Photomask, and method for producing display device

Abstract

To provide a photomask having excellent transfer performance for transferring a fine hole pattern on a body to be transferred, by exposing with mid-ultraviolet exposure light.SOLUTION: There is provided a photomask for producing a display device to form a hole pattern on a substrate by using mid-ultraviolet exposure light, wherein the phase difference θ between a transmissive portion and a phase shift film with respect to light of a reference wavelength λ1 contained in the mid-ultraviolet exposure light for exposing the photomask is within the range of 180±15 degrees; the numerical aperture NA of the projection optical system of the exposure apparatus in which the photomask is used is 0.08 or more and 0.20 or less; the mid-ultraviolet exposure light has intensity peaks at two or more wavelengths among 313 nm, 334 nm, and 365 nm; and the reference wavelength λ1 is 313 nm or 334 nm.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a photomask, particularly to a photomask that is advantageous for manufacturing high-definition display devices, and to a method for manufacturing a display device using the same. [Background technology]

[0002] Patent Document 1 describes a phase shift mask blank for use in manufacturing a display device, and a phase shift mask manufactured using the phase shift mask blank, and further describes that the phase shift mask is exposed to composite light including i-line, h-line, and g-line.

[0003] Patent Document 2 describes a phase shift mask blank for use in manufacturing a display device, which includes a phase shift film that exhibits optical properties with reduced wavelength dependency on exposure light, and in which the phase shift film has a transmittance at a wavelength of 365 nm in the range of 3.5% to 8%, a phase difference at a wavelength of 365 nm in the range of 160 degrees to 200 degrees, and a wavelength-dependent change in transmittance in the wavelength range of 365 nm to 436 nm inclusive of 5.5% or less. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-194531 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-102633 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for display devices, including LCDs (liquid crystal displays) and OLED displays (organic light-emitting diode displays), that not only offer bright, high-resolution display performance, but also power savings and fast video response times. This has led to demand for increasingly finer and more highly integrated photomask patterns, which are used in the manufacturing process of these display devices. Furthermore, there is a demand for technology that can precisely resolve the photomask patterns onto the substrate (such as a display panel substrate).

[0006] However, unless the transfer pattern on the photomask can be optically resolved onto the transfer target, it is impossible to create a display device with the intended fine pattern. Here, the spatial resolution of the optical image can be expressed by Rayleigh's resolution criterion, i.e., the following equation (1).

[0007] δ=k1×λ / NA (1) Here, δ is the minimum resolution linewidth, λ is the exposure wavelength, NA is the numerical aperture of the optical system of the exposure tool, and k1 is a coefficient also called the k1 factor.

[0008] 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, light of a wavelength band (hereinafter also referred to as broadband) that includes and mixes multiple wavelengths of light is used, and in particular, the application of exposure light that includes light of three wavelengths, namely g-line (436 nm), h-line (405 nm), and i-line (365 nm), which are wavelengths included in the light of a high-pressure mercury lamp, is known (see Patent Documents 1 and 2).

[0009] On the other hand, according to the above formula (1), in order to improve the resolution of fine patterns (i.e., to reduce the minimum resolvable linewidth δ), it is effective to reduce λ or increase the NA. However, according to the following formula (2), it can be understood that increasing the NA relatively deteriorates the stability of the lithography process because it reduces the depth of focus. Formula (2) is also known as the Rayleigh depth of focus formula.

[0010] DOF=k2×λ / NA 2 ···(2) Here, DOF (Depth of Focus) means the depth of focus, and k2 is a coefficient.

[0011] The magnitude of the value on the left side of equation (2) has the opposite relationship to the resolution standard equation (equation (1)). In other words, a small value on the left side of equation (1) is preferable, but a large value is desirable in equation (2).

[0012] Therefore, there is a trade-off between the minimum resolution linewidth δ and DOF. However, because the DOF expressed in equation (2) deteriorates in proportion to the square of the NA, assuming the same level of resolution improvement, it can be said that shortening the wavelength of the exposure light is more rational than increasing the NA. In other words, it is possible to suppress the decrease in DOF while improving resolution.

[0013] One possible method for easily achieving shorter wavelengths in the above broadband exposure environment is to switch to exposure using a single i-line wavelength instead of mixed wavelength exposure including g-line, h-line, and i-line, thereby effectively reducing the wavelength. However, this method would mean cutting off the contribution of two of the three wavelengths mentioned above, which means that the amount of work per unit time would drop to one-third by simple calculation. In the FPD production field, in addition to the above resolution, another important factor is production efficiency, making it difficult to adopt a single wavelength.

