JP3712998B2 - Magnetization pattern forming method of magnetic recording medium and mask - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mask unit and a magnetization pattern forming method used when forming a magnetization pattern of a magnetic recording medium used in a magnetic recording apparatus.
[0002]
[Prior art]
A magnetic recording device represented by a magnetic disk device (hard disk drive) is widely used as an external storage device of an information processing device such as a computer, and in recent years, it is also used as a recording device for a moving image recording device or a set top box. It's getting on.
[0003]
A magnetic disk device usually has a shaft for fixing one or more magnetic disks in a skewered manner, a motor for rotating a magnetic disk joined to the shaft via a bearing, and a magnetic used for recording and / or reproduction. The head includes a head, an arm to which the head is attached, and an actuator that can move the head to an arbitrary position on the magnetic recording medium via the head arm. The recording / reproducing head is usually a flying head and moves on the magnetic recording medium with a constant flying height. In addition to the floating type head, use of a contact head (contact type head) has been proposed in order to further reduce the distance from the medium.
[0004]
A magnetic recording medium mounted on a magnetic disk device is generally formed by forming a NiP layer on the surface of a substrate made of an aluminum alloy and the like, performing a necessary smoothing process, texturing process, etc., and then forming a metal underlayer thereon. The magnetic layer (information recording layer), the protective layer, the lubricating layer, and the like are sequentially formed. Alternatively, it is manufactured by sequentially forming a metal underlayer, a magnetic layer (information recording layer), a protective layer, a lubricating layer, and the like on the surface of a substrate made of glass or the like. Magnetic recording media include in-plane magnetic recording media and perpendicular magnetic recording media. In-plane magnetic recording media are usually subjected to longitudinal recording.
[0005]
Increasing the density of magnetic recording media is increasing year by year, and there are various techniques for realizing this. For example, the magnetic head flying height can be reduced, a GMR head can be used as the magnetic head, the magnetic material used for the recording layer of the magnetic disk can be improved, and information recording tracks of the magnetic disk can be used. Attempts have been made to reduce the interval between the two. For example, 100Gbit / inch²In order to realize the above, the track density is required to be 100 ktpi or more.
[0006]
Each track has a control magnetization pattern for controlling the magnetic head. For example, a signal used for position control of a magnetic head or a signal used for synchronization control. When the information recording track interval is narrowed to increase the number of tracks, the signal used for position control of the data recording / reproducing head (hereinafter also referred to as “servo signal”) is also adjusted in the radial direction of the disc. On the other hand, it is necessary to provide dense control, that is, to provide more precise control.
[0007]
There is also a demand to increase the data recording capacity by reducing the area other than that used for data recording, that is, the area used for the servo signal and the gap between the servo area and the data recording area. large. For this purpose, it is necessary to increase the output of the servo signal and the accuracy of the synchronization signal.
Conventionally, the method widely used in manufacturing is to make a hole near the head actuator of a drive (magnetic recording device), insert a pin with an encoder in that portion, engage the actuator with the pin, A servo signal is recorded by driving to a position. However, since the center of gravity of the positioning mechanism and the actuator are at different positions, high-precision track position control cannot be performed, and it is difficult to accurately record the servo signal.
[0008]
On the other hand, there has also been proposed a technique for forming a concave / convex servo signal by irradiating a magnetic disk with a laser beam to locally deform the disk surface to form physical irregularities. However, the flying head becomes unstable due to the unevenness, which adversely affects recording and reproduction, and it is necessary to use a laser beam having a large power to form the unevenness, which is costly, and it takes time to form the unevenness one by one. There was a problem.
[0009]
For this reason, a new servo signal forming method has been proposed.
An example is a method in which a servo pattern is formed on a master disk having a magnetic layer with a high coercive force, the master disk is brought into close contact with a magnetic recording medium, and a magnetizing pattern is transferred by applying an auxiliary magnetic field from the outside (USP 5,991, 104).
Another example is a method in which the medium is magnetized in one direction in advance, and a soft magnetic layer having a high magnetic permeability and a low coercive force is patterned on the master disk so that the master disk is in close contact with the medium and an external magnetic field is applied. . The soft magnetic layer acts as a shield, and a magnetization pattern is transferred to an unshielded region (Japanese Patent Laid-Open No. 50-60212 (USP 3,869,711), Japanese Patent Laid-Open No. 10-40544 (EP 915456)), See "Readback Properties of Novel Magnetic Contact Duplication Signals with High Recording Density FD" (Sugita, Ret.al, Digest of InterMag 2000, GP-06, published by IEEE)).
[0010]
This technique uses a master disk and forms a magnetization pattern on a medium by a strong magnetic field.
In general, since the strength of a magnetic field depends on a distance, when recording a magnetization pattern with a magnetic field, the pattern boundary tends to be unclear due to a leakage magnetic field. Therefore, in order to minimize the leakage magnetic field, it is essential to bring the master disk and the medium into close contact with each other. And, as the pattern becomes finer, it is necessary to make it closely adhere to each other without any gap, and usually both are pressure-bonded by vacuum suction or the like.
[0011]
Also, the higher the coercive force of the medium, the larger the magnetic field used for transfer and the greater the leakage magnetic field, so it is necessary to make it more intimately contact. Therefore, the above technique is easy to apply to a magnetic disk having a low coercive force and a flexible floppy (registered trademark) disk that can be easily pressed, but has a coercive force of 3000 Oe or more for high-density recording using a hard substrate. It is very difficult to apply to such a magnetic disk.
[0012]
That is, there is a risk that a hard substrate magnetic disk may cause a minute defect or the like to be sandwiched between the two when it comes into close contact, causing a defect in the medium, or damaging an expensive master disk.
In particular, in the case of a glass substrate, there is a problem that adhesion is insufficient due to dust sandwiching and magnetic transfer cannot be performed, or cracks are generated in the magnetic recording medium.
Further, in the technique described in Japanese Patent Laid-Open No. 50-60212 (USP 3,869,711), a pattern having an oblique angle with respect to the track direction of the disc can be recorded, but the signal intensity There was a problem that only weak patterns could be made. For magnetic recording media with a high coercive force having a coercive force of 2000 to 2500 Oe or more, the pattern ferromagnetic material (shield material) of the master disk is a saturated magnetic flux such as permalloy or sendust in order to ensure the magnetic field strength of the transfer. A soft magnetic material with a high density must be used.
[0013]
However, in the oblique pattern, the magnetization reversal magnetic field is perpendicular to the gap formed by the ferromagnetic layer of the master disk, and the magnetization cannot be tilted in a desired direction. As a result, a part of the magnetic field escapes to the ferromagnetic layer, and it is difficult to apply a sufficient magnetic field to a desired portion during magnetic transfer, and a sufficient magnetization reversal pattern cannot be formed, making it difficult to obtain a high signal intensity. With such an oblique magnetization pattern, the reproduction output is greatly reduced more than the azimuth loss with respect to the pattern perpendicular to the track.
[0014]
On the other hand, the technique described in the specification of Japanese Patent Application Nos. 2000-134608 and 2000-134611 forms a magnetization pattern on a magnetic recording medium by combining local heating and application of an external magnetic field. For example, the medium is magnetized in one direction in advance, irradiated with an energy ray or the like through a patterned mask and locally heated, and an external magnetic field is applied while lowering the coercivity of the heating area, Recording with an external magnetic field is performed to form a magnetization pattern.
[0015]
According to the present technology, since the external magnetic field is applied by lowering the coercive force by heating, the external magnetic field need not be higher than the coercive force of the medium, and recording can be performed with a weak magnetic field. The area to be recorded is limited to the heating area, and recording is not performed even if a magnetic field is applied to the area other than the heating area, so that a clear magnetization pattern can be recorded without bringing a mask or the like into close contact with the medium. For this reason, the defect of the medium is not increased without damaging the medium or the mask by the pressure bonding.
[0016]
In addition, the present technology can satisfactorily form an oblique magnetization pattern. This is because it is not necessary to shield the external magnetic field by the soft magnetic material of the master disk as in the prior art.
[0017]
[Problems to be solved by the invention]
As described above, the above-described magnetization pattern forming technique is an excellent technique that can efficiently and accurately form various fine magnetization patterns and that does not increase the number of defects in the medium without damaging the medium or the mask. According to this method, since the same magnetization pattern can be formed on a plurality of media by repeatedly using the same mask, the magnetization pattern can be formed easily and at low cost.
[0018]
As this mask, a photomask having an energy ray transmission part and a non-transmission part (hereinafter sometimes referred to as a non-transmission layer, a light shielding layer, or a light shielding part) is often used. Photomasks are well known in the manufacturing processes of semiconductors and liquid crystals, but their production is generally performed as follows.
That is, a metal such as chromium is formed by sputtering on a transparent substrate such as quartz glass or soda lime glass, a photoresist is applied thereon, and desired transmissive portions and non-transmissive portions are formed by etching or the like. A photomask used for the magnetization pattern forming method is also usually produced by the same method.
[0019]
Chromium is a very good light-shielding material because it has a high melting point, high hardness, and is hardly damaged. Therefore, it is widely used as a layer for forming an energy ray non-transmissive portion. However, when the same mask is repeatedly used many times, for example, 10,000 times or more, there is a problem that the chromium layer as the light shielding portion deteriorates and the mask cannot be used continuously.
[0020]
If the mask cannot be used continuously and the frequency of replacement increases, it is not only complicated, but also the production cost increases. Moreover, every time the mask is replaced, the production line must be stopped, and the production efficiency is also deteriorated.
In view of the above problems, the present invention provides a highly durable mask in a technique for forming a pattern on a magnetic recording medium by a combination of local heating and magnetic field application, thereby forming a fine magnetization pattern efficiently at a low cost. An object of the present invention is to provide a method for forming a magnetic pattern. As a result, it is an object to provide a magnetic recording medium and a magnetic recording apparatus capable of recording at higher density in a short time and at a low cost.
[0021]
[Means for Solving the Problems]
  Of the present inventionMagnetization pattern forming methodThe magnetic layer on the substrateAnd lubricating layer containing fluorineThe magnetic recording medium having the above is irradiated with energy rays through a mask,SaidA method for forming a magnetization pattern, comprising: heating an irradiated portion of a magnetic layer; and applying an external magnetic field to the magnetic layer,The mask has a layer of a non-transmission part with respect to the energy beam mainly composed of silicon on a transparent substrate.
[0023]
  Of the present inventionmaskThe magnetic layer on the substrateAnd lubricating layer containing fluorineThe magnetic recording medium having the above is irradiated with energy rays through a mask,SaidA mask for use in a method for forming a magnetic pattern comprising a step of heating an irradiated portion of a magnetic layer and a step of applying an external magnetic field to the magnetic layer,On a transparent substrateIt is characterized by having a non-transparent part layer mainly composed of silicon..
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The present invention relates to a method of forming a magnetization pattern by a local heating process and a magnetic field application process in which an energy beam is irradiated onto a magnetic recording medium through a mask, and the energy beam non-transmission part is mainly composed of silicon (Si) as a mask. A mask having a layer to be used is used.
[0025]
Conventionally, a mask having chromium as a non-transmissive portion has been very commonly used in manufacturing processes of semiconductors, liquid crystals, and the like. However, according to the study of the present inventors, it has been found that in the magnetic pattern forming process of the magnetic recording medium which is the object of the present invention, the mask having chromium as a non-transmissive portion is likely to be deteriorated in pattern.
As a result of the examination of the cause by the present inventor, it has been found that the fluorine-based lubricant applied on the magnetic recording medium is decomposed by irradiation with energy rays in the heating process and generates hydrofluoric acid. Furthermore, it has been found that chromium has a catalytic action on the decomposition of the lubricant and accelerates the decomposition. And it discovered that the damage by the thermal shock of energy ray irradiation and the corrosion by hydrofluoric acid combined, and the chromium of the non-permeation | transparent part was corroded and deteriorated remarkably.
[0026]
Therefore, in the present invention, the non-transmissive portion includes a layer mainly composed of silicon (Si). Since silicon is very stable chemically and has a strong resistance to hydrofluoric acid, there is an advantage that corrosion due to hydrofluoric acid can be prevented. “Containing silicon as a main component” usually means containing 80 atomic% or more of silicon. More preferably, it contains 90 atomic% or more of silicon.
[0027]
In addition, since silicon has a melting point exceeding 1000 ° C. and is thermally stable, it has an advantage of improving the thermal durability of the mask.
Furthermore, since silicon has excellent adhesion to a glass substrate, there is an advantage that peeling does not easily occur.
Combined with these effects, it is considered that a mask including a layer containing silicon (Si) as a main component in the non-transmissive portion can withstand both thermal shock by laser and chemical erosion by hydrofluoric acid.
[0028]
According to the present invention, a highly productive pattern can be formed even on an object containing a fluorine-based compound and capable of generating hydrofluoric acid, so that the magnetic recording medium and the mask after application of the fluorine-based lubricant are brought close to or in close contact with each other. In this state, there is an advantage that the magnetization pattern can be formed without any problem.
Although the problem of mask deterioration can also be reduced by forming the magnetization pattern before applying the lubricant, it becomes impossible to perform inspection by the magnetic head before the magnetization pattern formation step. However, if the inspection with the magnetic head is performed after forming the magnetization pattern, the transferred pattern disappears. That is, when the magnetization pattern is formed before applying the lubricant, there is a problem that it is difficult to inspect with a magnetic head. Therefore, in order to perform the inspection process using the magnetic head, it is necessary to perform the magnetization pattern forming process after applying the lubricant.
