Package-induced stress changes the sensitivity of planar Hall plates via the piezo-Hall effect. In this paper, we present a novel stress sensor that allows us to compensate for this undesired mechanical cross-sensitivity. The new CMOS-compatible sensor is based on a Wheatstone bridge built of eight appropriately arranged n- and p-doped piezoresistors. The differential output signal $V_{\rm bridge}$ of the sensor is proportional to the sum of in-plane normal stresses $\sigma_{xx}+\sigma_{yy}$ with the sensitivity $S_{{\rm bridge},\sigma}=\partial\left(V_{\rm bridge}/V_{\rm bias}\right)/\partial\left(\sigma_{xx}+\sigma_{yy}\right)=-0.047~{\rm GPa}^{-1}$. Doping concentrations larger than $10^{19}~{\rm cm}^{-3}$ for both the n- and p-type resistors are used to minimize the parasitic resistor mismatch due to the junction field effect. Simultaneously, the highly doped resistors keep the relative thermal cross-sensitivity of the sensor as small as $74~{\rm ppm~K}^{-1}$. In contrast to conventional sensor rosettes, the new sensor has the advantage of offering a differential output signal. The measured signal is successfully used to decrease the stress-impact on the sensitivity of CMOS Hall sensors by a factor of five.

The combination of integrated magnetic concentrators (IMC) and modern CMOS Hall sensor technology extends the frontiers of magnetic sensing to new dimensions. Single-axis sensors are turned into multi-axis sensors while signal quality and resolution are enhanced by up to one order of magnitude. Integrated Magnetic Concentrators have a deep impact on sensor system design. On one hand, the material properties of the added magnetic layer and the tolerances arising from its deposition and structuring have to be taken into account. On the other hand multi-axis sensors offer the possibility to work with ratios of magnetic field components rather than with a single field component. This results in ageing and drift effects of sensor and magnet being virtually eliminated

Contactless magnetic position sensors are used in countless industrial and automotive applications. However, as a consequence of the electrification trend the sensors can be exposed to parasitic magnetic stray fields, and their desired robustness may be compromised. In this paper we publish for the first time how this challenge is addressed and constructively solved using a complete paradigm change leaving conventional magnetic field measurement behind and entering into the realm of magnetic field gradient measurement. Our novel sensor system consists of an integrated Hall sensor realized in 0.18 μm CMOS technology with magnetic concentrators and a four-pole permanent magnet. The intrinsic angular accuracy was assessed comparing the rotary position of the permanent magnet with the sensor output showing angle errors below 0.3°. Additional end-of-line calibration can be applied using built-in memory and processing capability to further increase the accuracy. Finally, we demonstrate the immunity against stray fields of 4000 A/m which led to errors below 0.1°, corresponding to 0.06% of the sensors fullscale angular range. In conclusion, this novel sensor system offers a compact and flexible solution for stray-field immune rotary position measurement in harsh environment.

This paper experimentally demonstrates the stray-field robustness capability of a novel Hall-based rotary position sensor concept (Huber, S., et al, 2018). The sensor targets safety-related automotive applications, for example powertrain and power steering. In these applications, the safety requirement specifies a maximum stray-field induced error of 0.4°. Therefore, the robustness in corner cases needs to be assessed. We demonstrate the stray-field immunity in multiple corner cases for temperature from −40 °C up to 160 °C and over lifetime. The impact of a uniform 5 mT stray field over all conditions (3σ) is shown to be less than 0.25°. The fully-integrated automotive-qualified sensor is implemented in a 0.18-μm CMOS technology, and achieves 0.7° of angular accuracy.

In automation, transportation, and consumer applications, countless products rely on low-cost, accurate angle sensors. A common method to realize such an angle sensor in CMOS technology utilizes two Vertical Hall Devices (VHDs) to measure the direction of the in-plane magnetic field components of a rotating permanent magnet through corresponding sine and cosine signals. However, the accuracy of VHD based angle sensors was found to be compromised by, e.g., misalignment and imperfections of the fabrication processes and mechanical stress due to the piezo-Hall effect leading to non-orthogonality due to crosstalk between sine and cosine signals originating from stress-related changes of the sensitive directions. In this work we present an active compensation method for the shear stress related directional sensitivity of VHD based angle sensors. The method translates the signal of a cointegrated piezoresistive shear stress sensor into cross-talk compensation counterbalancing the direction changes and therefore re-establishing orthogonality between sine and cosine signals. The method was demonstrated with CMOS-integrated VHD and stress sensors exposed to in-plane shear stress in a torsional bridge setup at temperatures between 26°C and 96°C. As a result, at 26°C and 21 MPa stress, the standard deviation of the measured orthogonality error decreased from 2.5° to a noise-limited 0.28°, while the systematic orthogonality error was significantly reduced from 3.6° to 0.1° after compensation. This significant improvement underscores the effectiveness of the active compensation method in mitigating the impact of mechanical stress, thereby enhancing the accuracy and reliability of VHD-based angle sensors.

This paper presents a solution for on-chip temperature and mechanical stress measurement in CMOS integrated circuits. Thereby both temperature and stress sensors are realized as resistive Wheatstone bridges. By design, both sensors show outputs affected by non-linearities and parasitic cross-sensitivities. The novelty presented in this work is to combine both non-ideal sensor outputs by applying a two-dimensional Newton-Raphson method to extract the actual values of temperature and mechanical stress which were obtained with errors of less than 0.5 K and 0.5 MPa.