JP6063293B2 - Vapor growth method - Google Patents

Description

  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.

  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.

  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).

JP 2008-262967 A

  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.

  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.

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 .

  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.

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. It is an II-II arrow line view of FIG. 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).

  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.

  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.

  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.

  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.

  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

  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.

  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.

  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.

  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 (1)

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 .

Images