JP5531405B2 - Periodic pattern unevenness inspection method and inspection apparatus - Google Patents

Description

The present invention relates to an unevenness inspection method and an inspection apparatus for inspecting unevenness of a pattern in an inspection object having a periodic pattern.
Here, the periodic pattern refers to an aggregate of patterns having a constant interval. For example, a striped periodic pattern in which patterns are arranged at a predetermined pitch, or a pattern of openings is two-dimensional with a predetermined period. This corresponds to a matrix-like pattern or the like arranged in a regular manner. In addition, examples of the inspection object having a periodic pattern include a photomask used in an exposure process of a photolithography process when manufacturing a semiconductor device, an imaging device, a display device, and the like.

Conventionally, as a photomask used in a manufacturing process of a semiconductor device, an imaging device, a display device and the like, a photomask that is configured by partially removing a light-shielding film such as chromium on a transparent substrate such as glass in a certain pattern. Are known.
Uneven defects in periodic patterns such as photomasks are usually caused by the regular arrangement of fine pitch deviations and positional deviations, and are therefore difficult to find by individual pattern inspection. However, this is a defect recognized for the first time when the periodic pattern is observed in a wide area.

  In the conventional unevenness inspection for periodic patterns, imaging is performed using coaxial transmitted illumination, flat illumination, or reflected illumination, and the normal portion and the uneven portion are visually recognized by comparing the light intensity in each image. Yes. However, the difference in light intensity between the normal part and the uneven part is not always large, and the contrast of the obtained image is low. For this reason, the contrast difference is devised for an image having a low contrast to improve the contrast, thereby extracting the uneven portion and performing the inspection (see Patent Document 1).

However, in the above-described conventional technique, in the imaging of the black matrix unevenness of the lattice-like periodic pattern, particularly the black matrix unevenness having a large opening, the contrast between the normal portion and the uneven portion is not expected to be improved. However, the inspection in the case of an image having a low contrast of the original image has a problem that only an inspection ability lower than the visual sensory inspection method can be achieved.
On the other hand, with the miniaturization of semiconductors and the increase in electronic components having fine displays and bright screens, the above-described tendency of miniaturization of the periodic pattern or an increase in the opening ratio is progressing. In the future, there will be a need for a non-uniformity inspection apparatus and method for a periodic pattern with a finer shape and a larger opening. That is, there is a limit in the conventional output with only the intensity (brightness) of light based on the amplitude of light.

Therefore, for the purpose of providing a periodic pattern unevenness inspection apparatus capable of capturing and detecting periodic patterns such as black matrix unevenness stably and with high accuracy, illumination light is irradiated to the object to be inspected. As an inspection apparatus for inspecting transmitted diffracted light generated by a pattern, for example, an inspection apparatus as disclosed in Patent Document 2 has been proposed.
In such an inspection apparatus, since the shape and pitch of the openings are constant in the normal part of the periodic pattern, they interfere with each other and generate diffracted light in a certain direction. On the other hand, since the shape and pitch of the opening are irregular in the uneven portion, diffracted light is generated with various intensities in various directions according to the shape and pitch.
Such an inspection apparatus employs a method of detecting the uneven portion from the difference in diffracted light intensity contrast between the normal portion and the uneven portion. However, the diffracted light intensity contrast in the original captured image obtained by this method is weak, and in order to perform actual unevenness inspection / determination processing, some image processing is applied to the original captured image, Extraction with emphasis on is necessary.

The processing method for the original captured image in the above-described prior art cuts out the entire periodic pattern area on the target substrate and defines it as a calculation region, and separately determines the luminance value in each pixel in the calculation region in the vertical and horizontal directions. Integration is performed to obtain integrated value data.
By the way, in a periodic pattern, for example, a photomask, the drawing pattern has been miniaturized rapidly. Particularly, in a photomask for a CCD / CMOS imager, the cell pitch at the time of pattern transfer to a wafer approaches 1 μm. The generation is progressing.

