JP4822471B1 - EUV mask inspection apparatus and EUV mask inspection method - Google Patents

Abstract

To provide an EUV mask inspection apparatus capable of performing a highly sensitive inspection using an EUV light source.
An EUV (Extreme Ultra Violet) mask inspection apparatus includes an EUV light source, an illumination optical system, a Schwarzschild optical system, and a TDI camera. The illumination optical system illuminates the EUV mask blank 110 with the EUV light EUV 11 from the EUV light source 101. The Schwarzschild optical system 108 condenses the scattered light S1 and S2 generated when the EUV light EUV11 is irradiated onto the defect on the EUV mask blank 110. The TDI camera 109 detects the collected scattered lights S1 and S2 and acquires a dark field image of the defect on the EUV mask blank 110. The EUV light EUV11 includes EUV light having a wavelength range of 10.5 nm to 13.1 nm. The incident angle of the EUV light EUV11 with respect to the EUV mask blanks 110 is 15.2 ° or more and 39.3 ° or less.
[Selection] Figure 1

Description

  The present invention relates to an EUV mask inspection apparatus, and more particularly to an EUV mask inspection apparatus having high detection sensitivity.

  With regard to lithography technology that is responsible for semiconductor miniaturization, ArF lithography using an ArF excimer laser with an exposure wavelength of 193 nm as an exposure light source is currently being mass-produced. In addition, an immersion technique (ArF immersion lithography) for increasing the resolution by filling the space between the objective lens of the exposure apparatus and the wafer with water has begun to be used for mass production. In order to realize further miniaturization, various technical developments have been made for practical use of EUVL (Extreme Ultra Violet Lithography) with an exposure wavelength of 13.5 nm.

  FIG. 7 is a cross-sectional view showing the structure of a general EUV (Extreme Ultra Violet) mask. In the EUV mask 700, as shown in FIG. 7, a multilayer film 702 which is a reflection mirror of EUV light is formed on a substrate 701 made of low thermal expansion glass. The multilayer film 702 usually has a structure in which several tens of layers of molybdenum and silicon are alternately stacked. With this structure, about 65% of EUV light with a wavelength of 13.5 nm incident perpendicularly to the multilayer film 702 can be reflected. On the multilayer film 702, an absorber 703 that absorbs EUV light is formed. Mask blanks are constituted by the substrate 701, the multilayer film 702, and the absorber 703. However, a protective film (a film called a buffer layer or a capping layer) 704 is formed between the absorber 703 and the multilayer film 702. In order to produce an EUV mask that is actually used for exposure, a resist pattern is formed on a mask blank. Then, etching with the resist pattern as a mask completes the patterned EUV mask.

  In the following description, the EUV mask includes a substrate, a mask blank, and a patterned EUV mask unless there is a particular need for distinction.

  In EUV masks, the minimum size and depth of unacceptable defects, especially in substrates and mask blanks, is very small compared to conventional ArF masks. This makes it difficult to detect unacceptable defects. On the other hand, when the inspection light source is inspected with EUV light, that is, illumination light having a wavelength of 13.5 nm, which is the same wavelength as the exposure light, it is also possible to detect a minute uneven defect having a wavelength of about 1/10. Such a method of performing inspection at the same wavelength as the exposure light is called actinic inspection. In order to detect minute defects, actinic inspection is indispensable particularly in EUV masks. For example, Non-Patent Document 1 discloses an actinic inspection apparatus for mask blanks of EUV masks.

  The power of the EUV light source used for the actinic inspection of the EUV mask is sufficient to be 2 to 3 orders of magnitude lower than the EUV light source having an average power of 100 to 300 W required for the EUV light source for the EUV exposure apparatus. For this reason, a structurally simple discharge plasma (hereinafter referred to as DPP: Discharge Produced Plasma) light source using xenon gas is often used as an actinic inspection light source for an EUV mask. Hereinafter, a DPP light source using xenon gas is referred to as a xenon-based DPP light source.

  Note that a light source that emits light by generating small plasma in xenon gas is called microplasma, but microplasma is a kind of DPP in a broad sense. Therefore, in the following, xenon-based DPP is assumed to contain microplasma.

