Mechanical and electrical properties of DC magnetron sputter deposited amorphous silicon nitride thin films

Amorphous silicon nitride SiNx thin films in a thickness range of 40 to 500 nm were deposited onto (100) silicon wafers using DC magnetron sputtering. The biaxial stress of the films was found to be tuneable in the range of -1300 MPa (compressive) to almost 0 by varying the plasma power density and the back pressure in the deposition chamber. The films were close to stoichiometric composition with x ranging from 1.27 to 1.34. The refractive index n decreases from 2.10 to 1.97 with increasing back pressure, indicating compositional changes in the thin films. This finding, however, was not confirmed by Fourier-Transform Infrared Spectroscopy measurements. On the other hand, lower wet chemical etch rates revealed a larger robustness of layers deposited at conditions where the mean kinetic energy of the sputtered particles is higher. Temperature dependent leakage current measurements using Au/Cr/SiNx/Si MIS (metal-insulator-semiconductor) structures between 25 and 300 degrees C have shown that ohmic and Poole-Frenkel conduction mechanisms dominate the leakage current behaviour at electrical fields ranging up to 0.5MV/cm. The extracted physical parameters such as the corresponding activation energies were found to be mildly affected by the deposition parameters. (C) 2015 Elsevier B.V. All rights reserved.