JP2008241688A - Defect inspection method and defect inspection apparatus - Google Patents

Abstract

A defect inspection apparatus and a defect inspection method are provided that increase the capture range of light scattered from a minute defect and increase the signal intensity.
A stage unit 300 on which a substrate 1 to be inspected is mounted and movable relative to the optical system, an illumination optical system 100 that illuminates an inspection region 4 on the substrate 1 to be inspected, and an inspection region of the substrate 1 to be inspected 4, a detection optical system 200 that detects light from the image 4, an image sensor 205 that converts an image formed by the detection optical system 200 into a signal, and a signal processing unit 402 that processes a signal of the image sensor 205 and detects a defect. And a planar reflecting mirror 501 that is disposed between the detection optical system 200 and the substrate to be inspected 1 and transmits light from above the substrate to be inspected 1 to the detection optical system 200.
[Selection] Figure 6

Description

  The present invention relates to a defect inspection method and a defect inspection apparatus, and particularly occurs in a manufacturing process of forming an object by forming a pattern on a substrate, such as a semiconductor manufacturing process, a liquid crystal display element manufacturing process, and a printed circuit board manufacturing process. The present invention relates to a technique suitable for inspecting the occurrence of defects such as foreign matters in a manufacturing process in which defects such as foreign matters are detected, analyzed, and countermeasures are taken.

  In a semiconductor manufacturing process, if foreign matter is present on a substrate to be inspected (wafer), it may cause defects such as wiring insulation failure or short circuit. Further, when fine foreign matter is present with the miniaturization of the semiconductor element, the fine foreign matter may cause a defective insulation of the capacitor or a breakdown of the gate oxide film or the like. These foreign substances are mixed in various states such as those generated from the moving parts of the transfer device, those generated from the human body, those generated by reaction in the processing apparatus by the process gas, and those containing chemicals and materials. Is done.

  Similarly, in the manufacturing process of a liquid crystal display element, if foreign matter adheres to the pattern formed on the liquid crystal display element substrate and some defect occurs, the liquid crystal display element cannot be used as a display element. The situation is the same in the manufacturing process of the printed circuit board, and the adhesion of foreign matters causes short circuit of the pattern and defective connection.

  Conventionally, as one of the techniques for detecting foreign matter on this type of substrate to be inspected, as described in Patent Document 1, a laser is irradiated on the substrate to be inspected and the foreign matter adheres on the substrate to be inspected. By detecting the scattered light from the foreign material that occurs when the product is inspected and comparing it with the inspection result of the same type of substrate to be inspected immediately before, there is no false information due to the pattern, and highly sensitive and highly reliable foreign material and defect inspection What makes it possible is disclosed. Further, as disclosed in Patent Document 2, a laser beam is irradiated on the substrate to be inspected to detect scattered light from the foreign material that is generated when the foreign material adheres to the substrate to be inspected. Some foreign materials are analyzed by an analysis technique such as laser photoluminescence or two-dimensional X-ray analysis (XMR).

  As a technique for inspecting the foreign matter, there is a method of irradiating a wafer with coherent light and removing light emitted from a repetitive pattern on the wafer with a spatial filter to emphasize and detect a foreign matter or defect having no repeatability. It is disclosed. In addition, the circuit pattern formed on the wafer is irradiated from a direction inclined 45 degrees with respect to the main straight line group of the circuit pattern, and the zero-order diffracted light from the main straight line group enters the aperture of the detection lens. A foreign substance inspection apparatus which is not allowed to be used is known in Patent Document 3. This Patent Document 3 also describes that other straight line groups that are not main straight line groups are shielded by a spatial filter. In addition, as a conventional technique related to a defect inspection apparatus and method for foreign matter or the like, Patent Document 4 describes that the detection pixel size is changed by switching the detection optical system. Patent Document 5 and Patent Document 6 are disclosed for measuring the size of foreign matter. In Patent Document 7, as a defect detection technique on a thin film, a laser beam is narrowed down to form a narrow beam spot in a direction perpendicular to the stage moving direction, and detection is performed in a direction perpendicular to the illumination direction.

JP-A-62-89336 JP-A 63-135848 Japanese Patent Laid-Open No. 1-117024 JP 2000-105203 A JP 2001-60607 A JP 2001-264264 A JP 2004-177284 A

  In order to detect a defect to be miniaturized, the signal intensity of the defect can be increased by expanding the range in which the detection optical system captures light scattered from the defect. For this purpose, increasing the NA (Numerical Aperture) of the detection optical system disposed above is effective, but if the lens diameter is not enlarged, it is necessary to reduce the distance between the lens tip and the substrate to be inspected. The angle of oblique illumination from outside the optical axis of the detection optical system cannot be increased, the power applied to the defect is reduced, and as a result, the detection signal cannot be increased. On the other hand, if the lens diameter is increased, the distance between the lens tip and the substrate to be inspected can be increased. However, if the NA ratio is large, the ratio of the lens diameter / focal length also increases, so that the size of the optical system is greatly increased. A new problem that becomes difficult to install in the device occurs.

  In order to capture light scattered from defects reflected outside the capture range of the detection optical system of the vertical optical axis, a mechanism for tilting the optical axis of the detection optical system is added to the detection optical system, and the system is tilted and detected, or There is a method to add an oblique detection system. However, when the optical axis of the upper detection lens or the additional oblique detection system is below a certain elevation angle, it comes into contact with the surface of the substrate to be inspected and cannot be detected at a low elevation angle. In order to avoid contact at a lower elevation angle, the NA of the detection optical system can be reduced to reduce the lens barrel diameter of the detection system lens. Decreases. Furthermore, the above-described method requires a mechanism for tilting the upper optical system, or an image sensor for oblique detection, a lens, a spatial filter unit, and a detection region observation optical system. This causes problems such as an increase in the number of man-hours for adjustment.

  One object of the present invention is to provide a defect inspection apparatus and a defect inspection method that increase the signal capture intensity by expanding the capture range of light scattered from fine defects.

  One feature of the present invention is a method of illuminating a substrate to be inspected, forming an image of light obtained from the illumination region, converting the formed image into signal intensity, and inspecting the substrate to be inspected with light, In this inspection method, light is transmitted between an inspection substrate and an image through an optical element.

  In addition, another feature of the present invention is that a stage on which a substrate to be inspected is mounted and which can move relative to the optical system, an illumination system that illuminates an inspection area on the substrate to be inspected, and light from the substrate to be inspected A detection optical system capable of imaging light from the inspection region on the inspection substrate on the image sensor, an image sensor for converting an image formed by the detection optical system into a signal, and a defect from the signal of the image sensor. It comprises a signal processing system that can be detected and an optical element disposed between the detection optical system and the substrate to be inspected, and can transmit light from the substrate to be inspected through the optical element. Inspection equipment.

  Still another feature of the present invention is that a plane reflecting mirror is disposed between the detection lens and the substrate to be inspected, and light obtained from the illumination area is reflected by the plane reflecting mirror and imaged on the image sensor. The inspection is realized.

  According to the present invention, an oblique inspection with a high NA and a low elevation angle can be easily realized, and an increase in the number of detectable defect types and an increase in the number of detection can be expected.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, equivalent functional parts will be described with the same reference numerals.

  An embodiment of a defect inspection apparatus according to the present invention will be described with reference to FIG.

  The illustrated defect inspection apparatus includes a stage unit 300 on which a substrate 1 to be inspected is mounted, an illumination optical system 100 that irradiates a beam spot 3 that is a slit-shaped illumination region on the substrate 1 to be inspected, and a detection region 4 of an image sensor. Detection optical system 200 that detects scattered light from the light source, and a control system 400 that executes various arithmetic processes.

  The stage unit 300 scans an inspection area in the substrate 1 to be inspected in the X and Y directions and can move relative to the optical system. The Z stage can focus on the surface of the substrate 1 to be inspected. 303, a theta (θ) stage 304, and a stage controller 305.

