U.S. patent application number 13/189776 was filed with the patent office on 2012-02-16 for cubic silicon carbide film manufacturing method, and cubic silicon carbide film-attached substrate manufacturing method.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Yukimune WATANABE.
Application Number | 20120037067 13/189776 |
Document ID | / |
Family ID | 45563841 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120037067 |
Kind Code |
A1 |
WATANABE; Yukimune |
February 16, 2012 |
CUBIC SILICON CARBIDE FILM MANUFACTURING METHOD, AND CUBIC SILICON
CARBIDE FILM-ATTACHED SUBSTRATE MANUFACTURING METHOD
Abstract
A method for manufacturing a cubic silicon carbide film
includes: a first step of introducing a carbon-containing gas onto
a silicon substrate and rapidly heating the silicon substrate to an
epitaxial growth temperature of cubic silicon carbide so as to
carbonize a surface of the silicon substrate and form a cubic
silicon carbide film; and a second step of introducing a
carbon-containing gas and a silicon-containing gas onto the cubic
silicon carbide film while maintaining the cubic silicon carbide
film at the epitaxial growth temperature of cubic silicon carbide,
so as to allow further epitaxial growth of the cubic silicon
carbide film.
Inventors: |
WATANABE; Yukimune;
(Hokuto-shi, JP) |
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
45563841 |
Appl. No.: |
13/189776 |
Filed: |
July 25, 2011 |
Current U.S.
Class: |
117/89 |
Current CPC
Class: |
C30B 25/14 20130101;
C30B 25/186 20130101; C30B 25/18 20130101; C30B 25/10 20130101;
C30B 29/36 20130101 |
Class at
Publication: |
117/89 |
International
Class: |
C30B 25/16 20060101
C30B025/16; C30B 25/18 20060101 C30B025/18; C30B 25/02 20060101
C30B025/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2010 |
JP |
2010-181206 |
Claims
1. A method of manufacturing a cubic silicon carbide film,
comprising: introducing a first gas that contains carbon onto a
silicon substrate or onto a monocrystalline silicon film disposed
on the substrate, forming a first cubic silicon carbide film by
heating the silicon substrate or the monocrystalline silicon film
to an epitaxial growth temperature of cubic silicon carbide so as
to carbonize a surface of the silicon substrate or the
monocrystalline silicon film; and forming a second cubic carbide
film by introducing the first gas that contains carbon and a second
gas that contains silicon onto the first cubic silicon carbide film
while maintaining the first cubic silicon carbide film at the
epitaxial growth temperature of cubic silicon carbide so as to
perform further epitaxial growth of cubic silicon carbide film.
2. The method according to claim 1, further comprising: forming a
monocrystalline silicon film on the second cubic silicon carbide
film by introducing the second gas that contains silicon onto the
second cubic silicon carbide film, a temperature of the second
cubic silicon carbide film being set to the epitaxial growth
temperature of monocrystalline silicon; after the forming the
monocrystalline silicon on the second cubic silicon carbide film,
introducing the first gas that contains the carbon; forming a third
cubic silicon carbide film by heating the monocrystalline silicon
film to an epitaxial growth temperature of cubic silicon carbide so
as to carbonize a surface of the monocrystalline silicon film; and
forming a fourth cubic carbide film by introducing the first gas
that contains the carbon and the second gas that contains silicon
onto the third cubic silicon carbide film while maintaining the
third cubic silicon carbide film at the epitaxial growth
temperature of cubic silicon carbide so as to perform further
epitaxial growth of the cubic silicon carbide film.
3. The method according to claim 1, a rate of temperature rising of
the heating being in a range of 5.degree. C./sec to 200.degree.
C./sec.
4. The method according to claim 1, switching of the first gas and
the second gas being performed by controlling a flow rate of the
first gas and a flow rate of the second gas.
5. The method according to claim 1, the first gas containing
hydrocarbon.
6. The method according to claim 1, the second gas containing
silane.
7. A method of manufacturing a substrate including cubic silicon
carbide film the method comprising: introducing a first gas that
contains carbon onto a silicon substrate or onto a monocrystalline
silicon film disposed on the substrate, forming a first cubic
silicon carbide film by heating the silicon substrate or the
monocrystalline silicon film to an epitaxial growth temperature of
cubic silicon carbide so as to carbonize a surface of the silicon
substrate or the monocrystalline silicon film; and forming a second
cubic carbide film by introducing the first gas that contains
carbon and the second gas that contains silicon onto the first
cubic silicon carbide film while maintaining the first cubic
silicon carbide film at the epitaxial growth temperature of cubic
silicon carbide so as to perform further epitaxial growth of cubic
silicon carbide film.
