BG113812A - Two-axis vector hall microsensor - Google Patents

Abstract

The two-axis Hall vector microsensor contains a current source (1) in the DC generator mode and a square semiconductor substrate (2) of n-type impurity conductivity. On one side of it in the central region, a square ohmic contact (3) is formed. Towards its four sides and at equal distances from them, one rectangular ohmic contact is located, respectively (4), (5), (6) and (7), the length of which is equal to the side of the square 3. The four contacts (4), (5), (6) and (7) are covered by a ring (8) of the same semiconductor with p-type conductivity, embedded in the substrate (2), penetrating the volume and having the shape of a symmetrical Maltese cross. The opposite side of the one with the contacts (4), (5), (6) and (7) and the ring (8) contains a highly conductive layer (9), representing an ohmic contact. The square contact (3) is electrically connected to the layer (9) via the current source (1). The pairs of opposite contacts (4) and (6), and (5) and (7) respectively with respect to the square (3) are the differential outputs (10) and (11) for the two orthogonal planar components of the magnetic field (12), which is in the plane of the substrate (2) and has an arbitrary orientation.

Description

TWO-AXIS VECTOR HALL MICROSENSOR

TECHNICAL FIELD

The invention relates to a two-axis vector Hall microsensor, applicable in the field of medicine, including robotic and minimally invasive surgery; robotics and mechatronics; artificial intelligence systems; low-field and high-precision magnetometry; navigation; process and device control, including contactless automation; control and measurement technology; 2D positioning of objects in the plane; electric vehicle construction; remote measurement of angular and linear displacements; military and security - ground, air and underwater surveillance and prevention systems; counterterrorism, etc.

PRIOR ART

A two-axis vector Hall microsensor is known, measuring simultaneously and independently the two planar components of the magnetic field, containing a square /r-type semiconductor (silicon) substrate, on one side of which in the central region a central ohmic contact with a square shape is formed. At distances and symmetrically with respect to its four sides there is successively one rectangular inner ohmic contact and one rectangular outer ohmic contact, all of the same dimensions. The four outer contacts are electrically connected and through a current source in the constant voltage generator mode are connected to the central contact. The measured magnetic field is in the plane of the substrate and has an arbitrary orientation. The pairs of inner contacts opposite to the central one are the outputs for the two orthogonal planar components of the magnetic field, [1-6].

A disadvantage of this two-axis vector Hall microsensor is the low measurement accuracy as a result of the parasitic inter-channel influence and the chaotic fluctuations in the Hall voltages, introducing metrological errors in both outputs due to the unregulated leakage of part of the supply current along the substrate surface.

Another disadvantage is the reduced magnetic sensitivity of both channels when powered by a constant voltage generator due to: 1. the leakage of part of the supply current along the surface of the substrate, not participating in the formation of the conversion efficiency (sensitivity) of the microsensor, and 2. the dependence of the sensitivity on the change in the ambient temperature, which changes the mobility and concentration of electrons in the substrate.

TECHNICAL ESSENCE

The task of the invention is to create a two-axis vector Hall microsensor with high measurement accuracy and magnetic sensitivity of both output channels by reducing the surface current, inter-channel influence, fluctuations, as well as temperature stabilization of the conversion efficiency.

This problem is solved with a two-axis vector Hall microsensor containing a current source in the DC generator mode and a square semiconductor substrate with i-type impurity conductivity. On one side of it in the central region, a square ohmic contact is formed. Relative to its four sides and at equal distances from them, a rectangular ohmic contact is located, the length of which is equal to the side of the square. The four contacts are covered by a ring built into the substrate from the same semiconductor with p-type conductivity, penetrating the volume and having the shape of a symmetrical Maltese cross. The opposite side of the one with the contacts and the ring contains a highly conductive layer, representing an ohmic contact. The square contact is electrically connected to the highly conductive layer through the current source. The pairs of contacts opposite to the square are the differential outputs for the two orthogonal planar components of the magnetic field, which is in the plane of the substrate and has an arbitrary orientation.

An advantage of the invention is the high measurement accuracy of the two sensor outputs as a result of the absence of inter-channel influence and chaotic fluctuations due to the drastic minimization of the leakage of part of the supply current along the substrate surface through the built-in deep p-type ring in the shape of a Maltese cross.

Another advantage is the high sensitivity (conversion efficiency) of the two sensor channels due to the participation of practically the entire supply current in the magnetoelectric conversion, as well as the design of the microsensor, in which the distance between the two supply contacts is large enough, allowing the Lorentz forces to divert a significant amount of electrons from the substrate volume to the areas with the pairs of output contacts. In addition, the p-type ring prevents the leakage of the current carriers concentrated by the Lorentz forces into the areas with the output contacts, which also increases the sensitivity.

Another advantage is the temperature-stabilized magnetic sensitivity due to the DC generator power supply mode, which maintains the electron concentration in the transport and galvanomagnetic process in the substrate and minimizes the temperature change of their mobility. This guarantees unchanged conversion of the magnetic field in a wide temperature range without any additional electronic circuits and components.

