JP3312150B2 - Method of doping impurities into silicon carbide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for doping silicon carbide with impurities.

[0002]

2. Description of the Related Art SiC (silicon carbide) is easy to control p-type and n-type valence electrons, and is composed of Si (silicon) and GaAs.
(Gallium arsenide) has attracted attention as a material for a semiconductor device that can be used in various environments because it has many excellent physical properties that are not available in (gallium arsenide).

[0003] SiC has a larger band gap than Si or GaAs, and can maintain p-type or n-type up to a high temperature. Therefore, when SiC is used, a high-temperature operation device is realized. Further, since the saturation drift speed of electrons is high, high-frequency operation is possible and a large current can flow. Therefore, a high-frequency device and a high-power device can be realized. Furthermore, since it has a high dielectric breakdown field, a high breakdown voltage device can be realized.

[0004] Since SiC is rich in heat resistance and radiation resistance, it is expected to be used as a material for environment-resistant devices that can be used in severe environments such as nuclear reactors, space, oceans, and deep underground. Further, since SiC can be made into p-type and n-type by doping impurities, it is most promising as a material for a visible short-wavelength light-emitting device that emits blue or violet light or a sensor for detecting short-wavelength light such as ultraviolet light. Have been.

Conventionally, in order to dope a p-type or n-type impurity element into SiC, an ion implantation / annealing method or a method of doping an impurity element during epitaxial growth of SiC has been used.

In the ion implantation / annealing method, Si is used at room temperature.
After the impurity element is ion-implanted into C, the impurity element is doped into SiC by performing a high heat treatment at 1600 ° C. or higher. On the other hand, in the method of doping an impurity element during epitaxial growth of SiC, for example, CVD is used.
SiH ₄ (silane) and C ₃ H ₈ (propane) are reacted with each other by a chemical vapor deposition method to
While epitaxially growing SiC on a C substrate, p
Al (CH ₃ ) ₃ (trimethylaluminum) is added at the time of forming the mold, and N ₂ (nitrogen) or NH ₃ (ammonia) is added at the time of forming the n-type, and SiC is doped with an impurity element.

[0007]

When SiC is doped with a p-type or n-type impurity element by using the ion implantation / annealing method as described above, the ion implantation and annealing are performed.
Many defects are generated in the iC epitaxial layer, and the crystallinity is not completely restored even in the region where the ion implantation is performed even if annealing treatment is performed, and there is a problem that the activation rate of the implanted impurity element is low.

On the other hand, the method of doping an impurity element during epitaxial growth has a problem that the distribution of the doped impurity element is not uniform. Therefore, it has been desired to develop a method of uniformly doping an impurity element into SiC without impairing crystallinity and a method of doping an impurity element into SiC at a low temperature without impairing crystallinity.

Therefore, an object of the present invention is to provide a method for uniformly doping an impurity element into SiC without impairing its crystallinity. Another object of the present invention is to provide a method for doping an impurity element into SiC at a low temperature without impairing its crystallinity.

[0010]

According to a first aspect of the present invention, there is provided a method for doping impurities into silicon carbide, the method comprising irradiating the silicon carbide with gamma rays or neutron rays to obtain a predetermined isotope of the silicon isotopes in the silicon carbide. Is converted into an acceptor impurity or a donor impurity.

In particular, it is preferable to simultaneously irradiate the silicon carbide with laser light during irradiation with gamma rays or neutron rays. Further, the silicon carbide may be subjected to an annealing treatment after irradiation with gamma rays or neutron rays.

By controlling the energy or irradiation time of gamma rays or neutron rays, the doping amount of acceptor impurities or donor impurities can be controlled. In the method of doping silicon carbide with impurities according to the second invention, the same substrate is irradiated with positive or negative ions selected by mass separation from positive or negative ions of isotopes of silicon and negative or positive ions of carbon. Forming silicon carbide on the substrate by irradiating the silicon carbide on the substrate with gamma rays or neutron rays to convert predetermined isotopes of silicon isotopes in the silicon carbide into acceptor impurities or donor impurities. Things.

