A method for preparing high uniformity diamond nitrogen termination by MPCVD

Abstract

The application relates to a method for preparing a high-uniformity diamond nitrogen terminal by using MPCVD, and relates to a method for preparing a high-uniformity diamond nitrogen terminal. In order to solve the problem of uneven nitrogen coverage on the surface of the diamond nitrogen terminal prepared by the existing method, and the problem of surface damage of the diamond nitrogen terminal prepared by the existing technology, the method comprises the following steps: cleaning a microwave plasma chemical vapor deposition equipment substrate and a cavity wall with anhydrous ethanol and deionized water, and pre-etching an MPCVD reaction cavity through a mixed plasma of hydrogen and oxygen; placing the diamond substrate into the MPCVD reaction cavity after cleaning and drying; starting the microwave through a low-flow plasma; the microwave is difficult to start under a pure atmosphere, and the low flow can avoid the generation of a diamond hydrogen terminal; introducing, regulating and controlling microwave power, cavity pressure and substrate temperature, forming a purple-red N plasma, and in-situ constructing a C-N bond N terminal on the diamond surface. The application belongs to the technical field of diamond surface terminal preparation.

Description

Technical Field

[0001] This invention relates to a method for preparing highly uniform diamond nitrogen terminals, belonging to the field of diamond surface terminal preparation technology. Background Technology

[0002] Diamond, as a wide bandgap semiconductor material (bandgap width 5.5 eV), also possesses ultra-high thermal conductivity (approximately 2000 W). High breakdown strength (approximately 20 MV) With its excellent chemical stability, diamond has irreplaceable application value in fields such as quantum sensing (nitrogen-vacancy (NV) color center core carrier), high-frequency high-power electronic devices, anti-corrosion coatings, and optical windows. Surface terminal states are a key factor determining diamond performance. Nitrogen-terminated diamond, with its unique surface electronic structure, interfacial water layer control capability, and high matching degree with NV color centers, exhibits extremely low mineral scaling tendency, excellent electrochemical stability, and high spin manipulation compatibility, making it a core research direction for quantum device fabrication, anti-scaling functional coatings, and semiconductor interface engineering. Microwave plasma chemical vapor deposition (MPCVD), due to its high plasma density, uniform energy distribution, absence of electrode contamination, and precise control of reaction parameters, has become the mainstream technology for high-quality diamond synthesis and surface functionalization modification.

[0003] However, traditional techniques often introduce nitrogen atoms into the diamond interior through high-temperature annealing, radio-frequency nitrogen plasma treatment, or ion implantation, followed by vacuum heat treatment to induce nitrogen atom segregation to the surface and form nitrogen terminals. However, this method easily leads to uneven nitrogen atom diffusion depth, large surface concentration gradients, and the high-temperature process easily introduces crystal defects such as vacancies and dislocations, making it difficult to obtain a dense and uniform surface nitrogen-terminated layer. While nitrogen ion implantation or high-energy nitrogen plasma bombardment can directly achieve nitriding treatment on the diamond surface, high-energy ions easily cause sputtering damage to the diamond lattice, forming dangling bonds and amorphous carbon layers. This results in increased surface roughness and weak bonding between nitrogen groups and the substrate, making nitrogen terminal desorption and performance degradation more likely during subsequent use. Furthermore, uneven plasma flux distribution directly causes significant differences in the surface nitrogen terminal coverage. Summary of the Invention

[0004] To address the issues of uneven nitrogen coverage on the surface of diamond nitrogen terminals prepared by existing methods and surface damage in diamond nitrogen terminals prepared by existing technologies, this invention proposes a method for preparing highly uniform diamond nitrogen terminals using MPCVD.

