CN106597807B

CN106597807B - Method for manufacturing photomask, photomask and method for manufacturing display device

Info

Publication number: CN106597807B
Application number: CN201610076681.9A
Authority: CN
Inventors: 李锡薰; 金台勋
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2015-10-20
Filing date: 2016-02-03
Publication date: 2020-06-02
Anticipated expiration: 2036-02-03
Also published as: TW201715291A; KR101771341B1; JP6586344B2; KR20170046050A; JP2017078764A; TWI598681B; CN106597807A

Abstract

A method for manufacturing a photomask, a photomask and a method for manufacturing a display device, wherein the photomask is provided with a transfer pattern with higher CD precision. Comprises the following steps: preparing a photo mask blank having a light-shielding film formed on a transparent substrate; patterning the light-shielding film to form a light-shielding portion; forming a semi-light-transmitting film on the patterned light-shielding film; and patterning the semi-light-transmitting film to form a 1 st semi-light-transmitting portion formed of a semi-light-transmitting film on the transparent substrate, a 2 nd semi-light-transmitting portion formed of a semi-light-transmitting film having a smaller film thickness than the semi-light-transmitting film in the 1 st semi-light-transmitting portion on the transparent substrate, and a light-transmitting portion exposing the transparent substrate, wherein the semi-light-transmitting film is formed of a material etched with the same etchant as the light-shielding film. In the step of patterning the semi-transparent film, substantially only the semi-transparent film is etched.

Description

Method for manufacturing photomask, photomask and method for manufacturing display device

Technical Field

The present invention relates to a photomask useful for manufacturing a display device typified by a liquid crystal display device or an organic EL (electroluminescence) display device, a method for manufacturing the photomask, and a method for manufacturing a display device using the photomask.

Background

Conventionally, a multi-tone photomask including a transfer pattern formed by patterning a light-shielding film and a semi-light-transmitting film formed on a transparent substrate is known. For example, patent document 1 describes a 4-tone photomask and a method for manufacturing the same. Patent document 2 discloses a method for manufacturing a multi-tone photomask, the method including: which utilizes subtractive film of resist patterns to reduce the number of times of drawing and development. The following describes the manufacturing method of the photomask described in each patent document in order.

Fig. 7 is a process diagram illustrating a method for manufacturing a 4-tone photomask described in patent document 1.

In this manufacturing method, finally, as shown in fig. 7 (I), the 4-tone photomask 100 having a transfer pattern including the translucent portion 140, the light shielding portion 130, the 1 st translucent portion 150A, and the 2 nd translucent portion 150B can be obtained. The respective steps will be explained below.

First, as shown in fig. 7 (a), a photomask blank 200 is prepared, and the photomask blank 200 is obtained by sequentially forming a 1 st semi-transmissive film 170A and a light-shielding film 180, which are made of materials having resistance to each other with respect to an etchant, on a light-transmissive substrate 160.

Next, as shown in fig. 7 (B), a 1 st resist pattern 210 having the transparent portion 140 and the 2 nd semi-transparent portion 150B as opening regions is formed on the light-shielding film 180 of the photomask blank 200.

Next, as shown in fig. 7 (C), the light shielding film 180 is etched using the 1 st resist pattern 210 as a mask.

Next, as shown in fig. 7 (D), the 1 st resist pattern 210 is removed (lifted off).

Next, as shown in fig. 7 (E), the 1 st semi-transmissive film 170A is etched using the light shielding film 180 as a mask.

Next, as shown in fig. 7 (F), a 2 nd semi-transmissive film 170B is formed on the light-transmissive substrate 160 and the light-shielding film 180.

Next, as shown in fig. 7 (G), a 2 nd resist pattern 250 having the translucent portion 140 and the 1 st translucent portion 150A as opening regions is formed on the 2 nd translucent film 170B.

Next, as shown in fig. 7 (H), after the 2 nd semi-transmissive film 170B and the light-shielding film 180 are etched using the 2 nd resist pattern 250 as a mask, as shown in fig. 7 (I), the 2 nd resist pattern 250 is removed.

Through the above manufacturing process, the 4-tone photomask 100 described above can be obtained.

Fig. 8 is a process diagram illustrating a method for manufacturing a multi-tone photomask described in patent document 2.

In this manufacturing method, finally, as shown in fig. 8 (F), the multi-tone photomask 300 having a transfer pattern including the light-transmitting portion 320, the light-shielding portion 310, and the semi-light-transmitting portion 315 can be obtained. The respective steps will be explained below.

First, as shown in fig. 8 (a), a photomask blank 400 is prepared, and the photomask blank 400 is obtained by forming a semi-light transmissive film 302 and a light blocking film 303 in this order on a transparent substrate 301 and forming a resist film 304 on the uppermost layer. The semi-transparent film 302 is made of a material containing a metal material such as molybdenum (Mo) or (Ta) and silicon (Si), and can be etched with a fluorine (F) -based etching solution. The light-shielding film 303 is made of a material that can be etched with an etching solution for chromium.

Next, as shown in fig. 8 (B), the photomask blank 400 is subjected to laser drawing and development, thereby forming the 1 st resist pattern 304p covering the formation region of the light-shielding portion 310 and the formation region of the semi-light-transmitting portion 315. The 1 st resist pattern 304p is formed such that the thickness of the resist film 304 in the formation region of the translucent portion 315 is thinner than the thickness of the resist film 304 in the formation region of the light shielding portion 310.

Next, as shown in fig. 8 (C), the light shielding film 303 is etched using the 1 st resist pattern 304p as a mask, thereby forming a light shielding film pattern 303 p. Then, the semi-transmissive film 302 is further etched with the 1 st resist pattern 304p as a mask, thereby forming a semi-transmissive film pattern 302p, thereby partially exposing the transparent substrate 301. The light-shielding film 303 is etched using the above-described etching solution for chromium. The etching of the semi-transmissive film 302 is performed using a fluorine (F) -based etching liquid (or etching gas).

Next, as shown in fig. 8D, the 1 st resist pattern 304p is thinned (the film thickness is reduced) so that the light-shielding film 303 is exposed in the formation region of the semi-transmissive portion 315. At this time, the resist film 304 remains in the formation region of the light shielding portion 310 where the resist film 304 is thick. Thereby, the 2 nd resist pattern 304 p' covering the formation region of the light shielding portion 310 is formed.

Next, as shown in fig. 8 (E), the light-shielding film 303 is further etched using the 2 nd resist pattern 304 p' as a mask, and the semi-light-transmitting film 302 is exposed. The light-shielding film 303 is etched using a chromium etchant in the same manner as described above.

Next, as shown in fig. 8 (F), the 2 nd resist pattern 304 p' is removed.

Through the above manufacturing process, the multi-4-tone photomask 300 can be obtained.

[ patent document 1 ] Japanese patent application laid-open No. 2007-249198

[ patent document 2 ] Japanese patent laid-open No. 2012-8545

In a manufacturing process of a display device, a photomask having a transfer pattern based on a design of a device to be finally obtained is often used. As a device, a liquid crystal display device or an organic EL display device mounted on a smartphone, a tablet terminal, or the like is required to have not only a bright screen, excellent power saving performance, and high operating speed, but also high image quality such as high resolution, a large viewing angle, and the like. Therefore, as a trend of transferring patterns of photomasks used for the above-mentioned applications, miniaturization and high density are required.

Electronic devices such as display devices are formed in a three-dimensional manner by laminating a plurality of thin films (layers) having patterns formed thereon. Therefore, improvement of the coordinate accuracy of each of the plurality of layers and mutual coordinate matching are critical. That is, if all the pattern coordinate accuracies of the respective layers do not satisfy the predetermined level, a malfunction or the like may be caused in the completed device. Further, the pattern structure of each layer tends to be finer and denser. Therefore, the allowable range of the coordinate deviation required for each layer tends to be increasingly strict.

For example, in a color filter applied to a liquid crystal display device, in order to realize a brighter display screen, the arrangement area of an optical gap control material (PS) such as a Black Matrix (BM), a main-optical gap control material (main-photo spacer) and a sub-optical gap control material (sub-photo spacer) is further reduced. Further, if the optical gap control materials are arranged to overlap on the black matrix, color filters more advantageous in terms of brightness and power consumption can be manufactured as compared with the case where they are arranged independently. Therefore, in the transfer pattern provided in the photomask, it is necessary to improve the accuracy of CD (Critical Dimension, hereinafter referred to as "pattern width") and the positional accuracy.

As a method for forming the above-described black matrix and optical gap control material (photo spacer) on a transfer object (display panel substrate or the like), there is a method of: two photomasks each having a transfer pattern suitable for each other are sequentially attached to an exposure apparatus and exposed to light, whereby the transfer patterns of the photomasks are transferred to a transfer target. However, in the method of transferring the transfer patterns of the two photomasks onto the object to be transferred while overlapping with each other, misalignment is likely to occur between the photomasks. Therefore, in order to eliminate the alignment deviation, the following method is considered: each transfer pattern was formed on 1 photomask, and each transfer pattern was transferred to a transfer target by 1 exposure step. When this method is employed, not only the Overlay position accuracy (so-called Overlay accuracy) is improved, but also the method is advantageous in terms of cost.

However, in this case, it is necessary to form a transfer pattern having a pattern for forming a black matrix and a pattern for forming an optical gap control material in a lump on 1 photomask. Therefore, the pattern for transfer of the photomask used for exposure becomes more complicated. In the 1-time exposure step, it is desirable to use a photomask having a multi-tone transfer pattern including patterns having different light transmittances corresponding to the main and sub optical gap control materials, as a pattern for forming the photomask. Specifically, a photomask of 4 gradations may be used as the transfer pattern, and the photomask of 4 gradations includes the 1 st translucent portion and the 2 nd translucent portion in addition to the translucent portion and the light shielding portion.

Patent document 1 describes a method for manufacturing such a 4-tone photomask. However, the present inventors have noticed that the problem to be solved also in this production method is present. The following description is made.

First, in the steps shown in (G) to (H) of fig. 7, the 2 nd semi-transmissive film 170B and the light-shielding film 180 are etched using the 2 nd resist pattern 250 as a mask. Specifically, the 2 nd translucent film 170B formed on the translucent substrate 160 is removed by etching in a region corresponding to the translucent portion 140 (hereinafter referred to as "1 st region"), so that the translucent substrate 160 is exposed. In a region corresponding to the 1 st semi-light-transmitting portion 150A (hereinafter referred to as "2 nd region"), the 2 nd semi-light-transmitting film 170B and the light-shielding film 180 on the 1 st semi-light-transmitting film 170A are removed by etching in this order on the light-transmitting substrate 160, and the 1 st semi-light-transmitting film 170A is exposed. In this case, etching is simultaneously performed in the 1 st region and the 2 nd region in parallel.

