Fabrication of Panel-Level Glass Substrates with Complete Design Freedom using LIDE

Abstract

In this work, we present examples of highly reproducible, accurate and extremely cost-effective wafer- and panel-level fabrication of glass interposers, free of any process-dependent design limitations where any distribution and density of Through-Glass Vias (TGV) with any cross-section geometries and aspect-ratios, is possible. Glass has recently garnered significant interest for its many applications in the semiconductor packaging industry, particularly as a core substrate material for interposer applications. Glass has a unique set of material properties with great relevance for this industry, such as very high electrical resistivity, low loss tangent and low dielectric constant. Glass also exhibits low warpage due to its relatively low Young‘s Modulus while still being compatible with Silicon in terms of CTE and, when processed using a technology that doesn’t induce the generation of any defects such as microcracks or thermally-induced stress, it is highly reliable during processing and operation. Laser Induced Deep Etching (LIDE®) technology is a 2.5D glass processing technology with complete design freedom purposedly developed for cost-effective, high-volume fabrication of defect-free glass components. Despite its many advantages as an interposer material in relation to Si, its application has been hindered by the lack of reliable, precise, and cost-effective processing technologies. LIDE® consists of a two-step process: i) a very fast maskless and direct-write laser process induces subtle and very localized modification in the glass substrate, requiring a single laser pulse to modify the whole glass thickness; and ii) a wet-etching process done in batch, where the whole glass substrate is subjected to the action of an etchant and where the removal of glass occurs at an accelerated rate in the laser-modified regions. This process flow allows LIDE to fabricate several thousands of TGV per second, completely free of any defects, with a sub-micron point-to-point accuracy and ± 5 µm accuracy (cumulative) across a 510 mm x 515 mm glass panel (Cp > 1.33), in any glass type, with aspect-ratios from 1:10 to 1:50 (diameter:depth).