JP2006323927A - Manufacturing method of master disk and stamper for manufacturing optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a master disk for manufacturing a substrate of an optical information medium having high recording quality in a manufacturing method of the master disk for manufacturing the optical information recording medium, by smoothing edges of a groove and pit, and roughness of a side wall without problem of resist contraction. <P>SOLUTION: The manufacturing method of the master disk for manufacturing the optical information recording medium has a main constitution such as featured by including processes: to form a resist film on the master disk; to expose the resist film; to develop the resist film; and to smooth micro unevenness of a resist surface by exposing the developed resist film to plasma. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a master for manufacturing an optical information recording medium and a method for manufacturing a stamper for manufacturing an optical information recording medium, and more particularly to a method characterized by a vacuum processing step of a resist film.

  Conventionally, in an optical disc, binary digital data is formed on a spiral or concentric track by forming embossed uneven pits (ROM disc) or holes in inorganic / organic recording films (recordable disc). It is recorded due to the difference in crystal state (phase change disc).

  When reproducing these recorded data, the track is irradiated with a laser beam to detect a difference in intensity of the reflected light and obtain a reproduction signal. The obtained reproduction signal is judged based on, for example, a constant threshold value, and binary data is detected.

  A ROM disk, such as a CD, CD-ROM, or DVD-ROM, can be produced in large quantities at low cost by transferring uneven pits formed on a master to a molding plate, and is used for distribution.

  The concave and convex pits of the master are formed by forming a resist on a glass substrate or the like, irradiating this with laser light to form a latent image, and developing. The write-once disc, phase change disc, etc. have a guide groove for tracking on the medium in the same way as a ROM disc, such as CD-R, CD-RW, DVD-R, DVD + RW, etc. A guide groove and the like are transferred from a formed master to a molding plate, and a recording material such as an inorganic / organic recording film is provided thereon, and information is recorded by a user with a recording / reproducing apparatus (CD-R drive, etc.). The

  As a method of increasing the capacity of such an information recording medium, there is a method of miniaturizing guide grooves or pits. Currently, a recording apparatus using an optical system having a laser beam wavelength of λ405 nm and a condensing lens NA0.85 has been put into practical use, and the guide groove pitch in a recording medium has been reduced to 0.32 μm.

  In the above optical disk master manufacturing method, it is common to form a positive resist film on a glass substrate and form pits or grooves according to the desk pattern. In this case, an unexposed portion is formed on the substrate as a pattern. Remain. Due to rotation unevenness and development unevenness at the time of laser exposure for forming this pattern, the edges and side walls of the resist remaining as a pattern become rough, and the rough state is transferred to a stamper or an optical disk substrate. Such roughness of the groove edge or the side wall becomes regenerated signal noise, and its adverse effect becomes more serious as the recording / reproducing beam diameter becomes finer.

  When a polycarbonate resin substrate is molded using a stamper whose edges and side walls of the groove and pit pattern are rough, transfer the stamper pits and guide grooves by controlling the filling amount in the mold and the mold temperature. There is a method of obtaining an optical disc substrate in which the roughness is smoothed and the roughness is smoothed. However, since the fluidity of the resin is different between the inner peripheral portion and the outer peripheral portion of the disk, it is difficult to obtain a uniform shape over the entire surface of the disk. Furthermore, the mold temperature fluctuation margin in continuous molding is small. For the above reasons, it can be said that it is not appropriate to reduce the roughness of the stamper in the substrate forming process.

  Conventionally, after developing the resist film, a heat treatment is performed for 30 minutes to 60 minutes at a temperature of 130 to 150 ° C. which is not lower than the heat deformation temperature of the resist film and not higher than the heat deterioration temperature due to cross-linking curing, thereby smoothing the roughness. A method has been proposed (see, for example, Patent Document 1).

Further, a method of heating and smoothing only the resist without heating the master by a method of irradiating infrared rays after developing the resist film has been proposed (see, for example, Patent Document 2).
JP-A-6-36536 JP 2003-36571 A

  However, in the method of Patent Document 1, the roughness of the resist film edge and side wall can be smoothed. However, since the heat treatment is performed for about 30 minutes in the drying furnace, the entire resist film is deteriorated. It becomes difficult to remove the resist film. The method of Patent Document 2 also has a problem that resist shrinkage cannot be made zero because the resist material absorbs IR light and exceeds the heat deformation temperature over several nm from the surface.

