The purpose of this work is to relate desorption studies on spin-on-glass with electrical data on via resistance and yield. This will allow for a more detailed understanding of the in situ degas process preceding hot aluminum filling. It is shown that;he degas temperature and time need to be tuned for both physical and chemical water desorption. Insufficient degassing leaves the chemisorbed components unreleased and has a large impact on the electrical behavior of dense via structures, while the isolated ones are unaffected. More evidence for this density effect in the degas characteristic is provided by focused ion beam techniques.