Precursors and chemistry for the atomic layer deposition of metallic first row transition metal films

Recent trends in the microelectronics industry are requiring the growth of metallic first row transition metal films by the atomic layer deposition (ALD) method. The ALD growth of noble metal thin films has been well developed in the past ten years, due to the positive electrochemical potentials of these metal ions and attendant ease of reduction to the metallic state. By contrast, the ALD growth of metallic first row transition metal films remains poorly documented, in large part because of the negative electrochemical potentials of most of the ions and a corresponding lack of powerful reducing co-reagents that can convert precursors in positive oxidation states to the metals. In this short review, we discuss progress that has been made to date in the ALD growth of metallic first row transition metal films. The low temperature ALD of high purity, low resistivity Cu films has been reported, but optimum ALD processes for the other first row transition metals are still elusive. The current state of precursor and reducing co-reagent development is overviewed, and key future challenges are outlined.