular
region 550 required to rotate the robot. The magnetically coupled
robot also provides a second mode in which both motors cause the
magnet clamps 524, 526 to rotate in opposite directions at the same
speed. This second mode is used to extend the wafer blades 520, 522
of the wafer blade assembly 640 through the passages 310 and into
the processing regions 618, 620 or, conversely, to withdraw the
blades therefrom. Other combinations of motor rotation can be used
to provide simultaneous extension or retraction of the wafer blade
assembly 540 as the robot 500 is being rotated about axis A.
[0072] To keep the wafer blades 520, 522 of the wafer blade
assembly 540 directed radially away from the rotational axis A, an
interlocking mechanism is used between the pivots or cams 512, 518
to assure an equal and opposite angular, rotation of each pivot.
The interlocking mechanism may take on many designs, including
intermeshed gears or straps pulled around the pivots in a figure-8
pattern or the equivalent. One preferred interlocking mechanism is
a pair of metal straps 542, and 544 that are coupled to and extend
between the pivots. 512, 518 of the wafer blade assembly 540. The
straps 542, 544 cooperate to form a figure-8 around the pivots 512,
518. However, it is preferred that the straps 542, 544 be
individually adjustable and positioned one above the other. For
example, a first end of the first strap 542 may pass around the
back side of pivot 512 and be fixedly coupled thereto, while a
second end passes around the front side of pivot 518 and is
adjustably coupled, thereto. Similarly, a first end of the second
strap 544 may pass around the back side of pivot 518 and be fixedly
coupled thereto, while a second end passes around the front side of
pivot 512 and is adjustably coupled thereto. The adjustable
couplings between the straps and the front sides of the pivots 512,
518 are preferably provided with a spring that pulls a precise
tension on the strap. Once the tension is established, the end of
the strap is firmly held in position with a screw or other
fastener. In FIGS. 15 and 16, the straps are also shown passing
around a rod 546 at the base of the U-shaped dual blade.
[0073] FIG. 16 shows the robot arms and blade assembly of FIG. 15
in an extended position. This extension is accomplished by the
simultaneous and equal rotation of magnet clamp 526 in a clock-wise
direction and magnet clamp 524 in a counter-clockwise rotation. The
individual blades 520, 522 of the wafer blade assembly 540 are
sufficiently long to extend through the passages 310 and center the
wafers 502 over the pedestals 628 (See FIG. 19). Once the wafers
502 have been lifted from the blades by a pair of lift pin
assemblies, then the blades are retracted and the passages 310 are
closed by a slit valve and actuator as described above.
[0074] FIG. 17 shows a cross sectional view of a robot drive system
mounted to the central opening 306 in the bottom 304 of the
transfer chamber 104. The magnetic coupling assembly is configured
to rotate magnetic retaining rings 524, 526 about the central axis
A, thereby providing a drive mechanism to actuate the wafer blade
assembly 540 within the system, both rotationally and linearly.
Additionally, the magnetic coupling assembly provides rotational
movement of the magnetic retaining rings 524, 526 with minimal
contacting moving parts within the transfer chamber 104 to minimize
particle generation. In this embodiment, the robot features are
provided by fixing first and second stepper or servo motors in a
housing located above or below the transfer chamber 104, preferably
below, and coupling the output of the motors to magnetic ring
assemblies located inwardly of and adjacent to a thin wall 560. The
thin wall 560 is connected to the upper or lower wall 304 of the
transfer chamber 104 at a sealed connection to seal the interior of
the transfer chamber from the environment outside of the chamber.
Magnetic retaining rings 524, 526 are located on the vacuum side of
transfer chamber 104, adjacent to and surrounding the thin wall
560.
[0075] A first motor output 562 drives a first shaft 572 and
intermeshed gears 580 to provide rotation to the first magnetic
ring assembly 582 that is magnetically coupled to the first
magnetic retaining ring 524. A second motor output 564 drives a
second shaft 586 and intermeshed gears 590 to provides rotation to
the second magnetic ring assembly 592. (a concentric cylindrical
member disposed about assembly 582) that is magnetically coupled to
a second magnetic retaining ring 526. Rotation of each motor
provides rotational outputs 562, 564 that rotate the magnet ring
assemblies 582, 592 which magnetically couple the rotary output
through the thin wall 560 to magnetic retaining rings 524, 526,
thereby rotating the struts 504, 506, respectively, and imparting
rotational and translational motion to the wafer blade assembly
540.
[0076] To couple each magnet ring assembly to its respective
magnetic retaining ring, each magnet ring assembly 582, 592 and
magnetic retaining ring 524, 526 preferably include an equal
plurality of magnets paired with one another through wall 560. To
increase magnetic coupling effectiveness, the magnets may be
positioned with their poles aligned vertically, with pole pieces
extending therefrom and toward the adjacent magnet to which it is
coupled. The magnets which are coupled are flipped, magnetically,
so that north pole to south pole coupling occurs at each pair of
pole pieces located on either side of the thin walled section.
While magnetic coupling is preferred, direct coupling of the motors
to the retaining rings may also be employed.
Optimal Path Trajectory of Robot
[0077] The movement of the robot 500 while transferring wafers is
primarily constrained by reliance on friction between the wafer and
the dual wafer blades 520, 522 for gripping the wafers. Both linear
and rotational movement of each wafer blade 520, 522 must be
controlled to avoid misalignment of the wafers. Movement of the
robot is preferably optimized to provide a minimum wafer transfer
time to improve productivity while avoiding wafer misalignment.
