Inspection of the Contact Block Reduction method for quantum transport simulation of FinFETs

FinFETs is expected to replace the conventional bulk MOSFET beyond the 22 nm node due to the latter´s scaling challenges. For the extremely scaled dimensions, quantum effects play an important role in determining the device characteristics. These effects can be accurately predicted only using quantum mechanical based device simulation. The contact block reduction (CBR) method is capable of treating quantum transport efficiently under the umbrella of the non-equilibrium Green´s function (NEGF). A key parameter in the CBR method is the number of eigenstates used in the simulation. The fewer the eigenstates are, the faster the simulation and the lower accurate are the results. It is known in the literature that less than 5% eigenstates of the total device eigenstates is needed for acceptable accuracy in the simulation of nanoscale devices in general. The needed number of eigenstates for FinFET simulation was not studied before. In this article, the CBR method is used to simulate nanoscale FinFET with channel lengths of 15 and 5 nm. It is shown that the needed percentage of eigenstates is bias dependent, and can vary from 6% in the on-state to 40% in the off-state.