Ma Xu, Arce Gonzalo R, Li Yanqiu
Key Laboratory of Photoelectronic Imaging Technology and System of Ministry of Education of China, School of Optoelectronics, Beijing Institute of Technology, Beijing, China.
Appl Opt. 2011 Oct 1;50(28):5567-76. doi: 10.1364/AO.50.005567.
Gradient-based phase-shifting mask (PSM) optimization methods have emerged as an important tool in computational lithography to solve for the inverse lithography problem under the thin-mask assumption, where the mask is considered a thin two-dimensional object. As the critical dimension printed on the wafer shrinks into the subwavelength regime, thick-mask effects become prevalent and thus these effects must be taken into account in PSM optimization methods. Thick-mask effects are particularly aggravated and pronounced in etching profiles with abrupt discontinuities and trench depths. PSM methods derived under the thin-mask assumption have inherent limitations and perform poorly in the subwavelength scenario. This paper focuses on developing three-dimensional PSM optimization methods that can overcome the thick-mask effects in lithography systems with partially coherent illumination. The boundary layer model is exploited to simplify and characterize the thick-mask effects, leading to a gradient-based PSM optimization method. Several illustrative simulations are presented.
基于梯度的相移掩模（PSM）优化方法已成为计算光刻中的一种重要工具，用于在薄掩模假设下解决逆光刻问题，其中掩模被视为薄二维物体。随着晶圆上印刷的关键尺寸缩小到亚波长范围，厚掩模效应变得普遍，因此在PSM优化方法中必须考虑这些效应。厚掩模效应在具有突然不连续性和沟槽深度的蚀刻轮廓中尤为严重和明显。在薄掩模假设下推导的PSM方法存在固有局限性，在亚波长场景中表现不佳。本文重点开发三维PSM优化方法，以克服部分相干照明光刻系统中的厚掩模效应。利用边界层模型简化和表征厚掩模效应，从而得到基于梯度的PSM优化方法。给出了几个说明性模拟。
