Study on morphology of copper-through silicon vias based on electron backscatter diffraction

• Main Author: Zhuo, Guoping.
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Materials::Electronic packaging materials
• Online Access: http://hdl.handle.net/10356/44765
• Institution: Nanyang Technological University

In this project, the effect of annealing conditions: without annealing, annealing at 250oC and annealing at 400oC is studied with the use of Electron Backscatter Diffraction (EBSD) on Copper-Through Silicon Via (Cu-TSV). As EBSD is a surface characterisation, the sample preparation is important in order to detect high quality Electron Backscatter Pattern (EBSP). Specimens were prepared with both manual polishing and ion milling. Morphology-related data were extracted from the EBSD orientation maps in the form of grain size distribution, pole figures, inverse pole figures and misorientation angle distribution. The data were then used to relate to Cu-TSV reliability phenomena such as Cu pumping which was reported in previous studies. Specimens that were manual polished were unable to generate high quality EBSP for orientation mapping to be done. This could be likely due to the copper vias having undergone oxidation as there was a period of waiting time before EBSD analysis was carried out. In addition, manual polishing may had resulted in surface damage of the specimens. Grain growth was seen in the ion-milled Cu-TSV specimen where similar orientation maps (as compared to previous studies by Okoro.C) were generated. The median grain diameter value is of more significance in estimating the grain diameter of the specimen. Although the pole figures of the specimens show no evidence of texture, analysis of the inverse pole figures and misorientation angle distribution showed there may be grain texture parallel to the TSV length. Atomic Force Microscopy (AFM) photographs showed evidence of Cu protrusion in all of the 3 test conditions. This narrowed down the mechanism of Cu pumping to the composition of the plating chemistry.