WO2015045627A1 - 炭化珪素半導体装置の製造方法 - Google Patents
炭化珪素半導体装置の製造方法 Download PDFInfo
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- H01L21/0445—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 crystalline silicon carbide
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Definitions
- the present invention relates to a silicon carbide semiconductor device. More specifically, the present invention relates to a method for manufacturing a silicon carbide semiconductor device.
- silicon carbide semiconductor devices have been put into practical use as power semiconductor devices. This is because by using a silicon carbide material for a semiconductor device, a higher breakdown voltage and a lower on-resistance can be expected as compared with a semiconductor device using a silicon material which is currently mainstream.
- impurities are doped into the semiconductor substrate by, for example, an ion implantation method (see, for example, Japanese Patent Application Laid-Open No. 2001-68428 (Patent Document 1)).
- the doping region formed by ion implantation or the like is activated by performing annealing thereafter. Since the annealing temperature at this time reaches a high temperature of 1500 ° C. or higher, sublimation or the like may occur on the upper surface of the substrate, and surface roughness may occur. When the surface roughness occurs in this way, the manufacturing yield of the semiconductor device decreases.
- Patent Document 1 discloses a method in which a protective film is formed on the upper surface of a silicon carbide substrate and then annealed. When this method is used, sublimation is suppressed by the protective film, and surface roughness on the upper surface of the substrate can be prevented.
- a method for manufacturing a silicon carbide semiconductor device includes a step of preparing a silicon carbide substrate having a first main surface and a second main surface located on the opposite side of the first main surface; Forming a doped region in the silicon carbide substrate by doping an impurity into the first main surface; forming a first protective film on the first main surface; and on the second main surface Forming a second protective film, and the step of forming the first protective film is performed after the step of forming the doping region, and at least a part of the first main surface is the first. And the step of activating impurities contained in the doping region by annealing in a state where at least a part of the second main surface is covered with the second protective film.
- the silicon carbide semiconductor device can be manufactured with a high yield.
- this embodiment an outline of an embodiment of the present invention (hereinafter also referred to as “this embodiment”) will be described in the following (1) to (9).
- the present inventor conducted intensive research to solve the above problems, and as the substrate diameter increases, the adhesion between the susceptor supporting the silicon carbide substrate and the silicon carbide substrate decreases during annealing.
- the inventors have found that the sublimation of atoms also occurs from the lower surface of the substrate, which causes problems such as warping of the substrate, and have completed the present embodiment. That is, the method for manufacturing a silicon carbide semiconductor device according to the present embodiment has the following configuration.
- a step S4 of forming the second protective film 20, and the step S3 of forming the first protective film 10 is performed after the step S2 of forming the doping region, and further includes at least the first main surface P1.
- Step S5 for activation is provided
- the surface roughness of the substrate is the upper surface (first main surface) of the substrate. It was a problem only on the P1) side. This is presumably because there was no gap between the substrate and the susceptor in the case of a substrate having a relatively small diameter.
- the aperture of the substrate is increased, atoms are sublimated from the substrate in a slight gap generated between the substrate and the susceptor, and surface roughness occurs locally on the lower surface (second main surface P2). Then, the surface roughness becomes a starting point, causing the substrate to warp, and further, the gap increases due to the warping of the substrate, and the surface roughness on the lower surface is promoted.
- the first protective film 10 is formed on the upper surface of the silicon carbide substrate 100
- the second protective film 20 is formed on the lower surface of the silicon carbide substrate 100, so that the surface is also roughened on the lower surface of the substrate. Can be suppressed and the warpage of the substrate can be prevented.
- At least one of the first protective film 10 and the second protective film 20 is preferably an organic film. This is because the organic film is carbonized into a carbon film in the temperature rising process of activation annealing. Thereby, a protective film that can withstand activation annealing can be obtained.
- the organic film for example, a photoresist generally used for manufacturing a semiconductor device can be used.
- At least one of the first protective film 10 and the second protective film 20 is preferably a diamond-like carbon film.
- a diamond-like carbon film (hereinafter also referred to as “DLC (Diamond-Like Carbon) film”) can have heat resistance capable of withstanding activation annealing.
- the DLC film can be easily formed by a method such as ECR (Electron Cyclotron Resonance) sputtering.
