JP2020090421A - Polycrystalline silicon carbide substrate and method for producing the same - Google Patents
Polycrystalline silicon carbide substrate and method for producing the same Download PDFInfo
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims abstract description 208
- 239000000758 substrate Substances 0.000 title claims abstract description 106
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 25
- 229910021420 polycrystalline silicon Inorganic materials 0.000 title abstract description 10
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- 238000005245 sintering Methods 0.000 claims abstract description 80
- 238000000034 method Methods 0.000 claims abstract description 60
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 45
- 238000010438 heat treatment Methods 0.000 claims abstract description 29
- 229910001873 dinitrogen Inorganic materials 0.000 claims abstract description 17
- 239000012298 atmosphere Substances 0.000 claims abstract description 15
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 239000012159 carrier gas Substances 0.000 description 5
- 238000005520 cutting process Methods 0.000 description 5
- 229910052710 silicon Inorganic materials 0.000 description 5
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- 238000002490 spark plasma sintering Methods 0.000 description 3
- 238000001947 vapour-phase growth Methods 0.000 description 3
- 229910052984 zinc sulfide Inorganic materials 0.000 description 3
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 229910003902 SiCl 4 Inorganic materials 0.000 description 2
- 238000012790 confirmation Methods 0.000 description 2
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- 238000000815 Acheson method Methods 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 239000004215 Carbon black (E152) Substances 0.000 description 1
- 241000220317 Rosa Species 0.000 description 1
- HMDDXIMCDZRSNE-UHFFFAOYSA-N [C].[Si] Chemical compound [C].[Si] HMDDXIMCDZRSNE-UHFFFAOYSA-N 0.000 description 1
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Abstract
Description
本発明は、炭化珪素多結晶基板およびその製造方法に関する。 The present invention relates to a silicon carbide polycrystalline substrate and a method for manufacturing the same.
多結晶膜の材料として用いられる炭化珪素は、珪素と炭素で構成される化合物半導体材料である。絶縁破壊電界強度が珪素の１０倍であり、バンドギャップが珪素の３倍と優れているだけでなく、デバイスの作製に必要なｐ型、ｎ型の制御が広い範囲で可能であることなどから、珪素の限界を超えるパワーデバイス用材料として期待されている。 Silicon carbide used as a material for the polycrystalline film is a compound semiconductor material composed of silicon and carbon. The breakdown field strength is 10 times that of silicon and the bandgap is 3 times that of silicon, and the p-type and n-type control required for device fabrication is possible over a wide range. , Is expected as a material for power devices that exceeds the limit of silicon.
また、炭化珪素は、より薄い厚さでも高い耐電圧が得られるため、薄く構成することにより、ＯＮ抵抗が小さく、低損失の半導体が得られることが特徴である。 Further, since silicon carbide can obtain a high withstand voltage even if it has a smaller thickness, it is characterized in that it has a small ON resistance and a low loss semiconductor when it is made thin.
しかしながら、炭化珪素半導体は、広く普及するＳｉ半導体と比較し、大面積のウェハが得られず、製造工程も複雑であることから、Ｓｉ半導体と比較して大量生産ができず、高価であった。 However, since a silicon carbide semiconductor cannot obtain a large-area wafer and the manufacturing process is complicated as compared with a widely spread Si semiconductor, it cannot be mass-produced and is expensive as compared with the Si semiconductor. ..
そこで、炭化珪素半導体のコストを下げるため、様々な工夫が行われてきた。例えば、特許文献１には、炭化珪素基板の製造方法が開示されており、その特徴として、少なくとも、マイクロパイプの密度が３０個／ｃｍ2以下の炭化珪素単結晶基板と炭化珪素多結晶基板とを貼り合わせる工程を行い、その後、炭化珪素単結晶基板を薄膜化する工程を行うことで、炭化珪素多結晶基板上に炭化珪素単結晶層を形成した基板を製造することが記載されている。 Therefore, various measures have been taken to reduce the cost of the silicon carbide semiconductor. For example, Patent Document 1 discloses a method for manufacturing a silicon carbide substrate, which is characterized by at least a silicon carbide single crystal substrate having a micropipe density of 30/cm 2 or less and a silicon carbide polycrystalline substrate. It is described that a substrate in which a silicon carbide single crystal layer is formed on a silicon carbide polycrystalline substrate is manufactured by performing a step of laminating, and then performing a step of thinning the silicon carbide single crystal substrate.
更に、特許文献１には、炭化珪素単結晶基板と炭化珪素多結晶基板とを貼り合わせる工程の前に、炭化珪素単結晶基板に水素イオン注入を行って水素イオン注入層を形成する工程を行い、炭化珪素単結晶基板と炭化珪素多結晶基板とを貼り合わせる工程の後、炭化珪素単結晶基板を薄膜化する工程の前に、３５０℃以下の温度で熱処理を行い、炭化珪素単結晶基板を薄膜化する工程を、水素イオン注入層にて機械的に剥離する工程とする炭化珪素基板の製造方法が記載されている。 Further, in Patent Document 1, before the step of bonding the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate, a step of performing hydrogen ion implantation into the silicon carbide single crystal substrate to form a hydrogen ion implantation layer is performed. After the step of bonding the silicon carbide single crystal substrate and the silicon carbide polycrystalline substrate, and before the step of thinning the silicon carbide single crystal substrate, heat treatment is performed at a temperature of 350° C. or lower to form the silicon carbide single crystal substrate. A method of manufacturing a silicon carbide substrate is described, in which the step of thinning the film is a step of mechanically peeling the hydrogen ion-implanted layer.
このような方法により、１つの炭化珪素の単結晶のインゴットから、より多くの炭化珪素ウェハが得られるようになった。 By such a method, more silicon carbide wafers can be obtained from one silicon carbide single crystal ingot.
しかしながら、上記の炭化珪素ウェハの製造方法は、水素イオン注入を行って薄いイオン注入層が形成された炭化珪素単結晶基板と、炭化珪素多結晶基板と、を貼り合わせたのちに加熱して炭化珪素単結晶基板を剥離することによって製造されているので、炭化珪素ウェハは、厚さの大部分が炭化珪素多結晶基板である。このため、炭化珪素ウェハは、研磨などハンドリングの際に損傷しないよう機械的な強度が必要である。 However, in the above-mentioned method for manufacturing a silicon carbide wafer, the silicon carbide single crystal substrate on which a thin ion-implanted layer is formed by performing hydrogen ion implantation and the silicon carbide polycrystal substrate are bonded and then heated and carbonized. Since the silicon carbide wafer is manufactured by peeling off the silicon single crystal substrate, most of the thickness of the silicon carbide wafer is a silicon carbide polycrystalline substrate. Therefore, the silicon carbide wafer needs to have mechanical strength so as not to be damaged during handling such as polishing.
