Aerial image prediction for mask defect in extreme ultraviolet lithography

Abstract

Simulation has been used to predict the aerial image for masks with perfect (defect free) multilayer mirror. However, in reality, defect is easily produced in extreme ultraviolet (EUV) lithography mask fabrication process because 40 Mo/Simultilayer films are stacked and each stack is made from 2 to 4nm. Thus, it needs to be really simulated a plate substrate with defects in EUV lithography. Many electromagnetic phenomena must be considered including geometrical shadowing, light penetration into the multilayer regions of tapered mask edges, and diffraction spreading and propagation in the presence of confining boundaries. Each of these phenomena potentially leads to worse than the ideal imaging performance. The electromagnetic near and far fields are calculated for ideal plate substrate case (defect free) and for non-planar substrate case (defect) mask structures by using finite difference time domain (FDTD) and transfer matrices and then, the results will be compared. Consequently, the aerial images with defects are also predicted from mask structure.