Low Temperature Metallorganic Chemical Vapor Deposition Routes to Chromium Metal Thin Films Using Bis(benzene)chromium

Abstract

Different routes to control carbon incorporation into Cr‐based coatings grown by metallorganic chemical vapor deposition (MOCVD) using as precursor have been explored. In agreement with partial equilibrium thermodynamic calculations, the reduction and even the suppression of carbon incorporation into the chromium layers from the decomposition of the input gas mixture is possible only under or near atmospheric pressure. However, these deposition conditions do not allow for the development of a process for large scale applications since they lead to a poor uniformity and a low growth rate of the metal thin films. Hard chromium metal coatings are more conveniently deposited at low temperature (623-673 K) by addition of small amounts of to the input gas phase. This MOCVD process operates at low pressure even with the use of inert carrier gas unlike the first route. Under these conditions, a good throwing power is obtained leading to a promising process for industrial applications. The influence of the growth conditions on the properties of the films is described, and some properties of the chromium coatings are presented. Interestingly, they exhibit a very high hardness (∼21 GPa) and good adhesion to steel substrates. A growth mechanism supported by on‐line mass spectrometry analyses is discussed. The molecules favor a reaction pathway which is not expected on the basis of predictions from thermodynamic calculations. The successful growth of vanadium metal thin films from bis(benzene)vanadium and under related conditions suggests that the proposed mechanism may be extended to the deposition of other transition metals starting from their bis(arene)metal complexes as precursors. © 1999 The Electrochemical Society. All rights reserved.