Synthesis of Si nanoparticles within buried layers of SiO2

A combination of SiO vapor deposition and direct wafer bonding is used to produce buried layers of SiOx. Film stress in the SiOx is identified as the major factor inhibiting the wafer bonding process. By thermally induced decomposition, Si nanocrystals embedded in SiO2 are obtained. Decomposition of the silicon sub-oxide is studied by observing; the Si-O-Si stretching vibration in the infrared range. Phase separation is found to start as low as 400 degrees C and to be mostly complete after 1 hour at 800 degrees C. Annealing at 1000 degrees C: yields well established Si nanocrystallites of considerable density buried in the interface layer between the bonded silicon wafers. An intense photoluminescence emission centered around 820 nm is observed for crystalline nanoparticles of diameter 2.8 +/- 0.7 nm.