Hidenori Miyamoto

Physically Based Compact Mobility Model for Organic Thin-Film Transistor

A physically based compact mobility model for organic thin-film transistors (OTFTs) with an analysis of bias-dependent Fermi-energy (EF) movement in the bandgap (Eg) is presented. Mobility in the localized and extended energy states predicts the drain-current behavior in the weak and strong accumulation operations of OTFTs, respectively. A hopping mobility model as a function of the surface potential is developed to describe the carrier transport through localized energy states located inside Eg. The Poole-Frenkel parallel-field-effect mobility and vertical-field-effect mobility are considered to interpret the bandlike carrier transport in the extended energy states. The parallel field effect on mobility is more pronounced for shorter channel length OTFTs and is considered by developing a channel-length-dependent mobility model. The vertical field effect on mobility is included to account for the effect of mobility on carrier transport at high gate-voltage-induced fields. We also compared the model results with 2-D device simulations and measurements to verify the developed mobility model.

Modeling of electrostatically actuated fluid flow system for mixed-domain simulation

Modeling of an electrically driven fluid flow system for multi-domain simulation is reported. The electrically driven actuator force is considered by an actuator component model, based on a spring-mass-damper system with force balance formulation. The fluid flow model is developed on the basis of a Kirchhoffian network which is derived from the mass transport equation. The actuator and the fluid models are coupled through equivalent circuits, leading to a consistent approach of mixed-domain system simulation. This approach is applied to design a flexible blood pumping system where the blood flow is driven by electrical organic actuators. Modeled results are compared with 2D device simulation based on the finite element method.

Compact modeling of carrier trapping for accurate prediction of frequency dependent circuit operation

We have investigated the influence of carrier traps on device characteristics in TFTs. In particular, our focus was given on transient characteristics influenced by carrier trapping during device operations. A compact model for circuit simulation of TFTs has been developed by considering the time constant of the trapping. The model was verified with measured frequency dependent TFT characteristics.

Circuit-aging modeling based on dynamic MOSFET degradation and its verification

The reported investigation aims at developing a compact model for circuit-aging simulation. The model considers dynamic trap-density increase during circuit operation in a consistent way. The model has been applied to an SRAM cell, where it is believed that the NBTI effect dominates. Our simulation verifies that the hot-carrier effect has a compensating influence on the NBTI aging of SRAM cells.

Mixed-domain compact modeling framework for fluid flow driven by electrostatic organic actuators

A new modeling framework of an electrically driven fluid flow system for mixed-domain circuit simulation is reported. Coupling between electrical and fluidic domains is implemented by developing an organic actuator compact model. The actuator model is based on force balance spring-mass-damper system equation. Fluid compact model is derived from mass transport equation. The actuator and the fluid models are connected using circuit network. As an example, we applied the modeling framework for designing and optimizing an electrically driven blood flow system. We also compared the modeled results with finite element method (FEM) based numerical simulation.

Mobility model for advanced SOI-MOSFETs including back-gate contribution

In this report it is verified that advanced SOI-MOSFETs with very thin silicon-on-insulator (SOI) and buried oxide (BOX) layers require an improved mobility modeling which considers the contributions of the back-gate field. Furthermore, a newly developed compact mobility model is presented, which satisfies these advanced SOI-MOSFET needs and still preserves the universality of the low-field mobility. The important novel modeling property is that the effective electric field is not only determined by the field induced at the surface but is modified by the potential distribution across SOI and BOX layers. With the developed model accurate reproduction of measured current characteristics under a wide variety of bias conditions becomes possible.

Compact modeling of dynamic trap density evolution for predicting circuit-performance aging

Abstract It is shown that a compact MOSFET-aging model for circuit simulation is possible by considering the dynamic trap-density increase, which is induced during circuit operation. The dynamic trap/detrap phenomenon, which influences the switching performance, is also considered on the basis of well-known previous results. Stress-dependent hot-carrier effect and NBTI effect, origins of the device aging, are modeled during the circuit simulation for each device by integrating the substrate current as well as by determining the oxide-field change due to the trapped carriers over the individual stress-duration periods. A self-consistent solution can be obtained only by iteratively solving the Poisson equation including the dynamically changing trap density, which is achieved with negligible simulation time penalty. To enable accurate circuit-aging simulation, even for high-voltage MOSFETs, the carrier traps within the highly resistive drift region are additionally considered.

Compact modeling of normally-on mosfet applicable for any technology generations

A physics-based, compact modeling approach is applied to normally-on MOSFET, resulting to a complete description of the device internal potential distribution. The surface current and the resistive current in the neutral region are expressed as a function of the calculated potential distribution. The model is verified to reproduce total drain current as well as capacitances for different device generations. It is demonstrated that the coupling between the charge induced at the surface and that induced due to the p/n junction modify the potential distribution under different conditions, which leads to the carrier mobility modification as well.

Modeling of dynamic trap density increase for aging simulation of any MOSFET circuits

A compact aging model for circuit simulation has been developed by considering all possible trapped carriers within MOSFETs. The hot carrier effect and the N(P)BTI effect are modeled by integrating the substrate current as well as the oxide field change due to the trapped carriers. Additionally, the carriers trapped within the highly resistive drift region are included for high-voltage (HV)-MOSFET modeling. The aging model considers the dynamic trap-density increase as a function of circuit-operation time with dynamically varying stress conditions for each individual MOSFET. A self-consistent solution is obtained by iteratively solving the Poisson equation including the trap density. The model is verified to be applicable for any type of MOSFETs covering advanced technologies as well as HV-MOSFETs.

Compact Electro-Mechanical-Fluidic Model for Actuated Fluid Flow System

This paper presents a compact electro-mechanical-fluidic system-modeling method for multidomain system simulation based on multidomain physics that considers the total energy conservation condition, in terms of respective potential and flow quantities. Models for electrical, mechanical, and fluidic domains are developed to design the example of a blood pumping system, where the blood flow is driven by electrically controlled organic actuators. The electrical domain includes an organic mosfet-based control circuit, the mechanical domain includes organic actuators, and the fluidic domain includes a flexible fluid-flow channel. Control circuit, actuators, and fluid models are coupled through equivalent circuits, where interconnection relationships between two neighboring domains are expressed using the energy conservation concept. The model accuracy is verified with finite element method (FEM) based numerical simulation. Significantly faster simulation speed than with FEM and good accuracy were achieved.