Gallium Oxide Crystal and Its Heteroepitaxial Method

Abstract

The present invention provides a gallium oxide crystal and a method for heteroepitaxy thereof, which are applied to the field of semiconductor technology. The method includes: preparing a sapphire substrate with a specific bi-directional tilt angle; growing a gallium oxide crystal on the sapphire substrate; and depositing a functional material on the gallium oxide crystal to obtain a target device. The heteroepitaxy method of the gallium oxide crystal provided by the present invention introduces a three-dimensional torsion-oriented design to prepare a sapphire substrate with a specific bi-directional tilt angle. The atomic spacing and atomic step height corresponding to different tilt angles in the sapphire substrate are different, thereby effectively restricting the in-plane growth anisotropy of β-phase gallium oxide. Growing a gallium oxide crystal on a sapphire substrate with a specific bi-directional tilt angle can effectively improve the consistency of the growth orientation of the β-phase gallium oxide crystal, thereby improving the quality of the gallium oxide crystal.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and specifically, to a gallium oxide crystal and a method for heteroepitaxy thereof. Background Art

[0002] Due to its wide bandgap, high breakdown field strength, and high Baliga figure of merit, gallium oxide material has become an ideal material for fabricating electronic devices.

[0003] When using a planar c-plane sapphire substrate to prepare a gallium oxide crystal, the prepared gallium oxide crystal will have problems of in-plane deflection and symmetry, resulting in a low quality of the gallium oxide crystal. Therefore, the existing methods for heteroepitaxy of gallium oxide crystals usually perform an oblique cut on the sapphire substrate at a single angle. Summary of the Invention

[0004] (I) Technical Problems to be Solved

[0005] The present invention provides a gallium oxide crystal and a method for heteroepitaxy thereof, which are used to at least partially solve one of the above technical problems.

[0006] (II) Technical Solutions

[0007] An embodiment of the present invention provides a method for heteroepitaxy of a gallium oxide crystal, including: preparing a sapphire substrate with a specific deflection angle, where the specific deflection angle is a bidirectional deflection angle; growing a gallium oxide crystal on the sapphire substrate; and depositing a functional material on the gallium oxide crystal to obtain a target device.

[0008] Optionally, preparing a sapphire substrate with a specific deflection angle includes: determining the crystal structure, crystal phase, and crystal plane of the substrate; and polishing the substrate to obtain a sapphire substrate with a specific deflection angle.

[0009] Optionally, polishing the substrate to obtain a sapphire substrate with a specific deflection angle includes: cleaning the surface of the substrate; adjusting the parameters of the polishing machine according to the properties of the substrate and the target polishing effect; and polishing the surface of the substrate based on the polishing machine to obtain a sapphire substrate with a specific deflection angle.

[0010] Optionally, adjusting the parameters of the polishing machine includes: adjusting the polishing angle of the polishing machine according to a preset specific deflection angle.

[0011] Optionally, polishing the surface of the substrate based on the polishing machine includes: determining the positions of two non-polar planes of the sapphire substrate and the intermediate direction between the positions of the two non-polar planes; and polishing along the intermediate direction of the two non-polar planes of the sapphire substrate; where the included angle between the polishing surface of the sapphire substrate and the C plane ranges from 0.1° to 30°.

[0012] Optionally, the polished sapphire substrate has a bidirectional tilt angle with the C plane tilted towards the a plane and the C plane tilted towards the m plane at the same time. Among them, the atomic spacing and atomic step height corresponding to different tilt angles are different.

[0013] Optionally, the method further includes: performing a high-temperature treatment on the polished sapphire substrate.

[0014] Optionally, growing a gallium oxide crystal on the sapphire substrate includes: determining the matching relationship between the crystal orientation of the substrate and the growth direction of the gallium oxide crystal; growing a gallium oxide crystal on the sapphire substrate based on the matching relationship, where the thickness of the gallium oxide crystal is 10 nm to 1 mm.

[0015] Another aspect of the embodiments of the present invention provides a gallium oxide crystal, including: a sapphire substrate having a specific bidirectional tilt angle; a gallium oxide crystal grown on the sapphire substrate, where the surface of the gallium oxide crystal is used for depositing a functional material to obtain a target device.

[0016] Optionally, the specific tilt angle of the sapphire substrate includes the tilt angle of the C plane towards the a plane and the tilt angle of the C plane towards the m plane. Among them, the atomic spacing and atomic step height corresponding to different tilt angles are different.