[0029]
Another feature of silicon is high reflectivity in a short wavelength region of 500 nm or less. Accordingly, silicon has an advantage that light absorption is small in a short wavelength region, and therefore, a rise in the temperature of the mask due to laser irradiation is small. In particular, the reflectance is higher than that of chromium at a wavelength of 300 nm or less. For example, at 248 nm, the reflectivity of chromium is approximately 50%, whereas silicon has a reflectivity of 70% or more.
[0030]
While there is a demand for finer magnetic pattern formation for high-density recording, the wavelength of energy rays used for laser processing tends to be shorter, but the mask of the present invention has such a short wavelength. It is particularly excellent as a mask for microfabrication.
The mask according to the present invention can be continuously used for forming a magnetization pattern as many as 100,000 times or more, for example, and the mask replacement frequency can be reduced. This not only reduces the replacement work, but also reduces the production cost of the magnetic recording medium and increases the production efficiency.
[0031]
Further, for a magnetic recording medium having a high coercive force (for example, a medium having a coercive force of 3000 Oe or more), as described above, it is necessary to increase the power of the irradiated energy beam, and the effect of applying the mask according to the present invention. Is big.
Silicon also has the advantage that it is harmless compared to chromium and can be obtained at low cost.
[0032]
In addition, from the viewpoint of hydrofluoric acid resistance, noble metals such as gold and platinum are excellent, but these metals have a drawback of poor adhesion to glass as a substrate and cannot withstand the thermal shock of a laser. Moreover, since it is expensive, it is disadvantageous from a cost aspect.
Here, an example of the magnetization pattern forming method according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining an example of a magnetization pattern forming method according to the present invention. The in-plane magnetic recording medium 1 is uniformly magnetized in advance in one circumferential direction by an external magnetic field. Thereafter, the mask 2 is placed on the medium 1 and fixed with a retaining screw (not shown).
The mask 2 includes a transparent substrate 6 made of quartz and a light shielding layer 7. The light shielding layer 7 forms a shape corresponding to the magnetization pattern to be formed together with the light transmitting portion where the light shielding layer does not exist.
[0033]
A laser beam 4 is irradiated here, and an external magnetic field 3 is applied simultaneously. The irradiated energy rays are blocked by the non-transmissive layer 6, and the density of the energy rays is generated on the magnetic disk. The density of the energy rays becomes the temperature difference of the magnetic disk as it is, and the magnetization pattern is formed using this temperature difference. This external magnetic field is in the opposite direction to the external magnetic field when it is first magnetized uniformly.
[0034]
In this way, a fine magnetization pattern can be formed efficiently and accurately. At this time, the distance between the mask and the magnetic disk does not need to be constant over the entire surface, and the distance may be appropriately adjusted by a spacer or the like. Accordingly, the density of the energy beam can be easily adjusted without finely adjusting the power of the energy beam and the pattern line width of the mask depending on the line width of the pattern, and a desired magnetization pattern can be obtained.
[0035]
The material of the mask substrate is not particularly limited as long as sufficient transparency can be obtained with respect to the wavelength used for the energy rays, and glass, resin, etc. can be used, but preferably the transmittance is 80% or more. Preferably, the nonmagnetic material is 90% or more. By using a material with such a high transmittance, energy rays can be used efficiently. However, even a highly permeable material has some absorption of energy rays, so it needs to have some resistance to energy rays and heat.
[0036]
In the case of a mask used for forming a magnetization pattern, the mask is preferably made of a nonmagnetic material. A magnetized pattern can be formed with uniform clarity in any pattern shape, and a uniform and strong reproduction signal can be obtained. In the case of a mask containing a ferromagnetic material, the magnetic field distribution is disturbed by magnetization. Due to the nature of ferromagnetism, in the case of a pattern shape inclined in the radial direction of the magnetic disk or an arc-shaped pattern extending in the radial direction, the magnetic domains do not sufficiently oppose each other at the magnetization transition portion, so that it is difficult to obtain a high-quality signal.
[0037]
For the reasons described above, a glass-based material is preferable in the mask according to the present invention. Further, in the present invention, since it is necessary to form a fine pattern, quartz glass that can efficiently handle short wavelength energy rays is used. It is good to use.
Although quartz glass is relatively expensive, it has an advantage that an energy ray having a short wavelength of 300 nm or less, which is particularly easy to perform microfabrication, can be used because it has a high transparency to energy rays in the ultraviolet region. When using energy beams with longer wavelengths, it is better to use optical glass from the viewpoint of cost. The thickness of the substrate is not limited, but it is usually preferably about 1 to 10 mm in order to prevent the substrate from being bent and to stably provide flatness.
[0038]
In terms of flatness, from the viewpoint of correcting the distortion of the disk at the time of mounting, it is preferable that the undulation is small. In order to obtain a pattern of submicron or less, the undulation is preferably 2 μm or less.
In the present invention, the material of the non-transmissive layer (light shielding layer) is mainly composed of silicon, and particularly preferably contains 90 atomic% or more of silicon. Most preferred from the viewpoint of resistance to hydrofluoric acid is a layer consisting essentially of silicon. However, other elements may be included for another purpose, for example, to refine the crystal. Examples of other elements here include hydrogen, oxygen, nitrogen, Cr, Mo, Al, Pt, Au, Ag, Cu, Pd, Ti, Ni, Ta, Mg, Se, Hf, Zr, V, Nb, One or more selected from Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Ge, Te, Pb, Po, Sn, Bi, B, and the like can be given. Further, in the case of manufacturing by a sputtering method or the like, a sputtering gas such as argon may be mixed in the film. In consideration of corrosion due to decomposition components of the lubricant, the additive element is preferably a noble metal such as Pt, Au, or Rh, or oxygen, hydrogen, or nitrogen. One kind of these other elements may be used, but two or more kinds may be used. The content is usually preferably about 10 atomic% or less.
[0039]
The method for forming the light shielding layer is not particularly limited, and film formation methods such as sputtering, electron beam evaporation, thermal evaporation, and CVD can be used. However, the film is dense and hardly peels off against thermal shock. From the viewpoint of high speed film formation, sputtering is preferred.
If necessary, the light shielding layer may be a plurality of two or more layers. Alternatively, another layer may be provided on the light shielding layer. For example, a layer such as chromium oxide may be provided in order to reduce the reflectance of the light shielding layer surface.
[0040]
The film thickness of the light-shielding layer is not limited as long as sufficient non-transparency (energy-beam light-shielding property), desired reflectance, and energy-ray durability can be obtained, and also varies depending on the denseness of the film, that is, the film formation method. However, approximately 30 nm or more is preferable. If energy ray durability is regarded as important, the thickness is preferably 50 nm or more, more preferably 70 nm or more so that the heat capacity is increased. However, if the thickness is too thick, the transmittance of the energy beam decreases and the film formation time becomes too long. Therefore, the thickness is preferably 500 nm or less, more preferably 400 nm or less, and particularly preferably 300 nm or less.
When a magnetization pattern is formed by repeatedly using a single mask, foreign matters such as a lubricating layer of the magnetic recording medium may adhere to the surface of the mask, albeit little by little. When a large amount of foreign matter adheres, the intensity distribution of energy rays is affected, and the formed magnetization pattern may be adversely affected. Therefore, it is preferable to clean the mask surface every time the mask is used a predetermined number of times. For example, it is preferable to clean the mask surface every time it is used for forming a magnetization pattern about 1000 to 3000 times (each time it is irradiated with energy rays).
[0041]
In general, when cleaning the mask, the mask is applied at the edge (inner edge and / or outer edge, inner edge and / or outer edge) so as not to damage the pattern area. Hold and wash. For example, a method of cleaning using a PVA sponge or the like while rotating the peripheral edge portion of the mask fitted to a plurality of pulleys is conceivable. At this time, since the mask holding member, for example, a pulley is in contact with the edge portion of the mask and the vicinity thereof, the light shielding layer formed on the outermost peripheral portion may be damaged or the light shielding layer may be peeled off. The light shielding layer piece peeled off from the mask surface may directly adhere to the mask and adversely affect the formation of the magnetization pattern, or may damage the mask or disk when the mask and the magnetic recording medium are brought close to each other.
Therefore, it is preferable not to provide a light shielding layer on the edge portion of the mask and the vicinity thereof, which may come into contact with a holding member such as a pulley. Thereby, damage and peeling of the light shielding layer can be suppressed. The area where the light-shielding layer is not provided may be any one of the outer peripheral edge part and the inner peripheral edge part and the vicinity thereof, or both of them and the vicinity thereof, but generally the outer peripheral edge part is a mask. Therefore, it is preferable not to provide a light-shielding layer at the outer peripheral edge portion and in the vicinity thereof. The area where the light shielding layer is not provided is generally a circumferential area having a predetermined width in the vicinity of the edge portion, but may have other shapes.
[0042]
The range in which the light shielding layer is not provided is not particularly limited as long as it includes a region in contact with the mask holding member. However, if it is too small, the effect may not be obtained. It is preferable that the light shielding layer is not formed. More preferably, it is 1 mm or more. However, since the effect does not change even if it is too wide, it is preferably 5 mm or less from the edge portion. More preferably, it is 4 mm or less.
Examples of a method for manufacturing such a mask include a method in which the outermost peripheral portion and / or the innermost peripheral portion of the mask is covered with a holder or the like when the light shielding layer is sputtered so that the light shielding layer is not formed on that portion. be able to.
Further, on the light shielding layer thus formed, SiO₂It is preferable to provide a protective layer such as a wide area so as to cover the light shielding layer because peeling of the light shielding layer can be further suppressed. More preferably, a dielectric layer is provided up to the edge portion. As the protective layer, a dielectric layer described later can be preferably used.
As a method for forming such a protective layer, the protective film may be formed by removing the holder from the outermost peripheral part and / or innermost peripheral part of the mask during sputtering of the protective layer.
[0043]
In the present invention, it is preferable to form a dielectric layer transparent to energy rays on the outermost layer (side facing the medium) of the light shielding portion. One of the purposes is to reduce the reflectance of the light shielding portion on the medium side. If the reflectance of this surface is high, the light reflected from the medium is directed again to the medium, so that the temperature immediately below the light-shielding portion of the medium that is not originally recorded rises and the transfer signal is disturbed.
[0044]
Examples of the dielectric layer used here include silicon oxide, aluminum oxide, and titanium oxide. Silicon oxide is preferable from the viewpoint of durability against hydrofluoric acid and the adhesion to the glass substrate.
Silicon oxide produced by sputtering is particularly dense and has better durability against hydrofluoric acid than quartz glass, which is the same silicon oxide substrate. It is preferable that Thereby, the corrosion resistance of quartz glass can also be improved.
[0045]
In the case where the dielectric layer is provided only on the light shielding portion, the silicon-containing layer for light shielding and the dielectric layer can be continuously formed at the initial film formation stage. In the case where a dielectric is provided in both the light shielding portion and the light transmitting portion, it can be produced by a method of forming a pattern of the light transmitting portion and the light shielding portion and then sputtering silicon oxide on the entire surface.
As a method for manufacturing the dielectric layer, when a metal target is reactively sputtered with oxygen, nitrogen or the like, the film quality can be controlled by the partial pressure of the reactive gas or the film forming power. Therefore, it is preferable to use reactive sputtering in order to obtain a sufficiently transparent film quality and also from the viewpoint of film formation speed. The thickness of the dielectric is preferably 10 nm or more. More preferably, it is 20 nm or more.
On the other hand, if it is too thick, the film formation time becomes longer and optical influences are caused. More preferably, it is 200 nm or less.
[0046]
Another object of providing the dielectric layer is to improve the durability against the impact of the mask. By providing the dielectric layer as the outermost layer, the light shielding layer can be covered with the dielectric layer, thereby protecting the light shielding layer. Further, by selecting a material having a small friction coefficient as the material of the dielectric layer, the mask is hardly damaged. For example, when silicon oxide is used as the dielectric layer, since silicon oxide has a smaller friction coefficient than silicon, even when it collides with some foreign matter, it is difficult to be damaged.
Improvement of the durability against the impact of the mask is a very advantageous effect in handling the mask. For example, when transferring the mask and the magnetic recording medium close to each other, even if there is a foreign object between the mask and the magnetic recording medium, the mask can be prevented from being damaged. In addition, when dirt such as organic substances adheres during use of the mask and it is necessary to clean the mask, by providing a dielectric layer, the mask surface is damaged during the mask cleaning, and the dielectric layer By covering the light shielding layer with, peeling of the light shielding layer during mask cleaning can be suppressed.
[0047]
However, even on the surface of the mask with respect to the magnetic recording medium, the dielectric layer may or may not be formed on the outermost layer except for the region corresponding to the magnetization pattern formation region.
The mask described above is not limited to the magnetic pattern formation method, and can be suitably used as a general laser processing mask for semiconductors, liquid crystals, etc. in addition to the pattern formation of an optical recording medium. It is particularly suitable when laser processing is performed on an object that can generate hydrofluoric acid.
[0048]
In addition, the mask according to the present invention is highly effective when applied to a method of irradiating the mask with pulsed energy rays, which generally have higher power peak values than those of continuous energy rays and easily cause damage to the mask. In particular, the power per pulse of the pulsed energy line is 10 mJ / cm.²1000 mJ / cm²This is the case.
[0049]
Next, the mask manufacturing method according to the present invention will be described.
The concave portion corresponding to the pattern on the mask substrate can be manufactured by subjecting the mask substrate to chemical etching or physical etching. Chemical etching is a method in which etching is performed by corroding the mask substrate by causing a chemical reaction, and physical etching is a method in which the surface of the mask is physically removed by etching using a machine or the like.
