JP6120224B2 - Semiconductor device and manufacturing method thereof - Google Patents

Semiconductor device and manufacturing method thereof Download PDF

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JP6120224B2
JP6120224B2 JP2013543023A JP2013543023A JP6120224B2 JP 6120224 B2 JP6120224 B2 JP 6120224B2 JP 2013543023 A JP2013543023 A JP 2013543023A JP 2013543023 A JP2013543023 A JP 2013543023A JP 6120224 B2 JP6120224 B2 JP 6120224B2
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公平 佐々木
公平 佐々木
東脇　正高
正高 東脇
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Tamura Corp
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    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
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    • 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
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
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    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
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    • H01L29/24—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22
    • H—ELECTRICITY
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    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
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    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
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    • H01L29/76—Unipolar devices, e.g. field effect transistors
    • H01L29/772—Field effect transistors
    • H01L29/80—Field effect transistors with field effect produced by a PN or other rectifying junction gate, i.e. potential-jump barrier
    • H01L29/812—Field effect transistors with field effect produced by a PN or other rectifying junction gate, i.e. potential-jump barrier with a Schottky gate
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    • H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
    • H01L29/86—Types of semiconductor device ; Multistep manufacturing processes therefor controllable only by variation of the electric current supplied, or only the electric potential applied, to one or more of the electrodes carrying the current to be rectified, amplified, oscillated or switched
    • H01L29/861—Diodes
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
    • H01L29/40—Electrodes ; Multistep manufacturing processes therefor
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Description

本発明は、半導体素子及びその製造方法に関する。   The present invention relates to a semiconductor device and a manufacturing method thereof.

従来のＧａ2Ｏ3（酸化ガリウム）単結晶の表面へ電極を形成する技術として、Ｔｉ電極を用いる技術（例えば、特許文献１参照）、Ｇａ2Ｏ3単結晶にプラズマ処理を施した後にＴｉ電極を接続する技術（例えば、特許文献２参照）、Ｉｎ電極を接続した後に６００〜１０００℃でＧａ2Ｏ3単結晶に熱処理を施す技術（例えば、特許文献３参照）が知られている。As a technique for forming an electrode on the surface of a conventional Ga 2 O 3 (gallium oxide) single crystal, a technique using a Ti electrode (see, for example, Patent Document 1), a plasma treatment is performed on a Ga 2 O 3 single crystal and then Ti is applied. A technique for connecting electrodes (for example, see Patent Document 2) and a technique for performing heat treatment on a Ga 2 O 3 single crystal at 600 to 1000 ° C. after connecting an In electrode (for example, see Patent Document 3) are known.

特開２００９−８１４６８号公報JP 2009-81468 A 特開２００９−１３００１３号公報JP 2009-130013 A 特開２００９−３０２２５７号公報JP 2009-302257 A

しかしながら、特許文献１や特許文献２に記載された技術は、Ｇａ2Ｏ3装置を実用化するために要求される接触抵抗を満足するには至っていない。また、特許文献３に記載された技術は、熱処理によって良好なオーミック接触が得られるものの、必要とされる熱処理温度がＩｎの融点（１５６．４℃）よりも遥かに高く、熱処理中に試料全体がＩｎ蒸気に晒されることとなるため、Ｉｎ汚染によるデバイス特性劣化が懸念される。However, the techniques described in Patent Document 1 and Patent Document 2 do not satisfy the contact resistance required for putting the Ga 2 O 3 device into practical use. Further, although the technique described in Patent Document 3 can obtain good ohmic contact by heat treatment, the required heat treatment temperature is much higher than the melting point of In (156.4 ° C.), and the entire sample is subjected to the heat treatment. Is exposed to In vapor, there is a concern about deterioration of device characteristics due to In contamination.

したがって、本発明の目的は、Ｇａ2Ｏ3系単結晶に電極を低抵抗で接続することができる半導体素子の製造方法、及び低抵抗で接続されたＧａ2Ｏ3系単結晶と電極を含む半導体素子を提供することにある。Accordingly, an object of the present invention includes a method for manufacturing a semiconductor element capable of connecting an electrode to a Ga 2 O 3 single crystal with a low resistance, and a Ga 2 O 3 single crystal and an electrode connected with a low resistance. It is to provide a semiconductor device.

本発明の一態様は、上記目的を達成するために、下記［１］、［２］の半導体素子の製造方法、［３］〜［７］の半導体素子を提供する。 In order to achieve the above object, one embodiment of the present invention provides the following [1] and [2] semiconductor device manufacturing method and [3] to [7] .

［１］Ｇａ２Ｏ３系単結晶の表面にＢＣｌ ３ を含むガスを用いた反応性イオンエッチングを施し、変質領域を形成する工程と、前記変質領域上に、前記変質領域とオーミック接合する金属電極を形成する工程と、を含む半導体素子の製造方法。 [1] A step of performing reactive ion etching using a gas containing BCl 3 on the surface of a Ga 2 O 3 single crystal to form an altered region, and a metal that is in ohmic contact with the altered region on the altered region And a step of forming an electrode.

［２］前記Ｇａ ２ Ｏ ３ 系単結晶の前記表面の一部に前記反応性イオンエッチングを施し、前記変質領域を形成する、前記［１］に記載の半導体素子の製造方法。 [2] The method of manufacturing a semiconductor element according to [1] , wherein the reactive ion etching is performed on a part of the surface of the Ga 2 O 3 single crystal to form the altered region.

［３］Ｇａ２Ｏ３系単結晶からなる基板と、前記基板の第１の面、又は前記第１の面上のＧａ２Ｏ３系単結晶からなる第１の結晶層の前記基板と反対側の面に、酸素原子又はＧａ原子のエッチングガスイオンによる置換、エッチングガスイオンの結晶格子間への侵入、又は結晶構造の変化（乱れ）のうちの少なくとも１つを含む変質領域と、前記変質領域上に形成され、前記変質領域とオーミック接合する金属電極と、を含む半導体素子。 [3] a substrate made of Ga 2 O 3 single crystal, a first surface of the substrate, or the first of said substrate crystal layer made of Ga 2 O 3 single crystal on the first surface opposite An alteration region including at least one of substitution of oxygen atoms or Ga atoms with etching gas ions, penetration of etching gas ions between crystal lattices, or change (disturbance) of crystal structure on the side surface, and the alteration A semiconductor element comprising a metal electrode formed on the region and in ohmic contact with the altered region.

［４］前記基板の前記第１の面と反対側の第２の面、又は前記第２の面上のＧａ２Ｏ３系単結晶からなる第２の結晶層の前記基板と反対側の面上に形成されたアノード電極と、を有し、前記金属電極がカソード電極である、前記［３］に記載の半導体素子。 [4] A second surface of the substrate opposite to the first surface, or a surface of the second crystal layer made of Ga 2 O 3 based single crystal on the second surface opposite to the substrate. The semiconductor element according to [3] , further including an anode electrode formed thereon, wherein the metal electrode is a cathode electrode.

