Preparation process of quartz glass crucible and application method of quartz glass crucible for polycrystalline silicon ingot casting
阅读说明：本技术 石英玻璃坩埚制备工艺及其用于多晶硅铸锭的使用方法 (Preparation process of quartz glass crucible and application method of quartz glass crucible for polycrystalline silicon ingot casting ) 是由 李健 高源� 刘丽丽 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种石英玻璃坩埚制备工艺及其用于多晶硅铸锭的使用方法,属于坩埚制备领域,其中石英玻璃坩埚制备包括石英玻璃坩埚坯体制备、石英玻璃坩埚坯体打磨和为石英玻璃坩埚坯体添加氮化硅涂层；将制备的石英玻璃坩埚用于多晶硅铸锭的方法包括以下步骤：(1)多晶硅装料；(2)安装石墨护板；(3)通过加热阶段、熔化阶段、长晶阶段、退火阶段和冷却阶段完成多晶硅铸锭。本发明所述的一种石英玻璃坩埚制备工艺及其用于多晶硅铸锭的使用方法,其效果明显优于熔融石英坩埚。(The invention discloses a quartz glass crucible preparation process and a use method thereof for polycrystalline silicon cast ingots, belonging to the field of crucible preparation, wherein the quartz glass crucible preparation comprises quartz glass crucible blank preparation, quartz glass crucible blank polishing and silicon nitride coating addition for the quartz glass crucible blank; the method for applying the prepared quartz glass crucible to polycrystalline silicon ingot casting comprises the following steps: (1) charging polycrystalline silicon; (2) installing a graphite guard plate; (3) and completing the polycrystalline silicon ingot casting through a heating stage, a melting stage, a crystal growing stage, an annealing stage and a cooling stage. The quartz glass crucible preparation process and the use method of the quartz glass crucible for polycrystalline silicon ingot casting have the effect obviously superior to that of a fused quartz crucible.)
1. A quartz glass crucible preparation process is characterized by comprising the following steps,
(S1) preparing a quartz glass substrate using a chemical deposition method, a hot-melt drawing method, an electric melting method, or a gas refining method;
(S2) dividing the quartz glass substrate into a bottom plate and side walls, grinding four grooves at the appointed positions of the bottom plate, and taking the four side walls to fix the four grooves in the four grooves respectively; placing the assembled bottom plate and side wall into a high-temperature homogenizing furnace, and fusing the bottom plate and the side wall into a whole at 1800 plus 2000 ℃ to form a crucible blank;
(S3) grinding the prepared crucible blank;
(S4) adding a silicon nitride coating to the polished crucible blank by using a vapor deposition method.
2. The process for producing a quartz glass crucible according to claim 1, characterized in that: the chemical deposition method refers to the step of adding SiCl4Introducing into a rectifying tower for rectification and purification, gasifying by an evaporator, taking out vapor from the evaporator by purified nitrogen, and introducing into SiCl in flame of a quartz burner4The steam is thermally hydrolyzed in an oxyhydrogen flame to produce silica particles, which are deposited in layers on the base target surface in a deposition furnace to melt the synthetic quartz glass substrate.
3. The process for producing a quartz glass crucible according to claim 1, characterized in that: the hot-melt drawing method is characterized in that after quartz glass is softened at the temperature of 1800-2000 ℃, the softened quartz glass is drawn to the specified required size through a certain external force to form a quartz glass substrate.
4. The process for producing a quartz glass crucible according to claim 1, characterized in that: the electric melting method comprises the specific steps of putting one or two of quartz sand and quartz glass powder into a graphite crucible, heating the graphite crucible to 1800-2000 ℃ in a vacuum electric melting furnace, vacuumizing the graphite crucible to maintain the vacuum degree at 1-10Pa, and finally introducing high-pressure gas to prepare the quartz glass substrate with the specified required size.
5. The process for producing a quartz glass crucible according to claim 1, characterized in that: the gas refining method is characterized in that one or two of quartz sand and quartz glass powder are melted on a carrier layer by using the heat of fuel combustion, and the quartz sand and the quartz glass powder grow continuously to prepare a quartz glass substrate.
