Abstract: The present paper focuses on various aspects regarding Hall Effect sensors’design, integration, and behavior analysis. In order to assess their performance, differentHall Effect geometries were tested for Hall voltage, sensitivity, offset, and temperaturedrift.
The residual offset was measured both with an automated measurement setup and bymanual switching of the individual phases. To predict Hall sensors performance prior tointegration, three-dimensional physical simulations were performed.Keywords: Hall Effect sensors; residual offset; absolute sensitivity; temperature effects1.
IntroductionHall Effect sensors are widely used in industrial applications for a series of low power applications,including current-sensing, position detection, and contactless switching. Such magnetic sensors,integrated in regular CMOS technology, prove to be cost-effective and offer high performance . Inorder to guarantee Hall Effect sensors optimal behavior, high sensitivity, low offset, and lowtemperature drift are performance aspects that need to be achieved. Previous papers by the authorsinvestigated the temperature effects on both sensitivity and offset [2,3]. The present paper is highlyfocused on Hall Effect sensors design, integration, and performance investigation. To achieve goodresults while still preserving the integration process, the sensors geometrical configuration is to beexploited [4,5]. As the extensive measurements performed and presented by the authors  prove,there is offset variance with geometry.
The project specifications, a few times better than the actualOPEN ACCESSJ. Sens. Actuator Netw. 2013, 2 86state-of-the-art in terms of offset and its drift, have been reached and various good candidates havebeen revealed. The present paper is structured as follows. The second section is intended to offer anoverview on Hall Effect sensors basic considerations and the most important equations governing theirbehavior. Within this section, arguments for sensors geometry selection and design details arepresented.
Extensive measurements results concerning the sensors sensitivity, offset, and itstemperature drift are incorporated in the third part of the present paper. The fourth section is devoted topresenting three-dimensional physical simulations used to predict the sensors’ behavior. The resultsand discussion are part of the fifth section of this work. Finally, the conclusions are drawn.2. Hall Effect Sensors Design and Integration2.
1 Hall Effect Sensors Basic ConsiderationsFigure 1 presents the classical Greek-cross shape of a Hall Effect sensor. We can observe thesymmetrical and orthogonal character of the shape. The figure also depicts the biasing and sensingcontacts. If a current is applied between two contacts (let us say b and d) and the probe is placed undera magnetic field, the carriers will be deviated by the Lorentz force and a voltage drop which is calledthe Hall voltage will appear between the other two opposite contacts (a and c).Figure 1. Classical Greek-cross Hall Effect sensor representation.In Hall Effect sensors performance assessment, the Hall voltage and sensitivity are importantparameters. By consequence, the Hall voltage is defined by the relation:????? ? ??????(1 (??????J.
Sens. Actuator Netw. 2013, 2 87where G is the geometrical correction factor, rH is the scattering factor of Silicon, (usually 1.
15), n isthe carrier density, t is the thickness of the active region, Ibias is the biasing current, and B is themagnetic field induction, .For a cross-like Hall cell, the geometrical correction factor G is defined as follows:? ? 1 ? 5.0267??tan ????? ?? ???2??? (2)where L and W are the sensor’s length and width respectively, according to Figure 1, and ?? is the Hallangle .The above equation has an accuracy better that 0.5% if ??? ? 0.39, where ? ? ???? is the length ofthe arms.
The absolute, current-related, and voltage-related sensitivities of a Hall sensor are given by thefollowing relations:?? ? ?????? ; ?? ? ???????; ?? ? ??????? (3)From Equations (1) and (3) we can see that the Hall voltage and absolute sensitivity are inverselyproportional to the n-well doping concentration. Therefore, in order to achieve high sensitivities, alightly doped n-well is normally used in the fabrication process of these magnetic sensors.