JP2003307501A - Defect inspection method and defect inspection device of gray tone mask, and defect inspection method and defect inspection device of photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect inspection method, and a defect inspection device for inspecting a place detected as a pseudo-defect of a transmissivity signal without detecting the place as the pseudo-defect. <P>SOLUTION: This defect inspection method of a gray tone part in a gray tone mask is characterized by including a process (a drawing 1 (3)) of applying gradating processing for flattening the signal when there is a periodic change as indicated in a drawing 1 (2) in the transmissivity signal obtained by scanning a gray tone part as indicated in a drawing 1 (1). <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method and a defect inspection device for a photo mask including a gray tone mask and a fine pattern.

[0002]

2. Description of the Related Art Recently, in the field of masks for large LCDs, attempts have been made to reduce the number of masks by using gray tone masks (monthly FPD Intelligence, 1999).
May year). Here, the gray-tone mask is shown in FIG.
As shown in FIG. 1, a light-shielding portion 1 and a transmitting portion 2 are formed on a transparent substrate.
And a graytone portion 3. Gray tone part 3
Is, for example, a large LCD using a gray tone mask
Is a region where the light-shielding pattern 3a is formed below the resolution limit of the exposure machine for use, and the amount of light transmitted through this region is reduced and the irradiation amount in this region is reduced to selectively change the film thickness of the photoresist. It is formed for the purpose of changing. 3b is a fine transmission part in the gray tone part 3 which is below the resolution limit of the exposure device. Both the light-shielding portion 1 and the light-shielding pattern 3a are usually formed of a film made of the same material such as chromium or a chromium compound and having the same thickness. Both the transmissive portion 2 and the fine transmissive portion 3b are portions of the transparent substrate on which a light shielding film or the like is not formed. The resolution limit of a large LCD exposure machine using a gray tone mask is about 3 μm for a stepper type exposure apparatus and about 4 μm for a mirror projection type exposure apparatus. Therefore, for example, in FIG. 6A, the space width of the transmissive portion 3b in the gray tone portion 3 is set to 3 μm.
The line width of the light-shielding pattern 3a that is less than m and less than the resolution limit of the exposure device is less than 3 μm. When exposed by the above-described large LCD exposure machine, the exposure light that has passed through the graytone portion 3 is insufficient in the overall exposure amount, so that the thickness of the positive photoresist exposed through the graytone portion 3 becomes thin. Just remain on the substrate. That is, since the resist has different solubility in the developing solution between the portion corresponding to the normal light-shielding portion 1 and the portion corresponding to the gray-tone portion 3 due to the difference in the exposure amount, the resist shape after development is as shown in FIG. ), The portion 1'corresponding to the normal light shielding portion 1 is, for example, about 1.3 μm, and the portion 3'corresponding to the gray tone portion 3 is
Is about 0.3 μm, and the portion corresponding to the transmissive portion 2 is the resist-free portion 2 ′. Then, the first etching of the substrate to be processed is performed on the non-resist portion 2 ', the resist on the thin portion 3'corresponding to the gray tone portion 3 is removed by ashing or the like, and the second etching is performed on this portion. The number of masks is reduced by performing the process for two conventional masks with one mask.