[0078] Optimization of robotic movement has been described in
publications, such as Z. Shiller and S. Dubowsky, "Time Optimal
Path Planning for Robotic Manipulators with Obstacles, Actuator,
Gripper and Payload Constraints", International Journal of Robotics
Research, pp. 3-18, 1989, and Z. Shiller and H. H. Lu, "Comparison
of Time-Optimal Motions Along Specified Paths", ASME Journal of
Dynamic Systems, Measurements and Control, 1991, which provide
mathematical approaches to finding the time optimal path between
two or more points for a given robot configuration. The approach
generally involves a mathematical approximation of a specified path
and calculation of an optimal velocity profile, and the calculation
of an optimal path by varying path parameters to find the minimum
time required for the robot to follow a specified path within all
known constraints.
[0079] A mathematical solution to optimization of robot movement
typically involves the solution of multiple algebraic equations and
non-linear differential equations or non-linear matrix differential
equations, and is preferably assisted by a computer. However,
persons skilled in the optimization methods can often identify the
more optimum path without resolving the matrices or the
equations.
[0080] Optimization of wafer movement using the, robot 500
described above resulted in definition of several time optimal
paths which are expected to significantly improve productivity of
the processing system of the present invention. The times optimal
paths are shown in FIGS. 26-29. FIG. 26 shows the optimal paths
1500, 1502, 1504 for moving wafers between chambers positioned
180.degree. apart on the processing platform and FIG. 27 shows the
optimal velocity profile for a path 1500 halfway between paths
1502, 1504 taken by wafers on the dual wafer blades 520, 522. FIG.
28 shows the optimal paths 1510, 1512, 1514 for moving wafers
between chambers positioned 90.degree. apart on the processing
platform and FIG. 29 shows the optimal velocity profile for a path
1510 halfway between paths 1512, 1514 taken by wafers on the dual
wafer blades 520, 522.
[0081] FIGS. 27 and 29 also show the maximum velocities which can
be attained by the robot 500 along the paths 1500, 1510 when wafers
are not positioned on the dual wafer blades 520, 522. The robot 500
is preferably controlled so that the dual wafer blades 520, 522
follow the optimal paths using the optimal velocity profiles shown
in FIGS. 26-29 when moving wafers through the transfer chamber
104.
Process Chambers
[0082] FIG. 18 shows a perspective view of one embodiment of a
tandem processing chamber 106 of the present invention. Chamber
body 602 is mounted or otherwise connected to the transfer chamber
104 and includes two processing regions in which individual wafers
are concurrently processed. The chamber body 602 supports a lid 604
which is hindgedly attached to the chamber body 602 and includes
one or more gas distribution systems 608 disposed therethrough for
delivering reactant and cleaning gases into multiple processing
regions.
[0083] FIG. 19 shows a schematic cross-sectional view of the
chamber 106 defining two processing regions 618, 620. Chamber body
602 includes sidewall 612, interior wall 614 and bottom wall 616
which define the two processing regions 618, 620. The bottom wall
616 in each processing region 618, 620 defines at least two
passages 622, 624 through which a stem 626 of a pedestal heater 628
and a rod 630 of a wafer lift pin assembly are disposed,
respectively. A pedestal lift assembly and the wafer lift will be
described in detail below.
[0084] The sidewall 612 and the interior wall 614 define two
cylindrical annular processing regions 618, 620. A circumferential
pumping channel 625 is formed in the chamber walls defining the
cylindrical processing regions. 618, 620 for exhausting gases from
the processing regions 618, 620 and controlling the pressure within
each region 618, 620. A chamber liner or insert 627, preferably
made of ceramic or the like, is disposed in each processing region
618, 620 to define the lateral boundary of each processing region
and to protect the chamber walls 612, 614 from the corrosive
processing environment and to maintain an electrically isolated
plasma environment between the electrodes. The liner 627 is
supported in the chamber on a ledge 629 formed in the walls 612,
614 of each processing region 618, 620. The liner includes a
plurality of exhaust ports 631, or circumferential slots, disposed
therethrough and in communication with the pumping channel 625
formed in the chamber walls. Preferably, there are about twenty
four ports 631 disposed through each liner 627 which are spaced
apart by about 15.degree. and located about the periphery of the
processing regions 618, 620. While twenty four ports are preferred,
any number can be employed to achieve the desired pumping rate and
uniformity. In addition to the number of ports, the height of the
ports relative to the face plate of the gas distribution system is
controlled to provide an optimal gas flow pattern over the wafer
during processing.
[0085] FIG. 21 shows a cross sectional view of the chamber
illustrating the exhaust system of the present invention. The
pumping channels 625 of each processing region 618, 620 are
preferably connected to a common exhaust pump via a common exhaust
channel 619. The exhaust channel 619 is connected to the pumping
channel 625 of each region 618, 620 by exhaust conduits 621. The
exhaust channel 619 is connected to an exhaust pump via an exhaust
line (not shown). Each region is preferably pumped down to a
selected pressure by the pump and the connected exhaust system
allows equalization of the pressure within each region.
[0086] Referring back to FIG. 19, each of the processing regions
618, 620 also preferably include a gas distribution assembly 608
disposed through the chamber lid 604 to deliver gases into the
processing regions 618, 620, preferably from the same gas source.
The gas distribution system 608 of each, processing region includes
a gas inlet passage 640 which delivers gas into a shower head
assembly 642. The shower head assembly 642 is comprised of an
annular base plate 648 having a blocker plate 644 disposed
intermediate a face plate 646. An RF feedthrough provides a bias
potential to the showerhead assembly to facilitate generation of a
plasma between the face plate 646 of the showerhead assembly and
the heater pedestal 628. A cooling channel 652 is formed in a base
plate 648 of each gas distribution system. 608 to cool the plate
during operation. An inlet 655 delivers a coolant fluid, such as
water or the like, into the channels 652 which are connected to
each other by coolant line 657. The cooling fluid exits the channel
through a coolant outlet 659. Alternatively, the cooling fluid is
circulated through the manifold.
