Fabrication of TGVs using ECDD process for MEMS packaging applications

The combination of Micro-Electromechanical Systems (MEMS) with microelectronic circuits has revolutionized numerous high-tech industrial arenas, empowering the progress of production of miniature sensing, actuating devices with widespread applications in the fields of aerospace, healthcare, communication, and biotechnology [ 1 , 2 ]. The packaging process is an essential aspect of the efficient working of MEMS devices. The packaging of MEMS devices includes encapsulation of the micro-scale, fragile, moving structures in shielding enclosures for the protection from the external environment while establishing the electrical connections to exterior circuitry [ 3–5 ]. The through-substrate vias are crucial components in MEMS three-dimensional (3D) packaging, where the vertically oriented interconnect through the substrate serves the purpose of transmitting the input/output signals and power delivery between MEMS devices and external electronics (see Figure 6.1(a) ). The through-silicon vias (TSVs) are mainly employed in 3D MEMS packaging [ 8 ]. However, the issues associated with TSVs limit their broader usage. The major issues include the failure of the device due to electric crosstalk under high-frequency operation, as well as the need for an electric insulation layer. TGVs are a capable alternative to TSVs due to the promising properties of glass material, namely, optical transparency, good thermal expansion coefficient, electrical insulation, corrosion resistance, and low dielectric constant [ 9 ]. Insertion losses and Q factors for the TGV- and TSV-based microsystems have been measured and studied in the literature [ 10 ]. In the case of TSVs, a higher amount of insertion losses (reflection coefficients) is identified at higher frequency operations, as can be seen in Figure 6.1(b) . On the other hand, in the case of TGVs, the insertion losses are less at higher frequency operation, which led to improved performance with lesser chances of failure of the devices [ 7 ].