Wafer level packaging of micro-machined gas sensors

In the following paper, we present a novel approach to combine wafer level packaging (WLP) with micromachined hotplate gas-sensing elements [1]. This concept allows liquid tight sealing of gas sensor devices, protecting 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, sealing the wafer stack.