JP7589633B2 - METHOD FOR INSPECTING SUBSTRATE WITH MULTILAYER REFLECTIVE FILM AND METHOD FOR MANUFACTURING REFLECTIVE MASK BLANK - Google Patents

Description

This disclosure relates to a method for inspecting a substrate with a multilayer reflective film and a method for manufacturing a reflective mask blank.

In recent years, with the miniaturization of semiconductor devices, EUV lithography (EUVL), an exposure technology that uses extreme ultraviolet (EUV) light, has been developed. EUV includes soft X-rays and vacuum ultraviolet light, and specifically refers to light with a wavelength of about 0.2 nm to 100 nm. At present, EUV with a wavelength of about 13.5 nm is mainly being considered.

In EUVL, a reflective mask is used. A reflective mask includes a substrate such as a glass substrate, a multilayer reflective film formed on the substrate, and an absorbing film formed on the multilayer reflective film. An aperture pattern is formed in the absorbing film. In EUVL, the aperture pattern of the absorbing film is transferred to a semiconductor substrate.

In manufacturing reflective masks, it is important to identify the location of defects in the multilayer reflective film before forming an absorbing film on top of the multilayer reflective film. Defects in the multilayer reflective film are difficult to repair or remove. Therefore, a technique has been developed to correct the opening pattern of the absorbing film so that the defects in the multilayer reflective film are covered by the absorbing film. This technique is called mitigation.

Patent Document 1 discloses a technology for improving the accuracy of conversion from the coordinate system of a defect inspection device to the coordinate system of an electron beam lithography machine. The electron beam lithography machine writes a pattern on a resist film formed on an absorbing film. The resist film is then developed, and an opening pattern is formed in the absorbing film using the developed resist film.

International Publication No. 2020/095959

Defects in substrates with a multilayer reflective film are broadly divided into amplitude defects and phase defects. Amplitude defects change the amplitude of EUV light. Phase defects, on the other hand, change the phase of EUV light. Amplitude defects are mainly formed on the surface of the multilayer reflective film, whereas phase defects are mainly formed on the surface of the substrate or inside the multilayer reflective film. Amplitude defects and phase defects exist at different depths, so they are detected using different defect inspection devices and their positions are identified by the coordinates of separately set coordinate systems.

Previously, errors could occur when converting defect coordinates from one coordinate system to another. In addition, because defect inspection is performed over the entire quality assurance area of the board, it has previously been difficult to achieve both reduced inspection time and improved positional accuracy. For example, imaging the defect while the board is moving can reduce inspection time, but the positional accuracy of the defect decreases. On the other hand, imaging the defect while the board is stopped can improve the positional accuracy of the defect, but the area that can be inspected at one time is narrow, and the inspection time becomes too long.

One aspect of the present disclosure provides a technology that detects the coordinates of amplitude defects and phase defects with high accuracy in a short period of time.

The inspection method according to the first aspect of the present disclosure inspects a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film formed on the substrate that reflects EUV light. The inspection method according to the first aspect includes the following (A) to (D). (A) A first defect inspection device is used to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a first moving speed, thereby detecting an amplitude defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the amplitude defect in a first coordinate system set by the first defect inspection device. (B) A second defect inspection device different from the first defect inspection device is used to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a second moving speed, thereby detecting a phase defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the phase defect in a second coordinate system set by the second defect inspection device. (C) A coordinate conversion is performed to convert the coordinates of the amplitude defect from the first coordinate system to the second coordinate system. (D) Using the second defect inspection device, the multilayer reflective film-coated substrate is moved at a third moving speed slower than the first moving speed and the second moving speed, or the movement is stopped while capturing images of the coordinates of the amplitude defect and the phase defect in the second coordinate system, and the coordinates of the amplitude defect and the phase defect are acquired again.

The inspection method according to the second aspect of the present disclosure inspects a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film formed on the substrate that reflects EUV light. The inspection method according to the second aspect includes the following (E) to (H). (E) A first defect inspection device is used to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a first moving speed, thereby detecting an amplitude defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the amplitude defect in a first coordinate system set by the first defect inspection device. (F) A second defect inspection device different from the first defect inspection device is used to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a second moving speed, thereby detecting a phase defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the phase defect in a second coordinate system set by the second defect inspection device. (G) A coordinate conversion is performed to convert the coordinates of the phase defect from the second coordinate system to the first coordinate system. (H) Using the first defect inspection device, the multilayer reflective film-coated substrate is moved at a third moving speed slower than the first moving speed and the second moving speed, or the movement is stopped while capturing images of the coordinates of the amplitude defect and the phase defect in the first coordinate system, and the coordinates of the amplitude defect and the phase defect are acquired again.

