JP2013157544A - Silicon carbide semiconductor device manufacturing method - Google Patents

Silicon carbide semiconductor device manufacturing method Download PDF

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JP2013157544A
JP2013157544A JP2012018593A JP2012018593A JP2013157544A JP 2013157544 A JP2013157544 A JP 2013157544A JP 2012018593 A JP2012018593 A JP 2012018593A JP 2012018593 A JP2012018593 A JP 2012018593A JP 2013157544 A JP2013157544 A JP 2013157544A
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silicon carbide
hydrogen
carbide semiconductor
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semiconductor device
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JP5975460B2 (en
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Mitsuhisa Okamoto
光央 岡本
Yoichi Makibuchi
陽一 巻渕
Kenji Fukuda
憲司 福田
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Fuji Electric Co Ltd
National Institute of Advanced Industrial Science and Technology AIST
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Abstract

PROBLEM TO BE SOLVED: To inhibit increase in interface state density of a MOS interface caused by desorption of terminated hydrogen or a terminated hydrogen group to achieve high channel mobility even when polysilicon is deposited on an insulation film obtained by oxidation of (000-1) plane and (11-20) plane of a silicon carbide semiconductor in a wet atmosphere.SOLUTION: In a silicon carbide semiconductor device manufacturing method which includes a process of forming a gate insulation film on (000-1) plane or (11-20) plane of the silicon carbide semiconductor in contact with the plane of the silicon carbide semiconductor by performing thermal oxidation in a gas containing at least oxygen and moisture, and a process of depositing a polysilicon gate conductive film on the gate insulation film by a low pressure CVD method, hydrogen or a mixed gas of an inert gas and hydrogen is used in a standby atmosphere for temperature stabilization before deposition of the gate conductive film in a deposition apparatus, and in displacement of a process gas after deposition.

Description

本発明は炭化ケイ素基板を使用した半導体装置の製造方法に関わり、特にゲート絶縁膜の上に減圧ＣＶＤ法で導電膜を成膜する工程に特徴を有する、炭化ケイ素半導体装置の製造方法に関する。   The present invention relates to a method for manufacturing a semiconductor device using a silicon carbide substrate, and more particularly to a method for manufacturing a silicon carbide semiconductor device characterized by a step of forming a conductive film on a gate insulating film by a low pressure CVD method.

炭化ケイ素を用いたＭＯＳＦＥＴ等の半導体デバイスは、バイポーラトランジスタと比較して高速のスイッチングが可能となることから、近年、炭化ケイ素基板を用いた次世代半導体デバイスの研究開発が進められている。炭化ケイ素はシリコンと同様に熱酸化で絶縁膜を形成可能であるが、結晶面や酸化方法によってＭＯＳ界面のチャネル移動度が異なるという特性がある。
炭化ケイ素基板の代表的な面である（０００−１）面あるいは（１１−２０）面は、ウェット雰囲気で酸化すると（０００１）面に比べ高いチャネル移動度を示し、オン抵抗の低減し、消費電力を低減する上で有利である。
なお、チャネル移動度を代替的に評価する指標として界面準位密度があり、一般的には、界面準位密度が小さい方がチャネル移動度は大きくなる傾向が知られている。 Since semiconductor devices such as MOSFETs using silicon carbide can be switched at a higher speed than bipolar transistors, research and development of next-generation semiconductor devices using silicon carbide substrates have been promoted in recent years. Silicon carbide can form an insulating film by thermal oxidation like silicon, but has a characteristic that the channel mobility at the MOS interface differs depending on the crystal plane and the oxidation method.
The (000-1) plane or the (11-20) plane, which is a typical plane of a silicon carbide substrate, exhibits higher channel mobility than the (0001) plane when oxidized in a wet atmosphere, reduces on-resistance, and consumes. This is advantageous in reducing power.
Note that there is an interface state density as an index for alternatively evaluating the channel mobility, and it is generally known that the channel mobility tends to increase as the interface state density decreases.