- At least one of the first protective film 10 and the second protective film 20 is a carbon layer.
- the carbon layer can have heat resistance that can withstand activation annealing.
- the carbon layer is preferably formed by partially removing silicon from the silicon carbide substrate 100.
- the carbon layer thus formed can be a layer containing carbon derived from silicon carbide substrate 100. Since such a carbon layer can cover the surface of silicon carbide substrate 100 densely, sublimation of atoms from the substrate can be efficiently suppressed.
- the second protective film 20 covers the entire surface of the second main surface P2. Thereby, substantially all of the portion of silicon carbide substrate 100 used as a device can be covered. And the curvature of a board
- preparing step S1 a plurality of silicon carbide substrates 100 are prepared, and in the activation step S5, the plurality of silicon carbide substrates 100 are spaced one by one along the direction intersecting the first main surface P1. It is preferable that the annealing is performed in a state where the opening is held.
- the second protective film 20 is also formed on the second main surface P2, activation annealing can be performed with the second main surface P2 exposed. That is, the process restriction that silicon carbide substrate 100 must be held by a susceptor or the like during activation annealing is eliminated. Thereby, silicon carbide substrate 100 is stacked in a direction intersecting with first main surface P1 (for example, a vertical direction perpendicular to first main surface P1) with a gap therebetween, and a plurality of substrates are processed together. It becomes possible. Thereby, the productivity of the silicon carbide semiconductor device can be significantly improved.
- the silicon carbide substrate 100 preferably has a diameter of 100 mm or more.
- the diameter of silicon carbide substrate 100 can be set to 4 inches or more, for example.
- the thickness of the silicon carbide substrate 100 is preferably 600 ⁇ m or less.
- the substrate can be prevented from warping, and a thin substrate having a thickness of 600 ⁇ m or less can be manufactured.
- a thin substrate has a problem such that the substrate is warped at the time of annealing. Therefore, the substrate having a thickness exceeding 600 ⁇ m has been manufactured by activation annealing and then polishing.
- the substrate having a thickness of 600 ⁇ m or less can be activated and annealed, resources can be used more effectively than before.
- FIG. 14 is a flowchart schematically showing a method for manufacturing the silicon carbide semiconductor device according to the present embodiment.
- the method for manufacturing the silicon carbide semiconductor device of the present embodiment includes steps S1, S2, S3, S4, S5, S6, S7 and S8.
- the activation annealing (step S5) is performed in a state where at least a part of the second main surface P2 which is the lower surface of the substrate is covered with the second protective film 20, so that the substrate Sublimation on the lower surface (back surface) can be suppressed, and warpage of the substrate can be prevented.
- first protective film 10 and the second protective film 20 may be collectively referred to simply as “protective film”.
- FIG. 1 is a schematic cross-sectional view illustrating step S1 in the method for manufacturing the silicon carbide semiconductor device of the present embodiment.
- a silicon carbide substrate 100 having a first main surface P1 and a second main surface P2 located on the opposite side of first main surface P1 is prepared.
- Silicon carbide substrate 100 includes a silicon carbide single crystal substrate 80 and a silicon carbide epitaxial layer 81 epitaxially grown thereon.
- the diameter of silicon carbide substrate 100 is preferably 100 mm or more (for example, 4 inches or more). This is because the manufacturing cost of the silicon carbide semiconductor device can be reduced by using a large-diameter substrate having a diameter of 100 mm or more. Silicon carbide substrate 100 preferably has a thickness of 600 ⁇ m or less. Conventionally, such a large-diameter substrate and a thin substrate have a large substrate warp, and it has been difficult to produce them at a suitable yield. On the other hand, in this embodiment, as will be described later, since annealing is performed in a state in which protective films are formed on the first main surface P1 and the second main surface P2, a large-diameter substrate and a thin substrate are used.
- Silicon carbide substrate 100 has a diameter of more preferably 125 mm or more (for example, 5 inches or more), and particularly preferably 150 mm or more (for example, 6 inches or more). Further, the thickness of silicon carbide substrate 100 is more preferably 400 ⁇ m or less, and particularly preferably 300 ⁇ m or less. Thereby, further cost reduction of the silicon carbide semiconductor device is possible.
