JPH0585972B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a method of manufacturing an optical memory element for optically recording and reproducing information.

<Prior Art> In recent years, optical memory devices have attracted attention as high-density, large-capacity memory devices. The reason why this optical memory has a high density and large capacity is because the bit, which is the unit of recording information, is determined only by the beam diameter of the light, so its shape can be reduced to a size of about 1 μm. However, this imposes many limitations on the optical memory device. That is, in order to record information at a fixed location or to reproduce information recorded at a fixed location, the light beam must be positioned extremely accurately. In general, in read-only optical memory, address information can be stored in the recorded bits in advance, so the position of the light beam can be determined while reproducing the recorded information, but in additional recording memory or rewritable memory, information can be recorded. Sometimes it is extremely difficult to record even address information. Therefore, in the case of an additional recording memory or a rewritable memory, a method is adopted in which some guide tracks and guide addresses are previously written on the board.
For example, FIG. 7 shows a partial perspective view of a memory board of a conventional additional recording memory or rewritable memory.As shown in the figure, uneven grooves are formed on the board and information is recorded or A common method is to regenerate it. The uneven groove has a shape that is interrupted in the circumferential direction, and this provides bit information indicating the address of the groove. Several methods have already been proposed for forming these uneven grooves, and they can be roughly divided into the following three types.
There are different types. That is, (i) a method of creating the grooves by injection molding using acrylic resin or polycarbonate resin.
Through this molding, the shape of the Ni stamper on which guide tracks and guide addresses have been previously formed is copied.

(ii) A casting method in which acrylic resin is poured into a Ni stamper on which guide tracks and guide addresses have been formed in advance and hardened by applying temperature.

(iii) An ultraviolet curing resin is poured between a substrate such as an acrylic resin substrate or a glass substrate and the Ni stamper on which the guide tracks and guide addresses have been formed in advance, and ultraviolet rays are irradiated through the substrate;
The so-called 2P method involves curing the resin and then removing the Ni stamper.

It is.

However, since all of these methods use resin, there is a risk that oxygen, moisture, etc. may reach the recording medium through the resin. This has the disadvantage that the quality of the recording medium deteriorates. In order to deal with this drawback, the present inventor has already coated a photoresist material on a glass substrate, irradiated the photoresist material with laser light to record a guide pattern (guide track and guide address), and then A method of forming grooves in the shape of a guide pattern by etching was proposed in Japanese Patent Application No. 84613/1983.
However, this method has the disadvantage that each guide pattern must be sequentially recorded track by track using a laser beam, which requires a long time for recording, and is therefore unsuitable for mass production.

<Purpose> The present invention has been made in view of the above points, and uses a mask plate for manufacturing an optical memory element that has good ultraviolet transmittance and high adhesion, and has a recording medium that deteriorates due to oxygen or moisture. By manufacturing an optical memory element by forming an uneven guide pattern on the glass substrate of the optical memory element, it is possible to form grooves indicating information such as guide tracks and guide addresses on the glass substrate of the optical memory element in a short time. It is an object of the present invention to provide a novel method for manufacturing an optical memory element that can be performed with high density.

<Example> Hereinafter, an example of the method for manufacturing an optical memory element according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing, in order of steps, a method for manufacturing a substrate of an optical memory element according to the present invention.

Next, an embodiment of a method for manufacturing a substrate of an optical memory element according to the present invention will be explained in the order of steps with reference to the same figure.

Step (i)... A glass substrate for an optical memory element that is highly reliable against the passage of oxygen, moisture, etc. (does not allow oxygen, moisture, etc. to pass through) is cleaned, and a photoresist film 2 is formed on the glass substrate 1. Apply (Figure 1a). The thickness of this photoresist film 2 is preferably about 100 nm to 500 nm.

Step (ii)...A mask plate 3 patterned with guide tracks and guide information (to be described later) is brought into close contact with the glass substrate 1 coated with the photoresist film 2, and infrared rays A are irradiated through the mask plate 3 to form a mask. The mask pattern on the plate 3 is transferred onto the photoresist film 2 (FIG. 1b). Here, since the optical memory element is disk-shaped, it is desirable that the mask plate 3 is also disk-shaped.

Step (iii): Grooves are formed in the photoresist film 2 by passing the photoresist film 2 with the mask pattern written thereon through a development process (FIG. 1c).

Step (iv)...Photoresist film 2 with the grooves formed
In the coated state, grooves 4 are formed in the glass substrate 1 by wet etching or dry etching such as sputtering (reactive ion etching) in an etching guide such as CF ₄ or CHF ₃ (FIG. 1d).

