U.S. patent application number 11/367339 was filed with the patent office on 2006-09-21 for film formation method and apparatus for semiconductor process.
Invention is credited to Pao-Hwa Chou, Kazuhide Hasebe, Chaeho Kim, Byounghoon Lee, Mitsuhiro Okada.
Application Number | 20060207504 11/367339 |
Document ID | / |
Family ID | 37008987 |
Filed Date | 2006-09-21 |
United States Patent
Application |
20060207504 |
Kind Code |
A1 |
Hasebe; Kazuhide ; et
al. |
September 21, 2006 |
Film formation method and apparatus for semiconductor process
Abstract
A film formation apparatus for a semiconductor process includes
a process gas supply system configured to supply process gases. The
process gas supply system includes a gas mixture tank configured to
mix first and third process gases to form a mixture gas, a mixture
gas supply line configured to supply the mixture gas from the gas
mixture tank to a process field, a second process gas supply
circuit having a second process gas supply line configured to
supply a second process gas to the process field without passing
through the gas mixture tank, and first and second switching valves
disposed on the mixture gas supply line and the second process gas
supply line, respectively. A control section controls the first and
second switching valves to be opened and closed so as to
alternately and pulse-wise supply the mixture gas and the second
process gas to the process field.
Inventors: |
Hasebe; Kazuhide;
(Minamialps-shi, JP) ; Okada; Mitsuhiro; (Kai-shi,
JP) ; Kim; Chaeho; (Suwon-city, KR) ; Lee;
Byounghoon; (Yongin-city, KR) ; Chou; Pao-Hwa;
(Kai-shi, JP) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
37008987 |
Appl. No.: |
11/367339 |
Filed: |
March 6, 2006 |
Current U.S.
Class: |
118/715 ;
118/725 |
Current CPC
Class: |
C23C 16/509 20130101;
C23C 16/45531 20130101; C23C 16/45578 20130101; C23C 16/45512
20130101; C23C 16/45542 20130101; C23C 16/345 20130101 |
Class at
Publication: |
118/715 ;
118/725 |
International
Class: |
C23C 16/00 20060101
C23C016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 11, 2005 |
JP |
2005-070034 |
Jan 11, 2006 |
JP |
2006-004192 |
Claims
1. A film formation apparatus for a semiconductor process,
comprising: a process container having a process field configured
to accommodate a plurality of target substrates stacked at
intervals; a support member configured to support the target
substrates inside the process field; a heater configured to heat
the target substrates inside the process field; an exhaust system
configured to exhaust gas inside the process field; a process gas
supply system configured to supply process gases to the process
field so as to deposit a thin film on the target substrates,
wherein the process gases include a first process gas for providing
a main material of the thin film, a second process gas for reacting
with the first process gas, and a third process gas for providing a
sub-material of the thin film; a control section configured to
control an operation of the apparatus including the process gas
supply system, wherein the process gas supply system comprises a
gas mixture tank disposed outside the process container and
configured to mix the first and third process gases to form a
mixture gas, a mixture gas supply line configured to supply the
mixture gas from the gas mixture tank to the process field, first
and third process gas supply circuits configured to supply the
first and third process gases to the gas mixture tank,
respectively, a second process gas supply circuit having a second
process gas supply line configured to supply the second process gas
to the process field without passing through the gas mixture tank,
first and second switching valves disposed on the mixture gas
supply line and the second process gas supply line, respectively,
and wherein the control section controls the first and second
switching valves to be opened and closed so as to alternately and
pulse-wise supply the mixture gas from the gas mixture tank and the
second process gas from the second process gas supply circuit to
the process field.
2. The apparatus according to claim 1, wherein the control section
performs control to continuously supply the first and third process
gases from the first and third process gas supply circuits to the
gas mixture tank, while supplying the mixture gas pulse-wise from
the gas mixture tank to the process field.
3. The apparatus according to claim 1, wherein the control section
performs control to simultaneously supply the first and third
process gases pulse-wise in a first phase from the first and third
process gas supply circuits to the gas mixture tank, while
supplying the mixture gas pulse-wise in a second phase reverse to
the first phase from the gas mixture tank to the process field.
4. The apparatus according to claim 1, wherein the mixture gas
supply line and the second process gas supply line comprise first
and second supply ports, respectively, each of which comprises a
plurality of gas spouting holes arrayed over the target substrates
in a vertical direction to form gas flows parallel with the target
substrates.
5. The apparatus according to claim 1, wherein the third process
gas is supplied to the process field in an amount 1/100 or less of
the first process gas.
6. The apparatus according to claim 1, wherein the first process
gas contains a silane family gas, the second process gas contains a
nitriding gas or oxynitriding gas, and the third process gas
contains a doping gas.
7. The apparatus according to claim 6, wherein the process gas
supply system further comprises a fourth process gas supply circuit
configured to supply a fourth process gas containing a carbon
hydride gas to the gas mixture tank.
8. The apparatus according to claim 6, wherein the first process
gas contains at least one gas selected from the group consisting of
dichlorosilane, hexachlorodisilane, monosilane, disilane,
hexamethyldisilazane, tetrachlorosilane, disilylamine,
trisilylamine, and bistertialbutylaminosilane, the second process
gas contains at least one gas selected from the group consisting of
ammonia, nitrogen, dinitrogen oxide, and nitrogen oxide, and the
third process gas contains at least one gas selected from the group
consisting of BCl.sub.3, B.sub.2H.sub.6, BF.sub.3, and
B(CH.sub.3).sub.3.
9. The apparatus according to claim 1, further comprises an
exciting mechanism configured to activate the second process gas by
generating plasma.
10. The apparatus according to claim 9, wherein the exciting
mechanism comprises a plasma generation area disposed in a space
communicating with the process field and between a supply port of
the second process gas and the target substrates.
11. A film formation apparatus for a semiconductor process,
comprising: a process container having a process field configured
to accommodate a plurality of target substrates stacked at
intervals; a support member configured to support the target
substrates inside the process field; a heater configured to heat
the target substrates inside the process field; an exhaust system
configured to exhaust gas inside the process field; a process gas
supply system configured to supply process gases to the process
field so as to deposit a thin film on the target substrates,
wherein the process gases include a first process gas for providing
a main material of the thin film, a second process gas for reacting
with the first process gas, and a third process gas for providing a
sub-material of the thin film, and the third process gas is
supplied to the process field in an amount smaller than that of the
first process gas; a control section configured to control an
operation of the apparatus including the process gas supply system,
wherein the process gas supply system comprises a mixture gas
supply line configured to mix the first and third process gases to
form a mixture gas and supply the mixture gas to the process field,
first and third process gas supply circuits having first and third
process gas supply lines configured to supply the first and third
process gases to the mixture gas supply line, respectively, a
second process gas supply circuit having a second process gas
supply line configured to supply the second process gas to the
process field without passing through the mixture gas supply line,
first, second, and third switching valves disposed on the first,
second, and third process gas supply lines, respectively, a first
tank disposed on the first process gas supply line immediately
before the first switching valve to temporarily store the first
process gas, and wherein the control section controls the first,
second, and third switching valves to be opened and closed so as to
alternately and pulse-wise supply the mixture gas from the mixture
gas supply line and the second process gas from the second process
gas supply circuit to the process field.
12. The apparatus according to claim 11, wherein the control
section controls the first and third switching valve to be
simultaneously opened and closed.
13. The apparatus according to claim 11, wherein the process gas
supply system further comprises a second tank disposed on the third
process gas supply line immediately before the third switching
valve to temporarily store the third process gas
14. The apparatus according to claim 11, wherein the mixture gas
supply line and the second process gas supply line comprise first
and second supply ports, respectively, each of which comprises a
plurality of gas spouting holes arrayed over the target substrates
in a vertical direction to form gas flows parallel with the target
substrates.
