Impurity Effects in the Nucleation of Alpha (bcc)‐Tantalum or Beta‐Tantalum Films

Abstract

Although most studies report β‐Ta as the thin film phase deposited during cathodic sputtering, a few reports indicate that α(bcc)‐Ta is the initial phase, and β‐Ta occurs only because of reaction with oxygen or nitrogen. This study details qualitative evidence that an "X" impurity can exist which at low concentrations prevents the formation of β‐Ta and induces the formation of α‐Ta, but which may be deactivated by oxygen or nitrogen in a glow discharge. Monolayer films of carbon‐containing compounds can act as an X impurity. Organic polymers in particular can be used to nucleate low resistivity α‐Ta during deposition over large areas in vacuum stations which previously could only yield β‐Ta. Low resistivity α‐Ta has applications in thin film capacitors to achieve higher frequency performance.