TW202042965A - Thickness measurement of substrate using color metrology - Google Patents

Abstract

A system for obtaining a measurement representative of a thickness of a layer on a substrate includes a support to hold a substrate, an optical assembly to capture two color images with light impinging the substrate at different angles of incidence, and a controller. The controller is configured to store a function that provides a value representative of a thickness as a function of position along a predetermined path in a coordinate space of at least four dimensions. For a pixel in the two color images, the controller determines a coordinate in the coordinate space from the color data, determines a position of a point on the predetermined path that is closest to the coordinate, and calculates a value representative of a thickness from the function and the position of the point on the predetermined path.

Description

Thickness measurement of substrates using color metrology

This disclosure relates to optical metrology, for example, to detect the thickness of a layer on a substrate.

An integrated circuit is usually formed on a substrate by sequentially depositing a conductive layer, a semiconductor layer, or an insulating layer on a silicon wafer. One manufacturing step involves depositing and planarizing a filler layer on a non-planar surface. For some applications, the filler layer is planarized until the top surface of the patterned layer is exposed. For example, a conductive filler layer can be deposited on the patterned insulating layer to fill the trenches and holes in the insulating layer. After planarization, the portions of the metal layer remaining between the raised patterns of the insulating layer form vias, plugs and wiring, which provide conductive paths between the thin film circuits on the substrate. For other applications, a filler layer is deposited on top of the underlying topology provided by other layers, and the filler layer is planarized until a predetermined thickness is retained. For example, a dielectric filler layer can be deposited on the patterned metal layer and patterned to provide insulation between the metal regions and provide a flat surface for further photolithography.

Chemical mechanical polishing (CMP) is a recognized planarization method. This planarization method usually requires mounting the substrate on a carrier or a polishing head. The exposed surface of the substrate is usually placed against the rotating polishing pad. The carrier head provides a controllable load on the substrate to push the substrate toward the polishing pad. The abrasive slurry is usually supplied to the surface of the polishing pad.

Changes in slurry distribution, polishing pad conditions, relative speed between polishing pad and substrate, and load on the substrate may cause changes in material removal rate. These changes and changes in the initial thickness of the substrate layer result in changes in the time required to reach the polishing endpoint. Therefore, determining the polishing end point only based on the polishing time may result in over-polishing or insufficient polishing of the substrate.

Various optical metrology systems (for example, spectrometers or ellipsometers) can be used, for example, to measure the thickness of the substrate layer before and after polishing at an embedded or separate metrology station. In addition, various in-situ monitoring technologies (such as monochromatic optics or eddy current monitoring) can be used to detect the grinding endpoints.

In one aspect, a system for obtaining a measurement value representing the thickness of a layer on a substrate includes: a support for holding a substrate for integrated circuit manufacturing; an optical assembly, the optical assembly A support member for capturing at least a portion of the first color image of the substrate held by the support by irradiating the substrate with light at a first incident angle, and for capturing the substrate by irradiating the substrate with light at a different second angle of incidence The at least a part of the held second color image; and a controller. The controller is configured to receive the first color image and the second color image from the optical assembly; and store a function that provides a value representing the thickness according to a position along a predetermined path in a coordinate space of at least four dimensions. One dimension includes the first color channel and the second color channel from the first color image and the third color channel and the fourth color channel from the second color image; for the pixels of the first color image and the second color image The corresponding pixel determines the coordinates in the coordinate space from the color data for the pixel in the first color image and the color data for the corresponding pixel in the second color image; determines the position of the point closest to the coordinates on the predetermined path ; And from the function and the position of the point on the predetermined path to calculate the value of the representative thickness.

In other aspects, a computer program includes instructions for causing the processor to perform the operations of the controller, and a polishing method includes positioning the substrate for integrated circuit manufacturing in view of the color camera, and generating the color image of the substrate from the color camera , And perform operations.

The implementation of any of these aspects may include one or more of the following features.

The coordinate space can be four-dimensional, or the coordinate space can be six-dimensional. The first color channel and the second color channel can be selected from the group of color channels including hue, saturation, brightness, X, Y, Z, red chroma, green chroma, and blue chroma of the first color image. The third color channel and the fourth color channel can be selected from the group of color channels including hue, saturation, brightness, X, Y, Z, red chroma, green chroma, and blue chroma of the second color image. The first color channel and the third color channel may be red chromaticity, and the second color channel and the fourth color channel may be green chromaticity.

The first incident angle and the second incident angle may both be between about 20° and 85°. The first angle of incidence may be at least 5° greater than the second angle of incidence, for example, at least 10° greater.

In another aspect, a polishing system includes a polishing station that includes a platform for supporting the polishing pad; a support for holding the substrate; and an in-line measuring station that is used in the polishing station Measuring the substrate before and after polishing the surface of the substrate; and the controller. The built-in metrology station includes one or more elongated white light sources, each having a longitudinal axis and configured to direct light to the substrate at a non-zero angle of incidence, thereby forming an illuminated area on the substrate, which is scanned across the substrate The period extends along the first axis; a first color line scan camera with detector elements arranged to receive the light reflected from the substrate illuminating the substrate at a first incident angle, and form a scan on the substrate The image portion extending along the first axis during the period; a second color line scan camera with detector elements arranged to receive light reflected from the substrate illuminating the substrate at a different second angle of incidence, and A second image portion extending along the first axis formed during the scanning of the substrate; a frame supporting one or more light sources, a first color line scan camera, and a second color line scan camera; and a motor that causes the frame and support The relative movement between the parts along a second axis perpendicular to the first axis causes one or more light sources, the first color line scan camera and the second color line scan camera to scan on the substrate. The controller is configured to receive color data from the first color line scan camera and the second color line scan camera, generate a first two-dimensional color image from the color data from the first color line scan camera, and from the second color line The color data of the scanning camera generates a second two-dimensional color image, and the polishing at the polishing station is controlled based on the first two-dimensional color image and the second two-dimensional color image.

In other aspects, a computer program includes instructions for causing the processor to perform the operations of the controller, and a polishing method includes positioning the substrate for integrated circuit manufacturing in view of the color camera, and generating the color image of the substrate from the color camera , And perform operations.

The implementation of any of these aspects may include one or more of the following features.

One or more diffusers may be positioned in the light path between the one or more elongated white light sources and the substrate.

