Hemispherical-grained LPCVD-polysilicon films in use for MEMS applications

This paper describes the mechanical properties of hemispherical-grained (HSG) polysilicon. While HSG polysilicon can be fabricated in a manner similar to conventional LPCVD, it has mechanical properties and a morphology that are very different from those of conventional polysilicon and amorphous silicon: tensile stress built in an as-deposited film and large roughness located on the surface. The formation of HSG occurs on the amorphous surface, although polycrystallization due to annealing usually occurs on the silicon-to-dioxide interface surface.