原子力显微镜传感器的微机械加工技术的研究

分析了现有的AFM力传感器的工艺特点及问题。在此基础上研究用KOH溶液两步法P+自停止腐蚀制作厚度精确可控的单晶硅悬臂梁;以SiO2为掩模,SF6刻蚀硅,用RIE与各向同性湿法化学腐蚀相结合使悬臂梁探针一次成形和用湿法腐蚀锐化探针,针尖半径约50nm.制定了适于批量生产的AFM力传感器加工工艺。     

真空紫外硅闪耀光栅的制作

利用单晶硅在KOH溶液中的各向异性刻蚀特性,在相对Si(111)面切偏角为5°的单晶片上制作了1200gr/mm的真空紫外闪耀光栅。结合全息干涉曝光以及光刻胶灰化技术,在单晶硅表面得到了小占宽比的高质量光刻胶掩模,用湿法刻蚀将光栅掩模图形转移到单晶硅表面的天然氧化层上,并将其作为硅各向异性湿法刻蚀的掩模,成功获得了接近于理想锯齿槽形的闪耀光栅。用原子力显微镜分析光栅闪耀面,结果表明其表面均方根粗糙度约为0.2nm。在真空紫外波段对其进行衍射效率测量,发现光栅在135nm波长处显示出良好的闪耀特性。此方法可以应用于真空紫外和软X射线波段的光栅制作,在获得较高的槽形效率的同时,可以大大减少其制作难度及成本。     

基于感应耦合等离子刻蚀技术的三维微拉伸梁制作工艺

根据感应耦合等离子(Inductively coupled plasma,ICP)刻蚀的机理,针对热氧化硅薄膜微拉伸梁的结构特点,研究ICP刻蚀制作3D微拉伸梁结构的工艺并解决其中的难点问题。介绍ICP刻蚀工艺参数对刻蚀质量的影响,包括存在的微负载效应和深宽比效应。详细介绍热氧化硅薄膜微拉伸梁的制作,其关键步骤是双掩膜两次ICP刻蚀形成阶梯状窗口结构,并在硅衬底表面形成释放了的热氧化硅薄膜梁。利用ICP刻蚀对单晶硅的高选择性,此制作工艺适用于各种薄膜的微拉伸梁制作。     

复合湿法腐蚀工艺制备硅基三维曲面

提出了将各向异性湿法腐蚀与各向同性湿法腐蚀相结合的复合工艺,通过控制刻蚀工艺参数进行体硅加工,成功刻蚀了硅基材料三维曲面回转体结构.在各向同性腐蚀过程中,由各向异性刻蚀得到的多面体结构的表面垂直腐蚀速率与刻蚀液浓度呈指数关系,而搅拌使得多面体结构表面峰值与谷底的刻蚀液存在流速差,基于此原理可得到光滑的三维曲面.刻蚀过程中,通过各向异性湿法腐蚀控制结构深度,通过各向同性湿法腐蚀"抛光"结构曲面.最后,采用实验优化湿法腐蚀过程的工艺参数,基于直径为600～1 000 μm的圆形掩模板,在硅材料表面制备得到了高度为100～200μm的三维曲面回转结构.提出的工艺简单、有效且便于操作,有望用于制作不同曲面形状的三维硅结构及聚合物光学器件模具.     

微透镜阵列的离子束溅射刻蚀研究

利用扫描电子显微镜(SEM)和表面探针测试,分析了采用离子束溅射刻蚀技术制作的石英微透镜阵列器件的表面微观形貌,讨论了引起微透镜表面缺陷的原因及所采取的改善表面形貌的措施,研究了采用不同层次的光致抗蚀剂微透镜图形的固化技术后,经离子束溅射刻蚀制作出的微透镜阵列器件的表面形貌差异,定性给出了表面探针测试的适用范围,此外还介绍了对所制样品所做的几项主要的处理操作。     

LED蓝宝石衬底抛光表面原子台阶形貌及其周期性研究

LED蓝宝石衬底的表面质量会极大影响到后续外延质量,进而影响到LED器件性能。蓝宝石研磨片经Al2O3磨粒粗抛液、SiO2磨粒精抛液下进行化学机械抛光(CMP),最终表面经原子力显微镜(AFM)所测表面粗糙度达到0.101nm,获得亚纳米级粗糙度超光滑表面,并呈现出原子台阶形貌。同时,通过使用Zygo表面形貌仪、AFM观察蓝宝石从研磨片经Al2O3粗抛液、SiO2精抛液抛光后的表面变化,阐述蓝宝石表面原子台阶形貌的形成原因,提出蓝宝石原子级超光滑表面形成的CMP去除机理。通过控制蓝宝石抛光中的工艺条件,获得a-a型、a-b型两种不同周期规律性的台阶形貌表面,并探讨不同周期规律性台阶形貌的形成机理。     

基于拉曼光谱的微结构应力测试方法

讨论了利用拉曼光谱来定量分析由单晶硅和多晶硅材料构成的微机械结构应力测试方法,说明了该方法的基本原理,推导了单晶硅应力σ与相对拉曼频移△ω及多晶硅应力τ与相对拉曼频移△ω的关系,使基于硅体系的拉曼应力测试公式体系化.应用拉曼光谱测试方法对微加速度计悬臂梁和微谐振器支撑梁进行了应力测试.     

