22nm极紫外光刻物镜热和结构变形及其对成像性能影响

极紫外光刻技术(EUVL)是半导体制造实现22nm及其以下节点的下一代光刻技术。在曝光过程中,EUVL物镜的每一面反射镜吸收35%～40%的入射极紫外(EUV)能量,使反射镜发生热和结构变形,影响投影物镜系统的成像性能。基于数值孔径为0.3,满足22nm技术节点的产业化EUV投影物镜,采用有限元分析(FEA)的方法研究反射镜变形分布,再将变形导入光学设计软件CODE V中,研究反射镜变形其对成像特性的影响。研究结果表明:当达到硅片的EUV能量为321mW,产量为每小时100片时,反射镜最高升温9.77℃,通光孔径内的最大变形为5.89nm;若采用相干因子0.5的部分相干光照明,变形对22nm线宽产生6.956nm的畸变和3.414%的线宽误差。

Thermal and Structural Deformation of Projection Optics and Its Influence on Optical Imaging Performance for 22 nm Extreme Ultraviolet Lithography

Extreme ultraviolet lithography (EUVL) is the next generation lithography for the semiconductor manufacturer to achieve 22 nm node and below. In the process of exposure, the 35%～40% incident power will be absorbed by multilayers of extreme ultrauiolet (EUV) optics, resulting in the thermal and structural deformation of the mirror, and consequently affecting the optical performance of the projection optics (PO). It is based on a six-mirror PO designed for EUVL at 22 nm technology generation with an image numerical aperture of 0.3. Finite element analysis (FEA) method is used for the deformation analysis of the six-mirror PO, and then the deformation is introduced to CODE V to evaluate its effect on the PO. The results show that the maximum temperature increase is 9.77 ℃, and the maximum deformation at clear aperture is 5.89 nm, with the beam power of 321 mW onto the wafer and wafer throughtput reaches 100 wafers per hour. While it is partial coherently illuminated (partial coherent factor 0.5), the distortions of 22 nm line and space is 6.956 nm, critical dimension (CD) error is 3.414%.