［５］前記金属電極は、ソース電極、ドレイン電極、及び前記ソース電極と前記ドレイン電極の間のゲート電極である、前記［３］に記載の半導体素子。 [5] The semiconductor element according to [3] , wherein the metal electrode is a source electrode, a drain electrode, and a gate electrode between the source electrode and the drain electrode.

［６］前記変質領域は、前記基板又は前記第１の結晶層の一部に形成され、前記変質領域の表面の高さは、前記基板又は前記第１の結晶層の前記変質領域の形成されていない領域の表面の高さよりも低い、前記［３］に記載の半導体素子。 [6] The altered region is formed in a part of the substrate or the first crystal layer, and a height of a surface of the altered region is formed in the altered region of the substrate or the first crystal layer. The semiconductor element according to the above [3] , which is lower than the height of the surface of the unexposed region.

［７］前記第１の結晶層の前記変質領域が形成されない領域上のゲート電極を含み、前記第１の結晶層は導電型不純物を含み、前記金属電極は、前記ゲート電極の両側のソース電極及びドレイン電極である、前記［６］に記載の半導体素子。 [7] The first crystal layer includes a gate electrode on a region where the altered region is not formed, the first crystal layer includes a conductive impurity, and the metal electrode is a source electrode on both sides of the gate electrode. And the semiconductor element according to [6] , which is a drain electrode.

本発明によれば、Ｇａ2Ｏ3系単結晶に電極を低抵抗で接続することができる半導体素子の製造方法、及び低抵抗で接続されたＧａ2Ｏ3系単結晶と電極を含む半導体素子を提供することができる。According to the present invention, Ga 2 O 3 system single method for producing crystals in the electrode semiconductor device which can be connected with low resistance, and a semiconductor device including a Ga 2 O 3 system single crystal and electrode connected with a low resistance Can be provided.

図１は、第１の実施の形態に係るＳＢＤの断面図である。FIG. 1 is a cross-sectional view of the SBD according to the first embodiment. 図２Ａは、第１の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 2A is a cross-sectional view illustrating a manufacturing process of the SBD according to the first embodiment. 図２Ｂは、第１の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 2B is a cross-sectional view illustrating a manufacturing process of the SBD according to the first embodiment. 図２Ｃは、第１の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 2C is a cross-sectional view illustrating a manufacturing process of the SBD according to the first embodiment. 図２Ｄは、第１の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 2D is a cross-sectional view illustrating a manufacturing process of the SBD according to the first embodiment. 図３は、第２の実施の形態に係るＳＢＤの断面図である。FIG. 3 is a cross-sectional view of the SBD according to the second embodiment. 図４Ａは、第２の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 4A is a cross-sectional view illustrating a manufacturing process of the SBD according to the second embodiment. 図４Ｂは、第２の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 4B is a cross-sectional view illustrating a manufacturing process of the SBD according to the second embodiment. 図４Ｃは、第２の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 4C is a cross-sectional view illustrating a manufacturing process of the SBD according to the second embodiment. 図４Ｄは、第２の実施の形態に係るＳＢＤの製造工程を表す断面図である。FIG. 4D is a cross-sectional view illustrating a manufacturing process of the SBD according to the second embodiment. 図５は、第３の実施の形態に係るＭＥＳＦＥＴの断面図である。FIG. 5 is a cross-sectional view of a MESFET according to the third embodiment. 図６Ａは、第３の実施の形態に係るＭＥＳＦＥＴの製造工程を表す断面図である。FIG. 6A is a cross-sectional view illustrating a manufacturing process of the MESFET according to the third embodiment. 図６Ｂは、第３の実施の形態に係るＭＥＳＦＥＴの製造工程を表す断面図である。FIG. 6B is a cross-sectional view illustrating a manufacturing process of the MESFET according to the third embodiment. 図６Ｃは、第３の実施の形態に係るＭＥＳＦＥＴの製造工程を表す断面図である。FIG. 6C is a cross-sectional view illustrating a manufacturing step of the MESFET according to the third embodiment. 図６Ｄは、第３の実施の形態に係るＭＥＳＦＥＴの製造工程を表す断面図である。FIG. 6D is a cross-sectional view illustrating a manufacturing process of the MESFET according to the third embodiment. 図７Ａは、実施例に係るＧａ2Ｏ3基板の電流−電圧特性を示す。FIG. 7A shows current-voltage characteristics of the Ga 2 O 3 substrate according to the example. 図７Ｂは、実施例に係るＧａ2Ｏ3基板の電流−電圧特性を示す。FIG. 7B shows current-voltage characteristics of the Ga 2 O 3 substrate according to the example. 図８は、実施例に係るＳＢＤの順方向の電流−電圧特性を示す。FIG. 8 shows forward current-voltage characteristics of the SBD according to the example. 図９は、４種の反応ガスを用いて変質領域がそれぞれ形成された４つのＧａ2Ｏ3基板の電流−電圧特性を示す。FIG. 9 shows current-voltage characteristics of four Ga 2 O 3 substrates in which altered regions are formed using four kinds of reaction gases, respectively.

〔第１の実施の形態〕
第１の実施の形態では、半導体素子としてのショットキーバリアダイオード（ＳＢＤ）について説明する。[First Embodiment]
In the first embodiment, a Schottky barrier diode (SBD) as a semiconductor element will be described.

（ＳＢＤの構成）
図１は、第１の実施の形態に係るＳＢＤの断面図である。ＳＢＤ１０は、Ｇａ2Ｏ3系基板１１と、Ｇａ2Ｏ3系基板１１の上面（図１の上側の面）に形成された変質領域１２と、Ｇａ2Ｏ3系基板１１の下面（図１の下側の面）に形成されたＧａ2Ｏ3系単結晶層１３と、Ｇａ2Ｏ3系基板１１の変質領域１２上に形成されたカソード電極１４と、Ｇａ2Ｏ3系単結晶層１３のＧａ2Ｏ3系基板１１と反対側の面上に形成されたアノード電極１５と、を含む。(Configuration of SBD)
FIG. 1 is a cross-sectional view of the SBD according to the first embodiment. SBD10 includes a Ga 2 O 3 based substrate 11, and the upper surface affected region 12 formed on (the surface of the upper side in FIG. 1) of the Ga 2 O 3 based substrate 11, the lower surface of the Ga 2 O 3 based substrate 11 (FIG. 1 Ga 2 O 3 single crystal layer 13 formed on the lower surface), cathode electrode 14 formed on the altered region 12 of the Ga 2 O 3 substrate 11, and Ga 2 O 3 single crystal layer. 13, and an anode electrode 15 formed on the surface opposite to the Ga 2 O 3 based substrate 11.

