Method for evaluating substrate and device for evaluating substrate

Abstract

Provided is a technique for more suitably inspecting an anisotropic object in a substrate by using a laser light scattering method.　For each measurement region on a substrate surface, scattered light is measured using an optical system in a first direction and a second direction with reference to the measurement region to obtain first measurement data and second measurement data, and the first measurement data and the second measurement data are combined to generate composite data.

Description

Substrate evaluation method and substrate evaluation device

[0001] The present invention relates to a method and apparatus for evaluating a substrate using a laser light scattering method.

[0002] During the manufacturing and processing processes, semiconductor and other substrates can develop foreign particles on their surfaces or defects on their surfaces or inside. Since foreign particles and defects on substrates can lead to defective products, technology to evaluate substrates is essential. For example, in semiconductor devices manufactured using semiconductor substrates, the presence of foreign particles and defects can lead to reduced device performance or device malfunction.

[0003] In substrate inspection using the laser light scattering method, the surface or internal condition of a substrate can be inspected by irradiating the surface of the substrate with laser light and measuring the scattered light. In full-surface substrate inspection, a commonly used method is to scan the two-dimensional surface of the substrate with laser light and measure the scattered light generated in each area of ​​the substrate.

[0004] In substrate inspection using the laser light scattering method, the anisotropy of the object to be inspected affects the measurement data. In order to thoroughly inspect objects that are difficult to detect due to the anisotropy of the object to be inspected, Patent Document 1 describes the following surface condition inspection device.

[0005] In Patent Document 1, a surface condition inspection device for a flat substrate, which scans a surface of a flat substrate placed on an X-axis or Y-axis stage with a laser beam irradiated by a light projection system in either the X-axis or Y-axis direction by the X-axis or Y-axis stage, and sends the laser beam in an axial direction perpendicular to the scanning direction at predetermined intervals while receiving scattered light from the surface with a light receiving system, and inspects the entire surface condition of the flat substrate based on a detection signal corresponding to the intensity of the received light, includes at least two light projection systems that irradiate the surface of the flat substrate from different directions at a predetermined angle of incidence with respect to the substrate normal of the flat substrate on the surface side of the flat substrate, and a detection signal corresponding to the incident point of the laser beam, which is provided on the surface side and is opposite to the light projection systems the laser beam shaping means for shaping the laser beams so that the laser beam irradiation areas where the laser beams are irradiated onto the surface of the flat substrate are rectangular; irradiation area separation adjusting means for adjusting the light projecting systems and the light receiving systems so that the separation between the rectangular laser beam irradiation areas is a projection length of the rectangle in the scanning direction or a non-overlapping length where the laser beam irradiation areas do not overlap; and feed interval adjusting means for adjusting a predetermined interval fed in the axial direction to be equal to or greater than the projection length or the non-overlapping length, or to an integer multiple of the projection length or the non-overlapping length.

[0006] Japanese Patent Application Laid-Open No. 2015-075339

[0007] As a result of further investigation into the above-mentioned technology, the inventors have invented a method for improving the influence of anisotropy of a substrate on measurement and enabling more appropriate evaluation in substrate evaluation using laser light scattering. An object of the present invention is to provide a technology for more appropriately inspecting anisotropic objects on a substrate using laser light scattering.

[0008] [1] A method for evaluating a substrate using a laser light scattering method, comprising: a measuring step of measuring scattered light for each measurement area on the substrate surface using optical systems located in a first direction and a second direction relative to the measurement area to obtain first measurement data and second measurement data; and a combining step of combining the first measurement data and the second measurement data to generate combined data. [2] The substrate evaluation method according to [1], wherein the first direction and the second direction are different in-plane directions of the substrate. [3] The substrate evaluation method according to [1] or [2], wherein the first direction and the second direction are orthogonal in-plane directions. [4] The substrate evaluation method according to any of [1] to [3], wherein the optical system includes a light-receiving optical system that receives scattered light generated by the substrate, and the measuring step comprises measuring the scattered light using the light-receiving optical systems located in the first direction and the second direction relative to the measurement area to obtain the first measurement data and the second measurement data. [5] The evaluation method according to any one of [1] to [3], wherein the optical system includes a projection optical system that irradiates the surface of the substrate with laser light, and the measurement step uses the projection optical system in the first direction and the second direction relative to the measurement area to measure the scattered light generated, respectively, to obtain the first measurement data and the second measurement data. [6] The evaluation method according to any one of [1] to [5], wherein the measurement step includes measuring scattered light in each of the measurement areas of the substrate by scanning the surface of the substrate with laser light. [7] The evaluation method according to [6], wherein the first direction and the second direction are set relative to the scanning direction. [8] The evaluation method according to [6] or [7], wherein the measurement area is set so that its longitudinal direction is inclined relative to the scanning direction. [9] The evaluation method according to any one of [1] to [8], wherein the measurement step includes irradiating the surface of the substrate with laser light while rotating the substrate in an in-plane direction, and measuring the scattered light.

[10] The substrate evaluation method according to [9], wherein the measuring step irradiates the laser light on a rotational orbit of the substrate by rotating the substrate in an in-plane direction, and the in-plane direction of the first direction and the in-plane direction of the second direction are set at a first angle and a second angle with respect to the rotational orbit.

[11] The substrate evaluation method according to any of [1] to

[10] , wherein the measuring step includes a first measuring step and a second measuring step, wherein the first measuring step and the second measuring step measure scattered light by changing an orientation of the measurement area with respect to the optical system, the position of which is fixed, to thereby obtain the first measurement data and the second measurement data, and the combining step aligns positional information of the first measurement data and the second measurement data to generate the combined data.

[12] The substrate evaluation method according to

[11] , wherein the first measurement step involves scanning the substrate with a laser beam while rotating it in an in-plane direction and moving it in a first movement direction to obtain first measurement data, and the second measurement step involves scanning the substrate with a laser beam while rotating it in an in-plane direction and moving it in a second movement direction different from the first movement direction to obtain second measurement data.

[13] The substrate evaluation method according to

[11] or

[12] , wherein the second measurement step starts measurement in a state where the substrate is rotated 90 degrees or 270 degrees from the start of measurement in the first measurement step.

[14] The substrate evaluation method according to any of

[11] to

[14] , wherein the first measurement step and the second measurement step measure scattered light using the same optical system.

[15] The substrate evaluation method according to any of [1] to

[14] , wherein the measurement area is linear or rectangular.

[16] A substrate evaluation device using a laser light scattering method, comprising: a light projection optical system that irradiates a substrate with laser light; a light receiving optical system that measures scattered light; a stage having a three-axis drive unit that moves the substrate in a plane; and a control unit that controls movement of the stage to a reference position for the substrate that is a start position for each of a first measurement and a second measurement.

[17] The substrate evaluation device according to

[16] , wherein the stage further comprises a rotation drive unit that rotates the substrate, and the control unit controls planar movement of the stage by the three-axis drive unit in different feed directions for the first measurement and the second measurement while rotating the stage by the rotation drive unit.

[18] The substrate evaluation device according to

[16] or

[17] , wherein the control unit aligns the positions of two measurement data measured by moving the stage in the first movement direction and the second movement direction, and combines them into combined data.

[0009] According to the invention of [1], composite data of measurement data from two directions on a substrate can be generated, and a substrate including an anisotropic inspection target can be evaluated with high accuracy.

[0010] According to the invention [2], it is possible to accurately evaluate a substrate including an inspection object that is anisotropic in the in-plane direction.

[0011] According to the invention [3], measurement data with the maximum amount of information can be obtained in two directions.

[0012] According to the invention related to [4], by receiving scattered light in two directions, it is possible to accurately evaluate a substrate including an anisotropic inspection object.

[0013] According to the invention related to [5], scattered light is generated in two directions and the scattered light is measured, thereby enabling a substrate including an anisotropic inspection object to be evaluated with high precision.

