JPH06302018A - Method for manufacturing stamper having convex pattern - Google Patents

Abstract

(57) [Summary] [Object] To form a highly accurate convex pattern (in the present invention, the width of an etched region is larger than that of a non-etched region). [Structure] A step of applying a resist (2) to the surface of a first substrate (1) (first step), a step of exposing the resist (2) to a predetermined pattern (second step), and a patterning to a predetermined pattern by development. Then, a step of manufacturing a resist master (third step), a step of etching using the patterned resist (2) as a protective layer (fourth step), and a step of removing the resist remaining in the etched semi-finished product (first step) In a process of manufacturing a stamper having a convex pattern, which comprises 5 steps), a negative resist of alkaline type is used as a resist and an alkaline developing solution is used as a developing solution to manufacture a stamper having a convex 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 an optical information recording medium, and more particularly to a stamper for molding an information recording medium such as a video disc, a digital audio disc, a write-once disc and a rewritable disc. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Optical discs are roughly classified into a read-only type,
It can be classified into three types: a write-once type that can be recorded only once, a rewritable type that can be erased even if recorded once and can be recorded repeatedly. In the read-only type, the information has a width of 0.3 to 0.
It is expressed by the presence or absence of island-shaped protrusions or depressions called pits with a height or depth of about 4 μm and a height or depth of λ / 5n to λ / 6n (where λ is the wavelength of the light beam emitted during reproduction and n is the refractive index of the substrate). It

In the write-once type, the recording layer is generally composed of a metal thin film or an organic dye thin film which easily evaporates. By irradiating this recording layer with a light beam, holes called pits are formed. The information is represented by the presence or absence of this pit or the length of the pit. The rewritable type includes a phase change type recording medium and a magneto-optical recording medium. In both cases, pits (also called marks) having different optical properties are formed by the light beam on lands or grooves of the recording layer (the one closer to the objective lens is called the groove, and the farther one is called the land). Diameter 130
The rewritable optical disc of mm has an international standard (ISO standard). Generally, one groove and one land adjacent thereto are called a track. Currently, the ISO standard specifies that the track pitch is 1.6 μm. The width of the groove is 0.4 μm,
The depth is 950Å, the width of the pit is 0.4 μm, and the depth is 1400Å
It is a degree. However, with the increase in the amount of information, there is a demand for higher density and larger capacity of the optical disc. Therefore, the track pitch is further narrowed (narrow track), and the pit (information is the presence or absence of this pit or the pit (Expressed in length) is clearly towards the miniaturization. In the write-once type and the rewritable type, since a guide means for guiding the light beam along the track is required at the time of recording, a groove is generally formed between the lands.

The groove is formed in a spiral shape or a concentric shape. Information (pits) is recorded on the grooves or lands in the track longitudinal direction. Even in the write-once type and the rewritable type, pits (referred to as pre-pits), which are depressions indicating track numbers, sector numbers, etc., are formed in advance in a part of the medium. In any case, the optical disc needs to have predetermined fine irregularities such as pits and grooves. Therefore,
In order to inexpensively manufacture a large number of optical disks, it is preferable to use plastic (synthetic resin) and transfer fine irregularities onto the plastic by using a mold (mold) called a stamper. Transfer is performed at the same time as molding. The molding method can be classified into injection molding, cast molding, press molding and the like. As a result, a molded product having grooves and irregularities giving pre-pits can be obtained.

In the case of a read-only type (for example, a compact disc), since only the pits are needed, the molded product can be an optical disc as it is. However, in practice, a reflective layer of aluminum is vapor-deposited on the surface in order to enhance the reflectance. Often. In this sense, the molded product can also be called a precursor of an optical disk. In the write-once type and the rewritable type, a recording layer is naturally required, so a molded product having grooves and irregularities that give prepits is referred to as an optical disk precursor. There is also a precursor of an optical disc which is composed of a substrate and a groove material layer, and uses this groove material layer as a molded product. This is called a 2P (Photo polymer) substrate. Photo polymer is a radiation curable resin.

