Oriented wedge-like hillocks on Al-0.5 wt.%Cu/TiN/SiO2/Si multilayer structure

The wedge-like hillock, accompanied with the rounded hillock, was thermally induced on the surface of Al-0.5 wt.%Cu/TiN/SiO7/Si multilayer structure a fter heat treatment at 400 degrees C for 30 min. Atomic force microscopy, s canning electron microscopy, and transmission electron microscopy were used to characterize the topography and microstructure of the wedge-like hilloc k as well as the large rounded hillock. The wedge-like hillock can be: divi ded into the wedge-like extrusion which stands alone, and the wedge-like pl ateau which appears next to the large rounded hillock. It consists of more than 200 original columnar grains which extrude upwards to form an inclined surface with an off-surface angle of 0.6-3.5 degrees. It is found that the , wedge-like hillock is virtually oriented toward one of two in-plane Si[01 1] cleavage directions. The oriented configuration of wedge-like hillock ca n be correlated to the asymmetric distribution of Al(111) texture in the Al -0.5 wt.%Cu film. Dislocation creep is proposed to be the most likely forma tion mechanism of the wedge-like hillock. In contrast, the rounded hillock (0.2-0.7 mu m) is about one order of magnitude higher than the wedge-like h illock (0.025-0.09 mu m). It has a newly formed Al crystallite lying over m ore than 200 original columnar grains. Grain boundary diffusion is consider ed to be the dominant mechanism responsible for the formation of the rounde d hillock. (C) 2000 Elsevier Science S.A. All rights reserved.