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

Abstract

The present invention relates to a photomask, a method for manufacturing a photomask, and a method for manufacturing a device for a display device, and provides a photomask having excellent transfer performance for transferring a fine line pattern onto a transfer body by exposure using an exposure apparatus. A photomask for manufacturing a display device having a transfer pattern on a transparent substrate, wherein the transfer pattern includes a line pattern. The line pattern has an edge region formed along the outer edge with a width E and a central region with a width C formed in a portion other than the edge region. The edge region has a phase shift effect that shifts the phase of the exposure light for exposing the photomask by approximately 180 degrees, and has a transmittance T1 (%) (where 0 < T1 < 10) with respect to the exposure light. The central region is formed of a light-transmitting portion or a semi-light-transmitting portion.

Description

Technical Field

[0001] The present invention relates to a photomask suitable for manufacturing a display device, a method for manufacturing the photomask, and a method for manufacturing a device for a display device. Background Art

[0002] Patent document 1 describes a photomask having a transfer pattern on a transparent substrate, comprising a light-transmitting portion, a semi-transparent portion formed by a semi-transparent film that transmits a portion of the exposure light, and a light-shielding portion formed by a light-shielding film, wherein the semi-transparent film has a transmittance of 2 to 60% and a phase shift effect of 90 degrees or less with respect to a representative wavelength of the exposure light used in transferring the transfer pattern, and the edges of the semi-transparent portion and the light-shielding portion are adjacent to each other and are formed to a width that cannot be distinguished by an exposure device.

[0003] Patent Document 2 describes an exposure method in which light from an exposure light source is incident on an optical system through a halftone mask having a line pattern. The light, having passed through the optical system, is then irradiated onto a resist layer formed of a photosensitive material on a glass substrate for exposure. Patent Document 2 describes an exposure method using a halftone-type phase-shift mask, which achieves a deep depth of focus suitable for exposure used in manufacturing TFTs formed on substrates with widely varying thicknesses, such as glass substrates used in display panels.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2013-235036

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2006-330691 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] Display devices (so-called flat panel displays, FPDs) employing liquid crystal displays (LCDs) and organic EL (electroluminescence) are used in a wide range of social applications, including mobile devices such as smartphones. There is a strong market demand for brighter, more detailed images and videos. Consequently, there is a growing demand for display devices (devices) with high pixel density and excellent power efficiency.

[0010] With this trend, the device patterns formed on the photomasks used to manufacture these devices are also trending towards becoming increasingly miniaturized. Furthermore, when the photomask is exposed and the transfer pattern is transferred to the transfer target (such as a display panel substrate), the device pattern must be transferred with high precision.

[0011] Typically, the transfer performance of a pattern formed onto a transfer medium using exposure through a photomask depends on the optical system of the exposure apparatus. Specifically, as the pattern's critical dimension (CD) decreases, accurate transfer to the transfer medium becomes impossible unless a high-resolution exposure optical system is used.

[0012] In the field of photomasks used in semiconductor device (LSI) manufacturing, where integration is higher than that of display devices and pattern miniaturization has progressed significantly, the pursuit of high resolution has led to a trend toward reduced exposure using optical systems with high numerical apertures (e.g., greater than 0.2) in exposure equipment, and a trend toward shorter wavelengths of exposure light. As a result, KrF and ArF excimer lasers (single wavelengths of 248nm and 193nm, respectively) are used in this field. However, the situation in the display field is different.

[0013] In the field of display device manufacturing, projection exposure equipment with a magnification of 100%, and the NA of this optical system is approximately 0.08 to 0.15. Furthermore, i-line, h-line, or g-line light sources are primarily used as exposure light sources, and in many cases, light sources containing multiple wavelengths (hereinafter also referred to as broadband light sources) are used. Therefore, for use in display device manufacturing, emphasis is placed on production efficiency and cost advantages, such as obtaining the amount of light required to illuminate a photomask having a large area (e.g., a rectangular main surface with a side of 200 to 2000 mm, or 300 to 2000 mm).

[0014] Generally, if the NA of the optical system is increased, the resolution is improved. However, simply replacing the exposure device used in the field of display device manufacturing with a device with a larger NA may not necessarily be advantageous in terms of cost or technology. For example, changing the existing exposure device to a device with a higher NA means a huge investment for display panel manufacturers. In addition, the increase in NA also has disadvantages such as a decrease in the depth of focus (DOF). Therefore, in a photomask for a display device with an area larger than that of a photomask for LSI manufacturing, it may lead to a decrease in production stability or a decrease in yield.

[0015] The transfer pattern of the photomask used in display device manufacturing usually includes a line pattern. As an example of the use of the line pattern, Figure 1 1 shows a line-and-space pattern of a conventional photomask 100. It includes a line pattern formed by light-shielding portions 101 and a space pattern formed by light-transmitting portions 102. The line-and-space pattern can be formed by preparing a photomask blank having a light-shielding film formed on a transparent substrate and patterning the light-shielding film using a known photolithography process.

[0016] Furthermore, as mentioned above, the demand for miniaturization of such line patterns (or line-and-space patterns) is also increasing. Specifically, in display devices that attempt to use photomasks, the demand for high-definition and bright (or power-saving) display performance necessitates the densification of mask patterns and the miniaturization of CDs.

[0017] According to Patent Document 1, as the pitch of the line-space pattern decreases, the shape of the resist pattern formed on the transfer substrate by exposure through a photomask tends to deteriorate. This leads to problems such as the transfer pattern of the photomask not being accurately reflected in the resist pattern on the transfer substrate, and individual lines becoming indistinguishable. To address this issue, Patent Document 1 describes a photomask having a semi-transparent portion (this portion has a transmittance of 2 to 60% and a phase shift of 90 degrees or less).

