Graphene wrap-around contact
The present disclosure provides source/drain epitaxial structures and source/drain contacts wrapped with graphene layers in fin structures of field effect transistors, and fabricating methods thereof. In some embodiments, a disclosed semiconductor device includes a fin structure on a substrate. The fin structure includes an epitaxial region. The semiconductor device further includes a metal contact above the epitaxial region, and a graphene film covering a top surface and sidewalls of the epitaxial region and covering a bottom surface and sidewalls of the metal contact.
1. A method of forming a semiconductor device, comprising:
forming a fin structure with an epitaxial region on a substrate;
forming a first graphene film covering a top surface and sidewalls of the epitaxial region;
forming a metal contact above the epitaxial region; and
forming a second graphene film in contact with the first graphene film and covering a bottom surface and sidewalls of the metal contact.
2. The method of claim 1 , further comprising:
forming an etch stop layer on the epitaxial region;
forming an interlayer dielectric layer on the etch stop layer; and
forming a contact opening that traverses through the etch stop layer and the interlayer dielectric layer and exposes a top surface of the first graphene film.
3. The method of claim 2 , wherein forming the second graphene film comprises:
forming the second graphene film covering a bottom surface and sidewalls of the contact opening.
4. The method of claim 1 , wherein forming the first graphene film and the second graphene film comprises:
forming the first graphene film or the second graphene film by a segregation and transfer process or by a catalyst-assisted growth process.
5. The method of claim 1 , wherein forming the fin structure with the epitaxial region comprises:
forming a merged fin structure; and
forming a merged epitaxial region.
6. The method of claim 1 , further comprising:
forming an other fin structure, on the substrate, comprising an other epitaxial region having an opposite type from that of the epitaxial region; and
forming a third graphene film covering a top surface and sidewalls of the other epitaxial region.
7. The method of claim 6 , further comprising:
forming an other metal contact above the other epitaxial region; and
forming a fourth graphene film covering a bottom surface and sidewalls of the other metal contact.
8. A method of forming a semiconductor device, comprising:
forming a fin structure with a merged epitaxial region on a substrate;
forming a metal contact above the merged epitaxial region; and
forming a graphene film covering sidewalls of the merged epitaxial region and the metal contact, and in between the merged epitaxial region and the metal contact.
9. The method of claim 8 , wherein forming the graphene film comprises:
forming the graphene film by a gas phase synthesis process by using 1,2,3,4-tetraphenylnaphthalene (TPN), Pyrene, or Benzene as a carbon source.
10. The method of claim 8 , further comprising:
forming an other fin structure, on the substrate, comprising an other merged epitaxial region having an opposite type from that of the merged epitaxial region;
forming an other metal contact above the other merged epitaxial region; and
forming an other graphene film covering a top surface and sidewalls of the other merged epitaxial region, and in between the other merged epitaxial region and the other metal contact.
11. The method of claim 8 , wherein:
forming the fin structure comprises forming the merged epitaxial region between first and second fin portions of the fin structure; and
forming the graphene film comprises forming the graphene film under the merged epitaxial region and between the first and second fin portions.
12. The method of claim 8 , wherein forming the graphene film comprises:
forming a first portion of the graphene film on a slanted side surface of the merged epitaxial region and with a first thickness; and
forming a second portion of the graphene film on a vertical side surface of the merged epitaxial region and with a second thickness greater than the first thickness.
13. The method of claim 8 , wherein forming the graphene film comprises forming the graphene film on a curved upper surface of the merged epitaxial region.
14. A method, comprising:
forming a fin structure on a substrate;
forming a source/drain (S/D) structure on the fin structure;
forming a first graphene film over the S/D structure;
depositing a dielectric layer on the S/D structure;
etching the dielectric layer to form an opening that exposes the first graphene film; and
forming an S/D contact in the opening.
15. The method of claim 14 , wherein forming the first graphene film comprises:
performing a surface treatment on the S/D structure to form an epitaxial termination interface; and
forming a graphene seeding layer over the epitaxial termination interface.
16. The method of claim 14 , wherein forming the first graphene film comprises forming a conformal graphene seeding layer over the S/D structure by performing a gas phase synthesis process.
17. The method of claim 16 , wherein forming the first graphene film further comprises applying an ultraviolet cure, a laser treatment, or a thermal anneal on the conformal graphene seeding layer.
18. The method of claim 14 , wherein forming the first graphene film comprises tuning a Schottky barrier height of the S/D contact to reduce a resistivity of a contact between the S/D structure and the S/D contact.
19. The method of claim 14 , wherein forming the S/D contact comprises:
forming a second graphene film on side surfaces of the opening; and
forming a metal plug on the second graphene film.
20. The method of claim 19 , wherein forming the second graphene film comprises:
growing the second graphene film on a growth substrate; and
transferring the second graphene film to top and side surfaces of the S/D structure.