JP2012154976A - Manufacturing method of mask blank glass substrate, manufacturing method of mask blank, manufacturing method of transfer mask and manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance detection accuracy of an internal defect of a glass substrate by detecting an edge thereof even when a fluorescent light portion image is a haze-like image due to the internal defect of the glass substrate.SOLUTION: A manufacturing method of a mask blank glass substrate includes: a substrate preparation process for preparing a glass substrate having two main surfaces and four end surfaces when manufacturing the mask blank glass substrate; and a defect inspection process for detecting an internal defect by introducing inspection light having a wavelength of 200 nm or shorter into the glass substrate from any surface thereof. The defect inspection process determines whether or not fluorescent light generated due to the internal defect of the glass substrate exists by the inspection light and selects the glass substrate being determined that the fluorescent light does not exist by photographing the glass substrate from the any surface thereof and by performing image processing including a process for obtaining a light quantity difference by means of a remote difference with respect to the image being photographed.

Description

  The present invention relates to a mask blank glass substrate manufacturing method, a mask blank manufacturing method, a transfer mask manufacturing method, and a semiconductor device manufacturing method adapted to patterning with exposure light having a wavelength of 200 nm or less.

  In recent years, there has been an increasing demand for further pattern miniaturization in patterning using photolithography technology, and in response to this, the wavelength of exposure light used for patterning has been shortened and the output has been increasing. Specifically, a laser beam having a wavelength of 200 nm or less such as an ArF excimer laser having an exposure wavelength of 193 nm has been used.

  In the photolithography technology, a transfer mask having a thin film with a pattern formed on a glass substrate is used, and exposure light transmitted through the transfer mask is irradiated onto an object (such as a resist film on a semiconductor wafer). The pattern is transferred. It is necessary to use a glass substrate used for a transfer mask and a mask blank serving as an original plate thereof that does not have an optically nonuniform region that causes a reduction in the amount of exposure light. If there is an optically non-uniform region on the mask blank substrate, the exposure light incident on the glass substrate is optical when the transfer mask manufactured using this mask blank substrate is irradiated with exposure light to perform pattern transfer. Partly absorbed in the non-uniform region, the transmittance is locally reduced. If the exposure light whose light quantity has decreased is in a positional relationship such that it passes through a portion without a thin film pattern (light transmission part), the amount of exposure light that has passed through the light transmission part has decreased, so transfer The resist film on the target wafer cannot be sufficiently exposed. As a result, a defect is generated in the transfer pattern transferred to the resist film, transfer accuracy is lowered, and exposure transfer failure occurs.

  Until now, when manufacturing a glass substrate used for a mask blank, a defect inspection has been performed in which an optically non-uniform region is regarded as an internal defect and a glass substrate having no internal defect is selected. However, when laser light having a wavelength of more than 200 nm such as KrF excimer laser (wavelength: 248 nm) is applied to the exposure light, the transmittance does not decrease, but a high-energy laser such as an ArF excimer laser having a wavelength of 200 nm or less. In recent years, it has become clear that there is an internal defect, which is an optically non-uniform region where the transmittance decreases when light is applied to exposure light. It has been found that this type of internal defect has a characteristic of emitting fluorescence in addition to a characteristic of absorbing exposure light having a wavelength of 200 nm or less.

  A glass substrate used for a mask blank is generally a rectangular plate having two main surfaces on the front and back sides and four side surfaces orthogonal to the main surface. For example, the main surface has a rectangular shape of about 152 mm square. In this case, it has a thickness of about 6.3 mm. When inspecting an internal defect of this plate-like glass substrate, inspection light having a wavelength of 200 nm or less is incident from any side surface of the glass substrate, and image analysis is performed from any main surface orthogonal to the incident side surface. Images are taken with a CCD (Charge Coupled Device) camera and the obtained image is analyzed. For the analysis at this time, when a laser beam having a wavelength of 200 nm or less is incident, if the glass substrate has an internal defect, the absorbed light is converted and fluorescence is emitted at the internal defect portion. To do. As described above, a method of detecting an internal defect based on the presence or absence of a phenomenon that emits fluorescence with respect to a laser beam of 200 nm or less is used (see, for example, Patent Document 1).

JP 2007-86050 A

  When imaging the shape of the fluorescent light generated from an internal defect with a CCD camera, it is not known in advance where the internal defect exists, and the number of pixels of the CCD camera or the like is limited. It is necessary to use either a method for imaging the entire main surface of the substrate at a low magnification at a time, or a method for imaging the main surface of a glass substrate at a high magnification by dividing the main surface into a plurality of regions. However, when the entire main surface of the glass substrate is imaged at a low magnification at a time, the amount of fluorescence emitted from the internal defect is basically small, so the relative fluorescence area and the amount of fluorescence of the internal defect with respect to the whole become very small. Internal defects may not be detected. Therefore, generally, a method of dividing the image into a plurality of areas and imaging at a high magnification is used.

  Further, when detecting an internal defect by analyzing a captured image with an image analysis device, it is necessary to recognize an accurate shape of the internal defect in the image as much as possible. However, the impurities that generate fluorescence mixed into the internal defect may not only be concentrated and mixed with a high density, but also may be diffused and mixed with a low density. In this case, the area of the internal defect is a blurred haze-like image. In addition, even for impurities mixed in at a high density, if the image captured at the fluorescent emission point is not in focus, the area of the internal defect becomes a blurred haze-like image.

  In order to recognize the shape of the internal defect, conventionally, the light amount difference between each detected pixel to be processed and the adjacent pixel is finely differentiated (proximity difference differentiation process), and a predetermined slice level (threshold value) is obtained. ) The edge of the internal defect is obtained by discriminating pixels having the above differences, and the area of the internal defect is recognized. However, since the amount of fluorescent light emitted from the internal defect is basically small, the difference in the amount of light due to the differential processing of the proximity difference is very small, and the captured image may be the above-mentioned blurred haze-like defect image. Therefore, when the internal defect of the glass substrate is inspected using the invention described in Patent Document 1, the edge of the internal defect cannot be recognized and the internal defect may not be detected by the light amount difference by the differential processing of the proximity difference. .

  Further, the location of the internal defect on the glass substrate can be present not only on the surface layer of the substrate but also on the inside, and the depth of focus of the camera for image analysis is limited to a predetermined range. Therefore, when performing the differential processing of the proximity difference in order to grasp the shape of the internal defect, it is divided hierarchically in several steps in the thickness direction of the substrate according to the range of the depth of focus, and the focus is adjusted for each layer. It was necessary to image together. Therefore, when inspecting the internal defect of the glass substrate using the invention described in Patent Document 1, the main surface of the glass substrate is divided into a plurality of regions, and then the image is divided into several stages and focused and imaged. Thus, the processing speed of the inspection of the glass substrate may be deteriorated.

  Therefore, in order to solve the above problem, the object of the present invention is to improve the inspection processing speed when inspecting the internal defect of the glass substrate, and the fluorescent light emitting portion is blurred with a small light amount difference from the adjacent region. An object of the present invention is to provide a method of manufacturing a glass substrate for a mask blank in which an edge of an internal defect is detected and the detection accuracy of the internal defect is improved even in the case of a haze-like defect image.

  (1) In order to solve the above problems, in one aspect of the method for manufacturing a mask blank glass substrate according to the present invention, either a substrate preparation step of preparing a glass substrate having two main surfaces and four end surfaces, And a defect inspection step of detecting an internal defect by introducing inspection light having a wavelength of 200 nm or less from the surface into the glass substrate, wherein the defect inspection step is By photographing the glass substrate from the surface and performing image processing including processing for obtaining a light amount difference by remote difference with respect to the photographed image, presence or absence of fluorescence generated from an internal defect of the glass substrate by the inspection light. A glass substrate that is determined and determined to have no fluorescence is selected.

  In the present aspect described above, a process for taking a remote difference is employed instead of a conventional differential process for taking a proximity difference as a process for analyzing a captured image. In the conventional proximity difference differentiation process, the light amount difference between adjacent pixels of the captured image is calculated, whereas in the process of taking the remote difference in this aspect, the first processing target pixel and its first A light amount difference from a second pixel that is a predetermined pixel away from one processing target pixel is obtained. In general, an area of an internal defect in a captured image, that is, a fluorescent light emission portion extends over a plurality of pixels, and an edge of the fluorescent light emission portion also gradually decreases over a plurality of pixels.

  Therefore, in the process of taking a remote difference for obtaining a light amount difference between a pixel that is a predetermined pixel away from one processing target pixel in such an edge portion, the objective lens is placed on the fluorescent light emission portion of the mask blank glass substrate. Even if out of focus, or even if there is little difference in the difference in the proximity difference between adjacent pixels, the difference in the amount of light that is the sum of the difference in the difference in proximity between the adjacent pixels Thus, the light amount difference increases corresponding to the number of pixels up to the distant pixels. As a result, in this aspect, it becomes easier to detect the edge portion of the fluorescent emission point, which is difficult to detect in the image analysis using the conventional differential of the difference in the light amount distribution in the captured image plane. Since it is easy to detect the peak of the light quantity distribution, it is possible to easily identify the area of the internal defect.

(2) In another means of the method for manufacturing a mask blank glass substrate according to the present invention, the image processing calculates a light amount difference between a processing target pixel of the photographed image and a pixel not adjacent to the pixel. This is a process for creating a light amount distribution of a captured image.
In this means, the light quantity difference between adjacent pixels is calculated by creating the light quantity distribution of the picked-up image by using the two pixels for calculating the light quantity difference as the processing target pixel of the captured image and the pixels not adjacent to the pixel. As a result, the difference in the amount of light is greater than when creating a light amount distribution, making it easier to detect the edge of the fluorescent light emission point and the peak of the light amount distribution in the image plane. Can be easily identified.

