Characterization And Simulation Of Permittivity Enhancements Of Sio2/Si3n4 Nanolaminate Layers

Previous studies have demonstrated that at low frequencies nanopowders of SiO2 and Si3N4 can have an order of magnitude increase in the permittivity over bulk values due to anomalous interfacial dipole formation on the nanoparticles. In this paper, the authors have begun to study this phenomenon at the nanometer scale but in a more controlled geometry. They have fabricated a stack of thin, alternating layers (similar to 5-12 nm) of Si3N4 and SiO2 deposited using plasma-enhanced chemical vapor deposition(PECVD) underneath a comb capacitor structure to measure the effective permittivity of the nanocomposite. The preliminary measured capacitances and conductances of these devices show good conformity and repeatability. Using quasi-static electromagnetic assumptions with finite element method (FEM) simulations of these capacitor devices illustrate that ignoring the impact of dipole formation at the oxide/nitride interface consistently underestimates the actual capacitance of the devices. If a thin (similar to 1 nm) interfacial dielectric layer is included in the model to account for interfacial dipoles, then the effective permittivity of the interface between the layers can be extracted to fit the measured data. In fact, a high-k interfacial relative permittivity value is extracted to be k(int)similar to 100 for the 200 nm devices, and this empirically calibrated model is then used to predict the capacitance for both smaller (150 nm) and larger (1000 nm) devices. This extracted relative permittivity at the interface is more than an order of magnitude greater than the measured bulk permittivity of PECVD oxide and nitride materials, which are k(SiO2) = 4.4 and k(Si3N4) = 6.4, respectively.