JPH0322576A - Manufacture of laminated type magnetoresistance element - Google Patents

Abstract

PURPOSE:To protect a lower magnetoresistance film against corrosion when an upper conductive layer is chemically etched by a method wherein a magnetoresistance layer previously patterned into a prescribed shape is thoroughly covered with an insulating layer excluding a contact hole. CONSTITUTION:A magnetoresistance layer 1 with a prescribed pattern is formed on the surface of a substrate 2. Patterning is executed using either a wet etching method or a dry etching method. An insulating layer 4 is formed covering the whole surface of the substrate 2. The surface and the side face of the patterned magnetoresistance layer 1 are completely covered with the insulating layer 4. Then, a part of the insulating layer 4 is selectively etched to form an opening or a contact hole 5. A conductive layer 3 is formed on the whole surface of the insulating layer 4 and all the inside of the hole 5. The conductive layer 3 is filled into the the hole 5 and comes into electrical contact with the exposed surface of the magnetoresistance layer 1. Lastly, the uppermost conductive layer 3 is selectively wet-etched with an etching solution to remove the disused part so as to form an electrode with a prescribed form.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetoresistive element for detecting an external magnetic field that utilizes the so-called magnetoresistive effect in which electrical resistance changes by application of an external magnetic field. In particular, the present invention relates to a method of manufacturing a multilayer magnetoresistive element using ferromagnetic thin films.

[Conventional technology]

FIG. 2 is a schematic diagram for explaining the magnetoresistive effect of a ferromagnetic thin film. The magnetoresistive thin film 1 is formed into an elongated shape, for example, as shown in the figure. When an external magnetic field H is applied parallel to the surface of the magnetoresistive thin film 1 and across its longitudinal direction, the electrical resistance value of the thin film changes in accordance with the change in the external magnetic elevation H.

Therefore, when an electric current is passed along the longitudinal direction of the thin film, a potential difference corresponding to the change in electrical resistance is generated at both ends in the longitudinal force direction, and this is used as an output signal.

FIG. 3 is a diagram showing the layer structure of a multilayer magnetoresistive element using the magnetoresistive thin film 1 shown in FIG. A cross section cut along a plane perpendicular to the longitudinal direction of the thin film is shown. A magnetoresistive film 1 is formed on the surface of the substrate 2 by etching in a predetermined pattern. A conductive film 3 is formed so as to partially overlap the surface of the magnetoresistive film 1 . The conductive film 3 is similarly etched into a predetermined shape to form an electrode. When such a laminated magnetoresistive element is viewed from above, a pair of electrodes are electrically connected to both ends of the elongated magnetoresistive film in the longitudinal direction, and a current can flow between the pair of electrodes. drives the magnetoresistive element and converts the external magnetic field into a potential difference signal generated at both ends in the longitudinal direction.

[Problems to be solved by the invention]

The conventional multilayer magnetoresistive element shown in FIG. 3 is manufactured by sequentially forming a magnetoresistive film 1 and a conductive film 3 into a predetermined shape by selective etching. However, since the magnetoresistive film 1 and the conductive film 3 are in contact with each other, when performing wet or chemical etching, a common etching solution cannot be used, complicating the manufacturing process. In other words, after the magnetoresistive film in the lower intestine is treated with a specific etching solution, a conductive film is formed over the entire surface of the substrate. This is because there is a problem in that the underlying magnetoresistive 34 antibody film is also corroded at the same time.

[Means to resolve the gap]

In view of the problems of the conventional manufacturing method described above, an object of the present invention is to provide a method for manufacturing a multilayer magnetoresistive element in which the lower layer magnetoresistive film is not corroded when the upper layer conductive film is chemically etched. shall be.

FIGS. 1A to 1D are process diagrams showing the basic manufacturing process of a multilayer magnetoresistive element according to the present invention.

In the step shown in FIG. 1A, a magnetoresistive layer 1 having a predetermined pattern is formed on the surface of the substrate 2. In the step shown in FIG.

Batting is performed by either wet etching or dry etching. Dry etching includes, for example, sputter etching.

Next, in the step shown in FIG. 1B, an insulating layer 4 is formed to cover the entire surface of the board 2. As is clear from the figure, the insulating layer 4 completely covers the surface and edges of the battened magnetoresistive layer 1.

A portion of the insulating layer 4 is then removed by selective etching to form an opening or contact hole 5. The surface of the magnetoresistive layer 1 is exposed at the bottom of the contact 1 hole.

