JP2004151622A - Inspecting apparatus of mask defect and method for inspecting mask defect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect defects or classify defects with respect to inspecting defects in a halftone phase shift mask. <P>SOLUTION: The inspecting apparatus of mask defects to inspect defects in a halftone phase shift mask 2 having a mask pattern including a half-light shielding shifter pattern part and a transmitting opening pattern formed on a transparent substrate is equipped with: irradiating means (1, 3, 5) to irradiate the phase shift mask 2 with inspection light for inspecting defects; first image acquiring means (7, 8) to acquire images of transmitted light through the phase shift mask by irradiation with the inspection light; second image acquiring means (4, 9, 10) to acquire images of reflected light on the phase shift mask 4 by irradiation with the inspection light; and an inspecting means (13) to inspect defects in the phase shift mask 2 by using the images of transmitted light and images of reflected light. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mask defect inspection device and a mask defect inspection method for inspecting a defect of a photomask, and more particularly to a mask defect inspection device and a mask defect inspection method suitable for use in defect inspection of a halftone type phase shift mask. .
[0002]
[Prior art]
With the miniaturization of semiconductors, the size of a pattern formed on a photomask for exposure has become smaller and smaller. In contrast to a method of forming a finer pattern by shortening the exposure wavelength, a super-resolution technique has been widely and generally used in recent years as a measure for extending the life of an exposure apparatus. While super-resolution technology has the advantage of making patterns finer, it has the advantage that line width errors and defects that occur on the mask are transferred to the wafer compared to when the exposure wavelength is shortened. There is a disadvantage that the influence on the width is large.
[0003]
Until now, comparing the size of defects allowed on a photomask with a black defect and a pinhole defect, the pinhole defect has a smaller effect on the transfer line width on the wafer to a size larger than the black defect. I was However, in the case of a super-resolution technique using a halftone type phase shift mask, when a pattern having an exposure wavelength or less is formed, the transferability of pinhole defects on the mask is significantly increased. Therefore, when compared with the defect of the same size, the transfer line width variation of the pinhole defect is almost the same as that of the black defect.
[0004]
Further, in a mask defect inspection apparatus using transmitted light as described in Non-Patent Document 1 below, for example, detection of a white defect such as a pinhole defect has a smaller transmission portion compared to a black defect. Although it has been considered difficult to perform the detection, the necessary and sufficient detection sensitivity has been obtained because the influence on the pattern line width variation on the wafer is small as described above. Until now, detection of white defects has been enhanced by shortening the inspection light wavelength of a mask defect inspection apparatus, but it has become difficult to obtain sufficient defect detection sensitivity only by shortening the wavelength. .
[0005]
[Non-patent document 1]
"Proceedings of SPIE", 2001, Vol. 4186, p. 165-172
[0006]
[Problems to be solved by the invention]
In particular, when inspecting a defect of a halftone type phase shift mask using an image of transmitted light transmitted through the phase shift mask, a pattern portion formed of a semi-light-shielding shifter film (hereinafter, referred to as a “shifter”). In some cases, it may be difficult to detect a defect existing on the “pattern portion”), or even if this defect can be detected, it cannot be determined whether the defect is a pinhole defect or a black defect.
[0007]
That is, in a halftone type phase shift mask, a pinhole defect exists on a shifter pattern portion adjacent to a transmissive opening pattern portion (a hole pattern formed by opening a shifter film), and the defect size is determined by the mask. When the size of the pinhole defect is smaller than the wavelength of the inspection light used in the defect inspection apparatus, the size of the pinhole defect (pinhole size) becomes smaller as the size of the pinhole defect becomes smaller due to the phase shift effect of the phase shift mask. Light transmittance (hereinafter, also simply referred to as “transmittance”) decreases.
[0008]
Specifically, as shown in FIG. 4, as the size of the pinhole defect (pinhole size) decreases, the transmittance at the pinhole defect portion decreases accordingly. FIG. 5 is an image diagram showing the relationship between the size of the pinhole defect and the transmittance at the pinhole defect portion. As shown in FIGS. 5A to 5E, on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, the size of the pinhole defect Pd existing there (the diameter if the pinhole is a circle) is reduced. When the defect size gradually decreases, the transmittance at the pinhole defect Pd becomes equal to or lower than the transmittance of the shifter pattern portion Sp when the defect size is equal to or smaller than a certain size. Therefore, in a situation where the transmittance at the pinhole defect Pd becomes equal to the transmittance at the shifter pattern part Sp, this cannot be detected as a defect. Further, in a situation where the transmittance at the pinhole defect Pd portion is lower than the transmittance at the shifter pattern portion Sp, it becomes impossible to determine whether the defect is a pinhole defect or a black defect.
