Preparation method of composite material crucible upper for single crystal furnace and crucible upper

Abstract

The invention provides a preparation method of a composite material crucible upper for a single crystal furnace and the crucible upper, and the preparation method comprises the following steps: step S1, preparing a carbon fiber preform, then carrying out interface layer deposition through a CVI method, then carrying out slurry immersion treatment, and adding an antioxidant additive into the slurry; s2, composite densification treatment is conducted through low-temperature pyrolysis, high-temperature reaction sintering and PIP reinforcement, and the carbon-ceramic composite material crucible side of the multi-layer gradient structure is obtained; s3, an anti-oxidation coating is deposited on the inner surface of the carbon-ceramic composite material crucible upper, and then heat treatment is conducted; and S4, precisely machining to obtain the crucible upper size and appearance required by the single crystal furnace. According to the preparation method of the composite material crucible upper for the single crystal furnace and the crucible upper, the oxidation resistance can be improved, the reaction with a silicon melt is inhibited, the heat conductivity and the thermal field distribution are optimized, the mechanical strength and the thermal shock resistance are enhanced, and the preparation cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of single-crystal silicon production. Specifically, it relates to a method for preparing a composite crucible sidewall for a single-crystal furnace and the crucible sidewall. Background Art

[0002] Single-crystal silicon is a key basic material in industries such as semiconductors and photovoltaics. Its preparation mainly uses the Czochralski method (CZ method). The crucible sidewall of a single-crystal furnace (also known as the crucible support component) is one of the core components of a single-crystal furnace, directly affecting the growth quality and efficiency of single-crystal silicon. Currently, the crucible sidewalls of single-crystal furnaces mainly use the following several materials and technologies: high-purity graphite crucible sidewalls, quartz ceramic crucible sidewalls, carbon / carbon composite crucible sidewalls, and metal alloy crucible sidewalls (such as molybdenum, tungsten, etc.).

[0003] The high-purity graphite crucible sidewall has the following disadvantages: it is easily oxidized at high temperatures and needs to be used in an inert atmosphere or a vacuum environment; it will react when in contact with the silicon melt (C + Si → SiC), contaminating the single-crystal silicon; its mechanical strength is relatively low, and it is prone to deformation or cracking after long-term use. The quartz ceramic crucible sidewall has the following disadvantages: its thermal conductivity is low (~1.5 W / (m·K)), resulting in uneven thermal field distribution; its mechanical strength is relatively low and it is prone to brittle fracture; it is prone to crystallization after long-term high-temperature use, affecting its service life. The carbon / carbon composite crucible sidewall has the following disadvantages: the preparation cycle is long (requiring multiple CVI or PIP processes), and the cost is high; its oxidation resistance is poor and additional coating protection is required; its anisotropy is obvious and its properties are uneven. The metal alloy crucible sidewall has the following disadvantages: its density is large, increasing the equipment load; it is prone to react with silicon at high temperatures, contaminating the single crystal; the cost is high and the processing difficulty is large.

[0004] Based on the existing technologies, the crucible sidewall materials of single-crystal furnaces mainly have the following problems: 1) Insufficient oxidation resistance: Graphite and C / C materials are easily consumed in a high-temperature oxidation environment and rely on a protective atmosphere, increasing the complexity of the equipment; 2) Reaction with the silicon melt: Materials such as graphite and metal alloys will react with molten silicon to form SiC or metal silicides, affecting the purity of the single crystal; 3) Contradiction between thermal conductivity and thermal field uniformity: The thermal conductivity of quartz ceramics is low, resulting in uneven thermal fields. Graphite has good thermal conductivity but is prone to local overheating; 4) Insufficient mechanical strength and thermal shock resistance: Under long-term high-temperature cycling, the existing materials are prone to cracking or deformation, affecting the stability of single-crystal growth; 5) High preparation cost: The C / C composite material requires complex processes, and the metal alloy has a large processing difficulty, resulting in high production costs.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The object of the present invention is to provide a method for preparing a composite crucible sidewall for a single-crystal furnace and the crucible sidewall, aiming at the deficiencies of the existing technologies, which can improve the oxidation resistance, inhibit the reaction with the silicon melt, optimize the thermal conductivity and thermal field distribution, enhance the mechanical strength and thermal shock resistance, and reduce the preparation cost.

