WO2023199954A1 - Method for manufacturing impurity-doped semiconductor - Google Patents

Method for manufacturing impurity-doped semiconductor Download PDF

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WO2023199954A1
WO2023199954A1 PCT/JP2023/014925 JP2023014925W WO2023199954A1 WO 2023199954 A1 WO2023199954 A1 WO 2023199954A1 JP 2023014925 W JP2023014925 W JP 2023014925W WO 2023199954 A1 WO2023199954 A1 WO 2023199954A1
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semiconductor
impurity
doped
manufacturing
diamond
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French (fr)
Japanese (ja)
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広樹 奥野
泰斗 三宅
正 神原
敦 吉田
幸志 渡邊
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国立研究開発法人理化学研究所
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/04—Diamond
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B31/00—Diffusion or doping processes for single crystals or homogeneous polycrystalline material with defined structure; Apparatus therefor
    • C30B31/20—Doping by irradiation with electromagnetic waves or by particle radiation
    • C30B31/22—Doping by irradiation with electromagnetic waves or by particle radiation by ion-implantation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/20—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy
    • H01L21/2003—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy characterised by the substrate
    • H01L21/2015—Deposition of semiconductor materials on a substrate, e.g. epitaxial growth solid phase epitaxy characterised by the substrate the substrate being of crystalline semiconductor material, e.g. lattice adaptation, heteroepitaxy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/26—Bombardment with radiation
    • H01L21/261—Bombardment with radiation to produce a nuclear reaction transmuting chemical elements

Definitions

  • the present invention relates to a method for manufacturing an impurity-doped semiconductor.
  • Diamond is a wide band gap semiconductor with excellent dielectric breakdown strength and thermal conductivity, and a band gap of 5.5 eV. Wide bandgap semiconductors have excellent power conversion efficiency, so they can make a significant contribution to energy conservation. Furthermore, due to its physical properties, diamond semiconductors are thought to be able to achieve higher frequencies and higher output than conventional semiconductors, and are expected to enable high-capacity communications exceeding that of the fifth generation mobile communication system (5G). There is. Recently, high expectations and interest have been growing as it will become possible to perform imaging and sensing with sensitivity and spatial resolution that cannot be surpassed by extending conventional development technologies, and demonstrations of sensing of magnetism, temperature, electric fields, etc. have been held. ing.
  • Non-Patent Documents 1 and 2 In order for diamond to act as an n-type semiconductor, it is necessary to implant a pentavalent element such as phosphorus (P) as a donor, and in fact, research and development of P-implanted n-type semiconductor diamond is progressing.
  • P phosphorus
  • the donor level of P is about 0.6 eV, it is difficult to operate at room temperature, and there are restrictions on the environment in which it can be used.
  • the donor level of lithium (Li) is even shallower, about 0.1 eV, and that an n-type semiconductor capable of operating at room temperature can be manufactured (Non-Patent Documents 1 and 2).
  • Methods for injecting substances into diamond include chemical vapor deposition (CVD) and solid phase diffusion.
  • CVD chemical vapor deposition
  • the CVD method is a method in which diamond and the substance to be implanted are mixed in a gaseous state and incorporated simultaneously with crystal growth, but Li is highly reactive with water and air and is difficult to implant by CVD.
  • solid-phase diffusion method a substance is applied to the surface of diamond and heated to diffuse and inject the substance, but Li hardly diffuses in diamond, and this method also has problems.
  • Patent Document 1 In order to solve such problems, doping methods using nuclide transmutation have been proposed (Patent Document 1, Non-Patent Document 3).
  • Non-Patent Document 3 Popovici et al. report a study using nuclide transmutation of boron (B).
  • B A similar method is also proposed in Patent Document 1.
  • Diamond easily incorporates B even in nature, and operates as a p-type semiconductor, and B doping technology has also been established.
  • B has a characteristic that it has a very large absorption cross section for slow neutrons, and when irradiated with slow neutrons, only the B atoms in the crystal are converted into Li atoms through the reaction of 10 B(n, ⁇ ) 7 Li. It is possible to do so.
  • Direct ion implantation of Li into diamond can be considered, but since Li does not thermally diffuse in diamond, it is necessary to implant with high energy of several MeV to distribute Li evenly throughout diamond (see Figure 5). ). For this reason, lattice defects occur in diamond during ion implantation, and it is expected that it will be difficult for Li to function as a donor in the same way as when boron is used.
  • gallium oxide (Ga 2 O 3 ) is also a wide bandgap semiconductor and, like diamond, is a material for power devices. Since it is relatively easy to grow high-quality single crystals of gallium oxide, it is possible to supply devices with higher performance than Si devices to the market at a lower price than silicon carbide (SiC) and gallium nitride (GaN). It is expected that it will be possible.
  • Ga 2 O 3 becomes n-type when doped with Si or Sn, and the manufacturing technology for n-type semiconductors has been established.
  • p-type doping technology since p-type doping technology has not yet been established, it is necessary to devise device structures and consider introducing alternative p-type layers.
  • an object of the present invention is to provide a new method of doping impurities into a semiconductor.
  • One aspect of the present invention is a method for manufacturing an impurity-doped semiconductor, comprising: a first step of preparing a semiconductor doped with a radioactive isotope of an impurity different from the final impurity; A second step of converting the nuclide into an impurity.
  • beta decay is a type of nuclear decay, and includes electron capture without high-speed electron or positron emission, negative electron decay, and positron decay.
  • the final impurity can be doped by doping the semiconductor with a radioisotope that is easy to dope and then transmuting the nuclide by beta decay.
  • a semiconductor doped with is easily obtained.
  • the radiation emitted during nuclear decay does not cause many defects in the semiconductor lattice.
  • electron capture emits electron neutrinos that are electrically neutral and have almost zero mass, but does not emit high-energy radiation to the outside that would cause defects in the semiconductor lattice. Therefore, it is expected that electron capture does not cause lattice defects and the final impurity functions as a donor.
  • the first step may include the steps of irradiating the surface layer of the semiconductor with the radioisotope, and diffusing the irradiated radioisotope into the semiconductor by thermal diffusion. good.
  • the first step may further include a step of removing a defective portion of the semiconductor due to the irradiation, before or after the diffusing step.
