Nucleation and growth of CVD Al on different types of TiN

The deposition of Al by CVD on top of a Ti/TiN liner is a very promising approach for filling gaps with a high aspect ratio. In this work we have studied the nucleation and growth of CVD Al and its bulk properties as a function of the type of TiN used. For a given type of TiN we deposited films over a wide range of thickness (5-300 nm). The depositions were carried out in a cluster tool (Endura(TM)) where in some cases we deliberately allowed for a vacuum break prior to the Al deposition. Auger electron spectroscopy was used to measure the amount of Al deposited, thus yielding the kinetics of the Al growth. X-ray diffraction was used to determine the preferred orientation of the Al, which is important for electromigration resistance. The microstructure was studied by scanning and transmission electron microscopy and atomic force microscopy. We found that air exposure affects the nucleation, the rate of growth at the early stages, and the resultant morphology. A correlation exists between the nucleation stages of the growth and the bulk properties. (C) 1998 Elsevier Science S.A. All rights reserved.