An electron beam (EB) drawing device or a laser beam drawing device is generally used for pattern drawing in the periodic pattern. In these pattern drawing devices, the beam scanning area and the stage movement area on which the drawing object is placed are divided into fine rectangular areas, and the positional relationship between the drawing surface and the electron gun is changed, and the step and repeat method is used. A pattern is drawn by scanning the beam.
In a periodic pattern, for example, a photomask, it is known that pattern fluctuations such as a continuous pitch shift, dimension shift, and position shift of a drawing pattern occur on the order of several nanometers at the boundary portion of a rectangular region as described above. The mura defect is exactly caused by these pattern fluctuations, and it can be said that the occurrence pattern and the in-plane distribution of the mura defect in the periodic pattern region depend on the rectangular region shape. Accordingly, there is a need for a method for detecting a mura defect that pays attention to the size and shape of the rectangular area. In addition, in the application process of this inspection, it is necessary to pay attention to the detection of irregular irregularities caused by the process.
JP 2002-148210 A JP 2006-208084 A

  The present invention has been made to solve the above-described problems, and the object of the present invention is to apply a periodic pattern, particularly, an object to be inspected such as a photomask for a CCD / CMOS imager. An object of the present invention is to provide a mura inspection method and a mura inspection apparatus for accurately detecting mura defects caused by dimensional deviations and positional deviations on the order of nm.

In order to achieve the above object, the invention described in claim 1 irradiates an inspection object having a periodic pattern with illumination light, analyzes a two-dimensional gray image obtained by diffracted light generated by the periodic pattern, A method for inspecting unevenness of a periodic pattern by specifying a region having a high density or a region having a low density as a nonuniformity region of the two-dimensional grayscale image, and imaging means for imaging the two-dimensional grayscale image of the object to be inspected An image creation step of creating an original captured image by imaging, defining a rectangular calculation area having a smaller area than the original captured image on the original captured image, and vertically calculating a luminance value of each pixel in the rectangular calculation area An integrated value calculating step for calculating the integrated value by integrating separately in the lateral direction, defining an envelope width for the integrated value, obtaining a maximum value and a minimum value of the integrated value within the envelope width, and the envelope width The shifted The maximum value and the minimum value of the integrated value are searched while the curve connecting the searched maximum values is defined as the upper envelope data Sa, and the curve connecting the minimum values is derived as the lower envelope data Sb. A contrast ratio calculation step of obtaining a comparison reference value from the lower envelope data Sb , calculating a ratio between the comparison reference value and the integrated value to obtain contrast ratio data, and a calculation region defined in the integrated value calculation step Contrast that creates a two-dimensional contrast ratio distribution image by scanning the original captured image and performing the integrated value calculating step and the contrast ratio calculating step on the luminance values of all the pixels of the original captured image. A comparison calculation process is performed between the ratio distribution image creation step and a contrast ratio threshold value separately set for the two-dimensional contrast ratio distribution image. An object (for example, 0 as a white dot) is allocated to dots constituting a two-dimensional contrast ratio distribution image having contrast ratio data outside the threshold range by processing, and a background (for example, 1 as a black dot) is allocated to other dots. A binary image creating step for creating a value image, and a labeling process for the binary image, extracting the connected figure parts as a connected pixel part, calculating an area value of each of the connected pixel parts, Furthermore, a two-dimensional contrast ratio distribution image created in a coordinate value deriving step for deriving a coordinate value where each of the connected pixel portions is located on a coordinate axis defined for the object to be inspected, and a contrast ratio distribution image creating step In FIG. 5, the connected pixel portion position derived in the coordinate value deriving step is collated with the two-dimensional contrast ratio distribution image, and A large contrast ratio data is obtained for each of the connected pixel portions, and an evaluation value for each of the connected pixel portions is calculated by calculating a product of the maximum contrast ratio data and the area value in each of the obtained connected pixel portions. An evaluation value calculation step to calculate, and a non-uniformity determination step of performing a comparison calculation process with a threshold value separately set for the evaluation value, and determining a connected pixel portion exceeding the threshold value as a nonuniformity portion by the comparison calculation process. Features.

  According to a second aspect of the present invention, in the unevenness inspection method according to the first aspect, after the noise removal processing such as expansion / contraction is performed on the original captured image by a digital filter, the processing after the image creation step is performed. It is characterized by that.

