JPH0360169B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for forming a magnetic thin film pattern, which is used as a method for manufacturing a thin film magnetic head, etc., and is suitable for improving the magnetic properties of a magnetic head, etc.

[Background technology] Yoke of thin film magnetic head and magnetoresistive element (MR)
A magnetic thin film pattern such as an element) is formed, for example, by forming a solid film of a magnetic material on a substrate and then etching it by ion milling, leaving a predetermined shape.

In the case of fine magnetic poles, the magnetic domain structure generated in the magnetic poles has a large effect on head efficiency, frequency response characteristics, etc. Therefore, it is necessary to optimize the shape and axial direction of the magnetic thin film pattern so that the magnetic domain structure is simple, symmetrical, and stable.

For this reason, in thin-film magnetic heads, the magnetic poles are shaped like a ping-pong racket to eliminate instability of the magnetic domains (IEICE Technical Report, MR83-30, 43, 1983).
Proposals have been made to make the long axis of the MR element coincide with the axis of easy magnetization (Japanese Unexamined Patent Publication No. 1983-45619).

However, in the conventional magnetic thin film pattern forming method, for example, after forming a photoresist pattern on a magnetic thin film made of 80% by weight Ni and 20% by weight Fe, the photoresist pattern is etched by immersion in an etchant (etching liquid), or by etching using an ion beam. In the case of etching, as shown in FIG. 7, the shape edges 24 of the magnetic thin film pattern 22 formed on the substrate 20 are rough, producing magnetic poles at the sharp edges 26 and protrusions 28, and a magnetic field is generated from these edges. , which causes the magnetic domain structure of the magnetic pole to become complicated. Therefore, in addition to a decrease in head efficiency, there were also disadvantages in that the characteristics of the head deteriorated, such as fluctuations in output voltage and increase in Barkhausen noise.

[Object of the Invention] Taking the above facts into consideration, the object of the present invention is to obtain a method for forming a magnetic thin film pattern that can improve the magnetic properties of a magnetic head and the like.

[Structure of the Invention] The magnetic thin film pattern forming method according to the present invention includes the steps of laminating a magnetic thin film and an amphoteric metal film on a substrate;
A step of forming a predetermined resist pattern using a resist layer on the amphoteric metal film, a step of etching the magnetic thin film and the amphoteric metal film with an acidic etching solution, and a step of peeling off the resist layer.
Next, the method includes a step of etching the amphoteric metal film with an alkaline etching solution.

[Embodiments of the Invention] Hereinafter, an example of the process of the present invention will be described in detail with reference to FIG.

In FIG. 1, a magnetic thin film 12 made of, for example, a soft magnetic ferromagnetic material for forming a magnetic thin film pattern is formed on a substrate 10 (Step A).
Here, a Ni-Zn ferrite substrate or the like is used as the substrate 10, and the magnetic thin film 12 is formed by vapor-depositing a permalloy film, a sendust film, or a Co-Zr amorphous alloy film to a predetermined thickness by high-frequency sputtering. .

Next, immediately after forming the magnetic thin film 12, an amphoteric metal film 14 is formed on the magnetic thin film 12 (Step B). This amphoteric metal film 14 is made of an Al, Zn, Al-Cu, Al-Si film, etc. whose main component is an amphoteric metal such as Al or Zn, and is formed by vapor deposition to a predetermined thickness by DC sputtering. , magnetic thin film 12
Layer on top.

Here, the formation of the amphoteric metal film 14 prevents the surface of the magnetic thin film 12 from being oxidized and becomes passive during subsequent resist development processing, etc.
2, a better etching process is possible.

Next, a resist pattern of a predetermined shape is formed on the amphoteric metal film 14 (steps C, D, and E). That is,
For example, a positive photoresist coating film 16 is first formed on the amphoteric metal film 14, and then dried at a predetermined temperature to remove the solvent in the coating film (step C).
Here, the positive photoresist material is not particularly limited and commercially available products can be used, but an example of a suitable material is a quinonediazide photoresist, which is a condensation product of a phenol novolak resin and naphthoquinonediazide. For example, a photoresist consisting of: Note that the photoresist material may be of negative type.

