Observation of Asymmetric Wafer Bending for 3C-SiC Thin Films Grown on Misoriented Silicon Substrates
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1069-D07-09
Observation of Asymmetric Wafer Bending for 3C-SiC Thin Films Grown on Misoriented Silicon Substrates Marcin Zielinski1, Marc Portail2, Thierry Chassagne1, Slawomir Kret3, Maud Nemoz2, and Yvon Cordier2 1 NOVASiC, Savoie Technolac, Arche Bât.4, BP267, Le Bourget du Lac cedex, 73375, France 2 Centre de Recherche sur l'Hétéroépitaxie et ses Applications, CRHEA-CNRS, UPR10, rue Bernard Gregory, Valbonne, 06560, France 3 Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, Warsaw, 02668, Poland ABSTRACT We present an experimental study of asymmetric wafer deformation for 3C-SiC layers grown on deliberately misorientated silicon substrates. An asymmetric curvature has been observed both on (100) and (111) oriented layers. In this work we focus on the (100) oriented samples. The curvature of the wafers is studied as a function of wafer thickness and offcut angle. We look for the correlations between the observed asymmetric strain relaxation and the layer morphology and microstructure. We claim that different defect pattern, measured along [110] and [1-10] direction can be at the origin of almost complete relaxation of mismatch strain along the offcut direction. INTRODUCTION Cubic silicon carbide is considered as a potential candidate for development of power devices (performance of 3C-SiC MOSFET is better than that of 4H-SiC [1]). Its mechanical properties and chemical inertia make it an ideal candidate for MEMS applications working in harsh environment. 3C-SiC/Si is also successfully used as a template for the nitride growth, instead of more onerous 6H-SiC [2]. Since there is no native, bulk 3C-SiC substrate for homoepitaxial growth of cubic material (contrarily to hexagonal polytypes 4H, 6H, that can be obtained by sublimation methods), every deposition technique for 3C-SiC must include a stage of heteroepitaxial nucleation / growth. The problem of strain control, inherent of heteroepitaxy, has thus to be resolved in order to allow successful development of 3C-SiC based devices. Another problem intimately connected to the heteroepitaxial growth of 3C-SiC is the formation of planar defects, like antiphase boundaries (APB) on (100) silicon substrates or double positioning boundaries (DPB) on (111) orientation. A (partial) solution of these problems consists in growing the layer on vicinal substrate. However, for both orientations, the use of vicinal substrates, allowing the reduction of APB or DPB densities, results in anisotropic strain relaxation of the layer and asymmetric bending along two perpendicular directions. This type of wafer deformation makes particularly difficult some technological steps like polishing or photolithography. The purpose of this study is to investigate the anisotropy of strain, determined from the curvature measurements of 3C-SiC/Si wafers, and to discuss the correlation between strain and defect density in 3C-SiC layer.
EXPERIMENT The classical, low pressure, two stage growth process was applied [3] (carbonization at 1100°C followed by CVD step at 1350°C) using
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