The present application claims priority from Japanese application JP 2008-38163 filed on Feb. 20, 2008, the content of which is hereby incorporated by reference into this application.
1. Field of the Invention
The present invention relates to a high-recording density magnetic recording device and, more particularly, to a magnetic recording medium of a hard disk unit.
2. Background Art
Along with an increase in the recording density of a magnetic recording device, noise due to an disorder in the magnetized state of track edges arising in association with an increase in track density, a side-read phenomenon arising due to reading from adjacent tracks, damage to a magnetic recording medium due to a decreased floating amount of a magnetic head, and the like have become extremely critical issues. In order to solve these problems, there is an expectation for the realization of a discrete track medium the tracks of which are physically divided from one another.
In recent years, a study has been made of a discrete track medium and there is known a variety of materials, processes and the like used to physically fill up intertrack spaces (see JP Patent Publication (Kokai) Nos. 2006-196143 and 2006-92632). Since a concavo-convex shape remains on a surface of a recording medium if a refill material is formed on a convex portion of a track and a concave portion between tracks, the medium surface needs to be planarized. As a method for removing superfluous layers of resist and the refill material on the convex portion, there is known a liftoff method for removing the resist and the refill material adhering to the periphery of the resist using an organic solvent. In addition, a dry etching method, CMP and the like capable of selectively removing only the refill material on the convex portion have been applied on trial. As the dry etching method, there is known a method in which, for example, a stopper layer is formed on a magnetic recording layer and the entire medium surface including a concavo-convex shape is filled with the refill material. Next, only a mask material is selectively dry-etched by taking advantage of a etching rate ratio between the refill material and the mask material, in order to remove a superfluous amount of refill material formed on convex portions (JP Patent Publication (Kokai) No. 2006-196143).
In a discrete track medium having a conventional structure, a magnetic recording layer is formed on predetermined tracks and desired magnetic characteristics are obtained by a photolithography step or a nanoimprint step, and an etching step, an intertrack filling step and a surface planarization step, when forming intertrack grooves including a continuous magnetic recording layer. As an example,
According to, for example, JP Patent Publication (Kokai) No. 2006-196143, an oxide film made of SiO2 or the like formed by sputtering or a nonmagnetic metal is used as the refill material. Next, the substrate surface is planarized using ion beam etching, reactive ion etching (RIE) or the like, in order to remove superfluous portions of the refill material.
At the time of planarization, however, the conventional manufacturing method has had the following problems:
According to the present invention, the upper layer of the magnetic recording layer of a track and the refill layer are made of the same material, and an intermediate layer higher in etching rate than the refill material is inserted in the upper layer of the track. Thus, it is possible to planarize the medium surface when etching is finally completed.
After the magnetic recording layer is film-formed, a second intermediate layer 16 and a third intermediate layer 17 are film-formed sequentially using the same material as that of the refill material. Then, a resist layer 47 is laminated on the third intermediate layer 17. Next, the resist layer 47 is processed into the shape of a resist pattern layer 18 for the purpose of track pattern formation. After patterning is performed on the third intermediate layer 17, the second intermediate layer 16 and the magnetic recording layer 15 using this mask pattern, the resist pattern layer 18 is removed.
A refill material to be formed next is the same as that of the second intermediate layer 16. Since the ion milling rate of the third intermediate layer 17 is approximately three times as fast as those of the refill layer 19 and the second intermediate layer 16, the etching rate difference between concave and convex portions is adjusted. Thus, it is possible to realize an even more planar surface shape. In addition, there is no need for a stopper layer since the refill layer 19 and the second intermediate layer 16 are resistant to ion milling. Thus, it is possible to simplify a manufacturing process. Since the upper layer 16 of the magnetic recording layer 15 is a protective layer, it is also possible to reduce characteristic degradation due to argon ion collision. As a result, there are realized an improvement in surface planarity, a reduction in the number of manufacturing steps, and a reduction in characteristic degradation.
Firstly, the discrete track medium of the present invention makes it possible to enhance the planarity of a medium surface by forming the third intermediate layer 17 for adjusting the etching rate. Secondly, it is possible to reduce the number of manufacturing steps by forming the refill layer 19, the protective layer 21 and the second intermediate layer 16 from the same material. In addition, it is possible to reinforce the discrete track medium against impact when a magnetic head collides with a magnetic disk.
11 Substrate
12 Seed layer
13 Soft underlayer
14 First intermediate layer
15 Magnetic recording layer
16 Second intermediate layer
17 Third intermediate layer
18 Resist pattern layer
19 Refill layer
20 Lubricant layer
21 Protective layer
30 Three layers composed of seed layer 12, soft underlayer 13 and first intermediate layer 14
41 Track width
47 Resist layer
250 Magnetic disk
251 Spindle motor
252 Magnetic head
253 Access Arm
254 Actuator
255 Signal processing unit
In the best mode for carrying out the present invention, the upper layer of the magnetic recording layer of a track and the refill layer are made of the same material, and a coordination layer higher in etching rate than a refill material is inserted in the upper layer of the track.