[0009]
In particular, in the case of a phase shift mask, even if the pinhole defect has a small size smaller than the inspection light wavelength, the linewidth dimension of the transfer pattern on the wafer is increased due to the increase in the transferability of the pinhole defect by the super-resolution technique. Therefore, it is important to accurately detect and classify this in a mask defect inspection.
[0010]
[Means for Solving the Problems]
A mask defect inspection apparatus according to the present invention inspects a halftone type phase shift mask formed by forming a mask pattern including a semi-light-shielding shifter pattern portion and a transmissive opening pattern portion on a transparent substrate. A mask defect inspection apparatus for irradiating the phase shift mask with inspection light for defect inspection, and transmitting the phase shift mask through the phase shift mask when the phase shift mask is irradiated with inspection light. A first image acquisition unit for acquiring an image of light, and a second image acquisition unit for acquiring an image of light reflected by the phase shift mask when the phase shift mask is irradiated with inspection light by the irradiation unit. It is provided with a configuration.
[0011]
In the mask defect inspection apparatus having the above configuration, when the phase shift mask is irradiated with the inspection light by the irradiation unit, the image of the transmitted light transmitted through the phase shift mask is acquired by the first image acquisition unit, and the phase shift mask is acquired. By acquiring the image of the reflected light reflected by the second image acquiring means, the defect of the phase shift mask can be inspected using both the transmitted light image and the reflected light image. As a result, even for a defect that cannot be detected only from an image of transmitted light or a defect whose type cannot be classified, defect detection and defect classification can be performed accurately.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0013]
FIG. 1 is a schematic diagram illustrating a configuration example of a mask defect inspection apparatus according to an embodiment of the present invention. In FIG. 1, a light source 1 emits inspection light for defect inspection, and is a main part of an irradiation unit. As the inspection light emitted from the light source 1, for example, light having a wavelength of 266 nm can be used. An illumination lens 3, a half mirror 4, and a condenser lens 5 are provided between the light source 1 and the phase shift mask 2 to be inspected. Among them, the illumination lens 3 and the condenser lens 5 together with the light source 1 constitute irradiation means.
[0014]
The phase shift mask 2 includes a mask pattern including a semi-light-shielding shifter pattern portion (a pattern portion formed of a shifter film) and a transmissive opening pattern portion (a hole pattern in which the shifter film is opened), which is made of a transparent material such as glass. It is a halftone type phase shift mask formed on a substrate. The phase shift mask 2 is set horizontally on an inspection stage 6 movable in two horizontal axis directions (XY directions). An objective lens 7 is disposed on the opposite side of the condenser lens 5 (below the inspection stage 6) with the inspection stage 6 interposed therebetween. The objective lens 7 forms an image of the light transmitted through the phase shift mask 2 on the light receiving surface of the photoelectric conversion element 8 for capturing an image.
[0015]
On the other hand, an objective lens 9 is provided in the direction in which the light is reflected by the half mirror 4 (to the right in FIG. 1). The objective lens 9 forms an image of light reflected by the phase shift mask 2 and reflected by the half mirror 4 on a light receiving surface of a photoelectric conversion element 10 for capturing an image. Here, the photoelectric conversion element 8 constitutes first image acquisition means together with the objective lens 7, and the photoelectric conversion element 10 constitutes second image acquisition means together with the half mirror 4 and the objective lens 9. is there. As the photoelectric conversion elements 8 and 10, a CCD (Charge Coupled Device) image sensor can be used. The focus position of the transmitted light by the objective lens 7 and the focus position of the reflected light by the objective lens 9 can be automatically adjusted by a focus control circuit (not shown).
[0016]
The photoelectric conversion element 8 generates an analog image signal (image signal) according to the amount of light received for each of a plurality of minute areas (read pixels) partitioned on the light receiving surface. On the other hand, the A / D conversion circuit (analog / digital conversion circuit) 11 digitizes the analog image signal generated from the photoelectric conversion element 8 to generate a digital image signal. Similarly, the photoelectric conversion element 10 generates an analog image signal according to the amount of light received for each of a plurality of minute areas partitioned on the light receiving surface, and the corresponding A / D conversion circuit 12 generates the analog image signal. The analog image signal generated from the element 10 is digitized to generate a digital image signal.
