JP5090379B2 - Manufacturing method of glass substrate for mask blank, manufacturing method of mask blank, and manufacturing method of photomask for exposure - Google Patents

Description

  The present invention relates to a mask blank glass substrate manufacturing method, a mask blank manufacturing method, and an exposure photomask manufacturing method for inspecting an internal defect of a mask blank glass substrate and selecting one having no internal defect.

  In recent years, with the miniaturization of semiconductor devices, light having a short wavelength such as an ArF excimer laser (exposure wavelength 193 nm) has been used as exposure light in the photolithography technique. Further, also in the technical field of exposure photomasks used in photolithography technology and mask blanks for manufacturing this exposure photomask, a light-shielding film capable of blocking light from the above-mentioned short wavelength exposure light, Phase shift films that change the phase have been rapidly developed, and various film materials have been proposed.

  By the way, it is required that the mask blank glass substrate and the synthetic quartz glass substrate for manufacturing the mask blank glass substrate are free from defects such as foreign matters and bubbles. Patent Document 1 discloses an internal defect (foreign matter or bubble) present in a glass substrate by detecting fluorescence generated from the internal defect of the glass substrate when inspection light having a wavelength of 200 nm or less is introduced into the glass substrate. And the like are disclosed.

JP 2007-86050 A

  However, it has been found that even if the glass substrate is determined to have no internal defect by the above-described defect detection method, a minute defect may remain particularly in the vicinity of both the front and back main surfaces. As a result of investigating the cause of the present invention, the following has been found.

  FIG. 8 is an explanatory diagram of an internal defect inspection process of a conventional mask blank glass substrate, and FIG. 9 is a perspective view of the glass substrate 10 in FIG. 8 and 9, reference numeral 10 denotes a glass substrate to be inspected, and this glass substrate 10 has two main surfaces 11 and 12 and four end surfaces 13, 14, 15 and 16. Chamfered surfaces 13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b are formed at corners where the two main surfaces 11, 12 and the four end surfaces 13, 14, 15, 16 intersect. .

The inspection light L is irradiated perpendicularly to the end face 13 from the left side in the drawing and introduced into the glass substrate 10. The inspection light L has a width (vertical width) t _L slightly larger than the thickness tg of the glass substrate 10 and is substantially parallel light. Therefore, the inspection light L is actually introduced into the inside through the end surface 13 and the chamfered surfaces 13a and 13b. The horizontal width (the main surface direction parallel to the width) of the inspection light L also has a width of about substantially equal to the vertical width t _L. Therefore, the entire glass substrate is inspected by introducing the inspection light to the entire glass substrate by moving the glass substrate in a direction parallel to the main surface.

Here, although the inspection light L is incident from the end face 13 substantially perpendicularly, the light introduced into the inside through the chamfered faces 13a and 13b is incident at an angle of 45 ° with respect to these chamfered faces, and the glass substrate. 10 passes through the regions S1 and S2. For this reason, when incident from the chamfered surfaces 13a and 13b, reflection occurs on these surfaces, and the intensity of the inspection light incident from these surfaces and passing through the regions S1 and S2 is incident perpendicularly from the end surface 13. It is considered that the intensity of inspection light passing through other areas is considerably weakened. As a result, it is considered that the intensity of the inspection light applied to the defects Ka and Kb in the regions S1 and S2 is not sufficient, and the fluorescence generated from the minute defects Ka and Kb is not sufficient.

  The present invention has been made under the above-mentioned background, and the object thereof is to detect even minute internal defects near the main surface of a mask blank glass substrate without omission, and to detect substantially all areas. It is an object of the present invention to provide a defect inspection method for a mask blank glass substrate that can detect internal defects satisfactorily.

As means for solving the above-mentioned problem, the first means is:
A substrate preparation step of preparing a thin plate-like mask blank glass substrate having two main surfaces and four end surfaces;
A defect inspection step of inspecting internal defects by introducing inspection light having a wavelength of 200 nm or less into the glass substrate from any one of the end faces;
A method for producing a glass substrate for a mask blank having
The defect inspection step uses divergent light having a predetermined divergence angle as inspection light, and inspects the presence or absence of fluorescence generated from an internal defect by causing the inspection light to reach the entire predetermined region to be inspected in the glass substrate. And
A mask blank substrate is manufactured by selecting a glass substrate from which fluorescence is not detected and manufacturing a mask blank substrate.
The second means is
The method for producing a glass substrate for a mask blank according to the first means, wherein the glass substrate has a chamfered surface formed at a corner where the two main surfaces and the four end surfaces intersect. It is.
The third means is
The mask blank glass substrate according to any one of the first and second means, wherein the inspection light has a divergence angle that reaches the entire predetermined region when introduced into the glass substrate from one end surface. It is a manufacturing method.
The fourth means is
When the inspection light is introduced into the glass substrate from one end surface, the inspection light is close to the one end surface in a predetermined region divided by an intermediate surface set between the one end surface and the end surface facing the one end surface. The mask blank glass substrate according to any one of the first and second means has a divergence angle that does not reach the entire region in the side region and reaches the entire region in the region far from the one end face. It is a manufacturing method.
The fifth means is
The inspection light is introduced into the glass substrate from one end surface to inspect for the presence of fluorescence, and then the inspection light is introduced into the glass substrate from the end surface opposite to the one end surface to inspect for the presence of fluorescence. A method for manufacturing a glass substrate for a mask blank according to any one of the first to fourth means.
The sixth means is
For the mask blank according to any one of the first to fifth means, the inspection light is collimated light that is diverged by a concave lens or a concave mirror and is introduced into the glass substrate from an end surface. It is a manufacturing method of a glass substrate.
The seventh means is
The concave lens is a cylindrical lens disposed in front of an end face, and is a method for manufacturing a mask blank glass substrate according to a sixth means.
The eighth means is
The concave mirror is a cylindrical concave mirror disposed in front of an end face, and is a method for producing a mask blank glass substrate according to a sixth means.
The ninth means is
It has the process of forming the thin film for pattern formation on the main surface of the glass substrate for mask blanks manufactured by the manufacturing method of the glass substrate for mask blanks concerning any one of the 1st to 8th means. It is a manufacturing method of a mask blank.
The tenth means is
A method for producing a photomask for exposure, comprising a step of forming a fine pattern for exposure on the thin film for pattern formation of the mask blank produced by the method for producing a mask blank according to the ninth means. .
The eleventh means is
A substrate preparation step of preparing a thin plate-like mask blank glass substrate having two main surfaces and four end surfaces;
A thin film forming step of forming a thin film for pattern formation on the main surface of the glass substrate;
A defect inspection step of inspecting internal defects by introducing inspection light having a wavelength of 200 nm or less into the glass substrate from one end surface;
A mask blank manufacturing method comprising:
The defect inspection step uses divergent light having a predetermined divergence angle as inspection light, and inspects the presence or absence of fluorescence generated from an internal defect by causing the inspection light to reach the entire predetermined region to be inspected in the glass substrate. And
A mask blank manufacturing method comprising selecting a mask blank from which fluorescence is not detected.
The twelfth means is
A substrate preparation step of preparing a thin plate-like mask blank glass substrate having two main surfaces and four end surfaces;
A thin film forming step of forming a thin film for pattern formation on the main surface of the glass substrate;
A fine pattern forming step of forming a fine pattern for exposure on the thin film;
A defect inspection step of inspecting internal defects by introducing inspection light having a wavelength of 200 nm or less into the glass substrate from one end surface;
A method for producing a photomask for exposure comprising:
The defect inspection step uses divergent light having a predetermined divergence angle as inspection light, and inspects the presence or absence of fluorescence generated from an internal defect by causing the inspection light to reach the entire predetermined region to be inspected in the glass substrate. And
An exposure photomask manufacturing method comprising selecting an exposure photomask in which fluorescence is not detected.

