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题名	光学薄膜应力演化与面形控制
作者	方明
学位类别	博士
答辩日期	2009
授予单位	中国科学院上海光学精密机械研究所
导师	邵建达
关键词	光学薄膜 面形 应力实时测量 应力演化 薄膜厚度分布 牺牲层
其他题名	Stress evolution and surface figure control of optical thin films
中文摘要	随着光学系统向着大口径和高精密方向发展，它对光学元件的面形特征提出越来越高的要求。因此，精确地控制薄膜应力和光学薄膜元件的表面形貌有着特别重要的意义。本论文工作的目的是深入研究和控制光学薄膜对元件面形的影响。从薄膜应力演化特征和薄膜厚度分布形成过程两个方面研究了薄膜沉积过程对面形的影响，并在此基础上提出了基本控制思路。主要工作和结论包括： 在光学薄膜镀膜机上集成了双光束偏转薄膜应力实时测量平台。通过将薄膜制备过程分解为薄膜沉积、停镀、降温、放气和样品大气暴露五个过程，探索了单层HfO2和SiO2薄膜的应力和总力(薄膜应力乘以薄膜总厚度)演化特征。HfO2在生长过程中为张应力，而后的过程中张应力不断减小，最终稳定在约88±7.8MPa。而SiO2在生长过程中为压应力，在停镀到放气过程中压应力不断增大，但在大气暴露过程中，压应力不断减小，且与对数时间呈线性变化关系，最终稳定在约-98±2.1MPa。 实时测量了(H2L)6、(H2L)5H和(HL)7三个多层膜系的薄膜总力与单层膜应力演化。发现生长在HfO2表面的SiO2层压应力小于玻璃基底上获得结果，且越后生长的压应力值越小。而SiO2表面的HfO2的多层平均张应力随着SiO2的多层平均压应力的增加而增加。SiO2层的厚度比例和薄膜总厚度越大，在放气和大气暴露过程中产生的压应力也越大，且会影响大气时效过程中的应力发展方向。未观察到明显的HfO2/SiO2界面应力。 建立平面行星夹具的薄膜厚度分布数值分析模型，提出了均匀性的停留概率修正方法，在试验中获得了优于0.6%的修正结果。分析了薄膜厚度分布对面形的影响。结果显示PV可以通过修正挡板技术得到显著改进。GRMS在均匀性一致的条件下，对薄膜总厚度表现出线性关系，且修正挡板的引入会大幅度提高GRMS值。PSD谱对薄膜的厚度分布周期性特征很敏感，当行星夹具自转公转转速比设计不合理或使用修正挡板情况下，将在薄膜厚度中引入显著的厚度调制，在PSD谱中出现特征峰。试验结果证实了这些特征峰。 最后，针对由于薄膜应力或面形失控导致的元件失效问题，提出了在光学薄膜膜系中增加Sc2O3牺牲层的隔离技术。以此通过安全且高效的化学方法实现基底的还原。本论文工作中通过对添加了牺牲层的光学薄膜进行了阈值测试、应力问题等实验工作，初步验证了该方法的可行性。
英文摘要	Multilayer coatings on large apertures with increasingly high-precision requirement are essential for a lot of optical systems, placing stringent requirements on the surface figure control of coated optics. To meet these needs, strictly control of stress and surface figure of films are most important. Understanding the influence of thin film to the surface figure of coated optics and giving the control method are our goals of this project. We explored the goals from the control of film stress and the thickness distribution of thin films, on which we put forward the way for thin film to control the surface figure of coated optics. Three parts are included in this work: An in situ stress measurement based on wafer curvature measurement by optical deflection of two parallel light beams has been integrated with a local vacuum coater. A typical process for fabricating the optical thin films are divided into five subprocedures: thin film deposition, stopping deposition, cooling, venting the vacuum chamber and exposing coated optics to the atmosphere. With this system, the evolution of stress and force per unit width of HfO2 and SiO2 films were researched. HfO2 film has a tensile stress in growth which will decreases at later subprocedures and stablizes at 88±7.8MPa. While for the SiO2 film, the growth stress is compressive and increases in the next two subprocedures. In the process of venting and exposure, the compressive component increases rapidly with the admission of room air and then reaches saturation, followed by a logarithmic decrement of the compressive state in the succeeding hours and stabilizes at -98±2.1MPa. The evolution of stress and force per unit width of multilayer thin film, (H2L)6、(H2L)5H and (HL)7,consisted of HfO2 and SiO2 were researched. The stresses of SiO2 single layers deposited on the HfO2 are small than those grew on glass and get smaller as the multilayer thin film deposited. While the stresses of HfO2 films deposited on the SiO2 are positive correlation with the stress of SiO2; In the process of venting and exposure to the atmosphere, as the thickness ratio of SiO2 film and the thickness of multilayer increase, the absorption of water on the columnar film increases. The material of outer side will affect the aging rate in the atmospheric exposure. No surface stress was observed. A nondimensional flat planetary rotation system for physical vapour deposition was modeled. With analyzing the trace of substrate, the retention probability correction method was put forward to design an effective uniformity masking, and the experimental results agreed well with theoretical predictions. An improvement of thickness uniformity from 4% to 0.6% was achieved over a range of Φ560mm by a single stationary uniformity masking designed with the method. The effects of thin film thickness distribution on the surface figure of were researched. The PV can improve by the suitable mask. The GRMS are increased by the mask and the thickness of thin film. Some peaks observed in the PSD spectrum and the improper gear ratio and using of mask were regarded as the origin of these peaks, which also are proved experimentally. A Sc2O3 sacrificial film was put forward to peel the optical thin film completely from the substrate when the coated optics was failure because of the thin film. We confirmed this method experimentally.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15496]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	方明. 光学薄膜应力演化与面形控制[D]. 中国科学院上海光学精密机械研究所. 2009.

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