  The illumination optical system 100 includes a laser light source, a beam expander, an optical filter group and a mirror, an optical branching element (or mirror) switchable with a glass plate, and a beam spot imaging unit. As the laser light source of the illumination optical system 100, it is preferable to use the third harmonic THG of a high-power YAG laser and a wavelength of 355 nm, but it is not necessarily required to be 355 nm. That is, other light sources such as a laser light source Ar laser, a nitrogen laser, a He—Cd laser, and an excimer laser may be used.

  The detection optical system 200 is for upward inspection, and can detect a detection lens 201, a spatial filter 202, an imaging lens 203, a zoom lens group 204, a one-dimensional image sensor (image sensor) 205, and a detection area of the image sensor. It comprises an observation optical system (camera) 206, a polarization beam splitter 209, and a branch detection optical system 210 for performing simultaneous inspection of two sensors. The one-dimensional image sensor 205 may be a CCD or a TDI (Time Delay Integration) sensor. In the case of a CCD, since the pixel size is generally about 10 μm, it may be considered as linear detection, and there is no sensitivity reduction due to capturing an image that is not in focus in the scanning direction. On the other hand, in TDI, since images of a certain number of pixels are accumulated in the scanning direction, it is desirable to reduce the amount of images that are not in focus by taking measures such as reducing the illumination width or tilting the TDI sensor. The coordinate system is shown in the lower left of FIG. The XY axis is taken on the plane, and the Z axis is taken vertically upward. The optical axis of the detection optical system 200 is arranged along the Z axis.

  The control system 400 includes a signal processing unit 402, a control CPU unit 401, a display unit 403, and an input unit 404. The signal processing unit 402 includes an A / D conversion unit, a data memory that can be delayed, a difference processing circuit that takes a signal difference between chips, a memory that temporarily stores a difference signal between chips, and a threshold calculation that sets a pattern threshold It consists of a processing unit and a comparison circuit. The control CPU unit 401 stores a defect detection result such as a foreign substance and controls an output unit that outputs the defect detection result, driving of a motor, coordinates, and a sensor.

  With reference to FIG. 2, the sample which is the inspection target of the defect inspection apparatus according to the present invention will be described. A substrate 1a to be inspected shown in FIG. 2A has memory LSI chips 1aa arranged two-dimensionally at a predetermined interval. The memory LSI chip 1aa mainly has a memory cell area 1ab, a peripheral circuit area 1ac composed of a decoder, a control circuit, and the like, and another area 1ad. The memory cell region 1ab has a two-dimensional regular arrangement, that is, a repeated memory cell pattern. The peripheral circuit region 1ac has a non-repetitive pattern that is not regularly arranged in two dimensions, that is, irregularly arranged.

  A substrate to be inspected 1b shown in FIG. 2B has LSI chips 1ba such as a microcomputer arranged two-dimensionally at a predetermined interval. An LSI chip 1ba such as a microcomputer mainly has a register group area 1bb, a memory area 1bc, a CPU core area 1bd, and an input / output area 1be. FIG. 2B conceptually shows the arrangement of the memory area 1bc, the CPU core area 1bd, and the input / output area 1be. The register group region 1bb and the memory portion region 1bc are regularly arranged in two dimensions, that is, have a repetitive pattern. The CPU core area 1bd and the input / output area 1be have non-repeating patterns. As described above, the inspection object of the defect inspection apparatus according to the present invention generally has chips regularly arranged like the inspection substrate (wafer) 1 shown in FIG. 2, but the minimum line in the chip. The width varies from region to region, and includes a repeated pattern and a non-repeated pattern, and the forms are various.

  With reference to FIG. 3, the first to third beam spot imaging units 110, 120, and 130 of the illumination optical system 100 will be described. FIG. 3 is a view of the inspected substrate 1 as seen from above.

  The inspection illumination light 11 in the X-axis direction is irradiated through the first beam spot imaging unit 110, and the direction is inclined by −45 degrees with respect to the Y-axis through the second beam spot imaging unit 120. And the inspection illumination light 13 in the direction inclined by 45 degrees with respect to the Y axis is irradiated via the third beam spot imaging unit 130.

  These inspection illumination lights 11, 12, 13 are irradiated at a predetermined elevation angle α with respect to the surface of the substrate 1 to be inspected. In particular, the amount of scattered light detected from the lower surface of the transparent thin film can be reduced by reducing the elevation angle α of the illumination lights 12 and 13 for inspection. By these inspection illumination lights 11, 12, and 13, an elongated beam spot 3 is formed on the substrate 1 to be inspected. The beam spot 3 extends along the Y-axis direction. The length of the beam spot 3 in the Y-axis direction is larger than the detection area 4 of the image sensor of the one-dimensional image sensor 205 of the detection optical system 200.

  The reason why the three beam spot imaging units 110, 120, and 130 are provided in the illumination optical system 100 will be described. In the present example, φ1 = φ2 = 45 degrees, assuming that the angles formed by the images obtained by projecting the inspection illumination lights 12 and 13 on the XY plane and the X axis are φ1 and φ2, respectively. In this case, since the main direction of the non-repeated pattern on the substrate 1 to be inspected is an X-axis or Y-axis linear pattern, it is incident on the pattern from a 45 degree direction. For this reason, diffracted light enters the entrance pupil of the detection lens 201 as a component in the X-axis or Y-axis direction. However, when the illumination elevation angle α is low, the specularly reflected light also becomes low angle α, and the X-axis or Y-axis. Similarly, the component diffracted light is separated from the area of the entrance pupil of the detection lens 201 so that it can be prevented from entering the detection optical system 200. For example, as disclosed in Japanese Patent No. 3566689 (see paragraphs [0033] to [0036] in particular). This is described in detail, and a description thereof is omitted here.

  The non-repeating pattern on the substrate 1 to be inspected mainly consists of linear patterns formed in parallel and at right angles. These linear patterns extend in the X-axis or Y-axis direction. Since the pattern on the substrate 1 to be inspected is formed to protrude, a recess is formed between adjacent linear patterns. Therefore, the inspection illumination lights 12 and 13 irradiated from the direction inclined by 45 degrees with respect to the X axis and the Y axis are blocked by the protruding circuit pattern and cannot irradiate the concave portion between the linear patterns.

  Therefore, a first beam spot imaging unit 110 that generates the inspection illumination light 11 along the X-axis direction is provided. In this way, the inspection illumination light 11 can irradiate the recesses between the linear patterns, so that it is possible to detect a defect such as a foreign substance existing there. Depending on the direction of the linear pattern, the sample may be inspected by being rotated 90 degrees, or the inspection illumination light 11 may be irradiated along the Y-axis direction.

  In the case of irradiating the concave portions between the linear patterns along the X-axis direction like the inspection illumination light 11, the 0th-order diffracted light is used so that the image sensor does not detect the 0th-order diffracted light. It is necessary to shield the light. For this purpose, a spatial filter 202 is provided.

  A method for forming the elongated beam spot 3 will be described with reference to FIGS. 4 and 5, only the laser light source 101, the concave lens 102, the convex lens 103, and the illumination lens 104 in the illumination optical system 100 are shown, and other components are omitted.

  The illumination lens 104 is a cylindrical lens having a conical curved surface. As shown in FIG. 4A, the focal length changes linearly along the longitudinal direction (vertical direction in FIG. 4A). As shown in FIG. 4B, it has a cross section of a plano-convex lens. As shown in FIG. 5, it is possible to generate a slit-shaped beam spot 3 that is narrowed down in the Y direction and collimated in the X direction with respect to illumination light that is incident on the substrate 1 to be inspected at an angle. The angle (elevation angle) of the illumination light with respect to the surface of the inspected substrate 1 is α1, and the angle between the image of the inspection illumination light 11 projected on the inspected substrate 1 and the X axis is φ1.

