Modeling of Nanoelectronic Semiconductor Devices

Aggressive scaling of MOSFETs below 20 nm gate length makes the theoretical description and understanding of carrier transport in these devices challenging. Besides the degradation of electrostatic control also carrier transport in the channel is determined by quantum mechanical effects. The two major quantum effects to be taken into account are size quantization in the channel and quantum mechanical tunneling along the channel. Both effects call into question the use of powerful and well developed simulation methods based on the semi-classical Boltzmann equation. Instead, new simulation methods adequately describing carrier transport in nanoelectronic devices need to be developed. Established quantum transport formalisms are based on the density matrix, non-equilibrium Greens functions, or the Wigner function. In this project the latter formalism is used. Recently a Monte Carlo technique for the solution of the Wigner equation has been developed. It is based on the notion that the non-local potential operator acts as a generation term of positive and negative numerical particles. This Monte Carlo technique is extended to capture additional physical effects such as size quantization, a more realistic band structure, and a self- consistent potential. Size quantization affects both the scattering rates and the charge distribution. The proposed numerical model enables simulation of contemporary and future MOSFET architectures, involving transport in very thin semiconductor layers and charge control over a very short distance by means of double or triple-gate structures.

Aggressive scaling of MOSFETs below 20 nm gate length makes the theoretical description and understanding of carrier transport in these devices challenging. Besides the degradation of electrostatic control also carrier transport in the channel is determined by quantum mechanical effects. The two major quantum effects to be taken into account are size quantization in the channel and quantum mechanical tunneling along the channel. Both effects call into question the use of powerful and well developed simulation methods based on the semi-classical Boltzmann equation. Instead, new simulation methods adequately describing carrier transport in nanoelectronic devices need to be developed. Established quantum transport formalisms are based on the density matrix, non-equilibrium Green`s functions, or the Wigner function. In this project the latter formalism is used. Recently a Monte Carlo technique for the solution of the Wigner equation has been developed. It is based on the notion that the non-local potential operator acts as a generation term of positive and negative numerical particles. This Monte Carlo technique is extended to capture additional physical effects such as size quantization, a more realistic band structure, and a self- consistent potential. Size quantization affects both the scattering rates and the charge distribution. The proposed numerical model enables simulation of contemporary and future MOSFET architectures, involving transport in very thin semiconductor layers and charge control over a very short distance by means of double or triple-gate structures.