Study of PECVD SiOxNy films dielectric properties with different nitrogen concentration utilizing MOS capacitors

In this work metal/oxide/semiconductor (MOS) capacitors with different nitrogen content SiOxNy gate dielectric are fabricated and characterized. The dielectric films are deposited by the plasma enhanced chemical vapor deposition technique from N-2, N2O and SiH4 gaseous mixtures at low temperatures. The MOS capacitors were characterized by low and high frequency capacitance (C-V) measurements, from where the interface state density (D-it), the effective charge density (N-eff) and the dielectric constant (k) were extracted. The results show a dielectric constant varying linearly in function of the films nitrogen concentration, from a value of 3.9, corresponding to SiO2 to 7.2, corresponding to Si3N4. We observed a variation of D-it in function of the films nitrogen concentration, the smallest obtained value corresponding to the Si3N4 film (similar to1 x 10(11) cm(-2) eV(-1)), however this film presents higher leakage current density than others. In order to optimize both parameters a double dielectric layer is proposed, a first layer Of Si3N4 film, which presents the highest dielectric constant and best interface properties, and a second layer of SiOxNy with high nitrogen concentration, in order to maintain the equivalent dielectric constant high but minimizing the leakage current problems. (C) 2004 Elsevier B.V. All rights reserved.