Crushed silicon carbide crystal ingot repairing method

Abstract

The invention discloses a fragmented silicon carbide crystal ingot repairing method which comprises the following steps: splicing a plurality of silicon carbide fragments to form an integral silicon carbide crystal ingot, promoting macroscopic crack opening healing by adopting a liquid phase induction healing process, and then filling microscopic pores around cracks by adopting an in-situ gas phase permeation process to realize crack repairing of the fragmented silicon carbide crystal ingot. According to the provided broken silicon carbide crystal ingot repairing method, a liquid phase induction healing process is adopted, liquid silicon and silicon carbide react to fill gaps, then cooling is performed to form new silicon carbide bonding, macroscopic crack openings are promoted to be closed, and then an in-situ gas phase permeation process is adopted to repair the broken silicon carbide crystal ingot. A chemical covalent network is constructed by depositing and permeating silicon carbide in micro pores by using a silicon source and a carbon source, so that crack repair of the silicon carbide crystal ingot is realized. According to the method, the broken crystal ingot is repaired through physical reconstruction and chemical bonding, and the mechanical and electrical properties of the broken crystal ingot are recovered.

Description

Technical Field

[0001] The present invention relates to the field of crystal repair technology, and in particular to a method for repairing a broken silicon carbide ingot. Background Art

[0002] Silicon carbide single crystals are a key material for the fabrication of high-temperature, high-frequency, and high-power devices. However, their growth process is complex, and the crystals are prone to internal cracks or localized fragmentation due to uneven thermal stress or improper cooling rates. Currently, broken ingots are typically discarded, resulting in low material utilization and high production costs. A few repair methods, such as bonding and partial melting, suffer from insufficient repair strength, degraded electrical properties, or incompatibility with subsequent cutting, grinding, and polishing processes. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and provide a method for repairing a broken silicon carbide ingot.

[0004] The present invention solves the technical problem by adopting the following technical solutions.

[0005] The present invention provides a method for repairing a broken silicon carbide ingot, comprising: splicing multiple pieces of silicon carbide fragments to form an integral silicon carbide ingot, first using a liquid-phase induced healing process to promote the healing of macro crack openings, and then using an in-situ vapor infiltration process to fill microscopic pores around the cracks, thereby achieving crack repair of the broken silicon carbide ingot.

[0006] The present invention has the following beneficial effects:

[0007] The present invention provides a method for repairing a broken silicon carbide ingot. The method comprises: splicing multiple pieces of silicon carbide fragments to form a whole silicon carbide ingot, first using a liquid-phase induced healing process to promote the healing of the macro crack opening, and then using an in-situ vapor infiltration process to fill the micro pores around the crack to achieve crack repair of the broken silicon carbide ingot. The above-mentioned repair method firstly backfills the defects by newly generating silicon carbide in the crack, thereby achieving the healing of the macro crack opening, and then uses in-situ vapor infiltration to allow silicon carbide to infiltrate and fill the micro pores and rebuild the covalent bond network to achieve crack repair of the silicon carbide ingot. The method achieves the repair of the broken ingot through physical reconstruction and chemical bonding, and restores the mechanical and electrical properties of the broken silicon carbide ingot. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0009] Figure 1 A schematic diagram of the process of repairing a broken silicon carbide ingot provided by the present invention;

[0010] Figure 2 This is an appearance diagram of a fragmented silicon carbide ingot provided in Example 1 of the present invention that has only undergone liquid-phase induced healing treatment but not in-situ vapor infiltration treatment;

[0011] Figure 3 This is an appearance diagram of the fragmented silicon carbide ingot provided in Example 1 of the present invention after liquid-phase induced healing treatment and in-situ vapor infiltration treatment. DETAILED DESCRIPTION

[0012] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0013] The following is a detailed description of a method for repairing a broken silicon carbide ingot provided by an embodiment of the present invention.

[0014] Please refer to Figure 1 An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot, comprising: splicing multiple pieces of silicon carbide fragments to form an integral silicon carbide ingot, first using a liquid-phase induced healing process to promote the healing of macro crack openings, and then using an in-situ vapor infiltration process to fill the micro pores around the cracks, thereby achieving crack repair of the broken silicon carbide ingot.

[0015] An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot. The main repair idea is: first, a liquid-phase induced healing process is used to fill the splicing parts of the broken silicon carbide ingot, and the defects are backfilled by introducing an intercrystalline liquid film by controlling the micro-remelting of the grain boundaries, thereby achieving the healing of the macro crack openings. After that, an in-situ vapor infiltration process is used to fill the microscopic pores around the cracks by in-situ vapor deposition of silicon carbide, thereby achieving crack repair of the broken silicon carbide ingot.

