1. A photomask for use in manufacturing a display device, the photomask being used for forming a hole pattern having a dimension Dp, where Dp is 3 μm or less, on a transferred body using ultraviolet exposure light,

a transparent substrate having a pattern for transfer including a hole pattern,

the hole pattern in the transfer pattern is composed of a light transmitting portion surrounded by a half tone region,

the phase difference theta between the light transmission part and the half-tone region is approximately 180 degrees with respect to the light with the reference wavelength contained in the mid-ultraviolet exposure light for exposing the photomask, and

the transmittance T of the half-tone region for light of the reference wavelength is 10% or more and 35% or less.

2. The photomask of claim 1,

the hole pattern in the transfer pattern is formed of a light transmitting portion formed by patterning a phase shift film formed on the transparent substrate, the transparent portion exposing the transparent substrate,

in the half-tone region, the phase shift film is formed on the transparent substrate,

the phase shift film has a phase shift amount of substantially 180 degrees with respect to light of the reference wavelength and has a transmittance T, T being 10% T35%.

3. A photomask for use in manufacturing a display device, the photomask being used for forming a hole pattern having a dimension Dp, where Dp is 3 μm or less, on a transferred body using ultraviolet exposure light,

a transparent substrate having a pattern for transfer including a hole pattern,

the hole pattern in the transfer pattern is composed of a light transmitting portion surrounded by a half tone region,

when the reference wavelength is lambda 1 and lambda 1 is less than 365nm, the phase difference theta between the light transmission part and the half-modulation region is 180 degrees for the light with the wavelength of the lambda 1, and the transmissivity T of the half-modulation region for the light with the wavelength of the lambda 1 is more than or equal to 10% and less than or equal to 35%.

4. The photomask of claim 3,

the hole pattern in the transfer pattern is formed of a light transmitting portion formed by patterning a phase shift film formed on the transparent substrate, the transparent portion exposing the transparent substrate,

in the half-tone region, the phase shift film is formed on the transparent substrate,

the phase shift film has a phase shift amount of 180 degrees with respect to light of the wavelength of λ 1 and has a transmittance T, T being 10% or more and 35% or less.

5. The photomask of any of claims 1 to 4,

the transfer pattern includes an isolated hole pattern.

6. The photomask of any of claims 1 to 4,

the transfer pattern has an approach hole pattern including 2 or more hole patterns in close proximity.

7. The photomask of claim 6,

the distance between the centers of gravity of 2 of the hole patterns included in the proximity hole pattern is 9 [ mu ] m or less.

8. The photomask of any of claims 1 to 4,

when the size of the hole pattern in the transfer pattern is Dm, Dm is larger than Dp.

9. The photomask of any of claims 1 to 4,

the reference wavelength is 313nm or 334 nm.

10. The photomask of claim 8,

Dm/Dp is 1.1-1.8.

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

a step of preparing a photomask according to any one of claims 1 to 10; and

an exposure step of exposing the photomask with ultraviolet exposure light,

the light for mid-ultraviolet exposure contains a wavelength region with the wavelength lambda of 200 nm-400 nm, and does not contain the wavelengths with the lambda larger than 400nm and the lambda smaller than 200 nm.

12. The method for manufacturing a display device according to claim 11,

through the exposure step, a hole pattern having a dimension Dp of 3 μm or less is formed on the transferred object.

Background

Patent document 1 describes a phase shift mask blank for manufacturing a display device and a phase shift mask manufactured from the phase shift mask blank. Patent document 1 also describes a technique of exposing the phase shift mask with the use of composite light including i-lines, h-lines, and g-lines.

Patent document 2 describes a phase shift mask blank for manufacturing a display device, which is provided with a phase shift film having optical characteristics in which wavelength dependence on exposure light is suppressed. The transmittance of the phase shift film in the phase shift mask blank to a wavelength of 365nm is in a range of 3.5% to 8%, the phase difference at the wavelength of 365nm is in a range of 160 degrees to 200 degrees, and the amount of change in the transmittance in the range of 365nm to 436nm depending on the wavelength is within 5.5%.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 2014-194531

[ patent document 2] Japanese patent laid-open No. 2015-102633

Disclosure of Invention

[ problems to be solved by the invention ]

In recent years, display devices including LCD (liquid crystal display) and OLED display (organic EL display) have been demanded to have display performance such as power saving and response speed of moving images, in addition to bright and high-definition display performance. Therefore, it is considered that the pattern of the photomask used in the manufacturing process of these display devices is also required to be more miniaturized and highly integrated, and a technique for finely resolving the pattern of the photomask to a transfer object (a display panel substrate or the like) is also required.