[0014] Therefore, a method can be considered in which the center of gravity is shifted to the shorter wavelength side while maintaining a broadband exposure environment. In high-pressure mercury lamp light, there are several wavelength groups with peaks of light intensity on the shorter wavelength side than the i-line, and the above method utilizes light from these wavelength groups as exposure energy.

[0015] The present inventors have considered a new broadband exposure environment in which the wavelength range used in conventional exposure light has been shifted to the shorter wavelength side, and have conducted extensive research into what kind of photomask can be adapted to this environment and exhibit excellent transferability, and have completed the present invention. [Means for solving the problem]

[0016] A first aspect of the present invention is A photomask for manufacturing a display device, for forming a hole pattern having a size of Dp and Dp≦3 μm on a transfer target using mid-ultraviolet exposure light, A transfer pattern including a hole pattern is formed on a transparent substrate, the hole pattern in the transfer pattern is made of a light-transmitting portion surrounded by a halftone region, a phase difference θ between the light transmitting portion and the halftone region is approximately 180 degrees with respect to light of a reference wavelength included in mid-ultraviolet exposure light for exposing the photomask; The transmittance T of the halftone region for light of the reference wavelength is 10%≦T≦35%. It is a photomask.

[0017] A second aspect of the present invention is the hole pattern in the transfer pattern is formed by a light-transmitting portion that exposes the transparent substrate and is formed by patterning a phase shift film formed on the transparent substrate; the halftone region is formed by forming the phase shift film on the transparent substrate, In the photomask according to the first aspect, the phase shift film has a phase shift of approximately 180 degrees with respect to light of the reference wavelength, and has a transmittance T, where 10%≦T≦35%.

[0018] A third aspect of the present invention is A photomask for manufacturing a display device, for forming a hole pattern having a size of Dp and Dp≦3 μm on a transfer target using mid-ultraviolet exposure light, A transfer pattern including a hole pattern is formed on a transparent substrate, the hole pattern in the transfer pattern is made of a light-transmitting portion surrounded by a halftone region, When a reference wavelength is λ1 and λ1<365 nm, a phase difference θ between the light transmitting portion and the halftone region is 180 degrees with respect to light having a wavelength of λ1; and The transmittance T of the halftone region for light of the wavelength λ1 is 10%≦T≦35%. It is a photomask.

[0019] A fourth aspect of the present invention is the hole pattern in the transfer pattern is formed by a light-transmitting portion that exposes the transparent substrate and is formed by patterning a phase shift film formed on the transparent substrate; the halftone region is formed by forming the phase shift film on the transparent substrate, In the photomask according to the third aspect, the phase shift film has a phase shift of 180 degrees with respect to light having the wavelength λ1, and has a transmittance T, where 10%≦T≦35%.

[0020] A fifth aspect of the present invention is In the photomask according to any one of the first to fourth aspects, the transfer pattern includes an isolated hole pattern.

[0021] A sixth aspect of the present invention is In the photomask according to any one of the first to fifth aspects, the transfer pattern has a proximate hole pattern including two or more hole patterns that are in close proximity to each other.

[0022] A seventh aspect of the present invention is In the photomask according to the sixth aspect, the distance between the centers of gravity of two of the hole patterns included in the adjacent hole pattern is 9 μm or less.

[0023] An eighth aspect of the present invention is The photomask according to any one of the first to seventh aspects, wherein when the size of the hole pattern in the transfer pattern is Dm, Dm>Dp.

[0024] A ninth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The photomask according to the eighth aspect, wherein Dm / Dp is 1.1 or more and 1.8 or less.

[0025] A tenth aspect of the present invention is a method for manufacturing a semiconductor device comprising: The photomask according to any one of the first to ninth aspects, wherein the reference wavelength is 313 nm or 334 nm.

[0026] An eleventh aspect of the present invention is a method for manufacturing a semiconductor device comprising: A method for manufacturing a display device, comprising: A step of preparing a photomask according to any one of the first to tenth aspects; an exposure step of exposing the photomask to mid-ultraviolet exposure light; The mid-ultraviolet exposure light has a wavelength λ in a wavelength range that satisfies 200 nm≦λ≦400 nm, and does not include wavelengths that are λ>400 nm and λ<200 nm. A method for manufacturing a display device.

