椭球反射大孔径双通照明高分辨率共焦扫描测量方法与理论

In order to represent three dimensional weak scattering surfaces of micro-nano elements, principle and theories are investigated on elliptical mirror based scanning confocal microscopy with high focusing aperture and double pass illumination. Firstly, a focusing principle based on elliptical mirror is proposed to extend numerical aperture in the second pass illumination to 1, which is in theory the extreme aperture under non-immersion imaging systems. Secondly, a kind of double pass illumination is proposed to improve the sensitivity in scanning tomography by reflecting measuring beams passing over artifacts twice in one measurement, and then to establish a novel confocal response function compressing envelope of three dimensional response function. Thirdly, fluorescence effect introduced into industrial artifact measurement generates frequency shift in the second pass illumination, and thereby avoid cross-talking noises caused by double pass illumination. By simulations, in comparison with a conventional confocal system with NA=0.65, the transverse width of the response function envelopes will be compressed 2.16 and 2.65 times when the NA of first pass illumination objective is 0.1 and 0.65. And also, the corresponding envelopes in axial direction is compressed 5.72 and 4.52 times. The anticipated technique performances are listed to be 0.15um for lateral period scale resolution, less than 30nm compared error for transverse edge position identification and 1nm for axial position resolution in case of the height of the using standard grating lower than 50nm.

针对微/纳器件弱散射表面三维微结构表征问题，开展椭球反射大孔径双通照明高分辨率共焦显微测量机理研究，首先，提出椭球反射镜聚焦成像方法，将二次照明数值孔径拓展为"1"，达到非浸入成像系统孔径的理论极限；其次，提出双通照明方法，使测量光信号两次通过样品，构建新的共焦响应函数，实现三维共焦响应函数包络尺度压缩，提高层析扫描灵敏度；第三，在工业样品测量中引入荧光效应，在二次照明过程中产生信号频移，分离一次照明和二次照明的测量光，解决双通照明信号混叠干扰问题。仿真结果表明，当一次照明显微物镜NA=0.1和0.65时，与NA=0.65的传统共焦系统相比，其响应函数包络的横向宽度可被压缩2.16和2.65倍，轴向宽度可被压缩5.72和4.52倍。预期技术指标: 在标准样品台阶高度小于50nm 条件下，横向周期尺度分辨率为0.15um，横向边缘位置判别误差小于30nm，轴向位置分辨率达到1nm。

项目初步建立了高孔径椭球反射镜成像机制，给出系列高孔径椭球反射镜聚焦原始公式，并发展了反射成像系统的设计理论，开辟了基于高孔径椭球反射成像的光学显微仪器设计新途径。研究表明，椭球成像具有若干显著区别于透镜的聚焦特性，例如偶极子振动敏感性和纵向场能量集中等。相关椭球成像理论在航天、国防重大工程领域得到应用，实现了宽光谱、长工作距离显微测量，系统中心遮挡比与球面Schwarzschild物镜相比，遮挡比减小了77.5%。