Ping Ko

Temperature dependence of MOSFET substrate current

Hitherto, theoretical models for MOSFET substrate current predicted that substrate current is a strong function of temperature. However, experimental data presented in this and previous studies show that the ratio of substrate current to drain current is insensitive to temperature over the range 77 to 300 K. The authors propose a modified model for an electron mean-free path (MFP) in the substrate current based on the concept of energy relaxation. The different between the energy and momentum relaxation MFP is clarified, and it is shown that a substrate current model with modified MFP can explain the temperature dependence of the substrate current.<<ETX>>

A new approach for simulation of circuit degradation due to hot-electron damage in NMOSFETs

The authors present a novel approach for modeling hot-electron-induced change in drain current for both forward and reverse modes of operation. The change in drain current, Delta I/sub D/, is implemented as an asymmetrical voltage-controlled current source. The authors first present the physical basis of the model and derive the analytical model equations. the implementation scheme for the analytical Delta I/sub D/ model in the BERT (Berkeley Reliability Tool) simulator and a detailed evaluation of the model as a function of different device and circuit parameters are also given. Simulation results of unidirectional and bidirectional circuits based on the new model are presented.<<ETX>>

SOI MOSFET modeling using an AC conductance technique to determine heating

SOI technology is a prospect for future integrated circuits. It allows increased circuit speeds, simple device isolation, elimination of latchup, etc. However, SOI MOSFETs are susceptible to localized heating effects which reduces mobility and thus MOSFET current. We propose a new SPICE model for SOI MOSFETs which takes into account self-heating. Using an AC conductance measurement technique, we have isolated the MOSFETs IV without self-heating. Using the BSIM3 MOSFET model, we are able to model the heating-free IV characteristics. We use an RC circuit to model the heating and adjust the mobility accordingly.

A dynamic depletion SOI MOSFET model for SPICE

We show, using measurements, that a transition between partial and full depletion (PD and FD) modes of operation as terminal voltages vary with time (dynamic depletion) has a strong impact on thin film SOI MOSFET characteristics. A model incorporating this effect is presented. It includes floating body, backgate, and body contact nodes, as well as impact ionization, GIDL, diode leakage and parasitic bipolar currents. Self-heating is modeled by an auxiliary R/sub th/C/sub th/ circuit. The model uses a single smooth equation over all operating regimes for each current and charge and is fully scalable with T/sub si/, T/sub box/, T/sub ox/, W, and L.

Correlating the channel, substrate, gate and minority-carrier currents in MOSFETs

An evaluation of measured linear and power-law relationships among the channel, substrate and minority-carrier currents, will be reported. The results simplify the visualizing, testing and modeling of hot-electron currents that affect IC performance and reliability.

Design and performance of resistive-gated MOSFETs for analog integrated circuits

Polysilicon resistive-gated MOSFETs are shown to be useful components for linear MOS applications as well as for signal mixers. Gate-resistance values can be varied from an effective 1 Gigaohm to 10 kilohms using ion implantation with boron. Theory for the resistive-gated MOSFET predicts high gain at low power and wide dynamic range with low harmonic distortion. Measurements confirm this theory.