U.S. patent application number 10/881417 was filed with the patent office on 2005-12-29 for heating system for load-lock chamber.
This patent application is currently assigned to Taiwan Semiconductor Manufacturing Co., Ltd.. Invention is credited to Chang, Kou-Ien, Chen, Wen-Ming, Wang, Wen-Chi.
Application Number | 20050284572 10/881417 |
Document ID | / |
Family ID | 35504325 |
Filed Date | 2005-12-29 |
United States Patent
Application |
20050284572 |
Kind Code |
A1 |
Chen, Wen-Ming ; et
al. |
December 29, 2005 |
Heating system for load-lock chamber
Abstract
A system for heating a load-lock chamber, particularly that of a
plasma etching system for etching semiconductor wafer substrates.
The load-lock chamber heating system includes a heater that is
provided in fluid communication with a gas supply which contains an
inert gas such as nitrogen. A gas pump pumps the gas from the gas
supply through the heater, and from the heater into the load-lock
chamber. The gas heats the load-lock chamber to prevent or minimize
condensation of corrosive etching gases onto the interior surfaces
of the load-lock chamber as well as the surfaces of substrates
contained therein.
Inventors: |
Chen, Wen-Ming; (Jhunan
Township, TW) ; Wang, Wen-Chi; (Jhunan Township,
TW) ; Chang, Kou-Ien; (Yonghe city, TW) |
Correspondence
Address: |
TUNG & ASSOCIATES
Suite 120
838 W. Long Lake Road
Bloomfield Hills
MI
48302
US
|
Assignee: |
Taiwan Semiconductor Manufacturing
Co., Ltd.
|
Family ID: |
35504325 |
Appl. No.: |
10/881417 |
Filed: |
June 29, 2004 |
Current U.S.
Class: |
156/345.31 ;
137/1 |
Current CPC
Class: |
H01L 21/67201 20130101;
H01J 37/32871 20130101; Y10T 137/0318 20150401; H01L 21/67109
20130101; H01L 21/67207 20130101 |
Class at
Publication: |
156/345.31 ;
137/001 |
International
Class: |
C23F 001/00; E03B
001/00 |
Claims
What is claimed is:
1. A system for preventing condensation of a gas in a chamber,
comprising: a gas source for containing an inert gas; a heater
provided in fluid communication with said gas source for fluid
communication with the chamber and receiving the inert gas from
said gas source and heating the inert gas; and a pump provided in
fluid communication with said heater for pumping the gas from said
heater to the chamber.
2. The system of claim 1 further comprising a controller connected
to said heater for operating said heater.
3. The system of claim 1 further comprising a controller connected
to said pump for operating said pump.
4. The system of claim 3 wherein said controller is further
connected to said heater for operating said heater.
5. A method of preventing condensation of a gas in a chamber,
comprising the steps of: providing a heater in fluid communication
with the chamber; heating a heating gas by distributing said
heating gas through said heater; and distributing said heating gas
from said heater into the chamber.
6. The method of claim 5 wherein said heating gas comprises
nitrogen.
7. The method of claim 5 wherein said heating said heating gas
comprises heating said heating gas to a temperature of from about
70 degrees C. to about 100 degrees C.
8. The method of claim 7 wherein said heating gas comprises
nitrogen.
9. The method of claim 5 wherein said distributing said heating gas
from said heater into the chamber comprises distributing said
heating gas from said heater into the chamber at a flow rate of
from about 20 sccm to about 100 sccm.
10. The method of claim 9 wherein said heating gas comprises
nitrogen.
11. The method of claim 9 wherein said heating said heating gas
comprises heating said heating gas to a temperature of from about
70 degrees C. to about 100 degrees C.
12. The method of claim 11 wherein said heating gas comprises
nitrogen.
13. A method of preventing condensation of a gas in a load-lock
chamber, comprising the steps of: providing a heater in fluid
communication with the load-lock chamber; heating a heating gas to
a gas temperature by distributing said heating gas through said
heater; and distributing said heating gas from said heater into the
chamber at a gas flow rate.
14. The method of claim 13 wherein said heating gas comprises
nitrogen.
15. The method of claim 13 wherein said gas temperature is from
about 70 degrees C. to about 100 degrees C.
16. The method of claim 15 wherein said heating gas comprises
nitrogen.
17. The method of claim 13 wherein said gas flow rate is about 20
sccm to about 100 sccm.
18. The method of claim 17 wherein said gas temperature is from
about 70 degrees C. to about 100 degrees C.
19. The method of claim 17 wherein said heating gas comprises
nitrogen.
