A method for preparing low sheet resistance hydrogen-terminated diamond by a simple process
Patent Information
- Application Number
- CN202611325286.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-28
- Publication Date
- 2026-09-25
AI Technical Summary
[0006]本发明的目的是要解决现有氢终端金刚石的制备工艺复杂、电学性能有待提高的问题，而提供一种低方阻氢终端金刚石的制备方法
[0019]1、工艺简化、制备效率高。本发明摒弃传统长时间纯氢等离子体复杂处理流程，采用氢气预处理结合低浓度甲烷短时复合处理方式，步骤少、参数可控性强，大幅缩短制备周期，降低设备调控难度与生产成本，适合工业化批量制备。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultra-wide bandgap semiconductor material preparation technology, specifically relating to a simple process for efficiently preparing low sheet resistance hydrogen-terminated diamond, applicable to diamond-based electronic devices, radio frequency devices, sensors and other technical fields. Background Technology
[0002] Diamond, as an excellent semiconductor material, has broad application prospects in electronic devices, optoelectronic devices, and high-power applications due to its high thermal conductivity, high wear resistance, and excellent electrical insulation properties. In recent years, research on hydrogen-terminated diamond (H-terminated diamond) has received increasing attention, especially in high-frequency, high-power, and radio-frequency devices, where its superior electronic properties make it an ideal choice.
[0003] However, existing hydrogen-terminated diamond processes typically require multiple steps, including high-temperature hydrogen plasma treatment, surface cleaning, vacuum extraction, plasma parameter adjustment, and subsequent cooling and protection. These processes place high demands on process parameters such as substrate temperature, microwave power, cavity pressure, gas flow rate, and processing time. Some processes also require lengthy pure hydrogen plasma treatment or multiple surface activation and passivation processes. The process flow is lengthy, the operating window is narrow, and the requirements for equipment stability and operator skill are high, thus hindering the improvement of batch production efficiency.
[0004] Hydrogen end-processing typically relies on vacuum plasma equipment such as MPCVD. The preparation process requires maintaining high temperatures, high microwave power, and a stable vacuum environment. Long-term operation increases hydrogen consumption, energy consumption, and the operating costs of vacuum and microwave systems. When the processing cycle is long or the process is repeated many times, the equipment occupancy time and overall preparation cost per sample further increase, thus restricting its large-scale preparation and device application.
[0005] Furthermore, when using conventional or unoptimized hydrogen termination processes, the formation stability of the conductive layer on the diamond surface is insufficient, and the resulting samples may have a sheet resistance in the range of tens of kΩ / □ or even higher. A high sheet resistance leads to increased device series resistance, reduced current achievable at the same operating voltage, increased conduction losses, and localized heat generation, which is detrimental to achieving high current density, low power consumption, and stable high-frequency operation. Especially for applications such as diamond-based field-effect transistors, RF devices, sensors, and low-resistivity conductive substrates, a high and fluctuating sheet resistance further affects device transconductance, output current, RF performance, and batch consistency. Therefore, how to obtain low and stable surface sheet resistance while simplifying the process and reducing fabrication costs remains a problem that needs to be solved in the practical application of hydrogen-terminated diamond. Summary of the Invention
[0006] The purpose of this invention is to solve the problems of complex preparation process and insufficient electrical performance of existing hydrogen-terminated diamond, and to provide a method for preparing low sheet resistance hydrogen-terminated diamond.
[0007] The present invention provides a simple method for preparing low-sheet-resistance hydrogen-terminated diamond, which is implemented according to the following steps:
[0008] I. Cleaning:
[0009] A clean diamond substrate is obtained by acid washing and ultrasonic cleaning of the diamond substrate.
[0010] II. Initial Hydrogen Treatment:
[0011] A clean diamond substrate is placed in the cavity of the MPCVD system. After evacuation, hydrogen gas is introduced. Initial hydrogen treatment is carried out under the conditions of diamond substrate temperature of 800℃~1000℃, microwave power of 2000~2500W, and cavity pressure of 50~60 Torr.
[0012] III. Methane-assisted passivation treatment:
[0013] Maintain the initial hydrogen treatment temperature, microwave power, and cavity pressure, then introduce methane, controlling the volume concentration of methane in the cavity to be 1.5%~2.5%, to perform methane-assisted passivation treatment;
[0014] IV. Cooling down:
[0015] Stop the methane supply and cool the furnace to obtain low-square hydrogen-resistant terminal diamond.