[0016] In some optional embodiments, the liquid-phase induced healing treatment comprises the following steps:

[0017] Step S1: pre-pressing the splicing parts to align the fragments and reduce the interface gap;

[0018] Step S2, filling the cracks of the joints with excess silicon powder, heating the melted liquid silicon to react with silicon carbide to fill the cracks, and then cooling to form new silicon carbide bonds;

[0019] Step S3: After the reaction is completed, the silicon powder remaining on the surface is removed by etching with hydrofluoric acid.

[0020] An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot, comprising: using a liquid phase induced healing process to promote the healing of macro crack openings, wherein the repair process of the liquid phase induced healing process is as follows:

[0021] 1. Initial reaction between liquid silicon and silicon carbide

[0022] Wetting and Penetration: After filling the cracks at the joints of the fractured silicon carbide crystals with excess silicon powder, heating to a temperature above the melting point of 1414°C (1414°C) can cause the silicon powder to melt and form liquid silicon. Liquid silicon wets the silicon carbide surface at high temperatures (typically >1450°C) and penetrates into the cracks through capillary action. Liquid silicon exhibits excellent wettability to silicon carbide (typically with a contact angle <90°), especially in an inert atmosphere (such as Ar) or under vacuum conditions.

[0023] Interfacial dissolution: Liquid silicon dissolves the carbon and silicon on the surface of silicon carbide to form a silicon-rich melt, which causes the following reaction (this process is driven by temperature, and the amount of dissolution increases with increasing temperature (e.g., the solubility increases significantly at 1600°C):

[0024] SiC (solid) + Si (liquid) → Si (liquid) + C (dissolution) + Si (dissolution).

[0025] 2. Crack filling and silicon carbide regrowth

[0026] Migration of carbon and silicon atoms: The dissolved C and Si atoms on both sides of the crack migrate through liquid silicon to the unreacted area of the crack or the area with lower temperature (such as the crack tip).

[0027] Silicon carbide re-precipitation: When the melt reaches local supersaturation, silicon carbide will re-precipitate, and the reaction is: Si (liquid) + C (dissolution) → SiC (solid). The re-precipitated silicon carbide will match the original silicon carbide lattice in the initial growth mode (single crystal) or form a polycrystalline structure (polycrystalline).

[0028] 3. Cooling and bond formation: Controlling the cooling rate can reduce thermal stress and prevent cracking at the new bond. The reprecipitated silicon carbide is covalently bonded to the original silicon carbide. If the lattice orientation is consistent (such as single crystal repair), the interface is almost defect-free; if it is polycrystalline, grain boundaries may form.

[0029] As shown above, the liquid-phase induced healing process proceeds through three stages: Before repair: The SiC surfaces on both sides of the crack are clean. During repair: Liquid silicon penetrates the crack, dissolves the SiC, migrates atoms, and then precipitates SiC. After repair: The reprecipitated SiC forms an initial growth pattern that matches the original SiC lattice and bonds to the crack interface, achieving initial repair and healing of the macrocrack.

[0030] In some optional embodiments, in step S1, the temperature of the pre-pressing treatment is 800-1200° C., the pressure is 10-30 MPa, and the treatment atmosphere is a vacuum atmosphere.

[0031] An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot, which includes: after splicing the broken silicon carbide crystal, pre-pressing the spliced parts to align the fragments initially and reduce the interface gap. Since the plastic transition threshold of silicon carbide crystals is above 600°C, applying a pressure of 10-30MPa at a heating temperature of 800-1200°C can cause the silicon carbide to undergo plastic deformation, prompting dislocation slip on the contact surface of the fragments, thereby achieving preliminary mechanical interlocking of multiple irregular silicon carbide fragments, which is beneficial to the subsequent closure of macro cracks. When the heating temperature is lower than 800°C, the mechanical engagement and positioning between the fragments is poor, the repair effect is poor, and the fragments are easy to fall off. When the heating temperature is higher than 1200°C, the dislocation density of the silicon carbide crystal increases by 2-3 orders of magnitude, the grains grow abnormally, and the thermal stress caused by the temperature gradient causes the microcracks to expand, resulting in the inability to effectively close the defects in the subsequent hot pressing stage. Optionally, the heating temperature can be 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃, 1200℃ and any value between 800-1200℃, and the pressure can be 10MPa, 15MPa, 20MPa, 25MPa, 30MPa and any value between 10-30MPa.

