JP2003107667A - Photomask, its manufacturing method and method for forming magnetization pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photomask on which a mask pattern is formed with high accuracy. SOLUTION: In exposing procedures of a manufacturing method for the photomask having a process for forming a photoresist layer 13 on a transparent substrate base 10 having an energy ray shielding material layer 12 before an etching processing, a process for forming a resist pattern 13A by developing a latent image pattern after forming it by irradiating the photoresist layer 13 with an energy ray, a process for etching the energy ray shielding material layer 12 and a process for removing the resist 13A, a latent image 13b for diffraction slit is formed in a transmission area 15 without the energy ray shielding material layer 12 in outer peripherals of a mask pattern area by photoresist. The latent image 13b for diffraction slit is irradiated with laser beam 21 from the bottom of the transparent substrate base 10, a developer is supplied as detecting zero-order, 1st-order or 2nd-order diffracted lights and development is stopped at a point of time when light quantity ratio between diffracted lights becomes prescribed one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask manufacturing method, and more particularly to a photomask manufacturing method used for forming a magnetization pattern on a magnetic disk. The present invention also relates to a photomask manufactured by this method and a method for forming a magnetization pattern on a magnetic disk using this photomask.

[0002]

2. Description of the Related 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 a recording device for a moving image recording device or a set top box. It is also being used as a device.

A magnetic disk device usually has a shaft for fixing one or a plurality of magnetic disks in a skewered shape,
A motor for rotating a magnetic disk joined to the shaft through a bearing, a magnetic head used for recording and / or reproducing, an arm to which the head is attached, and a head for mounting the head on a magnetic recording medium. An actuator that can be moved to any position. The recording / reproducing head is usually a flying head, which moves on the magnetic recording medium with a constant flying height.

In addition to the flying head, in order to further reduce the distance to the medium, a contact head (contact head)
The use of is also suggested.

In a magnetic recording medium mounted on a magnetic disk device, a NiP layer is generally formed on the surface of a substrate made of an aluminum alloy or the like, and after performing a required smoothing treatment, texturing treatment, etc., a NiP layer is formed thereon. It is manufactured by sequentially forming a metal underlayer, a magnetic layer (information recording layer), a protective layer, a lubricating layer and the like. Alternatively, it is manufactured by sequentially forming a metal underlayer, a magnetic layer (information recording layer), a protective layer, a lubricating layer, etc. on the surface of a substrate made of glass or the like. The magnetic recording medium includes an in-plane magnetic recording medium and a perpendicular magnetic recording medium. Longitudinal recording is usually performed on the longitudinal magnetic recording medium.

The density of magnetic recording media is increasing every year, and there are various techniques for realizing this. For example, improvements such as making the flying height of the magnetic head smaller, adopting a GMR head as the magnetic head, and increasing the coercive force of the magnetic material used for the recording layer of the magnetic disk, and the information recording track of the magnetic disk Attempts have been made to reduce the interval between. For example, 100 Gb
To achieve it / inch ² , the track density is 10
0 ktpi or more is required.

A control magnetization pattern for controlling the magnetic head is formed on each track. For example, it is a signal used for position control of the magnetic head or a signal used for synchronization control. When the distance between the information recording tracks is narrowed and the number of tracks is increased, the signal used for position control of the data recording / reproducing head (hereinafter, also referred to as “servo signal”) is also aligned in the radial direction of the disk. On the other hand, it must be densely provided, that is, more, so that precise control can be performed.

In addition, it is desirable to increase the data recording capacity by reducing the area other than the area used for data recording, that is, the area used for servo signals and the gap between the servo area and the data recording area to widen the data recording area. Is also a big request. 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 for manufacturing is to make a hole in the vicinity of a head actuator of a drive (magnetic recording device), and insert a pin with an encoder into the hole.
The actuator is engaged with the pin, the head is driven to an accurate position, and the servo signal is recorded. However, since the center of gravity of the positioning mechanism and the center of gravity of the actuator are different from each other, highly accurate track position control cannot be performed, and it is difficult to accurately record the servo signal.

On the other hand, there is also proposed a technique of forming a concave / convex servo signal by irradiating a magnetic disk with a laser beam to locally deform the surface of the disk to form physical unevenness. However, the flying head becomes unstable due to the unevenness, which adversely affects recording / reproduction. 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 such a problem.

Therefore, a new servo signal forming method has been proposed.

One example is a method in which a servo pattern is formed on a master disk having a magnetic layer having a high coercive force, the master disk is brought into close contact with a magnetic recording medium, and a magnetic field is transferred by applying an auxiliary magnetic field from the outside (USP).
5,991,104).

In another example, the medium is magnetized in one direction in advance, a soft magnetic layer having a high magnetic permeability and a low coercive force is patterned on the master disk, and the master disk is brought into close contact with the medium and an external magnetic field is applied. Is the way. The soft magnetic layer acts as a shield, and the magnetization pattern is transferred to the unshielded region (Japanese Patent Laid-Open No. 60-60212 (USP 3,869,711), Japanese Patent Laid-Open No. 10-40).
544 (EP915456), Digest of Inte
rMag 2000, GP-06, see).

