Irradiation optical system and defect inspection device provided therewith

Abstract

In order to achieve the high-aspect ratio of a beam spot while keeping the cost of an illumination optical system low, and avoid damage and deterioration of each optical element constituting the illumination optical system, the present disclosure proposes an illumination optical system comprising: a light source; a beam expander that adjusts the diameter of a light beam emitted from the light source and outputs the light beam with an expanded diameter; and a light condensing optical system that forms a beam spot where an object to be irradiated is irradiated with the light beam with an expanded diameter. The light condensing optical system includes at least one first light condensing optical element that condenses, only in the longitudinal direction of the beam spot, the light beam with an expanded diameter, and a second light condensing optical element that condenses, at least in the lateral direction of the beam spot, the light beam with an expanded diameter (See Fig. 14).

Description

Irradiation optical system and defect inspection apparatus equipped with the same

[0001] The present disclosure relates to an illumination optical system and a defect inspection apparatus including the same.

[0002] In manufacturing lines for semiconductor substrates, thin film substrates, and the like, inspections for defects present on the surfaces of semiconductor substrates, thin film substrates, and the like are carried out in order to maintain and improve product yields. A so-called inspection device is used for defect inspection. For example, Patent Document 1 discloses the configuration of a conventional inspection device.

[0003] Patent No. 5945126

[0004] Here, a conventional illumination optical system, as typified by Patent Document 1, will be described with reference to FIG.

[0005] 1, light emitted from a laser light source 101 has its intensity adjusted by an attenuator 102 and is reflected by a mirror 103. The light whose intensity has been adjusted is shaped to a desired beam ellipticity by an anamorphic prism 104 consisting of four prisms. The elliptical beam is then reflected by a mirror 105 which irradiates an inspection object 107 at a desired elevation angle. Furthermore, the beam reflected by the mirror 105 is condensed by a rotationally symmetric condenser lens 106 and irradiates the inspection object 107.

[0006] The beam shape emitted from the laser light source 101 is approximately circular. Assume that the incident plane of the emitted beam is parallel to the longitudinal direction of the beam spot, and that the direction of action of the anamorphic prism 104 is parallel to the longitudinal direction of the beam spot. In this case, if the magnification of the anamorphic prism 104 is M and the elevation angle of the light beam relative to the object to be inspected is θ, the ratio of the lateral diameter to the longitudinal diameter of the linearly focused beam spot is expressed as 1 / (M sin θ). Thus, in the prior art, a linearly focused beam spot can be formed on the object to be inspected 107 by changing the ellipticity of the beam diameter incident on the condenser lens 106.

[0007] Meanwhile, recent technological innovations have led to smaller and smaller sizes of defects and foreign particles to be detected. To achieve higher inspection performance, an illumination optical system is required that can obtain a larger amount of scattered light from the inspection object 107. The amount of scattered light S from the inspection object 107 is described by the Rayleigh scattering equation shown in equation (1).

[0008] [Number 1]

[0009] In order to accurately detect defects on an inspection target, the illumination system installed in the inspection equipment must have the performance to obtain "(i) a shorter wavelength" and "(ii) a higher irradiation density." Furthermore, in order to shorten the total inspection time by expanding the inspection area and reducing the inspection time per wafer, the beam spot of the illumination system must have "(iii) a long irradiation area." For these reasons, it is desirable for the illumination beam spot irradiated on the wafer to be linear. Recent inspection equipment is required to perform defect inspection using a beam spot with an aspect ratio of 100:1 or more.

[0010] To achieve such a high aspect ratio beam spot using the technology disclosed in Patent Document 1, an elliptical beam is made incident on the condenser lens 106. In this case, to obtain a beam spot that is long in one axial direction, the minor axis direction of the elliptical beam incident on the condenser lens 106 is shortened. If an attempt is made to form a spot that is 1 mm in the longitudinal direction under the conditions shown in Figure 2, the diameter of the incident beam needs to be reduced to a width of about 50 μm.

[0011] However, if the incident beam diameter is made that small, the irradiation density of the beam incident on the optical element becomes too high, which can lead to damage and deterioration of the glass material and coating of the optical element. To avoid this, it is necessary to take measures such as: increasing the diameter of the condenser lens 106 and expanding the beam incident on the condenser lens (Measure 1); changing the condenser lens 106 to a highly durable glass material (Measure 2); or eliminating the coating on the condenser lens 106 (Measure 3).

[0012] Adopting Measure 1 would lead to an increase in the size of the device and the amount of material used. This would increase the amount of processing work, which would lead to higher costs. Measure 2 also leads to higher costs because highly durable glass materials have high added value. Furthermore, due to low production volumes, there is a risk of an unstable supply. According to Measure 3, eliminating the coating itself would lead to cost reductions, but doing so would reduce the amount of light that can reach the target, resulting in lower device performance. Furthermore, even if the coating were eliminated, there would still be a risk of damage to the glass material that makes up the condenser lens 106.

[0013] In view of this situation, the present disclosure proposes a technology that achieves a high aspect ratio while keeping costs low and that makes it possible to avoid damage and deterioration of each optical element that makes up the illumination optical system in an inspection device.

[0014] In order to solve the above problems, the present disclosure provides a light source and a focusing optical system that forms a beam spot by which a light beam emitted from the light source is irradiated onto an irradiation object, the focusing optical system including at least one first focusing optical element that focuses the light beam only in a first direction perpendicular to the irradiation direction of the light beam, and a second focusing optical element that focuses the light beam at least in a second direction perpendicular to the first direction, wherein a focal length of the focusing optical system in the first direction in which the first focusing optical element performs a focusing action is defined as fb, and a focal length of the focusing optical system in the first direction is defined as When the numerical aperture is NAb, the distance from the rear principal point position of the focusing optical system in a first direction to the object to be illuminated is Lb, the focal length of the focusing optical system in a second direction perpendicular to the first direction in which the first focusing optical element performs the focusing function is fa, the numerical aperture of the focusing optical system in the second direction is NAa, and the distance from the rear principal point position of the focusing optical system in the second direction to the object to be illuminated is La, we propose an illumination optical system that satisfies |fa|<|fb| and NAa>NAb, and where La is approximately equal to |fa| and |fb|≠Lb.

[0015] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0016] According to the technology of the present disclosure, it is possible to achieve a high aspect ratio of the irradiation beam spot while keeping the cost of the illumination optical system low, and to avoid damage and deterioration of each optical element that makes up the illumination optical system.

