Micromachining of thin 3C-SiC films for mechanical properties investigation
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1246-B09-04
Micromachining of thin 3C-SiC films for mechanical properties investigation J.F. Michaud1, S. Jiao1,2, A.E. Bazin1,3, M. Portail2, T. Chassagne4, M. Zielinski4 and D. Alquier1 1
Université François Rabelais, Tours, Laboratoire de Microélectronique de Puissance, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours Cedex 2, France 2 Centre de Recherche sur l’Hétéro-Epitaxie et ses Applications CNRS–UPR10, rue Bernard Gregory, 06560 Valbonne, France 3 STMicroelectronics, 16 rue Pierre et Marie Curie, BP 7155, 37071 Tours Cedex 2, France 4 NOVASiC, Savoie Technolac, Arche Bât 4, BP 267, 73375 Le Bourget du Lac Cedex, France
ABSTRACT In this work, the mechanical properties of cubic silicon carbide are explored through the analysis of the static and dynamic behavior of 3C-SiC cantilevers. The investigated structures were micro-machined using Inductively Coupled Plasma (ICP) etching of thin 3C-SiC films grown on silicon. The aim was to evaluate the influence of some basic parameters (film orientation, film thickness, defect density) on the mechanical properties of the material. X-Ray Diffraction was used to evaluate the crystalline quality of the epilayers. Scanning Electron Microscopy observations of static cantilever deflection highlight the major difference between the stress states of (100) and (111) oriented layers for which the intrinsic stresses are of opposite signs. The cantilever deflection is highly dependent on the film thickness, as stated for (100) oriented epilayers. The lowest deflection is obtained for the thickest layer. The Young’s modulus of 3C-SiC is calculated from the resonance frequency of clamped-free cantilevers, measured by laser Doppler vibrometry. The relatively low and orientation independent value of Young’s modulus (~350GPa) found on the samples is probably associated with the high defect density usually observed in very thin 3C-SiC films grown on Si. INTRODUCTION Since the last decades, silicon carbide (SiC) is the subject of intensive research and development activities. This growing attention is motivated by particular electrical, thermal and mechanical properties of this material. The electrical and thermal properties make silicon carbide a promising material for high power and high temperature electronic devices. Mature, industrial solutions based on hexagonal 4H-SiC polytype are already present in the market [1]. On the other hand, the chemical inertness of SiC can be of great benefit for the elaboration of MEMS devices operating in harsh environments. This field of SiC applications can be considered as the domain of the cubic polytype, 3C-SiC, the only one that can be hetero-epitaxially grown on cheap silicon substrates. According to its high chemical inertness already mentioned, plasma etching is the only method to achieve structures for most electronic and MEMS devices. Due to the 20% difference in lattice parameters and to the 8% difference in thermal expansion coefficients between SiC and Si, the hetero-epitaxial growth of 3C-SiC results in highly defective and stress
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