JP3280538B2 - Ferrite processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing ferrite, and more particularly to a method for processing ferrite used in a magnetic head used in a magnetic recording / reproducing apparatus such as a VTR, R-DAT, digital VTR, and the like.

[0002]

2. Description of the Related Art At present, VTR, R-DAT, digital V
In a magnetic recording / reproducing apparatus such as a TR, the recording density has been increased, and in order to achieve a higher density, it is required to control the track width of a magnetic head with high precision. That is, there is a demand for high precision processing of the magnetic head.

Hitherto, ferrite has been used as a material for a magnetic head. Ferrite is a material having excellent high-frequency characteristics because of its high magnetic permeability and high specific resistance. However, ferrite has a problem that it cannot be processed with high precision by ordinary machining.
In addition, there is a problem that a deteriorated layer is formed on the surface of the ferrite after the mechanical processing, and the magnetic characteristics are deteriorated.

As a processing method other than mechanical processing, a method of processing a processing object by irradiating the processing object immersed in an etching solution with a laser beam (laser induced etching (LAE)) is known. .

[0005] Laser-induced etching of ferrite has been conventionally performed using an aqueous solution containing phosphoric acid, hydrochloric acid, or nitric acid as an etching solution (for example, JP-A-6-280053).

FIG. 4 is a conceptual diagram for explaining the processing method. In the figure, 1 is ferrite, 4 is phosphoric acid aqueous solution, 5
Is a laser source, 6 is an etching container, 8 is a laser beam,
9 is a mirror and 10 is a condenser lens.

The processing is performed as follows. First, the ferrite 1 is immersed in the phosphoric acid aqueous solution 4 inside the etching container 6. Next, in this state, a laser beam 8 is emitted from the laser source 5 and irradiates the ferrite 1 via the mirror 9 and the condenser lens 10. Then, a thermochemical reaction between the ferrite 1 and the phosphoric acid aqueous solution 4 is induced, and the ferrite 1 is etched. At this time, the laser beam 8 is condensed by the condenser lens 10 to form a minute spot, and the ferrite 1 immersed in the etching solution 4 is moved at a constant speed in accordance with a desired processing pattern shape, thereby forming the ferrite 1. Processing can be performed to a desired shape.

[0008]

However, since the above-mentioned processing method is a processing like a so-called one-stroke drawing, the processing requires a long time and the throughput of the processing step is deteriorated.

Further, due to the intensity distribution of the laser beam 8, the etching amount is large in the central portion of the irradiation region of the focused laser beam 8, but is small in the peripheral portion. For this reason, there is a problem that the machined surface is sagged and the machining accuracy cannot be improved.

Furthermore, since it is necessary to control the position of the ferrite 1 and the distance between the ferrite 1 and the condenser lens 10 with high precision, it is necessary to construct a high-precision ferrite 1 moving system. However, there is a problem that the scale of the equipment is increased and the processing cost is increased.

In the processing of lead zirconate titanate and lead titanate, a mask of Au or Ag is previously formed on the surface of the lead zirconate titanate or lead titanate during laser-induced etching (etching solution: KOH). A known method is known (Japanese Patent Laid-Open No. 4-124078). Here, first, a mask made of Au or Ag is patterned on lead zirconate titanate or lead titanate. After that, lead zirconate titanate and lead titanate are converted to KOH
It is immersed in an aqueous solution and irradiated with an Ar ion laser in that state. At this time, a thermochemical reaction between the lead zirconate titanate or the lead titanate and the KOH aqueous solution is induced near the portion irradiated with the laser beam (the portion without the mask), and selective etching is performed near the portion. Will be

However, the method disclosed in Japanese Patent Laid-Open No.
When the method described in Japanese Patent Publication No. 8 is applied to ferrite processing, the processing cannot be performed with high accuracy. Because, in order to perform ferrite processing precisely, it is necessary to use an aqueous solution containing phosphoric acid, hydrochloric acid, or nitric acid instead of an aqueous KOH solution as an etching solution.
This is because the mask g is easily corroded. Further, since the Au or Ag mask has weak adhesion to ferrite, there is also a problem that the mask is easily peeled off by a stress caused by a mismatch of thermal expansion coefficients generated at the time of heating or other external force.

The present invention has been made in order to solve the above-mentioned problems, and is intended to reduce the cost of ferrite processing.
An object is to provide a processing method that can be performed with high accuracy.

[0014]

The ferrite processing method of the present invention is a ferrite processing method in which a ferrite immersed in an aqueous solution containing phosphoric acid, hydrochloric acid, or nitric acid is irradiated with laser light to etch the ferrite. Then, on the surface of the ferrite, Ta, Ti, Cu, Mo, N
It is characterized in that a mask made of any one metal of b and Cr is formed in advance.