[0016] This invention achieves a simplified hydrogenation modification process using an MPCVD system. It employs a composite treatment method combining high-temperature hydrogen pretreatment with low-concentration methane-assisted passivation. The prepared hydrogen-terminated diamond sheet resistance can be stably controlled at 1–5 kΩ / □, and the Raman spectrum shows only diamond characteristic peaks. It is free of impurities such as graphite and amorphous carbon, and forms good ohmic contact with the metal electrode, thus possessing the basic electrical conditions for device application.
[0017] The hydrogen-terminated diamond prepared using the simple process of this invention exhibits low sheet resistance, indicating that the synergistic effect of high-temperature hydrogen pretreatment and low-concentration methane-assisted passivation is beneficial for forming a stable surface conductive layer. This invention primarily addresses the problems of low batch preparation efficiency, high sheet resistance, and complex processes for hydrogen-terminated diamond. Furthermore, this process can be further optimized through subsequent annealing, surface finishing, and parameter fine-tuning to improve the stability and consistency of the sample's electrical properties, demonstrating good application scalability.
[0018] The simplified method of preparing low-sheet-resistance hydrogen-terminated diamond according to the present invention has the following beneficial effects:
[0019] 1. Simplified process and high preparation efficiency. This invention abandons the traditional long-term and complex pure hydrogen plasma treatment process, and adopts a hydrogen pretreatment combined with a short-time composite treatment with low-concentration methane. The process involves fewer steps, has strong parameter controllability, significantly shortens the preparation cycle, reduces the difficulty of equipment control and production costs, and is suitable for industrial-scale batch preparation.
[0020] 2. Excellent and controllable sheet resistance performance. By precisely matching the high-temperature hydrogen cleaning and low-concentration methane passivation processes, this invention can stably control the sheet resistance of hydrogen-terminated diamond surfaces within a low range of 1–5 kΩ / □, resulting in uniform conductivity and good batch consistency, meeting the requirements for low-resistivity conductive substrates.
[0021] 3. The process is green, safe, and widely adaptable. This invention uses only conventional process gases such as hydrogen and methane, which are non-corrosive and non-toxic. The preparation process is safe and environmentally friendly, and it is highly adaptable to various equipment, making it widely applicable to mass production processing on various MPCVD equipment. Attached Figure Description
[0022] Figure 1 A diagram showing the sheet resistance values of low sheet resistance hydrogen-terminated diamond prepared using a simplified process in this embodiment.
[0023] Figure 2 Raman spectra of low-sheet-resistance hydrogen-terminated diamond prepared by a simple process in this example;
[0024] Figure 3 XPS spectra of low sheet resistance hydrogen-terminated diamond prepared by a simple process in this example;
[0025] Figure 4 The KEITHLEY 4200-IV curve of low-sheet-resistance hydrogen-terminated diamond prepared by a simple process in this example is shown. Detailed Implementation
[0026] Specific Implementation Method 1: This simplified method for preparing low sheet resistance hydrogen-terminated diamond is implemented according to the following steps:
[0027] I. Cleaning:
[0028] A clean diamond substrate is obtained by acid washing and ultrasonic cleaning of the diamond substrate.
[0029] II. Initial Hydrogen Treatment:
[0030] A clean diamond substrate is placed in the cavity of the MPCVD system. After evacuation, hydrogen gas is introduced. Initial hydrogen treatment is carried out under the conditions of diamond substrate temperature of 800℃~1000℃, microwave power of 2000~2500W, and cavity pressure of 50~60 Torr.
[0031] III. Methane-assisted passivation treatment:
[0032] Maintain the initial hydrogen treatment temperature, microwave power, and cavity pressure, then introduce methane, controlling the volume concentration of methane in the cavity to be 1.5%~2.5%, to perform methane-assisted passivation treatment;
[0033] IV. Cooling down:
[0034] Stop the methane supply and cool the furnace to obtain low-square hydrogen-resistant terminal diamond.
[0035] This embodiment provides a highly efficient and simple-to-operate process for preparing hydrogen-terminated diamond. This process is technically simpler than existing processes. By precisely controlling the gas composition and temperature, it overcomes the limitation of hydrogen-terminated diamond in terms of large sheet resistance, thereby effectively improving the electronic properties of diamond and expanding its application in high-frequency, high-power electronic devices. Furthermore, by precisely controlling the gas composition and temperature, the electrical properties of diamond can be effectively improved, further expanding its application in high-frequency, high-power electronic devices.