  Note that in an EUV light source for an exposure machine that requires a high output, a light source that converts tin (Sn) into plasma is used. This light source is known to have higher luminous efficiency at 13.5 nm than xenon. However, since Sn is solid at room temperature, in order to turn it into plasma, it is necessary to devise such as liquefying Sn, and the structure of the light source becomes complicated. Therefore, a xenon-based DPP light source that can be converted into plasma with a simple structure is widely used as a light source for EUV mask inspection with a small required power.

  Next, a basic configuration of the EUV mask inspection apparatus will be described. Unlike a conventional photomask, an EUV mask is used by reflecting EUV light having a wavelength of 13.5 nm as exposure light. Therefore, also in the inspection of the EUV mask, the EUV mask is irradiated with illumination light from the inspection light source, and the reflected light is used for the inspection. However, there are two illumination methods: dark field illumination applied to the mask blank inspection apparatus described above and bright field illumination applied to pattern inspection.

  When dark field illumination is used in the blank inspection apparatus, the defect is detected by capturing reflected light scattered by the defect of the EUV mask with a light receiver. Therefore, in order to detect defects with high sensitivity, the EUV mask needs to have a high reflectance with respect to illumination light. On the other hand, even in a bright field illumination pattern inspection apparatus, reflected light from an EUV mask is captured by a light receiver and inspected. Therefore, in order to realize a high sensitivity or high speed inspection, it is advantageous that the reflected light is strong.

Tsuneo Terasawa, et.al., "EUVL Mask Inspection and Metrology Capability", The 2009 Lithography Workshop, June 30, 2009.

  The inventor has found that the conventional mask blank apparatus using a xenon-based DPP light source has the following problems. For example, when inspecting one blank in 2 hours in a mask blank inspection apparatus, the power of EUV light extracted from the EUV light source toward the inspection optical system is 50 to 100 mW. However, the power of EUV light actually irradiated on the blank surface is only 0.5 to 1 mW. That is, the mask blank inspection apparatus has a problem that the utilization efficiency of EUV light is extremely low.

  That is, a conventional EUV mask inspection apparatus using a xenon-based DPP light source cannot detect defects with high sensitivity because the illumination light power on the mask is low. This also makes it difficult to reduce the inspection time from the current level.

  In order to solve the above problem, it is necessary to increase the power of the illumination light, that is, to increase the emission power of the EUV light source itself. For this purpose, it is necessary to increase the discharge voltage of the EUV light source or increase the number of repetitions of the pulse operation. As a result, there arises a problem that the life of the electrodes of the EUV light source is shortened.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an EUV mask inspection apparatus capable of performing highly sensitive inspection using an EUV light source.

  An EUV mask inspection apparatus according to a first aspect of the present invention includes a light source that generates illumination light including EUV (Extreme Ultra Violet) light, and an illumination optical system that illuminates the EUV mask with the illumination light extracted from the light source. And, by detecting the scattered light collected by the condensing optical system, and condensing optical system that collects the scattered light generated by irradiating the defect on the EUV mask with the illumination light, A detector that acquires a dark field image of the defect, and the illumination light includes EUV light in a wavelength range of 10.5 nm to 13.1 nm, and an incident angle of the illumination light with respect to the EUV mask is: 15.2 ° or more and 39.3 ° or less. Thereby, EUV light having a light emission intensity greater than the path light wavelength and a wavelength shorter than the exposure wavelength can be used as illumination light.

  An EUV mask inspection apparatus according to a second aspect of the present invention is characterized in that, in the EUV mask inspection apparatus, the light source generates the EUV light by discharging a gas containing xenon. Thereby, EUV light having a light emission intensity greater than the exposure wavelength and a shorter wavelength than the exposure wavelength can be included in the illumination light.

  An EUV mask inspection apparatus according to a third aspect of the present invention is the above-described EUV mask inspection apparatus, wherein the illumination optical system is a first reflecting mirror inserted between the condensing optical system and the EUV mask. The first reflecting mirror reflects the illumination light from the light source toward the EUV mask. Thereby, the EUV mask can be illuminated with illumination light.

