Performance of nonplanar silicon diaphragms under large deflections

The successful realization of many high-performance microactuators, including many microvalves and micropumps, depends critically on the development of diaphragms which are capable of large displacements and free from fatigue. Thin nonplanar silicon diaphragms are promising candidates for such applications since they can be batch fabricated using techniques and materials that are compatible with the other portions of these devices. This paper reports the detailed simulation, fabrication, and characterization of such diaphragms, which are corrugated-bossed structures that unfold, accordion-like, to produce high boss deflections. Boron-doped diaphragms 1 mm on a side, 3 μm in thickness, and containing five 10-μm-deep corrugations produce boss deflections of more than 30 μm at 760 mmHg, in close agreement with simulations. The maximum deflection measured at diaphragm fracture is 38 μm under a 1050 mmHg differential pressure. The effects on load-deflection performance due to changes in diaphragm internal stress (residual stress), corrugation profile, and diaphragm thickness are also explored