According to a third aspect of the present invention, illumination light is irradiated onto an inspection object having a periodic pattern, a two-dimensional gray image obtained by diffracted light generated by the periodic pattern is analyzed, and a part of the two-dimensional gray image is analyzed. A non-uniformity inspection apparatus for inspecting periodic pattern unevenness by specifying a high-density region or a low-density region as a non-uniformity region, wherein the inspected object is placed and driven in the X-axis, Y-axis, and θ-axis directions And a conveying means having a mechanism for performing the image processing on the image obtained by irradiating the predetermined area of the inspection object with light and imaging the predetermined area, and positioning the inspection object in the in-plane direction of inspection Positioning means for performing illumination, illumination light source means including a light source that generates visible light as the illumination light, and an illumination head unit for guiding illumination light from the illumination light source means and irradiating the predetermined area with illumination light And before An irradiation angle of the illumination light with respect to the surface to be inspected of the object to be inspected is irradiated while irradiating illumination light to a predetermined region on the object to be inspected that supports the illumination head unit and is placed on the transport unit. An illumination head driving unit that controls an illumination light irradiation angle with respect to a vertical direction, an imaging unit that images diffracted light generated by illuminating the periodic pattern with illumination light by the illumination head unit, and the positioning unit Image input means using the video output of the image and the video output from the imaging means as image information, and a rectangular calculation area having a smaller area than the original captured image on the original captured image obtained by the image input means. , Processing for calculating the integrated value by separately integrating the luminance values of the respective pixels in the rectangular calculation area in the vertical and horizontal directions, defining an envelope width for the integrated value, and integrating the integrated value within the envelope width The maximum value and minimum value of the integrated value are searched while the envelope width is shifted, and a curve connecting the searched maximum values is defined as upper envelope data Sa, and a curve connecting the minimum values is obtained. A process of obtaining contrast ratio data by deriving as lower envelope data Sb, obtaining a comparison reference value from the upper envelope data Sa and lower envelope data Sb, and calculating a ratio between the comparison reference value and the integrated value; , By scanning the calculation area defined in the integrated value calculation process on the original captured image, the integrated value calculating process and the contrast ratio calculating process are performed on the luminance values in all pixels of the original captured image. A process of creating a two-dimensional contrast ratio distribution image by performing a comparison calculation process with a contrast ratio threshold set separately for the two-dimensional contrast ratio distribution image, The object (for example, 0 as a white dot) is assigned to the dots constituting the two-dimensional contrast ratio distribution image having the contrast ratio data outside the threshold range by the comparison calculation process, and the background (for example, 1 as a black dot) is assigned to the other dots. A process for creating a binary image, a labeling process is performed on the binary image, extracted figure parts connected to each other are extracted as connected pixel parts, an area value of each connected pixel part is calculated, and In the two-dimensional contrast ratio distribution image created by the process of deriving the coordinate value where each of the connected pixel portions is located on the coordinate axis defined for the object to be inspected, and the creation process of the contrast ratio distribution image, the coordinates The connected pixel portion position derived by the value deriving process is collated with the two-dimensional contrast ratio distribution image, and the maximum in the connected pixel portion is checked. The trust ratio data is obtained for each connected pixel portion, and the evaluation value for each connected pixel portion is calculated by calculating the product of the maximum contrast ratio data and the area value in each obtained connected pixel portion. Processing and a comparison calculation process with a threshold value set separately for the evaluation value, and a process of determining a connected pixel portion exceeding the threshold value as a nonuniformity portion by the comparison calculation process;
And processing / control means for controlling the transport means, the positioning means, the illumination light source means, the illumination head unit, the illumination head driving means, and the imaging means,
The image processing apparatus includes a display unit that displays an image captured by the positioning unit and the imaging unit and a processing result by the control unit.

  According to the periodic pattern unevenness inspection method and apparatus of the present invention, a periodic pattern, particularly an object to be inspected such as a photomask for a CCD / CMOS imager, is subject to a dimensional deviation or positional deviation on the order of several nm. The generated mura defect can be detected with high accuracy, and the mura defect can be identified and accepted or rejected.

