Pattern inspection method, photomask inspection apparatus, and method for manufacturing a photomask

Abstract

A pattern inspection method, a photomask inspection apparatus, and a method for manufacturing a photomask are provided. Even in a fine-width pattern, line width measurement can be stably and highly accurately performed. A process of irradiating light to an inspection area and obtaining a transmitted light image of the inspection area; a process of obtaining light intensity distribution data of the inspection area based on the obtained transmitted light image; a differential processing step of obtaining a light intensity change curve of a region including a first boundary which is a boundary portion between a first transmission control portion and a second transmission control portion and a second boundary which is a boundary portion between the second transmission control portion and a third transmission control portion by performing differential processing on a light intensity distribution curve obtained from the light intensity distribution data; a fitting step of fitting the obtained light intensity change curve to a model function; and a step of obtaining the size of the second transmission control portion based on the fitting result.

Description

Technical Field

[0001] The present invention relates to a pattern inspection method, a photomask inspection apparatus, a method for manufacturing a photomask, and a method for manufacturing a display device. In particular, the present invention is a method for inspecting a transfer pattern included in a photomask for manufacturing an electronic device, and more particularly, a photomask for manufacturing a display device (e.g., FPD: flat panel display), a photomask inspection apparatus, a method for manufacturing a photomask, and a method for manufacturing a display device. Background Art

[0002] Patent Document 1 describes a method for detecting the contour of a pattern by capturing an image of the pattern with a solid-state imaging device and a length measuring device.

[0003] Patent Document 2 describes a pattern size measuring device that measures the size of a pattern formed on a specimen based on a signal obtained by scanning the specimen with an electron beam.

[0004] Patent Document 3 describes a photomask having a transfer pattern on a transparent substrate, the transfer pattern including a light-transmitting portion, a semi-light-transmitting portion formed with a semi-light-transmitting film that transmits a part of exposure light, and a light-shielding portion formed with a light-shielding film. The semi-light-transmitting film has a transmittance of 2 to 60% and a phase shift effect of 90° or less for a representative wavelength of the exposure light used in the transfer of the transfer pattern. The semi-light-transmitting portion is adjacent to the edge of the light-shielding portion and is formed to have a width that cannot be resolved by an exposure apparatus.

[0005] [Prior Art Documents]

[0006] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Laid-Open No. 3-39603

[0008] [Patent Document 2] Japanese Patent Laid-Open No. 2012-002765

[0009] [Patent Document 3] Japanese Patent Laid-Open No. 2013-235036 Summary of the Invention

[0010] [Problems to be Solved by the Invention]

[0011] When manufacturing a photomask, an inspection is performed to confirm whether the specifications determined according to the use of the photomask are satisfied. Measurement of the line width of the transfer pattern is also one of such inspections.

[0012] According to Patent Document 1, the following problem is described: In existing length measuring devices, an analog optical image formed on the imaging surface of a camera is sampled in units of pixels of the imaging element. Therefore, when measuring the size of a pattern or the like based on the sampled image signal, there is a problem that the measurement accuracy below the pixel pitch of the imaging element cannot be obtained. Therefore, Patent Document 1 provides the following method that is particularly suitable for length measurement: An image of a pattern is captured using a solid-state imaging element and multi-level image processing is performed on the data, thereby automatically and precisely assigning the contour of the pattern with an accuracy less than or equal to the pixel pitch of the imaging element.

[0013] However, the quality (information amount) of the optical image formed on the imaging element changes not only according to the imaging element but also according to the resolution of the optical system used. However, in a measuring device used for measuring the CD (Critical Dimension: critical dimension, hereinafter used in the meaning of line width) of a photomask for manufacturing a display device, its performance is limited.

[0014] On the other hand, the pattern size measuring device described in Patent Document 2 uses an electron beam instead of light to obtain an SEM image.

[0015] In this way, as a method for measuring the pattern line width, a method using CD-SEM (Critical Dimension-Scanning Electron Microscope) that utilizes an electron beam is known. CD-SEM is a measuring device that applies a scanning electron microscope (SEM) and is mainly used for measuring the line width of fine patterns formed on a semiconductor wafer or a photomask (reticle) used for manufacturing the pattern. This measuring device has the advantage of being able to precisely measure fine patterns in the sub-micron range. However, for the following reasons, it is difficult to apply CD-SEM to the measurement of a so-called large photomask (usually, the main surface is a quadrilateral with one side being about 300 to 2000 mm and various sizes are mixed) for manufacturing a display device (for example, a flat panel display. Hereinafter simply referred to as FPD). When measuring the pattern line width using CD-SEM, the chamber (sample chamber) on which the photomask to be measured is placed is made into a vacuum or a high vacuum. Therefore, when applying CD-SEM to the measurement of a large photomask for manufacturing a display device, it is necessary to prepare a large chamber and make the chamber into a vacuum or a high vacuum, and there is a problem that the process load becomes very large. In this case, it is necessary to greatly change the device structure, and an increase in cost cannot be avoided.

[0016] Therefore, in the line width measurement of a photomask for a display device, an optical line width measuring device having an optical system and an imaging element and measuring the line width using the transmitted light of a transfer pattern is applied.

[0017] However, the CD of the pattern of the photomask for a display device has not been as fine as that of the photomask for semiconductor device manufacturing in the past, so no major problems have occurred.

[0018] However, in the technical field of display devices, as the performance requirements such as image quality and power saving from users of portable terminals or monitors are getting higher and higher, the necessity of miniaturization of the pattern of the photomask for manufacturing display devices has become significant. Therefore, in addition to the increased difficulty in photomask manufacturing, it has also become difficult to measure the line width of the formed transfer pattern. In addition, a pattern with characteristics specifically for display device manufacturing is also required.

[0019] In Patent Document 3, a photomask (transmission assist mask) is described, which has a line and space pattern as a transfer pattern. This is shown in Figure 1 Here, the line pattern has a structure in which first and second semi-transmissive portions 21A and 21B (semi-transmissive films with a transmittance of 20% and a phase difference of 45°) are provided adjacent to both side edges of the light-shielding portion 31. Here, the width of the light-shielding portion 31 is 1.5 μm, and the widths of the first and second semi-transmissive portions 21A and 21B adjacent to both side edges of the light-shielding portion 31 are 1.0 μm respectively.

[0020] As a photomask for a display device, a photomask with a pattern having such characteristics is desired. In addition, its CD also has a tendency to be miniaturized. According to the design of FPD devices, there has also begun to be a situation where a photomask with a finer pattern of less than 1 μm needs to be inspected. It is very difficult to measure the line width of such a fine pattern with the above optical line width measuring device.

[0021] Therefore, the inventor of the present invention has completed the present invention in order to solve the problems that occur in measuring the line width of the transfer pattern of the photomask for a display device even in the case of a pattern with a fine width.

