JPH043484B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic sensor that detects a magnetization pattern;
In particular, the present invention relates to a method of manufacturing a displacement detection device including a magnetic sensor including a magnetoresistive element.

An example of such a displacement detection device is a magnetic encoder, which generates output signals having a phase difference of 90° from two magnetic sensors. By appropriately processing these signals having a phase difference of 90°, the direction and amount of displacement can be detected. In order to extract two signals having a phase difference of 90°, conventionally, as shown in FIG. 1, first and second magnetic sensors 2A and 2B
are arranged side by side in a direction perpendicular to the displacement direction, and first and second magnetization pattern tracks 1A and 1B are formed on the recording medium 1 with the displacement direction shifted. However, with this method of recording the magnetization pattern tracks 1A and 1B with their phases shifted, crosstalk occurs between the two magnetization pattern tracks, the S/N of the signal decreases, and when recording the magnetization pattern tracks, However, it is difficult to record the two tracks by shifting them half a pitch at a time, making it difficult to obtain a signal with a desired phase difference, and the accuracy of detecting the amount of displacement is low.

In order to solve this problem, as shown in FIG. 2, first and second magnetic sensors 2A and 2B are placed above the magnetic recording medium 1' recording a single magnetization pattern track in the displacement direction. It is conceivable to arrange the magnetization patterns at A so as to be shifted from each other by half the pitch. However, with such a method, it is very difficult to accurately separate the two magnetic sensors 2A and 2B by a predetermined distance in the displacement direction. In particular, when the pitch of the magnetization pattern is narrowed in order to increase the displacement detection resolution, it becomes increasingly difficult to separate the magnetic sensors 2A and 2B by a predetermined distance. Therefore, this method also has the disadvantage that the amount of displacement cannot be detected accurately.

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and it is sufficient to record a single magnetization pattern track on the recording medium, and there is no need to shift the magnetic sensor in the direction of displacement, so that the desired In manufacturing a displacement detector that can accurately obtain signals with a phase difference, a displacement detector that allows the magnetization pattern and the common substrate to be easily and accurately tilted by a predetermined angle. The present invention aims to provide a method for manufacturing.

The present invention provides a method for manufacturing a displacement detector in which a common substrate on which at least two sets of magnetic sensors are mounted side by side and a magnetization pattern are arranged so as to be relatively inclined in a direction perpendicular to the direction of displacement. A common substrate equipped with a set of magnetic sensors is fixedly attached to a magnetic recording medium on which a magnetization pattern is to be recorded, and a recording head arranged rotatably in a direction orthogonal to the displacement direction is used to record the magnetic field. A magnetization pattern is recorded on a recording medium, and the recording head is rotated so that at least two signals obtained from a magnetic sensor have a predetermined phase difference in response to the recorded magnetization pattern. It is.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 is a diagram showing the basic configuration of a displacement detector to be manufactured by the method of the present invention. In the present invention, a single magnetization pattern is recorded on the magnetic recording medium 11. Further, the first and second magnetic sensors 12A and 12B are mounted side by side on the common substrate 13. The direction of relative displacement between the magnetic recording medium 11 and the magnetic sensors 12A, 12B is determined as shown by arrow A, and the magnetization pattern and the common substrate 13 are relatively inclined in a direction orthogonal to this displacement direction A. In Figure 3, the magnetization pattern is formed in a direction perpendicular to the displacement direction, so
The common substrate 13 is inclined at an angle θ with respect to a direction perpendicular to the displacement direction. In this way, by tilting the common substrate 13 with respect to the direction of the magnetization pattern, the two magnetic sensors 12A and 12
A signal having a phase difference determined by the angle θ is obtained from B. Then the inclination angle θ
The relationship between and phase difference will be explained. It is now assumed that the pitch of the magnetization pattern recorded on the recording medium 11 is p, that the magnetic sensors 12A and 12B each have a length l, and that they are arranged adjacent to each other on the substrate 13. Furthermore, if it is assumed that a phase difference β occurs between the two signals when the inclination angle is θ as shown in FIG. 4, then sinθ=p×β/360×l, and therefore θ=sin ^-1 (p×β/360×l). For example, the diameter of recording medium 11 is 20 mm.
1000 pulses were recorded around the drum using a 2.8 mm long magnetic sensor 12A and 1
2B are placed side by side on the substrate 13 to generate two signals with a phase difference β of 90°, the pitch p of the recorded magnetization pattern is 20×π/1000=0.063
mm, so θ=sin ^-1 (0.063×90/360×2.8)=0.32°. That is, by tilting the substrate 13 and the magnetization pattern by an angle of 0.32° in the direction orthogonal to the displacement direction, magnetic sensors 12A and 12B can detect two signals having a phase difference of 90° from each other.
Two signals will be obtained.

