Effect of the underlayer on the microstructure and surface evolution in Al-0.5wt.%Cu polycrystalline thin films

The effects of the Ti underlayer on the evolution of grain morphology, crystallographic texture, and surface roughness of Al-0.5wt.%Cu thin films during sputter deposition have been characterized. In comparison to SiO₂ substrates, Ti underlayers reduce the AlCu thickness at which film continuity is reached, reduce the AlCu columnar grain size, and allow exact Al (111) fiber texture development. The AlCu films on both Ti and SiO₂ are primarily randomly oriented at early stages of deposition. A near-(111) Al fiber texture in AlCu/SiO₂ films initiates during the preferential growth of ≈5° offset islands prior to film continuity, seeding the near Al (111) texture as film continuity is reached. The exact Al (111) fiber orientation in AlCu/Ti films develops after film continuity. The near-(111) and exact (111) fiber textures strengthen with further deposition due to combined normal and abnormal grain growth. Film coalescence and grain growth lead to a significant smoothing effect during the early stages of deposition.     

Texture and microstructure of thin copper films

Microstructure is an important factor influencing the reliability of thin film interconnects. The microstructure of copper films is of particular interest because of its use in numerous electronic applications. Pole figure x-ray diffraction and transmission electron microcopy were conducted on copper films deposited by several techniques: sputtering, partially ionized beam deposition, chemical vapor deposition, evaporation, and electroplating. Quantitative texture data are determined from fiber texture plots. A typical copper film consists of three texture components: (111), (200), and random. (220) and (511) texture components are possible under some deposition conditions. Compared to aluminum films, the fraction of the random texture component and the distribution of the (hkl) components in copper films are relatively large. Bimodal grain size distributions are observed in some films.     

Influence of initial microstructure and impurities on Cu room-temperature recrystallization (self-annealing)

The initial microstructure of thin electroplated Cu films was investigated for different layer thicknesses and plating conditions. The initial grain size of electroplated Cu thin films was found to be distributed homogeneously whereas the initial texture was inhomogeneous over film thickness. With increasing film thickness a transition occurs from a basis-oriented into a field-oriented texture. The knowledge about initial Cu microstructure for different plating conditions helped to clarify the factors of influence for Cu room-temperature recrystallization, called self-annealing. Furthermore, beside the microstructure also incorporated impurities were found to be of great importance for Cu self-annealing particularly in the case of a varying additive content in electrolyte.     

缓冲层厚度对透明导电薄膜ZnO:Zr性能的影响

利用直流磁控溅射法在有ZnO:Zr缓冲层的水冷玻璃衬底上成功制备出了ZnO:Zr透明导电薄膜,缓冲层的厚度介于35～208 nm.利用XRD、SEM、四探针测试仪和紫外-可见分光光度计研究ZnO:Zr薄膜的结构、形貌、电光性能.结果表明,薄膜的颗粒尺寸和电阻率对缓冲层厚度具有较强的依赖性.当缓冲层厚度从35 nm增加到103 nm时,薄膜的颗粒尺寸增大,电阻率减小.而当缓冲层厚度从103 nm增加到208 nm时,薄膜的颗粒尺寸减小,电阻率增大.当缓冲厚度为103 nm时,薄膜的电阻率最小为2.96×10-3 Ω·cm,远小于没有缓冲层时的12.9×10-3 Ω·cm.实验结果表明,在沉积薄膜之前先沉积一层适当的缓冲层是提高ZnO:Zr薄膜质量的一种有效方法.     

Tensile tests of micro anchors anodically bonded between Pyrex glass and aluminum thin film coated on silicon wafer

Micro anchor is a kind of typical structures in micro/nano electromechanical systems (MEMS/NEMS), and it can be made by anodic bonding process, with thin films of metal or alloy as an intermediate layer. At the relative low temperature and voltage, specimens with actually sized micro anchor structures were anodically bonded using Pyrex 7740 glass and patterned crystalline silicon chips coated with aluminum thin film with a thickness comprised between 50 nm and 230 nm. To evaluate the bonding quality, tensile pulling tests have been finished with newly designed flexible fixtures for these specimens. The experimental results exhibit that the bonding tensile strength increases with the bonding temperature and voltage, but it decreases with the increase of the thickness of Al intermediate layer. This kind of thickness effect of the intermediate layer was not mentioned in the literature on anodic bonding.     

