TW202208977A - Photomask, and method for manufacturing a display device - Google Patents

Abstract

To provide a photomask having an excellent transfer performance, which is capable of transferring a fine hole pattern on a transfer object by exposure using middle ultraviolet exposure light. A photomask for use in manufacture of a display device is adapted to form a hole pattern, which has a size Dp where Dp ≤ 3μm, on a transfer object by using middle ultraviolet exposure light. The photomask has a transfer pattern formed on a transparent substrate and including the hole pattern. The hole pattern in the transfer pattern comprises a light transmitting portion surrounded by a halftone region. With respect to a reference wavelength included in the middle ultraviolet light for exposure of the photomask, a phase difference 0 is approximately equal to 180 degrees between the light transmitting portion and the halftone region. A transmittance T of the halftone region with respect to the reference wavelength satisfies 10% ≤T ≤ 35%.

Description

Photomask and method for manufacturing display device

The present invention relates to a photomask, and more particularly, to a photomask that is favorable for the manufacture of high-definition display devices, and a manufacturing method of a display device using the photomask.

Patent Document 1 describes a phase-shift mask base for manufacturing a display device, and a phase-shift mask manufactured from the phase-shift mask base. In Patent Document 1, it is further described that the phase shift mask is exposed by compound light including i-rays, h-rays, and g-rays.

Patent Document 2 describes a phase-shift mask substrate for manufacturing a display device including a phase-shift film that exhibits optical properties that suppress wavelength dependence of exposure light. The transmittance of the phase shift film in the base of the phase shift mask is in the range of 3.5% or more and below 8% at the wavelength of 365 nm, and the retardation at the wavelength of 365 nm is in the range of 160 degrees or more and 200 degrees or more, and the wavelength is more than 365 nm. The wavelength-dependent change of transmittance in the range below 436 nm is within 5.5%. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2014-194531 [Patent Document 2] Japanese Patent Laid-Open No. 2015-102633

[Problems to be Solved by Invention]

In recent years, for display devices including LCD (liquid crystal display) or OLED (organic light emitting diode, organic light emitting diode) display (organic EL (Electroluminescence, electroluminescence) display), in addition to requiring bright and high-definition display performance In addition, display performance such as power saving and dynamic image response speed are also required. Therefore, it is considered that the pattern of the photomask used in the manufacturing process of these display devices is also expected to be more and more finer and more integrated, and further, it is required to accurately resolve the pattern of the photomask to the transfer object (display Panel substrate, etc.) technology.

In addition, as long as the transfer pattern possessed by the photomask cannot be optically resolved on the transfer target body, a display device having the desired fine pattern cannot be constructed. Here, the spatial resolution of the optical image can be expressed by the following formula (1), which is a reference formula of Rayleigh's resolving power.

δ=k1×λ/NA・・・(1) Here, δ is the minimum resolution line width, λ is the exposure wavelength, NA is the numerical aperture of the optical system of the exposure device, and k1 is a coefficient also called the k1 factor.

In the field of display devices (hereinafter also referred to as FPD (Flat Panel Display)), a specific wavelength range of a high-pressure mercury lamp is used as light for exposure. That is, it is well known to use light in a wavelength band (hereinafter also referred to as a broadband) that includes light of a plurality of wavelengths and mixed with light of these wavelengths, and it is particularly well known to apply exposure light including light from a high-pressure mercury lamp The included wavelength light is light with three wavelengths of g-ray (wavelength 436 nm), h-ray (wavelength 405 nm), and i-ray (wavelength 365 nm) (refer to Patent Documents 1 and 2).

On the other hand, according to the above formula (1), decreasing λ or increasing NA can effectively improve the resolution of fine patterns (ie, make the minimum resolution line width δ smaller). However, according to the following formula (2), it can be seen that the increase of NA reduces the depth of focus, so the stability of the lithography process is relatively deteriorated. Equation (2) is also known as Rayleigh's focal depth formula.

DOF=k2×λ/NA ²・・・(2) Here, DOF (Depth of Focus) means the depth of focus, and k2 is a coefficient.

Equation (2) is opposite to the above-mentioned resolution reference formula (Equation (1)) in the relationship between the pros and cons of the magnitude of the left value. That is, in equation (1), it is preferable that the left side value is small, but in equation (2), the left side value is required to be large.

Therefore, there is a trade-off relationship between the minimum resolution line width δ and the depth of focus DOF. However, the DOF shown in the formula (2) degrades in proportion to the square of NA. Therefore, assuming that the same level of resolution is improved, it is better to shorten the wavelength of the exposure light than to increase the NA. Reasonable. That is, it is possible to improve the resolution while suppressing the decrease in DOF.

