Determination of residual stress with high spatial resolution at TSVs for 3D integration: Comparison between HR-XRD, Raman spectroscopy and fibDAC

Abstract

Three different experimental methods have been used to determine mechanical stresses in silicon nearby tungsten TSVs - HR-XRD performed at a synchrotron beamline, microRaman spectroscopy and stress relief techniques put into effect by FIB ion milling. All methods possess, to a different extend, high spatial resolution capabilities. However they differ in their sensitivity and response to the particular stress tensor components relevant for the residual stress state nearby TSV structures. Stress measurements were performed on test samples with TSVs in thinned dies, which were SLID bonded to a thicker Si substrate die. The measurements captured stresses introduced by the W-TSV as well as by the wafer bonding process. A stress range from several MPa to hundreds of MPa could have been covered with a spatial allocation ranging from 100 nm to tens of microns. Measurement results were compared to each other and to simulated stresses from finite element analysis.