JPH09115190A - Production of stamper for optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to easily produce a stamper by incorporating a step of forming an easily removable auxiliary thin film having grooves for tracking into a production process. SOLUTION: The auxiliary thin-film layer 2 consisting of a material which is different from the material of a phase transition film 4 formed on a substrate 1 and is easily removable is formed by etching on the substrate 1 prior to the formation of the phase transition film 4 in the case of producing the stamper for optical disks by subjecting the phase transition film 4 to thermal recording of information by a laser beam L1 and etching this film and forming the signal ruggedness on the surface of the substrate 1 by utilizing difference in the etching rate between the phase transition parts and the phase non-transition parts. Grooves 3 for tracking are formed on this auxiliary thin-film layer 2 and, thereafter, the phase transition film 4 is formed on the auxiliary thin-film layer 2. As a result, the stamper is formed without using a high-accuracy recording machine used before.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk stamper used for manufacturing various optical disks.

[0002]

2. Description of the Related Art So-called compact discs, which have been developed as one of digital audio discs, are currently used not only for music software but also for various video software as well as signal processing technology and LSI or semiconductor laser technology. It is used as a package medium for information files, and is currently being further densified to obtain a larger storage capacity. In these optical discs, an uneven signal (pit or groove) is formed on one surface of the plastic transparent substrate, and this signal is generally a thermoplastic resin composition, and a metal mother die on which a minute uneven signal is formed. It is formed by pouring in a mold provided with a so-called metal stamper at a high temperature and then cooling it to cure the thermoplastic resin composition.

A metal stamper for forming signal pits or grooves on the surface of a transparent substrate of an optical disc is usually manufactured by electroforming (Actual No. Sho 56-61).
369 and JP-A-1-225788). Specifically, first, a photoresist is applied to a glass substrate, pre-baked, and after pre-baking, a signal is recorded on the photoresist surface by laser light, and then the photoresist is developed. Next, prior to the electroforming step, a metal film of nickel or the like is formed on the photoresist surface by a vacuum deposition method or a sputtering method in order to make the surface electrically conductive, and subsequently, a metal film is electroformed on the metal film by electroforming. Film forming is performed to form an electroformed film. After that, peel off this electroformed film from the glass substrate to remove the photoresist remaining on the electroformed film surface,
Then, this is punched into a predetermined size to obtain a metal stamper.

However, the method of manufacturing the metal stamper as described above has a problem that the time required for each step such as photoresist coating, exposure, development and electroforming is long and the manufacturing cost is high. Further, the area of the electroformed film reaches 3 to 4 times the required stamper area in order to make the thickness of the stamper uniform, and there is a loss of producing waste material. Therefore, in order to solve this problem, a phase change film is formed on the substrate, a signal is recorded in the phase change film by a heat mode, and the etching rate difference between the amorphous phase and the crystalline phase of the phase change film is recorded. Recently, a method of forming a concavo-convex signal using has been proposed (JP-A-3-127342). This method replaces the conventional photoresist, which is a signal recording layer, with a phase change film and uses a metal substrate having a predetermined shape as it is as a stamper, so that the stamper manufacturing process can be extremely simplified.

[0005]

However, in this method, the tracking of the recording head cannot correct the substrate to be recorded during signal recording as in the conventional recording system. Also, since the substrate feeding mechanism is required, the recording machine becomes large in size, and moreover, a high maintenance technique and a vibration isolation mechanism are required, which is expensive. In addition, when the substrate for recording has a groove for tracking of the recording head,
Although the problem as described above can be solved, in this case, it is necessary to form only the pits for signals without leaving the unnecessary tracking groove on the disc on the metal substrate, so that the metal substrate on which the groove is already formed can be formed. There is a problem that it cannot be used as a stamper substrate. In other words, the tracking groove that exists during signal recording is
The groove must disappear after it is finished as a stamper.