- Silicon carbide single crystal substrate 80 is made of, for example, polytype 4H hexagonal silicon carbide. Silicon carbide single crystal substrate 80 is prepared, for example, by slicing an ingot (not shown) made of silicon carbide single crystal. Silicon carbide single crystal substrate 80 contains an impurity such as nitrogen (N), for example, and has n-type conductivity.
- N nitrogen
- the lower surface of silicon carbide single crystal substrate 80 constitutes second main surface P ⁇ b> 2 in silicon carbide substrate 100.
- the upper surface of silicon carbide single crystal substrate 80 is a surface on which epitaxial growth is performed.
- Silicon carbide epitaxial layer 81 has, for example, a polytype 4H hexagonal crystal structure.
- the upper surface of silicon carbide epitaxial layer 81 constitutes first main surface P1.
- Silicon carbide epitaxial layer 81 has n-type conductivity, for example.
- the epitaxial growth of the silicon carbide epitaxial layer 81 is performed by, for example, CVD using a mixed gas of silane (SiH 4 ) and propane (C 3 H 8 ) as a source gas and using hydrogen (H 2 ) as a carrier gas, for example. (Chemical Vapor Deposition) method. At this time, it is preferable to introduce, for example, nitrogen (N) or phosphorus (P) as impurities. At this time, it is preferable to adjust the impurity concentration of silicon carbide epitaxial layer 81 to be lower than the impurity concentration of silicon carbide single crystal substrate 80.
- each doping region (p body layer shown in FIG. 7) is formed by forming a mask layer having a predetermined opening on first main surface P1 and selectively performing ion implantation. 82, n + layer 83 and p contact region 84). Note that although a method for forming a doping region by an ion implantation method is illustrated in this embodiment, the formation of the doping region may be epitaxial growth accompanied by addition of impurities. Further, the arrangement of each doping region shown in FIG. 7 is merely an example, and these arrangements can be changed as appropriate.
- a first mask layer 41 is formed on the first main surface P1.
- the first mask layer 41 is made of, for example, silicon dioxide, silicon nitride, silicon nitride oxide, or the like, and can be formed by, for example, a thermal CVD method or a photo CVD method.
- a thermal CVD method a low pressure thermal CVD method is suitable.
- TEOS Tetraethyl orthosilicate
- the pressure is 0.8 Torr or more.
- the first mask layer 41 includes a silicon dioxide layer (not shown) formed by thermally oxidizing the first main surface P1, an etching stop layer (not shown) made of polysilicon, and the like. You may go out. Since the first mask layer 41 includes the etching stop layer, damage to the substrate when the first mask layer 41 is etched later is reduced.
- the etching stop layer made of polysilicon is, for example, in a chamber in which the silicon carbide substrate 100 is disposed at a flow rate of 800 sccm or more and 1200 sccm or less of silane (SH 4 ) gas at a temperature of about 500 ° C. or more and 700 ° C. or less. It can be formed by supplying and adjusting the pressure to about 0.4 Torr or more and 0.8 Torr or less.
- a first opening 51 is formed in the first mask layer 41.
- the first opening 51 is formed by removing a part of the first mask layer 41 by etching using, for example, CF 4 or CHF 3 .
- the p body layer 82 is formed by performing ion implantation through the first mask layer 41.
- the impurity implanted here is, for example, a p-type impurity such as aluminum (Al) or boron (B).
- a second mask layer 42 is formed on the first mask layer 41.
- the second mask layer 42 is a silicon dioxide layer, for example, and can be formed by a low pressure CVD method.
- anisotropic etching is performed on the second mask layer 42 to remove a part of the second mask layer 42, and as shown in FIG. A narrow second opening 52 is formed.
- an n + layer 83 is formed.
- the implanted impurity is, for example, an n-type impurity such as phosphorus (P) or nitrogen (N).
- the third mask layer 43 having the third opening 53 narrower than the second opening 52 is formed by using the layer formation and the anisotropic etching together. Is done.
- the third mask layer 43 is a silicon dioxide layer, for example, and can be formed by a low pressure CVD method. Then, by performing ion implantation through the first mask layer 41, the second mask layer 42, and the third mask layer 43, the p contact region 84 is formed.