However, the time required until the etching is actually completed differs between the 1 st region and the 2 nd region. This is because, in the 1 st region, if the etching time corresponding to the film thickness of the 2 nd translucent film 170B has elapsed, the required etching is completed and the translucent substrate 160 is exposed, whereas in the 2 nd region, a time for further etching the light-shielding film 180 is required. As a result, at the time when the etching of the 2 nd region is completed, the undercut occurs in the 1 st region, and the pattern width (CD) changes. This phenomenon is particularly noticeable in wet etching having the property of isotropic etching. In general, the time required for etching the light-shielding film is longer than that of the semi-light-transmitting film.

Therefore, for example, while the etching for forming the 1 st semi-transmissive portion 150A is being performed in the 2 nd region, the precise etching time for forming the 1 st region as the transmissive portion 140 is completed, and thereafter, before the etching of the 2 nd region is completed, the side etching of the 2 nd semi-transmissive film 170B for defining and specifying the end portion (here, the right end) of the transmissive portion 140 occurs. As a result, the size of the light transmitting portion 140 is different from the design value. Further, as the etching time increases, CD variation generated in the entire photomask surface increases, and thus the CD accuracy of the finally obtained pattern may not satisfy a required level.

On the other hand, the method described in patent document 2 is advantageous in that a multi-tone photomask can be formed by 1 drawing and development. However, in order to form a transfer pattern of 3 gradations, the semi-light-transmitting film 302 and the light-shielding film 303 having etching selectivity to each other need to be used. Therefore, not only is there a limit to the selection of the film material, but also the load on the apparatus for forming or etching a material of a different material is increased. In the step shown in fig. 8 (E), when the light-shielding film 303 in the region corresponding to the translucent portion 315 is removed by etching, the side surface of the light-shielding film 303p and the side surface of the translucent film 302p that have been etched in the previous step are exposed at the periphery of the translucent portion 320, and thus undercut occurs. Therefore, it is difficult to maintain the CD accuracy of the transfer pattern.

As described above, there is still room for improvement in a method for manufacturing a photomask having a fine transfer pattern for use in manufacturing a high-precision product, and the present inventors have made intensive studies based on this finding and completed the present invention.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and a main object thereof is to realize a photomask having a transfer pattern with higher CD accuracy.

(1 st mode)

A first aspect of the present invention is a method for manufacturing a photomask, the photomask including a transfer pattern on a transparent substrate, the transfer pattern including a light transmitting portion, a light blocking portion, a 1 st semi-light transmitting portion, and a 2 nd semi-light transmitting portion, which are each formed by patterning a semi-light transmitting film and a light blocking film, the 1 st semi-light transmitting portion and the 2 nd semi-light transmitting portion having different light transmittances from each other, the method comprising:

a preparation step of preparing a photomask blank having a light-shielding film formed on the transparent substrate;

a light shielding film patterning step of patterning the light shielding film to form a light shielding portion;

a semi-light-transmitting film forming step of forming a semi-light-transmitting film on the light-shielding film after the patterning; and

a semi-transparent film patterning step of patterning the semi-transparent film to form a 1 st semi-transparent portion formed of a semi-transparent film on the transparent substrate, a 2 nd semi-transparent portion formed of a semi-transparent film having a smaller thickness than the semi-transparent film in the 1 st semi-transparent portion on the transparent substrate, and a transparent portion exposing the transparent substrate,

in the semi-light-transmitting film forming step, the semi-light-transmitting film is formed using a material that is etched with the same etchant as the light-shielding film,

in the semi-transparent film patterning step, substantially only the semi-transparent film is etched.

(2 nd mode)

A second aspect of the present invention is a method for manufacturing a photomask, the photomask including a transparent substrate and a transfer pattern including a light transmitting portion, a light blocking portion, a 1 st semi-light transmitting portion, and a 2 nd semi-light transmitting portion, which are formed by patterning a semi-light transmitting film and a light blocking film, respectively, and having light transmittances of the 1 st semi-light transmitting portion and the 2 nd semi-light transmitting portion different from each other, the method comprising:

a light shielding film patterning step of patterning the light shielding film;

a semi-light-transmitting film forming step of forming a semi-light-transmitting film on the patterned light-shielding film; and

a 1 st resist pattern forming step of forming a 1 st resist pattern by forming a resist film on the semi-light-transmitting film, and then drawing and developing the resist film, the 1 st resist pattern having an opening from which the resist is removed, a 1 st residual film portion in which the resist remains, and a 2 nd residual film portion in which a thinner resist remains than the 1 st residual film portion, the 1 st resist pattern having the opening corresponding to a region of the light-transmitting portion, the 1 st residual film portion corresponding to a region of the light-shielding portion and the 1 st semi-light-transmitting portion, and the 2 nd residual film portion corresponding to the 2 nd semi-light-transmitting portion;

a 1 st etching step of etching the semi-light transmissive film exposed in the opening portion using the 1 st resist pattern as a mask;

a 2 nd resist pattern forming step of forming a 2 nd resist pattern in which the semi-transparent film is newly exposed in a region corresponding to the 2 nd residual film portion by reducing a film thickness of the 1 st resist pattern; and

and a 2 nd etching step of etching the semi-transparent film of the newly exposed portion to reduce a film thickness of the semi-transparent film.

(3 rd mode)

The method of manufacturing a photomask according to claim 3 of the present invention is the method of manufacturing a photomask according to

claim

1 or 2, wherein the light-shielding film and the semi-light-transmitting film contain the same metal.

(4 th mode)

The 4 th aspect of the present invention is the method for manufacturing a photomask according to the 2 nd aspect, wherein the condition of R1 > R2 is satisfied where the etching rate in the 1 st etching step is R1 and the etching rate in the 2 nd etching step is R2.

(5 th mode)

A 5 th aspect of the present invention is the method for manufacturing a photomask according to the 2 nd aspect, wherein in the 1 st resist pattern forming step, the resist film is drawn using drawing data obtained by performing a size adjustment based on an alignment margin on a size of the region that is the 2 nd translucent portion.

(mode 6)

The 6 th aspect of the present invention is the method for manufacturing a photomask according to any one of the 1 st to 5 th aspects, wherein the 2 nd translucent portion and the light shielding portion are adjacent to each other in the transfer pattern.

(7 th mode)

The 7 th aspect of the present invention is the method for manufacturing a photomask according to any one of the 1 st to 5 th aspects, wherein the 2 nd translucent portion is adjacently surrounded by the light blocking portion in the transfer pattern.

(8 th mode)

An 8 th aspect of the present invention is a method for manufacturing a display device, including the steps of:

preparing a photomask manufactured by the method for manufacturing a photomask according to any one of claims 1 to 5; and

the photomask is irradiated with exposure light using an exposure device, and a transfer pattern provided in the photomask is transferred onto a transfer target.

(9 th mode)

A 9 th aspect of the present invention is a photomask including a pattern for transfer of at least 4 gradations, which is obtained by patterning a translucent film and a light-shielding film, respectively, on a transparent substrate, the photomask characterized in that,

the transfer pattern has:

a light-transmitting portion formed by exposing the transparent substrate;

a 1 st semi-light transmitting portion formed of the semi-light transmitting film on the transparent substrate;

a 2 nd semi-transparent portion formed of a semi-transparent film having the same composition as the semi-transparent film and having a smaller thickness than the 1 st semi-transparent portion on the transparent substrate; and

a light-shielding portion formed by sequentially laminating a light-shielding film and a semi-light-transmitting film on the transparent substrate,

the light shielding film and the semi-light transmissive film are composed of a material etched by the same etchant.

(10 th mode)

A photomask according to claim 9 of the present invention is characterized in that the light shielding portion has a portion adjacent to the 2 nd translucent portion, and a translucent film having a thickness thinner than that of the 1 st translucent portion is laminated on an edge portion adjacent to the 2 nd translucent portion.

(11 th mode)

The 11 th aspect of the present invention is the photomask according to the 9 th aspect, wherein the 1 st semi-transmissive portion and the 2 nd semi-transmissive portion do not have an adjacent portion in the transfer pattern.

(12 th mode)

A photomask according to claim 12 of the present invention is the photomask according to claim 9, wherein the 2 nd translucent portion is surrounded by the light blocking portion in the transfer pattern.

(mode 13)

A photomask according to claim 9 of the 13 th aspect of the present invention is characterized in that, in the transfer pattern, the 2 nd translucent portion is adjacently surrounded by the light shielding portion, and when widths of the light shielding portion at a position facing the 2 nd translucent portion are W1(μm) and W2(μm), respectively, a difference between W1 and W2 is 0.1(μm) or less.

(14 th mode)

A photomask according to claim 9 of the 14 th aspect of the present invention is characterized in that the light-shielding portion has a portion adjacent to the light-transmitting portion, and the light-shielding film has a reduced thickness by a portion at an edge portion adjacent to the light-transmitting portion.

(15 th mode)

A 15 th aspect of the present invention is a method for manufacturing a display device, including the steps of: preparing a photomask according to any one of the above 9 to 14; and irradiating the photomask with exposure light using an exposure device to transfer the transfer pattern of the photomask to the transferred object.

(mode 16)

A 16 th aspect of the present invention is the method for manufacturing a display device according to the 15 th aspect, wherein exposure light in a wavelength range including i-line, h-line, and g-line is applied when the exposure light is irradiated to the photomask by using the exposure apparatus.

According to the present invention, a photomask having a transfer pattern with higher CD accuracy can be realized. Further, a high-quality display device can be manufactured using the photomask.

Drawings

Fig. 1 is a diagram showing the structure of a photomask according to embodiment 1 of the present invention, where (a) is a side sectional view and (B) is a plan view.

Fig. 2 (a) to (F) are process diagrams (one of which) showing the method for manufacturing a photomask according to embodiment 1 of the present invention.

Fig. 3 (a) to (E) are process diagrams (two) showing the method for manufacturing a photomask according to embodiment 1 of the present invention.

Fig. 4 is a diagram showing the structure of a photomask according to embodiment 2 of the present invention, where (a) is a side sectional view and (B) is a top view.

Fig. 5 (a) to (F) are process diagrams (one of which) showing the method for manufacturing a photomask according to embodiment 2 of the present invention.

Fig. 6 (a) to (E) are process diagrams (two) showing the method for manufacturing a photomask according to embodiment 2 of the present invention.

Fig. 7 (a) to (I) are process diagrams showing a method for manufacturing a 4-tone photomask described in patent document 1.

Fig. 8 (a) to (F) are process diagrams showing a method for manufacturing the multi-tone photomask described in patent document 2.

