JPH0348581B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a reproduction-only, additional recording, or rewritable optical information recording medium that optically records, reproduces, and erases information.

[Conventional technology]

2. Description of the Related Art In recent years, optical memory devices having optical information recording media (hereinafter referred to as "medium") have attracted attention as high-density, large-capacity memory devices. The reason why this optical information recording medium has high density and large capacity is that the bit, which is the unit of recording information, is determined by the wavelength of light and the numerical aperture of the lens that focuses the light on the recording layer.
This is because the size can be reduced to about 1 μm. Note that reproduction is also performed by optically reading out the presence or absence of this bit. However, in order to accurately record and reproduce information, a precise mechanical mechanism with an electronic control system is required, which necessitates making the optical memory device larger. The structure shown is now adopted. In the figure, a medium substrate 1 is made of glass, and has a cylindrical through hole 1 in the center.
The recording layer is formed on the main surface 2 of the disk-shaped disk having a diameter of 1.a, and the main surface 2 has concentric guide grooves 3 formed by etching to facilitate the tracking of light for recording and reproducing information. (hereinafter referred to as "pregroup"), a small recess 4 (hereinafter referred to as
``Prepit''). The pre-group or pre-pit will hereinafter be collectively referred to as a guide section.

Conventionally, when manufacturing a media substrate having such a guide portion, a pattern for forming the guide portion is formed by photolithography and etching on a pattern-forming thin film deposited on the main surface of the glass substrate. A resist film is coated on the main surface of a disc-shaped glass substrate that will serve as a media substrate, and is then exposed to light through the mask and then developed. This was done by transferring the above pattern onto a film and finally etching the surface of the glass substrate using this patterned resist film as a mask.

[Problem that the invention seeks to solve]

However, the type, position, and shape of the guide portions are not always constant, and each time the pattern slightly changes, a new mask must be manufactured and the pattern transferred to form the media substrate. It didn't happen.

[Means for solving problems]

In order to solve these problems, the present invention first creates a first mask in which only a pattern common to multiple types of media substrates is formed at a predetermined position by photolithography, and then A second mask is created in which a common pattern is transferred by photolithography, and a unique pattern is formed by photolithography at a position different from the common pattern, and this is used to form a media substrate. It is.

[Effect]

When manufacturing a plurality of types of media substrates having a common pattern, the first mask is shared by the various substrates and is individually executed only from the stage of forming the second mask.

〔Example〕

Next, one embodiment of the present invention will be described using FIGS. 1 and 2. Note that FIG. 1 is a cross-sectional view showing the manufacturing process of the medium substrate, and FIG. 2 is a plan view of the completed medium substrate.

First, a first transparent substrate 11 made of quartz glass with an outer diameter of 130 mm, an inner diameter of 6 mm, and a thickness of 2.3 mm is prepared.
After precision polishing the main surface, a first pattern-forming thin film 12 made of chromium (Cr) with a thickness of about 700 Å was deposited by sputtering, and a positive electron beam resist 13 was further applied thereon. As the electron beam resist 13, PBS manufactured by Chitsuso was used. Next, a pattern of a common guide portion (pregroup in this embodiment) is exposed on the resist 13 by direct writing with an electron beam 14 (FIG. 1a).

Next, the exposed resist 13 is developed with a developer prepared by adding water to a mixture of 5-methyl 2-hexanone and 2-pentane to form a resist pattern. Next, using this resist pattern as a mask, the first pattern forming thin film 12 is etched using a mixed solution of ceric ammonium nitrate and perchloric acid. Thereafter, by removing the resist 13 with sulfuric acid, a first mask 16 having a common pattern 15 for forming a common guide portion is formed (FIG. 1b). Although not shown in the figure, the common pattern is assumed to be concentric grooves with a width of 1.0 μm formed at a pitch of 2.0 μm within a radius of 40 mm to 60 mm.

The main surface of a second light-transmitting substrate 17 made of a quartz glass substrate similar to the first light-transmitting substrate 11 described above is precisely polished, and a second pattern-forming thin film 18 (thickness: 700 Å) made of chromium is deposited. Further, a positive photoresist (AZ-1350 manufactured by Hoechst Co., Ltd. in this example) 19 was coated thereon. resist 1
No. 9 had a film thickness of 1000 Å. Next, the first mask 1
6 as a mask, the entire surface was irradiated with ultraviolet rays 20 to expose the resist 19 (FIG. 1c).

Next, development was performed using AZ Developer manufactured by Hoechst, and etching was performed to form a common pattern 21 similar to the common pattern 15 on the second pattern forming thin film 18 (FIG. 1d).

Next, an electron beam resist 22 similar to the resist 13 described above is applied to the entire main surface on which the common pattern 21 is formed, and by direct drawing with the electron beam 23, the resist 22 is formed at a position different from that of the common pattern 21. A pattern of unique guide portions other than the common guide portion to be formed is exposed (FIG. 1e).