15. The apparatus according to claim 11, wherein the third process
gas is supplied to the process field in an amount 1/100 or less of
the first process gas.
16. The apparatus according to claim 11, wherein the first process
gas contains a silane family gas, the second process gas contains a
nitriding gas or oxynitriding gas, and the third process gas
contains a doping gas.
17. The apparatus according to claim 16, wherein the process gas
supply system further comprises a fourth process gas supply circuit
configured to supply a fourth process gas containing a carbon
hydride gas to the mixture gas supply line.
18. The apparatus according to claim 16, wherein the first process
gas contains at least one gas selected from the group consisting of
dichlorosilane, hexachlorodisilane, monosilane, disilane,
hexamethyldisilazane, tetrachlorosilane, disilylamine,
trisilylamine, and bistertialbutylaminosilane, the second process
gas contains at least one gas selected from the group consisting of
ammonia, nitrogen, dinitrogen oxide, and nitrogen oxide, and the
third process gas contains at least one gas selected from the group
consisting of BCl.sub.3, B.sub.2H.sub.6, BF.sub.3, and
B(CH.sub.3).sub.3.
19. The apparatus according to claim 11, further comprises an
exciting mechanism configured to activate the second process gas by
generating plasma.
20. The apparatus according to claim 19, wherein the exciting
mechanism comprises a plasma generation area disposed in a space
communicating with the process field and between a supply port of
the second process gas and the target substrates.
21. A film formation method for a semiconductor process,
comprising: heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
supplying process gases to the process field to deposit a thin film
on the target substrates, wherein the process gases include a first
process gas for providing a main material of the thin film, a
second process gas for reacting with the first process gas, and a
third process gas for providing a sub-material of the thin film,
wherein said supplying the process gases comprises supplying the
first and third process gases to a gas mixture tank disposed
outside the process container to form a mixture gas, supplying the
mixture gas from the gas mixture tank to the process field, and
supplying the second process gas to the process field without
passing through the gas mixture tank, so as to alternately and
pulse-wise supply the mixture gas and the second process gas to the
process field.
22. A film formation method for a semiconductor process,
comprising: heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
supplying process gases to the process field to deposit a thin film
on the target substrates, wherein the process gases include a first
process gas for providing a main material of the thin film, a
second process gas for reacting with the first process gas, and a
third process gas for providing a sub-material of the thin film,
and the third process gas is supplied to the process field in an
amount smaller than that of the first process gas, wherein said
supplying the process gases comprises supplying the first and third
process gases to a mixture gas supply line to form a mixture gas
and supply the mixture gas to the process field, while temporarily
storing the first process gas in a first tank disposed immediately
before the mixture gas supply line, and supplying the second
process gas to the process field without passing through the
mixture gas supply line, so as to alternately and pulse-wise supply
the mixture gas and the second process gas to the process
field.
23. A computer readable medium containing program instructions for
execution on a processor, which, when executed by the processor,
cause a film formation apparatus for a semiconductor process to
execute heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
supplying process gases to the process field to deposit a thin film
on the target substrates, wherein the process gases include a first
process gas for providing a main material of the thin film, a
second process gas for reacting with the first process gas, and a
third process gas for providing a sub-material of the thin film,
wherein said supplying the process gases comprises supplying the
first and third process gases to a gas mixture tank disposed
outside the process container to form a mixture gas, supplying the
mixture gas from the gas mixture tank to the process field, and
supplying the second process gas to the process field without
passing through the gas mixture tank, so as to alternately and
pulse-wise supply the mixture gas and the second process gas to the
process field.
24. A computer readable medium containing program instructions for
execution on a processor, which, when executed by the processor,
cause a film formation apparatus for a semiconductor process to
execute heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
supplying process gases to the process field to deposit a thin film
on the target substrates, wherein the process gases include a first
process gas for providing a main material of the thin film, a
second process gas for reacting with the first process gas, and a
third process gas for providing a sub-material of the thin film,
and the third process gas is supplied to the process field in an
amount smaller than that of the first process gas, wherein said
supplying the process gases comprises supplying the first and third
process gases to a mixture gas supply line to form a mixture gas
and supply the mixture gas to the process field, while temporarily
storing the first process gas in a first tank disposed immediately
before the mixture gas supply line, and supplying the second
process gas to the process field without passing through the
mixture gas supply line, so as to alternately and pulse-wise supply
the mixture gas and the second process gas to the process field.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Applications No. 2005-070034,
filed Mar. 11, 2005; and No. 2006-004192, filed Jan. 11, 2006, the
entire contents of both of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a film formation apparatus
and method for a semiconductor process for forming a thin film on a
target substrate, such as a semiconductor wafer. The term
"semiconductor process" used herein includes various kinds of
processes which are performed to manufacture a semiconductor device
or a structure having wiring layers, electrodes, and the like to be
connected to a semiconductor device, on a target substrate, such as
a semiconductor wafer or a glass substrate used for an LCD (Liquid
Crystal Display) or FPD (Flat Panel Display), by forming
semiconductor layers, insulating layers, and conductive layers in
predetermined patterns on the target substrate.
[0004] 2. Description of the Related Art
[0005] In manufacturing semiconductor devices for constituting
semiconductor integrated circuits, a target substrate, such as a
semiconductor wafer, is subjected to various processes, such as
film formation, etching, oxidation, diffusion, reformation,
annealing, and natural oxide film removal. Jpn. Pat. Appln. KOKAI
Publication No. 6-34974 discloses a semiconductor processing method
of this kind performed in a vertical heat-processing apparatus (of
the so-called batch type). According to this method, semiconductor
wafers are first transferred from a wafer cassette onto a vertical
wafer boat and supported thereon at intervals in the vertical
direction. The wafer cassette can store, e.g., 25 wafers, while the
wafer boat can support 30 to 150 wafers. Then, the wafer boat is
loaded into a process container from below, and the process
container is airtightly closed. Then, a predetermined heat process
is performed, while the process conditions, such as process gas
flow rate, process pressure, and process temperature, are
controlled.
[0006] Conventionally, silicon oxide films (SiO.sub.2 films) are
mainly used as insulating films for semiconductor devices. However,
in recent years, owing to the demands of increased integration and
miniaturization of semiconductor integrated circuits, silicon
nitride films (Si.sub.3N.sub.4 films) are used in place of silicon
oxide films, as needed (Jpn. Pat. Appln. KOKAI Publication No.
6-34974). For example, silicon nitride films are disposed as films
resistant to oxidation, films for preventing impurity diffusion,
and sidewall films of gate electrode structures. Since silicon
nitride films provide a low coefficient of impurity diffusion and a
good barrier property against oxidation, they are very suitable as
insulating films for the purpose described above. Further, boron
nitride films (BN films) have also attracted attention for the same
reasons.
[0007] For example, where dichlorosilane (DCS) and NH.sub.3 are
supplied as a silane family gas and a nitriding gas, respectively,
to form a silicon nitride film (SiN), the process is performed, as
follows. Specifically, DCS and NH.sub.3 gas are alternately and
intermittently supplied into a process container with purge periods
interposed therebetween. When NH.sub.3 gas is supplied, an RF
(radio frequency) is applied to generate plasma within the process
container so as to promote a nitridation reaction. More
specifically, when DCS is supplied into the process container, a
layer with a thickness of one molecule or more of DCS is adsorbed
onto the surface of wafers. The superfluous DCS is removed during
the purge period. Then, NH.sub.3 is supplied and plasma is
generated, thereby performing low temperature nitridation to form a
silicon nitride film. These sequential steps are repeated to
complete a film having a predetermined thickness.
