Sapphire substrate-gallium oxide ordered thin film composite material and preparation method thereof

Abstract

The invention discloses a sapphire substrate-gallium oxide ordered thin film composite material and a preparation method thereof. A magnetron sputtering technology is adopted, a gallium oxide thin film is sputtered on a sapphire substrate, then high-temperature oxidation treatment is carried out, and the ordered thin film composite material is obtained. Ordered distribution is realized by means of lattice broken bonds on the surface of the sapphire substrate, and gallium oxide keeps inheritance to the crystal structure of the substrate, so that an ordered film of gallium oxide is formed on the surface of the substrate. The sapphire substrate-gallium oxide ordered thin film composite material prepared by the invention can replace gallium oxide single crystals and is used as a novel gallium oxide semiconductor material.

Description

Technical Field

[0001] This invention belongs to the field of functional materials, specifically relating to an ordered gallium oxide thin film with sapphire as a substrate and its preparation method. Background Technology

[0002] Gallium oxide single-crystal wafers are important semiconductor materials. Currently, gallium oxide single-crystal wafers are basically produced using the high-temperature melt-pulling method, which involves melting high-purity gallium oxide powder at high temperatures, then pulling a pre-placed seed crystal from a crucible to grow gallium oxide single crystals, which are then cut to obtain gallium oxide single-crystal wafers.

[0003] This fabrication process is widely used in the production of crystalline materials such as single-crystal silicon, silicon carbide, and sapphire, but it is not suitable for developing gallium oxide semiconductor materials. The main reason is that silicon, silicon carbide, and sapphire semiconductor wafers are readily available and inexpensive, with no limiting factors in supply and demand; while gallium is a relatively rare and dispersed element, with no independent gallium deposits in nature, and it can only be recovered as a byproduct of the aluminum smelting industry. Since the market capacity for metallic aluminum is essentially fixed, the demand and production of aluminum are unlikely to increase significantly, and as a byproduct of aluminum, the supply of gallium and gallium oxide is also unlikely to increase significantly.

[0004] Gallium's scarcity and refining difficulty keep its price high, and with the widespread application of gallium-based semiconductor materials such as gallium oxide and gallium nitride, its price is expected to rise rapidly. Developing gallium oxide semiconductor materials using existing technologies faces challenges in securing raw material supplies and maintaining a competitive price. Therefore, replacing three-dimensional single-crystal structures with two-dimensional ordered thin films represents the future direction for gallium-based semiconductor materials. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of limited production and high cost of gallium oxide single wafers in the prior art, and to provide a sapphire substrate-gallium oxide ordered thin film composite material and its preparation method that can replace gallium oxide single wafers.

[0006] To achieve the above-mentioned objectives, the specific technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a sapphire substrate-gallium oxide ordered thin film composite material, wherein gallium is orderly distributed on the sapphire surface by means of lattice bond breaking on the sapphire substrate surface, thereby forming an ordered gallium oxide thin film on the substrate surface, constituting a sapphire substrate-gallium oxide ordered thin film composite material.

[0007] Secondly, the present invention provides a method for preparing a sapphire substrate-gallium oxide ordered thin film composite material, the preparation steps of which are as follows: First, a sapphire single-crystal wafer with a polished and cleaned surface is used as a thin-film substrate, and a uniform gallium oxide film is deposited on the polished surface of the thin-film substrate by magnetron sputtering. Then, the sapphire substrate coated with gallium oxide film is placed in a heating furnace and heated to 750~950℃ in oxygen gas for heat treatment. After the heat treatment is completed, it is naturally cooled to room temperature to obtain the sapphire substrate-gallium oxide ordered thin film composite material.

[0008] As a preferred embodiment of the second aspect above, the thin film substrate is a thin sheet made of sapphire crystal by cutting and single-sided polishing, and its surface needs to be ultrasonically cleaned and dried with nitrogen before magnetron sputtering.

