JPH03178035A - Production of substrate for magnetic recording medium - Google Patents

Abstract

PURPOSE:To remove abnormal ruggedness from the surface of a substrate by providing grooves in circumferential direction on a photoresist applied on the substrate and etching the substrate to form a rugged pattern thereon. CONSTITUTION:Concentrical grooves are provided on a photoresist applied on the surface of a substrate for a magnetic recording medium, and then the substrate is etched to form a rugged pattern thereon. By masking the substrate with a photoresist and by etching, a rugged pattern can be designed and formed as desired, and therefore, different from a method of roughening by polishing with isolated abrasive particles, the roughness height or proportion of recessed area to projected area can be controlled. Thus, abnormal projections can be prevented, and a sticking problem can be solved by controlling the groove pitch or the proportion of recessed area to projected area.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method of manufacturing a substrate for a magnetic recording medium, which is a main part of a magnetic disk drive.

2. Description of the Related Art In general, magnetic disk drives, which are external storage devices for computers, are being actively developed in technology such as miniaturization, higher capacity, and shorter data reading time (1) (2). In order to realize miniaturization and increase in capacity of magnetic disk devices, magnetic heads form the vicinity of the magnetic gap using metallic magnetic materials with high saturation magnetic flux density in order to perform saturation recording on magnetic recording media with high coercive force. , so-called metal-in-gap magnetic heads are becoming mainstream.

On the other hand, with regard to magnetic recording media, technology for increasing coercive force and thinning the film has progressed, and metal thin film magnetic recording media, which are formed using thin film techniques such as sputtering from metal magnetic materials such as cobalt-nickel-chromium, are now mainstream. It is about to replace coated magnetic recording media. Metal thin film magnetic recording media are
Compared to metal oxide magnetic coating recording media, the flatness after forming the magnetic film is better, so the flying height of the magnetic head can be reduced to about 1/2 that of metal oxide coating magnetic recording media.
Recording performance and playback output at short wavelengths are improved.

Against this background, metal thin film magnetic recording media have recently been developed, and some of them are being put into practical use.

FIG. 2(a) is a cross-sectional diagram of a recently developed metal thin film magnetic recording medium. As shown in the figure, a highly hard non-magnetic film 12 such as nickel-phosphorus is coated on the surface of the substrate 11 for 10 to 2 times.
After forming about 0 μm, it is finished with good flatness using free abrasive grains such as aluminum oxide. Next, by using fixed abrasive grains such as a polishing tape or free abrasive grains such as aluminum oxide, roughness is formed in the circumferential direction of the substrate 11 which is rougher than the surface finish in the previous step.

FIG. 2(b) shows the surface shape processed using :i1 release abrasive grains. A protective film 14 of about 0.03 to 0.1 μm is coated on the machined surface to lubricate the magnetic film 13 such as cobalt-nickel-chromium and the magnetic head and to protect the magnetic film 13. It constitutes a recording medium.

Problems to be Solved by the Invention When the surface of a substrate is processed to have irregularities using an abrasive tape or free abrasive grains as described above, the height of the irregularities can be adjusted by changing the size of the abrasive grains as shown in Figure 2 (b). It is difficult to control the thickness, and abnormal unevenness occurs as shown in the figure.

Since the high convex portion is as large as 0.1 to 0.2 μm, it comes into contact with the magnetic head flying above the medium, and in the worst case, it causes a so-called head crash in which the magnetic head collides with the medium.

In a contact start/stop type magnetic disk drive, when the rotation of the medium stops, the contact area between the medium and the head is limited to a high convex portion, and this portion is subject to severe wear. Here, the protective film 14 has lubricating performance, but since it is thin at several hundred angstroms, it loses its lubricating performance as wear progresses.
There were problems such as head crashes.

An object of the present invention is to provide a surface roughening method for removing abnormal irregularities that cause the above-mentioned problems.

Means for Solving the Problems In order to solve the above problems, the present invention provides a magnetic recording medium substrate by polishing the surface of the substrate, applying a photoresist, providing circumferential grooves in the photoresist, and then etching the substrate. The surface is textured and the height and area of the texture are controlled to eliminate the cause of head crashes.

Effect When forming irregularities on the surface of a magnetic recording substrate as in the above method, using photoresist masking and etching techniques allows the roughness to be designed and processed, unlike roughness processing by polishing free abrasive grains. The height and area ratio of the unevenness are controlled, and as a result, the magnetic head does not collide with abnormal protrusions or strongly adhere to the surface of the recording medium.

Example An embodiment of the present invention will be described below with reference to FIG.

