Method for reducing dislocation density of gallium nitride thin film through multiple patterning and gallium nitride thin film prepared and formed through multiple patterning

Abstract

The invention relates to a method for reducing dislocation density of a gallium nitride thin film through multiple patterning and the gallium nitride thin film prepared through the method. The method comprises the following steps that a buffer layer is deposited on a heterogeneous substrate; epitaxially growing a GaN epitaxial layer on the buffer layer; constructing and obtaining a primary pattern structure on the buffer layer; epitaxial growth continues on the basis of the primary pattern structure, so that the primary pattern structure is healed and continues to grow to form a primary GaN film; constructing on the primary GaN thin film to obtain a secondary pattern structure; and on the basis of the secondary pattern structure, epitaxial growth continues to be carried out, so that the secondary pattern structure is healed and continues to grow to form a secondary GaN film. According to the method, the epitaxial transverse overgrowth capability of GaN epitaxial growth under different pattern structures is fully utilized, bending and closing of dislocation defects at holes and pattern structure interfaces are achieved through secondary or even multiple times of processing, and finally heteroepitaxial growth of the low-dislocation-density GaN thin film is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of epitaxial growth of semiconductor materials, and in particular to a method for reducing the dislocation density of a gallium nitride film by multiple patterning and a prepared gallium nitride film. Background Art

[0002] III-nitride semiconductor materials are widely used in high-frequency, high-voltage, microwave high-power devices and other fields. After more than a decade of rapid development, III-nitride devices also have very good application prospects and commercial value in full-color display and all-solid-state lighting. With the successful preparation of GaN-based purple, blue, and green heterostructure luminescent materials and devices, not only has the light storage density been increased exponentially, but it will also have a profound impact on the revolution of green lighting sources; in-depth exploration of III-nitride semiconductor materials will further promote the rapid development of ultraviolet radiation.

[0003] GaN devices play an increasingly important role in meeting the country's major strategic needs and daily life needs, but their development also faces some problems that need to be overcome. For example, the performance and service life of blue LED devices depend to a large extent on the epitaxial growth of high-quality GaN films. In the field of high-frequency interconnected communications, higher requirements are also placed on the stability and reliability of GaN devices under harsh working conditions, which requires the epitaxial quality of GaN films to be higher. Due to the large lattice constant and thermal expansion coefficient mismatch between GaN and heterogeneous epitaxial substrates (such as sapphire and silicon), there is a high stress in the epitaxially grown GaN film. The release of stress causes defects such as dislocations to form in the GaN epitaxial film. The existence of these dislocation defects will seriously affect the service life and performance of GaN devices. Therefore, it is of great practical significance to reduce the density of dislocation defects in GaN epitaxial films and further improve the stability and consistency of GaN films to improve the performance and product yield of GaN devices.

[0004] At present, the introduction of patterned sapphire substrate structure and deposited buffer layer structure is a common method to reduce the dislocation density of heteroepitaxial GaN films. The patterned sapphire substrate technology is to achieve lattice matching and reduce dislocation density by making a series of tiny grooves on the sapphire substrate; while the deposited buffer layer structure is to buffer the lattice mismatch, improve the crystal quality and reduce the dislocation density by growing a buffer layer on the sapphire substrate. The process of introducing the buffer layer structure is simple and the cost is low. Although the introduction of both can reduce the high dislocation density caused by lattice mismatch and thermal mismatch, there will still be a large number of dislocations propagating upward during the growth process, which is difficult to meet the demand for high-quality and low-dislocation-density films. Summary of the invention

[0005] In view of the high dislocation density problem of gallium nitride films, a method for reducing the dislocation density of gallium nitride films by multiple patterning and a prepared gallium nitride film are provided, aiming to effectively block the dislocations formed by lattice mismatch and thermal mismatch from propagating to the film surface and reduce the dislocation density of the film material.