[0018] On the other hand, Patent Document 2 discloses a halftone phase shift mask having a line-and-space pattern as a photomask that can achieve a deep depth of focus suitable for exposure of a resist for a glass substrate for a display panel.

[0019] Halftone phase-shift masks, primarily used in semiconductor device (LSI) manufacturing, are known to offer advantages over binary masks in terms of contrast and depth of focus in the light intensity distribution during transfer by utilizing the phase shift effect of transmitted light. However, the present inventors believe that the transfer performance of the photomasks described in the aforementioned document is insufficient to meet the trend toward miniaturization and that there is room for further improvement.

[0020] Masks used in display device manufacturing often incorporate designs containing line patterns. For example, these patterns are often used in wiring patterns or line-and-space patterns formed by arranging line patterns in pixel electrodes. As mentioned above, miniaturization of these patterns and technologies that enable precise transfer of these patterns to the substrate are crucial in order to achieve high-definition, bright display performance.

[0021] For example, when a photomask has a transfer pattern comprising a line pattern of a specific fine width or a line-space pattern with a fine pitch width, it is difficult to precisely transfer the pattern onto a transfer target (such as a display panel substrate) using conventional exposure equipment used in display device manufacturing. The present inventors conducted intensive research to develop a photomask capable of precisely transferring such a pattern while achieving excellent production stability, leading to the development of the present invention.

[0022] Means for solving problems

[0023] A first aspect of the present invention relates to a photomask for manufacturing a display device, the photomask comprising a transfer pattern on a transparent substrate, wherein:

[0024] The transfer pattern includes a line pattern.

[0025] The line pattern has an edge region with a width E formed along the outer edge, and a central region with a width C formed outside the edge region.

[0026] The edge region has a phase shifting effect that shifts the phase of the exposure light for exposing the photomask by approximately 180 degrees, and has a transmittance T1 (%) with respect to the exposure light (where 0 <T1<10),

[0027] The central area is formed by a light-transmitting portion or a semi-light-transmitting portion.

[0028] The second aspect of the present invention relates to the photomask according to the first aspect, wherein the width C and the width E are C <E。

[0029] A third aspect of the present invention is the photomask according to the first or second aspect, wherein the line pattern has a width L (μm), and 1.0≤L≤7.0.

[0030] A fourth aspect of the present invention is the photomask according to any one of the first to third aspects, wherein the central region has a width C1 (μm) with 0.1≤C1<2.0, and is formed of a light-transmitting portion exposed from the transparent substrate.

[0031] The fifth embodiment of the present invention relates to a photomask described in any one of the above-mentioned embodiments 1 to 3, wherein the above-mentioned central area has a width C2 (μm) and 0.1≤C2<2.0, and has a transmittance T2 (%) relative to the above-mentioned exposure light (wherein 30≤T2<100), and is formed by a semi-transparent portion having a semi-transparent film formed on the above-mentioned transparent substrate.

[0032] A sixth aspect of the present invention is the photomask according to the fifth aspect, wherein the semi-transparent film has substantially no phase shifting effect with respect to the exposure light.

[0033] A seventh aspect of the present invention is the photomask according to any one of the first to sixth aspects, wherein the transfer pattern has a line-space pattern including the line pattern having a width L and a space pattern having a width S (μm).

[0034] An eighth aspect of the present invention is the photomask according to the seventh aspect, wherein in the line-space pattern, the width L and the width S satisfy L=S.

[0035] A ninth aspect of the present invention relates to the photomask according to the seventh aspect, wherein in the line-space pattern, the width L and the width S satisfy L>S.

[0036] A tenth aspect of the present invention is the photomask according to any one of the seventh to ninth aspects, wherein a pitch P (μm) of the line-and-space pattern satisfies 4.0≤P≤8.0.

[0037] An eleventh aspect of the present invention relates to a method for manufacturing a device for a display apparatus, comprising the following steps:

[0038] a step of preparing the photomask according to any one of the first to tenth aspects; and

[0039] A step of exposing the photomask to light using an exposure device for a display device to transfer the transfer pattern to a transfer target.

[0040] A twelfth aspect of the present invention relates to a method for manufacturing a photomask for manufacturing a display device having a transfer pattern on a transparent substrate, wherein:

[0041] The transfer pattern has a line-space pattern including a line pattern and a space pattern,

[0042] The manufacturing method has the following steps:

[0043] a step of preparing a photomask blank having a phase shift film formed on the transparent substrate and a resist film formed on the outermost surface;

[0044] a step of drawing and developing the photomask blank to form a resist pattern; and

[0045] a first patterning step of patterning the phase shift film using the resist pattern to form the line-space pattern;

[0046] The phase shift film has a phase shifting function of shifting the phase of the exposure light for exposing the photomask by approximately 180 degrees, and has a transmittance T1 (%) with respect to the exposure light (where 0 <T1<10),

[0047] The line pattern has an edge region with a width E formed along the outer edge, and a central region with a width C formed outside the edge region.

[0048] The edge region is formed by forming the phase shift film on the transparent substrate.

[0049] The central area is formed by exposing the transparent substrate.

