JPS62131589A - Ferromagnetic magnetoresistance element and manufacture thereof - Google Patents

Abstract

PURPOSE:To implement high sensitivity at a low offset voltage and to improve reliability, by making the thickness of a magnetism sensing part of a ferromagnetic magnetoresistance element comprising a ferromagnetic thin film, which is in close contact with and formed on the surface of an insulating substrate in a required shape, thinner than the thickness of an electrode part. CONSTITUTION:An electrode thin film 2 comprising a ferromagnetic body is deposited and formed on an insulating substrate 1. Then, a required part of the electrode thin film 2 is etched. Thereafter, on the substrate 1, a ferromagnetic thin film 3, which has a magnetoresistance effect and has the same composition as that of an electrode material, is attached and formed on the entire surface. With the required part of the thin film 3 being made to remain, the thin film 3 is etched away, and a specified magnetism sensing pattern is formed. Thus, processes can be simplified, reproducibility and reliability in the electrode forming processes are enhanced, adhesion to a protecting layer is excellent and the reliability of the element is enhanced. Since a thin film, which is thicker than the magnetism sensing part and has a small resistance value, is used as a surrounding electrode part, an offset voltage is small and sensitivity becomes high.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a ferromagnetic magnetoresistive element and a method for manufacturing the same.

[Prior Art] Conventionally, as a manufacturing method for a magnetoresistive element, a ferromagnetic thin film having a magnetoresistive effect is formed on an insulating substrate by a method such as vacuum evaporation or sputtering, and then a predetermined position of the ferromagnetic thin film is deposited. Attempts have been made to form electrodes by plating and then perform etching to create magnetoresistive elements.

Fig. 7 (A) shows a conventional magnetoresistive element made by such a method, taking as an example an element in which the magnetic sensing part forms a bridge.
), as shown in FIG. 7(B). Figure 7 (A) is a top view;
Figure (B) is a sectional view taken along the line XX in FIG. 7. In the figure, 11 is a substrate, 13 is a ferromagnetic thin film, the narrow areas 13A, 13B, 13G, and 13D in the center are the magnetic sensing parts forming the bridge, and the wide areas at the periphery are the routing electrode parts. Become. 14A, 14B, 14C, 14D are electrodes for external connection, 17A, 17B, 17C, 170 are electrodes 148, 14B, 14[:, 14D are solder 1]
These are lead wires connected by 5Δ, 15B, 15G, and 15D. In addition, in FIG. 7(A) and FIG. 7(It), illustrations of the protective film, mold resin, etc. are omitted.

Since the magnetically sensitive part of a magnetoresistive element uses an extremely thin metal film, the sheet resistance of the ferromagnetic thin film is extremely high and it is difficult to function as an electrode for electrolytic plating, so electrodes are formed by plating directly on the ferromagnetic thin film. It was extremely difficult to do so. Furthermore, since the ferromagnetic R film is extremely thin, there is a problem in that the ferromagnetic film is corroded by the plating solution. Roughly speaking, if the resistances of 13A to 13D that make up the bridge of the magnetically sensitive part are different, the bridge becomes unbalanced and an offset voltage is generated. Since the width of the wafer is extremely narrow, there are limits to the control of its dimensions. Furthermore, since the ferromagnetic thin film leading electrode is thin, the resistance value is large, which causes a decrease in sensitivity. Moreover, if you try to lower the resistance and increase the sensitivity by plating Au or the like on the lead-out electrode, the adhesion with the protective film necessary for the element will be poor, and as mentioned above, there will be problems in the process. There was a problem in that reliability was impaired, such as etching when plating the boundary with the magnetically sensitive part. As described above, it has been difficult to manufacture electrodes using conventional methods, and industrial production of ferromagnetic magnetoresistive elements has been difficult due to reliability and yield problems.

