Oxide surface roughness optimization of BiCMOS beol wafers for 200 mm wafer level microfluidic packaging based on fusion bonding

200 mm wafer level microfluidic packaging is developed by low temperature oxide-oxide fusion bonding. The requirement for high quality fusion bonding is to have less than 1 nm microroughness on the wafer surfaces. An optimization process of the oxide deposition and planarization is done on the wafer surfaces. It is achieved to lower the microroughness from 2.08 nm to 0.4 nm without backside processes on the BiCMOS wafer and to 0.615 nm with backside processes on the BiCMOS processes after optimization.