Characterization of Ta and TaN diffusion barriers beneath Cu layers using picosecond ultrasonics
Characterization of Ta and TaN diffusion barriers beneath Cu layers using picosecond ultrasonics
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DOI：
10.1016/j.ultras.2006.05.097
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发表时间：
2006-12-22
期刊：
影响因子：
4.2
通讯作者：
Dual, Juerg
中科院分区：
文献类型：
--
作者：
Bryner, Juerg;Profunser, Dieter M.;Dual, Juerg
在计算机芯片中，为了生产更小、更快和更高效的电子设备，铝正在被铜取代。铜的使用允许比铝更高的电流密度和因此更高的封装密度。然而，铜导致新的挑战和问题。它具有不同的机械性能和迁移到周围电介质和/或半导体层中的趋势。这些扩散过程可以通过所谓的扩散阻挡层来防止。扩散阻挡层是由钽和氮化钽或钛和氮化钛组成的非常薄的层，沉积在铜和衬底之间。泵浦-探测装置用于确定阻挡层和铜层的机械性能。这种短脉冲激光声学方法是非接触和非破坏性的。机械波的激发和检测热弹性使用激光脉冲的持续时间为70 fs。提供了掩埋扩散层的薄膜测量，并与扫描电子显微镜（SEM）、透射电子显微镜（TEM）和卢瑟福背散射光谱测量（RBS）进行了比较。热弹性力学模拟的结果，并给出了一个简短的概述模拟过程。目前的限制所提出的方法进行了讨论，并提出了未来的研究方向正在进行的项目。(c)2006年爱思唯尔B。V.保留所有权利。
In computer chips, aluminum is being replaced with copper in order to produce smaller, faster and more effcient electronic devices. The usage of copper allows higher current densities and thus higher packaging densities than aluminum. However, copper leads to new challenges and problems. It has different mechanical properties and a tendency to migrate into the surrounding dielectric and/ or semiconducting layers. These diffusion processes can be prevented by so called diffusion barriers. A diffusion barrier is a very thin layer consisting of tantalum and tantalum nitride or titanium and titanium nitride, deposited between the copper and the substrate. A pump- probe setup is used to determine the mechanical properties of the barrier layers and of the copper layer. This short- pulselaseracoustic method is contact- free and non- destructive. Mechanical waves are excited and detected thermoelastically using laser pulses of 70 fs duration. Thin film measurements of buried diffusion layers are provided and compared with scanning electron microscopy ( SEM), transmission electron microscopy ( TEM), and Rutherford Backscattering Spectroscopy measurements ( RBS). Results of a thermo- elasto- mechanical simulation are presented and a short overview of the simulation procedure is given. Current limits of the presented method are discussed and future directions of the on- going research project are presented. (c) 2006 Elsevier B. V. All rights reserved.