The first incident angle and the second incident angle may both be between about 5° and 85°, for example, both are between about 20° and 75°. The first angle of incidence may be at least 5° greater than the second angle of incidence, for example, at least 10° greater. The first color line scan camera and the second line scan camera may be configured to image the overlapping area on the substrate. The one or more elongated light sources may include a first elongated light source for generating light that illuminates the substrate at a first angle of incidence, and a second elongated light source for generating light that illuminates the substrate at a second angle of incidence. The light from the first light source and the light from the second light source can illuminate overlapping areas on the substrate, for example, overlapping areas.

The frame can be fixed, and the motor can be coupled to the support, and the controller can be configured to cause the motor to move the support while one or more elongated light sources and the first color line scan the camera and the second color line at the same time The scanning camera remains fixed to scan on the substrate.

Implementation can include one or more of the following potential advantages. Can improve the accuracy of thickness measurement. This information can be used in feed-forward or feedback to control grinding parameters, thereby providing improved thickness uniformity. The algorithm used to determine the change may be simple and have a low computational load.

One or more implementation details are set forth in the accompanying drawings and the following description. Other aspects, features and advantages will be self-descriptive and schematic as well as self-applied patent scope is obvious.

The thickness of the layer on the substrate can be measured optically before or after polishing (for example, at an embedded or independent measuring station) or during polishing (for example, by an in-situ monitoring system). However, some optical techniques (such as spectrometry) require expensive spectrometers and heavy manipulation of spectral data calculations. Even in addition to the computational load, in some cases, the algorithm results cannot meet the ever-increasing accuracy requirements of users.

One measurement technique is to obtain the color image of the substrate and analyze the image in the color space to determine the thickness of the layer. In particular, the position along the path in the two-dimensional color space can provide information about the current state of grinding, for example, the amount of removal or the amount of remaining material. However, in some cases, it may be difficult to resolve the difference between colors in the image. By performing color correction on the image, the color contrast can be increased. Therefore, the thickness resolution can be enhanced, and the reliability and accuracy of thickness measurement can be improved.

Another problem is that the path in the two-dimensional color space may be degenerate. By increasing the dimensionality of the color space, the possibility of degeneracy can be reduced. One technique is to use a type of camera (for example, a hyperspectral camera) that produces images with four or more (for example, six to twenty) color channels. Another technique is to use multiple cameras with different incident angles (because the length of the light path through the film layer at different incident angles is different, different infringements and thus different colors will be produced).

Referring to FIG. 1, the polishing apparatus 100 includes an embedded (also referred to as in-sequence) optical metrology system 160, for example, a color imaging system.

The polishing apparatus 100 includes one or more carrier heads 126 (each of which is configured to carry the substrate 10), one or more polishing stations 106, and a transfer station for loading the substrate to the carrier head and Unload the substrate from the carrier head. Each polishing station 106 includes a polishing pad 130 supported on a platform 120. The polishing pad 130 may be a two-layer polishing pad with an outer polishing layer and a softer backing layer.

The carrying head 126 can be suspended from the support 128 and can be moved between grinding stations. In some implementations, the support 128 is an overhead rail, and the carrying head 126 is coupled to the bracket 108 to which the bracket 108 is mounted. The overhead track 128 allows each carriage 108 to be selectively positioned above the grinding station 124 and the transfer station. Alternatively, in some implementations, the support 128 is a rotatable turntable, and the rotation of the turntable causes the carrier head 126 to move along a circular path at the same time.

Each polishing station 106 of the polishing apparatus 100 may include a port (for example, at the end of the arm 134) to dispense a polishing liquid 136 (such as an abrasive slurry) onto the polishing pad 130. Each polishing station 106 of the polishing device 100 may also include a pad adjustment device to scrape the polishing pad 130 so as to maintain the polishing pad 130 in a uniform abrasion state.

Each carrier head 126 is operable to hold the substrate 10 against the polishing pad 130. Each carrier head 126 may have independent control of polishing parameters (eg, pressure) associated with each corresponding substrate. Specifically, each carrying head 126 may include a fixing ring 142 to fix the substrate 10 under the flexible membrane 144. Each carrier head 126 also includes a plurality of independently controllable and pressurizable chambers (for example, three chambers 146a to 146c) defined by the membrane, which can apply independently controllable pressurization to the The associated areas on the flexible membrane 144 are thus applied to the substrate 10. Although only three chambers are illustrated in Figure 1 for ease of description, there may be one or two chambers, or four or more chambers, for example, five chambers.

Each carrier head 126 is suspended from the support 128 and is connected to the carrier head rotation motor 156 via the drive shaft 154 so that the carrier head can rotate around the axis 127. Optionally, each carrier head 140 can oscillate laterally, for example, by driving the carriage 108 on the track 128, or by the rotatable oscillation of the turntable itself. In operation, the platform rotates around its central axis 121, and each carrier head rotates around its central axis 127 and translates laterally on the top surface of the polishing pad. The lateral sweep is in a direction parallel to the grinding surface 212. The lateral sweep can be linear or arc-shaped movement.

A controller 190 (such as a programmable computer) is connected to each monitor to independently control the rotation rate of the platform 120 and the carrying head 126. For example, each motor may include an encoder that measures the angular position or rotation rate of the associated drive shaft. Similarly, the controller 190 is connected to the actuator in each bracket 108 and/or the rotation motor of the turntable to independently control the lateral movement of each carrier head 126. For example, each actuator may include a linear encoder that measures the position of the carriage 108 along the track 128.

The controller 190 may include a central processing unit (CPU), memory, and supporting circuits, such as an input/output circuit system, a power supply, a clock circuit, a cache memory, and the like. The memory is connected to the CPU. The memory is a non-transitory computer-readable medium, and can be one or more kinds of easily accessible memory, such as random access memory (RAM), read only memory (read only memory; ROM). ), floppy disk, hard disk, or other forms of digital storage. In addition, although shown as a single computer, the controller 190 may be a distributed system, for example, including a plurality of independently operating processors and memories.

The embedded optical metrology system 160 is positioned in the polishing apparatus 100, but does not perform measurement during the polishing operation; and the measurement is performed between polishing operations (for example, when the substrate moves from one polishing station to another polishing station or from a transfer While the station moves to another transmission station).

The embedded optical metrology system 160 includes a sensor assembly 161 that is supported at a position between the two in the polishing station 106 (for example, between the two platforms 120). Specifically, the sensor assembly 161 is located at a position so that the carrier head 126 supported by the support 128 can position the substrate 10 above the sensor assembly 161.

