Improved manufacturability by OPC based on defocus data

The paper describes the advantages of optical proximity correction (OPC) based on defocus data instead of best focus data. By additionally accepting asymmetric variations of the dimension of different patterns e.g. for an isolated line that can become wider than its nominal width this method can deliver structures much more robust against opens and shorts than in the standard OPC approach which is based on data taken at best process conditions. The differences of both OPC methods are compared based on simulations and checked against experimental data of characteristic IC patterns.