[0009] As a preferred embodiment of the second aspect above, the ultrasonic cleaning is performed sequentially in acetone, anhydrous ethanol, and deionized water.

[0010] As a preferred embodiment of the second aspect above, the specific method of the magnetron sputtering process is as follows: placing the thin film substrate in the vacuum chamber of the magnetron sputtering equipment, and evacuating to 70°C. 10 -7 ~1 10 -6 After achieving a vacuum level of Torr, the temperature is increased to 500-700℃ at a heating rate of 3-8℃ / min, followed by Ar gas sputtering pretreatment for 15-30min to clean the substrate surface. Then, using gallium oxide ceramic with a purity of not less than 99.99% as the target material, and a gas mixture of Ar and O2 with a gas pressure of 3-10 mTorr as the sputtering atmosphere, sputtering is performed at a sputtering power of 100-200W for 30-120min to deposit a uniform gallium oxide film on the substrate. After the film deposition is completed, the temperature is cooled to room temperature to obtain a sapphire substrate coated with a gallium oxide film.

[0011] As a preferred embodiment of the second aspect above, in the magnetron sputtering process, the preferred operating parameters of the magnetron sputtering coating machine are: sputtering power controlled at 150W, Ar:O2 gas volume ratio in the sputtering atmosphere at 7:3, gas pressure at 6 mTorr, and gas flow velocity at 90 cm⁻¹. 3 / min, sputtering time 60min.

[0012] As a preferred embodiment of the second aspect above, the heating furnace is an airtight quartz tube furnace or an airtight corundum tube furnace.

[0013] As a preferred embodiment of the second aspect above, the oxygen source gas is carbon dioxide or oxygen.

[0014] As a preferred embodiment of the second aspect above, the heat treatment adopts a stepped heating method, in which the sapphire substrate coated with gallium oxide film in the heating furnace is heated from room temperature to 750~950°C, and the temperature is held constant for 1~2 hours at intervals of 100~200°C during the heating process, and the cumulative holding time during the heating process is not less than 6 hours.

[0015] Thirdly, the present invention provides a sapphire substrate-gallium oxide ordered thin film composite material prepared by the preparation method described in any of the second aspects above.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses a sapphire substrate-gallium oxide ordered thin film composite material and its preparation method. The method employs magnetron sputtering technology to sputter a gallium oxide thin film onto a sapphire substrate, followed by high-temperature oxidation to obtain the ordered thin film composite material. This invention achieves ordered distribution by utilizing the lattice breakage on the sapphire substrate surface, allowing gallium oxide to maintain its inheritance of the substrate's crystal structure, thereby forming an ordered gallium oxide thin film on the substrate surface. The sapphire substrate-gallium oxide ordered thin film composite material prepared by this invention can replace gallium oxide single crystals as a novel gallium oxide semiconductor material. Attached Figure Description

[0017] Figure 1 The X-ray diffraction pattern of the composite thin film material in Example 1; Figure 2 The X-ray diffraction pattern of the composite thin film material in Example 2; Figure 3 The image shows the X-ray diffraction pattern of the composite thin film material in Example 3. Detailed Implementation

[0018] The present invention will be further described and illustrated below with reference to specific embodiments. Technical features in various implementations can be combined without conflict, and do not constitute a limitation on the present invention.

[0019] This invention provides a sapphire substrate-gallium oxide ordered thin film composite material. In this material, gallium is orderly distributed on the sapphire surface through the lattice breakage of the sapphire substrate, thereby forming an ordered gallium oxide thin film on the substrate surface, constituting a sapphire substrate-gallium oxide ordered thin film composite material. In other words, in this composite material, the gallium oxide film is synthesized in situ on the sapphire surface, and the arrangement of gallium atoms is constrained by the Al-O broken bonds on the substrate surface, inheriting the ordered nature of the substrate lattice. The ordered gallium oxide thin film and the sapphire substrate lattice have an inherited epitaxial relationship.