ただし、炭化珪素多結晶基板では、所定の厚みで得られる炭化珪素半導体のＯＮ抵抗を小さくするためには、炭化珪素多結晶基板の抵抗値が低い必要がある。 However, in the silicon carbide polycrystalline substrate, the resistance value of the silicon carbide polycrystalline substrate needs to be low in order to reduce the ON resistance of the silicon carbide semiconductor obtained with a predetermined thickness.
従来、炭化珪素多結晶基板は、ＣＶＤ法等の気相成長法を用いて、窒素等のドーパントを加えながら、所定の厚さまで成膜を実施することで得ていた。しかしながら、気相成長法での炭化珪素多結晶の成膜速度は、一時間あたり数μｍ〜数十μｍであり、機械的強度を有する厚み（例えば、６インチの場合はＳｉＣ基板の厚みの規格は３９０μｍ±２０μｍ）の炭化珪素多結晶基板を得るためには、数十時間の成膜時間が必要となり、生産性の面で問題がある。 Conventionally, a silicon carbide polycrystalline substrate has been obtained by forming a film to a predetermined thickness using a vapor phase growth method such as a CVD method while adding a dopant such as nitrogen. However, the film formation rate of the silicon carbide polycrystal in the vapor phase growth method is several μm to several tens of μm per hour, and the thickness has mechanical strength (for example, in the case of 6 inches, the standard of the thickness of the SiC substrate is used). Of 390 μm±20 μm) requires a film forming time of several tens of hours to obtain a silicon carbide polycrystalline substrate, which is problematic in terms of productivity.
一方、バルクの材料を作成する方法として、気相成長法の他に、焼結による方法があるが、炭化珪素は、難焼結材に分類され、通常、ボロンやカーボンなどの焼結助剤を用いて焼結されるため、導電性が著しく低下する。焼結により得られた炭化珪素の電気比抵抗を低下させるために、炭化珪素の組織中に窒素を固溶させる試みは従来からなされており、数多く提案されている。例えば、特許文献２には炭化珪素を窒素雰囲気中で焼結する方法が示され、同様に特許文献３には炭化珪素を窒素雰囲気中でホットプレス焼結する方法が開示されている。しかしながら、単に窒素雰囲気中で炭化珪素を焼結処理するだけでは、窒素の固溶は円滑に進行せず、炭化珪素の比抵抗を十分に低減させることができない。 On the other hand, as a method of producing a bulk material, there is a method of sintering in addition to the vapor phase growth method. Silicon carbide is classified as a difficult-to-sinter material, and a sintering aid such as boron or carbon is usually used. As a result of sintering, the conductivity is significantly reduced. In order to reduce the electrical resistivity of silicon carbide obtained by sintering, attempts have been made to solid-dissolve nitrogen in the structure of silicon carbide, and many proposals have been made. For example, Patent Document 2 discloses a method of sintering silicon carbide in a nitrogen atmosphere, and Patent Document 3 similarly discloses a method of hot press sintering silicon carbide in a nitrogen atmosphere. However, by simply sintering silicon carbide in a nitrogen atmosphere, solid solution of nitrogen does not proceed smoothly, and the specific resistance of silicon carbide cannot be sufficiently reduced.
一方、炭化珪素の焼結体を高密度化させる方法として、特許文献４では、平均粒径が１００ｎｍ以下の炭化珪素粒子を利用し、熱間等方加圧焼結法、あるいはパルス通電焼結法による焼結が開示されている。この方法では、焼結助剤を用いず、相対密度は９９％以上の値が示されているが、表面に空隙の発生がある。炭化珪素多結晶基板にこの空隙があると、炭化珪素単結晶基板との貼り合せにおいては、この空隙が、貼り合わせができない欠陥となるため、貼り合わせ不良となり、デバイスの歩留まりを低下させてしまう問題が発生する。 On the other hand, as a method for densifying a sintered body of silicon carbide, in Patent Document 4, a silicon carbide particle having an average particle diameter of 100 nm or less is used, and a hot isostatic pressing method or pulse current sintering is used. Sintering by the method is disclosed. In this method, a sintering aid is not used and a relative density of 99% or more is shown, but voids are generated on the surface. If the silicon carbide polycrystalline substrate has this void, the void becomes a defect that cannot be bonded during bonding with the silicon carbide single crystal substrate, resulting in defective bonding and a reduction in device yield. The problem occurs.
上記の問題点に鑑み、本発明では、炭化珪素単結晶基板と炭化珪素多結晶基板との貼り合せに支障が生じるような空隙がなく、低抵抗で、ハンドリングで損傷しにくい炭化珪素多結晶基板、およびその製造方法を提供することを目的とする。 In view of the above problems, according to the present invention, there is no void that would hinder the bonding between the silicon carbide single crystal substrate and the silicon carbide polycrystal substrate, the resistance is low, and the silicon carbide polycrystal substrate is not easily damaged by handling. , And its manufacturing method.
本発明者らは、炭化珪素に対する窒素の固溶度合を高めて導電性の向上を図る簡便な製造手段について鋭意研究を重ねた。その結果、まず、炭素珪素粉末を窒素ガス雰囲気内で加熱し、その後、この炭化珪素微粉末を焼結し、得られて焼結体の表面に化学蒸着により薄膜の炭化珪素多結晶膜を積層することで、表面に空隙が無く、優れた導電性を有する炭化珪素多結晶基板を容易に得られることを確認した。 The present inventors have earnestly conducted research on a simple manufacturing means for improving the conductivity by increasing the solid solubility of nitrogen in silicon carbide. As a result, first, carbon silicon powder was heated in a nitrogen gas atmosphere, and then this silicon carbide fine powder was sintered, and a thin silicon carbide polycrystalline film was laminated on the surface of the obtained sintered body by chemical vapor deposition. By doing so, it was confirmed that a silicon carbide polycrystalline substrate having no voids on the surface and having excellent conductivity can be easily obtained.
上記課題を解決するために、本発明の炭化珪素多結晶基板の製造方法は、炭化珪素粉末を窒素ガス雰囲気下で加熱処理する加熱処理工程と、前記加熱処理工程後の前記炭化珪素粉末を、窒素ガス雰囲気下で焼結する焼結工程と、前記焼結工程により得た焼結体の表面に、化学蒸着によって炭化珪素多結晶膜を成膜する成膜工程を含む。 In order to solve the above problems, a method for manufacturing a silicon carbide polycrystalline substrate of the present invention is a heat treatment step of heat treating silicon carbide powder in a nitrogen gas atmosphere, and the silicon carbide powder after the heat treatment step, The method includes a sintering step of sintering in a nitrogen gas atmosphere, and a film forming step of forming a silicon carbide polycrystalline film on the surface of the sintered body obtained by the sintering step by chemical vapor deposition.
