薄膜与基体间的附着力测试

薄膜是一种特殊形态的材料,在微电子等领域得到了广泛的应用.薄膜与基体间的附着性能在很大程度上决定了薄膜应用的可能性和可靠性,但是,迄今为止对薄膜与基体间界面的了解还不够深入,也没有一种通用的测量技术.阐述了薄膜与基体间的附着机理和增加附着力的途径,介绍了胶粘法、划痕法等各种比较常用的附着力测试方法.     

脉冲激光沉积类金刚石膜技术

脉冲激光沉积(PLD)技术制备类金刚石(DLC)薄膜存在着金刚石相含量较低、石墨颗粒多、薄膜与衬底附着力差、膜内应力大等技术难题,为此,研究人员研究出了多种技术措施,如通过引入背景气体、超快激光、偏压、磁场以及加热等措施提高了薄膜金刚石相含量;采用金刚石或丙酮靶材、减小单脉冲能量等措施减少了石墨颗粒;采用间歇沉积、真空退火、超快激光等措施减少了膜内应力;合理没计过渡层改善了膜与衬底间的附着力等.这些技术有力地推动了脉冲激光沉积技术的发展.     

硫化锌衬底上氧化铪保护膜制备及性能研究

采用磁控溅射法在硫化锌衬底上制备了氧化铪薄膜,并对氧化铪薄膜的结构和性能进行了分析和测试.结果表明,制备的氧化铪薄膜结构为单斜相,膜层致密,在8～12 μm波段对硫化锌衬底的透过率没有明显影响,硬度显著高于衬底的硬度,且与衬底结合良好,适合用作硫化锌的红外保护膜.     

金属薄膜附着性的改进

根据薄膜附着机理,综述了影响金属薄膜附着性的因素。通过引入中间过渡层,减少应力来提高薄膜与衬底之间的结合强度,改善金属薄膜的性能。适当的热处理不仅能消除内应力,增强界面反应,而且对薄膜的性能有一定的影响。     

利用射频磁控溅射法在柔性衬底上制备ZnO∶Zr透明导电薄膜

利用射频磁控溅射法首次在室温水冷柔性衬底 PET上制备出了可见光透过率高、电阻率低的掺锆氧化锌(ZnO∶Zr)透明导电薄膜.X射线衍射和扫描电子显微镜表明,ZnO∶Zr薄膜为六角纤锌矿结构的多晶薄膜,且具有平行于衬底方向的择优取向.实验获得ZnO∶Zr薄膜的最小电阻率为1.55×10-3 Ω·cm.实验制备的ZnO∶Zr薄膜具有良好的附着性能,其可见光区平均透过率超过90%.     

衬底温度对ZnO:Al薄膜结构和性能的影响

利用射频磁控溅射法采用氧化锌铝(98%ZnO+2%Al2O3)为靶材在普通载玻片上制备了ZAO(ZnO:al)薄膜,研究了衬底温度对薄膜晶体结构,电学和光学性能的影响.利用X射线衍射仪、场扫描电镜对薄膜的结构及表面形貌进行了分析,利用分光光度计和电阻测试仪分别测试了薄膜的光电学性能.结果表明,衬底温度对薄膜结构及光电学性能影响最大.溅射功率120 W、衬底温度300℃、工作气压0.6 Pa制得的薄膜具有良好的光电学性能(可见光平均透过率为79.49%(考虑衬底的影响,电阻率为4.99×10-2 Ω·cm).     

透明导电薄膜ZnO∶Zr的制备及特性研究

利用直流磁控溅射法在玻璃衬底上制备出了可见光透过率高、电阻率低的ZnO∶Zr(ZZO)透明导电薄膜.讨论了溅射功率对ZZO薄膜结构、形貌及光电性能的影响.研究结果表明,溅射功率对ZZO薄膜的结构和电学性能有很大影响.实验制备的ZZO薄膜为六角纤锌矿结构的多晶薄膜,且具有垂直于衬底方向的c轴择优取向.在溅射功率为115 W时,ZZO薄膜的电阻率具有最小值1.9×10-3 Ω*cm,其霍尔迁移率和载流子浓度分别为18.7 cm2*V-1*s-1和2.07×1020 cm-3.所制备ZZO薄膜样品具有良好的附着性能,其可见光区平均透过率均超过92%.     

