Plasma-enhanced atomic layer deposition of Ta-N thin films

Abstract

The plasma-enhanced atomic layer deposition (PEALD) of tantalum nitrides (TaN) thin films has been performed using terbutylimidotris(diethylamido)tantalum and hydrogen radicals at a temperature of 260 degreesC. The film thickness per cycle is also self-limited at 0.8 Angstrom /cycle, which is thinner than that of the conventional atomic layer deposition (ALD), 1.1 Angstrom /cycle. X-ray diffraction analysis indicates that the as-deposited films are not amorphous but polycrystalline mixed with cubic TaN and TaC. The film crystallinity as well as the film density increases with the pulse time and the electrical power of the hydrogen plasma used. By using the hydrogen radical as a reducing agent instead of NH3, which is a typical reactant gas used in ALDs and metallorganic chemical vapor depositions of TaN, the films show a much lower electrical resistivity and show no aging effects under exposure to air, owing to the increased film density and crystallinity, and the presence of TaC bonding. In addition, it has been shown that films, which are formed by the PEALD, retain perfect step coverage on the submicrometer holes with an aspect ratio of 10:1. (C) 2001 The Electrochemical Society.