[0017]
The image signal generated from each of the A / D conversion circuits 11 and 12 is input to a common comparison circuit 13 together with mask data serving as design data (CAD data and the like) of the phase shift mask 2. The comparison circuit 13 develops each image signal provided from the A / D conversion circuits 11 and 12 into, for example, a two-dimensional image, and performs a defect inspection of the phase shift mask 2 using the two-dimensional image and the mask data. And outputs the inspection result as defect data.
[0018]
In the mask defect inspection apparatus having the above-described configuration, inspection light emitted from the light source 1 is converged by the condenser lens 5 and radiated to the phase shift mask 2 in a state of being made parallel by the illumination lens 3. At this time, the light transmitted through the phase shift mask 2 is captured as an image by the photoelectric conversion element 8 through the objective lens 7. The light reflected by the phase shift mask 2 reaches the half mirror 4 through the condenser lens 5, the optical path of which is bent (reflected) at a substantially right angle by the half mirror 4, and passes through the objective lens 9 to the photoelectric conversion element 10. Captured as an image. As a result, the photoelectric conversion element 8 acquires an image (mask image) of the transmitted light transmitted through the phase shift mask 2, and the photoelectric conversion element 10 acquires an image (mask image) of the reflected light reflected by the phase shift mask 2. Will be. The transmitted light image and the reflected light image obtained in this way are respectively supplied to a comparison circuit 13, and the comparison circuit 13 uses the respective images (the transmitted light image and the reflected light image) to generate the phase shift mask 2. Is inspected.
[0019]
Subsequently, a mask defect inspection method according to the embodiment of the present invention will be described. Here, a description will be given of a mask defect inspection method using the mask defect inspection apparatus having the above configuration as an example.
[0020]
First, when the inspection light emitted from the light source 1 is applied to the phase shift mask 2, the image of the transmitted light transmitted through the phase shift mask 2 and the image of the reflected light reflected by the phase shift mask 2 are respectively converted into photoelectric conversion elements. Acquired at 8,10. At this time, the transmitted light image acquired by the photoelectric conversion element 8 is taken into the comparison circuit 13 via the A / D conversion circuit 11, and the reflected light image acquired by the photoelectric conversion element 10 is acquired by the A / D conversion circuit. The signal is taken into the comparison circuit 13 via the line 12. The images of the transmitted light and the reflected light may be acquired at the same time, or one of them may be acquired first in any order.
[0021]
Next, the comparison circuit 13 extracts a defect included in each image using the image of the transmitted light and the image of the reflected light. Regarding the transmitted light image, the transmitted light image data and the reference mask data are compared and collated to confirm whether or not there is a difference between each of the inspection areas. Extract as a defect. Then, for each defect extracted from the transmitted light image, defect information such as its size (size data), position (coordinate data), and transmittance (hereinafter also referred to as “first defect information”) is obtained. . Similarly, regarding the image of the reflected light, the image data of the reflected light and the mask data are compared and collated to confirm whether or not there is a difference between the respective inspection areas. Extract as a defect. Then, for each defect extracted from the image of the reflected light, defect information (hereinafter also referred to as “second defect information”) such as its size (size data), position (coordinate data), and reflectance is obtained. . Here, the defect is extracted by comparing / collating the image data with the mask data. However, when sequentially acquiring images of the inspection area having the same pattern shape, a plurality of actually acquired image data are extracted. It is also possible to extract defects by comparing and matching.
[0022]
Next, the comparison circuit 13 detects the defect by comparing the first defect information and the second defect information with each other. In particular, when a defect exists on the shifter pattern portion adjacent to the opening pattern portion, this defect is detected as follows.
[0023]
First, when a pinhole defect exists on the shifter pattern adjacent to the rectangular opening pattern portion and the size of the pinhole defect is sufficiently large (that is, when the size of the pinhole defect is larger than the inspection light wavelength). In the first defect information obtained using the transmitted light image, the transmittance of the pinhole defect Pd is higher than the transmittance of the shifter pattern portion Sp, as shown in FIG. 2B, the reflectivity of the pinhole defect Pd portion is lower than the reflectivity of the shifter pattern portion as shown in FIG. 2B.