In an implementation in which the polishing apparatus 100 includes three polishing stations and the substrate is sequentially carried from the first polishing station to the second polishing station to the third polishing station, one or more sensor assemblies 161 may be positioned at Between the transfer station and the first polishing station, between the first and second polishing stations, between the second and third polishing stations, and/or between the third polishing station and the transfer station.

The sensor assembly 161 may include a light source 162, a light detector 164, and a circuit system 166 for sending and receiving signals between the controller 190, the light source 162 and the light detector 164.

The light source 162 is operable to emit white light. In one implementation, the emitted white light includes light having a wavelength of 200 to 800 nanometers. Suitable light sources are arrays of white-light light emitting diodes (LEDs), or xenon lamps or xenon mercury lamps. The light source 162 is oriented to direct the light 168 onto the exposed surface of the substrate 10 at a non-zero incident angle α. The incident angle α may be, for example, about 30° to 75°, for example, 50°.

The light source can illuminate an elongated area that is substantially straight across the width of the substrate 10. The light source 162 may include an optical element (for example, a beam expander) to spread the light from the light source into the elongated area. Alternatively or additionally, the light source 162 may include a linear array of light sources. The light source 162 itself and the illuminated area on the substrate can be elongated and have a longitudinal axis parallel to the surface of the substrate.

The light 168 from the light source 168 may be partially collimated.

The diffuser 170 may be placed in the path of the light 168, or the light source 162 may include a diffuser to diffuse the light before it reaches the substrate 10.

The detector 164 may be a color camera sensitive to light from the light source 162. The detector 164 includes an array of detection elements 178 for each color channel. For example, the detector 164 may include a CCD array for each color channel. In some implementations, the array is a single row of detector elements 178. For example, the camera may be a line scan camera. The array of detector elements can extend parallel to the longitudinal axis of the elongated area illuminated by the light source 162 or perpendicular to the direction of movement of the illuminated area on the substrate (Figure 1A schematically illustrates element 178, but these elements 178 Can be arranged in a row to extend beyond the plane of the drawing). In some implementations, the detector is a color camera based on a scorpion. The inside of the detector 164 splits the beam 168 into three separate beams, each of which is sent to a separate array of detector elements.

In the case where the light source 162 includes a row of light-emitting elements, the row of detector elements may extend along a first axis parallel to the longitudinal axis of the light source 162. The array of detector elements may include 1024 or more elements.

The parallel or vertical positioning of the detector elements should be determined by taking into account the reflection of the beam, for example, by folding mirrors or reflections from the surface.

The detector 164 is equipped with a suitable focusing optical element 172 to project the field of view of the substrate onto the array of detector elements 178. The field of view may be long enough to view the entire width of the substrate 10, for example, 150 mm to 300 mm long. The sensor assembly 161 (including the detector 164 and the associated optical element 172) can be configured such that individual pixels correspond to regions having a length equal to or less than about 0.5 mm. For example, assuming that the field of view is about 200 mm long and the detector 164 includes 1024 elements, the image produced by the line scan camera may have pixels with a length of about 0.5 mm. In order to determine the length resolution of the image, the length of the field of view (FOV) can be divided by the number of pixels on which the FOV is imaged to obtain the length resolution.

The detector 164 can also be configured such that the pixel width is equivalent to the pixel length. For example, the advantage of a line scan camera is its very fast frame rate. The frame rate can be at least 5 kHz. The frame rate can be set to a certain frequency so that when the imaging area is scanned on the substrate 10, the pixel width is equivalent to the pixel length, for example, equal to or less than about 0.3 mm. For example, the pixel width and length can be about 0.1 mm to 0.2 mm.

The light source 162 and the light detector 164 may be supported on the stage 180. In the case where the photodetector 164 is a line scan camera, the light source 162 and the camera 164 can move relative to the substrate 10 so that the imaging area can be scanned over the entire length of the substrate. In particular, the relative movement can be in a direction parallel to the surface of the substrate 10 and perpendicular to the row of detector elements of the line scan camera 164.

In some implementations, the stage 182 is fixed, and the carrier head 126 moves, for example, by the movement of the carriage 108 or by the rotation and oscillation of the turntable. In some implementations, the stage 180 is movable, while the carrier head 126 remains fixed for image acquisition. For example, the stage 180 can be moved along the track 184 by the linear actuator 182. In either case, this permits the light source 162 and the camera 164 to stay at a fixed position relative to each other when the scanned area moves on the substrate 10.

In addition, the substrate can be held by a robot and moved through the fixed optical assembly 161. For example, in the case of a cassette interface unit or other element interface unit, the substrate can be held by a robot that transfers the substrate to or from the box (rather than supporting it on a separate table). The photodetector can be a fixed element (for example, a line scan camera) in the box-type interface unit, and the robot can move the substrate through the photodetector to scan the substrate to generate an image.

The possible advantage of having a line scan camera and light source that move together on the substrate (for example, as compared to a conventional 2D camera), for different positions on the wafer, the relative angle between the light source and the camera remains constant . Therefore, artifacts caused by changes in viewing angle can be reduced or eliminated. In addition, line scan cameras can eliminate perspective distortion, while conventional 2D cameras exhibit inherent perspective distortion, which then needs to be corrected by image transformation.

The sensor assembly 161 may include a mechanism for adjusting the vertical distance between the substrate 10 and the light source 162 and the detector 164. For example, the sensor assembly 161 may be an actuator used to adjust the vertical position of the stage 180.

Optionally, the polarizing filter 174 may be positioned in the path of light, for example, between the substrate 10 and the detector 164. The polarizing filter 184 may be a circular polarizer (CPL). A typical CPL is a combination of a linear polarizer and a quarter wave plate. The proper orientation of the polarization axis of the polarizing filter 184 can reduce the haze in the image and sharpen or enhance the desired visual characteristics.

One or more baffles 188 may be placed near the detector 164 to prevent stray light or ambient light from reaching the detector 164 (see Figure 1C). For example, the baffle may be substantially parallel to the beam 168 and extend around the area where the beam enters the detector 164. In addition, the detector 164 may have a narrow allowable angle, for example, 1° to 10°. These mechanisms can improve image quality by reducing the influence of stray light or ambient light.

Assuming that the outermost layer on the substrate is a translucent layer (for example, a dielectric layer), the color of the light detected at the detector 164 depends on, for example, the composition of the substrate surface, the smoothness of the substrate surface, and/or The amount of interference between light reflected from different interfaces of one or more layers (for example, dielectric layers) on the substrate.

As described above, the light source 162 and the light detector 164 can be connected to a computing device (for example, the controller 190), the computing device is operable to control the operation of the light source 162 and the light detector 164 and receive the light source 162 and light detection 164 signal.

