JP2015042598A - Substrate having aluminum nitride (ain) film and method for manufacturing aluminum nitride (ain) film - Google Patents
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本発明は、窒化アルミニウム（ＡｌＮ）膜を、高温の窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス中で熱処理を行うことで、窒化アルミニウム結晶膜（以下、「ＡｌＮ膜」と記す）の高品質化を図った窒化アルミニウム（ＡｌＮ）膜を有する基板および窒化アルミニウム（ＡｌＮ）膜の製造方法に関する。 According to the present invention, an aluminum nitride (AlN) film is heat-treated in a high-temperature nitrogen / carbon monoxide (N 2 / CO) mixed gas to form an aluminum nitride crystal film (hereinafter referred to as “AlN film”). The present invention relates to a substrate having an aluminum nitride (AlN) film with improved quality and a method for manufacturing an aluminum nitride (AlN) film.
紫外発光素子は、蛍光灯の代替、高密度ＤＶＤ、生化学用レーザ、光触媒による公害物質の分解、Ｈｅ−Ｃｄレーザ、水銀灯の代替など、次世代の光源として幅広く注目されている。この紫外発光素子は、ワイドギャップ半導体と呼ばれるＡｌＧａＮ系窒化物半導体からなり、サファイアなどの異種基板上に積層される。 Ultraviolet light emitting devices are attracting widespread attention as next-generation light sources such as fluorescent lamp replacement, high-density DVD, biochemical laser, decomposition of pollutants by photocatalyst, He-Cd laser, and mercury lamp replacement. This ultraviolet light emitting element is made of an AlGaN-based nitride semiconductor called a wide gap semiconductor, and is laminated on a heterogeneous substrate such as sapphire.
しかし、サファイアは、ＡｌＧａＮとの格子不整合が大きいため、多数の貫通転位が存在し、非発光再結合中心となって内部量子効率を著しく低下させてしまう。 However, since sapphire has a large lattice mismatch with AlGaN, there are a large number of threading dislocations, and it becomes a non-radiative recombination center, thereby significantly reducing the internal quantum efficiency.
これに対して、ＡｌＮは、ＡｌＧａＮと格子定数が近く、２００ｎｍの紫外領域まで透明であるため、発光した紫外線を吸収することなく、紫外光を効率よく外部へ取り出すことができる。しかし、バルクの単結晶ＡｌＮ結晶は、高価で１インチサイズしか入手できないため、紫外発光素子の基板材料には不向きである。サファイアは、６インチサイズが安価で入手できる状況にある。このような状況を鑑み、高品質ＡｌＮ単結晶膜をサファイア基板上に作製することができれば、これを基板として用いてＡｌＧａＮ系発光素子を準ホモエピタキシャル成長させることにより、結晶の欠陥密度を低く抑えた紫外光発光素子を安価に作製することができる。 On the other hand, AlN has a lattice constant close to that of AlGaN and is transparent up to the ultraviolet region of 200 nm. Therefore, ultraviolet light can be efficiently extracted outside without absorbing emitted ultraviolet light. However, a bulk single crystal AlN crystal is expensive and only 1 inch size is available, so it is not suitable for a substrate material of an ultraviolet light emitting element. Sapphire is available in a 6-inch size at a low price. In view of such a situation, if a high-quality AlN single crystal film can be produced on a sapphire substrate, the defect density of the crystal can be kept low by using this as a substrate to perform quasi-homoepitaxial growth. An ultraviolet light-emitting element can be manufactured at low cost.
しかしながら、ＡｌＮはサファイアと格子不整合が大きいため、サファイア上に成長したＡｌＮ膜には多数の貫通転位が存在する。このため、ＡｌＧａＮ系発光素子用の基板として不適切である。 However, since AlN has a large lattice mismatch with sapphire, many threading dislocations exist in the AlN film grown on sapphire. For this reason, it is inappropriate as a substrate for an AlGaN-based light emitting device.
これに対し、上記問題に応えるものとして、ＭＯＶＰＥ法でサファイア上にＡｌＮ膜を成長させ、その後、熱処理によって酸素原子をＡｌＮ膜内に拡散させて転位の低減を図る方法が提案されている（例えば、特許文献１参照）。また、溝加工を施したサファイア基板上にＭＯＶＰＥ法でＡｌＮ膜を成長させ、溝を埋める過程で転位の低減を図る方法が提案されている（例えば、非特許文献１参照）。 In response to this problem, a method has been proposed in which an AlN film is grown on sapphire by the MOVPE method and oxygen atoms are diffused in the AlN film by heat treatment to reduce dislocations (for example, , See Patent Document 1). In addition, a method has been proposed in which an AlN film is grown by MOVPE on a sapphire substrate subjected to groove processing, and dislocations are reduced in the process of filling the groove (see, for example, Non-Patent Document 1).
ＡｌＮはサファイアと格子不整合が大きいため、サファイア上に成長したＡｌＮ膜には多数の貫通転位が存在する。ＡｌＧａＮ系発光素子用の基板として使用するためには、ＡｌＮ膜中の貫通転位密度の低減が課題である。特許文献１および非特許文献１に記載の方法では、酸素原子の拡散処理や溝加工などの煩雑な処理を行う必要があるという課題があった。 Since AlN has a large lattice mismatch with sapphire, many threading dislocations exist in the AlN film grown on sapphire. In order to use as a substrate for an AlGaN-based light emitting device, it is a problem to reduce threading dislocation density in the AlN film. The methods described in Patent Document 1 and Non-Patent Document 1 have a problem that it is necessary to perform complicated processing such as oxygen atom diffusion processing and groove processing.
本発明は、このような課題に着目してなされたもので、サファイア基板の溝加工など煩雑な処理を施さなくても、現在用いられているＭＯＣＶＤ法の成長条件を用いて、ＡｌＮ膜の結晶性を飛躍的に向上させることが可能となり、高効率のＬＥＤ（Ｌｉｇｈｔ Ｅｍｉｔｔｉｎｇ Ｄｉｏｄｅ）やＬＤ（Ｌａｓｅｒ ｄｉｏｄｅ）デバイスを作製することができる、窒化アルミニウム（ＡｌＮ）膜を有する基板および窒化アルミニウム（ＡｌＮ）膜の製造方法を提供することを目的とする。 The present invention has been made paying attention to such a problem, and without using a complicated process such as a groove processing of a sapphire substrate, a crystal of an AlN film can be formed using the growth conditions of the currently used MOCVD method. And a substrate having an aluminum nitride (AlN) film and an aluminum nitride (AlN) capable of manufacturing a highly efficient LED (Light Emitting Diode) or LD (Laser diode) device. It aims at providing the manufacturing method of a film | membrane.
