Electrochemical Deposition of CoP and CoNiP as Hard Magnetic Scales in a Position Measurement System

Abstract

The fabrication and design of hard magnetic materials for micro-electro-mechanical system applications by electrochemical deposition has to consider not only the intrinsic material properties but also the shape anisotropy of the micro-devices. Within the scope of the present work, an as-plated process for hard magnetic Co-based materials was developed, with the products intended to be used as magnetic scales in a positioning system with a resolution within the nanometer range. First, the process–material correlations are investigated in a laboratory-scale process. The CoP and CoNiP show a maximum coercivity of HC = 28 and 45 kA/m, respectively, as well as maximum remanence polarizations of JR = 0.65 and 0.40 T, respectively. The CoP process is transferred to a specially developed 20 L plating cell with paddle convection capabilities and a passive bezel to deposit 50 µm wide scales with different thicknesses of up to 55 µm in an integrated process. The in-plane magnetization of the scale bars shows higher remanence polarization than for the out-of-plane direction. Magnetic field-assisted electrochemical deposition promotes the vertical magnetization component resulting in a remanence polarization of 205 mT (out-of-plane) for a scale thickness of 25 µm.

PowderMEMS—A Generic Microfabrication Technology for Integrated Three-Dimensional Functional Microstructures

“…As already mentioned, wafers with embedded PowderMEMS microstructures are BEOL-compatible, i.e., wafer processing can be implemented on common cleanroom equipment without major process changes at process temperatures up to 425 °C. For example, to finalize the piezoelectric vibrational energy harvester shown in Figure 2 after micromagnet integration, post-processing includes various thin-film depositions as well as wet and dry etching of metals, dielectrics, and silicon [ 10 ].…”

“…With photolithography, patterning of thick layers in the range of several hundred µm can be achieved; however, the material choice is limited to (photosensitive) polymers [ 8 ]. Other techniques with intrinsic patterning—such as multilayer screen or inkjet printing [ 9 ], or electroplating [ 10 , 11 ]—have similar restrictions.…”

“…As the corresponding cross-sections in Figure 3 illustrate, some excess particles remain on the substrate surface on the front side of the substrate, as well as on its backside, After surface conditioning, the substrates can be further processed in the cleanroom if required. As already mentioned, wafers with embedded PowderMEMS microstructures are BEOL-compatible, i.e., wafer processing can be implemented on common cleanroom equipment without major process changes at process temperatures up to 425 • C. For example, to finalize the piezoelectric vibrational energy harvester shown in Figure 2 after micromagnet integration, post-processing includes various thin-film depositions as well as wet and dry etching of metals, dielectrics, and silicon [10].…”

Mechanism of bubbles formation and anomalous phase separation in the CoNiP system

“…Triple alloys are widely used in industry due to the possibility of wide variations in their properties by changing the composition. Numerous studies have been conducted on the development of triple CoNiP coatings due to their potential application in high-density recording and microelectromechanical systems 23 – 26 . In the research area of electrochemically deposited CoNiP alloys, it is of interest to clarify the mechanism of coating formation, the action of additives, and changes in the concentrations of electrolyte components.…”