JPS62208683A - Magnetic sensor - Google Patents

Abstract

PURPOSE:To reduce an offset voltage and to eliminate a detection error by arranging plural Hall elements on the same equi-distortion curve and in the symmetric orientations regarding a symmetric axis. CONSTITUTION:As the Hall element 1 and the Hall element 2 are on th same equi-distortion curve, the quantity of applied distortion is roughly equal. Accordingly, an offset voltage of the Hall element 1 (V02-V01) and an offset voltage of the Hall element 2 (V04-V03) are the same in their absolute values. Furthermore, the direction of a drive current of the Hall element 1 and that of the Hall element 2 are opposed regarding a center line and when current drive electrodes 201 and 202 of the respective elements are arranged, the polarities of the offset voltage of the Hall element 1 (V02-V01) and the offset voltage of the Hall element 2 (V04-V03) also become opposite mutually. Accordingly, when the offset voltages are added, the offset voltage of the whole magnetic sensor is cancelled and set off, so that the offset voltage becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a θ sensor used in a position detection device for a DC brushless smoke or a magnet.

[Summary of the invention]

In a magnetic sensor in which a plurality of Hall elements are formed on the same semiconductor chip, the plurality of Hall elements are arranged on the same iso-strain curve on the surface of the semiconductor knob and arranged symmetrically with respect to the center line of the semiconductor chip. By doing so, the offset output voltage due to the piezoresistive effect of each Hall element is canceled out, and a magnetic sensor without detection error is obtained.

[Conventional technology]

With the miniaturization and low-voltage operation of DC brasosure smoke and position detection devices, it has been necessary to increase the sensitivity of magnetic sensors.

Therefore, in the early days, high-sensitivity magnetic sensors using Hall elements were made using high-mobility semiconductor materials such as gallium arsenide and indium antimony. However, with the above-mentioned semiconductor materials, it is difficult to manufacture a one-chip magnetic sensor by integrating a comparator and a logic circuit in addition to the Hall element into one thousand knobs.

Therefore, in recent years, Hall element magnetic sensors using silicon single crystal as the material have been developed. This is because it is easy to integrate 1,000 knobs.

[Problem that the invention seeks to solve]

However, pole elements formed on silicon crystals have the following problems.

In other words, in silicon single crystal, the piezoresistance effect is remarkable and also has directional properties. The piezoresistance effect is a phenomenon in which when stress is applied to a semiconductor chip, resistance occurs in elements formed on the chip. Due to the piezoresistance effect, a DJ offset voltage is generated at the output terminal of the pole element of the Noricon chip I-. ``F7 node voltage is the voltage that occurs at the output terminal even though there is no external magnetic field. In silicon chip Hall elements, this offset voltage is large;
This was causing false detection. Note that chip mounting (guibond, mold l) can be considered as a cause of external stress. Now, assuming that the magnetic sensitivity of the Hall element is 20 mV/K Ganss, if an offset voltage of 1 mV is generated due to the piezoresistance effect, a detection error of 50 Ganss will occur. J Normally at -30°C to 100°C] It fluctuated by more than O0Ganss, which was a problem.

[Means for solving problems]

The present invention aims to solve the problems of the prior art described above. For this purpose, we obtained a magnetic sensor with a small offset voltage as shown in Fig. 1 (tel, ib).

FIG. 1 (al and (bl) respectively show a plan view and a cross-sectional view of a magnetic sensor according to the present invention. 0 is a semiconductor chip. 1 and 2 are two Hall elements formed on the surface of the semiconductor chip. For example, it forms a MOS type.
In the sectional view shown in FIG. 1, reference numeral 11 denotes a substrate or lead frame on which the semiconductor chip 0 is mounted, and the semiconductor chip O is mounted via an adhesive 12. Thereafter, although not shown, the semiconductor chip 0 is wire-bonded and resin molded. Returning to the plan view again, the plurality of curves A are Newton rings on the surface of the semiconductor chip O observed by an optical interference microscope. This is Daihon 1′ knee tζ 2 yo 2
It is an iso-strain curve that shows the planar distribution of the generated strain. The fact that the line spacing becomes closer toward the periphery of the chip indicates that the stress (S11nos) in the periphery is large and therefore the strain is also large. Also, the dotted chain line r3 i is the central axis of symmetry of 1 semiconductor 1,000 knobs 0. Therefore, the direction of strain is also symmetrical with respect to this axis of symmetry.

