JP2020076574A - Pattern inspection device and pattern inspection method - Google Patents

Abstract

To provide a pattern inspection device and a pattern inspection method capable of improving defect detection sensitivity.SOLUTION: A pattern inspection apparatus 100 according to the present invention includes: a polarization control unit 103 that changes the polarization state of a part of illumination light to generate the illumination light that has a beam La including first linearly polarized light, a beam Lb including second linearly polarized light with a polarization direction different from that of the first linearly polarized light, and a beam Lc including circularly polarized light; an objective lens 105 that illuminates an inspection object by condensing the illumination light having the beams La to Lc and collects light Da from the inspection object illuminated by the beam La, light Db from the inspection object illuminated by the beam Lb and light Dc from the inspection object illuminated by the beam Lc; a polarization splitting unit 109 that guides each light of Da to Dc collected by the objective lens 105 to the detectors 120a to 120c, wherein the inspection object is inspected based on the light Da to Dc detected by the detectors 120a to 120c.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pattern inspection device and a pattern inspection method, for example, a pattern inspection device and a pattern inspection method for inspecting a defect of a photomask used in a semiconductor manufacturing process.

  Generally, as a method for inspecting a defect of a mask on which a pattern is formed, a comparison inspection method between a mask pattern and design data (generally called a die-to-database comparison method) and two circuit patterns having the same shape. There are two widely known methods: a comparison inspection method (generally referred to as a Die-to-Die comparison method) for comparing the two.

  In both methods, a minute part of the mask pattern (hereinafter referred to as an observation region) is magnified by an objective lens, and the magnified optical image is detected by a CCD camera for inspection. In many cases, TDI (Time Delay Integration) is used as the CCD camera. Therefore, the CCD camera is called a TDI camera or a TDI sensor.

  Further, as a light source for illuminating the observation region, a laser continuously operating in the ultraviolet region or a point light source lamp having a spectrum in the ultraviolet region is used. Methods of using the ultraviolet light extracted from these lasers and lamps as illumination light include transmission illumination and reflection illumination. The transmitted illumination illuminates the mask from the side opposite to the objective lens. On the other hand, the reflective illumination illuminates the mask from the objective lens side. These transmitted illumination and reflected illumination are used properly according to the type of defect to be detected. This is because when an image is formed on a TDI camera or the like by the transmitted illumination and the reflected illumination, the appearance of the optical image of the pattern is different, and thus the detectable defect is different.

  Here, the configuration of an optical system using reflected illumination in a general pattern inspection apparatus 900 will be described with reference to FIG. FIG. 9 is a configuration diagram illustrating a pattern inspection apparatus. FIG. 9 shows a case where a laser device (not shown) is used as the inspection light source. The laser beam L901 including the linearly polarized S wave generated from the laser device enters the optical system as illumination light for illuminating the inspection target. The laser beam L901 that has entered the optical system is reflected by the polarization beam splitter (PBS) 901 and travels downward. The reason why the laser light L901 is linearly polarized with the S wave is to have a polarization direction that is efficiently reflected by the polarization beam splitter 901.

  The laser light L901 reflected by the polarization beam splitter 901 is converted from linearly polarized S wave to circularly polarized light by passing through the λ / 4 wavelength plate 902. Here, the S wave is converted into clockwise circularly polarized light. The laser light L901 converted so as to include circularly polarized light illuminates the pattern surface of the mask 904 via the objective lens 903. The light from the pattern surface comes to include the reverse polarization direction, that is, the counterclockwise circular polarization. The light from the pattern surface illuminated by the laser light L901 includes at least one of reflected light and diffracted light.

  The light from the pattern surface including the circularly polarized light passes through the λ / 4 wavelength plate 902 again via the objective lens 903. As a result, circularly polarized light is returned to linearly polarized light. In that case, this time it is converted into a linearly polarized P wave. The linearly polarized P wave is transmitted through the polarization beam splitter 901. The light from the pattern surface including the linearly polarized P wave is condensed by the projection lens 905 and reaches the TDI camera 906. At this time, the pattern surface of the mask 904 is projected onto the TDI camera 906 by the objective lens 903 and the projection lens 905. As a result, a magnified image within the field of view of the objective lens 903 is captured, and the defect in the pattern can be inspected.

  On the other hand, Patent Document 1 describes that an observation region of the mask 904 is illuminated with illumination light of different polarization states to create optical images that make the mask pattern look different. The pattern inspection apparatus of Patent Document 1 inspects optical images having different appearances using different TDI cameras. In the pattern inspection apparatus of Patent Document 1, for example, reflective illumination is used on the half side of the field of view of the objective lens and transmitted illumination is used on the other side. As a result, it is possible to simultaneously observe optical images having different appearances.

  By the way, an EUV mask is called a reflection type mask because it reflects X-rays having a wavelength of 13.5 nm, which is exposure light, to expose a pattern on a wafer. FIG. 10 is a cross-sectional view illustrating the EUV mask 914. As shown in FIG. 10, the EUV mask 914 includes a substrate 10, a multilayer film 11, a protective film 12, and an absorber 13. A multilayer film 11 made of Mo / Si that reflects X-rays is provided on the substrate 10. An absorber 13 that does not reflect X-rays is provided on the multilayer film 11 via a protective film 12.

  A general pattern inspection apparatus can be used for the pattern inspection of the EUV mask 914. However, since the EUV mask 914 does not transmit light, it can be inspected only by reflection illumination as an illumination method. That is, the reflected light from the multilayer film 11 is detected on the pattern surface illuminated with the illumination light. By projecting the optical image of the pattern surface by this reflected light on the TDI camera, the pattern shape is imaged and the defect is inspected.

  For the purpose of inspecting at high speed or with high sensitivity, the EUV mask 914 may be illuminated with two types of illumination light having different polarization states, and the reflected light from the EUV mask 914 may be inspected using two detectors. is there. Even when only such reflective illumination is used, it is possible to observe optical images in which the mask patterns look different by illuminating with illumination light of different polarization states.

