JP2019144069A - Inspection device and inspection method - Google Patents

Abstract

To provide an inspection device and an inspection method with which it is possible to suppress the sticking of debris to a first mirror and reduce the burden of maintaining the first mirror.SOLUTION: An inspection device 100 according to the present invention comprises: a light source unit 100a for irradiating a drop 103 of a prescribed material with a laser beam IR2 and causing a plasm to occur, thereby generating an illumination light EUV101; a first mirror of an oblique incident mirror 111 where the incidence angle of the illumination light EUV101 is 70° or greater, and which is the mirror the generated illumination light EUV101 enters first; heating means for heating the first mirror to the melting point of the prescribed material or higher; an illumination optical system for illuminating an inspection object 115 by an illumination light EUV104; and a detection optical system for detecting light EUV105 from the inspection object 115 irradiated with the illumination light EUV104 and acquiring an image of the inspection object 115.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an inspection apparatus and an inspection method. For example, the present invention relates to an inspection apparatus and an inspection method for detecting defects in an EUV mask used in EUV lithography (Extremely Ultraviolet Lithography) as a lithography process in a semiconductor manufacturing process. The EUV mask to be inspected is, for example, a patterned EUV mask in which a multilayer film and an absorber are provided on a substrate (called a substrate), and the absorber is patterned.

  With regard to lithography technology for miniaturization of semiconductors, ArF lithography using an ArF excimer laser with an exposure wavelength of 193 nm as an exposure light source is currently being mass-produced. An immersion technique (called ArF immersion lithography) that fills the space between the objective lens of the exposure apparatus and the wafer with water to increase the resolution is also used for mass production. Furthermore, in order to realize further miniaturization, various technical developments have been made for practical use of EUVL with an exposure wavelength of 13.5 nm.

  As shown in FIG. 8, the EUV mask 10 is provided with a multilayer film 12 for reflecting EUV light on a substrate 11 made of low thermal expansion glass as a laminated structure. The multilayer film 12 usually has a structure in which several tens of layers of molybdenum and silicon are alternately stacked. Thereby, the multilayer film 12 can reflect about 65% of EUV light having a wavelength of 13.5 nm vertically. An absorber 13 that absorbs EUV light is provided on the multilayer film 12. Blanks can be formed by patterning the absorber 13. However, a protective film 14 (a film called a buffer layer and a capping layer) is provided between the absorber 13 and the multilayer film 12. In order to actually use for exposure, the absorber 13 is patterned by a resist process. In this way, a patterned EUV mask is completed.

  The size of an unacceptable defect in the EUV mask 10 is significantly smaller than that of a conventional ArF mask, making it difficult to detect. Accordingly, an actinic inspection that uses EUV light, that is, illumination light having the same wavelength as that of exposure light having a wavelength of 13.5 nm, is indispensable for pattern inspection. Note that the actinic inspection apparatus for blanks of the EUV mask 10 is disclosed in Non-Patent Document 1 below, for example. A light source that generates EUV light having a wavelength of 13.5 nm is sometimes referred to as an actinic light source. Here, it is referred to as an EUV light source.

  As a general basic configuration of an inspection apparatus for the EUV mask 10, EUV light extracted from an EUV light source is guided to the EUV mask 10 by an illumination optical system including only a multilayer mirror for EUV. Illuminates a minute inspection area on the pattern surface. The pattern of the EUV mask 10 in this inspection region is projected (imaged) onto the surface of a two-dimensional image sensor of a CCD camera or a TDI (Time Delay Integration) camera by an magnifying optical system composed only of a multilayer mirror. Then, the observed pattern is analyzed to determine whether the pattern is correct. In this way, the pattern inspection of the EUV mask 10 is performed.

  In general, in an EUV light source, plasma is generated by condensing laser light with respect to a drop of tin (Sn) or lithium (Li) ejected in the form of a minute drop. And EUV light is produced | generated with generation | occurrence | production of minute plasma. For this reason, the illumination optical system of the inspection apparatus for the EUV mask 10 is preferably configured to project a bright spot with a minute plasma onto the inspection area of the EUV mask 10. However, since only a mirror can be used for the illumination optical system, for example, an optical system using one or two rotating ellipsoidal mirrors (hereinafter simply referred to as an ellipsoidal mirror) is used.

