Variation of the Strength of a Grain in Polycrystalline Copper Thin Films of Semiconductordevice Based on the Order of Atom Arrangement

摘要

Copper has been applied to the TSV interconnection structure used in microelectronic devices because of its excellent electrical and mechanical properties. However, the physical properties of copper thin film interconnections were found to vary drastically depending on their micro texture and this serious degradation of physical properties was caused by its high-volume ratio of porous grain boundaries and fine columnar grains. Thus, the long-term reliability of products cannot be guaranteed and it is largely dominated by the strength of grain boundaries. In this study, a highly-reliable evaluation method of the strength of a grain and a grain boundary in polycrystalline copper thin films was used to determine a relationship between the crystallinity and their effective strength by using EBSD (Electron Back-scattered Diffraction) analysis and micro tensile test system. The crystallinity of a grain and a grain boundary was quantitatively evaluated by using IQ (Image Quality) value calculated from the Kikuchi pattern obtained from the EBSD analysis. And the strength of a grain and a grain boundary in polycrystalline copper thin films was evaluated by using the developed micro tensile test. Finally, it was found that there was a strong crystallinity dependence of the strength of a copper grain in electroplated copper thin films. In particular, the critical resolved shear stress (CRSS) ofa grainsignificantly decreased with the increase of the IQ value at the grain boundary.