JP4798498B2 - Magnetic sensor and magnetic encoder - Google Patents

Description

The present invention is a magnetic sensor that detects an external magnetic field, and has the same electrical resistance and the same electrical resistance as a magnetosensitive sensor element formed with the same film configuration as a spin valve giant magnetoresistive film or a coupled giant magnetoresistive artificial lattice film. The present invention relates to a magnetic sensor and a magnetic encoder including a fixed resistance element having a temperature characteristic of resistance.

In the field of industrial measurement, low-cost magnetosensitive elements such as Hall elements are often used to detect physical variables such as position and rotation angle without contact with a magnetic medium. When it is necessary to perform detection with high sensitivity, a magnetic sensor having an anisotropic magnetoresistive film (hereinafter referred to as an AMR film) whose relative speed with respect to a magnetic medium does not depend on reproduction output is used. However, since the magnetic sensor using the AMR film has a small magnetoresistance change rate of about 3%, the output signal voltage obtained is small. Therefore, a magnetic sensor having a giant magnetoresistive film (hereinafter referred to as a GMR film) that has a large magnetoresistive change rate and has an advantage that it can be handled as a simple two-terminal resistor on a circuit has been attracting attention. It is being considered.

As the GMR film, a coupled giant magnetoresistive artificial lattice film (hereinafter referred to as a coupled GMR film) in which the magnetization directions of adjacent magnetic layers are opposite to each other via a nonmagnetic layer is known. Since the combined GMR film has the same resistance change characteristic with respect to the magnetic field change as the AMR film, it is easy to use AM.
Replacement from the R film is possible. Since the combined GMR film has a large resistance change rate of 10% or more, a large output can be obtained. However, since the operating magnetic field intensity causing the maximum resistance change is large, a large operating magnetic field generating means is required. In addition, since the electrical resistance of the coupled GMR film is as small as about 1/2 to 1/3 that of the AMR film, it is difficult to reduce the power consumption of the magnetic sensor. Therefore, there is a problem that the magnetic sensor using the coupled GMR film is subject to application restrictions.

As a film showing a magnetoresistance change rate comparable to that of a coupled GMR film in a relatively weak magnetic field strength region,
There is a spin valve type giant magnetoresistive film (hereinafter referred to as SVGMR film). The SVGMR film is used for a magnetic head of a hard disk storage device (HDD). The SVGMR film is
As disclosed in Patent Document 1, a magnetization fixed layer and a nonmagnetic conductive layer whose magnetization direction does not change even if the direction of the external magnetic field changes, and a magnetization free layer whose magnetization direction changes following the change of the external magnetic field It is composed of A sensor element processed with an SVGMR film (hereinafter referred to as an SVGMR element) has an electric resistance that is 5 to 6 times higher than that of a sensor element processed with a combined GMR film. easy. Moreover, 1-160 (A / m) [about 0.
[006 to 20 (Oe)] and operates in a relatively small magnetic field strength region.

Japanese Patent No. 3040750

FIG. 16 shows a magnetic sensor and a magnetic medium. A magnetic sensor 60 is disposed opposite to the rotating magnetic medium 61 with a predetermined gap (gap). The magnetic sensor 60 includes a plurality of magnetic sensor elements 51. The magnetic sensor element 51 includes a magnetosensitive sensor element 27 whose electric resistance changes with a magnetic field and a fixed resistance element 28 formed of a film whose electric resistance hardly changes with a magnetic field. Connected in series. The other end of the fixed resistance element 28 is grounded, and the magnetic sensor element 2
The other end of 7 is connected to the power supply voltage Vcc. A midpoint potential is taken from the connection point 31 between the magnetosensitive sensor element 27 and the fixed resistance element 28, and this voltage becomes the output voltage of the magnetic sensor 60. Since the electric resistance of the fixed resistance element 28 does not change due to the magnetic field, the electric resistance is substantially constant and acts as a comparison resistance of the magnetosensitive sensor element 27. When the magnetic sensor element 27 detects the leakage magnetic field of the magnetic medium 61, the electrical resistance changes and the midpoint potential changes. This change in midpoint potential is represented by the magnetic medium 6.
1 and a relative position signal of the magnetic sensor 60.

A bridge can be formed by using two magnetic sensor elements 51. FIG. 17 shows a magnetic sensor element 52 having a bridge. The magnetic sensor elements 51 are connected in parallel in the reverse direction. By assembling the bridge in this way, it is possible to obtain an effect of further amplifying the amount of change in the electric resistance by the magnetic sensor elements 27a and 27b in which the electric resistance changes due to the magnetic field. Connection point 34a
16b, an output voltage approximately twice that of the connection point 31 of FIG. 16 is obtained.

However, when the magnetic sensor element 51 is formed using a magnetoresistive film and a fixed resistance film made of a metal conductor such as copper (Cu), the magnetic sensor is heated to a high temperature or a low temperature due to a difference in temperature characteristics of the electric resistance of the film. When used in an exposed ambient environment, the midpoint potential of the magnetic sensor element changes, making it impossible to detect displacement with high accuracy. When a magnetic sensor is used as a vehicle-mounted sensor, heat resistance of 150 ° C. or higher is required. For example, the temperature coefficient of Cu is 4.3 × 10 ^−3.
(Deg. ⁻¹ ), whereas the temperature coefficient of the SVGMR film is 1.0 to 1.3 × 10 ^−
3 (deg. ⁻¹ ), the midpoint potential of the bridge circuit changes due to a change in ambient temperature. The temperature coefficient of metal aluminum, gold, and silver used for other conductors is 4
. 0 to 4.2 × 10 ⁻³ (deg. ⁻¹ ), and the difference from the temperature coefficient of the SVGMR element is large.

A metal close to the temperature coefficient of the electrical resistance of the SVGMR film can be selected from an alloy system. For example, there are alumel of nickel alloy containing aluminum and manganese, brass of alloy of copper and zinc, alloy of platinum and rhodium, and the temperature coefficient thereof is 1.2 to 1.4 × 10 ⁻³ (deg. ^−
1 ) is very close to the SVGMR film, but not the same value. Also, since the sheet resistance value is different from that of the SVGMR film, it is very difficult to match the electric resistance value by changing the shape and thickness of the element.
Further, an extra film forming apparatus and a sputtering target material are required to obtain the fixed resistance film.

