Arizona Patent of the Month – July 2023

In the realm of sensing technologies, magnetoresistive sensors play a vital role in detecting and measuring magnetic fields. They are utilized in various applications, including electronic compasses, motion sensors, and more. However, traditional magnetoresistive sensors often suffer from limitations in size, sensitivity, and temperature dependence. To overcome these challenges, Everspin Technologies, Inc. has revolutionized the integration of magnetoresistive sensors through an innovative manufacturing method.

Headquartered in Chandler, Arizona, Everspin Technologies is the worldwide leader in designing, manufacturing, and commercially shipping discrete and embedded Magnetoresistive RAM (MRAM) and Spin-transfer Torque MRAM (STT-MRAM) into markets and applications where data persistence and integrity, low latency, and security are paramount.

Everspin Technologies’ method focuses on fabricating an integrated magneto-resistive sensor with reduced die footprint and three-dimensional responsiveness to applied magnetic fields. The process begins by depositing a first insulating material on or over a substrate. One or more flux guides, comprising a magnetic material, are then formed on or in the first insulating material. These flux guides act as conduits for magnetic flux, enhancing the sensor’s sensitivity and responsiveness.

The next step involves the formation of a plurality of magneto-resistive sensor elements on or over the first insulating material. Each sensor element consists of a reference layer, a sensing layer, and an intermediate layer between them. The reference layer establishes a baseline, while the sensing layer detects changes in the applied magnetic field. The intermediate layer enhances the performance and stability of the sensor.

To interconnect the magneto-resistive sensor elements, conductors are formed, creating bridge circuits. These circuits enable the subtraction of resistances, resulting in improved sensitivity and accurate measurement of magnetic fields. The conductors also include input and output connections for voltage source and detection circuit connectivity, respectively.

Throughout the manufacturing process, Everspin Technologies utilizes materials such as nickel, iron, cobalt, or their alloys, for the magnetic components and insulating materials. These choices contribute to the sensor’s robustness, performance, and compatibility with complementary metal-oxide-semiconductor (CMOS) technology.

The integration of these components into a single chip configuration offers numerous advantages. Firstly, the reduced die footprint enables smaller and more compact sensor designs, ideal for mobile applications. Secondly, the three-dimensional responsiveness allows the sensor to detect magnetic fields in all orthogonal directions accurately. This eliminates the need for separate chips or complex packaging, reducing costs and facilitating chip-scale packaging.

Everspin Technologies’ breakthrough in magnetoresistive sensor integration addresses the limitations of existing sensing technologies, opening new possibilities for advancements in mobile devices, navigation systems, and other magnetic field sensing applications. By leveraging their innovative manufacturing method, Everspin Technologies is driving the industry forward with smaller, more accurate, and cost-effective magnetoresistive sensors.

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