JP6063293B2

JP6063293B2 - Vapor growth method

Info

Publication number: JP6063293B2
Application number: JP2013033796A
Authority: JP
Inventors: 和正池永
Original assignee: Taiyo Nippon Sanso Corp
Current assignee: Taiyo Nippon Sanso Corp
Priority date: 2013-02-22
Filing date: 2013-02-22
Publication date: 2017-01-18
Anticipated expiration: 2033-02-22
Also published as: JP2014165282A

Description

本発明は、気相成長方法に関し、詳しくは、サファイア基板にＧａＮ（窒化ガリウム）の薄膜を気相成長させる気相成長方法に関する。 The present invention relates to a vapor phase growth method, and more particularly, to a vapor phase growth method in which a GaN (gallium nitride) thin film is vapor grown on a sapphire substrate.

窒化物半導体の一つであるＧａＮ半導体を製造する装置は、例えば、石英製のチャンバー内にサファイア製の基板を配置して該基板を所定の温度に加熱するとともに、前記チャンバー内に、原料ガスとしてトリメチルガリウムとアンモニアとを導入し、該原料ガスを前記基板の表面付近で反応させることにより、基板の表面にＧａＮを気相成長させて窒化ガリウム半導体を形成する。 An apparatus for producing a GaN semiconductor that is one of nitride semiconductors, for example, arranges a sapphire substrate in a quartz chamber, heats the substrate to a predetermined temperature, and supplies a source gas in the chamber. As a result, trimethylgallium and ammonia are introduced, and the source gas is reacted in the vicinity of the surface of the substrate, whereby GaN is vapor-phase grown on the surface of the substrate to form a gallium nitride semiconductor.

このような気相成長装置では、原料ガスの状態や基板温度等の成膜条件の最適化だけでなく、各成膜時における成膜条件の均一性を確保することも重要な問題であった。このため、新品あるいは洗浄後のチャンバーを使用する際に、チャンバー内に原料ガスを導入してチャンバー内の原料ガスに接触する面を意図的に汚れた状態にすること、いわゆるプリコートを行うことによって各成膜時における成膜条件の均一化を図ったり、逆に、成膜後にチャンバーを洗浄して常に清浄な状態にすることによって各成膜時における成膜条件の均一化を図ったりすることが行われている（例えば、特許文献１参照。）。 In such a vapor phase growth apparatus, not only optimization of film formation conditions such as the state of the source gas and the substrate temperature, but also ensuring uniformity of film formation conditions during each film formation was an important problem. . For this reason, when using a new or cleaned chamber, by introducing the source gas into the chamber and intentionally making the surface in contact with the source gas in the chamber dirty, that is, by performing so-called pre-coating Uniform film formation conditions at each film formation, or conversely, uniform film formation conditions at each film formation by cleaning the chamber after film formation to always keep it clean. (For example, refer to Patent Document 1).

特開２００８−２６２９６７号公報JP 2008-262967 A

しかし、プリコートを行うためには、原料ガスの無駄が発生するだけでなく、プリコートを行っている間は成膜操作を行えないため、製造コストの増加や生産性の低下を招いてしまう。また、各成膜操作毎に清浄なチャンバーを使用するためには、成膜操作後のチャンバーを取り外して清浄なチャンバーに交換する手間が掛かり、チャンバー交換に要する時間も必要であり、生産性の低下を招いてしまう。 However, in order to perform the pre-coating, not only is the source gas wasted, but the film forming operation cannot be performed while the pre-coating is being performed, leading to an increase in manufacturing cost and a decrease in productivity. In addition, in order to use a clean chamber for each film forming operation, it takes time and effort to remove the chamber after the film forming operation and replace it with a clean chamber. It will cause a decline.

そこで本発明は、高品質なＧａＮ薄膜を安定して得ることができる気相成長方法を提供することを目的としている。 Accordingly, an object of the present invention is to provide a vapor phase growth method capable of stably obtaining a high-quality GaN thin film.