20. The method of claim 19 wherein said gas temperature is from
about 70 degrees C. to about 100 degrees C.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to etching chambers used in
the etching of material layers on a semiconductor wafer substrate
to fabricate semiconductor integrated circuits on the substrate.
More particularly, the present invention relates to a heating
system for heating a loadlock chamber in a semiconductor substrate
etching system to reduce or eliminate condensation of etchant gases
in the chamber.
BACKGROUND OF THE INVENTION
[0002] In the semiconductor production industry, various processing
steps are used to fabricate integrated circuits on a semiconductor
wafer. These steps include deposition of a conducting layer on the
silicon wafer substrate; formation of a photoresist or other mask
such as titanium oxide or silicon oxide, in the form of the desired
metal interconnection pattern, using standard lithographic
techniques; subjecting the wafer substrate to a dry etching process
to remove the conducting layer from the areas not covered by the
mask, thereby etching the conducting layer in the form of the
masked pattern on the substrate; removing or stripping the mask
layer from the substrate typically using reactive plasma and
chlorine gas, thereby exposing the top surface of the conductive
interconnect layer; and cooling and drying the wafer substrate by
applying water and nitrogen gas to the wafer substrate.
[0003] Etching processes used to fabricate integrated circuits on
substrates include "wet" etching, in which one or more chemical
reagents are brought into direct contact with the substrate, and
"dry" etching, such as plasma etching. In wet etching, liquid
chemicals such as acids, bases and solvents are used to chemically
remove wafer surface material. Wet etching is generally applicable
only for geometries having a size larger than 3 m. Dry etching, on
the other hand, is useful for smaller geometries and includes
plasma etching, one of the most widely-used forms of etching.
[0004] In plasma etching processes, a gas such as HBr or Cl.sub.2
is first introduced into a reaction chamber and then plasma is
generated from the gas. This is accomplished by dissociation of the
gas into ions, free radicals and electrons by using an RF (radio
frequency) generator, which includes one or more electrodes. The
electrodes are accelerated in an electric field generated by the
electrodes, and the energized electrons strike gas molecules to
form additional ions, free radicals and electrons, which strike
additional gas molecules, and the plasma eventually becomes
self-sustaining. The ions, free radicals and electrons in the
plasma react chemically with the layer material on the
semiconductor wafer to form residual products which leave the wafer
surface and thus, etch the material from the wafer.
[0005] FIG. 1 illustrates a typical conventional wafer processing
station 10 such as a plasma etcher used in etching material layers
on semiconductor wafers 14. The processing station 10 typically
includes a loading port 13 which receives a cassette holder 12 from
an automatic guided vehicle (AGV), overhead transport (OHT) vehicle
or other pod transfer vehicle (not illustrated) in the cleanroom. A
robot or other wafer transfer device 20 unloads the wafers 14 from
a wafer cassette 15 inside the cassette holder 12 and transfers the
wafers 14 through a wafer transfer chamber 18 to a load-lock
chamber 22. A wafer transfer robot 26 in a wafer transfer chamber
24 transfers the wafers 14 from the load-lock chamber 22 to a
process chamber 28.
[0006] The wafer transfer robot 26 positions each wafer 14 on a
corresponding set of multiple wafer lift pins (not shown) which are
upwardly extended from a heater block 30 contained inside the
process chamber 28. The lift pins are vertically slidably disposed
in respective lift pin openings (not illustrated) in the heater
block 30 and contact the bottom surface or backside of the wafer 14
in order to lower the wafer 14 to rest on the heater block 30 prior
to the etching process and also lift the wafer 14 from the heater
block 30 after the etching process. In the process chamber 28, the
heater block 30 heats the wafer 14 to temperatures typically in the
range of about 200 degrees C.-250 degrees C. during the etching
process as reactive plasma or reactive gases such as chlorine
and/or hydrogen bromide are used to etch the unmasked conductive
layer or layers from each wafer.
[0007] After completion of the etching process, the wafer transfer
robot 26 transfers the wafers 14 from each process chamber 28 back
to the load-lock chamber 22. Finally, the cooled wafers 14 are
loaded on the wafer transfer robot or devices 20 in the wafer
transfer chamber 18 and transferred to a cassette holder 16 at an
unloading port 17, where the wafers 14 are removed from the wafer
processing station 10 for subsequent transfer of the wafers 14 to
another processing station or tool (not illustrated) in the clean
room.
[0008] One of the problems frequently associated with etching
wafers 14 in the process chambers 28 is that some of the residual
HBr and Cl.sub.2 gases used in the etching process drift from the
process chambers 28 into the loadlock chamber 22, where the gases
condense onto the surfaces of the loadlock chamber 22. This can
cause contamination of wafers 14 therein, as well as contribute to
poor KLA performance and corrosion of the loadlock chamber 22, and
may cause release of excessive concentrations of the gases into the
environment of the station 10 when wafers 14 are loaded into and
unloaded from the wafer cassettes 15 in the cassette holders 12.
