Self-aligned isolation for self-aligned contacts for vertical FETS
A method for manufacturing a vertical FET device includes providing a semiconductor substrate structure including a semiconductor substrate and a first semiconductor layer coupled to the semiconductor substrate. The first semiconductor layer is characterized by a first conductivity type. The method also includes forming a plurality of semiconductor fins coupled to the first semiconductor layer. Each of the plurality of semiconductor fins is separated by one of a plurality of recess regions. The method further includes epitaxially regrowing a semiconductor gate layer including a surface region in the plurality of recess regions. The method also includes forming an isolation region within the surface region of the semiconductor gate layer. The isolation region surrounds each of the plurality of semiconductor fins. The method includes forming a source contact structure coupled to each of the plurality of semiconductor fins and forming a gate contact structure coupled to the semiconductor gate layer.
1. A vertical FET device comprising:
a semiconductor substrate;
a first epitaxial semiconductor layer coupled to the semiconductor substrate, wherein the first epitaxial semiconductor layer is characterized by a first conductivity type;
a plurality of semiconductor fins disposed on the first epitaxial semiconductor layer, wherein each of the plurality of semiconductor fins is separated by one of a plurality of recess regions;
a semiconductor gate layer epitaxially regrown in the plurality of recess regions;
an electrically semi-insulating III-nitride isolation region disposed within a portion of the semiconductor gate layer, wherein the electrically semi-insulating III-nitride isolation region surrounds each of the plurality of semiconductor fins;
a source contact structure coupled to each of the plurality of semiconductor fins; and
a gate contact structure coupled to the semiconductor gate layer.
2. The vertical FET device of claim 1 wherein the semiconductor gate layer comprises:
an active region in which the plurality of semiconductor fins are formed and a terminal region adjacent the active region, and
a tapered element in the terminal region.
3. The vertical FET device of claim 1 further comprising:
a first interlayer dielectric layer deposited overlying the source contact structure and the gate contact structure, wherein the first interlayer dielectric layer has a first opening exposing a portion of an upper surface of each of the plurality of semiconductor fins;
a second interlayer dielectric layer deposited on the first interlayer dielectric layer, where the second interlayer dielectric layer has a second opening exposing the portion of the upper surface of each of the plurality of semiconductor fins; and
a pad metal layer electrically coupled to the portion of the upper surface of each of the plurality of semiconductor fins.
4. The vertical FET device of claim 3 wherein the first interlayer dielectric layer comprises nitride and the second interlayer dielectric layer comprises oxide.
5. The vertical FET device of claim 1 wherein the source contact structure comprises:
a first source metal layer coupled to each of the plurality of semiconductor fins, wherein the first source metal layer comprises Ti;
a second source metal layer coupled to the first source metal layer, wherein the second source metal layer comprises Al; and
a third source metal layer coupled to the second source metal layer, wherein the third source metal layer comprises Mo.
6. The vertical FET device of claim 1 wherein the gate contact structure comprises:
a first gate metal layer coupled to the semiconductor gate layer, wherein the first gate metal layer comprises Ni;
a second gate metal layer coupled to the first gate metal layer, wherein the second gate metal layer comprises Au;
a third gate metal layer coupled to the second gate metal layer, wherein the third gate metal layer comprises Mo; and
a fourth gate metal layer coupled to the third gate metal layer, wherein the fourth gate metal layer comprises Au.
7. The vertical FET device of claim 1 further comprising:
a graded semiconductor layer disposed between the first epitaxial semiconductor layer and the plurality of semiconductor fins, wherein a graded conductivity of the graded semiconductor layer varies as a function of distance from the first epitaxial semiconductor layer.
8. The vertical FET device of claim 7 wherein the graded semiconductor layer is disposed between the first epitaxial semiconductor layer and the semiconductor gate layer.
9. The vertical FET device of claim 8 wherein the graded semiconductor layer disposed between the first epitaxial semiconductor layer and the plurality of semiconductor fins is thicker than the graded semiconductor layer disposed between the first epitaxial semiconductor layer and the semiconductor gate layer.
10. The vertical FET device of claim 1 wherein the plurality of semiconductor fins are aligned in a same crystallographic direction.
11. The vertical FET device of claim 1 wherein the source contact structure covers a portion of the electrically semi-insulating III-nitride isolation region.
12. The vertical FET device of claim 1 wherein the gate contact structure does not cover a portion of the electrically semi-insulating III-nitride isolation region.
13. The vertical FET device of claim 3 wherein the first interlayer dielectric layer has a third opening exposing a portion of an upper surface of the gate contact structure, and the second interlayer dielectric layer has a fourth opening exposing the portion of the upper surface of the gate contact structure.
14. The vertical FET device of claim 3 wherein the first interlayer dielectric layer comprises nitride and the second interlayer dielectric layer comprises oxide.
15. The vertical FET device of claim 1 wherein:
a cross-section of the plurality of semiconductor fins is substantially circular; and
the electrically semi-insulating III-nitride isolation region is substantially circular.
16. The vertical FET device of claim 1 wherein:
a cross-section of the plurality of semiconductor fins is substantially rectangular; and
the electrically semi-insulating III-nitride isolation region is substantially rectangular.
17. The vertical FET device of claim 2 wherein a conductivity of the semiconductor gate layer varies in the terminal region.