Plasma-Assisted ALD of Al2O3 at Low Temperatures: Reaction Mechanism and Material Properties

Multiple in situ diagnostics have been employed to study the reaction mechanism of plasma-assisted ALD of Al2O3 and the influence of the substrate temperature on the material properties obtained. The results demonstrate that the ALD mechanism is governed by the formation of –CH3 surface groups and CH4 by-products upon Al(CH3)3 adsorption, while-OH surface groups and H2O, CO, and CO2 by-products are formed during the remote O2 plasma step. It has been observed that the amount of –OH involved in the ALD process increases with decreasing substrate temperatures which can account for the increase in growth per cycle at lower substrate temperatures. Moreover for substrate at 25 ºC, it has been found that a prolonged plasma exposure in the ALD cycle is effective in improving the film quality by a reduction of the impurity content and an increase in the mass density