[0087] The chamber body 602 defines a plurality of vertical gas
passages for each reactant gas and cleaning gas suitable for the
selected process to be delivered in the chamber through the gas
distribution system. Gas inlet connections 641 are disposed at the
bottom of the chamber 106 to connect the gas passages formed in the
chamber wall to the gas inlet lines 639. An O-ring is provided
around each gas passage formed through the chamber wall on the
upper surface of the chamber wall to provide sealing connection
with the lid as shown in FIG. 21. The lid includes matching
passages to deliver the gas from the lower portion of the chamber
wall into a gas inlet manifold 670 positioned on top of the chamber
lid as shown in FIG. 20. The reactant gases are delivered through a
voltage gradient feed-through 672 and into a gas outlet manifold
674 which is connected to a gas distribution assembly.
[0088] The gas input manifold 670 channels process gases from the
chamber gas feedthroughs into the constant voltage gradient gas
feedthroughs, which are grounded. Gas feed tubes (not shown)
deliver or route the process gases through the voltage gradient gas
feedthroughs 672 and into the outlet manifold 674. Resistive
sleeves surround the gas feed tubes to cause a linear voltage drop
across the feedthrough preventing a plasma in the chamber from
moving up the gas feed tubes. The gas feed tubes are preferably
made of quartz and the sleeves are preferably made of a composite
ceramic. The gas feed tubes are disposed within an isolating block
which contains coolant channels to control temperature and prevent
heat radiation and also to prevent liquefaction of process gases.
Preferably, the insulating block is made of Delrin. The quartz feed
tubes deliver gas into a gas output manifold 674 which channels the
process gases to the blocker plate 644 and into the gas
distribution plate 646.
[0089] The gas input manifold 670 (see FIG. 20) also defines a
passage which delivers cleaning gases from a chamber gas
feedthrough into the remote plasma source. These gases bypass the
voltage gradient feedthroughs and are fed into a remote plasma
source where the gases are activated into various excited species.
The excited species are then delivered to the gas distribution
plate at a point just below the blocker plate through a conduit
disposed in gas inlet passage 640. The remote plasma source and
delivery of reactant cleaning gases will be described in detail
below.
[0090] The gas lines 639 which provide gas into the gas
distribution systems of each processing region are preferably
connected to a single gas source line and are therefore shared or
commonly controlled for delivery of gas to each processing region
618, 620. The gas line(s) feeding the process gases to the
multi-zone chamber are split to feed the multiple process regions
by a t-type coupling. To facilitate flow into the individual lines
feeding each process region, a filter, such as a sintered nickel
filter available from PALL or Millipore, is disposed in the gas
line upstream from the splitter. The filter enhances the even
distribution and flow of gases into the separate gas feed
lines.
[0091] The gas distribution system comprises a base plate having a
blocker plate disposed adjacent to its lower surface. A face plate
is disposed below the blocker plate to deliver the gases into the
processing regions. In one embodiment, the base plate defines a gas
passage therethrough to deliver process gases to a region just
above the blocker plate. The blocker plate disperses the process
gases over its upper surface and delivers the gases above the face
plate. The holes in the blocker plate can be sized and positioned
to enhance mixing of the process gases and distribution over the
face plate. The gases delivered to the face plate are then
delivered into the processing regions in a uniform manner over a
wafer positioned for processing.
[0092] A gas feed tube is positioned in the gas passage and is
connected at one end to an output line from a remote plasma source.
One end of the gas feed tube extends through the gas outlet
manifold to deliver gases from the remote plasma source. The other
end of the gas feed tube is disposed through the blocker plate to
deliver gases beyond the blocker plate to the region just above the
face plate. The face plate disperses the gases delivered through
the gas feed tube and then delivers the gases into the processing
regions.
[0093] While this is a preferred gas distribution system, the gases
from the remote plasma source can be introduced into the processing
regions through a port provided through the chamber wall. In
addition, process gases could be delivered through any gas
distribution system which is presently available, such as the gas
distribution system available from Applied Materials, Inc. of Santa
Clara, Calif.
Heater Pedestal
[0094] FIG. 19 shows a heater pedestal 628 which is movably
disposed in each processing region 618, 620 by a stem 626 which is
connected to the underside of a support plate and extends through
the bottom of the chamber body 602 where it is connected to a drive
system 603. The stem 626 is preferably a circular, tubular,
aluminum member, having an upper end disposed in supporting contact
with the underside of the heater pedestal 628 and a lower end
closed off with a cover plate. The lower end of the stem is
received in a cup shaped sleeve, which forms the connection of the
stem to the drive system. The stem 626 mechanically positions the
heater pedestal 628 within the processing region and also forms an
ambient passageway through which a plurality of heater plate
connections can extend. Each heater pedestal 628 may include
heating elements to heat a wafer positioned thereon to a desired
process temperature. The heating elements may include for example a
resistive heating element. Alternatively, the heater pedestal may
be heated by an outside heating element such as a lamp. A pedestal
used to advantage in the present invention is available from
Applied Materials, Inc., of Santa Clara, Calif. The pedestal may
also support an electrostatic chuck, a vacuum chuck or other
chucking device to secure a wafer thereon during processing.
[0095] The drive system includes linear electric actuators made by
Industrial Device Corporation located in Novabo, Calif. The heater
assembly is raised and lowered by moving the transfer housing up or
down to a process, clean, lift and release position. The transfer
housing is connected to the actuator on one side and a linear slide
on the other through a carriage plate. The connection between the
actuator and the carriage is made via a flexible (ball and socket)
joint to allow for any misalignment. The linear slide and carriage
plate are biased against one another to prevent rotation and
bending thereof. A bellows surrounds the stem of the heater and
connects to the chamber bottom on one end and to the transfer
housing on the other end. A seal ring is provided in a groove in
the stem to seal the outer surface of the lower end of the stem in
the sleeve. Leveling of the heater with respect to the faceplate is
achieved with the use of three screws.