上記目的を達成するため、本発明の気相成長方法は、原料ガス導入部及びガス排出部を備えたチャンバー内に、サセプタで保持したサファイア基板を配置し、該基板を加熱するとともに、前記原料ガス導入部からガス排出部に向けてチャンバー内に原料ガスを導入し、チャンバー内で原料ガスを反応させて前記基板面にＧａＮ薄膜を形成する気相成長方法において、前記基板のガス流れ方向上流側で、前記原料ガスに接触するガス接触面を有する複数のガス接触部材を着脱交換可能に形成するとともに、前記基板面にＧａＮ薄膜を形成する操作で前記ガス接触面にガリウム化合物が付着したガス接触部材を清浄なガス接触部材に交換する際に、１回目の交換作業では、ガス接触面にガリウム化合物が付着したガス接触部材の少なくとも一つを残して他のガス接触部材を清浄なガス接触部材に交換し、２回目の交換作業では、前記１回目の交換作業で交換したガス接触部材を残して、前記１回目の交換作業で交換しなかったガス接触部材を清浄なガス接触部材に交換し、前記１回目の交換作業と前記２回目の交換作業とを交互に繰り返すことを特徴としている。 In order to achieve the above object, the vapor phase growth method of the present invention includes a sapphire substrate held by a susceptor in a chamber having a source gas introduction part and a gas discharge part, and heats the substrate, In a vapor phase growth method in which a raw material gas is introduced into a chamber from a gas introduction part toward a gas discharge part, and a raw material gas is reacted in the chamber to form a GaN thin film on the substrate surface, upstream of the substrate in the gas flow direction A plurality of gas contact members having a gas contact surface in contact with the source gas are detachably replaceable, and a gas in which a gallium compound adheres to the gas contact surface by an operation of forming a GaN thin film on the substrate surface When replacing the contact member with a clean gas contact member, in the first replacement operation, at least one of the gas contact members having the gallium compound adhered to the gas contact surface is removed. The other gas contact member is replaced with a clean gas contact member, and in the second replacement operation, the gas contact member replaced in the first replacement operation is left and not replaced in the first replacement operation. The gas contact member is replaced with a clean gas contact member, and the first replacement operation and the second replacement operation are alternately repeated .

本発明の気相成長方法によれば、ガス接触部材を清浄なガス接触部材に交換する際に、少なくとも一つを残すようにしているので、原料ガス導入部から導入した原料ガスが、ガス接触面にガリウム化合物が付着したガス接触部材に接触することにより、サーマルクリーニング工程にてサファイア基板上にＧａが飛散することで成膜条件が安定化し、結晶性や表面モフォロジーが良好なＧａＮ薄膜を得ることができる。 According to the vapor phase growth method of the present invention, when the gas contact member is replaced with a clean gas contact member, at least one is left, so that the source gas introduced from the source gas introduction unit is in gas contact. By contacting a gas contact member with a gallium compound attached to the surface, the film formation conditions are stabilized by Ga scattering on the sapphire substrate in the thermal cleaning process, and a GaN thin film with good crystallinity and surface morphology is obtained. be able to.

本発明の気相成長方法を実施する気相成長装置の一例を示す断面正面図である。1 is a cross-sectional front view illustrating an example of a vapor phase growth apparatus that performs a vapor phase growth method of the present invention. 図１のII−II矢視図である。It is an II-II arrow line view of FIG. 実験結果を示すもので、成膜操作回数と測定したＸ線半値幅（ＦＭＨＷ）との関係を示す図である。FIG. 9 shows experimental results and is a diagram showing a relationship between the number of film forming operations and a measured X-ray half width (FMHW).

