FinFET SRAM Cell Optimization Considering Temporal Variability due to NBTI/PBTI and Surface Orientation

Abstract

This paper analyzes the impact of intrinsic process variation and NBTI/PBTI induced time-dependent variations on the stability/variability of 6T FinFET SRAM cells with various surface orientations. Due to quantum confinement, (110)-oriented pull-down devices with fin Line Edge Roughness (LER) show larger Vread,0 and Vtrip variations, thus degrading RSNM and its variability. (100)-oriented pull-up devices with fin LER show larger Vwrite,0 and Vtrip variations, hence degrade the variability of WSNM. The combined effects of intrinsic process variation and NBTI/PBTI induced variations have been examined to optimize the FinFET SRAM cells. Pull-up devices with (110) orientation suffer larger NBTI, resulting in large Vtrip variation and significant degradation of RSNM. Our study indicates that consideration of NBTI/PBTI induced temporal variation changes the optimal choice of FinFET SRAM cell surface orientations in term of mu RSNM/sigma RSNM.