(Embodiment 1)
Hereinafter, an embodiment of a periodic pattern unevenness inspection method and an inspection apparatus to which the present invention is applied will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing an example of a non-uniformity inspection apparatus to which the nonuniformity inspection method according to the present invention is applied. FIG. 1 shows an example of the configuration of an unevenness inspection apparatus for obtaining transmitted diffracted light. This apparatus is a dark environment where disturbance light and stray light are reduced as much as possible, and a clean environment that prevents foreign matter from adhering to the substrate to be inspected. It is desirable to operate.

As shown in FIG. 1, the unevenness inspection apparatus is driven in the X-axis-Y-axis and θ-axis directions that allow positioning operation and substrate transport operation of the transmitted illumination unit 10 and the substrate 60 to be inspected. XY-θ stage section (corresponding to the transport means described in the claims) 20, an alignment imaging section 30 for positioning the substrate 60 to be inspected, and an inspection image acquisition The imaging unit 40 and the processing / control unit 100 are configured.
Here, a periodic pattern is formed on the substrate surface of the inspected substrate 60. The substrate surface here is a surface located on one side in the thickness direction of the inspected substrate 60.

  The processing / control unit 100 controls the operation of the devices constituting the transmitted illumination unit 10, the XY-θ stage unit 20, the alignment imaging unit 30, and the imaging unit 40, and the alignment imaging unit 30 and imaging unit. The output from 40 is taken in as image information or signal information, and calculation processing is performed. Further, the processing result and the processed image are displayed on the display means 104.

  In the transmissive illumination unit 10, an arc rail 11 is installed, and an illumination head 12 is provided on the arc rail 11, and light from the light source 13 is guided to the illumination head 12 via a light guide 14. It is configured to be. By moving the illumination head 12 along the arc rail 11 on the arc rail 11, the irradiation angle φ of the illumination head 12 with respect to the normal L perpendicular to the substrate surface of the substrate 60 to be inspected can be adjusted (note that This drive axis is defined as the φ axis). Therefore, the illumination head 12 is adjusted so that it can irradiate illumination light to a predetermined position on the XY-θ stage unit 20 at any position on the arc rail 11. Transmission illumination from various irradiation angles can be performed on the substrate surface of the inspected substrate 60 on the −Y−θ stage unit 20.

  The illumination head 12 is provided with a parallel optical system. The light source 13 is provided with a filter changer mechanism, and a plurality of wavelength selection filters can be used. Further, the present embodiment is characterized in that a metal halide lamp is used as the light source 13, and a light amount fluctuation range with respect to the operation time is 1% or less and the light amount stability is high.

  The inspected substrate 60 is placed at a predetermined position of the XY-θ stage unit 20. The placement portion of the XY-θ stage portion 20 on which the substrate 60 to be inspected is placed is characterized by being hollow. The XY-θ stage unit 20 has a function of translating the inspected substrate 60 in the X-axis direction and the Y-axis direction in FIG. 2 and a normal L of the substrate surface orthogonal to the substrate surface. It has a function of rotating 360 ° around the center axis (this axis of rotation is the θ axis). As a result, the inspected substrate 60 is driven in the X-axis and Y-axis directions according to a preset operation procedure. Further, by rotating the inspected substrate 60 in the plane about the θ axis, it is possible to adjust the illumination irradiation direction in the substrate surface of the inspected substrate 60.

The alignment imaging unit 30 includes a camera 31 and a lens 32 that are disposed above the substrate 60 to be inspected and directed toward the substrate surface, an illumination 33 and an illumination control device 34 for the illumination 33.
The region including the alignment mark on the inspected substrate 60 is irradiated with the illumination light of the illumination 33 in the coaxial epi-illumination format, and the observation image is captured by the camera 31.
Note that the illumination control device 34 can turn on / off the illumination 33 and adjust the illumination light intensity, and the actual control operation is performed by the processing / control unit 100. In this embodiment, an area CCD camera is used as the camera 31, a coaxial incident type fixed magnification telecentric lens is used as the lens 32, and a high brightness spot type white LED is used as the illumination 33. Yes.