  An EUV mask inspection apparatus according to a fourth aspect of the present invention is the above EUV mask inspection apparatus, wherein the first reflecting mirror is a concave mirror, and the illumination light from the light source is condensed on the EUV mask. It is characterized by doing. Thereby, the micro area | region on an EUV mask can be illuminated with illumination light.

  An EUV mask inspection apparatus according to a fifth aspect of the present invention is the above-described EUV mask inspection apparatus, wherein the illumination optical system has an illumination light passage hole through which the illumination light from the light source incident from the back surface passes. A second reflecting mirror provided on the second reflecting mirror, and a third reflecting mirror that reflects the illumination light that has passed through the illumination light passage hole toward the mirror surface of the second reflecting mirror, and The second reflecting mirror reflects the illumination light from the third reflecting mirror toward the first reflecting mirror, and the first reflecting mirror passes the scattered light to the condensing optical system. Scattered light passing holes are provided. Thereby, the EUV mask can be illuminated from the entire circumference by the illumination light.

  An EUV mask inspection apparatus according to a sixth aspect of the present invention is characterized in that, in the above EUV mask inspection apparatus, the second reflecting mirror is a concave mirror. Thereby, the micro area | region on an EUV mask can be illuminated with illumination light.

  An EUV mask inspection apparatus according to a seventh aspect of the present invention is the above EUV mask inspection apparatus, wherein the illumination optical system reflects the illumination light from the light source toward the first reflecting mirror. The first reflecting mirror reflects a part of the illumination light toward the EUV mask and transmits a part of the scattered light, and the illumination light is The light is condensed on the EUV mask by a concave mirror. Thereby, while irradiating an EUV mask with illumination light, scattered light can be guide | induced to a condensing optical system.

  An EUV mask inspection apparatus according to an eighth aspect of the present invention is characterized in that, in the above EUV mask inspection apparatus, the first reflecting mirror is constituted by a flat-plate-shaped polarization separation film. This makes it possible to illuminate the EUV mask with the illumination light using the polarization directions of the illumination light and the scattered light, and to guide the scattered light to the condensing optical system.

  An EUV mask inspection apparatus according to a ninth aspect of the present invention is characterized in that, in the above EUV mask inspection apparatus, the condensing optical system is a Schwarzschild optical system. Thereby, scattered light can be guided to the detector.

  An EUV mask inspection apparatus according to a tenth aspect of the present invention is the above EUV mask inspection apparatus, wherein the condensing optical system is reflected by a second concave mirror that reflects the scattered light and the second concave mirror. And a convex mirror that reflects the scattered light toward the detector. Thereby, scattered light can be guided to the detector.

  ADVANTAGE OF THE INVENTION According to this invention, the EUV mask inspection apparatus which can perform a highly sensitive test | inspection using an EUV light source can be provided.

1 is a configuration diagram showing a cross-sectional structure of an EUV mask inspection apparatus 100 according to a first embodiment. It is a graph which shows the emission spectrum from the discharge plasma of xenon. It is a graph which shows the wavelength characteristic of the reflectance of a multilayer mirror. It is a graph which shows the relationship between the reflectance curve of a multilayer film mirror, and the incident angle of EUV light. It is a block diagram which shows the cross-section of the EUV mask inspection apparatus 200 concerning Embodiment 2. FIG. It is a block diagram which shows the cross-section of the EUV mask inspection apparatus 300 concerning Embodiment 3. FIG. It is sectional drawing which shows the structure of a general EUV (Extreme Ultra Violet) mask.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary.

Embodiment 1
An EUV mask inspection apparatus according to Embodiment 1 of the present invention will be described. The EUV mask inspection apparatus according to the first embodiment is an apparatus for inspecting an EUV mask, and detects defects in EUV mask blanks by dark field illumination. FIG. 1 is a configuration diagram illustrating a cross-sectional structure of an EUV mask inspection apparatus 100 according to the first embodiment. As shown in FIG. 1, the EUV mask inspection apparatus 100 includes an EUV light source 101, a multilayer concave mirror 102, an XY stage 105, spherical multilayer mirrors 106 and 107, and a TDI camera 109. In the EUV mask inspection apparatus 100, the multilayer concave mirror 102 constitutes an illumination optical system. The spherical multilayer mirrors 106 and 107 constitute a Schwarzschild optical system 108 that is a condensing optical system. The spherical multilayer mirror 106 is a convex mirror. The spherical multilayer mirror 107 is a concave mirror.