Conventionally, as a method of inspecting a mask consisting of a light-shielding portion and a light-transmitting portion, for example, there is a comparative inspection method of comparing mask patterns with each other using two optical systems. The method will be specifically described below. Figure 7 (1)
Indicates a state in which a white defect 11 (pinhole) is generated in the light-shielding portion 1 and a black defect 12 (spot) is generated in the transmission portion 2, and the arrow indicates one lens of the comparative inspection apparatus (hereinafter referred to as the upper lens).
The scanning state of is shown. FIG. 7 (2) shows the transmittance signal 13 obtained along the scanning line of the lens. The transmittance signal 13 is, for example, a CCD arranged in each lens unit.
It is detected by the line sensor. The level of the transmittance signal 13 is B in the light shielding portion 1 and W in the light transmitting portion 2, and the transmittance of the light shielding portion 1 is set to 0% and the transmittance of the light transmitting portion 2 is set to 100%. The transmittance signal 13 is basically composed of a pattern edge line signal (pattern shape signal) generated at the edge of the pattern (border between the light shielding portion and the light transmitting portion), and when a defect occurs, it occurs in the light shielding portion 1. White defect signal 1
1 ', a black defect signal 12' appearing in the transmissive portion 2 appears.
FIG. 7 (3) shows the transmittance signal 13 'obtained by the other lens (hereinafter referred to as the lower lens) when the pattern is the same as that of FIG. 7 (1) and no defect occurs. Figure 7
(4) is the difference signal 14 obtained by subtracting (difference) the transmittance signals obtained by the respective lenses. More specifically, it is a difference signal obtained by subtracting the transmittance signal 13 ′ of FIG. 7 (3) from the transmittance signal 13 of FIG. 7 (2). In the difference signal 14, the pattern edge line signal is removed from the transmittance signal of each lens, and only the pattern defect signals 11 'and 12' are extracted. In FIG. 7 (5), in the difference signal 14 obtained by extracting only the pattern defect signal, a threshold value necessary for extracting the defect of the light shielding portion 1 and the transmission portion 2 is set, and the threshold value 1 on the plus side is set.
5a shows a state in which a white defect has been detected, and a negative threshold value 15b has shown a black defect, respectively. The lower the threshold value, the higher the detection sensitivity, but it is necessary to set the threshold value to a level at which a pseudo defect is not detected. In order to determine which defect has occurred in which lens, for example, in the circuit of the upper lens, compare with the signal of the lower lens (subtract the signal of the lower lens from the signal of the upper lens), A white defect and a black defect of the upper lens are detected by outputting a defect signal to the plus side when a white defect occurs in the light-shielding part 1 and to a minus side when the black defect occurs in the transmission part 2 of the upper lens ( Figure 7 above
(2) to (5)). Similarly, for example, in the circuit of the lower lens, the signal of the upper lens is compared (the signal of the upper lens is subtracted from the signal of the lower lens), and when a white defect occurs in the light shielding portion 1 of the lower lens, the plus side, When a black defect occurs in the transmissive portion 2 of the lens, a defect signal is output to the negative side to detect the white defect and the black defect of the lower lens.

[0004]

Since the above-mentioned conventional comparative inspection method is an apparatus for inspecting a conventional mask consisting only of a light shielding portion and a transmission portion, it inspects a graytone mask having a graytone portion. Not suitable for.
Specifically, the conventional comparative inspection method has the following problems in inspecting the gray tone mask. That is, the defect signal of the gray tone portion is weak because the defect itself is minute, and it is difficult to detect unless the threshold value is lower than the threshold value used for the inspection of the normal light shielding portion when using the conventional comparative inspection device. Is. However, for example, when the gray tone portion is an area where a fine pattern having a resolution limit of the exposure machine using the gray tone mask or less is formed, as shown in FIG. Unique base signal level (noise band) 16
Cause In the comparison inspection, the transmittance signal obtained by each lens is subtracted (difference) to obtain the difference signal, and only the pattern defect signal is extracted, but there is a slight pattern shift between the fine light-shielding patterns in the gray tone part. If it occurs, the base signal level is amplified (maximum 2 times), and a defect that should not be a defect is detected as a defect (pseudo-defect). Therefore, it is impossible to lower the threshold value, and high sensitivity is achieved. There is a problem that inspection is not possible. Furthermore, since the conventional comparative inspection is for inspecting white defects and black defects, it is difficult to guarantee the transmittance, which is the most important factor in the gray tone mask. That is, for example, when the line width of the light-shielding pattern in the gray tone part is under (large line width) or over (small line width) the design dimension over the entire mask and exceeds the allowable value of the transmittance, , If the transmissivity of the semi-transmissive film forming the gray tone part exceeds the allowable value, the difference signal is obtained by subtracting the transmissivity signals obtained by each lens in the comparative inspection, so the difference appears. Therefore, there is a problem that such a transmittance defect cannot be detected. This becomes a problem especially when there is no shape defect in the gray tone portion. Further, in the gray tone part, it is not necessary to detect as a defect if the transmittance is within the allowable range, but in the conventional comparative inspection, it is detected as a shape defect,
In some cases, the transmittance was within the allowable range even if it was detected by the conventional inspection. As a result, even defects that do not have to be originally detected are detected, and there is a problem in the accuracy (ability) of the inspection. Further, the same problem also occurs in a photomask having a fine pattern such as a photomask for forming a TFT channel portion or a photomask having a fine and highly precise pattern such as a line & space having a line width of 3 μm or less. I can say. For example, TFT
In the photomask for forming a channel, with the miniaturization of the TFT channel portion, the pattern tends to be miniaturized rapidly. When such a pattern is also inspected by using the conventional method, a pseudo defect due to the vibration of the stage of the inspection machine or the image shift of the upper and lower lenses, and other pseudo defects peculiar to the fine pattern are generated. If the sensitivity is lowered to a level at which no defect is detected, there is a problem that the defect detection guarantee level cannot be obtained.