In each of these methods, a master disk is used and a magnetic pattern is formed on the medium by a strong magnetic field.

Generally, the strength of the magnetic field depends on the distance.
When recording a magnetization pattern with a magnetic field, the leakage magnetic field tends to obscure the pattern boundaries. Therefore,
Intimate contact between the master disk and the medium is essential to minimize stray magnetic fields. Further, as the pattern becomes finer, it is necessary to completely adhere to each other without a gap, and usually, both are pressure-bonded by vacuum suction or the like.

Also, the higher the coercive force of the medium, the larger the magnetic field used for transfer and the larger the leakage magnetic field.
Furthermore, it is necessary to make them adhere completely.

Therefore, the above technique is easily applied to a magnetic disk having a low coercive force and a flexible floppy (registered trademark) disk which is easily adhered to a master disk, but it is used for high density recording using a hard substrate. It is very difficult to apply to a magnetic disk having a coercive force of 3000 Oe or more.

In other words, the magnetic disk of the hard substrate has a risk that minute dust or the like may be caught in the medium when it comes into close contact with the master disk, or the expensive master disk may be damaged. In particular, in the case of a glass substrate, there are problems that the adhesion is insufficient due to the inclusion of dust, magnetic transfer cannot be performed, and cracks occur in the magnetic recording medium.

Further, Japanese Patent Laid-Open No. 60-60212 (USP
3, 869, 711),
The pattern having an oblique angle with respect to the track direction of the disk has a problem that only a pattern having weak signal strength can be formed although recording is possible. Coercive force is 2000 ~
For a magnetic recording medium having a high coercive force of 2500 Oe or more, in order to secure the magnetic field strength for transfer, the pattern ferromagnetic material (shield material) of the master disk is made of soft magnetic material such as permalloy or sendust having a large saturation magnetic flux density. I have no choice but to use my body.

However, in the oblique pattern, the magnetic field of the magnetization reversal is perpendicular to the gap formed by the ferromagnetic layer of the master disk, and the magnetization cannot be tilted in the 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 it is difficult to form a sufficient magnetization reversal pattern and it is difficult to obtain high signal strength. Such an oblique magnetization pattern causes the reproduction output to be reduced more than azimuth loss with respect to the pattern perpendicular to the track.

In order to solve such a problem, the present applicant has filed Japanese Patent Application Nos. 2000-134608 and 200.
No. 0-134611 proposes a method of forming 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, and an energy ray is irradiated through a patterned mask to locally heat the medium, and an external magnetic field is applied while lowering the coercive force of the heated region. Magnetization is applied by an external magnetic field to form a magnetization pattern.

According to the present technology, since the coercive force is lowered by heating and the external magnetic field is applied, the external magnetic field does not need to be higher than the coercive force of the medium, and recording can be performed with a weak magnetic field. Since the area to be recorded is limited to the heating area and the area other than the heating area is not recorded even when a magnetic field is applied, a clear magnetization pattern can be recorded without bringing a mask or the like into close contact with the medium.
Therefore, the medium and the mask are not damaged by the pressure bonding, and the defects of the medium are not increased.

Further, since it is not necessary to shield the external magnetic field by the soft magnetic material of the master disk, a diagonal magnetization pattern can be formed well.

In the method of irradiating an energy ray through such a photomask to locally heat the magnetic layer and applying an external magnetic field to form a magnetization pattern, a laser beam is mainly used as an energy ray at present. It is used. Further, a mask pattern made of an energy ray blocking material layer is formed on the photomask in a pattern matching the magnetization pattern to be formed. As the photomask, a photomask in which a mask pattern made of a chromium-based material is formed on a transparent substrate made of quartz glass is mainly used. As the chrome-based material, a material formed of only a metal chromium layer; or a material in which a chromium oxide layer is formed on the surface of the metal chromium layer is mainly used.

A method of forming this photomask will be briefly described below.

As the transparent substrate body, a transparent substrate made of quartz glass and an energy ray blocking material layer uniformly formed on one surface thereof is used.

Photoresist containing a photo-curable resin is applied to the transparent substrate body to a predetermined thickness and baked (pre-baked) if necessary.

The photoresist is irradiated with a laser beam to form a latent image pattern. This latent image pattern is a pattern that matches the mask pattern to be formed.

A developing solution is supplied onto this substrate to remove the exposed photoresist (developing step), and then, if necessary, baking (post-baking) is performed to form a resist pattern.

Next, the energy ray blocking material layer is etched, and finally, the remaining resist pattern is dissolved and removed (removed). As a result, a photomask having a mask pattern formed on the transparent substrate is manufactured.

In the above developing process, conventionally, the developing solution is supplied onto the substrate for a predetermined time by a timer.

[0032]

In the case of a system in which a developing solution is supplied onto a substrate for a predetermined time by a timer, when there is a disturbance such as fluctuation of power of exposure laser or fluctuation of photoresist sensitivity, overdevelopment occurs. On the contrary, development shortage occurs,
The accuracy of the mask pattern after development may be deteriorated.

