Olivier Le Neel

Micromachined passive magnetostatic relays for portable applications

A passive MEMS magnetostatic relay using only one electroplated magnetic layer was presented. The relay consists of an electroplated Ni80Fe20 plate supported by a pair of torsion bars from two sides. The relay is actuated by approaching an external magnet to the relay. The switching-on magnetic field is about 4.8 mT and the contact resistance is about 3 Ohms with gold contact. The lifetime testing shows more than 7.5 million hot switching cycles with 1–2 mA current. This passive magnetic relay could find applications in portable electronics, such as cellular phones, personal data assistant (PDA), pace makers, hearing aids, etc.

A Magnetostatic MEMS Switch Designed for Portable Applications

A passive magnetostatic microelectromechanical systems (MEMS) switch using only one electroplated soft magnetic layer of nickel-iron (Ni80Fe20) alloy was designed, fabricated, and characterized. The switch is composed of an electroplated Ni80Fe20 plate supported by a pair of torsion bars from two sides. The Ni80Fe20 plate is patterned into long and narrow strips to improve the sensitivity. The switch is actuated by bringing an external magnet closer to the switch. Therefore, no internal electrical power is consumed by the device for actuation. The magnetic field required to turn on the switch is 4.8 mT, and the initial contact resistance is 0.5 Ω with gold contacts. The switch has been tested to pass more than 34 million hot-switching cycles at 2-mA current at room temperature when packaged at the wafer level with SU-8 sealing. The die size is 2.1 × 1.94 × 1.1 mm3. The magnetic switch of this paper has the potential to replace the conventional reed switch in portable electronics such as laptops, cellular phones, personal data assistants, pacemakers, and hearing aids.

A MEMS micro-reed switch designed for portable applications

This paper presents the design, the fabrication and the characterization of a novel MEMS micro-reed switch, which consists of two Ni80Fe20 magnetic plates as micro-reeds. One is embedded in a silicon trench. The other is suspended above the substrate and supported by a pair of crab-leg flexures from the two sides. Both Ni80Fe20 plates are split into two long, narrow strips to improve the sensitivity. The switch is actuated by bringing an external magnet closer to the switch. The magnetic field required to turn on the switch can be as low as 1 mT. The contact force is estimated to ∼20 µN and the initial contact-resistance is < 10 Ω with gold contacts. The switch has been tested to pass more than 40 million hot switching cycles at 2 mA current at room temperature when packaged at wafer level with SU-8 sealing. The die size is 1.7×1.8×1.1 mm3. The proposed micro-reed switch can be used as the proximity sensor to sense the magnetic field. It also has the potential to replace the conventional reed switch in portable electronics, such as cellular phones, hearing aids and laptops, where conserving battery power and device size is critical.

Reliability analysis of CrSi Thin Film Resistors

CrSi Thin Film Resistor (TFR) is mainly used due to its high precision of less than 1% standard deviation and low thermal coefficient of resistance (TCR) with zero drift with temperature. Reliability characterization is studied on CrSi Thin Film Resistors (TFRs) to understand the reliability behaviour of CrSi Thin Film Resistors. Current sweep is performed on TFRs structures to determine current density threshold before catastrophic resistance degradation. Constant Current stress is performed at several currents to characterize the resistance change of TFRs with current. 2 models are proposed for lifetime stability prediction of TFRs.