Accordingly, a system is needed for introducing a heated gas such
as nitrogen into a load-lock chamber for the purpose of preventing
or minimizing condensation of hydrogen bromide, chlorine and/or
other corrosive gases in the load-lock chamber.
[0009] An object of the present invention is to provide a system
for heating a chamber of a processing system.
[0010] Another object of the present invention is to provide a
system for preventing or minimizing condensation of corrosive gases
in a chamber.
[0011] Still another object of the present invention is to provide
a system which is suitable for preventing or minimizing the
condensation of corrosive gases such as hydrogen bromide and
chlorine in a load-lock chamber of an etching system for
semiconductors.
[0012] Yet another object of the present invention is to provide a
chamber heating system which is capable of reducing the frequency
of wet chamber cleanings.
[0013] A still further object of the present invention is to
provide a chamber heating system which is capable of reducing the
time required to carry out a wet chamber cleaning.
[0014] Still another object of the present invention is to provide
a system for heating a load-lock chamber, which system
substantially reduces the concentrations of corrosive etching gases
in an environment surrounding the chamber.
[0015] Another object of the present invention is to provide a
load-lock heating chamber system which enhances wafer throughput
through an etching system.
[0016] A still further object of the present invention is to
provide a load-lock heating chamber system which is capable of
reducing a temperature gradient between a load-lock chamber, a
buffer chamber and a process chamber.
[0017] Yet another object of the present invention is to provide a
novel method of reducing or preventing condensation of corrosive
gases in a load-lock chamber of a semiconductor processing tool or
system.
SUMMARY OF THE INVENTION
[0018] In accordance with these and other objects and advantages,
the present invention is generally directed to a novel system for
heating a load-lock chamber, particularly that of a plasma etching
system for etching semiconductor wafer substrates. The load-lock
chamber heating system includes a heater that is provided in fluid
communication with a gas supply which contains an inert gas such as
nitrogen. A gas pump pumps the gas from the gas supply through the
heater, and from the heater into the load-lock chamber. The gas
heats the load-lock chamber to prevent or minimize condensation of
corrosive etching gases onto the interior surfaces of the load-lock
chamber as well as the surfaces of substrates contained
therein.
[0019] The present invention further includes a method of
preventing condensation of corrosive gases on surfaces in a
load-lock chamber. The operational speed of the pump may be
controlled to facilitate a desired flow rate of the gas from the
heater into the load-lock chamber. In a preferred embodiment, the
flow rate of the gas is from about 20 sccm to about 100 sccm. The
temperature of the heating gas is typically from about 70 degrees
C. to about 100 degrees C., and preferably, about 80 degrees C.
[0020] Reduction or elimination of corrosive gas condensation in a
load-lock chamber prolongs the time available for operation of the
etching or other processing system by reducing the frequency of
wet-cleanings required for the load-lock chamber. Furthermore, the
time required for carrying out each wet cleaning is reduced because
particle contamination caused by gas condensation is
correspondingly reduced or eliminated. The lifetime of system
elements such as SMIF (standardized mechanical interface) systems
used to load wafers into and unload wafers from the processing
system is also increased, due to the reduction or elimination of
the corrosive gases.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The invention will now be described, by way of example, with
reference to the accompanying drawings, in which:
[0022] FIG. 1 is a schematic view of a typical conventional wafer
processing station for the etching of semiconductor wafer
substrates;
[0023] FIG. 2 is a schematic view of a wafer processing system in
conjunction with a load-lock chamber heating system of the present
invention; and
[0024] FIG. 3 is a flow diagram illustrating sequential process
steps in typical implementation of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] The present invention has particularly beneficial utility in
preventing the condensation of hydrogen bromide, chlorine or other
corrosive gases used to etch material layers on semiconductor wafer
substrates on the interior surfaces of a load-lock chamber in an
etching system. However, the invention is not so limited in
application and while references may be made to such etching
chambers and load-lock chambers, the invention is more generally
applicable to preventing or minimizing condensation of gases on
interior chamber surfaces in a variety of industrial and mechanical
applications.
[0026] In a preferred embodiment, the present invention includes a
heating system for a load-lock chamber and includes a heater the
inlet end of which is provided in fluid communication with a supply
of an inert gas such as nitrogen. The outlet end of the heater is
provided in fluid communication with the load-lock chamber. A fan,
blower or pump is provided for flowing the gas at a selected gas
flow rate from the gas supply through the heater, which heats the
gas to a selected temperature, and from the heater into the
load-lock chamber.