Step (v): The resist film 2 is removed by sputtering or the like in a solvent such as acetone or _O2 . As a result, grooves 4 remain in the glass substrate 1 (FIG. 1e).

Through the above steps, a guide substrate having grooves indicating guide tracks and guide address information is completed. According to this process, a mask plate patterned with guide tracks and guide information is created in advance, and the mask plate is sequentially brought into close contact with a glass substrate coated with a photoresist film to transfer the pattern of the mask plate. This allows the recording time of the guide pattern to be extremely shortened. Here, the mask plate and the glass substrate coated with the photoresist film need to be in close contact with each other in order to transfer the pattern with high precision. At the same time, this mask plate is also required to have sufficiently good transmittance to ultraviolet rays. Substrate materials used for mask plates generally include resin and glass, but glass has better UV transmittance than resin, so glass is better as a substrate material for mask plates. However, from the viewpoint of reliability, when a glass substrate is used as the substrate of an optical memory element and also as a substrate of a mask plate, the glass substrate generally has a
Since there is a warp of 10 μm or more, it is difficult to bring the glass substrate of the mask plate and the glass substrate of the optical memory element into close contact even if pressure is applied between the two. Therefore, the mask plate used in the present invention has a unique structure shown below to solve this problem.

Next, the manufacturing method of the mask plate described above will be explained in detail in the order of steps.

FIG. 2 is an explanatory diagram showing a method of manufacturing a mask plate.

Step (i)... First, a disc-shaped low-reflection Cr mask blank 5 is prepared. FIG. 2a is a partial side sectional view of the mask blank 5. FIG. 6 is a quartz glass substrate that allows ultraviolet rays to pass through (depending on the type of ultraviolet ray A, it may be made by polishing ordinary soda lime glass with high precision), and 7 is an ultraviolet curing type that has sufficient flexibility than the glass substrate 6. resin layer, 8a is CrOx film, 9 is Cr film, 8
b is a CrOOx film. The structure of this mask blank 5 includes a Cr single layer film, Cr film, CrOx
The film may have a two-layer structure.

Step (ii): A photoresist film 10 is coated on the mask blank 5 (FIG. 2b). As this photoresist film 10, for example,
A positive type such as AZ-1400 manufactured by Shipley may be used. This photoresist film 10
The thickness of the coating depends on the power of the laser beam used in the next step (iii), but considering the ease of coating,
Approximately 100 nm to 500 nm is appropriate.

Step (iii)...Ar laser light is focused on the mask blank 5 coated with the photoresist film 10 to record a guide track and a guide address (FIG. 2c). Using an Ar laser with a wavelength of 4579 Å, the objective lens 11 with an NA of 0.75 has a diameter of 0.5 μm.
When the Ar laser beam is focused to have a spot diameter of about 100 nm, it is possible to obtain a laser power of about 10 mW on the surface of the photoresist film 10 and record a track with a width of 0.6 μm. Here, as the light for forming the pattern, it is appropriate to use a laser with a wavelength shorter than 5000 Å in order to miniaturize the pattern of the guide track and guide address and to increase the sensitivity of the photoresist film 10, and other than Ar laser. Krypton lasers are useful for this purpose.

Step (iv)...Grooves are formed in the photoresist film 10 by passing the mask blank 5 on which the guide track and guide address have been recorded in the photoresist film 10 in step () to a developing step (Fig. 2). d). In addition, from this figure 2 d onwards,
The magnification in the horizontal direction is increased up to Figure f.

Step (v)...Photoresist film 1 with the above grooves formed
Etching is performed in the coating state of 0,
Cr film 9 and a predetermined portion on glass substrate 6
The CrOx films 8a and 8b are removed (FIG. 2e).

Step (vi): The remaining photoresist film 10 is removed by sputtering in a solvent such as Ascent or _O2 (FIG. 2f). As a result,
A Cr film 9 having grooves indicating guide track and guide address information on a glass substrate 6;
A laminated film of CrOx films 8a and 8b can be obtained.

Through the above steps, a disk-shaped mask plate is obtained, in which track addresses are recorded, for example, in the form of a spiral guide track with a pitch of 2 μm and a width of 1 μm, and a continuation of the guide track. Note that the quality of the address signal after forming the groove on the glass substrate 1 will be better if the width of the track address portion is made narrower.

