U.S. patent application number 11/155629 was filed with the patent office on 2005-12-22 for film formation apparatus and method for semiconductor process.
Invention is credited to Chou, Pao-Hwa, Hasebe, Kazuhide, Kim, Chaeho.
Application Number | 20050282365 11/155629 |
Document ID | / |
Family ID | 35481159 |
Filed Date | 2005-12-22 |
United States Patent
Application |
20050282365 |
Kind Code |
A1 |
Hasebe, Kazuhide ; et
al. |
December 22, 2005 |
Film formation apparatus and method for semiconductor process
Abstract
A film formation apparatus for a semiconductor process includes
a source gas supply circuit to supply into a process container a
source gas for depositing a thin film on target substrates, and a
mixture gas supply circuit to supply into the process container a
mixture gas containing a doping gas for doping the thin film with
an impurity and a dilution gas for diluting the doping gas. The
mixture gas supply circuit includes a gas mixture tank disposed
outside the process container to mix the doping gas with the
dilution gas to form the mixture gas, a mixture gas supply line to
supply the mixture gas from the gas mixture tank into the process
container, a doping gas supply circuit to supply the doping gas
into the gas mixture tank, and a dilution gas supply circuit to
supply the dilution gas into the gas mixture tank.
Inventors: |
Hasebe, Kazuhide;
(Minamialps-shi, JP) ; Chou, Pao-Hwa; (Kai-shi,
JP) ; Kim, Chaeho; (Kofu-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
35481159 |
Appl. No.: |
11/155629 |
Filed: |
June 20, 2005 |
Current U.S.
Class: |
438/513 ;
118/715 |
Current CPC
Class: |
Y10T 117/1024 20150115;
C23C 16/24 20130101; C23C 16/45523 20130101 |
Class at
Publication: |
438/513 ;
118/715 |
International
Class: |
H01L 021/26; C23C
016/00; H01L 021/42 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 21, 2004 |
JP |
2004-182361 |
May 13, 2005 |
JP |
2005-141401 |
Claims
What is claimed is:
1. A film formation apparatus for a semiconductor process,
comprising: a process container configured to accommodate a
plurality of target substrates stacked at intervals; a support
member configured to support the target substrates inside the
process container; a heater configured to heat the target
substrates inside the process container; an exhaust system
configured to exhaust gas inside the process container; a source
gas supply circuit configured to supply a source gas into the
process container, the source gas being for depositing a thin film
on the target substrates; a mixture gas supply circuit configured
to supply a mixture gas into the process container, the mixture gas
containing a doping gas for doping the thin film with an impurity
and a dilution gas for diluting the doping gas; and a control
section configured to control an operation of the apparatus
including the mixture gas supply circuit, wherein the mixture gas
supply circuit comprises a gas mixture tank disposed outside the
process container and configured to mix the doping gas with the
dilution gas to form the mixture gas, a mixture gas supply line
configured to supply the mixture gas from the gas mixture tank into
the process container, a doping gas supply circuit configured to
supply the doping gas into the gas mixture tank, and a dilution gas
supply circuit configured to supply the dilution gas into the gas
mixture tank.
2. The apparatus according to claim 1, wherein the mixture gas
supply circuit includes a merged gas line for the doping gas and
the dilution gas from the doping gas supply circuit and the
dilution gas supply circuit to be merged therein and then supplied
into the gas mixture tank.
3. The apparatus according to claim 1, wherein the mixture gas
supply circuit further comprises a first switching valve disposed
on the mixture gas supply line, and the control section is
configured to keep the first switching valve closed so as to store
the doping gas and the dilution gas from the doping gas supply
circuit and the dilution gas supply circuit within the gas mixture
tank, and to then open the first switching valve so as to supply
the mixture gas into the process container.
4. The apparatus according to claim 3, wherein the mixture gas
supply circuit further comprises a pressure meter configured to
measure pressure inside the gas mixture tank, and the control
section is configured to open and close the first switching valve,
based on measurement values by the pressure meter.
