U.S. patent application number 12/295675 was filed with the patent office on 2009-07-30 for exhaust structure of film-forming apparatus, film-forming apparatus, and method for processing exhaust gas.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Einosuke Tsuda.
Application Number | 20090191109 12/295675 |
Document ID | / |
Family ID | 38563691 |
Filed Date | 2009-07-30 |
United States Patent
Application |
20090191109 |
Kind Code |
A1 |
Tsuda; Einosuke |
July 30, 2009 |
EXHAUST STRUCTURE OF FILM-FORMING APPARATUS, FILM-FORMING
APPARATUS, AND METHOD FOR PROCESSING EXHAUST GAS
Abstract
A film-forming apparatus 100 includes a processing chamber 11,
and TiCl.sub.4 gas and NH.sub.3 gas are supplied into the
processing chamber 11 for forming a TiN film on a substrate W in
the processing chamber 11 by CVD. The processing chamber 11 has a
gas exhaust system 300. The gas exhaust system 300 includes a gas
exhaust pipe 51 for exhausting the exhaust gas in the processing
chamber 11, a trap mechanism 54 provided to the gas exhaust pipe 51
for trapping a by-product in the exhaust gas, and a heated reaction
gas supply mechanism 60 for supplying a heated reaction gas into
the exhaust gas. The heated reaction gas is adapted to react with a
component in the exhaust gas to produce a by-product. Specifically,
NH.sub.3 gas is supplied by the heated reaction gas supply
mechanism 60 as the heated reaction gas, and NH.sub.4Cl is produced
as the by-product.
Inventors: |
Tsuda; Einosuke; (Yamanashi,
JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
TOKYO
JP
|
Family ID: |
38563691 |
Appl. No.: |
12/295675 |
Filed: |
April 2, 2007 |
PCT Filed: |
April 2, 2007 |
PCT NO: |
PCT/JP07/57398 |
371 Date: |
October 1, 2008 |
Current U.S.
Class: |
423/240R ;
118/722; 422/169; 423/210 |
Current CPC
Class: |
C23C 16/4412 20130101;
C23C 16/34 20130101 |
Class at
Publication: |
423/240.R ;
423/210; 422/169; 118/722 |
International
Class: |
B01D 53/64 20060101
B01D053/64; B01D 53/68 20060101 B01D053/68; B01D 50/00 20060101
B01D050/00; C23C 16/54 20060101 C23C016/54 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2006 |
JP |
2006-102920 |
Mar 15, 2007 |
JP |
2007--066650 |
Claims
1. A gas exhaust system of a film-forming apparatus for forming a
film by CVD on a substrate placed in a processing chamber by
supplying a processing gas into the processing chamber, the gas
exhaust system of the film-forming apparatus comprising: a gas
exhaust pipe connected to the processing chamber, for exhausting an
exhaust gas in the processing chamber; a trap mechanism provided to
the gas exhaust pipe, for trapping a by-product in the exhaust gas;
and a heated reaction gas supply mechanism for supplying a heated
reaction gas into the exhaust gas, the heated reaction gas adapted
to react with a component in the exhaust gas to produce a
by-product.
2. The gas exhaust system of claim 1, wherein a TiN film is formed
by CVD on the substrate placed in the processing chamber by
supplying TiCl.sub.4 gas and NH.sub.3 gas as the processing gas
into the processing chamber and, at the same time, NH.sub.4Cl is
produced as a by-product by supplying NH.sub.3 gas as the heated
reaction gas from the heated reaction gas supply mechanism.
3. The gas exhaust system of claim 2, wherein the NH.sub.3 gas as
the heated reaction gas is supplied while being heated at about
170.degree. C. or higher.
4. The gas exhaust system of claim 1, wherein the heated reaction
gas supply mechanism supplies the heated reaction gas to an
upstream side of the trap mechanism on the gas exhaust pipe via a
pipe.
5. The gas exhaust system of claim 1, wherein the heated reaction
gas supply mechanism supplies the heated reaction gas to the trap
mechanism via a pipe.
6. The gas exhaust system of claim 1, wherein the heated reaction
gas supply mechanism includes a reaction gas heating unit for
heating a reaction gas, and the reaction gas heating unit has a
heating chamber for heating the reaction gas therein and a coiled
heating element disposed in the heating chamber.
7. The gas exhaust system of claim 1, wherein a bypass pipe for
exhausting the processing gas without passing through the
processing chamber is connected to an inlet side of the processing
chamber.
8. The gas exhaust system of claim 7, further comprising a
heating/mixing chamber for heating and mixing the processing gas
flowing through the bypass pipe and the heated reaction gas
supplied from the heated reaction gas supply mechanism.