[0096] Alternatively, the drive system 603 includes a motor and
reduction gearing assembly suspended below the chamber 106 and
connected to a drive belt to a conformable coupling and lead screw
assembly. A transfer housing is received on the lead screw
assembly, which is guided up and down and held against rotation by
a linear slide. The heater lift mechanism is held against the
chamber with the drive collar. The heater assembly is raised and
lowered by a lead screw which is driven by a stepper motor. The
stepper motor is mounted to the heater lift assembly by a motor
bracket. The stepper motor drives the lead screw in a bellows. The
bellows turn the lead screw to raise or lower the heater assembly
to the process, lift and release positions. A seal ring is provided
in a groove in the stem to seal the outer surface of the lower end
of the stem in the sleeve.
Wafer Positioning Assembly
[0097] The stem 626 moves upwardly and downwardly in the chamber to
move the heater pedestal 628 to position a wafer thereon or remove
a wafer therefrom for processing. A wafer positioning assembly
includes a plurality of support pins 651 which move vertically with
respect to the heater pedestal 628 and are received in bores 653
disposed vertically through the pedestal. Each pin 651 includes a
cylindrical shaft 659 terminating in a lower spherical portion 661
and an upper truncated conical head 663 formed as an outward
extension of the shaft. The bores 653 in the heater pedestal 628
include an upper, countersunk portion sized to receive the conical
head 663 therein such that when the pin 651 is fully received into
the heater pedestal 628, the head does not extend above the surface
of the heater pedestal.
[0098] The lift pins 651 move partially in conjunction with, and
partially independent of, the heater pedestal 628 as the pedestal
moves within the processing region. The lift pins can extend above
the pedestal 628 to allow the robot blade to remove the wafer from
the processing region, but must also sink into the pedestal to
locate the wafer on the upper surface of the pedestal for
processing. To move the pins 651, the wafer positioning assembly
includes an annular pin support 655 which is configured to engage
lower spherical portions 661 of the lift pins 651 and a drive
member which positions the pin support 655 to selectively engage
the lift pins 651 depending on the position of the heater pedestal
628 within the processing region. The pin support 655, preferably
made from ceramic, extends around the stem 626 below the heater
pedestal 628 to selectively engage the lower spherical portions of
the support pins.
[0099] A drive assembly lifts and lowers the shaft 630 and
connected pin support 655 to move the pins 651 upwardly and
downwardly in each processing region 618, 620. The pin drive member
is preferably located on the bottom of the chamber 106 to control
the movement of the pin support platform 655 with respect to the
pedestal heater 628.
Vacuum System and Chamber Pumps
[0100] The vacuum control system for the processing system 100 of
the present invention may include a plurality of vacuum pumps in
communication with various regions of the system, with each region
having its own setpoint pressure. However, the transfer of wafers
from one chamber or region to another chamber or region requires
the opening of slit valves which allow the environments of the
communicating regions to mix somewhat and the pressures to
equilibrate.
[0101] FIG. 22a shows a schematic diagram of the vacuum system 700
of the present invention. The loadlock chamber 112 and the transfer
chamber 104 preferably share a vacuum pump 121 mounted on the main
frame 101 of the system adjacent the loadlock chamber and the
transfer-chamber. The loadlock chamber 112 is pumped down from
atmosphere by pump 121 through exhaust port 280 disposed through
the body of the loadlock chamber. The vacuum pressure in the
transfer chamber 104, as indicated by pressure gauge 705, is
provided by communication with the loadlock chamber 112 so that the
pressure in the transfer chamber is always equal to or greater than
the pressure in the loadlock chamber and any particles present in
the loadlock chamber will not be drawn into the transfer chamber
104. Exhaust port 280 in loadlock chamber 112 is connected to pump
121 via exhaust line 704. A pressure gauge 706 is positioned along
exhaust line 704 upstream from an isolation valve 708 to monitor
the pressure in the loadlock chamber at any given time. Isolation
valve 708 is located in exhaust line 704 between the pressure gauge
706 and the pump 121 to regulate the pressure in the loadlock
chamber. A vacuum switch 710 is also provided in communication with
the exhaust line between the isolation valve 708 and the pump 121.
The pump 121 is preferably a roughing pump, but depending on the
application may be any type of pump such as a turbomolecular pump,
a cryogenic pump or the like. Gas vent lines 712, 714 are connected
to the loadlock chamber 112 and the transfer chamber 104,
respectively, to provide a vent gas, such as nitrogen, into these
chambers.
[0102] Process chambers 106 are connected to a pump 720, such as a
roughing pump, cryogenic pump or turbomolecular pump, via exhaust
port 619 and exhaust line 722. A throttle valve 724, or the like,
is located in the exhaust line to regulate the pressure in the
processing regions 618, 620 of chambers 106 during operation. A
valve controller 726, preferably a part of the system controller,
provides a control signal to the throttle valve 724 based upon the
pressure indicated by the vacuum gauge 728. Preferably, an exhaust
port. 619 is in communication with each processing region (shown in
FIG. 21) and an exhaust line from each processing region tees into
a single exhaust line 722 which is connected to the pump 720.
[0103] According to one aspect of the present invention, the slit
valves in communication with the transfer chamber 104 and the
vacuum controllers of each chamber 106 and the loadlock chamber 112
are operated in a manner that reduces the amount of contaminants
entering the transfer chamber from either the loadlock chamber or
any of the chambers 106. The invention requires the pressure in the
loadlock chamber to be greater than or equal to, preferably greater
than, the pressure in an adjacent chamber or region prior to
opening the slit valve that will provide communication
therebetween. The loadlock pressure should only be greater than
atmospheric when open to the front end. The pressure should be
lower than the transfer chamber pressure when opening to transfer
in vacuum. It is particularly important that the transfer chamber
104 be at a high relative pressure when placed in communication
with a process chamber, because the contaminant levels can be
particularly great. For example, where the setpoint pressure in a
processing chamber 106 is about 10.sup.-3 torr, the pressure in the
transfer chamber should be greater than or equal to 10.sup.-3 torr,
most preferably greater than about 10.sup.-2 torr, before opening
the slit valves to transfer wafers into or out of the chamber
106.
