Precise Manipulation of Amorphous Wires for Wafer-Level Fabrication of GMI Sensors

Amorphous wires, with high permeability, near-zero magnetostriction, and excellent sensitivity, have shown significant advantages in weak magnetic sensor applications. However, the mass production of amorphous wire based magnetic sensor presents challenges due to the filamentary morphology of the material, which makes it difficult to handle and not compatible to microfabrication processes. Here, we report a method for manipulating filament like material to achieve wafer-level fabrication of amorphous wire sensors. Amorphous wires are accurately aligned and placed into the microgrooves formed by polyimide and temporarily fixed by using a permanent magnet. Then copper micro-coil is fabricated by photolithography and electroplating, which is wrapped around the amorphous wire. The proposed method is compatible with standard Micro-Electro-Mechanical System (MEMS) process and does not need special equipment to manipulate amorphous wires. The average lateral offset of the amorphous wires from the groove centers in the randomly selected devices is less than 30 µm, demonstrating the feasibility of the proposed method. This work provides a wafer-level manufacturing process for amorphous wire based Giant Magneto-Impedance (GMI) sensors.