  • the first step includes a step of preparing a solution in which the semiconductor and the radioisotope are dissolved, and a step of producing a crystal containing the semiconductor and the radioisotope using the solution. , may also be included.
  • the semiconductor may be diamond, the final impurity may be 7 Li, and the radioisotope may be 7 Be.
  • the semiconductor may be Ga2O3 , the final impurity may be 67Zn , and the radioisotope may be 67Ga .
  • FIG. 1 is a diagram illustrating a manufacturing method of Embodiment 1.
  • FIG. 3 is a diagram illustrating the experimental results of Embodiment 1.
  • FIG. 7 is a diagram illustrating a manufacturing method of Embodiment 2.
  • FIG. 7 is a diagram illustrating a manufacturing method of Embodiment 3. It is a figure explaining the manufacturing method of a conventional example.
  • the present invention involves doping with a radioactive isotope of an impurity whose nuclide is different from that which is easy to dope, and then the radioisotope is released by nuclear decay.
  • This method of manufacturing an impurity-doped semiconductor is characterized by waiting for the nuclide to be converted into a target dopant. Since beta decay does not generate radiation that would cause semiconductor defects, it is expected that the dopant will function as a donor without causing defects in the semiconductor lattice.
  • the radioactive isotope is required to be transmuted into the intended dopant through nuclear decay and to be easy to dope into semiconductors, but other conditions are not particularly imposed.
  • the semiconductor doped with a radioactive isotope may be prepared by any method.
  • This embodiment is a method for manufacturing an n-type diamond semiconductor in which a diamond semiconductor is doped with lithium (Li).
  • a Li-doped diamond semiconductor is manufactured using nuclide transmutation of 7 Be, which is a radioactive isotope of beryllium (Be), by nuclear decay of 7 Be ⁇ 7 Li.
  • FIG. 1 is a diagram explaining this embodiment. This embodiment will be described below with reference to FIG.
  • 7 Be is created using an accelerator, and a 7 Be ion beam is irradiated onto a diamond substrate using an RI ion implantation device.
  • ions are implanted only into the surface layer of the diamond substrate with an energy of about several tens of keV (100 keV or less, more preferably 30 keV or less).
  • heat treatment is performed to diffuse 7Be into the diamond substrate other than the surface layer by thermal diffusion.
  • a diamond substrate doped with 7 Be can be obtained. Because 7Be is distributed using thermal diffusion, lattice defects do not occur, and the surface layer where defects can occur is removed by ion implantation, so a 7Be -doped diamond semiconductor without lattice defects is finally obtained. .
  • Electron capture is a reaction of 7 Be + e ⁇ ⁇ 7 Li + ⁇ e , in which electrons outside the nucleus are captured by the nucleus and electron neutrinos are released. Since electron capture occurs naturally, the 7 Be-doped diamond semiconductor can be left alone. Furthermore, since the half-life is 53.2 days, if it is left for more than 7 half-lives (approximately 372 days), 99% will be converted to 7Li .
  • the electron neutrinos emitted by electron capture have relatively high energy, they are electrically neutral and have extremely close to zero mass, so it is assumed that they will not cause defects in the diamond lattice. Since there are no lattice defects, 7 Li is expected to function as a donor and function as an n-type semiconductor.
  • BeO beryllium oxide
  • BeO negative ion beam was loaded into a cesium sputter type negative ion source to generate a BeO negative ion beam.
  • BeO ions were accelerated to an energy of about 20 keV, and after mass separation, the ions were implanted into the diamond sample.
  • the diamond into which Be was ion-implanted was heat-treated at about 800° C. in a nitrogen atmosphere using the RTA method (Rapid Thermal Annealing).
  • Figure 2 shows the distribution of Be in diamond after performing RTA for 1 hour, 13 hours, and 36 hours on the same sample into which Be was ion-implanted, showing the thermal diffusion of Be in diamond due to RTA treatment. was observed. Note that although this experiment used the stable isotope 9 Be, the results would not change even if the radioactive isotope 7 Be was used.
  • the surface layer portion where lattice defects may occur due to ion implantation can be removed, and thermal diffusion does not cause lattice defects, resulting in a 7 Be-doped diamond semiconductor having no lattice defects. After waiting for 7 Be to decay, a 7 Li-doped diamond semiconductor is obtained.
  • the present embodiment is a method for manufacturing an n-type diamond semiconductor in which a diamond semiconductor is doped with lithium (Li), as in the first embodiment. They are the same in that a 7 Be-doped diamond semiconductor is prepared and nuclide conversion is performed by electron capture, but the process for preparing the 7 Be-doped diamond semiconductor is different. In this embodiment, a microwave plasma CVD method is used.
  • FIG. 3 is a diagram explaining this embodiment.
  • a diamond crystal is grown by a microwave plasma CVD method using a microwave plasma CVD apparatus.
  • a rod (or a tray loaded with powder) made of 7 Be is supported on the feedthrough and inserted into the plasma.
  • the rod is etched in the plasma, and 7Be is diffused into the atmosphere.
  • the diffused 7 Be is incorporated into the crystal as the diamond grows, and a diamond semiconductor doped with 7 Be is obtained.
  • the doping concentration can be controlled by the insertion distance of the rod (or tray).
  • a high pressure and high temperature method may be used instead of the microwave plasma CVD method.
  • HPHT high pressure and high temperature method
  • 7 Be may be thermally diffused into the diamond by introducing 7 Be into the furnace.
  • This embodiment is a method for manufacturing a p-type semiconductor in which gallium oxide (Ga 2 O 3 ) is doped with zinc (Zn).
  • gallium oxide Ga 2 O 3
  • Zn zinc
  • nuclide conversion 67 Ga +e ⁇ ⁇ 67 Zn + ⁇ e
  • FIG. 4 is a diagram explaining this embodiment.
  • a target containing Zn or a target enriched with 67 Zn is irradiated with a proton beam to generate 67 Ga by a 67 Zn(p,n) 67 Ga reaction.
  • targets containing 67 Ga and Zn are dissolved.
  • Ga and Zn coexist and changing the pH Ga is selectively extracted.