As a method to easily achieve shorter wavelengths from the above-mentioned broadband exposure environment, it can be considered that the wavelength can be effectively reduced by switching to exposure using a single wavelength of i-rays instead of mixed wavelength exposure including g-rays, h-rays, and i-rays. . However, this method cuts off the contribution of 2 of the above 3 wavelengths, which means that the workload per unit time is reduced to 1/3 in a simple calculation. In the field of FPD production, in addition to the above-mentioned resolution, another important factor is production efficiency, so there are cases where it is difficult to use a single wavelength.

Therefore, a method of shifting the center of gravity to the short wavelength side while maintaining the broadband exposure environment is considered. In the high-pressure mercury lamp, there are several wavelength groups with peaks of light intensity on the wavelength side shorter than the i-ray, so the above method is a method of using the light of the wavelength group as the exposure energy.

When considering a new wideband exposure environment in which the wavelength range used by the previous exposure light was shifted to the short wavelength side, the inventors of the present invention conducted a study on what kind of photomask is suitable for the environment and exhibits excellent transferability. As a result of earnest research, the present invention was completed. [Technical means to solve problems]

A first aspect of the present invention is a photomask, It is a photomask used for the manufacture of display devices, which is used to form hole patterns with a size of Dp and Dp≦3 μm on a transfer body using medium ultraviolet exposure light. The transparent substrate has a pattern for transfer including a hole pattern, The hole pattern in the above-mentioned pattern for transfer includes a light-transmitting portion surrounded by a halftone region, The phase difference θ of the light-transmitting portion and the halftone region with respect to the light of the reference wavelength included in the ultraviolet exposure light used for exposing the mask is about 180 degrees, and The transmittance T of the halftone region to the light of the reference wavelength is 10%≦T≦35%.

A second aspect of the present invention is the photomask described in the first aspect, wherein the hole pattern in the pattern for transfer includes a light-transmitting portion, the light-transmitting portion being formed on the transparent substrate by The phase shift film is patterned and formed, and the above-mentioned transparent substrate is exposed, The above-mentioned halftone region is formed by forming the above-mentioned phase shift film on the above-mentioned transparent substrate, The phase shift film has a phase shift amount of approximately 180 degrees with respect to the light of the reference wavelength, and has a transmittance T, 10%≦T≦35%.

A third aspect of the present invention is a photomask, It is a photomask used for the manufacture of display devices, which is used to form hole patterns with a size of Dp and Dp≦3 μm on a transfer body using medium ultraviolet exposure light. The transparent substrate has a pattern for transfer including a hole pattern, The hole pattern in the above-mentioned pattern for transfer includes a light-transmitting portion surrounded by a halftone region, When the reference wavelength is set as λ1, and λ1<365 nm, the phase difference θ between the light-transmitting portion and the halftone region with respect to the light with the wavelength of λ1 is 180 degrees, and The transmittance T of the above-mentioned halftone region to the above-mentioned λ1 wavelength light is 10%≦T≦35%.

A fourth aspect of the present invention is the photomask described in the third aspect, wherein the hole pattern in the pattern for transfer includes a light-transmitting portion, the light-transmitting portion being formed on the transparent substrate by a The phase shift film is patterned and formed, and the above-mentioned transparent substrate is exposed, The above-mentioned halftone region is formed by forming the above-mentioned phase shift film on the above-mentioned transparent substrate, The above-mentioned phase shift film has a phase shift amount of 180 degrees with respect to the above-mentioned λ1 wavelength light, and has a transmittance T, 10%≦T≦35%.

A fifth aspect of the present invention is the photomask according to any one of the first to fourth aspects, wherein the pattern for transfer includes an isolated hole pattern.

A sixth aspect of the present invention is the photomask according to any one of the first to fourth aspects, wherein the pattern for transfer has a proximity hole pattern, and the proximity hole pattern includes two or more holes at a close distance pattern.

A seventh aspect of the present invention is the photomask according to the sixth aspect, wherein the distance between the centers of gravity of the two hole patterns included in the proximity hole pattern is 9 μm or less.

An eighth aspect of the present invention is the photomask according to any one of the first to seventh aspects, wherein Dm>Dp when the size of the hole pattern in the transfer pattern is defined as Dm.

A ninth aspect of the present invention is the photomask according to any one of the first to eighth aspects, wherein the reference wavelength is 313 nm or 334 nm.

A tenth aspect of the present invention is the photomask described in the eighth aspect, wherein Dm/Dp is 1.1 to 1.8.

An eleventh aspect of the present invention is a method of manufacturing a display device, It is a method of manufacturing a display device, comprising: the steps of preparing a photomask as described in any one of aspects 1 to 10 above; and an exposure step of exposing the above-mentioned photomask with medium-ultraviolet exposure light; and The above-mentioned mid-ultraviolet exposure light includes the wavelength range where the wavelength λ satisfies the wavelength range of 200 nm≦λ≦400 nm, and does not include the wavelengths of λ>400 nm and λ<200 nm.

