Trade-off between hot carrier effect and current driving capability due to drain contact structures in deep submicron MOSFETs

Abstract

We, for the first time, have analyzed the contact structure dependent hot carrier effect in quarter-micron n-channel metal semiconductor held effect transistor (nMOSFETs). We measured the DC stressed current degradation characteristics, the substrate current characteristics, and the hot carrier induced photon emission characteristics of MOSFETs with W/L = 20/0.25 microns having various contact structures. From experiments, we consistently observed that the degradation increases rapidly as the number of contact holes increases while current driving capability improves moderately. We also calculated the average electron temperature in devices with different contact structures from the energy distribution of emitted photons. The electron temperatures of 3- and 26-contact hole devices were about 4700 K and 6000 K, respectively. We have developed a HSPICE circuit model to simulate various contact structures. Both simulation and experimental results indicate that the current driving capability saturates at more than 5 contact holes of n-channel MOSFET with W/L = 20/0.25 microns.