Optical resolution enhancement techniques and applications in optical lithography

Abstract

Lithographic improvements applying scattering bars, reducing wavelength from 248nm to 193nm, using attenuated PSM over binary mask and comparing conventional with annular illumination have been studied to extend optical lithography to 90nm node and below. Extracting from Fraunhofer diffraction equation for a double slit and incorporating contrast overlapping factor, a modified Rayleigha??s equation that considers influence of coherencies on lithographic resolution has been proposed. Experiments confirm that lithographic performance can be predicted more accurately by the modified equation. The application of shifter-width biasing combined with best taper-angle wedge chrome-face wall is proposed for altPSM image imbalance correction. The design is verified using geometrical theory of diffraction and industry standard simulator, SOLID-CM. The strength of TM-polarization is deduced to be sum of all horizontal components of the E-field for any illumination scheme. Single-exposure illumination can be achieved with self-polarized light, by incorporating fine wire mesh on top surface of the mask.