A twelfth aspect of the present invention is the method of manufacturing a display device according to the eleventh aspect, wherein a hole pattern having a size Dp≦3 μm is formed on the transfer target body by the exposure step. [Effect of invention]

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

<The first embodiment of the present invention> The photomask of the present invention is a photomask for medium-ultraviolet exposure, and is a photomask for applying medium-ultraviolet light as exposure light. Here, the mid-ultraviolet light refers to exposure light having the following wavelength range, the exposure light including a plurality of wavelengths in the wavelength range of 200-400 nm and excluding wavelengths less than 200 nm and more than 400 nm. As the light source of the above-mentioned exposure light, for example, a suitable part of the wavelength range of a high-pressure mercury lamp can be preferably used. In this case, it is preferable to use, for example, a broadband wavelength including two or more of 313 nm, 334 nm, and 365 nm (i-rays) having an intensity peak, but h-rays and g-rays are not included. In addition, in this specification, "A-B" means the numerical range of "more than A and less than B".

Such exposure light can be set as broadband light having a wavelength range shifted to the short wavelength side compared to the wavelength range including i-rays, h-rays, and g-rays in exposure apparatuses previously used for display device manufacturing. According to the research of the present inventors, when such exposure light is used to form a hole pattern, it is particularly advantageous in terms of resolution and does not cause inefficiencies such as single-wavelength exposure (eg, reduced production efficiency).

The photomask of the present invention is used to form a photomask for ultraviolet exposure in a hole pattern with a size of Dp (μm) (wherein Dp≦3) on a transfer object. The transparent substrate has a pattern for transfer including a hole pattern, The hole pattern in the above-mentioned pattern for transfer includes a light-transmitting portion surrounded by a halftone region, The phase difference θ of the transmitted light of the light-transmitting portion and the transmitted light of the halftone region with respect to the light of the reference wavelength included in the ultraviolet exposure light used for exposing the mask is about 180 degrees, and The transmittance T (%) of the halftone region to the light of the reference wavelength is 10≦T≦35.

FIG. 1 illustrates the first mask 10 of the present invention. The pattern for transfer of the first mask 10 has an isolated hole pattern including a light-transmitting portion 12 surrounded by a halftone region 11 . In addition, the isolated hole pattern means that no other hole pattern exists in a region within a specific proximity distance (details will be described later) from one hole pattern.

Moreover, in FIG.2(a), the 2nd mask 20 of this invention is illustrated. The second mask 20 has a proximity hole pattern, the proximity hole pattern includes a light-transmitting portion 12 surrounded by the halftone region 11 , and a plurality of hole patterns spaced apart by a specific proximity distance are arranged in parallel. In FIG. 2( a ), two hole patterns separated by a close distance are arranged side by side. Such a hole pattern is also called a duplex hole pattern. Here, the case where two hole patterns are arranged side by side with the same shape (square) and the same size is exemplified. FIG.2(b) is an example of the cross-sectional shape of the resist pattern formed by exposing the 2nd photomask 20 of this invention.

The proximity distance refers to the distance of the degree to which the transmitted light of the hole patterns optically interacts with each other when the exposure light is received.

In addition, in order to distinguish the hole pattern of the pattern for transfer of the photomask from the hole pattern formed on the object to be transferred, there is a hole pattern that the pattern for transfer of the photomask has is called the mask hole pattern. Condition.

By exposing the mask hole pattern of the photomask of this embodiment with an exposure apparatus having the above-mentioned light source of exposure light, a hole pattern having a size Dp (μm) can be formed on a transfer object (display panel substrate, etc.). Here, in the case where fine pores such as Dp≦3 are formed, the effect of the present invention is remarkably obtained. In addition, with the trend toward further miniaturization, the present invention can also be effectively applied to the formation of holes with Dp≦2 or Dp≦1.5. Moreover, it is preferable that it is 0.5≦Dp.

Such a pattern for transfer is useful for a layer (eg, a hole layer) for obtaining a contact hole required for the formation of a display panel substrate of a display device (including liquid crystal and organic EL). In the case of the hole pattern formed on the transfer object being a circular shape, set its diameter as Dp, and in the case of other shapes, set it as the diameter approximated (converted) to a circle with the same area as the shape. is Dp.

When the Dp exceeds 3 μm, a previous photomask (such as a binary photomask) can be used to obtain the desired hole pattern on the transferred body by the previous exposure device used in the manufacture of display devices specific resolution performance. However, the present inventors paid attention to the problem that when the size Dp of the hole pattern to be obtained on the transfer object is 3 μm or less, a transfer image with sufficient resolution cannot be obtained with the conventional photomask. .