  A scattered light passage hole for allowing the scattered light S1 and S2 to pass therethrough is provided at the center of the spherical multilayer mirror 107. Since FIG. 1 shows a cross-sectional structure of the EUV mask inspection apparatus 100, the spherical multilayer mirror 107 is displayed in a form separated by scattered light passage holes.

The EUV light source 101 generates EUV light EUV11 that is illumination light. As the EUV light source 101, for example, a light source such as HYDRA ⁴ -ABI ^™ manufactured by NANO-UV (France) can be used. The EUV light EUV 11 enters the inspection optical system and is reflected by the multilayer concave mirror 102 obliquely downward, that is, toward the EUV mask blanks 110 held on the XY stage 105. The reflected EUV light EUV 12 is collected by the multilayer concave mirror 102 and illuminates a minute region having a diameter of less than 1 mm on the EUV mask blanks 110.

  When a defect exists in this minute region, the EUV light EUV12 is scattered by the defect. The scattered light S1 or S2 that is the scattered EUV light is reflected by the spherical multilayer mirrors 106 and 107 constituting the Schwarzschild optical system 108 and reaches the TDI camera 109 that is a detector. Thereby, the TDI camera 109 can acquire a dark field image of the mask blanks 110. Thereby, the defect on the mask blank 110 can be detected.

  The EUV light EUV12 as illumination light is incident on the EUV mask blank 110 at a constant incident angle θ. In the present embodiment, the incident angle is about 27 degrees. However, the EUV light EUV12 is not a parallel beam, but has a beam shape that travels while being focused by the multilayer concave mirror 102. Therefore, the incident angle has a spread. In this case, the spread of the incident angle is in a range from 17 degrees to 37 degrees.

  The EUV light source 101 in the present embodiment is a xenon-based DPP light source. FIG. 2 is a graph showing an emission spectrum from the discharge plasma of xenon. As shown in FIG. 2, the xenon-based DPP light source emits light more strongly in the vicinity of the wavelength of 10.5 to 13.1 nm than in the vicinity of the exposure wavelength of 13.5 nm of EUV lithography.

  However, as can be seen from the reflectance curve of the multilayer mirror formed on the EUV mask (EUV mask blanks), the multilayer mirror can hardly reflect EUV light in the vicinity of a wavelength of 10.5 to 13.1 nm. . FIG. 3 is a graph showing the wavelength characteristics of the reflectance of the multilayer mirror. As shown in FIGS. 2 and 3, the multilayer mirror reflects EUV light having a wavelength of about 13.5 nm, but hardly reflects EUV light having a wavelength of 10.5 to 13.1 nm. Therefore, the EUV mask inspection apparatus using a conventional xenon-based DPP light source cannot use EUV light having a wavelength of 10.5 to 13.1 nm as illumination light.

  On the other hand, in the EUV mask inspection apparatus 100, the EUV light EUV 12 is incident on the EUV mask blanks 110 obliquely. That is, the EUV light EUV12 is incident at a certain incident angle on the EUV mask blanks 110 on which the multilayer reflective film is applied. As a result, the wavelength at which the reflectance increases is shifted to a wavelength shorter than 13.5 nm, which is the design wavelength of the EUV mask.

  Assuming that the incident angle is θ and the design wavelength λ0 for normal incidence, the wavelength λ that is strongly reflected is shifted to the short wavelength side by λ0 × cos (θ). For this reason, when illumination light having a wavelength of 13.5 nm, which is an exposure wavelength, is incident on the EUV mask blank 110 obliquely, the reflectance decreases.

  FIG. 4 is a graph showing the relationship between the reflectance curve of the multilayer mirror and the incident angle of EUV light. When the incident angle is 30 °, the center wavelength of the reflectance curve is about 12.0 nm. When the incident angle is 40 °, the center wavelength of the reflectance curve is about 10.5 nm. When the incident angle is about 27 degrees as in the present embodiment, as shown in FIG. 4, EUV light having a wavelength in the vicinity of 11 to 13 nm can be reflected. That is, the power of the reflected light of the EUV light EUV12 in the EUV mask blanks 110 can be increased.