  • the extracted Ga is mixed with a Ga raw material melt, and Ga 2 O 3 crystals are created by the Czochralski (CZ) method, the floating zone (FZ) method, the EFG (edge-defined growth) method, or the like. As a result, a Ga 2 O 3 crystal doped with 67 Ga is obtained.
  • CZ Czochralski
  • FZ floating zone
  • EFG edge-defined growth
  • the present invention has been described above with reference to specific examples, the present invention is not limited to the above.
  • the step of preparing a semiconductor doped with a radioactive isotope before nuclide conversion may be performed by a method other than the above.
  • Li doping into a diamond semiconductor and Zn doping into a gallium oxide semiconductor have been described, this does not preclude the use of semiconductor substrates and dopants other than those described above.
  • Ga 2 O 3 may be doped with 67 Ga using the methods of Embodiments 1 and 2, and Zn-doped Ga 2 O 3 may be created by nuclide conversion.
  • diamond may be doped with 67 Ga using the methods of Embodiments 1 and 2, and Zn-doped diamond may be created by nuclide transmutation.
  • Ga 2 O 3 may be doped with 7 Be using the method of Embodiment 1-3 to create Li-doped Ga 2 O 3 through nuclide transmutation.
  • nuclear decay the radiation emitted by nuclide transmutation by negative electron decay and positron decay (these are examples of beta decay) is thought not to cause lattice defects in semiconductor crystals, so it can produce the same effect as electron capture. It will be done.

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Abstract

Provided is a method for manufacturing an impurity-doped semiconductor, the manufacturing method comprising: a first step in which a semiconductor doped with a radioactive isotope of an impurity differing from a final impurity is prepared; and a second step in which the radioactive isotope is nuclide-transformed through beta decay to the final impurity. Through the manufacturing method of the present invention, a semiconductor doped with a final impurity that is difficult to directly dope can be manufactured. The first step may comprise a step for irradiating a surface layer of the semiconductor with the radioactive isotope, and a step for diffusing the irradiated radioactive isotope into the semiconductor through thermal diffusion. The first step may further include, before or after the diffusion step, a step for removing a defective portion of the semiconductor caused by the irradiation. For example, the semiconductor may be diamond, the final impurity may be 7Li, and the radioactive isotope may be 7Be.

Description

不純物ドープ半導体の製造方法Method for manufacturing impurity-doped semiconductors
　本発明は、不純物ドープ半導体の製造方法に関する。 The present invention relates to a method for manufacturing an impurity-doped semiconductor.
　ダイヤモンドは絶縁破壊強度や熱伝導度が優れ、バンドキャップが５．５ｅＶのワイドバンドギャップ半導体である。ワイドバンドギャップ半導体は電力の変換効率に優れるため、省エネルギーに大きく貢献することが可能とされる。さらに、ダイヤモンド半導体はその物性から、従来の半導体よりも高周波化、高出力化を実現できると考えられ、第五世代移動通信システム（５Ｇ）を超える大容量の通信も実現可能になると期待されている。最近では、従来の開発技術の延長では超えられない感度と空間分解能を持つイメージングやセンシングが可能になるとして、高い期待と関心が高まっており、磁気・温度・電場等のセンシングのデモンストレーションが行われている。 Diamond is a wide band gap semiconductor with excellent dielectric breakdown strength and thermal conductivity, and a band gap of 5.5 eV. Wide bandgap semiconductors have excellent power conversion efficiency, so they can make a significant contribution to energy conservation. Furthermore, due to its physical properties, diamond semiconductors are thought to be able to achieve higher frequencies and higher output than conventional semiconductors, and are expected to enable high-capacity communications exceeding that of the fifth generation mobile communication system (5G). There is. Recently, high expectations and interest have been growing as it will become possible to perform imaging and sensing with sensitivity and spatial resolution that cannot be surpassed by extending conventional development technologies, and demonstrations of sensing of magnetism, temperature, electric fields, etc. have been held. ing.
　このように、ダイヤモンド半導体を新産業として確立できれば、様々な面でこれからの社会の豊かさを実現することが期待される。ただし、いずれの技術にもダイヤモンドを「ｎ型半導体」として作用させることのブレークスルーが鍵となっている。 In this way, if diamond semiconductors can be established as a new industry, it is expected that future society will be enriched in various ways. However, the key to both technologies is the breakthrough in making diamond act as an "n-type semiconductor."
　ダイヤモンドをｎ型半導体として作用させるには、リン（Ｐ）などの５価元素をドナーとして注入する必要があり、実際、Ｐを注入したｎ型半導体ダイヤモンドの研究開発が進められている。しかしながら、Ｐのドナー準位は０．６ｅＶ程度なので、室温で動作させることは難しく、使用環境に制限がある。一方、リチウム（Ｌｉ）のドナー準位は０．１ｅＶ程度とさらに浅く、室温動作を可能とするｎ型半導体を作製できることが理論的に提案されている（非特許文献１，２）。 In order for diamond to act as an n-type semiconductor, it is necessary to implant a pentavalent element such as phosphorus (P) as a donor, and in fact, research and development of P-implanted n-type semiconductor diamond is progressing. However, since the donor level of P is about 0.6 eV, it is difficult to operate at room temperature, and there are restrictions on the environment in which it can be used. On the other hand, it has been theoretically proposed that the donor level of lithium (Li) is even shallower, about 0.1 eV, and that an n-type semiconductor capable of operating at room temperature can be manufactured (Non-Patent Documents 1 and 2).
　ダイヤモンド中に物質を注入する方法として、化学気相堆積（ＣＶＤ： chemical vapor deposition）法や固相拡散法がある。ＣＶＤ法はダイヤモンドと注入したい物質を気体の状態で混合し、結晶成長と同時に取り込ませる手法であるが、Ｌｉは水や空気との反応性が高く、ＣＶＤによって注入することは困難である。固相拡散法では、ダイヤモンドの表面に物質を塗布し、熱を加えることで物質を拡散注入させる手法であるが、ダイヤモンド中においてＬｉはほとんど拡散せず、こちらの方法でも問題がある。 Methods for injecting substances into diamond include chemical vapor deposition (CVD) and solid phase diffusion. The CVD method is a method in which diamond and the substance to be implanted are mixed in a gaseous state and incorporated simultaneously with crystal growth, but Li is highly reactive with water and air and is difficult to implant by CVD. In the solid-phase diffusion method, a substance is applied to the surface of diamond and heated to diffuse and inject the substance, but Li hardly diffuses in diamond, and this method also has problems.
