U.S. patent application number 09/092091 was filed with the patent office on 2002-04-25 for method of producing thin films using current of process gas and inert gas colliding with each other and apparatus for producing thin films for practicing the same method.
Invention is credited to MORIYAMA, TSUYOSHI.
Application Number | 20020048860 09/092091 |
Document ID | / |
Family ID | 15445848 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020048860 |
Kind Code |
A1 |
MORIYAMA, TSUYOSHI |
April 25, 2002 |
METHOD OF PRODUCING THIN FILMS USING CURRENT OF PROCESS GAS AND
INERT GAS COLLIDING WITH EACH OTHER AND APPARATUS FOR PRODUCING
THIN FILMS FOR PRACTICING THE SAME METHOD
Abstract
The present invention provides a heat treatment apparatus
capable of forming a uniform thin layer on the substrate provided
with a furnace core pipe, a substrate supporting boat for
supporting a lot of substrates disposed in the furnace core pipe
and a process gas injector pipe having many blowing holes for
spouting the process gas toward the substrate, the supporting boat
having a rotation mechanism to rotate around the normal line
passing through one principal face of the substrate as a rotation
axis. In the apparatus, an inert gas injector pipe has the same
number of inert gas or nitrogen gas blowing holes as the number of
process gas blowing holes and is provided at an approximately
symmetrical position relative to the center line of the rotation
axis.
Inventors: |
MORIYAMA, TSUYOSHI; (TOKYO,
JP) |
Correspondence
Address: |
FOLEY & LARDNER
WASHINGTON HARBOUR
3000 K STREET N W SUITE 500
P O BOX 25696
WASHINGTON
DC
200078696
|
Family ID: |
15445848 |
Appl. No.: |
09/092091 |
Filed: |
June 5, 1998 |
Current U.S.
Class: |
438/149 ;
438/153 |
Current CPC
Class: |
C30B 31/16 20130101;
H01L 21/67109 20130101 |
Class at
Publication: |
438/149 ;
438/153 |
International
Class: |
H01L 021/00; H01L
021/84; H01L 021/31 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 5, 1997 |
JP |
9-148126 |
Claims
What is claimed is:
1. A method of producing a thin film on a substrate disposed in a
furnace core pipe, which comprising a step of making the substrate
to rotate around a center axis in accompany with allowing a first
gas to spout toward the substrate, said center axis being a normal
line passing through the center of one principal face of the
substrate, said first gas consisting essentially of a process gas,
wherein the thin film is formed on the substrate while allowing a
second gas to spout via the center axis in the colliding direction
to the first gas, said second gas consisting essentially of an
inert gas or nitrogen gas.
2. A method according to claim 1, wherein said second gas spouts
along a direction approximately opposite to the spout direction of
the first gas.
3. A method according to claim 2, wherein the locations for
supplying the first gas and the second gas are approximately
symmetrically positioned with each other with respect to said
center axis, the first gas being simultaneously supplied with the
second gas.
4. A method according to claim 3, wherein approximately the same
amounts of said first gas and said second gas are supplied.
5. A method according to claim 4, wherein said first gas and said
second gas are supplied at an approximately same temperature with
each other.
6. A method according to claim 4, wherein said first gas and said
second gas are supplied at an approximately same flow speed with
each other.
7. A method according to claim 4, wherein said first gas comprises
a component that forms a phosphosilicate glass film as a reaction
product after a reaction.
8. A method according to claim 4, wherein said first gas comprises
a component that forms a silicon oxide film after a reaction.
9. A method according to claim 4, wherein the substrate consists
essentially of a glass substrate or a silicon wafer and has a
surface on which said thin film is formed comprises a glass
surface.
10. An apparatus for producing thin films comprising: a furnace
core pipe; a substrate supporting boat for supporting a lot of
substrates disposed in said furnace core pipe; a first gas injector
pipe having many first blowing holes for spouting the first gas
comprising a process gas toward the substrate, the supporting boat
having a rotation mechanism for allowing the boat to rotate using a
normal line passing through the center of a principal face of the
substrate as a rotation axis; and a second gas injector pipe having
second blowing holes for spouting a second gas and being provided
at an opposite position at which the second gas collides with said
first gas on a surface of the substrate, said second gas consisting
essentially of an inert gas or nitrogen gas.
