Atomic force microscope study of amorphous silicon and polysilicon low-pressure chemical-vapor-deposited implanted layers

The roughness of the poly/interpoly oxide interface plays a most important role in the performance of devices; it is expected that for a smoother inte rface, the double-polysilicon structure will present better electrical prop erties, such as higher breakdown voltage, and will be more reliable. To obt ain the best electrical properties of the oxide layer, it is, therefore, es sential to control the polysilicon morphological properties. The overall pe rformances will be affected by the postdeposition process: implantation (do se, energy, and ion), oxidation (temperature, time, ambient), and preoxidat ion cleaning procedures. In this study, polysilicon and amorphous silicon f ilms were produced under different controlled process conditions and were a nalyzed using atomic force microscopy (AFM). Significant differences in mor phology between polysilicon and amorphous silicon films were obtained. Poly silicon roughness is an order of magnitude higher than amorphous silicon. R oughness of amorphous silicon films increased after rapid thermal annealing treatment performed after deposition. Phosphorus implantations at doses of 3 X 10(15) cm(-2) and energy of 40 keV affect the grain size. Implantation doses between 0.8 x 10(15) and 2 x 10(15) cm(-2) and implantation energies between 40 and 100 keV do not affect the topography. The roughness of the amorphous silicon film increased as a result of the cleaning process, which involves growing an oxide layer and stripping it with hydrofluoric acid. P oor morphology information was gained from high resolution scanning electro n microscopy imaging of these films. We conclude that AFM scanning can obta in quantitative and qualitative morphology information of amorphous and pol ysilicon layers deposited on silicon wafers. (C) 2000 American Vacuum Socie ty.