  The present invention has been made in consideration of the above-described circumstances, and provides a master for manufacturing an optical information medium substrate with high recording quality by smoothing the edges of the grooves and pits and the roughness of the sidewalls without causing problems of resist shrinkage. Objective.

  In order to solve the above problems, an invention of a manufacturing method of a master for manufacturing an optical information recording medium according to claim 1 is a manufacturing method of a master for manufacturing an optical information recording medium, wherein a resist is formed on the master. A step of forming a film, a step of exposing the resist film, a step of developing the exposed resist film, and a step of exposing the developed resist film to plasma to smooth out micro unevenness on the resist surface. It is characterized by becoming.

  The invention according to claim 2 is the method according to claim 1, wherein in the step of smoothing the minute irregularities on the resist surface, the plasma gas used for exposure to the plasma is at least one of helium or hydrogen. It is characterized by including.

The invention described in claim 3 is characterized in that, in the process of smoothing minute irregularities on the resist surface in claim 1 or 2, the process is performed under a high vacuum with a degree of vacuum of 10 ⁻² Torr or more. And

  An invention of a manufacturing method of a stamper for manufacturing an optical information recording medium according to claim 4 is a manufacturing method of a stamper for manufacturing an optical information recording medium, the step of forming a resist film on a master, and the resist film A step of developing the exposed resist film, a step of exposing the developed resist film to plasma to smooth minute irregularities on the resist surface, and an uneven shape composed of resist on the master And forming a transferred stamper.

  According to a fifth aspect of the present invention, in the fourth aspect of the present invention, in the step of smoothing the micro unevenness on the resist surface, the plasma gas species used when exposed to the plasma includes at least one of helium or hydrogen. It is characterized by that.

The invention described in claim 6 is characterized in that, in the process of smoothing minute irregularities on the resist surface according to claim 4 or 5, the process is performed under a high vacuum with a degree of vacuum of 10 ⁻² Torr or more. And

  According to the present invention, there is provided a method of manufacturing a master for manufacturing an optical information recording medium, the step of forming a resist film on the master, the step of exposing the resist film, the step of developing the resist film, and the development The portion of the optical disk substrate for the pits and grooves edges and side walls by the method for producing a master for producing an optical information recording medium comprising the step of smoothing the micro unevenness of the resist surface by the step of exposing the resist film to plasma in a vacuum apparatus It is possible to obtain a master for producing an optical information recording medium free from roughening.

  Further, in the step of exposing to plasma in a vacuum apparatus, it is possible to smooth the fine irregularities of the resist film without etching the master. Furthermore, the minute unevenness of the resist film can be smoothed without deteriorating the shape.

  In addition, it is possible to obtain a stamper for manufacturing an optical information recording medium in which there are no rough portions on the edges and side walls of the pits and grooves of the optical disk substrate. Furthermore, since the ions in the plasma collide and scatter frequently and the energy of the ions colliding with the stamper manufacturing master is low, it is possible to smooth the fine irregularities of the resist film without deteriorating the shape.

  Hereinafter, a method for manufacturing an optical information recording medium manufacturing master and a method for manufacturing an optical information recording medium manufacturing stamper according to the present invention will be described in detail with reference to the drawings.

A process from master to stamper production according to the present invention is shown in FIG.
(1) Master cleaning: Polished glass is generally used as a master material, but of course, metal or silicon may be polished. Here, a general polished glass plate 1 is used. By subjecting the glass plate surface to surface treatment with an ultraviolet ozone treatment apparatus called UV / O3 for about 2 minutes, the glass plate surface is hydrophilized and activated, and organic substances on the glass plate surface are removed.

Thereafter, impurities floating on the surface of the glass plate are completely washed and removed by a high pressure pure water shower or a pure water shower to which ultrasonic waves are applied, and then dried by high-speed rotary shaking and N ₂ blow. As another cleaning method, for example, if the surface is cleaned (removal of organic substances) with a solvent such as isopropyl alcohol and then sufficiently cleaned with pure water, the glass surface can be replaced with hydrophilic. However, UV / O ₃ treatment is the most excellent method in terms of environmental impact, cost, and workability, such as excellent removal of organic substances and the absence of chemicals.
If the thickness of the glass plate is too thin, the glass plate will be warped by internal stress during the subsequent nickel electroforming. On the other hand, if it is too thick, it will become heavy and impair the workability. Is desirable (see FIG. 1A).

