SUBSTRATE BIAS DEPENDENCE OF THE TRANSCONDUCTANCE OF DEEP-SUBMICRON SILICON NMOSFETS

Transconductance enhancement due to substrate bias in deep submicron M OSFETs is studied over a large temperature range, from 300 down to 30 K. This effect is explained by Fermi potential gradient enhancement wh ich occurs in short channel devices. For longer MOSFETs, the impact of the substrate bias on the Fermi potential is weak and the degradation of mobility explains the transconductance reduction. In cryogenic ope ration, numerical simulation has shown that the channel potential grad ient increases and, therefore, the transconductance enhancement with s ubstrate bias is larger at low temperature for deep submicron devices. (C) 1998 Elsevier Science Ltd. All rights reserved.