Very Low Pressure Selective Aluminum Chemical Vapor Deposition Using Dimethylaluminum Hydride Without  H 2 Carrier Gas

Abstract

Very low pressure aluminum chemical vapor deposition (Al CVD) using only dimethylaluminum hydride (DMAH) as a source gas has been examined and the resultant growth chemistry and Al film properties have been compared with those resulting from the use of conventional gas supply systems. DMAH is supplied without carrier gas by vaporizing liquid DMAH just before Al CVD and film deposition progresses efficiently at a DMAH pressure of 0.9–2.2 mTorr. Because the addition of gas to DMAH does not increase the deposition rate, the reaction leading to Al growth seems to be due to the thermal decomposition of DMAH rather than to hydrogen reduction. At temperatures lower than 340°C, deposition is governed by the rate of a surface reaction with an activation energy of about 0.4 eV. The surface morphology, crystallinity, and step coverage of films grown without gas are almost the same as those of films grown with a conventional gas system. The carbon concentration in the films deposited using only DMAH is slightly lower than that of those using In the application of this new deposition process to LSI interconnections, via holes only 0.15 μm in diam are filled by selective Al CVD and the via resistance is found to be only 3 Ω. Very low pressure selective Al CVD is shown to be a promising technique for making the interconnects of the 0.1 μm generation of ultralarge‐scale integrated circuits.