本発明者らは、上記課題について熱力学的な検討を重ねた結果、任意の製膜法によりサファイア基板上にＡｌＮ膜を成長させ、これを窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス雰囲気中で１５００℃以上の温度で熱処理することで、ＡｌＮ膜の結晶性を飛躍的に改善できることを見出して、本発明に至った。 As a result of repeated thermodynamic studies on the above problems, the present inventors have grown an AlN film on a sapphire substrate by an arbitrary film forming method, and this is grown into a nitrogen / carbon monoxide (N 2 / CO) mixed gas. It has been found that the crystallinity of the AlN film can be drastically improved by heat treatment at a temperature of 1500 ° C. or higher in an atmosphere, and the present invention has been achieved.
すなわち、本発明に係るＡｌＮ膜を有する基板は、サファイア基板、炭化ケイ素（ＳｉＣ）基板、または窒化アルミニウム（ＡｌＮ）基板上に、膜厚１００〜１０００ｎｍの窒化アルミニウム（ＡｌＮ）膜を形成した後、１５００℃以上の高温で熱処理して形成されたことを特徴とする。本発明に係るＡｌＮ膜を有する基板は、前記熱処理後の基板上にＡｌＮ膜の再成長を行ったことが好ましい。また、窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス中で前記熱処理を行ったことが好ましい。また、前記熱処理の温度ならびに前記窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率は、Ａｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図に基づき決定されることが好ましい。また、前記熱処理後の(１０−１２)面のＸ線回折ロッキングカーブの半値幅が３００ａｒｃｓｅｃ以下であることが好ましい。また、表面平均二乗粗さが１．５ｎｍ以下であることが好ましい。 That is, a substrate having an AlN film according to the present invention is formed after an aluminum nitride (AlN) film having a thickness of 100 to 1000 nm is formed on a sapphire substrate, a silicon carbide (SiC) substrate, or an aluminum nitride (AlN) substrate. It is formed by heat treatment at a high temperature of 1500 ° C. or higher. In the substrate having an AlN film according to the present invention, the AlN film is preferably regrown on the substrate after the heat treatment. The heat treatment is preferably performed in a nitrogen / carbon monoxide (N 2 / CO) mixed gas. Further, the temperature of the heat treatment and the ratio of the nitrogen / carbon monoxide (N 2 / CO) mixed gas are preferably determined based on an Al 2 O 3 —AlN—C—N 2 —CO system phase stability diagram. . The half width of the X-ray diffraction rocking curve of the (10-12) plane after the heat treatment is preferably 300 arcsec or less. Moreover, it is preferable that the surface mean square roughness is 1.5 nm or less.
本発明に係るＡｌＮ膜を有する基板は、ＡｌＮ膜を有する基板を窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス中で熱処理して形成され、前記熱処理の温度ならびに前記窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率は、Ａｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図に基づき決定されてもよい。本発明に係るＡｌＮ膜を有する基板で、前記熱処理の温度および前記窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率は、それぞれＡｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図のＡｌＮ相とＡｌ２Ｏ３相との化学平衡共存状態を示す温度および混合比の近傍に決定されることが好ましい。 A substrate having an AlN film according to the present invention is formed by heat-treating a substrate having an AlN film in a nitrogen / carbon monoxide (N 2 / CO) mixed gas, and the temperature of the heat treatment and the nitrogen / carbon monoxide ( N ratio of 2 / CO) gas mixture, Al 2 O 3 -AlN-C -N 2 based on the -CO-based phase stability diagram may be determined. In the substrate having the AlN film according to the present invention, the temperature of the heat treatment and the ratio of the nitrogen / carbon monoxide (N 2 / CO) mixed gas are Al 2 O 3 —AlN—C—N 2 —CO based phase, respectively. It is preferable to be determined in the vicinity of the temperature and the mixing ratio indicating the chemical equilibrium coexistence state of the AlN phase and the Al 2 O 3 phase in the stability diagram.
本発明に係るＡｌＮ膜の製造方法は、膜厚１００〜１０００ｎｍの窒化アルミニウム（ＡｌＮ）膜を１５００℃以上の高温で熱処理することを特徴とする。本発明に係るＡｌＮ膜の製造方法は、前記窒化アルミニウム（ＡｌＮ）膜を窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス中で前記熱処理を行うことが好ましい。また、前記熱処理の温度ならびに前記窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率は、Ａｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図に基づき決定されることが好ましい。また、前記窒化アルミニウム（ＡｌＮ）膜は、サファイア基板、炭化ケイ素（ＳｉＣ）基板、またはＡｌＮ基板上に作製された膜であることが好ましい。また、前記窒化アルミニウム（ＡｌＮ）膜を熱処理後にＡｌＮ膜の再成長を行うことが好ましい。 The method for producing an AlN film according to the present invention is characterized in that an aluminum nitride (AlN) film having a thickness of 100 to 1000 nm is heat-treated at a high temperature of 1500 ° C. or higher. In the AlN film manufacturing method according to the present invention, it is preferable that the aluminum nitride (AlN) film is subjected to the heat treatment in a nitrogen / carbon monoxide (N 2 / CO) mixed gas. Further, the temperature of the heat treatment and the ratio of the nitrogen / carbon monoxide (N 2 / CO) mixed gas are preferably determined based on an Al 2 O 3 —AlN—C—N 2 —CO system phase stability diagram. . The aluminum nitride (AlN) film is preferably a film formed on a sapphire substrate, a silicon carbide (SiC) substrate, or an AlN substrate. Further, it is preferable that the AlN film is regrown after the aluminum nitride (AlN) film is heat-treated.
