薄膜界面特性对多层膜纳米光栅线宽粗糙度的影响

The precise measurement of the nanoscale linewidth is one of the core technologies for the large scale integrated circuit. The measuring instruments, like scanning electron microscope, etc., have intrinsic measurement errors, and they must be calibrated by the nanosclae length transfer standards to precisely determine the value of the nanoscale linewidth. The multilayer gratings are mainly used as length transfer standards whose length is less than 50 nm. The linewidth accuracy of the multilayer grating is mainly dependent on the line width roughness (LWR). The large scale integrated circuit requires that the LWR must be less than 4% of the linewidth. The interfacial characteristics of multilayer have the biggest influence on the LWR of multilayer grating. Previous studies focused on the interfacial roughness but neglected the contribution from the interfacial diffusion layer. Without a comprehensive understanding of this issue, the LWR of multilayer gratings is still not low enough to meet the requirement of 14 nm length transfer standard. A new solution is proposed here to investigate the influence of both interfacial diffusion layer and interfacial roughness on the LWR of multilayer grating. By controlling the fabrication parameters, the dependence of LWR on the interfacial diffusion layer and interfacial roughness is studied in isolation, which helps to find the direction for material selection and process optimization. Then the fabrication process is optimized to control the interfacial diffusion layer and interfacial roughness simultaneously. With the optimal fabrication parameters that lead to the minimized LWR, the 14 nm multilayer grating transfer standard is prepared.

纳米级线宽尺寸的精确表征是大规模集成电路的核心技术之一。扫描电子显微镜等测量工具均存在误差，需使用纳米级长度传递标准校正，才能精确测定线宽尺寸。50nm以下长度传递标准主要使用多层膜光栅。多层膜光栅的线宽精度取决于线宽粗糙度的大小，大规模集成电路要求线宽粗糙度小于线宽的4%。薄膜界面特性是影响多层膜光栅线宽粗糙度的关键因素，已有研究主要关注薄膜界面粗糙度的影响而忽略了薄膜界面扩散层的作用，认识不够全面；降低多层膜光栅线宽粗糙度的研究遇到了瓶颈，至今仍未能实现14nm多层膜光栅传递标准。本项目提出了综合考虑薄膜界面扩散层和界面粗糙度对多层膜光栅线宽粗糙度影响的新思路。通过制备工艺控制，孤立因素，分别研究界面扩散层和界面粗糙度对多层膜光栅线宽粗糙度的影响规律，明确薄膜材料选择和制备工艺的优化方向。探索综合控制界面扩散层和界面粗糙度的光栅制备技术，降低线宽粗糙度，研制14nm多层膜光栅传递标准。