[0017] 1 is a diagram showing an example of the configuration of an illumination optical system according to the prior art; FIG. 2 is a diagram showing a list of optical conditions according to the prior art; FIG. 3 is a diagram showing an example of the schematic configuration of a defect inspection apparatus 10 according to the present embodiment; FIG. 4 is a schematic diagram showing a cross section of the incident plane (a plane including the illumination optical axis and the sample surface normal) of oblique incidence illumination (a configuration in which illumination light is obliquely irradiated onto the sample W via the illumination intensity distribution control unit 7 in FIG. 3); FIG. 5 is a schematic diagram showing a cross section of a plane including the sample surface normal and perpendicular to the incident plane of oblique incidence illumination for perpendicular illumination (a configuration in which illumination light is perpendicularly irradiated onto the sample W via the illumination intensity distribution control unit 7v in FIG. 3); FIG. 6 is a schematic diagram showing a cross section of the incident plane of oblique incidence illumination when optical elements constituting the illumination intensity distribution control unit 7 are installed tilted with respect to the optical axis; FIG. 7 is a schematic diagram showing a cross section of a plane including the sample surface normal and perpendicular to the incident plane of oblique incidence illumination when an illumination intensity distribution represented by a Gaussian distribution is realized by oblique incidence illumination; FIG. 8 is a schematic diagram showing a cross section of a plane including the sample surface normal and perpendicular to the incident plane of oblique incidence illumination when a uniform illumination intensity distribution is realized by perpendicular illumination. 1 is a diagram showing an example of optical elements constituting the illumination intensity distribution control unit 7 and the like. FIG. 1 is a diagram showing an illuminance distribution shape (illumination spot 20) formed on the sample surface by the illumination unit 401. FIG. 2 is a diagram for explaining a method of scanning the sample with the illumination spot 20 by the illumination unit 401. FIG. 3 is a diagram showing an example of the arrangement of the entire detection unit 402 when viewed from directly above. FIG. 4 is a diagram showing an example of the arrangement of the entire detection unit 402 when viewed from the side. FIG. 5 is a diagram showing an example of the configuration of the illumination unit 401 according to Example 1. FIG. 6 is a diagram showing the condenser of the illumination unit 401. FIG. 7 is a diagram showing a list of optical conditions according to this embodiment. FIG. 8 is a diagram showing an example of the configuration of the illumination unit 401 according to Example 2. FIG. 9 is a diagram showing an example of the installation conditions of a two-lens combination in which the focal length of the condensing optical system is −1000 mm. FIG. 10 is a diagram showing an example of the configuration in which a half mirror 2001 is placed between the condenser lens 1505 and the convex cylindrical lens 1802, and an optical system is added that reflects light reflected and returned by the inspection object (irradiation object) 1506, and forms an image on the camera 2003 via the imaging lens 2002. 20 is a table showing the diameter of a spot formed on an inspection object 1506 when the distance between a concave cylindrical lens 1801 and a convex cylindrical lens 1802 having the focal lengths shown in Fig. 19 is changed. Fig. 21 is a diagram showing an example of the configuration of an illumination unit 401 according to a third embodiment.

[0018] This embodiment relates to an illumination optical system that irradiates the surface of an inspection object with light, and a defect inspection device that includes the illumination optical system and detects foreign particles on the inspection object by detecting reflected and scattered light from the inspection object. More specifically, in the illumination optical system, a focusing optical system that forms a beam spot that irradiates the inspection object (irradiation object) with a light beam having an expanded diameter includes at least one first focusing optical element (focusing optical element B) that focuses the expanded diameter light beam only in the longitudinal direction of the beam spot, and a second focusing optical element (focusing optical element A) that focuses the expanded diameter light beam at least in the lateral direction of the beam spot. This makes it possible to achieve a high aspect ratio of the beam spot while keeping the cost of the illumination optical system low and to avoid damage and deterioration of each optical element that constitutes the illumination optical system.

[0019] Hereinafter, embodiments and examples of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the technology of the present disclosure is not limited to the following embodiments and examples, and various modifications are possible. The embodiments and examples described below are described in detail to clearly explain the technology of the present disclosure, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one example with another example. Furthermore, it is possible to add another example to the configuration of one example. Furthermore, it is possible to delete or replace part of the configuration of each example, or to add other configurations.

[0020] 3 is a diagram showing a schematic configuration example of a defect inspection apparatus 10 according to this embodiment. The defect inspection apparatus 10 includes, as its main components, an illumination unit 401, a detection unit 402, photoelectric conversion units 403-1 and 403-2, a stage 404 on which a sample W can be placed and which can be moved in directions perpendicular to the surface (X direction and Z direction) by an actuator, a signal processing device 405, a control device 53, a display device 54, and an input device 55.

[0021] The illumination unit 401 includes a laser light source 2, an attenuator 3, an emitted light adjustment unit 4, a beam expander 5, a polarization control unit 6, an illumination intensity distribution control unit 7, and an illumination intensity distribution control unit 7 v. These components of the illumination unit 401 are connected to a control device 53, and are configured so that their operations are controlled by the control device 53.

[0022] The attenuator 3 adjusts the laser light beam emitted from the laser light source 2 to a desired beam intensity. The emitted light adjustment unit 4 adjusts the laser light beam, whose beam intensity has been adjusted, to a desired beam position and beam propagation direction. The beam expander 5 changes (adjusts) the diameter of the laser light beam, whose beam position and propagation direction have been adjusted, to a desired size. The polarization control unit 6 adjusts the laser light beam, whose beam diameter size has been adjusted, to a desired polarization state. The illumination intensity distribution control unit 7 adjusts the laser light beam, whose polarization state has been adjusted, to a desired intensity distribution. The laser light beam having the desired intensity distribution is illuminated onto an inspection target area of ​​the sample W.

[0023] The incident angle of the illumination light (laser beam) on the sample surface can be determined by adjusting (controlling) the position and angle of the reflecting mirror, a component of the output light adjustment unit 4 arranged in the optical path of the illumination unit 401. The incident angle of the illumination light is set to an angle suitable for detecting minute defects. The larger the illumination incident angle, i.e., the smaller the illumination elevation angle (the angle between the sample surface and the illumination optical axis), the weaker the scattered light from minute irregularities on the sample surface (called haze), which becomes noise compared to the scattered light from minute foreign particles on the sample surface. Therefore, a larger illumination incident angle is more suitable for detecting minute defects. Therefore, if scattered light from minute irregularities on the sample surface interferes with the detection of minute defects, the incident angle of the illumination light is preferably set to 75 degrees or more (elevation angle 15 degrees or less). On the other hand, in oblique incidence illumination, the smaller the illumination incident angle, the greater the absolute amount of scattered light from minute foreign particles. Therefore, if insufficient scattered light from defects hinders the detection of microdefects, the incident angle of the illumination light is preferably set to 60 degrees or more and 75 degrees or less (elevation angle 15 degrees or more and 30 degrees or less). Furthermore, when performing oblique incidence illumination, the polarization control unit 6 of the illumination unit 401 controls the polarization of the illumination light to be P-polarized, thereby increasing the amount of scattered light from defects on the sample surface compared to other polarizations. Furthermore, if scattered light from minute irregularities on the sample surface hinders the detection of microdefects, the polarization of the illumination light to be S-polarized can be reduced compared to other polarizations. The setting of the illumination incident angle (or illumination elevation angle) (setting and adjusting the illumination type (e.g., oblique illumination or vertical illumination)) and whether the illumination light is P-polarized or S-polarized (setting and adjusting the polarization state) can be determined based on the type and condition of the sample, the recipe, etc. Furthermore, the user may adjust the illumination type and polarization state as appropriate during observation (measurement).

