Micro-XRD characterization of a single copper filled through-silicon via

Three single through-silicon vies (TSVs) of 6 x 50 mu m(2) in size with Ta barrier-Cu seed only, barrier-seed electroplated un-annealed and annealed at 420 degrees C for 30 min have been investigated by conventional XRD technique using 20 mu m and 50 mu m beams. The cross section of the Cu seed TSV was divided into three zones, 10 gm in depth for the bottom zone, the middle and the top zone each 20 mu m in depth. The diffractograms obtained with the 20 mu m beam indicated the presence of CuTa2O6 at top and bottom zones along with additional alpha-Ta planes at the bottom zone compared to the 50 mu m beam. After electroplating, the beta-Ta phase and an additional Cu (200) plane appeared. The annealed TSV showed the existence of predominantly alpha-Ta phases. The stress measurements revealed that annealed TSVs have a tensile stress compared to the un-annealed. This can be attributed the Cu grain growth. It is clearly observed that conventional XRD can greatly help to understand and optimize the TSV's development parameters. (C) 2015 Elsevier B.V. All rights reserved.