In any case, in the manufacturing process of the optical disc,
A mold called a stamper is required. Conventionally, a stamper was manufactured in the following process (see FIG. 2). First step: a step of applying a positive photoresist (2) on the surface of the first substrate (1) (FIG. 2a); a second step: exposing the positive photoresist (2) with a laser beam and developing it. By this, a step of patterning a predetermined pattern (FIG. 2b); (Because it is a positive photoresist, the exposed portion is removed. The one thus formed is referred to as a resist master.) Third step: Ni sputtering or electroless Ni A step of making the surface of the patterned resist (2) conductive by plating, and then forming a thick Ni electroformed layer (5) by electroforming;
In c, the conductive layer and the electroformed layer are combined to form a Ni layer (5). Fourth step: The Ni stamper made of the thick Ni layer (5) is peeled off from the positive photoresist (2), and the peeled Ni stamper is peeled off. A step of removing the residual positive photoresist on the surface by ashing (dry etching using oxygen gas) (FIG. 2d). In addition to this, there is a stamper made of plastic, and the manufacturing method includes the following steps (see FIG. 3). First step: a step of applying a positive photoresist (2) on the first substrate (1) (a in FIG. 3); a second step: exposing the resist (2) to a predetermined pattern and developing it. Patterning into a predetermined pattern by the method described above, and thereby producing a resist master (see FIG. 3).
b); Third step: a step of forming a release layer (6) made of a metal thin film or the like on the resist master by RF sputtering or the like (FIG. 3c); Fourth step: radiation-curable on the release layer (6) Resin (4),
For example, a UV curable resin is applied and a thickness of 1 to
Step of placing 2 mm glass second substrate (3) (FIG. 3d); Fifth step: When the resin (4) spreads over the entire surface of the second substrate (3), the resin (4) is exposed to radiation, for example, ultraviolet rays. The step of irradiating and curing; the seventh step: the step of peeling from the interface between the peeling layer (6) and the resist (2) (FIG. 3e);

Further, as a stamper for injection molding and 2P casting method, there is also a method for manufacturing a glass stamper having a concave pattern by wet or dry etching a glass master. A substrate was manufactured by using a resin such as a polycarbonate resin using this glass stamper. The photoresist is classified into a positive type and a negative type. The positive type photoresist has a property of removing the photoresist in a region irradiated with light at the time of exposure, and the negative type photoresist has a property of removing the photoresist in a region not irradiated with light. Conventionally, a positive photoresist has been used in the manufacture of stampers. The positive photoresist is generally an alkali development type which is composed of a novolac resin having a phenolic hydroxyl group and naphthoquinonediazide and is developed with an alkaline solution. As a characteristic of this alkali development type photoresist, since it is possible to clearly form a region which is not developed and a region which is not developed due to no swelling, the processing accuracy is good and it is suitable for fine processing of an optical recording medium or the like. It has been used conventionally.

[0008]

In the production of a stamper, a positive type photoresist is used as in the conventional case, and a convex pattern (in the present invention, the width of the region to be etched is larger than the width of the region not to be etched). Indicates)
When forming, it is necessary to increase the irradiation spot diameter of the light irradiated during exposure. However, when the irradiation spot diameter is increased, the light energy of the spot is dispersed. In particular, since the energy near the outer circumference of the spot is small, it is not possible to supply enough light energy to expose the photoresist. There was a problem that was not suitable.

An image reversal method is one of the techniques using a positive photoresist. This method applies a positive photoresist, then exposes it, and then heats it in an atmosphere of ammonia, amine, etc., so that the negative photoresist is used even though the positive photoresist is used. This is a method in which the photoresist in the region not irradiated with light is removed in the same manner as in. However, this method has a problem that the working environment is deteriorated because the vapor of ammonia, amine, etc. is required, and the working efficiency is lowered.