[0050] A thirteenth aspect of the present invention relates to a method for manufacturing a photomask for manufacturing a display device having a transfer pattern on a transparent substrate, wherein:

[0051] The transfer pattern has a line-space pattern including a line pattern and a space pattern,

[0052] The manufacturing method has the following steps:

[0053] a step of preparing a photomask blank having a phase shift film formed on the transparent substrate and a resist film formed on the outermost surface;

[0054] a step of drawing and developing the photomask blank to form a resist pattern; and

[0055] A first patterning step of patterning the phase shift film using the resist pattern to form a phase shift film pattern; and

[0056] a second patterning step of patterning the semi-transparent film formed on the transparent substrate having the phase shift film pattern formed thereon to form the line-space pattern;

[0057] The phase shift film has a phase shifting function of shifting the phase of the exposure light for exposing the photomask by approximately 180 degrees, and has a transmittance T1 (%) (where 0 <T1<10),

[0058] The semi-transparent film does not substantially have a phase shifting effect on the exposure light.

[0059] The line pattern has an edge region with a width E formed along the outer edge, and a central region with a width C formed outside the edge region.

[0060] The edge region is formed by forming the phase shift film on the transparent substrate.

[0061] The central area is formed by forming the semi-transparent film on the transparent substrate.

[0062] A fourteenth aspect of the present invention relates to the method for manufacturing a photomask according to the twelfth or thirteenth aspect, wherein:

[0063] The photomask blank includes an etching mask film between the phase shift film and the resist film.

[0064] In the first patterning step, the etching mask film is etched using the resist pattern as a mask, and the phase shift film is patterned using the obtained etching mask film pattern as a mask.

[0065] A fifteenth aspect of the present invention relates to a method for manufacturing a photomask for manufacturing a display device having a transfer pattern on a transparent substrate, wherein:

[0066] The transfer pattern has a line-space pattern including a line pattern and a space pattern,

[0067] The manufacturing method has the following steps:

[0068] a step of preparing a photomask blank having a semi-transparent film formed on the transparent substrate and a resist film formed on the outermost surface;

[0069] a step of drawing and developing the photomask blank to form a resist pattern;

[0070] A first patterning step of patterning the semi-transparent film using the resist pattern to form a semi-transparent film pattern; and

[0071] a second patterning step of patterning the phase shift film formed on the transparent substrate having the semi-transparent film pattern formed thereon to form the line-space pattern;

[0072] The phase shift film has a phase shifting function of shifting the phase of the exposure light for exposing the photomask by approximately 180 degrees, and has a transmittance T1 (%) (where 0 <T1<10),

[0073] The semi-transparent film does not substantially have a phase shifting effect on the exposure light.

[0074] The line pattern has an edge region with a width E formed along the outer edge, and a central region with a width C formed outside the edge region.

[0075] The edge region is formed by forming the phase shift film on the transparent substrate.

[0076] The central area is formed by forming the semi-transparent film on the transparent substrate.

[0077] A sixteenth aspect of the present invention relates to the method for manufacturing a photomask according to the fifteenth aspect, wherein:

[0078] The photomask blank includes an etching mask film between the semi-transparent film and the resist film.

[0079] In the first patterning step, the etching mask film is etched using the resist pattern as a mask, and the semi-transparent film is patterned using the obtained etching mask film pattern as a mask.

[0080] Effects of the Invention

[0081] The photomask of the present invention has excellent transfer performance for transferring a fine line pattern onto a transfer target by exposure using an exposure device. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 FIG. 1 is a schematic plan view of a conventional photomask 100 .

[0083] Figure 2 FIG. 1 is a schematic plan view of a conventional photomask 110 .

[0084] Figure 3 1 is a schematic plan view of the photomask 1 of the present invention.

[0085] Figure 4 1 is a schematic plan view of the photomask 2 of the present invention.

[0086] Figure 5 It is a schematic cross-sectional view of a resist pattern in an optical simulation of the photomask 1 of the present invention.

[0087] Figure 6 It is a figure which shows the optical simulation result of the photomask 1 of this invention.

[0088] Figure 7 1 and 2 are diagrams showing the results of optical simulation of the photomask 2 of the present invention.

[0089] Figure 8 In the drawings, (a) is a schematic diagram of a resist pattern in an optical simulation of the photomask 1 of the present invention, and (b) is a schematic diagram of a resist pattern in an optical simulation of the photomask 2 of the present invention.

[0090] Figure 9 In FIG. 1 , (a) to (h) are schematic cross-sectional views for explaining an example of a method for manufacturing the photomasks 1 and 2 of the present invention. DETAILED DESCRIPTION

[0091] <First embodiment of the present invention>

[0092] (1) About Photomask 1

[0093] As mentioned above, Figure 1 , a photomask 100 (reference example 1) based on a known binary mask (having a line pattern formed by a light-shielding portion 101 and a gap pattern formed by a light-transmitting portion 102 on a transparent substrate) is shown. Figure 2 The phase shift portion 103 (a portion having a predetermined transmittance with respect to the exposure light and having a phase shift of approximately 180 degrees) is formed in place of Figure 1 A photomask 110 (reference example 2) based on a halftone phase shift mask (also referred to as Attn.PSM) having light-shielding portions 101 in FIG.

[0094] On the other hand, Figure 3 The photomask 1 of the present invention having a line-and-space pattern on a transparent substrate is illustrated. Different from the line patterns of the photomasks of Reference Examples 1 and 2, the line pattern 10 of this photomask 1 has two edge regions 11 each formed with a width E (μm) along two outer edges of each line pattern. It should be noted that in this specification, the outer edges of the line pattern refer to one end and the other end in the width direction of the line pattern, and are not limited to the entire edge surrounding the line pattern. In addition, the line pattern 10 has a central region 12 with a width C1 (μm) formed in a portion other than the edge regions 11. That is, the central region 12 is located between two edge regions 11 formed along two opposite ends (side ends) of the line pattern 10. Preferably, the central region 12 is formed by being sandwiched between the two edge regions 11 in contact. In addition, a space pattern 13 with a width S (μm) is formed between two adjacent line patterns 10.

