JP2013228222A - Magnetic field measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field measuring device that reduces an off-set voltage by considering a positional relationship between a substrate and a magnetic convergence plate, and a Hall element.SOLUTION: The crystal orientation of longer and transverse directions of a silicon substrate 31 is equivalent to <110>, and when the silicon substrate 31 and a magnetic convergence plate 32 are viewed in plan view, an axis 21a of a first terminal pair of the Hall element 20 is substantially parallel to a tangential direction N on an outer edge of the magnetic convergence plate 32 of a contact point between a minimum radius circle in contact with an outer edge of the magnetic convergence plate 32 having a center M of the Hall element 20 as a circle center and the outer edge of the magnetic convergence plate 32. The Hall element 20 is formed on a surface of the silicon substrate 31 so that the axis 21a of the first terminal pair forms an angle of 45 degrees with the longer direction or transverse direction of the silicon substrate 31.

Description

  The present invention relates to a magnetic field measuring apparatus having a magnetic converging plate, and more particularly to a magnetic field measuring apparatus that reduces an offset voltage by considering the positional relationship among a Hall element, a substrate, and a magnetic converging plate.

In general, a magnetic sensor is known as a magnetic field measuring apparatus that can reduce the influence of an element offset voltage of a Hall element and can also reduce the influence of an input offset voltage generated in an amplifier.
In order to obtain an accurate comparison result according to the strength of the magnetic field, it is necessary to suppress the offset signal component included in the signal output from the amplifier and to suppress the variation in the signal output from the amplifier. The main factors that cause the offset signal component are an offset signal component (element offset voltage) included in the output voltage of the Hall element and an offset signal component (input offset voltage) present at the input terminal of the amplifier. The element offset voltage is mainly generated by the stress that the Hall element body receives from the package. The input offset voltage is mainly generated due to variations in the characteristics of elements constituting the input circuit of the amplifier.

  FIG. 1 is a circuit diagram showing a conventional magnetic sensor in which the influence of an offset voltage is reduced. The Hall element used in the magnetic sensor is formed in a plate shape having a geometrically equivalent shape with respect to the four terminals A, C, B, and D. Here, the geometrically equivalent shape means a state in which the four terminals A-C and B-D are rotated by 90 degrees as in the case of the square Hall element 1 (A-C matches BD). This means that the shape in the rotated state is the same. Such a voltage generated between the terminals BD when a power supply voltage is applied between the terminals AC of the Hall element 1 and a voltage generated between the terminals AC when the power supply voltage is applied between the terminals BD. In terms of voltage, the effective signal component corresponding to the strength of the magnetic field is in phase, and the element offset voltage is in reverse phase.

  First, at the first timing, a power supply voltage is applied between the terminals A and C of the Hall element 1 via the switch circuit 2, and a voltage between the terminals B and D is input to the voltage amplifier 3. Therefore, the voltage amplifier 3 outputs a voltage V1 proportional to the sum of the voltage between the terminals BD and the input offset voltage of the voltage amplifier 3. Further, at the first timing, the switch 4 is closed to charge the capacitor 4 to the voltage V1.

Next, at the second timing, a power supply voltage is applied between the terminals BD of the Hall element 1 via the switch circuit 2, and the terminal C-A has a polarity opposite to that of the first timing. The voltage between them is input to the voltage amplifier 3. Therefore, the voltage amplifier 3 outputs a voltage V2 proportional to the sum of the voltage between the terminals C-A and the input offset voltage of the voltage amplifier 3.
Since the influence of the input offset voltage is the same as that of the first timing regardless of the polarity of the input voltage, the output voltage V2 of the voltage amplifier 3 is input to the voltage between the terminals C-A having the opposite polarity to the first timing. The voltage is proportional to the sum of the offset voltage.

  Further, at this second timing, the switch 5 is opened, and the inverting output terminal 3a and the non-inverting output terminal 3b of the voltage amplifier 3 and the capacitor 4 are connected in series between the output terminals 6-7. . At this time, the charging voltage of the capacitor 4 does not change while being held at the output voltage V1 of the voltage amplifier 3 at the first timing. The voltage (output voltage of the magnetic field sensor) V between the output terminals 6-7 is based on the voltage V2 of the non-inverting output terminal 3b when the inverting output terminal 3a of the voltage amplifier 3 is used as a reference, and the terminal 4b of the capacitor 4 is used as a reference. Is the sum of the voltage -V1 at the terminal 4a, that is, the voltage V2 minus the voltage V1. Therefore, a voltage V that cancels the influence of the input offset voltage is obtained as the output voltage of the magnetic field sensor.

  Further, for example, Patent Document 1 proposes a highly accurate and stable magnetic sensor that solves the problem of variations in sensitivity characteristics of the magnetic sensor due to the influence of the positional deviation of the magnetic focusing plate. The thing of this patent document 1 pays attention to the positional relationship of a magnetic converging plate and a magnetic sensing part. Especially, the sensitivity and offset drift due to stress or thermal stress are reduced by making the shape of the magnetic converging plate circular. It is made to let you. Further, for example, Patent Document 2 discloses a magnetic sensor having a magnetic focusing plate.

