Interconnect level structures for confining stitch-induced via structures
A design layout is provided such that an underlying conductive line structure underlies a stitch region in an overlying conductive line structure. A stitch-induced via structure can be formed between the underlying conductive line structure and the overlying conductive line structure when a stitch region in a hard mask layer is etched multiple times. At least one of the underlying conductive line structure and the overlying conductive line structure is electrically isolated from other conductive line structures in a same design level so as to avoid unintentional electrical shorts.
1. A method of forming a metal interconnect structure, said method comprising:
forming an underlying conductive line structure embedded in a dielectric material layer, wherein a top surface of said underlying conductive line structure is coplanar with a top surface of said dielectric material layer;
forming another dielectric material layer over said dielectric material layer and said underlying conductive line structure; and
forming a patterned hard mask layer over said another dielectric material layer, said patterned hard mask layer comprising a first pattern region in which a portion of a top surface of said patterned hard mask layer is recessed relative to a topmost surface of said patterned hard mask layer by a first recess depth, a second pattern region in which another portion of said top surface of said patterned hard mask layer is recessed relative to said topmost surface of said patterned hard mask layer by a second recess depth, and a third pattern region adjoining said first pattern region and said second pattern region that is recessed relative to said topmost surface of said patterned hard mask layer by a third recess depth that is greater than said first recess depth and is greater than said second recess depth, wherein an entirety of an area of said third pattern region is within an area of said underlying conductive line structure in a see-through top-down view along a direction perpendicular to said topmost surface of said patterned hard mask layer.
2. The method of claim 1 , further comprising transferring a pattern in said patterned hard mask layer into said another dielectric material layer by an anisotropic etch, wherein line trenches are formed in said first and second pattern regions in said another dielectric material layer, and a via cavity is formed in said third pattern region.
3. The method of claim 2 , wherein said via cavity extends to a top surface of said underlying conductive line structure, and a bottommost surface of said line trenches is located above said top surface of said dielectric material layer.
4. The method of claim 3 , further comprising forming a contiguous conductive structure filling said via cavity and one of said line trenches.
5. The method of claim 4 , wherein said contiguous conductive structure comprises a conductive line structure and a via structure, wherein said via structure contacts said conductive line structure and contacts, or overlies without contacting, said underlying conductive line structure.
6. The method of claim 5 , wherein at least one of said conductive line structure and said underlying line structure does not contact any conductive structure other than said via structure.
7. The method of claim 6 , wherein said conductive line structure does not contact any conductive structure other than said via structure.
8. The method of claim 6 , wherein said underlying conductive line structure does not contact any conductive structure other than said via structure.
9. The method of claim 6 , wherein said conductive line structure and said underlying conductive line structure do not contact any conductive structure other than said via structure.
10. The method of claim 6 , further comprising forming yet another conductive line structure embedded in yet another dielectric material layer above said dielectric material layer, wherein said another dielectric material layer is formed above said yet another dielectric material layer.