[0008] On the other hand, in recent years, increasing the operation
speed of semiconductor devices is also an important factor. In this
respect, silicon nitride films have a relatively high dielectric
constant, which increases parasitic capacitance and thus is
problematic. Specifically, with an increase in parasitic
capacitance, the mobility of electrons is suppressed, so the device
operation speed decreases. Further, where a silicon nitride film is
used for a sensor of the charge storage type, there is a problem in
that parasitic capacitance increases a background level.
[0009] Under the circumstances, it has been proposed to dope a
silicon nitride film with an impurity, so as to decrease the
dielectric constant while maintaining the impurity diffusion
coefficient and oxidation barrier property. Jpn. Pat. Appln. KOKAI
Publication No. 2004-6801 discloses a method of forming a silicon
nitride film doped with boron (B) as an impurity, by CVD (Chemical
Vapor Deposition). Silicon nitride films doped with boron (SiBN)
have not only a low coefficient of impurity diffusion and a good
barrier property against oxidation, but also a very low dielectric
constant, so they are very useful as insulating films.
[0010] However, as described later, the present inventors have
found that, where a process gas in a small amount, such as a doping
gas, is used in conventional vertical heat-processing apparatuses
(of the so-called batch type), the inter-substrate uniformity in
the composition of deposited films tends to be deteriorated.
BRIEF SUMMARY OF THE INVENTION
[0011] An object of the present invention is to provide an
apparatus and method for a semiconductor process, which can
uniformly supply a process gas in a small amount, such as a doping
gas, into a process container in the vertical direction, thereby
improving the inter-substrate uniformity in the composition of
deposited films.
[0012] According to a first aspect of the present invention, there
is provided a film formation apparatus for a semiconductor process,
comprising:
[0013] a process container having a process field configured to
accommodate a plurality of target substrates stacked at
intervals;
[0014] a support member configured to support the target substrates
inside the process field;
[0015] a heater configured to heat the target substrates inside the
process field;
[0016] an exhaust system configured to exhaust gas inside the
process field;
[0017] a process gas supply system configured to supply process
gases to the process field so as to deposit a thin film on the
target substrates, wherein the process gases include a first
process gas for providing a main material of the thin film, a
second process gas for reacting with the first process gas, and a
third process gas for providing a sub-material of the thin
film;
[0018] a control section configured to control an operation of the
apparatus including the process gas supply system,
[0019] wherein the process gas supply system comprises
[0020] a gas mixture tank disposed outside the process container
and configured to mix the first and third process gases to form a
mixture gas,
[0021] a mixture gas supply line configured to supply the mixture
gas from the gas mixture tank to the process field,
[0022] first and third process gas supply circuits configured to
supply the first and third process gases to the gas mixture tank,
respectively,
[0023] a second process gas supply circuit having a second process
gas supply line configured to supply the second process gas to the
process field without passing through the gas mixture tank,
[0024] first and second switching valves disposed on the mixture
gas supply line and the second process gas supply line,
respectively, and
[0025] wherein the control section controls the first and second
switching valves to be opened and closed so as to alternately and
pulse-wise supply the mixture gas from the gas mixture tank and the
second process gas from the second process gas supply circuit to
the process field.
[0026] According to a second aspect of the present invention, there
is provided a film formation apparatus for a semiconductor process,
comprising:
[0027] a process container having a process field configured to
accommodate a plurality of target substrates stacked at
intervals;
[0028] a support member configured to support the target substrates
inside the process field;
[0029] a heater configured to heat the target substrates inside the
process field;
[0030] an exhaust system configured to exhaust gas inside the
process field;
[0031] a process gas supply system configured to supply process
gases to the process field so as to deposit a thin film on the
target substrates, wherein the process gases include a first
process gas for providing a main material of the thin film, a
second process gas for reacting with the first process gas, and a
third process gas for providing a sub-material of the thin film,
and the third process gas is supplied to the process field in an
amount smaller than that of the first process gas;
[0032] a control section configured to control an operation of the
apparatus including the process gas supply system,
[0033] wherein the process gas supply system comprises
[0034] a mixture gas supply line configured to mix the first and
third process gases to form a mixture gas and supply the mixture
gas to the process field,
[0035] first and third process gas supply circuits having first and
third process gas supply lines configured to supply the first and
third process gases to the mixture gas supply line,
respectively,
[0036] a second process gas supply circuit having a second process
gas supply line configured to supply the second process gas to the
process field without passing through the mixture gas supply
line,
[0037] first, second, and third switching valves disposed on the
first, second, and third process gas supply lines,
respectively,
[0038] a first tank disposed on the first process gas supply line
immediately before the first switching valve to temporarily store
the first process gas, and
[0039] wherein the control section controls the first, second, and
third switching valves to be opened and closed so as to alternately
and pulse-wise supply the mixture gas from the mixture gas supply
line and the second process gas from the second process gas supply
circuit to the process field.
[0040] According to a third aspect of the present invention, there
is provided a film formation method for a semiconductor process,
comprising:
[0041] heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
[0042] supplying process gases to the process field to deposit a
thin film on the target substrates, wherein the process gases
include a first process gas for providing a main material of the
thin film, a second process gas for reacting with the first process
gas, and a third process gas for providing a sub-material of the
thin film,
[0043] wherein said supplying the process gases comprises
[0044] supplying the first and third process gases to a gas mixture
tank disposed outside the process container to form a mixture
gas,
[0045] supplying the mixture gas from the gas mixture tank to the
process field, and
[0046] supplying the second process gas to the process field
without passing through the gas mixture tank,
[0047] so as to alternately and pulse-wise supply the mixture gas
and the second process gas to the process field.
[0048] According to a fourth aspect of the present invention, there
is provided a film formation method for a semiconductor process,
comprising:
[0049] heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
[0050] supplying process gases to the process field to deposit a
thin film on the target substrates, wherein the process gases
include a first process gas for providing a main material of the
thin film, a second process gas for reacting with the first process
gas, and a third process gas for providing a sub-material of the
thin film, and the third process gas is supplied to the process
field in an amount smaller than that of the first process gas,
[0051] wherein said supplying the process gases comprises
[0052] supplying the first and third process gases to a mixture gas
supply line to form a mixture gas and supply the mixture gas to the
process field, while temporarily storing the first process gas in a
first tank disposed immediately before the mixture gas supply line,
and
[0053] supplying the second process gas to the process field
without passing through the mixture gas supply line,
[0054] so as to alternately and pulse-wise supply the mixture gas
and the second process gas to the process field.
[0055] According to a fifth aspect of the present invention, there
is provided a computer readable medium containing program
instructions for execution on a processor, which, when executed by
the processor, cause a film formation apparatus for a semiconductor
process to execute
[0056] heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
[0057] supplying process gases to the process field to deposit a
thin film on the target substrates, wherein the process gases
include a first process gas for providing a main material of the
thin film, a second process gas for reacting with the first process
gas, and a third process gas for providing a sub-material of the
thin film,
[0058] wherein said supplying the process gases comprises
[0059] supplying the first and third process gases to a gas mixture
tank disposed outside the process container to form a mixture
gas,
[0060] supplying the mixture gas from the gas mixture tank to the
process field, and
[0061] supplying the second process gas to the process field
without passing through the gas mixture tank,
[0062] so as to alternately and pulse-wise supply the mixture gas
and the second process gas to the process field.