5. The apparatus according to claim 1, wherein the gas mixture tank
has a volume of 200 to 5,000 cc.
6. The apparatus according to claim 1, wherein the mixture gas
supply circuit further comprises a first switching valve disposed
on the mixture gas supply line, and the control section is
configured to pulse-wise open and close the first switching valve
while the doping gas and the dilution gas are continuously supplied
from the doping gas supply circuit and the dilution gas supply
circuit into the gas mixture tank.
7. The apparatus according to claim 6, wherein the mixture gas
supply circuit further comprises a pressure meter configured to
measure pressure inside the gas mixture tank, and the control
section is configured to pulse-wise open and close the first
switching valve, based on measurement values by the pressure
meter.
8. The apparatus according to claim 6, wherein the source gas
supply circuit comprises a source gas supply line configured to
supply the source gas into the process container, and a second
switching valve disposed on the source gas supply line, and the
control section is configured to pulse-wise open and close the
second switching valve in synchronism with operation to pulse-wise
open and close the first switching valve.
9. The apparatus according to claim 8, wherein the apparatus
further comprises a purge gas supply circuit configured to supply a
purge gas into the process container, the purge gas supply circuit
comprises a purge gas supply line configured to supply the purge
gas into the process container, and a third switching valve
disposed on the purge gas supply line, and the control section is
configured to pulse-wise close and open the third switching valve
in synchronism with operation to pulse-wise open and close the
first and second switching valves.
10. The apparatus according to claim 9, wherein the purge gas
supply line is connected to the mixture gas supply line downstream
from the first switching valve.
11. A film formation method for a semiconductor process,
comprising: heating a plurality of target substrates stacked at
intervals inside a process container; supplying a source gas into
the process container, the source gas being for depositing a thin
film on the target substrates; and supplying a mixture gas from a
gas mixture tank disposed outside the process container into the
process container, while supplying a doping gas for doping the thin
film with an impurity and a dilution gas for diluting the doping
gas into the gas mixture tank to form the mixture gas.
12. The method according to claim 11, comprising performing
operation to pulse-wise supply the mixture gas from the gas mixture
tank into the process container, while continuously supplying the
doping gas and the dilution gas into the gas mixture tank.
13. The method according to claim 12, comprising performing
operation to pulse-wise supply the mixture gas, based on
measurement values by a pressure meter configured to measure
pressure inside the gas mixture tank.
14. The method according to claim 12, comprising performing
operation to pulse-wise supply the source gas in synchronism with
operation to pulse-wise supply the mixture gas.
15. The method according to claim 14, comprising performing
operation to pulse-wise supply a purge gas into the process
container in synchronism with an operation to pulse-wise supply the
mixture gas and the source gas, in opposite phase.
16. 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 inside a process container; supplying a source gas into
the process container, the source gas being for depositing a thin
film on the target substrates; and supplying a mixture gas from a
gas mixture tank disposed outside the process container into the
process container, while supplying a doping gas for doping the thin
film with an impurity and a dilution gas for diluting the doping
gas into the gas mixture tank to form the mixture gas.
17. The medium according to claim 16, wherein the program
instructions, when executed by the processor, cause the
film-formation apparatus to execute performing operation to
pulse-wise supply the mixture gas from the gas mixture tank into
the process container, while continuously supplying the doping gas
and the dilution gas into the gas mixture tank.
18. The medium according to claim 17, wherein the program
instructions, when executed by the processor, cause the
film-formation apparatus to execute performing operation to
pulse-wise supply the mixture gas, based on measurement values by a
pressure meter configured to measure pressure inside the gas
mixture tank.
19. The medium according to claim 17, wherein the program
instructions, when executed by the processor, cause the
film-formation apparatus to execute performing operation to
pulse-wise supply the source gas in synchronism with operation to
pulse-wise supply the mixture gas.