Description of the reference symbols

10: photomask and method of manufacturing the same

11: light transmission part

12: light shielding part

13: 1 st semi-transparent part

14: 2 nd semi-transparent part

15: transparent substrate

16: light shielding film

17: semi-light-transmitting film

18: resist film

19: resist film

20: photo mask blank

Detailed Description

Embodiments of the present invention will be described in detail below with reference to the drawings.

< 1 > Structure of photomask of embodiment 1

Fig. 1 is a diagram showing the structure of a photomask according to embodiment 1 of the present invention, where (a) is a side sectional view and (B) is a plan view. In fig. 1 (B), the same hatching as (a) is performed to facilitate easy understanding of the correspondence relationship with the side cross-sectional view of (a).

The illustrated photomask 10 includes a 4-tone transfer pattern including a light transmitting portion 11, a light shielding portion 12, a 1 st translucent portion 13, and a 2 nd translucent portion 14. The light-transmitting portion 11 is formed in a state where the transparent substrate 15 is partially exposed. The light-shielding portion 12 is formed by forming a light-shielding film 16 and a semi-light-transmitting film 17 described later on a transparent substrate 15. The 1 st translucent portion 13 is formed by forming a 1 st translucent film 17a on the transparent substrate 15, and the 2 nd translucent portion 14 is formed by forming a 2 nd translucent film 17b on the transparent substrate 15. The 1 st semi-transmissive film 17a and the 2 nd semi-transmissive film 17b are semi-transmissive films having the same composition as each other. In the present specification, the 1 st semi-transmissive film 17a and the 2 nd semi-transmissive film 17b are simply referred to as "semi-transmissive films 17" without particularly distinguishing them. The light-shielding film 16 and the semi-light-transmitting film 17 are made of materials that are etched with the same etchant (etching solution).

The thickness of the 1 st semi-transmissive film 17a constituting the 1 st semi-transmissive portion 13 and the thickness of the 2 nd semi-transmissive film 17b constituting the 2 nd semi-transmissive portion 14 are different from each other. Specifically, the thickness of the 1 st semi-transmissive film 17a is larger than the thickness of the 2 nd semi-transmissive film 17 b. Therefore, the light transmittance (hereinafter, also simply referred to as "light transmittance") with respect to the representative wavelength of the exposure light irradiated to the photomask 10 is also different between the 1 st translucent portion 13 and the 2 nd translucent portion 14.

In the light-shielding portion 12, a light-shielding film 16 and a semi-light-transmitting film 17 are sequentially stacked on a transparent substrate 15. As shown in fig. 1 (B), the 1 st translucent portion 13 is surrounded by the light shielding portion 12 adjacent thereto. The 2 nd translucent portion 14 is also surrounded by the light shielding portion 12 adjacent thereto. Further, the light shielding portion 12 is interposed between the 1 st translucent portion 13 and the 2 nd translucent portion 14, and the light shielding portion 12 surrounds the 2 nd translucent portion 14. Therefore, the illustrated transfer pattern of the photomask 10 has no adjacent portion where the 1 st translucent portion 13 and the 2 nd translucent portion 14 are adjacent to each other. In the light shielding portion 12 adjacent to the 1 st translucent portion 13 and surrounding the 1 st translucent portion 13, only the translucent film 17a is present on the light shielding film 16. On the other hand, in the light shielding portion 12 adjacent to the 2 nd translucent portion 14 and surrounding the 2 nd translucent portion 14, both the 1 st translucent film 17a and the 2 nd translucent film 17b exist on the light shielding film 16. The 2 nd translucent film 17b is located at an edge E1 on the 2 nd translucent portion 14 side (inside) in the pattern width direction of the light shielding film 16.

< 2 > method for manufacturing photomask of embodiment 1

Next, a method for manufacturing a photomask according to embodiment 1 of the present invention will be described with reference to fig. 2 and 3. The method for manufacturing a photomask (manufacturing step) according to the present embodiment includes a preparation step, a light-shielding film patterning step, a 1 st resist removal step, a semi-transmissive film forming step, a semi-transmissive film patterning step, and a 2 nd resist removal step. The light shielding film patterning process includes a resist patterning process and a light shielding film etching process. The semi-transmissive film patterning step includes a resist film forming step, a 1 st resist pattern forming step, a 1 st etching step, a 2 nd resist pattern forming step, and a 2 nd etching step. The respective steps will be explained in turn.

[ preparation Process ]

First, in the preparation step, as shown in fig. 2 (a), a resist-equipped photomask blank 20 is prepared in which the light-shielding film 16 is formed on the transparent substrate 15 and the resist film 18 is formed on the front surface of the light-shielding film 16. As a method for forming the light shielding film 16, a known method such as a sputtering method can be used. The light shielding film 16 may have a film thickness

To the extent of (c). The resist film 18 may be formed by a coating method, and a known coater such as a spin coater or a slit coater may be used. The thickness of the resist film 18 can be set to

To the extent of (c).

As the transparent substrate 15, a substrate obtained by polishing a transparent material such as quartz glass flat and smooth can be used. As a transparent substrate used in a photomask for manufacturing a display device, a transparent substrate having a main surface of a quadrilateral shape with each side of 300 to 1500mm and a thickness of 5 to 15mm is preferably used.

The material of the light-shielding film 16 may be a film material containing, for example, Cr (chromium), Ta (tantalum), Zr (zirconium), Mo (molybdenum), W (tungsten), and the like, and an appropriate material may be selected from a monomer or a compound thereof (oxide, nitride, carbide, oxynitride, oxycarbonitride, and the like). Although not shown, a functional layer such as an antireflection layer or an etching rate adjustment layer may be provided on the front surface side (the side opposite to the transparent substrate 15) of the light-shielding film 16 or on the surface layer on the back surface side. When the antireflection layer is provided on the front surface side of the light shielding film 16, the drawing accuracy can be improved by suppressing reflection of light used for drawing the resist film 18. When an etching rate adjusting layer functioning as an etching rate reducing layer is provided on the front surface side of the light shielding film 16, the etching rate is reduced by the etching rate adjusting layer, thereby maintaining a predetermined film thickness.

The antireflection layer may be provided as a layer containing at least one of an oxide, a nitride, a carbide, an oxynitride, and a carbonitride of a metal (e.g., Cr) contained in the light-shielding film 16. Further, with respect to the antireflection layer and/or the etching deceleration layer, the composition formed as the surface layer portion may be different from the inner portion in the depth direction of the light-shielding film 16. In this case, a clear boundary may exist between the surface portion and the inner portion of the light-shielding film 16, or the composition may gradually change continuously or stepwise in the depth direction of the light-shielding film 16. The Optical Density (OD) of the light-shielding film 16 with respect to the exposure light is preferably 3.0 or more, more preferably 4.0 or more.

In the present embodiment, the light-shielding film 16 laminated on the transparent substrate 15 is made of Cr as a main component, and the light-shielding film 16 is formed with an antireflection layer made of CrO on its front surface side. The resist applied to the resist film 18 is a photoresist. The photoresist applied to the resist film 18 may be a positive photoresist or a negative photoresist, and in the present embodiment, the resist film 18 is formed of a positive photoresist. In this regard, the same applies to a resist used in a resist film formation step described later.

[ light-shielding film patterning Process ]

Next, a light shielding film patterning step of patterning the light shielding film 16 is performed. In the light shielding film patterning step, a resist pattern forming step and a light shielding film etching step are performed in this order.

(resist Pattern Forming Process)

In the resist pattern forming step, as shown in fig. 2 (B), the resist film 18 is drawn and developed, thereby forming a resist pattern 18p on the light shielding film 16 of the transparent substrate 15. The resist pattern 18p is obtained by drawing a desired pattern on the resist film 18 of the photomask blank 20 using a drawing apparatus not shown and then developing the pattern. The drawing device may be, for example, an electron beam or a laser beam, and any of them may be used. In this embodiment mode, laser drawing is applied. This is also true in the 1 st resist pattern forming step described later.

The resist pattern 18p is used to form the light-shielding portion 12 in the transfer pattern of the photomask 10 to be finally obtained. Therefore, the drawing apparatus draws the resist film 18 using drawing data for defining the light-shielding portion 12 and other regions in the final photomask 10 (see fig. 1). Then, the resist film 18 is developed to remove the exposed portion of the resist film 18, thereby obtaining a resist pattern 18 p. At this time, the light shielding film 16 is exposed in the portion where the resist film 18 is removed.

(photomask etching Process)

In the light shielding film etching step, as shown in fig. 2 (C), the light shielding film 16 is etched using the resist pattern 18p as a mask, thereby forming a pattern of the light shielding film 16 on the transparent substrate 15. In the following description, the light shielding film 16 after patterning is referred to as a light shielding film pattern 16 p. The light shielding film pattern 16p is used to define a region defining the light shielding portion 12 in the transfer pattern of the photomask 10 to be finally obtained. In this embodiment, wet etching is used for etching the light shielding film 16. Cerium ammonium nitrate was used as an etchant (etching solution).

In the present embodiment, the light shielding film 16 (single film) is the only object to be etched. The time required for this etching depends on the composition of the light-shielding film 16 and the film thickness. Therefore, the time required for etching can be determined in advance by experiments, simulations, or the like.

[ 1 st resist removal Process ]

In the 1 st resist removal step, as shown in fig. 2 (D), the resist pattern 18p is removed (stripped). Thereby, only the light-shielding film pattern 16p is formed on the main surface of the transparent substrate 15. On the main surface of the transparent substrate 15, the portions not covered with the light shielding film pattern 16p are exposed from the transparent substrate 15.

[ semi-light-transmitting film formation Process ]

In the semi-light-transmitting film forming step, as shown in fig. 2 (E), a semi-light-transmitting film 17 is formed on the transparent substrate 15 having the light-shielding film pattern 16p formed on the main surface thereof by a predetermined film forming method. As a method for forming the semi-light transmissive film 17, a sputtering method or the like can be used as in the light shielding film 16 described above. Thereby, the semi-transmissive film 17 is laminated on the exposed portion of the transparent substrate 15 and the light-shielding film pattern 16 p.

The material of the semi-light-transmitting film 17 may be a film material containing, for example, Cr (chromium), Ta (tantalum), Zr (zirconium), Si (silicon), or the like, and an appropriate material may be selected from compounds thereof (oxides, nitrides, carbides, or the like). As the Si-containing film, a compound of Si (SiON, etc.), a transition metal silicide (MoSi, etc.), or a compound thereof can be used. The compound of the transition metal silicide includes an oxide, a nitride, an oxynitride, and a oxycarbonitride, and preferably, an oxide, a nitride, an oxynitride, and an oxycarbonitride of MoSi. When the translucent film 17 is a Cr-containing film, a Cr compound (oxide, nitride, carbide, oxynitride, carbonitride, oxycarbonitride) can be used as appropriate.

