The mechanism of device damage during bump process for flip-chip package

Ring-type yield loss at wafer edge has been observed during flip-chip packaging process. The failure mechanism is attributed to the scrubber clean process step which generates a lot of charges. This in turn behaves like an electrostatic discharge (ESD) event and damages gate oxide of internal circuits. An equivalent circuit is proposed to analyze such a kind of ESD event and proves the importance of the parasitic capacitance of the interconnect metal.