Method for growing single-crystal diamond by using mpcvd method with stepwise nitrogen doping

Abstract

Disclosed in the present invention is a method for growing single-crystal diamond by using a MPCVD method with stepwise nitrogen doping, comprising: S1, placing a single-crystal diamond substrate in a CVD device; S2, introducing a carbon-containing gas into a chamber of the CVD device, and meanwhile, introducing a certain proportion of nitrogen gas; S3, controlling the pressure in the chamber to be 6.6 kPa to 26.6 kPa while introducing the gases, and applying the microwave power so as to raise the temperature of the interior of the chamber to 800℃ to 1200℃; and S4, performing epitaxial growth on primary surfaces of the single-crystal diamond substrate so as to synthesize single-crystal diamond, and separating the synthesized single-crystal diamond from the diamond single-crystal substrate by means of using laser, so as to obtain the single-crystal diamond. The present invention increases the growth rate of diamond, changes the crystallinity of the single-crystal diamond so as to suppress the development of cracks, and further effectively avoids forming obvious boundaries between nitrogen-doped layers and non-nitrogen-doped layers.

Description

A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD Technical Field

[0001] The present invention relates to the technical field of single crystal diamond growth, and in particular to a method for growing single crystal diamond by stepwise nitrogen doping using an MPCVD method. Background Art

[0002] Single-crystal diamond exhibits excellent mechanical, thermal, and optical properties, and is therefore widely used in optical devices, semiconductors, and electronic components. Many single-crystal diamond products can be made from either natural or synthetic diamond. Currently, the main methods for synthesizing diamond are high-temperature, high-pressure (HTHP) and chemical vapor deposition (CVD). For diamond to be used in devices, good toughness is crucial, so nitrogen is added during the growth process to produce diamond with improved mechanical properties. Single-crystal diamond typically has a very tight lattice, and the ingress of impurities often results in significant distortion. Nitrogen readily incorporates into the diamond lattice because it releases some distortion energy when combined with vacancies. However, a distinct boundary between the nitrogen-doped and non-nitrogen-doped layers is observed. Summary of the Invention

[0003] In response to the shortcomings of the prior art, the present invention aims to provide a method for growing single-crystal diamond using MPCVD with stepwise nitrogen doping, which increases the diamond growth rate, changes the crystallinity of the single-crystal diamond to inhibit crack propagation, and effectively avoids the formation of a clear boundary between the nitrogen-doped layer and the non-nitrogen-doped layer. To achieve the above-mentioned purpose and other advantages of the present invention, a method for growing single-crystal diamond using MPCVD with stepwise nitrogen doping is provided, comprising:

[0004] S1, placing a single crystal diamond substrate in a CVD device;

[0005] S2. Introducing carbon-containing gas into the chamber of the CVD device and simultaneously introducing a certain proportion of nitrogen gas;

[0006] S3, controlling the pressure in the chamber to 6.6 kPa to 26.6 kPa while introducing the gas, and applying microwave power to heat the chamber to a temperature of 800° C. to 1200° C.;

[0007] S4. Epitaxially grow synthetic single crystal diamond on the main surface of the single crystal diamond substrate, and separate the synthetic single crystal diamond from the diamond single crystal substrate by laser to obtain single crystal diamond.

[0008] Preferably, the carbon-containing gas includes CH4, C2H6, C2H4, C2H2, CH3OH, (CH3)2CO, CO or CO2.

[0009] Preferably, in step S2, nitrogen can be introduced into the synthetic single crystal diamond as an impurity by introducing nitrogen gas into the chamber together with the carbon-containing gas, and the concentration of the impurity nitrogen in the synthetic single crystal diamond will change by controlling the amount of nitrogen added to the gas introduced into the chamber.

[0010] Preferably, the single crystal diamond includes a pair of main interfaces and a plurality of main surfaces, and a first change direction and a second change direction perpendicular to the first change direction are provided on the main interfaces and the plurality of main surfaces.

[0011] Preferably, the first change direction and the second change direction on the main interface are oriented differently from the first change direction and the second change direction on the plurality of main surfaces, and the impurity concentration first changes along the first change direction and then changes along the second change direction.

