Preparation of Hafnium‐Tantalum Nitride Films by Reactive Alloy Sputtering

Abstract

Thin films of hafnium nitride and tantalum nitride with resistivities of 1010 and 104 ohm‐cm, respectively, have been deposited by rf + d‐c reactive sputtering. By sputtering hafnium‐tantalum mixtures in pure nitrogen at , the complete range of resistivities is obtained, with a linear increase between 105–09 ohm‐cm, corresponding to a relative hafnium content of 40–70%. For a fixed Hf:Ta ratio, the resistivity, deposition rate, and nitrogen content of the films depend on the pressure and substrate temperature. For pure tantalum a dinitride is deposited, but for pure hafnium the dinitride has not been obtained. An alloy nitride containing 60% Hf can be represented by the formula , where increases from 1.2 to 1.4 as the substrate temperature increases from 225° to 400°C. A sequence of reaction steps on the substrate surface is proposed to explain the deposition rates observed in reactive sputtering.