9. A film-forming apparatus for forming a film on a substrate,
comprising: a processing chamber in which a substrate is placed; a
processing gas supply mechanism for supplying a processing gas into
the processing chamber where the substrate is placed; a unit for
causing a film forming reaction on the substrate by imparting
energy to the processing gas; and a gas exhaust system for
exhausting an exhaust gas in the processing chamber and processing
the exhaust gas, wherein the gas exhaust system includes: a gas
exhaust pipe for exhausting the exhaust gas in the processing
chamber; a trap mechanism provided to the exhaust pipe, for
trapping a by-product in the exhaust gas; and a heated reaction gas
supply mechanism for supplying a heated reaction gas into the
exhaust gas, the heated reaction gas adapted to react with a
component in the exhaust gas to produce a by-product.
10. The film-forming apparatus of claim 9, wherein the processing
gas supply mechanism is provided with a unit for heating the
substrate placed in the processing chamber to form a TiN film by
causing a film forming reaction on the substrate by supplying
TiCl.sub.4 gas and NH.sub.3 gas as the processing gas into the
processing chamber, and NH.sub.4Cl is produced as a by-product by
supplying NH.sub.3 gas as the heated reaction gas from the heated
reaction gas supply mechanism.
11. A method for processing an exhaust gas in a film-forming
apparatus for forming a film by CVD on a substrate placed in a
processing chamber by supplying a processing gas into the
processing chamber, the method comprising: exhausting the exhaust
gas in the processing chamber through a gas exhaust pipe connected
to the processing chamber; forming a by-product by supplying a
heated reaction gas into the exhaust gas flowing in the gas exhaust
pipe, the heated reaction gas adapted to react with a component in
the exhaust gas; and trapping the by-product by a trap
mechanism.
12. The method of claim 11, wherein a TiN film is formed by CVD on
a substrate placed in the processing chamber by supplying
TiCl.sub.4 gas and NH.sub.3 gas as the processing gas into the
processing chamber and, at the same time, NH.sub.4Cl is produced as
the by-product by supplying NH.sub.3 gas as the heated reaction
gas, which reacts with TiCl.sub.4 in the exhaust gas, into the
exhaust gas flowing in the gas exhaust pipe and, then, the produced
NH.sub.4Cl as the by-product is trapped by the trap mechanism.
13. A computer-readable storage medium storing software for
executing a control program in a computer, wherein, when executed,
the control program controls a method for processing an exhaust gas
in a film-forming apparatus for forming a film by CVD on a
substrate placed in a processing chamber by supplying a processing
gas into the processing chamber, the method comprising: exhausting
an exhaust gas in the processing chamber through a gas exhaust pipe
connected to the processing chamber; forming a by-product by
supplying a heated reaction gas into the exhaust gas flowing in the
gas exhaust pipe, the heated reaction gas adapted to react with a
component in the exhaust gas; and trapping the by-product by a trap
mechanism.
14. A computer program for, when executed on a computer,
controlling a film-forming apparatus to perform a method for
processing an exhaust gas in the film-forming apparatus for forming
a film by CVD on a substrate placed in a processing chamber by
supplying a processing gas into the processing chamber, the method
comprising: exhausting an exhaust gas in the processing chamber
through a gas exhaust pipe connected to the processing chamber;
forming a by-product by supplying a heated reaction gas into the
exhaust gas flowing in the gas exhaust pipe, the heated reaction
gas adapted to react with a component in the exhaust gas; and
trapping the by-product by a trap mechanism.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a gas exhaust system of a
film-forming apparatus for forming a predetermined film by CVD, a
film-forming apparatus having the gas exhaust system, and a method
for processing an exhaust gas.
BACKGROUND OF THE INVENTION
[0002] In manufacturing semiconductor devices, various processes,
such as film formation, quality modification, oxidation/diffusion,
etching and the like, are performed on a semiconductor wafer as a
substrate to be processed.
[0003] For the film formation, there is widely used a CVD (Chemical
Vapor Deposition) method for forming a predetermined film through a
chemical reaction by introducing a predetermined processing gas
into a chamber accommodating a semiconductor wafer. In the CVD
method, a film is formed by the reaction of the processing gas on
the semiconductor wafer as a substrate to be processed. At this
time, however, only 10% of the processing gas contributes to the
reaction, and most of the processing gas remains unreacted.
[0004] The unreacted processing gas reacts with a reaction gas in
the chamber or in a gas exhaust pipe into which the reaction gas is
introduced, to produce a by-product. The by-product thus produced
flows together with a by-product produced when forming a TiN film.
When the by-products are cooled, a pipe is clogged or a vacuum pump
is damaged. To that end, in general, a trap mechanism for trapping
a by-product is provided at the gas exhaust pipe extending from the
chamber.
