JPH06195759A - Manufacture of original plate of optical disc - Google Patents

Abstract

PURPOSE:To form pit patterns on a substrate in a simple and safe process and to improve the recording density. CONSTITUTION:While the volume is changed by thermal recording in order to increase the film thickness of pit patterns of a film 3 which changes the phase by thermal recording and etching, projecting and recessed patterns are formed on the phase changing film 3, and the film is etched in a manner to leave only the projecting parts as pit patterns. After the phase changing film 3 is thermally recorded, the phase changing film is thermally treated either before or after the etching or at both points. The phase changing film 3 uses a material not including poisonous Te, Sb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical disk master for copying an optical disk by transferring a concave-convex pattern of a master as a mold onto a polymer material.

[0002]

2. Description of the Related Art Generally, a digitized signal of a music CD (compact disc), a read-only optical disc used as a video and information file, and a tracking signal of a recordable optical disc are compatible. By an injection molding method using a master having an uneven pattern (pit) or a stamper duplicated from the master,
The concavo-convex pattern is inverted and transferred to the thermoplastic resin. Then, a mirror surface treatment, coating of a protective film thereof, and printing are performed on the reversely transferred polymer substrate to manufacture an optical disk.

To explain the conventional method of manufacturing a master as a base material for this duplication, a photoresist of a polymer material should be first coated on a polished glass substrate, and then the focused laser beam should be recorded. The photoresist is exposed by irradiating the photoresist according to a signal, and then developed to form a glass master, and thereafter, a glass master is subjected to a conductive treatment and electroforming to be peeled.

That is, in the conventional manufacturing method, in order to transfer and copy to a polymer material, the original master on which the concavo-convex pattern on the glass master surface is reversely copied is used as it is, or the electroconductivity treatment, the electroforming and the peeling are repeated. A stamper having a thickness that can withstand injection molding is required. Moreover, the manufacturing process of such a conventional optical disk master is complicated,
Also, since there are many wet treatment processes, there are large costs associated with wastewater treatment, a large clean room, large power consumption, wet plating tanks, pure water, quality control of photoresists, etc. Also, since the manufacturing process is long, it lacks immediate response. There is a problem such as.

In recent years, in order to cope with such a problem, a phase change thin film is irradiated with light to locally generate a phase change, and an etching rate difference between a phase change region and a non-phase change region is used. Then, a method of manufacturing a master by forming a concavo-convex pattern and etching the base substrate using this as a mask has been developed.

Conventionally, in this method of manufacturing a master, GeTe has been used as the material of the phase change film, as disclosed in Japanese Patent Laid-Open No. 13323/1991, or Japanese Patent Laid-Open No.
InSb is used as disclosed in Japanese Patent No. 127342. Since these materials have been originally developed as a high-sensitivity recording medium, the recording sensitivity is high and the change in optical characteristics due to the phase change is large.

[0007]

However, in the above-mentioned conventional manufacturing method, GeTe or InSb is used as the phase change film.
Therefore, there is a problem in that it is difficult to form a pit pattern because the etching rate is large when plasma etching using argon gas is performed, and the etching rate difference due to the phase change is small. For example, the etching rate ratios of these materials to the unrecorded portion due to thermal recording are 0.7 to 0.9, and the thickness of the phase change film after forming the etching pattern becomes small. Therefore, these materials are used as a mask. The underlying substrate cannot be etched.

As a method of preventing this, a phase change may be generated in a thick phase change film with a large recording power, but in this case, the pit pattern width becomes large and the recording density decreases. Furthermore, since these materials contain the highly toxic elements Te and Sb, they are restricted in working conditions and pollution problems.

In view of the above-mentioned conventional problems, the present invention provides a method for manufacturing an optical disk master that can form a pit pattern on a substrate in a simple and safe process and can improve the recording density. The purpose is to do.

[0010]

In the present invention, in order to achieve the above-mentioned object, a phase change film which undergoes phase change and volume change by thermal recording is formed on a substrate.
That is, according to the present invention, a phase change film that changes in phase and changes in volume due to thermal recording is formed on a substrate, and the phase change film on the substrate is phase-changed according to a pit pattern,
There is provided a method for manufacturing an optical disc master in which a pit pattern is formed on the substrate by etching so as to leave the phase-changed portion and etching the substrate using the remaining phase-changed portion as a mask.