Figure 5 is a graph showing the change in output amplitude due to tilting the magnetization pattern and the magnetic sensor.The horizontal axis plots the phase difference β between the two signals and the associated tilt angle θ, and the vertical axis is the relative output V(β)/to the output when the tilt angle θ=0.
V (β=0) is plotted. As in the above example, when obtaining a signal with a phase difference β=90° with the inclination angle θ being 0.32°, the relative output is 90% or more, indicating that a sufficiently large output can be obtained. In this way, in the displacement detector of the present invention, a magnetic recording medium having a single magnetization pattern track is used, and the common board on which two magnetic sensors are mounted is tilted by an angle θ with respect to the magnetization pattern. Two signals having the desired phase difference β will be obtained.

Next, the magnetic sensor used in the displacement detector to be manufactured by the method of the present invention will be explained in detail.

FIG. 6A is a diagrammatic plan view showing the configuration of an example of the magnetic sensor of the present invention, and FIG. 6B is a diagrammatic perspective view. In FIGS. 6A and 6B, the upper insulating layer is omitted for clarity, and the magnetoresistive film is shown with diagonal lines in FIG. 6A. In this example, four magnetoresistive elements MR1 to MR4 are used.
It has elements MR1 and MR2 and
MR3 and MR4 are formed by patterning the same magnetoresistive film, respectively, and elements MR1 and MR
3 and MR4 are stacked one above the other. These elements are formed on a silicon substrate S,
An insulating film INS is interposed between the elements MR1, MR3 and MR2, MR4. The four magnetoresistive elements MR1 to MR4 are connected to form a bridge circuit as shown in FIG. 6C. That is, one end of the lower elements MR1 and MR2 is connected to the contact point C1.
and C2 to the inductor L1, which is connected to the terminal T1. Upper element MR3 and
One end of MR4 is connected at contacts C3 and C4 to conductor L2, which is connected to terminal T2. The other end of the lower element MR1 is connected to the terminal T3 via the contact C5 and the conductor L3, and the upper element
The other end of MR3 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 contact C8. and is connected to terminal T6 via conductor L6. In FIG. 6A, the contacts for the lower elements MR1 and MR2 are shown double-framed. As shown in FIG. 6C, 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, and 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 T3 and T4 and T5 and T6 can each be made into one terminal, but in order to perform a short-circuit test of the magnetoresistive element during the manufacturing process, separate terminals may be provided as described above. It is preferable to keep it. In such a configuration, the mutual bias due to the bias effect is caused by applying a bias magnetic field upward from the bottom of the paper to elements MR2 and MR3 in FIG.
A bias magnetic field is applied to MR1 and MR4 from the top to the bottom of the page, resulting in a coupling that yields an output signal. Therefore, the magnetic detection output can be obtained from the output terminal of the differential amplifier DA at high speed without being affected by noise. In addition, although a silicon substrate is used as the substrate S, silicon has a thermal conductivity more than 10 times that of glass, so it has a high heat dissipation effect and effectively dissipates the Joule heat generated by the magnetoresistive element. be able to. 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 can be easily obtained in good quality in the field of manufacturing semiconductor devices.

