JP7229138B2 - Pattern inspection method, photomask inspection apparatus, photomask manufacturing method, and display device manufacturing method - Google Patents

Description

The present invention relates to a pattern inspection method, a photomask inspection apparatus, a photomask manufacturing method, and a display device manufacturing method. In particular, a transfer pattern inspection method, a photomask inspection apparatus, and a photomask possessed by a photomask suitable for manufacturing a display device (e.g., a flat panel display), particularly for manufacturing an electronic device and a method for manufacturing a display device.

Japanese Patent Laid-Open No. 2002-200002 describes a method and a length measuring device for capturing an image pattern with a solid-state imaging device and detecting the contour of the read pattern.

Patent Document 2 describes a pattern dimension measuring apparatus that measures the dimension of a pattern formed on a sample based on a signal obtained by scanning the sample with an electron beam.

In Patent Document 3, a transparent substrate is provided with a light-transmitting portion, a semi-light-transmitting portion formed with a semi-light-transmitting film that partially transmits exposure light, and a light-shielding portion formed with a light-shielding film. A photomask is described with a pattern for transfer having a The semi-transparent film has a transmittance of 2 to 60% and a phase shift effect of 90° or less with respect to a representative wavelength of exposure light used for transferring the transfer pattern, and the semi-transparent portion Adjacent to the edge of the light shielding portion, it is formed with a width that cannot be resolved by the exposure device.

JP-A-3-39603 JP 2012-002765 A JP 2013-235036 A

During the production of photomasks, an inspection is carried out to confirm whether or not the specifications determined according to the use of the photomask are satisfied. Line width measurement of a transfer pattern is one of such inspections.

According to Patent Document 1, in a conventional length measuring device, an analog optical image formed on an imaging surface of an imaging camera is sampled in units of pixels of an imaging device. It is described that when measuring, there is a problem that a measurement accuracy equal to or less than the pixel pitch of the image sensor cannot be obtained. Therefore, in Patent Document 1, an image pattern is picked up by a solid-state imaging device, and the data is subjected to multi-stage image processing to automatically and precisely give the contour of the pattern with an accuracy equal to or less than the pixel pitch of the imaging device. It is said to provide a method suitable for length measurement.

By the way, the quality (amount of information) of the optical image formed on the imaging device varies depending on the resolving power of the optical system used in addition to the imaging device. , hereinafter used in the sense of line width), there is a limit to the performance of the measuring apparatus used for the measurement.

On the other hand, the pattern dimension measuring apparatus described in Patent Document 2 obtains an SEM image using an electron beam instead of light.

Thus, it is known to use a CD-SEM (Critical Dimension-Scanning Electron Microscope) using an electron beam as means for pattern line width measurement. CD-SEM is a measuring device that applies a scanning electron microscope (SEM), and is mainly used to measure line widths of patterns formed on semiconductor wafers and fine patterns of photomasks (reticles) used to manufacture such patterns. used for measurement. This apparatus has the advantage of being able to precisely measure submicron-order fine patterns. However, for the following reasons, the CD-SEM is used as a so-called large photomask for manufacturing display devices (eg, flat panel display, hereinafter referred to as FPD) (generally, the main surface is a square with a side of about 300 to 2000 mm). , various sizes) are difficult to apply. When measuring the pattern line width by CD-SEM, a chamber (specimen chamber) in which a photomask to be measured is placed is evacuated or highly evacuated. For this reason, when a CD-SEM is applied to the measurement of large photomasks for manufacturing display devices, a large chamber must be prepared and the chamber must be evacuated or highly vacuumed. There is an inconvenience that it becomes large. In this case, a drastic change in the configuration of the device is required, and an increase in cost is inevitable.

For this reason, an optical line width measuring apparatus, which includes an optical system and an imaging element and performs line width measurement using light transmitted through a transfer pattern, is applied to measure the line width of a photomask for a display device.

However, since the CD of the pattern of the photomask for display devices has not been as fine as the CD of the photomask for manufacturing semiconductors, no serious problem has arisen.

By the way, in the technical field of display devices, users of portable terminals and monitors are demanding higher performance for image quality, power saving, etc., and accordingly, there is a need for finer patterning of photomasks for display devices for manufacturing these devices. gender is prominent. For this reason, in addition to increasing the difficulty in manufacturing the photomask, it is becoming difficult to measure the line width of the formed transfer pattern. There is also a need for distinctive patterns that are specialized for display device manufacturing.

Patent Document 3 describes a photomask (transmission auxiliary mask) having a line-and-space pattern as a transfer pattern. This is shown in FIG. Here, the line pattern has a configuration in which the first and second semi-transparent portions 21A and 21B (made of a semi-transparent film having a transmittance of 20% and a phase difference of 45°) are provided adjacent to both edges of the light shielding portion 31. is. Here, the width of the light shielding portion 31 is 1.5 μm, and the widths of the first and second semi-transmitting portions 21A and 21B adjacent to both side edges are each 1.0 μm.

A photomask having such a characteristic pattern is desired as a photomask for a display device, and its CD tends to be miniaturized. Depending on the design of the FPD device, a situation is beginning to arise in which photomasks with even finer patterns of less than 1 μm are inspected. It is very difficult to measure the line width of such a fine pattern with the optical line width measuring device.

Therefore, the present inventor has completed the present invention to solve the problem that has arisen in measuring the line width of a transfer pattern of a photomask for a display device even when the pattern has a fine width.

(First aspect)
A first aspect of the present invention is
A pattern inspection method for inspecting a transfer pattern of a photomask having a transfer pattern on a transparent substrate, comprising:
The transfer pattern has a first transmission control portion having a transmittance of T1 (%), a second transmission control portion having a transmittance of T2 (%), and a transmittance of T3 (%) with respect to exposure light. When the third transmission control section includes inspection areas arranged adjacently in this order, T1 and T3 are different from T2, and T1 is the same or different from T3,
a step of irradiating the inspection area with light and acquiring a transmitted light image of the inspection area;
a step of obtaining light intensity distribution data of the inspection area from the acquired transmitted light image;
By differentiating the light intensity distribution curve obtained from the light intensity distribution data, a first boundary, which is a boundary portion between the first transmission control section and the second transmission control section, and the second transmission control a differential processing step of obtaining a light intensity change curve in a region including a second boundary that is a boundary portion between the section and the third transmission control section;
a fitting step of fitting the obtained light intensity change curve to a model function;
obtaining the dimensions of the second transmission control section from the result of the fitting;
It is a pattern inspection method.