6. The process for producing a quartz glass crucible according to claim 1, characterized in that: the crucible blank prepared by polishing adopts one or a combination of manual loose abrasive and a flat grinding disc.
7. The process for producing a quartz glass crucible according to claim 1, characterized in that: the vapor deposition method is characterized in that silicon tetrachloride is fed into a rectifying tower for rectification and purification and then fed into an evaporation system to generate gas-phase silicon tetrachloride, and high-purity nitrogen and hydrogen are used as carrier gases, so that generated silicon nitride particles are gradually deposited on the inner surface of a quartz glass crucible.
8. The use method of the quartz glass crucible prepared by the preparation process of claim 1 for polycrystalline silicon ingot casting is characterized by comprising the following steps:
(S1) according to a certain sequence, the silicon materials used for the polycrystalline silicon ingot casting comprise primary polycrystalline bar materials with different sizes and forms, primary polycrystalline block materials, polycrystalline silicon ingot circulating materials, single crystal bar head tailing materials, silicon chip fragments and granular silicon according to the proportion of (30-40): (30-70): (20-40): (5-10): (5-30): (5-20) filling the mixture into a quartz glass crucible in percentage;
(S2) adding graphite guard plates with proper size and regular shape at the periphery and the bottom of the quartz glass crucible, and fixing the graphite guard plates with bolts;
(S3) heating stage: after the ingot casting furnace chamber is closed and sealed, vacuumizing is started, and meanwhile, heating is started through a graphite heater in the furnace chamber;
a melting stage: when the temperature in the furnace chamber reaches 1100-;
crystal growth stage: after the silicon material is completely melted, the temperature of the silicon liquid close to the inner bottom of the quartz glass crucible is reduced by means of slowly reducing the power of the heater, opening the heat insulation cage, increasing the height of the heater and the like, the silicon liquid is slowly solidified and crystallized first and then grows from bottom to top along the vertical direction until the silicon liquid is completely solidified and crystallized into a polycrystalline silicon square ingot;
and (3) annealing stage: after the crystal growth is finished, in order to eliminate the internal stress in the polycrystalline silicon ingot, the temperature in the furnace chamber is slowly reduced to about 1200-1300 ℃ according to the speed of 10-15 ℃/min;
and (3) a cooling stage: after the annealing is finished, reducing the power of the heater to zero, completely opening the heat insulation cage, introducing large-flow argon at the flow rate of 200-.
Technical Field
The invention relates to a preparation method of a quartz glass crucible, in particular to a preparation process of the quartz glass crucible and a use method of the quartz glass crucible for polycrystalline silicon ingot casting, and belongs to the field of crucible preparation.
Background
The fused quartz crucible is a unique disposable container specially used for polycrystalline silicon ingot casting at present, which is prepared by taking fused quartz as a raw material through the working procedures of crushing, forming, drying, sintering, checking and the like, and is an important auxiliary material at the upstream of a polycrystalline silicon battery industrial chain in the photovoltaic industry. The using conditions are harsh, and the polycrystalline silicon material with specific weight is loaded in a polycrystalline ingot furnace and is subjected to stages of heating, melting, crystal growth, cooling, annealing and the like to grow into the polycrystalline silicon ingot which can be used for cutting silicon wafers. The performance and quality of the fused quartz crucible are directly related to the quality of the polycrystalline silicon ingot, and further the performance indexes of the solar cell piece, such as photoelectric conversion efficiency, service life and the like, are influenced.