  In particular, by using two orthogonal polarization directions (P wave and S wave), whichever of the vertical line (vertical line) and the horizontal line (horizontal line) on the mask pattern surface is used. It will be possible to detect with high sensitivity. For example, when polarized light in a direction parallel to the line direction of a pattern having a line shape (which becomes an S wave) is used, imaging performance is good and detection can be performed with high sensitivity. The above is described in, for example, Patent Document 2 or 3 below.

Patent No. 4701460 JP, 2009-223095, A JP 05-109601 A JP, 2013-024772, A JP, 2017-0093379, A JP, 2017-090147, A JP, 2014-048217, A JP-A-4-289409 JP, 2003-344306, A JP, 2009-216648, A JP, 2010-092984, A JP2012-127856A

  The mask pattern is becoming finer year by year. In particular, when the pitch of the pattern is miniaturized to be below the resolution limit of the pattern inspection apparatus, it is not possible to improve the defect detection sensitivity by using either the P-wave or S-wave linearly polarized light. is there. However, it was found from an actual inspection that the use of circularly polarized illumination light improves the defect detection sensitivity as compared with the case of using linearly polarized P and S waves.

  FIG. 11A is a diagram exemplifying a program defect 909 protruding to one side of the line 907 in the mask 904 having a large number of lines 907 and spaces 908 arranged in one direction, and FIGS. 3 is a projection image illustrating a mask 904 illuminated with horizontally polarized light, vertically polarized light, and circularly polarized light. The half pitch of the line 907 and the space 908 is 56 [nm]. The program defect 909 is a defect that is intentionally added. The half pitch is 56 [nm].

  Comparing the projected images shown in FIGS. 11B to 11D, in the projected image (d) by the circularly polarized illumination light, the program defect is larger than that in the horizontally polarized light (b) and the vertically polarized light (c). 909 appears more prominent. That is, the sensitivity of defect detection can be improved by using the circularly polarized illumination light.

  Therefore, in the case of the program defect 909 having the shape as shown in FIG. 11A, the pattern inspection may be performed using only circularly polarized light. However, when the pitch of the line 907 and the space 908 is large, the detection sensitivity can be improved by using the illumination light including the linearly polarized P wave and S wave. Therefore, it is desirable to be able to simultaneously use three types of polarization states of P-wave and S-wave linearly polarized light and circularly polarized light. However, it is difficult to form illumination light including such three types of polarization states.

  It is an object of the present invention to provide a pattern inspection apparatus and a pattern inspection method that can improve defect detection sensitivity by using illumination light including a plurality of linearly polarized light and circularly polarized light having different polarization directions.

  The pattern inspection apparatus according to the present invention changes a polarization state of a part of illumination light, and includes a first beam including a first linearly polarized light and a second beam including a second linearly polarized light having a polarization direction different from that of the first linearly polarized light. And a polarization control unit that generates the illumination light having a third beam including circularly polarized light, and an inspection target by condensing the illumination light having the first beam, the second beam, and the third beam. The first light from the inspection target illuminated with the first beam, the second light from the inspection target illuminated with the second beam, and the inspection target illuminated with the third beam An objective lens that collects the third light from the first light, the first light, the second light, and the third light that are collected by the objective lens, respectively, as a first detector, a second detector, and a third detector. A polarization splitting section for guiding to a detector, the first light detected by the first detector, the second light detected by the second detector, and the third light detected by the third detector. The inspection target is inspected based on the third light. With such a configuration, it is possible to improve the defect detection sensitivity by using illumination light including a plurality of linearly polarized light and circularly polarized light having different polarization directions.

  Further, the pattern inspection method according to the present invention changes a polarization state of a part of the illumination light, and includes a first beam including a first linearly polarized light and a second linearly polarized light having a polarization direction different from that of the first linearly polarized light. Generating the illumination light having two beams and a third beam including circularly polarized light, and condensing the illumination light having the first beam, the second beam and the third beam by an objective lens. Illuminating the inspection target with the first beam from the inspection target illuminated with the first beam, the second light from the inspection target illuminated with the second beam, and the third beam. A step of condensing the third light from the inspection object by the objective lens; a first detector for respectively the first light, the second light and the third light condensed by the objective lens; Leading to a second detector and a third detector, the first light detected by the first detector, the second light detected by the second detector, and the first light detected by the third detector Inspecting the inspection object based on three lights. With such a configuration, it is possible to improve the defect detection sensitivity by using illumination light including a plurality of linearly polarized light and circularly polarized light having different polarization directions.

  Furthermore, an inspection apparatus according to the present invention includes a laser light source described above, an illumination optical system that illuminates an inspection target with the laser light, and a condensing optical system that condenses light from the inspection target illuminated with the laser light. And a detector that detects light from the inspection target and acquires an image of the inspection target. With such a configuration, the accuracy of inspecting the inspection target can be improved.

  According to the present invention, it is possible to provide a pattern inspection device and a pattern inspection method capable of improving the defect detection sensitivity.

1 is a configuration diagram illustrating a pattern inspection apparatus according to a first embodiment. FIG. 3 is a configuration diagram illustrating a polarization controller of the pattern inspection apparatus according to the first embodiment. FIG. 3 is a perspective view illustrating a polarization controller of the pattern inspection apparatus according to the first embodiment. FIG. 3 is a diagram exemplifying a polarization state within a field of view of an objective lens of the pattern inspection device according to the first embodiment. FIG. 3 is a flowchart illustrating the pattern inspection method according to the first embodiment. 6 is a configuration diagram illustrating a roof mirror and a detector of the pattern inspection apparatus according to the second embodiment. FIG. FIG. 6 is a configuration diagram illustrating a transmissive member and a detector of the pattern inspection apparatus according to the third embodiment. FIG. 9 is a configuration diagram illustrating a polarization control unit of the pattern inspection device according to the third embodiment. It is a block diagram which illustrated the pattern inspection apparatus. It is sectional drawing which illustrated the EUV mask. (A) is the figure which illustrated the program defect which jumped out to one side of the line in the mask which has many lines & space arranged in the perpendicular direction, (b)-(d) is horizontal polarization and vertical polarization, respectively. 3 is a projection image illustrating a mask illuminated with circularly polarized illumination light.

