变形反射镜薄膜应力与元件变形有限元研究

残余应力是变形反射镜面临的一个重要问题。考虑薄膜中残余应力的起源,利用有限元软件建立了变形反射镜有限元模型。基于所建立的有限元模型,计算变形镜各部分受薄膜残余应力作用后的变形与应力分布。与试验测量结果进行对比,计算结果表明,建立的模型是合理的,薄膜产生的残余应力为张应力,氟化物薄膜产生的张应力大于ZnS薄膜产生的压应力,残余应力主要集中在变形反射镜镜面上,基本呈放射状分布,外圈驱动器受到应力较大。     

类金刚石薄膜残余应力的研究进展

类金刚石薄膜由于存在很大的残余应力,在实际应用中薄膜易产生裂纹、破裂甚至脱落。这些问题导致类金刚石薄膜在使用过程中过早失效。因此,缓解残余应力是类金刚石薄膜急需解决的问题和实际应用的需要。介绍了类金刚石薄膜残余应力的产生,对国内外调控残余应力的途径以及研究进展进行综述。使用有限元分析法模拟薄膜的残余应力可为类金刚石薄膜的制备和工艺设计提供参考。     

压头晶体各向异性对纳米压痕变形机理的影响

为了研究压头晶体各向异性对纳米压痕变形机理的影响,用多尺度准连续介质(QC)法模拟了不同晶向的Ni压头与Ag薄膜的纳米压痕过程,对比不同晶向的压头在薄膜的弹-塑性转变点和最大载荷时薄膜中的原子滑移带,发现压头的晶向是决定薄膜开启原子滑移系的难易的关键因素。研究了压头在不同晶向下纳米压痕过程中Ag薄膜的变形机理,发现薄膜中原子滑移大都由压头拐角处触发。用RiceThomson位错模型计算得到压头表面正应力和切应力的分布图,借助应力分布图讨论了薄膜原子滑移的开启机理。     

半球谐振子金属化镀膜残余应力的测量方法及影响因素研究

半球谐振子金属化镀膜是半球谐振陀螺制造的重要工艺环节.镀膜过程所产生的薄膜残余应力对谐振子Q值有较大影响,决定着半球谐振陀螺零偏稳定性等最终性能.本文采用X射线衍射法测量薄膜残余应力,研究了镀膜工艺参数和膜层厚度对残余应力的影响,结果表明:薄膜残余应力均呈压应力状态;随着沉积速率的增大,薄膜应力先增大后减小,有转化为拉...     

基于膜系设计控制薄膜残余应力的研究

残余应力大的薄膜,容易产生脱膜现象,使得薄膜失去所需功能.在激光薄膜领域,残余应力也是薄膜激光损伤阈值难以提高的原因之一.基于热收缩效应模型和弹性力学原理,从薄膜膜系着手提出了控制薄膜残余热应力的膜系设计原则,将该原则的评价函数用于薄膜膜系设计中,采用优化方法可以设计出残余热应力可接受的薄膜.     

不同厚度纳米Ti薄膜的力学性能

通过直流磁控溅射方法制备出四个不同厚度的纳米Ti薄膜,并分别采用纳米压痕仪、电子薄膜应力分布测试仪研究了Ti薄膜的力学性能和残余应力大小,结合分形维数方法和原子力显微镜对薄膜表面粗糙度和表面形貌进行了分析。实验结果表明:随Ti薄膜厚度的增加,薄膜晶粒尺寸逐渐增大,表面粗糙度和残余应力值随厚度的增加先增大后减小,而Ti薄膜弹性模量和硬度随薄膜厚度增加呈现出先减小随后增大的趋势。当薄膜厚度为600,2400,3600nm时薄膜中存在残余压应力,厚度为1200nm时存在残余拉应力,薄膜中残余应力分布最为均匀,但此时薄膜具有较低的硬度和弹性模量值。分析得出Ti薄膜中存在残余拉应力会使薄膜硬度和弹性模量值变小,残余压应力反之。     

纳米薄膜力学性能的尺寸相关性及其残余应力分析

系统地分析了纳米薄膜残余应力产生的物理机制，重点讨论了表面应力对纳米薄膜的影响，解释了纳米薄膜特殊的力学性能尺寸相关性，并通过考虑表面应力的有限元模型给出了纳米薄膜单轴拉伸的数值模拟结果。     

