CN112578631A

CN112578631A - Pattern inspection method, photomask inspection apparatus, and photomask manufacturing method

Info

Publication number: CN112578631A
Application number: CN202011021526.XA
Authority: CN
Inventors: 尾崎太一
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2019-09-27
Filing date: 2020-09-25
Publication date: 2021-03-30
Also published as: KR20210037564A; JP7229138B2; JP2021056293A; TW202127140A

Abstract

Provided are a pattern inspection method, a photomask inspection apparatus, and a photomask manufacturing method. Even in a fine width pattern, line width measurement can be performed stably and with high accuracy. Irradiating the inspection region with light to obtain a transmitted light image of the inspection region; obtaining light intensity distribution data of the inspection area from the obtained transmitted light image; a differential processing step of obtaining a light intensity change curve of a region including a 1 st boundary, which is a boundary portion between the 1 st transmission control unit and the 2 nd transmission control unit, and a 2 nd boundary, which is a boundary portion between the 2 nd transmission control unit and the 3 rd transmission control unit, by performing differential processing on a light intensity distribution curve obtained from the light intensity distribution data; fitting, namely fitting the obtained light intensity change curve to a model function; and a step of obtaining the size of the 2 nd transmission control part according to the fitting result.

Description

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

Technical Field

The invention relates to a pattern inspection method, a photomask inspection apparatus, a photomask manufacturing method, and a display apparatus manufacturing method. In particular, the present invention relates to a method for inspecting a transfer pattern of a photomask used for manufacturing an electronic device, particularly a photomask suitable for manufacturing a display device (for example, an FPD, a flat panel display), an apparatus for inspecting a photomask, a method for manufacturing a photomask, and a method for manufacturing a display device.

Background

Patent document 1 describes a method of capturing an image of a pattern by a solid-state imaging device and detecting an outline of the captured pattern, and a length measuring device.

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

Patent document 3 describes a photomask having a transfer pattern on a transparent substrate, the transfer pattern having a translucent portion, a translucent portion formed with a translucent film for transmitting a part of exposure light, and a light-shielding portion formed with a light-shielding film. The semi-transparent film has a transmittance of 2 to 60% and a phase shift effect of 90 DEG or less with respect to a representative wavelength of exposure light used for transferring the transfer pattern. The translucent portion is formed adjacent to an edge of the light shielding portion, and has a width that cannot be resolved by an exposure device.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 3-39603

[ patent document 2] Japanese patent laid-open No. 2012 and 002765

[ patent document 3] Japanese patent laid-open publication No. 2013-235036

Disclosure of Invention

[ problems to be solved by the invention ]

When a photomask is produced, an inspection is performed to confirm whether or not the photomask satisfies specifications determined in accordance with the use of the photomask. Measurement of the line width of the transfer pattern is also one of such inspections.

Patent document 1 describes that the following problems exist: in the conventional length measuring device, since a simulated optical image formed on the imaging surface of the camera is sampled in units of pixels of the imaging element, there is a problem that measurement accuracy equal to or less than the pixel pitch of the imaging element cannot be obtained when measuring the size of a pattern or the like from the sampled image signal. Therefore, patent document 1 provides a method particularly suitable for length measurement as follows: a pattern of an image is captured by a solid-state imaging device and a multi-stage image processing is performed on the data, thereby automatically and precisely giving an outline of the pattern with a precision equal to or less than a pixel pitch of the imaging device.

However, the optical image formed on the image pickup device has a quality (information amount) that varies depending on the resolution of the optical system used in addition to the image pickup device, but has a limited performance in a measuring apparatus used for measuring the CD (Critical Dimension: hereinafter, used in the sense of line width) of a photomask for manufacturing a display device.

On the other hand, the pattern size measuring apparatus described in patent document 2 uses an electron beam instead of light to obtain an SEM image.

Thus, as a method for measuring a pattern line width, a method using a CD-SEM (Critical Dimension-Scanning Electron Microscope) using an Electron beam is known. The CD-SEM is a measuring device to which a Scanning Electron Microscope (SEM) is applied, and is mainly used for measuring a line width of a pattern formed on a semiconductor wafer or a fine pattern of a photomask (Reticle) used for manufacturing the pattern. The measuring apparatus has an advantage of being capable of precisely measuring a submicron-sized fine pattern. However, it is difficult to apply the CD-SEM to the measurement of a so-called large photomask (generally, a main surface is a quadrangle with about 300 to 2000mm on one side, and various sizes are mixed) for manufacturing a display device (for example, a flat panel display, hereinafter abbreviated as FPD) for the following reasons. When measuring the pattern line width by the CD-SEM, a chamber (sample chamber) on which a photomask to be measured is placed is evacuated or highly evacuated. Therefore, when the CD-SEM is applied to the measurement of a large photomask for manufacturing a display device, it is necessary to prepare a large chamber and then to make the chamber into a vacuum or a high vacuum, which may cause a problem that a process load is very large. In this case, the apparatus configuration needs to be changed significantly, and an increase in cost cannot be avoided.

Therefore, in line width measurement of a photomask for a display device, an optical line width measuring device is used which has an optical system and an image pickup device and performs line width measurement using transmitted light of a transfer pattern.

However, the CD of the pattern of the photomask for display device is not as fine as the CD of the photomask for semiconductor device production in the past, and therefore, no significant problem arises.

However, in the field of display device technology, as the performance required for image quality, power saving, and the like from users of portable terminals and monitors has become higher, the need for miniaturization of the patterns of photomasks for display devices used for manufacturing them has become significant. Therefore, in addition to the increase in difficulty in manufacturing a photomask, difficulty has begun to occur in measuring the line width of the formed transfer pattern. In addition, a characteristic pattern particularly used for manufacturing a display device is also required.

Patent document 3 describes a photomask (transmission assist mask) having a Line and space pattern (Line and space pattern) as a transfer pattern. This is shown in fig. 1. Here, the line pattern has a structure in which the 1 st and 2 nd

translucent portions

21A and 21B (translucent films having a phase difference of 45 ° based on a transmittance of 20%) are provided adjacent to both side edges of the light shielding portion 31. Here, the width of light-shielding portion 31 is 1.5 μm, and the widths of 1 st and 2 nd

translucent portions

21A and 21B adjacent to both side edges of light-shielding portion 31 are 1.0 μm, respectively.

