U.S. patent application number 15/091421 was filed with the patent office on 2017-02-09 for manufacturing method and apparatus for manufacturing silicon carbide epitaxial wafer.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Yasuhiro KIMURA, Yoichiro MITANI, Takuma MIZOBE, Akihito OHNO, Masashi SAKAI, Nobuyuki TOMITA, Takahiro YAMAMOTO.
Application Number | 20170040166 15/091421 |
Document ID | / |
Family ID | 57853944 |
Filed Date | 2017-02-09 |
United States Patent
Application |
20170040166 |
Kind Code |
A1 |
OHNO; Akihito ; et
al. |
February 9, 2017 |
MANUFACTURING METHOD AND APPARATUS FOR MANUFACTURING SILICON
CARBIDE EPITAXIAL WAFER
Abstract
A manufacturing method for manufacturing a silicon carbide
epitaxial wafer includes: introducing a cleaning gas into a growth
furnace to remove dendrite-like polycrystal of silicon carbide
attached to an inner wall of the growth furnace; after introducing
the cleaning gas, bringing a silicon carbide substrate in the
growth furnace; and growing a silicon carbide epitaxial layer on
the silicon carbide substrate by introducing a processing gas into
the growth furnace to manufacture a silicon carbide epitaxial
wafer, wherein the cleaning gas having fluid energy of 1.6E-4 [J]
or higher is introduced into the growth furnace.
Inventors: |
OHNO; Akihito; (Tokyo,
JP) ; SAKAI; Masashi; (Tokyo, JP) ; MITANI;
Yoichiro; (Tokyo, JP) ; YAMAMOTO; Takahiro;
(Tokyo, JP) ; KIMURA; Yasuhiro; (Tokyo, JP)
; MIZOBE; Takuma; (Tokyo, JP) ; TOMITA;
Nobuyuki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
57853944 |
Appl. No.: |
15/091421 |
Filed: |
April 5, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 21/0262 20130101;
B08B 9/093 20130101; H01L 21/02378 20130101; C30B 25/00 20130101;
C23C 16/4405 20130101; C23C 16/4412 20130101; H01L 21/02529
20130101; C30B 29/36 20130101; C11D 11/0041 20130101; C23C 16/455
20130101 |
International
Class: |
H01L 21/02 20060101
H01L021/02; C23C 16/44 20060101 C23C016/44; B08B 9/093 20060101
B08B009/093; C23C 16/455 20060101 C23C016/455 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2015 |
JP |
2015-155235 |
Claims
1. A manufacturing method for manufacturing a silicon carbide
epitaxial wafer comprising: introducing a cleaning gas into a
growth furnace to remove dendrite-like polycrystal of silicon
carbide attached to an inner wall of the growth furnace; after
introducing the cleaning gas, bringing a silicon carbide substrate
in the growth furnace; and growing a silicon carbide epitaxial
layer on the silicon carbide substrate by introducing a processing
gas into the growth furnace to manufacture a silicon carbide
epitaxial wafer, wherein the cleaning gas having fluid energy of
1.6E-4 [J] or higher is introduced into the growth furnace and
wherein the cleaning gas includes only an inert gas, only hydrogen,
or only a combination of an inert gas and hydrogen.
2. (canceled)
3. A manufacturing method for manufacturing a silicon carbide
epitaxial wafer comprising: bringing a silicon carbide substrate in
a growth furnace; growing a silicon carbide epitaxial layer on the
silicon carbide substrate by introducing a processing gas into the
growth furnace to manufacture a silicon carbide epitaxial wafer,
and introducing a cleaning gas into the growth furnace to remove
dendrite-like polycrystal of silicon carbide attached to an inner
wall of the growth furnace, wherein the cleaning gas having fluid
energy of 1.6E-4 [J] or higher is introduced into the growth
furnace, and wherein the cleaning gas includes only an inert gas,
only hydrogen, or only a combination of an inert gas and
hydrogen.
4. The manufacturing method for manufacturing a silicon carbide
epitaxial wafer of claim 3, wherein a shutter is disposed on the
silicon carbide epitaxial wafer when the cleaning gas is introduced
into the growth furnace.
