Batch growth method of monocrystal diamond

Abstract

The invention belongs to the technical field of single crystal diamond growth, and particularly relates to a single crystal diamond batch growth method which comprises the following steps: single crystal diamond with crystallographic orientation of (100) is used as seed crystal, and the seed crystal comprises a bottom surface and a growth surface which are oppositely arranged; seed crystals located at the corners of the monocrystal diamond seed crystal array are cut, edges and corners, away from the center of the monocrystal diamond seed crystal array, of seed crystal growth faces are removed, cutting faces are formed on the seed crystals, and then microwave plasma chemical vapor deposition treatment is carried out. By cutting the edge angles of the seed crystals at the edge of the monocrystal diamond seed crystal array, the edge effect can be weakened, the thickness of single growth can be increased, the growth period for reaching the thickness of a finished product can be shortened, and the production efficiency and the economic benefit can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of single crystal diamond growth, and particularly relates to a method for batch growth of single crystal diamond. Background Art

[0002] Single crystal diamond has wide applications in semiconductors, electronic devices, precision cutting materials, and optical materials. In addition, gem-grade single crystal diamond is favored by many young people as jewelry. Therefore, it is of great significance to synthesize high-quality, large-size single crystal diamond at high speed.

[0003] MPCVD (Microwave Plasma Chemical Vapor Deposition) stands out among many methods for artificial synthesis of diamond because of its unique advantages such as non-polar discharge, less pollution, and high plasma density.

[0004] The seed crystal of single crystal diamond is cubic in shape, and its growth surface is perpendicular to the side surface. During the preparation of single crystal diamond by the MPCVD method, the electric field strength at the corners of the seed crystal array is higher than that of the growth surface, which leads to an increase in the concentration of carbon-containing precursors at the corners of the seed crystal array, resulting in a higher temperature at the edge of the single crystal diamond at the corners of the seed crystal array than the central deposition temperature. This phenomenon is also called the edge effect. The existence of the edge effect causes polycrystalline diamond to easily grow at the edges and corners of the single crystal diamond seed crystal during growth in the plasma. As the synthesis time increases, the polycrystalline diamond gradually grows and the temperature rises. As Figure 1 shown, it finally burns at the edges and corners, causing the growth of the entire batch of diamonds to be forced to stop, resulting in a smaller thickness for single growth and reducing the production efficiency. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for batch growth of single crystal diamond to solve the problem of the smaller thickness of single growth during the batch growth of existing single crystal diamond.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] A method for batch growth of single crystal diamond, comprising the following steps: using a single crystal diamond with a crystallographic orientation of (100) as the seed crystal, the shape of the seed crystal being a cube or a cuboid, the seed crystal including a bottom surface and a growth surface arranged opposite to each other; performing a cutting process on the seed crystal located at the corners of the single crystal diamond seed crystal array, removing the edges and corners of the growth surface of the seed crystal away from the center of the single crystal diamond seed crystal array to form a cutting surface on the seed crystal, and then performing microwave plasma chemical vapor deposition treatment.

[0008] The beneficial effects of the above technical solution are as follows: The present invention is an improved invention. By cutting the seed crystals at the corners of the single-crystal diamond seed crystal array, the seed crystals form inclined surfaces that deviate from the growth surface by a certain angle, thereby weakening the electric field strength at the corners of the single-crystal diamond seed crystal array, reducing the edge effect, and suppressing polycrystalline growth. It can avoid the problem of a relatively small thickness of single growth caused by the forced stop of the growth of the whole batch of seed crystals due to the polycrystalline combustion at the edge corners of the peripheral seed crystals during the growth process. The method of the present invention can increase the thickness of single growth, shorten the growth cycle to reach the finished product thickness, and improve production efficiency and economic benefits. Moreover, the cutting volume of the seed crystals in the present invention is small, which does not affect the subsequent growth of the seed crystals and the design and cutting after they grow into finished products.

[0009] The single-crystal diamond seed crystal array includes multiple single-crystal diamond seed crystals arranged in an array. Further, the present invention does not limit the number and arrangement of the seed crystals in the single-crystal diamond seed crystal array, as long as the multiple arranged seed crystals can be symmetric up, down, left, and right on the substrate stage. For example, to improve production efficiency, the number of seed crystals can be selected according to the coverage area of the plasma sphere. For example, the number of seed crystals can be 24, 37, 45, or 52.

[0010] As a further improvement, the cutting surface is a plane inclined downward, and the included angle between the cutting surface and the single-crystal diamond growth surface is 150 - 170°.