[Embodiment 1]
Hereinafter, specific means for fabricating the magnetic recording medium of the present invention will be described using
As shown in
The substrate 11 is made of glass, alumina, silicon or the like. The magnetic recording layer 15 is composed of, for example, a granular perpendicular recording medium formed of a Co, Cr and Pt-based alloy and a nonmagnetic substance, such as SiO2. The second intermediate layer 16 and the refill material 19 are made of diamond-like carbon (DLC) which is a nonmagnetic material. The thickness of the second intermediate layer 16 is preferably 3 nm or larger since the minimum film thickness for DLC to function as a protective layer is 3 nm. The third intermediate layer 17 is formed of, for example, SiO2 or resist and is preferably have a thickness equal to or larger than the thickness of the second intermediate layer 16. Hence, the film thickness of the third intermediate layer 17 is set to approximately 10 nm. As will be described later, the film thickness is set to 10 nm as a thickness with which planarity is finally reached, taking into consideration the etching rate difference between DLC and SiO2. Examples of the resist include a resist used for photoresist masks that can be subjected to exposure and patterning using electron beams and a resist used for nanoimprinting.
Next, as shown in
Using a dry etching process such as ion beam etching, the structure of the resist pattern 18 is transferred onto the third intermediate layer 17, the second intermediate layer 16 and the magnetic recording layer 15, as shown in
The resist pattern 18 is removed by means of RIE, using an oxygen gas or the like, or ashing. If at this time, there is the re-deposition on the sidewalls of the resist 18, third intermediate layer 17, second intermediate layer 16 or magnetic recording layer 15, the re-eposition may be removed by ion beam etching or the like.
The third intermediate layer 17, if made of SiO2 or the like, is resistant to an RIE gas used to remove the resist pattern 18. Accordingly, the resist pattern 18 can be removed by an ion beam etching method using an etching gas containing an oxygen gas.
After this, as shown in
SOG that can be hardened at or below such a temperature as not to degrade the magnetic recording characteristics or SiO2 deposited by a sputtering method may be used as the refill layer 19. In this case, however, the material of the third intermediate layer 17 serving as a coordination layer for adjusting the etching rate must be higher in ion beam etching rate than SOG or SiO2.
Next, the rugged surface of the third intermediate layer 17 is planarized using ion beam etching. In the case of ion beam etching, the incident angle of a beam is within the range of 80°±5°, assuming that the normal line of the substrate 11 is 0°.
The reason for the angle of etching in the step of
At the time of etching, the glass substrate is spinning around an axis oriented in the direction of the substrate's normal line. As etching proceeds, the concavo-convex shape of the surface of the refill layer 19 approximates to planarity, as shown in
The state of etching can be monitored during etching by means of Secondary Ion Mass Spectroscopy or the like. Accordingly, the third intermediate layer 17 may have the function as an etching monitor layer.
If Secondary Ion Mass Spectroscopy is carried out concurrently with ion beam etching, it is known, at the moment a signal from the third intermediate layer 17 disappears, that the surfaces of the second intermediate layer 16 and the refill layer 19 have aligned with each other. Accordingly, etching may be finished at this moment.
Since the second intermediate layer 16 is the same in etching rate as the refill layer 19, the layers may be etched several nanometers further, so as not to expose the surface of the magnetic recording layer 15 (see
As shown in
A lubricant layer 20 made of a fluorine-based perfluoropolyether (PEPE) lubricant is coated on the medium surface using a dipping method when the refill layer 19 is planarized. This is because a refill material on the upper portion of the magnetic recording layer 15 has the function as a protective layer. The magnetic recording medium is thus completed, as shown in
[Embodiment 2]
In the same way as in embodiment 1, a magnetic recording medium is fabricated according to the steps of
If argon ions have impinged on the surface of the magnetic recording medium at the time of planarization and DLC of the uppermost surfaces of the second intermediate layer 16 and the refill layer 19 can no longer function as a protective layer, etching or ashing is performed up to a refill layer in the upper layer of the magnetic recording layer 15, as shown in
Even if the DLC of the uppermost surfaces of the second intermediate layer 16 and the refill layer 19 suffers damage when planarization is performed using a chemical-mechanical polishing method (CMP) or gas cluster ion beams (GCIB), it is possible to also use the steps of embodiment 2.
[Embodiment 3]
The refill material 19 is made of DLC, which is a material conventionally used as a protective layer. There is a case that the leading end of the magnetic head 252 collides with the surface of the magnetic disk 250 when the magnetic disk 250 and the magnetic head 252 are actually in operation as a hard disk drive. Hence, there is concern that a structural distortion arising due to impact at this moment in the magnetic recording layer 15, the first intermediate layer 14, the soft underlayer 13 and the like may cause characteristic degradation. However, if intertrack spaces are filled with such a material as DLC having a high degree of hardness, the material has the function of reducing structural disorder cased by impact.
The present invention can also be applied to, for example, patterned media.
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Number | Date | Country | |
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