Linewidth control using anti-reflective coating for optical lithography

Several types of anti-reflective (AR) coating, including TiW, V, polysilicon films, and spun-on layer incorporated with an absorbing dye have been investigated to eliminate the light reflection from layers under resist. The exposure latitude can be widely extended by the AR coating. Both the standing wave effect and the linewidth change with respect to variation in exposure dose can also be reduced significantly. This simple and convenient technique can be effectively applied to reduce linewidth variations at step cross-over for wafers with vertical aluminum steps less than 0.8 µm height.