A MEMS-Relay for Power Applications

Contact travel and heat dissipation are important requirements of electrical power switching devices such as MEMS-relays and MEMS-switches. Whereas low-power MEMS-based RF switches have been vigorously studied, few studies have been reported on high-power MEMS-relays. This paper presents a MEMS-relay for power applications. The device is capable of make-break switching; has large contact travel, on the order of 10's of µm; and has low contact resistance, on the order of 120 mOmega. Testing has demonstrated current carrying capacity on the order of several amperes and hot-switching of inductive loads, on the order of 10mH, without performance degradation.

The MEMS-relay is bulk micromachined in (100) silicon and bonded to a glass substrate. Anisotropic etching is used to fabricate the oblique and parallel (111) contact surfaces, having nanometer-scale surface roughness. An offset between the wafer-top and the wafer-bottom KOH masks produces the contact geometry shown. The silicon contact metal surfaces are created by evaporation and electroplating with a conductive film. A thermal oxide layer provides insulation between the actuators and the contacts. Deep reactive ion-etching (DRIE) is used to pattern a parallelogram-flexure compliant mechanism and a pair of rolling-point “zipper” electrostatic actuators. Nested masks are used to pattern both wafer-through etches.