[0095] Here, the edge region 11 has a phase shift effect of shifting the phase of the exposure light for exposing the photomask 1 by approximately 180 degrees. Therefore, the edge region 11 can also be referred to as a phase shift region. Approximately 180 degrees is within the range of 180 ± 20 degrees, and more preferably within the range of 180 ± 10 degrees.

[0096] In addition, the edge region 11 has a transmittance T1 (%) with respect to the exposure light. 0 < T1 < 10%, and more specifically, it preferably satisfies 4 ≤ T1 < 7. Here, the transmittance is a value based on the transmittance of the transparent substrate (100%), and the same applies hereinafter. When the range of the transmittance T1 is within the above range, it is preferable to produce a balance of the interaction of the exposure light described later, and it is easy to improve the transferability.

[0097] The exposure light is the light irradiated by the light source of the exposure apparatus for manufacturing a display device. For example, light with a wavelength of 300 to 500 nm can be used. It should be noted that in this specification, "A to B" means a numerical range of "A or more and B or less". As the exposure light, a single wavelength (for example, i-line with a wavelength of 365 nm) can be used, or a light source including two or more wavelengths (hereinafter also referred to as a wide wavelength light source) can also be used. Regarding the above-described phase shift amount and transmittance with respect to the exposure light, in the case where the exposure light is formed of a single wavelength, it refers to the phase shift amount and transmittance with respect to that wavelength, and in the case of using a wide wavelength light source, it refers to the phase shift amount and transmittance with respect to any wavelength (referred to as a representative wavelength) included in the wavelength region of the wide wavelength light source.

[0098] Figure 3The central region 12 shown in the photomask 1 has a width C1 and is formed in a slit shape. In this first embodiment, this portion is a narrow-width light-transmitting portion formed by exposing the transparent substrate, and the transmittance with respect to the exposure light is 100%.

[0099] The line pattern 10 has a width L (μm), where L = 2×E + C1. Also, the width L can be 1.0 ≤ L ≤ 7.0.

[0100] The width E of the edge region 11 can be, for example, 0.4 ≤ E ≤ 2.0, and more specifically, can be 0.8 ≤ E ≤ 1.8.

[0101] In addition, the width C1 of the central region 12 can be 0.1 ≤ C1 < 2.0, and more specifically, can be 0.5 ≤ C1 ≤ 1.5. Here, the width C1 and the width E are preferably C1 < E. Further, the ratio (C1 / L) of the width C1 to the width L is preferably 0.05 to 0.4, more specifically 0.15 to 0.3, and further 0.2 to 0.3, and thus has advantages such as improving the DOF improvement effect described later.

[0102] The width C1 of the central region 12 is preferably a fine width smaller than the width E and smaller than the width S.

[0103] In addition, regarding the ratio of the width dimensions of the gap pattern 13 through which the exposure light passes to the width of the central region 12, considering the influence on their interaction, the ratio (C1 / S) of the width C1 to the width S is preferably 0.05 to 0.8, more specifically 0.1 to 0.7, and further 0.3 to 0.6, and thus excellent optical characteristics can be obtained.

[0104] That is, it is preferable that such a narrow-width slit (central region 12) is disposed at the center in the width direction of the line pattern 10 and the edge regions 11 sandwich the slit from both sides. The width C1 of the central region 12 is smaller than the resolution limit of the exposure apparatus for manufacturing the display device, and thus is not independently transferred onto the transfer body. However, the present inventors have found that when transferring the line pattern 10 (or line-and-gap pattern), excellent effects are exhibited in a plurality of evaluation items indicating its transfer performance. Here, the center in the width direction of the line pattern 10 means that the center in the width direction of this slit (central region 12) coincides with the center in the width direction of the line pattern 10, but also includes cases where a positional deviation occurs within a range of ±10 nm.

[0105] Figure 3The line-space pattern is shown as a regular arrangement of the line patterns 10. As described above, in this line-space pattern, line patterns 10 of width L and gap patterns 13 of width S are regularly arranged alternately. The width S can be 0.3≤S≤3.5, more specifically, 0.8≤S≤3.0.

[0106] The repetitive pitch P (μm) of the line-and-space pattern is preferably 4.0 ≤ P ≤ 8.0. When the pitch P is greater than 8.0 μm, a certain degree of transferability can be achieved using existing photomasks 100 and 110 (binary masks, Attn. PSM), and thus the effects of the present invention are not significant. On the other hand, when the pitch P is less than 4.0 μm, it tends to be difficult to design a processable central region 12.

[0107] Here, the width L and the width S can be L=S, or L≠S. For example, L>S or L <S。 Figure 3 shows the case where L>S. That is, the ratio of width S to width L (S / L) can be in the range of 0.2 to 1.0, more specifically 0.3 to 0.9, and when it is 0.3 to 0.7, more significantly advantageous optical performance can be obtained in the DOF and other aspects described later.

[0108] Here, in the transfer pattern of photomask 1, a ratio L > S is advantageous in the following circumstances. Specifically, after pattern transfer using photomask 1, an etching process is performed on the object to be transferred (display panel substrate) using the resulting resist pattern as a mask after development. When wet etching is employed, undercuts occur in the object being etched (e.g., a thin film of electrode material). Therefore, it is advantageous to pre-set the width L slightly larger than the final target size.

[0109] When the optical function of the photomask 1 was simulated as described later, extremely advantageous results were obtained in several characteristics compared to the photomask 110 of Reference Example 2.