本発明に係るＡｌＮ膜の製造方法は、ＡｌＮ膜を有する基板を窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス中で熱処理し、前記熱処理の温度ならびに前記窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率は、Ａｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図に基づき決定されてもよい。本発明に係るＡｌＮ膜の製造方法で、前記熱処理の温度および前記窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率は、それぞれＡｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図の化学平衡状態を示す温度および混合比の近傍に決定されることが好ましい。 In the method of manufacturing an AlN film according to the present invention, a substrate having an AlN film is heat-treated in a nitrogen / carbon monoxide (N 2 / CO) mixed gas, and the temperature of the heat treatment and the nitrogen / carbon monoxide (N 2 / The ratio of the (CO) gas mixture may be determined based on the Al 2 O 3 —AlN—C—N 2 —CO phase stability diagram. In the method for producing an AlN film according to the present invention, the temperature of the heat treatment and the ratio of the nitrogen / carbon monoxide (N 2 / CO) mixed gas are Al 2 O 3 —AlN—C—N 2 —CO based phase, respectively. It is preferable to be determined in the vicinity of the temperature and the mixing ratio indicating the chemical equilibrium state of the stability diagram.
本発明によれば、サファイア基板の溝加工など煩雑な処理を施さなくても、現在用いられているＭＯＣＶＤ法の成長条件を用いて、ＡｌＮ膜の結晶性を飛躍的に向上させることが可能となり、高効率のＬＥＤ（Ｌｉｇｈｔ Ｅｍｉｔｔｉｎｇ Ｄｉｏｄｅ）やＬＤ（Ｌａｓｅｒ ｄｉｏｄｅ）デバイスを作製することができる、窒化アルミニウム（ＡｌＮ）膜を有する基板および窒化アルミニウム（ＡｌＮ）膜の製造方法を提供することができる。 According to the present invention, it is possible to dramatically improve the crystallinity of the AlN film by using the growth conditions of the MOCVD method currently used without performing complicated processing such as groove processing of the sapphire substrate. It is possible to provide a substrate having an aluminum nitride (AlN) film and a method for manufacturing an aluminum nitride (AlN) film, which can produce a highly efficient LED (Light Emitting Diode) or LD (Laser diode) device.
以下、本発明の実施の形態の窒化アルミニウム（ＡｌＮ）膜を有する基板および窒化アルミニウム（ＡｌＮ）膜の製造方法について、図面を参照しながら詳細に説明する。 Hereinafter, a substrate having an aluminum nitride (AlN) film and a method for manufacturing an aluminum nitride (AlN) film according to an embodiment of the present invention will be described in detail with reference to the drawings.
本発明の実施の形態の窒化アルミニウム（ＡｌＮ）膜の製造方法では、ＡｌＮ膜を形成したサファイア基板を窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス雰囲気中で熱処理する。図１は、熱処理装置の構成例を示す図である。この熱処理装置は、黒鉛製反応容器１と、加熱ヒータ２と、ガス導入部３と、ガス排気部４と、基板保持具５とを備え、ＡｌＮ膜を形成したサファイア基板６を均熱部に配置する。基板保持具５は、耐高温性のものが用いられ、例えば、窒化アルミニウム、窒化ボロン、黒鉛などを用いることができる。 In the method of manufacturing an aluminum nitride (AlN) film according to the embodiment of the present invention, the sapphire substrate on which the AlN film is formed is heat-treated in a nitrogen / carbon monoxide (N 2 / CO) mixed gas atmosphere. FIG. 1 is a diagram illustrating a configuration example of a heat treatment apparatus. This heat treatment apparatus includes a graphite reaction vessel 1, a heater 2, a gas introduction part 3, a gas exhaust part 4, and a substrate holder 5, and a sapphire substrate 6 on which an AlN film is formed is used as a soaking part. Deploy. The substrate holder 5 has a high temperature resistance, and for example, aluminum nitride, boron nitride, graphite or the like can be used.
ＡｌＮ膜を形成したサファイア基板６には、ＭＯＶＰＥ法によってサファイア基板上に製膜したものを用いる。ただし、ＡｌＮ膜を製膜する方法は、ＭＯＶＰＥ法に限らず、任意の製膜法が適用される。例えば、スパッタ法、ハイドライド気相成長（ＨＶＰＥ）法、分子線エピタキシャル（ＭＢＥ）法などが適用される。また、ＡｌＮ膜を製膜する基板材料は、サファイア基板に限られず、ＳｉＣ基板、ＡｌＮ基板なども適用できる。 As the sapphire substrate 6 on which the AlN film is formed, the one formed on the sapphire substrate by the MOVPE method is used. However, the method of forming the AlN film is not limited to the MOVPE method, and any film forming method is applied. For example, a sputtering method, a hydride vapor phase epitaxy (HVPE) method, a molecular beam epitaxial (MBE) method, or the like is applied. The substrate material for forming the AlN film is not limited to the sapphire substrate, and an SiC substrate, an AlN substrate, or the like can also be applied.
ＡｌＮ膜を形成したサファイア基板（以降、ＡｌＮ／サファイア基板と記す）の加熱処理の方法を説明する。ＡｌＮ／サファイア基板を図１に示すように、反応容器１の均熱部に配置する。まず、反応容器１の内部をロータリーポンプで排気した後、Ｎ２／ＣＯ混合ガスをガス導入部３より導入する。 A method for heat treatment of a sapphire substrate (hereinafter referred to as an AlN / sapphire substrate) on which an AlN film is formed will be described. As shown in FIG. 1, the AlN / sapphire substrate is disposed in the soaking part of the reaction vessel 1. First, the inside of the reaction vessel 1 is evacuated with a rotary pump, and then a N 2 / CO mixed gas is introduced from the gas introduction unit 3.
熱処理の温度およびＮ２／ＣＯ混合ガス比率は、以下の熱力学的考察より決定される。図２に、Ａｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図を示す。本図は、炭素飽和かつＮ２とＣＯのガス分圧の和が１ａｔｍであるという条件下で、Ａｌ２Ｏ３およびＡｌＮ安定領域を温度およびＮ２／ＣＯ混合ガス比率の関数として示している。この図を用いると、ＡｌＮが安定領域になるように温度およびＮ２／ＣＯ混合ガス比率を選択することができる。 The temperature of the heat treatment and the N 2 / CO mixed gas ratio are determined from the following thermodynamic considerations. FIG. 2 shows an Al 2 O 3 —AlN—C—N 2 —CO phase stability diagram. This figure shows the Al 2 O 3 and AlN stable regions as a function of temperature and N 2 / CO gas mixture ratio under conditions of carbon saturation and the sum of gas partial pressures of N 2 and CO of 1 atm. . Using this figure, the temperature and the N 2 / CO mixed gas ratio can be selected so that AlN is in the stable region.