Fused silica crucibles have a number of excellent properties, such as: the material has the advantages of small thermal expansion coefficient, good electrical property, chemical resistance and thermal shock stability, capability of being continuously used even if a small amount of crystallization occurs, and the like. However, fused silica crucibles also have significant drawbacks: (1) the fused silica crucible is brittle, and hidden cracks are possibly generated by vibration, collision and smashing in the processes of logistics transportation, manual transportation and large-volume silicon material filling. (2) The fused silica is in a metastable state in thermodynamics and can be transformed into crystalline cristobalite at a certain temperature, and once the cristobalite is formed in a product, the performance of the crucible is greatly influenced because the thermal expansion coefficient of the crystallized cristobalite is greatly different from that of the fused silica. (3) The silicon material contains excessive alkali metal and alkaline earth metal elements. Alkali metal elements and alkaline earth metal elements represented by K, Na, and Mg lower the crystallization temperature of fused silica. If a large amount of such elements exist in the silicon material, the inner wall of the crucible is obviously cracked, and the silicon liquid is permeated through long-time erosion. (4) The fused silica crucible has cracks, pores or structural defects with inhomogeneous structure in the manufacturing process. (5) The low volume density and high porosity of the fused quartz crucible are easy to shrink in the ingot casting process, the silicon material expands in a certain volume before being melted, and the crucible is supported by the expanded silicon material to be cracked. In view of the above-mentioned drawbacks of the fused silica crucible, it is necessary to develop a novel crucible.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects in the prior art, the invention provides a quartz glass crucible preparation process.
The technical scheme is as follows: in order to achieve the above object, the present invention provides a process for preparing a quartz glass crucible, comprising the steps of,
(S1) preparing a quartz glass substrate using a chemical deposition method, a hot-melt drawing method, an electric melting method, or a gas refining method;
(S2) dividing the quartz glass substrate into a bottom plate and side walls, grinding four grooves at the appointed positions of the bottom plate, and taking the four side walls to fix the four grooves in the four grooves respectively; placing the assembled bottom plate and side wall into a high-temperature homogenizing furnace, and fusing the bottom plate and the side wall into a whole at 1800 plus 2000 ℃ to form a crucible blank;
(S3) grinding the prepared crucible blank;
(S4) adding a silicon nitride coating to the polished crucible blank by using a vapor deposition method.
Further, the chemical deposition method refers to the step of adding SiCl4Introducing into a rectifying tower for rectification and purification, gasifying by an evaporator, taking out vapor from the evaporator by purified nitrogen, and introducing into SiCl in flame of a quartz burner4The steam is thermally hydrolyzed in an oxyhydrogen flame to produce silica particles, which are deposited in layers on the base target surface in a deposition furnace to melt the synthetic quartz glass substrate.
Further, the temperature of the silica glass substrate is 1800-2000 ℃ when the hot-melt drawing method is performed.
Further, the electric melting method comprises the specific steps of placing one or two of quartz sand and quartz glass powder into a graphite crucible, heating the graphite crucible to 1800-2000 ℃ in a vacuum electric melting furnace, vacuumizing the graphite crucible to maintain the vacuum degree at 1-10Pa, and finally introducing high-pressure gas to prepare the quartz glass substrate with the specified required size.
Further, the gas refining method is to melt one or two of quartz sand and quartz glass powder on a carrier layer by using the heat of fuel combustion, and the quartz sand and the quartz glass powder grow continuously to prepare a high-purity quartz glass substrate.
Further, the crucible blank prepared by grinding adopts one or a combination of a manual loose abrasive and a flat grinding disc.
Further, the vapor deposition method is that silicon tetrachloride is fed into a rectifying tower for rectification and purification and then fed into an evaporation system to generate silicon tetrachloride vapor, and high-purity nitrogen and hydrogen are used as loading gases, and generated silicon nitride particles are gradually deposited on the inner surface of a quartz glass crucible.