[0017] (III) Beneficial effects

[0018] The gallium oxide crystal and its heteroepitaxial method provided by the present invention at least include the following beneficial effects:

[0019] The heteroepitaxial method of the gallium oxide crystal provided by the present invention introduces a three-dimensional torsion-oriented design to prepare a sapphire substrate with a specific bidirectional tilt angle. The atomic spacing and atomic step height corresponding to different tilt angles in the sapphire substrate are different, thereby effectively restricting the in-plane growth anisotropy of β-phase gallium oxide. Growing a gallium oxide crystal on a sapphire substrate with a specific bidirectional tilt angle can effectively improve the consistency of the growth orientation of β-phase gallium oxide crystals, thereby improving the quality of gallium oxide crystals. Description of the drawings

[0020] Figure 1 Schematically shows a flowchart of the heteroepitaxial method of the gallium oxide crystal provided by the embodiments of the present invention;

[0021] Figure 2 Schematically shows a schematic diagram of the polishing processing direction of the sapphire substrate provided by the embodiments of the present invention;

[0022] Figure 3 Schematically shows the gallium oxide growth surface of the sapphire substrate with a specific tilt angle in the embodiments of the present invention;

[0023] Figure 4 Schematically shows the structural diagram of the gallium oxide crystal provided by the embodiments of the present invention. Detailed implementation manners

[0024] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Apparently, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0025] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The terms "comprising", "including" and the like used herein indicate the presence of the described features, steps, operations and / or components, but do not preclude the presence or addition of one or more other features, steps, operations or components.

[0026] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed" and the like shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral one; it may be a mechanical connection, an electrical connection or a communication connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention may be understood according to specific circumstances.

[0027] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the subsystem or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0028] Throughout the drawings, the same elements are denoted by the same or similar reference numerals. When it may cause confusion in the understanding of the present invention, the conventional structures or configurations will be omitted. In addition, the shapes, sizes and positional relationships of the components in the drawings do not reflect the actual sizes, proportions and actual positional relationships. Further, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claims.

[0029] Similarly, to streamline the present invention and assist in understanding one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. Descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0030] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0031] Figure 1 A flowchart of a method for heteroepitaxy of gallium oxide crystals provided by an embodiment of the present invention is schematically shown.

[0032] As Figure 1 shown, the method for heteroepitaxy of gallium oxide crystals provided by an embodiment of the present invention includes operation S110 to operation S130.

[0033] In operation S110, a sapphire substrate with a specific bi-directional tilt angle is prepared.

[0034] In some embodiments, operation S110 includes: determining the crystal structure, crystal phase, and crystal plane of the substrate. Performing a polishing process on the substrate to obtain a sapphire substrate with a specific bi-directional tilt angle. The polished sapphire substrate has a bi-directional tilt angle with respect to both the C-plane towards the a-plane and the C-plane towards the m-plane. The atomic spacing and atomic step height corresponding to different tilt angles are different, where the C-plane is the basal plane.

[0035] In operation S120, gallium oxide crystals are grown on the sapphire substrate.

[0036] In some embodiments, operation S120 includes: determining the matching relationship between the crystal direction of the substrate and the growth direction of the gallium oxide crystals. Growing gallium oxide crystals on the sapphire substrate based on the matching relationship. Wherein, the thickness of the gallium oxide crystals is 10 nm to 1 mm, and the regulation range of the carrier concentration of gallium oxide is 10 14 ~10 20 cm -3 .

[0037] In operation S130, a functional material is deposited on the gallium oxide crystal to obtain a target device.

[0038] In some embodiments, after the growth of the gallium oxide crystal is completed, a functional material can also be deposited on the gallium oxide crystal to obtain a target device. Among them, the target device can be, for example, typical power devices such as a transistor (MOSFET), a Schottky diode (SBD), etc. When preparing a MOSFET, gallium oxide can be used as a substrate material; when preparing an SBD, gallium oxide can be used as the bottom layer or insulating layer of the device. By depositing other functional materials (such as metals, semiconductors, etc.) on the surface of the gallium oxide crystal, a target device with specific functions is prepared.

[0039] In another embodiment, the gallium oxide crystal can also be prepared into a gallium oxide stacked film, which is composed of multiple layers of gallium oxide films stacked together and can be used in the fields of optoelectronic devices, optical devices, etc. During the preparation process, the stacking of multiple layers of gallium oxide can be achieved by controlling the deposition conditions and layer thickness. The thickness and properties of each layer of gallium oxide film can be adjusted according to specific application requirements.