[0022] [Means for Solving the Problem]

[0023] (First Embodiment)

[0024] The first embodiment of the present invention,

[0025] A pattern inspection method for inspecting the transfer pattern of a photomask having a transfer pattern on a transparent substrate, wherein,

[0026] The pattern for transfer includes an inspection area, in which a first light transmission control part having a light transmittance T1 for exposure light, a second light transmission control part having a light transmittance T2 for exposure light, and a third light transmission control part having a light transmittance T3 for exposure light are arranged adjacent to each other in this order, where the light transmittances T1, T2, and T3 are percentages respectively. When T1 and T3 are different from T2 respectively and T1 is the same as or different from T3, the pattern inspection method includes the following steps:

[0027] A step of irradiating light to the inspection area and obtaining a transmitted light image of the inspection area;

[0028] A step of obtaining light intensity distribution data of the inspection area based on the obtained transmitted light image;

[0029] A differential processing step of obtaining a light intensity change curve of an area including a first boundary which is a boundary part between the first light transmission control part and the second light transmission control part and a second boundary which is a boundary part between the second light transmission control part and the third light transmission control part by performing differential processing on a light intensity distribution curve obtained from the light intensity distribution data;

[0030] A fitting step of fitting the obtained light intensity change curve to a model function; and

[0031] A step of obtaining the size of the second light transmission control part based on the fitting result.

[0032] (The second mode)

[0033] The second mode of the present invention is based on the pattern inspection method of the first mode,

[0034] T1>T2>T3.

[0035] (The third mode)

[0036] The third mode of the present invention is based on the pattern inspection method of the first or second mode,

[0037] The first light transmission control part constitutes a light transmitting part formed by exposing the transparent substrate,

[0038] The second light transmission control part constitutes a semi-light transmitting part formed by forming a semi-light transmitting film on the transparent substrate,

[0039] The third light transmission control part constitutes a light shielding part formed by at least forming a light shielding film on the transparent substrate,

[0040] The light transmittance of the semi-light transmitting part for the exposure light is 10 to 60%.

[0041] (The fourth mode)

[0042] The fourth aspect of the present invention is a pattern inspection method according to any one of the first to third aspects.

[0043] The width W (μm) of the second transmission control unit satisfies 0.1 ≤ W ≤ 1.5.

[0044] (Fifth aspect)

[0045] The fifth aspect of the present invention is a pattern inspection method according to any one of the first to fourth aspects.

[0046] The transfer pattern includes line and space patterns.

[0047] (Sixth aspect)

[0048] The sixth aspect of the present invention is a pattern inspection method according to any one of the first to fifth aspects.

[0049] The model function includes a first model function corresponding to the first boundary and a second model function corresponding to the second boundary.

[0050] (Seventh aspect)

[0051] The seventh aspect of the present invention is a pattern inspection method according to the sixth aspect.

[0052] In the fitting process, fitting is performed so that the difference between the composite curve and the light intensity change curve is minimized, where the composite curve is obtained by combining a first model curve obtained from the first model function and a second model curve obtained from the second model function.

[0053] (Eighth aspect)

[0054] The eighth aspect of the present invention is a pattern inspection method according to the seventh aspect.

[0055] Let the first model curve and the second model curve be Gaussian curves respectively.

[0056] (Ninth aspect)

[0057] The ninth aspect of the present invention is a pattern inspection method according to the seventh or eighth aspect.

[0058] Based on the peak position of the first model curve and the peak position of the second model curve, the size of the second transmission control unit is obtained.

[0059] (Tenth aspect)

[0060] The tenth aspect of the present invention is a method for manufacturing a photomask, including the pattern inspection method according to any one of the first to ninth aspects.

[0061] (The 11th mode)

[0062] The 11th embodiment of the present invention is a method for manufacturing a display device, including: exposing a photomask manufactured by the manufacturing method described in the 10th mode by an exposure device, and transferring the transfer pattern onto a transfer target.

[0063] (The 12th mode)

[0064] The 12th mode of the present invention is an inspection device for a photomask, which inspects the transfer pattern of the photomask having the transfer pattern on a transparent substrate, wherein

[0065] the transfer pattern includes an inspection area, in which a first transmission control part having a transmittance T1 for exposure light, a second transmission control part having a transmittance T2 for exposure light, and a third transmission control part having a transmittance T3 for exposure light are arranged adjacent to each other in this order, where T1, T2, and T3 are percentages respectively. When T1 and T3 are different from T2 respectively, and T1 is the same as or different from T3,

[0066] the photomask inspection device includes:

[0067] an imaging element that acquires an image of the inspection area of the transfer pattern; and

[0068] an arithmetic unit that, based on the acquired image, obtains light intensity distribution data, fits a light intensity change curve obtained by differentiating the light intensity distribution curve obtained from the light intensity distribution data to a model function, and thereby calculates the size of the second transmission control part included in the inspection area.

[0069] (The 13th mode)

[0070] The 13th mode of the present invention is based on the photomask inspection device described in the 12th mode,

[0071] T1>T2>T3.

[0072] (The 14th mode)

[0073] The 14th mode of the present invention is based on the photomask inspection device described in the 12th or 13th mode,

[0074] the model function includes a first model function corresponding to a first boundary that is a boundary part between the first transmission control part and the second transmission control part, and a second model function corresponding to a second boundary that is a boundary part between the second transmission control part and the third transmission control part,

[0075] The arithmetic unit performs fitting to minimize the difference between the synthesized curve and the light intensity change curve, where the synthesized curve is obtained by synthesizing a first model curve obtained from the first model function and a second model curve obtained from the second model function.

[0076] [Advantages of the Invention]

[0077] According to the present invention, even in a fine-width pattern, line width measurement can be stably and highly accurately performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 is a schematic top view of a photomask (transmission assist mask) having a line and space pattern as a transfer pattern described in Patent Document 3.

[0079] Figure 2 is a diagram showing the Figure 1 transmission light image of the photomask described above obtained by an optical line width measurement device.

[0080] Figure 3 is a diagram showing Figure 2 the same inspection area of the transfer pattern as a secondary electron image obtained by a FIB (Focused Ion Beam) correction device.

[0081] Figure 4 is a diagram showing an example of the outline of the pattern inspection method of the photomask of the present invention.

[0082] Figure 5 is a diagram showing the process of obtaining the line width (dimension) of the second transmission control part (semi-transmissive part) of the inspection area included in the transfer pattern.

[0083] Figure 6 is a diagram showing a transmission light image obtained by irradiating light to a reference area including a transfer pattern of a reference mask by an optical line width measurement device having a halogen lamp as a light source and using a microscope having a CCD as an imaging element.

[0084] Figure 7 is a diagram showing a light intensity distribution curve showing light intensity distribution data of a reference area obtained by representing, as a curve, a transmission light image obtained using 5 reference masks.

[0085] Figure 8 is a diagram showing a light intensity change curve 1 regarding the boundary between the light transmissive part and the semi-transmissive part.

[0086] Figure 9 is a diagram showing a light intensity change curve 2 regarding the boundary between the semi-transmissive part and the light shielding part.

[0087] Figure 10 It is a graph depicting the data in Table 1 with the horizontal axis being the transmittance T2 of the semi-transmissive portion and the vertical axis being the amplitude A or the width σ.

[0088] Figure 11 It is a graph showing the model function obtained from a linear function.

[0089] Figure 12 It is a graph showing a transmitted light image obtained by irradiating light on an inspection region including a transfer pattern of an inspection target photomask with an optical line width measurement device having a halogen lamp as a light source and using a microscope with a CCD as an imaging element.

[0090] Figure 13 It is a graph showing the light intensity distribution curve of the inspection target photomask.

[0091] Figure 14 It is a graph showing the light intensity change curve of each boundary portion with respect to the absolute value obtained by performing a first-order differential process on the light intensity distribution curve (or light intensity distribution data).

