利用X射线光刻技术研制X射线相衬成像光栅

X-ray phase contrast imaging would be widely used because of the superiority over the absorption contrast imaging on soft tissues of tumour. The X-ray phase contrast imaging research is limited by the lack of phase contrast imaging gratings with excellent high aspect ratio. We fabricate the phase contrast grating with excellent qualities using X-ray lithography and test it with X-ray phase contrast imaging facilities. The simulation of the imaging process will be firstly carried out with different parameters and errors of the gratings to evaluate the effect on the imaging of the gratings and the optimization of the grating is carried out according to the simulation result. The nanopillar technique developed in our lab will be employed and the strengthened structure will be introduced to avoid the collapse of the PMMA structure. The electroplating facility will be improved and the electroplating liquid will be adjusted to keep the stability and uniformity of the electroplating process. The gratings with period of 4~6μm and height of more than 46μm will be eventually fabricated. The X-ray self-imaging and phase contrast imaging with X-ray phase contrast imaging facilities will be carried out for the performance test of the grating.

X射线相衬成像对癌症肿瘤等软组织的成像质量远高于传统的吸收成像，因此具有广阔的应用前景。但由于高深宽比X射线光栅的研制困难，国内相衬成像研究受到很大限制。本项目利用X射线光刻技术研制X射线光栅并研究其性能。首先模拟计算不同参数光栅结构对成像质量的影响，并据此优化光栅结构。研究采用本实验室开创的纳米岛技术及加强筋结构解决PMMA支撑结构变形和倒塌问题。通过对电镀装置的改造、电镀过程的监控调节等研究解决电镀均匀性与稳定性问题。研制出周期4~6μm，高度大于46μm的吸收光栅。采用同步辐射X射线成像装置研究光栅自成像和相衬成像性能。

X射线相衬成像技术相比传统的吸收成像更清晰，能反映出更多的样品信息，尤其在医疗方面有重要的应用前景。X射线相衬成像技术近年来发展迅速，但国内成像研究受困于大高宽比的吸收光栅的缺乏，目前国内的成像实验所用到的吸收光栅基本都是从欧洲购买的。本项目研究采用X射线深度光刻的优势，研制大高宽比的吸收光栅，为国内相衬成像研究提供关键元器件。首先通过模拟计算，优化确定了光栅参数。重点解决了厚胶样品制备中的粘附性与内应力问题，制备出了符合本研究的厚胶样品。通过改进X射线掩模制作工艺，制备了高质量的X射线光刻掩模，并进行了X射线光刻。通过对电镀池的改造及电镀电源稳定性的提升，电镀出了满足目标参数的大高宽比光栅。光栅参数如下：有效面积20mm×20mm，周期4μm，占空比约0.5（即线条与间距比例约1:1），厚度达到99μm，远超过预期的46微米。采用RIE刻蚀方法对电镀后的样品进行去胶，得到硅衬底的光栅样品。通过光学显微镜及扫描电镜等进行了光栅性能参数的测量表征。本项目研制的光栅得到了研究同行的高度评价，目前中科院高能所朱佩平老师团队正在搭建测试成像系统，采用本项目研制的光栅进行成像实验。同时北京师范大学的刘志国老师团队也与本项目负责人探讨，计划采用该光栅进行成像实验研究。