  The reason is that one ellipsoidal mirror has two condensing points, and the light generated from one condensing point has the property of condensing at the other condensing point. . Two condensing points of the ellipsoidal mirror are defined as a first condensing point and a second condensing point. The EUV light source, the ellipsoidal mirror, and the EUV mask 10 are arranged so that the first focal point matches the bright spot of the plasma and the second focal point matches a minute inspection region in the EUV mask 10. Deploy. Thereby, it is possible to guide and illuminate EUV light up to a minute inspection region. The EUV light source is shown in Non-Patent Documents 2 and 3 below, for example.

  The principle is the same when two ellipsoidal mirrors are used. In other words, the first light condensing point of one ellipsoidal mirror is aligned with the bright spot of the plasma, and the second condensing point is aligned with the first condensing point of the other ellipsoidal mirror. . Further, the second condensing point of the other ellipsoidal mirror is matched with the inspection region.

  On the other hand, the problem of the light source that generates EUV light is that when EUV light is generated from the generated minute plasma, materials such as tin scatter and adhere to the mirror on which EUV light first enters. . Here, a mirror on which EUV light generated from plasma is first incident is referred to as a first mirror. The material scattered from the plasma is called debris. Due to debris adhesion, the reflectivity of the first mirror decreases. For this reason, it is necessary to suppress adhesion of debris. For example, the debris scattering direction is bent by flowing argon gas between the plasma and the first mirror. In this way, it is conceivable to suppress debris adhesion to the first mirror.

US Pat. No. 9,476,841

A. Tchikoulaeva, et.al., “EUV actinic blank inspection: from prototype to production”, Proceedings of SPIE Volume 8679, Extreme Ultraviolet (EUV) Lithography IV; 86790I (2013). P. A. Blackborow, et.al., “EUV Source development for AIMS and Blank Inspection”, Proceedings of SPIE Volume 7636, Extreme Ultraviolet (EUV) Lithography; 763609 (2010). S. Ellwi, et.al., “High-brightness LPP source for actinic mask inspection”, Proceedings of SPIE Volume 7969, Extreme Ultraviolet (EUV) Lithography II; 79690C (2011). H. Takenaka, et. Al., “Heat-Resistance of Mo / Si Multilayer EUV Mirrors with Interleaved Carbon Barrier-Layers”, OSA TOPS on Extreme Ultraviolet Lithography, Vol. 4, (1996). M. J. Neumann, et.al., “Effect of Deposition, Sputtering, and Evaporation of Lithium Debris Buildup on EUV optics”, SPIE Volume 6517, Emerging Lithographic Technologies XI; 65172Y (2007). F. R. Powell, et. Al., “Filter windows for EUV lithography”, SPIE Volume 4343, Emerging Lithographic Technologies V (2001).

  There is room for improvement in the method of suppressing the adhesion of debris to the first mirror.

  An object of the present invention is to solve such a problem, and to provide an inspection apparatus and an inspection method capable of suppressing adhesion of debris to a first mirror.

  An inspection apparatus according to the present invention includes a light source unit that generates illumination light by irradiating laser light onto a drop of a predetermined material to generate plasma, and a first mirror on which the generated illumination light is first incident. The incident angle of the illumination light is 70 [°] or more, the first mirror of the oblique incidence mirror, heating means for heating the first mirror to a melting point of the predetermined material, and the illumination light. An illumination optical system that illuminates the inspection object, and a detection optical system that detects light from the inspection object illuminated by the illumination light and acquires an image of the inspection object. By setting it as such a structure, adhesion of debris with respect to a 1st mirror can be suppressed.

  The inspection method according to the present invention includes a step of generating illumination light by irradiating laser light onto a drop of a predetermined material to generate plasma, and a first mirror on which the generated illumination light first enters. The step of heating the first mirror of the oblique incidence mirror having an incident angle of the illumination light of 70 [°] or more to be equal to or higher than the melting point of the predetermined material, and illuminating the inspection object with the illumination light. A step of detecting light from the inspection object illuminated by the illumination light to acquire an image of the inspection object, and inspecting the inspection object based on the image. With such a configuration, it is possible to suppress debris adhesion to the first mirror.

  ADVANTAGE OF THE INVENTION According to this invention, the inspection apparatus and inspection method which can suppress adhesion of debris to a 1st mirror and can reduce the burden of the maintenance of a 1st mirror are provided.