[0027] The heated gas flowing into the load-lock chamber raises the
temperature of internal surfaces in the chamber and thereby
prevents the condensation of hydrogen bromide, chlorine or other
corrosive gases used in the etching process onto the chamber
surfaces. This reduces the frequency of wet chamber cleanings
necessary to maintain the interior of the load-lock chamber in
optimum condition for the processing of substrates, and eliminates
or substantially reduces the deposition of particles onto interior
chamber surfaces, including the surfaces of WIP substrates.
Furthermore, leakage of the corrosive gases from the load-lock
chamber through the entry and exit ports of the etching system is
substantially reduced or eliminated, thus enhancing the working
environment around the etching system and minimizing or reducing
corrosion of mechanical systems which are associated with the
etching system, such as SMIF (standardized mechanical interface)
arms used to load and unload wafer cassettes in the system.
[0028] The present invention further includes a method of
preventing condensation of corrosive gases on surfaces in a
load-lock chamber. The operational speed of the pump may be
controlled to facilitate a desired flow rate of the gas from the
heater into the load-lock chamber, and the temperature of the gas
may be controlled to impart a desired temperature to the interior
surfaces of the load-lock chamber. In a preferred embodiment, the
flow rate of the gas is from about 20 sccm to about 100 sccm. The
temperature of the heating gas is typically from about 70 degrees
C. to about 100 degrees C., and preferably, about 80 degrees C. The
gas may be introduced into the load-lock chamber for a period of
typically from about 30 seconds to about 2 minutes to thoroughly
warm the interior surfaces of the chamber after an etching process
and prevent the condensation of corrosive gases that have a
tendency to drift from a process chamber onto the interior surfaces
of the load-lock chamber.
[0029] Referring to FIG. 2, a wafer processing station 40 such as
an etching system for the etching of semiconductor wafer substrates
44 is shown schematically in implementation of the present
invention. It is understood that the wafer processing station 40
shown in FIG. 2 and hereinafter described is just one example of a
wafer processing station or tool which is suitable for
implementation of the present invention, and the invention may be
suitable for use with wafer processing tools having designs which
depart from that of the wafer processing station 40. The wafer
processing station 40 includes a wafer transfer chamber 48 to which
is attached a cassette holder 42 with a loading port 43 and an
adjacent cassette holder 46 with an unloading port 47. A load-lock
chamber 52 is provided adjacent to the wafer transfer chamber 48.
Wafer transfer devices 50 are provided in the wafer transfer
chamber 48 for transferring semiconductor wafers 44 from the
cassette holder 42 into the load-lock chamber 52, and from the
load-lock chamber 52 into the cassette holder 46. A wafer transfer
chamber 54 is provided adjacent to the load-lock chamber 52, and
contains a wafer transfer robot 56 which transfers the wafers 44
between the load-lock chamber 52 and a process chamber 58. Each
process chamber 58 may contain a heater block 60 for controlling
the temperature of a wafer 44 placed thereon by the wafer transfer
robot 56 during etching of material layers on the wafer 44.
[0030] According to the present invention, a heating system 36 for
the load-lock chamber 52 includes a heater 62 the outlet end of
which is provided in fluid communication with the load-lock chamber
52 through a heater outlet conduit 66. Multiple heating coils or
elements 63 are provided in the heater 62 and may be operably
connected through heater control wiring 67 to a controller 65 which
controls the heat of the heating elements 63, according to the
knowledge of those skilled in the art. Through a gas distribution
conduit 76, the inlet end of the heater 62 is provided in fluid
communication with a gas supply reservoir 72 which contains an
inert gas 70 such as nitrogen. A gas blower, fan or pump 74 is
typically provided in the heater outlet conduit 66 for pumping the
gas 70 from the gas supply 72, through the heater 62 and into the
load-lock chamber 52 at a selected flow rate. The controller 65 may
be operably connected, according to the knowledge of those skilled
in the art, to the gas pump 74 through pump control wiring 75 to
control the operational speed of the gas pump 74, and thus, the
flow rate of the gas into the load-lock chamber 52.
[0031] In typical application of the present invention, the loading
port 43 of the wafer processing station 40 receives a cassette
holder 42, which contains a wafer cassette 45 holding multiple
semiconductor wafers 44, from an automatic guided vehicle (AGV),
overhead transport (OHT) vehicle or other pod or container transfer
vehicle (not illustrated) in the cleanroom. The wafer transfer
device 50 unloads individual wafers 44 from the wafer cassette 45
inside the cassette holder 42 and transfers the wafers 44 through
the wafer transfer chamber 48 into the load-lock chamber 52. The
wafer transfer robot 56 in the wafer transfer chamber 54 transfers
the wafer 44 from the load-lock chamber 52 to the process chamber
58.
