Structural investigation of LPCVD poly-silicon layers used in surface micromachining

In this application oriented study, we have investigated the microstructure changes of LPCVD poly-silicon layers after phosphorus doping and/or an additional annealing step, compared to the as-deposited layers. X-ray diffraction (XRD) and atomic force microscopy (AFM) investigation techniques were used to obtain information on the grain size, structure, texture, crystalline fraction and surface roughness. We found that deposition of poly-silicon layers in a mixed amorphous/crystalline state at 610°C with a small crystalline fraction and subsequent crystallization induced by additional phosphorus doping and/or annealing steps provide stable films of superior quality.