PHOSPHORUS DOPED POLYSILICON FOR DOUBLE POLY STRUCTURES .1. MORPHOLOGY AND MICROSTRUCTURE

In double poly structures, the isolation between the two polysilicon films is achieved by oxidation of the first poly film. The breakdown characteristics and conductivity of the interpoly oxide depend on the surface morphology of the polysilicon film. The surface morphology and microstructure are investigated at various stages in the fabrication process for polysilicon films prepared by five different methods. A high surface quality in combination with a high doping level is only achieved for in situ doped films, deposited in the amorphous state.