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 temper ature by remote microwave plasma-enhanced chemical vapor deposition using a n oxygen plasma and a mixture of trimethylaluminum and argon injected in th e afterglow. Although the pressure and the total flow rate were low (respec tively 2 Pa and 178 sccm), the deposition rate was high (250 nm.min(-1)) an d the films contained only hydrogen as impurity. The most influential param eter on the quality of the film was the temperature which had to reach 550 degreesC to obtain good quality films. A lower pressure made possible a bet ter desorption of the by-products which induced a higher deposition rate an d a lower etch rate in a 2%wt hydrofluoric acid solution. In the standard c onditions, in presence of a large excess of oxygen (oxygen/trimethylaluminu m > 18), the trimethylaluminum. precursor was fully transformed. The qualit y of the coatings was almost independent on the microwave power.