[0024] 3, a mirror 21 may be inserted into the optical path of the illumination unit 401, and other mirrors may be placed as needed to change (split) the illumination optical path and configure an illumination optical system that irradiates the sample surface with illumination light from a direction substantially perpendicular to the surface (perpendicular illumination). In this case, the illumination intensity distribution on the sample surface is controlled by the illumination intensity distribution control unit 7v in the same manner as in oblique incidence illumination. Incidentally, by inserting a beam splitter in the same position as the mirror 21, oblique incidence illumination and perpendicular illumination can be performed simultaneously. Perpendicular illumination, which is incident substantially perpendicularly on the sample surface, is suitable for obtaining scattered light from concave defects on the sample surface (polishing scratches or crystal defects in crystalline materials).

[0025] When detecting minute defects near the surface of a sample, the laser light source 2 can be one that emits a short-wavelength (355 nm or less) ultraviolet or vacuum ultraviolet laser beam that has a wavelength that does not easily penetrate the interior of the sample, and has a high output of 2 W or more. In this case, the diameter of the emitted beam will be about 1 mm. On the other hand, when detecting defects inside the sample, one that emits a visible or infrared laser beam with a wavelength that easily penetrates the interior of the sample is used.

[0026] The attenuator 3 can be configured with a first polarizing plate, a half-wave plate rotatable around the optical axis of the illumination light, and a second polarizing plate. The light incident on the attenuator 3 (the laser light beam emitted from the laser light source 2) is converted into linearly polarized light by the first polarizing plate, and the polarization direction is rotated in an arbitrary direction according to the slow axis azimuth angle of the half-wave plate before passing through the second polarizing plate. By controlling the azimuth angle of the half-wave plate, the light intensity of the laser light beam can be adjusted (dimmed) at an arbitrary ratio. However, if the degree of linear polarization of the light incident on the attenuator 3 is sufficiently high, the first polarizing plate is not necessarily required. The attenuator 3 is configured such that the relationship between the input signal and the dimming rate is calibrated in advance. The attenuator 3 can also be configured using an ND filter with a gradation density distribution, or by switching between ND filters with different densities.

[0027] The output light adjustment unit 4 can be configured with multiple reflecting mirrors. While FIG. 3 shows an example in which it is configured with two reflecting mirrors, this is not limiting, and the output light adjustment unit 4 may be configured using three or more reflecting mirrors as appropriate. Here, a three-dimensional Cartesian coordinate system (XYZ coordinates shown in FIG. 3 ) is defined, and it is assumed that light incident on the reflecting mirrors travels in the +X direction. The first reflecting mirror is installed to deflect the incident light in the +Y direction (incidence and reflection in the XY plane). The second reflecting mirror is installed to deflect the light reflected by the first reflecting mirror in the +Z direction (incidence and reflection in the YZ plane). Each reflecting mirror is installed so that the position and propagation direction (angle) of the light emitted from the output light adjustment unit 4 can be adjusted by translation and tilt angle adjustment. In this way, by arranging the incident / reflecting surface (XY plane) of the first reflecting mirror and the incident / reflecting surface (YZ plane) of the second reflecting mirror so that they are perpendicular to each other, it is possible to independently adjust the position and angle of the light (traveling in the +Z direction) emitted from the emitted light adjustment unit 4 in the XZ plane and the position and angle in the YZ plane.

[0028] The beam expander 5 includes two or more lens groups and functions to expand the diameter of the incident parallel beam. For example, a Galilean beam expander including a combination of concave and convex lenses can be used. The beam expander 5 is mounted on a translation stage with two or more axes and is configured to be positionally adjustable so that its center coincides with a predetermined beam position. The beam expander 5 also has a function for adjusting the overall tilt angle of the beam expander 5 so that its optical axis coincides with the optical axis of a predetermined beam. The beam expander 5 can control the expansion ratio of the beam diameter by adjusting the spacing between the lenses (zoom mechanism). Furthermore, if the light incident on the beam expander 5 is not parallel, adjusting the spacing between the lenses simultaneously expands and collimates the beam diameter (to make the beam quasi-parallel). The beam collimation can also be achieved by installing a collimating lens upstream of the beam expander 5, independent of the beam expander 5. The beam diameter expansion ratio achieved by the beam expander 5 is approximately 5 to 10 times. Therefore, the beam emitted from the laser light source 2, which has a diameter of 1 mm, is expanded to about 5 mm to 10 mm.

[0029] The polarization control unit 6 is composed of a half-wave plate and a quarter-wave plate, and controls the polarization state of the illumination light to an arbitrary polarization state.

[0030] The beam monitor 22 measures the state of light incident on the beam expander 5 in the optical path of the illumination unit 401. When measuring the state of light incident on the illumination intensity distribution control unit 7, the beam monitor 22 may be configured to be installed immediately before the illumination intensity distribution control unit 7.

[0031] 4 to 8 are schematic diagrams showing the positional relationship between the illumination optical axis 420 guided to the sample surface from the illumination unit 401 and the illumination intensity distribution shape. Note that the configuration of the illumination unit 401 in Figures 4 to 8 shows only a part of the configuration of the illumination unit 401, and the emitted light adjustment unit 4, mirror 21, beam monitor 22, etc. are omitted.

[0032] FIG. 4 is a schematic diagram showing a cross section of the incident plane (plane including the illumination optical axis and the normal to the sample surface) of oblique incidence illumination (a configuration in which illumination light is obliquely irradiated onto the sample W via the illumination intensity distribution control unit 7 in FIG. 3). The oblique incidence illumination is inclined with respect to the sample surface within the incident plane. In this case, as one form, the illumination unit 401 can create a substantially uniform illumination intensity distribution within the incident plane. The length of the portion with uniform illumination intensity can be approximately 100 μm to 4 mm in order to inspect a wide area per unit time.

[0033] FIG. 5 is a schematic diagram showing a cross section of a plane that includes the sample surface normal and is perpendicular to the plane of incidence for oblique incidence illumination, illustrating perpendicular illumination (a configuration in which illumination light is irradiated perpendicularly onto the sample W via the illumination intensity distribution control unit 7v in FIG. 3). The illumination intensity distribution on the sample surface within this plane exhibits an illumination intensity distribution in which the intensity is weaker at the periphery than at the center. More specifically, the illumination intensity distribution resembles a Gaussian distribution that reflects the intensity distribution of light incident on the illumination intensity distribution control unit 7v, or a first-order Bessel function or sinc function that reflects the aperture shape of the illumination intensity distribution control unit 7v. The length of the illumination intensity distribution within this plane (the length of the region with an illumination intensity equal to or greater than 13.5% of the maximum illumination intensity) is shorter than the length of the portion of the incident plane where the illumination intensity is uniform, approximately 2.5 μm to 20 μm. This is to reduce haze generated on the sample surface. The illumination intensity distribution control unit 7 and the illumination intensity distribution control unit 7v each include optical elements, such as an aspherical lens, a diffractive optical element, a cylindrical lens array, and a light pipe, as described below. The optical elements constituting the illumination intensity distribution control unit 7 or 7v are installed perpendicular to the illumination optical axis, as shown in Figures 4 and 5. However, as shown in Figure 6, the optical elements constituting the illumination intensity distribution control unit 7 can also be installed tilted with respect to the optical axis. Furthermore, as shown in Figures 7 and 8, it is also possible to interchange the intensity distribution at the incident plane of oblique incidence illumination shown in Figures 4 and 5 with the intensity distribution at the plane perpendicular to the incident plane. In other words, a configuration may be adopted in which the portion of uniform illumination intensity at the incident plane is shorter than the portion of uniform illumination intensity at the plane perpendicular to the incident plane.