  Further, an EUV mirror having a high reflectivity with respect to EUV light having a wavelength of 13.5 nm and an incident angle of 6 ° will be examined. This mirror reflects light with a wavelength of 10.5 nm most strongly at an incident angle of about 39.3 degrees. This mirror reflects light with a wavelength of 13.1 nm most strongly at an incident angle of about 15.2 degrees.

  Therefore, when the incident angle is 15.2 ° to 39.3 °, the center wavelength of the reflectance curve is 13.1 nm to 10.5 nm. As shown in FIG. 2, this wavelength range corresponds to a wavelength band where the emission intensity in the emission spectrum of xenon is the strongest. Therefore, a large amount of EUV light can be reflected by irradiating EUV light in the wavelength range of 10.5 nm to 13.1 nm.

  Therefore, in the EUV mask inspection apparatus 100, light having a wavelength of at least 10.5 nm to 13.1 nm that is emitted by discharge of a gas containing xenon can be used as illumination light. It is preferable to irradiate EUV light in this wavelength range with respect to the EUV mask blanks 110 (EUV mask) at an incident angle of 15.2 ° to 39.3 °.

  Although the EUV mask inspection apparatus 100 according to the embodiment uses dark field illumination, the intensity of scattered light by the dark field illumination is proportional to the reflectance. Therefore, according to this configuration, the power of the scattered light S1 and S2 can be increased by increasing the reflectance of the EUV light EUV12. Thereby, the defect detection sensitivity of the EUV mask inspection apparatus can be increased. In addition, a more compact EUV light source can be used due to improved sensitivity. Further, it is possible to improve the inspection speed.

Embodiment 2
Next, an EUV mask inspection apparatus according to the second embodiment of the present invention will be described. The EUV mask inspection apparatus according to the second embodiment is an apparatus for inspecting an EUV mask, as in the first embodiment. FIG. 5 is a configuration diagram illustrating a cross-sectional structure of the EUV mask inspection apparatus 200 according to the second embodiment. As shown in FIG. 5, the EUV mask inspection apparatus 200 differs from the EUV mask inspection apparatus 100 according to the first embodiment in a method for introducing EUV light from the EUV light source 101 to the EUV mask blanks 110.

  In the EUV mask inspection apparatus 200, a conical multilayer mirror 202, a multilayer concave mirror 203 with a passage hole, and a multilayer film with a passage hole are provided in an optical path for guiding EUV light from the EUV light source 101, which is a xenon-based DPP light source, to the EUV mask blanks 110. An ellipsoidal mirror 204 is arranged. The EUV light EUV21 extracted from the EUV light source 101 is reflected toward the multilayer concave mirror 203 (multilayer concave mirrors 203a and 203b) with a passage hole at an angle spread by the conical multilayer mirror 202.

  In FIG. 5, when the multilayer concave mirror 203 with a passage hole is observed from the direction A, an illumination light passage hole for allowing the EUV light EUV21 to pass through is provided at the center. Since FIG. 5 shows a cross-sectional structure of the EUV mask inspection apparatus 200, the multilayer concave mirror 203 with a passage hole is displayed as multilayer concave mirrors 203a and 203b separated by the illumination light passage hole. The EUV light EUV21 reflected by the conical multilayer mirror 202 is reflected by the multilayer concave mirrors 203a and 203b toward the multilayer elliptical mirror 204 with a through hole (multilayer elliptical mirrors 204a and 204b).

  In FIG. 5, the multilayer elliptical mirror 204 with a passage hole is provided with a scattered light passage hole for allowing the scattered light S1 and S2 to pass therethrough when observed from the direction B. Therefore, like the multilayer concave mirror 203 with a passage hole, the multilayer elliptical mirror 204 with a passage hole is displayed as the multilayer elliptic mirrors 204a and 204b separated by the scattered light passage hole. The EUV light EUV21 reflected by the multilayer concave mirror 203a is reflected by the multilayer ellipsoidal mirror 204a and irradiated to the EUV mask blank 110 as the EUV light EUV22a. The EUV light EUV21 reflected by the multilayer concave mirror 203b is reflected by the multilayer ellipsoidal mirror 204b and irradiated to the EUV mask blank 110 as the EUV light EUV22b. That is, in the EUV mask inspection apparatus 200, the conical multilayer mirror 202, the multilayer concave mirror 203 with a passage hole, and the multilayer elliptical mirror 204 with a passage hole constitute an illumination optical system.

