Whisker-originated short in the self-aligned contact (SAC) W polymetal gate was directly observed for the first time. Short points between gate electrodes and poly-Si plugs in the test structure were identified by emission microscope and cross-sectional TEM samples of those points were made by using focused ion beam (FIB).
Whiskers are formed during high-temperature processing such as LP-CVD SiN. We have proposed that NH3 de-oxidation step inserted in the SiN deposition sequence is effective for suppressing whisker growth.  In this study it was also confirmed that 600°C NH 3 pre-flow improved leakage current between gate electrode and contact plugs.