[0005] Although it is preferable that the by-product is trapped by
the trap mechanism in the form of a compound that is easily trapped
and has a comparatively stable structure, the by-product produced
at a flow rate ratio of each processing gas for film formation is
not necessarily turned into a desired compound. Therefore, Japanese
Patent Laid-open Publication No. 2001-214272 discloses a technique
for producing a trappable by-product by introducing directly into a
trap mechanism or into an upstream pipe a reaction gas that reacts
with an impurity gas discharged from the chamber.
[0006] In theory, a desired stable by-product that is easily
trapped can be produced by introducing a specific reaction gas. In
practice, however, the reaction may proceed insufficiently, so that
an unstable by-product or a by-product having an indefinite
structure such as a complex or the like may be produced.
Accordingly, the trap mechanism needs to be scaled up due to hard
to trap the by-product and, also, the trap mechanism may be
irregularly clogged due to an unreliable generation state (density
or the like) of a reaction product.
SUMMARY OF THE INVENTION
[0007] In view of the above, the present invention provides a gas
exhaust system of a film-forming apparatus which is capable of
stably trapping a desired high-density by-product, a film-forming
apparatus having the gas exhaust system, and a method for
processing an exhaust gas.
[0008] In accordance with an aspect of the invention, there is
provided a gas exhaust system of a film-forming apparatus for
forming a film by CVD on a substrate placed in a processing chamber
by supplying a processing gas into the processing chamber, the gas
exhaust system of the film-forming apparatus including: a gas
exhaust pipe connected to the processing chamber, for exhausting an
exhaust gas in the processing chamber; a trap mechanism provided to
the gas exhaust pipe, for trapping a by-product in the exhaust gas;
and a heated reaction gas supply mechanism for supplying a heated
reaction gas into the exhaust gas, the heated reaction gas adapted
to react with a component in the exhaust gas to produce a
by-product.
[0009] Preferably, a TiN film is formed by CVD on the substrate
placed in the processing chamber by supplying TiCl.sub.4 gas and
NH.sub.3 gas as the processing gas into the processing chamber and,
at the same time, NH.sub.4Cl is produced as a by-product by
supplying NH.sub.3 gas as the heated reaction gas from the heated
reaction gas supply mechanism.
[0010] Preferably, the NH.sub.3 gas as the heated reaction gas is
supplied while being heated at about 170.degree. C. or higher.
[0011] Preferably, the heated reaction gas supply mechanism
supplies the heated reaction gas to an upstream side of the trap
mechanism on the gas exhaust pipe via a pipe.
[0012] Preferably, the heated reaction gas supply mechanism
supplies the heated reaction gas to the trap mechanism via a
pipe.
[0013] Preferably, the heated reaction gas supply mechanism
includes a reaction gas heating unit for heating a reaction gas,
and the reaction gas heating unit has a heating chamber for heating
the reaction gas therein and a coiled heating element disposed in
the heating chamber.
[0014] Preferably, a bypass pipe for exhausting the processing gas
without passing through the processing chamber is connected to an
inlet side of the processing chamber.
[0015] Preferably, the gas exhaust system further includes a
heating/mixing chamber for heating and mixing the processing gas
flowing through the bypass pipe and the heated reaction gas
supplied from the heated reaction gas supply mechanism.
[0016] In accordance with another aspect of the invention, there is
provided a film-forming apparatus for forming a film on a
substrate, including: a processing chamber in which a substrate is
placed; a processing gas supply mechanism for supplying a
processing gas into the processing chamber where the substrate is
placed; a unit for causing a film forming reaction on the substrate
by imparting energy to the processing gas; and a gas exhaust system
for exhausting an exhaust gas in the processing chamber and
processing the exhaust gas, wherein the gas exhaust system
includes: a gas exhaust pipe for exhausting the exhaust gas in the
processing chamber; a trap mechanism provided to the exhaust pipe,
for trapping a by-product in the exhaust gas; and a heated reaction
gas supply mechanism for supplying a heated reaction gas into the
exhaust gas, the heated reaction gas adapted to react with a
component in the exhaust gas to produce a by-product.
[0017] Preferably, the processing gas supply mechanism is provided
with a unit for heating the substrate placed in the processing
chamber to form a TiN film by causing a film forming reaction on
the substrate by supplying TiCl.sub.4 gas and NH.sub.3 gas as the
processing gas into the processing chamber, and NH.sub.4Cl is
produced as a by-product by supplying NH.sub.3 gas as the heated
reaction gas from the heated reaction gas supply mechanism.
