Exploring Nitrogen vacancy center-based magnetic imaging for next-generation MRAM devices

The rapid growth of AI-driven applications today is pushing conventional charge-based memory technologies to their limits due to the concerns in reliability, scalability, and volatility. This pushes a pressing need for alternative memory solutions that offer faster operation, higher endurance, and non-volatile data storage.

Spintronics, which leverages the electron’s spin in addition to its charge, offers a promising pathway for next-generation memory technologies. Magnetic Random-Access Memory (MRAM) combines these advantages, offering high endurance and fast read/write speeds, making it a strong candidate for future memory technologies. A leading MRAM technology, Spin-Transfer-Torque MRAM (STT-MRAM) is a fast, non-volatile memory that is currently developing for applications like cache memory, and Internet of Thing devices. While it offers high speed, the large currents required for writing can limit device reliability, highlighting the need for improved memory technologies.

To address the limitations of conventional MRAM, Spin-Orbit Torque MRAM (SOT-MRAM) has emerged as a promising alternative. In SOT-MRAM, magnetization switching is induced by an electrical current flowing through an adjacent heavy metal layer, enabling a separation between the write and read paths. This architecture enables faster switching and improved reliability, making SOT-MRAM a promising candidate for future high-performance and energy-efficient memory systems [1]. However, operation of SOT-MRAM devices requires an external in-plane magnetic field to induce reliable magnetization switching. This requirement limits practical device application. As a result, significant research efforts have focused on achieving field-free switching through material design or new device architecture. At imec, we have demonstrated an integration-friendly approach by embedding an in-plane Cobalt ferromagnet in the hard mask used to shape the SOT track during device fabrication process. This Cobalt magnetic hard mask generates an in-plane stray field large enough to induce magnetization switching SOT MRAM memory element without the need of external magnetic field. However, the impact of the in-plane magnetic configuration of Co on the switching dynamics of SOT-MRAM has not yet been thoroughly explored. Studying this relationship will help to connect magnetic behaviours to device performance and guide the development of future high-performance spintronic memory devices.

Therefore, the aim of this internship is to explore the use of advanced scanning probe microscopy (SPM)–based magnetic imaging techniques to probe the in-plane magnetic configuration of Cobalt layers and study its correlation with the switching behaviours of SOT-MRAM devices. Specifically, the main focus will be on scanning nitrogen-vacancy magnetometry (SNVM), a technique that allows for highly sensitive, quantitative mapping of magnetic stray fields with nanoscale spatial resolution. Indeed, recent collaboration between imec and Qnami has showcased the successful application of SNVM for characterization of individual MRAM bits without disturbing the device. [2]. This technique supports probing magnetic uniformity of memory cell beyond conventional methods, offering a powerful tool for optimizing MRAM performance and advancing next-generation memory technologies.

By directly visualizing magnetic domain states, this internship project will gain a deep understanding of how nanoscale magnetic state influence real device performance, bridging fundamental physics and practical memory operation. We seek a candidate with a physics or engineering background, a strong interest in experimental work, and a passion for cutting-edge science and technology, particularly in the fast-growing area of memory technology.

References:

1. https://www.nature.com/articles/s44306-024-00044-1

2. https://www.nature.com/articles/s44306-024-00016-5