[0006] The specific technical solutions are as follows: The first aspect of the present invention is to provide a method for reducing the dislocation density of a gallium nitride film by multiple patterning, comprising the following steps: S1. Depositing a buffer layer on a foreign substrate; S2, epitaxially growing a GaN epitaxial layer on the buffer layer; S3, performing a patterning process on the GaN epitaxial layer to construct a pattern structure on the buffer layer; S4, continuing epitaxial growth on the basis of the primary graphic structure, so that the primary graphic structure is healed and continues to grow to form a primary GaN film; S5, performing secondary patterning on the primary GaN film to construct a secondary pattern structure on the primary GaN film; S6, continuing epitaxial growth on the basis of the secondary graphic structure, so that the secondary graphic structure is healed and continues to grow to form a secondary GaN film; Among them, the upper and lower adjacent graphics in the primary graphic structure and the secondary graphic structure are staggered left and right; the height of the graphics in the primary graphic structure and the secondary graphic structure is 100-300nm, the characteristic size is 400-600nm, and the axial distance between the left and right adjacent graphics is 0.5-2μm.

[0007] Furthermore, the method further includes step S7, which is: repeating steps S5 and S6 once or more to allow the i-th graphic structure to heal and continue to grow to form an i-th GaN film.

[0008] Furthermore, the shape of the graphics obtained by each graphics processing is the same.

[0009] Furthermore, the shape of the graphics obtained by each graphics processing is different.

[0010] The above method also has the feature that the shape of the figure obtained by each figure processing is one of cylindrical, strip, conical or hemispherical.

[0011] Further, the foreign substrate is made of sapphire, silicon carbide, silicon, gallium oxide, aluminum nitride, diamond, silicon oxide or quartz glass.

[0012] Furthermore, the GaN epitaxial layer is one of GaN, n-GaN, p-GaN, AlGaN, and InGaN epitaxial layers.

[0013] The second aspect of the present invention is to provide a gallium nitride film prepared according to the above method.

[0014] The beneficial effects of the above scheme are: The present invention makes full use of the epitaxial lateral overgrowth capability of GaN epitaxial growth under different graphic structures, realizes the bending and closure of dislocation defects at holes and graphic structure interfaces through secondary or even multiple processing, and finally realizes heteroepitaxial growth of low dislocation density GaN film. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a method provided in an embodiment of the present invention; Figure 2 It is a comparison diagram of the pattern healing during GaN epitaxial growth under different pattern structures in the embodiment of the present invention.

[0016] In the attached figure: 1. Heterogeneous substrate; 2. Buffer layer; 3. GaN epitaxial layer; 4. Primary graphic structure; 5. Primary GaN thin film; 6. Secondary graphic structure; 7. Secondary GaN thin film. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0019] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0020] The present invention provides a method for reducing the dislocation density of a gallium nitride film by multiple patterning, which comprises the following steps: S1, forming an AlN buffer layer 2 by sputtering deposition on a foreign substrate 1 (in the present invention, the foreign substrate 1 is made of sapphire, silicon carbide, silicon, gallium oxide, aluminum nitride, diamond, silicon oxide or quartz glass) to reduce the lattice mismatch and thermal expansion coefficient mismatch between the GaN epitaxial layer and the foreign substrate; S2, epitaxially growing a GaN epitaxial layer 3 on the AlN buffer layer 2; S3, etching the GaN epitaxial layer 3 by using photolithography technology, so as to etch the GaN epitaxial layer 3 and construct a primary graphic structure 4 on the AlN buffer layer 2 (the shape of the graphic in the primary graphic structure 4 is one of cylindrical, long strip, conical or hemispherical, the height of the graphic is 100-300nm, the characteristic size is 400-600nm, and the axial center distance between the left and right adjacent graphics is 0.5-2μm); S4, continuing epitaxial growth on the basis of the primary graphic structure 4, so that the primary graphic structure 4 is healed and continues to grow to form a primary GaN film 5; S5. Etching is performed on the primary GaN film 5 using a photolithography technique to construct a secondary pattern structure 6 on the primary GaN film (the shape of the pattern in the secondary pattern structure 6 is one of a cylindrical shape, a long strip shape, a conical shape or a hemispherical shape, the height of the pattern is 100-300 nm, the characteristic size is 400-600 nm, and the axis distance between left and right adjacent patterns is 0.5-2 μm); S6 . Continue epitaxial growth on the basis of the secondary graphic structure 6 , so that the secondary graphic structure 6 is healed and continues to grow to form a secondary GaN film 7 .

