Nitrogen-induced interface defects in Si oxynitride

Based on first-principles density-functional calculations, we propose N-associated defects at Si/SiO2 interface, which behave as dominant interface states in Si oxynitrides instead of conventional P-b centers in pure SiO2. These defects involve an N interstitial, and their energy levels lie in the broad range, from the midgap to the conduction-band edge of Si, depending on local oxidation status near N, while electrical states from P-b-type centers are removed by substitutional N atoms. Our results provide a mechanism for degradations related to the interface defects in Si oxynitrides which are used in state-of-the-art metal-oxide-semiconductor devices.