Through-thickness characterization of copper electrodeposit

Through-thickness crystallographic texture, defect structure, and tensile embrittlement of 35 μm thick electrodeposit are characterized by successive thinning. An initially random grain structure, inherited from the substrate, evolves into a strong <220> fiber texture. The random to oriented grain transformation begins at the inception of thickening and is complete after about 15 μm deposit thickness, where about 0.9 volume fraction of grains become oriented near <220>. Further thickening of the deposit sharpens the texture, reducing the scatter around the <220> ideal orientation. A duplex coarse/fine particle (coherent domain) structure is obtained. Coarse particles along <220> are less defective and have smaller lattice strains; fine particles along <200>, presumably associated with the random grains, are defect-saturated with finely spaced twins, high dislocation density and enhanced lattice strains. With increasing distance from the shiny surface (of initial film formation), especially following the initial 10 μm deposit thickness, (a) along <220>: particle size and twin spacing increase whereas dislocation density and root mean square (rms) strains decrease, (b) along <200>: particle size increases gradually, dislocation density and rms strains increase sharply and the already fine twin spacing remains unchanged, and (c) the effective particle size ratio D_eff<220>:D_eff<200> exceeds 1.4, suggesting a twinning-induced z-direction particle shape anisotropy. A substantial decrease in tensile elongation is observed at 180°C. The embrittlement increases with the deposit thickness, attributed to the development of low density regions in the morphological boundaries. High elongation and embrittlement directional anisotropies are observed near the shiny surface, perhaps due to preferred nucleation on the substrate asperities.     

Evolution of Annealing Twins in Sputtered Cu Films

The Monte Carlo Potts model with n-fold method was used to simulate grain structure evolution in thin Cu films according to energetic competition principles. Surface/interface, grain boundary, and strain energy factors were applied to determine grain growth and crystallographic texture evolution as a function of film thickness. Furthermore, annealing twins were simulated through specific criteria that arbitrarily insert twin grains into the structure through grain boundary energy considerations. Four different types of microstructures were observed experimentally and simulated by the Monte Carlo technique.     

衬底温度对超声喷雾法制备大面积绒面SnO_2:F薄膜特性影响的研究

详细研究了衬底温度对超声喷雾热分解工艺制备的大面积绒面SnO2:F薄膜的影响和薄膜微结构与薄膜电学、光学性能之间的关系。试验曲线和SEM图的研究结果表明,将衬底温度从370℃提高到470℃以上薄膜结晶程度大大提高,晶粒尺寸明显增大;温度在470℃左右绒度达到13%。文章同时对超声喷雾热分解工艺制备大面积绒面SnO2:F薄膜做了工艺探索,并将实验制得的薄膜用于制备非晶硅薄膜电池,其效率达到了6.46%。     

Mechanical properties of thin-film materials evaluated from amplitude-dependent internal friction

A method is presented to evaluate the mechanical properties of thin-film materials from measurements of the amplitude-dependent internal friction. According to the constitutive equation, the internal friction in the film can be determined separately from measured damping of the film/substrate composite. The internal friction in aluminum films is dependent on the strain amplitude that is approximately two orders of magnitude higher than that for bulk aluminum. On the basis of the microplasticity theory, the amplitude-dependent internal friction in the film can be converted into the plastic strain as a function of effective stress on dislocation motion. The mechanical responses thus obtained for aluminum films show that the plastic strain of the order of 10⁻⁹ increases nonlinearly with increasing stress. These curves tend to shift to a higher stress with decreasing film thickness and also with decreasing temperature, both indicating a suppression of microplastic flow. The microflow stress at a constant level of the plastic strain varies inversely with the film thickness, provided the grain size is larger than the film thickness. The film thickness effect in the microplastic range can be well explained by the bowing of a dislocation segment whose ends are pinned at the film surface and at the film/substrate interface.     

0.7BiFeO_3-0.3PbTiO_3薄膜结构与电学性能的厚度效应

以溶胶–凝胶法在Pt/Ti/SiO2/Si(111)基底上制备了厚度为30~1 110 nm的0.7BiFeO3-0.3PbTiO3(0.7BFO-0.3PT)薄膜,研究了薄膜厚度对0.7BFO-0.3PT薄膜的结构与电学性能的影响。结果表明,随着膜厚的增加,晶格常数c与a的比值c/a以及晶粒尺寸都呈现先增大后减小的趋势,但其剩余极化强度及介电常数却均与薄膜厚度呈正比。厚度为180 nm的0.7BFO-0.3PT薄膜具有最大的矫顽场(2.99×105V/cm)和晶粒均匀度(42 nm),同时其晶格常数比c/a也达到最大,为1.129 9。     

