JP2002373456A - Method for manufacturing stamper for optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a stamper for an optical recording medium, by which the rectangular property of an uneven pattern which is to be formed on a substrate of the optical recording medium can be enhanced. SOLUTION: This method for manufacturing the stamper comprises a step of making the surface of a positive photoresist layer insolubilize, on which a latent image having the prescribed pattern is formed by exposing it to a laser beam, by treating it with a low-concentration alkaline developer and a step to furthermore develop the latent image by using the alkaline developer to form the prescribed pattern.

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 a stamper for an optical recording medium, and more particularly to a method for manufacturing a stamper for an optical recording medium for performing high-density recording such as a DVD.

[0002]

2. Description of the Related Art Optical recording media, such as optical disks, are known as recording media capable of recording and reproducing data at high density, having high reliability, and having a large capacity. In an optical recording medium, information is recorded / reproduced using a minute light spot. On the surface of the optical recording medium, a guide groove (groove) for positioning the light spot and recording / reproduction of format information and the like are required. The information is formed in advance as a concavo-convex pattern on the substrate. The substrate of such an optical recording medium is formed by injection molding a thermoplastic resin such as a polycarbonate resin or an acrylic resin using a stamper having an uneven surface corresponding to the information described above. The stamper for an optical recording medium to be used is usually manufactured as follows.

[0003] First, a positive photoresist layer is formed on a master disk made of glass or the like whose surface is polished to a mirror surface to prepare a photoresist master disk. The photoresist layer of the obtained photoresist master is irradiated with a laser beam modulated in accordance with predetermined information to form an exposed portion (latent image) of a predetermined pattern, and then the exposed portion is exposed with an alkali developing solution. Is dissolved and removed to make the uneven pattern visible. Thereafter, the surface of the photoresist layer on which the concavo-convex pattern is formed is made conductive by forming a conductive film such as a metal film by means such as vacuum film formation, and the conductive film is used as an electrode to electroform nickel or the like. An electroformed layer is formed. The electroformed layer thus obtained is peeled from the glass master to obtain a stamper.

[0004] In the developing process, the exposed portion is dissolved and removed with an alkali developing solution to make the concavo-convex pattern visible, and before the development, a pre-water washing process for improving the wettability of the photoresist layer surface is performed. In general, a predetermined uneven pattern is formed by developing with an alkali developing solution.

The prior art will be described below with reference to the drawings. In the following description, a case where the cross-sectional shape of the recording mode is a rectangular groove will be described.
The same applies to V-shaped and U-shaped grooves, U-shaped grooves, pits, and the like.

Prior Art 1 FIG. 1 is a flowchart illustrating a conventional process from resist coating to developing process. A quinonediazide-based photoresist is diluted on a glass master with ethyl cellosolve acetate, spin-coated on the glass master, and then heated to form a photoresist master having a predetermined thickness. Ar laser light (wavelength 457.9) modulated on the photoresist master surface for an optical recording medium and focused by an objective lens
nm) to form a latent image. After that, a washing process (pre-washing process) is performed to improve the wettability of the photoresist surface with the alkali developing solution, and then development is performed with the alkali developing solution.

FIG. 2 is a view for explaining a latent image pattern after exposure and a pattern formed after development when processed by the method of the prior art 1 described above. Since the laser light condensed by the objective lens has an intensity distribution having a Gaussian pattern, the latent image exposed by the laser light also has a latent image pattern derived from the decomposition threshold of the photosensitive agent. Also,
In the conventional developing process, the dissolution of the photoresist in the vertical direction (thickness direction) causes the dissolution of the pattern edge portion in the horizontal direction (in-plane direction), so that the rectangularity of the pattern is considerably larger than that of the latent image pattern. Had declined. Therefore, there is a problem that the rectangularity of the pattern of the obtained stamper and the resin substrate formed by the stamper is also reduced, and the reproduced signal derived from the unevenness of the pattern is reduced.

