Hall Effect Sensors Design, Integration and Behavior Analysis  

Abstract: The present paper focuses on various aspects regarding Hall Effect sensors’
design, integration, and behavior analysis. In order to assess their performance, different
Hall Effect geometries were tested for Hall voltage, sensitivity, offset, and temperature
drift. The residual offset was measured both with an automated measurement setup and by
manual switching of the individual phases. To predict Hall sensors performance prior to
integration, three-dimensional physical simulations were performed.
Keywords: Hall Effect sensors; residual offset; absolute sensitivity; temperature effects
1. Introduction
Hall 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 [1]. In
order to guarantee Hall Effect sensors optimal behavior, high sensitivity, low offset, and low
temperature drift are performance aspects that need to be achieved. Previous papers by the authors
investigated the temperature effects on both sensitivity and offset [2,3]. The present paper is highly
focused on Hall Effect sensors design, integration, and performance investigation. To achieve good
results while still preserving the integration process, the sensors geometrical configuration is to be
exploited [4,5]. As the extensive measurements performed and presented by the authors [6] prove,
there is offset variance with geometry. The project specifications, a few times better than the actual
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J. Sens. Actuator Netw. 2013, 2 86
state-of-the-art in terms of offset and its drift, have been reached and various good candidates have
been revealed. The present paper is structured as follows. The second section is intended to offer an
overview on Hall Effect sensors basic considerations and the most important equations governing their
behavior. Within this section, arguments for sensors geometry selection and design details are
presented. Extensive measurements results concerning the sensors sensitivity, offset, and its
temperature drift are incorporated in the third part of the present paper. The fourth section is devoted to
presenting three-dimensional physical simulations used to predict the sensors’ behavior. The results
and discussion are part of the fifth section of this work. Finally, the conclusions are drawn.
2. Hall Effect Sensors Design and Integration
2.1 Hall Effect Sensors Basic Considerations
Figure 1 presents the classical Greek-cross shape of a Hall Effect sensor. We can observe the
symmetrical and orthogonal character of the shape. The figure also depicts the biasing and sensing
contacts. If a current is applied between two contacts (let us say b and d) and the probe is placed under
a magnetic field, the carriers will be deviated by the Lorentz force and a voltage drop which is called
the 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 important
parameters. By consequence, the Hall voltage is defined by the relation:
????? ? ?
??
???
(1 (??????
J. Sens. Actuator Netw. 2013, 2 87
where G is the geometrical correction factor, rH is the scattering factor of Silicon, (usually 1.15), n is
the carrier density, t is the thickness of the active region, Ibias is the biasing current, and B is the
magnetic field induction, [7].
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 Hall
angle [8].
The above equation has an accuracy better that 0.5% if ?
?? ? 0.39, where ? ? ???
? is the length of
the arms.
The absolute, current-related, and voltage-related sensitivities of a Hall sensor are given by the
following relations:
?? ? ?????
? ; ?? ? ??
?????
; ?? ? ??
?????
(3)
From Equations (1) and (3) we can see that the Hall voltage and absolute sensitivity are inversely
proportional to the n-well doping concentration. Therefore, in order to achieve high sensitivities, a
lightly doped n-well is normally used in the fabrication process of these magnetic sensors. 

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