Mask error enhancement factor variation with pattern density

Abstract

The mask error enhancement factor (MEEF) minimization is much emphasized due to the reduction of the device technology node. The MEEF is defined as how mask critical dimension (CD) errors are translated into wafer CD errors. We found that the pattern density had influenced the MEEF and the MEEF changed with the pattern density variation. We also tried to obtain the 90 nm CD value with optimized diffusion length of the chemically amplified resist. It turned out that a very small diffusion length should be used to get the desired 90 nm line width with 193 nm. We used line and space (L/S) dense bars, 3 L/S bars only and isolated line pattern for the pattern density dependency and to obtain different MEEFs. In order to determine the MEEF by the various pattern densities, a commercial simulation tool, Solid-E, was used. We could obtain the minimum MEEF values for the different pattern densities by using this procedure.