Prior Art 2 In order to solve the above-mentioned problem of the prior art 1, for example, as disclosed in Japanese Patent Application Laid-Open No. 8-235645,
A method of performing development in two stages has been proposed. FIG. 3 is a flowchart illustrating the steps from the photoresist coating step to the developing step in the two-stage developing method. 1 is the same as the prior art 1 described with reference to FIG. 1 up to the step of exposing with a laser beam.
Short-time development is performed for 10 to 60 seconds with an alkali developing solution of 17 to 0.19 N, and a pattern is formed halfway through a predetermined resist pattern through a washing and drying process for terminating the first-stage development. Subsequently, the alkaline developing solution having the same normality (0.17 to 0.19 N) as that of the first stage development was used for 40 to 1 day.
A predetermined resist pattern is formed through a second-stage development in which development is performed for 00 seconds and a second washing and drying process.

FIG. 4 is a view for explaining a latent image pattern after exposure and a pattern formed after development when processed by the method of the above-mentioned prior art 2. The surface of the positive photoresist once immersed in an alkaline developer undergoes a surface modification that is less likely to be dissolved than the surface of the undeveloped positive photoresist, so that a short-time First
After the step development, the surface of the positive type photoresist is modified by temporarily stopping the development by washing and drying, and then the second step development is performed with a developer having the same concentration as the developer used in the first step development. By doing so, the dissolution rate of the photoresist in the horizontal direction (in-plane direction) can be reduced, and the rectangularity can be improved as compared with the resist pattern obtained by Conventional Technique 1.

However, since the photoresist is partially developed in the first-stage development, the dissolution of the upper portion of the photoresist layer is progressing, and the rectangularity of the resist pattern is not always sufficient. Further, since the development is temporarily stopped in the washing and drying process in the middle, there is a problem that unevenness of development and development stain are easily generated in the second stage development.

[0011]

As the density of an optical recording medium increases, a higher resolution is required for a concavo-convex pattern formed after development. It is known that the generally formed minimum pattern diameter d is expressed by the following equation 1. In an exposure apparatus, the wavelength of an exposure laser is reduced and the NA of a lens is increased.

D = kλ / NA (Equation 1) where λ is the wavelength of light, NA is the numerical aperture of the objective lens, and k is a coefficient determined by factors other than the resist material and the developing method, etc. Some resist materials have been improved to reduce k.

As an improvement of the developing method, as described above,
For example, Japanese Patent Publication No. 4-11024 and Japanese Patent Application Laid-Open No.
As disclosed in Japanese Patent No. 5645, there has been proposed a method of performing development in two steps. By these methods, the pattern edge can be sharpened as compared with the normal developing method, and the rectangularity of the pattern can be improved (resolution can be improved). However, with these methods,
By performing development to a predetermined depth in the first stage of development,
Since the pattern edge is widened, a sufficient effect of improving the resolution cannot be obtained, and furthermore, a washing and drying step is added between the first stage development and the second stage development, resulting in uneven development.
There has been a problem that development stains and the like easily occur.
Therefore, an object of the present invention is to provide a method of manufacturing a stamper for an optical recording medium, which further sharpens the pattern edge, improves the rectangularity, simplifies the developing operation, and does not cause unevenness of development and development spots. Is to provide.

[0014]

According to a method of manufacturing a stamper for an optical recording medium of the present invention, a step of forming a positive type photoresist layer on a master, and a step of forming
An optical recording medium having a process of exposing a predetermined pattern by a laser beam to form an exposed portion, and a pattern forming process of forming an uneven pattern by removing the exposed portion formed on the photoresist layer with an alkali developing solution. In the method of manufacturing a stamper, after exposure of the photoresist layer and before a pattern forming step, the surface of the photoresist layer is treated with an alkali developing solution having a lower concentration than an alkali developing solution used in the pattern forming step. Is a method for manufacturing an optical recording medium stamper. Here, the normality of the alkali developer used for the processing is 0.01 N or more and 0.03 N or more.
Or less, and the processing time is preferably 30 seconds or more and 400 seconds or less. In the method of manufacturing a stamper for an optical recording medium according to the present invention, it is preferable that the stamping is performed continuously without a washing step or a drying step between the treatment and the pattern forming step.