In particular, it is preferable to simultaneously irradiate the silicon carbide with laser light during irradiation with gamma rays or neutron rays. After the irradiation with gamma rays or neutron rays, the silicon carbide on the substrate may be subjected to an annealing treatment.

By controlling the energy or irradiation time of gamma rays or neutron rays, the doping amount of acceptor impurities or donor impurities can be controlled. The method of doping silicon carbide according to the third invention is to form an impurity element layer containing an impurity element on silicon carbide, and irradiate the impurity element layer with a high-energy electron beam. Is to be doped.

After the electron beam irradiation, the silicon carbide may be subjected to an annealing treatment. By controlling the irradiation time of the electron beam, the amount of the impurity element to be doped can be controlled.

[0016]

In the method of doping silicon carbide with impurities according to the first aspect of the invention, when silicon carbide is irradiated with gamma rays, silicon having a mass number of 28 among silicon isotopes in silicon carbide is converted into aluminum by a nuclear reaction. And become an acceptor impurity. In this case, the gamma ray has a mass number of 2
Reacts only with silicon 8 and not with other silicon isotopes. When silicon carbide is irradiated with a neutron beam, silicon having a mass number of 30 among silicon isotopes in silicon carbide is converted into phosphorus by a nuclear reaction and becomes a donor impurity. In this case, the neutron beam reacts only with silicon having a mass number of 30 and does not react with other silicon isotopes. Thus, the impurity element can be uniformly doped into the silicon carbide without substantially impairing the crystallinity of the silicon carbide.

In particular, when laser light is simultaneously irradiated on silicon carbide during irradiation with gamma rays or neutron rays, doping of acceptor impurities or donor impurities can be performed while removing damage to silicon carbide crystals by a photoreaction. Further, by performing annealing treatment on silicon carbide after irradiation with gamma rays or neutron rays, the crystallinity of the doped silicon carbide can be easily and almost completely recovered.

According to the method of doping silicon carbide with impurities according to the second aspect of the present invention, the positive or negative ion selected by mass separation from the positive or negative ion of silicon isotope and the negative or positive ion of carbon are the same. By irradiating on the substrate, silicon carbide containing a desired amount of a desired isotope of silicon is formed on the substrate. When silicon carbide on the substrate is irradiated with gamma rays, silicon having a mass number of 28 among silicon isotopes of silicon in silicon carbide is converted into aluminum by a nuclear reaction and becomes an acceptor impurity. Further, when neutron rays are irradiated on silicon carbide on the substrate, silicon having a mass number of 30 is converted into phosphorus by a nuclear reaction and becomes a donor impurity.
Thereby, a desired amount of the impurity element can be uniformly doped into the silicon carbide without substantially impairing the crystallinity of the silicon carbide.

In particular, when silicon carbide is irradiated with laser light simultaneously during irradiation with gamma rays or neutron rays, doping of acceptor impurities or donor impurities can be performed while removing damage to silicon carbide crystals by a photoreaction. Further, by subjecting silicon carbide on the substrate to an annealing treatment after irradiation with gamma rays or neutron rays, the crystallinity of silicon carbide can be easily and almost completely recovered.

According to the method of doping silicon carbide with impurities according to the third aspect of the present invention, the impurity element is doped on the silicon carbide at room temperature by irradiating the impurity element layer on the silicon carbide with a high energy electron beam. You. Thereby, without substantially impairing the crystallinity of silicon carbide,
In addition, impurities can be doped into silicon carbide at a low temperature.

In particular, by subjecting silicon carbide to an annealing treatment after irradiation with an electron beam, the crystallinity of silicon carbide can be almost completely recovered. When laser annealing is used as the annealing treatment, the crystallinity of silicon carbide can be easily recovered at a low temperature.

[0022]

Embodiment (1) First Embodiment FIGS. 1 and 2 are views showing an impurity doping method according to a first embodiment of the present invention. FIG. 1 shows a method of doping SiC with a p-type impurity, and FIG. 2 shows a method of doping SiC with an n-type impurity.