残余应力对压头诱导的硬质薄膜/韧性基底材料体系界面分层机制的影响

硬质薄膜在工程应用中经常承受高载荷作用。在接触载荷下,薄膜/基底体系通常产生剪切分层破坏和法向分层破坏,并直接影响材料的可靠性。硬质薄膜中较大的残余应力对界面分层破坏影响不容忽视。该文基于内聚力模型,采用有限元方法模拟残余应力对压头诱导的硬质薄膜/韧性基底界面分层破坏的影响规律;给出在不同残余应力下薄膜/基底界面分层破坏时的临界压入深度以及临界载荷;获得考虑残余应力时硬质薄膜/韧性基底界面分层破坏失效图,进而对薄膜材料的工程应用和采用压痕法测量界面结合性能提供指导。     

残余应力对固体氧化物燃料电池弹塑性性能的影响

半电池结构NiO-YSZ/YSZ由于弹性模量不同和热膨胀系数不匹配,导致烧结过程中产生残余应力. 残余应力对于燃料电池的性能和使用带来一定的影响, 本文把残余应力引入到计算薄膜性能的逆向分析模型中, 建立了考虑残余应力影响的薄膜的纳米压痕分析模型. 利用纳米压痕方法测试了离双层材料界面不同距离处的载荷-位移曲线和相应的材料性能, 用本文建立的模型计算了不同点的性能的变化, 发现离界面越远, 电解质YSZ薄膜的硬度越大. 将热力分析得到的残余应力场作为压痕模拟的初始应力场, 计算三棱锥压头下压痕载荷-位移曲线, 结果显示考虑残余应力时的载荷-位移曲线更接近实验曲线, 并给出了残余应力下压痕形貌图, 发现有残余应力时的压痕形貌更深更大.     

非平衡磁控溅射DLC薄膜应力研究

类金刚石（DLC）薄膜可用作红外增透保护膜,高的薄膜残余应力造成薄膜附着力下降是目前应用中存在的主要问题之一。本文从DLC薄膜作为红外增透保护膜的需求出发,采用非平衡磁控溅射技术生长DLC薄膜。实测了薄膜的残余应力,分析研究了薄膜残余应力在不同工艺条件下的变化情况。探讨了薄膜残余应力与薄膜厚度、光学透过率、离子能量、沉积速率以及能流密度之间的关系。研究结果表明,薄膜残余应力平衡值在0．9～2．2GPa之间,相应的单面镀膜样片的透过率在4μm波长处为69％～63％,随工艺的不同而变化。工艺优化后薄膜残余应力显著下降。硅基底上薄膜与基底剥离的力的临界值大于2160GPa．nm,最大薄膜厚度≥2400nm;锗基底上最大薄膜厚度≥2000nm,可以满足整个红外波段的需求。     

Effects of rapid thermal annealing on nucleation, growth, and properties of lead zirconate titanate films

The nucleation and growth behavior of solgel-derived lead zirconate titanate (PZT) films was investigated at different rapid thermal annealing (RTA) processes. The effects of RTA on PZT film surface morphology, crystal orientation, residual stress, and properties were also studied and are discussed. PZT nucleation and growth behavior were found to be more sensitive to heating rate than to hold time during RTA. Higher heating rates were preferred for uniform PZT nucleation and grain growth, which resulted in dense microstructures, smooth surfaces, and better film ferroelectric properties. Lower heating rates led to strong PZT (100) orientation, better film piezoelectric properties, and low residual stress, but at the risk of film cracks caused by arbitrarily distributed large crystallites with diameters of approximately 300 nm among crystallites with diameters of approximately 30 nm. Furthermore, the residual stress of the PZT film was found to be effectively reduced by extending the hold time.     

Alteration of internal stresses in SiO2/Cu/TiN thin films by X-ray and synchrotron radiation due to heat treatment

A break of wiring by stress-migration becomes a problem with an integrated circuit such as LSI. The present study investigates residual stress in SiO₂/Cu/TiN film deposited on glass substrates. A TiN layer, as an undercoat, was first deposited on the substrate by arc ion plating and then Cu and SiO₂ layers were deposited by plasma coating. The crystal structure and the residual stress in the deposited multi-layer film were investigated using in-lab. X-ray equipment and a synchrotron radiation device that emits ultra-high-intensity X-rays. It was found that the SiO₂ film was amorphous and both the Cu and TiN films had a strong {1 1 1} orientation. The Cu and TiN layers in the multi thick (Cu and TiN:1.0 μm)-layer film and multi thin (0.1 μm)-layer film exhibited tensile residual stresses. Both tensile residual stresses in the multi thin-layer film are larger than the multi thick-layer film. After annealing at 400 °C, these tensile residual stresses in both the films increased with increasing the annealing temperature. Surface swelling formations, such as bubbles were observed in the multi thick-layer film. However, in the case of the multi thin-layer films, there was no change in the surface morphology following heat-treatment.     

