模拟空间环境下电接触薄膜失效行为及机理研究

发布时间：2018-06-10 05:02

本文选题：Au/Cu薄膜 + 环境失效　；参考：《北京科技大学》2017年博士论文

【摘要】：纳米或微米量级的电接触材料及器件因能够作为电互连线或接触电极而常用于诸如微电子、保护涂层和微电子机械系统等应用中。这些电接触薄膜材料主要是由金、银、铜、镍的金属膜层构成,因而具有良好的导电性能和化学惰性。双层Au-Cu电接触薄膜作为一种基础材料体系,在航天航空电系统中得到了广泛的应用。这些由电接触薄膜材料组成的器件服役在低地球轨道环境中并遭受空间环境的影响。同时随着电接触器件尺寸的不断减小,衍生出一些苛刻的服役条件,如高的电流强度以及对应高的局部温度等。在这些服役耦合条件下,薄膜以及多层体系可能会发生严重的互扩散现象,导致材料的失效并影响器件甚至整个系统的可靠性。因此,对电接触薄膜服役环境下进行失效行为和机理的分析和评价,对完善和开发电接触薄膜体系具有十分重要的意义。本论文针对电接触薄膜材料应用的多因素复杂空间环境,采用俄歇电子能谱(AES)、X射线光电子能谱(XPS)、高分辨透射电镜(HRTEM)、原子力显微镜(AFM)等多种分析方法,表征并研究分析Au/Cu薄膜在模拟环境条件和模拟直流电条件下失效行为的演变规律。围绕结构演变和性能演变之间的关系,系统研究Au/Cu薄膜在模拟空间环境下微结构演变以及结构缺陷的形成过程。并结合界面热力学,分析出Au/Cu薄膜在实验模拟的单因素以及耦合因素环境下本质的失效模式和机理。主要研究内容和结论如下：(1)设计并搭建两种空间环境模拟装置。一种是搭建的小型低地球轨道空间环境模拟装置,该装置主要用于薄膜样品在热环境、紫外辐照、气氛、直流电以及相关的耦合因素组成的模拟空间环境下的失效处理；另一种是搭建的电子元器件环境失效准原位模拟装置,该装置主要用于模拟环境条件主要包括了热环境、直流电以及相关的耦合因素组成的空间环境下薄膜样品的表面温度测量以及准原位分析。(2)研究在工作温度以及模拟空间环境中的其他典型因素耦合作用过程中的Au/Cu薄膜表面与界面结构的变化。环境温度升高能够致使薄膜表面产生缺陷,为膜层Cu原子向薄膜表面层的扩散提供扩散通道,从而导致薄膜的表面结构与成分的变化。根据界面热力学分析证实金属间化合物AuCu相最先在Au晶界内形成,从而引起Au层内应力梯度的产生,最后导致Cu原子通过Au晶界向自由面的扩散。(3) Au/Cu薄膜样品的温度在真空环境中紫外辐照作用下处理120 min后由室温上升至44℃,而后随着处理时间延长而保持稳定升高。计算结果表明Au/Cu薄膜在紫外辐照处理360 min后,Au/Cu界面处的Cu原子浓度梯度田起初的3.45下降至2.24。这是由于紫外辐照诱导Au层晶界内缺陷的增多,促使相对于Au原子具有较低功函数的Cu原子通过Au层内晶界向表面层跃迁。(4)研究真空环境中在紫外辐照与恒压直流电耦合作用下,Au/Cu和Cu/Si界面处缺陷的形成以及纳米级结构演变。这种耦合作用能够促使薄膜异质界面层以及表面层内缺陷增多,为原子的转移提供更多的扩散通道。直流电作用引起薄膜内原子团簇的定向迁移加剧了界面缺陷的扩展,并驱使Au-Cu金属间化合物的形成。研究同时发现Au/Cu薄膜与Si基底的界面处孔洞的形成主要与金属间化合物Au2Cu3目的生成有关。(5)研究真空环境中在恒压直流电作用下,Au/Cu薄膜层内相关Au-Cu金属间化合物的结构演变以及缺陷的形成过程。证实了在电子风力驱使下Cu原子向薄膜表面层的定向迁移和扩散,导致Au层晶界内亚稳态的固溶体向稳态的金属间化合物相转变时界面能的提高。持续增强的电子风力提高了薄膜层中Au-Cu金属间化合物的微结构演变速率,最终导致Cu层内孔洞缺陷的形核。在电子风力影响后期阶段,孔洞缺陷的长大以及Cu_20氧化物线的增厚与Cu层内间隙氧原子的定向迁移有关。(6)研究真空环境中在恒压直流电作用下,Au/Cu薄膜与Si基底之间的基底界面处缺陷的形成以及生长过程。真空环境中直流电作用能够引起薄膜Cu层内无定形Cu_2O氧化物线以及孔洞缺陷的生成,并在电子风力驱使下向着基底界面方向进行扩展。在结构缺陷迁移至基底界面处时,Cu-Si-O键被发现存在于无定形SiO2结构层内。在电子风力进一步驱使下Cu_20氧化物和孔洞缺陷最终以稳定形态存在于基底界面层附近。本论文从材料缺陷的角度探讨电接触薄膜材料在特定环境下的失效行为及失效机理,论文的结论及方法对电子器件的失效分析以及可靠性的研究具有理论指导意义。
[Abstract]:Nanoscale or micron magnitude electrical contact materials and devices are commonly used in applications such as microelectronics, protective coatings and microelectronic mechanical systems because they can be used as electrical interconnects or contact electrodes. These electrical contact films are made up mainly of metal films of gold, silver, copper and nickel, thus having good conductivity and chemical inertness. Double A U-Cu electrical contact film, as a basic material system, has been widely used in aerospace electric system. These devices consist of electrical contact film materials in the low earth orbit environment and suffer from the influence of space environment. At the same time, with the continuous reduction of the size of electrical contact devices, some harsh service conditions are derived. Such as high current intensity and corresponding high local temperature. Under these coupling conditions, thin films and multilayer systems may have serious mutual diffusion, resulting in the failure of the material and the reliability of the whole system. Therefore, the analysis and evaluation of the failure behavior and mechanism of the electrical contact film under the service environment. It is of great significance for the improvement and development of electrical contact film systems. In this paper, a variety of analytical methods, such as Auger electron spectroscopy (AES), X ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM), are used to characterize and analyze Au for the application of electrical contact thin film materials. Au The evolution of the failure behavior of /Cu films under simulated environmental conditions and simulated direct current conditions. Around the relationship between structural evolution and performance evolution, the evolution of microstructures and the formation of structural defects of Au/Cu films in the simulated space environment are systematically studied. The single cause of the experimental simulation of Au/Cu films in the experimental simulation is analyzed with the interfacial thermodynamics. The main research contents and conclusions are as follows: (1) to design and build two spatial environment simulation devices. One is a small and low earth orbit space environment simulation device, which is mainly used in the thermal environment, ultraviolet radiation, atmosphere, direct current and correlation film samples. The coupling factor consists of the failure processing in the simulated space environment, and