Zhang Changxing, Qu Zhe, Fang Xufei, Feng Xue, Hwang Keh-Chih
Appl Opt. 2015 Feb 1;54(4):721-7. doi: 10.1364/AO.54.000721.
Thin film stresses in thin film/substrate systems at elevated temperatures affect the reliability and safety of such structures in microelectronic devices. The stresses result from the thermal mismatch strain between the film and substrate. The reflection mode digital gradient sensing (DGS) method, a real-time, full-field optical technique, measures deformations of reflective surface topographies. In this paper, we developed this method to measure topographies and thin film stresses of thin film/substrate systems at elevated temperatures. We calibrated and compensated for the air convection at elevated temperatures, which is a serious problem for optical techniques. We covered the principles for surface topography measurements by the reflection mode DGS method at elevated temperatures and the governing equations to remove the air convection effects. The proposed method is applied to successfully measure the full-field topography and deformation of a NiTi thin film on a silicon substrate at elevated temperatures. The evolution of thin film stresses obtained by extending Stoney's formula implies the "nonuniform" effect the experimental results have shown.
薄膜/衬底系统在高温下的薄膜应力会影响微电子器件中此类结构的可靠性和安全性。这些应力源于薄膜与衬底之间的热失配应变。反射模式数字梯度传感（DGS）方法是一种实时、全场光学技术，用于测量反射表面形貌的变形。在本文中，我们开发了这种方法来测量薄膜/衬底系统在高温下的形貌和薄膜应力。我们对高温下的空气对流进行了校准和补偿，这对光学技术来说是一个严重问题。我们阐述了反射模式DGS方法在高温下进行表面形貌测量的原理以及消除空气对流影响的控制方程。所提出的方法成功应用于测量硅衬底上NiTi薄膜在高温下的全场形貌和变形。通过扩展斯托尼公式得到的薄膜应力演变意味着实验结果所显示的“不均匀”效应。
