Effect of effective modulus on hillock formations in Al lines on glass

The formations of top and side hillocks in aluminum (Al) lines on glass substrate were studied through scanning electron microscopy (SEM) images. The density of top hillock in Al lines with Mo capping layer was smaller than that of Al film without capping layer because the capping layer physically suppressed the formation of top hillock. Instead, side hillock as well as top hillock was observed in the lines. The density of side hillock increased when thicker capping layer was deposited on Al line. Based on the results of the finite element method (FEM) simulation, it is determined that this is because thicker capping layer causes the larger effective modulus in the line center part and the smaller effective modulus in the line edge part.