[0020] In this invention, sapphire is a single crystal formed by the high-temperature crystallization of Al₂O₃ melt, while the substrate is a thin sheet made by cutting and polishing the sapphire crystal. Sapphire's chemical composition is aluminum oxide, a cheap and widely available industrial raw material, while gallium is a rare and dispersed element, with a global annual production of only a few hundred tons of gallium oxide. Replacing gallium oxide single crystals with sapphire substrate-gallium oxide ordered thin film composites means replacing millimeter-thick wafers with nanometer-thick films, significantly reducing gallium oxide usage, which is beneficial for ensuring raw material supply and slowing the depletion of this rare resource. Furthermore, gallium cannot form independent minerals in nature, not only due to its low abundance but, more importantly, its poor crystallinity. Gallium has an average abundance of 13 ppm in the Earth's crust and no independent minerals; while boron and beryllium, with even lower abundances, can aggregate into large deposits as independent minerals such as borax and beryl. Gallium's poor crystallinity means that the artificial synthesis of gallium oxide crystals is technically difficult, costly, and has a low yield. This invention uses a sapphire substrate-gallium oxide ordered thin film composite material to replace gallium oxide single crystal, which can reduce the technical threshold and preparation cost of gallium oxide semiconductor material application, and is conducive to the promotion and application of this material.

[0021] The above-mentioned sapphire substrate-gallium oxide ordered thin film composite material of the present invention can be prepared by the following method: 1) Polish the surface of a sapphire single crystal wafer cut to an appropriate thickness, and then perform ultrasonic cleaning in acetone, anhydrous ethanol and deionized water in sequence to obtain a thin film substrate.

[0022] 2) A uniform gallium oxide film is deposited on the polished surface of a thin film substrate by magnetron sputtering.

[0023] The specific method of the magnetron sputtering process in this invention can be implemented as follows: the cleaned thin film substrate is rapidly transferred to the vacuum chamber of the magnetron sputtering equipment, and the vacuum level is 70°C. 10 -7 ~1 10 -6 After achieving a vacuum level of Torr, the temperature is increased to 500-700℃ at a heating rate of 3-8℃ / min, followed by Ar gas sputtering pretreatment for 15-30min to clean the substrate surface. Then, using gallium oxide ceramic with a purity of not less than 99.99% as the target material, and a gas mixture of Ar and O2 with a gas pressure of 3-10 mTorr as the sputtering atmosphere, sputtering is performed at a sputtering power of 100-200W for 30-120min to deposit a uniform gallium oxide film on the substrate. After the film deposition is completed, the heating is turned off and the temperature is lowered to room temperature to obtain a sapphire substrate coated with a gallium oxide film.

[0024] The magnetron sputtering equipment can be a commercially available magnetron ion sputtering coating machine, such as the Line PVD750 coating machine from Cortex Corporation. The operating parameters of the aforementioned magnetron sputtering coating machine can be optimized and adjusted according to actual results. Here, a further preferred setting is: sputtering power controlled at 150W, Ar:O2 gas volume ratio in the sputtering atmosphere of 7:3, gas pressure of 6 mTorr, and gas velocity of 90 cm⁻¹. 3 / min, sputtering time 60min.

[0025] During sputtering, the gallium oxide target evaporates and ionizes into plasma under the influence of Ar ions, forming a gallium oxide precipitate upon contact with the substrate surface. The sapphire substrate surface contains numerous broken Al-O bonds. Due to the identical valence states and similar ionic radii of aluminum and gallium, the attractive force of the Al-O bonds on the substrate provides the sapphire surface with chemical attraction and wettability for the evaporated gallium oxide. Furthermore, under the constraint of an external magnetic field, gallium oxide does not agglomerate on the sapphire surface but is uniformly distributed and arranged in an ordered manner along the crystal lattice orientation of the sapphire surface.

