Electrodeposited Magnetic Alloys for Surface Micromachining

Abstract

Electrode osited magnetic materials are of great interest in surface micromachining, as they can be used for transformation of L e s in both actuators and sensors. Magnetic alloys of the ferrous metal family with different characteristics can readily be electrodeposited. An advanced lithographic process was performed in order to generate resist molds for electrodeposition. By means of standard ultraviolet aligners and immersion development, photoresist layers up to 80 pm were patterned in a single shot. Repeated exposure and development were successfully used for structuring thicker resist layers. Hi h aspect ratios and steep edges were achieved with a sufficiently high resolution. The resulting resist patterns were molfed via electroplating. For microsystem applications, magnetic alloys such as NiFe and NiCo are of special interest. The deposited material was characterized in relation to its mechanical and magnetical properties. Some examples of microsystem components using magnetic properties are given. The active part of a magnetically driven microvalve containing a membrane with integrated force amplifier from NiFe alloy as well as a microturbine with NiCo rotator were fabricated and tested.

Electrodeposition of Iron and Iron Alloys

“…When employed for discrete elements, they are frequently deposited as a full film and the magnetic pattern is then defined with an etch resist [94]. One paper mentioned a micromachining technique for producing a microcantilever, three-dimensional microcoil with an integrated magnetic core, a magnetically driven microvalve, and a microturbine using an electroforming technique of iron-nickel alloy deposits [95]. The bath compositions and operating conditions for the production of magnetic ironÀ nickel alloy plating were surveyed in literature [96] and are presented in Table 11.2.…”

Electrodeposition Science and Technology in the Last Quarter of the Twentieth Century

“…More recently, high aspect ratio through mask electroplating has been applied to the fabrication of Xray masks, sensors and tiny turbines among other. Overviews of the LIGA process and similar processes are available, 31,32 as well as a discussion of early experimental work on X-Ray lithography performed in the U.S. 6 At the time of this writing the indistrial impact of the LIGA process is still limited, but as the technology matures one may expect that many uses will rapidly develop. Resists have recently been developed for LIGA applications, which permit the irradiation with much cheaper UV instead of synchrotron radiation.…”

“…They allow fabrication of high aspect ratio structures by several subsequent irradiation steps. 32 At present, predominantly nickel is used in the LIGA process, but Ni-Fe alloys and copper have also been plated. In the US a complete thin film magnetic micro motor was recently built by through mask electroplating with the aim to demonstrate the outstanding capabilities of this technology.…”

The iron-nickel-molybdenum (Fe-Ni-Mo) electrodeposited alloy on n-type silicon

“…Electrodeposition of alloys, binary and ternary ones, has received attention in recent years due to their magnetic properties [7][8][9][10][11][12]. Thus, different alloys can be electrodeposited to attain useful soft magnetic films and prepare materials for highly functional magnetic recording [13][14][15][16][17][18].…”