Surface chemistry of In2O3 deposition using In(CH3)3 and H2O in a binary reaction sequence

Sequential surface chemical reactions for the controlled deposition of In2O3 were examined using transmission Fourier transform infrared (FTIR) spectroscopy. In this study, the binary reaction (2In(CH3)3+3H2O→In2O3+6CH4) was separated into two half-reactions: (A) InOH∗+In(CH3)3→In–O–In(CH3)∗2+CH4; (B) InCH∗3+H2O→InOH∗+CH4, where the asterisks designate the surface species. The InOH* and InCH3* surface species were monitored by the infrared absorbances of the InO–H and InC–H3 stretching vibrations. The reactions were thermally activated and the maximum reaction temperature was limited to 525 K because of trimethylindium (TMIn) pyrolysis. At 525 K, the (A) reaction saturated after depletion of ∼60% of the InOH* coverage. In contrast, the (B) reaction went to completion and was self-limiting. Despite these observed surface reactions, the growth of conformal In2O3 films was not achieved on Si(100) at 525 K. Very rough In2O3 films with low growth rates were also observed at 675–775 K in previous studies using InCl3 and H2O in a binary reaction sequence. The thermal stabilities of the InOH* and InCH3* surface species were measured from 300–900 K. The low coverage of surface species at the various reaction temperatures may explain the rough In2O3 films and low In2O3 growth rates.