8. The method according to claim 7, further comprising: forming a
monocrystalline silicon film on the second cubic silicon carbide
film by introducing a second gas that contains silicon onto the
second cubic silicon carbide film, a temperature of the second
cubic silicon carbide film being set to the epitaxial growth
temperature of monocrystalline silicon; after the forming the
monocrystalline silicon on the second cubic silicon carbide film,
introducing the first gas that contains the carbon; forming a third
cubic silicon carbide film by heating the monocrystalline silicon
film to an epitaxial growth temperature of cubic silicon carbide so
as to carbonize a surface of the monocrystalline silicon film; and
forming a fourth cubic carbide film by introducing the first gas
that contains the carbon and the second gas that contains the
silicon onto the third cubic silicon carbide film while maintaining
the third cubic silicon carbide film at the epitaxial growth
temperature of cubic silicon carbide so as to perform further
epitaxial growth of the cubic silicon carbide film.
Description
[0001] The entire disclosure of Japanese Patent Application No.
2010-181206, filed Aug. 13, 2010 is expressly incorporated by
reference herein.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to cubic silicon carbide film
manufacturing methods, and cubic silicon carbide film-attached
substrate manufacturing methods. Specifically, the invention
relates to a cubic silicon carbide film manufacturing method that
forms a cubic silicon carbide (SiC) film, an expected wide bandgap
semiconductor, on a silicon substrate or on a monocrystalline
silicon film formed on the substrate, and to a method for
manufacturing a cubic silicon carbide film-attached substrate that
includes a cubic silicon carbide film formed on a silicon substrate
or on a monocrystalline silicon film formed on the substrate.
[0004] 2. Related Art
[0005] Silicon carbide (SiC), a wide bandgap semiconductor having a
bandgap of 2.2 eV (300 K) more than twice as large as that of
silicon (Si), has generated interest as semiconductor material for
power devices, or as material for high-voltage devices.
[0006] The crystal forming temperature of silicon carbide (SiC) is
higher than that of silicon (Si), and obtaining silicon carbide
(SiC) single crystal ingots by a pull method from a liquid phase is
not as easy as in silicon. An alternative method, called a
sublimation method, is thus used to form silicon carbide (SiC)
single crystal ingots. However, it is difficult with the
sublimation method to obtain large-diameter silicon carbide (SiC)
single crystal ingots that have few crystal defects. This has
limited the diameter of the currently available silicon carbide
(SiC) substrates in the market to 3 to 4 inches, and has made the
price of these products very expensive.
[0007] Cubic silicon carbide (3C--SiC), a variation of silicon
carbide (SiC), has relatively low crystal forming temperature, and
can be epitaxially grown (heteroepitaxy growth) on inexpensive
silicon substrates. The heteroepitaxial technique has thus been
studied as one way of increasing the diameter of silicon carbide
(SiC) substrates.
[0008] The cubic silicon carbide has a lattice constant of 4.359
angstroms, about 20% smaller than the lattice constant (5.4307
angstroms) of monocrystalline silicon. This, combined with
different coefficients of thermal expansion, makes it very
difficult to obtain a high-quality epitaxial film that has few
crystal defects.
[0009] Further, because the monocrystalline silicon and the cubic
silicon carbide have different coefficients of thermal expansion,
bending of the silicon substrate generates stress while the
substrate is cooled to room temperature after the epitaxial growth
of the cubic silicon carbide film. The stress translates into
crystal defects in the cubic silicon carbide film. The adverse
effect of such stress can be effectively avoided by lowering the
epitaxial growth temperature.
[0010] Generally, epitaxial growth involves growth in a gas phase
(CVD method). In the CVD method, the growth temperature can be
lowered, for example, by (1) allowing growth under a high vacuum,
or (2) by using a source gas that easily decomposes at low
temperatures, or a source gas that has Si--C bonds. A drawback of
lowering growth temperature is that it slows the growth rate.
[0011] As a countermeasure, a method has been proposed in which
silicon source gas and carbon source gas are alternately flowed to
enable formation of a cubic silicon carbide (3C--SiC) epitaxial
film with few crystal defects at a practical growth rate (see
JP-A-2001-335935).
[0012] While the method of the foregoing publication enables
formation of an epitaxial film with few crystal defects with the
alternately flowed silicon source gas and carbon source gas, the
epitaxial growth temperature of the cubic silicon carbide (3C--SiC)
remains at 1,200.degree. C. to 1,300.degree. C., a temperature
range no different from the epitaxial growth temperatures of common
cubic silicon carbides (3C--SiC). Thus, the different coefficients
of thermal expansion cause stress while cooling the substrate, and
the stress translates into crystal defects. It has thus been
difficult to reduce the crystal defects of the cubic silicon
carbide film.
SUMMARY
[0013] An advantage of some aspects of the invention is to provide
a cubic silicon carbide film manufacturing method with which a
high-quality cubic silicon carbide film with few crystal defects
can be grown at high speed, and a cubic silicon carbide
film-attached substrate manufacturing method with which a
high-quality cubic silicon carbide film with few crystal defects
can be grown at high speed on a silicon substrate, or on a
monocrystalline silicon film formed on the substrate.
