JPH0372949B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thin film magnetic sensor in which two types of magnetic thin films with different coercive forces are stacked and formed by vacuum evaporation, electron beam evaporation, or sputtering evaporation, and a coil is provided using photolithography technology for these thin films. It is. That is, two layers of magnetic thin films made of Fe-Co-V are stacked with different composition ratios on a glass, porcelain, or silicon (Si) wafer with a non-magnetic oxide film on its surface. This thin-film magnetic sensor is constructed by forming a pickup coil on top of the pickup coil through an insulating film, and then molding it. Conventionally, many sensors using semiconductor materials, magnetic materials, etc. have been developed and put into practical use as magnetic sensors that detect the amount of change or change in an external magnetic field. For example, those using semiconductor materials,
There are Hall elements and FET elements. These are InSb,
Compounds such as GaAs, Si or Ge are mainly used. Items using magnetic materials include memory elements, magnetoresistive elements, and magnetic heads, including permalloy, sendust, Ni-Zn, and Mn-
Zn ferrite etc. are used. In addition, Japanese Patent Application Laid-open No. 53-137641 discloses that a magnetic wire is mechanically and thermally treated to change the magnetic properties of a layer near the surface of the magnetic wire (second magnetic part).
A magnetic device has been disclosed in which the coercive force is made larger than the magnetic property of the inside (first magnetic part) and the coercive force is wound around the coercive force. This is because the coercive force of the second magnetic portion is greater than the coercive force of the first magnetic portion. That is, it has a structure in which a magnetic part with a small coercive force is covered in the circumferential direction by a magnetic part with a large coercive force. For example, when this magnetic device changes the magnitude and direction of an external magnetic field in the longitudinal direction of a wire, the part with a large coercive force interacts magnetically with the part with a small coercive force, so the direction of magnetization of both changes. When the magnetic field is in the same direction but opposite to the external magnetic field, the magnetization reversal of the part with a small coercive force occurs in an external magnetic field that is greater than the coercive force H _C1 and smaller than the coercive force H _C2 of the part with a large coercive force. Also, the magnetization direction of the external magnetic field and the part with large coercive force are the same,
If only the magnetization direction of the parts with low coercive force is opposite to those, the parts with high coercive force will help the magnetization reversal of the parts with low coercive force, and the magnetic field of about H _C1 will cause the magnetization to change more rapidly. Then, magnetization reversal occurs in the part where the coercive force is small. An electromagnetic induction phenomenon occurs due to magnetization reversal due to the influence of an external magnetic field in these parts with low coercive force, and a current is generated in the pickup coil wound around the wire, causing a small pulse voltage in the former case, a small pulse voltage in the latter case A large pulse voltage can be obtained. The magnitude and steepness of this pulse voltage are far superior to those made of the first magnetic material. In addition, for those made of a single magnetic material, the width of the pulse generated in the pick-up coil depends on the speed of change of the external magnetic field; the slower the speed, the wider the pulse.
