Submicron Via-Hole Filling using Al Low-Pressure Seed Process

Abstract

The submicron via-hole filling using a two-step Al sputtering process which consists of an Al low-pressure seed (ALPS) process and physical vapor deposition (PVD) Al, is described in this paper. The effect of the type of intermetal dielectric (IMD) material used, such as hydrogen silsesquioxane (HSQ), high-density plasma (HDP) oxide, and siloxane silicon-on-glass (SOG), on the via esistance and via-hole filling capability was evaluated and discussed. The Al film behavior after ALPS deposition, preheating, and PVD Al were investigated and it was determined that the out-gassing of moisture from siloxane SOG IMD significantly affects the via resistance and the key-hole formation in the via. A comparison of the via resistances of the Al-plug and W-plug was made. On the basis of the results, Al plugging with IMD materials such as HSQ or HDP oxide is considered to be superior to W plugging because of the lower via resistance and cost.