A study on resistance of PECVD silicon nitride thin film to thermal stress-induced cracking

A potentiostatic method was used to investigate the ability of Plasma-Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films to protect aluminum bonding areas of integrated circuit chips. Four different films in thicknesses of about 5 kÅ were deposited on 0.9-mm-thick stainless steel substrate and CERDIP test chips by varying deposition variables. Ultimate strain of the films was measured by controlled strain apparatus and was constant at about 0.2%. Thermal shock and cycling test was conducted to investigate the resistance of the films to thermal stress-induced cracking. After the test, the number of cracked bondpads on the CERDIP test chips was counted and corrosion current through cracks of the films on the stainless steel substrate was measured. The results showed that more tensile films were more susceptible to crack-induced failure.