BG112676A - Magnetic field sensor - Google Patents

Abstract

The magnetic field sensor contains two identical rectangular semiconductor wafers with n-type hopping conduction - first (1) and second (2), perpendicular to each other, formed on a common third wafer (3) of the same p-type conductivity semiconductor. On the upper sides of the wafers (1 and 2) and at distances from each other there are consecutively four rectangular ohmic contacts, parallel to their long sides - first (4 and 5), second (6 and 7), third (8 and 9), and fourth (10 and 11), as the all of which are perpendicular to the long sides of the wafers (1 and 2). The fourth contact (10) of the wafer (1) is connected to the first contact (5) of the second wafer (2) and to one of terminals of a current source (12). The second contact (6) of the wafer (1) is connected to the third contact (9) of the wafer (2) and to the other terminal of the current source (12). The third contact (8) of the wafer (1) is connected to the fourth contact (11) of the second wafer (2), and the contact (4) of the wafer (1) is connected to the contact (7) of the second wafer (2). The contacts (4 and 8) of the wafer (1) are an output (13) of the sensor, as the measured magnetic field (14) lies in the planes of the wafers (1, 2 and 3), and has an arbitrary orientation to the contacts (4, 5, 6, 7, 8, 9, 10 and 11).

Description

MAGNETIC FIELD SENSOR

TECHNICAL FIELD

The invention relates to a magnetic field sensor applicable in the field of robotics and mechatronics; micro- and nano-electronics; control and measurement technology; navigation; contactless automation; weak-field magnetometry; energy; automotive industry, including electric vehicle construction; biomedical research; positioning of objects in the plane and space; military affairs and security, including underwater, ground and air systems for surveillance and prevention, counterterrorism, etc.

PRIOR ART

A magnetic field sensor is known, comprising a semiconductor substrate with n-type impurity conductivity and a rectangular shape. On one side of it, at distances from each other, four rectangular ohmic contacts are formed sequentially, parallel to their long sides - first, second, third and fourth, all of which are simultaneously perpendicular to the two long sides of the substrate. The first and third contacts are connected to the terminals of a current source, and the second and fourth are the differential output of the sensor. The measured magnetic field lies in the plane of the substrate and is parallel to the long sides of the contacts, [1 - 5].

A disadvantage of this magnetic field sensor is the metrological error of the output due to the presence of offset (parasitic output voltage in the absence of a magnetic field instead of the absence of an output signal) from technological imperfections in the implementation and, above all, from mechanical stresses (contraction, stretching, bending) in the substrate, which most often occur during the process of encapsulating the chips with the sensors.

Another disadvantage is the need for mechanical adjustment in the orientation of the sensor pad relative to the magnetic field source so that the magnetic vector is not parallel to the short sides of the contacts, a position in which there is no output metrological voltage.

TECHNICAL ESSENCE

The task of the invention is to create a magnetic field sensor with reduced metrological offset error and to eliminate the mechanical adjustment of the sensor relative to the direction of the magnetic field.

This problem is solved with a magnetic field sensor containing two identical rectangular semiconductor substrates with n-type impurity conductivity - first and second, perpendicular to each other, which are formed on a common third substrate of the same semiconductor with p-type conductivity. On the upper sides of the first and second substrates and at distances from each other, there are successively four rectangular ohmic contacts, parallel to their long sides - first, second, third and fourth, all of which are perpendicular to the long sides of the first and second substrates. The fourth contact of the first substrate is connected to the first contact of the second and to one terminal of a current source. The second contact of the first substrate is connected to the third contact of the second and to the other terminal of the current source. The third contact of the first substrate is connected to the fourth contact of the second, and the first contact of the first substrate - to the second contact of the second. The first and third contacts of the first pad are the output of the sensor, as the measured magnetic field lies in the planes of the pads and is of arbitrary orientation relative to the contacts.

An advantage of the invention is the reduced metrological error from the offset due to the first and second pads being perpendicularly positioned to each other, thus compensating for the main root cause - the inevitable stresses (mechanical contractions, stretching, bending) in them during encapsulation, as these negative impacts in the selected orthogonal orientation of the pads are generally of opposite sign and in a first approximation are compensated and neutralized.

Another advantage is the elimination of the need for mechanical adjustment in the orientation of the sensor relative to the source of the measured magnetic field, since due to the orthogonal arrangement of the first and second pads and the connection of the corresponding contacts, a metrological signal is always present at the output.

Another advantage is the reduced negative impact of stresses (compression, stretching, bending) in the first and second pads on the magnetic sensitivity of the sensor due to their orthogonal orientation and the method of connecting the contacts.

DESCRIPTION OF THE APPENDIX FIGURES

The invention is explained in more detail with an exemplary embodiment thereof, given in the attached Figure 1.

