Fabrication and Characterization of Si-on-SiC Hybrid Substrates

Detta är en avhandling från Uppsala : Acta Universitatis Upsaliensis

Sammanfattning: In this thesis, we are making a new approach to fabricate silicon on insulator (SOI). By replacing the buried silicon dioxide and the silicon handling wafer with silicon carbide through hydrophilic wafer bonding, we have achieved silicon on crystalline silicon carbide for the first time and silicon on polycrystalline silicon carbide substrates at 150 mm wafer size. The conditions for the wafer bonding are studied and the surface and bond interface are characterized. Stress free and interfacial defect free hybrid wafer bonding has been achieved.The thermally unfavourable interfacial oxide that originates from the hydrophilic treatment has been removed through high temperature annealing, denoted as Ox-away. Based on the experimental observations, a model to explain the dynamics of this process has been proposed. Ox-away together with spheroidization are found to be the responsible theories for the behaviour. The activation energy for this process is estimated as 6.4 eV.Wafer bonding of Si and polycrystalline SiC has been realised by an intermediate layer of amorphous Si. This layer recrystallizes to some extent during heat treatment.Electronic and thermal testing structures have been fabricated on the 150 mm silicon on polycrystalline silicon carbide hybrid substrate and on the SOI reference substrate. It is shown that our hybrid substrates have similar or improved electrical performance and 2.5 times better thermal conductivity than their SOI counterpart. 2D simulations together with the experimental measurements have been carried out to extract the thermal conductivity of polycrystalline silicon carbide as ?pSiC = 2.7 WK-1cm-1.The realised Si-on-SiC hybrid wafer has been shown to be thermally and electrically superior to conventional SOI and opens up for hybrid integration of silicon and wide band gap material as SiC and GaN.