  Hereinafter, a specific configuration of this 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)
<Structure of pattern inspection device>
The pattern inspection apparatus according to the first embodiment will be described. The pattern inspection apparatus according to the present embodiment is, for example, a pattern inspection apparatus that detects a defect in a photomask (or a reticle, but also referred to as a mask here) used in a semiconductor manufacturing process. FIG. 1 is a configuration diagram illustrating a pattern inspection apparatus 100 according to the first embodiment.

  As shown in FIG. 1, the pattern inspection apparatus 100 includes lenses 101a to 101d, a homogenizer 102, a polarization controller 103, a half mirror 104, an objective lens 105, mirrors 107a to 107c, a projection lens 108, a polarization splitter 109, and a detector. It is provided with 120a to 120c.

  The pattern inspection apparatus 100 inspects, for example, a pattern of the EUV mask 106 as an inspection target and inspects a pattern for defects. Illumination light that illuminates the inspection target is, for example, laser light. A linearly polarized laser beam L1 is emitted from a laser device (not shown). Here, in order to explain the pattern inspection apparatus 100, an XYZ orthogonal coordinate system is introduced. For example, for convenience, the + Z axis direction is referred to as the upper side and the −Z axis direction is referred to as the lower side. The laser light L1 is emitted in the −Y axis direction, for example. The emitted laser light L1 is condensed by the lens 101a and enters the homogenizer 102.

  The homogenizer 102 is, for example, an optical member including a glass rod, and has a shape extending in the Y-axis direction. Both ends of the homogenizer 102 in the Y-axis direction have rectangular end faces. The homogenizer 102 spatially uniformizes the intensity distribution of incident illumination light. Specifically, the laser beam L1 that has entered the homogenizer 102 proceeds while repeating total internal reflection. Laser light L2 having a spatially uniform intensity distribution is emitted from the emission surface of the homogenizer 102.

  The laser light L2 emitted from the homogenizer 102 enters the lens 101b. The laser light L2 is, for example, divergent light. The laser light L2 that has passed through the lens 101b is converted into a parallel beam. The laser light L2 converted into a parallel beam is condensed by passing through the lens 101c. The laser light L3 condensed by the lens 101c is convergent light. An image on the exit surface of the homogenizer 102 is projected on the condensing part of the lens 101c by the lenses 101b and 101c. Therefore, an intermediate projection image is formed on the condensing part of the lens 101c.

  The polarization control unit 103 is arranged at the position of the condensing unit of the lens 101c. That is, the polarization controller 103 is arranged at a position conjugate with the exit surface of the homogenizer 102. The illumination light that has passed through the homogenizer 102 enters the polarization controller 103.

  FIG. 2 is a configuration diagram illustrating the polarization controller 103 of the pattern inspection apparatus 100 according to the first embodiment. FIG. 3 is a perspective view illustrating the polarization controller 103 of the pattern inspection apparatus 100 according to the first embodiment. As shown in FIGS. 2 and 3, the polarization controller 103 includes λ / 4 wave plates 103a and 103b. The λ / 4 wave plates 103a and 103b partially overlap each other in the optical axis LC direction of the laser light L3.

  For example, the λ / 4 wave plate 103a is inserted into the optical path from below so as to receive the lower 2/3 of the cross section orthogonal to the optical axis of the laser light L3. The λ / 4 wave plate 103b is inserted into the optical path from below so as to receive the lower ⅓ of the cross section orthogonal to the optical axis of the laser light L3. Therefore, the λ / 4 wave plate 103a and the λ / 4 wave plate 103b overlap with each other in the lower 1/3 of the cross section. Further, the upper end of the λ / 4 wave plate 103a is displaced upward from the upper end of the λ / 4 wave plate 103b. For example, when the beam diameter of the condensing portion of the laser light L3 is 1 [mm], the upper end of the λ / 4 wave plate 103a is 0.3 [mm] more than the upper end of the λ / 4 wave plate 103b. It is shifted upward.

  The laser light L3 condensed by the lens 101c enters the polarization controller 103. The lower 2/3 portion of the cross section orthogonal to the optical axis LC of the laser light L3 passes through the λ / 4 wave plate 103a. On the other hand, the upper ⅓ portion of the cross section of the laser beam L3 does not pass through the λ / 4 wave plate 103a and the λ / 4 wave plate 103b. The polarization state of the illumination light does not change in the upper ⅓ portion of the laser light L4. The upper 1/3 portion of the laser beam L4 is a beam La including linearly polarized light having a phase difference of 0 [°] with the laser beam L3 before entering the polarization control unit 103.

  The lower half of the laser beam L3 that has passed through the λ / 4 wave plate 103a passes through the λ / 4 wave plate 103b. Therefore, the lower ⅓ portion of the cross section of the laser beam L3 passes through the λ / 4 wavelength plate 103a and the λ / 4 wavelength plate 103b. As a result, the lower ⅓ portion of the laser light L4 is subjected to the same action as passing through the λ / 2 wave plate. That is, the lower 1/3 portion of the laser beam L4 is a beam Lb including linearly polarized light having a polarization direction different from that of the beam La. For example, the polarization direction of the beam Lb rotates 90 degrees with respect to the polarization direction of the beam La. Therefore, it becomes linearly polarized light in a direction orthogonal to the polarization direction of the laser light L3 before entering the polarization control unit 103.