[0026] 3) Place the sapphire substrate coated with gallium oxide film into a heating furnace and heat it to 750~950℃ in oxygen gas for heat treatment. After the heat treatment is completed, allow it to cool naturally to room temperature to obtain the sapphire substrate-gallium oxide ordered thin film composite material.

[0027] In this invention, the thin film substrate is a sapphire crystal sheet that has been cut and polished on one side. Before magnetron sputtering, its surface needs to be ultrasonically cleaned and dried with nitrogen. Ultrasonic cleaning is preferably performed sequentially in acetone, anhydrous ethanol, and deionized water.

[0028] The heating furnace used in this invention is an airtight quartz tube furnace or an airtight corundum tube furnace. The oxygen source gas used is carbon dioxide (CO2) or oxygen (O2). Using an oxygen source gas as a protective atmosphere can prevent atmospheric nitrogen from entering the gallium oxide lattice and improve the purity of the gallium oxide thin film.

[0029] In addition, a stepped heating method is required during the heat treatment process. Specifically, the sapphire substrate coated with gallium oxide film is heated from room temperature to 750~950℃ in the furnace. During the heating process, the temperature is held constant for 1~2 hours at intervals of 100~200℃, and the total holding time during the heating process is not less than 6 hours.

[0030] Gallium oxide (GaO) is an ultra-wide bandgap semiconductor material with excellent properties, making it suitable for high-voltage power electronic devices due to its high-temperature stability, high-frequency power, and low energy loss. However, due to the scarcity of gallium, the production volume of traditional GaO single crystal wafers is limited and the cost is high. The sapphire substrate-gaO ordered thin film composite material prepared in this invention can replace GaO single crystals and serve as a novel GaO semiconductor material for applications such as high-voltage power electronic devices.

[0031] The specific implementation of the present invention will be described in detail below with reference to the embodiments.

[0032] Example 1 The C-side sapphire was cut into 3cm x 3cm slices, which were then ultrasonically cleaned sequentially in acetone, anhydrous ethanol, and deionized water. After being dried under high-pressure nitrogen, these slices served as the thin film substrate. The substrate was immediately transferred to the vacuum chamber of a magnetron sputtering apparatus, and a vacuum was drawn up to 70°C. 10 -7 After achieving a basic vacuum level of Torr, the thin film substrate was heated to 650°C at a heating rate of 5°C / min and maintained at this temperature for 20 minutes underwent Ar pre-sputtering to clean the substrate surface. Then, gallium oxide ceramic with a purity of not less than 99.99% was used as the target, and an Ar:O2 mixed gas flow with a volume ratio of 7:3 was used as the sputtering atmosphere at a gas pressure of 6 mTorr and a gas flow velocity of 90 cm⁻¹. 3 Sputtering was performed at a sputtering power of 150 W for 60 minutes to deposit a uniform gallium oxide film on the substrate. After the gallium oxide film deposition was complete, the heating was turned off, and the sample was removed after cooling to room temperature, resulting in a sapphire substrate coated with gallium oxide. Finally, the sapphire substrate coated with gallium oxide was placed in a heating furnace, and a step heating process was carried out in an oxygen atmosphere. The sample was gradually heated from room temperature to 800℃ at a heating rate of 10℃ / min to achieve heat treatment. During the step heating process, the temperature was maintained at 800℃ for 1 hour at every 100℃ interval. After maintaining the temperature at 800℃ for 1 hour, the heat treatment was completed, and the sample was naturally cooled to room temperature to obtain a sapphire substrate-gallium oxide ordered thin film composite material.

[0033] XRD tests were performed on the sapphire substrate-gallium oxide ordered thin film composite material obtained in this embodiment. Figure 1 The diffraction pattern of the composite film is shown, revealing that gallium oxide mainly grows along the (-201) crystal plane, and the diffraction peak at approximately 42 degrees is that of sapphire. Therefore, this embodiment forms an ordered gallium oxide film on the surface of a sapphire substrate, and this sapphire substrate-gallium oxide ordered film composite material can serve as a novel gallium oxide semiconductor material.

