HBM ESD failures caused by a parasitic pre-discharge current spike

A new tester-induced HBM current waveform anomaly was discovered as a result of efforts to understand the cause of low level HBM failures seen on 65 nm CMOS products. The anomaly, which consists of a current spike occurring just prior to the actual HBM pulse, was found to be caused by contact misalignment in the tester¿s discharge relay.