[0018] In accordance with still another aspect of the invention,
there is provided a method for processing an exhaust gas in a
film-forming apparatus for forming a film by CVD on a substrate
placed in a processing chamber by supplying a processing gas into
the processing chamber, the method including: exhausting the
exhaust gas in the processing chamber through a gas exhaust pipe
connected to the processing chamber; forming a by-product by
supplying a heated reaction gas into the exhaust gas flowing in the
gas exhaust pipe, the heated reaction gas adapted to react with a
component in the exhaust gas; and trapping the by-product by a trap
mechanism.
[0019] Preferably, a TiN film is formed by CVD on a substrate
placed in the processing chamber by supplying TiCl.sub.4 gas and
NH.sub.3 gas as the processing gas into the processing chamber and,
at the same time, NH.sub.4Cl is produced as the by-product by
supplying NH.sub.3 gas as the heated reaction gas, which reacts
with TiCl.sub.4 in the exhaust gas, into the exhaust gas flowing in
the gas exhaust pipe and, then, the produced NH.sub.4Cl as the
by-product is trapped by the trap mechanism.
[0020] In accordance with still another aspect of the invention,
there is provided a computer-readable storage medium storing
software for executing a control program in a computer, wherein,
when executed, the control program controls a method for processing
an exhaust gas in a film-forming apparatus for forming a film by
CVD on a substrate placed in a processing chamber by supplying a
processing gas into the processing chamber, the method including:
exhausting an exhaust gas in the processing chamber through a gas
exhaust pipe connected to the processing chamber; forming a
by-product by supplying a heated reaction gas into the exhaust gas
flowing in the gas exhaust pipe, the heated reaction gas adapted to
react with a component in the exhaust gas; and trapping the
by-product by a trap mechanism.
[0021] In accordance with still another aspect of the invention,
there is provided a computer program for, when executed on a
computer, controlling a film-forming apparatus to perform a method
for processing an exhaust gas in the film-forming apparatus for
forming a film by CVD on a substrate placed in a processing chamber
by supplying a processing gas into the processing chamber, the
method including: exhausting an exhaust gas in the processing
chamber through a gas exhaust pipe connected to the processing
chamber; forming a by-product by supplying a heated reaction gas
into the exhaust gas flowing in the gas exhaust pipe, the heated
reaction gas adapted to react with a component in the exhaust gas;
and trapping the by-product by a trap mechanism.
[0022] In accordance with the present invention, by supplying the
heated reaction gas adapted to react with a component in the
exhaust gas to produce a by-product, the reaction for producing a
by-product can proceed sufficiently with an increased productivity,
so that a stable by-product can be produced to be trapped by the
trap mechanism. Accordingly, it is possible to suppress the
production of a by-product having a highly indefinite element, so
that the trap efficiency can be increased.
[0023] Particularly, in case TiCl.sub.4 gas and NH.sub.3 gas are
used as the processing gas and NH.sub.3 gas is supplied to the gas
exhaust pipe by the heated reaction gas supply mechanism, a
high-density stable NH.sub.4Cl can be produced as the by-product.
This by-product can be easily trapped and the irregular clogging of
the trap mechanism can be reduced. As a consequence, the by-product
can be trapped efficiently without scaling up the trap
mechanism.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic view of a film-forming apparatus
having a gas exhaust system in accordance with an embodiment of the
present invention;
[0025] FIG. 2 shows a schematic view of a heated reaction gas
supply mechanism used in the gas exhaust system of the film-forming
apparatus shown in FIG. 1;
[0026] FIG. 3 provides a partially cutaway perspective view of a
trap mechanism used in the gas exhaust system of the film-forming
apparatus shown in FIG. 1;
[0027] FIG. 4 describes a schematic view of another example of a
connection of a heated reaction gas supply mechanism in the gas
exhaust system of the film-forming apparatus shown in FIG. 1;
and
[0028] FIG. 5 offers a schematic view of an example in which a
processing gas flowing in a bypass pipe and a heated reaction gas
are mixed in a heating/mixing chamber in the exhaust structure of
the film-forming apparatus shown in FIG. 1.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0029] Embodiments of the present invention will be described with
reference to the accompanying drawings which form a part hereof. In
the present embodiment, there will be described, as an example, a
case where a TiN film is formed by CVD on a surface of a
semiconductor wafer (hereinafter, referred to as "wafer") as a
substrate to be processed.
[0030] FIG. 1 is a schematic view of a film-forming apparatus
having a gas exhaust system in accordance with an embodiment of the
present invention.
[0031] A film-forming apparatus 100 includes a film-forming
processing unit 200 and a gas exhaust system 300.
