Case study of SRAM threshold voltage shift caused by doping defects

Static Random Access Memory (SRAM) array is routinely designed in IC chip during process development. Its' high density and addressable structure allows for better defect isolation and faster feedback of process performance. Hence, identification the root cause of SRAM bit failure is very important for process corrections and yield improvement. This paper presented two case studies of threshold voltage (Vt) shift caused by doping defects. The combination of Nanoprobe technique and chemical stain method was proved to be very effective in finding SRAM area doping defects.