Diffusion and reaction kinetics governing surface blistering in radio frequency sputtered hydrogenated a-SixGe1-x (0 ≤ x ≤ 1) thin films

The preparation of blister free layers of hydrogenated a-SixGe1-x (0 ≤ x ≤ 1) is a primary requisite for their technological applications. In RF (Radio Frequency) sputtered layers the formation of blisters is temperature dependent, as also shown here. This dependence is used to propose a theoretical model aimed at a better understanding of the mechanisms determining the blistering. Beside the reaction kinetics responsible for the release of H atoms from SiH and/or GeH complexes the model takes into particular account the contribution of the diffusion of H. The activation energy for blistering also enters in the model. The validation of the theoretical frame of the model is confirmed by the fact that it predicts a blistering threshold temperature in reasonable agreement with the experiment. The amorphous hydrogenated thin layers were deposited on polished silicon by RF co-sputtering. They were annealed between 150 and 350 °C. The structural changes of the surface of the SiGe films have been explored systematically by light beam reflection, scanning electron microscopy while the depth distribution of hydrogen was measured by secondary neutral mass spectrometry.