(3) In other means of the method for manufacturing a mask blank glass substrate according to the present invention, the image processing calculates a light amount difference with a pixel that is 20 pixels or more away from a processing target pixel of the captured image. It is a process for creating a light amount distribution of a captured image.
In this means, the two pixels for calculating the light amount difference are set as a processing target pixel of the captured image and a pixel that is 20 pixels or more away from the pixel, and a light amount difference between adjacent pixels is created by creating a light amount distribution of the captured image. Since the difference in light quantity is clearly larger than when creating a light quantity distribution by calculating, it becomes easier to detect the edge part of the fluorescence emission point, and it becomes easier to detect the peak of the light quantity distribution in the image plane, It is possible to easily identify the area of the internal defect.

(4) In another means of the method for manufacturing a glass substrate for mask blank according to the present invention, the surface into which the inspection light is introduced is one of four end surfaces of the glass substrate, and the glass substrate is photographed. The surface to be performed is one of the two main surfaces of the glass substrate.
In this means, the inspection light is introduced from the end face of the glass substrate and the image is taken from the main surface, so that the thickness direction of the glass substrate is limited, so that high magnification imaging with a short working distance is possible. Therefore, the amount of fluorescence received due to minute internal defects can be increased, and detection can be facilitated.

(5) In another means of the method for producing a mask blank glass substrate according to the present invention, the surface for introducing the inspection light and the surface for photographing the glass substrate are polished to a mirror surface. .
In this means, the surface for introducing inspection light (for example, one of the end surfaces) and the surface to be photographed (for example, any of the main surfaces) in the mask blank glass substrate are polished to a mirror surface, so that the boundary surfaces thereof are polished. Inspection light and fluorescence scattering can be suppressed.

(6) The manufacturing method of the mask blank which concerns on this invention is on the main surface of the glass substrate for mask blanks manufactured with the manufacturing method of the glass substrate for mask blanks in any one of said (1)-(5). It has the process of forming the thin film for pattern formation.
In this means, the mask blank is manufactured by forming a thin film for pattern formation on the main surface of the glass substrate for mask blank manufactured by the method according to any one of (1) to (5) above. There is no internal defect which appears only with a laser beam having a wavelength of 200 nm or less on the glass substrate, and a high-quality mask blank can be provided. In addition, the yield is not deteriorated when the mask is inspected using laser light having a wavelength of 200 nm or less as inspection light.

(7) The transfer mask manufacturing method according to the present invention includes a step of forming a transfer pattern on the pattern forming thin film of the mask blank manufactured by the mask blank manufacturing method according to (6) above. Features.
In this means, since the mask blank described in the above (6) is used, the yield is not deteriorated when the transfer pattern is inspected using laser light having a wavelength of 200 nm or less as inspection light.

(8) A method of manufacturing a semiconductor device according to the present invention is characterized in that a circuit pattern is formed on a semiconductor wafer using the transfer mask described in (7) above.
In this means, since the transfer mask described in the above (7) is used, the yield is not deteriorated when the circuit pattern is formed on the semiconductor wafer using the laser light having a wavelength of 200 nm or less as the exposure light.

  (9) The mask blank manufacturing method according to the present invention includes a mask blank preparation step of preparing a mask blank including a thin film for pattern formation on one main surface of a glass substrate having two main surfaces and four end surfaces; A mask blank manufacturing method comprising: a defect inspection step of detecting an internal defect by introducing inspection light having a wavelength of 200 nm or less into the glass substrate from any surface, wherein the defect inspection step includes a pattern forming thin film The glass substrate is imaged by the inspection light by photographing the glass substrate from any surface other than the surface on which the light is formed and performing image processing including processing for obtaining a light amount difference by remote difference with respect to the photographed image. The presence or absence of fluorescence generated from the internal defect is determined, and a mask blank determined to have no fluorescence is selected.

  In this means, when inspecting the mask blank, the glass substrate is imaged from the main surface on the side where the thin film for pattern formation is not formed, and the presence or absence of fluorescence is obtained by obtaining a light amount difference by a remote difference with respect to the captured image. Since a mask blank is selected, a moire-like internal defect that appears only with a laser beam having a wavelength of 200 nm or less can be found by inspection even for a mask blank having a pattern forming thin film on the main surface. In addition, the yield is not deteriorated when the mask is inspected using laser light having a wavelength of 200 nm or less as inspection light.

  (10) The other means of the mask blank manufacturing method according to the present invention is such that the image processing calculates a light amount difference between a processing target pixel of the photographed image and a pixel not adjacent to the pixel. This is a process for creating a light amount distribution of a captured image.

  In this means, the light quantity difference between adjacent pixels is calculated by creating the light quantity distribution of the picked-up image by using the two pixels for calculating the light quantity difference as the processing target pixel of the captured image and the pixels not adjacent to the pixel. As a result, the difference in the amount of light is greater than when creating a light amount distribution, making it easier to detect the edge of the fluorescent light emission point and the peak of the light amount distribution in the image plane. Can be easily identified.

(11) According to another aspect of the mask blank manufacturing method of the present invention, the image processing may be performed by calculating a light amount difference with a pixel that is 20 pixels or more away from a processing target pixel of the captured image. It is a process for creating a light quantity distribution.
In this means, the two pixels for calculating the light amount difference are set as the processing target pixel of the photographed image and the pixel 20 pixels or more away from the pixel, and the light amount difference between adjacent pixels is created by creating the light amount distribution of the captured image. Since the difference in light quantity is clearly larger than when creating a light quantity distribution by calculating, it becomes easier to detect the edge part of the fluorescence emission point, and it becomes easier to detect the peak of the light quantity distribution in the image plane, It is possible to easily identify the area of the internal defect.

(12) In the method for manufacturing a transfer mask according to the present invention, a transfer pattern is applied to the pattern forming thin film of the mask blank manufactured by the mask blank manufacturing method according to any one of (9) to (11) above. It has the process of forming, It is characterized by the above-mentioned.
In this means, since the mask blank manufactured by the mask blank manufacturing method according to any one of (9) to (11) is used, a laser beam having a wavelength of 200 nm or less is used as the inspection light. The yield is not deteriorated when the transfer pattern is inspected.

(13) A method of manufacturing a semiconductor device according to the present invention is characterized in that a circuit pattern is formed on a semiconductor wafer using the transfer mask described in (12) above.
In this means, since the transfer mask described in the above (12) is used, the yield can be improved even when a circuit pattern is formed on the semiconductor wafer by using laser light having a wavelength of 200 nm or less as exposure light.

  According to the manufacturing method of the present invention, when an internal defect of a glass substrate is inspected, the processing speed of the inspection can be improved, and when the light amount difference between the region and the adjacent region is small and the fluorescent light emission point is in focus. Even in the case of a non-blurred haze-like defect image, the edge of the internal defect can be detected to increase the detection accuracy of the internal defect.

It is a manufacturing process figure which shows one Embodiment in the manufacturing method of the glass substrate for mask blanks which concerns on this invention, the manufacturing method of a mask blank, and the manufacturing method of the mask for transfer. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment in the defect inspection apparatus of the glass substrate which concerns on this invention, (a) is a side view which shows the defect inspection apparatus installed in a clean room, (b) is an outline of a defect inspection apparatus. It is a perspective view which shows the whole structure, (c) is a block diagram which shows the functional block of a defect inspection apparatus. (A), (b) is a side view which shows the positional relationship of the ArF excimer laser beam introduce | transduced from the laser irradiation apparatus of FIG. 2, and the glass substrate for mask blanks, (c) is the glass substrate for mask blanks, and CCD It is a figure which shows the relationship of the detection visual field which can be detected with a camera. (A) is a figure which shows the image which the computer of FIG. 2 image-received and received the dot-like defect which received light, (b) is the image which the computer of FIG. FIG. (A) is a figure which shows the graph of the luminance value which the computer of FIG. 2 image-processed and output the luminance value of the received spot-like defect for every pixel of a X direction, (b) is a figure of the received haze-like defect. 3 is a graph of luminance values output by the computer of FIG. 2 performing image processing for each pixel in the X direction. It is a figure which shows the positional relationship of two pixels from which the remote difference of this invention is taken. It is a graph which shows the difference of the luminance value which calculated | required the blue type | mold haze defect in Example 1, 2 by the remote difference of this invention. It is a graph which shows the difference of the luminance value which calculated | required the blue type | mold haze defect in Example 3, 4 by the remote difference of this invention. It is a graph which shows the difference of the luminance value which calculated | required the blue type | mold haze defect in the comparative examples 1 and 2 by the proximity | contact difference. It is a graph which shows the difference of the luminance value which calculated | required the blue-type point defect in the reference example 1 by the proximity difference. It is a graph which shows the difference of the luminance value which calculated | required the yellowish haze defect in Example 5, 6 by the remote difference of this invention. It is a graph which shows the difference of the luminance value which calculated | required the yellowish haze defect in Example 7 by the remote difference of this invention. It is a graph which shows the difference of the luminance value which calculated | required the yellowish haze defect in the comparative examples 3 and 4 by the proximity | contact difference.

  DESCRIPTION OF EMBODIMENTS Embodiments of a mask blank glass substrate manufacturing method, a mask blank manufacturing method, a transfer mask manufacturing method, and a semiconductor device manufacturing method for inspecting defects in the synthetic quartz glass substrate of the present invention will be described. Before, based on FIG. 1, an example is briefly shown about the outline | summary of each process. In the following description, the exposure light and the inspection light are ArF excimer laser light 25 (wavelength: 193 nm, pulsed laser) having an exposure wavelength and an inspection light wavelength of 200 nm or less.