The photomask of the present embodiment may be one having a pattern for transfer formed on the main surface of a flat and smooth transparent substrate processed from a transparent material such as quartz.

In the first mask 10 and the second mask 20 of the present embodiment, the mask hole pattern included in the transfer pattern is a quadrangular hollow pattern surrounded by four sides, and can be formed to expose the light-transmitting portion 12 of the transparent substrate. Furthermore, the four corners of the quadrilateral do not necessarily have to be completely 90 degrees, and the four corners and their vicinity may form an arc-like shape within a range that does not impair the effect of the present invention.

Preferably, the shape of the mask hole pattern is a quadrangle (square or rectangle), more preferably a square. When the diameter of the mask hole pattern or the size of one side is set to Dm (μm), it can be set to Dm≦3.5. If it is a square, the length of one side (eg CD-X) is equal to the length of one side perpendicular to it (CD-Y), and the length is set as Dm. In addition, if it is a rectangle, the long side (for example, CD-X) is set to Dm. When Dm≦2.0, the effect of the present invention is remarkable. In addition, in a square mask hole pattern, when both CD-X and CD-Y are 2 μm or less, the effect of the present invention can be obtained particularly remarkably. Furthermore, CD is also described as Critical Dimension. In this specification, CD-X means the pattern size in the X direction, and CD-Y means the pattern size in the Y direction. Here, the X direction means one direction on the main surface of the photomask, and the Y direction means the other direction perpendicular to the X direction.

In addition, the mask hole pattern (the isolated hole pattern illustrated in the first mask 10 or the proximity hole pattern illustrated in the second mask 20 ) is surrounded by the halftone region 11 on the transparent substrate. The halftone region 11 of the present embodiment is formed by forming a phase shift film on the main surface of the transparent substrate, and the phase shift film has a phase shift amount of approximately 180 degrees with respect to the exposure light of the reference wavelength λ1 (nm). Therefore, the light-transmitting portion 12 and the halftone region 11 have a phase difference θ of approximately 180 degrees with respect to the exposure light of the reference wavelength λ1. Here, approximately 180 degrees means within a range of 180±60 degrees, more preferably within a range of 180±30 degrees, and more preferably within a range of 180±15 degrees. The phase difference θ (the amount of phase shift possessed by the phase shift film) should just be about 180 degrees, and it is more preferably 180 degrees (meaning exactly 180 degrees) in particular. The reference wavelength λ1 will be described in detail later.

In addition, the transmittance T (%) of the halftone region 11 to the exposure light of the reference wavelength λ1 satisfies 10≦T≦35. That is, the phase shift film in the halftone region 11 of the present embodiment has a transmittance T with respect to the exposure light of the reference wavelength λ1. If the value of T is too large, the resist pattern formed on the transfer target body is easily damaged by the exposure of the mask, and if the value of T is too small, the required exposure tends to increase. The transmittance T (%) of the halftone region 11 to the exposure light of the reference wavelength λ1 is preferably 12≦T≦30, more preferably 14≦T≦25. In addition, unless otherwise stated, the transmittance (%) in this specification means the value obtained by converting the transmittance of the transparent substrate as a reference (100%).

In the case of a transfer pattern including an isolated hole pattern (eg, the first photomask 10 ), it is preferably 10≦T≦35, more preferably 10≦T≦25, and more preferably 12≦T≦25. Moreover, in the case of including the transfer pattern of the proximity hole pattern (for example, the second photomask 20 ), it is more preferable that it is 10≦T≦22. That is, in the transfer pattern provided in one photomask, considering the case of including both the isolated hole pattern and the proximity hole pattern, the transmittance of the halftone region 11 is preferably set to 10≦T≦22, more preferably 12≦T≦22, more preferably 15≦T≦22.

In the above, as the reference wavelength λ1 of the phase shift amount and the transmittance, any wavelength included in the wavelength range (200 to 400 nm) of the above-mentioned medium-ultraviolet exposure light can be used. The reference wavelength λ1 can preferably be set to 250 nm≦λ1≦400 nm, and more preferably can be set to 250 nm<λ1<400 nm. The reference wavelength λ1 is preferably set to a shorter wavelength than the i-ray. Specifically, the reference wavelength λ1 can be set to λ1<365 nm, preferably set to 200 nm≦λ1<365 nm, more preferably set to 250 nm≦λ1<365 nm, and more preferably set to 250 nm< λ1<365 nm. In this embodiment, as an example, the wavelength of 334 nm is set as the reference wavelength λ1. This wavelength is close to the weighted average value of the intensity distribution in the wavelength region of the mid-ultraviolet light, and has a specific intensity (peak height) in the spectrum of the high-pressure mercury lamp, and is suitable as a reference related to the phase shift effect , not only that, but also the most advantageous in obtaining the DOF (depth of focus) improvement effect described later. Furthermore, the reference wavelength λ1 may also be set to 313 nm.

