Fabrication of 3D-IC Interposers

Abstract

Interposer fabrication has gained a lot of attention in the area of three-dimensional integrated circuit (3D-IC) integration. Glass has many properties that make it well suited for interposer substrates, such as adjustable coefficient of thermal expansion, advantaged electrical properties and unique forming processes. Furthermore, glass based solutions can also provide significant cost advantages in substrate material, via formation, and subsequent processing. In this paper, we will cover how fusion formed glass provides cost-effective solutions for the manufacturing of interposer substrates. Leveraging the ability to create through-glass-via (TGV) substrates in as-formed 100 μm thick precision glass, with a pristine surface, can avoid the need for back grinding and polishing operations. This has the potential to eliminate several manufacturing steps for polishing and thinning, while providing associated cost savings. Significant progress has been made in demonstration of TGV technology. Fully populated wafers with 100,000s of through or blind holes (≥ 25 μm diameter) are fabricated today, and 10–20 μm diameters are in development. We will report on important quality parameters measured on TGV wafers and positive implications with respect to product quality and strength. The ability to leverage industry metallization techniques and performance characteristics will also be reported. Finally, we will discuss opportunities to leverage cost-effective glass interposer solutions.