JPS60197960A - Manufacture of optical memory element - Google Patents

Abstract

PURPOSE:To obtain an element having high accuracy by applying a flexible photoresist film to a glass substrate, superposing a metallic film mask on which a guide pattern has been formed, on said film surface, irradiating ultraviolet rays, using a pattern transferred to the resist film as a mask, and etching the substrate. CONSTITUTION:A flexible photoresist film 2 is applied onto a glass substrate 1, a mask plate 3 which has pinched a metallic film having a removed part in a shape of a guide pattern between a mask use glass substrate and a flexible resin material is made to adhere tightly and superposed on the film 2, ultraviolet rays A are irradiated as indicated with an arrow, and the guide pattern is transferred to the resist film 2. After removing the mask 3 and developing the film 2, the substrate 1 is etched by using the film 2 as a mask and a groove 4 is formed on the substrate 1, and therefore, the film 2 is removed. In this way, the guide pattern is formed directly on the glass substrate, on which a necessary recording layer, etc. are formed, and a precise optical memory element is obtained with a good productivity.

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 a large capacity is that 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 certain fixed location or to reproduce information recorded at a certain fixed location, the light beam must be positioned extremely accurately. In general, in playback-only optical memory, address information can be stored in the recorded bits in advance, so while playing back the recorded information, the optical
However, in an additional recording memory or a rewritable memory, it is extremely difficult to record address information at the same time as recording information. Therefore, in the case of additional recording memory or rewritable memory, a method is adopted in which some guide tracks and guide addresses are stored in advance on the memory board. For example, the seventh
The figure 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 reproduced along these grooves. is common. 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 for forming the uneven grooves have already been proposed, and can be roughly divided into the following three types. That is, (i) a method of creating the grooves by injection molding using acrylic resin or polycarbonate resin. Through this molding, the guide track and guide address were formed in advance on the Ni
Copy the shape of the stamper.

(11) A casting method in which acrylic resin is poured into the Ni stamper on which the guide tracks and guide addresses have been formed in advance, and is heated to harden it.

(ni) An ultraviolet curable 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 to cure the resin. The soot is cured, and then the Ni stamper is removed, the so-called 2P method.

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 Japanese Patent Application No. 58-84618 proposes a method of forming grooves in the shape of a guide pattern by etching.

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 not suitable for mass production.

<Purpose> The present invention has been made in view of the above points, and by improving the manufacturing described in the above-mentioned Japanese Patent Application No. 58-84618, guide tracks, guide addresses, etc. for the substrate of an optical memory element can be manufactured. The purpose is to provide a new manufacturing method that can form grooves indicating information in a short time and with precision.

<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 (1)...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 placed on the glass substrate. (Fig. 1(a)). The thickness of this photoresist film 2 is preferably about 1100 nm to 500 nm.

Step (11)...Glass substrate coated with the photoresist film 2! A mask plate 8 patterned with guide tracks and guide information, which will be described later, is brought into close contact with the mask plate 3, and ultraviolet A is irradiated through the mask plate 3 to transfer the mask pattern of the mask plate 3 onto the photoresist film 2 (the first Figure (b)
). Here, since the optical memory element is disk-shaped, it is desirable that the mask plate 8 is also disk-shaped.

Step (iN): forming a groove in the photoresist film 2 by passing the photoresist film 2 on which the mask pattern has been written through a development process (FIG. 1(c)) 0 Process axis: the above groove Wet etching or CF4
, Dry etching such as sputtering (reactive ion etching) in an etching gas such as CHF3 is performed to form grooves 4 in the glass substrate l (see Fig. 1(d)).
)).

Step (V): The resist film 2 is coated with a solvent such as acetone.

It is removed by sputtering etc. in 02. As a result, grooves 4 remain in the glass substrate 1 (FIG. 1(e)).

Through the above steps, a glass substrate having grooves indicating guide track 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 successively brought into close contact with a glass substrate coated with a photoresist film to transfer the turns of the mask plate. This allows the recording time of the guide pattern to be extremely shortened.The mask plate and the glass substrate coated with the photoresist film must be in close contact with each other in order to transfer the pattern with high precision. However, glass substrates generally have a thickness of several tens of μm.
Due to the warpage described above, it is difficult to achieve close contact between the mask plate and the glass plate even if pressure is applied between the mask plate and the glass plate. However, the mask plate according to the present invention solves this problem with the unique structure shown below. .