It is not possible to obtain a constant pulse voltage, as the faster it is, the narrower it is. In this way, the one published in Japanese Patent Application Laid-Open No. 53-137641 is
Although magnetic devices have excellent characteristics, their manufacturing methods are complicated, and it is difficult to manufacture them with a high yield. Also, although a thin wire with a diameter of 250 microns is used, it would be very difficult or even impossible to create smaller devices. Furthermore, when creating a matrix by arranging a large number of such devices or creating a magnetic sensor that detects a minute magnetic field, it is not possible to create a magnetic device suitable for this purpose. The present invention seeks to significantly solve these problems and difficulties. That is, by forming a thin film structure, (1) it is possible to create a minute magnetic sensor with a size of several microns to several tens of microns. (2) Since the integration density can be increased, a matrix consisting of a large number of sensors can be formed at a high density. (3) Manufacturing is easier. (4) Highly mass-producible. It provides excellent features such as: An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the configuration of an embodiment of the present invention. The thin film magnetic sensor of this embodiment is made of Fe-Co-V, and two magnetic thin films 2 and 3 with different coercive forces are formed on a substrate 1 shown in FIG. 2 by vacuum evaporation, electron beam evaporation, or sputtering evaporation. Precipitates in layers. In order to vary the coercive force, the component ratio of the Fe-Co-V composition is changed. A partial investigation of the relationship between the composition and coercive force of the Fe--Co--F magnetic material revealed that it was roughly as shown in Figure 1. In this region, the amount of V added most effectively influences the coercive force. Therefore, the structure consists of two layers of magnetic thin films with different coercive forces, that is, the magnetic thin film 2 with a small coercive force and the magnetic thin film 3 with a large coercive force, but even if the difference in size is too large, the resulting pickup coil It is difficult to obtain the generated pulse voltage. In experiments conducted by the inventor, the coercive force of a magnetic thin film with a large coercive force (hereinafter referred to as a hard film) is approximately 5 times that of a magnetic thin film with a small coercive force (hereinafter referred to as a soft film). Pulse characteristics were obtained over a range of about 20 times. However, when the magnification is further increased, the pulse voltage gradually becomes smaller. Furthermore, even if the magnification is made smaller than this, the pulse voltage becomes smaller and the pulse width becomes wider, probably because the interaction between the soft film and the hard film is weak. This is because if the coercive force of the hard film is too large, the magnetization direction of the soft film is forcibly directed to the magnetization direction of the hard film even in the absence of an external magnetic field, making it difficult to obtain a pulse voltage. Furthermore, if the coercive force of the hard film is larger than but close to that of the soft film, it will not be possible to effectively suppress or assist magnetization reversal of the soft film in response to an external magnetic field, and the pulse voltage will be close to that of a single film. It seems that you will be able to get it. In order to effectively generate an interaction between the coercive forces of the soft film and the hard film in response to an external magnetic field, it is preferable to select the component ratio of the soft film and the hard film to the above-mentioned ratio in FIG. That is, the composition of the soft film is Fe: 35 to 52% by weight, Co: 41 to 63% by weight, V: 1 to 8% by weight, and the composition of the hard film is Fe: 25 to 51% by weight,
Co: 40-63% by weight, V: 2-15% by weight. Note that the combination of coercive forces of magnetic materials other than these Fe-Co-V composition ratios can be chosen appropriately, but as will be described later, if the coefficient of thermal expansion of the substrate is significantly different from that of the magnetic film, the two-layer When deposited as a film, the apparent coercive force changes, making it difficult to decide on the combination of the soft film 2 and hard film 3, and making it difficult to produce stably under various production conditions. Such soft film 2 and hard film 3 are formed by vapor deposition on substrate 1 by the method described above, but if the magnetization directions of the films are isodirectional, desired pulses cannot be obtained. Both films have easy axes of magnetization and must be parallel to each other. In order to make the film have easy magnetization axes and to make the directions parallel to each other, it is necessary to form the film using a method such as evaporation in a magnetic field. In addition, when forming the soft film 2 and hard film 3 on the substrate 1, they are deposited in a vacuum chamber, but at this time, moisture and
Or an oxide film caused by other adsorbed gases, etc.
Alternatively, if a layer is formed whose magnetic properties have significantly changed due to strain or the like, interaction between the two films cannot be obtained. To prevent this, it is necessary to deposit the soft film 2 and the hard film 3 in succession in the same tank without breaking the vacuum. Furthermore, since strain greatly changes even the magnetic properties of the film itself, it is important to match the coefficient of thermal expansion, which is a physical constant, of the substrate 1 as much as possible, especially with that of the soft film. Furthermore, if the thermal expansion coefficient of the hard film 3 is not significantly different from that of the substrate 1 or the soft film, variations in the magnetic field in which pulses are generated will be reduced. If the hard film 3 is formed on a substrate and then the soft film 2 is formed overlappingly, even if the thermal expansion coefficient of the substrate 1 is made to match the value of the soft film 2 as much as possible in advance, it will not be directly affected by the hard film 3. As a result, a large amount of strain is applied to the soft film 2, and its magnetic properties vary. This is also sensitive to the thickness of the hard film 3. However, if the soft film 2 is deposited on the substrate 1 and then the hard film 3 is formed on top of the soft film 2, these effects can be improved. The two magnetic thin films 2 and 3 thus formed overlappingly on the substrate 1 can be easily formed into, for example, a tanzag shape of an appropriate size by using a photolithography technique. In this example, AZ1350J manufactured by Shipley Co., Ltd. was used as the photoresist, and a 40 micron x 250 micron strip-shaped photoresist was created.