前記炭化珪素粉末の平均粒径が１００ｎｍ以下であってもよい。 The average particle size of the silicon carbide powder may be 100 nm or less.
前記加熱処理の処理温度は１５００〜２０００℃であってもよい。 The treatment temperature of the heat treatment may be 1500 to 2000°C.
前記焼結工程は、温度条件が１８００〜２０００℃、圧力条件が５０〜７０ＭＰａであり、放電プラズマ焼結法、ホットプレス焼結法、熱間等方加圧焼結法、またはパルス通電焼結法により焼結する工程であってもよい。 The sintering step has a temperature condition of 1800 to 2000° C. and a pressure condition of 50 to 70 MPa, and is a discharge plasma sintering method, a hot press sintering method, a hot isostatic pressing sintering method, or pulse current sintering. It may be a step of sintering by a method.
前記成膜工程は、平均膜厚が１〜１０００μｍの炭化珪素多結晶膜を成膜する工程であってもよい。 The film forming step may be a step of forming a silicon carbide polycrystalline film having an average film thickness of 1 to 1000 μm.
また、上記課題を解決するために、本発明の炭化珪素多結晶基板は、炭化珪素の焼結体と、前記焼結体の表面に化学蒸着によって成膜した炭化珪素多結晶膜と、を備え、前記炭化珪素多結晶膜は、平均膜厚が１〜１０００μｍ、空隙が０個／μｍ2である、電気抵抗が３．０５×１０-5Ω・ｍ〜４．３０×１０-5Ω・ｍの炭化珪素多結晶基板である。 In order to solve the above problems, a silicon carbide polycrystalline substrate of the present invention comprises a sintered body of silicon carbide and a silicon carbide polycrystalline film formed on the surface of the sintered body by chemical vapor deposition. The polycrystalline silicon carbide film has an average film thickness of 1 to 1000 μm, voids of 0/μm 2 , and electric resistance of 3.05×10 −5 Ω·m to 4.30×10 −5 Ω·. It is a silicon carbide polycrystalline substrate of m.
本発明によれば、炭化珪素粉末を窒素処理し、これを焼結処理し、さらに表面に化学蒸着による被膜を形成する工程を経ることで、効率よく導電性およびハンドリングに優れた炭化珪素多結晶基板を製造することが可能となる。したがって、導電性が要求される各種の機械部品および電気部品を工業的に製造する技術としての有用性が期待される。 According to the present invention, a silicon carbide polycrystal having excellent conductivity and handling efficiency can be obtained by subjecting the silicon carbide powder to nitrogen treatment, sintering the same, and further forming a coating film on the surface by chemical vapor deposition. It becomes possible to manufacture a substrate. Therefore, it is expected to be useful as a technique for industrially manufacturing various mechanical parts and electric parts that require conductivity.
以下、本発明の具体的な実施形態について、説明する。 Hereinafter, specific embodiments of the present invention will be described.
［炭化珪素多結晶基板］
本発明の炭化珪素多結晶基板は、炭化珪素の焼結体と、焼結体の表面に成膜した炭化珪素多結晶膜とを備える。炭化珪素単結晶基板を貼り合わせて得られる炭化珪素半導体のＯＮ抵抗を考慮して、炭化珪素多結晶基板の電気抵抗が３．０５×１０-5Ω・ｍ〜４．３０×１０-5Ω・ｍの範囲である。電気抵抗が３．０５×１０-5Ω・ｍ未満の場合には、抵抗の観点からは問題ないが、抵抗を低くするために、機械的強度を満足するための十分な厚みがある基板とならないおそれがある。また、電気抵抗が４．３０×１０-5Ω・ｍよりも大きい場合には、炭化珪素半導体とした場合のＯＮ抵抗が大きくなることで、本来の炭化珪素半導体の特徴が充分に発揮できなくなるおそれがある。
[Silicon Carbide Polycrystalline Substrate]
The silicon carbide polycrystalline substrate of the present invention includes a sintered body of silicon carbide and a silicon carbide polycrystalline film formed on the surface of the sintered body. Considering the ON resistance of the silicon carbide semiconductor obtained by bonding the silicon carbide single crystal substrates, the electric resistance of the silicon carbide polycrystalline substrate is 3.05×10 −5 Ω·m to 4.30×10 −5 Ω.・It is a range of m. When the electric resistance is less than 3.05×10 −5 Ω·m, there is no problem from the viewpoint of resistance, but in order to reduce the resistance, a substrate having a sufficient thickness to satisfy the mechanical strength is used. It may not happen. Further, when the electric resistance is larger than 4.30×10 −5 Ω·m, the ON resistance of the silicon carbide semiconductor becomes large, so that the original characteristics of the silicon carbide semiconductor cannot be sufficiently exhibited. There is a risk.
〈焼結体〉
炭化珪素の粉末が熱により固まって緻密な状態となったものである。炭化珪素半導体の製造工程において、炭化珪素単結晶基板の損傷を防ぐためには、機械的強度を有するべく、炭化珪素多結晶基板としてある程度の厚みが必要である。この厚みを焼結体により確保することが重要であり、特に限定されないが、炭化珪素基板の厚みの規格値（３９０±２０μｍ）から化学蒸着により成膜する炭化珪素多結晶膜の膜厚を減じた厚みであることが好ましく、例えば厚みを２００μｍ〜４１０μｍ程度とすることが好ましい。焼結体の厚みが２００μｍ未満の場合には、機械的強度を満足しないことで、炭化珪素単結晶基板が損傷するおそれがある。また、焼結体の厚みが４１０μｍよりも厚いと、炭化珪素基板の厚みの規格から大幅に外れてしまう場合があるのみならず、電気抵抗が大きくなり、炭化珪素半導体とした場合のＯＮ抵抗が大きくなることで、本来の炭化珪素半導体の特徴が充分に発揮できなくなるおそれがある。
<Sintered body>
The silicon carbide powder is hardened by heat to be in a dense state. In order to prevent damage to the silicon carbide single crystal substrate in the manufacturing process of the silicon carbide semiconductor, the silicon carbide polycrystalline substrate needs to have a certain thickness in order to have mechanical strength. It is important to secure this thickness by the sintered body, and although not particularly limited, the thickness of the silicon carbide polycrystalline film formed by chemical vapor deposition is subtracted from the standard value of the thickness of the silicon carbide substrate (390±20 μm). It is preferable that the thickness is 200 μm to 410 μm. If the thickness of the sintered body is less than 200 μm, the mechanical strength may not be satisfied, and the silicon carbide single crystal substrate may be damaged. Further, if the thickness of the sintered body is thicker than 410 μm, not only may the thickness of the silicon carbide substrate deviate significantly from the standard, but also the electrical resistance will increase, and the ON resistance in the case of using a silicon carbide semiconductor will increase. When the size becomes large, the original characteristics of the silicon carbide semiconductor may not be sufficiently exhibited.
