A highly efficient optimization algorithm for pixel manipulation in inverse lithography technique

An efficient algorithm based on the pixel-based mask representation is proposed for fast synthesis of model-based inverse lithography technology (ILT) to improve the resolution and pattern fidelity in optical lithography. This new algorithm reduces N² intensity computations to three (3) equivalent intensity computations per iteration, where N² is the total number of pixels in a mask. This algorithm has been demonstrated using different critical dimensions (CDs) and different mask technologies with incoherence and partial-coherence image models. This algorithm is about 60 times faster and more effective than the current gradient-based algorithm. The final image fidelity has quite a weak dependence on the initial condition. Good fidelity images are achieved when CD is reduced to 45 nm.