However, if the transfer pattern of the photomask cannot be optically resolved onto the object to be transferred, a display device having a desired fine pattern cannot be configured. Here, the spatial resolution of the optical image can be expressed by the Rayleigh (Rayleigh) resolution reference equation, that is, the following equation (1).

δ＝k1×λ/NA…(1)

Where δ is the minimum resolving line width, λ is the exposure wavelength, NA is the numerical aperture of the optical system of the exposure apparatus, and k1 is a coefficient also called the k1 factor.

In the field of Display devices (hereinafter also referred to as FPDs (Flat Panel displays)), a specific wavelength region of a high-pressure mercury lamp is used as light for exposure. That is, the following applications of exposure light are known: the exposure light is light of a wavelength band (hereinafter, also referred to as a broad wavelength band) in which light of a plurality of wavelengths is included and mixed, and particularly light of 3 wavelengths including g-line (wavelength 436nm), h-line (wavelength 405nm), and i-line (wavelength 365nm) of light of a wavelength included in light of a high-pressure mercury lamp (see patent documents 1 and 2).

On the other hand, according to the above equation (1), in order to improve the resolution (that is, to reduce the minimum resolution line width δ) with respect to a fine pattern, it is effective to reduce λ or increase NA. However, as for the increase in NA, the following formula (2) can reduce the depth of focus, and thus it can be understood that the stability of the photolithography process is relatively deteriorated. Equation (2) is also called a Rayleigh (Rayleigh) focal depth equation.

DOF＝k2×λ/NA²…(2)

Here, dof (depth of focus) means a depth of focus, and k2 is a coefficient.

The magnitude of the value on the left side of equation (2) is inversely related to the superiority and inferiority of the resolution reference equation (1)). That is, in the formula (1), the left value is preferably small, but in the formula (2), the left value is conversely expected to be large.

Thus, the minimum resolution linewidth δ and the depth of focus DOF show a trade-off correlation. However, since DOF shown in expression (2) deteriorates in proportion to the square of NA, if the resolution is increased at the same level, it can be said that it is more reasonable to shorten the wavelength of exposure light than to increase NA. That is, the decrease in DOF can be suppressed while improving the resolution.

As a method for easily achieving a shorter wavelength from the above-described broadband exposure environment, instead of a mixed wavelength exposure including g-line, h-line, and i-line, it is conceivable to effectively reduce the wavelength by switching to an exposure based on a single wavelength of i-line. However, this method means that the contribution of 2 wavelengths among the above 3 wavelengths is cut off, and the work amount per unit time is reduced to 1/3 by simple calculation. In the field of FPD production, in addition to the above resolution, another important factor is production efficiency, and thus it is sometimes difficult to adopt a single wavelength.

Therefore, a method of shifting the center of gravity to the short wavelength side while maintaining a broadband exposure environment is considered. In the high-pressure mercury lamp, since several wavelength groups having a peak of light intensity exist on a shorter wavelength side than the i-line, the above method is a method using light of the wavelength group as exposure energy.

The present inventors have made extensive studies on a photomask which exhibits excellent transferability in response to a new broadband exposure environment in which the wavelength region used in conventional exposure light is shifted to the short wavelength side, and have completed the present invention.

[ means for solving the problems ]

The invention according to claim 1 is a photomask for manufacturing a display device, the photomask being used for forming a hole pattern having a dimension Dp of 3 μm or less on a transfer object by using ultraviolet exposure light,

a transparent substrate having a pattern for transfer including a hole pattern,

the hole pattern in the transfer pattern is composed of a light transmitting portion surrounded by a half tone region,

a phase difference theta between the light transmitting portion and the half-tone region is substantially 180 degrees with respect to light of a reference wavelength included in mid-ultraviolet exposure light for exposing the photomask,

and the transmittance T of the half-tone region for light of the reference wavelength is 10% or more and T or less and 35% or less.

The 2 nd aspect of the present invention is the photomask according to the 1 st aspect, wherein the hole pattern in the transfer pattern is formed of a light transmitting portion formed by patterning a phase shift film formed on the transparent substrate, the transparent substrate being exposed in the light transmitting portion,

in the half-tone region, the phase shift film is formed on the transparent substrate,

the phase shift film has a phase shift amount of substantially 180 degrees with respect to light of the reference wavelength and has a transmittance T of 10% T35%.

A third aspect of the present invention is a photomask for manufacturing a display device, the photomask being used for forming a hole pattern having a dimension Dp of 3 μm or less on a transfer object using ultraviolet exposure light,

a transparent substrate having a pattern for transfer including a hole pattern,

the hole pattern in the transfer pattern is composed of a light transmitting portion surrounded by a half tone region,

when the reference wavelength is lambda 1 and lambda 1 is less than 365nm, the phase difference theta between the light transmission part and the half-modulation region is 180 degrees for the light with the wavelength of the lambda 1, and the transmissivity T of the half-modulation region for the light with the wavelength of the lambda 1 is more than or equal to 10% and less than or equal to 35%.