The use method of the quartz glass crucible prepared by the preparation process for the polycrystalline silicon ingot casting comprises the following steps:
(S1) according to a certain sequence, the silicon materials used for the polycrystalline silicon ingot casting comprise primary polycrystalline bar materials with different sizes and forms, primary polycrystalline block materials, polycrystalline silicon ingot circulating materials, single crystal bar head tailing materials, silicon chip fragments and granular silicon according to the proportion of (30-40): (30-70): (20-40): (5-10): (5-30): (5-20) filling the mixture into a quartz glass crucible in percentage;
(S2) adding graphite guard plates with proper size and regular shape at the periphery and the bottom of the quartz glass crucible, and fixing the graphite guard plates with bolts;
(S3) heating stage: after the ingot casting furnace chamber is closed and sealed, vacuumizing is started, and meanwhile, heating is started through a graphite heater in the furnace chamber;
a melting stage: when the temperature in the furnace chamber reaches 1100-;
crystal growth stage: after the silicon material is completely melted, the temperature of the silicon liquid close to the inner bottom of the quartz glass crucible is reduced by means of slowly reducing the power of the heater, opening the heat insulation cage, increasing the height of the heater and the like, the silicon liquid is slowly solidified and crystallized first and then grows from bottom to top along the vertical direction until the silicon liquid is completely solidified and crystallized into a polycrystalline silicon square ingot;
and (3) annealing stage: after the crystal growth is finished, in order to eliminate the internal stress in the polycrystalline silicon ingot, the temperature in the furnace chamber is slowly reduced to about 1200-1300 ℃ according to the speed of 10-15 ℃/min;
and (3) a cooling stage: after the annealing is finished, reducing the power of the heater to zero, completely opening the heat insulation cage, introducing large-flow argon at the flow rate of 200-.
Has the advantages that: according to the preparation process of the quartz glass crucible and the use method of the quartz glass crucible for the polycrystalline silicon cast ingot, the defects of the existing fused quartz crucible can be avoided, the volume density, the apparent porosity, the compressive strength, the flexural strength, the elastic modulus, the refractoriness under load and the thermal conductivity are obviously improved, and the requirement of the polycrystalline silicon cast ingot on the limit use temperature can be better met.
Detailed Description
The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
Example one
A quartz glass crucible preparation process comprises the following steps:
(S1) adding SiCl4Introducing into a rectifying tower for rectification and purification, gasifying by an evaporator, taking out vapor from the evaporator by purified nitrogen, and introducing into SiCl in flame of a quartz burner4The steam is thermally hydrolyzed in an oxyhydrogen flame to produce silica particles, which are deposited in layers on the base target surface in a deposition furnace to melt the synthetic quartz glass substrate.
(S2) four grooves are ground at the appointed position of the bottom plate, and four side walls are taken and fixed in the four grooves respectively; and (3) putting the assembled bottom plate and side wall into a high-temperature homogenizing furnace, and fusing the bottom plate and the side wall into a whole at 2000 ℃ to form a crucible blank.
(S3) the crucible blank is ground into a frosted rough shape by using a manual loose abrasive.
(S4) introducing the silicon tetrachloride into a rectifying tower for rectifying and purifying, then introducing into an evaporation system to generate gas-phase silicon tetrachloride, and gradually depositing the generated silicon nitride particles on the inner surface of the quartz glass crucible by taking high-purity nitrogen and hydrogen as carrier gases.
The quartz glass crucible prepared by the method is used for preparing a polycrystalline silicon ingot, and comprises the following steps:
(1) polycrystalline silicon charge
Silicon materials for polycrystalline silicon ingot casting, including primary polycrystalline bar materials with different sizes and shapes, primary polycrystalline block materials, polycrystalline silicon ingot circulating materials, single crystal bar head tailing materials, silicon chip pieces and granular silicon, are filled into a high-purity quartz glass ingot casting crucible according to a ratio of 40:50:20:5:20: 10.
(2) Installing graphite guard board
Graphite guard plates with proper size and regular appearance are additionally arranged on the periphery and the bottom of the crucible and are mutually fixed by bolts.
