BG113809A - Vertical hall microsensor - Google Patents

Abstract

The vertical Hall microsensor comprises a semiconductor substrate (1) with n-type impurity conductivity, on one side of which four rectangular ohmic contacts are formed at a distance from each other in succession - first (2), second (3), third (4) and fourth (5), arranged parallel to their long sides. The first (2) and second (3) contacts are in close proximity, and on their other long sides a p-type rectangular confinement zone (6) is formed, parallel to contacts (2), (3), (4) and (5), and penetrating into the volume of the substrate (1). On both long sides of the fourth contact (5) and in their proximity there is another p-type rectangular confinement zone (7), penetrating into the volume. The third contact (4) is arranged in the middle between the second (3) and the fourth (5). The plane opposite to the one with contacts (2), (3), (4) and (5) contains a highly conductive layer (8). The second (3) and fourth (5) contacts are directly electrically connected to a current source (9), and the first (2) and third (4) are the differential output (10) of the microsensor. The measured magnetic field (11) is parallel to both the plane of the substrate (1) and the long sides of the contacts (2), (3), (4) and (5).

Description

VERTICAL HALL MICROSENSOR

TECHNICAL FIELD

The invention relates to a vertical Hall microsensor applicable in the field of robotics and mechatronics; quantum communication and navigation; the automotive industry, including hybrid vehicles and electric vehicles; process automation, including contactless automation; security systems with artificial intelligence; robotic and minimally invasive surgery; low-field and high-precision magnetometry; in underwater, ground and air surveillance and prevention systems; counterterrorism, etc.

PRIOR ART

A vertical Hall microsensor is known, comprising a semiconductor (silicon) substrate with n-type impurity conductivity, on one side of which four rectangular ohmic contacts are formed at equal distances from each other in sequence - first, second, third and fourth, located parallel to their long sides. The first and third contacts are connected through a current source, and the second and fourth contacts are the differential output of the microsensor, with the measured magnetic field being parallel to both the plane of the substrate and the long sides of the rectangular contacts, [1-5].

A disadvantage of this vertical Hall microsensor is the low magnetic sensitivity (conversion efficiency) as a result of the horizontal flow of part of the supply current through the output contacts, planarly located simultaneously with the supply contacts on the same surface of the substrate, which lowers the output Hall voltage, respectively, the magnetic sensitivity decreases.

Another disadvantage is the reduced metrological accuracy due to the reduced sensitivity and signal-to-noise ratio, leading to a noticeable presence in the output voltage of parasitic signals from typical sensor deficiencies such as temperature drift, fluctuations, hysteresis, internal 1//(flicker) noise, offset, etc.

TECHNICAL ESSENCE

The task of the invention is to create a vertical Hall microsensor with increased magnetic sensitivity and measurement accuracy.

This problem is solved with a vertical Hall microsensor, containing a semiconductor substrate with i-type impurity conductivity, on one side of which four rectangular ohmic contacts are formed at distances from each other in sequence - first, second, third and fourth, located parallel to their long sides. The first and second contacts are close, and on their other long sides there is formed one p-type rectangular limiting zone, parallel to the ohmic contacts and penetrating into the volume of the substrate. On both long sides of the fourth contact and near them there is another /?-type rectangular limiting zone, penetrating into the volume. The third contact is located in the middle between the second and fourth. The opposite plane of the one with the contacts contains a highly conductive layer. The second and fourth contacts are directly electrically connected to a current source, and the first and third are the differential output of the microsensor. The measured magnetic field is parallel to both the substrate plane and the long sides of the contacts.

An advantage of the invention is the high magnetic sensitivity as a result of the following factors: 1. The limiting p-type zones near the first and second contacts as well as the same p-type zones located on both long sides of the fourth contact contribute to significantly deeper penetration into the volume of the entire supply current entering the substrate, which significantly increases its Lorentz deviation in a magnetic field; 2. The horizontal component of the supply current in the near-surface region of the substrate is drastically reduced by the formed pairs of deep p-type zones; 3. The output Hall voltage is further increased by the accumulated negative and positive charges in a magnetic field with the limiting p-type buffers (zones) to the first and third contacts; and 4. The presence of a highly conductive layer on the opposite side of the substrate reduces the effective resistance of the structure, also contributing to the penetration of the current into the volume. That is why the larger supply current in the Hall mechanism and the features of the microsensor configuration generate a significantly higher output voltage value, i.e. magnetosensitivity.

Another advantage is the increased metrological resolution when detecting the minimum magnetic induction B _min , due to the increased signal-to-noise ratio through the high sensitivity and the greatly reduced noise fluctuations using the deep p-type buffers surrounding the first and second, and fourth contacts, respectively.

