JP2010285325A - Method for producing nitride semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a nitride semiconductor substrate, by which contour processing (particularly, orientation-flat processing and index-flat processing) on a nitride semiconductor substrate can be easily carried out with high accuracy. <P>SOLUTION: The method for producing a nitride semiconductor substrate includes steps of: forming a protective film having a bored portion in a desired shape on a base substrate; growing a nitride semiconductor layer in the bored portion; and peeling the nitride semiconductor layer. The desired shape includes an orientation-flat portion and/or an index-flat portion in the nitride semiconductor substrate. The protective film includes an oxide film, a metal film or a nitride film. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a nitride semiconductor substrate, and more particularly to a method for manufacturing a nitride semiconductor substrate capable of easily forming an orientation flat or an index flat of the substrate.

  A high-quality nitride semiconductor substrate is required to produce a long-life blue laser, a high-intensity blue LED (Light Emitting Diode), a high-performance electronic device, and the like. In recent years, free-standing GaN substrates manufactured by the HVPE method (Hydride Vapor Phase Epitaxy) or the like have been used as epitaxial wafer substrates for these devices.

  In order to manufacture an epitaxial wafer, the GaN substrate is usually subjected to the following processing. Processing for adjusting the outer diameter of the substrate is performed in order to set the epitaxial wafer manufacturing apparatus on the susceptor. Chamfering is performed to prevent cracking and chipping. Orientation flat (OF) processing is performed as a mark for the crystal orientation of the substrate, and index flat (IF) processing and matte-shaped back surface processing are performed as marks for distinguishing the front and back surfaces. In order to uniformly form a layer to be deposited on the substrate, the substrate surface is planarized. As the flattening process, grinding, lapping, and polishing processes are generally performed.

  Processing for adjusting the substrate shape (outer diameter processing, OF / IF processing, chamfering) is often performed in the following procedure using an NC processing machine or a copying type processing machine. The grown crystal ingot is subjected to cylindrical grinding, then flat (OF or IF) is ground and formed, and then sliced into a wafer. In this case, when forming a flat (OF or IF), the crystal orientation is discriminated by performing X-ray diffraction measurement or the like on a cylindrically ground ingot. Another procedure is to form a flat (OF or IF) by cleaving after slicing the wafer.

  Since ingot growth of nitride semiconductor crystals is difficult with current technology, nitride semiconductor substrates are manufactured one by one by a method in which a thick film of nitride semiconductor crystals is grown on a different substrate and then peeled off. . Therefore, the formation of the flat is performed by a method by cleavage.

  However, the hexagonal nitride semiconductor crystal has a problem that it is less cleaved than a cubic system such as Si or GaAs and is easily displaced from the cleavage plane. Further, since the nitride semiconductor substrate is transparent, it is easy to cause a problem that the front and back of the substrate are mistaken after peeling.

  For example, Patent Document 1 discloses a method for punching a circular wafer in a mold by applying ultrasonic processing to a circular wafer having a periphery that is smaller than that of a circular wafer and having an OF / IF shape. Is disclosed. According to Patent Document 1, by adopting such a method, OF / IF processing can be performed simultaneously, and the processing time can be greatly shortened. Patent Document 2 discloses a method of growing a crystal by protecting a portion serving as a reference for crystal orientation with a protective film.

JP 2006-339431 A JP-A-5-55143

Y. Oshima, T. Eri, M. Shibata, H. Sunakawa, K. Kobayashi, T. Ichihashi and A. Usui: Jpn. J. Appl. Phys. 42 (2003) L1.

  As described above, the nitride semiconductor substrate has a problem that OF / IF processing on the wafer is difficult. The method described in Patent Document 1 has the advantage that the processing time of OF / IF can be significantly reduced, but the processing speed is further increased because the GaN substrate is a hard and brittle material (the processing time is further reduced). Is difficult. Accordingly, an object of the present invention is to provide a method for manufacturing a nitride semiconductor substrate capable of accurately and easily performing outer shape processing (particularly OF / IF processing) on the nitride semiconductor substrate.

  In order to achieve the above object, the present invention provides a method for manufacturing a nitride semiconductor substrate, comprising a step of forming a protective film having a portion hollowed out in a desired shape on a base substrate, and the hollowed out portion. The method further includes the steps of growing a nitride semiconductor layer and peeling the nitride semiconductor layer.

In order to achieve the above object, the present invention can be modified or changed as follows in the method for manufacturing a nitride semiconductor substrate according to the present invention.
(1) The desired shape includes an orientation flat and / or an index flat in the nitride semiconductor substrate.
(2) The protective film is an oxide film, a metal film, or a nitride film.

  According to the present invention, in the manufacture of a nitride semiconductor substrate, outer shape processing (particularly OF / IF processing) can be easily performed on the nitride semiconductor substrate. In addition, OF / IF positioning can be performed with high accuracy by using OF of the sapphire substrate with accuracy as a reference for crystal orientation.