<< Transfer Mask Manufacturing Method >>
For example, a translucent synthetic quartz glass substrate is processed into a mask blank glass substrate and a mask blank as described below, and a transfer pattern is formed on the thin film on the mask blank by photolithography. Is manufactured.

<Substrate Preparation Step> A synthetic quartz glass substrate 4 shown in FIG. 1A is cut out and manufactured from a light-transmitting synthetic quartz glass ingot. The size of the synthetic quartz glass substrate 4 is, for example, about 152 mm × about 152 mm × about 6.5 mm, or about 152.4 mm × about 152.4 mm × about 6.85 mm. The upper and lower surfaces of the synthetic quartz glass substrate 4 are the main surfaces 5 and 6, and a thin film (light-shielding film) 8 is formed to form the thin film pattern 13 in a later step. Further, chamfering is performed between the upper and lower main surfaces 5 and 6 of the synthetic quartz glass substrate 4 and the respective side surfaces 2, 3, 18, and 19 (see FIG. 2) orthogonal to each other to obtain a chamfered surface (52 in FIG. 3). And 53) formed.

  Next, among the side surfaces 2, 3, 18, and 19 of the synthetic quartz glass substrate 4, at least one end face (for example, the end face 51 in FIG. 3) is inspection light (ArF excimer laser light 25) that is also light having an exposure wavelength. ) Is polished to a mirror surface to such an extent that it can be introduced. Further, the surface photographed by the camera in order to detect the fluorescence emitted from the internal defect is also polished to a mirror surface. The surface into which the inspection light is introduced may be any of the four end surfaces and the two main surfaces. A configuration in which the inspection light is introduced from any one of the end faces is preferable because the internal region of the substrate to which the introduced inspection light reaches is wide, and the number of steps for moving the light source of the inspection light can be reduced. On the other hand, when the inspection light is introduced from one of the main surfaces, it is necessary to consider that when the inspection light is introduced from one of the end faces, an area where the inspection light does not reach is generated by the chamfered surface as described later. Disappears. Further, the surface for photographing the fluorescence emitted from the internal defect with the camera may be any of the four end surfaces and the two main surfaces, but it is preferable to photograph from one of the main surfaces because the captured image has higher definition. . In order to prevent the inspection light from entering the camera from being damaged, the inspection light source and the arrangement of the camera are adjusted, or the inspection light is placed between the camera and the surface to be imaged. An apparatus configuration that takes measures such as providing a wavelength filter that cuts the wavelength but transmits fluorescence emitted from an internal defect is also preferable.

  If only the purpose of performing the defect inspection process for detecting internal defects is taken into consideration, the two surfaces of the synthetic quartz glass substrate 4 may be polished to a mirror surface. However, in order to make the synthetic quartz glass substrate 4 selected as having no internal defects in the defect inspection process applicable as the mask blank substrate 7, all of the main surfaces 5, 6, each end surface and each chamfered surface are used. Must be polished to a mirror surface. Before the defect inspection process, when the three end surfaces that have not been mirror-polished are mirror-polished, the surfaces of the end surfaces that have already been mirror-polished may be roughened. Become. In addition, when one of the main surfaces is taken by the camera, it is difficult to polish only one of the main surfaces to a mirror surface and to mirror it, and both main surfaces need to be polished simultaneously. There is. Furthermore, in consideration of the detection accuracy of the defect inspection, it is desirable that the surface photographed by the camera to detect the fluorescence emitted from the internal defect is any main surface. For these reasons, it is desirable to polish the two main surfaces 5, 6, each end surface and each chamfered surface to a mirror surface before the defect inspection step. The surface roughness Ra (arithmetic average roughness) of the main surfaces 5 and 6 of the synthetic quartz glass substrate 4 is set to about 0.5 nm or less, and the surface roughness Ra (arithmetic average roughness) of the end faces 2 and 3 and each chamfered surface is set. The thickness is about 0.03 μm or less. Further, the surface roughness of main surfaces 5 and 6 is preferably 0.2 nm or less in terms of root mean square roughness (Rq).

<Defect inspection process>
The defect shown in FIGS. 2A to 2C is subjected to defect inspection for detecting an internal defect (an optically non-uniform region) that may cause a problem in transfer accuracy with respect to the synthetic quartz glass substrate 4, and the internal defect is detected. A substrate in which no is detected is selected to obtain a mask blank glass substrate 7 (see FIG. 1B). In the previous substrate preparation step, if the synthetic quartz glass substrate 4 to be inspected for defects has a main surface, an end surface, and a chamfered surface that are not polished to a mirror surface, it is selected as an internal defect not detected. The synthetic quartz glass substrate 4 is subjected to precision polishing, ultraprecision polishing, mirror polishing of the end face, etc. on the main surface to obtain a glass substrate 7 for mask blank.

  In general, the theoretical transmittance of the mask blank substrate 7 made of synthetic quartz glass with respect to ArF excimer laser light is 100% (actual transmittance is about 91% because of actual surface reflection and the like). When the internal defect that absorbs the exposure light as described above is locally present, the transmitted light amount of the exposure light is greatly reduced. For this reason, if there is an internal defect on the light transmitting portion of the pattern forming thin film of the transfer mask 14, the transmitted light amount of the exposure light incident on the synthetic quartz glass substrate 4 is greatly reduced by the internal defect and is emitted from the light transmitting portion. The amount of exposure light to be greatly reduced. As a result, the exposure amount of the photosensitive portion on the resist film 10 added on the wafer of exposure transfer destination or the like is insufficient, and an exposure transfer defect occurs. For this reason, it is necessary to use a synthetic quartz glass substrate 4 used for the transfer mask 14 that does not have such an internal defect that causes such a reduction in exposure light. A defect inspection for selecting 4 is performed.

<Mask blank 9 formation process>
In the defect inspection step, a pattern forming thin film (light-shielding film) 8 is formed on the main surface 5 of the mask blank glass substrate 7 determined to have no internal defects, and the mask blank 9 shown in FIG. And The thin film (light-shielding film) 8 is formed, for example, by sputtering (DC sputtering, RF sputtering, ion beam sputtering, or the like) of a material mainly composed of chromium, transition metal silicide, or tantalum.

<Resist film 10 formation process>
A photoresist liquid is spin-coated on the surface of the thin film 8 for pattern formation of the mask blank 9 and then dried to form a resist film 10 to obtain a mask blank 11 with a resist film shown in FIG.

<Resist pattern 12 formation process>
The resist film of the mask blank 11 with resist film is subjected to electron beam drawing / exposure, and then the exposed resist film 10 is subjected to predetermined post-exposure baking, development, cleaning, and the like. Then, a resist pattern 12 is formed as shown in FIG.

<Resist pattern 12 formation process>
Dry etching is performed using the formed resist pattern 12 as a mask to remove the thin film 8 in a region not covered with the mask, and a thin film pattern 13 is formed under the resist pattern 12 as shown in FIG. .

<Transfer Mask 14 Formation Process>
The upper resist pattern 12 is removed and a predetermined cleaning process is performed to obtain a transfer mask 14 shown in FIG. 1G in which the thin film pattern 13 is formed on the mask blank glass substrate 7.

  In the manufacturing method of the glass substrate 7 for mask blanks, the manufacturing method of the mask blank 9, the manufacturing method of the transfer mask 14, and the manufacturing method of the semiconductor device according to the present invention, there is a possibility that a problem in transfer accuracy may occur due to substrate defect inspection. A substrate for the mask blank 9 having no internal defect can be selected. Therefore, it is possible to perform exposure transfer of the transfer pattern to the resist film 10 on the wafer using the transfer mask 14 produced using the transfer mask 14, and it is possible to manufacture a high-quality semiconductor device free from malfunction defects.

<Defect Inspection for Detecting Internal Defects (Optically Nonuniform Area) of this Embodiment>
Since the internal defect inspection apparatus 20 of this embodiment needs to be installed in an environment free from contaminants in the air, it is desirable to install it in the clean room 41 as shown in FIG. As a result, when the mask blank 9 is manufactured, the atmosphere (atmosphere) is free of contaminants, and in particular, contaminants can be excluded from the atmosphere around the synthetic quartz glass substrate 4 in the present embodiment. When a causative substance that absorbs laser light and generates heat adheres to the surface (especially, the main surfaces 5 and 6) of the synthetic quartz glass substrate 4, ArF excimer laser light is applied to the end surface of the synthetic quartz glass substrate 4 in the inspection process as in this embodiment. When 25 is introduced, the synthetic quartz glass substrate 4 may be damaged due to heat generation of the causative substance. However, by manufacturing in the clean room 41, such damage can be eliminated.

  The clean room 41 is formed inside the filter chamber 42. A filter (for example, a chemical filter 44 using activated carbon) is installed at a substantially central position in the vertical direction of a partition wall 45 that divides the internal space A of the clean room 41 and the filter chamber 42. For example, a lattice-shaped facing wall 46 is provided on the wall surface of the clean room 41 facing the partition wall 45. An air flow passage 47 is formed between the bottom of the filter chamber 42 and the clean room 41. A fan 43 is provided at the bottom of the filter chamber 42 outside the clean room 41.

  An air flow is generated by the fan 43, and the air in the filter chamber 42 passes through the chemical filter 44 in the partition wall 45 and enters the internal space A of the clean room 41. The air that has entered the internal space A passes through the opposing wall 46, passes through the air flow passage 47 at the bottom of the clean room 41, is returned to the filter chamber 42 and circulates. In the internal space A of the clean room 41, since air flows in through the chemical filter 44, causative substances adhering to the synthetic quartz glass substrate 4 such as contaminants are removed and circulates in a clean air atmosphere.

