Lithographic method for creating damascene metallization layers

A method of performing a lithographic dual damascene etch for forming a dual damascene metallization structure on a layer stack disposed above a substrate, said layer stack comprising an underlying layer, said method comprising:

• depositing a first photoresist layer above said layer stack;
• forming an opening in a top surface of said first photoresist layer, said opening being positioned over said underlying layer of said layer stack, said opening extending down through said first photoresist layer to said underlying layer;
• depositing a second photoresist layer over said first photoresist layer and filling said opening;
• forming a trench in a top surface of said second photoresist layer and a via underlying said trench through said first photoresist layer, said via being coincident with said opening, said trench being in communication with said via;
• depositing a metal layer over said top surface of said second photoresist layer and filling said trench and said via;
• planarizing said metal layer down to about a level of said top surface of said second photoresist layer to define a top surface of a metal line, wherein said planarizing leaves a portion of said metal layer in said trench and in said via, thus forming said metal line in said trench and forming, in said via, an underlying metal plug disposed below said metal line;
• removing said first photoresist layer and said second photoresist layer, wherein said removing leaves gaps around said metal line and around said underlying metal plug disposed below said metal line;
• and
• depositing a dielectric material to fill said gaps around said metal line and around said underlying plug disposed below said metal line up to about said top surface of said metal line.

A method of performing a lithographic dual damascene etch on a layer stack disposed above a substrate, said layer stack comprising an underlying layer, said method comprising:

• depositing a photoresist layer having a top surface above said layer stack;
• forming a via in said photoresist layer by exposing an unmasked first portion of said photoresist layer to a first intensity of light, said via extending through said photoresist layer, said via being positioned over said underlying layer of said layer stack;
• forming a trench in said photoresist layer by exposing an unmasked second portion of said photoresist layer to a second intensity of light, said second intensity of light being less than said first intensity of light such that said trench has a depth that is less than a thickness of said photoresist layer, said trench being in communication with said via:
• depositing a metal layer over said top surface of said photoresist layer, said metal layer filling said trench and said metal layer filling said via to form an underlying metal plug in said via;
• planarizing said metal layer down to about a level of said top surface of said photoresist layer to define a top surface of a metal line, said metal line being that portion of said metal layer that remains in said trench;
• removing said photoresist layer, wherein said removing leaves gaps around said metal line and around said underlying metal plug disposed below said metal line, said gaps having been occupied by said photoresist layer before said removing;
• and
• depositing a dielectric material to fill said gaps around said metal line and said underlying plug disposed below said metal line up to a level of about said top surface of said metal line.