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An ionized cluster beam (ICB) source has been developed for high rate deposition, and its possible application to ultra large scale integrated circuit (ULSI) metallization was investigated. Aluminum films were deposited onto oxidized silicon wafers using the ICB source. It was shown that an electrical resistivity was almost the same as the value for bulk aluminum, and the surface morphology of deposited films was improved by controlling the ionization and acceleration conditions of the cluster beam. It was confirmed that the ICB method showed an excellent coverage profile in contact holes when compared with the conventional sputtering method. Using the directivity of cluster beams, contact holes of 1.5 in aspect ratio were successfully metallized. From these results, it became evident that the ICB source is a favorable method for ULSI metallization.

A simple deposition model of evaporated species into quarter-micron contacts on an 8-inch diameter wafer, considering the scattering by gas molecules, predicted that the narrow angular distribution of evaporated species and deposition under low vacuum pressure are essential conditions for sufficient coverage of the contacts. An ionized cluster-beam (ICB) technique satisfies these essential conditions. The bottom coverage of TiN barrier film deposited by ICB under a nitrogen pressure of less than 10−2 Pa into contacts with an aspect ratio of 4 was improved to about 30% and the bottom coverage uniformity was about ±5% within the wafer. The crystal structure of the film was confirmed to be (111) orientation, which is necessary to form a preferentially oriented aluminum layer with a high durability against electromigration on TiN barrier film.

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