The detection and investigation of SRAM data retention soft failures by voltage contrast inspection

The research was aimed at the inline detection of the electron leakage leading to end-of-the-line soft failures. The electron beam inspection was applied to detect the voltage contrast signal by the PMOS leakage, and the leakage would lead to SRAM data retention failures in CP test during 40nm technology development. A series of experiments, including retargeting the CD of NP lithography process and re-tape-out the mask with new optical proximity correct (OPC), were set up according to the inline detectable VC inspection method, and an optimal process integration condition without failures was achieved.