- the impurity implanted here is, for example, a p-type impurity such as aluminum (Al) or boron (B).
- the first mask layer 41, the second mask layer 42, and the third mask layer 43 are removed.
- the mask layer is a silicon dioxide layer
- the mask layer can be removed, for example, by wet etching using hydrofluoric acid.
- the layer made of polysilicon can be removed by dry etching, for example.
- FIG. 8 is a schematic cross-sectional view illustrating step S3.
- step S3 for forming first protective film 10 on the doping region in first main surface P1 is performed.
- the first protective film 10 covers at least a part of the first main surface P1. Thereby, sublimation of atoms from the first main surface P1 can be prevented.
- the first protective film 10 preferably covers each doping region. That is, it is preferable to cover all the parts used as devices in the first main surface P1. This is because sublimation is particularly likely to occur in the doping region. More preferably, the first protective film 10 substantially covers the entire first main surface P1.
- the material which comprises the 1st protective film 10 is mentioned later.
- FIG. 9 is a schematic cross-sectional view illustrating step S4.
- second protective film 20 is formed on second main surface P2.
- the second protective film 20 covers at least a part of the second main surface P2. Thereby, sublimation of atoms from the second main surface P2 can be suppressed, and surface roughness and warpage of the substrate can be prevented.
- the second protective film 20 preferably covers most of the second main surface P2 (that is, 50% or more of the second main surface P2). Thereby, sufficient substrate quality can be ensured. More preferably, it is preferable to cover the entire region inside 2 mm from the edge portion of the second main surface P2 (that is, the second protective film 20 covers substantially the entire second main surface P2. Preferably).
- step S4 the process flow in which the process S4 is executed after the process S3 is illustrated, but the process S4 can be performed at any timing before the process S5 (that is, activation annealing). May be executed. Further, step S3 and step S4 may be performed substantially simultaneously.
- the first protective film 10 and the second protective film 20 formed in the steps S3 and S4 may be formed of different materials, but are preferably formed of the same material. This is because the process burden can be reduced by using the same material.
- the first protective film 10 and the second protective film 20 preferably have heat resistance that can withstand activation annealing. For example, a carbon film, a DLC film, and a carbon layer obtained by heating and carbonizing an organic film are used. Is preferred.
- Organic film Since the organic film contains carbon atoms (C), it can be carbonized into a carbon film in the temperature raising process of activation annealing.
- This carbon film can be a protective film that can withstand activation annealing performed at a temperature exceeding 1500 ° C.
- carbon atoms in the vicinity of the surface of silicon carbide epitaxial layer 81 can be bonded to carbon atoms in the protective film, the adhesion between silicon carbide epitaxial layer 81 and the protective film is improved, and silicon carbide epitaxial layer 81 is improved. The sublimation of atoms from can be effectively prevented.
- an organic film for example, various resins such as an acrylic resin, a phenol resin, a urea resin, and an epoxy resin can be used.
- action of light can also be used.
- the photosensitive resin a positive type or negative type photoresist generally used for manufacturing a semiconductor device can be used.
- a photoresist is suitable because a coating technique by spin coating has been established and the thickness can be easily controlled.
- the material is disposed on the first main surface P1 and the second main surface P2, and then baked at a temperature of, for example, about 100 ° C. to 200 ° C. to volatilize the solvent and fix the material. It is preferable to make it.
- a DLC film can also be used as the first protective film 10 and the second protective film 20.
- the DLC film can also have heat resistance that can withstand activation annealing, and can prevent sublimation of atoms from the substrate surface.
- the DLC film can be easily formed by, for example, ECR sputtering.
- First protective film 10 and second protective film 20 may be carbon layers formed by partially removing silicon from silicon carbide substrate 100.
- the first main surface P1 or the second main surface P2 is subjected to thermal etching at a temperature of 700 ° C. or higher and 1000 ° C. or lower in a reactive gas atmosphere containing chlorine (Cl 2 ).
- Silicon can be partially (selectively) removed from main surface P1 or second main surface P2 to form a carbon layer.
- the carbon layer thus formed can also have heat resistance that can withstand activation annealing, and can prevent sublimation of atoms from the substrate surface.
