Abstract
Based on the MEMS fabrication processes and the circuit design of Wheatstone bridge, GMR magnetic-driven field sensors are successfully proposed. Sensors rely on the GMR effect have high sensitivity and adjustable linearly sensing region, and these lead the GMR sensing elements to be more applicable for delicate field measurement than what base on AMR effect. Since various factors as material and the dimensions of film affect the sensor electrical and magnetic characteristics, means the sensitivity, greatly, it is therefore of essence to find out the best operating parameters in accords with the user demands. In this thesis, the optimization of the output signal of GMR sensing elements for customizations is implemented through changing the multi-layer structure and the film aspect ratio of spin valves. In addition, by using the dual-Wheatstone bridge design, it is not only the output voltage can be significantly enlarged due to a larger filed-dependent resistance variation can be induced, but also diminishes the noise. The phase difference in a right angle can also be obtained by adjusting the gap distance between magnetic bars. The functional test of sensors is conducted on a linear motion platform. Integrate spin valve design into the sensors, not only can the 100 mV output be achieved at 5 V input, but also significantly increases two-phase signal output by double up the gap distance between magnetic bars in dual-Wheatstone bridge circuit design.