Vertical FET process with controlled gate length and self-aligned junctions
View Patent ↗Method and structure of forming a vertical FET. The method includes depositing a bottom source-drain layer over a substrate; depositing a first heterostructure layer over the bottom source-drain layer; depositing a channel layer over the first heterostructure layer; depositing a second heterostructure layer over the channel layer; forming a first fin having a hard mask; recessing the first and the second heterostructure layers to narrow them; filling gaps with an inner spacer; laterally trimming the channel layer to a narrower width; depositing a bottom outer spacer over the bottom source-drain layer; depositing a high-k layer on the bottom outer spacer, the first fin, and the hard mask; and depositing a metal gate layer over the high-k and top outer spacer to produce the vertical FET. Forming another structure by recessing the metal gate layer below the second inner spacer.
1. A vertical field-effect transistor (FET) structure comprising:
a substrate of a first type;
a highly doped bottom source-drain layer disposed on the substrate of the first type;
a dielectric bottom outer spacer disposed on the highly doped bottom source-drain layer;
a recessed first heterostructure layer disposed on the highly doped bottom source-drain layer;
a channel layer disposed on the recessed first heterostructure layer;
a recessed second heterostructure layer disposed on the channel layer;
a first dielectric inner spacer disposed between the dielectric bottom outer spacer and the recessed first heterostructure layer;
a fin including the recessed first and the second heterostructure layers and the channel layer;
a high-k dielectric layer disposed on the dielectric bottom outer spacer and the channel layer;
a metal gate layer disposed on top of the high-k dielectric layer;
a dielectric top outer spacer disposed on top of the high-k dielectric layer and the metal gate layer;
a second dielectric inner spacer disposed between the dielectric top outer spacer and the recessed second heterostructure layer; and
a top source-drain epitaxial layer of a second type disposed on the first fin and the dielectric top inner spacer and the dielectric top outer spacer.
2. The vertical FET structure of claim 1 , wherein the first dielectric inner spacer comprises silicon-boron-carbon-nitride (SiBCN).
3. The vertical FET structure of claim 1 , wherein the second dielectric inner spacer comprises silicon-boron-carbon-nitride (SiBCN).
4. The vertical FET structure of claim 1 , further comprising a first contact disposed on the top source-drain epitaxial layer.
5. The vertical FET structure of claim 1 , further comprising a second contact disposed on the highly doped bottom source-drain layer.
6. The vertical FET structure in claim 1 , further comprising an interlayer dielectric oxide between the first contact and the second contact.
7. The vertical FET structure of claim 1 , wherein the recessed first heterostructure layer comprises silicon germanium.
8. The vertical FET structure of claim 1 , wherein the recessed second heterostructure layer comprises silicon germanium.
9. The vertical FET structure of claim 1 , wherein the channel layer has a thickness of between 3 nm to 10 nm.
10. The vertical FET structure of claim 1 , wherein the dielectric bottom outer spacer has a thickness of between 5 nm to 15 nm.
11. A vertical field-effect transistor (FET) structure comprising:
a substrate of a first type;
a highly doped bottom source-drain layer disposed on the substrate of the first type;
a dielectric bottom outer spacer disposed on the highly doped bottom source-drain layer;
a recessed first heterostructure layer disposed on the highly doped bottom source-drain layer;
a channel layer disposed on the recessed first heterostructure layer;
a recessed second heterostructure layer disposed on the channel layer;
a first dielectric inner spacer disposed between the dielectric bottom outer spacer and the recessed first heterostructure layer;
a fin including the recessed first and the second heterostructure layers and the channel layer;
a high-k dielectric layer disposed on the bottom outer spacer and the channel layer;
a dielectric top outer spacer disposed on top of the high-k dielectric layer;
a second dielectric inner spacer disposed between the dielectric top outer spacer and the recessed second heterostructure layer;
a metal gate layer disposed on top of the high-k dielectric layer and directionally recessed below the second dielectric inner spacer; and
a top source-drain epitaxial layer of a second type disposed on the first fin, the dielectric top inner spacer, and the dielectric top outer spacer.
12. The vertical FET structure of claim 11 , wherein the first dielectric inner spacer comprises silicon-boron-carbon-nitride (SiBCN).
13. The vertical FET structure of claim 11 , wherein the second dielectric inner spacer comprises silicon-boron-carbon-nitride (SiBCN).
14. The vertical FET structure of claim 11 , further comprising a first contact disposed on the top source-drain epitaxial layer.
15. The vertical FET structure of claim 11 , further comprising a second contact disposed on the highly doped bottom source-drain layer.
16. The vertical FET structure in claim 11 , further comprising an interlayer dielectric oxide between the first contact and the second contact.
17. The vertical FET structure of claim 11 , wherein the recessed first heterostructure layer comprises silicon germanium.
18. The vertical FET structure of claim 11 , wherein the recessed second heterostructure layer comprises silicon germanium.
19. The vertical FET structure of claim 11 , wherein the channel layer has a thickness of between 3 nm to 10 nm.
20. The vertical FET structure of claim 11 , wherein the dielectric bottom outer spacer has a thickness of between 5 nm to 15 nm.