Reduction of mask error enhancement factor (MEEF) by the optimum exposure dose self-adjusted mask

摘要

To reduce mask error enhancement factor (MEEF), we have developed the new type half-tone phase shift mask (HTPSM) in which transparent regions are surrounded by opaque rims. We evaluated the imaging performance of contact hole patterns including the MEEF and the depth of focus (DOF). Using this new method, we obtained about 2.0 MEEF and 0.7-μm DOF for 180-nm isolated hole, which was much better than that in the conventional mask such as binary mask or HTPSM (the MEEF more than 3). The advantage of our method was that it was possible to attain both the MEEF reduction and the DOF enhancement by the optimization of mask hole size and rim width. Furthermore, we confirmed that this new method was effective not only for improving the exposure dose latitude but also for attenuating side-peak effect.