Another advantage is the increased measurement accuracy as a result of the high sensitivity and reduced parasitic noise fluctuations through the restrictive p-type regions.

DESCRIPTION OF THE APPENDIX FIGURES

The invention is explained in more detail by an exemplary embodiment thereof, schematically shown in the attached Figure 1, representing the cross-section of the Hall microsensor.

EXAMPLES OF IMPLEMENTATION

The vertical Hall microsensor contains a semiconductor substrate 1 with i-type impurity conductivity, on one side of which four rectangular ohmic contacts are formed at a distance from each other in succession - first 2, second 3, third 4 and fourth 5, located parallel to their long sides. The first 2 and second 3 contacts are in close proximity, as on their other long sides a p-type rectangular boundary zone 6 is formed, parallel to contacts 2, 3, 4 and 5, and penetrating into the volume of the substrate 1. On both long sides of the fourth contact 5 and in their vicinity there is another p-type rectangular boundary zone 7, penetrating into the volume. The third contact 4 is located in the middle between the second 3 and the fourth 5. The opposite plane of the one with the contacts 2, 3, 4 and 5 contains a highly conductive layer 8. The second 3 and the fourth 5 contacts are directly electrically connected to a current source 9, and the first 2 and the third 4 are the differential output 10 of the microsensor. The measured magnetic field 11 is parallel to both the plane of the substrate 1 and the long sides of the contacts 2, 3, 4 and 5.

The operation of the vertical Hall microsensor according to the invention is as follows. When the current source 9 is connected to the contacts 3 and 5, the supply current / ₃ , ₅ flows through the volume of the substrate 1. As a result of the original technical solution - the low-doped p-type buffers (zones) 6 and 7 formed near the contacts 3 and 5, the entire current / ₃ , ₅ penetrates into the depth of the substrate 1 without lateral scattering. Buffers 6 and 7 do not allow the occurrence of a horizontal flow of part of the supply current along the surface with contacts 2, 3, 4 and 5 to form a parasitic component. As a result, the fluctuations of the output 10 are also drastically reduced. The degree of current penetration depends on the width of the supply electrodes 3 and 5, the current strength / _3}5 , the depth of the p-type zones 6 and 7, and the effective resistance R* of the substrate 1, formed by the concentration of the doping impurity, for example phosphorus P, and by the presence of the highly conductive layer 8. The trajectory of the electrons in the substrate 1 is curvilinear, [2,3,5]. It starts, for example, from contact 3, penetrates vertically into the volume, then becomes parallel to the upper side of the substrate 1, and finally is vertical again to contact 5. A prerequisite for the vertical penetration w of the current /3.5 is also the equipotentiality of the ohmic contacts 3 and 5 in the absence of a magnetic field B 11. In general, the depth w for a fixed concentration of the donor impurity N _D = const in the m-type substrate 1 provided that the p-type regions 6 and 7 are absent, depends on the ratio M between the width /1 of the supply contacts 3 and 5 and the distance 1 ₂ between them, Μ = Z1//2, [6]. The calculated depth w at the most commonly used in microelectronics concentration in Si of doping donor impurities N _D ~ 10 cm' and, for example, a distance / ₂ ~ 25 pm is about ω ~ 30 pm. The proximity of the low-doped p-type buffers (zones) 6 and 7 to the corresponding p ⁺ contacts is determined by the technological processes used to realize the sensor IC. The kinetics of the electrons is also determined by the highly conductive layer 8 with a floating potential on the opposite side, Figure 1. At the same time, the p-type limiting zones 6 and 7 prevent the flow of the supply current along the surface of the substrate 1. By varying the distance between the first 2 and the second 3 contacts, i.e. the potential of the output terminal 2, or by computer simulation of this process, a reduction of the parasitic offset U n2l (^ = 0) » 0 is achieved. As a result of these conditions, metrological errors and fluctuations of the output 11 are greatly minimized, as the accuracy is increased.

In the presence of an external magnetic field B 11, the individual parts of the nonlinear current / _3;5 are subjected to the deflecting action of the Lorentz forces +F _{L i} = ±gVdr ^x B, where q is the elementary charge of the electron, and Vd _r is the vector of the average drift velocity of the current carriers. For this reason, the current lines / ₃₅ are deformed. This behavior is determined by the directions of the field ±B 11 and the current ±/ _3>5 . In the area under electrode 3, the Lorentz force deflects the electrons, for example, to the left, and in the area between contacts 3 and 5, the current lines deviate towards layer 8. Thus, the non-equilibrium current carriers generated by the forces accumulate/accumulate in the areas of the output contacts 2 and 4. They are retained there by buffers 6 and 7, preventing them from spreading over the surface of the substrate 1. Their concentration, for example, negative charges on contact 2 and positive ones on terminal 4, significantly increases the output voltage of the Hall UnglF) Y. By means of the forces F _L>i, the current lines / ₃₅ are “collapsed” towards the upper side of the substrate 1, or “unfolded” in its volume. In fact, the vertical component / ₃ of the current / ₃₅ is generated by the Hall potential Und(^) on the output contact 2, and the horizontal one - on contact 4, UtsdSL).

The unexpected positive effect of the new technical solution lies in the specific design. With the help of the pairs of p-type buffers (zones) 6 and 7, the entire incoming current penetrates deep into the volume of the substrate 1. For the first time in this class of four-contact Hall elements, an approach is used that increases the magnetic sensitivity through the entire supply current / _{3 5} . In the new configuration, Figure 1, the output terminal 2 is located significantly closer to the supply contact 3 in contrast to the previously widespread location of all electrodes being equidistant. The proposed solution contains the following advantages: a) the magnetic sensitivity increases; b) the signal-to-noise ratio increases simultaneously with the metrological resolution when detecting the minimum magnetic induction B _min 11, including the measurement accuracy increases.

The planar Hall-type microsensor can be implemented with CMOS, BiCMOS or micromachining microelectronic technologies. The ohmic contacts 2, 3, 4 and 5 are highly doped n ⁺ regions formed by epitaxy and with a depth of about 1 pm. The low-doped /2-type regions 6 and 7, which are often formed by BiCMOS, can be replaced by so-called “trench” or “trench” of appropriate depth (trench etch depth) by the chemical etching procedure. The highly conductive layer 8 is implemented both by metallization and by a highly conductive “buried” (buried) n ⁺ layer. This formation 8 essentially represents an output electrode on which a corresponding Hall potential ±Vh,s(^) is generated in a magnetic field B 11. For example, the voltage ±Vh4,s(^) between contacts 4 and 8 further expands the usability of the element from Figure 1. The vertical or planar-sensitive microsensor can operate in a wide temperature range, including in a cryogenic environment, which improves its main 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 element can be located between two identical field concentrators B 11 made of ferrite or μ-metal. For even higher magnetoelectric conversion, the n-GaAs semiconductor from the AB 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] H.S. Rumenin, P.T. Kostov, Hall Sensor, Avt. witness No. BG 41974/06.05.1986; S. Roumenin, Parallel-field Hall microsensor, Compt. rendus ABS, 40(11) (1987) pp. 59-62.

[2] C. Roumenin, Solid State Magnetic Sensors, Elsevier, Amsterdam, 1994, p. 450; ISBN: 0 444 89401.

[3] A.M.J. Huiser, H.P. Baltes, Numerical modeling of vertical Hall-effect devices, IEEE Electr. Device Letters, 5(9) (1984) pp. 482-484.

[4] C. Roumenin, Microsensors for magnetic field, Chap. 9, in "MEMS - a practical guide to design, analysis and applications", ed. by J. Korvink and

0. Paul, William Andrew PubL, USA, 2006, pp. 453-523; ISBN: 0-81551497-2.

[5] C.S. Roumenin, Parallel-field Hall microsensors - An overview, Sensors and Actuators, A 30 (1992) pp. 77-87.

[6] T. Kaufmann, On the offset and sensitivity of CMOS-based five-contact vertical Hall devices, in "MEMS Technology and Engineering", v. 21, Der Andere Verlag, 2013, p. 147.

Claims (1)

PATENT CLAIMS A vertical Hall microsensor, comprising a semiconductor substrate of n-type impurity conductivity, on one side of which four rectangular ohmic contacts are formed at a distance from each other in succession — first, second, third and fourth, arranged parallel to their long sides, the second and fourth contacts are directly electrically connected to a current source, and the first and third are the differential output of the microsensor, with the measured magnetic field being parallel to both the plane of the substrate and the long sides of the contacts, CHARACTERIZED in that the first (2) and second (3) contacts are in close proximity, with one p-type rectangular limiting zone (6) formed on each of their other long sides, parallel to contacts (2), (3), (4) and (5), and penetrating into the volume of the substrate (1), on both long sides of the fourth contact (5) and in their vicinity there is another p-type rectangular a limiting zone (7) penetrating the volume, the third contact (4) is located in the middle between the second (3) and the fourth (5) as the opposite plane to that with the contacts (2), (3), (4) and (5) contains a highly conductive layer (8).