[0007] To achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0008] A method for preparing a composite crucible wall for a single crystal furnace, comprising the following steps:

[0009] Step S1: Prepare a carbon fiber preform, then deposit an interface layer by the CVI method, and then perform slurry impregnation treatment, with an antioxidant additive added to the slurry;

[0010] Step S2: Perform composite densification treatment by low-temperature pyrolysis, high-temperature reaction sintering, and PIP reinforcement to obtain a multi-layer gradient structure carbon-ceramic composite crucible wall;

[0011] Step S3: Deposit an antioxidant coating on the inner surface of the carbon-ceramic composite crucible wall, and then perform heat treatment;

[0012] Step S4: Precision machining to process to the size and shape of the crucible wall required for the single crystal furnace.

[0013] Further, in step S1, a three-dimensional orthogonal braiding of carbon fibers is performed to obtain a three-dimensional braided carbon fiber body as the carbon fiber preform. The interface layer deposition is to perform PyC interface layer deposition or BN interface layer deposition on the surface of the carbon fiber preform, and a SiC precursor is mixed with an antioxidant additive to form a slurry, which is impregnated into the carbon fiber preform.

[0014] Further, the SiC precursor is at least one of polycarbosilane, methyltrichlorosilane, and silane;

[0015] Further, the antioxidant additive is at least one of SiB4, ZrB2, B2O3, and Si3N4.

[0016] Further, in step S2, the low-temperature pyrolysis temperature is 800 - 1000 °C, and the high-temperature reaction sintering temperature is 1400 - 1600 °C.

[0017] Further, in step S2, the PIP reinforcement is to repeat impregnation-pyrolysis 2 - 3 times.

[0018] Further, in step S3, a SiC antioxidant coating with a thickness of 10 - 50 μm is deposited on the inner surface of the carbon-ceramic composite crucible wall by chemical vapor deposition; the high-temperature heat treatment includes reactive atmosphere heat treatment by the CVD method and CVI reinforcement using a CH4 / H2 mixed gas, and the high-temperature heat treatment temperature is 1400 - 2000 °C.

[0019] Furthermore, in the reactive atmosphere heat treatment using the CVD method, the atmosphere combination is Si vapor infiltration, and the temperature is 1500 - 1600 °C; for CVI reinforcement using a CH4 / H2 mixed gas, pyrolytic carbon is deposited by CH4 cracking at 1400 °C.

[0020] A crucible wall is made by using the above - mentioned method for preparing a composite crucible wall for a single - crystal furnace. This crucible wall is a carbon - ceramic composite crucible wall, including the following components in volume parts: 50 - 70 parts of SiC matrix, 20 - 35 parts of three - dimensional woven carbon fiber preform, and 5 - 15 parts of antioxidant additive.

[0021] Furthermore, the multi - layer gradient structure of the carbon - ceramic composite crucible wall sequentially includes from the inside to the outside: a dense SiC working layer with a thickness of 2 - 5 mm, a C / SiC transition layer with a thickness of 3 - 8 mm, and a carbon - fiber - reinforced heat - insulating layer with a thickness of 5 - 10 mm.

[0022] Furthermore, micro - grooves are formed on the inner surface of the crucible wall, and the depth of the micro - grooves is 0.1 - 0.3 mm; reinforcing ribs are arranged on the outer side of the crucible wall, and the reinforcing ribs are formed by weaving and slurry impregnation of the three - dimensional woven carbon fiber preform in the carbon - fiber preform.

[0023] Furthermore, the micro - grooves are trapezoidal grooves, and one groove is opened every 50 - 70 mm from the upper edge of the crucible wall.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. The method for preparing the composite crucible wall for a single - crystal furnace and the crucible wall of the present invention can achieve the following beneficial effects through the interface design between the three - dimensional woven carbon fiber preform and the SiC matrix, the composition and property regulation of the multi - layer gradient structure, the parameter control of the composite densification process, the synergistic action mechanism of the antioxidant system, and the optimized design of the surface microstructure: ① Improve the antioxidant performance: The antioxidant additive is added to the impregnation slurry + antioxidant coating to form an antioxidant system. Through the combination of the SiC matrix and the antioxidant additive, plus the antioxidant coating, the high - temperature oxidation loss is effectively reduced; ② Inhibit the reaction with the silicon melt: The dense SiC working layer is used to reduce the diffusion of carbon elements into the silicon melt; ③ Optimize the thermal conductivity and thermal field distribution: Through carbon - fiber reinforcement and gradient structure design, the thermal conductivity and thermal field uniformity are balanced; ④ Enhance the mechanical strength and thermal shock resistance: The three - dimensional woven carbon fiber is used for reinforcement, combined with the multi - layer gradient structure, to improve the high - temperature stability; ⑤ Reduce the preparation cost: The CVI + PIP composite process is used to shorten the production cycle and improve the material utilization rate.