[0050]
In the present invention, a method by chemical etching is preferable in that a fine pattern can be formed and a mask according to the present invention can be formed easily and inexpensively.
As a chemical etching procedure, prior to the etching process, first, a light shielding layer containing silicon for forming a light shielding portion is formed on the mask substrate. After forming a photoresist layer, irregularities corresponding to the magnetization pattern are usually formed on the photoresist layer by exposure and development (photolithography).
The formation of the photoresist layer is usually performed by a spin coating method. At this time, if a foreign substance is present on the surface of the light shielding layer, the thickness of the photoresist layer is uneven. For example, when foreign matter exists on the surface of the light shielding layer, hemispherical protrusions are generated on the photoresist layer. If there is such a thickness unevenness, exposure and development cannot be performed well, and a pattern cannot be accurately formed on the mask. Therefore, in order to remove such foreign matters, it is preferable to perform cleaning before or after the formation of the light shielding layer, or both. Examples of the cleaning method include a method of scrubbing with a PVA sponge using a detergent containing a surfactant. In this case, in order to prevent foreign matters from adhering again after washing, it is preferable to wash away the detergent with pure water.
In general, the exposure can be performed by a so-called laser drawing apparatus that irradiates or cuts a focused laser according to data. Etching is then performed. The etching is roughly divided into two methods: one is wet etching and the other is dry etching.
[0051]
Wet etching is a method in which a mask base having a photoresist layer corresponding to the above-described magnetization pattern is immersed in an etching solution, and an exposed portion of the light shielding layer is corroded and dissolved. According to this method, the corrosion proceeds substantially isotropically, and the light-shielding layer pattern cross section is formed in a semicircular shape.
Dry etching is a method of removing a mask substrate having a photoresist layer corresponding to the above-described magnetization pattern by gasifying the substrate by applying plasma-containing fluoride-containing gas to the exposed portion of the mask substrate. This method is called reactive ion etching (RIE), and the etching rate varies depending on the direction in which the gas particles come in. Normally, the etching proceeds specifically in the depth direction. Therefore, the cross section of the light shielding layer pattern is usually formed in a shape close to a rectangle.
[0052]
In the manufacture of the mask according to the present invention, since the shape of the pattern wall is rectangular, it is possible to form a mask with a fine pattern more stably, and to control the roughness of the groove bottom appropriately. In view of the possibility, it is preferable to prepare by dry etching. In the etching of a layer containing silicon, the etching rate of silicon is high, and the etching rate of resist and substrate (glass) is low (that is, SF having a high selectivity).₆Or CF_FourEtc. are preferably used. These gases include oxygen or N₂It is also possible to improve the etching rate by mixing an oxidizing gas such as O.
When a layer containing silicon is formed, the formed silicon layer may be oxidized during the formation process, and a silicon oxide layer may exist as the outermost layer. Since silicon oxide has a slower etching rate than silicon, it takes more time than etching only the silicon layer. Therefore, when etching is performed, it is preferable to determine the etching processing time in consideration of the etching rate of the substance existing in the etching region.
[0053]
Further, the etching rate slightly varies depending on the plasma state during etching and the variation of the thickness of the light shielding layer to be etched. If the light-shielding layer remains in the light-transmitting part due to insufficient etching, the energy beam in that part is blocked and the transmittance of the energy beam is lowered, which adversely affects the magnetization pattern to be formed. Therefore, the etching process time is preferably determined with a margin, and it is preferable to perform the etching for a time slightly longer than the time t obtained by dividing the thickness of the light shielding layer by the etching rate. Preferably it is 1.1t or more, More preferably, it is 1.2t or more. However, if the etching is performed too long, the substrate is etched deeply, and the surface of the substrate becomes rough, which is not preferable. This is because if the surface is too rough, the energy rays are diffused and the density of the energy rays varies, which adversely affects the magnetization pattern to be formed. Therefore, it is preferably 2 t or less, more preferably 1.8 t or less.
If the etching power (RF output) is too large, the amount etched at a time becomes large, so that fine etching cannot be performed. Therefore, the etching power is preferably 200 W or less, and more preferably 100 W or less. However, in order to obtain an appropriate etching rate, it is preferably 30 W or more.
[0054]
After the etching process, the photoresist layer remaining on the light shielding layer of the mask is removed with a remover. After removing the photoresist layer from the mask with a remover, oxygen or N₂It is preferable to add a step of removing the remaining photoresist by using plasma of oxidizing gas such as O gas. This makes it possible to completely remove the photoresist layer that could not be removed with the remover, or the photoresist that had adhered to the translucent part when removed with the remover. Without giving, the magnetization pattern can be formed more accurately.
[0055]
Further, by adding a step of removing the photoresist with an oxidizing gas, the surface of the light shielding layer can be oxidized at the same time. Since the oxide layer provided in this step is obtained by oxidizing the light shielding layer itself, the adhesion with the light shielding layer is much better than the oxide layer provided through another step such as sputtering. In general, an oxide layer has polarity, and those having polarity have a property of high adhesion. Therefore, using this property, when an oxide layer is further provided on the oxide layer, the adhesion is increased. Can be very effective. In the present invention, when a dielectric layer such as silicon oxide is further provided on the silicon layer as the light shielding layer, the adhesion between the dielectric layer and the light shielding layer can be improved.
Note that the resist can be removed only by plasma of oxidizing gas. According to this method, the step of removing the photoresist layer with the remover can be omitted, so that the mask manufacturing process can be simplified.
[0056]
Next, a magnetization pattern forming method using the mask according to the present invention will be described.
First, a technique of forming a magnetization pattern on a magnetic recording medium by combining local heating and external magnetic field application according to the present invention will be described.
Preferably, in the magnetization pattern forming method of the present invention, the first external magnetic field is applied to uniformly magnetize the magnetic layer in a desired direction in advance, and then the magnetic layer is locally heated and simultaneously applied with the second external magnetic field. A magnetization pattern is formed by magnetizing the heating portion in a direction opposite to the desired direction. Thereby, since magnetic domains opposite to each other are clearly formed, a magnetization pattern having a high signal intensity and a good C / N and S / N can be obtained.
[0057]
First, a strong first external magnetic field is applied to the magnetic recording medium to uniformly magnetize the entire magnetic layer in a desired magnetization direction. As a means for applying the first external magnetic field, a magnetic head may be used, or an electromagnet or a permanent magnet may be used so that a magnetic field is generated in a desired magnetization direction. Further, these means may be used in combination.
The desired magnetization direction is the same as or opposite to the traveling direction of the data recording / reproducing head (the relative movement direction of the medium and the head) in the case of a medium whose easy axis is in the in-plane direction. When the easy magnetization axis is perpendicular to the in-plane direction, it is either the vertical direction (upward or downward). Therefore, the first external magnetic field is applied so as to be magnetized as such. When the medium has a disk shape, the application direction of the first external magnetic field is preferably any one of a circumferential direction, a radial direction, and a direction perpendicular to the plate surface.
[0058]
Further, to uniformly magnetize the entire magnetic layer in a desired direction means to magnetize all of the magnetic layer in almost the same direction, but not strictly all, at least the region where the magnetization pattern is to be formed is in the same direction. It only needs to be magnetized.
The strength of the first external magnetic field may be set in accordance with the coercive force of the magnetic layer, but it is preferable that the first external magnetic field is magnetized by a magnetic field that is at least twice the coercive force (static coercive force) of the magnetic layer at room temperature. If it is weaker than this, magnetization may be insufficient. However, normally, it is about 5 times or less the coercive force of the magnetic layer at room temperature because of the ability of the magnetizing device used for magnetic field application. The room temperature is, for example, 25 ° C. The coercivity of the magnetic recording medium is substantially the same as the coercivity of the magnetic layer (recording layer).
[0059]
The magnetic layer generally has a static coercive force (sometimes simply referred to as a coercive force) and a dynamic coercive force, but it is sufficient that the local heating can be performed at least to a temperature at which the dynamic coercive force of the magnetic layer is reduced to some extent. . Of course, you may heat to the temperature where static coercive force falls. Preferably it heats to 100 degreeC or more. Magnetic layers that are affected by an external magnetic field at a heating temperature of less than 100 ° C. tend to have low magnetic domain stability at room temperature.
[0060]
However, it is desirable that the heating temperature be low in a range where a desired reduction in coercive force can be obtained. For example, up to the vicinity of the magnetization disappearance temperature or the Curie temperature of the magnetic layer. If the heating temperature is too high, heat diffusion to areas other than the region to be heated tends to occur, and the pattern may be blurred. In addition, the magnetic layer may be deformed. In addition, a lubricating layer made of a lubricant is usually formed on the surface of the magnetic recording medium, and the lower the heating temperature is preferable in order to prevent adverse effects such as deterioration of the lubricant due to heating. Heating may cause degradation such as decomposition or vaporization and decrease due to heating, and the vaporized lubricant may adhere to a mask or the like particularly in the case of proximity exposure. Therefore, it is desirable that the heating temperature be as low as possible in order to industrially apply the magnetization pattern forming method of the present invention to a magnetic recording medium having a lubricating layer.
[0061]
For this reason, it is preferable that the heating temperature is not higher than the Curie temperature of the magnetic layer. Next, the direction of the second external magnetic field applied simultaneously with heating is generally opposite to the first external magnetic field. When the medium has a disk shape, the application direction of the second external magnetic field is preferably any of a circumferential direction, a radial direction, and a direction perpendicular to the plate surface.
[0062]
When using a pulsed energy beam for heating, the second external magnetic field may be applied continuously or pulsed. When the second external magnetic field is a pulsed magnetic field, only the pulsed magnetic field component or a combination of the pulsed magnetic field component and the static magnetic field component may be used. At this time, the sum of the pulsed magnetic field component and the static magnetic field component is taken as the strength of the second external magnetic field.
[0063]
The stronger the maximum intensity of the second external magnetic field, the easier the magnetization pattern is formed. Although the optimum strength varies depending on the characteristics of the magnetic layer of the magnetic recording medium, when the second external magnetic field is a static magnetic field, it is preferably 1/8 or more of the coercivity at room temperature (static coercivity). If it is weaker than this, the heating part may be magnetized again in the same direction as the surroundings under the influence of the magnetic field from the surrounding magnetic domains during cooling. However, the coercive force at room temperature of the magnetic layer is preferably 2/3 or less, and more preferably 1/2 times or less. If it is larger than this, the magnetic domains around the heating part may be affected.
[0064]
When the second external magnetic field is a pulsed magnetic field, it is preferably 2/3 or more of the coercivity (static coercivity) at room temperature. If it is too weak, the heating area may not be magnetized well. More preferably, it is 3/4 or more of the static coercivity at room temperature. A magnetic field stronger than the static coercivity at room temperature may be applied. However, the magnetic field is smaller than the dynamic coercive force at room temperature of the magnetic layer. This is because if the second external magnetic field is larger than this, the magnetization of the non-heated region is affected.
[0065]
In the present invention, the magnetic field strength value H (Oe) can be replaced by the magnetic flux density value B (Gauss). In general, there is a relationship of B = μH (where μ represents a magnetic permeability), but since the normal magnetization pattern is formed in the air, the magnetic permeability is 1, and the relationship of B = H is established. is there.
As the means for applying the second external magnetic field, a magnetic head may be used, or a plurality of electromagnets or permanent magnets may be used so as to generate a magnetic field in a desired magnetization direction. You may use it in combination. In order to efficiently magnetize a high coercive force medium suitable for high density recording, permanent magnets such as ferrite magnets, neodymium rare earth magnets, and samarium cobalt rare earth magnets are suitable.
[0066]
When the second external magnetic field is a pulsed magnetic field, only the pulsed magnetic field applying unit may be used, or a combination of the pulsed magnetic field applying unit and the static magnetic field applying unit may be used.
For example, in the former, only a pulsed magnetic field is generated by an electromagnet or the like. For example, in the latter case, a static magnetic field of a certain magnitude is given by a permanent magnet or an electromagnet, and a magnetic field higher than that is applied in pulses by the electromagnet. It is preferable to use an air-core coil with a small inductance because the pulse width can be narrowed and the magnetic field application time can be shortened. Further, other yoke type electromagnets may be used instead of the permanent magnets.
[0067]
Combining a static magnetic field and a pulsed magnetic field can reduce the magnetic field applied in a pulsed manner. In general, an electromagnet becomes difficult to shorten the pulse width as the magnetic field increases, and therefore the pulse width is easily shortened accordingly.
Alternatively, the pulsed magnetic field can be applied by a method in which a magnet that constantly generates a magnetic field is brought close to the magnetic recording medium for a short time. For example, the medium may be rotated at a predetermined speed or higher while applying a magnetic field to a part of the magnetic recording medium with a permanent magnet.
[0068]
When the second external magnetic field is a combination of a static magnetic field and a pulsed magnetic field, the magnetic field strength of the static magnetic field is made smaller than the static coercive force of the magnetic layer at room temperature. Preferably, the static coercive force is 2/3 or less, more preferably 1/2 times or less. If it is too large, it affects the formed magnetization pattern and not only lowers the output, but also deteriorates the modulation. There is no particular lower limit, but if it is too weak, the meaning of using a static magnetic field is reduced, so that the static coercivity of the magnetic layer at room temperature is, for example, 1/8 or more.
[0069]
Next, the pulse width when the second external magnetic field is a pulsed magnetic field will be described.
In the present invention, the pulse width of the pulsed magnetic field component of the second external magnetic field is simply referred to as the pulse width of the second external magnetic field. Here, the pulse width of the magnetic field refers to the half width.