薄膜中晶粒正常生长过程的研究

通过建立一个理论模型研究了薄膜中正常晶粒生长过程中晶粒的变化情况。晶粒按照边长数被分成不同的组,可以通过晶粒消失与晶界转换两种方式来改变边长的数目,在不同组之间进行转换。晶粒的长大与缩小由边长数与晶粒大小决定。计算机模拟的结果表明平均晶粒尺寸随时间呈线性增长,晶粒尺寸分布与已报道的结果基本一致。     

Atomic layer chemical vapour deposition of copper

Copper films with (1 1 1) texture are of crucial importance in integrated circuit interconnects. We have deposited strongly (1 1 1)-textured thin films of copper by atomic layer deposition (ALD) using [2,2,6,6-tetramethyl-3,5-heptadionato] Cu(II), Cu(thd)₂, as the precursor. The dependence of the microstructure of the films on ALD conditions, such as the number of ALD cycles and the deposition temperature was studied by X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy. Analysis of (1 1 1)-textured films shows the presence of twin planes in the copper grains throughout the films. SEM shows a labyrinthine structure of highly connected, large grains developing as film thickness increases. This leads to low resistivity and suggests high resistance to electromigration.     

Effects of Substrate Bias on Microstructure of Osmium-Ruthenium Coatings for Porous Tungsten Dispenser Cathodes

Osmium-ruthenium (Os-Ru) films used as coatings for porous tungsten (W) dispenser cathodes were investigated in this study. By applying different levels of substrate biasing power during sputtering, the texture of deposited Os-Ru films varied between {0002}, {10-10}, and {10-11} in this hexagonal close-packed alloy. Furthermore, film texture changed from one preferred orientation to other preferred orientation(s) during annealing (at 1050^degC_B for 10 min), during which the microstructure of certain Os-Ru films changed from a columnar to an equiaxed grain morphology. Due to a low degree of texture transition during annealing and due to the high compositional and structural stability of the Os-Ru grains, a 5 W bias power appears to be best for film deposition. In addition, the 5 W biased Os-Ru films transformed completely into a basal plane texture, which has the highest planar density, and grain size increased significantly (from ~20 to ~100 nm) during annealing, all while maintaining a columnar grain structure. These characteristics are believed to be helpful in inhibiting interdiffusion between the W substrate and the Os-Ru film. Preventing or slowing the interdiffusion of W atoms can improve the lifetime and even the performance of dispenser cathodes.     

The effect of thin film structure and properties on gold ball bonding

The gold ball bonding process is widely used for making interconnections between integrated circuit chips and package lead frames, yet the relationships between the wire/substrate materials properties and the bond formation processes are not yet well understood. While the creation of a metallurgical bond at the interface between the wire and substrate is required, the deformation of the wire and substrate also play an important role in bond formation. Bonding to thin film substrates is of particular interest, since thin films often exhibit mechanical behavior distinctly different from bulk materials. In the present study, a systematic investigation has been conducted to understand the effects of the structure and properties of aluminum thin films on the quality of gold ball bonds. A series of aluminum thin films was fabricated with systematic variations in hardness, roughness, thickness, and composition. Gold wires were ball bonded to these substrates, and the bondability and bond shear strengths were assessed. Metallographic sections of several of these specimens were made and examined in the scanning electron microscope. The results show that the film thickness has the most dominant effect on the bondability and bond strength; films that were 0.5 μm thick often exhibited low strength or poor bondability. Very hard films also gave poor results. Ultimately, these results can be used to predict the wire bond reliability expected from various types of thin film metallization.     

Thickness dependent physical properties of chemically deposited nanocrystalline MgSe thin films deposited at room temperature by solution growth method

Chemical bath deposition method has been employed to deposit nanocrystalline magnesium selenide thin films of thickness 104–292 nm onto glass substrates at room temperature. The deposition bath consists of magnesium chloride, triethanolamine (TEA) and selenium dioxide. The as deposited films were characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption, electrical resistivity and thermo-emf measurements. The X-ray diffraction (XRD) studies revealed that the crystallinity of the magnesium selenide thin film increases with thickness. SEM studies reveal that MgSe films exhibit uniform distribution of round shaped grains over the entire substrate surface.The optical band-gap and electrical resistivity of MgSe film decrease as the film thickness increases. Such type of dependence is attributed to the quantum size effect that is observed in nanocrystalline semiconductors.The thermo-emf measurement confirms its p-type conductivity.     

