JPS59114413A - Magnetic detector with magneto-resistance element - Google Patents

Abstract

PURPOSE:To improve the detection accuracy remarkably with an equal magnetic characteristic by coinciding magneto-resistance elements stacked precisely in the dimensions and shape while the magneto-resistance elements arranged side by side are made of the same magneto-resistance film. CONSTITUTION:First and second magneto-resistance elements MR1 and MR2 are formed by patterning a first magneto-resistance film provided on a silicon substrate S and third and fourth magneto-resistance elements MR3 and MR4 are formed so as to align with the magneto-resistance elements MR1 and MR2 by patterning a second magneto-resistance film separated from the first magneto- resistance film through insulation film INS. These first-fourth magneto-resistance elements are connected so that the first and third magnetic resistance elements and the second and fourth magneto-resistance elements constitute bridges to be biased to each other magnetically.

Description

[Detailed Description of the Invention] A magnetic detection device comprising a magnetoresistive element for reading information recorded on a magnetic recording medium such as a magnetic tape or a magnetic disk. It is related to vessels.

As a magnetic detector equipped with such a magnetoresistive element, a device in which two layers of magnetoresistive elements were placed on top and bottom with an insulating film sandwiched between them, and magnetic bias was applied to each other, was proposed.
It is described in Japanese Patent No. 37204 and Japanese Patent No. 53-37205, and is well known. For example, Tokuko Sho 53-3
In the magnetic detector described in Publication No. 7204, 2N magnetoresistive elements are stacked one above the other, and a bias magnetic field is applied to the other magnetoresistive element by a magnetic field generated by a drive current flowing through one magnetoresistive element. , this is hereinafter referred to as the primary bias method. Furthermore, in the magnetic detector described in Japanese Patent Publication No. 53-87205, a magnetic field generated by a drive current flowing through one magnetoresistive element is applied to the other magnetoresistive element, and the magnetization in the other magnetoresistive element is changed. One component generates a reverse magnetic field, and this reverse magnetic field is applied to one of the magnetoresistive elements as a bias magnetic field.This is hereinafter referred to as a secondary bias method.

Figure $1 is a circuit diagram of a magnetic detector described in the above-mentioned Japanese Patent Publication No. 58-87204. First and second magnetoresistive elements MR arranged in #Ii layers above and below with an insulating film interposed therebetween
I and MB2 are connected in parallel between the constant current source S and the ground potential, and the constant current source S and the magnetoresistive elements MRI and MB2 are connected in parallel.
The difference between the voltages v0 and v2 appearing at the connection point between the two is determined by a differential amplifier DA.

Such a mutual magnetic bias type magnetic detector is constructed by sequentially depositing a first magnetoresistive film, an insulating film, and a second magnetoresistive film on a glass substrate, for example, but it does not provide stable detection output. In order to obtain this, it is necessary that the first and second magnetoresistive films have the same magnetic properties. A method for manufacturing such a magnetic detector is to deposit a first magnetoresistive film and an electrode film on a substrate, pattern it by photo etching, etc., then deposit an insulating film, and then deposit a second magnetoresistive film on the substrate. A commonly considered method is to deposit a resistive film and an electrode film and then pattern them.

However, in such a manufacturing method, the first and second magnetoresistive elements are formed from different magnetoresistive films, so that the film thickness, specific resistance, temperature coefficient of resistance, etc. are the same.
<, there is a drawback that the magnetic properties are not uniform. Furthermore, since the first and second magnetoresistive elements are formed by patterning in separate steps, they have poor dimensional accuracy and do not have the same dimensions, resulting in a disadvantage that differences appear in their magnetic properties.

Therefore, an unbalanced voltage, which is an output voltage in the absence of a magnetic field, is generated, and this voltage drifts depending on the temperature, so that accurate magnetic detection cannot be performed.

Furthermore, in such a magnetic detector, in order to obtain a detection output with a large gain and a high S/N ratio, it is necessary to flow a large current through the magnetoresistive element, but it is necessary to reduce the thickness of the magnetoresistive element. If the dimensions are made smaller and the detection sensitivity and resolution are increased, a large current cannot flow. This is because when a large current flows, the Joule heat generated thereby is accumulated in the magnetoresistive element, deteriorating its characteristics.

Therefore, conventional magnetic detectors have the drawback of not being able to pass a large drive current and having low detection sensitivity.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and improve the film thickness.

