Authors: A. Schenk and A. Wettstein
Affilation: Swiss Fed. Inst. of Technology, Switzerland
Pages: 552 - 555
Keywords: density gradient method, decananometer MOSFETs, deep sub-micron devices, source-to-drain tunneling, TCAD
The density gradient method is able to reproduce the quantum-mechanical charge density in CMOS devices. Its ability to describe gate tunneling currents is still a matter of dispute. This paper presents the first 2-dimensional application of the density gradient model to decananometer MOSFETs. By shrinking the effective channel length to zero it is found that the degradation of the sub-threshold swing due to source-to-drain tunneling is weak and nearly independent of the channel length. It is shown that the presence of the abrupt oxide potential barrier pins the height of the source-drain barrier and limits tunneling of the confined electrons in the channel. As a result, thermionic emission determines the off-state current at 300 K even for vanishing channel length. It is concluded that 1D calculations of source-to-drain tunneling are inadequate, since they neglect the dominant influence of the Si-SiO2 potential barrier on the transport in channel direction.