  The upper half of the laser beam L3 that has passed through the λ / 4 wave plate 103a passes through as it is. Therefore, the central portion ⅓ of the laser beam L4 passes only through the λ / 4 wavelength plate 103a. As a result, the central portion ⅓ of the laser beam L4 becomes a beam Lc including circularly polarized light.

  In this way, the polarization control unit 103 changes the polarization state of a part of the incident illumination light, the beam La including the same linearly polarized light as before the incident, the beam Lb including the linearly polarized light having a polarization direction different from that before the incident, and , Illuminating light having a beam Lc containing circularly polarized light. In the present embodiment, the beam La is illumination light that has been transmitted through portions other than the λ / 4 wave plate 103a and the λ / 4 wave plate 103b, and the beam Lb is the λ / 4 wave plate 103a and the λ / 4 wave plate 103b. Is the illumination light transmitted through the overlapping portion, and the beam Lc is the illumination light transmitted through only the λ / 4 wavelength plate.

  The laser light L4 whose polarization state is partially changed by the polarization control unit 103 is converted into a parallel beam through the lens 101d. The laser light L5 converted into parallel light by the lens 101d is reflected by the mirror 107a. For example, the laser light L5 reflected by the mirror 107a proceeds in the + Z axis direction. The laser beam L5 reflected by the mirror 107a is reflected by the mirror 107b. For example, the laser beam L5 reflected by the mirror 107b proceeds in the + Y axis direction. The laser light L5 reflected by the mirror 107b enters the half mirror 104.

  Part of the laser light L5 that has entered the half mirror 104 is reflected by the half mirror 104 and travels downward, that is, in the −Z axis direction. For example, of the laser light L5, the laser light L5 having a power of about 50% proceeds downward like the laser light L6.

  The laser beam L6 traveling downward passes through the objective lens 105 and is focused on a minute area on the pattern surface of the EUV mask 106 to be inspected. In the present embodiment, the lens 101d and the objective lens 105 form a relay optical system. The polarization controller 103 is arranged at a position conjugate with the inspection target. Therefore, the intermediate projection image in the vicinity of the polarization controller 103 is projected on the surface of the EUV mask 106, that is, the pattern surface. Therefore, the pattern surface of the EUV mask 106 is illuminated with the laser light L6 having a uniform intensity distribution as illumination light.

  FIG. 4 is a diagram exemplifying the polarization state in the visual field 110 of the objective lens 105 of the pattern inspection apparatus 100 according to the first embodiment. In the field of view 110 of the objective lens 105, the pattern surface of the EUV mask 106 is illuminated in a polarized state as shown in FIG. For example, the field of view 110 of the objective lens 105 includes a portion illuminated by the beam La, a portion illuminated by the beam Lb, and a portion illuminated by the beam Lc. The beam La includes, for example, a horizontal polarization direction (horizontal polarization) in a plane parallel to the pattern surface. The beam Lb includes, for example, a vertical polarization direction (vertical polarization) in a plane parallel to the pattern surface. The beam Lc includes, for example, circularly polarized light in a plane parallel to the pattern surface.

  The field of view 110 of the objective lens 105 includes an inspection region 111 to be inspected. The inspection area 111 is, for example, a rectangular area in the visual field 110. For example, when the inspection area 111 is divided into three equal parts, 1/3 of the inspection area 111 is a portion illuminated by the beam La, 1/3 is a portion illuminated by the beam Lb, and 1/3. Is a portion illuminated by the beam Lc. The part illuminated by the beam Lc is arranged between the part illuminated by the beam La and the part illuminated by the beam Lb.

  In this way, the objective lens 105 illuminates the inspection target by condensing the illumination light having the beam La, the beam Lb, and the beam Lc on the inspection target.

  The light D1 from the inspection target illuminated with the illumination light may include reflected light of the illumination light reflected by the inspection target, diffracted light diffracted by the inspection target, fluorescence from the inspection target, and the like. The light D1 from the inspection target includes the pattern information of the EUV mask 106 that is the inspection target. The light D1 from the inspection target includes the light Da from the portion illuminated with the beam La, the light Db from the portion illuminated with the beam Lb, and the light Dc from the portion illuminated with the beam Lc.

  The objective lens 105 collects the light Da from the inspection target illuminated with the beam La, the light Db from the inspection target illuminated with the beam Lb, and the light Dc from the inspection target illuminated with the beam Lc. Therefore, the objective lens 105 collects the light D1 including the light Da, the light Db, and the light Dc.

  The light D1 condensed by the objective lens 105 travels upward, that is, in the + Z-axis direction, and enters the half mirror 104. Part of the light D1 incident on the half mirror 104 passes through the half mirror 104. The light D2 transmitted through the half mirror 104 is reflected by the mirror 107c and travels in the −Y axis direction, for example. The light D2 reflected by the mirror 107c is condensed by the projection lens 108. A polarization splitting unit 109 is arranged near the light collecting unit of the projection lens 108. The light D3 collected by the projection lens 108 enters the polarization splitting unit 109.

  The polarization splitting unit 109 includes space splitting mirrors 109a and 109b. The space division mirror 109a is arranged so that the upper ⅓ portion of the light D3 from the inspection target is reflected. Therefore, the space division mirror 109a reflects the light Da from the inspection target illuminated with the beam La. The space division mirror 109b is arranged so that the lower 1/3 portion of the light D3 from the inspection target is reflected. Therefore, the space division mirror 109b reflects the light Db from the inspection target illuminated with the beam Lb. The central portion of the light D3 from the inspection target does not enter the space division mirrors 109a and 109b, but passes between the space division mirrors 109a and 109b.

  The light Da reflected by the space division mirror 109a enters the detector 120a. The detectors 120a to 120c are, for example, TDI cameras or sensors of TDI cameras. The light Db reflected by the space division mirror 109b is incident on the detector 120b. The light Dc that does not enter the space division mirrors 109a and 109b but passes through between the space division mirrors 109a and 109b enters the detector 120c.

