Through-package-via formation and metallization of glass interposers

Abstract

Interposer technology has evolved from ceramic to organic materials and most recently to silicon. Organic substrates exhibit poor dimensional stability, thus requiring large capture pads which make them unsuitable for very high I/Os with fine pitch interconnections. Therefore, there has been a trend to develop silicon interposers. Silicon interposers however, suffer in two ways; 1) they are expensive to process due to the need for electrical insulation around via walls, and 2) they are limited in size by the silicon wafer from which they originate. In this paper, glass is proposed as a superior alternative interposer technology to address the limitations of both silicon and organic interposers. The inherent electrical properties of glass, together with large area panel size availability, make it superior compared to organic and silicon-based interposers. Glass however, is not without its challenges. It suffers in two ways: 1) formation of vias at low cost, and 2) its lower thermal conductivity compared to silicon. This research explores glass as an interposer material, and addresses the above key challenges in through package via (TPV) formation and subsequent low cost and large area metallization to achieve very high I/Os at fine pitch.