Quartz crucible for semiconductor monocrystalline silicon growth and preparation method thereof

Abstract

The invention discloses a quartz crucible for semiconductor monocrystalline silicon growth and a preparation method thereof, and relates to the technical field of crucibles, the quartz crucible does not contain bubbles and is composed of a supporting layer and a transparent layer, the supporting layer contains a glass phase and a cristobalite phase, and the cristobalite phase is uniformly dispersed in the glass phase; and the thickness of the transparent layer is smaller than 1 / 4 of the wall thickness of the crucible. According to the quartz crucible prepared by the invention, the proportion of the transparent layer is small, and the transparent layer can be mechanically removed and re-deposited to generate the transparent layer, so that the regeneration of the crucible is realized.

Description

Technical Field

[0001] This invention relates to the field of crucible technology, and specifically to a quartz crucible for growing semiconductor single crystal silicon and its preparation method. Background Technology

[0002] Quartz crucibles possess properties such as cleanliness, homogeneity, and high-temperature resistance. From a physical and thermal perspective, the deformation point of a quartz crucible is approximately 1100℃, its softening point is approximately 1730℃, and its maximum continuous operating temperature is approximately 1100℃, capable of reaching 1450℃ for short periods. Its high purity and high temperature resistance ensure the quality of silicon rod single-crystal pulling and make it one of the key auxiliary materials in single-crystal pulling systems.

[0003] Quartz crucibles for crystal pulling typically have a multi-layered composite structure. The innermost layer is usually a transparent layer, about 3-5 mm thick, comprising one-third of the wall thickness, with a low bubble content. The outer layer has a higher bubble content, serving to support the crucible's deformation strength and ensure uniform heat radiation. With technological advancements, quartz crucibles have evolved into three-layer structures: a transparent layer, a bubble-filled transparent layer, and a thin outer bubble layer. Additionally, techniques exist to coat the innermost layer with an alkali metal (such as barium) ion solution or to add ultra-high purity synthetic quartz, aiming to improve quality or optimize costs.

[0004] Quartz crucibles are classified into semiconductor (electronic grade) quartz crucibles and photovoltaic (solar grade) quartz crucibles according to their applications. Semiconductor quartz crucibles are mainly used for growing semiconductor single-crystal silicon, which is used to manufacture integrated circuits, microelectronic devices, etc. Photovoltaic quartz crucibles are mainly used for growing photovoltaic single-crystal silicon, which is used to manufacture solar cells, photovoltaic modules, etc.

[0005] Crucibles are classified into synthetic quartz crucibles and natural quartz crucibles based on the type of quartz used in their inner layer. Synthetic quartz crucibles use high-purity synthetic quartz sand for their inner layer and are suitable for drawing high-grade silicon rods for semiconductors. Natural quartz crucibles use natural quartz sand as their inner layer and are suitable for manufacturing silicon rods for photovoltaic applications and those with lower requirements.

[0006] However, since quartz sand accounts for 70% of the cost of quartz crucibles, and the higher the purity of the quartz sand used (mainly for the transparent layer), the higher the cost of the crucible. But reducing the thickness of the transparent layer will cause the air bubbles in the support layer to expand during the silicon melting process, and they can easily penetrate the transparent layer into the silicon melt, affecting the quality of the crystal rod. Therefore, how to reduce the proportion of the transparent layer and the cost of using quartz crucibles for semiconductor single crystal silicon growth has become an urgent technical problem to be solved in this field. Summary of the Invention

[0007] To address the problems of high transparent layer ratio and high cost in existing semiconductor single-crystal silicon growth quartz crucibles, this invention provides a semiconductor single-crystal silicon growth quartz crucible and its preparation method. The resulting quartz crucible has a small transparent layer ratio, and the transparent layer can be mechanically removed and re-deposited to generate a new transparent layer, thus achieving crucible regeneration.

[0008] The technical problem to be solved by this invention is achieved by the following technical solution:

[0009] The first objective of this invention is to provide a quartz crucible that is bubble-free and consists of a support layer and a transparent layer, wherein the support layer contains a glass phase and a cristobalite phase, the cristobalite phase being uniformly dispersed in the glass phase; and the wall thickness of the transparent layer is less than 1 / 4 of the total wall thickness of the crucible.

