Impact of work function design on the stability and performance of Ultra-Thin-Body SOI subthreshold SRAM

This paper analyzes and compares the stability, margin, and performance of ultra-thin-body (UTB) SOI 6T SRAM cells operating in subthreshold region with single mid-gap and dual work function (WF) design. Our results indicate that UTB SOI 6T SRAM cells using dual quarter band-gap WF devices (NFET/PFET = 4.35 eV/4.95 eV) show comparable read static noise margin (RSNM) and 84% improvement in write static noise margin (WSNM) as comparaed with that using the single mid-gap WF devices. The ldquocellrdquo access time improves significantly with correspondingly higher stand-by leakage. Our study suggests that the quarter band-gap WF devices not only support the high performance applications but also meet the stability requirement and offer higher performance while trading-off leakage for subthreshold SRAM applications.