20. The medium according to claim 19, wherein the program
instructions, when executed by the processor, cause the
film-formation apparatus to execute performing operation to
pulse-wise supply a purge gas into the process container in
synchronism with an operation to pulse-wise supply the mixture gas
and the source gas, in opposite phase.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Applications No. 2004-182361,
filed Jun. 21, 2004; and No. 2005-141401, filed May 13, 2005, 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
doped with an impurity (dopant), such as phosphorous (P) or boron
(B), 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, oxidation, diffusion, reformation, annealing, and
etching. As CVD (Chemical Vapor Deposition) used as a film
formation process, there is a method of simultaneously supplying a
source gas for film formation and a doping gas for doping the
deposition film with an impurity. Jpn. Pat. Appln. KOKAI
Publication No. 2003-282566 discloses a CVD method of this kind
performed in a vertical heat processing apparatus. According to
this method, a number of semiconductor wafers are accommodated at
intervals in the vertical direction within a vertical process
container. Then, a film formation gas and a doping gas containing
an impurity are supplied into the process container while the
wafers are being heated. As a consequence, a thin film is deposited
on the wafers, while being doped with the impurity. For example, in
a process where poly-crystalline silicon doped with phosphorous is
deposited, PH.sub.3 gas is used as a doping gas.
[0006] Where a doping gas of this kind is a material having a high
vapor pressure, the doping gas can be supplied in a pure state from
a storage tank into a process container at a controlled flow rate.
However, in general, doping gases of this kind have a very low
vapor pressure. Accordingly, where a doping gas in a pure state is
supplied into a process container, it cannot diffuse sufficiently,
thereby resulting in a less uniform doping distribution.
[0007] For this reason, in general, where a doping gas of this kind
is supplied, this doping gas is diluted in advance to, e.g., about
1% by an inactive gas, such as N.sub.2, and is stored in a storage
cylinder. When used, this diluted 1% doping gas is discharged from
the storage cylinder at a controlled flow rate, and is supplied
into a process container with a high diffusion rate. In this case,
i.e., where the diluted doping gas is supplied from the storage
cylinder into the process container, the gas flow rate per unit
time becomes larger by that much corresponding to dilution. As a
consequence, the doping gas can swiftly and uniformly diffuse in a
short time within the process container, which has a relatively
large volume.
[0008] However, in this case, as described above, the consumption
(outflow) per unit time of the diluted doping gas from the storage
cylinder is very high. As a consequence, the storage cylinder needs
to be replaced with a new one in a relatively short time, thereby
resulting in a low productivity and thus a low throughput.
Particularly, as the wafer size increases from 8 inches to 12
inches (300 mm), the volume of batch-type process containers
greatly increases. Under the circumstances, it has become more
necessary for a doping gas being supplied to swiftly and uniformly
diffuse within a process container while maintaining high
throughput of the process.
BRIEF SUMMARY OF THE INVENTION
[0009] An object of the present invention is to increase the
diffusion rate of a doping gas within a process container, while
decreasing the exchange frequency of a doping gas source, thereby
improving the productivity or throughput in a film formation
apparatus and method for a semiconductor process.
[0010] According to a first aspect of the present invention, there
is provided a film formation apparatus for a semiconductor process,
comprising:
[0011] a process container configured to accommodate a plurality of
target substrates stacked at intervals;
[0012] a support member configured to support the target substrates
inside the process container;
[0013] a heater configured to heat the target substrates inside the
process container;
[0014] an exhaust system configured to exhaust gas inside the
process container;
[0015] a source gas supply circuit configured to supply a source
gas into the process container, the source gas being for depositing
a thin film on the target substrates;
[0016] a mixture gas supply circuit configured to supply a mixture
gas into the process container, the mixture gas containing a doping
gas for doping the thin film with an impurity and a dilution gas
for diluting the doping gas; and
[0017] a control section configured to control an operation of the
apparatus including the mixture gas supply circuit,
[0018] wherein the mixture gas supply circuit comprises
[0019] a gas mixture tank disposed outside the process container
and configured to mix the doping gas with the dilution gas to form
the mixture gas,
[0020] a mixture gas supply line configured to supply the mixture
gas from the gas mixture tank into the process container, a doping
gas supply circuit configured to supply the doping gas into the gas
mixture tank, and a dilution gas supply circuit configured to
supply the dilution gas into the gas mixture tank.
