大高宽比硬X射线波带片制作及聚焦测试

Fabrication and focusing test of hard X-ray zone plates with high aspect ratio

为得到同步辐射光源硬X射线波段(>2keV)需要的高宽比高分辨率波带片,本文利用高加速电压(100kV)电子束光刻配合Si3N4镂空薄膜直写来减少背散射的方法,对硬X射线波带片制作技术进行了蒙特卡洛模拟和电子束光刻实验。模拟结果显示:Si_3N_4镂空薄膜衬底可以有效降低电子在抗蚀剂中传播时的背散射,进而改善高密度大高宽比容易引起的结构倒塌和粘连问题。通过调整电子束的曝光剂量,在500nm厚的镂空Si_3N_4薄膜衬底上制备出最外环宽度为150nm、金吸收体的厚度为1.6μm,高宽比大于10的硬X射线波带片。同时,引入随机支撑点结构,实现了波带片结构自支撑,提高了大高宽比波带片的稳定性。将利用该工艺制作的波带片在北京同步辐射装置X射线成像4W1A束线8keV能量下进行了聚焦测试,得到清晰的聚焦结果。

The high resolution hard X ray(>2keV)Fresnel zone plates with high density and high aspect ratio was fabricated for Synchrotron Radiation Light Source.The electron beam lithography and the fabrication of hard X ray zone plates were simulated with Monte Carlo method by combining high accelerating voltage(100kV)with Si3N4self standing film to reduce the backscattering.The simulation result shows that Si3N4self standing film substrate effectively reduces backscattering when electrons propagate in the resist,so that the structure collapse and adhesion caused by high density and high aspect ratio are overcome.By adjusting the electron beam exposure dose,hard X ray Fresnel zone plates with the outermost ring width of150nm,gold absorber thickness of1.6μm and the aspect ratio more than10were fabricated on a500nm Si3N4self standing film.Meanwhile,a random support structure was introduced to realize the self support of the zone plates and to improve their stability.The focusing properties of the zone plates fabricated were tested with energy of8keV at4W1A beamline of Beijing Synchrotron Radiation Facility,and a clear focusing result was obtained.