　このような問題を解決するために、核種変換を用いたドープ方法が提案されている（特許文献１、非特許文献３）。非特許文献３において、Popoviciらはホウ素（Ｂ）の核種変換を利用した研究を報告している。また、同様の手法が特許文献１でも提案されている。ダイヤモンドは天然でもＢが取り込まれやすく、ｐ型半導体として動作し、Ｂのドーピング技術も確立されている。加えて、Ｂは低速中性子の吸収断面積が非常に大きい特徴があり、低速中性子を照射して結晶内のＢ原子のみを１０Ｂ（ｎ，α）７Ｌｉの反応により、Ｌｉ原子に核種変換することが可能である。しかしながら、この核反応で放出されるα線は数ＭｅＶ程度のエネルギーを持ち、ダイヤモンドの格子構造に欠損を生じさせる。このため、Popoviciらの研究ではＬｉを注入したダイヤモンドが作製されたが、Ｌｉがドナーとして機能することは確認できていない。 In order to solve such problems, doping methods using nuclide transmutation have been proposed (Patent Document 1, Non-Patent Document 3). In Non-Patent Document 3, Popovici et al. report a study using nuclide transmutation of boron (B). A similar method is also proposed in Patent Document 1. Diamond easily incorporates B even in nature, and operates as a p-type semiconductor, and B doping technology has also been established. In addition, B has a characteristic that it has a very large absorption cross section for slow neutrons, and when irradiated with slow neutrons, only the B atoms in the crystal are converted into Li atoms through the reaction of 10 B(n,α) 7 Li. It is possible to do so. However, the α rays emitted by this nuclear reaction have an energy of about several MeV and cause defects in the lattice structure of diamond. For this reason, in the research of Popovici et al., Li-injected diamond was produced, but it has not been confirmed that Li functions as a donor.
　Ｌｉをダイヤモンドに直接イオン注入することも考えられるが、Ｌｉはダイヤモンド中で熱拡散しないため、ダイヤモンド中に満遍なくＬｉを分布させるには数ＭｅＶ程度の高いエネルギーで注入する必要がある（図５参照）。このため、イオン注入時にダイヤモンドに格子欠損が生じ、ホウ素を利用した場合と同様に、Ｌｉがドナーとして機能するのは困難であると予想される。 Direct ion implantation of Li into diamond can be considered, but since Li does not thermally diffuse in diamond, it is necessary to implant with high energy of several MeV to distribute Li evenly throughout diamond (see Figure 5). ). For this reason, lattice defects occur in diamond during ion implantation, and it is expected that it will be difficult for Li to function as a donor in the same way as when boron is used.
　また、酸化ガリウム（Ｇａ２Ｏ３）もワイドバンドギャップ半導体であり、ダイヤモンドと同様にパワーデバイスの材料である。酸化ガリウムは、高品質な単結晶の育成が比較的容易であることから、Ｓｉ製デバイスよりも高性能な素子を、シリコンカーバイド(ＳｉＣ)や窒化ガリウム(ＧａＮ)よりも低価格で市場に供給できることが期待されている。 Further, gallium oxide (Ga 2 O 3 ) is also a wide bandgap semiconductor and, like diamond, is a material for power devices. Since it is relatively easy to grow high-quality single crystals of gallium oxide, it is possible to supply devices with higher performance than Si devices to the market at a lower price than silicon carbide (SiC) and gallium nitride (GaN). It is expected that it will be possible.
　Ｇａ２Ｏ３はＳｉやＳｎドープによってｎ型となることが知られており、ｎ型半導体の製造技術は確立されている。一方で、ｐ型のドーピング技術はまだ確立されていないため、素子構造の工夫や、代わりのｐ型層の導入等の検討が必要となっている。 It is known that Ga 2 O 3 becomes n-type when doped with Si or Sn, and the manufacturing technology for n-type semiconductors has been established. On the other hand, since p-type doping technology has not yet been established, it is necessary to devise device structures and consider introducing alternative p-type layers.
特開平４－３４８５１４号公報Japanese Patent Application Publication No. 4-348514
　このように、ダイヤモンドへのＬｉのドープ技術や、酸化ガリウムへのｐ型のドープ技術は確立されておらず、新規のドープ方法が求められる。 As described above, the technology for doping diamond with Li and the technology for doping p-type into gallium oxide have not been established, and a new doping method is required.
　そこで、本発明は、半導体へ不純物をドープする新規な方法を提供することを目的とする。 Therefore, an object of the present invention is to provide a new method of doping impurities into a semiconductor.
　本発明の一態様は、不純物ドープ半導体の製造方法であって、最終不純物とは異なる不純物の放射性同位体がドープされた半導体を用意する第１工程と、ベータ崩壊により前記放射性同位体を前記最終不純物に核種変換する第２工程と、を含むことを特徴とする。ここで、ベータ崩壊は核壊変の一種であり、高速の電子あるいは陽電子の放出を伴わない電子捕獲、および、陰電子崩壊、陽電子崩壊を含む。 One aspect of the present invention is a method for manufacturing an impurity-doped semiconductor, comprising: a first step of preparing a semiconductor doped with a radioactive isotope of an impurity different from the final impurity; A second step of converting the nuclide into an impurity. Here, beta decay is a type of nuclear decay, and includes electron capture without high-speed electron or positron emission, negative electron decay, and positron decay.
　本態様によれば、最終不純物（ドーパント）を直接に半導体にドープすることが困難な場合でも、半導体へのドープが容易な放射性同位体をドープした後にベータ崩壊により核種変換することで、最終不純物がドープされた半導体が容易に得られる。ここで、核壊変において放出される放射線により半導体格子の欠損はあまり生じない。特に、電子捕獲は、電気的に中性であり質量がほぼゼロの電子ニュートリノを放出するが、半導体格子を欠損するような高エネルギーの放射線を外部に放出しない。したがって、電子捕獲では格子欠損が生じず最終不純物がドナーとして機能することが期待される。 According to this aspect, even if it is difficult to directly dope the final impurity (dopant) into the semiconductor, the final impurity can be doped by doping the semiconductor with a radioisotope that is easy to dope and then transmuting the nuclide by beta decay. A semiconductor doped with is easily obtained. Here, the radiation emitted during nuclear decay does not cause many defects in the semiconductor lattice. In particular, electron capture emits electron neutrinos that are electrically neutral and have almost zero mass, but does not emit high-energy radiation to the outside that would cause defects in the semiconductor lattice. Therefore, it is expected that electron capture does not cause lattice defects and the final impurity functions as a donor.
