Impact of Thermal Treatment on PECVD Al2O3 Passivation Layers

We present a detailed study about the influence of post-deposition temperature treatment on PECVD Al2O3 passivation layers. Fourier transform infrared spectroscopy (FTIR) and quasi-steady-state photoconductance (QSSPC) were applied for characterization. We observed several indications of structural changes of the Al2O3 layer with annealing duration, temperature and layer thickness. A shift and an increase of the Si-O vibrational mode (1100- 980 cm-1) in the FTIR measured with changing temperature and layer thickness is presented. Structural changes of the Al 2 O 3 layer with annealing duration, temperature, and layer thickness, caused by changes in the oxygen concentration within the SiO x layer are observed for the different FTIR spectra. We also detected a water band at 1650-1630 cm-1 and other OH components around 3200 cm-1-400cm-1 depending on annealing temperature and time. For a temperature of 820 °C, a dramatic change of the Al 2 O 3 peak (650-700 cm-1) is observed. This is probably due to the crystallization of the film.