The role of hydrogen in the deposition, composition, and structure of semi-insulating polycrystalline silicon films

Semi-insulating polycrystalline silicon films have been grown by a low-pressure chemical vapor deposition process between 565 and 623 °C. Rutherford backscattering spectrometry and nuclear reaction analysis were used to determine the layer composition and thickness. The O/Si concentration ratio in the films increases with increasing N2O/SiH4 input for N2O/SiH4<0.6. For N2O/SiH4>0.6, a saturation effect in the oxygen uptake was observed. Furthermore the O/Si ratio increases with increasing growth temperature. The hydrogen concentration increases more than linearly with the N2O/SiH4 input ratio for N2O/SiH4<0.5 up to an amount of 8.5 at. % at 600 °C. For N2O/SiH4>0.5 a saturation effect was observed in the hydrogen uptake. We suggest that the hydrogen is bound to silicon atoms, which are further coordinated with three oxygen atoms. Based on this model, the growth mode of the films at the temperatures considered is discussed.