Forming isolated fins from a substrate
A method of isolating a semiconductor fin from an underlying substrate including forming a masking layer around a base portion of the fin, forming spacers on a top portion of the fin above the masking layer, removing the masking layer to expose the base portion of the fin, and converting the base portion of the fin to an isolation region that electrically isolates the fin from the substrate. The base portion of the fin may be converted to an isolation region by oxidizing the base portion of the fin, using for example a thermal oxidation process. While converting the base portion of the fin to an isolation region, the spacers prevent the top portion of the fin from also being converted.
1. A method of isolating a semiconductor fin from a substrate, the method comprising:
forming a hard mask layer on a top surface of the fin;
forming a masking layer around a base portion of the fin and the substrate;
forming spacers on a top portion of the fin above the masking layer;
removing the masking layer to expose the base portion of the fin and the substrate; and
forming an isolation region from the base portion of the fin, the isolation region electrically insulating the top portion of the fin from the substrate, wherein forming an isolation region from the base portion of the fin comprises oxidizing or nitriding the base portion of the fin, and wherein the oxidizing or nitriding comprises performing an ion implantation of the isolation region with a species selected from the group consisting of oxygen and nitrogen.
2. The method of claim 1 , wherein the masking layer comprises an optical dispersive layer.
3. The method of claim 1 , wherein the masking layer has a thickness ranging from approximately 10 nm to approximately 30 nm.
4. The method of claim 1 , wherein the spacers have a thickness sufficient to prevent the top portion of the fin from being converted to an isolation region while forming an isolation region from the base portion of the fin.
5. The method of claim 1 , wherein the substrate comprises a bulk semiconductor substrate.
6. A method of forming a semiconductor device, the method comprising:
forming a fin on a bulk semiconductor substrate, wherein the fin has a top surface and sidewalls;
forming a hard mask on the top surface of the fin
depositing an insulating layer on the bulk semiconductor substrate, wherein the insulating layer surrounds a first base portion of the fin adjacent to the bulk semiconductor substrate;
forming a sacrificial gate over the fin;
depositing an interlevel dielectric layer around the sacrificial gate;
removing the sacrificial gate to form a gate recess region exposing the fin;
forming a masking layer around a second base portion of the fin above the first base portion of the fin;
forming spacers on the sidewalls of the fin above the masking layer;
removing the masking layer to expose the second base portion of the fin and the insulating layer;
forming an isolation region from the second base portion of the fin, the isolation region electrically insulating the fin above the isolation region from the bulk semiconductor substrate, and wherein forming an isolation region from the second base portion of the fin comprises oxidizing or nitriding the second base portion of the fin, and further comprising performing an ion implantation of the isolation region with a species selected from the group consisting of oxygen and nitrogen.
7. The method of claim 6 , wherein the masking layer comprises an optical dispersion layer.
8. The method of claim 6 , wherein the masking layer has a thickness ranging from approximately 10 nm to approximately 30 nm.
9. The method of claim 6 , wherein the spacers have a thickness sufficient to prevent the portion of the fin above the second base portion from being converted to an isolation region while forming an isolation region from the second base portion of the fin.
10. The method of claim 6 , wherein the substrate comprises a bulk semiconductor substrate.
11. The method of claim 1 , wherein the masking layer includes an optical dispersive layer (ODL).
12. The method of claim 6 , wherein the masking layer includes an optical dispersive layer (ODL).