1. Production requirements of polysilicon
Polysilicon is a form of silicon. When molten elemental silicon solidifies under supercooling conditions, silicon atoms are arranged into many crystal nucleus in the form of a diamond lattice. If these crystal nuclei grow into crystal grains with different crystal plane orientations, then these crystalline grains combine to polysilicon.
One of the biggest characteristics of the polysilicon industry in swir applications is that it has very high requirements for product quality scores. The quality scores of solar grade and electronic grade polysilicon are required to reach at least 6N (99.9999%) and 8N (99.999999%) respectively, and its impurity content is also recognized as one of the important parameters to measure the quality of polysilicon materials.
2. Application of short wave IR camera
A short wave IR camera can clearly detect the carbon impurities in polysilicon. During the test, a short wave IR camera is matched with an 8mm short-wave infrared lens and a halogen light source to observe the impurities in the silicon ingot. Polysilicon is transparent under light sources above 1200nm wavelength band, while impurities such as carbon cannot transmit light above 1200nm wavelength band, so it appears black.
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