The present invention provides a photomask manufacturing method capable of efficiently manufacturing a photomask having a highly accurate mask pattern, a photomask manufactured by this method, and a magnetization pattern using this photomask. And a forming method.

[0034]

A method of manufacturing a photomask according to the present invention is a method of manufacturing a photomask in which a mask pattern made of an energy ray blocking material layer is formed by etching in a pattern forming region on a transparent substrate. hand,
A step of forming a photoresist layer on a transparent substrate body provided with an energy ray blocking material layer before etching, and a latent image pattern according to the mask pattern is formed by irradiating the photoresist layer with energy rays. A latent image pattern forming step, a developing step of developing the photoresist layer to form a resist pattern on the energy ray blocking material layer, an etching step of etching the energy ray blocking material layer, and a resist pattern of removing the resist pattern In the method for manufacturing a photomask, which comprises a removing step, the transparent substrate element has a transparent region having no energy ray blocking material layer in at least a part other than the pattern forming region, and the latent image In the pattern formation process, the transmission area is irradiated with energy rays to diffract the transmission area. It is characterized in that a latent image for lit is formed, in the developing step, the transmitted light is detected while irradiating the latent image for the diffraction slit with light, and the development is performed until the transmitted light reaches a predetermined state. It is a thing.

In the photomask manufacturing method of the present invention, the latent image for the diffraction slit is irradiated with light during development,
Since the progress of development is detected from the transmitted light, the development can always be properly performed without excess or deficiency. This allows
A photomask having a highly accurate mask pattern can be manufactured.

In the developing step, the latent image for the diffraction slit is irradiated with laser light as light, and any two of the 0th-order diffracted light, the 1st-order diffracted light and the 2nd-order diffracted light are detected to monitor the light intensity ratio. Is preferable, and especially 0 order diffracted light and 1
It is preferable to monitor the intensity ratio of the secondary diffracted light or the intensity ratio of the primary diffracted light and the secondary diffracted light.

In the present invention, it is preferable that the energy ray blocking material layer before etching is circular, and the transmission region is arranged on the outer peripheral side thereof.

The latent image for the diffraction slit is preferably provided in a circular shape or a spiral shape concentric with the circular energy ray blocking material layer.

The photomask of the present invention is manufactured by the method for manufacturing a photomask of the present invention.

The method of forming a magnetic pattern in a magnetic disk according to the present invention comprises irradiating a magnetic disk having a magnetic layer with energy rays through a photomask, thereby locally heating the magnetic layer while externally heating the magnetic layer. In a method of applying a magnetic field to form a magnetization pattern, the photomask manufactured by the method of the present invention is used as the photomask.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a photomask of the present invention is a method for producing a photomask in which a mask pattern made of an energy ray blocking material layer is formed by etching in a pattern formation region on a transparent substrate, A step of forming a photoresist layer on a transparent substrate body provided with an energy ray blocking material layer before etching, and a latent image pattern according to the mask pattern is formed by irradiating the photoresist layer with energy rays. A latent image pattern forming step, a developing step of developing the photoresist layer to form a resist pattern on the energy ray blocking material layer, an etching step of etching the energy ray blocking material layer, and a resist pattern of removing the resist pattern A method of manufacturing a photomask, comprising: The body has a transmissive region not having the energy ray blocking material layer in at least a part other than the pattern forming region, and in the latent image pattern forming step, the transmissive region is irradiated with an energy ray to transmit the light. A latent image for a diffraction slit is formed in a region, the transmitted light is detected while irradiating the latent image for the diffraction slit with light in the developing step, and development is performed until the transmitted light reaches a predetermined state. It is a feature.

The transparent substrate is preferably a transparent quartz substrate,
It is not limited to this. The shape of the transparent substrate is arbitrary and may be square or circular.

The energy ray blocking material layer formed on the transparent substrate is preferably a metal chromium film or a film in which a chromium oxide layer is formed on the surface of the metal chromium film, but the material is not limited to this.

As the photoresist, it is preferable to use a photo-curable synthetic resin or an electron beam-curable synthetic resin as a main component, and the energy beam with which the photoresist layer is irradiated is preferably a laser beam or an electron beam. is there.

It is preferable that the energy ray blocking material layer before the etching treatment is formed in a circular shape on the transparent substrate layer, and the transmission region is formed outside the circular energy ray blocking material layer. The width of the transparent region is preferably about 0.5 to 10 mm. In this transmission region, a latent image for one or a plurality of ring-shaped diffraction slits is formed by exposure of the photoresist, preferably concentrically with the circular energy ray blocking material layer, and the diffraction slits are gradually developed in the subsequent development process. Is coming.

Hereinafter, the developing process of the photomask manufacturing method according to the embodiment of the present invention will be described in detail with reference to the drawings. 1A, 1 </ b> B, and 1 </ b> C are schematic explanatory views showing the developing process of the photomask according to the embodiment.

