Minimization of X-ray mask distortion by two-dimensional finite element method simulation

X-ray mask distortion caused by absorber stress is quantitatively analyzed by using two-dimensional simulation. Simulated results successfully predict the mask pattern distortion in practical mask structures. A square mask window is better than a circular one because the distortion for square windows can be minimized by reducing the pattern length. In addition, it is found that the maximum distortion is virtually the same regardless of the number of LSI chips within the square window mask.