Structure, morphology and electrical resistance of W x N thin film synthesized by HFCVD method with various N 2 contents
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Rare Met. DOI 10.1007/s12598-016-0696-5
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Structure, morphology and electrical resistance of WxN thin film synthesized by HFCVD method with various N2 contents Somayeh Asgary, Mohammad Reza Hantehzadeh, Mahmood Ghoranneviss* , Arash Boochani
Received: 18 August 2015 / Revised: 14 October 2015 / Accepted: 19 January 2016 Ó The Nonferrous Metals Society of China and Springer-Verlag Berlin Heidelberg 2016
Abstract Tungsten nitride (WxN) thin films with good crystalline structure, high quality and relatively low resistivity were deposited by hot filament chemical vapor deposition (HFCVD) technique at different mixtures of N2 and Ar gases. Experimental data demonstrate that different N2 contents in gas mixture strongly affect microstructure, phase formation, texture morphology and resistivity of the WxN films. According to X-ray diffraction (XRD) patterns, the growth of tungsten nitride films promotes d-WN phase for lower N2 contents in gas mixture. At higher N2 contents, a phase transition is observed in the tungsten nitride films. Both hexagonal d-WN and cubic b-W2N phases coexist, and WN phase approximately disappears with N2 contents in the gas mixture increasing. Scanning electron microscope (SEM) images for deposited films at lower N2 contents in gas mixture indicate a definite dense columnar nanostructure. The electrical resistivity results exhibit a significant drop for the WxN thin films with N2 contents in the mixed gas increasing. The changes in N2 content in gas mixture are found to be responsible for variation in the film resistivity values. Thus, the deposited tungsten nitride thin film at higher N2 contents in gas mixture has noncolumnar microstructure and lower resistivity, which may be used as a superior diffusion barrier. Keywords Tungsten nitride; Thin film; HFCVD; Electrical resistivity; Diffusion barriers S. Asgary, M. R. Hantehzadeh, M. Ghoranneviss*, A. Boochani Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran 14665-678, Iran e-mail: [email protected] A. Boochani Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah 6718997551, Iran
1 Introduction WxN appertains to a class of refractory metal nitrides that have promising properties including excellent hardness [1], high conductivity [2], chemical inertness, high melting point, good chemical stability [3], good thermal stability [4], thermal conductivity [5] and a relative low band gap (2.2 eV) [6]. As a result, they were extensively studied in recent years and have become technologically important for applications such as diffusion barriers in microelectronic devices at elevated temperatures [7], storage nodes in flash memories, Schottky contacts to GaAs [8], cathode catalysts for fuel cells [9], optical coatings in industry, as selective windows and X-ray mirrors [10], gate electrodes in metal oxide–semiconductor field effect transistors [11], decoration as well as sensors [12], hard wear-resistant protective coatings for cutting tools [1
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