General framework for parameter optimization in imaging interferometric lithography

S. R. J. Brueck University of New Mexico Department of Electrical and Computer Engineering Department of Physics and Astronomy Albuquerque, New Mexico 87131 and Center for High Technology Materials University of New Mexico Albuquerque, New Mexico 87106 E-mail: [email protected] Abstract. Imaging interferometric lithography (IIL) employs the resolution enhancement technique (RET) of off-axis illumination (OAI) to overcome the spatial frequency resolution limitations that are imposed by the band limitedness of a conventional optical lithography system. IIL improves upon the aerial image resolution of a conventional optical lithography system by providing a wavelength division multiplexing approach toward the attainment of the maximum spatial frequency coverage of 2/l, which is independent of the numerical aperture of the optical system. IIL combines OAI, which provides access to higher spatial frequencies of the mask, with multiple exposures and several different configurations of the polarization parameters, the frequency parsing parameters, and the exposure energy ratios are possible. Although experiments detailing the resolution enhancement capabilities of IIL in isolated parameter settings exist, a unified approach toward parameter optimization in IIL that would enable automated software for TCAD is presently lacking. With the objective of providing a framework for parameter optimization in IIL, we propose in this paper, an approach that encompasses: (a) polarization diversity in the different on-axis or off-axis exposures of IIL, (b) an aggregate error metric for evaluating aerial image quality, (c) a blockbased optimization process that incorporates the proposed error metric on representative, smaller blocks of the mask, (d) an optimization process that determines the optimal parameter settings for the entire mask using the lessons learned from the blocks. This framework for optimization of parameters in IIL enables comparison of IIL with other contemporary RETs and also enables the study and analysis of hybrid approaches such as combinations of IIL with optimal proximity correction. Simulation results that demonstrate the efficacy of the IIL-based approach and reinforce its capabilities as a viable RET for subwavelength optical lithography are presented. © 2005 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.1898246]