阅读说明：本技术 一种基于定向凝固法铸造多晶硅的工艺 (Process for casting polycrystalline silicon based on directional solidification method ) 是由 谢宇 张发云 饶森林 于 2019-10-10 设计创作，主要内容包括：本发明公开了一种基于定向凝固法铸造多晶硅的工艺,其包括以下步骤,步骤一：装料,把多晶硅原料装进石英坩埚中；步骤二：抽真空,关闭炉腔,启动真空泵系统；步骤三：加热,控制温度上升至接近1175℃,然后继续加热升温至硅熔点以上；步骤四：熔化,温度上升到最后的熔化温度1500℃；步骤五：降温拉晶,在融化过程结束后,将温度由1500℃降到1425℃；步骤六：长晶,将温度下降到1385℃-1405℃,进入长晶过程；步骤七：退火,控制退火温度为1300℃,关闭隔热屏使炉内温度分布均匀,进入冷却阶段；步骤八：当温度降到300℃时,冷却炉子,完成整个长晶循环。本发明的优点：制成的晶粒生长整齐,硅锭性能良好。(The invention discloses a process for casting polycrystalline silicon based on a directional solidification method, which comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible; step two: vacuumizing, closing the furnace chamber, and starting a vacuum pump system; step three: heating, controlling the temperature to rise to approximately 1175 ℃, and then continuing heating to rise the temperature to be above the melting point of silicon; step four: melting, and raising the temperature to the final melting temperature of 1500 ℃; step five: cooling and pulling crystal, and after the melting process is finished, cooling the temperature from 1500 ℃ to 1425 ℃; step six: crystal growth, namely reducing the temperature to 1385-1405 ℃ and entering the crystal growth process; step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to ensure that the temperature in the furnace is uniformly distributed, and entering a cooling stage; step eight: when the temperature is reduced to 300 ℃, the furnace is cooled, and the whole crystal growth cycle is completed. The invention has the advantages that: the prepared crystal grains grow tidily, and the silicon ingot has good performance.)

1. A process for casting polycrystalline silicon based on a directional solidification method is characterized in that: the method comprises the following steps of: charging; step two: vacuumizing; step three: heating; step four: melting; step five: cooling and pulling crystal; step six: crystal growth, step seven: and (5) annealing, step eight: and (6) cooling.

2. The process for casting polycrystalline silicon based on the directional solidification method as set forth in claim 1, wherein: which comprises the following steps of,

the method comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible;

step two: vacuumizing, closing the furnace chamber, starting a vacuum pump system, and pumping out moisture carried by the crucible and the silicon material;

step three: heating, controlling the temperature to rise to approximately 1175 ℃, and then continuing heating to rise the temperature to be above the melting point of silicon;

step four: melting, and raising the temperature to the final melting temperature of 1500 ℃;

step five: cooling and pulling crystal, and after the melting process is finished, cooling the temperature from 1500 ℃ to 1425 ℃;

step six: crystal growth, namely reducing the temperature to 1385-1405 ℃ and entering the crystal growth process;

step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to ensure that the temperature in the furnace is uniformly distributed, and entering a cooling stage;

step eight: when the temperature is reduced to 300 ℃, the heat shield is completely opened, gas is discharged, the furnace is completely cooled, and the whole crystal growth cycle is completed.

3. The process for casting polycrystalline silicon based on the directional solidification method as set forth in claim 1, wherein: which comprises the following steps of,

the method comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible;

step two: vacuumizing, closing the furnace chamber, starting a vacuum pump system, and pumping out moisture carried by the crucible and the silicon material;

step three: heating, controlling the temperature to rise to approximately 1175 ℃, keeping the temperature unchanged for a period of time at 1175 ℃, then continuing heating to rise the temperature to be above the melting point of silicon, and entering a melting stage.

Step four: melting, wherein the temperature is raised to the final melting temperature of 1500 ℃, and the temperature is kept for 45min to completely melt the silicon material;

step five: cooling and pulling crystal, after the melting process is finished, reducing the temperature from 1500 ℃ to 1425 ℃, keeping the temperature for 1425 ℃ for 15min, and preparing to enter a crystal growth process;

step six: crystal growth, namely reducing the temperature to 1385-1405 ℃, entering a crystal growth process and continuing for 300 min;

step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to enable the temperature in the furnace to be uniformly distributed for 30min, switching the power control mode of the furnace, and entering a cooling stage;

step eight: when the temperature is reduced to 300 ℃, the heat shield is completely opened, gas is discharged, the furnace is completely cooled, and the whole crystal growth cycle is completed.