An inspection method according to a third aspect of the present disclosure inspects a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film formed on the substrate that reflects EUV light. The inspection method according to the third aspect includes the following (I) to (L). (I) A first defect inspection device is used to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a first moving speed, thereby detecting an amplitude defect present in the multilayer reflective film-coated substrate, and obtaining coordinates of the amplitude defect in a first coordinate system set by the first defect inspection device. (J) A second defect inspection device different from the first defect inspection device is used to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a second moving speed, thereby detecting a phase defect present in the multilayer reflective film-coated substrate, and obtaining coordinates of the phase defect in a second coordinate system set by the second defect inspection device. (K) converting the coordinates of the amplitude defect from the first coordinate system to a third coordinate system different from the first coordinate system and the second coordinate system, and converting the coordinates of the phase defect from the second coordinate system to the third coordinate system. (L) using a third defect inspection device different from the first defect inspection device and the second defect inspection device, moving the multilayer reflective film-coated substrate at a third moving speed slower than the first moving speed and the second moving speed, or stopping the movement, imaging the coordinates of the amplitude defect and the phase defect in the third coordinate system, and acquiring the coordinates of the amplitude defect and the phase defect again.

According to one aspect of the present disclosure, images of amplitude defects and phase defects are captured while the multilayer reflective film-coated substrate is moving at high speed, the approximate coordinates of the amplitude defects and phase defects are identified, and then images of the amplitude defects and phase defects are captured again while the multilayer reflective film-coated substrate is moving at low speed or is stopped. Therefore, the coordinates of the amplitude defects and phase defects can be detected with high accuracy in a short time.

FIG. 1 is a flowchart showing a method for manufacturing a reflective mask blank according to an embodiment. FIG. 2 is a cross-sectional view showing a substrate of a reflective mask blank according to one embodiment. FIG. 3 is a plan view of the substrate of FIG. FIG. 4 is a cross-sectional view showing an example of a reflective mask blank. FIG. 5 is a cross-sectional view showing an example of a reflective mask. FIG. 6 is a cross-sectional view showing an example of a defect in a multilayer film-coated substrate. FIG. 7 is a cross-sectional view showing an example of an opening pattern of the absorbing film covering the defect of FIG. FIG. 8 is a flowchart showing a method for inspecting a multilayer film-coated substrate according to an embodiment. FIG. 9 is a diagram showing an example of coordinates of an amplitude defect in the first coordinate system. FIG. 10 is a diagram showing an example of coordinates of a phase defect in the second coordinate system. FIG. 11 is a diagram in which the origin of the first coordinate system shown in FIG. 9 and the origin of the second coordinate system shown in FIG. 10 are superimposed. FIG. 12 is a diagram showing an example of a result of transforming the coordinates of an amplitude defect from the first coordinate system to the second coordinate system.

Below, the embodiments for carrying out the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding configurations are given the same reference numerals, and the description may be omitted. In the specification, "~" indicating a numerical range means that the numerical values before and after it are included as the lower and upper limits.

As shown in FIG. 1, the method for manufacturing a reflective mask blank has steps S1 to S7. For example, a substrate 2 shown in FIG. 2 and FIG. 3 is used to manufacture a reflective mask blank. The substrate 2 includes a first main surface 21 and a second main surface 22 facing opposite to the first main surface 21. The first main surface 21 is rectangular. In this specification, a rectangular shape includes a shape with chamfered corners. The rectangle also includes a square. The second main surface 22 faces opposite to the first main surface 21. The second main surface 22 is also rectangular, like the first main surface 21.

The substrate 2 also includes four end faces 23, four first chamfered faces 24, and four second chamfered faces 25. The end faces 23 are perpendicular to the first main surface 21 and the second main surface 22. The first chamfered faces 24 are formed at the boundaries between the first main surface 21 and the end faces 23. The second chamfered faces 25 are formed at the boundaries between the second main surface 22 and the end faces 23. In this embodiment, the first chamfered faces 24 and the second chamfered faces 25 are so-called C-chamfered faces, but may be R-chamfered faces.

The substrate 2 is, for example, a glass substrate. The glass of the substrate 2 is preferably quartz glass containing _TiO2 . Quartz glass has a smaller linear expansion coefficient and a smaller dimensional change due to temperature change than general soda-lime glass. The quartz glass may contain 80% to 95% by mass of _SiO2 and 4% to 17% by mass of _TiO2 . When the _TiO2 content is 4% to 17% by mass, the linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. The quartz glass may contain a third component or impurity other than _SiO2 and _TiO2 .

In plan view, the size of the substrate 2 is, for example, 152 mm in length and 152 mm in width. The length and width may be 152 mm or more.

The substrate 2 has a central region 27 and a peripheral region 28 on the first main surface 21. The central region 27 is a square region 142 mm long and 142 mm wide, excluding the rectangular frame-shaped peripheral region 28 that surrounds the central region 27, and is processed to the desired flatness in steps S1 to S4, and is a quality assurance region. The four sides of the central region 27 are parallel to the four end faces 23. The center of the central region 27 coincides with the center of the first main surface 21.