In order to solve such a problem, the applicant of the present invention has previously found that a transmission signal obtained by scanning a pattern in a mask is not a comparison inspection but a transmission defect which is provided in advance. An application was filed for a method of detecting a defect using a threshold value (Japanese Patent Application No. 2001-244071).
issue). Hereinafter, a specific example of this method will be described. Figure 4 (1)
Indicates a case where no defect has occurred in any of the light shielding portion 1, the transmission portion 2, and the gray tone portions 3 and 5, and the arrow indicates the scanning direction (inspection direction) of the lens of the inspection device. Figure 4
(2) is the transmittance signal 7 obtained along the scanning direction
Indicates. The transmittance signal has a transmittance of 0% at the light-shielding portion 1, a transmittance of 100% at the transmitting portion 2, and a transmittance of 5 at the graytone portions 3 and 5.
It is 0%. Here, as shown in FIG. 4B, for example, the threshold value of the transmittance defect in the gray tone part (upper limit side 8
a, the lower limit side 8b) is provided, and when these threshold values are exceeded, it is determined that a transmittance defect has occurred in the gray tone portion. In this case, as shown in FIG. 1B, the threshold value of the transmittance defect in the normal light shielding portion and the transmission portion (the transmission portion side 9a,
By further providing a light-shielding portion side 9b) and determining that a transmittance defect has occurred in the light-shielding portion or the light-transmitting portion when these threshold values are exceeded, deterioration of the light-shielding property in the light-shielding portion or transparency in the light-transmitting portion is detected. It is preferable because it is possible to simultaneously detect semi-transmissivity transmittance defects such as deterioration defects. Further, in this case, the transmittance defect extraction threshold value 8 for the gray tone part
a and 8b and the transmittance defect extraction thresholds 9a and 9b for the normal light-shielding portion and the transparent portion, the transmittance defect region 10 is formed.
By using a and 10b, the transmittance defect can be detected regardless of the inspection region. That is, the transmittance defect areas 10a, 1
If it is in 0b, it can be determined that there is a transmittance defect regardless of the inspection region. According to the above inspection method, it is possible to directly inspect the transmittance itself, and therefore it is possible to guarantee the transmittance in the gray tone portion. Further, since the inspection method does not perform pattern recognition, it is possible to avoid the problem that pseudo defects occur due to the unique pattern shape during fine pattern inspection (the problem that the threshold cannot be lowered), and therefore the threshold can be lowered. Thus, it is possible to obtain sensitivity that satisfies the required accuracy (specification) of a gray-tone mask or a photomask including a fine pattern.
Further, not the pattern defect signal based on the comparison of patterns but the transmittance defect extraction threshold value provided in advance for the transmittance signal is used, so that the fine pattern which becomes a problem by taking the difference signal between the transmittance signals in the comparison inspection. It is possible to avoid the problem of amplification of the base signal level (problem that the threshold cannot be lowered) peculiar to the above, and therefore, it is possible to lower the threshold and increase the sensitivity to meet the required accuracy of the gray-tone mask and the photomask including a fine pattern. It is possible to obtain. Furthermore, since it does not require a comparison object,
Inspection with a single eye is possible. Furthermore, by changing the transmittance defect extraction threshold value for the graytone portion, it becomes possible to guarantee the transmittance in accordance with the exposure conditions of the graytone mask used by the user.