[0034] Example 2 The C-face sapphire was cut into 3cm x 3cm slices, which were then ultrasonically cleaned sequentially in acetone, anhydrous ethanol, and deionized water. After being dried under high-pressure nitrogen, these slices served as the thin film substrate. The substrate was immediately transferred to the vacuum chamber of a magnetron sputtering apparatus, and a vacuum was drawn until 1... 10 -6 After achieving a base vacuum of Torr, the thin film substrate was heated to 650°C at a heating rate of 5°C / min and maintained at this temperature for 15 minutes for Ar pre-sputtering to clean the substrate surface. Then, gallium oxide ceramic with a purity of not less than 99.99% was used as the target, and an Ar:O2 mixed gas flow with a volume ratio of 7:3 was used as the sputtering atmosphere at a gas pressure of 6 mTorr and a gas flow velocity of 90 cm⁻¹. 3 Sputtering was performed at a sputtering power of 180 W for 120 minutes to deposit a uniform gallium oxide film on the substrate. After the gallium oxide film deposition was complete, the heating was turned off, and the sample was removed after cooling to room temperature, resulting in a sapphire substrate coated with gallium oxide. Finally, the sapphire substrate coated with gallium oxide was placed in a heating furnace, and a step heating process was carried out in an oxygen atmosphere. The sample was gradually heated from room temperature to 750°C at a heating rate of 5°C / min to achieve heat treatment. During the step heating process, the temperature was maintained at 150°C for 1.5 hours. Finally, after maintaining the temperature at 750°C for 2 hours, the heat treatment was completed, and the sample was naturally cooled to room temperature to obtain a sapphire substrate-gallium oxide ordered thin film composite material.

[0035] XRD tests were performed on the sapphire substrate-gallium oxide ordered thin film composite material obtained in this embodiment. Figure 2 The diffraction pattern of the composite film is shown, revealing that gallium oxide mainly grows along the (-201) crystal plane, with a small amount growing along the (-401) and (-601) planes. Therefore, this embodiment forms an ordered gallium oxide film on the surface of a sapphire substrate, and this sapphire substrate-gallium oxide ordered film composite material can serve as a novel gallium oxide semiconductor material.

[0036] Example 3 The C-face sapphire was cut into 3cm x 3cm slices, which were then ultrasonically cleaned sequentially in acetone, anhydrous ethanol, and deionized water. After being dried under high-pressure nitrogen, these slices served as the thin film substrate. The substrate was immediately transferred to the vacuum chamber of a magnetron sputtering apparatus, and a vacuum was drawn until 1... 10 -6After achieving a base vacuum of Torr, the thin film substrate was heated to 650°C at a heating rate of 5°C / min and maintained at this temperature for 15 minutes for Ar pre-sputtering to clean the substrate surface. Then, gallium oxide ceramic with a purity of not less than 99.99% was used as the target, and an Ar:O2 mixed gas flow with a volume ratio of 7:3 was used as the sputtering atmosphere at a gas pressure of 6 mTorr and a gas flow velocity of 90 cm⁻¹. 3 Sputtering was performed at a sputtering power of 150 W for 40 minutes to deposit a uniform gallium oxide film on the substrate. After the gallium oxide film deposition was complete, the heating was turned off, and the sample was removed after cooling to room temperature, resulting in a sapphire substrate coated with gallium oxide. Finally, the sapphire substrate coated with gallium oxide was placed in a heating furnace, and a step heating process was carried out in an oxygen atmosphere. The sample was gradually heated from room temperature to 800℃ at a heating rate of 8℃ / min to achieve heat treatment. During the step heating process, the temperature was maintained at 200℃ for 2 hours. After maintaining the temperature at 800℃ for 2 hours, the heat treatment was completed, and the sample was naturally cooled to room temperature to obtain a sapphire substrate-gallium oxide ordered thin film composite material.