As shown in the figure, in order to protect the substrate l whose surface has been polished, such as soft aluminum, from being deformed by the strong mechanical contact of the magnetic head, a highly hard and non-magnetic nickel-phosphorous alloy thin film 2 with a thickness of 10 to 20 μm is applied to the substrate. Above 1; this is provided. After forming the unevenness having the effect of the present invention on this non-magnetic film 2, a cobalt film having a thickness of 500 to 1000 angstroms is coated.
A magnetic film 3 made of nickel-chromium alloy or the like is made, and a protective film 4 of several hundred angstroms is formed on top of the magnetic film 3 to prevent rust and maintain lubricity with the magnetic head, thereby creating a multilayered magnetic recording medium. To manufacture.

FIG. 1(b) shows measurement data of the roughness of the surface of the nonmagnetic film 2.

Next, the manufacturing method will be explained in more detail.

A highly hard nonmagnetic film 2 made of nickel phosphorous or the like is formed to a thickness of about 10 to 20 μm on the surface of a substrate 1 made of aluminum or the like whose surface has been finished using a diamond lathe or fixed abrasive. Next, surface roughness (R,
, x) to a 1' knee finish of 300 angstroms or less. In some cases, finishing is done so that machining marks remain in the circumferential direction, taking into account the magnetic anisotropy caused by the machining marks. Next, a photoresist is uniformly applied onto the nonmagnetic film 2 using a spinner or the like, and developed using a photoresist or a laser beam so that grooves are formed at a pitch of about 1 μm in the circumferential direction. Then, it is immersed in an etching solution to create irregularities on the nonmagnetic film. In addition to using an etching solution, the grooves may also be created by dry etching using argon ions or the like. Next, the photoresist 7 is removed by an oxygen plasma etching method, etc., and a magnetic film 3 made of f&ml chrome alloy or the like and a protective film 4 having lubricating properties made of carbon or the like are formed.
A magnetic recording medium is manufactured by forming a bottom film using a sputtering method or the like.

The media manufactured by this method has no abnormal protrusions and no contact, as shown in FIG. 1(b).

The contact area during starting and stopping is reasonably large, so head crashes do not occur. However, if the contact area is too large, the adhesion between the head and the medium will be strong and smooth contact, start, and stop operations will not be obtained, which poses a problem. However, according to the manufacturing method of the present invention, the groove pitch of the photomask, Since the area ratio of the convex portions can be adjusted, problems caused by adsorption can be solved.

Effects of the Invention In general, roughening the surface of the nonmagnetic film 2 to form irregularities is an effective means of maintaining an appropriate contact area between the head and the medium and solving problems that occur when contacting, starting, and stopping the magnetic head. It is.

In other words, if the tip area of the convex portion is small and there are few contact points, adhesion and head crushing are likely to occur. On the other hand, if the surface of the magnetic film 3 is too smooth, the contact area will be large and the head will be strongly attracted to the medium surface, making it impossible to achieve smooth head running.

Therefore, as in the present invention, a photoresist is applied to the surface of a non-magnetic film with a well-finished planarity, grooves are formed in the photoresist in a controlled circumferential direction, and then irregularities are processed by etching. It is possible to prevent the occurrence of irregularities in size, to make the height uniform, and to appropriately set the contact area of the head at the time of contact, start, and stop. In addition, if a paste or oil type lubricant is used, or if the atmosphere in which the recording medium is used is high in humidity, contact and start may occur depending on the area ratio of unevenness on the medium surface.

The relationship between stop life becomes deeper, and when the total area of the four parts is wider than the total area of the convex parts, the life becomes longer.

After polishing the surface of the substrate as described above, a photoresist is applied, circumferential grooves are formed in the photoresist, developed and etched to design and process irregularities on the substrate surface, thereby increasing the recording density. Reliability when a magnetic head runs over a high-quality medium with a narrow gap is dramatically improved.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1(a) is a cross-sectional diagram of an embodiment of the magnetic recording medium of the present invention, and FIG. 1(b) shows the surface roughness of the nonmagnetic film in FIG. 1(a). FIG. 2(a) is a cross-sectional diagram of a conventional magnetic recording medium, and FIG. 2(b) is a diagram of the surface roughness of the nonmagnetic film in FIG. 2(a). 1...Substrate, 2...Nonmagnetic film.

Claims (2)

[Claims] (1) For magnetic recording media, after polishing the surface of the substrate, a photoresist is applied, circumferential grooves are provided in the photoresist, and then etching is performed to create irregularities due to the grooves on the surface of the substrate. Substrate manufacturing method. (2) The method of manufacturing a substrate for a magnetic recording medium according to claim 1, wherein the total area of the concave portions of the substrate is larger than the total area of the convex portions.