(Second aspect)
A second aspect of the present invention is
The pattern inspection method according to the first aspect, wherein T1>T2>T3.

(Third aspect)
A third aspect of the present invention is
The first transmission control section constitutes a light transmission section in which the transparent substrate is exposed,
The second transmission control section constitutes a semi-transparent section in which a semi-transparent film is formed on the transparent substrate,
The third transmission control section constitutes a light shielding section in which at least a light shielding film is formed on the transparent substrate,
The pattern inspection method according to the first or second aspect, wherein the transmissivity of the semi-transparent portion with respect to the exposure light is 10 to 60%.

(Fourth aspect)
A fourth aspect of the present invention is
The pattern inspection method according to any one of the first to third aspects, wherein the width W (μm) of the second transmission control section satisfies 0.1≦W≦1.5.

(Fifth aspect)
A fifth aspect of the present invention is
The pattern inspection method according to any one of the first to fourth aspects, wherein the transfer pattern includes a line-and-space pattern.

(Sixth aspect)
A sixth aspect of the present invention is
The model function according to any one of the first to fifth aspects above, wherein the model function includes a first model function corresponding to the first boundary and a second model function corresponding to the second boundary. It is a pattern inspection method.

(Seventh aspect)
A seventh aspect of the present invention is
In the fitting step, a difference between the light intensity change curve and a synthesized curve obtained by synthesizing a first model curve obtained from the first model function and a second model curve obtained from the second model function is minimized. The pattern inspection method according to the sixth aspect, wherein fitting is performed as described above.

(Eighth aspect)
An eighth aspect of the present invention is
The pattern inspection method according to the seventh aspect, wherein the first model curve and the second model curve are Gaussian curves.

(Ninth aspect)
A ninth aspect of the present invention is
The pattern inspection method according to the seventh or eighth mode, wherein the dimension of the second transmission control section is obtained from the peak position of the first model curve and the peak position of the second model curve.

(Tenth aspect)
A 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.

(Eleventh aspect)
An eleventh aspect of the present invention is
A method for manufacturing a display device, comprising exposing a photomask according to the manufacturing method according to the tenth aspect with an exposure device and transferring the transfer pattern onto a transfer target.

(Twelfth aspect)
A twelfth aspect of the present invention is
A photomask inspection apparatus for inspecting a transfer pattern of a photomask having a transfer pattern on a transparent substrate,
The transfer pattern has a first transmission control portion having a transmittance of T1 (%), a second transmission control portion having a transmittance of T2 (%), and a transmittance of T3 (%) with respect to exposure light. When the third transmission control section includes inspection areas arranged adjacently in this order, T1 and T3 are different from T2, and T1 is the same or different from T3,
The photomask inspection device includes:
an imaging element for acquiring an image of the inspection area of the transfer pattern;
Light intensity distribution data is obtained from the acquired image, and the light intensity change curve obtained by differentiating the light intensity distribution curve obtained from the light intensity distribution data is fitted to the model function to perform the inspection. a calculation means for calculating the dimension of the second transmission control section included in the region;
A photomask inspection apparatus having

(13th aspect)
A thirteenth aspect of the present invention is
The photomask inspection apparatus according to the twelfth aspect, wherein T1>T2>T3.

(14th aspect)
A fourteenth aspect of the present invention comprises:
The model function includes a first model function corresponding to a first boundary, which is a boundary portion between the first transmission control section and the second transmission control section, and the second transmission control section and the third transmission control section. and a second model function corresponding to a second boundary that is a boundary portion of
The computing means is configured to minimize the difference between the light intensity change curve and the synthetic curve obtained by synthesizing the first model curve obtained from the first model function and the second model curve obtained from the second model function. 2, the photomask inspection apparatus according to the twelfth or thirteenth aspect, wherein fitting is performed.

According to the present invention, line width measurement can be performed stably and with high accuracy even for a fine width pattern.

FIG. 1 is a schematic plan view of a photomask (transmission auxiliary mask) having a line-and-space pattern as a transfer pattern, described in Patent Document 3. FIG. FIG. 2 is a diagram showing a transmitted light image of the photomask shown in FIG. 1, acquired by an optical line width measuring device. FIG. 3 is a diagram showing a secondary electron image obtained by an FIB (Focused Ion Beam) correcting device of the inspection area of the same transfer pattern as in FIG. FIG. 4 is a diagram showing an example of an outline of a photomask pattern inspection method according to the present invention. FIG. 5 is a diagram showing a flow for obtaining the line width (dimension) of the second transmission control portion (semi-transparent portion) in the inspection area included in the transfer pattern. FIG. 6 was obtained by using a microscope with a CCD as an image pickup element and irradiating light from an optical line width measuring device having a halogen lamp as a light source to an area including the reference area of the transfer pattern of the reference mask. It is a figure which shows a transmitted light image. FIG. 7 is a diagram showing a light intensity distribution curve representing light intensity distribution data of a reference area obtained from transmitted light images obtained using five kinds of reference masks. FIG. 8 is a diagram showing a light intensity change curve 1 for the boundary between the translucent portion and the semi-translucent portion. FIG. 9 is a diagram showing a light intensity change curve 2 for the boundary between the translucent portion and the light shielding portion. FIG. 10 is a diagram in which the data in Table 1 are plotted with the transmittance T2 of the semi-transparent portion on the horizontal axis and the amplitude A or width σ on the vertical axis. FIG. 11 is a diagram showing a model function obtained from a linear function. FIG. 12 is obtained by irradiating light from an optical line width measuring device having a halogen lamp as a light source to an area including the inspection area of the transfer pattern of the mask to be inspected, and using a microscope having a CCD as an imaging element. FIG. 10 is a diagram showing a transmitted light image; FIG. 13 is a diagram showing a light intensity distribution curve of a mask to be inspected. FIG. 14 is a diagram showing light intensity change curves at respective boundaries with respect to absolute values obtained by subjecting the light intensity distribution curve (or light intensity distribution data) to first-order differential processing. FIG. 15 is a diagram showing how a synthetic curve is obtained. FIG. 16 is a diagram showing how the line width of the semi-transparent portion is calculated from the composite curve.

Embodiments of a photomask, a method of manufacturing a photomask, and a method of manufacturing a display device according to the present invention will be described below.

Photomasks for display devices tend to introduce finer patterns more and more as the definition of display devices increases.

