Optical inspection apparatus and optical inspection method

Abstract

The present disclosure is an optical inspection apparatus that inspects a test sample (101), which includes an illumination optical system (A) that has a light source, a beam control mechanism, and a condensing optical unit, irradiates a light beam emitted from the light source to a surface of the test sample through the condensing optical unit, a regular reflection light observation unit (F) that monitors regular reflection light from the surface of the test sample, and a control device that controls the illumination optical system based on the regular reflection light. The regular reflection light observation unit has a first image pickup element (F4a), a second image pickup element (F4b), and a first light splitting element (F3) that splits the regular reflection light to be respectively incident on the first image pickup element and the second image pickup element. The control device independently controls at least any one of a shift, a tilt, and a condensing position of the light beam incident on the condensing optical unit by the beam control mechanism based on information on a position or a size of a first light beam (1) received by the first image pickup element and information on a position or a size of a second light beam (2) received by the second image pickup element.

Description

Technical Field

[0001] This disclosure relates to optical inspection apparatus and optical inspection methods. Background Technology

[0002] In semiconductor manufacturing processes, defects present on the surface of semiconductor wafers are inspected to maintain or improve product yield. With the miniaturization of semiconductor processes, the need arises to detect and manage minute defects (a few nanometers or larger) on semiconductor wafers.

[0003] Optical semiconductor inspection devices irradiate a laser beam onto a semiconductor wafer and detect defects by detecting the light from the defects present on the semiconductor wafer. Optical semiconductor inspection devices are required to (1) detect minute defects, (2) measure the size of the detected defects with high precision, (3) measure the location of the detected defects with high precision, and (4) inspect multiple wafers within a certain time (high throughput), etc.

[0004] To detect even smaller defects, it is necessary to increase the amount of light emanating from the defect. Methods to increase the light amount include shortening the wavelength of the laser source, increasing its output, and reducing the laser irradiation area on the wafer. Shortening the wavelength of the laser source increases the cross-sectional area of ​​the light beam from the defect and thus increases the amount of light. Increasing the output of the laser source and reducing the laser irradiation area both increase the amount of light irradiating the defect and thus increase the amount of light emanating from the defect.

[0005] To reduce the laser irradiation area on the wafer, the laser beam is focused onto the wafer, forming a spot of tens to hundreds of micrometers. The amount of light from defects is affected by the shape and intensity of the spot; therefore, stabilizing the shape and intensity of the spot is essential for high-precision measurement of defect dimensions. Furthermore, the location of the defect is estimated based on the timing of the light received by the detector. In other words, stabilizing the spot position is indispensable for high-precision measurement of defect location.

[0006] Patent Document 1 discloses the following technique: the position of the illumination light is measured by beam monitors 22 and 23, and adjusted by the emitted light adjustment unit 4 to return the position or angle of the illumination light to a predetermined position or angle (see paragraphs 0026-0027 of Patent Document 1). Furthermore, Patent Document 1 describes "measuring the height of the sample surface, and correcting any deviation in height by adjusting the height based on the Z-axis of the illumination intensity distribution control unit 7 or the worktable 103" (see paragraph 0029 of Patent Document 1).

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2012-137350 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] Patent document 1 describes a technique related to the correction of illumination light, but further development of a technique to stabilize the quality of the light spot is desired.

[0012] Therefore, this disclosure provides a technique for stabilizing the light spot irradiated onto a sample in an optical inspection apparatus.

[0013] Methods for solving problems

[0014] To address the aforementioned issues, this disclosure relates to an optical inspection apparatus that inspects a sample based on light reflected or scattered from its surface. The apparatus comprises: an illumination optical system having a light source, a beam control mechanism, and a focusing optical unit, through which a beam emitted from the light source is directed to the surface of the sample; an orthorhombic reflection observation unit that monitors orthorhombic reflection from the surface of the sample; and a control device that controls the illumination optical system based on the orthorhombic reflection monitored by the observation unit. The orthorhombic reflection observation unit includes: a first imaging element; a second imaging element; and a first light splitting element that splits the orthorhombic reflection and directs it to the first and second imaging elements respectively. The control device, based on information about the position or size of a first beam received by the first imaging element and information about the position or size of a second beam received by the second imaging element, independently controls, via the beam control mechanism, at least one of the following: the deflection, tilt, and focusing position of the beam directed to the focusing optical unit.

[0015] Further features relating to this disclosure become apparent from the description and accompanying drawings. Furthermore, this disclosure is implemented through elements and various combinations of elements, as well as the subsequent detailed description and appended technical solutions. The description in this specification is merely exemplary and does not limit the technical solutions or applications of this disclosure in any way.

[0016] Invention Effects

[0017] According to the technology disclosed herein, it is possible to stabilize the light spot irradiating the sample in an optical inspection apparatus. Other issues, structures, and effects beyond those described above will become clear through the following description of embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing a structural example of the defect inspection device according to the first embodiment.

[0019] Figure 2This is a schematic diagram showing the scanning path of the scanning device on the sample.

[0020] Figure 3 This is a schematic diagram illustrating another example of the scanning path of the scanning device on the sample.

[0021] Figure 4 This is a schematic diagram showing an example of the structure of an attenuator.

[0022] Figure 5 This is a schematic diagram showing an example of the structure of an illumination observation unit.

[0023] Figure 6 It is a schematic diagram showing the positional relationship between the optical axis of the illumination light guided to the surface of the sample and the shape of the illumination intensity distribution.

[0024] Figure 7 This is a schematic diagram illustrating a structural example of a positive reflection light observation unit.

[0025] Figure 8A This diagram is used to explain the reasons for setting up the illumination observation unit.

[0026] Figure 8B This diagram is used to explain the reasons for setting up the illumination observation unit.

[0027] Figure 9 This is a diagram illustrating an example of the correction process for illumination light.

[0028] Figure 10A This is a diagram used to illustrate the observation unit for positive reflection light.

[0029] Figure 10B This is a diagram used to illustrate the observation unit for positive reflection light.

[0030] Figure 10C This is a diagram used to illustrate the observation unit for positive reflection light.

[0031] Figure 11 This is a diagram illustrating an example of the correction process for light incident into a focusing optical unit.

[0032] Figure 12 This is a diagram illustrating an example of the beam position correction process in wafer inspection.

[0033] Figure 13 This is a schematic diagram illustrating the structure of the defect inspection device according to the second embodiment.

