XPS study of the nitridation of hafnia on silicon

• Hf 4 f peaks identified for hafnia, hafnium silicate, and their nitrided forms. • The composition of nitrided hafnia is HfO 1.66 N 0.33 . • A Si 2+ -2N 1- dipole layer at the interface causes a shift of the spectra. • Saturation shows that excited N 2 + ions are the nitridation agent for hafnia. • Hafnium silicate nitrides sooner than hafnia in HfO 2 /Si structures. • Lower plasma pressure enhances the nitridation of hafnia. We report a comprehensive quantitative ARXPS study of 20-cycle ALD-grown HfO 2 films on Si (0 0 1) substrates with and without remote plasma nitridation. The films comprised a 0.6 nm HfO 2 layer atop a 1 nm hafnium-rich silicate interlayer. A detailed analysis of the Hf 4 f , Si 2 p , O 1 s , C 1 s , and N 1 s core level spectra is presented for samples with and without nitridation. The fitting of the Hf 4 f spectra reveals four contributing components associated with silicate, hafnia, and their respective nitrided species. The Hf 4 f , O 1 s , and C 1 s spectra exhibit a negative binding energy shift of about 0.2 eV upon nitridation induced by a Si 2+ -N dipole formed at the interface. Quantitative ARXPS analysis, employing the MultiLayer Model, enabled the determination of the thicknesses, and composition together with their associated uncertainties. The analysis showed that the composition of the nitrided hafnia is HfO 1.66 N 0.33 . There is a higher degree of nitridation in the silicate interlayer compared to the overlying hafnia layer. The degree of nitridation is found to increase with plasma power; N 2 + is identified as the primary plasma species responsible for the nitridation of hafnia.