However, when the transmittance of the gray tone portion composed of a fine pattern as shown in FIG. 1A is measured by scanning in the direction of the arrow using the method as described above, the transmission of the fine pattern area is originally assumed. When the ratio should be uniform, for example, 50%, the transmittance may fluctuate along the shape of the fine pattern as shown in FIG. 1 (2). The threshold value of the transmittance defect (upper limit side 8a, lower limit side 8b) is exceeded,
Since it is detected as a pseudo defect of the transmittance, there is a problem that the transmittance defect cannot be substantially detected. This means that the transmittance characteristics of the gray tone part obtained by the inspection device and the transmittance characteristics of the gray tone part when the transfer pattern is actually obtained on the resist of the transfer target substrate by using the gray tone mask are transferred. It may be caused by the fact that there are cases where the optical conditions of the exposure apparatus used for are different. Therefore, under the setting conditions of the exposure device used for transfer, it is conceivable that the gray tone portion should have a uniform transmittance (for example, 50%), but the transmittance signal of the inspection device may not.
Further, the same problem also occurs in a photomask having a fine pattern such as a photomask for forming a TFT channel portion or a photomask having a fine and highly precise pattern such as a line & space having a line width of 3 μm or less. I can say.

The present invention has been made in order to solve the above problems, and as a pseudo defect of a transmittance signal due to a change in transmittance along the shape of a fine pattern as shown in FIG. 1 (2). An object of the present invention is to provide a defect inspection method, a defect inspection apparatus, and the like that can inspect even if there is a portion that is detected, without detecting this portion as a pseudo defect.

[0008]

