JPH06148861A - Photomask and its production - Google Patents

Abstract

PURPOSE:To suppress the diffraction of light, to form patterns with good accuracy and to inexpensively form patterns by providing the light transparent parts of a light transparent substrate having the light transmissive parts and light non-transmissive parts with convex lens functions. CONSTITUTION:The surface of the mask substrate 1 consisting of light transmissive for example, glass, quartz, etc., is provided with the light non-transmissive parts 2... and the light transmissive parts 3.... These light non-transmissive parts 2... are obtd. by forming the patterns on the base of the design pattern drawings of the constituting members of, for example, a micromachine on the mask substrate 1. The light transmissive parts 3... are formed with lens parts 4... as the very small convex lens shapes having the diameter of nearly the same size as the size of the light transmissive parts 3... so that only the light past the light transmissive parts 3... is converged to a photoresist 5 as the photosensitive material applied on a substrate 6 by the lens parts 4....

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used for exposing a photosensitive material and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a method of exposing a photosensitive material to record a pattern has been used in many fields including semiconductor device manufacturing. In the field of so-called micromachines, in recent years, an attempt has been made to create a minute constituent member that constitutes a micromachine by utilizing a photolithography method among the above-mentioned recording methods by exposure.

By the way, as a method for forming a minute constituent member using the photolithography method, for example, FIG.
As shown in (a), a metal thin film 35 is formed on a substrate 36, and a photoresist 34, which is a photosensitive material, is applied thickly on the metal thin film 35. 31 is irradiated with ultraviolet rays having a wavelength λ through a photomask on which a light-impermeable pattern 32 is formed, and then development is performed to form an uneven pattern corresponding to the pattern of the photomask on the substrate 36, and thereafter, As shown in FIG. 7B, the exposed portion of the metal thin film 35 in the concave portion formed by the photoresist 34 is plated with the metal 37 to the same height as the convex portion of the photoresist 34, and the remaining photoresist There is one in which 34 is removed by etching or the like to obtain a minute constituent member of a micromachine.

By using the above-mentioned photolithography method, it is possible to form a structure made of metal having the same thickness as that of the photoresist 34 applied to the substrate 36. Therefore, depending on the thickness of the photoresist 34 applied. The thickness of the metal 37 can be easily changed. Further, since ultraviolet rays are used as a light source for exposing, it is possible to use a conventionally used exposure apparatus, it is not necessary to create a special exposure apparatus, and it is possible to produce a micro component member of a micromachine more inexpensively. can do.

[0005]

However, in the above photolithography method, light is diffracted at the edge of the pattern during exposure to form a blurred pattern image on the photoresist 34, and the photoresist 34 is thick. In this case, since the influence of light diffraction becomes significant, the pattern on the photomask cannot be accurately transferred onto the photoresist 34.

Therefore, for example, a thickness of 500 μm and a width of 50
When a micro metal constituent member of a micromachine of about μm is formed, the pattern image on the photoresist 34 becomes blurred due to the diffraction of the irradiation light, and the pattern on the photomask cannot be accurately transferred. As
There is a problem that the molding accuracy of the minute metal component is lowered.

Further, there is a method of using a parallel X-ray beam generated from SOR (Sincrotron Orbital Radiation) as a light source in order to accurately form a pattern on the thick photoresist 34 by eliminating light diffraction. Extremely large and expensive.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a photomask capable of forming a pattern on a thick photoresist accurately and inexpensively, and a method for manufacturing the same. To provide.

[0009]

A photomask according to a first aspect of the present invention comprises a light-transmissive substrate having a light-transmitting portion and a light-non-transmitting portion, and the light-transmitting portion has a convex lens function. It is characterized by.

A photomask manufacturing method according to a second aspect is
A method of manufacturing a photomask according to claim 1, comprising:
A step of applying a photoresist to a light-transmitting mask substrate, a step of exposing and developing the photoresist to form a desired photoresist pattern, and a baking step to form the photoresist pattern into a lens-shaped cross-sectional shape. A step of forming a lens shape on the mask substrate by dry etching the photoresist having the lens-shaped cross-sectional shape and the mask substrate, forming a metal thin film on the mask substrate, and forming the lens shape. And a step of removing only the metal thin film in the formed portion.

