BARC technology for 1.35 NA lithography

The work shown in this paper examines the effect of single and dual BARC on reflectivity at 1.35 NA using reflectivity simulations, coupled with process windows and swing curves, to gauge the effectiveness of reflection control for various BARCs on wafer. The BARC refractive index should be determined by the application, which in this case is the word line gate layer for 40 nm Flash memory. The materials required for best reflection control depends upon the film stack beneath it and the illumination used. An additional constraint is the thickness of the BARC film being scaled to thinner values as required by the future scaling of resist critical dimensions. Results from using two single layer BARCs and a dual organic BARC show what impact reflectivity has on various performances for gates in the center and edge of the array.