[0036] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the diamond substrate in step one is a high-temperature, high-pressure diamond.
[0037] In this embodiment, the crystal orientation of the diamond substrate is (100).
[0038] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the pickling in step 1 involves immersing the diamond substrate in a mixed solution of concentrated sulfuric acid and concentrated nitric acid, and then heating it at 300°C for 1-2 hours.
[0039] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method Three in that the mass concentration of concentrated sulfuric acid is 98%, the mass concentration of concentrated nitric acid is 65%, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:1.
[0040] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the initial hydrogen treatment time in step 2 is 10 min to 20 min.
[0041] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the initial hydrogen treatment in step two is performed for 10 to 15 minutes at a temperature of 800℃~900℃, a microwave power of 2400W, and a cavity pressure of 55~60 Torr.
[0042] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the volume concentration of methane in the cavity is controlled to be 2% to 2.5% in step three.
[0043] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the time for methane-assisted passivation treatment in step three is 40 min to 60 min.
[0044] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the hydrogen flow rate is controlled at 196 sccm and the methane flow rate at 4 sccm in step three.
[0045] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 8 in that the sheet resistance range of the low sheet resistance hydrogen-terminated diamond obtained in step 4 is 1.5~4.5kΩ / □.
[0046] Example 1: The simplified process for preparing low sheet resistance hydrogen-terminated diamond in this example is implemented according to the following steps:
[0047] I. Cleaning:
[0048] Intrinsically synthesized diamond using a high-temperature and high-pressure process was selected as the substrate, with dimensions of 3mm × 3mm × 0.1mm and a crystal orientation of (100). The diamond substrate was immersed in a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 for acid washing for 2 hours, with the temperature controlled at 300℃. The substrate was then ultrasonically cleaned sequentially with deionized water, ethanol, and acetone, and finally dried with high-purity nitrogen to obtain a clean diamond.
[0049] II. Initial Hydrogen Treatment:
[0050] Clean diamond was placed inside the chamber of the MPCVD system (model ARDIS-300), and the vacuum level inside the chamber was evacuated to 1.2 × 10⁻⁶ using a mechanical pump and a molecular pump. -6 Below Torr, hydrogen gas is introduced at a flow rate of 200 sccm. When the gas pressure inside the cavity rises to 10 Torr, the microwave power supply is started with 900W as the base state. Then, initial hydrogen treatment is performed for 10 minutes at a temperature of 900℃, a microwave power of 2400W, and a cavity pressure of 55 Torr to regulate the arrangement of carbon atoms on the surface and lay the foundation for subsequent hydrogen terminal construction.
[0051] III. Methane-assisted passivation treatment:
[0052] Methane was then introduced, and the methane flow rate was set to 4 sccm. The hydrogen flow rate was changed to 196 sccm. After the gas pressure in the chamber stabilized, methane-assisted passivation treatment was performed for 50 minutes. Low concentration of methane was used to suppress excessive surface etching, assist in regularizing the surface structure, and synergistically achieve the construction of a low sheet resistance conductive layer.
[0053] IV. Cooling down:
[0054] The hydrogen flow rate was adjusted to 200 sccm, and the gas was gradually cooled under pure hydrogen conditions. During the cooling process, the gas pressure and power were reduced synchronously until the initial ignition pressure and power were reached. The radio frequency power supply and hydrogen flow valve were then turned off, and the chamber was kept for 15 minutes to maintain the surface hydrogen saturation termination state, thereby avoiding surface oxidation and contaminant adsorption and ensuring the stability of the hydrogen terminal structure. The chamber was then opened to take a sample, and low sheet resistance hydrogen-terminated diamond was obtained.
[0055] This embodiment utilizes the HPS2526 precision four-probe sheet resistance tester and a KEITHLEY 4200 device for testing. Figure 1 As can be seen, the sheet resistance of the sample is in the range of 1.6~3.5kΩ / □, with stable values and good uniformity, indicating that this embodiment can achieve efficient preparation of low sheet resistance hydrogen-terminated diamond.
[0056] Figure 2 This is the Raman spectrum of the hydrogen-terminated diamond prepared in this embodiment. The spectrum is at 1332 cm⁻¹. -1 The presence of diamond characteristic peaks nearby, with no obvious graphite D peaks, G peaks, or amorphous carbon characteristic signals observed, indicates that the low-sheet hydrogen-resistant terminal diamond sample did not undergo significant graphitization.