  In this way, the polarization splitting unit 109 guides the light Da, the light Db, and the light Dc collected by the objective lens 105 to the detector 120a, the detector 120b, and the detector 120c, respectively. Specifically, by the polarization splitting unit 109, each 1/3 of the cross section of the light Da including the horizontally polarized light, the light Db including the vertically polarized light, and the light D3 having the light Dc including the circularly polarized light is respectively TDI. It is projected on the sensor of the camera.

  The pattern inspection apparatus 100 inspects an inspection object based on the light Da detected by the detector 120a, the light Db detected by the detector 120b, and the light Dc detected by the detector 120c. For example, the pattern inspection apparatus 100 includes a processing unit (not shown) such as a PC (Personal Computer), and inspects an inspection target from an image processed using each light detected by each detector.

<Pattern inspection method>
Next, the pattern inspection method will be described. FIG. 5 is a flow chart illustrating the pattern inspection method according to the first embodiment. As shown in step S11 of FIG. 5, illumination light including a plurality of linearly polarized light and circularly polarized light having different polarization directions is generated. Specifically, the polarization state of a part of the laser light L3, which is the illumination light, is changed to include a beam La containing the same linearly polarized light as the laser light L3, a beam Lb containing linearly polarized light having a different polarization direction from the laser light L3, , Illuminating light having a beam Lc containing circularly polarized light.

  When the illumination light is generated, the polarization controller 103 including the λ / 4 wavelength plate 103a and the λ / 4 wavelength plate 103b which are partially overlapped with each other in the optical axis LC direction of the illumination light is used. For example, the end portion of the λ / 4 wavelength plate 103a is displaced in the direction orthogonal to the optical axis LC with respect to the end portion of the λ / 4 wavelength plate 103b. Then, the beam La is used as illumination light that has passed through portions other than the λ / 4 wavelength plate 103a and the λ / 4 wavelength plate 103b, and the beam Lb has illumination that has passed through the λ / 4 wavelength plate 103a and the λ / 4 wavelength plate 103b. The light beam Lc is used as illumination light that passes through only the λ / 4 wave plate 103a.

  The polarization controller 103 is arranged at a position conjugate with the inspection target. When generating the illumination light, the illumination light that has passed through the homogenizer that makes the intensity distribution uniform is incident on the polarization control unit 103.

  Next, as shown in step S12, the inspection target is illuminated. Specifically, the inspection object is illuminated by converging the illumination light having the beam La, the beam Lb, and the beam Lc by the objective lens.

  Next, as shown in step S13, the light from the inspection target is collected. Specifically, the light Da from the inspection object illuminated by the beam La, the light Db from the inspection object illuminated by the beam Lb, and the light Dc from the inspection object illuminated by the beam Lc are condensed by the objective lens. ..

  Next, as shown in step S14, the light from the inspection target is divided by the illumination light including a plurality of linearly polarized lights and circularly polarized lights having different polarization directions. Then, each divided light is guided to the detector. Specifically, the light Da, the light Db, and the light Dc from the inspection target collected by the objective lens 105 are guided to the detector 120a, the detector 120b, and the detector 120c, respectively.

  When guiding each light to each detector, a polarization splitting unit 109 including a space division mirror 109a that reflects the light Da and a space division mirror 109b that reflects the light Db may be used. In this case, the light Dc passes through the space division mirror 109a and the space division mirror 109b without being incident, and is guided to the detector 120c.

  Next, as shown in step S15, the inspection target is inspected. Specifically, the inspection target is inspected based on the light Da detected by the detector 120a, the light Db detected by the detector 120b, and the light Dc detected by the detector 120c. In this way, the inspection target is inspected.

  Next, the effect of this embodiment will be described. The pattern inspection apparatus 100 and the pattern inspection method according to the present embodiment use illumination light including a plurality of linearly polarized lights and circularly polarized lights having different polarization directions. As a result, the defect detection accuracy can be improved.

  For example, when the pitch of the mask pattern is below the resolution limit of a general pattern inspection apparatus, the defect detection sensitivity cannot be improved by using either P wave or S wave polarization. Sometimes. However, even in such a case, it has been found that the defect detection sensitivity is improved and the defect can be detected by using the circularly polarized illumination light. Since the illumination light of this embodiment includes circularly polarized light, it is possible to improve the defect detection sensitivity even when the pattern pitch is less than or equal to the resolution limit.

  Further, the polarization controller 103 includes a λ / 4 wave plate 103a and a λ / 4 wave plate 103b which are partially overlapped with each other in the optical axis direction of the illumination light. Then, the simple configuration is such that the end of the λ / 4 wave plate 103a is displaced from the end of the λ / 4 wave plate 103b by the diameter of the beam Lc. Therefore, it is easy to adjust the diameter of each beam. Further, the inspection cost can be suppressed.

  Since the polarization control unit 103 is arranged at a position conjugate with the inspection target, when illuminating the inspection target with the illumination light including the beam La, the beam Lb, and the beam Lc, each beam is projected onto the minute inspection region 111. Can be made Therefore, it is possible to improve the defect detection sensitivity and the inspection accuracy.

  Illumination light that has passed through a homogenizer that makes the intensity distribution spatially uniform is incident on the polarization control unit 103. Further, the mask surface to be inspected is illuminated by a relay optical system having an intermediate projection image. Therefore, an optical surface having a uniform intensity distribution can be projected onto the mask surface. As a result, the defect detection sensitivity can be improved and the inspection accuracy can be improved.

(Embodiment 2)
Next, a second embodiment will be described. In the pattern inspection apparatus of this embodiment, the polarization splitting unit 109 includes a roof mirror 109d. FIG. 6 is a configuration diagram illustrating the roof mirror 109d and the detectors 120a to 120c of the pattern inspection apparatus according to the second embodiment.