[0014] According to the invention of [6], by scanning the laser light, the scattered light in each of the plurality of measurement regions can be measured, and the scattered light over the entire surface of the substrate can be evaluated.

[0015] According to the invention of [7], by setting two directions with respect to the scanning direction and performing scanning, measurement data in two directions can be obtained over the entire surface of the substrate.

[0016] According to the invention of [8], the width of the measurement area is widened for scanning, thereby shortening the scanning time.

[0017] According to the invention of [9], scattered light can be measured at high speed over the entire surface of the substrate by irradiating the laser light with rotation.

[0018] According to the invention of

[10] , measurement is performed by setting two angles with respect to the rotation orbit, so that measurement data can be obtained in two directions over the entire surface of the substrate.

[0019] According to the invention of

[11] , by changing the orientation of the measurement area in the two measurement steps, it becomes possible to obtain measurement data with one optical system.

[0020] According to the invention of

[12] , measurement data in two directions can be obtained by rotating and moving the substrate.

[0021] According to the invention of

[13] , the substrate is rotated at the start of measurement, so that measurement can be started in a state where the substrate position is aligned.

[0022] According to the invention described in

[14] , it is possible to suppress differences in the results of measurement data due to individual differences in optical systems.

[0023] According to the invention of

[15] , the width of the measurement area is widened for measurement, so that the measurement can be completed in a short time.

[0024] According to the invention of

[16] , when two different measurement data are measured, it is possible to realize stage control to a position suitable for alignment.

[0025] According to the invention of

[17] , by moving the stage in different feed directions during rotational scanning, it is possible to obtain results of measuring scattered light in different directions for a certain region of the substrate.

[0026] According to the invention of

[18] , by aligning the positions of two different measurement data, it is possible to generate composite data for evaluating a substrate including an anisotropic test object.

[0027] According to the present invention, it is possible to provide a technique for more suitably inspecting an anisotropic object on a substrate by using a laser light scattering method.

[0028] 1 is a schematic diagram of a substrate evaluation method; a configuration diagram of an evaluation device; a schematic diagram of a measurement area according to an embodiment; a schematic diagram of a measurement area according to an embodiment; a schematic diagram of a measurement process according to Example 1; a schematic diagram of a measurement process according to Example 2; a schematic diagram of a measurement process according to Example 3; a diagram showing the direction in which strong scattered light is measured in each measurement process; an explanatory diagram of a measurement process during scanning; an explanatory diagram of a position alignment process; an example of measurement data; an example of combined data.

[0029] Preferred embodiments of a substrate evaluation method and a substrate evaluation device according to the present invention will be described in detail below with reference to the accompanying drawings. The technical scope of the present invention is not limited to the embodiments shown in the accompanying drawings, and appropriate modifications are possible within the scope of the claims. In the following description of the embodiments and the accompanying drawings, similar components are designated by the same reference numerals, and duplicated explanations will be omitted.

[0030] 1 is a schematic explanatory diagram of a substrate evaluation method according to the present invention. As shown in FIG. 1, an evaluation device 1 includes a light projecting optical system 10 and a light receiving optical system 20.

[0031] The light projection optical system 10 includes a laser output unit 11, a filter 12, a wave plate 13, and a condenser lens 14.

[0032] The light receiving optical system 20 includes an objective lens 21, an imaging lens 22, a slit 23, and a light receiving sensor 24. The light receiving sensor 24 converts the intensity of the scattered light into an electrical signal to generate measurement data.

[0033] The substrate 100 may be a semiconductor wafer, a mask, a disk substrate, a liquid crystal substrate, a glass substrate, a transparent film, etc. In this embodiment, an example in which the substrate 100 is a semiconductor single crystal will be described in particular.

[0034] The substrate 100 includes, as inspection targets, surface inspection targets such as fine dust particles and other foreign matter attached to the surface, scratches, cracks, and surface irregularities, as well as internal inspection targets such as crystal defects and processing-affected layers that occur internally. The inspection targets generate scattered light when irradiated with laser light. Therefore, the evaluation device 1 can inspect the presence and degree of the inspection targets included in the substrate 100 by measuring the scattered light.

[0035] The substrate 100 is, for example, a semiconductor material manufactured through a process including at least one of a slicing process, a polishing process, and a grinding process. An example of a semiconductor substrate manufactured through these processes is a silicon (Si) substrate. The slicing, polishing, and grinding processes described above may introduce a process-affected layer that adversely affects device manufacturing. Recent research has revealed that process-affected layers can adversely affect device performance, particularly in compound semiconductor materials, which are classified as difficult-to-process materials.

[0036] The semiconductor single crystal can be made of silicon or a compound semiconductor. Compound semiconductors include SiC, GaN, AlN, and Ga. ２ O ３ , sapphire, etc. In this embodiment, the substrate 100 will be described using single crystal SiC as an example, but is not limited to this.

[0037] The process-affected layer includes distortions in the crystal lattice that occur internally due to processing of the substrate. Distortions that adversely affect semiconductor device manufacturing are located in depth ranges of 1 μm to 20 μm, 1 μm to 10 μm, 1 μm to 8 μm, and 1 μm to 6 μm below the surface of the semiconductor substrate. The inspection area in the depth direction of the evaluation device 1 is at least in the depth ranges of up to 20 μm, up to 10 μm, up to 8 μm, and up to 6 μm below the surface of the semiconductor substrate.

[0038] Distortion refers to the deviation of an actual crystal lattice from an ideal crystal lattice. The amount of distortion is a value indicating the degree of distortion. The evaluation method of the present invention involves evaluating the amount of distortion, its distribution, or its uniformity of a substrate.

[0039] The light projection optical system 10 irradiates the surface of the substrate 100 with incident light L1. The incident light L1 is branched at the surface of the substrate 100 into reflected light L2, surface scattered light L3, and transmitted light L4. In this embodiment, it is preferable that the reflected light L2 does not enter the light receiving optical system 20. The surface scattered light L3 can enter the light receiving optical system 20. The transmitted light L4 can enter the interior of the substrate 100 and enter the light receiving optical system 20 as internal scattered light L5.

[0040] The light-receiving optical system 20 forms an image of the surface scattered light L3 and the internal scattered light L5 on the light-receiving sensor 24 using the objective lens 21 and the imaging lens 22. The slit 23 selectively blocks the surface scattered light L3 and the internal scattered light L5 that are imaged on the light-receiving sensor 24. For example, the slit 23 can be arranged to selectively block only the surface scattered light L3, only the internal scattered light L5, or both the surface scattered light L3 and the internal scattered light L5. Furthermore, the slit 23 can be arranged to selectively block the internal scattered light L5 that occurs at a given depth from the surface of the substrate 100. The slit 23 may be a variable slit that can select the range of scattered light to be blocked.

[0041] The scattered light may include surface scattered light and internal scattered light. The surface scattered light may include scattered light from surface deposits, scattered light from surface irregularities, and scattered light from lattice defects. The internal scattered light may include scattered light from lattice defects and scattered light from internal strain.

[0042] Here, particularly when measuring internal scattered light L5 due to internal strain, it is preferable to suppress the generation and / or detection of scattered light other than the internal strain scattered light, including scattered light due to surface attachments, scattered light due to surface irregularities, and scattered light due to lattice defects, by an appropriate method. However, the scattered light may include scattered light other than the internal strain scattered light, as long as the intensity of the scattered light due to internal strain can be distinguished.

[0043] When measuring the internal scattered light L5 due to internal strain, the surface of the substrate 100 is planarized by the planarization process, which makes it difficult for the surface scattered light L3 to be generated or reduces the intensity of the surface scattered light L3, thereby increasing the proportion of scattered light generated in the process-affected layer below the surface.