JP 2012-47708 A US Pat. No. 6,545,462 (B2)

  As described above, various attempts have been made to reduce the offset of the Hall element. However, the conventional technique has a problem that a large offset voltage is generated with respect to the stress applied to the Hall element by the magnetic focusing plate. It was. Further, since the hole arrangement was not such that the influence on the offset voltage due to the stress from the magnetic flux concentrating plate was small, the offset was large.

In addition, although the above-described Patent Document 1 discloses a magnetic sensor that reduces the influence of an offset voltage, it has a configuration that takes into account the piezoresistance coefficient and stress as in the present invention described above. Not. The same applies to each Patent Document 2 described above.
The present invention has been made in view of such a situation, and an object of the present invention is to measure a magnetic field in which an offset voltage is reduced by considering a positional relationship between a Hall element, a substrate, and a magnetic focusing plate. To provide an apparatus.

  The present invention has been made to achieve such an object, and the invention according to claim 1 is a rectangular silicon substrate, and is formed on a surface of the silicon substrate and provided at a position facing each other. At least one hole having a first terminal pair and a second terminal pair made of two terminals, and wherein the axis of the first terminal pair and the axis of the second terminal pair are orthogonal to each other In a magnetic field measurement apparatus comprising an element and a magnetic focusing plate provided on the surface of the silicon substrate, the crystal orientations in the longitudinal direction and the short direction of the silicon substrate are directions equivalent to <110>, When the silicon substrate and the magnetic converging plate are viewed in plan, the axis of the first terminal pair of the Hall element is a minimum radius circle that is in contact with the outer edge of the magnetic converging plate whose center is the center of the Hall element. An outer edge of the magnetic focusing plate; A contact is parallel to a tangential direction on the outer edge of the magnetic focusing plate, and an axis of the first terminal pair forms an angle of 45 degrees with a longitudinal direction or a lateral direction of the silicon substrate. The Hall element is formed on a surface of the silicon substrate.

The invention of claim 2 is the invention according to claim 1, the offset voltage generated in the Hall _{element, Voffset = r0 · (π L} -π T) · (σx-σy) · I / Noting that in the second relationship (Note, I is the current flowing through the Hall element, r0 piezo resistance when no stress is applied, [pi _L piezo resistance coefficient in the longitudinal direction, [pi _T is the lateral direction of the piezoresistive The coefficients σx and σy are stresses applied in the longitudinal direction of the piezoresistor and the stresses applied in the short direction of the piezoresistor)), and the Hall element is different in the piezoresistive coefficient of the piezoresistor. In order to reduce the offset voltage generated by the piezoresistor between the pair of terminals is arranged so that the difference between the piezoresistance coefficient in the longitudinal direction and the piezoresistance coefficient in the short direction is small, and In order to reduce the offset voltage generated due to the difference in stress received from the air focusing plate, the difference between the stress applied in the longitudinal direction of the piezoresistor and the stress applied in the transversal direction of the piezoresistor is reduced. It is arranged parallel to the edge.

According to a third aspect of the present invention, in the first or second aspect of the present invention, when the magnetic focusing plate is a plan view of the silicon substrate and the magnetic focusing plate, the second terminal pair It is characterized by a line-symmetric shape with the axis as a symmetry axis.
The invention according to claim 4 is the invention according to claim 1, 2, or 3, wherein the magnetic flux concentrating plate is any one of a circular shape, a polygonal shape, an elliptical shape, and a semicircular shape. And

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the output of the Hall element is set in a direction parallel to the longitudinal direction or the lateral direction of the silicon substrate by arithmetic processing. It is characterized by being converted to a reference output.
According to a sixth aspect of the present invention, there is provided a substrate having a predetermined crystal orientation, a Hall element provided on the substrate, and the Hall element disposed on the Hall element so that the Hall element is disposed at an end. In the magnetic field measuring apparatus provided with the magnetic converging plate, the Hall element has one terminal pair consisting of two terminals provided at positions facing each other and the other terminal pair, and the Hall element includes Note that the offset voltage generated has a relationship of Voffset = r0 · (π _L −π _T ) · (σx−σy) · I / 2 (where I is the current flowing through the Hall element, r0 is the stress piezoresistive value when not applied, the piezo resistance coefficient of [pi _L is longitudinal, [pi _T is the lateral direction of the piezo resistance coefficient, sigma] x and σy are stress one is applied in the longitudinal direction of the piezoresistive, other piezoresistive Stress in the short direction In order to reduce the offset voltage caused by the difference in the piezoresistance coefficient of the piezoresistor, the Hall element has a piezoresistance coefficient in the longitudinal direction and a piezoresistance in the short direction of the piezoresistor between the terminal pairs. In order to reduce the offset voltage generated by the difference in stress received from the magnetic converging plate, the stress applied in the longitudinal direction of the piezoresistor and the short direction of the piezoresistor It is arranged in parallel with the edge of the magnetic converging plate so that the difference in stress applied to the magnetic converging plate becomes small.

  According to the present invention, by considering the positional relationship between the Hall element and the substrate and the magnetic focusing plate, the piezoresistance coefficient in the longitudinal direction of the piezoresistance of the Hall element modeled by the Wheatstone bridge circuit of the piezoresistance element, It is possible to realize a magnetic field measuring apparatus that can reduce the offset voltage generated by the difference in the piezoresistance coefficient in the short direction of the piezoresistor and the offset voltage generated by the difference in the stress applied to the Hall element from the magnetic convergence plate.

