It has long been no secret that with the 3-nm process technology, transistors will switch from vertical FinFET “ribbed” channels to horizontal nanopage channels completely surrounded by gates or GAA (gate-all-around). Today, the French CEA-Leti Institute has shown how you can use the manufacturing processes of FinFET transistors to produce multi-level GAA transistors. And maintaining the continuity of technological processes is a reliable basis for rapid transformation.
For the VLSI Technology & Circuits 2020 symposium, CEA-Leti specialists prepared a report on the production of a seven-level GAA transistor (special thanks to the coronavirus pandemic, thanks to which the speech documents finally began to appear promptly, and not months after the conferences). French researchers have proven that they can produce GAA transistors with channels in the form of a whole “stack” of nanopages using the widely used technology of the so-called RMG process (replacement metal gate or, in Russian, replacing (temporary) metal shutter). At one time, the RMG manufacturing process was adapted for the production of FinFET transistors and, as we see, can be extended to the production of GAA transistors with a multi-level arrangement of nanopage channels.
Samsung, as far as we know, plans to produce two-level GAA transistors with two flat channels (nanopages) located one above the other, surrounded by a gate on all sides, with the start of production of 3-nm chips. CEA-Leti experts have shown that it is possible to produce transistors with seven channels-nanopages and at the same time set the channels to the desired width. For example, an experimental seven-channel GAA transistor was released in versions ranging in width from 15 nm to 85 nm. It is clear that this allows you to set the transistors accurate characteristics and guarantee their repeatability (reduce the spread of parameters).
According to the French, the more channel levels in a GAA transistor, the greater the effective width of the total channel and, therefore, the better controllability of the transistor. Also in the multilayer structure less leakage currents. For example, a seven-level GAA transistor has three times lower leakage currents than a two-level (conditionally – like Samsung GAA). Well, the industry finally found a way up, moving away from the horizontal placement of elements on the crystal to the vertical. It seems that microcircuits still do not have to increase the area of crystals in order to become even faster, more powerful and energy efficient.
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