1 is a configuration diagram illustrating an inspection apparatus according to a first embodiment. It is the graph which illustrated the simulation result of the reflectance characteristic of the oblique incidence mirror by which the ruthenium film was coated on the reflective surface, a horizontal axis shows an oblique incidence angle, and a vertical axis shows reflectance. 5 is a flowchart illustrating an inspection method using the inspection apparatus according to the first embodiment. FIG. FIG. 6 is a configuration diagram illustrating a grazing incidence mirror container of an inspection apparatus according to a second embodiment. FIG. 6 is a configuration diagram illustrating a grazing incidence mirror container of an inspection apparatus according to a third embodiment. In the inspection apparatus which concerns on Embodiment 3, it is the graph which illustrated the simulation result of the temperature change of the oblique incidence mirror which is a 1st mirror, a horizontal axis shows the elapsed time after a heating start, and a vertical axis | shaft shows temperature. FIG. 10 is a configuration diagram illustrating a grazing incidence mirror container of an inspection apparatus according to a fourth embodiment. It is sectional drawing which illustrated the EUV mask.

  Hereinafter, a specific configuration of the present embodiment will be described with reference to the drawings. The following description shows preferred embodiments of the present invention, and the scope of the present invention is not limited to the following embodiments. In the following description, the same reference numerals indicate substantially the same contents.

(Embodiment 1)
The inspection apparatus according to Embodiment 1 will be described with reference to the drawings. First, the configuration of the inspection apparatus will be described. Thereafter, an inspection method using the inspection apparatus will be described. FIG. 1 is a configuration diagram illustrating an inspection apparatus 100 according to the first embodiment. As shown in FIG. 1, the inspection apparatus 100 includes a light source unit 100a and an apparatus main body unit 100b.

  The light source unit 100a includes a light source container 101, a bottle 102, a catcher 104, a lens 106, and a near infrared laser (not shown). The light source container 101 can control the internal pressure. Inside the light source container 101, a bottle 102, a catcher 104, and a lens 106 are arranged.

  The bottle 102 stores a predetermined material that generates plasma. The bottle 102 stores, for example, liquid tin (Sn) as a predetermined material. Drop-shaped tin (tin drop 103) is ejected from the bottle 102 at high speed. A near-infrared laser (not shown) emits near-infrared laser light IR1. The near-infrared laser beam IR1 emitted from the near-infrared laser is incident on the lens 106 through the window 105 provided in the light source container 101. The near-infrared laser beam IR2 collected by the lens 106 irradiates the tin drop 103. Thereby, plasma is generated and illumination light EUV101 is generated. The illumination light EUV101 includes, for example, EUV light. The tin drop 103 is received by the catcher 104 and stored. As described above, the light source unit 100a generates the illumination light EUV101 by generating plasma by irradiating laser light onto a drop of a predetermined material.

  The apparatus main body 100b includes an oblique incident mirror container 121, an oblique incident mirror 111, a heater 120, an apparatus container 110, an oblique incident mirror 112, a plane mirror 113, a stage 114, a Schwarzschild optical system 116, a plane mirror 117, a concave mirror 118, and a detector 119. It has. The Schwarzschild optical system 116 is a magnifying optical system including a concave mirror 116a and a convex mirror 116b. For example, an EUV mask is placed on the stage 114 as the inspection object 115.

  The oblique incidence mirror container 121 can control the internal pressure. For example, the oblique incidence mirror container 121 is connected to a pressure adjusting means such as an exhaust pump (not shown) via an exhaust duct 122. Thereby, the inside of the oblique incidence mirror container 121 can be depressurized to a predetermined pressure.

  The oblique incidence mirror 111 and the heater 120 are disposed inside the oblique incidence mirror container 121. The oblique incidence mirror 111 includes, for example, a substrate containing quartz and a metal film coated on the surface of the substrate. The quartz of the substrate is, for example, synthetic quartz. The metal film is, for example, a ruthenium (Ru) film. The surface coated with the ruthenium film is the reflecting surface. Thus, the oblique incidence mirror 111 is a kind of metal mirror because the reflecting surface contains metal. The oblique incidence mirror 111 is an ellipsoidal mirror. Of the two light condensing points, the first light condensing point is disposed at the bright spot of the plasma. The oblique incidence mirror 111 is a first mirror on which the illumination light EUV101 generated from plasma is first incident.

  The oblique incidence mirror 111 is a metal mirror that is used by making a light beam incident at an incident angle of the illumination light EUV101 as large as 70 [°] or more. Since the incident angle is as large as 70 [°] or more, it can be said that the angle from the reflecting surface is a shallow angle. That is, the oblique incident angle is 90 [°] −incident angle. Such a grazing incidence mirror 111 can reflect a certain amount of light having a short wavelength such as an X-ray which is hardly reflected at normal incidence. For example, in order to reflect EUV light having a wavelength of 13.5 [nm], a multilayer mirror composed of a multilayer film of molybdenum (Mo) and silicon (Si) is generally used. However, if the incident light is incident at an oblique incident angle, the EUV light can be reflected even by a metal mirror.