[0034] Figure 14 This is a diagram illustrating an example of the correction process for light incident into the focusing optical unit in the second embodiment. Detailed Implementation

[0035] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, the application of the technology of the present disclosure to a defect inspection apparatus used in a manufacturing process of semiconductors, etc. By using the defect inspection apparatus, it is possible to achieve (1) detection of minute defects, (2) high-precision measurement of detected defects, (3) high-precision measurement of defect location, and (4) high-throughput inspection, etc.

[0036] [First Implementation]

[0037] <Example of the structure of a defect inspection device>

[0038] Figure 1 This is a schematic diagram showing a structural example of the defect inspection apparatus 100 (optical inspection apparatus) according to the first embodiment. (See diagram below.) Figure 1 As shown, an orthogonal XYZ coordinate system is defined with the vertical direction as the Z-axis and the X and Y axes as the horizontal directions. The defect inspection device 100 is configured to inspect the sample 101 for defects such as abnormal film formation and foreign matter adhesion on the surface of the sample 101. The defect inspection device 100 uses a rotary scanning method to scan the sample 101 by rotating it circumferentially (θ direction) while moving it radially (R direction).

[0039] The defect inspection apparatus 100 can also inspect unpatterned semiconductor silicon wafers (substrates). Alternatively, the defect inspection apparatus 100 can also be used to inspect patterned wafers on which dies are arranged in a matrix along the XY direction on the surface of the substrate. A pattern (microstructure) of fine circuits is densely formed on a die. The unit that is exposed once to form the die is called an exposure area (shot). Assuming that the die and the exposure area are essentially the same area in the manufacturing process of sample 101, there are also cases where multiple dies are contained in the same exposure area. In the case where multiple dies are contained in the same exposure area, there are cases where all the dies in the exposure area have the same pattern, and there are also cases where the dies contained in the same exposure area have different patterns from each other.

[0040] The defect inspection device 100 includes a worktable ST, an illumination optical system A, multiple detection optical systems B1~Bn (n=1,2,…), sensors C1~Cn (n=1,2,…), a signal processing device D, a storage device DB, a control device E1, an input device E2, a monitor E3, and a positive reflection light observation unit F.

[0041] -Workbench-

[0042] The worktable ST has a sample stage ST1 and a scanning device ST2. The sample stage ST1 is a platform that supports the sample 101. The scanning device ST2 is a device that drives the sample stage ST1 to change the relative position of the sample 101 and the illumination optical system A. Although not shown in the figure, the scanning device ST2 has a translation stage, a rotary stage, and a Z-stage. The rotary stage is mounted on the translation stage via the Z-stage, and the sample stage ST1 is supported on the rotary stage. The translation stage and the rotary stage move together in the horizontal direction. The rotary stage rotates (spins) around a vertically extending rotation axis. The Z-stage functions to adjust the height of the surface of the sample 101.

[0043] Figure 2 This is a schematic diagram showing the scanning path of the scanning device ST2 on the sample 101. As will be described later, the illumination light emitted from the illumination optics system A has a tiny point as the incident area, i.e., the light spot BS, relative to the surface of the sample 101, such as... Figure 2 As shown, it has a relatively long illumination intensity distribution in one direction. The long axis direction of the light spot BS is defined as s2, and the short axis direction, orthogonal to the long axis, is defined as s1. As the rotary table rotates, the sample 101 rotates, and the light spot BS scans relative to the surface of the sample 101 along the s1 direction. As the translational table translates, the sample 101 moves in the horizontal direction, and the light spot BS scans relative to the surface of the sample 101 along the s2 direction. Through the operation of this scanning device ST2, the sample 101 rotates and translates simultaneously, thus achieving the desired illumination intensity distribution. Figure 2 As shown, the light spot BS moves in a spiral trajectory from the center to the outer edge of the sample 101, scanning the entire surface of the sample 101. During one rotation of the sample 101, the light spot BS moves a distance less than the length of the s2 direction in the s2 direction.

[0044] Figure 3 This is a schematic diagram showing another example of the scanning path of the scanning device ST2 for the sample 101. Generally, there are also scanning devices that replace the rotary stage with another translational stage whose axis extends in a direction intersecting the translational stage's axis in the horizontal plane. In this case, such as... Figure 3 As shown, the light spot BS scans the surface of the sample 101 not along a spiral track but by superimposing linear tracks. Specifically, the first translation stage is driven to translate at a constant speed along the s1 direction, and the second translation stage is driven along the s2 direction a predetermined distance (e.g., a distance less than the length of the light spot BS in the s2 direction) before the first translation stage is folded back along the s1 direction and driven to translate again. Thus, the light spot BS repeatedly performs linear scanning in the s1 direction and movement in the s2 direction to scan the entire surface of the sample 101. Figure 3 Compared to the XY scanning method shown, Figure 2The rotary scanning method shown in this embodiment does not involve repeated acceleration and deceleration reciprocating motion, thus shortening the inspection time of sample 101.

[0045] -Illumination Optical System-

[0046] return Figure 1 The illumination optics system A has an assembly of optical elements for illuminating the sample 101 placed on the sample stage ST1 with the desired illumination light. (See description below.) Figure 1 As shown, the illumination optical system A includes a laser light source A1, an attenuator A2 (beam control mechanism), an emitted light adjustment unit A3 (beam control mechanism), a beam shaping unit A4 (beam control mechanism), a polarization control unit A5 (beam control mechanism), an illumination light observation unit A6, a focusing optical unit A7, a reflector A8, a reflector A9 (beam control mechanism), and a reflector A10.

[0047] Laser source

[0048] Laser source A1 is a unit that emits a laser beam as illumination light. When using the defect inspection device 100 to inspect minute defects near the surface of the sample 101, laser source A1 is a light source that uses a short-wavelength (wavelength below 355 nm) ultraviolet or vacuum ultraviolet light laser beam with high output (output above 2 W) that oscillates under ultraviolet or vacuum ultraviolet light, making it difficult to penetrate the interior of the sample 101. The diameter of the laser beam emitted by laser source A1 is typically about 1 mm. When using the defect inspection device 100 to inspect internal defects of the sample 101, laser source A1 is a light source that uses a visible or infrared laser beam with a long wavelength that easily penetrates the interior of the sample 101.