  According to the above-mentioned means, the inspection step uses the diverging light having a diverging angle at which the inspection light introduced from one end surface in the glass substrate reaches the entire predetermined region to be inspected, as the inspection light. It is easy to ensure that the inspection light introduced inside the glass substrate reaches a predetermined area near the main surface of the glass substrate, and even minute internal defects near the main surface of the mask blank glass substrate can be detected without omission. It became easy and it became possible to easily obtain a product having no defects.

It is explanatory drawing regarding the defect inspection process of the glass substrate for mask blanks concerning Embodiment 1 of this invention. It is the A section enlarged view of FIG. It is explanatory drawing of the divergence angle (theta) c. It is a figure which shows the apparatus structure for implementing the defect inspection process of the glass substrate for mask blanks concerning Embodiment 1 of this invention. It is explanatory drawing of a defect detection. It is explanatory drawing regarding the defect inspection process of the glass substrate for mask blanks concerning Embodiment 2 of this invention. It is explanatory drawing regarding the defect inspection process of the glass substrate for mask blanks concerning Embodiment 3 of this invention. It is explanatory drawing of the defect inspection process of the conventional glass substrate for mask blanks. It is a perspective view of the glass substrate 10 in FIG.

(Embodiment 1)
1 is an explanatory diagram relating to an internal defect inspection process for a mask blank glass substrate according to a first embodiment of the present invention, FIG. 2 is an enlarged view of a portion A in FIG. 1, FIG. 3 is an explanatory diagram of a divergence angle θc, and FIG. The figure which shows the apparatus structure for implementing the internal defect inspection process of the glass substrate for mask blanks concerning Embodiment 1 of this invention, FIG. 5 is explanatory drawing of a defect detection. Hereinafter, a method for manufacturing a glass substrate for a mask blank, a method for manufacturing a mask blank, and a method for manufacturing a photomask for exposure according to Embodiment 1 of the present invention will be described with reference to these drawings. In addition, since the glass substrate for mask blanks which is an inspection object of this Embodiment 1 is the same as the glass substrate for mask blanks which is the object of the inspection method of the above-mentioned conventional mask blank glass substrate, the same part In the description, the same reference numerals are given.

  The manufacturing method of the mask blank glass substrate according to the first embodiment includes (1) a grinding process of a mask blank glass substrate to be subjected to a defect inspection, (2) a defect inspection process of the mask blank glass substrate, (3) It consists of a polishing process for a mask blank glass substrate. Moreover, the manufacturing method of the mask blank concerning Embodiment 1 performs the manufacturing process of (4) mask blank with respect to the glass substrate for mask blanks manufactured at the process of said (1)-(3). Furthermore, the manufacturing method of the photomask for exposure concerning Embodiment 1 performs the manufacturing process of the photomask for exposure with respect to the mask blank manufactured at the process of (4). Among the above steps, the greatest feature of the present embodiment is (2) a method for inspecting internal defects of the mask blank glass substrate used in the defect inspection step of the mask blank glass substrate, and the other steps are generally known. Therefore, in the following description, the description of the known process is minimized, and the defect inspection method for the mask blank glass substrate will be mainly described.

  In addition, the defect inspection process of the glass substrate for mask blanks (2) The glass substrate after the polishing process of the glass substrate for mask blanks, (4) The mask blank after the mask blank manufacturing process, (5) Even if it is performed on the exposure photomask after the exposure photomask manufacturing process, there is no substantial difference in the accuracy of the internal defect inspection. However, after (3) the polishing process of the glass substrate for mask blank, (4) the manufacturing process of the mask blank, and (5) the manufacturing process of the photomask for exposure, there is no defect with internal defects. Since polishing and thin film formation are performed on all glass substrates including those that are acceptable, it is preferably performed before the polishing step (3). When placing emphasis on finding internal defects more reliably, a glass substrate for a mask blank in which the polishing process of the glass substrate has been completed, or a mask blank in which a thin film for pattern formation is formed on the glass substrate Alternatively, the defect inspection process may be performed using an exposure photomask.

(1) Grinding process of glass substrate for mask blank to be subjected to internal defect inspection Synthetic quartz glass ingot prepared by a known method (for example, see JP-A-8-31723, JP-A-2003-81654, etc.) From about 152.4 mm × about 152.4 mm × about 6.85 mm to obtain a glass substrate of synthetic quartz. This glass substrate has two main surfaces facing each other and four end surfaces orthogonal to both the main surfaces.