  By inspecting internal defects in the clean room 41, contaminants are removed in the internal space A, and contaminants adhere to the surface of the synthetic quartz glass substrate 4, particularly the mirror-polished main surfaces 5 and 6, and are deposited. The problem is that the adhered matter and deposits are heated by absorbing the ArF excimer laser beam 25, which is high-energy light, and the surface of the synthetic quartz glass substrate 4 is locally heated to damage the surface. Can do.

  In the internal space A of the clean room 41, a synthetic quartz as an object to be inspected placed on a laser irradiation device 21, an XYZ stage 22, a CCD camera 23, and an XYZ stage 22, which are part of an internal defect inspection device 20 described later. A glass substrate 4 is accommodated.

  The internal defect inspection apparatus 20 includes a laser irradiation device 21, an XYZ stage 22, a CCD camera 23, and a computer 27, and an internal defect 16 (an optically non-uniform region that causes a local change in optical characteristics during pattern transfer). Sense or detect.

<Configuration of internal defect inspection apparatus 20>
The laser irradiation device 21 is a light introduction unit that introduces ArF excimer laser light 25 that is light having an exposure wavelength (that is, light having the same wavelength as the exposure wavelength) from one end face 51 of the synthetic quartz glass substrate 4. While the XYZ stage 22 moves the synthetic quartz glass substrate 4 in the Y direction, the laser irradiation device 21 sends ArF excimer laser light 25 in the Y direction on the end surface 51 of the synthetic quartz glass substrate 4 (that is, the longitudinal direction of the end surface 51). ) Are introduced sequentially from each position. As shown in FIGS. 3A and 3B, the side surface 2 of the synthetic quartz glass substrate 4 has an end surface 51 orthogonal to the main surface 5 or 6, and the end surface 51 and the main surfaces 5 and 6. Chamfered surfaces 52 and 53 are provided. The width W of the side surface 2 is the sum of the width W1 of the end surface 51, the width W2 of the chamfered surface 52, and the width W3 of the chamfered surface 53. For example, W = 6.35 mm.

Since the chamfered surfaces 52 and 53 are largely inclined with respect to the end surface 51, the ArF excimer laser beam is irradiated from the chamfered surfaces 52 and 53 to the substrate even when parallel ArF excimer laser light is applied perpendicularly to the end surface 51. It cannot be introduced inside. That is, the internal defect cannot be inspected with respect to the inside of the chamfered surfaces 52 and 53 in the thickness direction of the synthetic quartz glass substrate 4. In order to allow ArF excimer laser light to strike an area inside the substrate where ArF excimer laser light cannot be introduced by a normal incidence method, for example, as shown in Japanese Patent Application Laid-Open No. 2010-160450, parallel ArF excimer laser light is cylindrical In the method of introducing divergent light having a predetermined divergence angle and then introducing the light into the substrate from the end face 51, or as disclosed in JP 2010-175655, ArF excimer laser light is applied to the main surfaces 5 and 6 from the normal direction of the end face 51. For example, a method of introducing the substrate from the end surface 51 into the substrate in a direction inclined to any of the above may be applied. The laser irradiation device 21 has a beam cross-sectional shape of 7.0 mm × 4.0 mm, an energy per pulse of 6 mJ, an energy per unit area of 21.4 mJ / cm ² , a wavelength λ ₁ (193 nm), as a light source. ArF excimer laser light 25, which is a pulse laser having a frequency of 1000 Hz, is used, and a plurality of cylindrical lenses are combined. Thereby, the ArF excimer laser beam 25 is adjusted to an optimal divergence angle and an optimal beam cross-sectional shape, and is introduced perpendicularly to the end surface 51 of the side surface 2.

  The XYZ stage 22 mounts the synthetic quartz glass substrate 4 as shown in FIG. 2B, and the placed synthetic quartz glass substrate 4 is moved in the X direction with respect to the laser light emitted from the laser irradiation device 21. , Y direction, and Z direction.

As shown in FIGS. 2B and 2C, the CCD camera 23 is installed on the main surface 5 side of the synthetic quartz glass substrate 4 placed on the XYZ stage 22, and the CCD element and the CCD element are to be imaged. And an objective lens 61 for inputting fluorescence 15 from the object, and has a detection visual field 24 capable of detecting any one of the partial areas 91 to 99 of the synthetic quartz glass substrate 4 as shown in FIG. It is a light receiving means. The detection visual field 24 is laterally scanned on the synthetic quartz glass substrate 4 by the XYZ stage 22 along the partial areas 91 to 96 in the width direction (that is, the irradiation direction of the laser light emitted from the laser irradiation device 21). After that, vertical scanning is performed up to the level of the partial region 99 for the next horizontal scanning in a direction perpendicular to the width direction of the end face 51. The CCD camera 23 emits fluorescence 15 and 17 having a wavelength longer than the wavelength λ ₁ emitted from the internal defect 16 of the synthetic quartz glass substrate 4 by the ArF excimer laser light 25 (wavelength λ ₁ : 193 nm). Are received from the main surface 5 side of the synthetic quartz glass substrate 4 at each position in the Y direction.

  The CCD camera 23 of the present embodiment is a camera that can acquire a color image, and receives light by dividing the brightness of the fluorescence 15 and 17 into three primary colors. The fluorescent lights 15 and 17 are condensed by the objective lens 61 and divided into three by the spectroscopic prism 62, and are respectively R (red) CCD image sensor 63, G (green) CCD image sensor 64, and B (blue). Incident on the CCD image sensor 65. Outputs of the CCD image sensors 63 to 65 are amplified, A / D converted, synthesized, and the like by the signal processing circuit 66 to become image signals and output to the computer 27. The objective lens 61 has a function of focusing in the thickness direction of the synthetic quartz glass substrate 4.

  The CCD image sensors 63 to 65 photoelectrically convert the brightness of the image formed on the light receiving surface (not shown) into the amount of electric charges, sequentially read out the signal by the signal processing circuit 66, and convert it into an electric signal. To the computer 27. In the CCD camera 23 according to this embodiment, the light receiving element is a CCD image sensor. However, the present invention is not limited to this, and any other optical sensor such as a photoresistor may be used. Can do.

  The computer 27 controls the entire internal defect inspection apparatus 20 and is connected to the CCD camera 23 using the USB cable 26 and is also a detection means for detecting internal defects from the input image signal. The computer 27 stores the image signal input from the CCD camera 23 in the storage circuit 72. In that case, for example, fluorescence luminance distribution image data is charted and stored so that the luminance value (light quantity value) of each pixel of the image is the same as the arrangement of each pixel in the display image. Thereafter, the computer 27 compares the stored image signal with a predetermined threshold value as shown in FIGS. 5A and 5B, which will be described later, and detects an X coordinate region whose luminance exceeds the threshold line. The region is determined as the region of the internal defect 16 of the synthetic quartz glass substrate 4. 5A and 5B, the horizontal axis indicates coordinates in the X direction (see FIG. 2B), and the vertical axis indicates luminance.

  When determining the area of the internal defect by the conventional method, the computer 27 selects one of the stored pixel values by the pixel selection unit 73, and further, for example, a pixel next to the pixel, The values of the upper pixel and the diagonally upper pixel are also selected, and the difference between the adjacent pixels is differentiated by the differentiating circuit 74 (proximity difference) to obtain a light amount difference. An image acquired by the CCD, value data obtained by proximity difference, a graph, and the like are output to a display 77 such as a liquid crystal screen. The control circuit 71 controls each part in the computer 27 and also controls a stage control unit 81 for controlling the output of the laser irradiation device 21 and the operation of the XYZ stage 22.

  As a control method of the stage control unit 81 by the computer 27, for example, the XYZ stage 22 is controlled so as to acquire each image of the partial areas 91 to 99 of the synthetic quartz glass substrate 4 in order. Then, the light amounts (luminance) of the fluorescence 15 and 17 received by the CCD camera 23 at each position in any one of the partial areas 91 to 99 are analyzed in relation to the X-direction position of the synthetic quartz glass substrate 4. At that time, the computer 27 determines whether the light amounts of the fluorescent lights 15 and 17 have a local light amount equal to or larger than a predetermined threshold value. The area 15 is determined as the internal defect 16 and is detected by specifying the position of the internal defect 16 (the position in the X direction and the Y direction in the synthetic quartz glass substrate 4).

<Operation of Internal Defect Inspection Apparatus 20>
When the ArF excimer laser beam 25 is introduced into the synthetic quartz glass substrate 4 by the control of the computer 27 as described above in the configuration of the internal defect inspection apparatus 20 as described above, the internal defects are introduced into the synthetic quartz glass substrate 4. When (optical non-uniformity) 16 exists, fluorescence 15 having a wavelength longer than that of the ArF excimer laser beam 25 is emitted from the main surface 5 of the synthetic quartz glass substrate 4 from the internal defect 16. On the other hand, fluorescent light 17 having a wavelength longer than the wavelength of the ArF excimer laser light 25 is also emitted from the main surface 5 of the synthetic quartz glass substrate 4 from a region other than the internal defect 16 of the synthetic quartz glass substrate 4. Is not as large as the fluorescence 15, for example, this is a noise level when the fluorescence 15 is detected. The fluorescent lights 15 and 17 are received by the CCD camera 23, and the internal defect 16 is detected by the computer 27 based on the difference in the amount of light (brightness) of the received fluorescent lights 15 and 17.

<Internal defect 16: optically non-uniform region>
When the ArF excimer laser beam 25 is introduced into the mask blank glass substrate 7, the internal defect 16 causes a local change in optical characteristics locally as a defect. The internal defect 16 emits fluorescence 15 having a wavelength longer than that of the ArF excimer laser beam 25.

