Microsampling technique for EBSP inspection on the cross-sections of copper trench lines in ULSIs

Abstract

The crystal microstructure of copper interconnects in ultra large scale integrations (ULSIs), depends on factors such as the trench line width and patterns. Therefore, inner crystal characterisation of the desired trench lines composed of copper is required. Electron backscatter diffraction pattern (EBSP) inspection has become a powerful technique for analysing the crystal characterisation of interconnects. However, EBSP inspection is sensitive to surface conditions such as contamination and strain. In this study, we applied the focused ion beam (FIB) technology, particularly, the microsampling technique to the preparation of samples for EBSP inspection on the cross-sections of the copper trench lines. As a result, we demonstrate that a damaged layer composed of a crystalline substance is formed on the plane of the copper as revealed by the 30 kV Ga(+) FIB milling, but an EBSP signal is detectable. In conclusion, the cross-sectional sample preparation technique employing microsampling is found to be very powerful for analysing the inner crystal characteristics of the desired copper trench lines by EBSP inspection.