The present invention has the following configuration. (Structure 1) A light-shielding portion, a light-transmitting portion, and a gray area for which the amount of light transmitted through this area is adjusted and the thickness of the photoresist is selectively changed by reducing the amount of light transmitted therethrough. A graytone mask having a tone portion, wherein the graytone portion comprises a region in which a light-shielding pattern is formed at a resolution limit or less of an exposure machine using the graytone mask. A step of scanning the graytone portion to obtain a transmittance signal, and performing a correction process on the transmittance signal to approximate the transmittance characteristic of the graytone portion when the graytone mask is used. When the transmittance signal after the correction processing exceeds a threshold value of the transmittance defect in the gray tone portion which is provided in advance, a defect occurs in the gray tone portion. And a step of determining that the graytone mask is defective. (Structure 2) A light-shielding portion, a light-transmitting portion, and an area in which the amount of light transmission is adjusted, and a gray color for reducing the amount of light transmitted through this area and selectively changing the film thickness of the photoresist. A graytone mask having a tone portion, wherein the graytone portion comprises a region in which a light-shielding pattern is formed at a resolution limit or less of an exposure machine using the graytone mask. Wherein the step of scanning the gray tone portion to obtain a transmittance signal, and the step of performing a blurring process for flattening the signal when there is a periodic fluctuation in the transmittance signal, And a step of determining that a defect has occurred in the graytone portion when the transmittance signal after the blurring process exceeds a threshold value of the transmittance defect in the graytone portion which is provided in advance. A method for inspecting a defect of a gray tone mask, which comprises: (Structure 3) A defect inspection method for a fine pattern portion in a photomask having a light shielding portion, a transparent portion, and a fine pattern portion, the step of scanning the fine pattern portion to obtain a transmittance signal, When there is a periodic variation in the rate signal, a step of performing a blurring process for flattening the signal, and the transmittance signal after the blurring process is performed by setting a threshold value of the transmittance in a fine pattern portion provided in advance. And a step of determining that a defect has occurred in the fine pattern portion when the number exceeds the limit. (Structure 4) Since the fine pattern portion has a (periodic) variation in the transmittance signal, the threshold value of the transmittance defect in the fine pattern portion which is provided in advance exceeds the threshold value and is detected as a pseudo defect of the transmittance. 4. The method for inspecting a defect of a photomask according to structure 3, wherein the defect inspection is a fine pattern. (Structure 5) A light-shielding part, a transmissive part, and a region where the amount of transmission is adjusted, and the amount of light transmitted through this region is reduced to selectively change the film thickness of the photoresist. A defect inspection apparatus for a gray-tone mask having a tone portion, wherein a pattern formed in the mask is scanned by a parallel light source and a light-receiving lens to detect a transmittance signal, and the gray level is included in the transmittance signal. A means for performing a correction process that approximates the transmittance characteristic of a gray tone portion when using a tone mask (for example, a means for performing a blurring process for flattening the transmittance signal when there is a periodic variation). ) And the transmittance signal,
A defect inspection apparatus comprising: at least means for setting a threshold value of a transmittance defect in a graytone portion; and means for determining that a transmittance defect has occurred in the graytone portion when the threshold value is exceeded. (Structure 6) A defect inspection apparatus for a photomask having a light shielding portion, a transmission portion, and a fine pattern portion that is usually difficult to inspect, wherein a pattern formed in the mask is scanned by a parallel light source and a light receiving lens, A means for detecting a transmittance signal; and a means for performing a correction process on the transmittance signal to approximate the transmittance characteristic of a gray tone portion when the gray tone mask is used (for example, the transmittance signal is subject to periodic fluctuations). In some cases, means for performing blurring processing for flattening the signal), means for setting at least a threshold value of the transmittance in the fine pattern portion for the transmittance signal, and a fine pattern when the threshold value is exceeded. And a means for determining that a defect has occurred in the part. (Structure 7) A method for manufacturing a gray-tone mask, comprising a defect inspection step of performing a defect inspection using the method according to Structure 1 or 2. (Structure 8) A method of manufacturing a photomask, comprising a defect inspection step of performing a defect inspection using the method according to Structure 3 or 4.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the method and apparatus for inspecting a graytone mask of the present invention, a transmittance signal obtained by scanning a graytone portion is converted into a transmittance signal as shown in FIG.
When there is a periodic fluctuation as shown in (2), the blurring process for flattening the signal is applied to
The transmittance signal as shown in (3) can be obtained, and the original transmittance characteristic (transmittance characteristic when using a gray tone mask), for example, can be corrected to a uniform transmittance signal around 50%. By performing a defect inspection based on this signal, it is possible to inspect a portion that would be detected as a pseudo defect of the transmittance signal when the blurring process is not performed, without detecting it as a pseudo defect. Therefore, it is possible to guarantee the transmittance of a portion that is detected as a pseudo defect of the transmittance signal when the blurring process is not performed.
Note that the blurring process of the present invention is a process of blurring the obtained signal to a point where the signal is most flattened in the measurement region, and this blurring process is a blurring function that has been conventionally used in image processing. Etc. can be used. Further, in the present invention, since it is sufficient to obtain the same effect as the blurring process, the transmittance signal obtained by scanning the graytone portion is approximated to the transmittance characteristic of the graytone portion when the graytone mask is used. The case where a correction process is performed is included.

In the present invention, the threshold value of the transmittance defect in the gray tone portion is preferably set to a level exceeding the base signal level 16 peculiar to the gray tone portion shown in FIG. As a result, the influence of the base signal level peculiar to the gray tone part can be eliminated. In this case, it is preferable that the transmittance defect extraction threshold value is set with reference to the center value of the base signal level 16. Also,
By setting the transmittance defect extraction thresholds at the upper and lower limits of the allowable transmittance of the gray tone portion, the transmittance of the gray tone portion can be guaranteed. Incidentally, since a normal gray tone mask for semiconductors has a small size, it is possible to perform a transmittance inspection of a gray tone portion or the like by a transmittance inspection machine or the like integrated with a microscope even if it takes some time and labor to some extent. In the case of a gray tone mask for LCD manufacturing, since the size is large and there are many places which are detected as pseudo defects of the transmittance signal when the above-mentioned blurring process is not performed, such inspection method requires a great burden on the process. Above, such a transmittance inspection is difficult, and therefore the defect inspection method of the present invention is indispensable for putting a gray tone mask for LCD manufacturing into practical use. This applies not only to the LCD (liquid crystal display) manufacturing mask but also to other display devices. In addition,
The LCD manufacturing mask includes all the masks necessary for manufacturing the LCD, for example, a mask for forming a TFT (thin film transistor), a low temperature polysilicon TFT, a color filter and the like. Other display device manufacturing masks include all masks required for manufacturing an organic EL (electroluminescence) display, a plasma display, and the like.

