Wafer Level Packaging of Micromachined Gas Sensors

This paper presents a novel approach to combine wafer level packaging (WLP) with micromachined hotplate gas-sensing elements. This concept allows liquid-tight sealing of gas sensor devices, which protects them during production (e.g., wafer dicing) and later in the application while still allowing the target gases to reach the sensing layer. The basis of the WLP is the combination of a structured Pyrex wafer with a micromachined substrate wafer. Thereafter, thick-film SnO ₂ layers are deposited and stabilized before a diffusion membrane is attached, which seals the wafer stack