[0012] Preferably, the impurity concentration changes periodically along the first change direction, and the distance of the impurity concentration change process from high concentration and impurities to low concentration impurity layer at the main interface and multiple main surfaces is 0.1 to 1000 between.

[0013] Preferably, the starting point of the change from high concentration and impurities to low concentration impurity layer may not be inside the predetermined interval of the surface end, and the impurity concentration may be periodic along the first change direction on at least a portion of each main surface.

[0014] Preferably, in each main surface, the arrangement of the layer with high impurity concentration and the layer with low impurity concentration is centrally symmetrical, and in the periodicity of the impurity concentration, each period has the same length, and the layer with lower impurity concentration is symmetrical along the central layer with the highest impurity concentration, wherein each period has the same length and the width corresponding to each period has the same length.

[0015] Compared with existing technologies, this invention offers the following advantages: by gradually incorporating nitrogen at higher and higher concentrations through a stepwise increase in concentration, the diamond growth rate is increased and the crystallinity of the single-crystal diamond is modified to inhibit crack propagation, thereby improving its wear resistance as a cutting tool. Furthermore, gradually increasing the nitrogen concentration effectively avoids the formation of a distinct boundary between the nitrogen-doped and non-doped layers. This results in a single-crystal diamond with significantly improved mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a diagram of a single crystal diamond according to a first embodiment of a method for growing single crystal diamond by stepwise nitrogen doping using MPCVD according to the present invention;

[0017] FIG2 is a graph showing exemplary changes in the impurity concentration of the main surface of a single crystal diamond along the X-axis direction in the method for growing single crystal diamond by stepwise nitrogen doping using the MPCVD method according to the present invention;

[0018] FIG3 is a schematic diagram of an exemplary method for manufacturing single-crystal diamond according to a first embodiment of the method for growing single-crystal diamond by stepwise nitrogen doping using MPCVD method according to the present invention;

[0019] [Corrected 18.06.2024 according to Rule 91] Figure 4 is a simplified schematic diagram of the three-dimensional structure of a single crystal diamond substrate in the method for growing single crystal diamond by stepwise nitrogen doping using the MPCVD method according to the present invention. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0021] 1-4 , a method for growing single crystal diamond by stepwise nitrogen doping using MPCVD method includes: S1, placing a single crystal diamond substrate in a CVD device;

[0022] S2. Introducing carbon-containing gas into the chamber of the CVD device and simultaneously introducing a certain proportion of nitrogen gas;

[0023] S3, controlling the pressure in the chamber to 6.6 kPa to 26.6 kPa while introducing the gas, and applying microwave power to heat the chamber to a temperature of 800° C. to 1200° C.;

[0024] S4. Epitaxially grow synthetic single crystal diamond on the main surface of the single crystal diamond substrate, and separate the synthetic single crystal diamond from the diamond single crystal substrate by laser to obtain single crystal diamond. Example

[0025] The following describes a single-crystal diamond according to a first embodiment with reference to FIG1 . FIG1 is a plan view of the single-crystal diamond and a perspective view of the single-crystal diamond according to the first embodiment. The term "plan view" refers to a view viewed from above the main surface of the single-crystal diamond. In this specification, the main surface area refers to the surface with the largest area among the surfaces of the single-crystal diamond.

[0026] As shown in Figure 1, single-crystal diamond 10 includes a pair of opposing primary surfaces. This set of surfaces contains no impurities. On the other primary surfaces, the impurity concentration gradually increases and then decreases, remaining symmetrically distributed along the highest concentration. Nitrogen is added sequentially from one primary surface to the next, with nitrogen concentrations of 1:0.03%; 2:0.06%; 3:0.09%; 4:0.12%; and 5:0.15%. Once the nitrogen concentration reaches the set maximum value of 0.15%, the nitrogen concentration is gradually reduced until the next impurity-free primary surface is reached. There are no specific restrictions on the growth time for each region; it only needs to be symmetrical along the highest impurity concentration. The growth time can be set based on the different growth rates at different impurity concentrations.

[0027] In the main surface of the single crystal diamond 10, the length or width of the impurity region in the X-axis direction is preferably 1 1000 More preferably 5 Above 300 .

[0028] Adjusting the length range described above and using the single crystal diamond tool can effectively suppress uneven wear rates (non-uniform wear) in specific portions of the wear surface due to differences in plane orientation. It should be noted that the width of the impurity concentration region can be the same as or different from the width of the non-impurity concentration region.

[0029] FIG2 shows a graph of exemplary changes in the impurity concentration of the main surface of the single crystal diamond 10 of FIG1 along the X-axis direction. As shown in FIG2, on the main surface, the impurity concentration changes along the X-axis direction. Specifically, the impurity concentration depends on the nitrogen doping content. As the nitrogen doping content increases during the growth process, the rate of increase of the impurity concentration also increases. When the nitrogen doping content begins to decrease, the rate of increase of the impurity concentration slows down. Therefore, the predetermined concentration is within the range of 10 ppb to 10,000 ppb, and the width of each impurity concentration region is within 0.5 Above 500 The impurity-free region is a region where the impurity concentration is less than 60% of the maximum value.

[0030] The impurity concentration in the Y-axis direction perpendicular to the X-axis direction is preferably substantially uniform in the main surface of the single crystal diamond 10. Here, the expression "substantially uniform impurity concentration" means that the concentration falls within the range of -20% to +20% of the average value.

[0031] The impurity concentration in the main surface of the single crystal diamond 10 is preferably 10 ppb to 10,000 ppm. When the impurity concentration is less than 10 ppb, cracks are likely to propagate, and a sufficient crack propagation suppression effect cannot be achieved, resulting in a decrease in cutting resistance. On the other hand, when the impurity concentration exceeds 10,000 ppm, wear resistance is significantly reduced. The impurity concentration is more preferably 100 ppb to 1,000 ppm, and even more preferably 500 ppb to 100 ppm.

[0032] In the main surface of the single crystal diamond 10, the maximum value of the impurity concentration is preferably 1 ppm or more and 10,000 ppm or less, more preferably 5 ppm or more and 1,000 ppm or less. In addition, the minimum value of the impurity concentration is preferably 10 ppb or more and 100 ppm or less, more preferably 100 ppb or more and 50 ppm or less. The ratio of the minimum value to the maximum value of the impurity concentration (minimum value / maximum value) is preferably greater than or equal to 10-6 and less than 0.8, more preferably 10-4 or more and 0.5 or less. Thus, when using single crystal diamond as the material of a processing tool, the uneven wear of the material originating from the difference in impurity concentration is offset by the uneven wear originating from the difference in plane orientation, thereby suppressing the uneven wear of the tool as a whole. In the main surface of the single crystal diamond, the plane orientation in the direction in which the impurity concentration is substantially uniform is preferably different from the plane orientation in the direction in which the impurity concentration changes. More preferably, the orientation that results in the minimum wear rate corresponds to the direction in which the impurity concentration is substantially uniform, or corresponds to the direction in which the impurity concentration changes. Typically, the difference in wear rate depends on the plane orientation or the impurity concentration. Therefore, by appropriately combining the wear rate difference resulting from the plane orientation difference and the wear rate difference resulting from the impurity concentration difference, the wear rate differences can be offset, thereby achieving uneven wear.

[0033] An exemplary method for producing single-crystal diamond according to the first embodiment will now be described with reference to FIG3 . FIG3 illustrates an exemplary method for producing single-crystal diamond according to the first embodiment. In this embodiment, the method for producing single-crystal diamond includes: obtaining diamond by stepwise nitrogen-doped growth via vapor deposition; and slicing the synthesized single-crystal diamond along a direction in which the impurity concentration varies.

[0034] First, as shown in FIG3 , a single crystal diamond substrate 4 is prepared. As the single crystal diamond substrate 4, for example, a flat plate-shaped single crystal substrate composed of diamond produced by a high temperature and high voltage method can be used, which is type Ib. The single crystal diamond substrate 4 has: a main surface composed of a 100 face; and side surfaces perpendicular to the main surface and composed of a 001 face and a 010 face. It should be noted that there is no particular limitation on the shape of the single crystal diamond substrate 4, and any desired shape can be adopted. In addition, the main surface of the diamond single crystal substrate is preferably smoothed by mechanical polishing or the like, and is preferably polished by reactive ion etching for about 1 minute. to 50 Etching.

[0035] Next, the single-crystal diamond substrate 4 is placed in a CVD apparatus, and a vapor deposition method is used to achieve an impurity concentration along the direction of crystal growth to synthesize single-crystal diamond (Figure 3). Specifically, a carbon-containing gas is introduced into the chamber, while a certain proportion of nitrogen is introduced, to epitaxially grow synthetic single-crystal diamond on the main surface of the single-crystal diamond substrate 4.

[0036] Carbon in the gas serves as a carbon source for synthesizing single-crystal diamond. Examples of carbon-containing gases include CH₄, C₂H₆, C₂H₄, C₂H₂, CH₃OH, and (CH₃)₂CO. Note that in addition to these gases, CO and CO₂ can also be used. Among these, CH₄ is ​​preferred because it easily generates carbon radicals, which serve as a precursor to the resulting diamond film.

[0037] By introducing nitrogen gas into the chamber along with a carbon-containing gas, nitrogen can be introduced as an impurity into the synthetic single-crystal diamond. By controlling the amount of nitrogen added to the gases introduced into the chamber, the concentration of nitrogen as an impurity in the synthetic single-crystal diamond can be varied. In addition to the flow rate ratio of the added gases, the impurity concentration can be varied along the growth direction by varying the total pressure, supplied power, substrate temperature, and other factors.

[0038] In addition to nitrogen, boron, aluminum, silicon, phosphorus, and other gases can be introduced as impurities into synthetic single-crystal diamond. Examples of gases that can be used include diborane, trimethylaluminum, silane, phosphine, and hydrogen sulfide. When using elements other than aluminum, commonly known organic gases can be used.

[0039] While the above-mentioned gases are being introduced, the pressure in the chamber is controlled to 6.6 kPa to 26.6 kPa, microwave power is applied to heat the chamber to a temperature of 800° C. to 1200° C., and then synthetic single-crystal diamond is epitaxially grown on the main surface of the single-crystal diamond substrate 4. As a method for forming the epitaxial growth layer, for example, a microwave plasma CVD method (MP-CVD method), a hot filament (HF) CVD method, a DC plasma method, or the like can be used.

[0040] Next, the synthesized single-crystal diamond is separated from the diamond single-crystal substrate 4 using a laser, thereby obtaining single-crystal diamond. Besides using a laser, separation can also be performed by electrochemical etching. In this case, a graphite layer must be formed in the substrate by ion implantation before crystal growth. The resulting single-crystal diamond has a surface as a major surface that is substantially parallel to the crystal growth direction of the synthetic single-crystal diamond. Therefore, in this case, the impurity concentration in the major surface of the single-crystal diamond varies along the crystal growth direction.

[0041] Furthermore, in step S2, nitrogen can be introduced into the synthetic single crystal diamond as an impurity by introducing nitrogen gas into the chamber together with the carbon-containing gas, and the concentration of the impurity nitrogen in the synthetic single crystal diamond will change by controlling the amount of nitrogen added to the gas introduced into the chamber.

[0042] Furthermore, the single crystal diamond includes a pair of main interfaces and multiple main surfaces, and a first change direction and a second change direction perpendicular to the first change direction are provided on the main interfaces and the multiple main surfaces. Such a single crystal diamond can be obtained, and its mechanical properties are significantly improved.

[0043] Furthermore, the first and second changing directions on the main interface are oriented differently from the first and second changing directions on multiple main surfaces, resulting in a single-crystal diamond that effectively suppresses uneven wear when used as a tool material. Furthermore, the impurity concentration first changes along the first changing direction and then along the second changing direction, with the impurity concentration changing uniformly along the second changing direction. This single-crystal diamond exhibits significantly improved mechanical properties. The impurity concentration exhibits central symmetry along the first changing direction, making this single-crystal diamond suitable for various tools.

[0044] The impurities include at least one element selected from the group consisting of nitrogen, boron, aluminum, silicon, phosphorus, and sulfur. When these elements are present in the single crystal diamond, they can change the crystallinity of the single crystal diamond to inhibit crack propagation, thereby improving cutting resistance.

[0045] The single-crystal diamond tools produced by this method achieve a good balance between wear resistance and cutting resistance, and have excellent tool life. Such single-crystal diamond, when used as a tool material, can more uniformly machine workpieces.

[0046] Furthermore, the impurity concentration changes periodically along the first change direction, and the distance of the impurity concentration change process from high concentration and impurities to low concentration impurity layer at the main interface and multiple main surfaces is 0.1 to 1000 For example, not all phases have fixed durations. Phase durations can change in the middle of a series of consecutive reactions.

[0047] Furthermore, the starting point of the change from high concentration and impurities to low concentration impurity layer may not be inside the predetermined interval of the surface end, and the impurity concentration may be periodic along the first change direction on at least a portion of each main surface.

[0048] Furthermore, within each major surface, the arrangement of layers with high and low impurity concentrations is centrosymmetric. Within the periodicity of the impurity concentrations, each period has the same length, and the layers with lower impurity concentrations are arranged symmetrically around the central layer with the highest impurity concentration. The periods have the same length, and the corresponding widths of each period have the same length. During the staged growth process, the impurity concentration does not change abruptly at the boundary between the higher and lower impurity concentrations.

[0049] The number of devices and processing scales described herein are intended to simplify the description of the present invention, and applications, modifications, and variations of the present invention will be apparent to those skilled in the art.

[0050] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD, characterized in that: The following steps are involved: S1, placing a single crystal diamond substrate in a CVD device; S2, introducing a carbon-containing gas into the chamber of the CVD device and simultaneously introducing a certain proportion of nitrogen; S3, while introducing the gas, controlling the pressure in the chamber to 6.6 kPa to 26.6 kPa, and applying microwave power to heat to a chamber temperature of 800° C. to 1200° C.; S4. Epitaxially grow synthetic single crystal diamond on the main surface of the single crystal diamond substrate, separate the synthetic single crystal diamond from the diamond single crystal substrate by laser, and obtain single crystal diamond.

2. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 1, characterized in that: The carbon-containing gas includes CH4, C2H6, C2H4, C2H2, CH3OH, (CH3)2CO, CO or CO2.

3. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 2, characterized in that: In step S2, nitrogen can be introduced into the chamber together with the carbon-containing gas to introduce nitrogen as an impurity into the synthetic single crystal diamond, and the concentration of impurity nitrogen in the synthetic single crystal diamond will change by controlling the amount of nitrogen added to the gas introduced into the chamber.

4. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 3, characterized in that: The single crystal diamond comprises a pair of main interfaces and a plurality of main surfaces, and a first change direction and a second change direction perpendicular to the first change direction are arranged on the main interfaces and the plurality of main surfaces.

5. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 4, characterized in that: The first change direction and the second change direction on the main interface are oriented differently from the first change direction and the second change direction on the plurality of main surfaces, and the impurity concentration first changes along the first change direction and then changes along the second change direction.

6. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 5, characterized in that: The impurity concentration changes periodically along the first change direction, and the distance of the impurity concentration change process from high concentration and impurities to low concentration impurity layers on the main interface and multiple main surfaces is 0.1 to 1000 between.

7. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 6, characterized in that: The starting point of the change process of the impurity concentration from the high concentration and impurities to the low concentration impurity layer may not be inside the predetermined interval of the surface end, and the impurity concentration may have periodicity along the first change direction on at least a portion of each main surface.

8. A method for growing single crystal diamond by stepwise nitrogen doping using MPCVD as claimed in claim 7, characterized in that: In each main surface, the arrangement of the layer with high impurity concentration and the layer with low impurity concentration is centrally symmetrical. In the periodicity of the impurity concentration, each period has the same length, and the layer with lower impurity concentration is symmetrical along the central layer with the highest impurity concentration, wherein each period has the same length and each period has the same length corresponding to the width.

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