Surface roughening treatment process for silicon carbide seed crystal

Abstract

The invention discloses a silicon carbide seed crystal surface roughening treatment process which comprises the following steps: S1, placing a silicon carbide seed crystal to be treated on a bearing frame in a treatment tank and fixing the silicon carbide seed crystal; s2, adding deionized water into the treatment tank until the seed crystals are completely immersed; s3, a driving device is started, and the multiple rotary drill bits are driven to rotate at the same time; s4, the drill bit is controlled to move downwards, so that the drill bit makes contact with the seed crystal bonding surface, and a plurality of evenly-distributed micropores are drilled in the surface of the seed crystal bonding surface; s5, after drilling is completed, the seed crystals are taken out of the treatment tank, and surface roughening treatment is completed; and S6, washing the treated seed crystal with deionized water, and drying. According to the equipment, seed crystals are immersed in deionized water for micropore treatment so as to realize rough treatment on the surfaces of the seed crystals, the operation is convenient and simple, the safety is high, toxic waste liquid is not generated, and the equipment is environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of seed crystal processing technology, and in particular to a surface roughening process for silicon carbide seed crystals. Background Technology

[0002] When preparing silicon carbide crystals using the physical vapor phase method, seed crystals are usually bonded to the crucible with an adhesive. Before bonding the seed crystals, the bonding surface of the seed crystals is usually roughened, typically by etching, to ensure the bonding effect.

[0003] During the etching process, strong acids, strong alkalis, or oxidizing solutions (such as hydrofluoric acid and ferric chloride) are required, which can easily generate toxic waste liquid. Improper handling can pollute the environment and endanger the health of operators. Therefore, it is necessary to design a seed crystal processing equipment that does not generate toxic waste liquid and is environmentally friendly and safe to meet the requirements. Summary of the Invention

[0004] The purpose of this application is to provide a surface roughening process for silicon carbide seed crystals to solve the technical problems mentioned in the background above.

[0005] To achieve the above objectives, this application provides the following technical solution: a surface roughening process for silicon carbide seed crystals, comprising the following steps,

[0006] S1: Place the silicon carbide seed crystal to be processed on the support frame in the processing tank and fix it;

[0007] S2: Add deionized water to the treatment tank until the seed crystal is completely submerged;

[0008] S3: Start the drive unit to drive multiple rotary drill bits to rotate simultaneously;

[0009] S4: Control the drill bit to move downwards, so that the drill bit contacts the seed crystal bonding surface and drills multiple uniformly distributed microholes on its surface;

[0010] S5: After drilling is completed, the seed crystal is removed from the processing tank to complete the surface roughening treatment;

[0011] S6: After the seed crystals have been processed, they are washed with deionized water and then dried.

[0012] In a preferred embodiment of this example, in step S3, during the drilling process, the treatment tank is pressurized so that the air pressure above the liquid surface is greater than atmospheric pressure, and the pressure is maintained at 1.3 to 1.6 times the normal atmospheric pressure.

[0013] In a preferred embodiment of this example, in step S2, 0.5%-2% by mass of nano-sized silica particles are added to the deionized water in the treatment tank, and 1%-3% by mass of silane coupling agent is added as a dispersant. The mixture is then stirred for 20-30 minutes using a stirring device.

[0014] In a preferred embodiment of this example, in step S2, an ultrasonic transducer is installed in the processing tank. Initial ultrasonic dispersion is performed for 10-15 minutes with an ultrasonic power of 100-150W, and then the ultrasonic power is adjusted to 200-300W and ultrasonication continues for 20-25 minutes.

[0015] In a preferred embodiment of this invention, after ultrasonic stirring, the mixed liquid in the treatment tank is heated by a heating device to control the heating temperature between 45-55°C and maintain this temperature for 20-30 minutes.

[0016] In a preferred embodiment of this invention, during the heating process, a small amount of nitrogen gas with a flow rate of 0.5-1.5 L / min is introduced into the treatment tank through a gas distributor to form uniform microbubbles. The diameter of the microbubbles is controlled between 50-100 μm, and the microbubbles are allowed to remain in the mixed liquid for 3-5 minutes.

[0017] As a preferred embodiment of this invention, when the drill bit contacts the bonding surface of the seed crystal during drilling, a variable frequency motor is used to control the rotation speed of the drill bit, which is dynamically adjusted within the range of 550-750 rpm. At the same time, a precision feed device is used to control the feed speed of the drill bit to 0.15-0.25 mm / min.

