无压力辅助硅/玻璃激光局部键合

提出了一种新的无需外压力作用的硅/玻璃激光局部键合方法,通过对晶圆进行表面活化处理,选择合适的激光参数及加工环境,成功地实现了无压力辅助硅/玻璃激光键合.同时研究了该键合工艺参数如激光功率、激光扫描速度、底板材料等的影响.实验表明,激光功率越大,扫描速度越小,键合线的宽度就越大.实验结果显示,该方法能有效减少键合片的残余应力,控制键合线宽,并能得到较好的键合强度.该工艺可为MEMS器件的封装与制造提供简洁、快速、键合区可选择的新型键合方法.     

激光键合的有限元仿真及工艺参数优化

在硅/玻璃激光键合中,温度场的分布是影响晶片能否键合的关键因素.本文利用有限元法建立了移动高斯热源作用下硅/玻璃激光键合的三维温度场数值分析模型.运用该模型计算了不同的工艺参数条件下硅/玻璃的温度场分布,并由此得出键合线宽.然后通过漏选试验确定影响激光键合的主要工艺参数有激光功率、激光扫描速度及键合初始温度.最后通过对仿真结果进行回归分析,得到激光键合工艺的最优参数,为进一步研究激光键合工艺提供了理论依据.     

激光键合的有限元仿真及工艺参数优化

在硅/玻璃激光键合中,温度场的分布是影响晶片能否键合的关键因素.本文利用有限元法建立了移动高斯热源作用下硅/玻璃激光键合的三维温度场数值分析模型.运用该模型计算了不同的工艺参数条件下硅/玻璃的温度场分布,并由此得出键合线宽.然后通过漏选试验确定影响激光键合的主要工艺参数有激光功率、激光扫描速度及键合初始温度.最后通过对仿真结果进行回归分析,得到激光键合工艺的最优参数,为进一步研究激光键合工艺提供了理论依据.     

硅/玻璃紫外固化中间层键合

利用玻璃的透光特性和紫外固化的成熟技术,研究了一种使用紫外固化胶作为中间层的玻璃/硅室温键合工艺.通过选择一定波段的紫外固化胶,旋涂紫外胶后使用365nm光刻机作为紫外光源控制紫外固化,从而实现了硅/玻璃的中间层键合.分析测试结果表明,紫外固化辅助的中间层键合可以成功应用于硅/玻璃键合,中间层厚5～6μm,键合强度达到26MPa.该工艺只需室温条件,简单高效,成本低廉,无需额外的压力或电场,对于硅/玻璃低温键合封装具有潜在的应用价值.     

硅/玻璃紫外固化中间层键合

利用玻璃的透光特性和紫外固化的成熟技术,研究了一种使用紫外固化胶作为中间层的玻璃/硅室温键合工艺.通过选择一定波段的紫外固化胶,旋涂紫外胶后使用365nm光刻机作为紫外光源控制紫外固化,从而实现了硅/玻璃的中间层键合.分析测试结果表明,紫外固化辅助的中间层键合可以成功应用于硅/玻璃键合,中间层厚5～6μm,键合强度达到26MPa.该工艺只需室温条件,简单高效,成本低廉,无需额外的压力或电场,对于硅/玻璃低温键合封装具有潜在的应用价值.     

硅玻静电键合工艺研究

硅玻静电键合工艺是通过在较高温度和静电场作用下硅玻界面发生电化学反应,产生共价键O-Si-O的原理来完成键合过程的。目前,该工艺在制作微传感器和微机械系统中得到广泛应用。通过键合试验与结果分析,总结了键合温度、键合电压、压力、金属台阶对键合结果的影响,优化了硅玻静电键合的工艺参数及对金属台阶的要求。     

基于Rogers 5880复合介质基板的金丝楔焊键合工艺参数研究

运用正交试验法对键合效果进行了工艺参数优化方案设计和试验验证,以金丝键合强度为目标分别考察了键合功率、键合压力和键合时间3个工艺参数对键合金丝压点形态变化的影响,最终获取最优工艺参数组合为键合功率100 mW,键合时间220 ms,键合压力18 g,达到了提高金丝键合工艺可靠性的目的.     