A photomask having a pattern with such characteristics is desired as a photomask for a display device, and the CD thereof tends to be miniaturized. Depending on the design of FPD devices, inspection of photomasks formed with finer patterns of less than 1 μm has also begun to occur. It is very difficult to measure the line width of such a fine pattern with the above optical line width measuring device.

Therefore, the present inventors have completed the present invention in order to solve the problem that occurs in the line width measurement of a transfer pattern for a photomask for a display device even when the pattern has a fine width pattern.

[ means for solving problems ]

(1 st mode)

In the first mode of the present invention according to the present invention,

a pattern inspection method for inspecting a transfer pattern of a photomask having the transfer pattern on a transparent substrate,

the pattern for transfer includes an inspection region in which a 1 st transmission control section having a transmittance of T1 for exposure light, a 2 nd transmission control section having a transmittance of T2 for exposure light, and a 3 rd transmission control section having a transmittance of T3 for exposure light are adjacently arranged in this order, wherein the transmittances T1, T2, and T3 are percentages, respectively, and when T1 and T3 are different from T2, and T1 is the same as or different from T3, the pattern inspection method includes the steps of:

irradiating the inspection region with light to obtain a transmitted light image of the inspection region;

obtaining light intensity distribution data of the inspection region from the acquired transmitted light image;

a differential processing step of obtaining a light intensity change curve of a region including a 1 st boundary, which is a boundary portion between the 1 st transmission control unit and the 2 nd transmission control unit, and a 2 nd boundary, which is a boundary portion between the 2 nd transmission control unit and the 3 rd transmission control unit, by performing differential processing on a light intensity distribution curve obtained from the light intensity distribution data;

fitting the obtained light intensity change curve to a model function; and

and a step of obtaining the size of the 2 nd transmission control part according to the fitting result.

(2 nd mode)

The 2 nd aspect of the present invention is the pattern inspection method according to the 1 st aspect,

T1>T2>T3。

(3 rd mode)

The 3 rd aspect of the present invention is the pattern inspection method according to the 1 st or 2 nd aspect,

the 1 st transmission control part forms a light transmission part formed by exposing the transparent substrate,

the 2 nd transmission control part is a semi-transparent part formed by forming a semi-transparent film on the transparent substrate,

the 3 rd transmission control part is formed on the transparent substrate and at least forms a light shielding part of a light shielding film,

the semi-light-transmitting section has a transmittance of 10 to 60% with respect to the exposure light.

(4 th mode)

The 4 th aspect of the present invention is the pattern inspection method according to any one of the 1 st to 3 rd aspects,

the width W (mum) of the 2 nd transmission control part is more than or equal to 0.1 and less than or equal to 1.5.

(fifth mode)

The 5 th aspect of the present invention is the pattern inspection method according to any one of the 1 st to 4 th aspects,

the transfer pattern includes a line and space pattern.

(mode 6)

The 6 th aspect of the present invention is the pattern inspection method according to any one of the 1 st to 5 th aspects,

the model functions include a 1 st model function corresponding to the 1 st boundary and a 2 nd model function corresponding to the 2 nd boundary.

(7 th mode)

The 7 th aspect of the present invention is the pattern inspection method according to the 6 th aspect,

in the fitting step, fitting is performed so that a difference between a synthetic curve obtained by synthesizing a 1 st model curve obtained from the 1 st model function and a 2 nd model curve obtained from the 2 nd model function and the light intensity change curve is minimized.

(8 th mode)

The 8 th aspect of the present invention is the pattern inspection method according to the 7 th aspect,

and respectively setting the 1 st model curve and the 2 nd model curve as Gaussian curves.

(ninth mode)

The 9 th aspect of the present invention is the pattern inspection method according to the 7 th or 8 th aspect,

and determining the size of the 2 nd transmission control part according to the peak position of the 1 st model curve and the peak position of the 2 nd model curve.

(10 th mode)

A 10 th aspect of the present invention is a method for manufacturing a photomask, including the pattern inspection method according to any one of the 1 st to 9 th aspects.

(11 th mode)

An 11 th embodiment of the present invention is a method for manufacturing a display device, including: the photomask manufactured by the manufacturing method according to claim 10 is exposed to light by an exposure apparatus, and the transfer pattern is transferred to a transfer target.

(twelfth mode)

The 12 th aspect of the present invention is a photomask inspecting apparatus for inspecting a transfer pattern of a photomask having the transfer pattern on a transparent substrate, wherein,

the transfer pattern includes an inspection region in which a 1 st transmission control section having a transmittance of T1 for exposure light, a 2 nd transmission control section having a transmittance of T2 for exposure light, and a 3 rd transmission control section having a transmittance of T3 for exposure light are adjacently arranged in this order, wherein T1, T2, and T3 are percentages, respectively, and when T1 and T3 are different from T2, and T1 is the same as or different from T3,

the photomask inspection apparatus includes:

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

and an arithmetic unit that obtains light intensity distribution data from the acquired image, and fits a light intensity change curve obtained by performing a differentiation process on a light intensity distribution curve obtained from the light intensity distribution data to a model function, thereby calculating the size of the 2 nd transmission control unit included in the inspection region.

(mode 13)

The 13 th aspect of the present invention is the photomask inspection apparatus according to the 12 th aspect,

T1>T2>T3。

(14 th mode)

The 14 th aspect of the present invention is the photomask inspection apparatus according to the 12 th or 13 th aspect,

the model functions include a 1 st model function corresponding to a 1 st boundary, which is a boundary portion of the 1 st transmission control part and the 2 nd transmission control part, and a 2 nd model function corresponding to a 2 nd boundary, which is a boundary portion of the 2 nd transmission control part and the 3 rd transmission control part,

the operation unit performs fitting so that a difference between a synthetic curve obtained by synthesizing a 1 st model curve obtained from the 1 st model function and a 2 nd model curve obtained from the 2 nd model function and the light intensity change curve becomes minimum.

[ Effect of the invention ]

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

Drawings

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. 2 is a diagram showing a transmitted light image of the photomask shown in fig. 1, which is obtained by an optical line width measuring device.

Fig. 3 is a diagram showing an examination area of the same transfer pattern as that of fig. 2 as a secondary electron image by an FIB (Focused Ion Beam) correction device.

