多晶硅微悬臂梁断裂失效强度的尺寸效应

为了了解构件尺寸的微型化给材料的强度和弹性模量带来的影响,利用纳米硬度计通过微悬臂梁的弯曲实验来测量其力学特性.该方法可精确测量微悬臂梁纳米级弯曲形变,但必须考虑压头在微悬臂梁上的压入及微悬臂沿宽度方向的挠曲.试验研究表明,多晶硅微悬臂梁的平均弹性模量为156GPa±(4.52～9.83)GPa,其失效断裂强度表现出对构件有效体积和表面积的尺寸效应.由实验测得的失效强度得到KC=1.62MPa*m1/2,计算出的缺陷尺寸a为58～117nm.     

《机械工程学报》英文版2000年第13卷第4期目次、摘要预告

通过规划加速度抑制柔性臂残余振动的研究朱 建(香港城市大学制造工程及工程管理学系)邵 浩 王兴松(哈尔滨工业大学)(东南大学)摘要 ： 探索了一种通过规则加速度来抑制柔性臂残余振动的方法。在建立数学模型的基础上,从理论上推导出柔性臂振动与加速度,振动频率,阻尼及时间的函数关系式。根据柔性臂的振动频率及阻尼进行试验,在对应的时刻施加于柔性臂对应的加速度,以抑制柔性臂的残余振动,获得很好的结果。叙词：柔性臂 抑制控制 加速度中图分类号：TG580纳米硬度计研究多晶硅微悬臂梁的弯曲形变丁建宁 孟永钢 温诗铸(清华大学摩擦…     

多晶硅微电子机械构件材料强度尺寸效应研究

为了解构件尺寸的微型化给材料的强度带来的影响 ,利用纳米硬度计通过微悬臂梁的弯曲试验法来测量多晶硅微构件弯曲强度 ,利用电磁驱动微拉伸装置测试了抗拉强度。试验研究表明 ,多晶硅微构件的弯曲强度和抗拉强度表现出随构件尺寸的减小而增加的尺寸效应。统计分析表明 ,多晶硅微构件的平均弯曲强度为 ( 2 .885± 0 .40 8)GPa ,其平均抗拉强度为 ( 1.36± 0 .14 )GPa。研究结果为微机械构件的可靠性设计提供依据     

碳纳米管压阻微悬臂梁红外热探测器的研究

研究了压阻复合层微机械悬臂梁红外探测器的热挠曲理论模型。利用IC工艺和微机械加工技术设计制作了一种硅/铝/碳纳米管三层微机械悬臂梁红外探测器,该探测器基于硅和铝两种材料热膨胀系数的差异,存在双物质效应,不同温度下梁的挠度不同,其形变可通过梁根部的压敏电桥检测。为提高探测器的红外吸收特性,实验探索出了在微机械悬臂梁上涂敷碳纳米管吸热层的工艺方法。实验研究了具有碳纳米管薄膜吸热层的三层微机械悬臂梁红外热探测器对红外辐射的响应规律,结果表明涂敷碳纳米管吸热层使响应灵敏度提高近一倍。     

多晶硅薄膜离面疲劳特性研究

多晶硅薄膜材料为微电子机械系统(MEMS)器件最重要的材料之一,对其疲劳特性的研究是现阶段失效分析研究的热点和重点.利用表面加工的多晶硅矩形微悬臂梁结构对该问题展开实验研究.通过干法刻蚀在微悬臂梁根部制作纵向应力集中区,利用静电激励激励微悬臂梁进行离面振动,谐振频率检振方法跟踪微悬臂梁机械性能的变化.结果证明在1010～1011次循环振动载荷作用后,微悬臂梁结构刚度下降,谐振频率减小,频率最大绝对偏移量达到1.544 kHz,相对偏移量达到结构本征频率的1.3%.这些结果首次验证了MEMS结构在离面振动方向上也存在显著疲劳现象.和已有文献相比,实验中结构所受应力幅度较其小2个数量级(约1～10 MPa量级),而频率偏移量却高于其数十倍.这很可能是因为纵向干法刻蚀引入了较大的粗糙度,显著加速了多晶硅结构的晶界分离速度,因而也加速了疲劳.     

Ag-GNSs/SnAgCu钎料纳米压痕变形行为研究

为了研究Ag-GNSs/SnAgCu钎料在微纳米尺度下的变形行为,采用恒加载速率/载荷法在室温下对复合钎料进行纳米压痕试验,通过载荷-压痕深度曲线分析,并结合压痕形貌,研究载荷-压痕深度曲线中出现屈服台阶(pop-in)现象的机制,以及复合钎料在纳米压痕试验中的变形情况。结果表明,载荷-深度曲线中存在的"pop-in"是由于纳米压痕过程发生了弹塑性变形的转变。弹塑性转变与位错的形核与生成有关,并且通过透射电子显微镜在压痕点附近观察到交错的位错网络。通过观察复合钎料的压痕形貌,发现了压痕附近存在明显的凸起现象,这与材料的屈服应力与弹性模量之比有关。凸起现象将导致通过Oliver-Pharr方法计算的接触面积比实际值小,而引起纳米压痕试验方法测量的硬度和弹性模量数值偏大。应用"半椭圆模型"对产生凸起现象的接触面积进行修正,再基于Oliver-Pharr方法求得硬度和弹性模量,修正后的结果与修正前相比,硬度降低了18.3%,弹性模量降低了9.5%。     

表面微加工悬臂梁断裂失效可靠度预测

MEMS的可靠性已经成为它能否成功地实现商品化的乙的一个基本结构,阐述了多晶硅微悬臂梁的断裂失效机理.利用宏观机械理论中的应力-强度干涉理论对表面微加工的多晶硅微悬臂梁的断裂可靠性进行预测,建立了在均匀的表面载荷下的断裂可靠度预测模型.     

