CMUT on Glass Substrate for Next-Generation Medical Imaging and Beyond

CMUT technology was invented and has been widely researched on silicon substrates. In recent years, fabrication of CMUT on glass substrates has raised significant interests because a number of advantages it can offer. First, parasitic capacitance could be easily reduced since glass is an insulating material. Second, insulation steps required in the silicon-based CMUT fabrication process could be avoided, leading to a reduced fabrication complexity. Third, anodic bonding can be used when the substrate is borosilicate glass, which is a low-temperature bonding technique and has a high tolerance to bonding surface area and roughness in addition to the advantages of silicon wafer bonding. Moreover, glass transparency can enable novel applications beyond pulse-echo ultrasound medical imaging and enlarge the potential markets of CMUTs.