Development of Soft X-Ray Sources and Optical Elements for X-Ray Lithography

本文研究了用调Q Nd：YAG激光器（Quanta-Ray DCR-2（10））在Fe、W、Sm、Yb等金属靶上产生的激光等离子体。发现激光束到靶的20-30度入射角是掩模对靶材料沉积的污染水平和软X射线输出的有用水平之间的最佳折衷。60-90秒在使用Fe靶的（600-900个脉冲）曝光中，在光刻胶中完全再现了0.0005 mm分辨率的金中的聚酰亚胺支持的分辨率测试图案（Hitachi Kasei RE-5000 P），显示出500 nm或更好的分辨率。其通过具有0.01nm厚度灵敏度的椭圆偏振计原位监测。Mo-Si 27层反射镜在垂直入射（9.6度）下在13.8nm的波长处显示出17.5%的峰值反射率。用WYCO表面轮廓仪测得基片和多层膜的RMS粗糙度约为0.6nm。由此研制的软X射线源和多层膜反射镜显示了其在软X射线光刻中的应用潜力。

Laser-produced plasmas generated on Fe, W, Sm, Yb targets by a Qswitched Nd:YAG laser (Quanta-Ray DCR-2(10)) have been studied for the purpose of a soft x-ray source for x-ray lithography. 20-30 degree angle of incidence of laser beam to the target was found to be best compromise between a contamination level og a mask fue to deposition of target material and a useful level of the soft x-ray output. With 60-90 sec (600-900 pulses) exposures using a Fe target, a polyimide supported resolution-test pattern in gold for 0.0005 mm resolution was fully reproduced in photo-resist (Hitachi Kasei RE-5000P), showing a resolution of 500 nm or better.Multilayer mirrors were fabricated by ion-beam sputtering, which was in-situ monitored by an ellipsometer having 0.01 nm thickness sensitivity. A Mo-Si 27-layer mirror showed a peak reflectivity of 17.5% at a wavelength of 13.8 nm at normal incidence (9.6 degrees). Using a WYCO surface profiler, RMS roughness of the substrates and the multilayers was found to be about 0.6nm.The soft x-ray source and the multilayer mirror thus developed have shown their potentiality for the application to soft x-ray lithography.