U.S. patent application number 16/125524 was filed with the patent office on 2019-01-03 for aluminum nitride film, method of manufacturing aluminum nitride film, and high withstand voltage component.
This patent application is currently assigned to SHIBAURA INSTITUTE OF TECHNOLOGY. The applicant listed for this patent is SHIBAURA INSTITUTE OF TECHNOLOGY, TOSHIBA MATERIALS CO., LTD.. Invention is credited to Takashi HINO, Tetsuo INOUE, Shuichi SAITO, Mari SHIMIZU, Atsushi YUMOTO.
Application Number | 20190002281 16/125524 |
Document ID | / |
Family ID | 59789275 |
Filed Date | 2019-01-03 |
United States Patent
Application |
20190002281 |
Kind Code |
A1 |
YUMOTO; Atsushi ; et
al. |
January 3, 2019 |
ALUMINUM NITRIDE FILM, METHOD OF MANUFACTURING ALUMINUM NITRIDE
FILM, AND HIGH WITHSTAND VOLTAGE COMPONENT
Abstract
An aluminum nitride film includes a polycrystalline aluminum
nitride. A withstand voltage of the aluminum nitride film is 100
kV/mm or more.
Inventors: |
YUMOTO; Atsushi; (Tokyo,
JP) ; SHIMIZU; Mari; (Tokyo, JP) ; INOUE;
Tetsuo; (Yokohama, JP) ; HINO; Takashi;
(Yokohama, JP) ; SAITO; Shuichi; (Yokohama,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHIBAURA INSTITUTE OF TECHNOLOGY
TOSHIBA MATERIALS CO., LTD. |
Tokyo
Yokohama-shi |
|
JP
JP |
|
|
Assignee: |
SHIBAURA INSTITUTE OF
TECHNOLOGY
Tokyo
JP
TOSHIBA MATERIALS CO., LTD.
Yokohama-shi
JP
|
Family ID: |
59789275 |
Appl. No.: |
16/125524 |
Filed: |
September 7, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2017/008487 |
Mar 3, 2017 |
|
|
|
16125524 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C01P 2002/76 20130101;
H05B 3/12 20130101; H01L 23/3731 20130101; H01L 21/67103 20130101;
C23C 14/28 20130101; H05B 3/84 20130101; C01B 21/0728 20130101;
C01P 2002/74 20130101; C01P 2006/40 20130101; C23C 24/04 20130101;
C23C 26/00 20130101; H05B 3/06 20130101; C01P 2002/72 20130101;
C23C 14/0617 20130101; C01P 2006/90 20130101; C01P 2002/60
20130101 |
International
Class: |
C01B 21/072 20060101
C01B021/072; H01L 21/67 20060101 H01L021/67; H01L 23/373 20060101
H01L023/373; H05B 3/12 20060101 H05B003/12; C23C 14/06 20060101
C23C014/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2016 |
JP |
2016-044525 |
Claims
1. An aluminum nitride film, comprising a polycrystalline aluminum
nitride, wherein a withstand voltage of the aluminum nitride film
is 100 kV/mm or more.
2. The aluminum nitride film according to claim 1, wherein: the
polycrystalline aluminum nitride contains a plurality of aluminum
nitride crystal grains; and a proportion of the grains in the
aluminum nitride film is not less than 90 volume % nor more than
100 volume %.
3. The aluminum nitride film according to claim 2, wherein an
average grain diameter of the grains is 30 nm or less.
4. The aluminum nitride film according to claim 1, wherein the
withstand voltage is 200 kV/mm or more.
5. The aluminum nitride film according to claim 1, wherein an X-ray
diffraction pattern obtained by an X-ray diffraction analysis of
the aluminum nitride film has a diffraction peak positioned at a
diffraction angle 2.theta. of 33.2.+-.1.degree..
6. The aluminum nitride film according to claim 1, wherein: an
X-ray diffraction pattern obtained by an X-ray diffraction analysis
of the aluminum nitride film has a first diffraction peak
positioned at a diffraction angle 2.theta. of 33.2.+-.1.degree. and
a second diffraction peak positioned at a diffraction angle
2.theta. of 43.5.+-.1.degree.; and a ratio of intensity of the
second diffraction peak to intensity of the first diffraction peak
is 0.01 or more.
