Electrodeposition of hard magnetic CoPtP material and integration into magnetic MEMS

Abstract

This paper reports on the electrodeposition at room temperature and the characterization of hard magnetic CoPtP material. An acidic bath has been set up to be compatible with the use of photoresist for micro technologies processes. X-ray diffraction (XRD) diagrams show that CoPtP alloy crystallizes in the hexagonal system. The film growth is generally columnar with a pronounced ⟨0 0 2⟩ texture associated with preferential out-of-plane magnetization. Using particular electrodeposition conditions, in-plane magnetization can be recovered and coercivities as high as 2800 Oe are reached for patterned layers. So a room temperature electroplating process able to produce patterned micromagnets usable in magnetic applications has been set up. Examples of the integration of CoPtP micromagnets are described through the fabrication of three devices: a multilayered giant magneto-resistive sensor biased by five electroplated magnets, a vertical magnetic bistable microactuator and a horizontal magnetic bistable microswitch. The main challenge for the last two devices was to demonstrate the actuation of a moving micromagnet without any mechanical guiding during commutation. The demonstrated bistability provided by the use of micromagnets emphasizes the interest in these devices for many applications.

Microelectromechanical Systems

“…For example, permament magnet arrays of CoNiMnP have been electroplated [108] and used for vertical microactaution. In other implementations, CoPtP has been used for biasing of magnetoresistive sensors, vertical microactuators, and horizontal microswitches [109]. …”

Toward targeted retinal drug delivery with wireless magnetic microrobots

“…The system uses a 40 mm × 40 mm × 20 mm NdFeB magnet with the north and south poles on the largest faces, and a field value of 0.41 T measured in the center of the north pole face. In addition to the measured data, we simulated a microrobot made of permanent-magnetic material with a remanence magnetization of 4 × 10 5 A/m, which is a value that can currently be achieved using microfabrication techniques [21].…”

Micromachined Energy-Harvester Stack With Enhanced Electromagnetic Induction Through Vertical Integration of Magnets

“…have been developed for integrating permanent magnets with micromachined silicon structure, but the quality of such processed magnets has not been good [18]- [20]. For example, 10 μm thick Nd-Fe-B/Ta was sputter-deposited as micromagnets in a microfabricated electromagnetic energy harvester [21], which showed a relatively low power density of 1.2 nW/cm 3 .…”