多物理场耦合作用下极紫外光源驱动激光指向精度动态特性研究

Extreme-ultraviolet (EUV) lithography is a key technology for high-volume manufacturing of semiconductor devices with sub-10nm solution. Laser produced plasma EUV source is core component in EUV lithography system. Drive laser has the characteristic of high power, complicated structure and long transmission distance. Pointing precision of drive laser is influenced by multiple factors such as laser, thermal effect and vibration. Study on the pointing precision characteristic and structure optimization of drive laser is a main challenge for developing EUV source with high conversion efficiency. In previous studies, laser vibration data has been experimentally measured and thermal deformation model of optical elements has been established. On this basis, accuracy calculation of pointing precision and transmission characteristic of high power laser under coupled vibration and thermal deformation will be deeply studied in this work. Mode recognition method will be adopted to establish the relationship between pointing precision and vibration mode of high power laser. Dynamic beam propagation model will be established to calculate the pointing precision variation during transmission. The relationship between drive laser targeting precision and module beam pointing will be built, and allocation method for drive laser pointing error will be proposed. Successful implementation of this work will provide theoretical and experimental support for optimizing drive laser system, and moreover, will accumulate key technologies for development of EUV source with high conversion efficiency.

极紫外光刻是10nm及以下节点半导体制造的关键技术。极紫外光源采用驱动激光辐射锡液滴产生等离子体以获得13.5nm极紫外光，是极紫外光刻系统核心组成。驱动激光具有功率高、结构复杂和传输距离长等特点，传输时指向精度受光-热-振动等多因素耦合影响，研究驱动激光指向分布特性，优化驱动激光结构以提高极紫外光转换效率是极紫外光源面临的技术挑战。申请人在激光器振动数据实验测量及光学元件热变形理论与仿真等领域开展了研究初探，在此基础上，本项目针对高功率激光器指向精度精确表征及振动与热变形耦合影响下高功率激光传输特性进行深入研究。拟采用模式识别理论建立激光器振动模式与光束指向的关系；构建光-热-振动多物理场耦合作用下激光传输动力学模型以表征激光指向动态变化；建立驱动激光打靶精度与单元指向精度的联系，探索指向误差分配方法。本项目成功实施为驱动激光优化设计提供理论依据，为高转换效率极紫外光源研制进行技术储备。

驱动激光指向精度直接影响极紫外光源的转换效率。针对驱动激光指向精度的影响因素复杂、不同因素对指向影响定量表征较难等问题，本项目基于实验室搭建的驱动激光原理样机，从驱动激光振动响应测量、驱动激光指向稳定性分析、光热耦合仿真、指向误差分配方法等方面开展研究，取得了以下研究成果：在驱动激光振动响应测量方面，基于非接触振动测量技术系统地开展了驱动激光的种子激光器、激光放大器和光束传输系统关键光学元件的振动数据实验测量研究，对比分析了静止/工作状态下时域和频域的数据分布变化；在驱动激光指向稳定性测量方面，测量了驱动激光工作过程指向稳定性动态分布数据，提出一种基于回波特性与偏振隔离的等效实验测量方法，研究了小角度倾斜入射对驱动激光指向精度的影响；在光热耦合仿真方面，基于射线追迹理论建立了驱动激光准直聚焦的传输过程，针对驱动激光窄脉冲高重频特点，开展了光学元件光热耦合仿真方法研究；在指向误差分配建模方面，建立了单元抖动与打靶精度的关系，基于线性加权法建立了驱动激光指向误差分配模型，定量表征了各组成单元对驱动激光打靶精度的影响。本项目研究成果可以为极紫外光源工程样机研制中的系统集成及指向控制提供设计依据与技术参考。