〈炭化珪素多結晶膜〉
上記の焼結体の表面に化学蒸着（ＣＶＤ）によって成膜した膜であり、平均膜厚が１〜１０００μｍである。平均膜厚がこの範囲にあることで、炭化珪素多結晶膜が焼結体の表面を平滑に被覆することができるため、炭化珪素単結晶基板との貼り合せが容易となり、また、貼り合わせ不良といった問題も生じない。平均膜厚が１μｍ未満の場合、処理対象となる焼結体の表面において、炭化珪素多結晶膜が成膜せずに焼結体の表面が露出する部分が生じるおそれがあり、焼結体の表面に凹凸があることで炭化珪素単結晶基板との貼り合せに不具合が生じることにより、デバイスの歩留まりを低下させてしまうおそれがある。また、平均膜厚が１０００μｍより厚くても、平滑性に問題は無く、炭化珪素単結晶基板との貼り合せに支障は生じないが、成膜に時間がかかってしまうおそれがある。
<Polycrystalline silicon carbide film>
It is a film formed by chemical vapor deposition (CVD) on the surface of the above-mentioned sintered body, and has an average film thickness of 1 to 1000 μm. When the average film thickness is in this range, the silicon carbide polycrystalline film can cover the surface of the sintered body evenly, which facilitates the bonding with the silicon carbide single crystal substrate and also causes the bonding failure. Such a problem does not occur. If the average film thickness is less than 1 μm, there is a possibility that the surface of the sintered body will be exposed without forming a silicon carbide polycrystalline film on the surface of the sintered body to be treated. The unevenness on the surface causes a problem in bonding with the silicon carbide single crystal substrate, which may reduce the device yield. Further, even if the average film thickness is thicker than 1000 μm, there is no problem in smoothness and no problem occurs in bonding with the silicon carbide single crystal substrate, but film formation may take time.
平均膜厚は、例えば、炭化珪素多結晶基板を切断してＳＥＭ（走査型電子顕微鏡）等により断面観察することで測定可能であり、例えば炭化珪素多結晶基板の中央部分の１点と、両端の端部より１０ｍｍ内側の２点の合計３点における炭化珪素多結晶膜の膜厚の平均を平均膜厚とすることができる。 The average film thickness can be measured, for example, by cutting a silicon carbide polycrystalline substrate and observing a cross section with an SEM (scanning electron microscope) or the like. For example, one point at the central portion of the silicon carbide polycrystalline substrate and both ends thereof can be measured. The average of the film thicknesses of the silicon carbide polycrystalline film at the total of 3 points of 2 points located 10 mm inside from the end can be taken as the average film thickness.
また、炭化珪素多結晶膜は、空隙が０個／μｍ2であり、すなわち表面に空隙が存在しない膜である。空隙が存在すると、炭化珪素単結晶基板との貼り合せにおいて、貼り合わせができない欠陥となることで、貼り合わせ不良となり、デバイスの歩留まりを低下させてしまうおそれがある。本発明であれば、空隙が存在しないために、炭化珪素単結晶基板の貼り合わせの不良に起因して歩留まりが低下する問題は生じない。なお、空隙の有無は、ＳＥＭ等により炭化珪素多結晶膜の表面を観察することにより、確認することができる。 Further, the silicon carbide polycrystalline film has 0 voids/μm 2, that is, a film having no voids on the surface. The presence of the voids results in defects that cannot be bonded in bonding with the silicon carbide single crystal substrate, resulting in defective bonding and a reduction in device yield. According to the present invention, since there are no voids, there is no problem that the yield is reduced due to defective bonding of the silicon carbide single crystal substrates. The presence or absence of voids can be confirmed by observing the surface of the silicon carbide polycrystalline film by SEM or the like.
図１に、本発明の炭化珪素多結晶基板の一例についての側面断面図を示す。図１（ａ）に示す炭化珪素多結晶基板１００は、例えば平板状の焼結体１０の第１面１１に炭化珪素多結晶膜２０ａが成膜している。また、図１（ｂ）に示すように、第１面１１に加え、第１面１１とは反対の面である第２面１２に炭化珪素多結晶膜２０ｂが成膜した炭化珪素多結晶基板１１０や、図１（ｃ）に示すように、さらに側面１３にも成膜し、焼結体１０の表面全体を炭化珪素多結晶膜２０ｃが被覆した炭化珪素多結晶基板１２０も、本発明に含まれる。
FIG. 1 shows a side sectional view of an example of the silicon carbide polycrystalline substrate of the present invention. In silicon
炭化珪素多結晶基板が上記の構成であれば、焼結体によって機械的強度を満足する基板の厚さを確保しつつ、抵抗の上昇を抑えることができる。そして、炭化珪素多結晶膜によって、基板の表面の平滑性を確保し、炭化珪素単結晶基板の貼り合わせの不良を防止することができる。 When the silicon carbide polycrystalline substrate has the above-mentioned structure, the sintered body can suppress the increase in resistance while ensuring the thickness of the substrate that satisfies the mechanical strength. Then, the silicon carbide polycrystalline film can secure the smoothness of the surface of the substrate and prevent the bonding failure of the silicon carbide single crystal substrate.
［炭化珪素多結晶基板の製造方法］
次に、上記の本発明の炭化珪素多結晶基板について、その製造方法の一例を説明する。
[Method for manufacturing silicon carbide polycrystalline substrate]
Next, an example of a method for manufacturing the above-mentioned silicon carbide polycrystalline substrate of the present invention will be described.
本発明の炭化珪素多結晶基板の製造方法は、加熱処理工程と、焼結工程と、成膜工程を含む。 The method for manufacturing a silicon carbide polycrystalline substrate of the present invention includes a heat treatment step, a sintering step, and a film forming step.
〈加熱処理工程〉
本工程は、炭化珪素粉末を窒素ガス雰囲気下で加熱処理する工程である。加熱処理によって、焼結する前の炭化珪素粉末に窒素を固溶させることで、焼結体の抵抗を下げることができ、炭化珪素多結晶基板としての抵抗の上昇を抑えることができる。また、窒素が焼結助剤として作用することで、焼結の難しい炭化珪素を一般的な条件により焼結させることができる。
<Heat treatment process>
This step is a step of heat-treating silicon carbide powder in a nitrogen gas atmosphere. By heat-dissolving nitrogen in the silicon carbide powder before sintering as a solid solution, the resistance of the sintered body can be reduced, and an increase in the resistance of the silicon carbide polycrystalline substrate can be suppressed. Moreover, since nitrogen acts as a sintering aid, silicon carbide, which is difficult to sinter, can be sintered under general conditions.