The photomask manufacturing method according to claim 3 is
A method of manufacturing a photomask according to claim 1, comprising:
A step of applying a photoresist to a light-transmissive mask substrate, a step of exposing and developing the photoresist to form a minute disk-shaped photoresist pattern on the entire surface of the mask substrate, and a step of baking to perform the photoresist A step of forming a resist pattern in a lens-shaped cross-sectional shape; a step of dry etching the photoresist having the lens-shaped cross-sectional shape and the substrate to form a plurality of minute lens shapes on the entire surface of the mask substrate; The method includes a step of forming a metal thin film thereon and a step of removing the metal thin film so as to form a desired mask pattern with one of the minute lens shapes as a unit.

[0012]

According to the structure of the first aspect, since the light transmitting portion has the function of a convex lens, it is possible to suppress the diffraction of light, so that an accurate photomask pattern can be transferred to the photoresist. Further, by appropriately shifting the focus of the light from the light transmitting portion, it is possible to change the width of the pattern transferred to the photoresist to an arbitrary size at least within the range of the spot diameter to the diameter of the light transmitting portion. A pattern can be accurately formed even on a thick photoresist. Further, since it is possible to suppress the diffraction of light, it is possible to use, for example, conventional ultraviolet rays as the light source, and thus the conventional exposure apparatus can also be used. Therefore,
The pattern can be formed on the photoresist accurately and inexpensively.

According to the structure of the second aspect, when the photomask is manufactured, dry etching is performed on the mask substrate and the photoresist pattern having a lens-shaped cross section until the photoresist is completely removed. As a result, the lens shape can be formed on the mask substrate, so that the lens shape can be easily formed without requiring a complicated process for forming the lens shape on the mask substrate. Further, by forming the metal thin film on the lens-shaped mask substrate and then removing the metal thin film only on the lens-shaped portion, the lens-shaped portion can be made a light transmitting portion and the other portions can be made a light non-transmitting portion. Therefore, a photomask having a lens function can be easily manufactured.

According to the third aspect of the invention, when manufacturing a photomask, dry etching is performed on the mask substrate and the photoresist pattern having a lens-shaped cross section until the photoresist is completely removed. As a result, the lens shape can be formed on the mask substrate, so that the lens shape can be easily formed without requiring a complicated process for forming the lens shape. Also,
After forming a metal thin film on the lens-shaped substrate,
When the light-transmitting portion is formed by removing the metal thin film so that a desired pattern can be obtained with the lens shape formed on the substrate as one unit, the light-transmitting portion is patterned with one minute lens shape as one unit. Is formed, the light transmitting portion can act as a lens. Furthermore, since a desired pattern is formed after forming a plurality of lens shapes on the entire surface of the mask substrate, only one master photomask for forming the lens shape is required, and the desired pattern is formed on the photomask. It is possible to reduce the number of master photomasks for the purpose, and it is possible to easily form a photomask pattern each time by preparing a plurality of mask substrates with a plurality of lens shapes formed on the entire surface in advance. can do. Therefore, a photomask having a lens function can be manufactured more inexpensively and easily.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

As shown in FIG. 1, the photomask according to this embodiment has a light non-transmissive portion 2, ..., A light transmissive portion 3, ... Is provided.

The light non-transmissive portions 2 ... Are formed on the mask substrate 1 with a pattern created based on, for example, a design pattern diagram of constituent members of a micromachine.

Further, the light transmissive portions 3 ... Are formed with lens portions 4 ... In the form of minute convex lenses having a diameter substantially the same as the size of the light transmissive portions 3. When the photomask is irradiated with light, only the light passing through the light transmitting portions 3 ... Is converged on the photoresist 5 as the photosensitive material applied on the substrate 6 by the lens portions 4. Has become.

Here, the characteristics of the lens portions 4 ... Will be described below with reference to FIG.