[0010] Further, the cristobalite phase has a grain size of 5–15 μm and a content greater than 5%. Preferably, the cristobalite phase has a grain size of 5–10 μm and a content greater than 5%.

[0011] Furthermore, the purity (SiO2 content) of the support layer is not less than 4N8.

[0012] Furthermore, the purity of the transparent layer is greater than 6N.

[0013] Furthermore, the density of the support layer is 2.2–2.6 g / cm³. 3 .

[0014] Furthermore, the support layer is completely transformed into the cristobalite phase through heat treatment. Preferably, the heat treatment temperature is 1200–1600°C.

[0015] A second objective of this invention is to provide a method for preparing a quartz crucible, comprising the following steps:

[0016] S1. After uniformly mixing glassy synthetic quartz sand with cristobalite, green molding is carried out to obtain a support layer green blank.

[0017] S2. Sinter the green blank of the support layer to obtain the support layer;

[0018] S3. A transparent layer is formed by depositing a silicon source on the inner surface of the support layer to obtain a quartz crucible.

[0019] Furthermore, the proportion of cristobalite is ≤5%, based on the total mass of glassy synthetic quartz sand and cristobalite.

[0020] Furthermore, the glassy synthetic quartz sand has a D50 particle size ≤ 100 μm and a purity of not less than 5N.

[0021] Furthermore, the cristobalite has a D50 particle size ≤ 10 μm and a purity of not less than 5N.

[0022] Furthermore, the method for forming the green body includes, but is not limited to, centrifugal forming, slip casting, and compression molding. When using slip casting, a binder and water are added to prepare a slurry. The binder is one or more water-based binders such as polyvinyl alcohol (PVA) and polyvinyl butyral (PVB); the amount of binder used is 2-10% of the slurry mass.

[0023] Furthermore, the sintering temperature is lower than the melting point of cristobalite. Preferably, the sintering temperature is 1200–1600°C, and the sintering time is 0.5–10 h.

[0024] Furthermore, the sintering atmosphere is a vacuum or a non-reactive atmosphere (such as argon).

[0025] Furthermore, the silicon source includes, but is not limited to, one or more of silicon tetrachloride, silica, and synthetic high-purity quartz sand.

[0026] Furthermore, the deposition method includes, but is not limited to, one of chemical deposition (such as flame hydrolysis) and melting methods.

[0027] A third objective of this invention is to provide the application of the quartz crucible in the growth of semiconductor single-crystal silicon.

[0028] The beneficial effects of this invention are:

[0029] 1. This invention uses a mixture of glassy synthetic quartz sand and cristobalite as the material for preparing the support layer. By uniformly nucleating and forming a consistent phase inside and out, the stability of the support layer is significantly improved. Since the support layer has a dense structure and no bubbles, it completely transforms into the cristobalite phase after heating. Therefore, the quartz crucible prepared by this invention has good heat resistance and stable strength, effectively solving the problem that the support layer (bubble layer) of existing quartz crucibles becomes brittle after heat crystallization.

[0030] 2. The crucible made by the present invention has a thin transparent layer, low cost, and can be mechanically removed after one use, and the transparent layer can be re-deposited to regenerate the crucible. Attached Figure Description

[0031] Figure 1 XRD pattern of the support layer prepared in Example 1;

[0032] Figure 2 SEM image of the support layer prepared in Example 1;

[0033] Figure 3 XRD pattern of the support layer prepared in Example 2;

[0034] Figure 4 SEM image of the support layer prepared in Example 2;

[0035] Figure 5 XRD pattern of the support layer prepared in Example 3;

[0036] Figure 6 SEM image of the support layer prepared in Example 3;

[0037] Figure 7 XRD pattern of the support layer prepared in Example 4;

[0038] Figure 8 SEM image of the support layer prepared in Example 4;

[0039] Figure 9 XRD pattern of the support layer prepared for Comparative Example 1;

[0040] Figure 10 SEM image of the support layer prepared for Comparative Example 1;