(2) Photoresist layer formation: A photoresist layer 2 is formed by spin-coating a photoresist on the master of (1), followed by heating, drying and cooling (see FIG. 1B). At this time, when an adhesion enhancer such as a silane coupling agent or a titanium coupling agent is applied onto the glass plate, the adhesion of the photoresist to the glass plate can be improved, and this is generally performed. The photoresist is heated under a temperature range of 90 ° C. to 120 ° C. using a heating means such as an oven, for example, in a range of 30 minutes to 1 hour. As the photoresist material, when high density recording is required, a high resolution type for short wavelength ultraviolet exposure is suitable. The film thickness of the photoresist layer is adjusted to be equal to the required groove pattern depth of the optical disk medium.

(3) Exposure: The master produced in (2) is exposed through the objective lens 4 with a blue-violet or ultraviolet exposure beam 3. A spiral latent image 5 is formed on the photoresist layer by exposing the master while rotating and feeding it laterally (see FIG. 1C). The width of the groove formed in the photoresist layer can be controlled by adjusting the amount of exposure light. A schematic diagram of the optical system of the exposure apparatus is shown in FIG. In the exposure apparatus of FIG. 3, the light beam emitted from the laser light source 11 passes through the stabilizer 12, the modulator, and the polarizer 13, is reflected by the mirror 14, is condensed by the objective lens 4, and is focused on the master 15. Is irradiated. The master 15 is placed on a turntable 16 and is rotated by a rotary motor 17 to form a circular latent image. The movement in the radial direction is performed by the slider 18. By moving the slider 18 while continuing the irradiation, the latent image becomes spiral.

(4) Development: The glass plate exposed in (3) is developed with an alkaline developer, washed with pure water and shaken and dried at high speed. The exposed portion (the portion where the latent image is formed) of the photoresist layer is removed by the development process, and a groove pattern is formed (see FIG. 1D). Finally, shake and dry at high speed. If the glass plate after forming the groove pattern is left in the air as it is, the surface of the master will be damaged and deteriorated by moisture and oxygen in the air, and the hydrophilicity will be reduced. It is desirable to do it. However, when time is required in the process, the above-mentioned problem is prevented by storing the master in an inert gas such as dry nitrogen or argon, or in a vacuum atmosphere under reduced pressure.

(5) Flattening of resist fine irregularities: After transporting the master on which the resist pattern of (4) is formed to a vacuum apparatus, evacuating to the 10 ⁻⁴ Torr range, and then gas is applied so that the pressure becomes about 10 ⁻² Torr. Is discharged, + ions 7 are irradiated, and the master is exposed to the plasma 6 state (see FIG. 2E).

  The vacuum device has a gas flow rate control device, an atmospheric pressure measurement device, and a voltage application device in addition to a vacuum chamber and a vacuum pump. The gas pressure is introduced into the processing chamber via the gas flow control device. The pressure in the processing chamber is measured, for example, by a Baratron vacuum gauge, and the degree of opening and closing of the exhaust valve leading to the vacuum pump is controlled so that the desired pressure is achieved. To do. An outline of a vacuum apparatus used for smoothing fine irregularities is shown in FIG. In use for smoothing the fine unevenness shown in FIG. 4, the plasma gas is controlled to a desired flow rate by the gas flow rate control device 16 and introduced into the vacuum chamber. The vacuum chamber is evacuated by a vacuum pump 24. At this time, the pressure in the vacuum chamber is measured by the atmospheric pressure measuring device 22, and the valve opening / closing degree provided in the middle of the vacuum pump from the vacuum chamber is adjusted by the valve opening / closing control device 23 so as to be a desired pressure. It can be discharged by applying a direct current or alternating current voltage to the electrode facing the substrate to be processed 25 by the voltage application device 21.

As the gas, inert gases such as He, Ne, Ar, Kr, Xe, N ₂ , H _{2, and the} like are suitable. Among these, H ₂ and He having a small molecular weight or a mixed gas thereof are most preferable. The pressure can be discharged at 10 ^-1 Torr to 10 ^-3 Torr and the conditions can be set in the above range, preferably 10 ^-2 Torr or more. In the pressure range, damage to the master can be kept low by ion scattering. . Most preferably, it is 1 × 10 ⁻² Torr to 7 × 10 ⁻² Torr, which is a range having stability in plasma state.