First, assuming that the focal length of the lens unit 4 is F, the lens diameter is R, and the wavelength of light used for exposure is λ, the spot diameter r formed by image formation is r / 2≈λ / (R / F ) ... It is represented by. Further, the depth of focus D at this time is expressed as D / 2≈λ / (R / F) ² ...

Next, using the above formula, with the wavelength λ of the light used for exposure being 0.4 μm, various focal lengths F,
Spot diameter r from combination of lens diameter R and wavelength λ
Table 1 shows the results of obtaining the depth of focus and the depth of focus D.

[0022]

[Table 1]

From Table 1 above, for example, the focal length F is 550.
μm and lens diameter R is 50 μm, spot diameter r
Is about 8.8 μm and the depth of focus D is about 400 μm.
A pattern can be formed with a width of μm and a minimum width of 8.8 μm. Further, when the minute pattern as described above is not necessary, a large pattern can be obtained by shifting the substrate 6 from the focus of the lens portions 4 ... Therefore, by forming the lens portions 4 ... Having the characteristics as shown in Table 1 above in the light transmitting portions 3, ..., It is possible to accurately transfer a fine pattern having a desired thickness and width to the photoresist 5. It is like this. However, the width of the pattern is limited to the range from the lens diameter to the spot diameter.

The width of the pattern, that is, the width of the light transmitting portions 3 and the diameter R of the convex lens portion 4 are formed to have substantially the same size as shown in FIG. Without being limited to this, for example, as shown in FIGS. 3A and 3B, the light transmitting portions 10 between the light non-transmitting portions 9 ... Even when a plurality of lens units 11 ... Is provided, it is possible to have the same function as the lens units 4 shown in FIG. 1 and, as shown in FIGS. Even when a plurality of small convex lenses 12 are provided in the transmissive portion 10, it is possible to have the same function as the lens portions 4 shown in FIG. However, when a plurality of small convex lenses 12 are provided in the light transmitting portion 10, it is necessary to expose the entire lens 12 to the light transmitting portion 10 of the pattern.

Here, an example of a method for manufacturing the above photomask will be described below with reference to FIG. 2 [manufacturing method 1].

First, as shown in FIG. 2A, a positive type is formed on the surface of a light-transmissive substrate 1 made of, for example, glass or quartz, which has been subjected to a wafer pretreatment so that a photoresist can be easily applied. The photoresist 7 is uniformly applied.
In this embodiment, this photoresist is 100 ° C.
Although AZ1400 manufactured by Shipley Co., which deforms at ˜130 ° C., is used, it is not particularly limited.

Next, as shown in FIG.
After exposure using a master photomask on which a required pattern is formed by the D method or the like, development is performed,
An uneven pattern of the photoresist 7 is formed on the substrate 1.

Then, as shown in FIG. 2 (c), 110
Baking is performed at ˜130 ° C., and the photoresist 7 having the uneven pattern is formed to have a lens-shaped cross-sectional shape.

Then, as shown in FIG. 2D, the substrate 1 having the lens-shaped photoresist 7 is CF ₄ , C
Dry etching is performed by a gas such as HF ₃ until the photoresist 7 is removed to form convex lens portions 4 ... On the substrate 1.

Further, as shown in FIG. 2 (e), the substrate 1
A metal thin film 2 of Cr, Ta, Al, Ni, or an alloy thereof, for example, is formed on the formation side of the lens portions 4 by the vapor deposition or sputtering method.

Then, as shown in FIG. 2 (f), a photoresist 8 is further applied on the substrate 1 on which the metal thin film 2 is formed, and the photoresist 8 is removed only at the portions corresponding to the lens portions 4 ... After exposure, development is performed as described above.

Then, as shown in FIG. 2 (g), after the photoresist 8 in the portion corresponding to the lens portions 4 is removed, the exposed metal thin film 2 is nitric acid, sulfuric acid, hydrofluoric acid,
Wet etching is performed with hydrochloric acid or a mixed solution thereof to expose the convex lens portions 4 on the substrate 1. Further, dry etching is performed until the remaining photoresist 8 is removed by a gas such as CF ₄ or CHF ₃ , and as shown in FIG. 2 (h), the metal thin film forming the pattern forms the light non-transmissive portions 2. Then, a photomask in which the convex lens portions 4 ... Form the light transmitting portions 3 ... Is manufactured.