[Problems to be Solved by the Invention] The present invention eliminates these conventional drawbacks and provides a ferromagnetic magnetoresistive element with low offset voltage, high sensitivity, and excellent 4yg reliability, and a method for manufacturing the same. The purpose is to

[Means for Solving the Problems] In order to achieve the above object, the ferromagnetic magnetoresistive element of the present invention is made of a ferromagnetic thin film densely formed in a desired shape on the surface of an insulating substrate. A ferromagnetic magnetoresistance element having a magnetically sensitive part and an electrode part, in which the thickness of the magnetically sensitive part is smaller than the thickness of the electrode part.

Further, the method for manufacturing a ferromagnetic magnetoresistive element of the present invention includes at least a step of depositing an electrode material made of a ferromagnetic thin film on an insulating substrate, and etching the deposited electrode material into a desired shape. Step: Depositing a ferromagnetic thin film having the same composition as the electrode material on the substrate and the etched electrode material; etching the deposited ferromagnetic film 11 into a desired shape to form a magnetically sensitive part pattern. It includes the process of

[Function] Since a ferromagnetic thin film of the same composition is formed on the electrode thin film, there is no reduction in reliability due to etching of the magnetically sensitive part, which was seen in the past, in the electrode forming process, and reproducibility is improved. The reliability of the element is high due to the good adhesion with the protective layer.Also, the leading electrode uses a thin film that is thicker specifically for the electrode than the magnetically sensitive part. The resistance value of the part can be lowered, and the offset voltage can be kept low. Since the i11 pole material and the material forming the magnetically sensitive part have the same composition, the manufacturing process is simplified, and there is no need to worry about diffusion between materials or migration due to heating, which is the case when different materials are used. Since the substrate can be heated to a high temperature during formation of the magnetic thin film, sensitivity can be further increased.

[Example] The present invention will be described below with reference to the drawings.

FIG. 1(A) is a top view of an embodiment of the ferromagnetic magnetoresistive element of the present invention, and FIG. 1(B) is a sectional view taken along line A--A in FIG. 1(A). This example shows an example of a bridge type element, which is the same as the conventional example shown in FIG.

In Fig. 1 (A) and CB), l is an insulating substrate, and 2
is a thin electrode film made of ferromagnetic material formed on a substrate. A ferromagnetic thin film having the same composition as the electrode thin film 2 is provided on the substrate 1 with a portion overlapping the electrode thin film 2,
3A and 3B shown in FIG. 1(A).

The wide part 1o where 3G and 30 form the magnetic sensing part is a routing electrode part. Electrode PJIII2 and magnetic sensing part 3A
Since the ferromagnetic material 3 forming ~3D has the same composition, as a result of the two-step film formation, the ferromagnetic material forms a single layer film with steps between the magnetic sensing part and the electrode. 4A, 4B, 4G, 40 are electrode parts for external connection, and each electrode part has a rieet wire 7.
8, 7B, 7C, 7D are solder 5A, 58.5G, 50
An example is shown in which the connection is made through the . The magnetic sensing part and the electrode part are covered with a protective coating 6, and the vicinity of the lead wire connection part is covered with resin 8. However, Fig. 1 (A)
Protective film 6. The illustration of the mold resin 8 is omitted.

Generally, ferromagnetic magnetoresistive elements are required to have high resistance due to high sensitivity, high output, and low power consumption. For this reason, it is preferable to form the film thinly. Therefore, the substrate l should have a mirror-like surface with very few irregularities, preferably one with a surface roughness of 100 Å or less. Further, the substrate needs to be insulating or at least have an insulating surface.

In addition, it is preferable to use a material that is stable up to at least 400°C.

Therefore, the substrate l is generally a substrate of a semiconductor element (ff
It may be an insulating substrate such as a glass substrate, a ceramic substrate, a quartz glass substrate, a sapphire substrate,
A preferred material is a silicon substrate with an oxide film.