Ｎ２／ＣＯ混合ガスを導入し、１．０ａｔｍに達したら、ＡｌＮ／サファイア基板の加熱を開始する。熱処理中、混合ガスは、２．０Ｌ／ｍｉｎの流速で流し続け、ガス排気部４より反応容器１の外部に排出される。このとき、Ｎ２／ＣＯ混合ガス比率および熱処理温度は、図２を用いて選択され、Ｎ２／ＣＯ＝０．９０／０．１〜０．６／０．４、熱処理温度１５００〜１７００℃（１７７３〜１９７３Ｋ）である。 When the N 2 / CO mixed gas is introduced and reaches 1.0 atm, heating of the AlN / sapphire substrate is started. During the heat treatment, the mixed gas continues to flow at a flow rate of 2.0 L / min and is discharged from the gas exhaust unit 4 to the outside of the reaction vessel 1. At this time, the N 2 / CO mixed gas ratio and the heat treatment temperature are selected using FIG. 2, and N 2 /CO=0.90/0.1 to 0.6 / 0.4, the heat treatment temperature 1500 to 1700 ° C. (1773-1973K).
図２において、太い実線Ａは、ＡｌＮとＡｌ２Ｏ３とが平衡相として共存できる条件を示しており、その実線より上部はＡｌＮ相が安定して存在する領域、実線より下部はＡｌ２Ｏ３相が安定して存在する領域を示す。サファイア基板上に作製したＡｌＮ膜を熱処理する場合は、ＡｌＮ膜の安定領域内でありながら、基板であるサファイア（Ａｌ２Ｏ３）の安定領域からも近い条件を選択する必要がある。すなわち、図２においてＡｌＮとＡｌ２Ｏ３との平衡共存線（太実線Ａ）より５０ｋＪ上部の領域を細い実線Ｂで示すが、太実線Ａと細実線Ｂとで挟まれた領域が熱処理するのに適した条件である。ここで、熱処理中、この熱処理に適した条件を実現することが重要である。そのため、設定した混合比の混合ガスを一定量流入、排出する開放系の黒鉛製反応容器１を用いたが、容器内での不要ガスや不要分子の発生が十分に低く抑えられ、一定の雰囲気を実現できる場合は、混合ガスの流入、排出を行わない密封系の黒鉛製反応容器でも良い。 In FIG. 2, a thick solid line A indicates a condition in which AlN and Al 2 O 3 can coexist as an equilibrium phase. A region above the solid line is a region where the AlN phase is stably present, and a portion below the solid line is Al 2 O. The region where the three phases exist stably is shown. When heat-treating an AlN film produced on a sapphire substrate, it is necessary to select conditions that are close to the stable region of sapphire (Al 2 O 3 ) that is the substrate while being within the stable region of the AlN film. That is, in FIG. 2, a region 50 kJ above the equilibrium coexistence line of AlN and Al 2 O 3 (thick solid line A) is shown by a thin solid line B, but the region sandwiched between the thick solid line A and the thin solid line B is heat-treated This is a suitable condition. Here, during the heat treatment, it is important to realize conditions suitable for the heat treatment. For this reason, the open graphite reaction vessel 1 that flows in and out a certain amount of the mixed gas with the set mixing ratio is used, but the generation of unnecessary gas and unnecessary molecules in the vessel is sufficiently suppressed, and a constant atmosphere is maintained. Can be used, it may be a sealed graphite reaction vessel in which the mixed gas does not flow in and out.
加熱速度は約１０℃／ｍｉｎで、所定の熱処理温度まで加熱し、２時間保持する。その後、１５分間にわたり、Ｎ２ガスのみを１０Ｌ／ｍｉｎで流すことによって、反応容器１の内部のＣＯガスを排出した後、加熱ヒータ２の出力を切り、約４時間で室温まで冷却する。 The heating rate is about 10 ° C./min, and the temperature is heated to a predetermined heat treatment temperature and held for 2 hours. Thereafter, the CO gas inside the reaction vessel 1 is discharged by flowing only N 2 gas at 10 L / min for 15 minutes, and then the output of the heater 2 is turned off and cooled to room temperature in about 4 hours.
Ｎ２ガスには市販の液体窒素ボンベから得られるガスならびに市販の高重度窒素ガスボンベから得られるガスを用いることができる。ＣＯガスには、市販の高純度ＣＯガスボンベから得られるガスを用いることができる。 As the N 2 gas, a gas obtained from a commercially available liquid nitrogen cylinder and a gas obtained from a commercially available high-strength nitrogen gas cylinder can be used. As the CO gas, a gas obtained from a commercially available high purity CO gas cylinder can be used.
以上説明したように、ＡｌＮ／サファイア基板をＮ２／ＣＯ混合ガス雰囲気中で熱処理することによって、結晶性の良好なＡｌＮ膜を形成することができる。 As described above, an AlN film with good crystallinity can be formed by heat-treating an AlN / sapphire substrate in an N 2 / CO mixed gas atmosphere.
さらに、熱処理を行ったＡｌＮ／サファイア上にＡｌＮを５００ｎｍ以上再成長させることで、表面平坦性に優れ、且つ結晶性が良好なＡｌＮ膜を得ることができる。 Furthermore, by re-growing AlN over 500 nm on the heat-treated AlN / sapphire, an AlN film having excellent surface flatness and excellent crystallinity can be obtained.
以下、実施例を用いて本発明を説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited to these Examples.