The imaging unit 40 includes a camera 41 disposed above the substrate 60 to be inspected and facing the substrate surface, and a parallel optical system 42. The camera 41 desirably includes a photoelectric conversion element having spectral sensitivity characteristics in the visible light range.
In the processing / control unit 100, the information processing unit 101 performs operation management and control of the transmitted illumination unit 10, the XY-θ stage unit 20, the imaging unit 30 for alignment, and the imaging unit 40. The camera 31 of the alignment imaging unit 30 is connected to the information processing means 101 via the signal input device 103, and the camera 41 of the imaging unit 40 is connected to the information processing means 101 via the signal input device 102.

  Utilizing the above-described components, after the positioning by the alignment imaging unit 30, the inspected substrate 60 is imaged by the imaging unit 40, an original captured image is acquired, and the mura defect detection / determination process is performed. Note that the inspection conditions such as the irradiation angle φ of the illumination head 12 in the transmissive illumination unit 10 are, for example, “the inspection condition setting method in the periodic pattern unevenness inspection apparatus already proposed by the present applicant in Japanese Patent Application No. 2008-248753. By applying “”, it is possible to set automatically.

FIG. 2 is a flowchart showing an inspection procedure of the unevenness inspection method according to the first embodiment of the present invention.
The unevenness inspection method according to the first embodiment of the present invention is performed by a series of steps S1 to S10 shown in FIG. Hereinafter, the contents of each step will be described in the order of steps with reference to FIGS. Note that operation operations such as attachment / detachment of the inspected substrate 60 are omitted from the flow shown in FIG.

  The inspected substrate 60 is imaged by the imaging unit 40, and an original captured image is acquired. Further, as shown in FIG. 3, a process of cutting out an area portion including the periodic pattern from the original captured image is performed (step S1). In the present embodiment, a line sensor camera having 4096 pixels is used as the camera 41 in the imaging unit 40. Delay and Integration) A line sensor camera may be used. Further, by providing a plurality of cameras having different performances and a camera switching mechanism, it may be possible to select an optimal one for each measurement by switching the camera used. Further, the lighting head 12 may be a line type lighting head.

In the image cut out in step S1 (hereinafter referred to as a cut-out image), a rectangular calculation area having a smaller area than the cut-out image is defined, and the luminance value at each pixel in the rectangular calculation area is separately set in the vertical and horizontal directions. Integration is performed and an integrated value is calculated (step S2). The integrated value is an average value divided by the integrated number of pixels as shown in FIG.
In addition, about the designation | designated method of a rectangular calculation area, the example in the case of integrating | accumulating with respect to a cut-out image horizontal direction is shown typically in FIG. When integration is performed in the horizontal direction with respect to the cutout image, the vertical size of the cutout image is matched with the vertical size of the rectangular calculation area. The same applies to the case where integration is performed in the vertical direction. Further, as shown in FIG. 3, the central portion of the rectangular calculation area is set as a target pixel line, and this is set as a reference position of the rectangular calculation area. This rectangular calculation area width is set in accordance with the rectangular area size in the drawing apparatus described above. However, in order to be able to change the rectangular integrated area width for each drawing apparatus used for drawing the periodic pattern, A value may be set each time.

A comparison reference value for the integrated value calculated in step S2 is calculated (step S3). FIG. 4 schematically shows the derivation of the comparison reference value from the integrated value. In this embodiment, envelope processing is used as a method for deriving a comparison reference value, but moving average processing may be used in some cases.
The purpose of the envelope process and the moving average process is to derive a comparison reference value that follows the gradation gradation tendency on the image. Hereinafter, the envelope processing will be briefly described with reference to FIG.

The flow of the envelope processing is shown in FIG.
First, in step S31, an envelope width is defined for the integrated value, and a maximum value and a minimum value of the integrated value are obtained within the envelope width. As shown in FIG. 6, the envelope width is defined from the left end of the integrated value curve as a base point, and the maximum value and the minimum value are searched for each time while sequentially shifting in the right direction of the curve. In the next step S32, a curve connecting the searched maximum value and the minimum value is obtained, and the curve connecting the maximum value is set as the upper envelope data Sa, and the curve connecting the minimum value is generated as the lower envelope data Sb. And derive each. In the next step S33, a comparison reference value So = (Sa + Sb) / 2 is calculated from the upper envelope data Sa and the lower envelope data Sb.