As shown in FIG. 1A, the SiC substrate 1
A ²⁸ Si ⁺ ion beam 3 and a ¹² C ⁻ ion beam 4 are simultaneously irradiated thereon. As a result, a ²⁸ Si ¹² C epitaxial layer 2 is formed on the SiC substrate 1 as shown in FIG. Thereafter, as shown in FIG. 1C, the ²⁸ Si ¹² C epitaxial layer 2 on the SiC substrate is irradiated with the gamma rays 5 and the excimer laser light 6 is irradiated in a pulsed manner. As a result, being damaged SiC crystal by photoreaction removed is converted to ²⁸ Si is ²⁷ Al of ²⁸ Si ¹² C epitaxial layer 2 by a nuclear reaction, as in shown in (d) of FIG. 1, SiC substrates ²⁷ Al dope on 1
^{The 28} Si ¹² C epitaxial layer 2a is formed. Doping of an acceptor impurity or a donor impurity can be performed.

As shown in FIG. 2A, the SiC substrate 1
1 is simultaneously irradiated with a ³⁰ Si ⁺ ion beam 13 and a ¹² C ⁻ ion beam 14. As a result, a ³⁰ Si ¹² C epitaxial layer 12 is formed on the SiC substrate 11 as shown in FIG. Thereafter, the ³⁰ Si ¹² C epitaxial layer 12 on the SiC substrate 11 is irradiated with the thermal neutron beam 15 and the excimer laser light 16 is irradiated in a pulsed manner. As a result, damage to the SiC crystal by photoreaction is converted into ³⁰ Si is ³¹ P in ³⁰ Si ¹² C epitaxial layer 12 by a nuclear reaction being removed, as shown in FIG. 2 (d), SiC substrate 11 ³¹ P dope on top ³⁰
An Si ¹² C epitaxial layer 12a is formed.

As the SiC substrates 1 and 11, 6H-Si
Single-crystal SiC substrates of various polytypes such as C and 3C-SiC can be used. Alternatively, a substrate on which single crystal SiC is epitaxially grown may be used.

In the impurity doping method of the present embodiment, the energy or the irradiation time of the gamma rays 5 and the thermal neutron rays 15 are controlled so that the SiC substrates 1 and 11 are controlled.
The doping amount of the impurity element therein can be controlled.

FIG. 3 is a schematic diagram of a material synthesizing apparatus used for forming a SiC epitaxial layer in this embodiment. Film quality 3
The substrate holder 32 is disposed in the substrate holder 1. Substrate holder 3
2, the SiC substrate 1 or 11 is mounted. Film quality 31
The inside is maintained in a vacuum state by a vacuum pump 33.

Positive ion source 34 generates Si positive ions, which are extracted at a predetermined voltage. Positive ions extracted from the positive ion source 34 are guided to a mass spectrometric electromagnet 35, and only desired positive ions are selected by mass separation and irradiated onto the SiC substrate 1 or 11 through a deceleration lens 36.

On the other hand, negative ions of C (carbon) are generated by the negative ion source 37 and are extracted at a predetermined voltage. Negative ions extracted from the negative ion source 37 are guided to a mass spectrometric electromagnet 38, and only desired negative ions are selected by mass separation and passed through a deceleration lens 39 to the SiC substrate 1 or 1.
Irradiated on 1

In front of the deceleration lenses 36 and 39, shutters 40a and 40b are provided to be openable and closable. The shutters 40a and 40b can be independently opened and closed at an arbitrary timing.

FIG. 4 is a schematic view of an energy beam irradiation apparatus used for irradiation of gamma rays or neutron rays and excimer laser light in this embodiment. Quartz glass windows 42 and 43 are provided at predetermined locations in the reaction chamber 41, and a substrate holder 44 is installed in the reaction chamber 41. The substrate holder 44 has the SiC substrate 1
Or 11 is attached. Vacuum pump 4 inside reaction chamber 41
5 keeps the vacuum.