The object of the present invention is to form a fixed resistance element with a magnetoresistive effect element film having the same temperature characteristics of the magnetoresistive sensor element, the electrical resistivity, and the electrical resistance, and obtain a stable output characteristic even when the ambient temperature changes. And providing a magnetic encoder.

The magnetic sensor of the present invention is a magnetic sensor that detects an external magnetic field, and is made of a GMR film whose electrical resistance changes in response to the external magnetic field, and is made of the same film material as the magnetic sensor element. It is preferable to have fixed resistance elements that have the same film stacking order and the same stacked film thickness and that hardly change in resistance by an external magnetic field.

The magnetic sensor element and the fixed resistance element have the same film material and the same film stacking order and the same film thickness. It is important that the film has a structure that can provide a good magnetoresistance effect. By setting the film thickness variation within a range in which a good magnetoresistance effect can be obtained, it is possible to reduce not only the magnetoresistance change rate but also the electrical resistivity and the temperature coefficient variation of the electrical resistance. The laminated film thickness is G
It means the thickness of each layer constituting the MR film and the total thickness of the laminated layers. Hereinafter, the thickness of each layer and the entire thickness may be simply referred to as a film thickness.

The feature of the present invention is that the resistance of the fixed resistance element hardly changes in the external magnetic field, although it has the same film configuration as that of the magnetic sensor element whose electric resistance changes in the external magnetic field. By preventing the magnetoresistive effect from appearing in the GMR film of the fixed resistance element portion, the fixed resistance element and the magnetosensitive sensor element can have the same electric resistivity and the same temperature coefficient of electric resistance. The method for preventing the magnetoresistive effect from appearing in the GMR film of the fixed resistance element will be described in detail later, but a method of increasing the surface roughness of the base of the fixed resistance film and a method of heating the GMR film are employed. Can do. Although it is stated that the magnetoresistance of the fixed resistance element hardly changes, its magnetoresistance change rate dR
/ R means 0.2% or less. Since the value is lower than the measurement limit value 0.2% of the measuring instrument, the magnetoresistance change rate is at a level that can be said to be substantially zero.

In order to make the fixed resistance element and the magnetosensitive sensor element have the same electric resistance value by a method in which the magnetoresistive effect is not exhibited in the GMR film, it is necessary to change the element dimensions. In the method of increasing the surface roughness of the base of the fixed resistance film, if the element dimensions are mechanically the same, the electric resistance increases by 2 to 20%. This is because the GMR film is formed following the surface roughness and surface undulation, and the substantial element size becomes long. Therefore, it is necessary to increase the cross-sectional area of the element or shorten the length of the element to match the electric resistance. In the method of heat-treating the GMR film, since the magnetic sensor element and the fixed resistance element are formed on the ground with the same surface roughness, the substantial element dimensions do not change. It can be patterned to the same cross-sectional area and the same length.

The wiring part connecting the fixed resistance element and the magnetic sensor element and the wiring part connecting the magnetic sensor elements when the magnetic sensor elements are arranged in a ninety-nine fold shape are magnetically applied to the GMR film in the same manner as the fixed resistance element. It is preferable not to cause the expression of the resistance effect. These wiring portions are preferably formed of a non-magnetic metal, but a lot of man-hours are required to form the wiring. By using a GMR film that does not cause the magnetoresistive effect in the wiring portion, the number of manufacturing steps can be reduced.

The GMR film of the magnetic sensor of the present invention is preferably a coupled GMR film or an SVGMR film.

The coupled GMR film is formed on the top layer of a single layer or a plurality of layers formed on a wafer, a nonmagnetic conductive layer, at least two ferromagnetic layers adjacent to each other via the nonmagnetic conductive layer. It consists of a protective layer.

The SVGMR film is formed of a single layer or a plurality of layers formed on a wafer, a nonmagnetic conductive layer, a magnetization fixed layer and a magnetization free layer sandwiching the nonmagnetic conductive layer, and an antiferroelectric formed next to the magnetization fixed layer. It is composed of a multilayer part composed of a magnetic layer and a protective film formed on the top. In the multilayer portion, the magnetization fixed layer and / or the magnetization free layer is preferably composed of a single layer or a plurality of layers.

The SVGMR film may have any structure of a bottom type, a top type, a laminated ferri fixed layer type, a laminated ferri free layer type, a dual type, a specular type, and a spin filter type. In addition, self-pin type and anti-coercive force type SVGM without antiferromagnetic layer
An R film may be used. In addition, plasma treatment can be performed for the purpose of planarizing the interface at any of the stacked interfaces.

In the magnetic sensor of the present invention, the lower ground roughness Ra1 of the magnetosensitive sensor element is preferably 0.5 nm or less, and the lower ground roughness Ra2 of the fixed resistance element is preferably 5.0 nm or more.

The surface roughness Ra of the base necessary for exhibiting a good magnetoresistance effect in the GMR film is 0.5 nm or less. The surface roughness Ra of the substrate can be measured using a measuring instrument such as a non-contact surface roughness meter using a laser or an atomic force microscope (AFM), and the center line average roughness specified in JIS B0601. Ask for. By setting the surface roughness of the base of the fixed resistance element or the wiring portion to 5.0 nm or more, the magnetoresistive effect of the GMR film can be suppressed. In the case of the SVGMR film, when the surface roughness of the base is about 0.3 nm <Ra <0.7 nm, the interface roughness between the magnetization free layer and the nonmagnetic conductive layer and between the nonmagnetic conductive layer and the magnetization fixed layer also increases. Peel coupling increases, and the ferromagnetic coupling (Hint) between the magnetization fixed layer and the magnetization free layer via the nonmagnetic conductive layer increases. Since Hint appears as a shift amount from the zero magnetic field of the MR curve, for example, when Hint is larger than the operating magnetic field range of the magnetosensitive sensor element, the resistance of the magnetosensitive sensor element varies depending on the magnetic field, but the surface roughness is large. The resistance of the fixed resistance element formed on the ground does not change. When the surface roughness of the base is 5.0 nm or more, the thickness of each of the GMR films stacked is as thin as 1 nm to several nm, so that the parallel part and the slope part of the film forming source (target) are the same. Since it does not become a film of thickness, a difference appears in the magnetoresistance change rate, and it is considered that the magnetoresistance effect does not appear.