先ず、ＭＯＶＰＥ法で成長温度１１５０℃にて、直径２インチのｃ面サファイア基板上にＡｌＮ膜を約３００ｎｍ製膜した。このＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸ線ロッキングカーブ（ＸＲＣ）の半値幅（ＦＷＨＭ）で９０ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、１２７８ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、１５０８ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、３．１０ｎｍであった。このＡｌＮ／サファイア基板を４等分し、そのうち１片を以下の熱処理に用いた。なお、（０００２）、（１０−１２）、（１０−１０）は、ウルツ鉱構造を有するＡｌＮの結晶格子面を、ミラー指数を用いた４軸で表示したものである。 First, an AlN film of about 300 nm was formed on a c-plane sapphire substrate having a diameter of 2 inches at a growth temperature of 1150 ° C. by the MOVPE method. The crystallinity of this AlN film is 90 arcsec at the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) of (0002) AlN, (10-12) FWHM of XRC of AlN is 1278 arcsec, (10-10) AlN The XRC FWHM was 1508 arcsec. The mean square roughness (RMS) of the surface was 3.10 nm. This AlN / sapphire substrate was divided into four equal parts, one of which was used for the following heat treatment. In addition, (0002), (10-12), and (10-10) are the crystal lattice planes of AlN having a wurtzite structure displayed on four axes using the Miller index.
このＡｌＮ／サファイア基板を、図１に示すように、反応容器１の均熱部に配置した。まず、反応容器１の内部をロータリーポンプで排気した後、Ｎ２／ＣＯ混合ガスをガス導入部３より導入した。Ｎ２／ＣＯ混合ガス比率は、Ｎ２／ＣＯ＝０．７０／０．３０であった．Ｎ２／ＣＯ混合ガスを導入し、１．０ａｔｍに達したら、ＡｌＮ／サファイア基板の加熱を開始した。加熱処理中、混合ガスは、２．０Ｌ／ｍｉｎの流速で流し続け、ガス排気部４より反応容器１の外部に排出した。加熱速度は約１０℃／ｍｉｎで、１６５０℃まで加熱し、２時間保持した。その後、１５分間にわたり、Ｎ２ガスのみを１０Ｌ／ｍｉｎで流すことによって、反応容器１の内部のＣＯガスを排出した後、加熱ヒータ２の出力を切り、約４時間で室温まで冷却した。 This AlN / sapphire substrate was placed in the soaking part of the reaction vessel 1 as shown in FIG. First, the inside of the reaction vessel 1 was evacuated with a rotary pump, and then a N 2 / CO mixed gas was introduced from the gas introduction unit 3. The N 2 / CO mixed gas ratio was N 2 /CO=0.70/0.30. When the N 2 / CO mixed gas was introduced and reached 1.0 atm, heating of the AlN / sapphire substrate was started. During the heat treatment, the mixed gas continued to flow at a flow rate of 2.0 L / min and was discharged from the gas exhaust unit 4 to the outside of the reaction vessel 1. The heating rate was about 10 ° C./min, the temperature was increased to 1650 ° C. and held for 2 hours. Thereafter, only the N 2 gas was allowed to flow at 10 L / min for 15 minutes to discharge the CO gas inside the reaction vessel 1, and then the output of the heater 2 was turned off and cooled to room temperature in about 4 hours.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで３２ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、４２４ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、５３２ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、０．４９ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。ここで、表面の滑らかさを、上記したように飛躍的に改善するために、熱処理中、図２の太実線Ａで示される化学的平衡状態に近い状態を、安定に実現することが重要であることを本発明では見出した。 As a result, the crystallinity of the AlN film was 32 arcsec for (0002) AlN XRC FWHM, 424 arcsec for (10-12) AlN XRC FWHM, and 532 arcsec for (10-10) AlN XRC FWHM. It was. Further, the mean square roughness (RMS) of the surface was 0.49 nm, which showed better crystallinity and surface smoothness than before the heat treatment. Here, in order to dramatically improve the smoothness of the surface as described above, it is important to stably realize a state close to the chemical equilibrium state indicated by the thick solid line A in FIG. 2 during the heat treatment. It has been found in the present invention.
用いたＡｌＮ／サファイア基板は、実施例１において、ＭＯＶＰＥ法で作製し、４等分されたもののうちの１片である。このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．８０／０．２０とすること、および熱処理温度を１６００℃とすること以外は、実施例１と同様にして、熱処理を行った。 The AlN / sapphire substrate used is one piece of the substrate produced in Example 1 by the MOVPE method and divided into four equal parts. Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio is N 2 /CO=0.80/0.20, and the heat treatment temperature is 1600 ° C. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで９７ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、４６８ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、６６２ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、０．６３ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 97 arcsec for (0002) AlN XRC FWHM, 468 arcsec for (10-12) AlN XRC FWHM, and 662 arcsec for (10-10) AlN XRC FWHM. It was. Further, the mean square roughness (RMS) of the surface was 0.63 nm, which showed better crystallinity and surface smoothness than before the heat treatment.
用いたＡｌＮ／サファイア基板は、実施例１において、ＭＯＶＰＥ法で作製し、４等分されたもののうちの１片である。このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．８５／０．１５とすること、および熱処理温度を１５５０℃とすること以外は、実施例１と同様にして、熱処理を行った。 The AlN / sapphire substrate used is one piece of the substrate produced in Example 1 by the MOVPE method and divided into four equal parts. Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio is N 2 /CO=0.85/0.15, and the heat treatment temperature is 1550 ° C. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで４３ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、５７９ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、８６７ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、１．２１ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 43 arcsec for the XRC FWHM of (0002) AlN, 579 arcsec for the XRC FWHM of (10-12) AlN, and 867 arcsec for the XRC FWHM of (10-10) AlN. It was. The mean square roughness (RMS) of the surface was 1.21 nm, indicating better crystallinity and surface smoothness than before the heat treatment.
用いたＡｌＮ／サファイア基板は、実施例１において、ＭＯＶＰＥ法で作製し、４等分されたもののうちの１片である。このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．９０／０．１０とすること、および熱処理温度を１５００℃とすること以外は、実施例１と同様にして、熱処理を行った。 The AlN / sapphire substrate used is one piece of the substrate produced in Example 1 by the MOVPE method and divided into four equal parts. Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio was set to N 2 /CO=0.90/0.10, and the heat treatment temperature was set to 1500 ° C., as in Example 1. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで３６ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、７３０ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、１１４４ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、２．６５ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 36 arcsec for the (0002) AlN XRC FWHM, 730 arcsec for the (10-12) AlN XRC FWHM, and 1144 arcsec for the (10-10) AlN XRC FWHM. It was. The mean square roughness (RMS) of the surface was 2.65 nm, indicating better crystallinity and surface smoothness than before the heat treatment.