  As shown in FIG. 6, the polarization splitting unit 109 includes a roof mirror 109d having a planar reflecting surface 112 and a reflecting surface 113. The reflecting surface 112 and the reflecting surface 113 are arranged adjacent to each other. For example, the angle formed by the reflecting surface 112 and the reflecting surface 113 is an obtuse angle. Both the reflecting surface 112 and the reflecting surface 113 are illuminated with the light D3 from the inspection target. For example, the reflecting surface 113 is formed on the peripheral portion of the roof mirror 109d.

  Of the light D3 entering the polarization splitting unit 109, the lower 2/3 part of the cross section orthogonal to the optical axis is arranged to enter the roof mirror 109d. Of the light D3 entering the polarization splitting unit 109, the upper ⅓ portion of the cross section does not enter the roof mirror 109d and passes through the roof mirror 109d. Further, the upper ⅓ portion of the cross section includes the light Da from the inspection object illuminated by the beam La. The detector 120a is arranged so that the light Da that has passed through the roof mirror 109d is incident.

  Of the light D3 entering the polarization splitting unit 109, the lower ⅓ portion of the cross section is arranged to be reflected by the reflecting surface 112. Further, the lower ⅓ portion of the cross section includes the light Db from the inspection object illuminated by the beam Lb. The detector 120b is arranged so that the light Db reflected by the reflecting surface 112 enters.

  Of the light D3 entering the polarization splitting unit 109, the central portion ⅓ of the cross section is arranged to be reflected by the reflecting surface 113. Further, the central portion ⅓ of the cross section includes the light Dc from the inspection object illuminated with the beam Lc. The detector 120c is arranged so that the light Dc reflected by the reflecting surface 113 enters.

  As described above, in the present embodiment, when the lights Da to Dc from the inspection target are guided to the detectors 120a to 120c, respectively, the roof having the reflection surface 112 that reflects the light Db and the reflection surface 113 that reflects the light Dc. The mirror 109d is used. Since only the roof mirror 109d is used as the polarization splitting unit 109, the number of parts can be reduced. The other configurations and effects are included in the description of the first embodiment.

(Embodiment 3)
Next, a third embodiment will be described. In the pattern inspection apparatus of this embodiment, the polarization splitting section 109 includes a transmissive member. FIG. 7 is a configuration diagram illustrating the transmissive members 109e to 109f and the detectors 301a to 301c of the pattern inspection apparatus according to the third embodiment.

  As shown in FIG. 7, the polarization splitting unit 109 of this embodiment includes transmission members 109e and 109f. The transmissive members 109e and 109f are, for example, arranged at intervals in the direction orthogonal to the optical axis of the light D3 from the inspection target. The transmissive members 109e and 109f refract incident light.

  Of the light D3 entering the polarization splitting unit 109, the upper ⅓ portion of the cross section orthogonal to the optical axis is arranged to enter the transmitting member 109e. Further, the upper ⅓ portion of the cross section includes the light Da from the inspection object illuminated by the beam La. The transmissive member 109e refracts the incoming and outgoing light Da. The detector 301a is arranged so that the light Da that is refracted and emitted enters. The detector 301a is, for example, a sensor of the TDI camera 301.

  Of the light D3 entering the polarization splitting unit 109, the lower ⅓ portion of the cross section is arranged to enter the transmitting member 109f. The lower 1/3 portion of the cross section contains the light Db from the inspection object illuminated with the beam Lb. The transmissive member 109f refracts the incoming and outgoing light Db. The detector 301b is arranged so that the light Db that is refracted and emitted is incident. The detector 301b is, for example, a sensor of the TDI camera 301.

  Of the light D3 entering the polarization splitting unit 109, the central portion 1/3 passes through between the transmissive member 109e and the transmissive member 109f. Further, the central portion ⅓ of the cross section includes the light Dc from the inspection object illuminated with the beam Lc. The detector 301c is arranged so that the light Dc passing through between the transmissive member 109e and the transmissive member 109f is incident. The detector 301c is, for example, a sensor of the TDI camera 301.

  In this embodiment, the sensors of the TDI camera 301 are used as the detectors 301a to 301c. That is, one TDI camera 301 that integrates three TDI cameras is used. In the TDI camera 301, the distance between adjacent sensors is, for example, 10 [mm]. In the light D3 before entering the polarization splitting unit 109, the light Da, the light Db, and the light Dc are collected. Therefore, as it is, the respective lights Da to Dc cannot be made incident on the respective sensors of the TDI camera 301 functioning as the respective detectors 301a to 301c. However, the transmission members 109e and 109f of the polarization splitting unit 109 can refract the light Da and the light Db and separate them from the light Dc. Therefore, each light Da-Dc can be made to inject into each sensor, ie, each detector 301a-301c.

  As described above, the present embodiment uses the polarization splitting unit 109 including the transmissive member 109e that refracts the light Da and the transmissive member 109f that refracts the light Db to guide the light Da to Dc to the detectors 301a to 301c, respectively. ing. The polarization splitting unit 109 of the present embodiment does not need to change the optical path by reflecting at least one of the lights Da to Dc as in the above-described embodiments. The lights Da to Dc can be parallel to each other. Therefore, the TDI camera 301 in which three TDI cameras are integrated can be used. This is equivalent to inspecting with one TDI camera. Therefore, the inspection cost can be reduced. Other configurations and effects are included in the description of the first and second embodiments.

(Embodiment 4)
Next, a fourth embodiment will be described. In the pattern inspection apparatus of this embodiment, the polarization controller 103 includes three wave plates. FIG. 8 is a configuration diagram illustrating the polarization controller 103 of the pattern inspection apparatus according to the third embodiment.