In the case of a coupled GMR film, the interface roughness between the nonmagnetic conductive layer and the ferromagnetic layer increases as the surface roughness of the base increases, and the ferromagnetic layer becomes antiferromagnetic via the nonmagnetic conductive layer. The area to be coupled is reduced and no resistance change is shown. By increasing the surface roughness, it is considered that one of the magnetoresistive effect expression conditions is not satisfied.

Even if the same GMR film is formed by making the surface roughness Ra2 of the base of the fixed resistance element or the wiring part as rough as 5.0 nm or more than the surface roughness Ra1 of the base where the magnetic sensor element is formed The magnetosensitive sensor element portion exhibits a magnetoresistive effect, and the fixed resistor element and the wiring portion do not exhibit a magnetoresistive effect. As described above, since the GMR film having the same material, the same thickness, and the same film stacking order configuration is used for the fixed resistance element portion, the fixed resistance element portion and the magnetosensitive sensor element portion have the same electric resistivity and the same. It can be a temperature coefficient of electrical resistance. Thereby, even if there is a change in the use environment temperature, it is possible to eliminate the change in the midpoint potential of the magnetic sensor element due to the temperature.

Even a wafer having an unevenness amount (spacing between a peak and a valley bottom) similar to the surface roughness described above cannot suppress the magnetoresistive effect if the uneven pitch is large. That is, on the surface having a large period of undulation, even if the unevenness amount is large, the expression of the magnetoresistive effect cannot be suppressed. It is considered that on the surface having a large period of undulations, the parallel portion and the slope portion of the film forming source (target) are formed into films having substantially the same thickness. The pitch of the unevenness is preferably 0.5 μm or less. When the waviness is large, even if the macroscopic dimensions (patterned element dimensions) are the same, since the film is formed along the waviness on a micro scale, the length of the element changes, and the electric resistance of the fixed resistance element 28 is changed. Resistance increases. However, in the magnetic sensor of the present invention, since the material of the magnetosensitive sensor element and the fixed resistance element are the same and the temperature coefficient is equal, by adjusting the width of the fixed resistance element or shortening the length, etc. The electric resistance values of the magnetosensitive sensor element and the fixed resistance element can be easily matched.

Non-magnetic and insulating glass or ceramic can be used for the wafer forming the magnetic sensor element. When a silicon substrate is used, it is preferable to form an insulating aluminum oxide (alumina), silicon oxide (SiO ₂ ), or the like on the silicon substrate surface.

A wafer having a surface roughness Ra1 that exhibits a good magnetoresistive effect is etched to increase the surface roughness Ra2 only to a portion where a fixed resistance element and a wiring portion are formed using a photolithographic technique. After the GMR film is formed on the wafer having the part Ra2 having the large surface roughness and the part Ra1 having the small surface roughness, the magnetosensitive sensor part, the fixed resistance part, the wiring part and the like are patterned. For wafer Ra2 processing, either dry etching or wet etching can be used.
You can also select the wafer material. A mechanical processing method such as sandblasting can also be used.

When a silicon wafer is used, the unevenness can be formed by using an anisotropic etching effect depending on the crystal direction of silicon. One side of 0.1 μm to 0.
When a photoresist pattern having a square hole of about 5 μm is formed and wet etching is performed using a potassium hydroxide solution or the like, an inverted pyramid type etch pit is obtained. After removing the photoresist pattern, an insulating film made of silicon oxide, alumina, or the like is formed to a thickness of about 100 nm, whereby a silicon wafer having a rough surface roughness Ra2 at a portion where the fixed resistance element and the wiring portion are formed can be obtained.

When a polycrystalline ceramic, for example, alumina, is used for the wafer, it is difficult to polish to Ra1 that exhibits a good magnetoresistance effect due to a partial composition change of alumina and a difference in crystal plane. Even if it can be polished, it becomes a very expensive wafer and is difficult to use industrially. The surface roughness of the wafer is Ra2, which does not exhibit the magnetoresistive effect, and an alumina or silicon oxide film is formed to a thickness of about 300 nm at the site where the magnetosensitive sensor element is to be formed, so that the magnetoresistive sensor element exhibits the magnetoresistive effect. Ra1. It is preferable that the end portions of the alumina or silicon oxide film have a slope instead of a right angle because a continuous GMR film can be easily formed.

In the magnetic sensor of the present invention, it is preferable to form a fixed resistance element by spot heating the GMR film.

A heating method can be used to suppress the magnetoresistive effect of the GMR film in the fixed resistance element and the wiring portion. The GMR film of the fixed resistance element and the wiring portion is spot-heated to 350 ° C. or higher to suppress the magnetoresistive effect. The alloy is not manufactured by heating and melting, but rather weakens or eliminates the exchange coupling between the laminated films and the pinning magnetic field, and does not need to be raised to the melting temperature.

Examples of the spot heating method include infrared beam irradiation, laser irradiation, high frequency heating, and AC spot heating. It is preferable to use a laser from the viewpoint of ease of control of the heating range, the rate of temperature rise, and the like. By controlling the heating range using a laser, it is possible to clarify the boundary between the magnetic sensor element and the fixed resistance element, the magnetic sensor element and the wiring part, and minimize the influence of heat on the magnetic sensor element. .

When the GMR film is heat-treated in a spot manner, if the temperature is raised to a high temperature that oxidizes in the air, the electrical resistivity and the temperature coefficient of the electrical resistance change and cannot be used. In order to prevent oxidation, heat treatment may be performed in an inert gas or in a vacuum, but this is not preferable because the apparatus becomes large and workability deteriorates. Further, when the heating temperature is increased, heat is transmitted to the magnetosensitive sensor element portion, which may reduce the performance of the magnetoresistive effect. Therefore, it is preferable to perform the heat treatment at a temperature that is several tens of degrees Celsius to 100 degrees Celsius higher than the temperature at which the magnetoresistive effect does not appear.