　本態様において、前記第１工程は、前記半導体の表層に前記放射性同位体を照射する工程と、熱拡散により、前記照射された前記放射性同位体を前記半導体中に拡散させる工程と、を含んでもよい。この場合、前記第１工程は、前記拡散させる工程の前または後に、前記半導体のうち前記照射による欠損部を除去する工程をさらに含んでもよい。 In this aspect, the first step may include the steps of irradiating the surface layer of the semiconductor with the radioisotope, and diffusing the irradiated radioisotope into the semiconductor by thermal diffusion. good. In this case, the first step may further include a step of removing a defective portion of the semiconductor due to the irradiation, before or after the diffusing step.
　あるいは、本態様において、前記第１工程は、前記半導体と前記放射性同位体が溶解された溶液を用意する工程と、前記溶液を用いて前記半導体と前記放射性同位体を含む結晶を作製する工程と、を含んでもよい。 Alternatively, in this aspect, the first step includes a step of preparing a solution in which the semiconductor and the radioisotope are dissolved, and a step of producing a crystal containing the semiconductor and the radioisotope using the solution. , may also be included.
　本態様の一例では、前記半導体はダイヤモンドであり、前記最終不純物は７Ｌｉであり、前記放射性同位体は７Ｂｅであってよい。あるいは、前記半導体はＧａ２Ｏ３であり、前記最終不純物は、６７Ｚｎであり、前記放射性同位体は、６７Ｇａであってよい。 In one example of this embodiment, the semiconductor may be diamond, the final impurity may be 7 Li, and the radioisotope may be 7 Be. Alternatively, the semiconductor may be Ga2O3 , the final impurity may be 67Zn , and the radioisotope may be 67Ga .
　本発明によれば、直接ドープすることが困難な最終不純物がドープされた半導体を製造することができる。 According to the present invention, it is possible to manufacture a semiconductor doped with a final impurity that is difficult to dope directly.
実施形態１の製造方法を説明する図である。1 is a diagram illustrating a manufacturing method of Embodiment 1. FIG. 実施形態１の実験結果を説明する図である。FIG. 3 is a diagram illustrating the experimental results of Embodiment 1. 実施形態２の製造方法を説明する図である。FIG. 7 is a diagram illustrating a manufacturing method of Embodiment 2. 実施形態３の製造方法を説明する図である。FIG. 7 is a diagram illustrating a manufacturing method of Embodiment 3. 従来例の製造方法を説明する図である。It is a figure explaining the manufacturing method of a conventional example.
　本発明は、直接に半導体に入れることが困難なドーパント（最終不純物）をドープするために、ドーピングが容易な核種が異なる不純物の放射性同位体をドーピングして、その後に核壊変より放射性同位体が目的とするドーパントに核種変換されるのを待つことを特徴とする不純物ドープ半導体の製造方法である。ベータ崩壊では半導体欠損が生じるような放射線が発生しないため、半導体格子に欠損が生じずドーパントがドナーとして機能することが期待される。 In order to dope a dopant (final impurity) that is difficult to directly introduce into a semiconductor, the present invention involves doping with a radioactive isotope of an impurity whose nuclide is different from that which is easy to dope, and then the radioisotope is released by nuclear decay. This method of manufacturing an impurity-doped semiconductor is characterized by waiting for the nuclide to be converted into a target dopant. Since beta decay does not generate radiation that would cause semiconductor defects, it is expected that the dopant will function as a donor without causing defects in the semiconductor lattice.
　放射性同位体は、核壊変により目的とするドーパントに核種変換されることと、半導体へのドーピングが容易であることが求められるが、それ以外の条件は特に課されない。 The radioactive isotope is required to be transmuted into the intended dopant through nuclear decay and to be easy to dope into semiconductors, but other conditions are not particularly imposed.
　また、放射性同位体がドーピングされた半導体はどのような手法により用意されてもよい。 Further, the semiconductor doped with a radioactive isotope may be prepared by any method.
　以下、具体的な実施形態に基づいて本発明を説明するが、本発明は以下の実施形態に限定解釈されるものではなく、本発明の技術的思想の範囲内で適宜変形可能である。 The present invention will be described below based on specific embodiments, but the present invention is not limited to the following embodiments and can be modified as appropriate within the scope of the technical idea of the present invention.
＜実施形態１＞
　本実施形態は、ダイヤモンド半導体にリチウム（Ｌｉ）がドープされたｎ型ダイヤモンド半導体の製造方法である。本実施形態では、ベリリウム（Ｂｅ）の放射性同位体である７Ｂｅの７Ｂｅ→７Ｌｉの核壊変による核種変換を利用して、Ｌｉドープダイヤモンド半導体を作製する。 <Embodiment 1>
This embodiment is a method for manufacturing an n-type diamond semiconductor in which a diamond semiconductor is doped with lithium (Li). In the present embodiment, a Li-doped diamond semiconductor is manufactured using nuclide transmutation of 7 Be, which is a radioactive isotope of beryllium (Be), by nuclear decay of 7 Be→ 7 Li.
　図１は本実施形態を説明する図である。以下、図１を参照して本実施形態について説明する。 FIG. 1 is a diagram explaining this embodiment. This embodiment will be described below with reference to FIG.
　まず、加速器で７Ｂｅを作成して、ＲＩイオン注入装置を用いて、ダイヤモンド基板に７Ｂｅイオンビームを照射する。ここでは、数十ｋｅＶ程度（１００ｋｅＶ以下、より好ましくは、３０ｋｅＶ以下）のエネルギーでダイヤモンド基板の表層のみにイオン注入を行う。 First, 7 Be is created using an accelerator, and a 7 Be ion beam is irradiated onto a diamond substrate using an RI ion implantation device. Here, ions are implanted only into the surface layer of the diamond substrate with an energy of about several tens of keV (100 keV or less, more preferably 30 keV or less).