[0032] The film-forming processing unit 200 has a substantially
cylindrical chamber (processing chamber) 11 made of aluminum or
aluminum alloy (e.g., JIS A5052). In the chamber 11, a susceptor 12
for horizontally supporting a wafer W as a substrate to be
processed is supported by a cylindrical supporting member 13
provided at a central bottom portion thereof. A heater 14 is buried
in the susceptor 12 to heat the wafer W to a predetermined
temperature.
[0033] A shower head 20 serving as a gas injection member is
provided at an upper portion of the chamber 11. The shower head 20
is formed in a disk shape and has a gas diffusion space 21 therein
and a plurality of gas injection openings 22 formed at a bottom
portion thereof. Moreover, a gas supply port 23 is provided at an
upper central portion of the shower head 20.
[0034] A circular opening 31 is formed at a central portion of a
bottom wall of the chamber 11, and a gas exhaust chamber 32
projects downward to cover the opening 31. A gas exhaust port 33 is
formed in a bottom surface of the gas exhaust chamber 32. Besides,
a loading/unloading port 35 for loading/unloading the wafer W is
formed in a sidewall of the chamber 11. The loading/unloading port
35 is openable/closable by a gate valve 36.
[0035] A processing gas supply system 40 for supplying a processing
gas for film formation is connected to the shower head 20 via a
pipe 41, and an opening/closing valve 42 is provided in the middle
of the pipe 41. The processing gas supply system 40 has a plurality
of gas supply sources for supplying TiCl.sub.4 gas, NH.sub.3 gas,
N.sub.2 gas and the like, and the gases can be supplied into the
chamber 11 via the pipe 41 and the shower head 20 at respective
flow rates controlled by a flow rate controller such as a mass flow
controller. Further, although the pipe 41 is illustrated as a
single pipe for convenience, the gases may be supplied through
separate pipes.
[0036] Meanwhile, the gas exhaust system 300 has a gas exhaust pipe
51 connected to the gas exhaust port 33. As for the gas exhaust
pipe 51, there is used one that is made of stainless steel and has
an inner diameter of about 5 to 10 cm. On the gas exhaust pipe 51,
there are provided an opening/closing valve 52, a pressure control
valve 53, a trap mechanism 54 for trapping a reaction by-product in
an exhaust gas, a vacuum pump 55 for evacuating the chamber 11 and
a waste gas scrubber 56 for completely removing impurity remaining
in the exhaust gas, all being disposed in that order from the
upstream side. Further, as shown in FIG. 1, the pressure control
valve 53 may be provided between the trap mechanism 54 and the
vacuum pump 55 to reduce the reaction by-product adhered to the
pressure control valve 53, so that the maintenance cycle of the
pressure control valve 53 can be lengthened.
[0037] A bypass pipe 58 is connected between an upstream portion of
the opening/closing valve 42 in the pipe 41 and a downstream
portion of the pressure control valve 53 in the gas exhaust pipe
51. The bypass pipe 58 is provided with an opening/closing valve
59. The bypass pipe 58 is used for directly exhausting a processing
gas supplied to stabilize a gas flow rate to the gas exhaust pipe
51 without passing through the chamber 11.
[0038] The upstream side of the trap mechanism 54 in the gas
exhaust pipe 51 is connected to a pipe 61 extending from a heated
reaction gas supply mechanism 60 via a nozzle 62. The heated
reaction gas supply pipe 61 is provided with a flow rate controller
63 such as a mass flow controller and an opening/closing valve 64.
Further, when the heated reaction gas is supplied from the heated
reaction gas supply mechanism 60 to the by-product or the unreacted
processing gas flowing in the gas exhaust pipe 51 via the heated
reaction gas supply pipe 61 and the nozzle 62, it is possible to
produce a stable high-density by-product that is easily trapped. In
the present embodiment, a heated NH.sub.3 gas is typically supplied
as the heated reaction gas.
[0039] As illustrated in FIG. 2, the heated reaction gas supply
mechanism 60 includes a reaction gas supply source 65 and a
reaction gas heating unit 66. The reaction gas heating unit 66 has
a gas heating vessel 67 for heating a reaction gas and a heating
element 68 disposed therein. The heating element 68 is coiled in a
specific shape to have a considerably large heating area. The
heating element 68 instantly heats the reaction gas supplied to the
gas heating vessel 67. A power supply 69 is connected to the
heating element 68, so that the reaction gas is heated to a desired
temperature by controlling the output of the power supply 69. At
this time, the temperature of the heated reaction gas is preferably
higher than or equal to about 170.degree. C. in view of ensuring
the desired reaction. Further, it is preferably lower than or equal
to about 400.degree. C. in view of ensuring safety of equipments,
and more preferably about 200 to 350.degree. C. Further, when the
processing gas supply system 40 includes the reaction gas, it is
possible to omit the reaction gas supply source 65, and the
reaction gas can be supplied from the processing gas supply system
40.
