MODIFICATION OF POROUS ALUMINA MEMBRANES USING AL2O3 ATOMIC LAYER CONTROLLED DEPOSITION

Al2O3 films were deposited with atomic layer control inside the pores of Anodisc alumina membranes. To achieve this controlled deposition on a high aspect ratio structure, a binary reaction for Al2O3 chemical v apor deposition (2Al(CH3)(3) + 3H2O --> Al2O3 + 6CH(4)) was separated into two half-reactions: (A) AlOH + Al(CH3)(3) --> Al-O-Al(CH3)(2)* CH4 and (B) AlCH3 + H2O --> AlOH* + CH4, where the asterisks designa te the surface species. The trimethylaluminum [Al(CH3)(3)] (TMA) and H 2O reactants were employed alternately in an ABAB... binary reaction s equence to deposit the Al2O3 film Because each half-reaction is self-l imiting, atomic layer controlled Al2O3 deposition was achieved on the surface of the high aspect ratio pores. To determine the necessary rea ction conditions, surface species during each half-reaction were perio dically monitored using in situ transmission FTIR spectroscopy. Ex sit u gas flux and permporometry measurements were also performed to deter mine the effect of the binary reaction sequence on the pore diameter. Gas flux measurements for H-2 and N-2 were consistent with a progressi ve pore size reduction versus the number of AB reaction cycles. The pe rmporometry measurements showed that the original pore diameter of sim ilar to 220 Angstrom was reduced to similar to 140 Angstrom after 120 AB reaction cycles.