分辨力增强技术的频谱分析

Spatial Frequency Analysis of Resolution Enhancement Technology

离轴照明和衰减型相移掩模作为重要的分辨力增强技术,不仅可以提高光刻的分辨力,同时还可以改善成像焦深,扩大光刻工艺窗口,实现65-32 nm分辨成像。从频谱的角度分析了离轴照明和衰减型相移掩模对成像系统交叉传递函数和像场空间频率分布的影响,研究这两种技术的物理光学本质,由此进一步优化光学成像系统设计、分辨力增强技术和确定设备使用的参量。对分辨力增强技术的频谱分析研究表明,分辨力增强技术通过调整像场频谱分布,改善了光学光刻的图形质量。对于65 nm密集图形,离轴照明和相移掩模结合后可以使成像衬比度最高达到0.948,工艺窗口在5%曝光范围内焦深达到0.51μm。

As two of the most important resolution enhancement technology （RET）, off-axis illumination （OAI） and attenuated phase-shift mask （AttPSM） can not only improve image quality, but also improve the depth of focus （DOF） to get a better process window which make a great contribution to the realization of 65-32 nm technological mode. A consistent frequency-space analysis of the off-axis illumination and attenuated phase-shift mask is presented here to explain its influence to the transmission cross coefficient （TCC） and image frequency distribution. Study on the optical mechanism of these resolution erbancement technology can benefit the design of projection lens optical system, optimization of resolution enhancement technology and the parameter setting of lithographic tool . It shows resolution erbancement technology can adjust image frequency distribution to enhance the lithographic resolution and image quality. As for 65 nm node pattern, off-axis illumination and phase-shift mask can improve image contrast to 0. 948, process window to depth of focus 0.51 μm while exposure latitude is 5 %.