Optical proximity correction on attenuated phase-shifting photo mask for dense contact array

The application of attenuated PSM to dense contact array is restricted by intense optical interference of sidelobe peaks around hole pattern which is called proximity effect. In order to reduce the effect of proximity, it is necessary to optimize the transmittance of mask field and the exposing energy which cause mask bias. The vast of data are required for doing above job. Using simulation, however, by sidelobe, E- D curves can not be used directly to find the depth of focus. The criterion for sidelobe was defined to find process window from E-D curve. To reduce sidelobe in dense contact hole array, the auxiliary patterns were placed between holes. By simulations and experiments, attenuated PSM with auxiliary pattern could be applied effectively to the dense contact hole of 64MDRAM.