[0024]
On the other hand, if there is a black defect due to the attachment of foreign matter such as dust on the shifter pattern portion adjacent to the opening pattern portion, regardless of the size of the defect, the black defect is obtained using the transmitted light image. In the first defect information obtained, the transmittance of the black defect portion becomes lower than the transmittance of the shifter pattern portion, and in the second defect information obtained by using the image of the reflected light, the reflectance of the black defect portion becomes the shifter pattern portion. Lower than the reflectance.
[0025]
In this case, depending on whether the defect included in the first defect information obtained using the image of the transmitted light is a pinhole defect or a black defect, a large difference occurs in the transmittance of light transmitted through each defective portion. Occurs. Therefore, whether the defect existing on the shifter pattern portion Sp is a pinhole defect or a black defect can be accurately determined (determined) only by the first defect information based on the transmitted light image. That is, if the transmittance of the defect existing on the shifter pattern portion Sp adjacent to the opening pattern portion Hp is higher than the transmittance of the shifter pattern portion Sp, it is determined to be a pinhole defect, and if it is lower, it is determined to be a black defect. .
[0026]
On the other hand, when a pinhole defect is present on the shifter pattern adjacent to the opening pattern portion and the size of the pinhole defect is reduced to a certain size or less (that is, the inspection light wavelength or less), the influence of the phase shift effect in the phase shift mask. Thus, the transmittance at the pinhole defect portion is equal to or lower than the transmittance of the shifter pattern portion.
[0027]
When the transmittance at the pinhole defect portion is equal to the transmittance of the shifter pattern portion, the pinhole defect does not appear in the image of the transmitted light. A defect inspection is performed using both information. That is, in the first defect information obtained using the transmitted light image, as shown in FIG. 2C, the transmittance of the pinhole defect Pd portion is equal to the transmittance of the shifter pattern portion Sp. In the second defect information obtained by using the image of the reflected light without the existence of the defect itself, as shown in FIG. 2D, the reflectivity of the pinhole defect Pd is the reflection of the shifter pattern portion Sp. Lower than the rate. Therefore, a defect that satisfies this condition, that is, a defect that is not recognized as a defect in the first defect information and appears with a lower reflectance than the shifter pattern portion Sp in the second defect information is defined as a pinhole defect Pd. To detect. In other words, when a defect not included in the first defect information and included in the second defect information exists on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, this defect is detected as a pinhole defect.
[0028]
If the transmittance at the pinhole defect portion is lower than the transmittance of the shifter pattern portion, the pinhole defect appears in the transmitted light image in the same state as the black defect. A defect inspection is performed using both the information and the second defect information. That is, in the first defect information obtained by using the image of the transmitted light, as shown in FIG. 2E, the transmittance of the pinhole defect Pd becomes lower than the transmittance of the shifter pattern portion Sp, and the reflection occurs. Even in the second defect information obtained using the light image, as shown in FIG. 2F, the reflectance of the pinhole defect Pd portion is lower than the reflectance of the shifter pattern portion Sp. In this case, although the existence of the defect itself can be detected, the type of the defect (pinhole defect / black defect) is determined (classified) from the difference in transmittance in the first defect information and the difference in reflectance in the second defect information. )Can not do it. Therefore, in the present invention, the type of a defect is determined as follows using the phase shift effect of the phase shift mask.
[0029]
In other words, for a pinhole defect of a single minute size (smaller than the wavelength of the inspection light) existing on the shifter pattern portion, the position where the transmittance is reduced due to the pinhole defect is different from the position where the reflectance is reduced. It becomes. This is because, as described above, when the pinhole defect Pd of a minute size exists on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, the secondary peak of light generated near the edge of the opening pattern portion Hp and the pinhole defect This is due to the phenomenon that the peak of the light transmitted through the defect Pd interferes and the position where the light is blocked by the pinhole defect Pd is shifted from the position where the pinhole defect Pd actually exists. Therefore, as shown in FIG. 3A, when inspecting the phase shift mask 2 in which the pinhole defect Pd of a minute size has occurred on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, the reflected light image As shown in FIG. 3B, the pinhole defect Pd appears at the same position as the actual defect position (the position of the pinhole defect Pd shown in FIG. 3A). Due to the interference between the light transmitted through the defect Pd and the light transmitted through the opening pattern portion Hp near the pinhole defect Pd, the position of the pinhole defect Pd is shifted from the actual defect position as shown in FIG. Also appear in a state shifted to the opening pattern portion Hp side.
