Nano Porous Gold as a Capping Layer for Thin Film Encapsulation

This paper reports Nano Porous Gold (NPG) thin film as a cap layer for encapsulating MicroElectroMechanical System (MEMS) devices. The uniformly distributed zig-zag nanopores in the NPG cap structure reduce the release time as well as protect the MEMS devices from the mass loading during the sealing process, thus solving the two main problems in thin film encapsulation (TFE) process. Using 0.5-μm thick NPG cap in combination with silicon dioxide as sacrificial layer, we could release 400 μm×400 μm×3 μm cavities in vapor-HF within 10 min, which is 16 times faster than the TFE fabricated using a conventional sidewall located release channel with nonporous films. No mass loading and damage were noticed while sealing the cap using silicon dioxide.