Now, in the present invention, the Hall element 1 and the Hall element 2 are arranged on the same iso-strain curve and are arranged in symmetrical directions with respect to the axis of symmetry 13.

[Effect]

Since the two Hall elements are arranged on the same iso-strain curve, the amount of strain is the same, and therefore the magnitude of the offset voltage caused by the piezoresistive effect based on the strain is also equal.

Furthermore, since the two Hall elements are arranged symmetrically, the strain directions are opposite to each other, and therefore the offset voltages have opposite polarities. Therefore, if the two Hall elements are connected appropriately and the offset voltages are added, the offset voltage of the magnetic sensor as a whole is canceled out by -4 = cancellation, and the offset voltage becomes extremely small.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

In the fn magnetic sensor shown in Fig. 2, two Hall elements having almost the same characteristics are formed on the same chinobu-1, and are arranged on the same iso-strain curve A and arranged symmetrically with respect to the center line of the semiconductor chip. ing. The wires are connected so that the respective Hall voltages can be added, increasing the sensitivity and making it possible to cancel each offset voltage.

0 is a semiconductor chip, which is a P-silicon competitive crystal plate (1
00). 1 and 2 are Hall elements having almost the same characteristics. These Hall elements are formed, for example, as MOS type on the semiconductor chip 0''.

101 and 102 are drive current electrodes of the Hall element 1, and 101 is a drain through the P channel transistor 4. , and 102 is connected to the resistor 5 as a source.
Through ■5. (ground). The drive type l#t is indicated by the arrow small - J, 1, ·) from electrodes 101 to 10.
Flows towards 2. Similarly, 201 and 202 are drive current electrodes of the pole element 2, and 201 (train) is connected to von via the P-channel transistor 6.
202 (source) via n-channel transistor 7; (ground). The drive current flows from electrode 201 to 202 as shown by the arrow.

As can be seen from FIG. 2, since the pole element 1 and the Hall element 2 are arranged line-symmetrically, the directions of the drive currents flowing through each Hall element are opposite to each other. The polarity of is also opposite.This point will be explained further later.H and H2 are Hall output terminals of Hall element I and exhibit voltage fluctuations opposite to each other.I+ and 1]4 are Hall output terminals of Hall element 2. -t7 is a Hall output terminal and shows opposite voltage fluctuations. 3 is a comparator and Hall output terminal H2 shows opposite voltage fluctuations.
It inputs the signals from H3 and H3 and outputs the signal to the gate of the n-channel transistor 7.

Now, comparator 3 is Hall output 11□ of Hall element 1
and the voltage of the Hall output lI3 of the ball element 2,
The voltage of Hall output ■ is Hall output H.

The gate of n-channel transistor 7 is driven to equal the voltage of . When the resistance between the channels changes due to the gate voltage of the n-channel transistor 7, the voltages of the drive current terminals 201 and 202 of the Hall element 2 change in conjunction with this, and the voltage of the pole output 113 changes to the voltage of the Hall output 11□. is adjusted to be equal to

The resistor 5 keeps the voltage of the current drive electrode 102 of the Hall element l at a slightly higher voltage than the ground voltage, and the Hall outputs H2 and H
Regardless of the size of 3, it is inserted in order to activate the voltage adjustment function of ``comi''. Therefore, if the distance from the current drive electrode 101 of the pole element 1 to the Hall output terminal H+, Hz is made shorter than that of the Hall element 2, the resistor 5 can be omitted.

Note that the n-channel transistors 4 and 6 have the role of supplying the same constant current to the ball elements 1 and 2, respectively.

That is, the potential difference between the current drive electrodes of each of the Hall elements 1 and 2 is kept constant and equal to 2.

Now, FIG. 3 illustrates the operation when a magnetic field is applied to the magnetic sensor. When the Hall output voltages of the Hall elements 1 and 2 change due to an external magnetic field, a circuit including the comparator 3 shown in FIG. 2 operates to equalize the voltage 2 of the Hall output H and the voltage V3 of the Hall output H3. At this time, the voltages VDt and VSg of the current drive terminals 201 and 202 of the Hall element 2 maintain a constant potential difference, and the voltages of the Hall element 1 of Hall voltage Δ■□ minutes (i.e. V
2Vl) upward. Therefore, the Hall voltage V of the entire magnetic sensor, (that is, the Hall output ■■1 and H,
(potential difference) is Vo = (Vz
-Vl)+(V4 -V3) -2Δ■□. That is, each time the Hall voltages of the two Hall elements can be added.