Next, consider the unbalanced voltage in the magnetic sensor of this example. Now, the specific resistance with the temperature coefficient of the first magnetoresistive film constituting the first and second elements MR1 and MR2 is ρ ₁ (T), the film thickness is t ₁ , and the third
The specific resistance of the second magnetoresistive film constituting the fourth elements MR3 and MR4 is ρ ₂ (T), the film thickness is t ₂ , and the pattern shape coefficient of the first and third elements MR1 and MR3 (i.e. length/width) is _k1 , and the pattern shape coefficient of the second and fourth elements MR2 and MR4 is _k2 , then the resistance values _R1 to R4 of the first to fourth magnetoresistive elements MR1 to _MR4 are as follows. become that way.

R ₁ = ρ ₁ (T)・k ₁ /t ₁ R ₂ = ρ ₁ (T)・k ₂ /t ₁ R ₃ = ρ ₂ (T)・k ₁ /t ₂ R ₄ = ρ ₂ (T)・k ₂ /t ₂ Therefore, the unbalanced voltage ΔV when there is no magnetic field to be detected is, where the voltage of power supply E is V _S , ΔV = V ₁ − V ₂ = V _S・R ₂ /R ₁ + R ₂ − V _S・R ₄ /R ₃ +R ₄ =V _S
・ρ ₁ (T)・k ₂ /t ₁ /ρ ₁ (T)・k ₁ /t ₁ +ρ ₁ (T)
・k ₂ /t ₁ −V _S・ρ ₂ (T)・k ₂ /t ₂ /ρ ₂ (T)・k ₁ /t ₂ +ρ
₂ (T)·k ₂ /t ₂ =V _S {k ₂ /k ₁ +k ₂ −k ₂ /k ₁ +k ₂ }=0. In other words, even if ρ ₁ (T)≠ρ ₂ (T), t ₁ ≠t ₂ or k ₁ ≠k ₂ , the unbalanced voltage ΔV will always be zero, and there will be no offset or temperature drift, ensuring accurate magnetic detection. can be done.

Next, a method for manufacturing the above-described magnetic sensor will be described. As shown in FIG. 7, a first insulating film 22 made of Ta ₂ O ₅ with a thickness of 500 Å and a first magnetoresistive film made of 81% Ni-19% Fe permalloy with a thickness of 300 Å are deposited on a silicon substrate 21. 23.Thickness 1500Å
A second insulating film 24 made of SiO ₂ with a thickness of 500 Å
A third insulating film 25 made of Ta ₂ O ₅ with a thickness of 300 Å
A second magnetoresistive film 26 made of NiFe permalloy and a fourth insulating film 27 made of SiO ₂ with a thickness of 1500 Å.
6 layers are sequentially deposited. This vapor deposition is performed by heating the silicon substrate 21 to a temperature of 300°C. next,
A positive type photoresist film is applied. During this vapor deposition, the substrate 21 is heated to a temperature of, for example, 300°C. As the photoresist film, for example, AZ-1350 for dry etching can be used.

Next, as shown in FIG. 8, light is selectively irradiated using a photomask M1 having a desired pattern corresponding to the pattern of the magnetoresistive element to be formed, and the light transmitted through the transparent portion M1a of the photomask M1 is Remove the uncured portion of the photoresist film that was hit. In this example, the length L of the magnetoresistive element formed by the photomask M1 is approximately 1 mm, and the width W is approximately 1 mm.
Set to 50μ. This patterning is based on _{Ta2O5 and}
CF ₄ gas to remove the insulating film made of SiO ₂ ;
CCl ₄ gas to remove the magnetoresistive film made of FeNi,
Dry etching is performed using a gas containing O ₂ gas to assist the action of CCl ₄ gas. In this way, all six layers are removed by a single etching process, which simplifies the process and allows the dimensions and shapes of the magnetoresistive elements stacked above and below to be perfectly matched, making it easy to create magnetoresistive elements with the same characteristics. can get. 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. 9, after depositing a new negative type photoresist film 28, an opaque portion is formed at a position where a contact with the lower first magnetoresistive film 23 is to be formed, as shown in FIG. A hole 28a is made at a corresponding position in the photoresist film 28 using the photomask M2 with the hole M2a formed thereon.