Another example of the method for manufacturing the above photomask will be described below with reference to FIG. For convenience of description, members having the same member numbers as in FIG. 1 are regarded as the same members, and the description thereof will be omitted [Manufacturing method 2].

First, a photoresist (not shown) is applied to the transparent substrate 1 made of glass, quartz, etc.
As shown in (a), a master photomask in which a plurality of circular patterns are formed so that the lens portions 4 ... Designed based on the design guidelines for the lens portion in Table 1 above are formed on the entire surface of the substrate 1. After exposure using, the development is performed. Then, after development, baking is performed to form a plurality of circular patterns, which are convex portions of the concave-convex pattern formed on the entire surface of the substrate 1, into a convex lens shape. As the photoresist used here, AZ1400 manufactured by Shipley Co., which is deformable at 100 ° C. to 130 ° C., is used similarly to the one used in the manufacture of the above-mentioned photomask, but it is not particularly limited. . Thereafter, a lens portion corresponding to the plurality of convex lens portions 4 formed on the substrate 1 is formed by the photoresist, and dry etching is performed until the photoresist is exhausted by a gas such as CF ₄ , CHF ₃ or the like. A plurality of convex lens portions 4 ... Are formed on the surface 1.

Next, a metal thin film of, for example, Cr, Ta, Al, Ni, or an alloy thereof is formed on the entire surface of the substrate 1 on which the convex lens portions 4 are formed along the shape of the lens portions 4. It is formed by vapor deposition or sputtering. Further, a photoresist is applied on the substrate 1, and exposed using a photomask having a desired pattern,
After the development, the exposed and developed portion of the metal thin film is exposed. Then, corresponding to the exposed metal thin film, wet etching is performed with nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, or a mixture thereof to expose the convex lens portions 4 ... On the substrate 1. After that, dry etching is performed until the metal thin film is exposed by removing the photoresist remaining by the gas such as CF ₄ , CHF _{3 and the} like, as shown in FIG.
A photomask having the light non-transmissive portions 2 ...

However, in the above-mentioned manufacturing method 2, since the plurality of lens portions 4 are previously formed on the entire surface of the substrate 1, in order to act as a lens, at least one lens portion 4 in the pattern is used as a unit to transmit light. It is necessary to form a part.

From the above, the production of the constituent members in a micromachine such as a micromachine utilizing the pattern formation by the photomask in this embodiment will be described below with reference to FIG.

First, a photomask having a required pattern is provided on a metal substrate 6 having a photoresist 5 applied on its surface. After that, the photoresist 5 is exposed through the photomask by an exposure device that radiates ultraviolet rays, for example. Since the exposed portion is melted by the developer, an uneven pattern corresponding to the pattern formed on the photomask by the photoresist 5 is formed on the substrate 6.

Next, the concave portion formed on the substrate 6 is plated with a metal to the same thickness as the coating thickness of the photoresist 5, and then the photoresist is removed by dry etching to obtain a structure made of a metal.

As described above, when a fine pattern is formed by the photolithography method or the like, the lens portion 4 having the function of a convex lens is formed on the light transmitting portions 3 of the photomask.
.. is formed, the irradiation light can be suppressed and the irradiation light can be focused on the photoresist 5. Therefore, a desired pattern can be accurately transferred regardless of the thickness of the photoresist. In addition, since it can suppress the diffraction of light, it can be used as a SOR (Sincrotoron Orbital) light source.
Since it is not necessary to use a parallel X-ray beam generated from radiation and ultraviolet rays can be used, a conventional exposure apparatus can be used, and a pattern can be formed inexpensively and accurately.