Further, according to the photomask manufacturing method and the manufacturing apparatus of the present invention, the pattern portion is scanned even for a fine and highly accurate pattern such as a line & space having a line width of 3 μm or less in the photomask. By performing a blurring process on the signal obtained in this way, a certain uniform transmittance is obtained, and by performing a defect inspection such as a shape and a size based on this signal, a fine and highly accurate defect can be detected. A photomask including such a fine pattern is a photomask for LCD manufacturing, a photomask for manufacturing a display device such as an organic EL display or a plasma display, and is a fine mask for forming a TFT channel portion, a contact hole portion, or the like. Examples thereof include a photomask having a pattern.

[0012]

EXAMPLES A defect inspection method and a defect inspection apparatus for a graytone mask having a graytone portion will be specifically described below. (Embodiment 1) In Embodiment 1, as shown in FIG. 2A, a defect inspection of a gray tone portion (transmittance 30%) is performed. The defect inspection apparatus used here is an apparatus having the following configuration. The defect inspection apparatus has means for scanning the pattern formed in the mask with a parallel light source and a light receiving lens to detect a transmittance signal. In particular,
For example, a parallel light source (a spot light source corresponding to a lens or a mask whole surface irradiation light source) provided on one side of the mask, a light receiving lens provided on the other side of the mask, and the mask and the lens are moved relative to each other. And a means for scanning the entire area (usually a mask stage moving means), by which the transmitted light is received by the lens along the scanning direction.
Further, for example, the CCD line sensor arranged in the lens unit detects the transmittance signal. Further, this defect inspection device has a function for blurring the detected transmittance signal.

The transmissivity signal is sent to a defect detection circuit having a transmissivity defect extraction threshold of a gray tone part and a transmissivity defect extraction threshold of a normal part, and a transmissivity defect is determined. In the defect detection circuit, when the transmittance signal having the transmittance in the intermediate region for a certain period of time exceeds the upper limit or the lower limit of the transmittance defect extraction threshold for the gray tone part, it is determined to be the transmittance defect of the gray tone part. Further, if the transmittance signal in the vicinity of 0% transmittance for a certain period of time is higher than the transmittance defect extraction threshold for the light shielding portion, it is determined to be the transmittance defect of the light shielding portion. Similarly, when the transmittance signal in the vicinity of 100% transmittance for a certain period of time is lower than the transmittance defect extraction threshold value for the transparent portion, it is determined to be the transmittance defect of the transparent portion. In these cases, the edge signal or the like is not determined to be a transmittance defect. Further, it can be determined in which area the defect has occurred depending on which threshold is used for detection.

Using such a device, defect inspection was performed in the following procedure. First, the lens of the inspection device was scanned in the gray tone portion in the direction of the arrow in FIG. 2 (1), and the transmittance signal was detected by the CCD line sensor arranged in the lens unit. The transmittance signal at this time is shown in FIG. Next, blurring processing was performed using the blurring processing function provided in the above apparatus. In this blurring process, first, in order to determine the best blurring point at which the transmittance is 30% and a constant transmittance signal is obtained, an experiment in which the blurring amount is changed as shown in FIG. Figure 2
(4) was determined as the best blur point. Then, blurring processing was performed by applying this filter coefficient. Next, as shown in FIG. 2 (4), when the transmittance signal after the blurring process determined in the above step is inspected, it is detected as a pseudo defect of the transmittance signal when the blurring process is not performed. It was possible to inspect without detecting a defective portion as a pseudo defect. Therefore, it becomes possible to guarantee the transmittance of a portion which is detected as a pseudo defect of the transmittance signal when the blurring process is not performed.