In the present invention, the treatment of the surface of the photoresist layer with an alkali developing solution means that the surface of the photoresist layer is wetted with the alkali developing solution for a predetermined time, that is, the surface of the photoresist layer and the alkali developing solution Is to keep the contact state for a predetermined time. Specifically, for example, while rotating a photoresist master held horizontally at a predetermined speed, a predetermined amount of an alkali developing solution is supplied to a substantially central portion thereof. Spraying a predetermined amount of an alkali developing solution onto the photoresist layer surface while rotating the photoresist master held horizontally at a predetermined speed, causing the photoresist master surface to flow down, the entire photoresist master, or at least the photoresist The surface of the layer is immersed in an alkali developer for a predetermined time.

Hereinafter, the present invention will be described in more detail.

According to the present invention, the surface of the photoresist layer after exposure is treated with an alkali developing solution diluted to such an extent that the photoresist is hardly dissolved, for a predetermined time, thereby substantially dissolving and removing the surface of the photoresist layer. A method for producing a stamper for an optical recording medium, characterized by having a surface insolubilization step that makes it hardly soluble without a normal concentration or slightly lower than the normal concentration after this surface insolubilization step. By developing the photoresist layer to a predetermined shape with a concentrated alkali developing solution, a pattern edge is sharply formed, and a rectangular shape which cannot be achieved by the conventional developing method is obtained. Furthermore, since there is no processing for temporarily stopping development such as a washing and drying step between the surface insolubilizing step and the pattern forming step, development is performed continuously with the surface insolubilizing step. Can be suppressed.

Although it is not clear why the photoresist becomes hardly soluble by flowing an alkaline developer diluted to a low concentration on the photoresist surface, the effect of the alkaline development of the quinonediazide-based photosensitizer in the photoresist is not clear. There are two types, a resist dissolution accelerating effect and a resist insolubilizing effect. It is presumed that the resist insolubilizing effect becomes dominant when a diluted alkali developer is used.

FIG. 5 is a flowchart illustrating an example of the present invention from the photoresist coating step to the developing step. 1 and 3 are the same as the prior arts 1 and 2 up to the exposure step using a laser beam, but using the same alkaline developer as in the development step for pattern formation instead of the pre-washing process or the first-stage development, A diluent diluted to a normality of 0.01 to 0.03 N is allowed to flow on the photoresist surface for 50 to 400 seconds. Next, an alkaline developer having a normality of 0.12 to 0.2 N is allowed to flow on the photoresist surface for 60 to 100 seconds to dissolve the photoresist and form a pattern.

FIG. 6 is a view for explaining a latent image pattern after exposure when processed by the above-described developing method and a pattern formed after development. Unlike FIG. 2 and FIG. 4, in the alkali developing solution diluted to a normality of 0.01 to 0.03 N used in the hard-solubilizing step, the hard-solubilizing speed is higher than the dissolving speed of the photoresist, and thus the hard-solubilizing of the photoresist surface Happens. Therefore, even in the portion where the latent image pattern of the photoresist is formed, the photoresist layer is hardly dissolved in the surface insolubilization step, and the formation of the insoluble layer occurs preferentially. Therefore, even in the subsequent development (pattern forming step) in which a pattern is formed with an alkali developer of 0.12 to 0.2 N, the hardly-solubilized layer on the photoresist surface is moved horizontally (in-plane direction) of the upper pattern edge. Reduce dissolution rate. As a result, it is possible to improve the rectangularity of the resist pattern as compared with the developing methods of Conventional Techniques 1 and 2.