[0026] 2. The method for preparing the composite crucible wall for a single - crystal furnace and the crucible wall of the present invention have a 40 - 60% increase in high - temperature strength. Compared with the ordinary carbon - carbon crucible wall with a density of 1.8 - 1.9 g / cm 3 , the current carbon - ceramic crucible wall has a density of 2.85 - 2.95 g / cm3 , the bending strength ≥ 300 MPa (at 1600 °C), the thermal conductivity can reach 85 W / (m·K), the thermal field uniformity is improved by 35%, and the thermal expansion coefficient matches well with the graphite component (4.5 - 5.5×10 -6 / K), with excellent oxidation resistance and a weight loss rate < 0.3% / 100 h (in air at 1600 °C).

[0027] 3. The preparation method and the crucible sidewall of the single crystal furnace composite material crucible sidewall of the present invention can have a continuous service life of more than 2200 hours, the oxygen content of the single crystal is reduced by 30%, the number of thermal shock cycles > 100 times (room temperature ←→ 1600 °C), the surface erosion rate < 0.01 mm / h (in contact with silicon melt), the reactivity with silicon melt is low, and the purity of the single crystal is improved.

[0028] 4. The present invention adopts the CVI + PIP composite process. By adding the CVI process and using pulsed or low-pressure CVI (such as ICVI), the gas diffusion depth can be enhanced, and the waste caused by the number of impregnation times can be reduced. The sequence design of CVI and PIP: CVI → PIP → CVI: First, the matrix skeleton is constructed by CVI, the macropores are filled by PIP, and finally the micropores are repaired by CVI. By alternately performing CVI and PIP multiple times through the alternating process, such as 2 times CVI + 3 times PIP, the density of the dense SiC working layer is gradually increased. Compared with the production of ordinary crucible sidewalls, the number of impregnation times is reduced, the preparation cycle is shortened by 30 - 40%, and the energy consumption is reduced by 15 - 20%; a pyrolytic carbon (PyC) or boron nitride (BN) interface layer is pre-deposited on the fiber surface to slow down the stress concentration during PIP cracking and reduce the material loss caused by microcracks; the cracking gas can be recycled, and the gases generated by PIP cracking (such as methane and hydrogen) can be purified and reused as CVI precursors; the solid by-products can be utilized, and the free silicon or carbon remaining after cracking can be recovered by pickling and used to prepare new precursors. The overall materials and time of the present invention are better utilized, the material cost is reduced by 20 - 30% after conversion, there is no pollution discharge, and the recyclability is high.

[0029] 5. The present invention is used for the crucible sidewall of the single crystal furnace composite material. A micro-groove structure is provided on the inner surface of the crucible sidewall to further improve the thermal field uniformity; reinforcing ribs are provided on the outer side of the crucible sidewall to improve the overall mechanical strength.

[0030] 6. The preparation method and the crucible sidewall of the single crystal furnace composite material crucible sidewall of the present invention are applicable to the 32 - 42-inch thermal field of the 160-type single crystal furnace and can be popularized for semiconductor crystal growth equipment such as GaAs and SiC, and have a broad market in the fields of photovoltaic and integrated circuits. Description of the Drawings

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 Structural diagram of the three-dimensional carbon fiber braided body of the present invention;

[0033] Figure 2 Schematic diagram of the micro-groove structure on the inner surface of the crucible wall of the present invention.