The magnetic film was etched using an aqueous solution of iron chloride. A SiO ₂ film 4 is formed on the entire surface of the magnetic thin films 2 and 3 made up of two layers in the shape of a tangent by sputtering vapor deposition in order to provide electrical insulation. The thickness of the SiO ₂ film 4 was approximately 5000 Å. Next, an Al film for forming a pick-up coil was deposited on the entire surface of the SiO ₂ film 4, and then a pick-up coil 5 was formed on the strip-shaped magnetic thin films 2 and 3 by photolithography. Note that 6 and 6' in FIG. 2 are electrode pads. Examples of the present invention will be specifically described below. Example 1 Fe:Co:V=35~ as magnetic material for soft film
Those with a composition ratio of 52:41 to 63:1 to 8 (weight ratio),
Fe:Co:V=25～ as magnetic material for hard film
The composition ratio of 51:40 to 63:2 to 5 (wt%) was used. For the substrate 1, borosilicate glass was used. The thermal expansion coefficient of this substrate 1 is approximately 55
It can vary from 10 ^-7 /°C to 80×10 ^-7 /°C. A soft film 2 with a thickness of 3000 Å was deposited on the substrate 1 by electron beam evaporation, and then a hard film 3 with a thickness of 2500 Å was deposited over the soft film 2. Various combinations of soft film 2 and hard film 3 were deposited as shown in Table 1. This two-layer film is 40 microns
It was formed into a 250 micron strip using photolithography technology. Etching was carried out using water-soluble ferric chloride. Next, a SiO ₂ film 4 was deposited on the entire surface of the tangle-shaped magnetic thin film by a sputtering method. this
The thickness of the SiO ₂ film 4 was approximately 5000 Å. The coil 5 was formed by depositing Al on the entire surface of the substrate in a vacuum state. Al film thickness is 0.8
Micron, the number of turns was 8 turns. Next, they are cut into chips using a dicing machine, and then mounted on a lead frame.
25 micron Al wire to coil electrode pad 6,
6' and the lead frame for connection by wire bonding and finally molding. The device made in this way was placed in a solenoid, an external magnetic field was applied, and the voltage of the aforementioned pulses generated at both ends of the pickup coil was measured. FIG. 4 shows a measuring device for measuring pulse voltage. In the figure, 11 is a power source for applying an alternating voltage, 12 is a solenoid coil to which the alternating voltage is applied, and 13 is arranged inside the solenoid coil 12. 14 is a two-layer magnetic thin film provided on the thin film magnetic sensor 13; 15 is a pick-up coil; 16 is an electrode of the pick-up coil; 17;
is an oscilloscope for evaluating the pulses generated at both ends of the pickup coil 16. To explain the operation of this measuring device, first, when an alternating voltage is applied to the solenoid coil 12 by the power supply 11, an alternating magnetic field is generated within the solenoid coil 12. This alternating magnetic field is applied in one direction within the plane of the magnetic thin film 14 of the thin film magnetic sensor 13 disposed within the solenoid coil 12 . The magnetic thin film 14 is magnetized by the solenoid coil 1 due to magnetization reversal.