[0006] The present invention focuses on the above problems,
The invention was devised to solve this effectively, and the purpose thereof is to manufacture an optical disk stamper which can be easily manufactured by incorporating a step of forming an auxiliary thin film having a groove for tracking, which is easy to remove. To provide a method.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention performs thermal recording of information on a phase change film formed on a substrate by laser light, and etches this to change the phase change portion. In the method for manufacturing a stamper for an optical disc in which signal irregularities are formed on the surface of the substrate by utilizing the difference in etching rate between the phase-changed portion and An auxiliary thin film layer made of a material different from that of the phase change film and easily removable by etching is formed, and a groove for tracking is formed in the auxiliary thin film layer, and then the phase is formed on the auxiliary thin film layer. It is configured to form a change film. As described above, first, an auxiliary thin film layer that can be easily removed by etching or the like is formed on the substrate surface made of metal or the like before forming the phase change film, and the auxiliary thin film layer is used for tracking by photolithography. To form the groove.

Next, the phase change film is formed on the entire surface of this thin film layer. Then, information is thermally recorded on the bottom of the groove by laser light to selectively change the phase. Next, etching is performed using this phase change portion as a mask, whereby signal pits having irregularities corresponding to the phase change portion and the phase non-change portion are formed on the substrate surface. In this case, as a matter of course, the etching rates of the phase change portion and the phase non-change portion are different, and this pattern is copied as it is on the substrate surface. As the auxiliary thin film layer, a single layer film such as a silicon film or a silicon oxide film can be used. The auxiliary thin film layer is not limited to a single-layer film, and the auxiliary thin film layer has a two-layer structure including a first auxiliary thin film made of a silicon film or a silicon oxide film and a second auxiliary thin film made of, for example, a photoresist film formed on the film. May be In this case, a tracking groove is formed in the second auxiliary thin film made of a photoresist film.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method for manufacturing an optical disk stamper according to the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a process diagram showing a first embodiment of a method for manufacturing an optical disk stamper according to the present invention. The outline of the present invention is as follows. First, an auxiliary thin film layer that can be easily removed by, for example, plasma etching is formed on a surface of a substrate made of, for example, and a groove for tracking is formed in this thin film layer by, for example, photolithography. Next, a phase change film is formed as a signal recording layer on the entire surface. Then, while performing tracking while referring to the groove, thermal recording with laser light is performed on the phase change film, and thereafter,
By etching this, signal irregularities are formed on the substrate surface.

First, as shown in FIG. 1 (A), one surface (upper surface in the drawing) is mirror-polished to a predetermined shape, for example, a disk-shaped metal plate having a hole in the center, for example, the mirror surface side of a nickel substrate 1 is etched. The auxiliary thin film layer 2 made of a material that can be easily removed is formed by, for example, a sputtering method. At this time, the material of the auxiliary thin film layer 2 and the conditions for selecting the etching method are selected such that the signal pattern of the phase change film as a signal recording layer to be formed thereon functions as an etching mask. Is selected. As a material of the auxiliary thin film layer 2, for example, a silicon film, a silicon oxide film, or a photoresist film can be used. Next, as shown in FIG. 1B, a tracking groove 3 is formed in a spiral shape on the surface of the auxiliary thin film layer 2 by using a photolithography technique. The depth of this groove 3 is the wavelength λ of the laser light used for recording a signal.
The thickness of the auxiliary thin film layer 2 is set thicker than the depth of the groove 3 in order to prevent the surface of the lower substrate 1 from being exposed.

Next, as shown in FIG. 1C, a phase change film 4 to be a signal recording layer is formed by sputtering, for example, to cover the entire surface of the auxiliary thin film layer 2 in which the groove 3 is formed.
The material of the phase change film 4 is a material which the present inventors have already proposed as an excellent lithography material, for example, GeSn ('94 Autumn Applied Physics Society Proceedings Proceedings p764.
) Can be used, and this GeSn becomes a good etching mask when oxygen or carbon tetrafluoride (CF ₄ ) is used as the plasma etching gas. GeSn
For example, when oxygen is used as the etching gas, it has a high selection ratio with respect to the polymer material, and when CF ₄ gas is used as the etching gas, it has a high selection ratio with respect to Si and SiO _2. Have In addition, on the surface of the phase change film 4,
The uneven groove 3 of the lower auxiliary thin film layer 2 is projected.

