Lithographic performance enhancement using top antireflective coating compositions made from water-soluble polymers

Abstract

Antireflective Coatings (A.R.C.'s) are widely used for reducing reflectivity problems in microlithography. As optical lithography pushes towards shorter wavelengths and device CD's shrink, thin film interference effects and reflectivity problems become more critical. Therefore, the use of dyed resist and top or bottom antireflective coating is becoming more prevalent. Severe swings in the intensity of such thin film interference are seen as the exposure wavelength decreases. Bottom antireflective coatings are very effective to suppress reflective notching, standing wave effects, and reduce swing ratio. The use of dyed resists as bottom antireflective coatings for absorption of the light can cause sublimation or diffusion of dye molecules into the adjacent photoresist layer during baking. An experimental top antireflective composition is developed from a water-soluble Aquazol R , polymer, with varying molecular weight. The Cauchy coefficients and n and k values were determined for these top antireflective coating compositions. These compositions and the existing commercial product AZ R Aquatar R (A.R.C.) were evaluated with AZ R 7908 and other experimental resists for lithographic performance. The comparative data of the performance enhancement in terms of resolution, DOF, linearity will be discussed.