JP2527745B2 - Method for manufacturing ferromagnetic magnetoresistive element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a ferromagnetic magnetoresistive element used for detecting a magnetic field.

[Prior Art] A conventional magnetoresistive element has a cross section thereof as shown in FIG. 4, and a magnetic sensitive section (sensor section) made of Fe—Ni alloy or the like and having a thickness of several hundred to several thousand Å is formed on a glass substrate 1. ) 2, a wiring part 3 made of the same material as or a material different from that of the magnetic sensing part and a terminal part 4 for external connection are provided, and the resin layer 5 as a protective film includes the substrate 1, the magnetic sensing part 2, the wiring part 3, the terminal. It was provided so as to cover the portion 4 and the lead wire 10. When the resin layer is used as the protective film in this way,
Generally, the resin has a high moisture permeability, so in order to ensure sufficient reliability of the device under an environment of high temperature and high humidity, the resin layer 5
Is required to have a thickness of several hundred μm or more. Therefore, it becomes impossible to sufficiently bring the magnetic sensitive section 2 and the magnetic field to be detected close to each other, and it is inevitable that the output is lowered, and it is difficult to detect a weak magnetic field. For example, when detecting and controlling the rotation speed of the motor, the sensor unit 2 cannot be brought sufficiently close to the magnetized rotor of the motor. Therefore, a weak magnetic field with a narrow magnetization pitch is detected to detect the rotation speed of the motor. I couldn't control it.

FIG. 5 shows a sectional view of another example of the conventional ferromagnetic magnetoresistive element. In this conventional example, the magnetic sensitive portion 2, the wiring portion 3 and a part of the terminal portion 4 are formed by a vacuum deposition method and have a thickness of 5 μm.
The resin 8 is covered with the above protective film 6 made of SiO or SiO _2.
It is sealed with. In this conventional example, the moisture permeability of the SiO or SiO ₂ film is extremely low, and the thickness thereof can be made thinner than that of the resin protective layer 5 in the conventional example of FIG. The objective is to make the distance sufficiently short so as to maintain the reliability of the device under a high temperature and high humidity environment without lowering the output.

However, the vacuum deposition method has a poor step coverage as shown in FIG. 6, and a thin portion 6A is likely to be formed on the protective film 6.
In order to secure sufficient durability for that, the film thickness should be 5
It must be at least μm. However, a thickness of 5 μm or more
When the SiO film or the SiO ₂ film is formed, cracks are easily generated in the film, and sufficient durability cannot always be obtained.

[Problems to be Solved by the Invention] An object of the present invention is to provide a ferromagnetic magnetoresistive element having a protective film which is thin and has excellent durability, which solves the above-mentioned conventional drawbacks. .

[Means for Solving the Problems] In order to achieve such an object, the present invention forms a magnetic sensing part, a wiring part and a terminal part of a predetermined shape and size on an insulating substrate, One of the SiO ₂ layer and the SiON layer is directly formed in a thickness of 0.5 to 4 μm on the entire surface of the wiring portion and a required portion of the terminal portion by a plasma CVD method.

Further, according to the present invention, a magnetic sensing part, a wiring part and a terminal part having a predetermined shape and dimensions are formed on an insulating substrate, and the entire surface of the magnetic sensing part and the wiring part and a desired part of the terminal part are covered with SiO 2. ₂
Layer and SiON layer by plasma CVD method
It is characterized in that it is directly formed with a film thickness of 0.5 to 4 μm, and at least one of an insulating inorganic thin film and a heat resistant polymer thin film is further formed.

[Operation] According to the present invention, SiO ₂ or S is formed by the plasma CVD method.
iON protective film is formed. SiO ₂ and SiON have good adhesion to the ferromagnetic material forming the magnetically sensitive portion, and play a role of enhancing the durability of the device under a high temperature and high humidity environment. Further, when the film is formed by the plasma CVD method, the step coverage is superior to that of the film formed by the vacuum deposition method, and the durability can be secured with a thin film thickness. Further, since the film thickness is thin, the internal stress is small and no cracks occur, so that the durability is not deteriorated by the cracks.

Furthermore, an insulating inorganic thin film and a heat-resistant polymer thin film can be formed on the SiO ₂ film or SiON film by the plasma CVD method to enhance the rubbing strength at the time of mounting.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a sectional view of an example of a ferromagnetic magnetoresistive element manufactured according to the present invention.

A magnetic sensitive part 2, a wiring part 3 and a terminal part 4 having a desired shape and size were formed on a glass substrate 1. The material forming each of these portions may be any conventionally used material and is not limited. As a method for forming each of these portions, a sputtering method, a plating method, or any other method can be used.

Next, a SiO ₂ film 7 was formed by a plasma CVD method so as to cover the entire surface of the magnetic sensing portion 2, the wiring portion 3 and a predetermined portion of the terminal portion 4. The SiO ₂ film forming conditions were as follows.