RF磁控溅射法原位制备C轴择优取向ZnO薄膜

采用RF磁控溅射法在玻璃衬底上原位低温生长ZnO薄膜.生长出的薄膜对可见光具有高于90%的透射率,该薄膜具有良好的C轴取向.利用X射线衍射(XRD)的测试结果,分析了溅射工艺条件如衬底温度、氩氧比和溅射气压等对薄膜性能的影响,得到最佳的生长工艺条件为:衬底温度300 ℃,溅射气压1 Pa,氩氧比为25 sccm∶15 sccm.在此条件下生长的ZnO薄膜具有良好的C轴择优取向,并且薄膜的结晶性能良好.采用这种方法制备的ZnO薄膜适合用于制备平板显示器的透明薄膜晶体管和太阳电池的透明导电电极.     

陶瓷电路基板的新型金属化技术

研制成功一种新型的陶瓷电路基板的金属化技术，它兼容了薄膜和厚膜技术的优点，采用ＳＥＭ研究了陶瓷基体的浸蚀特性。测量了金属化导体的附着强度、可焊性、薄层电阻、导热能力及微波损耗，并进行了温循和老化等可靠性试验。测试及应用结果表明，采用该技术可在氧化铝瓷基板上制作附着牢固的铜金属化电路图形，其机、电、热性能优良，可靠性好，为微波和混合集成电路衬底金属化技术开辟了新的工艺途径。     

衬底温度对ZnO薄膜特性的影响

用脉冲激光沉积(PLD)的方法制备ZnO薄膜。通过对薄膜的X射线衍射(XRD)测试,分析了不同衬底温度下薄膜的结晶状况;通过对薄膜的光致发光谱线的测试,分析了不同衬底温度下薄膜的光致发光状况,同时进行了薄膜表面结构的测试。结果显示,衬底温度为400℃的样品结晶质量较高,具有C轴的择优取向,同时发光性能达到相对优化。     

LCP柔性基板的薄膜电阻制作技术

针对液晶聚合物(LCP)柔性基板高频电子封装应用需求,采用一种薄膜溅射工艺直接在LCP柔性基板上制作TaN薄膜电阻,研究不同等离子体预处理方式对LCP表面形貌和LCP表面薄膜金属膜层附着强度的影响,进一步研究溅射气压和氮气体积分数等参数对电阻性能的影响,考察LCP柔性基板上的TaN薄膜电阻精度及电阻温度系数(TCR),并制备出50Ω的薄膜电阻。结果表明:当射频功率为300 W的氧等离子体预处理600 s时,LCP表面的面粗糙度低,LCP基板表面薄膜金属膜层附着强度高,其值>5.0 N/mm²;当溅射功率为400 W、氮气体积分数为3%、溅射气压为0.2 Pa时,制备的TaN薄膜电阻的阻值精度高,阻值精度≤±4%,TCR电阻稳定性能好。     

Electromechanical properties of printed copper ink film using a white flash light annealing process for flexible electronics

We report on a systematic study of the electromechanical properties of flexible copper (Cu) thin film for flexible electronics. Cu ink is synthesized with chemical reduction process. Cu ink film spin-coated on a polyimide substrate is annealed with white flash light, also known as intense pulsed light (IPL), which guarantees a room temperature and sub-second process in ambient conditions. IPL annealed Cu film shows the electrical resistivity of 4.8 μΩ cm and thickness of 200 nm. The electromechanical properties of IPL annealed Cu film are investigated via outer/inner bending, stretching, and adhesion tests, and it is compared with conventional electron-beam evaporated Cu film. IPL annealed Cu film shows a constant electrical resistance within a bending radius of 6 mm. The bending fatigue test shows that the Cu film can withstand 10,000 bending cycles. In the stretching test, the Cu film shows a 50% increase in resistance when a strain of 2.4% was induced. At 4% strain, the resistance increases more than 200%. Meanwhile, the electron-beam evaporated film shows a constant resistance up to a strain of 4%. Lower stretchability of IPL annealed Cu film is attributed to its inherent cracks and porous film morphologies. IPL annealing induces the local melting at the interface between the substrate and Cu film, which increases the adhesion strength of the Cu film. These results provide useful information regarding the mechanical flexibility and durability of the nanoparticle films for the development of flexible electronics.     