[0034] Explanation of reference numerals: Micro-groove - 1. Specific embodiments

[0035] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. For those not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0036] A method for preparing a composite crucible wall for a single crystal furnace includes the following steps:

[0037] S1. Prepare a carbon fiber preform, then perform interfacial layer deposition by chemical vapor infiltration (CVI) method, and then perform slurry impregnation treatment, with an antioxidant additive added to the slurry;

[0038] Preferably, a three-dimensional orthogonal carbon fiber braided body is obtained by three-dimensional orthogonal braiding of carbon fibers as the carbon fiber preform to ensure balanced mechanical properties in all directions;

[0039] Preferably, the interfacial layer deposition is pyrolytic carbon (PyC) interfacial layer deposition or boron nitride (BN) interfacial layer deposition on the surface of the carbon fiber preform to deposit an interfacial layer on the surface of the carbon fiber preform to optimize the fiber / matrix interfacial bonding;

[0040] Preferably, the SiC precursor and the antioxidant additive are mixed into a slurry and impregnated into the carbon fiber preform;

[0041] Preferably, the SiC precursor is at least one of polycarbosilane (PCS), methyltrichlorosilane (CH3SiCl3), and silane (SiH4);

[0042] Preferably, the antioxidant additive is at least one of SiB4, ZrB2, B2O3, and Si3N4;

[0043] Preferably, the antioxidant additive is ZrB2. After oxidizing the crucible wall with ZrB2 added for 100 h at 1600 °C, the weight loss is only 0.3%;

[0044] S2. Perform composite densification treatment through low-temperature pyrolysis, high-temperature reaction sintering, and PIP reinforcement (polymer impregnation pyrolysis) to obtain a carbon-ceramic composite crucible wall;

[0045] Preferably, the low-temperature pyrolysis temperature is 800 - 1000 °C, including but not limited to 800 °C, 850 °C, 900 °C, 950 °C, and 1000 °C, to pyrolyze the SiC precursor and initially form a SiC matrix;

[0046] Preferably, the high-temperature reaction sintering temperature is 1400 - 1600 °C, including but not limited to 1400 °C, 1450 °C, 1500 °C, 1550 °C, and 1600 °C, to promote the growth of SiC grains and improve the density;

[0047] Preferably, the PIP reinforcement is repeated impregnation - pyrolysis 2 - 3 times. The impregnation is the slurry impregnation in step S1, and the pyrolysis is low-temperature pyrolysis and high-temperature reaction sintering to fill the pores and improve the material density, finally forming a dense SiC working layer with a density ≥ 2.8 g / cm 3 ;

[0048] S3. Post-treat the carbon-ceramic composite crucible wall, deposit an antioxidant coating on the inner surface of the crucible wall, and then perform high-temperature heat treatment;

[0049] Preferably, use chemical vapor deposition (CVD) to deposit a 10 - 50 μm thick SiC antioxidant coating on the inner surface of the carbon-ceramic composite crucible wall. The thickness includes but is not limited to 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm;

[0050] Preferably, the high-temperature heat treatment temperature is 1400 - 2000 °C, including but not limited to 1400 °C, 1500 °C, 1600 °C, 1700 °C, 1800 °C, 1850 °C, 1900 °C, 1950 °C, and 2000 °C, to improve the crystallinity of SiC and enhance the high-temperature stability;

[0051] Preferably, the high-temperature heat treatment includes reactive atmosphere heat treatment (modification and strengthening) by chemical vapor deposition (CVD) and reinforcement by CH4 / H2 mixed gas (CVI), synchronously achieving heat treatment and chemical modification;

[0052] Preferably, in the reactive atmosphere heat treatment by chemical vapor deposition (CVD), the atmosphere combination is Si vapor infiltration (Si + Ar), the temperature is 1500 - 1600 °C, and the Si vapor partial pressure needs to be controlled to avoid excessive Si residue; the reaction is C + Si(g) → SiC, filling pores and increasing the density by 10 - 15%;

[0053] Preferably, the reinforcement by CH4 / H2 mixed gas (CVI) is to deposit pyrolytic carbon by CH cracking at 1400 °C to repair the carbon phase defects;

[0054] S4. Precision machining;

[0055] Preferably, the crucible wall of the carbon-ceramic composite material is machined to the required size and shape of the crucible wall of the single crystal furnace by a numerically controlled machine tool;

[0056] Preferably, the single crystal furnace is a 160-type single crystal furnace and can be used in a 32 - 42-inch hot field.