[0092] Figure 15 It is a graph for explaining the case of obtaining a composite curve.

[0093] Figure 16 It is a graph for explaining the case of calculating the line width of the semi-transmissive portion based on the composite curve. Detailed Embodiments

[0094] Hereinafter, embodiments of the photomask, the method for manufacturing the photomask, and the method for manufacturing the display device of the present invention will be described.

[0095] With the increasing high definition of display devices, the introduction of fine patterns in photomasks for display devices has been increasingly developed.

[0096] The miniaturization of the wiring pattern of the display device not only improves the image quality such as the brightness and response speed of the screen, but is also advantageous from the viewpoint of energy saving. Therefore, in recent years, further miniaturization of the wiring pattern of the display device has been required, and along with this, there has been a tendency to expect fine line width accuracy for the photomask for the display device.

[0097] According to Patent Document 3, it is described that in a binary mask having a line and space pattern composed of a light-shielding portion and a light-transmitting portion, when the pitch of the line and space pattern is gradually reduced and miniaturized, it is impossible to transfer the correct line and space pattern to the resist film on the transfer body. This is because, as the line width of the space pattern composed of the light-transmitting portion becomes fine, the light intensity reaching the resist film decreases.

[0098] Therefore, a photomask (transmission assist mask) is proposed in Patent Document 3. The photomask has a transfer pattern on a transparent substrate. The transfer pattern has a light-transmitting portion, a semi-transmitting portion formed with a semi-transmitting film that allows a part of the exposure light to pass through, and a light-shielding portion formed with a light-shielding film. The semi-transmitting portion is adjacent to the edge of the light-shielding portion and is formed with a width that cannot be resolved by the exposure apparatus. In Patent Document 3, it is described that by adopting such a structure, a fine pattern can be reliably and precisely transferred onto the transfer body.

[0099] As Figure 1 (corresponding to Figure 10 (a) of Patent Document 3) shown, the semi-transmitting portion of the photomask of Patent Document 3 has a certain width and is disposed adjacent to the opposite edges of the light-shielding portion respectively. Here, the width of the semi-transmitting portion formed adjacent to the edge of the light-shielding portion is preferably 1 μm or less (the preferred range is 0.1 - 1 μm).

[0100] However, in the manufacturing process of the photomask, before leaving the factory, various inspections are carried out to confirm that the specifications required by the mask user are met. One of these inspections is the CD (line width) inspection. In this CD inspection, the line width of the important part included in the transfer pattern is measured, and the obtained line width value is compared with the specifications.

[0101] To measure the line width, it is useful to detect the pattern profile of the measurement object. For example, in a so-called binary mask, when measuring the line width of a line pattern formed by a light-shielding portion in the light-transmitting portion, the boundary between the light-transmitting portion and the light-shielding portion, that is, the edge of the light-shielding portion adjacent to the light-transmitting portion, is detected in the captured image. However, the photomask of Patent Document 3 includes a fine transfer pattern, and moreover, the transmittance difference of the inspection light between the first and second semi-transmitting portions and the adjacent light-transmitting portion or the adjacent light-shielding portion is small. The present inventor found that in a photomask including such a transfer pattern, it is difficult to detect the profile (edge) of the pattern to be measured, and it is not easy to measure the line width.

[0102] Figure 2 It shows a transmitted light image (Reference Example 1) of a photomask having a line pattern as shown in Figure 1 obtained by an optical line width measuring device. Specifically, Figure 2 it shows the transmitted light image of the transmitted light when the portion corresponding to (A) surrounded by the dotted line in Figure 1 is used as the inspection area and the inspection light (wavelength λ = 400 - 550 nm) is irradiated on this area using a halogen lamp. This line pattern has semi-transmitting portions with a width of 0.5 μm disposed on both sides of a light-shielding portion with a width of 3.0 μm, and the transmittance of the semi-transmitting portion for the exposure light is 30%.

[0103] From Figure 2As can be seen, in the transmitted light image, it is not easy to clearly identify the semi-transmissive portion with a specified width adjacent to the edges on both sides of the light-shielding portion. Therefore, it is difficult to measure the line width of the semi-transmissive portion using this transmitted light image.

[0104] In addition, Figure 3 The inspection area of the same transfer pattern is obtained as a secondary electron image by a FIB (Focused Ion Beam) correction device (Reference Example 2). The FIB correction device converges the ion beam obtained from a gallium plasma source, scans it on the specimen, and detects the secondary electrons generated. From Figure 3 As can be seen, according to this image, the semi-transmissive portion with a specified width formed adjacent to the edge of the light-shielding portion can be clearly identified. Therefore, it is considered that the line width of the semi-transmissive portion can also be measured. However, if the line width is measured using a FIB correction device, there is a risk of damaging the transfer pattern.

[0105] On the other hand, for the large-size of the display device and the reduction of production costs, the photomask for the display device is relatively large-sized, and there are also various sizes. Therefore, it is difficult to apply the above CD-SEM to line width measurement.

[0106] Under such circumstances, it is desired to use an excellent measuring device to accurately measure the line width (CD) of a fine pattern without damaging the photomask, thereby improving the process management accuracy, the yield, and the production efficiency. Therefore, the present inventor has completed the invention in response to such a need.

[0107] <Pattern inspection method>

[0108] Figure 4 It is an example showing the outline of the pattern inspection method of the photomask of the present invention.

[0109] In the case of a photomask having a transfer pattern like the portion (A) surrounded by a dotted line in Figure 1 It is considered that the light intensity changes significantly at the boundary between the transmissive portion and the semi-transmissive portion, and at the boundary between the semi-transmissive portion and the light-shielding portion. Therefore, the light intensity distribution obtained from the transmitted light image of the portion (A) in Figure 1 can be theoretically considered to form the distribution shown by the dotted line in Figure 4 (a). In addition, Figure 4 the horizontal axis of (a) in Figure 1 represents the position (the horizontal position in

[0110] In this Figure 4In the light intensity distribution shown by the dashed line in (a), the portion where the light intensity changes sharply is clear. Since the portion where the light intensity changes sharply is the boundary between the light-transmitting portion and the semi-light-transmitting portion, or the boundary between the semi-light-transmitting portion and the light-blocking portion, if the Figure 4 light intensity distribution shown in (a) can be obtained, the line width of the semi-light-transmitting portion can be easily obtained.

[0111] However, in the case where the line width of the semi-light-transmitting portion is small, the actual light intensity distribution forms Figure 4 a smooth curve shown by the solid line in (a). In Figure 4 the curve shown by the solid line in (a), the boundary between the light-transmitting portion and the semi-light-transmitting portion, and the boundary between the semi-light-transmitting portion and the light-blocking portion are not clear, and it is not easy to obtain the line width of the semi-light-transmitting portion.

[0112] However, according to the research of the present inventor, even if the light intensity distribution curve is smooth, the amount of change in the light intensity at each boundary, that is, the change in the slope of the light intensity distribution curve, should be larger than that of other portions. Therefore, the present inventor focused on the fact that if the light intensity distribution curve is differentiated, a curve having peaks at positions corresponding to each boundary is obtained.

[0113] Figure 4 (b) is a conceptual diagram of a curve (light intensity change curve) obtained by plotting the absolute value of the value obtained by differentiating the curve shown by the solid line in (a) of Figure 4 . The vertical axis represents the light intensity change amount, and the horizontal axis represents the position. In Figure 4 (b), sharp peaks can be seen at positions corresponding to each boundary.