The 4 th aspect of the present invention is the photomask according to the 3 rd aspect,

the hole pattern in the transfer pattern is formed of a light transmitting portion formed by patterning a phase shift film formed on the transparent substrate, the transparent portion exposing the transparent substrate,

the half-tone region is formed with the phase shift film on the transparent substrate,

the phase shift film has a phase shift amount of 180 degrees with respect to light of the wavelength of λ 1 and has a transmittance T of 10% or more and 35% or less.

The 5 th aspect of the present invention is the photomask according to the 1 st to 4 th aspects,

the transfer pattern includes an isolated hole pattern.

The 6 th aspect of the present invention is the photomask according to the 1 st to 4 th aspects,

the transfer pattern has an approach hole pattern including 2 or more hole patterns located at an approach distance.

Mode 7 of the invention according to the photomask described in mode 6,

the distance between the centers of gravity of 2 of the hole patterns included in the proximity hole pattern is 9 [ mu ] m or less.

The 8 th aspect of the present invention is the photomask according to any one of the 1 st to 7 th aspects,

when the size of the hole pattern in the transfer pattern is Dm, Dm is larger than Dp.

The 9 th aspect of the present invention is the photomask according to any one of the 1 st to 8 th aspects,

the reference wavelength is 313nm or 334 nm.

The 10 th aspect of the present invention is the photomask according to the 8 th aspect,

Dm/Dp is 1.1-1.8.

An eleventh 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 1 to 10 aspects; and

an exposure step of exposing the photomask with ultraviolet exposure light,

the light for mid-ultraviolet exposure contains a wavelength region with the wavelength lambda of 200 nm-400 nm, and does not contain the wavelengths with the lambda larger than 400nm and the lambda smaller than 200 nm.

A twelfth aspect of the present invention is the method for manufacturing a display device according to the eleventh aspect, wherein a hole pattern having a size Dp of 3 μm or less is formed on the transferred object in the exposure step.

[ Effect of the invention ]

The photomask of the present invention has excellent transfer performance for transferring a fine hole pattern to a transfer object by exposure to light for mid-ultraviolet exposure described later.

Drawings

FIG. 1 is a schematic top view of photomask 10 of the present invention 1.

Fig. 2 (a) is a schematic plan view of the 2 nd photomask 20 of the present invention, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the 2 nd photomask 20 to light.

Fig. 3 (a) is a schematic plan view of the photomask of reference example 1, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of reference example 1 to light.

Fig. 4 (a) is a schematic plan view of the photomask of reference example 2, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of reference example 2 to light.

FIG. 5 is a graph showing the properties of the films of example 1 of the present invention and reference examples 1 to 4.

FIG. 6 is a graph showing the results of optical simulations of example 1 of the present invention and reference examples 1 to 4.

Fig. 7 (a) is a schematic plan view of the photomask of reference example 3, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of reference example 3 to light.

Fig. 8 (a) is a schematic plan view of the photomask of reference example 4, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of reference example 4 to light.

Fig. 9 (a) is a schematic plan view of the photomask of reference example 5, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of reference example 5 to light.

Fig. 10 (a) is a schematic plan view of the photomask of reference example 6, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of reference example 6 to light.

Fig. 11 is a graph showing the results of the optical simulation of reference examples 5 and 6.

Description of the reference symbols

10 st photomask

11 half tone region

12 light transmission part

13 partition wall

14 light-shielding area

20 nd 2 photo mask

Detailed Description

< embodiment 1 of the present invention >

The photomask of the present invention is a photomask for mid-ultraviolet exposure, which uses mid-ultraviolet light as exposure light. Here, the "mid-ultraviolet light" refers to exposure light having the following wavelength ranges: the wavelength region includes a plurality of wavelengths in a wavelength region of 200-400 nm and does not include wavelengths less than 200nm and wavelengths more than 400 nm. As the light source of the exposure light, for example, an appropriate portion of a wavelength range of a high-pressure mercury lamp can be appropriately used. In this case, for example, it is preferable to apply a broad band wavelength including 2 or more of 313nm, 334nm, and 365nm (i-line) having an intensity peak, but not including h-line and g-line. In the present specification, "a to B" means a numerical range of "a to B inclusive".

