Weighted iterative algorithm for beam alignment in scanning beam interference lithography.

Abstract

To obtain low phase errors and good interference fringe contrast, an automated beam alignment system is used in scanning beam interference lithography. In the original iterative algorithm, if the initial beam deviation is large or the optical parameters are inappropriate, the beam angle (or position) overshoot may exceed the detector's range. To solve this problem, a weighted iterative algorithm is proposed in which the beam angle and position overshoots can be suppressed by adjusting the weighting coefficients. The original iterative algorithm is introduced. The weighted iterative algorithm is then presented and its convergence is analyzed. Simulation and experimental results show that the proposed weighted iterative algorithm can reduce the beam angle and position overshoots at the expense of convergence speed, avoiding the alignment failure caused by exceeding the detector's range. Besides, the original and weighted iterative algorithms can be combined to optimize the iteration.