The electrode thin film in the element of the present invention preferably has low resistance as an electrode. Therefore, it is preferable to form the film as thick as possible. In addition, the ferromagnetic magnetoresistive element is
Since it is necessary to reduce the offset voltage, the shape accuracy of the magnetically sensitive part pattern is required. In the element of the present invention, at the time of forming the magnetically sensitive part pattern, the structure is such that a step equal to the thickness of the electrode thin film is formed between the part where the magnetically sensitive part pattern is formed and the other part. . Since this level difference is closely related to the offset voltage of the element, a wood-like upper limit occurs in the film thickness of the electrode portion. That is, if this level difference is too large, the shape precision of the magnetically sensitive portion pattern will deteriorate and the offset voltage will increase.

Therefore, the thickness of the electrode thin film 2 needs to be less than a certain thickness, and considering both the shape and resistivity of the electrode thin film and the allowable offset voltage, the critical step difference is 5.0 μm or less, preferably 3.0 μm or less. 0μ peak or less, more preferably 1.
It is 0 μm or less.

As the material for the ferromagnetic thin film 3, alloys having a small coercive force are preferable, and in practical terms, they are more preferable than Ni--Fe alloys and N1--Go gold alloys, which have a large magnetoresistive effect. Further, the thickness of the ferromagnetic material 5X film 3 is preferably 50
00 Å or less. If it exceeds this range, the resistance of the element becomes low and it is impossible to manufacture an element with a practical output due to the relationship with the pattern shape. Therefore, the thickness of the ferromagnetic thin film of the magnetically sensitive part is preferably 2000 Å or less, and even more preferably 200 to 1000.

The protective film 6 serves to prevent contamination and corrosion of the magnetic sensing part and the electrode part. The material of the protective film 6 may be an inorganic insulating film generally used in semiconductor devices, such as 81L203, Si3N4, 5i02.

Phosphorus glass and multilayer films thereof are preferably used. In this embodiment, the insulating film is formed to have a thickness of about 1 to 15 μm. In this embodiment, as an example of externally connecting the element of the present invention, an example was shown in which the electrode 4 and the Riet wire were bonded by solder, but other bonding methods,
For example, wire bonding, lead bonding,
FX+, <11 is required.

The element of the present invention may be resin molded if necessary. The material of the mold resin 8 is generally preferably one having high heat resistance and moisture resistance, such as epoxy resin. Further, the entire element may be molded, or only a portion may be molded to reinforce lead wires or the like.

Next, regarding the manufacturing method of the ferromagnetic magnetoresistive element of the present invention,
This will be described with reference to FIGS. 2, 3, and 4. FIG. 2 is an example of a process diagram, FIG. 3 is a top view of the element in each step, and FIG. 4 is a sectional view taken along the line BB in FIG. 3.

The step of forming an electrode thin film in FIG. 2 is a step of heating and holding an insulating substrate l at a required temperature and depositing an electrode thin film 2 made of a ferromagnetic material by a method such as vacuum evaporation, sputtering, or plating. It is.

Figure 3 (A) and Figure 4 (A) show the state of the device after this process.
Shown below.

Next is Den-g! This is a step of etching a required portion of the R film 2. This is a step of etching away the portion of the electrode section 1 that will form the magnetically sensitive section. Through this process, the device becomes as shown in FIGS. 3(B) and 4(B)! becomes Δ.

The ferromagnetic thin film forming process is a process of depositing and forming a ferromagnetic thin film to become a magnetically sensitive part, in which the substrate 1 is heated and held at a required temperature, preferably 250° C. or higher, to produce a magnetoresistive effect on the substrate 1. In this step, a ferromagnetic thin film 3 having the same composition as the electrode material is deposited on the entire surface by a method such as vacuum evaporation, MBE, or sputtering. Through this process, the device is manufactured as shown in Fig. 3(C).
, the state shown in FIG. 4(C) is reached.

The magnetically sensitive part pattern forming process is a process in which the ferromagnetic thin film 3 formed in the previous process is removed by etching, leaving only the required parts, and the magnetically sensitive part pattern determined by the design is shown in FIG. 3(D). , as shown in FIG. 4(D).

