JPH07240368A - Autoalignment marker forming method of thin film magnetic head substrate - Google Patents

Abstract

PURPOSE:To enable a substrate and a photomask to be aligned with high precision by the high reflecting output given when beams are irradiated for the autoalignment of a laminated pattern in the wafer process for manufacturing thin film magnetic head. CONSTITUTION:The purpose of the autoalignment marker forming method is to form the marker parts 20, 22 for distinct and dark visions. Firstly, a resist is formed on the surface of an alumina protective film to dig in the marker part about 5000Angstrom thick by ion milling process making an Ar incident angle of almost 0 deg. for evaporating a Ti reflecting film 24 on the marker part. At this time, a gap making alumina sputter film is formed on the Ti reflecting film about 1500Angstrom thick not to remove the alumina sputter film formed on the Ti film but leaving it intact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an auto-alignment marker (marker for optically performing automatic positioning) on a substrate, which is used for alignment of laminated patterns in a wafer process for manufacturing a thin film magnetic head. is there.

[0002]

2. Description of the Related Art As is well known, in a wafer process for manufacturing a thin film magnetic head, a large number of head elements are collectively formed on one substrate. Each head element is formed by sequentially laminating various types of films having a predetermined pattern using a photolithography technique. To give a specific example, a substrate having an alumina protective film formed as a base film on the surface of a mixed ceramic plate of alumina and titanium carbide is used, and a lower magnetic film (for example, Fe—Ni alloy film) and a gap film to be a head gap are used. (Eg alumina sputtered film), lower insulating film (eg polyimide film), coil film (eg copper film), upper insulating film (eg polyimide film),
An upper magnetic film (e.g. Fe-Ni alloy film) forming a magnetic core integrally with the lower magnetic film, a bump for taking out a lead wire (e.g. a copper film), a protective film for protecting an element (e.g. an alumina sputter film). Are sequentially formed in this order. For that purpose, it is necessary to accurately align the substrate and the photomask in each step.

As a technique for performing such alignment,
For example, in a semiconductor device manufacturing process or the like, automation by an auto alignment marker is performed. However, in the case of a thin film magnetic head substrate, as described above, since the substrate is formed by forming an alumina protective film on a mixed ceramic plate of alumina and titanium carbide, there is a marker portion that can obtain the necessary high reflection output. Cannot be formed. Therefore, in the conventional technique, a marker pattern for manual alignment is printed on a substrate, and an operator uses a microscope to
Positioning was visually performed using the marker pattern.

[0004]

If the operator uses such a marker pattern for manual alignment to perform visual alignment, the alignment accuracy varies greatly, reproducibility is poor, and man-hours are increased. There was a problem such as being expensive.

An object of the present invention is to solve the above-mentioned technical problems, and for automatic alignment of a laminated pattern in a wafer process for manufacturing a thin film magnetic head, when light is irradiated, a high reflection output is generated and a substrate and a substrate are formed. It is to provide a method for forming an auto-alignment marker on a thin-film magnetic head substrate, which enables highly accurate alignment with a photomask.

[0006]

SUMMARY OF THE INVENTION The present invention provides a bright-field and dark-field auto system on a thin-film magnetic head substrate having an alumina protective film on the surface thereof for manufacturing a thin-film magnetic head (wafer process). This is a method of forming an alignment marker. In this method, a resist is formed on the surface of the alumina protective film, the marker portion is dug by ion milling with an incident angle of argon of approximately 0 °, and a titanium reflection film is vapor-deposited thereon. The amount of excavation in the marker part is about 500
It is preferably about 0Å. The thickness of titanium reflection film is 1
Set to 500 to 2000Å. An alumina sputtered film for forming a gap is provided on the titanium reflection film. In that case, the thickness of the titanium reflection film is set to about 1500Å, and it is not necessary to remove the alumina sputtered film provided thereon. You can leave it as it is.

The bright field concave groove marker portions are arranged at two positions on the edge of the substrate so as to face each other. The dark-field convex stripe marker portions are arranged so as to face each other at two locations on the edge of the substrate in a direction orthogonal to the direction connecting the both bright-field marker portions. That is, two marker portions are provided for each of the bright field and the dark field per substrate.