[0032] In some optional embodiments, the method further includes: prior to the pre-pressing treatment, plasma etching is performed on the crack surface of the silicon carbide crystal in an inert atmosphere to remove the oxide layer and form a nano-scale rough surface. Before the pre-pressing treatment, the spliced parts of the fragmented silicon carbide crystal are plasma-etched to remove oxide impurities in the crack damage area, eliminating the need for mechanical processing such as grinding and cutting on the damaged area of the parent material, thereby reducing parent material damage.

[0033] In some optional embodiments, in step S2, the temperature of the liquid phase induced healing treatment is 1500-1700° C., and the treatment atmosphere is an inert atmosphere.

[0034] An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot, which comprises: after the pre-pressing treatment is completed, performing a liquid phase induced healing treatment, preferably, the temperature of the liquid phase induced healing treatment is between 1500-1700°C, and any temperature within this temperature range is lower than the decomposition temperature of silicon carbide, but sufficient to promote the dissolution and re-precipitation of silicon carbide. If the temperature is too high (>1800°C), it may cause excessive decomposition of silicon carbide or volatilization of silicon. Optionally, the temperature of the liquid phase induced healing treatment can be 1500°C, 1550°C, 1600°C, 1650°C, 1700°C and any value between 1500-1700°C. It is worth noting that: excessive silicon powder filling is required to ensure that the cracks are completely filled, but excessive amount will result in residual silicon phase (which can be removed by subsequent HF acid etching). The atmosphere of the liquid phase induced healing treatment is an inert gas (such as Ar) or a vacuum to prevent oxidation of the silicon carbide crystals.

[0035] In some optional embodiments, in step S3, the cooling rate is 5-10°C / min.

[0036] An embodiment of the present invention provides a method for repairing a fractured silicon carbide ingot, comprising: after completing a liquid-phase induced healing process, slowly cooling the ingot to room temperature to prevent cracking at new bonds. Specifically, controlling the cooling rate (e.g., 5-10°C / min) can reduce thermal stress and prevent cracking at new bonds. During cooling, the remaining liquid silicon further reacts with unreacted carbon to form silicon carbide or solidifies into a silicon filler phase (which requires subsequent etching removal).

[0037] In some optional embodiments, the in-situ vapor infiltration treatment utilizes a silicon source and a carbon source to react to form silicon carbide to fill the microscopic pores around the cracks.

[0038] In some optional embodiments, the silicon source includes silane, the carbon source includes methane, and the molar ratio of the silicon source to the carbon source is 1:1. During the in-situ vapor infiltration process, the temperature is controlled to be 1800±100°C and the pressure is controlled to be 1000±100 Pa.

[0039] An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot, which includes: after liquid-phase induced healing treatment is performed on the spliced silicon carbide crystals, the macro cracks can be preliminarily repaired and closed, and then an in-situ vapor deposition treatment is performed, and silicon carbide is filled into the micro pores around the macro pores by in-situ vapor infiltration. Silane and methane are diluted by an inert carrier gas argon. At a temperature of 1800±100°C and a pressure of 1000±100 Pa, the gas diffusion rate is increased, gas phase nucleation is reduced, and the silicon carbide generated by the reaction is filled into the micro pores and forms a covalent bond network with the atoms in the gaps, thereby increasing the bonding force and achieving densification repair of the damaged area. Due to chemical bonding, the chemical bonds in the micro pores are more firmly bonded to the silicon carbide crystal matrix, and secondary fragmentation is less likely to occur.

[0040] In some optional embodiments, the repair method further comprises: performing a cooling treatment after the in-situ vapor infiltration treatment is completed to eliminate residual stress and avoid secondary cracking.

[0041] In some optional embodiments, the cooling treatment includes: performing gradient cooling at a rate of ≤5°C / min, and applying an oscillating pressure with a frequency of 1-10 Hz while performing the gradient cooling.

[0042] An embodiment of the present invention provides a method for repairing a broken silicon carbide ingot, which includes: after the broken silicon carbide crystal is treated with in-situ vapor infiltration, a gradient cooling treatment is performed, and while cooling, an oscillating pressure of a certain frequency needs to be applied. The periodic pressure change will generate an alternating stress field inside the silicon carbide material, reduce the atomic diffusion activation energy, and accelerate the migration of vacancies / interstitial atoms, thereby more efficiently eliminating defects such as dislocations and grain boundaries. In addition, the pressure oscillation can induce local plastic deformation, promote grain refinement or amorphous transformation (such as the recrystallization process in silicon annealing), reduce internal stress, and avoid secondary cracking.

[0043] The present invention will be further described below with reference to the embodiments.