[0030]
Therefore, when a common defect included in both the first defect information and the second defect information exists on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, this defect has a minute size smaller than the inspection light wavelength. In the case of the pinhole defect Pd, there is a relative shift (ΔX) between the position (center position) of the defect appearing in the image of transmitted light and the position (center position) of the defect appearing in the image of reflected light. On the other hand, when a small-sized black defect exists on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, the position where the transmittance is reduced and the position where the reflectance is reduced due to the black defect are the same as each other. Become. Therefore, in the case of a black defect, there is no relative displacement between the position of the defect appearing in the transmitted light image and the position of the defect appearing in the reflected light image irrespective of the defect size.
[0031]
From these facts, due to the effect of the phase shift effect in the phase shift mask, a defect having a size (micro size) in which the transmittance at the pinhole defect portion is lower than the transmittance of the shifter pattern portion is present on the shifter pattern portion. When the defect appears, the position of the defect in the first defect information and the position of the defect in the second defect information are compared with each other, and the type of the defect is determined based on the relative positional deviation ΔX. I do. In other words, when there is a common defect included in both the first and second defect information and having a lower transmittance than the shifter pattern portion Sp on the shifter pattern portion Sp adjacent to the opening pattern portion Hp, The type of the defect is determined based on the relative positional deviation amount ΔX of the common defect.
[0032]
Specifically, the relative positional deviation amount ΔX of the common defect included in the first and second defect information is obtained by, for example, coordinate calculation, and the obtained relative positional deviation amount ΔX is set in advance. Check whether it is over the reference amount. If the relative displacement amount ΔX is equal to or larger than the reference amount, the defect is determined to be a pinhole defect Pd. If the relative displacement ΔX is less than the reference amount, the defect is determined to be a black defect.
[0033]
Incidentally, the relative positional shift amount ΔX generated when the minute-sized defect included in the first and second defect information is the pinhole defect Pd is determined by the wavelength of the inspection light in the mask defect inspection apparatus, the halftone type. It depends on the exposure wavelength when exposing the phase shift mask. Therefore, using a test mask (halftone type phase shift mask) in which a fine pinhole defect Pd of a minute size is intentionally formed in advance, the size of the pinhole defect Pd and the relative displacement amount caused by each defect size It is desirable to measure ΔX experimentally and set the above-mentioned reference amount for judging the type of defect based on the measurement result.
[0034]
As an example, when the wavelength of the inspection light of the mask defect inspection apparatus is 266 nm and the exposure wavelength of the half-tone type phase shift mask is 193 nm, the reference light amount is set to 1 μm so that the image of the transmitted light and the reflection For a common defect appearing in both light images, the relative position shift ΔX of the common defect included in the first and second defect information obtained from each image is obtained, and the position shift ΔX Are 1 μm or more as pinhole defects Pd, and those with a size of less than 1 μm are determined as black defects.
[0035]
In the above embodiment, as a configuration of the mask defect inspection apparatus, the transmitted light image and the reflected light image captured by the respective photoelectric conversion elements 8 and 10 are compared via A / D conversion circuits 11 and 12, respectively. The comparison circuit 13 performs the defect inspection of the phase shift mask 2. However, the present invention is not limited to this. For example, the image of the transmitted light captured by the photoelectric conversion elements 8 and The image of light may be displayed on a monitor screen, and a defect inspection of the phase shift mask 2 may be performed on the monitor screen by visual inspection of an inspector.
[0036]
【The invention's effect】
As described above, according to the present invention, when inspecting a defect of a halftone type phase shift mask, the defect is detected by using both the image of the transmitted light transmitted through the phase shift mask and the image of the reflected light reflected by the phase shift mask. By performing the inspection, defect detection and defect classification can be accurately performed even for a defect that cannot be detected or classified only from an image of transmitted light. Accordingly, even when a pinhole defect of a minute size (not more than the inspection light wavelength) exists on the shifter pattern portion adjacent to the opening pattern portion, the pinhole defect can be reliably detected by distinguishing it from the black defect. As a result, the reliability of the defect inspection of the phase shift mask can be improved, and the variation of the transfer line width dimension can be suppressed by performing an appropriate correction process on the phase shift mask having the micro-sized pinhole defect. Can be.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration example of a mask defect inspection apparatus according to an embodiment of the present invention.