Such exposure light can be a broadband light having a wavelength region shifted to a shorter wavelength side than a wavelength region including i-line, h-line, and g-line, which is conventionally used in an exposure apparatus for manufacturing a display device. According to the studies of the present inventors, such exposure light is particularly advantageous in terms of resolution when used for forming a hole pattern, and does not cause inefficiencies (e.g., a reduction in production efficiency) such as single-wavelength exposure.

The photomask of the present invention is a photomask for mid-ultraviolet exposure, for forming a hole pattern having a dimension Dp (mu m) (wherein Dp is 3 or less) on a transfer object,

a transparent substrate having a pattern for transfer including a hole pattern,

the hole pattern in the transfer pattern is constituted by a light transmitting portion surrounded by a half tone (half tone) region,

a phase difference θ between the transmitted light of the light transmission part and the transmitted light of the half-tone region is substantially 180 degrees with respect to light of a reference wavelength included in the mid-ultraviolet exposure light for exposing the photomask,

the half-tone region has a transmittance T (%) of 10 < T < 35 for light of the reference wavelength.

FIG. 1 illustrates a 1 st photomask 10 of the present invention. The pattern for transfer of the 1 st photomask 10 has an isolated hole pattern formed of a light transmitting portion 12 surrounded by a half tone region 11. The isolated hole pattern means that no other hole pattern is present in a region within a predetermined proximity distance (described later in detail) from 1 hole pattern.

Fig. 2 (a) illustrates a 2 nd photomask 20 according to the present invention. The 2 nd photomask 20 is formed of a light transmitting portion 12 surrounded by a half-tone region 11, and has an adjacent hole pattern in which a plurality of hole patterns separated by a predetermined adjacent distance are arranged. In fig. 2 (a), 2 hole patterns separated by a close distance are arranged in line. Such a hole pattern is also referred to as a double hole pattern. Here, the case where 2 hole patterns are arranged in a row with the same shape (square shape) and the same size is exemplified. Fig. 2 (b) shows an example of the cross-sectional shape of a resist pattern formed by exposing the 2 nd photomask 20 of the present invention.

The proximity distance is a distance to the extent that transmitted light of the hole patterns optically interacts with each other when exposure light is received.

Hereinafter, the hole pattern included in the transfer pattern of the photomask may be referred to as a mask hole pattern in order to distinguish the hole pattern from a hole pattern formed in the object to be transferred.

By exposing the mask hole pattern of the photomask of the present embodiment with an exposure apparatus having the light source for exposure light, a hole pattern having a dimension Dp (μm) can be formed on a transfer object (display panel substrate or the like). Here, when the fine pores having Dp. ltoreq.3 are formed, the effect of the present invention is remarkably obtained. Further, with the progress of further miniaturization, the present invention can be usefully applied also to the formation of pores having Dp. ltoreq.2 or Dp. ltoreq.1.5. Further, Dp is preferably 0.5. ltoreq.Dp.

Such a transfer pattern is useful for a layer (for example, an aperture layer) of a contact hole required for obtaining a structure of a display panel substrate of a display device (including liquid crystal and organic EL). When the hole pattern formed on the object to be transferred is circular, the diameter is Dp, and when the hole pattern is other shapes, the diameter is Dp when the hole pattern is approximated (converted) to a circle having the same shape and area.

When Dp exceeds 3 μm, a predetermined resolution performance for obtaining a desired hole pattern on a transfer object by an exposure apparatus for manufacturing a conventional display device is obtained by using a conventional photomask (for example, a binary mask). However, the present inventors have focused on the problem that when the size Dp of a hole pattern to be obtained on a transfer target is 3 μm or less, a transfer image having sufficient resolution cannot be obtained with a conventional photomask.

The photomask according to the present embodiment may be a photomask in which a transfer pattern is formed on a main surface of a transparent substrate formed by processing a transparent material such as quartz flat and smoothly.

In the 1 st photomask 10 and the 2 nd photomask 20 of the present embodiment, the mask pattern included in the transfer pattern is a rectangular dummy pattern surrounded on all sides, and can be formed as a transparent portion 12 in which the transparent substrate is exposed. The 4 corners of the quadrangle do not need to be completely 90 degrees, and the 4 corners and the vicinity thereof may be formed in an arc shape within a range not impairing the effect of the present invention.

The shape of the mask hole pattern is preferably a quadrangle (square or rectangle), more preferably a square. When the diameter or 1-side dimension of the mask hole pattern is Dm (μm), Dm can be 3.5 or less. In the case of a square, the length of one side (for example, CD-X) is equal to the length of the side perpendicular thereto (CD-Y), and the length is defined as Dm. In addition, in the case of a rectangle, the longer side (for example, CD-X) is designated as Dm. When Dm is less than or equal to 2.0, the effect of the invention is remarkable. In addition, the effect of the present invention is particularly remarkably obtained when both CD-X and CD-Y are 2 μm or less in the mask hole pattern of a square shape. In addition, CD is also referred to as Critical Dimension, and in the present specification, CD-X refers to the Dimension of the pattern in the X direction, and CD-Y refers to the Dimension of the pattern in the Y direction. Here, the X direction refers to one direction on the main surface of the photomask, and the Y direction refers to the other direction perpendicular to the X direction.

