Integrated With Si-based Amr Effect Switch Chip Preparation

Due to the high Curie temperature and large anisotropic magnetoresistive(AMR) effect,NiFe is widely used in magnetic field sensors and its derivative current sensors. Integration of the sensitive material with signal processing circuit on a chip produces switch chips. These chips have a wide range of applications in modern electronic devices such as cell phones. This dissertation will focus on the design and preparation of materials and ultimately produce the chips.In this paper, RF and DC magnetron sputtering were used to prepare NiFe films on Si substrates coated which about 200nm thick Si3N4. The influence of the Ta buffer layer on the properties of NiFe films were carefully investigated, including the sputtering power and the thickness of Ta buffer layer. The results show that when the power is 120W, the NiFe films have the maximum MR value about 1.45%. XRD patterns showed that when the thickness of Ta is 5 nm there are the strongest of NiFe (111) diffraction peaks. AFM results showed that under such condition the NiFe film has the largest grains.In order to prepare the sensitive units on 6 inch Si substrate, the uniformity of the film is crucial to improve production yields. We proposed off-centric sputtering geometry in order to improve the homogeneity of the film thickness. The optimized off-center distance was 3.5 cm.The photolithography and lift-off techniques were used to prepare the patterned unit where a Wheatstone bridge was formed. The thickness of NiFe film on the performance of the bridge was studied. We found that as the thickness of the NiFe increased the MR values also increased. When the thickness of the NiFe film was about 100 nm, the largest MR value was obtained. However, the sensitivity of the unit to the magnetic field decreased with the increasing thickness.The photolithography and lift-off techniques were transferred to produce the units on a 6-inch wafer where the signal processing circuit was fabricated. Sample magnetic switch chips were obtained after package. The chips meet the request of our initial designs.