Method of forming vertical field effect transistors with self-aligned gates and gate extensions and the resulting structure
Disclosed is a method of forming an integrated circuit (IC) that incorporates multiple vertical field effect transistors (VFETs) (e.g., in a VFET array). In the method, self-aligned gates for each pair of VFETs and a self-aligned gate extension for contacting those self-aligned gates are essentially simultaneously formed such that the gates wrap around a pair of semiconductor fins, which are in end-to-end alignment, and such that the gate extension fills the space between adjacent ends of those semiconductor fins. By forming self-aligned gates and a self-aligned gate extension for a pair of VFETs, the method avoids the need for lithographically patterning extension cut isolation regions between adjacent pairs of VFETs in a VFET array. Thus, the method enables implementation of VFET array designs with a reduced fin pitch without incurring defects caused, for example, by overlay errors. Also disclosed herein is an IC formed according to the method.
1. An integrated circuit structure comprising:
a substrate; and
a pair of transistors on the substrate and comprising:
a pair of semiconductor fins, the semiconductor fins in the pair extending vertically between lower source/drain regions in the substrate and upper source/drain regions, respectively, and the semiconductor fins being in end-to-end alignment;
gates positioned laterally adjacent to outer ends and opposing sides of the semiconductor fins;
a gate extension above an isolation region and extending laterally between and in direct contact with adjacent ends of the semiconductor fins and with the gates; and
a spacer above the gate extension and further above the gates and wrapping around the upper source/drain regions.
2. The integrated circuit structure of claim 1 , wherein sidewalls of the spacer are aligned vertically with sidewalls of the gates and the gate extension below.
3. The integrated circuit structure of claim 1 , the isolation region being between the lower source/drain regions.
4. The integrated circuit structure of claim 1 , further comprising a spacer layer on the substrate and electrically isolating the gates from the lower source/drain regions.
5. The integrated circuit structure of claim 1 , further comprising a gate contact extending through interlayer dielectric material and the spacer to the gate extension.
6. The integrated circuit structure of claim 1 , further comprising an extension cut isolation region extending through interlayer dielectric material, the spacer and the gate extension to the isolation region.
7. The integrated circuit structure of claim 1 , further comprising a second pair of transistors on the substrate and parallel to the pair of transistors, wherein interlayer dielectric material electrically isolates second gates and a second gate extension of the second pair of transistors from the gates and the gate extension of the pair of transistors.