[0040] As depicted in the enlarged view of FIG. 3, the trap
mechanism 54 has a cylindrical housing 71. Formed at an upper
portion of a sidewall of the housing 71 are an exhaust gas inlet 72
and an exhaust gas outlet 73. A cylindrical cooling chamber 74 is
formed on the side of the exhaust gas outlet 73 of the housing 71
so as to be eccentric with respect to the housing 71. In the
housing 71, the cooling chamber 74 and the outside thereof
communicate with each other at the bottom portion of the housing
71. In the outside of the cooling chamber 74 in the housing 71, a
plurality of horizontal trap plates 75 having a plurality of gas
through holes 75a are vertically arranged. Meanwhile, also in the
inside of the cooling chamber 74, a plurality of horizontal trap
plates 76 having a plurality of gas through holes 76a are
vertically arranged. In the cooling chamber 74, a cooling water
pipe 77 is provided to penetrate the trap plates 76, and the trap
plates 76 are cooled by circulating cooling water in the cooling
water pipe 77. Further, a cooling water supply pipe 78a and a
cooling water discharge pipe 78b which are connected to the cooling
water pipe 77 are provided outside the housing 71.
[0041] In the trap mechanism 54, the exhaust gas introduced through
the exhaust gas inlet 72 into the housing 71 flows downward through
the gas through holes 75a of the trap plates 75 and then reaches
the cooling chamber 74 at the bottom portion of the housing 71. In
the cooling chamber 74, the exhaust gas flows upward through the
gas through holes 76a of the cooled trap plates 76 and is then
discharged through the exhaust gas outlet 73. At this time, the
by-product is trapped by the trap plates 75 and 76. The trap plates
76 are cooled by the cooling water, so that the trap efficiency can
be increased.
[0042] The pipe 41, the bypass pipe 58 and the gas exhaust pipe 51
are respectively wound by tape heaters 81, 82 and 83, as indicated
by dashed lines in the drawings. By heating them to a predetermined
temperature, gaseous components are prevented from being condensed
inside the pipes. Further, the heated reaction gas supply pipe 61
is wound by a tape heater 84, so that it is possible to avoid the
decreases of the temperature of the heated reaction gas supplied
from the heated reaction gas supply mechanism 60.
[0043] Each part of the film-forming apparatus 100 is connected to
and controlled by a process controller 110 including a micro
processor (computer). Further, a user interface 111 is connected to
the process controller 110. The user interface 111 includes, e.g.,
a keyboard for a process manager to input a command to operate the
film-forming apparatus 100, a display for showing an operational
status of the process controller 110 and the like. Moreover,
connected to the process controller 110 is a storage unit 112 for
storing therein, e.g., control programs to be used in realizing
various processes, which are performed in the film-forming
apparatus 100 under the control of the process controller 110 and
programs, i.e., recipes to be used in operating each part of the
film-forming apparatus 100 to carry out processes in accordance
with processing conditions. The recipes can be stored in a hard
disk or a semiconductor memory, or can be set at a certain position
of the storage unit 112 while being recorded on a portable storage
medium such as a CDROM, a DVD and the like. Further, the recipes
can be transmitted from another device via, e.g., a dedicated line.
If necessary, the process controller 110 executes a recipe read
from the storage unit 112 in response to instructions from the user
interface 111, thereby implementing a required process in the
film-forming apparatus 100 under the control of the process
controller 50.
[0044] Hereinafter, a processing operation of the film-forming
apparatus configured as described above will be described.
[0045] First of all, the chamber 11 is evacuated to vacuum by
operating the gas exhaust system 300. Next, the wafer W is loaded
into the chamber 11 and mounted on the susceptor 12. Thereafter,
the wafer W is heated to a predetermined temperature by the heater
14. In that state, TiCl.sub.4 gas, NH.sub.3 gas and N.sub.2 gas are
made to flow at respective flow rates from the processing gas
supply system 40 to the bypass pipe 58, thereby performing a
pre-flow process. After the flow rates of the gases become stable,
the gases are supplied into the chamber 11 via the shower head 20
through the pipe 41 and, at the same time, the pressure control
valve 53 is driven to maintain the inside of the chamber 11 at a
predetermined pressure. In that state, the TiCl.sub.4 gas and the
NH.sub.3 gas react on the wafer W maintained at a predetermined
temperature on the susceptor 12, thereby depositing a TiN film on
the surface of the wafer W.