7. The aluminum nitride film according to claim 1, wherein an X-ray
diffraction pattern obtained by an X-ray diffraction analysis of
the aluminum nitride film has a diffraction peak based on an
aluminum nitride crystal, and does not have a diffraction peak
other than the diffraction peak based on the aluminum nitride
crystal.
8. The aluminum nitride film according to claim 1, wherein the
polycrystalline aluminum nitride includes hexagonal aluminum
nitride and cubic aluminum nitride.
9. The aluminum nitride film according to claim 1, wherein a
surface roughness Ra of the aluminum nitride film is 3 .mu.m or
less.
10. The aluminum nitride film according to claim 1, wherein a
thickness of the aluminum nitride film is 1 .mu.m or more.
11. A high withstand voltage component, comprising: a base
material; and the aluminum nitride film according to claim 1, being
provided on the base material.
12. The high withstand voltage component according to claim 11,
wherein the high withstand voltage component is a semiconductor
element mounting substrate, a component for heater, or a component
for semiconductor manufacturing apparatus.
13. A method of manufacturing an aluminum nitride film, comprising
forming the aluminum nitride film according to claim 1 through a
supersonic free jet physical vapor deposition method using an
aluminum nitride powder.
14. The method according to claim 13, wherein the aluminum nitride
film is formed under an inert atmosphere containing nitrogen.
15. The method according to claim 14, wherein the inert atmosphere
further contains helium.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of prior International
Application No. PCT/JP2017/008487, filed on Mar. 3, 2017 which is
based upon and claims the benefit of priority from Japanese Patent
Application No. 2016-044525, filed on Mar. 8, 2016; the entire
contents of all of which are incorporated herein by reference.
FIELD
[0002] Embodiments described herein generally relate to an aluminum
nitride film, a method of manufacturing an aluminum nitride film,
and a high withstand voltage component.
BACKGROUND
[0003] Aluminum nitride (AlN) is used for, for example, a
semiconductor element mounting substrate, a component for heater, a
component for semiconductor manufacturing apparatus, and the like,
by utilizing its high thermal conductivity. As aluminum nitride,
there is known an aluminum nitride sintered compact having thermal
conductivity of 200 W/mK or more, for example. The aforementioned
aluminum nitride sintered compact has high thermal conductivity
through addition of sintering aids and performance of predetermined
sintering process. The aforementioned aluminum sintered compact is
used for a semiconductor element mounting substrate or the like,
for example.
[0004] A withstand voltage of an aluminum nitride substrate which
is sintered after sintering aids are added thereto is, for example,
not less than 10 kV/mm nor more than 20 kV/mm. For this reason, a
thickness of the aluminum nitride substrate is normally about 0.635
mm. Meanwhile, in an aluminum nitride single phase (single crystal
of aluminum nitride), a theoretical value of thermal conductivity
is about 320 W/mK, and a theoretical value of a withstand voltage
is about 1170 kV/mm. Specifically, the withstand voltage of the
aluminum nitride sintered compact has a small value of about 1 to
2% of the value of the single crystal of aluminum nitride.
[0005] As a method of increasing a withstand voltage of aluminum
nitride, for example, there can be cited a method of forming an
aluminum nitride film with high resistance by using a supersonic
free jet physical vapor deposition method (SFJ-PVD method). The
aluminum nitride film formed by the SFJ-PVD method has volume
resistivity of 13.7.times.10.sup.12 .OMEGA.cm, for example. The
volume resistivity is a physical property value indicating
difficulty in conducting electricity in a material.
[0006] Meanwhile, a withstand voltage of the aforementioned
aluminum nitride film is about 50 kV/mm. The withstand voltage is a
voltage value at which an insulating state can be maintained. The
withstand voltage is also simply referred to as a withstand
voltage. If dielectric breakdown tentatively occurs on a
semiconductor element mounting substrate, it is not possible to
maintain insulation performance of the substrate. Accordingly, this
causes a trouble of a semiconductor device. Therefore, it has been
required to improve a withstand voltage of an aluminum nitride film
for maintaining insulation performance of a substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1 is a view illustrating one example of a semiconductor
element mounting substrate.
[0008] FIG. 2 is a view illustrating one example of a substrate for
heater.
[0009] FIG. 3 is a view illustrating one example of a component for
semiconductor manufacturing apparatus.
DETAILED DESCRIPTION
[0010] An aluminum nitride film of the present embodiment includes
a polycrystalline aluminum nitride. A withstand voltage of the
aluminum nitride film is 100 kV/mm or more.