Next, a mask 18 is brought into contact with the surface of the positive photoresist coating film 16, and exposed to light in a predetermined pattern through the mask (Step D). Then mask 18
The photoresist 16 is removed and immersed in an inorganic or organic alkaline developer for resist to remove the pattern of the positive photoresist 16 corresponding to the exposed portion. As a result, a pattern of positive photoresist 16 corresponding to the exposed portion remains (Step E).

Then, the amphoteric metal film 14 and the magnetic thin film 12 are immersed in an acidic etchant (etching solution), leaving the resist pattern portion remaining on the amphoteric metal film 14, and chemically etched at the same time (step F).

For example, an amphoteric metal film 1 is used as an acidic etchant.
4. Mixing nitric acid, which has a good etching reaction on both the magnetic thin film 12, phosphoric acid, which has an effect as a reaction accelerator and buffer for the magnetic thin film, acetic acid, which acts as a reaction inhibitor, and water in a predetermined volume ratio. Hydrochloric acid, sulfuric acid, etc. can be used.

For reference, aluminum alloy amphoteric metal film 14 with Al95.5wt% Cu4.5wt% and Ni80wt% Fe20wt%
Figures 2 and 3 show how the etching time changes when the volume concentration of nitric acid in the etchant is changed for each single layer and laminated layer of the permalloy magnetic thin film 12, using temperature and film thickness as appropriate parameters.
Permalloy magnetic thin film 1 of Ni80wt%Fe20wt%
FIG. 4 shows how the etching rate changes when the volume concentration of phosphoric acid in the etchant is changed for the monolayer of No. 2.

Through this etching process, patterns of the amphoteric metal film 14 and magnetic thin film 12 corresponding to the resist pattern are obtained. At this time, the end portion of the magnetic thin film 12 becomes smooth and bowl-shaped.

Further, the positive type photoresist 16 on the amphoteric metal film 14 is removed using a photoresist remover (Step G).

Next, it is immersed in an alkaline etchant such as IN sodium hydroxide solution to etch only the amphoteric metal film 14, leaving the magnetic thin film 12 (H step). As a result, a magnetic thin film 12 consisting of a magnetic thin film pattern having a predetermined shape and having smooth edges can be obtained.

When forming other magnetic thin film patterns on the magnetic thin film 12 via an insulating layer such as SiO ₂ , the same processing steps as described above may be performed.

Example 1 Ni 80% by weight and Fe 20% by weight were applied to a mirror-finished substrate by high-frequency sputtering at a sputtering power of 2.64 W/cm ² in an argon gas atmosphere of 2.0×10 ^-2 Torr.
A permalloy film with a thickness of 3.0 μm was formed, and then,
By direct current sputtering with a sputtering power of 4.94w/ ^cm2 in an argon gas atmosphere of 2.0×10 ^-3 Torr.
A 1.2 μm thick Al-based amphoteric metal film containing 95.5% by weight Al and 4.5% by weight Cu was laminated.

Next, while rotating the substrate at a rotation speed of 4000 rpm using a spinner, 40 cp-
Apply a solution of OFPR-800 (quinonediazide-based positive photoresist, manufactured by Tokyo Ohka Co., Ltd.) and
The solution was baked for 25 minutes to remove the solvent in the solution, and a positive photoresist film with a thickness of 1.4 μm was formed. After that, a positive photoresist film (OFPR) was applied.
A mask was brought into contact with the -800) surface, and contact exposure was carried out with ultraviolet rays in a predetermined pattern through this mask.

Next, OFPR of the pattern corresponding to the exposed part
800 film diluted 1:1 with OFPR-3 developer (Tokyo Ohka
Co., Ltd., an alkaline developer for resists made of inorganic alkalis such as sodium metasilicate and sodium phosphate).

