EPI T-gate structure for CoSi
View Patent ↗A semiconductor process and apparatus provide a T-shaped structure ( 96 ) formed from a polysilicon structure ( 10 ) and an epitaxially grown polysilicon layer ( 70 ) and having a narrower bottom critical 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 ( 90 ) of the T-shaped structure ( 96 ) 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 a plurality of etched polysilicon base structures over the first insulating layer, each said etched polysilicon base structure having a first base width and a first height;
forming a recessed spacer on at least one side of each etched polysilicon base structure having a height that is less than the first height of the etched polysilicon base structure and having a total spacer width;
forming a patterned mask to cover the substrate except for an opening formed over each etched polysilicon base structure in alignment with the recessed spacer to expose a region over each etched polysilicon base structure;
clearing at least a top surface of each etched polysilicon base structure while otherwise leaving the substrate covered by the patterned mask;
epitaxially growing a polysilicon layer at any exposed surface of each 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 recessed spacer on at least one side of each etched polysilicon base structure comprises:
forming a protective oxide layer on top and side surfaces of each etched polysilicon base structure and on any exposed surface of the substrate;
forming a nitride layer on the protective oxide layer; and
anisotropically etching the nitride layer to form recessed nitride sidewall spacers on the protective oxide layer at each side of each etched polysilicon base structure.
7. The method of claim 1 , where clearing at least the top surface of each etched polysilicon base structure comprises removing any spacer material from a top surface of each etched polysilicon base structure and from an upper portion of a sidewall surface of each etched polysilicon base structure.
8. The method of claim 6 , where clearing at least the top surface of each etched polysilicon base structure comprises clearing the protective oxide layer from at least the top and an upper part of the side surfaces of each etched polysilicon base structure while otherwise leaving the substrate covered by the protective oxide layer.
9. The method of claim 1 , where forming the patterned mask comprises forming a patterned resist layer having an opening formed in alignment with each recessed spacer to expose a region over each etched polysilicon base structure but to otherwise cover the substrate.
10. The method of claim 1 , where forming the patterned mask comprises patterning a layer of resist using a gate mask.
11. The method of claim 9 , where forming the patterned resist layer comprises:
applying a resist coating over the substrate;
forming an opening in the resist coating that is aligned with the recessed spacer to expose a region over each etched polysilicon base structure without otherwise exposing the substrate.
12. The method of claim 1 , where clearing at least the top surface of each etched polysilicon base structure comprises polishing any spacer material from a top surface each etched polysilicon base structure and from an upper portion of a sidewall surface of each etched polysilicon base structure using a CMP process.
13. A method for forming a T-gate electrode on a substrate, comprising:
forming a plurality of etched gate structures having a first height over a gate dielectric layer, each etched gate structure comprising a polysilicon layer formed over the substrate;
forming a protective oxide layer on top and side surfaces of each etched gate structure and on any exposed surface of the substrate;
forming a recessed sidewall spacer on the protective oxide layer adjacent to each etched gate structure having a height that is less than the first height of the etched gate structure;
forming a patterned mask to cover the substrate except for an opening formed over each etched gate structure in alignment with the recessed sidewall spacer to expose a region over each etched gate structure;
clearing at least the top surface of each etched gate structure while otherwise leaving the substrate covered by the protective oxide layer; and
epitaxially growing a first polysilicon layer in contact with at least any exposed surface of the polysilicon layer in the etched gate structure, thereby forming a T-gate electrode having a wider upper region and a narrower base region.
14. The method of claim 13 , further comprising forming silicide in an upper region of the T-gate electrode.
15. The method of claim 14 , where the silicide comprises cobalt silicide or nickel silicide.
16. The method of claim 13 , where forming a recessed sidewall spacer comprises:
forming one or more dielectric layers over the etched gate structure; and
removing the one or more dielectric layers to form a recessed sidewall spacer on at least one side of each etched gate structure having a height that is less than the first height of the etched gate structure prior to epitaxially growing the first polysilicon layer.
17. The method of claim 13 , where forming a patterned mask comprises forming a patterned resist layer over the protective oxide layer, where the patterned resist layer has an opening formed in alignment with each etched gate structure but otherwise covering the substrate, where the patterned resist layer is used to selectively etch the protective oxide layer from the top surface and an upper part of the side surface of each etched gate structure while otherwise leaving the substrate covered by the protective oxide layer.
18. The method of claim 13 , where clearing at least the top surface of each etched gate structure comprises applying a chemical mechanical polish process to clear at least the top surface of the etched gate structure.
19. A method for fabricating a polysilicon structure having a wider upper structure and a narrower base structure, comprising:
forming a plurality of etched polysilicon base structures over a substrate;
selectively forming one or more dielectric layers on each side of each etched polysilicon base structure and over any exposed surface of the substrate;
forming a patterned photoresist layer over the one or more dielectric layers with an opening formed over each etched polysilicon base structure;
selectively etching through each opening in the patterned photoresist layer to clear at least a top surface of each etched polysilicon base structure while otherwise leaving the substrate covered by the patterned photoresist layer so that only a top surface and an upper portion of a sidewall surface of each etched polysilicon base structure are cleared; and
epitaxially growing a first polysilicon layer over each etched polysilicon base structure in contact with at least any exposed surface of each polysilicon base structure while the substrate is otherwise covered by the one or more dielectric layers, said first polysilicon layer forming the wider upper structure.
20. The method of claim 19 , further comprising forming silicideregions in the wider upper structure.