  By using such an illumination lens 104, it is possible to realize illumination having parallel light in the X direction and around φ1 = 45 degrees. A method for manufacturing the illumination lens 104 having a conical curved surface is described in detail in, for example, Japanese Patent No. 3566589 (see particularly paragraphs [0027] to [0028]), and can be manufactured by a known method.

(First embodiment)
A first embodiment of the oblique inspection according to the present invention will be described with reference to FIG. An object of the present embodiment is to realize a system characterized by enabling oblique inspection with an upper detection optical system in order to detect defects on the substrate 1 to be inspected by light.

  A plane reflecting mirror 501 is disposed between the detection lens 201 and the substrate 1 to be inspected. The plane reflecting mirror 501 reflects oblique scattered light obtained from the detection region 4 of the image sensor on the substrate 1 to be inspected. The scattered light reflected by the plane reflecting mirror 501 forms an image on the image sensor 205 by the detection optical system. For this purpose, the reflecting surface of the plane reflecting mirror is arranged parallel to the pixel direction (longitudinal direction) of the image sensor and inclined with respect to the optical axis of the detection lens. The detection region 4 does not need to coincide with the optical axis of the detection lens, and can be set to be shifted in the direction perpendicular to the pixel direction of the image sensor 205, that is, in the X-axis direction and inspected obliquely.

  In order to eliminate the “clearance” of the optical path, the shape of the planar reflecting mirror 501 in the Y direction needs to be sufficiently larger than the optical path diameter corresponding to the NA of the detection lens 201. If the detection elevation angle β for oblique detection is determined, the length of the reflection surface is a distance that does not contact the detection lens 201 and the substrate 1 to be inspected when switching between upward detection and oblique detection, for example, about 0.2 to 1 mm. It is desirable to make the maximum dimension while ensuring a gap. In this case, if the lower surface and the upper surface of the flat reflecting mirror 501 are made horizontal, the reflection area can be secured to the maximum. It is desirable that the position of the plane reflecting mirror 501 in the X direction is a position where the NA of incident light can be maximized.

  When the light from the detection area 4 of the image sensor is imaged on the image sensor 205, it is necessary to make the focus of the detection lens 201 coincide with the detection area 4 of the image sensor. For this purpose, in the present embodiment, the Z stage 303 is raised to the focus height of the detection lens 201 with respect to the detection area 6 for the upper inspection, and the focus is matched with the detection area 4 for the oblique inspection by the autofocus mechanism. It is desirable to make it. If the optical axis of the autofocus mechanism passes through the detection lens, no change is required during the oblique inspection, but if off-axis autofocus that does not pass through the detection system lens is used, It is necessary to move the autofocus mechanism by + ΔZ in the Z-axis direction in accordance with the movement amount ΔZ. A method is also possible in which the XYZ coordinates of the substrate 1 to be inspected are stored in advance to obtain the distribution of the surface height and reproduced during inspection. Further, when the light from the detection area 4 of the image sensor is imaged on the image sensor 205, it is desirable that the center and angle of the distribution of the beam spot 3 coincide with the detection area 4 of the image sensor.

  The plane reflecting mirror 501 is a mechanism that can be taken in and out of the optical path by the switching mechanism 502. In the present embodiment, when the light from the detection region 6 of the image sensor at the time of the upper inspection is imaged on the image sensor 205 by the detection optical system 200 for inspection (upper inspection), the planar reflecting mirror 501 is placed outside the optical path. Evacuate. When the detection region 4 of the image sensor is imaged on the image sensor 205 by the detection optical system 200 and inspected (in the case of oblique inspection), the plane reflecting mirror 501 is returned to the position shown in FIG.

  As a result, a detection optical system for oblique inspection with the plane reflecting mirror 501 in the optical path, or a detection optical system for upward inspection in a state where the planar reflecting mirror 501 is not in the optical path can be formed. An inspection can be selected. The inspection results of the upper inspection and the oblique inspection are obtained in two inspections. For the defect having the same coordinate, the defect size is calculated from the signal intensity and the defect area obtained by the upper inspection and the oblique inspection. Classification can be made highly accurate.

  It is desirable that the elevation angle of the light incident on the plane reflecting mirror 501 be a mechanism that can be changed according to the scattered light distribution of the defect to be detected. Oblique inspection at different detection elevation angles, signal strength and coordinates are stored in the memory of each signal processing system, and signal intensity obtained by oblique inspection with different detection elevation angles is compared to make defect extraction and classification more accurate can do. In FIG. 6, the elevation angle of the scattered light to be detected is determined by moving the two planar reflecting mirrors 501 that make the scattered light of two types of elevation angles β1 and β2 incident on the detection lens 201 in the direction of the white arrow by the switching mechanism 502. The oblique inspection can be performed on scattered light having different detection elevation angles by changing the angle of the reflecting surface of the plane reflecting mirror 501. The detection elevation angle β is preferably such that the remaining NA can be divided by β1 and β2 with respect to the NA of the upper detection lens 201. As a result, the scattered light of the defect can be detected with NA of 0.9 or more in the X-axis direction, and the signal intensity of the defect whose scattered light distribution is directional can be increased and the sensitivity can be improved. Thus, according to the present embodiment, it is possible to increase the signal intensity by expanding the capture range of light scattered from fine defects. This effect can be similarly obtained in the following embodiments.

  In order to change the magnification of the inspection image, the zoom lens is also used when the detection area 4 of the image sensor is obliquely in the same manner as when the position of the zoom lens group 204 is changed when the detection area 6 of the image sensor is inspected upward. Inspection can be performed by changing the position of the group 204. As a result, the detection pixel size of the substrate 1 to be inspected can be changed, so that the S / N (= defect signal intensity / pattern signal intensity) can be improved when the pixel size is reduced, and the pixel size is increased. Can reduce throughput.

  Similarly to the fact that the Fourier transform image of the detection area 6 of the image sensor can be filtered by the spatial filter 202 during the upper inspection, the Fourier image in the pixel direction also depends on the pattern pitch during the oblique inspection. It is possible to filter the Fourier transform image of the detection region 4 with the spatial filter 202.

  The detection region 4 of the image sensor can be observed with the observation optical system 206 of the detection optical system in the same manner as the detection region 6 of the image sensor can be observed with the observation optical system 206 during the upper inspection. This eliminates the need for an additional oblique inspection function.

(Second Embodiment)
A second embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The purpose of this embodiment is to adjust the focus height of the autofocus system within the pull-in range by matching the stage height during upward inspection using the detection optical system and the stage height during oblique inspection to the same height or in the vicinity thereof. This is a realization of a method that enables an upward inspection and an oblique inspection without changing the stage height as in the first embodiment. For this purpose, the optical path length correction element 503 is arranged between the plane reflecting mirror (in this example, the reflection surface 506 of the optical path length correction element 503) and the detection optical system 200, so that the inspection area on the substrate 1 to be inspected. It is desirable to extend the optical path length from to the detection lens 201. The optical path length can be extended by 1 / (1-refractive index) of the optical path length passing through the correction element 503. A feature of the present invention is that the optical path length correction element 503 can be made a prism so that the correction amount can be increased as compared with a third embodiment to be described later. A dielectric multilayer coating for reflecting incident light with high reflectivity is formed on one surface (reflection surface 506) of the optical path length correction element 503. In FIG. 7, two optical path length correction elements 503 having different angles of the reflection surface 506 for allowing the two types of elevation scattered light of β1 and β2 to enter the detection lens 201 are moved by the switching mechanism 502 in the direction of the white arrow. Thus, the elevation angle of the scattered light to be detected can be switched. In the first embodiment described above, the Z stage 303 is raised and the focus of the detection optical system is adjusted when shifting from the upper inspection to the oblique inspection. However, by arranging the optical path length correcting element 503, the image can be obtained. The upper inspection can be performed at the same stage height as when detecting scattered light from the detection area 4 for the oblique inspection of the sensor, and the correction amount of the stage height and the coarse movement mechanism are not required.