4. The process for casting polycrystalline silicon based on the directional solidification method as set forth in claim 1, wherein: which comprises the following steps of,

the method comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible;

step two: vacuumizing, closing the furnace chamber, starting a vacuum pump system, pumping out water and pollution impurities carried by the crucible and the silicon material, keeping the furnace in a vacuum state, and preparing to start heating;

step three: heating, controlling power, continuously transmitting the heat of the heater into the silicon material, continuously increasing the temperature of the silicon material and the directional solidification block, controlling the temperature to be increased to nearly 1175 ℃, keeping the temperature unchanged for a period of time at 1175 ℃, then continuously heating to be increased to more than 1420 ℃ of silicon, and entering a melting stage.

Step four: melting, keeping the temperature to rise to the final melting temperature of 1500 ℃ at a certain slope, and keeping the temperature of 1500 ℃ for 45min to completely melt the silicon material;

step five: cooling and pulling crystal, after the melting process is finished, reducing the temperature from 1500 ℃ to 1425 ℃, keeping the temperature for 1425 ℃ for 15min, and preparing to enter a crystal growth process;

step six: crystal growth, namely reducing the temperature to 1385-1405 ℃, entering a crystal growth process, slowly lifting a heat shield upwards to expose the lower surface of the directional solidification block, cooling the lower surface of the directional solidification block firstly to form an upper and lower vertical temperature gradient, so that the silicon melt is gradually solidified and crystallized from bottom to top from the bottom of the crucible until all the silicon melt is solidified and crystallized, and the whole crystal growth process lasts for 300 min;

step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to enable the temperature in the furnace to be uniformly distributed for 30min, switching the power control mode of the furnace after eliminating the temperature gradient, and entering a cooling stage.

Step eight: when the temperature is reduced to 300 ℃, the heat shield is completely opened, gas is discharged, the furnace is completely cooled, and the whole crystal growth cycle is completed.

Technical Field

The invention relates to a process for casting polycrystalline silicon based on a directional solidification method, and belongs to the technical field of polycrystalline silicon.

Background

Since the development of the crystalline silicon solar cell, the polycrystalline silicon solar cell has unique advantages compared with the monocrystalline silicon solar cell. In the production of single crystal silicon solar cells, high purity single crystal silicon rods are used, and the process is complex and requires a large amount of electric energy to be consumed. In addition, the monocrystalline silicon rod is pulled into the cylinder, and the solar cell is manufactured by utilizing the slices, so that the utilization rate of the solar module is low. The production of the polycrystalline silicon solar cell has the advantages of simple process, low cost and large-scale production; and the single polycrystalline silicon ingot furnace has large capacity, the finished product is beneficial to slicing, the material utilization rate is high, and the requirement on silicon raw materials is slightly low. Therefore, polysilicon cells have become the focus of investment research by developers since the 80 s.

The melting of silicon material and the crystal growth are realized by heat flow transmission, and the process is from disordered melt to ordered crystal. Determines the shape of a solid-liquid interface, controls the growth speed and further influences the quality of the whole crystal. The proper crystal growth condition is mainly to maintain a proper phase change driving force field, wherein the phase change driving force field is a temperature field. The thermal field in the ingot furnace mainly comprises three parts of heat conduction, heat convection and heat radiation. Thermal conduction describes heat conduction inside a solid, thermal convection describes heat conduction in a fluid, and thermal radiation describes heat conduction from a heater to the surroundings.

The directional solidification of polysilicon is a method for concentrating impurities outwards when crystal grains grow by utilizing a segregation phenomenon. How well this method is used must be known about the speed at which the crystal solidifies and the temperature. In 1953, Chalmers and other scholars of the united states proposed the theory of composition undercooling on the basis of studying the morphological evolution of the solid-liquid interface of metals by using the directional solidification method. The principle of component supercooling means that during the directional solidification and growth process of crystals, the concentration of solute at a growth interface is changed due to the redistribution phenomenon of the solute, the theoretical solidification temperature of the crystals is changed due to the phenomenon, at the moment, the crystallization phenomenon does not occur when the temperature of a melt is at the theoretical solidification temperature, the crystallization temperature in the actual growth process is lower than the theoretical crystallization temperature, and the phenomenon is called component supercooling. The supercooling of the component is determined by the actual temperature at the front edge of the solid-liquid interface and the liquidus temperature distribution. The difference between the actual temperature during crystal growth and the theoretical temperature is called the degree of supercooling.

In the crystal growth, the size of the supercooling degree is closely related to the growth speed of the crystal, and when the supercooling degree is larger, the axial temperature gradient of the crystal is larger, and the growth rate is higher. How to adjust and control a proper growth rate is a major point, that is, the control of the temperature when the crystal grows is one of the important points of research.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a process for casting polycrystalline silicon based on a directional solidification method, and a proper growth rate is regulated and controlled through the regulation and control of each step.

The invention is realized by the following scheme: a process for casting polycrystalline silicon based on a directional solidification method comprises the following steps: charging; step two: vacuumizing; step three: heating; step four: melting; step five: cooling and pulling crystal; step six: crystal growth, step seven: and (5) annealing, step eight: and (6) cooling.