Next, the fourth insulating film 27, the second magnetoresistive film 26, and the third insulating film 25 are etched to form a through hole 30 that reaches the second insulating film 24, as shown in FIG. In this case as well, the CF ₄ gas and CCl ₄ gas used in the process shown in FIG.
Dry etching using gas or O ₂ gas can be used. This step only needs to be carried out until the surface of the second insulating film 24 is exposed, and the second insulating film may be etched to some extent, so it is not necessary to control the etching very strictly. This etching can also be performed by wet etching, in which case a hydrofluoric acid etchant is used for SiO ₂ , an alkaline etchant is used for Ta ₂ O ₅ , and an alkaline etchant is used for FeNi, which constitutes the magnetoresistive film. A strong acid mixture etchant can be used.

Next, as shown in FIG. 12, after depositing a negative type polyimide-based insulating photoresist film 31, holes 31a and 3 are formed in the photoresist film 31 using a photomask M3 as shown in FIG.
Open 1b. The hole 31a is formed at the bottom of the above-described through hole 30, and the corresponding opaque portion of the photomask M3 is indicated by the symbol M3a. Further, the other opaque portion M3b is a hole 31b for forming a contact with the upper magnetoresistive film 26.
It corresponds to Further, an opaque portion M3c is formed in the photomask M3, but this is for removing the insulating photoresist film 31 in this portion for bonding later, and the hole in the photoresist film 31 corresponding to this portion is formed. is not shown in FIG.

Next, as shown in FIG. 14, a second insulating film 24 made of SiO 2 and a fourth insulating film 27 made of SiO ₂ are formed through holes 31a and 31b made in the photoresist film 31 by selectively removing SiO _{2 .} The holes 24a and 27a reaching the first and second magnetoresistive films 23 and 26, respectively, are removed by wet etching with an etchant that attacks Ta ₂ O ₅ but not Ta 2 O 5, such as HF+6NH ₄ F, which is a hydrofluoric acid etchant.
form. In this way, since the holes are formed using an etchant that selectively corrodes and removes SiO ₂ , the first and second magnetoresistive films 23 and 26 are
can effectively prevent short circuits through pinholes.

Next, as shown in FIG. 15, a 2000 Å thick Mo film and a 5000 Å thick
A metal film 33 is formed by sequentially depositing Au films.
During this time, the substrate 21 is heated to a temperature of about 250°C.

Next, after a positive type photoresist film is deposited, the metal film 33 is patterned using a photomask M4 shown in FIG. 16 to form a conductor pattern as shown in FIG. 17.

Next, as shown in Fig. 18, a 1μ thick Au layer was deposited on a 5μ thick Ni layer on an insulating substrate made of glass epoxy, and then predetermined patterning was performed. Metal portion 35a of common board 34
Two magnetic sensors 36 and 37 each having four magnetoresistive elements formed as described above are placed side by side on top, and silicon substrate 21 is bonded to metal portion 35a. This metal part 3
By making 5a a large area, the effect of promoting heat dissipation through this can be obtained. As mentioned above, each magnetic sensor 36 and 37 has four
The conductor terminals T1 to T6 and T1' to T6' of each magnetic sensor are connected to conductor portions 35a and 35b of a common substrate 34 via fine wires 38, respectively. In order to perform this wire bonding well, the insulating photoresist film 31 is removed below the conductor terminals T1-T6, T1'-T6' as described above.