Although not shown, the second main surface 22 of the substrate 2 also has a central region and a peripheral region, similar to the first main surface 21. The central region of the second main surface 22, like the central region of the first main surface 21, is a square region 142 mm long and 142 mm wide, and is the region that is processed to the desired flatness by steps S1 to S4 in FIG. 1 and is a quality assurance region.

First, in step S1, the first main surface 21 and the second main surface 22 of the substrate 2 are polished. In this embodiment, the first main surface 21 and the second main surface 22 are polished simultaneously by a double-sided polisher (not shown), but they may be polished sequentially by a single-sided polisher (not shown). In step S1, the substrate 2 is polished while a polishing slurry is supplied between the polishing pad and the substrate 2.

The polishing pad may be, for example, a urethane-based polishing pad, a nonwoven fabric-based polishing pad, or a suede-based polishing pad. The polishing slurry contains an abrasive and a dispersion medium. The abrasive is, for example, cerium oxide particles. The dispersion medium is, for example, water or an organic solvent. The first main surface 21 and the second main surface 22 may be polished multiple times with abrasives of different materials or particle sizes.

The abrasive used in step S1 is not limited to cerium oxide particles. For example, the abrasive used in step S1 may be silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, silicon carbide particles, etc.

Next, in step S2, the surface shapes of the first main surface 21 and the second main surface 22 of the substrate 2 are measured. To measure the surface shape, for example, a non-contact measuring machine such as a laser interference type is used so as not to scratch the surface. The measuring machine measures the surface shape of the central region 27 of the first main surface 21 and the central region of the second main surface 22.

Next, in step S3, the first main surface 21 and the second main surface 22 of the substrate 2 are locally processed to improve flatness, referring to the measurement results of step S2. The first main surface 21 and the second main surface 22 are locally processed in order. The order may be any one of them first, and is not particularly limited. The method of local processing is, for example, the GCIB (Gas Cluster Ion Beam) method or the PCVM (Plasma Chemical Vaporization Machining) method. The method of local processing may be a polishing method using a magnetic fluid, a polishing method using a rotating polishing tool, or the like.

Next, in step S4, the first main surface 21 and the second main surface 22 of the substrate 2 are subjected to finish polishing. In this embodiment, the first main surface 21 and the second main surface 22 are polished simultaneously by a double-sided polisher (not shown), but they may be polished sequentially by a single-sided polisher (not shown). In step S4, the substrate 2 is polished while a polishing slurry is supplied between the polishing pad and the substrate 2. The polishing slurry contains an abrasive. The abrasive is, for example, colloidal silica particles.

Next, in step S5, a conductive film 5 as shown in FIG. 4 is formed in the central region 27 of the first main surface 21 of the substrate 2. The conductive film 5 is used to attach the reflective mask to the electrostatic chuck of the exposure device. The conductive film 5 is made of, for example, chromium nitride (CrN). The conductive film 5 is formed, for example, by sputtering.

Next, in step S6, the multilayer reflective film 3 shown in FIG. 4 is formed in the central region of the second main surface 22 of the substrate 2. The multilayer reflective film 3 reflects EUV. The multilayer reflective film 3 is, for example, a laminate of high-refractive index layers and low-refractive index layers alternately. The high-refractive index layers are made of, for example, silicon (Si), and the low-refractive index layers are made of, for example, molybdenum (Mo). The multilayer reflective film 3 is formed, for example, by a sputtering method such as ion beam sputtering or magnetron sputtering.

Finally, in step S7, an absorbing film 4 shown in FIG. 4 is formed on the multilayer reflective film 3 formed in step S6. The absorbing film 4 absorbs EUV. The absorbing film 4 is formed of a single metal, alloy, nitride, oxide, oxynitride, or the like containing at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd). The absorbing film 4 is formed, for example, by sputtering.

Note that in this embodiment, steps S6 and S7 are performed after step S5, but they may also be performed before step S5.

The above steps S1 to S7 result in the reflective mask blank 1 shown in Figure 4. The reflective mask blank 1 has a first main surface 11 and a second main surface 12 facing opposite to the first main surface 11, and has, in this order from the first main surface 11 side to the second main surface 12 side, a conductive film 5, a substrate 2, a multilayer reflective film 3, and an absorbing film 4.

Although not shown, the reflective mask blank 1 has a central region and a peripheral region on the first main surface 11, similar to the substrate 2. The central region is a square region 142 mm long and 142 mm wide, excluding the rectangular frame-shaped peripheral region surrounding the central region, and is a quality assurance region. Similarly to the substrate 2, the reflective mask blank 1 also has a central region and a peripheral region on the second main surface 12. The central region is a square region 142 mm long and 142 mm wide, excluding the rectangular frame-shaped peripheral region surrounding the central region, and is a quality assurance region.

The reflective mask blank 1 may include other films in addition to the conductive film 5, the substrate 2, the multilayer reflective film 3, and the absorbing film 4.