[0057] A crucible wall of a single crystal furnace composite material prepared by the above preparation method, the crucible wall is a crucible wall of a carbon-ceramic composite material, and includes the following components in volume parts: 50 - 70 parts of SiC matrix, 20 - 35 parts of three-dimensional carbon fiber braid, and 5 - 15 parts of antioxidant additive; the SiC matrix provides high-temperature strength and chemical stability; the three-dimensional carbon fiber braid enhances toughness and improves thermal shock resistance; the antioxidant additive improves high-temperature oxidation resistance;

[0058] Preferably, the crucible wall of the carbon-ceramic composite material is a multi-layer gradient structure, which sequentially includes from the inside to the outside: a dense SiC working layer with a thickness of 2 - 5 mm, a C / SiC transition layer with a thickness of 3 - 8 mm, and a carbon fiber-reinforced heat insulation layer with a thickness of 5 - 10 mm; the dense SiC working layer is in direct contact with the silicon melt to prevent carbon diffusion; the C / SiC transition layer can balance thermal stress and improve thermal shock resistance; the carbon fiber-reinforced heat insulation layer is a carbon fiber preform, and the carbon fiber-reinforced heat insulation layer can reduce heat loss and improve the uniformity of the hot field;

[0059] Preferably, micro-grooves 1 are formed on the inner surface of the crucible wall, and the micro-grooves 1 are cut on the inner surface of the crucible wall by machining to optimize heat convection, reduce the temperature gradient, and reinforcing ribs are arranged on the outer side of the crucible wall;

[0060] Preferably, the depth of the micro-grooves is 0.1 - 0.3 mm, including but not limited to 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm;

[0061] Preferably, the micro-groove 1 is a trapezoidal groove, and a groove is opened every 50-70 mm from the upper edge of the crucible wall;

[0062] Preferably, the reinforcing rib is made by weaving the carbon fibers in a three-dimensional braided structure of the carbon fiber preform and impregnating with a slurry. The main frame of the carbon fiber filaments inside the reinforcing rib is similar to building steel bars, and the slurry impregnation is similar to concrete, which improves the overall mechanical strength.

[0063] Example 1

[0064] A method for preparing a composite crucible wall for a single crystal furnace, comprising the following steps:

[0065] S1. Obtain a three-dimensional braided carbon fiber body through three-dimensional orthogonal weaving of carbon fibers as a carbon fiber preform. Deposit a PyC interface layer by the CVI method, and then perform slurry impregnation treatment. The slurry is composed of a SiC precursor PCS and an antioxidant additive ZrB2;

[0066] S2. Perform composite densification treatment through low-temperature pyrolysis at 800 °C, high-temperature reaction sintering at 1600 °C, and repeating impregnation-pyrolysis 2-3 times to finally form a dense SiC working layer with a density ≥ 2.8 g / cm 3 to obtain a carbon-ceramic composite crucible wall;

[0067] S3. Deposit a 10-μm-thick SiC antioxidant coating on the inner surface of the carbon-ceramic composite crucible wall by the CVD method, and then perform high-temperature heat treatment. The high-temperature heat treatment includes reactive atmosphere heat treatment by the CVD method and CVI reinforcement using a CH4 / H2 gas mixture. In the reactive atmosphere heat treatment by the CVD method, the atmosphere combination is Si vapor infiltration (Si + Ar), and the temperature is 1500 °C. CVI reinforcement using a CH4 / H2 gas mixture is to deposit pyrolytic carbon by CH4 cracking at 1400 °C to repair carbon phase defects;

[0068] S4. Precision machining, and machining the carbon-ceramic composite crucible wall to the required crucible wall size and shape of the single crystal furnace by a numerical control machine tool.

[0069] Example 2

[0070] A method for preparing a composite crucible wall for a single crystal furnace, comprising the following steps:

[0071] S1. Obtain a three-dimensional braided carbon fiber body through three-dimensional orthogonal weaving of carbon fibers as a carbon fiber preform. Deposit a BN interface layer by the CVI method, and then perform slurry impregnation treatment. The slurry is composed of a SiC precursor methyltrichlorosilane and an antioxidant additive SiB4;

[0072] S2. Conduct composite densification treatment through low-temperature pyrolysis at 900 °C, high-temperature reaction sintering at 1500 °C, and repeating the impregnation-pyrolysis process 2 to 3 times, and finally form a dense SiC working layer with a density ≥ 2.8 g / cm 3 to obtain a carbon-ceramic composite crucible wall;

