Atomic layer controlled deposition of Al2O3 films using binary reaction sequence chemistry

Al2O3 films with precise thicknesses and high conformality were deposited using sequential surface chemical reactions. To achieve this controlled deposition, a binary reaction for Al2O3 chemical vapor deposition (2Al(CH3)3 + 3H2O → Al2O3 + 6CH4) was separated into two half-reactions: (A) AlOH∗ + Al(CH3)3 → AlOAl(CH3)2∗ + CH4, (B) AlCH3∗ + H2O → AlOH∗ + CH4, where the asterisks designate the surface species. Trimethylaluminum (Al(CH3)3) (TMA) and H2O reactants were employed alternately in an ABAB … binary reaction sequence to deposit Al2O3 films on single-crystal Si(100) and porous alumina membranes with pore diameters of ∼ 220 Å. Ellipsometric measurements obtained a growth rate of 1.1 Å/AB cycle on the Si(100) substrate at the optimal reaction conditions. The Al2O3 films had an index of refraction of n = 1.65 that is consistent with a film density of ϱ = 3.50 g/cm3. Atomic force microscope images revealed that the Al2O3 films were exceptionally flat with a surface roughness of only ±3 Å (rms) after the deposition of ∼ 270 Å using 250 AB reaction cycles. Al2O3 films were also deposited inside the pores of Anodisc alumina membranes. Gas flux measurements for H2 and N2 were consistent with a progressive pore reduction versus number of AB reaction cycles. Porosimetry measurements also showed that the original pore diameter of ∼ 220 Å was reduced to ∼ 130 Å after 120 AB reaction cycles.