JPS60226042A - Information glass substrate and its production - Google Patents

Abstract

PURPOSE:To enable formation of a rugged information layer having high uniformity by forming silicon nitride on one main plane of a glass substrate and subjecting said nitride to dry etching. CONSTITUTION:The silicon nitride layer 2 and photoresist 3 are formed on the disk-shaped soda lime glass substrate 1. Laser light is irradiated according to an information signal to said substrate 1 while the substrate is rotating to form a resist pattern 4. The layer 2 is subjected to plasma etching with the pattern 4 as a mask by which ruggedness is formed thereon and an information layer 5 is thus formed. The sodium ions from the substrate 1 do not diffuse into the silicon nitride 2 unlike silicon oxide and therefore the formation of the exact ruggedness meeting the pattern 4 with good reproducibility is made possible.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an optical memory disk or a magneto-optical disk.

An informational glass substrate used as an information recording substrate for video discs, compact discs, etc., or as an information master for manufacturing these information recording substrates.
G Dye Soki Jusha R Hohan 1 [Prior Art] Conventionally, each rice memory disk described above is formed, for example, as follows. First, a photoresist is spread on one main surface of a glass substrate, then irradiated with intensity-modulated laser light, and then developed to form a desired resist pattern and use it as an information master. Next, the main surface having the resist pattern is coated with a thin film of metal such as silver in order to have conductivity, and then nickel plating is applied to a thickness of about 0.3 m. This nickel layer is peeled off from the information master disk to create a master disk, the surface of which is then oxidized with dichromic acid, etc., nickel is plated again, and the nickel layer is peeled off to form a mother disk. Thereafter, a stamper is made using this mother board in the same manner as described above. A resin is placed between the meta/bar and the glass substrate, and is cured by heat or ultraviolet rays to transfer the unevenness of the stamper to form an information recording substrate. Here, the above-mentioned unevenness is used in the guide groove and positioning pre-groove that constitute the information recording track, and 2) 4. In order to form various recording thin films and protective layers on the uneven surface of the resin layer of the information recording substrate mentioned in @1, and to further increase the density of recorded information and extend its life as necessary. A memory disk is formed by bonding two such substrates together with the information recording layer facing inside.

However, with this method, defects on the stamper are directly transferred to the resin layer, so it is necessary to make a stamper without defects. It is difficult to uniformly apply the photoresist, and the resulting photoresist film also has the disadvantage of being weak in strength.

Instead of using such a photoresist, it has been proposed to provide an information master by providing unevenness on a silicon oxide layer formed on a glass substrate (Japanese Unexamined Patent Publication No. 59-3731). However, soda-lime glass is usually used for information masters due to its cost, but when a silicon oxide layer is formed on this soda-lime glass substrate by vapor deposition or sputtering, the sodium ions contained inside the glass substrate are removed. diffuses into the silicon oxide layer, making it difficult to form fine irregularities with good controllability by dry etching using a gas such as CF4. In particular, since the etching rate is greatly affected by the concentration of sodium ions, it is difficult to form irregularities of uniform depth.

Furthermore, even at the stage of making an information recording substrate using the information master thus formed and the stamper formed therefrom, the resin layer must be uniformly formed;
In particular, it is necessary to form an optically uniform layer by minimizing the effects of birefringence, etc., and it is necessary to form a stamper on this resin layer.
There were some manufacturing difficulties, such as the need to accurately transfer the minute irregularities on the top.

[Object and structure of the invention]

The present invention was made in view of the above circumstances, and its purpose is to have a highly uniform uneven information layer that can be used as an information master disc or information recording substrate, and has excellent moisture and weather resistance and mechanical strength. An object of the present invention is to provide a high information glass substrate and a manufacturing method thereof.

In order to achieve such an object, the information glass substrate according to the present invention has an uneven information layer made of silicon nitride on one main surface of a disk-shaped glass substrate.

In addition, in order to obtain such an information glass substrate, the method for manufacturing an information glass substrate according to the present invention involves forming a silicon nitride layer on a glass substrate, and then forming desired irregularities by dry etching. . Hereinafter, the present invention will be explained in detail using Examples.

〔Example〕

1 to 4 are process cross-sectional views showing one embodiment of the present invention. First, the outer diameter is 200 yr and the inner diameter is 15 II r.
Disc-shaped soda lime glass substrate 1 with a thickness of 10+m
200% by vacuum evaporation method or sputtering method.
A silicon nitride layer 2 having a constant thickness of OA is formed. After that, a silazane treatment is applied to strengthen the adhesion to the resist, and then a photoresist, such as A
Z1350 (manufactured by Hoechst, USA) 3 to 0.4 to 4
µm coating and pre-baking (Fig. 1).

Next, while rotating this substrate, a laser beam focused to a diameter of 0.6 to 1 μm is irradiated according to the information signal to expose the photoresist, and then development is performed to form a resist pattern 4 (first step). Figure 2).

After drying and post-baking, plasma etching is performed using the resist pattern 4 as a mask to form irregularities in the silicon nitride layer 2 to form the information layer 5 (FIG. 3).

Plasma etching is performed using a parallel plate plasma etching apparatus using oxygen gas at a partial pressure of 0.27 orr and oxygen gas at a partial pressure of 0.27 orr.
The test was carried out in a mixed gas of ITorr with CF4 gas under conditions of high frequency output of 200 W (o, 44 W/d). The etching depth is calculated as follows, where λ is the wavelength of the laser beam used later to record information on the information recording track of the memory disk and playback thereof, and n is the refractive index of the memory disk substrate.
It is necessary to set it to approximately λ/41 or λ/8n, and in this example, it was set to 1300 to 1400 A. Since sodium ions from the glass substrate 1 do not diffuse into silicon nitride, which is different from silicon oxide, accurate unevenness can be formed with good reproducibility according to the photoresist pattern.