[0114] Therefore, by obtaining the distance between the peak corresponding to the boundary between the light-transmitting portion and the semi-light-transmitting portion and the peak corresponding to the boundary between the semi-light-transmitting portion and the light-blocking portion, the line width of the semi-light-transmitting portion can be obtained.

[0115] Next, a method for inspecting the pattern of the photomask will be described in more detail.

[0116] The object to be inspected is the transfer pattern of a photomask having a transfer pattern on a transparent substrate. The transfer pattern includes an inspection area in which a first transmission control portion having a transmittance T1 (%) for exposure light, a second transmission control portion having a transmittance T2 (%) for exposure light, and a third transmission control portion having a transmittance T3 (%) for exposure light are arranged in sequence. That is, the second transmission control portion is interposed between the first transmission control portion and the third transmission control portion. One edge of the second transmission control portion is adjacent to the first transmission control portion, and the other edge of the second transmission control portion is adjacent to the third transmission control portion. T1 and T3 are each different from T2, and T1 may be the same as or different from T3.

[0117] The exposure light is the exposure light used when exposing a photomask having the transfer pattern. The wavelength λ (nm) of the exposure light can be 250 < λ < 400. For example, the exposure light can include at least one of i-line, h-line, and g-line. In addition, light in a wide wavelength region including i-line, h-line, and g-line can also be used as the exposure light. When the exposure light includes light of multiple wavelengths, any wavelength included in the region of i-line to g-line can be used as the representative wavelength. As the transmittance for this representative wavelength (e.g., g-line), it can be expressed as T1, T2, T3.

[0118] In the present embodiment, the case where T1 > T2 > T3, the first transmittance control portion is a light-transmitting portion, the second transmittance control portion is a semi-light-transmitting portion, and the third transmittance control portion is a light-shielding portion will be described as an example. Therefore, in the present embodiment, when the transmittance T1 of the light of the light-transmitting portion is 100%, the transmittance of the light of the semi-light-transmitting portion as the second transmittance control portion is T2, and the transmittance of the light of the light-shielding portion as the third transmittance control portion is T3. However, the transmittance T3 of the light of the light-shielding portion in the present embodiment is substantially zero (e.g., optical density OD ≥ 3). And in the present embodiment, the size (line width) of the second transmittance control portion, i.e., the semi-light-transmitting portion, is obtained.

[0119] The light-transmitting portion can be formed by exposing a transparent substrate. The light-shielding portion can be formed by forming at least one light-shielding film on the transparent substrate. In the light-shielding portion, a film different from the light-shielding film (e.g., a semi-light-transmitting film described later) can also be formed on the light-shielding film or between the transparent substrate and the light-shielding film.

[0120] There is no particular limitation on the material of the light-shielding film, but the following materials are preferably used. For example, as the material of the light-shielding film, in addition to Cr or Cr compounds (Cr oxides, nitrides, carbides, oxynitrides, carbon oxynitrides, etc.), Ta, Mo, W, and their compounds (e.g., TaSi, MoSi, WSi, or their metal silicon compounds such as nitrides and oxynitrides) can also be preferably used. In addition, these materials can be used alone or in combination of two or more.

[0121] The light-shielding film can have a functional layer such as an antireflection layer on its surface side (the side opposite to the transparent substrate). The antireflection layer can improve the drawing accuracy by suppressing the reflection of the drawing light in the resist film. For example, when the light-shielding film contains Cr, the antireflection layer can be set as a layer containing at least any one of Cr oxides, nitrides, carbides, oxynitrides, and carbon oxynitrides.

[0122] The antireflection layer can be formed by a compositional change in the film thickness direction of a light-shielding film including the antireflection layer. This compositional change can vary continuously or stepwise in the thickness direction of the light-shielding film, or there can be a clear boundary between the antireflection layer of the light-shielding film and the layer other than the antireflection layer.

[0123] The semi-transmissive portion can be a portion where a semi-transmissive film is formed on a transparent substrate. In the present embodiment, the semi-transmissive portion has an auxiliary function for the transmitted light amount of the light-transmissive portion. If the transmittance T2 (%) of the semi-transmissive portion is too small, the auxiliary function for the transmitted light amount of the light-transmissive portion cannot be fully exerted. If the transmittance T2 is too large, the difficulty of mask manufacturing such as film thickness control of the semi-transmissive film becomes high. Considering this point, the transmittance T2 (%) of the semi-transmissive portion can be, for example, 2 ≤ T2 ≤ 60. The transmittance T2 (%) of the semi-transmissive portion is preferably 10 ≤ T2 ≤ 60, more preferably 10 ≤ T2 ≤ 35, and further preferably 15 ≤ T2 ≤ 30.

[0124] The line width (dimension) W (μm) of the semi-transmissive portion is preferably 0.1 ≤ W ≤ 1.5, more preferably 0.3 ≤ W ≤ 1.0. If the line width of the semi-transmissive portion is too large, when pattern transfer is performed using this photomask, the side shape of the resist pattern on the transfer object may be inclined. On the other hand, if the line width of the semi-transmissive portion is too small, the function of assisting the transmitted light amount of the auxiliary light-transmissive portion becomes insufficient. If the line width of the semi-transmissive portion is within the above range, the inclination of the side shape of the resist pattern can be suppressed, a resist pattern with a good side shape can be formed, and the transmitted light amount of the light-transmissive portion can be sufficiently assisted.

[0125] In addition, for the representative wavelength of the exposure light described above, the phase shift amount (degrees) of the phase shift amount of the semi-transmissive portion is preferably more preferably further preferably By making the phase shift amount of the semi-transmissive portion within the above range, the cancellation of the light intensity at the boundary between the semi-transmissive portion and the light-transmissive portion can be suppressed, and the transmitted light amount of the light-transmissive portion can be assisted. Therefore, even when the pattern size is miniaturized and the photomask is exposed, the decrease in the light intensity peak position of the light-transmissive portion can be suppressed, and a resist pattern with a good side shape can be formed.

[0126] As a raw material for the semi-transmissive film, for example, Cr compounds (oxides, nitrides, carbides, oxynitrides, oxynitride carbides, etc. of Cr), Si compounds (SiO2, SOG), metal silicides (TaSi, MoSi, WSi or their nitrides, oxynitrides, etc.), and Ti compounds such as TiON can be used. They can be used alone, or two or more of them can be used in combination.

[0127] The pattern inspection method of the photomask of the present embodiment includes the following steps:

[0128] A step of irradiating light on the transfer pattern and obtaining a transmitted light image of the inspection area;

[0129] A step of obtaining light intensity distribution data of the inspection area based on the obtained transmitted light image;

[0130] A differentiation step of obtaining a light intensity change curve in a region including a first boundary that is a boundary portion between the first transmission control portion and the second transmission control portion and a second boundary that is a boundary portion between the second transmission control portion and the third transmission control portion by differentiating a light intensity distribution curve obtained from the light intensity distribution data;

[0131] A fitting step of fitting the obtained light intensity change curve to a model function;

[0132] A step of obtaining the size of the second transmission control portion based on the result of the above fitting.

[0133] Figure 5 It shows a process of obtaining the line width (size) of the second transmission control portion (semi-transmissive portion) of the inspection area included in the transfer pattern. Refer to Figures 5 to 16 , for Figure 5 each step is specifically described.

