JPS62123094A - Susceptor for vapor growth of semiconductor - Google Patents

Abstract

PURPOSE:To prevent contamination of impurities from a carbonaceous substrate and form a high-quality semiconductor film, by coating the surface of the carbonaceous substrate with a crystalline aluminum nitride film deposited from the vapor phase. CONSTITUTION:A crystalline aluminum nitride film having >=5mu thickness is formed from the vapor phase on the surface of a carbonaceous substrate by a chemical vapor deposition method. As for raw materials, an aluminum halide or organoaluminum compound is used as an aluminum source and NH3 is used as a nitrogen source. If this susceptor is used to carry out vapor-phase growth of a semiconductor, particularly a III-V compound semiconductor, contamination of impurities from the carbonaceous substrate is prevented to afford the aimed high-quality III-V compound semiconductor film.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 本発明は半導体、特にＧａＡｓ　、　　ＩｎＰ等のＩＴ
Ｉ　−Ｖ族化合物半導体の気相成長に用いられるサセプ
タに関するものである。[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to semiconductors, particularly IT devices such as GaAs and InP.
The present invention relates to a susceptor used for vapor phase growth of I-V compound semiconductors.

〔従来技術とその問題点〕[Prior art and its problems]

■−ｖ族化合物半導体（混晶を含む）は、キャリア易動
度が高く高速素子として用いられている他、発光素子と
して用いられている等、シリコン半導体に見られない特
徴を有することから、活発な研究開発が行なわれている
。そのためデバイス形成に必要な■−ｖ族化合物半導体
エピタキシャルウェハの量産が進められておυ、特に高
性能デバイス用の高品質エピタキシャルウェハに対する
需要が急速に高まりつつある。■-V group compound semiconductors (including mixed crystals) have characteristics not found in silicon semiconductors, such as having high carrier mobility and being used as high-speed devices, as well as being used as light-emitting devices. Active research and development is underway. For this reason, mass production of ■-V group compound semiconductor epitaxial wafers necessary for device formation is progressing, and demand for high-quality epitaxial wafers for high-performance devices in particular is rapidly increasing.

エビタキシャ〃ウェハの製造は量産性の面から気相成長
法により行なわれる事が多い。気相成長法では化合物半
導体の原料ガス、例えばＧａＡｓの場合にはＧａ　源と
してＧａＣ６３やＧａ（ＣＨ，）３を、Ａｓ源としてＡ
ｓ４やＡｓＨ３を、Ｈ２などのキャリアガスにより気相
成長炉内に搬送する。成長炉内にはＧａＡｓ基板ウェハ
がサセプタ上に置かれており、高周波誘導加熱方式や赤
外ランプ加熱方式により基板加熱が行なわれる。サセプ
タは炭素（黒鉛を含む）鯛で、炭素中の不純物による汚
染を防ぐためにＳｉＣや熱分解黒鉛により被覆されてい
る。このようなサセプタは、シリコン半導体の気相成長
用として従来からＩｔ、ｌいられていたものを化合物半
導体用に転用したものであるが、高品質の化合物半導体
膜を成長させる場合に問題を生じていた。即ち、サセプ
タ表面のＳｉＣや熱分解黒鉛ＩＪ！！覆自身はＣＶＤ法
により形成されており高純度であるが、被覆物質が周期
律表第■属の元素から構成されているため、これらが■
−■族化合物半導体中に混入すると電気的特性が低下す
る。特にサセプタと基板ウェハは高温で直接接触してい
るため、ＳｉＣや黒鉛のサセプタ上の被覆物質が基板ウ
ェハ側に拡散等して、成長する化合物半導体膜の電気特
性低下を招く可能性が非常に高かったのである。From the viewpoint of mass production, the production of Ebitaxia wafers is often carried out by vapor phase growth. In the vapor phase growth method, the raw material gas for compound semiconductors, for example, in the case of GaAs, GaC63 or Ga(CH,)3 is used as a Ga source, and A as an As source.
s4 and AsH3 are transported into a vapor phase growth reactor using a carrier gas such as H2. A GaAs substrate wafer is placed on a susceptor in the growth furnace, and the substrate is heated by a high frequency induction heating method or an infrared lamp heating method. The susceptor is made of carbon (including graphite) and is coated with SiC or pyrolytic graphite to prevent contamination from impurities in the carbon. This kind of susceptor was originally used for vapor phase growth of silicon semiconductors, but was repurposed for compound semiconductors, but it caused problems when growing high-quality compound semiconductor films. was. That is, SiC and pyrolytic graphite IJ on the surface of the susceptor! ! The coating itself is formed by the CVD method and has high purity, but since the coating material is composed of elements from group Ⅰ of the periodic table, these are
- If mixed into a group compound semiconductor, the electrical characteristics will deteriorate. In particular, since the susceptor and the substrate wafer are in direct contact at high temperatures, there is a strong possibility that the coating material on the SiC or graphite susceptor will diffuse toward the substrate wafer, leading to a decrease in the electrical properties of the growing compound semiconductor film. It was expensive.