[0063] According to a sixth aspect of the present invention, there
is provided a computer readable medium containing program
instructions for execution on a processor, which, when executed by
the processor, cause a film formation apparatus for a semiconductor
process to execute
[0064] heating a plurality of target substrates stacked at
intervals within a process field in a process container; and
[0065] supplying process gases to the process field to deposit a
thin film on the target substrates, wherein the process gases
include a first process gas for providing a main material of the
thin film, a second process gas for reacting with the first process
gas, and a third process gas for providing a sub-material of the
thin film, and the third process gas is supplied to the process
field in an amount smaller than that of the first process gas,
[0066] wherein said supplying the process gases comprises
[0067] supplying the first and third process gases to a mixture gas
supply line to form a mixture gas and supply the mixture gas to the
process field, while temporarily storing the first process gas in a
first tank disposed immediately before the mixture gas supply line,
and
[0068] supplying the second process gas to the process field
without passing through the mixture gas supply line,
[0069] so as to alternately and pulse-wise supply the mixture gas
and the second process gas to the process field.
[0070] Additional objects and advantages of the invention will be
set forth in the description which follows, and in part will be
obvious from the description, or may be learned by practice of the
invention. The objects and advantages of the invention may be
realized and obtained by means of the instrumentalities and
combinations particularly pointed out hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
[0071] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0072] FIG. 1 is a sectional view showing a film formation
apparatus (vertical CVD apparatus) according to a first embodiment
of the present invention;
[0073] FIG. 2 is a sectional plan view showing part of the
apparatus shown in FIG. 1;
[0074] FIG. 3 is a timing chart of the gas supply and RF (radio
frequency) application of a film formation method according to a
first embodiment;
[0075] FIG. 4 is a sectional view showing a film formation
apparatus (vertical CVD apparatus) according to a second embodiment
of the present invention;
[0076] FIG. 5 is a view showing part of a gas supply system used in
a film formation apparatus according to a modification of the
second embodiment; and
[0077] FIG. 6 is a block diagram schematically showing the
structure of a main control section.
DETAILED DESCRIPTION OF THE INVENTION
[0078] In the process of developing the present invention, the
inventors studied problems caused in conventional film formation
apparatuses for a semiconductor process, where a plurality of
source gases were used to perform a film formation process, such as
a process for forming a thin film doped with an impurity. As a
result, the inventors have arrived at the findings given below.
[0079] Specifically, where a plurality of source gases are used to
perform a film formation process, it is important to control the
ratio of film composition elements of to be a predetermined value,
so as to attain high film quality. However, for example, where the
source gases includes a main source gas containing a main component
element of a deposition film and a doping gas, the supply amount of
the doping gas is far smaller than the supply amount of the main
source gas, in general. In this case, since the supply amount of
the doping gas supplied into a vertical process container is small,
a problem arises such that an element derived from the doping gas
is taken into deposited films on wafers in varying amounts,
depending on the wafer position in the vertical direction.
Consequently, the inter-substrate uniformity in the composition of
the deposited films tends to be lower. This problem is caused due
to differences in the adsorptivity of the source gas relative to
the wafer surface and in the flow rate of the source gases.
[0080] For this reason, where the supply amount of a gas, such as a
doping gas, supplied into a vertical process container is small,
countermeasures are required to supply the gas at a uniform supply
amount in the vertical direction. For example, a gas nozzle having
a number of gas spouting holes at predetermined intervals is
disposed to extend in the longitudinal direction of the vertical
process container, and the doping gas is delivered from the holes.
Alternatively, the supply time of the doping gas is shortened to
increase the flow rate of the gas per unit time. However, even with
the former countermeasure, where a very small gas supply amount is
handled, the flow rate from gas spouting holes at the upstream side
tends to be higher than the flow rate from gas spouting holes at
the downstream side. In this respect, it is not easy to optimize
the dimensions and so forth of gas spouting holes, so as to
uniformize the flow rate from the gas spouting holes, for a small
gas supply amount.
[0081] Further, where the supply amount of a gas, such as a doping
gas, is very small, the gas can be mixed with an inactive carrier
gas to increase the total flow rate, as a countermeasure. In this
case, however, due to the presence of the carrier gas, the partial
pressure of the doping gas decreases and thus the adsorption rate
of the doping gas decreases by that much.
[0082] Embodiments of the present invention achieved on the basis
of the findings given above will now be described with reference to
the accompanying drawings. In the following description, the
constituent elements having substantially the same function and
arrangement are denoted by the same reference numerals, and a
repetitive description will be made only when necessary.
[0083] <First Embodiment>
[0084] FIG. 1 is a sectional view showing a film formation
apparatus (vertical CVD apparatus) according to a first embodiment
of the present invention. FIG. 2 is a sectional plan view showing
part of the apparatus shown in FIG. 1. The film formation apparatus
2 has a process field configured to be selectively supplied with a
first process gas containing dichlorosilane (DCS) gas as a silane
family gas, a second process gas containing ammonia (NH.sub.3) gas
as a nitriding gas, and a third process gas containing BCl.sub.3
gas as a boron-containing gas. The film formation apparatus 2 is
configured to form an SIBN (boron doped silicon nitride) film on
target substrates by CVD in the process field. Accordingly, the
boron-containing gas is used as a doping gas. The process field is
further configured to be selectively supplied with a fourth process
gas containing C.sub.2H.sub.4 gas (ethylene gas) as a carbon
hydride gas, as needed.
[0085] The apparatus 2 includes a process container 4 shaped as a
cylindrical column with a ceiling and an opened bottom, in which a
process field 5 is defined to accommodate and process a plurality
of semiconductor wafers (target substrates) stacked at intervals in
the vertical direction. The entirety of the process container 4 is
made of, e.g., quartz. The top of the process container 4 is
provided with a quartz ceiling plate 6 to airtightly seal the top.
The bottom of the process container 4 is connected through a seal
member 10, such as an O-ring, to a cylindrical manifold 8. The
process container may be entirely formed of a cylindrical quartz
column without a manifold 8 separately formed.
[0086] The manifold 8 is made of, e.g., stainless steel, and
supports the bottom of the process container 4. A wafer boat 12
made of quartz is moved up and down through the bottom port of the
manifold 8, so that the wafer boat 12 is loaded/unloaded into and
from the process container 4. A number of target substrates or
semiconductor wafers W are stacked on a wafer boat 12. For example,
in this embodiment, the wafer boat 12 has struts 12A that can
support, e.g., about 50 to 100 wafers having a diameter of 300 mm
at essentially regular intervals in the vertical direction.
[0087] The wafer boat 12 is placed on a table 16 through a
heat-insulating cylinder 14 made of quartz. The table 16 is
supported by a rotary shaft 20, which penetrates a lid 18 made of,
e.g., stainless steel, and is used for opening/closing the bottom
port of the manifold 8.
[0088] The portion of the lid 18 where the rotary shaft 20
penetrates is provided with, e.g., a magnetic-fluid seal 22, so
that the rotary shaft 20 is rotatably supported in an airtightly
sealed state. A seal member 24, such as an O-ring, is interposed
between the periphery of the lid 18 and the bottom of the manifold
8, so that the interior of the process container 4 can be kept
sealed.
[0089] The rotary shaft 20 is attached at the distal end of an arm
26 supported by an elevating mechanism 25, such as a boat elevator.
The elevating mechanism 25 moves the wafer boat 12 and lid 18 up
and down integratedly. The table 16 may be fixed to the lid 18, so
that wafers W are processed without rotation of the wafer boat
12.