The manufacturing of the magnetic sensor of the present invention includes the steps of forming a portion having a different surface roughness Ra at the position where the magnetosensitive sensor element and the fixed resistance element are formed on the wafer, forming the GMR film, and using the GMR film as the magnetosensitive sensor element. It is preferable to have a step of patterning the shape of the fixed resistance element and the wiring portion, and a step of dividing the wafer into pieces and forming a magnetic sensor.

The manufacturing of the magnetic sensor of the present invention includes a step of forming a GMR film on the wafer, a step of patterning the GMR film into a magneto-sensitive sensor element and a fixed resistance element, and a shape of a wiring portion, and a step of spot heating the fixed resistance element and the wiring portion. It is preferable to have a step of separating the wafer into pieces and forming a magnetic sensor.

The magnetic encoder of the present invention is a magnetic encoder for detecting a magnetic field generated from a magnetic medium by a magnetic sensor, and a magnetic sensor element formed of a GMR film whose electric resistance changes in response to an external magnetic field of the present invention; It is preferable to use a magnetic sensor in which a bridge circuit is formed by a fixed resistance element having the same film material, film thickness, and film stacking order configuration as that of the magnetosensitive sensor element and hardly changing in resistance by an external magnetic field.

By forming a fixed resistance element with a GMR film that has the same temperature characteristics of the magnetic sensor element, electrical resistivity, and electrical resistance, it is possible to realize a magnetic sensor and a magnetic encoder that can obtain stable output characteristics against changes in ambient temperature. It was.

Hereinafter, the present invention will be described in detail based on examples with reference to the drawings. In order to make the explanation easy to understand, the same reference numerals are used for the same parts and parts.

FIG. 1 shows the configuration of an antiferromagnetic layer-underlying laminated ferri pinned layer type (bottom laminated ferri pinned layer type) SVGMR film. Fig. 1a) shows the membrane structure, and Fig. 1b) shows the material of the membrane. On the glass wafer 11, an underlayer 12, an antiferromagnetic layer 13, a magnetization fixed layer 14, and a nonmagnetic conductive layer 1
5 is a bottom laminated ferri pinned layer type SVGMR film 101 formed by sputtering in the order of the magnetization free layer 16 and the protective layer 17. The magnetization of the magnetization free layer 16 is rotated by the external magnetic field, and the electrical resistance changes depending on the relative angle formed with the magnetization direction of the magnetization fixed layer 14. From the glass wafer 11 side having electrical insulation, NiFeCr (4 nm) / MnPt (12 nm) / CoFe (1
. 8nm) -Ru (0.9nm) -CoFe (2.0nm) / Cu (2nm) / CoFe
Sputtered films were stacked in the order of (1 nm) -NiFe (3 nm) / Ta (3 nm). Ni
FeCr is an underlayer 12, MnPt is an antiferromagnetic layer 13, Ru and CoFe sandwiching this are magnetization fixed layers 14, Cu is a nonmagnetic conductive layer 15, CoFe and NiFe on the protective layer side are magnetization free layers 16,
Ta corresponds to the protective layer 17.

In order to determine the surface roughness Ra (surface roughness of the wafer 11 at a portion where the fixed resistance element and the wiring portion are formed) Ra2 where the magnetoresistive effect between the fixed resistance element and the wiring portion does not appear, Ra is applied to one glass wafer. The site | part which changed from 0.3 nm to 10 nm was formed. By forming portions with different Ra on the glass wafer and forming the SVGMR film, the influence between lots of the SVGMR film was eliminated. Ra was changed by changing the ion milling time. In order to accurately measure the magnetoresistive change rate, a test pattern having a size of 10 mm × 10 mm was used.

FIG. 2 shows the relationship between the base surface roughness Ra and the magnetoresistance change rate. Surface roughness in the figure 0.3 nm to 0
. 5 nm is the surface roughness of the place where ion milling is not performed, and is the surface roughness Ra1 of the base of the magnetosensitive sensor element. The magnetoresistance change rate (dR / R) at Ra1 is 13.1 (%). Ra
The magnetoresistive change rate decreased with increasing value, the magnetoresistive change rate became substantially zero at Ra 4.6 nm, and the magnetoresistive effect was not exhibited. Measure by increasing the production lot of GMR film,
It was confirmed that the magnetoresistive effect can be suppressed by setting Ra to 5.0 nm or more even when the variation is taken into consideration.

FIG. 3 shows the manufacturing process of the magnetic sensor element in which the surface roughness Ra1 of the base of the magnetosensitive sensor element forming portion is 0.3 nm and the surface roughness Ra2 of the base of the fixed resistance element and the wiring portion is 5.0 nm. I will explain. The formed magnetic sensor element 52 is shown in FIG. 3g), and pp ′ of FIG. 3g).
The manufacturing process will be described using the cross section. The magnetic sensor element 52 in FIG. 3g) represents the bridge type in FIG. 17 in element shape. The surface roughness Ra1 of the glass wafer 11 is
Photoresist 20 is formed on the magnetic sensor element forming portion [FIG. 3a]. The glass wafer 11 is dry-etched with an ion milling apparatus [FIG. 3b]. Taking out from the ion etching apparatus, the photoresist 20 is removed with an organic solvent, and the surface roughness of the base of the magnetosensitive sensor element forming portion is Ra1, and the surface roughness of the base of the portion where the fixed resistance element and the wiring portion are formed is Ra2
A glass wafer was obtained [Fig. 3c]. In order to make it easy to understand, the Ra2 portion is displayed with a thick line added. The SVGMR film 101 is formed by sputtering [FIG. 3d]. A photoresist 20 was applied on the SVGMR film 101 to obtain a pattern of a magnetosensitive sensor element, a fixed resistance element, and a wiring portion. After exposure and development, the SVGMR film 101 was patterned by ion milling [FIG. 3e]. . The photoresist 20 is removed with an organic solvent, and the magnetic sensor element 5
2 was obtained [Fig. 3f] and Fig. 3g]].

