MEMS & MOEMS reliability: wafer-level packaging and low-temperature processing issues

As MEMS and MOEMS are leaving the laboratories to become industrial products, production yield and reliability issues are playing a key role. MEMS failure mechanisms are quite diversified, due to the very nature of these components. If sticking, particle contamination, and ESD (electrostatic discharges) are often mentioned, other, more exotic effects do exist, which often are not well understood. MEMS packaging plays an essential role in protecting the microsystems from the external world: and devising a good package is often the key to a successful application. Wafer level (WL) packaging offers an interesting alternative for MEMS, and for this reason has often been proposed. However, ensuring a good WL sealing requires temperatures above 300-400 °K, which may prove detrimental to some systems. An MOEMS example is discussed in detail, together with the possible solutions.