(Embodiment 2) Embodiment 2 is the same as Embodiment 1 except that the graytone portion to be inspected is a graytone portion having a line width error as shown in FIG. 3 (1). The test was performed using the method. FIG. 3B is the same as FIG.
It is a transmittance signal when the graytone part of (1) is scanned in the direction of the arrow. FIG. 3C shows a transmittance signal obtained by adding blurring processing to the transmittance signal. An inspection was performed in advance using a defect threshold value set to a level exceeding the base signal level peculiar to the gray tone part, and FIG.
As shown in, the transmission defect based on the line width error could be detected. Further, similarly to the first embodiment, it is possible to inspect a portion which is detected as a pseudo defect of the transmittance signal when the blurring process is not performed, without detecting it as a pseudo defect. From these facts, it becomes possible to guarantee the transmittance and the line width for a portion which is detected as a pseudo defect of the transmittance signal when the blurring process is not performed.

(Example 3) In Example 3, the same method as in Example 2 was applied to the case where fine protrusion defects (black defects) were present in the line-and-space gray tone portion (transmittance 50%). Was used to perform the inspection. As a result,
In the same manner as shown in (4), the transmittance defect based on the minute protrusion defect could be detected.

The present invention is not limited to the above-described embodiments and the like. In the above embodiment, the defect inspection of only the gray tone part was described.
As described in the description of No. 244071, the transmittance defect inspection of the light shielding portion and the light transmitting portion may be simultaneously performed. However, blurring processing is not required in the inspection of the light-shielding portion and the light-transmitting portion. Further, in the above embodiment, the inspection of the graytone portion of the graytone mask has been described.
The present invention is not limited to this, and can be applied to, for example, a photomask including a fine pattern similar to that of the gray tone part, such as a photomask for forming a TFT channel part. Even in that case, it is possible to perform a highly accurate defect inspection without detecting a portion which is detected as a pseudo defect of the transmittance signal when the blurring process is not performed, as a pseudo defect.

[0018]

As described above, according to the present invention, since the transmittance signal obtained by the inspection apparatus is subjected to the correction processing so as to approximate the transmittance characteristic when the gray tone mask is used, the gray tone It is possible to guarantee the defect of the part with high accuracy and the guarantee of the transmittance. Further, it is possible to inspect a photomask including a graytone portion of a graytone mask and a fine pattern without detecting a portion which is detected as a pseudo defect of the transmittance signal when the blurring process is not performed as a pseudo defect. Become. Therefore, it is possible to guarantee the transmittance of a portion that is detected as a pseudo defect of the transmittance signal when the blurring process is not performed. Further, it is possible to detect a line width error and a fine protrusion defect in a photo mask including a gray tone portion of the gray tone mask and a fine pattern.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an outline of a defect inspection method of the present invention.

FIG. 2 is a diagram for explaining a defect inspection method according to the first embodiment.

FIG. 3 is a diagram illustrating a defect inspection method according to a second embodiment.

FIG. 4 is a diagram for explaining a defect inspection method according to a prior application by the applicant of the present application.

FIG. 5 is a diagram for explaining a base signal level specific to a gray tone part.

6A and 6B are views for explaining a gray-tone mask, where FIG. 6A is a partial plan view and FIG. 6B is a partial sectional view.

