JPH07105080B2 - Method of manufacturing optical memory device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an optical memory element for optically recording and reproducing information.

<Prior Art> In recent years, an optical memory device has attracted attention as a high density and large capacity memory device. The reason why the optical memory has a high density and a large capacity is that the bit, which is a recording unit of information, is determined only by the diameter of the light beam, so that its shape can be about 1 μm. However, this puts many restrictions on the optical memory device. That is, in order to record information in a certain fixed place or reproduce information recorded in a certain fixed place, the light beam must be positioned extremely accurately. Generally, in a read-only optical memory, the address information can be put in the recorded bits in advance, so the light beam can be positioned while reproducing the recorded information, but in the additional recording memory or the rewritable memory, information recording is possible. Sometimes it is extremely difficult to record even address information in one place. Therefore, in the additional recording memory or the rewritable memory, a method of previously inserting some guide signal and some guide address in the memory substrate is adopted. For example, FIG. 4 shows a partial perspective view of a memory substrate of a conventional additional recording memory or rewritable memory. As shown in FIG. 4, concave and convex grooves are formed on the substrate and information is recorded along the grooves. Alternatively, a method of reproducing is common. The uneven groove has a circumferentially interrupted shape, which gives bit information indicating the address of the groove. Several methods have already been proposed for forming the uneven groove. For example, as shown in FIG. 5, a method of directly transferring the concave and convex grooves to a resin substrate 2 such as acrylic or polycarbonate by injection molding using a Ni stamper 1 having concave and convex grooves, or glass or acrylic as shown in FIG. A method (2P method) in which the ultraviolet curable resin 3 is inserted between the substrate 4 and the stamper 1 having the concave and convex grooves and the concave and convex grooves are transferred to the ultraviolet curable resin.
However, since all of these methods use a resin, oxygen or water or the like reaches the recording medium through the resin, so that the quality of the recording medium deteriorates.

In view of this drawback, the present inventors have already proposed a manufacturing method capable of forming concave and convex grooves on a substrate of an optical memory element without using a resin material (Japanese Patent Application No. 58-84613).

<Purpose> The present invention improves the shape of the groove by further improving the manufacturing method capable of forming the concave and convex grooves on the substrate of the optical memory element without using the above-mentioned resin, thereby forming a recording on the substrate. The purpose is to improve the shape of the medium.

<Example> An example of a method for manufacturing an optical memory device according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory view showing a method of manufacturing a substrate of an optical memory device according to the present invention in the order of steps.

Next, one embodiment of a method of manufacturing a substrate of an optical memory device according to the present invention will be described in order of steps with reference to FIG.

Step (i) ... A resist film 6 is applied on a glass substrate 5 that is highly reliable against the passage of oxygen, moisture, etc. (oxygen, moisture, etc. does not pass) (FIG. 1 (a)).

Step (ii) ... The resist film 6 coated on the glass substrate 5 is irradiated with light 7 such as Ar laser through the objective lens 8 or light 9 such as ultraviolet light through the Cr mask 10. Then, a line having the same width as the width of the guide groove (see FIG. 4) of the optical memory device (or an intermittent line for recording an address signal) is written (FIGS. 1B and 1F).

Step (iii) ... The resist film 6 in which the line (or the interrupted line) is written is passed through a developing process, whereby the resist film 6 is formed.
Is subjected to a developing process to form concave and convex grooves in the resist film 6 (FIG. 1 (c)).

Step (iv) ... Sputtering (reactive ion etching) is performed in a mixed gas in which O ₂ gas is mixed with an etching gas such as CF ₄ and CHF ₃ in a state of being covered with the resist film 6 in which the concave and convex grooves are formed. Grooves 11 are formed in the substrate 5 (FIG. 1 (d)).

Step (v) ... The resist film 6 is treated with a solvent such as acetone, O ₂
It is removed by sputtering (ashing) in the inside. As a result, the groove 11 remains on the glass substrate 5 (FIG. 1 (e)).

