DEPOSITION OF THICK DOPED POLYSILICON FILMS WITH LOW-STRESS IN AN EPITAXIAL REACTOR FOR SURFACE MICROMACHINING APPLICATIONS

Polysilicon films were deposited in an epitaxial batch reactor at a hi gh deposition rate. The effect of the deposition temperature, total pr essure, source gas flow and in situ doping on the deposition rate and morphological and electrical properties of these films was studied. La yers with thicknesses up to 12 mu m were deposited on a sacrificial ox ide covered with a thin polysilicon nucleation layer, which was formed in a low pressure chemical vapour deposition reactor. The thick polys ilicon layers were characterized in terms of the surface roughness, gr ain growth and concentration and distribution of dopants. The residual stress and stress gradient were also determined. This material was fo und to be highly suitable for surface micromachining applications beca use of its low residual stress level, homogeneous doping profile and e xcellent mechanical properties.