- the thickness of the first protective film 10 and the second protective film 20 is preferably 0.5 ⁇ m or more from the viewpoint of preventing surface roughness and warpage of the substrate, and from the viewpoint of material usage.
- the thickness is preferably 10 ⁇ m or less.
- the thicknesses of the first protective film 10 and the second protective film 20 are more preferably 1 ⁇ m or more and 5 ⁇ m or less.
- the thicknesses of the first protective film 10 and the second protective film 20 can be set to about 3 ⁇ m, for example.
- step S5 annealing is performed in a state where the first protective film 10 and the second protective film 20 are formed, and the impurities contained in each doping region are activated. Thereby, a desired carrier is generated in each doping region.
- the temperature of activation annealing is preferably 1500 ° C. or higher and 2000 ° C. or lower, for example, about 1800 ° C.
- the activation annealing time can be, for example, about 30 minutes.
- the activation annealing is preferably performed in an inert gas atmosphere, and can be performed, for example, in an argon (Ar) atmosphere.
- annealing is performed in a state where the first protective film 10 and the second protective film 20 are formed. For example, even if the substrate has a large diameter of 100 mm or more, the surface of the substrate A high-quality substrate can be manufactured without roughening or warping.
- the second protective film 20 it is possible to anneal in a state where the second main surface P2 is opened.
- a substrate is held in a susceptor or the like and placed in a furnace, and annealing is performed. Therefore, a certain amount of restriction is imposed on the processing amount in the process.
- a plurality of silicon carbide substrates 100 can be stacked and held on a predetermined jig 70 or the like for annealing.
- a plurality of silicon carbide substrates 100 are prepared in the preparing step S1, and in the step S5 of activating, the plurality of silicon carbide substrates 100 are spaced one by one along the direction intersecting the first main surface P1. It can be annealed in an open and held state. That is, it is possible to provide a manufacturing method suitable for mass production of large-diameter substrates by effectively using the space in the furnace of the existing equipment. Thereby, the processing efficiency of activation annealing can be greatly improved, and the manufacturing cost of the silicon carbide semiconductor device can be reduced.
- Step S6> After step S5, the first protective film 10 and the second protective film 20 are removed.
- the removal of the protective film is not particularly limited and can be performed by any method.
- the protective film is a photoresist, it can be removed by, for example, photoexcitation ashing or plasma ashing. Further, wet cleaning using a predetermined cleaning solution can be used in combination.
- Gate insulating film 91 is, for example, a silicon dioxide film, and is preferably formed by thermal oxidation.
- gate insulating film 91 which is a silicon dioxide film can be formed by heating silicon carbide substrate 100 to about 1300 ° C. in an atmosphere containing oxygen.
- NO annealing using nitrogen monoxide (NO) gas as an atmospheric gas may be performed. The NO annealing is performed, for example, by holding for about 1 hour at a temperature of 1100 ° C. or higher and 1300 ° C. or lower.
- NO nitrogen monoxide
- gate electrode 92 is formed.
- the gate electrode 92 is formed on the gate insulating film 91.
- the gate electrode 92 is made of polysilicon containing an impurity such as phosphorus, and can be formed by a low pressure CVD method.
- Gate electrode 92 is formed on gate insulating film 91 so as to oppose p body layer 82 and n + layer 83.
- an interlayer insulating film 93 is formed in contact with the gate electrode 92 and the gate insulating film 91 so as to surround the gate electrode 92 by, for example, a plasma CVD method.
- Interlayer insulating film 93 is made of, for example, silicon dioxide.
- Gate insulating film 91 and interlayer insulating film 93 formed opposite to n + layer 83 and p contact region 84 are removed by, for example, dry etching. Further, a metal film containing, for example, titanium (Ti), aluminum (Al), and silicon (Si) is formed in contact with n + layer 83, p contact region 84, and gate insulating film 91 by sputtering. Subsequently, by heating silicon carbide substrate 100 on which the metal film is formed, for example, to about 1000 ° C., the metal film is alloyed, and source electrode 94 that is in ohmic contact with silicon carbide substrate 100 is formed.
- a metal film containing, for example, titanium (Ti), aluminum (Al), and silicon (Si) is formed in contact with n + layer 83, p contact region 84, and gate insulating film 91 by sputtering.