联合载荷作用下悬臂梁大变形分析的打靶法

利用微积分基本知识，这里导出了集中力和任意横向分布载荷作用下悬臂梁的挠曲线微分方程。基于两点边值问题的打靶法，分别计算了两种联合载荷作用下悬臂粱的大变形。所得微分方程不仅具有普遍性，而且本文的计算方法对类似问题的解决具有一定的借鉴意义。     

不同晶粒尺寸和晶向分布多晶硅片弯曲应力的有限元模拟

采用光致发光晶向识别技术分辨多晶硅片晶向的分布情况,通过纳米压痕试验测试多晶硅片在不同晶向上的弹性模量;然后利用有限元方法建立包含晶粒尺寸和晶向分布信息的多晶硅片有限元模型,将纳米压痕试验测得的不同晶向的弹性模量带入此模型,模拟得到了不同晶粒尺寸和晶向分布下多晶硅片的弯曲应力,最后通过三点弯曲试验对模拟结果进行了验证。结果表明:多晶硅片在不同晶向上的弹性模量和硬度不同;晶向分布会影响多晶硅片的最大弯曲应力和最大挠度的位置,晶粒形状会影响多晶硅片的最大弯曲应力;减小晶粒尺寸可以降低多晶硅片的最大弯曲应力;三点弯曲试验验证了所建模型的正确性。     

Fe_(60)Cr_5Mo_2Ni_2W_2Mn_1C_4Si_7B_(17)非晶合金的纳米压痕力学性能

采用甩带法制备出新型Fe60Cr5Mo2Ni2W2Mn1C4Si7B17非晶合金,在室温、不同峰值载荷(3,5,7,9,12mN)和不同加载速率(1,2,3,4,5mN·s-1)下对此非晶合金进行纳米压痕试验,研究了加载速率和峰值载荷对其弹性模量、纳米压痕硬度和蠕变行为的影响。结果表明:试验合金为完全非晶态,其纳米压痕硬度和弹性模量均较高;随着峰值载荷的增大(即压入深度的增大),试验合金的纳米压痕硬度减小,表现出较明显的尺寸效应,弹性模量略有降低;随着加载速率的增加,纳米压痕硬度和弹性模量均增大;在纳米压痕试验的保载阶段,试验合金发生蠕变,其最大蠕变位移随峰值载荷或加载速率的增加而增大,蠕变应力指数则随峰值载荷的增加或加载速率的减小而增大。     

MECHANICAL DEFLECTION OF POLYSILICON MICROCANTILEVER BEAMS USING NANOINDENTATION

0INTRODUCTIONThe miniaturization of microelectronic device is now reaching the mechanical field, allowing the integration of micromechanisms together with their operation electronics in a single device. This leads to interesting perspectives in the design of monolithic microrobtic systems by the micromachining techniques directly derived from standard silicon technology. Scientists have already moved MEMS into various stages of conception and development for making laboratories on chips,…     

Monitoring the chemical changes in Pd induced by hydrogen absorption using microcantilevers

The reactivity of the palladium shaped as a microcantilever is investigated as a function of the hydrogen stoichiometry. A small cell holding the microcantilever is designed to monitor the deflection and the flexural resonance response from high vacuum to a hydrogen gas pressure of several bars. The measurements show that the Young's modulus is accurate if the cantilever is thick enough to be described by a continuum mechanics approach. The orientation distribution function of the palladium grains determined by X-ray diffraction enables to correlate Young's modulus measured using microcantilevers with the elastic constant tensor issued from the literature. The surface stress induced by the dissociation of H(2) in palladium surface depends mainly on the cantilever cross-section. Cantilever response was found to be extremely sensitive to both the palladium lattice expansion induced by the insertion of hydrogen atoms into octahedral sites of palladium and the electronic affinity between palladium and hydrogen.     

Robust determination of Young's modulus of individual carbon nanotubes by quasi-static interaction with Lorentz forces

Young's modulus of an individual multi-wall carbon nanotube has been determined by the method of quasi-static transverse bending due to a Lorentz force observed in situ in a transmission electron microscope. The deflection of the nanotube allows the determination of Young's modulus using Euler-Bernoulli's beam equation. Because we determine the specific dependence of the deflection on the position along the nanotube axis, it is possible to gain insight into the type of mountings and furthermore allows for an estimation of the homogeneity of the nanotube. Both properties have been found to be of importance to determine Young's modulus. It was found to be higher by up to a factor of 1.6 compared to the value obtained by assuming rigid mountings.     

