JPH11251657A - Magnetic sensor and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To the input resistance to be higher, by forming a magnetically sensitive layer on the (111)-plane of a semiconductor substrate of a magnetic sensor having the InSb magnetically sensitive layer. SOLUTION: An InSb magnetically sensitive layer 2 is formed crosswise on a GaAs(111)A-plane substrate 1 with Ohmic electrodes 3a-3d provided at the four top ends. The Ohmic electrodes 3a-3d have steps along the surface shape of the InSb magnetically sensitive layer 2, and a protective film 4 is provided on an exposed face of the GaAs(111)A-plane substrate 1 and that of the InSb magnetically sensitive layer 2. A (111)A-InSb hall element is formed on the InSb magnetically sensitive layer 2 formed on the GaAs(111)A-plane substrate 1 and revealed a very high input resistance measured between the electrodes 3a at room temp. 4.5 times as high as that of the conventional one, and hence the input resistance can be made high by forming a magnetically sensitive layer on the (111)-plane of a semiconductor substrate, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic sensor utilizing the Hall effect and a method of manufacturing the same, and more particularly to a magnetic sensor used for detecting the position of a device such as a brushless motor and a method of manufacturing the same.

[0002]

2. Description of the Related Art A brushless motor used for driving a CD-ROM or a VTR (video tape recorder) is a rotor having a permanent magnet formed in a cylindrical shape, a stator having two or more permanent magnets arranged symmetrically close to each other. It is composed of a drive coil (armature) wound around the stator, a yoke for fixing the stator, and the like, and is characterized in that it has no brush. A rotating magnetic field is formed by switching the current applied to the driving coil in a commutation circuit configured using an IC, a transistor, and the like, and the rotor is rotated by the permanent magnet. In the brushless motor, the armature must be excited in accordance with the position of the magnetic poles (N, S) of the rotor in order to maintain a relationship in which a rotational force is always generated between the permanent magnet and the armature. In general, a Hall sensor is used to detect the magnetic pole position of the rotor. The Hall sensor is disposed at a position facing the rotor at the tip end surface of the stator, and a Hall output voltage (rotor position signal) is output each time the magnetic pole of the rotor passes. Occurs.

A Hall sensor is a magnetic sensor made of GaAs (gallium arsenide) or InSb (indium antimonide), which is a III-V semiconductor crystal having high mobility in a semiconductor chip. Specifically, the semiconductor chip is configured by providing four ohmic electrodes on one surface of the semiconductor chip, a DC power supply is connected between a pair of electrodes, and an output terminal is formed between the other pair of electrodes. When a magnetic field is applied in the thickness direction of the semiconductor chip with the Hall input current flowing from the DC power supply, a Hall output voltage corresponding to the magnitude of the magnetic field is output.

[0004] InSb has a band gap of 0.1 at room temperature.
Since the electron concentration is as narrow as 18 eV, the electron concentration is as high as about 2 × 10 ¹⁶ cm ⁻³ even if impurity doping is not performed.
The mobility of electrons in b is also 75,000 cm ² / Vs and III
It is the largest among -V compound semiconductors. For this reason, the resistivity of InSb, which is given by the reciprocal of the product of the electron concentration and the electron mobility, is extremely smaller than the resistivity of another compound semiconductor such as GaAs. Therefore, a Hall element having InSb as a magnetic sensing part (hereinafter referred to as “InSb Hall element”) tends to have a low input resistance.

The power W consumed by the InSb Hall element in the constant voltage drive is given by the following equation, where I is the current, V is the voltage, and R is the resistance. W = IV = V ² / R As is clear from the above equation, when the value of the resistor R is small, the power consumption W increases in inverse proportion to the value.

[0006]

However, according to the conventional magnetic sensor, the input resistance of the InSb Hall element is low, so that there is a problem that power consumption becomes large at the time of constant voltage driving. Generally, when a semiconductor element is used in a high-temperature environment, carriers are thermally excited, so that the carrier concentration in the semiconductor tends to increase. In particular, a semiconductor having a narrower band gap, such as InSb, has a larger tendency. Therefore, when an element having low resistance and high power consumption, that is, an element having a large amount of heat generation, is used at a certain temperature or higher, the carrier concentration increases → resistance decreases → heat generation increases → carrier concentration increases → A vicious cycle that repeats the situation can eventually lead to destruction. As described above, the InSb Hall element having a low input resistance has a problem that the reliability of operation at a high temperature is lacking.

Accordingly, it is an object of the present invention to provide a magnetic sensor capable of increasing the input resistance and a method for manufacturing the same.

[0008]

According to a first aspect of the present invention, there is provided a magnetic sensor having a magnetosensitive layer formed of InSb, wherein the magnetosensitive layer is formed of a semiconductor. (11) of substrates such as substrates and semi-insulating substrates
1) To provide a magnetic sensor characterized by being formed on a surface.