Next, FIG. 4 illustrates the operation when no magnetic field is applied to the magnetic sensor. Offset voltage (■.z
Vow) occurs. Similarly, an off-cent potential (Va4Voz) is generated in the Hall element 2 as well. Although its size is exaggerated in the figure, it is actually on the order of mV or less. Now, since Hall element 1 and Hall element 2 are on the same iso-strain curve, the amount of strain they receive is approximately equal. Therefore, the Hall element I
Off-cent voltage (Voz Vow) and Hall element 2
The offset voltages (VO4Vo3) have the same absolute value.

Furthermore, the direction of the drive current of the pole element 1 and the direction of the drive current of the Hall element 2 are opposite to each other with the center line as a boundary, as shown in FIG. Offset voltage (V o z V
o + ) and the offset voltage of Hall element 2 (Vo4
The polarities of Voi) are also opposite to each other. As if the line segment ■ in Figure 4. 1. ■. 2 and ■. ,.

It is as if v04 exists symmetrically about the virtual center line B.

Now, from what has been described above, both offset voltages are canceled or offset by 11111'j by lv+ of the comparator 3 and the like mentioned above. As a result, the offset voltage of the entire magnetic sensor (that is, the difference in non-magnetic field special potential between Hall output 111 and Hall output 1' (4)) can be further reduced.

FIG. 5 shows another embodiment of the present invention in which the circuit configuration of the magnetic sensor shown in FIG. 2 is simplified. The same numbers correspond to the same numbers as in FIG. For the purpose of adding up the Hall voltages generated in the individual Hall elements, it is not necessary to simultaneously vary the voltages of both current drive electrodes 201 and 202 of the Hall element 2, as shown in FIG. In FIG. 5, only the voltage of the current drive electrode 202 of the Hall element 2 is changed to equalize the voltages of the Hall outputs H and H3. Even in this case, the individual Hall voltages are generally extremely small compared to the voltage applied between the current drive electrodes 201 and 202, so even if the voltage of the current drive electrode 202 fluctuates by the Hall voltage, the magnetic field of the Hall element 2 The sensitivity is considered to be the same as the magnetic sensitivity of the Hall element 1. Therefore, in this case as well, it is possible to obtain a total pole voltage output that is approximately twice the Hall voltage. Note that an n-channel transistor 9ε, to which a voltage of VB is applied to the gate, is used in the same way as the resistor 5 in FIG.

In the embodiment shown in FIG. 5 as well, Hall elements 1 and 2 are located on the same strain curve and are disposed opposite to each other on the left and right with the center line of the depth as a boundary. Therefore, the offset voltages of both Hall elements have the same absolute value and opposite polarity. Therefore, it is canceled by adding both offset and offset voltages.

Finally, the present invention is not limited to the arrangement in which two Hall elements are coupled, and three or more Hall elements may be used.

〔Effect of the invention〕

According to the present invention, since a plurality of Hall elements are arranged on the same semiconductor chip on the same strain curve and arranged symmetrically with respect to the center line of the chip, the offset voltages can be canceled out, and the offset voltage as a whole can be reduced. This has the effect of reducing the size and eliminating detection errors.

[Brief explanation of drawings]

Figures 1(a) and fbl are a plan view and a cross-sectional view of the magnetic sensor chip, respectively, Figure 2 is a diagram showing the arrangement and electrical connections of the magnetic sensor, and Figure 3 is a diagram of the magnetic sensor when an external magnetic field is present. FIG. 4 is a diagram illustrating the operation of the magnetic sensor in the absence of an external magnetic field, and FIG. 5 is a diagram illustrating another embodiment of the magnetic sensor. 0-1 Semiconductor chip 1.2- Hall element A----Equistrain curve B----Above the center line of the chip Applicant Seiko Electronics Co., Ltd.-12= Liu 2 diagram

Claims (2)

[Claims] (1) A magnetic sensor that is formed on a semiconductor chip and includes a plurality of Hall elements each consisting of first and second Hall output terminals and a pair of current drive electrodes that exhibit voltage fluctuations that are opposite to each other in response to an external magnetic field. A magnetic sensor characterized in that the plurality of Hall elements are arranged on the same iso-strain curve on the surface of the semiconductor chip and are arranged symmetrically with respect to the symmetry axis of the semiconductor chip. (2) There is a plurality of Hall elements, and the patent claim includes means for adjusting the potential of the current drive electrode of each Hall element in order to match the potentials of the first and second Hall output terminals between different Hall elements. A magnetic sensor according to scope 1.