[0014] An aspect of the invention is directed to a method for
manufacturing a cubic silicon carbide film, the method including: a
first step of introducing a carbon-containing gas onto a silicon
substrate or onto a monocrystalline silicon film formed on the
substrate, and rapidly heating the silicon substrate or the
monocrystalline silicon film to an epitaxial growth temperature of
cubic silicon carbide so as to carbonize a surface of the silicon
substrate or the monocrystalline silicon film and form a cubic
silicon carbide film; and a second step of introducing a
carbon-containing gas and a silicon-containing gas onto the cubic
silicon carbide film while maintaining the cubic silicon carbide
film at the epitaxial growth temperature of cubic silicon carbide,
so as to allow further epitaxial growth of the cubic silicon
carbide film.
[0015] According to the cubic silicon carbide film manufacturing
method of the aspect of the invention, a carbon-containing gas is
introduced onto the silicon substrate or the monocrystalline
silicon film, and the silicon substrate surface or the
monocrystalline silicon film is rapidly heated to the epitaxial
growth temperature of cubic silicon carbide to carbonize the
silicon substrate surface or the monocrystalline silicon film with
the carbon-containing gas and form a cubic silicon carbide
film.
[0016] Further, a carbon-containing gas and a silicon-containing
gas are introduced onto the cubic silicon carbide film while
maintaining the cubic silicon carbide film at the epitaxial growth
temperature of the cubic silicon carbide, so as to allow further
epitaxial growth of the cubic silicon carbide film.
[0017] In this way, a high-quality cubic silicon carbide film with
few crystal defects can be formed more quickly than when the cubic
silicon carbide film is epitaxially grown at a constant
temperature.
[0018] A high-quality cubic silicon carbide film with few crystal
defects can thus be obtained at high speed.
[0019] The cubic silicon carbide film manufacturing method
according to the aspect of the invention may further include a
third step of forming a monocrystalline silicon film on the cubic
silicon carbide film by introducing a silicon-containing gas onto
the cubic silicon carbide film epitaxially grown in the second
step, with the cubic silicon carbide film being set to an epitaxial
growth temperature of monocrystalline silicon, wherein the first
step and the second step are sequentially performed after the third
step.
[0020] In the cubic silicon carbide film manufacturing method of
this configuration, the third step is performed that forms a
monocrystalline silicon film on the cubic silicon carbide film by
introducing a silicon-containing gas onto the cubic silicon carbide
film epitaxially grown in the second step, with the cubic silicon
carbide film being set to an epitaxial growth temperature of
monocrystalline silicon, and the first and second steps are
sequentially performed after the third step. Thus, the cubic
silicon carbide film can be obtained in a desired thickness as a
laminate of epitaxially grown cubic silicon carbide layers. In this
way, a high-quality cubic silicon carbide film of a desired
thickness with few crystal defects can easily be obtained at high
speed.
[0021] In the cubic silicon carbide film manufacturing method
according to the aspect of the invention, the rapid heating may be
performed at a rate of temperature increase of from 5.degree.
C./sec to 200.degree. C./sec.
[0022] With the rapid heating being performed a rate of temperature
increase of from 5.degree. C./sec to 200.degree. C./sec, in the
cubic silicon carbide film manufacturing method according to the
aspect of the invention, a high-quality cubic silicon carbide film
with few crystal defects can be obtained at even higher speed.
[0023] In the cubic silicon carbide film manufacturing method
according to the aspect of the invention, the carbon-containing gas
and the silicon-containing gas may be switched by controlling a
flow rate of the carbon-containing gas and a flow rate of the
silicon-containing gas.
[0024] In the cubic silicon carbide film manufacturing method of
this configuration, switching between the carbon-containing gas and
the silicon-containing gas can be easily and conveniently performed
by controlling the flow rate of the carbon-containing gas and the
flow rate of the silicon-containing gas.
[0025] In the cubic silicon carbide film manufacturing method
according to the aspect of the invention, the carbon-containing gas
may contain hydrocarbon gas.
[0026] In the cubic silicon carbide film manufacturing method of
this configuration, the carbon atoms contained in the
carbon-containing gas bind to the silicon atoms in the
monocrystalline silicon film to generate a cubic silicon carbide
film. In this way, a cubic silicon carbide film can easily be
formed on the surface of the silicon substrate.
[0027] In the cubic silicon carbide film manufacturing method
according to the aspect of the invention, the silicon-containing
gas may contain silane gas.
[0028] In the cubic silicon carbide film manufacturing method of
this configuration, the silicon atoms generated by the
decomposition of the silicon-containing gas form a monocrystalline
silicon film on the silicon substrate or the monocrystalline
silicon film. In this way, the monocrystalline silicon film can
easily be formed.