基于DOE和BP神经网络对Al线键合工艺优化

Al丝超声引线键合工艺被广泛地应用在大功率器件封装中,以实现大功率芯片与引 线框架之间的电互连.Al丝引线键合的质量严重影响功率器件的整体封装水平,对其工艺参数的优化具有重要工业应用意义.利用正交实验设计方法,对Al丝引线键合工艺中的三个最重要影响因数(超声功率P/DAC、键合时间t/ms、键合压力F/g)进行了正交实验设计,实验表明拉力优化后的工艺参数为:键合时间为40 ms,超声功率为25 DAC,键合压力为120g;剪切推力优化的工艺参数为:键合时间为50 ms,超声功率为40 DAC,键合压力为120 g.基于BP神经网络系统,建立了铝丝超声引线键合工艺的预测模型,揭示了Al丝超声键合工艺参数与键合质量之间的内在联系.网络训练结果表明训练预测值与实验值之间符合很好,检验样本的结果也符合较好,其误差基本控制在10%以内.     

硅基MEMS加工技术及其标准工艺研究

本文论述了硅基MEMS标准工艺,其中包括三套体硅标准工艺和一套表面牺牲层标准工艺.深入地研究了体硅工艺和表面牺牲层工艺中的关键技术.体硅工艺主要进行了以下研究:硅/硅键合、硅/镍/硅键合、硅/玻璃键合工艺及其优化;研究了高深宽比刻蚀工艺、优化了工艺条件;解决了高深宽比刻蚀中的Lag效应;开发了复合掩膜高深宽比多层硅台阶刻蚀和单一材料掩膜高深宽比多层硅台阶刻蚀工艺研究.表面牺牲层工艺主要进行了下列研究:多晶硅薄膜应力控制工艺;防粘附技术的研究与开发.     

单片集成MEMS中的阳极键合工艺

分析了阳极键合工艺的原理及其工艺条件对CMOS电路的影响，并通过理论分析和实验研究了单片集成MEMS中的两种阳极键合方法：对于玻璃在硅片上方的键合方式，通过在电路部分上方玻璃上腐蚀一定深度的腔及用氮化硅层保护电路可以在很大程度上减轻阳极键合工艺的影响；而玻璃在硅片下方的键合方式，硅片上的电路几乎不受阳极键合工艺的影响，两种方法各有优缺点。     

镀钛玻璃与PET之间的激光透射连接及其性能

激光透射连接具有生物相容性的异种材料在生物医学植入体及其封装中具有良好的应用前景。利用半导体激光器对镀钛玻璃与聚对苯二甲酸乙二酯(PET)进行激光透射连接试验,其中玻璃上镀钛薄膜是通过射频磁控溅射方法完成的镀膜。通过单因素工艺研究了主要工艺参数激光功率、扫描速度和镀钛薄膜的厚度对连接强度的影响,并探讨了玻璃基片的表面粗糙度对镀钛薄膜粗糙度以及其连接强度的影响。通过搭接剪切试验得到镀钛玻璃与PET之间的连接强度,采用真彩共聚焦材料显微镜对拉伸失效后的试样表面进行观测和失效分析,使用X射线光电子能谱(XPS)检测激光透射连接过程中镀钛玻璃与PET之间化学键的形成信息。结果表明:主要工艺参数激光功率、扫描速度对连接强度有着重要影响,增加玻璃基片的粗糙度和镀钛薄膜的厚度可以提高其连接强度,为激光透射连接镀钛玻璃与聚合物提供了参考。     

Using Transmission Laser Bonding Technique for Line Bonding in Microsystem Packaging

