A method for growing wafer-scale large-size diamond by MPCVD

Abstract

The application discloses a method for growing wafer-level large-size diamond by using MPCVD, and comprises the following steps: pretreating a self-supporting diamond substrate; manufacturing a transition layer on the self-supporting diamond substrate; placing the self-supporting diamond substrate with the transition layer into an MPCVD device to deposit and grow target diamond on the transition layer; and separating the target diamond from the self-supporting diamond substrate along the interface of the transition layer. The application uses a self-supporting diamond sheet as a substrate for growing wafer-level large-size diamond by using MPCVD, constructs a high-temperature-resistant transition layer between the diamond substrate and the target diamond, effectively blocks the formation of SP3 carbon-carbon bonds between the substrate and the target diamond through the transition layer, solves the technical problems that a traditional homogeneous diamond substrate and epitaxial diamond are prone to be bonded, cannot be separated and the substrate cannot be recycled, and realizes efficient and lossless preparation of wafer-level large-size diamond and recycling of the substrate.

Description

Technical Field

[0001] This invention relates to the field of diamond preparation technology, and in particular to a method for growing wafer-scale large-size diamonds using MPCVD. Background Technology

[0002] Microwave plasma chemical vapor deposition (MPCVD) is currently the core process for preparing high-quality, large-size diamond wafers. With its advantages such as high deposition rate, uniform film quality, and low impurity content, it has become the mainstream technology for mass production of wafer-level diamonds.

[0003] In traditional MPCVD diamond growth processes, if ordinary heterogeneous substrates or ordinary pads are used as growth carriers, the uneven temperature distribution on the substrate surface during the high-temperature growth process of MPCVD leads to significant temperature differences within the diamond thick film growth plane, inducing severe internal stress. This ultimately causes quality defects such as stress cracking and overall bending deformation in the diamond wafer, making it difficult to produce large-size diamonds. If a homogeneous diamond substrate is used, SP3 carbon-carbon bonds are easily formed between the substrate and the target diamond, causing the substrate and the target diamond to completely adhere and making effective separation impossible. The substrate is used only once and cannot be reused, which greatly increases the manufacturing cost of large-size diamond wafers and further limits the large-scale mass production of wafer-level large-size diamonds.

[0004] Therefore, in the traditional MPCVD diamond growth process, due to the technical bottlenecks of existing processes and substrate systems, the MPCVD method has an extremely low yield when preparing large-size, especially wafer-level diamond self-supported wafers with a diameter of 8 inches or more, making it difficult to achieve large-scale commercialization. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for growing large-size wafer-level diamonds using MPCVD. This method utilizes a self-supporting diamond wafer as the growth substrate and constructs a transition layer between the substrate and the target diamond. This transition layer blocks the sputtering between the target diamond and the diamond substrate. 3 The formation of carbon-carbon bonds enables effective separation between the grown substrate and the target diamond, and the diamond substrate can be reused.

[0006] The objective of this invention is achieved through the following technical solution: A method for growing wafer-scale large-size diamonds using MPCVD includes the following steps: S1, Pretreated self-supporting diamond substrate; S2. Fabricate a transition layer on a self-supporting diamond substrate; S3. Place the self-supporting diamond substrate with the transition layer into the MPCVD equipment and deposit and grow the target diamond on the transition layer. S4. Separate the target diamond from the self-supporting diamond substrate along the transition layer interface.

[0007] Furthermore, the method for growing wafer-level large-size diamond using MPCVD includes the following steps: S1, Pretreated self-supporting diamond substrate; S2. Fabricate a transition layer on a self-supporting diamond substrate; S3. Place the self-supporting diamond substrate with the transition layer into the MPCVD equipment, and form a diamond nucleation layer on the transition layer using bias nucleation. S4. Continue to deposit and grow the target diamond on the transition layer; S5. Separate the target diamond from the self-supporting diamond substrate along the transition layer interface.

[0008] Furthermore, the method for growing wafer-level large-size diamond using MPCVD includes the following steps: S1, Pretreated self-supporting diamond substrate; S2. Fabricate a transition layer on a self-supporting diamond substrate; S3. Coat the transition layer with a diamond seed layer. The method for coating the diamond seed layer is at least one of dip coating, smear coating, scraping coating, spin coating, spraying, printing, and ultrasonic treatment. The diamond nanoparticles in the diamond seed layer preferably have a particle size of less than 10 nm to ensure uniform nucleation.

[0009] S4. Place the self-supporting diamond substrate with the transition layer into the MPCVD equipment and deposit and grow the target diamond on the transition layer. S5. Separate the target diamond from the self-supporting diamond substrate along the transition layer interface.