Au/Cd复合电极沉积方法对其与(111)面CdZnTe衬底接触性能的影响

CdZnTe晶片是HgCdTe外延薄膜的理想衬底。为了优化CdZnTe衬底的电学接触性能,作者基于真空蒸发法和磁控溅射法分别在p型导电性CdZnTe晶片(111)B (富碲面)制备Au/Cd复合电极。通过接触粘附试验,研究了复合电极的制备方法对电极与衬底之间的粘附性;利用卢瑟福背散射光谱法（RBS）比较了不同沉积方法下样品的元素深度分布;采用电流-电压(I-V)测试比较了两种制备工艺对Au/Cd复合电极与CdZnTe衬底欧姆接触特性的影响,从而确定了最佳复合电极的制备工艺。     

碲镉汞材料提纯研究

杂质是影响碲镉汞器件性能的重要因素之一。对于碲锌镉衬底晶体和窄禁带碲镉汞材料来说,杂质的影响更加显著。主要论述了碲镉汞材料中常见的杂质类型以及杂质在材料中的作用,并分析了影响器件性能的主要杂质。采用辉光放电质谱法(Glow Discharge Mass Spectrometry, GDMS)测试了材料中的杂质含量,同时通过改进的区熔工艺降低了碲锌镉衬底及液相外延生长的碲镉汞薄膜材料中的杂质含量,提高了碲镉汞薄膜的电学性能,从而满足高性能碲镉汞红外探测器的制备要求。     

A comparative study on the measurement of toughness of stacks containing low-k dielectric films

Good adhesion strength of thin film stack is desirable for the integrated circuits (IC) manufacturing stage such as chemical mechanical planarisation (CMP). The scratch test and four-point bending test are two most commonly used methods to find the adhesion properties of thin film because of their simplicity and quantifiability. In this research, scratch test is used to find the practical adhesion energy (W_pa) of thin film stack and four-point bending test is used to find the critical strain energy release rate (G_c). The comparison of W_pa from scratch test and G_c from four-point bend test reveals that, for the same thin film stack, W_pa value is comparatively higher than G_c. The scratch test is semi-quantitative, in that the normal load at which a predefined failure event or delamination occurs is defined as a measure of adhesion. However, the four-point bending test is more quantitative in finding the adhesion properties. Thus, for practical application, such as CMP process, the G_c measurements from four-point bending test are recommended as references.     

Silicon and Nanoscale Metal Interface Characterization Using Stress-Engineered Superlayer Test Methods

Thin film layers are utilized in emerging microelectronics, optoelectronics, and microelectromechanical systems (MEMS) devices. Typically, these thin film layers are composed of different materials with dissimilar properties. A common mode of failure for thin films is delamination caused by external loading or intrinsic stress present in the materials. To characterize bonded thin film material systems, it is necessary to measure the interfacial fracture toughness. When material thicknesses approach micro- and nanoscales, interfacial fracture toughness measurement is a challenging task. Accordingly, innovative test techniques need to be developed to study interfacial fracture parameters. The ongoing research at Georgia Institute of Technology is developing fixtureless delamination test techniques that can be used to measure interfacial properties of micro- and nanoscale thin films. The single substrate decohesion test (SSuDT) and the single-strip decohesion Test (SSDT) are such fixtureless tests under development. In these tests, a thin film interface material of interest is deposited on a substrate. Then, delamination is driven by a superlayer material on top of the interface material. This superlayer material is sputter deposited and has high intrinsic stress. A deposited release layer material allows for the contact area between the interface material and the substrate to be controlled. These tests differ in geometry, but share the same generic methodology and can be used for a number of material systems over a wide range of mode mixities. This paper presents the methodology and implementation of the SSuDT and SSDT tests and compares results to better understand their scope. A case study of the interfacial fracture toughness as a function of mode mixity for titanium and silicon interface was performed.      

