Microelectronic magnetic sensors are essential in diverse applications, including automotive, industrial, and consumer electronics. Hall-effect devices hold the largest share of the magnetic sensor market, and they are particularly valued for their reliability, low cost and CMOS compatibility. This paper introduces a novel 3-axis Hall-effect sensor element based on an inverted pyramid structure, realized by leveraging MEMS micromachining and CMOS processing. The devices are manufactured by etching the pyramid openings with TMAH and implanting the sloped walls with n-dopants to define the active area. Through the use of various bias-sense detection modes, the device is able to detect both in-plane and out-of-plane magnetic fields within a single compact structure. In addition, the offset can be significantly reduced by one to three orders of magnitude by employing the current-spinning method. The device presented in this work demonstrated high in-plane and out-of-plane current- and voltage-related sensitivities ranging between 64.1 to 198 V A⁻¹ T⁻¹ and 14.8 to 21.4 mV V⁻¹ T⁻¹, with crosstalk below 4.7%. The sensor exhibits a thermal noise floor which corresponds to approximately 0.5μT/Hz at 1.31 V supply. This novel Hall-effect sensor represents a promising and simpler alternative to existing state-of-the-art 3-axis magnetic sensors, offering a viable solution for precise and reliable magnetic field sensing in various applications such as position feedback and power monitoring. (Figure presented.)

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This paper reports on the creation of a novel 3D Hall-effect sensor based on an anisotropically etched, inverted pyramid structure. Specific biasing and sensing contact configurations are employed to extract the in-plane or out-of-plane components of the magnetic field, eliminating cross-sensitivity by symmetry. Simulations were performed to verify the functionality and performance of the device, and the results suggested that sensitivity can be manipulated by varying the size-to-contact ratio. MEMS and CMOS processes were leveraged to create small-footprint, single-structure magnetometers with high in-plane/out-of-plane sensitivity. Four different geometries were characterized and maximum in-plane sensitivities of 80.1 V/A/T and 22.3 mV/V/T and in-plane to out-of-plane sensitivity ratios of up to 0.77/1.09 (current/voltage-related) were measured. The presented pyramid structure enables a path toward CMOS-integrated, spatially isotropic magnetometers using a single Hall sensor.@en