Next, as shown in FIG. 1D, the phase change film 4 is irradiated with a laser beam L1 modulated with a recording signal to perform thermal recording, and a phase change is generated in accordance with the recording signal. . The shaded portion in the figure indicates the phase change portion 5. At this time, since the groove is formed by being copied on the surface of the phase change film 4, the reflected signal from the groove 3 is referred to for tracking, so that the recording head is precisely fed in the radial direction, that is, tracking is performed. It becomes possible. Such a recording head feeding mechanism is a method that has been generally adopted in a write-once or rewritable optical disk using a semiconductor laser as a recording head, and is used in a cutting machine which is a conventional recording machine for an optical disk master. It is cheaper in comparison. When the phase change film 4 is used as a lithographic material, high density recording is possible even by recording with a long wavelength laser, and in a cutting machine which is a conventional recording machine, recording is performed on a photoresist. A small and inexpensive semiconductor laser can be used as compared with a short wavelength laser.

Next, the auxiliary thin film layer 2 is etched by using the unevenness signal formed by the phase change portion 5 generated by the laser beam L1 as described above, that is, the etching rate difference between the amorphous phase and the crystalline phase, as an etching mask. As shown in FIG. 1 (E), the substrate 1 is etched by using the auxiliary thin film pattern corresponding to the signal pattern as an etching mask to form the surface of the substrate 1 as shown in FIG. 1 (F). An uneven signal is formed on. Normally, nickel is used for the stamper, which is a mold for optical disk molding, and the etching of nickel is performed by ion milling or sputter etching in which argon ions are irradiated. The material used for the phase change film 4 generally has a very high etching rate by argon ion irradiation, and the auxiliary thin film layer 2 substantially serves as an etching mask for the metal substrate 1. Since the phase change film pattern has disappeared when the etching of the metal substrate 1 is completed, the stamper 6 as shown in FIG. 1G is obtained by further etching and removing the auxiliary thin film layer 2. According to the method described above, the phase change portion 5 which is the signal concavo-convex pattern of the phase change film 4 functions as an etching mask for etching the auxiliary thin film layer 2 having two kinds of thickness, and therefore the same etching condition is used. The etching rate of the auxiliary thin film layer 2 must be sufficiently higher than that of the phase change film 4. As the phase change film 4, the crystal phase signal film of the phase change film GeSn and the auxiliary thin film layer 2 which the present inventors have already proposed.
Table 1 shows the etching rate ratios of some materials. Here, a parallel plate type plasma etching apparatus is used as the etching apparatus.

[0014]

[Table 1]

As is clear from Table 1, when CF ₄ gas or oxygen gas is used as the etching gas, the Si film or its oxide film (the etching gas is CF ₄ ) or using an organic film such as photoresist (when the etching gas is oxygen), the etching route ratio is 4 in all cases.
Since it is 0 or more, a sufficiently large selection ratio can be obtained.
As described above, a groove for tracking, which is required only during signal recording, is formed in the auxiliary thin film layer 2, signal recording is performed with reference to the groove, and after recording, the groove can be erased without being left on the substrate. Therefore, it becomes possible to manufacture the stamper using a simple and inexpensive recording machine using a semiconductor laser as a recording head. Further, by recording on the bottom of the groove, it becomes possible to prevent the deformation of the pit plane shape, which has been a problem in the conventional heat mode recording. In addition, the conventional series of processes from glass substrate polishing to punching of the plating board can be separated into the process from substrate preparation to the process after signal recording and the process can be shortened, contributing to productivity with less equipment cost. can do.

In the first embodiment, the auxiliary thin film layer 2 is a single thin film, but the present invention is not limited to this, and an auxiliary thin film layer composed of a plurality of, for example, two thin films may be used. May be. FIG. 2 is a main process diagram for explaining a method of manufacturing the optical disk stamper according to the second embodiment. In the second embodiment, first, as shown in FIG.
As shown in (A), a disk-shaped nickel substrate 1 having an inner diameter H1 of 35.6 mm, an outer diameter H2 of 128 mm, and a thickness T1 of 0.25 mm whose one surface is mirror-polished is used as the substrate 1. On the mirror surface of, a silicon film having a thickness of 100 nm was formed as the first auxiliary thin film 2A by the sputtering method. Next, as shown in FIG. 2B, a positive photoresist is formed as a second auxiliary thin film 2B on the surface of the silicon 2A, and a spiral pattern is formed on the resist 2B by photolithography to form a groove for tracking. 3 is provided. The hard mask used at this time was a glass mask on which a pattern having a width of 1 μm and a track pitch of 1.6 μm was drawn, and the exposure was by a contact exposure method. In this case, the auxiliary thin film layer 2 is composed of the first auxiliary thin film 2A and the second auxiliary thin film 2B. After development and post-baking, as shown in FIG. 2C, a phase change film 4 made of a GeSn film was formed on the entire surface of the substrate by a sputtering method. The thickness of the GeSn phase change film 4 is 150 nm. On this phase change film 4, the concave and convex grooves 3 of the lower layer are copied and projected.

