Researchers from research institute imec have demonstrated a new type of transistor that should make it possible to build chips on nodes of less than 2nm. The transistors are called forksheet transistors.
The forksheet transistors were demonstrated at the Symposia on VLSI Technology and Circuits and would be a suitable candidate for sub-2nm nodes. A direct relationship of a node name and the actual transistor dimensions has long since disappeared: the forksheet transistors have a gate length of 22nm and metal contacts with a mutual distance of 17nm.
Forksheet transistors seem to be a good successor to so-called gate-all-around, or gaa-transistors. The gaa transistor, in turn, is a successor to the well-known finfet transistor currently applied to the 5nm and 7nm nodes. The gaa structure increases the contact area of the gate, so that higher control currents can be used and the ‘leakage’, the current consumption when the transistor is off, is reduced. Gaa transistors would be deployed by Samsung on the 3nm node, while TSMC would then continue to use finfets.
The forksheet transistors further increase the contact area of the gate, which in particular would further reduce the leakage currents. The forksheets owe their name to a trigate structure, in which a dielectric between the gate structures provides the necessary electrical insulation, so that mutual distances can be reduced. The size of cell tracks, a measure of the area of logic on a wafer, is reduced from 5T to 4.3T while increasing performance.
At the VLSI 2021 symposium, imec researchers demonstrated the electrical characteristics of the forksheet transistors, which performed similarly to 22nm gate length gaa transistors. The 17nm gate length of the forksheet transistors yields 35 percent smaller transistors, and thus density on a chip, than current finfet transistors. The forksheet transistors would not make their appearance in mass production until well after 2022: first, gaa transistors still have to follow the finfet.
imec forksheet transistor