The miniaturization of the wiring pattern of the display device is advantageous not only from the viewpoint of improving image quality such as screen brightness and response speed, but also from the viewpoint of energy saving. For this reason, in recent years, there has been a demand for further miniaturization of wiring patterns in display devices, and along with this, there is a tendency to expect fine line width accuracy in photomasks for display devices.

According to Patent Document 3, in a binary mask having a line-and-space pattern consisting of a light-shielding portion and a light-transmitting portion, when the pitch is gradually reduced to make it finer, the resist film on the transferred body is exposed to light. , that accurate line-and-space patterns are not transferred. It is said that this is because the light intensity reaching the resist film decreases as the line width of the space pattern made up of the light-transmitting portions becomes finer.

Therefore, in Patent Document 3, on a transparent substrate, a light-transmitting portion, a semi-light-transmitting portion having a semi-light-transmitting film that partially transmits exposure light, and a light-shielding portion having a light-shielding film are formed. , wherein the semi-transparent portion is formed adjacent to the edge of the light-shielding portion and has a width that cannot be resolved by an exposure device (transmission auxiliary mask). are doing. It is described that by adopting such a structure, it becomes possible to reliably and precisely transfer a fine pattern onto a transferred object.

As shown in FIG. 1 (corresponding to FIG. 10(a) of Patent Document 3), the semi-transparent portion of the photomask of Patent Document 3 has a constant width and is adjacent to the opposite edge of the light blocking portion. is provided. Here, the width of the semi-transparent portion formed adjacent to the edge of the light shielding portion is preferably 1 μm or less (preferred range is 0.1 to 1 μm).

By the way, in the photomask manufacturing process, several kinds of inspections are performed before shipping to confirm that the specifications required by the mask user are satisfied. One of these inspections is a CD (line width) inspection. In this CD inspection, the line width of an important portion included in the transfer pattern is measured, and the obtained numerical value of the line width is compared with the specification.

For line width measurement, it is useful to detect the contour of the pattern to be measured. For example, in a so-called binary mask, when measuring the line width of a line pattern composed of a light-shielding portion formed in a 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 further, the first and second semi-transmissive portions are interposed between the adjacent translucent portions or between the light-shielding portions. The transmittance difference is small. The inventors of the present invention have found that it is difficult to detect the contour (edge) of the pattern to be measured in a photomask including such a transfer pattern, and line width measurement is not easy.

FIG. 2 shows a transmitted light image of a photomask having a line pattern like the pattern shown in FIG. 1, obtained by an optical line width measuring device (Reference Example 1). Of the line pattern of this photomask, a portion corresponding to (A) surrounded by a dashed line in FIG. 1 shows a transmitted light image by transmitted light when irradiating with . In this line pattern, semi-transparent portions with a width of 0.5 μm are arranged on both sides of a light-shielding portion with a width of 3.0 μm, and the semi-transparent portions have a transmittance of exposure light of 30%.

As is clear from FIG. 2, in this transmitted light image, it is not easy to clearly identify the semi-transparent portions of a predetermined width adjacent to the edges on both sides of the light shielding portion. Therefore, it is difficult to measure the line width of the translucent portion from this image.

FIG. 3 is obtained as a secondary electron image of the inspection area of the same transfer pattern by an FIB (Focused Ion Beam) correction device (reference example 2). The FIB correction device focuses an ion beam obtained from an ion source such as gallium, scans the sample, and detects secondary electrons generated. As is clear from FIG. 3, according to this image, a semi-transparent portion having a predetermined width formed adjacent to the edge of the light shielding film can be clearly identified. Therefore, it is considered possible to measure the line width of the semi-transparent portion. However, when line width measurement is performed with an FIB correction device, there is a risk of damaging the transfer pattern.

On the other hand, in order to increase the size of display devices and reduce production costs, photomasks for display devices are becoming relatively large in size, and there are various sizes. Therefore, it is difficult to apply the above CD-SEM.

Under these circumstances, the line width (CD) of a fine pattern can be measured with high precision using an excellent measurement device without damaging the photomask, thereby increasing the accuracy of process control. Improvements in yield and production efficiency are desired. Therefore, the present inventor completed the invention to meet such needs.

<Pattern inspection method>
FIG. 4 is an example showing an outline of a photomask pattern inspection method according to the present invention.

In the case of a photomask having a transfer pattern, such as the portion (A) surrounded by a dashed line in FIG. Since it is considered that the light intensity changes greatly at the boundary, the light intensity distribution obtained from the transmitted light image of the portion (A) in FIG. 1 is theoretically the distribution shown by the dotted line in FIG. is considered to form Note that the horizontal axis of FIG. 4A indicates the position (position in the horizontal direction in FIG. 1 and corresponds to the pixel position on the imaging surface), and the vertical axis indicates the light intensity.

In the light intensity distribution shown by the dotted line in FIG. 4(a), it is clear where the light intensity changes abruptly. Since the location where the light intensity changes abruptly is the boundary between the translucent portion and the semi-translucent portion or the boundary between the semi-translucent portion and the shading portion, as shown in FIG. If a uniform light intensity distribution is obtained, the line width of the semi-transparent portion can be easily obtained.

However, when the line width of the semi-transparent portion is small, the actual light intensity distribution forms a gentle curve as indicated by the solid line in FIG. 4(a). In the curved line indicated by the solid line in FIG. 4A, 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-shielding portion are unclear, and the line width of the semi-light-transmitting portion is Not easy to ask for.

However, according to the study of the present inventors, even if the light intensity distribution curve is gentle, the amount of change in light intensity at each boundary, that is, the change in the slope of the light intensity distribution curve, is greater than at other locations. should be. Therefore, the inventor of the present invention focused on the fact that a curve having peaks at positions corresponding to each boundary can be obtained by differentiating the light intensity distribution curve.

FIG. 4(b) is a conceptual diagram of a curve (light intensity change curve) obtained by plotting the absolute values of the curve shown by the solid line in FIG. The amount of change and the horizontal axis indicate the position. In FIG. 4(b), sharp peaks can be seen at positions corresponding to each boundary.

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 distance between the peaks corresponding to the boundary between the semi-light-transmitting portion and the light-shielding portion, the line width of the semi-light-transmitting portion can be calculated. can ask.

Next, the method for inspecting the pattern of the photomask will be described more specifically.