The mask hole pattern (isolated hole pattern exemplified by the 1 st photomask 10 or proximity hole pattern exemplified by the 2 nd photomask 20) is surrounded by the half-tone region 11 on the transparent substrate. The half-tone region 11 of the present embodiment has a phase shift film formed on the main surface of the transparent substrate, the phase shift film having a phase shift amount of substantially 180 degrees with respect to the exposure light having the reference wavelength λ 1 (nm). Therefore, the transmissive portion 12 and the half-tone region 11 have a phase difference θ of substantially 180 degrees with respect to the exposure light of the reference wavelength λ 1. Here, the approximate 180 degrees is within a range of 180 ± 60 degrees, more preferably within a range of 180 ± 30 degrees, and still more preferably within a range of 180 ± 15 degrees. The phase difference θ (the amount of phase shift of the phase shift film) may be substantially 180 degrees, but is more preferably 180 degrees (exactly 180 degrees). The reference wavelength λ 1 will be described later in detail.

Further, the transmittance T (%) of the half-tone region 11 with respect to the exposure light of the reference wavelength λ 1 satisfies 10. ltoreq. T.ltoreq.35. That is, the phase shift film in the half-tone region 11 of the present embodiment has the transmittance T for the exposure light of the reference wavelength λ 1. If the value of T is too large, a defect that the resist pattern formed on the transfer object is damaged by exposure of the photomask is likely to occur, and if the value of T is too small, the required exposure amount tends to be large. The transmittance T (%) of the half-tone region 11 with respect to the exposure light of the reference wavelength λ 1 is preferably 12. ltoreq. T.ltoreq.30, more preferably 14. ltoreq. T.ltoreq.25. The transmittance (%) in the present specification means a value obtained by converting the transmittance of the transparent substrate to a reference value (100%) unless otherwise specified.

In the case of a transfer pattern including an isolated hole pattern (e.g., the 1 st photomask 10), T.ltoreq.35 is preferably 10. ltoreq. T.ltoreq.35, more preferably 10. ltoreq. T.ltoreq.25, and still more preferably 12. ltoreq. T.ltoreq.25. In addition, in the case of a transfer pattern including a pattern of proximity holes (e.g., the 2 nd photomask 20), T.ltoreq.22 is more preferably 10. ltoreq.T. That is, considering the case where both the isolated hole pattern and the proximity hole pattern are included in the transfer pattern provided in one photomask, the transmittance of the half-tone region 11 is preferably 10. ltoreq. T.ltoreq.22, more preferably 12. ltoreq. T.ltoreq.22, and still more preferably 15. ltoreq. T.ltoreq.22.

In the above, the reference wavelength λ 1 as the phase shift amount and the transmittance may be any wavelength included in the wavelength region (200 to 400nm) of the above-described mid-ultraviolet exposure light. The reference wavelength λ 1 may be more preferably 250nm ≦ λ 1 ≦ 400nm, and still more preferably 250nm < λ 1 < 400 nm. The reference wavelength λ 1 is preferably a wavelength shorter than the i-line. Specifically, the reference wavelength λ 1 may be λ 1 < 365nm, preferably 200nm ≦ λ 1 < 365nm, more preferably 250nm ≦ λ 1 < 365nm, and further preferably 250nm < λ 1 < 365 nm. In the present embodiment, the wavelength of 334nm is set as the reference wavelength λ 1, for example. This wavelength is close to a weighted average in consideration of the intensity distribution in the wavelength region of the intermediate ultraviolet light, and is most advantageous in terms of obtaining the DOF (depth of focus) improvement effect described later as well as being suitable as a reference for the phase shift effect in terms of having a predetermined intensity (peak height) in the spectrum of the high-pressure mercury lamp. The reference wavelength λ 1 may be 313 nm.

The transfer pattern of the present embodiment can obtain a particularly significant effect when it includes a proximity hole pattern as in the case of the 2 nd photomask 20. In the proximity hole pattern, the distance between the mask hole patterns is preferably set so that the distance between the centers of gravity (hereinafter, also referred to as pitch P (μm)) of the proximity hole patterns is 9 μm or less, and more preferably 2. ltoreq. P.ltoreq.9. More preferably, the present invention is more advantageous when the pitch P is 2. ltoreq. P.ltoreq.6 and the pitch P is 2. ltoreq. P.ltoreq.4.

