A study of variation in characteristics and subthreshold humps for 65-nm SRAM using newly developed SRAM cell array test structure

Variation in the characteristics (Vth and Ion) of driver and load MOSFETs in SRAM cells was investigated by using a newly developed SRAM cell array test structure and is reported here for the first time. Subthreshold humps were also monitored in SRAM cells. By extracting the variations in MOSFET characteristics and by estimating the impact of subthreshold humps in SRAM cells, it is possible to design SRAM circuits more accurately.