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类型 基础研究 预答辩日期 2018-03-12
开始(开题)日期 2015-06-18 论文结束日期 2017-11-24
地点 东南大学(江宁)机械工程学院327会议室 论文选题来源 国家自然科学基金项目     论文字数 6.68 (万字)
题目 石英各向异性湿法刻蚀机理及工艺模型研究
主题词 MEMS,石英,各向异性,工艺模拟
摘要 三方晶系晶体材料各向异性湿法刻蚀是MEMS微机电系统结构加工的重要研究方向之一。本论文以α石英晶体为研究对象,通过实验和理论相结合的方式研究了石英各向异性湿法刻蚀特性和形貌预测方法。实验方面,设计实验获取了石英晶体在不同刻蚀条件下的各向异性刻蚀速率和形貌结构特征,并基于台阶流动理论从原子角度分析了石英晶体的刻蚀过程,解释了不同类型的原子在晶面刻蚀过程中的作用;理论方面,提出了利用进化蒙特卡罗算法模拟石英湿法刻蚀速率和形貌结构的方法,实现了对全晶面刻蚀速率以及不同切型晶片任意掩膜下刻蚀结构和表面形貌的精确模拟。此外,基于表面激活能理论和原子间键能关系提出了微观原子激活能理论,成功地解释了石英晶体刻蚀各向异性的作用机理。论文主要内容如下: 首先,针对石英晶体刻蚀衬底建模和表面原子类型划分问题,通过对石英晶体原子结构以及晶面原子排列特征与刻蚀速率之间对应关系的分析,提出了石英类硅键角原子模型和六指数键角分类方法并以此构建了刻蚀衬底模型和界定了表面原子类型。石英晶体不同晶面具有不同的表面原子结构,其刻蚀速率、表面形貌等特性受硅硅以及硅氧原子间相对位置和角度关系影响密切。模型中,表面原子类型由其邻原子数目及夹角关系决定;不同晶面的表面原子类型和所占比例不同。 其次,针对石英晶体在刻蚀过程中呈现的各向异性刻蚀形貌和结构特征,提出了石英晶体刻蚀的台阶流动刻蚀理论并分析了台阶处不同类型原子在刻蚀过程中的作用。为了直观地展示不同类型表面原子移除概率的差异,以原子模型理论为基础构建了石英表面原子移除概率函数(QUARTZ-RPF),以及石英各主要晶面的蒙特卡罗刻蚀衬底形貌仿真模型,明确了晶面原子排列结构与其各向异性刻蚀特性之间以及微观原子刻蚀概率与宏观晶面刻蚀速率之间的关系。 再次,为了实现对不同刻蚀工艺条件下石英晶体全晶面刻蚀速率以及不同切型晶面任意掩膜形状刻蚀结构和表面形貌的准确模拟计算,建立了进化蒙特卡罗湿法刻蚀工艺模型(EMC)。依靠少量典型晶面(速率极值处)的实验刻蚀速率,EA进化算法通过不断修正MC刻蚀模型中QUARTZ-RPF方程能量参数的取值来调整各类型表面原子的移除概率以及校核晶面仿真刻蚀速率,最终使各晶面(h k m l)仿真刻蚀速率比值与实验数据趋于一致。此时,QUARTZ-RPF方程具备了精确约束各类型表面原子刻蚀概率和描述石英晶体刻蚀结构和形貌特征的能力。 然后,为了充分研究石英晶体的各向异性刻蚀特征以及外部条件对其刻蚀特性的影响作用,设计了相关实验对石英晶体在不同刻蚀条件下的全晶面刻蚀速率和多种切向掩膜晶片(Z_cut、At_cut和Bt_cut)的三维刻蚀结构和表面形貌进行了研究,获得了石英晶体刻蚀各向异性特征的变化规律,明确了刻蚀速率极值处晶面在掩膜特征结构面形成过程中的作用以及探寻了晶面激活能与石英刻蚀各向异性刻蚀速率的关系,为建立的石英刻蚀结构和形貌模拟仿真模型提供了实验和理论依据。 最后,为了验证提出的进化蒙特卡罗湿法刻蚀工艺模型的模拟精度,建立了相关模型对不同刻蚀工艺条件下石英全晶面刻蚀速率以及Z_cut、At_cut和Bt_cut掩膜晶片刻蚀结构和形貌进行了预测,并从基于表面激活能理论从微观原子激活能角度解释了石英晶体湿法刻蚀产生各向异性现象的原因。通过对比仿真数据和实验结果表明了EMC石英刻蚀工艺模型可以有效地模拟石英刻蚀速率、结构形貌等各向异性特征。
英文题目 THE ETCHING MECHANISM AND PROCESS MODEL RESEARCH FOR QUARTZ ANISOTROPIC WET ETCHING
英文主题词 MEMS, Quartz, Anisotropic etching, Simulation.
英文摘要 Although the anisotropic etching of quartz has been widely used in the fabrication of microelectromechanical systems (MEMS), the etching process and results are difficult to control and predict because of its complicated anisotropic etching characteristics. This study combines wet etching experiments and the Evolutionary Monte Carlo (EMC) method to describe the global etch rates, etched structures and surface morphologies of quartz in different etching conditions, as well as reveals the anisotropic etching mechanism of quartz from the perspective of microscopic atomic energy. In addition, the etching process of quartz is analyzed based on the step flow theory at the atomic level, and the roles of different types of atoms in the etching process of crystal plane are also explained. The main research contents are as follows: Firstly, based on the particular atomistic structure of quartz and the relationship between crystal plane atomic arrangements and corresponding etch rates, a suitable classification of the neighborhood of the surface atoms and a corresponding quartz-based removal probability function(QUARTZ-RPF) are put forward, which enables describing the removal rate of every surface atom as an explicit function of the occupation state of the neighborhood. Besides, the step flow etching theory is introduced to explain the etching process of quartz, and the roles of some typical surface atoms are identified in terms of their special position in etching substrate. The removal probabilities of surface atoms located in step are much higher than the probabilities of atoms in terrace. In fact, one of the primary causes that result in quartz anisotropic etching is surface atom types and distributions in crystal planes. Secondly, An EMC etching model of quartz is proposed to carry out simulation calculations on the etched microstructures and surface morphologies of quartz crystal on the basis of above researches,which clearly confirms the relationship among the macroscopic etch rates of crystal planes, microscopic activation energy and atomic removal probability. Furthermore, an evolutionary algorithm is used to properly transform the (facet specific) macroscopic etch rates of several crystal planes parallel to the X (electric) and Y (mechanical) axes into suitable values for the (atom specific) microscopic removal probabilities. To improve the computational efficiency of the evolutionary search we make use of a transformation matrix (TM), effectively constraining the evolutionary search space. Thirdly, a large number of etching experiments were implemented to explore the etch rate anisotropy of quartz in saturated NH4HF with different concentration ratios and temperatures for the first time by using the single-crystal quartz hemisphere, and the influences of etching conditions on the anisotropic etching characteristics of quartz are analyzed as well in detail. Further more, the three-dimensional structures and surface topography etched on Z_cut, AT_cut and BT_cut substrates using some mask patterns are also obtained in above experiments. Based on above experimental results, the effects of crystal planes with local extreme etch rates on the formation of etched structures as well as the apparent activation energy of a plane on its etch rate are all identified, which provides the experimental and theoretical basis for the establishment of the EMC etching model. Lastly, lots of simulation calculations of the EMC etching model on the etched microstructures and surface morphologies of quartz have been carried out in this research, and the final results indicate the EMC etching model has a good ability to predict the etch rates of a wide range of crystallographic facets as well as the three-dimensional microstructures and topography etched on Z_cut, AT_cut and BT_cut substrates using some mask patterns.In addition, the proposed Microscopic Activation Energy Evaluation function (MAEE) derived from Monte Carlo etching theory transforms the apparent activation energy of crystal planes into suitable values for the (atom specific) microscopic activation energy, which is the first to explain the cause of quartz anisotropic etching mechanism from the perspective of microscopic atomic energy, and specifies the roles of different types atoms in the anisotropic etching process of quartz.
学术讨论
主办单位时间地点报告人报告主题
东南大学 20130915 机械楼308 张辉 单晶硅湿法刻蚀成型技术学习
东南大学 20131228 机械楼报告厅 Kazuo SATO The anisotropic etching and mechanical properties of single crystal silicon
东南大学 20140321 南京英特神斯有限公司 Miguel A. Gosálvez The of anisotropic etching simulation using kinetic Monte Carlo and cellular automata methods
东南大学 20140422 机械楼308 张辉 复杂晶体材料湿法刻蚀工艺的表面演化机制
东南大学 20150409 机械楼报告厅 李源 元胞自动机方法在单晶硅离子束加工中的应用研究
东南大学 20151224 机械楼403 张辉 石英晶体材料各向异性湿法刻蚀特征MC方法模拟分析
东南大学 20171111 机械楼报告厅 成利 ON-GOING RESEARCH ON SOUND AND VIBRATION
东南大学 20171119 机械楼308 张辉 The application of Kinetic Monte Carlo model in wet etching of α-quartz
     
