A method for planarizing epitaxial diamond semiconductor

Abstract

The application provides a preparation method of a flat epitaxial diamond semiconductor and relates to the technical field of diamond semiconductor preparation. The preparation method comprises the following steps: cleaning a microwave plasma device chamber, pretreating a single crystal diamond substrate, etching the single crystal diamond substrate and preparing a hydrogen-terminated diamond semiconductor, wherein a magnetic field generated by a magnetic excitation coil is used to constrain the microwave plasma in the microwave vapor deposition device, so that carbon atoms are uniformly and rapidly deposited on the single crystal diamond substrate, and finally, a single crystal diamond epitaxial layer with a flat surface is obtained. The preparation method of the application can synergistically optimize the carrier mobility, surface density and square resistance of the hydrogen-terminated diamond semiconductor, is simple and easy to operate, has low cost and low energy consumption, is high in efficiency, and is beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] This invention relates to the technical field of diamond semiconductor fabrication, and in particular to a method for fabricating planar epitaxial diamond semiconductors. Background Technology

[0002] Diamond possesses numerous superior properties and is a promising ultra-wide bandgap semiconductor material, considered the optimal solution for future power device fabrication. Compared to traditional semiconductor materials, ultra-wide bandgap semiconductors theoretically offer advantages in extreme environments such as high temperature, high pressure, and strong radiation. However, during single-crystal diamond growth, changes in growth parameters often affect the plasma state in microwave vapor deposition equipment, reducing the uniformity and quality of the homogeneous diamond epitaxial layer. This, in turn, limits carrier transport in the hydrogen-terminated diamond conductive channel, reducing carrier mobility.

[0003] Meanwhile, the surface roughness of single-crystal diamond epitaxial layers significantly affects surface state density and carrier mobility, thereby influencing key parameters such as device switching characteristics, transconductance, and cutoff frequency. Therefore, post-diamond growth surface polishing is a common practice. However, due to the extreme hardness and surface inertness of diamond, efficient surface processing is difficult to achieve. Typically, single-crystal mechanical polishing results in varying degrees of sub-damage on the single-crystal diamond surface, often manifesting as crack layers and residual stress layers. The presence of these surface sub-damage layers introduces numerous defect states, leading to increased leakage current and reduced reliability. Therefore, achieving high-quality, flat diamond fabrication is considered a key technological challenge in improving the performance of diamond semiconductors. To obtain hydrogen-terminated diamonds with excellent performance, high-quality single-crystal diamonds, flat surfaces, and substrates free from substructural damage are essential requirements.

[0004] Fully leveraging the superior performance of hydrogen-terminated diamond semiconductor materials is a crucial prerequisite for driving breakthroughs in next-generation power electronic devices. However, optimizing the high-quality preparation of single-crystal diamond has always been a significant obstacle in the development of diamond semiconductor devices, especially in the hydrogen-termining stage. The currently common "epitaxy followed by polishing and then hydrogenation" method still has significant shortcomings. The polishing process easily causes lattice damage and defect exposure on the diamond surface, which is difficult to completely repair in subsequent hydrogenation treatment, thus affecting the uniformity and stability of the hydrogen terminator and restricting the full realization of the superior performance of diamond semiconductor materials. Currently, the growth of homoepitaxial diamond itself also faces many limitations. Due to factors such as plasma density, shape, and temperature uniformity, the thickness consistency of large-size single-crystal diamond epitaxial layers is poor. The growth rate of microwave vapor deposition is usually <5-10μm / h, and millimeter-thick films require hundreds of hours, resulting in high time costs. The high proportion of equipment depreciation and consumable costs such as gases further increases costs. The scheme of preparing hydrogen-terminated diamond semiconductors through high-quality epitaxy followed by polishing and hydrogenation has a long cycle and is accompanied by multiple problems such as mechanical polishing damage.

[0005] Chinese patent CN116190215A discloses a method for preparing a diamond semiconductor device. However, this method suffers from several technical defects, including interference from various deposition techniques, difficulty in precisely controlling the doping concentration, and difficulty in ensuring surface smoothness.

[0006] Chinese patent CN115424928A discloses diamond-based epitaxial structures and their preparation methods, as well as methods for preparing semiconductor devices. However, these preparation methods suffer from technical defects such as cumbersome multi-substrate processes, difficulty in controlling the filling accuracy of trench preparation, and persistent lattice mismatch issues.

[0007] Chinese patent CN113089093A discloses a method for forming a diamond semiconductor structure. However, this method has technical defects such as unresolved thick film growth cracking issues, stress concentration caused by multilayer diamond mismatch, and incompatibility of substrate materials.

[0008] Chinese patent CN117059475A discloses a method for preparing silicon-terminated diamond semiconductors. However, this method has technical defects such as high polishing time and cost, easy formation of redundant surface bonds, and poor surface flatness and stability. Summary of the Invention

[0009] The main objective of this invention is to address the technical problems in existing diamond semiconductor fabrication technologies, such as slow growth rate, poor uniformity, and difficulty in forming planar surfaces in diamond epitaxial layers. Therefore, a method for fabricating planar epitaxial diamond semiconductors is proposed, which solves the aforementioned problems.

[0010] The technical solution is as follows:

[0011] A method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0012] S1. Cleaning of microwave plasma equipment chamber: Place the molybdenum tray in a beaker, ultrasonically clean and dry it, place the cleaned molybdenum tray on the equipment deposition stage, introduce hydrogen gas and adjust the microwave power and chamber pressure, control the temperature and dry burn to eliminate impurities adsorbed on the chamber wall and obtain a clean chamber.

