JPH03219683A - Magnetoresistance element - Google Patents

Abstract

PURPOSE:To enable corrosion resistance of a magnetic film to be improved by providing an intermediate layer with improved corrosion resistance on the magnetic film and then providing a conductive film through a lead hole and a through hole which are provided at the intermediate layer. CONSTITUTION:An intermediate layer 3 with improved corrosion resistance is clad on a magnetic film 2, the intermediate layer is punched through, a lead hole 3a along the pattern shape of a lead region is provided at the lead region 9b of an element 9a, a barber ball type through hole 3b passing through the magnetic film skewly is provided at a detection region 9c, and the magnetic film is exposed from these lead hole and through hole. On the other hand, an adhesive layer 4 and a conductive film 5 are etched in a larger pattern shape so that they cover the peripheral part of the lead hole and the through hole, thus enabling a pattern edge part where the adhesive layer and the conductive film overlap is placed at the peripheral part of the lead hole 3a or the through hole 3b of the intermediate layer 3. Then, the pattern edge part where the adhesive layer and the conductive film overlap and a current- conductive adhesive surface with the magnetic film are built into a hook mold, thus enabling the magnetic film to be completely covered with the conductive film through the intermediate layer and the adhesive layer.

Description

[Detailed Description of the Invention] [Summary] Regarding a magnetoresistive element, the present invention aims to improve the corrosion resistance of a magnetic film constituting the magnetoresistive element, and includes a substrate, a magnetic film, an intermediate layer, an adhesive layer, and a conductor. and a protective film, the substrate supports the element and has insulating properties, and the magnetic film is adhered to the substrate in the pattern shape of the element. , has ferromagnetism, and the intermediate layer is adhered to a magnetic film and has insulating properties, and the intermediate layer has ferromagnetic properties in the lead region of the element. The lead hole to be exposed and the through hole in the detection area through which the magnetic film is exposed in a barber pole pattern shape are respectively provided, and the adhesive layer is used to maintain close contact between the conductive film and the magnetic film or the intermediate layer. The conductive film is a film that maintains conductivity and is adhered to the intermediate layer and the magnetic film exposed from the lead holes and through holes of the intermediate layer, and has electrical conductivity. , the adhesive layer is directly deposited and etched together with the adhesive layer, and has a pattern shape large enough to cover the peripheral edges of each of the lead hole and the through hole, and the conductor film is attached to the adhesive layer and etched together with the adhesive layer. The protective film is applied to the magnetic film through each of the lead hole and the through hole through the layer, and the protective film is applied to the intermediate layer excluding the terminal and the conductive film. , and is configured to have insulating properties.

[Industrial application field]

The present invention relates to a magnetoresistive element, and particularly to a structure of a barber pole type magnetoresistive element with excellent corrosion resistance.

A magnetoresistive element is a type of sensor that utilizes the magnetoresistive effect of a ferromagnetic material such as permalloy (trade name of various Fe alloys with high magnetic permeability that are mainly composed of Ni). Output is obtained and temperature stability is achieved.
High sensitivity.

Therefore, it has the potential to be used as a variety of sensors, such as a magnetic pattern reading sensor, a position sensor, and a power sensor.

Recently, it has also been attracting attention, particularly in applications such as vehicle height sensors and acceleration sensors, that is, in the field of car electronics.

However, in this field, the environment in which they are used is extremely harsh and high reliability is required.

[Conventional technology]

3 is a diagram showing an example of the structure of a magnetoresistive element, FIG. 4 is a partially enlarged plan view of FIG. 3, and FIG. 5 is a partially enlarged sectional view of FIG. 4.

In the figure, 1 is a substrate, 2 is a magnetic film, 5 is a conductor film, 4 is an adhesive layer, 6 is a protective film, 7 is a terminal, and 9 is a magnetoresistive element.

As the substrate I, for example, a glass substrate having a thickness of several hundred μm or a silicon wafer whose surface is coated with SiO2, SiN, or the like is used.

On the substrate 1, a magnetic film 2 made of a ferromagnetic material such as permalloy and having a thickness of several tens to several hundred nm is provided, for example, by vapor deposition.

This magnetic film 2 is etched into the pattern shape of the element 9a by mask vapor deposition or photolithography.

Next, Ti or Cr with a thickness of several tens of nanometers is placed on top of the magnetic film 2.
A conductive film 5 made of Au or the like having a thickness of several hundred nm is provided on the adhesive layer 4 by vapor deposition, sputtering, etc., respectively.

