Application of new thin BARC technology for KrF lithography at 80-nm node device

Abstract

The new thin BARC has been developed for the application of small size patterning below 100nm by the optimized simulation and the evaluations on each substrate condition of silicon nitride and silicon oxide. The optical parameters of thin BARC of Exp225 are 1.81 and 0.58 for n and k values, respectively. They are obtained by the simulation for the lower reflectivity at the conditions of silicon nitride and silicon oxide. The optimized BARC thickness of Exp225 are 320Å and 460Å for silicon nitride and oxide substrate, respectively, at the condition of reflectivity. These thickness are much lower than those of commercial BARC of DUV44 for the same substrate conditions. The pattern profile and process margin are compared between the inorganic SiON and organic BARC. The dense L/S pattern profile of 100nm size on SiON shows the severe standing wave and undercutting. However, the pattern on Exp225 is much stable and gives wider depth of focus margin than that of SiON condition. The 85nm dense L/S pattern with feasible process margin is obtained by the application of Exp225 at the thickness of 320Å. The baking temperature is also investigated for the application of mass production. The most optimized baking temperature ranges of Exp225 are between 205°C and 225°C. From the experimental results, it is confirmed that the application of thin BARC is much effective for the small size patterning of 80nm node device. And it is thought that 80nm node device by KrF lithography is possible under the conditions of thin BARC, high contrast resist and high NA exposure tool.