Wafer bonding of Si for hybrid photonic devices
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Wafer bonding of Si for hybrid photonic devices Eric Le Bourhis1, Konstantin Pantzas1,2, Gilles Patriarche2, Anne Talneau2, Isabelle Sagnes2, and David Troadec3 1 Institut P’, CNRS - Université de Poitiers – ENSMA - UPR 3346, SP2MI-Téléport 2-Bd Marie et Pierre Curie, B.P. 30179, 86962 Futuroscope-Chasseneuil Cedex, France 2 Laboratoire de Photonique et de Nanostructures, UPR 20 CNRS, Route de Nozay, 91460 Marcoussis, France 3 Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), Avenue Poincaré, 59652 Villeneuve d'Ascq cedex, France ABSTRACT InP membranes have been bonded both oxide free and oxide mediated onto a Si substrate. The mechanical responses of the obtained thin (0.4 µm) membranes could be tested by nanoindentation and compared. Delamination of the membrane was observed to occur when the indenting load reached 55 mN for an oxide mediated bonded structure and 80 mN for an oxide free bonded one. Weibull analysis of these events yielded a modulus m of magnitude 6 to 10, indicating that delamination fracture is relatively predictable with a stronger interface obtained in oxide free approach. Delamination of the membrane is the result of constraint of plastic flow by the InP/Si interface. Membrane rotation is induced and increases with the indentation load, until it is sufficient to induce and propagate an interfacial crack. INTRODUCTION Development of hybrid integrated optics on silicon is garnering significant attention, taking advantage of the excellent performances of silicon on insulator -SOI- optical waveguides at telecom wavelengths. Hybrid integration of III-V-based materials, and especially InP-based materials, on Silicon is the best choice for emission/amplification at 1.55 µm. In this configuration, InP dies are bonded on a SOI wafer, and then processed to fabricate devices lithographically aligned to the underneath silicon waveguide. Until recently, bonding of III-V materials on Si was achieved by including an intermediate material as the bonding agent, usually an amorphous oxide [1-3]. There is a significant gain to not only decrease the oxide thickness to a minimum, but actually achieve oxide-free bonding at the InP-Si interface. Such a bonding was recently demonstrated by the present group [4]. In oxide-free bonding, a perfect reconstruction of molecular bonds at the interface between InP and Si is paramount to the success of the bonding. To evaluate to which extent this is the case, instrumented nanoindentation has already proven its value in other cases of adherence studies [5]. In the present contribution, further insights into interfacial fracture mechanisms of membranes obtained by oxide-free and oxide mediated bonding during indentation experiments is presented. EXPERIMENT (001) InP and Si substrates were used for the study. 400 nm thick (001) InP membranes were either bonded oxide-free or oxide-mediated onto a Si substrate. A 300 nm thick InGaAs sacrificial layer was first grown on the InP substrate before the InP membrane to allow the InP substrate removing after bo
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