Photomask and manufacturing method of display device

Abstract

The present application provides a photomask and a manufacturing method of a display device, having excellent transfer performance for transferring a fine hole pattern on a transfer body by using a mid-ultraviolet exposure light. A photomask is a photomask for manufacturing a display device, and is used for forming a hole pattern with a size of Dp and Dp≤3 μm on a transfer body using a mid-ultraviolet exposure light. The photomask has a transfer pattern including the hole pattern on a transparent substrate. The hole pattern in the transfer pattern is composed of a light-transmitting portion surrounded by a half-tone area. The phase difference θ of the light-transmitting portion and the half-tone area is substantially 180 degrees for light of a reference wavelength included in the mid-ultraviolet exposure light used for exposing the photomask. The transmittance T of the half-tone area for the light of the reference wavelength is 10%≤T≤35%.

Description

Technical Field

[0001] This invention relates to photomasks, and more particularly to photomasks that facilitate the manufacture of high-precision display devices, and a method for manufacturing a display device using the photomask. Background Technology

[0002] Patent Document 1 describes a phase-shifting mask blank for manufacturing a display device, and a phase-shifting mask manufactured from the phase-shifting mask blank. Patent Document 1 also describes a technique for exposing the phase-shifting mask using composite light comprising i-lines, h-lines, and g-lines.

[0003] Patent Document 2 discloses a phase-shift mask blank for manufacturing a display device, which has a phase-shift film exhibiting optical properties that suppress the wavelength dependence of the exposure light. The phase-shift film in this phase-shift mask blank has a transmittance of 3.5% to 8% for a wavelength of 365 nm, a phase difference of 160 degrees to 200 degrees at a wavelength of 365 nm, and a transmittance variation depending on wavelength of 5.5% or less for a wavelength range of 365 nm to 436 nm.

[0004] [Existing technical documents]

[0005] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2014-194531

[0007] [Patent Document 2] Japanese Patent Application Publication No. 2015-102633 Summary of the Invention

[0008] [The problem the invention aims to solve]

[0009] In recent years, in addition to bright and high-resolution display performance, there has been a growing demand for display performance characteristics such as power saving and fast dynamic image response in display devices, including LCD (Liquid Crystal Display) and OLED (Organic Electron Display). Therefore, it is expected that the patterns of photomasks used in the manufacturing process of these display devices will become increasingly miniaturized and highly integrated, and further, there is a desire for technology that can precisely resolve the patterns of the photomasks onto the substrate (such as the display panel substrate).

[0010] However, if the transfer pattern of the photomask cannot be optically resolved onto the transfer object, it is impossible to construct a display device with the desired fine pattern. Here, the spatial resolution of the optical image can be expressed by Rayleigh's resolution standard, namely, the following equation (1).

[0011] δ=k1×λ / NA…(1)

[0012] Here, δ is the minimum resolution linewidth, λ is the exposure wavelength, NA is the numerical aperture of the optical system of the exposure device, and k1 is a coefficient also known as the k1 factor.

[0013] In the field of display devices (hereinafter also referred to as FPDs (Flat Panel Displays)), specific wavelength ranges of high-pressure mercury lamps are used as the light for exposure. That is, there are known applications of exposure light that use light in a band (hereinafter also referred to as a broadband band) that includes light of multiple wavelengths and mixes them, especially light of the three wavelengths included in the light of high-pressure mercury lamps: the g-line (wavelength 436 nm), h-line (wavelength 405 nm), and i-line (wavelength 365 nm) (see Patent Documents 1 and 2).

[0014] On the other hand, according to equation (1) above, in order to improve the resolution for fine patterns (i.e., reduce the minimum resolvable linewidth δ), it is effective to decrease λ or increase NA. However, for increasing NA, according to equation (2) below, since the depth of focus is reduced, it is understood that it will relatively deteriorate the stability of the lithography process. Equation (2) is also known as Rayleigh's depth of focus equation.

[0015] DOF = k2 × λ ​​ / NA 2 …(2)

[0016] Here, DOF (Depth of focus) refers to the depth of focus, and k2 is a coefficient.

[0017] The magnitude of the value on the left side of Equation (2) is the opposite of the relative merits of the resolution benchmark formula (Equation (1)) mentioned above. That is, in Equation (1), it is preferred that the value on the left side be small, but in Equation (2), it is conversely desired that the value on the left side be large.

[0018] Therefore, the minimum resolvable linewidth δ and the depth of focus (DOF) exhibit a trade-off relationship. However, as shown in Equation (2), the DOF deteriorates proportionally to the square of the NA. Therefore, if we assume the same level of resolution improvement, it is more reasonable to shorten the wavelength of the exposure light than to increase the NA. That is, it is possible to improve the resolution while suppressing the decrease in DOF.