Fig. 4 is a diagram showing an example of an outline of a method for inspecting a pattern of a photomask according to the present invention.

Fig. 5 is a diagram showing a flow of determining the line width (size) of the 2 nd transmission control portion (semi-transmissive portion) of the inspection region included in the transfer pattern.

Fig. 6 is a diagram showing a transmitted light image obtained by irradiating a region of a reference region including a transfer pattern of a reference mask with light using an optical line width measuring device having a halogen lamp as a light source and using a microscope having an image pickup device as a CCD.

Fig. 7 is a graph showing a light intensity distribution curve representing light intensity distribution data of a reference region obtained from transmitted light images obtained using 5 kinds of reference masks.

Fig. 8 is a diagram showing a light intensity change curve 1 for a boundary between the transparent portion and the semi-transparent portion.

Fig. 9 is a diagram showing a light intensity change curve 2 with respect to a boundary between the translucent portion and the light shielding portion.

Fig. 10 is a graph in which the horizontal axis represents transmittance T2 of the translucent portion and the vertical axis represents amplitude a or width σ, and the data in table 1 is plotted.

Fig. 11 is a diagram showing a model function obtained from a linear function.

Fig. 12 is a diagram showing a transmitted light image obtained by irradiating a region of an inspection region including a transfer pattern of an inspection target photomask with light using an optical line width measuring device having a halogen lamp as a light source and using a microscope having a CCD as an imaging device.

Fig. 13 is a diagram showing a light intensity distribution curve of the photomask to be inspected.

Fig. 14 is a graph in which the light intensity distribution curve (or light intensity distribution data) is subjected to first differentiation processing, and the absolute values thereof indicate the light intensity change curves of the respective boundary portions.

Fig. 15 is a diagram for explaining a case where a synthetic curve is obtained.

Fig. 16 is a diagram for explaining a case where the line width of the semi-light-transmitting portion is calculated from the synthetic curve.

Detailed Description

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

With the development of a photomask for a display device, introduction of a fine pattern tends to be advanced with high definition of the display device.

Miniaturization of the wiring pattern of the display device is advantageous not only in improving image quality such as luminance and response speed of the screen but also from the viewpoint of energy saving. Therefore, in recent years, further miniaturization of wiring patterns of display devices has been demanded, and accordingly, fine line width accuracy is also expected for photomasks for display devices.

Patent document 3 describes that in a binary mask having line and space patterns including a light-shielding portion and a light-transmitting portion, when the pitch of the line and space patterns is gradually reduced and the line and space patterns are miniaturized, the resist film on the object to be transferred cannot be transferred with an accurate line and space pattern. This is because the light intensity reaching the resist film decreases as the line width of the space pattern formed by the light transmitting portion becomes finer.

In view of the above, patent document 3 proposes a photomask (transmission assist mask) including a transfer pattern having a light transmitting portion, a semi-light transmitting portion formed with a semi-light transmitting film for transmitting a part of exposure light, and a light shielding portion formed with a light shielding film, the semi-light transmitting portion being adjacent to an edge of the light shielding portion and having a width that cannot be resolved by an exposure apparatus, on a transparent substrate. Patent document 3 describes that a fine pattern can be reliably and finely transferred onto a transfer target by adopting such a configuration.

As shown in fig. 1 (corresponding to fig. 10(a) of patent document 3), the semi-transmissive portion of the photomask of patent document 3 has a certain width and is provided adjacent to each of the opposing edges of the light-shielding portion. Here, the width of the semi-transmissive portion formed adjacent to the edge of the light shielding portion is preferably 1 μm or less (preferably, 0.1 to 1 μm.

However, in the photomask manufacturing process, before shipment, various inspections are performed to confirm that specifications required by mask users are satisfied. One such inspection is a CD (line width) inspection. In the CD inspection, the line width of an important part included in the transfer pattern is measured, and the obtained value of the line width is compared with the specification.

In order 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, in the case of measuring the line width of a line pattern formed of a light-shielding portion in a light-transmitting portion, the boundary of 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 a captured image. However, the photomask of patent document 3 includes a fine transfer pattern, and the difference in transmittance with respect to the inspection light between the 1 st and 2 nd translucent portions and the adjacent translucent portions or between the adjacent light-shielding portions is small. The present inventors have found that, in a photomask including such a transfer pattern, detection of the outline (edge) of the pattern to be measured is difficult, and it is not easy to measure the line width.

Fig. 2 shows a transmitted light image of a photomask having a line pattern such as the pattern shown in fig. 1, which is obtained by an optical line width measuring device (reference example 1). Specifically, fig. 2 shows a transmitted light image of transmitted light when a portion of the line pattern of the photomask corresponding to (a) surrounded by a chain line in fig. 1 is defined as an inspection region, and the region is irradiated with inspection light (wavelength λ is 400 to 550nm) using a halogen lamp. In this line pattern, semi-transmissive portions having a width of 0.5 μm were disposed on both sides of a light-shielding portion having a width of 3.0 μm, and the transmittance of the semi-transmissive portions for exposure light was 30%.

As is clear from fig. 2, in the transmitted light image, it is not easy to clearly recognize the translucent portions of a predetermined width adjacent to the edges on both sides of the light shielding portion. Therefore, it is difficult to perform line width measurement of the semi-transmissive portion using the transmitted light image.

Fig. 3 shows an inspection area of the same transfer pattern as a secondary electron image by an FIB (Focused Ion Beam) correction device (reference example 2). The FIB correction device condenses an ion beam obtained from a gallium plasma source, scans the sample, and detects generated secondary electrons. As is clear from fig. 3, the semi-transmissive portion having a predetermined width formed adjacent to the edge of the light-shielding portion can be clearly recognized from the image. Therefore, it is considered that the line width of the translucent portion can be measured. However, if the line width is measured by the FIB correction device, the transfer pattern may be damaged.

On the other hand, for the purpose of upsizing a display device and reducing production cost, a photomask for a display device is relatively upsized, and in addition, there are various sizes. Therefore, it is difficult to apply the above CD-SEM to line width measurement.

Under such circumstances, it is desired to measure the line width (CD) of a fine pattern with high accuracy without damaging the photomask by an excellent measuring apparatus, thereby improving the process control accuracy, the yield, and the production efficiency. Accordingly, the present inventors have completed the invention in order to meet such a demand.