The magnetic detector is configured so that it can perform accurate magnetic detection even if there are differences in magnetic properties such as specific resistance and temperature coefficient of resistance, and can also conduct high-sensitivity magnetic detection by passing a large drive current. This is what we are trying to provide.

The magnetic detector of the present invention includes first and second magnetoresistive elements formed by patterning a first magnetoresistive film provided on a silicon substrate, and a magnetoresistive element formed by patterning a first magnetoresistive film provided on a silicon substrate. eighth and fourth magnetoresistive elements formed by patterning a second magnetoresistive film separated by the above-described method so as to be aligned with the first and second magnetoresistive elements; The fourth magnetoresistive element is connected so that the first and eighth magnetoresistive elements and the second and fourth magnetoresistive elements magnetically bias each other and form a bridge circuit. It is something.

Hereinafter, the present invention will be described in detail with reference to the drawings.・Second
Figure A is a diagrammatic plan view showing the configuration of an example of the magnetic detector of the present invention, and Figure 2B is a diagrammatic perspective view. Figure 2A
In FIG. 2 and B, the upper insulating layer is omitted for clarity, and in FIG. 2A, the magnetoresistive film is shown with diagonal lines.

In this example, four magnetoresistive elements MRI to MR4 are provided, and the elements MRI and MB2 and MB3 and MB2 are formed by patterning the same magnetoresistive film, respectively, and the elements MRI and MB3 and MB2 are formed by patterning the same magnetoresistive film. MB2 is stacked one above the other. These elements are formed on a silicon substrate S, and the elements MR1, MR1 and MB2,
An insulating film INS is interposed between it and MB2. The four magnetoresistive elements MRI to MR4 are connected to form a bridge circuit as shown in FIG. 2C. That is, one ends of the lower elements MRI and MB2 are connected to the conductor L1 at contacts C1 and 02, and this conductor is connected to the terminal T]. One end of the upper elements MR8 and MB2 is a contact point C
3 and C4 to conductor L2, which is connected to terminal T2.4. The other end of the lower element MHI is connected to terminals Ta& through contact C5 and conductor L3.
The other end of upper element MR8 is connected to terminal T4 via contact C6 and conductor L4, the other end of lower element MR2 is connected to terminal T5 via contact C7 and conductor L5, and the other end of upper element MR4 is connected to terminal T5 via contact C7 and conductor L5. is connected to terminal T6 via contact C8 and conductor L6. In FIG. 2A, the contacts for the lower elements MRI and MR2 are shown with double frames. 9J12 As shown in Figure C, terminals T1 and T2 are the output terminals of the bridge circuit and are connected to the differential input terminals of the differential amplifier DA, terminals T3 and T4 are commonly connected to the positive terminal of the power supply E, Terminals T5 and T6 are commonly connected to the negative terminal. Therefore terminals T8 and T4 and T5 and T6
can be made into one terminal each, but in order to perform short-circuit tests of magnetoresistive elements during the manufacturing process, etc.
It is preferable to provide separate terminals as described above. In such a configuration, the mutual bias due to the secondary bias effect is generated between elements MHI and MR8 in FIG. 2C.
A bias magnetic field directed upward from the bottom of the page is applied to elements MR2 and MR4, and a bias magnetic field directed downward from the top of the page is applied to elements MR2 and MR4, resulting in a coupling that yields an output signal. Therefore, a magnetic detection output can be obtained with high sensitivity from the output terminal of the differential amplifier DA without being affected by noise. Furthermore, although a silicon substrate is used as the substrate S, silicon has a thermal conductivity 10 times higher than that of glass, so it has a high heat dissipation effect and can effectively dissipate the Joule heat generated by the magnetoresistive element. I can do it. Therefore, since a large drive current can be passed, there is an advantage that detection sensitivity is extremely high. Another advantage of silicon substrates is that they are difficult to obtain of high quality in the field of manufacturing semiconductor devices.

Next, consider the unbalanced voltage in the magnetic detector of this example. Now, connect the first and second elements MRI and MR2 □
The specific resistance with temperature coefficient of the first magnetoresistive film is ρ, (T), the film thickness is t□, and the third and fourth elements M
The specific resistance of the second magnetoresistive film constituting R3 and MR4 is R2(T), the film thickness is R2, and the pattern shape coefficient (i.e. length 7 width) of the first and eighth elements MHI and MR8 is If □ and the turn shape coefficient of the second and third elements MR2 and MR4 are 2, then the resistance values R1 to R- of the first to fourth magnetoresistive elements MRI to MR4 are as follows. Become.