单晶硅微薄膜V形缺口疲劳特性研究

采用微疲劳试验机与光学显微镜搭建一套微观疲劳试验系统。在室温条件下,通过控制载荷对单侧V形缺口的单晶硅微薄膜进行脉动拉伸疲劳试验,研究其疲劳特性。首先将单晶硅微薄膜V形缺口试样疲劳试验数据与单晶硅微薄膜光滑试样疲劳试验数据进行对比,分析发现V形缺口的引入会使单晶硅试样的疲劳强度及其抵抗弯矩的能力显著降低。试验结果表明,缺口试样发生破坏的应力幅度界限分明,与光滑试样相比,其破坏特性更趋近于宏观脆性断裂。通过扫描电镜分别对单晶硅微薄膜光滑试样与V形缺口试样进行断口分析,发现单晶硅微薄膜在循环应力作用下出现脆性疲劳破坏行为,其断口形貌特征与晶体结构密切相关。     

硅基周期槽结构的刻蚀工艺研究

针对微电子机械系统(MEMS)湿法槽刻蚀技术,基于硅材料各向异性腐蚀特性研究了硅基周期槽的湿法刻蚀工艺,得出了优化的光刻参数。通过对比实验详细分析了搅拌在腐蚀过程中起到的重要作用,实验结果显示,搅拌可以增加腐蚀溶液的流通性,使硅表面不易产生气泡形成"伪掩膜"阻碍反应的进行,从而制备出表面光滑平整的周期槽结构。同时,在搅拌的条件下对槽深和腐蚀时间的关系也做出了相应的分析。为硅微机械加工技术的进一步研究提供了参考。     

各向异性湿法刻蚀z切石英后结构侧壁形貌的预测

基于石英晶体各晶面的湿法刻蚀速率,研究了石英微结构侧壁形貌的预测方法,讨论了各向异性湿法刻蚀石英的规律.首先,总结了石英各主要晶面的相对刻蚀速率,分别绘制了x、y族刻蚀速率矢量图.然后,在掩模层的边缘处,通过绘制相应的晶面刻蚀速率矢量图,得到各速率矢量的晶面线,晶面线所围成的最小轮廓即是石英微结构的刻蚀形貌.最后,利用该方法预测了x向和y向石英梁的侧壁形貌.在70℃的氢氟酸和氟化铵混合溶液内刻蚀5h,制作了厚度均为500μm的x向和y向两种石英微梁.结果显示,y向梁的-x向侧壁有一均匀整齐的晶棱,棱高210 μm,而+z向侧壁平滑.x向梁的侧壁均有晶棱,+y向晶棱较大,棱高为450 μm,-y向晶棱棱高为240 μm.所制作梁的侧壁形貌与预测结论基本吻合,验证了预测方法的正确性.基于该方法可在石英微结构的设计阶段,通过引入工艺因素对微结构进行优化.     

硅台面结构凸角腐蚀原因探析

本文探讨了硅台面结构凸角腐蚀的原因。指出非理想的直角掩膜结构导致了凸角腐蚀，凸角处侧壁由横向腐蚀速率最快的晶面所构成。     

全息离子束摆动刻蚀凸面闪耀光栅制备技术

高衍射效率的凸面闪耀光栅是高光谱分辨率成像光谱仪的核心分光元件,其制作方法包括机械刻划法、电子束直写法、X射线光刻法、全息离子束刻蚀法等,其中全息离子束刻蚀法因为具备良好的各向异性,不受尺寸与曲面形状限制,杂散光低,完全没有鬼线,制造时间短等优点成为现今光栅制造领域常用方法之一.传统全息离子束刻蚀凸面光栅时基底的弯曲会...     

〈111〉晶向标定方法及其在湿法刻蚀硅光栅中的应用

在利用单晶硅的各向异性腐蚀制作光栅的过程中,掩模与硅晶向的精密对准是获取大尺寸光栅结构的前提条件,高对准精度将显著降低光栅槽型侧壁粗糙度。设计并制作了一种扇形图案,通过以该图案为掩模的预刻蚀,可快速准确发现硅基底内晶格取向。通过此方法进行晶向标定,并利用紫外光刻与湿法刻蚀,成功研制了尺寸为15mm×15mm、高度为48.3μm、周期为5μm、高宽比为20的矩形光栅结构,线条侧壁粗糙度RMS值为0.404nm;利用全息光刻与湿法刻蚀成功研制了大高宽比深槽矩形光栅及三角形槽光栅。矩形槽光栅尺寸为50mm×60mm,高度为4.8μm,周期为333nm,高宽比为100,侧壁粗糙度RMS值为0.267nm。三角形槽光栅周期为2.5μm,侧壁粗糙度RMS值为0.406nm。     

多次掩模湿法腐蚀硅微加工过程的蒙特卡罗仿真

探讨利用蒙特卡罗 (Monte Carlo, MC) 法模拟硅微加工各向异性湿法腐蚀的仿真,实现连续多次掩模,多步硅微加工工艺过程的仿真.介绍MC法的使用特点及其在湿法腐蚀硅微加工中的应用,仿真使用腐蚀概率方程确定表面原子适当的MC转移概率,模拟方法支持氧化硅和氮化硅掩模层作用下的各向异性腐蚀加工和多次掩模的传递过程.编制的仿真程序通过模拟一个原子力显微镜探针阵列多掩模连续6步工艺的硅微加工过程验证了MC法的正确性.     

