集成电路互连薄膜机械性能多参数的表面波无损表征研究

With the rapid development of very large scale integrated circuits (ULSI), mechanical properties of new developed interconnect films become the key problems affecting the chip fabrication, performance, reliability, and the life of the ULSI chip. The suitable advanced characterization technology for measuring the mechanical properties of new interconnect films is highly desired. Based on the dispersion properties of surface acoustic waves (SAW) propagating on the layered structure, nondestructive characterization of key mechanical properties of Young's modulus, adhesion of interconnect films by SAW will be investigated in detail. This technology could overcome the shortcomings such as inaccurate, film damage in the traditional nano-indentation method for Young's modulus measurement. The idea of nondestructive and quantitative measuring the adhesion between the film and the substrate by SAW has been proposed firstly by our group. This method could overcome the disadvantages such as non-quantitative, film damage in the conventional methods of four-point bending, scratch, tape pasting, drawing method, and so on. The research will reveal the mechanism of the key parameters such as the surface roughness, the interface conditions and the film thickness on the wave propagation and the dispersion features during the SAW propagating on the layer structure. Make clear the error sources in the Young's modulus characterization by SAW, and propose the revised scheme. Study the correlation of sensitive parameters respect to the film adhesion in the spring hypothesis model and cohesive zone model proposed in the SAW characterization technology. Enhance the accuracy and reliability of nondestructive surface acoustic wave detection for the mechanical properties of the interconnect films. Contribute this advanced technology to the development and fabrication of the new interconnect films in the ULSI industry.

随着超大规模集成电路的快速发展，芯片互连系统中不断更新的互连薄膜机械特性成为影响芯片制备、性能、可靠性、寿命的关键参数，亟需发展适合新型互连薄膜特点的先进测试技术。本项目基于超声表面波在分层材料上的频散特性，对互连薄膜的杨氏模量、粘附性等关键机械参数进行无损表征研究。此技术可以克服传统纳米压痕法测试薄膜杨氏模量结果不准确、薄膜受损等缺点。薄膜粘附性的表面波无损检测方法是本研究组在国际上率先提出的，可以克服四点弯曲法、划痕法、粘揭法、拉伸法等方法不能连续量化表征、对薄膜造成损伤等缺点。研究将揭示薄膜表面粗糙度、界面条件、膜厚等关键因素对表面波传输和频散效应的作用机制，明确影响杨氏模量表征结果的误差来源，给出修正方案。对表征薄膜粘附性的弹簧假设模型和内聚力模型的敏感参数进行研究和对比。提升表面波无损检测互连薄膜机械特性的准确性和可靠性，服务于集成电路新型互连薄膜研制和生产中的无损检测。

随着超大规模集成电路（ULSI）的快速发展，芯片的互连薄膜机械特性成为影响芯片制备、性能、可靠性等的一个关键参数。本项目利用超声表面波(SAW)在分层结构中传播时的频散现象，重点研究了ULSI互连薄膜机械性能多参数的表面波无损表征。项目引入内聚力模型（CZM）和声弹性理论，实现SAW技术定量、精确、无损地表征出薄膜界面的粘附性和薄膜残余应力，提出了一种基于SAW技术的判定不同薄膜/衬底结构的界面间粘附质量的方法。研究了界面粘附性和薄膜残余应力和对SAW技术测量薄膜杨氏模量时的影响，对造成的测量误差进行了修正，并提出了一种同时测量薄膜杨氏模量和薄膜/衬底间界面粘附性的方法，提高了检测结果的可靠性。提出了一种SAW表征薄膜厚度的优化算法，将测量误差降至2%。研究了表面/界面粗糙度对SAW测量薄膜杨氏模量和界面粘附性的影响程度。研究表明：研究的样片范围内，粗糙度对表面波测量影响小于5%。本研究所选的激光器脉宽为800 ps，当激光聚焦线元宽度控制到约为10 μm以下时，激发出的信号同时具有较大的幅值和频域宽度。设计了一款手持式的双探头的压电转换探头和一种适用于压电转换器表面波检测实验的对准装置，得到频宽为250 MHz的表面波实验信号。对多种重要的集成电路互连薄膜进行了相应参量的SAW表征。测试对象主要包括互连绝缘材料SiO2、纳米多孔SiO2、掺Cs的多孔SiO2、致密Black Diamond、纳米多孔Black Diamond、多孔有机硅酸盐玻璃（OSG）等薄膜，薄膜厚度范围覆盖300-1000 nm。实验中，表面波法的杨氏模量表征精度可达0.1 GPa，粘附性表征精度可达0.1 PPa/m，与传统方法测量结果进行了对比，验证了表面波法的正确性和可靠性。. 总体上，本项目顺利完成了研究内容，实现了研究目标，获得了预期的科研成果。培养多名青年研究骨干和研究生，发表7篇期刊论文，其中6篇被SCI检索，2篇EI国际会议论文，申请16项中国发明专利，授权2项实用新型，开展了多次国内外科研合作与交流。