Da-Wei Wang

Wideband Modeling of Graphene-Based Structures at Different Temperatures Using Hybrid FDTD Method

An efficient finite-difference time-domain (FDTD) algorithm is proposed for studying frequency- and temperature-dependent characteristics of some graphene-based structures, with auxiliary differential equation-FDTD method and its conformal modification technique integrated together for handling such atomically thin and electrically dispersive periodic geometries. Numerical results are presented to show their tunable transmittances, surface plasmon polarization-mode characteristics and Fano resonances, where the effects of chemical potential of graphene, biasing electric field strength, as well as operating temperature are captured and investigated in detail.

Electrothermal Effects on Hot-Carrier Reliability in SOI MOSFETs—AC Versus Circuit-Speed Random Stress

Computational study of electrothermal effects on hot-carrier injection (HCI) in 100-nm silicon-on-insulator (SOI) MOSFET for digital integrated circuit is performed using in-house developed time-domain finite element algorithm. The simulated I-V curve is obtained by solving diffusive carrier transport equations, and it agrees well with our measured results. The time-dependent thermal conduction equation is solved to get the transient temperature response of the device. Furthermore, according to the transient temperature responses to different signal stresses, including step pulse, ac signal, and pseudorandom binary sequence (PRBS), HCI-induced threshold voltage shift (TVS) is captured by accounting for the temperature dependence of HCI. It is shown that the TVS of device under PRBS stress, which is used to mimic the circuit speed operation, is slightly larger than that of the device under ac signal with the same frequency. With the frequency of signal stress decreasing from gigahertz to tens of megahertz, TVS becomes more severe, because the temperature during ON-state is higher for the SOI MOSFET under low-frequency stress. Thick buried oxide leads to high temperature in channel and deteriorates the HCI. The method presented in this paper should also be applicable to the other MOSFET counterparts.

Electrical Modeling of On-Chip Cu-Graphene Heterogeneous Interconnects

In this letter, novel Cu-graphene heterogeneous interconnects are studied by virtue of the equivalent circuit model. The effective resistances of such interconnects are extracted numerically, with the Cu/graphene and graphene/ graphene interface resistances treated appropriately. It is shown that such interconnects can provide superior performance and reliability over Cu wires for an on-chip interconnect applications.

Modeling of TSV-based solenoid inductors for 3-D integration

Circuit model for TSV-based solenoid inductors is presented and investigated. Based on the measurement, the related lumped circuit elements can be extracted, and they are independent of the operating frequency by virtue of the RL ladder. Hence, the circuit model is compatible with the SPICE simulators. Based on the circuit model, the impacts of design parameters on the quality factor and inductance are studied. Finally, the frequency-thermal analysis of TSV-based solenoid inductors is carried out.

Modeling and characterization of Cu-graphene heterogeneous interconnects

In order to exploit graphene materials efficiently, some researcher have proposed Cu-graphene heterogeneous interconnects. In this study, an equivalent circuit model of such novel interconnect is presented, with the interfacial resistance treated appropriately. Then, the electrothermal characterization is carried out based on our self-developed TD-FEM algorithm. It is found that Cu-graphene heterogeneous interconnects could provide superior performance and reliability over the conventional Cu wires.

Modelling of multilayer graphene (MLG)-based structures at different temperatures

A FDTD method with the conformal modification is proposed to study electromagnetic properties of multilayer graphene (MLG). The vector fitting technique is employed to change the MLG conductivity model into an appropriate form for the FDTD implementation by an auxiliary differential equation formulation. Some numerical results are presented with the accuracy of our developed algorithm validated by comparing our results to the analytical ones, and the effects of layer number of MLG in the MLG-based structures as well as operating temperature are examined in detail.