このような炭化ケイ素基板を用いた半導体デバイスの製造方法に関し、下記の特許文献１には、界面準位密度を低下させるために、炭化ケイ素基板の（０００−１）面をウェット雰囲気で熱酸化することにより高いチャネル移動度を得る方法が示されており、具体的には、ゲート絶縁膜を形成するための酸化後に、水素あるいは水蒸気雰囲気中でアニールを行っている。   With respect to a method for manufacturing a semiconductor device using such a silicon carbide substrate, the following Patent Document 1 discloses that the (000-1) plane of the silicon carbide substrate is thermally oxidized in a wet atmosphere in order to reduce the interface state density. Thus, a method of obtaining high channel mobility is shown. Specifically, after oxidation for forming a gate insulating film, annealing is performed in a hydrogen or water vapor atmosphere.

特許第４３７４４３７号公報Japanese Patent No. 4374437

しかし、炭化ケイ素基板の（０００−１）面あるいは（１１−２０）面をウェット雰囲気で酸化して得られたＭＯＳ界面の界面準位密度は、後工程の不活性ガス雰囲気での熱処理、例えばメタルのオーミックコンタクトを形成するための不活性ガス中のアニールで大きくなり、ＭＯＳ界面特性が劣化することが知られている。
すなわち、ウェット雰囲気の熱酸化で界面準位密度が低減されるのは、水素あるいは水酸基が界面準位を終端するためであるといわれているが、不活性ガス中のアニールにより、終端している水素あるいは水酸基が脱離することにより界面準位密度が大きくなり、ＭＯＳ界面特性が劣化するものと推測されている。 However, the interface state density of the MOS interface obtained by oxidizing the (000-1) plane or the (11-20) plane of the silicon carbide substrate in a wet atmosphere is a heat treatment in an inert gas atmosphere in a later step, for example, It is known that MOS interface characteristics deteriorate due to an increase in annealing in an inert gas for forming a metal ohmic contact.
That is, it is said that the interface state density is reduced by thermal oxidation in a wet atmosphere because hydrogen or a hydroxyl group terminates the interface state, but is terminated by annealing in an inert gas. It is presumed that the interface state density is increased by desorption of hydrogen or a hydroxyl group, and the MOS interface characteristics are deteriorated.

この熱アニールによるＭＯＳ界面特性劣化は、炭化ケイ素（０００１）面上に作製したＭＯＳデバイスでは発生しないため、炭化ケイ素（０００−１）面上あるいは炭化ケイ素（１１−２０）面と、（０００１）面上のＭＯＳデバイスとではデバイスプロセスに異なった工夫を行い、ＭＯＳ界面特性劣化を防止することが必要となる。
ところで、ゲート絶縁膜の上に形成される導電膜（ゲート電極）はアルミニウムなどの金属、ポリシリコンあるいはポリシリコンと金属との溶融材料などが用いられる。ポリシリコンは高温プロセスが可能である等のアルミよりも優れた特性があり、シリコン半導体デバイスではポリシリコンを用いたゲート電極が主流である。ポリシリコンは減圧ＣＶＤ法を用いて６００℃前後の成膜温度で形成される。 Since the MOS interface characteristic deterioration due to the thermal annealing does not occur in the MOS device fabricated on the silicon carbide (0001) surface, the silicon carbide (000-1) surface or the silicon carbide (11-20) surface, and (0001) It is necessary to devise a device process different from the MOS device on the surface to prevent the deterioration of the MOS interface characteristics.
By the way, the conductive film (gate electrode) formed on the gate insulating film is made of metal such as aluminum, polysilicon, or a molten material of polysilicon and metal. Polysilicon has characteristics superior to aluminum, such as being capable of high-temperature processing, and a gate electrode using polysilicon is the mainstream in silicon semiconductor devices. Polysilicon is formed at a film forming temperature of around 600 ° C. using a low pressure CVD method.

同一の条件で（０００−１）面あるいは（１１−２０）面を、ウェット雰囲気で酸化して得られたＭＯＳ界面に対し、ゲート電極を減圧ＣＶＤ法で堆積したポリシリコンとした場合の界面準位密度が、ゲート電極を常温で蒸着したアルミとした場合の界面準位密度よりも大きくなる問題がある。
これは、実際の減圧ＣＶＤ炉でのポリシリコン成膜では、ＳｉＨ4等を流してポリシリコンを成膜する前に、温度の安定のため、不活性ガスを流しての保持時間や、成膜後にＳＨ4等を不活性ガスで置換するプロセスが含まれることが原因と考えられる。つまり、実質、不活性ガス中での熱処理が含まれており、これが、終端している水素あるいは水酸基を脱離させ、界面準位密度を増加させる要因となっていると考えられる。 Interface conditions when the gate electrode is made of polysilicon deposited by the low pressure CVD method with respect to the MOS interface obtained by oxidizing the (000-1) surface or the (11-20) surface in a wet atmosphere under the same conditions. There is a problem that the unit density becomes larger than the interface state density when the gate electrode is aluminum deposited at room temperature.
This is because in the actual polysilicon film formation in a low pressure CVD furnace, before the polysilicon film is formed by flowing SiH 4 or the like, the holding time and the film formation with an inert gas flow are added to stabilize the temperature. The cause is considered to include a process of replacing SH 4 and the like with an inert gas later. That is, the heat treatment in an inert gas is substantially included, and this is considered to cause the termination of hydrogen or hydroxyl group and increase the interface state density.