11. An apparatus according to claim 10, wherein said first gas
injector pipe is provided at an approximately symmetrical position
against the second gas injection pipe relative to the center line
of the rotation axis.
12. an apparatus according to claim 11, said first and said second
gas injector pipes making a pair of pipes as a first pair of pipes,
said apparatus further comprising another pair of pipes similar to
said first pair of pipes as a second pair of pipes, each of said
second pair of pipes being provide in a different position from
said first pair of pipes but having the same position relation
relative to the center line as said first pair of pipes.
13. An apparatus according to claim 11, wherein the first and the
second blowing holes are provided in the first and the second gas
injectors, respectively, at the positions where the first and the
second gases are blown along the direction in confronting relation
with each other.
14. An apparatus according to claim 13, wherein said first and said
second gases are simultaneously supplied with each other along the
substrate face.
15. An apparatus according to claim 14, wherein said first gas and
said second gas are approximately equal in a supplied amount to
each other.
16. An apparatus according to claim 15, further comprising gas
heating means for supplying said first and second gases,
respectively, approximately at the same temperature with each
other.
17. An apparatus according to claim 15, further comprising gas
supply control means for supplying said first and second gases,
respectively, approximately at the same flow speed with each
other.
18. An apparatus according to claim 15, wherein said first gas
contains a component that forms a phosphosilicate glass after a
reaction.
19. An apparatus according to claim 15, wherein said first gas
contains a component that forms a silicon oxide film as a reaction
product after a reaction.
20. An apparatus according to claim 15, wherein the substrate
consists essentially of a glass substrate or a silicon wafer and
has a surface on which the thin film is formed comprises a glass
surface.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method of producing thin
films and apparatus, such as, a heat treatment apparatus, for
producing the same.
[0003] 2. Description of the Related Art
[0004] A vertical type diffusion furnace has been used for forming
diffusion layer films. The conventional vertical type diffusion
furnace is provided, as main parts, with a furnace core cylinder, a
substrate supporting boat, a process gas injector pipe having a lot
of holes and disposed in the furnace core cylinder, a purge gas
supply tube and a heat insulating cylinder. A lot of substrates can
be mounted on the substrate supporting boat, which is provided with
a mechanism to make the boat to rotate together with the beat
insulating cylinder around a center axis or line of the heat
insulating cylinder as a rotation axis.
[0005] In forming a diffusion layer film on the substrate by the
use of this conventional vertical type furnace, a process gas is
supplied from many blowing holes provided at the process gas
injector pipe toward the center line of the rotation axis, so that
the gas flow is made parallel to the surface of each substrate.
[0006] The process gas is supplied on the substrate from the
process gas injector pipe and is spouted toward the center of the
substrate by being spread perpendicular to the spouting direction
of the process gas in the conventional vertical type diffusion
furnace. Since the substrate is rotated by the boat rotating
mechanism, a small amount of the process gas tends to be supplied
at the peripheral area of the substrate while a large amount of the
gas is supplied at the center of the substrate.
[0007] Accordingly, the thin film thus formed has the film
thickness, which has a tendency to have a hill-like film thickness
distribution in which the film thickness is gradually increased
from the peripheral region to the center of the substrate with
exhibiting a deficiency to become large at the center of the
substrate.
SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the present invention to
provide a method for forming thin films capable of providing a
uniform film thickness on the substrate.
[0009] It is another object of the present invention to provide an
apparatus for practicing the method for forming the thin film
described above.
[0010] According to one aspect of the present invention, there is
provided a method of producing a thin film on a substrate disposed
in a furnace core pipe, which comprises a step of making the
substrate to rotate around a center axis in accompany with allowing
a first gas to spout toward the substrate. The center axis is a
normal line passing through the center of one principal face of the
substrate. The first gas consists essentially of a process gas. In
the method of the aspect of the present invention, the thin film is
formed on the substrate while allowing a second gas to spout via
the center axis in the colliding direction to the first gas. The
second gas consists essentially of an inert gas or nitrogen
gas.
[0011] It is preferable that the second gas spouts along a
direction approximately opposite to the spout direction of the
first gas.
[0012] It is more preferable that the locations for supplying the
first gas and the second gas are approximately symmetrically
positioned with each other with respect to the center axis. The
first gas is simultaneously supplied with the second gas.
