Silicon nanocrystallites in buried SiOx layers via direct wafer bonding

A combination of SiO vapor-deposition and direct wafer bonding is used to produce buried layers of SiOx. By thermally induced decomposition, Si nanocrystals embedded in SiO2 are obtained. Decomposition of the silicon suboxide is observed by studying the Si-O-Si stretching vibration in the infrared range. This phase separation process is found to start already at 400 °C and to be mostly complete after 1 h at 800 °C. Annealing at 1000 °C yields well established Si nanocrystallites of considerable density with diameters about 4 nm buried in the interface layer between the bonded silicon wafers.