Nitrogen profile engineering in the interfacial SiON in a HfAlO/SiON gate dielectric by NO Re-oxidation

The effects of the nitrogen profile in the SiON-interfacial layer (IL) on the mobility in FETs employing a HfAlO/SiON gate dielectric have been investigated. In order to suppress the interdiffusion between HfAlO and SiON, the nitrogen concentration in SiON should be higher than 15 at%, while the substrate interface should be oxygen-rich in order to suppress the mobility reduction. By using an NO reoxidation of NH₃ formed 0.4-nm-thick silicon nitride, the mobility reduction due to the SiON-IL was successfully suppressed, and electron and hole mobility of 92% and 88% of those for SiO₂ at V_g=1.1 V were obtained for HfAlO/SiON with equivalent oxide thickness (EOT) of 1.1 nm. By using nitrogen profile engineered SiON-IL, good equvalent oxide thickness (EOT) uniformity, low EOT, low gate leakage current, low defect density, and symmetrical threshold voltage were all achieved, indicating that a poly-Si/HfAlO/SiON gate stack would be a candidate as an alternative gate structure for low standby power FETs of half-pitch (hp)65 and hp45 technology nodes.