  As shown in FIG. 8, the polarization controller 103 includes a λ / 4 wave plate 103d, a λ / 4 wave plate 103e, and a (−λ / 4) wave plate 103f. The (-? / 4) wave plate 103f is a wave plate that gives a phase difference of (-? / 4). The λ / 4 wave plate 103d, the λ / 4 wave plate 103e, and the (−λ / 4) wave plate 103f partially overlap with each other in the optical axis LC direction of the laser light L3. For example, the λ / 4 wave plate 103d is arranged so as to receive the entire laser beam L3. The λ / 4 wave plate 103e is inserted into the optical path from below so as to receive the lower 2/3 of the cross section orthogonal to the optical axis of the laser light L3. The (−λ / 4) wave plate 103f is inserted into the optical path from above so as to receive the upper 2/3 of the cross section orthogonal to the optical axis of the laser light L3. Therefore, the λ / 4 wave plate 103e and the (−λ / 4) wave plate 103f overlap each other at the central portion ⅓ of the cross section.

  The laser light L3 condensed by the lens 101c enters the polarization controller 103. Then, the laser light L3 passes through the λ / 4 wavelength plate 103d. Of the laser light transmitted through the λ / 4 wave plate 103d, the lower 2/3 portion of the cross section orthogonal to the optical axis LC passes through the λ / 4 wave plate 103e. On the other hand, the upper ⅓ portion of the cross section orthogonal to the optical axis LC does not pass through the λ / 4 wave plate 103e, but passes through the (−λ / 4) wave plate 103f.

  Therefore, of the laser light L3 that has entered the polarization control unit 103, the upper ⅓ portion of the cross section passes through the λ / 4 wave plate 103d and the (−λ / 4) wave plate 103f. As a result, the polarization state of the illumination light does not change in the upper ⅓ portion of the laser light L4 that has passed through the polarization controller 103. The upper 1/3 portion of the laser beam L4 is a beam La including linearly polarized light having a phase difference of 0 [°] with the laser beam L3 before entering the polarization control unit 103.

  The lower half of the laser beam L3 that has passed through the λ / 4 wave plate 103e does not pass through the (−λ / 4) wave plate 103f. Therefore, the lower ⅓ portion of the laser light L3 incident on the polarization controller 103 passes through the λ / 4 wavelength plate 103d and the λ / 4 wavelength plate 103e. As a result, the lower ⅓ portion of the laser beam L4 that has passed through the polarization control unit 103 is subjected to the same action as that through the λ / 2 wave plate. That is, the lower 1/3 portion of the laser beam L4 is a beam Lb including linearly polarized light having a polarization direction different from that of the beam La. For example, the polarization direction of the beam Lb rotates 90 degrees with respect to the polarization direction of the beam La. As a result, linearly polarized light in a direction orthogonal to the polarization direction of the laser light L3 before entering the polarization control unit 103 is obtained.

  The upper half of the laser beam L3 that has passed through the λ / 4 wave plate 103e passes through the (−λ / 4) wave plate 103f. Therefore, the central portion ⅓ of the laser beam L4 passes through the λ / 4 wave plate 103d, the λ / 4 wave plate 103e, and the (−λ / 4) wave plate 103f. As a result, the central portion ⅓ of the laser beam L4 that has passed through the polarization controller 103 is subjected to the same action as that of passing through the λ / 4 wave plate. Therefore, the central portion ⅓ of the laser beam L4 is a beam Lc including circularly polarized light.

  In this way, the polarization control unit 103 changes the polarization state of a part of the incident illumination light, the beam La including the same linearly polarized light as before the incident, the beam Lb including the linearly polarized light having a polarization direction different from that before the incident, and , Illuminating light having a beam Lc containing circularly polarized light. In the present embodiment, the beam La is illumination light transmitted through a portion where only the λ / 4 wave plate 103d and the (−λ / 4) wave plate 103f overlap, and the beam Lb is the λ / 4 wave plate 103d and λ. The beam Lc is the illumination light that has passed through the overlapping portion of only the / 4 wave plate 103e, and the beam Lc is a portion of the overlapping portion of the λ / 4 wave plate 103d, the λ / 4 wave plate 103e, and the (-λ / 4) wave plate 103f. It is the transmitted illumination light.

  According to this embodiment, it is possible to improve the degree of freedom of the configuration when generating the illumination light having the beams La to Lc. Other configurations and effects are included in the description of the first to third embodiments.

  Although the embodiments of the present invention have been described above, the present invention includes appropriate modifications without impairing the objects and advantages thereof, and is not limited by the above embodiments. Moreover, you may combine suitably the structure in Embodiments 1-4.

10 substrate 11 multilayer film 12 protective film 13 absorber 100 pattern inspection device 101a, 101b, 101c, 101d lens 102 homogenizer 103 polarization control units 103a, 103b, 103d, 103e λ / 4 wave plate 103f-λ / 4 wave plate 104 half Mirror 105 Objective lens 106 EUV masks 107a, 107b, 107c Mirror 108 Projection lens 109 Polarization splitting sections 109a, 109b Space splitting mirror 109d Roof mirrors 109e, 109f Transmission member 110 Field of view 111 Inspection area 112, 113 Reflective surfaces 120a, 120b, 120c Detection Device 301 TDI camera 120a, 120b, 120c, 301a, 301b, 301c Detector 900 Pattern inspection device 901 Polarization beam splitter 902 λ / 4 wavelength plate 903 Objective lens 904 Mask 905 Projection lens 906 TDI camera 907 Line 908 Space 909 Program defect 914 EUV mask D1, D2, D3, Da, Db, Dc Light LC Optical axis L1, L2, L3, L4, L5, L6, L901 Laser light La, Lb, Lc beam

Claims (16)