As shown in FIG. 1A, the exposed transparent substrate body 10 with photoresist is placed on the turntable 1, and the turntable 1 is rotated at a constant angular velocity. The transparent substrate body 10 includes a transparent substrate 11 made of quartz glass and an energy ray blocking material layer 12 formed uniformly on the upper surface of the transparent substrate 11. A photoresist layer 13 is formed on the energy ray blocking material layer 12 and exposed.

The energy ray blocking material layer 12 has a circular shape, and the transmission region 15 (FIG. 1B) without the energy ray blocking material layer 12 is provided on the outer peripheral side thereof. The photoresist layer 13 is formed with a uniform thickness over the entire area so as to cover the entire energy ray blocking material layer 12 and the transmission area 15.

The exposure of the photoresist layer 13 is performed on both the energy ray blocking material layer 12 and the transmission region 15. As shown in FIG. 1B, a mask pattern latent image 13 a is formed by exposure on the energy ray blocking material layer 12, and a plurality of diffraction slit latent images 13 b are formed by exposure on the transmission region 15. Each diffraction slit latent image 13b has a narrow ring shape concentric with the circular energy ray blocking material layer 12. The period (track pitch) of the diffraction slit is 1.5 to 5.
It is preferably about 0 times, for example, He with a wavelength of 633 nm.
When a -Ne laser is used, it is preferably about 1.0 to 3.0 μm. The groove width is preferably half the track pitch or less. The number of grooves is preferably 200 to 4000 (200 to 4000 tracks in the case of spiral).

After the exposure of the photoresist layer 13, the transparent substrate body 10 is heated if necessary to post-bake the photoresist layer 13.

The transparent substrate body 10 (of FIG. 1B) having the photoresist layer 13 thus exposed is arranged such that the energy ray blocking material layer 12 is coaxial with the turntable 1. Place on. And FIG.
As shown in (a), the turntable 1 is rotated at a constant angular velocity, and the developing solution 3 is supplied onto the transparent substrate body 10 at a constant flow rate from the solution supply nozzle 2 arranged above the turntable 1. Developer 3 supplied on transparent substrate body 10
Moves toward the outer peripheral edge of the transparent substrate body 10 while spreading on the transparent substrate body 10 by the centrifugal force, and eventually falls from the outer peripheral edge. The development of the photoresist layer 13 is performed while the developing solution 3 moves on the transparent substrate body 10.

The photoresist layer 13 in the exposed areas other than the latent images 13a and 13b is gradually washed away by the developing solution 3, and the mask pattern resist 13A derived from the latent image 13a is energized as shown in FIG. 1 (c). Line blocking material layer 12
Diffraction slit 13 developed on and derived from latent image 13b
B is developed in the transparent region 15.

During this developing step, as shown in FIG. 1A, a laser beam 21 is emitted from a laser light source 20 disposed below the transmissive region 15 of the transparent substrate body 10 to the diffraction slit latent image 1.
3b, and the amount of transmitted light is detected by the photodetector 3
It is detected by 0, 31, 32. Photo detector 3
0 detects the 0th order diffracted light, the photodetector 31 detects the 1st order diffracted light, and the photodetector 32 detects the 2nd order diffracted light.

The amount of each diffracted light changes as the unexposed photoresist layer 13 is removed by the developing solution.
Then, from this amount of diffracted light, the unexposed photoresist layer 13
The removal status (development progress status) is detected, and the supply of the developer 3 is stopped when the development progress status reaches a predetermined state.

In order to detect the progress of development, the intensity ratio I ₀ / I ₁ of the 0th-order diffracted light and the 1st-order diffracted light or the intensity ratio I ₁ / I ₂ of the _1st-order diffracted light and the 2nd-order diffracted light is calculated. The development is stopped when this ratio reaches a predetermined ratio. As the development progresses, I ₀ / I ₁ increases, and I ₁ / I ₂
Decreases. However, it starts to increase when the groove width becomes more than half of the track pitch.

As described above, since the progress of development can be accurately detected from the diffraction of the laser beam 21, the photoresist layer 13 can be properly developed without excess or deficiency.

The laser beam 21 for monitoring the development status is preferably red (for example, He—Ne laser having a wavelength of 633 nm) so as not to expose the photoresist. The thickness of the photoresist layer 13 is
If it is too thin, the resist will run out during etching, and if it is too thick, it will be difficult to expose it.
10000Å is suitable.

After this development, if necessary, the transparent substrate body 1
0 is heated and the resist 13A is post-baked. After that, the energy ray blocking material layer 12 of the transparent substrate body 10
The energy ray blocking material layer 1 by contacting with the etching solution
After etching 2, the resist 13A and the diffraction slits 13B are removed by bringing them into contact with a remove liquid. As a result, a photomask having a mask pattern made of a predetermined energy ray blocking material layer is manufactured. As mentioned above,
Since the photoresist layer 13 is properly developed, the accuracy of this mask pattern is extremely high.

