The effect of pumping methods on wet etching processes

Abstract

Experiments were conducted in conventional wet bath and single wafer process tools to investigate the effect of pumping methods on the etching of PE-TEOS wafers. Etch rate, etch rate uniformity, and wafer-to-wafer uniformity, for various pumping methods, were measured. The within-wafer etch uniformity is found to be lower for the MLC pump when compared to D1 and D2 pumps. For both MLC and D2 pumps, the etch rate is found to be higher for the wafer positioned in the left side of the bath when compared to that of wafers in center and right side. MLC pump operated in a swing mode shows a much lower value because of the additional impact from non-fluctuating flow. Like etch rate uniformity, the wafer-to-wafer uniformity is also higher for the D1 pump owing to the high frequency of pump pulsations. The MLC pump operated in swing mode is preferred for single wafer etching process as it shows high etch rate with lower etch rate uniformity.