< Pattern inspection method >

Fig. 4 is a schematic diagram illustrating an example of a method for inspecting a pattern of a photomask according to the present invention.

In the case of a photomask having a transfer pattern such as the portion (a) surrounded by a dashed-dotted line in fig. 1, it is considered that the light intensity greatly changes at the boundary between the translucent portion and at the boundary between the translucent portion and the light shielding portion. Therefore, the light intensity distribution obtained from the transmitted light image of part (a) in fig. 1 can be theoretically considered to form the distribution shown by the broken line in fig. 4 (a). In fig. 4 (a), the horizontal axis represents position (position in the horizontal direction in fig. 1, corresponding to a pixel position on the imaging surface), and the vertical axis represents light intensity.

In the light intensity distribution shown by the broken line in fig. 4 (a), a portion where the light intensity changes rapidly is clear. Since the portion where the light intensity changes rapidly is the boundary between the translucent portion and the translucent portion or the boundary between the translucent portion and the light shielding portion, if the light intensity distribution shown in fig. 4 (a) can be obtained, the line width of the translucent portion can be easily determined.

However, the actual intensity distribution of light when the line width of the translucent portion is small forms a smooth curve as shown by the solid line in fig. 4 (a). In the graph shown by the solid line in fig. 4 (a), the boundary between the translucent portion and the semi-translucent portion and the boundary between the semi-translucent portion and the light-shielding portion are not clear, and it is not easy to obtain the line width of the semi-translucent portion.

However, according to the study of the present inventors, even if the light intensity distribution curve is smooth, the amount of change in light intensity at each boundary, that is, the change in the slope of the light intensity distribution curve should be larger than at other portions. Therefore, the present inventors have focused on obtaining a curve having a peak at a position corresponding to each boundary if a differentiation process is performed on the light intensity distribution curve.

Fig. 4 (b) is a conceptual diagram illustrating a curve (light intensity change curve) obtained by differentiating the absolute value of the curve indicated by the solid line in fig. 4 (a), in which the vertical axis represents the amount of change in light intensity and the horizontal axis represents the position. In fig. 4 (b), sharp peaks are seen at positions corresponding to the boundaries.

Therefore, by determining the distance between the peak corresponding to the boundary between the translucent portion and the semi-translucent portion and the peak corresponding to the boundary between the semi-translucent portion and the light shielding portion, the line width of the semi-translucent portion can be determined.

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

The inspection object is a transfer pattern of a photomask having the transfer pattern on a transparent substrate. The transfer pattern includes an inspection region in which a 1 st transmission control section having a transmittance T1 (%) for exposure light, a 2 nd transmission control section having a transmittance T2 (%) for exposure light, and a 3 rd transmission control section having a transmittance T3 (%) for exposure light are arranged in this order. That is, the 2 nd transmission control part is interposed between the 1 st transmission control part and the 3 rd transmission control part. One edge of the 2 nd transmission control part is adjacent to the 1 st transmission control part, and the other edge of the 2 nd transmission control part is adjacent to the 3 rd transmission control part. T1 and T3 are different from T2, and T1 is the same as 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 may be 250< λ < 400. For example, the exposure light may include at least one of i-line, h-line, and g-line. Further, light in a wide wavelength region including i-line, h-line, and g-line may be used as exposure light. When the exposure light includes light of a plurality of wavelengths, an arbitrary wavelength included in a region from i-line to g-line may be used as a representative wavelength, and transmittance with respect to the representative wavelength (for example, g-line) may be expressed as T1, T2, and T3.

In the present embodiment, a case where T1> T2> T3, the 1 st transmission control portion is a light transmitting portion, the 2 nd transmission control portion is a semi-light transmitting portion, and the 3 rd transmission 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 passing portion is 100%, the transmittance of the light passing through the semi-light transmitting portion as the 2 nd transmission control portion is T2, and the transmittance of the light passing through the light blocking portion as the 3 rd transmission control portion is T3. However, the light transmittance T3 of the light shielding portion of the present embodiment is substantially zero (for example, the optical density OD. gtoreq.3). In the present embodiment, the size (line width) of the translucent portion, which is the 2 nd transmission control portion, is determined.

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

The material of the light-shielding film is not particularly limited, but the following materials are preferably used. For example, as a material of the light-shielding film, Ta, Mo, W, and a compound thereof (for example, a metal silicon compound such as TaSi, MoSi, WSi, or a nitride or oxynitride thereof) may be used in addition to Cr or a Cr compound (such as an oxide, nitride, carbide, oxynitride, or oxynitride of Cr). These materials may be used alone in 1 kind, or 2 or more kinds may be used in combination.

The light-shielding film may have a functional layer such as an antireflection layer on a surface layer on the front side (the side opposite to the transparent substrate). The antireflection layer can improve the drawing accuracy by suppressing reflection of the drawing light in the resist film. For example, when the light-shielding film contains Cr, the antireflection layer may be provided as a layer containing at least one of an oxide, nitride, carbide, oxynitride, and nitride carbide of Cr.

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

The semi-transmissive portion may 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 of the transmitted light amount of the transmissive portion. If the transmittance T2 (%) of the semi-light-transmissive portion is too small, the auxiliary function of the transmitted light amount of the light-transmissive portion cannot be sufficiently exhibited, and if the transmittance T2 is too large, difficulty in manufacturing the mask such as film thickness control of the semi-light-transmissive film increases. In view of this, the transmittance T2 (%) of the translucent portion may be, for example, 2. ltoreq. T2. ltoreq.60. The transmittance T2 (%) of the translucent portion is preferably 10. ltoreq. T2. ltoreq.60, more preferably 10. ltoreq. T2. ltoreq.35, and further preferably 15. ltoreq. T2. ltoreq.30.

The line width (size) W (mum) of the semi-light-transmitting part is preferably not less than 0.1 and not more than 1.5, more preferably not less than 0.3 and not more than 1.0. If the line width of the translucent portion is too large, there is a possibility that the side shape of the resist pattern on the transfer target may be inclined when the pattern transfer is performed using the photomask, while if the line width of the translucent portion is too small, the function of assisting the transmitted light amount of the translucent portion becomes insufficient. If the line width of the semi-light transmitting portion is within the above range, the inclination of the side surface shape of the resist pattern can be suppressed, a resist pattern having a good side surface shape can be formed, and the amount of transmitted light of the light transmitting portion can be sufficiently assisted.

