MOS Electrical characteristics of low pressure re-oxidized nitrided-oxide

The electrical characteristics of 12 nm MOS gate dielectrics formed by low pressure nitridation of SiO2followed by an oxygen anneal (re-oxidation) are described. Capacitor measurements indicate that the re-oxidized nitrided-oxide (ROXNOX) dielectric shows reduced interface state generation and reduced electron trapping under electrical stress as compared to thermal oxide with pre-stress midgap Ditand Vfbapproaching those of oxide. Channel hot-electron stressing of NMOS transistors verify that transconductance degradation in ROXNOX devices is much less than in oxide devices. In addition, inversion layer mobility measurements indicate that nitridation can reduce electron and hole mobilities. A recent model is discussed [1] which attributes mobility degradations to coulombic scattering by fixed charges and electron traps. Further evidence for the mobility model is provided by 1/f noise measurements which indicate that nitridation introduces interface electron traps situated near the Si conduction band and that re-oxidation eliminates these electron traps. With lighter nitridations and a re-oxidation, inversion layer mobilities and 1/f noise magnitudes of ROXNOX devices approach those of oxide devices while maintaining better stability under electrical stress.