数字光刻缩微投影系统物镜的设计

Design of Reduced Projection Lens for Digital Lithography

针对高精度数字光刻的缩微光学投影系统,提出并设计了一种适用于0.7XGA型数字微反射镜(DMD)的6片式数字光刻缩微投影物镜。通过优化和拼接三片式物镜结构,得到数值孔径NA=0.1,放大倍率为-0.2558,分辨力达3.5μm,不受DMD栅格效应影响且达到衍射极限的缩微物镜。经过Zemax软件模拟得到其全视场光程差小于λ/5,145cycles/mm处的调制传递函数(MTF)大于0.58,充分说明该缩微物镜已经达到光刻物镜设计要求。利用Monte Carlo分析方法,模拟加工装配了100组镜头,设定空间频率为145cycles/mm时,90%的镜头FMTF>0.55,验证了加工装配实际可行。

For the reduced-magnification optical projection system in high precision digital lithography, a kind of digital lithography projection lens, composed of six lenses and suitable for 0.7XGA Digital Micro-mirror Device （DMD）, is developed and designed. Through optimizing and splicing the three pieces of lens＇ structure, the objective lens, of which numerical aperture NA=0.1, magnification -0.255 8 and resolution 3.5 pm, is obtained. The results of Zemax software show that it reaches the diffraction limit, which is not affected by DMD grid effect. The optical path difference is less than 2/5 and MTF is more than 0.58 at 145 cycles/mm, which shows that it meets the requirement of the lithography lens＇ design. Utilizing Monte Carlo method to analyze the tolerance, 100 groups of lenses＇ assembling and fabricating are simulated. The result indicates 90% of the lenses＇ FMTF〉0.55 when setting the space frequency to 145 cycles/mm, which verifies the practicability of lenses＇ assembling and fabricating.