[0034] <Regarding Generation of Illumination Intensity Distribution> The illumination intensity distribution control unit 7 and the illumination intensity distribution control unit 7v (hereinafter, collectively referred to as the "illumination intensity distribution control unit 7, etc.") include optical elements that affect the phase distribution and intensity distribution of incident light. FIG. 9 is a diagram showing examples of optical elements constituting the illumination intensity distribution control unit 7, etc. The illumination intensity distribution control unit 7, etc. uses a diffractive optical element 71 (DOE) as the optical element. The diffractive optical element 71 is formed by forming a fine undulation pattern with dimensions equal to or smaller than the wavelength of the light on the surface of a substrate made of a material that transmits incident light. For ultraviolet light, fused silica is used as the material that transmits incident light. To suppress attenuation of light passing through the diffractive optical element 71, a diffractive optical element coated with an anti-reflection film may be used. Lithography is used to form the fine undulation pattern of the diffractive optical element.

[0035] The quasi-parallel light that has passed through the beam expander 5 passes through the diffractive optical element 71, forming an illumination intensity distribution on the sample surface according to the undulating shape of the diffractive optical element 71. The undulating shape of the diffractive optical element 71 is designed and manufactured to a shape calculated based on Fourier optics theory so that the illumination intensity distribution formed on the sample surface becomes a long, uniform distribution within the incident plane. The optical elements included in the illumination intensity distribution control unit 7 and the like are equipped with two or more translation adjustment mechanisms and two or more rotation adjustment mechanisms to enable adjustment of the relative position and angle with respect to the optical axis of the incident light. Furthermore, the optical elements include a focus adjustment mechanism that moves along the optical axis. Alternative optical elements with similar functions to the diffractive optical element 71 may include an aspherical lens, a combination of a cylindrical lens array and a cylindrical lens, or a combination of a light pipe and an imaging lens.

[0036] Modifications of the illumination intensity distribution formed on the sample surface by the illumination unit 401 are described below. Instead of an illumination intensity distribution that is elongated (linear) in one direction and has substantially uniform intensity in the longitudinal direction, an illumination intensity distribution with a Gaussian distribution in the longitudinal direction can also be used. A Gaussian distribution illumination that is elongated in one direction can be formed by configuring the illumination intensity distribution control unit 7 to include a spherical lens and forming an elliptical beam elongated in one direction using the beam expander 5, or by configuring the illumination intensity distribution control unit 7, etc., with multiple lenses including cylindrical lenses. Furthermore, by arranging some or all of the spherical or cylindrical lenses of the illumination intensity distribution control unit 7, etc., parallel to the sample surface, an illumination intensity distribution that is elongated in one direction on the sample surface and narrow in the perpendicular direction can be formed. Compared to creating a uniform illumination intensity distribution, this method has the advantages of less fluctuation in the illumination intensity distribution on the sample surface due to fluctuations in the state of light incident on the illumination intensity distribution control unit 7, etc., resulting in a more stable illumination intensity distribution. It also has the advantage of higher light transmittance and better efficiency compared to using a diffractive optical element or a microlens array in the illumination intensity distribution control unit 7, etc.

[0037] <Measurement (Monitoring) of the Illumination Light State> The state of the illumination light in the illumination unit 401 is measured by the beam monitor 22. When the beam monitor 22 is installed at the position shown in FIG. 3 , it measures and outputs the position and angle (traveling direction) of the illumination light that has passed through the output light adjustment unit 4. When measuring the position and wavefront of the illumination light incident on the illumination intensity distribution control unit 7, the beam monitor 22 is installed between the polarization control unit 6 and the illumination intensity distribution control unit 7. The position of the illumination light is measured by measuring the center of gravity of the light intensity of the illumination light. Specific position measurement means may include a position sensitive detector (PSD) or an image sensor such as a CCD sensor or CMOS sensor. The angle of the illumination light is measured by a position sensor or image sensor installed at a position farther away from the laser light source 2 than the position measurement means or at the position where the light is focused by the collimating lens. Information on the illumination light position and illumination light angle detected by each sensor is input to the control device 53 and displayed on the screen of the display device 54. If the illumination light position or angle deviates from the predetermined position or angle, the control device 53 adjusts it to return to the predetermined position by controlling the tilt angle of the reflecting mirror of the emitted light adjustment unit 4.

[0038] The wavefront measurement of the illumination light described above is performed to measure the parallelism of light incident on the illumination intensity distribution control unit 7 or the like. If the wavefront measurement reveals that the light incident on the illumination intensity distribution control unit 7 or the like is not quasi-parallel but is diverging or converging, the control device 53 can make the light closer to quasi-parallel by displacing the lens group of the upstream beam expander 5 in the optical axis direction. Furthermore, if the wavefront measurement reveals that the wavefront of the light incident on the illumination intensity distribution control unit 7 or the like is partially tilted, a spatial light phase modulation element, which is a type of spatial light modulator (SLM), may be inserted upstream of the illumination intensity distribution control unit 7 or the like. This provides an appropriate phase difference at each position on the light beam cross section to flatten the wavefront, thereby making the illumination light closer to quasi-parallel light. The above-described wavefront accuracy measurement and adjustment functions (realized by the control device 53, the beam monitor 22, the beam expander 5, the additional spatial light modulation element, etc.) make it possible to suppress the wavefront accuracy (deviation from a predetermined wavefront (design value or initial state)) of light incident on the illumination intensity distribution control unit 7, etc. to a deviation of λ / 10 rms or less.

[0039] The illumination intensity distribution on the sample surface adjusted by the illumination intensity distribution control unit 7 can be measured by monitoring scattered light from the sample surface with the illumination intensity distribution monitor 24. Similarly, when vertical illumination is used, the illumination intensity distribution on the sample surface adjusted by the illumination intensity distribution control unit 7v can be measured by monitoring scattered light with the illumination intensity distribution monitor 24.