[0013] According to another aspect of the present invention, there
is provided an apparatus for producing thin films, which comprises
a furnace core pipe, a substrate supporting boat for supporting a
lot of substrates disposed in the furnace core pipe, a first gas
injector pipe having many first blowing holes for spouting the
first gas comprising a process gas toward the substrate, the
supporting boat having a rotation mechanism for allowing the boat
to rotate using a normal line passing through the center of a
principal face of the substrate as a rotation axis, and a second
gas injector pipe having second blowing holes for spouting a second
gas and being provided at an opposite position at which the second
gas collides with the first gas on a surface of the substrate. The
second gas consists essentially of an inert gas or nitrogen
gas.
[0014] It is preferable that the first gas injector pipe is
provided at an approximately symmetrical position against the
second gas injection pipe relative to the center line of the
rotation axis.
[0015] More preferably in the aspect of the present invention, the
first and the second gas injector pipes makes a pair of pipes as a
first pair of pipes. The apparatus further comprises another pair
of pipes similar to the first pair of pipes as a second pair of
pipes. Each of the second pair of pipes is provided in a different
position from the first pair of pipes but has the same position
relation relative to the center line as the first pair of
pipes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is an illustrative view showing a vertical type
diffusion furnace as a conventional apparatus for forming thin
films;
[0017] FIG. 2 is a cross sectional view taken along the line II-II
in FIG. 1;
[0018] FIG. 3 is an illustrative view showing the constitution of
an apparatus for forming thin films in the example according to the
present invention;
[0019] FIG. 4A is a cross sectional view taken along the line
IVA-IVA in FIG. 3;
[0020] FIG. 4B is a cross sectional view taken along the line
IVB-IVB in FIG. 4A;
[0021] FIG. 4C is a cross sectional view taken along the line
IVC-IVC in FIG. 4B; and
[0022] FIG. 5 is a cross sectional view taken along the line V-V in
FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] For easy comprehension of the present invention, a
conventional vertical type furnace and a method for forming a
diffusion layer using the same will be described hereinafter with
reference to FIGS. 1 and 2.
[0024] Referring to FIG. 1, the major part of the diffusion furnace
7 is provided with a core furnace pipe 9 forming an outer core. A
substrate supporting boat 11 is disposed on the center axis of the
core furnace pipe 9. A process gas injector pipe 13 has a lot of
holes and is disposed around the substrate supporting boat 11 in
the core furnace pipe 9. A purge gas supply pipe 15 is also
disposed for heating an atmosphere in the core furnace pipe and
keeping the atmosphere at a constant temperature at the periphery
of the core furnace pipe 9. A heat-insulating cylinder 17 is
disposed at the bottom of the substrate supporting boat 11. A
plurality of substrates 19 can be placed with a given space left
therebetween on the substrate supporting boat 11. A rotation
mechanism (not shown) is for allowing the substrates to rotate
around the center axis of the heat-insulating cylinder 17 together
with the heat-insulating cylinder 17 and is provided for the
substrate supporting boat 11.
[0025] The process gas injector pipe 13 penetrates into the furnace
through the bottom of the core furnace pipe 9, and is elongated to
the bottom of the furnace by making a U-turn after being elongated
to the top of the furnace along the inner wall of the core furnace
pipe 9. The process gas injector pipe 13 has many blowing holes not
shown in the figure. These blowing holes are disposed so as to
supply the process gas in parallel relation to the surface of the
substrate 19 along with supplying the process gas toward the center
line of the rotation axis. A diffusion layer film is formed on the
substrate 19 with the gas supplied form this blowing holes.
[0026] Referring to FIG. 2 corresponding to the cross section II-II
in FIG. 1, a process gas is supplied on the substrate 19 by means
of the process gas injector pipe 13. The process gas is spouted
toward the center of substrate 19 by being spread perpendicular to
the spouting direction of the process gas. Because the substrate 19
is rotating by the boat rotation mechanism, relatively a small
amount of the process gas is liable to be supplied at the periphery
of the substrate 19 while a large amount of the process gas is
supplied at the center of substrate 19. Accordingly, the film
thickness of the thin film thus formed has a tendency to have a
hill-like film thickness distribution in which the film thickness
is gradually increased from the peripheral region to the center of
the substrate 19.
