基于像散面约束的镜片柔性支撑结构优化设计方法

Optimization Design Method for Flexible Support Structure of Lens Based on Astigmatism Constraints

为提高高精度光机系统中光学元件支撑后的面形精度,在考虑冲击、振动、压力及温度等因素的影响下,设计了一种整体式多弹片定位的光学镜片支撑结构。在静力学条件下,通过有限元分析法计算整体结构的固有频率及支撑结构对镜片面形的影响,一阶固有频率达到366.13 Hz,镜片面形峰谷值为13.923 nm,均方根值为2.499 nm。基于像散面约束的条件,分析了支撑结构的变形对镜片面形的劣化程度,镜片面形峰谷值劣化至119.62 nm,均方根值劣化至20.69 nm。提出了一种镜片支撑结构的优化方法,构建高阶响应面近似模型以描述输入参数与响应值之间的函数关系,采用遗传算法寻优的优化方式提高镜片面形精度,镜片面形峰谷值改善率约18%,均方根值改善率约19%。实验检测对比优化结果,镜片面形峰谷值相对检测结果的偏差率约9%,均方根值相对检测结果的偏差率约12%,验证了优化设计可行性。研究结果可为高精度光机系统中光学元件支撑结构的设计及优化提供理论依据。

With the rapid development of semiconductor technology,the manufacturing level of ultra large scale integrated circuits is constantly changing,and the manufacturing level of integrated circuits depends on high-precision semiconductor manufacturing equipment and cutting-edge lithography technology.In high-precision semiconductor manufacturing equipment,both deep ultraviolet and extreme ultraviolet lithography projection lenses require extremely high accuracy,which requires extremely high precision for the optical components in their optical systems.How to design and optimize the support structure of optical components is one of the problems that must be solved to meet the surface shape accuracy indicators.This paper focuses on high-precision optical systems,such as 193 nm lithography projection objective,and provides a detailed theoretical introduction to the support principle of spring and the analysis principle of surface shape error.On the premise of fully considering the design specifications of the opto-mechanical system,in order to improve the surface shape accuracy of the optical components after support,an integrated multi spring positioning optical lens support structure is designed,taking into account factors such as impact,vibration,pressure,and temperature.And through theoretical analysis and calculation of the support of the spring,the flexible deformation value of the spring is controlled.Under static conditions,finite element analysis is used to calculate the natural frequency of the overall structure and the influence of the support structure on the accuracy of lens surface shape.The first-order frequency reaches 366.13 Hz,the peak-to-valley value of the lens surface shape is 13.923 nm,and the root-mean-square value is 2.499 nm.The overall structure meets the design requirements under static conditions.In response to the issue of change in the surface shape accuracy of optical components during the integration process of the lens group and how to optimize and improve it,the degradation degree of lens surface shape caused by deformation of the support structure is analyzed based on the astigmatic constraint condition.The peak-to-valley value deteriorates to 119.62 nm,and the root-mean-square value deteriorates to 20.69 nm.The main cause for degradation is due to the influence of astigmatism constraints on the bottom reference plane of the lens group.And the shape of lens deformation is related to the type of bottom constraints of the lens support structure,exhibiting a distribution of astigmatism.A method for optimizing the lens support structure is proposed to improve the accuracy of lens surface shape.Firstly,through sensitivity analysis of lens support structure parameters,parameters with high sensitivity can be given special consideration,which can reduce the design space of the optimization process,obtain optimization results as soon as possible,and save time and cost.Secondly,a high-order response surface approximation model is constructed to describe the functional relationship between input parameters and response values.The analysis of fit goodness proves that the response surface model has high accuracy and can better map the relationship between design variables and optimization objectives.Finally,genetic algorithm optimization is used to improve the accuracy of lens surface shape.The improvement rates of peak-to-valley value and root-mean-square value are about 18%and 19%,respectively.The Zeiss gantry coordinate measuring instrument is used to detect the flatness of the lens holder,and the ZYGO 12 inch vertical interferometer is used to detect the surface shape error of the lens.Through experimental results and comparison of optimization results,the deviation rate of the peak-to-valley value relative to the detection result is about 9%,and the deviation rate of the root-mean-square value relative to the detection result is about 12%,which accurately verifies the optimization design conclusion.The research results indicate that the proposed lens support structure,integrated surface analysis and optimization method can provide reference for the support design of optical components in high-precision optomechanical systems.