Sodium Metasilicate-Based Inorganic Composite for Heterogeneous Integration of Microsystems

Electronic microsystems are foundational to today's computational, sensing, communication, and information processing capabilities, therefore impacting industries, such as microelectronics, chemical, healthcare, manufacturing, and aerospace. As demand grows for more capable microsystems to help address today's rapidly growing needs, new packaging materials that are compatible with high-precision silicon microfabrication must be developed in order to enable the integration of individual and disparate components into systems with complex functionality. This article aims to demonstrate the potential for using a silicate-based inorganic composite to encapsulate and three-dimensionally integrate individual components into complex systems in a heterogeneous 3-D integration approach. Through the use of liquid alkali sodium silicate (water glass) and nanoparticle fillers, composites can be synthesized and cured at low temperatures into chemically, mechanically, and thermally (up to 400 °C) stable structures using high-throughput processing methods, such as spin and spray coating. This work demonstrates that this material can be processed into thick layers (tens to hundreds of micrometers), can fill high aspect ratio gaps (13:1), can withstand common microfabrication processes (wet process chemicals, photolithography, polishing, and thermal stability), and have its coefficient of thermal expansion tailored for compatibility with a variety of substrates. These demonstrations position this composite material for use in heterogeneous 3-D integration approaches that enable a wider range of complex microsystems.