[0015]

The inventor of the present application is based on Ta, Ti, Cu, Mo, N
Experiments have shown that any one of the metals b and Cr has good corrosion resistance in laser-induced etching using an aqueous solution containing phosphoric acid, hydrochloric acid or nitric acid as an etching solution. According to the present invention, since a metal is used as a mask material in laser-induced etching of ferrite, the mask pattern is not etched during processing. Also, Ta, Ti, Cu, Mo, N
Since the adhesion between one of the metals b and Cr and the ferrite is good, peeling of the mask pattern can be suppressed.

Further, since an aqueous solution containing phosphoric acid, hydrochloric acid or nitric acid is used as an etching solution, ferrite can be processed with high precision.

Further, since the processing is performed based on the mask pattern, it is possible to suppress the drooping of the processing surface caused by the intensity distribution of the laser beam. Also, if the size of the mask pattern is reduced, regardless of the diameter of the laser beam,
Since fine processing can be realized, a wide range of processing can be performed at a time by increasing the diameter of the laser beam, and the throughput of the processing step is improved.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, in laser-induced etching of ferrite using an aqueous solution containing phosphoric acid, hydrochloric acid or nitric acid as an etching solution, a mask made of a high melting point metal is previously formed on the surface of ferrite.

FIG. 3 shows Ta, Ti, Cu, Mo, Nb,
FIG. 3 is a diagram showing an etch rate when a metal such as Cr is subjected to laser-induced etching (etching solution: 85% phosphoric acid aqueous solution). This figure also shows the MnZn ferrite etch rate for comparison.

The etch rate was measured as follows.
First, by vapor deposition or sputtering on a glass substrate ,
Metals such as Ta, Ti, Cu, Mo, Nb, Cr , M
A sample is prepared by forming nZn ferrite. Next, while the sample was immersed in an 85% phosphoric acid aqueous solution, an Ar ion laser (wavelength: 514.5 n) was applied to the surface of the sample.
m, intensity: 90 mW). Thereafter, the sample is washed with pure water, and the depth of the pit at the etched portion is measured.

FIG. 3 shows that Ta, Cr, Nb, Ti, M
It can be seen that the etch rate is lower in the order of o and Cu, and the etch rate is 100 ° / sec or less even with Cu. That is, the metal is seen to have a good corrosion resistance in the laser-induced etching.

In particular, for Ta, no etching was observed after etching for 10 seconds. Then, the laser induced etching (etching solution: 85% phosphoric acid) for 8 minutes was tried, but in this case, Ta was hardly etched. In a 4% hydrochloric acid aqueous solution, and 85% phosphoric acid and 3%
Even in laser-induced etching in a mixed solution of 5% hydrochloric acid and 60% nitric acid, almost no etching was performed by etching for 8 minutes. Therefore, it is understood that Ta has very good corrosion resistance in laser-induced etching using an aqueous solution containing phosphoric acid, hydrochloric acid, or nitric acid as an etching solution.

On the other hand, as shown in FIG. 3, MnZn ferrite is about 1400 ° / sec by laser-induced etching.
Etching is performed at a high speed of c. Therefore, Ta, T
By laser-induced etching using a metal such as i, Cu, Mo, Nb, and Cr , particularly Ta as a mask material, selective etching of ferrite alone can be realized.

Hereinafter, a method of laser-induced etching of ferrite according to the present invention will be described in detail with reference to FIGS. FIG. 1 is a conceptual diagram illustrating a processing method by laser-induced etching according to the present invention. FIG. 2 is a diagram illustrating the processing steps. In the figure, substantially the same parts as those of the conventional example are denoted by the same symbols.

The MnZn ferrite substrate 1 serving as the substrate of the magnetic head is rubbed and cleaned with a neutral detergent or the like to clean its surface.

A Ta film 2 is formed on the MnZn ferrite substrate 1 by a method such as vapor deposition or sputtering (FIG. 2A). The thickness was set to 0.1 to 1 μm.

A resist pattern 3 is formed on the Ta film 2 by photolithography or the like (FIG. 2B).

The portion of the Ta film 2 where there is no resist pattern 3 on the surface is etched, and the resist pattern 3 is removed with an organic solvent or oxygen plasma. Thereby, a mask pattern by the Ta film 2 is formed.
(C)). The Ta film 2 is etched by, for example, a reactive ion etching method using a mixed gas of CF4 and O2. Generally, the above metal is easily etched by plasma of a mixed gas of CF ₄ and O ₂ , and the etching can have high anisotropy by using the reactive ion etching method. This allows
Side etching hardly occurs, and the Ta film 2 can be processed with the accuracy of photolithography.

With the processing system shown in FIG. 1, MnZ
The n ferrite substrate 1 is processed. The method will be described below with reference to FIG.