A method of forming a magnetization pattern on a magnetic disk (magnetic recording medium) using the photomask thus manufactured will be described with reference to FIGS. 2A is a plan view showing a method of forming a magnetization pattern according to the embodiment, FIG. 2B is a sectional view taken along line BB of FIG. 2A, and FIG. 3 is a schematic view showing magnetic flux. FIG. 4 is an enlarged sectional view of the magnetic recording medium.

In this magnetization pattern forming method, as shown in FIG. 4, a magnetic layer 41b is provided on a substrate 41a, and the magnetic layer 41b is magnetized substantially uniformly in a predetermined direction within the surface to provide in-plane magnetic recording. As shown in FIG. 2 (b), the medium 41 is irradiated with energy rays 45 to locally heat the magnetic layer 41b, and at the same time, an external magnetic field is applied to the magnetic layer 41b using a magnet 42 so that the heating portion is moved in the predetermined direction. A magnetization pattern is formed by magnetizing in the opposite direction. The magnetic recording medium 41 is placed and fastened on a turntable (not shown).

The light shielding plate 43 is used to limit the irradiation area of the energy rays 45. Energy ray 45
Passes through the fan-shaped window hole 43a of the light shielding plate 43, further passes through the photomask 44, and is irradiated onto the magnetic recording medium 1.

The magnet 42 has an N pole (reference numeral N in the figure).
And S pole (symbol S in the figure). This magnet 4
2 are arranged on both sides (upper and lower sides of FIG. 2B) of the disk-shaped magnetic recording medium 41. The magnetic flux from the N pole of the upper magnet 42 to the S pole and the N of the lower magnet 42
The magnetic flux from the pole to the S pole cancels out vertical components in the magnetic layer 41b, and only the in-plane component is magnetic layer 41b.
applied to b. As a result, the magnetic layer 41b comes to be magnetized in the in-plane direction. A top yoke 46 is arranged at the end of each magnet 42 near the center of the magnetic recording medium 1. This is to compensate for the weakening of the magnetic field near the end.

Although not shown, the photomask 44 includes
An energy ray blocking material layer pattern matching the magnetization pattern to be formed is formed by the method of the present invention.
A spacer 47 is provided between the mask 44 and the magnetic recording medium 41.
Is intervening.

While rotating the magnetic recording medium 41 uniformly magnetized in a predetermined direction, the magnetic recording medium 41 is locally heated by irradiating it with energy rays 45, and the magnetic recording medium 41 is heated by the magnetic flux from the magnet 42. Magnetization is performed in the inward direction according to the pattern in the opposite direction to the predetermined direction to form a magnetization pattern.

In this magnetization pattern forming method, preferably, a pattern forming process is performed on the magnetic recording medium which is magnetized uniformly in a predetermined direction (for example, the circumferential direction) in advance. A method of previously magnetizing the magnetic recording medium uniformly in a predetermined direction is arbitrary. Usually, the magnetic recording medium immediately after manufacturing is randomly magnetized, so it is preferable to uniformly magnetize it with another external magnetic field.

As a means for applying the external magnetic field, a magnetic head may be used, or an electromagnet or a permanent magnet may be arranged so as to generate a magnetic field in a desired magnetization direction. You may use two or more. Furthermore, these different means may be used in combination.

The predetermined direction is the same as or opposite to the running direction of the data write / playback head (the relative movement direction of the medium and the head). In a disk-shaped magnetic recording medium, it is usually in the circumferential direction of the medium. Therefore, an external magnetic field is applied so as to be magnetized as such.

Further, to uniformly magnetize the entire magnetic layer in a desired direction means to magnetize all of the magnetic layers in substantially the same direction, but not exactly all, and at least form the magnetization pattern of the medium. It suffices that the regions to be magnetized are magnetized in the same direction.

The strength of this magnetic field varies depending on the characteristics of the magnetic layer of the magnetic recording medium, but it depends on the coercive force of the magnetic layer at room temperature, which is 2
It is preferable to magnetize by a magnetic field more than double. If it is weaker than this, the magnetization may be insufficient. The upper limit of this magnetic field is about 5 times or less the coercive force of the magnetic layer at room temperature.

In the method for forming a magnetic pattern according to the present invention, after the magnetic layer is magnetized uniformly in a predetermined direction in this way, the magnetic layer is locally heated and at the same time an external magnetic field is applied to apply the heating portion to the predetermined direction. Magnetize in the direction opposite to the direction to form a magnetization pattern. According to this, magnetic domains in opposite directions are clearly formed, so that the signal strength is high and C / N and S are high.
A magnetization pattern with a good / N is obtained.

When the magnetic recording medium is heated by irradiating it with energy rays, the heating temperature is equal to or higher than the temperature at which the coercive force of the magnetic layer is lowered, for example, near the magnetization disappearing temperature of the magnetic layer and the Curie temperature. In the present invention, it is preferable to use a magnetic recording medium whose temperature is 100 ° C. or higher. A magnetic recording medium whose temperature is lower than 100 ° C. tends to have low stability of magnetic domains at room temperature. The heating temperature is preferably 700 ° C or lower. If the heating temperature is too high, the magnetic recording medium may be deformed.