The transfer pattern of the present embodiment has a particularly remarkable effect when the second mask 20 includes a proximity hole pattern. In the proximity hole pattern, the distance between the mask hole patterns is preferably the distance between the centers of gravity (hereinafter also referred to as the pitch P (μm)) of 9 μm or less, preferably 2≦P≦9. More preferably, the pitch P is 2≦P≦6, and when the pitch P is 2≦P≦4, the advantages of the present invention are even greater.

In addition, the design of the pattern for transfer is not limited to the design of the pattern for transfer which the 1st mask 10 and the 2nd mask 20 have. Especially when the photomask has a proximity hole pattern, in addition to the above-mentioned duplex hole pattern, an additional proximity hole pattern can also be formed. For example, three or more proximity hole patterns of the same shape may be regularly arranged in one direction at a pitch P, or they may be regularly arranged at a fixed pitch P two-dimensionally. The pitch P is not fixed.

Moreover, in addition to the case where the size of each hole pattern is the same, hole patterns with different sizes may be mixed.

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

In addition, the hole patterns need not be in contact with each other, but the shortest distance d between the edges (outer edges) of the hole patterns is preferably 0.5 to 2.0 μm.

The first photomask 10 and the second photomask 20 of the present embodiment are photomasks for the manufacture of display devices, for example, they can be used as the main body of a quadrilateral transparent substrate with a side of 300 to 1800 mm and a thickness of 5 to 16 mm. A pattern for transfer is formed on the surface.

The photomask is used for exposure by an exposure device used in the manufacture of display devices. For example, the numerical aperture NA of the projection optical system of the exposure device is about 0.08 to 0.20, and the light source of the exposure light has the above-mentioned middle ultraviolet range.

The photomask of this embodiment can be a photomask obtained by patterning a phase shift film formed on a transparent substrate to form a hollow pattern corresponding to a mask hole pattern. For example, in the second photomask 20 of FIG. 2( a ), a double hole pattern in which two hollow patterns are close to each other is formed. The mask hole pattern portion is the light-transmitting portion 12 exposing the transparent substrate, and the periphery thereof is the halftone region 11 formed by forming the phase shift film on the transparent substrate.

The dimension Dm of the mask hole pattern in this embodiment is preferably larger than Dp (Dm>Dp). That is, it is preferable to form a dimension Dm (β=Dm−Dp) obtained by adding the mask deviation β (μm) to the dimension Dp of the hole pattern formed on the transfer object.

The mask deviation can be set, for example, so that Dm/Dp is 1.1 to 1.8. In particular, in the case of a pattern for transfer including a near hole pattern (here, double-pass), it is preferable to set Dm/Dp to 1.2 to 1.7, and more preferably to set to 1.25 to 1.65. In this case, the transmittance T of the phase shift film is preferably set to 10 to 22%, more preferably 12 to 22%. When the mask is exposed in this way, not only the DOF and the required exposure amount are in the preferred range, but also, as shown in FIG. 2(b), the resist pattern formed on the transferred body (here In the case of positive photoresist), there is no damage in the partition wall 13 (details will be described later) formed between the double hole patterns, and it is not easy to cause the poor connection of the double hole patterns. [Example 1]

The second mask 20 shown in FIG. 2( a ) is set as Example 1, in order to be compatible with the binary mask of Reference Example 1 shown in FIG. 3( a ) and the Reference Example 2 shown in FIG. 4( a ) The halftone type phase-shift mask (the one whose reference wavelength is set to i-ray) was compared, and the transfer characteristics of each were optically simulated.

In the second mask 20 of Example 1, the phase shift film for the halftone region 11 is set to have a phase shift of 180 degrees and a transmittance of 16.1% ( Refer to “Mid-UV PSM (Phase Shift Mask)” in FIG. 5 .

In addition, regarding the mask of Reference Example 1, on the region (light-shielding region 14 ) corresponding to the halftone region 11 of Example 1, a light-shielding film (a film that does not substantially transmit exposure light) is formed without forming a phase shift film. .

In the mask of Reference Example 2, a phase shift film having a phase shift amount of 180 degrees and a transmittance of 5.2% was formed on the halftone region 11 of Example 1 with respect to the i-ray (365 nm) as a reference wavelength. In this case, the transmittance of the phase shift film in the above-mentioned Patent Document 2 is referred to as about 5 to 6%.