〔問題点を解決するだめの手段〕[Failure to solve the problem]

本発明者等は従来のサセプタの前記問題点を解決するた
めに、炭素製サセプタからの不純物汚染を防止し、かつ
化合物半導体に対して電気的に中性な材料からなる被＆
層の開発について検討し、ｔｒｔ　−ｖ族化合物半導体
材料と同族元素からなるＡｔＮ被覆層が好ましい性能を
有することを見出し、特に炭素基材の表面を気相から析
出した結晶質窒化アルミニウム（ＡｔＮ　）膜により被
覆した場合に最も性能の安定したサセプタが得られるこ
とを見出だした。即ち本発明は、炭素基材の表面を気相
から析出した結晶質窒化アルミニウム膜により被覆した
ことを特徴とする半導体気相成長用サセプタである。In order to solve the above-mentioned problems of conventional susceptors, the present inventors have attempted to prevent impurity contamination from carbon susceptors, and to prevent impurity contamination from carbon susceptors, and to
We investigated the development of the layer and found that an AtN coating layer made of a trt-v group compound semiconductor material and an element in the same group has favorable performance. In particular, we developed a coating layer of crystalline aluminum nitride (AtN) deposited from the gas phase on the surface of a carbon substrate. It has been found that a susceptor with the most stable performance can be obtained when coated with a membrane. That is, the present invention is a susceptor for semiconductor vapor phase growth, characterized in that the surface of a carbon base material is coated with a crystalline aluminum nitride film deposited from the vapor phase.

ＡｔＮ膜は化学気相蒸着（ＣＶＤ　）法により気相から
炭素残材表面上に析出される。原料としてＡ／−源には
ＡｔＣ／＝、やＡｔＢｒ３などのハロゲン化アルミニウ
ムやＡｔＥｔ３（）リエチルアルミニウム）などの有機
アルミニウム化合物が用いられ、Ｎ源にはＮＨ，が一般
に用いられる。ＮＨ３はＡｔ源に対して七ル比で０．５
から２０倍、より好ましくは１〜５倍の割合で供給する
のがよい。The AtN film is deposited on the carbon residue surface from the gas phase by a chemical vapor deposition (CVD) method. As raw materials, aluminum halides such as AtC/=, AtBr3, and organic aluminum compounds such as AtEt3 (ethylaluminum) are used as the A/- source, and NH is generally used as the N source. NH3 has a ratio of 0.5 to the At source.
It is preferable to supply at a rate of 20 times, more preferably 1 to 5 times.

ＮＨ，の供給量が少いと反応率が低下してＡｔ源が無駄
になり、また多すぎると過剰のＮＨ３によってＣＶＤ反
応室の腐食等がおこり好ましくないからである。Ａｔ源
のハロゲン化アルミニウム、有機アルミニウム化合物は
常温で固体もしくは液体であるので、適当な蒸気圧が得
られる温度まで加熱して、Ｎ２やＮ２　　などのキャリ
アガスにより気体原料としてＣＶＤ反応炉内に送られる
。反応炉内には基材（この場合には所定のサセプタの形
状に加工された炭素基材）が置かれ、所定の温度・圧力
等の条件の下、基材表面にＡｔＮが析出される。この時
の温度・圧力条件等によって析出するＡｔＮ膜の性状が
変化するが、本発明が目的とするサセプタとして好まし
い特性のものはＡｔＮ膜が結晶質の場合にのみ得られ、
非晶質ＡｔＮ膜ではサセプタに好ましくない。This is because if the amount of NH3 supplied is too small, the reaction rate will decrease and the At source will be wasted, while if it is too large, corrosion of the CVD reaction chamber will occur due to excessive NH3, which is undesirable. Aluminum halides and organoaluminum compounds that are At sources are solid or liquid at room temperature, so they are heated to a temperature at which an appropriate vapor pressure is obtained, and then sent as gaseous raw materials into the CVD reactor using a carrier gas such as N2 or N2. It will be done. A base material (in this case, a carbon base material processed into the shape of a predetermined susceptor) is placed in a reactor, and AtN is deposited on the surface of the base material under conditions such as predetermined temperature and pressure. The properties of the AtN film deposited change depending on the temperature and pressure conditions at this time, but the desirable characteristics as a susceptor, which is the object of the present invention, can be obtained only when the AtN film is crystalline.
An amorphous AtN film is not suitable for a susceptor.

