Published online by Cambridge University Press: 16 February 2011
Gate dielectric-quality silicon nitride films were deposited on a tunnel oxide from an SiH4/N2 gas mixture using an electron cyclotron resonance (ECR) plasma. Electrical characteristics depend not only upon the quality of the nitride film but also upon the state of the interfacial oxide. Quasi-static and 1 MHz capacitance-voltage measurements show that a nitride film deposited at 200°C on 2 nm thick thermally-grown oxide (tunnel oxide) on an unbiased Si substrate have an interface state density of l.5×1011/cm2-eV. Time-of-flight elastic recoil detection (TOF-ERD) was used to examine the level of mixing between the tunnel oxide and the deposited silicon nitride as a function of bias voltage. TOF-ERD showed that for an applied bias of −350 V (ion energy ≈ 380 eV), the deposition of a 10 nm thick film was completely mixed to form an oxynitride whereas the tunnel oxide remained intact for an unbiased sample. (Interdiffusion resulting from energetic-beam heating was ruled-out as a possibility for the mixing.)