上記の問題に鑑み、本発明の目的は、炭化ケイ素半導体の（０００−１）面、（１１−２０）面をウェット雰囲気で酸化して得られた絶縁膜上にポシリコンを成膜しても、終端している水素あるいは水酸基の脱離によるＭＯＳ界面の界面準位密度の増加を抑制し、高いチャネル移動度を実現する炭化ケイ素半導体装置の製造方法を提供することにある。   In view of the above problems, an object of the present invention is to form a polysilicon film on an insulating film obtained by oxidizing the (000-1) plane and the (11-20) plane of a silicon carbide semiconductor in a wet atmosphere. An object of the present invention is to provide a method for manufacturing a silicon carbide semiconductor device that suppresses an increase in interface state density at the MOS interface due to elimination of hydrogen or hydroxyl groups that are terminated, and realizes high channel mobility.

上記の目的を達成するため、本発明の炭化ケイ素半導体装置の製造方法では、次のような技術的手段を講じた。すなわち、
（１）炭化ケイ素半導体の（０００−１）面上、あるいは（１１−２０）面上に、少なくとも酸素と水分を含むガス中で熱酸化を行い、前記炭化ケイ素半導体の面上に接するようにゲート絶縁膜を形成する工程と、該ゲート絶縁膜の上に減圧ＣＶＤ法でポリシリコンのゲート導電膜を成膜する工程とを有する炭化ケイ素半導体装置の製造方法において、前記ゲート導電膜の成膜装置内での成膜前の温度安定のための待機時の雰囲気、及び、成膜後のプロセスガスの置換に、水素、あるいは、不活性ガスと水素の混合ガスを用いた。 In order to achieve the above object, the following technical means were taken in the method for manufacturing a silicon carbide semiconductor device of the present invention. That is,
(1) Thermal oxidation is performed in a gas containing at least oxygen and moisture on the (000-1) plane or the (11-20) plane of the silicon carbide semiconductor so as to be in contact with the plane of the silicon carbide semiconductor. In the method for manufacturing a silicon carbide semiconductor device, the method includes: forming a gate insulating film; and forming a polysilicon gate conductive film on the gate insulating film by a low pressure CVD method. Hydrogen or a mixed gas of an inert gas and hydrogen was used for the standby atmosphere for temperature stabilization before film formation in the apparatus and for the replacement of the process gas after film formation.

（２）前記不活性ガスと水素の混合ガスとして、窒素、ヘリウム、アルゴンの何れかと水素の混合ガスを使用した。 (2) As a mixed gas of the inert gas and hydrogen, a mixed gas of nitrogen, helium, or argon and hydrogen was used.

（３）前記不活性ガスと水素の混合ガス中の水素濃度を１％以上４％以下とした。 (3) The hydrogen concentration in the mixed gas of the inert gas and hydrogen is 1% or more and 4% or less.

（４）前記ゲート絶縁膜を成膜する工程を、水分を含まない乾燥酸素中で熱酸化を行った後、水分を含むガス中での熱酸化を組み合わせた工程とした。 (4) The step of forming the gate insulating film is a step in which thermal oxidation is performed in dry oxygen not containing moisture and then thermal oxidation in a gas containing moisture is combined.

（５）前記ゲート絶縁膜を成膜する工程を、絶縁膜を堆積させた後、水分を含むガス中での熱酸化を組み合わせた工程とした。 (5) The step of forming the gate insulating film is a step in which after the insulating film is deposited, thermal oxidation in a gas containing moisture is combined.