[0019] As a method to easily achieve shorter wavelengths from the aforementioned wide-band exposure environment, and as an alternative to mixed-wavelength exposure including g-lines, h-lines, and i-lines, it is possible to effectively reduce the wavelength by switching to exposure based on a single i-line wavelength. However, this method means cutting off the contribution from two of the three wavelengths, reducing the work done per unit time to one-third simply by calculation. In the field of FPD production, in addition to the aforementioned resolution, another important factor is production efficiency, thus sometimes making single-wavelength exposure difficult to implement.

[0020] Therefore, a method is considered to maintain a wide-band exposure environment and shift its center of gravity towards the shorter wavelength side. In high-pressure mercury lamps, there are several wavelength groups with peak light intensity on the shorter wavelength side than the i-line, so the above method uses the light of this wavelength group as the exposure energy.

[0021] The inventors, taking into account the new broadband exposure environment after shifting the wavelength range used for conventional exposure light to the shorter wavelength side, conducted in-depth research on what kind of photomask exhibits excellent transferability to adapt to this environment, and thus completed the present invention.

[0022] [Methods used to solve problems]

[0023] The first aspect of the present invention is a photomask, which is a photomask used for manufacturing a display device. The photomask is used to form a hole pattern with a size Dp and Dp≤3μm on a substrate using medium ultraviolet light exposure.

[0024] A transfer pattern containing a hole pattern is formed on a transparent substrate.

[0025] The perforation pattern in the transfer pattern is composed of light-transmitting portions surrounded by halftone areas.

[0026] For the reference wavelength contained in the mid-ultraviolet exposure light used to expose the photomask, the phase difference θ between the transparent portion and the halftone region is approximately 180 degrees.

[0027] Furthermore, the transmittance T of the halftone region for the reference wavelength is 10% ≤ T ≤ 35%.

[0028] The second aspect of the present invention uses the photomask described in the first aspect, wherein the hole pattern in the transfer pattern is composed of light-transmitting portions, which are formed by patterning a phase-shifting film formed on the transparent substrate, and the transparent substrate is exposed in the light-transmitting portions.

[0029] The phase-shifting film is formed on the transparent substrate in the halftone region.

[0030] The phase-shifting film has a phase shift of approximately 180 degrees for the reference wavelength and a transmittance T of 10% ≤ T ≤ 35%.

[0031] The third aspect of the present invention is a photomask, which is a photomask used in the manufacture of a display device. The photomask is used to form a hole pattern with a size Dp and Dp≤3μm on a substrate using medium ultraviolet light exposure.

[0032] A transfer pattern containing a hole pattern is formed on a transparent substrate.

[0033] The perforation pattern in the transfer pattern is composed of light-transmitting portions surrounded by halftone areas.

[0034] When the reference wavelength is λ1 and λ1 < 365 nm, for light of wavelength λ1, the phase difference θ between the light-transmitting part and the halftone region is 180 degrees, and the transmittance T of the halftone region for light of wavelength λ1 is 10% ≤ T ≤ 35%.

[0035] The fourth aspect of the present invention is based on the photomask described in the third aspect.

[0036] The hole pattern in the transfer pattern is composed of light-transmitting portions, which are formed by patterning a phase-shifting film formed on the transparent substrate, in which the transparent substrate is exposed.

[0037] The phase-shifting film is formed on the transparent substrate in the halftone region.

[0038] The phase-shifting film has a phase shift of 180 degrees for light of wavelength λ1 and a transmittance T of 10% ≤ T ≤ 35%.

[0039] The fifth aspect of the present invention is based on the photomask described in aspects 1 to 4.

[0040] The transfer pattern includes an isolated hole pattern.

[0041] The sixth aspect of the present invention is based on the photomask described in aspects 1 to 4.

[0042] The transfer pattern has a proximity hole pattern, which includes two or more hole patterns located at a proximity distance.

[0043] The seventh aspect of the present invention is based on the photomask described in the sixth aspect.

[0044] The distance between the centroids of the two hole patterns included in the proximity hole pattern is less than 9 μm.

[0045] The eighth aspect of the present invention is based on the photomask described in aspects 1 to 7.

[0046] When the size of the hole pattern in the transfer pattern is Dm, Dm > Dp.

[0047] The ninth aspect of the present invention is based on the photomask described in aspects 1 to 8.

[0048] The reference wavelength is 313nm or 334nm.

[0049] The tenth aspect of the present invention uses the photomask described in the eighth aspect.

[0050] Dm / Dp is 1.1 to 1.8.

[0051] The eleventh aspect of the present invention is a method for manufacturing a display device, comprising the following steps:

[0052] The process of preparing the photomask described in any one of the methods 1 to 10 above; and

[0053] The exposure process involves exposing the photomask to medium ultraviolet light.

[0054] The light used for ultraviolet exposure includes wavelengths λ that satisfy 200nm≤λ≤400nm, but does not include wavelengths λ>400nm or λ<200nm.

[0055] The twelfth aspect of the present invention is a method for manufacturing a display device according to the eleventh aspect described above, wherein a hole pattern with a size Dp≤3μm is formed on a transfer substrate by means of the exposure process.

[0056] [Invention Effects]

[0057] The photomask of the present invention is exposed using the medium ultraviolet light described later, and has excellent transfer performance in transferring fine hole patterns onto the substrate. Attached Figure Description

[0058] Figure 1 This is a top view schematic diagram of the first photomask 10 of the present invention.

[0059] Figure 2 (a) is a top view of the second photomask 20 of the present invention, and (b) is a cross-sectional view of the resist pattern formed by exposing the second photomask 20.

[0060] Figure 3 (a) is a top view of the photomask of Reference Example 1, and (b) is a cross-sectional view of the resist pattern formed by exposing the photomask of Reference Example 1.

[0061] Figure 4(a) is a top view of the photomask of Reference Example 2, and (b) is a cross-sectional view of the resist pattern formed by exposing the photomask of Reference Example 2.

[0062] Figure 5 This is a diagram showing the characteristics of the membranes of Embodiment 1 and Reference Examples 1 to 4 of the present invention.

[0063] Figure 6 The figure shows the results of optical simulations of Embodiment 1 and Reference Examples 1 to 4 of the present invention.

[0064] Figure 7 (a) is a top view of the photomask of Reference Example 3, and (b) is a cross-sectional view of the resist pattern formed by exposing the photomask of Reference Example 3.

[0065] Figure 8 (a) is a top view of the photomask of Reference Example 4, and (b) is a cross-sectional view of the resist pattern formed by exposing the photomask of Reference Example 4.

[0066] Figure 9 (a) is a top view of the photomask of Reference Example 5, and (b) is a cross-sectional view of the resist pattern formed by exposing the photomask of Reference Example 5.

[0067] Figure 10 (a) is a top view of the photomask of Reference Example 6, and (b) is a cross-sectional view of the resist pattern formed by exposing the photomask of Reference Example 6.

[0068] Figure 11 This is a graph showing the results of the optical simulations of Reference Examples 5 and 6.

[0069] Label Explanation

[0070] 10 First photomask

[0071] 11 Halftone Zone

[0072] 12 Light-transmitting section

[0073] 13. Partition wall

[0074] 14 Shading Area

[0075] 20 Second photomask Detailed Implementation

[0076] <First Embodiment of the Invention>

[0077] The photomask of the present invention is a photomask for mid-ultraviolet exposure, used for applying mid-ultraviolet light as exposure light. Here, mid-ultraviolet light refers to exposure light having a wavelength range that includes multiple wavelengths in the range of 200-400 nm, but excludes wavelengths less than 200 nm and greater than 400 nm. As the light source for the aforementioned exposure light, a suitable portion of the wavelength range of a high-pressure mercury lamp can be appropriately used, for example. In this case, it is preferable, for example, to use two or more broad-band wavelengths including 313 nm, 334 nm, and 365 nm (i-line) which have intensity peaks, but excluding h-line and g-line. It should be noted that in this specification, "A-B" refers to a numerical range of "A or more and B or less".

[0078] This type of exposure light, compared to conventional exposure apparatuses used in display device manufacturing that include i-lines, h-lines, and g-lines, can be a wide-band light with a wavelength region shifted towards shorter wavelengths. According to the inventors' research, this type of exposure light is particularly advantageous in terms of resolution when used to form aperture patterns, and it does not produce the inefficiencies (e.g., reduced production efficiency) of single-wavelength exposure.

[0079] The photomask of the present invention is a photomask for mid-ultraviolet exposure, used to form a hole pattern with a size of Dp (μm) (where Dp≤3) on the substrate to be transferred.

[0080] A transfer pattern containing a hole pattern is formed on a transparent substrate.

[0081] The perforation pattern in the transfer pattern consists of a light-transmitting portion surrounded by a halftone area.

[0082] For the reference wavelength light included in the mid-ultraviolet exposure light used to expose the aforementioned photomask, the phase difference θ between the transmitted light from the aforementioned transparent portion and the transmitted light from the aforementioned halftone region is approximately 180 degrees, and...

[0083] The transmittance T (%) of the halftone region to the reference wavelength is 10 ≤ T ≤ 35.

[0084] Figure 1 An example of the first photomask 10 of the present invention is shown. 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. In addition, an isolated hole pattern refers to a region in which no other hole patterns exist within a predetermined proximity distance (described in detail later) from a single hole pattern.

[0085] In addition, Figure 2Example (a) illustrates the second photomask 20 of the present invention. The second photomask 20 is composed of a light-transmitting portion 12 surrounded by a halftone region 11, and has a proximity hole pattern formed by arranging a plurality of hole patterns separated by a predetermined proximity distance. Figure 2 In (a), two hole patterns are arranged at approximately the same distance apart. Such a hole pattern is also called a double hole pattern. Here, an example is shown where the two hole patterns are arranged with the same shape (square) and the same size. Figure 2 (b) is an example of the cross-sectional shape of the resist pattern formed by exposing the second photomask 20 of the present invention.

[0086] The so-called proximity distance refers to the distance at which the transmitted light from the aperture patterns will interact optically with each other when exposed to light.

[0087] In addition, in order to distinguish the hole pattern of the transfer pattern of the photomask from the hole pattern formed on the substrate, it is sometimes referred to as the mask hole pattern.

[0088] By exposing the mask hole pattern of the photomask of this embodiment to an exposure apparatus equipped with the aforementioned exposure light source, a hole pattern having a size Dp (μm) can be formed on the transfer substrate (display panel substrate, etc.). Here, the effects of the present invention are significantly obtained when forming micro-holes such as Dp ≤ 3. Furthermore, with the development of further miniaturization trends, the present invention can also be usefully applied in the formation of holes with Dp ≤ 2 or Dp ≤ 1.5. Preferably, 0.5 ≤ Dp.

[0089] Such transfer patterns are useful for the layers (e.g., hole layers) required to form the contact holes in the display panel substrate of a display device (including liquid crystal and organic EL). When the hole pattern formed on the transfer body is circular, its diameter is denoted as Dp; in other shapes, the diameter is denoted as Dp when it is approximated (converted) to a circle of the same shape and area.

[0090] When the aperture diameter (Dp) exceeds 3 μm, conventional photomasks (e.g., binary masks) are used to obtain the desired aperture pattern on the substrate using conventional exposure apparatuses for manufacturing display devices, achieving the required resolution. However, the inventors have addressed the issue that when the aperture pattern size Dp to be obtained on the substrate is 3 μm or less, it becomes impossible to obtain a transfer with sufficient resolution using conventional photomasks.

[0091] The photomask of this embodiment can be a photomask on the main surface of a transparent substrate that has a transfer pattern formed on it by processing a transparent material such as quartz flat and smooth.

[0092] In the first photomask 10 and the second photomask 20 of this embodiment, the mask pattern of the transfer pattern is a quadrilateral pattern with a blank space surrounded on all sides, which can be formed into the light-transmitting portion 12 exposed by the transparent substrate. It should be noted that the four corners of the quadrilateral do not need to be exactly 90 degrees. Without impairing the effect of the present invention, the four corners and their vicinity can also be formed into an arc shape.

[0093] The shape of the mask aperture pattern is preferably quadrilateral (square or rectangle), more preferably square. When the diameter or side dimension of the mask aperture pattern is set to Dm (μm), Dm can be ≤ 3.5. If it is a square, the length of one side (e.g., CD-X) and the length of the side perpendicular to it (CD-Y) are equal, and this length is set to Dm. If it is a rectangle, its longer side (e.g., CD-X) is set to Dm. When Dm ≤ 2.0, the effects of the present invention are significant. Furthermore, in quadrilateral mask aperture patterns, the effects of the present invention are particularly significant when both CD-X and CD-Y are 2 μm or less. Additionally, CD is also referred to as Critical Dimension. In this specification, CD-X refers to the size of the pattern in the X direction, and CD-Y refers to the size of the pattern in the Y direction. Here, the X direction refers to a direction on the main surface of the photomask, and the Y direction refers to other directions perpendicular to the X direction.

[0094] Furthermore, the mask aperture pattern (the isolated aperture pattern exemplified by the first photomask 10, or the proximity aperture pattern exemplified by the second photomask 20) ​​is surrounded by the halftone region 11 on the aforementioned transparent substrate. In this embodiment, the halftone region 11 has a phase-shifting film formed on the main surface of the transparent substrate, and this phase-shifting film has a phase shift of approximately 180 degrees relative to the exposure light at the reference wavelength λ1 (nm). Therefore, the light-transmitting portion 12 and the halftone region 11 have a phase difference θ of approximately 180 degrees with respect to the exposure light at the 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 possessed by the phase-shifting film) only needs to be approximately 180 degrees, but 180 degrees (meaning exactly 180 degrees) is particularly preferred. The reference wavelength λ1 will be described in detail later.

[0095] Furthermore, the transmittance T (%) of the halftone region 11 for exposure light at the reference wavelength λ1 satisfies 10 ≤ T ≤ 35. That is, the phase shift film in the halftone region 11 of this embodiment has a transmittance T for exposure light at the reference wavelength λ1. If the value of T is too large, it is easy to cause damage to the resist pattern formed on the transfer substrate due to exposure of the photomask. If the value of T is too small, there is a tendency for the required exposure amount to increase. The transmittance T (%) of the halftone region 11 for exposure light at the reference wavelength λ1 is preferably 12 ≤ T ≤ 30, and more preferably 14 ≤ T ≤ 25. It should be noted that, unless otherwise specified, the transmittance (%) in this specification refers to the value obtained by converting the transmittance of the transparent substrate to a reference (100%).