[0134] First, a model function used when obtaining the line width of the semi-transmissive portion is generated.

[0135] To generate a model function, a plurality of reference masks are prepared. These reference masks may include a photomask having a transfer pattern with a portion where a light-transmitting portion (first light-transmission control portion) and a semi-transmitting portion (second light-transmission control portion) are adjacent, and a photomask having a transfer pattern with a portion where a semi-transmitting portion (second light-transmission control portion) and a light-blocking portion (third light-transmission control portion) are adjacent. In the present embodiment, as the reference mask, a photomask having a transfer pattern with any one of a portion where a light-transmitting portion (first light-transmission control portion) and a semi-transmitting portion (second light-transmission control portion) are adjacent, and a portion where a semi-transmitting portion (second light-transmission control portion) and a light-blocking portion (third light-transmission control portion) are adjacent is used. The light-transmitting portion (first light-transmission control portion) and the light-blocking portion (third light-transmission control portion) do not necessarily be adjacent to the same semi-transmitting portion (second light-transmission control portion), and may be adjacent to different semi-transmitting portions (second light-transmission control portion). In the present embodiment, in the transfer pattern, a region where the light-transmitting portion (first light-transmission control portion), the semi-transmitting portion (second light-transmission control portion), and the light-blocking portion (third light-transmission control portion) are arranged in this order is used as a reference region. The line width of the semi-transmitting portion in the reference region is preferably large enough. By "large enough" it means to the extent that it does not hinder the calculation of the model function described later. In addition, the portion where the light-transmitting portion (first light-transmission control portion) and the semi-transmitting portion (second light-transmission control portion) are adjacent, and the portion where the semi-transmitting portion (second light-transmission control portion) and the light-blocking portion (third light-transmission control portion) are adjacent do not necessarily be included in one reference region. In this case, a region including the portion where the light-transmitting portion (first light-transmission control portion) and the semi-transmitting portion (second light-transmission control portion) are adjacent is used as the first reference region, and a region including the portion where the semi-transmitting portion (second light-transmission control portion) and the light-blocking portion (third light-transmission control portion) are adjacent is used as the second reference region, and the transmitted light images described later are obtained for these two reference regions respectively, and a light intensity distribution curve may be generated.

[0136] (1) Obtain the transmitted light image of the reference mask

[0137] Images of the transfer patterns of a plurality of reference masks are obtained. In addition, in the present embodiment, as an example of the image, a transmitted light image is used, but it is not limited thereto. As long as the effects / functions of the present invention are not hindered, an image different from the transmitted light image (for example, a reflected light image) may also be used.

[0138] In the present embodiment, a region of the reference region of the reference mask including the transfer pattern is irradiated with light by an optical line width measuring device having a halogen lamp as a light source, and a transmitted light image is obtained using a microscope with a CCD as an imaging element ( Figure 6 ). The wavelength of the light (inspection light) at this time is preferably any wavelength in the wavelength region of 400 to 550 nm, for example, 525 nm.

[0139] In addition, for the purpose of obtaining a model function, a plurality of reference masks with different transmittances of the semi-transmissive portion are prepared here, and transmitted light images (not shown) of the transfer patterns of these reference masks are obtained respectively. In the present embodiment, when the transmittance T1 of the light-transmissive portion is set to 100%, the transmittances of the semi-transmissive portions of the plurality of reference masks for the light of the g-line, that is, the transmittances T2 are 28%, 38%, 50%, 67%, and 79% respectively. That is, in the present embodiment, five reference masks are prepared. In any of the reference masks, the transmittance T3 of the light-shielding portion is substantially zero.

[0140] In Figure 6 , the region including the first boundary between the light-transmissive portion and the semi-transmissive portion, and the second boundary between the semi-transmissive portion and the light-shielding portion ( Figure 6 the region surrounded by the dashed line) is used as the reference region.

[0141] (2) Generation of the light intensity distribution curve of the reference mask

[0142] Based on the transmitted light images obtained using the above five reference masks, the light intensity distribution data of the reference region is obtained (not shown). Furthermore, a light intensity distribution curve representing this light intensity distribution data with a curve ( Figure 7 ) is obtained.

[0143] For example, a straight line perpendicular to the boundary line between the light-transmissive portion and the semi-transmissive portion, or a straight line perpendicular to the boundary line between the semi-transmissive portion and the light-shielding portion (for example Figure 6 the arrow part) is drawn within the reference region of the transmitted light image obtained in the above (1), and using known image processing software, the light intensity values on this straight line are quantized to 256 grayscales. Thus, a light intensity distribution curve like Figure 7 can be made. The straight line for obtaining the light intensity can be set at any position within the reference region so that it is parallel to the direction of the dimension to be measured. In addition, in Figure 7 , the vertical axis represents the light intensity quantized to 256 grayscales, and the horizontal axis represents the pixel position in the transmitted light image.

[0144] (3) Generation of the light intensity change curves of the first boundary between the light-transmissive portion and the semi-transmissive portion, and the second boundary between the semi-transmissive portion and the light-shielding portion

[0145] The light intensity distribution curve (or light intensity distribution data) obtained in the above (2) is subjected to a first-order differential process to obtain a light intensity change curve (light intensity change data) (differential process step). Figure 8 The light intensity change curve 1 representing the first boundary between the light-transmissive portion and the semi-transmissive portion is Figure 9 The light intensity change curve 2 representing the second boundary between the semi-transmissive portion and the light-shielding portion is. In Figure 8 and 8 andFigure 9 in which, the vertical axis represents the change in light intensity, and the horizontal axis is the same as Figure 7 also represents the pixel position (where the vertical axis is the absolute value of the change in light intensity and is a positive value).

[0146] (4) Perform fitting (least squares method) using the Gaussian function

[0147] Approximate the light intensity change curves obtained in the above (3) respectively through known functions. Here, using the Gaussian function (Equation (1)) shown below, perform fitting using the least squares method to obtain the coefficients A and σ of the Gaussian function corresponding to each light intensity change curve.

[0148] [Equation 1]

[0149] Here, y: change in light intensity, A: amplitude of the Gaussian function, σ: standard deviation of the Gaussian function, x: pixel position, p: peak position of the Gaussian function in the x direction. In addition, the standard deviation σ can be used as an index representing the width of the Gaussian function and is described as width σ in this specification.

[0150] The fitting results are shown in Table 1 below.

[0151]

Table 1

[0152]

[0153] (5) Model function generation

[0154] Let the horizontal axis be the transmittance T2 of the semi-transmissive portion, and let the vertical axis be the amplitude A or the width σ. The results after plotting the data in Table 1 are shown in Figure 10 . Approximate the above data obtained for the first boundary between the transmissive portion and the semi-transmissive portion and the second boundary between the light-shielding portion and the semi-transmissive portion as linear functions respectively, and obtain the slope a and intercept b of the linear function. That is, for the amplitude A, approximate as A = a × T2 + b, and for the width σ, approximate as σ = a × T2 + b. Thus, for each amplitude A and width σ, obtain the slope a and intercept b.

[0155] In Figure 10 , the left vertical axis represents the amplitude A, the right vertical axis represents the width σ, and the straight line represents the linear function obtained through approximation. In addition, in the example of Figure 10 , Qz-HT represents the first boundary portion between the transmissive portion and the semi-transmissive portion, and HT-Cr represents the second boundary portion between the semi-transmissive portion and the light-shielding portion.