[0037] XRD tests were performed on the sapphire substrate-gallium oxide ordered thin film composite material obtained in this embodiment. Figure 3 The diffraction pattern of the composite film is shown, revealing that gallium oxide mainly grows along the (-201) crystal plane. Therefore, this embodiment forms an ordered gallium oxide film on the surface of a sapphire substrate, and this sapphire substrate-gallium oxide ordered film composite material can serve as a novel gallium oxide semiconductor material.

[0038] The embodiments described above are merely some preferred embodiments of the present invention, but are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A sapphire substrate-gallium oxide ordered thin film composite material, characterized in that, Gallium is distributed in an ordered manner on the surface of sapphire by means of lattice breaking on the surface of the sapphire substrate, thereby forming an ordered thin film of gallium oxide on the substrate surface, which constitutes a sapphire substrate-gallium oxide ordered thin film composite material.

2. A method for preparing a sapphire substrate-gallium oxide ordered thin film composite material, characterized in that, Its preparation steps are as follows: First, a sapphire single-crystal wafer with a polished and cleaned surface is used as a thin-film substrate, and a uniform gallium oxide film is deposited on the polished surface of the thin-film substrate by magnetron sputtering. Then, the sapphire substrate coated with gallium oxide film is placed in a heating furnace and heated to 750~950℃ in oxygen gas for heat treatment. After the heat treatment is completed, it is naturally cooled to room temperature to obtain the sapphire substrate-gallium oxide ordered thin film composite material.

3. The preparation method according to claim 2, characterized in that, The thin film substrate is a thin sheet made of sapphire crystal through cutting and single-sided polishing, and its surface needs to be ultrasonically cleaned and dried with nitrogen before magnetron sputtering.

4. The preparation method according to claim 3, characterized in that, The ultrasonic cleaning process needs to be carried out sequentially in acetone, anhydrous ethanol, and deionized water.

5. The preparation method according to claim 2, characterized in that, The specific method of the magnetron sputtering process is as follows: the thin film substrate is placed in the vacuum chamber of the magnetron sputtering equipment, and the vacuum level is 70°C. 10 -7 ~1 10 -6 After achieving a vacuum level of Torr, the temperature is increased to 500-700℃ at a heating rate of 3-8℃ / min, followed by Ar gas sputtering pretreatment for 15-30min to clean the substrate surface. Then, using gallium oxide ceramic with a purity of not less than 99.99% as the target material, and a gas mixture of Ar and O2 with a gas pressure of 3-10 mTorr as the sputtering atmosphere, sputtering is performed at a sputtering power of 100-200W for 30-120min to deposit a uniform gallium oxide film on the substrate. After the film deposition is completed, the temperature is cooled to room temperature to obtain a sapphire substrate coated with a gallium oxide film.

6. The preparation method according to claim 2, characterized in that, In the magnetron sputtering process, the preferred operating parameters of the magnetron sputtering coating machine are: sputtering power controlled at 150W, Ar:O2 gas volume ratio in the sputtering atmosphere at 7:3, gas pressure at 6 mTorr, and gas flow velocity at 90 cm⁻¹. 3 / min, sputtering time 60min.

7. The preparation method according to claim 2, characterized in that, The heating furnace is an airtight quartz tube furnace or an airtight corundum tube furnace.

8. The preparation method according to claim 2, characterized in that, The oxygen source gas is either carbon dioxide or oxygen.

9. The preparation method according to claim 2, characterized in that, The heat treatment employs a stepped heating method, in which the sapphire substrate coated with gallium oxide film is heated from room temperature to 750~950℃ in a heating furnace, and the temperature is held constant for 1~2 hours at intervals of 100~200℃ during the heating process, with a total holding time of no less than 6 hours.

10. A sapphire substrate-gallium oxide ordered thin film composite material prepared by the preparation method according to any one of claims 2 to 9.

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