Using FlexRay in Computational Lithography

Abstract

FlexRay programmable illumination and LithoTuner software is combined in several use cases. The first use case is source mask optimization (SMO) in which the process window is maximized for a static random access memory (SRAM) design. In a 55 nm half-pitch contact hole array (k1 = 0.38, NA= 1.35, λ= 193 nm), the process window (PW) with FlexRay programmable illumination is twice as large as the PW with cQuad illumination defined through completely refractive illumination. The second use case is optical proximity error (OPE) minimization in which the large PW from SMO is realized on every scanner in the fab. The OPE error is reduced by 17% with LithoTuner and FlexRay. The third use case is matching two ArF scanners, a 1950i with FlexRay to a 1700i with diffractive optical element (DOE) illumination. With LithoTuner and FlexRay, the root means squared (rms) critical dimension (CD) error is reduced by 29% in this third use case. The last use case, intrafield dose optimization with DoseMapper is combined with FlexRay programmable source optimization to reduce the CD error on a wafer from a mean-to-target critical dimension (CD) error in the mask manufacturing process. This combination was optimized with LithoTuner to reduce the root mean square (rms) wafer CD error by 30%.