Microelectronic assemblies with pillar-first conductive via formation in glass cores

A microelectronic assembly, comprising:

• a layer of glass comprising a substantially rectangular prism volume;
• and
• a via extending from a first side of the substantially rectangular prism volume to a second side of the substantially rectangular prism volume, the via comprising an insulator material on a sidewall of the via, and further comprising a conductive material,
• wherein the insulator material is between the sidewall of the via and the conductive material, and
• wherein, in a cross-sectional side view in a plane perpendicular to the first side of the substantially rectangular prism volume, the conductive material tapers from the first side towards the second side, and the sidewall of the via is substantially perpendicular to the first side.

A method of fabricating a microelectronic assembly, the method comprising:

• forming a metal pillar on a support;
• providing a glass volume with an opening extending from a first face of the glass volume towards a second face of the glass volume;
• and
• inserting the metal pillar into the opening,
• wherein the opening includes a filler material at least partially surrounding the metal pillar in the opening.