High-dielectric-constant silicon nitride thin films fabricated by radio frequency sputtering in Ar and Ar/N2 gas mixture

Abstract

In this work, dielectric behaviour, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) analyses of silicon nitride (Si-nitride) dielectric films sputtered with radio frequency and Si3N4 sputtering target under pure Ar and Ar/N2 (50/50) mixed gas flow sputtering ambient. The dielectric constant of sputtered Si-nitride dielectric film with Ar/N2 (50/50) mixed gas flow sputtering ambient can be up to 17, which is higher than that with pure Ar gas flow sputtering ambient. In addition, the dielectric constant of 17 is higher than all the reported dielectric constants of sputtered Si-nitride dielectric films and matches the dielectric constant of the Si-nitride dielectric films fabricated by the chemical vapour deposition process. XPS analysis shows that N-deficient SiNx is the major phase (approximately 54.7%) in the Si-nitride dielectric film sputtered with Ar/N2 mixed gas flow. The N species (neutral and ionized N) generated in the sputtering ambient enable the formation of the N-deficient SiNx phase in the Si-nitride dielectric film. N vacancy defects with negative charges in the Si-nitride film prepared with Ar/N2 (50/50) mixed gas flow are responsible for the enhancement of the spontaneous polarization under the electric field and the dielectric constant. PL analysis also confirms that the Si-nitride film prepared with Ar/N2 (50/50) mixed gas flow contains more N vacancies than the Si-nitride film prepared with pure Ar gas flow.