[0027] A twelfth aspect of the present invention is a method for manufacturing a semiconductor device comprising: In the method for producing a display device according to the eleventh aspect, a hole pattern having a size Dp≦3 μm is formed on the transfer target by the exposure step. [Effects of the Invention]

[0028] The photomask of the present invention has excellent transferability for transferring a fine hole pattern onto a transfer-receiving material by exposure to mid-ultraviolet exposure light, which will be described later. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a schematic plan view of a first photomask 10 of the present invention. [Figure 2]Fig. 2(a) is a schematic plan view of a second photomask 20 of the present invention, and Fig. 2(b) is a schematic cross-sectional view of a resist pattern formed by exposing the second photomask 20. [Figure 3] Fig. 3(a) is a schematic plan view of the photomask of Reference Example 1. Fig. 3(b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of Reference Example 1. [Figure 4] Fig. 4(a) is a schematic plan view of the photomask of Reference Example 2. Fig. 4(b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of Reference Example 2. [Figure 5] FIG. 5 is a diagram showing the properties of the films according to Example 1 and Reference Examples 1 to 4. [Figure 6] FIG. 6 is a diagram showing the results of optical simulations according to Example 1 and Reference Examples 1 to 4. In FIG. [Figure 7] Fig. 7(a) is a schematic plan view of the photomask of Reference Example 3. Fig. 7(b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of Reference Example 3. [Figure 8] Fig. 8(a) is a schematic plan view of the photomask of Reference Example 4. Fig. 8(b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of Reference Example 4. [Figure 9] Fig. 9(a) is a schematic plan view of the photomask of Reference Example 5. Fig. 9(b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of Reference Example 5. [Figure 10] Fig. 10(a) is a schematic plan view of the photomask of Reference Example 6. Fig. 10(b) is a schematic cross-sectional view of a resist pattern formed by exposing the photomask of Reference Example 6. [Figure 11] FIG. 11 is a diagram showing the results of optical simulations according to Reference Examples 5 and 6. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0030] <First embodiment of the present invention> The photomask of the present invention is a photomask for mid-ultraviolet exposure, and is a photomask for applying mid-ultraviolet light as the exposure light. Here, mid-ultraviolet light refers to exposure light having a wavelength range that includes multiple wavelengths in the 200-400 nm wavelength range, but does not include wavelengths shorter than 200 nm or longer than 400 nm. As a light source for the exposure light, for example, an appropriate portion of the wavelength range of a high-pressure mercury lamp can be suitably used. In this case, for example, it is preferable to use a broadband wavelength that includes two or more of 313 nm, 334 nm, and 365 nm (i-line), which have an intensity peak, but does not include h-line or g-line. In this specification, "A to B" means a numerical range of "not less than A and not more than B."

[0031] Such exposure light can be broadband light having a wavelength range shifted to the shorter wavelength side compared to the wavelength range including i-line, h-line, and g-line that has been conventionally used in exposure devices for manufacturing display devices. According to the inventors' investigations, when used for forming hole patterns, this is particularly advantageous in terms of resolution, and does not cause inefficiencies (e.g., reduced production efficiency) that occur with single-wavelength exposure.

[0032] The photomask of the present invention comprises: A photomask for manufacturing a display device, for forming a hole pattern having a size of Dp and Dp≦3 μm on a transfer target using mid-ultraviolet exposure light, A transfer pattern including a hole pattern is formed on a transparent substrate, the hole pattern in the transfer pattern is made of a light-transmitting portion surrounded by a halftone region, a phase difference θ between the transmitted light of the light-transmitting portion and the transmitted light of the halftone region is approximately 180 degrees with respect to light of a reference wavelength contained in mid-ultraviolet exposure light for exposing the photomask; The transmittance T of the halftone region for light of the reference wavelength is 10%≦T≦35%.

[0033] 1 shows an example of a first photomask 10 of the present invention. The transfer pattern of the first photomask 10 has an isolated hole pattern consisting of a light-transmitting portion 12 surrounded by a halftone region 11. Note that an isolated hole pattern means that no other hole patterns exist within a region within a predetermined proximity distance (details will be described later) from one hole pattern.

[0034] FIG. 2(a) illustrates a second photomask 20 of the present invention. The second photomask 20 includes a light-transmitting portion 12 surrounded by a halftone region 11 and has a proximity hole pattern in which multiple hole patterns are arranged side by side, spaced a predetermined distance apart. In FIG. 2(a), two hole patterns are arranged side by side, spaced a predetermined distance apart; this type of hole pattern is also called a double hole pattern. Here, the example illustrates two hole patterns that have the same shape (square) and size and are arranged side by side. FIG. 2(b) illustrates an example of the cross-sectional shape of a resist pattern formed by exposing the second photomask 20 of the present invention.

[0035] The close distance is a distance at which light transmitted through hole patterns can optically interact with each other when exposed to exposure light.

[0036] In the following description, the hole pattern of the transfer pattern of the photomask may be referred to as a mask hole pattern in order to distinguish it from the hole pattern formed on the transfer target.