- Source wiring layer 95 is formed so as to be electrically connected to the source electrode 94.
- Source wiring layer 95 may include aluminum, for example, and may be formed to cover interlayer insulating film 93.
- drain electrode 96 is formed so as to be in contact with second main surface P2 of silicon carbide substrate 100.
- the silicon carbide semiconductor device can be manufactured with a high yield.
- a planar MOSFET Metal Oxide Semiconductor Field Effect Transistor
- the silicon carbide semiconductor device may be a trench MOSFET.
- the silicon carbide semiconductor device may be, for example, an IGBT (Insulated Gate Bipolar Transistor) or an SBD (Schottky Barrier Diode).
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Abstract
Description
まず、本願発明の実施の形態(以下「本実施の形態」とも記す)の概要を以下の(1)~(9)に列記して説明する。
以下、本実施の形態の炭化珪素半導体装置の製造方法について、より詳細に説明するが、本実施の形態はこれらに限定されるものではない。
図14は、本実施の形態に係る炭化珪素半導体装置の製造方法の概略を示すフローチャートである。図14に示すように、本実施の形態の炭化珪素半導体装置の製造方法は、工程S1、S2、S3、S4、S5、S6、S7およびS8を備える。本実施の形態では、基板の下面である第2の主面P2の少なくとも一部が第2の保護膜20により覆われた状態で、活性化アニール(工程S5)が実行されるため、基板の下面(裏面)における昇華を抑制し、基板の反りを防止することができる。
図1は、本実施の形態の炭化珪素半導体装置の製造方法における工程S1を図解する模式的な断面図である。図1を参照して、第1の主面P1と第1の主面P1の反対側に位置する第2の主面P2を有する炭化珪素基板100が準備される。炭化珪素基板100は、炭化珪素単結晶基板80とその上にエピタキシャル成長させられた炭化珪素エピタキシャル層81とを含む。
図2~図7は、工程S2を図解する模式的な断面図である。図2~図7を参照して、第1の主面P1に所定の開口部を有するマスク層を形成して選択的にイオン注入を行なうことにより、図7に示す各ドーピング領域(pボディ層82、n+層83およびpコンタクト領域84)が形成される。なお、本実施の形態では、イオン注入法によって、ドーピング領域を形成する方法を例示しているが、ドーピング領域の形成は、不純物の添加を伴うエピタキシャル成長であってもよい。また、図7に示す各ドーピング領域の配置はあくまでも例示であり、これらの配置は適宜変更することができる。
図8は、工程S3を図解する模式的な断面図である。図8を参照して、炭化珪素エピタキシャル層81内に各ドーピング領域が形成された後、第1の主面P1におけるドーピング領域上に第1の保護膜10を形成する工程S3が実行される。図8に示すように、第1の保護膜10は、第1の主面P1の少なくとも一部を覆う。これにより、第1の主面P1からの原子の昇華を防止することができる。第1の保護膜10は、各ドーピング領域を覆うことが好ましい。すなわち、第1の主面P1のうちデバイスとして利用される部分のすべて覆うことが好ましい。ドーピング領域では、特に昇華が起こりやすいからである。より好ましくは、第1の保護膜10は、実質的に第1の主面P1の全体を覆う。なお、第1の保護膜10を構成する材料については後述する。
図9は、工程S4を図解する模式的な断面図である。図9を参照して、第2の主面P2上に第2の保護膜20が形成される。第2の保護膜20は、第2の主面P2の少なくとも一部を覆う。これにより、第2の主面P2からの原子の昇華を抑制して、基板の表面荒れおよび反りを防止することができる。第2の保護膜20は、第2の主面P2の大部分(すなわち、第2の主面P2の50%以上)を覆うことが好ましい。これにより、十分な基板品質を確保することができる。より好ましくは、第2の主面P2のエッジ部から2mmより内側の領域のすべてを覆うことが好ましい(すなわち、第2の保護膜20は、実質的に第2の主面P2の全体を覆うことが好ましい)。なお、本実施の形態では、工程S3の後、工程S4が実行される工程フローを例示しているが、工程S4は、工程S5(すなわち、活性化アニール)の前であれば、いずれのタイミングで実行されてもよい。また、工程S3と工程S4は実質的に同時に行なわれてもよい。