（６）前記減圧ＣＶＤ法でシリコンゲート導電膜を成膜する工程で、シラン（ＳｉＨ4）あるいはジシラン（ＳｉＨ8）が含まれた原料ガスを使用した。 (6) In the step of forming a silicon gate conductive film by the low pressure CVD method, a source gas containing silane (SiH 4 ) or disilane (SiH 8 ) was used.

本発明によれば、炭化ケイ素半導体の（０００−１）面上に形成したゲート絶縁膜の上に、減圧ＣＶＤ法を用いてポリシリコンを成膜するときに、ポリシリコン成膜前の温度安定のための待機時の雰囲気や、成膜後のプロセスガスの置換に不活性ガスと水素の混合ガスを用いているので、ポリシリコン成膜のためのアニールにより、終端している水素あるいは水酸基が脱離するのを、混合ガス中の水素分圧により抑止し、界面準位密度の上昇によるＭＯＳ界面特性の劣化を効果的に防止することができる。   According to the present invention, when a polysilicon film is formed on the gate insulating film formed on the (000-1) plane of the silicon carbide semiconductor by using a low pressure CVD method, temperature stabilization before the polysilicon film formation is achieved. Since a mixed gas of an inert gas and hydrogen is used to replace the process gas after film formation and the standby atmosphere for film formation, the termination of hydrogen or hydroxyl groups is caused by annealing for polysilicon film formation. Desorption can be suppressed by the partial pressure of hydrogen in the mixed gas, and deterioration of MOS interface characteristics due to an increase in interface state density can be effectively prevented.

ＭＯＳキャパシタの構成を示す図The figure which shows the constitution of the MOS capacitor 従来の製造方法で作製されたＭＯＳキャパシタと本発明の製造方法で作製されたＭＯＳキャパシタを測定して得られた界面準位密度の分布を示す図The figure which shows the distribution of the interface state density obtained by measuring the MOS capacitor produced with the conventional manufacturing method, and the MOS capacitor produced with the manufacturing method of this invention

以下、炭化ケイ素半導体装置として、ＭＯＳキャパシタを製造する際の本発明の実施例を説明する。   Hereinafter, an embodiment of the present invention when manufacturing a MOS capacitor as a silicon carbide semiconductor device will be described.

ゲート電極としてポシリコンを成膜してもＭＯＳ界面の界面準位密度の増加が抑えられるような、ポシリコン成膜方法について実施例を用いて説明する。
図１はＭＯＳキャパシタの構成を示す図である。
本実施例では、結晶構造が４Ｈ−ＳｉＣの（０００−１）基板１（０〜８°オフ基板）にドナー密度１Ｅ＋１６ｃｍ3程度のｎ型エピタキシャル膜２を５〜１０μｍ成長させ、洗浄した後、１０００℃のウェット熱酸化を３０分行い、厚さ約５０ｎｍの絶縁膜３を形成した。なお、水分を含まない乾燥酸素中で熱酸化を予め行った上で、ウェット熱酸化を組み合わせてもよい。 A polysilicon film forming method that suppresses an increase in interface state density at the MOS interface even when polysilicon film is formed as a gate electrode will be described with reference to examples.
FIG. 1 is a diagram showing the configuration of a MOS capacitor.
In this example, an n-type epitaxial film 2 having a donor density of about 1E + 16 cm 3 is grown on a (000-1) substrate 1 (0-8 ° off substrate) having a crystal structure of 4H—SiC, and is cleaned, Wet thermal oxidation at 1000 ° C. was performed for 30 minutes to form an insulating film 3 having a thickness of about 50 nm. In addition, after performing thermal oxidation in dry oxygen which does not contain water in advance, wet thermal oxidation may be combined.

次に、ゲート電極の形成するため、減圧ＣＶＤ炉に導入した。温度の安定させるために不活性ガスと水素の混合ガスを流しながら５７０℃で３０分保持した後、原料ガスとして、ＳｉＨ4（シラン）、ＰＨ3を流しながらリンドープされたポリシリコンを５００ｎｍ成膜した。成膜後は、ＳｉＨ4、ＰＨ3を、不活性ガスと水素の混合ガスで置換した後、取出した。なお、原料ガスとしては、ＳｉＨ4（シラン）、ＰＨ3のほか、ジシラン（ＳｉＨ8）を使用してもよい。 Next, it was introduced into a low pressure CVD furnace in order to form a gate electrode. In order to stabilize the temperature, a mixed gas of inert gas and hydrogen is flowed and maintained at 570 ° C. for 30 minutes, and then phosphorus-doped polysilicon is formed to a thickness of 500 nm while SiH 4 (silane) and PH 3 are flowed as source gases. did. After film formation, SiH 4 and PH 3 were replaced with a mixed gas of an inert gas and hydrogen and then taken out. In addition to SiH 4 (silane) and PH 3 , disilane (SiH 8 ) may be used as the source gas.