[0104] The pressure in the transfer chamber is controlled in two
ways. First, the vacuum in the transfer chamber is established by
opening the slit valve(s) between the loadlock chamber 112 and the
transfer chamber 104 and then pulling a vacuum in the loadlock
chamber 112. In this manner, the pressure in the transfer chamber
should never be lower than the pressure in the loadlock chamber and
the only gas flow therebetween should be from the transfer chamber
to the loadlock chamber 112. It is anticipated that so long as the
transfer chamber is not in communication with any processing
chambers, the slit valves between the transfer chamber and the
loadlock chamber may remain open. Second, the transfer chamber is
provided with a purge gas inlet, such as from an argon or nitrogen
source. The purge gas may be delivered to the transfer chamber,
continuously or only as needed to provide a sufficient high
pressure to cause a positive gas flow out of the transfer
chamber.
[0105] In a particularly preferred mode, the slit valves to the
loadlock chamber 112 should always be closed during wafer transfer
between the transfer chamber 104 and a processing chamber 106, in
order to avoid the possibility of drawing the pressure in the
transfer chamber down below the pressure in the processing chamber.
This condition could result in a multitude of contaminants from the
processing chamber entering the transfer chamber and even the
loadlock, thereby exposing an entire cassette of wafers.
[0106] FIG. 22b shows a schematic diagram of two pumping systems
used to advantage with the dual chamber loadlock described above.
As can be seen from the figure, the two compartments can be pumped
down together or selectively pumped down to a desired vacuum.
Gas Box and Supply
[0107] Outside of the chamber on the back end of the system, there
is a gas supply panel containing the gases that are to be used
during deposition and cleaning. The particular gases that are used
depend upon the materials to be deposited onto the wafer or removed
from the chamber. The process gases flow through an inlet port into
the gas manifold and then into the chamber through a shower head
type gas distribution assembly. An electronically operated valve
and flow control mechanism control the flow of gases from the gas
supply into the chamber.
[0108] In one embodiment of the invention the precursor gases are
delivered from the gas box to the chamber where the gas line tees
into two separate gas lines which feed gases through the chamber
body as described above. Depending on the process, any number of
gases can be delivered in this manner and can be mixed either
before they are delivered to the bottom of the chamber or once they
have entered the gas distribution plate.
Power Supplies
[0109] An advanced compact RF ("CRF") power delivery system is used
for each processing region 618, 620 with one system connected to
each gas distribution system. A 13.56 MHz RF generator, Genisis
Series, manufactured by ENI, is mounted on the back end of the
system for each chamber. This high frequency generator is designed
for use with a fixed match and regulates the power delivered to the
load, eliminating the concern about forward and reflected power. Up
to 1250 watts may be supplied into load impedances with a VSWR of
less than or equal to 1:5. To interface a high frequency RF
generator and a low frequency RF generator to a process chamber, a
low pass filter is designed into the fixed match enclosure.
[0110] A 350 kHz RF generator manufactured by ENI, is located in an
RF generator rack on the back end of the system and linked to the
fixed RF match by coaxial cable. The low frequency RF generator
provides both low frequency generation and fixed match elements in
one compact enclosure. The low frequency RF generator regulates the
power delivered to the load reducing the concern about forward and
reflected power.
Remote Clean Module
[0111] FIGS. 23 and 24 show a perspective and cross sectional view
of a remote clean module 800 of the present invention. In
accordance with the invention, the remote clean module 800 is
connected to the processing regions 618, 620 of chamber 106 through
the inlet port 820. The remote clean module 800 supplies gas that
is used to remove deposited material from the interior surfaces of
the chamber after a sequence of process runs.
[0112] The remote clean module 800 includes a source of a precursor
gas 804, a remote activation chamber 806 which is located outside
of the processing chamber 106, a power source 808 for activating
the precursor gas within the remote activation chamber, an
electronically operated valve and flow control mechanism 810, and a
conduit or pipe 812 connecting the remote chamber to the processing
chamber via a conduit 811. The valve and flow control mechanism 810
delivers gas from the source of precursor gas 804 into the remote
activation chamber 806 at a user-selected flow rate. The activation
chamber 806 includes an aluminum enclosure 803 having a gas feed
tube 813 disposed therethrough. The power source 808 generates
microwaves which are guided by a wave guide 805 into the enclosure
803. The tube 813 is transparent to microwaves so that the
microwaves penetrate the tube and activate the precursor gas to
form a reactive species which is then flowed through the conduit
812 into the gas distribution assembly and then into a processing
chamber. In other words, the upper electrode or shower head 608 is
used to deliver the reactive gas into the processing regions of the
chamber. In the described embodiment, the remote-chamber is a
ceramic tube and the power source is a 2.54 GHz microwave generator
with its output aimed at the ceramic tube.
[0113] Optionally, there may also be a source of a minor carrier
gas 814 that is connected to the remote activation chamber through
another valve and flow control mechanism 816. The minor carrier gas
aids in the transport of the activated species to the deposition
chamber. The gas can be any appropriate nonreactive gas that is
compatible with the particular cleaning process with which it is
being used. For example, the minor carrier gas may be argon,
nitrogen, helium, hydrogen, or oxygen, etc. In addition to aiding
in the transport of activated species to the deposition chamber,
the carrier gas may also assist in the cleaning process or help
initiate and/or stabilize the plasma in the deposition chamber.