[0008]

When a resist is formed on the surface of the alumina protective film and the marker portion is dug by ion milling so that the incident angle of argon is approximately 0 °, a steep step having an edge that is approximately a right angle is formed. When a titanium reflection film is formed thereon by vapor deposition, a beautiful surface condition can be obtained while maintaining a steep step, and the reflectance is high. When such a marker is irradiated with light, it is reflected at the edge of the step, but the edge is close to a right angle and the reflection is strong. Therefore, when the reflected light in a certain direction is detected, the intensity signal shows a sharp and large peak. . By setting the half-value width center of this peak as the edge position of the marker portion, it becomes possible to perform the alignment with the photomask side automatically and with high accuracy.

[0009]

EXAMPLE FIG. 1 shows an example of an auto-alignment marker formed according to the present invention. FIG. A is a plan view of the substrate. As shown, the thin film magnetic head substrate 1
On the 0, an automatic alignment marker for bright field and for dark field is provided. The bright field marker portions 20 are arranged so as to face each other on both sides (in FIG. A, the left and right edges of the substrate) of the thin film magnetic head substrate 10, and the dark field marker portions 22 are It is arranged so as to face the edge portion of the substrate in a direction orthogonal to the direction connecting the two bright-field marker portions 20 (vertical direction in FIG. A).

Here, the magnetic head substrate 10 is formed by forming an alumina protective film 14 on the surface of a substrate body 12 made of a mixed ceramic of alumina and titanium carbide by sputtering. The bright field marker portion 20 is a linear groove, while the dark field marker portion 22 is
Is a linear ridge. Each cross section is shown in FIG. 1B (view taken along the line XX in FIG. A) and FIG. 1C (view taken along the line YY in FIG. A). The marker portions 20 and 22 have a structure in which the alumina protective film 14 is dug out to about 5000 Å and a titanium reflection film 24 is deposited on the surface.

The formation of such an auto-alignment marker is performed, for example, in the steps shown in FIG. In the figure, A is a bright-field marker portion, and B is a dark-field marker portion, but the steps are the same except for the shape. First, a desired pattern is formed by the resist 26 on the surface of the alumina protective film 14. This pattern is a pattern in which a linear opening with a width of several μm is provided for a bright field, and a linear portion with a width of several μm is left for a dark field, and a wide linear opening is provided on both sides thereof. Next, the alumina protective film 14 is subjected to ion milling with argon (Ar ⁺ ) at an incident angle of 0 ° to form an alumina step of about 5000Å. After the O ₂ plasma is applied, the resist 26 is peeled off, the substrate is scrubbed with acetone, and the O ₂ plasma is further applied to form a marker portion of the alumina step. After that, a titanium reflection film 24 (film thickness of about 1500 Å) is deposited. Although not shown, alumina is sputtered to form a gap in a later step. The alumina sputtered film is not removed but left as it is in the marker portion.

FIG. 3 shows an automatic alignment method using such an automatic alignment marker. The photoresist 32 is applied on the substrate 30 on which the auto-alignment marker has been formed in the above-described process, and is aligned with a photomask (not shown). FIG. A shows the case of bright field.
When the substrate 30 is irradiated with light from above, the light is reflected by the step edge of the bright field marker portion 34 of the substrate 30. If only the light in a certain direction is detected from this reflected light,
An intensity signal with a peak is obtained. The position with the photomask is aligned using the half-width center of this peak. The same figure B shows the case of the dark field. When the substrate 30 is irradiated with light obliquely from above, the dark field marker portion 36 of the substrate 30 is irradiated.
Light is reflected at the edge of the step. When only the light in a certain fixed direction is detected from the reflected light, an intensity signal having a peak is obtained. The position with the photomask is aligned using the half-width center of this peak. It goes without saying that light having a wavelength that the photoresist does not sensitize is used as irradiation light.

In such automatic alignment,
In order for the auto-alignment marker to perform its function sufficiently, it is important to generate a reflection intensity signal having a sharp peak and exhibiting a required output value. In the ion milling process, the incident angle of argon is set to approximately 0 ° in order to obtain such a reflection intensity signal. The incident angle of argon is 0 °, 10 °, 20 °, 30 °,
As a result of conducting experiments on 5 stages of 45 °, ion milling efficiency increases as the incident angle increases (etching rate increases), which is preferable in terms of work efficiency, but a large reflected light intensity and a sharp peak are obtained. The
An incident angle of 0 ° was able to be aligned with high accuracy.
This is because it turned out to be By the way, in the dark field, when the argon incident angle is 30 ° and 45 °, the step edge of the marker portion becomes gentle, the reflection intensity signal is low, and the waveform is widened, so that automatic alignment cannot be performed at all. It was It is considered that this is because the smaller the incident angle is, the steeper the step becomes, and when the incident angle is 0 °, an edge close to a right angle can be formed. Further, since the titanium reflection film is formed after the ion milling step, the incident angle of argon during the ion milling should be approximately 0 °, considering that the edge of the alumina protective film is further blunted.