[0040] The illumination intensity distribution monitor 24 focuses the image of the sample surface on an image sensor such as a CCD sensor or CMOS sensor via a lens and detects it as an image. The control device 53 processes the image of the illumination intensity distribution detected by the illumination intensity distribution monitor 24 and calculates the position of the center of gravity of the illumination intensity, the maximum intensity, the position of the maximum intensity, the width and length of the illumination intensity distribution (the width and length of the illumination intensity distribution region where the intensity is equal to or greater than a predetermined intensity or where the ratio of the maximum intensity is equal to or greater than a predetermined ratio), etc. The display device 54 then displays the calculated information on its display screen together with the contour shape and cross-sectional waveform of the illumination intensity distribution.

[0041] <Regarding Disturbances in Illumination Intensity Distribution> When performing oblique incidence illumination, variations in the height of the sample surface cause variations in the illumination intensity distribution position and disturbances in the illumination intensity distribution due to defocusing. To prevent this, the height of the sample surface is measured, and if there is a deviation in height, the deviation can be corrected by adjusting the height using the Z axis of the stage 404 or by adjusting the focus position using the illumination intensity distribution control unit 7 (see, for example, FIG. 15 ).

[0042] <Regarding Sample Scanning> Fig. 10 is a diagram showing the illuminance distribution shape (illumination (beam) spot 20) formed on the sample surface by the illumination unit 401. Fig. 11 is a diagram for explaining a method of scanning the sample with the illumination spot 20 by the illumination unit 401.

[0043] For example, assume that the sample W is a circular semiconductor silicon wafer. The stage 404 includes a translation stage, a rotation stage, and a Z-stage (none of which are shown) for adjusting the height of the sample surface. As described above, the illumination spot 20 has an illumination intensity distribution that is long in one direction (aspect ratio of 100:1 or more). Furthermore, the longitudinal direction of the illumination spot 20 is designated S2, and the direction substantially perpendicular to S2 is designated S1 (see FIG. 10 ).

[0044] Due to the rotational movement of the rotation stage of the stage 404, the illumination spot 20 moves on the sample W in the circumferential direction S1 of a circle centered on the rotation axis of the rotation stage, and further moves in the translation direction (longitudinal direction S2) of the translation stage due to the translational movement of the translation stage. As a result, while the illumination spot 20 makes one rotation of the sample by scanning in the circumferential direction S1, it moves in the translation direction S2 (scans on the sample W) by a distance equal to or less than the length in the longitudinal direction of the illumination spot 20. By repeating this rotational movement and translational movement, the illumination spot 20 traces a spiral trajectory T on the sample W, making it possible to scan the entire surface of the sample W.

[0045] <Configuration of the detection unit 402> The following describes the pupil-split detection unit. FIGS. 12 and 13 are diagrams showing examples of the arrangement of the detection unit 402 relative to the sample W and the illumination spot 20. FIG. 12 shows an example of the arrangement when the entire detection unit 402 is viewed from directly above. FIG. 13 shows an example of the arrangement when the entire detection unit 402 is viewed from the side. In addition, in FIGS. 12 and 13, the angle between the normal 1201 of the sample W and the detection direction by the detection unit 402 is defined as the detection zenith angle. Furthermore, in FIG. 12, the angle between the traveling direction of the oblique incidence illumination and the detection direction in a plane parallel to the surface of the sample W is defined as the detection azimuth angle.

[0046] 12 , the detection unit 402 includes, for example, a front detection unit 402f, a rear detection unit 402b, and a front detection unit 402f′ and a rear detection unit 402b′ that are positioned symmetrically with respect to the illumination incident plane, and these are arranged in plurality so as to detect scattered light in a plurality of azimuths emitted from the illumination spot 20. For example, the front detection unit 402f is installed so that the detection azimuth angle is between 0 degrees and 90 degrees, and the rear detection unit 402b is installed so that the detection azimuth angle is between 90 degrees and 180 degrees. However, the number and positions of the detection units may be changed as appropriate.

[0047] As shown in FIG. 13, each of the split detectors 402b, 402f, 402b', and 402f' includes a high-angle detector 402h whose zenith angle is equal to or less than a predetermined angle and a low-angle detector 402l whose detected zenith angle is equal to or greater than a predetermined angle (see FIG. 13). The high-angle detector 402h and the low-angle detector 402l each detect scattered light using a common objective lens. However, the scattered light is split at the Fourier plane of the common objective lens and detected by the high-angle detector 402h and the low-angle detector 402l. The boundary between the detected zenith angle of the high-angle detector 402h and the detected zenith angle of the low-angle detector 402l can be easily changed.

[0048] (2) Examples <Example 1> Fig. 14 is a diagram showing an example of the configuration of the illumination unit 401 according to Example 1. Fig. 15 is a diagram showing a light collecting unit of the illumination unit 401. Note that since light is irradiated perpendicularly to the sample 1506 (sample W) (perpendicular illumination), Fig. 14 shows the path of light passing through the illumination intensity distribution control unit 7v in Fig. 3.

[0049] 14 , light (laser light beam) emitted from a laser light source 1501 has its intensity adjusted by an attenuator 1502 and is reflected by a mirror 1503. For simplicity, optical components such as the emitted light adjusting unit 4, beam expander 5, polarization control unit 6, and illumination intensity distribution control unit 7 are omitted from FIG. 14 . The light whose intensity has been adjusted then passes through a cylindrical lens 1504, which is the converging optical element B, and passes through a rotationally symmetric converging lens 1505, which is the converging optical element A, and is perpendicularly incident on an inspection object 1506. The converging optical element B and the converging optical element A are a group of optical elements that form at least a part of the internal configuration of the illumination intensity distribution control unit 7v.

[0050] 15, the focal point of the beam spot in the lateral direction coincides with the object to be inspected. For example, if a beam spot with a longitudinal focal diameter of 1 mm is to be created under the conditions of FIG. 16, the incident beam diameter corresponding to the longitudinal direction at the condenser lens 1505 is 11 mm, and the difference between the focal point in the lateral direction and the focal point 1507 in the longitudinal direction is 10 mm. As mentioned above, in the conventional technology, a beam with a beam diameter of 50 μm had to be incident, so it is now possible to obtain a beam spot of the same diameter by expanding the beam diameter at the condenser lens by 200 times or more.

[0051] Furthermore, as mentioned above, the wavelengths of light sources used in semiconductor substrate inspection equipment are becoming shorter, and it is not uncommon for UV light sources to emit light with wavelengths of 360 nm or less to be used. As wavelengths become shorter, photon energy increases, increasing the likelihood of damage to glass materials and lens coating materials. To minimize damage and extend the life of optical components, it is desirable to input light at the lowest possible irradiation density.