Ｇａ2Ｏ3系基板１１は、Ｇａ2Ｏ3系単結晶からなる。ここで、Ｇａ2Ｏ3系単結晶とは、Ｇａ2Ｏ3単結晶、又はＡｌ等の不純物を含むＧａ2Ｏ3単結晶をいう。また、Ｇａ2Ｏ3系基板１１は、Ｓｉ、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｒｕ、Ｒｈ、Ｉｒ、Ｃ、Ｓｎ、Ｇｅ、Ｐｂ、Ｍｎ、Ａｓ、Ｓｂ、Ｂｉ、Ｆ、Ｃｌ、Ｂｒ、又はＩ等のｎ型ドーパントを含む。Ｇａ2Ｏ3系基板１１のドナー濃度は、例えば、１×１０19／ｃｍ3である。The Ga 2 O 3 based substrate 11 is made of a Ga 2 O 3 based single crystal. Here, the Ga 2 O 3 single crystal refers to a Ga 2 O 3 single crystal or a Ga 2 O 3 single crystal containing impurities such as Al. Further, the Ga 2 O 3 based substrate 11 is made of Si, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Ru, Rh, Ir, C, Sn, Ge, Pb, Mn, As, Sb, Bi. , F, Cl, Br, or I. The donor concentration of the Ga 2 O 3 based substrate 11 is, for example, 1 × 10 19 / cm 3 .

変質領域１２は、ドライエッチングにより変質したＧａ2Ｏ3系基板１１の表面の領域である。この変質領域１２に生じている変質は、例えば、酸素欠損、Ｇａ欠損、酸素サイトへのＧａ原子の移動、Ｇａサイトへの酸素原子の移動、酸素原子又はＧａ原子のエッチングガスイオンによる置換、エッチングガスイオンの結晶格子間への侵入、又は結晶構造の変化（乱れ）であり、これらのうちの複数の変質が複合的に生じていてもよい。The altered region 12 is a region on the surface of the Ga 2 O 3 based substrate 11 that has been altered by dry etching. The alteration occurring in the altered region 12 includes, for example, oxygen deficiency, Ga deficiency, movement of Ga atoms to the oxygen site, movement of oxygen atoms to the Ga site, substitution of oxygen atoms or Ga atoms with etching gas ions, etching It is the penetration of gas ions into the crystal lattice or the change (disturbance) of the crystal structure, and a plurality of alterations of these may occur in combination.

変質領域１２においては、ドナー濃度の上昇、又は界面準位の発生が生じているものと考えられ、変質領域１２は、カソード電極１４とオーミック接合する。例えば、ドライエッチングによりＧａ2Ｏ3系単結晶層２６の表面の酸素が欠損して変質領域１２が形成された場合、欠損により形成される酸素欠陥がドナーとして機能する。変質領域１２は、Ｇａ2Ｏ3系基板１１の上面の全面に形成されてもよく、Ｇａ2Ｏ3系基板１１の上面の一部に形成されてもよい。In the altered region 12, it is considered that a donor concentration is increased or an interface state is generated, and the altered region 12 is in ohmic contact with the cathode electrode 14. For example, when oxygen on the surface of the Ga 2 O 3 single crystal layer 26 is deficient and the altered region 12 is formed by dry etching, the oxygen defect formed by the deficiency functions as a donor. Affected region 12 may be formed on the entire upper surface of the Ga 2 O 3 based substrate 11 may be formed on a part of the upper surface of the Ga 2 O 3 based substrate 11.

Ｇａ2Ｏ3系単結晶層１３は、Ｇａ2Ｏ3系単結晶からなる結晶層である。Ｇａ2Ｏ3系単結晶層１３は、Ｓｉ、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｒｕ、Ｒｈ、Ｉｒ、Ｃ、Ｓｎ、Ｇｅ、Ｐｂ、Ｍｎ、Ａｓ、Ｓｂ、Ｂｉ、Ｆ、Ｃｌ、Ｂｒ、又はＩ等のｎ型ドーパントを含む。Ｇａ2Ｏ3系単結晶層１３のドナー濃度は、例えば、４×１０16／ｃｍ3である。The Ga 2 O 3 single crystal layer 13 is a crystal layer made of a Ga 2 O 3 single crystal. The Ga 2 O 3 single crystal layer 13 is made of Si, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Ru, Rh, Ir, C, Sn, Ge, Pb, Mn, As, Sb, Bi. , F, Cl, Br, or I. The donor concentration of the Ga 2 O 3 single crystal layer 13 is, for example, 4 × 10 16 / cm 3 .

カソード電極１４は、Ｔｉ等の金属からなる金属電極であり、変質領域１２とオーミック接合する。また、カソード電極１４は、異なる金属膜を積層した多層構造、例えば、ＴｉとＡｕ又はＡｌの２層構造、を有してもよい。カソード電極１４は、Ｇａ2Ｏ3系基板１１の上面の全面に形成されてもよく、Ｇａ2Ｏ3系基板１１の上面の一部に形成されてもよい。The cathode electrode 14 is a metal electrode made of a metal such as Ti, and is in ohmic contact with the altered region 12. The cathode electrode 14 may have a multilayer structure in which different metal films are stacked, for example, a two-layer structure of Ti and Au or Al. The cathode electrode 14 may be formed on the entire upper surface of the Ga 2 O 3 based substrate 11 may be formed on a part of the upper surface of the Ga 2 O 3 based substrate 11.

アノード電極１５は、Ｐｔ、Ｎｉ等の金属からなる金属電極であり、Ｇａ2Ｏ3系単結晶層１３とショットキー接合する。また、アノード電極１５は、異なる金属膜を積層した多層構造、例えば、ＰｔとＡｕ又はＡｌの２層構造、を有してもよい。The anode electrode 15 is a metal electrode made of a metal such as Pt or Ni, and is in Schottky junction with the Ga 2 O 3 single crystal layer 13. The anode electrode 15 may have a multilayer structure in which different metal films are stacked, for example, a two-layer structure of Pt and Au or Al.

なお、Ｇａ2Ｏ3系単結晶層１３は、ＳＢＤ１０に含まれなくてもよい。その場合、アノード電極１５は、Ｇａ2Ｏ3系基板１１とショットキー接合する。The Ga 2 O 3 single crystal layer 13 may not be included in the SBD 10. In that case, the anode electrode 15 is in Schottky junction with the Ga 2 O 3 substrate 11.

（ＳＢＤの製造方法）
以下に、本実施の形態のＳＢＤ１０の製造方法の一例を示す。(Manufacturing method of SBD)
Below, an example of the manufacturing method of SBD10 of this Embodiment is shown.

図２Ａ〜図２Ｄは、第１の実施の形態に係るＳＢＤの製造工程を表す断面図である。   2A to 2D are cross-sectional views illustrating manufacturing steps of the SBD according to the first embodiment.

まず、図２Ａに示されるように、Ｇａ2Ｏ3系基板１１を用意する。First, as shown in FIG. 2A, a Ga 2 O 3 based substrate 11 is prepared.

次に、図２Ｂに示されるように、Ｇａ2Ｏ3系基板１１の下面にｎ型ドーパントを含むＧａ2Ｏ3系単結晶をエピタキシャル成長させ、Ｇａ2Ｏ3系単結晶層１３を形成する。Next, as shown in FIG. 2B, a Ga 2 O 3 single crystal layer 13 is formed by epitaxially growing a Ga 2 O 3 single crystal containing an n-type dopant on the lower surface of the Ga 2 O 3 substrate 11.

