Chemical Vapor Deposition of Solar Cells
The production of polysilicon for solar cells is based on the TC3 or Siemens process wherein a gaseous silicon compound, trichlorosilane (SiHCl3 or TC3) and hydrogen are fed into a process chamber where it makes contact with silicon rods heated to near 1100°C. The TC3 pyrolyzes or breaks apart into a thin layer of silicon and gaseous hydrogen chloride, the latter being pumped away as a waste product.
As pioneers in high temperature microbalances, or mass measuring devices, Colnatec has developed a 500°C sensor that can duplicate the hot silicon rod surface. This sensor can, in real time, measure the deposition rate of the polysilicon film as it pyrolyzes. Such information can be used to monitor, control and even fine tune the chemical kinetics of the polysilicon process, resulting in increased yield, lower energy costs and even higher throughput. The sensor can also be used to monitor the composition of the incoming and exhaust streams using a tunable temperature controlled housing.
Additional applications for this revolutionary sensor include controlling the kinetics of the TC4 to TC3 reconversion process, detection of waste products in process scrubbers, and basic research investigations into high temperature CVD and gas phase reactions encountered routinely in silicon solar cell production systems.