[0005] The technical solution adopted by the present invention to solve the above problems is as follows: The steps of the present invention include: Step 1: Clean the MPCVD equipment substrate and cavity wall with anhydrous ethanol and deionized water, and pre-etch the MPCVD reaction cavity with a mixed plasma of hydrogen and oxygen. Step 2: Pre-treat the diamond sample; after cleaning and drying, place the diamond substrate into the microwave plasma chemical vapor deposition reaction chamber; Step 3: Turn on the microwave using low-flow hydrogen plasma; Step 4: Prepare in-situ nitrogen terminals; introduce nitrogen gas, adjust microwave power, cavity pressure, and substrate temperature to form a purplish-red nitrogen plasma, and construct CN-bonded nitrogen terminals in-situ on the diamond surface; Step 5: Characterize the nitrogen-terminated diamond using X-ray photoelectron spectroscopy (XPS) and compare the 1332 nm of the diamond before and after nitrogen-termination treatment using Raman spectroscopy. The Raman peak changes were observed, and a polarizing microscope was used to examine the diamond surface for any damage.

[0006] Furthermore, in step 1, the water-cooled stage and cavity walls of the 2.5 GHz MPCVD equipment were wiped clean with anhydrous ethanol and deionized water, and the molybdenum substrate containing the diamond was ultrasonically cleaned sequentially with anhydrous ethanol and deionized water for 20 minutes each, passing through a 392 sccm... With 8 sccm The mixed plasma pre-etches the MPCVD reaction chamber to prevent the diamond sample from being contaminated by impurities remaining in the chamber.

[0007] Furthermore, the dimensions of the metallic molybdenum are Φ52 mm × 3 mm.

[0008] Furthermore, in step 2, the diamond has a crystal phase of 100 and a size of Φ5 mm × 0.5 mm.

[0009] Furthermore, in step 3, the microwave power during the start-up of the MPCVD equipment is 0.6 kW, and the gas pressure inside the cavity is 0.5 kPa. The flow rate is 5 sccm.

[0010] Furthermore, after the MPCVD equipment is started up in step four, it is gradually turned on... Flow rate up to 50 sccm, then turn off. The flow valve gradually increases the gas pressure and microwave power in the CVD reaction chamber until the temperature of the diamond in the CVD reaction chamber reaches 800℃.

[0011] Furthermore, in step four, the gas pressure in the MPCVD reaction chamber is adjusted to 12 kPa, the microwave power of MPCVD is 1.5kW, and the temperature of the diamond in the CVD reaction chamber is 800℃.

[0012] Furthermore, in step five, X-ray photoelectron spectroscopy was used to characterize the N-terminated diamond, and Raman spectroscopy was used to compare the 1332 nm of diamond before and after N-termination treatment. The Raman peak changes were observed, and a polarizing microscope was used to examine the diamond surface for any damage.

[0013] The beneficial effects of this invention are: 1. This invention exhibits high interfacial bonding strength: During nitrogen-termination, interfacial chemical bonding (CN covalent bonds) is simultaneously induced, reducing the interfacial state density to ≤5× e The desorption probability of nitrogen-terminated groups is reduced by more than 90%, significantly improving the long-term stability of the device under high humidity and high voltage conditions.

[0014] 2. The preparation process of the present invention is highly efficient: The diamond N-terminal preparation method based on MPCVD of the present invention is simple, requires no additional post-processing steps, improves the preparation efficiency by more than 60%, can be adapted to substrates of different sizes from 2 to 12 inches and different crystal orientations such as (100) / (111), is compatible with semiconductor-grade wafer manufacturing processes, and reduces the cost of large-scale production.

[0015] 3. This invention features low defects and high reliability: it avoids lattice damage and stress inhomogeneity caused by high nitrogen concentration, and the prepared nitrogen-terminated diamond has a surface roughness Ra ≤ 0.5 nm and an internal defect density ≤ It can achieve continuous growth with a thickness of ≥5 mm, meeting the material quality requirements of high-end devices.

