Gallium oxide heteroepitaxial substrate and preparation method thereof

Abstract

The invention relates to the technical field of semiconductors, in particular to a gallium oxide heteroepitaxial substrate and a preparation method thereof. The gallium oxide heteroepitaxial substrate comprises: a sapphire substrate; the sapphire substrate is provided with a beveled surface; a periodic pattern structure is arranged on the beveled surface of the sapphire substrate; the depth of a repetitive unit of the periodic pattern structure is 200 nm to 20 [mu] m, the maximum envelope size is 100 nm to 50 [mu] m, and the period interval is 200 nm to 100 [mu] m. The sapphire substrate is subjected to beveling processing and patterning processing, lattice mismatch is remarkably relieved, stress is released, accordingly, dislocation density is reduced, defects in the gallium oxide thin film are reduced, the gallium oxide single crystal thin film with better crystal quality is obtained, and the method has important application value in the field of gallium oxide thin film semiconductor material preparation.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and particularly to a gallium oxide heteroepitaxial substrate and a preparation method thereof. Background Art

[0002] Sapphire is widely used as a semiconductor epitaxial substrate due to its high mechanical strength, chemical inertness, and thermal stability for the heteroepitaxy of gallium oxide (Ga2O3) thin films. The sapphire substrate has good stability, mature preparation processes, and low cost. Generally, the heteroepitaxy of gallium oxide thin films is carried out on a planar c-plane sapphire substrate. However, due to the differences in lattice constants and thermal expansion coefficients between sapphire and gallium oxide, problems such as lattice mismatch and interfacial stress occur during the heteroepitaxy of gallium oxide thin films on a planar sapphire substrate, increasing the generation of defects such as dislocations, and it is difficult to obtain high-quality gallium oxide single crystal thin films.

[0003] In order to solve this problem, existing research has adopted various improvement methods. For example, an obliquely cut sapphire substrate is used to suppress the occurrence of the six-fold domain phenomenon and improve the crystal quality of the epitaxial gallium oxide thin film. However, this is still not sufficient to solve the problems of lattice mismatch and thermal mismatch between gallium oxide and the substrate material. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a gallium oxide heteroepitaxial substrate, a preparation method thereof, and an application.

[0005] In a first aspect, the present invention provides a gallium oxide heteroepitaxial substrate, comprising: a sapphire substrate; the sapphire substrate has an obliquely cut surface; a periodic pattern structure is provided on the obliquely cut surface of the sapphire substrate; The depth of the repeating unit of the periodic pattern structure is 200 nm to 20 μm, the maximum envelope size is 100 nm to 50 μm, and the period spacing is 200 nm to 100 μm.

[0006] The envelope size refers to the maximum external dimension of an object or structure, that is, the maximum range that the object can reach in all directions. It is usually used to describe the size, shape, and capacity of an object, similar to putting an object in the smallest box, and the size of the box is the envelope size of the object.

[0007] Due to the differences in lattice constants and thermal expansion coefficients between sapphire and gallium oxide, problems such as lattice mismatch and interfacial stress occur during the heteroepitaxy of gallium oxide thin films on a planar sapphire substrate, increasing the generation of defects such as dislocations, and it is difficult to obtain high-quality gallium oxide single crystal thin films. The present invention improves the gallium oxide heteroepitaxial substrate by using a processing method of obliquely cutting + periodic pattern structure, and the grown gallium oxide crystal of the obtained product has higher quality.

[0008] Benefits of beveling the sapphire substrate: 1. After beveling, continuous atomic steps are formed on the surface of the sapphire substrate (as shown in Figure 1 ). At an appropriate bevel angle, the migration distance of adsorbed Ga atoms is similar to the step width, and Ga atoms will preferentially incorporate into the step edges for nucleation, forming a stable step-flow growth; 2. Gallium oxide belongs to the monoclinic system, while sapphire belongs to the hexagonal system. During heteroepitaxy, the gallium oxide crystal exhibits six different growth directions, resulting in the deterioration of the crystal quality of the gallium oxide thin film. The beveled sapphire substrate can, to a certain extent, inhibit the multiple growth orientations of gallium oxide.