The adhesive layer 4 and the conductor film 5 are then finished into a so-called barber pole type element 9a resembling a herringbone pattern by photolithography.

Finally, except for the terminal 7 part, the whole
Made of materials with excellent corrosion resistance such as SiN and SiN, the film thickness is 1 μm.
The magnetoresistive element 9 is completed by covering with a protective film 6 having a thickness of about m.

In this case, the circuit configuration is a half bridge with two terminals 7a and one common terminal 7b, and although not shown, it is connected to a differential amplifier circuit or the like and used as a detector. .

In order to use this magnetoresistive element 9 as a sensor, initial magnetization 9d is first performed in the longitudinal direction of the magnetoresistive element 9.

When detecting the external magnetic field, an external magnetic field 9e in a direction perpendicular to the longitudinal direction of the magnetoresistive element 9 is detected.

By the way, in FIG. 5, the film structure of the conventional magnetoresistive element 9 is such that, for example, while the thickness of the protective film 6 is about 1 μm, the combined film thickness of the adhesive layer 4 and the conductive film 5 is about the same. Yes, the pattern has large differences.

However, if the pattern step is large, fine cracks will occur, causing corrosion of the magnetic film 2.

Furthermore, the thickness of the protective film 6 cannot be increased because the mechanical strain imparted to the magnetic film has a negative effect on the magnetoresistive characteristics. Therefore, the protective film 6 cannot completely cover the magnetic film 2, and corrosion of the magnetic film 2 occurs from time to time.

[Problem to be solved by the invention]

As mentioned above, in conventional magnetoresistive elements that use a ferromagnetic material with high magnetic permeability, such as permalloy, as a magnetic film, the thickness of the protective film is small compared to the thickness of the protective film. There is a large pattern step difference due to the combined thickness of the adhesive layer and conductor film.

Therefore, there is a problem in that minute cracks occur in the protective film, causing corrosion of the magnetic film.

On the other hand, if the protective film becomes thick and mechanical strain is applied to the magnetic film, the linearity of the magnetoresistive characteristics becomes poor and hysteresis appears.

Therefore, even if a protective film with excellent corrosion resistance such as 5i02 is used, the film thickness cannot be increased, and therefore, there is a problem that corrosion of the magnetic film cannot be completely prevented.

The present invention provides a magnetoresistive element in which the corrosion resistance of the magnetic film is improved by providing an intermediate layer with good corrosion resistance on a magnetic film and providing a conductive film through lead holes and through holes provided in the intermediate layer. The purpose is to

[Means to solve the problem]

The problem described above is that the substrate includes a substrate, a magnetic film, an intermediate layer, an adhesive layer, a conductive film, and a protective film, and the substrate supports an element and has insulating properties. The magnetic film is deposited on the substrate in the shape of an element pattern and has ferromagnetism; The intermediate layer is deposited on the magnetic film, The intermediate layer has lead holes in which the magnetic film is exposed in the lead region of the element, and through holes in which the magnetic film is exposed in a barber pole pattern shape in the detection region. The adhesive layer maintains adhesion between the conductive film and the magnetic film or the intermediate layer, and the adhesive layer maintains adhesion between the conductive film and the magnetic film or the intermediate layer, and the adhesive layer maintains the adhesion between the conductive film and the magnetic film or the intermediate layer, and the adhesive layer maintains the adhesion between the conductive film and the magnetic film or the intermediate layer, and the adhesive layer maintains the adhesion between the conductive film and the magnetic film or the intermediate layer, and the adhesive layer maintains the adhesion between the conductive film and the magnetic film or the intermediate layer. The conductive film is applied to the adhesive layer and is etched together with the adhesive layer, and the conductive film is applied to the adhesive layer and is etched together with the adhesive layer, and the conductive film is attached to the adhesive layer and is etched together with the adhesive layer, and the conductive film is attached to the adhesive layer and is etched together with the adhesive layer. The conductor film has a pattern shape that is large enough to cover the respective peripheral edges, and the conductor film is electrically attached to the magnetic film through each of the lead hole and the through hole via an adhesive layer, The protective film is applied to the intermediate layer excluding the terminal and the conductive film, and is solved by a magnetoresistive element configured to have insulating properties.

