A method for reducing mutual interference in diamond crystal growth based on edge coating treatment

Abstract

The present invention provides a method for reducing mutual interference in the growth of diamond crystals based on edge coating treatment, which belongs to the field of diamond growth. The following steps are included: S1: Select suitable diamond seeds and clean the diamond seeds; S2: Perform coating treatment on the four sides of the diamond; S3: Place the seeds into the MPCVD chamber to grow diamond blanks; S4: Treat the blanks after the growth is completed to remove the polycrystalline and graphite at the edges to form diamond single crystals. The beneficial effect of the present invention is that, compared with the prior art: the present invention performs coating treatment on the seeds, so that the edges of the diamond seeds are no longer diamonds, do not have diamond lattices and atoms, and when diamond atoms fall onto the upper surface of the film, only polycrystalline diamond or graphite will be formed, which prevents the seeds from growing horizontally along the edges, thereby preventing the seeds from expanding horizontally and reducing mutual interference in the growth of diamond crystals.

Description

Technical Field

[0001] The invention belongs to the field of diamond growth and relates to a method for reducing mutual interference in the growth of diamond crystals based on edge coating treatment. Background Art

[0002] Diamond is a cubic crystal composed of carbon. Diamond has the highest hardness among all known materials, as well as excellent optical and thermal properties, and is widely used in various industrial processing and semiconductor industries.

[0003] There are two technical paths for the growth of diamond crystals. One is high temperature and high pressure, which simulates the formation of diamond crystals under natural geological conditions. Generally, 4-7GPa high pressure and 1000-1500℃ high temperature conditions are used. The other method is the CVD method. Under vacuum conditions, diamond atoms grow in layers on diamond seeds to form diamond crystals. Among various CVD growth methods for diamond growth, MPCVD growth has gradually become the mainstream growth method due to its advantages of high purity and high crystal quality.

[0004] In MPCVD growth, the selection and treatment of crystal seeds have always been the core factors for improving production yield. The selection of crystal seeds is generally controlled by parameters such as the size, crystal orientation, and crystal face of the crystal seeds. In current MPCVD growth, based on factors such as cost and process, diamond seeds with (001) crystal faces are generally selected. The side length of the crystal seeds is generally between 7 and 40 mm, and the thickness of the crystal seeds is generally between 0.3 and 1.5 mm. For the crystal orientation of the four sides of the crystal seeds, there are generally two types in MPCVD growth. One type has four sides that are <100> The other is the four sides are <110> These two crystal directions are relatively easy to control the growth direction and can ensure the yield of diamond growth.

[0005] In the process of growing diamond by MPCVD, if a microwave frequency of 2.45 GHz is used, the current growth table diameter is between 50 mm and 100 mm; if a microwave frequency of 915 MHz is used, the growth table diameter is between 100 and 300 mm. Since the size of the seed crystal is much smaller than the growth table, the conventional practice is to place as many seed crystals as possible on the growth table to increase batch output and reduce production costs. Common placement methods include:

[0006] 1) Zero gap placement, the seeds are close to each other, and the growth of the seeds will affect each other;

[0007] 2) Clearance placement, see Figure 1, the gap between the seeds is controlled between 0.3 and 1.5 mm, and the choice of the gap matches the process parameters. In this growth mode, both seeds are used in the growth. Due to the anisotropy of diamond growth rate, the interaction between seeds is divided into the following two situations;

[0008] for <100> The seeds on the edge will generally grow outward in the direction of the seed plane, which will eventually cause the two adjacent seeds to contact each other. The surface of the last seed will extend to the surface of another seed, and finally cause a part of the surface of the covered seed to have no single crystal growing in the vertical direction. For the seeds with extended crystal faces, the extended part of the crystal is generally difficult to use, which eventually leads to a decrease in yield;

[0009] for <110> During the crystal growth process, <110> The edges will shrink inward, causing the growth surface to shrink and eventually form a cone, which will ultimately lead to a decrease in overall output.

[0010] In summary, both methods will lead to reduced output and yield. Based on this, how to reduce mutual interference during the growth of diamond crystals is a problem that the existing technology urgently needs to solve. Summary of the invention

[0011] In order to solve the above problems, the purpose of the present invention is to provide a method for reducing mutual interference in the growth of diamond crystals based on edge coating treatment, which can avoid mutual interference and extrusion between diamond crystals during the growth process and ensure that all seed crystals on the growth table can grow in a balanced and stable manner.

[0012] In order to achieve the above object, the technical solution of the present invention is as follows.

[0013] The present invention provides a method for reducing mutual interference in the growth of diamond crystals based on edge coating treatment, comprising the following steps:

[0014] S1: Select appropriate diamond seed crystals and clean them;

[0015] S2: Coating the four sides of the diamond;

[0016] S3: placing the seed crystal into the MPCVD chamber to grow the diamond blank;

[0017] S4: Cut and grind the finished blank to remove the polycrystalline and graphite at the edge to obtain a diamond single crystal.

[0018] Furthermore, in step S1, the side length of the diamond seed is between 7 and 50 mm, and the directions of the four sides are <100> The crystal phases are parallel.

[0019] Furthermore, in step S1, the cleaning process of the diamond seed crystal is: acid cleaning, organic solvent cleaning, and deionized water cleaning to remove attachments on the surface of the seed crystal.

[0020] Furthermore, in step S2, after the edge of the diamond seed crystal is coated, the edge of the diamond seed crystal is no longer diamond and does not have diamond lattices and atoms. When diamond atoms fall onto the upper surface of the film, these atoms will only form polycrystalline diamond or graphite, preventing the seed crystal from growing horizontally along the edge of the single crystal, thereby preventing the seed crystal from expanding horizontally and reducing mutual interference in the growth of diamond crystals.

[0021] Further, step S2 includes:

[0022] S21: depositing a photoresist on the surface of the diamond seed crystal to form a photoresist layer;

[0023] S22: exposing the photoresist layer and cleaning it with an organic solvent to expose the diamond surface in the area where the coating is required;

[0024] S23: performing physical vapor deposition coating on the diamond seed crystal;

[0025] S24: placing the seed crystal into a degumming solvent to dissolve the photoresist layer, thereby exposing the diamond surface in the uncoated area.

[0026] Furthermore, in step S21, the method of depositing the photoresist layer includes but is not limited to spin coating.

[0027] Furthermore, in step S23, physical vapor deposition includes magnetron sputtering and arc vapor deposition.

[0028] Furthermore, in step S23, the material used for physical vapor deposition is a material with a high melting point and promoting the growth of polycrystalline or graphite, including but not limited to high melting point metals, high melting point oxides, graphite, and silicon.

[0029] Furthermore, when high melting point metals are used for coating, the film thickness exceeds 50nm. The high melting point metals used include molybdenum and tungsten, and the melting point exceeds 1500°C. When high melting point oxides are used for coating, the film thickness exceeds 50nm and the melting point exceeds 1500°C. When graphite and silicon are used, the film thickness exceeds 500mm.

[0030] Further, in step S23, the process of physical vapor deposition is: placing the diamond seed crystal in a high-temperature furnace for heat treatment, the heat treatment atmosphere is air or oxygen, the heat treatment temperature exceeds 600°C, the heat treatment time is not less than 1 minute, so that the exposed diamond surface is converted into graphite, and the thickness of the converted graphite exceeds 0.05 mm.

[0031] Further, in step S3, the growth conditions are:

[0032] Process gas: carrier gas is H2, with a flow range of 500sccm to 10slm; carbon source is CH4, with a flow rate of 6-14% of H2; coloring gas is N2, which is added in the form of pure nitrogen or mixed gas, with the N2 content ranging from 10ppm to 8000ppm of CH4;

[0033] Growth pressure: 80-250Torr;

[0034] Growth power: microwave power 5kW to 70kW;

[0035] Growth temperature: 900-1300 degrees Celsius;

[0036] Growth rate: 6-500um / hr.

[0037] The beneficial effect of the present invention is that, compared with the prior art, the present invention performs a coating process on the seed crystal, so that the edge of the diamond seed crystal is no longer diamond, does not have diamond lattices and atoms, and when diamond atoms fall onto the upper surface of the film, only polycrystalline diamond or graphite is formed, thereby preventing the seed crystal from growing horizontally along the edge of the single crystal, thereby preventing the seed crystal from expanding horizontally and reducing mutual interference in the growth of diamond crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a microscopic photograph of diamond seed crystals after growth when placed in gaps in the prior art.

[0039] Figure 2 This is a microscopic photograph of the diamond seed crystal after edge coating treatment in Example 1.

[0040] Figure 3 Schematic diagram of the structure of the diamond seed after edge coating treatment in Example 1. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] To achieve the above objectives, the technical solution of the present invention is as follows.

[0043] See also Figure 2-3 ,

[0044] Embodiment 1:

[0045] This embodiment provides a method for reducing mutual interference in the growth of diamond crystals based on edge coating treatment, comprising the following steps:

[0046] S1: Select appropriate diamond seed crystals and clean them;

[0047] S2: Coating the four sides of the diamond;

[0048] S3: placing the seed crystal into the MPCVD chamber to grow the diamond blank;

[0049] S4: Cut and grind the finished blank to remove the polycrystalline and graphite at the edge to obtain a diamond single crystal.

[0050] Furthermore, in step S1, the diamond seed crystal has a side length of 7 mm, and the directions of the four sides are <100> The crystal phases are parallel.

[0051] Furthermore, in step S1, the cleaning process of the diamond seed crystal is: acid cleaning, organic solvent cleaning, and deionized water cleaning to remove attachments on the surface of the seed crystal.

[0052] Furthermore, in step S2, after the edge of the diamond seed crystal is coated, the edge of the diamond seed crystal is no longer diamond and does not have diamond lattices and atoms. When diamond atoms fall onto the upper surface of the film, these atoms will only form polycrystalline diamond or graphite, preventing the seed crystal from growing horizontally along the edge of the single crystal, thereby preventing the seed crystal from expanding horizontally and reducing mutual interference in the growth of diamond crystals.

[0053] Further, step S2 includes:

[0054] S21: depositing a photoresist on the surface of the diamond seed crystal to form a photoresist layer;

[0055] S22: exposing the photoresist layer and cleaning it with an organic solvent to expose the diamond surface in the area where the coating is required;

[0056] S23: performing physical vapor deposition coating on the diamond seed crystal;

[0057] S24: placing the seed crystal into a degumming solvent to dissolve the photoresist layer, thereby exposing the diamond surface in the uncoated area.

[0058] Furthermore, in step S21, the method of depositing the photoresist layer is spin coating.

[0059] Furthermore, in step S23, the physical vapor deposition adopts a magnetron sputtering method.

[0060] Furthermore, in step S23, the material used for physical vapor deposition is high melting point metals such as molybdenum and tungsten, the film thickness is more than 50nm, and the melting point is more than 1500°C.

[0061] Further, in step S23, the process of physical vapor deposition is: placing the diamond seed crystal in a high-temperature furnace for heat treatment, the heat treatment atmosphere is air or oxygen, the heat treatment temperature exceeds 600°C, the heat treatment time is not less than 1 minute, so that the exposed diamond surface is converted into graphite, and the thickness of the converted graphite exceeds 0.05 mm.

[0062] Further, in step S13, the growth conditions are:

[0063] Process gas: carrier gas is H2, flow rate is 500sccm; carbon source is CH4, flow rate is 6 of H2; coloring gas is N2, N2 is added in the form of pure nitrogen or mixed gas, N2 content is 10ppm of CH4;

[0064] Growth pressure: 80Torr;

[0065] Growth power: microwave power 5kW;

[0066] Growth temperature: 900 degrees Celsius;

[0067] Growth rate: 6um / hr.

[0068] pass Figure 2 and Figure 1 By comparison, it can be seen that after the edge of the seed crystal is processed by the edge coating process, the growth of the seed crystal along the horizontal direction can be reduced and mutual interference during the growth of the seed crystal can be avoided.

[0069] Embodiment 2:

[0070] This embodiment provides a method for reducing mutual interference in the growth of diamond crystals based on edge coating treatment, comprising the following steps:

[0071] S1: Select appropriate diamond seed crystals and clean them;

[0072] S2: Coating the four sides of the diamond;

[0073] S3: placing the seed crystal into the MPCVD chamber to grow the diamond blank;

[0074] S4: Cut and grind the finished blank to remove the polycrystalline and graphite at the edge to obtain a diamond single crystal.

[0075] Furthermore, in step S1, the diamond seed crystal has a side length of 50 mm, and the directions of the four sides are <100> The crystal phases are parallel.

[0076] Furthermore, in step S1, the cleaning process of the diamond seed crystal is: acid cleaning, organic solvent cleaning, and deionized water cleaning to remove attachments on the surface of the seed crystal.

[0077] Furthermore, in step S2, after the edge of the diamond seed crystal is coated, the edge of the diamond seed crystal is no longer diamond and does not have diamond lattices and atoms. When diamond atoms fall onto the upper surface of the film, these atoms will only form polycrystalline diamond or graphite, preventing the seed crystal from growing horizontally along the edge of the single crystal, thereby preventing the seed crystal from expanding horizontally and reducing mutual interference in the growth of diamond crystals.

[0078] Further, step S2 includes:

[0079] S21: depositing a photoresist on the surface of the diamond seed crystal to form a photoresist layer;

[0080] S22: exposing the photoresist layer and cleaning it with an organic solvent to expose the diamond surface in the area where the coating is required;

[0081] S23: performing physical vapor deposition coating on the diamond seed crystal;

[0082] S24: placing the seed crystal into a degumming solvent to dissolve the photoresist layer, thereby exposing the diamond surface in the uncoated area.

[0083] Furthermore, in step S21, the method of depositing the photoresist layer is spin coating.

[0084] Furthermore, in step S23, the physical vapor deposition adopts a magnetron sputtering method.

[0085] Furthermore, in step S23, the material used for physical vapor deposition is high melting point metals such as molybdenum and tungsten, the film thickness is more than 50nm, and the melting point is more than 1500°C.

[0086] Further, in step S23, the process of physical vapor deposition is: placing the diamond seed crystal in a high-temperature furnace for heat treatment, the heat treatment atmosphere is air or oxygen, the heat treatment temperature exceeds 600°C, the heat treatment time is not less than 1 minute, so that the exposed diamond surface is converted into graphite, and the thickness of the converted graphite exceeds 0.05 mm.

[0087] Further, in step S23, the growth conditions are:

[0088] Process gas: carrier gas is H2, flow rate is 10slm; carbon source is CH4, flow rate is 14% of H2; coloring gas is N2, N2 is added in the form of pure nitrogen or mixed gas, N2 content is 8000ppm of CH4;

[0089] Growth pressure: 250Torr;

[0090] Growth power: microwave power 70kW;

[0091] Growth temperature: 1300 degrees Celsius;

[0092] Growth rate: 500um / hr.

[0093] The above embodiments are only used to illustrate the present invention, and the protection scope of the present invention is not limited to the above embodiments. Ordinary technicians in the technical field can achieve the purpose of the present invention based on the above disclosure of the present invention and the range of each parameter.

Claims

1. A method for reducing mutual interference in diamond crystal growth based on edge coating treatment, comprising the following steps: S1: Select appropriate diamond seed crystals and clean them; S2: Coating the four sides of the diamond; S3: placing the seed crystal into the MPCVD chamber to grow the diamond blank; S4: Processing the finished blank to remove the polycrystalline and graphite at the edge to obtain a diamond single crystal; In step S1, the side length of the diamond seed is between 7 and 50 mm, and the directions of the four sides are <100> Crystallographic directions are parallel; In step S2, after coating the edge of the diamond seed crystal, the edge of the diamond seed crystal is no longer diamond and does not have diamond lattices and atoms. When diamond atoms fall onto the upper surface of the film, these atoms will only form polycrystalline diamond or graphite, preventing the seed crystal from growing horizontally along the edge of the single crystal, thereby preventing the seed crystal from expanding horizontally and reducing mutual interference in the growth of diamond crystals.

2. The method for reducing mutual interference of diamond crystal growth based on edge coating treatment as claimed in claim 1, characterized in that: In step S1, the cleaning process of the diamond seed crystal is: acid cleaning, organic solvent cleaning, and deionized water cleaning to remove the attachments on the surface of the seed crystal.

3. The method for reducing mutual interference of diamond crystal growth based on edge coating treatment as claimed in claim 1, characterized in that: Step S2 includes: S21: depositing a photoresist on the surface of the diamond seed crystal to form a photoresist layer; S22: exposing the photoresist layer and cleaning it with an organic solvent to expose the diamond surface in the area where the coating is required; S23: performing physical vapor deposition coating on the diamond seed crystal; S24: placing the seed crystal into a degumming solvent to dissolve the photoresist layer, thereby exposing the diamond surface in the uncoated area.

4. The method for reducing mutual interference of diamond crystal growth based on edge coating treatment as claimed in claim 3, characterized in that: In step S23, physical vapor deposition includes magnetron sputtering and arc vapor deposition.

5. The method for reducing mutual interference of diamond crystal growth based on edge coating treatment as claimed in claim 3, characterized in that: In step S23, the material used for physical vapor deposition is a material with a high melting point and promoting the growth of polycrystalline or graphite, including but not limited to high melting point metals, high melting point oxides, graphite, and silicon.

6. The method for reducing mutual interference in diamond crystal growth based on edge coating treatment as claimed in claim 5, characterized in that: In step S23, when high melting point metals are used for coating, the film thickness exceeds 50nm. The high melting point metals used include molybdenum and tungsten, and the melting point exceeds 1500°C; when high melting point oxides are used for coating, the film thickness exceeds 50nm and the melting point exceeds 1500°C; when graphite and silicon are used, the film thickness exceeds 500mm.

7. The method for reducing mutual interference in diamond crystal growth based on edge coating treatment as claimed in claim 1, characterized in that: In step S3, the growth conditions are: Process gas: carrier gas is H2, with a flow range of 500sccm to 10slm; carbon source is CH4, with a flow rate of 6-14% of H2; coloring gas is N2, which is added in the form of pure nitrogen or mixed gas, with the N2 content ranging from 10ppm to 8000ppm of CH4; Growth pressure: 80-250Torr; Growth power: microwave power 5kW to 70kW; Growth temperature: 900-1300 degrees Celsius; Growth rate: 6-500um / hr.

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