Non-self-aligned wrap-around contact in a tight gate pitched transistor
An integrated circuit (IC) is provided. The IC includes a substrate that includes first and second channels. A shared source or drain (S/D) region is between the first and second channels. The shared source or drain region includes an uppermost surface and further includes a second surface recessed from the uppermost surface and sidewalls extending from the uppermost surface to the second surface to define a recess. First and second gate structures including gate metal are disposed on the first and second channels. An S/D wrap-around contact (WAC) includes a first portion which extends into the recess to contact the second surface and the sidewalls and is wrapped around the S/D region at an exterior of the recess.
1. An integrated circuit (IC) comprising:
a substrate comprising first and second channels;
a shared source or drain (S/D) region between the first and second channels, the shared source or drain region comprising an uppermost surface and further comprising a second surface recessed from the uppermost surface and sidewalls extending from the uppermost surface to the second surface to define a recess;
first and second gate structures comprising gate metal disposed on the first and second channels; and
an S/D wrap-around contact (WAC), which comprises a first portion which extends into the recess to contact the second surface and the sidewalls and which is wrapped around the S/D region at an exterior of the recess,
wherein the S/D region comprises epitaxy having a negatively profiled section, the S/D WAC forms an elongate void under the negatively profiled section of the epitaxy of the S/D region and the negatively profiled section and the longest dimension of the elongate void are correspondingly angled relative to the substrate.
2. The semiconductor device according to claim 1 , wherein:
the S/D WAC is not self-aligned owing to an absence of a dielectric capping layer on the gate metal, and
the S/D WAC further comprises an uppermost edge coplanar with an uppermost edge of the gate metal.
3. The semiconductor device according to claim 1 , wherein:
the epitaxy of the S/D region has a first negatively profiled section at a first side thereof and a second negatively profiled section at a second side thereof,
the first negatively profiled section and the second negatively profiled section are oppositely angled relative to one another, and
the S/D WAC contacts a respective entirety of each of the first and second negatively profiled sections of epitaxy of the S/D region.
4. The semiconductor device according to claim 3 , wherein:
the S/D WAC forms a first elongate void under the first negatively profiled section of the epitaxy of the S/D region,
the S/D WAC forms a second elongate void under the second negatively profiled sections of the epitaxy of the S/D region,
the first negatively profiled section and the first elongate void are correspondingly angled relative to the substrate,
the second negatively profiled section and the second elongate void are correspondingly angled relative to the substrate, and
the first elongate void and the second elongate void are oppositely angled relative to one another.
5. The semiconductor device according to claim 1 , wherein the first and second channels are each fin-shaped.
6. The semiconductor device according to claim 1 , wherein the first and second channels are each a stack of spaced-apart nanosheets.
7. A method of forming a portion of an IC, according to the IC of claim 1 , the method comprising:
forming a sacrificial layer;
forming a pattern configured to define a part of a contact opening having an overlay error margin;
applying a non-selective etch through the pattern without an etch stop to open the contact opening through the sacrificial layer and a dielectric to form the contact opening and the recess in the shared region; and
applying an isotropic etch through the pattern to enlarge a width and a depth of the recess.
8. The method according to claim 7 , further comprising forming a FinFET or a nanosheet FET.
9. The method according to claim 7 , wherein the sacrificial layer comprises silicon nitride and the dielectric comprises silicon dioxide.
10. The method according to claim 7 , wherein the sacrificial layer comprises a thickness of about 3 nm to about 15 nm.
11. The method according to claim 7 , wherein the contact opening comprises a width of less than about 10 nm.
12. The method according to claim 7 , wherein the sacrificial layer prevents vertical erosion of the dielectric during the isotropic etch.
13. The method according to claim 7 , further comprising forming a S/D contact by depositing a conductive material in the opening and the recess.
14. A method of forming a portion of an IC, according to the IC of claim 1 , the method comprising:
forming a sacrificial layer;
forming a pattern configured to define a part of a contact opening having an initial width;
using the pattern and a removal process to form the contact opening through the sacrificial layer, through the dielectric, and into the recess of the shared region;
forming an increased width of the contact opening, an increased width of the recess, and an increased depth of the recess by removing an additional region of the dielectric and an additional region of the recess;
removing the sacrificial layer; and
removing a capping layer from the shared S/D region.
15. The method according to claim 14 , further comprising forming a FinFET or a nanosheet FET.
16. The method according to claim 14 , wherein the sacrificial layer comprises silicon nitride and the dielectric comprises silicon dioxide.
17. The method according to claim 14 , wherein the sacrificial layer comprises a thickness of about 3 nm to about 15 nm.
18. The method according to claim 14 , wherein the increased width of the contact opening comprises a width of less than about 10 nm.
19. The method according to claim 14 , wherein:
removing the additional region of the dielectric and the additional region of the recess comprises applying isotropic etching; and
the sacrificial layer prevents vertical erosion of the dielectric during the isotropic etching.
20. The method according to claim 14 , further comprising forming a wrap-around S/D contact by depositing a conductive material in the opening and the recess.