加熱処理は、例えば炭化珪素粉末を密閉式の高周波誘導炉内にセットし、炉内に窒素ガスを導入し、加熱することにより行うことができる。窒素ガスの導入量は、適量に設定することができる。 The heat treatment can be performed, for example, by setting silicon carbide powder in a closed high-frequency induction furnace, introducing nitrogen gas into the furnace, and heating. The introduction amount of nitrogen gas can be set to an appropriate amount.
加熱処理温度は、１５００〜２０００℃の範囲であることが望ましい。この温度範囲であることで、炭化珪素が焼結することなく窒素を固溶させることが容易となる。加熱処理温度が１５００℃以下では、炭化珪素への窒素の侵入が少ないことで、窒素が十分に固溶しないおそれがある。また、加熱処理温度が２０００℃以上では、炭化珪素粉末の粒成長が発生し、後の焼結工程において焼結性が悪化するおそれがある。 The heat treatment temperature is preferably in the range of 1500 to 2000°C. Within this temperature range, it becomes easy to form a solid solution of nitrogen without sintering silicon carbide. When the heat treatment temperature is 1500° C. or less, nitrogen is less likely to enter silicon carbide, which may result in insufficient solid solution of nitrogen. Further, when the heat treatment temperature is 2000° C. or higher, grain growth of the silicon carbide powder occurs, which may deteriorate the sinterability in the subsequent sintering step.
（炭化珪素粉末）
閃亜鉛鉱型構造のβ型炭化珪素や、閃亜鉛鉱型とこれと同形質であるウルツ鉱型の構造の組み合わせで示されるα型炭化珪素等が挙げられ、一般的にはβ型炭化珪素が焼結用として用いられるが、本発明では価格等も考慮していずれの型のものも用いることができる。炭化珪素は、工業的にはアチソン法や、固相反応、気相反応等による合成法により製造することができ、本発明ではいずれの方法により得られた炭化珪素粉末も使用することができる。
(Silicon carbide powder)
Examples thereof include β-type silicon carbide having a zinc blende type structure, and α type silicon carbide which is represented by a combination of a zinc blende type structure and a wurtzite type structure having the same characteristics as the β type silicon carbide. Is used for sintering, but in the present invention, any type can be used in consideration of price and the like. Silicon carbide can be industrially produced by the Acheson method or a synthetic method such as a solid phase reaction or a gas phase reaction. In the present invention, the silicon carbide powder obtained by any method can be used.
炭化珪素粉末の平均粒径は１００ｎｍ以下であることが好ましい。このように細かい粉末であれば、加熱処理によって窒素の固溶を０．５質量％以上とすることが可能となり、抵抗の上昇を抑える点や焼結助剤としての役割の観点から、有効である。平均粒径は５０ｎｍ以下であることがより好ましく、これにより、窒素の固溶を１質量％程度まで上げることが可能となる。なお、炭化珪素粉末の平均粒径は、レーザ回折法により測定することができる。 The average particle size of the silicon carbide powder is preferably 100 nm or less. With such a fine powder, the solid solution of nitrogen can be made 0.5 mass% or more by heat treatment, which is effective from the viewpoint of suppressing the increase in resistance and the role as a sintering aid. is there. The average particle diameter is more preferably 50 nm or less, which makes it possible to increase the solid solution of nitrogen to about 1% by mass. The average particle size of the silicon carbide powder can be measured by a laser diffraction method.
〈焼結工程〉
本工程は、加熱処理工程後の炭化珪素粉末を、窒素ガス雰囲気下で焼結する工程である。これにより、炭化珪素の粉末が熱により固まって緻密な状態となった焼結体を得ることができる。焼結は、固溶した窒素の含有用を安定させ、また、焼結に伴い副反応が生じないように、窒素ガス雰囲気下で行う。窒素ガスの導入量は、適量に調節することができる。
<Sintering process>
This step is a step of sintering the silicon carbide powder after the heat treatment step in a nitrogen gas atmosphere. This makes it possible to obtain a sintered body in which the powder of silicon carbide is hardened by heat to be in a dense state. Sintering is performed under a nitrogen gas atmosphere so that the content of solid-dissolved nitrogen is stabilized and side reactions do not occur during sintering. The introduction amount of nitrogen gas can be adjusted to an appropriate amount.
焼結方法は特に限定されないが、製造量やコストを考慮して、例えば、放電プラズマ焼結法、ホットプレス焼結法、熱間等方加圧焼結法、またはパルス通電焼結法を適宜用いることができる。また、焼結体の厚さも、適宜設定することができる。 The sintering method is not particularly limited, but in consideration of the production amount and the cost, for example, a discharge plasma sintering method, a hot press sintering method, a hot isostatic pressing sintering method, or a pulse current sintering method is appropriately used. Can be used. Further, the thickness of the sintered body can be set as appropriate.
放電プラズマ焼結法（ＳＰＳ：Ｓｐａｒｋ Ｐｌａｓｍａ Ｓｉｎｔｅｒｉｎｇ）を一例として説明すると、この方法は、放電プラズマ焼結装置を使用して、焼結する方法である。具体的には、それぞれがカーボン（黒鉛）製の筒状のダイ一対と、ダイの上部および下部にあるパンチ（電極）とでキャビティを形成し、該キャビティに加熱処理工程後の炭化珪素粉末を充填する。そして、この状態で、ダイの上下間にパルス電流を流すとともに、ダイも抵抗発熱させ、さらに、上下のパンチで加圧して、焼結加工を行うものである。一般に放電プラズマ焼結法は、短時間での焼結が可能で、焼結助剤の添加が不要な焼結法であり、炭化珪素を焼結させることのできる有効な方法である。 The discharge plasma sintering method (SPS: Spark Plasma Sintering) will be described as an example. This method is a method of sintering using a discharge plasma sintering apparatus. Specifically, a cavity is formed by a pair of cylindrical dies each made of carbon (graphite) and punches (electrodes) at the top and bottom of the die, and the silicon carbide powder after the heat treatment step is placed in the cavity. To fill. Then, in this state, a pulse current is passed between the upper and lower sides of the die, and the die is also resistance-heated and further pressed by the upper and lower punches to perform the sintering process. Generally, the spark plasma sintering method is a sintering method that enables sintering in a short time and does not require addition of a sintering aid, and is an effective method that can sinter silicon carbide.
