JPS6132240A - Production of stamper for optical disk - Google Patents

Abstract

PURPOSE:To decrease defect density and to improve the quality of an optical disk by mounting a glass substrate provided with an electrode film to a sputtering device prior to a plating treatment, executing sputtering in a gaseous oxygen atmosphere and cleaning the electrode film. CONSTITUTION:Pregrooves 3 are patterned on a resist film 2 and thereafter the glass substrate 1 is mounted to a vaccum deposition device, by which Ni is deposited by evaporation to 300Angstrom thickness onto the substrate while the substrate is kept heated at 140 deg.C in the same manner as heretofore. The electrode film 4 is thus formed. The substrate is then transferred into a high-frequency sputtering device and is subjected to the sputtering for 20min under the conditions of 2.3X10<-2>Torr gaseous oxygen pressure, 13.36MHz frequency and 200W electric power. The sputtering of the film 4 does not progress under such conditions and only the oxidation of the org. material sticking to the surface progresses. The org. material is gasified and removed. The substrate is dipped in a plating soln. in the same manner as in the conventional practice after such treatment, by which the wettability of the film 4 is improved remarkably and the defect density of a stamper 6 is considerably decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a stamper for optical discs with reduced defect density.

Optical disks are memory devices that use laser light to record and play back information, and they have excellent features such as being capable of large-capacity recording, non-contact recording and playback, and being unaffected by dust. We are prepared.

That is, the laser beam can be focused by the lens into a small optical spout with a diameter of about 1 μm.

Therefore, the area required to record 1 bit of information is 1 μm2
It is possible to record a much larger capacity of information than with a magnetic disk, which requires an area of several tens to hundreds of square meters or +1 m2 to record one hint of information.

Furthermore, since the laser beam focused by the lens can reach the recording medium surface at a distance of 1 to 2 mm, a light spot can be directed to the recording medium through a transparent cover about 11 cm thick.

Therefore, it is possible to have a non-contact structure, and even if there is dust on the cover, the diameter of the light beam on the top surface of the cover is as large as about 1 ml, so even if there is dust on the order of several 10μm, it will not be possible to record. It has almost no effect on playback.

Optical discs with these characteristics are made of nickel (N,i)
After forming a film of the recording medium on the transparent substrate made in this way using a resin mold using a stamper made by the manufacturer, the two substrates were used in an air-sand inch structure with the recording medium side facing inside. ing.

The present invention relates to a method of manufacturing a stamper for manufacturing such an optical disk substrate.

[Conventional technology]

The stamper coats a smooth glass substrate with resist, uses photolithography to create concentric pre-groups, and then coats the resist-coated substrate with Ni.
It is made by vacuum evaporating the film, then plating with Ni using the Ni evaporated film as a cathode, and peeling it off from the glass substrate.

FIGS. 1 to 5 show this process, and an example will be explained as follows.

A resist 11U2 with a thickness of about 0.1 μm is formed by a spin code method on a glass substrate l with a thickness of about 1 cm whose surface has been polished and made flat (FIG. 1).

Next, a pre-group 3 is patterned on the resist film 2 using photolithography.

Here, the pre-group 3 serves as a recording position of information and has a width of, for example, 0.5 to 0.7 μII+. 6μm
A large number of concentric circles are formed at intervals (Fig. 2).

Next, an electrode film 4 is formed by vacuum evaporating N1 to a thickness of about 300 nm on the surface of the substrate (FIG. 3).

Next, this electrode film 4 is used as a cathode and immersed in a Ni plating bath, and electrolysis is performed to form a layer of about 300 μm thick on the electrode film 4.
A plating layer 5 is formed (FIG. 4).

Next, the plating film 5 is peeled off from the glass substrate 1 to produce a stamper 6 as shown in FIG.

The stamper 6 thus made is used as a mold, and a large number of optical disk substrates are made by molding transparent resin such as acrylic resin.

Here, the necessary conditions for the stamper 6 are that the pregroove pattern is accurately formed and that the content of defects is small.

Note that the term "defect" as used herein refers to irregularities with a diameter of 0.5 μm or more.

