JPH11126311A - Substrate for thin film magnetic head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease burrs produced near markings to a specified dimension or smaller, to avoid deformation of a substrate when the substrate is fixed with a jig, and to prevent production of head crush by using an etching method selected from among ion milling, reactive ion etching and chemical etching to form markings for head tractability having depth of <= a specified value. SOLUTION: A substrate for a thin film magnetic head comprising Al2 O3 -TiC ceramic material is produced by hot-press and calcination, and the substrate is ground and polished to obtain surface roughness Ra of <=50 Å to be used as a substrate. The obtd. substrate is subjected to marking with <=0.3 μm depth by a method selected from among ion milling, reactive ion etching and chemical etching. Thereby, characters can be formed with extremely uniform depth and stably formed to be shallow. By this method, strong thermal shock like a YAG laser is not given to the substrate, so that the change rate in the flatness of the substrate before and after the process is small as <=0.05 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a thin-film magnetic head used for a hard disk drive or a tape drive as a recording device of a computer.

[0002]

2. Description of the Related Art For example, about 2000 thin-film magnetic head substrates are manufactured from one wafer (φ3 ″ disk-shaped substrate), and the position of each head is determined by the matrix number for the wafer. Marked for traceability.

[0003] This marking is a description of the wafer number, the position number of the head in the substrate in the column direction and the row direction on the back surface of the substrate (the surface opposite to the surface on which the elements are formed). YAG) It is provided before or after the element is formed by a laser from a laser oscillation tube. Thus, the head can be traced by confirming the marking No. of the head manufactured at any position on the substrate even after the head is incorporated in the hard disk.

[0004]

However, in the marking using the YAG laser as described above, since the substrate surface is locally heated and melted, a molten material adheres around the marking portion, and "burrs" are generated. This “burr” is a factor that deforms when the substrate is fixed to a jig in the element forming process.

When the laser-processed surface is viewed with a scanning electron microscope (1500 times), a large number of microcracks due to thermal shock were confirmed, which caused particles to drop off when used as a head. There is also a problem that burrs cause a head crash.

[0006] Furthermore, the size of the marking characters tends to decrease with downsizing of the head. Therefore, when marking is performed with a YAG laser, the display quality of the characters is reduced when the character height is 0.1 mm or less. It deteriorated, and it became difficult to discriminate between very similar character shapes such as "8" and "B".

[0007] Further, in the transmitter of the YAG laser, the depth and position accuracy vary due to the influence of temperature change and ambient temperature change.
You have to do more. By providing such a depth, the processed portion of the marking surface is heated to a high temperature, and fine micro cracks are generated.As a result, due to such thermal stress and deterioration of the material, and due to the generation of cracks, Also, there is a problem that the flatness of the substrate changes before and after the marking.

Accordingly, the present invention has been completed in view of the above circumstances, and an object thereof is to reduce or eliminate burrs as much as possible, thereby eliminating deformation of a substrate when a jig is fixed, and further reducing the head. An object of the present invention is to provide a substrate for a thin film magnetic head in which a crash does not occur.

Another object of the present invention is to provide a thin film magnetic head which eliminates microcracks on a processing surface due to laser heat, prevents particles from falling off, and prevents the flatness of a substrate from changing before and after marking. To provide a substrate for use.

Still another object of the present invention is to provide a thin-film magnetic head substrate having improved display quality of marked characters.

[0011]

Means for Solving the Problems The thin film magnetic head substrate of the present invention is provided with a head traceability marking having a depth of 0.3 μm or less by an etching method selected from ion milling, reactive ion etching and chemical etching. The burrs around the markings are set to 0.1 μm or less.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described below with reference to Al ₂ O ₃ —Ti
This will be described in detail with a substrate for a thin film magnetic head made of C-based ceramics. It is baked by a hot press method to produce an Al ₂ O ₃ —TiC-based substrate having an average crystal grain size of 1 μm, and then grinding the substrate. ) Was polished by a double-side polishing machine to make the surface roughness Ra 50 ° or less, thereby obtaining a disk-shaped substrate having a diameter of 5 ″ and a thickness of 1.25 mm.

The substrate was marked as shown in FIG. 1 by an etching method selected from ion milling, reactive ion etching and chemical etching. In the figure, "0987156",
"0987157", "0988156", "0988"
157 "is marked on the same surface.