A gamma ray 5 generated from a gamma ray source (not shown) or a neutron ray 15 generated from a neutron ray source (not shown) passes through a quartz glass window 42 and the SiC substrate 1 or 11 in the reaction chamber 41. Excimer laser beams 6 and 16 emitted from an excimer laser (not shown)
Irradiate the iC substrate 1 or 11.

In this example, a plurality of samples were prepared using the substance synthesizing apparatus shown in FIG. 3 and the energy ray irradiation apparatus shown in FIG. 4 under the following conditions. The gamma ray 5 and the thermal neutron ray 15 were irradiated using a nuclear reactor of Kyoto University (Kumatori-cho, Osaka).

Table 1 shows the conditions for forming the ²⁸ Si ¹² C epitaxial layer 2 in this embodiment.

[0035]

[Table 1]

As shown in Table 1, as the SiC substrate 1, 6
An H-SiC single crystal substrate was used. FIG. 3 shows the SiC substrate 1
Attached to the substrate holder 32 of the material synthesizing apparatus shown
The inside of the film forming chamber 31 was maintained at a high vacuum by the pump 33. Deposition chamber
The ultimate pressure in 31 is 5 × 10 ^-TenTorr. Correct
Silicon tetrachloride (SiCl_Four) Introduce gas
And the negative ion source 37 receives carbonic acid (CO_Two) Gas
And positive ions of Si are generated by the positive ion source 34.
Then, negative ions of C were generated by the negative ion source 37.
In addition, instead of silicon tetrachloride gas, silane (SiH_Four)
Gas may be used.

Positive ions were extracted from the positive ion source 34 at a voltage of −20 kV, and only ²⁸ Si ⁺ was selected and guided into the film forming chamber 31 by the mass spectrometric electromagnet 35. Negative ion source 3
Negative ions were extracted from 7 at a voltage of 20 kV, and only ¹² C ⁻ was selected by the mass spectrometry electromagnet 38 and guided into the film forming chamber 31. ²⁸ Si ⁺ and ¹² C ^- of 50eV kinetic energy by the respective deceleration lens 36, 39 in the film forming chamber 31
And the shutters 40a and 40b were simultaneously opened to irradiate the SiC substrate 1 at the same time. The incident angles of ²⁸ Si ⁺ and ¹² C ⁻ with respect to the SiC substrate 1 were each set to 30 °. At this time, the ion current value of ²⁸ Si ⁺ and ¹² C
^- the ion current value were respectively 60 .mu.A. The substrate temperature was kept at room temperature.

In this manner, a film having a thickness of 1
A 00 nm ²⁸ Si ¹² C epitaxial layer 2 was formed.
Thereafter, the ²⁸ Si ¹² C epitaxial layer 2 on the SiC substrate 1 was irradiated with gamma rays 5 and excimer laser light 6 using the energy ray irradiation apparatus shown in FIG.

Table 2 shows the irradiation conditions of the gamma rays 5 and the excimer laser light 6.

[0040]

[Table 2]

As shown in Table 2, the pressure in the reaction chamber 41 was maintained at 10 ^-3 to 10 ^-6 Torr, and the gamma rays 5 were irradiated on the ²⁸ Si ¹² C epitaxial layer 2 on the SiC substrate 1 for one minute. At the same time, a KrF excimer laser is used as an excimer laser, and excimer laser light 6 having a wavelength of 248 nm is
Light was condensed on an area of the C substrate 1 having a diameter of 5 mm. SiC substrate 1
The energy density of the laser light above was 1 J / cm ² . Irradiation of 10 shots (shots) at 1 Hz was repeated every 10 shots for 1 msec during the irradiation of the gamma rays 5.
The half width of each pulse was 17 ns. During the irradiation with the gamma rays 5 and the excimer laser beam 6, the SiC substrate 1 was kept at room temperature. In this manner, ²⁷ Al doping is performed on the SiC substrate 1.
^{The 28} Si ¹² C epitaxial layer 2a was formed.

Table 3 shows the conditions for forming the ³⁰ Si ¹² C epitaxial layer 12 in this embodiment.