[0046] When the TiN film is formed by supplying the TiCl.sub.4 gas,
the NH.sub.3 gas and the N.sub.2 gas, the exhaust gas is exhausted
via the gas exhaust pipe 51. In that case, the processing gas
consumed by the reaction is only about 10%, and most of the
processing gas remains unreacted. The unreacted processing gas
reacts with a reaction gas in the chamber 11 or in the gas exhaust
pipe into which the reaction gas is introduced to produce a
by-product. The by-product thus produced flows in the gas exhaust
pipe 51 together with a by-product produced when forming the TiN
film.
[0047] At this time, if NH.sub.4Cl is mainly produced as the
by-product by causing the reaction of the following Eq. (1) in the
chamber 11 and the gas exhaust pipe 51, it can be easily trapped by
the trap mechanism 54 in the form of a stable high-density
by-product. In other words, in the present embodiment, NH.sub.4Cl
is a by-product to be trapped by the trap mechanism 54.
6TiCl.sub.4+32NH.sub.3.fwdarw.6TiN+24NH.sub.4Cl+N.sub.2 Eq. (1)
[0048] Meanwhile, when the TiN film is formed, the TiCl.sub.4 gas
and the NH.sub.3 gas of the processing gas are introduced into the
chamber 11 at substantially the same flow rates, so that the
NH.sub.3 gas is insufficient for causing the reaction of Eq. (1) to
occur. Therefore, in the present embodiment, the NH.sub.3 gas is
supplimentarily supplied from the heated reaction gas supply
mechanism 60 to the pipe 51 in order to cause the reaction of Eq.
(1) to take place. At this time, according to Eq. (1), the flow
rate of the NH.sub.3 gas supplimentarily supplied is preferably
four times greater than that of the NH.sub.3 gas for film
formation.
[0049] In that case, if the NH.sub.3 gas is introduced at a room
temperature, even through the trap efficiency of the trap mechanism
54 increases, the reaction of Eq. (1) proceeds insufficiently,
producing a complex (TiCl.sub.4.4NH.sub.3) as an indefinite element
obtained by the following Eq. (2). TiCl.sub.4.4NH.sub.3 is
difficult to be trapped by the trap mechanism 54, so that the trap
mechanism 54 needs to be scaled up. Moreover, TiCl.sub.4.4NH.sub.3
has a low density and a high volume. Therefore, if the amount of
TiCl.sub.4.4NH.sub.3 increases, the trap mechanism 54 may be
clogged at an initial stage. Besides, the generation amount of
TiCl.sub.4.4NH.sub.3 is not determined, so that the trap mechanism
is clogged irregularly.
TiCl.sub.4+4NH.sub.3.fwdarw.TiCl.sub.4.4NH.sub.3 Eq. (2)
[0050] According to the research on the cause of the above
problems, it has been found that when the NH.sub.3 gas is
introduced as it is into the gas exhaust pipe 51, the heat energy
for the reaction of Eq. (1) is insufficient. Also, it has been
found that the NH.sub.3 gas needs to be heated and supplied to the
gas exhaust pipe 51 in order to make the reaction of Eq. (1)
predominant while suppressing the reaction of Eq. (2).
[0051] In the present embodiment, by introducing the heated
NH.sub.3 gas from the heated reaction gas supply mechanism 60 to
the gas exhaust pipe 51, the by-product mainly formed of NH.sub.4Cl
is produced by the reaction of eq. (1) while suppressing the
reaction of eq. (2) and is trapped by the trap mechanism 54. At
this time, the temperature of the heated NH.sub.3 gas is preferably
higher than or equal to about 170.degree. C. in view of ensuring
the reaction of Eq. (1). Further, it is preferably lower than or
equal to about 400.degree. C. in view of ensuring safety of
equipments. When the by-product is trapped by the trap plates 75
and 76 in the trap mechanism 54, NH.sub.4Cl is cooled by the trap
plates 76 cooled in the cooling chamber 74, so that the higher trap
efficiency can be maintained.
[0052] Here, TiCl.sub.4.4NH.sub.3 is a complex in which four
NH.sub.3 molecules are coordinate-covalent-bonded with a TiCl.sub.4
molecule, and NH.sub.4Cl is an ionically bonded salt having a large
chemical bonding force. Therefore, if the by-product mainly formed
of NH.sub.4Cl is produced by suppressing the generation of
TiCl.sub.4.4NH.sub.3 as an indefinite element, it is possible to
obtain a high-density stable by-product that is easily trapped.
Besides, the irregular clogging of the trap mechanism 54 can be
reduced. As a consequence, the by-product can be trapped reliably
and efficiently without scaling up the trap mechanism 54 and,
hence, the maintenance cycle of the trap mechanism can be greatly
lengthened. Furthermore, in case the average maintenance cycle is
made to be equal to that of a conventional trap mechanism, the trap
mechanism 54 can become compact in size.
