Nanostructuring magnetic thin films using interference lithography

Abstract

Proliferation of data caused by rapid increases in computer power and the rise of the internet have caused an acute need for advanced data storage technology. Patterned magnetic media and magneto-resistive random-access memory (MRAM) can potentially fulfill this need. The technique of interference lithography is examined in the context of patterning ~100 nm size features. An interferometer is designed and built which will allow exposure of gratings and grids with a minimum spatial period of ~ 170 nm. Etching methods, especially ion-beam etching, or ion milling, is investigated as the optimal choice for patterning sub-100 nm features in thin magnetic films and multi-layer thin film stacks. The advantages and disadvantages of a variety of resist stacks and etch masks are presented. An optimal process for linewidth control and preservation of magnetic properties is found to include a thin phase-shifting resist stack and a tungsten hardmask.