FIG. 3 is an external perspective view of the completed mask plate 12,
FIG. 4a shows a partially enlarged plan view thereof, and FIG. 4b shows a cross-sectional view taken along line a-a'. As shown in FIG. 3, a hole 13 is formed in the center of the mask plate 12. This hole 13 is designed to facilitate rotational driving during manufacturing of the mask plate 12. That is, the hole 13 at the center of the mask plate 12 is used to hold screws or a magnetic chuck, and by holding the mask plate 12 in place, the rotation operation of the mask plate 12 can be performed stably. However, if a mechanism for holding the outer peripheral portion of the mask plate 12 or a mechanism for holding the entire surface of the mask plate 12 by vacuum suction is employed, the hole 13 in the center of the mask plate is not necessarily required. At 14, a pattern of a guide track of the optical memory element is formed, and at 15, a pattern of a guide address of the optical memory element is formed.

The structure of the mask plate 12 described above is such that a resin layer 7 having sufficient flexibility than the glass substrate 1 is provided on a glass substrate 6, and a Cr film is formed on the resin layer 7, which is hollowed out in a guide pattern so that ultraviolet rays can pass therethrough. It has a structure in which reflective metal films such as the following are laminated. The resin layer 7
Since the mask plate 3 is more flexible than the glass substrate 6 and the glass substrate 1, the mask plate 3 was pressure-bonded to the photoresist 2 on the substrate 1 of the optical memory element by applying mechanical pressure or drawing a vacuum. At the same time, resin layer 7
is deformed according to the shape of the surface of the optical memory element, so that the mask plate 3 and the photoresist 2 on the substrate 1 of the optical memory element can be brought into close contact.

Next, a description will be given of the configuration of an apparatus that performs the step of recording guide tracks and guide addresses on the photoresist film 10 coated on the mask blank 5 by condensing an Ar laser as shown in FIG. 2c. FIG. 5 shows an explanatory diagram of the device configuration.
Laser light with a wavelength of 4579 Å emitted from the Ar laser light source 16 enters the beam splitter 20 via a lens 18 that increases the efficiency of the optical modulator 17, an optical modulator 17, and a lens 19 that increases the efficiency of the optical modulator 17.
A portion of the light is taken out by the beam splitter 20 and its power is monitored by the photodetector 21. The modulator 17 is controlled by the output of the photodetector 21, and the output power of the laser beam is adjusted to be constant. This is done to suppress the fact that the output power of the laser beam changes due to fluctuations in environmental conditions such as room temperature. 22 is a mirror that changes the optical path of the laser beam; 23 is a modulator that modulates the light to record the guide address on the photoresist film 10; and 24 and 25 are lenses that increase the efficiency of the modulator 23. . The optical path of the laser beam is further changed by a mirror 26 and enters a beam splitter 27 for monitoring modulated light. A part of the light is taken out by the modulated light monitoring beam splitter 27 and its power is monitored by the photodetector 28. 29 is a dichroic mirror, and after passing through the dichroic mirror 29, the laser beam is focused by a spot lens 30 and guided to an objective lens 32 by a polarizing beam splitter 31. 33 is a He-Ne laser 3 for servo which will be described later.
A quarter wavelength plate 35 is adapted to the wavelength of 4, and 35 is an objective lens drive unit that moves the objective lens up and down and applies servo so that the light is always focused on the surface of the mask plate 12. 34 is a He-Ne laser used as a servo laser. The He-Ne
The optical path of the light emitted from the laser 34 is changed by the mirror 36 and reaches the same optical path as the laser optical path by the Ar laser light source 16 by the dichroic mirror 29. Here, the dichroic mirror 29 uses Ar laser wavelength light (4579 Å).
A device that allows the He-Ne laser wavelength light (6328 Å) to pass through and totally reflects the light is used. In addition, as the polarized beam splitter 31, S of the He-Ne laser beam is used.
A device that reflects waves, allows P waves to pass, and totally reflects Ar laser light is used. 37 is a cylindrical lens, and 38 is a four-part detector. Part 4
The light reflected from the mask plate 12 enters the divided detector 38, and focus servo is applied by the output of this four-divided detector 38. A portion 39 surrounded by a dotted line in the figure can be moved by riding on a moving device such as an air slider. By operating the Ar laser while moving this moving device in the radial direction of the rotating mask plate 12, the spiral guide track and guide address can be recorded on the photoresist film 10 in the form of a latent image.

When forming guide tracks and guide address grooves on the substrate of the optical memory element described above, the shape of the grooves may be concentric circles, and the guide address information is not limited to once per round, but once every two or three rounds. It may be provided once or several times per round.