[0013] S2. Pretreatment of single-crystal diamond substrate: The copper clamp of the adhered diamond substrate is inserted into the fixture of the single-crystal mechanical polishing machine for mechanical polishing; then the mechanically polished diamond substrate is acid-washed and ultrasonically cleaned, and dried to obtain a clean diamond substrate.

[0014] S3. Single-crystal diamond substrate etching: The clean diamond substrate from S2 is placed into the clean molybdenum support chamber from S1. The chamber vacuum is reduced to 10 using a two-step vacuum method involving a forepump and a molecular pump. -7 Under Torr, after reaching the ultimate vacuum, the valve is closed and hydrogen gas is introduced to ignite and excite the plasma. The etching parameters are set to etch the single-crystal diamond substrate to obtain the etched diamond substrate.

[0015] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced, while the hydrogen flow rate remains constant and the oxygen flow rate is reduced. Methane is then introduced. Subsequently, the current in the magnetic coil is increased while the microwave power and chamber pressure are slowly increased. After the gas and plasma states within the chamber stabilize, the growth parameters are adjusted to generate a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0016] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, the hydrogenation process parameters are set for hydrogenation treatment, and finally a planarized hydrogen-terminated diamond semiconductor is obtained.

[0017] Optionally, in S1, ultrasonic cleaning is performed sequentially with acetone, anhydrous ethanol, and deionized water at an ultrasonic frequency of 40-60 kHz for 10-20 min; the flow rate of hydrogen gas is 400-600 sccm; the microwave power is adjusted to 4-6 kW; the chamber pressure is 150-160 Torr; the temperature is controlled at 850-950℃; and the chamber is left to burn for 3-4 hours.

[0018] Optionally, in S2, the mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 700-800g, and polishing for 20-30 minutes for rough polishing. Then, the load is changed to 500-600g, and polishing is performed for 10-20 minutes. The surface roughness of the diamond substrate after mechanical polishing is 0.4-0.6nm.

[0019] Optionally, in S2, acid washing uses a 98% sulfuric acid / nitric acid solution, and the polished sample needs to be placed in the sulfuric acid / nitric acid solution and heated to boiling for 20-30 minutes; ultrasonic cleaning is performed by sequentially using acetone, anhydrous ethanol and deionized water, with an ultrasonic frequency of 50-70 kHz and a time of 10-20 minutes.

[0020] Optionally, in S3, a two-step vacuum method using a backing pump and a molecular pump is employed to reduce the chamber vacuum to 10. -7 Below Torr: Turn on the forepump to evacuate the chamber vacuum to below 0 Torr, then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Torr below.

[0021] Optionally, in S3, the flow rate of hydrogen gas introduced through the closed valve is 300-500 sccm, and the etching parameters are set as follows: microwave power of 4-6 kW, chamber pressure of 140-150 Torr, control temperature of 880-920℃, hydrogen flow rate of 400-500 sccm, oxygen flow rate of 2-3 sccm, and etching time of 15-30 min.

[0022] Optionally, in S4, the microwave power, chamber pressure, and temperature within the cavity are all reduced to 33±2% of the etching parameters in S3. Specifically, the microwave power is adjusted to 3-4kW, the chamber pressure is adjusted to 120-130Torr, and the temperature is controlled at 750-800℃.

[0023] Optionally, when the gas and plasma states in the S4 chamber are stable, the magnetic coil current needs to reach 1-2A.

[0024] Optionally, the growth parameters in S4 can be adjusted as follows: microwave power of 4-6kW, chamber pressure of 140-150Torr, growth temperature of 830-860℃, hydrogen flow rate of 400-500sccm, methane flow rate of 10-30sccm, oxygen flow rate of 0.5-1.5sccm, and magnetic field current of 1-2A.

[0025] Optionally, the hydrogenation process parameters in S5 are set as follows: microwave power of 2-3kW, chamber pressure of 80-90Torr, hydrogenation temperature of 720-750℃, hydrogen flow rate of 400-500sccm, and hydrogenation time of 10-20min.

[0026] Optionally, S5 contains a planarized hydrogen-terminated diamond semiconductor with the following performance parameters: surface roughness of 0.3-0.5 nm, nitrogen impurity concentration of 1-2 ppb, hole mobility of 200-230 cm² / (V·s), stability at 200-300℃ for 60-90 h, and output power of 870-920 MW / cm². 2 It is suitable for high-frequency scenarios of up to 70-100Hz.

[0027] Technical principle of the invention:

[0028] This invention utilizes a confined magnetic field to induce a uniform and efficient reaction of functional groups within a microwave plasma, enabling carbon atoms to fully coat the surface of a single-crystal diamond substrate and complete bonding deposition, resulting in a smooth single-crystal diamond epitaxial layer. This addresses the problems of slow growth, poor thickness uniformity, and low deposition quality inherent in traditional diamond epitaxial layer preparation processes. Furthermore, it reduces defects and damage caused by post-processing of the epitaxial layer, effectively lowering the subsequent processing costs of the diamond surface.

[0029] Specifically, the key technology of this invention lies in:

[0030] 1. To ensure a clean deposition environment, the chamber and the growth molybdenum support are ultrasonically cleaned and dried using acetone, anhydrous ethanol, and deionized water. Then, hydrogen plasma is used to perform long-term dry burning on the chamber walls to eliminate impurities adsorbed on the chamber walls and ensure a clean environment in the deposition equipment chamber.

[0031] 2. To ensure the purity of the environment for high-quality diamond growth, a two-step vacuum method using a forepump and a molecular pump is employed to reduce the chamber vacuum to 10. -7 Under Torr conditions, an ultimate vacuum is achieved to reduce impurities and contamination during the preparation of high-quality diamonds.