  The optical path length correction element 503 desirably has an imaging aberration correction function. It is possible to form a curve for correcting aberration on the exit surface of the optical path length correction element 503 so that the imaging performance is not deteriorated. As a result, the aberration of light passing through the peripheral portion of the high NA detection optical system can be corrected, so that the intensity distribution of the image received by the image sensor can be reduced and the sensitivity unevenness can be reduced.

(Third embodiment)
A third embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The purpose of this embodiment is to adjust the focus height of the autofocus system within the pull-in range by matching the stage height at the time of upper inspection using the detection optical system and the stage height at the oblique inspection to the same height, This is the realization of a method that enables upward inspection and oblique inspection without changing the stage height. For this purpose, it is desirable to extend the optical path length by disposing the optical path length correction element 504 or 505 between the plane reflecting mirror 501 and the detection optical system 200. The optical path length can be extended by 1 / (1-refractive index) of the optical path length passing through the correction element. In FIG. 8, two plane reflecting mirrors 501 having different angles at which two kinds of scattered light of β1 and β2 are incident on the detection lens 201 are moved by the switching mechanism 502 in the direction of the white arrow to thereby detect the detection elevation angle. It can be switched. The optical path length correction elements 504 and 505 are provided above the two plane reflecting mirrors 501, respectively. Further, the optical path length correction elements 504 and 505 are required to be aspherical on their emission surfaces so as not to deteriorate the imaging performance. As a result, the aberration of light passing through the peripheral portion of the high NA detection optical system can be corrected. Therefore, the intensity distribution of the image received by the image sensor 205 can be reduced, and the sensitivity unevenness can be reduced. In this embodiment, the shape of the optical path length correction element is a lens shape compared to the second embodiment, so that aspherical processing is easy. However, since the optical path length is short, the correction amount is small and the elevation angle β of the oblique detection system is If it is lowered, the correction amount is insufficient. Therefore, it is desirable to use the prism type of the second embodiment at a low elevation angle β.

(Fourth embodiment)
A fourth embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The object of the present embodiment is to realize a system that enables inspection of light from the same detection area (detection area 6 in this example) with one or a plurality of image sensors in one inspection. In other words, the light from the detection region 6 of the image sensor can be detected by the image sensor 205 used for the upper inspection and the image sensor 207 added for the oblique inspection. For this purpose, the position of the plane reflecting mirror 501 is detected. It is desirable to adopt a system in which the light that is shifted from the optical axis of the optical system 200 and reflected by the plane reflecting mirror 501 is incident on the periphery of the detection lens 201. An optical path branching plane reflecting mirror 208 is disposed in the optical path of the light reflected by the plane reflecting mirror 501, and the light scattered obliquely from the detection region 6 of the image sensor is reflected by the optical path generating planar reflecting mirror 208 to detect the oblique direction. The image is formed on the image sensor 207. At this time, since the optical path of the oblique inspection is different from the optical path of the upper inspection (broken line), if the optical path branching plane reflecting mirror 208 is outside the upper inspection region (outside the upper inspection optical path), the upper inspection and the oblique inspection are performed simultaneously. Inspection is possible. At this time, an optical path length correction element may be added to the oblique detection optical system as in the second embodiment or the third embodiment.

  The effect of simultaneous inspection is a reduction in inspection time. Since two types of signals with different detected elevation angles can be simultaneously captured and checked while being calculated, hardware memory capacity can be saved, software processing time can be reduced, and load can be reduced. In the present embodiment, by making the inspection illumination light 12 and the inspection illumination light 13 have different wavelengths and polarization, information of different signal intensities can be obtained by the two image sensors 205 and 207 in one inspection. Since the light scattered from the defect has different signal intensity depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with higher accuracy using the signal intensity ratio of the two image sensors 205 and 207 as a feature amount.

(Fifth embodiment)
A fifth embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The object of the present embodiment is to realize a method that enables an upper inspection in which light from the detection region 6 is detected by the image sensor 205 and an oblique inspection in which light from the detection region 4 is detected by the image sensor 207 can be simultaneously inspected. is there. For this purpose, it is desirable to shift the position of the plane reflecting mirror 501 from the optical axis of the detection optical system 200 so that the light reflected by the plane reflecting mirror 501 enters the periphery of the detection lens 201. At this time, an optical path length correction element may be added to the oblique detection optical system as in the second embodiment or the third embodiment. The difference from the fourth embodiment is that the detection region 4 of the image sensor for oblique inspection is arranged at a position shifted from the detection region 6 of the image sensor for upward inspection. In order to image the detection area 4 of the image sensor on the image sensor 207 which is an oblique inspection sensor, the optical path branching plane reflecting mirror 208 is arranged in the optical path of the light reflected by the plane reflecting mirror 501 and branched. At this time, since the optical path for the upper inspection is a broken-line optical path, the upper inspection and the oblique inspection can be performed at the same time if the optical path splitting plane reflecting mirror 208 is outside the upper inspection area (outside the upper inspection optical path).

  The effect of the above configuration is a reduction in inspection time. Two types of signals with different detection elevation angles can be captured simultaneously, and inspection can be performed while performing computations. Therefore, the memory capacity of hardware can be saved, and the time required for software processing and the load can be reduced. The difference from the effect of the fourth embodiment is that the detection position 4 for oblique inspection is shifted from the detection area 6 for upward inspection, and the incident position of the light reflected by the plane reflecting mirror 501 on the detection lens 201 is the fourth embodiment. Since the visual field of the detection optical system 200 can be reduced by approaching the optical axis of the detection optical system 200 as compared with the form, it is possible to reduce the deterioration of the imaging performance that has passed through the periphery of the lens. Further, the illumination direction, elevation angle, polarization, and wavelength can be selected as illumination conditions, and inspection can be performed by forming images on a plurality of image sensors. Also in this embodiment, the inspection illumination lights 12 and 13 have different directions, elevation angles, wavelengths, and polarizations as in the above-described fourth embodiment. Information of different signal strengths is obtained at 207. Since the light scattered from the defect has different signal intensity depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with higher accuracy using the signal intensity ratio of the two image sensors 205 and 207 as a feature amount.

(Sixth embodiment)
A sixth embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The object of the present embodiment is to realize a method characterized in that the detection region 4 of the image sensor is simultaneously detected by two sensors when polarized light is selected as the illumination condition. For this purpose, the detection region 4 of the image sensor is irradiated with two types of polarized light, P-polarized light and S-polarized light, the optical path is branched by the polarization beam splitter 209, and S-polarized light and P-polarized light can be detected by separate sensors 205 and 207. It is desirable. A beam spot 3 is formed on the detection region 4 of the image sensor that is offset from the optical axis of the detection lens 201 and is parallel to the Y axis. In this embodiment, the inspection illumination light 12 is S-polarized light, and the inspection illumination light 13 is P-polarized light. The light obtained from the detection region 4 is reflected by the reflecting surface 506 of the plane reflecting mirror 501 that is a mirror tilted so that the detection elevation angle selected by the mirror switching mechanism 502 is β1 or β2, and is incident on the detection lens 201. . The light from which the pattern noise has been cut by the spatial filter 202 installed on the Fourier transform surface of the detection lens 201 is imaged on the image sensor 205 by the imaging lens 203 and the zoom lens group 204 at a predetermined magnification. The observation optical system 206 can observe the detection region 4 or the surface of the spatial filter 202. In the present embodiment, the polarization beam splitter 209 is inserted between the detection optical system 200 and the image sensor, so that the optical path is branched and two image sensors 207 and 205 are imaged.