次に、図２Ｃに示されるように、Ｇａ2Ｏ3系基板１１の上面にＲＩＥ等のドライエッチングを施し、変質領域１２を形成する。Next, as shown in FIG. 2C, dry etching such as RIE is performed on the upper surface of the Ga 2 O 3 substrate 11 to form the altered region 12.

ＲＩＥにより変質領域１２を形成する場合、反応ガスとして、例えば、流量３５ｓｃｃｍのＢＣｌ3ガスと流量５ｓｃｃｍのＡｒガスを用いる。また、圧力、出力、処理時間は、例えば、それぞれ５．０Ｐａ、１００〜１５０Ｗ、１〜３ｍｉｎである。When the altered region 12 is formed by RIE, for example, BCl 3 gas having a flow rate of 35 sccm and Ar gas having a flow rate of 5 sccm are used as the reaction gas. Moreover, a pressure, an output, and processing time are 5.0 Pa, 100-150 W, and 1-3 min, respectively, for example.

なお、これらの処理条件はエッチングレートやエッチング量に影響を与えるが、変質領域１２とカソード電極１４と間のオーミック特性にはほとんど影響を与えない。   These processing conditions affect the etching rate and the etching amount, but hardly affect the ohmic characteristics between the altered region 12 and the cathode electrode 14.

変質領域１２をＧａ2Ｏ3系基板１１の上面の一部に形成する場合は、Ｇａ2Ｏ3系基板１１の上面を所定のパターンを有するマスクで覆った状態でエッチングを行う。この場合、Ｇａ2Ｏ3系基板１１のエッチングされた領域である変質領域１２の表面の高さは、Ｇａ2Ｏ3系基板１１のエッチングされていない領域の表面の高さよりも低くなる。When forming a modified region 12 in a part of the upper surface of the Ga 2 O 3 based substrate 11 is etched while covering the upper surface of the Ga 2 O 3 based substrate 11 with a mask having a predetermined pattern. In this case, the height of the etched area and is affected region 12 the surface of the Ga 2 O 3 based substrate 11 is lower than the height of the surface of the area not etched in Ga 2 O 3 based substrate 11.

次に、図２Ｄに示されるように、変質領域１２及びＧａ2Ｏ3系単結晶層１３に、カソード電極１４及びアノード電極１５をそれぞれ接続する。なお、良好なオーミック接合を得るためには変質領域１２を形成した直後にカソード電極１４を形成することが好ましい。なお、変質領域１２を形成する前にアノード電極１５を形成してもよい。Next, as shown in FIG. 2D, a cathode electrode 14 and an anode electrode 15 are connected to the altered region 12 and the Ga 2 O 3 based single crystal layer 13, respectively. In order to obtain a good ohmic junction, it is preferable to form the cathode electrode 14 immediately after the altered region 12 is formed. Note that the anode electrode 15 may be formed before the altered region 12 is formed.

〔第２の実施の形態〕
第２の実施の形態は、変質領域がＧａ2Ｏ3系基板上のＧａ2Ｏ3系単結晶層に形成される点において、第１の実施の形態と異なる。なお、第１の実施の形態と同様の点については、説明を省略又は簡略化する。[Second Embodiment]
The second embodiment, in that the affected region is formed on the Ga 2 O 3 system single crystal layer on the Ga 2 O 3 based substrate, different from the first embodiment. Note that the description of the same points as in the first embodiment will be omitted or simplified.

（ＳＢＤの構成）
図３は、第２の実施の形態に係るＳＢＤの断面図である。ＳＢＤ２０は、Ｇａ2Ｏ3系基板１１と、Ｇａ2Ｏ3系基板１１の上面（図３の上側の面）に形成されたＧａ2Ｏ3系単結晶層２６と、Ｇａ2Ｏ3系単結晶層２６の上面（図３の上側の面）に形成された変質領域２２と、Ｇａ2Ｏ3系基板１１の下面（図１の下側の面）に形成されたＧａ2Ｏ3系単結晶層１３と、Ｇａ2Ｏ3系単結晶層２６の変質領域２２上に形成されたカソード電極１４と、Ｇａ2Ｏ3系単結晶層１３のＧａ2Ｏ3系基板１１と反対側の面上に形成されたアノード電極１５と、を含む。(Configuration of SBD)
FIG. 3 is a cross-sectional view of the SBD according to the second embodiment. SBD20 is, Ga and 2 O 3 based substrate 11, and Ga 2 O 3 system single crystal layer 26 formed on the upper surface (upper surface in FIG. 3) of the Ga 2 O 3 based substrate 11, Ga 2 O 3 system single The altered region 22 formed on the upper surface (upper surface in FIG. 3) of the crystal layer 26 and the Ga 2 O 3 single layer formed on the lower surface (lower surface in FIG. 1) of the Ga 2 O 3 substrate 11. The cathode layer 14 formed on the crystalline layer 13, the altered region 22 of the Ga 2 O 3 single crystal layer 26, and the surface of the Ga 2 O 3 single crystal layer 13 opposite to the Ga 2 O 3 substrate 11 And an anode electrode 15 formed thereon.

変質領域２２は、Ｇａ2Ｏ3系単結晶層２６の酸素が欠損したドナー濃度の高い領域であり、Ｇａ2Ｏ3系単結晶層２６の表面にＲＩＥ等のドライエッチングを施すことにより形成される。The altered region 22 is a region having a high donor concentration in which Ga 2 O 3 single crystal layer 26 is deficient in oxygen, and is formed by subjecting the surface of Ga 2 O 3 single crystal layer 26 to dry etching such as RIE. The

Ｇａ2Ｏ3系単結晶層２６は、Ｇａ2Ｏ3系単結晶からなる結晶層である。Ｇａ2Ｏ3系単結晶層２６は、Ｓｉ、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｒｕ、Ｒｈ、Ｉｒ、Ｃ、Ｓｎ、Ｇｅ、Ｐｂ、Ｍｎ、Ａｓ、Ｓｂ、Ｂｉ、Ｆ、Ｃｌ、Ｂｒ、又はＩ等のｎ型ドーパントを含む。Ｇａ2Ｏ3系単結晶層２６のドナー濃度は、例えば、１×１０18／ｃｍ3である。また、Ｇａ2Ｏ3系単結晶層２６の厚さは、例えば、３０ｎｍである。The Ga 2 O 3 single crystal layer 26 is a crystal layer made of a Ga 2 O 3 single crystal. The Ga 2 O 3 single crystal layer 26 is made of Si, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Ru, Rh, Ir, C, Sn, Ge, Pb, Mn, As, Sb, Bi. , F, Cl, Br, or I. The donor concentration of the Ga 2 O 3 single crystal layer 26 is, for example, 1 × 10 18 / cm 3 . The thickness of the Ga 2 O 3 single crystal layer 26 is, for example, 30 nm.

