Method and apparatus for forming metal-metal oxide etch stop/barrier for integrated circuit interconnects
View Patent ↗Described is a method and apparatus for forming interconnects with a metal-metal oxide electromigration barrier and etch-stop. In one embodiment of the invention, the method includes depositing a metal layer on the top of a planarized interconnect layer, the interconnect layer having an interlayer dielectric (ILD) with a top that is planar with the top of an electrically conductive interconnect. In one embodiment of the invention, the method includes reacting the metal layer with the ILD to form a metal oxide layer on the top of the ILD. At the same time, the metal layer will not be significantly oxidized by the electrically conductive interconnect, thus forming a metal barrier on the electrically conductive interconnect to improve electromigration performance. The metal barrier and metal oxide layer together comprise a protective layer. A second ILD may be subsequently formed on the protective layer, and the protective layer may act an etch-stop during a subsequent etch of the second ILD.
1. A method, comprising:
forming a metal oxide layer over an interconnect layer by depositing a metal layer by one of chemical vapor deposition and physical vapor deposition on an exposed portion of a first interlayer dielectric (ILD) and on an exposed portion of an interconnect formed within the first ILD, the metal oxide layer comprising a reaction product of the first ILD and the deposited metal layer; and
depositing a second ILD on the metal oxide layer.
2. The method of claim 1 , wherein the first ILD is a material that includes an amount of oxygen sufficient to react with the metal layer as the metal layer is being deposited to form the metal oxide layer.
3. The method of claim 1 , further comprising:
etching a via in the second ILD, the metal oxide layer acting as an etch-stop.
4. The method of claim 3 , wherein etching the via includes utilizing an etchant that will etch the second ILD without significantly etching the metal oxide layer.
5. The method of claim 1 , wherein depositing the metal layer includes depositing the metal layer to a thickness between approximately 10 Å to 100 Å.
6. The method of claim 1 , wherein the first interconnect comprises copper and the metal layer comprises a material selected from the group consisting of cobalt, aluminum, tantalum, chromium, and titanium.
7. A method, comprising:
depositing a metal on an exposed top portion of a first ILD and on an exposed top portion of an interconnect, wherein the metal reacts on contact with the first ILD to form a metal oxide on the first ILD, and the metal forms an electromigration barrier over the first interconnect, wherein the electromigration barrier is the same material as the metal; and
depositing a second ILD on the metal oxide and the electromigration barrier.
8. The method of claim 7 , further comprising:
depositing the first ILD over a substrate;
forming a first via and a first trench in the first ILD;
filling the first via and the first trench with an electrically conductive material; and
planarizing the electrically conductive material equivalent to a top surface of the first ILD, thus forming the interconnect within the first ILD, the interconnect have an exposed top portion and the first ILD having an exposed top portion.
9. The method of claim 8 , wherein the metal oxide and the electromigration barrier together define a protective layer over the first ILD and first interconnect, and further comprising:
etching and cleaning a second via and second trench in the second ILD, the protective layer acting as an etch-stop during etching and cleaning.
10. The method of claim 9 , further comprising:
forming a second interconnect within the second via and trench, the electromigration barrier to prevent the first interconnect from diffusing into any one of the first ILD and the second ILD.
11. The method of claim 10 , wherein etching the second via includes utilizing an etchant that will etch the second ILD without significantly etching the protective layer.
12. The method of claim 7 , wherein the metal does not completely react with the first ILD, thus producing a superfluous metal layer above the metal oxide, and further comprising etching back the superfluous metal layer to the top of the metal oxide.
13. The method of claim 7 , wherein depositing the metal includes depositing the metal to a thickness between approximately 10 Å to 100 Å.
14. The method of claim 7 , wherein the first interconnect comprises copper.
15. The method of claim 7 , wherein the metal comprises a material selected from the group consisting of cobalt, aluminum, tantalum, chromium, and titanium.
16. The method of claim 7 , wherein the first ILD comprises a material selected from the group consisting of SiO 2 , SiOF, and CDO.
17. A method comprising:
depositing a continuous metal layer on an exposed top portion of a first ILD and on an exposed top portion of an interconnect, wherein a portion of the metal layer forms a metal cap over the exposed top portion of the interconnect, and a portion of the metal layer consumes a part of the exposed top portion of the first ILD to from a metal oxide layer on the first ILD;
forming a second ILD on the metal oxide layer and over the metal cap; and
etching the second ILD until at least a portion of the metal cap is exposed.
18. The method of claim 17 , further comprising:
forming the first ILD;
forming a first via and trench in the first ILD;
filling the first via and the trench with an electrically conductive material; and
planarizing the electrically conductive material equivalent to a top surface of the first ILD, thus forming the interconnect within the first ILD, the interconnect having an exposed top portion and the first ILD having an exposed top portion.
19. The method of claim 17 , wherein etching the second ILD until at least a portion of the metal cap is exposed exposes at least a portion of the metal oxide layer.
20. The method of claim 17 , further comprising, prior to forming the second ILD on the metal oxide layer:
etching superfluous metal on the metal oxide layer to expose the metal oxide layer.