非晶質ＡｔＮ　１１４はＣＶＤ温度が低い場合（たとえ
ば５００℃）に得られるが、このような膜は繰り返しの
加熱冷却によりクツツクの発生を起こしやすく、も（材
炭素の不純物がクラック部分から出て来るという問題が
ある。また非晶質ＡｔＮ膜は空気中の水分により容易に
加水分解するためその取り扱いが著しく困難で、実用性
に著しい難点がある。これに対し、６ｏｏ℃以上、より
好ましくは８００℃以上の高温でＡｔＮ膜のＣＶＤを行
うと結晶質の朕が得られる。結晶質ＡｔＮ　１９はサセ
プタのように繰り返しの加熱冷却を受ける場合でもクラ
ックの発生を起こすことがなく、壕だ加水分解性もない
のでサセプタ彼役として）ψれた特性を有している。Ａ
ｔＮ自身が■族（Ａｔ）　　とＶ族（Ｎ）の化合物であ
るのでＳｉＣ被覆サセプタを用いる場合のような■−ｖ
族化合物半導体への■族元素の混入汚染という問題がな
く、また本発明におけるＡｔＮ　ｉｌｌ、覆は気相から
の析出により形成されるので極めて高純度であり、他の
不純物による汚染の心配もない。Amorphous AtN 114 can be obtained when the CVD temperature is low (for example, 500°C), but such a film is prone to cracking due to repeated heating and cooling, and also (impurities in the material carbon come out from the cracks). In addition, since amorphous AtN films are easily hydrolyzed by moisture in the air, they are extremely difficult to handle and are extremely difficult to put into practical use. A crystalline film can be obtained by CVDing an AtN film at a high temperature of 800°C or higher.Crystalline AtN 19 does not generate cracks even when subjected to repeated heating and cooling like a susceptor, and is highly resistant to hydration. Since it is not decomposable, it has unique characteristics as a susceptor. A
Since tN itself is a compound of Group ■ (At) and Group V (N), ■-v such as when using a SiC coated susceptor
There is no problem of contamination of group compound semiconductors with group elements, and since the AtN layer in the present invention is formed by precipitation from the gas phase, it has extremely high purity and there is no fear of contamination by other impurities. .

このため本発明のサセプタは高品質の■−Ｖ族化合物半
導体を気相成長させる上で最適の特性を有するものであ
る。Therefore, the susceptor of the present invention has optimal characteristics for vapor phase growth of high-quality -V group compound semiconductors.

サセプタを構成する炭素基材は高純度のものが好ましく
、灰分０．１％以下であることが望まれる。またＡｔＮ
被覆層の厚さは５μｍ以上が好ましい。灰分が０．１チ
を越える炭素基材を用いたり、ＡｔＮ層が５μｍ未満で
あると基材炭素中の不純物がＡｔＮ層を拡散して外部に
出現し、成長膜を汚染するからである。尚、ＡｔＮ層を
ＣＶＤ法により析出させる際に高周波プラズマやマイク
ロ波プラズマを併用するプラズマＣＶＤ法を採用するこ
とも勿論可能である。The carbon base material constituting the susceptor is preferably of high purity, and desirably has an ash content of 0.1% or less. Also AtN
The thickness of the coating layer is preferably 5 μm or more. This is because if a carbon base material with an ash content exceeding 0.1 inch is used or the AtN layer is less than 5 μm, impurities in the base carbon will diffuse through the AtN layer and appear outside, contaminating the grown film. Note that when depositing the AtN layer by the CVD method, it is of course possible to employ a plasma CVD method that uses high frequency plasma or microwave plasma in combination.