  For mask blanks, after chamfering the corner where the main surface and end face of the glass substrate intersect, the end face where inspection light is introduced is mirror-polished so that the inspection light can be introduced into the glass substrate. A glass substrate 10 is obtained. This glass substrate 10 is the same as the glass substrate for mask black shown in FIGS. 8 and 9, and has two main surfaces 11, 12, four end surfaces 13, 14, 15, 16, and eight chamfered surfaces 13a, 13b. , 14a, 14b, 15a, 15b, 16a, 16b. Here, the surface roughness Ra (arithmetic mean roughness) of the end face (one end face) 13 for introducing the inspection light is set to about 0.03 μm or less. Since all four end surfaces are mirror-polished in the mask blank polishing step, the other end surfaces 14, 15 and 16 may be mirror-polished in this grinding step. The mask blank glass substrate 10 thus obtained is supplied to an internal defect inspection process which is the next process.

(2) Mask Blank Glass Substrate Defect Inspection Step In this step, the mask blank glass substrate 10 obtained as described above is inspected for the presence of internal defects by a defect inspection method described below. Hereinafter, the inspection method of the glass substrate for mask blanks used at this process is demonstrated. FIG. 1 is an explanatory diagram of a method for inspecting a mask blank glass substrate according to the first embodiment, and is a diagram for explaining the principle thereof. In FIG. 1, inspection light L which is substantially parallel light having a divergence angle of 2 mrad is made divergent by a concave lens 28 and introduced into the glass substrate 10 from the end face 13 of the glass substrate 10 (light indicated by a solid line in FIG. 1). ) And inspecting the presence or absence of fluorescence generated from the internal defect due to the irradiation of the inspection light at that time.

  In this case, among the inspection light L introduced into the glass substrate 10, the light beams introduced into the glass substrate through the corners where the end face 13 and the chamfered surfaces 13a and 13b intersect are denoted as L1 and L2. The light rays L1 and L2 intersect the boundary surfaces E and F (see FIGS. 2 and 3) on the front and back main surfaces 11 and 12 side of the predetermined region and the boundary surface B on the end surface 13 side of the predetermined region. The divergence angle of the inspection light is set so as to be on the lines Be and Bf or closer to the end face 13 side.

  Here, the divergence angle refers to the light rays L1 and L2 that are introduced into the glass substrate 10 through the corners where the end surface 13 and the chamfered surfaces 13a and 13b intersect before being introduced into the glass substrate 10. In the state after the substantially parallel inspection light L is diverged by the concave lens 28, as shown in FIG. 3, the extension lines of the light beams L1 and L2 intersect with each other. An angle (θc) formed by a line (when the inspection light beams L1 and L2 are introduced into the glass substrate 10 from the end face 13, the angle of the light beam is determined by the difference in refractive index between the air and the glass substrate 10). Therefore, the angle formed by the extended lines of the light beams L1 and L2 in the glass substrate 10 is not the same as θc.)

  Here, the range of the mask blank glass substrate in the predetermined region in the thickness direction (the direction between the main surface 11 and the main surface 12) does not necessarily require the inspection light to reach the entire region in the thickness direction. is not. In the case where a defect inspection process is performed after the grinding process is finished, a predetermined amount of glass is scraped off in the thickness direction from both sides by polishing the main surfaces 11 and 12 in the subsequent polishing process (FIG. 2). Therefore, even if there is an internal defect in the area to be scraped, the internal defect is removed in the completed glass substrate for mask blank. However, considering that the amount of polishing on the main surface on the side on which the thin film for pattern formation is formed and the main surface on the opposite side are slightly different, both main surfaces are not completely flat, etc. It is better to give some margin to the region where the inspection light in the thickness direction reaches.

For example, in the case of a mask blank glass substrate having a main surface (including a chamfered portion) having a size of about 152 mm × 152 mm, the plate thickness (thickness in the thickness direction) is the plate thickness 6 after completion of the grinding process.
. Polishing with a target of 85 mm to 6.35 mm. Considering the above margin, the inspection light only needs to reach a region having a thickness of at least 6.4 mm with respect to the substrate center in the thickness direction. That is, in the glass substrate after the grinding process, a portion outside 6.4 mm with respect to the center of the substrate in the thickness direction is removed in a subsequent polishing process. That means there is no problem.

  On the other hand, the range on the main surface side of the predetermined region is that when a mask blank is manufactured using a glass substrate for mask blank and an exposure photomask is produced based on the mask blank, a transfer pattern is formed on the thin film. It is only necessary to cover at least the area. This is because when a photomask for exposure is produced based on this glass substrate for mask blank, and this is placed on a photomask stage of an exposure apparatus and pattern transfer to a transfer object (wafer or the like) is performed, a transfer pattern This is because the exposure light in the regions of the main surfaces 11 and 12 outside the region where the film is formed is blocked by the thin film, so that even if there is an internal defect in the region, the transfer object is not adversely affected. .

  For example, in the case of the mask blank glass substrate having a main surface size of about 152 mm × 152 mm, the region where the transfer pattern is formed may be an inner region of 132 mm × 132 mm with respect to the center of the mask blank. It is common. In this case, the boundary surface B of the predetermined region may be set at a minimum at a distance of 66 mm from the center of the mask blank toward the end surface 13 in parallel with the end surface 13. The positions of the light rays L1 and L2 in the glass are on the intersecting lines Be and Bf where the boundary surface B and the boundary surfaces E and F on the main surfaces 11 and 12 side cross each other or on the end surface 13 side. In addition, the divergence angle θc may be selected. The exposure photomask is placed on the photomask stage of the exposure apparatus such that the main surface on the side where the thin film is not formed faces the light source side of the exposure light. For this reason, since exposure light is irradiated to the inside of the glass substrate 10 also in the area | region outside a predetermined area | region, if there exists an internal defect, fluorescence will generate | occur | produce from there. When the internal defect is in the vicinity of the boundary surface B of the predetermined region, the fluorescence emitted from the internal defect may adversely affect the pattern transfer onto the transfer object. In consideration of this, it is preferable to set the predetermined area with a margin of 142 mm × 142 mm inside with reference to the center of the mask blank. If a further margin is provided, it is more preferable that the predetermined area is an inner area of, for example, 146 mm × 146 mm.