[0090] A gas supply system is connected to the side of the manifold
8 to supply predetermined process gases to the process field 5
within the process container 4. Specifically, the gas supply system
includes a second process gas supply circuit 28, a first process
gas supply circuit 30, a third process gas supply circuit 32, and a
purge gas supply circuit 36, and, as needed, a fourth process gas
supply circuit 34. The first process gas supply circuit 30 is
arranged to supply a first process gas containing a silane family
gas, such as DCS (dichlorosilane) gas. The second process gas
supply circuit 28 is arranged to supply a second process gas
containing a nitriding gas, such as ammonia (NH.sub.3) gas. The
third process gas supply circuit 32 is arranged to supply a third
process gas containing a boron-containing gas (doping gas), such as
BC1.sub.3 gas. The fourth process gas supply circuit 34 is arranged
to supply a fourth process gas containing a carbon hydride gas,
such as C.sub.2H.sub.4 gas (ethylene gas). The purge gas supply
circuit 36 is arranged to supply an inactive gas, such as N.sub.2
gas, as a purge gas. Each of the first, second, and fourth process
gases is mixed with a suitable amount of carrier gas, as needed.
However, such a carrier gas will not be mentioned, hereinafter, for
the sake of simplicity of explanation.
[0091] More specifically, the first, third, and fourth process gas
supply circuits 30, 32, and 34 are connected to a common mixture
gas supply circuit 35. The mixture gas supply circuit 35 has a gas
mixture tank configured to mix the first and third process gases,
and further the fourth process gas in addition thereto, as needed.
The gas mixture tank 42 is designed to have a volume for uniformly
mixing the gases and temporarily store a sufficient supply amount
of the mixture gas, such as a volume of, e.g., about four liters
(to be changed depending on the gas flow rate). The gas mixture
tank 52 is connected to a gas distribution nozzle 40 formed of a
quartz pipe through a mixture gas supply line 44 provided with a
switching valve 44A. On the other hand, the second process gas
supply circuit 28 is connected to a gas distribution nozzle 38
formed of a quartz pipe.
[0092] The gas distribution nozzles 38 and 40 penetrate the
sidewall of the manifold 8 from the outside and then turn and
extend upward. The gas distribution nozzles 38 and 40 respectively
have a plurality of gas spouting holes 38A and 40A, each set of
holes being formed at predetermined intervals in the longitudinal
direction (the vertical direction) over all the wafers W on the
wafer boat 12. Each of the gas spouting holes 38A and 40A delivers
the corresponding process gas almost uniformly in the horizontal
direction, so as to form gas flows parallel with the wafers W on
the wafer boat 12. The purge gas supply circuit 36 includes a short
gas nozzle 46, which penetrates the sidewall of the manifold 8 from
the outside.
[0093] The gas mixture tank 52 is connected to gas sources 30S,
32S, and 34S of DCS gas, BC1.sub.3 gas, and C.sub.2H.sub.4 gas,
respectively, through gas supply lines (gas passages) 50, 52, and
54 of the first, third, and fourth process gas supply circuits 30,
32, and 34, respectively. The gas distribution nozzle 38 of the
second process gas supply circuit 28 is connected to a gas source
28S of NH.sub.3 gas through a gas supply line (gas passage) 48. The
nozzle 46 of the purge gas supply circuit 36 is connected to a gas
source 36S of N.sub.2 gas through gas supply lines (gas passage)
56. The gas supply lines 48, 50, 52, 54, and 56 are provided with
switching valves 48A, 50A, 52A, 54A, and 56A and flow rate
controllers 48B, 50B, 52B, 54B, and 56B, such as mass flow
controllers, respectively. With this arrangement, NH.sub.3 gas, DCS
gas, BCl.sub.3 gas, C.sub.2H.sub.4 gas, and N.sub.2 gas can be
supplied at controlled flow rates.
[0094] A gas exciting section 66 is formed at the sidewall of the
process container 4 in the vertical direction. On the side of the
process container 4 opposite to the gas exciting section 66, a long
and thin exhaust port 68 for vacuum-exhausting the inner atmosphere
is formed by cutting the sidewall of the process container 4 in,
e.g., the vertical direction.
[0095] Specifically, the gas exciting section 66 has a vertically
long and thin opening 70 formed by cutting a predetermined width of
the sidewall of the process container 4, in the vertical direction.
The opening 70 is covered with a quartz cover 72 airtightly
connected to the outer surface of the process container 4 by
welding. The cover 72 has a vertical long and thin shape with a
concave cross-section, so that it projects outward from the process
container 4.
[0096] With this arrangement, the gas exciting section 66 is formed
such that it projects outward from the sidewall of the process
container 4 and is opened on the other side to the interior of the
process container 4. In other words, the inner space of the gas
exciting section 66 communicates with the process field 5 within
the process container 4. The opening 70 has a vertical length
sufficient to cover all the wafers W on the wafer boat 12 in the
vertical direction.
[0097] A pair of long and thin electrodes 74 are disposed on the
opposite outer surfaces of the cover 72, and face each other along
the longitudinal direction (the vertical direction). The electrodes
74 are connected to an RF (Radio Frequency) power supply 76 for
plasma generation, through feed lines 78. An RF voltage of, e.g.,
13.56 MHz is applied to the electrodes 74 to form an RF electric
field for exciting plasma between the electrodes 74. The frequency
of the RF voltage is not limited to 13.56 MHz, and it may be set at
another frequency, e.g., 400 kHz.
[0098] The gas distribution nozzle 38 of the second process gas is
bent outward in the radial direction of the process container 4, at
a position lower than the lowermost wafer W on the wafer boat 12.
Then, the gas distribution nozzle 38 vertically extends at the
deepest position (the farthest position from the center of the
process container 4) in the gas exciting section 66. As shown also
in FIG. 2, the gas distribution nozzle 38 is separated outward from
an area sandwiched between the pair of electrodes 74 (a position
where the RF electric field is most intense), i.e., a plasma
generation area PS where the main plasma is actually generated. The
second process gas containing NH.sub.3 gas is spouted from the gas
spouting holes 38A of the gas distribution nozzle 38 toward the
plasma generation area PS. Then, the second process gas is excited
(decomposed or activated) in the plasma generation area PS, and is
supplied in this state onto the wafers W on the wafer boat 12.
[0099] An insulating protection cover 80 made of, e.g., quartz is
attached on and covers the outer surface of the cover 72. A cooling
mechanism (not shown) is disposed in the insulating protection
cover 80 and comprises coolant passages respectively facing the
electrodes 74. The coolant passages are supplied with a coolant,
such as cooled nitrogen gas, to cool the electrodes 74. The
insulating protection cover 80 is covered with a shield (not shown)
disposed on the outer surface to prevent RF leakage.
[0100] At a position near and outside the opening 70 of the gas
exciting section 66, the gas distribution nozzle 40 of the mixture
gas supply circuit 35 is disposed to vertically extend upward. The
mixture gas (a mixture gas of the first and third process gases,
and further the fourth process gas in addition thereto, as needed)
is spouted from the gas spouting holes 40A of the gas distribution
nozzle 40 toward the center of the process container 4.
[0101] On the other hand, the exhaust port 68, which is formed
opposite the gas exciting section 66, is covered with an exhaust
port cover member 82. The exhaust port cover member 82 is made of
quartz with a U-shape cross-section, and attached by welding. The
exhaust cover member 82 extends upward along the sidewall of the
process container 4, and has a gas outlet 84 at the top of the
process container 4. The gas outlet 84 is connected to a
vacuum-exhaust system GE including a vacuum pump and so forth.
[0102] The process container 4 is surrounded by a heater 86, which
is used for heating the atmosphere within the process container 4
and the wafers W. A thermocouple (not shown) is disposed near the
exhaust port 68 in the process container 4 to control the heater
86.