The pulse width of the second external magnetic field is usually 100 msec or less. Preferably it is 10 msec or less. The shorter the pulse width of the second external magnetic field, the larger the upper limit value of the magnetic field that can be applied. This is because the value of the dynamic coercive force changes depending on the application time of the magnetic field, and the dynamic coercive force of the magnetic layer at room temperature increases as the pulse width of the second external magnetic field is shortened. More preferably, it is 1 msec or less.
[0070]
However, it is preferably 10 nsec or more. If it is too short, the dynamic coercive force increases accordingly, and the second external magnetic field necessary for magnetizing the heating region increases. Although depending on the magnitude of the magnetic field, it takes time for the magnetic field to rise and fall due to the characteristics of the electromagnet, so there is a limit to shortening the pulse width. More preferably, it is 100 nsec or more. Here, the pulse width of the magnetic field indicates a half width.
[0071]
When a pulsed energy beam is used for local heating, the pulse width of the second external magnetic field is set to be equal to or greater than the pulse width of the pulsed energy beam. If it is less than this, the magnetic field will change during local heating, so that the magnetization pattern will not be formed well.
Further, it is preferable that the pulsed energy beam and the pulsed second external magnetic field are synchronized and applied simultaneously. Normally, it is considered that the pulse width of the magnetic field is longer than the pulse width of the energy beam. In this case, a pulse of the second external magnetic field is applied, and control is performed so that the pulse of the energy beam is applied at the maximum magnetic field. Is preferred.
[0072]
A magnetic recording medium or an AFC medium with an increased dynamic coercive force is particularly effective when a pulsed magnetic field is applied as the second external magnetic field. For example, a magnetic recording medium including two magnetic layers having a stabilizing magnetic layer for keeping thermal stability together with a magnetic layer for recording can be mentioned. Since the stabilizing magnetic layer functions to suppress instantaneous magnetization reversal of the recording magnetic layer, the dynamic coercive force is high, and it is difficult to form a magnetization pattern by the conventional method. When an external magnetic field in the vicinity of the static coercive force or higher is applied to such a medium in a pulse shape, a good magnetization pattern can be formed.
[0073]
The second external magnetic field can also form a plurality of magnetization patterns at once by applying the external magnetic field over the heated wide region.
When local heating can be performed on the entire surface of the magnetic recording medium at once, it is desirable to form a magnetization pattern by applying a second external magnetic field to the entire surface of the medium simultaneously with heating. As a result, the magnetization pattern can be formed in a shorter time and the cost can be greatly reduced. Also, in order to apply a magnetic field only to a part of the medium, the magnet arrangement is often devised or specific measures are taken so that the magnetic field does not reach other areas, but it is necessary to apply it to the entire surface. Absent. In addition, since a rotating mechanism or a moving mechanism is not necessary, the apparatus configuration is simplified and a magnetic recording medium can be obtained at a low cost.
[0074]
FIG. 2 shows an example of a specific transfer mechanism according to the present invention. A mask 14 is placed on the magnetic disk 11 via a spacer 17, a light shielding plate 13 is disposed above the mask 14, and an energy beam 15 is irradiated through the opening 13 a. The mask 14 is formed with a transmission part and a light shielding part according to the magnetization pattern to be formed as described above.
[0075]
Permanent magnets 12a (N poles) and 12b (S poles) are attached to the light shielding plate 13 on both sides of the opening 13a, and air-core coils (electromagnets) 18a and 18b each having a coil wound several tens of times in a loop shape. It arrange | positions along this permanent magnet 12a, 12b. In addition, permanent magnets 12c (N pole) and 12d (S pole) are attached to the opposite surface of the magnetic disk 11, and air-core coils (electromagnets) 18a and 18b each having a coil wound several tens of times in a loop are provided. It arrange | positions along the permanent magnets 12c and 12d.
[0076]
The air-core coils 18a and 18b are connected to each other by a conducting wire, and both ends are connected to a DC power source 21, a capacitor 22 and a thyristor 23 as shown in the figure. Further, the air core coils 18a and 18b are bent in a dogleg shape so that the magnetic disk 11 can be easily attached and detached.
Here, by the permanent magnets 12a to 12d, in the direction opposite to the uniform magnetization in the circumferential direction of the magnetic disk, about 1.7k gauss in the disk inner circumferential area (position of radius 21mm), the disk outer circumferential area (radius 46.5mm). The magnetic field of about 1.9k Gauss is always applied at the position of
[0077]
In order to apply a pulsed external magnetic field, the capacitor 22 is first given a potential difference of 750 V by the DC power source 21. Next, when a trigger signal is generated from the trigger device 24 in accordance with the timing at which an external magnetic field is to be applied and is input to the gate terminal of the thyristor 23, current is supplied to the air-core coils 18a and 18b due to the potential difference accumulated in the capacitor 22. It flows at a stretch. The pulse current causes a pulse width of 200 μsec around the coil, about 1.8 k gauss in the inner circumference of the disk (position of radius 21 mm), and maximum intensity of about 2 in the outer circumference of the disk (position of radius 46.5 mm). A pulsed magnetic field of about 0.0 k Gauss is generated.
[0078]
As shown in FIG. 2 (b), the magnetic field generated by the air-core coils 18a and 18b works to assist the magnetic field generated by the permanent magnets 12a to 12d, so that the total is about 3 in the disk inner peripheral area (position of radius 21 mm). A pulsed magnetic field having a maximum intensity of about 3.9 kGauss is applied in the outer periphery of the disk (position of radius 46.5 mm). On the other hand, a trigger signal from the trigger device 24 is input to an energy ray source 26 such as an excimer laser (wavelength 248 nm) through a delay device (delay) 25, thereby generating a pulsed energy ray. The energy ray passes through a programmable shutter, a beam expander, a prism array, etc. (not shown), and then, for example, a pulse width of several tens of nsec and an energy density of 100 to 200 mJ / cm²Pulse
Irradiated as a state energy beam 5.
[0079]
Normally, it takes time for the magnetic field to rise and fall due to the characteristics of the electromagnet, so that the energy beam 15 is emitted by the delay device 25 so that the energy beam 15 is irradiated just when the magnetic field strength becomes maximum. Adjust.
As a result, a pulsed magnetic field of about 3000 Oe in total is applied simultaneously with the irradiation of the energy beam 15. Since the dynamic coercive force of the heating area of the magnetic disk 11 is reduced to 3000 Oe or less, only the heating area is reversed and magnetized by the pulsed magnetic field, and a magnetization pattern is formed. Note that a pulsed current may be directly supplied from a DC power supply without using a capacitor or the like.
[0080]
For example, if the medium is a small-diameter disk-shaped magnetic recording medium having a diameter of 2.5 inches or less, it is preferable that the entire surface of the disk can be irradiated with energy rays and applied with a magnetic field by simple arrangement and means. More preferably, the diameter is 1 inch or less.
In addition, when a magnetic field is applied to the disk-shaped magnetic recording medium in the circumferential direction, a circumferential magnetic field can be easily generated by flowing a large pulse current in the vertical direction to the center of the medium. This is particularly preferable when applied to a small-diameter disk-shaped magnetic recording medium having a diameter of 1 inch or less.
[0081]
The present invention is suitable for forming a magnetization pattern having control information for controlling a recording / reproducing magnetic head. For example, it is a pattern that generates a signal corresponding to the position of the head.
The control information is used to control the recording / reproducing means such as a magnetic head using the information. For example, the servo information for positioning the magnetic head on the data track, the position of the magnetic head on the medium, and the like. Address information shown, synchronization information for controlling the recording / reproducing speed of the magnetic head, and the like. Alternatively, reference information for writing servo information later is also included.
[0082]
These control magnetization patterns need to be formed with high accuracy. Especially, since the servo pattern is a data track position control pattern, if the servo pattern accuracy is poor, the head position control becomes coarse. A data pattern having a higher positional accuracy cannot theoretically be recorded. Therefore, the servo pattern needs to be formed with higher accuracy as the recording density of the medium increases.
[0083]
Since a highly accurate servo pattern or reference pattern can be obtained in the present invention, the present invention is particularly effective when applied to a magnetic recording medium for high-density recording in which the track density is 40 kTPI or more.
Next, a method for locally heating the magnetic layer in the present invention will be described.
The heating means only needs to have the function of partially heating the surface of the magnetic layer, but considering the prevention of thermal diffusion to unnecessary parts and controllability, the power control and the size of the heated part can be easily controlled. Use energy rays such as laser.
[0084]
Here, by using the mask together, it is possible to irradiate the energy beam through the mask and form a plurality of magnetization patterns at once, so that the magnetization pattern forming process is short and simple.
It is preferable to control the heating part and the heating temperature by making the energy rays pulse rather than continuous irradiation. The use of a pulse laser light source is particularly suitable. The pulsed laser light source oscillates the laser intermittently in a pulsed manner, as compared to intermittently pulsing a continuous laser with an optical component such as an acousto-optic device (AO) or an electro-optic device (EO). A laser with a high power peak value can be irradiated in a very short time, and heat accumulation is unlikely to occur.
[0085]
When a continuous laser is pulsed by optical components, it has substantially the same power over the pulse width within the pulse. On the other hand, a pulse laser light source, for example, accumulates energy by resonance in the light source and emits a laser as a pulse at a time, so that the power of the peak is very large within the pulse and then decreases. In the present invention, in order to form a highly accurate magnetic pattern with high contrast, it is preferable to rapidly heat and then rapidly cool in a very short time, so that a pulsed laser light source is suitable.
[0086]
The medium surface on which the magnetized pattern is formed preferably has a large temperature difference between when the pulsed energy beam is irradiated and when it is not irradiated in order to increase the pattern contrast or increase the recording density. Therefore, it is preferable that the temperature is about room temperature or lower when the pulsed energy beam is not irradiated. Room temperature is about 25 ° C.
When using the pulsed energy beam, the external magnetic field may be applied continuously or pulsed.
[0087]
The wavelength of the energy beam is preferably 1100 nm or less. If the wavelength is shorter than this, the diffraction effect is small and the resolution is increased, so that it is easy to form a fine magnetization pattern. More preferably, the wavelength is 600 nm or less. In addition to high resolution, since the diffraction is small, the space between the mask and the magnetic recording medium due to the gap is wide and easy to handle, and the magnetic pattern forming apparatus can be easily constructed. The wavelength is preferably 150 nm or more. If it is less than 150 nm, the absorption of the synthetic quartz used for the mask increases, and heating tends to be insufficient. If the wavelength is 350 nm or more, optical glass can be used as a mask.
[0088]
Specifically, excimer laser (157, 193, 248, 308, 351 nm), YAG Q-switched laser (1064 nm), second harmonic (532 nm), third harmonic (355 nm), or fourth harmonic (266 nm), Ar laser (488 nm, 514 nm), ruby laser (694 nm), and the like.
The power of the energy beam may be selected according to the magnitude of the external magnetic field, but the power per pulse of the pulse energy beam is 1000 mJ / cm.²The following is preferable. If a power larger than this is applied, the surface of the magnetic recording medium may be damaged and deformed by pulsed energy rays. If the roughness Ra of the medium is increased to 3 nm or more and the waviness Wa is increased to 5 nm or more due to the deformation, there is a possibility that the traveling of the flying / contact type head may be hindered.
[0089]
More preferably 500 mJ / cm²Or less, more preferably 200 mJ / cm.²It is as follows. In this region, it is easy to form a magnetization pattern with high resolution even when a substrate with relatively large thermal diffusion is used. The power is 10mJ / cm²The above is preferable. If it is smaller than this, the temperature of the magnetic layer will not rise easily and magnetic transfer will hardly occur. In addition, since the influence of the diffraction of the energy beam varies depending on the pattern width, the optimum power also varies depending on the pattern width. Also, the shorter the wavelength of the energy beam, the lower the upper limit value of the power that can be applied.
[0090]
If there is a concern about damage to the magnetic layer, protective layer, or lubricating layer due to energy rays, means for reducing the power of the pulsed energy rays and increasing the strength of the magnetic field applied simultaneously with the pulsed energy rays. It can also be taken. In addition, when irradiating the pulsed energy beam through the protective layer and the lubricating layer, it may be necessary to re-apply after irradiation in consideration of damage (decomposition, polymerization) and the like received by the lubricant.
[0091]
The pulse width of the pulsed energy beam is desirably 1 μsec or less.
If the pulse width is wider than this, the heat generated by the energy applied to the magnetic recording medium is dispersed and the resolution tends to be lowered. When the power per pulse is the same, the thermal diffusion is smaller and the resolution of the magnetization pattern tends to be higher when the pulse width is shortened and the strong energy is irradiated at once. More preferably, it is 100 nsec or less. In this region, it is easy to form a magnetized pattern with high resolution even when a substrate such as Al having a relatively large thermal diffusion is used. When forming a pattern with a minimum width of 2 μm or less, the pulse width is preferably 25 nsec or less. That is, if the resolution is important, the shorter the pulse width, the better. The pulse width is preferably 1 nsec or more. This is because it is preferable to keep heating until the magnetization reversal of the magnetic layer is completed.
[0092]
In the present invention, the minimum width of the pattern means the narrowest length in the pattern. A rectangular pattern has a short side, a circle has a diameter, and an ellipse has a short diameter.
As a kind of pulsed laser, there is a laser that can generate picosecond and femtosecond level ultrashort pulses at a high frequency, such as a mode-locked laser. In the period in which the ultrashort pulse is irradiated at a high frequency, a very short time between each ultrashort pulse is not irradiated with the laser, but is a very short time, so the heating part is hardly cooled. For example, the region once heated to 200 ° C. is kept at approximately 200 ° C.
