Continuous hot-wire chemical vapor deposition on moving glass substrates

Hot Wire Chemical Vapor Deposition (HWCVD) is a very suitable technique for homogeneous deposition of thin films on continuously moving substrates in an in-line manufacturing system. This process is further aided by the fact that transport of insulating substrates (such as glass) during deposition can be easily arranged as the substrate is not part of the decomposition mechanism as in plasma enhanced CVD. Rigorous grounding of the moving substrates is not required, and no special care needs to be taken to make shields or liners equipotential planes. Moreover, as the creation of dust particles in the gas phase can be avoided, deposition could be undertaken with the substrates facing upward, thus further simplifying the mounting of the substrates. Amorphous as well as microcrystalline silicon thin films with device-quality properties have been achieved on moving substrates. The first p-i-n solar cells made with a 300-nm thick i-layer that was deposited on a linearly moving substrate already showed efficiencies of 6.4%, despite two air breaks that were needed in these tests.