(3) Polycrystalline silicon ingot
A heating stage: after the ingot casting furnace chamber is closed and sealed, vacuumizing is started, and meanwhile, heating is started through a graphite heater in the furnace chamber;
a melting stage: and when the temperature in the furnace chamber reaches 1100 ℃, starting to melt the polysilicon material, and introducing argon for protection at the moment, wherein the flow rate is 200 ml/min. With the continuous increase of the heating power and the continuous rise of the temperature, the silicon material in the crucible is completely melted;
crystal growth stage: after the silicon material is completely melted, the temperature of the silicon liquid close to the inner bottom of the crucible is reduced by means of slowly reducing the power of the heater, opening the heat insulation cage, increasing the height of the heater and the like, and the silicon liquid is slowly solidified and crystallized first. Then growing from bottom to top along the vertical direction until the silicon liquid is completely solidified and crystallized into a polycrystalline silicon square ingot;
and (3) annealing stage: after the crystal growth is finished, in order to eliminate the internal stress in the polycrystalline silicon ingot, the temperature in the furnace chamber is slowly reduced to about 1200 ℃ according to the speed of 10 ℃/min;
and (3) a cooling stage: after annealing is finished, the power of the heater is reduced to zero, the heat insulation cage is completely opened, and argon gas with large flow rate is introduced at the flow rate of 200 ml/min. And when the temperature in the furnace chamber is reduced to about 350 ℃, opening the furnace chamber and taking out the silicon ingot.
Example two
A quartz glass crucible preparation process comprises the following steps:
(S1) softening the silica glass at the temperature of 1800-2000 ℃, and then stretching the softened silica glass to the specified required size by a certain external force to form the silica glass substrate.
(S2) four grooves are ground at the appointed position of the bottom plate, and four side walls are taken and fixed in the four grooves respectively; and (3) putting the assembled bottom plate and side wall into a high-temperature homogenizing furnace, and fusing the bottom plate and the side wall into a whole at 2000 ℃ to form a crucible blank.
(S3) the crucible blank is ground into a frosted rough shape by using a manual loose abrasive.
(S4) introducing the silicon tetrachloride into a rectifying tower for rectifying and purifying, then introducing into an evaporation system to generate gas-phase silicon tetrachloride, and gradually depositing the generated silicon nitride particles on the inner surface of the quartz glass crucible by taking high-purity nitrogen and hydrogen as carrier gases.
The quartz glass crucible prepared by the method is used for preparing a polycrystalline silicon ingot, and comprises the following steps:
(1) polycrystalline silicon charge
Silicon materials for polycrystalline silicon ingot casting, including primary polycrystalline bar materials with different sizes and shapes, primary polycrystalline block materials, polycrystalline silicon ingot circulating materials, single crystal bar head tailing materials, silicon chip pieces and granular silicon, are filled into a high-purity quartz glass ingot casting crucible according to a ratio of 40:50:20:5:20: 10.
(2) Installing graphite guard board
Graphite guard plates with proper size and regular appearance are additionally arranged on the periphery and the bottom of the crucible and are mutually fixed by bolts.
(3) Polycrystalline silicon ingot
A heating stage: after the ingot casting furnace chamber is closed and sealed, vacuumizing is started, and meanwhile, heating is started through a graphite heater in the furnace chamber;
a melting stage: and when the temperature in the furnace chamber reaches 1100 ℃, starting to melt the polysilicon material, and introducing argon for protection at the moment, wherein the flow rate is 200 ml/min. With the continuous increase of the heating power and the continuous rise of the temperature, the silicon material in the crucible is completely melted;
crystal growth stage: after the silicon material is completely melted, the temperature of the silicon liquid close to the inner bottom of the crucible is reduced by means of slowly reducing the power of the heater, opening the heat insulation cage, increasing the height of the heater and the like, and the silicon liquid is slowly solidified and crystallized first. Then growing from bottom to top along the vertical direction until the silicon liquid is completely solidified and crystallized into a polycrystalline silicon square ingot;
and (3) annealing stage: after the crystal growth is finished, in order to eliminate the internal stress in the polycrystalline silicon ingot, the temperature in the furnace chamber is slowly reduced to about 1200 ℃ according to the speed of 10 ℃/min;
and (3) a cooling stage: after annealing is finished, the power of the heater is reduced to zero, the heat insulation cage is completely opened, and argon gas with large flow rate is introduced at the flow rate of 200 ml/min. And when the temperature in the furnace chamber is reduced to about 350 ℃, opening the furnace chamber and taking out the silicon ingot.
