Optimization for imaging interferometric lithography in technology computer-aided design

Imaging Interferometric Lithography (IIL) exploits light interference to overcome the spatial frequency resolution limitation (∼ NA/λ) imposed by a conventional optical lithography system. IIL improves the resolution of aerial images to produce sub wavelength structures, and in the process provides a simple approach towards the ultimate optical spatial frequency coverage of 2/λ. Different than other imaging schemes in optical lithography, IIL modeling in Technology Computer-Aided Design (TCAD) requires specific attention to polarization effects in illumination light with high incident angles and spatial frequency shift-back characteristic via an extra reference plane wave after proper energy adjustments. In this dissertation, involving the use of multiple exposures and off-axis illumination that are similar to a filter bank structure in signal processing, automated software strategies based on image processing algorithms are developed to find the optimal solution that makes the best compromise between all of the desirable specifications needed for the lithography process and produces a robust, manufacturable low-cost process.; In the first promising IIL experiments, IIL different three-exposure strategies containing the same spatial frequency coverage were empirically investigated and results were significantly different. As a first step towards successful process configurations in IIL discussed in this dissertation, we examine pertinent equations for IIL theory to understand the factors that can play essential roles in the constructing of a fine-resolution aerial image/intensity and establish a special rigorous IIL modeling for lithography process. From a comprehensive grating-based analysis in the Fourier domain, we derive a set of optimal parameters for exposure energy ratio among exposures and search a proper set to improve the aerial image quality based on an evaluative error function to quantify the quality of images. Additionally, in comparing with the more traditional partial-coherent illumination imaging by common performance measures, we examine the relative strengths and weaknesses of IIL through different analyses. These signal-processing studies do provide additional support for IIL as a promising alternative Resolution Enhancement Technique (RET) for deep sub-wavelength optical lithography.