[0021] In the present invention, the upper and lower adjacent graphics in the primary graphic structure 4 and the secondary graphic structure 6 are staggered left and right, so that the secondary graphic structure 6 is used to fill the gap position in the construction process of the primary GaN nanographic structure to shield the dislocations of the primary graphic structure 4 that propagate upward during growth, and finally close the unshielded dislocation defects in the primary graphic structure 4 on the secondary graphic structure 6 during the upward propagation of secondary growth.

[0022] On the basis of the above scheme, further, the present application may also include step S7, which is: repeating steps S5 and S6 once or more to allow the i-th graphic structure (the height of the graphic in the i-th graphic structure 6 is 100-300nm, the characteristic size is 400-600nm, and the axial distance between the left and right adjacent graphics is 0.5-2μm) to heal and continue to grow to form an i-th GaN film. The above multiple patterning can further reduce the dislocation density of the film.

[0023] like Figure 2As shown in (a) and 2(b), in the present invention, a graphic structure 4 is constructed in a cylindrical shape (height is 200nm, bottom radius is 500nm, and the axial center distance between the left and right adjacent graphics is 1μm) and a strip shape (height is 200nm, bottom side length is 500nm, and the axial center distance between the left and right adjacent graphics is 1μm). The Lammps molecular dynamics simulation results show that (the dotted box in the figure is the heterogeneous substrate 1) the construction of the above two types of graphics can make the GaN epitaxial structure adsorbed and healed on the top of the graphic, thereby forming a hole structure at the interface. The existence of the above hole structure can promote the annihilation of dislocations at the interface at the hole.

[0024] like Figure 2 As shown in (c) and 2(d), in the present invention, a graphic structure 4 is constructed in a conical shape (the height is 200nm, the bottom radius is 500nm, and the axial center distance between the left and right adjacent graphics is 1μm) and a hemispherical shape (the height is 200nm, the bottom radius is 500nm, and the axial center distance between the left and right adjacent graphics is 1μm). Simulation experiments show that the construction of the above two types of graphics can promote the bending of dislocations at the interface toward the side wall of the graphic, thereby improving the lateral epitaxial overgrowth ability of the GaN film.

[0025] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing the dislocation density of a gallium nitride film by multiple patterning, characterized in that: The steps include: S1. Depositing a buffer layer on a foreign substrate; S2, epitaxially growing a GaN epitaxial layer on the buffer layer; S3, performing a patterning process on the GaN epitaxial layer to construct a pattern structure on the buffer layer; S4, continuing epitaxial growth on the basis of the primary graphic structure, so that the primary graphic structure is healed and continues to grow to form a primary GaN film; S5, performing secondary patterning on the primary GaN film to construct a secondary pattern structure on the primary GaN film; S6, continuing epitaxial growth on the basis of the secondary graphic structure, so that the secondary graphic structure is healed and continues to grow to form a secondary GaN film; Among them, the upper and lower adjacent graphics in the primary graphic structure and the secondary graphic structure are staggered left and right; the height of the graphics in the primary graphic structure and the secondary graphic structure is 100-300nm, the characteristic size is 400-600nm, and the axial distance between the left and right adjacent graphics is 0.5-2μm.

2. The method according to claim 1, characterized in that The method further includes step S7, which is: repeating steps S5 and S6 once or more to allow the i-th graphic structure to heal and continue to grow to form an i-th GaN film.

3. The method according to claim 1 or 2, characterized in that The shape of the graphics obtained by each graphics processing is the same.

4. The method according to claim 1 or 2, characterized in that The shape of the graphics obtained by each graphics processing is different.

5. The method according to claim 1 or 2, characterized in that The shape of the figure obtained by each figure processing is one of cylindrical, strip, conical or hemispherical.

6. The method according to claim 1, characterized in that The foreign substrate is made of sapphire, silicon carbide, silicon, gallium oxide, aluminum nitride, diamond, silicon oxide or quartz glass.

7. The method according to claim 1, characterized in that The GaN epitaxial layer is one of GaN, n-GaN, p-GaN, AlGaN, and InGaN epitaxial layers.

8. A gallium nitride thin film, characterized in that: Prepared according to the method according to any one of claims 1 to 7.

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