Pad etch optimization to minimize polymer

In this article, passivation layer etch process was studied to minimize polymer along sidewall and to prevent bond pad peeling. It was identified that SiN breakthrough etching step caused more polymers compared to main etching. The effects of power, CF4 and O2 gas flow on polymer generation during the SiN breakthrough etching have been studied. Scanning electron microscope and Auger electron spectroscopy were used to inspect and analyze polymer. Defects scan and review were performed by EV300™ after etching and wet clean. The etching condition corresponding to 250 W, 20 sccm O2, and 40 sccm CF4 was found to be the optimum condition to minimize polymer without attacking the copper surface.