The transmission laser bonding (TLB) technique has been developed for the formation of continuous line bonds for microsystem packaging applications. Line bonds are generated by overlapping single bonding spots, in which the degree of overlapping is achieved by varying the scanning speed of the laser as it irradiates the bonding wafers. An analytical model has been developed to guide the TLB process, attaining a uniform laser intensity that produces uniform bonds, satisfying the bonding requirements. Guided by this model, experiments have been conducted to bond Pyrex glass-to-Si wafers at various bonding conditions. To demonstrate the reliability of the technique and the model developed, the strength of the resulting bonded pairs has been evaluated by a micro tensile tester. At contact pressures higher than 1 MPa, the strength of bonded lines can reach a stable value of 9.2 MPa, which is comparable to those obtained by other major bonding processes. To further understand the associated bonding mechanism, the bonded interface has also been analyzed using auger electron spectroscopy and X-ray photoelectron spectroscopy, quantifying the drifting or diffusion of atoms that occurs between glass and Si wafers during the bonding process     

激光电视的消干涉

由于背景干涉条纹的影响,在激光视频显示系统中,通常获得的激光视频图像不仅对比度降低,而且像质较差.通过采用多像素扫描法,成功地突破了投影显示方式的技术瓶颈,消除了这种显示方式产生的干涉条纹,使激光显示与传统显示方式相比在像质上有了很大的提高.通过对激光显示过程中激光形成干涉机制的深入分析和研究,提出了"多像素扫描法",并设计了相关装置.该方法既可以用来实现投影显示,又可用来消除激光干涉.多像素扫描法既克服了扫描式激光显示的技术缺陷又解决了投影式存在的激光干涉条纹问题,获得了很好的显示效果.实践表明,该方法为激光显示研究提供了一种切实可行的方法.     

Non-silicon applications of direct bonding

Four examples of direct bonding in non-silicon applications will be considered. Fusing, locally by laser scribing or integrally by annealing, gives an increased bond strength, since a chemical reaction or interdiffusion process takes place at the interface. Direct bonding of magnetic materials is a special case due to the contribution of magnetic forces to the bond strength. This process has been used to design an optimized axial-field motor. Direct bonding of an optical-fibre plate and a fluorescent-garnet substrate makes it possible to achieve an electron-microscopic detector with a high resolving power. A polymer direct-bonded to a superfinish-polished metal can be used in an x-ray reflector as a surface-protective element.     

Investigation of ultrasonic vibrations of wire-bonding capillaries

Ultrasonic energy is widely used in wire bonding for microelectronics packaging. It is necessary to ensure that the maximum ultrasonic vibration displacement occurs at or near the tip of the bonding tool (capillary) for optimal performance. In this study, amplitude profiles of ultrasonic vibrations along capillaries were measured with load using a laser interferometer. This provided valuable information in understanding and improving capillary performance. The method was applied to real time applications to optimize capillary designs and bonding processes for specific bonding applications. First, the application of a new capillary material with different zirconia compositions was evaluated. The new material with certain amount of zirconia composition showed that it was the capillary material of choice for ultra-fine pitch wire bonding. Next, comparative analysis was conducted to investigate the ultrasonic energy transfer of a new ‘slimline’ bottleneck and the conventional bottleneck. The actual bonding response of the molded slimline bottleneck showed comparable performance with the ground conventional bottleneck using the same bonding parameters. Finally, optimization of a 60-μm-bond-pad-pitch process was performed on a wire bonder. Within the optimized parameter ranges, the ultrasonic displacement of the capillary was monitored. For all possible combinations of bond force and bond power, the ultrasonic displacement of the capillary increased with increasing bond power, without drastic changes caused by bond force changes. This indicated that the selected process window was located in a stable region.     

