Charge trapping and low frequency noise in SOI buried oxides

We have studied the 1/f noise and total-dose response associated with the buried oxides (BOX) of fully depleted nMOS silicon-on-insulators (SOI) transistors. Silicon implantation in the BOX creates a higher density of oxygen vacancy-related defects that reduce the net oxide-trap charge, but increase the back-channel 1/f noise. The 1/f noise of MOSFETs fabricated on silicon-implanted SOI BOX shows little change after 1 Mrad(SiO₂) irradiation. Silicon implantation also creates shallow electron traps in the BOX, leading to large bias instabilities. Whether these traps are filled or empty does not significantly affect the 1/f noise. A detailed study of the 1/f noise, temperature dependence of charge trapping, and radiation response of these SOI nMOSFET transistors shows that charge exchange with shallow electron traps in the BOX occurs mostly via tunneling. Low frequency noise in the double-gate (DG) mode of device operation is also investigated, and found to help mitigate the 1/f noise in fully depleted SOI MOSFETs.