LAUSR

Abstract Thermal cycling during annealing step can induce stresses and consequently lead to the Cu protrusion in through-silicon via (TSV) structures. However, the relationship between the thermal stress in Si and the consequent Cu protrusion behavior is still unclear, due to lacking of direct evidence of stress evolution during temperature variation. In this work, the Si stress distribution in Cu filled TSVs was characterized by in-situ μ-Raman spectroscopy (μ-RS) at different annealing temperatures. A considerable increase of the compressive stress (nearly 600 MPa) of the Si near the Cu interconnect was detected after the annealing step. Based on the assumption that the radial stress and circumferential stress were equal to each other in value but with opposite sign, the measured stresses were simplified as the axial stresses. The stresses measurement result indicated that the axial stress exhibited a linear relationship with the Cu protrusion height. The in-situ μ-RS characterization at different temperatures allows quantification of TSV protrusion during thermal cycling.