[0027] By considering the problems as hitherto described, the
preferred embodiment according to the present invention will be
described hereinafter with reference to FIGS. 3 to 5. The parts
having the same names as in the examples shown in FIG. 1 and FIG. 2
are expressed by the same reference numerals in FIG. 3 to FIG.
5.
[0028] Referring to FIG. 3, a constitution of the major part of the
vertical type diffusion furnace 23 constitutes an apparatus for
forming thin films. The apparatus is provided with a furnace core
pipe 7, a substrate supporting boat 11 supporting the substrates, a
process gas injector 13, a purge gas supply pipe 15 and a
heat-insulation cylinder 17 for mounting the substrate supporting
boat 11. In the apparatus, the supporting boat has a rotation
mechanism (not shown in the figure) to make the substrates to
rotate together with the heat-insulation cylinder 17. Its rotation
axis is directed along the normal line passing through the center
of the substrate 19. These components have the same construction as
in the conventional examples.
[0029] The apparatus for forming thin films according to the
present invention differs from the conventional one in that the
former has an inert gas injector pipe 25. Referring to FIG. 4A, the
inert gas injector pipe 25 is provided at an approximately
symmetrical position against the process gas injector pipe 13
relative to the center line of the rotation axis. In the similar
manner to the process gas injector pipe 13, this inert gas injector
pipe 25 penetrates into the furnace core pipe 9 from its bottom and
makes a U-turn to be elongated to the bottom after being elongated
to the top along the inner wall of the furnace core pipe 9. These
two injector pipes 13 and 25 have the same construction with each
other. The inert injector pipe 25 and the process gas injector pipe
13 may be provided in any different position on a concentric circle
with a center as a center line, in which position the inert gas and
the process gas will collide with each other on the substrate.
[0030] As shown in FIG. 4B, the injector pipes 13 and 25 have a
plurality of gas blowing holes 27 and 29. Actually, the diameter of
the injector pipes 13 and 25, and their configurations and number
of the blowing holes 27 and 29 are identical with each other. The
blowing holes 27 and 29 are positioned so as to spout a gas onto
the surface of the substrate 19. The blowing holes 27 and 29 are so
constructed as to spout the supplied gas parallel to the surface of
the substrate 19 toward the center of the substrate 19.
[0031] The injector pipes 13 and 25 are elongated from the bottom
to the top and from the top to the bottom with a U-turn at the top.
Each of the injector pipes 13 and 15 serves as a gas heating member
in order to heat the gas supplied from these pipes 13 and 25 at the
same temperature as in the furnace core pipe 9.
[0032] In the present invention, a glass plate can be used for the
substrate 19 in place of a Si wafer. The substrate may not be
limited to these, as far as a thin film can be formed on a surface
thereof.
[0033] For forming a thin film using the apparatus for forming thin
films according to the examples of the present invention, a purge
gas, usually nitrogen gas, is supplied to the furnace core pipe 9
through the purge gas supply pipe 15 to purge the furnace core pipe
9. Then, a process gas is supplied to the substrate 19 via the
process gas injector pipe 13. An inert gas or nitrogen gas is
supplied onto the substrate 19 via the inert gas injector pipe 25
simultaneously with the process gas while allowing the substrate 19
to rotate at a rotation speed of 1 to 5 rpm by the rotation
mechanism of the substrate supporting boat 11.
[0034] The inert gas or the nitrogen gas is controlled of the flow
rate with a mass flow controller (not shown in the figure). The
mass flow controller comprises a gas supply control member which is
provided at the inlet of the gas injector pipes 13 and 25. The gas
injector pipes 13 and 25 are situated at outside of the furnace
core pipe 9.
[0035] Preferably, the inert gas or the nitrogen gas is supplied
with the same flow rate as that of the process gas at a process
temperature of 700 to 1000.degree. C. The blowing rate from the
blowing holes 27 is adjusted to 100 to 6000 cc/min. While the gas
supply rate to be controlled is practically determined by the
process temperature and by a characteristic equation, details of
the procedure is omitted herein.
[0036] Referring to FIG. 5, the inert gas injector pipe 25 has the
same configuration as the process gas injector pipe 13 is disposed
at the opposite side of the latter pipe 13 relative to the center
of the substrate 19. The process gas and the inert gas or the
nitrogen gas are supplied preferably with the same flow rate as the
flow rate of the process gas at the process temperature by the use
of the process injector pipe 13 and the inert gas injector pipe
25.