[0029] Another aspect of the invention is directed to a method for
manufacturing a cubic silicon carbide film-attached substrate that
includes a cubic silicon carbide film formed on a silicon substrate
or on a monocrystalline silicon film formed on the substrate, the
method including: a first step of introducing a carbon-containing
gas onto the silicon substrate or the monocrystalline silicon film,
and rapidly heating the silicon substrate or the monocrystalline
silicon film to an epitaxial growth temperature of cubic silicon
carbide so as to carbonize a surface of the silicon substrate or
the monocrystalline silicon film and form the cubic silicon carbide
film; a second step of introducing a carbon-containing gas and a
silicon-containing gas onto the cubic silicon carbide film while
maintaining the cubic silicon carbide film at the epitaxial growth
temperature of cubic silicon carbide, so as to allow further
epitaxial growth of the cubic silicon carbide film.
[0030] According to the cubic silicon carbide film-attached
substrate manufacturing method of the aspect of the invention, a
carbon-containing gas is introduced onto the silicon substrate or
the monocrystalline silicon film, and the silicon substrate surface
or the monocrystalline silicon film is rapidly heated to the
epitaxial growth temperature of cubic silicon carbide to carbonize
the silicon substrate surface or the monocrystalline silicon film
with the carbon-containing gas and form a cubic silicon carbide
film.
[0031] Further, a carbon-containing gas and a silicon-containing
gas are introduced onto the cubic silicon carbide film while
maintaining the cubic silicon carbide film at the epitaxial growth
temperature of cubic silicon carbide, so as to allow further
epitaxial growth of the cubic silicon carbide film.
[0032] In this way, a high-quality cubic silicon carbide film with
few crystal defects can be formed more quickly than when the cubic
silicon carbide film is epitaxially grown at a constant
temperature.
[0033] A substrate including such a high-quality cubic silicon
carbide film with few crystal defects can thus be obtained at high
speed.
[0034] The cubic silicon carbide film-attached substrate
manufacturing method according to the aspect of the invention may
further include a third step of forming a monocrystalline silicon
film on the cubic silicon carbide film by introducing a
silicon-containing gas onto the cubic silicon carbide film
epitaxially grown in the second step, with the cubic silicon
carbide film being set to an epitaxial growth temperature of
monocrystalline silicon, wherein the first step and the second step
are sequentially performed after the third step.
[0035] In the cubic silicon carbide film-attached substrate
manufacturing method of this configuration, the third step is
performed that forms a monocrystalline silicon film on the cubic
silicon carbide film by introducing a silicon-containing gas onto
the cubic silicon carbide film epitaxially grown in the second
step, with the cubic silicon carbide film being set to an epitaxial
growth temperature of monocrystalline silicon, and the first and
second steps are sequentially performed after the third step. Thus,
the cubic silicon carbide film can be obtained in a desired
thickness as a laminate of epitaxially grown cubic silicon carbide
layers. In this way, a substrate including a high-quality cubic
silicon carbide film of a desired thickness with few crystal
defects can be obtained at high speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0037] FIG. 1 is a cross sectional view illustrating a cubic
silicon carbide film-attached substrate of an embodiment of the
invention.
[0038] FIG. 2 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of a temperature cycle of
Example 1 of the invention.
[0039] FIG. 3 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of a temperature cycle of
Example 2 of the invention.
[0040] FIG. 4 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of a temperature cycle of
Example 3 of the invention.
[0041] FIG. 5 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of a temperature cycle of
Example 4 of the invention.
[0042] FIG. 6 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of a temperature cycle of
Example 5 of the invention.
[0043] FIG. 7 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of a temperature cycle of
Example 6 of the invention.
[0044] FIG. 8 is a diagram representing the growth time dependence
of the thickness of a cubic silicon carbide film formed in Example
6 of the invention, and of the thickness of a cubic silicon carbide
film formed by a continuous process.
[0045] FIG. 9 is a diagram representing the relationship between
the rate of temperature increase and the thickness of the cubic
silicon carbide film of Example 7 of the invention.
[0046] FIG. 10 is a diagram representing changes in substrate
temperature with the rate of temperature increase solely varied for
the temperature increase of from 900.degree. C. to 950.degree.
C.
[0047] FIG. 11 is a diagram representing the thickness of a carbide
layer formed by the rapid heating of a substrate from 900.degree.
C. to 950.degree. C., and of a carbide layer formed by low-speed
heating.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0048] An embodiment of a cubic silicon carbide film manufacturing
method and a cubic silicon carbide film-attached substrate
manufacturing method according to the invention is described
below.
[0049] For ease of explaining the content of the invention, the
dimensions including the shapes of the structural components
described herein do not necessarily reflect the actual
measurements.