Next, steps such as etching of the lead-out portion and formation of electrode pad portions for external connection, which are carried out in normal device manufacturing, continue. In order to roughly cover the surface of the magnetic sensing part, the electrode lead-out part, etc. with an insulating protective film 6, the process of forming the protective film is followed by a cutting process using dicing, which is carried out in ordinary semiconductor electronic parts, etc. Processes such as bonding and molding are then performed to complete the manufacture of the ferromagnetic magnetoresistive element of the present invention.

Since the element of the present invention has the above-described structure, a thin magnetically sensitive thin film having the same composition can be formed after forming an electrode thin film made of a ferromagnetic material. Therefore, the electrode pattern can be formed with good reproducibility and high reliability. Furthermore, by controlling the thickness of the electrode thin film, it is possible to precisely etch a pattern of a magnetically sensitive part made of a thin film of a ferromagnetic material having the same composition. Furthermore, since a thin film with a thickness that provides a sufficiently small resistance value is used for the leading electrode portion, it is possible to manufacture a device with high sensitivity and low offset. Electrode materials that have high adhesion to amorphous insulators, high heat resistance, and a high melting point can be used as electrodes, and the upper layer includes a ferromagnetic thin film that has good adhesion to protective layers such as 5i02. It is possible to form a film with good retention. This protective film can also protect the magnetically sensitive surface of the element from mechanical friction. Therefore, the device has a structure that can ensure extremely high reliability and can be easily mass-produced. By using an electrode material with roughly the same composition as the magnetically sensitive part, the ferromagnetic thin film of the magnetically sensitive part, which produces the magnetoresistive effect, can be formed at high temperatures, which improves the crystallinity and magnetic anisotropy of the ferromagnetic thin film. It is possible to manufacture magnetoresistive elements with high sensitivity and high output.

Furthermore, according to the manufacturing process of the present invention, it is possible to manufacture elements without damaging the magnetically sensitive part of the ferromagnetic thin film, and it is also possible to form a protective film such as 5i02 with a thickness of 10 μm or more, which is not found in ordinary semiconductors. It is possible to manufacture an element that can protect the magnetically sensitive surface against tm mechanical external forces such as friction, and has greatly improved long-term reliability such as moisture resistance.

A specific manufacturing example of the element will be described below.

300 2 inch square glass substrates with mirror polished surfaces
54% N+ -46 with a thickness of 0.2 μm, heated and maintained at ℃
%GO alloy thin film was formed by sputtering. Next, a portion of the 54% Ni-46% CO alloy thin film was removed by etching using an ammonium persulfate-based etchant as shown in FIG. 3(B). Next, the substrate was heated and held at 300° C., and 600 thin alloy films having the same composition were formed on the entire surface of the substrate by sputtering. Next, using an ammonium persulfate-based etchant, etching was performed to form the basic pattern of the magnetically sensitive portion as shown in FIG. 3(D). Next, using a photoresist (0FPR800 manufactured by Tokyo Ohka Kogyo ■), a pattern plating method was applied in which only the required areas were plated.
An AU layer with a thickness of 3 μm was formed using a Ni sulfate bath, and a Ni layer with a thickness of 3 μm was formed in a portion corresponding to 48 to 4D in FIG. 1 to form an electrode pad portion for external connection. Next, use the photoresist as an etching mask and etch the lead-out portion.
Four terminal portions of the magnetoresistive element were formed. Next, cover the parts corresponding to 4A to 4D in Figure 1 with a metal mask,
A 5i02 film 6 of 1.5 μI was formed. After that, 60%
It was placed in a molten solder bath having a composition of 5n-40% Pb to form solder parts 5A to 5D. Through this process, about 70 ferromagnetic magnetoresistive elements are placed on a 2-inch square glass substrate.
Formed during surveying.

This cutting board was cut into 4.3+nm x 7 pieces using a dicing saw.
．． It was cut into 2 mm element chips. After solder-bonding four wooden lead wires to each element chip, epoxy resin was applied and hardened as shown at 8 in Figure 1.
A ferromagnetic magnetoresistive element of the present invention was manufactured, as shown in A) and CB), which is a single layer and has a step between the magnetic sensing part and the electrode part.

The device characteristics are shown in Table 1.