EXAMPLE III
A quartz glass crucible preparation process comprises the following steps:
(S1) a graphite crucible containing materials is arranged in a graphite heating furnace, a tungsten powder sintering layer is coated on the inner wall of the graphite crucible, the purity of the tungsten powder is more than 99.95 percent, the granularity is 300 meshes and 400 meshes, quartz powder is placed in the graphite crucible, a vacuum electric melting furnace is adopted to heat the graphite crucible to 2000 ℃, vacuum pumping is carried out, the vacuum degree is maintained at 1-10Pa, and finally high-pressure gas is introduced, so that the high-purity quartz glass substrate is obtained.
(S2) four grooves are ground at the appointed position of the bottom plate, and four side walls are taken and fixed in the four grooves respectively; and (3) putting the assembled bottom plate and side wall into a high-temperature homogenizing furnace, and fusing the bottom plate and the side wall into a whole at 1800 ℃ to form a crucible blank.
(S3) the crucible blank is ground into a frosted rough shape by using a manual loose abrasive.
(S4) introducing the silicon tetrachloride into a rectifying tower for rectifying and purifying, then introducing into an evaporation system to generate gas-phase silicon tetrachloride, and gradually depositing the generated silicon nitride particles on the inner surface of the quartz glass crucible by taking high-purity nitrogen and hydrogen as carrier gases.
The quartz glass crucible prepared by the method is used for preparing a polycrystalline silicon ingot, and comprises the following steps:
(1) polycrystalline silicon charge
Silicon materials for polycrystalline silicon ingot casting, including primary polycrystalline bar materials with different sizes and shapes, primary polycrystalline block materials, polycrystalline silicon ingot circulating materials, single crystal bar head tailing materials, silicon chip pieces and granular silicon, are filled into a high-purity quartz glass ingot casting crucible according to a ratio of 40:50:20:5:20: 10.
(2) Installing graphite guard board
Graphite guard plates with proper size and regular appearance are additionally arranged on the periphery and the bottom of the crucible and are mutually fixed by bolts.
(3) Polycrystalline silicon ingot
A heating stage: after the ingot casting furnace chamber is closed and sealed, vacuumizing is started, and meanwhile, heating is started through a graphite heater in the furnace chamber;
a melting stage: and when the temperature in the furnace chamber reaches 1100 ℃, starting to melt the polysilicon material, and introducing argon for protection at the moment, wherein the flow rate is 200 ml/min. With the continuous increase of the heating power and the continuous rise of the temperature, the silicon material in the crucible is completely melted;
crystal growth stage: after the silicon material is completely melted, the temperature of the silicon liquid close to the inner bottom of the crucible is reduced by means of slowly reducing the power of the heater, opening the heat insulation cage, increasing the height of the heater and the like, and the silicon liquid is slowly solidified and crystallized first. Then growing from bottom to top along the vertical direction until the silicon liquid is completely solidified and crystallized into a polycrystalline silicon square ingot;
and (3) annealing stage: after the crystal growth is finished, in order to eliminate the internal stress in the polycrystalline silicon ingot, the temperature in the furnace chamber is slowly reduced to about 1200 ℃ according to the speed of 10 ℃/min;
and (3) a cooling stage: after annealing is finished, the power of the heater is reduced to zero, the heat insulation cage is completely opened, and argon gas with large flow rate is introduced at the flow rate of 200 ml/min. And when the temperature in the furnace chamber is reduced to about 350 ℃, opening the furnace chamber and taking out the silicon ingot.
Example four
A quartz glass crucible preparation process comprises the following steps:
(S1) subjecting one or both of the silica sand and the silica glass powder to a gas refining process, i.e., oxidizing SiCl with an oxygen-argon flame4And melting and cooling the quartz glass substrate on the carrier layer by layer to obtain the high-purity quartz glass substrate.