The embedded optical metrology system 160 is positioned in the polishing apparatus 100, but does not perform measurement during the polishing operation; and the measurement is performed between polishing operations (for example, when the substrate moves from one polishing station to another polishing station or from a transfer While the station moves to another transmission station).

The embedded optical metrology system 160 includes a sensor assembly 161 that is supported at a position between the two in the polishing station 106 (for example, between the two platforms 120). Specifically, the sensor assembly 161 is located at a position so that the carrier head 126 supported by the support 128 can position the substrate 10 above the sensor assembly 161.

Referring to FIG. 1B, the polishing apparatus 100' includes an in-situ optical monitoring system 160', for example, a color imaging system. The in-situ optical monitoring system 160' is similar in structure to the embedded optical metrology system 160, but the various optical components of the sensor assembly 161 (for example, the light source 162, the light detector 164, the diffuser 170, the focusing optical element 172 and The polarizing filter 174) can be positioned in the groove 122 in the platform 120. When the substrate contacts the polishing pad 130 and is polished by the polishing pad 130, the light beam 168 can pass through the window 132 to illuminate the surface of the substrate 10. The rotation of the platform 120 causes the sensor assembly 161 (and therefore the light beam 168) to sweep across the substrate 10. When the sensor assembly 161 scans below the substrate 10, a 2D image can be reconstructed from the sequence of linear images. The stage 180 is not necessary because the movement of the sensor assembly 161 is provided by the rotation of the platform 120.

Referring to Figure 2, the controller assembles the individual image lines (whether it is an embedded metrology system or an in-situ monitoring system) from the light detector 164 into a two-dimensional color image (step 200). As a color camera, the light detector 164 may include separate detector elements for each of red, blue, and green. The two-dimensional color image may include monochrome images 204, 206, and 208 for the red, blue, and green color channels, respectively.

The controller may apply offset and/or gain adjustment to the intensity value of the image in each color channel (step 210). Each color channel can have a different offset and/or gain.

In order to set the gain, the reference substrate (for example, bare silicon wafer) can be imaged by the measurement performed by the systems 160 and 160'. You can then set the gain for each color channel so that the reference substrate appears gray in the image. For example, the gain can be set so that the red, green and blue channels can all give the same 8-bit value, for example, RGB=(121,121,121) or RGB=(87,87,87). The same reference substrate can be used to perform gain calibration for multiple systems.

Depending on the situation, the image can be normalized (step 220). For example, the difference between the measured image and the standard predefined image can be calculated. For example, the controller can store a background image for each of the red, green, and blue color channels, and can subtract the background image from the measured image of each color channel. Alternatively, the measured image can be divided by a standard predefined image.

The image can be filtered to remove low-frequency spatial variations (step 230). In some implementations, the image is converted from the red green blue (RGB) color space to the hue saturation luminance (HSL) color space, a filter is applied in the HSL color space, and then the image Convert back to red, green and blue (RGB) color space. For example, in the HSL color space, the luminance channel can be filtered to remove low-frequency spatial changes, that is, the hue and saturation channels are not filtered. In some implementations, the luminance channel is used to generate filters, which are then applied to red, green, and blue images.

In some implementations, smoothing is performed only along the first axis. For example, the brightness values of the pixels along the direction of travel 186 can be averaged together to provide an average brightness value that is only a function of the position along the first axis. Then, each row of image pixels can be divided by the corresponding portion of the average brightness value, which is a function of the position along the first axis.

Perform color correction to increase the color contrast in the image (step 235). Although shown after the filtering in step 230, the color correction can be performed before the filtering, but after the normalization in step 220. Additionally, color correction may be performed later, for example, before the thickness calculation (in step 270).

The color correction can be performed by multiplying the value in the color space by the color correction matrix. This can be expressed as the operation I _CORR = I _ORIG X CCM, where I _ORIG is the original uncorrected image, CCM is the color correction matrix, and I _CORR is the corrected image.

（方程式1） 其中I_O1 、I_O2 及I_O3 為來自色彩空間（例如，HSL色彩空間、RGB色彩空間，等等）之三個色彩通道的原始值，a11 ... a33為色彩校正矩陣之值，且I_C1 、I_C2 及I_C3 為色彩空間中之三個色彩通道的經校正值。可使用伽馬函數而非具有恆定值之色彩校正矩陣。More formally, color correction can be performed as a matrix multiplication as shown below:

(Equation 1) where I _O1 , I _O2 and I _O3 are the original values of the three color channels from the color space (for example, HSL color space, RGB color space, etc.), a11 ... a33 is the color correction matrix Value, and I _C1 , I _C2 and I _C3 are the corrected values of the three color channels in the color space. A gamma function can be used instead of a color correction matrix with a constant value.

As shown in Figures 9A and 9B, applying color correction causes the scale of the histogram to increase. This may make the determination of the layer thickness easier, because it is easier to distinguish different points in the histogram due to the larger separation. Therefore, the thickness resolution can be enhanced.

The color correction matrix can be generated by producing the color image of the reference substrate with multiple preselected colors. Measure the value of each color channel, and then calculate the optimal matrix for transforming a low-contrast image into a higher-contrast image.

The controller may use image processing technology to analyze the image to locate the wafer orientation feature 16 (eg, wafer notch or wafer) on the substrate 10 (see FIG. 4) (step 240). Image processing technology can also be used to locate the center 18 of the substrate 10 (see Figure 4).

Based on this data, the image is transformed (eg, zoomed and/or rotated and/or translated) into a standard image coordinate system (step 250). For example, the image can be translated so that the center of the wafer is at the center of the image, and/or the image can be zoomed so that the edge of the substrate is at the edge of the image, and/or the image can be rotated so that the x-axis of the image There is an angle of 0° with the radial section connecting the center of the wafer and the orientation feature of the wafer.

Optionally, an image mask can be applied to filter out multiple parts of the image data (step 260). For example, referring to FIG. 3, a typical substrate 10 includes a plurality of dies 12. The scribe line 14 can separate the die 12. For some applications, it may be useful to process only the image data corresponding to the die. In this case, referring to FIG. 4, the image mask can be stored by the controller, which has an unmasked area 22 corresponding to the die 12 and a masked area 24 corresponding to the scribe line 14 in a spatial position. The image data corresponding to the masked area 24 is not processed or used during the thresholding step. Alternatively, the masked area 24 may correspond to a die so that the unmasked area corresponds to a scribe line, or the unmasked area may be only a part of each die and the rest of each die is masked, or The unmasked area can be the specific die(s) and the remaining die and scribe lines are masked. The unmasked area can be only a part of the specific die(s), and the remaining part of each die on the substrate Is masked. In some implementations, the user can use the graphical user interface on the controller 190 to define the mask.

