By Topic

Fabrication of monolithic multilevel high-aspect-ratio ferromagnetic devices

Sign In

Cookies must be enabled to login.After enabling cookies , please use refresh or reload or ctrl+f5 on the browser for the login options.

Formats Non-Member Member
$31 $13
Learn how you can qualify for the best price for this item!
Become an IEEE Member or Subscribe to
IEEE Xplore for exclusive pricing!
close button

puzzle piece

IEEE membership options for an individual and IEEE Xplore subscriptions for an organization offer the most affordable access to essential journal articles, conference papers, standards, eBooks, and eLearning courses.

Learn more about:

IEEE membership

IEEE Xplore subscriptions

7 Author(s)
Tao Wang ; Int. Mezzo Technol. Inc., Baton Rouge, LA, USA ; McCandless, A.B. ; Lienau, R.M. ; Kelly, K.W.
more authors

This paper describes a process to fabricate monolithic multilevel high-aspect-ratio microstructures (HARMs) for ferromagnetic devices built on silicon wafers using aligned X-ray lithography in conjunction with electrodeposition. Two X-ray masks were fabricated, each consisting of gold (Au) absorber structures on a transparent polyimide membrane. One mask was used to print a polymethyl methacrylate (PMMA) resist layer. Then, a second PMMA layer was applied to the same wafer, and the second mask was used to pattern it. Transparent alignment windows in the second mask, combined with a piezoelectrically controlled X-ray aligner, allowed for high alignment accuracy between the two print patterns over large areas (>4 inch in diameter). Au circuits were electroplated into first PMMA layer from a sulfite-based electrolyte, and nickel-iron (NiFe) ferromagnetic HARMs were formed in second PMMA resist from a sulfate-based bath. The deposition resulted in well-defined NiFe structures with aspect-ratios up to 67:1 as well as smooth sidewalls and top surfaces. Chemical composition measurements with energy X-ray dispersive spectroscopy (EDS) and wavelength X-ray dispersive spectroscopy (WDS) showed that Fe content increased during the electrodeposition process. To electrically isolate the NiFe posts and Au circuits, both wet chemical etching and sputter etching were explored to remove the exposed seed layer, and the latter approach completely removed the seed layers without damaging the electroplated features.

Published in:

Microelectromechanical Systems, Journal of  (Volume:14 ,  Issue: 2 )