Next, the process proceeds to step S4 shown in FIG. 2, and contrast ratio data as shown in FIG. 7 is calculated. This contrast ratio is obtained by the following equation (1).
(Contrast ratio) = (integrated value / comparative reference value) −1 (1)

  Next, in step S5, it is determined whether the integrated value calculation, that is, the processing in steps S2 to S4 has been performed on the entire image range. Here, when it is determined that the integrated value calculation for the entire image range has not been performed, the process proceeds to step S6, and the rectangular calculation area is shifted pixel by pixel in the integration direction with reference to the target pixel line shown in FIG. Then, the processes in steps S2 to S5 are repeatedly executed for the entire image range. When the integration in the X direction is completed, the integration in the Y direction is performed in the same manner. Thereafter, in step S7, it is determined whether the integrated value calculation has been completed in the X and Y directions of the image. If the integrated value calculation has not ended, the processes of steps S2 to S7 are repeatedly executed until the integrated value calculation ends.

If it is determined in step S7 that the integrated value calculation has been completed in the X and Y directions of the image, the process proceeds to step S8 to create a contrast ratio distribution image as schematically shown in FIG.
In the present embodiment, calculation using an 8-bit image is performed, and the subsequent processing is performed after the luminance value 128 is assigned to the pixel portion where the contrast ratio = 0, that is, the base portion where no mura defect exists. .

  First, in the contrast ratio distribution image created in step S8, a binarization process is performed from a comparison calculation process with a separately set threshold value (step S9). At this time, if it is desired to extract a portion having a higher luminance value than the base portion, that is, a white unevenness portion, a brightness value larger than that of the base portion is set as a white unevenness detection threshold, and white unevenness detection is performed. A binary image is created by assigning 0 as a white dot to a pixel having a luminance value larger than the threshold value and assigning 1 as a black dot to other portions. Similarly, when it is desired to extract a portion having a lower luminance value than the base portion, that is, a black uneven portion, a luminance value smaller than that of the base portion is set as a black unevenness detection threshold, and black unevenness detection is performed. A binary image is created by assigning 1 as a black dot to pixels having a luminance value smaller than the threshold value and assigning 0 as a white dot to the other portions. In this embodiment, since calculation is performed using an 8-bit image, a luminance value 255 is assigned as a white dot, and a luminance value 0 is assigned as a black dot. An example of creating a white unevenness binary image and a black unevenness binary image in this case is shown in FIG.

Next, a labeling process is performed on the binary image processed in step S9, pixel portions connected to each other are extracted as connected pixel portions, and their area values and coordinate values on the inspected substrate 60 are calculated ( Step 10). If it is desired to detect both white unevenness and black unevenness, in step 10, both the white unevenness binary image and the black unevenness binary image are created and buffered, and each binary image is labeled. After the processing, the area values and coordinate values of white unevenness and black unevenness may be integrated into one piece of image information.
In the contrast ratio distribution image created in step S8, the coordinate value of the uneven portion and the uneven region are specified based on the binarization processing result in step S9. Further, in the next step S11, the product of the maximum value of the contrast ratio in the uneven area and the area value of the uneven area is defined as an evaluation value, and this is calculated.

A comparison calculation process with a separately set threshold value is performed on the evaluation value calculated in step S11, and a nonuniform portion exceeding the threshold value is determined to be NG (step S12). At this time, OK / GRAY / NG three-step determination criteria are provided, and two threshold values Th_Gr and Th_NG are defined for determination.
If (evaluation value) <Th_GR, it is determined as OK,
If Th_GR ≦ (evaluation value) <Th_NG, it is determined as GRAY,
If Th_NG ≦ (evaluation value), it is determined as NG.

  As described above, according to the unevenness inspection method shown in this embodiment, in an inspection apparatus for a product having a periodic pattern such as a photomask or a black matrix, a periodic pattern, particularly for a CCD / CMOS imager. By incorporating a calculation method that utilizes a rectangular area corresponding to the drawing area unique to the drawing apparatus for the inspected object such as a photomask, it is possible to accurately detect uneven defects caused by dimensional deviations and positional deviations on the order of several nanometers. In addition, it is possible to identify mura defects and determine pass / fail.

