Fabrication of Floating-Gate-Type Fin-Channel Double- and Tri-Gate Flash Memories and Comparative Study of Their Electrical Characteristics

Abstract

Floating-gate (FG)-type fin-channel double-gate (DG) and tri-gate (TG) flash memories with different control-gate (CG) lengths (LCG) from 76 to 256 nm have successfully been fabricated by using (110)-oriented silicon on insulator (SOI) wafers, and their electrical characteristics have been comparatively investigated. It was experimentally found that better short channel effect (SCE) immunity, smaller threshold voltage (Vt) variations, and a higher program speed are obtained in the TG-type flash memories than in the DG-type memories. The higher performance of the TG-type flash memory is partly due to the additional top gate and recessed buried oxide (BOX) region, which strengthen the controllability of the channel potential and increase the coupling ratio of the FG to CG. Moreover, it was also found that the measured source–drain (SD) breakdown voltage (BVDS) is higher than 3.2 V even when LCG was reduced to 76 nm. Therefore, the developed fin-channel TG structure is expected to be very useful for the fabrication of scaled NOR-type flash memory.