Next, the sample was immersed in an etchant containing a mixture of nitric acid: phosphoric acid: acetic acid: water at a volume ratio of 20:300:40:15 for 4 minutes at 40°C, leaving behind the remaining patterned portion of the photoresist. The amphoteric metal film and permalloy film were etched at the same time.

Then, the sample was immersed in acetone, and the OFPR-800 film was peeled off from the basic surface.

Next, the sample was immersed in IN sodium hydroxide solution at room temperature for 4 minutes to etch the remaining Al-based amphoteric metal film on the permalloy film.

As a result of observation with an electron microscope, simultaneous etching of the Al-based amphoteric metal film and the permalloy film resulted in a substantially trapezoidal permalloy film with a smooth bowl-shaped end on the substrate, and a flat plate-like permalloy film, as shown in Figure 5. It was confirmed that the Al-based amphoteric metal films were stacked, and that by etching the Al-based amphoteric metal film, a permalloy film pattern with smooth edges was formed as shown in FIG.

Comparative Example 1 A permalloy film with a thickness of 3.0 μm containing 80% Ni by weight and 20% Fe was formed on a substrate by high-frequency sputtering at a sputtering power of 2.64 W/cm ² in an argon gas atmosphere of 2.0 ^× 10 −2 Torr. on this permalloy film
After forming a prescribed resist pattern of OFPR-800, the passive layer on the surface of the permalloy film was clouded with concentrated hydrochloric acid vapor, and the volume ratio of nitric acid:acetic acid:water was 1:1:
Chemical etching was performed at 40°C using an etchant with a volume ratio of 4. Then, the remaining resist layer was removed.

As a result of observation with an electron microscope, the permalloy film pattern had many rough edges and sharp edges.

Comparative Example 2 After forming a permalloy film on a substrate in the same manner as in Comparative Example 1 and forming a prescribed resist pattern on the permalloy film, ion beam etching was performed using argon gas to remove the remaining resist layer.

As a result of observation with an electron microscope, the results were similar to those of Comparative Example 1.

[Effects of the Invention] In the method for forming a magnetic thin film pattern according to the present invention, the end portion of the magnetic thin film pattern can be made into a smooth bowl shape, so that magnetic poles are not generated at the edges or end faces, and the end portion of the magnetic thin film pattern can be formed into a smooth bowl shape. By suppressing the generation of complex domain walls from the magnetic thin film pattern, it is possible to create a good magnetic domain structure in the magnetic thin film pattern, thereby suppressing the decline in efficiency of magnetic circuits such as magnetic heads, and reducing output fluctuations and Barkhausen noise. At the same time, it has the excellent effect of making it possible to improve frequency response.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of the magnetic thin film pattern forming method of the present invention in the order of steps, and Figs. 2 and 3 show the nitric acid concentration in the etchant and the dissolution rate for single layer and stacked layers of magnetic thin film and amphoteric metal film. Figure 4 is a diagram showing the relationship between the phosphoric acid concentration in the etchant and the dissolution rate of the magnetic thin film. Figure 5 is a cross section of the pattern after simultaneous etching of the magnetic thin film and amphoteric metal film stack. 6 is a cross-sectional view showing the cross-sectional shape of the pattern of the magnetic thin film after etching the amphoteric metal film. FIG. 7 is a schematic diagram showing the cross-sectional shape of the pattern of the magnetic thin film after chemical etching by the conventional method. It is a diagram. 10...Substrate, 12...Magnetic thin film, 14...Amphoteric metal film, 16...Positive photoresist coating film, 18...Mask.

Claims (1)

[Claims] 1 A process of sequentially laminating a magnetic thin film and an amphoteric metal film on a substrate, a process of forming a predetermined resist pattern using a resist layer on the amphoteric metal film, and a process of laminating the magnetic thin film and an amphoteric metal film using an acidic etching solution. A magnetic thin film pattern forming method comprising the steps of etching, peeling off a resist layer, and then etching an amphoteric metal film with an alkaline etching solution.