[0044] The surface of the substrate 100 of semiconductor material is planarized by a planarization process such as chemical mechanical polishing. Quantitatively, the surface includes a surface having an arithmetic mean roughness (Ra) of 0.5 nm or less. Preferably, the surface includes a surface having an arithmetic mean roughness (Ra) of 0.4 nm or less, 0.3 nm or less, or 0.2 nm or less.

[0045] 2 shows an example of a configuration diagram of the evaluation device 1. The evaluation device 1 includes a light projecting optical system 10, a light receiving optical system 20, a stage 30, a housing 40, and a control unit 50.

[0046] The light projection optical system 10 irradiates the substrate 100 with laser light having a wavelength that allows transmission therethrough.

[0047] The incident angle θ of the laser light by the projection optical system 10 can be set to 0°≦θ<90°. The incident angle θ of the laser light is not limited to perpendicular irradiation, where 0°=θ.

[0048] The incident angle θ of the laser light preferably satisfies the lower limit of 40°≦θ, 45°≦θ, or 50°≦θ, and the upper limit of θ≦80°, θ≦75°, or θ≦70°.

[0049] When the incident angle θ is near the Brewster angle of the substrate 100 (Brewster angle ±approximately 10°), the P-polarized light penetrates deeper into the substrate 100, making it possible to detect an object deep below the surface.

[0050] The projection optical system 10 can change the angle of incidence with respect to the substrate 100. The angle of incidence of the projection optical system 10 is adjusted according to angle control instructions from the control unit 50. When the measurement area 101 is irradiated with laser light at different angles of incidence, the direction of irradiation of the laser light with respect to the inspection object changes, resulting in different patterns of scattered light. In one aspect, the measurement process can measure the intensity of the scattered light at a certain angle of incidence, and then further measure the intensity of the scattered light by changing the angle of incidence.

[0051] The laser output unit 11 is a source of laser light, and may be, for example, a gas laser such as a He-Ne laser, a semiconductor laser, or a solid-state laser such as a YAG laser. Note that the fundamental wavelength of the laser light output from the laser output unit 11 may be converted, and wavelengths such as second harmonic and third harmonic may be used.

[0052] In this embodiment, when the substrate 100 is made of a semiconductor material, it is desirable that the wavelength of the laser light has a photon energy greater than the band gap. That is, it is desirable that the wavelength λ of the laser light satisfies the relational expression "λ [nm]≦1239.8 / band gap [eV]".

[0053] Specifically, when the object to be measured is 4H—SiC, it is desirable to set the wavelength to 380 nm or less (λ [nm]≦1239.8 / 3.26 eV), and when the object to be measured is GaN, it is desirable to set the wavelength to 365 nm or less (λ [nm]≦1239.8 / 3.39 eV).

[0054] The filter 12 is configured as a wavelength filter that transmits laser light of a specific wavelength or a wavelength filter that blocks laser light of a specific wavelength. A wavelength filter corresponding to the wavelength of the laser light to be used can be used as the filter 12. The laser light becomes a single wavelength by passing through the filter 12. Laser light with a wide spectral width excites photoluminescence inside the substrate 100, causing measurement noise. Furthermore, when the fundamental wavelength is converted to a second harmonic, a third harmonic, or the like, other wavelengths not used in the measurement can cause noise. In this embodiment, it is preferable that the laser light be made a single wavelength by using the filter 12.

[0055] The wave plate 13 has a rotation mechanism and can polarize the polarization direction of the passing laser light to P polarization or S polarization. The wave plate 13 can convert the laser light into an arbitrary polarized beam in accordance with a polarization instruction from the control unit 50. Since the P-polarized and S-polarized laser lights have different transmittances for the substrate 100, the wave plate 13 is controlled in accordance with the depth of the target inspection object. The polarization state of the wave plate 13 is controlled in accordance with a polarization control instruction from the control unit 50.

[0056] The condenser lens 14 is a lens that focuses the laser light into a spot on the surface of the substrate 100. The condenser lens 14 may be a lens that shapes the laser light into any beam shape, such as a circular, elliptical, rectangular, or linear shape. In this embodiment, a cylindrical lens is used as the condenser lens 14. The cylindrical lens focuses parallel light into a rectangular or linear spot. By tilting the longitudinal direction of this rectangular or linear spot with respect to the scanning direction, a wide area can be measured in one scan, achieving high-speed measurement.

[0057] The light receiving optical system 20 measures the intensity of scattered light generated by the substrate 100. The light receiving optical system 20 is preferably disposed at an angle that prevents light reflected on the surface of the substrate 100 from entering.

[0058] The measurement angle φ of the light-receiving optical system 20 can be 0°≦θ<90°, and is not limited to being installed upwards so that 0°=φ. The measurement angle φ of the light-receiving optical system 20 preferably satisfies a lower limit of 20°≦φ, 25°≦φ, or 30°≦φ, and an upper limit of φ≦70°, φ≦65°, or φ≦60°. A preferred measurement angle φ can suppress the entry of scattered light at a depth close to the surface of the substrate 100.

[0059] The light-receiving sensor 24 converts the scattered light that passes through the slit 23 and forms an image into an electrical signal according to its intensity. The light-receiving sensor 24 may be a photomultiplier tube, a photodiode, or the like. The light-receiving sensor 24 has adjustable light-receiving sensitivity. For example, when targeting weak scattered light such as scattered light resulting from internal distortion, the light-receiving sensor 24 can be set to have a high light-receiving sensitivity.

[0060] The light receiving optical system 20 preferably further includes a wavelength filter. The wavelength filter is arranged to match the wavelength of the laser light output from the light projecting optical system 10 and block light of wavelengths other than that wavelength. The wavelength filter blocks wavelengths that may become noise in measuring the intensity of scattered light, such as photoluminescence generated on the substrate 100.

[0061] The substrate 100 is placed on the stage 30. The stage 30 includes a three-axis drive unit 31 and a rotation drive unit 32. The stage 30 can move in the X and Y directions, which are a two-dimensional plane. The stage 30 can also rotate in the two-dimensional plane. By moving and / or rotating in the two-dimensional plane, the stage 30 can scan the substrate 100 with laser light.

[0062] The stage 30 can move in the horizontal and vertical directions by driving the three-axis drive unit 31 in accordance with movement instructions from the control unit 50. The stage 30 can rotate by driving the rotation drive unit 32 in accordance with rotation instructions from the control unit 50.

[0063] The movement and / or rotation of the stage 30 is controlled based on stage position information. The stage position information has a Cartesian coordinate system (X, Y, Z) and a rotating coordinate system (r, θ). The rotating coordinate system is represented by a feed position r relative to the radial direction of the substrate 100 due to feed movement and a rotation angle θ. The direction of the feed movement corresponds to the X-axis and Y-axis directions of the Cartesian coordinate system and is controlled by driving the three-axis drive unit 31. In the rotating coordinate system, the substrate 100 at the feed position r is effectively moved in the r direction by moving along the X-axis or Y-axis while rotating in the θ direction. The feed position r due to feed movement in the rotating coordinate system and the Cartesian coordinate position XY due to horizontal movement in the Cartesian coordinate system are each distinguished as position information.

[0064] The stage 30 may be configured such that its movement and / or rotation is controlled based on substrate position information. The substrate position information has a Cartesian coordinate system (X, Y, Z) and / or a rotational coordinate system (r, θ). The substrate position information is information indicating a position on the substrate 100. In the evaluation of the substrate 100 according to this embodiment, the distribution of the objects to be inspected contained on the substrate 100 can be evaluated from the measurement results of the scattered light intensity at each position on the substrate 100 indicated by the substrate position information.

[0065] The housing 40 supports the light projecting optical system 10 and the light receiving optical system 20. The housing 40 may be movable in the horizontal and vertical directions. The housing 40 can be configured to scan the laser light by moving in accordance with a movement instruction from the control unit 50.