In the step shown in FIG. 1C, a conductive layer 3 is formed on the entire surface of the insulating layer 4 and inside the contact hole 5. As is clear from the figure, the conductive@layer 3 has a contact hole 5
The inside of the magnetoresistive layer 1 is filled with clay and electrically connected to the exposed surface of the magnetoresistive layer 1.

Finally, in the step shown in Figure 1D, the uppermost conductive layer 3
An electrode having a predetermined shape is formed by selectively removing unnecessary portions by a wet etching method using an etching solution.

Preferably, the insulating layer 4 is formed of a silicon dioxide film.

Further, the magnetoresistive layer 1 is formed of, for example, a permalloy film of a ferromagnetic alloy, and the conductive layer 3 is formed of, for example, a metal aluminum film. In addition, these two types of metal films are sequentially chemically etched using a common etching solution.

Alternatively, in order to manufacture a more precise and finer multilayer magnetoresistive element, the magnetoresistive layer may be processed by sputter etching, and the conductive layer that does not require high cutting precision may be processed by normal wet etching. good.

[For production]

According to the manufacturing method according to the present invention, the magnetoresistive layer, which has been patterned in advance into a predetermined shape, is completely covered with the insulating layer except for the contact hole portion. A particularly important point is that in addition to the surface portion of the magnetoresistive layer, the end surface portion thereof is also completely shielded from the outside by the insulating layer. Subsequently, the conductive layer formed on top of the insulating layer is treated by mixed etching, but since the etching solution used at that time is blocked by the insulating layer, there is no risk of corroding the underlying magnetoresistive layer. In particular, since the edges of the magnetoresistive layer are also covered with the insulating layer, side etching, which has been a problem in the past, does not occur. In this way, the etching solution used for wet etching of the conductive layer has no effect on the magnetoresistive layer, so an appropriate chemical composition can be freely selected depending on the working conditions and the type of resist film used. For example, if the magnetoresistive layer is treated with a specific etching solution, the conductive layer can also be treated with a common etching wave. Further, even when the magnetoresistive layer is made of a ferromagnetic alloy permalloy and treated by dry etching, an etching solution suitable for etching the conductive layer can be selected regardless of the texture of the magnetoresistive layer. Even if the selected etching solution corrodes the ferromagnetic alloy Permalloy due to its woody nature, the manufacturing method of the present invention eliminates the problem because there is no risk of the etching solution coming into contact with the underlying magnetoresistive layer. Does not occur.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a method for manufacturing a multilayer magnetoresistive element according to the present invention will be described in detail below with reference to the accompanying drawings.

FIGS. 4A to 4I are process diagrams for explaining an embodiment of the manufacturing method of the present invention.

In the step shown in FIG. 4A, a silicon wafer/X commonly used in semiconductor manufacturing is used as the substrate 2. The top surface of the silicon Ueno is covered with a thermal oxidation layer 6 having a thickness of about 1 μm by heat treatment in advance. The base layer 7 covers the entire surface of the thermal oxidation layer 6.
is formed by electron beam vacuum evaporation. The base layer 7 is made of silicon dioxide, for example, and has a thickness of about 2000 nm.

Magnetoresistive layers 1 are similarly formed over the entire surface of the underlayer 7 by electron beam vacuum evaporation. The magnetoresistive layer 1 is made of, for example, permalloy, which is a ferromagnetic alloy of nickel and iron, and has a thickness of 3 to 500 mm. In particular, permalloy having a composition of nickel 83 diiron 17 has an inverse magnetostriction constant of 0 and is an excellent ferromagnetic material. A blocking layer 8 is formed over the entire surface of the magnetoresistive layer 1 by electron beam vacuum evaporation. The blocking layer 8 is made of silicon dioxide, for example, and has a thickness of at least 1000 nm or more. As will be described later, the blocking layer 8 has the function of blocking the reactive plasma used to ash the etching resist layer, and protects the underlying magnetoresistive layer during the manufacturing process. A surface layer 9 is formed over the entire surface of the blocking layer 8 by electron beam vacuum evaporation. The surface layer 9 is made of alumina, for example, and has a thickness of at least 200 mm. This surface layer 9 has excellent adhesion to the etching resist layer.

In the step shown in FIG. 4B, unnecessary portions of the stack formed in the previous step are removed by dry etching or sputter etching using the resist layer 10 patterned into a predetermined shape.

As the material of the resist layer 10, it is preferable to use a photosensitive positive organic material. The positive resist layer 1 has better sputter etching resistance and resolution than the negative resist layer, and is therefore suitable for high-precision etching.