[0011] The beneficial effects of the above technical solution are as follows: When the included angle between the cutting surface and the single-crystal diamond growth surface is within the above range, the electric field strength at the cutting surface can be effectively weakened, and the edge effect can be effectively reduced, further increasing the thickness of single growth. If the included angle between the cutting surface and the single-crystal diamond growth surface is too small, the cutting removal volume is too large, resulting in excessive loss of single-crystal diamond. If the included angle between the cutting surface and the single-crystal diamond growth surface is too large, the cutting removal volume is too small, and the improvement effect on the edge effect is small, and the improvement effect on the single growth thickness is small.

[0012] As a further improvement, the seed crystal growth surface has an intersecting first edge and second edge, the cutting surface includes a first cutting point and a second cutting point, the first cutting point is located on the first edge, and the second cutting point is located on the second edge; the ratio of the distance between the first cutting point and the corner to be removed to the length of the first edge is 0.1 - 0.2, and the ratio of the distance between the second cutting point and the corner to be removed to the length of the second edge is 0.1 - 0.2.

[0013] The beneficial effects of the above technical solution are as follows: With the above design, the problem of relatively small thickness in single growth caused by combustion at the edges can be solved more effectively. Moreover, the present invention has a smaller cutting volume for the seed crystal, which does not affect the subsequent growth of the seed crystal and the design and cutting of the finished product.

[0014] As a further improvement, after forming a cutting surface on the seed crystal, the cut seed crystal is subjected to acid treatment, and then sequentially washed with water, acetone, and alcohol.

[0015] The beneficial effects of the above technical solution are as follows: Through acid treatment, metals and organic residues on the surface of the seed crystal can be removed; through washing with water, acetone, and alcohol, impurities or contaminants adsorbed on the surface of the seed crystal can be removed; through the above operations, the quality of the seed crystal can be improved, and the quality of the grown single-crystal diamond can be further improved.

[0016] Further, the acid treatment includes: placing the seed crystal in a container filled with a strong acid solution and heating. The strong acid solution is a mixed solution of concentrated hydrochloric acid and concentrated nitric acid, and the volume ratio of concentrated hydrochloric acid to concentrated nitric acid in the strong acid solution is 3:1, and the heating time is 30 - 60 min.

[0017] The washing includes: placing the seed crystal successively in containers filled with water, acetone, and alcohol, and placing the containers in an ultrasonic cleaning tank for water washing, acetone washing, and alcohol washing respectively. The water washing, acetone washing, and alcohol washing times are 10 - 30 min.

[0018] Further, when performing microwave plasma chemical vapor deposition treatment, the temperature of the seed crystal is raised to 800 - 1000 °C, and gases such as H2, CH4, and N2 are introduced. Under the above conditions, the seed crystal can grow.

[0019] The method of the present invention can achieve a single growth thickness of 3 - 5 mm and a total wafer thickness of 5 - 10 mm (the total wafer thickness is the thickness of the seed crystal before growth + the sum of the thicknesses of multiple growths), shorten the growth cycle to reach the finished product thickness, and improve production efficiency and economic benefits. Description of the Drawings

[0020] Figure 1 is a photograph of the single-crystal diamond seed crystal at the edge of the carrier substrate stage burning after 120 h of single growth during the growth process of the existing single-crystal diamond;

[0021] Figure 2 is a structural comparison diagram of the single-crystal diamond seed crystal before cutting and after cutting in Example 1 of the present invention. In the figure, θ refers to the angle between the cutting surface and the growth direction of the single-crystal diamond;

[0022] Figure 3 is a three-dimensional view of the single-crystal diamond seed crystal after cutting in Example 1 of the present invention;

[0023] Figure 4 It is a layout diagram of multiple seeds on the carrier substrate table in Embodiment 1 of the present invention;

[0024] Figure 5 It is a photo of the corner of the single-crystal diamond seed array at 200 h of single growth during the growth process of single-crystal diamond in Embodiment 1 of the present invention;

[0025] Figure 6 It is a photo of the corner of the single-crystal diamond seed array at 200 h of single growth during the growth process of single-crystal diamond in Embodiment 2 of the present invention;

[0026] Figure 7 It is a photo of the corner of the single-crystal diamond seed array at 200 h of single growth during the growth process of single-crystal diamond in Embodiment 3 of the present invention. Detailed implementation manners

[0027] Refer to Figure 1 , during the batch growth process of existing single-crystal diamond, the temperature at the corner of the single-crystal diamond seed array is relatively high. As the synthesis time increases, the edges of the single-crystal diamond seeds at the corner of the single-crystal diamond seed array burn, which will cause the growth of the whole batch of diamonds to be forced to stop, resulting in a small thickness of single growth. That is to say, there is a problem of small thickness of single growth in the batch growth process of existing single-crystal diamond.

