Abstract: With the rapid development of technology and increasingly high requirements of industry，Al2O3 in the form of thin films begin to draw attention with increasing needs.Inorganic AlCl3，which was cheap and easily obtained，was chosen as alu- minum precursor.Al2O3 thin film was obtained by the reaction of AlCl3 with H2O through ALD.Dense and uniform films can be obtained at a wide temperature range（50~40 ℃），and with corresponding deposition rate varying at 0.03~0.11 nm/cycle.This enabled the method in this work to meet various technological requirements.Film components were analyzed by XPS.After etching，atomic percent ratio of Al and O were 2∶（2.89~3.2），which is quite coincident with Al2O3.Total contents of the impurities can be as low as 1.3%（atomic percent ratio），illustrating the high purity of these films.

Key words: aluminum oxide, thin film, precursor, ALD