The design of the transfer pattern is not limited to the design of the transfer patterns of the 1 st photomask 10 and the 2 nd photomask 20. In particular, in the case where the photomask has a proximity hole pattern, an additional proximity hole pattern may be formed in addition to the above-described double hole pattern. For example, 3 or more proximity hole patterns of the same shape may be regularly arranged in one direction at a pitch P, or they may be two-dimensionally regularly arranged at a certain pitch P. Alternatively, the pitch P may not necessarily be fixed.

In addition, other than the case where the hole patterns have the same size, hole patterns having different sizes may be mixed.

However, as described above, when the distance between centers of gravity (pitch P) between the proximity hole patterns is 9 μm or less, the effect of the invention is further enhanced.

Further, the hole patterns must not contact each other, but the shortest distance d between edges (outer edges) of the hole patterns is preferably 0.5 to 2.0. mu.m.

The 1 st photomask 10 and the 2 nd photomask 20 of the present embodiment are photomasks for manufacturing a display device, and for example, a transfer pattern can be formed on a main surface of a rectangular transparent substrate having one side of 300 to 1800mm and a thickness of 5 to 16 mm.

The photomask is used for exposure by an exposure apparatus for manufacturing a display device. For example, the numerical aperture NA of the projection optical system of the exposure apparatus is about 0.08 to 0.20, and the light source of the exposure light has the above-mentioned mid-ultraviolet region.

The photomask of the present embodiment may be a photomask obtained by patterning a phase shift film formed on a transparent substrate to form a blank pattern corresponding to a mask hole pattern. For example, in the 2 nd photomask 20 of fig. 2 (a), a double-hole pattern in which 2 blank patterns are close to each other is formed. The mask hole pattern portion is a light transmitting portion 12 where the transparent substrate is exposed, and a half-tone region 11 where a phase shift film is formed on the transparent substrate is formed around the light transmitting portion.

The size Dm of the mask hole pattern of the present embodiment is preferably larger than Dp (Dm > Dp). That is, Dm (β — Dm-Dp) is preferably formed with a size obtained by adding a mask offset β (μm) to the size Dp of the hole pattern formed on the object to be transferred.

The mask bias can be set to Dm/Dp of 1.1-1.8, for example. Particularly, in the case of a transfer pattern including a pattern of proximity holes (herein, double holes), Dm/Dp is preferably 1.2 to 1.7, more preferably 1.25 to 1.65. In this case, the transmittance T of the phase shift film is preferably 10 to 22%, more preferably 12 to 22%. Accordingly, when the photomask is exposed, not only DOF and the required exposure amount are in a preferable range, but also, as shown in fig. 2 (b), in a resist pattern (here, a positive type resist) formed on a transfer target, a partition wall 13 (described in detail later) formed between the double-hole patterns is not damaged, and a defect that the double-hole patterns are connected is unlikely to occur.

[ example 1]

Since the 2 nd photomask 20 shown in fig. 2 (a) was used as example 1, optical simulations were performed on the transfer characteristics of the binary mask of reference example 1 shown in fig. 3 (a) and the half-tone phase shift mask (i-line mask with reference wavelength) of reference example 2 shown in fig. 4 (a) in order to compare them with each other.

In the 2 nd photomask 20 of example 1, the phase Shift film used in the half-tone region 11 is a phase Shift film having a phase Shift amount of 180 degrees and a transmittance of 16.1% with respect to the exposure wavelength of the middle ultraviolet (reference wavelength 334nm) (see "middle ultraviolet psm (phase Shift mask)" in fig. 5).

In the photomask of reference example 1, a light-shielding film (a film that substantially does not transmit exposure light) is formed in a region (light-shielding region 14) corresponding to the half-tone region 11 in example 1, instead of the phase shift film.

The photomask of reference example 2 formed a phase shift film having a phase shift amount of 180 degrees and a transmittance of 5.2% for the i-line (365nm) as the reference wavelength in the half-tone region 11 of example 1. This refers to the case where the transmittance of the phase shift film is about 5 to 6% in patent document 2.

The transfer pattern used for evaluating the transfer performance of the photomask of the above-described film structure was designed to be a close (double-hole) mask hole pattern. Further, the following items were evaluated with the aim of forming a pattern of double holes having a diameter of 1.5 μm on the object to be transferred. The shapes of the transfer patterns of example 1, reference example 1, and reference example 2 are shown in fig. 2 (a), fig. 3 (a), and fig. 4 (a), respectively. The characteristics of the film in the half tone region 11 (light shielding region 14 in the binary mask of reference example 1) are shown in fig. 5.