[0103] The film formation apparatus 2 further includes a main
control section 60 formed of, e.g., a computer, to control the
entire apparatus. The main control section 60 can control the film
formation process described below in accordance with the process
recipe of the film formation process concerning, e.g., the film
thickness and composition of a film to be formed, stored in the
memory 212 thereof in advance. In the memory 212, the relationship
between the process gas flow rates and the thickness and
composition of the film is also stored as control data in advance.
Accordingly, the main control section 60 can control the elevating
mechanism 25, gas supply circuits 28, 30, 32, 34, 35 and 36,
exhaust system GE, gas exciting section 66, heater 86, and so
forth, based on the stored process recipe and control data.
[0104] Next, an explanation will be given of a film formation
method (so called ALD (Atomic Layer Deposition) film formation)
performed in the apparatus shown in FIG. 1. In this film formation
method, an insulating film of SiBN is formed on semiconductor
wafers by CVD. In order to achieve this, a first process gas
containing dichlorosilane (DCS) gas as a silane family gas, a
second process gas containing ammonia (NH.sub.3) gas as a nitriding
gas, and a third process gas containing BC1.sub.3 gas as a
boron-containing gas are selectively supplied into the process
field 5 accommodating wafers W. At this time, the first process gas
and third process gas are mixed in the gas mixture tank 42, and the
mixture gas thus formed is supplied into the process field. It
should be noted that this film formation method is an example where
a fourth process gas containing C.sub.2H.sub.4 gas (ethylene gas)
as a carbon hydride gas is not supplied.
[0105] At first, the wafer boat 12 at room temperature, which
supports a number of, e.g., 50 to 100, wafers having a diameter of
300 mm, is loaded into the process container 4 heated at a
predetermined temperature, and the process container 4 is
airtightly closed. Then, the interior of the process container 4 is
vacuum-exhausted and kept at a predetermined process pressure, and
the wafer temperature is increased to a process temperature for
film formation. At this time, the apparatus is in a waiting state
until the temperature becomes stable. Then, while the wafer boat 12
is rotated, the first to third process gases are intermittently
supplied from the respective gas distribution nozzles 38 and 40 at
controlled flow rates.
[0106] Specifically, the first process gas containing DCS gas and
the third process gas containing BCl.sub.3 gas are supplied into
the gas mixture tank 42 to form a mixture gas. The mixture gas is
supplied from the gas spouting holes 40A of the gas distribution
nozzle 40 to form gas flows parallel with the wafers W on the wafer
boat 12. While being supplied, molecules of DCS gas and BC1.sub.3
gas and molecules and atoms of decomposition products generated by
their decomposition are adsorbed on the wafers W.
[0107] On the other hand, the second process gas containing
NH.sub.3 gas is supplied from the gas spouting holes 38A of the gas
distribution nozzle 38 to form gas flows parallel with the wafers W
on the wafer boat 12. The second process gas is selectively excited
and partly turned into plasma when it passes through the plasma
generation area PS between the pair of electrodes 74. At this time,
for example, radicals (activated species), such as N*, NH*,
NH.sub.2*, and NH.sub.3*, are produced (the symbol .left
brkt-top.*.right brkt-bot. denotes that it is a radical). The
radicals flow out from the opening 70 of the gas exciting section
66 toward the center of the process container 4, and are supplied
into gaps between the wafers W in a laminar flow state.
[0108] The radicals react with molecules of DCS gas adsorbed on the
surface of the wafers W, so that a thin film is formed on the
wafers W. Further, at this time, B atoms generated by decomposition
of BC1.sub.3 gas are taken into the thin film, so a film of SiBN
doped with boron as an impurity is formed. Alternatively, when DCS
gas and BC1.sub.3 gas flow onto radicals adsorbed on the surface of
the wafers W, the same reaction is caused, so an SIBN film doped
with boron is formed on the wafers W.
[0109] FIG. 3 is a timing chart of the gas supply and RF (radio
frequency) application of a film formation method according to the
first embodiment. As shown in FIG. 3, the film formation method
according to this embodiment is arranged to alternately repeat
first to fourth steps T1 to T4. A cycle comprising the first to
fourth steps T1 to T4 is repeated a number of times, and thin films
of SiBN formed by respective cycles are laminated, thereby arriving
at an SiBN film having a target thickness.
[0110] Specifically, the first step T1 is arranged to perform
supply of the mixture gas of the first process gas (denoted as DCS
in FIG. 3) and the third process gas (denoted as BCl.sub.3 in FIG.
3) to the process field 5, while stopping supply of the second
process gas (denoted as NH.sub.3 in FIG. 3) to the process field 5.
The second step T2 is arranged to stop supply of the mixture gas of
the first and third process gases and the second process gas to the
process field 5. The third step T3 is arranged to perform supply of
the second process gas to the process field 5, while stopping
supply of the mixture gas of the first and third process gases to
the process field 5. Further, halfway through the third step T3,
the RF power supply 76 is set in the ON state to turn the second
process gas into plasma by the gas exciting section 66, so as to
supply the second process gas in an activated state to the process
field 5 during a sub-step T3b. The fourth step T4 is arranged to
stop supply of the mixture gas of the first and third process gases
and the second process gas to the process field 5.
[0111] In the third step T3, the RF power supply 76 is turned on
after a predetermined time .DELTA.t passes, to turn the second
process gas into plasma by the gas exciting section 66, so as to
supply the second process gas in an activated state to the process
field 5 during the sub-step T3b. The predetermined time .DELTA.t is
defined as the time necessary for stabilizing the flow rate of
NH.sub.3 gas, which is set at, e.g., about 5 seconds. However, the
second process gas may be turned into plasma by the gas exciting
section 66 over the entire period of supplying the second process
gas. Since the RF power supply is turned on to generate plasma
after the flow rate of the second process gas is stabilized, the
uniformity of radical concentration among the wafers W (uniformity
in the vertical direction) is improved.
[0112] Each of the second and fourth steps T2 and T4 is used as a
purge step to remove the residual gas within the process container
4. The term "purge" means removal of the residual gas within the
process container 4 by vacuum-exhausting the interior of the
process container 4 while supplying an inactive gas, such as
N.sub.2 gas, into the process container 4, or by vacuum-exhausting
the interior of the process container 4 while stopping supply of
all the gases. In this respect, the second and fourth steps T2 and
T4 may be arranged such that the first half utilizes only
vacuum-exhaust and the second half utilizes both vacuum-exhaust and
inactive gas supply. Further, the first and third steps T1 and T3
may be arranged to stop vacuum-exhausting the process container 4
while supplying each of the first to third process gases. However,
where supplying each of the first to third process gases is
performed along with vacuum-exhausting the process container 4, the
interior of the process container 4 can be continuously
vacuum-exhausted over the entirety of the first to fourth steps T1
to T4.
[0113] In FIG. 3, the first step T1 is set to be within a range of
about 1 to 20 seconds, and, for example, at about 10 seconds, the
second step T2 is set to be within a range of about 5 to 15
seconds, and, for example, at about 10 seconds, the third step T3
is set to be within a range of about 1 to 30 seconds, and, for
example, at about 20 seconds, the sub-step T3b is set to be within
a range of about 1 to 25 seconds, and, for example, at about 10
seconds, and the fourth step T4 is set to be within a range of
about 5 to 15 seconds, and, for example, at about 10 seconds. In
general, the film thickness obtained by one cycle of the first to
fourth steps T1 to T4 is about 0.11 to 0.13 nm. Accordingly, for
example, where the target film thickness is 70 nm, the cycle is
repeated about 600 times. However, these values of time and
thickness are merely examples and thus are not limiting.
