On the impact of carbon content on the quality of polysilicon
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Dear seniors: Regarding finished polycrystalline silicon, it is necessary to provide customers with the carbon content specification. According to the requirements of the \"Specifications for Solar-grade Polycrystalline Silicon (Draft for Approval)\\", the carbon content in solar-grade grade 3 products must not exceed 4.5*10^16 atoms/cm3. This is already the highest concentration; any higher and no one will want it. However, there is no clear consensus regarding the impact of carbon content on quality, as there is for impurities III and VI. What exactly are the drawbacks of too high a carbon content? Does it easily cause carbon-oxygen polymers, or does it generate non-melting substances during single crystal pulling? Is there a clear theoretical explanation? Please, an expert, give some guidance.
Looking forward to answers from experts. I think that when the carbon content is high, during the process of pulling single crystals, differences in the melting points and expansion coefficients of the two substances may lead to the formation of fracture layers
The carbon content has not much impact on the quality of polysilicon
Carbon does not introduce electroactive defects in silicon, so it has little impact on polycrystals. However, carbon can react with oxygen as well as combine with interstitial atoms and vacancies, existing in silicon crystals in a striated form. When the carbon concentration exceeds its solubility, tiny carbon precipitates form, affecting the breakdown voltage and leakage current of the device. During the pulling of single crystals, if the carbon concentration exceeds its saturation level, SiC particles will form, leading to the creation of polycrystals. I suddenly remembered that my previous answers received such low scores, so that’s all I’ll say:@