Prediction of in-plane distortions due to mask fabrication processes

In the fabrication of a typical refractory X-ray lithography mask, the pattern transfer process subjects the membrane/pattern to the non-uniform deposition and removal of multiple stressed layers. This removal process can result in unacceptably large pattern distortions in the final mask. This paper presents relationships obtained from finite element (FE) modeling, between pattern distortions and the following mask parameters: membrane material, thickness, size and stress, and the removed film material, thickness and stress. In addition, the sensitivity of the distortions was investigated for stress gradients present in the removed film. Finally, the capability of these models to predict pattern specific distortions (PSD) is demonstrated.