Next, the resist 22 is developed and the second pattern forming thin film 18 is etched in the same manner as the resist 13 described above (FIG. 1f), and the resist 22 is removed in the same manner as described above.
A second mask 25 is formed in which a unique pattern 24 is added to the common pattern 21 (FIG. 1g). It is assumed that the unique pattern 24 has grooves each having a width of 1 μm formed concentrically at a pitch of 2 μm within a radius of 35 mm to 40 mm.

Next, a third transparent substrate 26 made of soda lime glass was prepared, which was processed into a disk shape with an outer diameter of 130 mm, an inner diameter of 15 mm, a thickness of 1.2 mm, and an eccentricity of 10 μm or less. Then, on one main surface of this substrate 26, which has been precision polished and subjected to low-temperature ion exchange treatment, a pattern forming thin film 27 made of silicon oxide (SiO ₂ ) for forming guide portions is deposited to a thickness of 1500 Å by vapor deposition. It was covered. The above-mentioned resist 19 is applied thereon through an intermediate layer 28 made of hexamethyldisilazane.
A photoresist 29 similar to that described above was coated. middle layer 2
8 is for increasing the adhesion between the pattern forming thin film 27 and the resist 29. resist 2
The film thickness of No. 9 was 1000 Å. Next, the second mask 2
5 as a mask, the resist 29 was exposed by contact exposure with ultraviolet rays 30 (FIG. 1h).

The exposed resist 29 is the resist 19 described above.
The resist was developed in the same manner as above, and the pattern forming thin film 27 was dry etched using the resist as a mask. Prior to etching, resist 29 was post-baked at 100°C for 30 minutes. Etching gas uses CF ₄ , flow rate 30sccM, total pressure
The experiment was conducted under the conditions of 0.2 Torr and high frequency power density of 0.2 W/cm ² . After etching, the remaining resist is removed by ashing using oxygen gas, and the medium substrate 3 having the common guide portion 31 and the unique guide 32 is removed.
3 (Fig. 1i and Fig. 2).

The method for creating the medium substrate 33 is as described above, but when creating another medium substrate having the common guide portion 31, the first mask 16 described above can be shared. There is no need to perform the step of creating the first mask 16 anew, and it is sufficient to start from the step of FIG. 1c for transferring the common pattern 15 to the second pattern-forming thin film 18. The time can be reduced by about 30 minutes.

Next, two media substrates provided with such guide parts were prepared, and a recording layer made of tellurium (Te) was coated to a thickness of 300 Å on each guide part to allow additional recording. These recording layers were placed facing each other and fixed by placing spacers on the outer periphery of the substrate and near the through hole, respectively, to create a sandwich-like medium having voids inside.

In addition, in the manufacturing process of the medium substrate described above, positive resists were used in all cases, but negative resists may be used, or both resists may be used in combination. for example,
In the step shown in FIG. 1e, a negative resist (for example, manufactured by Mead Chemical Co.
COP), the electron beam is irradiated only on the parts of the unique pattern formation area that will not become grooves.

Further, in the steps shown in FIGS. 1a and 1e described above, direct drawing was performed using an electron beam resist, but a photoresist may be applied and exposed through a desired mask.

In addition, in the above-mentioned embodiments, all positive resists were used in order to finally use the groove portions without the pattern forming thin film 27 as guide parts, but for example, in the step of FIG. Using a negative resist, a thin film 18 for forming the second pattern of the common pattern 21 and the unique pattern 24 is formed.
A portion of the pattern forming thin film 27 corresponding to the portion where the pattern forming film 27 is present may be removed by etching, and this portion may be used as a guide portion.

Furthermore, the portion (convex portion) where the pattern forming thin film 27 is present may be used as the guide portion.

Although the example in which the pit group is provided as the guide section has been described above, the same applies to the case where the prepit group or both of them are provided. Further, in that case, the common guide portion may be only the pre-group, conversely, only the pre-pit, or both.

In addition, in the embodiment described above, the light-transmitting substrate 2
6 uses a glass plate strengthened by ion exchange treatment, so it will not break even if rotated 20,000 times per minute. In addition, the surface hardness is improved by 50 to 100 kg/mm ² compared to those without the same treatment, making the surface less likely to be scratched. Furthermore, deterioration due to precipitation of Na ions can be prevented, and a decrease in light transmittance can be prevented. As an example, Fig. 3 shows the change over time in the light transmittance of the substrate measured at a temperature of 60°C and a relative humidity of 90% RH. In the figure, A indicates the case according to the above example, and B indicates the case where ion exchange treatment was not performed, and it can be seen that the characteristics were significantly improved by the ion exchange treatment.

Note that although a low temperature ion exchange method was used in the above embodiments, the same effects can be obtained, at least in terms of preventing destruction and scratches as described above, by using a high temperature ion exchange method or an air-cooling strengthening method. Further, the same effect can be obtained not only when using soda lime glass but also when using other glasses such as borosilicate glass or aluminosilicate glass.