FIG. 3 is a schematic plan view of a c-plane sapphire single crystal substrate having a diameter of 62 mm used as a base substrate. It is a plane schematic diagram of the base substrate which formed the void part in the surface area. It is a plane schematic diagram of the base substrate which apply | coated the photoresist on the void part. It is a plane schematic diagram of the mask pattern used for photolithography. It is a plane schematic diagram of the base substrate from which the photoresist other than the photosensitive portion is removed. FIG. 6 is a schematic plan view of a base substrate in which a SiO ₂ film is formed on the entire surface of the base substrate of FIG. It is a plane schematic diagram of the base substrate from which the SiO ₂ film on the photoresist is removed. FIG. 3 is a schematic plan view of a nitride semiconductor substrate peeled after HVPE growth.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment taken up here.

  A nitride semiconductor substrate was manufactured according to the following procedure according to the manufacturing method of the present invention. First, a c-plane sapphire single crystal substrate 11 having a diameter of 62 mm was prepared as a base substrate (see FIG. 1).

  (A) A 300 nm-thick GaN thin film was grown on the c-plane sapphire single crystal substrate 11 by metal organic chemical vapor deposition (MOCVD).

  (B) A Ti thin film with a thickness of 20 nm was deposited on the GaN thin film by vacuum evaporation. Thereafter, a heat treatment was performed at 1060 ° C. for 30 minutes in a mixed atmosphere of ammonia and hydrogen to form a network-like TiN nanomask and generate a large number of voids at the Ti / GaN interface (void portions 22 in the surface region of the underlying substrate). (See Fig. 2).

  (C) A negative type photoresist 32 was uniformly applied with a spin coater on the base substrate 21 on which the void portion 22 was formed, and prebaked (see FIG. 3).

  (D) After that, the mask 40 as shown in FIG. 4 is used, and exposure is performed at the same magnification with the mask 40 and the base substrate 31 being brought into close contact with each other. Formed. After confirming that unnecessary photoresist was completely removed, post-baking was performed to obtain a base substrate 51.

(E) A SiO ₂ film 62 was formed on the entire surface of the base substrate 51 shown in FIG. 5 by sputtering (see FIG. 6).

(F) Next, the SiO ₂ film 62 on the photoresist 32 is lifted off from the base substrate 61 with the SiO ₂ film formed on the entire surface by using a stripping solution to obtain the base substrate 71 as shown in FIG. It was.

(G) A GaN film having a thickness of 600 μm was grown on the base substrate 71 by hydride vapor phase epitaxy (HVPE). The raw materials used for the growth were NH ₃ and GaCl, and the growth temperature was 1060 ° C. The growth was carried out at normal pressure, the GaCl partial pressure and NH ₃ partial pressure of the supply gas were 8 × 10 ⁻³ atm and 8 × 10 ⁻² atm, respectively, and N ₂ was used as the carrier gas.

In the above HVPE growth, a GaN film was grown on the void portion 22, but no growth of the GaN film was observed on the SiO ₂ film 62. Further, the GaN film can be easily peeled off from the GaN / TiN interface in the void portion 22, and a nitride semiconductor substrate 81 having a desired shape can be obtained (see FIG. 8). Note that the peeled nitride semiconductor substrate 81 may be subjected to precision outside diameter processing, high precision OF processing, and chamfering as necessary.

  As a method for growing a nitride semiconductor crystal in the present invention, for example, a void formation peeling method (see Non-Patent Document 1) can be preferably used. Alternatively, metal organic chloride vapor deposition (MOHVPE) or metal organic chemical vapor deposition (MOCVD) may be used.

11 ... c-plane sapphire single crystal substrate,
21 ... A base substrate having a void portion formed on the surface region, 22 ... a void portion,
31 ... Underlying substrate with photoresist applied on the void, 32 ... Photoresist,
40 ... Mask, 41 ... Mask pattern transmission part, 42 ... Mask pattern light shielding part,
51. Base substrate from which photoresist other than photosensitive portion is removed,
61 ... Underlying substrate with SiO ₂ film formed on the entire surface, 62 ... SiO ₂ film,
71: the base substrate from which the SiO ₂ film on the photoresist is removed,
81: Nitride semiconductor substrate.

Claims (3)

  A method of manufacturing a nitride semiconductor substrate, the step of forming a protective film having a portion hollowed out in a desired shape on a base substrate, and the step of growing a nitride semiconductor layer on the hollowed out portion And a step of peeling the nitride semiconductor layer. A method of manufacturing a nitride semiconductor substrate, comprising:   The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the desired shape includes an orientation flat and / or an index flat in the nitride semiconductor substrate.   The method for manufacturing a nitride semiconductor substrate according to claim 1, wherein the protective film is an oxide film, a metal film, or a nitride film.

Images