Nanosheet channel-to-source and drain isolation
A method and structures are used to fabricate a nanosheet semiconductor device. Nanosheet fins including nanosheet stacks including alternating silicon (Si) layers and silicon germanium (SiGe) layers are formed on a substrate and etched to define a first end and a second end along a first axis between which each nanosheet fin extends parallel to every other nanosheet fin. The SiGe layers are undercut in the nanosheet stacks at the first end and the second end to form divots, and a dielectric is deposited in the divots. The SiGe layers between the Si layers are removed before forming source and drain regions of the nanosheet semiconductor device such that there are gaps between the Si layers of each nanosheet stack, and the dielectric anchors the Si layers. The gaps are filled with an oxide that is removed after removing the dummy gate and prior to forming the replacement gate.
1. A structure used to fabricate a nanosheet semiconductor device, the structure comprising:
a substrate;
a set of silicon layers formed above the substrate, wherein the silicon layers of the set of silicon layers are parallel to each other and include gaps between adjacent ones of the silicon layers of the set of silicon layers, wherein each of the gaps defines a region that is parallel to the silicon layers of the set of silicon layers and extends from a first end to a second end of each of the adjacent ones of the silicon layers of the set of silicon layers;
an inner spacer at the first end and at the second end of each of the gaps between the adjacent ones of the silicon layers of the set of silicon layers; and
an oxide between the first end and the second end in each of the gaps between the adjacent ones of the silicon layers of the set of silicon layers.
2. The structure according to claim 1 , wherein the inner spacer includes silicon nitride (SiN).
3. The structure according to claim 1 , wherein the inner spacer is a low-k spacer.
4. The structure according to claim 3 , wherein the low-k spacer includes silicon boron carbon nitride (SiBCN).
5. The structure according to claim 3 , wherein the low-k spacer includes silicon oxycarbonitride (SiOCN).
6. The structure according to claim 3 , wherein the low-k spacer includes silicon oxynitride (SiON).
7. The structure according to claim 1 , further comprising doped silicon germanium adjacent to each side of the set of silicon layers and to the first end and the second end of each of the gaps between the adjacent ones of the silicon layers of the set of silicon layers.
8. The structure according to claim 7 , wherein the doped silicon germanium is a source or a drain.
9. The structure according to claim 7 , further comprising additional ones of the inner spacers adjacent to and opposite a side of the doped silicon germanium that is adjacent to the set of silicon layers.
10. The structure according to claim 7 , further comprising silicon nitride (SiN) adjacent to and above the doped silicon germanium.
11. The structure according to claim 10 , further comprising an oxide layer above the SiN.
12. The structure according to claim 11 , wherein the oxide is an interlayer dielectric.