  FIG. 2 is a graph illustrating a simulation result of reflectance characteristics of a grazing incidence mirror whose reflecting surface is coated with a ruthenium film, in which the horizontal axis represents the oblique incidence angle and the vertical axis represents the reflectance. As shown in FIG. 2, when the oblique incidence angle is 15 [°] (incident angle is 75 [°]), the oblique incidence mirror reflects EUV light as much as 80%.

  The oblique incidence mirror 111 is in contact with the heater 120 on the surface opposite to the reflecting surface. Therefore, the heater 120 is disposed on the back side of the substrate. The heater 120 is a heating mechanism that heats the oblique incidence mirror 111. The heater 120 heats the oblique incidence mirror 111 above the melting point of a predetermined material that generates plasma. For example, the heater 120 heats the oblique incidence mirror 111 to 600 [° C.] or more. The melting point of tin is 231.9 [° C.], and the inside of the oblique incidence mirror container 121 is in a reduced pressure state. Therefore, the tin that contacts the oblique incidence mirror 111 evaporates. Therefore, it is possible to prevent tin from adhering to the reflecting surface of the oblique incidence mirror 111 as a solid or a liquid. Further, the evaporated tin is exhausted to the outside through the exhaust duct 122. The oblique incidence mirror 111 is not limited to a substrate containing quartz and a metal film coated on the surface of the substrate as long as it can be heated above the melting point of a predetermined material that generates plasma. It may be done.

  The oblique incidence mirror container 121 may be connected to the light source container 101 via the connection portion 107. For example, the illumination light EUV 101 generated by the light source unit 100 a passes through the connection portion 107 and enters the oblique incidence mirror 111.

  The oblique incidence mirror container 121 is provided with an opening 108 for taking out the illumination light EUV102 reflected by the oblique incidence mirror 111. The illumination light EUV 102 reflected by the oblique incident mirror 111 passes through the opening 108 and enters the oblique incident mirror 112. At this time, it is preferable that a condensing point IF (Intermediate Focus) of the illumination light EUV 102 is located in the opening 108. Thereby, the diameter of the opening part 108 can be made small and it can suppress that the vapor | steam of tin leaks from the opening part 108. FIG.

A gas injection pipe 130 is connected to the oblique incidence mirror container 121. Thereby, a predetermined gas can be supplied into the oblique incidence mirror container 121. For example, hydrogen gas can be supplied into the oblique incidence mirror container 121 through the gas injection pipe 130. Therefore, the inside of the oblique incidence mirror container 121 contains low-pressure hydrogen gas. Tin reacts with hydrogen to form stannane (SnH ₄ ). Accordingly, tin that has entered the inside of the oblique incidence mirror container 121 can be stannated and exhausted to the outside of the oblique incidence mirror container 121. In particular, tin in contact with the heated oblique incidence mirror 111 becomes a high temperature, and the reactivity increases. Therefore, stannous conversion of tin can be facilitated.

  The device container 110 may also be capable of controlling the internal pressure. Inside the apparatus container 110, an oblique incidence mirror 112, a plane mirror 113, a stage 114, a Schwarzschild optical system 116, a plane mirror 117, a concave mirror 118, and a detector 119 are disposed. As in the case of the oblique incidence mirror 111, the oblique incidence mirror 112 includes a substrate containing quartz and a metal film formed on the surface of the substrate. The metal film is, for example, a ruthenium film. The reflection surface of the oblique incidence mirror 112 is also a surface coated with a ruthenium film. The oblique incidence mirror 112 is also a kind of metal mirror and is an ellipsoidal mirror. The first condensing point of the oblique incidence mirror 112 is made to coincide with the condensing point IF of the illumination light EUV 101 so that the second condensing point matches the inspection region to be inspected.

  The illumination light EUV102 reflected by the oblique incidence mirror 111 proceeds while being narrowed down and is collected at the condensing point IF. The condensing point IF is located at the opening 108. The illumination light EUV102 condensed at the condensing point IF spreads after the condensing point IF. Thereafter, the illumination light EUV 102 is reflected by the oblique incidence mirror 112. The illumination light EUV103 reflected by the oblique incidence mirror 112 proceeds while being narrowed down, enters the plane mirror 113, and is reflected. The illumination light EUV 104 reflected by the plane mirror 113 illuminates the inspection area of the inspection object 115. Thus, the inspection apparatus 100 includes an illumination optical system that illuminates the inspection object 115 with the illumination light EUV 104. The illumination optical system includes, for example, a grazing incidence mirror 111, a grazing incidence mirror 112, and a plane mirror 113.