  According to the above configuration, since the signal intensity of the light scattered from the defect differs depending on the polarization direction, the light obtained from the same defect is branched by the polarization beam splitter 209, and light of different polarization components is sent to the two image sensors 205 or 207. An image can be formed, and defect classification can be performed from the signal intensity ratio. If the polarization beam splitter 209 is changed to an element capable of wavelength separation, information on two types of signal intensities can be obtained simultaneously in one inspection by making the inspection illumination lights 12 and 13 different in wavelength. Since the light scattered from the defect varies in signal intensity depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with higher accuracy using the signal intensity ratio of the two sensors 205 and 207 as a feature amount.

(Seventh embodiment)
A seventh embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The object of the present embodiment is to realize a system characterized by simultaneous detection with two elevation angles. For this purpose, it is desirable to arrange two planar reflecting mirrors 501 having different angles β1 and β2 between the detection lens 201 and the substrate to be inspected 1 simultaneously in the optical path from the detection region 4 or 5 to the detection lens 201, respectively. . In this embodiment, the beam spot 3 by the inspection illumination light 12 is formed on the detection region 4 of the image sensor offset from the optical axis of the detection lens 201 and parallel to the Y axis. The light obtained from the detection region 4 of the image sensor is reflected by the reflecting surface 506 of the plane reflecting mirror 501 inclined so that the detection elevation angle is β1, and is incident on the detection lens 201. The light that is reflected by the plane reflecting mirror 501 and whose pattern noise is cut by the spatial filter 202 installed on the Fourier transform plane of the detection lens 201 is imaged on the image sensor 205 by the imaging lens 203 and the zoom lens group 204 at a predetermined magnification. . The observation optical system 206 can observe the detection region 4 or the surface of the spatial filter 202. On the other hand, the beam spot 3 by the inspection illumination light 13 is formed on the detection region 5 of the image sensor that is offset from the optical axis of the detection lens 201 and parallel to the Y axis. The light obtained from the detection area 5 of the image sensor is reflected by the reflecting surface 506 of the plane reflecting mirror 501 which is a mirror tilted so that the detection elevation angle becomes β2, and enters the detection lens 201. An optical path branching plane reflecting mirror 208 is inserted between the detection optical system 200 and the image sensor, so that the optical path of the light from the detection region 5 is branched to form an image on the image sensor 207.

  According to the above configuration, light obtained at different angles from the detection regions 4 and 5 passes through different positions of the detection optical system 200, so that it can be imaged on the two image sensors 205 and 207, and is obtained from defects. Can be obliquely inspected at two elevations at the same time in one inspection, so by combining the upper inspection and the oblique inspection of the present embodiment, for example, high NA detection of NA 0.9 or more is possible, Most of the light scattered from the defect can be taken in, and the detection type and the number of detection of the defect can be increased. Further, by making the inspection illumination lights 12 and 13 different in wavelength and polarization as in the fourth embodiment described above, information of different signal intensities can be obtained from the two image sensors 205 and 207 in one inspection. . Since the light intensity scattered from the defect varies in signal intensity depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with high accuracy using the signal intensity ratio of the two image sensors 205 and 207 as a feature amount.

(Eighth embodiment)
The eighth embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The object of the present embodiment is to install two mechanisms opposite to each other so that the detection area is shifted in a direction perpendicular to the pixel direction (longitudinal direction) of the image sensor (in this example, the X-axis direction), and the oblique inspection can be performed once. It is to realize that two types of oblique inspection can be performed simultaneously in the inspection. That is, two planar reflecting mirrors 501 that face each other and have different angles (or may have the same angle) are arranged between the detection lens 201 and the substrate 1 to be inspected, and each inspection illumination is applied to each of the image sensor detection regions 4 and 5. It is desirable to irradiate the lights 12 and 13. Since the optical paths of the scattered light by the inspection illumination lights 12 and 13 bent by the two plane reflecting mirrors 501 are different optical paths in the detection optical system 200, they can be imaged on the image sensors 205 and 207, respectively. Is possible. A beam spot 3 by the inspection illumination light 13 is formed on the detection region 4 of the image sensor offset from the optical axis of the detection lens 201 and parallel to the Y axis. The light obtained from the detection region 4 of the image sensor is reflected by the reflecting surface 506 of the plane reflecting mirror 501 that is a mirror inclined so that the detection elevation angle becomes β1, and is incident on the detecting lens 201. On the other hand, the beam spot 3 with the illumination azimuth 12 is formed on the detection region 5 of the image sensor that is offset from the optical axis of the detection lens 201 and parallel to the Y axis. The light obtained from the detection area 5 of the image sensor is reflected by the reflecting surface 506 of the plane reflecting mirror 501 which is a mirror tilted so that the detection elevation angle becomes β2, and enters the detection lens 201. The light from each plane reflecting mirror 501 that has passed through the detection optical system 200 is branched by an optical path branching plane reflecting mirror 208 inserted between the detection optical system 200 and the image sensor. Imaged.

  In addition, it is possible to perform an upward inspection in which the image sensor 205 forms an image by inserting and removing the plane reflecting mirror 501 with the switching mechanism 502 (see FIG. 6) or the like. The light from which the pattern noise has been cut by the spatial filter 202 installed on the Fourier transform surface of the detection lens 201 is imaged on the image sensor 205 by the imaging lens 203 and the zoom lens group 204 at a predetermined magnification. The observation optical system 206 can observe the detection region or the surface of the spatial filter 202.

  Also in this example, by making the inspection illumination lights 12 and 13 different in wavelength and polarization as in the above-described fourth embodiment, information of different signal intensities can be obtained simultaneously from two image sensors 207 in one inspection. can get. Since the signal intensity of light scattered from the defect varies depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with high accuracy using the signal intensity ratio of the two image sensors 207 as a feature amount.

(Ninth embodiment)
A ninth embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The purpose of this embodiment is to arrange two types of mechanisms capable of performing oblique inspection, two types of oblique inspection using the two types of oblique inspection image sensors and upper inspection using the upper inspection image sensor. It is to realize a method that enables one inspection to be executed by one inspection.

  For this purpose, two planar reflecting mirrors 501 facing each other and having different angles (or the same) may be disposed between the detection lens 201 and the substrate 1 to be inspected, and the inspection illumination lights 12 and 13 are provided in the image sensor detection region 6. By irradiating, it is desirable to form the beam spot 3 on the detection region 6 of the image sensor located at a position parallel to the Y axis on the optical axis of the detection lens 201. Since the optical path of the scattered light by the inspection illumination lights 12 and 13 bent by the two plane reflecting mirrors 501 is another optical path of the detection optical system 200, the scattered light by the inspection illumination lights 12 and 13 correspond to each other. It is possible to form an image on the image sensor 207 for oblique inspection and the image sensor 205 for upward inspection. As a result, three inspection optical paths can be realized, so that two oblique inspections and upward inspection can be performed simultaneously.

  In the first optical path, the light obtained from the detection region 6 of the image sensor is reflected by the reflecting surface 506 of the plane reflecting mirror 501 that is a mirror tilted so that the detection elevation angle is β1, and is incident on the detecting lens 201. The The light from which the pattern noise has been cut by the spatial filter 202 installed on the Fourier transform plane of the detection lens 201 is imaged on the image sensor 205 by the imaging lens 203 and the zoom lens group 204 at a predetermined magnification. The observation optical system 206 can observe the detection region 6 or the surface of the spatial filter 202. In the second optical path, the light obtained from the detection area 6 of the image sensor is reflected by the reflecting surface 506 of the plane reflecting mirror 501 that is a mirror tilted so that the detection elevation angle is β2, and is incident on the detecting lens 201. The In the third optical path, light from the detection region 6 of the image sensor is directly incident on the detection lens 201. The first optical path and the second optical path that have passed through the detection optical system 200 are imaged on different image sensors 207 by another optical path branching plane reflecting mirror 208 inserted between the detection optical system 200 and the image sensor. The The third optical path is directly imaged on the image sensor 205 via the detection optical system 200. Further, by installing lens type optical path length correction elements 504 and 505 between the detection lens 201 and the respective plane reflecting mirrors 501, the object point planes of the three detection optical paths can be focused, and the magnification in the Y direction can be adjusted. Is also possible. On the other hand, different signals from the image sensor 205 and the two image sensors 207 in one inspection by making the inspection illumination light 12 and the inspection illumination light 13 different in wavelength and polarization as in the fourth embodiment described above. Strength information can be obtained. Since the signal intensity of light scattered from the defect varies depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with high accuracy using the signal intensity ratio of the three sensors as a feature quantity.

