In order to improve the selectivity and the surface morphology of aluminum (A1) films, new deposition technologies such as selective cycle chemical vapor deposition (CVD) and the periodic combination process with A1 metalorganic chemical vapor deposition (MOCVD) and TiN atomic layer deposition (ALD) were developed.
The selectivity of A1 films grown by selective cycle CVD has been improved by controlling DVEAA injection time and Ar purge time. For selective A1 film depositions, dimethylethylamine alane (DMEAA) is used as metal organic precursors. In the perfect selectivity model, the perfect selectivity theoretically was acquired and was extracted the most important two process parameters such as deposition thickness per cycle on ＄SiO_2＄ substrate and embryo retro-growth rate. By decreasing DMEAA injection time and increasing purge time, the nucleation density and the average nuclei growth rate were decreased. That is, the selectivity improvement was due to the decrease of DMEAA injection time and the increase of the purge time.
The surface morphology of A1 films by MOCVD has been improved by inserting 1.0nm thick titanium nitride (TiN) layers between every 90 nm thick A1 layers. For multilayered A1/TiN film depositions, dimethylaluminum-hydride (DMAH) and tetrakis(dimethylamido) titanium (TDMAT) are used as metal organic precursors. For uniform and conformal TiN layers with 1.0nm ALD was employed in a same reaction chamber with the A1 MOCVD. The surface morphology of the films was evaluated by measuring the optical reflectance In the early stage of A1 MOCVD, the reflectance versus film thickness curve shows a rapid decrease because of the scattering of incident light from the A1 nuclei. And then, it increases sharply to a maximum reflectance until the completion of islands coalescence. However, it monotonously decays again with A1 thickness due to the non-uniform grain growth. By inserting 1.0nm TiN layer on the A1 layer at the maximum reflectance, the reflectance is resumed again to the peak reflectance like a sinusoid waveform. Moreover, the multi-layered A1/TiN films have a strong (Ⅲ) preferred crystal orientation, and small and uniform sized A1 grains, which is expected to provide higher electromigration resistance.
Therefore, the selective cycle CVD and the combined deposition technique with A1 MOCVD and TiN ALD are thought a promising candidate to make A1 MOCVD useful in future microelectronic applications.