The color data at this stage can be used to calculate the value representing the thickness (step 270). This value can be the thickness, or the amount of material removed, or a value indicating the progress of the polishing process (for example, compared with the reference polishing process). This calculation can be performed for each unoccluded pixel in the image. This value can then be used in the feed-forward or feedback algorithm used to control the grinding parameters to provide improved thickness uniformity. For example, the value of each pixel can be compared with the target value to generate an error signal image, and this error signal image can be used for feedforward or feedback control.

Some backgrounds that help understand the calculations represented by the values will be discussed. For any given pixel from a color image, a pair of values corresponding to one of the two color channels can be extracted from the color data of the given pixel. Therefore, each pair of values can define the coordinates in the coordinate space of the first color channel and the different second color channel. Possible color channels include hue, saturation, brightness, X, Y, Z (for example, from the CIE 1931 XYZ color space), red chromaticity, green chromaticity, and blue chromaticity. According to known algorithms, the values of these color channels can be calculated based on tuples of values from other channels (for example, X, Y, and Z can be calculated from R, G, and B).

Referring to FIG. 5, for example, when grinding starts, the value pair (for example, V1 ₀ , V2 ₀ ) defines the initial coordinates 502 in the coordinate space 500 of the two color channels. However, because the spectrum of the reflected light changes as the grinding progresses, the color composition of the light changes, and the values (V1, V2) in the two color channels will change. Therefore, as the grinding progresses, the coordinate positions in the coordinate space of the two color channels will change, thereby drawing a path 504 in the coordinate space 500.

Referring to FIGS. 6 and 7, in order to calculate the value representing the thickness, the predetermined path 604 in the coordinate space 500 of the two color channels is stored (for example, in the memory of the controller 190) (step 710). The predetermined path is generated before the measurement of the substrate. The path 404 can travel from the start coordinate 402 to the end coordinate 406. The path 404 may represent the entire polishing process, where the start coordinate 402 corresponds to the starting thickness of the layer on the substrate, and the end coordinate corresponds to the final thickness of the layer. Alternatively, the path may only represent a part of the polishing process, for example, the expected distribution of layer thickness on the substrate at the polishing end point.

In some implementations, in order to create the predetermined path 404, the installed substrate is ground to approximately the target thickness to be used for the device substrate. The optical measurement system 160 or the optical monitoring system 160' is used to obtain the color image of the set substrate. Because the polishing rate on the substrate is usually not uniform, different positions on the substrate will have different thicknesses, and thus reflect different colors, and thus have different coordinates in the coordinate space of the first color channel and the second color.

Referring to Figure 8, use the pixels contained in the unmasked area to calculate a two-dimensional (2D) histogram. That is, using the color-corrected color image, using the coordinate values of some or all of the pixels from the uncovered part of the set substrate, the scatter plot 800 is generated in the coordinate space of the first color channel and the second color channel. Each point 802 in the scatter diagram is a value pair (V1, V2) for two color channels of a specific pixel. The scatter chart 800 can be displayed on the controller 190 or the display of another computer.

及

定義，其中R、G及B為色彩影像之紅色、綠色及藍色色彩通道的強度值。As mentioned above, possible color channels include hue, saturation, brightness, X, Y, Z (for example, from the CIE 1931 XYZ color space), red chromaticity, green chromaticity, and blue chromaticity. In some implementations, the first color channel is red chromaticity (r) and the second color channel is green chromaticity (g), which can be represented by r=

and

Definition, where R, G, and B are the intensity values of the red, green, and blue color channels of the color image.

The thickness path 604 can be manually generated by a user (for example, an operator of a semiconductor manufacturing facility) using a graphical user interface in conjunction with a computer (for example, the controller 190). For example, while displaying the scatter graph, the user can manually construct a path that follows the scatter graph and covers the scatter graph, for example, using a mouse operation to click on selected points displayed in the scatter graph.

Alternatively, software may be used to automatically generate the thickness path 604, which is designed to analyze the set of coordinates in the scatter diagram and, for example, use topological skeletonization to generate paths that fit the points in the scatter diagram 800.

The thickness path 604 can be provided by a variety of functions, for example, using a single line, a polyline, one or more arcs, one or more Bezier curves, and the like. In some implementations, the thickness path 604 is provided by a polyline, which is a collection of line segments drawn between discrete points in coordinate space.

Returning to Figure 6, the function provides the relationship between the position on the predetermined thickness path 604 and the thickness value. For example, the controller 190 may store a first thickness value for the start point 602 of the predetermined thickness path 604 and a second thickness value for the end point 606 of the predetermined thickness path 604.

The first and second thickness values can be obtained by measuring the thickness of the substrate layer at the position corresponding to the pixel provided at the point 802 closest to the start point 602 and the end point 606 by using a conventional thickness measurement system.

， 其中T1為起點602之值，T2為終點606之厚度，L為起點602與終點606之間沿該路徑之總距離，且D為起點602與給定點610之間沿該路徑之距離。In operation, the controller 190 can calculate a value representing the thickness of a given point 610 on the path 604 by interpolating between the first and second values based on the distance from the starting point 602 to the given point 610 along the path 604. For example, if the controller can calculate the thickness T of the given point 610 according to the following equation:

, Where T1 is the value of the start point 602, T2 is the thickness of the end point 606, L is the total distance between the start point 602 and the end point 606 along the path, and D is the distance between the start point 602 and the given point 610 along the path.

As another example, the controller 190 may store the thickness value of each vertex on the predetermined thickness path 604, and calculate a value representing the thickness of a given point on the path based on the interpolation between the two closest vertices. For this configuration, various values of the apex can be obtained by measuring the thickness of the substrate layer at the position corresponding to the pixel at the point 802 closest to the apex using a conventional thickness measurement system.

Other functions that correlate the position on the path with the thickness are possible.

In addition, it is possible to calculate the thickness based on the optical model instead of using the measurement system to measure the thickness of the set substrate.

If we use theoretical simulation or empirical learning based on the known "set" wafers, the thickness value can be the actual thickness value. Alternatively, the thickness value at a given point on the predetermined thickness path may be, for example, a relative value with respect to the degree of polishing of the substrate. The latter value can be scaled in the downstream process to obtain an empirical value, or can be simply used to indicate an increase or decrease in thickness without specifying an absolute thickness value.