[0011] A withstand voltage of an aluminum nitride film of the
present embodiment is 100 kV/mm or more. The withstand voltage of
the aluminum nitride film of the present embodiment is preferably
200 kV/mm or more. The withstand voltage is measured based on
JIS-C-2110-1 (2010). As measurement conditions, an AC dielectric
breakdown voltage is measured, and a voltage increase speed is set
to 100 V/sec. A combination of electrodes for measurement is any of
(1) a combination of an upper electrode having a diameter of 25 mm
and a columnar shape and a lower electrode having a diameter of 75
mm and a columnar shape, (2) a combination of an upper electrode
having a diameter of 25 mm and a columnar shape and a lower
electrode having a diameter of 25 mm and a columnar shape, and (3)
a combination of an upper electrode having a diameter of 20 mm and
a spherical shape and a lower electrode having a diameter of 25 mm
and a disk shape. As a base material for measuring the withstand
voltage of the aluminum nitride film, it is preferable to use a
conductive material such as a copper plate.
[0012] The aluminum nitride film of the present embodiment contains
polycrystalline aluminum nitride as a main component. A proportion
of aluminum nitride crystal grains in the aluminum nitride film
which contains polycrystalline aluminum nitride as a main component
is not less than 90 volume % nor more than 100 volume %. When an
additional film is provided on a surface of the aluminum nitride
film, the proportion of the aluminum nitride crystal grains is
determined by excluding the additional film. In a similar manner,
when an additional film is provided between the aluminum nitride
film and a base material, the proportion of the aluminum nitride
crystal grains is determined by excluding the additional film.
[0013] An average grain diameter of the aluminum nitride crystal
grains is preferably 30 nm or less. When the average grain diameter
of the aluminum nitride crystal grains exceeds 30 nm, pores may be
formed in the aluminum nitride film. The formation of pores leads
to dielectric breakdown. Further, by reducing the grain diameter,
it is possible to extend a path of grain boundary. By extending the
path of grain boundary, it is possible to improve the withstand
voltage. The average grain diameter of the aluminum nitride crystal
grains is more preferably 25 nm or less. Although a lower limit
value of the average grain diameter is not particularly limited, it
is preferably 5 nm or more. When the average grain diameter is less
than 5 nm, there is a possibility that management of manufacturing
processes becomes complicated.
[0014] The average grain diameter is determined, based on Scherrer
equation, from a half value width of a diffraction peak of
hexagonal aluminum nitride (PDF#25-133 (100) plane) determined
through an X-ray diffraction (XRD) analysis. The Scherrer equation
is represented by an equation .tau.=k.lamda./.beta. cos .theta..
.tau. indicates an average grain diameter, k indicates a form
factor, .lamda. indicates a wavelength of X-ray, .beta. indicates a
full width at half maximum of peak, and .theta. indicates a Bragg
angle. In the Scherrer equation, it is set that the wavelength
.lamda. of X-ray uses a Cu target (K.alpha.-Cu), and the form
factor k is 0.9. As the diffraction peak of hexagonal aluminum
nitride (PDF#25-1133 (100) plane), a diffraction peak positioned at
a diffraction angle (2.theta.) of 33.2.+-.1.degree. is used.
[0015] The XRD analysis is performed through a focusing method or a
thin film method. When the XRD analysis is performed through the
focusing method, a base material made of a material which exerts no
influence on XRD peak detection is used. As the aforementioned base
material, for example, an amorphous substrate can be cited. A film
thickness of aluminum nitride is 5 .mu.m or more, for example. When
the XRD analysis is performed through the thin film method, an
incident angle is set to 5.degree. or less, and it is preferably
set to 1.degree.. In the above-described method, it is possible to
detect the XRD peak without being influenced by the base
material.
[0016] A diffraction pattern obtained by the XRD analysis of the
aluminum nitride film of the present embodiment preferably has a
diffraction peak positioned at a diffraction angle 2.theta. of
33.2.+-.1.degree.. Further, it is preferable that the
aforementioned diffraction pattern has a diffraction peak
I.sub.33.2.degree. positioned at a diffraction angle 2.theta. of
33.2.+-.1.degree. and a diffraction peak I.sub.43.5.degree.
positioned at a diffraction angle 2.theta. of 43.5.+-.1.degree.,
and I.sub.43.5.degree./I.sub.33.2.degree. being an intensity ratio
of the diffraction peak I.sub.43.5.degree. to the diffraction peak
I.sub.33.2.degree. is preferably 0.01 or more. Furthermore, it is
preferable that the aforementioned diffraction pattern has a
diffraction peak based on an aluminum nitride crystal, and does not
have a peak other than the diffraction peak based on the aluminum
nitride crystal. As an analysis method of XRD, the focusing method
or the thin film method is used, as described above.
