Raised source/drain and gate portion with dielectric spacer or air gap spacer
A semiconductor structure and method of manufacturing the same are provided. The semiconductor device includes epitaxial raised source/drain (RSD) regions formed on the surface of a semiconductor substrate through selective epitaxial growth. In one embodiment, the faceted side portions of the RSD regions are utilized to form cavity regions which may be filled with a dielectric material to form dielectric spacer regions. Spacers may be formed over the dielectric spacer regions. In another embodiment, the faceted side portions may be selectively grown to form air gap spacer regions in the cavity regions. A conformal spacer layer with interior and exterior surfaces may be formed in the cavity region, creating an air gap spacer defined by the interior surfaces of the conformal spacer layer.
1. A method of forming a semiconductor device, comprising:
forming a gate portion on a surface of a semiconductor substrate, the gate portion having gate sidewalls;
forming gate spacers over the gate sidewalls and the surface of the semiconductor substrate, the gate spacers having first sidewalls;
forming a sacrificial layer on the surface of the semiconductor substrate contacting the first sidewalls;
forming second spacers on a top surface of the sacrificial layer and on the first sidewalls, the second spacers having second sidewalls;
removing the sacrificial layer to expose a bottom surface of the second spacers and the surface of the semiconductor substrate; and
forming raised source/drain (RSD) regions on the surface of the semiconductor substrate, the RSD regions having a faceted side portion contacting the gate sidewalls at the surface of the semiconductor substrate, thereby forming an air gap region in a region defined by a lower portion of the gate sidewalls, the bottom surface of the second spacers, and by the faceted side portions of the RSD regions.
2. The method of claim 1 , wherein the forming RSD regions comprises selectively growing the faceted side portion to contact a portion of the bottom surfaces of the second spacers, thereby causing the air gap region to have a substantially triangular profile.
3. The method of claim 1 , wherein the forming RSD regions comprises selectively growing the RSD regions in two layers:
a first layer having a faceted side portion contacting the first sidewalls at the surface of the semiconductor substrate and having a top surface contacting a substantial portion of the bottom surfaces of the second spacers; and
a second layer formed on the top surface of the first layer having a faceted side portion contacting the second sidewalls at the top surface of the first layer; thereby
causing the air gap region to have a substantially triangular profile defined by a lower portion of the first sidewalls, the bottom surfaces of the second spacers, and the faceted side portion of the RSD regions.
4. The method of claim 1 , wherein the forming RSD regions comprises selectively growing the faceted side portion to rise in a direction normal the surface of the semiconductor substrate at an angle from approximately 30 degrees to approximately 75 degrees relative to a bottom surface of the RSD regions.
5. The method of claim 1 , wherein the forming RSD regions comprises selectively growing the faceted side portion to rise in a direction normal to the surface of the semiconductor substrate at an angle from approximately 20 degrees to approximately 60 degrees relative to a bottom surface of the RSD regions.
6. The method of claim 5 , further comprising forming a conformal spacer layer with interior surfaces and with external surfaces overlying the second sidewalls, the first sidewalls, and RSD regions, etching the conformal layer to form conformal spacers with external surfaces overlying the second sidewalls, the first sidewalls, and a portion of the faceted side portion of the RSD regions, and thereby forming an air gap region having a substantially triangular profile defined by the interior surfaces of the conformal spacer layer.
7. A semiconductor device, comprising:
a gate portion on a surface of a semiconductor substrate, the gate portion having gate sidewalls;
gate spacers overlying the gate sidewalls of said gate portion and the surface of the semiconductor substrate, the gate spacers having first sidewalls;
second spacers formed on the first sidewalls, the second spacers having second sidewalls and bottom surfaces;
raised source/drain (RSD) regions adjacent to the gate portion, the RSD regions having an upper surface and a faceted side portion contacting the first sidewalls at the surface of the semiconductor substrate;
cavity regions defined by the faceted side portion of the RSD regions, the first sidewalls, and the bottom surfaces of the second spacers; and
dielectric regions formed in the cavity regions.
8. The device of claim 7 , further comprising a silicide layer formed on the upper surface of the RSD regions, the silicide layer contacting the second sidewalls.
9. The device of claim 7 , wherein the dielectric regions are comprised of a low-k dielectric material with a dielectric constant less than approximately 4.0.
10. The device of claim 7 , wherein the dielectric regions are comprised of a dielectric material with a dielectric constant ranging from approximately 4.0 to approximately 7.0.
11. The device of claim 7 , wherein the faceted side portion rises in a direction normal to the surface of the semiconductor substrate at an angle ranging from approximately 30 degrees to approximately 75 degrees relative to a bottom surface of the RSD regions.
12. The device of claim 7 , wherein the faceted side portion rises in a direction normal to the surface of the semiconductor substrate at an angle ranging from approximately 20 degrees to approximately 60 degrees relative to a bottom surface of the RSD regions.
13. The device of claim 12 , further comprising conformal spacers having interior surfaces and having external surfaces overlying the second sidewalls, the first sidewalls, and a portion of the faceted side portion, the interior surfaces of the conformal spacer forming an air gap region having a substantially triangular profile.