JPH02266356A - Manufacture of photomask for optical memory element - Google Patents

Abstract

PURPOSE:To accurately transfer the pattern of a photomask to a substrate by providing resist directly on the mask substrate, exposing it with light beams differing in intensity, forming >=2 kinds of grooves differing in depth by etching, forming a light shield film over the entire surface of the mask substrate and removing the light shield film of the part expect the grooves. CONSTITUTION:The light-transmissive mask substrate 2 is coated with the resist 6, which is exposed to at least two kinds of light A and A' differing in intensity and then developed; and etching is carried out successively to form at least two kinds of recessed parts 3 and 4 which differ in depth on the mask substrate 2 and the light shield film 8 is stuck on the surface of the mask substrate 2 including the recessed parts 3 and 4 and then the light shield film 8 stuck to the part except the recessed parts 3 and 4 is revoved. Therefore, when the resist 6 is exposed, excessive light is transmitted through the light- transmissive mask substrate 2, so the temperature rise of the resist 6 is suppressed and the exposure pattern to the resist 6 is accurately controlled. Consequently, the pattern of the photomask is accurately transferred to the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a photomask used for processing a substrate for an optical memory element.

[Conventional technology]

In recent years, optical memory devices have been actively developed as high-density, large-capacity memory devices. This optical memory device can be classified into read-only memory, additionally recordable memory, and rewritable memory depending on the type of use.

Among these, optical memory devices used as additional recordable memory and rewritable memory are capable of recording, reproducing information,
In order to guide the light beam for erasing to a predetermined position on the optical memory element, a guide track and a track address indicating the number of the guide track are usually formed in advance as grooves or protrusions on the substrate. It is provided. Further, when managing information by dividing the inside of the guide track into a plurality of sectors, sector addresses are also provided on the board in advance.

In that case, the depth (in the case of a groove) or height (in the case of a convex part) of the guide track is preferably around λ/8n, where λ is the wavelength of the light used and n is the refractive index of the substrate. On the other hand, the depth or height of a track address or sector address is λ/4
It is known that a value around n is good, but in order to satisfy these conditions, it is necessary to provide two types of grooves or protrusions with different depths or heights on the substrate.

For example, in order to provide two types of grooves with different depths on a substrate for an optical memory element, a resist is applied to the substrate, and exposure for two types of grooves is performed using two types of laser beams with different intensities. First, two types of grooves with different depths are formed in the above-mentioned resist by developing the resist, and then dry etching etc. There is a problem in that it is not suitable for mass production because it requires .

Therefore, for example, a substrate for an optical memory element having two types of grooves with different depths can be manufactured using a photomask in which two types of light shielding parts with different thicknesses are provided on a transparent mask substrate. has been proposed (Japanese Unexamined Patent Publication No. 62-2411
(See Publication No. 49).

In this case, when a resist is formed on the optical memory element substrate and exposed through the photomask, the deep grooves are exposed by the strong light that passes through the parts of the photomask that do not have light shielding parts, and the light passes through the shallow light shielding parts. This weak light is used to expose shallow grooves. Further, the deep light-shielding part of the photomask hardly transmits light, but this part corresponds to the flat part of the substrate.

The above photomask is made by uniformly forming a metal light-shielding film such as Cr on a mask substrate, applying a resist to the metal light-shielding crotch, and then applying two types of laser beams with different intensities in the same manner as described above. After being exposed to light and developed, it is manufactured by performing dry etching or the like on a metal light-shielding film through a resist.

[Problem to be solved by the invention]

However, in the above method using a photomask, when the resist is exposed to laser light to manufacture the photomask, the laser light is absorbed by the metal light-shielding film and the temperature of the resist increases. There was a problem in that it was difficult to accurately control the pattern.

Furthermore, since the metal light-shielding film in the completed photomask protrudes above the mask substrate, it is difficult to bring the photomask into close contact with the substrate when exposing the substrate for the optical memory element through the photomask. Due to this difficulty, it has been impossible to accurately transfer the pattern of the photomask onto the substrate. As a result, there has been a problem in that the shape of the groove or convex portion formed on the substrate for the optical memory element cannot be accurately controlled.