[0032] 3. By using a special ratio of hydrogen-oxygen plasma etching process, the epitaxial diamond substrate is etched, which effectively suppresses the "inheritance" of impurities such as dislocations in the epitaxially grown single-crystal diamond. In addition, oxygen atoms, a purifying component, are introduced into the plasma environment, which effectively reduces and eliminates impurity components in the plasma environment.

[0033] By setting a magnetic field current, a confining magnetic field is constructed using a magnetic excitation coil and applied to microwave plasma, causing carbon atoms to be uniformly deposited on the surface of a single-crystal diamond substrate, thereby forming a flat diamond epitaxial layer.

[0034] The above technical solution has at least the following advantages compared with the existing technology:

[0035] The present invention proposes a method for preparing planar epitaxial diamond semiconductors, which can solve the technical problems in existing diamond semiconductor preparation technologies, such as slow growth rate, poor uniformity, and difficulty in forming a planar surface.

[0036] This invention utilizes the confinement magnetic field generated by the magnetic excitation coil to act on the microwave plasma in the microwave vapor deposition equipment, thereby enabling carbon atoms to be deposited uniformly and rapidly on the single-crystal diamond substrate, ultimately obtaining a single-crystal diamond epitaxial layer with a smooth surface.

[0037] This invention employs a multi-dimensional chamber cleaning process to ensure the cleanliness of the preparation environment. Impurity particles within the chamber are removed by wiping with a clean cloth, and hydrogen plasma is used for prolonged empty combustion to eliminate impurities adsorbed on the chamber walls, resulting in a clean chamber environment.

[0038] This invention employs a two-step vacuum method using a forepump and a molecular pump to reduce the chamber vacuum to 10. -7 Under Torr conditions, an ultimate vacuum is achieved to reduce impurities and contamination during the preparation of high-quality diamonds.

[0039] This invention uses the controlled ratio of hydrogen-oxygen plasma to etch an epitaxial diamond substrate. On the one hand, it suppresses the "inheritance" of defects such as dislocations in the epitaxial single-crystal diamond. On the other hand, it uses oxygen atoms introduced into the plasma environment to purify the components, thereby achieving efficient reduction and elimination of plasma impurities.

[0040] This invention is not limited to the size of the single-crystal diamond substrate. Even with a relatively large single-crystal diamond substrate sample, a uniform and flat diamond epitaxial layer can be grown under magnetic field confinement.

[0041] In summary, compared with traditional methods, the method of this invention obtains a planarized hydrogen-terminated diamond semiconductor through microwave plasma equipment chamber purification, single-crystal diamond substrate pretreatment, single-crystal diamond substrate etching, and hydrogen-terminated diamond semiconductor preparation. The carrier mobility, areal density, and sheet resistance of the hydrogen-terminated diamond semiconductor prepared by this method can be synergistically optimized. It is simple to operate, low in cost, low in energy consumption, and high in efficiency, which is conducive to large-scale industrial production and promotion. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1This is a flowchart of key steps in diamond surface coating, a method for enhancing the bonding strength between diamond particles and a copper substrate according to the present invention. Detailed Implementation

[0044] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0045] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0046] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0047] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0048] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0049] A method for preparing a planar epitaxial diamond semiconductor, wherein the method for preparing the planar epitaxial diamond semiconductor combines... Figure 1 Includes the following steps:

[0050] S1. Cleaning of microwave plasma equipment chamber: Place the molybdenum tray in a beaker, ultrasonically clean and dry it, place the cleaned molybdenum tray on the equipment deposition stage, introduce hydrogen gas and adjust the microwave power and chamber pressure, control the temperature and dry burn to eliminate impurities adsorbed on the chamber wall and obtain a clean chamber.

[0051] S2. Pretreatment of single-crystal diamond substrate: The copper clamp of the adhered diamond substrate is inserted into the fixture of the single-crystal mechanical polishing machine for mechanical polishing; then the mechanically polished diamond substrate is acid-washed and ultrasonically cleaned, and dried to obtain a clean diamond substrate.

[0052] S3. Single-crystal diamond substrate etching: The clean diamond substrate from S2 is placed into the clean molybdenum support chamber from S1. The chamber vacuum is reduced to 10 using a two-step vacuum method involving a forepump and a molecular pump. -7Under Torr, after reaching the ultimate vacuum, the valve is closed and hydrogen gas is introduced to ignite and excite the plasma. The etching parameters are set to etch the single-crystal diamond substrate to obtain the etched diamond substrate.

[0053] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced, while the hydrogen flow rate remains constant and the oxygen flow rate is reduced. Methane is then introduced. Subsequently, the current in the magnetic coil is increased while the microwave power and chamber pressure are slowly increased. After the gas and plasma states within the chamber stabilize, the growth parameters are adjusted to generate a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0054] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, the hydrogenation process parameters are set for hydrogenation treatment, and finally a planarized hydrogen-terminated diamond semiconductor is obtained.

[0055] Specifically, in S1, ultrasonic cleaning is performed sequentially with acetone, anhydrous ethanol, and deionized water at an ultrasonic frequency of 40-60kHz for 10-20 minutes; the flow rate of hydrogen gas is 400-600 sccm; the microwave power is adjusted to 4-6kW; the chamber pressure is 150-160 Torr; the temperature is controlled at 850-950℃; and the chamber is left to burn for 3-4 hours.

[0056] Specifically, in S2, the mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 700-800g, and polishing for 20-30 minutes for rough polishing. After that, the load is changed to 500-600g, and polishing is performed for 10-20 minutes. The surface roughness of the diamond substrate after mechanical polishing is 0.4-0.6nm.

[0057] Specifically, in S2, acid washing uses a 98% sulfuric acid / nitric acid solution, and the polished sample needs to be placed in the sulfuric acid / nitric acid solution and heated to boiling for 20-30 minutes; ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 50-70 kHz and a time of 10-20 minutes.