[0096] In the case of a transfer pattern including isolated aperture patterns (e.g., the 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 proximity aperture patterns (e.g., the second photomask 20), the transmittance is more preferably 10 ≤ T ≤ 22. That is, in a photomask having a transfer pattern, considering both isolated aperture patterns and proximity aperture patterns, the transmittance of the halftone region 11 is preferably 10 ≤ T ≤ 22, more preferably 12 ≤ T ≤ 22, and even more preferably 15 ≤ T ≤ 22.

[0097] In the above description, the reference wavelength λ1, which serves as the phase shift and transmittance, can be any wavelength within the wavelength range (200–400 nm) of the mid-ultraviolet exposure light described above. More preferably, the reference wavelength λ1 is 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, 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, a wavelength of 334 nm is set as the reference wavelength λ1. This wavelength is close to the weighted average of the intensity distribution in the aforementioned mid-ultraviolet wavelength region, and in the spectrum of a high-pressure mercury lamp, it is not only suitable as a reference for the phase-shifting effect at the point of having a specified intensity (peak height), but also most advantageous in terms of obtaining the DOF (depth of focus) improvement effect described later. Alternatively, the reference wavelength λ1 can also be set to 313 nm.

[0098] The transfer pattern of this embodiment, when including a proximity hole pattern as in the second photomask 20, can achieve particularly significant effects. In this proximity hole pattern, the distance between the mask hole patterns is preferably set such that the distance between their centroids (hereinafter also referred to as the spacing P (μm)) is 9 μm or less, more preferably 2 ≤ P ≤ 9. More preferably, the advantages of the present invention are even greater when the spacing P is 2 ≤ P ≤ 6 or 2 ≤ P ≤ 4.

[0099] Furthermore, the design of the transfer pattern is not limited to the design of the transfer patterns of the first photomask 10 and the second photomask 20. In particular, when the photomask has an approach hole pattern, in addition to the aforementioned double-hole pattern, an additional approach hole pattern can be formed. For example, three or more approach hole patterns of the same shape can be regularly arranged in one direction with a spacing P, or they can be regularly arranged in two dimensions with a certain spacing P. Alternatively, the spacing P may not be fixed.

[0100] In addition to the case where all hole patterns are the same size, hole patterns of different sizes can also be mixed together.

[0101] However, as mentioned above, the invention is more effective when the distance between the centers of gravity (pitch P) of the near hole patterns is less than 9 μm.

[0102] In addition, the hole patterns must not touch each other, but preferably the shortest distance d between the edges (outer edges) of the hole patterns is 0.5 to 2.0 μm.

[0103] The first photomask 10 and the second photomask 20 in this embodiment are photomasks for manufacturing a display device. For example, a transfer pattern can be formed on the main surface of a quadrilateral transparent substrate with sides of 300 to 1800 mm and a thickness of 5 to 16 mm.

[0104] This photomask is used for exposure by an exposure apparatus used in the manufacture of a display device. For example, the numerical aperture (NA) of the projection optics system of the exposure apparatus is about 0.08 to 0.20, and the light source for the exposure has the mid-ultraviolet region as described above.

[0105] The photomask in this embodiment can be a photomask obtained by patterning a phase-shifting film formed on a transparent substrate to form a blanking pattern corresponding to the mask hole pattern. For example, in Figure 2 In the second photomask 20 of (a), a double-hole pattern with two adjacent blank patterns is formed. The mask hole pattern portion is the light-transmitting portion 12 exposed on the transparent substrate, and its surrounding area is a halftone region 11 formed by forming a phase-shifting film on the transparent substrate.

[0106] In this embodiment, the size Dm of the mask hole pattern is preferably greater than Dp (Dm > Dp). That is, it is preferable to form a size Dm (β = Dm - Dp) that includes a mask bias β (μm) relative to the size Dp of the hole pattern formed on the transfer body.

[0107] The mask bias can be set, for example, to a Dm / Dp ratio of 1.1 to 1.8. Particularly in the case of transfer patterns including proximity hole patterns (in this case, dual holes), a Dm / Dp ratio of 1.2 to 1.7 is preferred, and 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%. Therefore, when exposing this photomask, not only are the DOF and the required exposure amount preferred, but also... Figure 2 As shown in (b), in the resist pattern (in this case, a positive photoresist) formed on the transfer substrate, the partition wall 13 (described in detail later) formed between the double hole patterns is not damaged, and the defect of the double hole patterns connecting is not easily generated.

[0108] [Example 1]

[0109] Will Figure 2 The second photomask 20 shown in (a) is an example of embodiment 1, in order to be compatible with... Figure 3 The binary mask of Reference Example 1 shown in (a) Figure 4 The halftone phase-shift mask (assuming the reference wavelength is the i-line mask) shown in (a) of Reference Example 2 was compared, and thus an optical simulation of their respective transfer characteristics was performed.

[0110] In the second photomask 20 of Example 1, the phase-shifting film used in the halftone region 11 is a phase-shifting film with a phase shift of 180 degrees and a transmittance of 16.1% for the mid-ultraviolet exposure wavelength (reference wavelength 334 nm) (see reference). Figure 5 The “Mid-UV PSM (Phase Shift Mask)”.

[0111] Furthermore, in the area (shading area 14) corresponding to the halftone area 11 in Example 1, the photomask of Reference Example 1 does not form a phase-shifting film, but rather a light-shielding film (a film that does not transmit light for exposure).

[0112] In the photomask of Reference Example 2, a phase-shifting film with a phase shift of 180 degrees and a transmittance of 5.2% for the i-line (365 nm) as the reference wavelength is formed in the halftone region 11 of Example 1. This is in reference to the case where the transmittance of the phase-shifting film in the aforementioned Patent Document 2 is about 5 to 6%.

[0113] The transfer pattern used to evaluate the transfer performance of the photomask for the above-mentioned film structure was designed to approximate a (dual-hole) mask aperture pattern. Furthermore, with the goal of forming a dual-hole pattern with a diameter of 1.5 μm on the substrate, the following aspects were evaluated. The shapes of the transfer patterns in Example 1, Reference Example 1, and Reference Example 2 are shown respectively. Figure 2 of (a), Figure 3 (a) and Figure 4 The properties of the film in halftone region 11 (shading region 14 in the binary mask of Example 1) are as follows: Figure 5 As shown.

[0114] (1) Exposure (mJ / cm) 2 )

[0115] The exposure amount here refers to the necessary exposure for obtaining a pattern of the target size on the transfer substrate. This necessary exposure amount is preferably small, for example, 50 mJ / cm². 2 the following.

[0116] (2)DOF(μm)

[0117] Here, DOF represents the depth of focus within ±10% of the target CD value. A relatively large DOF is preferred, for example, 15 μm or more.

[0118] (3) MEEF (Mask Error Enhancement Factor): Mask error enhancement factor

[0119] MEEF represents the ratio of the CD error of the transfer image formed on the substrate to the CD error of the photomask. A smaller MEEF is preferred. Furthermore, the CD error of the photomask refers to the actual CD error (offset) on the photomask relative to the target CD value. Additionally, the CD error of the transfer image formed on the substrate refers to the actual CD error (offset) of the transfer image relative to the target CD value of the transfer image formed on the substrate.

[0120] The optical simulation results of the transfer characteristics in Example 1, Reference Example 1, and Reference Example 2 are shown below. Figure 6 Furthermore, in Example 1, Reference Example 1, and Reference Example 2, the cross-sectional shapes of the resist patterns formed on the transfer substrate are respectively as follows: Figure 2 (b) Figure 3 (b) and Figure 4 As shown in (b).

[0121] Example 1 (binary mask) is a mask used as a reference, and will sometimes be referred to as a reference value. For example... Figure 3As shown in (b), in the photomask of Reference Example 1, in the resist pattern (here, a positive photoresist pattern) formed on the transfer substrate, a sufficient height and thickness of spacing (hereinafter referred to as partition wall 13) is formed between the double-hole patterns. On the other hand, as Figure 6 As shown, in the photomask of Reference Example 1, the DOF is less than 15 μm, resulting in insufficient process margin in the manufacturing of the display device.

[0122] In Reference Example 2, the improvement in DOF was observed similarly to that obtained with existing halftone phase-shift masks. However, in Reference Example 2, the required exposure was approximately 150% of that in Reference Example 1, resulting in reduced production efficiency of the display device, thus making it unsuitable for mass production.

[0123] In Example 1, while achieving sufficient DOF, the exposure amount was significantly reduced compared to Reference Examples 1 and 2 (50 mJ / cm²). 2 (The following), in addition, such as Figure 2 As shown in (b), the partition walls 13 located between the holes can also be appropriately formed in the cross-sectional shape of the resist pattern, which is extremely useful. In Example 1, a reduction effect was also confirmed for the MEEF value. In addition, in Example 1, the hole size on the mask was 2.1 μm relative to the target hole size of 1.5 μm formed on the substrate. That is, a mask bias β of Dm / Dp of 1.4 was obtained.

[0124] Here, to confirm, regarding Reference Examples 1 and 2, under the same bias as in Example 1, we verified whether the transferability was improved. In Reference Example 1, the case where the size of the mask hole pattern is 2.1 μm by applying a bias is taken as Reference Example 3. Figure 7 (a) In Reference Example 2, the case in Reference Example 4 is similarly assigned a bias. Figure 8 The results of optical simulations of their respective transfer performance are also in (a)). Figure 6 As shown in the image.

[0125] Based on the optical simulation results related to Reference Example 3 and Reference Example 4, in Reference Example 3, the exposure amount can be reduced by applying a bias, but the DOF is reduced to a level lower than the reference value (Reference Example 1). Furthermore, as... Figure 7 As shown in (b), if the cross-section of the resist pattern in Reference Example 3 is observed, the partition wall 13 between the double-hole patterns is not sufficiently formed, and the double-hole patterns are connected to each other. Furthermore, according to Reference Example 4, not only is the improvement effect of DOF still smaller than the reference value, but... Figure 8As shown in (b), when viewed from the cross-section of the resist pattern, the partition wall 13 between the two holes is very thin and easily damaged. In order to obtain a circuit pattern without defects in the desired display device, it is most preferable that the partition wall 13 of the resist pattern does not lose the initial thickness of the resist, preferably with a thickness of at least 50% or more remaining in the partition wall 13 relative to the initial thickness, more preferably with a thickness of at least 60% remaining.

[0126] As can be confirmed from the above, the photomask of this embodiment has excellent transfer performance.

[0127] [Example 2]

[0128] Figure 9 The photomask of Reference Example 5 shown in (a), and Figure 10 The photomask of Reference Example 6 shown in (a) is a photomask with a near-dual-aperture pattern, which is formed in the same manner as in Example 1 above, except that the transmittance of the phase-shifting film in the halftone region 11 is changed. In Reference Examples 5 and 6, similar to Example 1 above, the goal is to form a near-dual-aperture pattern with a size of 1.5 μm on the transfer substrate.

[0129] For Reference Examples 5 and 6, optical simulations of transfer performance were performed in the same manner as in Example 1. The evaluation criteria in these optical simulations were the same as in Example 1. The results of these optical simulations are as follows: Figure 11 As shown. Furthermore, in Reference Examples 5 and 6, the cross-sectional shapes of the resist patterns formed on the transfer substrate are respectively as shown in... Figure 9 (b) and Figure 10 As shown in (b).

[0130] In Example 5, the transmittance of the phase-shifting film used in halftone region 11 (based on the wavelength of the exposure light, 334 nm) was set to 8%. According to the simulation results, there were no particular problems with the DOF value and the cross-sectional shape of the resist pattern, but the effect of reducing the necessary exposure was almost negligible.

[0131] Furthermore, in Reference Example 6, when the transmittance (based on a wavelength of 334 nm) of the phase-shifting film in the halftone region 11 was set to 25%, no particular problems were found in terms of exposure, DOF, and MEEF. However, in Reference Example 6, as... Figure 10 As shown in (b), the partition walls 13 between the hole patterns cannot be sufficiently formed in the cross-sectional shape of the resist pattern.

[0132] Therefore, it is preferable that the transmittance of the halftone region 11 in the (double) hole pattern is smaller than that shown in Reference Example 6 (specifically, less than 22%). On the other hand, in the isolated hole pattern, even a transmittance of about 25% as shown in Reference Example 6 can be considered sufficiently practical.

[0133] The photomasks of the present invention, exemplified by the first photomask 10, the second photomask 20, etc., described above, can be manufactured using a photolithography process. That is, they can be manufactured using a photomask blank on the main plane of a substrate made of a transparent material such as quartz, on which a phase-shifting film has been formed. When forming the phase-shifting film on the transparent substrate, known methods such as sputtering can be used. This phase-shifting film (forming the halftone region 11) has a phase-reversal effect, for example, relative to the mid-ultraviolet wavelength region. Then, the phase-shifting film is patterned according to the desired device.

[0134] The materials used for the phase-shifting films applied to the first photomask 10 and the second photomask 20 are not particularly limited. For example, transition metal silicides are preferred. For example, molybdenum silicides (MoSi) and their compounds (MoSiO, MoSiN, MoSiC, MoSiON, MoSiCN, MoSiCO, MoSiCON, etc.) are preferred.

[0135] Alternatively, the material of the phase-shifting film can also be chromium (Cr) or its compounds (CrO, CrN, CrC, CrON, CrCN, CrCO, CrCON, etc.).

[0136] Furthermore, the material of the phase-shifting film, as a metallic component, can be exemplified by substances containing Ta (tantalum), Zr (zirconium), or Ti (e.g., Zr silicides, silicides containing Mo and Zr), or their compounds (oxides, nitrides, carbides, and other compounds listed above).

[0137] The first photomask 10 and the second photomask 20 of this method were simulated as photomasks using MoSi compounds as phase-shifting films. The thickness of the phase-shifting film can be set to 100-200 nm, and it can be formed by known film deposition methods such as sputtering. In addition, both dry etching and wet etching can be used in the patterning of the phase-shifting film, but wet etching is sometimes advantageous for large photomasks used in the manufacture of display devices.