That is, the concentration of the alkali developing solution used in the surface insolubilization step is set to a low concentration such that the photoresist is hardly dissolved and removed by development, and the surface insolubilization time is extended to increase the photosensitivity. By increasing the thickness of the hardly-solubilized layer on the surface of the resist layer, a pattern edge is formed sharply, and rectangularity that cannot be achieved by the conventional developing method is obtained. In addition, when a low-concentration alkaline developing solution is applied to the photoresist surface for a long time, a long-time development is required to form a predetermined pattern, which indicates that the photoresist surface becomes hardly soluble. I have.

Further, in the method of the present invention, since the development is not stopped or the resist surface is not dried on the way as in the prior art 2, the occurrence of uneven development and development spots can be suppressed.

The positive photoresist used in the present invention is not particularly limited as long as it is a quinonediazide-based photoresist. For example, an o-naphthoquinonediazide-based photoresist, a benzoquinonediazide-based photoresist, or the like can be used. As the alkali developer used in the above, not only an inorganic alkali developer such as sodium hydrogen phosphate, sodium hydroxide and potassium hydroxide, but also an organic alkali developer such as tetramethylammonium hydroxide can be used.

The normality of the alkali developer used in the step of making the surface hardly soluble in the present invention is preferably 0.01 to 0.03N. When the normality of the alkali developer used in the surface insolubilization step is less than 0.01 N, the effect of insolubilization is small, and
If it exceeds 3N, resist development occurs and the effect of improving rectangularity is diminished. In consideration of the rectangularity, the normality of the alkali developer is more preferably 0.02 to 0.03 N. Further, the treatment time in the surface insolubilization step is preferably 30 to 400 seconds. If the treatment time of the surface insolubilization step is less than 30 seconds, the effect of insolubilization is small, and if it exceeds 400 seconds, resist peeling due to swelling of the resist is likely to occur. Considering the rectangularity, the processing time in the surface hardly-solubilizing step is 300 to 40.
0 second is more preferable.

In the step of hardly dissolving the surface of the present invention, the treatment is preferably performed to such an extent that the dissolution and removal of the photoresist by development are hardly detected. It may be processing. In order to expect the effect of improving the rectangularity due to the insolubility of the surface, dissolution of the photoresist is 5n.
m or less.

The normality of the alkali developing solution used in the pattern forming step of the present invention is usually 0.1 to 0.3.
N may be used, but a slightly lower concentration of 0.1
The rectangularity can be further improved by using a material having a thickness of up to 0.2N. Further, the alkali developer used in the surface resolubilization step and the alkali developer used in the pattern formation step may be the same kind of alkali developer having only a different concentration, or may be both kinds of different alkali developer. good.

The specific method for treating the surface of the photoresist layer with an alkali developing solution in the surface insolubilizing step and the pattern forming step of the present invention is not particularly limited, and can be performed by a usual method. , Spin development, paddle development, dip development, and the like.

Using the photoresist master patterned as described above, a commonly used method, for example,
A conductive film is formed on the surface of the photoresist layer by sputtering or electroless plating, nickel is electroformed using the electrode as an electrode, and the obtained electroformed layer is peeled from the photoresist master to produce a stamper for an optical recording medium. can do.

[0029]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to only these examples.

(Example 1) A quinonediazide-based photoresist (trade name "TSMR-8900", manufactured by Tokyo Ohka Kogyo Co., Ltd.) was diluted on a glass master with ethyl cellosolve acetate, and spun on a 200 mm glass master. After coating, the substrate was baked at 95 ° C. for 15 minutes to prepare a photoresist master having a photoresist layer with a thickness of 150 nm. After irradiating the surface of the photoresist layer of the photoresist master with Ar laser light (wavelength 457.9 nm) modulated for an optical recording medium and focused by an objective lens to form a latent image, a series of images shown in FIG. By the treatment, an uneven pattern was formed on the surface of the photoresist layer.