The semi-transparent part has a phase shift amount with respect to the representative wavelength of the exposure light

(degree) is

Phase shift amount of semi-light transmission part

Preferably, it is

More preferably

Further preferred is

By making the phase shift of the semi-light-transmitting part

Within the above range, the cancellation of the light intensity at the boundary between the translucent portion and the light-transmitting portion can be suppressed, and the transmitted light amount of the light-transmitting portion can be assisted. Therefore, even if the pattern size is made finer, the reduction of the light intensity peak position of the light transmitting portion can be suppressed when the photomask is exposed, and a resist pattern having a good side surface shape can be formed.

As the material of the semi-transparent film, for example, Cr compound (oxide, nitride, carbide, oxynitride carbide, etc. of Cr), Si compound (SiO compound), and the like can be used₂SOG), metal silicide (TaSi, MoSi, WSi, or nitrides and oxynitrides thereof), and a Ti compound such as TiON. These can be used alone in 1, also can be used in 2 or more combinations.

The method for inspecting a pattern of a photomask according to the present embodiment includes the steps of:

irradiating the transfer pattern with light to obtain a transmitted light image of the inspection region;

a differentiation step of obtaining a light intensity change curve in a region including a 1 st boundary which is a boundary portion between the 1 st transmission control unit and the 2 nd transmission control unit and a 2 nd boundary which is a boundary portion between the 2 nd transmission control unit and the 3 rd transmission control unit by performing differentiation processing on a light intensity distribution curve obtained from the light intensity distribution data;

fitting the obtained light intensity change curve to a model function;

Fig. 5 shows a flow of determining the line width (size) of the 2 nd transmission control portion (semi-transmissive portion) of the inspection region included in the transfer pattern. The respective steps in fig. 5 will be specifically described with reference to fig. 5 to 16.

First, a model function used for determining the line width of the translucent portion is generated.

To generate the model function, a plurality of reference masks are prepared. These reference masks may include a photomask having a transfer pattern including a portion where a translucent portion (1 st transmission control portion) and a translucent portion (2 nd transmission control portion) are adjacent, and a photomask having a transfer pattern including a portion where a translucent portion (2 nd transmission control portion) and a light shielding portion (3 rd transmission control portion) are adjacent. In the present embodiment, a photomask having a transfer pattern including any one of a portion where a translucent portion (1 st transmission control portion) and a translucent portion (2 nd transmission control portion) are adjacent to each other and a portion where a translucent portion (2 nd transmission control portion) and a light shielding portion (3 rd transmission control portion) are adjacent to each other is used as the reference mask. The transmissive portion (1 st transmission control portion) and the light shielding portion (3 rd transmission control portion) are not necessarily adjacent to the same semi-transmissive portion (2 nd transmission control portion), and may be adjacent to different semi-transmissive portions (2 nd transmission control portions). In the present embodiment, in the transfer pattern, a region in which the light transmitting portion (1 st transmission control portion), the semi-light transmitting portion (2 nd transmission control portion), and the light shielding portion (3 rd transmission control portion) are arranged in this order is used as a reference region. The line width of the semi-transmissive portion in the reference region is preferably sufficiently large. Sufficiently large means that there is no obstacle to the calculation of the model function described later. In addition, a portion where the light transmitting portion (1 st transmission control portion) and the semi-light transmitting portion (2 nd transmission control portion) are adjacent to each other, and a portion where the semi-light transmitting portion (2 nd transmission control portion) and the light shielding portion (3 rd transmission control portion) are adjacent to each other may not necessarily be included in the 1 reference region. In this case, a region including a portion where the translucent portion (the 1 st transmission control portion) and the translucent portion (the 2 nd transmission control portion) are adjacent to each other may be set as the 1 st reference region, a region including a portion where the translucent portion (the 2 nd transmission control portion) and the light shielding portion (the 3 rd transmission control portion) are adjacent to each other may be set as the 2 nd reference region, and transmitted light images described later may be acquired for the 2 reference regions, and a light intensity distribution curve may be generated.

(1) Obtaining transmitted light images of a reference mask

Images of the transfer patterns are acquired for the plurality of reference masks. In the present embodiment, a transmitted light image is used as an example of an image, but the present invention is not limited to this. An image different from the transmitted light image (e.g., a reflected light image) may be used as long as the effect/action of the present invention is not hindered.

In the present embodiment, a region of the reference mask including the reference region of 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 having an image pickup device as a CCD (fig. 6). The wavelength of the light (inspection light) is preferably any wavelength in the wavelength region of 400 to 550nm, for example, 525 nm.

For the purpose of obtaining the model function, a plurality of reference masks having different transmittances of the translucent portion are prepared, and transmitted light images (not shown) of the transfer patterns of the reference masks are acquired. In the present embodiment, when the transmittance T1 of the translucent portion is 100%, the transmittances of the translucent portions of the plurality of reference masks, i.e., the transmittances T2, with respect to the light of the g-line are 28%, 38%, 50%, 67%, and 79%, respectively. That is, in the present embodiment, five kinds of reference masks are prepared. In any of the reference masks, the transmittance T3 of the light shielding portion is substantially zero.

In fig. 6, a region including the 1 st boundary between the translucent portion and the semi-translucent portion and the 2 nd boundary between the semi-translucent portion and the light-shielding portion (a region surrounded by a broken line in fig. 6) is referred to as a reference region.

(2) Reference mask light intensity profile generation

Light intensity distribution data (not shown) of the reference region is obtained from the transmitted light images obtained using the 5 kinds of reference masks. Further, a light intensity distribution curve (fig. 7) is obtained in which the light intensity distribution data is represented by a curve.

For example, a straight line perpendicular to the boundary line between the translucent portion and the translucent portion or a straight line perpendicular to the boundary line between the translucent portion and the light shielding portion (for example, an arrow portion in fig. 6) is drawn in the reference region of the transmitted light image obtained in (1) above, and the light intensity on the straight line is numerically controlled to 256 gradations using known image processing software. This makes it possible to produce a light intensity distribution curve as shown in fig. 7. The straight line for obtaining the light intensity may be set at an arbitrary position within the reference region so that it is parallel to the direction of the dimension to be measured. In fig. 7, the vertical axis represents light intensity numerically represented as 256 gradations, and the horizontal axis represents a pixel position in a transmitted light image.

