Measurement of full-field curvature and geometrical instability of thin film-substrate systems through CGS interferometry
Measurement of full-field curvature and geometrical instability of thin film-substrate systems through CGS interferometry
复制标题
DOI：
10.1016/j.jmps.2003.09.031
复制
发表时间：
2003-11
影响因子：
5.3
通讯作者：
T.-S. Park;S. Suresh;A. Rosakis;J. Ryu
中科院分区：
文献类型：
--
作者：
T.-S. Park;S. Suresh;A. Rosakis;J. Ryu
通过相干梯度传感 (CGS)，研究了厚得多的硅衬底上的薄钨薄膜分叉之前和之后的大变形行为，这是一种光学、全场和振动不敏感的技术。由于CGS获得的条纹通过适当的光学器件代表了面外位移的梯度轮廓，因此可以直接从条纹数密度获得晶片的曲率。两个正交主方向上的测量曲率，其值与基于大变形理论的解析和数值预测相当一致，清楚地表明，当分叉发生时，晶片的平衡形状从球体变为椭球体。与仅提供单个法向（或直接）曲率分量的一维扫描方法相比，当晶片相对于其平坦区域旋转时，可以获得扭曲（或剪切）以及曲率的法向分量。经典的莫尔圆表示也用于合理化扭曲曲率的演变。最后，可以使用图像处理分析通过全场曲率图捕获由于不均匀薄膜应力导致的局部曲率变化。
Large deformation behavior prior to and after bifurcation of thin W films on much thicker Si substrates is investigated by recourse to coherent gradient sensing (CGS), which is an optical, full-field and vibration-insensitive technique. Since fringes obtained by CGS represent the contours of gradient in out-of-plane displacement through appropriate optics, curvature of the wafer can be obtained directly from the fringe number density. The measured curvatures in two orthogonal principal directions, whose values agree reasonably with both analytical and numerical predictions based on large deformation theory, clearly show that the equilibrium shape of the wafer changes from a sphere to an ellipsoid when bifurcation occurs. In contrast to the one-dimensional scanning method, which provides only a single normal (or direct) curvature component, twist (or shear) as well as normal components of curvatures can be obtained as the wafer is rotated with respect to its flat zone. A classical Mohr's circle representation is also used to rationalize evolution of the twist curvatures. Finally, local curvature variations due to non-uniform film stresses can be captured by full-field curvature maps using image processing analysis.