焼結の条件は、特に限定されないが、温度条件を１８００〜２０００℃、圧力条件を５０〜７０ＭＰａとし、焼結時間を５分〜１時間とすることが好ましい。 The sintering condition is not particularly limited, but it is preferable that the temperature condition is 1800 to 2000° C., the pressure condition is 50 to 70 MPa, and the sintering time is 5 minutes to 1 hour.
温度条件が上記の範囲であることにより、問題なく焼結が進行し、得られた焼結体の機械的強度や抵抗値に問題が生じない。１８００℃未満の温度条件では、焼結が進まないことで焼結密度が上がらずに緻密な焼結体を得ることができず、機械的強度を満足できないおそれがある。また２０００℃より高い温度条件では、固溶した窒素が分離してしまうことで焼結助剤としての効果が薄れてしまい、焼結が進まないことで焼結密度が上がらずに緻密な焼結体を得ることができず、機械的強度を満足できないおそれがある。 When the temperature condition is within the above range, the sintering proceeds without problems, and the mechanical strength and the resistance value of the obtained sintered body do not cause any problems. Under a temperature condition of less than 1800° C., the sintering does not proceed, the sintered density does not increase, and a dense sintered body cannot be obtained, so that the mechanical strength may not be satisfied. Further, under a temperature condition higher than 2000° C., the solid solution nitrogen is separated, so that the effect as a sintering aid is weakened, and the sintering does not proceed, so that the sintering density does not increase and the dense sintering is performed. There is a possibility that the body cannot be obtained and the mechanical strength cannot be satisfied.
また、圧力条件が上記の範囲であることにより問題なく焼結が進行し、得られた焼結体の機械的強度や抵抗値に問題が生じない。５０ＭＰａより低い圧力条件の場合には、焼結密度が上がらずに緻密な焼結体を得ることができず、機械的強度を満足できないおそれがある。一方で、７０ＭＰａよりも高い圧力条件としなくても、性能を十分に満足する焼結体を得ることが可能であり、また、圧力を高くするための特別な設備が必要となるおそれがある。 Further, when the pressure condition is within the above range, the sintering proceeds without any problem, and there is no problem in the mechanical strength and the resistance value of the obtained sintered body. When the pressure condition is lower than 50 MPa, the sintered density does not increase, a dense sintered body cannot be obtained, and mechanical strength may not be satisfied. On the other hand, it is possible to obtain a sintered body that sufficiently satisfies the performance without requiring a pressure condition higher than 70 MPa, and there is a possibility that special equipment for increasing the pressure is required.
〈成膜工程〉
本工程は、焼結工程により得た焼結体の表面に、化学蒸着によって炭化珪素多結晶膜を成膜する工程である。化学蒸着の具体例としては、成膜装置を用いて、加熱した焼結体の表面に、炭化珪素多結晶膜の成分を含む原料ガスやキャリアガス等を供給し、１２００℃以上の環境下で焼結体の表面や気相での化学反応により、炭化珪素多結晶膜を堆積する方法が挙げられる。
<Film forming process>
This step is a step of forming a silicon carbide polycrystalline film by chemical vapor deposition on the surface of the sintered body obtained by the sintering step. As a specific example of chemical vapor deposition, a raw material gas containing a component of a silicon carbide polycrystalline film, a carrier gas, or the like is supplied to the surface of a heated sintered body by using a film forming apparatus, and the temperature is set to 1200° C. or higher. A method of depositing a polycrystalline silicon carbide film by a chemical reaction on the surface of the sintered body or in the vapor phase can be mentioned.
（原料ガス）
炭化珪素多結晶膜を成膜することができれば、特に限定されず、一般的に使用される原料ガスを用いることができる。例えば、ＳｉＣｌ4ガスやＳｉＣｌ3ＣＨ3ガス等の珪素塩化物のガスや、ＣＨ4ガスやＣ3Ｈ8ガス等の炭化水素のガスを用いることができる。
(Raw material gas)
There is no particular limitation as long as the polycrystalline silicon carbide film can be formed, and a commonly used source gas can be used. For example, a silicon chloride gas such as SiCl 4 gas or SiCl 3 CH 3 gas, or a hydrocarbon gas such as CH 4 gas or C 3 H 8 gas can be used.
（キャリアガス）
炭化珪素多結晶膜の成膜を阻害することなく、原料ガスを基板へ展開することができれば、一般的に使用されるキャリアガスを用いることができる。例えば、Ｈ2ガス等をキャリアガスとして用いることができる。
(Carrier gas)
If the source gas can be spread on the substrate without disturbing the formation of the silicon carbide polycrystalline film, a commonly used carrier gas can be used. For example, H 2 gas or the like can be used as a carrier gas.
成膜工程によって、平均膜厚が１〜１０００μｍの炭化珪素多結晶膜を成膜することが好ましい。平均膜厚がこの範囲にあることで、炭化珪素多結晶膜が焼結体の表面を平滑に被覆することができるため、炭化珪素単結晶基板との貼り合せが容易となり、また、貼り合わせ不良といった問題も生じない。平均膜厚が１μｍ未満の場合、処理対象となる焼結体の表面において、炭化珪素多結晶膜が成膜せずに焼結体の表面が露出する部分が生じるおそれがあり、焼結体の表面に凹凸があることで炭化珪素単結晶基板との貼り合せに不具合が生じることにより、デバイスの歩留まりを低下させてしまうおそれがある。また、平均膜厚が１０００μｍより厚くても、平滑性に問題は無く、炭化珪素単結晶基板との貼り合せに支障は生じないが、成膜に時間がかかってしまうおそれがある。 It is preferable to form a silicon carbide polycrystalline film having an average film thickness of 1 to 1000 μm by the film forming process. When the average film thickness is in this range, the silicon carbide polycrystalline film can cover the surface of the sintered body evenly, which facilitates the bonding with the silicon carbide single crystal substrate and also causes the bonding failure. Such a problem does not occur. When the average film thickness is less than 1 μm, there is a possibility that the surface of the sintered body may be exposed without forming a silicon carbide polycrystalline film on the surface of the sintered body to be treated. The unevenness on the surface causes a problem in bonding with the silicon carbide single crystal substrate, which may reduce the device yield. Further, even if the average film thickness is more than 1000 μm, there is no problem in smoothness and no problem occurs in bonding with the silicon carbide single crystal substrate, but film formation may take time.
