Process yields for laser repair of aged, stiction-failed, MEMS devices

Stiction, the adhesion of micromachined components to each other or the substrate, decreases production yields and operational lifetimes for MEMS devices. A recent study demonstrated the feasibility of using a Nd:YAG, 1063 nm laser to repair 2 /spl mu/m thick polycrystalline silicon microcantilevers with lengths up to 1000 /spl mu/m which had adhered to the substrate. This investigation examines the influence of sample age at the time of laser irradiation on the repair of stiction-failed MEMS structures. The operating conditions for the 1064 nm, Nd:YAG laser included a fluence of 70 mJ/cm/sup 2/, a repetition rate of 20 Hz, a pulse duration of 20 ns, and an exposure time of 60 s. For samples irradiated on the same day of release, repair yields were 100% for beams up to 500 /spl mu/m in length. For 1000 /spl mu/m long beams, the 10- and 30-/spl mu/m-wide cantilevers had same-day repair yields of 56% and 71%, respectively. The experimental results show that increasing the amount of time the microstructures are adhered to the substrate before laser irradiation decreases the ability to repair stiction-failed devices with delays of longer than 1 month resulting in a decreased repair yield.