Methods of forming interlayer dielectrics having air gaps
Methods of forming an interlayer dielectric having an air gap are provided including forming a first insulating layer on a semiconductor substrate. The first insulating layer defines a trench. A metal wire is formed in the trench such that the metal wire is recessed beneath an upper surface of the first insulating layer. A metal layer is formed on the metal wire, wherein the metal layer includes a capping layer portion filling the recess, a upper portion formed on the capping layer portion, and an overhang portion formed on the portion of the first insulating layer adjacent to the trench protruding sideward from the upper portion. The first insulating layer is removed and a second insulating layer is formed on the semiconductor substrate to cover the metal layer, whereby an air gap is formed below the overhang portion of the metal layer. A portion of the second insulating layer is removed to expose the upper portion of the metal layer. The upper portion and the overhang portion of the metal layer are removed. A third insulating layer is formed on the semiconductor substrate from which the upper portion and the overhang portion have been removed to maintain the air gap.
1. A method of forming an interlayer dielectric having an air gap, the method comprising:
forming a first insulating layer on a semiconductor substrate, the first insulating layer defining a trench;
forming a metal wire in the trench such that the metal wire is recessed beneath an upper surface of the first insulating layer;
forming a metal layer on the metal wire, wherein the metal layer comprises a capping layer portion filling the recess, a upper portion formed on the capping layer portion, and an overhang portion formed on the portion of the first insulating layer adjacent to the trench protruding sidewards from the upper portion;
removing the first insulating layer;
forming a second insulating layer on the semiconductor substrate to cover the metal layer, whereby an air gap is formed below the overhang portion of the metal layer;
removing a portion of the second insulating layer to expose the upper portion of the metal layer;
removing the upper portion and the overhang portion of the metal layer; and
forming a third insulating layer on the semiconductor substrate from which the upper portion and the overhang portion have been removed to maintain the air gap.
2. The method of claim 1 , wherein forming the first insulating layer is preceded by forming an etch stop layer on the semiconductor substrate.
3. The method of claim 1 , wherein forming the metal wire is preceded by forming a barrier layer on sidewalls and a bottom of the trench.
4. The method of claim 1 , wherein the metal wire is formed by electroless plating.
5. The method of claim 1 , wherein the metal wire comprises at least one layer of copper (Cu), platinum (Pt) and/or silver (Ag).
6. The method of claim 5 , wherein the metal wire comprises an impurity of P, B, W, Mn, or Mo.
7. The method of claim 1 , wherein the metal layer is formed by electroless plating.
8. The method of claim 1 , wherein the metal layer comprises at least one layer of Co, Ni, Pt, Pd, Rh, Ru, and/or Re.
9. The method of claim 8 , wherein the metal layer comprises an impurity of P, B, W, Mn, or Mo.
10. The method of claim 1 , wherein the second insulating layer has a void between the metal wires.
11. The method of claim 1 , wherein the first insulating layer is selectively removed by wet etching.
12. The method of claim 1 , wherein the metal layer is removed by wet etching using a mixed solution of phosphoric acid, acetic acid, and nitric acid.
13. The method of claim 1 , wherein the second insulating layer comprises a low-k dielectric having a dielectric constant of from about 1.5 to about 4.0.
14. The method of claim 13 , wherein the second insulating layer comprises one selected from the group consisting of HOSP, HSQ, SiLK™, Flare™, Black-Diamond™, and these materials with increased porosity.
15. The method of claim 1 , wherein the third insulating layer comprises the same material as that of the second insulating layer.
16. The method of claim 1 , wherein the third insulating layer comprises silicon oxide.