カソード電極１４は、変質領域２２とオーミック接合する。アノード電極１５は、Ｇａ2Ｏ3系単結晶層１３とショットキー接合する。なお、Ｇａ2Ｏ3系単結晶層１３は、ＳＢＤ２０に含まれなくてもよい。その場合、アノード電極１５は、Ｇａ2Ｏ3系基板１１とショットキー接合する。The cathode electrode 14 is in ohmic contact with the altered region 22. The anode electrode 15 is in Schottky junction with the Ga 2 O 3 single crystal layer 13. The Ga 2 O 3 single crystal layer 13 may not be included in the SBD 20. In that case, the anode electrode 15 is in Schottky junction with the Ga 2 O 3 substrate 11.

（ＳＢＤの製造方法）
以下に、本実施の形態のＳＢＤ２０の製造方法の一例を示す。(Manufacturing method of SBD)
Below, an example of the manufacturing method of SBD20 of this Embodiment is shown.

図４Ａ〜図４Ｄは、第２の実施の形態に係るＳＢＤの製造工程を表す断面図である。   4A to 4D are cross-sectional views illustrating the manufacturing process of the SBD according to the second embodiment.

まず、図４Ａに示されるように、Ｇａ2Ｏ3系基板１１の上面にｎ型ドーパントを含むＧａ2Ｏ3系単結晶をエピタキシャル成長させ、Ｇａ2Ｏ3系単結晶層２６を形成する。First, as shown in FIG. 4A, a Ga 2 O 3 -based single crystal layer 26 is formed by epitaxially growing a Ga 2 O 3 -based single crystal containing an n-type dopant on the upper surface of the Ga 2 O 3 -based substrate 11.

次に、図４Ｂに示されるように、Ｇａ2Ｏ3系基板１１の下面にｎ型ドーパントを含むＧａ2Ｏ3系単結晶をエピタキシャル成長させ、Ｇａ2Ｏ3系単結晶層１３を形成する。Next, as shown in FIG. 4B, a Ga 2 O 3 single crystal layer 13 is formed by epitaxially growing a Ga 2 O 3 single crystal containing an n-type dopant on the lower surface of the Ga 2 O 3 substrate 11.

次に、図４Ｃに示されるように、Ｇａ2Ｏ3系単結晶層２６の上面にＲＩＥ等のドライエッチングを施し、変質領域２２を形成する。変質領域２２は、第１の実施の形態の変質領域１２と同様の処理条件により形成することができる。Next, as shown in FIG. 4C, dry etching such as RIE is performed on the upper surface of the Ga 2 O 3 based single crystal layer 26 to form the altered region 22. The altered region 22 can be formed under the same processing conditions as the altered region 12 of the first embodiment.

次に、図４Ｄに示されるように、変質領域２２及びＧａ2Ｏ3系単結晶層１３に、カソード電極１４及びアノード電極１５をそれぞれ接続する。なお、良好なオーミック接合を得るためには変質領域２２を形成した直後にカソード電極１４を形成することが好ましいため、アノード電極１５よりも前にカソード電極１４を形成することが好ましい。Next, as shown in FIG. 4D, the cathode electrode 14 and the anode electrode 15 are connected to the altered region 22 and the Ga 2 O 3 based single crystal layer 13, respectively. In order to obtain a good ohmic junction, it is preferable to form the cathode electrode 14 immediately after the altered region 22 is formed. Therefore, it is preferable to form the cathode electrode 14 before the anode electrode 15.

〔第３の実施の形態〕
第３の実施の形態は、半導体素子としてのＭＥＳＦＥＴ（Metal Semiconductor Field Effect Transistor）について説明する。なお、第１の実施の形態と同様の点については、説明を省略又は簡略化する。
[Third Embodiment]
In the third embodiment, a MESFET (Metal Semiconductor Field Effect Transistor) as a semiconductor element will be described. Note that the description of the same points as in the first embodiment will be omitted or simplified.

（ＭＥＳＦＥＴの構成）
図５は、第３の実施の形態に係るＭＥＳＦＥＴの断面図である。ＭＥＳＦＥＴ４０は、Ｇａ2Ｏ3系基板３１と、Ｇａ2Ｏ3系基板３１の上面（図５の上側の面）に形成されたＧａ2Ｏ3系単結晶層４６と、Ｇａ2Ｏ3系単結晶層４６の上面に形成された変質領域４２ａ、４２ｂと、変質領域４２ａ、４２ｂの上面にそれぞれ形成されたソース電極３３ａ及びドレイン電極３３ｂと、Ｇａ2Ｏ3系単結晶層４６の上面の変質領域４２ａ、４２ｂが形成されない領域上のソース電極３３ａとドレイン電極３３ｂの間のゲート電極３４と、を含む。(Configuration of MESFET)
FIG. 5 is a cross-sectional view of a MESFET according to the third embodiment. MESFET40 includes a Ga 2 O 3 based substrate 31, and Ga 2 O 3 system Ga 2 O 3 system single crystal layer 46 formed on the upper surface (upper surface in FIG. 5) of the substrate 31, Ga 2 O 3 system single Alteration of the altered regions 42a and 42b formed on the upper surface of the crystal layer 46, the source electrode 33a and the drain electrode 33b respectively formed on the upper surfaces of the altered regions 42a and 42b, and the alteration of the upper surface of the Ga 2 O 3 single crystal layer 46 And the gate electrode 34 between the source electrode 33a and the drain electrode 33b on the region where the regions 42a and 42b are not formed.

Ｇａ2Ｏ3系基板３１は、Ｇａ2Ｏ3系単結晶からなる。Ｇａ2Ｏ3系基板３１は、アンドープの高抵抗基板、又はＭｇ、Ｈ、Ｌｉ、Ｎａ、Ｋ、Ｒｂ、Ｃｓ、Ｆｒ、Ｂｅ、Ｃａ、Ｓｒ、Ｂａ、Ｒａ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｐｄ、Ｃｕ、Ａｇ、Ａｕ、Ｚｎ、Ｃｄ、Ｈｇ、Ｔｌ、Ｐｂ、Ｎ、又はＰ等のｐ型ドーパントを添加することにより高抵抗化した高抵抗基板である。The Ga 2 O 3 based substrate 31 is made of a Ga 2 O 3 based single crystal. The Ga 2 O 3 based substrate 31 is an undoped high resistance substrate, or Mg, H, Li, Na, K, Rb, Cs, Fr, Be, Ca, Sr, Ba, Ra, Mn, Fe, Co, Ni, This is a high-resistance substrate having a high resistance by adding a p-type dopant such as Pd, Cu, Ag, Au, Zn, Cd, Hg, Tl, Pb, N, or P.

変質領域４２ａ、４２ｂは、Ｇａ2Ｏ3系基板３１の酸素が欠損したドナー濃度の高い領域であり、Ｇａ2Ｏ3系基板３１の表面にＲＩＥ等のドライエッチングを施すことにより形成される。変質領域４２ａ、４２ｂを形成するためのドライエッチングの条件は、第１の実施の形態の変質領域１２と同様である。The altered regions 42a and 42b are regions having a high donor concentration in which Ga 2 O 3 substrate 31 is deficient in oxygen, and are formed by subjecting the surface of Ga 2 O 3 substrate 31 to dry etching such as RIE. The dry etching conditions for forming the altered regions 42a and 42b are the same as those in the altered region 12 of the first embodiment.