5. (canceled)
6. A manufacturing apparatus for manufacturing a silicon carbide
epitaxial wafer comprising: a growth furnace in which epitaxial
growth is performed; a wafer holder provided in the growth furnace
and on which a silicon carbide substrate is mounted; a processing
gas introduction port introducing a processing gas into the growth
furnace; a processing gas exhaust port discharging the processing
gas from the growth furnace; a cleaning gas introduction port
introducing, into the growth furnace, a cleaning gas for removing
dendrite-like polycrystal of silicon carbide attached to an inner
wall surface of the growth furnace; and a cleaning gas exhaust port
discharging the cleaning gas from the growth furnace, wherein the
cleaning gas having fluid energy of 1.6E-4 [J] or higher is
introduced into the growth furnace through the cleaning gas
introduction port, and wherein the cleaning gas includes only an
inert gas, only hydrogen, or only a combination of an inert gas and
hydrogen.
7. The manufacturing apparatus for manufacturing a silicon carbide
epitaxial wafer of claim 6, wherein a mount surface of the wafer
holder is opposed to a ceiling surface of the growth furnace, and
the cleaning gas introduction port is provided in a side of the
growth furnace at a position higher than the wafer holder such that
the cleaning gas flows along the ceiling surface of the growth
furnace.
8. The manufacturing apparatus for manufacturing a silicon carbide
epitaxial wafer of claim 6, wherein the cleaning gas exhaust port
is provided in a bottom surface of the growth furnace.
9. The manufacturing apparatus for manufacturing a silicon carbide
epitaxial wafer of claim 6, further comprising a shutter disposed
on the silicon carbide epitaxial wafer when the cleaning gas is
introduced into the growth furnace.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a manufacturing method and
apparatus for manufacturing a silicon carbide epitaxial wafer.
Background Art
[0002] In recent years, a silicon carbide (hereinafter referred to
as SiC) semiconductor has attracted attention mainly as a material
for power devices for power control because its bandgap, dielectric
breakdown electric field intensity, saturated drift speed and
thermal conductivity are higher than those of silicon
semiconductors. In fact, a power device using the SiC semiconductor
is capable of largely reducing power loss, being reduced in size
and realizing energy saving at the time of power supply power
conversion and can therefore be a key device for, for example,
improving the performance of electric vehicles and improving the
functions of solar battery systems or the like in realization of a
low-carbon society.
[0003] In making a SiC power device, a layer to be provided as an
active region of the semiconductor device is generally grown
epitaxially on a SiC bulk monocrystal substrate by thermal chemical
vapor deposition (thermal CVD) or the like. The term "active
region" refers here to a region which is built by precisely
controlling doping concentration in a crystal and its film
thickness, and which has a section containing a growth direction
axis. The reason why such an epitaxially grown layer is required as
well as a bulk monocrystal substrate is that a doping concentration
and a film thickness are generally prescribed in accordance with
the specifications of a device and there is a demand for obtaining
the doping concentration and the film thickness with accuracies
higher than those attained for bulk monocrystal substrates in
ordinary cases.
[0004] A wafer having an epitaxially grown layer formed on a SiC
bulk monocrystal substrate will hereinafter be referred to as
"epitaxial wafer". A silicon carbide semiconductor device is
fabricated by performing various kinds of processing on a silicon
carbide epitaxial wafer. If the silicon carbide epitaxial wafer has
defects, the silicon carbide semiconductor device locally fails to
hold a high voltage, resulting in generation of a leak current. If
the density of such defects is increased, the nondefective rate in
manufacturing of the silicon carbide semiconductor device is
reduced.
[0005] When the silicon carbide epitaxial wafer is manufactured,
silicon carbide is attached not only to the wafer but also to inner
walls of a growth furnace and to surfaces of a wafer holder on
which the wafer is mounted. The attached silicon carbide is
structurally brittle and can therefore form silicon carbide
particles easily. If silicon carbide particles are attached to the
wafer surface, crystal defects such as downfalls and triangular
defects are generated starting from the attachment points.
[0006] As a method for reducing silicon carbide particles which can
be a cause of such crystal defects, a method of cleaning the wafer
holder by etching silicon carbide particles attached to the wafer
holder with chlorine trifluoride has been proposed (see, for
example, Japanese Patent No. 5542560). A method of removing silicon
carbide particles by using a cleaning gas containing iodine
heptafluoride without etching and damaging graphite which is the
basic material of a certain member has also been proposed (see, for
example, Japanese Patent Laid-Open No. 2014-154865).
