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

本文研究了q开关Nd:YAG激光器（quantum -ray DCR-2(10)）在Fe， W, Sm， Yb靶上产生的激光等离子体，用于x射线光刻的软x射线源。发现20-30度的激光束入射角是目标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。使用铁靶进行60-90秒（600-900脉冲）曝光，在光刻胶（日立Kasei RE-5000P）中完全再现了分辨率为0.0005 mm的黄金聚酰亚胺支持的分辨率测试图案，显示分辨率为500 nm或更高。采用离子束溅射法制备了多层反射镜，并用厚度灵敏度为0.01 nm的椭偏仪对多层反射镜进行了原位监测。Mo-Si 27层反射镜在正常入射（9.6度）波长为13.8 nm处的最大反射率为17.5%。使用WYCO表面轮廓仪，发现衬底和多层膜的RMS粗糙度约为0.6nm。由此研制的软x射线源和多层反射镜在软x射线光刻中显示出了应用的潜力。

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.