Optimisation of rim phase shift masks for contact holes
Cui Z., Prewett PD., Martin B.
Rim phase shift masks (PSMs) for contact holes have been evaluated using the SOLID software package. The image contrast is used as a criterion to determine the optimum rim width, taking account of the side-lobe effects. The optimum rim width is found to be 0.1λ/NA independent of feature sizes. In order to overcome the reduction of image intensity for small contact holes, a new design, called the partial rim PSM, is proposed for contact holes. Simulation results for the partial rim PSM are presented and compared with the biased rim PSM. The fabrication methods for the partial rim PSM are identical to those for the convetional rim PSM. © 1994.