In the magnetic sensor element 52, the magnetic sensor element 27 and the fixed resistance element 28 have the same shape,
The element width w = 8 μm and the element length L = 60 μm. The width of the wiring portion 25 varies depending on the location, but is approximately half the element width. The electrical resistances of the magnetic sensor element 27 and the fixed resistance element 28 are
It was the same value at 1380 (Ω). Since ion etching was used to form Ra2, the pitch of the undulations was 10-30 μm. The difference in electrical resistance between the fixed resistance element and the magnetic sensor element due to waviness was negligible, 0.1% or less, so the macro dimensions of the fixed resistance element and the magnetic sensor element are the same. did.

FIG. 4 shows the configuration of the SVGMR film of the antiferromagnetic layer-mounted laminated ferri pinned layer type (top laminated ferri pinned layer type). This is a structure in which the stacking order of the antiferromagnetic layer lower laminated ferri pinned layer type (bottom laminated ferri pinned layer type) SVGMR film of Example 1 is substantially reversed. As shown in FIG. 4, the top layer is formed by sputtering from the glass wafer 11 side in the order of the underlayer 12, the magnetization free layer 16, the nonmagnetic conductive layer 15, the magnetization fixed layer 14, the antiferromagnetic layer 13, and the protective layer 17. This is a ferri-fixed layer type SVGMR film 102. The material and the film thickness are NiFeCr (from the substrate 11 side).
4nm) / NiFe (3nm) -CoFe (1nm) / Cu (2nm) / CoFe (2n
m) -Ru (0.9 nm) -CoFe (1.8 nm) / MnPt (12 nm) / Ta (3
nm)).

Spot heating was performed using a laser to suppress the magnetoresistive effect of the GMR film. In order to accurately measure the relationship between the heating temperature and the rate of change in magnetoresistance, a test pattern having a size of 10 mm × 10 mm was used. In addition, the SVGMR film on the glass wafer was formed with a large number of test patterns, and the overheating temperature was changed for each test pattern, thereby eliminating the influence between lots of the SVGMR film. The laser used was a YAG laser and the laser beam diameter was 10 μm. The SVGMR film was heated by scanning the laser at a constant speed over the entire test pattern. The heating temperature was controlled by changing the laser output and the irradiation time, a sample with the superheating temperature changed from 180 ° C. to 450 ° C. was prepared, and the magnetoresistance change rate dR / R (%) was measured. Further, the sheet resistance Rs (Ω / □) was also measured. Since it is very difficult to directly measure the temperature of the portion heated by the laser beam, the temperature was obtained using the following method. Cut part of the glass wafer,
A chip on which an individual test pattern was formed was prepared, the chip was placed in an atmospheric furnace for about 10 seconds, heat treatment was performed, and the magnetoresistance change rate and sheet resistance were measured. The relationship between the furnace temperature, the magnetoresistance change rate, and the sheet resistance was obtained in advance, and the laser heating temperature was obtained from the magnetoresistance change rate and the sheet resistance of the test pattern heated by laser irradiation. Since the film is very thin, it is confirmed that the temperature of the film becomes the temperature of the furnace only by putting it in the furnace for about 10 seconds.

FIG. 5 shows the relationship between the laser heating temperature, the magnetoresistance change rate, and the sheet resistance. When the laser heating temperature is 270 ° C. or lower, the magnetoresistance change rate does not change, but when the temperature is higher than that, the magnetoresistance change rate decreases, and at 320 ° C., the magnetoresistance change rate becomes substantially zero, and the magnetoresistance effect does not appear. It was. The sheet resistance Rs did not change at 400 ° C. or lower, but the sheet resistance Rs began to increase at 400 ° C. or higher and increased rapidly at 450 ° C. This is presumably because the magnetoresistive film was oxidized. From the magnetoresistance change rate and the sheet resistance, the lower limit of the laser heating temperature is 320 ° C., and the upper limit is 400 ° C. In consideration of work variations and the like, it was confirmed that the heating temperature by laser irradiation was in the preferred range of 350 or more and 400 or less.

The manufacturing process of the magnetic sensor element will be described with reference to FIG. The formed magnetic sensor element 52 is shown in FIG. 6f), and the manufacturing process will be described using the pp ′ cross section of FIG. 6f). An SVGMR film 102 was formed on the 0.4 nm surface roughness Ra1 surface of the glass wafer 11 [
FIG. 6a)]. A photoresist 20 is applied on the SVGMR film 102 in order to obtain a pattern of a magnetosensitive sensor element, a fixed resistance element, and a wiring portion. After exposure and development, S is performed by ion milling.
The VGMR film 102 was patterned to obtain a magnetosensitive sensor element 27, a fixed resistance element 28 ′, and a wiring portion 25 ′ [FIGS. 3b] and 3c]. Since the fixed resistance element and the wiring portion formed in this step exhibit a magnetoresistive effect, they are distinguished from the fixed resistance element 28 ′ and the wiring portion 25 ′ by adding a symbol “′”. The fixed resistance element and the wiring portion were irradiated with laser in the atmosphere and heated to 380 ° C.
The laser was scanned as previously programmed [FIG. 6d]. The fixed resistance element irradiated with the laser and the SVGMR film 102 in the wiring portion did not exhibit the magnetoresistive effect, and the magnetosensitive sensor element obtained the magnetic sensor element 52 that exhibited the magnetoresistive effect [FIG. 6e] and FIG. 6f]].
In this embodiment, the SVGMR film 102 is patterned on each element and then laser irradiation is performed. However, the process may be reversed to irradiate a predetermined portion with a laser and then patterning each element shape. Since the electrical resistivity does not change by laser irradiation, the element dimensions of the magnetosensitive sensor element and the fixed resistance element are the same.

FIG. 7 shows the configuration of an antiferromagnetic layer-lowering type SVGMR film (bottom type SVGMR film). From the glass wafer 11 side, NiFeCr (4 nm) / MnPt (12 nm) / Co
Fe (2.5 nm) / Cu (2 nm) / CoFe (1 nm) -NiFe (3 nm) / Ta
This is an antiferromagnetic layer underlying type SVGMR film 103 formed by sputtering in the order of (3 nm).
NiFeCr is the underlayer 12, MnPt is the antiferromagnetic layer 13, CoFe on the underlayer side is the magnetization fixed layer 14, Cu is the nonmagnetic conductive layer 15, CoFe and NiFe on the protective layer side are the magnetization free layer 16, T
a corresponds to each of the protective layers 17.

