1×11亚波长结构Dammann光栅的研制

Study on 1×11 Dammann grating with sub-wavelength structure

论文基于严格耦合波理论(Rigorous Coupled-Wave Analysis,RCWA),并采用遗传算法进行优化,设计并制作了一种具有高衍射效率的亚波长结构Dammann光栅。光栅的分束比为1×11,最小特征尺寸为0.95μm,衍射效率设计值达到95%,优于传统Dammann光栅约15%,且均匀性设计值小于2%。论文采用电子束光刻直写技术和反应离子刻蚀技术在石英基底上制作出亚波长结构图形。实验结果表明,电子束扫描曝光可以获得纳米级的图形分辨率。对石英基底的反应离子刻蚀中,射频功率、工作气压及气体流量均对刻蚀速率和栅线的表面形貌产生不同程度的影响,论文主要针对该问题进行了讨论。同时,论文也对电子束光刻直写过程中产生的线宽误差因素进行了分析。

In this paper, a high-diffraction efficiency Dammann grating with sub-wavelength structure was designed and prepared based on the Rigorous Coupled-Wave Analysis （RCWA） theory and optimized by the genetic algorithm. The array number of diffractive spots was 11 and the minimum feature size achieved 0.95μm. The design value of diffraction efficiency can achieves 95%, around 15% more than conventional Dammann grating while the uniformity can be less than 2%. By using Electron Beam Direct Writing and Reactive Ion Etching, the sub-wavelength structure was patterned on the silica basement. The experimental results show that the sub-wavelength structure with nanometer resolution can be patterned by electron beam scanning exposure. In reactive ion etching, the etching rate and the grating line-shape can be affected by radio frequency （RF） power, system pressure and gas flow, and the line-width error in Electron Beam Direct Writing was also analyzed.