Method of forming an interconnect structure with enhanced corner connection
Interconnect structures and methods for forming the interconnect structures generally include forming a bulk metal encapsulated in first and second interlayer dielectrics, a liner layer about a lower surface of the bulk metal and a metal cap layer about an upper surface of the bulk metal. The liner layer is in the first interlayer dielectric and the metal cap layer is in the second interlayer dielectric, wherein liner layer and the metal cap layer are different metals.
1. A method of forming an interconnect structure, the method comprising:
forming a metal line or a metal plug in a first interlayer dielectric, wherein the metal line or metal plug comprises a conformal liner layer and a bulk metal therein, wherein the interlayer dielectric, the metal line or metal plug have coplanar top surfaces;
recessing the first interlayer dielectric to expose a portion of the liner layer;
selectively removing the exposed portion of the liner layer such that a remaining portion of the liner layer is disposed about a lower surface of the bulk metal;
selectively depositing a metal cap on exposed surfaces of the bulk metal to form the metal cap about an upper surface of the bulk metal, wherein the liner layer and the metal cap collectively encapsulate the bulk metal, and wherein the liner layer and the metal cap layer are different metals;
conformally depositing an etch stop layer, wherein a portion of the etch stop layer abuts the metal cap and is on the first interlayer dielectric;
depositing a second interlayer dielectric on the etch stop layer;
forming a self-aligned via to the etch stop layer fully aligned or partially aligned to a corner portion of the metal line or the metal plug exposing a portion of the etch stop layer;
removing the exposed portion of the etch stop layer to expose the metal cap at the corner portion; and
metallizing the self-aligned via.
2. The method of claim 1 , wherein forming the self-aligned via comprises a directional etch process.
3. The method of claim 1 , wherein the metal line or the metal plug has a tapered profile such that a bottom portion has a smaller width than a top portion.
4. The method of claim 1 , wherein the etch stop layer comprises a dielectric material.
5. The method of claim 4 , wherein the liner layer comprises tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, ruthenium nitride, ruthenium tantalum, ruthenium tantalum nitride, or tungsten nitride and the metal cap comprises ruthenium, cobalt, copper or alloys thereof.