Silica (SiO2)

1. CZ Single Crystal Ingot Silicon Wafer Production Process Silica (SiO2) Semiconductor or solar grade silicon is made from silica as the raw material through multi-production steps. Silica is the most abundant material in the earth’s crust. Silicon Wafer Flatness, particles, scratches, contaminations and other wafer deformations are the main concerns in the wafer process. The purity of the chemicals, water and the cleanliness of the process are key factors in production. Silicon Wafer Uses Solar cells Devices that convert photons from the sun (solar light) into electricity. Semiconductor Devices ICs, LSIs, VLSIs and discrete devices are the foundation of today’s and tomorrow’s advanced electronic devices. Refining / Reduction Elemental metallic silicon is made by the carbothermic reduction method in an electric furnace. Its purity is around 99% which is still too low for use as semiconductor grade silicon. (Si02 + 2CSi +2CO) Polishing Wafers are polished over and over again to get a mirror-like finish using a mechano-chemical process Ultra-pure polysilicon Rod Elemental silicon is again formed by the Siemens method. This rod is a polycrystal, but its purity is an astonishing 99.999999999% called “eleven-nines.” A purity of “nine-nines is acceptable for solar grade polysilicon.(HiSCl3+H2Si + 3HCl) Electronic-grade rod Solar Grade rod Single Crystal Silicon Ingot A dislocation-free single crystal ingot with definite orientation is grown from the melt of polysilicon by Czochralski (CZ), modified CZ, or a Multicrystalline casting process. In all processes, a small amount of agent (B, P, So, As) is doped to regulate resistivity and conductivity type. Slicing Single crystal silicon ingot is sliced into wafers using a diamond saw.