[0007] In the case of the method disclosed in Japanese Patent No.
5542560, not only the attached silicon carbide but also the silicon
carbide film formed as protective film on internal members of the
growth furnace and the wafer holder is etched and it is, therefore,
difficult to perform cleaning management. Also, special expelling
equipment is required to enable use of chlorine trifluoride, for
example, because it corrodes the apparatus and piping. The method
thus entails problems in terms of operation and cost. Further,
because the rate of etching of silicon carbide is lower than that
of etching of silicon, a long time is taken to complete cleaning
and it is difficult to completely remove silicon carbide.
[0008] In the case of the method disclosed in Japanese Patent
Laid-Open No. 2014-154865, iodine heptafluoride, which does not
etch graphite, is used but the silicon carbide film formed as
protective film on the wafer holder and internal members of the
growth furnace are thereby etched, as in the case of the method
disclosed in Japanese Patent No. 5542560, and it is difficult to
perform cleaning management. Thus, use of a fluorine-based gas as
cleaning gas entails the problem of members other than the attached
silicon carbide being etched.
SUMMARY OF THE INVENTION
[0009] In view of the above-described problem, an object of the
present invention is to provide a manufacturing method and
apparatus for manufacturing a silicon carbide epitaxial wafer with
reduced crystal defects while avoiding damaging internal members of
the growth furnace and the wafer holder.
[0010] According to the present invention, a manufacturing method
for manufacturing a silicon carbide epitaxial wafer includes:
introducing a cleaning gas into a growth furnace to remove silicon
carbide in polycrystalline form of dendrite-like structure attached
to an inner wall of the growth furnace; after introducing the
cleaning gas, bringing a silicon carbide substrate in the growth
furnace; and growing a silicon carbide epitaxial layer on the
silicon carbide substrate by introducing a processing gas into the
growth furnace to manufacture a silicon carbide epitaxial wafer,
wherein the cleaning gas having fluid energy of 1.6E-4 [J] or
higher is introduced into the growth furnace.
[0011] In the present invention, a cleaning gas having fluid energy
of 1.6E-4 [J] or higher is introduced into the growth furnace.
Therefore, the silicon carbide epitaxial wafer with reduced crystal
defects can be manufactured without damaging the internal members
of the growth furnace and the wafer holder.
[0012] Other and further objects, features and advantages of the
invention will appear more fully from the following
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a sectional view of an apparatus for manufacturing
a silicon carbide epitaxial wafer according to a first embodiment
of the present invention.
[0014] FIG. 2 is a flowchart showing a process of manufacturing the
silicon carbide epitaxial wafer according to the first embodiment
of the present invention.
[0015] FIG. 3 is a diagram showing the relationship between the
fluid energy of the cleaning gas in the growth furnace and a
relative value of the number of particles remaining in the growth
furnace.
[0016] FIG. 4 is a flowchart showing a silicon carbide epitaxial
wafer manufacturing process according to a second embodiment of the
present invention.
[0017] FIG. 5 is a sectional view of a modified example of the
silicon carbide epitaxial wafer manufacturing apparatus according
to the second embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] A manufacturing method and apparatus for manufacturing a
silicon carbide epitaxial wafer according to the embodiments of the
present invention will be described with reference to the drawings.
The same components will be denoted by the same symbols, and the
repeated description thereof may be omitted.
First Embodiment
[0019] FIG. 1 is a sectional view of an apparatus for manufacturing
a silicon carbide epitaxial wafer according to a first embodiment
of the present invention. A wafer holder 3 on which a silicon
carbide substrate 2 is mounted is provided in a growth furnace 1
(epitaxial growth furnace) in which epitaxial growth is performed.
A processing gas introduction port 4 introduces a processing gas
including a carrier gas and a raw-material gas into the growth
furnace 1 in an epitaxial growth step. A processing gas exhaust
port 5 discharges from the growth furnace 1 the processing gas
introduced through the processing gas introduction port 4.
[0020] A cleaning gas introduction port 6 introduces, into the
growth furnace 1, in a cleaning step, a cleaning gas for removing
silicon carbide in polycrystalline form of dendrite-like structure
attached to inner wall surfaces of the growth furnace 1. Gas
exhaust ports 7 discharge from the growth furnace 1 the cleaning
gas introduced through the cleaning gas introduction port 6. A gas
introduction condition control unit 8 controls a gas flow rate
controller and a pressure controller connected to the processing
gas introduction port 4 and the cleaning gas introduction port 6,
thereby controlling conditions for introduction of the processing
gas and the cleaning gas (the gas flow rate and pressure) in the
cleaning step or the epitaxial step. The cleaning gas introduction
port 6 is connected to a cleaning gas bomb (not shown) through the
gas introduction condition control unit 8.