[0037] By exposing the mask hole pattern of the photomask of this embodiment using an exposure device having the above-mentioned light source, a hole pattern having a size Dp can be formed on a transfer target (such as a display panel substrate). The effects of the present invention are particularly pronounced when forming fine holes, such as holes having Dp≦3 μm. Furthermore, as the trend toward further miniaturization progresses, the present invention can also be usefully applied to forming holes having Dp≦2 μm or Dp≦1.5 μm. Furthermore, it is preferable that Dp be 0.5 μm≦Dp.

[0038] Such a transfer pattern is useful as a layer (e.g., a hole layer) for obtaining contact holes necessary for constructing a display panel substrate for a display device (including liquid crystal and organic EL). If the hole pattern to be formed on the transfer target is circular, its diameter is defined as Dp. If the hole pattern has another shape, Dp is defined as the diameter when the hole pattern is approximated (converted) to a circle having the same area as the shape.

[0039] When Dp exceeds 3 μm, a predetermined resolution performance for obtaining a desired hole pattern on a transfer target using a conventional exposure apparatus for manufacturing a display device can be obtained by using a conventional photomask (e.g., a binary mask). However, the present inventors have noticed that when the size Dp of the hole pattern to be obtained on the transfer target is 3 μm or less, a transfer image with sufficient resolution cannot be obtained using a conventional photomask.

[0040] In the photomask of this embodiment, a transfer pattern can be formed on the main surface of a transparent substrate made of a transparent material such as quartz and processed to be flat and smooth.

[0041] The mask hole patterns of the transfer patterns in the first photomask 10 and the second photomask 20 of this embodiment are rectangular cutout patterns surrounded on all four sides, and can be formed as light-transmitting sections 12 where the transparent substrate is exposed. The four corners of the rectangle do not need to be at perfect 90 degrees, and the four corners and their vicinity may form arc-shaped sections as long as the effect of the present invention is not impaired.

[0042] The shape of the mask hole pattern is preferably quadrilateral (square or rectangle), more preferably square. When the diameter or size of one side of the mask hole pattern is Dm, Dm≦3.5 μm can be satisfied. If the shape of the mask hole pattern is square, the length of one side (e.g., CD-X) is equal to the length of the side perpendicular to it (CD-Y), and this length is defined as Dm. If the shape of the mask hole pattern is rectangular, the long side (e.g., CD-X) is defined as Dm. The effects of the present invention are significant when Dm≦2.0 μm. Furthermore, for a rectangular mask hole pattern, the effects of the present invention are particularly significant when both CD-X and CD-Y are 2 μm or less. Note that CD is also referred to as critical dimension, and in this specification, CD-X refers to the pattern dimension in the X direction, and CD-Y refers to the pattern dimension in the Y direction. Here, the X direction refers to one direction on the main surface of the photomask, and the Y direction refers to another direction perpendicular to the X direction.

[0043] Furthermore, this mask hole pattern (an isolated hole pattern exemplified in the first photomask 10 or a proximal hole pattern exemplified in the second photomask 20) ​​is surrounded by halftone region 11 on the transparent substrate. Halftone region 11 in this embodiment is formed by forming a phase shift film on the main surface of the transparent substrate, and this phase shift film has a phase shift of approximately 180 degrees with respect to the exposure light of reference wavelength λ1. Therefore, light-transmitting portion 12 and halftone region 11 have a phase difference θ of approximately 180 degrees with respect to the exposure light of reference wavelength λ1. Here, approximately 180 degrees is within the range of 180±60 degrees, more preferably within the range of 180±30 degrees, and even more preferably within the range of 180±15 degrees. The phase difference θ (the phase shift amount of the phase shift film) may be approximately 180 degrees, but is particularly preferably 180 degrees (meaning exactly 180 degrees). The reference wavelength λ1 will be described in detail below.

[0044] Furthermore, the transmittance T of halftone region 11 to exposure light having a reference wavelength λ1 satisfies 10%≦T≦35%. That is, the phase shift film in halftone region 11 of this embodiment has a transmittance T to exposure light having a reference wavelength λ1. If the value of T is excessively large, the resist pattern formed on the transfer target by exposure of the photomask is likely to be damaged, while if it is excessively small, the required exposure dose tends to be large. The transmittance T of halftone region 11 to exposure light having a reference wavelength λ1 is preferably 12%≦T≦30%, more preferably 14%≦T≦25%. Unless otherwise specified, the transmittance (%) in this specification refers to a value converted using the transmittance of the transparent substrate as the reference (100%).

[0045] In the case of a transfer pattern including an isolated hole pattern (e.g., first photomask 10), the transmittance is preferably 10%≦T≦35%, more preferably 10%≦T≦25%, and even more preferably 12%≦T≦25%. Furthermore, in the case of a transfer pattern including a proximal hole pattern (e.g., second photomask 20), the transmittance is more preferably 10%≦T≦22%. That is, when considering the case where a transfer pattern provided on one photomask includes both an isolated hole pattern and a proximal hole pattern, the transmittance of halftone region 11 is preferably 10%≦T≦22%, more preferably 12%≦T≦22%, and even more preferably 15%≦T≦22%.