On the other hand, as a method of manufacturing a photomask, in [manufacturing method 1], as shown in FIG. 2, the photoresist 7 is completely removed from the substrate 1 and the photoresist pattern having a lens-shaped cross section. Since the lens portions 4 ... Can be formed on the substrate 1 by performing dry etching until it is removed, the lens portions 4 ... Can be easily formed without requiring a complicated process for forming the lens portions 4. be able to. Further, after forming the metal thin film on the substrate 1 on which the lens portions 4 are formed, the metal thin film is removed only from the lens portions 4 so that the lens portions are light transmitting portions and the other portions are light non-transmitting portions. Therefore, a photomask having a lens function can be easily manufactured.

As a method of manufacturing a photomask, in [manufacturing method 2], as shown in FIG. 5, a metal thin film is formed on the substrate 1 on which the lens portions 4 are formed and then formed on the substrate 1. When the metal thin film is removed so that a desired pattern can be obtained by using one of the lens portions 4 formed as one unit, the portion from which the metal thin film is removed can be used as the light transmitting portion, and the light transmitting portion can be formed. Lens section 3 ...
Since it is formed so as to include at least one unit of, the light transmitting portions 3 ... Can act as a lens. Further, since the desired pattern is formed after the plurality of lens portions 4 are formed on the entire surface of the substrate 1, only one master photomask for forming the lens portions 4 is required, and the pattern is formed. Therefore, it is possible to reduce the number of master photomasks required, and by forming a plurality of substrates in which a plurality of lens portions are formed on the entire surface of the mask substrate in advance, a pattern can be formed as needed. Therefore, a photomask having a lens function can be manufactured more inexpensively and easily.

In this embodiment, the convex lens portion is provided in the light transmitting portion of the photomask, but the present invention is not limited to this, and it is assumed that the light transmitting portion of the photomask has a convex lens function. For example, as shown in FIG. 6, in the transparent mask substrate 21 having a light transmitting portion 23 ... And a light non-transmitting portion 22 ..., the light transmitting portion 23 ... Has a convex lens function by using the above-mentioned formula. In some cases, the refractive index distributions 24 are formed as described above to act as convex lenses in the light transmitting portions 23. In this case also, the convex shape formed in the light transmitting portions 3 in the above-described embodiment. It is possible to obtain the same effect as that of the lens section 4 ...

[0044]

As described above, the photomask of the present invention comprises a light-transmissive substrate having a light-transmitting portion and a light-non-transmitting portion, and the light-transmitting portion has a convex lens function. This is a feature.

Therefore, since the light transmitting portion has a convex lens function, it is possible to suppress the diffraction of light, so that it is possible to form a pattern accurately even when the applied photoresist is thick, and Since ultraviolet rays can be used as the light source, the conventional exposure apparatus can be used, and the pattern can be formed at a lower cost.

The photomask manufacturing method according to claim 2 is
As described above, a step of applying a photoresist to the light-transmitting mask substrate, a step of forming a desired photoresist pattern by exposing and developing the photoresist,
A step of forming the photoresist pattern into a lens-shaped cross-sectional shape by baking, a step of dry-etching the photoresist having the lens-shaped cross-sectional shape and the mask substrate, and forming a lens shape on the mask substrate,
The configuration is characterized by including a step of forming a metal thin film on the mask substrate and a step of removing only the metal thin film in the portion formed in the lens shape.

Therefore, since the lens portion is formed on the substrate by integrally processing the mask substrate and the photoresist by dry etching, it is not necessary to separately provide a mechanism for forming a lens shape on the mask substrate, and As a result, it is possible to easily form a lens shape in a necessary portion, and as a result, it is possible to easily manufacture a photomask having a convex lens function.

A method of manufacturing a photomask according to claim 3 is
As described above, a step of applying a photoresist to a light-transmitting mask substrate, a step of exposing and developing the photoresist to form a minute disk-shaped photoresist pattern on the entire surface of the mask substrate, and a baking step. And forming the photoresist pattern into a lens-shaped cross-sectional shape, and dry-etching the lens-shaped cross-sectional photoresist and the substrate to form a plurality of minute lens shapes on the entire surface of the mask substrate. And a step of forming a metal thin film on the mask substrate, and a step of removing the metal thin film so as to form a desired mask pattern with one of the minute lens shapes as one unit. is there.