本実施例では、不活性ガスと水素の混合ガスは窒素、ヘリウム、アルゴンの何れかと水素の混合ガスであり、不活性ガスと水素の混合ガス中の水素濃度は４％とした。
なお、不活性ガスと水素の混合ガスは、減圧ＣＶＤ炉による成膜プロセスに一般的に使用されている窒素、ヘリウム、アルゴン等のガスタンクに予め水素ガスを混入させて、所望の水素ガス濃度に調整している。 In this embodiment, the mixed gas of inert gas and hydrogen is a mixed gas of nitrogen, helium, or argon and hydrogen, and the hydrogen concentration in the mixed gas of inert gas and hydrogen is 4%.
Note that the mixed gas of the inert gas and hydrogen is mixed with hydrogen gas in a gas tank such as nitrogen, helium, and argon, which is generally used in a film forming process by a low pressure CVD furnace, to obtain a desired hydrogen gas concentration. It is adjusted.

電気測定用のアルミパッド５を蒸着で形成し、フォトリソグラフィとエッチングでパターニングした後、アルミ裏面電極６を蒸着した。
完成したＭＯＳキャパシタをＣ−Ｖ測定し、伝導帯からのエネルギー（ｅＶ）に対する界面準位密度（／ｃｍ2／ｅＶ）を算出したところ、図２に示すように、ポリシリコン成膜前の温度安定のための保持時間の雰囲気や、成膜後のプロセスガスの置換に不活性ガスを用いた従来よりも低減された。
これは、減圧ＣＶＤ炉で、ＳＨ4、ＰＨ3を流しながらリンドープされたポリシリコンを成膜するのに先だって、成膜温度に安定化させるまでの期間、不活性ガスと水素の混合ガスを供給するとともに、成膜終了後取り出す際にも、ＳＨ4、ＰＨ3を、不活性ガスと水素の混合ガスで置換したことにより、ポリシリコン成膜のためのアニールにより、終端している水素あるいは水酸基が脱離するのを、混合ガス中の水素分圧により抑止し、界面準位密度の上昇によるＭＯＳ界面特性の劣化を効果的に防止することによるものと推測される。 An aluminum pad 5 for electrical measurement was formed by vapor deposition, patterned by photolithography and etching, and then an aluminum back electrode 6 was vapor deposited.
The completed MOS capacitor was subjected to CV measurement, and the interface state density (/ cm 2 / eV) with respect to energy (eV) from the conduction band was calculated. As shown in FIG. The atmosphere of the holding time for stability was reduced as compared with the conventional case where an inert gas was used to replace the process gas after film formation.
This is because a mixed gas of inert gas and hydrogen is supplied in a low-pressure CVD furnace until the film is stabilized at the film-forming temperature prior to film formation of phosphorus-doped polysilicon while flowing SH 4 and PH 3. At the same time, when the film is taken out after completion of the film formation, hydrogen or hydroxyl group terminated by annealing for polysilicon film formation is obtained by replacing SH 4 and PH 3 with a mixed gas of an inert gas and hydrogen. It is presumed that the desorption is suppressed by the partial pressure of hydrogen in the mixed gas and effectively prevents the deterioration of the MOS interface characteristics due to the increase of the interface state density.

