EAGER: Ultra-Sensitive Resonant MEMS Magnetometers with Internal Thermal-Piezoresistive Amplification

目的：探索硅谐振微结构内部热压阻品质因子和位移放大效应在实现超高灵敏度低噪声磁强计中的潜力。将设计和制造由硅基谐振微结构和集成绝缘金属走线组成的MEMS磁强计。本文将对所制备器件的性能进行表征，并研究策略性设计的硅结构所提供的内部放大对磁强计灵敏度和噪声水平的影响。知识优势：提出的MEMS磁强计的工作原理是基于收集和内部放大洛伦兹力（施加在磁场中载流导体上的力）。利用内部热压阻放大效应，证明了极高的有效质量因子(Q)比谐振器的固有机械Q大~1000倍。预计如此高的Q值可以放大由洛伦兹力引起的振动幅度，而不会增加电子噪声水平，从而使所提出的传感器具有优越的性能。初步分析表明，在pT/Hz1/2范围内的噪声水平应该是可以达到的，这与一些最先进的技术提供的水平相当。提出的努力结合了硅基MEMS磁强计的简单性，小尺寸和易于/低成本制造，具有前所未有的高灵敏度。潜在的结果将是小尺寸，低成本和易于使用的超灵敏磁力计，绕过其他现有技术的缺点，例如需要低温冷却，集成外来材料，大尺寸和高功耗。更广泛的影响：高灵敏度、小尺寸和易于使用的磁力计可以在各个领域产生变革性影响，包括生物和生物医学工程、地质和矿产/石油勘探，以及监视和防御（通过墙壁/地下成像和目标跟踪）。例如，需要低温冷却的鱿鱼阵列目前被用于通过监测大脑神经元放电产生的小磁场（几十到几千个费特斯拉）来绘制大脑活动。所提出的微型设备提供的小尺寸和便利性可以导致大脑测绘的重大进展，并使先进的便携式大脑监测设备的开发成为可能。在教育方面，将培养一名博士后研究员、一名博士研究生和最多两名本科生，并直接参与研究活动。研究活动的结果将作为有趣的课程材料，丰富PIs正在进行的MEMS和微系统课程。PI在这个项目中获得的经验将为他在一个新的研究领域提供非常有价值的见解，这些见解将转移给现在和未来的学生。

Objective: The objective of this project is to explore the potentials of the internal thermal piezoresistive quality factor and displacement amplification effect in silicon resonant microstructures for realization of ultra-high sensitivity and low noise magnetometers. MEMS magnetometers consisting of silicon based resonant microstructures with integrated insulated metallic traces will be designed and fabricated. The performance of the fabricated devices will be characterized and the effect of internal amplification offered by the strategically designed silicon structure on sensitivity and noise level of the magnetometers will be investigated. Intellectual Merit: The proposed MEMS magnetometers operate based on harvesting and internally amplifying the Lorentz force (force applied to a current carrying conductor in a magnetic field). Extremely high effective quality factors (Q) up to ~1000X larger than the intrinsic mechanical Q of the resonator have been demonstrated using the internal thermal-piezoresistive amplification effect. It is expected that such high Q values can amplify vibration amplitude resulting from the Lorentz force without adding to the electronic noise level leading to superior performance for the proposed sensors. Preliminary analysis show that noise levels in the pT/Hz1/2 range should be within reach, which is comparable to that offered by some of the most sophisticated technologies available. The proposed effort combines the simplicity, small size, and ease/low cost of fabrication of silicon-based MEMS magnetometers with unprecedentedly high sensitivities. The potential outcome will be small size, low cost and easy to use ultra-sensitive magnetometers that circumvent shortcomings of other existing technologies such as the need for cryogenic cooling, integration of exotic materials, large size and high power consumption. Broader Impact: Highly sensitive, small size, and easy to use magnetometers can have transformative effects in various areas including biology and biomedical engineering, geology and mineral/oil exploration, as well as surveillance and defense (through wall/underground imaging and target tracking). For example, arrays of SQUIDs requiring cryogenic cooling are currently used for mapping brain activity by monitoring small magnetic fields (tens to thousands of femotTesla) resulting from firing of neurons in the brain. Small size and convenience offered by the proposed microscale devices can leads to significant advances in brain mapping and enable development of advanced portable brain monitoring devices. On the educational front, one postdoctoral researcher, one PhD level graduate student and up to two undergraduate researchers will be trained and directly involved in the research activities. Results from the research activities will serve as interesting course materials enriching the PIs ongoing courses in MEMS and microsystems. The experience gained by the PI during the course of this project will provide him with a highly valuable insight in a new field of research that will be transferred to current and future students.