High-Scalability CMOS Quantum Magnetometer With Spin-State Excitation and Detection of Diamond Color Centers

Magnetometers based on quantum mechanical processes enable high sensitivity and long-term stability without the need for re-calibration, but their integration into fieldable devices remains challenging. This article presents a CMOS quantum vector-field magnetometer that miniaturizes the conventional quantum sensing platforms using nitrogen-vacancy (NV) centers in diamond. By integrating key components for spin control and readout, the chip performs magnetometry through optically detected magnetic resonance (ODMR) through a diamond slab attached to a custom CMOS chip. The ODMR control is highly uniform across the NV centers in the diamond, which is enabled by a CMOS-generated similar to 2.87 GHz magnetic field with <5% inhomogeneity across a large-area current-driven wire array. The magnetometer chip is 1.5 mm(2) in size, prototyped in 65-nm bulk CMOS technology, and attached to a 300 x 80 mu m diamond slab. NV fluorescence is measured by CMOS-integrated photodetectors. This ON-chip measurement is enabled by efficient rejection of the green pump light from the red fluorescence through a CMOS-integrated spectral filter based on a combination of spectrally dependent plasmonic losses and diffractive filtering in the CMOS back-end-of-line (BEOL). This filter achieves a measured similar to 25 dB of green light rejection. We measure a sensitivity of 245 nT/Hz(1/2), marking a 130x improvement over a previous CMOS-NV sensor prototype, largely thanks to the better spectral filtering and homogeneous microwave generation over larger area.

Automated summary

This research introduces a quantum-based magnetometer that utilizes nitrogen-vacancy centers in diamond for high sensitivity and long-term stability, with miniaturization achieved through the integration of key components on a custom CMOS chip. Improved spectral filtering and homogeneous microwave generation over a larger area have resulted in a 130x sensitivity improvement compared to previous CMOS-NV sensor prototypes, enabling efficient on-chip magnetometry measurements.