Room temperature grain growth in electroplated copper thin films

The microstructural changes in copper thin films at room temperature after electrolytic deposition have been studied by X-ray diffraction, wafer curvature stress measurement, electrical resistance measurement, and local orientation mapping. Changes in texture and stress were found to take place earlier than grain growth became distinctly visible. Additionally, FIB cross sections showed the evolution of grains in third dimension. The results are discussed in terms of grain growth from the bottom to the top of the film.     

7B04铝合金板沿厚度方向显微组织、织构及力学性能的研究

本文通过扫描电镜(SEM)及常规力学性能试验对7B04铝合金板沿厚度方向的显微组织、织构及力学性能进行了详细的研究,结果显示:样品芯部及表层晶粒都沿轧制方向拉长,芯部基本未发生再结晶,小角度晶界的含量随着离芯部距离的增加而减少,再结晶程度逐渐加强;未回溶相S(Al2CuMg)、Al7Cu2Fe、Al18Cr2Mg3在芯部及表层尺寸无明显差别;芯部织构主要为铜织构copper{112}〈111〉、黄铜织构Brass{110}〈112〉(B)、S织构{123}〈634〉、{241}〈112〉,{113}〈332〉及{231}〈124〉,表层织构出现旋转立方织构r-cube{100}〈011〉及{111}〈110〉织构,且随芯部到表层织构在基体中的整体体积含量减少。     

FeS_2薄膜厚度对晶体生长及光吸收特性的作用

在单晶Si衬底上用磁控溅射Fe膜并硫化的方法 ,制备了不同厚度的FeS2 薄膜 ,测定了晶体结构及光学性能 .结果表明 ,薄膜晶体学位向分布随薄膜厚度的增大可发生一定程度的变化 .随着薄膜厚度增加到 330nm ,晶粒尺寸增加而晶格常数减小 ;但当薄膜厚度大于 330nm时 ,晶粒尺寸下降而晶格常数增大 .光吸收系数以及禁带宽度均随薄膜厚度的增加而下降 .相变应力、比表面积及晶体缺陷随薄膜厚度的变化是引起薄膜晶体生长行为及光吸收性能变化的主要原因     

MgO缓冲层对Si衬底上制备Fe3Si薄膜性能的影响

采用磁控溅射方法和热加工工艺在n型Si衬底上溅射不同厚度的MgO层并制备Fe-Si薄膜层,退火后形成Fe3Si/MgO/Si多层膜结构.利用MgO缓冲层对退火时Si衬底扩散原子进行屏蔽,并分析MgO层对Fe3Si薄膜结构和电学性质的影响.通过X射线衍射仪(XRD)、扫描电子显微镜(SEM)和四探针测试仪对Fe3Si薄膜的晶体结构、表面形貌、断面形貌和电阻率进行表征与分析.研究结果表明:当MgO层厚度为20 nm时生成Fe0.9Si0.1薄膜,当厚度为50,100,150和200 nm时都生成了Fe3Si薄膜,生成的Fe3Si和Fe0.9Si0.1薄膜以(110)和(211)取向为主.随MgO缓冲层厚度增加,Si衬底扩散原子对Fe3Si薄膜的影响减小,Fe3 Si薄膜的晶格常数逐渐减小,晶粒大小趋向均匀,平均电阻率呈现先增大后减小趋势.研究结果为后续基于Fe3 Si薄膜的器件设计与制备提供了参考.     

一步溶液法制备有机-无机杂化钙钛矿薄膜

有机-无机杂化钙钛矿薄膜作为太阳电池的光吸收层,其薄膜的形貌、结构以及结晶程度等因素对电池的光电转换效率起到了决定性的作用,而薄膜的质量主要取决于制备工艺.采用一步溶液法制备了有机-无机杂化钙钛矿(CH3NH3PbI3)薄膜,主要分析了在氟掺杂氧化锡(FTO)导电玻璃、玻璃和多晶硅3种不同衬底上生长CH3NH3PbI3薄膜的形貌和结构的差异.结果表明,在FTO导电玻璃和玻璃衬底上生长的薄膜的晶粒尺寸和晶粒分布均匀,而在硅衬底上生长的薄膜的边缘晶粒尺寸大于中心处的晶粒,并详细分析了造成这种现象的原因.此外,在50℃的低温下对在FTO导电玻璃衬底生长的CH3NH3PbI3薄膜进行了不同时间的退火处理.实验结果表明,随着热处理时间的增加,晶粒尺寸也增加,但是合成的CH3NH3PbI3薄膜部分发生了分解.