Studies on structural and electrical properties of silicon nitride films deposited by unbalanced magnetron sputter deposition

Unbalanced magnetron sputtering has been used to deposit silicon nitride films. Films were deposited at substrate temperature of 500 °C, nitrogen partial pressure of 1×10−4 mbar and sputtering pressure of 1×10−3 mbar. Substrate bias has been varied in order to change the energy of the ions bombarding the substrate. The structural and compositional characterization has been done using FTIR spectroscopy, atomic force microscopy, and Auger electron spectroscopy. A detailed study of electrical properties has been carried out in metal–insulator–semiconductor and metal–insulator–metal configurations. From the C–V measurements dielectric constant and interface charge density were calculated, while the I–V characteristics of the films were used to determine resistivity, dielectric strength and critical field. The deposited films showed resistivity of the order of 1012 Ω cm, dielectric constant 7.25, with an interface state density of 8×1010 eV−1 cm−2. The observed variation in the properties of the films has been explained in terms of changes in composition and microstructure of the films.