Residual stress measurement in filament-evaporated aluminium films on single crystal silicon wafers

Shadow Moire interferometry was used to determine the residual stresses in thin, filament-evaporated aluminium films deposited on (100) p-type, 10.16 cm diameter, 0.05 cm thick, circular single crystal silicon wafers. The aluminium film thicknesses ranged from 70 to 780 nm. Benchmark experiments on wafers without aluminium films showed that wafers possess in-plane residual stresses; the centre of the wafer is under tensile stresses of the order of 30 M Pa and these stresses decrease toward the edge of the wafers to approximately 10 M Pa. The deposition of aluminium films increases these tensile residual stresses by 3 to 15 M Pa depending on the film thickness. The increase in the stress is attributed to the stresses in the films.     

The effect of annealing on residual stress and dislocation propagation in silicon slices with damaged layer induced by scribing

The effect of annealing on residual stress and dislocation propagation in silicon slices with a damaged layer induced by diamond scribing, laser scribing and diamond blade cutting was studied by infra-red photoelastic measurements and dislocation pit observations. Residual stress and dislocation propagation both showed clear annealing temperature dependence at temperatures above 500° C, although the residual stress was greatly reduced by a small degree of dislocation propagation. The experimental results can be explained using the stress recovery theory by the model of the damaged layer with a mosaic crystal layer and a single crystal layer with micro-cracks and dislocations.     

Modeling of creep deformation and its effect on stress distribution in multilayer systems under residual stress and external bending

A general theoretical model was developed to predict the creep deformation and its effect on the stress relaxation and distribution in the multilayer systems under residual stress and external bending. Based on the proposed solution, a simplified solution for the special case of one film layer on a substrate is also presented. Finite element analysis was carried out to validate the presented model. Good agreements were observed between the finite element simulation and the prediction of the proposed model. In addition, the effects of film thickness on creep strain and stress distribution, the creep effect on neural axis location in the bilayer assembly subjected to the combination of residual stress and external bending were also discussed.     

导电聚噻吩薄膜材料的断裂机理分析

对用电化学方法制备的导电聚噻吩薄膜材料进行了拉伸破坏实验,并用电子散斑干涉法测量了力与变形关系同时用扫描电镜对材料的断口进行了断裂机理分析。研究结果表明:不同厚度的导电聚噻吩薄膜材料对其强度有较大的影响。引起薄膜材料力学特性变化的主要原因是其微结构生成机理不同,在较厚的薄膜自由表面上聚积有比较多的颗粒或大分子团结构,在干燥成型中形成一些微裂纹,这些微缺陷的存在严重影响了薄膜材料的承载能力,导致薄膜强度随厚度增加而降低。     

内嵌弹性区和结合力模型在薄膜/基底界面断裂中的应用

薄膜/基底结构是微电子学和材料科学中广泛应用的典型结构。由于加工工艺中材料力学、热学性能失配等原因导致的薄膜中出现的残余应力,是界面裂纹的萌生和扩展的重要原因。采用三参数(Γ₀, /σ_y,t)的修正的断裂过程区结合力模型,讨论了在塑性氛围下裂尖解理断裂的过程,裂尖应力分布,裂尖形貌和表征裂纹尖端断裂过程区特征参数对断裂过程的影响,并应用到均质金属薄膜/陶瓷基底结构中残余应力导致界面裂纹起裂和扩展的全过程分析中。     

Effect of residual stresses on the strength and fracture energy of the brittle film: Multiple cracking analysis

The aim of this paper was to address the effect of the residual stresses within the brittle film on the substrate on the film strength, fracture energy, and interfacial shear strength (IFSS). Special analyses were performed on the SiO_x film/polyethulene terephthalate substrate systems. The residual stresses were evaluated by using the curvature method. The film strength, fracture energy, and IFSS were estimated on the basis of the multiple cracking analyses. In the multiple cracking analyses, the system was subjected to the combination of the residual stresses and the unidirectionally applied stress. Results showed that the relationship between the crack density in the film and the applied strain can be predicted by adopting the energy criterion on the basis of the knowledge on the residual stress distributions in the film segment. The film strength and fracture energy for the initiation of film cracking were almost proportional to the compressive residual stresses in the film. With increasing the compressive residual stresses within the film, the IFSS also increased.     

Pb(Zr,Ti)O3薄膜微区残余应力的X射线面探扫描分析

根据在X射线二维衍射几何关系下建立的应力应变方程,提出了一种基于X射线多晶面探衍射仪系统分析射频磁控溅射制备的Pb(Zr,Ti)O3薄膜微区残余应力的测量方法,即通过基于X射线衍射圆锥形变的分析来表征薄膜的残余应力,试验结果表明薄膜所受为残余拉应力,同时利用X射线面探扫描方法评价了薄膜的残余应力分布.