(3) Generating light intensity variation curves of the 1 st boundary of the light transmission part and the semi-light transmission part and the 2 nd boundary of the semi-light transmission part and the light shielding part

The light intensity distribution curve (or light intensity distribution data) obtained in (2) above is subjected to a first differentiation process to obtain a light intensity change curve (light intensity change data) (differentiation process). Fig. 8 shows a light intensity change curve 1 at the 1 st boundary between the light-transmitting portion and the semi-light-transmitting portion, and fig. 9 shows a light intensity change curve 2 at the 2 nd boundary between the semi-light-transmitting portion and the light-shielding portion. In fig. 8, 8 and 9, the vertical axis represents the light intensity change, and the horizontal axis represents the pixel position (where the vertical axis represents the absolute value of the light intensity change, and is a positive value) as in fig. 7.

(4) Fitting with Gaussian (Gaussian) function (least squares)

The light intensity profiles obtained in (3) above are each approximated by a known function. Here, fitting is performed by the least square method using a gaussian function (equation (1)) shown below, and coefficients a and σ of the gaussian function corresponding to each light intensity change curve are obtained.

[ formula 1]

Here, y: light intensity change, a: amplitude of the gaussian function, σ: standard deviation of gaussian function, x: pixel position, p: the peak position in the x-direction of the gaussian function. The standard deviation σ may be used as an index indicating the width of the gaussian function, and is described as the width σ in the present specification.

The results of the fitting are shown in table 1 below.

[ TABLE 1]

(5) Model function generation

Fig. 10 shows the results of plotting the data in table 1, where the horizontal axis represents transmittance T2 of the translucent portion and the vertical axis represents amplitude a or width σ. The data obtained at the 1 st boundary between the light transmitting portion and the translucent portion and the 2 nd boundary between the light shielding portion and the translucent portion are approximated to linear functions, and the slope a and the intercept b of the linear functions are obtained. That is, the amplitude a is approximated to a × T2+ b, and the width σ is approximated to a × T2+ b. Thus, the slope a and the intercept b are obtained for each amplitude a and width σ.

In fig. 10, the left vertical axis represents the amplitude a, the right vertical axis represents the width σ, and the straight line represents a linear function obtained by approximation. In the example of fig. 10, Qz-HT denotes a 1 st boundary portion between the light-transmitting portion and the semi-light-transmitting portion, and HT-Cr denotes a 2 nd boundary portion between the semi-light-transmitting portion and the light-shielding portion.

The slope a and intercept b obtained by approximation are shown in table 2 below.

[ TABLE 2]

From the obtained linear function, coefficients a and σ of a gaussian function are obtained according to the transmittance T2 of the semi-transmissive portion. That is, gaussian functions as model functions corresponding to the transmittance T2 of the semi-transmissive portion can be obtained for the 1 st boundary portion between the transmissive portion and the semi-transmissive portion and the 2 nd boundary portion between the semi-transmissive portion and the light-shielding portion, respectively.

For example, when the transmittance T2 of the semi-transmissive portion is 10, 20, 30, 40, 50, or 60%, the model function obtained from the above linear function represents the curve as shown in fig. 11. Similarly, if the transmittance T2 of the translucent portion required for the size measurement is known, a model function suitable for the calculation of the line width of the translucent portion can be obtained from the transmittance T2 and the linear function described above. In fig. 11, the vertical axis represents the light intensity change, and the horizontal axis represents the pixel position as in fig. 7.

(6) Obtaining transmitted light image of mask to be inspected

A region of the inspection area including the transfer pattern of the inspection target mask was irradiated with light by an optical line width measuring device having a halogen lamp as a light source, and a transmitted light image was obtained using a microscope having a CCD as an imaging device (fig. 12). In the present embodiment, in order to suppress a decrease in inspection accuracy, the imaging conditions (optical system, wavelength of inspection light, and the like) for obtaining the transmitted light image of the inspection target mask are made the same as those for obtaining the transmitted light image of the reference mask.

In fig. 12, a region including the 1 st boundary between the light transmitting portion and the semi-light transmitting portion and the 2 nd boundary between the semi-light transmitting portion and the light shielding portion (a region surrounded by a broken line in fig. 12) is set as an inspection region. In the present embodiment, a case will be described as an example where 2 boundaries are provided in the inspection region of the inspection target mask, the boundary between the translucent portion and the semi-translucent portion (1 st boundary) and the boundary between the semi-translucent portion and the light shielding portion (2 nd boundary). That is, as shown in fig. 12, the transfer pattern of the inspection target mask of the present embodiment includes a 1 st translucent portion adjacent to a 1 st edge of the light shielding portion and a 2 nd translucent portion adjacent to a 2 nd edge of the light shielding portion. The 1 st and 2 nd translucent portions are adjacent to edges of the translucent portions, respectively. That is, the 1 st semi-transmissive portion and the 2 nd semi-transmissive portion are interposed between the transmissive portion and the light shielding portion, respectively.

(7) Generating a light intensity distribution curve of an inspection object mask

Similarly to the generation of the light intensity distribution curve of the reference mask in (2) above, a straight line (solid line arrow in fig. 12) parallel to the width direction of the translucent portion is drawn at an arbitrary position in the inspection region in the obtained transmitted light image of the inspection target mask, and the light intensity on the straight line is numerically controlled to 256 gradations. Thereby, light intensity distribution data (not shown) of the examination region is obtained. This results in a light intensity distribution curve as shown in fig. 13.

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

(8) Generating a light intensity profile of an examination region

Similarly to (3) above, the light intensity distribution degree curve (or light intensity distribution data) generated in (7) above is subjected to a first differentiation process, and a light intensity change curve at the 1 st and 2 nd boundary portions is generated for the absolute value thereof (fig. 14). In fig. 14, the vertical axis represents the light intensity change, and the horizontal axis represents the pixel position as in fig. 13. The same applies to fig. 15 and 16 described later.