[0050] FIG. 1 is a cross sectional view illustrating a cubic
silicon carbide film-attached substrate of an embodiment of the
invention. As illustrated in the figure, a cubic silicon carbide
film-attached substrate 1 includes a cubic silicon carbide
(3C--SiC) film 3 as a 20-layer laminate of cubic silicon carbide
(3C--SiC) films 3a to 3t formed on a surface 2a of a silicon (Si)
substrate 2.
[0051] In the cubic silicon carbide film-attached substrate 1, the
lamination of the cubic silicon carbide (3C--SiC) films 3a to 3t in
20 layers forms the cubic silicon carbide (3C--SiC) film 3 as a
high-quality laminate of a desired thickness with few crystal
defects.
[0052] A method for manufacturing the cubic silicon carbide
film-attached substrate 1 is described below.
[0053] First, the silicon substrate 2 is prepared, and housed in
the chamber of a heat treatment furnace. After creating a vacuum in
the chamber, the silicon substrate 2 is heated to raise the
substrate temperature to a predetermined temperature of, for
example, 750.degree. C., and heat-treated for a predetermined time
period of, for example, 5 minutes to clean the natural oxide film
and the like on the surface 2a of the silicon substrate 2.
[0054] Then, the temperature of the silicon substrate 2 is set to a
temperature of from room temperature to the epitaxial growth
temperature T1 of monocrystalline silicon. At temperature T1, the
epitaxial growth of the cubic silicon carbide proceeds slowly, and
thus the temperature T1 set for the temperature of the silicon
substrate 2 can limit the epitaxial growth to only the
monocrystalline silicon.
[0055] Thereafter, the silicon substrate 2 is rapidly heated to the
epitaxial growth temperature T2 of cubic silicon carbide higher
than the epitaxial growth temperature T1 of monocrystalline silicon
while introducing a carbon source gas (carbon-containing gas) onto
the silicon substrate 2.
[0056] The carbon source gas is preferably hydrocarbon gas.
Preferred examples include methane (CH.sub.4), ethane
(C.sub.2H.sub.6) acethylene (C.sub.2H.sub.2) ethylene
(C.sub.2H.sub.4), propane (C.sub.3H.sub.8), n-butane
(n-C.sub.4H.sub.10), isobutane (i-C.sub.4H.sub.10), and neopentane
(neo-C.sub.5H.sub.12). These may be used either alone or as a
mixture of two or more.
[0057] The rapid heating is the heating that raises the temperature
at a rate of temperature increase that exceeds the reference rate
of temperature increase of, for example, 10.degree. C./min. The
rate of temperature increase in rapid heating is preferably from
5.degree. C./sec to 200.degree. C./sec.
[0058] In rapid heating, a rate of temperature increase below
5.degree. C./sec is too slow, and may cause silicon to sublime from
the surface of the silicon substrate 2 and roughen the surface, if
the carbon gas supply is small. With a large carbon gas supply,
such a slow rate may lead to formation of a thin carbide layer on
the surface of the silicon substrate 2, preventing further growth
and impairing the growth rate increasing effect. On the other hand,
a rate of temperature increase in excess of 200.degree. C./sec in
rapid heating makes the heating too rapid, and fails to
sufficiently carbonize the surface of the silicon substrate 2,
resulting in insufficient silicon carbide generation.
[0059] For the introduction of the carbon source gas, only the
carbon source gas can be introduced by separately controlling the
flow rates of the carbon source gas and the silicon source gas
(silicon-containing gas).
[0060] In the process of rapid heating, the carbon source gas
carbonizes the surface of the silicon substrate 2, and forms a
cubic silicon carbide film.
[0061] Upon the substrate temperature reaching the cubic silicon
carbide epitaxial growth temperature T2, the temperature of the
silicon substrate 2 is held at epitaxial growth temperature T2, and
the flow rates of the carbon source gas and the silicon source gas
are set to the flow rates suitable for the epitaxial growth of
cubic silicon carbide.
[0062] The silicon source gas is preferably silane gas. Preferred
examples include monosilane (SiH.sub.4), disilane
(Si.sub.2H.sub.6), trisilane (Si.sub.3H.sub.8), tetrasilane
(Si.sub.4H.sub.10) dichlorosilane (SiH.sub.2Cl.sub.2),
tetrachlorosilane (SiCl.sub.4) trichlorosilane (SiHCl.sub.3), and
hexachlorodisilane (Si.sub.2Cl.sub.6). These may be used either
alone or as a mixture of two or more. During this process, the
cubic silicon carbide film 3a is formed on the cubic silicon
carbide film by the epitaxial growth of cubic silicon carbide.
[0063] Thereafter, the supply of the carbon source gas and the
silicon source gas is stopped, and the temperature of the silicon
substrate 2 is lowered to the epitaxial growth temperature T1 of
monocrystalline silicon.
[0064] Upon the silicon substrate 2 reaching the monocrystalline
silicon epitaxial growth temperature T1, the flow rate of the
silicon source gas is set to the flow rate suitable for the
epitaxial growth of monocrystalline silicon.