In the present embodiment, Cr-containing films are used for both the light-shielding film 16 and the semi-light-transmitting film 17. When the two films contain the same metal, the materials of the light-shielding film 16 and the semi-light-transmitting film 17 do not need to have etching selectivity (resistance to the etchant) to each other when the materials are selected, except for the fact that the film formation process can be performed efficiently. That is, as the material of the light-shielding film 16 and the semi-light-transmitting film 17, a material which is etched by the same etchant or a material which is etched by an etchant containing the same component can be used, and there is an advantage that material restriction can be relaxed in this regard. A 4-tone photomask can be formed using such a film having common etching characteristics. Of course, materials having etch selectivity with respect to each other may also be used. For example, the material having the etching selectivity may be the following case: the etchant for one film (A film) exhibits an etching rate of 1/100 or less of the etching rate of the A film in the other film (B film). In addition, in the present specification, the "etching rate" refers to the thickness of a film that is melted out per unit time by etching.

On the other hand, as the optical characteristics of the semi-transparent film 17, for example, a semi-transparent film having a transmittance of exposure light of 10 to 80% can be used. More preferably, a semi-transparent film having a transmittance of exposure light of 10 to 60% may be used, and still more preferably, a semi-transparent film having a transmittance of exposure light of 10 to 40% may be used.

The thickness of the semi-transparent film 17 can be appropriately determined according to the target light transmittance, and may be set to, for example

To the extent of (c). In the present invention, the thickness of the semi-transmissive film 17 is determined according to the transmittance of the exposure light in the region of the 1 st semi-transmissive portion 13. In addition, in the semi-transmissive film 17, in order to form the 2 nd translucent portion 14 having a higher light transmittance than the 1 st translucent portion 13 by reducing the film thickness (subtraction film) of the semi-transmissive film 17 in the 2 nd etching step described later, it is preferable to determine the film thickness of the semi-transmissive film 17 in consideration of the subtraction film amount.

The semi-transparent film 17 is preferably a low phase shift film having a phase shift amount phi (degree) with respect to the exposure light of 3 phi < 90. The amount of phase shift φ (degree) of the semi-transparent film 17 with respect to the exposure light is more preferably 3 ≦ φ ≦ 60.

The semi-transparent film 17 may be a so-called phase shift film having a phase shift amount phi (degree) with respect to the exposure light of 90 < phi ≦ 270. In the present embodiment, the semi-transparent film 17 is a low phase shift film.

Here, the exposure light is irradiation light of an exposure apparatus used when performing exposure using the photomask 10 of the present embodiment, and includes exposure light including at least 1 of i-line, h-line, and g-line. By using a light source having a wavelength range including a plurality of wavelengths, preferably all of i-line, h-line, and g-line, a larger irradiation amount can be obtained. In this case, the photomask 10 can be designed such that the light transmittance and the phase shift amount with respect to the representative wavelength are within the above ranges with reference to the representative wavelength (for example, i-line) included in the wavelength range. It is more preferable that all of the 3 wavelengths are within the above range.

[ semi-transparent film patterning Process ]

Next, a semi-transparent film patterning step of patterning the semi-transparent film 17 is performed. In the semi-transparent film patterning step, a resist film forming step, a 1 st resist pattern forming step, a 1 st etching step, a 2 nd resist pattern forming step, and a 2 nd etching step are performed in this order. In the semi-transmissive film patterning step, substantially only the semi-transmissive film 17 is etched.

(resist film formation Process)

In the resist film forming step, as shown in fig. 2 (F), a resist film 19 is formed on the transparent substrate 15 on which the semi-light-transmitting film 17 is formed, in a state of covering the semi-light-transmitting film 17. The method of forming the resist film 19 and the type of resist used in the method are the same as in the case of the resist film 18 described above.

(1 st resist Pattern Forming Process)

In the 1 st resist pattern forming step, as shown in fig. 3 (a), the resist film 19 is drawn and developed to form a resist pattern 19 p. The resist pattern 19p obtained by the drawing and development here corresponds to the 1 st resist pattern. The resist pattern 19p has a stepped shape in which the thickness of the resist residual film differs depending on the region. That is, the resist pattern 19p has: an opening 21 where the resist residual film is substantially zero; a 1 st residual film portion 22 where the resist remains; and a 2 nd residual film portion 23 in which a resist thinner than the 1 st residual film portion 22 remains.

The opening 21 is a portion opened by drawing and developing the resist film 19 and removing the resist. The opening 21 is a region corresponding to the light transmitting portion 11. The 1 st residual film portion 22 is a portion having the largest residual film thickness, and is a region corresponding to the light shielding portion 12 and the 1 st translucent portion 13. The 2 nd residual film portion 23 is a portion having a film thickness smaller than that of the 1 st residual film portion, and is a region corresponding to the 2 nd translucent portion 14. Such a resist pattern 19p can be formed by the following method, for example.

Namely, the following drawing method is used: with the drawing device, the irradiation energy is made different for each region of the resist film 19 to be drawn (herein, referred to as "gradation drawing method" for convenience). For example, when drawing is performed using a laser drawing apparatus, the resist is exposed by irradiating the resist with laser light at different doses (irradiation amounts) depending on the region of a desired pattern. Specifically, a dose for completely exposing the resist film 19 to light is applied to the opening 21, and a dose smaller than that for completely exposing the resist film 19 to light is applied to the 2 nd residual film portion 23.

In the method of drawing the resist film 19 by scanning with a laser beam, drawing data is separated in advance, scanning with a laser beam is performed a plurality of times in 1-time drawing process, and the irradiation amount per region is adjusted by applying different scanning times per region. Thereby, the gradation drawing method can be implemented. For example, when the irradiation of the laser beam is performed in two divided portions, two scans are performed at a dose of about 50% when the dose for sufficiently (completely) exposing the resist film 19 is 100%. Thus, the portion subjected to only 1 of the two scans (the portion corresponding to the 2 nd residual film portion 23) is the portion subjected to irradiation with a dose of about 50%, the portion subjected to two scans (the portion corresponding to the opening 21) is the portion subjected to irradiation with a dose of 100%, and the portion not subjected to scanning in the 1 st pass is the portion not subjected to irradiation with the laser light (the portion corresponding to the 1 st residual film portion 22). Here, the irradiation with the laser beam is performed twice at a dose of 50%, but the present invention is not limited thereto, and the irradiation may be performed under the condition that the total dose of the plural laser beam irradiations is 100%. Specifically, the irradiation with the laser beam may be performed sequentially at a dose of 30% and a dose of 70%, for example, or may be performed at a combination of doses other than the above.

In addition, in 1 scan, a gradation drawing method may be performed by changing the dose according to the region. In any case, the portion of the resist irradiated with the laser light is exposed to light in accordance with the irradiation energy of the laser light at that time, and is melted out at the time of development in accordance with the degree of exposure. Therefore, after development, resist patterns (which can be said to be resist patterns having steps) having different thicknesses of resist residual films are formed depending on regions.

According to the above method, the resist pattern 19p which can be applied to the patterning in two etching steps, the 1 st etching step and the 2 nd etching step, which will be described later, can be formed by 1 drawing and developing step.

In the case of performing the gradation drawing method by a plurality of scans, the gradation drawing method can be performed in a state where the photomask substrate is placed on the drawing device. This makes it possible to zero the misalignment that occurs each time the device is placed. In the present specification, the drawing performed in a state where the photomask substrate (the transparent substrate 15 in the present embodiment) is placed on the drawing device is referred to as "1-time drawing". Therefore, for example, the following case is also referred to as "1-time drawing": after a photomask blank is placed on a drawing device and drawn in accordance with certain drawing data, the photomask blank is not detached from the drawing device and is again drawn in accordance with other drawing data.

As described above, by performing the drawing of the resist film 19 by the grayscale drawing method, the drawing of the multi-pass configuration of the semi-transmissive film 17 can be performed by 1-pass drawing. Therefore, there are the following advantages: it is possible to eliminate the misalignment of drawing which is likely to occur in the manufacturing process of a multi-tone photomask.

However, misalignment may occur between the case of drawing the resist film 19 in this step and the case of drawing the resist film 18 in the step shown in fig. 2 (B). In general, when a photomask substrate is mounted on a drawing apparatus, alignment of the photomask substrate is performed using an alignment mark or the like. However, in the multiple drawing, it is difficult to completely zero the alignment deviation due to the placement accuracy of the photomask substrate and the like.

therefore, in the present embodiment, with respect to the drawing data applied to the drawing of the resist film 19, the size of the 2 nd residual film portion 23 to be drawn (laser irradiation) is corrected as follows, that is, the size adjustment considering the alignment margin α (based on the alignment margin α) with respect to the size of the 2 nd semi-transmissive portion 14 defined by the light shielding film 16 is performed in the drawing data, and thereby, the size L1 of the 2 nd residual film portion 23 to be drawn is set to be larger than the size L2 of the region to be the 2 nd semi-transmissive portion 14, and when the maximum deviation amount that can occur as the above-mentioned alignment deviation is δ, it is preferable to set the alignment margin α to a size obtained by adding at least the above-mentioned deviation amount δ to the size L2 of the region to be the 2 nd semi-transmissive portion 14, and the resist film 19 is drawn by performing such size adjustment on the drawing data, and thereby, it is possible to prevent the deterioration of the pattern accuracy due to the alignment deviation occurring between the drawing of the resist film 18 and the drawing of the resist film 19, and, for example, the alignment margin α of the 2 nd semi-transmissive portion 14 can be set to 0.0 μm, 0.5 μm, which is excellent as the size adjustment of the alignment of the drawing data.

(etching step 1)

In the 1 st etching step, as shown in fig. 3 (B), the semi-transparent film 17 is etched using the resist pattern 19p as a mask. In this way, the semi-transmissive film 17 exposed in the opening 21 is removed by etching. As a result, the transparent substrate 15 is exposed to the opening 21.