図１及び図２は、本発明の気相成長方法を実施するための気相成長装置の一例を示すもので、１回の操作で複数の基板面に均一にＧａＮ薄膜を形成することができる自公転型の気相成長装置を示している。この自公転型の気相成長装置は、石英ガラス製の偏平円筒状のチャンバー１１内に、チャンバー１１の底面部分を貫通した支持軸１２により円盤状のサセプタ１３を支持し、前記支持軸１２の上部に、放射状に原料ガスを流出させる原料ガス導入部１４を設けるとともに、チャンバ１１の外周部にガス排出部１５を設けている。 1 and 2 show an example of a vapor phase growth apparatus for carrying out the vapor phase growth method of the present invention, and a GaN thin film can be uniformly formed on a plurality of substrate surfaces in one operation. A self-revolving vapor phase growth apparatus is shown. This self-revolving vapor phase growth apparatus supports a disc-shaped susceptor 13 in a flat cylindrical chamber 11 made of quartz glass by a support shaft 12 penetrating the bottom surface of the chamber 11. In the upper part, a raw material gas introduction part 14 for letting the raw material gas flow out radially is provided, and a gas discharge part 15 is provided in the outer peripheral part of the chamber 11.

サセプタ１３の下方には、支持軸１２を囲むようにしてヒーター１６が設けられ、ヒーター１６の周囲にはリフレクター１７が設けられている。サセプタ１３の上面には、内周側に石英中央カバー１８が、該石英中央カバー１８の外周側に、複数の収容部１９を周方向に等間隔で形成したサセプタカバー２０が、それぞれ着脱可能な状態で載置され、前記収容部１９に、プレートリング２１を介してサファイア基板２２がそれぞれ支持されている。 A heater 16 is provided below the susceptor 13 so as to surround the support shaft 12, and a reflector 17 is provided around the heater 16. On the upper surface of the susceptor 13, a quartz central cover 18 is detachable on the inner peripheral side, and a susceptor cover 20 is formed on the outer peripheral side of the quartz central cover 18. The sapphire substrate 22 is supported by the accommodating portion 19 via a plate ring 21.

前記原料ガス導入部１４と前記サファイア基板２２との間、すなわち、サファイア基板２２のガス流れ方向上流側で、原料ガス導入部１４からチャンバー１１内に導入された原料ガスが接触するガス接触面を有するガス接触部材は、本形態例では、前記石英中央カバー１８、前記サセプタカバー２０、プレートリング２１、チャンバー１１の天井板１１ａの４種類であって、これらのガス接触部材は、基板面にＧａＮ薄膜を形成する操作を行うと、加熱された原料ガスの反応や分解によって生じたガリウム化合物、例えば、ＧａＮがガス接触面に付着する。 A gas contact surface between the source gas introduction unit 14 and the sapphire substrate 22, that is, on the upstream side of the sapphire substrate 22 in the gas flow direction, with which the source gas introduced from the source gas introduction unit 14 into the chamber 11 contacts. In this embodiment, there are four types of gas contact members including the quartz center cover 18, the susceptor cover 20, the plate ring 21, and the ceiling plate 11 a of the chamber 11. When an operation for forming a thin film is performed, a gallium compound, for example, GaN, produced by reaction or decomposition of the heated source gas adheres to the gas contact surface.

ガス接触面へのガリウム化合物の付着量が多くなると、パーティクルの発生など、基板面に形成するＧａＮ薄膜に悪影響を与えるため、ガス接触面へのガリウム化合物の付着量が多くなる前に、ガリウム化合物が付着したガス接触部材を清浄なガス接触部材に交換する必要がある。 If the adhesion amount of the gallium compound on the gas contact surface increases, it will adversely affect the GaN thin film formed on the substrate surface, such as generation of particles. Therefore, before the gallium compound adhesion amount on the gas contact surface increases, It is necessary to replace the gas contact member to which the gas adheres with a clean gas contact member.