First, a Ta film 2 as shown in FIG.
The MnZn ferrite substrate 1 patterned by the mask is immersed in an 85% phosphoric acid aqueous solution 4. Then, an Ar ion laser beam 8 (wavelength 514.5 nm) from the laser source 5
And MnZn is passed through the mirror 9 and the lens 10.
Irradiation is performed on the surface of the ferrite substrate 1 to perform laser-induced etching of the MnZn ferrite substrate 1 in a portion where the mask made of the Ta film 2 is not formed. At this time, the moving table 7
The laser beam 8 is scanned on the MnZn ferrite substrate 1 by moving the container 6 containing the 85% phosphoric acid aqueous solution 4 by moving.

[0031] The MnZn ferrite substrate 1 after the process is taken out from the phosphoric acid solution 4, sufficiently washed with water, CF ₄
The Ta film 2 is removed by plasma of a mixed gas of O ₂ and O ₂ . Since the etching by the plasma of the mixed gas of CF ₄ and O ₂ has a very high selectivity between the Ta film 2 and the MnZn ferrite substrate 1, the MnZn ferrite substrate 1 is etched and its processing pattern is etched. Does not collapse.

The MnZn ferrite substrate 1 is processed by the above steps (1) to (4). In this example, since the 85% phosphoric acid aqueous solution 4 is used as the etching solution, high-precision processing can be realized.

Since the Ta film 2 is used as a mask material, the MnZn ferrite substrate 1
The portion where the Ta film 2 is not formed is etched by the thermochemical reaction, but the portion where the Ta film 2 is formed is not etched due to the corrosion resistance of the Ta film 2. Therefore, it is possible to process the MnZn ferrite substrate 1 with high accuracy according to the pattern shape of the Ta film 2.

Further, since the processing is performed based on the mask pattern of the Ta film 2, it is possible to prevent the processed surface from sagging due to the intensity distribution of the laser beam 8. Furthermore, if the size of the mask pattern is reduced, fine processing can be realized irrespective of the diameter of the laser beam 8, so that a wide range of processing can be performed at once by increasing the diameter of the laser beam 8. In addition, the throughput of the processing step is improved.

Furthermore, since the adhesion between the Ta film 2 and the MnZn ferrite is good, separation of the mask pattern during laser-induced etching can be suppressed.

Although the Ta film 2 is removed in the above process, the Ta film 2 is removed even after processing the MnZn ferrite substrate 1 by utilizing the extremely high adhesion between the Ta film 2 and the MnZn ferrite substrate 1. They can be left without being used for later processing. For example, MnZn ferrite substrate 1
When used in a magnetic head, as a base layer of a magnetic film such as a NiFe film or a FeAlSi film or an insulating film such as SiO ₂ or Al ₂ O ₃ which is required in a manufacturing process of the magnetic head,
The Ta film 2 can be used as it is.

The laser beam 8 is not limited to the Ar ion laser beam, but may be a YAG laser beam, an excimer laser beam, or the like.
u, Mo, Ti, Nb, metallic film such as Cr can be used. However, these materials are more easily etched by laser induced etching than Ta, as shown in FIG.

Further, even when an aqueous solution containing hydrochloric acid or nitric acid is used as an etching solution, it is possible to perform processing with high precision. When the processing was actually performed in the above steps 1 to 4 using a 4% hydrochloric acid aqueous solution as an etching solution,
Although the etch rate of the nZn ferrite substrate 1 was 1/10 (114 ° / sec) of the case of using an 85% phosphoric acid aqueous solution, high-precision processing could be realized.

It is needless to say that the working method of this embodiment can be applied to the processing of ferrites other than MnZn ferrite.

[0040]

As described above, according to the present invention, in laser-induced etching of ferrite, Ta, T
Since metals such as i, Cu, Mo, Nb, and Cr are used, fine processing of ferrite can be performed with high accuracy and at high speed. Therefore, a ferrite magnetic head used in a magnetic recording device for high-density recording can be manufactured with high precision and at low cost.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a processing method of the present invention.

FIG. 2 is a cross-sectional view illustrating a processing step of the present invention.

3 is a diagram showing the etch rate of each Tanekin genus and MnZn ferrite.

FIG. 4 is a conceptual diagram illustrating a conventional processing method.

[Explanation of symbols]

 Reference Signs List 1 MnZn ferrite substrate 2 Ta film 4 85% phosphoric acid aqueous solution 8 Laser beam

Claims (1)

(57) [Claims] 1. A ferrite processing method for irradiating a ferrite immersed in an aqueous solution containing phosphoric acid, hydrochloric acid, or nitric acid with a laser beam to etch the ferrite, the method comprising : Ti, Cu, M
A method for processing ferrite, comprising forming a mask made of any one of o, Nb, and Cr .