Glass Interposer Substrates: Fabrication, Characterization and Modeling

Abstract

There is growing interest in applying glass as a substrate for 2.5D/3D applications. Glass has many material properties that make it well suited for interposer substrates. Glass based solutions provide significant opportunities for cost reduction by leveraging economies of scale as well as forming substrates at design thickness. A lot of work is being done to validate the value of glass as an interposer substrate. One important area is the electrical performance of glass relative to silicon. Because glass is an insulator, an interposer made with glass should have better electrical performance than one made with silicon. Electrical characterization and electrical models confirm this advantage, and its positive impact on functional performance. Further advantages are anticipated in reliability, driven by the ability to tailor thermal properties such as coefficient of thermal expansion (CTE) of glass. Modeling results will be presented that show how the proper choice of CTE can significantly lower stack warpage. Additionally, significant progress has been made in the demonstration of glass interposer fabrication. Fully patterned wafers and panels with through holes and blind holes are being fabricated today. It is equally important to be able to demonstrate the ability to leverage existing downstream processes for metallization of these substrates. The ability to apply existing downstream processes to make functional glass interposers using both through and blind via technology will be presented.