Transistor gate contacts and methods of forming the same
In an embodiment, a device includes: a first insulating fin; a second insulating fin; a nanostructure between the first insulating fin and the second insulating fin; and a gate structure wrapping around the nanostructure, a top surface of the gate structure disposed above a top surface of the first insulating fin, the top surface of the gate structure disposed below a top surface of the second insulating fin.
1. A method comprising:
forming a nanostructure;
forming a first insulating fin and a second insulating fin adjacent to the nanostructure;
recessing a first top surface of the first insulating fin below a second top surface of the second insulating fin; and
forming a gate structure on the first top surface of the first insulating fin and around the nanostructure.
2. The method of claim 1 , wherein forming the gate structure comprises:
forming a work function tuning layer on the first insulating fin, on the second insulating fin, and around the nanostructure;
recessing a third top surface of the work function tuning layer below the second top surface of the second insulating fin; and
depositing a fill layer on the third top surface of the work function tuning layer and on the first top surface of the first insulating fin.
3. The method of claim 2 , wherein the third top surface of the work function tuning layer is recessed to be flush with the first top surface of the first insulating fin.
4. The method of claim 2 , wherein the third top surface of the work function tuning layer is recessed below the first top surface of the first insulating fin.
5. The method of claim 2 , wherein depositing the fill layer comprises selectively depositing fluorine-free tungsten on the work function tuning layer.
6. The method of claim 1 , wherein recessing the first top surface of the first insulating fin below the second top surface of the second insulating fin comprises:
depositing a mask layer on the first insulating fin and the second insulating fin;
patterning the mask layer to have a portion covering the second insulating fin and to not have portions covering the first insulating fin; and
etching the first insulating fin using the mask layer as an etching mask.
7. The method of claim 6 , wherein patterning the mask layer comprises:
patterning a recess in the mask layer, the recess overlapping the first insulating fin; and
thinning the mask layer.
8. The method of claim 1 further comprising:
forming a source/drain region adjacent a channel region of the nanostructure, the source/drain region contacting a sidewall of the first insulating fin and a sidewall of the second insulating fin.
9. A method comprising:
forming a first nanostructure and a second nanostructure;
forming a first insulating fin between the first nanostructure and the second nanostructure;
recessing the first insulating fin;
growing a p-type source/drain region and an n-type source/drain region adjacent the first nanostructure and the second nanostructure, respectively, the first insulating fin disposed between the p-type source/drain region and the n-type source/drain region; and
forming a gate structure on the first insulating fin, around the first nanostructure, and around the second nanostructure.
10. The method of claim 9 , wherein forming the gate structure comprises:
depositing a first work function material around the first nanostructure;
depositing a second work function material around the second nanostructure, the second work function material being different from the first work function material; and
depositing a fill layer on the first work function material and the second work function material.
11. The method of claim 9 , further comprising:
forming a third nanostructure; and
forming a second insulating fin between the second nanostructure and the third nanostructure, wherein the first insulating fin is recessed to have a lesser height than the second insulating fin.
12. The method of claim 11 , further comprising:
planarizing a top surface of the gate structure to be coplanar with a top surface of the second insulating fin.
13. The method of claim 9 , wherein the first insulating fin comprises a first layer and a second layer on the first layer, the first layer comprising a first dielectric material, the second layer comprising a second dielectric material.
14. The method of claim 13 , wherein recessing the first insulating fin comprises recessing the second layer with an etching process that selectively etches the second dielectric material.
15. The method of claim 13 , wherein the second dielectric material has a higher k-value than the first dielectric material.
16. A method comprising:
forming a first nanostructure, a second nanostructure, and a third nanostructure;
forming a first insulating fin and a second insulating fin, the first insulating fin formed between the first nanostructure and the second nanostructure, the second insulating fin formed between the second nanostructure and the third nanostructure;
forming a mask covering the first insulating fin and exposing the second insulating fin;
etching the second insulating fin using the mask, wherein after the etching the first insulating fin has a first height and the second insulating fin has a second height that is less than the first height; and
removing the mask.
17. The method of claim 16 , wherein the first insulating fin and the second insulating fin each comprise a first insulating layer and a second insulating layer on the first insulating layer, and wherein etching the second insulating fin comprises etching the second insulating layer of the second insulating fin.
18. The method of claim 17 , wherein the second insulating layer has a higher dielectric constant than the first insulating layer.
19. The method of claim 16 , wherein forming the mask comprises:
depositing a mask layer over the first insulating fin and the second insulating fin;
forming a recess in the mask layer over the second insulating fin by performing a first etching process, the recess extending only partially through the mask layer; and
after forming the recess, thinning the mask layer until the recess exposes the second insulating fin by performing a second etching process, the second etching process being different from the first etching process.
20. The method of claim 16 , further comprising:
forming a first gate structure and a second gate structure, the first gate structure disposed around the first nanostructure, the second gate structure disposed around the second nanostructure and the third nanostructure, the first gate structure separated from the second gate structure by the first insulating fin, the second gate structure extending over the second insulating fin.