In the present embodiment, since the semi-transmissive film 17 is a Cr-containing film as in the light-shielding film 16, the semi-transmissive film 17 can be wet-etched using an etchant (etching solution) having the same composition as the etchant (etching solution) used for etching the light-shielding film 16. In this step, the etching target is only the semi-transparent film 17 (single film). Therefore, the required time for etching depends on the composition and film thickness of the semi-light-transmitting film 17. Therefore, the time required for etching can be determined in advance by experiments, simulations, or the like.

in the present embodiment, the translucent film 17 is etched as described above, whereby a part of the transparent substrate 15 is exposed, and the exposed part becomes the translucent portion 11, and the part of the translucent film 17 surrounding the translucent portion 11 becomes the 1 st translucent portion 13. therefore, the transfer pattern of the photomask 10 finally obtained has a part where the translucent portion 11 and the 1 st translucent portion 13 are adjacent to each other, but the film thickness of the translucent film 17 is sufficiently thin as described above, and the amount of undercut by wet etching is very small, and therefore, there is substantially no influence on the patterning accuracy, and further, in the case where it is intended to obtain high CD accuracy which causes a problem even with such slight undercut, it is preferable to correct the size of the opening 21 to be drawn in the drawing data applied to the drawing of the resist film 19, that is, to estimate that the etching β (see (a) of fig. 3) taking into consideration in the size L3 of the translucent portion 11 to be finally obtained, so that the size of the translucent film 11 can be formed by adjusting the size of the translucent film 17 so as to match the size of the translucent portion 11.

In this way, in this step, the translucent portion 11 is formed by etching and removing the translucent film 17. However, in this step, the semi-transparent film 17 may not be completely removed, but a part of the film thickness may remain at this stage. In this case, when the semi-light transmissive film 17 is etched in the second etching step 2 described later, the remaining film may be further etched with the same etching solution and finally completely removed.

(2 nd resist Pattern Forming Process)

in the second resist pattern forming step, as shown in fig. 3C, a process (hereinafter, also referred to as "resist reduction process") of reducing the film thickness of the resist pattern 19p by a predetermined amount from the outermost surface is performed to form a resist pattern 19p '. the resist pattern 19p ' corresponds to the second resist pattern.A resist reduction process is performed under a condition that the resist is left in the first remaining film portion 22 while covering the semi-transparent film 17, and the resist is completely removed in the second remaining film portion 23. by performing the resist reduction process under such a condition, the resist is removed and opened in the second remaining film portion 23. then, the resist pattern 19p ' in a state where the semi-transparent film 17 (i.e., the formation region of the second semi-transparent film portion 14) is newly exposed in the opening portion can be obtained, and, as described above, in the second remaining film portion 23, in a state where the drawing data is newly exposed by estimating the alignment α and size adjustment is performed, the light-shielding film 16p in the alignment portion is also in a state where the semi-transparent film 17 is newly exposed.

The resist film reducing process is performed by, for example, ashing or the like of the resist pattern 19 p. Specifically, for example, plasma ashing, ozone ashing (ashing with ozone gas or ozone water), or the like can be applied. In addition, for example, the resist pattern 19p may be thinned with a developer.

(etching step 2)

In the second etching step, as shown in fig. 3D, a process (hereinafter, also referred to as a "semi-transparent film reduction process") of reducing the film thickness of the semi-transparent film 17 by etching the semi-transparent film 17 newly exposed by the resist reduction process is performed. In the semi-transparent film reduction process, the thickness of the semi-transparent film 17 is reduced by using the same etchant (etching solution) as described above with the resist pattern 19 p' as a mask. When the film thickness reaches a desired value of the exposure light transmittance required for the 2 nd translucent portion 14, the etching is stopped.

The etchant used for etching the portion of the semi-transparent film 17 exposed in the opening 21 may be the same as or different from the etchant used for etching the portion of the semi-transparent film 17 in this step.

In the present embodiment, the semi-transmissive film 17 is made of a Cr-based film, and therefore an etchant using an etchant for Cr can be used. However, the composition of the etching solution may be the same or different in the 1 st etching step and the 2 nd etching step. For example, when the etching rate when the semi-light transmissive film 17 is etched by the 1 st etching step is R1 and the etching rate when the semi-light transmissive film 17 is etched by the 2 nd etching step is R2, it is preferable to etch the semi-light transmissive film 17 under the condition of R1 > R2. Thus, the etching of the semi-transmissive film 17 in the semi-transmissive film reduction process proceeds relatively slowly. Therefore, the film-reducing amount of the semi-transparent film 17 by the semi-transparent film reduction treatment can be easily made to accurately meet the target value.

In order to realize different etching rates in the two steps as described above, for example, the following means can be used. That is, when the same etching solution is used in the two steps, the concentration of the etching solution used in one step is set to be different from the concentration of the etching solution used in the other step. Specifically, in the step of increasing the etching rate, a relatively high concentration of the etching solution is used, and in the step of decreasing the etching rate, a relatively low concentration of the etching solution is used. In addition, the temperature of the etching solution used in each step may be different. Alternatively, the components of the etching solution used in the respective steps may be partially or entirely different. As a means for varying the etching rate, the following method may be applied: the semi-light transmitting film 17 is formed by making the components of the semi-light transmitting film 17 different on the upper surface side and the lower surface side of the semi-light transmitting film 17.

More preferably, the semi-light-transmitting film 17 is etched under conditions of R2 × 100 > R1 > R2 × 10, more preferably R2 × 80 > R1 > R2 × 15, by making the composition of the semi-light-transmitting film 17 uniform so that the materials or the composition ratios of the etchant used in the first etching step and the etchant used in the second etching step are different from each other.

In this step, not only the semi-transmissive film 17 directly covering the transparent substrate 15 but also the semi-transmissive film 17 covering the edge E1 of the light-shielding film 16 adjacent to the 2 nd semi-transmissive portion 14 is also attenuated in the portion that was the 2 nd residual film portion 23 before the resist attenuation treatment. In addition, when the film reduction treatment of the semi-transmissive film 17 is performed in this step, there are a portion where the film is reduced and a portion where the film is not reduced. The part of the semi-transparent film 17 not to be attenuated is the 1 st semi-transparent film 17a, and the part of the semi-transparent film 17 to be attenuated is the 2 nd semi-transparent film 17 b. Thus, the 2 nd semi-transmissive portion 14 is formed by the 2 nd semi-transmissive film 17b in the portion that was the 2 nd residual film portion 23. In addition, the light-shielding film 16 adjacent to the 2 nd semi-light-transmitting portion 14 is in a state where the 1 st semi-light-transmitting film 17a and the 2 nd semi-light-transmitting film 17b having different thicknesses coexist.

[ resist removal step 2 ]

In the 2 nd resist removal step, as shown in fig. 3 (E), the resist pattern 19 p' is removed (lifted off). Thus, in the portion which was the 1 st residual film portion 22, the 1 st semi-transparent film 17a which was not thinned in the semi-transparent film thinning process is newly exposed. In addition, in the portion which was the 1 st residual film portion 22, the 1 st semi-light transmitting portion 13 is formed by the 1 st semi-light transmitting film 17a directly covering the transparent substrate 15.

Through the above steps, the photomask 10 (see fig. 1) including the 4-gradation transfer pattern including the light transmitting portion 11, the light shielding portion 12, the 1 st translucent portion 13, and the 2 nd translucent portion 14 is completed.

The transfer pattern of the photomask 10 has the following structure.

That is, the transfer pattern has: a light-transmitting portion 11 in which the transparent substrate 15 is exposed; a 1 st semi-light transmitting portion 13 formed of a 1 st semi-light transmitting film 17a on the transparent substrate 15; a 2 nd translucent portion 14 formed with a 2 nd semi-transmissive film 17b having the same composition as the 1 st translucent portion 13 and having a smaller film thickness than the 1 st translucent portion 13 on the transparent substrate 15; and a light-shielding portion 12 in which a light-shielding film 16 and a semi-light-transmitting film 17 are sequentially laminated on a transparent substrate 15, the light-shielding film 16 and the semi-light-transmitting film 17 being made of a material etched with the same etchant.

In the above configuration, the phrase "the 1 st translucent portion 13 formed of the 1 st translucent film 17a on the transparent substrate 15" refers to the 1 st translucent portion 13 in which the 1 st translucent film 17a is formed on the transparent substrate 15 and the light shielding film 16 is not formed. Similarly, the phrase "the 2 nd translucent portion 14 formed of the 2 nd translucent film 17b having the same composition as that of the 1 st translucent portion 13 and having a smaller film thickness than that of the 1 st translucent portion 13 on the transparent substrate 15" refers to the 2 nd translucent portion 14 as follows: a2 nd translucent film 17b having the same composition as the 1 st translucent portion 13 and a smaller thickness than the 1 st translucent portion 13 is formed on the transparent substrate 15, and the light shielding film 16 is not formed.

The light transmittances of the 1 st semi-transmissive portion 13 and the 2 nd semi-transmissive portion 14 with respect to the representative wavelength of the exposure light are different depending on the difference in film thickness between the 1 st semi-transmissive film 17a and the 2 nd semi-transmissive film 17 b. Specifically, the 1 st semi-transmissive section 13 has a lower light transmittance with respect to the representative wavelength of the exposure light than the 2 nd semi-transmissive section 14. The difference between the light transmittances of the 1 st translucent portion 13 and the 2 nd translucent portion 14 may be set to 3 to 15%, for example. The light transmittance of the 1 st semi-transmissive portion 13 with respect to the representative wavelength of the exposure light may be set to 15 to 60%, and the light transmittance of the 2 nd semi-transmissive portion 14 may be set to 18 to 75%, for example.

in addition, as a preferable mode here, there is a portion where the light shielding portion 12 and the 2 nd semi-transmissive portion 14 are adjacent, further, the 1 st semi-transmissive portion 13 and the 2 nd semi-transmissive portion 14 are separated by the light shielding film 16 interposed therebetween, and the semi-transmissive film 17 laminated on the light shielding film 16 includes both the 1 st semi-transmissive film 17a located on the 1 st semi-transmissive portion 13 side and the 2 nd semi-transmissive film 17b located on the 2 nd semi-transmissive portion 14 side, further, at the edge portion E1 of the light shielding film 16 where the light shielding portion 12 adjacent to the 2 nd semi-transmissive portion 14 is formed, the 2 nd semi-transmissive film 17b having a smaller film thickness than the 1 st semi-transmissive film 17a is laminated, at the 2 nd semi-transmissive portion 14 adjacent to the 2 nd semi-transmissive film 17b is also laminated at the same film thickness as the above edge portion E1, further, the size L5 (see (D) of the light shielding film 16) of the 2 nd semi-transmissive film 17b laminated at the edge portion E1 is a size corresponding to the above-application size adjustment (see fig. 3 a) of the above-transmissive data.

In another preferred embodiment, the 1 st translucent portion 13 and the 2 nd translucent portion 14 are not adjacent to each other. Specifically, the light shielding portion 12 (light shielding film 16) is interposed between the 1 st translucent portion 13 and the 2 nd translucent portion 14, and the 1 st translucent portion 13 and the 2 nd translucent portion 14 are separated by the light shielding portion 12. In such a configuration, the boundary between the 1 st translucent portion 13 and the light shielding portion 12 and the boundary between the 2 nd translucent portion 14 and the light shielding portion 12 are defined by the light shielding portion 12. The light shielding portion 12 is formed by a light shielding film 16 made of a single film. Therefore, if the manufacturing method of the present embodiment is applied to a transfer pattern in which the 2 nd translucent portion 14 is adjacent to the light shielding portion 12 and the light shielding portion 12 surrounds the 2 nd translucent portion 14, an advantage can be obtained that CD accuracy can be maintained with higher accuracy. The reason for this is as follows.

