7. June 2021

We address this question in one of our research projects, in cooperation with TU Wien: NEDEVS (Nanoelectronic Device Simulation), an FFG national bridge project, which was started at the end of last year and will continue for 2,5 more years.

Technology computer-aided design (TCAD) tools are used in semiconductor industry to assist in the development of integrated circuits at practically all stages. State-of-the-art TCAD tools for device design are based on semi-classical transport models such as the drift-diffusion model or the Boltzmann transport equation. With continuing feature size reduction, however, device behavior is affected by quantum-mechanical short channel effects, such as tunneling through energy barriers and quantum interference effects. Since these effects cannot be captured by the semi-classical models, a transition to a quantum-mechanical transport description has to be made. Several theoretical formulations of quantum transport exist, which differ by the state function used to describe the non-equilibrium state of the charge carriers in the device.

The state functions considered here are the density matrix, the non-equilibrium Green’s functions, and the Wigner function. These descriptions differ in physical accuracy and computational cost when solved numerically. In this project these quantum transport models will be analyzed with respect to their applicability to emerging technologies and their usability in device TCAD. Also the numerical aspects associated with each model have to be considered. Our goal in this project is to select that transport model which represents a good trade off between physical accuracy and computational demand. Our second goal is the development and validation of an efficient numerical solver for the selected transport model. The resulting software module will be integrated in GTS Nano Device Simulator. Finally, the developed tool will be applied to emerging devices in order to further improve the models and model parameters. Structures of interest include the FinFET in the scaling limit, nanowire transistors and the emerging nanosheet transistors, and devices with a channel formed by a two-dimensional material such as graphene and MoS2.

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