[0093]
Therefore, in such a case, a continuous irradiation period (a continuous irradiation period including a time during which the laser between ultrashort pulses is not irradiated) is set to one pulse. Also, the integral value of the irradiation energy amount during the continuous irradiation period is expressed as the power per pulse (mJ / cm²).
In addition, energy beams such as lasers generally have an intensity distribution (energy density distribution) within a beam spot, and a difference in temperature rise due to energy density occurs even when the energy beam is irradiated and locally heated. For this reason, a difference in transfer strength locally occurs due to uneven heating. Therefore, it is preferable to make the intensity distribution uniform in advance on the energy rays. The distribution of the heating state in the irradiated region can be kept small, and the distribution of the magnetic strength of the magnetization pattern can be kept small. Therefore, when reading the signal intensity using the magnetic head, it is possible to form a magnetization pattern with high signal intensity uniformity.
[0094]
Examples of the intensity distribution homogenization process include the following processes. For example, homogenizers and condenser lenses are used for homogenization, or only a portion where the intensity distribution of the energy rays is small is transmitted through a light shielding plate or slit, and enlarged as necessary.
The mask of the present invention is a so-called photomask having an energy ray transmission part and a light shielding part, and changes the intensity distribution of the energy ray corresponding to the magnetization pattern to be formed, and the density of the energy ray on the magnetic disk surface ( Intensity distribution). As a result, a plurality of or large area magnetization patterns can be formed at a time, so that the magnetization pattern forming process is short and simple.
[0095]
The mask does not have to cover the entire surface of the magnetic disk. If there is a size including the repeating unit of the magnetization pattern, it can be used by moving it.
Further, although the material of the mask is not limited, it is preferable that the mask is made of a non-magnetic material in the present invention because a magnetized pattern can be formed with uniform clarity in any pattern shape, and a uniform and strong reproduction signal can be obtained.
[0096]
When a mask containing a ferromagnetic material is used, the magnetic field distribution may be disturbed by magnetization. Due to the nature of ferromagnetism, in the case of a pattern shape inclined in the radial direction of the magnetic disk or an arc-shaped pattern extending in the radial direction, the magnetic domains do not sufficiently oppose each other at the magnetization transition portion, so that it is difficult to obtain a high-quality signal.
The mask is disposed between the energy ray light source and the magnetic recording medium. If importance is placed on the accuracy of the magnetization pattern, it is preferable that all or part of the mask is brought into contact with the medium. The influence of diffraction of laser light can be minimized, and a magnetized pattern with high resolution can be formed. For example, when the mask is left on the medium, a portion that does not come into contact with the medium is formed by the undulation of about several μm on the surface of the medium. However, the pressure applied to the mask and the medium is 100 g / cm so as not to form indentation or damage to the medium.²The following.
[0097]
However, in order to reduce defects and scratches, it is preferable to provide a gap between the mask and the medium at least in the region where the magnetization pattern of the medium is formed. It is possible to suppress damage to the medium and the mask and the occurrence of defects due to the inclusion of dust or the like.
In addition, when the lubricant layer is provided before the magnetization pattern is formed, it is particularly preferable to provide a gap between the mask and the medium. This is to minimize the adhesion of the lubricant to the mask. Also, if a high-power energy beam is irradiated while the disk with the lubricant layer is in contact with the mask, the lubricant will explode due to rapid vaporization of the lubricant, causing the lubricant to scatter or even damage the mask. It is because there is a possibility of doing.
[0098]
As a method for maintaining the gap between the magnetization pattern forming region of the magnetic recording medium and the mask, any method can be used as long as both can be maintained at a constant distance. For example, the mask and the medium may be held by a specific device to maintain a certain distance. Further, a spacer may be inserted between the two at a place other than the magnetization pattern formation region. A spacer may be formed integrally with the mask itself.
[0099]
If a spacer is provided between the mask and the magnetic recording medium at the outer peripheral portion and / or inner peripheral portion of the magnetic pattern forming region of the medium, the effect of correcting the waviness on the surface of the magnetic recording medium is produced, so that the accuracy of forming the magnetic pattern increases. So good.
The spacer material should be hard. Further, since an external magnetic field is used for pattern formation, it is preferable that the pattern is not magnetized. Preferred are metals such as stainless steel and copper, and resins such as polyimide. Although the height is arbitrary, it is usually 0.1 μm to several hundred μm.
[0100]
It is preferable that the minimum gap between the mask and the magnetic recording medium is 0.1 μm or more, so that it is possible to suppress damage to the magnetic recording medium and the mask and generation of defects due to sandwiching of dust or the like. That is, by setting the interval to 0.1 μm or more, it is possible to prevent the magnetized pattern forming portion from causing unexpected contact with the mask due to the undulation of the medium surface. Therefore, since the thermal conductivity of the medium changes at the contact portion, the magnetism easily changes so much, and there is no problem that the magnetization pattern is not formed as desired.
More preferably, it is 0.2 μm or more. However, the interval is preferably 1 mm or less. Thereby, there is no problem that the diffraction of the energy beam is small and the magnetization pattern is blurred.
[0101]
For example, when an excimer laser (248 nm) is used and a 2 × 2 μm pattern (a pattern having alternating 2 μm transmissive portions and 2 μm non-transmissive portions) formed on a mask is transferred to the medium, it is between the mask and the medium. The distance must be kept at about 25 to 45 μm or less. If the distance is longer than this, the bright and dark pattern of the laser beam becomes unclear due to the diffraction phenomenon. In the case of a 1 × 1 μm pattern (a pattern having alternating 1 μm transmissive portions and 1 μm non-transmissive portions), the distance is about 10 to 15 μm or less.
[0102]
When using a mask, it is preferable to make the distance from the medium as short as possible within the range of the above conditions. This is because the longer the distance is, the more easily the magnetization pattern is blurred due to the wraparound of the irradiated energy rays. In order to improve this and obtain a clearer pattern, a thin transmissive part that acts as a diffraction grating is formed outside the transmissive part of the mask, or a means that acts as a half-wave plate is provided. The sneak light can be canceled out by interference.
[0103]
A magnetic disk may have a magnetic layer formed on both main surfaces of the disk. In this case, the magnetization pattern formation of the present invention may be performed sequentially one side at a time, or a mask, an energy irradiation system and an external magnetic field may be applied. By applying means for applying to both sides of the magnetic disk, the magnetization pattern can be formed simultaneously on both sides.
If two or more magnetic layers are formed on one surface and you want to form different patterns for each layer, each layer can be heated individually by focusing the energy rays to be irradiated on each layer to form individual patterns. .
[0104]
When forming a magnetized pattern, a light-shielding plate that can partially shield the energy rays is provided in the region where it is not desired to irradiate the energy rays between the light source and the mask or between the mask and the medium. A structure that prevents re-irradiation of energy rays is preferable. The light shielding plate may be any material that does not transmit the wavelength of the energy beam to be used, and may reflect or absorb the energy beam. However, when energy rays are absorbed, they are heated and affect the magnetization pattern, so that those having good thermal conductivity and high reflectance are preferable. For example, a metal plate such as Cr, Al, or Fe.
[0105]
Preferably, a reduction imaging technique (imaging optical system) is used for the optical system. Patterned energy lines having an intensity distribution corresponding to the magnetization pattern to be formed are reduced and imaged on the medium surface. According to this, when the energy beam is focused by the objective lens and then passed through the mask, that is, compared with the case of proximity exposure, the accuracy of the magnetization pattern is not limited by the mask patterning accuracy and alignment accuracy. A fine magnetization pattern can be formed with high accuracy. Further, since the mask and the medium are separated from each other, they are hardly affected by dust on the medium.
[0106]
According to the present technology, the intensity distribution of the energy rays emitted from the light source is changed through the mask, and reduced and imaged on the surface of the medium through imaging means such as an imaging lens. Note that the imaging lens may be referred to as a projection lens, and the reduced imaging may be referred to as reduced projection.
Next, the configuration of the magnetic recording medium of the present invention will be described.
[0107]
As the substrate in the magnetic recording medium according to the present invention, it is necessary that the substrate does not vibrate even when rotated at a high speed during high-speed recording / reproduction, and a hard substrate is usually used. In order to obtain sufficient rigidity that does not vibrate, the substrate thickness is generally preferably 0.3 mm or more. However, if it is thick, it is disadvantageous for making the magnetic recording device thin, so that it is preferably 3 mm or less. For example, an Al alloy substrate such as Al—Mg alloy containing Al as a main component, an Mg alloy substrate such as Mg—Zn alloy containing Mg as a main component, ordinary soda glass, aluminosilicate glass, amorphous glass, etc. For example, a substrate made of any of silicon, titanium, ceramics, and various resins, or a combination of them can be used. Among them, it is preferable to use an Al alloy substrate or a glass substrate such as crystallized glass in terms of strength and a resin substrate in terms of cost.
[0108]
The present invention is highly effective when applied to a medium having a hard substrate. In a conventional magnetic transfer method, a medium having a hard substrate tends to be insufficiently adhered to the master (master disk), resulting in scratches and defects, or unclear boundaries of the transferred magnetic domain, which tends to spread PW50. However, the present invention does not cause such a problem because the mask and the medium are not pressure-bonded. In particular, it is effective for a medium having a substrate that is easily cracked, such as a glass substrate.
[0109]
In the manufacturing process of the magnetic recording medium, the substrate is usually first washed and dried. In the present invention, it is desirable to perform washing and drying before formation from the viewpoint of ensuring the adhesion of each layer. .
In manufacturing the magnetic recording medium of the present invention, a metal layer such as NiP or NiAl may be formed on the substrate surface.
[0110]
In the case of forming the metal layer, a method used for forming a thin film such as an electroless plating method, a sputtering method, a vacuum evaporation method, or a CVD method can be used as the method. In the case of a substrate made of a conductive material, electrolytic plating can be used. The film thickness of the metal layer is preferably 50 nm or more. However, considering the productivity of the magnetic recording medium, it is preferably 20 μm or less. More preferably, it is 10 μm or less.
[0111]
Further, the region where the metal layer is formed is preferably the entire surface of the substrate, but only a part, for example, a region where texturing is performed can be performed.
Further, concentric texturing may be applied to the surface of the substrate or the surface on which the metal layer is formed on the substrate. In the present invention, concentric texturing means, for example, mechanical texturing using free abrasive grains and textured tape, texturing using laser light, or the like, or by using these in combination, by polishing in the circumferential direction. A state in which a large number of minute grooves are formed in the circumferential direction of the substrate is referred to.
[0112]
In general, mechanical texturing is performed in order to provide in-plane anisotropy of the magnetic layer. If it is desired to form an in-plane isotropic magnetic layer, it is not necessary to apply it.
In general, texturing using a laser beam or the like is performed in order to improve CSS (contact start and stop) characteristics. There is no need to apply the magnetic recording apparatus in a system (load / unload system) in which the head is retracted outside the magnetic recording medium when not driven.
[0113]
Alumina abrasive grains are widely used as abrasive grains used in mechanical texturing, but diamond abrasive grains are extremely important from the viewpoint of an in-plane orientation medium in which the axis of easy magnetization is oriented along the texturing grooves. Demonstrate good performance. Of these, those whose surface is graphitized are most preferred.
A head flying height as small as possible is effective for realizing high-density magnetic recording, and one of the features of these substrates is excellent surface smoothness, so that the substrate surface roughness Ra is preferably 2 nm or less, More preferably, it is 1 nm or less. In particular, 0.5 nm or less is preferable. The substrate surface roughness Ra is a value calculated according to JIS B0601 after measurement at a measurement length of 400 μm using a stylus type surface roughness meter. At this time, the tip of the measuring needle has a radius of about 0.2 μm.
[0114]
Next, an underlayer or the like may be formed on the substrate between the magnetic layer. For the purpose of making the crystal fine and controlling the orientation of the crystal plane, the base layer is preferably composed mainly of Cr.
As the material of the underlayer containing Cr as a main component, in addition to pure Cr, V, Ti, Mo, Zr, Hf, Ta, W, Ge, Nb, Si are added to Cr for the purpose of crystal matching with the recording layer. In addition, alloys containing one or more elements selected from Cu, B, Cr oxide, and the like are also included.
[0115]
Among them, pure Cr or an alloy obtained by adding one or more elements selected from Ti, Mo, W, V, Ta, Si, Nb, Zr and Hf to Cr is preferable. The optimum content of these second and third elements varies depending on the respective element, but generally 1 atomic% to 50 atomic% is preferable, more preferably 5 atomic% to 30 atomic%, still more preferably 5 atomic%. % To 20 atomic%.
[0116]
The film thickness of the underlayer is not particularly limited so long as it can exhibit this anisotropy, but is preferably 0.1 to 50 nm, more preferably 0.3 to 30 nm, and still more preferably 0.5 to 10 nm. The substrate heating may or may not be performed at the time of forming the underlayer mainly composed of Cr.
A soft magnetic layer may be provided on the underlayer between the recording layer and the recording layer. In particular, a keeper medium with little magnetization transition noise or a perpendicular recording medium in which the magnetic domain is perpendicular to the in-plane of the medium has a great effect and is preferably used.
[0117]
The soft magnetic layer only needs to have a relatively high magnetic permeability and low loss, but NiFe or an alloy to which Mo or the like is added as a third element is preferably used. The optimum magnetic permeability varies greatly depending on the characteristics of the head and recording layer used for data recording, but in general, the maximum magnetic permeability is preferably about 10 to 1,000,000 (H / m).
[0118]
Or you may provide an intermediate | middle layer as needed on the base layer which has Cr as a main component. For example, it is preferable to provide a CoCr-based intermediate layer because the crystal orientation of the magnetic layer can be easily controlled.
