Laser-based plasma diagnostics for PECVD of silicon thin films

We present two laser systems to monitor plasma conditions in a plasma-enhanced chemical vapor deposition chamber. The first optical system is a high-resolution quantum cascade laser-based infrared absorption spectrometer designed to measure the input silane depletion fraction (dissociation efficiency) and to determine the amorphous-to-microcrystalline silicon transition regime. The second optical system is a compact and low-cost laser light scattering device designed to detect the formation of powder particles. In the absence of such particles, the silane depletion fraction provides an in situ measurement of the film growth rate.