In the present invention, after the thermal recording of the phase change film, the phase change film is heat-treated before and / or after the etching. That is, according to the present invention, a phase change film that undergoes phase change due to thermal recording is formed on a substrate, the phase change film on the substrate is phase-changed according to a pit pattern, and the phase-changed portion is left. In the method for manufacturing an optical disk master to be etched, after the thermal recording, the phase change film is heat-treated at one or both of the time before the etching and after the etching, and the remaining phase-changed portion is used as a mask on the substrate. A method for manufacturing an optical disk master is provided, in which a pit pattern is formed on the substrate by etching.

[0012]

According to the present invention, since the phase change film that changes in phase and changes in volume due to thermal recording is formed on the substrate, the film thickness of the pit pattern increases as the volume changes due to light irradiation. The etching rate is GeT of the conventional example.
By halving it compared with the case of e or InSb, the etching selection ratio with respect to the underlying film can be increased, and thus a uniform pit pattern can be formed.

The present invention also provides that after thermal recording of the phase change film,
Since the phase change film is heat-treated before or after etching or before and after etching, it is possible to increase the etching selection ratio and to form a pit pattern with a small film thickness. It was possible to shorten and form a uniform pit pattern with little change in pit width and variation in a large area.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram showing a first embodiment of a method of manufacturing an optical disc master according to the present invention, FIG. 2 is an explanatory view showing the height of a pit pattern in the first embodiment and a conventional example, and FIG.
FIG. 4 is an explanatory diagram showing the height of a pit pattern with respect to the plasma etching time in the first example and the conventional example.

First, an outline of a method of manufacturing the optical disc master of the present embodiment shown in FIG. 1 will be described. First, as shown in FIG. 1A, a masking film 2 and a phase change film 3 are sequentially deposited on a substrate 1 whose surface is mirror-polished as a master by a sputtering method or a vacuum evaporation method.

Next, as shown in FIG. 1B, the phase change film 3
By irradiating a laser beam on the top, a phase change portion 4 is generated in an area corresponding to the data, and then, as shown in FIG. Etching is performed so that the light irradiation region 4 remains by using the difference in etching rate of the light irradiation portion, and a pit pattern is formed. In addition,
In FIG. 1C, reference numerals 5 and 6 respectively denote an outer holder and an inner holder for supporting the base 1. The holders 5 and 6 also etch the outer circumference and the inner circumference of the base 1, respectively. Also used as a mask.

After the masking film 2 is selectively etched using the phase change film 3 as a mask, the substrate 1 is selectively used with the phase change film 3 and the masking film 2 as a mask as shown in FIG. By etching and then removing the phase change film 3 and the masking film 2 remaining on the substrate 1, a master 7 having an uneven pit pattern is manufactured as shown in FIG. 1 (e).

Here, the reason why the masking film 2 is inserted between the substrate 1 and the phase change film 3 is that the etching rate of the phase change film 3 is large, and only the phase change film 3 has a large etching selection ratio with the substrate 1. This is because the pit pattern of the phase change film 3 is once transferred to the masking film 2 and the substrate 1 is etched using the masking film 2 as a mask in order to increase the etching selection ratio. Further, in this new method of manufacturing the master 7, all the processes are dry type, the equipment is small and the size can be easily reduced, and the manufacturing process time is short, so that the productivity can be remarkably improved. it can.

In this embodiment, the volume of the phase change film 3 is changed by thermal recording in order to increase the thickness of the pit pattern of the phase change film 3 by thermal recording and etching.
A concavo-convex was formed on the upper surface, etching was performed so that only the convex portion remained as a pit pattern, and a toxic phase change material containing no Te or Sb was used.

From the viewpoint of toxicity, the inventor has investigated group IV elements, specifically C, Si, Ge and Sn.
Note that these elements C, Si, and Ge except Sn are usually amorphous in a film-formed state. Among these, carbon C has an excessively high melting point, and silicon Si has a small absorptance due to the wavelength of a laser beam used for recording, so that a phase change hardly occurs, and germanium Ge was an element suitable for the purpose. However, when silicon Si was appropriately combined with germanium Ge, a phase change occurred and it was possible to meet the purpose.

