Sintered solder for fine pitch first-level interconnect (fli) applications

A method of forming a foundation layer, the method comprising:

• forming a plurality of via openings in a photoresist layer;
• forming a fiducial on the photoresist layer;
• depositing a solder paste in the plurality of via openings in the photoresist layer;
• and
• sintering the solder paste to form a plurality of conductive vias in the via openings in the photoresist layer.

A method of forming an interconnect structure, the method comprising:

• forming a plurality of foundation layers, the forming comprising:
• forming a plurality of via openings in a photoresist layer;
• forming a fiducial on the photoresist layer;
• depositing a solder paste in the plurality of via openings in the photoresist layer;
• and
• sintering the solder paste to form a plurality of conductive vias in the via openings in the photoresist layer;
• and
• stacking the plurality of foundation layers by coupling the plurality of conductive vias of the plurality of foundation layers, wherein the fiducial on the photoresist layer of each foundation layer is used to align the plurality of foundation layers for the stacking.