[0049] Attenuator

[0050] Figure 4This is a schematic diagram illustrating an example structure of attenuator A2. Attenuator A2 is a unit that attenuates the light intensity of illumination light from laser source A1. As an example, the attenuator A2 in this embodiment has a structure composed of a first polarizing plate A2a, a half-wavelength plate A2b, and a second polarizing plate A2c. The half-wavelength plate A2b is configured to rotate around the optical axis of the illumination light. After the illumination light incident on attenuator A2 is converted into linearly polarized light by the first polarizing plate A2a, its polarization direction is adjusted to the slow axis azimuth angle of the half-wavelength plate A2b and passes through the second polarizing plate A2c. By adjusting the azimuth angle of the half-wavelength plate A2b, the light intensity of the illumination light is attenuated at an arbitrary rate. Although the figure is omitted, a mechanism for adjusting the azimuth angle of the half-wavelength plate A2b is provided, and its drive is controlled by the control device E1. When the linear polarization degree of the illumination light incident on attenuator A2 is sufficiently high, the first polarizing plate A2a can be omitted. Attenuator A2 uses an attenuator whose relationship between the incident illumination light and the attenuation rate has been pre-calibrated. It should be noted that attenuator A2 is not limited to... Figure 4 The illustrated structure. For example, attenuator A2 can be constructed using an ND filter with a gradually varying concentration distribution. Alternatively, attenuator A2 can also be configured to adjust the attenuation effect by combining multiple ND filters of different concentrations.

[0051] • Emitted light adjustment unit

[0052] return Figure 1 The emitted light adjustment unit A3 is a unit that adjusts the position and angle of the optical axis of the illumination light attenuated by the attenuator A2. In this embodiment, the emitted light adjustment unit A3 has multiple reflectors A3a and A3b. It is configured such that the illumination light is reflected sequentially by the reflectors A3a and A3b. In this embodiment, the incident / emission surface of the illumination light relative to the reflector A3a is configured to be orthogonal to the incident / emission surface of the illumination light relative to the reflector A3b. The incident / emission surface is a surface that includes the optical axis of the light incident into the reflector and the optical axis of the light emitted from the reflector. In the case where the illumination light is incident into the reflector A3a in the +X direction, the schematic diagram is used... Figure 1 The difference is that, for example, the illumination light travels in the +Y direction through mirror A3a, and then changes its direction in the +Z direction through mirror A3b. In this example, the incident / exit surface of the illumination light relative to mirror A3a is defined as the XY plane, and the incident / exit surface of the illumination light relative to mirror A3b is defined as the YZ plane.

[0053] Although the illustrations are omitted, reflectors A3a and A3b are equipped with mechanisms for translating and tilting respectively (a four-axis structure). As such translation (offset) and tilting mechanisms, the emitted light adjustment unit A3 includes a stage for mounting reflectors A3a and A3b, and a motor or actuator for driving the stage. The driving of these translation and tilting mechanisms is controlled by a control device E1. With this structure, reflectors A3a and A3b can move parallel to, for example, the direction in which the illumination light is incident or emitted relative to itself, and tilt about the normal to the incident / emission surface. Thus, for example, with respect to the optical axis of the illumination light emitted from the emitted light adjustment unit A3 in the +Z direction, the offset and angle in the XZ plane and the offset and angle in the YZ plane can be adjusted independently. An example using two reflectors A3a and A3b is shown, but a structure using three or more reflectors is also possible.

[0054] • Beam shaping unit

[0055] The beam shaping unit A4 is a unit that arbitrarily magnifies or reduces the size of the incident illumination light. The beam shaping unit A4 is, for example, composed of a beam expander, a cylindrical lens, a deformable prism, or a combination thereof.

[0056] A Galilean-type beam expander using concave and convex lenses can be cited as an example. Although the illustration is omitted, the beam expander includes a lens spacing adjustment mechanism (zoom mechanism), which changes the magnification of the beam diameter by adjusting the lens spacing. The zoom mechanism, for example, includes a guide rail for mounting each lens and a motor that drives the guide rail. The motor of the zoom mechanism is controlled by a control device E1. The beam diameter magnification of the beam expander is, for example, about 5 to 10 times. In this case, if the beam diameter of the illumination light emitted from the laser source A1 is 1 mm, the beam diameter of the illumination light is expanded to about 5 to 10 mm. Even if the illumination light entering the beam expander is not a parallel beam, it can be collimated along with the beam diameter (quasi-parallelization of the beam) by adjusting the lens spacing. However, beam collimation can also be achieved by a collimating lens positioned upstream of the beam expander, separate from the beam expander.

[0057] It should be noted that the beam expander is mounted on a translation stage with two or more axes (two degrees of freedom), thus enabling its position to be adjusted so that its center is aligned with the incident illumination light. Furthermore, to ensure the incident illumination light is aligned with the optical axis, the beam expander also features tilt angle adjustment functionality along two or more axes (two degrees of freedom). The translation stage of the beam expander is controlled by control device E1.

[0058] In the case of using cylindrical lenses, one example is using two cylindrical lenses with different focusing distances. A cylindrical lens has the effect of focusing light only along one axis perpendicular to the optical axis. Therefore, by using two cylindrical lenses with different focusing distances, it is possible to change the dimension of any axial direction perpendicular to the incident optical axis, thereby forming an elliptical illumination beam shape. Similarly, a deformable prism can also change the dimension of any axial direction perpendicular to the incident optical axis, just like a cylindrical lens. By combining them, any shape of illumination beam can be formed.

[0059] • Polarization control unit

[0060] The polarization control unit A5 is an optical system that controls the polarization state of the illumination light. The polarization control unit A5 has a 1 / 2 wavelength plate A5a and a 1 / 4 wavelength plate A5b. For example, by using the polarization control unit A5 to make the illumination light P-polarized, the amount of scattered light from defects on the surface of the sample 101 can be increased compared to polarized light other than P-polarized light. When the scattered light from minute irregularities on the surface of the sample 101 (called haze) hinders the detection of minute defects, by making the illumination light S-polarized, the haze can be reduced compared to polarized light other than S-polarized light. The polarization control unit A5 can also make the illumination light circularly polarized, or a 45-degree polarized light intermediate between P-polarized and S-polarized light.

[0061] • Illumination observation unit

[0062] Figure 5 This is a schematic diagram illustrating an example of the structure of the illumination light observation unit A6. The illumination light observation unit A6 includes a beam sampler A6a, a semi-reflective mirror A6b, and two imaging elements A6c and A6d (a third and a fourth imaging element). The beam sampler A6a samples the illumination light emitted from the polarization control unit A5, and the sampled light is split by the semi-reflective mirror A6b. The split light then travels through different optical path lengths and is captured by the imaging elements A6c and A6d.

[0063] The beam sampler A6a is used to guide (sample) light of any quantity to the illumination light observation unit A6. As a beam sampler, optical elements with light-splitting capabilities, such as beam splitters, polarization beam splitters, and thin-film beam splitters, can also be used. The sampled light is split into two by a half-reflector. The half-reflector can be any optical element with light-splitting capabilities, such as a beam splitter, polarization beam splitter, or thin-film beam splitter.