[0040] The method for heteroepitaxy of gallium oxide crystals provided by the present invention makes the atomic spacing and atomic step height corresponding to different tilt angles in the sapphire substrate different by preparing a sapphire substrate with a specific bi-tilt angle. When the substrate has a specific bi-tilt angle, a certain strain will be introduced into the lattice, so that the growth of gallium oxide crystals is restricted during the growth process, effectively reducing the in-plane growth anisotropy of β-phase gallium oxide and improving the quality of gallium oxide crystals.

[0041] Figure 2 Schematically shows a schematic diagram of the polishing processing direction of the sapphire substrate provided by the embodiment of the present invention.

[0042] As Figure 2 shown, the polished sapphire substrate in the embodiment of the present invention includes a tilt angle of the C plane towards the a plane and a tilt angle of the C plane towards the m plane. In the specific implementation process, the substrate is polished to obtain a sapphire substrate with a specific tilt angle, including: cleaning the surface of the substrate; adjusting the parameters of the polishing machine according to the properties of the substrate and the target polishing effect; polishing the surface of the substrate based on the polishing machine to obtain a sapphire substrate with a specific tilt angle.

[0043] Cleaning the substrate surface can ensure that the surface of the sapphire substrate is flat, clean, free of impurities and defects. According to the surface properties and polishing effect of the substrate, a suitable polishing pad and polishing liquid are selected, and the parameters of the polishing machine are adjusted. Then, the substrate surface is polished by the polishing machine, so that the polishing pad is in uniform contact with the substrate surface and starts to move along a predetermined direction, where the predetermined direction is the intermediate direction between the two non-polar planes of the sapphire substrate. Further, during the polishing process, the polishing depth and uniformity can also be monitored in real time to adjust the polishing parameters in real time to ensure the accuracy of polishing.

[0044] In the embodiments of the present disclosure, the angle of the polishing machine can be determined according to the required deflection angles of the C plane towards the a plane and the C plane towards the m plane. By adjusting the angle of the polishing machine, the required deflection angle is formed between the polishing machine and the intermediate direction of the non-polar plane of the sapphire substrate.

[0045] Then, the substrate is placed on the polishing machine and polished according to the set angle, so as to obtain a sapphire substrate with a deflection angle of the C plane towards the a plane and a deflection angle of the C plane towards the m plane, where the atomic spacing and atomic steps corresponding to different deflection angles are different. The included angle between the polished surface of the sapphire substrate with a specific bidirectional deflection angle and the C plane of the sapphire substrate ranges from 0.1° to 30°.

[0046] After obtaining the polished sapphire substrate, the polished sapphire substrate needs to be subjected to high-temperature annealing to remove the oxides on the surface of the sapphire substrate, reduce the interference of the oxides on the epitaxial growth, and improve the quality of crystal growth.

[0047] Figure 3 Schematically shows the gallium oxide growth surface on the sapphire substrate with a specific deflection angle in the embodiments of the present invention.

[0048] As Figure 3 shown, gallium oxide is grown on the surface of the sapphire substrate with a specific bidirectional deflection angle after high-temperature annealing treatment. It should be noted that when growing gallium oxide, since the sapphire substrate has a bidirectional specific deflection angle, therefore, when growing gallium oxide, it is necessary to determine the matching relationship between the crystal direction of the substrate and the crystal growth direction of gallium oxide, and grow gallium oxide on the sapphire substrate based on the matching relationship, so as to improve the quality of heteroepitaxial gallium oxide crystals.

[0049] In the specific implementation process, the growth methods of gallium oxide can include, for example, halide vapor phase epitaxy (HVPE), mist chemical vapor deposition (Mist-CVD), metalorganic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), low-pressure chemical vapor deposition (LPCVD), laser pulse deposition (PLD), high-temperature physical vapor transport (PVT), magnetron sputtering (Sputtering), etc.

[0050] The grown gallium oxide crystal has a thickness of 10 nm to 1 mm, and the regulation range of the carrier concentration is 10 14 ~10 20 cm -3 . During the growth process of the gallium oxide crystal, the types of oxygen sources used can be, for example, oxygen, water, ozone, etc. The growth temperature is 600 - 1200 °C, and the specific temperature depends on the growth method and the required crystal quality, which is not limited in this invention. During the growth process of the gallium oxide crystal, the carrier concentration and type of the gallium oxide crystal are adjusted by dopants. Among them, the types of dopants can include elements such as silicon (Si), germanium (Ge), tin (Sn), iron (Fe), carbon (C), cobalt (Co), nitrogen (N), etc.

[0051] Based on the above heterogeneous epitaxial method of gallium oxide crystal, an embodiment of the present invention also provides a gallium oxide crystal.

[0052] Figure 4 Schematically shows the structural diagram of the gallium oxide crystal provided by the embodiment of the present invention.