[0114] The process conditions of the film formation process are as
follows. The flow rate of DCS gas is set to be within a range of 50
to 2,000 sccm, e.g., at 1,000 sccm (1 slm). The flow rate of
NH.sub.3 gas is set to be within a range of 500 to 5,000 sccm,
e.g., at 1,000 sccm. The flow rate of BC1.sub.3 gas is set to be
within a range of 1 to 15 sccm, e.g., at 2 sccm. Accordingly, the
flow rate of BC1.sub.3 gas is far smaller than the flow rate of DCS
gas.
[0115] The process temperature is lower than ordinary CVD
processes, and is set to be within a range of 300 to 700.degree.
C., and preferably a range of 550 to 630.degree. C. If the process
temperature is lower than 300.degree. C., essentially no film is
deposited because hardly any reaction is caused. If the process
temperature is higher than 700.degree. C., a low quality CVD film
is deposited, and existing films, such as a metal film, suffer
thermal damage.
[0116] The process pressure is set to be within a range of 13 Pa
(0.1 Torr) to 1,330 Pa (10 Torr), and preferably a range of 40 Pa
(0.3 Torr) to 266 Pa (2 Torr). For example, the process pressure is
set at 1 Torr during the first step (adsorption step) T1, and at
0.3 Torr during the third step (nitridation step using plasma) T3.
If the process pressure is lower than 13 Pa, the film formation
rate becomes lower than the practical level. If the process
pressure is higher than 1,330 Pa, it becomes difficult to generate
plasma.
[0117] As described above, the first process gas containing DCS gas
for providing the main material of a thin film, and the third
process gas containing BCl.sub.3 gas for providing a sub-material
of the thin film are uniformly mixed at first in the gas mixture
tank 42 to form a mixture gas. The mixture gas is then
intermittently supplied into the process field 5 through a
plurality of gas spouting holes 40A arrayed at intervals in the
vertical direction. In this case, although the amount of BCl.sub.3
gas is small, it can be essentially uniformly distributed within
the process container 4 in the vertical direction without using a
carrier gas. Consequently, the ratio of the composition elements in
SiBN thin films to be formed becomes more uniform, regardless of
wafer position.
[0118] In other words, the supply amount of the third process gas
is far smaller than the supply amount of the first process gas. In
this case, the third process gas in a smaller supply amount is made
to accompany the first process gas in a larger supply amount, so
that it can be uniformly distributed within the process container 4
in the vertical direction. Particularly, where the supply amount of
one source gas is 1/100 or less of the supply amount of the other
source gas, the above-described effect of uniformizing the ratio of
the composition elements in films is more influential.
[0119] When BC1.sub.3 gas is adsorbed on the wafer surface, the
adsorption amount depends on the partial pressure of BC1.sub.3 gas.
According to this embodiment, BCl.sub.3 gas is supplied into the
process container 4 uniformly in the vertical direction without
using a carrier gas. In this case, the partial pressure of
BC1.sub.3 gas can be higher than that in the case of a carrier gas
being used, so adsorption of BCl.sub.3 gas on the wafer surface is
promoted. Consequently, while the film formation rate per unit
cycle is maintained, the time necessary for one cycle is shortened,
so the throughput is improved.
[0120] For example, in an experiment, a conventional film formation
method took about 15 seconds until BCl.sub.3 gas was sufficiently
adsorbed on a wafer surface. On the other hand, the present
embodiment took only two or three seconds for the same.
Accordingly, the conventional method took about 30 seconds for one
cycle, while the present embodiment shortened this period to only 8
seconds.
[0121] Typically, the mixture gas may be formed and supplied by
either of the following two methods. The first method comprises
continuously supplying the first and third process gases from the
first and third process gas supply circuits 30 and 32 into the gas
mixture tank 42, while supplying the mixture gas pulse-wise from
the gas mixture tank 42 into the process field 5. The second method
comprises simultaneously supplying the first and third process
gases pulse-wise in a first phase from the first and third process
gas supply circuits 30 and 32 into the gas mixture tank 42, while
supplying the mixture gas pulse-wise in a second phase reverse to
the first phase from the gas mixture tank 42 into the process field
5.
[0122] In order to realize these methods, the switching valves 50A
and 52A of the first and third process gas supply circuits 30 and
32 and the switching valve 44A of the mixture gas supply circuit 35
are opened and closed in accordance with instructions from the main
control section 60, as follows. In the first method, over a
plurality of cycles from the start to the end of the film formation
process, the switching valves 50A and 52A are kept opened and the
switching valve 44A is opened and closed pulse-wise. In the second
method, over a plurality of cycles from the start to the end of the
film formation process, the switching valves 50A and 52A are opened
and closed pulse-wise while the switching valve 44A is closed and
opened pulse-wise in the reverse phase.
[0123] In the film formation method described above, the fourth
process gas containing C.sub.2H.sub.4 gas (ethylene gas) as a
carbon hydride gas is not supplied, but the fourth process gas may
be supplied, as needed. In this case, the fourth process gas is
supplied into the gas mixture tank 42 at a controlled flow rate,
simultaneously with the first and third process gases. Where a
mixture gas of the first, third, and fourth process gases is used,
a thin film to be formed is an insulating film of SiBCN (boron
doped silicon carbon nitride) containing carbon.
[0124] <Second Embodiment>
[0125] FIG. 4 is a sectional view showing a film formation
apparatus (vertical CVD apparatus) according to a second embodiment
of the present invention. This film formation apparatus 2X has the
same structure as the film formation apparatus 2 shown in FIG. 1
except for the first, third, and fourth process gas supply circuits
30, 32, and 34 and the mixture gas supply circuit 35. Accordingly,
an explanation will be give of the film formation apparatus 2X,
focusing on the difference from the film formation apparatus 2.
[0126] In the film formation apparatus 2X, the first, third, and
fourth process gas supply circuits 30, 32, and 34 are connected to
a common mixture gas supply circuit 35X. The mixture gas supply
circuit 35X includes a mixture gas supply pipe 40X configured to
mix the first and third process gases, and further the fourth
process gas in addition thereto, as needed. The mixture gas supply
pipe 40X is formed of a quartz pipe, which is a proximal end
portion of a gas distribution nozzle 40.
[0127] The first, third, and fourth process gas supply circuits 30,
32, and 34 have tanks 102, 104, and 106, respectively, disposed
immediately before the mixture gas supply pipe 40X to temporarily
store the corresponding process gases. Since the tanks 102 and 106
need to handle a large gas flow rate, they are larger than the tank
104. For example, each of the tanks 102 and 106 has a volume of
about four liters, while the tank 104 has a volume of about 0.05
liters (both to be changed depending on the gas flow rate). The
tanks 102, 104, and 106 are connected to the mixture gas supply
pipe 40X through gas supply lines 103, 105, and 107 provided with
switching valves 103A, 105A, and 107A, respectively.
[0128] The tanks 102, 104, and 106 of the first, third, and fourth
process gas supply circuits 30, 32, and 34 are connected to gas
sources 30S, 32S, and 34S of DCS gas, BC1.sub.3 gas, and
C.sub.2H.sub.4 gas, respectively, through gas supply lines (gas
passages) 50, 52, and 54. The gas supply lines 50, 52, and 54 are
provided with switching valves 50A, 52A, and 54A and flow rate
controllers 50B, 52B, and 54B, such as mass flow controllers,
respectively. With this arrangement, DCS gas, BC1.sub.3 gas, and
C.sub.2H.sub.4 gas can be supplied at controlled flow rates.