Ro-ρ□(T)・k,/l R2-ρ□(Tl・k 2/l l R8-R2(T)・k1/12 R1-R2(T)・k2/12 Therefore, the detected magnetic field is If there is no complaining mine, the pressure ΔV is as follows: ΔV−V knee v2 S ρ, (T)・k, /lt+ρ□fTl・k,/l□
becomes. That is, R1(T++ρ2(1°), t1″
Even if +t2 or 1″+2, unbalanced mine, pressure Δ
Since V is always G, it is possible to perform accurate magnetic detection without offset or temperature drift.

Next, a method for manufacturing the magnetic detector described above will be explained. As shown in FIG. 3, a first insulating film 12 made of Ta205 with a thickness of 500A is formed on a silicon substrate 1, and a first magnetoresistive film made of permalloy with a thickness of 3008(7)81%Ni-19%Fe. Membrane 18, thickness] 5in2 to 500
4. A third insulating film made of Ta205 with a thickness of 500 mm] 5. A second magnetoresistive film 16 made of NiFe permalloy with a thickness of 300 mm; 4 Insulating film] Six layers of 7 are sequentially deposited using G. This vapor deposition is carried out by heating the silicon substrate to a temperature of 300°C. Next, a positive type photoresist film is deposited. During this vapor deposition, the substrate 1 is, for example,
Heat to a temperature of 0°C. As the photoresist film, for example, AZ-1850 for dry etching can be used.

Next, as shown in FIG. 4, light is selectively irradiated using a photomask having a desired pattern corresponding to the pattern of the magnetoresistive element to be formed, and light is transmitted through the transparent portion 1a of the photomask. The uncured portion of the photoresist film that has been exposed to the light is removed.

In this example, the length L of the magnetoresistive element formed by the photomask 1 is approximately 1 m, and the width W is 50 μ. This patterning was performed using OF4 gas to remove the insulating film made of Ta2O and 5in2, 00'/4 gas to remove the magnetoresistive film made of FeNi, and this aCt.

This is carried out by dry etching using a gas containing 0□ gas which assists the action of the gas. In this way, all six layers are removed in one etching process, which simplifies the process and allows the dimensions and shapes of the magnetoresistive elements stacked above and below to be completely matched, making it possible to create magnetoresistive elements with the same characteristics. easily obtained.

Furthermore, since the first and second magnetoresistive elements are formed from the first resistance film, and the third and fourth magnetoresistive elements are formed from the second magnetoresistive film, their film thicknesses and characteristics are also the same. becomes.

Next, as shown in FIG. 5, after depositing a new negative type photoresist film 18, as shown in FIG. Holes 18a are formed at corresponding positions in the photoresist film 18 using the photomask 2 with holes 2a formed thereon.

Next, the fourth insulating film 17, the second magnetoresistive film 16 and the third
The insulating film 16 is etched to form a through hole 20 that reaches the second insulating film 14 as shown in FIG. In this case as well, the OF4 gas, CCl4 gas used in the process shown in FIG. Dry etching using gas can be used. This step only needs to be carried out until the surface of the second insulating film 14 is exposed, and the second insulating film may be etched to some extent, so the etching can be controlled by
There is no need to be very strict). In addition, this etching can also be performed by wet etching, in which case SiO2 is treated with a hepta-acid etchant, Ta
It is possible to use an alkaline etchant for 205 and a strong acid mixed etchant for yeNi forming the magnetoresistive film.

Next, as shown in FIG. 8, after depositing a negative type boronimide insulating photoresist film 21, holes are formed in the photoresist film 21 using a photomask 8 as shown in FIG. Open +111a and 21b. The hole 21a is formed at the bottom of the through hole 20 described above, and the corresponding opaque part of the photomask 8 is designated by reference numeral 8.
Indicated by a. Further, the other opaque portion 8b corresponds to the hole 21b for forming a contact point to the upper magnetoresistive film 16).

In addition, an opaque part +@3C is formed in the photomask 8%, but this is to remove the insulating photoresist film 21 in this part for later bonding, and the photoresist corresponding to this part is The number of holes in the streak film 21 is 98.
The figure shows no A.