以铝作过渡层的c轴取向Si基ZnO晶体薄膜的生长及其肖特基二极管的研制

利用直流反应磁控溅射方法在金属Al过渡层上沉积了Si基Zn O晶体薄膜,并利用X射线衍射、扫描电子显微镜和扩展电阻测试仪对Zn O薄膜的晶体质量和电学性能进行了分析.结果表明,Zn O薄膜具有高度的c轴取向,样品表明光洁、平整,薄膜与衬底之间有清晰的过渡区.在此Zn O薄膜上成功地制备了肖特基二极管的原型器件,室温下的I- V测试结果表明该Au/ Zn O/ Al肖特基二极管具有明显的整流特性     

Stretchable Mesh-Patterned Organic Semiconducting Thin Films on Creased Elastomeric Substrates

Recently, many researchers have tried to develop stretchable semiconducting thin films that can maintain their electrical performance under stretching. However, the fabrication processes have not been sufficiently practical and feasible to be used for soft electronics. Here, a stretchable high-performance organic semiconducting thin film is fabricated by exploiting simultaneous patterning and pinning of a polymer semiconductor solution on an elastomeric substrate in which creasing-instability has occurred. As a result, a mesh-like polymer semiconducting thin film having vacant regions in the crease centers and surrounding crystalline regions near them can be fabricated. Due to the mesh-like morphology and the percolated crystalline regions, the polymer semiconducting thin film shows superior stretchability and charge-transport performance compared to the reference flat polymer thin film. When incorporated into organic thin-film transistors, the DPP-DTT polymer semiconducting thin film maintains its high field-effect carrier mobility (0.53 ± 0.03 cm² (V s)⁻¹) under a strain ε of 80% and is highly stable under repeated stretching cycles at an ε of 50%.     

Highly reliable flip-chip-on-flex package using multilayered anisotropic conductive film

Anisotropic conductive film (ACF) has been used as interconnect material for flat-panel display module packages, such as liquid crystal displays (LCDs) in the technologies of tape automated bonding (TAB), chip-on-glass (COG), chip-on-film (COF), and chip-on-board (COB). Among them, COF is a relatively new technology after TAB and COG bonding, and its requirement for ACF becomes more stringent because of the need of high adhesion and fine-pitch interconnection. To meet these demands, strong interfacial adhesion between the ACF, substrate, and chip is a major issue. We have developed a multilayered ACF that has functional layers on both sides of a conventional ACF layer to improve the wetting properties of the resin on two-layer flex for better interface adhesion and to control the flow of conductive particles during thermocompression bonding and the resulting reliability of the interconnection using ACF. To investigate the enhancement of electrical properties and reliability of multilayered ACF in COF assemblies, we evaluated the performance in contact resistance and adhesion strength of a multilayered ACF and single-layered ACF under various environmental tests, such as a thermal cycling test (−55°C/+160°C, 1,000 cycles), a high-temperature humidity test (85°C/85% RH, 1,000 h), and a high-temperature storage test (150°C, 1,000 h). The contact resistance of the multilayered ACF joint was in an acceptable range of around a 10% increase of the initial value during the 85°C/85% RH test compared with the single-layered ACF because of the stronger moisture resistance of the multilayered ACF and flex substrate. The multilayered ACF has better adhesion properties compared with the conventional single-layered ACF during the 85°C/85% RH test because of the enhancement of the wetting to the surface of the polymide (PI) flex substrate with an adhesion-promoting nonconductive film (NCF) layer of multilayered ACF. The new ACF of the multilayered structure was successfully demonstrated in a fine-pitch COF module with a two-layer flex substrate.