[0073] S3. Deposit a 50-μm-thick SiC anti-oxidation coating on the inner surface of the carbon-ceramic composite crucible wall by CVD method, and then conduct high-temperature heat treatment. The high-temperature heat treatment includes reactive atmosphere heat treatment by CVD method and CVI reinforcement using CH4 / H2 mixed gas. In the reactive atmosphere heat treatment by CVD method, the atmosphere combination is Si vapor infiltration (Si + Ar), the temperature is 1550 °C, and the CVI reinforcement using CH4 / H2 mixed gas is to deposit pyrolytic carbon by CH4 cracking at 1400 °C to repair carbon phase defects;

[0074] S4. Precision machining: Machine the carbon-ceramic composite crucible wall to the required crucible wall size and shape for the single crystal furnace through a numerical control machine tool.

[0075] Example 3

[0076] A method for preparing a composite crucible wall for a single crystal furnace includes the following steps:

[0077] S1. Obtain a three-dimensional orthogonal woven carbon fiber body as a carbon fiber preform through three-dimensional orthogonal weaving of carbon fibers, deposit a PyC interface layer by CVI method, and then conduct slurry impregnation treatment. The slurry is composed of a SiC precursor silane and an anti-oxidation additive B2O3;

[0078] S2. Conduct composite densification treatment through low-temperature pyrolysis at 1000 °C, high-temperature reaction sintering at 1400 °C, and repeating the impregnation-pyrolysis process 2 to 3 times, and finally form a dense SiC working layer with a density ≥ 2.8 g / cm 3 to obtain a carbon-ceramic composite crucible wall;

[0079] S3. Deposit a 50-μm-thick SiC anti-oxidation coating on the inner surface of the carbon-ceramic composite crucible wall by CVD method, and then conduct high-temperature heat treatment. The high-temperature heat treatment includes reactive atmosphere heat treatment by CVD method and CVI reinforcement using CH4 / H2 mixed gas. In the reactive atmosphere heat treatment by CVD method, the atmosphere combination is Si vapor infiltration (Si + Ar), the temperature is 1600 °C, and the CVI reinforcement using CH4 / H2 mixed gas is to deposit pyrolytic carbon by CH4 cracking at 1400 °C to repair carbon phase defects;

[0080] S4. Precision machining: Machine the carbon-ceramic composite crucible wall to the required crucible wall size and shape for the single crystal furnace through a numerical control machine tool.

[0081] Example 4

[0082] The difference between this embodiment and Embodiment 1 is as follows: Micro-grooves 1 are formed on the inner surface of the crucible skirt. The micro-grooves 1 are cut on the inner surface of the crucible skirt by machining. The micro-grooves 1 are trapezoidal grooves with a depth of 0.1 mm, and a groove is opened every 50 mm from the upper edge of the crucible skirt. After optimizing the micro-groove structure, the thermal field uniformity is further improved. The thermal field uniformity can be observed through the state of the melt in the crucible: If the crucible skirt is used for single crystal silicon growth, the thermal field uniformity can be deduced by observing the fluctuation of the molten silicon liquid level or the shape of the solid-liquid interface (such as through a CCD camera). The improvement in uniformity is manifested as an enhanced symmetry of melt convection or a reduced interface curvature.

[0083] Embodiment 5

[0084] The difference between this embodiment and Embodiment 1 is as follows: Micro-grooves 1 are formed on the inner surface of the crucible skirt. The micro-grooves 1 are cut on the inner surface of the crucible skirt by machining. The micro-grooves 1 are trapezoidal grooves with a depth of 0.3 mm, and a groove is opened every 70 mm from the upper edge of the crucible skirt. After optimizing the micro-groove structure, the thermal field uniformity is significantly improved, and the symmetry of melt convection is enhanced or the interface curvature is reduced.

[0085] Embodiment 6

[0086] The difference between this embodiment and Embodiment 4 is as follows: Reinforcing ribs are arranged on the outer side of the crucible skirt. The reinforcing ribs are made by weaving carbon fibers in a three-dimensional carbon fiber braid in a carbon fiber preform and impregnating with slurry.

[0087] Test example:

[0088] The test results of the performance of the composite crucible skirt of the single crystal furnace of the present invention are shown in Table 1.