Here, the laser in the present embodiment is an inexpensive semiconductor laser having an emission wavelength λ of 600 to 900 nm. The reason for using this inexpensive semiconductor laser is that the purpose of the manufacturing method according to the present invention is conventional. This is because a cutting machine that is simple and inexpensive is used instead of an expensive cutting machine that is expensive and difficult to maintain.

FIG. 2 shows that the phase change surface is generated by irradiating the phase-change surface with a semiconductor laser beam focused to about 1 μm, and the height of the pit pattern due to the volume change of the laser-light-irradiated portion with the laser-light-irradiated portion as a reference. And the reference numeral 21 is germanium Ge.
In the case of, the reference numeral 22 indicates the case of InSb used in the conventional example. The horizontal axis shows the recording linear velocity.

When germanium Ge is used, the film is easily broken when the recording linear velocity is small, and the cross section is formed by a dome-shaped convex portion as the recording linear velocity is increased, and the etching rate is further reduced in this portion. Therefore, it is very advantageous for forming a pit pattern. In comparison with the conventional phase change material, GeTe has no shape change, and InSb has a slight volume decrease due to the phase transition from the amorphous phase to the crystalline phase by laser light irradiation as shown in FIG. .

FIG. 3 shows the height of the pit pattern with respect to the plasma etching time using Ar gas.
In the case of germanium Ge, reference numeral 32 shows a change with the same initial film thickness in the case of GeTe used in the conventional example. The recording linear velocity was 2.5 m / s in all cases, and the substrate used was a mirror-polished nickel disk on which silicon was deposited. The time T1 on the horizontal axis is the time when the etching of the germanium Ge amorphous phase is completed, and the time T2 is the time when the etching of the GeTe amorphous phase is completed.

As shown in FIG. 3, the film thickness of the pit pattern is increased as the volume is changed by light irradiation, and
By halving the etching rate as compared with the case of GeTe or InSb of the conventional example, it was possible to increase the etching selectivity with respect to the underlying film, and thus to form a uniform pit pattern. Further, even if the etching selection ratio is small, the pit pattern can be formed on the substrate with a small film thickness, so that the etching step time can be shortened and a uniform pit pattern can be formed in a large area.

Next, a specific example of the above manufacturing process will be described. First, the mirror-polished outer diameter is 128 mm and the inner diameter is 3 mm.
After ion bombarding on a nickel disk of 5.6 mm and 0.8 mm in thickness, SiO ₂ 100 nm, then Ge
Was deposited with a film thickness of 200 nm using an EB (electron beam) vapor deposition apparatus as shown in FIG.

Next, while rotating the disk, the germanium surface was irradiated with a laser beam having a diameter of about 1 μm, and a pit pattern for unevenness was recorded as shown in FIG. 1 (b). The recording linear velocity at the laser light irradiation point is 2.5 m / s, and the maximum output of the recording laser light is 8 mW.

Next, the disk was irradiated with argon ions in a vacuum chamber for etching to form a pit pattern of germanium. The irradiated argon ions were 0.4 mA / cm ² . Next, parallel plate type reactive plasma etching was performed with CF ₄ gas in another vacuum chamber to form a pit pattern of SiO ₂ film as shown in FIG. 1 (c). The germanium layer was extremely thin at the time when the nickel surface of the substrate was exposed in a portion other than the bit pattern.

Next, as shown in FIG. 1 (d), the disk is irradiated with argon ions in the above-described germanium etching tank to etch the nickel surface, and finally this disk is placed in another vacuum tank. , CF ₄ gas was used to carry out reactive plasma etching to remove the rest of SiO ₂ to obtain a nickel integrated master as shown in FIG. When this master was mounted on an injection molding machine and an optical disk was duplicated, the performance and productivity of the disk were the same as those of the conventional stamper.

Next, a second embodiment will be described with reference to FIGS. 4 and 5. In this second embodiment, in order to increase the pit pattern film thickness of the phase change film 3 due to thermal recording and etching, the etching rate difference due to the phase change of the phase change film 3 is increased by heat treatment, and the phase change due to etching is changed. The dimensional change of the pit pattern is small by increasing the residual film ratio of the film 3 and decreasing the etching rate of the phase change film 3 itself on which the pit pattern is formed to increase the selection ratio with the underlying masking film 2. Uniform etching was performed. Also in the second embodiment, similarly, a material (G
e, Si) was used as the phase change film 3.