EXAMPLES OF IMPLEMENTATION

The magnetic field sensor contains two identical rectangular semiconductor substrates with i-type impurity conductivity - a first 1 and a second 2, perpendicular to each other, which are formed on a common third substrate 3 of the same semiconductor with p-type conductivity. On the upper sides of the pads 1 and 2 and at distances from each other there are successively four rectangular ohmic contacts, parallel to their long sides first 4 and 5, second 6 and 7, third 8 and 9, and fourth 10 and 11, all of which are perpendicular to the long sides of the pads 1 and 2. The fourth contact 10 of the pad 1 is connected to the first contact 5 of the second 2 and to one terminal of a current source 12. The second contact 6 of the pad 1 is connected to the third contact 9 of the second 2 and to the other terminal of the current source 12. The third contact 8 of the pad 1 is connected to the fourth contact 11 of the second 2, and contact 4 of the pad 1 - to contact 7 of the second 2. Contacts 4 and 8 of the pad 1 are the output 13 of the sensor as the measured magnetic field 14 lies in the planes of pads 1, 2 and 3, and is of arbitrary orientation relative to contacts 4, 5, 6, 7, 8, 9, 10 and 11.

The operation of the magnetic field sensor according to the invention is as follows. In accordance with Figure 1, pads 1 and 2 together with contacts 4, 6, 8 and 10, and respectively with 5, 7, 9 and 11 represent four-contact Hall elements with planar magnetic sensitivity. When connecting the power contacts 5 and 10 to one terminal of the current source 12, and contacts 6 and 9 to its other terminal, two independent and equal currents 7 _5>9 and /u,b, /5,9 = To,6· Ohmic contacts 5, 9, 6 and 10 represent equipotential planes. As a result, the current trajectories / _5>9 and I _w $ in the volumes of pads 1 and 2 are curvilinear. Initially, they are perpendicular to contacts 5 and 10, then they change their direction, becoming parallel to the upper surfaces of pads 1 and 2, and then they are again orthogonal to the upper planes of pads 1 and 2 in the areas with contacts 6 and 9. Since pads 1 and 2 with contacts 4, 5, 6, 7, 8, 9, 10 and 11 are topologically identical, it is assumed that in the absence of a magnetic field B 14 the electric potentials on contacts 8 and 7 on the one hand, and 4 and 11 on the other, respectively, at currents /5,9 = /ωb are equal in value, Vs ~ V ₇ and V4 ~ ¥ц. The connection of contacts 8 and 11, and 4 and 7 in a first approximation balances the output signal 13 in such a way that the offset V^siP = 0) ~ 0. Another important condition of the connection of contacts 8 and 11, and 4 and 7, with orthogonality of pads 1 and 2 is that the mechanical stresses (contraction, stretching, bending), generating an offset at the output 13 during the encapsulation or from temperature effects, mutually compensate. The electrical insulation of the two Hall elements 1 and 2 with planar magnetic susceptibility is carried out by the third pad 3 of the same semiconductor, but with 72-type conductivity.

The sensing mechanism for measuring the magnetic field B 14, after compensating or balancing the offset by connecting the contacts 8 11, and 4 - 7, Figure 1, is the Hall effect. The measured magnetic field B 14, lying in the plane of pads 1, 2 and 3, leads to the emergence of a Lorentz force deflecting the electrons = qV _dr x B, where q is the elementary charge of the electron, and V _dr is the average drift velocity of the carriers in pads 1 and 2, [3-5]. This deflection contracts or expands the trajectory of the force lines /5,9 and /10,6. As a result, additional unbalanced electric charges are generated on the upper surfaces of pads 1 and 2, where ohmic contacts 4 and 8, and 7 and 11, respectively, are formed. Since the magnetic field B 14 acts on the current lines /5,9 and / _10>6 through the components B _x and B _y , Figure 1, the potentials V ₈ and V^, and V ₄ and V ₇ , respectively, are of the same polarity +V ₈ ^and +V11, -V ₄ and -Vq. Therefore, the connection of contacts 4 and 7, and 8 and 11, respectively, forms the differential output Tdd 13 of the magnetic field sensor.

Until recently, in the theory of the Hall effect, it was assumed that the additional electrons concentrated by the force on a certain area of the surface of the Hall elements (Figure 1) are also stationary, as are the positive donor ions N _D+ “bare” by the same force F^ on its reciprocal part. According to the research of Rumenin, Lozanova, etc. [6], the existence of a magnetically controlled surface current M ₅ (Ι _ο β) in the Hall structures was discovered, where / ₀ is the supply current. The current is a fundamental regularity, further clarifying the Hall phenomenon and contributing to an increase in magnetic susceptibility, as is the case for the elements of Figure 1. It was discovered as a result of the concept of mobile, not static, current carriers (electrons), generated by the Lorentz force F _L on the corresponding Hall zone.

