Effect of substrate-enhanced and inhibited growth on atomic layer deposition and properties of aluminum-titanium oxide films

Atomic layer deposition of aluminum-titanium oxide films from different precursor combinations was investigated. In addition to well-known TiCl4-H2O, AlCl3-H2O and Al(CH3)3-H2O ALD processes, combination of hydrogen-free TiCl4-O3 and AlCl3-O3 processes was used. Most of the films were grown at 350 °C because this temperature ensured reliable growth of TiO2 and Al2O3 in all processes combined. The films were deposited using supercycles that contained 1-60 successive cycles for deposition of TiO2 followed by 1-3 cycles for deposition of Al2O3. The films were amorphous, when 15 or less TiO2 cycles per Al2O3 cycle were applied in a supercycle, and contained anatase when ≥ 30 TiO2 cycles were applied. A marked increase in the Al deposition per cycle was observed with the increase of the number of TiO2 cycles per supercycle from 0 to 5-10. With the further increase of the number of TiO2 cycles from 15 per supercycle to higher values, the Al deposition per cycle depended on the precursor combination used. The Ti deposition per cycle depended, in turn, on the precursor system used for deposition of Al2O3 layers. Deposition of Ti was most significantly hindered on Al2O3-rich surface deposited from AlCl3-O3 and markedly enhanced on Al2O3 deposited from Al(CH3)3-H2O. In addition, the phase composition markedly influenced the growth rate of both components as well as the mean growth rate and surface roughness of the films.