A portion of the glass wafer 11 having a surface roughness Ra of 0.3 nm where the fixed resistance element and the wiring portion are formed was roughened by ion milling to Ra 5.0 nm. 7 was formed on the glass wafer 11, and a magnetic sensor element was formed by using a photolithography technique and ion milling. The manufacturing process of the magnetic sensor element is shown in Example 1.
And the same.

FIG. 8 shows a film configuration of an antiferromagnetic layer-mounted SVGMR film (top type SVGMR film). NiFeCr (4 nm) / NiFe (3 nm) -C from the alumina wafer 11 side
oFe (1 nm) / Cu (2 nm) / CoFe (2.5 nm) / MnPt (12 nm) /
This is an antiferromagnetic layer-mounted SVGMR film 104 formed by sputtering in the order of Ta (3 nm). NiFeCr is an underlayer 12, NiFe in contact with the underlayer, and CoFe formed thereon
Is the magnetization free layer 16, Cu is the nonmagnetic conductive layer 15, CoFe on the protective layer side is the magnetization fixed layer 16, M
nPt corresponds to the antiferromagnetic layer 13, and Ta corresponds to the protective layer 17.

The alumina wafer was mirror-polished to obtain a surface roughness of Ra 5.5 nm. Ra 5.5nm
Even if an SVGMR film was formed on this surface, no magnetoresistive effect was exhibited. Therefore, an alumina film having a thickness of 300 nm was formed by sputtering on the part where the magnetosensitive sensor element was to be formed, and the surface was smoothed. The surface roughness Ra of the alumina film surface was 0.4 nm, and when the SVGMR film was formed, the magnetoresistance effect could be expressed.

The manufacturing process of the magnetic sensor element will be described with reference to FIG. The formed magnetic sensor element 52 is shown in FIG. 9g), and the manufacturing process will be described using the pp ′ cross section of FIG. 9g). A stencil-shaped (mushroom-shaped) photoresist 21 was formed on the surface roughness Ra2 surface of the alumina wafer 11 [FIG. 9a]. The opening of the photoresist 21 is a place where a magnetosensitive sensor element is formed. An alumina film 43 was formed to a thickness of 300 nm [FIG. 9b]. At the mushroom umbrella portion of the stencil-shaped photoresist 21, the attachment of the film is hindered, and the alumina film can be inclined to the root of the mushroom stem. The photoresist length of the protruding portion of the umbrella on one side was set to 1.2 μm. The photoresist 21 was removed with an organic solvent, and a wafer having an alumina film 43 and a surface roughness Ra1 of 0.4 nm was obtained [FIG. 9c].
. The SVGMR film 104 is formed [FIG. 9d]. After applying the photoresist 20 and patterning it into each element shape, the SVGMR film 104 was patterned by ion milling [FIG. 9e].
. The photoresist 20 was removed with an organic solvent to obtain a magnetic sensor element 52 [FIG. 9f] and FIG. 9g). By making the end of the alumina film a gentle inclined surface, the connection between the magnetosensitive sensor element and the wiring part or fixed resistance element becomes smooth, and disconnection at the connection part and increase in electrical resistance can be prevented. It was.

FIG. 10 shows a film configuration of a bottom laminated ferri pinned layer and a laminated ferri free layer type SVGMR film. NiFeCr (4 nm) / MnPt (12 nm) / C from wafer 11 side
oFe (1.8 nm) -Ru (0.9 nm) -CoFe (2 nm) / Cu (2 nm) / C
oFe (1 nm) -NiFe (2 nm) -Ru (0.9 nm) -NiFe (2 nm) / T
It is a bottom laminated ferri pinned layer and a laminated ferri free layer type SVGMR film 105 in which sputtered films are laminated in the order of a (3 nm). NiFeCr is an underlayer 12, MnPt is an antiferromagnetic layer 13, Ru on the underlayer side and CoFe sandwiching the Ru are magnetization fixed layers 14, Cu is a nonmagnetic conductive layer 15, CoFe on the protective layer side and CoFe are formed thereon. Ru and NiFe sandwiching this correspond to the magnetization free layer 16 and Ta correspond to the protective layer 17, respectively.

The manufacturing process of the magnetic sensor element will be described with reference to FIG. The formed magnetic sensor element 52 is shown in FIG. 11i), and the manufacturing process will be described using the pp ′ cross section of FIG. 11i). The surface of the silicon wafer 11 on which the magnetic sensor element is formed is a crystal plane (100) [FIG.
a)]. Photoresist 20 is applied to the silicon wafer 11, and a photoresist 22 having a large number of 0.2 μm square holes is formed at a portion where the fixed resistance element and the wiring portion are to be formed [FIG.
1b)]. The silicon wafer 11 was immersed in the etching solution 41 and wet etching was performed [FIG. 11c]. A potassium hydroxide (KOH) solution was used as an etching solution. The portions where the photoresists 20 and 22 are removed with an organic solvent and the fixed resistance element and the wiring portion are formed are:
An inverted pyramid-type etch pit 42 having a side w of 0.2 μm was formed, and the magnetosensitive sensor element forming portion obtained a silicon wafer having an unetched silicon surface [FIG.
d]. Silicon oxide (SiO ₂ ) for electrical insulation and smooth corners of etch pits
46 was formed with a thickness of 300 nm [FIG. 11e]. The surface roughness of the silicon oxide film is Ra1 and R
It becomes a2. In this embodiment, the surface roughness Ra1 of the ground surface of the magnetic sensor element is 0.3 nm, and the surface roughness Ra2 of the ground surface of the fixed resistance element and the wiring portion is 8 nm. The SVGMR film 105 formed on the surface having the surface roughness Ra2 of 8 nm cannot exhibit the magnetoresistance effect. An SVGMR film 105 was formed on the silicon oxide film by sputtering [FIG. 11f]. After applying a photoresist 20 on the SVGMR film 105 and patterning it into each element shape, S is performed by ion milling.
The VGMR film 105 was patterned [FIG. 11g]. The photoresist 20 was removed with an organic solvent to obtain a magnetic sensor element 52 [FIG. 11h) and FIG. 11i)].