[0052] Here, fa is the focal length (composite focal length of converging optical elements A and B) in the direction in which converging optical element B performs the converging action (longitudinal direction of the beam spot) in the converging optical system consisting of converging optical element A and converging optical element B. fb is the focal length (composite focal length of converging optical elements A and B) in the direction (short-side direction of the beam spot) perpendicular to the direction in which converging optical element B performs the converging action (longitudinal direction of the beam spot) in the converging optical system consisting of converging optical element A and converging optical element B. Also, NAb is the numerical aperture of the converging optical system (converging optical elements A+B) in the direction in which converging optical element B performs the converging action (longitudinal direction of the beam spot). NAa is the numerical aperture of the converging optical system (converging optical elements A+B) in the direction (short-side direction of the beam spot) perpendicular to the direction in which converging optical element B performs the converging action. Furthermore, Lb is defined as the distance from the rear principal point position in the focusing direction (longitudinal direction of the beam spot) of the focusing optical system (focusing optical elements A+B) to the inspection object (sample W), and La is defined as the distance from the rear principal point position in the focusing direction (transverse direction of the beam spot) orthogonal to the focusing direction (longitudinal direction of the beam spot) of the focusing optical system (focusing optical elements A+B) to the inspection object (sample W).

[0053] With these definitions, when the conditions in Fig. 16 are satisfied, fa = 100 mm, fb = 210 mm, La = 100 mm, and Lb = 200 mm. When the conditions in Fig. 16 are satisfied, |fa| < |fb|, La is approximately equal to |fa|, and Lb is smaller or larger than |fb| (i.e., |fb| ≠ Lb).

[0054] Furthermore, when considering narrowing the beam spot to a thin line, it is desirable that the numerical aperture NAa in the lateral focusing direction of the beam spot be larger than the numerical aperture NAb in the longitudinal direction. Referring to Figure 15, the longitudinal focusing point 1507 is formed on the side of the inspection object 1506 in the direction of travel of the light beam (to the right of the inspection object 1506), but this is not limitative and it may be formed on the light source side of the inspection object 1506 (to the left of the inspection object). Meanwhile, the lateral focusing point of the beam spot is formed on the inspection object 1506.

[0055] As described above, since the focusing effect in the short-side direction of the beam spot is not particularly affected, the adoption of the configuration of the illumination unit 401 according to the present disclosure does not change the focusing performance or the beam diameter of the intermediate optical path in the short-side direction. Therefore, by adopting the technology of the present disclosure, it is possible to achieve a beam diameter width in the long-side direction without affecting performance in the short-side direction. Furthermore, it is also possible to reduce only the irradiation density during transmission through the focusing optical element A, thereby reducing the load and extending the lifespan. Note that, although specific lens focal lengths and the like are shown in FIG. 16 in Example 1, the combinations are not limited to those shown in FIG. 16.

[0056] <Example 2> Fig. 17 is a diagram showing an example of the configuration of the illumination unit 401 according to Example 2. In the case of Fig. 17, light is irradiated perpendicularly to the sample 1506 (sample W) (perpendicular illumination), and therefore Fig. 17 also shows the path passing through the illumination intensity distribution control unit 7v in Fig. 3, similar to Fig. 14.

[0057] The difference between Example 2 and Example 1 is that the cylindrical lens 1504, which constitutes the converging optical element B, is replaced with one concave cylindrical lens 1801 and one convex cylindrical lens 1802. In Example 1, the focal length required for the converging optical element B is extremely long, approximately 1000 mm, as shown in FIG. 16 . If a single lens were to be used to achieve such a long focal length, the radius of curvature of the lens surface would also be large. In this case, the amount of polishing required from the parallel plate would be reduced, making lens fabrication difficult and significantly increasing the impact of even slight processing errors on focal length fluctuations. Furthermore, the distance between the converging optical element A and the converging optical element B would be increased, resulting in an increase in the size of the device. Alternatively, the increase in size of the device could be avoided by using multiple mirrors to fold the beam between the converging optical element A and the converging optical element B, but the increased cost of installing multiple mirrors would be unavoidable.

[0058] As is well known, the focal length f of a lens composed of two single lenses can be expressed as f = f1 * f2 / (f1 + f2 - d). Here, f is the composite focal length of the two single lenses, f1 and f2 are the focal lengths of the individual single lenses, and d is the distance between the two single lenses, where the single lenses are thin lenses. From this equation, by combining two single lenses as a concave and convex lens and adjusting the distance d, the focal length of the combined lens can be set long even if the focal length of each single lens is relatively short. Furthermore, because the focal length of each single lens is short, a sufficient amount of polishing can be ensured, making it easier to manufacture the lens. It also makes it possible to reduce the size of the total optical system.

[0059] 18 shows an example of the installation conditions for a two-lens combination that results in a focal length of −1000 mm for the focusing optical system. When a two-lens combination is used as in Example 2, the focal length of the focusing optical element B can be changed by driving at least one of the concave cylindrical lens 1801 or the convex cylindrical lens 1802 in the optical axis direction, and the diameter of the longitudinal spot formed on the inspection object 1506 can be adjusted.

[0060] In actual products, variations in the diameter of the emitted beam from the laser light source and manufacturing and assembly errors of each lens result in variations in the diameter of the spot formed on the object under inspection (object to be irradiated) 1506. Therefore, adding a mechanism for monitoring the spot diameter is considered. FIG. 19 shows an example configuration in which a half mirror 2001 is placed between the condenser lens 1505 and the convex cylindrical lens 1802, and an optical system is added that reflects the light reflected by the object under inspection 1506 and forms an image on a camera 2003 via an imaging lens 2002. Adding such an optical system makes it possible to observe the beam spot irradiated / formed on the object under inspection 1506. Using such an observation optical system, the spot diameter can also be observed, allowing the amount of deviation of the spot diameter from the target value to be determined. The observed deviation can then be adjusted by changing the distance between the concave cylindrical lens 1801 and the convex cylindrical lens 1802.

[0061] FIG. 20 is a table showing the diameter of the beam spot formed on the inspection object 1506 when the distance between the concave cylindrical lens 1801 and the convex cylindrical lens 1802 having the focal lengths shown in FIG. 19 is changed. As is clear from FIG. 20 , the diameter of the beam spot on the inspection object 1506 changes as the distance between the concave cylindrical lens 1801 and the convex cylindrical lens 1802 is changed. The beam spot formed on the inspection object 1506 is elliptical, but according to the conventional example, the diameter does not necessarily deviate from the desired value while maintaining the ratio of the minor axis to the major axis. On the other hand, according to the configuration of Example 2, the concave cylindrical lens 1801 and the convex cylindrical lens 1802 act only in the major axis direction of the beam spot. Therefore, changing the distance between the concave cylindrical lens 1801 and the convex cylindrical lens 1802 changes only the beam spot diameter in the major axis direction. Therefore, by using the configuration shown in Example 2, even if the ratio of the short diameter to the long diameter of the beam spot deviates from the desired value, the aspect ratio of the beam spot can be easily corrected to the desired value by changing the spacing between the concave cylindrical lens 1801 and the convex cylindrical lens 1802.

[0062] 17 and 19, the concave cylindrical lens 1801 and the convex cylindrical lens 1802 are arranged in the order of concave cylindrical lens → convex cylindrical lens from the light source side, but this is not limiting and the order may be reversed. Also, in FIGS. 17 and 19, the focusing optical element B is configured with two lenses, but it may be configured with three or more lenses. Furthermore, in FIG. 19, the half mirror 2001 may be removed from the optical path when the camera is not in use to ensure the amount of light that reaches the inspection object 1506.