Further, when a negative photoresist is used, light irradiated during exposure forms a region which becomes insoluble in the developing solution, but the developing solution swells up to this region as well. Therefore, the processing accuracy of the unevenness due to etching is lowered, the dimensional stability of the unevenness is lowered, and it is not suitable for fine processing. Therefore, the negative photoresist is generally not used for manufacturing a stamper. Further, a typical rubber-based photoresist component of the negative type photoresist is mainly composed of a cyclized rubber and a bisazide photocrosslinking agent.
When developing a resist of such a component, it is developed with an aromatic hydrocarbon-based organic solvent such as xylene and washed with an organic solvent such as ethyl acetate, which causes a problem that the working environment is deteriorated.

[0011]

The present inventors have found a method of manufacturing a stamper having a convex pattern that can be microfabricated by using a negative photoresist without deteriorating the working environment. In view of this, the present invention is, firstly, "first step: a step of applying a resist on the surface of a first substrate; second step: a step of exposing a predetermined pattern to the resist; third step: developing the resist. To form a resist master by patterning the resist into a predetermined pattern by the above; 4th step: etching using the patterned resist as a protective layer; 5th step: removing the resist remaining in the etched semi-finished product In the process for producing a stamper having a convex pattern, the resist is an alkali-soluble negative photoresist, and the developing solution used for development is an alkaline developing solution. Manufacturing method (claim 1) ".

Secondly, "a method for producing a stamper having a convex pattern according to claim 1, wherein the main component of the resist is a polymer compound having a bisazide compound and a phenolic hydroxyl group (claim 2). "I will provide a.

[0013]

The photoresist used in the present invention is an alkali-soluble negative photoresist. Since this resist contains a compound having a phenolic hydroxyl group, it is soluble in alkali. Examples of the compound having a phenolic hydroxyl group include novolak resins such as phenol novolac resin and cresol novolac resin, as well as homopolymers and copolymers of p-vinylphenol and p-phenolmaleimide. These substances are substances that pose no problems in the working environment. A convex pattern is obtained by using these.

According to the present invention, a so-called negative photoresist is used which reduces the solubility of alkali in that region by irradiation with light. A typical negative photoresist is rubber-based and contains a bisazide photocrosslinking agent as a main component. The bisazide photocrosslinking agent can synthesize mainly p-azidobenzaldehyde and a compound such as cyclohexanone or isophorone in the presence of an alkali catalyst. The product of such a synthesis releases nitrogen by being irradiated with light to generate a nitrene radical. This nitrene radical abstracts the hydrogen of the phenolic hydroxyl group, making it difficult to dissolve in alkali. As described above, the resist pattern is formed through the photoreaction by utilizing the difference in the solubility with respect to the alkali.

The following reaction formula shows the reaction mechanism of the bisazide compound by light irradiation.

[0016]

[Chemical 1]

Or

[0018]

[Chemical 2]

[0019]

[Chemical 3]

Or

[0021]

[Chemical 4]

[0022]

【Example】

(1) Preparation of resist p-Vinylphenol (Marca Linker; manufactured by Maruzen Sekiyu): 120 g p-Azidobenzaldehyde and isophorone (1: 1 mo
The photocrosslinking agent synthesized in 1): 27.6 g Ethyl cellosolve: 1054 g was weighed to prepare a photosensitizing composition solution. This is filtered with a membrane filter 0.2 μm,
A photoresist was prepared. (2) Fabrication of stamper (see Fig. 1) First step: 350 mm outer diameter and 70 inner diameter with smooth surface polishing
Hexamethyldisilazane (HMDS) as a coupling agent is applied by spin coating on the surface of a quartz glass plate having a thickness of 6 mm and a thickness of 6 mm to improve the adhesion between the photoresist and the glass (not shown). When the coupling agent is applied, since the hydroxyl group (OH group) existing on the glass surface is a hydrophilic group, water easily penetrates into the boundary between the glass and the photoresist, and the adhesion between the photoresist and the glass decreases. However, it has a function of preventing the photoresist from being easily peeled off. The glass plate used may be ordinary blue plate glass, but if it is composed of the same chemical composition, for example, quartz glass, the etching rate will be more constant, and a stamper with a uniform groove depth will be formed. can get. As the coupling agent, a compound having an alkoxy group, a silane coupling agent, a titanium coupling agent, and hexamethyldisilazane (HMDS)
And so on. Then, the resist (2) prepared in (1) above was applied to a film thickness of 180 nm (FIG. 1a), and dried in a clean oven at 100 ° C. for 30 minutes.