The titanium reflective film is formed on the alumina protective film because the alumina protective film alone produces a small amount of reflection when irradiated with light. When the titanium film is vapor-deposited, the reflection intensity increases and the alignment accuracy improves. The reason for using the titanium film is that it is stable in nature and has a small particle size and a dense structure compared to other metals used in the current process, such as Fe-Ni alloy and copper. This is because the reflection efficiency of is considered to be the best. The thickness of the titanium reflection film is set to 1500 to 2000Å because the surface is scraped by the subsequent ion milling, but the final remaining thickness can be set to 1000 to 1500Å. The amount of alumina protective film dug by ion milling is about 500.
0 Å means that if it is too shallow (for example, about 3000 Å or less), the step edge of the marker portion becomes gentle due to the film formed thereon, and a good reflection intensity signal cannot be obtained. 7,000Å or more),
This is because the ion milling with an incident angle of 0 ° results in poor efficiency and takes too much time, and the experimental results show that the margin in the bright field marker portion is smaller than when the engraved amount is 5000 Å, which is not preferable.

When the alumina sputtered film for forming the gap is left, the titanium reflection film may be thin. However, in the case of only the titanium reflection film, in order to perform auto-alignment as it is after the film is formed once until the final step, about 650 in consideration of the film thickness reduction due to ion milling several times.
A film thickness of 0Å or more is required. However, if the titanium film is thickened to 3000 Å or more, black soot will adhere thinly during vapor deposition and become dark, and if the film thickness becomes thicker, the surface tends to be rougher than when thin. There is not preferable. The alumina sputtered film for forming the gap can be completely removed by an ion milling method or a wet etching method using phosphoric acid, but the surface state of the titanium vapor deposition film does not change, which is not preferable. From these experimental results, it is optimal to dig about 5000 Å of the alumina protective film on the substrate body, provide about 1500 Å of titanium protective film on it, and leave the alumina sputtered film on it as it is.

[0016]

As described above, the present invention is a method for forming an auto-alignment marker in which an alumina protective film is dug by ion milling with an incident angle of argon of approximately 0 ° and a titanium reflective film is provided thereon. In the wafer process of a thin film magnetic head substrate, when a marker portion for bright field and dark field is irradiated with light, a high reflection output signal having a sharp peak and a sufficiently large reflection intensity is obtained from the marker portion, Highly accurate automatic alignment is possible. As a result, it is possible to perform the processing efficiently in an extremely short time and with little variation in the alignment as compared with the alignment performed by the operator's eyes.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the positions and shapes of a thin film magnetic head substrate and a marker portion.

FIG. 2 is a process explanatory view showing a method of forming a marker portion.

FIG. 3 is a schematic diagram of an automatic alignment method.

[Explanation of symbols]

 10 Thin Film Magnetic Head Substrate 12 Substrate Main Body 14 Alumina Protective Film 20 Marker Part for Bright Field 22 Marker Part for Dark Field 24 Titanium Reflective Film

Claims (5)

[Claims] 1. A method for providing a bright-field and dark-field auto-alignment marker on a thin-film magnetic head substrate having an alumina protective film on its surface, wherein a resist is formed on the surface of the alumina protective film, and argon is incident. An auto-alignment marker for a thin film magnetic head substrate, characterized in that a marker portion is dug by ion milling with an angle of about 0 °, the resist is removed, and then a titanium reflection film is deposited on the dug alumina protection film. Forming method. 2. The method for forming an auto-alignment marker according to claim 1, wherein the dug amount of the alumina protective film in the marker portion is about 5000Å. 3. The titanium reflective film having a thickness of 1500Å to 20
The method for forming an auto-alignment marker according to claim 2, wherein the length is 00Å. 4. The auto-alignment marker according to claim 2, wherein the titanium reflection film has a thickness of about 1500Å, an alumina sputtered film for forming a gap is provided thereon, and the alumina sputtered film is not removed but left as it is. Forming method. 5. The bright field concave groove marker portions are arranged on both sides of the substrate so as to face each other, and the dark field convex stripe marker portions are orthogonal to the direction connecting both bright field marker portions. The method for forming an automatic alignment marker according to claim 1, wherein the substrates are arranged so as to face each other on both sides of the substrate in the direction.