Effect of Process Pressure on Atomic Layer Deposition of Al2O3

Abstract

Aluminum oxide (Al2O3) thin films have been prepared by the atomic layer deposition (ALD) using trimethylaluminum (TMA) and ozone (O3) as precursors. The process pressure was varied from 200-1000 mTorr at lower deposition temperature of 320oC and compared its effects on the properties with increasing deposition temperature to 460oC. The film growth rate and the film properties of thickness uniformity, impurity incorporation and the step coverage in high aspect ratio features were characterized. It was found that the deposition temperature decrease leads to film property deterioration and film growth rate increase. Increasing process pressure at lower temperature can not only help to retrieve the film properties but further increase the film growth rate. These improvements can be attributed to the change of surface saturation level, the enhancement of precursor diffusion condition, as well as the higher probability for surface reactions to occur at the active sites. It suggests that increasing process pressure may reduce the necessary cycle times to obtain qualified film properties, which brings advantages of throughput for ALD semiconductor applications.