For comparison, the values of the conventional example are shown at the same time, but it is clear that the offset of the element of this example is more than one order of magnitude smaller than that of the conventional element, and the sensitivity is about 1.7 times higher. Furthermore, the results of long-term reliability evaluation are shown in Table 2. It is clear that no change in characteristics was observed in the 1000-hour long-term humidity and heating test, and that it has extremely good reliability. Furthermore, there was no deterioration due to etching or the like at the boundary between the electrode part and the magnetically sensitive part, and the reliability of electrode formation was high, and sufficient reproducibility was also confirmed.

Table 1 Results after being left at 85°C and 985% relative humidity for 1,000 hoursAlso, although we have so far described a bridge-type element, the present invention is based on a structure in which the magnetic sensing parts 98 and 9B are orthogonal to each other as shown in FIG. Needless to say, the present invention can also be applied to a type of ferromagnetic magnetoresistive element or a ferromagnetic magnetoresistive element having a magnetically sensitive portion 9C as shown in FIG. In addition, in Figures 5 and 6, 4E, 4F, 4G
is an electrode for external connection.

[Effects of the Invention] As explained above, in the present invention, a ferromagnetic thin film of the same composition is formed on an electrode thin film made of a ferromagnetic material, so the manufacturing process is simplified and the reproducibility in the electrode forming process is simplified. It has high properties and reliability, and has good adhesion with the protective layer, so the reliability of the device is high. Furthermore, since a thin film that is thicker than the magnetically sensitive part and has a lower resistance value is used for the leading electrode part, the offset voltage is small and the sensitivity is high. Furthermore, since ferromagnetic materials having the same composition are used in the electrode portion and the sensing portion, the substrate can be heated to a high temperature during formation of the ferromagnetic thin film, thereby making it possible to further increase the sensitivity.

[Brief explanation of drawings]

FIG. 1(A) is a top view of an embodiment of the ferromagnetic magnetoresistive element of the present invention, FIG. 1(B) is a sectional view taken along line A-^ of FIG. 1(A), and FIG. 3A to 3D are top views of the ferromagnetic magnetoresistive element in each step; Figures (A) to 4 (D) are respectively shown in Figure 3 (A).
) to 3(D) along the line BB, FIGS. 5 and 6 respectively show magnetically sensitive part patterns of still other embodiments of the ferromagnetic magnetoresistive element of the present invention. Top view, FIG. 7(A) is a top view of a conventional ferromagnetic magnetoresistive element,
FIG. 7(B) is a sectional view taken along the line XX of FIG. 7(A). 1.11... Insulating substrate, 2... Electrode thin film, 3.13... Ferromagnetic thin film, 3A, 3B, 3G, 3D... Magnetically sensitive part, 4A, 4B, 4
, 4D, 4E, 4F, 4G, 14A, 14B, 14G
, 140...External connection electrode, 5A, 5B, 5C, 5D, 15A, 15B, 15G, 1
5D...Solder, 6...Protective film, 7A, 7B, 7(:, 7D, 17A, 17B, 17c,
17D...Lead wire, 8...Mold resin, 9A, 9B, 9C...Magnetic sensitive part, IO...Leading electrode. 8 (A) Figure 1, Figure 2, etc.) Hano
V Fig. 5 9/': Fig. 6

Claims (1)

[Scope of Claims] 1) A ferromagnetic magnetoresistive element having a magnetically sensitive part and an electrode part made of a ferromagnetic thin film closely formed in a desired shape on the surface of an insulating substrate, A ferromagnetic magnetoresistive element characterized in that the thickness of the magnetic part is thinner than the thickness of the electrode part. 2) At least the following steps: [1] Depositing an electrode material made of a ferromagnetic thin film on an insulating substrate; [2] Etching the deposited electrode material into a desired shape; 3] Depositing a ferromagnetic thin film having the same composition as the electrode material on the substrate and the etched electrode material; [4] Etching the deposited ferromagnetic thin film into a desired shape; A method for manufacturing a ferromagnetic magnetoresistive element, comprising the step of forming a magnetic part pattern.