Two-dimensional modelling of SiH4-H2 radio-frequency discharges for a-Si:H deposition

A two-dimensional numerical code, including three fluid modules to account for the description of electrical, thermal and chemical phenomena, has been developed for the modelling of hydrogenated amorphous silicon deposition from SiH4-H-2 radio-frequency glow discharges in a cylindrical PECVD reactor. The results of the model are compared to experimental data, obtained by different diagnostic techniques. The calculated radical densities are compared to those measured by threshold ionization mass spectrometry, at the centre of the substrate; the calculated SIH density profile between the electrodes is compared to those measured by laser-induced fluorescence and the radial distribution of the deposition rate on the substrate is compared to profilometry measurements. Globally, the model correctly predicts the main discharge characteristics for experimental conditions normally used for amorphous silicon deposition in the dust-free regime. The moderate agreement between model and experiment occurring for the hydrogen-dominated condition can be attributed to the simplified surface kinetics adopted in the model.