Mechanical characterization of micro/nanoscale structures for MEMS/NEMS applications using nanoindentation techniques

Mechanical properties of micro/nanoscale structures are needed to design reliable micro/nanoelectromechanical systems (MEMS/NEMS). Micro/nanomechanical characterization of bulk materials of undoped single-crystal silicon and thin films of undoped polysilicon, SiO(2), SiC, Ni-P, and Au have been carried out. Hardness, elastic modulus and scratch resistance of these materials were measured by nanoindentation and microscratching using a nanoindenter. Fracture toughness was measured by indentation using a Vickers indenter. Bending tests were performed on the nanoscale silicon beams, microscale Ni-P and Au beams using a depth-sensing nanoindenter. It is found that the SiC film exhibits higher hardness, elastic modulus and scratch resistance as compared to other materials. In the bending tests, the nanoscale Si beams failed in a brittle manner with a flat fracture surface. The notched Ni-P beam showed linear deformation behavior followed by abrupt failure. The Au beam showed elastic-plastic deformation behavior. FEM simulation can well predict the stress distribution in the beams studied. The nanoindentation, scratch and bending tests used in this study can be satisfactorily used to evaluate the mechanical properties of micro/nanoscale structures for use in MEMS/NEMS.     

关于夹芯梁四点弯曲试验的计算分析

在材料力学推导出的矩形截面梁剪应力公式基础上,利用夹芯梁轴向位移,弯曲挠度与剪切应变的几何关系,推导出了夹芯梁截面弯曲应力及弯曲挠度表达式,弹性理论及有关试验结果都证明了该方法的计算精确度较高.理论计算分析表明:外载荷作用下夹芯梁四点弯曲时,在外载荷作用处夹芯梁面板与芯材结合部位应采用强度理论进行校核;均布载荷作用下剪...     

线性分布载荷作用下双模量圆板的计算分析

双模量圆板在线性载荷作用下,会形成各向同性的拉伸区和压缩区.可将双模量圆板看成两种各向同性材料组成的层合板,采用弹性理论建立双模量圆板在外载荷作用下的静力平衡方程,利用此静力平衡方程即可确定双模量圆板的中性面位置.建立双模量圆板在外载荷作用下的弯曲微分方程,求得双模量圆板在线性分布载荷作用下的挠度方程.通过算例讨论分析双模量对圆板弯曲变形的影响,得到圆板材料拉压弹性模量相差较大时,其挠度计算不宜采用相同弹性模量经典薄板理论,而应该采用双模量薄板理论的结论.     

Mechanical property measurements of nanoscale structures using an atomic force microscope

This paper describes nanometer-scale bending tests of fixed single-crystal silicon (Si) and silicon dioxide (SiO2) nanobeams using an atomic force microscope (AFM). The technique is used to evaluate elastic modulus of the beam materials and bending strength of the beams. Nanometer-scale Si beams with widths ranging from 200 to 800 nm were fabricated on a Si diaphragm using field-enhanced anodization using an AFM followed by anisotropic wet etching. Subsequent thermal oxidation of Si beams was carried out to create SiO2 beams. Results from the bending tests indicate that elastic modulus values are comparable to bulk values. However, the bending strength appears to be higher for these nanoscale structures than for large-scale specimens. Observations of the fracture surface and calculations of the crack length from Griffith's theory appear to indicate that the maximum peak-to-valley distance on the beam top surfaces influence the values of the observed bending strengths.     

Axially constrained beams on elastic foundation

The problem of bending in axially constrained beams on a Winkler-type elastic foundation is considered. This nonlinear problem is approached by a differential equation method as well as a finite element method. Numerical results are presented which show that for a low modulus of the foundation the linear solution for deflection (which neglects axial constraint effect) yields deflection values which may be several times higher than the exact solution. The two methods are shown to be in good agreement.     

Reliability of an overground oil and gas pipeline with initial bending

For a beam sector of an oil and gas pipeline with initial axial bending, a mathematical model is developed that simulates the probability of nondestruction when the pressure, diameter, wall thickness, load, span length, maximum deflection, elastic modulus, and Poisson ratio are normally distributed. The parameters that decrease the number of emergency failures are established.     

Analytical and experimental study of mismatch strain-induced microcantilever behavior during deposition

A model of mechanical behavior of microcantilever due to mismatch strain during deposition of MEMS structures is analytically derived and experimentally verified. First, a microcantilever, modeled as an Euler-Bernoulli beam, is subjected to deposition of another material and a linear ordinary differential equation which considers the throughthickness variation of the mismatch strain is derived. Second, the deposition analysis is experimentally verified by electroplating of nickel onto an AFM cantilever beam. The deflection of the AFM cantilever is measured in-situ as a function of the deposited thin film thickness through the optical method of Atomic Force Microscopy and the mismatch strain with the through-thickness variation is determined from the experiment results. The usefulness of these equations is that they are indicative of the real time behavior of the structures, i.e. it predicts the deflection of the beam continuously during deposition process.