蓝宝石衬底抛光过程磨粒轨迹与加工平整性研究

发布时间：2018-08-06 11:54

【摘要】：蓝宝石单晶具有优良的光学、力学、化学和电性能,其硬度高、强度高、耐高温、光透性好的特点,使其在光电子、通讯、国防等领域有着越来越广泛的应用。正因为蓝宝石具有稳定的化学性能和物理力学性能,这就大大增加了蓝宝石材料的加工难度。随着光学和微电子学及其相关技术的发展,不但要求高的加工效率,而且需要高的表面精度和低的表面及亚表面损伤,所以蓝宝石晶片的加工技术面临巨大挑战。作为典型的硬脆材料,蓝宝石的加工工艺还不成熟。由于蓝宝石在航空航天、深空探索等军事领域有着特殊的用途,因此,单晶蓝宝石的加工技术在西方极其保密。为实现单晶蓝宝石高效、高精度、高质量的平坦化加工,研磨抛光技术应运而生。研磨主要是通过磨粒的微切削去除晶片表面的微凸起部分,保证晶片的平面度;抛光主要是为了降低晶片的表面粗糙度,使加工表面镜面化,并且降低晶片表面与亚表面损伤。由于研磨抛光是一个系统工程,它需要一个高稳定性的工艺条件,其材料去除机理、材料非均匀性形成机制还不够完善,通过试验方法研究研磨抛光过程,往往受到试验条件的影响和试验成本限制,因而将试验与仿真方法相结合成为研究研磨抛光机理及优化加工工艺的一种有效手段。本文首先建立了工件与抛光盘之间的相对运动模型,运用“运动学原理”及“坐标变换”得出磨粒运动轨迹方程,推导了运动轨迹长度公式和轨迹曲线曲率公式。利用MATLAB软件分析模拟研磨抛光过程中转速比、偏心距、磨粒向径、初始角度对磨粒运动轨迹形态及轨迹曲线曲率的影响。在此基础上,本文通过“变异系数”来分析轨迹长度非均匀性、速度非均匀性、压力分布非均匀性,并利用“微积分”方法得出工件均匀磨损方程。为满足工件均匀磨损的条件,分别分析了抛光盘转速、工件转速、偏心距、磨粒向径对磨损因子的影响。为探索研磨抛光过程中工件接触处的应力变化情况,本文将利用商用有限元软件Abaqus建立工件、抛光盘、抛光垫、保持环之间相互接触的三维模型,仿真分析了下压力、抛光垫厚度、抛光垫弹性模量、抛光垫泊松比、工件与抛光垫之间摩擦系数对接触应力分布及应力分布非均匀性的影响规律。在上述理论与仿真模拟的基础上,本文将对蓝宝石衬底片进行抛光实验研究。通过单因素实验法研究不同压力、上下盘转速、抛光垫等工艺参数对蓝宝石衬底片化学机械抛光材料去除速率和表面粗糙度的影响。通过理论、仿真、实验来改善蓝宝石研磨抛光加工工艺,这为理解研磨抛光加工机理与研磨抛光机的设计提供理论指导。
[Abstract]:Sapphire single crystals have excellent optical, mechanical, chemical and electrical properties, high hardness, high strength, high temperature resistance and good light permeability, which make them more and more widely used in the fields of optoelectronics, communication, national defense and so on. Because sapphire has stable chemical and physical mechanical properties, this greatly increases the processing difficulty of sapphire material. With the development of optics, microelectronics and related technologies, high processing efficiency, high surface precision and low surface and sub-surface damage are required, so the fabrication technology of sapphire wafers is facing great challenges. As a typical hard and brittle material, the processing technology of sapphire is not mature. Because sapphire has special applications in aerospace, deep space exploration and other military fields, the processing technology of single crystal sapphire is extremely secret in the west. In order to achieve high efficiency, high precision and high quality flat machining of single crystal sapphire, grinding and polishing technology emerged as the times require. Grinding is mainly to remove the micro-protruding part of the wafer surface by micro-cutting of the abrasive particles to ensure the planeness of the wafer, and the polishing is mainly to reduce the surface roughness of the wafer, make the machined surface mirrorized, and reduce the surface and sub-surface damage of the wafer. As grinding and polishing is a systematic project, it needs a high stability process condition, its material removal mechanism and material non-uniformity formation mechanism are not perfect, the grinding and polishing process is studied by means of experimental method. Because of the influence of test conditions and the limitation of test cost, the combination of test and simulation is an effective means to study the mechanism of grinding and polishing and to optimize the processing technology. In this paper, the relative motion model between the workpiece and the polishing disc is established, and the kinematics principle and coordinate transformation are used to obtain the motion trajectory equation of the abrasive particle, and the formula of trajectory length and curve curvature are derived. The effects of rotational speed ratio, eccentricity, particle diameter and initial angle on the morphology and curve curvature of abrasive particles during grinding and polishing were analyzed by MATLAB software. On this basis, the variation coefficient is used to analyze the inhomogeneity of track length, velocity and pressure distribution, and the uniform wear equation of workpiece is obtained by "calculus" method. In order to satisfy the condition of uniform wear of workpiece, the effects of rotating speed, rotation speed, eccentricity and diameter of abrasive particle on wear factor were analyzed respectively. In order to explore the stress change of workpiece contact during grinding and polishing, a 3D model of workpiece, polishing pad, polishing pad and contact between workpiece, polishing pad and retaining ring is established by using commercial finite element software Abaqus, and the downward pressure is simulated and analyzed. The influence of thickness of polishing pad, elastic modulus of polishing pad, Poisson's ratio of polishing pad and friction coefficient between workpiece and polishing pad on contact stress distribution and non-uniformity of stress distribution. On the basis of the above theory and simulation, the polishing experiment of sapphire substrate will be carried out in this paper. The effects of different pressure, rotating speed of upper and lower disk and polishing pad on the removal rate and surface roughness of chemical-mechanical polishing material on sapphire substrate were studied by single factor experiment. The theory, simulation and experiment are used to improve the grinding and polishing process of sapphire, which provides theoretical guidance for understanding the mechanism of grinding and polishing and the design of grinding polishing machine.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O786

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