Electrical Characterization of Unipolar Bonded Si/Si Junctions

Low-temperature bonded Si/Si interfaces have been investigated by performing current and capacitance measurements as a function of applied voltage on two types of structures: Samples treated to become hydrophilic and samples treated in oxygen-plasma before bonding. The samples have been stored for more than five years. New interface state distributions have appeared together with mobile charges giving rise to hysteresis effects in electrical characteristics. The results indicate that mobile charges are trapped at the interfaces between an intermediate layer and the two silicon surfaces and with a metastable state at some distance from these interfaces. The concentration of interface states depends on the position of the mobile charges. A qualitative similarity exists between the samples with hydrophilic surface preparation before bonding and those treated in oxygen plasma