[0018] In a preferred embodiment of this example, in step S6, after drilling is completed, the seed crystal is removed from the processing tank and rinsed with deionized water. Then, the surface of the seed crystal is dried with filtered and purified compressed air. The pressure of the compressed air is controlled at 0.25-0.35 MPa, the blowing direction is at an angle of 30°-60° to the surface of the seed crystal, and the blowing distance is maintained at 5-10 cm.

[0019] In a preferred embodiment of this invention, after blowing, the seed crystal is placed in a vacuum drying oven, with the vacuum level controlled at 10. -3 -10 -4 Pa, while setting the drying temperature to 30-40℃ and the drying time to 30-60 minutes, and then storing the seed crystal in a vacuum environment.

[0020] In summary, the technical effects and advantages of this invention are as follows:

[0021] 1. The present invention has a reasonable structure. This equipment immerses the seed crystal in deionized water to perform microporous treatment to achieve roughening treatment of the seed crystal surface. It is convenient and simple to operate, has high safety, does not produce toxic waste liquid and is environmentally friendly.

[0022] 2. In this invention, nano-sized silica particles and silane coupling agents are added to deionized water. After the nano-sized silica particles enter the micropores, they can form a micro-rough structure, enhance the surface roughness of the seed crystal, and improve the bonding force with subsequent materials. The silane coupling agent can improve the compatibility between the nano-sized silica particles and deionized water and prevent agglomeration.

[0023] 3. In this invention, low-power ultrasound is used first, followed by high-power ultrasound. The initial low-power ultrasound dispersion can prevent particles from settling due to the sudden action of high power. Combined with stirring for initial mixing, the subsequent high-power ultrasound can generate a strong cavitation effect, further breaking up agglomerates. Stirring makes the liquid flow, ensuring uniform mixing throughout the treatment tank. In this way, when drilling, the distribution of nano-sized silica particles in the micropores is more uniform, improving the consistency of the roughing treatment effect. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This table presents experimental data on the bonding strength between seed crystals treated with this process and seed crystals treated with existing etching processes. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example: A surface roughening process for silicon carbide seed crystals, comprising the following steps,

[0028] S1: Place the silicon carbide seed crystal to be processed on the support frame in the processing tank and fix it;

[0029] S2: Add deionized water to the treatment tank until the seed crystal is completely submerged;

[0030] S3: Start the drive unit to drive multiple rotary drill bits to rotate simultaneously;

[0031] S4: Control the drill bit to move downwards, so that the drill bit contacts the seed crystal bonding surface and drills multiple uniformly distributed microholes on its surface;

[0032] S5: After drilling is completed, the seed crystal is removed from the processing tank to complete the surface roughening treatment;

[0033] S6: After the seed crystals have been processed, they are washed with deionized water and then dried.

[0034] This process involves immersing the seed crystal in deionized water and drilling holes to roughen the surface of the seed crystal. It is convenient, simple, safe, and environmentally friendly, and does not produce toxic waste liquid.

[0035] In a preferred embodiment of this example, in step S3, during the drilling process, the treatment tank is pressurized so that the air pressure above the liquid surface is greater than atmospheric pressure, and the pressure is maintained at 1.3 to 1.6 times the normal atmospheric pressure.

[0036] Applying pressure can improve the local compressive strength of the seed crystal, inhibit crack propagation, and the compressive stress can partially offset the tensile stress generated by drilling, reducing the risk of seed crystal breakage. The pressure should be maintained at 1.3 to 1.6 times the normal atmospheric pressure. If the value is too small, the effect of inhibiting breakage will be poor, and if the value is too large, it may cause the material to yield or generate new cracks.

[0037] In a preferred embodiment of this example, in step S2, 0.5%-2% by mass of nano-sized silica particles are added to the deionized water in the treatment tank, and 1%-3% by mass of silane coupling agent is added as a dispersant. The mixture is then stirred for 20-30 minutes using a stirring device.

[0038] Silane coupling agents can improve the compatibility of nano-sized silica particles with deionized water, prevent agglomeration, and when 0.5%-2% of nano-sized silica particles enter the micropores, they can form a micro-rough structure, enhance the surface roughness of the seed crystal, and improve the bonding force with subsequent materials. High-speed stirring ensures uniform dispersion, guarantees stable roughening treatment results, and improves product quality.

