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In the single-beam illuminating 3PIE (ptychographic iterative engine)method,the specimen is vertically illuminated without considering the influence of oblique illumination on the reconstruction result.In this paper,a dual-beam illuminating 3PIE method is proposed on the basis of the single-beam illuminating 3PIE method,and the simulation result shows that the reconstructed images are influenced by the phase inclination factor of the initial guessed illumination light beam.In the process of iterative recovery by the proposed method,two light beams are used to update the complex amplitude distribution of the same specimen area.The proposed method is demonstrated theoretically and experimentally. The results verify that the method can improve the convergence speed while weakening crosstalk between different specimen slices,and it is suitable for three-dimensional depth resolved imaging.

A dynamic source mask optimization (SMO) method is developed. The dynamic SMO method uses a dynamic fitness function in genetic algorithm to simulate the process variations in real lithography process. So the imaging quality of the optimized source and mask is not sensitive to the process errors. The dynamic SMO method can get similar result as the conventional weighted SMO method without the necessity of weighting coefficient optimization. Simulation results show that the dynamic method can get a usable defocus of 200 nm when the dose error is 15%. This is comparable with the optimized result of the weighted method. The dynamic SMO method can be also used to make the optimized source and mask less sensitive to other process errors, such as coma errors.