[0110] Next, an optical simulation performed to verify the operation of the photomask 1 of the present invention will be described.

[0111] Here, the photomask used in the simulation is a sample mask of the photomask 1 having a line-space pattern with a pitch P of 6 μm. Figure 6 It is described as Type 1 (a) to (e).

[0112] Regarding the optical simulation conditions, the same magnification projection exposure device for display device is used as the premise. Figure 5The conditions shown are simulation conditions: NA: 0.1 / coherence coefficient: 0.9, initial PR thickness: 1.40 μm. After exposing the photomask 1 having the above-mentioned line-space pattern, the cross-sectional shape of the resist pattern formed on the transfer object is obtained ( Figure 5 ), and find out the values ​​of multiple parameters that represent the transferability. Figure 6 .

[0113] It should be noted that the initial film thickness of the resist (positive type) is 1400 nm. In addition, the line-space pattern of the photomask 1 is formed by patterning a phase shift film with an exposure light transmittance of 5.2% and a phase shift of 180 degrees (all based on the i-line) on a transparent substrate. The width C1 of the central area 12 formed in the center of the width direction of the line pattern is Figure 6 The following conditions were set at this time: lines and spaces of the same size as the transfer pattern of the photomask 1 were transferred to the bottom of the resist pattern formed on the transfer target.

[0114] The evaluation items are as follows.

[0115] Eop(mJ / cm 2 )

[0116] Eop refers to the exposure light intensity required to obtain a transfer image of the target size on the transfer substrate. A lower Eop is preferred. Here, Eop refers to the exposure light intensity required to form a line-space pattern on the transfer substrate that is the same size as the transfer pattern on the photomask.

[0117] Resist pattern side tilt angle θ (degrees)

[0118] like Figure 5 As shown, the resist pattern side tilt angle θ represents the tilt angle of the side surface of the resist pattern formed on the transfer target. Specifically, it refers to the angle formed between the main surface of the transparent substrate (the surface where the phase shift film is formed) and the side surface of the resist pattern formed on the transfer target. The resist pattern side tilt angle θ is preferably large (close to 90 degrees).

[0119] DOF (Depth of Focus)

[0120] DOF stands for depth of focus. Here, the depth of focus required to achieve an accuracy within ±10% of the target CD is defined as DOF. A larger DOF value minimizes the CD of the pattern on the transfer substrate from being affected by factors such as the flatness of the transfer substrate surface, thus reducing CD variation.

[0121] EL (Exposure Latitude)

[0122] EL stands for exposure latitude. Here, the EL is the size of the exposure latitude required to achieve an accuracy within the range of ±10% relative to the target CD. A larger EL is preferred.

[0123] MEEF (Mask Error Enhancement Factor)

[0124] MEEF is a numerical value that represents the ratio of the CD error of the photomask to the CD error of the transferred image formed on the transfer substrate. The lower this value, the lower the CD error of the pattern formed on the transfer substrate. It should be noted that the CD error here refers to the difference between the target CD and the CD of the pattern on the photomask or transfer substrate.

[0125] NILS (Normalized Image Log Slope)

[0126] NILS is a value obtained by normalizing the edge tilt of the resist pattern formed on the transfer target (the tilt of the side surface in the cross section of the resist pattern), and a larger value is more preferable.

[0127] Depend on Figure 6 As can be seen, compared to Reference Example 2 (Attn.PSM with a line-space pattern without slits), the performance in all evaluation parameters was comparable or better. In particular, all sample masks of Photomask 1 (Types 1(a) to (e)) exhibited a DOF of 25μm or greater, demonstrating a wide process latitude in display device manufacturing.

[0128] Furthermore, the reduction in the Eop value is very advantageous as an exposure condition for a photomask used in manufacturing a display device having a large exposure area, and suggests that further improvement in productivity can be achieved.

[0129] Furthermore, the side tilt angle θ is closer to vertical, suggesting that in-plane CD deviation is also suppressed. DOF is greater than 25 μm and is significantly improved compared to the photomask 110 of Reference Example 2.

[0130] In addition, a significant trend of decreased MEEF and increased NILS was observed.

[0131] From the above, the excellent effects of the photomask 1 of the present invention have been confirmed.

[0132] The principle behind this effect can be considered as follows. When exposing a line-space pattern using a conventional binary mask, light transmitted through the space pattern creates a peak in the light intensity distribution on the transfer medium. Using an Attn.PSM improves contrast, but the peak height decreases slightly.

[0133] In contrast, in the photomask 1 of the present invention, light passing through the slit (central region 12) formed in the center of the width direction of the line pattern 10 interacts well with light passing through the gap pattern 13, thereby increasing the height of the peak and achieving a contrast enhancement effect based on the phase shift effect.

[0134] It should be noted that according to Figure 5 As can be seen from the cross-sectional view of the resist pattern shown in FIG, a depression is formed in the center of the upper surface of the resist corresponding to the line pattern 10. The inventors further studied the situation assuming that it is necessary to suppress this depression (thickness loss of the resist pattern) as much as possible. As a result, it was found that the effect was obtained by reducing the transmittance of the central area 12 to less than 100%. The photomask 2 is shown in FIG. Figure 4 .

[0135] (2) About Photomask 2

[0136] Figure 4 The photomask 2 shown is obtained by setting the transmittance T2 (%) of the central region 12 to exposure light to 30 ≤ T2 < 100. For example, the central region 12 may be formed as a portion formed by forming a semi-transparent film having a desired transmittance on a transparent substrate.