　その後に、加熱処理を行って熱拡散により７Ｂｅを表層以外のダイヤモンド基板内に拡散させる。 Thereafter, heat treatment is performed to diffuse 7Be into the diamond substrate other than the surface layer by thermal diffusion.
　熱拡散後にイオン注入により欠損が生じた可能性のある表層部分（欠損部）を除去する。なお、熱拡散前に除去処理を行ってもよいし、あるいは除去処理を行わなくてもよい。 After thermal diffusion, remove the surface layer parts (defects) where defects may have occurred due to ion implantation. Note that a removal process may or may not be performed before thermal diffusion.
　以上により７Ｂｅがドープされたダイヤモンド基板が得られる。熱拡散を用いて７Ｂｅを分布させているので格子欠損が生じず、またイオン注入により欠損が生じうる表層は除去されているので、最終的に格子欠損のない７Ｂｅドープダイヤモンド半導体が得られる。 Through the above steps, a diamond substrate doped with 7 Be can be obtained. Because 7Be is distributed using thermal diffusion, lattice defects do not occur, and the surface layer where defects can occur is removed by ion implantation, so a 7Be -doped diamond semiconductor without lattice defects is finally obtained. .
　次に、電子捕獲（ベータ崩壊の一種）により、７Ｂｅを最終ドーパントである７Ｌｉに核種変換する。これにより、７Ｌｉがドープされたダイヤモンド半導体が得られる。 Next, electron capture (a type of beta decay) converts the 7 Be into the final dopant, 7 Li. As a result, a diamond semiconductor doped with 7 Li is obtained.
　電子捕獲は７Ｂｅ ＋ ｅ－ → ７Ｌｉ ＋ νｅという反応であり、原子核外の電子が原子核によって捕獲されて電子ニュートリノが放出される。電子捕獲は自然に生じるので、７Ｂｅドープダイヤモンド半導体を放置しておけばよい。また、半減期が５３．２日であるので、７半減期以上（約３７２日）放置すれば、９９％が７Ｌｉに変換される。 Electron capture is a reaction of 7 Be + e − → 7 Li + ν e , in which electrons outside the nucleus are captured by the nucleus and electron neutrinos are released. Since electron capture occurs naturally, the 7 Be-doped diamond semiconductor can be left alone. Furthermore, since the half-life is 53.2 days, if it is left for more than 7 half-lives (approximately 372 days), 99% will be converted to 7Li .
　電子捕獲により放出される電子ニュートリノは比較的高エネルギーであるが、電気的に中性であり質量が限りなくゼロに近いため、ダイヤモンド格子を欠損することはないと想定される。格子欠損がないことから７Ｌｉがドナーとして機能し、ｎ型半導体として機能することが期待される。 Although the electron neutrinos emitted by electron capture have relatively high energy, they are electrically neutral and have extremely close to zero mass, so it is assumed that they will not cause defects in the diamond lattice. Since there are no lattice defects, 7 Li is expected to function as a donor and function as an n-type semiconductor.
（実験例）
　イオン注入および熱拡散によりベリリウム（Ｂｅ）がドープされたダイヤモンド基板を用意する実験を行った。 (Experiment example)
An experiment was conducted in which a diamond substrate doped with beryllium (Be) was prepared by ion implantation and thermal diffusion.
　まず、Ｂｅの試料を作成した。硝酸ベリリウム溶液を蒸発乾固させ、電気炉で加熱し酸化ベリリウム(ＢｅＯ）の粉末を作成した。ＢｅＯの粉末に重量比で４倍量のニオブ（Ｎｂ）を混合し、試料とした。 First, a sample of Be was created. The beryllium nitrate solution was evaporated to dryness and heated in an electric furnace to create beryllium oxide (BeO) powder. A sample was prepared by mixing BeO powder with four times the amount of niobium (Nb) by weight.
　その後、セシウムスパッター型負イオン源に装填し、ＢｅＯの負イオンビームを生成した。ＢｅＯイオンは２０ｋｅＶ程度のエネルギーまで加速され、質量分離後、ダイヤモンド試料へイオン注入された。 Thereafter, it was loaded into a cesium sputter type negative ion source to generate a BeO negative ion beam. BeO ions were accelerated to an energy of about 20 keV, and after mass separation, the ions were implanted into the diamond sample.
　次に、Ｂｅをイオン注入したダイヤモンドをＲＴＡ法（Rapid Thermal Annealing）により窒素雰囲気下で８００℃程度で加熱処理を行った。 Next, the diamond into which Be was ion-implanted was heat-treated at about 800° C. in a nitrogen atmosphere using the RTA method (Rapid Thermal Annealing).
　Ｂｅをイオン注入した同一の試料について、ＲＴＡを１時間、１３時間、３６時間実施した後のダイヤモンド中のＢｅの分布は図２のようになり、ＲＴＡ処理によりダイヤモンド中でＢｅが熱拡散する様子が観測された。なお、この実験は安定同位体9Ｂｅを用いているが、放射性同位体７Ｂｅを用いても結果は変わらない。 Figure 2 shows the distribution of Be in diamond after performing RTA for 1 hour, 13 hours, and 36 hours on the same sample into which Be was ion-implanted, showing the thermal diffusion of Be in diamond due to RTA treatment. was observed. Note that although this experiment used the stable isotope 9 Be, the results would not change even if the radioactive isotope 7 Be was used.
　イオン注入により格子欠損が生じうる表層部分は除去すれば良く、熱拡散では格子欠損が生じないので、結果として格子欠損のない７Ｂｅドープダイヤモンド半導体が得られる。後は、７Ｂｅが壊変するのを待てば、７Ｌｉがドープされたダイヤモンド半導体となる。 The surface layer portion where lattice defects may occur due to ion implantation can be removed, and thermal diffusion does not cause lattice defects, resulting in a 7 Be-doped diamond semiconductor having no lattice defects. After waiting for 7 Be to decay, a 7 Li-doped diamond semiconductor is obtained.
