Lai Y W, Hamann S, Ehmann M, Ludwig A
Institute for Materials, Chair for Materials for Microsystems, Ruhr-Universität Bochum, 44780 Bochum, Germany.
Rev Sci Instrum. 2011 Jun;82(6):063903. doi: 10.1063/1.3600594.
We report the development of an advanced high-throughput stress characterization method for thin film materials libraries sputter-deposited on micro-machined cantilever arrays consisting of around 1500 cantilevers on 4-inch silicon-on-insulator wafers. A low-cost custom-designed digital holographic microscope (DHM) is employed to simultaneously monitor the thin film thickness, the surface topography and the curvature of each of the cantilevers before and after deposition. The variation in stress state across the thin film materials library is then calculated by Stoney's equation based on the obtained radii of curvature of the cantilevers and film thicknesses. DHM with nanometer-scale out-of-plane resolution allows stress measurements in a wide range, at least from several MPa to several GPa. By using an automatic x-y translation stage, the local stresses within a 4-inch materials library are mapped with high accuracy within 10 min. The speed of measurement is greatly improved compared with the prior laser scanning approach that needs more than an hour of measuring time. A high-throughput stress measurement of an as-deposited Fe-Pd-W materials library was evaluated for demonstration. The fast characterization method is expected to accelerate the development of (functional) thin films, e.g., (magnetic) shape memory materials, whose functionality is greatly stress dependent.
我们报道了一种先进的高通量应力表征方法的开发，该方法用于在微加工悬臂阵列上溅射沉积的薄膜材料库，这些悬臂阵列由4英寸绝缘体上硅晶圆上的约1500个悬臂组成。采用一种低成本的定制数字全息显微镜（DHM）来同时监测薄膜厚度、表面形貌以及每个悬臂在沉积前后的曲率。然后根据所获得的悬臂曲率半径和薄膜厚度，通过斯托尼方程计算整个薄膜材料库中应力状态的变化。具有纳米级面外分辨率的DHM能够在很宽的范围内进行应力测量，至少从几兆帕到几吉帕。通过使用自动x - y平移台，在10分钟内就能高精度地绘制出4英寸材料库内的局部应力。与之前需要一个多小时测量时间的激光扫描方法相比，测量速度有了极大提高。为了进行演示，对沉积态的Fe - Pd - W材料库进行了高通量应力测量。这种快速表征方法有望加速（功能）薄膜材料的开发，例如（磁性）形状记忆材料，其功能很大程度上取决于应力。
