Air gap contact formation for reducing parasitic capacitance
A functional gate structure is located on a surface of a semiconductor material portion and including a U-shaped gate dielectric portion and a gate conductor portion. A source region is located on one side of the functional gate structure, and a drain region is located on another side of the functional gate structure. The source region and drain region both have a topmost surface that is above a topmost surface of the semiconductor material portion and another surface that touches a portion of the U-shaped gate dielectric. A contact structure is located on the topmost surface of the source region and/or the drain region. A middle-of-the-line air gap contact is located between the contact structure and the functional gate structure and above at least one of the source region and the drain region. The middle-of-the-line air gap contact is sealed by a portion of a conformal dielectric material.
1. A semiconductor structure comprising:
a functional gate structure located on a surface of a semiconductor material portion and including a U-shaped gate dielectric portion and a gate conductor portion, wherein sidewall surfaces of said semiconductor material portion are vertically aligned with sidewall surfaces of said functional gate structure;
a source region located on one side of the functional gate structure, wherein said source region has a topmost surface that is above a topmost surface of said semiconductor material portion and another surface that touches a portion of said U-shaped gate dielectric;
a drain region located on another side of the functional gate structure, said drain region has a topmost surface that is above a topmost surface of said semiconductor material portion and another surface that touches a portion of said U-shaped gate dielectric;
a contact structure located on said topmost surface of said at least one of said source region and said drain region; and
a middle-of-the-line air gap contact located between said contact structure and said functional gate structure and above at least one of said source region and said drain region, wherein said middle-of-the-line air gap contact is sealed by a portion of a conformal dielectric material.
2. The semiconductor structure of claim 1 , wherein said semiconductor material portion comprises a semiconductor fin, and said functional gate structure straddles said semiconductor fin.
3. The semiconductor structure of claim 1 , wherein said source region and said drain region comprise a semiconductor material having an epitaxial relationship with a surface of said semiconductor material portion.
4. The semiconductor structure of claim 1 , wherein said functional gate structure further includes a gate cap portion located on a topmost surface of said gate conductor portion.
5. The semiconductor structure of claim 1 , wherein said contact structure comprises a contact metal liner and a contact metal portion, wherein said contact metal liner and said contact metal portion have topmost surfaces that are coplanar with each other.
6. The semiconductor structure of claim 5 , wherein said topmost surfaces of said contact metal liner and said contact metal portion are located above a topmost portion of said middle-of-the-line air gap contact.
7. The semiconductor structure of claim 1 , wherein other portions of said conformal dielectric material extend above said contact structure and said functional gate structure.
8. The semiconductor structure of claim 1 , wherein said semiconductor material portion is located on a surface of an insulator layer.
9. The semiconductor structure of claim 1 , wherein a planarizing dielectric material is located above one of said source region or said drain region not including said contact structure and said middle-of-the-line air cap contact.
10. The semiconductor structure of claim 1 , wherein said U-shaped gate dielectric portion comprises a dielectric material having a dielectric constant greater than silicon dioxide.
11. The semiconductor structure of claim 1 , wherein each of said source region and said drain region has a faceted surface.
12. The semiconductor structure of claim 1 , wherein said middle-of-the-line air gap contact comprises a sealed air gap.
13. The semiconductor structure of claim 1 , wherein a topmost surface of said middle-of-the-line air gap contact is coplanar with a topmost surface of both said U-shaped gate dielectric portion and said gate conductor portion.
14. The semiconductor structure of claim 1 , wherein said semiconductor material portion is located on a surface of a remaining portion of a bulk semiconductor substrate, wherein said semiconductor material portion and said remaining portion of said bulk semiconductor substrate comprise a same semiconductor material.