[0114] In the described embodiment, there is a filter 818 in the
conduit or pipe through which the activated species passes before
entering the deposition chamber. The filter removes particulate
matter that might have been formed during the activation of the
reactive species. In the described embodiment, the filter is made
of ceramic material having a pore, size of about 0.01 to about 0.03
microns. Of course, other materials can also be used, for example,
Teflon.
[0115] It should be noted that the filter can also be used to
remove unwanted materials that might have been produced as by
products of the reaction within the remote chamber. For example, if
the reactive gas is CF.sub.4 or SF.sub.6, or some other halogen
compound containing either carbon or sulfur, an activated carbon or
sulfur species will be present as a byproduct of the activation
process. It is generally desired, however, that carbon and sulfur
not be present in the deposition chamber. This is why these
compounds are generally not used in conventional dry cleaning
processes where the activation occurs entirely within the
deposition chamber. However, when the activation is performed
remotely, as described herein, these materials can be easily
removed by using an appropriate filter material. Such filter
materials are readily available in the commercial market and are
well-known to persons of ordinary skill in the art.
[0116] In the described embodiment, the precursor is NF.sub.3. The
flow rate of activated species is about 0.5 liters to about 2
liters per minute and the chamber pressure is about 0.5 to about
2.5 Torr. To activate the precursor gas, the microwave source
delivers about 500 to about 1500 Watts to the activation chamber.
Within the deposition chamber, the RF sources supply about 100 to
about 200 Watts to the plasma. For the present system, this implies
a voltage between the upper and lower electrodes of about 15 to
about 20 volts. The precise voltage and current are pressure
dependent, i.e., the current is proportional to the pressure given
a fixed voltage. In any event, it is only necessary to induce a
gentle plasma within the chamber, which only need be strong enough
to sustain the activated species that has been flown into the
chamber from the remote source.
[0117] By using NF.sub.3 as the feed gas, chambers that have been
deposited with silicon (Si), doped silicon, silicon nitride
(Si.sub.3N+.sub.4) and silicon oxide (SiO.sub.2) can be cleaned.
The cleaning rate for deposited film is about 2 microns/minute for
silicon nitride and about 1 micron/minute for silicon, doped
silicon, and silicon oxide. These cleaning rates are two to four
times faster than the conventional cleaning process which employs
only a local plasma with a power level of about 1 to about 2
kilowatts at 13.56 MHz RF.
[0118] Though a microwave generator is used in the described
embodiment to activate the precursor gas, any power source that is
capable of activating the precursor gas can be used. For example,
both the remote and local plasmas can employ DC, radio frequency
(RF), and microwave (MW) based discharge techniques. In addition,
if an RF power source is used, it can be either capacitively or
inductively coupled to the inside of the chamber. The activation
can also be performed by a thermally based, gas break-down
technique, a high intensity light source, or an x-ray source, to
name just a few.
[0119] In general, the reactive gases may be selected from a wide
range of options, including the commonly used halogens and halogen
compounds. For example, the reactive gas may be chlorine, fluorine
or compounds thereof, e.g. NF.sub.3, CF.sub.4, SF.sub.6,
C.sub.2F.sub.6, CCl.sub.4, C.sub.2Cl.sub.6. Of course, the
particular gas that is used depends on the deposited material which
is being removed. For example, in a tungsten deposition system, a
fluorine compound gas is typically used to etch and/or remove the
deposited tungsten.
[0120] Because of the use of a local plasma in conjunction with the
remote plasma, the remote activation chamber can be placed farther
away from the chamber. Thus, only tubing is needed to connect the
two remote sources to the local source. Some quenching of the
activated species (i.e., deactivation of the activated species) may
occur during the transfer. However, the local source compensates
for any such quenching that may occur. In fact, some long lived
activated species (e.g. F*) typically do not return to the ground
state when quenched, but rather they transition to an intermediate
state. Thus, the amount of energy that is required to reactivate
the quenched species is much less than is required to activate the
gas in the remote activation chamber. Consequently, the local
activation source (e.g., plasma) need not be a high energy
source.
[0121] It should also be noted that by placing the remote source at
a distance from the deposition chamber, the short lived radicals
that are produced during the activation process will be quenched
more completely than the long lived radicals as both are
transferred to the deposition chamber. Thus, the reactive gas that
flows into the deposition chamber will contain primarily the long
lived radicals that have survived the transfer. For example, if
NF.sub.3 is the reactive gas, two radicals are produced in the
remote activation chamber, namely, N* and F*. The nitrogen radical
is short lived and the fluorine radical is long lived. The nitrogen
radical will typically not survive a long transfer from the remote
chamber to the deposition chamber, whereas a large percentage of
the fluorine radicals will survive. This is a form of natural
filtering that occurs in the system that may be very desirable. In
the case of nitrogen radicals, for example, it is sometimes
preferable that they not be present in the deposition chamber
because their presence may result in the formation of
N.sub.xH.sub.yF.sub.z compounds, which can harm the pump. When the
activation is performed in the deposition chamber, however, as in
the case of conventional cleaning techniques, there is no easy way
to eliminate the nitrogen radicals that are produced.
[0122] In the dry cleaning process, chamber pressure can be
selected to lie anywhere within a fairly broad range of values
without significantly affecting performance. The preferred pressure
range is from about 0.1 to about 2 Torr, although pressures outside
of that range can also be used. In addition, the frequencies that
were chosen for the described embodiment were merely illustrative
and the frequencies that may be used in the invention are not
restricted to those used in the described embodiment. For example,
with regard to the RF power source, any of a wide range of
frequencies (e.g., 400 KHz to 13.56 MHz) are typically used to
generate plasmas and those frequencies may also be used in the
invention. In general, however, it should be understood that the
power levels, flow rates, and pressure that are chosen are system
specific and thus the will need to be optimized for the particular
system in which the process is being run. Making the appropriate
adjustments in process conditions to achieve optimum of performance
for a particular system is well within the capabilities of a person
of ordinary skill in the art.