[0137] Here, unlike the so-called phase shift film, the semi-transparent film is preferably a film that does not substantially have a phase shift effect (does not have the function of reversing the phase of the exposure light). Specifically, the phase shift amount of the semi-transparent film relative to the above-mentioned exposure light is It is preferably less than 90 degrees, for example, in the range of 5 to 90 degrees. It is more preferably within the range of 60 degrees or less, and even more preferably within the range of 30 degrees or less.

[0138] In the following simulations, the central region 12 of the photomask 2 is a semi-transparent portion with a transmittance T2 of 55% (i-line reference). This central region 12 does not have a phase shifting effect (a phase shift of 0 degrees). Furthermore, in the pattern design of the photomask 2, the ranges of values ​​and the ratios of the values ​​of width L, width S, width E, and width C1 used in the photomask 1 can be similarly applied to the values ​​of width L, width S, width E, and width C2 used in the photomask 2.

[0139] Furthermore, since the transmittance T2 of the central region 12 of photomask 2 is lower than the transmittance (100%) of the central region 12 of photomask 1, to achieve the same level of light transmission, width C2 can be made slightly wider than width C1, thereby easing the difficulty of processing fine widths. In this case, for example, the ratio of width C2 to width L (C2 / L) can be set to 0.2 to 0.4, and the ratio of width C2 to width S (C2 / S) can be set to 0.5 to 1.0.

[0140] As described above, the photomask 2 has a further advantage in the shape of the resist pattern formed on the transfer target. In the case of the photomask 2, the following items were evaluated.

[0141] RPT (Residual Resist Thickness) and PR Loss (Resist Loss Rate)

[0142] The impact of a central depression in the resist pattern on the transferred object was evaluated at the center of the line pattern. Excessive depression can cause problems in the etching process using this resist pattern, while increased depression depth can lead to in-plane variations in depth.

[0143] Figure 7 The simulation results of the photomask 2 are shown in FIG. 1 . The photomask used in the simulation is a sample mask of the photomask 2. Figure 7 In the above examples, the types are 2(b) and 2(c). Figure 7 Compared to the resist patterns using photomask 1 (types 1(b) and 1(c)), the resist patterns using photomask 2 (types 2(b) and 2(c)) have larger RPTs and smaller PR Losses. This indicates that the concavity generated in the center portion of the resist pattern in the line width direction (the position corresponding to the central region 12 of photomask 2) formed on the transferred object is smaller than that in the case of photomask 1.

[0144] Figure 8 (a) shows an example of a resist pattern based on the photomask 1, Figure 8 (b) shows an example of a resist pattern using photomask 2. As can be seen from this, the resist pattern using photomask 2 has a shape in which the concavity in the center portion is significantly reduced compared to the resist pattern using photomask 1.

[0145] (3) Method for manufacturing a device for a display device

[0146] The present invention includes a method for manufacturing a display device using the aforementioned photomask 1 or photomask 2. Specifically, the method comprises preparing the aforementioned photomask 1 or photomask 2, using it and performing exposure using a display device exposure apparatus, transferring the aforementioned transfer pattern to a transfer target, and applying this process to manufacture a display device (or its component components).

[0147] The exposure apparatus used is a projection exposure method. Applicable apparatus has an NA of 0.08 to 0.20, a coherence coefficient σ of approximately 0.5 to 1.0, and an exposure light source containing wavelengths of i-line, h-line, or g-line. Of course, broad wavelength light containing any of these wavelengths can also be used. Equal magnification exposure is preferably used.

[0148] (4) Method for Manufacturing Photomasks 1 and 2

[0149] Refer to the following Figure 9 (a) to (h) describe methods for manufacturing the photomasks 1 and 2.

[0150] like Figure 9 As shown in (a), a photomask blank 20 is prepared, in which a phase shift film 22 and a resist film 24 are formed on a transparent substrate 21. The resist film 24 can be made of either a positive resist or a negative resist, with a positive resist being used here. Additional films may also be used within a range that does not impair the effects of the present invention. In this embodiment, an etching mask film 23 is sandwiched between the phase shift film 22 and the resist film 24. This film has the effect of improving adhesion with the resist film 24 and increasing the wet etching accuracy of the phase shift film 22. The phase shift film 22 and the etching mask film 23 can be formed using a known film forming apparatus such as a sputtering method.

[0151] The material of the phase shift film 22 is not particularly limited. When using the etching mask film 23, a material having different etching characteristics (etching selectivity) from the etching mask film 23 is preferably used. As the material of the phase shift film 22, for example, a material containing any of Zr, Nb, Hf, Ta, Mo, Ti, and Si, or a material containing oxides, nitrides, oxynitrides, carbides, or oxynitride-carbides of these materials can be used. More specific examples of the film material include a material containing Mo or Zr silicide.

[0152] The etching mask film 23 can be made of a material that is resistant to the etchant used for the phase shift film 22, and preferably has higher adhesion to the resist (e.g., positive resist) than the material of the phase shift film 22. The etching mask film 23 can be made of, for example, Cr or a compound thereof (oxide, nitride, carbide, oxynitride, or oxynitride carbide).

[0153] like Figure 9As shown in (b), the resist film 24 is drawn and developed to form a resist pattern 25. Drawing can be performed using a laser drawing device. The resist pattern 25 is formed to have openings in the region to be the gap pattern 13 and the region to be the central region 12.