上記の実施例では、不活性ガスと水素の混合ガス中の水素濃度は４％としたが、終端している水素あるいは水酸基がアニール中に脱離するのを抑止する観点では、水素濃度が高いほど有効であり、不活性ガスを混入せず水素ガス１００％とすることもできる。
しかし、実際の製造プロセスでは、水素ガス濃度を高めると、爆発等の危険を防止するためのコストを要し、しかも、実験結果によると、水素ガス濃度を１％から、界面準位密度の上昇を抑止する効果が確認でき、水素ガス濃度４％までその効果が急速に高まるが、４％を超えると、その効果が頭打ちになり、むしろ、爆発の危険性が顕著になる。
そこで、不活性ガスと水素の混合ガス中の水素濃度は、１％以上４％以下が好ましく、特に好ましく水素濃度が４％の場合が、界面準位密度の上昇を抑止する観点で特に顕著な効果が得られ、しかも、水素爆発の危険性も非常に少ない。 In the above embodiment, the hydrogen concentration in the mixed gas of the inert gas and hydrogen is 4%. However, the hydrogen concentration is high from the viewpoint of suppressing the termination of hydrogen or hydroxyl groups terminating during annealing. It is so effective that it can be made 100% hydrogen gas without mixing inert gas.
However, in the actual manufacturing process, if the hydrogen gas concentration is increased, the cost to prevent the danger of explosion etc. is required. Moreover, according to the experimental results, the hydrogen gas concentration is increased from 1% and the interface state density is increased. The effect of deterrence can be confirmed, and the effect rapidly increases up to a hydrogen gas concentration of 4%. However, when the concentration exceeds 4%, the effect reaches its peak, and the risk of explosion becomes rather remarkable.
Therefore, the hydrogen concentration in the mixed gas of the inert gas and hydrogen is preferably 1% or more and 4% or less, and particularly preferably the hydrogen concentration is 4% from the viewpoint of suppressing an increase in interface state density. The effect is obtained, and the danger of hydrogen explosion is very low.

また、上記の実施例では、結晶構造が４Ｈ−ＳｉＣの（０００−１）基板（０〜８°オフ基板）を使用したが、結晶構造が４Ｈ−ＳｉＣの（１１−２０）基板でも同様の効果が得られる。   In the above embodiment, a (000-1) substrate (0-8 ° off substrate) having a crystal structure of 4H—SiC was used, but the same applies to a (11-20) substrate having a crystal structure of 4H—SiC. An effect is obtained.

以上説明したように、本発明によれば、炭化ケイ素半導体の（０００−１）面上、あるいは（１１−２０）面上に、少なくとも酸素と水分を含むガス中で熱酸化を行った後、炭化ケイ素半導体の面上に接するようにゲート絶縁膜を形成し、このゲート絶縁膜の上に減圧ＣＶＤ法でポリシリコンのゲート導電膜を成膜する際、成膜温度に安定化させるまでの期間、不活性ガスと水素の混合ガスを供給するとともに、成膜終了後取り出す際にも、ＳＨ４、ＰＨ３を、不活性ガスと水素の混合ガスで置換したことにより、ポリシリコン成膜のためのアニールにより終端している水素あるいは水酸基が脱離するのを、混合ガス中の水素分圧により抑止し、界面準位密度の上昇によるＭＯＳ界面特性の劣化を効果的に防止することができる。
しかも、減圧ＣＶＤ炉による成膜プロセスに一般的に使用されている窒素、ヘリウム、アルゴン等のガスタンクに予め水素ガスを混入させて所望の水素濃度にするだけで、複雑な製造プロセスや、特殊な装置を必要としないので、コストアップを伴うことなく炭化ケイ素半導体装置の界面準位密度を低減し、チャネル移動度を高くできるので、炭化ケイ素半導体の製造プロセスに広く採用されることが期待できる。 As described above, according to the present invention, after performing thermal oxidation in a gas containing at least oxygen and moisture on the (000-1) plane or the (11-20) plane of the silicon carbide semiconductor, When a gate insulating film is formed so as to be in contact with the surface of the silicon carbide semiconductor, and a polysilicon gate conductive film is formed on the gate insulating film by a low pressure CVD method, the period until the film forming temperature is stabilized In addition to supplying a mixed gas of inert gas and hydrogen and also removing the film after film formation, SH 4 and PH 3 are replaced with a mixed gas of inert gas and hydrogen to form a polysilicon film. The termination of hydrogen or hydroxyl groups terminated by this annealing can be suppressed by the partial pressure of hydrogen in the mixed gas, and deterioration of MOS interface characteristics due to an increase in interface state density can be effectively prevented.
In addition, a complex manufacturing process or a special process can be performed simply by mixing hydrogen gas in a gas tank such as nitrogen, helium, and argon that is generally used in a film formation process by a low pressure CVD furnace to obtain a desired hydrogen concentration. Since no device is required, the interface state density of the silicon carbide semiconductor device can be reduced and the channel mobility can be increased without increasing the cost. Therefore, it can be expected to be widely adopted in the manufacturing process of silicon carbide semiconductors.