[0043]

[Table 3]

As shown in Table 3, as the SiC substrate 11,
A 6H-SiC single crystal substrate was used. Positive and negative ions
ON ion source, ultimate pressure, extraction voltage, kinetic energy
And substrate temperature²⁸Si¹²C epitaxial layer 2
It is the same as when forming. Here, the pulling from the positive ion source 34 is performed.
Of the extracted positive ions by the mass spectrometric electromagnet 35 ³⁰
Si⁺Only into the film formation chamber 11 and
Of negative ions extracted from the ion source 37
By stone 38¹²C^-Select only and lead it into the deposition chamber 31
Was.³⁰Si⁺Ion current value and¹²C^-The current value of
Each was 20 μA.

In this way, a ³⁰ Si ¹² C epitaxial layer 12 having a thickness of 90 nm was formed on the SiC substrate 11. After that, using the energy ray irradiation device of FIG.
The ³⁰ Si ¹² C epitaxial layer 12 on the C substrate 11 was irradiated with a neutron beam 15 and an excimer laser beam 16.

Table 4 shows the irradiation conditions of the neutron beam 15 and the excimer laser beam 16.

[0047]

[Table 4]

As shown in Table 4, the pressure in the reaction chamber 41 was maintained at 10 ^-3 to 10 ^-6 Torr, and the neutron beam 15 was
The ³⁰ Si ¹² C epitaxial layer 12 on the substrate 11 was irradiated for 10 seconds. At the same time, under the same irradiation conditions at the time of formation of the excimer laser beam 16 ²⁷ Al-doped ²⁸ Si ¹² C epitaxial layer 2a, and irradiated in the irradiation of the neutron beam 15. Thus, a ³¹ P-doped ³⁰ Si ¹² C epitaxial layer 12 a was formed on the SiC substrate 11.

The prepared sample was analyzed using a secondary ion mass spectrometer (SIMS) and a transmission electron microscope (TEM). FIG. 5 shows the results of analysis by the secondary ion mass spectrometer. Figure 5 (a) shows the distribution in the depth direction of the ²⁷ Al-doped ²⁸ Si ¹² C epitaxial layer 2a on the SiC substrate 1, (b) in FIG. 5 ³¹ P-doped on SiC substrate 11
The distribution in the depth direction of the ³⁰ Si ¹² C epitaxial layer 12a is shown.

[0050] As can be seen from FIG. 5 (a), ²⁷ in the Al-doped ²⁸ Si ¹² C epitaxial layer 2a, ²⁷ A
1 is doped to a depth of about 50 nm from the surface.
As can be seen from FIG. 5B, ³¹ P-doped ³⁰ S
In the i ¹² C epitaxial layer 12a, ³¹ P is doped to a depth of about 40 nm from the surface.

Further, from observation with a transmission electron microscope,
6H- on SiC substrate 1 and SiC substrate 11 respectively.
It was confirmed that the ²⁸ Si ¹² C layer and the 6H- ³⁰ Si ¹² C layer were epitaxially grown.

Thereafter, ²⁷ Al doped ^{28 is} deposited on the SiC substrate 1.
The plurality of samples having the Si ¹² C epitaxial layer 2a formed thereon and the plurality of samples having the ³¹ P-doped ³⁰ Si ¹² C epitaxial layer 12a formed on the SiC substrate 11
Annealing of the electric furnace at 1 ° C. for 1 hour, lamp annealing at 1050 ° C. for 2 minutes, and laser annealing at room temperature and 200 ° C. for 1 minute were performed, respectively. In the laser annealing, excimer laser light was irradiated in a pulse shape at an energy density of 1 J / cm ² .

When the crystallinity was measured by the RBS (Rutherford backscattering) method, Δmin (the ratio of the yield from a certain axis of the crystal to the random yield) was about 4% for all the samples. Recovery of crystallinity in the ²⁸ Si ¹² C epitaxial layer and the ³⁰ Si ¹² C epitaxial layer was confirmed.

