Advantages of bulk over SOI in performance of thyristor-based SRAM cell with selective epitaxy anode

Abstract

We fabricated alternative SRAM cells based on a thyristor using SOI and bulk Si wafers, and then compared their performance. A selective epitaxy technique was applied to form anode regions (SEA) for both types. These devices performed extremely well, with high-speed read/write, high lon/Ioff current ratio (>108), and low stand-by current (< 0.5 nA/cell). Write "1" (turn-on) and read performance were comparable for both bulk and SOI (< 100 ps). However, for write "0" (turn-off), the bulk type had much faster speed and lower voltage than the SOI type. In RAM operations, performance of the SOI type would be dominated by write "0" operation speed. These results suggest that the bulk type is more suitable than the SOI type for RAM devices that operate at highspeed.