[0066] In this embodiment, the stage 30 moves in the Z axis, which is the vertical direction, when aligning the spot of irradiation light with the surface of the substrate 100. Note that the housing 40 may be configured to move in the vertical direction when aligning the spot of irradiation light with the surface of the substrate 100.

[0067] The control unit 50 is connected to the stage 30 and controls the movement and rotation of the stage 30. The control unit 50 acquires measurement data from the light receiving optical system 20. The control unit 50 executes a synthesis process for the measurement data.

[0068] The control unit 50 includes a stage control unit 51 that controls the stage 30, a signal processing unit 52 that processes the signal as measurement data (measurement results) based on the intensity of the scattered light received by the light receiving sensor 24, and a synthesis processing unit 53 that synthesizes the measurement data as synthetic data based on at least two or more pieces of measurement data.

[0069] The control unit 50 controls the measurement mode depending on the inspection object. The measurement modes may include modes corresponding to the depth, type, etc. of the inspection object. The measurement modes include a surface measurement mode corresponding to the depth of the inspection object and an internal measurement mode. The surface measurement mode is a mode for measuring a surface inspection object such as a particle. The internal measurement mode is a mode for measuring an internal inspection object such as a processing-affected layer. The control unit 50 can output a control instruction to the wave plate 13 to use S-polarized light in the surface measurement mode, and a control instruction to the wave plate 13 to use P-polarized light in the internal measurement mode. Furthermore, in the internal measurement mode, the control unit 50 outputs a control instruction to the wave plate 13 to selectively switch between S-polarized light and P-polarized light depending on the target depth. For example, in the internal measurement mode, when targeting internal distortion of a processing-affected layer, the control unit 50 outputs a control instruction to the wave plate 13 to use S-polarized light.

[0070] The control unit 50 is configured with one or more processors such as a CPU (Central Processing Unit). The control unit 50 executes various processes as a stage control unit 51, a signal processing unit 52, and a synthesis processing unit 53 by executing programs stored in a storage device. The control unit 50 can accept input operations via the operation interface of the evaluation device 1 and execute a measurement process and a synthesis process in response to the input operations.

[0071] The evaluation method according to this embodiment includes a measurement step and a synthesis step. The measurement step is a step of irradiating the substrate 100 with laser light and measuring the intensity of the scattered light. In this embodiment, the measurement step includes a first measurement step and a second measurement step, and measurement data is obtained from each step. The synthesis step is a step of generating synthetic data based on the respective measurement data.

[0072] <Measurement Step> The light projecting optical system 10 irradiates a measurement area of ​​the substrate 100 with laser light. The light receiving optical system 20 measures scattered light generated by the laser light irradiated onto the measurement area.

[0073] In this embodiment, a measurement area is defined on the substrate 100. The measurement area is defined by an irradiation area (spot) of the laser light and / or a light-shielding area of ​​the slit 23. The measurement area on the substrate 100 is scanned by driving the stage 30, thereby measuring scattered light over the entire surface of the substrate 100.

[0074] In one embodiment, the measurement region can be defined as any size and shape by modifying the shape of the irradiated light spot. In another embodiment, the measurement region can be defined as any size and shape by limiting the range for receiving scattered light with a slit 23.

[0075] In the measurement process of this embodiment, for each measurement area on the substrate surface, optical systems are used in a first direction and a second direction relative to the measurement area to measure the intensity of scattered light, respectively, to obtain measurement data. The measurement data includes first measurement data from the first direction and second measurement data from the second direction. The measurement data may also include N-th measurement data from two or more directions (N≧2).

[0076] Here, the optical system includes the light-projecting optical system 10 and / or the light-receiving optical system 20. The optical system as viewed from the measurement region refers to at least one of the light-projecting optical system 10 and the light-receiving optical system 20. The first direction and the second direction are different directions in the in-plane direction of the XY plane of the substrate 100. When the measurement step acquires multiple pieces of measurement data, it is preferable that the respective measurement directions are at equally spaced angles in the in-plane direction. Specifically, when the measurement step acquires two pieces of measurement data, it is preferable that the first direction and the second direction are orthogonal in the in-plane direction.

[0077] When the optical system is a light-projecting optical system 10, the measurement process uses the light-projecting optical system 10 located in a first direction and a second direction as viewed from the measurement area to measure the scattered light generated, respectively, to obtain first measurement data and second measurement data, but at this time, the direction of the light-receiving optical system 20 is not restricted.

[0078] When the optical system is a light-receiving optical system 20, the measurement process uses the light-receiving optical system 20 located in a first direction and a second direction as viewed from the measurement area to measure the intensity of the scattered light, respectively, to obtain first measurement data and second measurement data, but at this time, the direction of the light-projecting optical system 10 is not restricted.

[0079] The measurement data measured by the measurement step includes the intensity of scattered light and position information. The position information is information indicating the position where the intensity of scattered light is measured, and can be either substrate position information of the substrate 100 or stage position information of the stage 30. When stage position information is used, a process is performed to convert the stage position information into substrate position information.

[0080] 3 and 4 are used as examples to define spatial coordinates based on the substrate 100, and to explain the measurement area. In the examples of FIGS. 3 and 4, the in-plane directions of the substrate 100 are represented by XY coordinates, and the height direction (depth direction) is represented by the Z coordinate. The measurement direction is defined as the direction of the light projecting optical system 10 and / or the light receiving optical system 20 relative to the measurement area. In other words, the measurement direction can be said to be the direction of the light projecting optical system 10 and / or the light receiving optical system 20 as seen from the measurement area. In this embodiment, the measurement direction includes at least two different directions (a first direction and a second direction), and measurement data in the two measurement directions is obtained.

[0081] Fig. 3(a) shows a view of the substrate 100 as seen from above. The measurement area 101 is represented by substrate position information in XY coordinates with the substrate 100 as the reference. The measurement area 101 is scanned across the surface of the substrate 100, thereby measuring the intensity of scattered light across the entire surface of the substrate 100. In Fig. 3(a), an example of a square measurement area 101 is shown, but this is not limiting. The shape of the measurement area 101 can be adjusted by the condenser lens 14 and the slit 23.

[0082] The scattered light in the measurement region 101 is measured in different measurement directions (light-receiving directions). FIG. 3A illustrates a light-receiving optical system 20A that detects scattered light from the X direction and a light-receiving optical system 20B that detects scattered light from the Y direction. In this manner, the measurement step measures scattered light in at least two directions in one measurement region 101. Here, the light-receiving optical systems 20A and 20B may be either the same optical system that sequentially measures scattered light in the two directions, or different optical systems that simultaneously measure scattered light in the two directions.

[0083] Here, the angle of incidence of light onto the measurement area 101 is not limited. The projection optical system 10 may irradiate the measurement area 101 with laser light obliquely, or may irradiate the measurement area 101 with laser light directly above. The projection optical system 10 preferably has an incident angle that increases the transmittance of the laser light into the substrate 100. When the laser light is P-polarized, the incident angle is preferably Brewster's angle. By increasing the transmittance of the laser light into the substrate 100, it is possible to measure an inspection object located deep below the surface of the substrate 100.

[0084] 3(b) shows the measurement of internal scattered light L5 when the cross section AA' in FIG. 3(a) is viewed in the direction of the arrow DA. The internal scattered light L5 is scattered in an oblique direction and has a horizontal component L51 in the X direction and a vertical component L52 in the Z direction. In FIG. 3(b), the light receiving optical system 20 can measure scattered light that depends on the horizontal component in the X direction and the vertical component in the Z direction.

[0085] 3(c) shows the measurement of internal scattered light L5 when the cross section BB' in FIG. 3(a) is viewed in the direction of the arrow DB. The internal scattered light L5 is scattered in an oblique direction and has a horizontal component L53 in the Y direction and a vertical component L54 in the Z direction. In FIG. 3(c), the light receiving optical system 20 can measure scattered light that depends on the horizontal component in the Y direction and the vertical component in the Z direction.