[0044] Example 1

[0045] A method for repairing a broken silicon carbide ingot comprises the following steps:

[0046] S1. Etching process:

[0047] In a xenon environment, the broken surface of the silicon carbide ingot is plasma etched to remove the oxide layer and form a nano-scale rough surface to enhance the subsequent bonding strength.

[0048] S2, liquid-induced healing treatment:

[0049] S21. Pre-pressing treatment: The surface-activated multiple silicon carbide fragments are spliced together to form a whole silicon carbide ingot, which is then placed in a vacuum hot pressing device and evacuated. After the vacuum degree reaches below 1Pa, heating is started. After the temperature is raised to 800°C, a directional pressure of 10MPa is applied to align the fragments preliminarily and reduce the interface gap.

[0050] S22, liquid phase induced healing treatment: under vacuum conditions, the silicon carbide crystal obtained in step S21 is heated at a temperature of 1500° C., and the liquid silicon reacts with the silicon carbide to fill the gap, thereby closing the macro crack opening.

[0051] S23. After the reaction is completed, the silicon powder remaining on the surface is removed by etching with hydrofluoric acid.

[0052] S24. In-situ vapor infiltration treatment: Silane and methane with a molar ratio of 1:1 are introduced into a vacuum hot pressing device. At a temperature of 1600°C and a pressure of 1000 Pa, silicon carbide deposits generated by the reaction of Si and C atoms produced by the decomposition of methane and silane are filled into the microscopic pores.

[0053] S3, Annealing and stress relief:

[0054] The temperature was gradually decreased at a rate of 2°C / min, and an oscillating pressure of 5 Hz was applied during the temperature reduction to eliminate residual stress and avoid secondary cracking.

[0055] The appearance of the broken silicon carbide ingot provided in Example 1 is shown in FIG. 1 , which has only been subjected to liquid phase induced healing treatment and has not been subjected to in-situ vapor infiltration treatment (including only steps S21 and S22). Figure 2 As shown in the figure, it can be seen that the macro cracks in the broken silicon carbide ingot are closed. Since there is no chemical bonding network between the two fragments, the bonding strength between the two is not high, and it is easy to crack again under the action of external force. Figure 3 It can be seen that: a number of fine crystals grow in the gap between the two fragments, so that the two are connected by chemical bonds, which improves the bonding strength between the two and makes it less likely to crack again.

[0056] Example 2

[0057] Compared with Example 1, the only difference is that the temperature of the pre-pressing treatment is 1000° C. and the pressure is 18 MPa.

[0058] Example 3

[0059] Compared with Example 1, the only difference is that the temperature of the pre-pressing treatment is 1200° C. and the pressure is 30 MPa.

[0060] Example 4

[0061] Compared with Example 1, the only difference is that the temperature of the liquid phase induced healing treatment is 1600°C.

[0062] Example 5

[0063] Compared with Example 1, the only difference is that the temperature of the liquid phase induced healing treatment is 1700°C.

[0064] Comparative Example 1

[0065] Compared with embodiment 1, the only difference is that steps S21 and S22 are not included.

[0066] Comparative Example 2

[0067] Compared with embodiment 1, the only difference is that step S23 is not included.

[0068] Comparative Example 3

[0069] Compared with embodiment 1, the only difference is that step S3 is not included.

[0070] Comparative Example 4

[0071] Compared with Example 1, the only difference is that the temperature of the pre-pressing treatment is 300° C. and the pressure is 3 MPa.

[0072] Comparative Example 5

[0073] Compared with Example 1, the only difference is that the temperature of the pre-pressing treatment is 600° C. and the pressure is 10 MPa.

[0074] Comparative Example 6

[0075] Compared with Example 1, the only difference is that the temperature of the pre-pressing treatment is 1300° C. and the pressure is 30 MPa.

[0076] Comparative Example 7

[0077] Compared with Example 1, the only difference is that the temperature of the liquid phase induced healing treatment is 1400°C.

[0078] Comparative Example 8

[0079] Compared with Example 1, the only difference is that the temperature of the liquid phase induced healing treatment is 2000°C.

[0080] The healing properties of the repaired silicon carbide crystals in the above examples and comparative examples were tested as follows: a pressure of 60 N was applied perpendicular to the direction of the macro crack on the repaired silicon carbide crystals, and the deformation of the repaired silicon carbide crystals during the stress process was observed and recorded in the following table:

[0081]

[0082]

[0083] From the results in the above table, it can be seen that after the broken silicon carbide is repaired by the solution provided by the embodiment of the present invention, after a certain pressure is applied, the result of cracking or falling off again will not occur, while the result of cracking or falling off again will occur in the comparative example. The reasons are speculated to be as follows:

[0084] In Comparative Example 1, liquid-phase induced healing treatment was not performed, and only vapor-phase infiltration treatment was used. The voids deep within the macro cracks may not be filled, resulting in poor healing of the repaired silicon carbide.