[0009] The present invention performs patterning on the basis of the beveled substrate: 1. The periodic graphic structure can be regarded as introducing a "buffer" or "gradual change" transition region between the substrate and the epitaxial layer. This structure helps to gradually adjust the lattice constant, enabling the lattice of the epitaxial layer to match more smoothly with the lattice of the substrate. 2. The mismatch in the coefficient of thermal expansion between the epitaxial layer and the substrate is one of the main reasons for residual stress. The periodic graphic structure adjusts the stress distribution during thermal expansion by changing the surface area and shape of the substrate. 3. The periodic graphic structure can also serve as a channel or trap for dislocation movement, promoting the movement, coalescence, and annihilation processes of dislocations. This helps to reduce the dislocation density in the epitaxial layer and further improve the quality of the epitaxial layer.

[0010] Furthermore, the beveled surface is used for epitaxial growth of gallium oxide crystals.

[0011] Furthermore, the graphic structure of the repeating unit includes one or more of: frustum of a cone, cone, hemisphere, pyramid, strip groove, cylinder, triangular prism, hexagonal prism, circular column, V-groove, T-groove, or spiral groove.

[0012] Furthermore, the repeating manner of the periodic graphic structure includes one or more of: random arrangement, rectangular lattice arrangement, or hexagonal close-packed arrangement.

[0013] Furthermore, the bevel angle of the beveled surface is: 1 to 10°.

[0014] Furthermore, the bevel direction of the beveled surface is: deviating from the c-plane towards the a-plane, or deviating from the c-plane towards the m-plane.

[0015] Furthermore, the thickness of the gallium oxide heteroepitaxial substrate is 300 to 1000 μm.

[0016] As a preferred specific embodiment, the bevel direction of the beveled surface is: deviating from the c-plane towards the a-plane with a bevel of 8°; or, deviating from the c-plane towards the m-plane with a bevel of 6°. In this beveling manner, the substrate obtained for epitaxial growth of gallium oxide single crystal has relatively better quality. The FWHM detection results for different bevel angles are as shown in Figure 2 .

[0017] In a second aspect, the present invention provides a gallium oxide single crystal, which is prepared from the aforementioned gallium oxide heteroepitaxial substrate.

[0018] In a third aspect, the present invention provides a method for preparing the aforementioned gallium oxide heteroepitaxial substrate, including: Obliquely cutting and polishing a sapphire substrate along the c-plane towards the a-plane or m-plane to obtain a sapphire substrate with an obliquely cut surface; Processing the obliquely cut surface to obtain a sapphire substrate with a periodically patterned surface.

[0019] Further, the processing includes one or more of: etching, dry etching, laser processing, or ion beam processing.

[0020] In a fourth aspect, the present invention provides the application of the aforementioned gallium oxide heteroepitaxial substrate in the preparation of gallium oxide-based semiconductor materials.

[0021] Further, the gallium oxide-based semiconductor materials can be used to prepare various electronic devices such as power devices, radio frequency devices, optoelectronic devices, and sensors.

[0022] The present invention has the following beneficial effects: The present invention provides a gallium oxide heteroepitaxial substrate by obliquely cutting and patterning a sapphire substrate. It can significantly alleviate lattice mismatch, release stress, thereby reducing the dislocation density and reducing the defects inside the gallium oxide thin film, and obtaining a gallium oxide single crystal thin film with better crystal quality. The gallium oxide heteroepitaxial substrate provided by the present invention can be used to prepare high-quality gallium oxide single crystal thin films, which has important application value in the technical field related to gallium oxide single crystal materials. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is the atomic force microscope (AFM) test surface topography map of the obliquely cut sapphire substrate provided by the present invention.

[0025] Figure 2 It is the graph of the crystallization quality (FWHM value) of the gallium oxide single crystal grown on the sapphire substrates obliquely cut along the a-plane from the c-plane and the m-plane from the c-plane varying with the obliquely cut angle provided by the present invention.

[0026] Figure 3 This is the method for preparing a gallium oxide thin film on a gallium oxide heteroepitaxial substrate provided in Embodiment 1 of the present invention.

[0027] Figure 4 This is the schematic diagram of the inclined plane and inclined angle of the sapphire substrate provided in Embodiment 1 of the present invention.

[0028] Figure 5 This is an example of a gallium oxide heteroepitaxial substrate provided in Embodiment 1 of the present invention; in the figure, 1 is the arrangement of the periodic graphic structure in the side view perspective, and 2 represents the gallium oxide heteroepitaxial substrate. Detailed implementation manners

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the present invention will be clearly and completely described below with reference to the accompanying drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0030] For the experimental methods involved in the following embodiments, unless otherwise specified, they are all conventional methods in the art. For example, they can be referred to the experimental manuals in the art or carried out according to the conditions recommended in the manufacturer's instructions.

