Pbysical-chemicaI Evolution of Hf-aluminates upon Thennal Treatments

摘要

This study presents an investigation on physical-chemical stability of(HfO_2)_x(Al_2O_3)_(1-x) alloys upon prolonged post-deposition annealings.Two different Hf-alrnninates were deposited by ALCVD,containing 34% and 74% Al_2O_3 mol% respectively.Post-deposition annealings (PDA) were calried out in O_2 or N_2 atmosphere,at 850 deg C and 900 deg C for 30 minutes.Interfacial layer (IL) increase after PDA was detected on all the samples,but with small differences between N_2 and O_2 treatments.Stack composition was chamcterized by means ofXRR,XRF,RBS and TOF-SIMS.Growth of interface layer was justified by limited oxygen incorporation ftom external ambient Silicon diffilsion ftom the substrate into high-k,material and aluminum/hafuiurn redistribution were observed and associated to annealing temperature.XRD and planar TEM analysis evidenced first grnin formation and then,in the case of Hf-rich samples, almost complete crystallization.Ovemll,Hf-alurninates were found to remain XRD amorphous during high temperature prolonged treatments up to 900 deg C for 74% and 850 deg C for 34% alloys respectively.