[0138] Furthermore, while both the first photomask 10 and the second photomask 20 described above use a phase-shifting film that reverses the exposure light in the mid-ultraviolet region within the halftone region 11, photomasks with different structures are also possible. For example, the halftone region 11 can use a semi-transparent film with a transmittance of T% (e.g., 10 ≤ T ≤ 35) for the exposure light and substantially no phase-reversal effect. "Substantially no phase-reversal effect" means that for a reference wavelength λ1, the phase shift is 90 degrees or less, preferably 60 degrees or less. On the other hand, the light-transmitting portion 12 constituting the mask aperture pattern can be formed by carving a portion of a predetermined thickness into the surface of the transparent substrate. This allows the phase difference θ between the light-transmitting portion 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 obtained in such a photomask.

[0139] In addition, for the photomask of the above embodiments, an additional film (reflection control film, etch stop film, etc.) may be formed on the transparent substrate without impairing the effect of the present invention.

[0140] This invention includes a method for manufacturing a display device using the aforementioned photomask. Here, the display device includes equipment constituting the display device.

[0141] In the exposure process of this invention, a projection exposure apparatus that performs equal-multiplied or reduced exposures with an NA of approximately 0.08 to 0.20 can be used. The NA is preferably 0.08 to 0.18, and more preferably 0.08 to 0.15.

[0142] The illumination system of the exposure apparatus can use ordinary illumination. Alternatively, it can use non-ordinary illumination, namely deformable illumination (illumination from the incident light toward the photomask after removing the perpendicular incident component).

[0143] In recent high-definition organic EL display (OLED) circuits, the usefulness of transfer patterns with two or more proximity hole patterns has increased due to the high precision of the circuits. The photomask of the present invention addresses this new technical challenge.

[0144] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from its spirit.

Claims

1. A photomask, said photomask being used in the manufacture of a display device, said photomask being used to form a hole pattern of size Dp on a transfer substrate using mid-ultraviolet light, wherein, 0.5μm≤Dp≤3μm A transfer pattern containing a hole pattern is formed on a transparent substrate. The perforation pattern in the transfer pattern is composed of light-transmitting portions surrounded by halftone areas. For the mid-ultraviolet exposure light used to expose the photomask, the reference wavelength λ1 is included, and the phase difference θ between the transmitted portion and the halftone region is 120 ≤ θ ≤ 240 degrees. The transmittance T of the halftone region for light at the reference wavelength λ1 is 10% ≤ T ≤ 35%. The numerical aperture of the projection optics system of the exposure apparatus using the photomask is 0.08 or higher and 0.20 or lower. The reference wavelength λ1 is 250nm < λ1 < 400nm. When the size of the hole pattern in the transfer pattern is Dm, Dm > Dp.

2. The photomask according to claim 1, wherein, The hole pattern in the transfer pattern is composed of light-transmitting portions, which are formed by patterning a phase-shifting film formed on the transparent substrate, in which the transparent substrate is exposed. The phase-shifting film is formed on the transparent substrate in the halftone region. The phase-shifting film has a phase shift of 120 ≤ θ ≤ 240 degrees for the reference wavelength λ1, and has a transmittance T of 10% ≤ T ≤ 35%.

3. The photomask according to claim 1 or 2, wherein, The transfer pattern includes an isolated hole pattern.

4. The photomask according to claim 1 or 2, wherein, The transfer pattern has a proximity hole pattern, which includes two or more hole patterns that are close to each other.

5. The photomask according to claim 4, wherein, The distance between the centroids of the two hole patterns included in the proximity hole pattern is less than 9 μm.

6. The photomask according to claim 1 or 2, wherein, The reference wavelength λ1 is 313nm or 334nm.

7. The photomask according to claim 1, wherein, Dm / Dp is 1.1 to 1.

8.

8. A method for manufacturing a display device, comprising the following steps: The process of preparing the photomask according to any one of claims 1 to 7; and The exposure process involves exposing the photomask to medium ultraviolet light. The medium-ultraviolet light used for exposure includes a wavelength region where wavelength λ satisfies 200nm ≤ λ ≤ 400nm, but does not include wavelengths where λ > 400nm or λ < 200nm. Furthermore, the numerical aperture of the projection optics system of the exposure apparatus using the photomask is 0.08 or higher and 0.20 or lower. The reference wavelength λ1 for the ultraviolet light used in the medium-ultraviolet exposure is 250nm < λ1 < 400nm.

9. The method for manufacturing a display device according to claim 8, wherein, Through the exposure process, a hole pattern of size Dp is formed on the substrate to be transferred. Wherein, 0.5μm≤Dp≤3μm.

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