{111} Si Etched Planar Electrical Contacts for Power MEMS-relays

We present the design of electrical contacts used in a MEMS-relay for power applications. The device is bulk micromachined in single crystalline silicon and bonded to a glass substrate. Anisotropic etching, using aqueous potassium hydroxide solution, is used to fabricate the oblique, complementary, planar and parallel (111) contact surfaces having nanometer-scale surface roughness. The silicon contact surfaces are evaporated with a conductive film. A thermal oxide layer provides insulation between the silicon substrate and the metal contacts. The contacts are capable of make-break switching resistive and inductive loads. The MEMS device has large contact travel, in the order of 30 mum and low contact resistance, in the order of 120 mOmega. Testing has demonstrated current carrying capacity in the order of 3 A and hot-switching of inductive loads, in the order of 10 mH, without low cycle performance degradation over approximately 30 switching cycles.