Second step: A desired signal is exposed and recorded on the resist (2) with a laser beam having a wavelength of 300 to 458 nm (FIG. 1b). At this time, the surface of the resist is replaced with nitrogen. Further, as the light source, Ar laser or Kr laser can be used for the exposure. In this embodiment, an Ar laser beam is used, the spot diameter is 0.45 μm, and the linear velocity is 2.8 m.
/ S, the irradiation intensity of the laser beam was 8 mW, and the track pitch was 1.2 μm.

Third step: Next, development was carried out using a 0.1 N aqueous solution of sodium triphosphate to obtain a resist master having a glass plate and a resist layer having a convex pattern (FIG. 1).
c). The alkaline liquid used here is, in addition to sodium triphosphate, an inorganic alkaline aqueous solution typified by sodium hydroxide, an aqueous solution of tetraalkylammonium hydroxide typified by tetramethylammonium hydroxide, and an organic solution composed of ethylenediamine and triethylamine. Alkaline solution may be used. Although the alkali concentration depends on the alkaline liquid used, it may be a dilute concentration of about 0.1 to 0.2N.

Fourth step: After that, methane trifluoride was used as an etching gas, and the resist (2) was etched as a protective film (mask) so that the groove depth became 70 nm (FIG. 1d). The etching gas used for etching may be methane tetrafluoride, silane tetrachloride, ammonium trifluoride, or the like. Fifth step: The etched semi-finished product is subjected to oxygen plasma ashing to remove the resist (2) and washed in a mixed solution of concentrated sulfuric acid / hydrogen peroxide solution to remove the resist which was the protective film at the time of etching. To do. Thus, a glass stamper (5) having a convex pattern with an etching width of 0.9 μm was obtained (FIG. 1e).

Both dry type and wet type can be used for etching. In the case of wet type, since the etching solution is used, the resist master having the resist layer is immersed in the etching solution, so that the resist layer is easily peeled off. The dry etching is preferable because of the problems such as

[0027]

According to the present invention, it is possible to manufacture a stamper having a highly precise convex pattern, which could not be manufactured with a positive photoresist. Further, when manufacturing the convex pattern, it is not necessary to increase the spot diameter of the laser beam as in the conventional case, so that the configuration of the optical system can be simplified.

It is possible to form a highly accurate convex pattern without causing deterioration of processing accuracy due to swelling, which is a problem of the negative photoresist. Further, the stamper can be manufactured with high processing accuracy without using a substance harmful to the human body. Further, since the stamper can be manufactured without using a harmful substance as in the conventional case, the working environment is not deteriorated and the working efficiency is improved.

[Brief description of drawings]

FIG. 1 is a process drawing showing a manufacturing process of a stamper according to the present invention.

FIG. 2 is a process diagram showing a manufacturing process of a conventional nickel stamper.

FIG. 3 is a process drawing showing a manufacturing process of a conventional plastic stamper.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Glass substrate (1st substrate) 2 ... Photoresist 3 ... Glass substrate (2nd substrate) 4 ... UV curable resin 5 ... Nickel layer 6 ... Release layer and above

Claims (2)

[Claims] 1. A first step: a step of applying a resist on a surface of a first substrate; a second step: a step of exposing a predetermined pattern to the resist; a third step: a predetermined pattern by developing the resist. Patterning to manufacture a resist master; fourth step: etching using the patterned resist as a protective layer; fifth step: removing the resist remaining in the etched semi-finished product; In the step of manufacturing a stamper having a mold pattern, the resist is an alkali-soluble negative photoresist, and the developing solution used for development is an alkaline developing solution. 2. The method for producing a stamper having a convex pattern according to claim 1, wherein the main components of the resist are a bisazide compound and a polymer compound having a phenolic hydroxyl group.