First, in the 1 st resist pattern forming step shown in fig. 3 (a), the irradiation energy at the time of drawing for forming the 2 nd residual film portion 23 is relatively smaller than the irradiation energy applied at the time of normal drawing. Therefore, the dose difference between the 1 st residual film portion 22 and the 2 nd residual film portion 23 is easily reduced, and the verticality of the cross section of the resist pattern of the 2 nd residual film portion 23 is easily lowered (the inclination of the cross section is easily conspicuous). Therefore, the resist reduction film for determining the CD needs to be strictly performed. In contrast, in the present embodiment, the 1 st translucent portion 13 is not disposed adjacent to the 2 nd translucent portion 14, and the light shielding portion 12 is disposed adjacent to the 2 nd translucent portion 14, with respect to the 2 nd translucent portion 14. In the case of such a pattern, when the light-shielding film 16 is patterned in the light-shielding film patterning step, the boundary between the 2 nd semi-transmissive portion 14 and the light-shielding portion 12 is already defined, and therefore the risk of deterioration in CD accuracy can be reduced. Therefore, CD accuracy can be maintained with higher accuracy.

in the first resist pattern forming step, an alignment margin α is set within the pattern width of the light shielding film pattern 16p obtained by patterning the light shielding film 16, and therefore, it is possible to absorb the misalignment that may occur between the drawing of the resist film 18 and the drawing of the resist film 19 by the alignment margin α, and therefore, it is possible to accurately divide and determine the region of the 2 nd translucent portion 14 in addition to the region of the light shielding film 12 by the light shielding film 16.

For example, as shown in fig. 1, a pattern in which the 2 nd translucent portion 14 is adjacent to the light shielding portion 12 and the 2 nd translucent portion 14 is surrounded by the light shielding portion 12 is more preferable because CD accuracy can be particularly maintained high.

In the transfer pattern of the photomask 10 of the present embodiment, the light transmitting portion 11 is adjacent to the 1 st translucent portion 13, and the 1 st translucent portion 13 surrounds the light transmitting portion 11.

In the transfer pattern shown in fig. 1, the pattern widths (CD) of two pattern portions of the light-shielding portion 12 adjacent to the 2 nd translucent portion 14, that is, two pattern portions at positions that are line-symmetrical with the 2 nd translucent portion 14 therebetween, that is, at positions facing each other with the 2 nd translucent portion 14 therebetween, of the light-shielding portions 12 adjacent to the 2 nd translucent portion 14 are W1(μm) and W2(μm), respectively. The design values of W1 and W2 are the same, and therefore W1 and W2 are formed (set) to the same size at the stage of drawing data. However, even if patterns having the same size are formed at the stage of drawing data, if the patterns are formed by drawing or etching a plurality of times, the patterns cannot be easily formed to have the same size as designed. That is, when drawing is performed a plurality of times, relative misalignment occurs, and the misalignment cannot be completely prevented. In the case of performing etching a plurality of times, after patterning by etching, the end face of the film after further contact with the liquid having an etching action recedes due to undercutting. Therefore, since there may be a factor that causes the final pattern CD to vary in size asymmetrically, it is not easy to form the W1 and the W2 to have the same size as designed.

However, in the present embodiment, as is clear from the above description of the manufacturing process, the region of the light shielding portion 12 is defined by the patterning of the light shielding film 16. In the patterning of the semi-transmissive film 17, only the semi-transmissive film 17 is to be etched. Therefore, the CD of the determined light shielding portion 12 is not affected. Therefore, in the case of the pattern having the same W1 and W2, W1 and W2 are substantially equal to each other on the transferred object in terms of design, and even if an error (difference) occurs between them, | W1-W2| ≦ 0.1 μm. The case where such an error occurs can be regarded as, for example, the following case: in-plane patterning variation occurs in a photomask main surface (mainly, a photomask main surface for manufacturing a display device is a quadrangle whose one side is 300mm or more).

< 3 > Structure of photomask of embodiment 2

Fig. 4 shows the structure of a photomask according to embodiment 2 of the present invention, where (a) is a side sectional view and (B) is a top view. In fig. 4 (B), the same hatching as (a) is performed to facilitate easy understanding of the correspondence relationship with the side cross-sectional view of (a). In the present embodiment, the same portions as those in embodiment 1 are denoted by the same reference numerals, and redundant description is omitted as much as possible.

The illustrated photomask 10 includes a 4-tone transfer pattern including a light transmitting portion 11, a light shielding portion 12, a 1 st translucent portion 13, and a 2 nd translucent portion 14. This transfer pattern is different from the case of embodiment 1 in the following points. That is, in the transfer pattern provided in the photomask 10 according to embodiment 2, the light-shielding portion 12 is adjacent to the light-transmitting portion 11, and the light-shielding portion 12 surrounds the light-transmitting portion 11. Further, the light transmitting portion 11 and the 2 nd translucent portion 14 are surrounded by different patterns of the light shielding portion 12, respectively.

< 4 > method for manufacturing photomask of embodiment 2

Next, a method for manufacturing a photomask according to embodiment 2 of the present invention will be described with reference to fig. 5 and 6. The method for manufacturing a photomask (manufacturing step) according to the present embodiment includes a preparation step, a light-shielding film patterning step (resist patterning step, light-shielding film etching step), a 1 st resist removing step, a semi-transmissive film forming step, a semi-transmissive film patterning step (resist film forming step, 1 st resist pattern forming step, 1 st etching step, 2 nd resist pattern forming step, 2 nd etching step), and a 2 nd resist removing step, as in embodiment 1. The respective steps will be explained in turn.

[ preparation Process ]

First, in the preparation step, as shown in fig. 5 (a), a resist-equipped photomask blank 20 is prepared in which the light-shielding film 16 is formed on the transparent substrate 15 and the resist film 18 is formed on the front surface of the light-shielding film 16.

[ light-shielding film patterning Process ]

(resist Pattern Forming Process)

In the resist pattern forming step, as shown in fig. 5 (B), the resist film 18 is drawn and developed, thereby forming a resist pattern 18p on the light shielding film 16 of the transparent substrate 15.

(photomask etching Process)

In the light-shielding film etching step, as shown in fig. 5 (C), the light-shielding film 16 is etched using the resist pattern 18p as a mask, thereby forming a light-shielding film pattern 16p on the transparent substrate 15.

[ 1 st resist removal Process ]

In the 1 st resist removal step, as shown in fig. 5 (D), the resist pattern 18p is removed (stripped).

[ semi-light-transmitting film formation Process ]

In the semi-light-transmitting film forming step, as shown in fig. 5 (E), a semi-light-transmitting film 17 is formed on the transparent substrate 15 having the light-shielding film pattern 16p formed on the main surface thereof by a predetermined film forming method.

[ semi-transparent film patterning Process ]

(resist film formation Process)

In the resist film forming step, as shown in fig. 5 (F), a resist film 19 is formed on the transparent substrate 15 on which the semi-transmissive film 17 is formed so as to cover the semi-transmissive film 17.

The steps up to this point are the same as those of embodiment 1 except that the light-shielding film 16 is patterned so that the light-shielding film pattern 16p remains in the region corresponding to the light-shielding portion 12 adjacent to the light-transmitting portion 11.

(1 st resist Pattern Forming Process)

In the 1 st resist pattern forming step, as shown in fig. 6 (a), the resist film 19 is drawn and developed to form a resist pattern 19 p. The resist film 19 is drawn using a drawing apparatus, and the gradation drawing method described in embodiment 1 above is applied to the drawing. This makes it possible to obtain a resist pattern (1 st resist pattern) 19p having a stepped shape as shown in the drawing.

here, since misalignment may occur between the case of drawing the resist film 19 in this step and the case of drawing the resist film 18 in the step shown in fig. 5 (B), in order to eliminate the possibility of this misalignment, the drawing data applied to the drawing of the resist film 19 is subjected to the size adjustment, specifically, as in the above-described embodiment 1, the size L1 of the 2 nd residual film portion 23 to be drawn is set to be larger than the size L2 of the region as the 2 nd semi-transmissive portion 14 by performing the size adjustment in the drawing data in consideration of the alignment margin α with respect to the size of the 2 nd semi-transmissive portion 14 defined by the light-shielding film 16.

in the present embodiment, the light transmitting portion 11 and the 1 st translucent portion 13 do not have a portion adjacent to each other in the transfer pattern to be finally obtained, and therefore, it is not necessary to consider the etching margin β (see fig. 3 a) described in the above-described embodiment 1, but the light transmitting portion 11 and the light shielding portion 12 are adjacent to each other, and therefore, in the present embodiment, the dimension L6 of the opening portion 21 to be drawn is set to be larger than the dimension L7 of the region serving as the light transmitting portion 11 by performing the dimension adjustment in consideration of the alignment margin α with respect to the dimension of the light transmitting portion 11 defined by the light shielding film 16 in the drawing data.

(etching step 1)

In the 1 st etching step, as shown in fig. 6 (B), the semi-transparent film 17 is etched using the resist pattern 19p as a mask. In this way, the semi-transmissive film 17 exposed in the opening 21 is removed by etching. As a result, the transparent substrate 15 is exposed to the opening 21.

In the present embodiment, since the semi-transmissive film 17 is a Cr-containing film similarly to the light-shielding film 16, the semi-transmissive film 17 can be wet-etched using an etchant (etching solution) having the same composition as the etchant (etching solution) used for etching the light-shielding film 16. In this step, the etching target is only the semi-transparent film 17 (single film). Therefore, the required time for etching depends on the composition and film thickness of the semi-light-transmitting film 17. Therefore, the time required for etching can be determined in advance by experiments, simulations, or the like.

in the present embodiment, the alignment margin α is added to the dimension L6 of the opening 21 as described above, and therefore, not only the semi-light transmissive film 17 directly laminated on the transparent substrate 15 but also a part of the semi-light transmissive film 17 laminated on the light shielding film 16 in the opening 21 is removed by etching, and therefore, after etching, the edge portion E2 of the light shielding film 16 is directly exposed in the opening 21, and the region of the edge portion E2 is formed based on the dimension of the alignment margin α applied to the dimension adjustment of the drawing data.

