Physics

Biography

Biography: Ulrich Wulf

Abstract

In a series of recent publications a semiempirical quantum model for conventional bulk- metal-oxide-semiconductor fieldeffect
transistor (MOSFETs) was developed. This model was verified comparing with the traces of a variety of experimental
devices. After reviewing the semiempirical model we demonstrate the essential extensions necessary to be able to describe silicon
on insulator field-effect transistor (SOIFETs) or fin field-effect transistor (FinFETs) used in state-of-the-art semiconductor
industry. In these devices the source- and the drain contact as well as the conduction channel of the transistor are confined
in depth direction to a thin silicon film (Si-film). In the first step we demonstrate that the quantum mechanical raise of the
Fermi energy in the source and the drain which is associated with the narrow confinement in the depth direction leads to
an increase of the effective channel length. This increase reduces a degradation of the output traces caused by source-drain
tunneling. In the second step we calculate the supply functions in our semiempirical model to assess the decrease of the usable
signal current through the conduction channel with decreasing width of the Si-film. In the third step we calculate the complete
output characteristics to compare bulk FETs with SOIFETs or FinFETs within the semiempirical model. The trade-off between
desirable reduction of source-drain tunneling on the one hand and detrimental decrease of signal current on the other hand
is discussed.