A first beam including a first linearly polarized light, which changes a polarization state of a part of the illumination light, a second beam including a second linearly polarized light having a polarization direction different from that of the first linearly polarized light, and a third beam including circularly polarized light. A polarization controller that produces the illumination light having a beam;
The inspection object is illuminated by condensing the illumination light having the first beam, the second beam, and the third beam, and the first light from the inspection object illuminated by the first beam, An objective lens that collects the second light from the inspection target illuminated by the second beam and the third light from the inspection target illuminated by the third beam;
A polarization splitting unit that guides the first light, the second light, and the third light collected by the objective lens to a first detector, a second detector, and a third detector, respectively.
Equipped with
The inspection target is inspected based on the first light detected by the first detector, the second light detected by the second detector, and the third light detected by the third detector. ,
Pattern inspection device. The polarization controller includes a first (λ / 4) wave plate and a second (λ / 4) wave plate partially overlapped with each other in the optical axis direction of the illumination light.
The first beam is the illumination light that has passed through portions other than the first (λ / 4) wave plate and the second (λ / 4) wave plate,
The second beam is the illumination light transmitted through a portion where the first (λ / 4) wave plate and the second (λ / 4) wave plate overlap,
The pattern inspection apparatus according to claim 1, wherein the third beam is the illumination light that has passed through only the first (λ / 4) wave plate. The polarization controller includes a first (λ / 4) wavelength plate, a second (λ / 4) wavelength plate, and a first (−λ / 4) wavelength plate that partially overlap with each other in the optical axis direction of the illumination light. Including the board,
The first beam is the illumination light transmitted through a portion where only the first (λ / 4) wave plate and the first (−λ / 4) wave plate overlap,
The second beam is the illumination light that has passed through a portion where only the first (λ / 4) wave plate and the second (λ / 4) wave plate overlap,
The third beam is transmitted through the first (λ / 4) wave plate, the second (λ / 4) wave plate, and the overlapping portion of the first (−λ / 4) wave plate. Is light,
The pattern inspection apparatus according to claim 1. The polarization control unit is arranged at a position conjugate with the inspection target,
The pattern inspection apparatus according to claim 1. Further comprising a homogenizer for making the intensity distribution of the illumination light uniform,
The illumination light transmitted through the homogenizer is incident on the polarization controller.
The pattern inspection apparatus according to claim 1. The polarization splitter includes a mirror that reflects the first light and a mirror that reflects the second light.
The pattern inspection apparatus according to claim 1. The polarization splitting part includes a roof mirror having a first reflecting surface that reflects the second light and a second reflecting surface that reflects the third light.
The pattern inspection apparatus according to claim 1. The polarization splitter includes a first transmissive member that refracts the first light and a second transmissive member that refracts the second light.
The pattern inspection apparatus according to claim 1. A first beam including a first linearly polarized light, which changes a polarization state of a part of the illumination light, a second beam including a second linearly polarized light having a polarization direction different from that of the first linearly polarized light, and a third beam including circularly polarized light. Generating the illumination light having a beam;
Illuminating an inspection object by collecting the illumination light having the first beam, the second beam, and the third beam by an objective lens;
First light from the inspection target illuminated with the first beam, second light from the inspection target illuminated with the second beam, and third light from the inspection target illuminated with the third beam Collecting light by the objective lens,
Guiding the first light, the second light, and the third light collected by the objective lens to a first detector, a second detector, and a third detector, respectively;
Inspecting the inspection target based on the first light detected by the first detector, the second light detected by the second detector, and the third light detected by the third detector,
A pattern inspection method equipped with. In the step of generating the illumination light,
When the illumination light is generated using a polarization controller including a first (λ / 4) wavelength plate and a second (λ / 4) wavelength plate that are partially overlapped in the optical axis direction of the illumination light,
The first beam is the illumination light that has passed through portions other than the first (λ / 4) wave plate and the second (λ / 4) wave plate,
The second beam is the illumination light transmitted through a portion where the first (λ / 4) wave plate and the second (λ / 4) wave plate overlap,
The pattern inspection method according to claim 9, wherein the third beam is the illumination light transmitted through only the first (λ / 4) wave plate. In the step of generating the illumination light,
A polarization controller including a first (λ / 4) wave plate, a second (λ / 4) wave plate, and a first (−λ / 4) wave plate partially overlapped in the optical axis direction of the illumination light is used. When generating the illumination light,
The first beam is the illumination light transmitted through a portion where only the first (λ / 4) wave plate and the first (−λ / 4) wave plate overlap,
The second beam is the illumination light transmitted through a portion where only the first (λ / 4) wave plate and the second (λ / 4) wave plate overlap,
The illumination light that has transmitted the third beam through a portion where the first (λ / 4) wave plate, the second (λ / 4) wave plate, and the first (−λ / 4) wave plate overlap each other. To do
The pattern inspection method according to claim 9. The polarization control unit is arranged at a position conjugate with the inspection target,
The pattern inspection method according to claim 10. In the step of generating the illumination light,
The illumination light that has passed through a homogenizer that makes the intensity distribution uniform is incident on the polarization controller.
The pattern inspection method according to claim 10. Leading to said first detector, second detector and third detector,
The first detector, the first light, the second light, and the third light, respectively, are formed by using a polarization splitting unit including a mirror that reflects the first light and a mirror that reflects the second light. Leading to the second detector and the third detector,
The pattern inspection method according to any one of claims 9 to 13. Leading to said first detector, second detector and third detector,
The first light, the second light, and the third light are formed by using a polarization splitting unit including a roof mirror having a first reflection surface that reflects the second light and a second reflection surface that reflects the third light. To the first detector, the second detector, and the third detector, respectively,
The pattern inspection method according to any one of claims 9 to 13. Leading to said first detector, second detector and third detector,
The first light, the second light, and the third light are respectively generated by using a polarization splitting unit including a first transmissive member that refracts the first light and a second transmissive member that refracts the second light. Leading to a first detector, the second detector and the third detector,
The pattern inspection method according to any one of claims 9 to 13.