In FIG. 4, when germanium is used as the material of the phase change film 3, a semiconductor laser beam focused to about 1 μm is irradiated on the phase change surface to generate a phase change, and then etching is not performed. The height of the pit pattern of the laser irradiation portion based on the irradiation portion is shown, and the horizontal axis shows the etching time.

Reference numeral 41 indicates the height of the pit pattern in the case where etching is performed by irradiating laser light and then argon ions, and time T indicates the etching end time of the portion not irradiated with laser light. The reference numeral 42 indicates the height of the pit pattern when the laser irradiation is performed, the heat treatment is performed, and then the etching is performed by the irradiation of argon ions.

The etching rate of the unirradiated portion of the laser light is the same regardless of the presence or absence of the heat treatment at the heat treatment temperature of about 300 ° C. or less, and therefore, the time T at which the etching of the unrecorded portion is finished has the same value. Indicated.

As shown in FIG. 4, the etching rate of the recording portion was decreased by the heat treatment, and the residual film rate of the pit pattern could be increased. Here, germanium is usually amorphous in the state after film formation and crystallizes by irradiation with laser light, but the effect of heat treatment on the etching rate is greater in the crystalline phase than in the amorphous state, and it is inactive. The sputtering effect due to ion irradiation is reduced. Also, as can be seen from FIG.
It is expected that not only the effect near the surface of the thin film but also the effect of reducing the sputtering effect exists inside the thin film.

FIG. 5 shows the results of measuring the etching rate by plasma etching of CF ₄ gas for such phase change germanium with respect to the heat treatment temperature in the atmosphere. Reference numeral 51 indicates the etching rate of the germanium film as the phase change material 3. Reference numeral 52 indicates the etching rate of SiO ₂ as the masking film 2 shown in FIG.

Here, when SiO ₂ or the like is used as the masking film 2, it must have a sufficient masking effect on the CF 4 plasma that is the etchant, but as shown in FIG. 5, the etching rate of the germanium film is increased. 51 is SiO by heat treatment at 350 to 400 ° C. or higher.
_{It is shown that} the etching rate is smaller than that of No. 2 and the heat treatment in the air after the formation of the pit pattern facilitates the formation of the pit pattern of the masking film 2.

Next, a concrete example of the manufacturing process of the second embodiment will be described. First, as in the first embodiment, the mirror-polished outer diameter is 128 mm, the inner diameter is 35.6 mm, and the thickness is 0. After ion bombarding on a 0.8 mm nickel disk, S
io ₂ was deposited to a thickness of 100 nm, and then Ge was deposited to a thickness of 200 nm using an EB vapor deposition apparatus as shown in FIG.

Next, while rotating this disk, the germanium surface was irradiated with a laser beam having a diameter of about 1 μm, and a pit pattern for unevenness was recorded as shown in FIG. 1 (b). The recording linear velocity at the irradiation point of the laser light is 2.5 m / s, as in the first embodiment, and the maximum output of the recording laser light is 8 mW. Then, in this second embodiment, this disk was heat-treated in the atmosphere on a hot plate at 320 ° C. for about 1 minute.

Next, the disk was irradiated with argon ions in a vacuum chamber and etched to form a pit pattern of germanium. The irradiated argon ions were set to 4 A / m ^{2 in} this second embodiment. Next, parallel plate type reactive plasma etching was performed with CF ₄ gas in another vacuum chamber to form a pit pattern of SiO ₂ film as shown in FIG. 1 (c).

Next, as shown in FIG. 1 (d), the disk was irradiated with argon ions in the above-described germanium etching tank to etch the nickel surface, and finally this disk was placed in another vacuum tank. , CF ₄ gas was used to carry out reactive plasma etching to remove the rest of SiO ₂ to obtain a nickel integrated master as shown in FIG. When this master was mounted on an injection molding machine and an optical disk was duplicated, the performance and productivity of the disk were the same as those of the conventional stamper.

