Structural and electrical properties of tantalum nitride thin films fabricated by using reactive radio-frequency magnetron sputtering

TL;DR

This study systematically investigates how varying nitrogen partial pressure during reactive RF sputtering influences the phase, structure, and electrical properties of tantalum nitride thin films, relevant for magnetic recording applications.

Contribution

It provides detailed insights into phase transitions, crystalline orientations, and resistivity changes of TaN films as a function of nitrogen partial pressure, advancing thin film fabrication knowledge.

Findings

Phase evolution from metallic Ta to TaN with increased N2 pressure.

Change in crystalline orientation from [100] to [111] with nitrogen content.

Resistivity varies from metallic to semiconductor-like behavior.

Abstract

TaN thin film is an attractive interlayer as well as a diffusion barrier layer in [FeN/TaN](n) multilayers for the application as potential write-head materials in high-density magnetic recording. We synthesized two series of TaN films on glass and Si substrates by using reactive radio-frequency sputtering under 5-mtorr Ar/N-2 processing pressure with varied N-2 partial pressure, and carried out systematic characterization analyses of the films. We observed clear changes of phases in the films from metallic bcc Ta to a mixture of bcc Ta(N) and hexagonal Ta2N, then sequentially to fcc TaN and a mixture of TaN with N-rich phases when the N2 partial pressure increased from 0.0% to 30%. The changes were associated with changes in the grain shapes as well as in the preferred crystalline orientation of the films from bcc Ta [100] to [110], then to random and finally to fcc TaN [111], correspondingly. They were also associated with a change in film resistivity from metallic to semiconductor-like behavior in the range of 77-295 K. The films showed a typical polycrystalline textured structure with small, crystallized domains and irregular grain shapes. Clear preferred (111) stacks parallel to the substrate surface with embedded amorphous regions were observed in the film. TaN film with [ 111]-preferred orientation and a resistivity of 6.0 m Omega cm was obtained at 25% N-2 partial pressure, which may be suitable for the interlayer in [FeN/TaN](n) multilayers.