〈その他の工程〉
本発明の炭化珪素多結晶基板の製造方法は、上記した加熱処理工程、焼結工程および成膜工程以外にも、他の工程を含むことができる。例えば、焼結工程により１０ｍｍ程度の厚みの焼結体を得てから、これをスライスして炭化珪素多結晶基板に適した厚みに調整する切断工程等を含むことができる。なお、焼結工程によって、炭化珪素多結晶基板に適した厚みの焼結体を得るのであれば、この切断工程は不要である。
<Other processes>
The method for manufacturing a silicon carbide polycrystalline substrate of the present invention can include other steps in addition to the above heat treatment step, sintering step and film forming step. For example, a cutting step of obtaining a sintered body having a thickness of about 10 mm by the sintering step, and slicing the sintered body to adjust the thickness suitable for the silicon carbide polycrystalline substrate can be included. If a sintered body having a thickness suitable for the silicon carbide polycrystalline substrate is obtained by the sintering step, this cutting step is unnecessary.
以下、実施例に基づいて本発明をさらに具体的に説明する。ただし、本発明は以下の実施例の内容に何ら限定されるものではない。 Hereinafter, the present invention will be described more specifically based on Examples. However, the present invention is not limited to the contents of the following examples.
〈実施例１〉
平均粒径３０ｎｍのβ型炭化珪素粉末を密閉式高周波誘導炉にセットし、炉内に窒素ガスを流入しながら１５℃／分の昇温速度で２０００℃まで上昇し、この温度で３０分加熱処理を実施した（加熱処理工程）。その後、加熱処理後のβ型炭化珪素粉末をカーボン（黒鉛）製の筒状のキャビティに充填し、この状態で、窒素雰囲気の中で、上・下間にパルス電流を流すとともに、ダイも抵抗発熱させ、さらに、上・下パンチで加圧して、放電プラズマ焼結法による焼結加工を行った（焼結工程）。焼結の条件は、温度２０００℃で圧力７０ＭＰａとし、１時間焼結処理した。得られた焼結体を厚さ３９０μｍにスライスし（切断工程）、化学蒸着によってこれに炭化珪素多結晶膜を成膜させた（成膜工程）。成膜には成膜装置を使用し、１３５０度の環境の中で、ＳｉＣｌ4ガスとＣＨ4ガスおよび窒素ガスを、キャリアガスの水素とともに装置内に導入し、２０分間の成膜を実施することで、炭化珪素多結晶膜の被膜を焼結体の両面に付着させた炭化珪素多結晶基板を得た（図１（ｂ））。なお、β型炭化珪素粉末の平均粒径は、レーザ回折式粒度分布測定装置（島津製作所製 ＳＡＬＤ−７５００ｎａｎｏ）を使用し、レーザ回折式粒度分布測定法により測定した体積基準の粒度分布の平均値である。
<Example 1>
A β-type silicon carbide powder having an average particle size of 30 nm was set in a closed type high frequency induction furnace, and while flowing nitrogen gas into the furnace, the temperature was raised to 2000° C. at a heating rate of 15° C./min, and heating was performed at this temperature for 30 minutes The treatment was performed (heat treatment step). After that, the heat-treated β-type silicon carbide powder is filled into a carbon (graphite) cylindrical cavity, and in this state, a pulse current is passed between the upper and lower sides in a nitrogen atmosphere, and the die is also resistant. Heat was generated, and pressure was applied by the upper and lower punches to perform sintering processing by the discharge plasma sintering method (sintering step). The sintering conditions were a temperature of 2000° C., a pressure of 70 MPa, and a sintering treatment for 1 hour. The obtained sintered body was sliced to a thickness of 390 μm (cutting step), and a silicon carbide polycrystalline film was formed thereon by chemical vapor deposition (film forming step). A film forming apparatus is used for film formation, and SiCl 4 gas, CH 4 gas, and nitrogen gas are introduced into the apparatus together with hydrogen as a carrier gas in an environment of 1350° C., and film formation is carried out for 20 minutes. As a result, a silicon carbide polycrystalline substrate having a silicon carbide polycrystalline film coating adhered to both surfaces of the sintered body was obtained (FIG. 1(b)). The average particle size of the β-type silicon carbide powder is an average value of volume-based particle size distribution measured by a laser diffraction type particle size distribution measuring method using a laser diffraction type particle size distribution measuring device (Shimadzu SALD-7500 nano). Is.
（電気抵抗の測定）
四端子法により、炭化珪素多結晶基板の電気抵抗を測定した。
(Measurement of electrical resistance)
The electrical resistance of the silicon carbide polycrystalline substrate was measured by the four-terminal method.
（炭化珪素多結晶膜の膜厚測定）
炭化珪素多結晶基板を切断してＳＥＭにより断面観察し、炭化珪素多結晶基板の中央部分の１点と、両端の端部より１０ｍｍ内側の２点の合計３点における炭化珪素多結晶膜の膜厚の平均を算出し、平均膜厚とした。
(Measurement of thickness of polycrystalline silicon carbide film)
A film of a silicon carbide polycrystalline film at one point at the central portion of the silicon carbide polycrystalline substrate and at two
（炭化珪素多結晶膜の表面の空隙の有無の確認）
ＳＥＭにより炭化珪素多結晶膜の表面を観察し、空隙の有無を確認した。
(Confirmation of voids on the surface of the silicon carbide polycrystalline film)
The surface of the silicon carbide polycrystalline film was observed by SEM to confirm the presence or absence of voids.
加熱処理工程、焼結工程および成膜工程の条件と、電気抵抗、膜厚および空隙の有無の確認結果について、表１に示す。 Table 1 shows the conditions of the heat treatment step, the sintering step, and the film forming step, and the confirmation results of the electric resistance, the film thickness, and the presence or absence of voids.
〈実施例２〉
焼結工程において、焼結温度を１８００℃にした以外は、実施例１と同じ条件で焼結を行い、炭化珪素多結晶基板を得た。
<Example 2>
In the sintering step, sintering was performed under the same conditions as in Example 1 except that the sintering temperature was set to 1800° C. to obtain a silicon carbide polycrystalline substrate.
〈実施例３〉
加熱処理工程における処理温度を１８００℃、焼結工程における圧力を５０Ｍｐａ、成膜工程における成膜時間を１０分間にした以外は、実施例１と同じ条件で処理を行い、炭化珪素多結晶基板を得た。
<Example 3>
The silicon carbide polycrystalline substrate was processed under the same conditions as in Example 1 except that the treatment temperature in the heat treatment step was 1800° C., the pressure in the sintering step was 50 MPa, and the film formation time in the film formation step was 10 minutes. Obtained.
〈実施例４〉
成膜工程における成膜時間を２分間にした以外は、実施例１と同じ条件で処理を行い、炭化珪素多結晶基板を得た。
<Example 4>
A treatment was performed under the same conditions as in Example 1 except that the film formation time in the film formation step was set to 2 minutes to obtain a silicon carbide polycrystalline substrate.
〈比較例１〉
加熱処理工程を行わなかった以外は、実施例１と同じ条件で処理を行い、炭化珪素多結晶基板を得た。
<Comparative Example 1>
A treatment was performed under the same conditions as in Example 1 except that the heat treatment step was not performed to obtain a silicon carbide polycrystalline substrate.
