Characterization of a simplified gas distribution for wafer cost reduction in a plasma metal etcher

Abstract

A perforated gas distribution plate (GDP) is currently the preferred method to provide uniform gas flow in plasma etch systems. Anodized gas distribution plates are consumable in metal etch systems because they are subject to erosion due to the high pressure Cl2 chemistry and the high velocity of the gas flow. This can result in potentially higher particle levels, higher cost of consumables, and lower mean number of wafers between wet cleans. A new simplified gas distribution plate (SGD) has been developed to replace the existing GDP. The ceramic SGD is less susceptible to corrosion and leads to a longer lifetime, resulting in reduction of the cost of consumables. An orthogonal design of experiments on the bulk etch of Al–Cu/TiW film stack etching was conducted. The plasma chamber lid was designed as one of the variables in this orthogonal design with GDP and SGD as the two levels. BCl3, Cl2, N2, CF4, pressure, backside He cooling, and power were the other variables in this orthogonal design at three levels. This allowed the effect of gas distribution and the other variables on nonuniformity of etch, metal etch rate, selectivity to photo-resist, and the profile to be studied. N2 flow, rf power, BCl3 flow and backside He cooling had a significant effect on the nonuniformity of the process in the range analyzed. The selectivity of the aluminum to photo-resist was significantly affected by power, Cl2 flow, pressure, and backside He cooling. The mode of gas distribution was found to have no significant effect on the nonuniformity of the process, metal etch rate, selectivity to photo-resist, and the profile.