Ｇａ2Ｏ3系単結晶層４６は、Ｇａ2Ｏ3系単結晶からなる結晶層である。Ｇａ2Ｏ3系単結晶層４６は、Ｓｉ、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｍｏ、Ｗ、Ｒｕ、Ｒｈ、Ｉｒ、Ｃ、Ｓｎ、Ｇｅ、Ｐｂ、Ｍｎ、Ａｓ、Ｓｂ、Ｂｉ、Ｆ、Ｃｌ、Ｂｒ、又はＩ等のｎ型ドーパントを含む。Ｇａ2Ｏ3系単結晶層４６は、ＭＥＳＦＥＴ４０のチャネル層として機能する。Ｇａ2Ｏ3系単結晶層４６のドナー濃度は、例えば、２×１０17〜３×１０17／ｃｍ3である。また、Ｇａ2Ｏ3系単結晶層１３の厚さは、例えば、３００ｎｍである。The Ga 2 O 3 single crystal layer 46 is a crystal layer made of a Ga 2 O 3 single crystal. The Ga 2 O 3 single crystal layer 46 is made of Si, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Ru, Rh, Ir, C, Sn, Ge, Pb, Mn, As, Sb, Bi. , F, Cl, Br, or I. The Ga 2 O 3 single crystal layer 46 functions as a channel layer of the MESFET 40. The donor concentration of the Ga 2 O 3 single crystal layer 46 is, for example, 2 × 10 17 to 3 × 10 17 / cm 3 . The thickness of the Ga 2 O 3 single crystal layer 13 is, for example, 300 nm.

ソース電極３３ａ及びドレイン電極３３ｂは、変質領域４２ａ、４２ｂとそれぞれオーミック接合し、変質領域４２ａ、４２ｂは、ソース電極３３ａ及びドレイン電極３３ｂのコンタクト領域としてそれぞれ機能する。   The source electrode 33a and the drain electrode 33b are in ohmic contact with the altered regions 42a and 42b, respectively, and the altered regions 42a and 42b function as contact regions for the source electrode 33a and the drain electrode 33b, respectively.

（ＭＥＳＦＥＴの製造方法）
以下に、本実施の形態のＭＥＳＦＥＴ４０の製造方法の一例を示す。(Method for manufacturing MESFET)
Below, an example of the manufacturing method of MESFET40 of this Embodiment is shown.

図６Ａ〜図６Ｄは、第３の実施の形態に係るＭＥＳＦＥＴの製造工程を表す断面図である。   6A to 6D are cross-sectional views illustrating the manufacturing process of the MESFET according to the third embodiment.

まず、図６Ａに示されるように、Ｇａ2Ｏ3系基板３１の上面にｎ型ドーパントを含むＧａ2Ｏ3系単結晶をエピタキシャル成長させ、Ｇａ2Ｏ3系単結晶層４６を形成する。First, as shown in FIG. 6A, Ga 2 on the upper surface of the O 3 based substrate 31 is epitaxially grown Ga 2 O 3 single crystal containing an n-type dopant to form a Ga 2 O 3 system single crystal layer 46.

次に、図６Ｂに示されるように、フォトリソグラフィ等により、Ｇａ2Ｏ3系単結晶層４６上に変質領域４２ａ、４２ｂのパターンを有するマスク４５を形成する。Next, as shown in FIG. 6B, a mask 45 having a pattern of altered regions 42a and 42b is formed on the Ga 2 O 3 single crystal layer 46 by photolithography or the like.

次に、図６Ｃに示されるように、マスク４５に覆われたＧａ2Ｏ3系単結晶層４６の上面にＲＩＥ等のドライエッチングを施し、変質領域４２ａ、４２ｂを形成する。Next, as shown in FIG. 6C, dry etching such as RIE is performed on the upper surface of the Ga 2 O 3 single crystal layer 46 covered with the mask 45 to form altered regions 42a and 42b.

次に、図６Ｄに示されるように、変質領域４２ａ、４２ｂにソース電極３３ａ及びドレイン電極３３ｂをそれぞれ接続し、Ｇａ2Ｏ3系単結晶層４６上のソース電極３３ａとドレイン電極３３ｂとの間の領域にゲート電極３４を接続する。ここで、ソース電極３３ａ及びドレイン電極３３ｂは、変質領域４２ａ、４２ｂ上、及びマスク４５上を覆うように金属膜を形成した後、金属膜のマスク４５上の部分をマスク４５と共に除去（リフトオフ）することにより形成される。Next, as shown in FIG. 6D, the source electrode 33a and the drain electrode 33b are connected to the altered regions 42a and 42b, respectively, and between the source electrode 33a and the drain electrode 33b on the Ga 2 O 3 based single crystal layer 46. The gate electrode 34 is connected to this region. Here, after forming a metal film so that the source electrode 33a and the drain electrode 33b cover the altered regions 42a and 42b and the mask 45, a portion of the metal film on the mask 45 is removed together with the mask 45 (lift-off). It is formed by doing.

（実施の形態の効果）
本実施の形態によれば、Ｇａ2Ｏ3系基板やＧａ2Ｏ3系基板上のＧａ2Ｏ3系単結晶層の表面にドライエッチングにより変質領域を形成することにより、金属電極を低抵抗でオーミック接合させることができる。それによって、動作性能に優れた半導体素子を形成することができる。(Effect of embodiment)
According to the present embodiment, the metal electrode is made to have a low resistance by forming an altered region by dry etching on the surface of the Ga 2 O 3 based single crystal layer on the Ga 2 O 3 based substrate or the Ga 2 O 3 based substrate. Can be ohmic-bonded. As a result, a semiconductor element having excellent operation performance can be formed.

なお、本発明は、上記実施の形態に限定されず、発明の主旨を逸脱しない範囲内において種々変形実施が可能である。また、発明の主旨を逸脱しない範囲内において上記実施の形態の構成要素を任意に組み合わせることができる。   The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention. In addition, the constituent elements of the above-described embodiment can be arbitrarily combined without departing from the spirit of the invention.

Ｇａ2Ｏ3基板の表面に変質領域を形成した場合、及び形成しない場合の、Ｇａ2Ｏ3基板の表面の電流−電圧特性を測定した。面方位が（０１０）のＧａ2Ｏ3基板の主面に直径０．２ｍｍの２つのＴｉ電極を接続して測定を行った。The current-voltage characteristics of the surface of the Ga 2 O 3 substrate when the altered region was formed on the surface of the Ga 2 O 3 substrate and when the altered region was not formed were measured. The measurement was performed by connecting two Ti electrodes having a diameter of 0.2 mm to the main surface of the (010) Ga 2 O 3 substrate.