Next, a recording layer (magnetic layer) is formed. Between the recording layer and the soft magnetic layer, a layer made of the same material as the underlayer or another nonmagnetic material may be inserted. During film formation of the recording layer, substrate heating may or may not be performed.
[0119]
As the recording layer, a Co alloy magnetic layer, a rare earth-based magnetic layer typified by TbFeCo, a transition metal-noble metal-based laminated film typified by a laminated film of Co and Pd, and the like are preferably used.
As the Co alloy magnetic layer, a Co alloy magnetic material generally used as a magnetic material such as pure Co, CoNi, CoSm, CoCrTa, CoNiCr, and CoCrPt can be used. These Co alloys may be further added with elements such as Ni, Cr, Pt, Ta, W and B and compounds such as SiO2. Examples thereof include CoCrPtTa, CoCrPtB, CoNiPt, and CoNiCrPtB. The thickness of the Co alloy magnetic layer is arbitrary, but is preferably 5 nm or more, more preferably 10 nm or more. Moreover, Preferably it is 50 nm or less, More preferably, it is 30 nm or less. Further, the present recording layer may be laminated with two or more layers via an appropriate nonmagnetic intermediate layer. At that time, the composition of the laminated magnetic material may be the same or different.
[0120]
As the rare earth magnetic layer, a general magnetic material can be used, and examples thereof include TbFeCo, GdFeCo, DyFeCo, and TbFe. Tb, Dy, Ho, etc. may be added to these rare earth alloys. Ti, Al, and Pt may be added for the purpose of preventing oxidative degradation. The film thickness of the rare earth magnetic layer is arbitrary, but is usually about 5 to 100 nm. Further, the present recording layer may be laminated with two or more layers via an appropriate nonmagnetic intermediate layer. At that time, the composition of the laminated magnetic material may be the same or different. In particular, the rare earth-based magnetic layer is an amorphous structure film and has magnetization in a direction perpendicular to the media plane, so that it is suitable for high recording density recording, and the method of the present invention can form a magnetization pattern with high density and high accuracy. It can be applied more effectively.
[0121]
Similarly, as the laminated film of transition metal and noble metal that can perform perpendicular magnetic recording, a general magnetic material can be used. For example, Co / Pd, Co / Pt, Fe / Pt, Fe / Au, Fe / Au Ag etc. are mentioned. The transition metal and noble metal of these laminated film materials may not be particularly pure and may be an alloy mainly composed of them. The thickness of the laminated film is arbitrary, but is usually about 5 to 1000 nm. Moreover, the lamination | stacking of 3 or more types of materials may be sufficient as needed.
[0122]
Recently, an AFC (Anti-Ferromagnetic coupled) medium has been proposed in order to increase the thermal stability of magnetic domains. Two or more magnetic layers (main magnetic layer and undercoat magnetic layer) are stacked via several angstroms of Ru layer, etc., and magnetically coupled above and below the Ru layer to increase the thermal stability of the main magnetic layer. It is an enhanced medium. This medium has an apparent coercive force, and a large magnetic field is required to reverse the magnetization.
[0123]
In the present invention, the recording layer is preferably thin. This is because if the recording layer is thick, heat transfer in the film thickness direction when the recording layer is heated is poor, and it may not be magnetized well. For this reason, the recording layer thickness is preferably 200 nm or less. However, the thickness of the recording layer is preferably 5 nm or more in order to maintain the magnetization.
In the present invention, the magnetic layer as the recording layer retains magnetization at room temperature and is demagnetized by applying an external magnetic field simultaneously with heating or magnetized in the reverse direction.
[0124]
The coercive force (static coercive force) at room temperature of the magnetic layer needs to maintain magnetization at room temperature and be uniformly magnetized by an appropriate external magnetic field. By setting the coercive force of the magnetic layer at room temperature to 2000 Oe or more, a medium suitable for high-density recording can be obtained that can maintain a small magnetic domain. More preferably, it is 3000 Oe or more.
In the conventional magnetic transfer method, transfer to a medium having a very high coercive force was difficult. However, in the present invention, the magnetic layer is heated to sufficiently reduce the coercive force to form a magnetized pattern. Application to a medium is preferred.
[0125]
However, it is preferably 20 kOe or less. If it exceeds 20 kOe, a large external magnetic field is required for collective magnetization, and normal magnetic recording may become difficult. More preferably, it is 15 kOe or less, More preferably, it is 10 kOe or less.
The coercivity, local heating temperature, and second external magnetic field strength of the magnetic layer will be described. For example, a medium having a coercivity of 3500 to 4000 Oe at room temperature usually has a coercivity of 10 to 15 Oe / ° C. as the temperature rises. It decreases linearly, for example, about 2000 Oe at 150 ° C. If it is about 3000 Oe, it can be easily generated by an external magnetic field applying means, so that a sufficient magnetization pattern can be formed even by heating at about 150 ° C.
[0126]
Now, the dynamic coercive force of the magnetic layer is large in order to stably hold information recorded at a high density. The dynamic coercive force is usually a coercive force measured when the magnetic field strength is changed in a short time of 1 sec or less, that is, a coercive force with respect to a magnetic field having a pulse width of 1 sec or less. However, the value varies depending on the application time of the magnetic field and heat.
Preferably, the dynamic coercive force in 1 sec is twice or more the static coercive force. However, if it is too large, a large magnetic field strength is required for magnetization by the second external magnetic field, so 20 kOe or less is preferable.
[0127]
An example of a procedure for measuring the dynamic coercivity of the magnetic recording medium (coercivity of the magnetic layer as the recording layer) will be described below.
1. The coercive force of the medium at the application time t = 10 sec is obtained.
1.1 Apply a magnetic field up to the maximum magnetic field strength (20 kOe) to saturate the medium.
1.2 Apply a magnetic field H1 of a predetermined strength in the negative direction (opposite the saturation direction).
1.3 Hold for 10 sec under the magnetic field.
1.4 Return the magnetic field to zero.
When the magnetization value at 1.5 1.4 is read, the residual magnetization value M1 is obtained.
1.6 The same measurement (1.1 to 1.5) is repeated while slightly changing the applied magnetic field strength. Residual magnetization values M1, M2, M3, and M4 are obtained at a total of four magnetic field strengths H1, H2, H3, and H4.
1.7 The applied magnetic field strength H at which the residual magnetization M becomes 0 is obtained from these four points. This is the coercive force of the medium at the application time t = 10 sec.
[0128]
2. The same measurement is performed for the application time t of 60 sec, 100 sec, and 600 sec, and the coercivity at each application time is obtained.
3. By extrapolating from the coercivity values obtained at 10 sec, 60 sec, 100 sec, and 600 sec, the coercivity at a shorter application time can be obtained.
[0129]
For example, the dynamic coercivity at an application time of 1 nsec is also required.
The magnetic layer needs to be magnetized with a weak external magnetic field at an appropriate heating temperature while maintaining magnetization at room temperature. Further, when the difference between the room temperature and the magnetization disappearance temperature is larger, the magnetic domain of the magnetization pattern is more easily formed. For this reason, the magnetization disappearance temperature is preferably higher, preferably 100 ° C. or higher, and more preferably 150 ° C. or higher. For example, there is a magnetization disappearance temperature near the Curie temperature (slightly below the Curie temperature) or near the compensation temperature.
[0130]
The Curie temperature is preferably 100 ° C. or higher. If it is less than 100 degreeC, there exists a tendency for the stability of the magnetic domain at room temperature to be low. More preferably, it is 150 degreeC or more. Moreover, it is preferably 700 ° C. or lower. This is because if the magnetic layer is heated too high, it may be deformed.
In the present invention, the Curie temperature of an AFC (Anti-Ferromagnetic coupled) medium refers to the apparent Curie temperature of the entire medium, not the Curie temperature of the main magnetic layer.
[0131]
If the magnetic recording medium is an in-plane magnetic recording medium, saturation recording is difficult with the conventional magnetic transfer method for a magnetic recording medium with high coercive force for high density, and it is difficult to generate a magnetic pattern with high magnetic field strength. Thus, the half-value width also widens. Even with an in-plane recording medium suitable for such a high recording density, a good magnetization pattern can be formed by this method. In particular, when the saturation magnetization of the magnetic layer is 50 emu / cc or more, the effect of applying the present invention is large because the influence of the demagnetizing field is large.
[0132]
The effect is higher at 100 emu / cc or more. However, if it is too large, it is difficult to form a magnetization pattern, so 500 emu / cc or less is preferable.
When the magnetic recording medium is a perpendicular magnetic recording medium and the magnetization pattern is relatively large and the unit volume of one magnetic domain is large, the saturation magnetization becomes large, and magnetization reversal is likely to occur due to magnetic demagnetization, which causes noise. Deteriorates the full width at half maximum. However, in the present invention, it is possible to perform good recording on these media in combination with an underlayer using soft magnetism.
[0133]
These recording layers may be provided in two or more layers in order to increase the recording capacity. At this time, another layer is preferably interposed therebetween.
In the present invention, it is preferable to form a protective layer on the magnetic layer. That is, the outermost surface of the medium is covered with a hard protective layer. The protective layer functions to prevent damage to the magnetic layer due to the head and collision with the mask such as dust and dirt. When a magnetic pattern forming method using a mask is applied as in the present invention, it also serves to protect the medium from contact with the mask.
[0134]
In the present invention, the protective layer also has an effect of preventing oxidation of the heated magnetic layer. The magnetic layer is generally easily oxidized and is further easily oxidized when heated. In the present invention, since the magnetic layer is locally heated with energy rays or the like, it is desirable to previously form a protective layer for preventing oxidation on the magnetic layer.
When there are a plurality of magnetic layers, a protective layer may be provided on the magnetic layer close to the outermost surface. The protective layer may be provided directly on the magnetic layer, or a layer having another function may be interposed between the protective layers as necessary.
[0135]
A part of the energy rays is also absorbed by the protective layer and functions to locally heat the magnetic layer by heat conduction. For this reason, if the protective layer is too thick, the magnetization pattern may be blurred due to heat conduction in the lateral direction. Further, the thinner one is preferable in order to reduce the distance between the magnetic layer and the head during recording and reproduction. Therefore, 50 nm or less is preferable, More preferably, it is 30 nm or less, More preferably, it is 20 nm or less. However, in order to obtain sufficient durability, the thickness is preferably 0.1 nm or more, more preferably 1 nm or more.
[0136]
The protective layer only needs to be hard and resistant to oxidation. Generally, carbon, hydrogenated carbon, nitrogenated carbon, amorphous carbon, SiC or other carbonaceous layer, SiO2, Zr2O3, SiN, TiN or the like is used. The protective layer may be a magnetic material.
In particular, in order to make the distance between the head and the magnetic layer as close as possible, it is preferable to provide a very hard protective layer thinly. Accordingly, a carbonaceous protective film is preferable in terms of impact resistance and lubricity, and diamond-like carbon is particularly preferable. Not only does it play a role in preventing damage to the magnetic layer by energy rays, but it is also extremely resistant to damage to the magnetic layer by the head. The magnetization pattern forming method of the present invention can also be applied to an opaque protective layer such as a carbonaceous protective layer.
[0137]
The protective layer may be composed of two or more layers. Providing a layer mainly composed of Cr as a protective layer immediately above the magnetic layer is preferable because it is effective in preventing oxygen permeation into the magnetic layer.
Furthermore, it is preferable to form a lubricating layer on the protective layer. It has a function to prevent damage by the mask of the medium and the magnetic head. The formation of the lubricating layer is generally performed by applying a lubricant. For example, an arbitrary coating process such as a spin coating method, a pulling coating method, or a spray coating method is used. In order to form a lubricating layer uniformly on a large amount of medium in a short time, the pulling coating method is suitable. You may form into a film by a vapor deposition method.
[0138]
Lubricants include fluorine-based lubricants, hydrocarbon-based lubricants, and mixtures thereof. Perfluoropolyether having an ester bond, dialkylamide carboxylic acid, perchloropolyether, stearic acid, sodium stearate , Phosphoric acid esters and the like are preferable. The ester bond may be anywhere in the molecule, but it is more preferable to have an ester bond functional group at the end because the movable part in the molecule becomes long and lubricity is easily obtained.
[0139]
Especially in the main chain -C_aF_2aA perfluoropolyether having an O-unit (where a is an integer of 1 to 4) and having a functional group of an ester bond at the terminal is preferable. More preferably, it is a perfluoroether represented by the following general formula (I).
R-O- (A¹-O-A²-O)_x-R (I)
(However, A¹, A²Is CF₂And / or C₂F_FourIt consists of A¹And A²CF that make up₂And C₂F_FourRatio (CF₂/ C₂F_Four) Is 5/1 to 1/5, X is 10 to 500, and R is a C1-20 alkyl group or a fluorine-substituted alkyl group containing a hetero atom. )
For example, Fomblin-Z-DOL manufactured by Augmont is CF₂CF₂O and CF₂It is a polymer of O, has a straight chain structure, and has ester groups —COOR (where R represents an alkyl group which may be substituted with fluorine) at both ends. In addition, the demnum type (SP or SY) manufactured by Daikin Industries, Ltd. is a homopolymer of hexafluoropropylene oxide, and has an ester group -COOR at one end (where R represents an alkyl group which may be substituted with fluorine). Have
[0140]
The number average molecular weight of the lubricant is preferably in the range of 100 to 10,000. More preferably, the number average molecular weight is 2000 to 6000. When the molecular weight is low, the vapor pressure is generally high, and after application, it evaporates little by little and moves away from the desired film thickness over time. Conversely, when the molecular weight is high, the viscosity is generally high and the desired lubricity may not be obtained.