学术会议
会议名称时间地点本人报告本人报告题目
MEMS2017 20160122-20160126 美国拉斯维加斯 THE STUDY OF SELF-LIMITED STATE PROFILE AND LEVEL SET SIMULATION OF ANISOTROPIC WET ETCHING ON QUARTZ
transducers2017 20170618-20170622 中国台湾高雄 EVOLUTIONARY KINETIC MONTE CARLO METHOD FOR THE SIMULATION OF ANISOTROPIC ETCHING OF Z-CUT, AT-CUT AND BT-CUT QUARTZ
MEMS2018 20180121-20180125 英国贝尔法斯特 THE MICROSCOPIC ACTIVATION ENERGY ETCHING MECHANISM IN ANISOTROPIC WET ETCHING OF QUARTZ
     
代表作
论文名称
Removal probability function for Kinetic Monte Carlo simulations of anisotropic etching of silicon i
Kinetic Monte Carlo method for the simulation of anisotropic wet etching of quartz
EVOLUTIONARY KINETIC MONTE CARLO METHOD FOR THE SIMULATION OF ANISOTROPIC ETCHING OF Z-CUT, AT-CUT A
THE STUDY OF SELF-LIMITED STATE PROFILE AND LEVEL SET SIMULATION OF ANISOTROPIC WET ETCHING ON QUAR
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
李东波 正高 教授 博导 南京理工大学机械工程学院
殷晨波 正高 教授 博导 南京工业大学机械与动力工程学院
张志胜 正高 教授 博导 东南大学机械工程学院
帅立国 正高 教授 博导 东南大学机械工程学院
毕可东 正高 教授 博导 东南大学机械工程学院
      
答辩秘书信息
姓名职称工作单位备注
戴敏 副高 副教授 东南大学机械工程学院