Fabrication of hierarchical micro/nanostructures via scanning probe lithography and wet chemical etching

In this study, we propose a simple and effective method for fabricating hierarchical silicon structures via the combination of scanning probe lithography (SPL) and wet chemical etching. Here, silicon oxide structures were protruded from a 100-oriented silicon surface, followed by the passivation of silicon nitride by AFM tip-induced local oxidation. Based on the two-dimensional (2D) silicon oxide patterns, three-dimensional (3D) microstructures with high aspect ratios were formed by wet etching with HF and KOH. A variety of combinations of SPL and the etching process allowed us to fabricate diverse silicon-based structures such as deep-etched microstructures and multi-terraced nanostructures.     

动力学蒙特卡罗法体硅湿法刻蚀工艺仿真的研究与开发

对比分析了BKL、二叉树搜索以及树状结构搜索算法(KLS) 3种动力学蒙特卡罗法的实现过程,讨论了它们在MEMS各向异性湿法刻蚀工艺仿真计算中的应用,阐述了应用特点.使用树状结构搜索算法实现了加工仿真程序,以(111)晶面的原子移除过程为例,解释了蒙特卡罗法在刻蚀中的计算特点.开发的系统模拟了(311)晶面在KOH刻蚀中表面形貌的演化过程,刻蚀面能够很好地再现出表面的微观特征.基于KLS的方法能对湿法硅微结构工艺进行仿真计算,不同刻蚀阶段的微结构能与实验结果相一致,较为合理准确.     

Nanofabrication of arbitrary patterns by nano plastic forming and etching (NPFE)

In this paper, flexibility of nano plastic forming and etching, an ultra-high resolution nanofabrication process developed recently by the authors, in terms of fabrication of arbitrary patterns as well as applicability to various work materials is demonstrated. First, a thin layer of nickel (Ni) is deposited on a silicon (Si) substrate. Then, it is directly patterned by nano plastic forming. Next, the patterned Ni mask is slightly etched by direct current sputter etching to transfer the pattern into the entire mask thickness and expose the surface of the substrate in the individual patterned areas. Afterward, the pattern is transferred onto the substrate by reactive ion etching. Finally, the remained Ni layer is removed from the substrate, and nanostructures fabricated on the surface of the substrate are revealed. Fabrication of grid patterns with various pitch settings on the surface of Si substrates is demonstrated. The experimental results indicate that the depth and width of the nanostructures can be controlled by the etching time. Also, it is confirmed from the results that the depth and width are not influenced by the pitch setting.     

Fabricating nanostructures through a combination of nano-oxidation and wet etching on silicon wafers with different surface conditions

This study investigates the surface conditions of silicon wafers with native oxide layers (NOL) or hydrogen passivated layers (HPL) and how they influence the processes of nano-oxidation and wet etching. We also explore the combination of nano-oxidation and wet etching processes to produce nanostructures. Experimental results reveal that the surface conditions of silicon wafers have a considerable impact on the results of nano-oxidation when combined with wet etching. The height and width of oxides on NOL samples exceeded the dimensions of oxides on HPL samples, and this difference became increasingly evident with an increase in applied bias voltage. The height of oxidized nanolines on the HPL sample increased after wet etching; however, the width of the lines increased only marginally. After wet etching, the height and width of oxides on the NOL were more than two times greater than those on the HPL. Increasing the applied bias voltage during nano-oxidation on NOL samples increased both the height and width of the oxides. After wet etching however, the increase in bias voltage appeared to have little effect on the height of oxidized nanolines, but the width of oxidized lines increased. This study also discovered that the use of higher applied bias voltages on NOL samples followed by wet etching results in nanostructures with a section profile closely resembling a curved surface. The use of this technique enabled researchers to create molds in the shape of a silicon nanolens array and an elegantly shaped nanoscale complex structures mold.     

Evaluation of demineralized dentin contraction by stereo measurements using environmental and conventional scanning electron microscopy

Numerous investigations of etched human dentin are performed using scanning electron microscopy (SEM). Usually specimens are fractured and cross sections of etched layers with underlying unaffected dentin are observed. Results from this study showed that the edge of the etched layer contracted and became curved after fracture of wet specimens and that tensile stresses were developed in this layer by acid etching. The degree of contraction was determined utilizing profiles of the specimen edges obtained with the help of stereo measurements. Fixation in glutaraldehyde decreased the contraction in wet specimens prepared for environmental scanning electron microscopy (ESEM). Fixation also decreased shrinkage of the demineralized layer due to gradual desiccation in the ESEM during observation. For conventional SEM, the contraction was minimized if specimens of etched and fixed dentin were fractured in the dry condition after dehydration.