[0064] The split lights respectively pass through different optical path lengths and are captured by imaging elements A6c and A6d. More specifically, when the optical path length from the half mirror A6b to the imaging element A6c is set as L1 and the optical path length from the half mirror A6b to the imaging element A6d is set as L2, the relationship of L1 < L2 is established. The reason for providing the illumination light observation unit A6 will be described later. The imaging elements A6c and A6d have the function of being able to capture one-dimensional or two-dimensional images of light. As an example, a high-speed and high-sensitivity camera equipped with a solid-state image receiving element such as a CCD, CMOS, or SPAD (Single Photon Avalanche Diode) can be cited. The imaging data of the imaging elements A6c and A6d is input into the signal processing device D.

[0065] ·Regarding oblique illumination

[0066] Figure 6 It is a schematic diagram showing the positional relationship between the optical axis of the illumination light guided to the surface of the specimen 101 by the illumination optical system A and the shape of the illumination intensity distribution. Figure 6 It schematically shows the cross-section of the specimen 101 cut by the incident surface of the illumination light incident on the specimen 101. The incident surface is a plane containing the optical axis OA of the illumination light incident on the specimen 101 and the normal line of the surface of the specimen 101. It should be noted that, in Figure 6 a part of the illumination optical system A is extracted for illustration, for example, the illustration of the outgoing light adjustment unit A3, the mirrors A8 to A10, and the illumination light observation unit A6 is omitted.

[0067] The illumination light emitted from the laser light source A1 is condensed by the condenser optical unit A7, reflected by the mirror A10, and obliquely incident on the specimen 101. In this way, the illumination optical system A is configured to obliquely incident the illumination light on the surface of the specimen 101. This oblique illumination controls the illumination intensity distribution within the incident surface by adjusting the light intensity with the attenuator A2, adjusting the shape of the illumination light with the beam shaping unit A4, and adjusting the polarized light with the polarization control unit A5. As shown in the illumination intensity distribution LD1 (illumination profile) in Figure 6 , the light spot formed on the specimen 101 has a Gaussian distribution-like light intensity distribution in the s2 direction, and the length of the beam width l1 defined by 13.5% of the peak is, for example, about 25 μm to 4 mm.

[0068] Furthermore, the incident angle of the oblique illumination relative to the sample 101 (the tilt angle of the incident optical axis relative to the normal of the sample surface) is adjusted by the position and angle of the reflectors A9 and A10 to an angle suitable for the detection of minute defects. The reflector A9 has two reflectors A9a and A9b, and a mechanism for adjusting their angles (not shown) (a four-axis structure). The angle of the reflector A10 is adjusted by the adjustment mechanism A10a. For example, the larger the incident angle of the illumination light relative to the sample 101 (the smaller the illumination elevation angle between the sample surface and the incident optical axis), the weaker the scattered light (haze) from the minute irregularities or patterns on the sample surface, which becomes noise relative to the scattered light from minute defects on the sample surface. From the viewpoint of suppressing the influence of haze on the detection of minute defects, the incident angle of the illumination light can be set to, for example, 75 degrees or more (elevation angle less than 15 degrees). On the other hand, in oblique illumination, the smaller the illumination incident angle, the greater the absolute amount of scattered light from tiny foreign objects. Therefore, from the viewpoint of seeking to increase the amount of scattered light from defects, the incident angle of the illumination light can be set to, for example, 60 degrees or more and 75 degrees or less (elevation angle of 15 degrees or more and 30 degrees or less).

[0069] -Detection Optical System-

[0070] return Figure 1 Explanation: Detection optical systems B1~Bn (n=1,2…) are units that focus the illumination scattered light from the sample surface. Detection optical systems B1~Bn have multiple optical elements, including a condenser lens (objective lens). The 'n' in detection optical system Bn represents the number of detection optical systems. Figure 1 Three detection optical systems B1 to B3 are shown. However, the number of detection optical systems B1 to Bn is not limited to a specific number; any one or more is acceptable.

[0071] -sensor-

[0072] Sensors C1 to Cn (n=1,2…) are sensors that convert the illumination scattered light converged by the corresponding detection optical systems B1 to Bn into electrical signals and output detection signals. Sensors C1, C2, and C3… correspond to detection optical systems B1, B2, and B3…, respectively. For these sensors C1 to Cn, single-pixel sensors such as photomultiplier tubes or SiPMs (silicon photomultiplier tubes) that perform photoelectric conversion of weak signals with high gain can be used. In addition, sensors with multiple pixels arranged in one or two dimensions, such as CCD sensors or CMOS sensors, are sometimes used for sensors C1 to Cn. The detection signals output from sensors C1 to Cn are continuously input to the signal processing device D.

[0073] -Control Device-

[0074] The control device E1 is a computer that uniformly controls the defect inspection device 100. The control device E1 includes a storage device including at least one of ROM, RAM, HDD, and SSD, a processing unit such as a CPU, GPU, or FPGA, and a timer. The control device E1 is connected to the input device E2, the monitor E3, and the signal processing device D via wired or wireless connection. The input device E2 is used by the user to input inspection condition settings into the control device E1. Various input devices such as a keyboard, mouse, and touch panel can be appropriately used as the input device E2.

[0075] The control device E1 receives the encoder output of the rotary stage and translation stage (the rθ coordinate of the light spot BS on the sample 101), and the inspection conditions input by the user via the input device E2. The inspection conditions include the type, size, shape, or material of the sample 101, the illumination conditions based on the illumination optical system A, and the detection conditions based on the detection optical system B and sensor C. Furthermore, the inspection conditions may include, for example, the sensitivity settings of each sensor C1 to Cn, the gain value for defect determination, the threshold, and the setting of the determination area (center angle α, etc.). When scanning the sample 101 in a rotary scanning manner, as described later, a difference is generated in the detection channel depending on the θ coordinate on the sample. The gain value, threshold, etc., can be set based on the θ coordinate and the coordinates within the die, taking into account this θ coordinate dependence. The detection channel is typically the output signals of sensors C1 to Cn, but may also include a subset of the output signals of these sensors C1 to Cn or a signal obtained by weighted summation of the output signals or subsets of sensors C1 to Cn. With the gain value and threshold set according to the θ coordinate and the internal coordinate of the bare die, the gain value and threshold change with the rotation period of the sample 101 for each detection channel.