In order to achieve the above object, the present invention provides, as a second feature, a substrate having a (111) plane;
Cross-shaped InSb formed on the (111) plane of the substrate
A magnetic sensor comprising: a magnetic sensing part layer; and ohmic electrodes formed at respective cross-shaped ends of the InSb magnetic sensing part layer. In order to achieve the above object, the present invention provides, as a third feature, (1)
11) Growing an InSb film on the surface, performing a cross-shaped etching on the InSb film to form an InSb magnetic sensing layer, and forming ohmic electrodes at four terminal portions of the magnetic sensing layer. A method for manufacturing a magnetic sensor is provided.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cubic lattice crystal direction for describing a method of manufacturing a magnetic sensor according to the present invention. In the figure, [] indicates a direction index, and () indicates a plane orientation.
Conventionally, when an InSb thin film is grown on GaAs to form a magnetosensitive layer, as shown in FIG.
InSb so as to be oriented to the (100) plane of the s cubic lattice
Was growing. However, we questioned whether this (100) plane selection is optimal or not.
InSb thin films were grown from each direction of the GaAs cubic lattice, and the input resistance was measured. As a result, FIG.
InS grown so as to be oriented on the (111) plane shown in FIG.
It has been found that a high input resistance can be obtained when the thin film b is used for the magneto-sensitive layer of the Hall element.

In particular, the InSb formed on the (111) plane of GaAs has an input resistance four times or more higher than that of InSb having the same thickness formed on the (001) plane of GaAs. Has been found. With such a high input resistance, power consumption is reduced. By reducing power consumption, the possibility of self-destruction due to heat generation can be reduced.

The InSb thin film is made of MBE (Molecular Beam).
Epitaxy: molecular beam epitaxy, MOVPE (Meta
l Organic Vapor Phase Epitaxy)
It can be formed by a method or an evaporation method. The GaAs substrate belongs to a zinc-blende type crystal structure. In addition to GaAs, a diamond type crystal structure,
A semiconductor having a zinc blende crystal structure or a wurtzite crystal structure can be used for the substrate. In either case,
An InSb thin film is formed on the (111) plane.

[0013]

Next, examples of the magnetic sensor of the present invention and a method for manufacturing the same and evaluation results will be described. First, a substrate temperature of 380 to 480 ° C. and a growth rate of 0.1 to 3.0 μm / m are formed on a semi-insulating GaAs (111) A-plane substrate (that is, a gallium plane of (111) plane orientation) by molecular beam epitaxy. h, Under the condition that the molecular beam intensity ratio of indium (In) as a group III atom and antimony (Sb) as a group V atom is V / III = 1.5 to 6.0, an InSb film having a thickness of 0.15 μm is formed. Grew.

Next, the semi-insulating GaAs substrate (11)
1) InSb formed on the A surface was processed into a cross shape by etching. In order to protect the magnetosensitive layer made of InSb, a SiO ₂ film was formed on the surface thereof by vapor deposition. Furthermore, the protective films at the four terminal portions of the cross-shaped magnetic sensing layer were removed, and the ohmic contact with Au / Ge was adjusted so that the ratio between the interelectrode distance and the width of the InSb magnetic sensing layer was 1.1. An active electrode was attached by vapor deposition to produce a Hall element.

FIG. 2 shows a magnetic sensor according to the present invention.
This figure shows a state in which an InSb magnetosensitive layer formed by etching is provided on an aAs substrate. Further, FIG.
The I-II cross section is shown. In FIG. 3, 1 is GaAs (1
11) A-side substrate, on which the InSb magnetosensitive layer 2 is formed in a cross shape. As shown in FIG. 2, ohmic electrodes 3a, 3b, 3c, and 3d are provided at the four tips of the InSb magnetosensitive layer 2. As shown in FIG. 3, the ohmic electrodes 3a to 3d
There is a step along the surface shape of the nSb magnetosensitive layer 2. Exposed surface of GaAs (111) A-plane substrate 1 and InS
The protection film 4 is provided on the exposed surface of the b-sensitive layer 2.

The present inventors have proposed a semi-insulating GaAs (10
(0) InSb formed on the surface substrate was used as the magnetosensitive layer (1).
00) -InSb Hall element (conventional product whose manufacturing method is as described above except that the selected crystal plane is different from the present invention =
Comparative Example) and semi-insulating GaAs by the method of the present invention described above.
A (111) A-InSb Hall element (product of the present invention) in which InSb formed on the s (111) A plane substrate 1 was used as the magnetosensitive layer 2 was prepared. Electrodes 3 of these two types of Hall elements
The resistance between a and the electrode 3c was measured at room temperature. Table 1 shows the results.

