Bi Ran, Chen Ruiying, Wu Shilin, Ma Haoyu, Zhang Huiquan, Liu Xinting, He Jinliang, Hu Jun
Department of Electrical Engineering, Tsinghua University, Beijing 100084, China.
Sensors (Basel). 2025 Mar 11;25(6):1730. doi: 10.3390/s25061730.
Accurate measurement of magnetic fields holds immense significance across various disciplines, such as IC circuit measurement, geological exploration, and aerospace. The sensitivity and noise parameters of magnetic field sensors play a vital role in detecting minute fluctuations in magnetic fields. However, the current detection capability of tunneling magnetoresistance (TMR) is insufficient to meet the requirements for weak magnetic field measurement. This study investigates the impact of structural and fabrication parameters on the performance of TMR sensors. We fabricated series-connected TMR sensors with varying long-axis lengths of the elliptical cross-section and adjusted their performance by modifying annealing magnetic fields and magnetic field bias along the easy axis. The results demonstrate that TMR sensitivity decreases with increasing long-axis length, increases initially and then decreases with an annealing magnetic field, and decreases with a higher bias magnetic field along the easy axis. The voltage noise level of TMR sensors decreases as the long-axis length increases. Notably, the detection capability of TMR sensors exhibits a non-monotonic dependence on long-axis length. Moreover, we optimized the hysteresis of TMR sensors by applying a magnetic field bias along the easy axis. When the bias along the easy axis reached 16 Oe or -40 Oe, the hysteresis level was reduced to below 0.5 Oe. After encapsulating the TMR devices into a full Wheatstone bridge structure, we achieved a detection capability of 17 nT/Hz@1Hz. This study highlights that the detection capability of TMR devices is jointly influenced by fabrication parameters. By optimizing parameter configuration, this work provides theoretical guidance for further enhancing the performance of TMR devices in magnetic field measurements.
精确测量磁场在诸如集成电路测量、地质勘探和航空航天等各个学科领域都具有极其重要的意义。磁场传感器的灵敏度和噪声参数在检测磁场的微小波动方面起着至关重要的作用。然而，隧穿磁阻（TMR）目前的检测能力不足以满足弱磁场测量的要求。本研究调查了结构和制造参数对TMR传感器性能的影响。我们制造了具有不同椭圆横截面长轴长度的串联连接TMR传感器，并通过改变退火磁场和沿易轴的磁场偏置来调整其性能。结果表明，TMR灵敏度随着长轴长度的增加而降低，随着退火磁场先增加后降低，并且随着沿易轴的更高偏置磁场而降低。TMR传感器的电压噪声水平随着长轴长度的增加而降低。值得注意的是，TMR传感器的检测能力对长轴长度呈现非单调依赖性。此外，我们通过沿易轴施加磁场偏置优化了TMR传感器的磁滞。当沿易轴的偏置达到16 Oe或 -40 Oe时，磁滞水平降低到0.5 Oe以下。将TMR器件封装成全惠斯通电桥结构后，我们实现了17 nT/Hz@1Hz的检测能力。本研究强调，TMR器件的检测能力受到制造参数的共同影响。通过优化参数配置，这项工作为进一步提高TMR器件在磁场测量中的性能提供了理论指导。