Therefore, in addition to the effect of the second aspect, by forming a plurality of lens shapes on the entire surface of the mask substrate, it is possible to provide a plurality of mask substrates on which a plurality of minute lens shapes are formed in advance. , A photomask having a required pattern can be easily manufactured each time, and only one master photomask for forming the lens shape on the mask substrate is required, so that the entire master when forming the pattern The number of types of photomasks can be reduced, and the manufacturing cost of the photomasks can be reduced.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an exposure action by a photomask in one embodiment of the present invention.

FIG. 2 shows a procedure for producing the photomask of FIG. 1, FIG. 2A is an explanatory view showing a state where a photoresist is applied to a transparent mask substrate, and FIG. It is explanatory drawing which shows the state which the pattern of the photoresist was developed, and the same figure (c) is explanatory drawing which shows the state in which the photoresist formed in the pattern was formed in the lens shape by baking. FIG. 3D is an explanatory view showing a state where a lens portion is formed on the mask substrate by dry etching, and FIG. 6E shows a state where a metal thin film is formed on the mask substrate surface where the lens portion is formed. FIG. 6F is an explanatory diagram showing a state in which a photoresist is applied on the metal thin film, and FIG.
[Fig. 3] is an explanatory diagram showing a state where the photoresist of only the lens portion is removed, and Fig. 6H is an explanatory diagram showing a state where the metal thin film of the lens portion is removed.

3A and 3B show a photomask according to another embodiment of the present invention, wherein FIG. 3A is a plan view and FIG. 3B is a sectional view taken along the line AA.

4A and 4B show a photomask according to still another embodiment of the present invention, wherein FIG. 4A is a plan view and FIG. 4B is a sectional view taken along the line BB.

FIG. 5 is a plan view showing a method of forming a photomask according to another embodiment of the present invention, wherein FIG. 5A shows a state where a circular pattern of photoresist is formed on the entire surface of a mask substrate. FIG. 3B is a plan view showing a state in which the pattern and the lens portion are formed on the mask substrate.

FIG. 6 is a configuration diagram showing a photomask in still another embodiment of the present invention.

7A and 7B show pattern formation by a conventional photomask, and FIG. 7A is an explanatory diagram showing a state in which a pattern is formed on a photoresist by a photomask, and FIG. FIG. 6 is an explanatory diagram showing a state in which the pattern formed above is plated with metal.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mask substrate 2 Light non-transmissive part 3 Light transmissive part 4 Lens part (lens shape) 5 Photoresist 21 Mask substrate 22 Light non-transmissive part 23 Light transmissive part 24 Refractive index distribution

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yorisei Ishii 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Kenji Ota 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Within the corporation

Claims (3)

[Claims] 1. A photomask comprising a light transmissive substrate having a light transmissive portion and a light non-transmissive portion, wherein the light transmissive portion has a convex lens function. mask. 2. A step of applying a photoresist to a light-transmitting mask substrate, a step of exposing and developing the photoresist to form a desired photoresist pattern, and baking to form the photoresist pattern into a lens shape. A step of forming a lens shape on the mask substrate by dry etching the photoresist having the lens-shaped cross section and the mask substrate, and a step of forming a metal thin film on the mask substrate. And a step of removing only the metal thin film in the lens-shaped portion. 3. A step of applying a photoresist to a light-transmissive mask substrate, a step of exposing and developing the photoresist to form a minute disk-shaped photoresist pattern on the entire surface of the mask substrate, and baking. And forming the photoresist pattern into a lens-shaped cross-sectional shape, and dry-etching the lens-shaped cross-sectional photoresist and the substrate to form a plurality of minute lens shapes on the entire surface of the mask substrate. And a step of forming a metal thin film on the mask substrate, and a step of removing the metal thin film so that one of the minute lens shapes forms a desired mask pattern as one unit. Production method.