With reference to Figures 6 and 7, for the pixel analyzed from the image of the substrate, the values of the two color channels are extracted from the color data of that pixel (step 720). This provides the coordinates 620 in the coordinate system 600 of two color channels.

Next, the point (for example, point 610) closest to the coordinate 620 of the pixel on the predetermined thickness path 604 is calculated (step 730). In this context, "closest" does not necessarily indicate geometric perfection. The "closest" point can be defined in various ways, and limitations in processing power, selection of search functions for ease of calculation, the existence of multiple local maxima in the search function, etc. can prevent the determination of geometric ideals, but still provide enough to use The result. In some implementations, the closest point is defined as the point on the thickness path 604 that defines the normal vector to the thickness path through the coordinates 620 of the pixel. In some implementations, the closest point is calculated by minimizing the Euclidean distance.

Next, the value representing the thickness is calculated based on the autofunction of the position of the point 610 on the path 604, as described above (step 740). The closest point is not necessarily one of the vertices of the polyline. As mentioned above, in this case, interpolation is used to obtain the thickness value (for example, based on a simple straight line interpolation between the nearest vertices of a polyline).

By repeating steps 720 to 740 for some or all pixels in the color image, a thickness map of the substrate layer can be generated.

For some layer stacks on the substrate, the predetermined thickness path crosses itself, which leads to a situation called degeneracy. A degenerate point (for example, point 650) on the predetermined thickness path has two or more thickness values associated with it. Therefore, without some additional information, it may not be possible to know which thickness value is the correct value. However, it is possible to analyze the nature of the coordinate clusters associated with pixels from a given physical area on the substrate (for example, within a given die) and use this additional information to resolve the degeneracy. For example, it can be assumed that the measured value in a given small area of the substrate will not change significantly, and therefore will occupy a small part along the scatter diagram, that is, it will not extend along two branches.

In this way, the controller can analyze the coordinate clusters associated with pixels from a given physical area on the substrate that surrounds the pixels that need to resolve degeneracy. Specifically, the controller can determine the principal axis of the cluster in the coordinate space. The branch of the predetermined thickness path that is most closely parallel to the main axis of the cluster can be selected and used to calculate the value representing the thickness.

Returning to Figure 2, as appropriate, uniformity analysis can be performed on each area of the substrate (for example, each die) or on the entire image (step 280). For example, the value of each pixel can be compared with the target value, and the total number of "failed" pixels (ie, not meeting the target value) in the die can be calculated for the die. The total number can be compared with a threshold value to determine whether the die is acceptable, for example, if the total number is less than the threshold value, the die is marked as acceptable. This gives a pass/fail indication for each die.

As another example, the total number of "failed" pixels in the uncovered area of the substrate can be calculated. The total number can be compared with a threshold value to determine whether the substrate is acceptable, for example, if the total number is less than the threshold value, the substrate is marked as acceptable. The threshold can be set by the user. This gives the pass/fail indication of the substrate.

In the case that the die or wafer is determined to be "failed", the controller 190 may generate an alarm or cause the polishing system 100 to take corrective actions. For example, an audible or visual alarm can be generated, or a data file indicating that a specific die is unavailable can be generated. As another example, the substrate can be sent back for rework.

Contrary to the spectral processing where pixels are usually represented by 1024 or more intensity values, in color images, pixels can be represented by only three intensity values (red, green, and blue), and only two color channels are needed for processing. Calculation. Therefore, the computational load of processing color images is significantly reduced.

However, in some implementations, the light detector 164 is a spectrometer rather than a color camera. For example, the light detector may include a hyperspectral camera. This spectroscopic camera can generate 30 to 200 (for example, 100) intensity values of different wavelengths for each pixel. Next, instead of the value pairs in the two-dimensional color space as described above, the technique (steps 210 to 270) is applied to an image with an N-dimensional color space with N color channels, where N is obviously greater than 2. For example, 10 to 1000 dimensions. For example, the thickness path 604 may be a path in an N-dimensional color space.

In some implementations, the dimensions of the color space and the number of color channels are not reduced in the subsequent steps; each dimension corresponds to the wavelength of the intensity value measured by the hyperspectral camera. In some implementations, the number of dimensions and channels of the color space is reduced by, for example, 10 to 100 times, for example, to 10 to 100 dimensions and channels. The number of channels can be reduced by selecting only certain channels (for example, certain wavelengths) or by combining channels (for example, combining (such as averaging) intensity values measured for multiple wavelengths). In general, a larger number of channels reduces the possibility of degeneracy in the path, but has a larger computer processing cost. The appropriate number of channels can be determined based on experience.

Another technique for increasing the dimensionality of color images is to use multiple light beams with different incident angles. Except for the following, this embodiment can be configured similarly to Figs. 1A and 1B. Referring to FIG. 1C, the sensor assembly 161 (of the built-in metrology system 160 or the in-situ monitoring system 160') may include a plurality of light sources, for example, two light sources 162a, 162b. Each light source generates a light beam (for example, light beams 168a and 168b), which are directed to the substrate 10 at different incident angles. The incident angles of the light beams 168a and 168b may be at least 5° apart, for example at least 10° apart, for example at least 20° apart. As shown in FIG. 1C, the light beams 168a and 168b can irradiate the same area on the substrate 10, for example, overlap on the substrate 10. Alternatively, the light beams can illuminate different areas, for example, areas that partially but not completely overlap, or areas that do not overlap.

The light beams 168a, 168b are reflected from the substrate 10, and the intensity values of multiple colors are measured at multiple pixels by two different arrays of detector elements 178a, 178b, respectively. As shown in Figure 1C, the detector elements 178a, 178b can be provided by different light detectors 164a, 164b. For example, the two detectors 164a, 164b can each be a color line scan camera. However, in some implementations, there is a single photodetector with a two-dimensional array, and beams 168a, 168b illuminate different areas of the array of detectors. For example, the detector can be a 2D color camera.

Using two beams with different incident angles effectively doubles the dimension of the color image. For example, using two light beams 168a, 168b (wherein each light detector 164a, 164b is a color camera), for a total of six color channels, each detector will use three color channels (for example, , Respectively, red, blue, and green color channels) output color images. This provides a larger number of channels and reduces the possibility of degeneracy in the path, but still has manageable processing costs.