The design of the pattern for transfer used to evaluate the transfer performance of the photomask composed of the above-mentioned film was set as a near (duplex) mask hole pattern. Furthermore, the aim was to form a double hole pattern with a diameter of 1.5 μm on the transfer target body, and evaluations related to the following items were performed. The shapes of the patterns for transfer in Example 1, Reference Example 1, and Reference Example 2 are shown in FIGS. 2( a ), 3 ( a ), and 4 ( a ), respectively. The characteristics of the film of the halftone region 11 (the light-shielding region 14 in the binary mask of Reference Example 1) are shown in FIG. 5 , respectively.

(1) Exposure amount (mJ/cm ² ) The exposure amount here represents the exposure amount required to obtain a pattern of a target size on a transfer object. The required exposure amount is preferably as small as possible, for example, preferably 50 mJ/cm ² or less.

(2)DOF(μm) The DOF here means the depth of focus within ±10% of the target CD value. The larger the DOF, the better, for example, it is preferably 15 μm or more.

(3) MEEF (Mask Error Enhancement Factor: Mask Error Enhancement Factor) MEEF represents the ratio of the CD error of the transfer image formed on the transferred body to the CD error of the photomask. The smaller the MEEF, the better. Furthermore, the CD error of the reticle means the actual CD error (offset) on the reticle relative to the target CD value on the reticle. The CD error of the transfer image formed on the transfer target body means the CD error (offset amount) of the actual transfer image relative to the target CD value of the transfer image formed on the transfer target body.

The optical simulation results of the transfer characteristics in Example 1, Reference Example 1 and Reference Example 2 are shown in FIG. 6 . In addition, in Example 1, Reference Example 1, and Reference Example 2, the cross-sectional shapes of the resist patterns formed on the transfer target body are shown in FIGS. 2(b), 3(b), and 4(b), respectively. b).

Reference Example 1 (binary mask) is a mask used as a reference, and may also be referred to below as a reference. As shown in FIG. 3( b ), in the photomask of Reference Example 1, in the resist pattern (here, the positive photoresist pattern) formed on the transferred body, double hole patterns are formed between each other The spacer (hereinafter referred to as the partition wall 13) has sufficient height and thickness. On the other hand, as shown in FIG. 6 , in the photomask of Reference Example 1, the DOF was small, less than 15 μm, and the manufacturing process range of the display device was insufficient.

In Reference Example 2, the same effect as that obtained by using the existing halftone type phase shift mask was observed, and the effect of improving the DOF was observed. However, in Reference Example 2, the required exposure amount is about 150% of that of Reference Example 1, and the production efficiency of the display device is lowered, and it is not suitable for mass production.

It can be seen that in Example 1, sufficient DOF was obtained, and compared with Reference Examples 1 and 2, the exposure amount could be greatly reduced (50 mJ/cm ² or less). In the cross-sectional shape of the etched pattern, the partition wall 13 between the access holes is appropriately formed, which is extremely useful. In Example 1, the reduction effect was also confirmed with respect to the numerical value of MEEF. In addition, in Example 1, the hole size on the photomask was set to 2.1 μm with respect to the target hole size 1.5 μm formed on the transfer target body. That is, the mask deviation β with Dm/Dp of 1.4 is given.

Here, in the case where the same deviations as in Example 1 were also given to Reference Example 1 and Reference Example 2 for confirmation, it was verified whether or not the transferability was improved. The size of the mask hole pattern was set to 2.1 μm by giving the deviation in Reference Example 1 as Reference Example 3 ( FIG. 7( a )), and the deviation in Reference Example 2 was set in the same way as the reference example. 4 ( FIG. 8( a )), and the results of optical simulation of the transfer performance of each are also shown in FIG. 6 .

According to the optical simulation results related to the reference example 3 and the reference example 4, in the reference example 3, although the exposure amount can be reduced by giving a deviation, the DOF is reduced to a level lower than that of the reference (reference example 1). Further, as shown in FIG. 7( b ), when the cross section of the resist pattern in Reference Example 3 is observed, it is found that the partition walls 13 are not sufficiently formed between the double hole patterns, and the double hole patterns are connected to each other. In addition, according to Reference Example 4, not only the improvement effect of DOF is still smaller than that of the reference, but also as shown in FIG. In the display device to be obtained, in order to obtain a circuit pattern without defects, it is preferable that the partition wall 13 of the resist pattern does not lose the initial thickness of the resist, but it is preferably at least 50% or more of the initial thickness. The thickness remains in the partition wall 13, more preferably 60% or more of the thickness remains.

From the above, it can be confirmed that the transfer performance of the photomask of this embodiment is very excellent. [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 with close (double) hole patterns, except that the halftone area 11 is The phase shift film was formed in the same manner as in Example 1 above except that the transmittance of the phase shift film was changed. Reference Example 5 and Reference Example 6 aimed to form a proximity (double) hole pattern of 1.5 μm size on a transfer target body in the same manner as in Example 1 described above.