[0086] Although the internal scattered light has been described as an example in FIGS. 3B and 3C, the scattered light that depends on the horizontal components in the X and Y directions can also be measured in the same way for surface scattered light.

[0087] If the inspection object has anisotropy in the X and Y directions on the substrate 100, a difference will occur in the measurement data from the two directions described above. If the inspection object is a thin scratch or defect, it will have anisotropy in the plane, which will appear as a difference in the measurement data from the two directions. If the inspection object is a minute defect or distortion, it will be distributed with anisotropy in the plane, which will appear as a difference in the measurement data from the two directions. If the inspection object is distortion, birefringence will occur in the plane, which will appear as a difference in the measurement data from the two directions. For example, if the inspection object is formed as a thin scratch or defect in the X direction, it will be understood that the intensity of scattered light in the X direction will be smaller than the intensity of scattered light in the Y direction.

[0088] In reality, the object to be inspected will have anisotropy in its plane due to the direction and distribution of scratches and defects, birefringence, etc. Therefore, in order to reduce the influence of anisotropy on an object to be inspected that has anisotropy, it is preferable to use a comprehensive evaluation method that refers to measurement data from multiple directions.

[0089] FIG. 4( a) is a top view of a substrate 100, and a measurement region 101 is defined on the substrate 100 in the same manner as in FIG. 3 . In FIG. 4( a), scattered light in the measurement region 101 is generated by laser light from different measurement directions (irradiation directions). FIG. 3( a) illustrates a projection optical system 10A that irradiates laser light from the X direction and a projection optical system 10B that irradiates laser light from the Y direction. The measurement step in FIG. 4 measures scattered light caused by irradiation of laser light from at least two directions in one measurement region 101. Here, the projection optical systems 10A and 10B may be either the same optical system that sequentially measures scattered light in two directions, or different optical systems that simultaneously measure scattered light in two directions.

[0090] Here, the arrangement of the light-receiving optical system 20 that measures scattered light in the measurement region 101 is not particularly limited as long as the light-projecting optical system 10 and the light-receiving optical system 20 are substantially collinear when viewed from above. The light-receiving optical system 20 may measure the scattered light from the measurement region 101 obliquely above, or may measure the scattered light from the measurement region 101 directly above. In this embodiment, the light-receiving optical system 20 is arranged above the substrate 100 on the opposite side of the light-projecting optical system 10 with the measurement region 101 in between, with the objective lens 21 facing the measurement region 101. The angle of the light-receiving optical system 20 is adjusted appropriately in accordance with the angle of incidence of the light-projecting optical system 10.

[0091] Figure 4(b) shows measurement using incident light as viewed in the direction of the arrow DC on the cross section AA' in Figure 4(a). In Figure 4, incident light L1 is obliquely incident and has a horizontal component L11 in the X direction and a vertical component L12 in the Z direction. As the incident light L1 is obliquely incident on the substrate 100, transmitted light L4 propagates obliquely inside the substrate 100. Therefore, like the incident light, transmitted light L4 has a horizontal component L41 in the X direction and a vertical component L42 in the Z direction. In Figure 4(b), scattered light that depends on the horizontal component in the X direction and the vertical component in the Z direction can be generated.

[0092] Figure 4(c) shows measurement using incident light when the cross section BB' in Figure 4(a) is viewed in the direction of the arrow DD. In Figure 4(c), the incident light L1 is obliquely incident and has a horizontal component L13 in the Y direction and a vertical component L14 in the Z direction. When the incident light L1 is obliquely incident on the substrate 100, the transmitted light L4 propagates obliquely inside the substrate 100 and, like the incident light, has a horizontal component L43 in the X direction and a vertical component L44 in the Z direction. In Figure 4(c), scattered light that depends on the horizontal component in the X direction and the vertical component in the Z direction can be generated.

[0093] As described above, as shown in FIGS. 3 and 4, the measurement process can obtain measurement data that depends on horizontal components in at least two directions in the measurement area 101.

[0094] Although the above-described measurement process has been described using an example in which two measurement directions are used, the measurement direction is not limited to two directions. For example, the measurement direction may be multidirectional, such as three, four, or five directions. In the case of multidirectional measurement, it is preferable to use measurement directions spaced at equal intervals.

[0095] Example 1 Fig. 5 is an explanatory diagram illustrating an outline of the measurement process. In Fig. 5, the evaluation device 1 measures the intensity of scattered light by scanning a measurement area 101 over the entire surface of the substrate 100. Scanning of the measurement area 101 is achieved by moving the stage 30 or by moving a housing 40 that supports the light-projecting optical system 10 and the light-receiving optical system 20.

[0096] In Fig. 5A, the substrate 100 has a reference point P as the reference position for substrate position information. In Fig. 5A, the light projecting optical system 10 and the light receiving optical system 20 are arranged to measure scattered light that depends on the horizontal component in the X direction. It is sufficient that at least one of the light projecting optical system 10 and the light receiving optical system 20 is arranged to measure scattered light that depends on the horizontal component in the X direction.

[0097] 5A, the measurement area 101 scans the laser light by moving in the X direction of the substrate 100. After completing scanning in the X direction from the left edge to the right edge of the substrate 100, the measurement area 101 moves a distance of a predetermined feed width in the feed direction (Y direction). After moving in the feed direction, the measurement area 101 is again scanned in the X direction from the left edge to the right edge of the substrate 100. By scanning by movement in the X direction and feed movement in the Y direction, it is possible to measure the entire surface of the substrate 100.

[0098] In Figure 5(b), reference point P indicates the same position as reference point P in Figure 5(a). In Figure 5(b), the light-projecting optical system 10 and the light-receiving optical system 20 are each arranged to measure scattered light that depends on the horizontal component in the Y direction. It is sufficient that at least one of the light-projecting optical system 10 and the light-receiving optical system 20 is arranged to measure scattered light that depends on the horizontal component in the Y direction.

[0099] 5B, the measurement area 101 scans the laser light by moving in the Y direction of the substrate 100. After completing scanning in the Y direction from the top to the bottom of the substrate 100, the measurement area 101 moves a distance of a predetermined feed width in the feed direction (X direction). After moving in the feed direction, the measurement area 101 is again scanned in the Y direction from the top to the bottom of the substrate 100. Measurement of the entire surface of the substrate 100 is completed by scanning by movement in the Y direction and feed movement in the X direction.

[0100] Example 2 Fig. 6 is an explanatory diagram illustrating an outline of the measurement process. In Fig. 6, the evaluation device 1 measures the intensity of scattered light by scanning a measurement area 101 over the entire surface of the substrate 100. Scanning of the measurement area 101 is achieved by rotating and moving the stage 30 in a plane, or by rotating the stage 30 and moving the housing 40 in a plane.

[0101] In FIG. 6( a), the measurement area 101 is scanned by rotating the substrate 100 in the rotation direction. After completing scanning by rotating the substrate 100 once, the measurement area 101 moves a distance of a predetermined feed width in the feed direction (Y direction). Note that the measurement area 101 may be seamlessly scanned by moving in the feed direction while rotating the substrate 100 once. The feed direction is a direction from the outer periphery of the substrate 100 toward the center point, or the reverse direction. In FIG. 6( a), the start position of the feed direction is a reference point P, and the end position is the center point. The start and end positions may be reversed. The reference point P is not particularly limited as long as it is on the outer periphery of the substrate 100. After moving in the feed direction, the measurement area 101 is scanned again by rotating the substrate 100 once. By these rotational scanning and feed movements, the entire surface of the substrate 100 can be measured. In FIG. 6A, the light projecting optical system 10 and the light receiving optical system 20 are arranged to measure scattered light that depends on the tangent direction of the concentric circles of the substrate 100.