  Of the internal defects 16 (optical non-uniform regions) existing in the synthetic quartz glass substrate 4, there is no problem in the case of an exposure light source (for example, KrF excimer laser (exposure wavelength: 248 nm)) having an exposure wavelength of more than 200 nm. There is an internal defect 16 which becomes a problem when the exposure light source has an exposure wavelength of 200 nm or less, such as ArF excimer laser beam 25 (exposure wavelength: 193.4 nm).

  These internal defects 16 are transferred using the transfer mask 14 manufactured from the synthetic quartz glass substrate 4 through the mask blank glass substrate 7 and the mask blank 9 and the exposure light having an exposure wavelength of 200 nm or less. In the pattern transfer for transferring the thin film pattern 13 of the mask 14 to the transfer object, any local or local change in optical characteristics (for example, a decrease in transmittance or a change in phase difference) is caused, which adversely affects pattern transfer. As a result, the transfer accuracy is lowered. Finally, due to the internal defect 16, a transfer pattern defect (a circuit pattern defect in a semiconductor device) of a transfer target (for example, a semiconductor device) occurs.

  These internal defects 16 are caused by “local striae”, “contents”, “foreign matter”, and the like. “Local striae” is a region in which a trace amount of metal element is mixed in synthetic quartz glass during the synthesis of synthetic quartz glass. If the local striae are present on the mask blank glass substrate 7 of the transfer mask 14, the transmittance is reduced by about 10 to 30% during pattern transfer, the transfer accuracy is lowered, and finally a transfer pattern defect is caused. . Further, the “content” is a region in which a metal element is mixed in synthetic quartz glass more than in the case of local striae. If the contents are present on the mask blank glass substrate 7 of the transfer mask 14, the transmittance is reduced by about 30 to 80% during pattern transfer, the transfer accuracy is lowered, and finally a transfer pattern defect occurs.

  The “foreign material” is an oxygen-excess region in which oxygen is excessively mixed in the synthetic quartz glass and does not recover after irradiation with high-energy light. If there is a foreign substance on the mask blank glass substrate 7 of the transfer mask 14, the transmittance is reduced by about 5 to 15% during pattern transfer, the transfer accuracy is lowered, and finally a transfer pattern defect is generated.

  The internal defect 16 that is a local optical non-uniformity that becomes a transfer pattern defect at the time of pattern transfer is not limited to “local striae”, “content”, and “foreign matter”. As the internal defect 16, when light having a wavelength of 200 nm or less, which is inspection light or exposure light, is introduced into the glass substrate 7 for mask blank, loss due to fluorescence generated locally or locally inside the substrate is 8% / cm. It is preferable that the optical non-uniformity part exceeds. Therefore, in the internal defect inspection step, it is preferable to select the mask blank glass substrate 7 in which the loss of light inside the mask blank glass substrate 7 is 8% / cm or less. In particular, in the case of the mask blank glass substrate 7 used for the phase shift mask, it is preferable to select the mask blank glass substrate 7 having a light loss of 3% or less in the inspection process.

  The wavelength of the fluorescence 15 emitted from the internal defect 16 is more than 200 nm and 600 nm or less, and the colors of the fluorescence 15 are purple (wavelength 400 to 435 nm), blue (wavelength 435 to 480 nm), green blue (480 to 490 nm), Blue-green (490-500 nm), green (500-560 nm), yellow-green (500-580 nm), yellow (580-595 nm), etc. are mentioned.

<When internal defect 16 is caused by high density foreign matter>
Optically non-uniform areas due to mixed foreign substances can be roughly classified into two types. One type thereof is an internal defect 16a in a state in which the mixed foreign matter is concentrated in the synthetic quartz glass substrate 4 at a high density and a relatively small defect region 101 as shown in FIGS. 4 (a) and 5 (a). This is the case. In that case, when the ArF excimer laser beam 25 is introduced into the synthetic quartz glass substrate 4, the local light quantity that is extremely larger than the predetermined threshold value from the defect region 101 of the internal defect 16a as shown in FIG. The fluorescence 15a is emitted. 5A shows the pixel position in the X direction on the synthetic quartz glass substrate 4, and the vertical axis shows the luminance of the fluorescent lights 15a and 17. The light amount difference between the light emitting region 151 in this case and the fluorescence 17 from the region other than the light emitting region 151 of the synthetic quartz glass substrate 4 is large because the light amount of the fluorescent light 15a is larger than a predetermined threshold value. Also grows.

  The computer 27 performs image processing on the image signals based on the fluorescence 15a and 17 by the differentiation circuit 74 and the like, obtains the outer peripheral end portion of the light emitting region 151 based on the light amount difference between adjacent pixels of the fluorescence 15a, and determines the shape of the generation portion of the fluorescence 15a. While analyzing, the position of the light emission area | region 151 which generate | occur | produces the fluorescence 15a is detected, and it detects that the defect area | region 101 (optical nonuniform area | region: internal defect 16a) exists in the position. The computer 27 further detects that the local light amount in the light emitting area 151 is equal to or greater than a predetermined threshold value, and determines that the internal defect 16a is an optically nonuniform area due to high-density foreign matter. In the calculation in the differentiation circuit 74 in this case, since the local light amount in the light emitting region 151 is much larger than the predetermined threshold value, the light amount difference for each pixel at the outer peripheral end of the light emitting region 151 is also large. When the luminance value between adjacent pixels is differentiated (proximity difference), a sufficient light amount difference (change rate) can be obtained. Therefore, it is easy to identify the internal defect 16a by fluorescence and to detect an optically nonuniform region.

<When internal defect 16 is caused by low density foreign matter>
Another type of optically non-uniform area due to the contaminated foreign matter is a defect area 102 having a low density and a relatively large amount of foreign matter within the synthetic quartz glass substrate 4 as shown in FIGS. 4B and 5B. This is a case where the internal defect 16b exists in a diffused state. In that case, when the ArF excimer laser beam 25 is introduced into the synthetic quartz glass substrate 4, the local light amount slightly larger than the predetermined threshold value from the defect region 102 of the internal defect 16 b as shown in FIG. 5B. The fluorescence 15b is emitted. In FIG. 5B, the horizontal axis indicates the pixel position in the X direction on the synthetic quartz glass substrate 4, and the vertical axis indicates the luminance of the fluorescence 15b and 17. The light amount difference between the light emitting region 152 in this case and the fluorescence 17 from the region other than the light emitting region 152 of the synthetic quartz glass substrate 4 is small because the light amount of the fluorescent light 15b is larger than a predetermined threshold value. Becomes smaller.

  The computer 27 performs image processing on the image signals based on the fluorescence 15b and 17 by the differentiation circuit 74 and the like, and performs a light amount difference for each adjacent pixel of the fluorescence 15b (for example, the pixels located at both ends of the pixel interval D1 in FIG. 5B). The outer peripheral end portion of the light emitting region 152 is obtained from the difference in each light quantity, and the shape of the fluorescent light 15b generating portion is analyzed, and the position of the light emitting region 152 generating the fluorescent light 15b is detected. Thereby, the computer 27 can detect that the defect area | region 102 (optical nonuniformity area | region: internal defect 16b) exists in the position. The computer 27 further determines that the internal defect 16b is an optically non-uniform area due to the low-density foreign matter because the local light quantity in the light emitting area 152 is equal to or greater than a predetermined threshold value. In the calculation in the differentiation circuit 74 in this case, the local light amount in the light emitting region 152 is larger than the predetermined threshold value, but the difference is small. Therefore, the light amount difference for each pixel at the outer peripheral edge of the light emitting region 152 is also small. Become. Accordingly, when the luminance value between adjacent pixels is differentiated (proximity difference), the light amount difference (change rate) is also reduced. For this reason, the identification of the internal defect 16b by fluorescence and the detection of the optically nonuniform region are not easy as compared with the light emitting region 151 of the fluorescence 15a described above.

  Furthermore, as described above, the CCD camera 23 of the present embodiment is a color camera, and the light and darkness of the fluorescent light 15b is received by being divided into three primary colors. For example, when it is an intermediate color of three primary colors such as yellow or orange, If the fluorescence is fluorescence 15c, the luminance of the fluorescence 15c may decrease to a level lower than the threshold value as shown in FIG. 5B. For example, if the fluorescence 15c is yellow, the R (red) CCD sensor 63 and the G (green) CCD sensor 64 are divided and received, and the light is filtered and photoelectrically converted into each color by each sensor. This is because there is a loss in the processing at each stage when A / D conversion is performed and the image is combined and output as an image signal. Therefore, the output level of the yellow image signal of the composite signal is, for example, lower than the output level of the image signal of the same conditions for the three primary colors blue, and the light amount difference for each pixel at the outer peripheral edge of the light emitting region is also reduced. When the luminance value between these pixels is differentiated (proximity difference), the light amount difference (change rate) may be small.

  Further, even when the optically nonuniform region due to the contaminated foreign matter exists as the internal defect 16a in a state where the mixed foreign matter is concentrated in the defect region 101 having a high density and a relatively small size like the fluorescent light 15a, If the objective lens 61 is not in focus and is not in the depth of field specification of the objective lens 61, the image signal output from the CCD camera 23 is out of focus, so the fluorescence 15c and Similarly, the light amount difference for each pixel at the outer peripheral edge of the light emitting region is also small, and when the luminance value between adjacent pixels is differentiated (proximity difference), the light amount difference (change rate) may be small.