[0017] When the diffraction peak is detected at the diffraction
angle 2.theta. of 33.2.+-.1.degree., this indicates that hexagonal
aluminum nitride exists. As a crystal structure of aluminum
nitride, there can be cited a hexagonal system (wurtzite structure)
and a cubic system (zinc blende structure). Hexagonal aluminum
nitride is thermally stable. For this reason, by making hexagonal
aluminum nitride exist, it is possible to improve heat radiation
property and plasma resistance.
[0018] When the diffraction peak is detected at the diffraction
angle (2.theta.) of 43.5.+-.1.degree., this indicates that cubic
aluminum nitride exists. When the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. is 0.01 or more, and further,
when it is 0.05 or more, this indicates that a predetermined amount
of cubic aluminum nitride exists with respect to hexagonal aluminum
nitride.
[0019] It is preferable that the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. is 0.1 or more even when a
spot diameter (or slit width) of X-ray is set to 100 .mu.m.
Further, it is preferable that the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. is 0.01 or more even when an
arbitrary portion of the aluminum nitride film is subjected to the
XRD analysis. When the predetermined intensity ratio can be
obtained at the time of measuring an arbitrary portion, this
indicates that hexagonal aluminum nitride and cubic aluminum
nitride are dispersed in a homogeneous manner. The coexistence of
hexagonal aluminum nitride and cubic aluminum nitride can improve
the withstand voltage.
[0020] When the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. is set to 0.01 or more, and
further, when it is set to 0.05 or more, it is possible to obtain
an aluminum nitride film which is resistant to heat and which has a
high withstand voltage. When the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. is increased to 0.1 or more,
and further, when it is increased to 0.3 or more, it is possible to
further improve the withstand voltage. Although an upper limit of
the intensity ratio is not particularly limited, the intensity
ratio I.sub.43.5.degree./I.sub.33.2.degree. is preferably 2.0 or
less. When the intensity ratio exceeds 2.0, a proportion of
hexagonal aluminum nitride is lowered. When the proportion of
hexagonal aluminum nitride is lowered, a proportion of hexagonal
system which is more stable in terms of energy is reduced, which
may reduce the plasma resistance.
[0021] It is preferable that when performing the XRD analysis, a
peak other than a diffraction peak based on the aluminum nitride
crystal is not detected. When the peak other than the diffraction
peak based on the aluminum nitride crystal is not detected, this
indicates that crystal grains other than those of aluminum nitride
and a sub-phase (grain boundary phase) do not exist. Specifically,
this indicates an aluminum nitride film made of only aluminum
nitride crystal grains (aluminum nitride crystal grains make up 100
mass %). This makes it possible to further improve the withstand
voltage.
[0022] A film thickness of the aluminum nitride film is preferably
1 .mu.m or more. When the film thickness is 1 .mu.m or more, it is
possible to increase the insulation performance. The film thickness
is more preferably 2 .mu.m or more. Although an upper limit of the
film thickness is not particularly limited, it is preferably 100
.mu.m or less. When the film thickness is not less than 1 .mu.m nor
more than 100 .mu.m, it is possible to use the aluminum nitride
film for a semiconductor element mounting substrate, a component
for heater, and a component for semiconductor manufacturing
apparatus to be described later, for example. A surface roughness
Ra of the aluminum nitride film is preferably 3 .mu.m or less, and
more preferably 2 .mu.m or less.
[0023] As described above, in the aluminum nitride film of the
present embodiment, the withstand voltage can be set to 100 kV/mm
or more, and further, it can be set to 200 kV/mm or more. Such an
aluminum nitride film is suitable for various components. A high
withstand voltage component of the present embodiment has an
aluminum nitride film on a base material. Note that an additional
film may be provided between the aluminum nitride film and the base
material according to need. In a similar manner, an additional film
may be provided on a surface of the aluminum nitride film. The high
withstand voltage component of the present embodiment is preferably
any one of a semiconductor element mounting substrate, a component
for heater, and a component for semiconductor manufacturing
apparatus.