The direction of the magnetic field applied at the same time as the heating is opposite to the direction of the above-mentioned uniform magnetization. Also, the stronger the magnetic field, the easier the formation of the magnetization pattern. Preferably, the magnetic field strength in the in-plane direction is 1/8 of the coercive force of the magnetic layer at room temperature.
The above magnetic field is used. If it is weaker than this, when the heating part is cooled, it may be magnetized again in the same direction as the surroundings under the influence of the magnetic field from the surrounding magnetic domains.

However, if the applied magnetic field at the time of heating is too strong, the magnetic domains around the heating portion may be affected. Therefore, the magnetic field strength applied to the heating region is preferably such that the magnetic field strength in the in-plane direction is smaller than the coercive force of the magnetic layer at room temperature, and particularly 2/3 or less of the coercive force of the magnetic layer at room temperature, especially 1 / It is preferably 2 or less.

In order to achieve the above magnetic field distribution, an external magnetic field is applied by arranging magnets 42 (magnet pairs) having magnetic poles opposite to each other on both sides of the magnetic recording medium 41 as shown in FIG. Is preferred. According to this method, as shown in FIG. 3, the magnetic field strength applied in the in-plane direction of the magnetic recording medium 1 is twice the in-plane direction component of the magnetic field applied from one magnet pair, and the vertical components cancel each other out. . This makes it possible to reduce the vertical component and increase only the in-plane direction component.

The vertical component can be significantly reduced by optimizing the strength and distance of the magnet.

Next, the irradiation mechanism of the energy ray 45 for locally heating the magnetic layer will be described.

As this energy ray, it is preferable to use a laser which can easily prevent heat diffusion to an unnecessary portion and control the power and can easily control the size of a portion to be heated.

Further, it is preferable that the laser is pulsed rather than continuous irradiation to control the heating portion and the heating temperature. Therefore, it is preferable to use a pulsed laser light source as the laser irradiation source. A pulsed laser light source oscillates a laser in a pulsed manner intermittently, and compared with a continuous laser that is intermittently pulsed by an optical component such as an acousto-optic device (AO) or an electro-optic device (EO), It is possible to irradiate a laser having a high power peak value in a very short time, and it is very preferable that heat is hardly accumulated.

When a continuous laser is pulsed by optical components, it has almost the same power within the pulse over its pulse width. On the other hand, the pulsed laser light source accumulates energy by resonance in the light source, for example, and emits the laser as a pulse at a time. Therefore, the power of the peak is very large in the pulse and then becomes small. A pulsed laser light source can be used to heat rapidly in a very short period of time and then cool rapidly. This makes it possible to form a highly accurate magnetic pattern with high contrast.

The surface of the medium on which the magnetization pattern is formed has a larger temperature difference between the irradiation of the pulsed laser and the non-irradiation,
It is preferable to increase the contrast of the pattern or increase the recording density. Therefore, it is preferable that the temperature is about room temperature or lower when the pulsed laser is not irradiated. What is room temperature 2
It is about 5 ° C.

When using a pulsed laser, the external magnetic field may be applied continuously or in a pulsed manner.

The wavelength of the laser is preferably 1100 nm or less. When the wavelength is shorter than 1100 nm, the diffraction effect is small and the resolution is improved, so that a fine magnetization pattern is easily formed. Laser light with a wavelength of 600 nm or less
Not only the resolution is high, but also the diffraction is small, so that the spacing between the mask and the magnetic recording medium can be widely taken due to the gap, and the handling is easy, and the magnetization pattern forming device can be easily configured. In addition, the wavelength of the laser light is preferably 150 nm or more. 150n
If it is less than m, the absorption of synthetic quartz used for the mask becomes large, and heating tends to be insufficient. If the wavelength is 350 nm or more, the optical glass can be used as a mask.

The laser light is specifically an excimer laser (157, 193, 248, 308, 351n).
m), 2 of YAG Q-switched laser (1064 nm)
Overtone (532nm), Overtone (355nm), or 4
Harmonics (266nm), Ar laser (488nm, 514nm)
nm), ruby laser (694 nm), etc. are suitable.

The power of the laser (irradiation energy per unit area) may be selected as an optimum value depending on the magnitude of the external magnetic field, but the power per pulse of the pulsed laser is 1000 mJ / cm ² or less. preferable. If a power higher than this is applied, the pulsed laser may damage the surface of the magnetic recording medium and cause deformation. If the roughness Ra increases to 3 nm or more and the waviness Wa increases to 5 nm or more due to the deformation, the running of the flying / contact type head may be hindered.

The laser power is more preferably 500.
mJ / cm ² or less, more preferably 200 mJ /
It is not more than cm ² . In this region, it is easy to form a magnetization pattern with high resolution even when a substrate having a relatively large thermal diffusion is used. The power is preferably 10 mJ / cm ² or more. If it is smaller than this, the temperature of the magnetic layer is hard to rise and magnetic transfer is hard to occur. Note that the required power tends to increase as the pattern width becomes narrower. Further, the shorter the wavelength of the laser, the lower the upper limit of the power that can be applied tends to decrease.