[0021] According to a second aspect of the present invention, there
is provided a film formation method for a semiconductor process,
comprising:
[0022] heating a plurality of target substrates stacked at
intervals inside a process container;
[0023] supplying a source gas into the process container, the
source gas being for depositing a thin film on the target
substrates; and
[0024] supplying a mixture gas from a gas mixture tank disposed
outside the process container into the process container, while
supplying a doping gas for doping the thin film with an impurity
and a dilution gas for diluting the doping gas into the gas mixture
tank to form the mixture gas.
[0025] According to a third 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
[0026] heating a plurality of target substrates stacked at
intervals inside a process container;
[0027] supplying a source gas into the process container, the
source gas being for depositing a thin film on the target
substrates; and
[0028] supplying a mixture gas from a gas mixture tank disposed
outside the process container into the process container, while
supplying a doping gas for doping the thin film with an impurity
and a dilution gas for diluting the doping gas into the gas mixture
tank to form the mixture gas.
[0029] 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
[0030] 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.
[0031] FIG. 1 is a structural view showing a vertical film
formation apparatus (CVD apparatus) according to an embodiment of
the present invention;
[0032] FIG. 2 is a view showing the gas inflow into a process
container, the gas inflow into a gas mixture tank, the open and
closed states of switching valves, and the pressure inside the gas
mixture tank and process container; and
[0033] FIG. 3 is a block diagram schematically showing the
structure of a main control section.
DETAILED DESCRIPTION OF THE INVENTION
[0034] An embodiment of the present invention 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.
[0035] FIG. 1 is a structural view showing a vertical film
formation apparatus (CVD apparatus) according to an embodiment of
the present invention. As shown in FIG. 1, the film formation
apparatus 2 includes a vertical process container 4, which is
cylindrical and opened at the bottom. The process container 4 is
made of, e.g., quartz, which is high in heat resistance. An exhaust
port 6 is formed at the top of the process container 4. The exhaust
port 6 is connected to, e.g., an exhaust nozzle 8 laterally bent at
right angles. The exhaust nozzle 8 is connected to an exhaust
system 14 including a pressure control valve 10 and a vacuum pump
12, provided thereon. The interior of the process container 4 is
vacuum-exhausted by the exhaust section 14.
[0036] The bottom of the process container 4 is supported by a
cylindrical manifold 16 made of, e.g., stainless steel. A sealing
member 20, such as an O-ring, is interposed between the bottom of
the process container 4 and manifold 16 to keep this portion
airtight. The manifold 16 has a port at the bottom, through which a
wafer boat 18 is loaded and unloaded. The wafer boat 18 is made of
quartz, and functions as holding means for holding semiconductor
wafers W at intervals in the vertical direction. In this
embodiment, the wafer boat 18 can support, e.g., 50 to 100 wafers W
each having a diameter of 300 mm, essentially at regular intervals
in the vertical direction. The manifold 16 may be made of quartz
and thus integrally formed with the process container 4.
[0037] The wafer boat 18 is placed on a table 24 through a
heat-insulating cylinder 22 made of quartz. The table 24 is
supported on the top of a rotary shaft 28, which penetrates a lid
26 used for opening/closing the bottom port of the manifold 16. The
portion of the lid 26 where the rotary shaft 28 penetrates is
provided with, e.g., a magnetic-fluid seal 30, so that the rotary
shaft 28 is rotatably supported in an airtightly sealed state. A
seal member 32, such as an O-ring, is interposed between the
periphery of the lid 26 and the bottom of the manifold 16, so that
the interior of the process chamber 4 can be kept sealed.