Programming
[0123] The system controller operates under the control of a
computer program stored on the hard disk drive of a computer. The
computer program dictates the process sequencing and, timing,
mixture of gases, chamber pressures, RF power levels, susceptor
positioning, slit valve opening and closing, wafer heating and
other parameters of a particular process. The interface between a
user and the system controller is preferably via a CRT monitor and
lightpen which is depicted in FIG. 8. In a preferred embodiment two
monitors are used, one monitor mounted in the clean room wall for
the operators and the other monitor behind the wall for the service
technicians. Both monitors simultaneously display the same
information but only one lightpen is enabled. The lightpen detects
light emitted by the CRT display with a light sensor in the tip of
the pen. To select a particular screen or function, the operator
touches a designated area of the display screen and pushes the
button on the pen. The display screen generally confirms
communication between the lightpen and the touched area by changing
its appearance, i.e. highlight or color, or displaying a new menu
or screen.
[0124] A variety of processes can be implemented using a computer
program product that runs on, for example, the system controller.
The computer program code can be written in any conventional
computer readable programming language such as for example 68000
assembly language, C, C++, or Pascal. Suitable program code is
entered into a single file, or multiple files, using a conventional
text editor, and stored or embodied in a computer usable medium,
such as a memory system of the computer. If the entered code text
is in a high level language, the code is compiled, and the
resultant compiler code is then linked with an object code of
precompiled library routines. To execute the linked compiled object
code, the system user invokes the object code, causing the computer
system to load the code in memory, from which the CPU reads and
executes the code to perform the tasks identified in the
program.
[0125] FIG. 25 shows an illustrative block diagram of a preferred
hierarchical control structure of the computer program 1410. A user
enters a process set number and process chamber number into a
process selector subroutine 1420 in response to menus or screens
displayed on the CRT monitor by using the lightpen interface. The
process sets provide predetermined sets of process parameters
necessary to carry out specified processes, and are identified by
predefined set numbers. The process selector subroutine 1420
identifies (i) the desired process chamber, and (ii) the desired
set of process parameters needed to operate the process chamber for
performing the desired process. The process parameters for
performing a specific process relate to process conditions such as,
for example, process gas composition and flow rates, temperature,
pressure, plasma conditions such as RF bias power levels and
magnetic field power levels, cooling gas pressure, and chamber wall
temperature and are provided to the user in the form of a recipe.
The parameters specified by the recipe are entered in any
conventional manner, but most preferably by utilizing the
lightpen/CRT monitor interface.
[0126] Electronic signals provided by various instruments and
devices for monitoring the process are provided to the computer
through the analog input and digital input boards of the system
controller. Any conventional method of monitoring the process
chambers can be used, such as polling. Furthermore, electronic
signals for operating various process controllers or devices are
output through the analog output and digital output boards of the
system controller. The quantity, type and installation of these
monitoring and controlling devices may vary from one system to the
next according to the particular end use of the system and the
degree of process control desired. The specification or selection
of particular devices, such as the optimal type of thermocouple for
a particular application, is known by persons with skill in the
art.
[0127] A process sequencer subroutine 1430 comprises program code
for accepting the identified process chamber number and set of
process parameters from the process selector subroutine 1420, and
for controlling operation of the various process chambers. Multiple
users can enter process set numbers and process chamber numbers, or
a user can enter multiple process chamber numbers, so the sequencer
subroutine 1430 operates to schedule the selected processes in the
desired sequence. Preferably, the process sequencer subroutine 1430
includes program code to perform the steps of (i) monitoring the
operation of the process chambers to determine if the chambers are
being used, (ii) determining what processes are being carried out
in the chambers being used, and (iii) executing the, desired
process based on availability of a process chamber and type of
process to be carried out. When scheduling which process is to be
executed, the sequencer subroutine 1430 can be designed to take
into consideration the present condition of the process chamber
being used in comparison with the desired process conditions for a
selected process, or the "age" of each particular user entered
request, or any other relevant factor a system programmer desires
to include for determining the scheduling priorities.
[0128] Once the sequencer subroutine 1430 determines which process
chamber and process set combination is going to be executed next,
the sequencer subroutine 1430 causes execution of the process set
by passing the particular process set parameters to a chamber
manager subroutine 1440a-c which controls multiple processing tasks
in a process chamber 106 according to the process set determined by
the sequencer subroutine 1430. For example, the chamber manager
subroutine 1440a comprises program code for controlling sputtering
and CVD process operations in the process chamber 106. The chamber
manager subroutine 1440 also controls execution of various chamber
component subroutines which control operation of the chamber
component necessary to carry out the selected process set. Examples
of chamber component subroutines are wafer positioning subroutine
1450, process gas control subroutine 1460, pressure control
subroutine 1470, heater control subroutine 1480, and plasma control
subroutine 1490. Those having ordinary skill in the art will
recognize that other chamber control subroutines can be included
depending on what processes are desired to be performed in the
process chamber 106. In operation, the chamber manager subroutine
1440a selectively schedules or calls the process component
subroutines in accordance with the particular process set being
executed. The chamber manager subroutine 1440a schedules the
process component subroutines similarly to how the sequencer
subroutine 1430 schedules which process chamber 106 and process set
is to be executed next. Typically, the chamber manager subroutine
1440a includes steps of monitoring the various chamber components,
determining which components need to be operated based on the
process parameters for the process set to be executed, and causing
execution of a chamber component subroutine responsive to the
monitoring and determining steps.