For example, the reflective mask blank 1 may further include a low-reflection film. The low-reflection film is formed on the absorbing film 4. Then, an opening pattern 41 is formed in both the low-reflection film and the absorbing film 4. The low-reflection film is used to inspect the opening pattern 41, and has lower reflection characteristics with respect to inspection light than the absorbing film 4. The low-reflection film is formed of, for example, TaON or TaO. The low-reflection film is formed, for example, by sputtering.

The reflective mask blank 1 may further include a protective film. The protective film is formed between the multilayer reflective film 3 and the absorbing film 4. The protective film protects the multilayer reflective film 3 so that the multilayer reflective film 3 is not etched when the absorbing film 4 is etched to form an opening pattern 41 in the absorbing film 4. The protective film is made of, for example, Ru, Si, or _TiO2 . The protective film is formed by, for example, sputtering.

As shown in FIG. 5, the reflective mask is obtained by forming an opening pattern 41 in the absorbing film 4. The opening pattern 41 is formed by photolithography and etching. Therefore, the resist film used to form the opening pattern 41 may be included in the reflective mask blank 1.

Figure 6 shows a substrate 7 with a multilayer reflective film. Hereinafter, the substrate 7 with a multilayer reflective film will also be simply referred to as substrate 7. The substrate 7 has at least a substrate 2 and a multilayer reflective film 3. In manufacturing a reflective mask, it is important to identify the location of defects in the multilayer reflective film 3 before forming an absorbing film 4 on the multilayer reflective film 3.

It is difficult to repair or remove defects in the multilayer reflective film 3. Therefore, as shown in FIG. 7, a technique has been developed to correct the opening pattern 41 of the absorbing film 4 so that the defects in the multilayer reflective film 3 are covered by the absorbing film 4. This technique is called mitigation.

The defects on the substrate 7 are broadly divided into amplitude defects 31 and phase defects 32. Amplitude defects 31 change the amplitude of EUV light. On the other hand, phase defects 32 change the phase of EUV light. Amplitude defects 31 are mainly formed on the surface of the multilayer reflective film 3, whereas phase defects 32 are mainly formed on the surface of the substrate 2 or inside the multilayer reflective film 3. Since amplitude defects 31 and phase defects 32 exist at different depths, they are detected using different defect inspection devices and their positions are identified by coordinates in separately set coordinate systems.

Conventionally, errors could occur when converting defect coordinates from one coordinate system to another. In addition, because defect inspection is performed over the entire quality assurance area of the substrate 7, it has been difficult to achieve both a shorter inspection time and improved positional accuracy. For example, imaging the defect while the substrate 7 is moving at high speed can shorten the inspection time, but the positional accuracy of the defect decreases. On the other hand, imaging the defect while the substrate 7 is moving at low speed or stopped can improve the positional accuracy of the defect, but the area that can be inspected at one time is narrow, and the inspection time becomes too long.

Next, a method for inspecting a substrate with a multilayer reflective film according to this embodiment will be described with reference to Figures 8 to 13. The inspection method includes steps S101 to S104. The order of steps S101 and S102 may be reversed, and step S101 may be performed after step S102.

First, in step S101, an image of the substrate 7 is taken while the substrate 7 is moved at a first moving speed V1 using a first defect inspection device (not shown), thereby detecting an amplitude defect 31 present on the substrate 7, and acquiring the coordinates of the amplitude defect 31 in a first coordinate system set on the substrate 7 by the first defect inspection device. Note that it is sufficient to image the substrate 7 while the substrate 7 is moving, and the detection (image processing) of the amplitude defect 31 and the identification of the coordinates of the amplitude defect 31 do not have to be performed while the substrate 7 is moving.

A commercially available device, such as a laser inspection device, is used as the first defect inspection device. The first defect inspection device is more suitable for detecting amplitude defects 31 than phase defects 32. However, the first defect inspection device is also capable of detecting not only amplitude defects 31 but also phase defects 32.

The first defect inspection device includes, for example, an inspection stage, a movement mechanism, a position measuring instrument, an illuminator, a detector, and an image processing device. The inspection stage holds the substrate 7 horizontally from below with the multilayer reflective film 3 facing upward. The movement mechanism moves the inspection stage in the horizontal direction. The position measuring instrument measures the position of the inspection stage. The position measuring instrument is, for example, a laser displacement meter.

The illuminator irradiates light onto the substrate 7 held on the inspection stage. The wavelength of the light is not particularly limited, but is, for example, 193 nm to 532 nm. Light with a wavelength of 193 nm to 532 nm is suitable for inspecting the surface of the multilayer reflective film 3 and is suitable for detecting amplitude defects 31.

The detector receives reflected or scattered light of the light irradiated by the illuminator onto the multilayer reflective film 3. The detector is an area sensor in which multiple light receiving elements are arranged in a matrix, but may also be a line sensor in which multiple light receiving elements are arranged in a row, or a sensor consisting of a single light receiving element. For example, a CCD image sensor or a CMOS image sensor is used as the area sensor. When a sensor consisting of a single light receiving element is used, the light irradiated by the illuminator onto the multilayer reflective film 3 is scanned using, for example, a galvanometer mirror or a polygon mirror, and the reflected or scattered light is received. For example, a PMT (Photomultiplier Tube) or an APD (Avalanche Photodiode) is used as the single light receiving element.