  Considering the above, when manufacturing a glass substrate for a mask blank of about 152 mm × 152 mm × 6.35 mm, the predetermined area to be inspected in the internal defect inspection process is at least 132 mm × 132 mm based on the substrate center. What is necessary is just to set it as the inside of a glass substrate of * 6.4mm. In addition, when a more reliable internal defect inspection is required, it is preferable that the predetermined area is inside the glass substrate of 142 mm × 142 mm × 6.45 mm with respect to the center of the substrate.

  By selecting the divergence angle θc in this way, the inspection light L is introduced into the glass substrate 10 from the end face 13 of the glass substrate 10 into the glass substrate 10, and the inspection light is applied to the entire predetermined region where the internal defect inspection of the glass substrate 10 is to be performed. Can be irradiated. This makes it possible to detect even minute internal defects in the vicinity of the front and back surfaces of the glass substrate 10 without omission.

  That is, as shown in FIG. 1, the inspection light L introduced into the glass substrate 10 from the end face 13 of the glass substrate 10 is the glass substrate 10 except for the regions S3 and S4 which are regions outside the light beams L1 and L2. To all other areas in the world. As a result, the inspection light L can be spread over the region in the glass substrate 10 where the transfer pattern is formed. By detecting the defect light generated at that time, defect detection without leakage can be performed relatively easily. it can.

In the embodiment described above, the divergence angle θc is specifically as follows.
Inspection light: ArF excimer laser light (exposure wavelength: 193 nm)
-Material of glass substrate 10: Synthetic quartz glass-Refractive index: 1.52 (at exposure wavelength: 193 nm)
・ Dimensions of glass substrate 10 length / width: 152 × 152 mm,
Thickness tg: 6.4 mm (target thickness after polishing process: 6.35 mm + error range)
Chamfering amount m (see FIG. 2): 0.6 mm
-Predetermined area: 132 mm x 132 mm x 6.4 mm (based on the substrate center)
Inspection light divergence angle θc: 4.8 °
Concave lens 28: Cylindrical lens (focal length: 300 mm)
-Distance d between the concave lens 28 and the end face 13: 10 mm

  The divergence angle θc in the above embodiment is an angle that is substantially the minimum that can cover the boundary surface B of the predetermined region on the end face 13 side. Considering only from the viewpoint of satisfying the function and effect of the present invention, the divergence angle θc may be larger than the minimum angle. However, as the divergence angle θc is increased, the light intensity (density) of the inspection light introduced into the glass substrate is decreased. Therefore, if the light intensity of the inspection light source is the same, the inspection light is irradiated. The light intensity of the fluorescence emitted from the internal defect also decreases, which may make it difficult to detect the fluorescence. This problem can be solved basically by increasing the light intensity of the inspection light source. However, if the light intensity of the inspection light source is increased too much, the inspection light energy increases and damages the inside of the substrate. It is concerned that it will give. In consideration of this point and the economical point related to facility enhancement, the divergence angle θc is the minimum that can cover the boundary surface B of the predetermined region on the end surface 13 side (end surface on the inspection light introduction side). An angle is preferred.

  For example, as described above, when the mask blank glass substrate is completed (after completion of the polishing process) and the vertical and horizontal dimensions are about 152 mm × 152 mm × 6.35 mm and the chamfering amount m is 0.6 mm, the minimum inspection light is allowed to reach. If the predetermined area is 132 mm × 132 mm × 6.4 mm, the divergence angle θc may be 4.8 ° or more. In addition, when the predetermined area to which the inspection light should reach is 142 mm × 142 mm × 6.45 mm with the same substrate dimensions, the divergence angle θc may be 10.3 ° or more. In view of a decrease in the light intensity of the inspection light by increasing the divergence angle diverged by the concave lens and the risk of damage to the substrate and an increase in the light intensity of the inspection light source, the divergence angle θc Is preferably 7.0 ° or less.

  In the present invention, since the concave lens 28 is necessary for diverging the substantially parallel inspection light from the inspection light source, even a spherical concave lens fulfills its function. However, what is required in the present invention is the divergence of the inspection light in the thickness direction of the substrate, and the divergence of the inspection light in the direction parallel to the main surface is not necessarily required. Conversely, in consideration of the decrease in the light intensity of the inspection light due to the divergence, it is preferable to minimize the divergence in the direction parallel to the main surface. Taking these into consideration, it is desirable to use a cylindrical lens as the concave lens 28 so that it mainly diverges only in the thickness direction of the substrate. In the present invention, any means may be used as long as substantially parallel inspection light can be diverging light, and a concave mirror may be used. Even in the case of this concave mirror, it is desirable to use a cylindrical concave mirror to diverge mainly only in the thickness direction of the substrate.

Next, with reference to FIG. 4, the apparatus configuration for carrying out the defect inspection process according to the above-described embodiment will be described, and the defect inspection process of the glass substrate for mask blank according to the embodiment of the present invention will be described. explain in detail. In FIG. 4, the code | symbol 20 is a defect inspection apparatus of a glass substrate. This glass substrate defect inspection apparatus 20 has a laser device 21 for generating inspection light L and irradiating the glass substrate, and a glass substrate 10 mounted thereon and moved in the X direction, the Y direction, and the Z direction, respectively, and its position. An XYZ stage 22 for sending information, a CCD camera 23 for detecting defective light generated on the glass substrate 10, image information from the CCD camera 23, position information from the XYZ stage 22, and the like are input to perform predetermined processing. A computer 27 and a cylindrical lens 28 for introducing the inspection light L into the glass substrate 10 as diverging light are provided.