[0129] Operation of particular chamber components subroutines will
now be described with reference to FIG. 25. The wafer positioning
subroutine 1450 comprises program code for controlling chamber
components that are used to load the wafer onto the pedestal 628,
and optionally to lift the wafer to a desired height in the chamber
106 to control the spacing between the wafer and the showerhead
642. When wafers are loaded into the chamber 106, the pedestal 628
is lowered and the lift pin assembly is raised to receive the wafer
and, thereafter, the pedestal 628 is raised to the desired height
in the chamber, for example to maintain the wafer at a first
distance or spacing from the gas distribution manifold during the
CVD process. In operation, the wafer positioning subroutine 1450
controls movement of the lift assembly and pedestal 628 in response
to process set parameters related to the support height that are
transferred from the chamber manager subroutine 1440a.
[0130] The process gas control subroutine 1460 has program code for
controlling process gas composition and flow rates. The process gas
control subroutine 1460 controls the open/close position of the
safety shut-off valves, and also ramps up/down the mass flow
controllers to obtain a desired gas flow rate. The process gas
control subroutine 1460 is invoked by the chamber manager
subroutine 1440a, as are all chamber components subroutines, and
receives from the chamber manager subroutine process parameters
related to the desired gas flow rate. Typically, the process gas
control subroutine 1460 operates by opening a single control valve
between the gas source and the chamber 106 gas supply lines, and
repeatedly (i) measuring the mass flow rate, (ii) comparing the
actual flow rate to the desired flow rate received from the chamber
manager subroutine 1440a, and (iii) adjusting the flow rate of the
main gas supply line as necessary. Furthermore, the process gas
control subroutine 1460 includes steps for monitoring the gas flow
rate for an unsafe rate, and activating a safety shut-off valve
when an unsafe condition is detected.
[0131] In some processes, an inert gas such as argon is provided
into the chamber 106 to stabilize the pressure in the chamber
before reactive process gases are introduced into the chamber. For
these processes, the process gas control subroutine 1460 is
programmed to include steps for flowing the inert gas into the
chamber 106 for an amount of time necessary to stabilize the
pressure in the chamber, and then the steps described above would
be carried out. Additionally, when a process gas is to be vaporized
from a liquid precursor, for example tetraethylorthosilane (TEOS),
the process control subroutine 1460 would be written to include
steps for bubbling a delivery gas such as helium through the liquid
precursor in a bubbler assembly. For this type of process, the
process gas control subroutine 1460 regulates the flow of the
delivery gas, the pressure in the bubbler, and the bubbler
temperature in order to obtain the desired process gas flow rates.
As discussed above, the desired process gas flow rates are
transferred to the process gas control subroutine 1460 as process
parameters. Furthermore, the process gas control subroutine 1460
includes steps for obtaining the necessary delivery gas flow rate,
bubbler pressure, and bubbler temperature for the desired process
gas flow rate by accessing a stored data table containing the
necessary values for a given process gas flow rate. Once the
necessary values are obtained, the delivery gas flow rate, bubbler
pressure and bubbler temperature are monitored, compared to the
necessary values and adjusted accordingly.
[0132] The pressure control subroutine 1470 comprises program code
for controlling the pressure in the chamber 106 by regulating the
size of the opening of the throttle valve in the exhaust system of
the chamber. The size of the opening of the throttle valve is
varied to control the chamber pressure at a desired level in
relation to the total process gas flow, the gas-containing volume
of the process chamber, and the pumping set point pressure for the
exhaust system. When the pressure control subroutine 1470 is
invoked, the desired set point pressure level is received as a
parameter from the chamber manager subroutine 1440a. The pressure
control subroutine 1470 operates to measure the pressure in the
chamber 106 using one or more conventional pressure manometers
connected to the chamber, compare the measured value(s) to the set
point pressure, obtain PID (proportional, integral, and
differential) control parameters from a stored pressure table
corresponding to the set point pressure, and adjust the throttle
valve according to the PID values obtained from the pressure table.
Alternatively, the pressure control subroutine 1470 can be written
to open or close the throttle valve to a particular opening size to
regulate the chamber 106 to the desired pressure.
[0133] The heater control subroutine 1480 comprises program code
for controlling the temperature of the lamp or heater module that
is used to heat the wafer 502. The heater control subroutine 1480
is also invoked by the chamber manager subroutine 1440a and
receives a desired, or set point, temperature parameter. The heater
control subroutine 1480 determines the temperature by measuring
voltage output of a thermocouple located in a pedestal 628,
compares the measured temperature to the set point temperature, and
increases or decreases current applied to the heater to obtain the
set point temperature. The temperature is obtained from the
measured voltage by looking up the corresponding temperature in a
stored conversion table, or by calculating the temperature using a
fourth order polynominal. When radiant, lamps are used to heat the
pedestal 628, the heater control subroutine 1480 gradually controls
a ramp up/down of current applied to the lamp. The gradual ramp
up/down increases the life and reliability of the lamp.
Additionally, a built-in-fail-safe mode can be included to detect
process safety compliance, and can shut down operation of the lamp
or heater module if the process chamber 106 is not properly set
up.
[0134] The plasma control subroutine 1490 comprises program code
for setting the RF bias voltage power level applied to the process
electrodes in the chamber 106, and optionally, to set the level of
the magnetic field generated in the chamber. Similar to the
previously described chamber component subroutines, the plasma
control subroutine 1490 is invoked by the chamber manager
subroutine 1440a.
[0135] While the system of the present invention was described
above with reference to a plasma enhanced CVD application, it is to
be understood that the invention also includes the use of high
density (HDP) CVD and PVD chambers as well as etch chambers. For
example, the system of the present invention can be adapted to
include tandem HDP CVD chambers for plasma processing. In one
alternative embodiment, the gas distribution/lid assembly could be
replaced with a dielectric dome having an inductive coil disposed
about the dome and an RF power supply connected to the coil to
enable inductive coupling of a high density plasma within the
chamber. Similarly, tandem PVD chambers could be configured with a
target assembly disposed thereon for a deposition material source.
DC power supplies could be connected the target assemblies to
provide sputtering power thereto.
[0136] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
* * * * *