[0017]

[Table 1]

As shown in Table 1, (111) A-I
The nSb Hall element exhibited an extremely large input resistance value of about 4.5 times as compared with the (100) -InSb Hall element. At room temperature, a voltage of 2 V is applied between the electrodes 3a and 3c of these two types of Hall elements, a magnetic east density of 0.1 T is applied from the upper surface of the Hall elements, and a voltage between the electrodes 3b and 3d of the Hall elements is increased. The results shown in Table 2 were obtained by measuring the Hall electromotive force generated in the above.

[0019]

[Table 2]

The magnitude of the Hall electromotive force indicates the sensitivity of the device. As is clear from Table 2, (11)
1) The Hall electromotive force of the A-InSb Hall element is (10
0) It is higher than the Hall electromotive force of the -InSb Hall element. From the above results, semi-insulating GaAs (11
1) The Hall element according to the present invention using InSb formed on the A-plane substrate as the magnetosensitive layer 2 is a semi-insulating GaAs (10
0) It has been found that the input resistance can be increased by a factor of four or more while maintaining an output Hall voltage equal to or higher than that of a conventional Hall element using InSb formed on a surface substrate as a magnetosensitive layer.

InS, which is the magnetic sensing part 2 of these Hall elements,
It was also found that the thickness of the b layer is desirably 0.05 to 2.0 μm. InS, the magneto-sensitive part of the Hall element
The same applies to the case where a GaAs (111) B surface substrate, an InP (111) A surface substrate, an InP (111) B surface substrate, a Si (111) substrate, a Ge (111) substrate, or the like is used as the substrate for forming the b layer. The effect was obtained.

The magnetic sensing part of these Hall elements, I
C (carbon), Si (silicon), S as impurities in the nSb layer
Similar effects were obtained by doping (sulfur), Ge (germanium), Te (tellurium), or Se (selenium) or by ion implantation. And
These impurity concentrations are 1.0 × 10 ¹⁴ cm ⁻³ or more.
Good results are obtained with less than 0 × 10 ¹⁹ cm ⁻³ .

[0023]

As is clear from the above, according to the magnetic sensor and the method of manufacturing the same of the present invention, the magnetosensitive layer made of InSb is formed on the (111) plane of a substrate such as a semiconductor substrate or a semi-insulating substrate. A magnetic sensor or a substrate having a (111) plane, and In grown on the (111) plane of the substrate.
An Sb layer and a cross-shaped InS formed on the InSb layer.
a magnetic sensor comprising a magnetic sensing layer b and ohmic electrodes formed at each of the cross-shaped ends of the InSb magnetic sensing layer, or on a substrate with a plane orientation of (111). A method for manufacturing a magnetic sensor in which an InSb film is grown on the substrate and a cross-shaped etching is performed on the InSb film to form an InSb magnetosensitive layer, the input resistance can be increased, and power consumption can be reduced. Therefore, reliability in operation in a high-temperature atmosphere can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a crystal direction of a cubic lattice for explaining a method of manufacturing a magnetic sensor of the present invention.

FIG. 2 is a plan view showing a magnetic sensor according to the present invention.

FIG. 3 is a sectional view showing a II-II section of FIG. 2;

[Explanation of symbols]

 Reference Signs List 1 GaAs (111) A surface substrate 2 InSb magnetosensitive layer 3a, 3b, 3c, 3d Ohmic electrode 4 Protective film

Claims (9)

[Claims] 1. A magnetic sensor having a magnetic sensing layer formed of InSb, wherein the magnetic sensing layer is formed on a (111) plane of a substrate such as a semiconductor substrate or a semi-insulating substrate. Characteristic magnetic sensor. 2. A substrate having a (111) plane, and a cross-shaped InSb formed on the (111) plane of the substrate.
A magnetic sensor comprising: a magnetic sensing layer; and ohmic electrodes formed at respective cross-shaped ends of the InSb magnetic sensing layer. 3. The magnetic sensor according to claim 2, wherein the substrate is a GaAs substrate. 4. The method according to claim 1, wherein the substrate has a diamond-type crystal structure,
3. The magnetic sensor according to claim 2, wherein the magnetic sensor has a zinc blende type crystal structure or a wurtzite type crystal structure. 5. An InSb film is grown on the (111) plane of the substrate, and the InSb film is subjected to a cross-shaped etching.
A method for manufacturing a magnetic sensor, comprising: forming a magnetic sensing layer; and forming ohmic electrodes at four terminal portions of the InSb magnetic sensing layer. 6. The method according to claim 5, wherein a substrate having a diamond-type crystal structure, a zinc-blende-type crystal structure, or a wurtzite-type crystal structure is used as the substrate. 7. The method according to claim 5, wherein GaAs is used as the substrate. 8. The formation of the InSb magnetosensitive layer is performed by MBE.
6. The method for manufacturing a magnetic sensor according to claim 5, wherein the method is performed using an MOVPE method, or an evaporation method. 9. The method according to claim 5, wherein, when forming the InSb film, C, Si, Ge, S, Te, or Se is doped or ion-implanted as an impurity.