[0024] FIG. 1 is a view illustrating one example of a semiconductor
element mounting substrate. A semiconductor element mounting
substrate 10 illustrated in FIG. 1 includes an aluminum nitride
film 1, and a base material 2. The aluminum nitride film 1 is
provided on the base material 2.
[0025] A semiconductor element 3 is provided on the semiconductor
element mounting substrate 10. As the semiconductor element 3, for
example, a light-emitting diode (LED) element, a power
semiconductor element, or the like, is used. In recent years,
reduction in size and realization of high power of a semiconductor
element have been promoted. In accordance with this, a heating
value has been increasing. For example, there is a possibility that
an operation guaranteed temperature (junction temperature) of a SiC
element or a GaN element exceeds 200.degree. C.
[0026] In a conventional semiconductor element mounting substrate,
an aluminum nitride sintered compact with a withstand voltage of
about 10 to 20 kV/mm has been used. A withstand voltage of another
ceramic substrate such as an alumina sintered compact substrate or
a silicon nitride sintered compact substrate is also about the same
as the above. On the other hand, the withstand voltage of the
aluminum nitride film of the present embodiment is 100 kV/mm or
more. For this reason, it is possible to reduce the thickness of
the aluminum nitride film. Further, since it is possible to realize
the insulation performance with the thin film, various substrates
such as a ceramic substrate, a metal substrate, and a resin
substrate can be used as the base material. Particularly, it is
advantageous to use a conductive material such as the metal
substrate.
[0027] Thermal conductivity of copper is about 398 W/mK. Thermal
conductivity of aluminum is about 236 W/mK. By providing the
aluminum nitride film on a base material being a metal substrate
made of each of these materials, it is possible to suppress
increase in thermal resistance due to the aluminum nitride film.
Further, since it is possible to form the aluminum nitride film
directly on the base material, there is no need to use a joining
material such as a brazing material. Also from this point, it is
possible to reduce the thermal resistance. Further, since the
joining material is not used, it is possible to simplify the
manufacturing processes. In other words, a semiconductor device
including the semiconductor element 3 mounted on the semiconductor
element mounting substrate 10 has high heat radiation property and
can be reduced in thickness.
[0028] FIG. 2 is a view illustrating one example of a substrate for
heater. A substrate for heater 20 illustrated in FIG. 2 includes an
aluminum nitride film 1, and a base material 2. The aluminum
nitride film 1 is provided on the base material 2. Further, a wire
for heater 4 is provided on the substrate for heater 20.
[0029] As the base material 2, for example, there can be cited
various substrates such as a ceramic substrate, a metal substrate,
and a resin substrate. As the wire for heater 4, a material which
generates heat through energization such as tungsten, for example,
is used. When the wire for heater 4 is subjected to energization, a
temperature of the substrate for heater 20 reaches a high
temperature. This heat can be effectively radiated. For this
reason, a heater having the wire for heater 4 provided on the
substrate for heater 20 has high heat radiation property and can be
reduced in thickness.
[0030] FIG. 3 is a view illustrating one example of a component for
semiconductor manufacturing apparatus. A component for
semiconductor manufacturing apparatus 30 illustrated in FIG. 3
includes an aluminum nitride film 1, and a base material 2. The
aluminum nitride film 1 is provided on the base material 2. As the
base material 2, for example, various materials such as ceramics,
metal, and resin are used. A shape of the base material 2 is not
limited to a plate shape, and it may employ various shapes such as
a spherical shape (including a hemispherical shape), a curved
shape, and a concavo-convex shape.
[0031] The aluminum nitride film 1 is excellent in not only the
insulation performance but also the heat radiation property and the
plasma resistance. For this reason, the component for semiconductor
manufacturing apparatus 30 can be used for various semiconductor
manufacturing processes in a CVD apparatus, a PVD apparatus, an
etching apparatus, and the like. In other words, in a semiconductor
manufacturing apparatus including the component for semiconductor
manufacturing apparatus 30, durability of the component for
semiconductor manufacturing apparatus 30 is excellent even if a
plasma atmosphere is used. Further, as one example of the component
for semiconductor manufacturing apparatus 30, an electrostatic
chuck can be cited.