[0038] The rotary shaft 28 is attached at the distal end of an arm
36 supported by an elevating mechanism 34, such as a boat elevator.
The elevating mechanism 34 moves the wafer boat 18 and lid 26 up
and down integratedly. The table 24 may be fixed to the lid 26, so
that the wafer boat 18 is not rotated in processing wafers W.
[0039] A heater 38 formed of carbon wires (for example, see Jpn.
Pat. Appln. KOKAI Publication No. 2003-209063) is disposed to
surround the process container 4. The heater 38 is arranged to heat
the atmosphere within the process container 4 so as to heat up the
semiconductor wafers W. The carbon wire heater is suitable for a
case where processes are serially performed, as described later,
because it can realize a clean process and has good characteristics
for increasing and decreasing the temperature. The heater 38 is
surrounded by a thermal insulator 40 to ensure thermal stability.
The manifold 16 is connected to several gas supply circuits to
supply various gases into the process container 4.
[0040] More specifically, the manifold 16 is connected to a source
gas supply circuit 42, deoxidizing gas supply circuit 44, and
mixture gas supply circuit 45. The gas supply circuits 42, 44, and
45 have gas nozzles 42A, 44A, and 45A, respectively. Each of the
gas nozzles 42A, 44A, and 45A penetrates the sidewall of the
manifold 16 and is bent at right angles to direct the distal end
upward.
[0041] The source gas supply circuit 42 is arranged to supply a
source gas, for depositing a thin film on the wafers, into the
process container 4. The deoxidizing gas supply circuit 44 is
arranged to supply a deoxidizing gas, for promoting decomposition
of the source gas, into the process container 4. The mixture gas
supply circuit 45 is arranged to supply a mixture gas, which
comprises a doping gas for doping the thin film with an impurity
and a dilution gas for diluting the doping gas, into the process
container 4. Further, a purge gas supply circuit 50 is connected to
the mixture gas supply circuit 45. The purge gas supply circuit 50
is arranged to supply an inactive gas used as a purge gas into the
process container 4.
[0042] In this embodiment, the source gas is a silane family gas,
such as SiCl.sub.4. The deoxidizing gas is hydrogen (H.sub.2) gas.
The doping gas is a gas for doping with phosphorous, such as
PH.sub.3 gas. The dilution gas and purge gas are nitrogen (N.sub.2)
gas. The dilution gas and purge gas may be another inactive gas,
such as Ar or He, in place of nitrogen.
[0043] Specifically, the gas nozzles 42A and 44A of the source gas
supply circuit 42 and deoxidizing gas supply circuit 44 are
connected to a source gas source 42S and a deoxidizing gas source
44S through a doping gas supply line 52 and a deoxidizing gas
supply line 54 (gas passages), respectively. The gas lines 52 and
54 are provided with switching valves 52A and 54A and flow rate
controllers 52B and 54B, such as mass flow controllers,
respectively. With this arrangement, the source gas and deoxidizing
gas can be supplied at controlled flow rates.
[0044] The gas nozzle 45A of the mixture gas supply circuit 45 is
connected to a gas mixture tank 66 outside the process container 4
through a mixture gas supply line (gas passage) 64. The gas line 64
is provided with a switching valve 64A. The gas mixture tank 66 has
a certain volume to mix the doping gas with the dilution gas,
thereby forming the mixture gas. The gas mixture tank 66 has a
volume within a range of, e.g., 200 to 5,000 cc, depending on the
volume of the process container 4. Particularly, where the process
container 4 is arranged to accommodate 50 to 100 wafers of 300 mm,
the volume of the gas mixture tank 66 is set to be within a range
of 600 to 700 cc. If the volume of the gas mixture tank 66 is less
than 200 cc, it is difficult to prepare a sufficient amount of
mixture gas necessary for film formation. If the volume of the gas
mixture tank 66 is larger than 5,000 cc, the entire apparatus
becomes undesirably large.