As described above, according to the doping method of the present embodiment, a pn junction can be easily formed on a SiC substrate, so that various SiC devices can be easily manufactured at room temperature. Become. (2) Second Embodiment FIG. 6 is a view showing an impurity doping method according to a second embodiment of the present invention. As shown in FIG.
After depositing an impurity element layer 22 containing a p-type or n-type impurity element on the substrate 21, the surface of the impurity element layer 22 on the SiC substrate 21 is irradiated with a high-energy electron beam 24 at room temperature.

As a result, as shown in FIG. 6B, the impurity element in the impurity element layer 22 is doped into the SiC substrate 21, and the impurity doped layer 23 is formed on the SiC substrate 21 below the impurity element layer 22. You.

As the SiC substrate 21, similarly to the first embodiment, single-crystal SiC substrates of various polytypes such as 6H-SiC and 3C-SiC can be used. Alternatively, a substrate on which single crystal SiC is epitaxially grown may be used.

For example, when doping Al as a p-type impurity, Al
It is deposited on the substrate 21. When doping B (boron) as a p-type impurity, B ₂ O ₃ (boron oxide) is deposited on the SiC substrate 21 as the impurity element layer 22.

In the impurity doping method of this embodiment, the doping amount of the impurity element in the SiC substrate 21 can be controlled by controlling the irradiation time of the high energy electron beam 24.

In this example, a plurality of samples were prepared under the following conditions. Table 5 shows the manufacturing conditions of the sample in this example.

[0060]

[Table 5]

As shown in Table 5, a 6H-SiC single crystal substrate was used as the SiC substrate 21, and a 200-500 nm thick AlC was deposited on the surface of the SiC substrate 21 in the reaction chamber.
Was formed. The degree of vacuum in the reaction chamber during vapor deposition was 1-2 × 10 ⁻⁶ Torr.

Thereafter, the surface of the impurity element layer 22 on the SiC substrate 21 was irradiated with an electron beam 24 of 42 MeV in the air. The irradiation time of the electron beam 24 is 5 to 30 seconds.
During the irradiation of No. 4, the SiC substrate 21 was kept at room temperature. afterwards,
HF (hydrogen fluoride) and HNO
₃ (Nitric acid) in a 1: 1 mixture or HNO ₃
Immersion in a 70-90% solution of
2 was removed.

The SiC doped with Al as described above
The Al distribution in the depth direction of the substrate 21 was measured by a secondary ion mass spectrometer (SIMS). FIG. 7 shows Al in the depth direction.
It is a figure showing the measurement result of distribution. FIG. 7 shows that Al atoms are doped to a depth of about 400 nm from the surface of the SiC substrate 21.

The plurality of samples thus prepared are:
Electric furnace annealing at 1300 ° C for 1 hour, 2 at 1050 ° C
Lamp anneal for 1 minute and 1 at room temperature and 200 ° C.
Laser annealing was performed for each minute. In laser annealing, excimer laser light is applied at an energy density of 1 J / cm.
Irradiation was carried out in pulse form at ² .

When the crystallinity of these samples was measured by the RBS (Rutherford backscattering) method, Δmin (the ratio of the yield from a crystal axis to the random yield) was about 4%,
Recovery of crystallinity in the impurity-doped layer was confirmed.

As described above, according to the doping method of this embodiment, a pn junction can be formed on the SiC substrate 21 at room temperature, so that various SiC devices can be easily manufactured at room temperature. become.

[0067]

According to the first aspect of the present invention, silicon carbide can be uniformly doped with acceptor impurities or donor impurities without substantially impairing the crystallinity of silicon carbide. Therefore, it becomes easy to manufacture semiconductor devices that can be used in various environments. In particular, by irradiating laser light simultaneously with gamma rays or neutron rays,
Impurity doping can be performed while removing damage to silicon carbide crystals. Further, by subjecting silicon carbide to an annealing treatment after irradiation with gamma rays or neutron rays, the crystallinity of silicon carbide can be easily and almost completely recovered.

According to the second aspect of the present invention, the impurity element can be uniformly doped into the silicon carbide while the crystallinity of the silicon carbide is hardly impaired and the concentration is precisely controlled. Therefore, it becomes easy to manufacture semiconductor devices that can be used in various environments.