As a surface insolubilization step, an alkaline developer (manufactured by Shipley Farist Co., Ltd.) is used while rotating the photoresist master on which the latent image has been formed by keeping the surface of the photoresist layer horizontal (150 rpm). , A brand name “Microposit Developer”) diluted with water, and an alkali developing solution having a normality of 0.018 to 0.03 N was dropped at the center of the surface of the photoresist layer for 50 to 400 seconds (350 cm ^3). / Min), and the surface of the photoresist layer was treated with an alkaline developer by flowing over the surface of the photoresist layer. Next, as a pattern forming step, the same developer as described above was diluted with water to an alkali developing solution having a normality of 0.12 to 0.2 N, and the alkaline developing solution was used for 60 to 10 N.
In the same manner as above, the photoresist was dropped and flowed over the surface of the photoresist layer to dissolve the photoresist to form a pattern. As a washing and drying step, pure water was supplied at a flow rate of 1500 cm ³ / min for 500 seconds while rotating at 100 rpm. Then, the resist was dried by blowing nitrogen of ² kg / cm ² for 300 seconds to form a resist pattern.

Table 1 shows the processing conditions of the surface insolubilizing step and the pattern forming step, the rectangularity of the formed resist pattern, and the presence or absence of development of the resist surface. Here, ◎, △, Δ, and × in the rectangularity in Table 1 and 、 and × in the development stain will be described. Rectangularity is SEM
(Scanning electron microscope), and the pattern slope angle at the intermediate position of the resist layer thickness was measured. As a result, in order to classify the rectangularity, 50, respectively, in the order of △, ○, Δ, ×
° or more, 45 ° or more and less than 50 °, 40 ° or more and less than 45 °, or less than 40 °. However, since this number changes depending on the resist film thickness and the rectangularity evaluation method, the absolute value of the numerical value has no meaning and is a relative comparison of each processing method. The evaluation of the development stain was performed by visually observing the photoresist master after the pattern forming step using a halogen light source lamp. Developing stains were observed as white turbidity on the surface by visual observation with a halogen light source lamp, and ○ was classified into those where no developing stains were observed and × were classified as those where developing stains were observed.

As shown in Table 1, before pattern formation, 0.01
It can be seen that by making the surface of the resist layer hardly soluble using an alkaline developer having a very low concentration of 8 to 0.03 N, the rectangularity of the obtained resist pattern is improved. In particular, the insolubilization of the resist layer surface is performed for a long time (300 to 400
Sec), and then performing long-term (50-100 seconds) development (pattern formation) using a low-concentration alkaline developer, it was recognized that the rectangularity was significantly improved.

Further, since a washing and drying step is not provided between the surface insolubilizing step and the pattern forming step, and the photoresist surface is not dried on the way, it is possible to suppress the occurrence of uneven development and development stain.

A nickel thin film is formed by sputtering on the surface of the photoresist layer on which the thus obtained uneven pattern has been formed, and electroforming is performed using the nickel thin film as an electrode. The optical recording medium was further peeled off to produce a stamper for an optical recording medium. The obtained stamper for an optical recording medium was very excellent in tracking characteristics, C / N, jitter characteristics, and the like.

[0036]

[Table 1] (Comparative Example 1) As shown in FIG. 1, a water-insoluble step was not provided, and as a pre-water-washing step for improving the wettability of the alkali developing solution to the photoresist surface, water washing with pure water was performed.
A pattern of a photoresist master was formed in the same manner as in Example 1 except that the stamping was performed for seconds, and a stamper for an optical recording medium was manufactured.

Table 1 shows the processing conditions of the pre-washing step and the pattern forming step, the rectangularity of the formed resist pattern, and the presence or absence of development on the resist surface. The rectangularity of the obtained resist pattern is sufficient. Was not.