＜実施形態２＞
　本実施形態は、実施形態１と同様にダイヤモンド半導体にリチウム（Ｌｉ）がドープされたｎ型ダイヤモンド半導体の製造方法である。７Ｂｅがドープされたダイヤモンド半導体を用意して、電子捕獲による核種変換を行う点は同じであるが、７Ｂｅドープダイヤモンド半導体を用意する工程が異なる。本実施形態では、マイクロ波プラズマＣＶＤ法を用いる。 <Embodiment 2>
The present embodiment is a method for manufacturing an n-type diamond semiconductor in which a diamond semiconductor is doped with lithium (Li), as in the first embodiment. They are the same in that a 7 Be-doped diamond semiconductor is prepared and nuclide conversion is performed by electron capture, but the process for preparing the 7 Be-doped diamond semiconductor is different. In this embodiment, a microwave plasma CVD method is used.
　図３は本実施形態を説明する図である。本実施形態では、マイクロ波プラズマＣＶＤ装置を用いて、マイクロ波プラズマＣＶＤ法によりダイヤモンド結晶を成長させる。この際、７Ｂｅで構成されたロッド（または粉末を載せたトレー）をフィードスルーに担持してプラズマ中に挿入する。すると、プラズマ中でロッドがエッチングされ、７Ｂｅが雰囲気中に拡散する。拡散された７Ｂｅはダイヤモンド成長とともに結晶中に取り込まれて、７Ｂｅがドープされたダイヤモンド半導体が得られる。なお、ドーピング濃度は、ロッド（またはトレー）の挿入距離により制御可能である。 FIG. 3 is a diagram explaining this embodiment. In this embodiment, a diamond crystal is grown by a microwave plasma CVD method using a microwave plasma CVD apparatus. At this time, a rod (or a tray loaded with powder) made of 7 Be is supported on the feedthrough and inserted into the plasma. Then, the rod is etched in the plasma, and 7Be is diffused into the atmosphere. The diffused 7 Be is incorporated into the crystal as the diamond grows, and a diamond semiconductor doped with 7 Be is obtained. Note that the doping concentration can be controlled by the insertion distance of the rod (or tray).
　また、マイクロ波プラズマＣＶＤ法ではなく高圧高温法（HPHT: High Pressure and High Temperature）を用いてもよい。具体的には、ダイヤモンド結晶を高圧下で熱処理する際に、炉内に７Ｂｅを導入することにより、ダイヤモンド内に７Ｂｅを熱拡散させてもよい。 Further, instead of the microwave plasma CVD method, a high pressure and high temperature method (HPHT) may be used. Specifically, when heat treating a diamond crystal under high pressure, 7 Be may be thermally diffused into the diamond by introducing 7 Be into the furnace.
　７Ｂｅドープダイヤモンド半導体が得られた後の処理は実施形態１と同様であるため、説明は省略する。 The processing after obtaining the 7Be -doped diamond semiconductor is the same as in Embodiment 1, and therefore the description thereof will be omitted.
　本実施形態によっても、欠損のない７Ｌｉドープダイヤモンド半導体が得られる。 According to this embodiment as well, a 7 Li-doped diamond semiconductor without defects can be obtained.
＜実施形態３＞
　本実施形態は、酸化ガリウム（Ｇａ２Ｏ３）に亜鉛（Ｚｎ）がドープされたｐ型半導体の製造方法である。本実施形態では、６７Ｇａの電子捕獲による核種変換（６７Ｇａ ＋ｅ－ → ６７Ｚｎ ＋ νｅ）を用いる。 <Embodiment 3>
This embodiment is a method for manufacturing a p-type semiconductor in which gallium oxide (Ga 2 O 3 ) is doped with zinc (Zn). In this embodiment, nuclide conversion ( 67 Ga +e − → 67 Zn + ν e ) by electron capture of 67 Ga is used.
　図４は本実施形態を説明する図である。 FIG. 4 is a diagram explaining this embodiment.
　まず、Ｚｎを含む標的や６７Ｚｎを濃縮した標的に陽子ビームを照射して、６７Ｚｎ（ｐ，ｎ）６７Ｇａ反応により、６７Ｇａを生成する。 First, a target containing Zn or a target enriched with 67 Zn is irradiated with a proton beam to generate 67 Ga by a 67 Zn(p,n) 67 Ga reaction.
　次に、６７ＧａとＺｎを含む標的を溶解する。Ｇａ，Ｚｎ共存下の溶液に抽出剤を加えてｐＨを変えることで、Ｇａを選択的に抽出する。 Next, targets containing 67 Ga and Zn are dissolved. By adding an extractant to a solution in which Ga and Zn coexist and changing the pH, Ga is selectively extracted.
　抽出したＧａをＧａの原料融液に混合して、チョクラルスキー（CZ）法やフローティングゾーン（FZ）法、EFG（edge-defined growth）法等でＧａ２О3の結晶を作成する。これにより、６７ＧａがドープされたＧａ２Ｏ３結晶が得られる。 The extracted Ga is mixed with a Ga raw material melt, and Ga 2 O 3 crystals are created by the Czochralski (CZ) method, the floating zone (FZ) method, the EFG (edge-defined growth) method, or the like. As a result, a Ga 2 O 3 crystal doped with 67 Ga is obtained.
　最後に、電子捕獲反応により６７Ｇａが６７Ｚｎに核種変換されるのを待つ。６７Ｇａの半減期は３．２６日なので７半減期以上（約２３日）放置すると９９％が６７Ｚｎに変換される。 Finally, wait for nuclide conversion of 67 Ga to 67 Zn by an electron capture reaction. The half-life of 67 Ga is 3.26 days, so if it is left for more than 7 half-lives (approximately 23 days), 99% will be converted to 67 Zn.
　本実施形態においても、放射性崩壊時に高エネルギーの電離放射線が発生しないので、格子欠損が生じない。したがって、酸化ガリウム（Ｇａ２Ｏ３）に亜鉛（Ｚｎ）がドープされたｐ型半導体が得られる。 Also in this embodiment, no lattice defects occur because high-energy ionizing radiation is not generated during radioactive decay. Therefore, a p-type semiconductor in which gallium oxide (Ga 2 O 3 ) is doped with zinc (Zn) is obtained.