(S2) four grooves are ground at the appointed position of the bottom plate, and four side walls are taken and fixed in the four grooves respectively; and (3) putting the assembled bottom plate and side wall into a high-temperature homogenizing furnace, and fusing the bottom plate and the side wall into a whole at 1800 ℃ to form a crucible blank.
(S3) the crucible blank is ground into a frosted rough shape by using a manual loose abrasive.
(S4) introducing the silicon tetrachloride into a rectifying tower for rectifying and purifying, then introducing into an evaporation system to generate gas-phase silicon tetrachloride, and gradually depositing the generated silicon nitride particles on the inner surface of the quartz glass crucible by taking high-purity nitrogen and hydrogen as carrier gases. The quartz glass crucible prepared by the method is used for preparing a polycrystalline silicon ingot, and comprises the following steps:
(1) polycrystalline silicon charge
Silicon materials for polycrystalline silicon ingot casting, including primary polycrystalline bar materials with different sizes and shapes, primary polycrystalline block materials, polycrystalline silicon ingot circulating materials, single crystal bar head tailing materials, silicon chip pieces and granular silicon, are filled into a high-purity quartz glass ingot casting crucible according to a ratio of 40:50:20:5:20: 10.
(2) Installing graphite guard board
Graphite guard plates with proper size and regular appearance are additionally arranged on the periphery and the bottom of the crucible and are mutually fixed by bolts.
(3) Polycrystalline silicon ingot
A heating stage: after the ingot casting furnace chamber is closed and sealed, vacuumizing is started, and meanwhile, heating is started through a graphite heater in the furnace chamber;
a melting stage: and when the temperature in the furnace chamber reaches 1100 ℃, starting to melt the polysilicon material, and introducing argon for protection at the moment, wherein the flow rate is 200 ml/min. With the continuous increase of the heating power and the continuous rise of the temperature, the silicon material in the crucible is completely melted;
crystal growth stage: after the silicon material is completely melted, the temperature of the silicon liquid close to the inner bottom of the crucible is reduced by means of slowly reducing the power of the heater, opening the heat insulation cage, increasing the height of the heater and the like, and the silicon liquid is slowly solidified and crystallized first. Then growing from bottom to top along the vertical direction until the silicon liquid is completely solidified and crystallized into a polycrystalline silicon square ingot;
and (3) annealing stage: after the crystal growth is finished, in order to eliminate the internal stress in the polycrystalline silicon ingot, the temperature in the furnace chamber is slowly reduced to about 1200 ℃ according to the speed of 10 ℃/min;
and (3) a cooling stage: after annealing is finished, the power of the heater is reduced to zero, the heat insulation cage is completely opened, and argon gas with large flow rate is introduced at the flow rate of 200 ml/min. And when the temperature in the furnace chamber is reduced to about 350 ℃, opening the furnace chamber and taking out the silicon ingot.
The crucibles obtained in example 1, example 2, example 3 and example 4 were measured for their properties, and the measurement indexes and the measurement results are shown in table 1, and compared with those of the conventional fused silica crucible.
TABLE 1 comparison of the properties of the quartz glass crucibles obtained in examples 1 to 4 with those of the fused silica crucibles
As can be seen from the above table, compared with the fused silica crucible, the fused silica crucible is obviously superior to the fused silica crucible in terms of volume density, apparent porosity, compressive strength, flexural strength, elastic modulus, refractoriness under load and thermal conductivity, and meets the requirement of the limit service temperature of the polycrystalline silicon ingot.
Meanwhile, the effect of the quartz glass crucibles obtained in example 1, example 2, example 3 and example 4 applied to the polycrystalline silicon ingot was compared with the effect of the fused quartz crucible in the polycrystalline silicon ingot.
TABLE 2 comparison of the effects of a quartz glass crucible and a fused quartz crucible after the application of a polycrystalline silicon ingot
As can be seen from Table 2 above, the effect of using the quartz glass crucible for the polycrystalline silicon ingot casting is significantly better than that of the fused quartz crucible.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.