A mechanism of stress-induced metal void in narrow aluminum-basedmetallization with the HDP CVD oxide dielectric

摘要

In 0.25 μm design-rule devices, notch-shaped micro-voids wereobserved in metal lines where high density plasma (HDP) chemical vapordeposition (CVD) oxide was used as an inter-metal dielectric (IMD)material. In this study, we have investigated the process conditionsrelated to the metal voiding. When the HDP CVD oxide depositiontemperature decreased, the void formations were reduced but stilloccurred at narrower metal lines with 0.64 and 0.75 μm pitches. Inthe case where TiN was used instead of Ti in the glue layer and Alcapping layer, metal voids were not observed. This result suggests thatthe tensile stress induced by the reaction between Ti and Al at hightemperature during HDP CVD oxide deposition is the major driving forcefor metal void formation. At high temperature, easy diffusionaccelerates the formation of metal voids. Heat treatment at 450° Cfor 30 min after metal patterning, which produces the Ti-Al reactionbefore deposition of the HDP CVD oxide, is proposed as the metal voidprevention method