Transistor contacts self-aligned two dimensions
Embodiments of the present invention provide an improved semiconductor structure and methods of fabrication that provide transistor contacts that are self-aligned in two dimensions. Two different capping layers are used, each being comprised of a different material. The two capping layers are selectively etchable to each other. One capping layer is used for gate coverage while the other capping layer is used for source/drain coverage. Selective etch processes open the desired gates and source/drains, while block masks are used to cover elements that are not part of the connection scheme. A metallization line (layer) is deposited, making contact with the open elements to provide electrical connectivity between them.
1. A semiconductor structure comprising:
a plurality of transistor gates;
a plurality of transistor source/drain contact areas;
a first capping layer disposed on a subset of the plurality of transistor gates;
a second capping layer disposed on a subset of the plurality of transistor source/drain contact areas; and
a metallization layer disposed on the first capping layer and second capping layer.
2. The semiconductor structure of claim 1 , wherein the metallization layer is in electrical contact with at least one transistor gate of the plurality of transistor gates.
3. The semiconductor structure of claim 1 , wherein the metallization layer is in electrical contact with at least one source/drain contact area of the plurality of transistor source/drain contact areas.
4. The semiconductor structure of claim 1 , further comprising a dielectric region bounding the metallization layer.
5. The semiconductor structure of claim 4 , further comprising a plurality of spacers adjacent to each transistor gate of the plurality of transistor gates.
6. The semiconductor structure of claim 5 , wherein the first capping layer is comprised of silicon nitride, the second capping layer is comprised of silicon oxide, the dielectric region is comprised of silicon oxycarbide, and the plurality of spacers are comprised of a material selected from the group consisting of silicon oxycarbide and silicon oxycarbonitride.