It is a circuit diagram which shows the conventional magnetic field sensor which reduced the influence by an offset voltage. (A), (b) is a figure which shows the bridge circuit of the piezoresistor which comprises the Hall element of the magnetic field measuring device which concerns on this invention. It is a figure which shows the relationship between the piezoresistance coefficient of the longitudinal direction of a piezoresistor with respect to the crystal orientation <110> of Si substrate, and the piezoresistance coefficient of a direction (short direction) perpendicular | vertical to a longitudinal direction. It is a figure which shows the bridge circuit for demonstrating the relationship between the stress in a Hall element of the magnetic field measuring device which concerns on this invention, and offset. (A), (b) shows that when the Hall element terminal pair is arranged parallel or perpendicular to the edge of the magnetic focusing plate, the Hall element terminal pair is inclined 45 degrees with respect to the edge of the magnetic focusing plate. It is a figure which shows the result of having simulated the temperature characteristic of one stress when arrange | positioning, and the other stress. It is a figure which shows the bridge circuit for demonstrating the relationship between the stress in a Hall element of the magnetic field measuring device which concerns on this invention, and offset. It is a block diagram for demonstrating Example 1 of the magnetic field measuring apparatus which concerns on this invention. FIG. 8 is a configuration diagram illustrating a tangential direction in FIG. 7 and a modification of the first embodiment. It is a block diagram which shows the further example of a change of Example 1 shown in FIG. It is a block diagram which shows the further another modification of Example 1 shown in FIG. It is a figure for demonstrating converting the output of a Hall element into the output on the basis of the direction parallel to the edge | side of a silicon substrate by arithmetic processing. It is a block diagram for demonstrating Example 2 of the magnetic field measuring device which concerns on this invention. It is a figure for description about the tangent direction in FIG. It is a block diagram for demonstrating Example 3 of the magnetic field measuring device which concerns on this invention. It is a figure for description about the tangent direction in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiment of the present invention, the longitudinal direction of the Si substrate is defined as the X-axis direction, and the lateral direction of the Si substrate is defined as the Y-axis direction.
2A and 2B are diagrams showing a piezoresistive bridge circuit constituting the Hall element of the magnetic field measuring apparatus according to the present invention. FIG. 2A is a bridge circuit, and FIG. The terminal shape of the element is shown. In the figure, A indicates the point where the excitation current of the Hall element flows from the terminal to the magnetic sensing part, and B indicates the point where the excitation current of the Hall element flows from the magnetic sensing part to the terminal. The axis of the terminal pair is a straight line connecting A and B.

The Hall element 10 shown in FIG. 2A is modeled by a bridge circuit composed of piezoresistors R1 to R4. Piezoresistance coefficient of the piezo resistors R1 to R4 [pi, there is a piezo resistance coefficient [pi _T in the longitudinal direction of the piezo resistance coefficient [pi _L and direction perpendicular to the longitudinal direction of the piezo resistors R1 to R4 (lateral direction) by the crystal orientation A change like FIG. 3 is shown.
FIG. 3 is a diagram showing the relationship between the piezoresistance coefficient in the longitudinal direction of the piezoresistance with respect to the crystal orientation <110> of the Si substrate and the piezoresistance coefficient in the direction perpendicular to the longitudinal direction (short direction). Piezoresistance coefficient [pi _T in the longitudinal direction of the piezo resistance coefficient [pi _L and a lateral direction of the piezo resistors R1 to R4 is at an angle from the crystal orientation of the Si substrate <110> 0 degrees (or 90 degrees) in the inclined direction, the difference between the piezo resistance coefficient [pi _L and piezoresistance coefficient [pi _T decreases, the 45-degree inclined direction, the difference between the piezo resistance coefficient [pi _L and piezoresistance coefficient [pi _T increases.

Therefore, in order to reduce the offset voltage generated by the difference of the piezo resistance coefficient of the piezoresistive constituting the Hall element, so that the difference between the piezo resistance coefficient [pi _L and piezoresistance coefficient [pi _T is reduced, the Hall element The direction of the piezoresistor to be configured is preferably selected to be the direction of the crystal orientation <110> of the Si substrate, and in order to select the direction of the piezoresistor to the direction of the crystal orientation <110> of the Si substrate, the direction of the Hall element terminal is selected. A direction inclined 45 degrees from the crystal orientation <110> of the Si substrate may be selected.

Piezo resistors R1 to R4, together with the changes by piezoresistance coefficient [pi _L and [pi _T, as the stress sigma _L parallel to the longitudinal direction of the piezo resistors R1 to R4, by a vertical stress sigma _T (Equation 1) To change.
R = R0 × (1 + π _L · σ _L + π _T · σ _T ) (1)
Incidentally, R0 is piezoresistive value when unstressed, [pi _L piezo resistance coefficient in the longitudinal direction, [pi _T is the lateral direction of the piezo resistance coefficient, sigma _L is the longitudinal direction of the stress piezoresistive receive, sigma _T piezo It shows the stress in the short direction that the resistance receives.