A pulse is generated at both ends of the electrode 5, and the pulse waveform can be observed with an oscilloscope 17 via an electrode 16. Table 1 shows the measurement results when a 1 KHz sine wave current was passed through the solenoid coil 15 to generate an external magnetic field. In this measurement, as shown in FIG. 5, the waveform of the pulse voltage in the external magnetic field is such that a pulse H _P with a high voltage value and a pulse L _P with a low voltage value are obtained with respect to the alternating magnetic field G.

[Table] Example 2 Using the magnetic material for soft film and the magnetic material for hard film used for sample No. 12 in Example 1, a borosilicate glass substrate 1 was prepared by electron beam evaporation.
A two-layer magnetic thin film is formed by first depositing a soft film on top and then depositing a hard film on top of it, and a second case in which a hard film is deposited first and then a soft film is deposited on top of it to form a two-layer magnetic thin film. A comparison was made with respect to the case where a magnetic thin film was formed. The method after the step of forming the magnetic thin film into a strip shape was the same as in Example 1. The thickness of the soft film and hard film is 3000mm each.
Å, 2500 Å. As a result, when the hard film was deposited first, even if the external magnetic field was made larger than the coercive force of the hard film, large and steep pulse characteristics could not be obtained, and only a small pulse of about 26 μV was obtained. If the soft film is formed first,
A pulse voltage as large as 1.75 millivolts and a pulse width of less than 0.1 microseconds were obtained. The relationship of pulse voltage to external magnetic field is expressed as
As shown in the figure. Two types of pulses with different sizes were obtained in the region where the external magnetic field was small. Example 3 For the sample No. 12 of Example 1, the magnetic thin film was formed as follows. That is, after a soft film was first deposited on the substrate, the vacuum of the vacuum chamber was broken and the film was once exposed to normal pressure air, and then this was put back into the vacuum to deposit the hard film on top of the soft film. The process of forming these two layers into a tanzak shape was carried out in the same manner as in Example 1. The thin film magnetic sensor thus created was placed in an external magnetic field and driven. As a result, even when a magnetic field greater than the coercive force of the hard film was applied, large and steep pulses could not be obtained. As shown in the examples above, in the present invention, the soft film and the hard film are deposited first by changing the composition ratio of Fe, Co, and V, and by appropriately selecting the thermal expansion coefficient of the substrate. Then, by depositing a hard film on top of the soft film, a large and steep pulse voltage can be obtained in the pick-up coil in response to changes in the magnitude and direction of the external magnetic field. Thin-film magnetic sensors with these characteristics are more effective than thin-film magnetic sensors that utilize magnetoresistive characteristics or Hall elements that utilize the Hall effect.
No load and high output voltage. Furthermore, since the output is obtained in the form of a pulse, it is useful as a sensor for obtaining digital signals. Furthermore, by making the film thinner, it can be miniaturized, making it useful for integrated circuits such as ICs.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the composition ratio of Fe-Co-V system, coercive force, and saturation magnetization, FIG. 3 is a diagram showing the relationship between the external magnetic field and pulse voltage of the thin film magnetic sensor created according to the present invention, FIG. 4 is a schematic diagram showing the configuration of a measuring device for measuring pulse voltage, and FIG. The figure is a waveform diagram of pulse voltage in an external magnetic field. 1...Substrate, 2, 3...Magnetic thin film, 4...
SiO ₂ film, 5...coil.

Claims (1)

[Claims] 1. On the substrate, Fe:Co:V=35-52:41-63:
A first magnetic layer film having a composition ratio of 1 to 8 (wt%) and a low coercive force is formed, and Fe:Co:V=25 to 51:40 to 63:2 is formed on the first magnetic layer film. A second magnetic layer film with a large coercive force of ~15 (wt%) is formed, and a pick-up thin film coil constructed using photolithography technology is provided on top of the second magnetic layer film with a non-magnetic film that is an electrical insulator. A thin film magnetic sensor characterized by: 2. The thin film magnetic sensor according to claim 1, wherein the ratio of the magnitude of coercive force of the first and second magnetic thin films having different coercive forces is 5 to 20 times.