[0154] like Figure 9 As shown in (c), the etching mask film 23 is patterned using the resist pattern 25 as a mask to form an etching mask film pattern. Thereafter, the phase shift film 22 is patterned using the resist pattern 25 and / or the etching mask film pattern as a mask. This forms a phase shift film pattern (first patterning step). In the case where the photomask blank 20 does not include the etching mask film 23, the phase shift film 22 can be patterned using the resist pattern 25 as a mask. In addition, although not shown, after stripping the resist pattern 25, the phase shift film 22 can be patterned using only the etching mask film pattern as a mask. The patterning of the etching mask film 23 and the phase shift film 22 in this embodiment can be performed by either wet etching or dry etching, preferably wet etching.

[0155] like Figure 9 As shown in FIG. 2 , the resist pattern 25 is peeled off, or the resist pattern 25 and the etching mask film pattern are peeled off, to form a photomask 1. In this photomask 1, the edge region 11 is formed by forming the phase shift film 22 on the main surface of the transparent substrate 21, and the central region 12 is formed by exposing the main surface of the transparent substrate 21. The line pattern of the photomask 1 includes the edge region 11 and the central region 12.

[0156] like Figure 9 As shown in FIG. 2 (e), in order to obtain a photomask 2, a semi-transparent film 26 is formed on the entire surface of a transparent substrate 21 having a patterned phase shift film 22 (phase shift film pattern). Sputtering or other methods can be used for this film formation. As described above, it is preferable to use a film that does not substantially have a phase shifting effect for this semi-transparent film 26.

[0157] The material of the semi-transparent film 26 preferably has etching selectivity with the phase shift film 22. When the phase shift film 22 is the phase shift film exemplified above, Cr or its compound (oxide, nitride, carbide, oxynitride, or oxynitride carbide) can be used as the material of the semi-transparent film 26.

[0158] like Figure 9 As shown in (f), a resist film 27 is further formed on the uppermost surface by coating. Here, the case of using a positive resist film is also shown as an example.

[0159] like Figure 9 As shown in (g), the resist film 27 is again subjected to drawing using a laser drawing apparatus or the like, and then developed to form a resist pattern 28 in which the resist remains in a portion to be the central region 12 .

[0160] like Figure 9 As shown in (h), using the resist pattern 28 as a mask, the unnecessary semi-transparent film 26 is removed by wet etching (second patterning step), and the resist pattern 28 is further peeled off to obtain the photomask 2. In this photomask 2, the edge region 11 is formed by forming the phase shift film 22 on the main surface of the transparent substrate 21, and the central region 12 is formed by forming the semi-transparent film 26 on the main surface of the transparent substrate 21. The line pattern of the photomask 2 includes the edge region 11 and the central region 12. In the edge region 11 of the photomask 2, only the phase shift film 22 is formed on the transparent substrate 21. In addition, in the central region 12 of the photomask 2, only the semi-transparent film 26 is formed on the transparent substrate 21. In other words, the line pattern of the photomask 2 does not include the laminated portion of the phase shift film 22 and the semi-transparent film 26.

[0161] While the above-described methods for manufacturing photomasks 1 and 2 describe a case where a photomask blank 20 having a phase shift film 22 formed on a transparent substrate 21 is used, the present invention is not limited thereto. For example, a photomask blank 20 may be prepared in which a semi-transparent film 26 is formed on the transparent substrate 21 in place of the phase shift film 22, and a resist film is formed on the outermost surface. The photomask blank 20 is then subjected to drawing and development to form a resist pattern. The semi-transparent film 26 is then patterned using the resulting resist pattern to form a semi-transparent film pattern (a first patterning step). Subsequently, the phase shift film 22 is formed on the transparent substrate having the semi-transparent film pattern formed thereon, and the phase shift film 22 is patterned to form a line-and-space pattern (a second patterning step). In other words, when using a photomask blank 20 having a semi-transparent film 26 formed on the transparent substrate 21, the phase shift film 22 and the semi-transparent film 26 used in the above-described methods for manufacturing photomasks 1 and 2 can be reversed.

[0162] In addition, the photomask blank 20 may have an etching mask film between the semi-transparent film 26 and the resist film. In this case, in the above-mentioned first patterning step, the etching mask film may be etched using the above-mentioned resist pattern as a mask, and the semi-transparent film 26 may be patterned using the obtained etching mask film pattern as a mask, or using the above-mentioned resist pattern and etching mask film pattern as a mask. The use of the photomasks exemplified by photomask 1 and photomask 2 is not particularly limited. Among them, the photomasks exemplified by photomask 1 and photomask 2 are distinguished from so-called multi-grayscale photomasks because the resist pattern formed on the transferred body by the photomasks exemplified by photomask 1 and photomask 2 is used for the purpose of the two-dimensional (on the plane) design formed by the bottom CD. The multi-grayscale photomask here refers to a photomask with halftones for making the thickness (height) of the resist pattern formed on the transferred body different depending on the region (i.e., forming a three-dimensional design).

[0163] Furthermore, the photomask of the present invention can be advantageously used in wiring patterns, pixel patterns, and the like of display devices requiring fine line-space patterns.

[0164] While the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

[0165] Explanation of symbols

[0166] 1 Photomask

[0167] 2 Photomask

[0168] 10 Line Pattern

[0169] 11 Marginal Area

[0170] 12 Central Area

[0171] 13 Gap Pattern

[0172] 20 Photomask blank

[0173] 21 Transparent substrate

[0174] 22 Phase shift film

[0175] 23 Etching mask film

[0176] 24 Resist film

[0177] 25 Resist pattern

[0178] 26 semi-transparent film

[0179] 27 Resist film

[0180] 28 Resist pattern

[0181] 100 Photomask

[0182] 101 Shading part

[0183] 102 light-transmitting part

[0184] 103 Phase Shift Unit

[0185] 110 Photomask

Claims

1. A photomask for manufacturing a display device, comprising a pattern for transfer on a transparent substrate, wherein: The transfer pattern has a line-space pattern including a line pattern with a width of L μm and a gap pattern with a width of S μm through which exposure light passes. The line pattern has an edge region formed along an outer edge with a width E, and a central region formed outside the edge region with a width C. The edge region has a phase shift function that shifts the phase of the exposure light for exposing the photomask by 180±20 degrees, and has a transmittance T1 (%) and 0 <T1<10, The central area is formed by a light-transmitting portion or a semi-light-transmitting portion.