[0032] Next, a method of manufacturing the aluminum nitride film of
the present embodiment will be described. Although the method of
the present embodiment is not particularly limited, the following
method can be cited as a method for efficiently obtaining the
aluminum nitride film.
[0033] In the method of the present embodiment, it is preferable to
form the aluminum nitride film through a supersonic free jet
physical vapor deposition method (SFJ-PVD method) by using an
aluminum nitride powder. Further, a film-forming process is
preferably carried out under an inert atmosphere containing
nitrogen.
[0034] The manufacturing method preferably has a process of forming
fumes with an average grain diameter of 500 nm or less by making a
raw material vaporization source to be subjected to laser
irradiation to perform melting, a process of cooling the fumes to
obtain a raw material powder, and a process of transporting the raw
material powder into a vacuum chamber using a supersonic gas and
making the raw material powder to be subjected to physical vapor
deposition on a base material. The process of performing the
physical vapor deposition is preferably the SFJ-PVD method.
[0035] As the SFJ-PVD method, for example, a method of using a
physical vapor deposition apparatus can be cited. First, a process
in which a thermoelectric element vaporization source is subjected
to laser irradiation to perform melting, to thereby form fumes with
an average grain diameter of 500 nm or less is performed. In the
SFJ-PVD method, an aluminum target or an aluminum nitride target is
set to a raw material vaporization source. Further, a purity of the
aluminum target or the aluminum nitride target is preferably 3 N or
more (99.9 mass % or more).
[0036] In the film-forming process, it is possible to form an
aluminum nitride film while making fumes of aluminum or aluminum
nitride to be subjected to nitriding in an inert atmosphere
containing nitrogen. By adjusting a laser output, the average grain
diameter of the fumes can be reduced to 500 nm or less, and
further, it can be reduced up to 100 nm or less. The laser output
is preferably not less than 3.0 W nor more than 5.0 W.
[0037] The inert atmosphere containing nitrogen is preferably a
mixed gas atmosphere of nitrogen gas and helium gas. The nitrogen
gas has a function of making the fumes of aluminum or aluminum
nitride to be subjected to nitriding. Meanwhile, the helium gas can
increase a flow velocity and thus it has a function of improving a
collision speed of nanoparticles. The mixed gas of the nitrogen gas
and the helium gas preferably satisfies a relation of [flow rate of
nitrogen gas/(flow rate of nitrogen gas+flow rate of helium
gas)].gtoreq.0.3. When [flow rate of nitrogen gas/(flow rate of
nitrogen gas+flow rate of helium gas)] is less than 0.3, the force
of the nitrogen gas is insufficient, resulting in that an
insufficiently nitrided raw material powder may be formed.
[0038] Next, the process of cooling the aforementioned fumes to
obtain the raw material powder is performed. The above-described
helium gas has an effect of making the raw material powder turn
into nanoparticles and cooling the fumes. By the cooling process,
it is possible to obtain an aluminum nitride powder being a
nanoparticle. The fumes are subjected to nitriding until when they
are cooled.
[0039] Next, the raw material powder is transported into a vacuum
chamber using an ultrasonic gas to make the raw material powder to
be subjected to physical vapor deposition on a base material.
First, the base material is disposed in the vacuum chamber. A
degree of vacuum is 1.3.times.10.sup.-3 Pa (1.times.10.sup.-5 Torr)
or less, and further, it is preferably 1.3.times.10.sup.-7 Pa or
less. By controlling the degree of vacuum, the raw material powder
(aluminum nitride powder) can be transported at high speed into the
vacuum chamber. This makes it possible to form a film of aluminum
nitride crystal grains on the base material.
EXAMPLES
Examples 1 to 7, Comparative Examples 1 and 2
[0040] Aluminum nitride films were formed by the SFJ-PVD method. As
each of base materials, a copper plate with a plate thickness of
0.3 mm was used. As a raw material vaporization source, an aluminum
target or an aluminum nitride target was used. A purity of each of
the targets was 99.9 mass % (3 N) or more. Flow rates of nitrogen
(N.sub.2) gas and helium (He) gas in a chamber to be
laser-irradiated to the raw material vaporization source were
adjusted to satisfy ratios shown in Table 1. Further, the laser was
output under conditions shown in Table 1. Furthermore, a pressure
in the vacuum chamber was set to 1.3.times.10.sup.-3 Pa or less.
Results thereof are shown in Table 1.
