光学表面离子束加工的材料去除机理及表面演化机制研究

发布时间：2017-12-28 11:13

本文关键词：光学表面离子束加工的材料去除机理及表面演化机制研究　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：193nm深紫外光刻机和下一代的13.5nm极紫外光刻机是我国半导体行业和超大规模集成电路战略的核心装备,光刻投影物镜是其中尤为关键的部件,镜面低空间频段的面形误差和中、高空间频段的粗糙度误差均有着亚纳米量级的超高精度的加工要求。离子束加工凭借其原子级别的去除能力、非接触式的加工方式和温和的束面相互作用机制,已应用于光刻物镜镜面的修形加工中。本文以投影光刻物镜所需的大口径(≥1OOmm)超精度光学元件为对象,对离子束加工过程中的材料去除机理,表面形貌和粗糙度、表面元素组成等演变机制和原子行为,以及基本加工工艺等关键问题进行了研究,论文主要工作主要有以下四个方面：其一,从载能离子与材料原子的相互作用出发,基于连续介质建立了一个包含离子溅射相关机理(初次溅射、二次溅射、表面反射、几何遮蔽效应、再沉积等)与表面扩散相关机理(热激发的自扩散、离子引发的有效扩散、离子增强的粘滞流、弹道位移和Ehrlich-Schwoebel效应等)的离子束去除速率模型,并以此研究了诸多原子机理对表面中、高频粗糙度的粗化特性和平滑特性。其二,基于晶格动力学和蒙特卡罗概率思想,建立了离子束作用过程的随机数学模型。从表面原子及其在离子束作用下的诸多原子行为来体现复杂的材料溅射和扩散机理,进而表征表面形貌和表面粗糙度的中、高空间频段的演变过程。研究发现表面原子的行为模式和作用程度以及它们各自的粗化和平滑特性,强烈地受表面形貌特征和束流工艺参数等支配。从垂直入射到大倾斜角的掠射,表面均呈现出先平滑、后粗化的时间演变规律,并且其表面粗糙度的增长均符合幂律规律。其三,针对广泛应用于光学镜面的多组分材料在离子束加工中的择优溅射现象,建立了离子束作用过程的多元介质双场耦合模型,并与晶格动力学蒙特卡罗模型和熔融石英实验比较分析,研究了择优溅射对光学元件表面的‘改组’特性以及表面组分的演变：对于石英材料,其表面硅元素含量经离子束加工后由溅射前的33%中增长至40%-42%,并通过表面光学性能的检测,其折射率比溅射前高出约35%,表明择优溅射所引起的材料表面层改组直接影响了表面的光学性能。其四,针对大口径镜面的离子束加工,基于CCOS工艺对离子束加工过程进行了连续介质方程建模。根据通过实验、晶格动力学模型与连续介质模型三种方法获得的离子束去除函数,本文对其在溅射时间、离子能量和入射角度等方面的特性进行了研究,结果表明离子束的去除速率函数具有良好的时间稳定性和小陡度稳定性,这为离子束的低频面形加工提供了基础。因此,对离子束加工方程展开并做离散矩阵转化后,以逆滤波去卷积算法求解驻留时间,最终获得了面形精度为1.175 nm RMS、表面粗糙度Rq值为0.56nmRMS的170mm口径的平面镜,和面形精度为1.08nmRMS、中心区域的表面粗糙度为0.4nmRMS、边缘区域表面粗糙度为0.6-0.7nmRMS的130mm口径的凹球面镜。
[Abstract]:193nm deep ultraviolet lithography and 13.5nm the next generation of extreme ultraviolet lithography machine is the core equipment of China's semiconductor industry and VLSI strategy, lithographic is one of key parts, the surface shape error of low spatial frequency and mirror, high spatial frequency roughness error has a sub the nano scale ultra high precision machining requirements. Ion beam machining has been applied to the modification of lithographic lens surface with its atomic level removal capability, non-contact processing mode and mild beam to surface interaction mechanism. Based on the projection lithography lens required large diameter (more than 1OOmm) of ultra precision optical components as the object, the removal mechanism of the ion beam in the process of material, surface morphology and roughness, surface element composition and evolution mechanism of atomic behavior, key problems and basic processing technology were studied, the main work of this paper mainly the following four aspects: first, starting from energetic interactions between ions and atomic materials, a mechanism based on the ion sputtering continuum (first two sputtering, sputtering, surface reflection, geometric shielding effect, and deposition) related to surface diffusion mechanism (self diffusion, thermal excitation the effective ion diffusion, ion enhanced viscous flow, ballistic displacement and Ehrlich-Schwoebel effect) of the ion beam removal rate model, and to study the mechanism of the surface of many atoms, The coarsening and smoothing characteristics of high frequency roughness. Secondly, based on the idea of lattice dynamics and Monte Carlo probability, a random mathematical model of the action process of ion beam is established. The mechanism of complex sputtering and diffusion is reflected from the surface atoms and their atomic behavior under the action of ion beam, and then the evolution process of the surface and surface roughness in the medium and high frequency bands is characterized. It is found that the behavior mode and action degree of surface atoms and their respective coarsening and smoothing characteristics are strongly controlled by surface morphology and beam processing parameters. From the vertical incidence to the large dip angle, the surface evolvement regularities of first smoothing and post coarsening, and the growth of surface roughness accords with the power law law. Third, which is widely used in optical mirror multi-component materials in ion beam processing of preferential sputtering phenomenon, established the role of ion beam process of multi medium coupling model, and compared with the lattice kinetic Monte Carlo model and experimental analysis of fused quartz, the evolution of "reorganization 'characteristics on the surface of the optical element with preferential sputtering and the surface components for quartz material, the silicon content on the surface by ion beam sputtering before processing by 33% increased to 40%-42%, and through the detection of surface optical properties, the refractive index is higher than that of about 35% before sputtering, surface layer of materials caused by the reorganization of the preferential sputtering directly affects the optical properties the surface of the. Fourthly, based on the ion beam processing of large aperture mirror, the continuous medium equation modeling was carried out on the ion beam processing process based on CCOS process. According to the ion obtained by experiment, lattice dynamics model and continuum model three methods of beam removal function, this paper studied the sputtering time, the ion energy and the incident angle and other aspects of the characteristics, results show that the rate of ion beam removal function has good stability and small slope stability, which provides the basis for the low frequency ion beam surface machining. Therefore, the ion beam processing equation and discrete matrix transformation, the inverse filtering deconvolution algorithm for solving the residence time, finally obtained the surface accuracy of 1.175 nm RMS, the Rq value of surface roughness of 0.56nmRMS 170mm diameter plane mirror, and surface accuracy for surface 1.08nmRMS, the central region of the roughness. 0.4nmRMS, the edge area of the surface roughness is 0.6-0.7nmRMS 130mm diameter of the concave spherical mirror.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN305.7

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