Precision Hand Assembly of MEMS Subsystems Using DRIE-Patterned Deflection Spring Structures: An Example of an Out-of-Plane Substrate Assembly

This paper describes a packaging concept for precise hand-assembly of microelectromechanical systems (MEMS) subsystems that uses mesoscaled deep-reactive ion etching (DRIE) patterned passive deflection spring clusters. The method is intended for applications that require decoupling of subsystem process flows to simplify device fabrication in order to attain macro three-dimensionality, or for cases where the device requires spatially referenced macro- and microfeatures with good precision. The design considerations for the deflection springs are presented, and a simple reduced-order model of the expected elastic behavior is proposed. The assembly concept is demonstrated with an electrospray array test structure. This test structure assembles perpendicularly two wafer substrates. The performance of the test structure is benchmarked using finite-element simulations and by measurements of the misalignment introduced by the assembly. A floor for the ultimate alignment accuracy of the assembly concept is proposed.