An analysis of double exposure lithography options

The current optical photolithography technology is approaching the physical barrier to the minimum achievable feature size. To produce smaller devices, new resolution enhancement technologies must be developed. Double exposure lithography has shown promise as potential pathway that is attractive because it is much cheaper than double patterning lithography and it can be deployed on existing imaging tools. However, this technology is not possible without the development of new materials with nonlinear response to exposure dose. The performance of existing materials such as reversible contrast enhancement layers (rCELs) and theoretical materials such as intermediate state two-photon (ISTP) and optical threshold layer (OTL) materials in double exposure applications was investigated through computer simulation. All three materials yielded process windows in double exposure mode. OTL materials showed the largest process window (DOF 0.137 μm, EL 5.06 %). ISTP materials had the next largest process window (DOF 0.124 μm, EL 3.22 %) followed by the rCEL (0.105 μm, 0.58 %). This study is an analysis of the feasibility of using the materials in double exposure mode.