An object to be inspected is a transfer pattern of a photomask having a transfer pattern on a transparent substrate. This transfer pattern has a first transmission control portion having a transmittance of T1 (%), a second transmission control portion having a transmittance of T2 (%), and a second transmission control portion having a transmittance of T3 (%) with respect to the exposure light. 3 includes inspection areas arranged in this order by the transmission control unit. That is, the second transmission control section is interposed between the first transmission control section and the third transmission control section. One edge of the second transmission control section is adjacent to the first transmission control section, and the other edge of the second transmission control section is adjacent to the third transmission control section. T1 and T3 are each different from T2, and T1 is the same or different from T3.

The exposure light is used for exposing the photomask having the transfer pattern, and 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. Light in a broad wavelength range including i-line, h-line and g-line can also be used as the exposure light. When light of multiple wavelengths is included in the exposure light, one of the wavelengths included in the region of i-line to g-line can be used as the representative wavelength, and the transmittance for this representative wavelength (eg, g-line) is T1 , T2, T3.

In the present embodiment, a case where T1>T2>T3 holds, the first transmission control section is a light transmission section, the second transmission control section is a semi-transmission section, and the third transmission control section is a light blocking section is taken as an example. ,explain. Therefore, in the present embodiment, when the light transmittance T1 of the light transmitting portion is 100%, the light transmittance of the semi-transparent portion, which is the second transmission control portion, is T2, and the third transmission control portion Let T3 be the light transmittance of a certain light shielding portion. However, the light transmittance T3 of the light shielding portion in this embodiment is substantially zero (for example, optical density OD≧3). Then, in this embodiment, the dimension (line width) of the semi-transparent portion, which is the second transmission control portion, is obtained.

The translucent part can be formed by exposing the transparent substrate. The light shielding part can be formed by forming at least one light shielding film on a transparent substrate. In the light-shielding portion, a film different from the light-shielding film (for example, a semitransparent film to be described later) may be formed on the light-shielding film or between the transparent substrate and the light-shielding film.

Materials for the light shielding film are not particularly limited, but the following materials can be preferably used. For example, materials for the light-shielding film include Cr or Cr compounds (Cr oxides, nitrides, carbides, oxynitrides, oxynitride carbides, etc.), as well as Ta, Mo, W and their compounds (eg, TaSi, MoSi, WSi or their nitrides, metal silicide compounds such as oxynitrides), etc. can be preferably used. Moreover, these materials may be used individually by 1 type, and may be used in combination of 2 or more type.

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

The antireflection layer can be formed by changing the composition of the light shielding film including the antireflection layer in the film thickness direction. This compositional change may be continuous or stepwise in the thickness direction of the light-shielding film, or there may be a clear boundary between the antireflection layer of the light-shielding film and layers other than the antireflection layer.

The semi-transparent portion can be formed by forming a semi-transparent film on a transparent substrate. In this embodiment, the semi-translucent portion has a function of assisting the amount of light transmitted through the translucent portion. If the transmittance T2 (%) of the semi-transparent film is excessively small, the function of assisting the amount of transmitted light in the light-transmitting portion cannot be sufficiently exhibited. , the difficulty of mask manufacturing increases. Considering this point, the transmittance T2 (%) of the semi-transparent portion can be, for example, 2≦T2≦60. The transmittance T2 (%) of the semi-transparent portion preferably satisfies 10≦T2≦60, more preferably 10≦T2≦35, and still more preferably 15≦T2≦30.

The line width (dimension) W (μm) of the semi-transparent portion preferably satisfies 0.1≦W≦1.5, more preferably 0.3≦W≦1.0. If the line width of the semi-transparent portion is too large, the lateral shape of the resist pattern may be slanted on the transferred body when pattern transfer is performed using this photomask. If the line width is too small, the function of assisting the amount of transmitted light in the translucent portion will be insufficient. If the line width of the semi-transparent portion is within the above range, the inclination of the side surface shape of the resist pattern can be suppressed, the resist pattern with a favorable shape can be formed, and the amount of transmitted light in the transparent portion can be sufficiently assisted. can do.

Further, the semi-transparent portion has a phase shift amount φ (degrees) of φ≦90 with respect to the representative wavelength of the exposure light. The phase shift amount φ of the semi-transparent portion preferably satisfies 0<φ≦90, more preferably 5≦φ≦60, and still more preferably 5≦φ≦45. When the phase shift amount φ of the semi-translucent portion is within the above range, cancellation of light intensity at the boundary between the semi-translucent portion and the translucent portion can be suppressed, and the amount of transmitted light in the translucent portion can be assisted. . Therefore, even if the pattern dimension is made finer, when the photomask is exposed, the light intensity peak position of the light-transmitting portion is prevented from being lowered, and a resist pattern having a good shape can be formed.

Materials for the semitransparent film include, for example, Cr compounds (Cr oxides, nitrides, carbides, oxynitrides, oxynitride carbides, etc.), Si compounds (SiO ₂ , SOG), metal silicide compounds (TaSi, MoSi , WSi or their nitrides, oxynitrides, etc.), and Ti compounds such as TiON can be used. These may be used individually by 1 type, or may be used in combination of 2 or more type.

The photomask pattern inspection method according to the present embodiment includes:
a step of irradiating the transfer pattern with light and obtaining a transmitted light image of the inspection area;
a step of obtaining light intensity distribution data of the inspection area from the acquired transmitted light image;
By differentiating the light intensity distribution curve obtained from the light intensity distribution data, a first boundary, which is a boundary portion between the first transmission control section and the second transmission control section, and the second transmission control a differentiation step of obtaining a light intensity change curve in a region including a second boundary, which is a boundary portion between the section and the third transmission control section;
a fitting step of fitting the obtained light intensity change curve to a model function;
a step of determining the dimensions of the second transmission control section from the result of the fitting;
have

FIG. 5 shows a flow for determining the line width (dimension) of the second transmission control portion (semi-transparent portion) in the inspection area included in the transfer pattern. Each step will be specifically described with reference to FIGS.

First, a model function to be used when determining the line width of the semi-transparent portion is created.

