Single Crystal and Polycrystalline 3C-SiC for MEMS Applications Anne Henry 1,a , Erik Janzén 1,b , Enrico Mastropaolo 2,c and Rebecca Cheung 2,d 1 Department of Physics, Chemistry and Biology, Linköping University SE-581 83 Linköping, SWEDEN 2 School of Engineering and Electronics, Scottish Microelectronics Center, The University of Edinburgh, Edinburgh EH9 3JF, UK a anhen@ifm.liu.se, b erija@ifm.liu.se, c e.mastropaolo@ed.ac.uk, d r.cheung@ed.ac.uk Keywords: 3C-SiC, MEMS, Young’s modulus Abstract. Cantilever resonators have been fabricated from two types of materials, single crystal and polycrystalline 3C-SiC films. The films have been grown in a hot-wall chemical vapor deposition reactor on 100 mm diameter p-type boron-doped (100) Si wafer without rotation of the wafer. The crystal structure of the films have been accessed with X-ray diffraction. The cantilever devices have been fabricated using a one-step etch and release process; the beam length has been varied between 50 and 200 µm. Resonant frequencies in the range 110 KHz – 1.5 MHz and 50 – 750 KHz have been obtained for single crystal and polycrystalline SiC devices, respectively. Furthermore, the experimental resonance frequencies have been used to calculate the Young’s Modulus E for the two different types of SiC. The single crystal SiC, possessing a very high Young’s Modulus (446 GPa), should be an optimal material for RF-MEMS applications. Introduction Silicon Carbide (SiC) micro electromechanical systems (MEMS) are promising devices for high efficiency radio frequency (RF) applications [1-4]. These applications include switches, oscillators or filters in wireless communications system. Among SiC unique material properties, the high value of the Young’s Modulus and the relatively low mass density permit to achieve higher resonant frequencies compared to other materials. Moreover, the mechanical strength, the high thermal conductivity and the high sublimation point improve considerably the robustness of SiC devices for harsh environment applications. However, even if in the past decade significant progress has been made in the processing of SiC structures, the growth and the etching technologies are still under study to improve the reliability of SiC MEMS. In this work, cantilever beam resonators have been fabricated from two types of material, single crystal and polycrystalline 3C-SiC films. The resonators have been actuated mechanically and the Young’s Modulus for both epi-layers has been calculated from the detected cantilever’s resonant frequencies. Experimental procedure and results Growth and characterization of the 3C films. Both types of materials, single crystal and polycrystalline 3C-SiC films have been grown in a hot-wall chemical vapor deposition reactor (CVD) [5] on 100 mm diameter p-type boron-doped (100) Si wafer without rotation of the wafer. Hydrogen purified through heated palladium cells mixed with 2 % of Ar has been used as carrier gas. The precursor gases were silane (SiH 4 ) and propane (C 3 H 8 ). The Si/H 2 ratio was typically 0.024 % and the C/Si ratio between 0.8 and 1. The layers were undoped. For the growth of the polycrystalline film the pressure was 400 mbar and the temperature about 1280 C. For the single crystal 3C growth the temperature has been fixed at 1350 C and the pressure at 300 mbar; in addition a carbonization layer prior the 3C growth have been made using maximal propane flow allowed by the system through the susceptor before and during the temperature ramp up. Materials Science Forum Vols. 615-617 (2009) pp 625-628 online at http://www.scientific.net © (2009) Trans Tech Publications, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 129.215.183.250-25/02/09,14:47:47)