[0041] Figure 11 XRD pattern of the support layer prepared for Comparative Example 2;

[0042] Figure 12 SEM image of the support layer prepared in Comparative Example 2;

[0043] Figure 13 XRD pattern of the support layer prepared for Comparative Example 3;

[0044] Figure 14 SEM image of the support layer prepared in Comparative Example 3;

[0045] Figure 15 XRD pattern of the support layer prepared in Comparative Example 4;

[0046] Figure 16 SEM image of the support layer prepared in Comparative Example 4;

[0047] Figure 17 XRD pattern of the support layer prepared for Comparative Example 8;

[0048] Figure 18 SEM image of the support layer prepared for Comparative Example 8;

[0049] Figure 19 XRD pattern of the support layer prepared for Comparative Example 12;

[0050] Figure 20 SEM image of the support layer prepared for Comparative Example 12;

[0051] Figure 21 A cross-sectional view (photograph) of a conventional quartz crucible in this field;

[0052] Figure 22 This is an image of the support layer prepared in Example 4 after heat treatment.

[0053] Figure 23 The image shows the appearance of the support layer prepared for Comparative Example 4 after heat treatment. Detailed Implementation

[0054] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments and illustrations.

[0055] The following examples and comparative examples illustrate the sources of raw materials:

[0056] Glassy synthetic quartz sand, purchased from Mitsubishi Chemical, Japan, model PS400, was crushed into the appropriate particle size according to the application requirements.

[0057] The quartz is obtained by heat-treating the above-mentioned glassy synthetic quartz sand at 1200℃ for 50 hours, and then crushed into the appropriate particle size according to the needs of use.

[0058] The adhesive, PVA, was purchased from Wuhan Meiqilin New Materials Co., Ltd., model MQ-35.

[0059] Silicon tetrachloride, with a purity of 99.9999%.

[0060] Silica with a particle size of 15nm and a purity of 99.9999%.

[0061] The intermediate layer sand was purchased from Jiangsu Pacific Quartz Co., Ltd., and the model number was PQSF.

[0062] The outer layer sand was purchased from Jiangsu Pacific Quartz Co., Ltd., and the quartz sand was of model PQSX1.

[0063] Example 1

[0064] S1. Glassy synthetic quartz sand (purity 5N, D50 = 100μm) and cristobalite (purity 5N, D50 = 4μm) are mixed evenly and then added to a freely tiltable molding die. The mixture is then centrifuged to obtain a green support layer. The mass percentage of cristobalite is 5%.

[0065] S2. The green support layer is sintered at 1550℃ and -0.1MPa for 0.5h, and then cooled to room temperature to obtain the support layer (wall thickness 14mm, diameter 100mm).

[0066] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (wall thickness of 2 mm) under the action of an oxyhydrogen flame, thus obtaining a quartz crucible.

[0067] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0068] Example 2

[0069] S1. Glassy synthetic quartz sand (purity 5N, D50 = 80μm) and cristobalite (purity 5N, D50 = 3μm) are mixed evenly and then added to a tiltable molding die. The mixture is then centrifuged to obtain the green support layer. The mass percentage of cristobalite is 4%.

[0070] S2. The green support layer is sintered at 1400℃ and -0.1MPa for 3 hours, and then cooled to room temperature to obtain the support layer (wall thickness 15mm, diameter 500mm).

[0071] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 3 mm) under the action of an oxyhydrogen flame, thus obtaining a quartz crucible.

[0072] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0073] Example 3

[0074] S1. Glassy synthetic quartz sand (purity 5N, D50 = 50μm) and cristobalite (purity 5N, D50 = 1.5μm) are mixed evenly and then added to a tiltable molding die. The mixture is then centrifuged to obtain the green support layer. The mass percentage of cristobalite is 0.1%.

[0075] S2. The green support layer is sintered at 1200℃ and -0.1MPa for 8 hours, and then cooled to room temperature to obtain the support layer (wall thickness 16mm and diameter 1000mm).

[0076] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0077] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0078] Example 4

[0079] S1. Glassy synthetic quartz sand (purity 5N, D50 = 80μm) and cristobalite (purity 5N, D50 = 3μm) are mixed evenly and then added to a tiltable molding die. The mixture is then centrifuged to obtain the green support layer. The mass percentage of cristobalite is 4%.