Prepare multiple reference masks to create the model function. This reference mask includes a photomask having a transfer pattern including a portion where a transparent portion (first transmission control portion) and a semi-transparent portion (second transmission control portion) are adjacent to each other; 2 transmission control part) and a light shielding part (third transmission control part) can include a photomask having a transfer pattern including a portion where the light shielding part (third transmission control part) is adjacent to each other. In this embodiment, as a reference mask, a portion where a transparent portion (first transmission control portion) and a semi-transparent portion (second transmission control portion) are adjacent to each other, and a semi-transparent portion (second transmission control portion) A photomask having a transfer pattern including both portions where the light shielding portion (third transmission control portion) and the light shielding portion (third transmission control portion) are adjacent to each other is used. The light-transmitting portion (first transmission control portion) and the light-shielding portion (third transmission control portion) do not necessarily have to be adjacent to the same semi-transmission portion (second transmission control portion), and different semi-transmission portions ( second transmission control unit). In the present embodiment, in this transfer pattern, a region in which a translucent portion (first transmission control portion), a translucent portion (second transmission control portion), and a light shielding portion (third transmission control portion) are arranged in this order. is the reference region. It is preferable that the line width of the semi-transparent portion in this reference area is sufficiently large. The term "sufficiently large" means that it does not interfere with the calculation of the model function, which will be described later. A portion where the translucent portion (first transmission control portion) and the semi-translucent portion (second transmission control portion) are adjacent to each other, and a portion where the translucent portion (second transmission control portion) and the light-shielding portion (third transmission control portion) are adjacent to each other. control unit) may not necessarily be included in one reference area. In this case, a region including a portion where a translucent portion (first transmission control portion) and a semi-translucent portion (second transmission control portion) are adjacent to each other is defined as a first reference region and a semi-transmissive portion (second transmission control portion). and a light shielding portion (third transmission control portion) are adjacent to each other as a second reference region, and a transmitted light image, which will be described later, is acquired for each of these two reference regions, and a light intensity distribution curve is created. do it.

(1) Acquisition of Transmitted Light Images of Reference Masks Images of transfer patterns are acquired for a plurality of reference masks. Note that although a transmitted light image is used as an example of an image in this embodiment, the image is not limited to this. An image different from the transmitted light image (for example, the reflected light image) may be used as long as the effects and functions of the present invention are not hindered.

In this embodiment, an area including the reference area of the transfer pattern of the reference mask is irradiated with light by an optical line width measuring device having a halogen lamp as a light source, and a microscope having a CCD as an imaging device is used to measure the transmitted light. A light image is obtained (FIG. 6). The wavelength of the light (inspection light) at this time is preferably 400 to 550 nm, for example, 525 nm.

For the purpose of obtaining the model function, a plurality of reference masks having different transmittances in the translucent portions are prepared, and transmitted light images (not shown) of the transfer patterns of these reference masks are obtained. do. In this embodiment, the transmittance of the semi-transparent portions of the plurality of reference masks for g-line light, that is, T2 is 28, 38, 50, 67, respectively, when the transmittance T1 of the light-transmitting portion is 100%. and 79%. The transmittance T3 of the light shielding portion is substantially zero.

In FIG. 6, the area including the boundary between the translucent part and the semi-translucent part and the boundary between the semi-translucent part and the light-shielding part (the area surrounded by the dotted lines in FIG. 6) is the reference area.

(2) Creation of Light Intensity Distribution Curve of Reference Mask Light intensity distribution data of the reference area is obtained from the transmitted light images obtained using the above five kinds of reference masks (not shown). Furthermore, a light intensity distribution curve (FIG. 7) representing the light intensity distribution data by a curve is obtained.

For example, in the reference area of the transmitted light image obtained in (1) above, a straight line perpendicular to the boundary between the light-transmitting portion and the semi-transparent portion, or a straight line perpendicular to the boundary between the semi-transparent portion and the light-shielding portion A straight line (for example, the arrow portion in FIG. 6) is drawn, and the light intensity on this straight line is digitized into 256 gradations using known image processing software. Thereby, a light intensity distribution curve as shown in FIG. 7 can be created. The straight line for obtaining the light intensity can be set at any position within the reference area so as to be parallel to the direction of the dimension to be measured. In FIG. 7, the vertical axis indicates the light intensity quantified in 256 gradations, and the horizontal axis indicates the pixel position in the transmitted light image.

(3) Creating light intensity change curves for the translucent part-semi-translucent part boundary and the semi-translucent part-shading part boundary For the light intensity distribution curve (or light intensity distribution data) obtained in (2), First-order differential processing is performed to obtain a light intensity change curve (light intensity change data) (differential processing step). FIG. 8 shows a light intensity change curve 1 for the boundary between the light-transmitting portion and the semi-light-transmitting portion, and FIG. 9 shows a light intensity change curve 2 for the boundary between the semi-light-transmitting portion and the light-shielding portion. 8 and 9, the vertical axis indicates the light intensity change, and the horizontal axis indicates the pixel position as in FIG. I have to).

(4) Fitting with Gaussian function (least squares method)
The light intensity change curve obtained in (3) is approximated by a known function. Here, the following Gaussian function (equation (1)) is fitted using the method of least squares to obtain the coefficients A and σ of the Gaussian function corresponding to each light intensity change curve.

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

The fitting results were as follows.

(5) Creation of Model Function FIG. 10 shows the data in Table 1 plotted with the transmittance T2 of the semi-transparent portion on the horizontal axis and the amplitude A or width σ on the vertical axis. The data obtained for the boundary between the light-transmitting portion and the semi-light-transmitting portion and the boundary between the light-shielding portion and the semi-light-transmitting portion are each approximated to a linear function, and the slope a and the intercept b of this linear function are obtained. Ask for That is, the amplitude A is approximated as A=a·T2+b, and the width σ is approximated as σ=a·T2+b. Thereby, the slope a and the intercept b are obtained for each amplitude A and width σ.

In FIG. 10, the left vertical axis indicates the amplitude A, the right vertical axis indicates the width σ, and the straight line indicates the linear function obtained by approximation. In the legend of FIG. 10, Qz-HT represents the boundary portion between the light-transmitting portion and the semi-light-transmitting portion, and HT-Cr represents the boundary portion between the semi-light-transmitting portion and the light-shielding portion.

The slope a and intercept b obtained by approximation are shown below.

From the obtained linear function, the coefficients A and σ of the Gaussian function can be obtained according to the transmittance T2 of the semi-transparent portion. That is, a Gaussian function as a model function corresponding to the transmittance T2 of the semi-transmissive portion at the boundary portion between the light-transmitting portion and the semi-transmitting portion and the boundary portion between the semi-transmitting portion and the light-shielding portion is Obtainable.

