应力对薄膜结构与性能影响的研究现状

产生薄膜应力是在沉积薄膜过程中普遍存在的现象。薄膜应力的存在将影响薄膜的微观结构和性能,如薄膜的光学、力学等物理性能。同时影响到薄膜与基体材料的结合度以及基体材料的基本性能。主要总结了薄膜应力的产生机理、测试方法及其对薄膜结构和性能的影响,同时对薄膜应力的有效控制提出了展望。     

残余应力对SrRuO3薄膜磁学及电输运性能的影响

采用射频磁控溅射法在单晶SrTiO₃ (STO)衬底和硅(Si)衬底上制备出不同取向的SrRuO₃ (SRO)薄膜, 对薄膜的残余应力进行了分析, 并研究了应力对不同取向SRO薄膜磁学性能与电输运特性的影响。根据X射线衍射(XRD)结果分析可知, Si基SRO薄膜为多晶单轴取向薄膜, 且应力来源主要为热失配拉应力; STO基SRO薄膜为外延薄膜, 其应力主要为热失配压应力和外延压应力; 磁学性能测试表明, (001)取向SRO薄膜比(110)取向薄膜拥有更高的居里温度T_C; 压应力提高了(001)取向SRO薄膜的T_C, 却降低了(110)取向薄膜的T_C。电阻性能测试表明, 对于在同种类型衬底上沉积的SRO薄膜, (001)取向的薄膜的剩余表面电阻比(RRR)高于(110)取向的薄膜。另外, 拉应力引起了薄膜微结构的无序度增加, 弱化了表面电阻率的温度依赖性, 提高了金属绝缘体转变温度(T_MI)。     

薄膜应力的研究

本文首先简述了薄膜应力研究的发展过程,并指出了薄膜应力在薄膜研究与生产中的普遍性和重要性。薄膜应力研究的基本问题包括应力的测量、应力产生的机制、应力的控制和应力的作用。应力与薄膜结构、性能之间存在着相互影响的复杂关系。在综述前人研究工作的基础上,本文还简要介绍了Co—Cr合金膜和Gd-Fe合金膜的应力研究结果。     

薄膜的应力控制技术研究现状

薄膜应力普遍存在于薄膜元器件中,从而影响薄膜器件性能,限制了其良好的应用前景.所以控制薄膜的应力,消除其不良影响,是薄膜生产工艺中不可或缺的技术手段.本文对此详细阐述了几种常用的薄膜应力控制方法,并对以后研究工作的开展提出几点要求.     

张应力对TbDy-Fe RGMF磁性能的影响

通过离子束溅射沉积法制备了受不同张应力作用的TbDy-Fe稀土超磁致伸缩薄膜样品。借助LK-G150激光微位移传感器和交变梯度磁强计分别测试薄膜的悬臂梁自由端偏转量与磁滞回线,通过微磁学模拟软件OOMMF模拟计算不同张应力作用下薄膜的磁性能;研究张应力对薄膜磁致伸缩性能及软磁性能的影响。结果表明:张应力能显著提高薄膜的低场磁敏性,但其饱和磁致伸缩性能有所降低;模拟计算结果与实验结果均表明:随着薄膜所受张应力的增加,薄膜的矫顽力逐渐减小,软磁性能得到了改善。     

衬底温度对直流磁控溅射法沉积ZnO∶Ti薄膜性能的影响

利用直流磁控溅射工艺,在石英玻璃衬底上沉积出了具有高度C轴择优取向的掺Ti氧化锌(ZnO∶Ti,TZO)透明导电薄膜。研究了衬底温度对TZO薄膜应力、结构和光电性能的影响。结果表明,衬底温度对TZO薄膜的结构、应力和电阻率有重要影响。TZO薄膜为六角纤锌矿结构的多晶薄膜。在衬底温度为100℃时,实验获得的TZO薄膜电阻率具有最小值2.95×10-4Ω.cm,400℃时薄膜出现孪晶,随着温度的升高,薄膜应力具有减小的趋势。实验制备的TZO薄膜附着性能良好,可见光区平均透过率都超过91%。     

基底温度对磁控溅射制备ZnO薄膜性能的影响

利用射频磁控溅射,在Si基底上制备了ZnO薄膜.采用电子薄膜应力分布测试仪、X射线衍射和傅立叶变换红外光谱仪等检测手段研究了基底温度对其应力、微结构及光学性能的影响.ZnO薄膜在(002)晶面具有良好的c轴取向.在基底温度为200～300 ℃范围内,ZnO薄膜具有良好的结晶性能和较均匀的应力分布.红外光谱在430cm-1附近出现了Zn-O键的振动吸收峰.     

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...     

