Flat beat

The relentless shrinking of device features on the surface of a wafer now threatens the survival of the planar bulk-silicon transistor. The problems that cause most concern for process engineers is a direct consequence of the way that the transistor channel has become progressively shorter. There is a clutch of problems referred to as ´short-channel effects´ but the industry´s biggest headache is drain-induced barrier lowering (DIBL). Normally, when the transistor is turned off, there is a large potential barrier that stops electrons moving through the channel even if there is a reasonably high voltage between the main current-carrying source and the drain contacts that would otherwise push the carriers along.