  The EUV light EUV22a and EUV22b illuminate a minute area of the EUV mask blanks 110. At this time, the incident angle of the EUV light EUV22a is about minus 27 degrees. The incident angle of the EUV light EUV22b is about plus 27 degrees. Since the other configuration of the EUV mask inspection apparatus 200 is the same as that of the EUV mask inspection apparatus 100 according to the first embodiment, the description thereof is omitted.

  Therefore, according to this configuration, as in the first embodiment, the power of the scattered light S1 and S2 is increased by increasing the reflectance of EUV light having a wavelength shorter than the exposure wavelength (13.5 nm). Can do. Thereby, the defect detection sensitivity of the EUV mask inspection apparatus can be increased. In addition, a more compact EUV light source can be used due to improved sensitivity. Further, it is possible to improve the inspection speed.

  Further, in this configuration, a mirror with a passage hole (a multilayer concave mirror 203 with a passage hole and a multilayer elliptic mirror 204 with a passage hole) is used. Thereby, unlike the EUV mask inspection apparatus 100 according to the first embodiment, the EUV mask inspection apparatus 200 can uniformly irradiate a minute region of the EUV mask blanks 110 from the entire circumferential direction. Therefore, according to this configuration, high-sensitivity inspection can be performed without depending on the directionality of the defect.

Embodiment 3
Next, an EUV mask inspection apparatus according to Embodiment 3 of the present invention will be described. The EUV mask inspection apparatus according to the third embodiment is an apparatus for inspecting an EUV mask, as in the first embodiment. FIG. 6 is a configuration diagram illustrating a cross-sectional structure of the EUV mask inspection apparatus 300 according to the third embodiment. As shown in FIG. 6, an EUV mask inspection apparatus 300 is obtained by replacing the EUV light source 101 of the EUV mask inspection apparatus 100 according to the first embodiment with an EUV light source 301. Further, the EUV mask inspection apparatus 300 differs from the EUV mask inspection apparatus 100 according to the first embodiment in a method for introducing EUV light from the EUV light source 301 to the EUV mask blanks 110.

  In the EUV mask inspection apparatus 300, a multilayer concave mirror 302 and an EUV polarization separation film 303 are arranged in an optical path for guiding EUV light from an EUV light source 301, which is a xenon-based DPP light source, to the EUV mask blanks 110. The EUV light EUV 31 extracted from the EUV light source 301 is reflected by the multilayer concave mirror 302 toward the EUV polarization separation film 303 as a broadened EUV light EUV 32.

  The EUV polarized light separation film 303 reflects about 30% of the EUV light EUV32 and transmits about 50% of the EUV light EUV32. Therefore, the EUV light EUV 32 is reflected toward the EUV mask blanks 110 as the EUV light EUV 33 by the EUV polarization separation film 303. The optical axis (beam center) of the EUV light EUV 33 is substantially perpendicular to the main surface of the EUV mask blank 110. However, as shown in FIG. 6, the EUV light EUV 33 is irradiated onto the EUV mask blank 110 with a large converging angle. Therefore, most of the light components in the EUV light EUV 33 are irradiated to the main surface of the EUV mask blank 110 at a certain incident angle θ. That is, 50% or more of the optical power is incident at an incident angle of 20 ° or more. As a result, in the EUV mask inspection apparatus 300, as in the first and second embodiments, EUV light having a wavelength shorter than the exposure wavelength (13.5 nm) is strongly reflected.

  That is, in the EUV mask inspection apparatus 300, the multilayer concave mirror 302 and the EUV polarization separation film 303 constitute an illumination optical system. Since the other configuration of the EUV mask inspection apparatus 300 is the same as that of the EUV mask inspection apparatus 100 according to the first embodiment, the description thereof is omitted.