[0156] The slope a and intercept b obtained through approximation are shown in Table 2 below.

[0157]

Table 2

[0158]

[0159] According to the obtained linear function, coefficients A and σ of the Gaussian function can be obtained based on the transmittance T2 of the semi-transmissive portion. That is, a Gaussian function as a model function corresponding to the transmittance T2 of the semi-transmissive portion can be obtained for the first boundary portion between the transmissive portion and the semi-transmissive portion and the second boundary portion between the semi-transmissive portion and the light-shielding portion, respectively.

[0160] For example, when the transmittance T2 of the semi-transmissive portion is 10, 20, 30, 40, 50, 60%, the model function obtained from the above linear function represents Figure 11 such a curve. Similarly, if the transmittance T2 of the semi-transmissive portion required for size measurement is known, a model function suitable for line width calculation of the semi-transmissive portion can be obtained based on this transmittance T2 and the above linear function. In Figure 11 the vertical axis represents the change in light intensity, and the horizontal axis represents the pixel position Figure 7 similarly.

[0161] (6) Obtain a transmitted light image of the mask to be inspected

[0162] Light is irradiated onto the inspection area of the mask to be inspected that includes the transfer pattern by an optical line width measurement device having a halogen lamp as a light source, and a transmitted light image is obtained using a microscope with a CCD as the imaging element ( Figure 12 ). In addition, in the present embodiment, in order to suppress a decrease in inspection accuracy, the imaging conditions (optical system, wavelength of inspection light, etc.) when obtaining the transmitted light image of the mask to be inspected are the same as those when obtaining the transmitted light image of the reference mask.

[0163] In Figure 12 the area including the first boundary between the transmissive portion and the semi-transmissive portion and the second boundary between the semi-transmissive portion and the light-shielding portion ( Figure 12 the area surrounded by the dashed line) is used as the inspection area. In addition, in the present embodiment, a case where there are two boundaries each between the transmissive portion and the semi-transmissive portion and between the semi-transmissive portion and the light-shielding portion in the inspection area of the mask to be inspected is taken as an example for explanation. That is, as Figure 12 shown, the transfer pattern of the mask to be inspected in the present embodiment includes a first semi-transmissive portion adjacent to the first edge of the light-shielding portion and a second semi-transmissive portion adjacent to the second edge of the light-shielding portion. The first semi-transmissive portion and the second semi-transmissive portion are respectively adjacent to the edges of the transmissive portion. That is, the first semi-transmissive portion and the second semi-transmissive portion are respectively interposed between the transmissive portion and the light-shielding portion.

[0164] (7) Generate a light intensity distribution curve of the mask to be inspected

[0165] Similar to the generation of the light intensity distribution curve of the reference mask in (2) above, in the transmitted light image of the mask to be inspected obtained, a straight line parallel to the width direction of the semi-transmissive portion is drawn at an arbitrary position within the inspection area ( Figure 12 solid arrow), and the light intensity values on this straight line are quantized into 256 grayscales. Thus, light intensity distribution data (not shown) of the inspection area is obtained. Thus, a Figure 13 light intensity distribution curve like that is obtained.

[0166] In Figure 13 , the vertical axis represents the light intensity, and the horizontal axis represents the pixel position ( Figure 12 horizontal position in

[0167] (8) Generate the light intensity change curve of the inspection area

[0168] Similar to (3) above, perform a first-order differential process on the light intensity distribution curve (or light intensity distribution data) generated in (7) above, and for its absolute value, generate the light intensity change curves of the first and second boundary portions ( Figure 14 ). In Figure 14 , the vertical axis represents the light intensity change, and the horizontal axis represents the pixel position in the same way as Figure 13 . The same applies to Figure 15 and Figure 16 described later.

[0169] (9) Perform fitting using a model function (generate a composite curve)

[0170] According to the transmittance T2 of the semi-transmissive portion of the mask to be inspected measured in advance, select from the above-obtained model functions the model function of the first boundary between the transmissive portion and the semi-transmissive portion (transmissive portion - semi-transmissive portion model function) and the model function of the second boundary between the semi-transmissive portion and the light-blocking portion (semi-transmissive portion - light-blocking portion model function) obtained in (5) above. Alternatively, a linear function can be pre-held, and according to this linear function and the transmittance T2 of the semi-transmissive portion, the corresponding model function can be calculated.

[0171] Then, as Figure 15 shown, in order to minimize the difference between the composite curve obtained by adding the light intensity changes of the curves (first model curve) represented by the transmissive portion - semi-transmissive portion model function (first model function) and the curves (second model curve) represented by the semi-transmissive portion - light-blocking portion model function (second model function), and the light intensity change curve of the mask to be inspected obtained in (8) above, the two model functions (model curves) are synthesized and fitted by the least squares method. That is, the relative position in the horizontal axis direction of the first model curve and the second model curve is determined such that the difference between the above composite curve and the light intensity change curve of the mask to be inspected is minimized. The model curves (first model curve and second model curve) are Gaussian curves.

[0172] As Figure 12 shown, the inspection region of the inspection target mask of this embodiment includes two semi-transmissive portions (the first semi-transmissive portion and the second semi-transmissive portion). However, since the calculation methods of the line widths of these two semi-transmissive portions are the same, in Figure 15 and the following Figure 16 , only the first semi-transmissive portion is shown ( Figure 12 the left semi-transmissive portion in Figure 13 and Figure 14 the portion enclosed by the dashed line), and the second semi-transmissive portion is omitted.

[0173] (10) Calculate the line width of the semi-transmissive portion

[0174] As Figure 16 shown, the peaks of the two model functions synthesized in the above (9) correspond to the first boundary between the transmissive portion and the semi-transmissive portion, and the second boundary between the semi-transmissive portion and the light-shielding portion. Therefore, find the positions of the peaks of these two model functions. Then, by finding the distance between these two peaks, the line width (size) of the semi-transmissive portion can be obtained.

[0175] Therefore, first, find the pixel positions corresponding to the above two peaks respectively. Based on these pixel positions, calculate the number of pixels between the peaks of the two model functions (Equation (2) below).

[0176] (Number of pixels between peaks)=|(Peak position of the model function of the transmissive portion - semi-transmissive portion)-(Peak position of the model function of the semi-transmissive portion - light-shielding portion)|... Equation (2)

[0177] The width of each pixel (pixel size) can be obtained in advance. For example, if the pixel size of the imaging device that pre-measures the light intensity distribution of the reference mask is obtained and the same imaging conditions are used for the inspection target mask, then this pixel size can be directly used for the image of the inspection target mask. By multiplying this pixel size by the obtained number of pixels between the peaks (Equation (3) below), the line width of the semi-transmissive portion within the inspection region can be obtained. For example, when the number of pixels between the peaks is 8.0 pixels and the pixel size is 0.03 μm / pixel, the distance between the peaks, that is, the line width of the semi-transmissive portion is 0.24 μm.

[0178] (Line width [μm])=(Number of pixels between peaks [pixels])×(Pixel size [μm / pixel])... Equation (3)

[0179] As described above, the line width of the semi-transmissive portion, which is the inspection target pattern, that is, the second transmission control portion, can be obtained.

