Progress in Fabrication and Test of Glass Interposer Substrates

Abstract

There is growing interest in applying glass as an interposer substrate for 2.5D/3D applications. Advantages of glass based solutions include significant opportunities for cost benefits 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, it is expected to have better electrical performance than silicon. Electrical characterization and electrical models demonstrate the advantages of the insulating properties of glass, and its positive impact on functional performance. Further advantages are anticipated in reliability performance, because of the ability to adjust thermal properties such as coefficient of thermal expansion (CTE) of glass. Progress in the ability to fabricate wafers and panels fully populated with through and blind holes has been reported. We describe the ability to leverage existing downstream processes such as via filling of both through and blind vias, as well as novel handling techniques to enable processing of thin glass. We also report progress in evaluating reliability through thermal cycle tests.