For example, when the transmissivity T2 of the translucent portion is 10, 20, 30, 40, 50, and 60%, the model function obtained from the above linear function shows a curve as shown in FIG. Similarly, if the transmittance T2 of the semi-transparent portion that requires dimensional measurement is known, a model function suitable for calculating the line width of the semi-transparent portion can be obtained from this transmittance T2 and the above linear function. . In FIG. 11, the vertical axis indicates the light intensity change, and the horizontal axis indicates the pixel position as in FIG.

(6) Acquisition of transmitted light image of mask to be inspected A region including the inspection region of the transfer pattern of the mask to be inspected is irradiated with light from an optical line width measuring device having a halogen lamp as a light source, and an image pickup device is used as a CCD. A transmitted light image is obtained using a microscope (FIG. 12). In this embodiment, in order to suppress deterioration in inspection accuracy, the imaging conditions (optical system, wavelength of inspection light, etc.) for obtaining the transmitted light image of the mask to be inspected are set to The imaging conditions were the same as those when

In FIG. 12, the area including the boundary between the translucent part and the semi-translucent part and the boundary between the semi-translucent part and the light-shielding part (the area surrounded by the dotted lines in FIG. 12) is the inspection area. Note that, in the present embodiment, the inspection area of the mask to be inspected includes the boundary (first boundary) between the light-transmitting portion and the semi-light-transmitting portion, and the boundary (second boundary) between the semi-light-transmitting portion and the light-shielding portion. ) will be described as an example. That is, the transfer pattern of the mask to be inspected according to the present embodiment includes a first semi-transparent portion adjacent to the first edge of the light-shielding portion and a second semi-transparent portion adjacent to the second edge of the light-shielding portion. and including. The first semi-translucent portion and the second semi-translucent portion are also adjacent to the edge of the translucent portion. That is, the first semi-translucent portion and the second semi-translucent portion are interposed between the translucent portion and the semi-translucent portion, respectively.

(7) Creation of the light intensity distribution curve of the mask to be inspected As in the creation of the light intensity distribution curve of the reference mask in (2) above, the acquired transmitted light image of the mask to be inspected is halfway at any position within the inspection area. A straight line (solid arrow in FIG. 12) parallel to the width direction of the transparent portion is drawn, and the light intensity on the straight line is digitized into 256 gradations. As a result, light intensity distribution data (not shown) of the inspection area is obtained. As a result, a light intensity distribution curve as shown in FIG. 13 is obtained.

In FIG. 13, the vertical axis indicates the light intensity, and the horizontal axis indicates the pixel position (horizontal position in FIG. 12).

(8) Creation of light intensity change curve for inspection area In the same manner as in (3) above, the light intensity distribution curve (or light intensity distribution data) created in (7) above is subjected to first-order differential processing. A light intensity change curve (FIG. 14) is created at each boundary for the absolute value. In FIG. 14, the vertical axis indicates the light intensity change, and the horizontal axis indicates the pixel position as in FIG. The same applies to FIGS. 15 and 16, which will be described later.

(9) Fitting with model function (composite curve creation)
According to the transmittance T2 of the semi-transparent portion of the mask to be inspected measured in advance, the model function at the boundary between the translucent portion and the semi-transparent portion obtained in (5) above (the ratio of the translucent portion to the semi-translucent portion model function) and a model function at the boundary between the semi-transparent portion and the light-shielding portion (model function of semi-transparent portion-light-shielding portion) are selected from the model functions obtained above. Alternatively, a linear function may be stored in advance, and a corresponding model function may be calculated from this linear function and the transmittance T2 of the semi-transparent portion.

Then, as shown in FIG. 15, a curve (first model curve) represented by a model function (first model function) of the translucent portion-semi-translucent portion and a model function (second model function) of the translucent portion-shading portion so that the difference between the synthesized curve obtained by adding the light intensity changes of the curves (second model curve) represented by the function) and the light intensity change curve of the mask to be inspected obtained in (8) above is minimized. Two model functions (model curves) are combined and fitted by the method of least squares. That is, the relative positions of the first model curve and the second model curve in the horizontal axis direction are determined so that the difference between the composite curve and the light intensity change curve of the mask to be inspected is minimized. Note that the model curves (the first model curve and the second model curve) are Gaussian curves.

As shown in FIG. 12, the inspection area of the mask to be inspected in this embodiment includes two semi-transparent portions (first semi-transparent portion and second semi-transparent portion). 15 and later-described FIG. 16, the first semi-transparent portion (the semi-transparent portion on the left side in FIG. 12, i.e., the dotted line in FIGS. 13 and 14) Only the portion shown is shown, and the second semi-transparent portion is omitted.

(10) Calculation of Line Width of Semi-Transparent Portion As shown in FIG. It corresponds to the boundary between the light part and the light shielding part. Therefore, the positions of the peaks of these two model functions are obtained. By obtaining the distance between these two peaks, the line width (dimension) of the semi-transparent portion can be obtained.

Therefore, first, pixel positions corresponding to the above two peaks are obtained. From this pixel position, the number of pixels between the peaks of the two model functions is calculated (equation (2) below).
(number of pixels between peaks)=|(peak position of model function of translucent portion-semi-translucent portion)-(peak position of model function of semi-translucent portion-shading portion)| Equation (2)

The width per pixel (pixel size) can be obtained in advance. For example, if the pixel size of the imaging device that captured the light intensity distribution of the reference mask is determined in advance and the same imaging conditions are adopted for the inspection target mask, the pixel size can be used as it is for the inspection target mask image. . By multiplying this pixel size by the obtained number of pixels between peaks (equation (3) below), the line width of the semi-transparent portion within the inspection area can be obtained. For example, when the number of pixels between peaks is 8.0 pixels and the pixel size is 0.03 μm/pixel, the distance between peaks, that is, the line width of the semi-transparent portion is 0.24 μm.
(line width [μm])=(peak-to-peak distance [pixel])·(pixel size [μm/pixel]) Equation (3)

As described above, the line width of the semi-transparent portion as the second transmission control portion, which is the pattern to be inspected, can be obtained.

<Photomask inspection equipment>
The pattern inspection method described above can be performed using the following photomask inspection apparatus. That is, in the photomask inspection apparatus of the present invention, the transfer pattern includes a transparent portion (first transmission control portion), a semi-transparent portion (second transmission control portion), and a light shielding portion (third transmission control portion). includes inspection areas arranged adjacently in this order, light intensity distribution data is obtained from the imaging element for acquiring the image of the inspection area, and the image of the inspection area acquired by the imaging element, and is obtained from the light intensity distribution data The dimension of the semi-transparent portion (second transmission control portion) included in the inspection area is calculated by fitting the light intensity change curve obtained by differentiating the light intensity distribution curve obtained by the differential processing to the model function. , and computing means.