[0021] FIG. 2 is a flowchart showing a process of manufacturing the
silicon carbide epitaxial wafer according to the first embodiment
of the present invention. The silicon carbide epitaxial wafer
manufacturing process will be described below with reference to
FIGS. 1 and 2.
[0022] First, in a state where the wafer holder 3 is set in the
growth furnace 1, the cleaning gas is introduced into the growth
furnace 1, thereby removing silicon carbide in polycrystalline form
of dendrite-like structure attached to the inner wall of the growth
furnace 1 and the wafer holder 3 (step S1). This step is called a
cleaning step. In a case where cleaning of the wafer holder 3 is
unnecessary, the wafer holder 3 may be placed out of the growth
furnace 1 at this stage. Conditions for introduction of the
cleaning gas in the cleaning step are described below.
[0023] Next, the silicon carbide substrate 2 is brought in the
growth furnace 1 by being mounted on the wafer holder 3 (step S2).
Subsequently, a silicon carbide epitaxial layer 9 is grown on the
silicon carbide substrate 2 by introducing the processing gas into
the growth furnace 1, thereby manufacturing a silicon carbide
epitaxial wafer 10 (step S3). The completed silicon carbide
epitaxial wafer 10 is thereafter taken out of the growth furnace 1
(step S4). The silicon carbide epitaxial wafer 10 is manufactured
by the above-described steps.
[0024] The significance of the cleaning step will now be described.
While the silicon carbide epitaxial layer 9 is grown on the silicon
carbide substrate 2 in the epitaxial growth step, silicon carbide
is simultaneously attached to the inner wall surfaces of the growth
furnace 1 and the wafer holder 3 and grown in polycrystalline form
of dendrite-like structure. Structurally weak thin portions of the
silicon carbide in polycrystalline form are cut and separated due
to fluctuation of the gas flow at the time of introduction of the
processing gas, thereby generating silicon carbide particles. If
the silicon carbide particles are not removed (by cleaning), the
silicon carbide particles are scattered in the growth furnace 1 to
be attached to the epitaxial growth surface of the silicon carbide
epitaxial wafer 10 in the subsequent epitaxial growth step due to
fluctuation of the flow of the introduced gas. The attachment of
silicon carbide particles entails generation of crystal defects.
The cleaning step (step S1) is a step for avoiding such an
event.
[0025] Conditions for introduction of the cleaning gas in the
cleaning step will subsequently be described. Fluid energy of the
gas will first be described. Fluid energy represents the total
amount of energy of the gas in the cleaning step. If the total mass
of the gas caused to flow in the cleaning step is m [kg] and the
velocity of flow of the gas in this situation is v [m/s], the fluid
energy E is defined by the following expression 1.
E = 1 2 mv 2 [ J ] [ Expression 1 ] ##EQU00001##
[0026] The total mass m of the gas is determined by the kind of the
gas and the total rate of flow of the gas, and the flow velocity v
is calculated from the gas flow rate, the sectional area of the
growth furnace 1 and the pressure in the growth furnace 1.
[0027] FIG. 3 is a diagram showing the relationship between the
fluid energy of the cleaning gas in the growth furnace and a
relative value of the number of particles remaining in the growth
furnace. After the cleaning gas controlled at a certain level of
fluid energy is introduced into the growth furnace 1, a silicon
wafer, for example, is brought in the growth furnace 1, and argon
gas, for example, is introduced. The silicon wafer is thereafter
taken out. Particles deposited on the silicon wafer taken out are
counted with a particle counter to obtain the "number of remaining
particles". The ordinate of FIG. 3 represents a relative number of
remaining particles assuming that the number of particles remains
when the fluid energy is 8.0E-5 [J] is unity. Referring to FIG. 3,
the relative value of the number of particles is abruptly reduced
to 0.08 or less when the fluid energy is 1.6E-4 [J]. This shows
that silicon carbide attached to the inner wall surfaces of the
growth furnace 1 and the wafer holder 3 can be removed by fluid
energy of 1.6E-4 [J] or higher. When the fluid energy is 8.1E-4
[J], the relative value of the number of particles can be further
reduced to 0.015 or less. Further, when the fluid energy is 2.0E-2
[J], the relative value of the number of particles can be reduced
to 0.005 or less. No particular upper limit value of fluid energy
is specified here. If the fluid energy is higher than 1.0[E]-1 [J]
in the case of an ordinary growth furnace, however, the cleaning
step time is considerably long and there is a possibility of a
reduction in productivity. It is, therefore, preferable that the
fluid energy be equal to or higher than 1.0E-1 [J].
