DMD数字光刻新型光学引擎耦合及其外腔反馈合束研究

With maskless digital lithography surging forward in industrial applications, DMD micromirror array due to diffraction resulting in the imaging quality reduction, binary on/off due to instability resulting in uneven and inadequate exposure will become urgent needs to solve the key problems. Methods having been reported at present still lack practical efficiency. We put forward to set up the novel optical engine, and establish the coupling and beam-combining in external cavity feedback. This is designed to solve in essence the problem of diffraction imaging as well as uniform and enough exposure. Preliminary experimental results show that，with the aid of LD coupling fiber gain characteristics as well as the coupling and beam-combining between the fiber end's optical isolator and the output coupler, the method is innovative; According to the external cavity feedback mechanism, the objective and image conjugate relations, partially coherent light superposition principle, etc to establish the coupling and beam-combining imaging theory, its theory have certain innovation. In order to cross-correlate and integrate the illumination system, DMD and projection lens system, it is necessary for solving optimal optical design and structure configuration and so on in the novel optical engine; Through establishing the dynamics and cooperativity effect of coupling and beam-combining in positive feedback, exploring its dynamic mechanism and the optical imaging theory, and solving the difficulties about digital lithography imaging quality and uniform and dose-enough exposure, it has realistic and far-reaching significance to deepen the digital dynamic lithography theory and develop the next generation lithography technology.

随着无掩模数字光刻在工业应用中的蓬勃兴起，DMD微镜阵列因衍射而使成像质量降低、二进制开关因不稳而使曝光难以均匀和足量就成为迫切需要解决的关键问题。目前已报道的方法尚缺乏实效，我们提出建立新型光学引擎、通过外腔光学反馈的耦合和合束，旨在从本质上解决其衍射成像和均匀足量曝光的科学技术问题。预实验的初步成效表明：利用LD耦合光纤的增益特性，使其尾端光隔离器与投影光学系统中的输出耦合镜之间形成耦合和合束，方法上具有创新性；根据外腔反馈机制、物像共轭关系和部分相干光叠加原理等建立耦合和合束成像理论，有一定的理论创新性。使照明系统与DMD和投影透镜系统等互关联融合，解决新型光学引擎最优光学设计和结构配置等问题；建立耦合和合束正反馈的动力学协同作用，探索其动力学机理和光学成像理论，解决提高数字光刻系统光学成像质量和均匀足量曝光的难点，对深化数字动态光刻理论、发展下一代光刻技术有现实和深远的意义。

针对数字光刻机存在的光效（曝光量）降低和成像质量下降等问题：设计了光源照明模组和投影系统光学成像模组；搭建了新型光学引擎系统和无掩模直写式光刻设备；研究了通过可调相干度来抑制数字微镜器件（DMD）微镜间固有空隙引起的成像缺陷；研究了通过调控曝光量和根据等弧平均切割法来光刻制作高填充率的六边形微透镜阵列。将整形和匀光后的光源、DMD、双远心投影成像透镜组相互关联耦合形成新型光学引擎，通过倾斜扫描技术，实现了600nm以上的亚微米以及微米分辨率的光刻，改善了成像质量及其曝光均匀性。通过分析DMD各像素对应于微透镜阵列所输出的耦合光强特性，根据图形优化、边缘临近效应矫正和吸收调制等状况，确定冗余曝光量和线条边沿补偿关系，按照角谱理论分析像素的衍射效应，获得改进的菲涅尔传输函数，便于简化像素的孔函数和计算光强分布的量变关系，对提高扫描无掩膜光刻效率和改善成像对比度很有价值。DMD微镜间隙透过投影物镜成像可能会形成缺陷，通过引入相干度的可调光源进行部分相干成像而曝光。研究表明：对不同波长光源、不同光学成像系统的数值孔径和不同线宽，理论模拟计算出最佳的临界部分相干因子，就能够抑制DMD微镜间隙引起的光强分布缺陷，不管目标图形多么复杂都能保持曝光强度面形的连续性和均匀性。制作占空比最高的六边形微透镜阵列，我们使用基于DMD的无掩模光刻技术，采取一种新的方法：按照不同半径的圆剖面以曝光量能够调制的方法重建在六角圆柱阵列上，再通过接触热回流的过程而光刻制作。将高填充率的六边形微镜及其非球面的抛物面，通过剂量调制，按照等弧平均切割的方法一层一层地光刻成随目标轮廓曲率变化的不同半径的圆形，剂量累积而多重曝光，得到一个高质量和表面光滑的六边形微透镜阵列，较其他方法更实时、快速和方便。通过本项目的研究，能有效地解决数字光刻中高质量图形成像和均匀足量曝光的关键科学技术问题，同时对于深化数字光刻理论、发展下一代光刻技术有重要意义。