Although Figure 1C illustrates each light beam 168a, 168b as having its own optical components (eg, diffuser 170, focusing optical element 172, and polarizer 174), it is also possible for the beams to share some components. For example, a single diffuser 170 and/or a single polarizer 174 may be placed in the path of the two light beams 168a, 168b. Similarly, although multiple light sources 162a, 162b are shown, the light from a single light source can be divided into multiple beams (for example, by a partial reflector).

The number of channels can be used to scale the color correction. For the color correction step, it is not that I _ORIG is a 1x3 matrix and CCM is a 3x3 matrix, but I _ORIG can be a 1xN matrix and CCM can be an NxN matrix. For example, for an embodiment in which two light beams are incident at different angles and measured by two color cameras, I _ORIG can be a 1x6 matrix and CCM can be a 6x6 matrix.

In general, data (such as the calculated thickness of the layer on the substrate) can be used to control one or more operating parameters of the CMP device. Operating parameters include, for example, the rotation speed of the platform, the rotation speed of the substrate, the polishing path of the substrate, the speed of the substrate on the board, the pressure applied to the substrate, the slurry composition, the slurry flow rate, and the temperature of the substrate surface. The operating parameters can be controlled in real time, and the operating parameters can be adjusted automatically without further manual intervention.

As used in this specification, the term substrate may include, for example, a product substrate (for example, it includes a plurality of memory or processor dies), a test substrate, a bare substrate, and a gate control substrate. The substrate may be at various stages of integrated circuit manufacturing, for example, the substrate may be a bare wafer, or it may include one or more deposited and/or patterned layers. The term substrate may include discs and rectangular sheets.

However, the above-mentioned color image processing technology can be particularly useful in the case of 3D vertical NAND (VNAND) flash memory. In particular, the layer stack used in VNAND manufacturing is so complicated that current measurement methods (for example, Nova spectroscopy) may not be able to perform with sufficient reliability when detecting areas of inappropriate thickness. In contrast, color image processing technology can have superior throughput.

The embodiments of the present invention and all the functional operations described in this specification can be implemented in a digital electronic circuit system, or in computer software, firmware, or hardware (including the structural components and structures disclosed in this specification, etc.) Effect), or in a combination thereof. The embodiments of the present invention can be implemented as one or more computer program products, that is, tangibly embodied in a non-transitory computer-readable storage medium for data processing equipment (eg, programmable processor, computer , Or multiple processors or computers) one or more computer programs that execute or control the operation of the data processing equipment.

The term relative positioning is used to refer to the positioning of the components of the system relative to each other, not necessarily with regard to gravity; it should be understood that the grinding surface and the substrate can be held in a vertical orientation or some other orientation.

Many implementations have been described. However, it will be understood that various modifications can be made. For example: ·A camera that images the entire substrate can be used instead of a line scan camera. In this case, no movement of the camera relative to the substrate is required. ·The camera can cover less than the entire width of the substrate. In this case, the camera needs to move in two vertical directions (for example, to be supported on an X-Y stage) in order to scan the entire substrate. ·The light source can illuminate the entire substrate. In this case, the light source does not need to move relative to the substrate. · Although the above discussed the coordinates represented by value pairs in a two-dimensional coordinate space, this technique is applicable to a coordinate space having three or more dimensions defined by three or more color channels. ·The sensor assembly does not require an embedded system positioned between the grinding stations or between the grinding stations and the transfer station. For example, the sensor assembly can be positioned in a transfer station, in a cassette interface unit, or a stand-alone system. ·The uniformity analysis step is optional. For example, the image generated by applying the threshold transformation can be fed into the feedforward process to adjust a subsequent processing step on the substrate, or fed into the feedback process to adjust the subsequent processing step on the substrate. ·For in-situ measurement, without constructing an image, the monitoring system can simply detect the color of the white light beam reflected from the spot on the substrate, and use this color data to determine the thickness at that spot using the above-mentioned technology. Although the description focuses on polishing, these techniques can be applied to other types of semiconductor manufacturing processes that add or remove layers and can be optically monitored, such as etching (for example, wet or dry etching), deposition (for example, chemical gas Phase deposition (chemical vapor deposition; CVD), physical vapor deposition (PVD) or atomic layer deposition (atomic layer deposition; ALD)), spin-on dielectric, or photoresist coating.

Therefore, other implementations are within the scope of the patent application.

10: substrate 12: Die 14: underline 16: Wafer orientation features 18: Center 22: uncovered area 24: Masked area 100: Grinding equipment 100': Grinding equipment 106: Grinding Station 108: bracket 120: platform 122: Groove 126: Carrier head 127: Axis 128: Support 130: polishing pad 132: Window 134: Arm 136: Grinding liquid 142: fixed ring 144: Flexible membrane 146a: Chamber 146b: Chamber 146c: Chamber 154: drive shaft 156: Carrying head rotation motor 160: Optical Metrology System 160': In-situ optical monitoring system 161: Sensor assembly 162: light source 162a: light source 162b: light source 164: Light detector 164a: Detector 164b: Detector 166: Circuit System 168: Light 168a: beam 168b: beam 170: diffuser 172: Focusing optics 174: Polarizing filter 178: Detector component 178a: Detector component 178b: Detector component 180: units 182: Linear Actuator 184: Orbit 186: Direction of Travel 188: bezel 190: Controller 200: step 210: Step 220: step 230: step 235: Step 240: step 250: step 260: Step 270: Step 280: Step 500: coordinate space 502: initial coordinates 504: Path 602: starting point 604: Scheduled Path 606: end 610: given point 620: Coordinates 650: point 710: step 720: step 730: step 740: step 800: Scatter chart 802: point

Figure 1A shows a schematic diagram of an example of an embedded optical measurement system.

Figure 1B shows a schematic diagram of an example of an in-situ optical measurement system.

Figure 1C shows a schematic diagram of an example of a part of the measurement system.

Figure 2 is a flow chart of the method for determining layer thickness.

Figure 3 is a schematic top view of the substrate.

Figure 4 is a schematic diagram of the mask.

Figure 5 illustrates an example graph showing the color evolution of light reflected from the substrate in the coordinate space of the two color channels.

Figure 6 shows an example graph showing the predetermined path in the coordinate space of the two color channels.

Figure 7 is a flowchart of the method for determining layer thickness from color image data.

Fig. 8 shows an example graph, which shows a histogram in the coordinate space of two color channels derived from the color image of the test substrate.

Figures 9A and 9B illustrate example graphs, which respectively show histograms in the coordinate space of the two color channels before and after color correction.

The same element symbols in the various drawings indicate the same elements.

