JPH0652421B2 - Photo mask - Google Patents

Description

The present invention relates to a photomask used for manufacturing an optical memory device such as a magneto-optical disk.

[Conventional technology]

Conventionally, in an optical memory element such as a magneto-optical disk for recording, reproducing and erasing information by light such as a laser beam, particularly in an optical memory element having a glass substrate, an alloy thin film of a rare earth element and a transition metal used as a recording medium, etc. In order to reduce deterioration due to moisture or oxygen, it is known that a guide groove is formed on the glass substrate by photoetching and the alloy thin film or the like is formed on the glass substrate provided with the guide groove. ing.

By the way, as a photomask used when engraving a guide groove on a glass substrate, for example, as shown in FIG. 4A, a metal film 2 is attached as a mask pattern on a transparent substrate 1. It has been known.

However, the above photomask has a drawback that the metal film 2 is easily peeled off in a cleaning process such as ultrasonic cleaning.

Further, as shown in FIG. 4B, a photomask in which a metal film 2 is embedded in a part of a transparent substrate 1 is also known, and this photomask can withstand ultrasonic cleaning for a long time. It has been confirmed.

However, in the photomask shown in FIG. 4B, when the photomask is brought into close contact with the resist formed on the glass substrate of the optical memory element, static electricity is generated on the transparent substrate 1 which is a non-conductor, and this static electricity is generated. Since the metal film 2 is often destroyed by the discharge (usually, the photomask becomes unusable due to the destruction of the metal film 2 by exposing a few glass substrates), the life of the photomask is not only shortened. In addition, it has a drawback that it adversely affects the mass productivity of optical memory devices.

On the other hand, Japanese Unexamined Patent Publication No. 62-201444 discloses a photomask in which a metal film is embedded in a transparent substrate with its surface side portion protruding from the transparent substrate.

In such a photomask, since the metal film of the photomask is adhered to the resist on the glass substrate of the optical memory element during use, generation or accumulation of static electricity on the substrate of the photomask is suppressed, and electrostatic discharge is caused. The metal film will be protected from destruction.

[Problems to be solved by the invention]

However, in the photomask disclosed in the above publication, since the metal film for light shielding is exposed, the metal film is easily damaged by repeated use and cleaning accompanying this, and the durability is still low. Is insufficient.

Therefore, the present invention can suppress the generation or accumulation of static electricity on the substrate of the photomask, protect the metal film from destruction due to discharge of static electricity, and also protect the metal film from mechanical external force. The purpose of this is to provide a photomask having high durability.

JP-A-54-71987 discloses a photomask in which a metal film for light shielding is formed on a substrate and a transparent dielectric film is formed on the substrate and the metal film. The transparent dielectric film in the mask makes it difficult for the photoresist to adhere to the photomask when the photomask is brought into close contact with the photoresist, and suppresses the generation or accumulation of static electricity on the substrate of the photomask to prevent static electricity. However, it does not protect the metal film from being destroyed by the electric discharge and does not solve the above problems.

[Means for solving problems]

In order to solve the above problems, the photomask of the present invention is characterized in that in the photomask in which the metal film in the substrate is embedded, a conductive film is formed on the surfaces of the substrate and the metal film. .

[Action]

According to the above configuration, since the conductive film is formed on the surface of the photomask substrate and the metal film, when the photomask is brought into close contact with the resist on the glass substrate of the optical memory device, the conductive film on the photomask surface portion is formed. By contacting the resist with the resist, generation or accumulation of static electricity on the substrate of the photomask is suppressed, and the metal film is protected from damage due to discharge of static electricity. Also, when using a photomask,
Also, at the time of cleaning accompanying this, the metal film is also protected by the conductive film from a mechanical external force. Moreover, since the above-mentioned metal film is embedded in the substrate and the above-mentioned conductive film is formed on the surfaces of the substrate and the metal film, the conductive film may be slightly thinner than the film thickness of the metal film. Is not exposed, and the dimensions are not so limited as long as the protective function of the metal film is not impaired. As a result, the metal film can be reliably covered with the conductive film, so that peeling of the metal film during cleaning of the photomask can be reliably prevented, and the mask pattern can be prevented from being damaged. Therefore, high durability can be provided.

Note that the above conductive film can have a light-transmitting property by being formed thinly.

[Embodiment 1] The following will describe one embodiment of the present invention with reference to FIG.

As shown in FIG. 1, a part of the transparent substrate 1 made of quartz or soda lime in the photomask is removed by etching, and the removed portion is made of metal such as Ta, Ti, Mo as a mask pattern. The membrane 2 is embedded. The portion where the metal film 2 is embedded is a portion where the resist is removed by development when a negative type resist is used for the glass substrate of the optical memory device (not shown), and when the positive type resist is used for the glass substrate. Is a portion where the resist remains after development.

