Nanosheet substrate isolated source/drain epitaxy by nitrogen implantation
Parasitic transistor formation under a semiconductor containing nanosheet device is eliminated by implantation of nitrogen into physically exposed surfaces of a semiconductor substrate after formation of a nanosheet stack of alternating nanosheets of a sacrificial semiconductor material nanosheet and a semiconductor channel material nanosheet on a portion of the semiconductor substrate. The nitrogen doped semiconductor region that is created by the nitrogen implantation is subsequently converted into a semiconductor nitride region (i.e., an isolation region) prior to the epitaxial growth of a semiconductor material that provides S/D regions from physically exposed sidewalls of each semiconductor channel material stack. The presence of the semiconductor nitride region prevents bottom up growth of the semiconductor material that provides the S/D regions.
1. A semiconductor structure comprising:
a plurality of stacked and suspended semiconductor channel material nanosheets located above a semiconductor substrate;
a functional gate structure surrounding a portion of each semiconductor channel material nanosheet of the plurality of stacked and suspended semiconductor channel material nanosheets;
a source/drain (S/D) region on each side of the functional gate structure and physically contacting sidewalls of each semiconductor channel material nanosheet of the plurality of stacked and suspended semiconductor channel material nanosheets;
an interlevel dielectric (ILD) material composed of a solid dielectric material located above and beneath each S/D region, wherein a bottommost surface of the ILD material that is located beneath each S/D region is in physical contact with a semiconductor nitride layer that is present on a surface of the semiconductor substrate, and wherein an entirety of an uppermost surface of the ILD material that is located beneath each S/D region is in physical contact with the S/D region; and
inner gate spacers contacting sidewalls of the functional gate structure and located on an outer portion of each semiconductor channel material nanosheet of the plurality of stacked and suspended semiconductor channel material nanosheets, wherein a surface of the semiconductor nitride layer contacts an entire bottommost surface of a bottommost inner gate spacer.
2. The semiconductor structure of claim 1 , wherein the surface of the semiconductor substrate contacting the semiconductor nitride layer is a concave surface.
3. The semiconductor structure of claim 1 , wherein each source/drain (S/D) region has a faceted upper surface and a curved bottom surface.
4. The semiconductor structure of claim 1 , wherein the ILD material atop each S/D region has a topmost surface that is coplanar with a topmost surface of the functional gate structure.
5. The semiconductor structure of claim 1 , wherein the sidewalls of each semiconductor channel material nanosheet of the plurality of stacked and suspended semiconductor channel material nanosheets are vertically aligned to each other.
6. The semiconductor structure of claim 1 , wherein the semiconductor nitride layer and each of the inner gate spacers are composed of silicon nitride.
7. The semiconductor structure of claim 1 , wherein the semiconductor substrate and each semiconductor channel material nanosheet of the plurality of stacked and suspended semiconductor channel material nanosheets are composed of a same semiconductor material.
8. The semiconductor structure of claim 1 , wherein no parasitic transistor is present beneath the plurality of stacked and suspended semiconductor channel material nanosheets.