FIG. 4 is a diagram showing a bridge circuit for explaining the relationship between stress and offset in the Hall element of the magnetic field measurement apparatus according to the present invention. When stress is applied to the piezoresistors R1 to R4 of the Hall element 10 as shown in FIG. 4, the piezoresistors R1 to R4 change as shown in the following (Equation 2), and when the current I flows (Equation 3) ) To produce an offset.
R1 = R3 = R0 × (1 + π _L · σ1 + π _T · σ2)
R2 = R4 = R0 × (1 + π _L · σ 2 + π _T · σ 1) (2)
Voffset = (R2-R3) · I / 2
= R0 · (π _L −π _T ) · (σ 2 −σ 1) · I / 2 (3)
Σ1 is a stress applied in the longitudinal direction of one opposing piezoresistors R1 and R3 (stress applied in the short direction of R2 and R4), and σ2 is a stress applied in the longitudinal direction of the other opposing piezoresistors R2 and R4 ( The stress applied in the short direction of R1 and R3).

From Equation 3, it can be seen that the offset can be reduced by reducing the difference between π _L and π _{T. From} FIG. 3, the longitudinal direction of the piezoresistor is the <110> crystal orientation of the Si substrate. Therefore, it can be understood that the stress applied to the Hall element can be reduced by arranging the longitudinal direction of the piezoresistor constituting the Hall element in the <110> crystal orientation of the Si substrate. In other words, this means that the Hall element terminals may be arranged at an angle of 45 degrees with respect to the XY axis direction parallel to the longitudinal direction and the short direction of the Si substrate. What is necessary is just to arrange | position with an angle of 45 degree | times with respect to crystal orientation <110>.

Conventionally, there has been a Hall sensor in which a Hall element and a magnetic flux concentrating plate are combined. However, stress is generated in the Hall element due to a difference in thermal expansion coefficient between the Hall element and the magnetic flux converging plate, which causes an offset.
The present invention has clarified from the simulation that the stress difference (σ2−σ1) in (Equation 3) can be reduced by optimizing the orientation of the Hall element with respect to the magnetic flux concentrating plate. As a result, the offset can be reduced from (Equation 3).

  5 (a) and 5 (b) show that when the Hall element terminal pair is arranged in parallel to the edge of the magnetic focusing plate, the Hall element terminal pair is inclined 45 degrees with respect to the edge of the magnetic focusing plate. FIG. 5A is a diagram showing the result of simulating the temperature characteristics of one stress σ1 and the other stress σ2 when placed, and FIG. 5A shows the terminal pairs of the Hall elements placed parallel to the edge of the magnetic convergence plate. FIG. 5 (b) shows the temperature characteristics of one stress σ1 and the other stress σ2 when the Hall element terminal pair is inclined by 45 degrees with respect to the edge of the magnetic convergence plate. The temperature characteristics of the stress σ1 and the other stress σ2 are shown. That is, in order to reduce the offset from (Equation 3), the stress difference (σ2−σ1) must be reduced. For this purpose, as shown in FIG. On the other hand, the terminal pairs of the Hall elements are arranged in parallel.

Thus, in order to achieve the object of the present invention, 1) in order to reduce the offset voltage generated due to the difference in the piezoresistance coefficient of the piezoresistors constituting the Hall element, the piezoresistance coefficient π _L and the piezoresistance coefficient as the difference between [pi _T decreases, the direction of the piezo resistors constituting a Hall element to place the Hall element so that the direction of the crystal orientation of the Si substrate <110>, i.e., the direction of the terminal of the Hall element In order to reduce the offset voltage generated by the difference in the stress that the Hall element receives from the magnetic focusing plate, the Hall element is arranged so as to be inclined by 45 degrees from the crystal orientation <110> of the Si substrate. Magnetic converging plate so that the difference between the stress σ1 applied in the longitudinal direction of one opposing piezoresistor and the stress σ2 applied in the longitudinal direction of the other opposing piezoresistor is reduced. It is necessary to arrange the terminal pair of the Hall element in parallel with the edge of this.

Below, each Example of the magnetic field measuring apparatus which concerns on this invention is described. First, the relationship between the piezoresistance constituting the Hall element and the stress received by the Hall element will be described.
FIG. 6 is a diagram showing a bridge circuit for explaining the relationship between stress and offset in the Hall element of the magnetic field measuring apparatus according to the present invention. The bridge circuit in FIG. 4 is inclined 45 degrees. When stress is applied to each of the piezoresistors r1 to r4 of the Hall element 20 as shown in FIG. 6, the piezoresistors r1 to r4 change as shown in (Equation 4), and when the current I flows, (Equation 5) As a result, an offset voltage is generated.
r1 = r3 = r0 × (1 + π _L · σy + π _T · σx)
r2 = r4 = r0 × (1 + π _L · σx + π _T · σy) (4)
Voffset = (r2-r3) · I / 2
= R0 · (π _L −π _T ) · (σx−σy) · I / 2 (5)

Incidentally, r0 is the piezo resistance, [pi _L when unstressed piezoresistance coefficient in the longitudinal direction, it is [pi _T piezoresistive coefficient transverse direction is the same as described in FIG. σx is the stress applied in the short direction (longitudinal direction of r2 and r4) of one opposing piezoresistors r1 and r3, and σy is the shortwise direction of the other opposing piezoresistors r2 and r4 (longitudinal direction of r1 and r3) It shows the stress applied to. Reference numeral 21 denotes a first terminal pair, 21a denotes an axis of the first terminal pair, 22 denotes a second terminal pair, and 22a denotes an axis of the second terminal pair.