[0076] In addition, the control device E1 outputs command signals instructing the operation of the worktable ST, the illumination optical system A, etc., according to the inspection conditions, or outputs the coordinate data of the spot BS synchronized with the defect detection signal to the signal processing device D. The control device E1 also enables the monitor E3 to display the inspection condition setting screen, the inspection data (inspection images, etc.) of the sample 101, etc. As inspection data, in addition to the final inspection result obtained by integrating the signals of each sensor C1 to Cn, the individual inspection results of each sensor C1 to Cn can also be displayed. In the inspection condition setting screen, a setting section can be displayed to set the aforementioned gain value, threshold, etc., according to the θ coordinate for each detection channel.

[0077] like Figure 1As shown, the control device E1 is sometimes connected to a DR-SEM (Defect Review-Scanning Electron Microscope) used for defect inspection via LAN or other means. In this case, the control device E1 can also receive defect inspection data from the DR-SEM and send it to the signal processing device D.

[0078] -Signal Processing Device-

[0079] The signal processing device D is a computer that processes the detection signals input from sensors C1 to Cn. Similar to the control device E1, the signal processing device D includes a storage device such as ROM, RAM, HDD, and SSD, and a computing device such as a CPU, GPU, or FPGA. The signal processing device D can be a single computer constituting a unit of the main body of the defect inspection device 100 (workbench ST, illumination optical system A, orthogonal reflection light observation unit F, detection optical systems B1 to Bn, sensors C1 to Cn, etc.). Alternatively, the signal processing device D can be composed of multiple computers connected to the defect inspection device 100 via a network. For example, it can be configured such that a computer attached to the main body of the defect inspection device 100 acquires the defect detection signals from the main body of the device, processes the detection data as needed, and sends it to a server, where the server performs defect detection, classification, and other processing.

[0080] -Observation Unit for Positive Reflection Light-

[0081] Figure 7 This is a schematic diagram illustrating a structural example of the orthographic reflection observation unit F. The orthographic reflection observation unit F includes a collimating lens F1, an attenuator F2, a semi-reflective mirror F3, two imaging elements F4a and F4b (a first imaging element and a second imaging element), and a condenser lens F5. Light converged onto the surface of the sample 101 by the illumination optical system A is reflected from the surface of the sample 101 and enters the orthographic reflection observation unit F. The light reflected from the surface of the sample 101 and diverging becomes parallel light through the collimating lens F1. This parallel light then passes through the attenuator F2 and is split into two (light 1 and light 2) by the semi-reflective mirror F3. The split light 1 (the first beam) is captured by the imaging element F4a while remaining parallel. On the other hand, the split light 2 (the second beam) is focused by the condenser lens F5 and captured by the imaging element F4b.

[0082] Collimating lens F1 is used to parallelize the divergent, orthogonal reflected light from sample 101 and guide it to imaging elements F4a and F4b. It is not limited to collimating lens; it can also be an optical element with the function of generating parallel light, such as a cylindrical lens or a parabolic mirror. The amount of transmitted light after parallelization is adjusted by attenuator F2. This is to adjust the brightness when the imaging elements F4a and F4b take pictures. In the optical inspection apparatus, the amount of light incident on the surface of sample 101 varies depending on the defect size of the object being inspected. Therefore, considering the amount of light incident on the surface of sample 101 and the dynamic range of the imaging elements, the amount of light transmitted through attenuator F2 is appropriately adjusted. Attenuator F2 needs to have variable transmittance according to the amount of light incident on the surface of sample 101; therefore, in addition to an attenuator, it can also be an ND filter with a gradient.

[0083] The semi-reflective mirror F3 is used to split the positively reflected light into two beams that are respectively incident on the imaging elements F4a and F4b. Here, the semi-reflective mirror F3 can be any optical element with the function of splitting light, such as a beam splitter, polarizing beam splitter, or thin-film beam splitter.

[0084] Image sensors F4a and F4b are capable of capturing one-dimensional or two-dimensional images of light. Examples include high-speed, high-sensitivity cameras equipped with solid-state image receiving elements such as CCD, CMOS, or SPAD (Single Photon Avalanche Diode). Furthermore, this embodiment describes the case where two image sensors are used, but more than two image sensors are also possible.

[0085] <Reasons for setting up the illumination and observation unit>

[0086] Figure 8A and Figure 8B This diagram illustrates the rationale for setting up the illumination light observation unit A6. As described above, the illumination light sampled from the illumination optical system A by the beam sampler A6a is divided by the semi-reflective mirror A6b. At this time, the light passing through the short optical path (optical path length L1) is captured by the imaging element A6c, and the light passing through the long optical path (optical path length L2) is captured by the imaging element A6d. Figure 8A This indicates the reference state where the optical axis and beam size have been adjusted according to the specifications. In this reference state, the brightness distribution when shooting with image sensor A6c is set to Im1, and the brightness distribution when shooting with image sensor A6d is set to Im2. At this time, the beam position (near beam position) of brightness distribution Im1 is set to X1, and the beam size is set to d1. The beam position (far beam position) of brightness distribution Im2 is set to X2, and the beam size is set to d2.

[0087] Figure 8BThe diagram illustrates the changes in at least one of the optical axis and beam size from a reference state. In this changed state, the brightness distribution captured by image sensor A6c is defined as Im3, and the brightness distribution captured by image sensor A6d is defined as Im4. At this time, the beam position (near beam position) of brightness distribution Im3 is defined as X3, and the beam size as d3. The beam position (far beam position) of brightness distribution Im4 is defined as X4, and the beam size as d4. It should be noted that the brightness distribution is described as one-dimensional, but two-dimensional representations are also considered.

[0088] At this point, the optical axis tilt T relative to the reference state is calculated as T = arctan((X4-X3)-(X2-X1)) / (L2-L1). The optical axis offset S relative to the reference state is calculated as S = (X4-X2)-L2sin(T) = (X3-X1)-L1sin(T). The change in the beam divergence angle θ relative to the reference state is calculated as θ = arctan((d4-d3)-(d2-d1)) / (2*(L2-L1)). The change in the magnification M relative to the reference state is calculated as M = (d4-d2) / 2-L2sin(θ) = (d3-d1) / 2-L1sin(θ). Furthermore, the total brightness of the image obtained by the imaging element A6c or A6d is proportional to the power of the illumination light. Therefore, when the total brightness of brightness distribution Im1 is set as IS1 and the total brightness of brightness Im3 is set as IS2, the change in beam power W of the changing state relative to the reference state is calculated as W = IS2 / IS1. These calculations can be performed by the signal processing device D.

[0089] In this way, by setting up the illumination light observation unit A6, it is possible to obtain the optical axis offset, tilt, divergence angle change, magnification change, and power change of the illumination optical system A relative to the reference state. Using this information, the illumination light can be corrected.