(6) Conductive film formation: Conductive film 8 is formed on the groove pattern surface side of the glass plate of (5) (see FIG. 2 (f)). The conductive film is preferably made of the same nickel as the next nickel electroforming. As a conductive film forming method, Sputtering method, 2. 2. Vacuum deposition method, There is an electroless plating method. If the thickness of the nickel coating is too thin, defects such as pits are likely to occur, and if it is too thick, cracks due to internal stress occur, so a thickness of about 50 nm to 200 nm is preferable. The master disc for the optical disc is completed through the steps so far.

(7) Nickel electroforming: After forming the conductive film of (6), a nickel electroforming process 9 is performed without taking time, and nickel is laminated to form a stamper (FIG. 2 (g)). This is because the conductive film deteriorates with time due to oxygen in the air, and a film defect appears, and the hydrophilicity of the film surface also decreases. If desired, the conductive film is not deteriorated within 6 hours after the formation of the conductive film, and it is convenient because the wettability to the electroforming liquid is maintained.

By energizing with a weak current density of less than 0.2 A / dm ^{2 for} 3 to 5 minutes after entering the master, the conductive film is adapted to the nickel electroforming solution, improving the wettability and generating pits. And peeling during electroforming can be prevented. Increasing the energizing current value after weak power distribution end, finally, raising the current value to 12A / dm ² ~20A / dm ² about keeping from constant until a predetermined electric ImakuAtsu (about 300 [mu] m) Continue energizing.

(8) Peeling of stamper: The stamper 10 is peeled off from the master plate after the nickel electroforming. At this time, care should be taken not to bend the stamper 10 by applying stress to the stamper 10 (see FIG. 2H).

By the above-described process according to the present invention, almost no photoresist remains on the peeled stamper surface. However, in the case of an extremely deep groove pattern, the photoresist may remain in the groove portion. In that case, the photoresist residue can be completely removed by subjecting the surface of the stamper after peeling to the above-described UV / O ₃ treatment and then washing with pure water or O ₂ plasma ashing treatment.

(9) Master stamper: A protective film is applied to the stamper of (8) with a plastic coat, and backside polishing is performed. Here, the backside polishing may be performed before the stamper peeling step (8). In this case, it is not necessary to attach a protective film. Thereafter, the master stamper is completed by pressing the inner and outer diameters to desired dimensions.

  EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, it is needless to say that the present invention is not limited to these examples and is not interpreted in a reduced manner.

1. Plate cleaning step: A glass master having a diameter of 200 mm and a thickness of 6 mm whose surface has been optically polished is irradiated with ultraviolet rays in an ozone atmosphere for 2 minutes using an ultraviolet ozone treatment apparatus to remove surface organic substances. Thereafter, foreign matters such as particles were completely removed by a high pressure pure shower.
Photoresist layer forming step: A positive resist AZ-exp-DVD having high sensitivity in the Deep UV wavelength region is spin-coated and baked at 90 degrees for 1 hour. Conditions were set so that the resist film thickness after baking was 20 nm.

2. Exposure step: Exposure was performed by setting exposure conditions such that the groove pitch was 0.32 μm and the half width of the groove was 0.16 μm by an exposure apparatus having an optical system with a Deep UV light wavelength and NA of 0.9.

3. Development step: 2. The glass plate exposed in step 1 is developed with an alkaline developer, washed with pure water, and shaken and dried at high speed.

4). 2. Resist fine unevenness flattening step: The master on which the resist pattern is formed is transported to a vacuum apparatus, evacuated to 10 ⁻⁴ Torr, then introduced with a gas, and then discharged to expose the master to a plasma state. Table 1 shows gas types and gas pressures in Examples 1 to 7.

5. Conductive film forming step: 4. A Ni thin film having a thickness of about 100 nm is formed on the surface of the groove pattern surface of the glass plate by a sputtering method to obtain a master for manufacturing an optical disk.

  Here, the rough edge is obtained by using the upper surface photograph of the master as the average value of the point coordinates (n = 306 points) of the black and white boundary as the center value, and the average value of the deviation amount from the center value of each point coordinate as the evaluation index. (Small characteristic).

