Printing 100-nm and sub-100-nm DRAM full-chip patterns with crosspole illumination in 0.63-NA ArF lithography

Abstract

To achieve lOOnm DRAM full chip with O.63NA ArF lithography we used a new type of off-axis illumination, crosspole illumination which has four poles on axis. For lower than 0.33 k1 process double exposure technology has been introduced which is exposing cell and core/periphery region separately with different illumination conditions. But with crosspole 0.33 to 0.3 1 k1 process could be possible without double exposure. Advantages and disadvantages of crosspole illumination and successful result of printing lOOnm DRAM full chip are shown in this paper. And also ArF lithography issues occurred during processing DRAM full chip are reported such as lens heating, contamination optics and reticles, overlay errors induced by electron beam curing process and so on. To simulate patterning result we used HOST(Hynix OPC simulation tool) based on diffused aerial image model(DAIM). For all kinds of lOOnm DRAM patterns, we could get sufficient process latitude, more than 10% exposure latitude(EL) and 0.4 jiiii depth of focus(DOF). Also 95nm DRAM cell patterns could be printed successfully with crosspole single exposure and this shows with 0.75NA and 0.85NA ArF tools we can print 8Onm and 7Onm DRAM patterns, respectively.