[0102] In FIG. 6( b ), the measurement area 101 is scanned by rotating the substrate 100 in the rotation direction. After completing scanning by rotating the substrate 100 once, the measurement area 101 moves a predetermined feed width in the feed direction (X direction). Note that, similar to FIG. 6( a ), the measurement area 101 may be scanned by moving the feed width in the feed direction while rotating the substrate 100 once. Note that the feed widths in the X and Y directions are the same. In FIG. 6( b ), the start position of the feed direction is the same as in FIG. 6( a ), and the end position is the center point. The start and end positions may be reversed. Note that the start position may be any point on the periphery different from the reference point P. In the measurement in FIG. 6( b ), the measurement is started with the substrate rotated 90 degrees or 270 degrees from the start of the measurement in FIG. 6( a ), so that the start position is aligned with the reference point P. After moving the distance of the feed width in the feed direction, the measurement area 101 is scanned by rotating the substrate 100 once again. By this rotational scanning and feed movement, it is possible to measure the entire surface of the substrate 100. In Figure 6(b), the light projecting optical system 10 and the light receiving optical system 20 are arranged to measure scattered light that depends on the normal direction of the concentric circles of the substrate 100.

[0103] 6(a) and 6(b) measure scattered light that depends on horizontal components in two orthogonal directions, the tangential direction and the normal direction of the concentric circles of the substrate 100. Note that the measurement area 101 is not limited to measuring scattered light that is orthogonal to the tangential direction and the normal direction. The measurement area 101 may be oriented in any direction as long as the direction of movement of the measurement area 101 relative to the substrate 100 is orthogonal to the direction of movement of the measurement area 101, thereby making it possible to measure scattered light that depends on horizontal components in two orthogonal directions.

[0104] 6(a) and 6(b) show examples in which the optical system is fixed in the X direction as the measurement direction, and the substrate 100 is rotated by 270 degrees or 90 degrees to measure orthogonal scattered light in the measurement region 101 where the substrate position information is the same. On the other hand, an embodiment may also be adopted in which the optical system is rotated by 90 degrees or 270 degrees so that the X direction and the Y direction become the measurement directions, and orthogonal scattered light is measured in the measurement region 101 where the substrate position information is the same.

[0105] Example 3 FIG. 7 is an explanatory diagram illustrating an outline of the measurement process. In FIG. 7, the measurement area 101 is rectangular or linear. By having the measurement area 101 have a width in the scanning direction, the measurement range can be widened and the measurement time can be shortened. In FIG. 7, similar to Example 2, the measurement area 101 is scanned by rotating and moving the stage 30 in a plane, or by rotating the stage 30 and moving the housing 40 in a plane. In Example 3, the longitudinal direction of the measurement area 101 is inclined with respect to the scanning direction (rotation direction). The inclination angle is preferably 45 degrees with respect to the scanning direction.

[0106] 7A, the longitudinal direction of the measurement area 101 is inclined at 45 degrees with respect to the scanning direction. The scanning area A moves in the feed direction (Y direction) from a reference point P, which is the outer periphery of the substrate 100, toward the center point while rotating the substrate 100, thereby measuring the intensity of scattered light over the entire surface of the substrate 100.

[0107] In Figure 7(b), the measurement area 101 measures the intensity of scattered light over the entire surface of the substrate 100 by moving in the feed direction (X direction) from the reference point P in Figure 7(a) toward the center point while rotating the substrate 100.

[0108] 7(a) and (b) show an example in which, as in Example 2, the direction of the optical system is fixed and the substrate 100 is rotated by 270 degrees or 90 degrees to measure orthogonal scattered light in the measurement region 101 where the substrate position information is the same. However, by rotating the optical system side by 270 degrees or 90 degrees, it is possible to measure orthogonal scattered light in the measurement region 101 where the substrate position information is the same.

[0109] The measurement by rotational scanning according to Examples 2 and 3 has advantages over the measurement according to Example 1 in that it has a short measurement time, suppresses resonance of the stage 30, and improves the ability of the spot to follow the deflection of the substrate 100.

[0110] 8(a) and 8(b) show the orientation of the inspection object measured as strong scattered light by the measurement steps of Fig. 7(a) and 7(b), respectively. The dotted line represents the scanning path of the measurement area 101 by feed movement. The solid line represents the orientation of strong scattering on the scanning path.

[0111] 8(a) and 8(b), the direction of strong scattering is tilted by 45 degrees depending on the tilt angle of the measurement region 101. Comparing the directions of strong scattering in FIGS. 8(a) and 8(b), the start position of the feed direction is shifted by 90 degrees within the substrate 100, resulting in the direction of strong scattering being reversed and perpendicular to the original direction.

[0112] 8(c) shows the result of superimposing FIGS. 8(a) and 8(b). Focusing on a certain measurement area 101, it can be seen that the directions of strong scattering are orthogonal to each other. In this way, the measurement process measures scattered light so that the directions of strong scattering are different across the entire surface of the substrate 100, thereby enabling high-speed measurement without overlooking any inspection target present on the substrate 100.

[0113] As shown in Examples 1 to 3 described above, the measurement process involves scanning laser light over the surface of the substrate 100, measuring scattered light in each of multiple measurement areas 101 on the substrate 100, and obtaining measurement data for the entire surface of the substrate 100 based on the multiple measurement areas 101.

[0114] In the measurement process, two measurement directions (a first direction and a second direction) are set relative to the scanning direction of the laser light. In Example 1, an X-direction measurement direction is set relative to the X-direction scanning direction, and a Y-direction measurement direction is set relative to the Y-direction scanning direction. In Example 2, the scanning direction corresponds to rotation, and a measurement direction that is a tangential direction of the concentric circles due to the rotation and a measurement direction that is a normal direction of the concentric circles due to the rotation are set. Note that, although Examples 1 and 2 show examples in which the scanning direction and the measurement direction are the same direction, this does not exclude the measurement direction being inclined relative to the scanning direction.

[0115] Fig. 9 is an explanatory diagram of the measurement direction set relative to the scanning direction due to rotation. In Fig. 9, the substrate 100 is rotated in the in-plane direction, and a laser beam is irradiated onto a rotational orbit C1 of the substrate 100 to perform scanning. Note that the rotational orbit C has a plurality of orbits with different radii. Alternatively, the rotational orbit C may be a spiral orbit whose radius gradually changes as the substrate 100 is rotated. Fig. 9 will be described with a focus on the measurement of points Q and R on the rotational orbit C1.

[0116] 9A is an explanatory diagram of the scanning direction of the substrate 100. The laser light is scanned at point Q in a scanning direction S1 in the X direction, and at point R in a scanning direction S2 in the Y direction.

[0117] 9B is an explanatory diagram of the measurement direction using an optical system (light-receiving optical system 20 in the illustrated example) in the first direction. Scattered light is measured in measurement direction M11 at point Q and in measurement direction M21 at point R. The measurement direction using light-projecting optical system 10 is similar.

[0118] 9C is an explanatory diagram of the measurement direction using an optical system (light-receiving optical system 20 in the illustrated example) in the second direction. Scattered light is measured in measurement direction M12 at point Q and in measurement direction M22 at point R. The measurement direction using light-projecting optical system 10 is also similar.

[0119] 9B and 9C, the position of the optical system is fixed, and points Q and R on the substrate 100 are measured by rotating the substrate 100, respectively.

[0120] 9(d) is an explanatory diagram of the measurement directions relative to the scanning direction. At point Q, scattered light is measured in a first measurement direction M11 and a second measurement direction M12 relative to the scanning direction S1. At point R, scattered light is measured in a first measurement direction M21 and a second measurement direction M22 relative to the scanning direction S2. Here, the first measurement directions M11 and M21 are the same direction relative to the scanning directions S1 and S2, and the second measurement directions M12 and M22 are also the same direction relative to the scanning directions S1 and S2.