  Therefore, according to this configuration, as in the first and second embodiments, the power of the scattered light S1 and S2 is increased by increasing the reflectance of EUV light having a wavelength shorter than the exposure wavelength (13.5n). Can be made. Thereby, the defect detection sensitivity of the EUV mask inspection apparatus can be increased. In addition, a more compact EUV light source can be used due to improved sensitivity. Further, it is possible to improve the inspection speed.

  Furthermore, according to the present configuration, as in the second embodiment, it is possible to uniformly irradiate the minute region of the EUV mask blank 110 with the EUV light from the entire circumferential direction. Therefore, according to this configuration, high-sensitivity inspection can be performed without depending on the directionality of the defect. In addition, the EUV mask inspection apparatus 300 can simplify the configuration of the illumination optical system as compared with the EUV mask inspection apparatus 200 according to the second embodiment.

Other Embodiments The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the spirit of the present invention. For example, the EUV mask inspection apparatus according to the first to third embodiments described above can detect defects in an EUV mask having no pattern such as a substrate (substrate) in the EUV mask, a blank having a multilayer film or a resist on the substrate, and the like. It is to detect. However, the embodiment is not limited to this. The EUV mask inspection apparatus according to the first to third embodiments can be applied to defect inspection of a mask on which a pattern is formed, such as an EUV mask on which a resist pattern is formed.

  The condensing optical system and the illumination optical system according to the first to fifth embodiments are merely examples. If the same function can be exhibited, a condensing optical system and an illumination optical system having other configurations can be used as appropriate.

100, 200, 300 EUV mask inspection apparatus 101, 301 EUV light source 102 Multilayer concave mirror 105 XY stage 106, 107 Spherical multilayer mirror 108 Schwarzschild optical system 109 TDI camera 110 Mask blank 202 Conical multilayer mirror 203 Multilayer with passage hole Membrane concave mirrors 203a and 203b Multilayer concave mirror 204 Multilayer elliptical mirrors 204a and 204b with through holes Multilayer elliptic mirror 302 Multilayer concave mirror 303 EUV polarization separation film 700 EUV mask 701 Substrate 702 Multilayer film 703 Absorber 704 Protective film EUV11 , EUV12, EUV21, EUV22a, EUV22b, EUV31 to EUV33 EUV light S1, S2 scattered light

Claims (24)