[0090] Figure 9 This diagram illustrates an example of the illumination light correction process. In step S11, the control device E1 determines whether the total brightness is within a specified (adjustment specification) range. If not, the process proceeds to step S12. If yes, the process proceeds to step S13. In step S12, the control device E1 controls the attenuator A2 based on information about the beam power change W obtained from the signal processing device D, thereby correcting the illumination light power.

[0091] In step S13, the control device E1 determines whether the beam position is within the specified (adjustment specification) range. If not, the process proceeds to step S14. If yes, the process proceeds to step S15. In step S14, the control device E1 controls the emitted light adjustment unit A3 based on the optical axis tilt amount T to correct the tilt amount of the illumination light. Additionally, the control device E1 controls the emitted light adjustment unit A3 based on the optical axis offset amount S to correct the offset amount of the illumination light. Thus, the basic optical axis of the illumination light is corrected. Alternatively, the tilt and offset of the emitted light adjustment unit A3 can also be adjusted based on the optical axis offset at the near beam position and the optical axis tilt amount at the far beam position.

[0092] In step S15, the control device E1 determines whether the beam size is within the specified (adjustment specification) range. If not, the process proceeds to step S16. If yes, the process proceeds to step S17. In step S16, the control device E1 controls the lens spacing adjustment mechanism of the beam shaping unit A4 (beam expander) based on the magnification change M to correct the beam size of the illumination light.

[0093] In step S17, the control device E1 determines whether the beam size ratio (divergence angle change) is within the specified (adjustment specification) range. If not, the process proceeds to step S18. If yes, the illumination light adjustment process ends. In step S18, the control device E1 controls the beam shaping unit A4 (beam expander) based on the divergence angle change θ to correct the divergence angle (collimation) of the illumination light. If the divergence angle is corrected, the size of the illumination light also changes, so the size of the illumination light needs to be corrected again after the divergence angle is corrected. Therefore, after step S18 is performed, the process of step S16 is performed again.

[0094] If the specified adjustment specifications are not met even after implementing the aforementioned series of corrections, the control device E1 determines that the device is in an abnormal state and outputs an error to the monitor E3. This prompts the user of the defect inspection device 100 to perform device maintenance, etc. It should be noted that the timing for the power adjustment in steps S11 and S12 can be... Figure 9 The process can be changed arbitrarily.

[0095] In this way, by setting up the illumination light observation unit A6, the optical axis offset, tilt, size, divergence angle, and power of the illumination light can be efficiently corrected, thus contributing to the stabilization of the illumination light. In particular, the correction of offset and tilt makes the optical axis of the illumination light incident on the beam shaping unit A4 consistent with the optical axis of the expander, etc., thereby achieving the effect of suppressing aberrations.

[0096] <Reasons for setting up the positive reflection light observation unit>

[0097] The rationale for providing the orthogonal reflection observation unit F will be explained. As described above, light passing through the focusing optical unit A7 is reflected from the surface of the sample 101 and enters the orthogonal reflection observation unit F. The focusing optical unit A7 includes a lens, a parabolic mirror, a cylindrical lens, and their driving mechanism. In optical inspection apparatuses, since a light spot of tens to hundreds of μm is formed on the surface of the sample 101, the shape and position of the light spot have a significant impact on the inspection results. When the axis of the focusing optical unit A7 is not aligned with the incident optical axis of the illumination light, aberrations occur, thereby changing the shape and position of the light spot. Furthermore, when the illumination light enters the optical element and is transmitted and reflected, due to the manufacturing and adjustment errors of the optical element itself, an increase in wavefront aberrations that is undesirable in the design occurs. If the wavefront aberration increases, the focusing performance of the illumination light deteriorates, resulting in an increase in the size and shape of the light spot. Therefore, in this embodiment, the orthogonal reflection observation unit F is used to stabilize the light focused on the surface of the sample 101. Furthermore, the reason for using the positive reflection light observation unit F to perform the correction of the illumination optical system A separately from the correction of the illumination optical system A by the illumination light observation unit A6 is to (1) make the optical axis of the light incident on the condensing optical unit A7 coincide with the axis of the condensing optical unit A7 to suppress aberrations, and (2) correct the thermal expansion of the optical system or its holding parts caused by internal thermal fluctuations, or the optical axis deviation after the illumination light observation unit A6 caused by mechanical vibration.

[0098] Figures 10A-10C This diagram illustrates the orthographic reflection observation unit F. The orthographic reflection observation unit F has an imaging optical system. For example, let the focal length of the condenser optical unit A7 be f1. Let the focal length of the collimating lens F1 be f2. Let the focal length of the condenser lens F5 be f3. Then, the distance from the condenser optical unit A7 to the collimating lens F1 is f1 + f2. The distance from the collimating lens F1 to the condenser lens F5 is f2 + f3. The distance from the condenser lens F5 to the imaging element F4b is set to f3. However, for example, the distance between the lenses may vary slightly depending on the refractive index of the optical elements inside the orthographic reflection observation unit F, such as the attenuator F2. Furthermore, the distance from the collimating lens F1 to the imaging element F4a can be arbitrary.

[0099] Figure 10A The diagram illustrates the case where the optical axis OA of the light incident on the condenser lens F5 is deflected. In this case, the position of the image of the imaging element F4b (the position of the condenser beam) remains unchanged, while only the position of the image of the imaging element F4a (the position of the parallel beam) changes. Therefore, the signal processing device D calculates the amount of deflection of the light before it enters the condenser lens F5 based on the position of the image of the imaging element F4a.

[0100] Figure 10BThe diagram illustrates the case where the optical axis OA of the light incident on the condenser lens F5 is tilted. In this case, the positions of the images of image elements F4a and F4b change, therefore the tilt amount is calculated.

[0101] Figure 10C The case where the position of the focusing optical unit A7 deviates in the optical axis direction is shown. In this case, the amount of focusing position deviation is calculated based on the deviation of the focusing point from the surface of the sample 101, the size of the image of the imaging element F4a (short axis beam size), and the size of the image of the imaging element F4b (long axis beam size).

[0102] In this way, by setting up the positive reflection light observation unit F, it is possible to obtain the optical axis offset, optical axis tilt, and focusing position deviation of the light before it enters the focusing optical unit A7. By using this information, it is possible to correct the light entering the focusing optical unit A7.

[0103] Figure 11 This diagram illustrates an example of the correction process for light incident on the focusing optical unit A7. In step S21, the control device E1 determines whether the beam position is within a specified (adjustment specification) range. If not, the process proceeds to step S22. If yes, the process proceeds to step S23. In step S22, the control device E1 controls the reflector A9 based on the tilt amount obtained from the signal processing device D to correct the tilt. Additionally, the control device E1 controls the reflector A9 based on the offset amount to correct the offset.