[0028] To solve the above technical problems, the present invention provides a batch growth method for single-crystal diamond, including the following steps: using a single-crystal diamond with a crystallographic orientation of (100) as a seed, the shape of the seed is a cube or a cuboid, and the seed includes a bottom surface and a growth surface arranged opposite to each other; cutting the seeds located at the corners of the single-crystal diamond seed array, removing the edges of the growth surface of the seeds far from the center of the single-crystal diamond seed array to form a cutting surface on the seeds, and then performing microwave plasma chemical vapor deposition treatment; wherein, the ratio of the area of the positive projection of the cutting surface on the bottom surface of the seed to the area of the bottom surface of the seed is 0.01 - 0.04.

[0029] The present invention weakens the electric field strength at the corner of the single-crystal diamond seed array by cutting the seeds at the corner of the single-crystal diamond seed array to form an inclined surface deviating from the growth surface by a certain angle, thereby weakening the edge effect during the wafer growth process, suppressing polycrystalline growth, and increasing the thickness of single growth.

[0030] The technical solutions of the present invention will be further described in detail below in conjunction with embodiments.

[0031] I. Specific embodiments of the batch growth method for single-crystal diamond of the present invention

[0032] Example 1

[0033] The batch growth method of single-crystal diamond in this example is specifically described as follows:

[0034] Select 45 single-crystal diamonds with a crystallographic orientation of (100), a size of 8 mm (length) × 8 mm (width) × 2 mm (thickness), no defects on the growth surface, and good edge quality as seed crystals; as Figure 2 and Figure 3 , cut and polish the edges and corners of 8 of the seed crystals to form a cutting surface deviating from the growth surface, and the angle θ between the cutting surface and the growth direction of the single-crystal diamond is 170°; the growth surface of the seed crystal has an intersecting first edge and a second edge, the cutting surface includes a first cutting point and a second cutting point, the first cutting point is located on the first edge, and the second cutting point is located on the second edge; the ratio of the distance between the first cutting point and the edge and corner to be removed to the length of the first edge is 0.1, and the ratio of the distance between the second cutting point and the edge and corner to be removed to the length of the second edge is 0.1.

[0035] Then place the seed crystals in a spatially appropriate polytetrafluoroethylene bracket in a single-piece form, and then place the bracket in a container filled with a strong acid mixed solution (the volume ratio of concentrated hydrochloric acid to concentrated nitric acid in the strong acid mixed solution is 3:1) and heat-treat with acid for 30 min to remove the metal and organic residues on the surface of the seed crystals; after acid treatment, transfer the polytetrafluoroethylene bracket to a container filled with pure water, place the container in an ultrasonic cleaning tank, and clean it ultrasonically for 10 min to remove the residual acid solution on the surface of the seed crystals; then transfer the bracket to a container filled with acetone solution, place the container in an ultrasonic cleaning tank, and clean it ultrasonically for 10 min; finally, transfer the bracket to a container filled with alcohol, place the container in an ultrasonic cleaning tank, and clean it ultrasonically again for 10 min to remove the impurities or contaminants adsorbed on the surface of the seed crystals; as Figure 4 , place the 45 seed crystals on the carrier substrate table in a symmetric arrangement of up, down, left, and right. The 8 seed crystals with cut edges and corners need to be placed at the corners of the single-crystal diamond seed crystal array. Transfer the carrier substrate table to the MPCVD cavity, adjust the temperature of the seed crystal to 800 - 1000 °C, and introduce reaction gases such as H2, CH4, and N2 to start growth; Figure 5 is a photo of the corner of the single-crystal diamond seed crystal array during the single-crystal diamond growth process when growing for 200 h at a time. It can be seen from Figure 5 that the wafers at the corners of the single-crystal diamond seed crystal array grow well, no polycrystalline balls are grown, and the wafers at the corners of the single-crystal diamond seed crystal array do not burn.

[0036] In the above implementation process, the MPCVD growth process of the single-crystal diamond seed crystal can be specifically carried out in the following manner: Transfer the carrier substrate stage to the MPCVD cavity (15kw dish-shaped resonator), close the cavity lid, evacuate the cavity vacuum value to below 3pa, then start heating up, set the power, gas pressure, and hydrogen flow rate to linearly rise to 14000W, 18Kpa, and 350sccm in 30 minutes. After the power, gas pressure, and hydrogen reach the target values, linearly introduce 2sccm of oxygen for 30 minutes for pre-growth etching in 1 minute, then close the oxygen, linearly introduce 30sccm of CH4 and 0.5sccm of N2 in 1 minute, and start growing. At this time, the seed crystal temperature is between 800 and 1000 °C.

