Thermal stability of CoSi2 layers implemented in a silicon-on-insulator substrate

A silicon-on-metal-on-insulator substrate, consisting of a top Si layer, a buried COSi2 layer and a buried SiO2 layer on a Si (100) substrate was formed using Co silicidation, wafer bonding and wafer splitting. It is shown that the buried silicide layers in this structure exhibit a much higher thermal stability than surface layers. Resistivity measurements and cross-sectional transmission electron microscopy investigations revealed that buried COSi2 layers withstand furnace anneals at 1000 degrees C up to 2 h, while surface COSi2 layers started to degrade after 10 min anneals at 1000 degrees C. The proposed substrate is most useful for BiCMOS applications.