  The stage 114 can move the inspection object 115 in a plane parallel to the upper surface of the stage 114. If the plane parallel to the upper surface of the stage 114 is an XY plane, the stage 114 can move the inspection object 115 in the X-axis direction and the Y-axis direction. By illuminating with the illumination light EUV104, the light EUV105 generated from the inspection object 115 is reflected by the concave mirror 106a and the convex mirror 106b. The light EUV 105 generated from the inspection object 115 is reflected light or diffracted light reflected by the inspection object 115 from the illumination light EUV 104, and includes pattern information in the inspection area.

  The light EUV 106 reflected by the concave mirror 106a and the convex mirror 106b is folded back by the plane mirror 117 and then further magnified by the concave mirror 118. The light EUV 106 magnified by the concave mirror 118 is projected onto a sensor surface disposed below the detector 119. Thereby, an image including the pattern of the inspection object 115 is acquired. Therefore, the inspection apparatus 100 includes a detection optical system that detects the light EUV 106 from the inspection object 115 illuminated by the illumination light EUV 105 and acquires an image of the inspection object 115. The detection optical system includes, for example, a Schwarzschild optical system 116, a plane mirror 117, a concave mirror 118, and a detector 119. The pattern in the acquired image is analyzed to detect defects and the like. Thus, for example, the inspection apparatus 100 according to the first embodiment uses the EUV mask as the inspection object 115 and inspects the pattern of the EUV mask.

  Next, an inspection method using the inspection apparatus 100 of this embodiment will be described. FIG. 3 is a flowchart illustrating the inspection method according to the first embodiment. First, as shown in step S11 of FIG. 3, illumination light EUV101 is generated. For example, illumination light is generated by generating plasma by irradiating laser light onto a drop of a predetermined material. Specifically, tin is used as a predetermined material in the light source unit 100a. The tin drop 103 is irradiated with near-infrared laser light to generate plasma, and illumination light EUV101 is generated.

  Next, as shown in step S12, the first mirror is heated. Specifically, it is a first mirror on which the illumination light EUV101 generated from the plasma is first incident, and the first mirror of the oblique incidence mirror 111 having an incident angle of the illumination light EUV101 of 70 [°] or more is applied to the plasma. The oblique incidence mirror is heated above the melting point of the predetermined material to be generated.

  Next, as shown in step S13, the inspection object 115 is illuminated with the illumination light EUV101. Specifically, using the illumination optical system of the inspection apparatus 100, the inspection object 115 is illuminated with the illumination light EUV 104 generated by the generation of plasma.

  Next, as shown in step S14, the light EUV 106 from the inspection object 115 illuminated by the illumination light EUV 104 is detected, and an image of the inspection object 115 is acquired. Specifically, an image of the inspection object 115 is acquired using the detection optical system of the inspection apparatus 100.

  Next, as shown in step S15, the inspection object 115 is inspected based on the image. In this way, the inspection object 115 can be inspected using the inspection apparatus 100.

Next, the effect of this embodiment will be described.
In the inspection apparatus 100 of the present embodiment, the first mirror is an oblique incidence mirror 111 that is a metal mirror, and is heated to a temperature higher than the melting point of the material that generates plasma such as tin in the light source unit 100a. Therefore, it is possible to evaporate the tin scattered when the plasma is generated, and to prevent the debris of tin from adhering to the first mirror. The reason why the first mirror can be heated in this way is that the oblique incidence mirror 111 that is a metal mirror is used. As shown in Non-Patent Document 4, when a multilayer mirror, which is a general EUV light mirror, is heated to 200 [° C.] or higher, molybdenum and silicon are mixed and reflectivity is lowered.

  In this embodiment, since the debris can be prevented from adhering to the first mirror, the reflectance does not decrease even when the illumination light EUV101 is reflected for a long time. Therefore, since the frequency of mirror replacement can be reduced and the operation time until the regular maintenance can be extended, the maintenance cost in the optical system can be greatly reduced.

(Modification)
Next, a modification of the first embodiment will be described. In this modification, a lithium (Li) drop is used in place of the tin drop 103 in generating plasma in the light source unit 100a. The melting point of lithium is 180.5 [° C.], which is lower than that of tin. Therefore, in the modification using the lithium drop, lithium can be evaporated more easily. Thereby, the heating temperature of a 1st mirror can be lowered | hung and the power consumption at the time of a heating can be made small.