TABLE-US-00001 TABLE 1 Flow Rate of Nitrogen Gas/ (Flow Rate of Raw
Material Nitrogen Gas + Laser Film Vaporization Flow Rate of Output
Thickness Source (Target) Helium Gas) (W) (.mu.m) Example 1 Al 1 3
10 Example 2 Al 1 4 3 Example 3 Al 1 3.5 3 Example 4 AlN 0.8 4 3
Example 5 Al 1 4.5 14 Example 6 Al 1 4 12 Example 7 Al 1 3.6 2.5
Comparative AlN 0.1 3 30 Example 1 Comparative AlN 0.2 3 10 Example
2
[0041] In Comparative Example 1 and Comparative Example 2, [flow
rate of nitrogen gas/(flow rate of nitrogen gas+flow rate of helium
gas)] is less than 0.3. Regarding the aluminum nitrogen films
according to Examples and Comparative Examples, the withstand
voltage, the average grain diameter, and the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. based on the XRD analysis
were determined. The measurement of the withstand voltage was
performed based on JIS-C-2110-1 (2010). Further, the measurement
was performed in a manner that an AC dielectric breakdown voltage
was measured, and a voltage increase speed was set to 100 V/sec.
Furthermore, a combination of an upper electrode having a spherical
shape and a lower electrode having a disk shape was employed.
[0042] The measurement of the average grain diameter and the
diffraction peak through the XRD analysis was performed based on
the thin film method by setting an incident angle to 1.degree. or
less. As measurement conditions of XRD, a Cu target (K.alpha.-Cu)
was used, a tube voltage was set to 45 kV, and a tube current was
set to 200 mA. From results of the XRD analysis,
I.sub.43.5.degree./I.sub.33.2.degree. being an intensity ratio of
the diffraction peak I.sub.43.5.degree. to the diffraction peak
I.sub.33.2.degree. was determined. Further, the average grain
diameter was calculated, based on Scherrer equation, from a half
value width of a diffraction peak of hexagonal aluminum nitride
(PDF#25-1133 (100) plane). Further, a form factor k in the Scherrer
equation was set to 0.9. Results thereof are shown in Table 2.
TABLE-US-00002 TABLE 2 Withstand voltage Average Grain Intensity
Ratio (kV/mm) Diameter (nm) (I.sub.43.5.degree./I.sub.33.2.degree.)
Example 1 170 17 0.14 Example 2 200 18.2 0.33 Example 3 460 19 1.6
Example 4 230 20 0.8 Example 5 110 16.6 0.08 Example 6 120 30.2
0.09 Example 7 680 12 0.05 Comparative 1 28 0 Example 1 Comparative
57 16.1 0.002 Example 2
[0043] As can be seen from Table, the withstand voltage of each of
the aluminum nitride films according to Examples was 100 kV/mm or
more. Further, in each of the aluminum nitride films according to
Examples, the withstand voltage was able to be increased to 170
kV/mm or more when the intensity ratio
I.sub.43.5.degree./I.sub.33.2.degree. was 0.01 or more. As
described above, even when the film thickness of each of the
aluminum nitride films according to Examples was thin, the
excellent property of withstand voltage was able to be obtained.
For this reason, the aluminum nitride film can be used for
components in various fields such as a semiconductor element
mounting substrate, a substrate for heater, and a component for
semiconductor manufacturing apparatus.
[0044] In Comparative Example 1, metal aluminum was formed,
although an amount thereof was small, and thus the withstand
voltage was lowered. It can be considered that this is because the
nitriding of the raw material was insufficient since the nitrogen
gas was not used at the time of performing the laser irradiation on
the raw material vaporization source. Further, in Comparative
Example 2, the withstand voltage was lowered since the flow rate of
the nitrogen gas was insufficient and thus the nitriding treatment
was performed in an inhomogeneous manner.
[0045] While certain embodiments of the present invention have been
exemplified, these embodiments have been presented by way of
example only, and are not intended to limit the scope of the
inventions. Indeed, the novel embodiments described herein may be
embodied in a variety of other forms; furthermore, various
omissions, substitutions, changes, and the like in the form of the
embodiments described herein may be made without departing from the
spirit of the inventions. The accompanying claims and their
equivalents are intended to cover such forms or modification
examples as would fall within the scope and spirit of the
inventions. Further, the aforementioned respective embodiments can
be mutually combined to be carried out.
* * * * *