[0065] During this process, a monocrystalline silicon film is
formed on the cubic silicon carbide film 3a by the epitaxial growth
of monocrystalline silicon.
[0066] The monocrystalline silicon epitaxial growth and the
subsequent steps are repeated until the resulting cubic silicon
carbide film has a desired thickness.
[0067] In this embodiment, the following steps (1) to (4) are
repeated. [0068] (1) The step of allowing monocrystalline silicon
to epitaxially grow on the cubic silicon carbide film 3a while
introducing silicon source gas, upon the substrate temperature
reaching the monocrystalline silicon epitaxial growth temperature
T1. [0069] (2) The step of rapidly heating the substrate to the
epitaxial growth temperature T2 of cubic silicon carbide while
introducing carbon source gas onto the monocrystalline silicon film
formed on the cubic silicon carbide film 3a. [0070] (3) The step of
allowing the cubic silicon carbide film to epitaxially grow while
introducing carbon source gas and silicon source gas at
predetermined flow rates, upon the substrate temperature reaching
the epitaxial growth temperature T2. [0071] (4) The step of
stopping the supply of the carbon source gas and the silicon source
gas, and lowering the substrate temperature to the monocrystalline
silicon epitaxial growth temperature T1.
[0072] By repeating these steps (1) to (4) multiple times, the
cubic silicon carbide film-attached substrate 1 can be obtained
that has the cubic silicon carbide film 3 of a desired
thickness.
[0073] For example, by repeating these steps 19 times, the cubic
silicon carbide film-attached substrate 1 can be obtained that has
the cubic silicon carbide film 3 formed as a 20-layer laminate of
the cubic silicon carbide films 3a to 3t, as illustrated in FIG.
1.
[0074] With the cubic silicon carbide film-attached substrate
manufacturing method of the present embodiment, the cubic silicon
carbide film-attached substrate 1 including the cubic silicon
carbide film formed in high quality with few crystal defects can be
quickly obtained at a low epitaxial growth temperature after the
repeated steps of generating and growing the cubic silicon carbide
film, generating a monocrystalline silicon film on the cubic
silicon carbide film, and generating and growing the cubic silicon
carbide film by the carbonization of the monocrystalline silicon
film.
EXAMPLES
[0075] The invention is described below in more detail based on
Examples. Note, however, that the invention is not limited by the
following Examples.
Example 1
[0076] FIG. 2 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of the temperature cycle of
Example 1. In this example, neopentane (neo-C.sub.5H.sub.12) and
dichlorosilane (SiH.sub.2Cl.sub.2) were used as carbon source gas
and silicon source gas, respectively. The monocrystalline silicon
epitaxial growth temperature T1 and cubic silicon carbide epitaxial
growth temperature T2 were 800.degree. C. and 1,000.degree. C.,
respectively.
[0077] The carbon source gas and the silicon source gas were set to
have optimum flow rates Fc1 to Fc4 and Fsi 1 to Fsi 4,
respectively, for section S1 (rapid heating carbonization process),
section S2 (cubic silicon carbide film epitaxial growth process),
section S3 (substrate temperature lowering process), and section S4
(monocrystalline silicon epitaxial growth process).
[0078] Here, because only the carbon source gas needs to be
introduced in section S1 (rapid heating carbonization process), the
carbon source gas flow rate Fc1=3 sccm, and the silicon source gas
flow rate Fsi 1=0 sccm.
[0079] In section S2 (cubic silicon carbide film epitaxial growth
process), both the carbon source gas and the silicon source gas
need to be introduced in good balance. Accordingly, the carbon
source gas flow rate Fc2=5 sccm, and the silicon source gas flow
rate Fsi 2=5 sccm.
[0080] Section S3 (substrate temperature lowering process) does not
require the supply of carbon source gas and silicon source gas.
Accordingly, the carbon source gas flow rate Fc3=0 sccm, and the
silicon source gas flow rate Fsi 3=0 sccm.
[0081] In section S4 (monocrystalline silicon epitaxial growth
process), only the silicon source gas needs to be introduced.
Accordingly, the carbon source gas flow rate Fc4=0 sccm, and the
silicon source gas flow rate Fsi 4=20 sccm.
[0082] By optimally setting the carbon source gas flow rates Fc1,
Fc2, Fc3, Fc4, and the silicon source gas flow rates Fsi 1, Fsi 2,
Fsi 3, Fsi 4 for sections S1 to S4, a cubic silicon carbide film
was quickly obtained in high quality with few crystal defects at a
low epitaxial growth temperature.
Example 2
[0083] FIG. 3 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of the temperature cycle of
Example 2. Example 2 differs from Example 1 in that the carbon
source gas flow rate Fc2=3 sccm, and that the silicon source gas
flow rate Fsi 2=0 sccm.