2. The photomask according to claim 1, wherein The width C and the width E satisfy C <E。 3. The photomask according to claim 1 or 2, wherein: The line pattern has the width L μm and 1.0≤L≤7.

0.

4. The photomask according to claim 1 or 2, wherein: The central region has a width C1 μm with 0.1≤C1<2.0, and is formed by a light-transmitting portion exposed from the transparent substrate.

5. The photomask according to claim 1 or 2, wherein: The central area is formed by a semi-transparent portion. The semi-transparent portion forms a semi-transparent film on the transparent substrate. The semi-transparent portion has a width C2 μm and 0.1≤C2<2.0, and has a transmittance T2% with respect to the exposure light and 30≤T2<100.

6. The photomask according to claim 5, wherein The semi-transparent film has substantially no phase shifting effect with respect to the exposure light.

7. The photomask according to claim 1 or 2, wherein: In the line-space pattern, the width L and the width S are L=S.

8. The photomask according to claim 1 or 2, wherein: In the line-space pattern, the width L and the width S are L>S.

9. The photomask according to claim 1 or 2, wherein: The pitch P (μm) of the line-space pattern is 4.0≤P≤8.

0.

10. A method for manufacturing a device for a display device, comprising the following steps: A step of preparing the photomask according to any one of claims 1 to 9; and A step of exposing the photomask to light using an exposure device for a display device to transfer the transfer pattern to a transfer target.

11. A method for manufacturing a photomask for use in manufacturing a display device, the method comprising: The transfer pattern has a line-space pattern including a line pattern and a space pattern through which exposure light passes. The manufacturing method has the following steps: a step of preparing a photomask blank having a phase shift film formed on the transparent substrate and a resist film formed on the outermost surface; a step of drawing and developing the photomask blank to form a resist pattern; as well as a first patterning step of patterning the phase shift film using the resist pattern to form the line-space pattern; The phase shift film has a phase shift function of shifting the phase of the exposure light for exposing the photomask by 180±20 degrees, and has a transmittance T1 (%) and 0 <T1<10, The line pattern has an edge region formed along an outer edge with a width E, and a central region formed outside the edge region with a width C. The edge region is formed by forming the phase shift film on the transparent substrate. The central area is formed by exposing the transparent substrate.

12. A method for manufacturing a photomask for use in manufacturing a display device, the method comprising: The transfer pattern has a line-space pattern including a line pattern and a space pattern through which exposure light passes. The manufacturing method has the following steps: a step of preparing a photomask blank having a phase shift film formed on the transparent substrate and a resist film formed on the outermost surface; a step of drawing and developing the photomask blank to form a resist pattern; as well as a first patterning step of patterning the phase shift film using the resist pattern to form a phase shift film pattern; as well as a second patterning step of patterning the semi-transparent film formed on the transparent substrate on which the phase shift film pattern is formed to form the line-space pattern; The phase shift film has a phase shift function of shifting the phase of the exposure light for exposing the photomask by 180±20 degrees, and has a transmittance of T1 (%) and 0 <T1<10, The semi-transparent film has substantially no phase shifting effect on the exposure light. The line pattern has an edge region formed along an outer edge with a width E, and a central region formed outside the edge region with a width C. The edge region is formed by forming the phase shift film on the transparent substrate. The central area is formed by forming the semi-transparent film on the transparent substrate.

13. The method for manufacturing a photomask according to claim 11 or 12, wherein: The photomask blank has an etching mask film between the phase shift film and the resist film. In the first patterning step, the etching mask film is etched using the resist pattern as a mask, and the phase shift film is patterned using the obtained etching mask film pattern as a mask.

14. A method for manufacturing a photomask for use in manufacturing a display device, the method comprising: The transfer pattern has a line-space pattern including a line pattern and a space pattern through which exposure light passes. The manufacturing method has the following steps: a step of preparing a photomask blank having a semi-transparent film formed on the transparent substrate and a resist film formed on the outermost surface; a step of drawing and developing the photomask blank to form a resist pattern; a first patterning step of patterning the semi-transparent film using the resist pattern to form a semi-transparent film pattern; as well as a second patterning step of patterning the phase shift film formed on the transparent substrate having the semi-transparent film pattern formed thereon to form the line-space pattern; The phase shift film has a phase shift function of shifting the phase of the exposure light for exposing the photomask by 180±20 degrees, and has a transmittance of T1 (%) and 0 <T1<10, The semi-transparent film has substantially no phase shifting effect on the exposure light. The line pattern has an edge region formed along an outer edge with a width E, and a central region formed outside the edge region with a width C. The edge region is formed by forming the phase shift film on the transparent substrate. The central area is formed by forming the semi-transparent film on the transparent substrate.

15. The method for manufacturing a photomask according to claim 14, wherein: The photomask blank has an etching mask film between the semi-transmissive film and the resist film. In the first patterning step, the etching mask film is etched using the resist pattern as a mask, and the semi-transparent film is patterned using the obtained etching mask film pattern as a mask.

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