また、結晶性ＡｔＮ膜を１０μｒＩＬ／ｈｒ　以上の高
蒸着速度で析出させるためにはＣＶＤを１００ＴＯｒｒ
以下の圧力で行うことが好ましい。これ以上の圧力で行
うと原料ガスが気１目中で反応してＡ／、Ｎ微粒子を形
成するため怜社蒸着速度が低下するばかりでなく、微粒
子が膜中に取り込壕れて欠陥となり、クラック発生を起
こしやすくなる等の悪影響を及ぼすからである。In addition, in order to deposit a crystalline AtN film at a high deposition rate of 10μrIL/hr or more, CVD should be performed at 100TOrr.
It is preferable to carry out the reaction at the following pressure. If the pressure is higher than this, the raw material gas will react in the atmosphere and form A/N fine particles, which will not only reduce the deposition rate, but also cause the fine particles to become trapped in the film and cause defects. This is because it has an adverse effect such as making it easier for cracks to occur.

次に実施例により本発明を更に詳しく説明する。Next, the present invention will be explained in more detail with reference to Examples.

〔実施例〕〔Example〕

Ａ／＝Ｃ／−３とＮＨ３を原料として、減圧Ｃ’ＶＤ法
によりサセプタ形状に加工した炭素基材上にＡｔＮ膜を
析出させた。Ａ　Ｌ　ＣＡｓをガス状原料として減圧Ｃ
ＶＤ炉内に搬送するため、Ａｔｃｔ３を入れた容器を１
７０℃に加熱し、この容器にキャリアガスとしてＮ、ガ
スを流し、Ａｔｃｔ３容器とＣＶＤ炉の間のＡ　Ｌ　Ｃ
Ａｓ供給用ガス配管部を２００℃に加熱してＡｔＣｌ３
の再析出を防止するようにした。Using A/=C/-3 and NH3 as raw materials, an AtN film was deposited on a carbon substrate processed into a susceptor shape by a reduced pressure C'VD method. Reduced pressure C using A L CAs as gaseous raw material
In order to transport the container into the VD furnace, the container containing Atct3 is
Heat to 70°C, flow N gas as a carrier gas into this container, and connect the A L C between the Atct3 container and the CVD furnace.
The As supply gas piping section is heated to 200°C and AtCl3
This prevents the re-precipitation of

ｋｌ、ｃｔ３の１７０℃における蒸気圧とキャリアＮ２
ガスの流量とからＡｔｃｔ３のＣＶＤ炉内への供給量が
計算できる。ＮＨ３の流量を１　ｔ／ｍｉｎとし、Ａｔ
ｃｔ３の流量が０．５　ｔ／ｍｉｎとなるようキャリア
Ｎ。Vapor pressure of kl, ct3 at 170°C and carrier N2
The amount of Atct3 supplied into the CVD furnace can be calculated from the gas flow rate. The flow rate of NH3 is 1 t/min, and At
Carrier N so that the flow rate of ct3 is 0.5 t/min.

ガスの流量を調節し、圧力５Ｔｏｒｒ、基材温度１００
０℃の条件で炭素拭材上にＡｔＮ膜を析出させた。Adjust the gas flow rate, pressure 5 Torr, base material temperature 100
An AtN film was deposited on the carbon wiping material at 0°C.

ＣＶＤを８時間行い、４００μｍの厚さのＡｔＮ膜を析
出させた（実施例）。Ｘ線回折法により析出膜を調べた
ところ、Ａ、ｔＮのシャープなＸ線回折ピークが測定さ
れ、結晶質Ａ、ｔＮ膜が析出していることが確認された
。比較のため、基材温度を４５０℃とした他は上と同一
の条件でＡｔＮ膜を析出させたが、Ｘ線回折を行っても
ピークは検出されず、非晶質Ａ　乙Ｎ膜であった（比較
例）。CVD was performed for 8 hours to deposit an AtN film with a thickness of 400 μm (Example). When the deposited film was examined by X-ray diffraction method, sharp X-ray diffraction peaks of A and tN were measured, and it was confirmed that a crystalline A and tN film was deposited. For comparison, an AtN film was deposited under the same conditions as above except that the substrate temperature was 450°C, but no peak was detected even when X-ray diffraction was performed, indicating that it was an amorphous A-N film. (Comparative example)

