Sputtered aluminum has been used for interconnection in integrated circuits because of its low resistivity. However conventional sputtered aluminum has two important drawbacks, poor step coverage and poor planarization, which make it unsuitable for eubmicron multi-level interconnect process. CVD tungsten is an attractive option for forming plugs and interconnects but suffers several drawbacks. It is therefore preferable to use aluminum for both plugs and interconnections due to its simplicity and established prior history. We have developed a fully planarieed aluminum metallization process which produces void free contact plugs.

In order to verify the filling of the contact plugs, we have carried out extensive SEM analysis using secondary electron and backscattered electron imaging methods with various SEM sample preparation methods, i.e. chemical etching to extract the metal plug without inducing any damage to the metal, SEM cross section prepared with some oxide (about 1000Å) left in front of the metal plug and standard SEM cross section through the metal plug. Complementary secondary and backscattered imaging has proven to be a reliable method for ascessing the filling of the contact holes. Wafer and package level reliability data for the planarized aluminum metallization used on a megabit device will also be presented.