|approved||cho_summary_osi_11.pdf||2015-04-06 10:21:59||Yujin Cho|
Author: Yujin Cho
Requested Type: Oral
Submitted: 2015-03-25 10:49:31
Co-authors: F. Shafiei, M. C. Downer, B. S. Mendoza
The University of Texas at Austin
Austin, Texas 78712
The semiconductor industry has been investigating various 3D integration techniques to improve electrical performance and reduce power consumption of integrated circuits. Through-Silicon-Vias (TSVs) are ~10-µm-diameter electrochemically-deposited copper (Cu) rods that connect vertically stacked silicon layers. Cu is the connector of choice because of its desirable electrical and mechanical properties and its compatibility with manufacturing processes. However, due to mismatched thermal expansion coefficients of Si and Cu, routine thermal cycling induces stress around TSV rods that degrades carrier mobility and precipitates cracking. In this work, we noninvasively measure stress fields around Cu rods using stress-induced Second Harmonic Generation (SHG) microscopy. High stress gradients strengthen SHG intensity, since they break local centrosymmetry. We determine inhomogeneous stress distribution around TSVs subjected to various thermal histories, and compare results with calculated stress fields and with the theory of stress-induced SHG.