Optimal tungsten through wafer via and process of fabricating same

A method of forming a tungsten through wafer structure comprising:

• providing a structure including a substrate having at least one aperture at least partially formed through said substrate, said at least one aperture having an aspect ratio of at least 20:1 or greater and said at least one aperture includes a sidewall profile comprising:
• a first comparatively wide region at a surface of the substrate;
• a constricted region contiguous with the first comparatively wide region;
• a second comparatively wide region contiguous with the constricted region;
• and an inward tapered region contiguous with the second comparatively wide region.
• forming a Ti-containing liner on bare sidewalls of said substrate within said at least one aperture;
• forming a W seed layer on said Ti-containing liner, said W seed layer is enriched with silicon and has a grain size of about 5 nm or less;
• forming a W nucleation layer on said W seed layer, said W nucleation layer is enriched with silicon and has a grain size of about 20 nm or greater;
• and
• forming a W layer on said W nucleation seed layer.

A through wafer via structure comprising:

• a substrate having at least one via formed through said substrate, said at least one via has an aspect ratio of at least 20:1 or greater and said at least one via includes a sidewall profile comprising:
• a first comparatively wide region at a surface of the substrate;
• a constricted region contiguous with the first comparatively wide region;
• a second comparatively wide region contiguous with the constricted region;
• and an inward tapered region contiguous with the second comparatively wide region;
• a refractory metal-containing liner located on bare sidewalls of said substrate within said at least one via;
• a conductive metal seed layer located on said refractory metal-containing liner, said conductive metal seed layer is enriched with silicon and has a grain size of about 5 nm or less;
• a conductive metal nucleation layer on said conductive metal seed layer, said conductive metal nucleation layer is enriched with silicon and has a grain size of about 20 nm or greater;
• and
• a conductive metal layer on said conductive metal nucleation layer.

A through wafer via structure comprising:

• a substrate having at least one via formed through said substrate, said at least one via has an aspect ratio of at least 20:1 or greater and said at least one via includes a sidewall profile comprising:
• a first comparatively wide region at a surface of the substrate:
• a constricted region contiguous with the first comparatively wide region;
• a second comparatively wide region contiguous with the constricted region;
• and an inward tapered region contiguous with the second comparatively wide region;
• a Ti/TiN liner located on bare sidewalls of said substrate within said at least one via;
• a W seed layer located on said Ti/TiN liner, said W seed layer is enriched with silicon and has a grain size of about 5 nm or less;
• a W nucleation layer on said W seed layer, said W nucleation layer is enriched with silicon and has a grain size of about 20 nm or greater;
• and
• a tungsten layer on said W nucleation layer.