Improvement of the Interface between Selectively Deposited Aluminum and Silicon by Annealing

Abstract

The interaction between Al deposited selectively by chemical vapor deposition (CVD) and Si has been investigated. The structure of Al depended on the size of contact holes. Single-crystalline Al was formed in 0.7 µm contact holes, but polycrystalline Al in 1.2 µm and 2.0 µm holes. In the case of single-crystalline Al, Si at the bottom of contact holes was eroded uniformly by Al after deposition and after annealing at 400° C. In the case of polycrystalline Al, Si was eroded non uniformly and Al spikes were formed. However, after annealing at 400° C, Al spikes disappeared and the surface of eroded Si became extremely flat. Junction leakage current of the 2.0 µm n+ contact was found to increase after Al deposition. However, after annealing at 400° C, increase of junction leakage current was not found to 10 V. This change may be due to the improvement of the interface. These results indicate that selective Al-CVD can be used as a contact-hole-filling method.