Surface Morphology Improvement of Metalorganic Chemical Vapor Deposition Al Films by Layered Deposition of Al and Ultrathin TiN

Abstract

The surface morphology of aluminum (Al) films grown by metalorganic chemical vapor deposition (MOCVD) has been improved by inserting a 1.0-nm-thick titanium nitride (TiN) layer between 90-nm-thick Al layers. For multilayered Al/TiN film depositions, dimethylaluminum-hydride (DMAH) and tetrakis(dimethylamido)titanium (TDMAT) are used as metalorganic precursors. For uniform and conformal TiN layers 1.0-nm-thick atomic layer deposition (ALD) was carried out in the same reaction chamber as the Al MOCVD. The surface morphology of the films was evaluated by measuring the optical reflectance. In the early stage of Al MOCVD, the reflectance versus film thickness curve shows a rapid decrease because of the scattering of incident light from the Al nuclei, and then it increases sharply to a maximum reflectance until the completion of island coalescence. However, it monotonically decays again with Al thickness due to the nonuniform grain growth. By inserting a 1.0 nm TiN layer on the Al layer at the maximum reflectance, the reflectance is restored again to the peak reflectance in the manner of a sinusoid waveform. Moreover, the multilayered Al/TiN films have a strong (111) preferred crystal orientation, and small and uniformly sized Al grains, which are expected to result in higher electromigration resistance. Therefore, the combined deposition technique with Al MOCVD and TiN ALD is considered a promising candidate to make Al MOCVD suitable for future microelectronic applications.