このため、従来は、ガリウム化合物が付着したガス接触部材の全てを清浄なガス接触部材に交換していたが、本発明では、ガス接触面にガリウム化合物が付着したガス接触部材の少なくとも一つを残して他のガス接触部材を清浄なガス接触部材に交換する。例えば、本形態例では、石英中央カバー１８、サセプタカバー２０、プレートリング２１及びチャンバー１１の天井板１１ａのなかで、１回目の交換作業では、石英中央カバー１８を残してサセプタカバー２０、プレートリング２１及びチャンバー１１の天井板１１ａを清浄なサセプタカバー２０、プレートリング２１及びチャンバー１１の天井板１１ａに交換し、２回目の交換作業では、サセプタカバー２０、プレートリング２１及びチャンバー１１の天井板１１ａを残して石英中央カバー１８を清浄な部材に交換する。 For this reason, conventionally, all of the gas contact members to which the gallium compound is adhered have been replaced with clean gas contact members. However, in the present invention, at least one of the gas contact members to which the gallium compound has adhered to the gas contact surface is replaced. The other gas contact member is replaced with a clean gas contact member. For example, in the present embodiment, among the quartz central cover 18, the susceptor cover 20, the plate ring 21 and the ceiling plate 11 a of the chamber 11, the susceptor cover 20 and the plate ring are left in the first replacement operation while leaving the quartz central cover 18. 21 and the ceiling plate 11a of the chamber 11 are replaced with a clean susceptor cover 20, the plate ring 21 and the ceiling plate 11a of the chamber 11, and in the second replacement operation, the susceptor cover 20, the plate ring 21 and the ceiling plate 11a of the chamber 11 are replaced. The quartz center cover 18 is replaced with a clean member leaving

このように、１回目の交換作業では、ガス接触面にガリウム化合物が付着したガス接触部材の少なくとも一つを残して他のガス接触部材を清浄なガス接触部材に交換し、２回目の交換作業では、１回目の交換作業で交換しなかったガス接触部材を含めて清浄なガス接触部材に交換することにより、原料ガスを導入して成膜する前に行われる、水素を含む雰囲気で１０００℃以上まで加熱するサーマルクリーニングの工程で、ＧａＮなどのガリウム化合物が付着したガス接触面からサファイア基板上にＧａが飛散することで、一般的な成膜条件でサファイア基板２２にＧａＮ薄膜を気相成長させた場合でも、得られるＧａＮ薄膜におけるＧａＮの結晶性を大幅に向上させることができ、表面モフォロジーも良好なものとすることができる。 Thus, in the first replacement operation, the other gas contact member is replaced with a clean gas contact member while leaving at least one of the gas contact members having the gallium compound adhered to the gas contact surface, and the second replacement operation is performed. Then, by replacing the gas contact member that has not been replaced in the first replacement operation with a clean gas contact member, 1000 ° C. in an atmosphere containing hydrogen, which is performed before introducing the source gas and forming the film. In the thermal cleaning process of heating up to the above, Ga is scattered on the sapphire substrate from the gas contact surface to which the gallium compound such as GaN is adhered, so that a GaN thin film is vapor-phase grown on the sapphire substrate 22 under general film formation conditions. Even in this case, the crystallinity of GaN in the obtained GaN thin film can be greatly improved, and the surface morphology can be improved.