In the present embodiment, the light-shielding film 16 and the semi-light-transmitting film 17 are both films containing Cr. Therefore, the light-shielding film material is in contact with the etchant at the edge portion E2 of the light-shielding film 16, and thus the surface portion thereof is sometimes slightly etched. In such a case, the surface of the light shielding film 16 may be slightly damaged or the film thickness may be slightly reduced at the edge portion E2, but the light shielding performance of the light shielding film 16 is not affected. When the surface of the light-shielding film 16 is affected by etching, the reduction in film thickness is also preferably 1/5 or less, more preferably 1/1000 to 1/10, and still more preferably 1/100 to 1/10, of the film thickness of the light-shielding film 16 other than the edge portion E2.

Therefore, even when the light shielding film 16 is affected by the etching solution of the semi-light transmissive film 17, the light shielding film 16 is not etched and removed, and only a part of the film thickness thereof is reduced. That is, only the semi-transmissive film 17 is to be removed by etching. In the present invention, such etching is included, and substantially a single film is etched. Therefore, it is not necessary to apply the step of continuously etching and removing two films as disclosed in patent document 1 to the method for manufacturing a photomask of the present invention.

Here, the time required for etching the removal target film is defined as "required etching time", and the required etching time of the light-shielding film 16 is T1 and the required etching time of the semi-light-transmitting film 17 (the semi-light-transmitting film 17 before the film subtraction in fig. 6 (D)) is T2. In this case, T1 > T2 is sufficient, and T2/T1 is preferably 1/4 to 1/20. In this case, even if the surface of the light shielding film 16 is partially etched at the edge portion E2, the light shielding property of the light shielding film 16 can be maintained in a more complete state. In addition, from the viewpoint of maintaining the light-shielding property of the light-shielding film 16, the film thickness of the light-shielding film 16 in the photomask blank 20 is preferably 5 to 50 times the film thickness of the semi-light-transmitting film 17. In addition, regarding the light-shielding property of the edge portion E2 described above in the light-shielding portion 12, the Optical Density (OD) of the light-shielding film 16 is preferably 2.0 or more, more preferably 3.0 or more, and further preferably 4.0 or more also in the edge portion E2.

(2 nd resist Pattern Forming Process)

In the 2 nd resist pattern forming step, as shown in fig. 6C, a process (resist reduction process) of reducing the film thickness of the resist pattern 19p by a predetermined amount from the outermost surface is performed to form a resist pattern 19 p' as a 2 nd resist pattern. Thus, the resist is removed and the opening is opened in the 2 nd residual film portion 23, and the semi-transmissive film 17 (i.e., the region where the 2 nd semi-transmissive portion 14 is formed) is newly exposed in the opening.

(etching step 2)

In the second etching step, as shown in fig. 6 (D), a process (semi-transmissive film reduction process) is performed in which the semi-transmissive film 17 newly exposed by the resist reduction process is etched to reduce the thickness of the semi-transmissive film 17. In the semi-transparent film reduction process, the thickness of the semi-transparent film 17 is reduced using the same etchant (etching solution) as in embodiment 1 above, with the resist pattern 19 p' as a mask. When the film thickness reaches a desired value, which shows the light transmittance required for the 2 nd semi-transmissive section 14, the etching is stopped. At this time, the semi-transmissive film 17 covering the edge portion E1 of the light-shielding film 16 is also attenuated together. Thus, the semi-transmissive film 17 is divided into a 1 st semi-transmissive film 17a which is not a light-reducing film in this step, and a 2 nd semi-transmissive film 17b which is a light-reducing film in this step. In addition, in the portion that was the 2 nd residual film portion 23, the 2 nd semi-transmissive portion 14 is formed by the 2 nd semi-transmissive film 17 b.

In this step, the light shielding film 16 exposed at the edge portion E2 is also in contact with the etching solution. In the present embodiment, since both the light-shielding film 16 and the semi-light-transmitting film 17 contain Cr, they are easily subjected to etching by the same etchant. However, in this step, the semi-transparent film 17 is not removed by etching, but the thickness of the semi-transparent film 17 is reduced, and the etching time is short. Therefore, even if the influence of the etching in the etching step 1 of fig. 6 (B) is combined, the light shielding performance is hardly affected.

[ resist removal step 2 ]

In the 2 nd resist removal step, as shown in fig. 6 (E), the resist pattern 19 p' is removed (lifted off). Thus, in the portion which was the 1 st residual film portion 22, the 1 st semi-transparent film 17a which was not thinned in the semi-transparent film thinning process is newly exposed. In addition, in the portion which was the 1 st residual film portion 22, the 1 st semi-light transmitting portion 13 is formed by the 1 st semi-light transmitting film 17a directly covering the transparent substrate 15.

Through the above steps, the photomask 10 (see fig. 4) including the 4-gradation transfer pattern including the light transmitting portion 11, the light shielding portion 12, the 1 st translucent portion 13, and the 2 nd translucent portion 14 is completed.

As in embodiment 1, the photomask 10 has the following transfer pattern.

That is, the transfer pattern has: a light-transmitting portion 11 in which the transparent substrate 15 is exposed; a 1 st semi-light transmitting portion 13 formed of a 1 st semi-light transmitting film 17a on the transparent substrate 15; a 2 nd translucent portion 14 formed of a 2 nd semi-translucent film 17b having the same composition as the 1 st translucent portion 13 and having a smaller film thickness than the 1 st translucent portion 13 on the transparent substrate 15; and a light-shielding portion 12 in which a light-shielding film 16 and a semi-light-transmitting film 17 are sequentially laminated on a transparent substrate 15, the light-shielding film 16 and the semi-light-transmitting film 17 being made of a material etched with the same etchant.

In the present embodiment, the phrase "the 1 st translucent portion 13 formed of the 1 st translucent film 17a on the transparent substrate 15" also means the 1 st translucent portion 13 in which the 1 st translucent film 17a is formed on the transparent substrate 15 and the light shielding film 16 is not formed. Similarly, the phrase "the 2 nd translucent portion 14 formed of the 2 nd translucent film 17b having the same composition as that of the 1 st translucent portion 13 and having a smaller film thickness than that of the 1 st translucent portion 13 on the transparent substrate 15" refers to the 2 nd translucent portion 14 as follows: a2 nd translucent film 17b having the same composition as the 1 st translucent portion 13 and a smaller thickness than the 1 st translucent portion 13 is formed on the transparent substrate 15, and the light shielding film 16 is not formed.

However, the present embodiment is different from embodiment 1 in that the light transmitting portion 11 and the 2 nd translucent portion 14 are adjacent to the light shielding portion 12 and surrounded by the light shielding portion 12. In the transfer pattern included in the photomask 10 of the present embodiment, it is preferable that adjacent portions where the 1 st translucent portion 13 and the 2 nd translucent portion 14 are adjacent to each other are not included. In this case, all the regions of the light transmitting portion 11, the light shielding portion 12, and the semi-light transmitting portions (13, 14) present on the transfer pattern are determined by the light shielding film patterning step. Therefore, there is an advantage that the Overlay (Overlay) accuracy of the pattern of the light-shielding film 16 and the pattern of the semi-transmissive film 17 is extremely high.

in addition, in the adjacent portion between the light shielding portion 12 and the 2 nd translucent portion 14, the 2 nd translucent film 17b having a smaller film thickness than the 1 st translucent film 17a is laminated at the edge portion E1 of the light shielding film 16, and the 2 nd translucent film 17b is also laminated at the same film thickness as the above-mentioned edge portion E1 on the 2 nd translucent portion 14 adjacent to the light shielding film 16, and further, the dimension L5 (see fig. 6D) of the 2 nd translucent film 17b laminated at the edge portion E1 of the light shielding film 16 is a dimension corresponding to the alignment margin α (see fig. 6 a) applied to the dimension adjustment of the above-mentioned drawing data.

On the other hand, in the edge portion E2 of the light shielding portion 12 adjacent to the light transmitting portion 11, the semi-light transmitting film 17 laminated on the light shielding film 16 is removed, and the light shielding film 16 is exposed. In the edge portion E2 of the light-shielding portion 12 adjacent to the light-transmitting portion 11, a part of the film thickness of the light-shielding film 16 forming the light-shielding portion 12 is reduced. In this regard, it is different from the above-described embodiment 1. The surface of the light shielding film 16 in the edge portion E2 may be partially removed by etching. In this case, the Optical Density (OD) of the light-shielding film 16 including the edge portion E2 is also maintained at 2.0 or more.

In the present embodiment, also in the pattern structure of the light shielding portion 12 adjacent to the 2 nd translucent portion 14, in the stage of drawing data, the pattern widths (CD) of two pattern portions, that is, W1 and W2, which are located at line-symmetric positions with the 2 nd translucent portion 14 therebetween, that is, at positions facing each other with the 2 nd translucent portion 14 therebetween, are formed to have the same size. As is clear from the above description of the manufacturing process, the regions of the light shielding portion 12 are defined by the light shielding film patterning process. In the semi-transmissive film patterning step, only the semi-transmissive film 17 is to be etched. Therefore, the pattern widths W1 and W2 of the light shielding portion 12 defined in the light shielding film patterning process are not affected by the semi-transmissive film patterning process. Therefore, W1 and W2 are substantially equal to each other on the transferred object, and | W1 to W2| ≦ 0.1 μm even if an error (difference) occurs between them. In this regard, the same applies to the pattern widths W3 and W4 of the light shielding portion 12 adjacent to the light transmitting portion 11.

< 5. common matters between embodiment 1 and embodiment 2 >

Next, the common matters between the above-described embodiment 1 and embodiment 2 will be described.

In the 4-tone photomask 10 of the present invention, the light transmittance of the 1 st semi-transmissive section 13 with respect to the representative wavelength of the exposure light is lower than that of the 2 nd semi-transmissive section 14, and the difference therebetween may be set to 3 to 15%, for example. For example, the light transmittance of the 1 st translucent portion 13 may be set to 15 to 60% and the light transmittance of the 2 nd translucent portion 14 may be set to 18 to 75%.

In the method for manufacturing a photomask according to the present invention, substantially a single film is etched and removed in all etching steps. Therefore, the etching end point can be determined based on the accurate etching time of the film to be removed by etching. That is, according to the method for manufacturing a photomask of the present invention, it is possible to eliminate the following problems occurring in the related art, that is: after the etching is completed, the cross section of the film is also exposed to the etching solution, thereby causing degradation in CD accuracy due to undercut. Therefore, the present invention is extremely advantageous in realizing a photomask for a high-precision product.