  The laser device 21 is provided on the end surface 13 side of the glass substrate 10 placed on the XYZ stage 22. The cylindrical lens 28 is provided along the end face 13 on the end face 13 side of the glass substrate 10. The inspection light L emitted from the laser device 21 is converted into a predetermined divergent light by the cylindrical lens 28 and then introduced into the glass substrate 10 through the end face 13.

  The inspection light emitted from the laser device 21 is a pulsed ArF excimer laser beam (wavelength: 193 nm) having a beam shape of 7.0 mm × 4.0 mm, a power of 6 mJ, and a frequency of 400 Hz. The glass substrate 10 is arranged in parallel with the end face 13 or 14 and is formed to have substantially the same length and width as those end faces. The function as a lens acts as a concave lens in a cut surface (substrate thickness direction) perpendicular to the longitudinal direction (direction parallel to the main surface of the substrate). The function as a concave lens is to make the inspection light L into divergent light having a predetermined divergence angle, as already described in detail. Note that there is no lens action in the longitudinal direction.

  The XYZ stage 22 is configured to place the glass substrate 10 and move it in the XYZ directions. The XYZ stage 22 moves the glass substrate to a desired position and sends the position information to the computer 27. In the case of performing this defect inspection, the glass substrate 10 is set at the inspection start position, and then the inspection light L is introduced into the glass substrate 0 by the laser device 21, and images of the fluorescence Lkc and Lkd at that time are introduced. Is imaged by the CCD camera 23, and the image information and the position information are sent to the computer 27 and stored. Next, the XYZ stage 22 is driven to move the glass substrate 10 in the Y direction by the width of the inspection light L. Similarly, the inspection light L is irradiated, and the images of the fluorescence Lk and Lk at that time are CCD cameras. 23, and the image information and the position information are sent to the computer 27. By repeating this operation, the inspection light L is introduced from all regions from one end of the end face 13 to the other end.

  Next, the glass substrate 10 is moved on the XYZ stage 22 and installed so that the end face 14 faces the cylindrical lens 28. Next, the inspection light L is introduced from the end face 14. And the same operation as the case where it introduce | transduces from the end surface 13 is repeated, and the test | inspection light L is introduce | transduced from all the areas from one end of the end surface 14 to the other end. As a result, all areas in the glass substrate 10 are irradiated with the inspection light L, and images of defect light in all areas in the glass substrate 10 are accumulated. As described above, if the laser device 21 and the cylindrical lens 28 are installed on the side of the end surface 14 in addition to the side of the end surface 13 of the glass substrate 10 (indicated by a dotted line in FIG. 4), the glass substrate 10 is The entire area can be inspected while being fixed on the XYZ stage 22.

  The CCD camera 23 is arranged on the surface 11 side (upper side in the figure), which is one of the front and back surfaces, and creates an image based on information on light emitted from the glass substrate 10. That is, the fluorescence Lkc and Lkd generated from the internal defect of the glass substrate 10 are detected, an image of the fluorescence is taken, and the image information is sent to the computer 27. In this embodiment, a so-called monochrome camera is used as the CCD camera 23.

The computer 27 inputs an image from the CCD camera 23, processes the image at each position in the Y direction of the glass substrate 10, and at each position in the Y direction of the glass substrate 10, the light Lkc received by the CCD camera 23 is received. The light amounts (intensities) of Lkd and Lg are analyzed in relation to the X direction position of the glass substrate 10. That is, when the light quantity of the light Lkc, Lkd, and Lg has a local light quantity that is equal to or greater than a predetermined threshold, the computer 27 emits the light Lkc and Lkd with a local light quantity that is greater than or equal to the predetermined threshold value due to the internal defects Kc and Kd. It is determined that the internal defects Kc, Kd are located from the positions of the internal defects Kc, Kd (positions in the X direction and Y direction on the glass substrate 10), and the local amounts of light Lkc, Lkd emitted from the internal defects Kc, Kd. The types of defects Kc and Kd (local striae, contents, and foreign substances) are specified and detected.

  For example, when local striae or contents exist as the internal defect Kc in the glass substrate 10, ArF excimer laser light from the laser irradiation device 21 is introduced into the glass substrate 10. As shown in FIG. 5A, the object emits light Lkc having a local light quantity equal to or greater than a predetermined threshold (1000 counts), and the region other than the local striae or contents of the synthetic quartz glass substrate 4 emits light Lg. The computer 27 determines that the internal defect Kc is a local striae or a foreign substance from the shape of the light Lkc having a local light amount equal to or greater than a predetermined threshold by performing image processing and analyzing the light Lkc and Lg received by the CCD camera 23. If the local striae or contents are present at a position where the light Lkc having a local light quantity equal to or greater than the predetermined threshold is emitted, the local striae or contents are detected together with the position. Here, in the case of FIG. 5A, the horizontal axis indicates the position in the X direction of the glass substrate 10, and the vertical axis indicates the amount of light (intensity) of the light Lkc and Lg.

  Further, when foreign substances exist as internal defects Kc and Kd in the glass substrate 10, ArF excimer laser light is introduced into the glass substrate 10 from the laser irradiation device 21, whereby the foreign substances are shown in FIG. As shown in FIG. 4, a local amount of light Lkd equal to or greater than a predetermined threshold (1000 counts) is emitted in a predetermined range (for example, 10 to 20 mm), and a region other than the foreign matter of the synthetic quartz glass substrate 4 emits light Lg. The computer 27 performs image processing on the light Lkd and Lg received by the CCD camera 23 and analyzes them to determine the internal defect Kd as a foreign substance from the shape of the light Lkd having a local light amount equal to or greater than a predetermined threshold, and Assuming that the extraneous matter is present at a position where the light Lkd having a local light quantity equal to or greater than a predetermined threshold is generated, the extraneous matter is detected together with the position. Here, also in the case of FIG. 5B, the horizontal axis represents the X-direction position of the glass substrate 10, and the vertical axis represents the detected light amount (intensity). The glass substrate 10 in which the internal defects Kc and Kd are not detected by the glass substrate defect inspection apparatus 20 is a product that has passed the inspection, and is supplied to the next polishing step.