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 (1): First, a disc-shaped low-reflection Cr mask blank 5 is prepared. Figure 2 (,) shows 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, a well-polished ordinary soda lime glass may be used), 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, 8b is CrOx
It is a membrane. The structure of this mask blank 5 is Cr.
The structure may be a single layer film or a two-layer film structure such as a Cr film or a CrOx film.

Step (11): A photoresist film 10 is coated on the mask blank 5 (FIG. 2(b)). As this photoresist film 10, for example, a positive type film such as AZ-1400 manufactured by 5hipleF may be used. The thickness of this photoresist film 10 depends on the power of the laser beam used in the next step (in), but from the viewpoint of ease of coating, it is appropriate to be about 1100 nm to 500 nm.

Step (fi+): Ar laser beam is focused on the mask blank 5 coated with the photoresist film 10 to record guide tracks and guide addresses (see FIG. 2(C)
)). Using an Ar laser with a wavelength of 4579X, N, A,
When the Ar laser beam is focused to have a spot diameter of about 0.5 μm using the objective lens 11 with Tracks can be recorded.

Here, as the light for forming the pattern, it is appropriate to use a laser with a wavelength shorter than 5oooX in order to miniaturize the pattern of the guide track and guide address and for the sensitivity of the photoresist film IO, and other than Ar laser. Krypton lasers are useful for this purpose.

Process line: Grooves are formed in the photoresist film 10 by passing the mask blank 5 on which the guide tracks and guide addresses have been recorded in the photoresist film 10 in step (1ii) to a development process (see FIG. 2(d)). )). Note that the magnification in the horizontal direction is increased from FIG. 2(d) to FIG. 2(f).

Step (V)...Photoresist film 1 with the grooves formed
Cr film 9 and Crux films 8a, 8 are etched in predetermined portions on glass substrate 6.
b (Fig. 2(e)).

Step (VD...The remaining photoresist film 10 is removed by sputtering in a solvent such as acetone, 02 (FIG. 2(f)). As a result, the glass substrate 6
It is possible to obtain a laminated film of the Cr film 9 and the Crux films 8g and 8b, each of which has grooves indicating guide track and guide address information thereon.

Through the above steps, a disk-shaped mask plate is obtained, in which track addresses are recorded, for example, by spiral guide tracks having a pitch of 2 μm and a width of 1 μm, and track addresses formed by the discontinuous shape of the guide tracks. Note that the narrower the width of the track address portion, the better the quality of the address signal after forming the groove on the glass substrate l.

Figure 3 is an external perspective view of the completed mask plate I2, and Figure 4 (
a) is a partially enlarged plan view, and FIG. 4(b) is a-a
A cross-sectional view taken along the ' line is shown. As shown in FIG. 3, a hole 18 is formed in the center of the mask plate 12. This hole 13
The mask plate 12 is designed to be easily rotated when manufacturing the mask plate 12. That is, the hole 1 in the center of the mask plate 12
Use 8 to hold the screws and use the magnetic chuck.
By holding it fixedly, the rotating operation of the υ mask plate 12 can be performed stably. However, the mask plate 12 may be removed by a mechanism that holds the outer peripheral portion of the mask plate 12 or by vacuum
If a mechanism for holding the entire surface of the mask plate is adopted, the hole 18 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 above mask plate] The structure of 2 is the glass substrate on the glass substrate 6! It has a structure in which a resin layer 7 having more sufficient flexibility is provided, and a reflective metal film such as a Cr film, which is hollowed out in a guide pattern so that ultraviolet rays can pass through, is laminated thereon. When pressure is applied mechanically between the mask plate and the glass substrate due to the presence of 7, or when pressure is applied by drawing a vacuum between the two plates, the resin layer 7
By bending this part, the drawing board can be brought into close contact with the drawing board.

In addition to this structure, as the structure of the mask plate +2, an acrylic resin substrate having sufficient flexibility than the glass substrate 1 is used in place of the glass substrate 6, and a Cr substrate with a guide pattern cut out on the acrylic resin substrate is used. film, Cr film, C
A structure in which reflective metal films such as a two-layer rOx film, a three-layer film of a CrOx film, a Cr film, and a CrOx film are laminated may be used. In this case, it is necessary that the acrylic resin substrate sufficiently transmits ultraviolet rays.

Next, as shown in FIG. 2(c), the photoresist film 1 coated on the mask blank 5 by focusing the Ar laser beam.
The configuration of an apparatus that performs the process of recording a guide track and a guide address in 0 will be described.