In order to improve the quality of optical disc substrates, the inventors
As a result of investigating the occurrence density of defects in each process shown in Figs. 5 to 5, it was found that the defect density was abnormally high at the stage where the electrode film 4 was plated with Ni to form a plated film, and then this was peeled off to form the stamper 6. It was found that there was an increase in

This means that after the electrode film 4 is vapor-deposited, the adhesion is poor when plating is performed using the electrode film 4 as a cathode.

[Problem that the invention seeks to solve]

As described above, the problem is that the defect density increases in the step of forming the plating layer 5 on the electrode film 4 in the step of forming the standby bar, resulting in a decrease in quality.

[Failure to solve the problem]

The above problem is solved by coating a glass substrate with a resist, forming a pregroove pattern that reaches the glass substrate using photolithography, and then forming an electrode film by evaporating nickel on the pregroove pattern. In the process of forming a stamper by performing nickel plating with nickel as a cathode, the glass substrate with the electrode film is mounted on a sputtering device before the plating process, sputtering is performed in an oxygen gas atmosphere, and the electrode film is cleaned. This can be solved by a method.

[Effect]

The increase in defect density at the stage of forming the stamper 6 is due to a portion of the electrode film 4 adhering to the resist film 2 when the plating layer 5 is peeled off from the glass substrate 1. This indicates that the adhesion between the film 4 and the plating layer 5 is insufficient.

The reason for this is that the film thickness of the electrode 1lU4 is extremely thin (approximately 300 mm), so there are many pinholes, through which it is inevitable for the resist to bleed, and also due to back diffusion of diffusion pump oil during the vacuum deposition process. It was presumed that the cause was that the membrane 4 was contaminated, resulting in poor wettability.

Therefore, the present invention removes the organic substances formed on the electrode film 4 during the vapor deposition process by performing high-frequency sputtering in an oxygen atmosphere to perform forced oxidation, thereby restoring the wettability of the electrode film 4.

〔Example〕

After forming a pattern of pregroups 3 on the resist film 2 as shown in Fig. 2, this glass substrate 1 was mounted on a vacuum evaporation device, and while heating the substrate at 140°C as in the conventional method, Ni was deposited by 300 people. The electrode film 4 was formed by vapor deposition to a thickness, and then transferred to a high-frequency sputtering device at an oxygen gas pressure of 2.3 Xl0-2 Torr and a frequency of 13.36 Mt.
Sputtering is performed alternately for 20 minutes under the conditions of 1z and power of 200 W. Under these conditions, the sputtering of the electrode film 4 does not proceed;
Only the oxidation of organic matter adhering to the surface progresses, and the organic matter is gasified and removed.

Note that if the power is increased or the sputtering time is extended beyond this, etching of the electrode film 4 will progress and the pattern accuracy will decrease.

After such treatment, when the electrode 1IQ4 is immersed in a plating solution as in the prior art, the wettability of the electrode 1IQ4 is extremely good, and the defect density of the stamper 6 can be significantly reduced.

Specifically, the defect density of conventional stampers was about 10-5 per bit, but with the implementation of the present invention, it has been reduced to 10-7.
This resulted in improved quality and yield.

〔Effect of the invention〕

As described above, by carrying out the present invention, it is possible to reduce the defect density that has increased in the stamper forming process, and by applying this, it is possible to improve the quality of optical discs.

[Brief explanation of drawings]

FIGS. 1 to 5 are cross-sectional views illustrating the manufacturing process of a stamper for manufacturing optical discs. In the figure, 1 is a glass substrate, 2 is a resist film, 3 is a pre-group, 4 is an electrode film, 5 is a plating layer, and 6 is a stamper.

Claims (1)

[Claims] After coating a glass substrate with resist and forming a pregroove pattern that reaches the glass substrate using photolithography, nickel is deposited on top of this to form an electrode film, and then nickel plating is performed using the electrode film as a cathode. A stamper for an optical disk, characterized in that in the step of forming a stamper by performing plating, a glass substrate with an electrode film is mounted on a sputtering device, sputtering is performed in an oxygen gas atmosphere, and the electrode film is cleaned. manufacturing method.