[0031] For the experimental materials and reagents involved in the following embodiments, unless otherwise specified, they can all be obtained from commercial channels.

[0032] Embodiment 1 The present invention provides a method for preparing a gallium oxide thin film on a gallium oxide heteroepitaxial substrate (as Figure 3 shown), including: (1) Obliquely cut (the oblique cutting angle is 8°) and surface polish a sapphire (with a thickness of 650 μm) along the c-plane towards the a-plane to obtain a sapphire substrate with a bias angle (as Figure 4 shown, after oblique cutting and polishing, the thickness is about 430 μm).

[0033] (2) Etch or corrode the surface of the sapphire substrate with a bias angle to obtain a sapphire substrate with a periodic graphic structure.

[0034] The repeating unit of the periodic graphic structure is a frustum of a cone, the depth of each repeating unit is 2 μm, the maximum envelope size is 5 μm, and the period spacing is 10 μm. The arrangement mode of the periodic graphic structure is a periodic hexagonal close-packed arrangement.

[0035] Figure 5Schematic diagram of a gallium oxide heteroepitaxial substrate. The upper figure is a top view, from which the arrangement of the periodic graphic structure can be seen in the top view perspective. The lower figure is a side view. In the figure, 1 is the arrangement of the periodic graphic structure in the side view perspective, and 2 represents the gallium oxide heteroepitaxial substrate.

[0036] On the sapphire substrate obtained by the above preparation method, a gallium oxide single crystal thin film including all crystal phases such as α-phase and β-phase can be epitaxially grown, and the film thickness ranges from 100 nm to 2000 μm.

[0037] Example 2 This example provides a method for preparing a gallium oxide thin film on a gallium oxide heteroepitaxial substrate. It is the same as Example 1, except that step (1) is replaced with: (1) The sapphire (with a thickness of 650 μm) is obliquely cut (the oblique cutting angle is 6°) along the c-plane towards the m-plane and surface polished to obtain a sapphire substrate with a bias angle.

[0038] Example 3 This example provides a method for preparing a gallium oxide thin film on a gallium oxide heteroepitaxial substrate. It is the same as Example 1, except that: the repeating unit of the periodic graphic structure is a strip-shaped groove, the depth of each repeating unit is 3 μm, the maximum envelope size is 6 μm, and the period spacing is 20 μm. The arrangement of the periodic graphic structure is a periodic hexagonal close-packed arrangement.

[0039] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A gallium oxide heteroepitaxial substrate, characterized in that, Comprising: A sapphire substrate; The sapphire substrate has a beveled surface; a periodic graphic structure is provided on the beveled surface of the sapphire substrate; The depth of the repeating unit of the periodic graphic structure is 200 nm to 20 μm, the maximum envelope size is 100 nm to 50 μm, and the period pitch is 200 nm to 100 μm; The beveled surface is inclined 7 - 9° with the c-plane biased towards the a-plane; or, the c-plane is biased towards the m-plane and inclined 5 - 7°.

2. The gallium oxide heteroepitaxial substrate according to claim 1, characterized in that, The graphic structure of the repeating unit includes: one or more of a frustum of a cone, a cone, a hemisphere, a pyramid, a strip groove, a cylinder, a triangular prism, a hexagonal prism, an annular cylinder, a V-groove, a T-groove or a spiral groove.

3. The gallium oxide heteroepitaxial substrate according to claim 1 or 2, characterized in that The repeating manner of the periodic graphic structure includes: one or more of random arrangement, rectangular lattice arrangement or hexagonal close packing arrangement.

4. The gallium oxide heteroepitaxial substrate according to claim 1 or 2, characterized in that The thickness of the gallium oxide heteroepitaxial substrate is 300 - 1000 μm.

5. A gallium oxide single crystal, characterized in that, The gallium oxide single crystal is prepared from the gallium oxide heteroepitaxial substrate according to any one of claims 1 - 4.

6. The preparation method of the gallium oxide heteroepitaxial substrate according to any one of claims 1-4, characterized in that, Comprising: The sapphire substrate is beveled and polished along the c-plane biased towards the a-plane or the m-plane to obtain a sapphire substrate with a beveled surface; The beveled surface is processed to obtain a sapphire substrate with a periodic graphic structure on the surface.

7. The method according to claim 6, characterized in that The processing includes: one or more of corrosion, etching, laser processing or ion beam processing.

8. Use of the gallium oxide heteroepitaxial substrate according to any one of claims 1 - 4 in the preparation of gallium oxide-based semiconductor materials.

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