[0058] Specifically, S3 employs a two-step vacuum method using a backing pump and a molecular pump to reduce the chamber vacuum to 10. -7 Below Torr: Turn on the forepump to evacuate the chamber vacuum to below 0 Torr, then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Torr below.

[0059] Specifically, in S3, the flow rate of hydrogen gas introduced through the closed valve is 300-500 sccm, and the etching parameters are set as follows: microwave power of 4-6 kW, chamber pressure of 140-150 Torr, control temperature of 880-920℃, hydrogen flow rate of 400-500 sccm, oxygen flow rate of 2-3 sccm, and etching time of 15-30 min.

[0060] Specifically, in S4, the microwave power, chamber pressure, and temperature within the cavity are all reduced to 33±2% of the etching parameters in S3. Specifically, the microwave power is adjusted to 3-4kW, the chamber pressure is adjusted to 120-130Torr, and the temperature is controlled at 750-800℃.

[0061] Specifically, when the gas and plasma states in the S4 chamber are stable, the magnetic coil current needs to reach 1-2A.

[0062] Specifically, the growth parameters in S4 are adjusted as follows: microwave power of 4-6kW, chamber pressure of 140-150Torr, growth temperature of 830-860℃, hydrogen flow rate of 400-500sccm, methane flow rate of 10-30sccm, oxygen flow rate of 0.5-1.5sccm, and magnetic field current of 1-2A.

[0063] Specifically, the hydrogenation process parameters in S5 are set as follows: microwave power of 2-3kW, chamber pressure of 80-90Torr, hydrogenation temperature of 720-750℃, hydrogen flow rate of 400-500sccm, and hydrogenation time of 10-20min.

[0064] Specifically, the S5 features a planarized hydrogen-terminated diamond semiconductor with the following performance parameters: surface roughness of 0.3-0.5 nm, nitrogen impurity concentration of 1-2 ppb, hole mobility of 200-230 cm² / (V·s), stability at 200-300℃ for 60-90 h, and output power of 870-920 MW / cm². 2 It is suitable for high-frequency scenarios of up to 70-100Hz.

[0065] Example 1

[0066] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0067] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate is placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 40 kHz for 10 minutes. After drying, the cleaned molybdenum plate is placed on the deposition stage of the equipment. Hydrogen gas is introduced and the microwave power and chamber pressure are adjusted. The temperature is controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate is 400 sccm, the microwave power is adjusted to 5 kW, the chamber pressure is 150 Torr, the temperature is controlled at 850℃, and the dry burning is carried out for 3 hours to obtain a clean chamber.

[0068] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 700g, and polishing for 20 minutes for rough polishing. Then, the load is changed to 500g, and polishing is performed for 10 minutes. The surface roughness of the mechanically polished diamond substrate is 0.4nm. Afterward, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% sulfuric acid solution, requiring the polished sample to be immersed in the sulfuric acid / nitric acid solution and heated to boiling for 20 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 70kHz and a time of 10 minutes. After drying, a clean diamond substrate is obtained.

[0069] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 150 Torr, temperature control of 900℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 2 sccm, and etching time of 20 min, to obtain the etched diamond substrate;

[0070] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 4kW, the chamber pressure to 120Torr, and the temperature to 750℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize, i.e., the magnetic coil current needs to reach 1A, the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 140Torr, growth temperature to 840℃, hydrogen flow rate to 500sccm, methane flow rate to 10sccm, oxygen flow rate to 0.5sccm, and magnetic field current to 1.2A, creating a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0071] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 85Torr, the hydrogenation temperature is 730℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 20min, finally obtaining a planarized hydrogen-terminated diamond semiconductor.

[0072] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.35 nm, nitrogen impurity concentration of 1.5 ppb, hole mobility of 210 cm² / (V·s), stability at 200℃ for 60 h, and a maximum output power of 870 MW / cm². 2 It is suitable for scenarios with a maximum frequency of 70Hz.

[0073] Example 2

[0074] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0075] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 50 kHz for 15 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 500 sccm, the microwave power was adjusted to 5 kW, the chamber pressure to 150 Torr, and the temperature was controlled at 900℃. Dry burning was carried out for 4 hours to obtain a clean chamber.

[0076] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 750g, and polishing for 25 minutes for rough polishing. Then, the load is changed to 550g, and polishing is performed for 15 minutes. The surface roughness of the mechanically polished diamond substrate is 0.5nm. Afterward, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% nitric acid solution, requiring the polished sample to be immersed in a sulfuric acid / nitric acid solution and heated to boiling for 30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 70kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0077] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 400 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 145 Torr, temperature control of 890℃, hydrogen flow rate of 400 sccm, oxygen flow rate of 2.5 sccm, and etching time of 30 min, to obtain the etched diamond substrate;

[0078] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 4kW, the chamber pressure to 125Torr, and the temperature to 780℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize, i.e., the magnetic coil current needs to reach 1.3A, the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 150Torr, growth temperature to 850℃, hydrogen flow rate to 500sccm, methane flow rate to 15sccm, oxygen flow rate to 0.6sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0079] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 2.5kW, the chamber pressure is 85Torr, the hydrogenation temperature is 740℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 15min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0080] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.43 nm, nitrogen impurity concentration of 1.2 ppb, hole mobility of 215 cm² / (V·s), stability at 230℃ for 65 h, and output power of 880 MW / cm². 2 It can be used in high-frequency scenarios up to 80Hz.

[0081] Example 3

[0082] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0083] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 50 kHz for 20 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 500 sccm, the microwave power was adjusted to 5 kW, the chamber pressure to 155 Torr, and the temperature was controlled at 895℃. Dry burning was carried out for 4 hours to obtain a clean chamber.

[0084] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 750g, and polishing for 30 minutes for rough polishing. Then, the load is changed to 550g, and polishing is performed for 10 minutes. The surface roughness of the mechanically polished diamond substrate is 0.45nm. Afterward, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% sulfuric acid solution, requiring the polished sample to be immersed in the sulfuric acid / nitric acid solution and heated to boiling for 25 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 65kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0085] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 6kW, chamber pressure of 145 Torr, temperature control of 920℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 2.5 sccm, and etching time of 15min, to obtain the etched diamond substrate;

[0086] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 4kW, the chamber pressure to 125Torr, and the temperature to 780℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize (i.e., the magnetic coil current needs to reach 1.3A), the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 140Torr, growth temperature to 85℃, hydrogen flow rate to 500sccm, methane flow rate to 20sccm, oxygen flow rate to 1.0sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is then set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0087] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 85Torr, the hydrogenation temperature is 740℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 20min, finally obtaining a planarized hydrogen-terminated diamond semiconductor.

[0088] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.36 nm, nitrogen impurity concentration of 1.5 ppb, hole mobility of 225 cm² / (V·s), stability at 200℃ for 70 h, and output power of 880 MW / cm². 2 It can be used in high-frequency scenarios up to 80Hz.

[0089] Example 4

[0090] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0091] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 60 kHz for 20 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 600 sccm, the microwave power was adjusted to 6 kW, the chamber pressure to 160 Torr, and the temperature was controlled at 950℃. Dry burning was carried out for 3 hours to obtain a clean chamber.

[0092] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 800g, and polishing for 20 minutes for rough polishing. Then, the load is changed to 600g, and polishing is performed for 10 minutes. The surface roughness of the mechanically polished diamond substrate is 0.46nm. Afterwards, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% nitric acid solution, requiring the polished sample to be immersed in a sulfuric acid / nitric acid solution and heated to boiling for 30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 60kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0093] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 6kW, chamber pressure of 145 Torr, control temperature of 910℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 2.5 sccm, and etching time of 25 min, to obtain the etched diamond substrate;

[0094] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 3.5kW, the chamber pressure to 125Torr, and the temperature to 770℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize (i.e., the magnetic coil current needs to reach 1.2A), the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 150Torr, growth temperature to 850℃, hydrogen flow rate to 500sccm, methane flow rate to 30sccm, oxygen flow rate to 1.5sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is then set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0095] S5. Preparation of hydrogen-terminated diamond semiconductor: After the high-quality single-crystal diamond epitaxial layer in S4 is prepared, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 90Torr, the hydrogenation temperature is 750℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 10min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0096] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.43 nm, nitrogen impurity concentration of 1.1 ppb, hole mobility of 227 cm² / (V·s), stability at 220℃ for 80 h, and output power of 890 MW / cm². 2 It can be used in high-frequency scenarios up to 90Hz.

[0097] Example 5

[0098] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0099] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate is placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 50 kHz for 15 minutes. After drying, the cleaned molybdenum plate is placed on the deposition stage of the equipment. Hydrogen gas is introduced and the microwave power and chamber pressure are adjusted. The temperature is controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate is 600 sccm, the microwave power is adjusted to 4-6 kW, the chamber pressure is 150 Torr, the temperature is controlled at 890℃, and the dry burning is carried out for 4 hours to obtain a clean chamber.

[0100] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 790g, and polishing for 25 minutes for rough polishing. Then, the load is changed to 580g, and polishing is performed for 15 minutes. The surface roughness of the mechanically polished diamond substrate is 0.56nm. Afterwards, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% sulfuric acid solution, requiring the polished sample to be immersed in the sulfuric acid / nitric acid solution and heated to boiling for 30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 70kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0101] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 145 Torr, temperature control of 900℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 2.5 sccm, and etching time of 20 min, to obtain the etched diamond substrate;

[0102] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 3.8kW, the chamber pressure to 125Torr, and the temperature to 780℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize (i.e., the magnetic coil current needs to reach 1.3A), the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 150Torr, growth temperature to 850℃, hydrogen flow rate to 500sccm, methane flow rate to 25sccm, oxygen flow rate to 1.3sccm, and magnetic field current to 1.8A, creating a balanced deposition growth environment. The required time is then set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0103] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 85Torr, the hydrogenation temperature is 740℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 15min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0104] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.32 nm, nitrogen impurity concentration of 1.6 ppb, hole mobility of 218 cm² / (V·s), stability at 230℃ for 65 h, and output power of 850 MW / cm². 2 It can be used in high-frequency scenarios up to 80Hz.

[0105] Example 6

[0106] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0107] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 60 kHz for 10 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 500 sccm, the microwave power was adjusted to 5 kW, the chamber pressure to 155 Torr, the temperature was controlled to 920℃, and the dry burning was carried out for 3.5 hours to obtain a clean chamber.

[0108] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 760g, and polishing for 25 minutes for rough polishing. Then, the load is changed to 560g, and polishing is performed for 15 minutes. The surface roughness of the mechanically polished diamond substrate is 0.55nm. Afterwards, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% nitric acid solution, requiring the polished sample to be immersed in a sulfuric acid / nitric acid solution and heated to boiling for 30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 65kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0109] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5.5 kW, chamber pressure of 143 Torr, control temperature of 895 ℃, hydrogen flow rate of 450 sccm, oxygen flow rate of 2.6 sccm, and etching time of 18 min, to obtain the etched diamond substrate;

[0110] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 4kW, the chamber pressure to 126Torr, and the temperature to 790℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize (i.e., the magnetic coil current reaches 1.0A), the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 146Torr, growth temperature to 855℃, hydrogen flow rate to 500sccm, methane flow rate to 25sccm, oxygen flow rate to 1.2sccm, and magnetic field current to 2.0A, creating a balanced deposition growth environment. The required time is then set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0111] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 90Torr, the hydrogenation temperature is 750℃, the hydrogen flow rate is 450sccm, and the hydrogenation time is 10min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0112] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.45 nm, nitrogen impurity concentration of 1.8 ppb, hole mobility of 219 cm² / (V·s), stability at 230℃ for 80 h, and output power of 910 MW / cm². 2 It can be used in high-frequency scenarios up to 100Hz.

[0113] Example 7

[0114] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0115] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate is placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 60 Hz for 20 minutes. After drying, the cleaned molybdenum plate is placed on the deposition stage of the equipment. Hydrogen gas is introduced and the microwave power and chamber pressure are adjusted. The temperature is controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate is 500 sccm, the microwave power is adjusted to 4-6 kW, the chamber pressure is 158 Torr, the temperature is controlled at 930℃, and the dry burning is carried out for 3 hours to obtain a clean chamber.

[0116] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 750g, and polishing for 20 minutes for rough polishing. Then, the load is changed to 530g, and polishing is performed for 15 minutes. The surface roughness of the mechanically polished diamond substrate is 0.56nm. Afterwards, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% nitric acid solution, requiring the polished sample to be immersed in a sulfuric acid / nitric acid solution and heated to boiling for 30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 65kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0117] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 150 Torr, temperature control of 920℃, hydrogen flow rate of 450 sccm, oxygen flow rate of 3 sccm, and etching time of 20 min, to obtain the etched diamond substrate;

[0118] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 3kW, the chamber pressure to 120Torr, and the temperature to 750℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize, i.e., the magnetic coil current needs to reach 1.2A, the growth parameters are adjusted: microwave power to 4-6kW, chamber pressure to 140Torr, growth temperature to 850℃, hydrogen flow rate to 500sccm, methane flow rate to 15sccm, oxygen flow rate to 0.8sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0119] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 2.5kW, the chamber pressure is 90Torr, the hydrogenation temperature is 720℃, the hydrogen flow rate is 460sccm, and the hydrogenation time is 12min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0120] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.39 nm, nitrogen impurity concentration of 1.6 ppb, hole mobility of 215 cm² / (V·s), stability at 200℃ for 65 h, and output power of 875 MW / cm². 2 It can be used in high-frequency scenarios up to 75Hz.

[0121] Example 8

[0122] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0123] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 50 kHz for 20 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 500 sccm, the microwave power was adjusted to 5 kW, the chamber pressure to 150 Torr, the temperature was controlled to 860℃, and the dry burning was carried out for 3.5 hours to obtain a clean chamber.

[0124] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 770g, and polishing for 25 minutes for rough polishing. Then, the load is changed to 570g, and polishing is performed for 15 minutes. The surface roughness of the mechanically polished diamond substrate is 0.60nm. Afterwards, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% sulfuric acid solution, requiring the polished sample to be immersed in the sulfuric acid / nitric acid solution and heated to boiling for 30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 70kHz and a time of 15 minutes. After drying, a clean diamond substrate is obtained.

[0125] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 140 Torr, temperature control of 890℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 2.5 sccm, and etching time of 30 min, to obtain the etched diamond substrate;

[0126] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 4kW, the chamber pressure to 130Torr, and the temperature to 760℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize, i.e., the magnetic coil current needs to reach 1.0A, the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 145Torr, growth temperature to 840℃, hydrogen flow rate to 450sccm, methane flow rate to 15sccm, oxygen flow rate to 0.8sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0127] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 88Torr, the hydrogenation temperature is 746℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 10min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0128] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.46 nm, nitrogen impurity concentration of 1.3 ppb, hole mobility of 221 cm² / (V·s), stability at 200℃ for 90 h, and output power of 900 MW / cm². 2 It can be used in high-frequency scenarios up to 90Hz.

[0129] Example 9

[0130] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0131] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 50 kHz for 20 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 500 sccm, the microwave power was adjusted to 6 kW, the chamber pressure to 160 Torr, and the temperature was controlled at 950℃. Dry burning was carried out for 3 hours to obtain a clean chamber.

[0132] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 800g, and polishing for 25 minutes for rough polishing. Then, the load is changed to 550g, and polishing is performed for 10 minutes. The surface roughness of the mechanically polished diamond substrate is 0.55nm. Afterward, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% sulfuric acid solution, requiring the polished sample to be immersed in the sulfuric acid / nitric acid solution and heated to boiling for 25 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 65kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0133] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 145 Torr, temperature control of 900℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 3 sccm, and etching time of 25 min, to obtain the etched diamond substrate;

[0134] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 3.5kW, the chamber pressure to 125Torr, and the temperature to 780℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize, i.e., the magnetic coil current needs to reach 1.3A, the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 146Torr, growth temperature to 850℃, hydrogen flow rate to 500sccm, methane flow rate to 25sccm, oxygen flow rate to 1.3sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0135] S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 80Torr, the hydrogenation temperature is 735℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 15min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0136] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.39 nm, nitrogen impurity concentration of 1.5 ppb, hole mobility of 228 cm² / (V·s), stability at 200℃ for 85 h, and output power of 895 MW / cm². 2 It can be used in high-frequency scenarios up to 85Hz.

[0137] Example 10

[0138] This embodiment discloses a method for preparing a planar epitaxial diamond semiconductor, the method comprising the following steps:

[0139] S1. Cleaning of the microwave plasma equipment chamber: The molybdenum plate was placed in a beaker and ultrasonically cleaned sequentially with acetone, anhydrous ethanol, and deionized water at a frequency of 50 kHz for 20 minutes. After drying, the cleaned molybdenum plate was placed on the deposition stage of the equipment. Hydrogen gas was introduced and the microwave power and chamber pressure were adjusted. The temperature was controlled for dry burning to eliminate impurities adsorbed on the chamber wall. The hydrogen gas flow rate was 500 sccm, the microwave power was adjusted to 5 kW, the chamber pressure to 150 Torr, the temperature was controlled to 920℃, and the dry burning was carried out for 3.5 hours to obtain a clean chamber.

[0140] S2. Pretreatment of Single-Crystal Diamond Substrate: The adhered diamond substrate is clamped into the fixture of a single-crystal mechanical polishing machine for mechanical polishing. The mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 750g, and polishing for 30 minutes for rough polishing. Then, the load is changed to 550g, and polishing is performed for another 20 minutes. The surface roughness of the mechanically polished diamond substrate is 0.41nm. Afterward, the mechanically polished diamond substrate undergoes acid washing and ultrasonic cleaning. Acid washing uses a 98% nitric acid solution, requiring the polished sample to be immersed in a sulfuric acid / nitric acid solution and heated to boiling for 25 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water, with an ultrasonic frequency of 65kHz and a time of 20 minutes. After drying, a clean diamond substrate is obtained.

[0141] S3. Single-crystal diamond substrate etching: Place the clean diamond substrate from S2 into the clean molybdenum tray of the chamber from S1. Turn on the equipment foreboard pump to evacuate the chamber vacuum to below 0 Torr, and then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Below Torr; after reaching the ultimate vacuum, the valve is closed and hydrogen gas with a flow rate of 300 sccm is introduced to ignite and excite the plasma. The etching parameters are set as follows: microwave power of 5kW, chamber pressure of 145 Torr, control temperature of 895℃, hydrogen flow rate of 500 sccm, oxygen flow rate of 2.5 sccm, and etching time of 15min, to obtain the etched diamond substrate;

[0142] S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced. The microwave power is adjusted to 4kW, the chamber pressure to 120Torr, and the temperature to 750℃. The hydrogen flow rate remains constant, the oxygen flow rate is reduced, and methane is introduced. Then, while slowly increasing the microwave power and chamber pressure, the current in the magnetic coil is increased. Once the gas and plasma states within the chamber stabilize, i.e., the magnetic coil current needs to reach 1.2A, the growth parameters are adjusted: microwave power to 5kW, chamber pressure to 145Torr, growth temperature to 850℃, hydrogen flow rate to 500sccm, methane flow rate to 15sccm, oxygen flow rate to 0.6sccm, and magnetic field current to 1.5A, creating a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer.

[0143] S5. Preparation of hydrogen-terminated diamond semiconductor: After the high-quality single-crystal diamond epitaxial layer in S4 is prepared, the methane control valve is closed, and the hydrogenation process parameters are set for hydrogenation treatment. The microwave power is 3kW, the chamber pressure is 85Torr, the hydrogenation temperature is 740℃, the hydrogen flow rate is 500sccm, and the hydrogenation time is 10min. Finally, a planarized hydrogen-terminated diamond semiconductor is obtained.

[0144] The hydrogen-terminated diamond semiconductor prepared in this embodiment has the following performance parameters: surface roughness of 0.43 nm, nitrogen impurity concentration of 1.6 ppb, hole mobility of 216 cm² / (V·s), stability at 200℃ for 85 h, and output power of 910 MW / cm². 2 It can be used in high-frequency scenarios up to 98Hz.

[0145] The present invention proposes a method for preparing planar epitaxial diamond semiconductors, which can solve the technical problems in existing diamond semiconductor preparation technologies, such as slow growth rate, poor uniformity, and difficulty in forming a planar surface.

[0146] This invention utilizes the confinement magnetic field generated by the magnetic excitation coil to act on the microwave plasma in the microwave vapor deposition equipment, thereby enabling carbon atoms to be deposited uniformly and rapidly on the single-crystal diamond substrate, ultimately obtaining a single-crystal diamond epitaxial layer with a smooth surface.

[0147] This invention employs a multi-dimensional chamber cleaning process to ensure the cleanliness of the preparation environment. Impurity particles within the chamber are removed by wiping with a clean cloth, and hydrogen plasma is used for prolonged empty combustion to eliminate impurities adsorbed on the chamber walls, resulting in a clean chamber environment.

[0148] This invention employs a two-step vacuum method using a forepump and a molecular pump to reduce the chamber vacuum to 10. -7Under Torr conditions, an ultimate vacuum is achieved to reduce impurities and contamination during the preparation of high-quality diamonds.

[0149] This invention uses the controlled ratio of hydrogen-oxygen plasma to etch an epitaxial diamond substrate. On the one hand, it suppresses the "inheritance" of defects such as dislocations in the epitaxial single-crystal diamond. On the other hand, it uses oxygen atoms introduced into the plasma environment to purify the components, thereby achieving efficient reduction and elimination of plasma impurities.

[0150] This invention is not limited to the size of the single-crystal diamond substrate. Even with a relatively large single-crystal diamond substrate sample, a uniform and flat diamond epitaxial layer can be grown under magnetic field confinement.

[0151] In summary, compared with traditional methods, the method of this invention obtains a planarized hydrogen-terminated diamond semiconductor through microwave plasma equipment chamber purification, single-crystal diamond substrate pretreatment, single-crystal diamond substrate etching, and hydrogen-terminated diamond semiconductor preparation. The carrier mobility, areal density, and sheet resistance of the hydrogen-terminated diamond semiconductor prepared by this method can be synergistically optimized. It is simple to operate, low in cost, low in energy consumption, and high in efficiency, which is conducive to large-scale industrial production and promotion.