(3) Polishing process of mask blank glass substrate (2) For glass substrate 10 that has passed the inspection in the defect inspection process, its main surfaces 11 and 12, end surfaces 13, 14, 15, and 16, chamfered surface 13a, 13b, 14a, 14b, 15a, 15b, 16a, and 16b are mirror-polished and precision-polished so as to have a desired surface roughness, respectively, and a cleaning process is performed to obtain a glass substrate 10 for mask blank. The surface roughness of the main surfaces 11 and 12 at this time is preferably 0.2 nm or less in root mean square roughness (Rms).

(4) Mask blank manufacturing process (manufacturing method)
Next, a thin film (halftone film) for forming a mask pattern is formed on the main surface 11 of the mask blank glass substrate 10 obtained as described above using a known sputtering apparatus, for example, a DC magnetron sputtering apparatus. Then, a halftone phase shift mask blank as a mask blank is obtained. As a material used for this halftone film, a material whose main component is a transition metal silicide composed of a transition metal silicide such as molybdenum, tantalum, tungsten, and zirconium and silicon is oxidized, nitrided, or oxynitrided. It is done. Further, the halftone film has a laminated structure of two or more layers of a transmittance adjusting layer that mainly adjusts the transmittance for exposure light and a phase adjusting layer that mainly adjusts the phase difference for the exposure light transmitted through the film. Also good.

(5) Manufacturing process of photomask for exposure (manufacturing method)
Next, a pattern is formed on the halftone film of the mask blank (halftone phase shift mask blank) by a known pattern forming method to obtain a Hearton phase shift mask as an exposure photomask. That is, after applying a resist to the surface of the halftone film, a heat treatment is performed to form a resist film, a predetermined pattern is drawn and developed on the resist film, a resist pattern is formed, and the resist pattern is masked Then, the halftone film is dry-etched to form a halftone film pattern, the resist pattern is removed, and an exposure photomask in which the halftone film pattern is formed on the glass substrate 10 is obtained.

  According to the embodiment, in the defect inspection process, the inspection light L having a divergence angle θc is introduced from the end face 13 of the glass substrate 10 to detect the defect light, and then from the end face 14 facing the end face 13. By introducing inspection light L and detecting defect light in the same manner, even when there is a chamfered surface, it is possible to reliably reach the inspection light near the surface inside the glass substrate, and at the same time, the divergence angle By minimizing the above, it is possible to suppress the attenuation of the inspection light to a small level and to surely detect the defect, thereby enabling efficient inspection.

  In the first embodiment, the CCD camera 23 that receives the light Lkc, Lkd, and Lg emitted from the internal defects Kc and Kd in the defect inspection step is shown on the main surface 11 side. You may arrange | position to the surface 12 side or the end surface 14,15,16 side. Further, as long as the end face is polished to such an extent that inspection light can be introduced, ArF excimer laser light may be introduced to the end face side other than the end face 13.

  In the first embodiment, the case where the exposure light source is an ArF excimer laser has been described. However, the light may be light having a wavelength of 200 nm or less, preferably 100 nm to 200 nm, and may be an F2 excimer laser. In addition, in order to obtain the same wavelength as the ArF excimer laser or the F2 excimer laser, the light having a central wavelength that is the same as that of the ArF excimer laser or the F2 excimer laser may be used by dispersing light from a light source such as a heavy water (D2) lamp. .

  In the first embodiment, an example in which a black and white camera is used as the CCD camera 23 has been described. However, when the CCD camera is a color camera, internal defects of the glass substrate 10 and regions other than the internal defects are emitted. The computer 27 receives and shoots light having a wavelength longer than the exposure wavelength of 200 nm or more, and the computer 27 performs image processing on the image of the CCD camera 23 for each color of red, green, and blue, and the light subjected to image processing for each color. The internal defect 16 may be detected from the intensity (light quantity) distribution. In this case, the computer 27 may detect an internal defect from information such as the color and wavelength of light subjected to image processing for each color. Moreover, you may implement an internal defect detection at the final stage of the manufacturing process of the glass substrate for mask blanks.

  Furthermore, in Embodiment 1 described above, the CCD camera 23 receives light having a wavelength longer than the exposure wavelength light emitted from the internal defect of the glass substrate 10 and the region other than the internal defect. The spectroscope may receive the light, and the internal defect may be detected by measuring the spectral characteristics (wavelength and intensity) of the internal defect and the intensity (light quantity) distribution of the light 15 and 17. Further, the fluorescence may be detected visually by an inspector.

In the first embodiment, the case of a halftone phase shift mask blank in which a halftone film is formed on a mask blank glass substrate has been described. However, the present invention is not limited to this. For example, a halftone phase shift mask blank having a halftone film on a glass substrate 10 and a light shielding film on the halftone film, or a so-called binary type in which a light shielding film is formed on a glass substrate 7 for mask blank. It may be a mask blank. Examples of the structure of the light shielding film in this case include a two-layer laminated structure of a light shielding layer and a front surface antireflection layer from the substrate side, and a three-layer laminated structure in which a back surface antireflection layer is added between the substrate and the light shielding layer. It is done. As a material used for the light shielding film, a material mainly composed of chromium is first mentioned, and this is appropriately used as a main component so as to satisfy the characteristics required for the back surface antireflection layer, the light shielding layer, and the surface antireflection layer. It is preferable to use materials oxidized, nitrided, carbonized, etc., respectively. In addition, examples of materials applicable to the light-shielding film other than chromium include transition metal silicides composed of silicon and transition metals such as molybdenum, tungsten, and zirconium. It is preferable to use a material oxidized, nitrided, carbonized or the like. In addition, a light shielding film having a two-layer laminated structure or a three-layer laminated structure may be formed using a material mainly composed of tantalum and appropriately oxidized, nitrided, carbonized, or the like. A resist film may be formed on the halftone phase shift mask blank and the light shielding film of the mask blank.

