An Innovative Method for Contact Hole Printing with Binary Mask and Single Exposure

Abstract

We have introduced a new method for fine contact hole printing using a specially designed binary mask and modified illumination in a single exposure, which can realize k1=0.3 lithography. The binary mask has periodic assist holes around the main holes and the illumination is the combination of strong and weak off-axis parts. Conventionally, assist holes are placed in longitudinal and lateral directions around the main holes or 45° to the main pattern. In this paper, we will show that a new kind of assist hole configuration can be applied to this method and that the new configuration has better imaging characteristics in some cases. Since these three configurations can be utilized with the same illumination, a combination of these configurations in the same mask leads to a wider application of this method because conflicting patterns are avoided.