[0080] S2. The green support layer is sintered in an argon atmosphere at 1400℃ for 3 hours and then cooled to room temperature to obtain the support layer (wall thickness 15mm, diameter 150mm).

[0081] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0082] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0083] Example 5

[0084] S1. Mix quartz sand, deionized water and binder MQ-35 evenly in a mass ratio of 16:3:2 to obtain a slurry; wherein the quartz sand is composed of glassy synthetic quartz sand (purity 5N, D50 = 80μm) and cristobalite (purity 5N, D50 = 2μm), with the cristobalite accounting for 2% of the mass; inject the slurry into a mold to form a green support layer.

[0085] S2. The green support layer is sintered at 1500℃ and -0.1MPa for 1.5h, and then cooled to room temperature to obtain the support layer (wall thickness 16mm, diameter 1000mm).

[0086] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0087] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0088] Example 6

[0089] S1. Mix quartz sand, deionized water, and binder MQ-35 evenly at a mass ratio of 16:3:1 to obtain a slurry; wherein the quartz sand is composed of glassy synthetic quartz sand (purity 5N, D50 = 80μm) and cristobalite (purity 5N, D50 = 2μm), with the cristobalite accounting for 5% of the mass; inject the slurry into a mold to form a green support layer (wall thickness 16mm, diameter 1000mm).

[0090] S2. The green support layer is sintered at 1500℃ and -0.1MPa for 1.5 hours, and then cooled to room temperature to obtain the support layer.

[0091] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0092] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0093] Example 7

[0094] S1. Mix quartz sand, deionized water and binder MQ-35 evenly in a mass ratio of 16:3:0.5 to obtain a slurry; wherein the quartz sand is composed of glassy synthetic quartz sand (purity 5N, D50=80μm) and cristobalite (purity 5N, D50=2μm), with the mass percentage of cristobalite being 0.1%; inject the slurry into a mold to form a green support layer.

[0095] S2. The green support layer is sintered at 1500℃ and -0.1MPa for 1.5h, and then cooled to room temperature to obtain the support layer (wall thickness 16mm, diameter 1000mm).

[0096] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0097] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0098] Example 8

[0099] S1. Mix quartz sand, deionized water and binder MQ-35 evenly in a mass ratio of 16:3:1 to obtain a slurry; wherein the quartz sand is composed of glassy synthetic quartz sand (purity 5N, D50 = 80μm) and cristobalite (purity 5N, D50 = 2μm), with the cristobalite accounting for 2% of the mass; inject the slurry into a mold to form a green support layer.

[0100] S2. The green support layer is sintered at 1200℃ and -0.1MPa for 5.5 hours and then cooled to room temperature to obtain the support layer (wall thickness 16mm and diameter 1000mm).

[0101] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0102] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0103] Example 9

[0104] S1. Glassy synthetic quartz sand (purity 5N, D50 = 100μm) and cristobalite (purity 5N, D50 = 4μm) are mixed evenly and then added to a mold. A pressure of 100MPa is applied to press and shape the mixture to obtain a green support layer. The mass percentage of cristobalite is 5%.

[0105] S2. The green support layer is sintered at 1550℃ and -0.1MPa for 0.5h, and then cooled to room temperature to obtain the support layer (wall thickness 16mm, diameter 1000mm).

[0106] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (with a wall thickness of 4 mm), thus obtaining a quartz crucible.

[0107] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0108] Example 10

[0109] S1. Glassy synthetic quartz sand (purity 5N, D50 = 80μm) and cristobalite (purity 5N, D50 = 3μm) are mixed evenly and then added to a mold. A pressure of 300MPa is applied for pressing to obtain a green support layer. The mass percentage of cristobalite is 4%.

[0110] S2. The green support layer is sintered at 1400℃ and -0.1MPa for 3 hours, and then cooled to room temperature to obtain the support layer (wall thickness 12mm, diameter 1000mm).