The above-described photomask inspection apparatus can include model function holding means for holding the transmittance of the second transmission control section with respect to the inspection light and the model function in association with each other. Alternatively, the inspection device may include linear function holding means for holding the above linear function.

The model function holding means and the linear function holding means do not necessarily have to be provided within 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 means and/or the linear function holding means. The inspection device can include function input means for inputting the acquired model function or linear function to the computing means.

The calculating means calculates a model function (a first model function and a second model function) corresponding to the second transmission control section based on the input linear function and the transmittance of the second transmission control section for the inspection light. You may Then, the calculating means obtains the peak position of the first model curve and the peak position of the second model function, and can calculate the dimension of the semi-transparent portion (second light transmission control portion) from these peak positions. .

The pattern inspection method and photomask inspection apparatus according to the present invention can stably and accurately measure the line width without damaging the photomask. In addition, there is an advantage that the line width of a fine transfer pattern of a large-sized photomask can be measured. That is, according to the present invention, it is possible to stably and highly accurately measure the line width of the transfer pattern while reducing the load on the process and the cost caused by the measurement of the transfer pattern.
The present invention applies to the case where the pattern width is small, for example, the dimension (line width) W (μm) is 0.1≦W≦1.5 (especially 0.3≦W≦1.0 μm). Therefore, even when measurement is difficult with an optical line width measuring device, stable and highly accurate measurement can be performed.
Alternatively, the difference in light transmittance between two adjacent regions with different light transmittances is relatively small, and even if the light intensity curve is obtained, the boundary cannot be clearly recognized. line width measurement can be performed precisely.
For example, the difference in light transmittance between the first transmission control section and the second transmission control section (absolute value of T1(%)-T2(%)) is 0<|T1(%)-T2(%)|≤ 80 (points), and/or the difference in light transmittance between the second transmission control section and the third transmission control section (absolute value of T2(%)-T3(%)) is 0<|T2 (%)-T3(%)|≤30 (points), the effect of the present invention is remarkable.

<Photomask manufacturing method>
The present invention includes a method of manufacturing a photomask inspected by the pattern inspection method described above. That is, the photomask manufacturing method of the present invention can include the pattern inspection method described above.

An example of a method for manufacturing a photomask will be described below. The photomask here can have the same configuration as the photomask to be inspected in the above-described inspection method.

First, a photomask blank is prepared. Here, a semi-transparent film and a light shielding film are formed in this order on a transparent substrate, and a photoresist film is further formed on the light shielding film. The photomask blank here may be a photomask intermediate in which part of the light shielding film and/or the semitransparent film has already been patterned. Note that the 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 drawing step, which will be described later.

Using a drawing machine, a pattern for forming a semi-transparent portion is drawn on the photoresist film. For example, a laser writer can be used.

Next, the photoresist film that has undergone the drawing process is developed to form a resist pattern.

Then, using the resist pattern as a mask, the light-shielding film is etched with an etchant for light-shielding film. Further, the semi-transparent film is etched with an etchant for semi-transparent film. Either wet etching or dry etching may be used for etching the light-shielding film and the semi-transparent film, but wet etching is preferable because the photomask for display devices is large.

Next, using the 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 light-shielding film. Here, a light shielding portion having a predetermined width is formed. Furthermore, since the side etching causes the edge of the light shielding portion to recede, a portion of the semitransparent film is exposed. Thereby, a semi-transparent portion having a predetermined width is formed adjacent to the light shielding portion.

After that, the resist pattern is peeled off, and a photomask before inspection is created.

Next, the photomask before inspection is inspected by the inspection method described above. For example, the line width of the translucent portion at the desired position of the transfer pattern of this photomask is measured. Then, a photomask in which the line width of the semi-transparent portion satisfies the specifications can be obtained as a finished product.

In the case of the photomask manufacturing method described above, materials having etching selectivity to each other are used for the semi-transparent film and the light shielding film. In addition, in the second etching process of the light shielding film, it is preferable to apply wet etching in order to use side etching by isotropic etching.

A transfer pattern of a photomask manufactured by the method of manufacturing a photomask of the present invention can have a light-transmitting portion, a semi-light-transmitting portion, and a light-shielding portion. The transfer pattern may have a first translucent portion and a second semi-translucent portion as semi-translucent portions.

The above-described first semi-translucent portion and second semi-translucent portion are formed to face each other symmetrically about the light shielding portion. Further, it is preferable that the first semi-transmissive portion and the second semi-transmissive portion have a constant width that is not resolved by the exposure device and that the widths are equal to each other. Here, the mutually equal width means that the difference between the line width of the first semi-transmissive portion and the line width of the second semi-transmissive portion is preferably within 0.1 μm, more preferably within 0.05 μm. is. By doing so, the assisting effect of the amount of transmitted light applied to the light-transmitting portion becomes symmetrical, and the line width accuracy of the pattern formed on the transferred material can be precisely controlled.

A photomask as described above can be used, for example, to form a line-and-space pattern with a line width and/or a space width of less than 3 μm on an object to be transferred. Here, the line pattern can be a configuration including a light shielding portion and a semi-transparent portion (first semi-transparent portion, second semi-transparent portion), and the space pattern can be composed of a transparent portion. Can be configuration. The line-and-space pattern pitch P (μm) can be 0<P≦10, more specifically, 4<P≦6. Alternatively, the transfer pattern of the photomask can include a hole pattern, which can be used to form holes having a diameter of less than 3 μm on the substrate.

There are no particular restrictions on the use of the photomask as described above. A photomask produced by the manufacturing method of the present invention can be used particularly advantageously as a photomask for manufacturing display devices. For example, the photomask according to the manufacturing method of the present invention can be used for each layer used in a display device (for example, a pixel layer and a photospacer layer for a color filter), and a lead wiring section provided near the end of a predetermined layer. can be advantageously used for forming. That is, the method of the present invention is applied to a photomask having a transfer pattern including a fine portion with a CD of 1.5 μm or less, or a photomask having a transfer pattern in which the fine portion is a semi-transparent portion. can be preferably used.

