Utilization of plasma hydrogenation in stacked SRAM's with poly-Si PMOSFET's and bulk-Si NMOSFET's

Poly-si PMOSFETs were utilized with bulk-Si NMOSFETs in stacked SRAM cells. Results regarding utilization of a plasma hydrogenation step in a stacked SRAM process sequence are reported. It is found that poly-Si PMOSFETs exhibit an increase in ON/OFF current ratio of four orders of magnitude. Bulk-Si NMOSFETs subjected to the same hydrogenation process exhibit no significant decrease in device lifetime or significant degradation in I-V characteristics compared to NMOSFETs which were not subjected to the plasma hydrogenation process. These results indicate that plasma hydrogenation can successfully be utilized to obtain improved performance stacked SRAMs.>