For Reference Example 5 and Reference Example 6, optical simulation of transfer performance was also performed in the same manner as in Example 1. The evaluation items in this optical simulation are the same as those in Example 1. The optical simulation results are shown in FIG. 11 . In addition, in Reference Example 5 and Reference Example 6, the cross-sectional shape of the resist pattern formed on the transfer target body is shown in FIGS. 9(b) and 10(b), respectively.

In Reference Example 5, the transmittance (based on the wavelength of exposure light, 334 nm) of the phase shift film used in the halftone region 11 was set to 8%. According to the simulation results, the DOF value and the cross-sectional shape of the resist pattern are not particularly problematic, but the effect of reducing the required exposure amount is hardly obtained.

Further, in Reference Example 6, the transmittance (based on wavelength of 334 nm) of the phase shift film of the halftone region 11 was set to 25%, and as a result, no particular problems were found in the exposure amount, DOF, and MEEF. However, in Reference Example 6, as shown in FIG. 10( b ), in the cross-sectional shape of the resist pattern, the partition walls 13 were not sufficiently formed between the hole patterns.

Therefore, it is considered that the transmittance of the halftone region 11 in the near (double) hole pattern is preferably smaller than that shown in Reference Example 6 (specifically, 22% or less). On the other hand, in the isolated hole pattern, the Reference Example The transmittance shown in 6 (about 25%) is also sufficient for practical use.

The photomasks of the present invention exemplified in the above-described first photomask 10, second photomask 20, and the like can be produced by a lithography process. That is, it can be manufactured by using a photomask base obtained by forming a phase shift film on the principal plane of a substrate containing a transparent material such as quartz. When forming a phase shift film on a transparent substrate, a well-known method, such as a sputtering method, may be used. The phase shift film (forming the halftone region 11 ) is, for example, set to have a phase inversion effect in the middle ultraviolet wavelength region. Furthermore, the phase shift film is patterned as desired based on the device to be obtained.

The material of the phase shift film applied to the first mask 10 and the second mask 20 is not particularly limited. For example, a silicide of a transition metal is preferably used. For example, molybdenum silicide (MoSi) or a compound thereof (MoSiO, MoSiN, MoSiC, MoSiON, MoSiCN, MoSiCO, MoSiCON, etc.) is desirable.

Alternatively, the material of the phase shift film may be chromium (Cr) or its compounds (CrO, CrN, CrC, CrON, CrCN, CrCO, CrCON, etc.).

Further, as the metal component of the material of the phase shift film, one containing Ta (tantalum), Zr (zirconium) or Ti (for example, Zr silicide, silicide containing Mo and Zr), or a compound thereof (oxide) can be exemplified , nitrides, carbides and other compounds listed above).

The first mask 10 and the second mask 20 of the present embodiment were simulated by using a MoSi compound as a phase shift film. This phase shift film can be made into a film thickness of 100-200 nm, and can be formed by a well-known film-forming method, such as a sputtering method. In addition, dry etching or wet etching may be used for patterning of the phase shift film, but as a large-scale photomask used in the manufacture of display devices, wet etching may be advantageous.

In addition, in the first mask 10 and the second mask 20 described above, although a phase shift film for inverting the exposure light in the middle ultraviolet region is used in the halftone region 11, it is also possible to have a structure different from these. the mask. For example, a translucent film having a transmittance of exposure light T% (for example, 10≦T≦35) and substantially no phase inversion can be used in the halftone region 11 . Substantially no phase inversion effect means that the amount of phase shift with respect to the reference wavelength λ1 is 90 degrees or less, preferably 60 degrees or less. On the other hand, the light-transmitting portion 12 constituting the mask hole pattern can be formed as an etched portion in which the surface of the transparent substrate is etched to a specific thickness. In this way, the phase difference θ between the light-transmitting portion 12 and the halftone region 11 can be about 180 degrees (or just 180 degrees), and the effect of the present invention can also be obtained in such a mask.

In addition, in the photomask of the above-described embodiment, an additional film (reflection control film, resist film, etc.) can be formed on the transparent substrate within the range that does not impair the effect of the present invention.

The present invention includes a method of manufacturing a display device using the above-described photomask. Here, the display device refers to a device including a display device.

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

The illumination system of an exposure apparatus can use normal illumination. Or in addition to normal illumination, anamorphic illumination (obtained by removing the normal incidence component from the light incident on the reticle) can also be used.

In recent circuits for high image quality organic EL displays (OLEDs), the use of patterns for transfer having double or more proximity hole patterns has been improved due to the high definition of circuits. The photomask of the present invention can cope with this new technical problem.

