Glass in wafer- and panel-level packaging: Changes, challenges, hurdles and barriers

In principle there exists a large variety of compositions for oxide glasses. Also a variety of hot forming processes is present for glasses, which allows near end shape processing. In particular thin glasses, directly drawn from a melt, are of interest as a substrate material for packaging of electronics with heterogeneous integration. One main reason seems to be economic manufacturing methods but also mechanic properties like stiffness, correlating to relatively large Youngs moduli, which is the basis for accurate manufacturing with single digit micrometer accuracy. The thermal expansion of glasses can in principle be tailored in a range from 2 ppm/K-12 ppm/K depending on the needs of particular applications. Structuring of glasses either with vias for IC packaging or in combination with cut-outs for fan-out embedding of active and passive components in the substrate layer are possible. Structuring methods which allow millions of vias and thousands of cut-outs in panel level formats are discussed. An efficient and economic metallization process with good adhesion and good electrical performance is a further step for commercializing structured glasses into packaging applications. High frequency applications like inclusion of antenna in package or high-speed digital applications with Gbit/s data rates give further demands on the properties of such structured glasses. In the current work we review the status of glasses for wafer- and panel level packaging. Glasses are available in a large variety; focusing and industrial standardization will speed up industrial readiness of glasses for electronic packaging.