In addition, as an advantage of the photomask of the present invention, the 1 st semi-transmissive film 17a forming the 1 st semi-transmissive portion 13 and the 2 nd semi-transmissive film 17b forming the 2 nd semi-transmissive portion 14 are originally semi-transmissive films 17 having the same composition. Therefore, the film can be formed in the same film forming step. That is, two semi-transmissive portions (13, 14) having different light transmittances can be formed by 1-time deposition of the semi-transmissive film 17. In this case, when a composition tilt occurs in the film thickness direction in the film forming process, the composition ratio may not be completely matched between the 1 st semi-transmissive portion 13 and the 2 nd semi-transmissive portion 14, but the photomask of the present invention is not necessarily excluded.

In other words, in the present invention, it is not necessary to form two types of semi-transmissive films having different compositions when forming two types of semi-transmissive portions having different exposure light transmittances. In the present invention, it is not necessary to laminate (form in multiple steps) the semi-light-transmitting films in order to obtain a desired light transmittance in each semi-light-transmitting section. Therefore, in designing a photomask for manufacturing a desired electronic device, the light transmittances of the 1 st translucent portion 13 and the 2 nd translucent portion 14 can be freely set. Further, the 1 st translucent portion 13 and the 2 nd translucent portion 14 can be accurately formed to match the target light transmittance.

Further, according to the method for manufacturing a photomask of the present invention, it is possible to form a pattern for transfer so as to have an extremely fine pattern size while suppressing deterioration in dimensional accuracy due to undercut of a film. This is because the etching time in the etching step can be an optimum etching end point based on the accurate etching time of each film. Further, since the etching time of the semi-light transmissive film 17 is short, the in-plane CD variation can be suppressed.

In the transfer pattern provided in the photomask 10 of the present invention, the 1 st translucent portion 13 and the 2 nd translucent portion 14 are not directly adjacent to each other, and the light shielding portion 12 is provided therebetween. Further, the light transmitting portion 11 and the 2 nd translucent portion 14 are not directly adjacent to each other. When the photomask 10 having such a transfer pattern is manufactured by the method for manufacturing a photomask of the present invention, the light-shielding film 16 (light-shielding film pattern 16p) patterned in the light-shielding film patterning step is used to define the light-transmitting portions 11, the light-shielding portions 12, the 1 st translucent portions 13, and the 2 nd translucent portions 14. Therefore, it is desirable in the following respects: without being affected by relative misalignment caused by multiple depictions.

The photomask 10 of the present invention is a 4-tone photomask having a light transmitting portion 11, a light shielding portion 12, a 1 st translucent portion 13, and a 2 nd translucent portion 14. Needless to say, a photomask having a different gradation or a phase shifter may be used as long as the effects of the present invention are not impaired. Further, films other than the light-shielding film 16, the 1 st semi-transmissive film 17a, and the 2 nd semi-transmissive film 17b, for example, an optical film (an antireflection film, a phase shift film, or the like) and a functional film (an etching mask film, an etching stopper film, or the like) may be provided within a range not to impair the effects of the present invention.

The application of the photomask 10 of the present invention is not particularly limited, and the present invention can be advantageously applied to a photomask for manufacturing a display device such as a liquid crystal display device or an organic EL display device in order to realize high integration and miniaturization of a pattern. And the design of the transfer pattern of the present invention is not particularly limited. That is, the present invention can be applied to, for example, a dot pattern, a dot-and-space pattern, and the like, in addition to the hole patterns illustrated in fig. 1 and 4.

Further, since the photomask of the present invention has extremely good CD accuracy, the present invention is advantageously applied to the production of a photomask in which the line width (CD) of the minimum pattern included in the transfer pattern is 3 μm or less, and can be applied to the production of a photomask in which the line width of the minimum pattern is less than 2.5 μm, and can be applied to the production of a photomask less than 2 μm as a more sophisticated product. The line width of the minimum pattern is usually 0.5 μm or more.

< 6. method for manufacturing display device

Next, a method for manufacturing a display device of the present invention will be described.

First, the use of the photomask of the present invention is not limited as described above. Furthermore, the photomask of the present invention can be particularly advantageously applied to a multi-tone photomask as follows: in a substrate for a display device formed by laminating a plurality of layers, the plurality of layers can be patterned by using 1 mask.

In this case, the method for manufacturing a display device of the present invention includes the following two steps. That is, the display device is manufactured through various other necessary steps including the following two steps: preparing a photomask obtained by the method for manufacturing a photomask of the present invention or the photomask of the present invention; and irradiating the prepared photomask with exposure light by using an exposure device, thereby transferring the transfer pattern provided in the photomask to the transferred object.

Since the photomask of the present invention is a multi-tone photomask having 4 tones or more including at least the light transmitting portion 11, the light shielding portion 12, the 1 st translucent portion 13, and the 2 nd translucent portion 14, it is possible to pattern two layers by using 1 photomask, for example. Therefore, for example, if the photomask of the present invention is applied to a manufacturing method of a liquid crystal display device, it is possible to form a pattern for black matrix formation and patterns for primary and secondary optical gap control materials by using 1 piece of photomask. Therefore, the photomask has obvious advantages in the aspects of improving the production efficiency of the display device and reducing the cost.

The photomask of the present invention can be exposed by using an exposure apparatus known in applications such as Liquid Crystal Displays (LCDs) and Flat Panel Displays (FPDs). In this case, the exposure apparatus can be, for example, a projection exposure apparatus using an equal-magnification exposure system using an exposure light including i-line, h-line, and g-line, and having an equal-magnification optical system with a Numerical Aperture (NA) of 0.08 to 0.15 and a coherence factor (σ) of 0.7 to 0.9. In the exposure, normal illumination (illumination in which zero-order light is incident perpendicularly to the photomask) or so-called anamorphic illumination such as annular illumination may be applied. Of course, other than this, for example, the photomask can be used for proximity exposure.

In addition, the use of a multi-tone photomask is advantageous in that the number of photomasks required for manufacturing a device such as a display device can be reduced, and thus the device such as a display device can be manufactured at low cost.

In the present invention, the following cost advantages are also added, namely: the number of times of drawing for forming a 4-gradation transfer pattern is only two, and the drawing apparatus takes less time, and can be produced with a short delivery date. That is, the photomask of the present invention defines each region by the wet-etched cross section formed only by the drawing and developing processes twice. Under such conditions, an ideal photomask free from misalignment can be manufactured, which is industrially significant.

The photomask according to the present invention is not limited to a photomask having a transfer pattern of 4 gradations, and includes a photomask having a transfer pattern of more than 4 gradations and a multi-gradation. For example, a photomask using another semi-transparent film, a photomask having an intermediate gray level by using an indistinguishable fine pattern in exposure, or the like is not excluded from the present invention as long as the whole or a part of the effects of the present invention are achieved.

Claims

1. A method for manufacturing a photomask, the photomask having a transfer pattern on a transparent substrate, the transfer pattern including a light transmitting portion, a light shielding portion, a 1 st semi-light transmitting portion and a 2 nd semi-light transmitting portion, which are obtained by patterning a semi-light transmitting film and a light shielding film, respectively, and the 1 st semi-light transmitting portion and the 2 nd semi-light transmitting portion having different light transmittances from each other, the method comprising:

a preparation step of preparing a photomask blank in which the light-shielding film is formed on the transparent substrate;

a light shielding film patterning step of patterning the light shielding film to form the light shielding portion;

a semi-light-transmitting film forming step of forming the semi-light-transmitting film on the transparent substrate including the light-shielding film after the patterning; and

a semi-transparent film patterning step of patterning the semi-transparent film to form a 1 st semi-transparent portion formed of the semi-transparent film on the transparent substrate, a 2 nd semi-transparent portion formed of a semi-transparent film having a smaller thickness than the semi-transparent film in the 1 st semi-transparent portion on the transparent substrate, and the transparent portion exposing the transparent substrate,

2. A method for manufacturing a photomask, the photomask having a transfer pattern on a transparent substrate, the transfer pattern including a light transmitting portion, a light shielding portion, a 1 st semi-light transmitting portion and a 2 nd semi-light transmitting portion, which are obtained by patterning a semi-light transmitting film and a light shielding film, respectively, and the 1 st semi-light transmitting portion and the 2 nd semi-light transmitting portion having different light transmittances from each other, the method comprising:

a light shielding film patterning step of patterning the light shielding film;

a semi-light-transmitting film forming step of forming the semi-light-transmitting film on the light-shielding film after the patterning;

3. The method of manufacturing a photomask according to claim 2,

the light-shielding film and the semi-light-transmitting film contain the same metal.

4. The method of manufacturing a photomask according to claim 2,

when the etching rate of the 1 st etching step is R1 and the etching rate of the 2 nd etching step is R2, the condition of R1 > R2 is satisfied.

5. The method of manufacturing a photomask according to claim 2,

in the first resist pattern forming step, the resist film is drawn using drawing data obtained by performing size adjustment based on an alignment margin on the size of the region that is the 2 nd translucent portion.

6. The method of manufacturing a photomask according to any one of claims 1 to 5,

in the transfer pattern, the 2 nd translucent portion and the light shielding portion are adjacent to each other.

7. The method of manufacturing a photomask according to any one of claims 1 to 5,

in the transfer pattern, the 2 nd translucent portion is adjacently surrounded by the light blocking portion.

8. A method for manufacturing a display device includes the steps of:

preparing a photomask produced by the method for producing a photomask according to any one of claims 1 to 5; and

9. A photomask comprising a pattern for transfer of at least 4 gradations obtained by patterning a semi-light-transmitting film and a light-shielding film on a transparent substrate,

the transfer pattern has:

a light-transmitting portion formed by exposing the transparent substrate;

a light shielding portion in which the light shielding film and the semi-light-transmitting film are laminated in this order on the transparent substrate,

10. The photomask of claim 9,

the light shielding portion has a portion adjacent to the 2 nd translucent portion, and the translucent film having a thickness thinner than that of the 1 st translucent portion is laminated on an edge portion adjacent to the 2 nd translucent portion.

11. The photomask of claim 9,

in the transfer pattern, the 1 st semi-transmissive portion and the 2 nd semi-transmissive portion do not have an adjacent portion.

12. The photomask of claim 9,

13. The photomask of claim 9,

in the transfer pattern, the 2 nd translucent portion is adjacently surrounded by the light shielding portion, and when widths of the light shielding portion at positions opposed to the 2 nd translucent portion are W1(μm) and W2(μm), respectively, a difference between the W1 and the W2 is 0.1(μm) or less.

14. The photomask of claim 9,

the light shielding portion has a portion adjacent to the light transmitting portion, and a film thickness of the light shielding film is reduced by a portion at an edge portion adjacent to the light transmitting portion.

15. A method for manufacturing a display device includes the steps of:

preparing a photomask according to any one of claims 9 to 14; and

16. The method for manufacturing a display device according to claim 15,

in the case of irradiating the photomask with exposure light using the exposure apparatus, exposure light in a wavelength range including i-line, h-line, and g-line is applied.