[Means to solve the problem]

In order to solve the above-mentioned problems, a method for manufacturing a photomask for an optical memory device according to the present invention includes a method for manufacturing a photomask for an optical memory device having at least two types of light shielding portions each having a different thickness. At least two types of recesses having different depths are formed in the mask substrate by applying a resist to the substrate, exposing the resist to at least two types of light having different intensities, developing it, and subsequently etching it. After applying a light-shielding film to the surface of the mask substrate including the recesses,
The present invention is characterized in that the light-shielding film adhering to areas other than the recessed portions is removed by lapping.

[For production]

In the above manufacturing method, first, two or more grooves with different depths are formed on the mask substrate by directly providing a resist on the mask substrate, exposing it to light of different intensities, and performing etching. Subsequently, after forming a light-shielding film on the entire surface of the mask substrate, the light-shielding portions Iff other than the grooves are removed, thereby manufacturing a photomask in which the light-shielding portions are embedded in the grooves.

According to the above method, when the resist is exposed to light, excess light passes through the light-transmitting mask substrate, so that the temperature rise of the resist is suppressed. This makes it possible to accurately control the exposure pattern on the resist. In addition, since the light-shielding film is embedded in the mask substrate, the photomask can be brought into close contact with the substrate of the optical memory element during the manufacture of the optical memory element, which allows the pattern of the photomask to be more accurately transferred to the substrate. It becomes like this.

[Embodiment 1] An embodiment of the present invention will be described below based on FIGS. 1 to 3.

As shown in FIG. 1(r), the photomask 1 for an optical memory element according to this embodiment has two types of grooves 3, 3, . . . and 4, 4, . are formed, and light-shielding materials 5, 5, etc. as light-shielding portions are embedded in these grooves 3, 3, 4, 4, and so on as concave portions, so that the whole is formed in a flat tn. . This photomask 1
On the substrate lO for the optical memory element shown in FIG. 3(d),
Guide tracks 12, 12... and track address 13
・13... are each formed as a convex portion.

As shown in FIG. 2, the shallow grooves 3, 3, .
The deep grooves 4, 4, . . . have shapes corresponding to the track addresses 13, 13, . . . on the substrate IO.

Hereinafter, the manufacturing procedure of the photomask 1 will be explained.

As shown in FIG. 1(a), first, a known resist 6 is applied to the surface of a mask substrate 2 having a light-transmitting property such as glass such as quartz.
Apply (photoresist).

Subsequently, as shown in FIG. 1(b), the resist 6 is exposed to light from a laser light source (not shown) through the objective lens 7. At this time, the exposure for the deep grooves 3, 3, . . . is carried out by a strong laser beam A, and the exposure for the shallow grooves 4, 4, . . . is carried out by a weak laser beam A'.

Next, when the resist 6 of the exposure method is developed, as shown in FIG. 1(C).
Deep grooves 3', 3', . . . and shallow grooves 4', 4', . . . are formed in the resist 6 as shown in FIG.

Subsequently, when the mask substrate 2 is etched through the resist 6 by a dry etching method using a gas such as CF4, the resist 6 is removed and the mask substrate 2 is etched as shown in FIG. 1(d). Groove 3, 3... and 4, 4...
... is formed. Note that after etching, the mask substrate 2
If the resist 6 remains on the resist 6, it may be removed by, for example, ashing in 0□ plasma.

Next, as shown in FIG. 1(e), the surface of the mask substrate 2 including the grooves 3, 3, 4, 4, .
A light shielding material such as Ta, Nb5Ni, etc. is deposited almost uniformly by sputtering, vapor deposition, etc. to form a light shielding film 8. Next, go! Lapping is performed using abrasive grains such as TO1, and the light shielding film 8 on the surface of the mask substrate 2 outside the inner edges of the grooves 3, 3, . . . and 4, 4, etc. is peeled off and removed. After that, groove 3.
The light shielding film 8 remaining in 3... 4, 4, . . . becomes light shielding materials 5, 5, .

Next, a procedure for processing the substrate 10 for an optical memory element using the photomask 1 will be described.

As shown in FIG. 3(a), first, a resist 11 is applied onto the substrate 10. As shown in FIG.

Subsequently, as shown in FIG. 3(b), a photomask I is placed on the substrate 10, and light B such as ultraviolet rays is emitted through the photomask L.
to expose. At this time, grooves 3 and 3 in the photomask 1
... The light B passes through the parts other than 4, 4, and so on, and some light B passes through the parts of the grooves 4, 4, and so on because the thickness of the light shielding materials 5, 5, and so on is relatively small. is transmitted. on the other hand,
Since the thickness of the light-shielding materials 5, 5, etc. is large in the grooves 3, 3..., almost no light B is transmitted therethrough.