[0111] S3. Using a flame hydrolysis method, gaseous silicon tetrachloride is deposited onto the inner surface of the support layer to form a transparent layer (wall thickness of 2 mm) under the action of an oxyhydrogen flame, thus obtaining a quartz crucible.

[0112] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0113] Example 11

[0114] S1. Glassy synthetic quartz sand (purity 5N, D50 = 50μm) and cristobalite (purity 5N, D50 = 1.5μm) are mixed evenly and then added to a mold. A pressure of 300MPa is applied for pressing to obtain a green support layer. The mass percentage of cristobalite is 0.1%.

[0115] S2. The green support layer is sintered at 1200℃ and -0.1MPa for 8 hours, and then cooled to room temperature to obtain the support layer (wall thickness of 12mm and diameter of 1000mm).

[0116] S3. Using a melting method, fumed silica (D50 = 15 nm) is placed in the cavity of the support layer and melted under the action of an oxyhydrogen flame. The support layer is rotated so that the molten fumed silica spreads on the inner surface of the support layer to form a transparent layer (wall thickness of 2 mm), thus obtaining a quartz crucible.

[0117] The purity of the transparent layer of the quartz crucible prepared in this embodiment is 6N.

[0118] Comparative Example 1

[0119] The method of Example 4 was followed, except that the particle size D50 of the synthetic quartz sand was adjusted to 150 μm.

[0120] Comparative Example 2

[0121] The method of Example 4 is followed, except that the particle size D50 of the cristobalite is adjusted to 20 μm.

[0122] Comparative Example 3

[0123] The method is the same as in Example 4, except that natural quartz sand is used instead of synthetic quartz sand.

[0124] Comparative Example 4

[0125] The method of Example 4 was followed, except that the sintering temperature was adjusted to 1750°C.

[0126] Comparative Example 5

[0127] The method is the same as in Example 6, except that the mass ratio of quartz sand, deionized water, and binder is adjusted to 16:5:7.

[0128] Comparative Example 6

[0129] The method of Example 6 is followed, except that the particle size D50 of the synthetic quartz sand is adjusted to 150 μm.

[0130] Comparative Example 7

[0131] The method is the same as in Example 6, except that natural quartz sand is used instead of synthetic quartz sand.

[0132] Comparative Example 8

[0133] The method of Example 6 is followed, except that the sintering temperature is adjusted to 1750°C.

[0134] Comparative Example 9

[0135] The method is the same as in Example 10, except that the particle size D50 of the synthetic quartz sand is adjusted to 150 μm.

[0136] Comparative Example 10

[0137] The method is the same as in Example 10, except that the particle size D50 of the cristobalite is adjusted to 20 μm.

[0138] Comparative Example 11

[0139] The method is the same as in Example 10, except that natural quartz sand is used instead of synthetic quartz sand.

[0140] Comparative Example 12

[0141] The method is the same as in Example 10, except that the sintering temperature is adjusted to 1750°C.

[0142] Comparative Example 13

[0143] The method is the same as in Example 2, except that only glassy synthetic quartz sand (purity 5N, D50 = 80μm) is used as raw material.

[0144] Comparative Example 14

[0145] The method is the same as in Example 2, except that only cristobalite (purity 5N, D50 = 80μm) is used as raw material and the calcination temperature is 1750℃.

[0146] Comparative Example 15

[0147] Preparation of quartz crucibles:

[0148] S1. Pour the outer layer of sand (80-130 mesh quartz sand, Jiangsu Pacific Quartz Co., Ltd., model PQSX1) into a rotating mold. Rotate the mold 45-56° and rotate at 70 rpm. Use a forming rod to melt and shape the sand.

[0149] S2. Pour the middle layer sand (60-120 mesh quartz sand, Jiangsu Pacific Quartz Co., Ltd., model PQSF) into the rotating mold that has completed the outer layer forming of the crucible. Rotate the mold 45-56° and rotate at 70 rpm. Use the forming rod to melt and form the sand.

[0150] S3. Pour the inner layer sand (50-100 mesh quartz sand, Unimin Corporation, USA, model ITOA-6) into the rotating mold that has completed the middle layer forming of the crucible. Rotate the mold 45-56° and rotate at 70 rpm. Use the forming rod to melt and form the sand.