(10th Embodiment)
A tenth embodiment of the oblique inspection according to the present invention will be described with reference to FIG. The present embodiment is an example in which an oblique inspection is performed with a prism-type plane reflecting mirror as compared with the ninth embodiment. That is, the inspection illumination lights 12 and 13 are illuminated on the detection region 6 of the image sensor located at a position parallel to the Y axis on the optical axis of the detection lens 201 to form the beam spot 3. In the first optical path, the light irradiated from the inspection illumination light 13 and obtained from the detection area 6 of the image sensor is reflected on the reflecting surface of the prism type optical path length correction element 503 inclined so that the detection elevation angle is β1. The light is reflected and enters the detection lens 201. In the second optical path, the light irradiated from the inspection illumination light 12 and obtained from the detection region 6 of the image sensor is reflected by the opposite optical path length correction element 503 of the prism type inclined so that the detection elevation angle becomes β2. The light is reflected by the surface and enters the detection lens 201. In the third optical path, light from the image sensor detection region 6 is directly incident on the detection lens 201. By installing the optical path length correcting element 503 between the detection lens 201 and the substrate 1 to be inspected, the object planes of the three detection optical paths can be focused, and the magnification in the Y-axis direction can also be adjusted. The first and second optical paths that have passed through the detection optical system 200 are respectively imaged on the corresponding image sensors 207 by different optical path branching plane reflecting mirrors 208 inserted between the detection optical system 200 and the image sensors. . The third optical path is directly imaged on the image sensor 205 via the detection optical system 200. The light from which the pattern noise has been cut by the spatial filter 202 installed on the Fourier transform surface of the detection lens 201 is imaged on the image sensor 205 by the imaging lens 203 and the zoom lens group 204 at a predetermined magnification. Further, the observation optical system 206 can observe the detection region 6 or the surface of the spatial filter 202.

  According to the above configuration, the inspection illumination lights 12 and 13 are different in wavelength and polarization as in the fourth embodiment, so that they differ from the image sensor 205 and the two image sensors 207 at the same time in one inspection. Signal strength information is obtained. Since the light scattered from the defect varies in signal intensity depending on the wavelength, polarization, or detection elevation angle, the defect classification information can be extracted with high accuracy using the signal intensity ratio of the three image sensors 205 and 207 as a feature amount.

  Here, the patterns and defects formed on the inspected substrate 1 to be detected by the defect inspection apparatus according to each of the above embodiments will be described in detail with reference to FIG.

  The direction of the pattern formed on the inspected substrate 1 is mainly the X and Y directions orthogonal to each other. FIG. 16 shows a pattern 553 on a straight line formed in the Y direction and a pattern 551 formed in the X direction. In general, a pattern is formed through an exposure / development / etching process. For example, a short defect caused by a process condition variation due to a focus shift at the time of exposure may be the shortest distance between wirings. . For example, a short defect of the Y direction pattern 553 is shown as a defect 554 interposed between wirings adjacent in the X direction, and a short defect of the X direction pattern 551 is shown as a defect 552 interposed between wirings adjacent in the Y direction. When oblique illumination is performed using the YZ plane as an incident surface to inspect such defects 552 and 554, the oblique illumination is parallel illumination for the pattern 553 and orthogonal illumination for the pattern 551. In this case, the defect 554 formed in the pattern 553 parallel to the illumination light 549 can secure a scattering cross section, but the defect 552 formed in the pattern 551 orthogonal to the illumination becomes a shadow of the pattern 551 and the defect 552. The amount of illumination light that hits is reduced. For this reason, the amount of scattered light from the defect 552 becomes small, and it becomes difficult to detect the defect 552. On the other hand, when the incident surface is tilted with respect to the YZ plane, the ratio that the defect 552 is shaded by the pattern 551 as viewed from the illumination direction decreases, and the amount of illumination light that hits the defect 552 increases. As a result, the amount of scattered light from the defect 552 increases, so that the defect 552 is easily detected. When the incident surface is inclined with respect to the YZ plane and the XZ plane, the illumination light 549 generates scattered light 556 from the X direction pattern 551, scattered light 570 from the defect 552 or 554, and scattered light 557 from the Y direction pattern 553. appear. The scattered light 556, 557, and 570 all indicate regular reflection light.

  In this way, it is possible to easily detect short-circuit defects between wires by tilting the illumination direction with respect to the X axis and the Y axis. However, depending on the illumination elevation angle, for example, a convex defect such as a foreign object or a scratch The shape of a defect that is easy to detect, such as a concave defect, changes. Therefore, not only the illumination direction but also the illumination elevation angle (or detection elevation angle) can be adjusted so that the condition for maximizing the inspection S / N can be selected in accordance with the pattern shape of the substrate to be inspected and the defect shape for inspection purposes. It is desirable to do.

  FIG. 17 shows the relationship between the direction in which scattered light is detected by the detection optical system 200 and the illumination direction. When a hemisphere centered at the center of the beam spot of the illumination light 549 (the origin) is virtually assumed on the inspected substrate 1, in FIG. 17, a plan view (XY plane) of the virtual hemisphere 550 is viewed from the Y-axis direction. The side view (XZ plane) and the side view seen from the direction orthogonal to the illumination azimuth | direction of the illumination light 549 are shown. Scattered light (specularly reflected light) 556, 557, and 570 (see FIG. 16) from the defect and the pattern spread in a hemispherical shape, and enter the regions 556A, 557A, and 570A on the virtual hemisphere 550 as shown in FIG. . Reference numeral 569 in the figure is a projection of the aperture of the upper detection system onto the virtual hemisphere 550. The illumination direction (incident surface) of the illumination light 549 is inclined by an angle γ with respect to the YZ plane, and the regular reflection light from the horizontal flat portion on the substrate 1 to be inspected is a virtual hemisphere as shown in FIG. The light enters the region 555A having a line (Z axis) drawn from the apex of 550 to the origin as the axis of symmetry. The regions 556A and 557A where the scattered lights 556 and 557 from the pattern are incident are shifted according to the angle γ and the elevation angle α of the inspection irradiation light 549.

  Assuming that normal patterns are mixed on the inspected substrate 1 in the X-axis direction and the Y-axis direction, the regular reflection light 556 from the X-direction pattern 551 as shown in FIG. It mainly gathers in a region 556A including the incident region 555A. This region 556A extends in the Y-axis direction. Further, the specularly reflected light 557 from the Y direction pattern 553 gathers in the region 557A including the specularly reflected light 555A of the flat portion. This region 557A extends in the X-axis direction. On the other hand, the specularly reflected light 570 from the defect having a shape different from that of the pattern enters the region 570A different from the specularly reflected lights 556 and 557 from the pattern. This region 570A overlaps part or all of the regions 556A and 557A depending on the angle γ of the illumination light 549 in addition to the region 555A. FIG. 17 exemplarily illustrates a case where the intensity of forward scattered light of the regular reflection light 570 from the defect is strong.