The image processing device processes the image captured by the detector and detects the amplitude defect 31. The image processing device also obtains the coordinates of the amplitude defect 31 in the image and the position of the inspection stage when the image was captured, in a first coordinate system set on the substrate 7.

As shown in FIG. 9, the origin of the first coordinate system (XY coordinate system) is set, for example, at the center of the quality assurance area 77 of the substrate 7. The quality assurance area 77 is, for example, a square area 142 mm long and 142 mm wide, and is the area that is processed to the desired flatness by steps S1 to S4 in FIG. 1.

The first coordinate system is a two-dimensional orthogonal coordinate system. The X-axis direction and the Y-axis direction are mutually orthogonal, and both are horizontal. The multiple light receiving elements constituting the detector are arranged in a matrix, with the row direction being the X-axis direction and the column direction being the Y-axis direction, for example. Note that, as described above, the multiple light receiving elements may be arranged in a row. Also, if the light irradiated to the multilayer reflective film 3 by the irradiator is scanned in the X-axis or Y-axis direction, the detector may be a single light receiving element.

The image processing device processes the image captured by the detector and detects the reference mark 71. The reference mark 71 is formed on the substrate 2 or the multilayer reflective film 3. By detecting the reference mark 71, the image processing device detects the center of the quality assurance area 77.

The reference marks 71 are formed, for example, outside the quality assurance area 77. The number of reference marks 71 is four in FIG. 9, but may be two or more. The shape of the reference marks 71 is cross-shaped in FIG. 9, but is not limited to a cross shape.

In step S101, the inspection stage and substrate 7 are moved at a first moving speed V1 while the substrate 7 is imaged. Therefore, the entire quality assurance area 77 can be imaged in a short time, and the inspection time can be shortened, compared to when the substrate 7 is imaged while moving at a third moving speed V3 (V3<V1) described below or while stopping the movement. In step S101, the approximate coordinates of the amplitude defect 31 can be obtained.

The first movement speed V1 is, for example, 10 mm/sec to 1000 mm/sec, and preferably 50 mm/sec to 200 mm/sec. The third movement speed V3 is, for example, 0 mm/sec to 50 mm/sec, and preferably 0 mm/sec to 10 mm/sec.

The pixel resolution of the image acquired in step S101 is lower than the pixel resolution of the image acquired in step S104 described below, and is, for example, 50 nm to 1000 nm, and preferably 50 nm to 400 nm. The pixel resolution is the actual size (X-axis dimension or Y-axis dimension) of the object imaged by one light receiving element, and is the maximum value of the X-axis dimension and the Y-axis dimension.

Next, in step S102, a second defect inspection device (not shown) is used to image the substrate 7 while moving the substrate 7 at a second moving speed V2, thereby detecting a phase defect 32 present on the substrate 7, and acquiring the coordinates of the phase defect 32 in the second coordinate system set on the substrate 7 by the second defect inspection device. Note that it is sufficient to image the substrate 7 while the substrate 7 is moving, and the detection (image processing) of the phase defect 32 and the identification of the coordinates of the phase defect 32 do not have to be performed while the substrate 7 is moving.

A commercially available device is used as the second defect inspection device, such as an ABI (Actinic Blank Inspection) device manufactured by Lasertec Corporation. The second defect inspection device is more suitable for detecting phase defects 32 than amplitude defects 31. However, the second defect inspection device is also capable of detecting amplitude defects 31 as well as phase defects 32.

The second defect inspection device, like the first defect inspection device, includes, for example, an inspection stage, a movement mechanism, a position measuring device, an illuminator, a detector, and an image processing device. The inspection stage holds the substrate 7 horizontally from below with the multilayer reflective film 3 facing upward. The movement mechanism moves the inspection stage in the horizontal direction. The position measuring device measures the position of the inspection stage. The position measuring device is, for example, a laser displacement meter or a laser interferometer.

The illuminator irradiates light onto the substrate 7 held on the inspection stage. The wavelength of the light is not particularly limited, but is, for example, 10 nm to 20 nm. Light with a wavelength of 10 nm to 20 nm is suitable for inspecting the inside of the multilayer reflective film 3 and is suitable for detecting phase defects 32.

The detector receives reflected or scattered light of the light irradiated onto the multilayer reflective film 3 by the irradiator. The detector is an area sensor in which multiple light receiving elements are arranged in a matrix, but it may also be a line sensor in which multiple light receiving elements are arranged in a row. As the area sensor, for example, a CCD image sensor or a CMOS image sensor is used.

The image processing device processes the image captured by the detector and detects the phase defect 32. The image processing device also obtains the coordinates of the phase defect 32 in a second coordinate system set on the substrate 7 from the coordinates of the phase defect 32 in the image and the position of the inspection stage when the image was captured.