(Embodiment 2)
In the first embodiment, the presence / absence of fluorescence in the predetermined region is inspected only by introducing inspection light from the end face 13. However, the inspection light that is substantially parallel to the inspection light source is divergent light by a concave lens. The light intensity per unit area decreases. In order to inspect the presence or absence of fluorescence in the entire predetermined region with inspection light (diverging light) introduced from one place on the end surface 13, the boundary surface D of the predetermined region on the end surface 14 side facing the end surface 13 (see FIG. 6). ) At least the intensity of light that can sufficiently detect the presence or absence of fluorescence is required. As described above, it is possible to increase the light intensity of the diverging light at the boundary surface D of the predetermined region on the end face 14 side by increasing the light intensity itself of the inspection light source. However, at this time, since the light intensity of the divergent light inside the substrate on the end face 13 side that is the inspection light introduction side inevitably increases, depending on the magnitude of the light intensity of the inspection light source to be increased, There is a possibility of damaging the inside of the substrate.

  The second embodiment solves the above problem by introducing divergent light of inspection light not only from the end face 13 side but also from the end face 14 side. In the second embodiment, as shown in FIG. 6, it passes through intermediate points C1, C2 on the main surfaces 11, 12 that bisect the distance between the end surface 13 and the end surface 14, and the end surface 13, the end surface 14, and The parallel intermediate plane C bisects a predetermined area where the inspection light needs to reach. Then, with the inspection light introduced from the end surface 13 side, at a minimum, the fluorescence of the region surrounded by the boundary surface B, the intermediate surface C, and the boundary surfaces E, F on the main surfaces 11 and 12 side of the predetermined region. The inspection light introduced from the side of the end surface 14 is minimally applied to the boundary surface D on the side of the end surface 14 and the boundary surface E and F on the side of both main surfaces 11 and 12 in the predetermined area. The presence or absence of fluorescence in the enclosed area is inspected. As a result, the diverging light to be introduced only needs to secure a light intensity that can at least check the presence or absence of fluorescence at the intermediate surface C, and damage to the inside of the substrate on the end face side where diverging light is introduced can be suppressed. In this case, if the outermost light rays of the inspection light L introduced into the glass substrate 10 are L1 and L2, the light rays L1 and L2 and the front and back main surfaces 11 and 2 of the predetermined region are provided. The divergence angle θc of the inspection light can be set so as to lie on the intersection lines Be, Bf, De, Df with the boundary surfaces E, F on the 12 side.

  In the second embodiment, after performing the internal defect inspection in which the inspection light is introduced from the end face 13 side, the method for introducing the inspection light from the end face 14 side which is the next step is as follows. The direction in which the substrate 10 is placed on the XYZ stage 22 may be changed so that the positions are switched. Further, as shown by a broken line in FIG. 4, the laser irradiation device 21 and the cylindrical lens 28 may be arranged on the end face 14 side as well. In the case of the second embodiment, at least the two end faces 13 and 14 for introducing the inspection light need to be mirror-polished. Other matters relating to the mask blank glass substrate manufacturing method, the mask blank manufacturing method, and the exposure photomask manufacturing method are the same as in the first embodiment.

(Embodiment 3)
In the third embodiment, similarly to the second embodiment, the inspection light is introduced not only from the end surface 13 side but also from the end surface 14 side, thereby causing damage due to the introduction of the inspection light into the glass substrate. However, the second embodiment is different from the second embodiment in that the light intensity of the inspection light source can be made substantially equal to that of the conventional internal defect inspection process using parallel light.

  In the third embodiment, as shown in FIG. 7, the inspection light introduced from the end face 13 side is, at a minimum, the intermediate face C, the end face 14 side face D, and the both main faces 11 and 12 side face. The region surrounded by E and F is inspected for the presence of fluorescence. Then, with the inspection light introduced from the end face 14 side, at least the presence or absence of fluorescence in the region surrounded by the intermediate face C, the boundary face B on the end face 13 side, and the boundary faces E and F on the main surfaces 11 and 12 side is determined. I try to inspect. In this case, if the outermost light rays of the inspection light L introduced into the glass substrate 10 are L3 and L4, the light rays L3 and L4 are the front and back main surfaces 11, The divergence angle θc of the inspection light can be set so as to lie on the intersection lines Ce, Cf, De, Df between the boundary surfaces E, F on the 12 side and the intermediate surface C. As a result, the divergence angle θc can be made considerably smaller than in the first and second embodiments, and the decrease in the light intensity of the inspection light due to the divergence can be minimized. As a result, the light intensity of the inspection light source can be made substantially the same level as in the case of the conventional internal defect inspection process using parallel light, and the damage caused by introducing the inspection light into the glass substrate is the same as in the prior art. It is suppressed to the same level.

  For example, when the mask blank glass substrate is completed (after completion of the polishing process), the vertical and horizontal dimensions are about 152 mm × 152 mm × 6.35 mm, and the chamfering amount k is 0.6 mm, the predetermined region where the inspection light should reach at least is set. If 132 mm × 132 mm × 6.4 mm, the divergence angle θc may be 0.7 ° or more.

  In the case of the internal defect inspection process of the third embodiment, the inspection light reaches the areas S3, S4, S5, and S6, which are areas where the inspection light does not physically reach in other embodiments. Therefore, in the case of the third embodiment, it is possible to perform the internal defect inspection for all the regions in the substrate 10 by slightly increasing the light intensity of the inspection light source. Other matters relating to the mask blank glass substrate manufacturing method, the mask blank manufacturing method, and the exposure photomask manufacturing method are the same as those in the first embodiment.

(Embodiment 4)
In the fourth embodiment, a defect inspection process, which is a process for inspecting an internal defect of a glass substrate, is not performed before (3) the polishing process of the glass substrate for mask blank, and (4) is performed after the manufacturing process of the mask blank. Thus, it is different from the first embodiment.

  (4) The internal defect of the glass substrate was inspected by the same method as the internal defect inspection step of (2) the mask blank glass substrate, with respect to the mask blank manufactured in the mask blank manufacturing process. The mask blank glass substrate is manufactured with the aim of a vertical and horizontal dimension of about 152 mm x 152 mm x 6.35 mm and a chamfering amount k of 0.6 mm. Assuming that the predetermined area is 132 mm × 132 mm × 6.4 mm, the divergence angle θc of the inspection light may be 4.8 ° or more. In view of a decrease in the light intensity of the inspection light by increasing the divergence angle diverged by the concave lens and the risk of damage to the substrate and an increase in the light intensity of the inspection light source, the divergence angle θc Is preferably 7.0 ° or less.