<Features of this embodiment>
The present embodiment is particularly suitable for defect inspection with respect to internal defects that have conventionally been impossible or difficult to detect. For example, (a) the image including the fluorescence emitted from the internal defect acquired by the CCD camera 23 is the fluorescence emitted from the internal defect of the low-density foreign matter, so that each pixel at the outer peripheral edge of the light emitting region (B) Although the image including the fluorescence emitted from the internal defect acquired by the CCD camera 23 is the fluorescence emitted from the internal defect of the high-density foreign matter, When the depth at which the internal defect exists is outside the specification of the depth of field of the objective lens 61, the image is blurred, resulting in a haze-like defect image in which the light amount difference for each pixel at the outer peripheral edge of the light emitting region is small. (C) The image including the fluorescence emitted from the internal defect from the CCD camera 23 is a color image acquired by the color CCD, and the fluorescence is an intermediate color of three primary colors such as yellow and orange, and the emission region If light amount difference of each pixel in the outer peripheral end portion of a relatively small defect image, and the like. In the case of these defect images, it is difficult to detect the light emission region of the fluorescence 15c because the light amount difference is small even if the luminance value between adjacent pixels is differentiated (proximity difference) as in the conventional case. Therefore, in this embodiment, instead of taking a difference (proximity difference) between adjacent pixels, as shown by D40 in FIG. 5B and FIG. On the other hand, a difference in luminance value is obtained from a pixel separated by about 40 pixels (remote difference is obtained). In this case, as shown in FIG. 6, the pixels 40 pixels apart in the horizontal direction along the X axis, the pixels 40 pixels away in the vertical direction along the Z axis, and the X axis and Z axis A luminance value difference (remote difference) is calculated with respect to each of three pixels that are 40 pixels apart in an oblique direction of 45 degrees with respect to both, and the maximum value of the difference is obtained.

When performing the process of obtaining the remote difference, it is necessary that at least 20 pixels or more be separated from the process target pixel as a pixel for which a difference is to be obtained (a comparison target for which a light amount difference is to be obtained). Also, considering the detection accuracy when the fluorescence is an intermediate color of three primary colors such as yellow and orange and the difference in the amount of light between the pixels is relatively small, it is preferable to separate 30 pixels or more, and when separating 40 pixels or more, various types of It is optimal because fluorescence can be detected with high accuracy.
As described above, even when the blue fluorescent light 15c is detected by the color camera outside the specification of the low-density foreign object or the depth of field of the objective lens, the remote difference of the luminance value is obtained between the pixels separated by 20 pixels or more in the present embodiment. Thus, a light amount difference (change rate) equal to or greater than a threshold value can be obtained.

  As described above, in the method of manufacturing the mask blank glass substrate 7 of the present embodiment, in the step of preparing the substrate, the step of preparing the synthetic quartz glass substrate 4 having two main surfaces and four end surfaces and inspecting for defects. Thus, inspection light having a wavelength of 200 nm or less is introduced into the synthetic quartz glass substrate 4 from any surface to detect internal defects. In the step of inspecting the defect, the synthetic quartz glass substrate 4 is photographed from any surface, and when performing image processing on the photographed image, a process for obtaining a light amount difference by a remote difference is performed. The fluorescence generated from the internal defect of the synthetic quartz glass substrate 4 is discriminated based on the light amount difference caused by the remote difference of the fluorescence generated when the inspection light is absorbed by the defect. The discrimination of the generated fluorescence is performed on the end of the fluorescent region, the range of the fluorescent region is detected, and the presence of the internal defect is determined by recognizing it as the internal defect region. Then, a synthetic quartz glass substrate 4 determined to have no such fluorescence, that is, no fluorescence region (= internal defect region) is selected.

  As described above, the internal defect has a dot shape and a haze shape, and in the case of the dot shape, it can be detected even if the conventional differential processing of the proximity difference is used for the processing when analyzing the captured image. In the case of a haze (particularly when yellow or orange fluorescence is imaged by a color camera), the brightness of a haze-like internal defect in the detected image may be below the detection threshold. In that case, it may not be detected by the conventional differential processing of the proximity difference. Therefore, in the manufacturing method of the glass substrate for mask blanks of this embodiment, the process by a remote difference is employ | adopted. That is, in the processing based on the remote difference of the present embodiment, the light amount difference between the first processing target pixel and the second pixel that is separated from the first processing target pixel by a predetermined pixel is obtained. In general, since the edge of the fluorescent emission point is gradually reduced across a plurality of pixels, the difference in the amount of light between the detected pixels can be increased by the processing based on the remote difference.

  Further, if the objective lens is not focused on the fluorescent light emitting portion in the mask blank glass substrate 7 and is out of the specification of the depth of field, even if the internal defect is punctiform, Edges may be blurred and unclear. Also in this case, the difference in the light amount of the differential result of the proximity difference between adjacent pixels is reduced, and the detection by the conventional proximity difference differentiation process becomes difficult as in the case of the haze-like internal defect. On the other hand, it may be possible to divide the imaging into multiple stages in the thickness direction of the substrate so that it is within the specifications of the depth of field, but each time the number of stages is increased, the inspection man-hours are doubled, which is realistic. is not. In particular, the presence of internal defects increases the problem in the range close to the main surface on which the thin film is formed, so focusing is often fixed in the range close to the main surface, and the depth of field Internal defects that deviate from the specifications are blurred and imaged. Therefore, by using the remote difference processing of the present embodiment even for such a blurred captured image, it becomes easy to detect the edge portion of the fluorescent light emission portion, which has been difficult to detect in the past, and in the image plane. Since it becomes easy to detect the peak of the light amount distribution, it is possible to easily identify the area of the internal defect.

  Further, the mask blank glass substrate 7 placed on the internal defect inspection apparatus 20 in the method for manufacturing the mask blank glass substrate 7 of the present embodiment introduces inspection light among the four end faces of the synthetic quartz glass substrate 4. The main surface on the side where the synthetic quartz glass substrate 4 is photographed is polished to a mirror surface. When the end surface for introducing the inspection light of the mask blank glass substrate 7 is not polished to a mirror surface, the inspection light is scattered at the end surface, and the amount of inspection light introduced into the synthetic quartz glass substrate 4 is reduced. When the end surface is polished to a mirror surface, the amount of inspection light introduced into the synthetic quartz glass substrate 4 increases. On the other hand, when the main surface from which the fluorescence of the mask blank glass substrate 7 is emitted is not polished to a mirror surface, the fluorescence is scattered on the main surface, and the amount of inspection light emitted from the synthetic quartz glass substrate 4 is reduced. When the main surface is polished to a mirror surface, the amount of fluorescence emitted from the synthetic quartz glass substrate 4 increases. In the present embodiment, the end surface of the mask blank glass substrate 7 into which the inspection light is introduced and the main surface to be photographed are polished to a mirror surface, thereby suppressing the scattering of the inspection light and the fluorescence at those boundary surfaces.

  Moreover, in the manufacturing method of the mask blank 9 of this embodiment, the thin film for pattern formation is formed in at least one main surface of the glass substrate 7 for mask blanks of this embodiment mentioned above. The mask blank glass substrate 7 of the present embodiment is a mask blank glass substrate 7 having no such internal defect, as found in a haze-like internal defect that appears only with a laser beam having a wavelength of 200 nm or less in the above inspection. Therefore, the mask blank 9 of this embodiment in which a thin film for pattern formation is formed on the main surface of the mask blank 9 has a yield due to haze-like internal defects even if the mask is inspected using laser light having a wavelength of 200 nm or less as inspection light. There is no worsening.

  The transfer mask 14 of the present embodiment forms a transfer pattern on the pattern forming thin film of the mask blank 9 of the present embodiment described above. As described above, the mask blank 9 of the present embodiment has no haze-like internal defects that appear only with laser light having a wavelength of 200 nm or less. Therefore, the yield is not deteriorated when the transfer pattern is inspected using laser light having a wavelength of 200 nm or less as inspection light.

  In the semiconductor device manufacturing method of the present embodiment, a circuit pattern is formed on the semiconductor wafer using the transfer mask 14 of the present embodiment described above. As described above, the transfer mask 14 of the present embodiment has no haze-like internal defects that appear only with laser light having a wavelength of 200 nm or less. Therefore, the yield is not deteriorated when a circuit pattern is formed on a semiconductor wafer using laser light having a wavelength of 200 nm or less as exposure light.

  In this embodiment, as shown in FIG. 1C, the synthetic quartz glass substrate 4 is subjected to a defect inspection for detecting the internal defect (optical nonuniform region) of the present embodiment, and the internal defect is detected. Although the substrate which was not detected is selected as the glass substrate 7 for mask blanks, it is not restricted to this. For example, you may make it perform the defect inspection which detects an internal defect with respect to the mask blank 9 provided with the thin film for pattern formation in one main surface. This case is shown below as another method for manufacturing the mask blank 9.

  In another manufacturing method of the mask blank 9 of this embodiment, in the mask blank 9 preparation step, a mask having a pattern forming thin film on one main surface of the synthetic quartz glass substrate 4 having two main surfaces and four end surfaces. A blank 9 is prepared. In the defect inspection step, inspection light having a wavelength of 200 nm or less is introduced into the synthetic quartz glass substrate 4 from any surface (for example, any end surface) to detect internal defects. In the defect inspection step, the synthetic quartz glass substrate 4 is photographed from any surface (for example, the main surface on the side where the pattern forming thin film is not formed) other than the surface on which the pattern forming thin film is formed. When performing image processing on the captured image, processing for obtaining a light amount difference by remote difference is performed. The fluorescence generated from the internal defect of the synthetic quartz glass substrate 4 is discriminated by performing a process for obtaining a light amount difference by a remote difference with respect to the fluorescence generated by the inspection light being absorbed by the defect. The discrimination of the generated fluorescence is performed on the end of the fluorescent region, the range of the fluorescent region is detected, and the presence of the internal defect is determined by recognizing it as the internal defect region. Then, a mask blank 9 determined to have no such fluorescence, that is, no fluorescence region (= internal defect region) is selected.

