EFFECTS OF SPUTTER ETCHING AND PROCESS TECHNIQUES ON THE PROPERTIES OF SPUTTERED ALUMINUM FILMS

Aluminum and aluminum-silicon alloys are frequently used for silicon wafer metallization using dc magnetron high rate sputtering sources. Processes using these sputtering sources have been investigated with special emphasis on the coating properties of film resistivity, surface reflectivity, and step coverage. The major thrust of this work has been to improve these coating properties in the production processes of high rate, fully automatic coating systems, using sputter etching prior to wafer coating. This paper presents the results of these investigations. Coating reflectivity was found to be highly dependent on the release of adsorbed residual gases during deposition. Similarly, film resistivity was affected by the same phenomenon. The increase of pumping speed for water vapor significantly improved coating cycle times and the reflectivity and resistivity of the coatings. An effect of sputter etching on desorption is indicated after reducing the effects of residual gas and temperature rise of the substrate. Step coverage was also dramatically improved by limiting the number of coating passes in front of a sputtering target. Film resistivity improved to within 90% of bulk values and step coverage was better than 50% on a 90 degree step.