[0085] In Comparative Example 2, no vapor infiltration treatment was performed, and only liquid-phase induced healing treatment was used. The pores around the macro cracks were not filled, resulting in a decrease in the bonding degree of the repaired silicon carbide cracks.

[0086] In Comparative Example 3, no cooling treatment was performed, and only liquid-phase induced healing treatment and vapor-phase infiltration treatment were used. This resulted in secondary cracking due to the high residual stress in the silicon carbide crystals.

[0087] Comparative Examples 4, 5, and 6 used pre-pressing at relatively low pressure and temperature. Low pressure resulted in poor initial meshing of the fragments, leading to poor repair and easy fall-off. Excessively high temperatures during pre-pressing can cause abnormal grain growth, local lattice distortion, and reduced mechanical properties.

[0088] In Comparative Examples 7 and 8, the melting point of silicon powder is 1414°C, which is lower than the melting point of silicon powder, resulting in it being unable to melt to form liquid silicon, which is not conducive to the re-reaction of liquid silicon with silicon carbide on both sides of the gap. Usually, silicon carbide crystals will undergo phase change above 1800°C. This phase change promotes the recrystallization process. At a high temperature of 2000°C, silicon carbide crystals will experience the problem of evaporation-condensation recrystallization.

[0089] In summary, the present invention provides a method for repairing broken silicon carbide ingots, which adopts a combined process of liquid-phase induced healing process and in-situ vapor-phase infiltration process to achieve physical reconstruction and chemical bonding of the broken ingots, so that the macro cracks in the broken silicon carbide crystals are fully closed, and the pores around the macro cracks are filled and the covalent bond network is rebuilt, thereby restoring its mechanical and electrical properties.

[0090] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for repairing a broken silicon carbide ingot, characterized in that: include: Multiple pieces of silicon carbide fragments are spliced together to form a whole silicon carbide ingot. The liquid-phase induced healing process is first used to promote the healing of the macro crack openings, and then the in-situ vapor infiltration process is used to fill the micro pores around the cracks to achieve crack repair of the broken silicon carbide ingot.

2. The method for repairing a broken silicon carbide ingot according to claim 1, wherein: The liquid phase induced healing process comprises the following steps: Step S1: pre-pressing the splicing parts to align the fragments and reduce the interface gap; Step S2, filling the cracks of the joints with excess silicon powder, heating the melted liquid silicon to react with silicon carbide to fill the cracks, and then cooling to form new silicon carbide bonds; Step S3: After the reaction is completed, the silicon powder remaining on the surface is removed by etching with hydrofluoric acid.

3. The method for repairing a broken silicon carbide ingot according to claim 2, wherein: In the step S1, the temperature of the pre-pressing treatment is 800-1200° C., the pressure is 10-30 MPa, and the treatment atmosphere is a vacuum atmosphere.

4. The method for repairing a broken silicon carbide ingot according to claim 3, wherein: Also includes: Before the pre-pressing treatment, the crack surface of the silicon carbide crystal is subjected to plasma etching in an inert atmosphere to remove the oxide layer and form a nano-scale rough surface.

5. The method for repairing a broken silicon carbide ingot according to claim 2, wherein: In step S2, the temperature of the liquid phase induced healing treatment is 1500-1700° C., and the treatment atmosphere is an inert atmosphere or a vacuum.

6. The method for repairing a broken silicon carbide ingot according to claim 2, wherein: In step S3, the cooling rate is 5-10°C / min.

7. The method for repairing a broken silicon carbide ingot according to claim 1, wherein: In-situ vapor infiltration treatment utilizes the reaction of silicon source and carbon source to form silicon carbide to fill the microscopic pores around the cracks.

8. The method for repairing a broken silicon carbide ingot according to claim 7, wherein: The silicon source includes silane, the carbon source includes methane, and the molar ratio of the silicon source to the carbon source is 1:

1. The temperature of the in-situ vapor infiltration treatment is 1800±100° C., and the pressure is 1000±100 Pa.

9. The method for repairing a broken silicon carbide ingot according to claim 1, wherein: The repair method further includes: performing a cooling treatment after the in-situ vapor infiltration treatment is completed to eliminate residual stress and avoid secondary cracking.

10. The method for repairing a broken silicon carbide ingot according to claim 9, wherein: The cooling treatment includes: gradient cooling at a rate of ≤5°C / min, and applying an oscillating pressure with a frequency of 1-10 Hz while the gradient cooling is performed.

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