[For production]

As mentioned above, in the film structure of a conventional magnetoresistive element, it is desirable to increase the thickness of the protective film because the pattern step is large. However, in the present invention, an intermediate layer is introduced to strengthen the protection of the magnetic film.

That is, a highly corrosion-resistant intermediate layer is deposited on top of a magnetic film such as permalloy, the intermediate layer is bored, lead holes are formed in the lead area of the element along the pattern of the lead area, and lead holes are formed in the sensing area. A barber pole-type through hole is provided that passes diagonally through the magnetic film.

The magnetic film is exposed from these lead holes and through holes.

On the other hand, the adhesive layer and the conductor film are etched in a large pattern around the edges of the lead hole and the through hole, so that the edge of the pattern where the adhesive layer and the conductor film overlap is formed.
It is arranged so that it rests on the periphery of the lead hole or through hole of the intermediate layer.

and a pattern end where the adhesive layer and the conductive film overlap,
Even the adhesion surface that can conduct with the magnetic film has an intricate hook-shaped configuration.

In this case, the magnetic film is completely covered with the intermediate layer and the conductive film via the adhesive layer, so that there is no part of the magnetic film covered only with the protective film as in the conventional case.

On the other hand, by interposing the intermediate layer, the pattern step difference is made smaller than in the conventional film structure in which a protective film is used directly on the magnetic film.

By doing so, it is possible not only to reduce the adverse effect of distortion of the protective film on the magnetic film (but also to prevent the occurrence of minute cracks in the protective film itself).

Thus, the film structure of the present invention provides the magnetic film with significantly superior corrosion resistance.

〔Example〕

FIG. 1 is a perspective view illustrating an embodiment of the present invention, and FIG. 2 is a partially enlarged sectional view of FIG. 1.

In the figure, l is the substrate, 2 is a magnetic film, 3 is an intermediate layer, 3a is a lead hole, 3b is a through hole 3b, 4 is an adhesive layer, 5 is a conductive film, 6 is a protective film, 7 is a terminal, and 9 is a magnetic 9a is a resistance element, 9b is a lead region, and 9C is a detection region.

In FIGS. 1 and 2, the substrate l has a thickness of, for example, 1
Thermal oxidation of the surface of a 700 μm glass substrate or 5 mm glass substrate
A silicon wafer coated with ins is used.

On the substrate 1, a magnetic film 2 made of a ferromagnetic material such as permalloy and having a thickness of, for example, one meter is provided by vapor deposition or the like. This magnetic film 2 is etched into the pattern shape of the element 9a by, for example, photolithography.

Next, on the magnetic film 2, for example, S with a film thickness of 400 nm is applied.
An intermediate layer 3 made of iN or the like is provided by plasma CVD or the like.

A lead hole 3a is provided in the lead region 9b of the element 9a, and a barber pole-type through hole 3 is provided in the detection region 9c.
b are provided by, for example, ion etching, and the magnetic film 2 is exposed from the lead holes 3a and through holes 3b.

Next, for example, Ti, Cr, TaMo with a film thickness of 50 nm is used.
An adhesive layer 4 made of the like is provided, and the adhesive layer 4
On top of this, a conductor film 5 such as AU with a film thickness of 400 nm is placed.
are provided by vapor deposition, sputtering, or the like.

Then, the adhesive layer 4 and the conductive film 5 are patterned by, for example, ion etching so as to cover the peripheral edges of the lead holes 3a and through holes 3b.

Finally, 5 iOz is sputtered to a thickness of 1 μm, for example, on the intermediate layer 3 and the conductor film 5 excluding the terminals 7, and the magnetoresistive element 9 is completed.

Reliability tests were conducted using 50 samples each of the thus produced magnetoresistive element 9 and a magnetoresistive element (conventional product) having a conventional film structure, and comparative evaluations were made.

Temperature cycle specified in MIL-3TD-883, i.e. -65°C: 10 minutes to 150°C: tO min to 1
After repeating 0 times, a 24 hour salt spray test was conducted.

First, when we investigated the operating characteristics during temperature cycling, we found that all samples of conventional products were affected by the distortion of the protective film 6, which deteriorated the linearity of the magnetoresistive characteristics and caused history to appear. Further, microscopic cracks were observed in the protective film 6 of the four samples when observed using a microscope.

However, in the magnetoresistive element according to the present invention, history appeared only in two samples.

In this way, it was confirmed that in the magnetoresistive element 9 that will be used as the main magnet, the pattern step difference is reduced by the thickness of the intermediate layer 3, so that the influence of distortion caused by the thickness of the protective film 6 is reduced. did it.

