A simplified version of BOX isolation technology is described. The new process has been greatly simplified over the original BOX by introducing an additional non-critical masking step. The body effect o b s e r v e d i n n a r r o w c h a n n e l d e v i c e s i s r e d u c e d i n t h e n e w s t r u c t u r e . T h e c a p a c i t a n c e m e a s u r e m e n t o n d i f f u s e d junctions in BOX structure shows smaller c o n t r i b u t i o n s f r o m d i o d e p e r i m e t e r a s compared to LOCOS structure. Hot electron reliability of small geometry MOSFETs has been also studied and the results are presented and discussed.

The characterization of polycrystalline silicon MOS transistors and its film properties are studied, with special emphasis on the relationship between crystalline defects and carrier transport phenomena. An increase in mobility with gate field in polycrystalline silicon MOS transistors and also with doping concentration in polycrystalline silicon films is observed. These phenomena are interpreted as space charge scattering effects caused by a high density of dislocations in the films. U-shaped drain current vs gate voltage curves are observed both in p-channel and n-channel polycrystalline silicon MOS transistors. The anomalous drain current in the accumulation region is interpreted as junction breakdown at the drain edge caused by crystalline imperfections in the films.

Utilizing a laser annealing technology, a drastic reduction in polysilicon sheet resistivity has been observed. The technology was successfully applied in MOS fabrication process steps, and practically no degradation in device characteristics was observed. Physical mechanism of polysilicon laser annealing is also presented, through a study of crystalline structure, mobility and carrier concentration, and the thermal instability during the subsequent thermal annealing.

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