Here, the silicon nitride layer 2 was formed thick at first, and half etching was performed so that the etching was completed when the recess reached a predetermined depth.
It is necessary to control the depth of the recess to a desired value by adjusting etching time and the like.

Another method for controlling the etching depth is to control the thickness of the silicon nitride layer 2 from the beginning to a value equivalent to the required etching depth, and then perform etching until the underlying layer is exposed. In this method, the etching rate of the underlayer is extremely low due to the sodium ions contained in the underlayer, and the underlayer is not substantially etched. Therefore, the etching speed of the silicon nitride layer may partially differ due to the performance of the dry etching equipment. In such cases, there is an advantage in that a uniform depth can be obtained without being affected by this.

After forming the uneven information layer 5 in this way, the remaining resist pattern 4 is removed using an organic solvent such as acetone or concentrated sulfuric acid to complete the information master (FIG. 4).

During the above process, the glass substrate 1 on which the silicon nitride layer 2 was formed was treated with silazane in order to increase the adhesion of the photoresist 3, but for the same purpose, a thin film of chromium or the like was formed and then A method of coating with resist is also effective. Furthermore, although a method was used in which the photoresist 3 was patterned by directly exposing it to laser light, it is of course possible to perform the exposure using a photomask.

Furthermore, as a method for forming the silicon nitride layer 2, in addition to the above-mentioned vacuum evaporation method and sputtering method, ion blasting method, CVD method, etc. can also be used.

Further, although a parallel plate type plasma etching apparatus is used to etch the silicon nitride layer 2, it goes without saying that a cylindrical type plasma etching apparatus or the like may also be used. In addition, a mixed gas of oxygen and CH4 was used as the etching gas to stabilize the etching conditions, but CF4 gas alone may also be used.
Other fluorine-based gases such as HF:l and C2F may also be used. Further, nitrogen, hydrogen, etc. may be mixed in place of oxygen for stabilization.

Further, as a method for removing the resist, in addition to the above-mentioned wet method, a plasma ashing method using oxygen gas as a main component may be used.

The above-mentioned embodiment is an example in which the present invention is applied to an information master disc. Using the information master disc formed in this way, a stand bar is formed in the same manner as before, and the unevenness is transferred to the resin layer to record information. A substrate for use can be formed.

At this time, in the information master according to the present invention, since the uneven information layer is made of dense and hard silicon nitride instead of the conventional soft resist, it is less likely to be scratched and the uneven information layer may peel off during cleaning. Therefore, dust and the like that cause defects in the information layer can be easily removed, and a high-quality stamper can be manufactured.

By applying the present invention to the information recording substrate itself, it is possible to easily form an information recording substrate having a highly uniform uneven information layer. That is, for example, the outer diameter 2001
1I++ Using a soda lime glass substrate with an inner diameter of 15M and a thickness of 1.2m as a starting material, a silicon nitride film is formed, and then a concavo-convex layer for the sible group is formed by a dry etching method to form an information recording substrate. can be formed.

In this case, the uneven information layer is formed of an inorganic material with higher moisture resistance than the conventional uneven information layer made of resin, and the information recording layer has much better weather resistance. A substrate for use can be obtained.

In addition, in the case of manufacturing the substrate directly as an information recording substrate in this way, if the silicon nitride layer is etched until the underlying soda lime glass substrate is exposed, for example, an information layer with unevenness and an information layer on top of the substrate may be etched. The diffusion of sodium ions into the recording medium can be prevented by interposing aluminum oxide, silicon compounds, etc. between the recording medium to be formed, and the life of the information recording substrate can be extended. can be easily achieved.

In addition, although we have explained the case where plasma etching is used as the etching method, other dry etching methods such as reactive etching, sputter etching, or ion beam etching can also be used to easily and reproducibly remove the unevenness. can be formed.

〔Effect of the invention〕

As explained above, according to the present invention, by providing the uneven information layer made of silicon nitride on the entire surface of the glass substrate, it is possible to use inexpensive soda lime glass and yet An information master with a highly uniform uneven information layer that prevents the diffusion of information and is resistant to plasma etching and has high mechanical strength, and an information record that also has a highly uniform uneven information layer and has excellent durability. substrates can be easily obtained. Especially for the latter, the manufacturing process is simplified since there is no need for a stamper, and even after the memory disk is completed, it is possible to prevent the recording medium from deteriorating due to sodium ions from the glass substrate. It has the advantage of being

[Brief explanation of drawings]

1 to 4 are process sectional views showing one embodiment of the present invention. 1. Fist - soda lime glass substrate, 2... ψ silicon nitride layer, 3... photoresist, 4... resist pattern, 5... information layer. Patent applicant Yasutani Glass Co., Ltd. Agent Masaki Yamakawa (and 2 others)

Claims (2)

[Claims] (1) A disk-shaped glass substrate and the -
1. An information glass substrate characterized by comprising an uneven information layer made of silicon nitride provided on a main surface. (2) A step of forming a silicon compound layer on one main surface of a disk-shaped glass substrate, and a step of forming an information layer by providing desired unevenness in the silicon nitride layer using a dry etching method. A method for manufacturing an information glass substrate.