[0046] In the above, the reference wavelength λ1 for the phase shift amount and transmittance can be any wavelength included in the wavelength range (200 to 400 nm) of the mid-ultraviolet exposure light described above. The reference wavelength λ1 is preferably 250 nm≦λ1≦400 nm, and even more preferably 250 nm<λ1<400 nm. The reference wavelength λ1 is preferably a wavelength shorter than the i-line. Specifically, the reference wavelength λ1 can be λ1<365 nm, and preferably 200 nm≦λ1<365 nm, more preferably 250 nm≦λ1<365 nm, and even more preferably 250 nm<λ1<365 nm. In this embodiment, as an example, the reference wavelength λ1 is 334 nm. This wavelength is not only appropriate as a reference for the phase shift effect because it is close to a weighted average taking into account the intensity distribution of the wavelength range of mid-ultraviolet light and has a predetermined intensity (peak height) in the spectrum of a high-pressure mercury lamp, but is also most advantageous in terms of obtaining the DOF (depth of focus) improvement effect described below. Note that setting the reference wavelength λ1 to 313 nm is also advantageous because it makes it easier to obtain the DOF improvement effect described below.

[0047] The transfer pattern of this embodiment has a particularly significant effect when it includes a proximal hole pattern, such as the second photomask 20. In the proximal hole pattern, the distance between the centers of gravity of the mask hole patterns (hereinafter also referred to as the pitch P) is preferably 9 μm or less, and more preferably 2 μm≦P≦9 μm. More preferably, the pitch P is 2 μm≦P≦6 μm, and the merits of the present invention are greater when the pitch P is 2 μm≦P≦4 μm.

[0048] The design of the transfer pattern is not limited to the design of the transfer pattern of the first photomask 10 and the second photomask 20. In particular, when the photomask has a proximity hole pattern, an additional proximity hole pattern may be formed in addition to the double hole pattern. For example, three or more proximity hole patterns of the same shape may be regularly arranged in one direction at a pitch P, or these may be regularly arranged two-dimensionally at a constant pitch P. Alternatively, the pitch P does not necessarily have to be constant.

[0049] Furthermore, the individual hole patterns may have the same size, or hole patterns of different sizes may be mixed.

[0050] However, as mentioned above, the effect of the present invention is greater when the distance between the centers of gravity of adjacent hole patterns (pitch P) is 9 μm or less.

[0051] Furthermore, it is necessary that the hole patterns do not come into contact with each other, and it is preferable that the shortest distance d between the edges (outer edges) of the holes is 0.5 to 2.0 μm.

[0052] The first photomask 10 and the second photomask 20 of this embodiment are photomasks for manufacturing display devices, and may be, for example, rectangular transparent substrates with sides of 300 to 1800 mm and thicknesses of 5 to 16 mm, on the main surface of which a transfer pattern is formed.

[0053] This photomask is intended to be exposed by an exposure tool used in manufacturing display devices. For example, the numerical aperture NA of the projection optical system of the exposure tool is about 0.08 to 0.20, and the exposure light source has the mid-ultraviolet range as described above.

[0054] The photomask of this embodiment can be obtained by patterning a phase shift film formed on a transparent substrate to form a hole pattern corresponding to the mask hole pattern. For example, the second photomask 20 shown in Figure 2(a) has a double hole pattern in which two hole patterns are adjacent to each other. The mask hole pattern portion is a light-transmitting portion 12 where the transparent substrate is exposed, and its periphery is a halftone region 11 where a phase shift film is formed on the transparent substrate.

[0055] In this embodiment, the size Dm of the mask hole pattern is preferably larger than Dp (Dm>Dp). That is, it is preferable to form a hole pattern having a size Dm obtained by adding a mask bias β to the size Dp of the hole pattern to be formed on the transfer target (β=Dm-Dp).

[0056] The mask bias β is preferably set so that Dm / Dp is 1.1 to 1.8. In particular, in the case of a transfer pattern including adjacent hole patterns (here, double holes), Dm / Dp is more preferably 1.2 to 1.7, and even more preferably 1.25 to 1.65. In this case, the transmittance T of the phase shift film is preferably 10 to 22%, and more preferably 12 to 22%. By doing so, when the photomask is exposed, not only are the DOF and required exposure dose within suitable ranges, but also, as shown in FIG. 2(b), in the resist pattern (here, a positive photoresist) formed on the transfer substrate, the partition walls 13 (details of which will be described later) formed between the double hole patterns are not damaged, and the problem of double hole patterns being connected together is less likely to occur. [Example]

[0057] The second photomask 20 shown in Figure 2(a) was used as Example 1, and optical simulations were performed on the transfer characteristics of each to compare it with the binary mask of Reference Example 1 shown in Figure 3(a) and the halftone phase shift mask (with i-line as the reference wavelength) of Reference Example 2 shown in Figure 4(a).

[0058] In the second photomask 20 of Example 1, the phase shift film used in the halftone region 11 had a phase shift of 180 degrees and a transmittance of 16.1% relative to the mid-ultraviolet exposure wavelength (reference wavelength 334 nm) (see "Mid-ultraviolet PSM (Phase Shift Mask)" in Figure 5).

[0059] In addition, in the photomask of Reference Example 1, a light-shielding film (a film that does not substantially transmit exposure light) was formed in the region (light-shielding region 14) corresponding to the halftone region 11 in Example 1, instead of a phase shift film.

[0060] In the photomask of Reference Example 2, a phase shift film having a phase shift amount of 180 degrees and a transmittance of 5.2% with respect to the reference wavelength i-line (365 nm) was formed in the halftone region 11 of Example 1 (see "i-line PSM" in FIG. 5). This was based on the fact that the transmittance of the phase shift film in the above-mentioned document (Patent Document 2) is about 5 to 6%.

[0061] The transfer pattern used to evaluate the transfer performance of the photomask with the above film configuration was designed as a proximity (double) mask hole pattern. The objective was to form a double hole pattern with a diameter of 1.5 μm on the transfer target, and evaluation was performed on the following items. The shapes of the transfer patterns in Example 1, Reference Example 1, and Reference Example 2 are shown in Figures 2(a), 3(a), and 4(a), respectively. The film characteristics of the halftone region 11 (light-shielding region 14 in the binary mask of Reference Example 1) are shown in Figure 5.

[0062] (1) Exposure dose (mJ / cm 2 ) The exposure dose here refers to the exposure dose required to obtain a pattern of the target dimensions on the transfer target. The required exposure dose is preferably small, for example, 50 mJ / cm. 2 It is preferable that:

[0063] (2) DOF (μm) Here, DOF refers to the depth of focus within ±10% of the target CD value. A larger DOF is preferable, for example, 15 μm or more.

[0064] (3) MEEF (Mask Error Enhancement Factor) MEEF indicates the ratio of the CD error of the transferred image formed on the transferred object to the CD error of the photomask. A smaller MEEF is preferable. The CD error of the photomask refers to the CD error (deviation) on the actual photomask relative to the target CD value on the photomask. The CD error of the transferred image formed on the transferred object refers to the CD error (deviation) of the actual transferred image relative to the target CD value of the transferred image formed on the transferred object.

[0065] The results of optical simulation of the transfer characteristics in Example 1, Reference Example 1, and Reference Example 2 are shown in Fig. 6. In addition, the cross-sectional shapes of the resist patterns formed on the transfer recipient in Example 1, Reference Example 1, and Reference Example 2 are shown in Fig. 2(b), Fig. 3(b), and Fig. 4(b), respectively.

[0066] Reference Example 1 (binary mask) is a reference mask, and may be referred to as "reference" hereinafter. As shown in Figure 3(b), in the photomask of Reference Example 1, a resist pattern (here, a positive photoresist pattern) formed on a transfer target has a partition (hereinafter, referred to as partition wall 13) of sufficient height and thickness between two consecutive hole patterns. On the other hand, as shown in Figure 6, the photomask of Reference Example 1 has a DOF of less than 15 μm, which is small, and the process margin for manufacturing a display device is insufficient.

[0067] In Reference Example 2, the DOF improvement effect is similar to that obtained with existing half-tone phase shift masks. However, as shown in Figure 6, in Reference Example 2, the required exposure amount is about 150% of that in Reference Example 1, which reduces the production efficiency of display devices and is therefore not suitable for mass production.

[0068] In Example 1, as shown in FIG. 6, a sufficient DOF is obtained, and the exposure dose can be significantly reduced (50 mJ / cm ) compared to Reference Examples 1 and 2. 2 2(b), the cross-sectional shape of the resist pattern also shows that the partition walls 13 between adjacent holes are properly formed, which proves to be extremely useful. In Example 1, the reduction effect is also observed in the MEEF value. In Example 1, the target hole size to be formed on the transfer target object was 1.5 μm, while the hole size on the mask was set to 2.1 μm. In other words, a mask bias β was applied such that Dm / Dp was 1.4.

