Increased contact area for FinFETs
A method for forming fin field effect transistors includes epitaxially growing source and drain (S/D) regions on fins, the S/D regions including a diamond-shaped cross section and forming a dielectric liner over the S/D regions. A dielectric fill is etched over the S/D regions to expose a top portion of the diamond-shaped cross section. The fins are recessed into the diamond-shaped cross section. A top portion of the diamond-shaped cross section of the S/D regions is exposed. A contact liner is formed on the top portion of the diamond-shaped cross section of the S/D regions and in a recess where the fins were recessed. Contacts are formed over surfaces of the top portion and in the recess.
1. A method for forming fin field effect transistors, comprising:
epitaxially growing source and drain (S/D) regions on fins, the S/D regions including a diamond-shaped cross section;
forming a dielectric liner over the S/D regions;
etching a dielectric fill formed over the S/D regions to expose a top portion of the diamond-shaped cross section;
recessing the fins into the diamond-shaped cross section;
exposing an outer surface of the diamond-shaped cross section of the S/D regions;
forming a contact liner on the exposed outer surface of the diamond-shaped cross section of the S/D regions and in a recess where the fins were recessed; and
forming contacts over surfaces of the top portion and in the recess.
2. The method as recited in claim 1 , wherein etching the dielectric fill includes performing a timed etch in accordance with a pattern to reach the top portion of the diamond-shaped cross section.
3. The method as recited in claim 1 , wherein recessing the fins into the diamond-shaped cross section includes performing a selective etch to etch a portion of the fins within the diamond-shaped cross section.
4. The method as recited in claim 3 , wherein performing the selective etch includes performing a reactive ion etch with an HBr chemistry.
5. The method as recited in claim 1 , further comprising forming gate structures on the fins.
6. The method as recited in claim 5 , wherein forming the gate structures on the fins includes constructing a replacement metal gate structure.
7. The method as recited in claim 1 , wherein exposing the outer surface of the diamond-shaped cross section of the S/D regions includes etching away the dielectric liner from the outer surface.
8. The method as recited in claim 1 , wherein forming contacts over surfaces of the top portion and in the recess includes forming the contacts over at least the outer surface of the diamond-shaped cross section of the S/D regions, and on exposed sidewalls in the recess where the fins were recessed.
9. The method as recited in claim 1 , wherein the fins are recessed such that a recessed fin height is less than 30% of an original fin height.
10. A method for forming fin field effect transistors, comprising:
forming fins from a silicon layer of a silicon-on-insulator substrate;
forming a dummy gate structure on the fins;
epitaxially growing source and drain (S/D) regions on the fins, the S/D regions including a diamond-shaped cross section;
forming a dielectric liner over the S/D regions;
depositing a dielectric fill over the dummy gate structure and the S/D regions;
replacing the dummy gate with a replacement metal gate structure and recessing the replacement metal gate structure;
etching the dielectric fill over the S/D regions to expose a top portion of the diamond-shaped cross section;
recessing the fins into the diamond-shaped cross section;
exposing an outer surface of the diamond-shaped cross section of the S/D regions;
forming a contact liner on the exposed outer surface of the diamond-shaped cross section of the S/D regions and in a recess where the fins were recessed; and
forming contacts over surfaces of the top portion and in the recess.
11. The method as recited in claim 10 , wherein etching the dielectric fill includes performing a timed etch in accordance with a pattern to reach the top portion of the diamond-shaped cross section.
12. The method as recited in claim 10 , wherein recessing the fins into the diamond-shaped cross section includes performing a selective etch to etch a portion of the fins within the diamond-shaped cross section.
13. The method as recited in claim 12 , wherein performing the selective etch includes performing a reactive ion etch with an HBr chemistry.
14. The method as recited in claim 10 , wherein exposing the outer surface of the diamond-shaped cross section of the S/D regions includes etching away the dielectric liner from the outer surface.
15. The method as recited in claim 10 , wherein forming contacts over surfaces of the top portion and in the recess includes forming the contacts over at least the outer surface of the diamond-shaped cross section of the S/D regions, and on exposed sidewalls in the recess where the fins were recessed.
16. The method as recited in claim 10 , wherein the fins are recessed such that a recessed fin height is less than 30% of an original fin height.