[0089] Table 1 Test results of the performance of the composite crucible skirt of the single crystal furnace of the present invention

[0090]

Claims

1. A method for preparing a composite crucible side for a single crystal furnace, characterized in that, It includes the following steps: Step S1: Prepare a carbon fiber preform, then deposit an interface layer by the CVI method, and then perform slurry impregnation treatment with an antioxidant additive added to the slurry; Step S2: Perform composite densification treatment through low-temperature pyrolysis, high-temperature reaction sintering, and PIP reinforcement to obtain a multi-layer gradient structure carbon-ceramic composite crucible wall; Step S3: Deposit an antioxidant coating on the inner surface of the carbon-ceramic composite crucible wall, and then perform heat treatment; Step S4: Perform precision machining to process to the size and shape of the crucible wall required for the single crystal furnace.

2. The method for preparing the composite crucible side for a single crystal furnace according to claim 1, wherein, In step S1, a three-dimensional orthogonal woven carbon fiber is used to obtain a three-dimensional woven carbon fiber body as the carbon fiber preform. The interface layer deposition is to deposit a PyC interface layer or a BN interface layer on the surface of the carbon fiber preform. The SiC precursor is mixed with the antioxidant additive to form a slurry and impregnated into the carbon fiber preform.

3. The method for preparing the composite crucible side for a single crystal furnace according to claim 2, characterized in that, It includes at least one of the following technical features: (1) The SiC precursor is at least one of polycarbosilane, methyltrichlorosilane, and silane; (2) The antioxidant additive is at least one of SiB4, ZrB2, B2O3, and Si3N4.

4. The method for preparing a composite crucible side for a single crystal furnace according to claim 1, wherein It includes at least one of the following technical features: (1) In step S2, the low-temperature pyrolysis temperature is 800 - 1000 °C, and the high-temperature reaction sintering temperature is 1400 - 1600 °C; (2) In step S2, the PIP reinforcement is to repeat impregnation-pyrolysis 2 - 3 times.

5. The method for preparing a composite crucible side for a single crystal furnace according to claim 1, characterized in that, In step S3, a SiC antioxidant coating with a thickness of 10 - 50 μm is deposited on the inner surface of the carbon-ceramic composite crucible wall by chemical vapor deposition; the high-temperature heat treatment includes reactive atmosphere heat treatment by the CVD method and CVI reinforcement with a CH4 / H2 mixed gas. The high-temperature heat treatment temperature is 1400 - 2000 °C.

6. The method for preparing the composite crucible side for a single crystal furnace according to claim 5, wherein In the reactive atmosphere heat treatment by the CVD method, the atmosphere combination is Si vapor infiltration, and the temperature is 1500 - 1600 °C; the CVI reinforcement with a CH4 / H2 mixed gas is to deposit pyrolytic carbon by CH4 cracking at 1400 °C.

7. A crucible sidewall, which is made by using the preparation method of the composite crucible sidewall for a single crystal furnace described in any one of claims 1 to 6, is characterized in that, This crucible wall is a carbon-ceramic composite crucible wall, including the following volume fraction components: 50 - 70 parts of SiC matrix, 20 - 35 parts of three-dimensional woven carbon fiber body, and 5 - 15 parts of antioxidant additive.

8. The ladle skirt according to claim 7, characterized in that The multi-layer gradient structure of the carbon-ceramic composite crucible wall sequentially includes from the inside to the outside: a dense SiC working layer with a thickness of 2 - 5 mm, a C / SiC transition layer with a thickness of 3 - 8 mm, and a carbon fiber-reinforced heat insulation layer with a thickness of 5 - 10 mm.

9. The crucible side according to claim 7 or 8, characterized in that, Micro-grooves (1) are provided on the inner surface of the crucible wall, and the depth of the micro-grooves (1) is 0.1 - 0.3 mm; reinforcing ribs are provided on the outer side of the crucible wall, and the reinforcing ribs are formed by weaving and slurry impregnation of the three-dimensional woven carbon fiber body in the carbon fiber preform.

10. The crucible sidewall according to claim 9, characterized in that, The micro-grooves (1) are trapezoidal grooves, and a groove is opened every 50 - 70 mm from the upper edge of the crucible wall.

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