  In this defect inspection apparatus, in order to detect only the scattered light 570 from the defect, the scattered light incident on the region 570A that does not overlap with the regions 556A and 557A where the scattered light 556 and 557 from the normal pattern can enter. The detection optical system 200 and the plane reflecting mirror 501 are arranged so that 570 can be supplemented as much as possible. For example, as shown in FIG. 17, the detection optical system is arranged so that the opening 558 projected onto the virtual hemisphere 550 does not cover the regions 556A and 557A but overlaps only the region 570A. Since the overlapping area of the opening 558 with respect to only the region 570A changes depending on the angle γ of the inspection illumination light 549 and the way of setting the opening 558 of the detection optical system, the angle γ is set so that the overlapping area of the opening 558 with respect to only the region 570A is as large as possible. Further, it is desirable to set the arrangement and size of the openings 558.

  The NA (numerical aperture) in the elevation direction (XZ plane) of the optical axis of the detection optical system is limited to a range in which the scattered light 556 and 557 from the pattern can be prevented from entering. Therefore, in order to increase the amount of scattered light to be captured, it is effective to expand the aperture 558 in the azimuth angle direction with respect to the optical axis of the detection optical system to efficiently capture only the scattered light 570 from the defect.

  Conventionally, it has been difficult to increase the NA of a detection optical system having a low elevation angle. In each embodiment of the present invention, the aperture 558 of the optical axis of the detection optical system is limited to the elevation direction, so that the azimuth direction of the optical axis of the detection optical system is equivalent to the NA of the detection lens, that is, the entire aperture (for example, NA 0. 6, NA 0.8, etc.). In the case where the optical axis is bent by a plane reflecting mirror as in each of the embodiments described above, the opening 558 can be expanded in the pixel direction of the image sensor up to the NA of the detection lens 201. Thereby, it is possible to suppress the supplement of the scattered light from the normal pattern while increasing the scattered light from the defect captured by the detection optical system, and to improve the inspection S / N.

  It should be noted that setting the aperture so that the value taken in the elevation direction of the optical axis of the detection optical system and the value taken in the horizontal direction of the detection optical system is not necessarily limited to the method using a mirror, and is separately detected. The structure which provides a lens may be sufficient. The following eleventh embodiment shows such a configuration example.

(Eleventh embodiment)
FIG. 20 is a conceptual diagram of an eleventh embodiment of oblique inspection according to the present invention. That is, in this embodiment, in addition to the above-described detection optical system 200, a low elevation angle detection optical system 573 for oblique inspection is disposed. The configuration of the low elevation angle detection optical system 573 is substantially the same as that of the detection optical system 200. However, the detection lens (objective lens) 572 of the low elevation angle detection optical system 573 is spatially limited by the substrate 1 to be inspected at the lower part and the detection optical system 200 at the upper part. The top and bottom of the lens 572 are cut so that the opening is limited in the elevation angle direction of the optical axis. It can also be configured in this way.

(Twelfth embodiment)
FIG. 18 is a conceptual diagram of the twelfth embodiment of the oblique inspection according to the present invention. This embodiment shows an optimal layout of an illumination optical system with respect to a detection optical system for oblique inspection. In this embodiment, an illumination optical system is provided with an illumination mirror 563 that reflects and folds the illuminated illumination light. As shown in the plan view of FIG. 18, when viewed from above, the illumination optical system emits the illumination light. The illumination light 549 is bent by the illumination mirror 563 to form the beam spot 3 on the substrate 1 to be inspected from the direction inclined by the angle γ with respect to the Y axis. For example, as in the first embodiment, the detection optical system 200 arranges the plane reflecting mirror 501 and the detection lens 201 on the X axis to supplement the scattered light from the defect. When viewed from the side (Y-axis direction), the illumination light 549 is bent by the illumination mirror 563 and illuminates the substrate 1 to be inspected with an illumination elevation angle α that forms an angle of about 90 ° with the detection elevation angle β of the detection optical system 200. .

  According to this configuration, the angle formed by the surface including the optical axis of the illumination light beam and the longitudinal axis (Y axis) of the beam spot 3 and the optical axis of the scattered light beam incident on the detection optical system 200 is approximately 90 °. By disposing the illumination mirror 563, the focus deviation does not occur even if the height of the substrate 1 to be inspected fluctuates. That is, the plane including the optical axis of the illumination light beam and the longitudinal axis of the beam spot 3 is the focal plane 560 of the detection optical system 200, and the optical axis of the illumination light 549 reflected by the illumination mirror 563 is on the focal plane 560. Therefore, when the height of the test substrate 1 changes, the position of the beam spot 3 by the illumination light 549 on the test substrate 1 moves along the focal plane 560. Since the beam spot 3 is always on the focal plane 560 as described above, if the detection optical system 200 is focused on the beam spot 3, the focus of the detection optical system 200 is illuminated regardless of the height of the substrate 1 to be inspected. The state of being matched with the beam spot 3 by the light 549 is maintained.

  The illumination of other elevation angles, for example, the illumination 571 from the YZ plane, is formed along the line of intersection between the YZ plane and the substrate 1 to be inspected, and moves along the YZ plane along with the substrate 1 to be inspected. For this reason, the beam spot of the illumination light 571 may deviate from the depth of focus 564 of the detection optical system 200. For example, when the substrate 1 to be inspected is lowered to the height 568, the beam spot of the illumination light 571 deviates from the focal depth 564, and a focus shift amount 565 is generated with respect to the scattered light by the illumination light 571. In the example of FIG. 17, when the inspected substrate 1 falls below the height 567, the beam spot by the illumination light 571 deviates from the depth of focus 564.

  An appropriate range of the illumination direction γ in the twelfth embodiment will be described with reference to FIG.

In the above-mentioned side view, the angle formed by the surface including the optical axis of the illumination light beam and the longitudinal axis of the beam spot 3 and the optical axis of the detection optical system is approximately 90 °, so the illumination direction γ is the longitudinal axis of the illumination light beam and the beam spot 3. From the elevation angle α of the surface including the axis and the detection optical system low elevation angle β,
sinγ = tan α · tan β (Expression 1)
Can be converted.

  A profile 561 shown in FIG. 19 is a scattered light amount distribution captured by the oblique detection optical system with respect to the detected elevation angle β. This scattered light amount distribution is obtained by converting the detected elevation angle β into the illumination direction γ according to the above (Equation 1). On the other hand, the profile 562 is a distribution of the amount of scattered light from the pattern captured by the oblique detection optical system with respect to the illumination direction γ. In addition, the detection elevation angle β needs to be set in a range of approximately γ> 10 ° when converted to the illumination direction γ due to mounting restrictions. Further, in order to avoid the influence of pattern scattered light, FIG. Based on the profiles 561 and 562, the range is generally limited to γ <25 °. Therefore, in this embodiment, it is preferable to determine the illumination azimuth γ around 17.5 ° which is the central value of 10 to 25 °.

  Although the embodiment of the present invention has been described above, the present invention can be further modified within the scope of its technical idea.

It is a figure which shows the example of the structure of the defect inspection apparatus by this invention. It is a figure which shows the to-be-inspected board | substrate with which the LSI which is a test object sample was arranged. It is a figure for demonstrating the three illumination lights for inspection produced | generated by the illumination optical system of the defect inspection apparatus by this invention. It is a figure which shows the optical system containing the illumination lens of the illumination optical system of the defect inspection apparatus by this invention. It is a figure which shows the function of the illumination lens of the illumination optical system of the defect inspection apparatus by this invention. It is a figure for demonstrating 1st Embodiment which concerns on this invention. It is a conceptual diagram of 2nd Embodiment which concerns on this invention. It is a conceptual diagram of 3rd Embodiment which concerns on this invention. It is a conceptual diagram of 4th Embodiment which concerns on this invention. It is a conceptual diagram of 5th Embodiment which concerns on this invention. It is a conceptual diagram of 6th Embodiment which concerns on this invention. It is a conceptual diagram of 7th Embodiment which concerns on this invention. It is a conceptual diagram of 8th Embodiment which concerns on this invention. It is a conceptual diagram of 9th Embodiment which concerns on this invention. It is a conceptual diagram of 10th Embodiment which concerns on this invention. It is a model figure showing the scattering direction of a pattern, a defect, and scattered light. It is the figure which showed the relationship between the azimuth | direction which detects scattered light with a detection optical system, and an illumination azimuth | direction. It is a conceptual diagram of 12th Embodiment of the oblique inspection which concerns on this invention. It is explanatory drawing of the appropriate range of the illumination azimuth in 12th Embodiment. It is a conceptual diagram of 11th Embodiment of the oblique inspection which concerns on this invention.