工程S3および工程S4において形成される第1の保護膜10および第2の保護膜20は、それぞれ異なる材料から形成されていてもよいが、同一の材料から形成されることが好ましい。同一の材料を用いることにより、工程負担を低減できるからである。第1の保護膜10および第2の保護膜20としては、活性化アニールに耐え得る耐熱性を有するものが好ましく、たとえば、有機膜を加熱して炭化させたカーボン膜、DLC膜およびカーボン層が好適である。
有機膜は炭素原子(C)を含むため、活性化アニールの昇温過程で、炭化してカーボン膜となることができる。そして、このカーボン膜は、1500℃を超える温度で行なわれる活性化アニールにも耐え得る保護膜となることができる。また、炭化珪素エピタキシャル層81の表面近傍の炭素原子と保護膜中の炭素原子とが結合することができるため、炭化珪素エピタキシャル層81と保護膜との密着性が向上し、炭化珪素エピタキシャル層81からの原子の昇華を効率的に防止することができる。
第1の保護膜10および第2の保護膜20として、DLC膜を用いることもできる。DLC膜も活性化アニールに耐え得る耐熱性を有することができ、基板表面からの原子の昇華を防止することができる。DLC膜は、たとえば、ECRスパッタリングによって容易に形成することができる。
第1の保護膜10および第2の保護膜20は、炭化珪素基板100から珪素を部分的に除去することにより形成されたカーボン層であってもよい。たとえば、第1の主面P1または第2の主面P2に対して、塩素(Cl2)を含む反応ガス雰囲気下、700℃以上1000℃以下の温度で熱エッチングを行なうことにより、第1の主面P1または第2の主面P2から珪素を部分的(選択的)に除去して、カーボン層を形成することができる。このようにして形成されたカーボン層も、活性化アニールに耐え得る耐熱性を有することができ、基板表面からの原子の昇華を防止することができる。
工程S5では、第1の保護膜10および第2の保護膜20が形成された状態でアニールが行なわれ、各ドーピング領域に含まれる不純物が活性化される。これにより、各ドーピング領域において、所望のキャリアが生成される。活性化アニールの温度は、好ましくは1500℃以上2000℃以下であり、たとえば1800℃程度である。活性化アニールの時間は、たとえば30分程度とすることができる。活性化アニールは、不活性ガス雰囲気下で行なわれることが好ましく、たとえばアルゴン(Ar)雰囲気下で行なうことができる。本実施の形態では、第1の保護膜10および第2の保護膜20が形成された状態でアニールが行なわれるため、たとえば、直径が100mm以上である大口径基板であっても、基板の表面荒れや反りが生じることなく、高品質な基板を製造することができる。
工程S5の後、第1の保護膜10および第2の保護膜20は除去される。保護膜の除去は、特に制限されることなく、任意の方法で行なうことができる。保護膜がフォトレジストである場合には、たとえば、光励起アッシングや、プラズマアッシングにより除去することができる。また、所定の洗浄溶液を用いたウェット洗浄を併用することもできる。
次に図10を参照して、ゲート絶縁膜91が形成される。ゲート絶縁膜91は、たとえば二酸化珪素膜であり、熱酸化により形成されることが好ましい。たとえば、酸素を含む雰囲気中において炭化珪素基板100を1300℃程度に加熱することにより、二酸化珪素膜であるゲート絶縁膜91を形成することができる。ゲート絶縁膜91を形成した後、雰囲気ガスとして一酸化窒素(NO)ガスを用いたNOアニールが行なわれてもよい。NOアニールは、たとえば、1100℃以上1300℃以下の温度で、1時間程度保持されることにより実行される。
次に図11を参照して、ゲート電極92が形成される。ゲート電極92は、ゲート絶縁膜91上に形成される。ゲート電極92は、たとえばリンなどの不純物を含むポリシリコンからなり、低圧CVD法によって形成することができる。ゲート電極92は、ゲート絶縁膜91上において、pボディ層82およびn+層83に対向して形成される。次に、たとえばプラズマCVD法によって、層間絶縁膜93が、ゲート電極92を取り囲むように、ゲート電極92およびゲート絶縁膜91に接して形成される。層間絶縁膜93は、たとえば二酸化珪素からなる。
Claims (9)
- 第1の主面と前記第1の主面の反対側に位置する第2の主面とを有する炭化珪素基板を準備する工程と、
前記第1の主面へ不純物をドーピングすることにより、前記炭化珪素基板内にドーピング領域を形成する工程と、
前記第1の主面上に第1の保護膜を形成する工程と、
前記第2の主面上に第2の保護膜を形成する工程と、を備え、
前記第1の保護膜を形成する工程は、前記ドーピング領域を形成する工程後に行なわれ、さらに、
