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10nm以下光刻技术牵引极紫外(EUV)光刻物镜向超高数值孔径(NA)、组合倍率设计形式发展,物镜系统的入射角和入射角范围因此急剧增大,传统规整膜和横向梯度膜难以满足该类物镜系统反射率及像质要求。为此,提出了横纵梯度膜组合法,用横向梯度膜提高反射率,用纵向梯度膜提高反射率均匀性,并补偿横向梯度膜引入的像差。应用该方法对一套NA为0.50的组合倍率EUV光刻物镜进行膜层设计,设计结果表明,在保证系统成像性能不变的情况下,平均每面反射镜的反射率大于60%,各反射镜的反射峰谷值均小于3.5%,满足光刻要求,验证了横纵梯度膜组合法的可行性。
Under the 10nm lithography technique, the EUV lithography objective has been developed to a high numerical aperture (NA) and combined magnification design. The incidence angle and incident angle range of the objective lens system thus sharply increase. Conventional regularization films and lateral gradient films Difficult to meet such objectives lens system reflectivity and quality requirements. For this reason, a combination of horizontal and vertical gradient films was proposed. The horizontal gradient film was used to increase the reflectivity. The vertical gradient film was used to improve the uniformity of reflectivity and compensate the aberration introduced by the transverse gradient film. The design of a set of combined magnification EUV lithography objective lens with NA of 0.50 was carried out by this method. The design results show that the average reflectance of each reflector is greater than 60% while the imaging performance of the system is not changed. The reflection peak and valley of the mirror are less than 3.5%, which meets the photolithographic requirements and verifies the feasibility of the horizontal and vertical gradient film combination method.