FIG. 5 shows an explanatory diagram of the device configuration. A laser beam with a wavelength of 4579^ emitted from the Ar laser light source 16 is passed through a lens 18. which increases the efficiency of the optical modulator 17. Optical modulator +7. The light enters the beam splitter 20 through 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 optical 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; 28
24 and 25 are modulators that modulate light in order to record guide addresses on the photoresist film 10 described above; 24 and 25 are the modulators 28;
This lens is designed to increase the efficiency of The laser beam is mirror 2
At step 6, the optical path is further changed and the beam enters the modulated light monitoring beam splitter 27. 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 the laser beam passes through the dichroic mirror 29, it passes through a spot lens 80.
The light is focused by the polarizing beam splitter 81 and guided to the objective lens 32. 83 is He-N for servo which will be described later.
A quarter wavelength plate 35 matches the wavelength of the e-laser 34, and an objective lens drive section 35 serves to move the objective lens up and down and apply servo so that the light is always focused on the surface of the mask plate 12. This is a He-Ne laser used as an 84Fi servo laser. The optical path of the light emitted from the He-Ne laser 34 is changed by a mirror 36, and the light path is changed by a dichroic mirror 2.
At step 9, the optical path reaches the same optical path as the laser optical path of the Ar laser light source 16. Here, as the dichroic mirror 29, one is used that allows Ar laser wavelength light (4579λ) to pass through and totally reflects He-Ne laser wavelength light (L128λ). The polarizing beam splitter 31 is one that reflects the S wave of the He-Ne laser beam, allows the P wave to pass through, and totally reflects the Ar laser beam. 87 is a cylindrical lens, and 88 is a four-part detector. The light reflected from the mask plate 12 enters the four-division detector 88, and focus servo is applied by the output of the four-division detector 88. A portion 39 surrounded by dotted lines 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 in the form of a latent image on the photoresist film IO.

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 2 or 8 rounds. It may be provided once, or even several times per round.

FIG. 6 shows a partial side sectional view of an optical memory element constructed using the 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 l, and an AtN film, a Si film, etc. having a refractive index larger than that of the glass substrate l is formed on the glass substrate l.
A dielectric film 40 such as an O film is coated. This dielectric film 40
The film thickness is about 500 to +oooX. The dielectric film 40 is coated with an alloy thin film 41 (recording medium) of a rare earth metal such as GdTbFe, TbFe, GdTbFe, etc. and a transition metal.

The thickness of the four alloy thin films is about 50 to 400X.

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 perpendicular magnetization film if the film thickness is less than about 50X, so the film thickness must be greater than about 50X. On the alloy thin film 41,
Dielectric film 42, such as tN, 5iOs+. and Cu, At.

A reflective film 4a made of a metal such as stainless steel or Ni is formed. The dielectric film 42 and the reflective film 43 have the function of promoting improvement of the characteristics of the magneto-optic effect and preventing oxygen and moisture from reaching the alloy thin film 41. 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 bonding two memory elements 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. Magneto-optical memory element with single layer film structure or Te
, TeS, TeOx, etc. as a recording medium can also be applied to an additional recording type optical memory element.

<Effects> According to the present invention, it is not necessary to use a resin material when forming the guide signal or guide address of the optical memory element, so that it is possible to prevent oxygen, moisture, etc. from reaching the recording medium.
Therefore, a highly reliable optical memory element can be obtained. Moreover, the grooves of the guide pattern formed on the substrate of the optical memory element can be formed efficiently and precisely, and the mass production of the optical memory element can be greatly improved.

[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, FIG. 2 is an explanatory diagram showing the manufacturing method of a mask plate, and FIG. 8 is an external perspective view of the mask plate. , Fig. 4(,) is a partially enlarged plan view of the mask plate, Fig. 4(b)
5 is a cross-sectional view taken along the line a-a', FIG. 5 is an explanatory diagram of the configuration of an apparatus for recording a guide track and a guide address, FIG. 6 is a partial side sectional view of an optical memory element, and FIG. The figure shows a partial perspective view of a conventional memory board. In the figure, 1: glass substrate 2: photoresist film 8: mask plate
4: Groove 5: Mask blank 6: Glass substrate

Claims (1)

[Claims] 1. A photoresist film is coated on a glass substrate for an optical memory element, and a metal film cut out in a guide pattern is coated on a resin material having sufficient flexibility than the glass substrate. A mask plate formed by the above-mentioned mask plate is placed on the glass substrate coated with the photoresist film, and the photoresist film is irradiated with ultraviolet rays through the mask plate to transfer the guide pattern of the mask plate to the photoresist film. . A method for manufacturing an optical memory element, characterized in that a guide pattern is etched into the glass substrate by etching after developing the photoresist film.