[0057] Figure 3 This is a high-resolution XPS spectrum of C1s on the hydrogen-terminated diamond surface prepared in this embodiment. After normalization, all three samples showed obvious C1s characteristic peaks around 284.5–285.0 eV. The peak shapes of each spectrum were basically consistent, and no obvious graphitization characteristic peaks or significant π–π* satellite peaks were observed. This indicates that the hydrogen-terminated diamond surface prepared in this embodiment is mainly composed of diamond-related carbon structures and no obvious surface graphitization has occurred.
[0058] Example 2: The simplified process for preparing low-sheet-resistance hydrogen-terminated diamond in this example is implemented according to the following steps:
[0059] I. Cleaning:
[0060] A diamond substrate synthesized using an intrinsic high-temperature and high-pressure process was selected, with dimensions of 3mm × 3mm × 0.1mm and a crystal orientation of (111). The diamond substrate was immersed in a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1 for acid washing for 2 hours, with the temperature controlled at 300℃. The substrate was then ultrasonically cleaned sequentially with deionized water, ethanol, and acetone, and finally dried with high-purity nitrogen to obtain a clean diamond.
[0061] II. Initial Hydrogen Treatment:
[0062] Clean diamond was placed inside the chamber of the MPCVD system (model HITLH-2450M), and the vacuum level inside the chamber was evacuated to 1.2 × 10⁻⁶ using a mechanical pump and a molecular pump. -6Below Torr, hydrogen gas is introduced at a flow rate of 200 sccm. When the gas pressure inside the cavity rises to 10 Torr, the microwave power supply is started with 900W as the base state. Then, initial hydrogen treatment is performed for 10 minutes at a temperature of 1000℃, a microwave power of 2400W, and a cavity pressure of 55 Torr to regulate the arrangement of carbon atoms on the surface and lay the foundation for subsequent hydrogen terminal construction.
[0063] III. Methane-assisted passivation treatment:
[0064] Methane was then introduced, and the methane flow rate was set to 4 sccm. The hydrogen flow rate was changed to 196 sccm. After the gas pressure in the chamber stabilized, methane-assisted passivation treatment was performed for 50 minutes. Low concentration of methane was used to suppress excessive surface etching, assist in regularizing the surface structure, and synergistically achieve the construction of a low sheet resistance conductive layer.
[0065] IV. Cooling down:
[0066] The hydrogen flow rate was adjusted to 200 sccm, and the gas was gradually cooled under pure hydrogen conditions. During the cooling process, the gas pressure and power were reduced synchronously until the initial ignition pressure and power were reached. The radio frequency power supply and hydrogen flow valve were then turned off, and the chamber was kept for 15 minutes to maintain the surface hydrogen saturation termination state, thereby avoiding surface oxidation and contaminant adsorption and ensuring the stability of the hydrogen terminal structure. The chamber was then opened to take a sample, and low sheet resistance hydrogen-terminated diamond was obtained.
[0067] This embodiment uses the HPS2526 precision four-probe sheet resistance tester and KEITHLEY4200 equipment for testing, and its sheet resistance range is 2~4.1kΩ / □.
[0068] Example 3: This example differs from Example 1 in that the diamond substrate is 3mm×3mm×0.1mm in size, and in step two, the initial hydrogen treatment is performed for 20 minutes at a temperature of 900℃, a microwave power of 2400W, and a cavity pressure of 55 Torr.
[0069] This embodiment uses the HPS2526 precision four-probe sheet resistance tester and KEITHLEY4200 equipment for testing, and its sheet resistance range is 3.2~4.4kΩ / □.
[0070] Comparative Example:
[0071] A diamond substrate synthesized using an intrinsic high-temperature and high-pressure process was selected, with dimensions of 3mm × 3mm × 0.1mm and a crystal orientation of (100). Pretreatment was then performed strictly according to the following steps:
[0072] 1. Pickling: Immerse the substrate in a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1, and heat at 300°C for 2 hours;
[0073] 2. Ultrasonic cleaning: The solution was ultrasonically cleaned sequentially with deionized water, ethanol, and acetone, with each solution requiring 5 minutes of ultrasonic cleaning time.
[0074] 3. Nitrogen drying: The sample is dried using high-purity nitrogen and then stored under vacuum to obtain the pretreated diamond substrate.