１ ｎ型 ４Ｈ−ＳｉＣ（０００−１）基板
２ ｎ型 エピタキシャル膜
３ 絶縁膜
４ ポリシリゲート電極
５ アルミパッド
６ アルミ裏面電極 1 n-type 4H-SiC (000-1) substrate 2 n-type epitaxial film 3 insulating film 4 polysilicon gate electrode 5 aluminum pad 6 aluminum back electrode

Claims (6)

炭化ケイ素半導体の（０００−１）面上、あるいは（１１−２０）面上に、少なくとも酸素と水分を含むガス中で熱酸化を行い、前記炭化ケイ素半導体の面上に接するようにゲート絶縁膜を形成する工程と、該ゲート絶縁膜の上に減圧ＣＶＤ法でポリシリコンのゲート導電膜を成膜する工程とを有する炭化ケイ素半導体装置の製造方法において、
前記ゲート導電膜の成膜装置内での成膜前の温度安定のための待機時の雰囲気、及び、成膜後のプロセスガスの置換に、水素、あるいは、不活性ガスと水素の混合ガスを用いることを特徴とする炭化ケイ素半導体装置の製造方法。 On the (000-1) surface or (11-20) surface of the silicon carbide semiconductor, thermal oxidation is performed in a gas containing at least oxygen and moisture, and the gate insulating film is in contact with the surface of the silicon carbide semiconductor. And a method of manufacturing a silicon carbide semiconductor device, comprising: forming a polysilicon gate conductive film on the gate insulating film by a low pressure CVD method.
Hydrogen or a mixed gas of inert gas and hydrogen is used to replace the process gas after film formation in the standby atmosphere for temperature stabilization before film formation in the gate conductive film formation apparatus. A method for manufacturing a silicon carbide semiconductor device, characterized by being used. 前記不活性ガスと水素の混合ガスが窒素、ヘリウム、アルゴンの何れかと水素の混合ガスであることを特徴とする請求項１に記載の炭化ケイ素半導体装置の製造方法。   2. The method of manufacturing a silicon carbide semiconductor device according to claim 1, wherein the mixed gas of the inert gas and hydrogen is a mixed gas of nitrogen, helium, or argon and hydrogen. 前記不活性ガスと水素の混合ガス中の水素濃度が１％以上４％以下であることを特徴とする請求項１または２に記載の炭化ケイ素半導体装置の製造方法。   3. The method for manufacturing a silicon carbide semiconductor device according to claim 1, wherein a hydrogen concentration in the mixed gas of the inert gas and hydrogen is 1% or more and 4% or less. 前記ゲート絶縁膜を成膜する工程が、水分を含まない乾燥酸素中で熱酸化を行った後、水分を含むガス中での熱酸化を組み合わせた工程であることを特徴とする請求項１、２または３に記載の炭化ケイ素半導体装置の製造方法。   The step of forming the gate insulating film is a step of combining thermal oxidation in a gas containing moisture after performing thermal oxidation in dry oxygen not containing moisture. 4. A method for producing a silicon carbide semiconductor device according to 2 or 3. 前記ゲート絶縁膜を成膜する工程が、絶縁膜を堆積させた後、水分を含むガス中での熱酸化を組み合わせた工程であることを特徴とする請求項１、２または３に記載の炭化ケイ素半導体装置の製造方法。   4. The carbonization according to claim 1, wherein the step of forming the gate insulating film is a step of combining thermal oxidation in a gas containing moisture after depositing the insulating film. A method for manufacturing a silicon semiconductor device. 前記減圧ＣＶＤ法でシリコンゲート導電膜を成膜する工程で、シラン（ＳｉＨ4）あるいはジシラン（ＳｉＨ8）が含まれた原料ガスを使用したことを特徴とする請求項１、２、３、４または５に記載の炭化ケイ素半導体装置の製造方法。
The source gas containing silane (SiH 4 ) or disilane (SiH 8 ) is used in the step of forming a silicon gate conductive film by the low pressure CVD method. Or the manufacturing method of the silicon carbide semiconductor device of 5.
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