引线键合的动力相图和等效受载模型

 使用常规、微观电镜、动力相图和统计时频分析等方法,进行了引线键合机理的实验研究.通过对换能系统和劈刀振速的高频分量、键合压力的测试,以及键合界面微观结构的观察,建立了键合区域宏观受载等效模型,和对键合机理的框架认识.可作为键合过程优化的指导,和键合动力学建模的依据.     

Mechanical Strength and Interface Characteristics of Transmission Laser Bonding

A laser-based bonding technique, called transmission laser bonding (TLB), is studied for the purposes of device and wafer-level packaging. The TLB technique uses the specific characteristics of a laser to bond a transparent wafer on top of an opaque wafer. When a laser beam with a specific wavelength is passed through a transparent wafer, high-density laser energy is absorbed by the opaque wafer and melts a thin surface layer, resulting in the formation of strong chemical bonds across the two wafers. A Nd:YAG pulse laser has been used to bond a transparent glass wafer to a Si substrate. The associated bond strengths under various bonding conditions are examined by a microtensile tester to quantify the bonding quality. With a contact pressure higher than 0.5 MPa, the TLB strength can reach a stable value of 10.5 MPa, which is comparable to those obtained by other popular bonding processes currently used by the packaging industry. The wafer surface conditions are evaluated by atomic force microscopy (AFM) and profilometry, while Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) are used to study the characteristics of bonding interfaces. The AFM and profilometry results reveal that the wafer roughness and flatness required by TLB can be less stringent than those specified in the current industrial standards. The AES and XPS results are used to interpret the chemical and physical aspects of TLB formation and to provide the rationale for obtaining high-quality and high-strength TLB.     

Direct gold and copper wires bonding on copper

The key to bonding to copper die is to ensure bond pad cleanliness and minimum oxidation during wire bonding process. This has been achieved by applying a organic coating layer to protect the copper bond pad from oxidation. During the wire bonding process, the organic coating layer is removed and a metal to metal weld is formed. This organic layer is a self-assembled monolayer. Both gold and copper wires have been wire-bonded successfully to the copper die even without prior plasma cleaning. The ball diameter for both wires are 60 μm on a 100 μm fine pitch bond pad. The effectiveness of the protection of the organic coating layer starts from the wafer dicing process up to the wire bonding process and is able to protect the bond pad for an extended period after the first round of wire bond process. In this study, oxidization of copper bond pad at different packaging processing stages, dicing and die attach curing, have been explored. The ball shear strength for both gold and copper ball bonds achieved are 5 and 6 g/mil² respectively. When subjected to high temperature storage test at 150 °C, the ball bonds formed by both gold and copper wire bond on the organic coated copper bondpad are thermally stable in ball shear strength up to a period of 1440 h. The encapsulated daisy chain test vehicle with both gold and copper wires bonding have passed 1000 cycles of thermal cycling test (−65 to 150 °C). It has been demonstrated that orientation imaging microscopy technique is able to detect early levels of oxidation on the copper bond pad. This is extremely important in characterization of the bondability of the copper bond pad surface.     

激光透射焊接聚碳酸酯的有限元分析

为了研究激光透射焊接塑料过程中温度分布对焊接显微结构和强度的影响,采用ABAQUS软件,建立了使用激光透射焊接技术焊接聚碳酸酯(PC)的三维有限元热分析模型,通过子程序DFLUX和FORTRAN语言编程实现超高斯型热源的动态加载,有限元分析得到激光透射连接过程中温度场的分布。结果表明:当激光功率P=40 W,焊接速度v=40 mm/s时,焊接温度达到333.8℃,焊接强度最高(1.3 kN),焊接质量最好;当焊接速度v=10 mm/s时,最高温度达到589.5℃,拉伸强度为0.4 kN。当激光功率为40 W,焊接速度为100 mm/s时,焊接温度达到165.5℃,拉伸强度为0.74 kN。焊缝成形的好坏主要与焊接温度有关,可通过选择合适的工艺参数对这些缺陷进行控制。