EUV掩模版在曝光过程中的热变形

极紫外光刻(EUVL)技术是实现45 nm特征尺寸的候选技术之一,产业化设备要求300 mm硅片的产率大于每小时80片(80 wafer/h),此时入射到掩模版上的极紫外光功率密度很高,掩模版上的吸收层和Mo/Si多层膜将分别吸收100%和35%的入射光能量,从而导致其热变形,引起光刻性能下降,因此必须分析和控制掩模热变形。利用有限元方法分析掩模版在不同功率密度下的热变形,结果表明,抗蚀剂灵敏度为7 mJ/cm2和5 mJ/cm2时,入射到掩模版上的光功率密度分别为259.24 W/cm2和184.38 W/cm2,掩模版图形区域x-y平面内最大变形分别为1.11 nm和0.71 nm,z方向最大变形分别为0.26 nm和0.19 nm。

Thermal Distortion of EUV Reticle during Exposure

Extreme ultraviolet lithography(EUVL) is one of all candidate next-generation lithography technologies targeting 45 nm features,the industrial throughput should be more than 80 wafers-per-hour.As the throughput requirements are increased,the incident EUV power on reticle density rise.About 100% the incident power is absorbed by the absorber layer and 35% is absorbed by Mo/Si multi-layers to result in a significant thermal distortion in the reticle.Such effects can contribute to reticle-wafer overlay error,so it is necessary to quantify the reticle distortion.In this work,detailed three-dimensional thermal and structure models have been developed using finite element methods.The results show that the maximum in-plane distortion in x-y plane and z indirection are respectively about 1.11 nm and 0.26 nm when the sensitivity of the resist and the EUV power density are respectively 7 mJ/cm~2 and 259.24 W/cm~2,and they are respectively about 0.71 nm and 0.19 nm when the sensitivity and the power density are 5 mJ/cm~2 and 184.38 W/cm~2 respectively.