[0016] 4. This invention has ultra-high uniformity: through multi-field coordinated regulation and precise control of zoned flow, the uniformity of nitrogen terminal concentration distribution in the diamond surface is ≤±5%, which is far superior to the existing process level of ±15%~±30%, meeting the stringent uniformity requirements of high-end applications such as quantum devices and semiconductor wafers.

[0017] 5. This invention possesses N-terminal stability: it cleans impurities from the diamond surface and can more effectively induce the formation of surface dangling bonds with active nitrogen atoms in situ. / Hybridization and reconstruction directly form strong CN covalent bonds. This preparation mechanism results in extremely tight bonding between the nitrogen terminator and the substrate. Attached Figure Description

[0018] Figure 1 This is a real-life image of the CVD window used to prepare diamond N-terminals by introducing N2 into the MPCVD plasma environment; Figure 2 (a) is the full X-ray photoelectron spectroscopy (XPS) spectrum of the diamond sample after being treated with nitrogen by the MPCVD method of the present invention; the characteristic peaks of C 1s (~285 eV) and O 1s (~532 eV) are clearly visible in the spectrum, and a significant characteristic peak of N 1s appears at a binding energy of ~400 eV. The appearance of this peak directly confirms that the method of the present invention can successfully introduce nitrogen into the diamond surface and achieve effective construction of nitrogen terminal; Figure 2 (b) is Figure 2 (a) High-resolution XPS peak fitting spectrum of the N 1s characteristic peak, used to further analyze the chemical bonding state of nitrogen-terminated diamond surface, CN single bond component at ~400.2 eV (green curve): corresponding to the diamond surface The hybrid carbon-nitrogen single bond structure provides direct evidence for the covalent bonding of nitrogen atoms with the diamond lattice; the C=N double bond composition at ~398.5 eV (blue curve): corresponds to the diamond surface. Hybrid carbon-nitrogen double bond structure is one of the core bonding forms of nitrogen-terminated structures. Detailed Implementation

[0019] Specific implementation method one: as follows Figure 1 and Figure 2 As shown in this embodiment, the method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD includes the following specific steps: Step 1: Clean the substrate and cavity walls of the microwave plasma chemical vapor deposition (MPCVD) equipment with anhydrous ethanol and deionized water, and then pass it through hydrogen gas (…). ) and oxygen ( The mixed plasma is used to pre-etch the MPCVD reaction chamber; the specific process is as follows: The water-cooled stage and cavity walls of the 2.45 GHz MPCVD equipment were cleaned by wiping with anhydrous ethanol and deionized water, and the molybdenum substrate containing diamond was ultrasonically cleaned sequentially with anhydrous ethanol and deionized water for 20 minutes each. Finally, it was subjected to a 392 sccm... With 8 sccm ( / A mixed plasma (2% concentration) is used to pre-etch the MPCVD reaction chamber to prevent the diamond sample from being etched by impurities remaining in the chamber (residual impurities in the CVD reaction chamber). (etc.) pollution; The size of the molybdenum metal is Φ52 mm×3 mm, which allows the nitrogen plasma to fully and uniformly contact the diamond sample during the subsequent nitrogen terminal treatment. Step 2, diamond sample pretreatment: After cleaning and drying, the diamond substrate is placed in the MPCVD reaction chamber; the crystal orientation of the diamond is (100) phase, and the size is Φ5 mm × 0.5 mm; Step 3, Low Flow Plasma activates microwaves: Microwaves are difficult to activate in pure plasma. It was started in a certain atmosphere, and to avoid high traffic. Generate diamond H-terminals; The microwave power at startup of the MPCVD equipment is 0.6 kW, and the gas pressure inside the cavity is 0.5 kPa. The flow rate is 5 sccm; Step 4, In-situ Nitrogen (N) Terminal Preparation: Introducing... By controlling microwave power, cavity pressure, and substrate temperature, a purplish-red nitrogen plasma is formed, and C-N bond N-terminated structures are constructed in situ on the diamond surface. After the dawn, it gradually began Flow rate up to 50 sccm, then turn off. The flow valve gradually increases the gas pressure and microwave power in the CVD reaction chamber until the temperature of the diamond in the CVD reaction chamber reaches 800℃. The gas pressure in the MPCVD reaction chamber was adjusted to 12 kPa, the microwave power of MPCVD was 1.5 kW, and the temperature of the diamond in the CVD reaction chamber was 800℃. Step 5: Characterize the N-terminated diamond using X-ray photoelectron spectroscopy and compare the 1332 nm of diamond before and after N-termination using Raman spectroscopy. Raman peak changes were observed, and a polarizing microscope was used to examine the diamond surface for any damage. The N-terminated diamond was characterized using X-ray photoelectron spectroscopy, and the 1332 nm of the diamond before and after N-termination was compared using Raman spectroscopy. The Raman peak changes were observed, and a polarizing microscope was used to examine the diamond surface for any damage.