[0037] Example 2

[0038] The batch growth method of single-crystal diamond in this example is specifically described as follows:

[0039] Other steps are the same as those in Example 1, except that: in Example 2, the angle between the cutting surface and the growth direction of the single-crystal diamond is 150°; Figure 6 is a photo of the corner of the single-crystal diamond seed crystal array during the single growth of 200h in the growth process of single-crystal diamond, taken by Figure 6 It can be seen that the wafers at the corners of the single-crystal diamond seed crystal array grow well, no polycrystalline balls are grown, and the wafers at the corners of the single-crystal diamond seed crystal array are not burned.

[0040] Example 3

[0041] The batch growth method of single-crystal diamond in this example is specifically described as follows:

[0042] Other steps are the same as those in Example 1, except that: the ratio of the distance between the first cutting point and the corner to be removed to the length of the first edge is 0.2, and the ratio of the distance between the second cutting point and the corner to be removed to the length of the second edge is 0.2; Figure 7 is a photo of the corner of the single-crystal diamond seed crystal array during the single growth of 200h in the growth process of single-crystal diamond, taken by Figure 7 It can be seen that the wafers at the corners of the single-crystal diamond seed crystal array grow well, no polycrystalline balls are grown, and the wafers at the corners of the single-crystal diamond seed crystal array are not burned.

[0043] II. Comparative Example

[0044] Comparative Example 1

[0045] Other steps are the same as those in Example 1, except that: in Comparative Example 1, the corners of the edge seeds are not cut, and other steps are the same as those in Example 1.

[0046] During the growth process of the single-crystal diamond in Comparative Example 1, when the growth time was 120 h, edge burning occurred. The photo of the edge burning is as Figure 1 shown.

[0047] III. Performance Test

[0048] The main performance test parameters of each example and comparative example are the single-round growth time, the single-round growth thickness, and the growth cycle to reach the finished thickness. Specifically, the time from when the CH4 gas is introduced to when the CH4 gas is turned off for the entire batch of products is the single-round growth time of this batch. The average thickness measured after the growth of the entire batch of products minus the average thickness before growth is the single-round average growth thickness. The number of growth rounds required to reach the finished thickness is its growth cycle. The performance test data of each example and comparative example are specifically shown in Table 1 below.

[0049] Table 1 Performance Test Results of Each Example and Comparative Example

[0050]

[0051]

[0052] Note: For both the comparative example and the examples, the thickness of the seed crystal before growth was 2 mm, the total thickness to reach the finished product was 10 mm, and the single-round average growth rate was calculated at 15 μm / h.

[0053] It can be seen from Table 1 that: in Examples 1, 2, and 3, the wafers at the corners of the single-crystal diamond seed crystal array grew well after single-round growth for more than 200 h, no polycrystalline spheres grew, the wafers at the corners of the single-crystal diamond seed crystal array did not burn, and the final single-round growth thickness was greater than 3 mm, and the growth cycle was less than 2.7 rounds. However, in the comparative example, the problem of polycrystalline sphere burning occurred within 150 h of growth, and the growth had to be stopped, resulting in a single-round growth thickness of less than 2.25 mm and a growth cycle of more than 3.5 rounds.

Claims

1. A method for batch growth of single crystal diamond, characterized in that, The method includes the following steps: Use a single-crystal diamond with a crystallographic orientation of (100) as the seed crystal. The shape of the seed crystal is a cube or a cuboid, and the seed crystal includes a bottom surface and a growth surface that are oppositely arranged; Cut the seed crystals at the corners of the single-crystal diamond seed crystal array, remove the edges and corners of the growth surface of the seed crystal that are far from the center of the single-crystal diamond seed crystal array, form a cutting surface on the seed crystal, and then perform microwave plasma chemical vapor deposition treatment.

2. The batch growth method of single crystal diamond according to claim 1, wherein, The cutting surface is an inclined downward plane, and the included angle between the cutting surface and the growth surface of the single-crystal diamond is 150-170°.

3. The batch growth method of single crystal diamond according to claim 2, characterized in that, There are an intersecting first edge and a second edge on the growth surface of the seed crystal. The cutting surface includes a first cutting point and a second cutting point. The first cutting point is located on the first edge, and the second cutting point is located on the second edge; the ratio of the distance between the first cutting point and the edge and corner to be removed to the length of the first edge is 0.1-0.2, and the ratio of the distance between the second cutting point and the edge and corner to be removed to the length of the second edge is 0.1-0.

2.

4. The method for batch growth of single-crystal diamond according to any one of claims 1-3, characterized in that, After forming the cutting surface on the seed crystal, perform acid treatment on the cut seed crystal, and then wash it successively with water, acetone, and alcohol.

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