Research On Influence Of Support Deformation On Surface Shape Detection Accuracy

Integrated circuit is the current focus of global attention,and lithography is the core equipment for manufacturing integrated circuit,its development level directly restricts the development of the integrated circuit industry.High-end lithography has extremely high requirements for the design,manufacture and assembly of its core component lithography objective lens,and thus the objective lens detection requirements are also very strict.The reproducibility of deep ultraviolet lithography objective lens surface shape detection has reached 0.5nm rms,while the results of extreme ultraviolet lithography objective lens surface shape detection reproducibility less than 0.1nm rms has not been found in public reports in China,partly due to the existence of errors in the support structure of the optical element during detection,resulting in its uneven force on the mirror surface.The main goal of this research is to improve the reproducibility of deep ultraviolet lithography objective lens surface shape detection to 0.3nm rms.Due to the influence of self-weight,the optical element will produce different deformation under different support structures.In addition,the actual detection process needs to constantly take and place the optical element,and the presence of human and environmental factors reduces the reproducibility of the optical element surface shape detection.Therefore,it is important to investigate the support structure in order to achieve the research goal.This paper explores the support methods for large-diameter optical elements in view of the high processing accuracy requirements for multi-point hard support structures and the unavoidable processing errors that affect the surface shape of the optical element,and selects the flexible structure to support the optical element after a comparative analysis of several support methods based on existing problems.The core component of the flexible support are elastic flakes,and the working principle of the flakes support optical element is equated to the cantilever beam model with the force concentrated at the free end,and the flexible support is designed after understanding the principle of deformation of the free end of the cantilever beam by the concentrated load.The first design is a integral multi-shrapnel support structure with a number of shrapnels extending from the ring to the centre of the circle.The second design is a linkage type multi-shrapnel support structure with independent shrapnel and bent fixed end based on the shortcomings of the integral shrapnel structure and the feasibility of the design is verified through experiments.The main work of the thesis is as follows:1.Several main support methods for large-diameter optical elements are described in detail.After comparing and analysing the advantages and disadvantages of different support methods and combining them with the main problems of current optical element support deformation,flexible support is chosen as the overall support method for optical element surface shape detection.2.The physical model of the force at the support point of the optical element supported by the elastic flake is constructed,which can be equated to the cantilever beam model with the force concentrated at the free end.A integral shrapnel structure with several shrapnels on the ring is designed,which has the advantages of simple structure and convenient to take and place.The influence of the parameters of the shrapnel on the surface shape accuracy of the optical element is discussed,the factors affecting the surface shape reproducibility of the optical element are analysed,the optimised parameters are determined according to the relationship between the surface shape reproducibility and the influencing factors,and the design of the integral multishrapnel support structure is completed.3.In view of the inevitable processing errors and the integral shrapnel structure cannot be finely adjusted separately after processing,a support structure with independent shrapnel is designed based on this design idea,and the length of the shrapnel is increased to increase the deformation deflection of the support point,and the fixed end of the elastic flake is bent due to the restricted space size.The factors affecting the surface shape reproducibility of the optical element are studied,and the relationship between the surface shape reproducibility and the influencing factors is used as the basis for analysis to gradually determine the parameters of the shrapnel,and the design of the linkage type multi-shrapnel support structure is completed and the structure is verified that can basically meet the goal of the optical element support surface shape reproducibility by machining the structure for experiment.