[0039] In a preferred embodiment of this example, in step S2, an ultrasonic transducer is installed in the processing tank. Initial ultrasonic dispersion is performed for 10-15 minutes with an ultrasonic power of 100-150W, and then the ultrasonic power is adjusted to 200-300W and ultrasonication continues for 20-25 minutes.

[0040] Preliminary low-power ultrasonic dispersion can prevent particles from settling due to sudden high-power action. Combined with initial mixing by stirring, subsequent high-power ultrasonication can generate a strong cavitation effect, further breaking up agglomerates. Stirring makes the liquid flow and ensures uniform mixing throughout the treatment tank. In this way, when drilling, the distribution of nano-sized silica particles in the micropores is more uniform, improving the consistency of roughing treatment results.

[0041] In a preferred embodiment of this invention, after ultrasonic stirring, the mixed liquid in the treatment tank is heated by a heating device to control the heating temperature between 45-55°C and maintain this temperature for 20-30 minutes.

[0042] Temperatures of 45-55℃ reduce the viscosity of deionized water and enhance its fluidity, which is beneficial for the diffusion of nano-sized silica particles. Continuous low-speed magnetic stirring prevents localized sedimentation of particles due to temperature increases, ensuring that the nano-sized silica particles remain uniformly dispersed in the deionized water. Simultaneously, appropriate temperatures enhance the interaction between the particles and the seed crystal surface and the inner walls of the micropores, improving particle adhesion stability and enhancing the roughening effect.

[0043] In a preferred embodiment of this invention, during the heating process, a small amount of nitrogen gas with a flow rate of 0.5-1.5 L / min is introduced into the treatment tank through a gas distributor to form uniform microbubbles. The diameter of the microbubbles is controlled between 50-100 μm, and the microbubbles are allowed to remain in the mixed liquid for 3-5 minutes.

[0044] The 50-100μm microbubbles formed by introducing a trace amount of nitrogen gas drive the liquid flow during their ascent, further agitating the liquid and making the nano-sized silica particles more evenly dispersed. The microbubbles remain for 3-5 minutes and can generate local high pressure and impact force when they break, which slightly impacts and cleans the surface of the seed crystal and the inner wall of the micropores, removing impurities and weakly bonded particles, improving surface quality, and optimizing the roughening effect.

[0045] As a preferred embodiment of this invention, when the drill bit contacts the bonding surface of the seed crystal during drilling, a variable frequency motor is used to control the rotation speed of the drill bit, which is dynamically adjusted within the range of 550-750 rpm. At the same time, a precision feed device is used to control the feed speed of the drill bit to 0.15-0.25 mm / min.

[0046] The variable frequency motor allows the drill bit to dynamically adjust its rotation speed from 550 to 750 rpm, which can better adapt to the needs of different drilling stages and ensure cutting effect. The feed rate of 0.15-0.25 mm / min, combined with real-time fine adjustment, can avoid problems such as drill bit overheating and seed crystal surface crack propagation caused by excessive feed, ensuring that high-quality and uniformly distributed microholes are drilled on the seed crystal surface, thus improving the roughing quality.

[0047] In a preferred embodiment of this example, in step S6, after drilling is completed, the seed crystal is removed from the processing tank and rinsed with deionized water. Then, the surface of the seed crystal is dried with filtered and purified compressed air. The pressure of the compressed air is controlled at 0.25-0.35 MPa, the blowing direction is at an angle of 30°-60° to the surface of the seed crystal, and the blowing distance is maintained at 5-10 cm.

[0048] The filtered and purified compressed air can prevent impurities from contaminating the surface of the seed crystal. The pressure of 0.25-0.35MPa can quickly dry the surface moisture without damaging the already formed rough structure and micropores due to excessive pressure.

[0049] A blowing direction of 30°-60° and a blowing distance of 5-10cm can ensure that the airflow acts evenly on the surface of the seed crystal, improve the drying efficiency, and maintain the roughing effect.

[0050] In a preferred embodiment of this invention, after blowing, the seed crystal is placed in a vacuum drying oven, with the vacuum level controlled at 10. -3 -10 -4 Pa, while setting the drying temperature to 30-40℃ and the drying time to 30-60 minutes, and then storing the seed crystal in a vacuum environment.

