Surface morphology control of Al-CVD for dual-damascene application

We investigated the method for suppressing the roughening of the Al film deposited by chemical vapor deposition of Al using dimethyl-aluminium-hydride (DMAE). The study focused on the roughening after the coalescence of the initial nuclei. Increasing the partial pressure of DMAH was effective for reducing the roughness of the film and for improving the gap-filling property. The reason for the improved surface morphology was supposed to be the reduction of the influence of the surface oxidation by the increased coverage of surface adsorbates during the deposition. The adsorbates also served to improve the gap-filling by approaching the kinetics of the deposition to 0-th order. In order to increase the partial pressure in the vicinity of the substrate, the deposition should be surface-reaction-limited, which was achieved by using the nozzle inlet which reduced the thickness of the boundary layer, The film deposited with the nozzle and the optimized condition filled the trenches completely with smooth surface morphology.