FIG. 7 is a configuration diagram for explaining the first embodiment of the magnetic field measurement apparatus according to the present invention. In the figure, reference numeral 31 denotes a silicon (Si) substrate, and 32 denotes a magnetic convergence plate. Note that the Hall element shown in FIG. 6 is rotated 45 degrees and arranged at the end of the magnetic flux concentrating plate. In the first embodiment, the magnetic flux converging plate overlaps to substantially the center of the Hall element.
The magnetic field measurement apparatus according to the first embodiment of the present invention is a first terminal including a substantially rectangular silicon substrate 31 and two terminals formed on the surface of the silicon substrate 31 and facing each other. The surface of the silicon substrate 31 and at least one Hall element 20 having the pair 21 and the second terminal pair 22, and the axis 21 a of the first terminal pair and the axis 22 a of the second terminal pair are orthogonal to each other And a circular magnetic convergence plate 32 provided on the top.

  The crystal orientations of the silicon substrate 31 in the longitudinal direction and the short direction are equivalent to <110>. When the silicon substrate 31 and the magnetic flux concentrating plate 32 are viewed in plan, the first terminal pair of the Hall element 20 The axis 21a is a tangential direction N on the outer edge of the magnetic converging plate 32 at the contact point between the outer edge of the magnetic converging plate 32 and the minimum radius circle that contacts the outer edge of the magnetic converging plate 32 centered on the center M of the Hall element 20. The Hall element 20 is formed on the surface of the silicon substrate 31 so that the axes 21a of the first terminal pairs form an angle of 45 degrees with the longitudinal direction or the short direction of the silicon substrate 31. ing.

  The shape of the magnetic flux concentrating plate 32 is not particularly limited, but when the silicon substrate 31 and the magnetic flux converging plate 32 are viewed in plan, the shape of the magnetic converging plate 32 that is line symmetric with respect to the axis 22a of the second terminal pair is stress. The difference between σx and stress σy becomes smaller, which is preferable. In the present embodiment, the magnetic flux concentrating plate 32 will be described as having a line-symmetric shape with the axis 22a of the second terminal pair as a symmetric axis when the silicon substrate 31 and the magnetic flux converging plate 32 are viewed in plan.

  The magnetic field measurement apparatus according to Example 1 of the present invention includes a substrate 31 having a predetermined crystal orientation, a Hall element 20 provided on the substrate 31, and the Hall element 20 disposed at the end. And a magnetic converging plate 32 having a magnetic amplification function provided on the Hall element 20. The Hall element 20 includes one terminal pair 21 including two terminals provided at positions facing each other and the other terminal. A pair 22. Piezoresistors r1 to r4 shown in a superimposed manner between these two terminals are obtained by modeling a Hall element with an equivalent circuit.

Further, the Hall element 20, the piezo resistors r1 to r4 piezoresistance coefficient [pi _{L of,} in order to reduce the offset voltage generated by the difference of [pi _T, the longitudinal direction of the piezo resistance coefficient of the piezo-resistors r1 to r4 between terminal pairs In order to reduce the difference between π _L and the piezoresistance coefficient π _{T in} the short direction, the orientation of the terminal pair of the Hall element is arranged in a direction inclined 45 degrees from a predetermined crystal orientation of the substrate 31. In order to reduce the offset voltage generated due to the difference between the stresses σx and σy received from the magnetic flux concentrating plate 32, the magnetic flux is arranged in parallel to the edge of the magnetic flux converging plate 32 so that the difference between the stress σx and the stress σy becomes small. ing. In other words, this means that the Hall element terminals may be arranged at an angle of 45 degrees with respect to the XY axis direction parallel to the longitudinal direction and the short direction of the Si substrate. What is necessary is just to arrange | position with an angle of 45 degree | times with respect to crystal orientation <110>.

  FIG. 8 is a configuration diagram illustrating the tangential direction in FIG. 7 and a modified example of the first embodiment. The axis 21a of the first terminal pair of the Hall element 20 has the center M of the Hall element 20 as the center of the circle. The figure for demonstrating the other example about being substantially parallel to the tangential direction N on the outer edge of the magnetic convergence board 32 of the minimum radius circle | round | yen which touches the outer edge of the magnetic convergence board 32, and the outer edge of the magnetic convergence board 32 It is. In FIG. 8, the Hall element and the magnetic converging plate partially overlap.

In the figure, P denotes a contact point between the minimum radius circle and the outer edge of the magnetic focusing plate 32, and Q denotes a minimum radius circle that touches the outer edge of the magnetic focusing plate 32 with the center M of the Hall element 20 as a circle center.
With such a configuration, by considering the positional relationship between the Hall element, the substrate, and the magnetic converging plate, the offset voltage and the Hall element generated due to the difference in the piezoresistance coefficient of the piezoresistors constituting the Hall element are separated from the magnetic converging plate. It is possible to realize a magnetic field measuring apparatus that can reduce an offset voltage generated due to a difference in received stress.