FIG. 7 is a diagram for explaining a conventional defect inspection method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light-shielding portion 2 light-transmitting portion 3 gray-tone portion 3a light-shielding pattern 3b light-transmitting portion 3c semi-transmissive film 5 gray-tone portion 7 transmittance signal 8a transmittance defect extraction threshold (upper limit) for gray-tone portion 8b transmittance for gray-tone portion Defect extraction threshold (lower limit) 9a Transmissivity defect extraction threshold 9b Transmissivity defect extraction threshold 11 White defect 12 Black defect 13 Transmittance signal

Claims (8)

[Claims] 1. A light-shielding portion, a light-transmitting portion, and a region in which the amount of transmission is adjusted, and an object thereof is to reduce the amount of light transmitted through this region and selectively change the film thickness of the photoresist. A graytone mask having a graytone portion, wherein the graytone portion is a defect inspection of the graytone portion in the graytone mask including a region formed with a light-shielding pattern below a resolution limit of an exposure machine using the graytone mask. A method, comprising: scanning the graytone portion to obtain a transmittance signal; and performing a correction process on the transmittance signal to approximate the transmittance characteristic of the graytone portion when the graytone mask is used. When the transmittance signal after the correction process exceeds the threshold value of the transmittance defect in the gray tone portion which is provided in advance, a defect is generated in the gray tone portion. A method of inspecting a defect of a gray tone mask, which comprises: 2. A light-shielding portion, a light-transmitting portion, and a region where the amount of transmission is adjusted, and the object is to reduce the amount of light transmitted through this region and selectively change the film thickness of the photoresist. A graytone mask having a graytone portion, wherein the graytone portion is a defect inspection of the graytone portion in the graytone mask including a region formed with a light-shielding pattern below a resolution limit of an exposure machine using the graytone mask. A method, wherein the step of scanning the graytone portion to obtain a transmittance signal, and a step of performing a blurring process for flattening the signal when the transmittance signal has periodic fluctuations, And a step of determining that a defect has occurred in the graytone part when the transmittance signal after the blurring process exceeds a threshold value of the transmittance defect in the graytone part which is provided in advance. A method for inspecting a defect of a gray tone mask, comprising: 3. A defect inspection method for a fine pattern portion in a photomask having a light shielding portion, a transparent portion, and a fine pattern portion, the method comprising: scanning the fine pattern portion to obtain a transmittance signal. When there is a periodic fluctuation in the transmittance signal, a step of performing blurring processing for flattening the signal, and the transmittance signal after the blurring processing is a threshold value of transmittance in a fine pattern portion provided in advance. And a step of determining that a defect has occurred in the fine pattern portion when the number of defects exceeds, and a defect inspection method for a photomask, comprising: 4. The fine pattern portion has a (periodic) variation in the transmittance signal, and therefore exceeds a threshold value of the transmittance defect in the fine pattern portion which is provided in advance, and is detected as a pseudo defect of the transmittance. The photomask defect inspection method according to claim 3, wherein the photomask has a fine pattern. 5. A light-shielding portion, a light-transmitting portion, and a region where the amount of transmission is adjusted, and an object thereof is to reduce the amount of light transmitted through this region and selectively change the film thickness of the photoresist. A device for inspecting a defect of a graytone mask having a graytone part, wherein a pattern formed in the mask is scanned by a parallel light source and a light receiving lens, and a transmittance signal is detected; Means for performing a correction process to approximate the transmittance characteristic of the graytone portion when using the graytone mask; means for setting the threshold value of the transmittance defect in at least the graytone portion for the transmittance signal; and exceeding the threshold value. And a means for determining that a transmissivity defect has occurred in the gray-tone portion in the case of the above. 6. A defect inspection apparatus for a photomask having a light-shielding portion, a transmission portion, and a fine pattern portion that is usually difficult to inspect, wherein a pattern formed in the mask is scanned by a parallel light source and a light-receiving lens. A means for detecting a transmittance signal; a means for performing a correction process on the transmittance signal to approximate the transmittance characteristics of a graytone portion when the graytone mask is used; and at least a fine pattern for the transmittance signal. A defect inspecting apparatus comprising: a unit for setting a threshold value of the transmittance of a portion; and a unit for determining that a defect has occurred in the fine pattern portion when the threshold value is exceeded. 7. A method of manufacturing a gray tone mask, comprising a defect inspection step of performing a defect inspection using the method according to claim 1. 8. A method of manufacturing a photomask, comprising a defect inspection step of performing a defect inspection using the method according to claim 3.