  In the first embodiment, hydrogen is injected from the gas injection pipe 130. In this modification, helium is injected instead of hydrogen. For example, helium plasma reacts with lithium and can be easily discharged from the oblique incidence mirror container 121. This is shown in Non-Patent Document 5, for example.

  Patent Document 1 describes that plasma is generated using lithium to generate EUV light. According to Patent Document 1, lithium debris scattered during generation of EUV light is removed using an EUV filter. In that case, the EUV filter is heated. By the way, the film material that transmits EUV light is limited to zirconium or silicon. Moreover, in order to transmit EUV light, it must be as thin as 100 [nm]. On the other hand, the EUV filter decreases in strength at high temperatures and melts in some cases. Therefore, the EUV filter needs to be thick to some extent. As a result, the transmittance of the EUV filter is lowered. For example, when the film thickness of zirconium is 100 [nm], the transmittance is reduced to about 60 [%]. The transmittance of the zirconium filter is shown in Non-Patent Document 6, for example.

  On the other hand, in this modification, it is not necessary to use an EUV filter when plasma is generated using lithium to generate illumination light EUV101 including EUV light. Therefore, since the inspection object 115 can be illuminated while maintaining the intensity of the illumination light EUV101, the inspection can be performed with high accuracy. Other configurations and effects of the inspection apparatus according to this modification are included in the description of the first embodiment.

(Embodiment 2)
Next, Embodiment 2 will be described. FIG. 4 is a configuration diagram illustrating the oblique incidence mirror container 121 of the inspection apparatus 200 according to the second embodiment. As shown in FIG. 4, a grazing incidence mirror 111, a grazing incidence mirror 125, and a heater 126 are arranged in the grazing incidence mirror container 121 of the present embodiment. In the present embodiment, the oblique incidence mirror 111 is not the first mirror. Further, the oblique incidence mirror 111 is not provided with the heater 120.

  The oblique incidence mirror 125 is a first mirror on which the illumination light EUV 121 generated together with the plasma is first incident. The oblique incidence mirror 125 includes a substrate containing quartz and a metal film formed on the surface of the substrate. The metal film is, for example, a ruthenium film. The oblique incidence mirror 125 is a kind of metal mirror. On the other hand, the oblique incidence mirror 125 is a plane mirror. A heater 126 is disposed on the back surface side of the oblique incidence mirror 125 opposite to the reflecting surface. The heater 126 is a heating unit for the oblique incidence mirror 125. The heater 126 can heat the oblique incidence mirror 125 to a temperature higher than the melting point of a predetermined material that generates plasma. The oblique incidence mirror 125 is not limited to a substrate containing quartz and a metal film coated on the surface of the substrate, and may be formed only of metal, for example, as long as it can be heated to a melting point or higher of a predetermined material that generates plasma. It may be done.

  Near-infrared laser light IR2 is focused on a drop 124 of a predetermined material that generates plasma such as tin or lithium. The illumination light EUV 121 generated thereby is incident on the oblique incidence mirror 125 as the first mirror while spreading. The illumination light EUV 121 incident on the oblique incident mirror 125 and reflected by the oblique incident mirror 125 enters the oblique incident mirror 111 while spreading. The illumination light EUV102 that has entered and reflected from the oblique incidence mirror 111 proceeds while being narrowed down, and is collected at the condensing point IF.

  In the present embodiment, the heater 126 can heat the oblique incidence mirror 125 to the melting point of the material that generates the plasma contained in the drop 124. Therefore, it is possible to evaporate the scattered tin and prevent the tin debris from adhering to the oblique incidence mirror 125 as the first mirror.

  Further, since the first mirror is a plane mirror, it can be placed close to the drop 124 for generating plasma. Therefore, since the beam diameter of the illumination light EUV 121 incident on the reflecting surface is small, the volume of the first mirror can be reduced as compared with the inspection apparatus 100 of the first embodiment. Thereby, the heat quantity for heating to the same temperature as the inspection apparatus 100 of Embodiment 1 can be reduced, and it can heat to target temperature in a short time. This is because the temperature rise is inversely proportional to the volume of the heated object. Moreover, the grazing incidence mirror 125 is disposed in the grazing incidence mirror container 121 in a decompressed state close to a vacuum. Therefore, the amount of heat lost due to heat conduction can be reduced, and a structure in which the temperature easily rises can be obtained. Other configurations and effects are included in the description of the first embodiment.