As shown in FIG. 10, the origin of the second coordinate system (UV coordinate system) is set, for example, at the center of the quality assurance area 77 of the substrate 7. The second coordinate system is a two-dimensional Cartesian coordinate system. The U-axis direction and the V-axis direction are mutually perpendicular and both are horizontal. The multiple light receiving elements that make up the detector are arranged in a matrix, with the row direction being the U-axis direction and the column direction being the V-axis direction, for example. Note that, as mentioned above, the multiple light receiving elements may also be arranged in a row.

The image processing device processes the image captured by the detector and detects the reference mark 71.

In step S102, the inspection stage and substrate 7 are moved at the second moving speed V2 while the substrate 7 is imaged. Therefore, the entire quality assurance area 77 can be imaged in a short time compared to when the substrate 7 is moved at a third moving speed V3 (V3<V2) described below or when the substrate 7 is imaged while stopped, thereby shortening the inspection time. In step S102, the approximate coordinates of the phase defect 32 can be obtained.

The second movement speed V2 is, for example, 10 mm/sec to 1000 mm/sec, and preferably 50 mm/sec to 200 mm/sec. On the other hand, as described above, the third movement speed V3 is, for example, 0 mm/sec to 50 mm/sec, and preferably 0 mm/sec to 10 mm/sec.

The pixel resolution of the image acquired in step S102 is lower than the pixel resolution of the image acquired in step S104 described below, and is, for example, 100 nm to 1000 nm, and preferably 100 nm to 500 nm. The pixel resolution is the actual size (U-axis dimension or V-axis dimension) of the object imaged by one light receiving element, and is the maximum value of the U-axis dimension and the V-axis dimension.

Figure 11 is a diagram in which the origin of the first coordinate system shown in Figure 9 and the origin of the second coordinate system shown in Figure 10 are superimposed. In Figure 11, the dashed line indicates the first coordinate system, and the solid line indicates the second coordinate system. The outline of the substrate 7 in the first coordinate system is misaligned with the outline of the substrate 7 in the second coordinate system. In addition, the reference mark 71 in the first coordinate system is misaligned with the reference mark 71 in the second coordinate system.

In step S103, a coordinate transformation is performed to transform the coordinates of the amplitude defect 31 from the first coordinate system to the second coordinate system. The coordinate transformation is performed, for example, based on a plurality of reference marks 71, for example, by translating, rotating, or scaling the first coordinate system so that the reference marks 71 in the first coordinate system coincide with the reference marks 71 in the second coordinate system.

The coordinate transformation is, for example, a Helmert transformation, an affine transformation, or a projective transformation. A Helmert transformation is performed based on two or more reference marks 71. An affine transformation is performed based on three or more reference marks 71. A projective transformation is performed based on four or more reference marks 71.

The coordinate transformation may be performed using a common defect instead of the reference mark 71. A common defect is a defect that is both a phase defect 32 and an amplitude defect 31. The common defect is detected in both step S101 and step S102.

By converting the coordinates of the amplitude defect 31 from the first coordinate system to the second coordinate system in step S103, the coordinates of the amplitude defect 31 and the coordinates of the phase defect 32 can be obtained in the same second coordinate system, as shown in FIG. 12.

In step S104, the second defect inspection device is used to move the substrate 7 at a third moving speed V3 (V3<V1, V2) or to stop the substrate 7 while capturing images of the coordinates of the amplitude defect 31 and the phase defect 32 in the second coordinate system (e.g., the coordinates shown in FIG. 12), and the coordinates of the amplitude defect 31 and the phase defect 32 are acquired again. This makes it possible to eliminate errors caused by the coordinate conversion. In addition, since the approximate coordinates of the amplitude defect 31 and the phase defect 32 have already been identified before step S104, the number of images captured while the substrate 7 is moving at a low speed or while it is stopped can be reduced, and the inspection time can be shortened. In addition, since the substrate 7 is captured while it is moving at a low speed or while it is stopped, clear images can be acquired and the coordinates of the defects can be acquired with high accuracy.

The pixel resolution of the image acquired in step S104 is, for example, 5 nm to 100 nm, and preferably 5 nm to 20 nm. The pixel resolution is the actual size (U-axis dimension or V-axis dimension) of the object imaged by one light receiving element, and is the maximum value of the U-axis dimension and the V-axis dimension.

In step S104, the cumulative amount of light irradiation per unit area may be increased compared to step S102. This allows a clearer image to be obtained, and the coordinates of the defect to be obtained with higher accuracy. The cumulative amount of light irradiation per unit area is controlled by the output of the light source, the light irradiation time, etc.

However, the coordinates of the amplitude defect 31 and the phase defect 32 identified before step S104 have low accuracy. Therefore, even if the coordinates identified before step S104 are imaged in step S104, it may not be possible to detect the amplitude defect 31 or the phase defect 32. In this case, step S104 includes shifting the imaged coordinates and re-imaging. For example, an area adjacent to an area already imaged is re-imaged. The image may be retaken until the amplitude defect 31 or the phase defect 32 is detected, or may be taken within a predetermined range.

