Spacer T-gate structure for CoSi
View Patent ↗A semiconductor process and apparatus provide a T-shaped structure ( 84 ) formed from a polysilicon structure ( 10 ) and polysilicon spacers ( 80, 82 ) and having a narrower bottom dimension (e.g., at or below 40 nm) and a larger top critical dimension (e.g., at or above 40 nm) so that a silicide may be formed from a first material (such as CoSi 2 ) in at least the upper region ( 100 ) of the T-shaped structure ( 84 ) without incurring the increased resistance caused by agglomeration and voiding that can occur with certain silicides at the smaller critical dimensions.
1. A method for forming a semiconductor device, comprising:
providing a substrate;
forming a first insulating layer over the substrate;
forming an etched polysilicon base structure over the first insulating layer, said etched polysilicon base structure having a first base width;
forming a spacer on at least one side of the etched polysilicon base structure having a total spacer width;
applying a photoresist layer over the etched polysilicon base structure and spacer;
forming an opening in the photoresist layer in alignment to overlap with the spacer to expose only a portion of the spacer to form a photoresist etch mask;
removing part of the spacer that is formed on at least one side of the etched polysilicon base structure from the upper sidewall surface of said etched polysilicon base structure using the photoresist etch mask;
removing the photoresist etch mask;
depositing a polysilicon layer in contact with at least any exposed surface of the etched polysilicon base structure;
anisotropically etching said polysilicon layer to form a polysilicon spacer on an upper sidewall surface of said etched polysilicon base structure, thereby forming a polysilicon structure having an upper region with a second width that is wider than the first base width; and
forming silicide in the upper region of the polysilicon structure.
2. The method of claim 1 , where the step of forming silicide comprises forming cobalt silicide in the upper region of the polysilicon structure.
3. The method of claim 1 , where the step of forming silicide comprises forming nickel silicide in the upper region of the polysilicon structure.
4. The method of claim 1 , where the polysilicon structure comprises a polysilicon line or gate electrode.
5. The method of claim 1 , where the first base width is 40 nm or less, and where the second width is 40 nm or more.
6. The method of claim 1 , where forming a spacer on at least one side of the etched polysilicon base structure comprises:
forming a spacer liner oxide on top and side surfaces of the etched polysilicon base structure;
forming nitride sidewall spacers on the spacer liner oxide; and
where removing part of the spacer comprises removing any spacer material from a top surface of the etched polysilicon base structure and from an upper portion of a sidewall surface of the etched polysilicon base structure prior to depositing the polysilicon layer.
7. The method of claim 6 , where the step of removing spacer material comprises recessing the nitride sidewall spacers.
8. The method of claim 6 , where the step of removing spacer material comprises clearing spacer liner oxide from at least the top and an upper part of the side surfaces of the etched polysilicon base structure.
9. The method of claim 1 , where removing part of the spacer comprises removing any spacer material from a top surface of the etched polysilicon base structure and from an upper portion of a sidewall surface of the etched polysilicon base structure prior to depositing the polysilicon layer.
10. The method of claim 1 , where forming an opening in the photoresist layer comprises patterning an opening in the photoresist layer using a gate mask stepper having an alignment capability that is less than half the total spacer width.
11. The method of claim 1 , where removing part of the spacer comprises:
using the photoresist etch mask to selectively remove any spacer material from a top surface of the etched polysilicon base structure and from an upper portion of a sidewall surface of the etched polysilicon base structure.
12. The method of claim 1 , further comprising polishing any spacer material from at least a top surface of the etched polysilicon base structure using a CMP process prior to depositing the polysilicon layer.
13. The method of claim 1 , where
applying a photoresist layer comprises applying an ultra-low viscosity planarizing resist coating to the semiconductor device; and where forming an opening in the photoresist layer comprises
using a timed ash to remove the planarizing resist from above the etched polysilicon base structure and to leave a resist mask protecting other areas of the semiconductor device.
14. A method for forming a T-gate electrode, comprising:
forming an etched gate structure over a gate dielectric layer, said gate structure comprising a polysilicon layer;
forming a sidewall spacer on one or more sides of the etched gate structure;
applying a photoresist layer over the etched gate structure and sidewall spacer;
forming an opening in the photoresist layer in alignment to overlap with the sidewall spacer to expose only a portion of the sidewall spacer to form a photoresist etch mask;
removing part of the sidewall spacer that is formed on at least one side of the etched gate structure from the upper sidewall surface of said etched gate structure using the photoresist etch mask;
removing the photoresist etch mask;
depositing a first polysilicon layer in contact with at least any exposed surface of the polysilicon layer in the etched gate structure;
anisotropically etching said first polysilicon layer to form a polysilicon spacer on an upper sidewall surface of said etched gate structure, thereby forming a T-gate electrode having a wider upper region and a narrower base region.
15. The method of claim 14 , further comprising forming silicide in an upper region of the T-gate electrode.
16. The method of claim 15 , where the silicide comprises cobalt silicide or nickel silicide.
17. The method of claim 14 , where forming a sidewall spacer comprises:
forming one or more dielectric layers over top and side surfaces of the etched gate structure; and
where removing part of the sidewall spacer comprises removing the one or more dielectric layers from a top surface of the etched gate structure and from an upper portion of a sidewall surface of the etched gate structure prior to depositing the first polysilicon layer.
18. The method of claim 17 , where removing the one or more dielectric layers comprises recessing said one or more dielectric layers to clear at least the top surface of the etched gate structure.
19. The method of claim 17 , where removing the one or more dielectric layers comprises applying a chemical mechanical polish process to clear at least the top surface of the etched gate structure.
20. A method for fabricating a polysilicon structure having a wider upper structure and a narrower base structure, comprising:
forming an etched polysilicon base structure over a dielectric layer;
forming a spacer on at least one side of the etched polysilicon base structure;
applying a photoresist layer over the etched polysilicon base structure and spacer;
forming an opening in the photoresist layer in alignment to overlap with the spacer to expose only a portion of the spacer to form a photoresist etch mask;
forming a sidewall spacer on each side of the etched polysilicon base structure using the photoresist etch mask to selectively etch the spacer so that a top surface and an upper portion of a sidewall surface of the etched polysilicon base structure are cleared;
depositing a first polysilicon layer over the etched polysilicon base structure in contact with at least any exposed surface of the etched polysilicon base structure; and
anisotropically etching the first polysilicon layer to form poly sidewall spacers, said poly sidewall spacers and an upper region of the etched polysilicon base structure forming the wider upper structure.