先ず、ＭＯＶＰＥ法で成長温度１１５０℃にて、直径２インチのｃ面サファイア基板上にＡｌＮ膜を約２００ｎｍ製膜した。このＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸ線ロッキングカーブ（ＸＲＣ）の半値幅（ＦＷＨＭ）で４３ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、１３８６ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、１６０２ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、２．４９ｎｍであった。このＡｌＮ／サファイア基板を４等分し、そのうち１片を以下の熱処理に用いた。 First, an AlN film of about 200 nm was formed on a c-plane sapphire substrate having a diameter of 2 inches at a growth temperature of 1150 ° C. by the MOVPE method. The crystallinity of this AlN film is 43 arcsec at the half width (FWHM) of the X-ray rocking curve (XRC) of (0002) AlN, and (10-12) FWHM of XRC of AlN is 1386 arcsec, (10-10) AlN. The XRC FWHM was 1602 arcsec. The mean square roughness (RMS) of the surface was 2.49 nm. This AlN / sapphire substrate was divided into four equal parts, one of which was used for the following heat treatment.
このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．８０／０．２０とすること、および熱処理温度を１６００℃とすること以外は、実施例１と同様にして、熱処理を行った。 Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio is N 2 /CO=0.80/0.20, and the heat treatment temperature is 1600 ° C. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで３６ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、４８２ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、６１９ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、１．５７ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 36 arcsec for the (0002) AlN XRC FWHM, the FWHM for the (10-12) AlN XRC was 482 arcsec, and the FWHM for the (10-10) AlN XRC was 619 arcsec. It was. Moreover, the mean square roughness (RMS) of the surface was 1.57 nm, showing better crystallinity and surface smoothness than before the heat treatment.
先ず、ＭＯＶＰＥ法で成長温度１１５０℃にて、直径２インチのｃ面サファイア基板上にＡｌＮ膜を約１００ｎｍ製膜した。このＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸ線ロッキングカーブ（ＸＲＣ）の半値幅（ＦＷＨＭ）で２８ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、１７７１ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、２２１７ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、１．５５ｎｍであった。このＡｌＮ／サファイア基板を４等分し、そのうち１片を以下の熱処理に用いた。 First, an AlN film of about 100 nm was formed on a c-plane sapphire substrate having a diameter of 2 inches at a growth temperature of 1150 ° C. by the MOVPE method. The crystallinity of this AlN film is 28 arcsec at the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) of (0002) AlN, (10-12) FWHM of XRC of AlN is 1771 arcsec, (10-10) AlN The XRC FWHM was 2217 arcsec. The surface mean square roughness (RMS) was 1.55 nm. This AlN / sapphire substrate was divided into four equal parts, one of which was used for the following heat treatment.
このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．８０／０．２０とすること、および熱処理温度を１６００℃とすること以外は、実施例１と同様にして、熱処理を行った。 Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio is N 2 /CO=0.80/0.20, and the heat treatment temperature is 1600 ° C. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで３９ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、６１５ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、８３８ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、０．５５ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 39 arcsec for (0002) AlN XRC FWHM, 615 arcsec for (10-12) AlN XRC FWHM, and 838 arcsec for (10-10) AlN XRC FWHM. It was. Further, the mean square roughness (RMS) of the surface was 0.55 nm, which showed better crystallinity and surface smoothness than before the heat treatment.
用いたＡｌＮ／サファイア基板は、実施例６において、ＭＯＶＰＥ法で作製し、４等分されたもののうちの１片である。このＡｌＮ／サファイア基板を用いて、実施例１と同様にして、熱処理を行った。 The AlN / sapphire substrate used is one piece of the substrate produced in Example 6 by the MOVPE method and divided into four equal parts. Using this AlN / sapphire substrate, heat treatment was performed in the same manner as in Example 1.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで７９ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、７３４ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、５４０ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、０．４３ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 79 arcsec for (0002) AlN XRC FWHM, 734 arcsec for (10-12) AlN XRC FWHM, and 540 arcsec for (10-10) AlN XRC FWHM. It was. Further, the mean square roughness (RMS) of the surface was 0.43 nm, which showed better crystallinity and surface smoothness than before the heat treatment.
先ず、ＭＯＶＰＥ法で成長温度１１５０℃にて、直径２インチのｃ面サファイア基板上にＡｌＮ膜を約６５０ｎｍ製膜した。このＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸ線ロッキングカーブ（ＸＲＣ）の半値幅（ＦＷＨＭ）で４７６ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、１０５６ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、１２８２ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、９．７８ｎｍであった。このＡｌＮ／サファイア基板を４等分し、そのうち１片を以下の熱処理に用いた。 First, an AlN film was formed to a thickness of about 650 nm on a c-plane sapphire substrate having a diameter of 2 inches at a growth temperature of 1150 ° C. by the MOVPE method. The crystallinity of this AlN film is 476 arcsec at the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) of (0002) AlN, (10-12) FWHM of XRC of AlN is 1056 arcsec, (10-10) AlN The XRC FWHM was 1282 arcsec. Further, the mean square roughness (RMS) of the surface was 9.78 nm. This AlN / sapphire substrate was divided into four equal parts, one of which was used for the following heat treatment.
このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．６０／０．４０とすること、および熱処理温度を１７００℃とすること以外は、実施例１と同様にして、熱処理を行った。 Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio was set to N 2 /CO=0.60/0.40, and the heat treatment temperature was set to 1700 ° C., as in Example 1. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで１３３ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、２５９ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、３７４ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、１．３４ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 133 arcsec for (0002) AlN XRC FWHM, 259 arcsec for (10-12) AlN XRC FWHM, and 374 arcsec for (10-10) AlN XRC FWHM. It was. Moreover, the mean square roughness (RMS) of the surface was 1.34 nm, showing better crystallinity and surface smoothness than before the heat treatment.