Next, another specific example will be described. First, after ion bombarding on a ring-shaped nickel disk similar to the above specific example, Si was deposited by 100 nm and Ge was deposited by 100 nm by an EB vapor deposition apparatus. Then, recording, heat treatment and etching were performed by laser light as in the above specific example. In addition,
The etching time of the phase change film 3 was 1/2 of that in the above specific example.

Next, this disk was heat-treated in the atmosphere on a hot plate at 400 ° C. for about 1 minute, and then this disk was etched by CF ₄ plasma in the same manner as in the above specific example, and again using Si as a mask, a nickel substrate was used. Was etched to obtain a nickel integrated master. In this case as well, when this master was mounted on an injection molding machine and an optical disc was duplicated, the performance and productivity of the disc were the same as those of the conventional stamper.

Therefore, according to this second embodiment,
Since the etching selection ratio can be increased, a pit pattern can be formed with a small film thickness.
By shortening the etching process time, it was possible to form a uniform pit pattern with little pit width variation and variation in a large area.

Further, according to the above first and second embodiments, since the film is formed by using a single element, the problems of composition deviation and stability can be solved, and the use of a highly toxic element is possible. Since it does not exist, working conditions and pollution problems can be resolved.

Further, germanium is very stable in an amorphous state and can be stored for a long time in a state before recording. Further, in the conventional example, a worker is freed from the work under special illumination such as a resist disk. be able to. Here, this long-term stability shows that the manufacturing area of the master can be configured only by the cutting machine and the etching equipment, and even if the substrate and the film forming process are far from the master manufacturing area in space and time. It is possible to improve the degree of freedom in arranging the good process.

Further, the etching work can be easily automated because gas replacement, change of applied power and transfer can be carried out in the same vacuum chamber, and the production can be carried out in a small local clean room. Cost can be reduced. Further, according to the manufacturing process of the present invention, the organic solvent, large-scale wastewater treatment facility, pure water manufacturing and its water distribution facility in the conventional method are unnecessary, and in addition, the unnecessary master is re-polished by re-polishing. Since it can be used, there is less waste from the factory, speed in production,
Cost, quality, pollution, etc. can all be improved.

[0047]

As described above, according to the present invention,
Since a phase change film that changes in phase and changes in volume due to thermal recording is formed on the substrate, the film thickness of the pit pattern increases as the volume changes due to light irradiation.
By halving the etching rate as compared with the case of GeTe or InSb of the conventional example, it was possible to increase the etching selectivity with respect to the underlying film, and thus to form a uniform pit pattern.

The present invention also provides that after thermal recording of the phase change film,
Since the phase change film is heat-treated before or after etching, or both of them, the etching selectivity can be increased, and the pit pattern can be formed with a small film thickness. By shortening the process time, it was possible to form a uniform pit pattern with little pit width variation and variation in a large area.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing the height of a pit pattern in the first embodiment and the conventional example.

FIG. 3 is an explanatory diagram showing the height of a pit pattern with respect to the plasma etching time in the first example and the conventional example.

FIG. 4 is an explanatory diagram showing heights of pit patterns before and after heat treatment in the second embodiment.

FIG. 5 is an explanatory diagram showing an etching rate in the second embodiment.

[Explanation of symbols]

 1 substrate 2 masking film 3 phase change film 4 phase change part (light irradiation area) 5, 6 holder 7 master

Claims (2)

[Claims] 1. A phase-change film that changes in phase and changes in volume due to thermal recording is formed on a substrate, and the phase-change film on the substrate is phase-changed according to a pit pattern. A method of manufacturing an optical disk master, wherein etching is performed so as to remain, and a pit pattern is formed on the substrate by etching the substrate using the remaining phase-changed portion as a mask. 2. A phase change film that undergoes a phase change due to thermal recording is formed on a substrate, the phase change film on the substrate is phase-changed according to a pit pattern, and etching is performed so as to leave the phase-changed portion. In the method for manufacturing an optical disc master, after the thermal recording, the phase change film is heat-treated at one or both of the time before the etching and the time after the etching, and the substrate is etched using the remaining phase-changed portion as a mask. Thus, a pit pattern is formed on the base, thereby manufacturing an optical disk master.