Eight magnetoresistive elements MR1 to MR4 formed in these two magnetic sensors 36 and 37 and
Since MR1' to MR4' are connected as shown in FIG.
9f is connected to the positive and negative terminals of the power supply E, respectively, and the terminals 39b and 39c are connected to the first differential amplifier.
DA, and terminals 39d and 39e are connected to the second
Each is connected to a differential amplifier DA'. The outputs of these differential amplifiers DA and DA′ have a predetermined phase difference β from each other, and these outputs are supplied to the signal processing circuit SPC where they are processed.
A signal representing the direction and amount of displacement will be output.

In the displacement detector described above, the common substrate on which two magnetic sensors are mounted side by side is tilted relative to the magnetization pattern in a direction perpendicular to the displacement direction, but this tilt angle θ is extremely large, for example 0.32°. Very little. In practice, it is very difficult to adjust to have such a small inclination angle θ, and it requires troublesome adjustment work and requires a highly accurate adjustment mechanism to be provided for each displacement detector. This will lead to higher costs. The present invention eliminates these drawbacks and makes it possible to easily and quickly tilt the common substrate and the magnetization pattern by a desired angle, while eliminating the need for each displacement detector to have a highly accurate and expensive adjustment mechanism. The present invention provides a method for manufacturing a displacement amount detector that eliminates the occurrence of defects. This manufacturing method will be explained below.

FIG. 20 is a plan view showing an embodiment of the displacement amount detector of the present invention, which uses a magnetic drum as a magnetic recording medium and detects the direction and amount of rotation thereof, and FIG. 21 is a sectional view. It is. The magnetic drum 41 is fixed to a shaft 44 rotatably supported by a substantially cylindrical holder 42 by a bearing 43. The holding body 42 has a common board 45 equipped with a magnetic sensor.
is attached via the mounting plate 46. Although magnetic sensors are not shown in FIGS. 20 and 21, in FIG. 21 they are mounted vertically on a common board 45, which is fixed to a mounting plate 46, The plate is fixed to the holder 42 by screws. Therefore, the common substrate 45 is the holder 42 and therefore the magnetic drum 4.
It is fixedly attached to 1. The shaft 44 is connected to a motor 47, and a rotary encoder 48 is connected to this motor. On the other hand, a magnetic head 49 is provided to record a magnetization pattern on the magnetic drum 41, and this magnetic head is connected to a rotating stage 51 via an arm 50.
to be able to rotate around line X-X.
The output of the rotary encoder 48 is transferred to the pulse generator 5.
2 to the shaft 44 and thus the rotating drum 41
A pulse is generated that corresponds completely one-to-one to the rotation of the magnetic head 49, and this pulse is supplied to the magnetic head 49 to record the magnetization pattern. The rotary encoder 48 and the pulse generator 52 are appropriately configured so that 1000 pulses can be recorded on the circumferential surface of the magnetic drum 41 at equal intervals.

Now, if the gap of the magnetic head 49 is parallel to the axis 44 as shown in FIG. 22A, the surface of the magnetic drum 41 will appear in a direction perpendicular to the displacement direction A as shown in FIG. 22B. The magnetization pattern will be recorded. On the other hand, when the rotary stage 51 is rotated by an angle, the gap of the magnetic head 49 is inclined by the angle with respect to the shaft 44, as shown in FIG. 23A. Therefore, in this case, a magnetization pattern tilted at an angle with respect to the direction orthogonal to the displacement direction A is recorded, as shown in FIG. 23B. Therefore, as shown in FIG. 21, the output signals from the two magnetic sensors mounted on the common board 45 are displayed on the monitor 53, and the rotary stage 51 is rotated so that these two signals have the desired phase difference β. If a magnetization pattern is recorded on the magnetic drum 41 during operation, the common substrate 45 and the magnetization pattern will be inclined by a desired angle θ in a direction perpendicular to the direction of displacement. in this case,
A new magnetization pattern may be superimposed and recorded on the magnetization pattern previously recorded by the magnetic head 49, but an erasing head may be provided as shown by the chain line in FIG. 20, or the magnetic head 49 may be used as an erasing head. It may also be used to erase previously recorded magnetization patterns.