(Comparative Example 1)
1. From the substrate cleaning step. The process up to the development step was performed in the same manner as in the example.
5. The resist fine unevenness flattening step was performed for 1 hour at 90 ° C., which is equal to or lower than the resist deformation temperature, after development.
6). The conductive film forming step was performed in the same manner as in the example.

(Comparative Example 2)
1. 3. From the washing process The process up to the development step was performed in the same manner as in the example.
5. In the resist fine unevenness flattening step, the post-development resist baking was performed at 150 ° C., which is higher than the resist deformation temperature, for 30 minutes.
6). The conductive film forming step was performed in the same manner as in the example.

As shown in FIG. 3, the roughness of the groove edge of the master was evaluated as follows.
Using the upper photo of the master as shown in FIG. 3, the average of point coordinates (n = 306 points) at the black-and-white boundary is used as the center value, and the average value of the deviation from the center value of each point coordinate is used as an index (desired Small characteristics).

Table 1 shows the amount of deviation and resist shrinkage in the examples and comparative examples.
In the example, since the amount of deviation is smaller than that of the comparative example, the resist roughness is smoothed.
In Comparative Example 2, the amount of misalignment is relatively small, but since the heat treatment is performed at a temperature equal to or higher than the resist deformation temperature, the resist flows in the direction of filling the groove, and as a result, the film thickness direction corresponding to the groove depth is greatly contracted. become. On the other hand, in the embodiment, since the resist smoothing does not involve the flow of the resist, the shrinkage in the film thickness direction is very small.

Compared with Examples 1 and 2, Examples 3 and 4 treated with light element plasma have no resist shrinkage.
In Examples 1 to 3, in which the plasma gas pressure is higher than those in Examples 5 to 7, the resist shrinkage is small.

It is explanatory sectional drawing which shows the first half of the process from the original disk of this invention to stamper manufacture. It is explanatory sectional drawing which shows the second half of the process from the original recording of this invention to stamper manufacture. It is a schematic block diagram of the optical system for original exposure of this invention. It is a schematic block diagram of the resist fine uneven | corrugated smoothing processing apparatus of this invention. It is an upper surface photograph of the master of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass plate 2 Photoresist 3 Exposure beam 4 Objective lens 5 Latent image 6 Plasma 7 + Ion irradiation 8 Conductive film 9 Electroformed nickel 10 Nickel stamper 11 Laser light source 12 Stabilizer 13 Deflector 14 Mirror 15 Master 16 Turntable 17 Rotating motor 18 Slider 21 Voltage application device 22 Barometric pressure measurement device 23 Valve open / close control device 24 Vacuum pump 25 Master to be processed 26 Gas flow control device 27 Gas introduction 28 Vacuum chamber

Claims (6)

  A method of manufacturing a master for producing an optical information recording medium, comprising: forming a resist film on the master; exposing the resist film; developing the exposed resist film; A method for producing a master for producing an optical information recording medium, comprising: exposing a resist film to plasma and smoothing fine irregularities on the resist surface.   2. The optical information recording medium according to claim 1, wherein in the step of smoothing the minute irregularities on the resist surface, the plasma gas species used when exposed to the plasma contains at least one of helium or hydrogen. A manufacturing method of a master for manufacturing. 3. The master for producing an optical information recording medium according to claim 1, wherein in the step of smoothing the micro unevenness on the resist surface, the step is performed under a high vacuum with a degree of vacuum of 10 ⁻² Torr or more. Manufacturing method.   A method for manufacturing a stamper for manufacturing an optical information recording medium, comprising: forming a resist film on a master; exposing the resist film; developing the exposed resist film; and the developed resist An optical information recording medium manufacturing comprising: a step of exposing a film to plasma to smooth out micro unevenness on a resist surface; and a step of forming a stamper to which an uneven shape composed of a resist on a master is transferred. Method for manufacturing stampers.   5. The optical information recording medium according to claim 4, wherein in the step of smoothing minute irregularities on the resist surface, a plasma gas species used when exposed to the plasma contains at least one of helium or hydrogen. A manufacturing method of a stamper for manufacturing. 6. The stamper for producing an optical information recording medium according to claim 4, wherein in the step of smoothing the minute irregularities on the resist surface, the step is performed under a high vacuum with a degree of vacuum of 10 ⁻² Torr or more. Manufacturing method.

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