[0141]
Preferably, Fomblin-Z-DOL (trade name), Fomblin-Z-Tetraol (trade name) manufactured by Augmont, etc. are used.
Examples of the solvent for dissolving them include chlorofluorocarbons, alcohols, hydrocarbons, ketones, ethers, fluorines, and aromatics.
In order to increase the chemical bond between the lubricant and the medium, it is preferable to perform a heat treatment after the formation of the lubricant layer. Although heating temperature is 50 degreeC or more, what is necessary is just to select suitably in the temperature range lower than the decomposition temperature of a lubricant. Usually 100 ° C. or lower.
[0142]
The coating thickness of the lubricant is preferably 10 nm or less. Even if it is too thick, a certain level of lubricity cannot be obtained, and excess lubricant moves to the outer peripheral side as the disk rotates, and the film thickness distribution tends to occur on the inner and outer periphery. However, if it is too thin, the desired lubricity cannot be obtained. More preferably, it is 1 nm or more, and particularly preferably 1.5 nm or more.
[0143]
According to the present invention, since the mask is not deteriorated even with respect to a lubricant capable of generating hydrofluoric acid by heating, even a fluorine-based lubricant such as the above perfluoropolyether can be used without any problem. Therefore, there is an advantage that the range of lubricant selection is widened. However, when energy rays are irradiated from above the lubricating layer, recoating or the like may be performed in consideration of damage (decomposition or polymerization) of the lubricant.
[0144]
Moreover, you may add another layer to the above layer structure as needed.
In order not to impair the running stability of the flying / contact type head, the surface roughness Ra of the medium after forming the magnetization pattern is preferably kept at 3 nm or less. Note that the media surface roughness Ra is the roughness of the media surface that does not include the lubricating layer, using a stylus type surface roughness meter (model name: Tencor P-12 disk profiler (manufactured by KLA Tencor)). It is a value calculated in accordance with JIS B0601 after measurement at a measurement length of 400 μm. More preferably, it is 1.5 nm or less.
[0145]
Desirably, the surface waviness Wa of the medium after forming the magnetic pattern is kept at 5 nm or less. Wa is the undulation of the surface of the medium that does not contain a lubricating layer. After measuring with a stylus type surface roughness meter (model name: Tencor P-12 disk profiler (manufactured by KLA Tencor)) at a measurement length of 2 mm, Ra It is a value calculated according to the calculation. More preferably, it is 3 nm or less.
[0146]
By the way, the formation of the magnetization pattern on the magnetic recording medium configured as described above is performed on the recording layer (magnetic layer). It is preferable to carry out by any of the methods described after forming a protective layer, a lubricating layer, etc. on the recording layer. However, if there is no risk of oxidation of the recording layer, it may be carried out immediately after the recording layer is formed.
Various film forming methods for forming each layer of the magnetic recording medium may be employed. For example, physical vapor deposition methods such as direct current (magnetron) sputtering, high frequency (magnetron) sputtering, ECR sputtering, and vacuum vapor deposition may be used. Can be mentioned.
[0147]
As conditions for film formation, the ultimate vacuum, the substrate heating method and substrate temperature, the sputtering gas pressure, the bias voltage, and the like are appropriately determined according to the characteristics of the medium to be obtained. For example, in sputtering film formation, the ultimate vacuum is usually 5 × 10^-6Below Torr, substrate temperature is room temperature to 400 ° C., sputtering gas pressure is 1 × 10^-3~ 20x10^-3The Torr and bias voltage is preferably 0 to -500V.
[0148]
When the substrate is heated, it may be heated before the underlayer is formed. Alternatively, when using a transparent substrate having a low heat absorption rate, in order to increase the heat absorption rate, the substrate is heated after forming a seed layer containing Cr as a main component or an underlayer having a B2 crystal structure. Thereafter, a recording layer or the like may be formed.
If the recording layer is a rare-earth magnetic layer, from the standpoint of corrosion and oxidation prevention, the innermost and outermost portions of the disk-shaped magnetic recording medium are first masked to form the recording layer, followed by protection. Removing the mask when forming the layer and covering the recording layer completely with a protective layer, or in the case of two protective layers, forming the film with the recording layer and the first protective layer masked, It is preferable to remove the mask when forming the second protective layer, and to completely cover the recording layer with the second protective layer, in order to prevent corrosion and oxidation of the rare earth magnetic layer.
[0149]
Next, the magnetic recording apparatus of the present invention will be described.
A magnetic recording apparatus according to the present invention includes a magnetic recording medium having a magnetization pattern formed by the above-described method, a drive unit that drives the magnetic recording medium in a recording direction, a magnetic head that includes a recording unit and a reproducing unit, and a magnetic head. Means for moving relative to the magnetic recording medium and recording / reproduction signal processing means for inputting a recording signal to the magnetic head and outputting a reproduction signal from the magnetic head. As the magnetic head, a floating / contact magnetic head is usually used in order to perform high-density recording.
[0150]
By using a magnetic recording medium on which a magnetic pattern such as a fine and high-precision servo pattern is formed by the method of the present invention, the magnetic recording apparatus can perform high-density recording. Further, since the medium is not damaged and has few defects, recording with few errors can be performed.
In addition, after the magnetic recording medium is incorporated in the apparatus, the magnetization pattern is reproduced by a magnetic head to obtain a signal, and the servo burst signal is recorded by the magnetic head using the signal as a reference. A precise servo signal can be easily obtained.
[0151]
In addition, after the servo burst signal is recorded by the magnetic head, if the signal recorded as the magnetization pattern according to the present invention remains in the area that is not used as the user data area, the magnetic head is displaced due to some disturbance. Since it is easy to return to a desired position, a magnetic recording apparatus in which signals by both writing methods exist has high reliability.
[0152]
A magnetic disk device, which is a typical magnetic recording device, will be described as an example.
A magnetic disk device usually has a shaft for fixing one or more magnetic disks in a skewered manner, a motor for rotating a magnetic disk joined to the shaft via a bearing, and a magnetic used for recording and / or reproduction. A head, an arm to which the head is attached, and an actuator that can move the head to an arbitrary position on the magnetic recording medium via the head arm. Moving with flying height. The recording information is converted into a recording signal through a signal processing means and recorded by a magnetic head. The reproduction signal read by the magnetic head is inversely converted through the signal processing means to obtain reproduction information.
[0153]
On the disc, information signals are recorded in units of sectors along concentric tracks. Servo patterns are usually recorded between sectors. The magnetic head reads the servo signal from the pattern, thereby accurately tracking the center of the track and reading the information signal of the sector. Similar tracking is performed during recording.
[0154]
As described above, a servo pattern that generates a servo signal is required to have a particularly high accuracy because of its nature of being used for tracking when recording information. In addition, since the servo patterns that are widely used at present consist of two sets of patterns shifted from each other by 1/2 pitch per track, it is necessary to form each pattern at every 1/2 pitch of the information signal, and double the accuracy. Is required.
[0155]
However, in the conventional servo pattern forming method, the write track width is limited to about 0.2 to 0.3 μm due to the influence of vibration caused by the difference between the center of gravity of the external pin and the actuator, and the accuracy of the servo pattern increases with the increase in track density. However, it is becoming difficult to improve the recording density and reduce the cost of the magnetic recording apparatus.
According to the present invention, a highly accurate magnetic pattern can be formed efficiently, so that a servo pattern can be formed with high accuracy in a much lower cost and in a shorter time than conventional servo pattern forming methods, for example, 40 kTPI or more. The track density of the medium can be increased. Therefore, a magnetic recording apparatus using this medium can perform recording at high density.
[0156]
In addition, when the phase servo system is used, a continuously changing servo signal can be obtained, so that the track density can be further increased, tracking at a width of 0.1 μm or less is possible, and higher density recording is possible.
As described above, in the phase servo system, for example, a magnetization pattern extending linearly obliquely with respect to the radius from the inner periphery to the outer periphery is used. Such a continuous pattern in the radial direction or an oblique pattern is difficult to produce by the conventional servo pattern forming method in which the servo signal is recorded track by track while rotating the disk, and complicated calculation and configuration are required.
[0157]
However, according to the present invention, once a mask corresponding to the shape is formed, the pattern can be easily formed only by irradiating the energy beam through the mask. Can be created inexpensively. As a result, a phase servo type magnetic recording apparatus capable of high-density recording can be provided.
The conventional mainstream servo pattern forming method is performed by using a dedicated servo writer in a clean room after a medium is incorporated in a magnetic recording device (drive).
[0158]
Each drive is mounted on a servo writer, and a servo writer pin is inserted through a hole on either the front or back of the drive, and the magnetic head is mechanically moved to record one pattern along the track. For this reason, it takes a very long time of about 15 to 20 minutes per drive. Since a dedicated servo writer is used and a hole is made in the drive, it is necessary to perform these operations in a clean room, which is cumbersome in the process and increases costs.
[0159]
In the present invention, a servo pattern or a reference pattern for servo pattern recording can be recorded in a lump by irradiating an energy beam through a mask in which a pattern is recorded in advance, and a servo pattern can be formed on a medium in a very simple and short time. it can. In the magnetic recording apparatus incorporating the medium on which the servo pattern is formed in this way, the servo pattern writing step is not necessary.
[0160]
Alternatively, a magnetic recording apparatus incorporating a medium on which a servo pattern recording reference pattern is formed can write a desired servo pattern in the apparatus based on the reference pattern, and the above servo writer is unnecessary, There is no need to work in a clean room.
Further, it is not necessary to make a hole on the back side of the magnetic recording apparatus, which is preferable in terms of durability and safety.
[0161]
Furthermore, in the present invention, since the mask and the medium do not need to be in close contact with each other, damage due to contact between the magnetic recording medium and other components, or damage to the medium due to pinching of fine dust or dirt is prevented. Can be prevented.
As described above, according to the present invention, a magnetic recording apparatus capable of high-density recording can be obtained at a low cost by a simple process.
[0162]
As the magnetic head, various types such as a thin film head, an MR head, a GMR head, and a TMR head can be used. By configuring the reproducing section of the magnetic head with an MR head, a sufficient signal intensity can be obtained even at a high recording density, and a magnetic recording apparatus with a higher recording density can be realized.
Further, when the magnetic head is floated at a low height of 0.001 μm or more and less than 0.05 μm, the output is improved and a high device S / N is obtained, and a large capacity and highly reliable magnetic recording is obtained. An apparatus can be provided.
[0163]
Further, the recording density can be further improved by combining the signal processing circuit based on the maximum likelihood decoding method. For example, when recording / reproducing at a recording density of 13 GTPI or more, linear recording density of 250 kFCI or more, and recording density of 3 Gbits per square inch or more. Sufficient S / N can be obtained.
Furthermore, the reproducing part of the magnetic head has a plurality of conductive magnetic layers that cause a large change in resistance due to relative changes in the magnetization directions of each other by an external magnetic field, and a conductive non-conductive layer disposed between the conductive magnetic layers. By using a GMR head composed of a magnetic layer or a GMR head using the spin valve effect, the signal intensity can be further increased, and reliability with a linear recording density of 10 Gbits per square inch or more and 350 kFCI or more. High magnetic recording apparatus can be realized.
[0164]
【Example】
Examples of the present invention will be described below. However, the present invention is not limited to these examples as long as the scope of the gist is not exceeded.
(Examples 1 and 2, Comparative Examples 1 and 2)
[Preparation of Mask of Example 1]
A 127 mm × 127 mm square, 2.3 mm thick quartz glass is used as a base, and a Si (silicon) layer having a thickness of 100 nm is formed on the surface of the magnetic disk by sputtering, and a 200 nm thick photoresist layer is sequentially formed by spin coating. Formed. After that, using a laser exposure apparatus, a pattern corresponding to the servo pattern to be formed on the magnetic recording medium was exposed and developed to form a concavo-convex pattern on the photoresist layer.
[0165]
Next, reactive ion etching (RIE) was performed on the opening of the resist using IE-500 manufactured by JVC. SF₆Etching of quartz glass was performed for 2 minutes using gas. Etching conditions are SF₆The flow rate is 100 sccm, the pressure is 30 mTorr, and the RF output is 50 W. The ratios (selectivity) of the etching rates of Si and photoresist and Si and quartz glass were 8: 1 and 10: 1, respectively. After RIE, the photoresist was removed using a remover.
[0166]
Next, the depth of the recess (groove) formed in the Si layer was measured with an AFM (Atomic Force Microscope: Nanoscope 3a D3100 type manufactured by Digital Instruments), and the groove depth was almost 100 nm over the entire surface. It was confirmed. That is, all Si was etched in the transmission part.
The produced mask has a pattern area with a radius of 20 to 46 mm, and a pattern having a pattern minimum line width of 0.7 μm (minimum width of 0.7 μm; both lines and spaces are 0.7 μm) is provided. The minimum pattern line width at the innermost periphery is 0.7 μm, and the minimum pattern line width at the outermost periphery is about 1.2 μm.
[0167]
Thereafter, a spacer made of a Cr layer was provided on the peripheral edge of the pattern region by a lift-off method. That is, in the range of the radius of about 47 to 48 mm, which is the outer peripheral portion outside the pattern region, approximately circular protrusions (spacers) having a height of 1.5 μm and a diameter of 50 μm are spaced at intervals of 100 μm and within a range of a radius of 15 to 16 mm. A mask on which spacers that are the same as the outer peripheral spacers were formed except that the height was 0.5 μm was obtained.
