Structural and Piezoresistive Characteristics of Amorphous Silicon Carbide Films Grown on AlN/Si Substrates

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Structural and Piezoresistive Characteristics of Amorphous Silicon Carbide Films Grown on AlN/Si Substrates Mariana A. Fraga1,2, Humber Furlan3, Rodrigo S. Pessoa2,4 and Luiz A. Rasia5 1 Institute for Advanced Studies, Department of Aerospace Science and Technology, 12228-001, S. J. dos Campos, Brazil 2 Plasma and Processes Laboratory, Department of Physics, Technological Institute of Aeronautics, 12228-900, S. J. dos Campos, SP, Brazil 3 Faculty of Technology of São Paulo, Praça Cel. Fernando Prestes, 30, São Paulo –SP, 01124-060, Brazil 4 IP&D, University of Vale do Paraíba, 12244-000, S. J. dos Campos, SP, Brazil 5 Regional University of Northwest Rio Grande do Sul State, Ijui- RS, 98700-000, Brazil ABSTRACT Amorphous silicon carbide (a-SiC) thin films have been grown on aluminum nitride (AlN) intermediate layers on (100) Si substrates by RF magnetron sputtering technique. Profilometry, four-point probe method, Rutherford backscattering spectroscopy (RBS) and Fourier transform infrared (FTIR) were employed to characterize the as-deposited SiC thin films. Test structures have been developed to investigate the piezoresistive properties. These structures consist of SiC thin-film resistors on AlN/Si substrates defined by reactive ion etching (RIE) with Ti/Au pads formed by lift-off process. Gauge factor (GF) and temperature coefficient of resistance (TCR) measurements have been performed and demonstrated the potential of these resistors to be used as sensing elements in devices for high temperature application. INTRODUCTION Silicon carbide and aluminum nitride have been much investigated due to their extraordinary properties that make them materials of great interest for electronic, microelectromechanical systems (MEMS) and opto-electronic applications [1, 2]. The advantages of SiC and AlN films for use in MEMS devices have been well-documented. It has been shown that devices based on SiC/AlN structure are more robust, exhibit improved chemical stability and thermal stability [3]. These characteristics have motivated studies on the growth of SiC on AlN or AlN on SiC by different techniques [4, 5]. In the case of the application of SiC films as sensing element in devices, many researchers have demonstrated their piezoresistive properties in amorphous or crystalline form grown onto an insulator layer on Si substrates [6, 7]. The majority of these studies are focused on 3C-SiC films grown on SiO2/Si or Si3N4/Si substrates. On the other hand, less attention is placed on the investigation of SiC films on AlN/Si, especially in their amorphous form. In this work, amorphous SiC thin films were grown on AlN/Si substrates and characterized to evaluate their potential use as a piezoresistive material for sensor applications. It were investigated the gauge factor (GF) and temperature coefficient of resistance (TCR) as well as film characteristics such as chemical composition, resistivity and thickness. Specific attention was given to analysis of the reproducibility of the films, considering that to have a reproducible method for