The inspection method disclosed herein is not limited to the above inspection method. For example, in step S103, a coordinate conversion may be performed to convert the coordinates of the phase defect 32 from the second coordinate system (UV coordinate system) to the first coordinate system (XY coordinate system). In this case, in step S104, the first defect inspection device is used to move the substrate 7 at a third speed or to stop the movement while capturing images of the coordinates of the amplitude defect 31 and the phase defect 32 in the first coordinate system, and the coordinates of the amplitude defect 31 and the phase defect 32 are acquired again.

Alternatively, in step S103, coordinate conversion may be performed to convert the coordinates of the amplitude defect 31 from the first coordinate system (XY coordinate system) to a third coordinate system, and to convert the coordinates of the phase defect 32 from the second coordinate system (UV coordinate system) to the third coordinate system. The third coordinate system is a coordinate system set on the substrate 7 by a third defect inspection device that is different from the first defect inspection device and the second defect inspection device.

In this case, in step S104, the third defect inspection device is used to move the substrate 7 at the third speed or to stop the movement while capturing images of the coordinates of the amplitude defect 31 and the phase defect 32 in the third coordinate system, and the coordinates of the amplitude defect 31 and the phase defect 32 are acquired again. The third defect inspection device includes, for example, an inspection stage, a movement mechanism, a position measuring device, an illuminator, a detector, and an image processing device. The inspection stage holds the substrate 7 horizontally from below with the multilayer reflective film 3 facing upward. The movement mechanism moves the inspection stage horizontally. The position measuring device measures the position of the inspection stage. The position measuring device is, for example, a laser displacement meter.

The illuminator irradiates light onto the substrate 7 held on the inspection stage. The wavelength of the light is not particularly limited, but is, for example, 10 nm to 532 nm. The wavelength of the light may be 10 nm to 20 nm, or 193 nm to 532 nm. The third defect inspection device may have two light sources with different wavelengths. Note that the first defect inspection device and the second defect inspection device may also have two light sources with different wavelengths.

The detector receives reflected or scattered light of the light irradiated onto the multilayer reflective film 3 by the irradiator. The detector is an area sensor in which multiple light receiving elements are arranged in a matrix, but it may also be a line sensor in which multiple light receiving elements are arranged in a row. As the area sensor, for example, a CCD image sensor or a CMOS image sensor is used.

The image processing device processes the image captured by the detector and detects the amplitude defect 31 and the phase defect 32. The image processing device also obtains the coordinates of the amplitude defect 31 and the phase defect 32 in a third coordinate system set on the substrate 7 from the coordinates of the amplitude defect 31 and the phase defect 32 in the image and the position of the inspection stage when the image was captured.

The above describes the method for inspecting a multilayer reflective film-coated substrate and the method for manufacturing a reflective mask blank according to the present disclosure, but the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. Naturally, these also fall within the technical scope of the present disclosure.

2 Substrate 3 Multilayer reflective film 4 Absorbing film

Claims (20)