[0180] <Inspection device for photomask>

[0181] The above-described pattern inspection method can be carried out using the following photomask inspection apparatus. That is, when the inspection region of the photomask of the present invention has a transfer pattern including a light-transmitting portion (first transmission control portion), a semi-light-transmitting portion (second transmission control portion), and a light-shielding portion (third transmission control portion) adjacent to each other and arranged in this order, the apparatus has: an imaging element that acquires an image of the inspection region; an arithmetic unit that, based on the image of the inspection region acquired by the imaging element, obtains light intensity distribution data, and calculates the size (width) of the semi-light-transmitting portion (second transmission control portion) included in the inspection region by fitting a light intensity change curve obtained by differentiating the light intensity distribution curve obtained from the light intensity distribution data to a model function.

[0182] The above-described photomask inspection apparatus may include a model function holding unit that holds the transmittance of the second transmission control portion with respect to the inspection light and the model function in correspondence with each other. Alternatively, the inspection apparatus may also include a linear function holding unit that holds the above-described linear function.

[0183] The model function holding unit and the linear function holding unit do not necessarily need to be provided inside the inspection apparatus, and may be provided separately from the inspection apparatus. For example, an external computer may be used as the model function holding unit and / or the linear function holding unit. The inspection apparatus may include a function input unit that inputs the acquired model function or linear function to the arithmetic unit.

[0184] The arithmetic unit may calculate model functions (first model function and second model function) corresponding to the second transmission control portion based on the input linear function and the transmittance of the second transmission control portion with respect to the inspection light. Then, the arithmetic unit obtains the peak positions of the first model function and the peak positions of the second model function, and may calculate the size of the semi-light-transmitting portion (second light-transmission control portion) based on these peak positions.

[0185] The pattern inspection method and the photomask inspection apparatus of the present invention do not cause damage to the photomask, and can stably and highly accurately measure the line width. In addition, it has the advantage of being able to measure the line width of a fine transfer pattern of a large-sized photomask. That is, according to the present invention, it is possible to reduce the load and cost on the process due to the measurement of the transfer pattern, and to stably and highly accurately measure the line width of the transfer pattern.

[0186] In the case where the pattern width is small in the present invention, for example, when the size (line width) W (μm) satisfies 0.1 ≤ W ≤ 1.5 (especially 0.3 ≤ W ≤ 1.0 μm), that is, even when it is difficult to measure using an optical line width measurement apparatus, it is possible to stably and highly accurately perform the measurement.

[0187] Alternatively, when the difference in light transmittance between two adjacent regions with different light transmittances is relatively small and the boundary cannot be clearly identified even if the light intensity curve is obtained, the line width measurement of the transfer pattern can be performed finely.

[0188] For example, the effect of the present invention is remarkable when the difference in light transmittance between the first light transmission control unit and the second light transmission control unit (the absolute value of T1(%) - T2(%)) satisfies 0 < |T1(%) - T2(%)| ≤ 80 (points), and / or the difference in light transmittance between the second light transmission control unit and the third light transmission control unit (the absolute value of T2(%) - T3(%)) satisfies 0 < |T2(%) - T3(%)| ≤ 30 (points).

[0189] <Method for manufacturing a photomask>

[0190] The present invention includes a method for manufacturing a photomask inspected by the above-described pattern inspection method. That is, the photomask manufacturing method of the present invention may include the above-described pattern inspection method.

[0191] An example of the method for manufacturing a photomask will be described below. The photomask here may have the same structure as the photomask to be inspected in the above inspection method.

[0192] First, a photomask blank is prepared. Here, a semi-transmissive film and a light-shielding film are sequentially formed on a transparent substrate, and a photoresist film is further formed on the light-shielding film. The photomask blank here may also be a photomask intermediate in which a part of the light-shielding film and / or the semi-transmissive film has been patterned. In addition, a photoresist film may not be formed on the light-shielding film of the photomask blank. In this case, a step of applying a photoresist film may be added before the subsequent drawing step.

[0193] Using a drawing machine, a pattern for forming a semi-transmissive portion is drawn on the photoresist film. As the drawing machine, for example, a laser drawing machine can be used.

[0194] Next, the photoresist film that has undergone the above-described drawing step is developed to form a resist pattern.

[0195] Then, using the above resist pattern as a mask, the light-shielding film is etched with a light-shielding film etchant. Further, the semi-transmissive film is etched with a semi-transmissive film etchant. In the etching of the light-shielding film and the semi-transmissive film, either wet etching or dry etching can be used, but since the photomask for a display device is large, wet etching is preferred.

[0196] Next, using the above resist pattern as a mask, the light-shielding film is etched for the second time. That is, the light-shielding film is side-etched with a wet etchant for the light-shielding film. Here, a light-shielding portion with a specified width is formed. Furthermore, since the edge of the light-shielding portion recedes due to side-etching, a part of the semi-transmissive film is exposed. Thus, a semi-transmissive portion with a specified width is formed adjacent to the light-shielding portion.

[0197] Then, the resist pattern is peeled off to fabricate the photomask before inspection.

[0198] Next, the photomask before inspection is inspected by the above inspection method. For example, the line width of the semi-transmissive portion at the desired position of the transfer pattern of the photomask is measured. And, a photomask in which the line width of the semi-transmissive portion meets the specifications can be regarded as a finished product.

[0199] In the case of the above method for manufacturing a photomask, the semi-transmissive film and the light-shielding film are made of materials having etching selectivity with respect to each other. In addition, in the etching step of the light-shielding film for the second time, since side-etching based on isotropic etching is used, wet etching is preferably applied.

[0200] The transfer pattern of the photomask manufactured by the method for manufacturing a photomask of the present invention may have a light-transmissive portion, a semi-transmissive portion, and a light-shielding portion. The transfer pattern may also have a first semi-transmissive portion and a second semi-transmissive portion as the semi-transmissive portions.

[0201] The above first semi-transmissive portion and second semi-transmissive portion are symmetrically and oppositely formed with the light-shielding portion as the center. In addition, the first semi-transmissive portion and the second semi-transmissive portion preferably have a certain width that cannot be resolved by the exposure apparatus and have equal widths with respect to each other. Here, by the so-called equal widths with respect to each other, it is preferred that the difference between the line width of the first semi-transmissive portion and the line width of the second semi-transmissive portion is within 0.1 μm, and more preferably within 0.05 μm. Thus, the auxiliary effect on the amount of transmitted light of the light-transmissive portion becomes symmetric, and the line width accuracy of the pattern formed on the transfer body can be finely controlled.

[0202] The above photomask can be used, for example, to form a line and space pattern on a transfer body in which the line width and / or the space width is less than 3 μm. Here, the line pattern may be a structure composed of a light-shielding portion and a semi-transmissive portion (first semi-transmissive portion, second semi-transmissive portion), and the space pattern may be a structure composed of a light-transmissive portion. The pitch P (μm) of the line and space pattern may be 0 < P ≤ 10, and more specifically, may be 4 < P ≤ 6. Alternatively, the transfer pattern of the photomask may include a hole pattern, and the hole pattern can be used to form a hole with a diameter of less than 3 μm on the transfer body.