The change in the orientation of the measured magnetic field B 14 relative to contacts 4, 5, 6, 7, 8, 9, 10 and 11 in the x-y plane of the pads 1, 2 and 3 leads to a simultaneous decrease in one vector component, for example B _x at the expense of the other B _y . According to the proposed connection of contacts 4-7, and respectively 8 - 11, the zero voltage UdDV) = θ will not be found on the differential output 13 (one potential increases at the expense of the other), as in the known solution. The voltage V ₄ $(B} 14 is a function of the magnetic field strength V and of the currents flowing in the two pads 1 and 2 D.h and The mutually orthogonal arrangement of pads 1 and 2 significantly reduces the influence of the mechanical stresses responsible for the origin of both the offset and the change in magnetic susceptibility. The new sensor significantly balances the sensitivity so that it remains unchanged by negative (internal) stresses.

The unexpected positive effect of the new technical solution is that in the metrology of the magnetic field a sensor is proposed in which the change in the orientation of the vector B 14 never leads to a zero output signal 13. By means of the orthogonal arrangement of pads 1 and 2, both the offset and the change in the magnetic susceptibility are successfully overcome. Negative mechanical stresses generate changes in the electrical state of pads 1 and 2 with opposite signs, which in a first approximation are neutralized. The compensation of the sensor deficiencies is also a result of the original connection of the contacts in the two Hall elements. In order to increase the metrological accuracy, the directions of the supply currents /5,9 and Zio,6 can be switched, and the results of the output 13 are summed algebraically.

If necessary, the registration of the direction of the magnetic field B 14 can be carried out by measuring the two separate magnetic components B _x and B _y by breaking the connections between contacts 4-7, and 8-11. Then each of the orthogonally arranged Hall elements of pads 1 and 2, having the same magnetic susceptibility, will generate individual output voltages VddS-vu) ^and V7,n(B _x ). They are a measure of the values and directions of the planar components B _x and B _y , i.e. of the magnetic vector B 14.

Technologically, the magnetic field sensor can be implemented with silicon microelectronics methods, for example with CMOS or BiCMOS processes, forming the Hall elements in epitaxial i-Si layers or "pockets" located on a />-Si substrate.

APPENDIX: one figure

LITERATURE

[1] H.S. Rumenin, P.T. Kostov, Hall Sensor, Avt. granted invention No. BG 41974 with priority from 05.06.1986.

[2] Ch.S. Roumenin, Parallel-field Hall microsensor, Compt. rendus ABS, 40(11) (1987) 59-62.

[3] Ch.S. Roumenin, "Solid State Magnetic Sensors" - Handbook of Sensors and Actuators, Elsevier, Amsterdam-Lausanne-New York-Oxford-ShannonTokyo, 1994, pp. 450; ISBN: 0 444 89401.

[4] Ch.S. Roumenin, Microsensors for magnetic field, in "MEMS - a practical guide to design, analysis and applications", Ch. 9, ed. by J. Korvink and O. Paul, William Andrew Publ., USA, 2006, pp. 453-523; ISBN: 0-8155-1497-2.

[5] S.V. Lozanova, Ch.S. Roumenin, Parallel-field silicon Hall effect microsensors with minimal design complexity, IEEE Sensors Journal, 9(7) (2009) 761-766.

[6] C. Roumenin, S. Lozanova, S. Noykov, Experimental evidence of magnetically controlled surface current in Hall devices, Sensors and Actuators, A 175 (2012) 45-52.

Claims (1)

PATENT CLAIMS Magnetic field sensor containing a rectangular semiconductor substrate with p-type impurity conductivity, on one side at a distance from each other are formed four rectangular ohmic contacts, parallel to their long sides - first, second, third and fourth, all simultaneously perpendicular to the two long sides of the substrate, the second and fourth contacts are connected to the terminals of the current source, and the first and third - are the differential output of the sensor as the measured magnetic field lies in the plane of the substrate, CHARACTERIZED by a second semiconductor substrate (2) with a n-type impurity conductivity identical to the first (1) and perpendicular to it, the two substrates (1) and (2) are formed on a common third substrate (3) of the same semiconductor with _a p-type conductivity, on one side of the pad (2) at a distance from each other imc. successively four rectangular ohmic contacts parallel to their long sides first (5), second (7), third (9) and fourth (11) all simultaneously perpendicular to the two long sides of the pad (2), the fourth contact (10) of the pad (1) is connected to the first contact (5) of the second (2), the second contact (6) of the pad (1) is connected to the third contact (9) of the second (2), the third contact (8) of the pad (1) is connected to the fourth contact (11) of the second (2), and the contact (4) of the pad (1) ) - with contact (7) of the second (2), the magnetic field (14) has an arbitrary orientation relative to contacts (4), (5), (6), (7), (8), (9), (10) ) and (11).