1. A method for inspecting a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film that reflects EUV light and is formed on the substrate, comprising:
using a first defect inspection device to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a first moving speed, thereby detecting an amplitude defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the amplitude defect in a first coordinate system set by the first defect inspection device;
using a second defect inspection device different from the first defect inspection device to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a second moving speed, thereby detecting a phase defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the phase defect in a second coordinate system set by the second defect inspection device;
performing a coordinate transformation to transform coordinates of the amplitude defect from the first coordinate system to the second coordinate system;
using the second defect inspection device to move the multilayer reflective film coated substrate at the first movement speed and a third movement speed slower than the second movement speed, or while stopping the movement, capture images of coordinates of the amplitude defect and the phase defect in the second coordinate system, and acquire the coordinates of the amplitude defect and the phase defect again;
The inspection method includes: The inspection method according to claim 1, wherein the pixel resolution of an image captured by the second defect inspection device while moving the multilayer reflective film-coated substrate at the second moving speed is lower than the pixel resolution of an image captured by the second defect inspection device while moving the multilayer reflective film-coated substrate at the third moving speed or while stopping the movement. The inspection method according to claim 1 or 2, wherein the movement of the multilayer reflective film-coated substrate is stopped while the coordinates of the amplitude defect and the phase defect in the second coordinate system are imaged. The inspection method according to claim 3, further comprising imaging the coordinates of the amplitude defect or the phase defect in the second coordinate system while the movement of the multilayer reflective film-coated substrate is stopped using the second defect inspection device, and if the amplitude defect or the phase defect cannot be detected, shifting the imaging coordinates and imaging again. 1. A method for inspecting a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film that reflects EUV light and is formed on the substrate, comprising:
using a first defect inspection device to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a first moving speed, thereby detecting an amplitude defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the amplitude defect in a first coordinate system set by the first defect inspection device;
using a second defect inspection device different from the first defect inspection device to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a second moving speed, thereby detecting a phase defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the phase defect in a second coordinate system set by the second defect inspection device;
performing a coordinate transformation to transform coordinates of the phase defect from the second coordinate system to the first coordinate system;
using the first defect inspection device to move the multilayer reflective film coated substrate at a third moving speed slower than the first moving speed and the second moving speed, or while stopping the movement, capture images of coordinates of the amplitude defect and the phase defect in the first coordinate system, and acquire the coordinates of the amplitude defect and the phase defect again;
The inspection method includes: The inspection method according to claim 5, wherein the pixel resolution of an image captured by the first defect inspection device while moving the multilayer reflective film-coated substrate at the first moving speed is lower than the pixel resolution of an image captured by the first defect inspection device while moving the multilayer reflective film-coated substrate at the third moving speed or while stopping the movement. The inspection method according to claim 5 or 6, wherein the movement of the multilayer reflective film-coated substrate is stopped while the coordinates of the amplitude defect and the phase defect in the first coordinate system are imaged. The inspection method according to claim 7, further comprising imaging the coordinates of the amplitude defect or the phase defect in the first coordinate system while the movement of the multilayer reflective film-coated substrate is stopped using the first defect inspection device, and if the amplitude defect or the phase defect cannot be detected, shifting the imaging coordinates and imaging again. 1. A method for inspecting a multilayer reflective film-coated substrate having a substrate and a multilayer reflective film that reflects EUV light and is formed on the substrate, comprising:
using a first defect inspection device to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a first moving speed, thereby detecting an amplitude defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the amplitude defect in a first coordinate system set by the first defect inspection device;
using a second defect inspection device different from the first defect inspection device to image the multilayer reflective film-coated substrate while moving the multilayer reflective film-coated substrate at a second moving speed, thereby detecting a phase defect present in the multilayer reflective film-coated substrate, and acquiring coordinates of the phase defect in a second coordinate system set by the second defect inspection device;
performing a coordinate transformation to transform coordinates of the amplitude defect from the first coordinate system to a third coordinate system different from the first coordinate system and the second coordinate system, and to transform coordinates of the phase defect from the second coordinate system to the third coordinate system;
using a third defect inspection device different from the first defect inspection device and the second defect inspection device, the multilayer reflective film-coated substrate is moved at a third moving speed slower than the first moving speed and the second moving speed, or the substrate is stopped while imaging the coordinates of the amplitude defect and the phase defect in the third coordinate system, and the coordinates of the amplitude defect and the phase defect are acquired again;
The inspection method includes: The inspection method according to claim 9, wherein the pixel resolution of an image captured by the first defect inspection device while moving the multilayer reflective film-coated substrate at the first moving speed and the pixel resolution of an image captured by the second defect inspection device while moving the multilayer reflective film-coated substrate at the second moving speed are lower than the pixel resolution of an image captured by the third defect inspection device while moving the multilayer reflective film-coated substrate at the third moving speed or while stopping the movement. The inspection method according to claim 9 or 10, wherein the movement of the multilayer reflective film-coated substrate is stopped while the coordinates of the amplitude defect and the phase defect in the third coordinate system are imaged. The inspection method according to claim 11, further comprising imaging the coordinates of the amplitude defect or the phase defect in the third coordinate system while the movement of the multilayer reflective film-coated substrate is stopped using the third defect inspection device, and, if the amplitude defect or the phase defect cannot be detected, shifting the imaging coordinates and imaging again. The inspection method according to any one of claims 1 to 12, wherein the first defect inspection device images the amplitude defect using reflected or scattered light of wavelengths of 193 nm to 532 nm. The inspection method according to any one of claims 1 to 13, wherein the second defect inspection device images the phase defect using reflected or scattered light of a wavelength of 10 nm to 20 nm. The inspection method according to any one of claims 9 to 12, wherein the third defect inspection device images the amplitude defect and the phase defect using reflected or scattered light of a wavelength of 10 nm to 532 nm. The inspection method according to any one of claims 1 to 15, wherein the pixel resolution of the image captured while moving the multilayer reflective film-coated substrate at the third moving speed or while stopping the movement is 5 nm to 100 nm. 17. The inspection method according to claim 1, wherein the multilayer reflective film coated substrate has a plurality of reference marks on the substrate or the multilayer reflective film, and the coordinate transformation is performed based on the plurality of reference marks. the multilayer reflective film-coated substrate has a plurality of common defects which are both the phase defects and the amplitude defects,
The inspection method according to any one of claims 1 to 17, wherein the coordinate transformation is performed based on a plurality of the common defects. The inspection method according to any one of claims 1 to 18, wherein the coordinate transformation is a Helmert transformation, an affine transformation, or a projective transformation. A method for manufacturing a reflective mask blank, comprising forming an absorbing film on the multilayer reflective film inspected using the inspection method according to any one of claims 1 to 19.

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