Explanation of symbols

1 Inspected substrate (wafer)
1a, 1b Inspected board 1aa Memory LSI chip 1ab Memory cell area chip 1ac Peripheral circuit area 1ad Other area 1ba LSI such as microcomputer
1bb register group area 1bc memory area 1bd CPU core area 1be input / output area 3 beam spot (illumination area)
4, 5, 6 Image sensor detection regions 11-13 Inspection illumination light 100 Illumination optical system 110 First beam spot imaging unit 120 Second beam spot imaging unit 130 Third beam spot imaging unit 200 Detection Optical system 201 Detection lens (objective lens)
202 Spatial filter 203 Imaging lens 204 Zoom lens group 205, 207 Image sensor 206 Observation optical system 208 Optical path branching plane reflecting mirror 209 Polarizing beam splitter 210 Branching detection optical system 300 Stage unit 301 to 304 XYZθ stage 305 Stage controller 400 Control system 401 Control CPU section 402 Signal processing section 403 Display section 404 Input section 501 Planar reflecting mirror 502 Switching mechanism 503, 504, 505 Optical path length correction element 506 Reflecting surface 548 Detection optical system 549 Illumination 550 Scattered light hemispherical distribution 551 X direction pattern 552 X-direction pattern defect 553 Y-direction pattern 554 Y-direction pattern defect 555 Point 556 where specularly reflected light intersects 550 Scatter distribution 557 from X-direction pattern 557 Scatter distribution 558 from Y-direction pattern High NA Scattered light intensity distribution of the outgoing type defects example that is trapped in the focal plane 561 detecting optical system of the opening 560 Detection system (converting the detection optics low elevation angle β to phi)
562 Pattern scattered light distribution 563 captured by the detection optical system 563 Illumination mirror 564 Depth of focus 565 of the detection optical system Defocus amount 566 Illumination direction (φ3)
567 Height of substrate to be inspected at depth limit 568 Height of substrate to be inspected when exceeding depth of focus limit 569 Upper detection system opening 570 Scattered light distribution 571 from defect Other elevation angle illumination 572 Open in two directions Lenses 573 with different numbers Low elevation angle detection optical system

Claims (21)

A defect inspection method for illuminating a substrate to be inspected, forming an image of light obtained from the illumination area, converting the formed image into signal intensity, and inspecting the substrate to be inspected with light,
A defect inspection method, wherein light is transmitted through an optical element between a substrate to be inspected and an image.   2. The defect inspection method according to claim 1, wherein the optical element is a reflecting mirror. A defect inspection method for detecting a defect of a substrate to be inspected by light,
An illumination system that irradiates the surface of the substrate to be inspected in a slit shape, a detection lens that captures light obtained from the illumination area and forms an image on the image sensor, one or more image sensors that convert the image into signal intensity, and the detection Using a defect inspection apparatus composed of a reflecting mirror disposed between a lens and a substrate to be inspected, light obtained from an illumination area is reflected by the reflecting mirror and incident on the detection lens, and imaged on the image sensor A defect inspection method characterized by oblique inspection.   4. The defect inspection method according to claim 3, wherein the illumination angle and direction, and the position and angle of the reflecting mirror are set so that zero-order reflected light is reflected by the reflecting mirror and does not enter the detection lens. Defect inspection method. A stage mounted with a substrate to be inspected and movable relative to the optical system;
An illumination system for illuminating the inspection area on the substrate to be inspected;
A detection optical system for detecting light from the inspection region of the substrate to be inspected;
An image sensor for converting an image formed by the detection optical system into a signal;
A signal processing system for processing the signals of the image sensor and detecting defects;
A defect inspection apparatus comprising: an optical element disposed between the detection optical system and a substrate to be inspected and transmitting light from the substrate to be inspected to the detection optical system.   6. The defect inspection apparatus according to claim 5, wherein the optical element is a reflecting mirror.   7. The defect inspection apparatus according to claim 6, wherein the reflecting surface of the reflecting mirror is arranged in parallel to the pixel direction of the image sensor and inclined with respect to the optical axis of the detection lens.   6. The defect inspection apparatus according to claim 5, wherein the reflecting mirror is a mechanism that can be taken in and out of the optical path by a switching mechanism, and the detection optical system for oblique inspection in which the reflecting mirror is put in the optical path or the reflecting mirror is in the optical path. A defect inspection apparatus characterized in that a detection optical system for an upper inspection in a state not in the above is created, and an oblique inspection and an upper inspection can be selected.   9. The defect inspection apparatus according to claim 8, comprising a plurality of the reflecting mirrors having different reflection surface angles.   6. The defect inspection apparatus according to claim 5, wherein an optical path length correction element is disposed between the reflecting mirror and the detection lens, and the optical path length from the inspection region on the inspection substrate to the detection lens is set by the optical path length correction element. A defect inspection apparatus characterized in that the stage height during oblique inspection can be inspected at or near the same as that during upward inspection.   6. The defect inspection apparatus according to claim 5, wherein an optical path length correction element having an imaging aberration correction function is disposed between the reflecting mirror and the detection lens.   6. The defect inspection apparatus according to claim 5, wherein an optical path branching reflector for branching light from the reflecting mirror emitted from the detection optical system, and an oblique light for converting the light branched by the optical path branching reflector into a signal. A defect inspection apparatus, further comprising an image sensor for side inspection.   13. The defect inspection apparatus according to claim 12, wherein the optical path branching reflecting mirror is disposed outside the optical path for upward inspection.   13. The defect inspection apparatus according to claim 12, wherein the detection area is set to be shifted in a direction perpendicular to the pixel direction of the image sensor with respect to the optical axis of the detection optical system.   15. The defect inspection apparatus according to claim 14, wherein the illumination direction, elevation angle, polarization, and wavelength can be selected as illumination conditions.   16. The defect inspection apparatus according to claim 15, wherein when polarized light is selected as an illumination condition, a beam splitter is disposed between the detection optical system and the image sensor, and light passing through the detection optical system differs depending on the beam splitter. A defect inspection apparatus characterized by separating light components into polarized light components and forming images on different image sensors.   15. The defect inspection apparatus according to claim 14, wherein two reflecting mirrors each having a detection area shifted in a direction perpendicular to a pixel direction of the image sensor are disposed opposite to each other.   18. The defect inspection apparatus according to claim 17, wherein the light from the two reflecting mirrors is formed on different oblique inspection image sensors, and at the same time, the light directly incident on the detection optical system from the inspection substrate is inspected upward. A defect inspection apparatus characterized in that an image is formed on an image sensor.   6. The defect inspection apparatus according to claim 5, wherein an angle formed by a surface including the optical axis of the illumination light beam and a longitudinal axis of the beam spot and an optical axis of light incident on the optical element from the beam spot is set to about 90 °. Defect inspection equipment.   20. The defect inspection apparatus according to claim 19, wherein an illumination direction is set from a scattered light amount distribution captured by the detection optical system and a pattern scattered light amount distribution captured by the detection optical system.   6. The defect inspection apparatus according to claim 5, wherein the numerical aperture in the azimuth direction with respect to the optical axis of the detection optical system is set equal to the numerical aperture of the detection optical system.

Images