Then, various thin-film magnetic head substrates standardized in the industry as shown in Table 1 were produced from the marked disk-shaped substrates. The table shows the size of the substrate for the thin-film magnetic head.
”,“ 70% (Mini Slider) ”,“ 50% (Nano Slider)
r) "," 30% (Pico Slider) ","<25% (FemtoS
lider), the approximate dimensions and volume ratio of the head are shown.

[0015]

[Table 1]

Next, the specifications of various markings will be described.
First, conventional marking using a YAG laser was described, and then similar marking was performed by ion milling, reactive ion etching, and chemical etching of the present invention.

YAG Laser (Comparative Example) A mark consisting of 7 characters per head block was marked at a character height of 0.1 mm. Then, the mark is formed on the entire surface of the disk-shaped substrate by setting the vertical pitch between the blocks to 0.5 mm and the horizontal pitch to 1.2 mm, and
Each of the 0 blocks was marked.

Ion milling A resist film is applied on the disc-shaped substrate, and a pattern is formed on the resist film by a photolithographic process. Thereafter, Ar ions are used in ion milling at an accelerating voltage of 600 V and a milling rate of 200 ° / And processed for 10 minutes.

Reactive Ion Etching A resist film is applied on the disk-shaped substrate, and a pattern is formed on the resist film by a photolithographic process. Then, CF ₄ is used as a reactive gas together with Ar ions in reactive ion etching. At an accelerating voltage of 300 V and an etching rate of 800 ° / min.
Processed for a minute.

Chemical etching In this etching method, instead of using Ar ions and CF _{4 in the} reactive ion etching,
Others were performed similarly using BCl ₃ gas.

Next, the marking accuracy, line width, character height, character depth, slag height, presence / absence of microcracks, and change in flatness of various marked substrates were measured. The results shown in Table 2 were obtained. was gotten.

The marking accuracy (vertical pitch accuracy and horizontal pitch accuracy) was measured using a tool microscope, and the line width and character height were calculated from a photograph of the marking portion taken with a scanning electron microscope at 1500 times magnification and from the photograph. . In addition, a step difference was measured with a contact-type surface roughness meter for the character depth and the height of the molten portion around the marking (slag height). Further, the presence or absence of microcracks is visually observed with the above-mentioned scanning electron microscope, and the amount of substrate deformation before and after marking is measured by a light interference type flatness measuring device for the substrate flatness before and after marking on the marking surface. The difference was calculated.

[0023]

[Table 2]

As is clear from this table, when the marking is performed using the YAG laser, the depth of the characters varies within the range of 0.4 to 1.6 μm over the entire surface of the substrate, and the height of the mark is 0.5 μm around the marking portion. A molten portion (slag) was generated. Further, microcracks were confirmed in the marking grooves by SEM (scanning electron microscope) observation, and the flatness of the substrate was changed by an average of about 0.27 μm before and after processing due to such thermal shock and the like.

On the other hand, when the marking is performed by the ion milling, the reactive ion etching, and the chemical etching of the present invention, the character depth is very uniform, and furthermore, it is very shallow and stably processed. . In addition, no slag was present at all, and no microcracks were found on the bottom of the marking groove. And Y
No strong thermal shock as in the case of the AG laser was applied, the marking depth became very shallow, and the change in the flatness of the substrate before and after processing was extremely small at 0.05 μm or less.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements may be made without departing from the scope of the present invention. For example, although described in thin-film magnetic head substrate made of Al ₂ O ₃ -TiC based ceramic in the present embodiment, sapphire Alternatively, silicon carbide, Cr ₂₃ O _8, B
_{The present} invention is also applicable to a thin-film magnetic head substrate made of ceramics or a single crystal material made of ₄ C, Fe ₂ B, VB ₂ or the like.

[0027]

As described above, according to the substrate for a thin film magnetic head of the present invention, a mark for head traceability having a depth of 0.3 μm or less can be formed by an etching method selected from ion milling, reactive ion etching and chemical etching. To reduce or eliminate burrs generated around the marking to 0.1 μm or less, thereby eliminating deformation of the substrate when the jig is fixed and preventing head crashes. To prevent particles from falling off, and to prevent the flatness of the substrate from changing before and after marking, resulting in excellent marking accuracy and high display quality of the marked characters. And a substrate for a thin film magnetic head.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a marking state.

Claims (1)

[Claims] 1. A head traceability marking having a depth of 0.3 μm or less is performed by an etching method selected from ion milling, reactive ion etching and chemical etching to reduce burrs around the marking to 0.1 μm or less. Substrate for thin film magnetic head.