Microwave plasma enhanced CVD of aluminum oxide films: Influence of the deposition parameter on the films characteristics

Thin films of aluminum oxide were deposited on silicon wafers at low temperature by remote microwave plasma-enhanced chemical vapor deposition using an oxygen plasma and a mixture of trimethylaluminum and argon injected in the afterglow. Although the pressure and the total flow rate were low (respectively 2 Pa and 178 sccm), the deposition rate was high (250 nm.min -1 ) and the films contained only hydrogen as impurity. The most influential parameter on the quality of the film was the temperature which had to reach 550°C to obtain good quality films. A lower pressure made possible a better desorption of the by-products which induced a higher deposition rate and a lower etch rate in a 2%wt hydrofluoric acid solution. In the standard conditions, in presence of a large excess of oxygen (oxygen/trimethylaluminum>18), the trimethylaluminum precursor was fully transformed. The quality of the coatings was almost independent on the microwave power.