Growth of aluminium nitride on porous silica by atomic layer chemical vapour deposition

Aluminium nitride (AN) was grown on porous silica by atomic layer chemical vapour deposition (ALCVD) from trimethylaluminium (TMA) and ammonia precurs ors. The ALCVD growth is based on alternating, separated, saturating reacti ons of the gaseous precursors with the solid substrate. TMA and ammonia wer e reacted at 423 and 623 K, respectively, on silica which had been dehydrox ylated at 1023 K and pretreated with ammonia at 823 K. The growth in three reaction cycles was investigated quantitatively by elemental analysis, and the surface reaction products were identified by IR and solid state Al-27 a nd Si-29 NMR measurements. Steady growth of about 2 aluminium and 2 nitroge n atoms/nm(silica)(2)/reaction cycle was obtained. The growth mainly took p lace through (i) the reaction of TMA which resulted in surface AI-Me and Si -Me groups, and (ii) the reaction of ammonia which replaced the aluminium-b onded methyl groups with amino groups. Ammonia also reacted in part with th e silicon-bonded methyl groups formed in the dissociative reaction of TMA w ith siloxane bridges. TMA reacted with the amino groups, as it did with sur face silanol groups and siloxane bridges. In general, the Al-N layer intera cted strongly with the silica substrate, but in the third reaction cycle Al N-type sites may have formed. (C) 2000 Elsevier Science B.V. All rights res erved.