As mentioned above, although embodiment of this invention was demonstrated concretely, this invention is not limited to the said embodiment, Various changes are possible in the range which does not deviate from the summary.

10: 1st mask 11: Halftone area 12: Translucent part 13: Distinguishing Walls 14: Shading area 20: 2nd mask d: shortest separation distance Dm: size Dp: size P: Pitch

FIG. 1 is a schematic plan view of a first photomask 10 of the present invention. (a) of FIG. 2 is a schematic plan view of the second photomask 20 of the present invention, and (b) is a schematic cross-sectional view of a resist pattern formed by exposing the second photomask 20 . (a) of FIG. 3 is a schematic top 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. (a) of FIG. 4 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. 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. FIG. 6 is a diagram showing the results of optical simulations of Example 1 of the present invention and Reference Examples 1 to 4. FIG. (a) of FIG. 7 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. FIG. (a) of FIG. 8 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. FIG. (a) of FIG. 9 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. FIG. (a) of FIG. 10 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. FIG. FIG. 11 is a graph showing the results of optical simulations of Reference Examples 5 and 6. FIG.

11: Halftone area

12: Translucent part

13: Distinguishing Walls

20: 2nd mask

d: shortest separation distance

Dm: size

Dp size

P-spacing

Claims (12)

A photomask, which is used for the manufacture of a display device for forming a hole pattern with a size of Dp and Dp≦3 μm on a transferred body using medium-ultraviolet exposure light, The transparent substrate has a pattern for transfer including a hole pattern, The hole pattern in the above-mentioned pattern for transfer includes a light-transmitting portion surrounded by a halftone region, The phase difference θ of the light-transmitting portion and the halftone region with respect to the light of the reference wavelength included in the ultraviolet exposure light used for exposing the mask is about 180 degrees, and The transmittance T of the halftone region to the light of the reference wavelength is 10%≦T≦35%. The photomask of claim 1, wherein the hole pattern in the pattern for transfer includes a light-transmitting portion formed by patterning a phase-shift film formed on the transparent substrate and exposing the transparent substrate, The above-mentioned halftone region is formed by forming the above-mentioned phase shift film on the above-mentioned transparent substrate, The phase shift film has a phase shift amount of approximately 180 degrees with respect to the light of the reference wavelength, and has a transmittance T, 10%≦T≦35%. A photomask, which is used for the manufacture of a display device for forming a hole pattern with a size of Dp and Dp≦3 μm on a transferred body using medium-ultraviolet exposure light, The transparent substrate has a pattern for transfer including a hole pattern, The hole pattern in the pattern for transfer includes a light-transmitting portion surrounded by a halftone region, When the reference wavelength is set as λ1, and λ1<365 nm, the phase difference θ between the light-transmitting portion and the halftone region relative to the light with the wavelength of λ1 is 180 degrees, and The transmittance T of the above-mentioned halftone region to the above-mentioned λ1 wavelength light is 10%≦T≦35%. The photomask of claim 3, wherein the hole pattern in the pattern for transfer includes a light-transmitting portion formed by patterning a phase-shift film formed on the transparent substrate and exposing the transparent portion substrate, The above-mentioned halftone region is formed by forming the above-mentioned phase shift film on the above-mentioned transparent substrate, The above-mentioned phase shift film has a phase shift amount of 180 degrees with respect to the above-mentioned λ1 wavelength light, and has a transmittance T, 10%≦T≦35%. The photomask according to any one of claims 1 to 4, wherein the pattern for transfer comprises an isolated hole pattern. The photomask according to any one of claims 1 to 4, wherein the pattern for transfer has a proximity hole pattern including two or more hole patterns at a close distance. The photomask of claim 6, wherein the distance between the centers of gravity of the two above-mentioned hole patterns included in the above-mentioned proximity hole patterns is 9 μm or less. The photomask according to any one of claims 1 to 4, wherein when the size of the hole pattern in the pattern for transfer is set as Dm, Dm>Dp. The photomask of any one of claims 1 to 4, wherein the above-mentioned reference wavelength is 313 nm or 334 nm. The photomask of claim 8, wherein Dm/Dp is 1.1-1.8. A method of manufacturing a display device, comprising: Steps for preparing a photomask as claimed in any one of claims 1 to 10; an exposure step of exposing the above-mentioned photomask with medium-ultraviolet exposure light; and The above-mentioned mid-ultraviolet exposure light includes the wavelength range where the wavelength λ satisfies the wavelength range of 200 nm≦λ≦400 nm, and does not include the wavelengths of λ>400 nm and λ<200 nm. The method for manufacturing a display device according to claim 11, wherein a hole pattern having a size Dp≦3 μm is formed on the transfer target body by the above-mentioned exposure step.

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