FIG. 9 is a block diagram showing a further modification of the first embodiment shown in FIG. 7 and shows an example in which the Hall element does not overlap the magnetic convergence plate. In FIG. 8, a part of the Hall element 20 overlaps the magnetic convergence plate 32, but in FIG. 9, the Hall element 20 does not overlap the magnetic convergence plate 32.
Even in such a case, since the positional relationship between the Hall element, the substrate, and the magnetic focusing plate in the first embodiment shown in FIG. 7 is satisfied, a magnetic field measurement apparatus that can reduce the offset voltage is realized. Can do.

  FIG. 10 is a block diagram showing still another modification of the first embodiment shown in FIG. 7. In FIG. 9, the Hall element 20 does not overlap the magnetic flux concentrating plate 32, but in FIG. Is arranged inside the magnetic converging plate 32. That is, the minimum radius circle Q in contact with the outer edge of the magnetic focusing plate 32 centered on the center M of the Hall element 20 is inscribed in the outer edge of the circular magnetic focusing plate 32 so that the Hall element 20 is completely magnetically focused. It overlaps the plate 32.

Even in such a case, since the positional relationship between the Hall element, the substrate, and the magnetic focusing plate in the first embodiment shown in FIG. 7 is satisfied, a magnetic field measurement apparatus that can reduce the offset voltage is realized. Can do.
With such a configuration, by taking into account the positional relationship between the Hall element and the substrate and the magnetic focusing plate, the piezoresistance coefficient in the longitudinal direction of the piezoresistance of the Hall element modeled by the Wheatstone bridge circuit of the piezoresistance element, It is possible to realize a magnetic field measuring apparatus that can reduce the offset voltage generated by the difference in the piezoresistance coefficient in the short direction of the piezoresistor and the offset voltage generated by the difference in the stress applied to the Hall element from the magnetic convergence plate.

FIG. 11 is a diagram for explaining that the output of the Hall element is converted into an output based on the direction parallel to the side of the silicon substrate by the arithmetic processing, and the direction of the magnetic field using the magnetic field measuring apparatus according to the present invention. It is a figure for demonstrating a measuring device.
A disc-shaped magnetic converging plate 100 is installed at the center on the surface of the silicon substrate 31. On the circumference of the magnetic flux concentrating plate 100, the X′-axis hall elements 111a and 111b and the Y′-axis hall elements 113a and 113b are installed at point-symmetrical positions with respect to the circle center point 119, respectively. That is, two line segments connecting the X′-axis Hall elements 111 and the Y′-axis Hall elements 113 intersect at the circle center point 119. Further, the distance from the circle center point 119 to the X′-axis hall element 111a is equal to the distance from the circle center point 119 to the X′-axis hall element 111b, and the distance from the circle center point 119 to the Y′-axis hall element 113a is the same. The distance and the distance from the circle center point 119 to the Y′-axis hall element 113b are equal. The directions of the X′-axis hall elements 111b to 111a and the Y′-axis hall elements 113b to 113a are the positive direction of the X ′ axis and the positive direction of the Y ′ axis, respectively.

Next, a method for detecting the rotation angle will be described. When a magnetic field (dotted arrow in FIG. 11) is applied as shown in FIG. 11, output differential voltages V (X ′ +), V (X′−), V from the Hall elements 111a, 111b, 113a, 113b. (Y ′ +) and V (Y′−) are a sine wave voltage and a cosine wave voltage as in the following equation (6).
V (X ′ +) = A × cos θ1
V (X ′ −) = − A × cos θ1
V (Y ′ +) = A × sin θ1
V (Y ′ −) = − A × sin θ1 (6)

Here, A is a proportional constant, and θ1 is an angle (magnetic field application angle) formed clockwise between the X′-axis direction in FIG. 11 and the direction of the magnetic field (arrow dotted line in FIG. 11). The output voltages Vx ′ and Vy ′ in the X′-axis direction and Y′-axis direction are derived by taking the difference between these output voltages as in the following equation (7).
Vx ′ = V1 (X ′ +) − V2 (X ′ −) = 2A × cos θ1
Vy ′ = V1 (Y ′ +) − V2 (Y ′ −) = 2A × sin θ1 (7)

The relative angle is calculated using the output voltages Vx ′ and Vy ′ created here.
As the signal processing, the magnetic field application angle θ1 can be calculated by dividing the following equation (8) and taking the arc tangent.
tan θ1 = Vy ′ / Vx ′
θ1 = arctan (Vy ′ / Vx ′) (8)
The magnetic field direction measuring apparatus using the magnetic field measuring apparatus according to the present invention converts the calculated magnetic field application angle θ1 into an angle based on the longitudinal direction of the Si substrate (direction equivalent to the crystal orientation <110>). That is, when the longitudinal direction of the Si substrate is the X-axis direction and the angle between the X-axis direction and the X′-axis direction is θ2, the magnetic field direction measuring apparatus according to the present invention calculates the magnetic field application angle as θ1 + θ2. It is calculated by converting into an angle based on the longitudinal direction of the Si substrate. The conversion method of the magnetic field application angle is not particularly limited, but is preferably performed by arithmetic processing (soft conversion).

  If the angle θ1 before the calculation process (soft conversion) is changed to the angle θ1 + θ2 after the conversion by the soft conversion, that is, the reference direction of the magnetic field application angle is soft and the longitudinal direction of the Si substrate (crystal orientation < 110 (direction equivalent to 110>), the user can use it easily. In the present embodiment, the longitudinal direction of the Si substrate is the X-axis direction, but the lateral direction may be the X-axis direction.

  FIG. 12 is a block diagram for explaining Example 2 of the magnetic field measurement apparatus according to the present invention, and FIG. 13 is a diagram for explaining the tangential direction in FIG. In the figure, reference numeral 41 denotes a silicon (Si) substrate, and 42 denotes a magnetic convergence plate. The configuration of the Hall element is the same as in FIG. The difference from the first embodiment described above is that the magnetic convergence plate in the second embodiment is rectangular.

  The magnetic field measurement apparatus according to the second embodiment of the present invention is a first terminal including a substantially rectangular silicon substrate 41 and two terminals formed on the surface of the silicon substrate 41 and facing each other. The surface of the silicon substrate 41 and at least one Hall element 20 having the pair 21 and the second terminal pair 22 and the axis 21a of the first terminal pair and the axis 22a of the second terminal pair orthogonal to each other And a substantially rectangular magnetic converging plate 42 provided thereon.

  Further, the crystal orientations in the longitudinal direction and the short direction of the silicon substrate 41 are equivalent to <110>, and the first terminal pair of the Hall element 20 is obtained when the silicon substrate 41 and the magnetic focusing plate 42 are viewed in plan view. Is a tangential direction on the outer edge of the magnetic converging plate 42 at the contact point P between the minimum radius circle Q contacting the outer edge of the magnetic converging plate 42 centered on the center M of the Hall element 20 and the outer edge of the magnetic converging plate 42. The Hall element 20 is on the surface of the silicon substrate 41 so that the axis 21a of the first terminal pair forms an angle of 45 degrees with the longitudinal direction or the lateral direction of the silicon substrate 41. Is formed.

The shape of the magnetic flux concentrating plate 42 may be square. In other words, this means that the Hall element terminals may be arranged at an angle of 45 degrees with respect to the XY axis direction parallel to the longitudinal direction and the short direction of the Si substrate. What is necessary is just to arrange | position with an angle of 45 degree | times with respect to crystal orientation <110>.
With such a configuration, by taking into account the positional relationship between the Hall element and the substrate and the magnetic focusing plate, the piezoresistance coefficient in the longitudinal direction of the piezoresistance of the Hall element modeled by the Wheatstone bridge circuit of the piezoresistance element, It is possible to realize a magnetic field measuring apparatus that can reduce the offset voltage generated by the difference in the piezoresistance coefficient in the short direction of the piezoresistor and the offset voltage generated by the difference in the stress applied to the Hall element from the magnetic convergence plate.

  FIG. 14 is a configuration diagram for explaining a third embodiment of the magnetic field measurement apparatus according to the present invention, and FIG. 15 is a diagram for explaining the tangential direction in FIG. 14. In the figure, reference numeral 51 denotes a silicon (Si) substrate, and 52 denotes a magnetic convergence plate. The configuration of the Hall element is the same as in FIG. The difference from the above-described first embodiment is that the magnetic flux concentrating plate in the third embodiment has a polygonal shape.

  The magnetic field measurement apparatus according to the third embodiment of the present invention is a first terminal including a substantially rectangular silicon substrate 51 and two terminals formed on the surface of the silicon substrate 51 and facing each other. The surface of the silicon substrate 51 and at least one Hall element 20 having the pair 21 and the second terminal pair 22 and having the axis 21a of the first terminal pair and the axis 22a of the second terminal pair orthogonal to each other And a magnetic converging plate 52 having a substantially polygonal shape provided thereon.

  The crystal orientations of the silicon substrate 51 in the longitudinal direction and the short direction are equivalent to <110>. When the silicon substrate 51 and the magnetic flux concentrating plate 52 are viewed in plan, the first terminal pair of the Hall element 20 The axis 21a is a tangential direction on the outer edge of the magnetic focusing plate 52 at the contact point P between the minimum radius circle Q contacting the outer edge of the magnetic focusing plate 52 and the outer edge of the magnetic focusing plate 52 centered on the center M of the Hall element 20 The Hall element 20 is placed on the surface of the silicon substrate 51 so that the axis 21a of the first terminal pair forms an angle of 45 degrees with the longitudinal direction or the lateral direction of the silicon substrate 51. Is formed.

In other words, this means that the Hall element terminals may be arranged at an angle of 45 degrees with respect to the XY axis direction parallel to the longitudinal direction and the short direction of the Si substrate. What is necessary is just to arrange | position with an angle of 45 degree | times with respect to crystal orientation <110>.
With such a configuration, by taking into account the positional relationship between the Hall element and the substrate and the magnetic focusing plate, the piezoresistance coefficient in the longitudinal direction of the piezoresistance of the Hall element modeled by the Wheatstone bridge circuit of the piezoresistance element, It is possible to realize a magnetic field measuring apparatus that can reduce the offset voltage generated by the difference in the piezoresistance coefficient in the short direction of the piezoresistor and the offset voltage generated by the difference in the stress applied to the Hall element from the magnetic convergence plate.