[0063] <Example 3> Fig. 21 is a diagram showing an example of the configuration of the illumination unit 401 according to Example 3. In the case of Fig. 21, light is irradiated obliquely onto the sample 1506 (sample W) (oblique incidence illumination), and therefore Fig. 21 shows the path of light passing through the illumination intensity distribution control unit 7 in Fig. 3.

[0064] The changes in Example 3 from Example 2 are that the focusing optical element A is changed from a rotationally symmetric focusing lens 1505 to a non-rotationally symmetric cylindrical mirror 2202, and that the angle of incidence of the light beam on the inspection object 406 is not 0°. In addition, an imaging lens 2203 and a camera 2204 are also added, which are used to observe the spot formed on the inspection object 1506.

[0065] By irradiating a light beam obliquely onto the wafer under inspection, anisotropy appears in the scattering distribution of the light irradiated on the foreign matter, enabling more accurate detection of foreign matters. For this reason, oblique incidence illumination is often adopted in semiconductor inspection equipment. Forming a uniform linear beam spot with a large aspect ratio by irradiating light beams obliquely like this is difficult to achieve with a rotationally symmetric focusing optical element. Therefore, as shown in FIG. 21 , using a non-rotationally symmetric focusing optical element such as a cylindrical mirror 2202 makes it possible to achieve a uniform linear beam spot with a large aspect ratio. The concave cylindrical lens 1801 and convex cylindrical lens 1802, which are focusing optical element B, act only in the plane direction of FIG. 21 (the longitudinal direction of the beam spot). In contrast, the cylindrical mirror 2202, which corresponds to focusing optical element A, acts only in the plane-perpendicular direction of FIG. 21 (the lateral direction of the beam spot).

[0066] The reflective surface of the cylindrical mirror 2202 is typically coated with a special coating to achieve high reflectivity. However, even with such a coating, irradiating it with light at a high irradiation density can damage the coating, resulting in a decrease in reflectivity and aberrations that can cause spots to not form. Furthermore, compared to rotationally symmetric optical systems, non-rotationally symmetric optical systems require at least one additional axis of adjustment in the direction of the rotation axis, which increases the adjustment time, making it desirable to avoid situations where replacement or readjustment is required. Therefore, even in reflective optical systems, it is desirable to irradiate the optical element with as low an irradiation density as possible to avoid coating damage to the cylindrical mirror surface.

[0067] Furthermore, when a reflective optical system is used, the angle of incidence of the light beam on the inspection target 1506 is often not 0°, as shown in FIG. 21 . However, according to Example 3, even when the converging optical element A is a reflective optical system and the angle of incidence of the light beam on the inspection target 1506 is not 0°, the effect of reducing the irradiation density on the converging optical element A can be achieved. Furthermore, as shown in FIG. 20 (Example 2), in an actual product, the spot diameter formed on the inspection target 1506 varies due to the influence of variations in the output beam diameter of the laser light source and manufacturing errors / assembly errors of each lens. In this regard, by observing the beam spot using the imaging lens 2203 and the camera 2204, the deviation of the beam spot diameter from the desired value (target value) can be measured, and the beam spot diameter can be adjusted by changing the distance between the concave cylindrical lens 1801 and the convex cylindrical lens 1802. Although FIG. 21 uses a cylindrical mirror 2202 as the optical element, a spherical mirror or a free-form surface mirror may also be used.

[0068] (3) Summary (i) In this embodiment (common to Examples 1 to 3), the illumination unit 401 is a focusing optical system (an internal optical system included in the illumination intensity distribution control unit 7, etc.) that forms a beam spot for irradiating light rays (UV light rays: wavelength 360 nm or less) on an object to be inspected (object to be irradiated: sample). The focusing optical system includes at least one first focusing optical element (focusing optical element B: as shown in FIG. 14 , it may be configured with one focusing optical element, or as shown in FIG. 17 , it may be configured with two or more focusing optical elements) that focuses the light rays only in a first direction (longitudinal direction of the beam spot) perpendicular to the light irradiation direction, and a second focusing optical element (focusing optical element A) that focuses the light rays at least in a second direction (transverse direction of the beam spot) perpendicular to the first direction. In this way, by providing the focusing optical element B that focuses light only in one direction, the diameter of the light rays incident on the focusing optical system can be increased (as opposed to the conventional system, it is not necessary to reduce the transverse size from the beginning to form an elliptical beam). This makes it possible to reduce the load on the focusing optical element, and to form a linear beam with a high aspect ratio with an inexpensive and compact configuration while maintaining high transmittance.

[0069] Furthermore, specific conditions for achieving a higher aspect ratio (100:1 or greater) are to configure the focusing optical system so that |fa| < |fb| and NAa > NAb are satisfied, La is approximately equal to |fa|, and |fb| ≠ Lb is satisfied. Here, fb represents the focal length of the focusing optical system in a first direction (longitudinal direction of the beam spot) in which the first focusing optical element (focusing optical element B) focuses light. NAb represents the numerical aperture of the focusing optical system in the first direction. Lb represents the distance from the rear principal point position of the focusing optical system in the first direction to the object to be inspected (object to be irradiated). Furthermore, fa represents the focal length of the focusing optical system in a second direction (short direction of the beam spot) perpendicular to the first direction in which the first focusing optical element (focusing optical element B) focuses light. NAa represents the numerical aperture of the focusing optical system in the second direction. La represents the distance from the rear principal point position of the focusing optical system in the second direction to the object to be illuminated.

[0070] Specifically, as shown in Fig. 15, the focusing optical system (focusing optical elements A and B) has a focusing point at a position different from the surface of the sample in the first direction (longitudinal direction of the beam spot), and has a focusing point on the surface of the sample in the second direction (lateral direction of the beam spot). In this way, the focusing optical system achieves the above-mentioned technical effect by making the focusing action different in the longitudinal direction and lateral direction of the beam spot.

[0071] (ii) According to Example 2, the first focusing optical element (focusing optical element B) is composed of two or more optical elements. At least one of the two or more optical elements is configured to be drivable in the direction of irradiation of the light beam. By moving the constituent optical elements, the distance between the two or more optical elements is changed, thereby changing the focal length of the first focusing optical element (focusing optical element B). In this way, if the ratio of the minor axis to the major axis of the beam spot deviates from the desired value, it can be corrected to the appropriate ratio (desired value).

[0072] (iii) In Examples 1 and 2, the second focusing optical element (focusing optical element A) is configured with a rotationally symmetric focusing lens 1505. This is advantageous when vertical illumination is employed. On the other hand, in Example 3, the second focusing optical element (focusing optical element A) is configured with a reflective optical element (cylindrical mirror 2202). This is advantageous when oblique incidence illumination is employed.

