High-resolution Rutherford backscattering spectrometry study on process dependent elemental depth profile change of hafnium silicate on silicon

Process characterization of HfSiO(N)/SiO(N) films was performed by nondestructive elemental depth profile analysis using high-resolution Rutherford backscattering spectrometry. As-grown atomic layer deposition HfSiO film (2 nm) was found not to be uniform but to have a gradient near the top surface with Si concentration higher than the bulk. Regardless of native oxide removal, HfSiO grown on HF-last Si results in an almost identical interfacial SiO(x) thickness with that of HfSiO grown on chemical oxide. Dependence of interfacial layer on oxygen transport behavior during high-temperature annealing was also investigated. Whereas only the upward oxygen outdiffusion from the HfSiO layer was observed for the films deposited on HF-last Si and SiON, downward oxygen transport to the bottom interfacial layer was also observed when HfSiO film was deposited on chemical oxide. This result indicates that the bonding properties of chemical oxide are different from those of SiO(2) and that chemical oxide can accommodate oxygen ions. Finally, thermal stability of nitrogen in HfSiO introduced by NH(3) annealing and plasma nitridation was compared. Nitrogen desorption by spike anneal was only observed for HfSiON film with nitrogen introduced by plasma nitridation process.