On the stamper substrate thus prepared, a signal was recorded on the groove bottom, that is, the in-groove, using a conventional write-once disc recorder. The wavelength of the semiconductor laser used is 780 nm, and the power on the recording disk surface is 8 mW. Next, the back surface of the nickel substrate 1 is spray-coated, and this is dipped in a nitric acid aqueous solution to form a pattern leaving only the recording portion, and then the photoresist 2B is formed by plasma etching using oxygen gas. ,
Next, the silicon 2A was locally removed by plasma etching using tetrafluoride gas, and then the nickel substrate surface was locally removed by sputter etching using argon gas. At the end of sputter etching using argon gas, the phase change film 4 in the portion recorded by the semiconductor laser had already disappeared. The pattern of the silicon 2A that functioned as an etching mask for forming fine irregularities on the nickel substrate 1 was removed again by plasma etching using carbon tetrafluoride gas. The characteristics of the optical disk injection-molded by the stamper thus obtained were the same as the characteristics of the optical disk injection-molded by the conventional stamper. However, in the same process, signal recording was performed on the land portion, that is, on-land recording, the deformation of the pit pattern after etching silicon was severe.
In the above embodiment, the case where the silicon film is used as the first auxiliary thin film 2A and the photoresist is used as the second auxiliary thin film 2B has been described as an example, but the present invention is not limited to this, and both films use the silicon film. You may do it.
FIG. 3 is a main process diagram for explaining a method of manufacturing the optical disk stamper according to the third embodiment.

In this third embodiment, FIG.
As shown in FIG. 1, 100 n of silicon is used as the first auxiliary thin film 2A on the entire mirror side of the disk-shaped nickel substrate 1 having the same thickness and inner and outer diameters as those of the second embodiment.
A film having a thickness of m was formed by a sputtering method. Next, a photoresist spiral pattern is formed on the surface of the silicon film 2A by photolithography, and then the spiral pattern of the silicon film 2A is formed by plasma etching using carbon tetrafluoride gas to form the tracking groove 3 Was set up. The remaining photoresist was removed by plasma etching using oxygen gas. FIG. 3B shows a spiral pattern of the silicon film 2A thus formed. Next, as shown in FIG. 3C, a 100 nm thick silicon film is formed as a second auxiliary thin film 2B on the entire surface of the substrate 1 by a sputtering method, and then a phase change film 4 made of a GeSn film is formed. Filmed Signals were recorded on the stamper substrate thus prepared in the same manner as in Example 2, and after development, silicon was formed by plasma etching using a carbon tetrafluoride gas, and then sputtering was performed using an argon gas. The nickel substrate surface was locally removed by etching. At the end of sputter etching using argon gas, the phase change film 4 in the portion recorded by the semiconductor laser had already disappeared. The silicon pattern functioning as an etching mask for forming fine irregularities on the nickel substrate surface was removed again by plasma etching using carbon tetrafluoride gas.

The characteristics of the optical disk injection-molded by the stamper thus obtained were the same as the characteristics of the optical disk injection-molded by the stamper manufactured by the conventional method.
However, in the same process, signal recording was performed on the land portion, that is, on-land recording, the deformation of the pit pattern after etching silicon was severe. In this case, the process after signal recording is shorter than that in the case of Example 2 because there is no etching step using oxygen plasma, and thus the lead time is shortened, and the substrate prepared before signal recording is a thermally stable inorganic material. Since it was composed of only one, it was excellent in storability. In the above-described embodiment, the case where each process is performed based on each substrate has been described as an example. However, in order to improve the productivity, a plurality of substrates are formed into one nickel substrate as in the fourth embodiment. It may be molded from a plate.

