Vertically stacked fin semiconductor devices
Semiconductor devices and methods of forming the same include forming a first dielectric layer around a semiconductor fin, formed from a first dielectric material, to a target height lower than a height of the semiconductor fin. A second dielectric layer is deposited on the first dielectric layer and is formed from a second dielectric material. A third dielectric layer, formed from the first dielectric material, is formed on the second dielectric layer. The second dielectric layer is etched away to expose a gap on the semiconductor fin. A portion of the semiconductor fin that is exposed in the gap is oxidized to form an isolation layer.
1. A method of forming a semiconductor device, comprising:
forming a first dielectric layer around a semiconductor fin, formed from a first dielectric material, to a target height lower than a height of the semiconductor fin;
depositing a second dielectric layer on the first dielectric layer, formed from a second dielectric material;
forming a third dielectric layer, formed from the first dielectric material, on the second dielectric layer;
etching away the second dielectric layer to expose a gap on the semiconductor fin; and
oxidizing a portion of the semiconductor fin exposed in the gap to form an isolation layer.
2. The method of claim 1 , wherein oxidizing the portion of the semiconductor fin is timed to produce the first vertical thickness of the isolation layer.
3. The method of claim 1 , wherein forming the first dielectric layer comprises:
treating an upper portion of the semiconductor fin down to the target height; and
depositing the first dielectric material using a process that does not adhere to the treated upper portion.
4. The method of claim 1 , wherein forming the first dielectric layer comprises:
depositing the first dielectric material around the semiconductor to a height above the height of the semiconductor fin; and
etching the first dielectric material down to the target height.
5. The method of claim 1 , wherein the first dielectric material is silicon nitride and the second dielectric material is an oxide.
6. The method of claim 5 , wherein the second dielectric material is silicon dioxide.
7. A method of forming semiconductor devices, comprising:
forming a first dielectric layer around a first semiconductor fin in a first device region, formed from a first dielectric material, to a first target height lower than a height of the first semiconductor fin;
depositing a second dielectric layer on the first dielectric layer, formed from a second dielectric material;
forming a third dielectric layer, formed from the first dielectric material, on the second dielectric layer;
etching away the second dielectric layer to expose a gap on the first semiconductor fin;
oxidizing a portion of the semiconductor fin exposed in the gap on the first semiconductor fin to form a first isolation layer having a first vertical thickness;
forming a fourth dielectric layer around a second semiconductor fin in a second device region, formed from the first dielectric material, to a second target height lower than a height of the second semiconductor fin;
depositing a fifth dielectric layer on the fourth dielectric layer, formed from the second dielectric material;
forming a sixth dielectric layer on the fifth dielectric layer, formed from the first dielectric material;
etching away the fifth dielectric layer to expose a gap on the second semiconductor fin; and
oxidizing a portion of the second semiconductor fin exposed in the gap on the second semiconductor fin to form a second isolation layer having a second vertical thickness.
8. The method of claim 7 , wherein oxidizing the portion of the first semiconductor fin is timed to produce the first vertical thickness of the isolation layer.
9. The method of claim 7 , wherein the first vertical thickness is different from the second vertical thickness.
10. The method of claim 7 , wherein the first target height is different from the second target height.
11. The method of claim 7 , wherein the first semiconductor fin and the second semiconductor fin have a same height.
12. The method of claim 7 , wherein the first dielectric material is silicon nitride and the second dielectric material is an oxide.
13. The method of claim 12 , wherein the second dielectric material is silicon dioxide.