It is a block diagram which shows an example of the nonuniformity inspection apparatus to which the nonuniformity inspection method which concerns on this invention is applied. It is a flowchart which shows the procedure of the nonuniformity test | inspection by the method of this invention. It is the figure which showed the setting method of the rectangular calculation area | region in embodiment of this invention. It is the figure which showed the calculation method of the comparison reference value from the integrated value in embodiment of this invention. It is the flowchart which performed the procedure of the envelope process in embodiment of this invention. It is the figure which showed the example which calculated | required the upper envelope, the lower envelope, and the comparison reference value using the envelope process in embodiment of this invention. It is the figure which showed the calculation method of the contrast ratio in embodiment of this invention. It is the figure which showed typically the contrast ratio distribution image in embodiment of this invention. It is the figure which showed the creation example of the white nonuniformity binary image and black nonuniformity binary image in embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Transmission illumination part, 11 ... Arc rail, 12 ... Illumination head, 13 ... Light source, 14 ... Light guide, 20 ... XY- (theta) stage part, 30 ... Imaging part for alignment, 31 …… Camera, 32 …… Lens, 33 …… Illumination, 34 …… Illumination control device, 40 …… Imaging unit, 41 …… Camera, 42 …… Parallel optics, 60 …… Substrate to be inspected, 100 …… Process Control unit 101 ... Information processing means 102 ... Signal input device 103 ... Signal input device 104 ... Display means 105 ... Interpersonal operation means

Claims (3)