[0075] The MPCVD equipment used in the experiment was an ARDIS-100, and hydrogen gas was used. The pretreated diamond substrate was placed in the center of the MPCVD equipment, and the vacuum level inside the chamber was evacuated to 1.2 × 10⁻⁶ using a mechanical pump and a molecular pump. -6 After the pressure drops below Torr, hydrogen gas is introduced at a flow rate of 200 sccm. When the internal pressure reaches 10 Torr, the microwave power supply is started with a base state of 900W. The internal pressure and microwave power are simultaneously increased to 55 Torr and 2400W, respectively, with the temperature range of 800℃ to 900℃. Processing is performed under these conditions for 30 minutes.
[0076] After processing, the hydrogen flow rate was adjusted to 200 sccm, and the gas was gradually cooled under pure hydrogen conditions. During the cooling process, the gas pressure and power were reduced synchronously until the initial ignition pressure and power were finally adjusted.
[0077] After shutting off the RF power supply and hydrogen flow valve, and maintaining the cavity for 15 minutes, the cavity was opened for sampling. The sample was then tested using an HPS2526 precision four-probe sheet resistance tester and a KEITHLEY4200 device. The sheet resistance range was 20~80kΩ / □.
[0078] Figure 4 The sheet resistance of the hydrogen-terminated diamond sample prepared in Example 1 (curves 1 and 2) is stable in the range of 1.0 to 3.5 kΩ / □, and its I-V curve has a large slope, which is consistent with the low resistance characteristic characterized by the four-probe sheet resistance test. In contrast, the sheet resistance of the diamond sample prepared in the comparative example (curve 3) is about 20 kΩ / □, and its I-V curve slope is significantly reduced, which is in stark contrast to the optimized sample.
Claims
1. A simple process for preparing low-shelf-resistance hydrogen-terminated diamond, characterized in that... A simplified method for preparing low-shelf-resistance hydrogen-terminated diamond is implemented according to the following steps: I. Cleaning: A clean diamond substrate is obtained by acid washing and ultrasonic cleaning of the diamond substrate. II. Initial Hydrogen Treatment: A clean diamond substrate is placed in the cavity of the MPCVD system. After evacuation, hydrogen gas is introduced. Initial hydrogen treatment is carried out under the conditions of diamond substrate temperature of 800℃~1000℃, microwave power of 2000~2500W, and cavity pressure of 50~60 Torr. III. Methane-assisted passivation treatment: Maintain the initial hydrogen treatment temperature, microwave power, and cavity pressure, then introduce methane, controlling the volume concentration of methane in the cavity to be 1.5%~2.5%, to perform methane-assisted passivation treatment; IV. Cooling down: Stop the methane supply and cool the furnace to obtain low-square hydrogen-resistant terminal diamond.
2. The method for preparing low sheet resistance hydrogen-terminated diamond using a simple process according to claim 1, characterized in that... The diamond substrate in step one is high-temperature, high-pressure diamond.
3. The method for preparing low-sheet-resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... The pickling process described in step one involves immersing the diamond substrate in a mixed solution of concentrated sulfuric acid and concentrated nitric acid, and then heating it at 300°C for 1-2 hours.
4. The method for preparing low-sheet-resistance hydrogen-terminated diamond using a simplified process according to claim 3, characterized in that... The mass concentration of concentrated sulfuric acid is 98%, the mass concentration of concentrated nitric acid is 65%, and the volume ratio of concentrated sulfuric acid to concentrated nitric acid is 3:
1.
5. The method for preparing low-sheet-resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... The initial hydrogen treatment time in step two is 10 min to 20 min.
6. The method for preparing low sheet resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... In step two, initial hydrogen treatment is carried out for 10 to 15 minutes at a temperature of 800℃~900℃, a microwave power of 2400W, and a cavity pressure of 55~60 Torr.
7. The method for preparing low-sheet-resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... In step three, the volume concentration of methane in the cavity is controlled to be 2%~2.5%.
8. The method for preparing low-sheet-resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... The methane-assisted passivation treatment in step three takes 40 to 60 minutes.
9. The method for preparing low sheet resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... In step three, the hydrogen flow rate is controlled at 196 sccm and the methane flow rate at 4 sccm.
10. The method for preparing low sheet resistance hydrogen-terminated diamond using a simplified process according to claim 1, characterized in that... The sheet resistance of the low sheet resistance hydrogen-terminated diamond obtained in step four ranges from 1.5 to 4.5 kΩ / □.