[0168]
[Production of Mask of Example 2]
After removing the photoresist after RIE in the same manner as in Example 1, the SiO 2 film was formed by reactive sputtering.₂The layer was provided with a thickness of 40 nm. Reactive sputtering was performed by sputtering a silicon target with a mixed gas of argon 70 ccm and oxygen 30 ccm.
[0169]
Finally, a spacer was produced in the same manner as in Example 1.
As a result, the transmission part is 40 nm thick SiO2 on quartz glass.₂A non-transparent portion is formed on a quartz glass with a Si layer having a thickness of 100 nm and a SiO layer having a thickness of 40 nm.₂A mask provided with a laminated film of layers was obtained.
[Manufacture of Mask of Comparative Example 1]
A 127 mm × 127 mm square, 2.3 mm thick quartz glass is used as a base, and a Cr (chrome) layer having a thickness of 100 nm is formed on the surface to be magnetically coated by sputtering, and a photoresist layer having a thickness of 200 nm is sequentially formed by spin coating. Formed. After that, using the laser exposure apparatus, the same pattern as in Example 1 was exposed and developed to form a concavo-convex pattern in the photoresist layer.
[0170]
Next, Cr was wet-etched at the opening portion of the photoresist with an etching solution containing cerium nitrate to produce a mask having the same pattern as in Example 1. In addition, all Cr was etched in the transmission part.
Thereafter, a spacer made of a Cr layer was provided in the peripheral portion of the pattern region in the same manner as in Example 1.
[0171]
[Production of Mask of Comparative Example 2]
After performing the photoresist removal after the wet etching in the same manner as in Comparative Example 1, the SiO 2 was formed by reactive sputtering.₂The layer was provided with a thickness of 40 nm. Reactive sputtering was performed by sputtering a silicon target with a mixed gas of argon 70 ccm and oxygen 30 ccm.
[0172]
Finally, a spacer was prepared in the same manner as in Comparative Example 1.
As a result, the transmission part is 40 nm thick SiO2 on quartz glass.₂A non-transparent portion is formed on a quartz glass with a Cr layer having a thickness of 100 nm and a SiO layer having a thickness of 40 nm.₂A mask provided with a laminated film of layers was obtained.
[Repeated Magnetization Pattern Formation Test Using Masks of Examples 1 and 2 and Comparative Examples 1 and 2] Using these masks, a repetitive transfer test was performed on a magnetic recording medium. The magnetic recording medium used was as follows.
[0173]
Cr on a 3.5 inch diameter NiP plated aluminum alloy substrate₉₀Mo_Ten10 nm, Co as the recording layer₆₄Cr₁₆Pt₁₂B₈12 nm, and 3 nm of carbon (diamond-like carbon) as a protective layer. On top of that, a fluorine-based lubricant is applied as a lubricating layer to a thickness of 0.5 nm, baked at 100 ° C. for 40 minutes, static coercive force at room temperature of 3600 Oe, dynamic coercive force of about 8000 Oe, saturation magnetization of 310 emu / For in-plane recording of cc.
[0174]
First, the magnetic field direction of the electromagnet is configured to be the same as the rotation direction of the disk on this medium, and is applied with an intensity of about 10 kOe (about 10 k Gauss), and the disk surface is magnetized uniformly (uniformly). .
Using the mask and medium, a magnetization pattern was formed by the magnetization pattern forming apparatus shown in FIG. The mask and the medium were integrated through a spacer and rotated at a speed of one rotation in 3.2 seconds. Here, an excimer pulse laser with a wavelength of 248 nm is applied with a pulse width of 25 nsec and power (energy density): 160 mJ / cm.²Beam shape: 10 mm × 30 mm (1 / e of peak energy²), And 32 pulses were irradiated per rotation at a repetition frequency of 10 Hz. When the heating temperature of the medium was determined by simulation, it was about 200 ° C.
[0175]
As a recording magnetic field, a magnetic field of about 3000 Oe and a length of 200 μs was applied.
FIG. 3 shows a temporal relationship between the magnetic field pulse and the laser light trigger pulse in the embodiment. Excimer pulse laser was irradiated about 4 μsec after the trigger pulse for laser light was emitted. As can be seen from FIG. 3, the timing was adjusted so that the pulsed laser was irradiated when the magnetic field intensity was substantially maximum.
[0176]
In this test, laser irradiation was repeated while continuously rotating the mask and the medium. The number of times each position of the mask was irradiated (that is, the number of times the mask was rotated) was defined as the number of times of irradiation. The medium was changed every 10000 irradiations.
When the predetermined number of irradiations was reached, the test medium was replaced with a signal measurement medium, and laser irradiation was performed only once to form a magnetization pattern. Thereafter, the medium was returned to the test medium, and a repeated irradiation test was performed. The above process was repeated.
[0177]
Laser irradiation was repeatedly performed on the masks of Examples 1 and 2 and Comparative Examples 1 and 2 by the above method.
The magnetization pattern was reproduced with a GMR head for hard disk having a reproducing element width of 0.4 μm on the signal measurement medium on which the magnetization pattern was formed by the above test. The result of measuring the change in the reproduction signal output at this time is shown in FIG. 6 (the output is standardized by the initial value). The decrease in output occurs because the mask pattern is deteriorated and the formation of the magnetization pattern is incomplete.
[0178]
Comparative Example 1 is not shown in FIG. 6 because the mask pattern was destroyed and became unmeasurable at the stage of 10000 times irradiation first measured after the initial characteristics.
As can be seen from FIG. 6, Example 1 and Example 2 withstood 100,000 times of repeated laser irradiation, showed sufficient durability, and showed a marked improvement over Comparative Example 2. However, at the stage where 100,000 times were exceeded, Example 2 showed slightly better durability than Example 1.
[0179]
When the mask surface after irradiation of 116000 times of Example 1 and after irradiation of 143,000 times of Example 2 was observed with a SEM (surface scanning electron microscope), the mask of Example 1 showed corrosion at the transmission part. (See FIG. 7). In Example 2, no significant corrosion was observed.
[Durability Evaluation Test of Masks of Examples and Comparative Example 1]
After dropping a fluorine-based lubricant (Fomblin, Z-Dol2000: manufactured by Augmont) on the masks of Example 1 and Comparative Example 1, a 3.5-inch diameter NiP-plated aluminum alloy substrate was interposed through a spacer. Opposed. In this state, an excimer pulse laser with a wavelength of 248 nm was irradiated from the mask side. Irradiation conditions are pulse width: 25 nsec, power (energy density): 160 mJ / cm²Beam shape: 10 mm × 30 mm (1 / e of peak energy²The same place was repeatedly irradiated at a repetition frequency of 50 Hz.
[0180]
FIG. 4 shows a photomicrograph of the mask of Example 1 after 100,000 times of laser irradiation, and FIG. 5 shows a photomicrograph of the mask of Comparative Example 1 after 30,000 times of laser irradiation. As can be seen from the photograph, the mask of Example 1 showed no deterioration of the silicon pattern until 100,000 times of laser irradiation, whereas the mask of Comparative Example 1 had almost no chromium pattern after 30,000 times of laser irradiation. Peeling occurred.
[0181]
(Example 3 and Comparative Example 3)
A 100 nm Si layer was formed on quartz glass in the same manner as in Example 1 (Example 3). When a tape peeling test was performed on this Si layer by making 10 slits at 1 mm intervals vertically and horizontally using a cutter knife, no peeling was observed.
Similarly, a 100 nm Pt layer was formed on quartz glass (Comparative Example 3). When the tape peeling test was conducted in the same manner as in Example 3, all the cut portions were peeled off.
[0182]
(Comparative Example 4)
A mask was produced in the same manner as in Example 1 except that molybdenum silicide (Mo: Si = 1: 1 in atomic%) was used instead of silicon.
The depth direction analysis of the film composition of this mask by XPS was performed. Next, the mask was immersed in a lubricant (Z-Dol2000) and heated to 600 ° C., and the depth direction analysis of the film composition by XPS was performed on the heated mask. A comparison of analysis results before and after heating is shown in FIG. After heating, Si remained in the film whereas Mo disappeared almost completely.
(Experimental Examples 1 and 2)
A 127 mm × 127 mm square, 2.3 mm thick quartz glass is used as a substrate, and a 100 nm thick Si layer is formed on one surface by sputtering and a 30 nm thick SiO film is formed by reactive sputtering.₂What provided the layer continuously was produced (Experimental example 1). Reactive sputtering was performed by sputtering a silicon target with a mixed gas of argon 70 ccm and oxygen 30 ccm.
In addition, SiO₂In the same manner except that no layer was provided, an Si layer having a thickness of 100 nm was prepared (Experimental Example 2).
A scratch test using a diamond needle having a radius of curvature of 0.05 mm was performed on the substrates obtained in Experimental Example 1 and Experimental Example 2.
The substrate of Experimental Example 1 was not scratched even at the maximum load of 400 g of the apparatus.
The substrate of Experimental Example 2 was scratched with a load of 40 g.
Thereby, it can be seen that the substrate provided with the dielectric layer is excellent in durability against impact.
[0183]
【The invention's effect】
According to the present invention, since the reflectance of the non-transmission part is particularly high in a short wavelength region, a laser processing mask with low energy beam absorption and high energy beam durability can be obtained. For this reason, the replacement frequency of the mask is reduced, the productivity is high, and the production cost is suppressed. In particular, this mask can be used suitably for microfabrication in which short wavelength energy rays are used.
[0184]
According to the present invention, a laser processing mask having high durability against hydrofluoric acid generated by decomposition of a lubricant or the like can be obtained. For this reason, the replacement frequency of the mask is reduced, the productivity is high, and the production cost is suppressed. In addition, a highly productive pattern can be formed on an object containing a fluorine compound and capable of generating hydrofluoric acid. Therefore, a magnetization pattern can be formed also on the magnetic recording medium after application of the fluorine-based lubricant. Further, a non-toxic and inexpensive mask can be obtained as compared with the case of using chromium.
[0185]
By applying this mask to a technique for forming a magnetization pattern on a magnetic recording medium by combining local heating and external magnetic field application, a fine pattern can be efficiently formed at low cost. Further, since the magnetization pattern can be formed on the medium after applying the lubricant, it is not necessary to form the magnetization pattern on the medium before applying the lubricant, which complicates the process, the production cost is suppressed, and the production efficiency is remarkably improved. As a result, it is possible to provide a magnetic recording medium and a magnetic recording apparatus capable of higher density recording in a short time and at a low cost.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an embodiment of a magnetization pattern forming method using a mask of the present invention.
2A and 2B are a plan view and a cross-sectional view showing a magnetization pattern forming method according to an embodiment of the present invention.
FIG. 3 is a diagram showing a temporal relationship between a magnetic field pulse and a laser light trigger pulse in an embodiment of the present invention.
FIG. 4 is a photomicrograph after 100,000 times of laser irradiation of the mask of Example 1 of the present invention.
FIG. 5 is a photomicrograph of the mask of Comparative Example 1 of the present invention after 30,000 times of laser irradiation.
FIG. 6 is a graph showing the relationship between the number of irradiations and signal amplitude in a repeated laser irradiation test of the mask of the example of the present invention.
7 is an electron micrograph of the mask of Example 1 of the present invention after a repeated laser irradiation test. FIG.
8 shows (a) the depth direction analysis result in the MoSi film by XPS in the initial stage and (b) the depth direction analysis result in the MoSi film by XPS after heating in the lubricant of the mask of Comparative Example 4 of the present invention. is there.
[Explanation of symbols]
1 Magnetic recording medium (magnetic disk)
2 mask
3 External magnetic field
4 Incident light (laser beam)
5 Spacer
6 Transparent substrate (quartz)
7 Light-shielding layer (silicon-containing layer)
8 Dielectric layer
11 Magnetic disk
12a, 12b, 12c, 12d Permanent magnet
13 Shading plate
13a opening
14 Mask
15 Energy rays
17 Spacer
18a, 18b, 19a, 19b, 19c, 19d Air-core coil (electromagnet)
21 DC power supply
22 capacitors
23 Thyristor
24 Trigger generator
25 Delay device
26 Energy source

Claims (7)

To the magnetic recording medium comprising a lubricant layer comprising a magnetic layer and a fluorine substrate, a step of irradiating an energy beam to heat the irradiated portion of the magnetic layer through a mask, the external magnetic field to the magnetic layer A method of forming a magnetization pattern including a step of applying
The method for forming a magnetic pattern , wherein the mask has a layer of a non-transmission part for the energy beam mainly composed of silicon on a transparent substrate . 2. The method for forming a magnetic pattern according to claim 1 , wherein a mask is used in which a dielectric layer mainly composed of silicon oxide is provided on the non-transparent portion layer mainly composed of silicon. 2. The method for forming a magnetic pattern according to claim 1 , wherein a mask having a dielectric layer mainly composed of silicon oxide provided on a surface of the mask facing the magnetic recording medium is used . To the magnetic recording medium comprising a lubricant layer comprising a magnetic layer and a fluorine substrate, a step of irradiating an energy beam to heat the irradiated portion of the magnetic layer through a mask, the external magnetic field to the magnetic layer A mask used for a magnetic pattern forming method including a step of applying
A mask comprising a non-transparent layer mainly composed of silicon on a transparent substrate . Opaque areas on a layer of mask of claim 4, the dielectric layer mainly made of silicon oxide is provided mainly containing silicon. Dielectric layer mainly comprising layer and the silicon oxide of the non-transmissive portion mainly composed of the silicon is characterized by forming by performing the removal of the photoresist by oxidizing gas after the chemical etching treatment The mask according to claim 5. The mask according to claim 4, wherein a dielectric layer mainly composed of silicon oxide is provided on a surface of the mask facing the magnetic recording medium.

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