[0051] 10 -3 -10 -4 A vacuum level of 10 Pa and a drying temperature of 30-40℃ can quickly remove residual moisture and gas from the seed crystal surface, preventing surface oxidation and corrosion. A drying time of 30-60 minutes ensures thorough drying. Storing the dried seed crystal in a vacuum environment effectively isolates it from air, maintains the good condition of the seed crystal surface after roughening treatment, and extends the storage time and usability of the seed crystal.

[0052] Five sets of seed crystals (numbered 1, 2, 3, 4, and 5) processed using this process, and one set of seed crystals (numbered 6) processed using an existing etching process, were bonded to the crucible lid under the same conditions. The bonding strength of each set of seed crystals was measured and set as follows. Figure 1 As shown;

[0053] Depend on Figure 1 It can be seen that the bonding strength between the seed crystal and the crucible lid after this process is greater than that of the seed crystal after the etching process.

[0054] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A surface roughening process for silicon carbide seed crystals, characterized in that: Includes the following steps, S1: Place the silicon carbide seed crystal to be processed on the support frame in the processing tank and fix it; S2: Add deionized water to the treatment tank until the seed crystal is completely submerged; S3: Start the drive unit to drive multiple rotary drill bits to rotate simultaneously; S4: Control the drill bit to move downwards, so that the drill bit contacts the seed crystal bonding surface and drills multiple uniformly distributed microholes on its surface; S5: After drilling is completed, the seed crystal is removed from the processing tank to complete the surface roughening treatment; S6: After the seed crystals have been processed, they are washed with deionized water and then dried.

2. The surface roughening process for silicon carbide seed crystals according to claim 1, characterized in that: In S3, during the drilling process, the treatment tank is pressurized so that the air pressure above the liquid surface is greater than atmospheric pressure, and the pressure is maintained at 1.3 to 1.6 times the normal atmospheric pressure. This increases the compressive stress of deionized water on the seed crystal, improves the local compressive strength of the seed crystal, and inhibits crack propagation.

3. The surface roughening process for silicon carbide seed crystals according to claim 1, characterized in that: In S2, 0.5%-2% by mass of nano-sized silica particles are added to the deionized water in the treatment tank, and 1%-3% by mass of silane coupling agent is added as a dispersant. The mixture is then stirred for 20-30 minutes using a stirring device.

4. The surface roughening process for silicon carbide seed crystals according to claim 3, characterized in that: In S2, an ultrasonic transducer is installed in the processing tank. Initial ultrasonic dispersion is performed for 10-15 minutes with an ultrasonic power of 100-150W. Then, the ultrasonic power is adjusted to 200-300W and ultrasonication continues for 20-25 minutes.

5. The surface roughening process for silicon carbide seed crystals according to claim 4, characterized in that: After ultrasonic stirring, the mixed liquid in the treatment tank is heated by a heating device, and the heating temperature is controlled between 45-55°C and maintained at this temperature for 20-30 minutes.

6. The surface roughening process for silicon carbide seed crystals according to claim 5, characterized in that: During the heat treatment process, a small amount of nitrogen gas with a flow rate of 0.5-1.5 L / min is introduced into the treatment tank through a gas distributor to form uniform microbubbles. The diameter of the microbubbles is controlled between 50-100 μm, and the microbubbles are allowed to remain in the mixed liquid for 3-5 minutes.

7. The surface roughening process for silicon carbide seed crystals according to claim 1, characterized in that: When drilling, the drill bit is in contact with the bonding surface of the seed crystal. A variable frequency motor is used to control the rotation speed of the drill bit, which is dynamically adjusted within the range of 550-750 rpm. At the same time, a precision feed device controls the feed speed of the drill bit to 0.15-0.25 mm / min.

8. The surface roughening process for silicon carbide seed crystals according to claim 7, characterized in that: In S6, after drilling is completed, the seed crystal is removed from the treatment tank and rinsed with deionized water. Then, the surface of the seed crystal is dried with filtered and purified compressed air. The pressure of the compressed air is controlled at 0.25-0.35MPa, the blowing direction is at an angle of 30°-60° to the surface of the seed crystal, and the blowing distance is maintained at 5-10cm.

9. The surface roughening process for silicon carbide seed crystals according to claim 8, characterized in that: After blowing, place the seed crystal in a vacuum drying oven, controlling the vacuum level at 10. -3 -10 -4 Pa, while setting the drying temperature to 30-40℃ and the drying time to 30-60 minutes, and then storing the seed crystal in a vacuum environment.

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