Impact of MOSFET Short Channel Characteristic on Digital Circuit Operation

The design of high density chips in MOS VLSI technology requires that the packing density of MOSFETs use in circuits is as high as possible and consequently, that the transistor are as small as possible. The reduction of the size i.e. dimensions of MOSFETs can change the MOSFET characteristic. In this paper we will examine in detail the non ideal effects on MOS characteristic. These are mainly due to the limitation impose on electrons drift characteristic in the channel and the modification of the threshold voltage due to the shortening channel length. The major short channel effects include the wear-out mechanisms of time dependent dielectric breakdown (TDDB) of gate dielectrics, Threshold voltage and body effects, hot carrier injection (HCI), negative bias temperature instability (NBTI), drain punch through and channel length modulation etc