前記第1の主面の少なくとも一部が前記第1の保護膜により覆われるとともに、前記第2の主面の少なくとも一部が前記第2の保護膜により覆われた状態でアニールを行なうことにより、前記ドーピング領域に含まれる前記不純物を活性化する工程を備える、炭化珪素半導体装置の製造方法。 - 前記第1の保護膜および前記第2の保護膜の少なくともいずれかは、有機膜である、請求項1に記載の炭化珪素半導体装置の製造方法。
- 前記第1の保護膜および前記第2の保護膜の少なくともいずれかは、ダイヤモンドライクカーボン膜である、請求項1に記載の炭化珪素半導体装置の製造方法。
- 前記第1の保護膜および前記第2の保護膜の少なくともいずれかは、カーボン層である、請求項1に記載の炭化珪素半導体装置の製造方法。
- 前記カーボン層は、前記炭化珪素基板から珪素を部分的に除去することにより形成される、請求項4に記載の炭化珪素半導体装置の製造方法。
- 前記第2の保護膜は、前記第2の主面の全面を覆う、請求項1~請求項5のいずれか1項に記載の炭化珪素半導体装置の製造方法。
- 前記準備する工程では複数の前記炭化珪素基板が準備され、
前記活性化する工程において、複数の前記炭化珪素基板は、前記第1の主面と交差する方向に沿って1枚ずつ間隔を開けて保持された状態でアニールされる、請求項1~請求項6のいずれか1項に記載の炭化珪素半導体装置の製造方法。 - 前記炭化珪素基板の直径は、100mm以上である、請求項1~請求項7のいずれか1項に記載の炭化珪素半導体装置の製造方法。
- 前記炭化珪素基板の厚さは、600μm以下である、請求項1~請求項8のいずれか1項に記載の炭化珪素半導体装置の製造方法。
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DE112014004465.2T DE112014004465T5 (de) | 2013-09-25 | 2014-08-05 | Verfahren zur Herstellung einer Siliziumkarbid-Halbleitervorrichtung |
US15/024,345 US9691616B2 (en) | 2013-09-25 | 2014-08-05 | Method of manufacturing silicon carbide semiconductor device by using protective films to activate dopants in the silicon carbide semiconductor device |
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JP2015065289A (ja) * | 2013-09-25 | 2015-04-09 | 住友電気工業株式会社 | 炭化珪素半導体装置の製造方法 |
CN106537568B (zh) * | 2014-07-30 | 2019-07-12 | 三菱电机株式会社 | 半导体装置的制造方法及半导体装置 |
CN109427665A (zh) * | 2017-08-25 | 2019-03-05 | 比亚迪股份有限公司 | 半导体器件及其制备方法 |
CN110112055B (zh) * | 2019-04-24 | 2021-10-15 | 芜湖启迪半导体有限公司 | 一种用于晶圆表面保护碳膜的去除方法 |
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JP2002343789A (ja) * | 2001-05-16 | 2002-11-29 | Mitsubishi Electric Corp | 補助保温治具、その製造方法、板状断熱材付きウエハボート、縦型熱処理装置、縦型熱処理装置の改造方法および半導体装置の製造方法 |
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- 2014-08-05 CN CN201480053018.6A patent/CN105580111A/zh active Pending
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WO2013011740A1 (ja) * | 2011-07-20 | 2013-01-24 | 住友電気工業株式会社 | 半導体装置の製造方法 |
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US9691616B2 (en) | 2017-06-27 |
JP2015065318A (ja) | 2015-04-09 |
CN105580111A (zh) | 2016-05-11 |
DE112014004465T5 (de) | 2016-06-09 |
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