A process for casting polycrystalline silicon based on a directional solidification method comprises the following steps,

the method comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible;

step two: vacuumizing, closing the furnace chamber, starting a vacuum pump system, and pumping out moisture carried by the crucible and the silicon material;

step three: heating, controlling the temperature to rise to approximately 1175 ℃, and then continuing heating to rise the temperature to be above the melting point of silicon;

step four: melting, and raising the temperature to the final melting temperature of 1500 ℃;

step five: cooling and pulling crystal, and after the melting process is finished, cooling the temperature from 1500 ℃ to 1425 ℃;

step six: crystal growth, namely reducing the temperature to 1385-1405 ℃ and entering the crystal growth process;

step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to ensure that the temperature in the furnace is uniformly distributed, and entering a cooling stage;

step eight: when the temperature is reduced to 300 ℃, the heat shield is completely opened, gas is discharged, the furnace is completely cooled, and the whole crystal growth cycle is completed.

A process for casting polycrystalline silicon based on a directional solidification method comprises the following steps,

the method comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible;

step two: vacuumizing, closing the furnace chamber, starting a vacuum pump system, and pumping out moisture carried by the crucible and the silicon material;

step three: heating, controlling the temperature to rise to approximately 1175 ℃, keeping the temperature unchanged for a period of time at 1175 ℃, then continuing heating to rise the temperature to be above the melting point of silicon, and entering a melting stage.

Step four: melting, wherein the temperature is raised to the final melting temperature of 1500 ℃, and the temperature is kept for 45min to completely melt the silicon material;

step five: cooling and pulling crystal, after the melting process is finished, reducing the temperature from 1500 ℃ to 1425 ℃, keeping the temperature for 1425 ℃ for 15min, and preparing to enter a crystal growth process;

step six: crystal growth, namely reducing the temperature to 1385-1405 ℃, entering a crystal growth process and continuing for 300 min;

step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to enable the temperature in the furnace to be uniformly distributed for 30min, switching the power control mode of the furnace, and entering a cooling stage;

step eight: when the temperature is reduced to 300 ℃, the heat shield is completely opened, gas is discharged, the furnace is completely cooled, and the whole crystal growth cycle is completed.

A process for casting polycrystalline silicon based on a directional solidification method comprises the following steps,

the method comprises the following steps: loading, namely loading a polycrystalline silicon raw material into a quartz crucible;

step two: vacuumizing, closing the furnace chamber, starting a vacuum pump system, pumping out water and pollution impurities carried by the crucible and the silicon material, keeping the furnace in a vacuum state, and preparing to start heating;

step three: heating, controlling power, continuously transmitting the heat of the heater into the silicon material, continuously increasing the temperature of the silicon material and the directional solidification block, controlling the temperature to be increased to nearly 1175 ℃, keeping the temperature unchanged for a period of time at 1175 ℃, then continuously heating to be increased to more than 1420 ℃ of silicon, and entering a melting stage.

Step four: melting, keeping the temperature to rise to the final melting temperature of 1500 ℃ at a certain slope, and keeping the temperature of 1500 ℃ for 45min to completely melt the silicon material;

step five: cooling and pulling crystal, after the melting process is finished, reducing the temperature from 1500 ℃ to 1425 ℃, keeping the temperature for 1425 ℃ for 15min, and preparing to enter a crystal growth process;

step six: crystal growth, namely reducing the temperature to 1385-1405 ℃, entering a crystal growth process, slowly lifting a heat shield upwards to expose the lower surface of the directional solidification block, cooling the lower surface of the directional solidification block firstly to form an upper and lower vertical temperature gradient, so that the silicon melt is gradually solidified and crystallized from bottom to top from the bottom of the crucible until all the silicon melt is solidified and crystallized, and the whole crystal growth process lasts for 300 min;

step seven: annealing, controlling the annealing temperature to be 1300 ℃, closing the heat shield to enable the temperature in the furnace to be uniformly distributed for 30min, switching the power control mode of the furnace after eliminating the temperature gradient, and entering a cooling stage.

Step eight: when the temperature is reduced to 300 ℃, the heat shield is completely opened, gas is discharged, the furnace is completely cooled, and the whole crystal growth cycle is completed.

The invention has the beneficial effects that: the whole crystal growth cycle is completed by experimental methods of loading, vacuumizing, heating, melting, cooling, crystal pulling, crystal growth, annealing and cooling, and the prepared crystal grains grow neatly and the performance of a silicon ingot is relatively good by adjusting and controlling each process and optimizing the process.

Detailed Description

The present invention is further illustrated below, but the scope of the invention is not limited to the disclosure.

In the following description, for purposes of clarity, not all features of an actual implementation are described, well-known functions or constructions are not described in detail since they would obscure the invention with unnecessary detail, it being understood that in the development of any actual embodiment, numerous implementation details must be set forth in order to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, changing from one implementation to another, and it being recognized that such development effort might be complex and time consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art.