Fabrication of nano-sheet transistors with different threshold voltages
View Patent ↗A method of forming two or more nano-sheet devices with varying electrical gate lengths, including, forming at least two cut-stacks including a plurality of sacrificial release layers and at least one alternating nano-sheet channel layer on a substrate, removing a portion of the plurality of sacrificial release layers to form indentations having an indentation depth in the plurality of sacrificial release layers, and removing a portion of the at least one alternating nano-sheet channel layer to form a recess having a recess depth in the at least one alternating nano-sheet channel layers, where the recess depth is greater than the indentation depth.
1. A method of forming two or more nano-sheet devices with varying electrical gate lengths, comprising:
forming at least two cut-stacks including a plurality of sacrificial release layers and at least one alternating nano-sheet channel layer on a substrate;
removing a portion of the plurality of sacrificial release layers to form indentations having an indentation depth in the plurality of sacrificial release layers; and
removing a portion of the at least one alternating nano-sheet channel layer to form a recess having a recess depth in the at least one alternating nano-sheet channel layer, where the recess depth is greater than the indentation depth.
2. The method of claim 1 , further comprising forming the plurality of sacrificial release layers and the at least one alternating nano-sheet channel layer on the substrate by an epitaxially growth process, patterning and etching the plurality of sacrificial release layers and the at least one alternating nano-sheet channel layer to form a channel stack, and forming a dummy gate on the channel stack.
3. The method of claim 2 , wherein the at least two cut-stacks are formed from the same channel stack.
4. The method of claim 1 , further comprising forming a mask on at least one of the at least two cut-stacks after removing a portion of the plurality of sacrificial release layers, and removing an additional portion of the plurality of sacrificial release layers from the unmasked cut-stacks.
5. The method of claim 4 , wherein the additional portion of the plurality of sacrificial release layers is removed using an isotropic wet etch.
6. The method of claim 1 , further comprising forming a mask on at least one of the at least two cut-stacks before removing a portion of the at least one alternating nano-sheet channel layer to form a recess in the unmasked cut-stacks.
7. The method of claim 6 , further comprising removing the mask from the at least one of the at least two cut-stacks after removing a portion of the at least one alternating nano-sheet channel layer, and removing a portion of the at least one alternating nano-sheet channel layer to form a recess in the previously masked at least one of the at least two cut-stacks and an additional portion of the at least one alternating nano-sheet channel layer from the unmasked at least one of the at least two cut-stacks.
8. The method of claim 7 , wherein the recess depth in the at least one of the at least two cut-stacks is greater than the recess depth in the other at least two cut-stacks.
9. The method of claim 1 , further comprising forming a source/drain on each of the at least two cut-stacks.
10. The method of claim 9 , wherein the source/drains are epitaxially grown on the exposed surfaces of the at least one alternating nano-sheet channel layer.
11. A method of forming two or more nano-sheet devices with varying electrical gate lengths, comprising:
forming a channel stack including a plurality of sacrificial release layers and at least one alternating nano-sheet channel layer on a substrate;
forming two or more dummy gates including a dummy gate fill and a side spacer on the channel stack;
removing exposed portions of the channel stack not covered by the two or more dummy gates to form two or more cut-stacks;
removing a portion of the plurality of sacrificial release layers to form indentations having an indentation depth in the plurality of sacrificial release layers;
forming an indentation fill layer in the indentations;
forming a mask on at least one of the two or more cut-stacks; and
removing a portion of the at least one alternating nano-sheet channel layer to form a recess in the unmasked cut-stacks.
12. The method of claim 11 , further comprising removing the mask from the at least one of the two or more cut-stacks after removing a portion of the at least one alternating nano-sheet channel layer, and removing a portion of the at least one alternating nano-sheet channel layer to form a recess in the previously masked at least one of the two or more cut-stacks and an additional portion of the at least one alternating nano-sheet channel layer from the at least one unmasked of the two or more cut-stacks.
13. The method of claim 12 , further comprising forming a source/drain on each of the two or more cut-stacks.
14. The method of claim 13 , further comprising removing the dummy gate fill and forming a gate structure on each of the two or more cut-stacks.