射频磁控溅射制备负热膨胀ZrW2O8薄膜的应力特性研究

采用ZrW2O8陶瓷靶材,以射频磁控溅射法在单晶硅基片上沉积制备了ZrW2O8薄膜。用X射线衍射仪和热膨胀仪分析了靶材的成分和热膨胀性能;用X射线光电子能谱仪和扫描电子显微镜分析了薄膜的组分及其表面形貌;用表面粗糙轮廓仪和薄膜应力分布测试仪测量了薄膜的厚度和应力。实验结果表明:制备的ZrW2O8靶材纯度高且具有良好的负热膨胀性能,磁控溅射沉积制备的ZrW2O8薄膜和靶材保持良好的化学成分一致性,且表面平滑、致密,在750℃热处理3 min后薄膜表面晶粒明显长大,并出现孔洞缺陷;衬底未加热时沉积制备的ZrW2O8薄膜选区应力差最小,应力分布最均匀,随着热处理温度和衬底温度的提高,由于薄膜和衬底的热膨胀系数的差异较大,薄膜选区内的应力差增加,薄膜应力分布不均性增大。     

多层薄膜的热应力研究

薄膜的应力对薄膜性能有着重要的影响.考虑了各个膜层弹性模量不同的情况,建立了多层薄膜热应力的数理模型,计算了典型多层薄膜体系中应力的分布.如果使用0级近似,每层薄膜中的热应力是由基底和膜层之间的热失配决定的,而不受其它膜层的约束;而使用一级近似,每一膜层中的热应力受其它膜层的影响.这种方法为多层薄膜应力的评价提供了依据.     

Numerical Study of Creep Damage Behavior of Thin Film/Substrate Systems under Indentation

A numerical study has been performed on the creep damage development of the thin film/substrate systems by the Kachanov‐Rabothov damage law. The emphasis was to study the influence of the modulus ratio of the substrate to the thin film, the size of the indenter and the indentation stress. Results show that two obvious damage zones are found ahead of the indenter. One is at the edge of the indenter, the other is at the interface ahead of the indenter edge. The influence of the modulus ratio of the substrate to the thin film on the indentation damage is not obvious before a certain creep time, and later, the greater modulus ratio of the substrate to the thin film has the smaller damage rate. And the indentation depth rate and the damage rate are also affected by the size of the indenter and indentation stress.     

薄膜电池封装膜弯曲疲劳寿命检测仪的研制

目的为了可靠地检测薄膜电池封装膜弯曲疲劳寿命,设计并制备一台封装膜弯曲疲劳寿命检测仪。方法仪器主要由机械运动机构、运动控制系统、固定保护机构等组成,使用此仪器对薄膜电池封装膜进行试验,研究循环弯曲对其的影响;利用有限元仿真,分析薄膜电池弯曲时封装膜内部的应力变化情况。结果随着弯曲角度的增大,封装膜所受的弯曲应力不断增大;在弯曲循环测试中,随着循环次数的增加,封装膜表面会产生疲劳裂纹,破坏了透明电极的胶合状态,影响了电池的光电性能;获得了封装膜在不同弯曲角度下的疲劳寿命曲线。结论该检测仪操作方便,基于此仪器进行弯曲疲劳寿命检测可有效提高薄膜电池封装的可靠性。     

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。     

A shaft-loaded blister test for elastic response and delamination behavior of thin film-substrate system

The elastic response of a thin film of photoresist deposited on a silicon wafer is studied by using a shaft-loaded blister test method developed recently. Experiment data are compared with an analytical solution. Results demonstrated that under shaft loading, the thin film underwent a pure bending mode at small deformation and gradually transformed to a pure stretching mode at larger deformation. The effect of residual stress on elastic response is also studied. The delamination of thin film from substrate can be successfully measured under displacement control mode by the shaft-loaded blister test.     

碳化硼薄膜制备的研究进展

综述了碳化硼材料的主要性能和制备碳化硼薄膜的主要方法,讨论了包括磁控溅射、离子束沉积和化学气相沉积等制备方法的优点及重要工艺参数,并就各方法指出了提高薄膜性能的主要措施,指出制备出更均匀、致密的碳化硼薄膜,提高薄膜与基体间的结合力,降低薄膜应力仍是今后研究的重点.     

Disappearance of stress singularity at interface edge due to nanostructured thin film

The purpose of this study is to examine the stress distribution near the interface between a nanostructured thin film and a solid body. We focus on a nanostructured thin film that consists of Ta₂O₅ helical nanosprings fabricated on a Si substrate by dynamic oblique deposition. The mechanical properties of the thin film are obtained by vertical and lateral loading tests using a diamond tip built into an atomic force microscope. The apparent shear and Young’s moduli, G′ and E′, of the thin film are 2-3 orders of magnitude lower than those of a conventional solid Ta₂O₅ film. Moreover, the thin film shows strong anisotropy. A finite element analysis for two types of components with different interface edges between the thin film and an elastic solid body is conducted under uniform displacement. One has a free edge where the surface-interface angle is 90°-90°, and the other has a short interface crack. These analyses indicate the absence of not only stress singularity but also high stress concentration near the free edge and the interface crack tip. The characteristic stress distributions near the interface are due to the nanoscopically discrete structure of the thin film.     