As mentioned above, according to the manufacturing method of the present invention,
The common substrate 45 equipped with the magnetic sensor is fixedly arranged with respect to the magnetic drum 41, and the magnetization pattern is made such that the recording head 49 is inclined with respect to the magnetic drum 41, so that the common substrate and the magnetization pattern can be easily and quickly connected. They can be relatively tilted by a predetermined angle. Moreover, the rotary stage 51 that rotatably holds the magnetic head 49 can be used in common for a large number of displacement detectors.
It can be implemented at low cost.

The present invention is not limited to the above-mentioned examples, but can be modified and modified in many ways. For example, in the above example, two magnetic sensors are used, and they are connected to each other.
We generated two signals with a 90° phase difference, but by using three magnetic sensors,
Generate three signals with a 45° phase difference,
It is also possible to use five magnetic sensors to generate five signals having a phase difference of 45° with respect to each other. Further, the magnetic recording medium is not limited to a magnetic drum, but can also be a magnetic disk, and can also be used as a linear encoder. Furthermore, instead of fixing the magnetic sensor and moving the magnetization pattern, it is also possible to fix the magnetization pattern and move the magnetic sensor. Furthermore, the magnetic sensor is not limited to the example described above, and magnetic sensors of various types and configurations can be used.
Furthermore, in the example shown in Fig. 21, two signals are reproduced and displayed on the monitor, and the rotating stage is rotated while viewing the signals. A servo loop may be provided to automatically rotate the .

As described above, according to the method of manufacturing a displacement detector according to the present invention, the common substrate and the magnetization pattern can be easily and accurately tilted by a predetermined angle, and each displacement detector has an adjustment mechanism. Since there is no need to provide a , it can be implemented at low cost.

[Brief explanation of drawings]

1 and 2 are diagrams showing the configuration of a conventional displacement amount detector, FIG. 3 is a diagram showing the principle configuration of a displacement amount detector to be manufactured by the method of the present invention, and FIGS. Figure 5 is a diagram for explaining the operation of the displacement detector to be manufactured by the method of the present invention, Figures 6A and B
and C are diagrams showing the configuration of an example of a magnetic sensor used in a displacement detector to be manufactured by the method of the present invention, FIGS. 7 to 18 are diagrams showing the sequential manufacturing steps of the magnetic sensor, and FIG. 20 and 21 are plan views and cross-sectional views for explaining the manufacturing method of the present invention, and FIG. 22 is a circuit diagram of the magnetic sensor.
Figures A and B and Figures 23A and 23B are also diagrams for explaining the manufacturing method. 11... Magnetic recording medium, 12A, 12B... Magnetic sensor, 13... Common substrate, A... Displacement direction,
θ...Tilt angle, β...Phase difference, 34...Common board, 36, 37...Magnetic sensor, 41...Magnetic drum, 42...Holder, 44...Axis, 45...Common board, 46 ...Mounting plate, 47...Motor, 48
...Rotary encoder, 49...Magnetic head,
51...Rotary table, 52...Pulse generator,
53...Monitor.

Claims (1)

[Claims] 1. In manufacturing a displacement detector in which a common substrate on which at least two sets of magnetic sensors are mounted side by side and a magnetization pattern are arranged so as to be relatively inclined in a direction perpendicular to the direction of displacement, at least two sets of magnetic sensors are mounted side by side. A common substrate equipped with a sensor is fixedly attached to a magnetic recording medium on which a magnetization pattern is to be recorded, and a recording head arranged rotatably in a direction perpendicular to the direction of displacement is used to record a magnetization pattern on the magnetic recording medium. A magnetic pattern is recorded, and in response to the recorded magnetization pattern, at least two signals are obtained from the magnetic sensor.
A method for manufacturing a displacement amount detector, characterized in that the recording head is rotated so that the two signals have a predetermined phase difference.