ここで、同一構成の気相成長装置を使用し、２回の成膜操作毎に、チャンバー１１の天井板１１ａを残して石英中央カバー１８、サセプタカバー２０及びプレートリング２１を清浄なものに交換する作業と、石英中央カバー１８、サセプタカバー２０及びプレートリング２１を残してチャンバー１１の天井板１１ａを清浄なものに交換する作業とを繰り返して行った場合（実施例）と、１回の成膜操作毎に、全てのガス接触部材を清浄な部材に交換した場合（比較例）とで、得られたＧａＮ薄膜のＸ線半値幅（ＦＷＨＭ）を測定した。なお、ガス接触部材の交換作業以外、温度条件等の成膜条件は全て同一としている。１回目の成膜操作から５回目の成膜操作で得られたＧａＮ薄膜のＸ線半値幅を測定し、実施例における測定結果を黒三角印で、比較例における測定結果を黒菱形印で、それぞれ図３に示す。図３から明らかなように、Ｘ線半値幅の値が小さくなり、良好なＧａＮ薄膜が得られていることがわかる。また、部材の交換も２回毎になるので、毎回交換する場合に比べて生産性の向上も図れる。 Here, using the vapor phase growth apparatus having the same configuration, the quartz center cover 18, the susceptor cover 20, and the plate ring 21 are replaced with clean ones, leaving the ceiling plate 11a of the chamber 11 every two film forming operations. A case in which the quartz center cover 18, the susceptor cover 20, and the plate ring 21 are left and the ceiling plate 11 a of the chamber 11 is replaced with a clean one (Example). The X-ray half-width (FWHM) of the obtained GaN thin film was measured when all gas contact members were replaced with clean members for each membrane operation (Comparative Example). The film forming conditions such as temperature conditions are all the same except for the replacement operation of the gas contact member. The X-ray half width of the GaN thin film obtained from the first film forming operation to the fifth film forming operation is measured, the measurement results in the examples are black triangle marks, the measurement results in the comparative examples are black rhombus marks, Each is shown in FIG. As can be seen from FIG. 3, the X-ray half-value width becomes small, and it can be seen that a good GaN thin film is obtained. In addition, since the replacement of the member is performed every two times, productivity can be improved as compared with the case of replacement every time.

なお、気相成長装置における基板の支持構造は任意であり、従来から広く知られている自公転型、公転型、自転型、横型、縦型といった各種構造の気相成長装置においても、ガス接触部材が複数あるものであれば、本発明方法を実施することが可能である。 In addition, the support structure of the substrate in the vapor phase growth apparatus is arbitrary, and in the vapor phase growth apparatus of various structures such as the revolution type, revolution type, revolution type, horizontal type, and vertical type, which are widely known in the past, gas contact is also possible. If there are a plurality of members, the method of the present invention can be carried out.

１１…チャンバー、１１ａ…天井板、１２…支持軸、１３…サセプタ、１４…原料ガス導入部、１５…ガス排出部、１６…ヒーター、１７…リフレクター、１８…石英中央カバー、１９…収容部、２０…サセプタカバー、２１…プレートリング、２２…サファイア基板 DESCRIPTION OF SYMBOLS 11 ... Chamber, 11a ... Ceiling board, 12 ... Support shaft, 13 ... Susceptor, 14 ... Raw material gas introduction part, 15 ... Gas discharge part, 16 ... Heater, 17 ... Reflector, 18 ... Quartz center cover, 19 ... Housing part, 20 ... susceptor cover, 21 ... plate ring, 22 ... sapphire substrate

Claims

A sapphire substrate held by a susceptor is placed in a chamber equipped with a source gas inlet and a gas outlet, and the substrate is heated, and source gas is introduced into the chamber from the source gas inlet to the gas outlet. In the vapor phase growth method of introducing and reacting a source gas in a chamber to form a GaN thin film on the substrate surface, a plurality of gas contact surfaces that contact the source gas on the upstream side in the gas flow direction of the substrate When the gas contact member is formed to be detachable and replaceable, and when the gas contact member having the gallium compound attached to the gas contact surface is replaced with a clean gas contact member by an operation of forming a GaN thin film on the substrate surface,
In the first replacement operation, the other gas contact member is replaced with a clean gas contact member while leaving at least one of the gas contact members having the gallium compound adhered to the gas contact surface ,
In the second replacement operation, leaving the gas contact member replaced in the first replacement operation, replacing the gas contact member not replaced in the first replacement operation with a clean gas contact member,
A vapor phase growth method in which the first exchange operation and the second exchange operation are alternately repeated .