FIG. 12 shows the film configuration of the dual type SVGMR film. NiF from wafer 11 side
eCr (4 nm) / MnPt (12 nm) / CoFe (1.8 nm) -Ru (0.9 nm
) -CoFe (2 nm) / Cu (2 nm) / CoFe (0.5 nm) -NiFe (3 nm)
) -CoFe (0.5 nm) / Cu (2 nm) / CoFe (2 nm) -Ru (0.9 nm)
) -CoFe (1.8 nm) / MnPt (12 nm) / Ta (3 nm). NiFeCr is the underlayer 12, MnPt on the underlayer side is the first antiferromagnetic layer 13A, Ru on the underlayer side and CoFe sandwiching this are the first.
The magnetization fixed layer 14A and the Cu on the underlayer side are the first nonmagnetic conductive layer 15A and the first nonmagnetic conductive layer 15A.
CoFe (0.5 nm) / NiFe (3 nm) / CoFe (0.5 nm) above is the magnetization free layer 16, Cu on the protective layer side is the second nonmagnetic conductive layer 15 B, Ru on the protective layer side, and CoF sandwiching this
e corresponds to the second magnetization fixed layer 14B, MnPt on the protective layer side corresponds to the second antiferromagnetic layer 13B, and Ta corresponds to the protective layer 17, respectively.

A manufacturing process of the magnetic sensor element will be described with reference to FIG. The formed magnetic sensor element 52 is shown in FIG. 13g), and the manufacturing process will be described using the pp ′ cross section of FIG. 13g). A photoresist 20 is formed on the surface of the glass wafer 11 having a surface roughness Ra1 of 0.4 nm so as to cover the magnetic sensor element forming portion [FIG. 3a]. The surface of the glass wafer 11 was roughened with a sand blasting apparatus [FIG. 3b]. 0.5mm alumina abrasive grain 45 1.8mmФ
The nozzle was discharged at a pressure of 2 (kg / cm ² ). The surface roughness was adjusted by the sandblasting time, and a surface of 12 nm was obtained with Ra2. The surface roughness of 12 nm is the surface roughness at which the SVGMR film 106 cannot exhibit the magnetoresistive effect. The photoresist 20 is removed with an organic solvent, and the surface roughness of the base of the magnetosensitive sensor element forming portion is Ra1, and the surface roughness of the base of the portion where the fixed resistance element and the wiring portion are formed is Ra2. I got a glass wafer that became [
FIG. 3c)]. The SVGMR film 106 is formed by sputtering [FIG. 3d]. A magnetoresistive sensor element 27, a fixed resistance element 28, and a resist pattern 20 of the wiring portion 25 were formed on the SVGMR film 106, and the SVGMR film 106 was patterned by ion milling [FIG. 3e]. The photoresist 20 was removed with an organic solvent to obtain a magnetic sensor element 52 [FIG. 3f] and FIG. 3g]. In this example, because the sandblasting device was used, the Ra2 part has a concavo-convex pitch of 1 to 5 μm.
The swell was formed. If the macroscopic dimensions of the magneto-sensitive sensor element and the fixed resistance element are the same, the electric resistance value of the fixed resistance element is increased by about 5%, so that the element length is 5% without changing the element width of the fixed resistance element. The electrical resistance values of the magnetosensitive sensor element and the fixed resistance element are matched with each other.

FIG. 14 shows a film configuration of the coupled GMR film. Fig. 14a) shows the membrane configuration, and Fig. 14b) shows the material of the membrane. After the underlayer 12 is formed on the wafer 11 by sputtering, the ferromagnetic layer 18 and the nonmagnetic conductive layer 15 are alternately formed on the underlayer 12 by sputtering, and the pair of ferromagnetic layers 18 and nonmagnetic conductive are formed. The layer 15 is a unit, and this unit is laminated 14 times. Further, the ferromagnetic layer 18 is formed by sputtering, and then the protective layer 17 is formed by sputtering on the uppermost layer.

The manufacturing process of the magnetic sensor element will be described with reference to FIG. The formed magnetic sensor element 52 is shown in FIG. 15g), and the manufacturing process will be described using the pp ′ cross section of FIG. 15g). A silicon oxide (SiO ₂ ) film 46 is formed on the silicon wafer 11 for insulation by 300 nm.
A thickness was formed by sputtering [FIG. 15a]. The surface roughness of the silicon oxide film 46 is 0.
It became 3 nm. A coupled GMR film 107 was formed on the silicon oxide film 46 [FIG. 15b].
]. A resist pattern 20 for each element is formed on the coupled GMR film 107, the coupled GMR film 107 is patterned by ion milling, and a magnetosensitive sensor element 27 and a fixed resistance element 28 'are formed.
Then, the wiring part 25 ′ was obtained [FIG. 15c] and FIG. 15d]]. Since the fixed resistance element and the wiring portion formed in this step exhibit a magnetoresistive effect, they are distinguished from the fixed resistance element 28 ′ and the wiring portion 25 ′ by adding a symbol “′”. The fixed resistance element 28 'and the wiring portion 25' were irradiated with laser in the atmosphere and heated to 380 ° C. The laser was scanned as pre-programmed [FIG. 16e)]. The coupled GMR film 107 of the fixed resistance element 28 and the wiring portion 25 irradiated with the laser did not exhibit the magnetoresistive effect, and the magnetosensitive sensor element 27 obtained the magnetic sensor element 52 that exhibited the magnetoresistive effect [FIG. 16f]. FIG. 16g]]. In this embodiment, the coupled GMR film 107 is patterned on each element and then irradiated with laser. However, the process may be reversed to irradiate a predetermined portion with laser and then patterned into each element shape.

