Characterization of 90 nm SOI SRAM Single Cell Failure by Nano Probing Technique and TCAD Simulation

The single cell failure of a 90 nm SOI SRAM cell presents a difficult challenge for physical failure analysis, including cross sectional TEM, planar TEM, PVC, and FIB. The physical analysis of the failing SRAM cells by these techniques often did not find any visual defects. In order to locate the defects of the failed SRAM cells, a characterization of the transistors of the failing SRAM is needed. A nano probing technique performed in a failure analysis lab allows us to identify anomalies of the transistor characteristics, like Vt asymmetry and low Id current. With the help of TCAD simulation, a correlation between the failure mode and electrical measurement can be established and a process fix can be implemented.