[0104] In step S23, the control device E1 determines whether the beam size is within the specified (adjustment specification) range. If not, the process proceeds to step S24. If yes, the correction process ends. In step S24, the control device E1 controls at least one of the parabolic mirror and cylindrical lens (at least one of these drive mechanisms) of the focusing optical unit A7 based on the focusing position deviation to correct the focusing position.

[0105] In this way, by setting the orthogonal reflection light observation unit F, it is possible to correct the tilt, offset, and focusing position deviation of the light incident on the focusing optical unit A7. As a result, it helps to stabilize the light spot formed on the surface of the sample 101. Moreover, the orthogonal reflection light observation unit F can observe the orthogonal reflection light during the inspection of the silicon wafer, thus having the advantage of being able to perform corrections during inspection.

[0106] Figure 12This diagram illustrates an example of the beam position correction process during wafer inspection. Wafer inspection is performed, for example, after the correction of the basic optical axis of the illumination light and the correction of the light incident on the focusing optical unit A7, as described above. After wafer inspection begins, in step S31, the control device E1 determines whether the beam position is within a specified (adjustment specification) range. If not, the process proceeds to step S32. If yes, the correction process ends. In step S32, the control device E1 controls the reflector A9 to correct tilt based on the focusing beam position obtained from the signal processing device D. It should be noted that only tilt correction during inspection is illustrated, but offset correction or correction of the focusing position deviation can also be performed additionally or alternatively.

[0107] <Summary of the First Implementation>

[0108] As described above, the defect inspection apparatus 100 of the first embodiment includes: an illumination optical system A, which illuminates the surface of a sample 101 with illumination light (beam) emitted from a laser source A1 through a focusing optical unit A7; a positive reflection light observation unit F, which monitors the positive reflection light from the surface of the sample 101; and a control device E1, which controls the illumination optical system A based on the monitored positive reflection light. The illumination optical system A includes a laser source A1, an attenuator A2 (beam control mechanism), an emitted light adjustment unit A3 (beam control mechanism), a beam shaping unit A4 (beam control mechanism), a polarization control unit A5 (beam control mechanism), a reflector A9 (beam control mechanism), and a focusing optical unit A7. The positive reflection light observation unit F includes: an imaging element F4a (first imaging element); an imaging element F4b (second imaging element); and a semi-reflective mirror F3 (first light splitting element), which splits the positive reflection light into a first beam and a second beam, which are respectively incident on the imaging elements F4a and F4b. Based on the position or size information (parallel beam position, short axis beam size) of light 1 (first beam) received by camera element F4a and the position or size information (focusing beam position, long axis beam size) of light 2 (second beam) received by camera element F4b, control device E1 independently controls at least one of the offset, tilt and focusing position of the beam incident on the focusing optical unit A7 via mirror A9 or focusing optical unit A7 (beam control mechanism).

[0109] This allows for the stabilization of the position, size, and intensity of the light spot formed on the surface of the sample 101. Consequently, the defect detection sensitivity of the defect inspection apparatus 100 and the coordinate accuracy of the detected defects can be stabilized. For example, as in Patent Document 1, when observing a light spot using an observation optical system positioned perpendicular to the wafer surface, it is necessary to scatter the laser light in a direction perpendicular to the wafer surface. In silicon wafers used in semiconductor manufacturing processes, the amount of light scattered in a direction perpendicular to the wafer surface is small, thus requiring the use of wafers with treated material and surface roughness for observation. In contrast, the defect inspection apparatus 100 according to this embodiment uses positively reflected light, eliminating the need for preparing additional wafers for spot observation or transporting such additional wafers. Therefore, the inspection throughput is not reduced. Furthermore, the ability to correct the beam during the inspection of the sample 101 also contributes to increased throughput.

[0110] [Second Implementation]

[0111] Aberrations that cause variations in the shape or position of the light spot on the surface of the sample 101 occur when the axis of the focusing optical unit A7 is not aligned with the incident optical axis of the illumination light, or when the surface shape of the optical element is spherical. In the second embodiment, the structure of the defect inspection device 100 will be described, which incorporates a control mechanism for handling such aberrations, namely, "wavefront aberration (the deviation of the actual wavefront from the ideal wavefront)".

[0112] The wavefront refers to the phase distribution of light, a characteristic of the illumination light itself. When illumination light enters an optical element and is transmitted and reflected, undesirable wavefront aberrations can increase due to manufacturing or adjustment errors in the optical element. The enlargement or deformation of the light spot size manifests as a deterioration in the focusing performance of the illumination light due to the increased wavefront aberrations. Wavefront aberrations are elements that cannot be controlled by the correction of tilt, offset, and focusing position deviation as described in the first embodiment. As will be discussed later, a more flexible light spot adjustment is possible by incorporating a wavefront aberration control mechanism.

[0113] Figure 13This is a schematic diagram showing the structure of the illumination optical system A and the orthographic reflection light observation unit F of the defect inspection apparatus according to the second embodiment. The wavefront aberration control mechanism of this embodiment includes a wavefront control element G1 and a wavefront observation element G2. The wavefront control element G1 is an element used to change / control the wavefront of the illumination light; for example, any deformable optical element will suffice. The light-incidence surface of the deformable element is deformed by an actuator. By changing the wavefront of the light in a way that reduces wavefront aberration through deformation, the focusing performance of the illumination light can be stabilized. Deformable elements are broadly classified into transmissive and reflective types. Transmissive deformable elements can be simply lenses or phase plates, resulting in a simple optical path, but there is a difficulty in improving the durability of light intensity. Low durability hinders the increase of the amount of illumination light on defects on the surface of the sample 101, making it unsuitable for a defect inspection apparatus. On the other hand, reflective deformable elements are mirrors, increasing the area occupied by the optical path, but in addition to the expected durability, there is a tendency for the wavefront control area to be wider than that of transmissive types. Therefore, a reflective deformable element (deformable mirror) is preferably used as the wavefront control element G1. The actuator for the deformable mirror can be, for example, a stacked piezoelectric element, a dual piezoelectric wafer type piezoelectric element, a MEMS, or a voice coil motor; any of these can be used. Furthermore, the wavefront control element G1 is included in the illumination optical system A in the optical path and can be placed in any position as long as it can be properly controlled. In the case based on the first embodiment, for example... Figure 13 As shown, the wavefront control element G1 can be positioned downstream of the beam shaping unit A4. Because it is a reflective type, simple reflectors G1a and G1b are positioned before and after the wavefront control element G1, and the optical path is not a straight line.

