为了实现掩膜面的均匀照明, 采用非球面技术对浸没式光刻照明系统中会聚镜进行了设计, 并对影响系统远心度的误差源进行了分析。设计的会聚镜数值孔径的一致性偏差在0.2%以内, 像方远心度小于0.2 mrad, 以系统的远心度变化0.1 mrad, 数值孔径一致性变化0.1%, 点列图变化20 μm, 焦距变化0.1 mm为公差基础值, 计算出会聚镜的厚度公差为±0.02 mm～±0.05 mm, 单面倾斜10″～20″。该浸没式光刻照明系统中会聚镜的设计合理, 制定的公差可行, 能够满足硅片面上照明非均匀性小于3%的要求。

In order to achieve uniform illumination of the mask surface, the converging lens of an immersion lithography illumination system was designed, and the error sources of the system telecentricity were analyzed. The uniformity deviation of the designed numerical aperture of the converging lens is within 0.2% , and the image telecentricity is less than 0.2 mrad . Taking the system’s telecentricity variation of 0.1 mrad , the numerical aperture uniformity variation of 0.1% , the point spread function variation of 20 μm and the focal length variation of 0.1mm as the tolerance basis values, the thickness tolerance of the converging lens is calculated to be ±0.02 mm to ± 0.05 mm and the surface inclination within 10" to 20". It is concluded that the design of the converging lens for the immersion lithographic illumination system is reasonable and the tolerance is practical to meet the non-uniformity lighting requirement on the wafer surface less than 3%.