A comparative study of the etching behavior of thin AlN and Al2O3

The etching behavior of thin AlN and Al2O3 films was investigated in RF plasmas using BCl3, Cl-2, and HCl as process gases and binary mixtures thereof Highest etch rates for AlN were obtained in Cl-2 only plasmas, while BCl3 only plasmas resulted in the highest etch rates for Al2O3 under identical process conditions The etch rates for AlN were found to increase with decreasing bond energy for the chlorine atom in the process gas, whereas the etch rates of Al2O3 were increasing with increasing molecular mass of the process gas. The results suggest that pattern transfer in AlN is due to chemical etching while pattern transfer in Al2O3 is dominated by physical bombardment. This interpretation is supported by the finding that etch rate non-uniformities obtained for Al2O3 were substantially higher than those obtained for AlN. An analysis of the optical endpoint signals obtained during pattern transfer in both materials was performed and allowed a quick assessment of the non-uniformity of the plasma processes confirming the results obtained from film thickness measurements.