Microfabrication Approaches on Magnetic Shape Memory Films

Abstract

Magnetic shape memory alloys are emerging multifunctional materials that enable applications like high‐stroke actuation, solid‐state refrigeration, and energy harvesting of waste heat. Thin films of these alloys promise integration in microsystems to exploit their multifunctional properties at the microscale. However, the microfabrication process of these Heusler alloys is difficult. Herein, different etching techniques are investigated for the microfabrication of epitaxial Ni‐Mn‐Ga films, the encountered challenges are explained, and ways to overcome them are demonstrated. The results show that wet chemical etching is suitable for large patterned structures, while reactive ion etching of Ni‐Mn‐Ga films is unsuitable due to redeposition. For patterning structures below 10 μm with clean and sharp edges, the best results are obtained by ion beam etching with adjusted sample‐stage tilt. Finally, a microfabrication process using Si microtechnology to fabricate partially freestanding structures is demonstrated. These findings give guidelines for the fabrication and integration of these smart materials in Si‐based microsystems.