[0032] The wafer transfer robot 56 typically positions each wafer
44 on a corresponding set of multiple wafer lift pins (not shown)
which are upwardly extended from the heater block 60 contained
inside the process chamber 58. The lift pins are vertically
slidably disposed in respective lift pin openings (not illustrated)
in the heater block 60 and contact the bottom surface or backside
of the wafer 44 in order to lower the wafer 44 to rest on the
heater block 60 prior to the etching process and also lift the
wafer 44 from the heater block 60 after the etching process. In the
process chamber 58, the heater block 60 heats the wafer 44 to
temperatures typically in the range of about 200 degrees C.-250
degrees C. during the etching process as reactive plasma or
reactive gases such as chlorine and/or hydrogen bromide are used to
etch the unmasked conductive layer or layers from each wafer 44 or
to perform STI (shallow trench isolation) procedures, for
example.
[0033] After completion of the etching process carried out in the
process chamber 58, most of the corrosive etchant gases are removed
from the process chamber 58 using an exhaust pump evacuating system
(not shown), as is known by those skilled in the art. However, some
residual gases typically remain in the process chamber 58 after the
evacuation process. Therefore, as the wafer transfer robot 56
subsequently transfers each wafer 44 from the process chamber 58
back to the load-lock chamber 52, these residual gases have a
tendency to drift from the process chamber 58 into the load-lock
chamber 52. Accordingly, in implementation of the present
invention, the heating system 36 is operated to heat the interior
surfaces of the load-lock chamber 52 to prevent the residual
etchant gases from cooling and condensing on those surfaces. First,
the desired temperature, the desired gas flow rate and the desired
gas flow time for the heating gas 70 is programmed into the
controller 65. As the wafer transfer robot 56 next transfers each
wafer 44 from the process chamber 58 into the load-lock chamber 52,
the heating gas 70, typically nitrogen, is drawn from the gas
supply 72, through the gas distribution conduit 76 and into the
heater 62, where the heating gas 70 is heated to the preset
temperature as programmed into the controller 65. In a preferred
embodiment, the heating gas 70 is heated to a temperature of from
about 70 degrees C. to about 100 degrees C., and preferably, about
80 degrees C. The controller 65 operates the gas pump 74 at the
preset operational speed to pump the heated gas 70 from the heater
62, through the heater outlet conduit 66 and into the load-lock
chamber 52, at the desired gas flow rate, typically about 20 sccm
to about 100 sccm, for a time period of typically from about 30
seconds to about 2 minutes. Accordingly, the heated nitrogen 70
contacts and heats the interior surfaces of the load-lock chamber
52 to a temperature which is roughly equal to the temperature of
the heated gas 70, thereby preventing residual corrosive etchant
gases from cooling and condensing on the interior surfaces of the
load-lock chamber 52, including on the surfaces of the wafer or
wafers 44 held therein. Continued operation of the gas evacuation
system (not shown) of the wafer processing station 40 evacuates
both the heating gas 70 and the uncondensed residual etchant gases,
which remain in the gaseous state, from the load-lock chamber 52.
Finally, the wafer 44 is loaded onto the wafer transfer device 50
in the wafer transfer chamber 48 and transferred to the cassette
holder 46 at an unloading port 47, where the wafers 44 are removed
from the wafer processing station 40 for subsequent transfer of the
wafers 44 to another processing station or tool (not illustrated)
in the clean room.
[0034] Referring next to the flow diagram of FIG. 3, a typical
process sequence in implementation of the present invention is
summarized. In process step 1, a wafer substrate is subjected to an
etching process, such as an STI (shallow trench isolation) process,
in an etching chamber. In process step 2, a selected gas
temperature and flow rate, as well as gas flow time, are programmed
into the temperature and flow rate controller. In process step 3,
the heating gas is pumped from the gas source into the heater. In
process step 4, the heater heats the gas to the preset temperature
programmed into the controller. In process step 5, the heated gas
is pumped into the load-lock chamber at the preset gas flow rate
programmed into the controller for the gas flow time period
programmed into the controller. In process step 6, the heated gas,
as well as the uncondensed etchant gases, are evacuated from the
load-lock chamber.
[0035] While the preferred embodiments of the invention have been
described above, it will be recognized and understood that various
modifications can be made in the invention and the appended claims
are intended to cover all such modifications which may fall within
the spirit and scope of the invention.
* * * * *