Domestic deposit information (please note in the order of deposit institution, date and number) no Foreign hosting information (please note in the order of hosting country, institution, date and number) no

10: substrate

161: Sensor assembly

162a: light source

162b: light source

164a: Detector

164b: Detector

168a: beam

168b: beam

170: diffuser

172: Focusing optics

174: Polarizing filter

178a: Detector component

178b: Detector component

184: Orbit

188: bezel

Claims (19)

A system for obtaining a measurement value representing a thickness of a layer on a substrate includes: A support member for holding a substrate used for integrated circuit manufacturing; An optical assembly for capturing a first color image of at least a part of the substrate held by the support by irradiating the substrate with light at a first incident angle, and using a different light The second incident angle of illuminating the substrate to capture a second color image of the at least a portion of the substrate held by the support; and A controller configured to Receiving the first color image and the second color image from the optical assembly, Store a function that provides a value representing a thickness according to a position along a predetermined path in a coordinate space of at least four dimensions, the at least four dimensions including a first color from the first color image Channel and a second color channel and a third color channel and a fourth color channel from the second color image, For a pixel in the first color image and a corresponding pixel in the second color image, from the color data for the pixel in the first color image and the color data for the corresponding pixel in the second color image Determine one of the coordinates in the coordinate space, Determine a position on the predetermined path closest to a point of the coordinate, and A value representing a thickness is calculated from the function and the position of the point on the predetermined path. The system according to claim 1, wherein the coordinate space is four-dimensional. The system according to claim 1, wherein the coordinate space is six-dimensional. The system according to claim 1, wherein the first color channel and the second color channel are selected from hue, saturation, brightness, X, Y, Z, red chroma, and green chroma of the first color image And the group of color channels of blue chromaticity, and the third color channel and the fourth color channel are selected from hue, saturation, brightness, X, Y, Z, red chromaticity, green color of the second color image A group of color channels of chroma and blue chroma The system according to claim 4, wherein the first color channel and the third color channel are red chromaticity, and the second color channel and the fourth color channel are green chromaticity. The system according to claim 1, wherein the first incident angle and the second incident angle are both between about 20° and 85°. The system according to claim 1, wherein the first angle of incidence is at least 5° greater than the second angle of incidence. The system according to claim 1, wherein the first angle of incidence is at least 10° greater than the second angle of incidence. A computer program product used to obtain a measurement value representing a thickness of a layer on a substrate. The computer program product is tangibly embodied in a non-transitory computer-readable medium and includes a processor for performing the following Instructions for each: Receiving a first color image of the substrate and a second color image of the substrate from one or more cameras; Store a function that provides a value representing a thickness based on a position along a predetermined path in a coordinate space of at least four dimensions, the at least four dimensions including a first color image from the first color image Color channel and a second color channel and a third color channel and a fourth color channel from the second color image; For a pixel in the first color image and a corresponding pixel in the second color image, from the color data for the pixel in the first color image and the color data for the corresponding pixel in the second color image Determine one of the coordinates in the coordinate space; Determine a position on the predetermined path that is closest to a point of the coordinate; and A value representing a thickness of a layer on the substrate is calculated from the function and the position of the point on the predetermined path. A method for obtaining a measurement value representing a thickness of a layer on a substrate includes the following steps: Whereas a color camera is used to position a substrate for integrated circuit manufacturing; One or more color cameras are used to generate a first color image of the substrate and a second color image of the substrate, the first color image being generated by light irradiating the substrate at a first incident angle, and The second color image is generated by light irradiating the substrate at a different second incident angle; Store a function that provides a value representing a thickness based on a position along a predetermined path in a coordinate space of at least four dimensions, the at least four dimensions including a first color image from the first color image Color channel and a second color channel and a third color channel and a fourth color channel from the second color image; For a pixel in the first color image and a corresponding pixel in the second color image, from the color data for the pixel in the first color image and the color data for the corresponding pixel in the second color image Determine one of the coordinates in the coordinate space; Determine a position on the predetermined path that is closest to a point of the coordinate; and A value representing a thickness of a layer on the substrate is calculated from the function and the position of the point on the predetermined path. A grinding system includes: A polishing station, which includes a platform for supporting a polishing pad; A support for holding a substrate; An embedded metrology station for measuring the substrate before and after polishing a surface of the substrate in the polishing station, the embedded metrology station including One or more elongated white light sources, each having a longitudinal axis and configured to direct light to the substrate at a non-zero angle of incidence, thereby forming an illumination area on the substrate, the illumination area scanning the substrate During which it extends along a first axis, A first color line scanning camera with a detector element, the detector elements are arranged to receive the light reflected from the substrate illuminating the substrate at a first incident angle, and are formed along the scanning period of the substrate An image portion extending from the first axis, A second color line scanning camera with detector elements arranged to receive the light reflected from the substrate irradiating the substrate at a different second incident angle and formed during the scanning of the substrate A second image portion extending along the first axis, A frame supporting the one or more light sources, the first color line scan camera and the second color line scan camera, and A motor that causes relative movement between the frame and the support along a second axis perpendicular to the first axis, thereby causing the one or more light sources, the first color line scanning camera, and the first axis A two-color line scan camera scans the substrate; and A controller configured to receive color data from the first color line scan camera and the second color line scan camera, and to generate a first two-dimensional color from the color data from the first color line scan camera Image and generate a second two-dimensional color image from the color data from the second color line scan camera, and control the grinding at the polishing station based on the first two-dimensional color image and the second two-dimensional color image. The system according to claim 11, comprising one or more diffusers in a light path between the one or more elongated white light sources and the substrate. The system according to claim 11, wherein the first incident angle and the second incident angle are both between about 5° and 85°. The system according to claim 13, wherein the first incident angle and the second incident angle are both between about 20° and 75°. The system according to claim 11, wherein the first angle of incidence is at least 5° greater than the second angle of incidence. The system according to claim 11, wherein the first incident angle is greater than the second incident angle by at least 10°. The system of claim 11, wherein the first color line scan camera and the second line scan camera are configured to image a coincident area on the substrate. The system according to claim 11, wherein the one or more elongated light sources include a first elongated light source for generating the light that illuminates the substrate at the first incident angle, and for generating the second incident angle A second elongated light source that irradiates the light on the substrate at an angle. The system of claim 11, wherein the frame is fixed, the motor is coupled to the support, and the controller is configured to cause the motor to move the support while the one or more The elongated light source and the first color line scanning camera and the second color line scanning camera are kept fixed for scanning on the substrate.

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