[0203] The use of the above-described photomask is not particularly limited. The photomask manufactured by the manufacturing method of the present invention is particularly advantageous for use as a photomask for manufacturing a display device. For example, the photomask manufactured by the manufacturing method of the present invention can be advantageously used for forming each layer used in a display device (e.g., a pixel layer or a light spacer layer of a color filter), and a lead wiring portion provided near an end portion of a specified layer. That is, the method of the present invention can be preferably used in a photomask having a transfer pattern including a fine portion with a CD (line width) of 1.5 μm or less, or a photomask having a transfer pattern in which the fine portion is a semi-transmissive portion.

[0204] The present invention includes a method for manufacturing a display device using a photomask manufactured by the manufacturing method of the present invention described above. For example, the method for manufacturing a display device of the present invention may include: a step of preparing a photomask manufactured by a manufacturing method including the pattern inspection method of the above-described embodiment; and a step of exposing the photomask using an exposure device to transfer the transfer pattern onto a transfer object. The display device manufactured by this manufacturing method further includes various devices constituting the display device.

[0205] As the exposure machine used when transferring the transfer pattern included in the photomask manufactured by the manufacturing method of the photomask of the present invention onto a transfer object, it may be an equal magnification projection exposure device or a proximity exposure device for a display device such as a so-called LCD (Liquid Crystal Display) or FPD. In addition to the above-described displays, the display device may further include a double-folded display and a rollable display.

[0206] As the optical system of the above-described exposure device, in the case of a projection exposure device, an optical system in the range of an NA (numerical aperture) of 0.08 to 0.15 and a coherence factor value of 0.5 to 0.9 can be preferably used.

[0207] <Modification Example>

[0208] The embodiments of the present invention have been specifically described above, but the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist thereof.

[0209] In the case of T1 > T2 > T3 adopted in the above-described embodiment, there are three transmittances in the transfer pattern constituted by the first transmittance control unit, the second transmittance control unit, and the third transmittance control unit. On the other hand, in the case of T1 = T3, the transmittances of the first transmittance control unit and the third transmittance control unit are equal. That is, the second transmittance control unit is interposed between the first transmittance control unit and the third transmittance control unit having equal transmittances. As a result, there are two transmittances in the transfer pattern formed by the first transmittance control unit, the second transmittance control unit, and the third transmittance control unit included in the transfer pattern. Even in the case where there are two transmittances, the technical idea of the present invention can be applied.

[0210] Specifically, the light intensity change curve of the second boundary, which is the boundary portion between the second transmittance control unit and the third transmittance control unit, is the same as the light intensity change curve of the first boundary, which is the boundary portion between the first transmittance control unit and the second transmittance control unit.

[0211] In the above-described embodiment, the imaging conditions (optical system, wavelength of inspection light, etc.) when obtaining the transmitted light image of the inspection object mask are the same as those when obtaining the transmitted light image of the reference mask, but the present invention is not limited thereto. As long as the light intensity distribution curve of the reference mask is associated with the light intensity distribution curve of the inspection object mask, the technical idea of the present invention can be applied. For example, even if the imaging conditions of the inspection object mask and the reference mask are different, a model function corrected for the difference in the imaging conditions can be used.

Claims

1. A pattern inspection method for inspecting a transfer pattern of a photomask having a transfer pattern on a transparent substrate, wherein, The pattern for transfer includes an inspection area, in which a first transmission control part having a transmittance T1 for exposure light, a second transmission control part having a transmittance T2 for exposure light, and a third transmission control part having a transmittance T3 for exposure light are arranged adjacent to each other in this order, where the transmittances T1, T2, and T3 are percentages respectively. When T1 and T3 are different from T2 respectively, and T1 is the same as or different from T3, the pattern inspection method includes the following steps: Irradiating the inspection area with light and obtaining a transmitted light image of the inspection area; Obtaining light intensity distribution data of the inspection area based on the obtained transmitted light image; A differentiation processing step of obtaining a light intensity change curve of a region including a first boundary which is a boundary part between the first transmission control part and the second transmission control part and a second boundary which is a boundary part between the second transmission control part and the third transmission control part by differentiating a light intensity distribution curve obtained based on the light intensity distribution data; A fitting step of fitting the obtained light intensity change curve to a model function; and A step of obtaining the size of the second transmission control part based on the result of the fitting.

2. The pattern inspection method according to claim 1, wherein, T1>T2>T3.

3. The pattern inspection method according to claim 1 or 2, wherein, The first transmission control part constitutes a light-transmitting part formed by exposing the transparent substrate; The second transmission control part constitutes a semi-transmitting part formed by forming a semi-transparent film on the transparent substrate; The third transmission control part constitutes a light-shielding part formed by forming at least a light-shielding film on the transparent substrate; The transmittance of the semi-transmitting part for the exposure light is 10 to 60%.

4. The pattern inspection method according to claim 1 or 2, wherein, The width W of the second transmission control part is 0.1≤W≤1.5, where the unit of W is μm.

5. The pattern inspection method according to claim 1 or 2, wherein, The pattern for transfer includes a line and a space pattern.

6. The pattern inspection method according to claim 1 or 2, wherein, The model function includes a first model function corresponding to the first boundary and a second model function corresponding to the second boundary.

7. The pattern inspection method according to claim 6, wherein, In the fitting step, fitting is performed such that the difference between the composite curve and the light intensity change curve is minimized, where the composite curve is a composite curve obtained by combining a first model curve obtained from the first model function and a second model curve obtained from the second model function.

8. The pattern inspection method according to claim 7, wherein, Let the first model curve and the second model curve be Gaussian curves respectively.

9. The pattern inspection method according to claim 7 or 8, wherein, Based on the peak position of the first model curve and the peak position of the second model curve, the size of the second transmission control part is obtained.

10. A method for manufacturing a photomask, comprising the pattern inspection method according to any one of claims 1 to 9.

11. A method for manufacturing a display device, comprising: Using an exposure device to expose a photomask manufactured by the manufacturing method according to claim 10, and transferring the pattern for transfer onto a transfer object.

12. A photomask inspection device for inspecting a transfer pattern of a photomask having a transfer pattern on a transparent substrate, wherein, The pattern for transfer includes an inspection area, in which a first transmission control part having a transmittance T1 for exposure light, a second transmission control part having a transmittance T2 for exposure light, and a third transmission control part having a transmittance T3 for exposure light are arranged adjacent to each other in this order, where T1, T2, and T3 are percentages respectively. When T1 and T3 are different from T2 respectively, and T1 is the same as or different from T3, The photomask inspection device includes: An imaging element that acquires an image of the inspection area of the transfer pattern; and An arithmetic unit that, based on the acquired image, obtains light intensity distribution data, fits a light intensity change curve of a region including a first boundary and a second boundary, which is obtained by differentiating a light intensity distribution curve obtained from the light intensity distribution data, to a model function, and calculates the size of the second transmission control unit included in the inspection area according to the fitting result, where the first boundary is a boundary portion between the first transmission control unit and the second transmission control unit, and the second boundary is a boundary portion between the second transmission control unit and the third transmission control unit.

13. The photomask inspection device according to claim 12, wherein,T1>T2>T3.

14. The photomask inspection apparatus according to claim 12 or 13, wherein, The model function includes a first model function corresponding to the first boundary and a second model function corresponding to the second boundary. The arithmetic unit performs fitting so that the difference between the composite curve, which is a composite curve obtained by combining a first model curve obtained from the first model function and a second model curve obtained from the second model function, and the light intensity change curve is minimized.

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