5. Summary and Outlook

The two-dimensional device simulator Minimos-NT has been expanded to a multi-dimensional device simulator which is capable to handle ortho-product, tetrahedral, or hybrid grids and any kind of three-dimensional geometries. Several existing two-dimensional libraries have been replaced by a new grid module and a quantity server suitable for the handling of both two- and three-dimensional devices. Interfaces have been developed to allow communication between Minimos-NT and arbitrary process simulators or gridding modules, enabling the use of several existing three-dimensional file formats.

To allow for appropriate control of the simulation flow, an object-oriented database has been developed, called Input Deck database. This database enables to build up arbitrary hierarchical structured data. This is especially useful to describe material properties, model parameters, or complex circuits. Moreover, the database provides a powerful description language. As the Input Deck database has been particularly designed to control complex TCAD applications it is used in several other TCAD applications too, such as the Wafer-State-Server (WSS), the Vienna Monte Carlo Simulator (VMC), and the Finite Element Diffusion and Oxidation Simulator (FEDOS).

The applicability of three-dimensional device simulation is demonstrated with several examples where typical state-of-the-art device structures have been considered. For example, the tradeoff between the on-resistance and the breakdown voltage in lateral double diffused MOSFETs has been investigated where the recently proposed superjunction concept has been applied. FinFET devices, which represent one of the most promising device structures to allow MOSFET scaling below $20\,{\mathrm{nm}}$ gate length, have been simulated. The influence of channel width and gate length as well as the effect of triple-gate structures could be demonstrated. Furthermore, three-dimensional MagFET and fully depleted silicon on insulator devices have been studied.

The ongoing miniaturization and increasing demands on semiconductor devices make the development of more and more complex structures necessary. To account for three-dimensional effects, which are inevitable in such advanced structures three-dimensional device simulation becomes more and more essential. The huge computational effort compared to two-dimensional simulations even with modern computer hardware poses a major handicap for practical applications. Therefore, one of the main challenging tasks will be the development of methods to improve simulation speed while maintaining accurate simulation results. A promising approach is the integration of adaptive three-dimensional grid refinement even for thermodynamic and hydrodynamic simulations. Moreover the applicability of different solver algorithms such as multigrid methods will be investigated.

Further work on the developed simulator will focus on improved interoperability with other existing tools such as process simulators and gridding modules. This can be achieved applying the WSS which was developed at the Institute for Microelectronics. This library enables the usage of several TCAD applications in a complete process flow. By coupling the WSS with Minimos-NT several file formats will be supported. As it is of utmost importance to study the influence of small variations in the three-dimensional geometries by inherent process inaccuracies, a tool to easily generate variants of existing device geometries will be integrated. Additional features to be included are advanced physical methods such as a Monte Carlo module or a Schrödinger solver.