図７Ａは、ドナー濃度が１×１０19ｃｍ-3のＧａ2Ｏ3基板の電流−電圧特性を示す。図７Ｂは、ドナー濃度が４×１０17ｃｍ-3のＧａ2Ｏ3基板の電流−電圧特性を示す。ここで、図７Ａ、図７Ｂの実線はドライエッチングにより変質領域が形成されたＧａ2Ｏ3基板の測定値、点線は変質領域が形成されていないＧａ2Ｏ3基板の測定値を示す。FIG. 7A shows current-voltage characteristics of a Ga 2 O 3 substrate having a donor concentration of 1 × 10 19 cm −3 . FIG. 7B shows the current-voltage characteristics of a Ga 2 O 3 substrate with a donor concentration of 4 × 10 17 cm −3 . Here, FIG. 7A, the solid line in FIG. 7B measure of Ga 2 O 3 substrate affected region is formed by dry etching, and the dotted line shows the measurements of Ga 2 O 3 substrate affected region is not formed.

図７Ａ、図７Ｂは、Ｇａ2Ｏ3基板に変質領域が形成されない場合にはＧａ2Ｏ3基板の表面と電極はショットキー接合しており、Ｇａ2Ｏ3基板に変質領域が形成される場合にはＧａ2Ｏ3基板の表面（変質領域）と電極はオーミック接合していることを示している。7A, 7B, the surface and the electrode of the Ga 2 O 3 substrate is Schottky junction, Ga 2 O 3 substrate in the affected region is formed when the affected region in the Ga 2 O 3 substrate is not formed In this case, the surface (modified region) of the Ga 2 O 3 substrate and the electrode are in ohmic contact.

次に、第１の実施の形態に係るＳＢＤ１０の順方向特性を調べた。ＳＢＤ１０のＧａ2Ｏ3系基板１１の上面に変質領域１２を形成した場合、及び形成しない場合の、Ｇａ2Ｏ3系基板１１の表面の電流−電圧特性を測定した。Next, the forward characteristics of the SBD 10 according to the first embodiment were examined. The current-voltage characteristics of the surface of the Ga 2 O 3 substrate 11 were measured when the altered region 12 was formed on the upper surface of the Ga 2 O 3 substrate 11 of the SBD 10 and when it was not formed.

ここで、測定に用いたＧａ2Ｏ3系基板１１は、ｎ型ドーパントとしてＳｉを含み、ドナー濃度が１×１０19ｃｍ-3である。また、Ｇａ2Ｏ3系単結晶層１３は、ｎ型ドーパントとしてＳｎを含み、ドナー濃度が４×１０16ｃｍ-3である。Here, the Ga 2 O 3 -based substrate 11 used for the measurement contains Si as an n-type dopant and has a donor concentration of 1 × 10 19 cm −3 . The Ga 2 O 3 single crystal layer 13 includes Sn as an n-type dopant and has a donor concentration of 4 × 10 16 cm −3 .

変質領域１２を形成するために、ＲＩＥの反応ガスとして、流量３５ｓｃｃｍのＢＣｌ3ガスと流量５ｓｃｃｍのＡｒガスを用いた。また、圧力、出力、処理時間は、それぞれ５．０Ｐａ、１５０Ｗ、３ｍｉｎとした。In order to form the altered region 12, BCl 3 gas having a flow rate of 35 sccm and Ar gas having a flow rate of 5 sccm were used as RIE reaction gases. The pressure, output, and processing time were 5.0 Pa, 150 W, and 3 min, respectively.

図８は、ＳＢＤ１０の順方向の電流−電圧特性を示す。ここで、図８の実線は変質領域が形成されたＧａ2Ｏ3系基板の測定値、点線は変質領域が形成されていないＧａ2Ｏ3系基板の測定値を示す。FIG. 8 shows a forward current-voltage characteristic of the SBD 10. Here, the solid line in FIG. 8 is the measured value of Ga 2 O 3 system board affected region is formed, and the dotted line shows the measurements of Ga 2 O 3 system board affected region is not formed.

ＳＢＤ１０のＧａ2Ｏ3系基板１１の上面に変質領域１２が形成されない場合は、Ｇａ2Ｏ3系基板１１の上面とカソード電極１４の接合は、接触抵抗の大きいショットキーライクな接合となるため、ＳＢＤ１０の順方向特性を悪化させる。そのため、図８の点線で示されるように、変質領域１２が形成されない場合は、順方向の立ち上がり電圧ＶTが２．１Ｖと大きい。When the altered region 12 is not formed on the upper surface of the Ga 2 O 3 based substrate 11 of the SBD 10, the upper surface of the Ga 2 O 3 based substrate 11 and the cathode electrode 14 are joined together in a Schottky-like manner having a large contact resistance. The forward characteristics of the SBD 10 are deteriorated. Therefore, as shown by the dotted line in FIG. 8, when the altered region 12 is not formed, the forward rising voltage V T is as large as 2.1V.

一方、ＳＢＤ１０のＧａ2Ｏ3系基板１１の上面に変質領域１２が形成される場合は、Ｇａ2Ｏ3系基板１１の上面（変質領域１２）とカソード電極１４の接合は、接触抵抗の小さいオーミック接合となる。そのため、図８の実線で示されるように、変質領域１２が形成される場合は、順方向の立ち上がり電圧ＶTが１．２Ｖ程度であり、変質領域１２が形成されない場合よりも小さい。これらの結果から、変質領域１２を形成することにより、ＳＢＤ１０の特性が大きく向上することが確認された。On the other hand, when the altered region 12 is formed on the upper surface of the Ga 2 O 3 substrate 11 of the SBD 10, the junction between the upper surface (the altered region 12) of the Ga 2 O 3 substrate 11 and the cathode electrode 14 has a small contact resistance. Ohmic junction. Therefore, as shown by the solid line in FIG. 8, when the altered region 12 is formed, the forward rising voltage V T is about 1.2 V, which is smaller than when the altered region 12 is not formed. From these results, it was confirmed that the characteristics of the SBD 10 are greatly improved by forming the altered region 12.

次に、反応性イオンエッチングにより変質領域を形成する場合の、反応性イオンエッチングに用いる反応ガスとＧａ２Ｏ３基板の電流−電圧特性を調べた。面方位が（０１０）、ドナー濃度が４×１０１７ｃｍ−３のＧａ２Ｏ３基板の主面に、直径０．１ｍｍの円形電極と、長さ０．０１ｍｍのすきまを空けてそれを取り囲むように作製した大面積電極、２つのＴｉ電極を接続して測定を行った。Next, the current-voltage characteristics of the reactive gas used for reactive ion etching and the Ga 2 O 3 substrate when the altered region was formed by reactive ion etching were examined. A circular electrode having a diameter of 0.1 mm and a gap having a length of 0.01 mm are formed around a main surface of a Ga 2 O 3 substrate having a plane orientation of (010) and a donor concentration of 4 × 10 17 cm −3. The measurement was performed by connecting the large-area electrode and the two Ti electrodes prepared as described above.