[0045] A doping gas supply circuit 46 and a dilution gas supply
circuit 48 are connected to the gas mixture tank 66. The doping gas
supply circuit 46 and dilution gas supply circuit 48 respectively
includes a doping gas source 56 and a dilution gas source 60
connected to the gas mixture tank 66 through a doping gas supply
line 58 and a dilution gas supply line 62 (gas passages). The
doping gas source 56 stores a pure doping gas without a dilution
gas. The gas lines 58 and 62 are provided with switching valves 58A
and 62A and flow rate controllers 58B and 62B, such as mass flow
controllers, respectively. With this arrangement, the doping gas
and dilution gas can be supplied at controlled flow rates. The gas
lines 58 and 62 are combined to be a merged gas line (merged gas
passage) 63 connected to the gas mixture tank 66. However, the gas
lines 58 and 62 may be separately connected to the gas mixture tank
66.
[0046] The gas line 64 of the mixture gas supply circuit 45 is also
used as a gas passage for the purge gas supply circuit 50. For
this, a portion of the gas line 64 downstream from the switching
valve 64A is connected to a purge gas source 50A through a purge
gas supply line (a gas passage) 68. The gas line 68 is provided
with a switching valve 68A and a flow rate controller 68B, such as
a mass flow controller. With this arrangement, the purge gas can be
supplied at a controlled flow rate.
[0047] The switching valves 52A, 54A, 64A, 68A, 58A, and 62A are
operated to be opened and closed, by a gas supply controller 70
formed of, e.g., a microcomputer. The gas mixture tank 66 is
provided with a pressure meter 72 for measuring the internal
pressure, which outputs pressure measurement values to the gas
supply controller 70 in real time. The gas supply controller 70 can
calculate the volume of the doping gas in real time, based on the
flow rate ratio between the doping gas and dilution gas, and the
pressure measurement value.
[0048] The film formation apparatus 2 further includes a main
control section 80 formed of, e.g., a computer, to control the
entire apparatus including the gas supply controller 70. The main
control section 80 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 thereof in advance. In the
memory, 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 80 can
control the gas supply controller 70, exhaust system 14, elevating
mechanism 34, heater 38, and so forth, based on the stored process
recipe and control data.
[0049] Next, an explanation will be given of a film formation
method according to an embodiment of the present invention,
performed in the film formation apparatus 2 described above. The
method according to this embodiment is characterized in that the
source gas, deoxidizing gas, and mixture gas of the doping gas and
dilution gas are respectively supplied into the process container 4
intermittently (pulse-wise). As a consequence, a thin film with a
thickness of an atomic layer level or molecular level is repeatedly
formed to deposit a poly-crystalline silicon film doped with
phosphorous. This kind of film formation is also called ALD (Atomic
Layer Deposition).
[0050] At first, when the film formation apparatus 2 is in a
waiting state with no wafers loaded therein, the interior of the
process container 4 is kept at a temperature lower than a process
temperature. On the other hand, a number of wafers W, e.g. 50
wafers, are transferred into the wafer boat 18 at a normal
temperature, which is then moved up from below into the process
container 4. Then, the bottom port of the manifold 16 is closed by
the lid 26 to airtightly seal the interior of the process container
4.
[0051] Then, the interior of the process container 4 is
vacuum-exhausted and kept at a predetermined process pressure. At
the same time, the power supplied to the heater 38 is increased, so
that the wafer temperature is raised and stabilized at a process
temperature for film formation. Then, predetermined process gases
necessary for each process step are supplied from the respective
gas nozzles 42A, 44A, and 45A of the gas supply circuits 42, 44,
and 45 at controlled flow rates, into the process container 4. As
described above, the gases are supplied intermittently (pulse-wise)
by the gas supply controller 70, which controls the switching
valves 52A, 54A, 64A, and 68A to perform supply and stop of the
gases.