(Embodiment 3)
Next, an inspection apparatus according to Embodiment 3 will be described. FIG. 5 is a configuration diagram illustrating the oblique incidence mirror container 121 of the inspection apparatus 300 according to the third embodiment. As shown in FIG. 5, an oblique incidence mirror 111 and an oblique incidence mirror 135 are arranged in the oblique incidence mirror container 121 of the present embodiment. Also in this embodiment, the oblique incidence mirror 111 is not the first mirror, and the oblique incidence mirror 111 is not provided with the heater 120.

  The oblique incidence mirror 135 includes a substrate containing silicon and a metal film coated on the surface of the substrate. The metal film is, for example, a ruthenium film. The surface coated with the metal film is the reflecting surface. The oblique incidence mirror 135 is a first mirror on which the generated illumination light EUV 131 is first incident. The oblique incidence mirror 135 is a kind of metal mirror and is a plane mirror. Since the oblique incidence mirror 135 is a plane mirror, it can be placed close to the drop 134 that generates plasma. Therefore, the beam diameter of the illumination light EUV 131 in the oblique incidence mirror 135 is small. Therefore, the reflection surface of the oblique incidence mirror 135 can be reduced.

  The oblique incidence mirror 135 is not provided with a heater. On the other hand, since the oblique incidence mirror 135 includes silicon, the oblique incidence mirror 135 itself absorbs the illumination light EUV 131 by about 20%. Thereby, the oblique incidence mirror 135 is heated. That is, the heating mechanism of the oblique incidence mirror 135 is based on the illumination light EUV 131 incident on the oblique incidence mirror 135 heating the oblique incidence mirror 135. In addition, since the reflecting surface of the oblique incidence mirror 135 can be reduced, the overall size of the oblique incidence mirror 135 can be reduced. Therefore, the oblique incidence mirror 135 can be maintained at a high temperature of several hundred degrees by absorption of the illumination light EUV 131.

  The temperature of the grazing incidence mirror 135 is maintained where the heat input by the absorbed illumination light EUV 131 and the radiation cooling from the front and back surfaces of the grazing incidence mirror 135 balance. Therefore, the temperature to be balanced is adjusted to be higher than the melting point of a predetermined material such as tin or lithium.

  For example, the emissivity is controlled by coating the back surface of the oblique incidence mirror 135 with a metal film. For example, the oblique incidence mirror 135 includes a gold film coated on the back surface. This reduces the emissivity. Therefore, the temperature to balance can be made high. The thickness of the silicon wafer is as thin as 0.5 to 0.7 [mm]. For this reason, by using a silicon wafer as the substrate for the oblique incidence mirror 135, the amount of radiation from the surrounding surface can be made small enough to be ignored.

  FIG. 6 is a graph illustrating a simulation result of the temperature change of the oblique incidence mirror, which is the first mirror, in the inspection apparatus 300 according to the third embodiment. The horizontal axis indicates the elapsed time after the start of heating, and the vertical axis Indicates temperature. As a simulation condition, a grazing incidence mirror 135 containing silicon is made a 1.0 cm square, and 1.0 [W] heat is always absorbed by the incidence of the illumination light EUV 131. This is because silicon absorbs 1.0 [W], which is 20%, when the total power of the illumination light EUV 131 is about 5 [W].

  Also, the reflecting surface of the oblique incidence mirror 135 is coated with a ruthenium film, and its emissivity is 0.2, and the back surface of the oblique incidence mirror 135 is coated with a gold film, and its emissivity is It was set to 0.1. As shown in FIG. 6, after about 2 minutes, the temperature reaches 600 [° C.], that is, a temperature higher than the melting point of a predetermined material that generates plasma such as tin and lithium, and becomes constant.

  According to the inspection apparatus 300 of the present embodiment, the oblique incidence mirror 135 of the first mirror is a plane mirror. Therefore, plasma can be generated and placed close to the drop 134, and the beam diameter on the reflecting surface can be reduced. Thereby, the reflective surface of the oblique incidence mirror 135 can be made small.

  The oblique incidence mirror 135 includes silicon in the substrate. Therefore, the oblique incidence mirror 135 absorbs the illumination light EUV 131 and becomes high temperature. Thereby, even if it does not provide the heater which heats the oblique incidence mirror 135, adhesion of debris can be suppressed.

  Also, a gold film is coated on the back surface opposite to the reflecting surface. Therefore, it is possible to balance heat input and heat dissipation in the oblique incidence mirror 135, and to maintain a desired temperature. Other configurations and effects are included in the descriptions of the first to third embodiments.