[0084] In section S2 (cubic silicon carbide film epitaxial growth
process), the carbon source gas flow rate Fc2=3 sccm, and the
silicon source gas flow rate Fsi 2=0 sccm. This creates an
atmosphere with the excess carbon source gas, and promotes
carbonization and thus the generation of the cubic silicon carbide
film.
Example 3
[0085] FIG. 4 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of the temperature cycle of
Example 3. Example 3 differs from Example 1 in that the carbon
source gas flow rate Fc1=Fc2=5 sccm, and Fc3=Fc4=0 sccm, and that
the silicon source gas flow rate Fsi 1=Fsi 2=Fsi 3=Fc4=20 sccm.
[0086] In section S1 (rapid heating carbonization process), here,
both the carbon source gas and the silicon source gas are
introduced. However, the introduction of the silicon source gas
does not pose any problem, because the effect of carbonization by
the carbon source gas far exceeds the growth by the silicon source
gas.
Example 4
[0087] FIG. 5 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of the temperature cycle of
Example 4. Example 4 differs from Example 1 in that the carbon
source gas flow rate Fc1=Fc2=Fc3=Fc4=5 sccm, and that the silicon
source gas flow rate Fsi 1=Fsi 2=Fsi 3=Fc4=20 sccm.
[0088] In section S4 (monocrystalline silicon epitaxial growth
process), both the carbon source gas and the silicon source gas are
introduced. However, the introduction of the carbon source gas and
the silicon source gas does not pose any problem, because this
temperature range is the silicon epitaxial growth range by the
silicon source gas, where there is no epitaxial growth of cubic
silicon carbide.
Example 5
[0089] FIG. 6 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of the temperature cycle of
Example 5. Example 5 differs from Example 1 in that the carbon
source gas flow rate Fc1=Fc2=Fc3=Fc4=5 sccm, and that the silicon
source gas flow rate Fsi 1=Fsi 2=Fsi 3=0 scam, Fc4=20 scam.
[0090] As in Example 4, both the carbon source gas and the silicon
source gas are introduced in section S4 (monocrystalline silicon
epitaxial growth process). However, the introduction of the carbon
source gas and the silicon source gas does not pose any problem,
because this temperature range is the silicon epitaxial growth
range by the silicon source gas, where there is no epitaxial growth
of cubic silicon carbide.
[0091] As in Example 1, a cubic silicon carbide film can be quickly
obtained in high quality with few crystal defects at a low
epitaxial growth temperature also in Examples 2 to 5, by optimally
setting the carbon source gas flow rates Fc1, Fc2, Fc3, Fc4, and
the silicon source gas flow rates Fsi 1, Fsi 2, Fsi 3, Fsi 4 for
each section.
Example 6
[0092] FIG. 7 is a diagram representing the relationship between
substrate temperature and the flow rates of carbon source gas and
silicon source gas in each section of the temperature cycle of
Example 6. In this example, neopentane (neo-C.sub.5H.sub.12) and
dichlorosilane (SiH.sub.2Cl.sub.2) were used as carbon source gas
and silicon source gas, respectively, and 5 cycles of epitaxial
growth were performed at the monocrystalline silicon epitaxial
growth temperature T1 and cubic silicon carbide epitaxial growth
temperature T2 of 900.degree. C. and 1,000.degree. C.,
respectively.
[0093] Section S1 (rapid heating carbonization process), section S2
(cubic silicon carbide film epitaxial growth process), section S3
(substrate temperature lowering process), and section S4
(monocrystalline silicon epitaxial growth process) were set to 60
seconds, 300 seconds, 120 seconds, and 300 seconds, respectively.
The flow rates of the carbon source gas were Fc1=1 sccm, Fc2=Fc3=5
sccm, Fc4=0 sccm. The flow rates of the silicon source gas were Fsi
1=0 sccm, Fsi 2=Fsi 3=Fsi 4=20 sccm.
[0094] The epitaxial growth was also performed in 10 cycles and in
20 cycles using the same temperature cycle.
[0095] FIG. 8 is a diagram representing the growth time dependence
of the thickness of the cubic silicon carbide film formed by the
cycle process of FIG. 7, and of the cubic silicon carbide film
formed by a common continuous process that involves epitaxial
growth at constant temperature.
[0096] The continuous process was performed under the conditions
of: substrate temperature=1,000.degree. C.; the flow rate of the
carbon source gas (neopentane (neo-C.sub.5H.sub.12))=5 sccm; and
the flow rate of the silicon source gas (dichlorosilane
(SiH.sub.2Cl.sub.2))=20 sccm.
[0097] The cycle process time is represented by the product of the
number of cycles and the total growth time in section S1 (rapid
heating carbonization process), section (cubic silicon carbide film
epitaxial, growth process), and section S3 (substrate temperature
lowering process).