[0010] Furthermore, in step S2, the method for creating the transition layer is at least one of dip coating, smear coating, scraping coating, spin coating, spraying, printing, electrochemical deposition, and physicochemical deposition.

[0011] Furthermore, the self-supporting diamond is a polycrystalline diamond grown by MPCVD, hot filament method or DC arc method.

[0012] Furthermore, the self-supporting diamond is a polycrystalline diamond formed by sintering diamond powder.

[0013] Furthermore, the self-supporting diamond has a thickness of 0.1-50 mm, a diameter of 1-300 mm, and a surface roughness of <1 μm.

[0014] Further, the transition layer is at least one of the following: graphite layer, amorphous carbon layer, silicon dioxide layer, aluminum oxide layer, zirconium oxide layer, chromium oxide layer, magnesium oxide layer, calcium oxide layer, beryllium oxide layer, yttrium oxide layer, silicon nitride layer, aluminum nitride layer, titanium nitride layer, zirconium nitride layer, silicon carbide layer, titanium carbide layer, zirconium carbide layer, tungsten carbide layer, molybdenum layer, tungsten layer, tantalum layer, titanium layer, iridium layer, nickel layer, iron layer, gold layer, copper layer, and silicon layer. The thickness of the transition layer is 0.01-1 μm. The transition layer material is selected from graphite, oxide, nitride, carbide, metal material, or composite system that can withstand temperatures above 900℃, and the thickness is controlled between 0.01 μm and 1 μm. A thickness less than 0.01 μm results in insufficient isolation and is prone to local bonding between the substrate and the target diamond. A thickness exceeding 1 μm is prone to generating intralayer stress during high-temperature growth, leading to premature cracking of the transition layer.

[0015] Furthermore, the target diamond is separated from the self-supporting diamond substrate along the transition layer interface using any one of the following methods: mechanical micro-exfoliation, thermal stress exfoliation, or chemical etching exfoliation. Preferably, high-temperature acid-base etching exfoliation is preferred for nitride and oxide transition layers; mechanical splitting and blade exfoliation are preferred for amorphous carbon and graphite carbonaceous transition layers; and acid etching exfoliation can be used for metallic transition layers.

[0016] The beneficial effects of this invention are: This invention utilizes MPCVD technology to grow wafer-scale large-size diamonds. A self-supporting diamond substrate is used as the growth substrate, and a transition layer is constructed between the substrate and the target diamond. This transition layer blocks the formation of SP3 carbon-carbon bonds between the target diamond and the diamond substrate, achieving effective separation of the substrate and target diamond after growth. Furthermore, the diamond substrate can be reused. This invention constructs a high-temperature resistant transition layer between the diamond substrate and the target diamond, effectively blocking the formation of SP3 carbon-carbon bonds between the substrate and the epitaxial diamond. This solves the technical problem of the inability to separate homogeneous diamond substrates from the target diamond due to adhesion, and the peeling process does not damage the diamond film layer, significantly improving the quality of the large-size diamond wafer. The diamond substrate after peeling can be repeatedly recycled, significantly reducing the manufacturing cost of wafer-scale large-size diamonds. Detailed Implementation

[0017] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0018] Example 1 A method for growing wafer-scale large-size diamonds using MPCVD, comprising the following steps: Step S1: Pretreatment of self-supporting diamond substrate A self-supporting polycrystalline diamond sheet prepared by hot filament method was selected as the substrate. The substrate diameter was 200 mm and the thickness was 5 mm. The upper and lower surfaces of the substrate were coarsely ground and finely ground with diamond abrasive. The roughness Ra of the upper surface of the substrate was less than 100 nm.

[0019] The surface was ultrasonically cleaned with acetone for 15 minutes, anhydrous ethanol for 10 minutes, and deionized water for 10 minutes in sequence to remove oil, polishing debris and particulate impurities. The product was then dried in an oven at 120°C for later use.

[0020] Step S2: Prepare aluminum nitride transition layer DC reactive magnetron sputtering equipment was used, with a target material of 99.99% high-purity aluminum and a target-to-substrate distance of 80 mm. Sputtering atmosphere: Argon flow rate 60 sccm, nitrogen flow rate 25 sccm; sputtering power 180W, cavity base vacuum 5×10 -4 Pa, substrate constant temperature 200℃; continuous deposition for 30 min, total thickness of aluminum nitride transition layer controlled at 200nm; aluminum nitride is a high temperature resistant nitride, which can withstand the high temperature of MPCVD diamond growth above 900℃, and can be removed by high temperature strong alkaline solution corrosion, as a sacrificial isolation layer.

[0021] Step S3: Spin-coating a diamond nano-seed layer Preparation of diamond nanoparticle dispersion: A mixed solution of DMSO, isopropanol, and acetone (volume fraction 5:3:2) was used as the dispersion solvent. The solid content of the diamond nanoparticles (particle size 5-8 nm) was 1 wt%. The mixture was magnetically stirred for 2 h and ultrasonically dispersed for 30 min. A spin coater was used to uniformly coat the aluminum nitride transition layer. The low-speed pre-coating speed was 500 r / min and the pre-coating time was 3 s. The high-speed spin-drying speed was 3000 r / min and the spin-drying time was 300 s, forming a uniform diamond seed layer on the surface of the transition layer.

[0022] Step S4: MPCVD deposition and growth of target polycrystalline diamond The workpiece with a substrate, transition layer, and seed layer is placed in a 915MHz MPCVD device with the transition layer and seed layer facing upwards. The cavity was evacuated to a base vacuum of 5×10⁻⁶. - 3 Torr; High-purity hydrogen and methane are introduced as growth gas sources: H2 flow rate 1200 sccm, CH4 flow rate 18 sccm, nitrogen-hydrogen mixture (nitrogen content 1.5%) 10 sccm; The cavity pressure is maintained at 120 Torr, the microwave power is 50 kW, and continuous deposition is carried out for 250 h until the target polycrystalline diamond film thickness reaches 500 μm. The microwave and gas sources are then turned off, and the furnace is cooled to room temperature.

[0023] Step S5: Separation of the target diamond from the substrate, and recycling and reuse of the substrate. After the workpiece is cooled to room temperature, a green laser is used to cut the edge: the laser wavelength is 532nm, the power is 30W, and the spot diameter is 20μm. The excess parts grown laterally and laterally are removed along the edge of the wafer, while the substrate with a diameter of 200mm and the target diamond are retained. The etching solution is prepared as follows: a mixed aqueous solution of 40wt% KOH and 20wt% NaOH, with the addition of 0.3wt% sodium dodecylbenzenesulfonate cationic surfactant; The workpiece was completely immersed in the etching solution, heated to 120°C in an oil bath, and subjected to ultrasonic vibration at 60W for 2 hours. The aluminum nitride transition layer was completely dissolved, and the target diamond self-supporting sheet automatically separated from the diamond substrate. After separation, the self-supporting diamond substrate can be neutralized with dilute hydrochloric acid, ultrasonically cleaned with deionized water, and repaired by nanopolishing before being reused in the next MPCVD growth cycle.

[0024] The 200mm diamond wafers prepared in this embodiment have no visible cracks, warpage <3μm / 200mm, internal stress ≤120MPa, and no diamond damage at the peeling interface.

[0025] Example 2 A method for growing wafer-scale large-size diamonds using MPCVD, comprising the following steps: Step S1: Pretreatment of self-supporting diamond substrate A self-supporting polycrystalline diamond substrate with a diameter of 200 mm and a thickness of 3 mm was prepared by hot filament method. The upper and lower surfaces were finely ground and polished, with the upper surface roughness Ra < 100 nm. The substrate was ultrasonically cleaned with 80 W: acetone for 15 min → ethanol for 10 min → deionized water for 10 min, and then dried in an oven at 120 °C for 30 min to remove carbon impurities and polishing dust from the surface.

[0026] Step S2: In-situ deposition of an amorphous carbon transition layer in the MPCVD chamber. The cleaned and dried diamond substrate was placed directly into a 915MHz MPCVD instrument, and the chamber was evacuated to a base vacuum of 5×10⁻⁶. -3 Torr; Introduce process mixed gas with a gas volume ratio of H2:CH4:N2=1000:100:15, a total gas flow rate of 1115 sccm, a stable chamber pressure of 60 Torr, and maintain the substrate temperature at 600℃. Continuously deposit for 20 min to obtain a uniform amorphous carbon transition layer with a thickness of 0.8 μm. After cooling, remove the diamond substrate with the transition layer. In this process, the methane / hydrogen ratio is >8% and the nitrogen / hydrogen ratio is >0.5%. Under low-temperature conditions, only amorphous carbon without sp³ bonds is generated, which will not form strong covalent bonds with the underlying diamond substrate and can be used as an isolation sacrificial layer.

[0027] Step S3: Apply composite seed layer Prepare a mixed nano-dispersion using anhydrous ethanol as solvent. The solid content of diamond nanoparticles (5-10 nm) is 0.6 wt%, the solid content of SiO2 nanoparticles (15 nm) is 0.2 wt%, and 0.1 wt% polyethylene glycol dispersant is added. Stir magnetically for 2 h and then ultrasonically disperse for 30 min. The spin coating process is the same as in Example 1: pre-coat at 500 r / min for 3 s, spin dry at 3000 r / min for 300 s, forming a composite nucleation seed layer on the surface of the amorphous carbon transition layer.

[0028] Step S4: MPCVD thick film growth of target diamond The workpiece, containing the substrate, transition layer, and seed layer, is placed in a 915MHz MPCVD machine, and the cavity is evacuated to a base vacuum of 5×10⁻⁶. -3 Torr, high-purity hydrogen and methane are introduced as growth gas sources: H2 flow rate 1200 sccm, CH4 flow rate 18 sccm, nitrogen-hydrogen mixture (nitrogen content 1.5%) 10 sccm; the cavity pressure is maintained at 120 Torr, microwave power is 50 kW, and continuous deposition is carried out for 250 h until the target polycrystalline diamond film thickness reaches 500 μm. The microwave and gas sources are then turned off, and the furnace is cooled to room temperature.

[0029] Step S5: Mechanically split and separate the workpiece After cooling, the green laser is used to trim the edge (the specific process is the same as in Example 1) to remove the edge protrusions; Using a cemented carbide cleaver, with the cleaver tip aligned with the amorphous carbon interface between the substrate and the target diamond, a small mechanical stress of 0.2 MPa is uniformly applied every 15° along the circumference of the wafer. After two cycles, the amorphous carbon interface breaks, thus separating the target diamond wafer from the diamond substrate without damage. The residual amorphous carbon on the substrate surface is cleaned with oxygen plasma (100W power, 10min). After separation, the diamond substrate is simply polished to remove the residual amorphous carbon on the surface and can be reused for the next batch of growth.

[0030] The 200mm diamond wafers prepared in this embodiment have a warpage of <2.8μm / 200mm, no stress cracks, a peeling breakage rate of <1%, and wafer uniformity that is better than the control group without a transition layer.

[0031] Example 3 A method for growing wafer-scale large-size diamonds using MPCVD differs from Example 1 in that: 1. Substrate: PCD polycrystalline diamond substrate was prepared by high-temperature and high-pressure sintering of diamond micropowder. The substrate was 3 mm thick and 50.8 mm in diameter. The sintering temperature was 1500℃ and the pressure was 5.5 GPa. The substrate surface was coarsely ground and finely ground with diamond abrasive, Ra < 80 nm. The cleaning and drying process was the same as in Example 1.

[0032] 2. Preparation of silicon carbide transition layer: medium-frequency magnetron sputtering PVD process, SiC composite target, target-substrate distance 70mm; argon flow rate 50sccm, sputtering power 220W, substrate constant temperature 250℃, deposition for 160min, silicon carbide transition layer thickness 0.8μm.

[0033] 3. Diamond seed layer: The substrate is completely immersed in the nano-dispersion of the formulation in Example 1 by ultrasonic impregnation. The substrate is ultrasonically impregnated at 80W for 25 minutes, and then dried at 100℃ for 30 minutes. Diamond nano-crystals are uniformly attached to the surface.

[0034] 4. MPCVD growth: 2.45GHz equipment, microwave power 5kW, substrate temperature 880℃, H2 flow rate 500sccm, CH4 flow rate 12sccm, deposition rate 1.3μm / h, continuous deposition for 462h, target diamond thickness 600μm.

[0035] 5. Peeling method: High-temperature molten alkaline solution corrosion, with a ratio of 55wt% KOH + 25wt% NaOH, heated to 180℃ in a molten state, soaked and ultrasonically treated for 3 hours, the silicon carbide layer is completely corroded and dissolved, achieving separation.

[0036] The 50.8mm diameter diamond wafer obtained in this embodiment is free from bending, has an internal stress of ≤135MPa, and has no interface adhesion defects.

[0037] Example 4 A method for growing wafer-scale large-size diamonds using MPCVD differs from Example 1 in that: 1. Self-supporting diamond substrate: hot-wire polycrystalline diamond, 1 mm thick, 50.8 mm in diameter; double-sided precision grinding, upper surface Ra < 90 nm, cleaning and drying process is the same as in Example 1.

[0038] 2. Silicon transition layer preparation: A 200 nm silicon transition layer was prepared on a diamond substrate by magnetron sputtering.

[0039] 3. MPCVD growth is a two-stage process: Bias nucleation stage: The above-mentioned workpiece with substrate and silicon transition layer is placed in the MPCVD equipment with H2 flow rate of 1000 sccm, CH4 flow rate of 20 sccm, cavity pressure of 90 Torr, microwave power of 2.0 kW, substrate temperature of 950℃, and DC negative bias voltage of -250V is applied for 30 min to increase the crystal nucleation density. Conventional growth stage: bias voltage off, microwave power adjusted to 5kW, substrate constant temperature 920℃, H2 flow rate 500sccm, CH4 flow rate 15sccm, deposition rate 2μm / h, continuous deposition for 200h, target diamond thickness 400μm.

[0040] 4. Stripping method: Immerse in a mixed solution of hydrofluoric acid and nitric acid, and then etch and strip along the silicon transition layer interface; the substrate can be reused for the next batch of growth after cleaning.

[0041] The 50.8mm diamond film prepared in this embodiment was unbroken, the interface was completely separated, and there was no damage from the peeling off of the substrate diamond.

[0042] Based on the disclosure in the foregoing specification, those skilled in the art can make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for growing wafer-scale large-size diamond using MPCVD, comprising using a self-supporting diamond as a substrate, MPCVD deposition of the target diamond, and separation of the target diamond, characterized in that: Includes the following steps: S1, Pretreated self-supporting diamond substrate; S2. Fabricate a transition layer on a self-supporting diamond substrate; S3. Place the self-supporting diamond substrate with the transition layer into the MPCVD equipment and deposit and grow the target diamond on the transition layer. S4. Separate the target diamond from the self-supporting diamond substrate along the transition layer interface.

2. The method for growing wafer-level large-size diamond using MPCVD according to claim 1, characterized in that: Includes the following steps: S1, Pretreated self-supporting diamond substrate; S2. Fabricate a transition layer on a self-supporting diamond substrate; S3. Place the self-supporting diamond substrate with the transition layer into the MPCVD equipment, and form a diamond nucleation layer on the transition layer using bias nucleation. S4. Continue to deposit and grow the target diamond on the transition layer; S5. Separate the target diamond from the self-supporting diamond substrate along the transition layer interface.

3. The method for growing wafer-level large-size diamond using MPCVD according to claim 1, characterized in that: Includes the following steps: S1, Pretreated self-supporting diamond substrate; S2. Fabricate a transition layer on a self-supporting diamond substrate; S3. Apply a diamond seed layer onto the transition layer; S4. Place the self-supporting diamond substrate with the transition layer into the MPCVD equipment and deposit and grow the target diamond on the transition layer. S5. Separate the target diamond from the self-supporting diamond substrate along the transition layer interface.

4. The method for growing wafer-level large-size diamond using MPCVD according to claim 3, characterized in that: In step S3, the method for coating the diamond seed layer is at least one of dip coating, smear coating, scraping coating, spin coating, spraying, printing, and ultrasonic treatment.

5. The method for growing wafer-level large-size diamond using MPCVD according to any one of claims 1 to 4, characterized in that: In step S2, the method for creating the transition layer is at least one of dip coating, trowel coating, scraping coating, spin coating, spraying, printing, electrochemical deposition, and physicochemical deposition.

6. The method for growing wafer-scale large-size diamond by MPCVD according to any one of claims 1 to 4, characterized in that: The self-supporting diamond is a polycrystalline diamond grown by MPCVD, hot filament method or DC arc method.

7. The method for growing wafer-scale large-size diamond by MPCVD according to any one of claims 1 to 4, characterized in that: The self-supporting diamond is a polycrystalline diamond formed by sintering diamond powder.

8. The method for growing wafer-level large-size diamond using MPCVD according to any one of claims 1 to 4, characterized in that: The self-supporting diamond has a thickness of 0.1-50 mm, a diameter of 1-300 mm, and a surface roughness of <1 μm.

9. The method for growing wafer-level large-size diamond using MPCVD according to any one of claims 1 to 4, characterized in that: The transition layer is at least one of the following: graphite layer, amorphous carbon layer, silicon dioxide layer, aluminum oxide layer, zirconium oxide layer, chromium oxide layer, magnesium oxide layer, calcium oxide layer, beryllium oxide layer, yttrium oxide layer, silicon nitride layer, aluminum nitride layer, titanium nitride layer, zirconium nitride layer, silicon carbide layer, titanium carbide layer, zirconium carbide layer, tungsten carbide layer, molybdenum layer, tungsten layer, tantalum layer, titanium layer, iridium layer, nickel layer, iron layer, gold layer, copper layer, and silicon layer. The thickness of the transition layer is 0.01-1 μm.

10. The method for growing wafer-level large-size diamond using MPCVD according to any one of claims 1 to 4, characterized in that: The target diamond is separated from the self-supporting diamond substrate along the transition layer interface by any one of the following methods: mechanical micro-exfoliation, thermal stress exfoliation, or chemical corrosion exfoliation.