[0121] 9(d), the in-plane direction of the first measurement direction may be set at a first angle with respect to the rotational orbit, and the in-plane direction of the second measurement direction may be set at a second angle with respect to the rotational orbit. The first angle and the second angle are angles with respect to a tangent to the rotational orbit. In a preferred embodiment of this embodiment, the first angle is 45 degrees with respect to the tangent to the rotational orbit, and the second angle is −45 degrees with respect to the tangent to the rotational orbit. In other words, the measurement direction is inclined at 45 degrees with respect to the scanning direction.

[0122] As described above, by setting the first measurement direction and the second measurement direction relative to the scanning direction, the scattered light measured in each of the multiple measurement areas 101 on the substrate 100 is in the same measurement direction, and appropriate measurement data can be obtained for the entire surface of the substrate 100.

[0123] 3 to 9, the two-directional measurement process includes a first measurement process for measuring in a first direction and a second measurement process for measuring in a second direction. In this embodiment, the first measurement process is performed first, followed by the second measurement process. By measuring using the same optical system, it is possible to suppress differences in measurement data caused by individual differences in output intensity from the laser output unit 11 and individual differences in light-receiving sensitivity of the light-receiving sensor 24. In particular, scattered light caused by distortion in the processing-affected layer is extremely weak, and slight individual differences in light-receiving sensitivity affect the measurement data.

[0124] In the first and second measurement steps, the position of the optical system is fixed, and the laser light is scanned by rotating and moving the substrate 100 in a plane. In the first measurement step, the scattered light in the measurement area is measured using the optical system whose position is fixed, and in the second measurement step, the orientation of the measurement area is changed and the scattered light is measured.

[0125] When the first measurement step and the second measurement step are performed twice using one optical system, the measurement data from the first measurement step and the second measurement step include scattered light intensity and stage position information. The measurement data from the first measurement step includes scattered light intensity measured in a first direction with respect to a certain measurement area and first stage position information. The measurement data from the second measurement step includes scattered light intensity measured in a second direction with respect to the measurement area and second stage position information.

[0126] In the first measurement step and the second measurement step, the intensities of scattered light measured in the same measurement region of the substrate 100 are combined in a combining step, which will be described later. The combined intensities of scattered light in the same measurement region are identified as having the same substrate position information. Because the position of the optical system is fixed in the first measurement step and the second measurement step, it becomes necessary to change the first direction and the second direction relative to the measurement region by rotating the substrate 100 in each step. Accordingly, when referring to the same substrate position information in the first measurement step and the second measurement step, the first stage position information and the second stage position information will indicate different stage positions.

[0127] The first stage position information and the second stage position information are aligned using substrate position information of a reference point P on the substrate 100. The alignment process refers to a process of aligning the first stage position information and the second stage position information, which indicate different stage positions, as if they indicate the same substrate position information. A plurality of reference points may be set on the substrate 100. In the first measurement process and the second measurement process, the respective stage position information to be aligned with the substrate position information serving as the reference point is acquired.

[0128] In this embodiment, the alignment process is performed in at least one of the measurement process and the synthesis process. The timing of the alignment process is not limited as long as the stage position information of the two measurement data is aligned as the same substrate position information and synthesis data of the intensities of scattered light in two directions is obtained.

[0129] The first measurement step acquires first measurement data including first stage position information and the intensity of scattered light in a first direction. The control unit 50 rotates and / or moves the stage 30 in a plane to acquire the first measurement data for the entire surface of the substrate 100. The first measurement step acquires substrate position information that serves as at least one or more reference points used in the alignment process, and first stage position information that is aligned with the substrate position information.

[0130] The second measurement step acquires second measurement data including second stage position information and the intensity of scattered light in a second direction. The control unit 50 rotates and / or moves the stage 30 in a plane to acquire the second measurement data for the entire surface of the substrate 100. The second measurement step acquires substrate position information that serves as at least one or more reference points used in the alignment process, and second stage position information that is aligned with the substrate position information.

[0131] The first measurement step and the second measurement step may be performed simultaneously by using two optical systems. As described above, even if there are individual differences between the two optical systems, measurements can be performed simultaneously in two directions by correcting the difference in measurement data due to those individual differences. This further speeds up the measurement steps.

[0132] When the first measurement step and the second measurement step are performed simultaneously using two optical systems, the measurement data from the first measurement step and the second measurement step include scattered light intensity and stage position information or substrate position information. In simultaneous measurements, the two measurement data include scattered light intensity for the same measurement region and the same substrate position information. Alternatively, in simultaneous measurements, the positional relationship between the two pieces of substrate position information is defined in advance, and measurement data that result in the same substrate position information based on the defined positional relationship are associated with each other.

[0133] <Control for Alignment Processing> Figure 10 is an explanatory diagram relating to control for alignment processing in the first measurement step and the second measurement step. Here, an example of control in the measurement step using rotational scanning is shown. In Figure 10, the substrate 100 measured in the first measurement step is shown by a solid line, and the substrate 100' measured in the second measurement step is shown by a dashed dotted line. The substrate 100' shows the state in which the substrate 100 has been rotated 270 degrees (3π / 2). Point P on the substrate 100 and point P' on the substrate 100' indicate the same substrate position.

[0134] 10, the position of the optical system (light-receiving optical system 20) is fixed at a position where points P and P' are measured. Point P is a reference point and is used in the alignment process between the stage position information and the substrate position information. The reference point is set in advance so as to be aligned with, for example, the edge or center of the substrate 100.

[0135] In the first measurement step, the control unit 50 controls the stage 30 so that the substrate position information corresponds to the reference point P, which is the starting position. Here, the first stage position information W1 and the substrate position information S1 for the reference point P are associated for the alignment process. The control unit 50 moves the stage 30 in a plane in the feed direction D1 (Y direction) while rotating the stage 30 (substrate 100), and acquires first measurement data. The first measurement data is time-series data of the scattered light intensity I1(t) and the first stage position information W1(t), with the measurement time t.

[0136] In the second measurement step, the control unit 50 rotates and moves the stage 30 in a plane so that the reference point P / P', which is the starting position, is positioned at a position where it coincides with the reference point P / P'. In FIG. 10, the stage 30 is rotated 270 degrees and then moved in a plane by a distance of radius r in the X and Y directions. Here, the second stage position information W2 and the substrate position information S1 of the reference point P / P' are associated for the alignment process. The control unit 50 moves the stage 30 in a plane in the feed direction D2 (X direction) while rotating the stage 30 (substrate 100) to acquire second measurement data. The second measurement data is time-series data of the scattered light intensity I2(t) and the second stage position information W2(t) with the measurement time t.

[0137] In the case of rotational scanning, the starting positions of the first and second measurement steps are set as reference points P / P', so that the respective rotational trajectories match. Therefore, if the first stage position information W1 and second stage position information W2 of the starting positions are aligned as substrate position information of reference point P, the substrate position information of the subsequent time-series data will also match. The aligned time-series data of the first and second measurement data will have substrate position information S(t), scattered light intensity I1(t), and scattered light intensity I2(t).

[0138] The first and second measurement steps are not limited to a configuration in which the start positions are aligned. In the first and second measurement steps, the substrate position information of the first measurement data and the second measurement data can be aligned as long as the substrate position information of the reference point P and the corresponding first stage position information and second stage position information are obtained.

[0139] Similarly, in planar movement scanning, if substrate position information serving as a reference point and corresponding first stage position information and second stage position information are obtained, the substrate position information of the first measurement data and the second measurement data can be aligned.

[0140] Although an example in which the reference point is set at the edge has been described herein, the center of rotation of the stage 30 (substrate 100) may also be used as the reference point. In this case, in the first measurement step, the substrate 100 is moved in a first movement direction (e.g., X direction) while being rotated, and first measurement data is obtained. In the second measurement step, the substrate 100 is moved in a second movement direction (e.g., Y direction) while being rotated, and second measurement data is obtained. The first and second movement directions are feed directions, which correspond to the radial direction of the substrate 100. The start position of the first and second measurement steps is the center of rotation set at the reference point, and the entire surface is measured by feeding and moving the substrate 100 outward. In this case, the measurement end position is the outer edge of the substrate 100.

