Hybrid airgap structure with oxide liner
View Patent ↗A technique relates to an airgap structure. A dielectric layer is formed on an underlying layer. Copper filled trenches are formed in the dielectric layer, and a metal liner lines the copper filled trenches. An oxide liner lines the metal liner and covers the dielectric layer. One or more airgaps are formed between the copper filled trenches in areas in which the oxide liner was not present on the dielectric layer. A cap layer is formed on top of the one or more airgaps, the copper filled trenches, and portions of the oxide liner.
1. A method of forming an airgap structure, the method comprising:
patterning trenches into a dielectric layer formed on an underlying layer;
disposing an oxide liner on top of the dielectric layer and in the trenches;
disposing a metal liner on top of the oxide liner, such that the metal liner lines the trenches;
disposing a copper layer on top of the metal liner such that the trenches are filled with the copper layer;
planarizing the copper layer to be coplanar with the oxide liner, such that the copper layer remaining forms copper filled trenches with the metal liner;
disposing a first cap layer on top of the copper filled trenches and the oxide liner, wherein the first cap layer is a sacrificial or permanent cap layer;
disposing a stack of sacrificial layers on top of the first cap layer;
patterning an opening into a top sacrificial layer of the stack of sacrificial layers;
etching the stack of sacrificial layers, the first cap layer, the metal liner, and the oxide liner according to a pattern of the opening, wherein an airgap pattern is formed in locations where the oxide liner is etched, wherein the airgap pattern leaves one or more exposed portions of the dielectric layer between the copper filled trenches;
removing the stack of sacrificial layers;
forming one or more airgaps between the copper filled trenches, wherein the one or more airgaps are formed by removing the one or more exposed portions of the dielectric layer between the copper filled trenches; and
disposing a second cap layer on top of the one or more airgaps, the copper filled trenches, and portions of the oxide liner.
2. The method of claim 1 , wherein disposing the stack of sacrificial layers on top of the first cap layer comprises disposing a bottom sacrificial layer on top of the first cap layer, disposing a middle sacrificial layer on top of the bottom sacrificial layer, and disposing the top sacrificial layer on top of the middle sacrificial layer.
3. The method of claim 2 , wherein removing the stack of sacrificial layers comprises removing the bottom, middle, and top sacrificial layers.
4. The method of claim 2 , wherein the bottom sacrificial layer is an organic planarization layer.
5. The method of claim 2 , wherein the middle sacrificial layer is an anti-reflective coating.
6. The method of claim 2 , wherein the top sacrificial layer is a photoresist layer.
7. The method of claim 1 , wherein non-exposed portions of the dielectric layer remain after the airgap pattern is formed.
8. The method of claim 7 , wherein the non-exposed portions of the dielectric layer support the second cap layer.
9. The method of claim 7 , wherein the non-exposed portions of the dielectric layer have the oxide liner on top.
10. The method of claim 1 , wherein the one or more airgaps have sidewalls formed of the oxide liner.