(1) Exposure (m J/cm)²)

The exposure amount here indicates a necessary exposure amount for obtaining a pattern of a target size on the transferred body. The necessary exposure amount is preferably small, for example, 50m J/cm²The following.

(2)DOF(μm)

The DOF here indicates a depth of focus within ± 10% with respect to the target CD value. DOF is preferably large, for example, 15 μm or more.

(3) MEEF (Mask Error Enhancement Factor)

The MEEF represents a ratio of a CD error of a transferred image formed on a transferred body to a CD error of a photomask. The MEEF is preferably small. The CD error of the photomask means an actual CD error (offset) on the photomask with respect to a target CD value on the photomask. The CD error of the transferred image formed on the transfer target object is a CD error (offset) of the actual transferred image with respect to a target CD value of the transferred image formed on the transfer target object.

Fig. 6 shows the results of optical simulation of transfer characteristics in example 1, reference example 1, and reference example 2. In addition, in example 1, reference example 1, and reference example 2, the sectional shapes of the resist patterns formed on the transferred body are shown in fig. 2 (b), fig. 3 (b), and fig. 4 (b), respectively.

Reference example 1 (binary mask) is a reference mask, and may be hereinafter referred to as a reference value. As shown in fig. 3 (b), in the photomask of reference example 1, in the resist pattern (here, a positive type resist pattern) formed on the object to be transferred, a space (hereinafter, referred to as a partition wall 13) having a sufficient height and thickness is formed between the double-hole patterns. On the other hand, as shown in fig. 6, in the photomask of reference example 1, DOF was less than 15 μm, and process margin in manufacturing the display device was insufficient.

In reference example 2, the DOF improvement effect was found, similarly to the effect obtained by the conventional half-tone phase shift mask. However, in reference example 2, the necessary exposure amount is about 150% of that in reference example 1, and the production efficiency of the display device is lowered, and therefore, it cannot be said that it is suitable for mass production.

In example 1, the exposure amount can be significantly reduced as compared with reference examples 1 and 2, even when sufficient DOF is obtained (50m J/cm)²Hereinafter), as shown in fig. 2 (b), it is found that the partition wall 13 located between the adjacent holes can be appropriately formed in the cross-sectional shape of the resist pattern, and therefore, this is extremely useful. In example 1, the effect of reducing the MEEF was also confirmed with respect to the numerical value thereof. In example 1, the size of the hole in the mask was 2.1 μm relative to the target size of 1.5 μm formed in the transferred body. That is, the mask bias β is obtained such that Dm/Dp becomes 1.4.

Here, in order to confirm that the transferability was improved in reference examples 1 and 2, even when the same offset as in example 1 was obtained. In reference example 1, the case where the mask hole pattern was 2.1 μm in size by applying an offset was referred to as reference example 3 (fig. 7 (a)), and in reference example 2, the case where an offset was similarly applied was referred to as reference example 4 (fig. 8 (a)), and the results of optical simulations of the respective transfer performances were also shown in fig. 6.

According to the optical simulation results of reference examples 3 and 4, in reference example 3, the exposure amount can be reduced by bias application, but DOF is reduced to a degree lower than the reference value (reference example 1). Further, as shown in fig. 7 (b), when the cross section of the resist pattern in reference example 3 is observed, the partition walls 13 between the two hole patterns cannot be sufficiently formed, and the two hole patterns are connected to each other. In addition, according to reference example 4, not only the DOF improvement effect is smaller than the reference value, but as shown in fig. 8 (b), the partition wall 13 between the two-hole patterns is very thin and easily broken when viewed from the cross section of the resist pattern. In the intended display device, in order to obtain a circuit pattern free from defects, it is most preferable that the partition walls 13 of the resist pattern do not lose the initial thickness of the resist, and at least 50% or more, more preferably 60% or more of the thickness of the partition walls 13 is left with respect to the initial thickness.

As can be seen from the above, the photomask of the present embodiment is extremely excellent in transfer performance.

[ example 2]

The photomask of reference example 5 shown in fig. 9 (a) and the photomask of reference example 6 shown in fig. 10 (a) are photomasks having a proximity (double) hole pattern, and are formed in the same manner as in example 1, except that the transmittance of the phase shift film in the half-tone region 11 is changed. In reference examples 5 and 6, as in example 1, the formation of a near (double) hole pattern having a size of 1.5 μm on the transferred object was targeted.

In reference examples 5 and 6, the optical simulation of transfer performance was also performed in the same manner as in example 1. The evaluation items in the optical simulation were the same as those in example 1. The optical simulation results are shown in fig. 11. In addition, in reference examples 5 and 6, the sectional shapes of the resist patterns formed on the transferred body are shown in fig. 9 (b) and 10 (b), respectively.

