Verification of the effect of mask bias on the mask error enhancement factor of contact holes

Abstract

The mask error enhancement factor for contact holes is experimentally determined for 180 nm features under a variety of exposure conditions. Since its magnitude depends, in part, upon the slope of the aerial image, the value is calculated as a function of binary and phase shift masks, mask bias, and conventional and quadrupole illumination. The primary purpose is to compare experimental results to a simulation study and determine which simulation trends are accurately predicted. The results show that isolated contacts have lower MEEF than dense contacts but that dense contacts do not necessarily have the largest error factor. The magnitude of MEEF and the optimal bias that minimizes it are show to be accurately predicted.