[0069] For confirmation, it was also verified whether or not the transferability improves when a bias similar to that in Example 1 is applied to Reference Example 1 and Reference Example 2. Reference Example 3 (FIG. 7(a)) is a case in which the size of the mask hole pattern is set to 2.1 μm by applying a bias in Reference Example 1, and Reference Example 4 (FIG. 8(a)) is a case in which a bias is applied in the same manner in Reference Example 2. The results of optical simulation of the transfer performance of each are also shown in FIG.

[0070] According to the optical simulation results for Reference Examples 3 and 4, although the exposure dose could be reduced by applying a bias in Reference Example 3, the DOF was reduced to a level below that of the reference (Reference Example 1). Furthermore, as shown in FIG. 7(b), the cross section of the resist pattern in Reference Example 3 showed that the partition walls 13 between the double hole patterns were not sufficiently formed, resulting in the double hole patterns being connected to each other. Furthermore, in Reference Example 4, not only was the DOF improvement effect smaller than that of the reference, but the cross section of the resist pattern, as shown in FIG. 8(b), revealed that the partition walls 13 between the double hole patterns were very thin and easily broken. To obtain a defect-free circuit pattern in the display device to be obtained, it is most preferable that the partition walls 13 of the resist pattern do not lose their initial thickness. However, it is preferable that at least 50% or more of the initial thickness remain in the partition walls 13, and more preferably 60% or more of the initial thickness remain.

[0071] From the above, it was confirmed that the transfer performance of the photomask of this embodiment is very excellent. [Example]

[0072] The photomask of Reference Example 5 shown in Fig. 9(a) and the photomask of Reference Example 6 shown in Fig. 10(a) are photomasks having a close (double) hole pattern, and were formed in the same manner as in Example 1, except that the transmittance of the phase shift film in halftone region 11 was changed. In Reference Examples 5 and 6, similar to Example 1, the goal is to form a close (double) hole pattern of 1.5 μm size on a transfer target.

[0073] For Reference Examples 5 and 6, optical simulation of transfer performance was performed in the same manner as in Example 1. The evaluation items in the optical simulation were the same as in Example 1. The results of the optical simulation are shown in Fig. 11. Furthermore, the cross-sectional shapes of the resist patterns formed on the transfer recipient in Reference Examples 5 and 6 are shown in Fig. 9(b) and Fig. 10(b), respectively.

[0074] In Reference Example 5, the transmittance (based on the wavelength of the exposure light of 334 nm) of the phase shift film used in halftone region 11 was set to 8%. According to the simulation results, there were no particular problems with the DOF value or the cross-sectional shape of the resist pattern, but the required exposure dose was hardly reduced.

[0075] In addition, in Reference Example 6, when the transmittance (based on a wavelength of 334 nm) of the phase shift film in the halftone region 11 was set to 25%, no particular problems were observed in the exposure dose, DOF, or MEEF. However, as shown in Figure 10(b), in the cross-sectional shape of the resist pattern, the partition walls 13 between the hole patterns could not be sufficiently formed.

[0076] Therefore, it is preferable that the transmittance of the halftone region 11 in the double adjacent hole pattern is smaller than that shown in Reference Example 6 (specifically, 22% or less), while in the isolated hole pattern, it is considered that a transmittance of approximately the transmittance shown in Reference Example 6 (25%) may be practically usable.

[0077] The photomasks of the present invention, such as the first photomask 10 and the second photomask 20, can be manufactured using a lithography process. That is, they can be manufactured using a photomask blank in which a phase shift film is formed on the main surface of a substrate made of a transparent material such as quartz. A known method such as sputtering may be used to form the phase shift film on the transparent substrate. This phase shift film (forming the halftone region 11) has a phase inversion effect in the mid-ultraviolet wavelength range, for example. The phase shift film is then patterned as desired based on the device to be obtained.

[0078] There are no particular restrictions on the material of the phase shift film used in the first photomask 10 and the second photomask 20. For example, a transition metal silicide is preferably used. For example, molybdenum silicide (MoSi) or its compounds (MoSiO, MoSiN, MoSiC, MoSiON, MoSiCN, MoSiCO, MoSiCON, etc.) are desirable.

[0079] Alternatively, the material of the phase shift film may be chromium (Cr) or a compound thereof (CrO, CrN, CrC, CrON, CrCN, CrCO, CrCON, etc.).

[0080] Furthermore, examples of the material for the phase shift film include those containing Ta (tantalum), Zr (zirconium), or Ti as a metal component (e.g., Zr silicide, silicide containing Mo and Zr), or compounds thereof (oxides, nitrides, carbides, and other compounds listed above).

[0081] Simulations were performed on the first photomask 10 and the second photomask 20 of this embodiment, assuming that a MoSi compound is used for the phase shift film. The phase shift film can have a thickness of 100 to 200 nm and can be formed by a known film formation method such as sputtering. The phase shift film can be patterned using either dry etching or wet etching, but wet etching may be advantageous for large photomasks used in manufacturing display devices.