(9) Fitting with model function (generating synthetic curve)

From the model functions obtained above, the model function of the 1 st boundary between the translucent portion and the translucent portion (the model function of the translucent portion-translucent portion) and the model function of the 2 nd boundary between the translucent portion and the light shielding portion (the model function of the translucent portion-light shielding portion) obtained in (5) above are selected based on the transmittance T2 of the translucent portion of the inspection target mask measured in advance. Alternatively, a linear function may be held in advance, and a corresponding model function may be calculated from the linear function and the transmittance T2 of the semi-transmissive portion.

Then, as shown in fig. 15, in order to minimize the difference between the combined curve obtained by adding the light intensity changes of the curve (1 st model curve) represented by the model function (1 st model function) of the light transmitting portion-translucent portion and the curve (2 nd model curve) represented by the model function (2 nd model function) of the translucent portion-light shielding portion and the light intensity change curve of the inspection target mask obtained in the above (8), two model functions (model curves) are combined and fitted by the least square method. That is, the relative positions of the 1 st model curve and the 2 nd model curve in the horizontal axis direction are determined so that the difference between the synthesized curve and the light intensity variation curve of the inspection target mask is minimized. The model curves (model 1 st curve and model 2 nd curve) are gaussian curves.

As shown in fig. 12, the inspection region of the inspection target mask of the present embodiment includes 2 semi-transparent portions (a 1 st semi-transparent portion and a 2 nd semi-transparent portion), but since the calculation methods of the line widths of the 2 semi-transparent portions are the same, only the 1 st semi-transparent portion (the left semi-transparent portion in fig. 12, that is, the portion surrounded by the broken line in fig. 13 and 14) is shown in fig. 15 and fig. 16 described later, and the 2 nd semi-transparent portion is omitted.

(10) Calculating the line width of the translucent part

As shown in fig. 16, the peak values of the 2 model functions synthesized in (9) above correspond to the 1 st boundary between the light-transmitting portion and the semi-light-transmitting portion and the 2 nd boundary between the semi-light-transmitting portion and the light-shielding portion. Therefore, the positions of the peaks of the two model functions are found. Then, by obtaining the distance between these 2 peaks, the line width (size) of the translucent portion can be obtained.

Therefore, first, pixel positions corresponding to the two peaks are obtained. From these pixel positions, 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 light-transmitting part-translucent part) - (peak position of model function of translucent part-light-shielding part) | … formula (2)

The width (pixel size) of each pixel can be found in advance. For example, if the pixel size of the imaging device for imaging the light intensity distribution of the reference mask is obtained in advance and the same imaging conditions are applied to the inspection target mask, the pixel size can be directly applied to the image of the inspection target mask. By multiplying the pixel size by the number of pixels between the obtained peaks (expression (3) below), the line width of the translucent portion in the inspection region 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 translucent portion is 0.24 μm.

(line width [ μm ]) (number of pixels between peaks [ pixel ]) × (pixel size [ μm/pixel ]) … formula (3)

As described above, the line width of the semi-transmissive portion serving as the 2 nd transmission control portion serving as the inspection target pattern can be obtained.

< inspection apparatus for photomask >

The pattern inspection method can be performed using the following photomask inspection apparatus. That is, the inspection apparatus for a photomask of the present invention, when the transfer pattern includes inspection regions in which a translucent portion (1 st transmission control portion), a semi-translucent portion (2 nd transmission control portion), and a light shielding portion (3 rd transmission control portion) are adjacent to each other and arranged in this order, includes: an image pickup device for acquiring an image of an inspection area; and a calculation unit that obtains light intensity distribution data from an image of the inspection region acquired by the imaging device, and calculates the size (width) of the translucent portion (2 nd transmission control unit) included in the inspection region by fitting a light intensity change curve obtained by differentiating a light intensity distribution curve obtained from the light intensity distribution data to the model function.

The photomask inspection apparatus may further include a model function holding unit for holding the transmittance of the inspection light by the 2 nd transmission control unit in accordance with a model function. Alternatively, the inspection apparatus may include a linear function holding unit that holds the linear function.

The model function holding means and the linear function holding means do not necessarily have to be provided in 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.

The arithmetic means may calculate model functions (1 st model function and 2 nd model function) corresponding to the 2 nd transmission control unit based on the input linear function and the transmittance of the 2 nd transmission control unit for the inspection light. Then, the arithmetic unit may calculate the peak position of the 1 st model function and the peak position of the 2 nd model function, and calculate the size of the translucent portion (the 2 nd light transmission control portion) from these peak positions.

The invention provides a pattern inspection method and a photomask inspection apparatus, which can stably and highly accurately measure a line width without damaging a photomask. In addition, there is an advantage that the line width measurement of a fine transfer pattern of a large-sized photomask can be performed. 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.

The present invention enables stable and highly accurate measurement even when the pattern width is small, for example, the dimension (line width) W (μm) is 0.1. ltoreq. W.ltoreq.1.5 (particularly, 0.3. ltoreq. W.ltoreq.1.0 μm), that is, even when measurement is difficult using an optical line width measuring apparatus.

Alternatively, when the difference in light transmittance between 2 adjacent regions having different light transmittances is relatively small and the boundary cannot be clearly recognized even if a light intensity curve is obtained, the line width measurement of the transfer pattern can be performed finely.

For example, the effect of the present invention is significant in the case where the difference in transmittance of light between the 1 st transmission control section and the 2 nd transmission control section (absolute value of T1 (%) -T2 (%)) satisfies 0< | T1 (%) -T2 (%) | ≦ 80 (dots), and/or the difference in transmittance of light between the 2 nd transmission control section and the 3 rd transmission control section (absolute value of T2 (%) -T3 (%)) satisfies 0< | T2 (%) -T3 (%) | ≦ 30 (dots).

< method for producing photomask >

The present invention includes a method of 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.

An example of a method for manufacturing a photomask will be described below. The photomask herein may have the same structure as the photomask as the inspection object in the above-described inspection method.

First, a photomask blank is prepared. Here, a semi-light transmissive film and a light blocking film are sequentially formed on a transparent substrate, and a photoresist film is further formed on the light blocking film. The photomask blank herein may also be a photomask intermediate in which a part of the light-shielding film and/or the semi-light-transmitting film has been patterned. Further, 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 drawing step described later.

A pattern for forming the translucent portion is drawn on the photoresist film using a drawing machine. As the drawing machine, for example, a laser drawing machine can be used.

Next, the photoresist film subjected to the above-described drawing step is developed to form a resist pattern.