＜その他の実施形態＞
　以上、具体例に沿って本発明を説明したが、本発明は上記には限定されない。例えば、核種変換前の放射性同位体がドープされた半導体を用意する工程は、上記以外の手法により行われてもよい。また、ダイヤモンド半導体へのＬｉのドーピングと、酸化ガリウム半導体へのＺｎドーピングを説明したが、上記以外の半導体基板やドーパントを採用することを妨げるものではない。例えば、実施形態１，２の方法で６７ＧａをＧａ２Ｏ３にドープして、核種変換によってＺｎがドープされたＧａ２Ｏ３を作成してもよい。あるいは、実施形態１，２の方法で、６７Ｇａをダイヤモンドにドープして、核種変換によってＺｎがドープされたダイヤモンドを作成してもよい。さらに、実施形態１－３の方法で、７ＢｅをＧａ２Ｏ３にドープして、核種変換によってＬｉがドープされたＧａ２Ｏ３を作成してもよい。 <Other embodiments>
Although the present invention has been described above with reference to specific examples, the present invention is not limited to the above. For example, the step of preparing a semiconductor doped with a radioactive isotope before nuclide conversion may be performed by a method other than the above. Furthermore, although Li doping into a diamond semiconductor and Zn doping into a gallium oxide semiconductor have been described, this does not preclude the use of semiconductor substrates and dopants other than those described above. For example, Ga 2 O 3 may be doped with 67 Ga using the methods of Embodiments 1 and 2, and Zn-doped Ga 2 O 3 may be created by nuclide conversion. Alternatively, diamond may be doped with 67 Ga using the methods of Embodiments 1 and 2, and Zn-doped diamond may be created by nuclide transmutation. Furthermore, Ga 2 O 3 may be doped with 7 Be using the method of Embodiment 1-3 to create Li-doped Ga 2 O 3 through nuclide transmutation.
　また、核壊変として電子捕獲以外の反応を利用してもよい。核壊変のうち、陰電子崩壊および陽電子崩壊（これらはベータ崩壊の一例）による核種変換で放出される放射線は、半導体結晶の格子欠損を生じないと考えられるので、電子捕獲と同様の効果が得られる。 Additionally, reactions other than electron capture may be used as nuclear decay. Of nuclear decay, the radiation emitted by nuclide transmutation by negative electron decay and positron decay (these are examples of beta decay) is thought not to cause lattice defects in semiconductor crystals, so it can produce the same effect as electron capture. It will be done.

Claims (8)

  1. 　不純物ドープ半導体の製造方法であって、
    　最終不純物とは異なる不純物の放射性同位体がドープされた半導体を用意する第１工程と、
    　ベータ崩壊により前記放射性同位体を前記最終不純物に核種変換する第２工程と、
    　を含む、不純物ドープ半導体の製造方法。     A method for manufacturing an impurity-doped semiconductor, comprising:
    a first step of preparing a semiconductor doped with a radioactive isotope of an impurity different from the final impurity;
    a second step of transmuting the radioactive isotope into the final impurity by beta decay;
    A method for manufacturing an impurity-doped semiconductor, comprising:
  2. 　前記ベータ崩壊は、電子捕獲である、
    　請求項１に記載の、不純物ドープ半導体の製造方法。     the beta decay is electron capture;
    The method for manufacturing an impurity-doped semiconductor according to claim 1.
  3. 　前記第１工程は、
    　前記半導体の表層に前記放射性同位体を照射する工程と、
    　熱拡散により、前記照射された前記放射性同位体を前記半導体中に拡散させる工程と、
    　を含む、請求項１に記載の不純物ドープ半導体の製造方法。     The first step is
    irradiating the surface layer of the semiconductor with the radioisotope;
    diffusing the irradiated radioisotope into the semiconductor by thermal diffusion;
    The method for manufacturing an impurity-doped semiconductor according to claim 1, comprising:
  4. 　前記第１工程は、前記拡散させる工程の前または後に、前記半導体のうち前記照射による欠損部を除去する工程をさらに含む、
    　請求項３に記載の不純物ドープ半導体の製造方法。     The first step further includes a step of removing a defective portion of the semiconductor due to the irradiation, before or after the diffusing step.
    The method for manufacturing an impurity-doped semiconductor according to claim 3.
  5. 　前記第１工程は、プラズマ中に前記放射性同位体を含めたマイクロ波プラズマＣＶＤ法または高圧高温法（HPHT）により、前記半導体を結晶させる工程を含む、
    　請求項１に記載の不純物ドープ半導体の製造方法。     The first step includes a step of crystallizing the semiconductor by a microwave plasma CVD method or a high pressure high temperature method (HPHT) in which the radioactive isotope is included in plasma.
    A method for manufacturing an impurity-doped semiconductor according to claim 1.
  6. 　前記第１工程は、
    　前記半導体と前記放射性同位体が溶解された溶液を用意する工程と、
    　前記溶液を用いて前記半導体と前記放射性同位体を含む結晶を作製する工程と、
    　を含む、請求項１に記載の不純物ドープ半導体の製造方法。     The first step is
    preparing a solution in which the semiconductor and the radioactive isotope are dissolved;
    producing a crystal containing the semiconductor and the radioactive isotope using the solution;
    The method for manufacturing an impurity-doped semiconductor according to claim 1, comprising:
  7. 　前記半導体は、ダイヤモンドであり、
    　前記最終不純物は、７Ｌｉであり、
    　前記放射性同位体は、７Ｂｅである、
    　請求項１に記載の不純物ドープ半導体の製造方法。     the semiconductor is diamond;
    The final impurity is 7 Li,
    the radioisotope is 7Be ;
    A method for manufacturing an impurity-doped semiconductor according to claim 1.
  8. 　前記半導体は、Ｇａ２Ｏ３であり、
    　前記最終不純物は、６７Ｚｎであり、
    　前記放射性同位体は、６７Ｇａである、
    　請求項１に記載の不純物ドープ半導体の製造方法。     The semiconductor is Ga 2 O 3 ,
    The final impurity is 67 Zn,
    the radioisotope is 67 Ga;
    A method for manufacturing an impurity-doped semiconductor according to claim 1.
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