Modeling of carrier transport in modern semiconductor devices has reached a point where the classic drift-diffusion model is no longer sufficient. While in the last decade reasonably good results could be obtained with the drift-diffusion model, a plethora of new effects needs to be considered in any accurate model. These effects include various quantum mechanical phenomena like carrier quantization in the channel, tunneling through oxides, and resonant tunneling, in addition to ballistic transport phenomena. Various models have been proposed to capture one or the other effect. In general, this involves a considerable amount of additional computational effort. For instance, to account for quantization in the channel, the Schrödinger equation has to be solved, while the quasi-ballistic transport regime is best captured by a Monte Carlo solution of the Boltzmann equation. However, for very small devices, Boltzmann's equation is no longer valid and has to be replaced, for instance, by the Wigner-Boltzmann equation. If device scales are of the order of a few nanometers, scattering effects might loose their importance and a coherent transport model based on Schrödinger's equation can be used.
Up to now, no established 'standard TCAD model' for end-of-the-roadmap semiconductor devices is available, leaving the device designer with many uncertainties regarding the best modeling approach. In particular, the best choice depends on the application at hand, where a good balance between accuracy and efficiency needs to be found. Since this often cannot be decided in advance, the most promising approaches need to be tried and the results compared. Therefore, a modern device simulator has to offer at least the most established approaches. However, it is essential that these approaches are implemented as consistently as possible, because, otherwise, one would not be able to perform a meaningful comparison.
To achieve this goal we have decided to provide all additional simulation modes, as a first step a Monte Carlo and a Schrödinger module, via Minimos-NT as a generalized interface. The Monte Carlo and Schrödinger solvers have been designed as libraries which obtain their data directly from Minimos-NT. For this, several regions can be defined in Minimos-NT. In these regions the original mesh can be used or a new mesh can be generated which is suitable for the specialized module. This new mesh can be of lower dimensionality, and a generalized interface is provided to extend the calculated result to the original mesh.
In addition, this approach has the advantage that all modules use the Minimos-NT material database and, when possible, the same material models. Inconsistencies can thus be avoided and a comparison of the models is made possible. In addition, the transport parameters required by Minimos-NT for the Monte Carlo table-based transport models can be generated directly by Minimos-NT.