An object having a periodic pattern is irradiated with illumination light, a two-dimensional gray image obtained by diffracted light generated by the periodic pattern is analyzed, and a region in which the two-dimensional gray image is partially high or low Is a method for inspecting periodic pattern unevenness by specifying as an uneven region,
An image creating step of capturing an image of the two-dimensional grayscale image of the object to be inspected by an imaging unit and creating an original captured image;
An integrated value that defines a rectangular calculation region having a smaller area than the original captured image on the original captured image, and calculates the integrated value by separately integrating the luminance value of each pixel in the rectangular calculated region in the vertical and horizontal directions. A calculation process;
An envelope width is defined for the integrated value, a maximum value and a minimum value of the integrated value are determined within the envelope width, and a maximum value and a minimum value of the integrated value are searched while shifting the envelope width, and the search is performed. A curve connecting the maximum values is set as the upper envelope data Sa, and a curve connecting the minimum values is derived as the lower envelope data Sb. A comparison reference value is obtained from the upper envelope data Sa and the lower envelope data Sb, and the comparison reference A contrast ratio calculation step of calculating a ratio of the value and the integrated value to obtain contrast ratio data;
By scanning the calculation area defined in the integrated value calculating step on the original captured image, the integrated value calculating process and the contrast ratio calculating process are performed on luminance values in all pixels of the original captured image. A contrast ratio distribution image creation step of creating a two-dimensional contrast ratio distribution image with
The two-dimensional contrast ratio distribution image is subjected to a comparison calculation process with a contrast ratio threshold value set separately, and the object (in the dot constituting the two-dimensional contrast ratio distribution image having the contrast ratio data outside the threshold range by the comparison calculation process) For example, a binary image creation step of creating a binary image by assigning 0) as a white dot and assigning a background (for example, 1 as a black dot) to other dots,
The binary image is subjected to a labeling process, the connected figure portions are extracted as connected pixel portions, the area values of the respective connected pixel portions are calculated, and the coordinate axes defined for the inspected object A coordinate value deriving step for deriving a coordinate value where each of the connected pixel portions is located;
In the two-dimensional contrast ratio distribution image created in the contrast ratio distribution image creation step, the connected pixel portion position derived in the coordinate value deriving step is collated with the two-dimensional contrast ratio distribution image, and the maximum contrast ratio data in the connected pixel portion. For each of the connected pixel portions, and calculating an evaluation value for each of the connected pixel portions by calculating a product of the maximum contrast ratio data and the area value in each of the obtained connected pixel portions. Process,
A non-uniformity determination step of performing a comparison calculation process with a separately set threshold for the evaluation value, and determining a connected pixel portion exceeding the threshold by the comparison calculation process as a non-uniformity part,
An unevenness inspection method comprising:   The unevenness inspection method according to claim 1, wherein after the noise removal processing such as expansion / contraction is performed on the original captured image by a digital filter, the processing after the image creation step is performed. An object having a periodic pattern is irradiated with illumination light, a two-dimensional gray image obtained by diffracted light generated by the periodic pattern is analyzed, and a region in which the two-dimensional gray image is partially high or low A non-uniformity inspection apparatus that inspects non-uniformity of a periodic pattern by specifying as a non-uniformity area,
A conveying means on which the object to be inspected is mounted and having a mechanism for driving in the X-axis, Y-axis, and θ-axis directions;
Positioning means for performing image processing on an image obtained by irradiating a predetermined area of the object to be inspected and imaging the predetermined area and positioning the object to be inspected in the in-plane direction;
Illumination light source means comprising a light source that generates visible light as the illumination light;
An illumination head for guiding illumination light from the illumination light source means and irradiating the predetermined area with illumination light; and
The irradiation angle of the illumination light with respect to the surface to be inspected of the object to be inspected is irradiated while irradiating illumination light to a predetermined region on the object to be inspected that supports the illumination head unit and is placed on the transport means. An illumination head driving means for controlling an illumination light irradiation angle with respect to a direction perpendicular to the surface;
Imaging means for imaging diffracted light generated by illuminating the periodic pattern with illumination light by the illumination head unit;
Image input means for using the video output from the positioning means and the video output from the imaging means as image information;
A rectangular calculation area having a smaller area than the original captured image is defined on the original captured image obtained by the image input means, and the luminance values of each pixel in the rectangular calculated area are integrated separately in the vertical and horizontal directions. Processing to calculate the integrated value,
An envelope width is defined for the integrated value, a maximum value and a minimum value of the integrated value are determined within the envelope width, and a maximum value and a minimum value of the integrated value are searched while shifting the envelope width, and the search is performed. A curve connecting the maximum values is set as the upper envelope data Sa, and a curve connecting the minimum values is derived as the lower envelope data Sb. A comparison reference value is obtained from the upper envelope data Sa and the lower envelope data Sb, and the comparison reference A process for calculating contrast ratio data by calculating a ratio between the value and the integrated value;
By scanning the calculation area defined in the integrated value calculation process on the original captured image, the integrated value calculation process and the contrast ratio calculation process are performed on the luminance values in all pixels of the original captured image. Processing to create a two-dimensional contrast ratio distribution image,
The two-dimensional contrast ratio distribution image is subjected to a comparison calculation process with a contrast ratio threshold value set separately, and the object (in the dot constituting the two-dimensional contrast ratio distribution image having the contrast ratio data outside the threshold range by the comparison calculation process) For example, assigning 0) as a white dot and assigning a background (for example, 1 as a black dot) to the other dots to create a binary image;
The binary image is subjected to a labeling process, the connected figure portions are extracted as connected pixel portions, the area values of the respective connected pixel portions are calculated, and the coordinate axes defined for the inspected object A process of deriving coordinate values where each of the connected pixel portions is located above;
In the two-dimensional contrast ratio distribution image created by the contrast ratio distribution image creation processing, the connected pixel portion position derived by the coordinate value derivation processing is collated with the two-dimensional contrast ratio distribution image, and the maximum in the connected pixel portion is obtained. The contrast ratio data is obtained for each of the connected pixel portions, and the evaluation value for each of the connected pixel portions is calculated by calculating the product of the maximum contrast ratio data and the area value in each of the obtained connected pixel portions. Processing,
A process of performing a comparison operation with a threshold value set separately for the evaluation value, and determining a connected pixel portion that exceeds the threshold value by the comparison operation process as a non-uniform portion;
And processing / control means for controlling the transport means, the positioning means, the illumination light source means, the illumination head unit, the illumination head driving means, and the imaging means,
Display means for displaying an image captured by the positioning means and the imaging means and a processing result by the control means;
A nonuniformity inspection apparatus comprising:

Images