A light source that generates illumination light including EUV (Extreme Ultra Violet) light;
The EUV mask multilayer reflective film is formed to reflect the EUV light irradiated at a predetermined incident angle at the time of exposure, an illumination optical system for Littelfuse bright by the illumination light taken from the light source,
A condensing optical system that condenses the scattered light generated when the illumination light is applied to the defect on the EUV mask;
A detector for acquiring a dark field image of the defect by detecting the scattered light collected by the condensing optical system, and
The illumination light includes EUV light in a wavelength range different from the exposure wavelength of the EUV mask ,
An incident angle of the illumination light with respect to the EUV mask is different from the predetermined incident angle.
EUV mask inspection equipment. The incident angle of the EUV light incident on the EUV mask at the time of exposure is 6 °,
The incident angle of the illumination light with respect to the EUV mask is 15.2 ° or more and 39.3 ° or less,
The EUV mask inspection apparatus according to claim 1. The exposure wavelength of the EUV mask is 13.5 nm,
The illumination light includes EUV light having a wavelength range of 10.5 nm to 13.1 nm.
The EUV mask inspection apparatus according to claim 1 or 2. The light source generates the EUV light by discharging a gas containing xenon.
The EUV mask inspection apparatus according to any one of claims 1 to 3 . The illumination optical system includes a first reflecting mirror inserted between the condensing optical system and the EUV mask,
The first reflecting mirror reflects the illumination light from the light source toward the EUV mask,
The EUV mask inspection apparatus according to any one of claims 1 to 4 . The first reflecting mirror is a concave mirror, and the illumination light from the light source is condensed on the EUV mask,
The EUV mask inspection apparatus according to claim 5 . The illumination optical system includes a second reflecting mirror provided in the center with an illumination light passage hole through which the illumination light from the light source incident from the back is passed.
A third reflecting mirror that reflects the illumination light that has passed through the illumination light passage hole toward the mirror surface side of the second reflecting mirror; and
The second reflecting mirror reflects the illumination light from the third reflecting mirror toward the first reflecting mirror;
The first reflecting mirror is provided with a scattered light passage hole that allows the scattered light to pass through the condensing optical system.
The EUV mask inspection apparatus according to claim 5 or 6 . The second reflecting mirror is a concave mirror,
The EUV mask inspection apparatus according to claim 7 . The illumination optical system further includes a first concave mirror that reflects the illumination light from the light source toward the first reflecting mirror,
The first reflecting mirror reflects a part of the illumination light toward the EUV mask and transmits a part of the scattered light,
The illumination light is condensed at a predetermined condensing angle on the EUV mask by the first concave mirror ,
The predetermined condensing angle is an angle at which a portion corresponding to 50% or more of the optical power of the illumination light reaching the EUV mask is incident at an incident angle of 20 ° or more .
The EUV mask inspection apparatus according to claim 5 . The first reflecting mirror is constituted by a plate-shaped polarization separation film,
The EUV mask inspection apparatus according to claim 9 . The condensing optical system is a Schwarzschild optical system,
The EUV mask inspection apparatus according to any one of claims 1 to 10 . The condensing optical system is
A second concave mirror that reflects the scattered light;
A convex mirror that reflects the scattered light reflected by the second concave mirror toward the detector.
The EUV mask inspection apparatus according to claim 11 . Generation of illumination light including EUV (Extreme Ultra Violet) light from the light source,
Illuminating the EUV mask formed with a multilayer reflective film that reflects EUV light irradiated at a predetermined incident angle during exposure with the illumination light,
Condensing the scattered light generated by irradiating the illumination light onto the defect on the EUV mask;
By detecting the collected scattered light, a dark field image of the defect is obtained,
The illumination light includes EUV light in a wavelength range different from the exposure wavelength of the EUV mask,
An incident angle of the illumination light with respect to the EUV mask is different from the predetermined incident angle.
EUV mask inspection method. The incident angle of the EUV light incident on the EUV mask at the time of exposure is 6 °,
The incident angle of the illumination light with respect to the EUV mask is 15.2 ° or more and 39.3 ° or less,
The EUV mask inspection method according to claim 13. The exposure wavelength of the EUV mask is 13.5 nm,
The illumination light includes EUV light having a wavelength range of 10.5 nm to 13.1 nm.
The EUV mask inspection method according to claim 13 or 14. The illumination light is generated by discharge of a gas containing xenon,
The EUV mask inspection method according to any one of claims 13 to 15. The illumination light is reflected toward the EUV mask by a first reflecting mirror,
The EUV mask inspection method according to claim 13. The first reflecting mirror is a concave mirror, and the illumination light from the light source is condensed on the EUV mask,
The EUV mask inspection method according to claim 17. The illumination light from the light source passes through the illumination light passage hole provided in the center of the second reflecting mirror from the back side,
The illumination light that has passed through the illumination light passage hole is reflected by the third reflecting mirror toward the mirror surface of the second reflecting mirror,
The scattered light is collected after passing through a scattered light passage hole provided in the first reflecting mirror,
The EUV mask inspection method according to claim 17 or 18. The second reflecting mirror is a concave mirror,
The EUV mask inspection method according to claim 19. The illumination light from the light source is reflected by the first concave mirror toward the first reflecting mirror,
The first reflecting mirror reflects a part of the illumination light toward the EUV mask and transmits a part of the scattered light,
The illumination light is condensed on the EUV mask by the first concave mirror,
The EUV mask inspection method according to claim 17. The first reflecting mirror is constituted by a plate-shaped polarization separation film,
The EUV mask inspection method according to claim 21. The scattered light is collected by a Schwarzschild optical system,
The EUV mask inspection method according to any one of claims 13 to 22. The Schwarzschild optical system is
A second concave mirror that reflects the scattered light;
A convex mirror that reflects the scattered light reflected by the second concave mirror toward the detector.
The EUV mask inspection method according to claim 23.

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