Deposition of SiNx:H thin films by the electron cyclotron resonance and its application to Al/SiNx:H/Si structures

We have analyzed the electrical properties and bonding characteristics of ${\mathrm{SiN}}_x:\mathrm{H}$ thin films deposited at 200 °C by the electron cyclotron resonance plasma method. The films show the presence of hydrogen bonded to silicon (at the films with the ratio $\mathrm{N/Si}\text{<1.33}$ ) or to nitrogen (for films where the ratio N/Si is higher than 1.33). In the films with the N/Si ratio of 1.38, the hydrogen content is 6 at. %. For compositions which are comprised of between $\mathrm{N/Si}\text{=1.1}$ and 1.4, hydrogen concentration remains below 10 at. %. The films with $\mathrm{N/Si}\text{=1.38}$ exhibited the better values of the electrical properties (resistivity, ${\text{6×10}}^{13}\mathrm{\hspace{0.17em}\Omega \hspace{0.17em}}\mathrm{cm};$ and electric breakdown field, 3 MV/cm). We have used these films to make metal-insulator-semiconductor (MIS) devices on $n$ -type silicon wafers. $\mathrm{C–V}$ measurements accomplished on the structures indicate that the interface trap density is kept in the range ${\text{(3–5)×10}}^{11}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-2}}{\mathrm{\hspace{0.17em}eV}}^{\mathrm{-1}}$ for films with the N/Si ratio below 1.38. For films where the N/Si ratio is higher than 1.4, the trap density suddenly increases, following the same trend of the concentration of N–H bonds in the ${\mathrm{SiN}}_x:\mathrm{H}$ films. The results are explained on the basis of the model recently reported by Lucovsky [J. Vac. Sci. Technol. B 14, 2832 (1996)] for the electrical behavior of (oxide–nitride–oxide)/Si structures. The model is additionally supported by deep level transient spectroscopy measurements, that show the presence of silicon dangling bonds at the insulator/semiconductor interface (the so-called $P_{b\mathrm{N}0}$ center). The concentration of these centers follows the same trend with the film composition of the interface trap density and, as a consequence, with the concentration of N–H bonds. This result further supports the N–H bonds located at the insulator/semiconductor interface which act as a precursor site to the defect generation of the type $•{\mathrm{Si\equiv Si}}_{\mathrm{3}},$ i.e., the $P_{b\mathrm{N}0}$ centers. A close relation between interface trap density, $P_{b\mathrm{N}0}$ centers and N–H bond density is established.