FIG. 2 is a diagram showing a transmitted light image and a reflected light image including a pinhole defect.
FIG. 3 is a diagram illustrating a shift of a defect position caused by a pinhole defect.
FIG. 4 is a diagram showing a relationship between the size of a pinhole defect and transmittance.
FIG. 5 is an image diagram showing a relationship between the size of a pinhole defect and transmittance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light source, 2 ... Phase shift mask, 8 and 10 ... Photoelectric conversion element, 13 ... Comparison circuit, Hp ... Open pattern part, Sp ... Shifter pattern part, Pd ... Pinhole defect

Claims (13)

A mask defect inspection device for inspecting a defect of a halftone type phase shift mask formed by forming a mask pattern including a semi-light-shielding shifter pattern portion and a transparent opening pattern portion on a transparent substrate,
Irradiation means for irradiating the phase shift mask with inspection light for defect inspection,
A first image acquisition unit that acquires an image of transmitted light transmitted through the phase shift mask when the phase shift mask is irradiated with the inspection light by the irradiation unit;
A mask defect inspection apparatus comprising: a second image acquisition unit configured to acquire an image of light reflected by the phase shift mask when the phase shift mask is irradiated with the inspection light by the irradiation unit. . Inspection means for inspecting the phase shift mask for defects using the transmitted light image acquired by the first image acquisition means and the reflected light image acquired by the second image acquisition means; The mask defect inspection apparatus according to claim 1, wherein: The inspection unit performs defect inspection by comparing first defect information obtained from the image of the transmitted light with second defect information obtained from the image of the reflected light. The mask defect inspection apparatus according to claim 2. The inspection means may include, in the comparison result of the first defect information and the second defect information, the second defect information not included in the first defect information on the shifter pattern portion adjacent to the opening pattern portion. 4. The mask defect inspection apparatus according to claim 3, wherein when a defect included in the defect information is present, the defect is detected as a pinhole defect. The inspection means may include, in a comparison result of the first defect information and the second defect information, both of the first and second defect information on the shifter pattern portion adjacent to the opening pattern portion. 4. When there is a common defect having a transmittance lower than that of the shifter pattern portion, the type of the defect is determined based on a relative displacement amount of the common defect. The mask defect inspection apparatus according to the above. 6. The mask defect according to claim 5, wherein the inspection unit determines that the defect is a pinhole defect when a relative displacement amount of the common defect is equal to or larger than a predetermined reference amount. Inspection equipment. 6. The mask defect inspection according to claim 5, wherein the inspection unit determines the defect as a black defect when a relative displacement amount of the common defect is smaller than a preset reference amount. apparatus. A mask defect inspection method for inspecting a defect of a halftone type phase shift mask formed by forming a mask pattern including a semi-light-shielding shifter pattern portion and a transmissive opening pattern portion on a transparent substrate,
Using the image of the transmitted light transmitted through the phase shift mask and the image of the reflected light reflected by the phase shift mask, the phase is obtained by irradiating the phase shift mask with inspection light for defect inspection. A mask defect inspection method for inspecting a shift mask for defects. The defect inspection is performed by comparing first defect information obtained from the transmitted light image with second defect information obtained from the reflected light image. Mask defect inspection method. In the comparison result of the first defect information and the second defect information, the first defect information is not included in the first defect information and is included in the second defect information on the shifter pattern portion adjacent to the opening pattern portion. 10. The mask defect inspection method according to claim 9, wherein when there is a defect to be detected, the defect is detected as a pinhole defect. As a result of comparison between the first defect information and the second defect information, both the first and second defect information are included on the shifter pattern portion adjacent to the opening pattern portion and the shifter pattern 10. The mask defect inspection according to claim 9, wherein when a common defect having a transmittance lower than that of the portion exists, the type of the defect is determined based on a relative displacement amount of the common defect. Method. 12. The mask defect inspection method according to claim 11, wherein the defect is determined as a pinhole defect when a relative displacement amount of the common defect is equal to or larger than a preset reference amount. 12. The mask defect inspection method according to claim 11, wherein the defect is determined as a black defect when a relative displacement amount of the common defect is less than a preset reference amount.

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