[0129] Next, an explanation will be given of a film formation
method (so called ALD (Atomic Layer Deposition) film formation)
performed in the apparatus shown in FIG. 4. It should be noted that
this film formation method is also an example where a fourth
process gas containing C.sub.2H.sub.4 gas (ethylene gas) as a
carbon hydride gas is not supplied. The gas supply and RF (radio
frequency) application of this film formation method are performed
in accordance with the timing chart shown in FIG. 3. At this time,
in order to form and supply a mixture gas (denoted as DCS+BC1.sub.3
in FIG. 3), the switching valves 103A and 105A are simultaneously
opened and closed to supply first and third process gases
temporarily stored in the tanks 102 and 104 into the mixture gas
supply pipe 40X and mix them in the pipe 40X. The mixture gas is
supplied from the gas spouting holes 40A of the gas distribution
nozzle 40 to form gas flows parallel with the wafers W on the wafer
boat 12. As a consequence, this apparatus can provide the same
operation and effect as those obtained in the apparatus shown in
FIG. 1.
[0130] Typically, the mixture gas may be formed and supplied by
either of the following two methods (also in the following
explanation, the fourth process gas is not supplied). The first
method comprises continuously supplying the first and third process
gases into the respective tanks 102 and 104 of the first and third
process gas supply circuits 30 and 32, while supplying the gases
pulse-wise from the respective tanks 102 and 104 into the mixture
gas supply pipe 40X. The second method comprises simultaneously
supplying the first and third process gases pulse-wise in a first
phase into the respective tanks 102 and 104 of the first and third
process gas supply circuits 30 and 32, while supplying the gases
pulse-wise in a second phase reverse to the first phase from the
respective tanks 102 and 104 into the mixture gas supply pipe
40X.
[0131] In order to realize these methods, the switching valves 50A
and 52A of the first and third process gas supply circuits 30 and
32 and the switching valves 103A and 105A downstream from the tanks
are opened and closed in accordance with instructions from the main
control section 60, as follows. In the first method, over a
plurality of cycles from the start to the end of the film formation
process, the switching valves 50A and 52A are kept opened and the
switching valves 103A and 105A are opened and closed pulse-wise. In
the second method, over a plurality of cycles from the start to the
end of the film formation process, the switching valves 50A and 52A
are opened and closed pulse-wise while the switching valves 103A
and 105A are closed and opened pulse-wise in the reverse phase.
[0132] FIG. 5 is a view showing part of a gas supply system used in
a film formation apparatus according to a modification of the
second embodiment (the fourth process gas supply circuit is not
shown). In this modification, the tank 104 of the third process gas
supply circuit 32 is omitted because the flow rate of the third
process gas containing BCl.sub.3 gas is far smaller than the flow
rate of the first process gas containing DCS gas. Even with this
arrangement, the third process gas in a smaller amount is made to
be uniformly mixed with the first process gas in a larger amount
within the mixture gas supply pipe 40X, so that the third process
gas is uniformly supplied.
[0133] <Common Matters to First and Second Embodiments>
[0134] Each of the methods according to the first and second
embodiments is performed under the control of the main control
section 60 in accordance with a process program, as described
above. FIG. 6 is a block diagram schematically showing the
structure of the main control section 60. The main control section
60 includes a CPU 210, which is connected to a storage section 212,
an input section 214, and an output section 216. The storage
section 212 stores process programs and process recipes. The input
section 214 includes input devices, such as a keyboard, a pointing
device, and a storage media drive, to interact with an operator.
The output section 216 outputs control signals for controlling
components of the processing apparatus. FIG. 6 also shows a storage
medium 218 attached to the computer in a removable state.
[0135] Each of the methods according to the first and second
embodiments may be written as program instructions for execution on
a processor, into a computer readable storage medium or media to be
applied to a semiconductor processing apparatus. Alternately,
program instructions of this kind may be transmitted by a
communication medium or media and thereby applied to a
semiconductor processing apparatus. Examples of the storage medium
or media are a magnetic disk (flexible disk, hard disk (a
representative of which is a hard disk included in the storage
section 212), etc.), an optical disk (CD, DVD, etc.), a
magneto-optical disk (MO, etc.), and a semiconductor memory. A
computer for controlling the operation of the semiconductor
processing apparatus reads program instructions stored in the
storage medium or media, and executes them on a processor, thereby
performing a corresponding method, as described above.
[0136] In the embodiments described above, for example, the
exciting section 66 for generating plasma of the film formation
apparatus 2 is integrally combined with the process container 4.
Alternatively, the exciting section 66 may be separately disposed
from the process container 4, so as to excite NH.sub.3 gas outside
the process container 4 (so called remote plasma), and then supply
the excited NH.sub.3 gas into the process container 4. Further,
NH.sub.3 gas may be supplied without being activated, and, in this
case, the members associating with the gas exciting section 66 are
not necessary. However, in this case, the process temperature needs
to be increased to some extent to compensate for energy decrease
due to no plasma being used.
[0137] In the embodiments described above, for example, the
distribution nozzle 40 having a number of gas spouting holes 40A is
used as a nozzle for supplying the mixture gas. Alternatively, a
linear or straight pipe similar to the gas nozzle 46, or a bent or
L-shaped pipe may be used for the same purpose. Where the straight
pipe or L-shaped pipe is used, the mixture gas is supplied from
below or above the process field 5. In this case, an exhaust port
68 is formed at the top or bottom of the process container 4 to
cause the mixture gas to sufficiently flow within the process field
5 in the vertical direction.
[0138] In the embodiments described above, for example, the first
process gas contains DCS gas as a silane family gas. In this
respect, the silane family gas may be one or more gases selected
from the group consisting of dichlorosilane (DCS),
hexachlorodisilane (HCD), monosilane (SiH.sub.4), disilane
(Si.sub.2Cl.sub.6), hexamethyl-disilazane (HMDS), tetrachlorosilane
(TCS), disilylamine (DSA), trisilylamine (TSA),
bistertial-butylaminosilane (BTBAS).
[0139] In the embodiments described above, the second process gas
contains a nitriding gas, which may be NH.sub.3 gas or N.sub.2 gas.
Where the present invention is applied to formation of a film based
on silicon oxynitride, an oxynitriding gas, such as dinitrogen
oxide (N.sub.2O) or nitrogen oxide (NO), may be used in place of
the nitriding gas. In this case, a film to be formed is a film
based on silicon oxynitride that contains oxygen (O).
[0140] In the embodiments described above, for example, the third
process gas contains BC1.sub.3 gas as a boron-containing gas. In
this respect, the boron-containing gas may be one or more gases
selected from the group consisting of BC1.sub.3, B.sub.2H.sub.6,
BF.sub.3, and B(CH.sub.3).sub.3.
[0141] In the embodiments described above, for example, the fourth
process gas contains ethylene gas as a carbon hydride gas. In this
respect, the carbon hydride gas may be one or more gases selected
from the group consisting of acetylene, ethylene, methane, ethane,
propane, and butane.
[0142] In the embodiments described above, for example, an SiBN
film or SiBCN film is formed. Alternatively, for example, the
present invention may be applied to a process for forming a BCN
film (carbon-containing boron nitride film). In this case, a
boron-containing gas and a carbon hydride gas are used as source
gases and mixed. The present invention can be applied to various
film formation processes which use a plurality of source gases that
does not cause any problem if they are mixed before being supplied
into a process container. For example, the present invention may be
applied to a film formation process using an oxidizing gas, such as
O.sub.2 gas, as a reaction gas.
[0143] A target substrate is not limited to a semiconductor wafer,
and it may be another substrate, such as an LCD substrate or glass
substrate.
[0144] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *