Diameter expanding method for single crystal diamond and growth base station

Abstract

The invention discloses a single crystal diamond expanding method and a growth base station. The growth base table comprises a molybdenum table base; the molybdenum table base is provided with a first circular groove, a second square groove and a third square groove, an insulating sleeve is laid in the first circular groove, and a square hole completely exposed out of the second square groove is formed in the middle of the insulating sleeve. And the sum of the depths of the second square groove and the third square groove is smaller than the sum of the depths of the second square groove and the third square groove and the thickness of the insulating sleeve. The diameter expanding method comprises the following steps: screening seed crystals, and chamfering and polishing; performing hydrogen plasma etching; in the growth base station, MPCVD diameter expansion growth is carried out under the condition that the bias voltage ranging from-180 V to-260 V is applied; and vacuum annealing. According to the invention, the electromagnetic field environment around the seed crystal is optimized through the abutment structure, and side epitaxy is promoted in combination with bias growth, so that high-quality and regular morphology diameter expansion of the square monocrystal diamond is realized, polycrystal generation is effectively inhibited, and stress is reduced.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material preparation technology, specifically to a growth abutment for expanding the diameter of single-crystal diamond and a method for expanding the diameter using the abutment. Background Technology

[0002] Large-size single-crystal diamonds have broad application prospects in high-power electronic devices, optical windows, and quantum information due to their excellent physicochemical properties. Microwave plasma chemical vapor deposition (MPCVD) is currently the mainstream technology for preparing high-quality single-crystal diamonds. To obtain large-size products, homoepitaxial diameter expansion growth is usually performed on a smaller seed crystal.

[0003] However, during diameter expansion growth, especially when using square {100} facet seed crystals, unfavorable crystal faces are easily generated at the edges and corners of the seed crystal, leading to problems such as polycrystalline formation, irregular growth morphology (e.g., becoming octagonal), and increased internal stress, severely affecting the diameter expansion effect and material quality. Existing technologies have addressed this problem by selecting seed crystals with special shapes (e.g., octagonal) or special crystal orientations, but this method limits the selection range of seed crystals and involves complex fabrication processes. Other methods focus on the arrangement and height control of multiple wafers growing simultaneously to avoid mutual interference, but do not optimize the diameter expansion morphology control of a single seed crystal.

[0004] Therefore, there is a need in the art for a method and apparatus that can directly perform high-quality, high-yield, and morphology-regular diameter expansion growth on conventional square seed crystals. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for expanding the diameter of single-crystal diamond and a growth platform to solve the problems of polymorphism, irregular morphology, and high stress in square single-crystal diamond seed crystals during the diameter expansion process.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a growth stage for expanding the diameter of single-crystal diamond, comprising a molybdenum stage base; the top of the molybdenum stage base is sequentially provided with a first circular groove, a second square groove, and a third square groove that are connected from top to bottom; an insulating sleeve is laid in the first circular groove, and a square hole is formed in the middle of the insulating sleeve, completely exposing the second square groove; the third square groove is used to accommodate a single-crystal diamond seed crystal; let the depth of the third square groove be D3, the depth of the second square groove be D2, the depth of the first circular groove be D1, the thickness of the insulating sleeve be T, and the thickness of the seed crystal be H, then satisfying: T>D1, D3+D2 <H<D2+D3+T。

[0007] Secondly, the present invention provides a method for expanding the diameter of single-crystal diamond, using the above-mentioned growth substrate, and including the following steps: S1. Seed crystal screening and processing: The growth surface and side surface are all (100) crystal planes, and the Raman half-width is ≤3cm. -1 A square single-crystal diamond seed crystal; the seed crystal is chamfered and removed, and the sides and growth surface of the seed crystal are polished; S2. Etching process: The processed seed crystal is placed in a microwave plasma chemical vapor deposition equipment for hydrogen plasma etching. S3, diameter expansion growth: The etched seed crystal is placed in the third-shaped groove (6) of the growth platform, and diameter expansion growth is performed in a microwave plasma chemical vapor deposition equipment under the condition of applying a bias voltage of -180V to -260V. S4. Vacuum annealing: Vacuum annealing is performed on the grown single crystal diamond.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: The combined growth platform designed in this invention, through the cooperation of a three-layer groove structure and an insulating sleeve, embeds and confines the seed crystal within a specific space. This structure optimizes the plasma distribution and thermal field near the seed crystal growth surface, reduces the "edge effect" at the seed crystal edge, provides an ideal physical environment for uniform and stable lateral diameter expansion, and suppresses the nucleation and growth of edge polycrystalline materials.

[0009] In this invention, a specific range of negative bias voltage is creatively introduced into the MPCVD diameter expansion growth step. Since the entire reaction chamber is grounded, an electric field is formed between the molybdenum stage base with the applied negative bias voltage and the chamber. This electric field promotes the diffusion of active carbon-containing groups in the plasma to the seed crystal surface, thereby accelerating the growth of the growth surface (100). The presence of the insulating sleeve maintains the electric field environment on the seed crystal side, which is beneficial for promoting epitaxial growth on the seed crystal side, ultimately achieving effective and regular lateral diameter expansion.

[0010] The four corners of the seed crystal are chamfered and removed, eliminating sharp corners that are prone to electric field and temperature concentration, thus reducing the risk of polycrystalline formation at the corners from the source.

[0011] The present invention introduces a high-temperature vacuum annealing step after growth, which can effectively reduce the stress accumulated inside the crystal during the diameter expansion growth process, repair some lattice defects, and thus further improve the crystallization quality and stability of single crystal diamond.

[0012] This invention combines a dedicated growth platform, a biased growth process, and vacuum annealing post-treatment to form a complete solution. Experiments show that this method can achieve high-quality diameter expansion on square {100} seed crystals, obtaining single-crystal diamonds with regular morphology (square), few or no polymorphism, small Raman full width at half maximum (FWHM), and low internal stress, solving the problems of uncontrollable morphology and unstable quality in traditional diameter expansion methods. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0014] In the attached diagram: Figure 1 This is a schematic diagram of the growth platform structure in an embodiment of the present invention.

[0015] Figure 2 This is a cross-sectional view of the growth platform in an embodiment of the present invention.

[0016] Figure 3 This is a process flow diagram of the present invention.

[0017] Wherein: 1—molybdenum platform base, 2—insulating sleeve, 3—seed crystal, 4—first circular groove, 5—second square groove, 6—third square groove. Detailed Implementation

[0018] A growth platform for expanding the diameter of single-crystal diamond, such as Figure 1 and 2 As shown, it includes: Molybdenum stage base 1; The top of the molybdenum platform base 1 is provided with a first circular groove 4, a second square groove 5, and a third square groove 6 that are connected from top to bottom. An insulating sleeve 2 is laid inside the first circular groove 4, and a square hole is opened in the middle of the insulating sleeve to completely expose the second square groove; The third-shaped groove 6 is used to accommodate the single-crystal diamond seed crystal 3; Let the depth of the third square groove 6 be D3, the depth of the second square groove 5 be D2, the depth of the first circular groove 4 be D1, the thickness of the insulating sleeve 2 be T, and the thickness of the seed crystal 3 be H. Then, the following conditions must be met: T > D1, D3 + D2. <H<D2+D3+T。

[0019] In a specific embodiment, the length of the third-dimensional groove 6 is ≥ the seed crystal length + 0.5 mm.

[0020] In a specific embodiment, the length of the square hole is ≥ the seed crystal length + 3mm.

[0021] In a specific embodiment, the insulating sleeve 2 is circular; the central axes of the insulating sleeve 2, the square hole, the first circular groove 4, the second square groove 5, and the third square groove 6 are coaxial.

[0022] A method for expanding the diameter of single-crystal diamond, using the aforementioned growth substrate, such as... Figure 3 As shown, it includes the following steps: S1. Seed crystal screening and processing: The growth surface and side surface are all (100) crystal planes, and the Raman half-width is ≤3cm. -1 Square single-crystal diamond seed crystal; the four corners of the seed crystal are chamfered and removed, and the sides and growth surface of the seed crystal are polished; S2. Etching process: The processed seed crystal is placed in a microwave plasma chemical vapor deposition equipment for hydrogen plasma etching. S3. Diameter expansion growth: The etched seed crystal is placed in the third-shaped groove 6 of the growth platform, and epitaxial growth is performed in a microwave plasma chemical vapor deposition equipment under a bias voltage of -180V to -260V. S4. Vacuum annealing: Vacuum annealing is performed on the grown single crystal diamond.

[0023] In a specific embodiment, in step S1, after chamfering and removing the seed crystal, the chamfer length is ≤1mm.

[0024] In a specific embodiment, in step S1, the side surface and growth surface of the seed crystal are polished to achieve a surface roughness of ≤10nm. Diamond seed crystals have extremely high hardness, and laser cutting will produce a large number of defects and cutting marks. The polishing process of this invention can reduce these defects.

[0025] In a specific embodiment, the process conditions for hydrogen plasma etching in step S2 are: temperature 800~850℃, pressure 17~25kPa, hydrogen flow rate 400~500sccm, and time 30~60min.

[0026] In a specific embodiment, the process conditions for the diameter expansion growth in step S3 are: hydrogen flow rate of 800~1000 sccm, methane concentration (V... 甲烷 / V 氢气 The oxygen concentration (V) is 6%~8%. 甲烷 / V 氧气 The concentration of the active ingredient (A) is 1% to 2%, the temperature is 870 to 910℃, the pressure is 18 to 21 kPa, and the time is 120 to 150 h.

[0027] In a specific embodiment, in step S4, the vacuum annealing process conditions are: temperature of 1200~1500℃ and time of 2~4h.

[0028] For the convenience of understanding the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0029] Unless otherwise defined, all the technical terms used hereinafter have the same meanings as those commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0030] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0031] Growth base structure As Figure 1 and Figure 2 shown, the growth base of the present invention includes a molybdenum base 1. The molybdenum base 1 is usually circular and is made of high melting point metals such as molybdenum or molybdenum alloy.

[0032] The top of the molybdenum base 1 is processed with three layers of grooves that are coaxially connected from top to bottom: a first circular groove 4, a second square groove 5, and a third square groove 6. The third square groove 6 is used to place a single crystal diamond seed crystal 3, and its size is slightly larger than the seed crystal, with a side length ≥ the side length of the seed crystal 3 + 0.5 mm, so as to ensure that the seed crystal 3 can be placed and there is a certain gap.

[0033] The groove depth needs to meet: T > D1, D3 + D2 < H < D2 + D3 + T. Where: the depth of the third square groove 6 is D3, the depth of the second square groove 5 is D2, the depth of the first circular groove 4 is D1, the thickness of the insulating sleeve 2 is T, and the thickness of the seed crystal 3 is H. This design ensures that after the seed crystal 3 is placed, its bottom is supported by the third layer of groove 6, and the top is lower than the upper surface of the insulating sleeve 2, thereby forming a relatively restricted and stable local environment in the initial stage of growth.

[0034] The insulating sleeve 2 is laid in the first circular groove 4, and a square hole that completely exposes the second square groove 5 is provided at the center thereof, and the side length of the square hole ≥ the side length of the seed crystal 3 + 3 mm.

[0035] The horizontal cross-section of the insulating sleeve 2 is circular; the central axes of the insulating sleeve 2, the square hole, the first circular groove 4, the second square groove 5, and the third square groove 6 are coaxial.

[0036] The following embodiments all use the growth base with the above structure, and a seed crystal with a size of 20 mm x 20 mm x 1.5 mm is selected. Each embodiment shows different implementation manners within the scope of the claims of the present invention and their good effects by changing process parameters.

[0037] Example 1 A method for expanding the diameter of single-crystal diamond, using the above-mentioned growth substrate, with the specific parameters of the growth substrate set as follows: seed crystal thickness H=1.5mm, depth of the third square groove D3=0.5mm, depth of the second square groove D2=0.5mm, depth of the first circular groove D1=0.4mm, thickness of the insulating sleeve T=1mm, side length of the third square groove is 20.5mm, and side length of the square hole is 23mm.

[0038] Includes the following steps: S1. Seed crystal screening and processing: The growth surface and side surface are all (100) crystal planes, with a Raman half-width of 2.6cm. -1 Square single-crystal diamond seed crystal; The four corners of the seed crystal are chamfered and removed, and the sides and growth surfaces of the seed crystal are polished to make the roughness of each surface ≤10nm, and the chamfer length is 0.5mm. S2. Etching process: The processed seed crystal is placed in a microwave plasma chemical vapor deposition equipment for hydrogen plasma etching. The process conditions for hydrogen plasma etching are: temperature of 800℃, pressure of 17kPa, hydrogen flow rate of 400sccm, and time of 30min. S3. Diameter Expansion Growth: The etched seed crystal is placed in the third-sided groove of the growth platform and epitaxial growth is performed in a microwave plasma chemical vapor deposition equipment. The process conditions are: hydrogen flow rate of 800 sccm, methane concentration of 6%, oxygen concentration of 1%, temperature of 870℃, pressure of 18kPa, bias voltage of -180V, and time of 12h. S4. Vacuum annealing: The single crystal diamond obtained after growth is subjected to vacuum annealing. The process conditions for vacuum annealing are: temperature of 1200℃ and time of 2h.

[0039] Example 2 This embodiment is basically the same as Embodiment 1, except that: The etching process conditions in step S2 are: temperature 850℃, pressure 25kPa, hydrogen 500sccm, and time 30min.

[0040] Example 3 This embodiment is basically the same as Embodiment 1, except that: The process conditions in step S3 are as follows: hydrogen flow rate is 800 sccm, methane concentration is 8%, oxygen concentration is 2%, temperature is 910℃, pressure is 21 kPa, bias voltage is -260 V, and time is 150 h.

[0041] Example 4 This embodiment is basically the same as Embodiment 1, except that: The process conditions in step S4 are: 1500℃, annealing for 4 hours.

[0042] Example 5 A method for expanding the diameter of single-crystal diamond, using the above-mentioned growth substrate, the specific parameters of which are the same as in Example 1.

[0043] Includes the following steps: S1. Seed crystal screening and processing: The growth surface and side surface are all (100) crystal planes, with a Raman half-width of 2.6cm. -1 Square single-crystal diamond seed crystal; The four corners of the seed crystal are chamfered and removed, and the sides and growth surfaces of the seed crystal are polished to make the roughness of each surface ≤10nm, and the chamfer length is 0.5mm. S2. Etching process: The processed seed crystal is placed in a microwave plasma chemical vapor deposition equipment for hydrogen plasma etching. The process conditions for hydrogen plasma etching are: temperature 850℃, pressure 25kPa, hydrogen flow rate 500sccm, and time 60min. S3. Diameter expansion growth: The etched seed crystal is placed in the third-shaped groove of the growth platform and epitaxial growth is performed in a microwave plasma chemical vapor deposition equipment. The process conditions are: hydrogen flow rate of 800 sccm, methane concentration of 8%, oxygen concentration of 2%, temperature of 910℃, pressure of 21 kPa, bias voltage of -260V, and time of 150h. S4. Vacuum annealing: The grown single crystal diamond is subjected to vacuum annealing. The process conditions for vacuum annealing are: temperature 1500℃, time 4h.

[0044] Example 6 This embodiment is basically the same as Embodiment 1, except that: The process conditions in step S3 are as follows: hydrogen flow rate is 800 sccm, methane concentration is 8%, oxygen concentration is 2%, temperature is 910℃, pressure is 21 kPa, and bias voltage is -220V.

[0045] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that the parameters of the growth platform are different.

[0046] The specific parameters of the growth substrate are set as follows: seed crystal thickness H=1.5mm, third square groove depth D3=0.5mm, second square groove depth D2=0.5mm, first circular groove depth D1=0.4mm, insulating sleeve thickness T=0.3mm, third square groove length and width are 20.5mm, and square hole side length is 23mm.

[0047] In this comparative example, the seed crystal thickness is greater than the combined thickness of the second square groove, the third square groove, and the insulating sleeve. The seed crystal is higher than the top of the insulating sleeve, and this structure is characterized as an open molybdenum platform.

[0048] Comparative Example 2 Comparative Example 2 is basically the same as Example 1, except that: The seed crystal selected in step S1 has a side crystal orientation of (110).

[0049] Comparative Example 3 This comparative example is basically the same as Example 1, except that: After processing in step S1, the chamfer length is 3mm.

[0050] Comparative Example 4 This comparative example is basically the same as Example 1, except that: The etching temperature in step S2 is 1000℃.

[0051] Comparative Example 5 This comparative example is basically the same as Example 1, except that: No bias voltage is applied during step S3.

[0052] Comparative Example 6 This comparative example is basically the same as Example 1, except that: The bias voltage for process step S3 is set to -100V.

[0053] Comparative Example 7 This comparative example is basically the same as Example 1, except that: The bias voltage for step S3 is set to -400V.

[0054] Comparative Example 8 This comparative example is basically the same as Example 1, except that: All process steps are the same as in Example 1, but the growth stage is replaced with a common planar molybdenum tray.

