<title>Design and simulation of an embedded DRAM cell made up of MOSFETs having alternative gate dielectrics</title>

Abstract

Design and construction of new sub-micron MOSFETs with alternative gate dielectrics has emerged as a new technology for use in high-performance logic or low power memory circuits. The modelling of the new devices needs to take into account the effects that the new dielectrics have on the MOS device performance. In this paper, we examine such effects in terms of both capacitance and leakage current effects. First, we investigate the role of the parasitic capacitances appearing at the MOS device due to either material related processes or metallization. These capacitances are modelled accordingly in order to derive the device characteristics. Then, leakage currents are taken into account and the whole device is simulated using a 90 nm technology based on the BSIM4 model equations, suitably modified to account for these effects. The application of such devices on memory circuits is examined in order to take into account device parameters such as the threshold voltage, ouput currents and timing. As a result, the design of an embedded DRAM based on the MOSFETs with the alternative gate dielectrics is presented and analysed. The single MOSFET behaviour and subsequently the DRAM circuit performance are presented and the relevant characteristics are derived. As a result, the simulation revealed low output currents for the MOSFETs and high refresh rates for the DRAM circuits. Deviations from the ideal case are examined and solutions and further work are proposed.