Next, Fig. 2 shows the case where the reactive ion etching is performed using only the etching gas such as CF ₄ and CHF _{3 as} in the conventional case, and the case where O ₂ gas is mixed with the etching gas such as CF ₄ and CHF ₃ The comparison figure at the time of performing active ion etching is shown. In the same figure, (a) and (d) show the respective resist films 6
3 is a partial cross-sectional view after development of FIG. FIG. 1B shows a partial cross-sectional view after etching is performed using only an etching gas such as CF ₄ and CHF _{3 as in the} conventional case, in which the resist film 6 is scraped off only from above by the glass substrate. The edge of the groove 11 formed in 5 is perpendicular to the plane of the glass substrate, and after removing the resist film 6, the rectangular groove 11 is formed as shown in FIG. On the other hand, FIG. 6 (e) shows an example after reactive ion etching is performed by mixing O ₂ gas in an etching gas such as CF ₄ or CHF _{3 at} a volume ratio of 5 to 10% with respect to the etching gas. Although the partial cross-sectional shape is shown, the resist film 6 is scraped off not only from above but also from the side surface edge during etching due to the effect of mixing O ₂ gas. Therefore, not only the thickness of the resist film 6 is reduced by etching, but also its width is gradually narrowed. As a result, the width of the groove 11 formed in the glass substrate is gradually widened, the edge of the groove 11 is inclined with respect to the plane of the glass substrate, and after removing the resist film 6, as shown in FIG. A trapezoidal groove 11 is formed as shown.

3 (a) and 3 (b) are respectively shown in FIG. 2 (c) and
It is a partial side sectional view of an optical memory device provided with a substrate having a groove shown in (f). 5 is a glass substrate having a groove formed therein, 12 is a dielectric film made of a nitride film such as an AlN film and a Si ₃ N ₄ film,
Reference numeral 13 is an alloy thin film (recording medium) of a rare earth element such as GdNdFe, GdTbFe, GdCo and a transition metal (recording medium), and 14 is a reflective film made of an Al film, a stainless film or the like. The dielectric film 12 and the reflective film 14 have the functions of promoting the improvement of the characteristics of the magneto-optical effect and preventing the oxygen and moisture from reaching the alloy thin film 13. 15 is an adhesive layer,
Reference numeral 16 is a protective plate made of glass, acrylic or the like, which is adhered by the adhesive layer 15. Instead of the protection plate 16, two memory elements can be attached back to back to form a double-sided memory element. Here, in the case of FIG.
At the edge of the groove 11, the film thickness of each layer of 12, 13, 14 is significantly thinner than that of the flat portion, which easily becomes a source of oxygen and moisture from the outside, and the film discontinuity generated at the edge of the groove 11 As a result, the signal quality deteriorates. However, with the trapezoidal groove shown in FIG. 3B formed in the present invention, discontinuity of the film does not occur at the edge, and the reliability and the signal quality are greatly improved.

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 13 shown in FIG. Magneto-optical memory device with single-layer film structure or Te, TeS, T
It is also applicable to an additional recording type optical memory device using eOx or the like as a recording medium.

<Effect> According to the present invention described above, since the guide groove of the substrate of the optical memory element and the recording medium formed on the substrate can be formed in a good shape, the reliability is improved and the noise of the reproduced signal is reduced. Can be done.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing an embodiment of a method for manufacturing an optical memory device of the present invention, FIG. 2 is an explanatory view showing a groove forming process, and FIG. 3 is a part of the optical memory device. FIG. 4 is a side sectional view, FIG. 4 is a partial perspective view of a conventional memory substrate, and FIGS. 5 and 6 are explanatory views showing a manufacturing process of the conventional memory substrate. In the figure 1: Ni stamper, 2: Resin substrate, 3: UV curable resin, 4: Substrate 5: Glass substrate, 6: Resist film 7: Laser light, 8: Objective lens 9: Ultraviolet light, 10: Mask 11: Groove , 12: Dielectric film 13: Alloy film, 14: Reflective film

Front page continuation (72) Inventor Toshihisa Exit 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Corporation (72) Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka Prefecture, Osaka Prefecture (56) References JP-A-61-26952 (JP, A)

Claims (1)

[Claims] 1. A substrate is coated with a resist film, the resist film is exposed to light such as laser light or ultraviolet light to expose the guide groove pattern, and the resist film exposed to the guide groove pattern is developed. A step of forming a guide groove in the substrate by performing reactive ion etching in the coated state of the resist film after development, CF ₄ which is an etching gas at the time of the reactive ion etching, some O in the CHF _3, etc. _{2. A} method for manufacturing an optical memory element, which comprises forming a substrate having a trapezoidal guide groove shape by mixing ₂ gases, and laminating a recording medium on the substrate to form an optical memory element.