先ず、ＭＯＶＰＥ法で成長温度１１５０℃にて、直径２インチのｃ面サファイア基板上にＡｌＮ膜を約１０００ｎｍ製膜した。このＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸ線ロッキングカーブ（ＸＲＣ）の半値幅（ＦＷＨＭ）で４３９ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、８７５ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、９５２ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、１４．２０ｎｍであった。このＡｌＮ／サファイア基板を４等分し、そのうち１片を以下の熱処理に用いた。 First, an AlN film of about 1000 nm was formed on a c-plane sapphire substrate having a diameter of 2 inches at a growth temperature of 1150 ° C. by the MOVPE method. The crystallinity of this AlN film is 439 arcsec at the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) of (0002) AlN, (10-12) FWHM of XRC of AlN is 875 arcsec, (10-10) AlN The XRC FWHM was 952 arcsec. The mean square roughness (RMS) of the surface was 14.20 nm. This AlN / sapphire substrate was divided into four equal parts, one of which was used for the following heat treatment.
このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．６０／０．４０とすること、および熱処理温度を１７００℃とすること以外は、実施例１と同様にして、熱処理を行った。 Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio was set to N 2 /CO=0.60/0.40, and the heat treatment temperature was set to 1700 ° C., as in Example 1. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで２０５ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、２８８ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、５１１ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、７．５０ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film was 205 arcsec for (0002) AlN XRC FWHM, 288 arcsec for (10-12) AlN XRC FWHM, and 511 arcsec for (10-10) AlN XRC FWHM. It was. Further, the mean square roughness (RMS) of the surface was 7.50 nm, showing better crystallinity and surface smoothness than before the heat treatment.
先ず、ＭＯＶＰＥ法で成長温度１２００℃にて、直径２インチのｃ面サファイア基板上にＡｌＮ膜を約３００ｎｍ製膜した。このＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸ線ロッキングカーブ（ＸＲＣ）の半値幅（ＦＷＨＭ）で８８ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、１１７１ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、１４４０ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、４．０５ｎｍであった。このＡｌＮ／サファイア基板を４等分し、そのうち１片を以下の熱処理に用いた。 First, an AlN film of about 300 nm was formed on a c-plane sapphire substrate having a diameter of 2 inches at a growth temperature of 1200 ° C. by the MOVPE method. The crystallinity of this AlN film is 88 arcsec at the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) of (0002) AlN, (10-12) FWHM of XRC of AlN is 1171 arcsec, (10-10) AlN The XRC FWHM was 1440 arcsec. The mean square roughness (RMS) of the surface was 4.05 nm. This AlN / sapphire substrate was divided into four equal parts, one of which was used for the following heat treatment.
このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガス比率をＮ２／ＣＯ＝０．６０／０．４０とすること、および熱処理温度を１７００℃とすること以外は、実施例１と同様にして、熱処理を行った。 Using this AlN / sapphire substrate, the N 2 / CO mixed gas ratio was set to N 2 /CO=0.60/0.40, and the heat treatment temperature was set to 1700 ° C., as in Example 1. Then, heat treatment was performed.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで７５ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、２９８ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、３７８ａｒｃｓｅｃであった。また表面の平均二乗粗さ（ＲＭＳ）は、０．９３ｎｍであり、熱処理前と比較して良好な結晶性および表面平滑性を示した。 As a result, the crystallinity of the AlN film is 75 arcsec for the (0002) AlN XRC FWHM, 298 arcsec for the (10-12) AlN XRC FWHM, and 378 arcsec for the (10-10) AlN XRC FWHM. It was. Further, the mean square roughness (RMS) of the surface was 0.93 nm, which showed better crystallinity and surface smoothness than before the heat treatment.
実施例１において、熱処理されたＡｌＮ／サファイア基板上に、ＭＯＶＰＥ法により、ＡｌＮ膜の再成長を行った。ＭＯＶＰＥ法の成長温度は、１４５０℃、成長圧力は３０Ｔｏｒｒ、ＮＨ３／ＴＭＡ（トリメチルアルミニウム）流量比は５８４で、ＡｌＮ膜を２０００ｎｍ製膜した。その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで１１０ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、３７０ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、４９８ａｒｃｓｅｃ、となり、再成長することによってさらにツイスト成分の結晶性の向上が見られた。また表面の平均二乗粗さは１．０４ｎｍであり、平滑な表面が得られることが分かった。 In Example 1, an AlN film was regrown on the heat-treated AlN / sapphire substrate by the MOVPE method. The growth temperature of the MOVPE method was 1450 ° C., the growth pressure was 30 Torr, the NH 3 / TMA (trimethylaluminum) flow rate ratio was 584, and an AlN film was formed to 2000 nm. As a result, the crystallinity of the AlN film is 110 arcsec for (0002) AlN XRC FWHM, 370 arcsec for (10-12) AlN XRC FWHM, and 498 arcsec for (10-10) AlN XRC FWHM. The crystallinity of the twist component was further improved by regrowth. The mean square roughness of the surface was 1.04 nm, indicating that a smooth surface was obtained.
実施例９において、熱処理されたＡｌＮ／サファイア基板上に、ＭＯＶＰＥ法により、ＡｌＮ膜の再成長を行った。ＭＯＶＰＥ法の成長温度は、１４５０℃、成長圧力は３０Ｔｏｒｒ、ＮＨ３／ＴＭＡ（トリメチルアルミニウム）流量比は５８４で、ＡｌＮ膜を２０００ｎｍ製膜した。その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで２１８ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、３５５ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、４１３ａｒｃｓｅｃ、となり、再成長することによってさらにツイスト成分の結晶性の向上が見られた。また表面の平均二乗粗さは３．２５ｎｍであり、平滑な表面が得られることが分かった。 In Example 9, the AlN film was regrown on the heat-treated AlN / sapphire substrate by the MOVPE method. The growth temperature of the MOVPE method was 1450 ° C., the growth pressure was 30 Torr, the NH 3 / TMA (trimethylaluminum) flow rate ratio was 584, and an AlN film was formed to 2000 nm. As a result, the crystallinity of the AlN film is 218 arcsec for the (0002) AlN XRC FWHM, the FWHM for the (10-12) AlN XRC is 355 arcsec, and the FWHM for the (10-10) AlN XRC is 413 arcsec. The crystallinity of the twist component was further improved by regrowth. The mean square roughness of the surface was 3.25 nm, indicating that a smooth surface was obtained.
