Ryu Sang, Lee Kyungchun, Ma Seungwhan, Kim Youngman
Department of Materials Science and Engineering, Chonnam National University, Gwangju 500-757, Korea.
J Nanosci Nanotechnol. 2007 Nov;7(11):4081-3. doi: 10.1166/jnn.2007.089.
The development of stress in metallic thin films, monitored by in-situ curvature measurements during deposition, is analyzed. Three distinct stress regions including initial compressive, broad tensile, and incremental compressive stress were reported in terms of the film thickness (deposition time) by F. Spaepen. An experimental set-up was assembled for the in-situ curvature measurements utilizing vacuum thermal evaporation and multi-beam laser reflection points arrayed in x- and y-axis. The change in the spacing of laser reflected points was converted to the curvature of specimen, in turn, to instantaneous stress levels in the growing films using Stoney's formula. To investigate the effect on the distinct stress regions, the flux of the depositing metallic atoms was used as an experimental variable in this study. For the lowest flux cases for Cu and Ag, an additional second compressive stress stages after tensile maximum stress was observed in this study. Initial compressive part and tensile maximum stress regions appeared in shorter period of time for the thin films deposited at higher flux of atoms. Thus the flux of depositing atoms may affect the mechanisms of each stage. The initial compressive stress is conjectured to stem from the state of thin film surfaces; dynamic and relaxed surface. A broad tensile region is reported from the fact that the reduction of excess volume associated with grain boundaries and/or the coalescence of grains for high mobility materials. The incremental compressive stress region may be related to surface state and atomic mobilities.
分析了在沉积过程中通过原位曲率测量监测的金属薄膜应力的发展情况。F. Spaepen根据薄膜厚度（沉积时间）报告了三个不同的应力区域，包括初始压缩应力、宽拉伸应力和增量压缩应力。利用真空热蒸发和排列在x轴和y轴上的多光束激光反射点，组装了一个用于原位曲率测量的实验装置。激光反射点间距的变化被转换为样品的曲率，进而使用斯托尼公式转换为生长薄膜中的瞬时应力水平。为了研究对不同应力区域的影响，在本研究中使用沉积金属原子的通量作为实验变量。对于铜和银的最低通量情况，本研究中观察到在拉伸最大应力之后出现了额外的第二个压缩应力阶段。对于以较高原子通量沉积的薄膜，初始压缩部分和拉伸最大应力区域在较短时间内出现。因此，沉积原子的通量可能会影响每个阶段的机制。推测初始压缩应力源于薄膜表面的状态；动态和松弛的表面。据报道，由于与晶界相关的多余体积的减少和/或高迁移率材料的晶粒聚结，出现了一个宽拉伸区域。增量压缩应力区域可能与表面状态和原子迁移率有关。