[0052] When the film formation process is started, the switching
valves 58A and 62A are set open, so that the doping gas and
dilution gas or N.sub.2 gas are always supplied from the doping gas
source 56 and dilution gas source 60. Thus, the doping gas and
dilution gas are continuously supplied at a predetermined flow rate
ratio into the gas mixture tank 66, and are uniformly mixed with
each other within the gas mixture tank 66 to form a mixture
gas.
[0053] On the other hand, while the doping gas and dilution gas are
continuously supplied into the gas mixture tank 66, the gas supply
controller 70 operates the switching valve 64A to be opened and
closed pulse-wise, so as to supply the mixture gas pulse-wise into
the process container 4. Further, in synchronism with the switching
valve 64A being opened and closed pulse-wise, the gas supply
controller 70 operates the switching valves 52A and 54A to be
opened and closed pulse-wise, so as to supply the source gas and
deoxidizing gas pulse-wise into the process container 4.
Furthermore, in synchronism with the switching valves 52A, 54A, and
64A being opened and closed pulse-wise, the gas supply controller
70 operates the switching valve 58A to be closed and opened
pulse-wise, so as to supply the purge gas pulse-wise into the
process container 4, in a phase opposite to the mixture gas, source
gas, and deoxidizing gas.
[0054] FIG. 2 is a view showing the gas inflow into the process
container 4, the gas inflow into the gas mixture tank 66, the open
and closed states of the switching valves 52A, 54A, 64A, and 68A,
and the pressure inside the gas mixture tank 66 and process
container 4.
[0055] At first, when the film formation process is started, both
the switching valves 58A and 62A are set open to start supply of
the doping gas or PH.sub.3 gas and the dilution gas or N.sub.2 gas,
which are then uniformly mixed within the gas mixture tank 66
(FIGS. 2, (D) and (E)). At this time, the switching valve 64A is in
the closed state, and the mixture gas does not flow out downstream.
After a predetermined amount of the mixture gas is stored within
the gas mixture tank 66, this mixture gas is intermittently
supplied into the process container 4 (FIG. 2, (B)). In synchronism
with this supply of the mixture gas, the source gas (SiCl.sub.4)
and deoxidizing gas (H.sub.2) are intermittently supplied into the
process container 4 to perform a film formation process (FIG. 2,
(A)). When the source gas, deoxidizing gas, and mixture gas are not
supplied into the process container 4, the purge gas or N.sub.2 gas
is supplied into the process container 4, to remove the residual
gas (FIG. 2, (C)).
[0056] The supply and stop of the gases relative to the process
container 4 are performed by the switching valves 52A, 54A, 64A,
and 68A being opened and closed, as shown in FIG. 2, (F) to (H). In
this case, as shown in FIG. 2, (I), the pressure inside the gas
mixture tank 66 is repeatedly varied from around a pressure P1 and
to around another pressure P2. Further, the pressure inside the
process container 4 is also repeatedly varied from around a
pressure P3 to around another pressure P4.
[0057] At this time, one supply period T1 of the source gas is set
to be within a range of, e.g., about 1 to 180 seconds. One purge
period T2 by N.sub.2 gas is set to be within a range of, e.g.,
about 1 to 180 seconds. The film formation temperature is set to be
within a range of, e.g., about 300 to 650.degree. C. The film
formation pressure is set to be within a range of, e.g., about 26.6
to 1333 Pa. The flow rate of SiCl.sub.4 gas is set to be within a
range of, e.g., about 200 to 5,000 sccm. The flow rate of N.sub.2
gas is set to be within a range of, e.g., about 200 to 5,000 sccm.
The flow rate of PH.sub.3 gas used as the doping gas is set to be
within a range of, e.g., about 0.1 to 1000 sccm. The flow rate of
N.sub.2 gas used as the dilution gas is set to be within a range
of, e.g., about 1 to 5,000 sccm.
