Efficient simulation and optimization of wafer topographies in double patterning

Abstract

As the technology marches toward the 32-nm node and beyond in semiconductor manufacturing, double-patterning and double-exposure techniques are currently regarded as the potential candidates to produce lines and spaces and contact holes, respectively. We employ the Waveguide method, a rigorous electromagnetic field (EMF) solver, to investigate the impact of wafer topographies on two specific double-patterning techniques. At first, the topography effects induced by the first patterning on the second lithography process in a lithography-etch-lithography-etch process are demonstrated. A new methodology of the bottom antireflective coating optimization is proposed to reduce the impact of wafer topography on resist profiles. Additionally, an optical proximity correction (OPC) of the second lithography mask is demonstrated to compensate the wafer-topography-induced asymmetric deformations of line ends. Rigorous EMF simulations of lithographic exposures are also applied to investigate wafer-topography effects in a freezing process. The difference between the optical properties of the frozen (first) resist and the second resist potentially causes linewidth variations. Quantitative criteria for tolerable refractive index and extinction differences between the two resist materials are given. The described studies can be used for the optimizations of topographic waferstacks, the OPC of the second litho mask, and for the development of resist materials with appropriate optical properties.