Subsequently, when development is performed, as shown in FIG.
-11 remains slightly, and most of the resist 11 remains in the areas corresponding to the grooves 3, 3, . . . .

After that, when etching is performed using a dry etching method or the like, the grooves 4, 4, and 4 of the photomask 1 are etched as shown in FIG.
Guide tracks 12.]2.. are placed in the corresponding parts.
・ is formed, and the guide track 12 ・ 12 ・ ・ The higher track address 1 is formed in the part corresponding to the groove 3 ・ 3 ・ ・
3.13... is formed.

[Example 2] Next, a second embodiment will be described.

This second embodiment relates to a photomask for forming guide trunks 15, 15, and track addresses 16, 16, etc. as grooves in a substrate 14 for an optical memory element, as shown in FIG. It is something.

As shown in FIG. 5, in this case, grooves 20, 20, . . . are provided in the mask substrate 18 of the photomask 17, and light shielding materials 21, 21, . embedded. Each groove 20 has both end portions 20a and 2 formed as deep recesses corresponding to the flat portion of the mask substrate 18.
0a, and a central portion 20b formed as a slightly shallow recess corresponding to the guide track 15.

In addition, the manufacturing procedure of photomask 17 and photomask 1
Since the processing procedure of the substrate 14 using No. 7 is almost the same as that of the first embodiment, the explanation will be omitted.

〔Effect of the invention〕

As described above, the method for manufacturing a photomask for an optical memory device according to the present invention includes a method for manufacturing a photomask for an optical memory device having at least two types of light-shielding portions each having a different thickness. At least two types of recesses each having a different depth are formed in the mask substrate by exposing the resist to at least two types of light having different intensities, developing it, and subsequently etching it. After a light-shielding film is attached to the surface of the mask substrate including the recesses, the light-shielding film deposited on areas other than the recesses is removed by lapping.

In this way, by providing a resist directly on the mask substrate, exposing it to light of different intensities, and performing etching, two or more types of grooves with different depths are first formed on the mask substrate, and then the mask substrate is etched. After forming a light shielding film on the entire surface of
By removing the light-shielding film in areas other than the grooves, a photomask in which the light-shielding portions are embedded in the grooves can be manufactured.

In addition, in this manufacturing method, when exposing the resist, excess light passes through the transparent mask substrate, so the temperature rise of the resist is suppressed, and as a result, the exposure pattern on the resist can be accurately controlled. becomes possible. Furthermore, since the light-shielding film is embedded in the mask substrate, the photomask can be brought into close contact with the substrate of the optical memory element during the manufacture of the optical memory element, so that the pattern of the photomask can be more accurately transferred to the substrate. Therefore, it is possible to more accurately control the shape of the grooves or protrusions formed on the substrate of the optical memory element.

1.17 is a photomask, 2.18 is a mask substrate, 3.
4 and 20 are grooves (four parts), 5 and 21 are light shielding materials (light shielding parts)
, 6 and 22 are resists, and 8 is a light shielding film.

[Brief explanation of drawings]

1 to 3 show embodiments of the present invention. FIGS. 1(a) to 1(f) are schematic vertical cross-sectional views showing the manufacturing procedure of a photomask for an optical memory element. FIG. 2 is a schematic perspective view of a photomask for an optical memory element. FIGS. 3(a) to 3(d) are schematic vertical cross-sectional views showing the processing procedure of the optical memory element substrate. FIGS. 4 and 5 show other embodiments of the present invention. FIG. 4 is a schematic vertical cross-sectional view showing the optical memory element. FIG. 5 is a schematic longitudinal sectional view showing a photomask for an optical memory element.

Claims (1)

[Claims] 1. A method for manufacturing a photomask for an optical memory device having at least two types of light-shielding portions each having a different thickness, comprising applying a resist to a light-transmitting mask substrate, and applying at least two types of light-shielding portions having different strengths to the resist. By exposing and developing with two types of light and subsequently etching, at least two types of recesses each having a different depth are formed in the mask substrate, and then the surface of the mask substrate including the recesses is shaded from light. 1. A method for manufacturing a photomask for an optical memory element, characterized in that, after the protective film is attached, the light-shielding film attached to areas other than the recessed portions is removed by lapping.