Aluminum films prepared by metal-organic low pressure chemical vapor deposition

In this study, we have chemically vapor deposited aluminum films by the pyrolysis of triisobutylaluminum, an aluminum alkyl, at temperatures of 220-300 °C onto silicon, SiO₂ and device wafer substrates. The step coverage of our films is good, as demonstrated by our ability to deposit films conformally in the 2.5 μm windows of a typical device. The optical reflectivity of the films is low because of surface roughness of the order of 1000-1500 Å, which also renders them frosty in appearance. The films are highly pure aluminum with resistivities ranging between 2.8 and 3.5 μΩ cm. Transmission electron microscopy examination of the films shows them to be composed of columnar grains 1-3 μm in width, whcch may either be strongly oriented with a 〈111〉 fiber texture or be randomly poriented, depending on the surface activation treatment. Chemically vapor-deposited aluminum films have potential as metallizations for future generations of very-large-scale integrated devices.