[0028] In the present embodiment, therefore, a cleaning gas having
fluid energy of 1.6E-4 [J] or higher with respect to the total
amount of gas in the cleaning step (step S1) is introduced into the
growth furnace 1 in the cleaning step. At this time, the gas
introduction condition control unit 8 controls the fluid energy of
the cleaning gas at 1.6E-4 [J] or higher. By performing this
cleaning step, silicon carbide in in polycrystalline form of
dendrite-like structure attached to the inner wall surfaces of the
growth furnace 1 and the wafer holder 3 can be removed before the
epitaxial step. Therefore, substantially no silicon carbide
particles are generated at the time of introduction of the
processing gas in the epitaxial growth step. The silicon carbide
epitaxial wafer 10 in which crystal defects due to silicon carbide
particles are largely reduced can thus be formed.
[0029] The cleaning gas is an inert gas such as argon gas or
nitrogen gas, or hydrogen gas. Since the cleaning gas is not an
etching gas which etches silicon carbide, there is no apprehension
of etching of the silicon carbide film formed as a protective film
on the internal members of the growth furnace 1 and the wafer
holder 3 in the cleaning step, and the facility with which the
process is managed is improved. The present embodiment thus
demonstrates that the silicon carbide epitaxial wafer 10 with
reduced crystal defects can be manufactured without damaging the
internal members of the growth furnace 1 and the wafer holder 3.
Further, a silicon carbide device having reduced crystal defects,
low-priced and producible at a high yield rate can be made by using
the silicon carbide epitaxial wafer 10.
[0030] The mount surface of the wafer holder 3 is opposed to the
ceiling surface of the growth furnace 1. Silicon carbide attached
to the ceiling surface (upper surface) of the growth furnace 1 in
such a position as to be opposed to the epitaxial growth surface of
the silicon carbide epitaxial wafer 10 can easily become a cause of
the crystal defects in comparison with silicon carbide attached to
other portions of the growth furnace 1. Also, the amount of silicon
carbide attached to the ceiling surface of the growth furnace 1 is
larger than the amount of silicon carbide attached to the other
portions of the growth furnace 1. There is, therefore, a need to
perform cleaning particularly effectively on the ceiling surface.
The cleaning gas exhaust port 6 is therefore provided in the side
of the growth furnace 1 at a position higher than that of the wafer
holder 3 such that the cleaning gas flows along the ceiling surface
of the growth furnace 1. As a result, silicon carbide attached to
the ceiling surface opposed to the epitaxial growth surface of the
silicon carbide epitaxial wafer 10 can be efficiently removed in a
short time. The cleaning gas exhaust ports 7 are gas exhaust ports
for the cleaning gas only, provided for the purpose of collecting
silicon carbide particles in the cleaning step. The processing gas
for epitaxial growth flows in a horizontal direction (a left-right
direction along the plane of FIG. 1) in the growth furnace 1. The
processing gas exhaust port 5 is therefore provided opposite from
the processing gas introduction port 4. In this case, silicon
carbide particles not having reached the processing gas exhaust
port 5 stay on the bottom surface of the growth furnace 1 instead
of being collected. The silicon carbide particles staying on the
bottom surface of the growth furnace 1 is flung up at the time of
introduction of the processing gas for epitaxial growth and
attached to the epitaxial growth surface of the silicon carbide
epitaxial wafer 10 to become a cause of crystal defects. The
cleaning gas exhaust ports 7 are therefore provided in the bottom
surface of the growth furnace 1. With this arrangement, silicon
carbide particles that have not reached the processing gas exhaust
port 5 and stay on the bottom surface of the growth furnace 1 can
be efficiently collected. As a result, silicon carbide particles
are not flung up at the time of introduction of the processing gas
for epitaxial growth, thus enabling reducing crystal defects. The
cleaning gas exhaust ports 7 can be used simultaneously with the
processing gas exhaust port 5, and components including a vacuum
pump and a pressure regulation valve can also be used at the time
of exhaust through the cleaning gas exhaust ports 7.