On the surface of the transparent substrate 1, a Ta thin film 3 having a thickness of about 2 to 10 nm as a conductive film is attached by a sputtering method or the like. The Ta thin film 3 has sufficient conductivity, and also has such a light transmitting property that the resist can be exposed to ultraviolet rays and the like through the photomask because it is formed thin as described above.

In the above structure, when the guide groove is formed on the glass substrate of the optical memory device, a resist is provided in advance on the surface of the glass substrate, and the Ta thin film 3 of the photomask is brought into contact with the resist to pass ultraviolet rays or the like through the photomask. Exposure is performed, and thereafter, a guide groove is formed in the glass substrate by developing and etching. Since the Ta thin film 3 which is the conductive film is in contact with the resist during the above exposure,
Generation or accumulation of static electricity on the transparent substrate 1 is suppressed.

The metal film 2 is also protected from the mechanical external force by the Ta thin film 3 during the use of the photomask and the accompanying cleaning. Moreover, the metal film 2 is the transparent substrate 1
Embedded in the surface of the substrate 1 and the metal film 2,
Since the Ta thin film 3 is formed as described above, the film thickness of the Ta thin film 3 for preventing the metal film 2 from being exposed is not so limited in size, and even if it is thinner than the metal film 2, There is no risk of the membrane 2 being exposed. Therefore, the metal film 2 can be reliably protected by the Ta thin film 3. Therefore, the present photomask can have high durability.

FIG. 2 shows the relationship between the film thickness of the Ta thin film 3 and the ultraviolet transmittance. As is clear from the figure, as the film thickness of the Ta thin film 3 becomes thicker, the transmittance of ultraviolet rays decreases, but if the irradiation time of ultraviolet rays is lengthened accordingly, a sufficient exposure amount can be secured. In addition, although the Ta thin film 3 is used as the conductive film in the above-described embodiment, instead of this, Ti, Mo,
Various conductive films such as other metal or alloy thin films such as Ni and AuCr, and In oxide thin films can be used.

[Second Embodiment] FIG. 3 shows a second embodiment. In the second embodiment, a part of the metal film 2 '... 2'of Ta, Ti, Ni, etc. embedded in the transparent substrate 1 made of quartz or soda lime is used as a conductor portion from the surface of the transparent substrate 1. It is projected to the outside. As a result, when the photomask is brought into close contact with the resist on the surface of the glass substrate of the optical memory device, the metal films 2 '... 2'contact the resist, so that static electricity on the transparent substrate 1 is generated as in the first embodiment. Occurrence or accumulation is suppressed. In both of the first and second embodiments, the frequency of occurrence of breakage of the metal film 2 or 2'is reduced by several orders of magnitude.

〔The invention's effect〕

As described above, the photomask according to the present invention has a structure in which the conductive film is formed on the surfaces of the substrate and the metal film.

Thus, when the photomask is brought into close contact with the resist on the glass substrate, the conductive film comes into contact with the resist, so that generation or accumulation of static electricity on the substrate of the photomask is suppressed. The metal film is also protected from mechanical external force by the conductive film during the use of the photomask and the accompanying cleaning. Moreover,
Since the above-mentioned metal film is embedded in the substrate and the above-mentioned conductive film is formed on the surfaces of the substrate and the metal film, the film thickness of the conductive film for preventing the metal film from being exposed is subject to dimensional restrictions. Instead, the metal film can be surely protected even if it is thinner than the metal film. Therefore, it is possible to provide high durability, and it is possible to contribute to the improvement in mass productivity of the glass substrate type optical memory device.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. FIG. 1 is a schematic vertical sectional view of the first embodiment, and FIG.
The graph which shows the relationship between the film thickness of the Ta thin film in the Example, and the transmittance | permeability of ultraviolet rays, FIG. 3 is a schematic longitudinal cross-sectional view of a 2nd Example,
4 (a) and 4 (b) are schematic vertical sectional views of a conventional example. Reference numeral 1 is a transparent substrate (substrate), 2 is a metal film, 2'is a metal film partially forming a conductor portion, and 3 is a Ta thin film (conductor portion).

Front page continuation (72) Inventor Yoshiyuki Nagahara 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within Sharp Corporation (56) Reference JP 62-201444 (JP, A) JP 54-71987 (JP, A) JP-A-55-161240 (JP, A) JP-A-56-19054 (JP, A)

Claims (2)

[Claims] 1. A photomask in which a metal film is embedded in a substrate, wherein a conductive film is formed on the surfaces of the substrate and the metal film. 2. The photomask according to claim 1, wherein the conductive film has a light-transmitting property by being formed thinly.