[0058] In this process, the gas supply controller 70 operates the
switching valves 52A, 54A, 64A, and 68A (set the supply pulse
widths of the gases) in accordance with a process recipe received
from the main control section 80. In this case, the timing of
supply and stop of the gases may be obtained by measuring the
periods T1 and T2 by a timer.
[0059] Alternatively, the timing of supply and stop of the gases
may be obtained on the basis of change in the pressure inside the
gas mixture tank 66 being monitored by the pressure meter 72. For
example, when the gas mixture tank 66 reaches a predetermined
pressure P1, the switching valve 64A is opened to start supply of
the mixture gas. At this time, an end pressure for stopping the
supply is immediately calculated, on the basis of the start
pressure P1 and a predetermined supply amount of mixture gas for
one pulse. Then, the supply of the mixture gas is maintained, and,
when the gas mixture tank 66 reaches the end pressure (a pressure
P2 in this case), the switching valve 64A is closed to stop the
supply of the mixture gas. In this case, the other switching valves
52A, 54A, and 68A are operated in synchronism with the switching
valve 64A being operated.
[0060] Further, where the timing of supply and stop of the gases is
obtained on the basis of change in the pressure inside the gas
mixture tank 66, it may be designed to set the switching valve 64A
open for a predetermined time from when the gas mixture tank 66
reaches a predetermined pressure P1. Also in this case, the other
switching valves 52A, 54A, and 68A are operated in synchronism with
the switching valve 64A being operated.
[0061] The method according to the embodiment is performed under
the control of the main control section 80 in accordance with a
process program, as described above. FIG. 3 is a block diagram
schematically showing the structure of the main control section 80.
The main control section 80 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. 3 also shows a storage medium 218 attached to the computer in
a removable state.
[0062] The method according to the embodiment 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.
[0063] According to the embodiment described above, the doping gas
source 56 is formed of a cylinder storing a pure doping gas without
mixture of a dilution gas. The pure doping gas from this cylinder
is supplied into the gas mixture tank 66 and is uniformly mixed
with a dilution gas to form a large amount of mixture gas in the
tank 66. This mixture gas is then supplied into the process
container 4. As a consequence, the diffusion rate of the doping gas
within the process container 4 is increased, so that the doping gas
is swiftly and uniformly diffused within the process container 4 in
a short time. Since the cylinder of the doping gas source 56 stores
a pure doping gas, the exchange frequency of the cylinder is
reduced, so that the productivity or throughput can be maintained
high. In place of a pure gas, the doping gas source 56 may store a
doping gas at a high concentration, such as more than 10%, to
obtain a certain effect.
[0064] The embodiment described above is exemplified by a film
formation method of a poly-crystalline silicon film doped with
phosphorous. The present invention may be applied to a film
formation method of doping a film with another impurity, or forming
a film of a different type. For example, the present invention may
be applied to a film formation method of forming an SiBN film,
using dichlorosilane (SiH.sub.2Cl.sub.2) and ammonia (NH.sub.3) as
source gases and BCl.sub.3 as a doping gas. The dilution gas is not
limited to an inactive gas, and it can be any gas that causes no
problem in use along with the doping gas (preferably a gas used for
the film formation). For example, in the case of formation of a
SiBN film described above, dichlorosilane used as a source gas for
film formation may be also used as a dilution gas. Further, in the
case of the apparatus shown in FIG. 1, SiCl.sub.4 used as a source
gas for film formation may be also used as a dilution gas.
[0065] The process container 4 of the heat processing apparatus is
not limited to a single-tube structure type shown in FIG. 1, and it
may be of a double-tube structure type, for example. A target
substrate is not limited to a semiconductor wafer, and it may be
another substrate, such as an LCD substrate or glass substrate.
[0066] 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.
* * * * *