Although the common guide portion 31 and the unique guide portion 32 are formed on the pattern forming thin film 27 adhered to the surface of the transparent substrate 26, it is not necessary to do so. It may be formed over both. Furthermore, although it may be formed directly on a light-transmitting substrate, considering the presence of uneven etching, scratches, bubbles, etc. due to compositional variations, it is necessary to use a transparent guide layer as a pattern-forming layer. Rather than using the surface layer of the photosensitive substrate itself, it is preferable to separately provide a dedicated thin film as in the above embodiment.

Note that, prior to forming the pattern-forming thin film 27, the surface of the transparent substrate 26 may be coated with aluminum oxide or the like, and the pattern-forming thin film 27 may be formed thereon to increase its adhesion.

Further, such a pattern forming thin film 27 is not limited to a silicon oxide film, but may be, for example, an element of a group, a group, or a group of the periodic table, or a compound thereof, an oxide or nitride film thereof, or a chalcogen element. Alternatively, a light-transmitting material such as a compound thereof or an oxide or nitride film thereof may be appropriately selected. This pattern-forming layer does not necessarily have to have a stoichiometric composition as long as it can be formed with unevenness by etching.

Further, depending on the material, the etching method for the pattern forming layer is arbitrary, and the etching method is not limited to the dry method, but may be a wet method.

Further, although the pattern is formed only on one main surface of the transparent substrate 26, it may be formed on both main surfaces.

In the above embodiments, Te is shown as the material of the write-once recording layer, but chalcogen elements other than Te such as Se, chalcogen compounds such as GeTe, chalcogen oxides such as TeOx, groups of the periodic table,
The material may be a group element, a compound thereof, an oxide or nitride thereof, or an organic substance to which a light absorber is added, and the material thereof is not particularly limited. Materials for the recording layer other than the additive type, for example, the rewritable type, include, in addition to the above, alloys whose main components are transition metals such as MnBi and elements of the periodic table group, transition metals such as GdFeCo, and rare earth elements. It is also possible to use an alloy containing as a main component. Furthermore, in the case of reproduction only, Au, Ag, Pt, Al,
It is also possible to use a material that has a high reflectance to the light used, such as Cu.

In addition, although the above embodiment shows an air sandwich type medium, other structures such as an air incident type or a close contact sandwich type may also be used.Also, two substrates each having a recording layer attached thereto are bonded together. Alternatively, a single substrate may be provided with a recording layer, and a simple light-transmitting substrate without a recording layer may be bonded to this for protection. Further, it is not necessarily necessary to have a bonded structure, and in that case, if light is irradiated from the recording layer side, the substrate does not necessarily have to be translucent.

Note that although an example in which quartz glass or soda lime glass is used as the transparent substrate 11, 17, or 26 has been described, other materials such as aluminosilicate glass, porosilicate glass, etc. may be used, and polymethyl methacrylate (PMMA ) or other plastics or ceramics. In addition, as mentioned above, when the optical information recording medium consists of one substrate provided with a recording layer and information is recorded or read from above the recording layer, the medium substrate may be made of, for example, an Al alloy. Metals such as may also be used.

In addition, the first and second pattern forming thin films 1
Although chromium is used as 2 and 18, in addition to chromium, elements of group 2 of the periodic table, chalcogen elements, compounds thereof, oxide films or nitride films thereof, etc. may be used.

〔Effect of the invention〕

As explained above, according to the present invention, a first mask having a common pattern is prepared in advance, the common pattern is transferred as needed, and only a unique pattern is newly added to the second mask. By forming the mask, the time required to create the second mask can be shortened, and a high-quality medium substrate with guide portions can be obtained at low cost. Moreover, since each pattern is formed by photolithography, the common pattern and the unique pattern can be formed at different positions with good workability and productivity.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams showing one embodiment of the present invention, where Figure 1 is a cross-sectional view of the process, Figure 2 is a plan view, and Figure 3 is a diagram showing changes in light transmittance of a glass substrate over time. , FIG. 4 is a perspective view showing an example of the structure of the medium substrate. 11...First light-transmitting substrate, 12...First pattern forming thin film, 15, 21... Common pattern,
16...First mask, 17...Second transparent substrate, 18...Second pattern forming thin film, 24...
Unique pattern, 25...Second mask, 26...
Third transparent substrate, 27... Thin film for pattern formation (layer for pattern formation), 31... Common guide portion, 3
2... Unique guide portion, 33... Medium substrate.

Claims (1)

[Claims] 1. A method for manufacturing an optical information recording medium in which a recording layer is formed on the main surface of a medium substrate, comprising: a pattern-forming thin film formed on the main surface of a transparent first substrate; A step of forming a first mask by forming a common pattern at a predetermined position using a photolithography method; forming a common pattern by photolithography and forming a unique pattern at a position different from the common pattern by photolithography to form a second mask; A method for manufacturing an optical information recording medium, comprising the step of transferring a common pattern and a unique pattern of a second mask to a pattern forming layer to form a medium substrate.