[0151] S4. Place the rotating mold with the outer, middle and inner layers of the crucible formed into a melting zone, and melt it for 10 minutes using the vacuum arc method. The vacuum pressure is -0.099MPa and the arc power is 10kW. Allow it to cool naturally and demold to obtain a quartz crucible (wall thickness 20mm, diameter 1000mm).

[0152] The mass ratio of the outer layer sand, the middle layer sand, and the inner layer sand is 3:4:3.

[0153] The crucibles prepared in Examples 1-11 and Comparative Examples 1-15 were subjected to structural and performance tests. The test results are shown in Tables 1-3.

[0154] Density was tested using the Archimedes displacement method; the grain size and content of the cristobalite phase were tested using X-ray diffraction; after the crucible was used for a period of time, the contaminated transparent layer was removed by sandblasting with 80μm quartz sand and 0.7MPa airflow, and a new transparent layer was re-deposited to generate the new transparent layer. The number of times the crucible could be reused was tested until the support layer cracked.

[0155] Table 1

[0156]

[0157] As shown in Table 1, Examples 1-4, using glassy synthetic quartz sand and cristobalite with specific particle size ranges as raw materials, obtained support layers with cristobalite grains of a certain size. This is likely because uniform nucleation occurred, preventing the generation of internal stresses that would lead to support layer failure. Comparative Examples 1-2, using glassy synthetic quartz sand or cristobalite with larger particle sizes as raw materials, also resulted in larger support layer grain sizes, leading to cracking. Comparative Example 3, using natural quartz sand (α-quartz), suffered from excessively large crystals due to the presence of gas-liquid inclusions. This also caused cracking. Comparative Example 4, due to its sintering temperature exceeding the melting point of cristobalite, resulted in a glassy support layer that could not crystallize uniformly and contained a certain amount of bubbles.

[0158] Table 2

[0159]

[0160] Table 2 shows that: Comparative Example 5, due to its high binder content, experienced binder removal during sintering, resulting in numerous pores and silicon melt penetration; Comparative Example 6, using large-particle-size synthetic quartz sand, led to non-uniform nucleation, resulting in large cristobalite grains in the support layer, causing crucible cracking. Comparative Example 7 used natural quartz sand (α-quartz), but the presence of gas-liquid inclusions in the natural quartz sand caused impurities in these inclusions during preparation, resulting in non-uniform nucleation of the support layer and excessively large crystals, leading to cracking of the support layer. Comparative Example 8, due to its sintering temperature exceeding the melting point of cristobalite, yielded a glassy support layer containing numerous bubbles.

[0161] Table 3

[0162]

[0163] Table 3 shows that in Comparative Examples 9 and 10, the use of larger-particle-size glassy synthetic quartz sand or cristobalite resulted in cracked support layers. This is likely due to non-uniform nucleation and large grain size in the support layers. Comparative Example 11 used natural quartz sand (α-quartz). Because natural quartz sand contains gas-liquid inclusions, impurities in these inclusions caused non-uniform nucleation of the support layer during preparation, leading to excessively large crystals and cracking. Comparative Example 12, due to its sintering temperature exceeding the melting point of cristobalite, yielded a glassy support layer containing numerous air bubbles. In Comparative Example 13, because glassy synthetic quartz sand lacks a fixed melting point, the particles soften and bind at lower temperatures. Without cristobalite as aggregate, air in the gaps was trapped by the softened quartz sand during sintering, making it difficult to expel and resulting in numerous air bubbles. Comparative Example 14, consisting entirely of cristobalite, was sintered at 1750℃ (above the melting point of cristobalite), resulting in a completely melted cristobalite and a transparent support layer (entirely glassy phase). The crucible prepared in Comparative Example 15 is a conventional quartz crucible. The support layer is made of outer and middle sand and contains air bubbles. During use, the air bubbles expand and gradually penetrate the transparent layer into the molten silicon. Moreover, due to the large number of air bubbles in the support layer and its porous structure, it changes from a glassy state to a crystalline state after use, becomes brittle, and cannot be reused.