When the substrate of the magnetic recording medium is a metal such as Al or an alloy, the heat conductivity is large, so that the heat applied locally spreads to other than the desired portion, which may distort the magnetization pattern. The power is preferably in the range of 30 to 120 mJ / cm ² so that there is no physical damage to the substrate due to excess energy.

When the substrate of the magnetic recording medium is a ceramic such as glass, the heat conduction is smaller than that of Al and the heat is accumulated much at the pulsed laser irradiation site, and therefore the power is 10 to 100 mJ / It is preferably in the range of cm ² .

When the substrate of the magnetic recording medium is a resin such as polycarbonate, the power is 10 to 80 mJ / cm because the amount of heat accumulated at the pulsed laser irradiation site is large and the melting point is lower than that of glass or the like. It is preferably in the range of ² .

If the magnetic layer, the protective layer and the lubricating layer may be damaged by the laser, the power of the pulsed laser may be reduced to increase the strength of the applied magnetic field. For example, in the case of an in-plane recording medium, the coercive force at room temperature is 25 to 7
A magnetic field as large as possible of 5% is applied to reduce the power of the irradiation laser.

When irradiating the pulsed laser through the protective layer and the lubricating layer, it may be necessary to re-apply after the irradiation in consideration of damage (decomposition, polymerization) to the lubricant.

The pulse width of the pulsed laser is 1 μsec.
The following is desirable. If the pulse width is wider than this, the heat generated by the energy given to the magnetic recording medium by the pulsed laser is dispersed, and the resolution is likely to be lowered. When the power per pulse is the same, when the pulse width is shortened and a strong laser is irradiated at one time, thermal diffusion tends to be small and the resolution of the magnetization pattern tends to be high. It is more preferably 100 nsec or less. In this region, it is easy to form a magnetization pattern with high resolution even when a substrate such as Al having a relatively large thermal diffusion is used. Minimum width is 2μ
When forming a pattern of m or less, a pulse width of 25n
It is better to be less than sec. That is, if the resolution is important, the shorter the pulse width, the better. The pulse width is 1 ns
It is preferably ec or more. This is because it is preferable to keep heating for the time until the magnetization reversal of the magnetic layer is completed. In the present application, the minimum width of the pattern means the narrowest length of the pattern. A square pattern has a short side, a circle has a diameter, and an ellipse has a short diameter.

As one type of pulsed laser, there is a laser capable of generating ultrashort pulses of picosecond or femtosecond level at high frequency, such as a mode-locked laser. During the period of irradiating the ultra-short pulse with a high frequency, the laser is not emitted for a very short time between the ultra-short pulses, but the heating portion is hardly cooled because it is a very short time. That is, the region once heated to the Curie temperature or higher is kept at the Curie temperature or higher.

In the present invention, by irradiating an energy ray through a mask and heating locally, it is possible to easily form a complicated pattern or a special pattern which is difficult to make by the conventional method.

For example, in the phase servo system of the magnetic recording medium, a magnetization pattern extending linearly obliquely to the radius and the track from the inner circumference to the outer circumference is used. Such a pattern continuous in the radial direction or a pattern oblique to the radius has been difficult to form by the conventional servo pattern forming method of recording a servo signal track by track while rotating the disk. According to the magnetization pattern forming method of the present invention,
Such a magnetization pattern can be formed easily and in a short time with a single irradiation, without requiring complicated calculations and complicated device configurations.

The photomask does not have to cover the entire surface of the magnetic disk, but may have a size including a repeating unit of the magnetization pattern. In the latter case, it is moved and used.

In addition, when a lubricating layer is provided on the magnetic disk before the formation of the magnetization pattern, a spacer is arranged between the mask and the medium in order to minimize the adhesion of the lubricant to the photomask. It is preferable to provide a gap.

[0097]

EXAMPLES Examples and comparative examples will be described below.

Example 1 A transparent substrate body in which a metallic chromium layer having a diameter of 112 mm and a thickness of 80 nm was uniformly formed on a quartz transparent substrate having a thickness of 2.3 mm and a side of 127 mm was formed by spin coating. Thickness of photoresist (dry thickness) 200
After coating to a thickness of 80 nm, prebaking was performed at 80 ° C. for 30 minutes. After exposure by irradiating with a Kr laser (λ = 413 mm), development, post-baking at 80 ° C. × 12 min, etching and removal were performed to manufacture a photomask having a mask pattern.

In this exposure and development step, as shown in FIG. 1, 1250 diffraction latent images 13b for a diffraction slit having a width of 300 nm, a pattern pitch of 1.6 μm and a thickness of 200 nm are formed, and a He—Ne laser 21 having a wavelength of 633 nm is formed. Was irradiated. Then, the light quantity ratio I _{2 of the second-order} diffracted light and the first-order diffracted light
/ I ₁ was monitored, and development was stopped when this ratio reached 55%. When developing, turntable 20
It was rotated at 0 rpm. After stopping the development, rinsing with pure water was performed, and then the number of revolutions was increased to 1500 rpm to drain water.

