Distortion analysis of stencil masks with stress-relief structures

We present an exact solution to an axially symmetric continuum model of distortion in stencil masks. A correction procedure is studied where the pattern displacement vectors are calculated from a linear approximation to the pattern distribution function. For practical mask patterns this can reduce distortion to near the levels needed for very large scale integration. Additional gains can be achieved by using a ring of perforations around the integrated circuit field to reduce stress. Corrected distortion figures below 20 nm on a 60 mm mask seem possible. (C) 1995 American Vacuum Society.