A method of tolerance analysis for wavefront error of lithographic projection lens

A simple and reliable method of tolerance analysis is proposed to ensure the performance of lithographic projection lens and minimize the manufacturing costs of lithographic projection lens. This method defines P-V wavefront error as merit function based on RMS wavefront error, and selects the optimal compensators. Compared to present methods, this method decreases mechanical complexity and minimizes the manufacturing costs by adopting less compensators, with both RMS wavefront error and P-V wavefront error achieving the requirement. As an example the method is applied to a refractive projection lens for 90nm resolution lithography projection lens designed by us. The results show that, only with 7 compensators, RMS wavefront error and P-V wavefront error at 97.7% probability are less than 0.0412 λ and 0.2469 λ, respectively. In conclusion, this method is able to meet the performance requirement of lithographic projection lens.