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

Next, the light shielding film is etched for the 2 nd time using the resist pattern as a mask. That is, the light-shielding film is side-etched with a wet etchant for the light-shielding film. Here, a light shielding portion having a predetermined width is formed. Further, since the edge of the light-shielding portion is receded by the side etching, a part of the semi-transmissive film is exposed. Thus, the translucent portion having the predetermined width is formed adjacent to the light blocking portion.

Then, the resist pattern is stripped off to produce a photomask before inspection.

Next, the photomask before the inspection is inspected by the above-described inspection method. For example, the line width of the translucent portion at a desired position of the pattern for transfer of the photomask is measured. Then, a photomask having a line width of the semi-transmissive portion satisfying the specification can be used as a finished product.

In the case of the above-described method for manufacturing a photomask, materials having etching selectivity with respect to each other are used for the semi-light transmissive film and the light shielding film. In the etching step of the light-shielding film 2, since side etching by isotropic etching is used, wet etching is preferably applied.

The transfer pattern of the photomask manufactured by the method for manufacturing a photomask of the present invention may have a light-transmitting portion, a semi-light-transmitting portion, and a light-shielding portion. The transfer pattern may have a 1 st translucent portion and a 2 nd translucent portion as the translucent portions.

The 1 st translucent portion and the 2 nd translucent portion are formed symmetrically and oppositely with respect to the light shielding portion. The 1 st translucent portion and the 2 nd translucent portion preferably have a certain width that cannot be resolved by the exposure apparatus and are equal to each other. Here, the widths equal to each other are preferably within 0.1 μm, more preferably within 0.05 μm, of the line width of the 1 st translucent portion and the line width of the 2 nd translucent portion. Thus, the auxiliary action of the transmitted light amount given to the light transmitting portion becomes symmetrical, and the line width accuracy of the pattern formed on the transferred body can be finely controlled.

The photomask can be used, for example, to form a line and space pattern having a line width and/or space width of less than 3 μm on a transferred body. Here, the line pattern may be configured by a light shielding portion and a semi-light transmitting portion (1 st semi-light transmitting portion, 2 nd semi-light transmitting portion), and the space pattern may be configured by a light transmitting portion. The pitch P (μm) of the line and space pattern may be 0< P.ltoreq.10, and more particularly, may be 4< P.ltoreq.6. Alternatively, the pattern for transfer of the photomask may include a hole pattern, and holes having a diameter of less than 3 μm may be formed on the transferred object using the hole pattern.

The use of the photomask is not particularly limited. The photomask manufactured by the manufacturing method of the present invention is particularly useful as a photomask for manufacturing a display device. For example, a photomask manufactured by the manufacturing method of the present invention can be advantageously used for the formation of each layer (e.g., a pixel layer or a light spacer layer of a color filter) used in a display device, and a lead-out wiring portion or the like provided in the vicinity of an end portion of a prescribed layer. That is, the method of the present invention can be preferably used for a photomask having a transfer pattern including a fine portion having a CD (line width) of 1.5 μm or less, a photomask having a transfer pattern in which the fine portion is a semi-light-transmitting portion, or the like.

The present invention includes a method of manufacturing a display device using a photomask manufactured by the above-described manufacturing method of the present invention. 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 embodiment; and a step of transferring the transfer pattern to a transfer object by exposing the photomask to light using an exposure device. The display device manufactured by the manufacturing method also includes various devices constituting the display device.

The exposure apparatus used when transferring the transfer pattern of the photomask manufactured by the photomask manufacturing method of the present invention to the object to be transferred may be a projection exposure apparatus or a proximity exposure apparatus of an equal magnification of an exposure apparatus 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 include a double-folding display and a scroll display (Rollable display).

As the optical system of the exposure apparatus, in the case of a projection exposure apparatus, an optical system having an NA (numerical aperture) of 0.08 to 0.15 and a Coherence factor (Coherence factor) of 0.5 to 0.9 can be preferably used.

< modification example >

The embodiments of the present invention have been described above in detail, but the technical scope of the present invention is not limited to the above embodiments, and various modifications can be made within the scope not departing from the gist thereof.

In the case of T1> T2> T3 employed in the above-described embodiment, there are three kinds of transmittances in the transfer pattern constituted by the 1 st, 2 nd, and 3 rd transmission control sections. On the other hand, when T1 is T3, the transmittances of the 1 st and 3 rd transmission control sections are equal. That is, the 2 nd transmission control part is interposed between the 1 st transmission control part and the 3 rd transmission control part, which have the same transmittance. As a result, there are two transmittances in the transfer pattern formed by the 1 st, 2 nd, and 3 rd transmission control portions included in the transfer pattern. The technical idea of the present invention can be applied even in the case where there are two kinds of transmittances.

Specifically, the light intensity change curve of the 2 nd boundary, which is the boundary portion between the 2 nd transmission control unit and the 3 rd transmission control unit, is the same as the light intensity change curve of the 1 st boundary, which is the boundary portion between the 1 st transmission control unit and the 2 nd transmission control unit.

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

Claims

1. A pattern inspection method for inspecting a transfer pattern of a photomask having the transfer pattern on a transparent substrate,

fitting the obtained light intensity change curve to a model function; and

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

3. The pattern inspection method according to claim 1 or 2,

4. The pattern inspection method according to claim 1 or 2, wherein a width W of the 2 nd transmission control portion is 0.1 ≦ W ≦ 1.5, where W is in μm.

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

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

7. The pattern inspection method according to claim 6, wherein in the fitting step, fitting is performed so that a difference between a synthetic curve obtained by synthesizing a 1 st model curve obtained from the 1 st model function and a 2 nd model curve obtained from the 2 nd model function and the light intensity change curve is minimized.

8. The pattern inspection method according to claim 7, wherein the 1 st model curve and the 2 nd model curve are each assumed to be a gaussian curve.

9. The pattern inspection method according to claim 7 or 8,

10. 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: the photomask produced by the production method according to claim 10 is exposed to light by an exposure apparatus, and the transfer pattern is transferred to a transfer target.

12. A photomask inspection apparatus for inspecting a transfer pattern of a photomask having the transfer pattern on a transparent substrate,

the photomask inspection apparatus includes:

13. The photomask inspection apparatus of claim 12, wherein T1> T2> T3.

14. The photomask inspection apparatus of claim 12 or 13,