According to this embodiment, the same effect as in the first embodiment can be obtained. Further, since the fluorescence is reflected at the interface between the main surface 11 of the substrate and the thin film, an effect that the presence or absence of the fluorescence can be more easily identified is also obtained. As a method for introducing the inspection light into the glass substrate 10 of the mask blank, as shown in the second embodiment, the diverging light of the inspection light is sequentially introduced not only from the end face 13 side but also from the end face 14 side. You may do it. Further, as a method for introducing the inspection light into the glass substrate 10 of the mask blank, as shown in the third embodiment, the end face 13 is used by using the diverging light inspection light having a divergence angle θc of 0.7 ° or more. The inspection light may be introduced sequentially from both the side and the end face 14 side.

  (5) The same internal defect inspection as that performed on the mask blank may be performed on the exposure photomask manufactured in the manufacturing process of the exposure photomask. In addition, since the amount of light generated from the internal defect due to the irradiation of the fluorescence varies greatly depending on the irradiation intensity and the size of the internal defect, if a more reliable internal defect is required, the unpolished glass substrate The internal defect inspection may be performed at any of a plurality of stages, a mask blank glass substrate stage, a mask blank glass stage, and an exposure photomask stage.

10 ... Glass substrate for mask blank 11, 12 ... Main surface (front and back)
13, 14, 15, 16 ... end faces 13a, 13b, 14a, 14b, 15a, 15b, 16a, 16b ... chamfered surface 20 ... glass substrate defect inspection device 21 ... laser device 22 ... XYZ stage 23 CCD camera 27 computer 28 concave lens (cylindrical lens)

Claims (12)

A substrate preparation step of preparing a thin plate-like mask blank glass substrate having two main surfaces and four end surfaces;
A manufacturing method of a glass substrate for a mask blank having a defect inspection step of inspecting an internal defect by introducing inspection light having a wavelength of 200 nm or less from one end surface into the glass substrate,
The defect inspection step uses divergent light having a divergence angle of 7.0 ° or less as inspection light, and makes the inspection light reach the entire predetermined region to be inspected in the glass substrate, and whether or not there is fluorescence generated from an internal defect Is to inspect
A method for producing a glass substrate for a mask blank, wherein a glass substrate from which fluorescence is not detected is selected.   2. The method for producing a glass substrate for a mask blank according to claim 1, wherein the glass substrate has a chamfered surface formed at a corner where the two main surfaces and the four end surfaces intersect.   The said inspection light has a divergence angle which reaches | attains the whole predetermined area | region when it introduce | transduces in a glass substrate from one end surface, The manufacturing of the glass substrate for mask blanks in any one of Claim 1 or 2 characterized by the above-mentioned. Method.   When the inspection light is introduced into the glass substrate from one end surface, the inspection light is close to the one end surface in a predetermined region divided by an intermediate surface set between the one end surface and the end surface facing the one end surface. 3. The mask blank glass substrate according to claim 1, wherein the mask blank glass substrate has a divergence angle that does not reach the entire region in the side region and reaches the entire region in the region far from the one end face. 4. Method.   The inspection light is introduced into the glass substrate from one end surface to inspect for the presence of fluorescence, and then the inspection light is introduced into the glass substrate from the end surface opposite to the one end surface to inspect for the presence of fluorescence. The manufacturing method of the glass substrate for mask blanks in any one of Claim 1 to 4 characterized by the above-mentioned.   The mask blank glass according to any one of claims 1 to 5, wherein the inspection light is introduced into the glass substrate from an end face by making parallel light into divergent light by a concave lens or a concave mirror. A method for manufacturing a substrate.   The said concave lens is a cylindrical lens arrange | positioned in front of an end surface, The manufacturing method of the glass substrate for mask blanks of Claim 6 characterized by the above-mentioned.   The said concave mirror is a cylindrical concave mirror arrange | positioned in front of an end surface, The manufacturing method of the glass substrate for mask blanks of Claim 6 characterized by the above-mentioned.   A mask comprising a step of forming a thin film for pattern formation on a main surface of a glass substrate for mask blank produced by the method for producing a glass substrate for mask blank according to claim 1. Blank manufacturing method.   A method for producing a photomask for exposure, comprising a step of forming a fine pattern for exposure on the thin film for pattern formation of the mask blank produced by the method for producing a mask blank according to claim 9. A substrate preparation step of preparing a thin plate-like mask blank glass substrate having two main surfaces and four end surfaces;
A thin film forming step of forming a thin film for pattern formation on the main surface of the glass substrate;
A manufacturing method of a mask blank having a defect inspection step of inspecting internal defects by introducing inspection light having a wavelength of 200 nm or less from one end surface into a glass substrate,
The defect inspection step uses divergent light having a divergence angle of 7.0 ° or less as inspection light, and makes the inspection light reach the entire predetermined region to be inspected in the glass substrate, and whether or not there is fluorescence generated from an internal defect Is to inspect
A method of manufacturing a mask blank, comprising selecting a mask blank from which fluorescence is not detected. A substrate preparation step of preparing a thin plate-like mask blank glass substrate having two main surfaces and four end surfaces;
A thin film forming step of forming a thin film for pattern formation on the main surface of the glass substrate;
A fine pattern forming step of forming a fine pattern for exposure on the thin film;
A method of manufacturing a photomask for exposure having a defect inspection step of inspecting internal defects by introducing inspection light having a wavelength of 200 nm or less from one end surface into a glass substrate,
The defect inspection step uses divergent light having a divergence angle of 7.0 ° or less as inspection light, and makes the inspection light reach the entire predetermined region to be inspected in the glass substrate, and whether or not there is fluorescence generated from an internal defect Is to inspect
An exposure photomask manufacturing method, wherein an exposure photomask in which fluorescence is not detected is selected.

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