サセプタとして使用される半を想定し、実施例と比較例
のサセプタをＮ、雰囲気中で高周波誘導加熱により６０
０℃に加熱した後、自然冷却するサイクルを繰り返し、
毎サイクルごとにサセプタ上のＡｔＮ被覆の様子を調べ
た。実施例のサセプタは２０回の加熱・冷却の繰り返し
後も何の変化も々く、ＡｔＮ層は強固に基材に付着し、
クラックの発生も全く認められなかった。これに対し比
較例のサセプタは第１回目のサイクルでクラックが無数
に発生し、ＡｔＮ層の部分的欠落が起きており、炭素基
材表面を被覆するＡｔＮ層が結晶質でなければならない
ことが明白に示された。Assuming that the susceptors will be used as susceptors, the susceptors of Examples and Comparative Examples were heated to 60°C by high-frequency induction heating in a N atmosphere.
Repeat the cycle of heating to 0°C and then cooling naturally,
The state of the AtN coating on the susceptor was examined every cycle. The susceptor of the example showed no change even after repeated heating and cooling 20 times, and the AtN layer firmly adhered to the base material.
No cracks were observed at all. On the other hand, in the susceptor of the comparative example, numerous cracks occurred in the first cycle, and the AtN layer was partially missing, indicating that the AtN layer covering the carbon base material surface must be crystalline. clearly shown.

また、２種のサセプタを温度２５℃、湿度６０チの条件
下で１ケ月放置した後、外観を検査したところ、実施例
のサセプタのＡｔＮ被覆層には何の変化も認められなか
ったが、比較例のサセプタではＡ／Ｊ被覆層が白色化し
、また無数のクラックが発生していた。In addition, when the two types of susceptors were left for one month at a temperature of 25°C and a humidity of 60°C, their appearance was inspected, and no change was observed in the AtN coating layer of the susceptor of the example. In the susceptor of the comparative example, the A/J coating layer turned white and numerous cracks were generated.

実施例のサセプタと従来のＳｉＣ被覆サセプタを用いて
Ｃ）ａＡｓウェハ上にＧａＡｓのエピタキシャル成長を
実施した。得られたエビタキンヤル膜中の不純物濃度を
測定したところ、実施例のサセプタを用いた場合には２
　Ｘ　１０’ａｔｏｍｓ／口３　と高純度であったが、
従来のＳｉＣ被覆サセプタを用いた場合には５Ｘ１ｇｌ
ｓ原子／ｃｍ３　　と１桁悪い純度となっていた。C) Epitaxial growth of GaAs was performed on an aAs wafer using the susceptor of the example and a conventional SiC-coated susceptor. When the impurity concentration in the obtained Evita Kinyal film was measured, it was found that when the susceptor of the example was used, it was 2.
Although it was highly pure with X 10'atoms/3,
5X1gl when using a conventional SiC coated susceptor
The purity was one order of magnitude worse at s atoms/cm3.

〔発明の効果〕〔Effect of the invention〕

本発明のサセプタを用いて■−Ｖ族化合物半導体の気相
成長を行えば、サセプタの基材炭素からの不純物混入が
抑止できるだけでなく、サセプタ被覆層物質の混入によ
る電気的特性低下がなくなるので、高品質の化合物半導
体膜を成長させることができる。By using the susceptor of the present invention to perform vapor phase growth of a -V group compound semiconductor, not only can the contamination of impurities from the base carbon of the susceptor be suppressed, but also the deterioration of electrical characteristics due to the contamination of the susceptor coating layer material can be eliminated. , high quality compound semiconductor films can be grown.

Claims (1)

【特許請求の範囲】[Claims] 炭素基材の表面を気相から析出した結晶質窒化アルミニ
ウム膜により被覆したことを特徴とする半導体気相成長
用サセプタ。A susceptor for semiconductor vapor phase growth, characterized in that the surface of a carbon base material is coated with a crystalline aluminum nitride film deposited from the vapor phase.