Next, as shown in FIG.
Same as insulating film 14 < Fourth insulating film made of Sing] 7
was removed by wet etching with HF + 6NH,F, an etchant that selectively attacks 5iC)2 but not Ta 205, and the first and second magnets, respectively. Holes 14a and 17a reaching resistive films 18 and 16 are formed. In this way, since the holes are formed using an etchant that selectively corrodes and removes 5i02, it is possible to effectively prevent short circuits between the first and second magnetoresistive films 13 and 16 (through pinholes). I can do it.

Next, as shown in FIG. 11, Mo[I! Then, a metal film 23 is formed by sequentially depositing 5,000 Au films. During this time, the substrate 11 is heated to a temperature of about 250°C.

Next, after depositing a positive type photoresist film (this is done using a photomask 4 shown in FIG. 12), the metal film 2 is
3 is patterned to form a conductor pattern as shown in FIG.

Next, as shown in FIG. 14, a 1μ thick Au layer was deposited on a 5μ thick Ni layer on an insulating substrate made of glass epoxy, and then patterned at a predetermined angle. The magnetoresistive element chips 26 and 27 formed as described above are placed on the metal portion 25a of the board 24, and the silicon substrate 1 is bonded to the gold portion 25a. By making the metal portion 25a large in area, the effect of promoting heat dissipation through the metal portion 25a can be obtained. As mentioned above, each chip 26 and 27 has four magnetoresistive elements, and the terminal T1 of the conductor of each chip
~T6 and TI'~T6' are each fine wire 2
8 to the conductor portions 25a and 25b of the board 24. In order to perform this wire bonding well, the insulating photoresist film 21 is removed below the conductor terminals T1 to T6 and TI' to T6' as described above.

These two magnetoresistive element chips 26 and 8 magnetoresistive elements MRI to MR4 and M formed on 27
Since R1' to M R4' are connected as shown in FIG. 15, terminals 29a and 29f on the board 24 are connected to the power supply E.
The terminals 29b and 290 are connected to the positive and negative terminals of the differential amplifier DA, respectively, the terminals 29b and 290 are connected to the differential amplifier DA, and the terminal 29d
and 29e are respectively connected to the second differential amplifier DA'.

The outputs of these differential amplifiers DA and DA' are supplied to a signal processing circuit SPO, where they are subjected to signal processing.

As shown in FIG. 16, the magnetic detector 30 of this example is used as an encoder, and a pair of magnetization patterns 31a and 81b magnetized in advance according to a predetermined pattern and magnetoresistive element chips 26 and 27 are out of phase. They are also arranged at two angles so that they face each other in a shifted state. Therefore, the signal processing circuit SPC outputs a signal representing the direction and amount of displacement.

The present invention is not limited to the embodiments described above, but can be modified and modified in many ways.

For example, the connection of the first to fourth magnetoresistive elements MRI to MR4 is not limited to the example described above, and a connection method as shown in FIG. 17 is also possible. In this example as well, due to the secondary bias effect, the first and second magnetoresistive elements MRI and MB2 receive a bias magnetic field directed downward from the top of the paper, and the eighth and fourth magnetoresistive elements MR8 and MB4 receive a bias magnetic field directed downward from the bottom of the paper. Receives a bias magnetic field towards the opposite direction. Moreover, the unbalanced voltage ΔV of this example is as follows, and exactly the same effect as the above-mentioned example can be obtained.

FIG. 18 shows still another example of the magnetic detector of the present invention. In this example, a bias magnetic field directed from the top to the bottom of the page is applied to the first and third magnetoresistive elements, and A bias magnetic field directed from the bottom to the top of the paper is applied to the second and fourth magnetoresistive elements. Further, the unbalanced voltage ΔV in this example does not become zero since the shape factor is generally not equal to 2, but since there is no variation due to humidity, no temperature drift occurs. In addition, this unbalanced type, pressure Δ
Since V is constant, it can be easily removed as an offset voltage.

Furthermore, although Sing and Ta205 were used as the insulating film in the above-mentioned embodiments, other oxides, tride, and tide can be used. For example, as the fluoride, M
SIBN4 can be used as the gF2s titanium compound. For etching, not only dry etching or wet etching, but also sputter etching in Ar gas can be used. Further, although the polyimide-based insulating photoresist film is left as is to serve as an insulating film, another insulating film may be applied and the photoresist film may be peeled off.

