高数值孔径光学光刻成像中的体效应

为有效控制成像线宽,研究了高数值孔径光学光刻中的体效应并提出一种光刻胶膜层优化方法,利用成像中的摇摆效应平衡体效应对成像线宽的影响.首先根据系统数值孔径和照明相干因子确定成像光入射角分布,相对所有入射光求出光刻胶底面单位体积吸收的能量平均值.然后用最小二乘法拟合得到能量平均值随光刻胶厚度变化的解析式并求能量平均值的导数.最后通过优化光刻胶膜层,使能量平均值的导数绝对值最小.按优化结果设计光刻胶膜层,利用商业光刻软件Prolith9.0得到成像线宽随光刻胶厚度的变化.结果表明,该方法能在30～40nm的光刻胶厚度范围,有效地减小由体效应引起的成像线宽的变化.

Bulk Effects in Hyper-Numerical Aperture Optical Lithography

To control critical dimension (CD) effectively, bulk effect is studied in hyper-numerical aperture (NA) optical lithography and a novel optimization strategy for resist film stacks is developed to balance bulk effect with appropriate swing effect. Firstly, the incident angle distribution of imaging light is evaluated based on NA and coherence factor σ settings, so that the average energy () absorbed per unit volume in the resist at the resist bottom surface is calculated over the whole range of incident angle. Secondly, the analytic relationship between and resist thickness (d) is obtained by fitting with least-squares procedure and the derivative of with respect to d is calculated. Lastly, the resist film stacks are optimized to minimize the derivative of . With the optimized thin-film stack structure design, the CD variation with resist thickness is obtained by using commercial software Prolith 9.0. The results show that the optimization strategy can effectively overcome CD variation from the bulk effect over the thickness range of 30～40 nm.