The present invention includes a method of manufacturing a display device using a photomask manufactured by the manufacturing method of the present invention described above. For example, the manufacturing method of the display device of the present invention includes the steps of preparing a photomask manufactured by the manufacturing method including the pattern inspection method of the above-described embodiment, exposing the photomask using an exposure apparatus, and performing the transfer. and a step of transferring the pattern for transfer onto a transfer target. The display device manufactured by this manufacturing method includes various devices that constitute the display device.

The exposure machine used for transferring the transfer pattern of the photomask manufactured by the method of manufacturing a photomask of the present invention onto a transfer target includes a display device such as a so-called LCD (Liquid Crystal Display) or FPD. It can be a 1:1 projection exposure system, or a proximity exposure system, which is considered an exposure system. In addition to the above, the display device may include a foldable display and a rollable display.

As the optical system of the exposure apparatus, in the case of a projection exposure apparatus, NA (numerical aperture) is in the range of 0.08 to 0.15, and the value of coherency factor (σ) is in the range of 0.5 to 0.9. can be preferably used.

<Modification>
Although the embodiments of the present invention have been specifically described above, 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 scope of the invention.

In the case of T1>T2>T3 adopted in the above embodiment, there are three types of transmittance in the transfer pattern formed by the first transmission control section, the second transmission control section, and the third transmission control section. On the other hand, when T1=T3, the transmittances of the first transmission control section and the third transmission control section are equal. That is, the second transmission control section is interposed between the first transmission control section and the third transmission control section which are equal to each other. As a result, the transfer pattern composed of the first transmission control section, the second transmission control section, and the third transmission control section included in the transfer pattern has two types of transmittance. Even if there are two types of transmittance, the technical idea of the present invention can be applied.

Specifically, the light intensity change curve at the second boundary between the second transmission control section and the third transmission control section is the boundary between the first transmission control section and the second transmission control section. It is similar to the light intensity change curve at a certain first boundary.

In the above-described embodiment, the imaging conditions (optical system, wavelength of inspection light, etc.) for obtaining the transmitted light image of the mask to be inspected are the same as the imaging conditions for obtaining the transmitted light image of the reference mask. The invention is not so limited. The technical idea of the present invention can be applied if the light intensity distribution curve of the reference mask and the light intensity distribution curve of the mask to be inspected are linked. For example, even if the imaging conditions differ between the mask to be inspected and the reference mask, the model function after correcting the difference in the imaging conditions may be used.

Claims (14)

A pattern inspection method for inspecting a transfer pattern of a photomask having a transfer pattern on a transparent substrate, comprising:
The transfer pattern has a first transmission control portion having a transmittance of T1 (%), a second transmission control portion having a transmittance of T2 (%), and a transmittance of T3 (%) with respect to exposure light. When the third transmission control section includes inspection areas arranged adjacently in this order, T1 and T3 are different from T2, and T1 is the same or different from T3,
a step of irradiating the inspection area with light and acquiring a transmitted light image of the inspection area;
a step of obtaining light intensity distribution data of the inspection area from the acquired transmitted light image;
By differentiating the light intensity distribution curve obtained from the light intensity distribution data, a first boundary, which is a boundary portion between the first transmission control section and the second transmission control section, and the second transmission control a differential processing step of obtaining a light intensity change curve in a region including a second boundary that is a boundary portion between the section and the third transmission control section;
a fitting step of fitting the obtained light intensity change curve to a model function;
obtaining the dimensions of the second transmission control section from the result of the fitting;
Pattern inspection method. 2. The pattern inspection method according to claim 1, wherein T1>T2>T3. The first transmission control section constitutes a light transmission section in which the transparent substrate is exposed,
The second transmission control section constitutes a semi-transparent section in which a semi-transparent film is formed on the transparent substrate,
The third transmission control section constitutes a light shielding section in which at least a light shielding film is formed on the transparent substrate,
The transmittance of the semi-transparent portion is 10 to 60% with respect to the exposure light.
3. The pattern inspection method according to claim 1. 4. The pattern inspection method according to claim 1, wherein the width W (μm) of said second transmission control section satisfies 0.1≦W≦1.5. 5. The pattern inspection method according to claim 1, wherein said transfer pattern includes a line-and-space pattern. The pattern according to any one of claims 1 to 5, wherein said model function comprises a first model function corresponding to said first boundary and a second model function corresponding to said second boundary. Inspection method. In the fitting step, a difference between the light intensity change curve and a synthesized curve obtained by synthesizing a first model curve obtained from the first model function and a second model curve obtained from the second model function is minimized. 7. The pattern inspection method according to claim 6, wherein fitting is performed as follows. 8. The pattern inspection method according to claim 7, wherein each of said first model curve and said second model curve is a Gaussian curve. 9. The pattern inspection method according to claim 7, wherein the dimension of said second transmission control section is obtained from the peak position of said first model curve and the peak position of said second model curve. A method for manufacturing a photomask, comprising the pattern inspection method according to any one of claims 1 to 9. 11. A method of manufacturing a display device, comprising exposing the photomask according to the manufacturing method according to claim 10 with an exposure device and transferring the transfer pattern onto a transfer target. A photomask inspection apparatus for inspecting a transfer pattern of a photomask having a transfer pattern on a transparent substrate,
The transfer pattern has a first transmission control portion having a transmittance of T1 (%), a second transmission control portion having a transmittance of T2 (%), and a transmittance of T3 (%) with respect to exposure light. When the third transmission control section includes inspection areas arranged adjacently in this order, T1 and T3 are different from T2, and T1 is the same or different from T3,
The photomask inspection device includes:
an imaging element for acquiring an image of the inspection area of the transfer pattern;
Light intensity distribution data is obtained from the acquired image, and a light intensity change curve obtained by differentiating the light intensity distribution curve obtained from the light intensity distribution data is fitted to the model function to perform the inspection. a calculation means for calculating the dimension of the second transmission control section included in the region;
A photomask inspection apparatus. 13. The photomask inspection apparatus according to claim 12, wherein T1>T2>T3. The model function includes a first model function corresponding to a first boundary, which is a boundary portion between the first transmission control section and the second transmission control section, and the second transmission control section and the third transmission control section. and a second model function corresponding to a second boundary that is a boundary portion of
The computing means is configured to minimize the difference between the light intensity change curve and the synthetic curve obtained by synthesizing the first model curve obtained from the first model function and the second model curve obtained from the second model function. 14. The photomask inspection apparatus according to claim 12 or 13, wherein the fitting is performed on the .

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