High Volume Manufacturing of Through Glass via (TGV) Wet Etch for Glass Core Substrates for High Density 3D Advanced Packaging Applications

Advanced semiconductor packaging use glass core for strength as well as coefficient of Thermal expansion (CTE) to accommodate high speed devices. Based on Yole report in 2020, it projected a 2.5~3 fold increase from 2019 to 2025 for the glass substrates. Glass interposer could become a leading processing technology in advanced Fan Out Panel Level Packaging (FOPLP). Cost effectiveness and high-frequency characteristics of glass laid strong pathways for Advanced Packaging Roadmaps. For glass interposer technology, Through Glass Vias (TGV) will be an essential technique like Through Silicon Vias (TSV) in silicon interposer. Hence, a closer look into the development of high volume Through Glass Via (TGV) processing is discussed in this paper. Chemistry options by glass types are discussed for two of high volume glass. A TGV system has been developed to enable the TGV processing of laser modified glasses with various types. The equipment developed with laminar flow from bottom of the chemical tank with a 0.5 ° C temperature variation for precision etching and uniformity of via holes. Etching characterization over bath life as well as with various Design of Experiments (DOE) was performed to address the HVM challenges. Cross sectional and chemical analyses were done to validate the studies and the data were used to enhance the HVM mode of the glass etching. Laser modified glass coupons with variable hole sizes with different pitch were etched and microscopic measurements with higher magnification were taken to verify the hole dimensions. Glass etch rate showed a linear variation with time and temperature. Etch rate of 20 μm/hour at 110°C was improved to 85 μm/hour at 130°C. Blanket panel etch characterization with temperature & time as well as other through-glass via hole characterizations will be presented.