90nm DUV光刻物镜重力变形及其对波像差影响分析

Effect of Gravity Deformation on the Wavefront of 90nm Deep Ultraviolet Lithography Projection Optics

本文基于数值孔径为0.75,满足90 nm技术节点的DUV光刻物镜系统,采用在透镜边缘施加支撑力的方式进行重力变形控制。采用有限元法研究透镜表面非球面变形与补偿力的关系,分析补偿后透镜重力变形对系统波像差的影响并与补偿前系统进行对比。结果表明:加边缘补偿力后,透镜非球面变形均方根最大值由50.877 nm减小至26.675 nm,但补偿后系统波像差均方根最大值由0.041λ增大到0.055λ。由此可以得出结论:该补偿方式能够有效补偿透镜表面非球面变形,但补偿后系统波像差反而增大,所以要降低系统的波像差,不仅需要减小透镜变形,同时还需考虑各透镜变形之间的相互补偿作用。

The gravity deformation of the lenses is controlled by force mounting in their under surface margin. Finite Element Analysis （FEA） method is used to analyze the relationship between the lens surface’s non-spherical deformation and the compensating force. The deformation data are fitted to Zernike coefficients. Compared with the wavefront of projection optics before and after compensation, the influence of gravity deformation can be evaluated. The results show that the max non-spherical deformation RMS is decreased from 50.877 nm to 26.675 nm because of compensating force. However, the max wavefront error-root mean square value of projection optics is increased from 0.041λ to 0.055λ. Although the gravity deformation can be controlled by the compensating force efficiently, the wavefront aberration of projection optics is increased. The gravity deformation cooperation of the lenses should be considered so as to achieve better wavefront.