A magnetic sensor and a magnetic encoder 63 as shown in FIG. 16 were produced using the magnetic sensor elements produced in Examples 1 to 7. The magnetic sensor elements of Examples 1 to 7 formed on the wafer 11 were separated with a diamond grindstone, and then a flexible printed circuit (FPC) was attached to obtain a magnetic sensor 60. In FIG. 16, illustration of FPC is omitted. As shown in FIG. 16, the magnetic sensor 60 and the magnetic medium 61 comprised the magnetic encoder, the temperature was raised by putting the magnetic encoder in a thermostat, and the change of the midpoint potential was measured. The temperature was −40 ° C. and 75 ° C.
The difference between the midpoint potential v1 at −40 ° C. and the midpoint potential v2 at 75 ° C. = | v1−v2 | For comparison, a conventional magnetic sensor using the GMR films of Examples 1 to 7 as the magnetosensitive sensor element, brass of an alloy of copper and zinc as the fixed resistance element, and aluminum as the wiring portion was also tested. The applied voltage Vcc is 5 (V).

The amount of change in the midpoint potential of the magnetic sensor of Examples 1 to 7 is 1 (mV) to 5 (mV), and the amount of change in the midpoint potential of the comparative magnetic sensor corresponding to the magnetic sensor of Examples 1 to 7 is 20 (m
V) to 100 (mV), about 20 times as large as those of Examples 1 to 7. The fact that the amount of change in the midpoint potential of Examples 1 to 7 is small means that a magnetic sensor and a magnetic encoder that are stable against changes in the ambient environment temperature, in other words, capable of obtaining highly accurate output characteristics, have been obtained. become. This is due to the effect that the temperature coefficient of electrical resistivity and electrical resistance can be made the same by making the film material and film thickness of the magneto-sensitive sensor element and the fixed resistance element the same, and the film configuration in the film stacking order. Is.

It is a figure explaining the antiferromagnetic layer bottom laminated ferri pinned layer type SVGMR film | membrane of this invention. It is a figure which shows the relationship between lower-surface roughness Ra of this invention, and magnetoresistance change rate (dR / R). It is a figure explaining the manufacturing process of the magnetic sensor element of this invention. It is a figure explaining the antiferromagnetic layer top laminated ferri fixed layer type SVGMR film | membrane which is 2nd Example of this invention. It is a figure which shows the laser heating temperature which is the 2nd Example of this invention, magnetoresistance change rate (dR / R), and sheet resistance Rs relationship. It is a figure explaining the manufacturing process of the magnetic sensor element which is 2nd Example of this invention. It is a figure explaining the antiferromagnetic layer bottom SVGMR film | membrane which is the 3rd Example of this invention. It is a figure explaining the SVGMR film | membrane on an antiferromagnetic layer which is the 4th Example of this invention. It is a figure explaining the manufacturing process of the magnetic sensor element which is the 4th Example of this invention. It is a figure explaining the bottom laminated ferri fixed layer and laminated ferri free layer type SVGMR film | membrane which are 5th Example of this invention. It is a figure explaining the manufacturing process of the magnetic sensor element which is the 5th Example of this invention. It is a figure explaining the dual type SVGMR film | membrane which is the 6th Example of this invention. It is a figure explaining the manufacturing process of the magnetic sensor element which is the 6th Example of this invention. It is a figure explaining the joint type GMR film | membrane which is the 7th Example of this invention. It is a figure explaining the manufacturing process of the magnetic sensor element which is the 7th Example of this invention. It is a figure explaining a magnetic sensor, a magnetic medium, and a magnetic encoder. It is a figure explaining the magnetic sensor element which built the bridge.

Explanation of symbols

11 substrate,
12 Underlayer,
13 antiferromagnetic layer,
14 magnetization fixed layer 15 nonmagnetic conductive layer,
16 magnetization free layer,
17 Protective layer,
18 Ferromagnetic layer 20, 21, 22 photoresist,
25 Wiring section,
27 Magnetic sensor element,
28 fixed resistance elements 31, 32, 33, 34 terminals,
41 Etching solution,
42 Etch pit,
43 Alumina membrane,
45 abrasive grains,
46 silicon oxide film,
51, 52 Magnetic sensor element,
60 magnetic sensor,
61 magnetic media,
63 Magnetic encoder,
101, 102, 103, 104, 105, 106, 107 Magnetoresistive (GMR) film.

Claims (8)

A magnetic sensor for detecting an external magnetic field has a magnetically sensitive sensor element formed by the giant magnetoresistive effect film whose electrical resistance varies in response to an external magnetic field, and a fixed resistance element little resistance change in the external magnetic field And
The fixed resistance element is the same material as the giant magnetoresistive effect film constituting the magnetosensitive sensor element, and the film stacking order is the same.
The giant magnetoresistive film is a spin valve giant magnetoresistive film,
The ground surface roughness Ra1 of the magnetic sensor element is 0.5 nm or less,
The fixed resistance element has a ground surface roughness Ra2 of 5.0 nm or more, and the undulation of the ground surface has an uneven pitch of 0.5 μm or less . The magnetic sensor according to claim 1, wherein Ra2 is 5.0 nm or more and 10 nm or less. The magnetic sensor according to claim 1, wherein the magnetosensitive sensor element and the fixed resistance element have the same element length. Forming a portion having a different surface roughness Ra at a position where the magnetosensitive sensor element and the fixed resistance element are formed on the wafer, forming a spin valve type giant magnetoresistive film on the wafer, and the giant magnetoresistive film A magnetic sensor element, a fixed resistance element, a step of patterning into the shape of a wiring portion, and a step of separating the wafer into pieces and forming a magnetic sensor ,
A method of manufacturing a magnetic sensor, wherein a surface at a position where a fixed resistance element is formed is roughened by ion etching in the step of forming portions having different surface roughness Ra . The method of manufacturing a magnetic sensor according to claim 4, wherein the ion etching is ion milling. In the step of forming different parts of the surface roughness Ra,
The ground surface roughness Ra1 of the magnetic sensor element is 0.5 nm or less,
6. The magnetic sensor according to claim 4, wherein the fixed resistance element has a ground surface roughness Ra <b> 2 of 5.0 nm or more, and the undulation of the ground surface has an uneven pitch of 0.5 μm or less. Production method. The method of manufacturing a magnetic sensor according to claim 6, wherein the Ra2 is 5.0 nm or more and 10 nm or less. A magnetic encoder for detecting a magnetic field generated from a magnetic medium with a magnetic sensor, wherein the magnetic sensor according to any one of claims 1 to 3 is used.

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