Another advantage is the increased metrological resolution when detecting the minimum value of the magnetic induction B _min through the increased signal-to-noise ratio as a result of the increased sensitivity and the absence of parasitic fluctuations in the output voltages due to the greatly reduced inter-channel influence.

Another advantage is the reduced number of contacts from 9 to 6, simplifying the technological implementation of the 2D vector microsensor.

DESCRIPTION OF THE APPENDIX FIGURES

The invention is explained in more detail by an exemplary embodiment thereof, schematically shown in the attached Figure 1.

EXAMPLES OF IMPLEMENTATION

The two-axis Hall vector microsensor contains a current source 1 in the DC generator mode and a square semiconductor substrate 2 with i-type impurity conductivity. On one side of it in the central region, a square ohmic contact 3 is formed. Relative to its four sides and at equal distances from them, one rectangular ohmic contact 4, 5, 6 and 7 is located, respectively, the length of which is equal to the side of the square 3. The contacts 4, 5, 6 and 7 are covered by a ring 8 of the same semiconductor with p-type conductivity, penetrating the volume and having the shape of a symmetrical Maltese cross, built into the substrate 2. The opposite side of the one with contacts 4, 5, 6 and 7 and the ring 8 contains a highly conductive layer 9, representing an ohmic contact. The square contact 3 is electrically connected to the highly conductive layer 9 through the current source 1. The pairs of opposite contacts 4 and 6, and respectively 5 and 7 relative to the square 3 are the differential outputs 10 and 11 for the two orthogonal planar components of the magnetic field 12, which is in the plane of the substrate 2 and has an arbitrary orientation.

The operation of the two-axis vector Hall microsensor, according to the invention, is as follows. When the terminals of the current source 1, operating in the DC generator mode / _3;9 = const, are turned on, depending on its polarities, a directed current ± /39 flows from the upper surface with contact 3 to the ohmic contact 9, or vice versa. A significant part of the electrons move symmetrically with respect to the central axis of symmetry of the configuration of Figure 1. The axis starts vertically from the center of the square ohmic contact 3 towards the highly conductive layer 9. The main part of the current /3 9 passes a distance equal to the geometric thickness cf ₃ .9 of the substrate 2. In fact, this is the smallest resistance R _3;9 between contacts 3 and 9. In addition, the layer 9 lowers the effective resistance R* of the substrate 2, also contributing to the flow of a significant part of the current / ₃₉ through the shortest geometric distance 0/3 9. The remaining part of the current lines /3 9 forms a "fan" in the volume, expanding towards the contact 9, as the electron trajectories are nonlinear. At the same time, due to the symmetry of the structure 2 with respect to the square contact 3 in the absence of a magnetic field 12 (B = 0), the potentials of the pairs of output terminals 4 and 6, and 5 and 7, respectively, are equivalent. Therefore, their potentials at a field B = 0 13 are practically equalized. This determines the minimum offsets of the pairs of output voltages 10 and 11, Вн4,6(^=0) ~ 0 and Вн5,7(^=0) « 0. In the new vector configuration, Figure 1, the presence of the p-type ring (buffer) 8, which tightly covers the structure - square contact 3 and rectangular electrodes 4, 5, 6 and 7, is of paramount importance. In fact, the p-type region 8 in the shape of a symmetrical Maltese cross greatly reduces the leakage of the supply current ± /3.9 along the surface of the substrate 2. Practically, a significant part of the supply will form the magnetic sensitivity of the microsensor channels. At the same time, the chaotic fluctuations of the two voltages 10 and 11 will be minimized, including the parasitic inter-channel influence. As a result of the built-in deep p-type ring, the causes of internal 1// (flicker) noise are greatly limited. Positioning the output contacts 4, 5, 6 and 7 outside the main current flow zone /3 9 also reduces internal 1// (flicker) noise and fluctuations at outputs 10 and 11. For these reasons, high measurement accuracy is achieved at the two sensor outputs 10 and 11. Also, the metrological resolution is increased when detecting the minimum value of the magnetic induction B _min 12 through the increased signal/noise ratio S/N. The circuitry of the new two-axis microsensor is simplified, since the number of contacts is reduced - from 9 in the known solution to 6 in the new one, Figure 1. This simplifies the technological implementation and reduces the connections between the contacts.

The measured magnetic field B 12 is in the x-y plane of the substrate 2, and is of arbitrary orientation. The two mutually perpendicular magnetic components B _x and B^ act on the moving carriers ± / _3j9 through the Lorentz forces, ±F _L>i = ±qV& χ B, where q is the elementary charge of the electron, and Vdr is the average drift velocity of the electrons in the semiconductor (silicon) substrate 2. Since the surface leakage of the supply current is drastically minimized, and the distance J3 9 between electrodes 3 and 9 is significant, the Lorentz deflection action ±F _Li is maximally effective. As a result, the forces ±F _L j act laterally on the current carriers. Thus, in the areas of the inner sides of the ring 8 in the shape of a symmetrical Maltese cross, where the pairs of contacts 4-6 and 5-7 are located, additional positive and negative charges are concentrated, which are not able to spread over the surface. In this way, the Hall voltages Vhio(^x) and Unpfu) on the output terminals 4-6 and 5-7 further increase. The high conversion efficiency further increases the signal-to-noise ratio S/N, which is the key factor for the metrological resolution for detecting the minimum value of the induction £ _min 12.

The temperature-stabilized magnetosensitivity of the two sensor channels 10 and 11 is a result of the DC generator power supply mode /3.9 = const. With this mode, the concentration N _D ~ and the electrons in their transport process in the substrate 2 are maintained constant, as well as the temperature change of their mobility μ _π is minimized at a fixed electric field £3 9(/3 9) in the structure 2. Thus, the sensitivity is maintained in a wide temperature range without additional electronic circuits and components. The absolute value of the field B 12 in the x-y plane and the angle Θ of the vector B relative to a fixed reference axis in the same plane are given by the expressions: \B\ = (B ² + B, ² )' ¹² and Θ = lanAVJByVJBf), [2, 6].

The unexpected positive effect of the new technical solution is contained in the built-in /?-type ring (buffer) 8 in the shape of a Maltese cross, eliminating the leakage of parasitic current along the surface of the substrate 2. Thus, the inter-channel influence is eliminated and the chaotic fluctuations of the output voltages 10 and 11 are minimized. The constant current generator mode provides temperature stabilization of the sensitivity, achieving high measurement accuracy. The innovation of forming output contacts 4-6 and 5-7 outside the main flow area of the supply current provides an increase in the signal/noise ratio. Thus, the metrological resolution B _min 12 increases.

The planar Hall microsensor can be implemented with CMOS, BiCMOS or micromachining microelectronic technologies. The ohmic contacts 3, 4, 5, 6 and 7 are heavily doped and ⁺ regions formed with epitaxy and a depth of about 1 pm. The low-doped p-type ling (buffer) 8, often formed with BiCMOS, can be replaced by the so-called “trench” or “trench” with an appropriate depth (trench etch depth) by chemical etching. The highly conductive layer 9 is implemented both by metallization and by a highly conductive “buried and ⁺ -layer” (buried and ⁺ -1auerg). This formation 9 essentially represents a power electrode. The two-axis vector Hall microsensor can function in a wide temperature range, including in a cryogenic environment, which improves its basic characteristics. For even higher conversion efficiency for the purposes of weak-field and high-precision magnetometry, seismology, counterterrorism, navigation, etc., the silicon chip with the Hall vector microsensor can be placed between suitable magnetic field concentrators B 12 made of ferrite or μ-metal. For even higher magnetoelectric conversion, the semiconductor /z-GaAs from the A ³ B ⁵ group should be used, whose electron mobility μ _η at room temperature T = 300 K is more than 8 times higher than that of n-Si.

APPENDIX: one figure

LITERATURE

[1] Infineon Technologies AG, Vertical Hall effect device, US Patent, US9425385 B2/23.08.2016.

[2] C.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.

[3] C. Schot, Vertical Hall sensor, US Patent Appl., No. US 2010/0133632 Al/03.06.2010.

[4] A. Bolshakova, R.L. Golyaka, O.Yu. McGdaugh, T.A. Marusenkova, Ηοβϊ constructions of conductive 2-D and 3-D sensors in the magnetic field, Zlektronika i svyazna, No. 2-3, (2009) 6-10 (in Ukrainian).

[5] S. Sander, M.-S. Vecchi, M. Cornils, O. Paul, From three-contact vertical Hall elements to symmetrized vertical Hall sensor with low offset, Sens. Actuators, A240 (2016) 92-102.

[6] C. Roumenin, Solid State Magnetic Sensors - Handbook of Sensors and Actuators, Elsevier, Amsterdam-Lausanne-New York, 1994, pp. 450; ISBN: 0 444 89401.

Claims (1)

PATENT CLAIMS A two-axis vector Hall microsensor, comprising a current source and a square semiconductor substrate with i-type impurity conductivity, on one side of which in the central region a square ohmic contact is formed, with respect to its four sides and at equal distances from them a rectangular ohmic contact is located, the pairs of contacts opposite to the square are the differential outputs for the two orthogonal planar components of the magnetic field, which is in the plane of the substrate and has an arbitrary orientation, CHARACTERIZED in that the current source (1) is in the DC generator mode, the length of the four rectangular contacts (4), (5), (6) and (7) is equal to the side of the square (3), the contacts (4), (5), (6) and (7) are covered by a ring (8) of the same semiconductor with /7-type conductivity, embedded in the substrate (2), penetrating the volume and having the shape of a symmetrical Maltese cross, the opposite side of the one with the contacts (4), (5), (6) and (7) and the ring (8) contains a highly conductive layer (9), representing an ohmic contact, the square contact (3) through the current source (1) is electrically connected to the layer (9).