[0055] During the experiments of Examples 1-6 and Comparative Examples 1-8, the growth rate of diameter expansion growth, the shape of the single crystal diamond obtained after vacuum annealing, the Raman full width at half maximum (FWHM), the appearance, and the mean stress were observed or tested, and the results are shown in Table 1.

[0056] Analysis of the data in Table 1 shows that the method of this invention (Examples 1-6) successfully achieved lateral diameter expansion (outer expansion width ≥ 1.45 mm) of square seed crystals with a regular morphology. The prepared single-crystal diamonds had narrow Raman half-heights (high crystal quality), no polycrystalline appearance, and relatively low average stress. In contrast, Comparative Example 1 (using an open substrate) resulted in severe edge polycrystalline formation and increased stress; Comparative Example 2 (seed crystal side with {110} crystal orientation) struggled to achieve effective lateral diameter expansion; Comparative Examples 5, 6, and 7 (no bias applied or bias value exceeding the range of this invention) resulted in irregular morphology (becoming octagonal) or increased polycrystalline formation and / or significantly increased stress after diameter expansion. This comprehensively demonstrates that the specific growth substrate structure of this invention, combined with the {100} growth surface and side seed crystals, and the negative bias growth process within the range of -180V to -260V, can achieve high-quality, regular morphology diameter expansion of square single-crystal diamonds.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A growth platform for expanding the diameter of single-crystal diamond, characterized in that, include: Molybdenum stage base (1); The top of the molybdenum platform base (1) is provided with a first circular groove (4), a second square groove (5) and a third square groove (6) that are connected from top to bottom. An insulating sleeve (2) is laid in the first circular groove (4), and a square hole is opened in the middle of the insulating sleeve to completely expose the second square groove; The third-shaped groove (6) is used to accommodate the single-crystal diamond seed crystal (3); Let the depth of the third square groove (6) be D3, the depth of the second square groove (5) be D2, the depth of the first circular groove (4) be D1, the thickness of the insulating sleeve (2) be T, and the thickness of the seed crystal (3) be H. Then, the following conditions must be met: T > D1, D3 + D2. <H<D2+D3+T。 2. The growth platform according to claim 1, characterized in that, The side length of the third-shaped groove (6) is greater than or equal to the side length of the seed crystal (3) + 0.5 mm.

3. The growth platform according to claim 1, characterized in that, The side length of the square hole is greater than or equal to the side length of the seed crystal (3) plus 3mm.

4. The growth platform according to claim 1, characterized in that, The horizontal cross-section of the insulating sleeve (2) is circular; the central axes of the insulating sleeve (2), the square hole, the first circular groove (4), the second square groove (5) and the third square groove (6) are coaxial.

5. A method for expanding the diameter of single-crystal diamond, characterized in that, Using the growth platform according to any one of claims 1 to 4, and comprising the following steps: S1. Seed crystal screening and processing: The growth surface and side surface are all (100) crystal planes, and the Raman half-width is ≤3cm. -1 A square single-crystal diamond seed crystal; the seed crystal is chamfered and removed, and the sides and growth surface of the seed crystal are polished; S2. Etching process: The processed seed crystal is placed in a microwave plasma chemical vapor deposition equipment for hydrogen plasma etching. S3, diameter expansion growth: The etched seed crystal is placed in the third-shaped groove (6) of the growth platform, and diameter expansion growth is performed in a microwave plasma chemical vapor deposition equipment under the condition of applying a bias voltage of -180V to -260V. S4. Vacuum annealing: The single-crystal diamond obtained after growth is subjected to vacuum annealing treatment.

6. The method according to claim 5, characterized in that, In step S1, after chamfering the seed crystal, the chamfer length is ≤1mm.

7. The method according to claim 5, characterized in that, In step S1, after polishing the side surface and growth surface of the seed crystal, the roughness is ≤10nm.

8. The method according to claim 5, characterized in that, In step S2, the process conditions for hydrogen plasma etching are: temperature of 800~850℃, pressure of 17~25kPa, hydrogen flow rate of 400~500sccm, and time of 30~60min.

9. The method according to claim 5, characterized in that, In step S3, the process conditions for the diameter expansion growth are: hydrogen flow rate of 800~1000 sccm, methane concentration of 6~8%, oxygen concentration of 1~2%, temperature of 870~910℃, pressure of 18~21 kPa, and time of 120~150 h.

10. The method according to claim 5, characterized in that, In step S4, the vacuum annealing process conditions are: temperature of 1200~1500℃ and time of 2~4h.

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