【作者】 聂磊；

【导师】 史铁林； 廖广兰；

【作者基本信息】 华中科技大学 ， 机械制造及其自动化， 2007， 博士

【摘要】 圆片键合是一种新兴的微电子制造技术,其特点是可将大尺寸的圆片材料一次性集成到一起,因此在材料制备、三维微结构集成和IC、MEMS器件制造及封装中应用日趋广泛。传统圆片键合技术通常需要在高温条件(>400℃)下进行,由此导致的热应力问题会造成器件工作不稳定和可靠性降低;同时过高的温度还会使圆片材料中的功能成分再度扩散,致使电学特性劣化。因此,低温,即400℃甚至300℃以下的圆片键合技术日益被重视,正逐步成为圆片级封装实用化和产业化的基础。所以,需要深入地研究低温圆片键合工艺机理,探索可行的键合手段并建立相应的抽象模型,为圆片级封装提供有效的方法和工具。本文立足于硅基圆片材料,对低温圆片键合的理论模型与机理、工艺、以及相应的检测技术进行了深入的研究,内容包括:对表面活化直接键合试验进行深入分析,研究了硅-硅直接键合的机理。通过分析各种分子原子力在键合过程中的作用,确定了低温键合模型。综合了各因素对最终键合质量的影响,提出了根据圆片表面形貌判定能否键合成功的标准。设计并完成了疏水性和亲水性表面活化直接键合的工艺试验,明确了各种活化配方和工艺流程对活化效果的影响。通过试验发现亲水性表面活化键合适用于低温键合,并根据试验结果提出了最佳活化配方和工艺。提出了一种将表面活化直接键合与激光局部键合相结合的键合技术。试验首先使用了亲水性表面活化溶液对键合片进行表面活化处理,并在室温下成功地完成了预键合。然后在不使用任何夹具施加外力辅助的情况下,利用波长1064nm的Nd:YAG连续式激光器,实现了激光局部键合,并取得了比较好的键合强度。试验结果表明,这种以表面活化预键合代替加压的激光局部键合技术克服了传统激光键合存在的激光对焦困难,压力不匀易损害键合片和玻璃盖板等缺点,同时缩短了表面活化直接键合的退火时间,提高了键合效率。将亲水性表面活化键合应用于图形圆片键合中,实验表明适合于裸片键合的活化工艺同样也能应用于低温图形圆片键合。利用低转化温度的玻璃中介材料实现了硅-硅中介键合,而且此玻璃中介材料膨胀系数与硅相接近,避免了热膨胀系数不匹配带来的热应力问题。试验结果表明键合界面均匀一致,界面两边的物质发生相互扩散,形成了牢固的连接,因此取得了较好的键合强度。对表现圆片键合质量的指标进行了全面的论述,并介绍了相应的检测手段及其优点和存在的问题。根据低温键合的特点,自行设计制造了红外检测系统。该系统主要用于对键合片进行红外透射无损检测,可对键合圆片进行静态和动态测试,为圆片键合的质量控制提供了高效快速的检测手段。更多还原

【Abstract】 Wafer bonding is an emerging micromanufacture technology. By this technology, the wafers with devices or not can be integrated into an entirety. Therefore it has been employed widely in materials manufacture, 3D microstrcture integration and IC MEMS devices fabrication and package. But the high temperature process often involved in the wafer bonding technology, which will cause the unstable and unreliable performance of the devices on wafers. And the impurity doped in wafers will be diffused again under the overhigh temperature. Thus the low temperature wafer bonding which performed under the temperature lower than 400℃or even 300℃attracts more and more attention over the world and will be the basic micromachining technology of wafer level package. So it is necessary to study the low temperature bonding mechanism and to find the reasonable process.This dissertation concentrated on the mechanism, process, and bonding quality measurement of low temperature wafer bonding and presented relative results.By analyzing of bonding experiments, the mechanism of low temperature Si-Si direct bonding was studied. Based on the analysis of roles of short distance forces in bonding processing and the threshold of wafer surface morphology for bonding was presented, the bonding model was definedThe low temperature hydrophobic and hydrophilic wafer bonding experiments were designed and performed. The results of experiments were analyzed carefully and by this means, the effect of different kinds of prescriptions and processes were discovered. It is obvious that the hydrophilic surface activated wafer bonding is much more suitable for low temperature Si-Si direct bonding than hydrophobic bonding and the RCA is the most proper activated solution for hydrophilic bonding.A new bonding technique to alleviate the high temperature adverse effect in silicon–glass bonding process is presented which combines the advantages of surface activated direct bonding and local laser bonding techniques. The hydrophilic surface activated solutions were used to make the bonding surfaces hydrophilic and the silicon-glass prebonding is accomplished at room temperature. The laser with a wavelength of 1064nm was used and its spot diameter was 500μm and the power is 70w. Without any external pressure, the prebonded pairs were bonded locally. The results of experiments shows that this bonding technique which employs surface activated prebonding to substitute pressure to maintain the intimate contact of bonding chips has overcome the disadvantages such as difficult focusing and easily breaking of bonding chips and glass cover in normal local laser bonding processing. This technique also improves the efficiency of surface activated direct bonding by shortening the annealing time.The hydrophilic surface activated bonding technology was used in pattern wafers bonding. The resuls of bonding experients indicted that this technology for bare wafers bonding is also fit for low temperature pattern wafers bonding.A low temperature Si-Si wafer bonding was realized by the aid of glass intermediate, the coefficient of thermal expansion of which is close to that of silicon. Thus the disadvantages caused by thermal stress were avoided. As shown in SEM figures, the cross section of bonding interface was smooth and the diffusion could be found around the interface. And the results of tension test indicated that the bonding strength is high enough.The typical manifestations of quality of wafer bonding were discussed, the relative test method was analyzed and the application environment was expounded. And for the sake of void detection, an infrared transmission inspection system was designed and built. The system can locate the void on the bonding interface and calculate the bonding rate nondestructively. And the inspection can be performed in static and dynamic mode. Thus, the system provides an effective and rapid measurement way for wafer bonding.更多还原