〈比較例２〉
焼結工程における雰囲気を大気にした以外は、実施例１を同じ条件で処理を行い、炭化珪素多結晶基板を得た。
<Comparative example 2>
Example 1 was processed under the same conditions except that the atmosphere in the sintering step was changed to the atmosphere, to obtain a silicon carbide polycrystalline substrate.
〈比較例３〉
成膜工程における成膜時間を１分間にした以外は、実施例１と同じ条件で処理を行い、炭化珪素多結晶基板を得た。
<Comparative Example 3>
A treatment was performed under the same conditions as in Example 1 except that the film formation time in the film formation step was set to 1 minute to obtain a silicon carbide polycrystalline substrate.
〈比較例４〉
成膜工程を行わなかった以外は、実施例１と同じ条件で処理を行い、炭化珪素多結晶基板を得た。
<Comparative Example 4>
A treatment was performed under the same conditions as in Example 1 except that the film forming step was not performed, to obtain a silicon carbide polycrystalline substrate.
表１の結果より、窒素ガス雰囲気下で加熱処理し、更に窒素ガス雰囲気下で焼結したものは、電気抵抗率は１０-4台の値であり、炭化珪素半導体とした場合にＯＮ抵抗が大きくなることで、本来の炭化珪素半導体の特徴が充分に発揮できなくなるといったおそれがない、良好な低抵抗の特性を示した（実施例１〜４）。また、成膜工程によって、１μｍ以上の炭化珪素多結晶膜を成膜したものは、炭化珪素多結晶基板の表面に空隙は認められなかった（実施例１〜４、比較例１、２）。 From the results shown in Table 1, those obtained by performing heat treatment in a nitrogen gas atmosphere and further sintering in a nitrogen gas atmosphere have an electric resistivity of the order of 10 −4 , and when the silicon carbide semiconductor is used, the ON resistance is It was shown that good characteristics of low resistance were exhibited without increasing the possibility that the original characteristics of the silicon carbide semiconductor would not be fully exhibited due to the increase (Examples 1 to 4). In addition, no void was observed on the surface of the silicon carbide polycrystalline substrate in the case where the silicon carbide polycrystalline film having a thickness of 1 μm or more was formed by the film forming process (Examples 1 to 4, Comparative Examples 1 and 2).
これ対して、加熱処理工程を実施しなかった比較例１の炭化珪素多結晶基板は、電気抵抗を測定した結果、他の例と比べて高抵抗となった。また、比較例２に示すように、加熱処理工程を行った粉末であっても、大気雰囲気で焼結を行った結果、炭化珪素多結晶基板の抵抗値が、実施例１〜４と比べて上昇した。 On the other hand, the silicon carbide polycrystalline substrate of Comparative Example 1 in which the heat treatment step was not performed showed a higher resistance than the other examples as a result of measuring the electric resistance. Further, as shown in Comparative Example 2, even if the powder was subjected to the heat treatment step, the resistance value of the silicon carbide polycrystalline substrate was higher than that in Examples 1 to 4 as a result of sintering in the air atmosphere. Rose.
更に、比較例３、比較例４のように化学蒸着による炭化珪素多結晶膜の被膜が薄いものや、成膜工程を実施しないことで炭化珪素多結晶膜の被膜の無いものでは、焼結体の表面に存在する空隙を埋めることができず、炭化珪素単結晶基板の貼り合わせに適した炭化珪素多結晶基板を得ることは出来なかった。 Further, as in Comparative Examples 3 and 4, when the film of the silicon carbide polycrystalline film formed by chemical vapor deposition is thin, or when the film forming step is not performed and the film of the silicon carbide polycrystalline film is not formed, a sintered body is obtained. It was not possible to fill the voids existing on the surface of, and it was not possible to obtain a silicon carbide polycrystalline substrate suitable for bonding a silicon carbide single crystal substrate.
［まとめ］
本発明の炭化珪素多結晶基板であれば、焼結体によって機械的強度を満足する基板の厚さを確保しつつ、抵抗の上昇を抑えることができ、そして、炭化珪素多結晶膜によって、基板の表面の平滑性を確保し、炭化珪素単結晶基板の貼り合わせの不良を防止することができる。また、本発明であれば、このような炭化珪素多結晶基板を容易に製造することができる。
[Summary]
With the silicon carbide polycrystalline substrate of the present invention, it is possible to suppress the increase in resistance while ensuring the thickness of the substrate that satisfies the mechanical strength by the sintered body, and the silicon carbide polycrystalline film enables the substrate to be formed. It is possible to secure the smoothness of the surface and prevent the defective bonding of the silicon carbide single crystal substrate. Further, according to the present invention, such a silicon carbide polycrystalline substrate can be easily manufactured.
１０ 焼結体
１１ 第１面
１２ 第２面
１３ 側面
２０ａ 炭化珪素多結晶膜
２０ｂ 炭化珪素多結晶膜
２０ｃ 炭化珪素多結晶膜
１００ 炭化珪素多結晶基板
１１０ 炭化珪素多結晶基板
１２０ 炭化珪素多結晶基板
DESCRIPTION OF
Claims (6)
前記加熱処理工程後の前記炭化珪素粉末を、窒素ガス雰囲気下で焼結する焼結工程と、
前記焼結工程により得た焼結体の表面に、化学蒸着によって炭化珪素多結晶膜を成膜する成膜工程を含む、炭化珪素多結晶基板の製造方法。 A heat treatment step of heat treating the silicon carbide powder in a nitrogen gas atmosphere,
A sintering step of sintering the silicon carbide powder after the heat treatment step in a nitrogen gas atmosphere,
A method of manufacturing a silicon carbide polycrystalline substrate, comprising a film forming step of forming a silicon carbide polycrystalline film on the surface of the sintered body obtained by the sintering step by chemical vapor deposition.
前記焼結体の表面に化学蒸着によって成膜した炭化珪素多結晶膜と、を備え、
前記炭化珪素多結晶膜は、平均膜厚が１〜１０００μｍ、空隙が０個／μｍ2である、
電気抵抗が３．０５×１０-5Ω・ｍ〜４．３０×１０-5Ω・ｍの炭化珪素多結晶基板。 A sintered body of silicon carbide,
A silicon carbide polycrystalline film formed by chemical vapor deposition on the surface of the sintered body,
The silicon carbide polycrystalline film has an average film thickness of 1 to 1000 μm and 0 voids/μm 2 .
A silicon carbide polycrystalline substrate having an electric resistance of 3.05×10 −5 Ω·m to 4.30×10 −5 Ω·m.
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