FIG. 5 shows a sputtering apparatus used for sputter etching processing. The sputtering apparatus is composed of a vacuum chamber 2l, and the vacuum chamber 2l is equipped with an inlet 22 for introducing gas and an exhaust port 23 for discharging the gas. The ceiling of the vacuum chamber 21 constitutes an anode electrode 24, and a cathode electrode 25 is housed inside the vacuum chamber 21 opposite to this. The inside of the cathode electrode 25 is ψ empty, and a coolant is introduced through the cooling pipe 26 to cool the sample substrate 2 placed on the upper surface of the cathode electrode 9 1 0 25 . A high frequency power source 28 is connected to the cathode electrode 25 via a matching box 27.

In order to perform sputter etching in the process shown in FIG. 4B, first, inert argon gas is introduced into the vacuum chamber 21 through the suction port 22. A high frequency voltage is applied between the anode electrode 24 and the cathode electrode 25 to turn the introduced argon gas into plasma.

The ionized argon particles are accelerated and collide with the sample air plate 2 to remove unnecessary laminated portions not covered by the resist layer IO.

Following the sputter etching process, an ashing process is performed using the same sputtering device in order to remove the unnecessary resist layer IO. The ashing process is performed by introducing reactive oxygen gas into a vacuum chamber. A high frequency voltage is applied between the anode electrode 24 and the cathode electrode 25, the introduced oxygen gas is turned into plasma, and the ionized oxygen particles are transferred to the resist layer 1 on the surface.
Collision with 0.

Since the resist layer 1O is made of an organic material, it reacts with reactive oxygen particles, is decomposed, and removed.

At this time, the blocking layer 8 prevents reactive oxygen particles from reaching the magnetoresistive layer 1 and prevents the reactive oxygen particles from reaching the magnetoresistive layer 1 during the manufacturing process.
This prevents the properties of the material from deteriorating.

In the step shown in FIG. 4C, the laminated layer and substrate surface etched into a predetermined shape in the previous step are covered with an insulating layer 4 by magnetron sputtering using the same sputtering device. The insulating layer 4 is made of silicon dioxide, for example, and has a thickness of approximately 3μ.
It has a film thickness of Since the film thickness is quite thick, not only the surface of the etched stack but also the end faces thereof are completely buried inside the insulating layer 4. In this way, the exposed end portions of the magnetoresistive layer 1 are also completely covered with the insulating layer 4. In forming the insulating layer 4, the Magne 1-Roncebatter method was used to form a dense glass structure at a relatively low temperature.
This is because it is possible to form a silicon dioxide insulating layer with a high temperature. The magnetron sputtering method is particularly effective when a ferromagnetic permalloy alloy whose properties tend to change due to thermal stress is used for the magnetoresistive layer.

In the step shown in FIG. 4D, reactive plasma etching is performed using the same spatter device using tetrafluoromethane 11 gas to selectively remove a predetermined portion of the insulating layer 4. The selective etching is performed until not only the thick portion of the insulating layer 4 but also the surface layer 9 and the blocking layer 8 are removed and the surface of the magnetoresistive layer 1 is finally exposed.

In this way, contacts 1 and holes 5 are formed.

Next, in the step shown in FIG. 4E, the substrate 2 is taken out from the sputtering device and put into a vacuum evaporation device. Conductive layer 3 is formed to cover the entire surface of insulating layer 4 by electron beam vacuum evaporation. At this time, the conductive layer 3 also fills the inside of the contact hole 5 and is electrically connected to the exposed magnetoresistive layer 1. The conductive layer 3 is made of metal aluminum, for example, and has a thickness of approximately 1.5 μm.

In the step shown in FIG.
- Form layer 11. The resist 1/layer 11 is composed of a positive or negative type photosensitive organic +4 material. In this example, a positive photosensitive material is used. In addition, when using a negative resist material, the chemical composition of the stripping solution required for stripping the magnetoresistive layer 12 is
Since it has the property of corroding the permalloy constituting the resistor layer 1, if the end face portion of the resistor layer 1 is not completely covered, corrosion due to side etching may occur. However, according to the manufacturing method according to the present invention, the magnetoresistive layer 1
Since the end face portion of is completely covered with the insulating layer 4, the risk of corrosion of the magnetoresistive layer is reduced.

Next, in step 2 shown in Figure 4G, unnecessary portions of the conductive layer 3 are removed by wet etching. The wet etching method was used because the allowable dimensional error range of the conductive layer 3 is larger than the allowable dimensional error range of the magnetoresistive layer 1. In this wet etching, an acidic etching solution, such as a phosphoric acid-based etching solution, is used. The conductive layer 3 made of metal aluminum is also corroded by an alkaline etching solution, but an alkaline etching solution such as a sodium hydroxide solution simultaneously corrodes the positive resist 1 and the layer 1.
This is not appropriate in this case because it violates l. The acidic etching solution used also has the property of corroding the magnetoresistive layer 1 made of 14 permalloy. Therefore, if the end face portion of the magnetoresistive layer 1 were exposed as in the conventional case, corrosion would occur due to side etching, which would cause problems, but in the manufacturing method according to the present invention, as described above, Since the end face portion of the magnetoresistive layer 1 is completely buried inside the insulating layer 4, such a problem of side etching does not occur.

