涡旋光诱导不透明亚波长激光直写

Based on technique of far fields modulating near fields, a novel laser direct writing technology, combining traditional focused laser lithography with vortex laser induced opacity of photochromic material, was first proposed. We call it the vortex laser induced opacity direct writing, which is capable of producing sub-wavelength patterns. A composite photoresist layer can be made by coating the photochromic material on the traditional photoresist layer, and a vortex light can be produced by the way of computer generated hologram, spatial light modulator or vortex phase plate.In votex laser direct writing system, the coaxial 405nm lithography laser and 532nm vortex laser through the same objective lens are focused on the composite photoresist layer.If focused vortex laser spot illuminates photochromic layer, some areas of the photochromic layer covered by the hollow part of vortex laser spot get low absorbance at 405nm, while those covered by the annual part of vortex laser get high one, then a transparent aperture for 405nm lithography laser in the photochromic layer is created. Thanks to the aperture, the exposure area of diffraction limited lithography laser spot gets extra constriction, so the super-resolution laser lithography at 100nm linewidth can be achieved.

以远场光调制近场光为基本原理，首次将涡旋光诱导光致变色材料不透明机制加入聚焦激光直写系统中，以实现亚波长线宽的激光直写，称之为涡旋光诱导不透明激光直写。将光致变色材料通过旋涂涂覆在传统光刻胶层上可形成复合光刻胶层；通过计算全息法、空间光调制器或涡旋相位板法可产生涡旋光。在涡旋光诱导不透明激光直写系统中，同轴的405nm的光刻光与532nm的涡旋光经物镜聚焦后形成重叠光斑，投射在复合光刻胶层上。当光致变色层被涡旋光斑照射时，涡旋光中空结构处的光致变色层对光刻光的吸光度减小、涡旋光环状结构处的光致变色层对光刻光的吸光度增加，从而在光致变色层中形成一个对于光刻光透明的圆形通光孔。衍射受限的光刻光在光刻胶层上的曝光区域因此受到此通光孔的进一步约束，从而实现100nm量级的超分辨激光光刻。

超分辨光刻能产生亚波长线条，可用于超表面、超材料等微纳结构。本研究以远场光调制近场光为基本原理，将涡旋光诱导光致变色材料不透明机制加入聚焦激光直写系统中，实现亚波长线宽制作。. 研究内容包括涡旋光约束曝光的机理、复合胶层的选择及调焦的实现方法。涡旋光由相位板产生，涡旋光的阶数l和相位板的级数m直接影响聚焦涡旋光斑的光场约束效果，仿真表明多级分数阶且l=1.5、m=2时，有最好的结果，实验在405nm入射波长下制备了线宽146.7nm的均匀线条。复合胶层采用MiR701正胶与DTE变色材料的PVA薄膜作为最佳双层膜结构，写入波长375nm，限制波长671nm，实现了66.6%的线宽压缩比。涡旋光束既用于光场约束，也被用来调焦，当聚焦涡旋光在基片表面返回后，通过平行平板进行剪切干涉，干涉图样能同时给出离焦量和离焦方向两个信息，从而实现所谓的涡旋光剪切干涉调焦。. 利用聚焦涡旋光的光场约束光刻是一种有效的超分辨加工手段，更高的线宽压缩比既依赖于高质量的涡旋光束，更有待于优异的变色材料。