Chemical vapour deposition of praseodymium oxide films on silicon: influence of temperature and oxygen pressure

Metal-organic chemical vapour deposition (MOCVD) of various phases in PrOx system has been studied in relation with deposition temperature (450–750 °C) and oxygen partial pressure (0.027–100 Pa or 0.2–750 mTorr). Depositions were carried out by pulsed liquid injection MOCVD using Pr(thd)3 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) precursor dissolved in toluene or monoglyme. By varying deposition temperature and oxygen partial pressure amorphous films or various crystalline PrOx phases (Pr2O3, Pr7O12, Pr6O11) and their mixtures can be grown. The pure crystalline Pr2O3 phase grows only in a narrow range of partial oxygen pressure and temperature, while high oxygen pressure (40–100 Pa) always leads to the most stable Pr6O11 phase. The influence of annealing under vacuum at 750 °C on film phase composition was also studied. Near 90% step coverage conformity was achieved for PrOx films on structured silicon substrates with aspect ratio 1:10. In air degradation of Pr2O3 films with transformation to Pr(OH)3 was observed in contrast to Pr6O11 films.