Micro-Raman spectroscopy and analysis of near-surface stresses in silicon around through-silicon vias for three-dimensional interconnects

Abstract

Three-dimensional integration with through-silicon vias (TSVs) has emerged as an effective solution to overcome the wiring limit imposed on device density and performance. However, thermal stresses induced in TSV structures raise serious thermomechanical reliability concerns. In this paper, we analyze the near-surface stress distribution in a TSV structure based on a semi-analytic approach and finite element method, in comparison with micro-Raman measurements. In particular, the depth dependence of the stress distribution and the effect of elastic anisotropy of Si are illustrated to properly interpret the Raman data. The effects of the surface oxide layer and metal plasticity of the via material on the stress and Raman measurements are discussed. The near-surface stress characteristics revealed by the modeling and Raman measurements are important for design of TSV structures and device integration.

Thermomechanical characterization and modeling for TSV structures

“…Clearly, a sub-micron resolution was achieved in the measurement, but the results provided only the sum of the two individual stress components in Si. Further understanding of the stress characteristics in the TSV structure requires detailed stress analysis to delineate the stress components and correlate the micro-Raman measurements with the thermal cycling experiments [6,9].…”

“…To measure the near surface stresses in Si, the micro-Raman spectroscopy technique was used [9]. Raman spectroscopy relies on the inelastic scattering (or Raman scattering) of Si, where the frequency shift of the Raman modes provides a measure of the stress in Si.…”

“…The local stress distribution near the Si surface around the Cu vias is important on device performance and interfacial reliability [7,8]. This was measured by micro-Raman spectroscopy [9]. The stresses measured by Raman spectroscopy can in turn be correlated to that observed by the wafer curvature method through finite element analysis (FEA), taking into account the reference temperature, which was also based on the wafer curvature measurements.…”

Characterization of thermal stresses and plasticity in through-silicon via structures for three-dimensional integration

“…However, Raman spectroscopy is limited to measuring the near-surface stresses in Si but lacking the ability to analyze the stresses in Cu. Resolving individual stress components can also be difficult and often requires detailed modeling [12]. More recently, synchrotron x-ray microdiffraction has been applied to measure the stress characteristics for TSV structures [13].…”

“…One widely used technique is the micro-Raman spectroscopy, which measures the frequency shift of the Raman modes caused by strain in the Si surrounding the TSVs [10][11][12]. Depending on the Si orientation and the Raman system configuration, certain stress components for Si or their combinations can be deduced.…”