[0082] While the first and second photomasks 10 and 20 described above both use a phase shift film in the halftone region 11 that inverts exposure light in the mid-ultraviolet region, photomasks with different configurations can also be used. For example, the halftone region 11 may be a semi-transparent film with a transmittance T (e.g., 10%≦T≦35%) for the exposure light, but with substantially no phase inversion. "Substantially no phase inversion" means that the phase shift amount relative to the reference wavelength λ1 is 90 degrees or less, preferably 60 degrees or less. On the other hand, the transparent portions 12 constituting the mask hole pattern can be formed as recesses in the surface of a transparent substrate by a predetermined thickness. This allows the phase difference θ between the transparent portions 12 and the halftone region 11 to be approximately 180 degrees (or exactly 180 degrees), and the effects of the present invention can also be achieved with such a photomask.

[0083] Furthermore, for the photomask of the above embodiment, an additional film (such as a reflection control film or an etching stop film) may be formed on the transparent substrate as long as the effects of the present invention are not impaired.

[0084] The present invention includes a method for manufacturing a display device using the above photomask. Here, the display device includes devices that constitute the display device.

[0085] For the exposure of the present invention, a projection exposure apparatus that performs exposure at the same magnification or reduced magnification and has an NA of about 0.08 to 0.20 can be used. The NA can be preferably 0.08 to 0.18, more preferably 0.08 to 0.15.

[0086] The illumination system of the exposure tool can use normal illumination, or alternatively, modified illumination (light incident on the photomask excluding the normal incident component) can be used.

[0087] In recent high-resolution organic light-emitting diode (OLED) display circuits, transfer patterns with two or more adjacent hole patterns are becoming increasingly useful due to the increasing fineness of the circuits. The photomask of the present invention addresses these new technical challenges.

[0088] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0089] 10 First photomask 11 Halftone Area 12 Translucent part 13 Division wall 14 Shading area 20 Second photomask

Claims

1. A photomask for manufacturing a display device, which is used to form a hole pattern on a transfer target using mid-ultraviolet exposure light, a phase shift film having a transfer pattern on a transparent substrate; the transfer pattern is a light-transmitting portion that is formed by patterning the phase shift film and exposes the transparent substrate, and includes a mask hole pattern for forming the hole pattern; a phase difference θ between the light transmitting portion and the phase shift film is within a range of 180±15 degrees with respect to light having a reference wavelength λ1 included in mid-ultraviolet exposure light for exposing the photomask; a numerical aperture NA of a projection optical system of an exposure apparatus in which the photomask is used is 0.08 or more and 0.20 or less; the mid-ultraviolet exposure light has intensity peaks at two or more wavelengths of 313 nm, 334 nm, and 365 nm; The reference wavelength λ1 is 313 nm or 334 nm. Photomask.

2. 2. The photomask according to claim 1, wherein the transmittance T of said phase shift film for light of said reference wavelength λ1 is 10%≦T≦35%.

3. 3. The photomask according to claim 1, wherein said transfer pattern includes an isolated hole pattern, said mask hole pattern being isolated.

4. 4. The photomask according to claim 1, wherein the transfer pattern has a proximity hole pattern, which is two or more of the mask hole patterns that are in close proximity to each other.

5. 5. The photomask according to claim 4, wherein the distance between the centers of gravity of two of said mask hole patterns included in said adjacent hole pattern is not less than 2 [mu]m and not more than 9 [mu]m.

6. 6. The photomask according to claim 5, wherein the shortest distance between the edges of the two mask hole patterns is 0.5 [mu]m or more and 2.0 [mu]m or less.

7. 7. The photomask according to claim 1, wherein the size Dm of the mask hole pattern is 3.5 μm or less.

8. A method for manufacturing a display device, comprising: A step of preparing a photomask according to any one of claims 1 to 7; an exposure step of exposing the photomask to mid-ultraviolet exposure light using an exposure apparatus having a projection optical system with a numerical aperture NA of 0.08 or more and 0.20 or less; the mid-ultraviolet exposure light has a wavelength λ in a wavelength range that satisfies 200 nm≦λ≦400 nm, and does not include wavelengths that satisfy λ>400 nm and λ<200 nm; The reference wavelength λ1 of the mid-ultraviolet exposure light is 313 nm or 334 nm; A method for manufacturing a display device.

9. 9. The method for manufacturing a display device according to claim 8, wherein the hole pattern having a size Dp (0.5 [mu]m≦Dp≦3 [mu]m) is formed on the transfer target by the exposure step.

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