the other is a quasi in-situ simulation device for the environmental failure of the electronic components. The device is mainly used to simulate the surface temperature of the film samples under the ambient conditions, including the thermal environment, the direct current and the related coupling factors. In situ analysis (2) the change of the surface and interface structure of the Au/Cu film during the coupling of other typical factors in the working temperature and the simulated space environment. The increase of the ambient temperature can cause the defect on the surface of the film, which provides the diffusion channel for the diffusion of the membrane Cu atoms to the surface layer of the film, thus leading to the surface junction of the film. According to the thermodynamic analysis of the interface, it is confirmed that the AuCu phase of the intermetallic compound is first formed in the Au grain boundary, which leads to the formation of the stress gradient in the Au layer, and finally causes the Cu atom to spread through the Au grain boundary to the free surface. (3) the temperature of the sample of the Au/Cu film is treated by the ultraviolet radiation of the vacuum ring at room temperature after the treatment of 120 min. It rises to 44 C, and then keeps steady with the treatment time. The results show that after the Au/Cu film is irradiated with 360 min, the Cu atom concentration gradient field at the Au/Cu interface at first descends to 2.24., which is due to the increase of the defect in the grain boundary of the Au layer induced by ultraviolet radiation, which leads to the lower function function relative to the Au atom. The Cu atoms transition from the grain boundary in the Au layer to the surface layer. (4) the formation of defects at the interface of Au/Cu and Cu/Si and the evolution of the nanoscale structure at the interface of ultraviolet radiation and constant pressure are studied in the vacuum environment. This coupling effect can increase the defects in the heterogeneous interface layer and the surface layer, and provide more for the transfer of the atoms. The directional migration of the atomic clusters in the film aggravates the expansion of the interface defects and drives the formation of Au-Cu intermetallic compounds. The formation of the pores at the interface between the Au/Cu film and the Si substrate is mainly related to the formation of the intermetallic compound Au2Cu3. (5) the study of the vacuum environment is constant. The structural evolution of the intermetallic intermetallic compounds in the Au/Cu film layer and the formation process of the defects in the film layer under the action of DC, confirmed the directional migration and diffusion of the Cu atoms to the surface layer of the film under the electronic wind force, which resulted in the increase of the interfacial energy when the solid solution in the Au layer was metastable to the steady state of the intermetallic compound. The continuous enhanced electron wind improves the microstructural evolution rate of Au-Cu intermetallic compounds in the film layer and eventually leads to the nucleation of the cavity defects in the Cu layer. In the late stage of the effect of the electronic wind, the growth of the hole defects and the thickening of the Cu_20 oxide line are related to the directional migration of oxygen atoms in the inner gap of the Cu layer. (6) study the vacuum environment. The formation of defects at the base interface between the Au/Cu film and the Si substrate is formed and the growth process under constant voltage direct current. The direct current in the vacuum environment can cause the amorphous Cu_2O oxide line in the Cu layer and the formation of the hole defects in the film. When migrating to the base interface, the Cu-Si-O bond is found to exist in the amorphous SiO2 structure. In the further drive of the electronic wind, the Cu_20 oxide and hole defects are finally located near the base interface layer. This paper discusses the failure behavior and failure of the electrical contact film material in a specific environment from the point of view of material defects. Mechanism, the conclusions and methods of the paper have theoretical guiding significance for failure analysis and reliability research of electronic devices.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB383.2

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