  In another method for manufacturing the mask blank 9 of the present embodiment, when the mask blank 9 is inspected, the synthetic quartz glass substrate 4 is photographed from the main surface on the side where the pattern forming thin film is not formed. And the mask blank 9 is selected by calculating | requiring the light quantity difference by the remote difference with respect to the picked-up image, and determining the presence or absence of fluorescence. Therefore, in the manufacturing method of the mask blank 9 according to the present embodiment, a haze-like internal defect that appears only with a laser beam having a wavelength of 200 nm or less is found by inspection even for the mask blank 9 having a pattern forming thin film on the main surface. Even when a mask is inspected using laser light having a wavelength of 200 nm or less as inspection light, the yield is not deteriorated. Other points are the same as in the above-described embodiment.

<Examples 1-4, Comparative Examples 1 and 2>
A synthetic quartz glass substrate 4 (152.1 mm × 152.1 mm × 6.35 mm) in which two main surfaces and four end surfaces were precisely polished was prepared. This synthetic quartz glass substrate 4 has an internal defect that emits blue fluorescence inside the substrate, and it has been confirmed in advance that an image taken with a CCD camera becomes a haze-like fluorescence image. The synthetic quartz glass substrate 4 is placed on the XYZ stage 22 of the internal defect inspection apparatus 20 shown in FIG. 2 and the like, and an ArF excimer laser beam is introduced into the substrate from the end face 51 by the laser irradiation apparatus 21. The portion where the internal defect 16b emitting blue fluorescence was present was irradiated. Then, by receiving ArF excimer laser light, the fluorescence 15b generated from the internal defect 16b is photographed with a color CCD camera 23 (CCD pixel number: 2048 × 2048, high school magnification: 0.7 times) to obtain a fluorescence image. Acquired. The acquired image was an image containing blue and haze-like fluorescence (internal defect).

  The blue haze-like fluorescent image was subjected to processing for obtaining a light amount difference by the remote difference according to the present invention. Specifically, first, the red luminance value (the broken line “R” in FIGS. 7 to 9), the green luminance value (the broken line “G” in FIGS. 7 to 9), and the blue of each pixel of the fluorescent image. A total luminance value (a broken line “ALL” in FIGS. 7 to 9) obtained by adding luminance values (a broken line “B” in FIGS. 7 to 9) was calculated. Next, using the total luminance value of each pixel, a light amount difference from the pixel 20 pixels away from the processing target pixel (<Example 1> broken line “dif20” in FIG. 7), a pixel 30 pixels away from the processing target pixel, and Difference in light amount (<Example 2> broken line “dif30” in FIG. 7), light amount difference from a pixel 40 pixels away from the pixel to be processed (<Example 3> broken line “dif40” in FIG. 8), and from the pixel to be processed The light amount difference from the pixels separated by 50 pixels (<Example 4> broken line “dif50” in FIG. 8) was calculated. Further, as a comparative example, the total luminance value of each pixel is used, and the light amount difference with the adjacent pixel of the processing target pixel (differentiation by proximity difference, <comparative example 1> broken line “dif1” in FIG. 9), from the processing target pixel The light amount difference (<comparative example 2> broken line “dif10” in FIG. 9) with pixels 10 pixels away from each other was also calculated. 7 to 9, the vertical axis represents luminance, and the horizontal axis represents the pixel number of the image.

  Next, the presence or absence of fluorescence was determined using the light amount difference obtained in each example and comparative example. The threshold value of the light amount difference (luminance), which is a reference value for determining the presence or absence of fluorescence, was set to 5. As a result, when a light amount difference is obtained from a pixel that is 20 pixels or more away from the processing target pixel, a blue haze-like fluorescent image can be recognized by a computer. On the other hand, when the light amount difference was obtained by differentiation of the conventional proximity difference as in Comparative Example 1, a blue haze-like fluorescent image could not be recognized by the computer. In addition, in the case where the light amount difference is obtained with a pixel that is 10 pixels away from the processing target pixel of Comparative Example 2, there are only a few pixels with a light amount difference of 5, but the reproducibility of recognition by the computer is low, It was found that a remote difference of about 10 pixels is not suitable for practical use.

  Based on these results, a mask blank substrate, a mask blank, and a transfer mask were manufactured. 50 sets × 4 sets of synthetic quartz glass substrates 4 each having two main surfaces and four end surfaces precisely polished (FIG. 1A) are prepared and processed by the internal defect inspection apparatus 20 in the same manner as in the first to fourth embodiments. Using the light amount difference obtained from the pixel 20 pixels (Example 1), 30 pixels (Example 2), 40 pixels (Example 3), and 50 pixels (Example 4) away from the target pixel, A defect inspection process for determining the presence or absence of defects was performed, and the synthetic quartz glass substrate 4 determined to have no fluorescence was selected as the mask blank substrate 7 (FIG. 1B). Next, on the main surface 5 of the mask blank substrate 7 selected in Examples 1 to 4, a pattern forming thin film 8 was formed by a sputtering method to manufacture the mask blank 7 (FIG. 1C). ). The thin film for pattern formation is MoSiN (film thickness 47 nm, film composition Mo: 9.9 at%, Si: 66.1 at%, N: 24.0 at%), MoSiN (film thickness 13 nm, film) from the main surface 5 side. A light-shielding film having a two-layer structure of composition Mo: 7.5 at%, Si: 50.5 at%, N: 42.0 at%) and an etching mask film containing Cr as a main component were used.

On the etching mask film of each of the manufactured mask blanks 7 of Examples 1 to 4, a chemically amplified resist film 10 for electron beam drawing exposure was formed by spin coating (FIG. 1D). Next, using an electron beam drawing apparatus, a transfer pattern including an L & S pattern of DRAM hp45 nm was exposed and drawn on the resist film 10, and further developed and washed to form a resist pattern 12 (FIG. 1 ( e)). Next, using the resist pattern 12 as a mask, the etching mask film was dry-etched using a mixed gas of chlorine and oxygen to form an etching mask film pattern. Subsequently, using the etching mask film pattern as a mask, the light shielding film was dry-etched using fluorine-based gas (SF ₆ ) to form a light shielding film pattern (thin film pattern) 13 (FIG. 1 (f)). Furthermore, the resist pattern 12 was removed, a predetermined cleaning process was performed, and each transfer mask 14 of Examples 1 to 4 having the thin film pattern 13 on the mask blank glass substrate 7 was obtained (FIG. 1 (g)). .

  Next, the process of carrying out exposure transfer of the transfer pattern was performed with respect to the resist film on the semiconductor wafer which is a transfer object, using each transfer mask 14 of Examples 1-4 produced. As the exposure apparatus, an immersion type apparatus using annular illumination using an ArF excimer laser as a light source was used. Specifically, each transfer mask 14 of Examples 1 to 4 was set on the mask stage of the exposure apparatus, and exposure transfer was performed on the resist film for ArF immersion exposure on the semiconductor wafer. The resist film after the exposure was subjected to a predetermined development process to form a resist pattern. Furthermore, a circuit pattern including a line & space (L & S) pattern having a DRAM half pitch (hp) of 45 nm was formed on a semiconductor wafer using the resist pattern.

  When the circuit pattern on the obtained semiconductor wafer was confirmed with an electron microscope (TEM), the specification of the L & S pattern having a DRAM half pitch (hp) of 45 nm was sufficiently satisfied. That is, it was confirmed that each of the transfer masks of Examples 5 to 7 can sufficiently transfer a circuit pattern including an L & S pattern having a DRAM half pitch (hp) of 45 nm onto a semiconductor wafer.

<Reference Example 1>
A synthetic quartz glass substrate 4 (152.1 mm × 152.1 mm × 6.35 mm) in which two main surfaces and four end surfaces were precisely polished was prepared. This synthetic quartz glass substrate 4 has an internal defect that emits blue fluorescence inside the substrate, and it has been confirmed in advance that an image photographed by a CCD camera becomes a dot-like fluorescence image. The synthetic quartz glass substrate 4 is placed on the XYZ stage 22 of the internal defect inspection apparatus 20 shown in FIG. 2 and the like, and an ArF excimer laser beam is introduced into the substrate from the end face 51 by the laser irradiation apparatus 21. The portion where the internal defect 16b emitting blue fluorescence was present was irradiated. Then, by receiving irradiation with ArF excimer laser light, the fluorescence 15b generated from the internal defect 16b was photographed by the color CCD camera 23 to obtain a fluorescence image. The acquired image was a blue image containing point-like fluorescence (internal defect).

  The blue dot-like fluorescence image was subjected to a process for obtaining a light amount difference by a proximity difference. Specifically, first, a red luminance value (a broken line “R” in FIG. 10), a green luminance value (a broken line “G” in FIG. 10), and a blue luminance value (see FIG. 10) of each pixel of the fluorescent image. The total luminance value (the broken line “ALL” in FIG. 10) obtained by adding 10 broken lines “B”) was calculated. Next, a light amount difference (<Reference Example 1> differentiation by proximity difference, broken line “dif1” in FIG. 10) with a pixel adjacent to the processing target pixel was calculated. Note that the vertical axis of the graph of FIG. 10 is the luminance, and the horizontal axis is the pixel number of the image.

  Next, the presence or absence of fluorescence was determined using the light amount difference obtained in this reference example. The threshold value of the light amount difference (luminance), which is a reference value for determining the presence or absence of fluorescence, was set to 5. As a result, in the case of a blue dot-like fluorescent image, even if the light amount difference is obtained by the differentiation of the conventional proximity difference, it can be accurately recognized by the computer.