[0114] The wavefront observation element G2 is also called a wavefront sensor. Used in conjunction with the wavefront control element G1, it observes the wavefront of the illumination light and stores the data in the signal processing device D. Based on the data obtained from the wavefront observation element G2, the signal processing device D calculates the wavefront of the target used for spot stabilization. As the wavefront sensor, any type of element can be used, such as a Shaker-Hartmann sensor, a wavefront curvature sensor, or a pyramid sensor. Many general cameras incorporate elements with structures for wavefront measurement, thus also having the function of capturing only the illumination light. In this wavefront sensor, any solid-state image receiving element can be used, such as a CCD, CMOS, or SPAD. Ideally, the wavefront sensor can observe the wavefront of the illumination light just before it focuses. Therefore, it is sufficient to place it as downstream of the optical path as possible. In the case based on the first embodiment, for example... Figure 13As shown, in the positive reflection light observation unit F, the imaging element F4a that allows the split light 1 (parallel light) to enter can be replaced by a wavefront observation element G2 (wavefront sensor). This is because, as mentioned above, the wavefront sensor can also be used as an imaging element.

[0115] The wavefront of the normally reflected light is constantly observed using the wavefront observation element G2. That is, in the normally reflected light observation unit F, in addition to the optical axis offset, optical axis tilt, and focusing position deviation of the light before it enters the focusing optical unit A7, the wavefront aberration of the light is also obtained. When using this information to correct the illumination light, a step of controlling the wavefront is added to the correction process.

[0116] Figure 14 This diagram illustrates an example of the correction process for light incident on the focusing optical unit A7 in the second embodiment. Figure 14 As shown, basically with Figure 11 The correction process is the same. However, the parallel beam position used in the beam position correction in step S22 is obtained from the wavefront observation element G2 (the camera device) instead of from the imaging device F4a, which is different from the previous process. Figure 11 Different. Furthermore, in the correction of the focusing position in step S24, the wavefront control element G1 (deformable mirror) is controlled based on the wavefront information of the illumination light (beam) obtained from the additional wavefront observation element G2 (camera device).

[0117] In this way, by setting up a wavefront aberration control mechanism (wavefront control element G1 and wavefront observation element G2), it is also possible to correct for illumination light that cannot be handled in the first embodiment, thereby improving its focusing performance. As a result, the size and shape of the light spot on the surface of the sample 101 can be further stabilized.

[0118] [Variation Example]

[0119] This disclosure is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are detailed for the purpose of easily understanding and illustrating this disclosure, and do not necessarily require all of the described structures. Furthermore, a portion of an embodiment can be replaced with the structure of another embodiment. Additionally, structures of other embodiments can be added to the structure of a certain embodiment. Furthermore, for a portion of the structure of each embodiment, a portion of the structure of another embodiment can be added, deleted, or replaced.

[0120] Explanation of reference numerals in the attached figures:

[0121] 100…Defect Inspection Device

[0122] 101…sample

[0123] A… Illumination Optical System

[0124] B1~B3…Detection Optical System

[0125] C1~C3…sensors

[0126] D…signal processing device

[0127] E1…Control device.

Claims

1. An optical inspection apparatus that inspects a sample based on light reflected or scattered from its surface, characterized in that, The optical inspection device includes: An illumination optical system having a light source, a beam control mechanism, and a focusing optical unit, wherein a beam emitted from the light source is irradiated onto the surface of the sample through the focusing optical unit; An orthogonal reflection observation unit monitors orthogonal reflections from the surface of the sample; and A control device controls the illumination optical system based on the orthoreflected light monitored by the orthoreflected light observation unit. The positive reflection light observation unit has: First camera element; Second camera element; and A first light splitting element splits the positively reflected light so that it is respectively incident on the first imaging element and the second imaging element. The control device, based on the position or size information of the first beam received by the first camera element and the position or size information of the second beam received by the second camera element, independently controls at least one of the offset, tilt, and focusing position of the beam incident on the focusing optical unit through the beam control mechanism.

2. The optical inspection device according to claim 1, characterized in that, The illumination optical system also includes wavefront control elements.

3. The optical inspection device according to claim 2, characterized in that, The second imaging element includes a wavefront sensor.

4. The optical inspection device according to claim 2, characterized in that, The beam control mechanism includes a size control mechanism configured to adjust the size of the beam emitted from the light source. The wavefront control element is positioned immediately following the size control mechanism.

5. The optical inspection device according to claim 1, characterized in that, The positive reflection light observation unit also includes a light-concentrating element disposed between the second camera element and the light splitting element.

6. The optical inspection apparatus according to claim 1, characterized in that, The focusing optical unit and the positive reflection light observation unit constitute an imaging optical system.

7. The optical inspection apparatus according to claim 1, characterized in that, The illumination optical system further includes an illumination light observation unit, which comprises: a third camera element and a fourth camera element that monitor the light beam; and a second light splitting element that splits the light beam and directs it onto the third camera element and the fourth camera element respectively. The third camera element is positioned closer to the light source than the fourth camera element. The control device, based on information about the intensity, position, or size of the third beam received by the third camera element and information about the intensity, position, or size of the fourth beam received by the fourth camera element, independently controls, through the beam control mechanism, at least one of the following: the offset, tilt, intensity, size, and divergence angle of the beam incident on the focusing optical unit.

8. The optical inspection apparatus according to claim 1, characterized in that, The beam control mechanism includes at least one of the beam intensity control mechanism, position control mechanism, angle control mechanism, and size control mechanism.

9. An optical inspection method, performed by an optical inspection device that inspects the sample based on light reflected or scattered from the surface of the sample, characterized in that... The optical inspection device includes: An illumination optical system comprising a light source, a beam control mechanism, and a focusing optical unit, wherein a beam of light emitted from the light source is directed through the focusing optical unit to illuminate the surface of the sample; and Control device, which controls the illumination optical system The illumination optical system further includes an illumination light observation unit, which has the following features: A first camera element and a second camera element monitor the light beam; and A light splitting element that divides the light beam and directs it onto the first imaging element and the second imaging element respectively. The first camera element is positioned closer to the light source than the second camera element. The optical inspection method includes: The control device acquires information on the intensity, position, or size of the first beam received by the first camera element and information on the intensity, position, or size of the second beam received by the second camera element; and The control device controls the beam control mechanism based on the acquired information, thereby independently controlling at least one of the following: the deflection, tilt, intensity, size, and divergence angle of the beam incident on the focusing optical unit.

Images