[0098] The growth rate in the cycle process was 33.1 nm/hour, as
opposed to 25.1 nm/hour in the continuous process, demonstrating
that the growth rate can be increased by performing the cycle
process, given the same process conditions.
[0099] The increase in growth rate over the continuous process is
only slightly higher than 1.3 fold in FIG. 8. This is because the
process time was not optimized for each section. The growth rate
can be further improved by optimizing the process time of each
section.
Example 7
[0100] FIG. 9 is a diagram representing the relationship between
the rate of temperature increase and the thickness of the cubic
silicon carbide film of Example 7. The figure represents the
thickness of the cubic silicon carbide film formed after heating
the silicon substrate to 600.degree. C., when (1) the substrate was
subsequently heated to 1,000.degree. C. at a rate of temperature
increase of 180.degree. C./sec, and carbonized at 1,000.degree. C.
for 10 minutes while introducing the carbon source gas ethylene
(C.sub.2H.sub.4) at a flow rate of 3 sccm, (2) the substrate was
subsequently heated to 1,000.degree. C. at a rate of temperature
increase of 150.degree. C./sec, and carbonized at 1,000.degree. C.
for 5 minutes while introducing the ethylene (C.sub.2H.sub.4) gas
at a flow rate of 10 sccm, and (3) the substrate was subsequently
heated to 1,000.degree. C. at a rate of temperature increase of
10'C/sec, and carbonized at 1,000.degree. C. for 5 minutes while
introducing the ethylene (C.sub.2H.sub.4) gas at a flow rate of 10
sccm.
[0101] It can be seen from the figure that the rapid heating to
1,000.degree. C. at the rate of temperature increase of 150.degree.
C./sec or more quickly forms a cubic silicon carbide film that is
about three times as thick as that formed without rapid
heating.
[0102] FIG. 10 is a diagram representing changes in substrate
temperature with the rate of temperature increase solely varied for
the temperature increase of from 900.degree. C. to 950.degree.
C.
[0103] In the figure, the solid line indicates temperature changes
in carbonization performed by increasing the temperature at a slow
rate of temperature increase of 10.degree. C./min until the
substrate temperature of 900.degree. C., followed by rapid heating
from the substrate temperature of 900.degree. C. to 950.degree. C.
at a rate of temperature increase of 5.degree. C./sec.
[0104] The broken line indicates temperature changes in the case
where the temperature was increased at a slow rate of temperature
increase of 10.degree. C./min until the substrate temperature
reached 950.degree. C.
[0105] FIG. 11 represents the thicknesses of carbide layers formed
after the carbonization performed at 950.degree. C. for 5 minutes
upon the temperature reaching 950.degree. C. along the paths of the
solid line and broken line in the presence of the carbon source gas
ethylene (C.sub.2H.sub.4) flowed at a rate of 10 sccm. It can be
seen from the figure that the rapid heating of the substrate from
900.degree. C. to 950.degree. C. promoted the carbonization
reaction further compared to the gradual heating, and formed the
carbide film in a shorter time period.
[0106] At temperatures of 900.degree. C. and lower, there was
epitaxial growth of monocrystalline silicon, but substantially no
epitaxial growth of the cubic silicon carbide film was observed.
Thus, by subjecting the substrate to repeated temperature changes
between the monocrystalline silicon epitaxial growth temperature
range of 900.degree. C. or less and the rapid heating range of from
900.degree. C. to 950.degree. C., it is possible to alternately
perform (1) the epitaxial growth of monocrystalline silicon, and
(2) the generation of the cubic silicon carbide film by the
carbonization of the monocrystalline silicon, and the epitaxial
growth of the cubic silicon carbide film.
[0107] The rapid heating allows the cubic silicon carbide film to
be formed more quickly than the common process, and thus enables
formation of the cubic silicon carbide film at high speed even at
relatively low temperatures.
[0108] Further, because the cubic silicon carbide film can be
formed at low temperature, generation of crystal defects due to the
difference in the thermal expansion of the silicon substrate and
the cubic silicon carbide film can be suppressed, and a
high-quality cubic silicon carbide film with few crystal defects
can be formed.
[0109] The cubic silicon carbide film-attached substrate 1 of the
present embodiment is configured to include the cubic silicon
carbide film 3 formed as a 20-layer laminate of the cubic silicon
carbide films 3a to 3t on the surface 2a of the silicon substrate
2. However, the number of the laminated layers in the cubic silicon
carbide film may be decided according to the required
characteristics.
[0110] Further, the invention is equally effective when the silicon
substrate 2 is replaced with a substrate that includes a
monocrystalline silicon film formed on the substrate surface. In
this case, the monocrystalline silicon film needs to be
sufficiently thick to allow carbonization by rapid heating.
[0111] The monocrystalline silicon carbide film-attached substrate
1 also can be used as semiconductor material for the next
generation of low-loss power devices.
* * * * *