A schematic view of a cross section of the manufactured photomask surface in a direction orthogonal to the mask pattern is shown in FIG. Dimension A in FIG. 5 is the width of the bottom surface of the groove, and B is the bottom width of the trapezoidal portion. The track pitch TP is TP = A + B. The value defined by A / TP, that is, A / (A + B) is the aperture ratio. Seven photomasks were manufactured so that the aperture ratio was 55% (0.55). Then, the aperture ratio of the inner peripheral portion (about 18 mm) of each mask is AFM (Dimension 3100 manufactured by Dia Instruments Co., Ltd., probe is OMCL-AC160TS manufactured by Olympus, and radius of curvature is 10 n).
m or less), the cross-sectional shape was measured in the circumferential direction of the pattern. The results are shown in Table 1. The error in the table is the square root of the root mean square of the differences between the measured values of the target values.

[0101]

[Table 1]

Comparative Example 1 A photomask was manufactured in the same manner as in Example 1 except that the developing solution was supplied for 25 seconds by a timer.

The manufactured photomask was measured and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0104]

[Table 2]

As is clear from the comparison between Tables 1 and 2, according to the first embodiment, a photomask having a small error from the target value and a high precision is manufactured.

[0106]

As described above, according to the present invention, a photomask having a mask pattern formed with high accuracy is provided. With this photomask, it is possible to manufacture a magnetic disk on which a magnetic pattern is formed with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a developing process used in a method for manufacturing a photomask according to an embodiment.

FIG. 2 is an explanatory diagram of a magnetization pattern forming method using a photomask.

FIG. 3 is a schematic diagram showing magnetic flux in the method of FIG.

FIG. 4 is a sectional view in the thickness direction of a magnetic recording medium.

FIG. 5 is a schematic cross-sectional view showing a mask pattern on the surface of a photomask.

[Explanation of symbols]

1 turntable 2 Liquid supply nozzle 3 developer 10 Transparent substrate body 11 Transparent substrate 12 Energy ray blocking material layer 13 Photoresist layer 15 Transparent area 20 laser light source Photodetector for 300th order light 31 Photodetector for primary light 32 Photodetector for secondary light 41 magnetic disk 42 magnet 44 Photomask

Continued front page    F-term (reference) 2H095 BA12 BB06 BB15 BE04                 2H097 LA20                 5D091 AA02 AA08 CC26 HH20                 5D112 AA05 GB01

Claims (8)

[Claims] 1. A method of manufacturing a photomask in which a mask pattern made of an energy ray blocking material is formed by etching in a pattern forming region on a transparent substrate, the method comprising a transparent layer having an energy ray blocking material layer before etching treatment. A step of forming a photoresist layer on the substrate body; a latent image pattern forming step of forming a latent image pattern according to the mask pattern by irradiating the photoresist layer with energy rays; and developing the photoresist layer. In the method for producing a photomask, which includes a developing step of forming a resist pattern on the energy ray blocking material layer, an etching step of etching the energy ray blocking material layer, and a resist pattern removing step of removing the resist pattern, The transparent substrate element has a small area other than the pattern formation area. Both have a transmissive region not having the energy ray blocking material layer, and in the latent image pattern forming step, the transmissive region is irradiated with an energy beam to form a latent image for a diffraction slit in the transmissive region. Then, in the developing step, the transmitted light is detected while irradiating the latent image for the diffraction slit with the light, and the development is performed until the transmitted light reaches a predetermined state. 2. The laser beam is irradiated as the light in the developing step, and at least two light quantities of the transmitted light, that is, the 0th-order diffracted light, the 1st-order diffracted light, and the 2nd-order diffracted light are detected, and the ratio thereof is detected. The method for producing a photomask, characterized in that development is performed until a predetermined ratio is obtained. 3. The method of manufacturing a photomask according to claim 2, wherein two light quantities of a first-order diffracted light and a second-order diffracted light are detected. 4. The method of manufacturing a photomask according to claim 2, wherein two light quantities of a 0th-order diffracted light and a 1st-order diffracted light are detected. 5. The energy beam blocking material layer before etching according to claim 1, wherein the energy beam blocking material layer has a circular shape, and the transmission region is outside the outer periphery of the circular energy beam blocking material layer. A method of manufacturing a photomask, wherein the photomask is arranged. 6. The method of manufacturing a photomask according to claim 5, wherein the latent image for forming the diffraction slit has a circular shape or a spiral shape concentric with the circular energy ray blocking material layer. 7. A magnetic disk having a magnetic layer is irradiated with energy rays through a photomask, thereby locally heating the magnetic layer and applying an external magnetic field to form a magnetization pattern. A photomask used for that purpose, which is manufactured by the method according to claim 1. 8. A magnetic disk having a magnetic layer is irradiated with energy rays through a photomask, thereby locally heating the magnetic layer and applying an external magnetic field to form a magnetization pattern. A method for forming a magnetization pattern in a magnetic disk, wherein the photomask is manufactured by the method according to any one of claims 1 to 6.