FIG. 6 shows a partial side sectional view of an optical memory element constructed using a substrate obtained by the manufacturing method shown in FIG. In the figure, uneven grooves 4 (i.e. guide tracks) are formed on a glass substrate 1, and a dielectric film such as an AlN film or a SiO film having a refractive index higher than that of the glass substrate 1 is formed on the glass substrate 1. A membrane 40 is coated. The film thickness of this dielectric film 40 is
It is about 500 to 1000 Å. on the dielectric film 40
A thin alloy film 41 (recording medium) of a rare earth metal such as GdTbFe, TbFe, or GdCoFe and a transition metal is coated.
The thickness of this alloy thin film 41 is approximately 50 to 400 Å.
The lower limit of the film thickness of this alloy thin film 41 is determined by the conditions for forming the perpendicularly magnetized film, and the upper limit is determined by the conditions for increasing the magneto-optic effect. Therefore, the appropriate thickness of the alloy thin film 41 depends on the film formation method. When the alloy thin film 41 is formed by sputtering, it is difficult to obtain a perpendicularly magnetized film if the film thickness is less than about 50 Å, so the film thickness must be greater than about 50 Å. On the alloy thin film 41, AlN,
A dielectric film 42 such as SiO ₂ and a reflective film 43 made of metal such as Cu, Al, stainless steel, and Ni are formed. The dielectric film 42 and the reflective film 43 promote improvement of the characteristics of the magneto-optic effect, and the alloy thin film 41
It has the effect of preventing oxygen and moisture from reaching the body. 44 is an adhesive layer, and 45 is a protective plate made of glass, acrylic, etc. that is adhered by the adhesive layer 44. Instead of this protective plate 45, it is also possible to make a double-sided memory element by pasting two sheets of the memory element back to back.

Although the example of the optical memory element described above is a magneto-optical memory element having a reflective film structure, the present invention has a structure in which the alloy thin film 41 shown in FIG. 6 is thickened and the reflective film 43 is removed. It is also applicable to a magneto-optical memory element with a single layer film structure or an optical memory element of an additional recording type using Te, TeS, TeOx, etc. as a recording medium.

<Effects> As described above, in the method for manufacturing an optical memory element according to the present invention, a flexible resin layer is formed on a glass substrate for a mask that transmits ultraviolet rays, and an optical memory element provided on the resin layer is formed. Since the mask plate is equipped with a reflective metal layer shaped according to the uneven guide pattern, the mask plate is made of a glass substrate with good ultraviolet transmittance, but is not compatible with the glass substrate for optical memory elements. It is possible to ensure good adhesion. The present invention also provides a method in which a photoresist film is coated on a glass substrate for an optical memory element, the above-mentioned mask plate is placed on the glass substrate for an optical memory element coated with the photoresist film, and the photoresist film is applied to the glass substrate for an optical memory element through the mask plate. The film is irradiated with ultraviolet rays, the guide pattern of the mask plate is transferred to the photoresist film, and after the photoresist film is developed, guide tracks and guide addresses are formed on the glass substrate for optical memory element by etching. Since guide patterns or guide addresses can be easily and efficiently formed on substrates made of glass instead of resin, mass production of optical memory devices can be greatly improved. Since glass material can be used, it is possible to provide an optical memory element having a structure that can prevent deterioration of the recording medium used in the optical memory element, which is sensitive to oxygen or moisture.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the manufacturing method of a substrate according to an embodiment of the method for manufacturing an optical memory element according to the present invention in the order of steps;
The figure is an explanatory diagram showing the manufacturing method of the mask plate, Fig. 3 is an external perspective view of the mask plate, Fig. 4 a is a partially enlarged plan view of the mask plate, and Fig. 4 b is a cut along line a-a'. FIG. 5 is a cross-sectional view, and FIG.
The figure shows a partial side sectional view of an optical memory element, and FIG. 7 shows a partial perspective view of a conventional memory board. In the figure, 1...Glass substrate, 2...Photoresist film, 3...Mask plate, 4...Groove, 5...Mask plank, 6...Glass substrate, 7...Resin film, 8
a, 8b...CrOx film, 9...Cr film, 10...photoresist film.

Claims (1)

[Claims] 1. A photoresist film is coated on a glass substrate for an optical memory element, a flexible resin layer is applied to a glass substrate for a mask that transmits ultraviolet rays, and an optical memory element provided on the resin layer is coated with a photoresist film. A mask plate provided with a reflective metal layer shaped according to the uneven guide pattern to be formed is placed on the glass substrate for an optical memory element coated with the photoresist film, and the The photoresist film is irradiated with ultraviolet rays to transfer the guide pattern of the mask plate onto the photoresist film, and after the photoresist film is developed, the guide pattern is dug into the optical memory element glass substrate by etching. A method for manufacturing an optical memory element.