As a fourth embodiment, for example, one surface is a mirror surface,
A silicon film is formed on the mirror surface side. Thickness 0.25
A photoresist film was thermocompression-bonded to the silicon surface of a nickel plate having a rectangular shape of mm, exposed with a film mask, and then developed. The pattern of this film mask has an inner diameter of 35.6 mm and an outer diameter of 128 mm, and FIG. 4 shows a 300 × 300 mm square nickel plate 7 thus obtained. The pattern for is drawn. This nickel plate 7 is subjected to silicon etching with a parallel plate type plasma etching device,
After that, a protective film (clean coat manufactured by Fine Chemical Japan Co., Ltd.) was formed on the back surface by spraying, and the nickel plate 1 was etched by a nitric acid aqueous solution shower to separate into pattern shapes, thereby forming four circular nickel substrates 1. . After that, a stamper was produced in the same manner as in Example 2 after forming the silicon film. This substrate has less burrs than the punched substrate, and the preformed silicon film also serves as a protective film for the nickel surface, preventing local oxidation of the nickel substrate surface during storage of the substrate and excellent storage stability. Was there. In addition, in the above embodiment, the case where nickel is used as the substrate material is described as an example, but the present invention is not limited to this.
Of course, other metal materials such as styrene steel, titanium, tantalum, molybdenum, platinum, etc. may be used.

[0021]

As described above, according to the method for manufacturing an optical disk stamper of the present invention, the following excellent operational effects can be exhibited. A groove for tracking, which is required only during signal recording, is formed in the auxiliary thin film layer that can be easily removed by etching, and this is removed in a later process, so the expensive and highly accurate recorder that was required in the past is not required. Therefore, it is possible to use a cutting machine that is a simple and inexpensive recorder that uses a semiconductor laser as a recording head, and a high-density and excellent pit-shaped heat mode that cannot be obtained by the conventional photon mode recording cutting method. A cutting method by recording can be realized. Further, by recording on the bottom of the tracking groove, it is possible to prevent the deformation of the pit plane shape, which has been a problem in the conventional heat mode recording.

[Brief description of the drawings]

FIG. 1 is a process drawing showing a first embodiment of a method for manufacturing an optical disk stamper according to the present invention.

FIG. 2 is a main process chart showing a second embodiment of a method for manufacturing an optical disk stamper according to the present invention.

FIG. 3 is a main process diagram showing a third embodiment of a method for manufacturing an optical disk stamper according to the present invention.

FIG. 4 is a main process chart showing a fourth embodiment of a method for manufacturing an optical disk stamper according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Auxiliary thin film layer, 2A ... 1st auxiliary thin film, 2
B ... second auxiliary thin film, 3 ... tracking groove,
4 ... Phase change film, 5 ... Phase change part, 6 ... Stamper.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Toyotosa Asanuma 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan, Ltd. (72) Inventor Tetsuya Suzuki 3-chome, Moriya-cho, Kanagawa-ku, Yokohama Address 12 Victor Company of Japan, Ltd.

Claims (4)

[Claims] 1. A substrate, wherein information is thermally recorded on a phase change film formed on a substrate by laser light, and the information is etched to utilize a difference in etching rate between a phase change part and a phase non-change part. In a method of manufacturing a stamper for an optical disc in which signal irregularities are formed on a surface, prior to forming the phase change film, a material different from the phase change film on the substrate can be easily removed by etching. A stamper for an optical disk characterized in that an auxiliary thin film layer made of a material is formed, a groove for tracking is formed in the auxiliary thin film layer, and then the phase change film is formed on the auxiliary thin film layer. Manufacturing method. 2. The method for manufacturing an optical disk stamper according to claim 1, wherein information is recorded by the laser beam on a bottom portion of the tracking groove. 3. The auxiliary thin film layer comprises a silicon film or a silicon oxide film.
A method for manufacturing the stamper for an optical disc as described above. 4. The auxiliary thin film layer comprises a first auxiliary thin film made of a silicon film or a silicon oxide film formed on the entire surface of the substrate, and a photo groove having the tracking groove formed on the first auxiliary thin film. Second consisting of resist film
3. The auxiliary thin film according to claim 1 or 2.
A method for manufacturing the stamper for an optical disc as described above.