Polysilicon is an important sputtering target material. Using magnetron sputtering method to prepare SiO2 and other thin films can make the matrix material have better optical, dielectric and corrosion resistance, which is widely used in touch screen, optical and other industries.
The process of casting long crystals is to realize the directional solidification of liquid silicon from the bottom to the top gradually by accurately controlling the temperature of the heater in the hot field of the ingot furnace and the heat dissipation of the thermal insulation material, and the solidification long crystals speed is 0.8~1.2cm/h. At the same time, in the process of directional solidification, the segregation effect of metal elements in silicon materials can be realized, most of the metal elements can be purified, and a uniform polycrystalline silicon grain structure can be formed.
Casting polysilicon also needs to be intentionally doped in the production process, in order to change the concentration of acceptor impurities in the silicon melt. The main dopant of p-type cast polysilicon in the industry is silicon boron master alloy, in which the boron content is about 0.025%. The doping amount is determined by the target resistivity of the silicon wafer. The optimal resistivity is 0.02 ~ 0.05 Ω • cm, and the corresponding boron concentration is about 2 × 1014cm-3。 However, the segregation coefficient of boron in silicon is 0.8, which will show a certain segregation effect in the directional solidification process, that is, the boron element is distributed in a gradient in the vertical direction of the ingot, and the resistivity gradually decreases from the bottom to the top of the ingot.
Post time: Jul-26-2022