図９は、Ａｒガス、ＣＦ4ガス、ＢＣｌ3ガス、ＢＣｌ3とＡｒとの混合ガスの４種の反応ガスを用いて変質領域がそれぞれ形成された４つのＧａ2Ｏ3基板の電流−電圧特性を示す。FIG. 9 shows the current-voltage of four Ga 2 O 3 substrates in which altered regions are formed using four kinds of reaction gases of Ar gas, CF 4 gas, BCl 3 gas, and mixed gas of BCl 3 and Ar, respectively. Show the characteristics.

図９は、変質領域がＡｒガス又はＣＦ4ガスを用いて形成される場合にはＧａ2Ｏ3基板の表面（変質領域）と電極はショットキー接合し、変質領域がＢＣｌ3ガス又はＢＣｌ3とＡｒとの混合ガスを用いて形成される場合にはＧａ2Ｏ3基板の表面（変質領域）と電極はオーミック接合することを示している。FIG. 9 shows that when the altered region is formed using Ar gas or CF 4 gas, the surface (modified region) of the Ga 2 O 3 substrate and the electrode are in Schottky junction, and the altered region is BCl 3 gas or BCl 3. In the case of using a mixed gas of Ar and Ar, the surface (modified region) of the Ga 2 O 3 substrate and the electrode are in ohmic contact.

この結果から、反応性イオンエッチングにより変質領域を形成する場合は、金属電極をオーミック接合させることができる変質領域を形成するための反応ガスとして、ＢＣｌ3を含むガスを使用できることがわかる。From this result, it can be seen that when the altered region is formed by reactive ion etching, a gas containing BCl 3 can be used as a reactive gas for forming the altered region capable of ohmic bonding the metal electrode.

以上、本発明の実施の形態及び実施例を説明したが、上記に記載した実施の形態及び実施例は特許請求の範囲に係る発明を限定するものではない。また、実施の形態及び実施例の中で説明した特徴の組合せの全てが発明の課題を解決するための手段に必須であるとは限らない点に留意すべきである。   While the embodiments and examples of the present invention have been described above, the embodiments and examples described above do not limit the invention according to the claims. It should be noted that not all combinations of features described in the embodiments and examples are necessarily essential to the means for solving the problems of the invention.

Ｇａ2Ｏ3系単結晶に電極を低抵抗で接続することができる半導体素子の製造方法、及び低抵抗で接続されたＧａ2Ｏ3系単結晶と電極を含む半導体素子を提供する。A method of manufacturing a semiconductor element capable of connecting an electrode to a Ga 2 O 3 single crystal with low resistance, and a semiconductor element including a Ga 2 O 3 single crystal connected with a low resistance and an electrode are provided.

１０、２０…ＳＢＤ、４０…ＭＥＳＦＥＴ、１１、３１…Ｇａ2Ｏ3系基板、１２、２２、４２ａ、４２ｂ…変質領域、１４…カソード電極、２６、４６…Ｇａ2Ｏ3系単結晶層、３３ａ…ソース電極、３３ｂ…ドレイン電極、３４…ゲート電極10,20 ... SBD, 40 ... MESFET, 11,31 ... Ga 2 O 3 based substrate, 12,22,42A, 42b ... affected region, 14 ... cathode electrode, 26, 46 ... Ga 2 O 3 system single crystal layer, 33a ... Source electrode, 33b ... Drain electrode, 34 ... Gate electrode

Claims (7)

Ｇａ２Ｏ３系単結晶の表面にＢＣｌ ３ を含むガスを用いた反応性イオンエッチングを施し、変質領域を形成する工程と、
前記変質領域上に、前記変質領域とオーミック接合する金属電極を形成する工程と、
を含む半導体素子の製造方法。 Performing reactive ion etching using a gas containing BCl 3 on the surface of a Ga 2 O 3 based single crystal to form an altered region;
Forming a metal electrode in ohmic contact with the altered region on the altered region;
A method for manufacturing a semiconductor device comprising: 前記Ｇａ ２ Ｏ ３ 系単結晶の前記表面の一部に前記反応性イオンエッチングを施し、前記変質領域を形成する、
請求項１に記載の半導体素子の製造方法。 Applying the reactive ion etching to a part of the surface of the Ga 2 O 3 based single crystal to form the altered region;
The method for manufacturing a semiconductor device according to claim 1 . Ｇａ２Ｏ３系単結晶からなる基板と、
前記基板の第１の面、又は前記第１の面上のＧａ２Ｏ３系単結晶からなる第１の結晶層の前記基板と反対側の面に、酸素原子又はＧａ原子のエッチングガスイオンによる置換、エッチングガスイオンの結晶格子間への侵入、又は結晶構造の変化（乱れ）のうちの少なくとも１つを含む変質領域と、
前記変質領域上に形成され、前記変質領域とオーミック接合する金属電極と、
を含む半導体素子。 A substrate made of a Ga 2 O 3 based single crystal;
The first surface of the substrate or the surface of the first crystal layer made of a Ga 2 O 3 based single crystal on the first surface opposite to the substrate is caused by oxygen atoms or etching gas ions of Ga atoms. An altered region including at least one of substitution, penetration of etching gas ions between crystal lattices, or change (disturbance) of crystal structure ;
A metal electrode formed on the altered region and in ohmic contact with the altered region;
A semiconductor device comprising: 前記基板の前記第１の面と反対側の第２の面、又は前記第２の面上のＧａ２Ｏ３系単結晶からなる第２の結晶層の前記基板と反対側の面上に形成されたアノード電極と、
を有し、
前記金属電極がカソード電極である、
請求項３に記載の半導体素子。 Formed on the second surface of the substrate opposite to the first surface, or on the surface opposite to the substrate of the second crystal layer made of a Ga 2 O 3 based single crystal on the second surface. An anode electrode,
Have
The metal electrode is a cathode electrode;
The semiconductor device according to claim 3 . 前記金属電極は、ソース電極、ドレイン電極、及び前記ソース電極と前記ドレイン電極の間のゲート電極である、
請求項３に記載の半導体素子。 The metal electrode is a source electrode, a drain electrode, and a gate electrode between the source electrode and the drain electrode.
The semiconductor device according to claim 3 . 前記変質領域は、前記基板又は前記第１の結晶層の一部に形成され、
前記変質領域の表面の高さは、前記基板又は前記第１の結晶層の前記変質領域の形成されていない領域の表面の高さよりも低い、
請求項３に記載の半導体素子。 The altered region is formed in a part of the substrate or the first crystal layer,
The height of the surface of the altered region is lower than the height of the surface of the region where the altered region of the substrate or the first crystal layer is not formed,
The semiconductor device according to claim 3 . 前記第１の結晶層の前記変質領域が形成されない領域上のゲート電極を含み、
前記第１の結晶層は導電型不純物を含み、
前記金属電極は、前記ゲート電極の両側のソース電極及びドレイン電極である、
請求項６に記載の半導体素子。 A gate electrode on a region where the altered region of the first crystal layer is not formed;
The first crystal layer includes a conductive impurity;
The metal electrode is a source electrode and a drain electrode on both sides of the gate electrode,
The semiconductor device according to claim 6 .
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