Further, in the above-described embodiment, the silicon substrate is bonded to a glass epoxy insulating board, but it can also be provided on a ceramic board on which an electrode pattern is adhered, and in this case, the heat dissipation effect will be even higher. In the above embodiment, a chip including four magnetoresistive elements was formed.
Any type of material may be used as long as two or more magnetoresistive elements are arranged in the vertical direction. In addition, although the above example describes a magnetic encoder, the magnetic encoder
- It can also be used as a head for reading information recorded on a recording medium such as a disk or a magnetic disk. In the example briefly described above, the etching mask was formed by selectively irradiating the photoresist film with light through a photomask, but it is also possible to use a resist film that is selectively hardened by electron beam irradiation. In such a case, a photomask is not required.Also, in the above example, the mutual bias was performed using the secondary bias method, but it may be performed using the -order bias method.

As described above, according to the magnetic detector of the present invention, the dimensions and shapes of the magnetoresistive elements stacked up and down are exactly the same, and the magnetoresistive elements arranged on the left and right are also made of the same magnetoresistive film. Therefore, one with equal magnetic properties can be obtained,
This has the advantage of significantly improving detection accuracy. Furthermore, in the embodiments described above, since the side walls of the through holes are covered with an insulating film before the metal film is deposited, short circuits can be effectively prevented. In this case, using an insulating resist film as the insulating film has the effect of further reducing the number of steps. Moreover, by selectively etching different types of insulating films, short circuits through pinholes can be more effectively prevented. Furthermore, since a silicone (with high thermal conductivity) is used as the substrate for I/X, the heat dissipation characteristics are good, and a larger snow removal + IT current can be passed through the magnetoresistive element. It also has the effect of enabling highly sensitive detection with high S/H. σ) Since silicon substrates are widely used in the semiconductor manufacturing field, they also have the advantage of being easily available in good quality. In addition, each magnetoresistive element &
Furthermore, since the structure is sandwiched between insulating films made of the same material, the magnetic characteristics (magnetic characteristics) are uniform, which has the advantage of enabling even more accurate detection power5.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of -f11 of a conventional magnetic detector; FIGS. 2A and B are plan and perspective views diagrammatically showing the configuration of an example of the magnetic detector of the present invention; Figure 2G is a circuit diagram also showing the connection, I'! 3 to 13 are diagrams showing the sequential manufacturing process and photomask for manufacturing the magnetic detector of the present invention, and FIG.
15 is a circuit diagram thereof, FIG. 16 is a diagram illustrating how it is used, and FIGS. 17 and 18 are magnetic detectors according to the present invention. FIG. 7 is a circuit diagram showing another example of the device. S...Silicon substrate MRI~MR4...Magnetoresistive element INS...Insulating film 01~C8...Contact L
1~L6...Conductor E...Yoi, source DA, D
A'...Differential amplifier 11...Silicon, substrate 13
, 16... Magnetoresistive film 12, 14.15.17... Insulating film 18, 21... Photoresist film 23... Metal film 1', 2.8... Photomask. Figure 2 C Figure 8 Figure 5 Figure 6 Figure 7 Figure 8 To I Figure 9 Figure 1θ Figure 11 Figure 12 Figure 18 Figure 14 Figure 15 m 16 r; 4 Figure 17 Figure 18 Procedural amendment document June 2, 1982 1. Indication of the case 1988 Patent Application No. 224121 2. Name of the invention Magnetic detector equipped with a magnetoresistive element 3. Person making the amendment Relationship to the case Patent Applicant Co., Ltd. Copal Telephone number (581) 2241 (representative) 5゜6. Subject of amendment Detailed explanation of the invention in the specification column 7. Contents of amendment (as attached) 1. Page 8 of the specification In the first line, "MRIJ f'MR2J8
0 2 on the 8th line of the same page (-11R2J is corrected to rMRIJ), 0 2 on the 8th line of the same page, ``Second magnetoresistive element -m=
"From the bottom of the page" to "fourth magnetoresistive element MHI and Mn
2 receives a bias magnetic field directed downward from the top of the paper, and the second and eighth magnetoresistive elements MR2 and Mn21 are applied from the bottom of the paper. bow·

Claims (1)

[Claims] L First and second magnetoresistive elements formed by patterning a first magnetoresistive film provided on a silicon substrate, and a second magnetoresistive element separated from the first magnetoresistive film via an insulating film. The first and second resistive films are patterned.
and third and fourth magnetoresistive elements formed to be aligned with the magnetoresistive element, and the first to fourth magnetoresistive elements are aligned with the first and third magnetoresistive elements and the second A magnetic detector comprising a magnetoresistive element, wherein the fourth magnetoresistive element magnetically biases each other and is connected to form a bridge circuit.