Nitrided thermal SiO2 for thin buried gate insulators in dual gate SOI-MOSFET

Nitrided thermal oxide (NOX) was used for reducing the degradation of a buried gate insulator during the fabrication of dual-gate Silicon-on-Insulator MOSFETs. The degradation was due to the exposure of the buried gate oxide to the epitaxial growth ambient. Nitridation of thermal SiO₂, resulted in a robust pinhole-free insulator after selective epitaxial growth of silicon (SEG) allowing for thinner buried gate insulators. A dual-gated fully-depleted SOI-MOSFET was fabricated with a 21.4 nm buried NOX gate and had a dynamic threshold voltage shift of ΔV_T,tap/ΔVC_G,huck=476 mV/V for submicron devices and as high as 550 mV/V for larger devices. Nitridation of the oxide had other benefits, such as reducing thermal-induced stress in the SEG and lowering the near sidewall defects at the SiO₂/Si interface