[0141] By setting the feed widths in the first measurement step and the second measurement step to the same distance, the radial feed positions r of the first measurement data and the second measurement data will match. Furthermore, by starting the second measurement step with the substrate 100 rotated 90 degrees or 270 degrees from the start of measurement in the first measurement step, the measurement end positions on the substrate 100 can be matched. Matching the measurement start and end positions on the substrate 100 is more preferable because it aligns the substrate position information of the first measurement data and the second measurement data.

[0142] <Measurement Data> Figure 11 shows measurement data from the measurement step of Example 3. Figure 11(a) is measurement data from the first measurement step, and is an image that reflects the scattered light intensity in the direction of strong scattering in Figure 8(a). Figure 11(b) is measurement data from the second measurement step, and is an image that reflects the scattered light intensity in the direction of strong scattering in Figure 8(b). The measurement data in Figure 11 is displayed in colors corresponding to the scattered light intensity, such as red, yellow, and green, in descending order. It can be understood that areas with high scattered light intensity indicate that there are many test objects present.

[0143] 11(a) and (b), the scattered light intensity appears at positions where the butterfly-like intensity distribution is reversed. This difference in intensity distribution is understood to be due to the fact that the strong scattering direction is perpendicular to the measurement direction. Furthermore, it is clear that it is difficult to grasp all of the inspection targets present on the substrate 100 by measuring from only one direction.

[0144] <Combining Step> The control unit 50 generates composite data based on the measurement data in the first direction and the second direction in the measurement region (combining step). The control unit 50 generates the composite data by a combining process that averages the measurement data from the first measurement step and the measurement data from the second measurement step. In this embodiment, the averaging is performed by dividing the total value of the scattered light intensity for each piece of position information by 1 / 2. Note that the averaging method is not limited to arithmetic mean, geometric mean, harmonic mean, and other methods can be used. Furthermore, the combining process is not limited to averaging, and other calculation methods can be used as long as they can suppress the dependency of scattered light on measurement data from different measurement directions.

[0145] The combining step aligns the position information of the first measurement data and the second measurement data to generate combined data. The control unit 50 acquires the first measurement data including scattered light intensity I1(t) and first stage position information W1(t) and the second measurement data including scattered light intensity I2(t) and second stage position information W2(t), and generates alignment data including substrate position information S(t), scattered light intensity I1(t), and scattered light intensity I2(t). The control unit 50 generates the combined data by averaging the scattered light intensity of each record of the alignment data.

[0146] FIG. 12 shows the composite data generated by the combining process. As in FIG. 11 , the composite data is displayed in colors corresponding to the scattered light intensity, such as red, yellow, and green, in descending order. The composite data has a value obtained by averaging the intensity values ​​of multiple pieces of measurement data. By combining measurement data from two directions, the composite data suppresses the influence of the intensity distribution that would otherwise appear inverted. Therefore, it can be said that the composite data more accurately represents the intensity distribution of scattered light on the substrate 100.

[0147] The quality of the substrate 100 is evaluated using the composite data described above. For example, a region in the composite data where the scattered light intensity is high can be evaluated as a region where the defect or processing-affected layer to be inspected is severe.

[0148] REFERENCE SIGNS LIST 1 Evaluation device 10 Light projection optical system 11 Laser output unit 12 Filter 13 Wave plate 14 Condenser lens 20 Light receiving optical system 21 Objective lens 22 Imaging lens 23 Slit 24 Light receiving sensor 30 Stage 31 Three-axis drive unit 32 Rotation drive unit 40 Housing 50 Control unit 51 Stage control unit 52 Signal processing unit 53 Synthesis processing unit 100 Substrate

Claims

1. A method for evaluating a substrate using a laser light scattering method, comprising: a measurement step for measuring, for each measurement area on the substrate surface, the scattered light using optical systems in a first direction and a second direction based on the measurement area to obtain first measurement data and second measurement data; and a synthesis step for synthesizing the first measurement data and the second measurement data to generate synthetic data.

2. The method for evaluating a substrate according to claim 1, wherein the first direction and the second direction are different in an in-plane direction of the substrate.

3. The method for evaluating a substrate according to claim 2, wherein the first direction and the second direction are orthogonal to each other in their in-plane directions.

4. A method for evaluating a substrate as described in claim 1, wherein the optical system includes a light-receiving optical system that receives scattered light generated by the substrate, and the measurement process uses the light-receiving optical system in the first direction and the second direction based on the measurement area to measure each scattered light and obtain the first measurement data and the second measurement data.

5. A method for evaluating a substrate as described in claim 1, wherein the optical system includes a projection optical system that irradiates laser light onto the surface of the substrate, and the measurement process uses the projection optical system in the first direction and the second direction based on the measurement area to measure the respective scattered lights generated, thereby obtaining the first measurement data and the second measurement data.

6. The method for evaluating a substrate according to claim 1, wherein the measuring step includes measuring scattered light in each of a plurality of measurement regions of the substrate by scanning a laser light on the substrate surface.

7. The method for evaluating a substrate according to claim 6, wherein the first direction and the second direction are set relative to a scanning direction of the scanning.

8. The method for evaluating a substrate according to claim 6, wherein the measurement area is set so as to be inclined with respect to the scanning direction of the scan.

9. The method for evaluating a substrate according to claim 1, wherein the measuring step includes irradiating a laser beam onto the surface of the substrate while rotating the substrate in an in-plane direction, and measuring the scattered light.

10. The method for evaluating a substrate as described in claim 9, wherein the measurement step includes irradiating the laser light onto a rotational orbit of the substrate by rotating the substrate in an in-plane direction, and the in-plane direction of the first direction and the in-plane direction of the second direction are set at a first angle and a second angle with respect to the rotational orbit.

11. A method for evaluating a substrate as described in claim 1, wherein the measurement process includes a first measurement process and a second measurement process, in which the first measurement process and the second measurement process obtain the first measurement data and the second measurement data by changing the orientation of the measurement area with respect to the optical system, the position of which is fixed, and measuring the scattered light, respectively, and the combination process aligns positional information of the first measurement data and the second measurement data to generate the combined data.

12. A method for evaluating a substrate as described in claim 11, wherein the first measurement step involves scanning a laser beam while rotating the substrate in an in-plane direction and moving the substrate in a first movement direction to obtain first measurement data, and the second measurement step involves scanning a laser beam while rotating the substrate in an in-plane direction and moving the substrate in a second movement direction different from the first movement direction to obtain second measurement data.

13. The method for evaluating a substrate according to claim 12, wherein the second measurement step starts measurement in a state in which the substrate is rotated 90 degrees or 270 degrees from the start of measurement in the first measurement step.

14. The method for evaluating a substrate according to claim 11, wherein the first measurement step and the second measurement step measure scattered light using the same optical system.

15. A method for evaluating a substrate according to any one of claims 1 to 14, wherein the measurement area is linear or rectangular.

16. An apparatus for evaluating a substrate using a laser light scattering method, comprising: a light projection optical system that irradiates a substrate with laser light; a light receiving optical system that measures scattered light; a stage having a three-axis drive unit that moves the substrate in a plane; and a control unit that controls the movement of the stage to a reference position for the substrate, which is a starting position for each of a first measurement and a second measurement.

17. The substrate evaluation device of claim 16, wherein the stage further comprises a rotation drive unit that rotates the substrate, and the control unit controls planar movement of the stage in different feed directions for the first measurement and the second measurement by the three-axis drive unit while rotating the stage by the rotation drive unit.

18. The substrate evaluation device according to claim 16 or 17, wherein the control unit aligns position information for two pieces of measurement data obtained by the first measurement and the second measurement, and synthesizes the data into synthetic data.