[0053] As Figure 4 shown, the gallium oxide crystal includes a sapphire substrate and a gallium oxide crystal.

[0054] In some embodiments, the substrate is a sapphire substrate with a two-way tilt angle of C-plane biased towards a-plane and C-plane biased towards m-plane. Among them, the atomic spacing and atomic step height corresponding to different tilt angles are different. The included angle range between the polished surface of the sapphire substrate with a specific two-way tilt angle and the C-plane of the sapphire substrate is 0.1° - 30°.

[0055] The tilt angle of the sapphire substrate introduces a certain strain in the lattice and is restricted during the thin film growth process, so that the β-phase gallium oxide crystal grown on this substrate is affected by the lattice structure and is more inclined to follow the structure of the substrate surface during in-plane growth, thereby restricting the in-plane growth anisotropy of the gallium oxide crystal and making its growth direction restricted by the substrate, effectively improving the quality of the gallium oxide crystal. As Figure 4 can be seen, the orientation consistency of the gallium oxide crystal prepared on the sapphire substrate with a specific two-way tilt angle is significantly improved and the dislocation density is significantly reduced.

[0056] The gallium oxide crystal grows on a sapphire substrate with a specific two-way tilt angle, with a thickness of 10 nm to 1 mm and a regulation range of the carrier concentration of 10 14 ~10 20 cm -3 .

[0057] Technicians can deposit functional materials on the gallium oxide crystal according to their own needs to obtain the target device. Among them, the target device can be, for example, a typical power device such as a transistor (MOSFET), a Schottky diode (SBD), etc. When preparing a MOSFET, gallium oxide can be used as a substrate material; when preparing an SBD, gallium oxide can be used as the bottom layer or insulating layer of the device. By depositing other functional materials (such as metals, semiconductors, etc.) on the surface of the gallium oxide crystal, a target device with specific functions is prepared. In addition, the gallium oxide crystal can also be a gallium oxide laminated film, which is composed of multiple layers of gallium oxide films stacked together and can be used in the fields of optoelectronic devices, optical devices, etc. During the preparation process, the stacking of multiple layers of gallium oxide can be achieved by controlling the deposition conditions and layer thickness. The thickness and properties of each gallium oxide film can be adjusted according to specific application requirements.

[0058] The gallium oxide crystal provided by the embodiment of the present invention is grown on a sapphire substrate with a specific bidirectional angle and has a consistent growth orientation, and its crystal structure is more complete and orderly. On this basis, when preparing a power device, the efficiency and performance of the power device can be effectively improved, which helps to achieve the consistency and stability of the device.

[0059] The specific embodiments described above further elaborate on the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for heteroepitaxy of gallium oxide crystals, characterized in that, Including: Preparing a sapphire substrate with a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane; Growing a gallium oxide crystal on the sapphire substrate; Depositing a functional material on the gallium oxide crystal to obtain a target device; The preparing of the sapphire substrate with a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane includes: determining the positions of two non-polar planes of the sapphire substrate and the intermediate direction between the two non-polar plane positions; polishing along the intermediate direction of the two non-polar planes of the sapphire substrate; wherein, the included angle between the polished surface of the sapphire substrate and the C plane ranges from 0.1° to 30°, and the polished sapphire substrate has a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane at the same time, wherein the atomic spacing and atomic step height corresponding to different angular deviations are different.

2. The method according to claim 1, characterized in that, The preparing of the sapphire substrate with a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane includes: Determining the crystal structure, crystal phase and crystal plane of the substrate; Performing a polishing treatment on the substrate to obtain a sapphire substrate with a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane.

3. The method according to claim 2, wherein The performing of the polishing treatment on the substrate to obtain a sapphire substrate with a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane includes: Cleaning the surface of the substrate; Adjusting the parameters of the polishing machine according to the properties of the substrate and the target polishing effect; Polishing the surface of the substrate based on the polishing machine to obtain a sapphire substrate with a bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane.

4. The method according to claim 3, characterized in that, The adjusting of the parameters of the polishing machine includes: Adjusting the polishing angle of the polishing machine according to the preset bidirectional angular deviation of the C plane towards the a plane and the C plane towards the m plane.

5. The method according to claim 1, wherein The method further includes: performing a high-temperature treatment on the polished sapphire substrate.

6. The method according to claim 5, characterized in that The growing of the gallium oxide crystal on the sapphire substrate includes: Determining the matching relationship between the crystal direction of the substrate and the growth direction of the gallium oxide crystal; Growing a gallium oxide crystal on the sapphire substrate based on the matching relationship, wherein the thickness of the gallium oxide crystal is 10 nm to 1 mm.

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