According to the third aspect of the invention, silicon carbide can be doped with an impurity element at a low temperature without substantially impairing the crystallinity of silicon carbide. Therefore,
Manufacturing of semiconductor devices that can be used in various environments is facilitated. Further, by performing an annealing treatment on the silicon carbide after the irradiation with the electron beam, the crystallinity of the silicon carbide can be easily and almost completely recovered.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a method of doping a p-type impurity according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a method of doping an n-type impurity according to a first embodiment of the present invention.

FIG. 3 is a schematic view of a material synthesizing apparatus used for forming a SiC epitaxial layer in the first embodiment.

FIG. 4 is a schematic diagram of an energy ray irradiation device used for irradiation of gamma rays or neutron rays and excimer laser light in the first embodiment.

FIG. 5 shows Al-doped SiC in the first embodiment.
Measurement result of depth distribution of epitaxial layer and P
It is a figure showing the measurement result of distribution of the depth direction of a doped SiC epitaxial layer.

FIG. 6 is a view illustrating an impurity doping method according to a second embodiment of the present invention.

FIG. 7 shows Al-doped SiC in the second embodiment.
FIG. 5 is a diagram showing a measurement result of Al distribution in a depth direction of a substrate.

[Description of Signs] 1 SiC substrate 2 ²⁸ Si ¹² C epitaxial layer 2 a ²⁷ Al-doped ²⁸ Si ¹² C epitaxial layer 3 ²⁸ Si ⁺ ion beam 4 ¹² C ⁻ ion beam 5 gamma ray 6 excimer laser beam 11 SiC substrate 12 ³⁰ Si ¹² C epitaxial layer 12 a ³¹ P doped ³⁰ Si ¹² C epitaxial layer 13 ³⁰ Si ⁺ ion beam 14 ¹² C ⁻ ion beam 15 neutron beam 16 excimer laser beam 21 SiC substrate 22 impurity element layer 23 impurity doped layer 24 electron beam

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshitake Nakata 4547-15, Tsuda, Oji, Hirakata City, Osaka Prefecture (72) Inventor Masanori Watanabe 4547-15, Tsuda, Oaza, Hirakata City, Osaka Aeon Co., Ltd. Examiner in the Institute of Engineering Akihiro Kunishima (56) References JP-A-57-111018 (JP, A) JP-A-52-70754 (JP, A) JP-A 8-264468 (JP, A) JP-A 8- 148443 (JP, A) JP-A-7-106267 (JP, A) JP-A-6-64914 (JP, A) JP-A-6-61261 (JP, A) JP-A-6-20982 (JP, A) JP-A-5-117088 (JP, A) JP-A-4-168722 (JP, A) JP-A-4-139721 (JP, A) JP-A-3-129883 (JP, A) JP-A-2-253622 (JP, A) JP-A-1-132120 (JP, A) JP-A Sho 62-257723 (JP, A) JP-A 62-95820 (JP, A) JP-A 60-176981 (JP, A) JP-A 57-72320 (JP, A) JP-A 50-126168 (JP, A) A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/261 C30B 29/36 C30B 31/20 H01L 21/22

Claims (4)

(57) [Claims] 1. A method according to claim 1, wherein a predetermined isotope of silicon isotopes in the silicon carbide is converted into an acceptor impurity or a donor impurity by irradiating the silicon carbide with gamma rays or neutron rays. Impurity doping method. 2. The method of doping silicon carbide according to claim 1, wherein the silicon carbide is simultaneously irradiated with a laser beam during the irradiation of the gamma rays or neutron rays. 3. The method of doping silicon carbide according to claim 1, wherein the silicon carbide is annealed after the irradiation with the gamma rays or neutron rays. 4. Irradiating a positive or negative ion selected from a positive or negative ion of a silicon isotope by mass separation and a negative or positive ion of carbon onto the same substrate to form silicon carbide on the substrate. Forming, by irradiating the silicon carbide on the substrate with a gamma ray or a neutron beam, a predetermined isotope of silicon isotopes in the silicon carbide into an acceptor impurity or a donor impurity. Method of doping silicon with impurities.