Electronic grade polysilicon: "Food" of electronic Information Industry

High purity polysilicon material is the basic raw material of information industry and solar photovoltaic power generation industry. Many developed countries regard it as a strategic material.  

Electronic-grade polysilicon is one of the most basic and main raw materials for manufacturing semiconductor silicon wafers, known as the "food" of the electronic information industry, with purity requirements of 99.999999999% ~ 99.999999999% (9N ~ 11N).

Classification and application of electronic grade polysilicon

Electronic-grade polysilicon requires high purity and is the purest material that can be obtained by human industrialization.  

Electronic grade polysilicon can be divided into electronic grade zone melting polysilicon and electronic grade direct drawing polysilicon.  The quality requirements of electronic zone fusion polycrystalline silicon are more demanding. The monocrystalline silicon produced by zone fusion method has low oxygen and carbon content, low carrier concentration and high resistivity. It is mainly used in the manufacture of IGBT, high voltage rectifier, thyristor, high voltage transistor and other high voltage and high power semiconductor devices.  The monocrystalline silicon chips produced by Zyla method are widely used in integrated circuit memory, microprocessor, mobile phone chips, low voltage transistors, electronic devices and other electronic products, and are more widely used, electronic grade zyla polycrystalline silicon market accounted for more than 90%.  

Analysis of electronic grade polysilicon production technology

From the current development of electronic polysilicon production technology in the world, the production process mainly includes silane method, gas-liquid deposition method, fluidized bed, improved Siemens and other processes.  

The production cost of silane method is high, and the silane used is explosive, flammable, poor safety, even at room temperature will be a fire hazard.  The gas-liquid deposition method is developed and controlled by Japan. The tubular reactor is mainly used in the production, and the operating temperature is controlled at 1500℃. Liquid silicon is directly generated in the gas.  Fluidized bed process is mainly to control the impurities in the product, so it can not produce high quality electronic polysilicon.  

Introduction of improved Siemens method

At present, the main production process of electronic polysilicon is improved Siemens method.  

The process flow of improved Siemens method is:  Silicon powder and silicon in high-intensity synthetic process to produce hydrogen, hydrogen chloride to produce chemical hydrogen silicon into the distillation process for purification, and produce high purity silicon chemical hydrogen, then high purity silicon chemical hydrogen and tail gas recycling workshop for making high purity hydrogen into the production of polycrystalline silicon reduction process, application of chemical deposition reduction workshop production of polysilicon, polysilicon and finally by the broken,  Weighing and packaging and other procedures after storage.  

This method originated around 1960, after more than half a century of development, has achieved the ultimate technology in all aspects.  The domestic improved Siemens method was initially used for photovoltaic polysilicon, but in the process of technological upgrading, there are difficult to overcome technical bottlenecks in many fields, limiting the development of electronic polysilicon.  There are still many deficiencies in the quality control of polysilicon products in the production process. At present, China has not fully mastered the core technology of Siemens method in the core technology testing of electronic polysilicon.  

The main advantage of using this method to produce electronic-grade polysilicon is that it has a reliable and mature process. However, the most obvious disadvantage of using this method to produce electronic-grade polysilicon is that it is difficult to effectively purify SiHCl3 as raw material. Compared with tail gas recovery and rectification, its requirements are more stringent.  In the actual production, the process is also more difficult to control, and electronic polysilicon in the reduction furnace performance and structure requirements are also very high;  In addition, due to the presence of Cl in the process gas, if the process production conditions are not effectively controlled, the corresponding facilities and pipelines will be severely corroded.