[0164] The crucibles prepared in Examples 1-11 and Comparative Examples 4, 5, 8, 12, and 13 were heat-treated at 1600°C for 10 hours to completely quartzize the support layer. The results are shown in Table 4.

[0165] Table 4

[0166] Is it cracked? Is it cracked? Example 1 no Comparative Example 4 yes Example 2 no Comparative Example 5 yes Example 3 no Comparative Example 8 yes Example 4 no Comparative Example 12 yes Example 5 no Comparative Example 13 yes Example 6 no Example 7 no Example 8 no Example 9 no Example 10 no Example 11 no

[0167] As can be seen from Table 4, the support layers obtained in Examples 1-11, after further heat treatment to complete cristobalite formation, did not crack (similar to...). Figure 22 This indicates that although the content of the cristobalite phase in the support layer increases during use, it can still be used stably because the nucleation of the cristobalite phase is uniform. The support layers obtained in Comparative Examples 4, 5, 8, and 12 cracked during heat treatment (similar to...). Figure 23 The results indicate that the crystallization process may be uneven, leading to stress cracking. Comparative Example 13 contains numerous air bubbles (similar to the support layer of a conventional crucible), resulting in low support layer strength. At high temperatures, the expansion of these bubbles causes the gas transparent layer to enter the molten silicon; furthermore, the uneven crystallization leads to cracking of the support layer. The support layer obtained in Comparative Example 14, being in a glassy state, has poor heat resistance, low strength at high temperatures, and is prone to deformation, also containing air bubbles. Since its sintering temperature must be higher than the melting point of cristobalite, the energy consumption is higher than that of conventional support layers, and the high hardness of cristobalite makes processing difficult.

[0168] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A quartz crucible, characterized in that: The quartz crucible is bubble-free and consists of a support layer and a transparent layer. The support layer contains a glass phase and a cristobalite phase, with the cristobalite phase uniformly dispersed in the glass phase. The wall thickness of the transparent layer is less than 1 / 4 of the total wall thickness of the crucible.

2. The quartz crucible according to claim 1, characterized in that: The cristobalite phase has a grain size of 5–15 μm and a content of more than 5%. Preferably, the cristobalite phase has a grain size of 5–10 μm and a content of more than 5%.

3. The quartz crucible according to claim 1, characterized in that: The purity of the support layer is not less than 4N8; Preferably, the purity of the transparent layer is greater than 6N; Preferably, the density of the support layer is 2.2–2.6 g / cm³. 3 .

4. The quartz crucible according to claim 1, characterized in that: The support layer is completely transformed into the cristobalite phase through heat treatment; Preferably, the heat treatment temperature is 1200–1600°C.

5. The method for preparing the quartz crucible according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. After uniformly mixing glassy synthetic quartz sand with cristobalite, green molding is carried out to obtain a support layer green blank. S2. Sinter the green blank of the support layer to obtain the support layer; S3. A transparent layer is formed by depositing a silicon source on the inner surface of the support layer to obtain a quartz crucible.

6. The preparation method according to claim 5, characterized in that: The proportion of cristobalite is ≤5%, based on the total mass of glassy synthetic quartz sand and cristobalite.

7. The preparation method according to claim 5, characterized in that: The glassy synthetic quartz sand has a D50 particle size ≤100μm and a purity of not less than 5N. Preferably, the cristobalite has a D50 particle size ≤10μm and a purity of not less than 5N; Preferably, the green body forming method is one of centrifugal forming, slip casting, or compression molding.

8. The preparation method according to claim 5, characterized in that: The sintering temperature is lower than the melting point of cristobalite; Preferably, the sintering temperature is 1200–1600℃, and the sintering time is 0.5–10 h; Preferably, the sintering atmosphere is a vacuum or a non-reactive atmosphere.

9. The preparation method according to claim 5, characterized in that: The silicon source is one or more of silicon tetrachloride, silica, and synthetic high-purity quartz sand. Preferably, the deposition method is one of chemical deposition or melting.

10. The application of the quartz crucible according to any one of claims 1 to 4 or the quartz crucible obtained by the preparation method according to any one of claims 5 to 9 in the growth of semiconductor single crystal silicon.

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