[0073] (iv) The defect inspection device according to this embodiment includes an illumination unit 401 according to any one of Examples 1 to 3, a detector (detection unit 402) that detects scattered light generated by irradiating an object to be inspected (object to be irradiated: sample) with a light beam, and a control device 53 that determines whether or not there is a defect on the object to be inspected based on a detection signal output by the detector. If there is a defect, the control device displays the defect on the screen of a display device 54.

[0074] The illumination unit 401 further includes a beam spot observation optical system (illumination intensity distribution monitor 24) for detecting reflected light from the inspection object (sample) and observing the beam spot. In Example 2, at least one of the two or more optical elements of the first focusing optical element (focusing optical element B) is configured to be movable in the direction of the light beam irradiation. The control device 53 then performs the following processes: calculating the deviation between the actual beam spot diameter and the desired beam spot diameter based on a detection signal from the beam spot observation optical system (illumination intensity distribution monitor 24); and adjusting the actual beam spot diameter by driving at least one of the two or more optical elements based on the deviation. This enables the ratio of the minor axis to the major axis of the beam spot to be corrected to the appropriate ratio (desired value) if it deviates from the desired value.

[0075] (v) The technology of the present disclosure is not limited to the configuration examples of the present embodiment and each example, and includes various modifications. The present embodiment and each example are provided to clearly explain the technology of the present disclosure. Therefore, the technology of the present disclosure is not necessarily limited to having all of the described configurations. Furthermore, the technology described in the present embodiment is not inherently related to any specific device and can be implemented by combining each component. Furthermore, various types of general-purpose devices can also be added. A dedicated device may be constructed to perform the functions of the present embodiment. Furthermore, various functions can be formed by appropriately combining multiple components disclosed in the present embodiment. For example, some components may be omitted from all of the components shown in the embodiment, or different components may be appropriately combined.

[0076] Although specific embodiments are described in this disclosure, they are in all respects illustrative and not limiting, and it will be appreciated by those skilled in the art that there are numerous combinations of hardware, software, and firmware suitable for implementing the technology of this disclosure.

[0077] Furthermore, in the above-described embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. All components may be interconnected.

[0078] In addition, other implementations of the present disclosure will be apparent to those skilled in the art from consideration of the present embodiments. The specification and examples are exemplary only, with the scope and spirit of the technology of the present disclosure being indicated by the following claims.

[0079] 2, 101, 1501 Laser light source 3, 102, 1502 Attenuator 4 Emitted light adjustment unit 5 Beam expander 6 Polarization control unit 7, 7v Illumination intensity distribution control unit 10 Defect inspection device 20 Illumination spot (beam spot) 21, 103, 105, 1503, 2201 Mirror 22 Beam monitor 24 Illumination intensity distribution monitor 53 Control unit 54 Display device 55 Input device 71 Diffractive optical element 104 Anamorphic prism 106, 1505 Rotationally symmetric condenser lens 107, 1506 Inspection object 401 Illumination unit 402 Detection unit 403-1, 403-2 Photoelectric conversion unit 404 Stage 405 Signal processing device 420 Illumination optical axis 1504 Cylindrical lens 1507 Focus point in the longitudinal direction of the beam spot 1801 concave cylindrical lens 1802 convex cylindrical lens 2001 half mirror 2002 imaging lens 2003 camera 2202 cylindrical mirror 2203 imaging lens 2204 camera

Claims

1. A system comprising: a light source; and a focusing optical system that forms a beam spot for irradiating a light beam emitted from the light source onto an irradiation object, wherein the focusing optical system includes at least one first focusing optical element that focuses the light beam only in a first direction perpendicular to the irradiation direction of the light beam, and a second focusing optical element that focuses the light beam at least in a second direction perpendicular to the first direction, wherein a focal length of the focusing optical system in the first direction in which the first focusing optical element performs a focusing function is defined as fb, a numerical aperture of the focusing optical system in the first direction is defined as NAb, and a distance from a rear principal point position of the focusing optical system in the first direction to the irradiation object is defined as Lb, a focal length of the focusing optical system in the second direction perpendicular to the first direction in which the first focusing optical element performs a focusing function is defined as fa, a numerical aperture of the focusing optical system in the second direction is defined as NAa, and a distance from a rear principal point position of the focusing optical system in the second direction to the irradiation object is defined as La, An illumination optical system that satisfies |fa|<|fb| and NAa>NAb, and further, La is approximately equal to |fa|, and |fb|≠Lb.

2. An illumination optical system according to claim 1, wherein the at least one first focusing optical element focuses the light beam only in the longitudinal direction of the beam spot, and the second focusing optical element focuses the light beam at least in the lateral direction of the beam spot.

3. An illumination optical system according to claim 2, wherein the focusing optical system has a focusing point at a position different from the surface position of the object to be irradiated in the first direction, and has a focusing point on the surface of the object to be irradiated in the second direction.

4. An illumination optical system according to claim 1, wherein the first focusing optical element includes two or more optical elements.

5. An illumination optical system according to claim 4, wherein at least one of the two or more optical elements of the first focusing optical element is configured to be drivable in the irradiation direction of the light beam, and the focal length of the first focusing optical element is changed by changing the distance between the two or more optical elements.

6. An illumination optical system according to claim 1, wherein the second light-collecting optical element is composed of a rotationally symmetric lens.

7. An illumination optical system according to claim 1, wherein the second light-collecting optical element is a reflecting optical element.

8. An illumination optical system according to claim 1, wherein the angle of incidence of the light beam on the object to be illuminated is between 0° and 90°.

9. An illumination optical system according to claim 1, wherein the light source emits a light beam having a wavelength shorter than 360 nm.

10. A defect inspection device comprising: an illumination optical system as described in claim 1; a detector that detects scattered light generated by irradiating the object to be irradiated with the light beam; and a control device that determines whether or not there is a defect on the object to be irradiated based on a detection signal output by the detector, wherein the control device displays the defect on a screen of a display device.

11. A defect inspection device according to claim 10, wherein the illumination optical system further includes a beam spot observation optical system for detecting reflected light from the object to be irradiated and observing the beam spot, and the first focusing optical element of the illumination optical system is configured so that at least one of two or more optical elements can be driven in the irradiation direction of the light beam, and the control device executes a process of calculating an amount of deviation between an actual beam spot diameter and a desired beam spot diameter based on a detection signal from the beam spot observation optical system, and a process of adjusting the actual beam spot diameter by driving at least one of the two or more optical elements based on the amount of deviation.

12. An illumination optical system comprising: a UV light source; a beam expander that adjusts the diameter of a UV light beam emitted from the UV light source and outputs a UV light beam with an expanded diameter; and a focusing optical system that forms a beam spot that irradiates an object with the UV light beam with an expanded diameter, wherein the focusing optical system includes at least one first focusing optical element that focuses the UV light beam with an expanded diameter only in the longitudinal direction of the beam spot, and a second focusing optical element that focuses the UV light beam with an expanded diameter at least in the transverse direction of the beam spot.

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