(Embodiment 4)
Next, a fourth embodiment will be described. FIG. 7 is a configuration diagram illustrating the oblique incidence mirror container 121 of the inspection apparatus 400 according to the fourth embodiment. As shown in FIG. 7, an oblique incidence mirror 111, a plurality of infrared lamps 141, and a reflector 142 are arranged in the oblique incidence mirror container 121 of the present embodiment. The oblique incidence mirror 111 is a first mirror on which the generated illumination light EUV 141 is first incident. The plurality of infrared lamps 141 and the reflector 142 are disposed on the reflection surface side of the oblique incidence mirror 111. Also in this embodiment, the oblique incident mirror 111 is not provided with the heater 120. Instead, a plurality of infrared lamps 141 are provided between the oblique incidence mirror 111 and the reflector 142. Infrared light generated from the infrared lamp 141 proceeds to the oblique incidence mirror 111 side and heats the reflection surface of the oblique incidence mirror 111.

  In the inspection apparatus 400 of this embodiment, the heating mechanism of the oblique incidence mirror 111 that is the first mirror is an infrared lamp that radiates far infrared rays. Therefore, the reflective surface of the first mirror is directly heated compared to the heater. Thereby, a reflective surface can be heated effectively. Other configurations and effects are included in the descriptions of the first to third embodiments.

  As mentioned above, although embodiment of this invention was described, this invention contains the appropriate deformation | transformation which does not impair the objective and advantage, Furthermore, it does not receive the restriction | limiting by said embodiment. Moreover, you may combine suitably the structure in Embodiment 1-4 and the structure of the modification of Embodiment 1. FIG.

DESCRIPTION OF SYMBOLS 10 EUV mask 11 Board | substrate 12 Multilayer film 13 Absorber 14 Protective film 100, 200, 300, 400 Inspection apparatus 100a Light source part 100b Main part 101 Light source container 102 Bottle 103 Tin drop 104 Catcher 105 Window 106 Lens 107 Connection part 108 Opening part 110 apparatus container 111 oblique incidence mirror 112 oblique incidence mirror 113 plane mirror 114 stage 115 inspection object 116 Schwarzschild optical system 116a concave mirror 116b convex mirror 117 plane mirror 118 concave mirror 119 detector 120 heater 121 oblique incidence mirror container 122 exhaust duct 124 drop 125 oblique incidence mirror 126 Heater 130 Gas injection tube 134 Drop 135 Oblique incidence mirror 141 Infrared lamp 142 Reflector EUV101, EUV102, EUV103, EUV104 Illumination light EUV 121, EUV131, EUV141 Illumination light EUV105, EUV106 Light IR1, IR2 Near infrared laser light

Claims (11)

A light source unit that generates illumination light by irradiating a drop of a predetermined material with laser light to generate plasma;
A first mirror on which the generated illumination light is first incident, and an incident angle of the illumination light is 70 [°] or more, and the first mirror of the oblique incidence mirror;
Heating means for heating the first mirror above the melting point of the predetermined material;
An illumination optical system that illuminates the inspection object with the illumination light;
A detection optical system that detects light from the inspection object illuminated by the illumination light and acquires an image of the inspection object;
Inspection device with The predetermined material is tin or lithium,
The inspection apparatus according to claim 1. The first mirror includes a substrate containing quartz, and a metal film coated on the surface of the substrate.
The inspection apparatus according to claim 1 or 2. The first mirror is an ellipsoidal mirror;
The inspection apparatus according to any one of claims 1 to 3. The first mirror is a plane mirror;
The inspection apparatus according to any one of claims 1 to 3. The heating means is a heater disposed on the back side of the first mirror.
The inspection apparatus according to any one of claims 1 to 5. The heating means is an infrared lamp that radiates far infrared rays.
The inspection apparatus according to any one of claims 1 to 5. The first mirror includes a substrate containing silicon, and a metal film coated on a surface of the substrate.
The inspection apparatus according to claim 1 or 2. The first mirror is a plane mirror;
The first mirror further includes a gold film coated on the back surface of the substrate.
The inspection apparatus according to claim 8. The heating unit is configured such that the illumination light incident on the first mirror heats the first mirror.
The inspection apparatus according to claim 8 or 9. Generating illumination light by irradiating laser light onto a drop of a predetermined material to generate plasma; and
The first mirror on which the generated illumination light is incident first, and the first mirror of the oblique incidence mirror having an incident angle of the illumination light of 70 [°] or more exceeds the melting point of the predetermined material. Heating, and
Illuminating the inspection object with the illumination light; and
Detecting light from the inspection object illuminated by the illumination light to obtain an image of the inspection object;
Inspecting the inspection object based on the image;
Inspection method with

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