Impacts of NBTI and PBTI on Ultra-Thin-Body GeOI 6T SRAM Cells

Abstract

This paper investigates the impacts of Negative and Positive Bias Temperature Instabilities (NBTI and PBTI) on the stability and performance of Ultra-Thin-Body (UTB) GeOI 6T SRAM cells compared with the SOI counterparts. Worst case stress scenarios for Read and Write operations are analyzed. For UTB GeOI SRAM cells, PBTI dominates the degradations in RSNM, HSNM, cell Read access time, and Time-to-Write, while for UTB SOI SRAM cells, NBTI dominates the degradations in RSNM, HSNM, and Time-to-Write. WSNM only slightly degrades due to NBTI/PBTI. Threshold voltage design and Word-Line Under-Drive (WLUD) Read-Assist techniques are analyzed to compensate the stability degradation due to NBTI/PBTI for UTB GeOI SRAM cells. Compared with the nominal UTB GeOI SRAM cells with low Vth design, UTB GeOI SRAM cells with high Vth design suffer less NBTI/PBTI degradations and exhibit significant improvement in RSNM and HSNM, and comparable performance compared with the nominal UTB SOI SRAM cells.