Second Embodiment
[0031] FIG. 4 is a flowchart showing a silicon carbide epitaxial
wafer manufacturing process according to a second embodiment of the
present invention. The same manufacturing apparatus as that in the
first embodiment is used for the manufacturing process in the
second embodiment.
[0032] First, a cleaning step (step S1), a silicon carbide
substrate 2 transport step (step S2) and an epitaxial growth step
(step S3) are carried out, as those in the first embodiment,
thereby forming the silicon carbide epitaxial wafer 10. These steps
are the same as those in the first embodiment and detailed
descriptions of them will not be repeated. After silicon carbide in
polycrystalline form of dendrite-like structure attached to the
inner wall surfaces of the growth furnace 1 and the wafer holder 3
is removed in the cleaning step (step S1), the epitaxial growth
step (step S3) is executed. Therefore, substantially no silicon
carbide particles are generated in the epitaxial growth step. The
silicon carbide epitaxial wafer 10 in which crystal defects due to
silicon carbide particles are largely reduced can thus be
formed.
[0033] Next, the cleaning step is executed without taking out the
completed silicon carbide epitaxial wafer 10 (step S5). The
completed silicon carbide epitaxial wafer 10 is thereafter taken
out from the growth furnace 1 (step S4). In the cleaning step (step
S5), not an etching gas which etches silicon carbide but a cleaning
gas having fluid energy of 1.6E-4 [J] or higher is introduced into
the growth furnace 1, as in the cleaning step (step S1) in the
first embodiment.
[0034] In the first embodiment, the cleaning step is executed after
the completed silicon carbide epitaxial wafer 10 is taken out from
the growth furnace 1. In the present embodiment, the cleaning step
is executed while the silicon carbide epitaxial wafer 10 is left in
the state of being set on the growth furnace 1. There is a
possibility of silicon carbide particles being attached to the
silicon carbide epitaxial wafer 10 in this case. However, since
this particle attachment occurs after the completion of the
epitaxial growth, the attachment silicon carbide particles cannot
be a cause of crystal defects. As a result, the silicon carbide
epitaxial wafer 10 with reduced crystal defects can be manufactured
without damaging the internal members of the growth furnace 1 and
the wafer holder 3.
[0035] FIG. 5 is a sectional view of a modified example of the
silicon carbide epitaxial wafer manufacturing apparatus according
to the second embodiment of the present invention. In a case where
the cleaning step is executed while the silicon carbide epitaxial
wafer 10 is left in the state of being set on the growth furnace 1,
a manufacturing apparatus having a shutter 11 on the silicon
carbide substrate 2 as shown in FIG. 5 may be used. The shutter 11
does not cover the silicon carbide substrate 2 in the epitaxial
step (step S3). The shutter 11 is disposed on the silicon carbide
epitaxial wafer 10 only in the cleaning step (step S5) in which the
cleaning gas is introduced into the growth furnace 1, thus enabling
prevention of attachment of silicon carbide particles on the
silicon carbide epitaxial wafer 10.
[0036] A cyclic purge to replace the growth gas in the growth
furnace 1 with an inert gas is typically performed before the
silicon carbide epitaxial wafer 10 having undergone the epitaxial
process is taken out. The cleaning step (step S5) and a cyclic
purge may therefore be combined. The influence of the cleaning step
on the manufacturing tact can be reduced thereby.
[0037] In the descriptions of the first and second embodiments,
applicable forms of the present invention are illustrated. The
present invention is not limited to the described forms.
Modifications and omissions can be made to the embodiments in the
scope of the present invention as desired, and the embodiments can
be freely combined. For example, the process can be changed as
indicated by a broken-line arrow in FIG. 4.
[0038] Obviously many modifications and variations of the present
invention are possible in the light of the above teachings. It is
therefore to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
[0039] The entire disclosure of Japanese Patent Application No.
2015-155235, filed on Aug. 5, 2015 including specification, claims,
drawings and summary, on which the Convention priority of the
present application is based, is incorporated herein by reference
in its entirety.
* * * * *