<Examples 5 to 7, Comparative Examples 3 and 4>
A synthetic quartz glass substrate 4 (152.1 mm × 152.1 mm × 6.35 mm) in which two main surfaces and four end surfaces were precisely polished was prepared. This synthetic quartz glass substrate 4 has an internal defect that emits yellow fluorescence inside the substrate, and it has been confirmed in advance that an image taken with a CCD camera becomes a haze-like fluorescence image. The synthetic quartz glass substrate 4 is placed on the XYZ stage 22 of the internal defect inspection apparatus 20 shown in FIG. 2 and the like, and an ArF excimer laser beam is introduced into the substrate from the end face 51 by the laser irradiation apparatus 21. The portion having the internal defect 16b emitting yellow fluorescence was irradiated. Then, by receiving irradiation with ArF excimer laser light, the fluorescence 15b generated from the internal defect 16b was photographed by the color CCD camera 23 to obtain a fluorescence image. The acquired image was an image including yellow and haze-like fluorescence (internal defect).

  The yellow haze-like fluorescent image was subjected to processing for obtaining a light amount difference by the remote difference of the present invention. Specifically, first, the red luminance value (the broken line “R” in FIGS. 11 to 13), the green luminance value (the broken line “G” in FIGS. 11 to 13), and the blue of each pixel of the fluorescent image. The total luminance value (the broken line “ALL” in FIGS. 11 to 13) obtained by adding the luminance values (the broken line “B” in FIGS. 11 to 13) was calculated. Next, using the total luminance value of each pixel, the light amount difference from the pixel 30 pixels away from the processing target pixel (<Example 5> broken line “dif30” in FIG. 11), the pixel 40 pixels away from the processing target pixel, and Difference (<Example 6> broken line “dif40” in FIG. 11) and light amount difference from the pixel 50 pixels away from the processing target pixel (<Example 7> broken line “dif50” in FIG. 12). . Further, as a comparative example, the total luminance value of each pixel is used, and the light amount difference from the pixel adjacent to the processing target pixel (differentiation by proximity difference, <comparative example 3> broken line “dif1” in FIG. 13), from the processing target pixel A light amount difference (<comparative example 4> broken line “dif10” in FIG. 13) with pixels 10 pixels away from each other was also calculated. In addition, the vertical axis | shaft of the graph of FIGS. 11-13 is a brightness | luminance, and a horizontal axis is a pixel number of an image.

  Next, the presence or absence of fluorescence was determined using the light amount difference obtained in each example and comparative example. The threshold value of the light amount difference (luminance), which is a reference value for determining the presence or absence of fluorescence, was set to 5. As a result, when a light amount difference was obtained from a pixel that is 30 pixels or more away from the processing target pixel, a yellow haze-like fluorescent image could be recognized by a computer. On the other hand, when the light amount difference is obtained by differentiation of the conventional proximity difference as in Comparative Example 3, or when the light amount difference is obtained with a pixel 10 pixels away from the processing target pixel of Comparative Example 4, A yellow haze-like fluorescent image could not be recognized by a computer.

  Based on these results, a mask blank substrate, a mask blank, and a transfer mask were manufactured. 50 sets × 3 sets of synthetic quartz glass substrates 4 each having two main surfaces and four end surfaces precision-polished are prepared (FIG. 1A) and processed by the internal defect inspection apparatus 20 in the same manner as in Examples 5-7. Defect inspection for determining the presence or absence of an internal defect using a light amount difference obtained from a pixel separated by 30 pixels (Example 5), 40 pixels (Example 6), and 50 pixels (Example 7) from the target pixel The process was performed, and the synthetic quartz glass substrate 4 determined to have no fluorescence was selected as the mask blank substrate 7 (FIG. 1B). Next, each mask blank 7 of Examples 5-7 was manufactured in the same procedure as Example 1 using the mask blank substrate 7 selected in Examples 5-7. Then, each transfer mask 14 of Examples 5-7 was produced in the same procedure as Example 1 using each manufactured mask blank 7 of Examples 5-7. Furthermore, the process of carrying out exposure transfer of the transfer pattern was performed with respect to the resist film on the semiconductor wafer which is a transfer object using each produced transfer mask 14 of Examples 5-7. As a result, when the circuit pattern on the obtained semiconductor wafer was confirmed with an electron microscope (TEM), the specification of the DRAM half pitch (hp) 45 nm L & S pattern was sufficiently satisfied. That is, it was confirmed that each of the transfer masks of Examples 5 to 7 can sufficiently transfer a circuit pattern including an L & S pattern having a DRAM half pitch (hp) of 45 nm onto a semiconductor wafer.

  Embodiments of the mask blank glass substrate 7 manufacturing method, mask blank 9 manufacturing method, transfer mask 14 manufacturing method, and semiconductor device manufacturing method according to the present invention are not limited to the above-described embodiments. Various other embodiments are included in the present invention.

A few sides,
4 synthetic quartz glass substrate,
5, 6 Main surface,
7 Glass substrate for mask blank,
8 Thin film (light-shielding film),
9 Mask blank,
10 resist film,
11 Mask blank with resist film,
12 resist pattern,
13 Thin film (light-shielding film) pattern, (mask pattern),
14 Transfer mask,
15, 15a, 15b fluorescence,
16, 16a, 16b Internal defect,
17 fluorescence,
18, 19 side surface (perpendicular to side surfaces 2 and 3),
20 Internal defect inspection device 20,
21 Laser irradiation device 21,
22 XYZ stage 22,
23 CCD camera,
24 detection field of view,
25 ArF excimer laser beam 25,
26 USB cable,
27 computers,
41 Clean room,
42 filter chamber,
43 fans,
44 Chemical filter,
45 Bulkhead,
46 opposite wall,
47 Air flow path,
51 end face,
52, 53 Chamfered surface,
61 objective lens,
62 Spectral prism,
63 R (red) CCD image sensor,
64 G (green) CCD image sensor,
65 B (blue) CCD image sensor,
66 signal processing circuit,
71 control circuit,
72 memory circuits,
73 pixel selector,
74 differentiation circuit,
77 display,
81 stage controller,
91-99, a partial region (of the synthetic quartz glass substrate 4),
101 defect area (high density and relatively small contamination),
102 defect area (low density and relatively large contamination),
151 emission region (of fluorescence 15a),
152 emission region (of fluorescence 15b),
a long side (of beam cross-sectional shape) b short side (of beam cross-sectional shape) A internal space,
D1 pixel spacing (for each adjacent pixel),
D40 A pixel interval (about 40 pixels apart from one pixel).
W (side 2) width,
W1 (end face 51) width,
W2 width (of chamfered surface 52),
W3 (Chamfered surface 53) width.

Claims (13)

A substrate preparation step of preparing a glass substrate having two main surfaces and four end surfaces;
A method for manufacturing a mask blank glass substrate having a defect inspection step of detecting an internal defect by introducing inspection light having a wavelength of 200 nm or less into the glass substrate from any surface,
The defect inspection process includes:
Take a picture of the glass substrate from either side,
By performing image processing including processing for obtaining a light amount difference by remote difference for the captured image, the presence or absence of fluorescence generated from an internal defect of the glass substrate is determined by the inspection light,
A glass substrate determined to have no fluorescence is selected. A method for manufacturing a mask blank glass substrate. The image processing is processing for creating a light amount distribution of a captured image by calculating a light amount difference between a processing target pixel of the captured image and a pixel not adjacent to the pixel. Item 2. A method for producing a glass substrate for a mask blank according to Item 1. The image processing is processing for creating a light amount distribution of a captured image by calculating a light amount difference with a pixel that is 20 pixels or more away from a processing target pixel of the captured image. Of manufacturing a glass substrate for a mask blank. The surface for introducing the inspection light is one of the four end surfaces of the glass substrate,
The method for producing a glass substrate for a mask blank according to any one of claims 1 to 3, wherein the surface on which the glass substrate is photographed is one of the two main surfaces of the glass substrate. The method for manufacturing a glass substrate for a mask blank according to any one of claims 1 to 4, wherein a surface for introducing the inspection light and a surface for photographing the glass substrate are polished to a mirror surface. It has a process of forming the thin film for pattern formation in the main surface of the glass substrate for mask blanks manufactured with the manufacturing method of the glass substrate for mask blanks in any one of Claim 1 to 5. Mask blank characterized by the above-mentioned. Manufacturing method. A method for producing a transfer mask, comprising a step of forming a transfer pattern on the thin film for pattern formation of the mask blank produced by the method for producing a mask blank according to claim 6. A circuit pattern is formed on a semiconductor wafer using the transfer mask according to claim 7. A mask blank preparation step of preparing a mask blank having a thin film for pattern formation on one main surface of a glass substrate having two main surfaces and four end faces;
A mask blank manufacturing method including a defect inspection step of detecting an internal defect by introducing inspection light having a wavelength of 200 nm or less into the glass substrate from any surface,
The defect inspection process includes:
Photograph the glass substrate from any surface other than the surface on which the pattern forming thin film is formed,
By performing image processing including processing for obtaining a light amount difference by remote difference with respect to the captured image, the presence or absence of fluorescence generated from an internal defect of the glass substrate by the inspection light is determined,
A mask blank determined to have no fluorescence is selected. A method of manufacturing a mask blank, comprising: The image processing is processing for creating a light amount distribution of a captured image by calculating a light amount difference between a processing target pixel of the captured image and a pixel not adjacent to the pixel. Item 10. A method for manufacturing a mask blank according to Item 9. The image processing is processing for creating a light amount distribution of a captured image by calculating a light amount difference with a pixel that is 20 pixels or more away from a processing target pixel of the captured image. Mask blank manufacturing method. It has the process of forming a transfer pattern in the said pattern formation thin film of the mask blank manufactured with the manufacturing method of the mask blank in any one of Claim 9 to 11. The manufacturing method of the transfer mask characterized by the above-mentioned. A circuit pattern is formed on a semiconductor wafer using the transfer mask according to claim 12. A method for manufacturing a semiconductor device, comprising:

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