[0053] In addition, according to a result of a test performed by
using the conventional trap mechanism as the trap mechanism 54, it
has been found that the volume of the by-product can be reduced to
about 1/3 and also that the maintenance cycle of the trap mechanism
54 can be lengthened by three times.
[0054] The exhaust gas remaining after the by-product is trapped by
the trap mechanism 54 is led to the waste gas scrubber 56 via the
vacuum pump 55, and impurity components are completely removed
therein. As the reaction proceeds according to Eq. (1), TiN as well
as NH.sub.4Cl can be trapped by the trap mechanism 54. Further,
since N.sub.2 is a harmless gas component, the amount of harmful
impurity components that are not trapped by the trap mechanism 54
can be minimized and, hence, the burden on the waste gas scrubber
56 can be reduced. As a result, the running cost of the waste gas
scrubber 56 can be reduced, and the lifespan thereof can be
extended.
[0055] Since the heated NH.sub.3 gas supplied from the heated
reaction gas supply mechanism 60 is supplied via the pipe 61, the
temperature thereof may decrease when it reaches the gas exhaust
pipe 51. However, the NH.sub.3 gas can be supplied at a desired
temperature by heating the pipe 61 with the tape heater 84 to
suppress the temperature decrease thereof.
[0056] In the present embodiment, the heated NH.sub.3 gas is
introduced into the gas exhaust pipe 51 and, thus, the reactivity
increases. As a consequence, when the heated NH.sub.3 gas is
supplied to the gas exhaust pipe 51, it is only required to connect
the nozzle 62 to the gas exhaust pipe 51. Moreover, due to the high
reactivity, the heated NH.sub.3 gas may be directly introduced into
the trap mechanism 54 by providing a gas inlet port 79 at the trap
mechanism 54 and connecting the pipe 61 thereto, as illustrated in
FIG. 4.
[0057] Moreover, instead of directly connecting the bypass pipe 58
to the gas exhaust pipe 51, it is possible to provide a
heating/mixing chamber 85 in the middle of the pipe 61 and connect
the bypass pipe 58 thereto, as can be seen from FIG. 5.
Accordingly, the processing gas flowing from the bypass pipe 58 can
be made to flow into the gas exhaust pipe 51, after being heated
and mixed with the heated NH.sub.3 gas. As a result, the trap
efficiency of the processing gas flowing through the bypass pipe 58
can be further increased.
[0058] The present invention can be variously modified without
being limited to the above embodiments. For example, in the above
embodiments, there has been described an example in which a TiN
film is formed by using TiCl.sub.4 gas and NH.sub.3 gas. However,
the present invention can be applied to various film forming
processes to be described below, without being limited to the above
example.
[0059] (1) When the present invention is applied to the case of
forming a Ti film by using TiCl.sub.4 gas and H.sub.2 gas, HCl is a
by-product to be trapped. By supplying a heated H.sub.2 gas as a
heated reaction gas into the exhaust gas, HCl can be trapped
stably.
[0060] (2) When the present invention is applied to the case of
forming a W film by using WF.sub.6 gas and SiH.sub.4 gas, SiF.sub.4
and HF are by-products to be trapped. By supplying a heated
SiH.sub.4 gas as a heated reaction gas into the exhaust gas,
SiF.sub.4 and HF can be trapped stably.
[0061] (3) When the present invention is applied to the case of
forming a W film by using WF.sub.6 gas and SiH.sub.2Cl.sub.2 gas,
SiF.sub.4, HF, HCl and Cl.sub.2 are by-products to be trapped. By
supplying a heated SiH.sub.2Cl.sub.2 gas as a heated reaction gas
into the exhaust gas, SiF.sub.4, HF, HCl and Cl.sub.2 can be
trapped stably.
[0062] (4) When the present invention is applied to the case of
forming a Ta.sub.2O.sub.5 film as a high-k dielectric film by using
Ta(OC.sub.2H.sub.5) gas, a high-density solid having an indefinite
composition can be stably trapped by supplying heated steam or
heated O.sub.2 gas as a heated reaction gas into the exhaust
gas.
[0063] Further, in the above embodiments, there has been described
an example in which NH.sub.3 gas as a reaction gas is heated while
passing through the heating element 68 that is coiled in a specific
shape in the gas heating chamber 67 to have a considerably large
heating area. However, the conventionally known gas heating unit
can be widely used without being limited to the above example.
[0064] In addition, the structure of the trap mechanism 54 is not
particularly limited, and a trap mechanism having a conventional
structure can be employed.
[0065] Furthermore, in the above embodiment, a semiconductor wafer
is used as an example of a substrate to be processed. However, it
is not limited thereto, and there may be used another substrate
such as a glass substrate for a flat panel display (FPD)
represented by a liquid crystal display (LCD).
* * * * *