JPH0435819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an information recording master such as an optical disk.

[Prior art] Master discs for optical discs are generally made by coating a positive photoresist on a glass substrate with a polished surface, and then applying a laser beam whose intensity is modulated according to the signal to be recorded on the photoresist. It is produced by irradiating and developing to remove the irradiated portion and form pits in accordance with the signal to be recorded.

As a typical positive photoresist
AZ series (Hoechst, Shitzpley),
There is the OFPR series (Tokyo Ohka), which generally consists of a quinone diad-based photodegradant, a phenol novolak resin, and a solvent.

The shape of the pits formed in the photoresist on the glass substrate by the method described above is determined by the application of the photoresist,
It is greatly influenced by various factors such as exposure and development conditions. Therefore, in order to obtain a high-quality master disc with the desired pit shape so that the recorded signal can be faithfully reproduced, the optimal conditions for each process are determined in advance through experiments, and each process is adjusted during actual manufacturing. We are trying to match those conditions.

[Problems to be Solved by the Invention] However, even if photoresist is applied under the same conditions, the photoresist coating conditions (film thickness, surface roughness, light absorption rate,
Some variation in the refractive index, water absorption, adhesion to the substrate, etc.) is unavoidable, and these variations affect exposure sensitivity or development sensitivity, so even if the exposure and development processes are performed under the same conditions, However, problems such as variations in the shape of the pits formed in the photoresist between master discs occurred, making it difficult to stably produce high-quality master discs.

An object of the present invention is to absorb slight variations in the state of photoresist between master discs, that is, factors that cause fluctuations in sensitivity, by controlling the development time, thereby making it possible to stably create high-quality master discs. It is an object of the present invention to provide a method for manufacturing an information recording master disk.

[Means for Solving the Problems] The present invention relates to a method of manufacturing an information recording master disc to achieve the above-mentioned object, and the present invention relates to a method of manufacturing an information recording master disc in order to achieve the above-mentioned object. Variations in light absorption, refractive index, water absorption, adhesion to the substrate, etc. are measured as variations in the reflectance of the photoresist, and the optimum development time corresponding to the reflectance is determined and used during actual manufacturing. The reflectance of the photoresist on the master is measured, and development is performed by selecting the optimum development time corresponding to the reflectance determined in advance from the reflectance.

[Example] Examples of the present invention will be described below based on FIGS. 1 to 3. Figure 1 shows the relationship between the reflectance and optimal development time corresponding to the coating state of positive photoresist.The variation in the state of each positive photoresist coated on multiple masters in advance is expressed as the variation in reflectance. It is obtained as a voltage signal by integrating the output signal of the photodetector, and was created by experimentally determining the optimum development time according to the reflectance. According to experiments, as shown in FIG. 1, it was found that the larger the reflectance, the better the development time should be lengthened.

In this way, the relationship between the reflectance of the positive photoresist and the optimum development time is determined in advance, and the master to be actually manufactured is prepared. First, a positive photoresist is applied to a glass substrate, and then the positive photoresist is exposed under certain conditions with a light beam modulated by a recording signal. Next, the reflectance of the positive photoresist is measured, and the optimum development time is determined from the relationship between the reflectance and the optimum development time determined in advance as described above, and development is performed.

FIGS. 2 and 3 each show an example of measuring the reflectance of a positive photoresist applied to a glass substrate, and in FIG. 2, the positive photoresist applied to the glass master 1 is not exposed. A light beam having a wavelength or intensity is emitted from a light source 2, reflected light is detected by a photodetector 3, and the reflectance is measured as an output voltage.

Note that the reflectance of the photoresist may be measured at a plurality of locations on the photoresist surface, and the average value thereof may be used.

In addition, in FIG. 3, the reflectance of the photoresist is measured at the same time as exposure.The laser power from the light source 1 is kept constant, and the laser beam is controlled by the light modulation element 4 according to the signal from the information signal source 5. is modulated on and off, and the modulated beam is passed through lens 6,
The beam is guided to the master disk 1 through the prism 7, the mirror 8, and the objective lens 9 to expose the photoresist, and the reflected beam from the master disk 1 is guided to the photodetector 3 through the objective lens 9, the mirror 8, and the prism 7. .

In the embodiment of FIG. 3, the light modulation element 4
The voltage level obtained by the photodetector 3 when the beam is on represents the reflectance. Therefore, variations in the output voltage of the photodetector 3 among a plurality of master discs result in variations in reflectance. In addition, in the method shown in FIG. 3, since the laser beam is focused on the upper surface of the glass master disk 1, the laser beam is spread out on the lower surface of the glass master disk 1, and the reflection from the lower surface can be ignored. I can do it.

[Effects of the Invention] As described above, the present invention measures the reflectance of the photoresist on each glass master to be manufactured, and selects the optimum development time corresponding to the reflectance determined in advance from this reflectance. Since the photoresist is developed, it is possible to prevent variations in the coating state of the photoresist between each of the glass masters to be manufactured from affecting the quality of the master, and it is therefore possible to stably produce high-quality masters. It has the advantage of being able to be manufactured in a number of ways.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the reflectance of the photoresist on a glass master disk and development time, Figure 2 is a principle diagram of reflectance measurement, and Figure 3 is a block diagram of reflectance measurement using an exposure device. be. 1...Glass master coated with photoresist,
2... Light source, 3... Photodetector, 4... Light modulation element, 5... Information signal source, 6... Lens, 7... Prism, 8... Mirror, 9... Objective lens.

Claims (1)

[Claims] 1. A method of manufacturing an information recording master by applying a photoresist to a glass master, exposing the photoresist to a light beam modulated by a signal to be recorded, and developing the photoresist, in which the photoresist is coated on a plurality of masters in advance. The variation in the state of each photoresist is measured as the variation in reflectance, and the optimum development time is determined in accordance with the reflectance.
The method is characterized in that the reflectance of the photoresist of the information recording master to be manufactured is measured, and the photoresist is developed by selecting a development time corresponding to the reflectance determined in advance from the reflectance. A method of manufacturing an information recording master.