[0037] At the center of the substrate 19, the process gas is
diluted in concentration with the inert gas or the nitrogen gas by
the procedure described above. The process gas flow spreads along
the direction indicated by an arrow 31 at the circumference of the
substrate 19, which is increased by taking advantage of the
resistance caused by the inert gas or nitrogen gas flow indicated
by an arrow 33. The former function of the inert gas or the
nitrogen gas serves for reducing the film thickness at the center
of the substrate 19. The latter of the inert gas or the nitrogen
gas serves, on the other hand, for increasing the film thickness at
the circumference of the substrate 19. Uniformity of the film
thickness of the film on the substrate can be improved by these two
functions of the inert gas or nitrogen gas.
[0038] Now descriptions will be made as regards embodiments for
forming a thin film using the apparatus for forming thin films
according to the examples of the present invention.
EXAMPLES 1
[0039] In example 1, a phosphosilicate glass is formed on the
substrate 19 as a diffusion layer using the vertical type diffusion
furnace. The apparatus for forming thin films is the same
constitution as shown in FIGS. 3 and 4. The inner diameters of the
injector pipes 11 and 25 were 5 mm. The blowing holes 27 and 29
assume a circle with a diameter of 0.1 mm. The number of the
blowing holes was 100 that was the same as the plate number of the
substrate 19. The substrate supporting boat 11 is rotated at the
rotation speed of 6 rpm. Through the same numbers of the blowing
holes 27 and 29 as the plate number of the substrates were used in
this example, they should not necessarily be the same with each
other. The pressure in the furnace is always kept at one
atmosphere.
[0040] An 8-inches Si wafer was used for the substrate 19 while a
mixed gas of a phosphorous compound (POCl.sub.3), oxygen and
nitrogen was used for the process gas. The gas supplied throughout
the inert gas injector pipe 25 was nitrogen.
[0041] The gases were supplied at a process temperature during
diffusion of 850.degree. C. with a feed rate of the blowing gas at
850.degree. C. of 3000 cc/min for 40 minutes.
[0042] The result showed that a film of phosphosilicate glass
having a mean film thickness of 20 .mu.m with a good uniformity of
the film thickness was formed on the Si wafer. The film thickness
was measured at each nine points on the substrate and uniformity of
the film was judged by the proportion (%) of the difference between
the maximum and minimum film thickness to the mean film thickness.
The phosphosilicate glass obtained in Example 1 was improved in
uniformity of the thickness by 1.5% as compared with the value of
3% obtained in the conventional art in which no nitrogen gas was
supplied.
EXAMPLE 2
[0043] A Si oxide film was formed using the same apparatus in
Example 1 while an oxidative gas was used as a process gas instead
of the phosphorous compound. An 8-inches silicon (Si) wafer was
used for the substrate 19 and steam was used for the oxidative gas.
Nitrogen gas was used as a feed gas from the inert gas injector
pipe 25. The gas was supplied at a process temperature of
950.degree. C. with a gas blow rate at 950.degree. C. of 3000
cc/min for 8 minutes. The interior of the furnace was always kept
at an atmospheric pressure. Consequently, a silicon (Si) oxide film
with a good uniformity with a thickness of 20 nm was obtained.
[0044] Although the examples in which a diffusion layer film or an
oxide film was formed using the vertical type diffusion furnace as
an apparatus for forming thin films were hitherto described in
detail, the kind of the heat treatment device and films are by no
means limited to the descriptions set forth herein.
[0045] As hitherto described, the inert gas injector pipe capable
of spouting an inert gas or nitrogen gas was provided so that the
gas confronts the process gas spouted from the conventional process
gas injector in the apparatus for forming thin films according to
the present invention. By simultaneously using the two kind of
gases, it is made possible to form thin films on the substrate with
uniform film thickness.
[0046] In the preferred embodiment of the present invention, only
one pair of the inert gas injector pipe 25 and the process gas
injector pipe 13 are provided in the furnace core pipe 9. However,
a plurality of pairs of the inert gas injector pipe 25 and the
process gas injector pipe 13 can be provide in different positions
on a concentric circle in the furnace core pipe 9 as far as the
process gas can be made uniform on a surface of the substrate, such
as the si wafer.
* * * * *