[0020] In this embodiment, MPCVD refers to microwave plasma chemical vapor deposition.

[0021] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD, characterized in that, The specific steps include: Step 1: Clean the MPCVD equipment substrate and cavity wall with anhydrous ethanol and deionized water, and pre-etch the MPCVD reaction cavity with a mixed plasma of hydrogen and oxygen. Step 2: Pre-treat the diamond sample; after cleaning and drying, place the diamond substrate into the microwave plasma chemical vapor deposition reaction chamber; Step 3: Turn on the microwave using low-flow hydrogen plasma; Step 4: Prepare in-situ nitrogen terminals; introduce nitrogen gas, adjust microwave power, cavity pressure, and substrate temperature to form a purplish-red nitrogen plasma, and construct CN-bonded nitrogen terminals in-situ on the diamond surface; Step 5: Characterize the nitrogen-terminated diamond using X-ray photoelectron spectroscopy (XPS) and compare the 1332 nm of the diamond before and after nitrogen-termination treatment using Raman spectroscopy. The Raman peak changes were observed, and a polarizing microscope was used to examine the diamond surface for any damage.

2. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 1, characterized in that, In step 1, the water-cooled stage and cavity walls of the 2.5 GHz MPCVD equipment were wiped clean with anhydrous ethanol and deionized water. The molybdenum substrate containing the diamond was then ultrasonically cleaned sequentially with anhydrous ethanol and deionized water for 20 minutes each, passing through a 392 sccm... With 8 sccm The mixed plasma pre-etches the MPCVD reaction chamber to prevent the diamond sample from being contaminated by impurities remaining in the chamber.

3. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 2, characterized in that, The dimensions of the molybdenum metal are Φ52 mm × 3 mm.

4. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 1, characterized in that, In step 2, the diamond has a crystal phase of 100 and a size of Φ5 mm × 0.5 mm.

5. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 1, characterized in that, In step 3, the microwave power during the start-up of the MPCVD equipment is 0.6 kW, and the gas pressure inside the cavity is 0.5 kPa. The flow rate is 5 sccm.

6. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 1, characterized in that, After the MPCVD equipment is started in step four, gradually turn on... Flow rate up to 50 sccm, then turn off. The flow valve gradually increases the gas pressure and microwave power in the CVD reaction chamber until the temperature of the diamond in the CVD reaction chamber reaches 800℃.

7. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 1, characterized in that, In step four, the gas pressure in the MPCVD reaction chamber is adjusted to 12 kPa, the microwave power of MPCVD is 1.5 kW, and the temperature of the diamond in the CVD reaction chamber is 800℃.

8. The method for preparing highly uniform diamond nitrogen-terminated diamond using MPCVD according to claim 1, characterized in that, In step five, X-ray photoelectron spectroscopy was used to characterize the N-terminated diamond, and Raman spectroscopy was used to compare the 1332 nm of diamond before and after N-termination treatment. The Raman peak changes were observed, and a polarizing microscope was used to examine the diamond surface for any damage.

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