1, 10 Hall element 2 Switch circuit 3 Voltage amplifier 4 Capacitor 5 Switch 21 First terminal pair 21a First terminal pair axis 22 Second terminal pair 22a Second terminal pair axis 31, 41, 51 Silicon ( Si) substrates 32, 42, 52 Magnetic converging plate 100 Magnetic converging plate 111 (111a, 111b) X-axis Hall element 113 (113a, 113b) Y-axis Hall element 119 Circle center point A The excitation current of the Hall element is from the terminal Point B that flows into the magnetosensitive part Point that the excitation current of the Hall element flows into the terminal from the magnetosensitive part M Center of the Hall element N Tangential direction P Contact point between the minimum radius circle and the outer edge of the magnetic focusing plate The center of the Hall element The smallest radius circle that touches the outer edge of the magnetic focusing plate with the circle center

Claims (6)

A first silicon substrate having a rectangular shape, and a first terminal pair and a second terminal pair which are formed on a surface of the silicon substrate and are provided at positions facing each other; In the magnetic field measurement apparatus comprising: at least one Hall element in which the axis of the terminal pair and the axis of the second terminal pair are orthogonal to each other; and a magnetic convergence plate provided on the surface of the silicon substrate,
The longitudinal and short crystal orientations of the silicon substrate are directions equivalent to <110>,
When the silicon substrate and the magnetic flux concentrating plate are viewed in plan, the axis of the first terminal pair of the Hall element is a minimum radius circle that is in contact with the outer edge of the magnetic flux concentrating plate with the center of the Hall element as a circle center. Parallel to a tangential direction on the outer edge of the magnetic focusing plate, and a contact point between the magnetic focusing plate and the outer edge of the magnetic focusing plate, and
The Hall element is formed on the surface of the silicon substrate such that an axis of the first terminal pair forms an angle of 45 degrees with a longitudinal direction or a short direction of the silicon substrate. Magnetic field measuring device. The offset voltage generated in the Hall element is
Voffset = r0 · (π _L −π _T ) · (σx−σy) · I / 2
Noting that there the relationship (Note, I is the current flowing through the Hall element, r0 piezo resistance when no stress is applied, the piezo resistance coefficient of [pi _L is longitudinal, [pi _T piezo resistance coefficient of the lateral direction , Σx and σy are stresses applied in the longitudinal direction of the piezoresistor, and the other is stress applied in the lateral direction of the piezoresistor).
In order to reduce the offset voltage generated by the Hall element due to the difference in piezoresistance coefficient of the piezoresistor, the difference between the piezoresistance coefficient in the longitudinal direction and the piezoresistance coefficient in the short direction of the piezoresistance between the terminal pairs is In order to reduce the offset voltage caused by the difference in stress received from the magnetic converging plate, the stress applied to the longitudinal direction of the piezoresistor and the stress applied to the transversal direction of the piezoresistor are reduced. The magnetic field measuring apparatus according to claim 1, wherein the magnetic field measuring apparatus is arranged in parallel to an edge of the magnetic flux concentrating plate so that the difference is reduced.   3. The magnetic focusing plate according to claim 1, wherein the magnetic focusing plate has a line-symmetric shape with the axis of the second terminal pair as an axis of symmetry when the silicon substrate and the magnetic focusing plate are viewed in plan. The magnetic field measurement apparatus described.   4. The magnetic field measuring apparatus according to claim 1, wherein the magnetic converging plate is any one of a circular shape, a polygonal shape, an elliptical shape, and a semicircular shape.   5. The magnetic field measurement according to claim 1, wherein the output of the Hall element is converted into an output based on a direction parallel to a longitudinal direction of the silicon substrate or a short side direction by arithmetic processing. apparatus. Magnetic field measurement comprising a substrate having a predetermined crystal orientation, a Hall element provided on the substrate, and a magnetic converging plate provided on the Hall element so that the Hall element is disposed at an end. In the device
The Hall element has one terminal pair composed of two terminals provided at positions facing each other and the other terminal pair,
The offset voltage generated in the Hall element is
Voffset = r0 · (π _L −π _T ) · (σx−σy) · I / 2
Noting that there the relationship (Note, I is the current flowing through the Hall element, r0 piezo resistance when no stress is applied, the piezo resistance coefficient of [pi _L is longitudinal, [pi _T piezo resistance coefficient of the lateral direction , Σx and σy are stresses applied in the longitudinal direction of the piezoresistor, and the other is stress applied in the lateral direction of the piezoresistor).
In order to reduce the offset voltage generated by the Hall element due to the difference in piezoresistance coefficient of the piezoresistor, the difference between the piezoresistance coefficient in the longitudinal direction and the piezoresistance coefficient in the short direction of the piezoresistance between the terminal pairs is In order to reduce the offset voltage caused by the difference in stress received from the magnetic converging plate, the stress applied to the longitudinal direction of the piezoresistor and the stress applied to the transversal direction of the piezoresistor are reduced. A magnetic field measuring apparatus, wherein the magnetic field measuring apparatus is arranged in parallel to an edge of the magnetic converging plate so as to reduce the difference.

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