Non-destructive micro-Raman analysis of Si near Cu through silicon via

Abstract

Silicon near Cu through-silicon vias (TSVs) develops stresses during processing steps, and the local stress of Si around Cu TSVs of sizes ranging from 4 to 8 mu m was characterized using micro-Raman spectroscopy as a function of processing steps. Micro-Raman measurements showed that the max stress sum, sigma (r) + sigma (theta), is size dependent, where the stress sum of 88.7 MPa in the compressive direction was measured in Si for 8 mu m sized Cu via, and this max stress sum, sigma (r) + sigma (theta), decreased to 21 MPa in compression for 4 mu m sized Cu via. With the deposition of oxide/nitride overlayers, the stress sum was found to switch sign to 138.9 MPa in the tensile direction for 8 mu m sized Cu via after deposition of the SiN overlayers with residual compressive stress caused by ion bombardment. The measured stresses by micro-Raman was used to determine the keep-off-zone that can be used in device design to ensure reliability, and compared against the TCAD simulations results.