Connect the substrate temperature 250 ° C. Pressure 47Pa reactive gas and the flow rate N ₂ leads 10 N ₂ O diluted to 80 vol% of SiH ₄ diluted to 20 vol% at 1800 sccm N ₂ 250 SCCM next terminal unit 4, finally The connection part was molded with the epoxy resin 8.

The SiO ₂ protective film formed by the plasma CVD method is the second
As shown in the cross section in the figure, the step coverage is excellent,
The thickness of the formed protective film 7 is not so different between the flat portion and the step portion. Therefore, even if the thickness of the protective layer is reduced, the protective function for the magnetic sensitive portion and the wiring portion, which are the base, is high.

Instead of the SiO ₂ film, a SiON film in which a part of oxygen is replaced with nitrogen may be formed as a protective film by the plasma CVD method.

In this case, the reaction gas is SiH ₄ / N ₂ 900SCCM, NH ₃
200SCCM, N ₂ 500SCCM, N ₂ O 400SCCM.

The function of covering the stepped portion of the formed SiON film is similar to that of the SiO ₂ film.

Table 1 shows the device manufactured by the present invention and the device manufactured by the conventional vapor deposition method at 5 V under the environment of 85 ° C and relative humidity of 85%.
The endurance test results after 1000 hours are compared and shown.

The results shown in Table 1 are the average values and variations of 100 elements. As can be seen from the table, the element according to the present invention has a resistance change of 1/40 or less and a midpoint potential change of 1/10 as compared with the conventional method.
It shows excellent durability as follows.

The thickness of SiO ₂ film or SiON film by plasma CVD is 0.5
If it is less than μm, sufficient durability cannot be secured. On the other hand, if the film thickness exceeds 4 μm, the internal stress increases and SiO ₂
The film is likely to be cracked, and both the protective function for the device and the yield of device fabrication are reduced. Therefore plasma
The optimum film thickness of SiO ₂ film and SiON film by the CVD method is 0.5 to 4
μm.

FIG. 3 shows another embodiment of the present invention. In this embodiment, a thickness of 1 to several μ is further formed on the SiO ₂ film 7 formed by the plasma CVD method.
It has a structure coated with an alcoholate insulating film 9 of m. With such a multilayer film structure, in addition to the moisture resistance of the element, it is possible to improve mechanical strength against rubbing or the like on the surface of the magnetic sensing part. Even if a heat-resistant polymer thin film such as polyimide is formed instead of the alcoholate-based film, the mechanical strength can be improved.

[Effects of the Invention] As described above, according to the present invention, the entire surface of the magneto-sensitive part and the wiring part of the ferromagnetic magnetoresistive element and the required part of the terminal part are covered with SiO ₂ by the plasma CVD method of 0.5 to 4 μm. SiON
By covering with, there is an effect that the durability of the element is significantly improved. Further, since the film thickness is thin, the film formation time is short and the productivity is high.

[Brief description of drawings]

FIG. 1 is a sectional view of a ferromagnetic magnetoresistive element according to an embodiment of the present invention, FIG. 2 is a sectional view showing a state of coating a step portion of a plasma CVD SiO ₂ film according to the present invention, and FIG. 3 is a sectional view of the present invention. FIG. 4 is a cross-sectional view of a ferromagnetic magnetoresistive element in another embodiment, FIG. 4 is a cross-sectional view of a conventional example when a resin is used as a protective film, and FIG. 5 is a protective film made of vapor-deposited SiO or SiO ₂ . FIG. 6 is a cross-sectional view of a conventional example of the case, and FIG. 6 is a cross-sectional view showing a covering state of a step portion by a conventional vacuum deposition method. 1 ... Glass substrate, 2 ... Magnetic sensitive part, 3 ... Wiring part, 4 ...
… Terminal part, 5 …… Protective film (resin), 6 …… Protective film (vapor deposition)
SiO or SiO ₂ ), 7 ... Protective film, 8 ... Mold resin, 9 ... Alcolate coating film, 10 ... Lead wire.

Claims (2)

(57) [Claims] 1. A magnetic sensing part, a wiring part, and a terminal part having a predetermined shape and dimensions are formed on an insulating substrate, and SiO ₂ is formed on the entire surface of the magnetic sensing part and the wiring part and a desired part of the terminal part. Layers and
0.5 ~ 4μ of one kind of SiON layer by plasma CVD method
A method of manufacturing a ferromagnetic magnetoresistive element, which comprises directly forming a film having a thickness of m. 2. A magnetic sensing part, a wiring part and a terminal part having a predetermined shape and dimensions are formed on an insulating substrate, and SiO ₂ is formed on the entire surface of the magnetic sensing part and the wiring part and a required part of the terminal part. Layers and
0.5 ~ 4μ of one kind of SiON layer by plasma CVD method
A method of manufacturing a ferromagnetic magnetoresistive element, which comprises directly forming a film having a thickness of m and further forming at least one of an insulating inorganic thin film and a heat-resistant polymer thin film.