[0152] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0153] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0154] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0155] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a planar epitaxial diamond semiconductor, characterized in that, The method for preparing the planar epitaxial diamond semiconductor includes the following steps: S1. Cleaning of microwave plasma equipment chamber: Place the molybdenum tray in a beaker, ultrasonically clean and dry it, place the cleaned molybdenum tray on the equipment deposition stage, introduce hydrogen gas and adjust the microwave power and chamber pressure, control the temperature and dry burn to eliminate impurities adsorbed on the chamber wall and obtain a clean chamber. S2. Pretreatment of single-crystal diamond substrate: The copper clamp of the adhered diamond substrate is inserted into the fixture of the single-crystal mechanical polishing machine for mechanical polishing; then the mechanically polished diamond substrate is acid-washed and ultrasonically cleaned, and dried to obtain a clean diamond substrate. S3. Single-crystal diamond substrate etching: The clean diamond substrate from S2 is placed into the clean molybdenum support chamber from S1. The chamber vacuum is reduced to 10 using a two-step vacuum method involving a forepump and a molecular pump. -7 Under Torr, after reaching the ultimate vacuum, the valve is closed and hydrogen gas is introduced to ignite and excite the plasma. The etching parameters are set to etch the single-crystal diamond substrate to obtain the etched diamond substrate. S4. Diamond Epitaxial Layer Growth: After etching in S3, the microwave power, chamber pressure, and temperature within the chamber are all reduced, while the hydrogen flow rate remains constant and the oxygen flow rate is reduced. Methane is then introduced. Subsequently, the current in the magnetic coil is increased while the microwave power and chamber pressure are slowly increased. After the gas and plasma states within the chamber stabilize, the growth parameters are adjusted to generate a balanced deposition growth environment. The required time is set to complete the preparation of a high-quality single-crystal diamond epitaxial layer. S5. Preparation of hydrogen-terminated diamond semiconductor: After the preparation of the high-quality single-crystal diamond epitaxial layer in S4 is completed, the methane control valve is closed, the hydrogenation process parameters are set for hydrogenation treatment, and finally a planarized hydrogen-terminated diamond semiconductor is obtained.

2. The method for preparing planar epitaxial diamond semiconductor according to claim 1, characterized in that, In S1, ultrasonic cleaning is performed sequentially with acetone, anhydrous ethanol, and deionized water at an ultrasonic frequency of 40-60 kHz for 10-20 min. The flow rate of hydrogen gas is 400-600 sccm, the microwave power is adjusted to 4-6 kW, the chamber pressure is 150-160 Torr, the temperature is controlled at 850-950℃, and the chamber is left to burn for 3-4 hours.

3. The method for preparing planar epitaxial diamond semiconductor according to claim 1, characterized in that, In S2, the mechanical polishing process requires setting the cast iron disc motor frequency to 50Hz, applying a load of 700-800g, and polishing for 20-30 minutes for rough polishing. Then, the load is changed to 500-600g, and polishing is performed for 10-20 minutes. The surface roughness of the diamond substrate after mechanical polishing is 0.4-0.6nm.

4. The method for preparing planar epitaxial diamond semiconductor according to claim 1, characterized in that, In S2, acid washing uses a 98% sulfuric acid / nitric acid solution. The polished sample needs to be placed in the sulfuric acid / nitric acid solution and heated to boiling for 20-30 minutes. Ultrasonic cleaning involves sequentially using acetone, anhydrous ethanol, and deionized water at an ultrasonic frequency of 40-70 kHz for 10-20 minutes.

5. The method for preparing planar epitaxial diamond semiconductor according to claim 1, characterized in that, In S3, a two-step vacuum method using a forepump and a molecular pump is employed to reduce the chamber vacuum to 10. -7 Below Torr: Turn on the forepump to evacuate the chamber vacuum to below 0 Torr, then use a molecular pump to reduce the reaction chamber vacuum to 10 Torr. -7 Torr below.

6. The method for preparing a planar epitaxial diamond semiconductor according to claim 1, characterized in that, In S3, the flow rate of hydrogen gas introduced by closing the valve is 300-500 sccm. The etching parameters are set as follows: microwave power of 4-6 kW, chamber pressure of 140-150 Torr, control temperature of 880-920℃, hydrogen flow rate of 400-500 sccm, oxygen flow rate of 2-3 sccm, and etching time of 15-30 min.

7. The method for preparing planar epitaxial diamond semiconductor according to claim 1, characterized in that, In S4, the microwave power, chamber pressure, and temperature within the cavity are all reduced to 33±2% of the etching parameters in S3. Specifically, the microwave power is adjusted to 3-4kW, the chamber pressure is adjusted to 120-130Torr, and the temperature is controlled at 750-800℃.

8. The method for preparing planar epitaxial diamond semiconductor according to claim 1, characterized in that, When the gas and plasma states in the S4 chamber are stable, the magnetic coil current needs to reach 1-2A.

9. The method for preparing a planar epitaxial diamond semiconductor according to claim 1, characterized in that, The growth parameters in S4 are adjusted as follows: microwave power 4-6kW, chamber pressure 140-150Torr, growth temperature 830-860℃, hydrogen flow rate 400-500sccm, methane flow rate 10-30sccm, oxygen flow rate 0.5-1.5sccm, and magnetic field current 1-2A.

10. The method for preparing a planar epitaxial diamond semiconductor according to claim 1, characterized in that, The hydrogenation process parameters set in S5 are as follows: microwave power of 2-3kW, chamber pressure of 80-90Torr, hydrogenation temperature of 720-750℃, hydrogen flow rate of 400-500sccm, and hydrogenation time of 10-20min.

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