In reference example 5, the transmittance of the phase shift film used in the half-tone region 11 (based on the wavelength 334nm of the exposure light) was set to 8%. From the simulation results, the DOF value and the cross-sectional shape of the resist pattern have no particular problem, but the effect of reducing the necessary exposure amount is hardly obtained.

In reference example 6, when the transmittance of the phase shift film in the half-tone region 11 (based on the wavelength of 334nm) was 25%, no particular problem was found in the exposure amount, DOF, and MEEF. However, in reference example 6, as shown in fig. 10 (b), the partition walls 13 between the hole patterns cannot be sufficiently formed in the cross-sectional shape of the resist pattern.

Therefore, the transmittance of the half-tone region 11 in the near (double) hole pattern is preferably smaller than the transmittance shown in reference example 6 (specifically, 22% or less), and on the other hand, even the transmittance of about the transmittance (25%) shown in reference example 6 in the isolated hole pattern can be considered to be sufficiently practical.

The photomask of the present invention exemplified by the 1 st photomask 10, the 2 nd photomask 20 and the like can be manufactured by a photolithography process. That is, the photomask blank can be manufactured using a photomask blank in which a phase shift film is formed on a principal plane of a substrate made of a transparent material such as quartz. When the phase shift film is formed on the transparent substrate, a known method such as a sputtering method may be used. The phase shift film (forming the half-tone region 11) has a phase reversal effect with respect to, for example, a wavelength region of the middle ultraviolet. The phase shift film is then subjected to a desired patterning based on the desired device.

The material of the phase shift film applied to the 1 st photomask 10 and the 2 nd photomask 20 is not particularly limited. For example, a silicide of a transition metal is preferably used. For example, molybdenum silicide (MoSi), its compounds (MoSiO, MoSiN, MoSiC, MoSiON, MoSiCN, MoSiCO, MoSiCON, and the like) are preferable.

Alternatively, the material of the phase shift film may be chromium (Cr) or a compound thereof (CrO, CrN, CrC, CrON, CrCN, CrCO, CrCON, or the like).

Further, as the metal component, a material of the phase shift film may be exemplified by a material containing Ta (tantalum), Zr (zirconium), or Ti (for example, Zr silicide, silicide containing Mo and Zr), or a compound thereof (such as the above-mentioned compounds as an oxide, nitride, carbide).

The 1 st photomask 10 and the 2 nd photomask 20 of the present embodiment were simulated using a MoSi compound photomask as a phase shift film. The phase shift film may have a film thickness of 100 to 200nm and may be formed by a known film forming method such as a sputtering method. In addition, dry etching or wet etching may be used for patterning the phase shift film, but wet etching is sometimes advantageous as a large photomask for manufacturing a display device.

In addition, although the phase shift films for inverting the exposure light of the intermediate ultraviolet region in the half-tone region 11 are used in both the 1 st photomask 10 and the 2 nd photomask 20, they may have different structures. For example, a semi-transmissive film having a transmittance of T% (e.g., 10. ltoreq. T. ltoreq.35) for exposure light and substantially no phase inversion effect can be used for the half tone region 11. The substantial absence of the phase reversal effect means that the phase shift amount is 90 degrees or less, preferably 60 degrees or less, with respect to the reference wavelength λ 1. On the other hand, the light-transmitting portion 12 constituting the mask hole pattern may be formed as a recessed portion that is formed by recessing the surface of the transparent substrate by a predetermined thickness. Accordingly, the phase difference θ between the light transmitting portion 12 and the half-tone region 11 can be made substantially 180 degrees (or exactly 180 degrees), and the operational effect of the present invention can be obtained also in such a photomask.

In the photomask of the above embodiment, additional films (such as an reflectance control film and an etching stopper film) may be formed on the transparent substrate within a range not to impair the effects of the present invention.

The present invention includes a method of manufacturing a display device using the above photomask. Here, the display apparatus includes devices constituting the display apparatus.

In the exposure of the present invention, a projection exposure apparatus for performing an exposure with an NA of about 0.08 to 0.20 with an equal magnification or reduction can be used. The NA may be preferably 0.08 to 0.18, and more preferably 0.08 to 0.15.

The illumination system of the exposure apparatus can use general illumination. Alternatively, an anamorphic illumination (illumination in which a vertically incident component is removed from light incident on the photomask) other than the normal illumination may be used.

In recent circuits for high-quality organic EL displays (OLEDs), a transfer pattern having a near-hole pattern of two or more holes has become highly useful due to high circuit definition. The photomask of the present invention supports such a new technical problem.

The embodiments of the present invention have been specifically described above, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention.