JP2003187503A - Method of manufacturing stamper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a master stamper of an optical disk which is small in surface roughness and is reduced in noise by omitting a process step of developing a photoresist after exposure. <P>SOLUTION: An organic dry film used for the photoresist or holography is applied at about 100 to 500 nm on an optical glass master disk and the optical glass master disk is exposed by using CW lasers, such as from 257 nmAr times waves, 266 nmYAG quaternary harmonics, 351 nmAr lasers and 413 nmKr lasers. Only the polymers of the segments exposed by the lasers are shrunk by the exposure treatment and the fine rugged patterns are formed. A conductive film is thereafter formed at about 50 nm on the master disk formed with such fine rugged patterns by electroless nickel plating or nickel sputtering, etc., without undergoing a developing process and the stamper is so manufactured by nickel electroplating as to attain a thickness of about 300 μm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stamper manufacturing method for producing an optical recording medium such as a disk and a card which utilizes light for recording and reproducing, particularly an optical recording medium for recording and reproducing such as magneto-optical property and phase change. Regarding

[0002]

2. Description of the Related Art Conventionally, in the case of manufacturing an optical disk, a lithographic technique used in a general semiconductor manufacturing process has been applied to create a fine pit pattern on a disk signal surface. However, recently, post DVD (D
DVD as the digital video disc
It is being developed with the same size as the above, aiming for a capacity of 15 GB or more. At this time, with respect to the formation of pits in the ROM disk, as the determination of the pattern resolution, it is possible to improve the wavelength of the exposure light source and the numerical aperture (hereinafter referred to as NA) of the objective lens for condensing it.

On the other hand, the pattern resolution when a photoresist is used is expressed by the Raighly resolution limit equation as follows. R = 0.61 × λ / NA (1) where R is the resolution and λ is the wavelength. FIG. 4 is an explanatory diagram showing the relationship between the wavelength and the resolution of the resist based on the equation (1). Here, the NA of the objective lens is 0.9. When a light source with a wavelength of 351 nm shown by frame A in the figure is used, the resolution limit is about 0.240 μm. In terms of disk capacity, the minimum pit length is 0.25μ.
m, track pitch (hereinafter referred to as tp.) 0.47
About 12 GB capacity can be achieved in the DVD size of μm.

On the other hand, when a light source having a wavelength of 266 nm shown by a frame B in the figure is used, the resolution limit is about 0.18 μm,
Similarly, in terms of disk capacity, the minimum pit length is 0.4
1 μm, tp. With a DVD size of 0.19 μm, a capacity of up to about 15 GB can be achieved. In fact, in a system with a wavelength of 266 nm and an objective lens NA of 0.9, using a novolac photoresist, 6.
A practical jitter value of 6% is achieved. The reproducing optical system at this time has a wavelength of 532 nm and NA = 0.94.
The system is 3.

[0005]

However, unlike the general semiconductors in the recent optical discs, not only the fine patterns are formed, but also the uniformity of individual patterns and the reduction of the edge roughness of the formed patterns, the fine patterns are formed. There has been a demand for control of the side wall inclination angle. This is because the reproduction wavelength of the optical disk is shortened from near infrared to blue, and the reproduction spot size is reduced and the MTF is increased as the numerical aperture of the optical pickup lens is increased. The problem of affecting is emerging.

A simple comparison between a CD spot size with a wavelength of 780 nm and a lens numerical aperture of 0.45 and a reading spot size with a wavelength of 405 nm and a lens numerical aperture of 0.85 according to the DVR-Blue standard is 0.2.
The jitter factor of the optical disk, which is mainly considered to be reduced by 7 times, is expressed by the following equation (2). Jitter ² = disk noise ² + cross talk ² + inter symbol interference ² + electrical noise ² (2) That is, the jitter factors are land area, disk noise due to pit shape, and from adjacent tracks. Cross talk, and inter symbol interferenc before and after the pit.
e) impact, and is classified as electrical noise that depends on the player.

Regarding crosstalk and intersymbol interference, it has already been performed on CDs and the like to reduce intersymbol interference noise and crosstalk noise by introducing recording compensation. The reproduced signal waveform is analyzed, the positions of the pits are slightly shifted back and forth, simulation is performed so that intersymbol interference and crosstalk are minimized, and the results are fed back to the formatter of the signal generation circuit, and cutting is performed again. A method of reducing the crosstalk and intersymbol interference noise by repeating this series of processes has also been taken.

Further, the disk noise is caused by nonuniformity of the resist pattern formed by development, edge roughness, roughness of the resist itself, etc., and it is very difficult to remove it by an electric circuit because it is random. In many cases, it is necessary to adjust the composition of the photoresist. Further, it has been known from the experimental results so far that non-uniformity of the resist pattern formed by development, edge roughness, etc. are the main factors of deterioration of jitter as disk noise. As the development of high-density discs with shorter wavelengths and higher NA has progressed, disc noise has become dominant.

As an example, a 20 GB ROM disk is used, and the track pitch is 0.36 μm and the bit length is 0.13 μm.
m / bit, light transmission layer thickness 100 μm, Al reflection film reflectance 20%, disk structure, reproduction wavelength 407 nmK
The measurement is performed using an optical system of r laser and NA 0.85, and the jitter value is measured to analyze the factors. Here, when the total jitter value is 8.6%, the analysis results of disk noise 5.3%, crosstalk 4.9%, intersymbol interference 4.4%, and electric noise 1.5% are obtained. . As described above, the disk noise is dominant, but it is very difficult to reduce it as in the past. Further, when recording / reproducing is performed from the film-forming side of the optical disc substrate such as DVR-Blue,
The shapes of the reflection film and the recording film are very important, and it is required to control the side wall inclination angle, side wall roughness, and edge shape of the pit or groove shape on the glass master.

Further, since the land portion which has not been exposed by the development is also slightly developed, the surface roughness is increased and the disk noise is increased, so that improvement is required. Further, for a high-density optical disc, reproduction with a short wavelength, reduction of the focal depth due to a high numerical aperture, and further improvement of C / N are pursued, and a groove groove depth of up to about λ / 12n is proposed. As a result, in the conventional fine pattern formation by exposure and development, there is an urgent need to uniformly apply a resist in the vicinity of 20 to 80 nm. However, the diameter 120
It is very difficult to apply the above-mentioned thickness evenly in the nm range, and there is no general-purpose method for accurately measuring the thickness around 20 nm while maintaining the resist function even when applied. Are also listed.

Further, even if the developing solution is flowed from the vicinity of the center of the disc and the development is performed while the glass master is rotated, a film reduction difference occurs between the inner and outer peripheries, and in the cutting of the land / groove, the duty ratio between the inside and outside is increased. Different problems are occurring. Furthermore, when the optimum asymmetry value and the optimum jitter value of a photoresist with a high γ value are in the middle of the γ inclination, it is very difficult to control the developing conditions such as the developer temperature, the developing time in seconds, and the rinsing constant. I know. The sensitivity and γ characteristic of photoresist are evaluated from its characteristic curve. The characteristic curve is generally obtained by plotting the logarithm of the exposure dose to the resist on the horizontal axis and the resist film thickness after development on the vertical axis, and the resist contrast is determined by the slope γ of the straight line portion in the characteristic curve.
FIG. 5 shows this characteristic curve, and the definition of γ is (3)
Shown in formula γ = 1 / (logE1−logE0) = (logE1 / logE
0) ^-1

Ideally, E0 represents the maximum exposure amount without film reduction, and E1 represents the minimum exposure amount with which the residual film rate becomes 0. However, in reality, the linear approximation is extrapolated by the data of the direct portion. The exposure amount that intersects the straight line with the remaining film ratio of 100% is E0, and conversely, the point that intersects with the remaining film ratio of 0% is E1 (FIG. 5). When there are few straight lines and it is difficult to estimate E0 and E1, the gradient near E1 / 2 is taken. Generally, a high resolution photoresist has a high γ value, but due to the optimum asymmetry setting of the optical disc, reproducibility becomes a serious problem when optimum conditions exist in the middle of this steep gradient. Eg 20
In the case of GB high density ROM, the shortest pit (3T) is 0.
Since the pit lengths of 22 μm and 11T are different from 0.81 μm, 11T has an overexposure due to the exposure amount convolution because of the exposure amount convolution, so that the pit width is wide and proper asymmetry cannot be obtained.

Next, the novolak photoresist (JS) was prepared when the concentration of the organic developer (tetraammonium hydride: TMAH, NMD-3: Tokyo Ohka Kogyo) was changed.
The surface roughness rms of R: GX250ESL) was measured by AFM, and the results are shown in Table 1 of FIG. The development time was all 15 seconds. The roughness of the photoresist surface was 0.229 nm when no development was performed.
When developed with a 2.38% developer for 15 seconds, the roughness is 0.
It is 782 nm, which is more than tripled. Further, it is said that the side wall roughness of the photoresist is proportional to the surface roughness by developing. Further, in order to obtain a desired resolution, there is a problem that, for example, the above-mentioned commercially available organic developer tetraammonium hydride 2.38% aqueous solution must be used.

Therefore, an object of the present invention is to eliminate the step of developing a photoresist after exposure, to reduce the surface roughness,
It is an object of the present invention to provide a stamper manufacturing method capable of manufacturing an optical recording medium with reduced noise.

[0015]

In order to achieve the above-mentioned object, the stamper manufacturing method of the present invention comprises a step of forming a fine concavo-convex pattern using a material material that contracts in volume by an exposure process, and a conductive film on the fine concavo-convex pattern. And a step of performing metal plating on the conductive film. In the stamper manufacturing method of the present invention, a fine uneven pattern that forms a pit row of information is created using a material material that contracts in volume by a photochemical reaction of the exposure process, and after the fine uneven pattern is created by the exposure process, development is performed. Since a fine concavo-convex pattern is obtained by performing volumetric contraction of the material material without performing a step, it is possible to manufacture a stamper with less surface roughness and less disk noise than conventional patterning by development. .

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a stamper manufacturing method according to the present invention will be described below. The embodiments described below are preferred specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is not limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

In the stamper manufacturing method according to the embodiment of the present invention, a step of forming a fine concavo-convex pattern using a material material that shrinks in volume by at least one of light, electron beam and X-ray exposure, and the fine concavo-convex pattern is formed. By performing the step of forming a conductive film by using at least one of electroless plating and sputtering and the step of performing metal plating by electroforming plating on the conductive film, a developing step is not performed after the exposure processing. The fine concavo-convex pattern is created by volume contraction due to a photochemical reaction. As will be described later, in the first embodiment of the present invention, a photoresist containing naphthoquinonediazide is used as the material material that contracts in volume, and in the second embodiment, a hologram recording material is used as the material material that contracts in volume. Is.

First, an organic dry film used for photoresist or holography is applied on an optical disk glass master by about 100 nm to 500 nm, and a CW laser such as a 257 nm Ar harmonic, a 266 nm YAG fourth harmonic, a 351 nm Ar laser, and a 413 nm Kr laser is used. The optical disc master is exposed. Here, the numerical aperture of the objective lens is 0.9.

FIG. 1 is a block diagram showing an optical disk cutting machine for performing such exposure processing. This optical disc cutting machine is 351nm
Ar laser 100 and 680nm laser diode 2
00 is mounted, the Ar laser 100 is arranged on the fixed part, and the laser diode 200 is arranged on the sliding table 500. And 351
The laser light from the Ar laser 100 of nm has an electro-optic modulator (EOM) 110 and a beam splitter (BS1) 1.
20, acousto-optic modulator (AOM) 130, beam splitter (BS2) 140, quarter wave plate (QWP) 15
0, the light passes through the dichroic mirror (DCM) 160, etc., and enters the objective lens (OL) 300. The objective lens (OL) 300 irradiates the signal surface of the glass master 400 driven by the spindle motor 410.

Further, the laser light from the laser diode 200 is polarized beam splitter (PBS) 210, 1 /
4-wave plate (QWP) 220, dichroic mirror (D
CM) 160, etc., and enters the objective lens (OL) 300, and the objective lens (OL) 300 irradiates the signal surface of the glass master 400 driven by the spindle motor 410. The cutting machine is provided with various photodetectors (PD), image pickup devices (CCD), and various optical systems such as lenses (L) and mirrors, which are not directly related to the present invention. Since this is a publicly known technique, description thereof will be omitted.

By the laser exposure process using such a cutting machine, only the polymer in the laser-exposed portion contracts, and a fine concavo-convex pattern is formed. Then, without passing through the development process, a conductive film of about 50 nm is formed by electroless nickel plating or nickel sputtering on the master on which the fine concavo-convex pattern is formed, and a thickness of about 300 μm is obtained by nickel plating on electric poles. Create a stamper.

Next, a specific first embodiment of the present invention will be described. In the first embodiment, a photoresist containing naphthoquinonediazide is used as the material material that contracts in volume. This utilizes the following principle. First, naphthoquinone diazide (NQD) is contained as a photosensitizer in the g, i-ray photoresist. This NQD
Plays a role of preventing dissolution of the novolak resin, which forms the main skeleton of the photoresist, in an alkaline solution before exposure.
However, NQD is photoreactive and when exposed to light, the
A chemical reaction occurs as shown in the chemical formula (1), nitrogen is evaporated, and then a carboxyl group is formed.

As a result, the alkali solution becomes soluble, and only the exposed portion is dissolved in the developing solution to form a fine uneven pattern. That is, as the nitrogen is generated, the volume of the photoresist shrinks. Since this volume contraction amount is proportional to this nitrogen (N2) production amount, NQ
By controlling the D content, the depth of the fine concavo-convex pattern can be controlled. Furthermore, in this example,
The fact that the absorption amount of the photoresist depends on the exposure wavelength is used.

In the first embodiment, first, g-line novolac resist GX250ESL (JSR) is applied to a glass master disk to a thickness of 200 nm, and the resist is dried in a reflux type bake oven under conditions of 60 degrees and 30 minutes. After that, wavelength 413n
Using a Kr laser of m, a groove shape with a track pitch of 0.8 μm is exposed to the resist with a power of 0.12 mJ / m, and a fine uneven groove pattern is formed by utilizing the fact that naphthoquinone diazide reacts and nitrogen is evaporated. .

The step formed as a result is measured by AFM. FIG. 3 shows an example of this measurement result. As shown, in this example, about 10n between the peaks of the peaks and valleys.
A groove shape having a step of m was obtained. Regarding the roughness of the side wall, the resist (rm
Very small value (0.4n)
m) was obtained. The concentration of the photosensitizer contained in the GX250SEL resist is 30 wt%. As a result, the groove depth can be linearly increased by increasing the concentration of the photosensitizer.

Next, a second embodiment of the present invention will be described. In the second embodiment, a hologram photopolymer is used as the material material that contracts in volume. First, a hologram photopolymer (HRF-150-38: DuPon
3 μm of t) is applied to a glass master, and the resist is dried in a reflux type bake oven at 60 ° C. for 30 minutes. After that, a groove shape having a track pitch of 0.8 μm at 0.40 mJ / m was exposed to the photopolymer with a 413 nm Kr laser. As a result, although not shown, the first
As a result of measuring the step difference in the same manner as in the example, a groove shape having a depth of 200 nm was obtained.

As described above, in the stamper manufacturing method according to the present embodiment, the use of the material that contracts in volume by photoexposure allows the developing process to be performed in comparison with the side wall roughness of the fine pits and grooves formed in the exposing and developing process. By not passing it, it is possible to reduce the roughness of the side wall. As a result, it is possible to reduce the pure jitter of the optical disc due to the unevenness of the pits and the groove shape due to the development, and the side wall roughness.
Further, as compared with the pattern formed by exposure and development, the edge portion has a rounded shape, and as a result, the film is formed with good uniformity during optical disk reflection and recording film formation, which improves jitter.
It is possible to improve the recording margin and reduce the error rate. Further, since the development process is not performed, the process is simplified and the process control is simplified as compared with the conventional method. Further, it is not necessary to apply the photoresist thinly, and it can be formed with a thickness within the measurement range of a thin film measuring device (ellipsometer), and the photoresist can be applied with a thickness and a viscosity that make it easy to obtain a uniform film thickness.

In the above examples, the photoresist material or holographic recording material containing naphthoquinonediazide was used as the material material that contracts in volume by the exposure process, but the present invention is not limited to these. Also,
Other methods can also be used for the exposure treatment, and light having a specific wavelength, electron beam, or X-ray exposure can be appropriately used according to the characteristics of the material material that contracts in volume.
Further, in the above example, the example of manufacturing the mask stamper of the optical disc has been described, but it may be used for the stamper manufacturing method of another optical recording medium.

[0029]

As described above, according to the stamper manufacturing method of the present invention, by forming the fine concavo-convex pattern forming the pit row of information by using the material material that contracts in volume by the photochemical reaction of the exposure process, After the fine uneven pattern is created by the exposure process, the fine uneven pattern is obtained by the volume contraction of the material material without performing the developing process, so that the surface roughness is smaller and the disk noise is generated as compared with the pattern creation by the conventional development. There is an effect that a reduced stamper can be manufactured.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical system of a cutting machine used in a stamper manufacturing method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a chemical formula of a novolak resist reaction mechanism used in the first embodiment of the present invention.

FIG. 3 is an explanatory view showing a photoresist cross section after exposure by the stamper manufacturing method of the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the exposure wavelength and the photoresist resolution used in conventional stamper manufacturing.

FIG. 5 is an explanatory diagram showing the relationship between the exposure amount and the residual film rate of a positive resist used in conventional stamper manufacturing.

FIG. 6 is an explanatory diagram showing specific examples of organic developer concentration and photoresist surface roughness used in conventional stamper manufacturing.

[Explanation of symbols]

100 ... Ar laser, 110 ... Electro-optical modulator (E
OM), 120 ... Beam splitter (BS1), 13
0 ... Acousto-optic modulator (AOM), 140 ... Beam splitter (BS2), 150 ... Quarter wave plate (QW)
P), 160 ... dichroic mirror (DCM), 2
00 ... Laser diode, 210 ... Polarizing beam splitter (PBS), 220 ... Quarter wave plate (QW)
P), 300 ... Objective lens (OL), 400 ... Glass master, 410 ... Spindle motor, 500 ... Sliding table.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G03F 7/20 503 G03F 7/20 503 504 504 504 505 505 F term (reference) 2H025 AB20 AC03 AC05 AC06 AD01 AD03 BE01 2H049 AA33 AA40 AA43 AA57 2H097 AA03 AB07 CA15 CA16 CA17 FA03 FA10 LA20 5D121 BA03 BB21 BB40 CB06

Claims (7)

[Claims] 1. A step of forming a fine concavo-convex pattern using a material material that contracts in volume by exposure treatment, a step of forming a conductive film on the fine concavo-convex pattern, and a step of performing metal plating on the conductive film. A stamper manufacturing method characterized by having. 2. The stamper manufacturing method according to claim 1, wherein the exposure processing includes at least one of light, electron beam, and X-ray exposure. 3. The stamper manufacturing method according to claim 1, wherein the conductive film is formed by using at least one of electroless plating and sputtering. 4. The stamper manufacturing method according to claim 1, wherein the metal plating is metal plating by electroforming. 5. The stamper manufacturing method according to claim 1, wherein the material material is a photoresist material containing naphthoquinonediazide. 6. The stamper manufacturing method according to claim 1, wherein the material is a hologram recording material. 7. The stamper manufacturing method according to claim 5, wherein the photoresist material is exposed to light to form fine pits and groove patterns without a developing process.