STI inner spacer to mitigate SDB loading
A shallow trench isolation (STI) structure is formed from a conventional STI trench structure formed of first dielectric material extending into the substrate. The conventional STI structure undergoes further processing, including removing a first portion of the dielectric material and adjacent portions of the semiconductor substrate to create a first recess, and then removing another portion of the dielectric material to create a second recess in just the dielectric material. A nitride layer is formed above remaining dielectric material and on the sidewalls of the substrate. A second dielectric material is formed on the spacer layer and fills the remainder of first and second recesses. The nitride layer provides an “inner spacer” between the first insulating material and the second insulating material and also separates the substrate from the second insulating material. An isotropic Fin reveal process is performed and the STI structure assists in equalizing fin heights and increasing active S/D region area/volume.
1. A method of fabricating a semiconductor device for use with one or more field-effect transistor (FinFET) devices, the method comprising:
forming a shallow trench isolation (STI) structure within a semiconductor substrate from a shallow trench of first insulating material, comprising,
forming a mask layer to selectively expose the first insulating material and adjacent portions of the semiconductor substrate,
removing a first portion of the first insulating material and the substrate using the mask layer to form a first recess in the substrate having a first depth and expose vertical sidewall portions of the substrate,
removing a second portion of the first insulating material using a chemical oxide removal process, thereby forming a second recess having a second depth wherein a third portion of the first insulating material remains,
forming an inner spacer layer on the third portion of the first insulating material and along the exposed vertical sidewalls of the substrate, and
forming a layer of second insulating material on the inner spacer layer and filling the first and second recesses with the second insulating material, thereby forming the STI structure comprising a lower portion of first insulating material and an upper portion of second insulating material separated by the inner spacer layer, and wherein portions of the inner spacer layer are disposed adjacent the vertical sidewall portions of the substrate; and
after forming the STI structure, performing an isotropic Fin reveal process to reveal one or more fin structures.
2. The method in accordance with claim 1 wherein performing the isotropic Fin reveal process comprises:
performing a chemical oxide removal (COR) process.
3. The method in accordance with claim 1 wherein the inner spacer layer comprises nitride.
4. The method in accordance with claim 3 wherein inner spacer layer has a thickness between about 2 and 7 nanometers.
5. The method in accordance with claim 1 wherein the mask layer is formed of polysilicon.
6. The method in accordance with claim 1 wherein the portions of the inner spacer layer disposed adjacent the vertical sidewall portions of the substrate are, in the vertical direction, on the order of resulting Fin heights.
7. The method in accordance with claim 1 wherein the inner spacer layer has a thickness between about 2 and 7 nanometers.
8. The method in accordance with claim 7 wherein the portions of the inner spacer layer disposed adjacent the vertical sidewall portions of the substrate are, in the vertical direction, on the order of resulting Fin heights.
9. A method of fabricating a semiconductor device for use with one or more field-effect transistor (FET) devices, the method comprising:
forming a shallow trench isolation (STI) structure from a shallow trench of first insulating material disposed within a semiconductor substrate, comprising,
forming a mask layer to selectively expose a surface of the first insulating material and surfaces of adjacent portions of the semiconductor substrate,
selectively removing a first portion the exposed first insulating material and the exposed semiconductor substrate to a first depth, thereby exposing a second portion of the first insulating material and forming exposed vertical sidewalls in the semiconductor substrate,
selectively removing another portion of the exposed second portion of first insulating material to a second depth, thereby exposing a third portion of the first insulating material,
forming a spacer layer on the exposed third portion of insulating material and on the exposed vertical sidewalls of the semiconductor substrate, and
forming a layer of second insulating material layer on the spacer layer;
forming a first field effect transistor (FET) on the substrate, the first FET having a gate structure, a first source/drain (S/D) region and a second S/D region, wherein the first S/D region is formed adjacent to the STI structure; and
after forming the STI structure, performing an isotropic Fin reveal process to reveal one or more fin structures.
10. The method in accordance with claim 9 wherein performing the isotropic Fin reveal process comprises:
performing a chemical oxide removal (COR) process.
11. The method in accordance with claim 10 wherein the spacer layer comprises nitride.
12. The method in accordance with claim 9 wherein the spacer layer comprises nitride.
13. The method in accordance with claim 9 wherein spacer layer has a thickness between about 2 and 7 nanometers.
14. The method in accordance with claim 9 wherein the mask layer is formed of polysilicon.