実施例１０において、熱処理されたＡｌＮ／サファイア基板上に、ＭＯＶＰＥ法により、ＡｌＮ膜の再成長を行った。ＭＯＶＰＥ法の成長温度は、１４５０℃、成長圧力は３０Ｔｏｒｒ、ＮＨ３／ＴＭＡ（トリメチルアルミニウム）流量比は５８４で、ＡｌＮ膜を２０００ｎｍ製膜した。その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで１１９ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、２７４ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、３７２ａｒｃｓｅｃ、となり、再成長することによってさらにツイスト成分の結晶性の向上が見られた。また表面の平均二乗粗さは１．１０ｎｍであり、平滑な表面が得られることが分かった。得られたＡｌＮ膜の断面の透過電子顕微鏡像を図３に示す。 In Example 10, the AlN film was regrown on the heat-treated AlN / sapphire substrate by the MOVPE method. The growth temperature of the MOVPE method was 1450 ° C., the growth pressure was 30 Torr, the NH 3 / TMA (trimethylaluminum) flow rate ratio was 584, and an AlN film was formed to 2000 nm. As a result, the crystallinity of the AlN film is 119 arcsec for (0002) AlN XRC FWHM, 274 arcsec for (10-12) AlN XRC FWHM, and 372 arcsec for (10-10) AlN XRC FWHM. The crystallinity of the twist component was further improved by regrowth. Further, the mean square roughness of the surface was 1.10 nm, and it was found that a smooth surface was obtained. A transmission electron microscope image of the cross section of the obtained AlN film is shown in FIG.
［比較例１］
用いたＡｌＮ／サファイア基板は、実施例６において、ＭＯＶＰＥ法で作製し、４等分されたもののうちの１片である。このＡｌＮ／サファイア基板を用いて、Ｎ２／ＣＯ混合ガスを用いる代わりにＮ２ガスのみをガス導入部３より導入すること以外は、実施例７と同様にして、熱処理を行った。
[Comparative Example 1]
The AlN / sapphire substrate used is one piece of the substrate produced in Example 6 by the MOVPE method and divided into four equal parts. Using this AlN / sapphire substrate, heat treatment was performed in the same manner as in Example 7 except that only N 2 gas was introduced from the gas introduction unit 3 instead of using the N 2 / CO mixed gas.
その結果、ＡｌＮ膜の結晶性は、（０００２）ＡｌＮのＸＲＣのＦＷＨＭで７５９ａｒｃｓｅｃ、（１０−１２）ＡｌＮのＸＲＣのＦＷＨＭは、９９７ａｒｃｓｅｃ、（１０−１０）ＡｌＮのＸＲＣのＦＷＨＭは、７７４ａｒｃｓｅｃ、であり、実施例７と比較して、結晶性は劣化した。 As a result, the crystallinity of the AlN film is 759 arcsec for the (0002) AlN XRC FWHM, 997 arcsec for the (10-12) AlN XRC FWHM, and 774 arcsec for the (10-10) AlN XRC FWHM. Yes, compared with Example 7, crystallinity deteriorated.
表１に、実施例１〜１３、比較例１の実験条件及びＡｌＮ結晶膜の評価の一覧を示す。これらの結果より、ＭＯＶＰＥ法でサファイア基板上に作製したＡｌＮ膜をＮ２／ＣＯ混合ガスを用いて熱処理することにより、ＡｌＮ膜の飛躍的な高品質化が達成できることが分かった。また、熱処理後にＭＯＶＰＥ法で再成長することにより、さらに結晶性の向上ができることが分かった。 Table 1 shows a list of the experimental conditions of Examples 1 to 13 and Comparative Example 1 and the evaluation of the AlN crystal film. From these results, it was found that the AlN film can be drastically improved in quality by heat-treating the AlN film produced on the sapphire substrate by the MOVPE method using the N 2 / CO mixed gas. It was also found that the crystallinity can be further improved by regrowth by the MOVPE method after the heat treatment.
上記したように、本発明によれば、サファイア基板あるいは炭化ケイ素（ＳｉＣ）基板、窒化アルミニウム（ＡｌＮ）基板等の基板上に、窒化アルミニウム（ＡｌＮ）膜を形成した後、１５００℃以上の高温で熱処理を行うことで、ＡｌＮ膜の表面粗さを飛躍的に改善し、滑らかにすることができる。 As described above, according to the present invention, after an aluminum nitride (AlN) film is formed on a substrate such as a sapphire substrate, a silicon carbide (SiC) substrate, or an aluminum nitride (AlN) substrate, at a high temperature of 1500 ° C. or higher. By performing the heat treatment, the surface roughness of the AlN film can be drastically improved and smoothed.
また、ＡｌＮ膜を有する基板を窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガス中で熱処理を行うことや、さらに熱処理の温度ならびに窒素／一酸化炭素（Ｎ２／ＣＯ）混合ガスの比率を、Ａｌ２Ｏ３−ＡｌＮ−Ｃ−Ｎ２−ＣＯ系相安定図（図２）の太実線Ａで示される化学的平衡状態に近い状態で、安定に実現することによって、表面平均二乗粗さが１．５ｎｍ以下というように飛躍的に表面の滑らかさを改善できるものである。 Further, the substrate having the AlN film is heat-treated in a nitrogen / carbon monoxide (N 2 / CO) mixed gas, and the heat treatment temperature and the ratio of the nitrogen / carbon monoxide (N 2 / CO) mixed gas are set. The surface mean square roughness is realized stably in a state close to the chemical equilibrium state indicated by the thick solid line A in the Al 2 O 3 —AlN—C—N 2 —CO phase stability diagram (FIG. 2). The surface smoothness can be drastically improved such that the thickness is 1.5 nm or less.
１ （黒鉛製）反応容器
２ 加熱ヒータ
３ ガス導入部
４ ガス排気部
５ 基板保持具
６ （ＡｌＮ膜を形成した）サファイア基板
1 (made of graphite) reaction vessel 2 heater 3 gas introduction part 4 gas exhaust part 5 substrate holder 6 sapphire substrate (with an AlN film formed)
Claims (15)
The temperature of the heat treatment and the ratio of the nitrogen / carbon monoxide (N 2 / CO) mixed gas are the temperature and the mixture indicating the chemical equilibrium state of the Al 2 O 3 —AlN—C—N 2 —CO system phase diagram, respectively. 15. The method of manufacturing an AlN film according to claim 14, wherein the AlN film is determined in the vicinity of the ratio.
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