Finite element analysis of the indentation stress characteristics of the thin film/substrate systems by flat cylindrical indenters

The indentation stress characteristics of thin film/substrate systems by the flat cylindrical indenters have been simulated by means of the finite element method (FEM). The emphasis was put on the stress distribution ahead of the indenters. The influences of the friction coefficient between the indenter and the thin film, the thickness and hardening modulus of the thin film have been considered. It is found that the stress distribution was not affected by the friction coefficient. But the influence of the thickness and hardening modulus of the thin film on the stress distribution was obvious. At small indentation depth, the plastic deformation occurs at the edge of the indenter only, and the zone will propagation both vertically and laterally with the indentation depth increasing. When the indentation depth reaches a certain value, the thin film at the interface will occur the deformation plastic zone for the case studied in this paper. At lager depths, the two plastic zones will connect, and then the plastic zone propagates along the lateral direction. Beside, it is also found that the maximum of the Mises stress and the shearing stress on the interface occur at 0.8r and r(r is the radius of the indenter), respectively.     

The effects of film thickness variations on the residual stress distributions in coated Cr thin films

Generally, the residual stress of thin film coatings is calculated using Stoney's equation. However, variables in the manufacturing of the coated film, such as crystalline particle size and the unevenness of the thickness of the film, cause the radius of curvature of the beam to vary all over the beam. The cantilever beam curves not only in the axial direction but also in the transverse direction. Therefore, the residual stress in a film coating comprises not only axial residual stress but also transverse residual stress, and its distribution is also not uniform. Under such conditions, Stoney's equation must be modified. In this study, Si was used as a substrate in the production of cantilever beam specimens. Chromium thin films of various thicknesses were coated onto the Si substrates. The 3D digital image correlation technique was used to measure the out‐of‐plane displacement of the specimens at various positions. Then the modified Stoney's equation was used to obtain the axial and transverse residual stress at each measurement point to study the effect of variations in the thickness of the thin film on the magnitude and uniformity of the distribution of the residual stresses. Three thin film thicknesses 1, 2, and 3 μm were studied, and three specimens for each thickness were used. For each specimen, axial and transverse residual stresses were obtained at nine test points, and the equivalent residual stress was calculated. The results of this study reveal that as the difference between the thicknesses of the coating increased, average equivalent residual stress decreased and the distribution of stresses became more uniform. By comparing the corresponding results for the 1‐ and 3‐μm‐thick films revealed that the confidence levels in the average value and uniformity of the equivalent residual stress distribution, which increased with thickness, were 92.81% and 80.57%, respectively.     

Channel cracking in thin films on substrates of finite thickness

Solutions are presented for the elastic plane-strain problem of a crack in a coating on a compliant substrate of finite thickness. Analysis of the problem shows that substrate thickness has a significant effect on the steady-state energy release rate for channel cracks. This is so over a wide range of elastic mismatch between film and substrate, but is especially important if the substrate is more compliant than the film. Relaxation of the film stress due to elastic deformation of the substrate also plays an important role. If the substrate is clamped around the edge, as would be the case for a coated membrane, the stress in the coating cannot relax and the energy release rate for channel cracking increases significantly with decreasing substrate thickness. If the film stress is allowed to relax, however, the driving force for cracking is reduced as the substrate thickness decreases. The results from this study are used to evaluate the change in curvature of a film/substrate assembly due to channel cracking, a quantity that is of interest for the experimental determination of stresses in thin films. An expression for the elastic extension of the substrate due to channel cracking is derived making it possible to evaluate the effect of cracking on the mechanical behavior of bilayer membranes. It is expected that the present study may lead to the development of new experimental techniques for measuring the fracture toughness of thin coatings.     

基于PZT薄膜面内极化工作的低应力压电微传声器

本文设计、制作并测试了一种基于压电PZT薄膜面内极化工作的压电微传声器.利用压电薄膜的纵向压电常数,并通过压电微传声器面内电极的设计提高电极间距,以提高压电微传声器的灵敏度.由于基于PZT薄膜的多层结构常具有很大的残余应力,通过5种不同振动膜材料与PZT薄膜的应力匹配实验,研究了降低振动膜应力的方法.结果表明,对于相同尺寸的膜片,PZT/ZrO2/LTO/Si3N4具有最小的变形,其中心处的变形(200 nm)仅为膜片PZT/ZrO2/Si3N4/SiO2中心处变形(17μm)的1%.采用体硅微加工工艺制作了具有方形振动膜(2 mm×2 mm)的压电微传声器结构,采用LTO/Si3N4多层结构作为振动膜结构,方形膜片中心的圆形结构为PZT薄膜,环形叉指结构为Au/Cr电极.压电微传声器在0.15 kHz~6 kHz频率范围内的灵敏度约为0.1 mV/Pa.