In the step shown in FIG. 4H, the unnecessary resist layer 1l is peeled off and removed using a special stripping solution.

In this way, the electrode 3 electrically connected to the magnetoresistive layer 1 and having a predetermined shape is formed.

Finally, in the step shown in FIG. 4, the protection layer 12 is formed by magnetron sputtering so as to cover the entire exposed surface. The protective layer 12, like the insulating layer 4, is made of a dense film of silicon dioxide and has a thickness of approximately 5 μm. Finally, the protective layer 12 is selectively wet-etched using a hydrofluoric acid-based etchant to expose a portion of the conductive layer 3 that forms the lower electrode, thereby forming the bonding pad 13. This bonding pad l3 is used for electrical connection with an external circuit.

〔Effect of the invention〕

As explained above, according to the present invention, the magnetoresistive layer constituting the multilayer magnetoresistive element is completely covered with the insulating layer, including the edge portion thereof.

Therefore, even when a conductive layer formed on an insulating layer is processed by wet etching to form an electrode for external electrical connection, the etching process used does not come into contact with the underlying magnetoresistive layer, so the magnetoresistive layer is It has the effect of not being subject to unexpected corrosion.

In addition, since the magnetoresistive layer and the conductive layer can be etched using the same etching solution or the same type of etching solution, the manufacturing process can be easily controlled. Furthermore, since the resist stripping solution does not come into direct contact with the underlying magnetoresistive film, the magnetoresistive layer will not be corroded even if a stripping solution exclusively used for negative photoresist films is used. Therefore, there is an effect that the degree of freedom in selecting the resist material as well as the etching solution is increased.

15 16

[Brief explanation of drawings]

1A to 1D are diagrams showing the basic manufacturing process of the multilayer magnetoresistive element according to the present invention, FIG. 2 is a perspective view for explaining the operating principle of the magnetoresistive element, and FIG. Figure 3 is a cross-sectional view of a conventional laminated magnetoresistive element, and Figures 4A to 4I.
5 is a process diagram showing an embodiment of the manufacturing method according to the present invention, and FIG. 5 is a sectional view showing the structure of a sputtering apparatus used in the manufacturing method according to the present invention. 1... Magnetoresistive layer 3... Conductive layer 5... Contact hole 7... Base layer 9... Curved surface layer 10, . ll...Resist I layer 13...Bonding pad 2...Substrate 4...Insulating layer 6...Thermal oxidation layer 8...Blocking layer l2...Protective layer

Claims (1)

[Claims] 1. Consisting of a substrate, a magnetoresistive layer formed on the substrate and having a predetermined pattern, and a conductive layer electrically connected to the magnetoresistive layer and having a predetermined shape. A method for manufacturing a multilayer magnetoresistive element, comprising: forming a magnetoresistive layer on the substrate surface; forming the magnetoresistive layer into a predetermined pattern by etching; and the etched magnetoresistive layer. a step of forming an insulating film so as to cover the surface and end faces of the insulating film; a step of selectively etching the insulating film to provide an opening to expose a part of the surface of the magnetoresistive layer; and a step of forming the opening on the insulating film. 1. A method for manufacturing a multilayer magnetoresistive element, comprising the steps of: forming a conductive layer so as to close the conductive layer; and forming the conductive layer into a predetermined shape by wet chemical etching. 2. The manufacturing method according to claim 1, wherein the insulating layer is formed of a silicon dioxide film. 3. The magnetoresistive layer is formed of a permalloy film, and the conductive layer is formed of an aluminum film,
2. The manufacturing method according to claim 1, wherein each of these films is formed into a predetermined pattern and shape by chemical etching using a common wet etching solution. 4. A claim in which the aluminum film is chemically etched to form a predetermined shape using a positive resist layer that can be removed with a stripping solution that does not attack the permalloy film, and an acidic etching solution that does not attack the positive resist layer. The manufacturing method according to item 3. 5. The manufacturing method according to claim 1, wherein the magnetoresistive layer is formed into a predetermined pattern with relatively high precision by sputter etching, and the conductive layer is formed into a predetermined shape with relatively low precision by chemical etching. .