(Comparative Example 2) A photoresist master was used in the same manner as in Example 1 except that a two-step development process was performed using an alkaline developer having the same concentration in a series of steps as shown in FIG. Was formed to produce a stamper for an optical recording medium. The development process was 0.096N and 0.1.
Using a 12N alkaline developer, the development time in the first stage development step was 3 seconds, and the development time in the second stage development step was 40 seconds. Further, between the first-stage development step and the second-stage development step,
1500 cm ³ / min while rotating at 100 rpm
Rinsing was performed by flowing pure water at a flow rate of 500 seconds for 500 seconds and then spraying nitrogen of ² kg / cm ² for 300 seconds to dry the resist.

Table 1 shows the processing conditions of the first-stage development step and the second-stage development step, the rectangularity of the formed resist pattern, and the presence or absence of development of the resist surface. As shown in Table 1, the results of the two-stage development with the same concentration of the alkali developing solution showed that although the rectangular pattern of the obtained resist pattern was improved, the washing and drying steps were introduced after the first stage development, so that the second stage was carried out. Development staining occurred after step development.

[0040]

According to the present invention, the surface of the positive photoresist layer on which a latent image having a predetermined pattern is formed by exposure to laser light is treated with a low-concentration alkali developing solution to make the surface of the photoresist layer hardly soluble. Furthermore, by performing pattern formation by developing with an alkaline developer, a resist pattern with improved rectangularity compared to the conventional developing method is obtained,
In addition, it is possible to obtain a resist pattern free from uneven development and development stains, and to obtain an optical recording medium stamper capable of manufacturing an optical recording medium substrate having excellent rectangularity of a concavo-convex pattern.

[Brief description of the drawings]

FIG. 1 is a flowchart showing processing of a conventional developing method.

FIG. 2 is a schematic diagram showing a photoresist pattern formed by a conventional developing method.

FIG. 3 is a flowchart showing processing of a conventional two-stage developing method.

FIG. 4 is a schematic view showing a photoresist pattern formed by a two-stage developing method.

FIG. 5 is a flowchart illustrating an example of a process according to the present invention.

FIG. 6 is a schematic view showing a photoresist pattern formed by the pattern forming method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass master 2 ... Photoresist coating master 3 ... Master after exposure which formed a latent image 4 ... Master after washing process 4A ... Master after first-stage development process 4B ... Master after second washing and drying process 4C … Master after surface insolubilization 5… master after pattern formation 6… master after final washing and drying

Claims (5)

[Claims] 1. A step of forming a positive photoresist layer on a master, a step of exposing the formed photoresist layer to a predetermined pattern by laser light to form an exposed portion, and In a method for manufacturing an optical recording medium stamper having a pattern forming step of forming a concavo-convex pattern by removing an exposed portion formed by an alkali developing solution, after exposing the photoresist layer and before the pattern forming step, A method of manufacturing a stamper for an optical recording medium, comprising treating the surface of the photoresist layer with an alkali developing solution having a lower concentration than an alkali developing solution used in the forming step. 2. The normality of an alkali developing solution used for treating the surface of a photoresist layer to be performed with an alkali developing solution having a lower concentration than an alkali developing solution used in a pattern forming step is 0.0
2. The method of manufacturing a stamper for an optical recording medium according to claim 1, wherein the stamper is 1N or more and 0.03N or less. 3. The processing time of the surface treatment of the photoresist layer performed with an alkali developing solution having a lower concentration than the alkali developing solution used in the pattern forming step is 30 seconds or more and 400 seconds or less. Of manufacturing a stamper for an optical recording medium. 4. An alkali developing solution used for treating the surface of the photoresist layer with an alkali developing solution having a lower concentration than the alkali developing solution used in the pattern forming step is different from the alkali developing solution used in the pattern forming step. The method for producing a stamper for an optical recording medium according to any one of claims 1 to 3, wherein the stamper is an alkaline developer. 5. The method according to claim 1, wherein there is no washing step or drying step between the patterning step and the processing of the photoresist layer surface performed with an alkali developing solution having a lower concentration than the alkali developing solution used in the pattern forming step. 5. The method according to claim 1, wherein the step of performing the step is performed continuously.
Item 13. The method for producing a stamper for an optical recording medium according to Item 1.