It was also confirmed that when polyimide was used as the material for the protective film 6, the influence of distortion was eliminated.

Next, as a result of a 24-hour salt spray test, nine samples of the conventional product showed deterioration in the linearity of magnetoresistive characteristics due to corrosion of the magnetic film 2, and four samples, including four samples that developed microcracks due to temperature cycles, were found to have deteriorated. Pattern breakage occurred in several samples.

In contrast, the magnetoresistive element 9 according to the present invention had no such problems.

This is because the magnetic film 2 of the magnetoresistive element 9 according to the present invention is covered with the intermediate layer 3 and the portions of the lead holes 3a and through holes 3b where the intermediate layer 3 is not covered with the adhesive layer 4 and the conductive film 5, respectively. There is. Moreover, the corrosion resistance of the magnetic film 2 is improved due to the effect of the intricate hook-shaped film structure between the pattern end where the adhesive layer and the conductor film overlap and the adhesion surface that can conduct with the magnetic film. It was confirmed that this film is significantly superior to conventional membrane configurations.

Various modifications can be made to the materials and film thicknesses of the substrate, magnetic film, intermediate layer, adhesive layer, conductor film, protective film, and the like.

Further, the feature of the present invention is the film structure of the magnetoresistive element, and various modifications can be made to the method of forming each film.

〔Effect of the invention〕

As mentioned above, in the magnetoresistive element of the present invention, the magnetic film, which has poor corrosion resistance, is electrically connected to the conductor film through the lead holes and through holes provided in the intermediate layer, which has excellent corrosion resistance. In this case, the magnetic film is covered with the intermediate layer and the conductive film, and then covered with the protective film, so that the corrosion resistance of the magnetic film is significantly improved.

Thus, according to the present invention, the magnetoresistive element can be used reliably even in harsh environments such as car electronics, and this contributes to improving the seismic disaster resistance and expanding the applications of the magnetoresistive element. It's large.

[Brief explanation of drawings]

FIG. 1 is a perspective view illustrating an embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of FIG. 1, FIG. 3 is a diagram showing an example of the configuration of a magnetoresistive element, and FIG. 3 is a partially enlarged plan view of FIG. 3, and FIG. 5 is a partially enlarged sectional view of FIG. 4. In the figure, (2) is a substrate, 3 is an intermediate layer, 3b is a through hole, 4 is an adhesive layer, 6 is a protective film, 9 is a magnetoresistive element, and 9b is a lead region. 2 is a magnetic film, 3a is a lead hole, 5 is a conductor film, 7 is a terminal, 9a is an element, 9C is a detection area. Figure fi3
Figure 9d - Partially large-scale cross-sectional view of the 3rd edition of Neiho Meiji Ihi Figure 4 Partially large-scale cross-sectional view of Figure 4 Figure 5

Claims (1)

[Scope of Claims] A substrate (1), a magnetic film (2), an intermediate layer (3), an adhesive layer (4), a conductor film (5), and a protective film (6), The substrate (1) supports the element (9a) and has insulating properties, and the magnetic film (2) is coated on the substrate (1) in the pattern shape of the element (9a). The intermediate layer (3) is attached to the magnetic film (2) and has insulating properties, and the intermediate layer (3) is attached to the magnetic film (2) and has insulating properties. layer(
3) a lead hole (3a) through which the magnetic film (2) is exposed in the lead region (9b) of the element (9a);
In the detection area (9c), the magnetic film (2) is exposed through a through hole (3b) in a barber pole pattern.
), and the adhesive layer (4) has the conductor film (5) and the magnetic film (2) or the intermediate layer (3).
), which maintains adhesion between the intermediate layer (
3) and the magnetic film (2) exposed from the lead hole (3a) and through hole (3b) of the intermediate layer (3), and is conductive. , the conductive film (5) is adhered to the adhesive layer (4) and etched together with the adhesive layer (4), and the conductive film (5) is formed to form the lead hole (3a) and the through hole (3b).
The conductive film (5) has a pattern shape large enough to cover the peripheral edge of each of the lead holes (3a) and the through holes (3b) via the adhesive layer (4). The protective film (6) is attached to the magnetic film (2) in a conductive manner through each of the intermediate layers (
3) and the conductive film (5),
A magnetoresistive element characterized by having insulating properties.