JP4554661B2 - Pattern inspection apparatus, pattern inspection method, and program - Google Patents

Description

  The present invention relates to a pattern inspection apparatus, a pattern inspection method, or a program for causing a computer to execute such a method. For example, the present invention relates to a pattern inspection technique for inspecting a pattern defect of an object serving as a sample used in semiconductor manufacturing. The present invention relates to an apparatus for inspecting defects of extremely small patterns such as a photomask, a wafer, or a liquid crystal substrate used when manufacturing a liquid crystal display (LCD) and an inspection method thereof.

  In recent years, the circuit line width required for a semiconductor element has been increasingly narrowed as a large scale integrated circuit (LSI) is highly integrated and has a large capacity. These semiconductor elements use an original pattern pattern (also referred to as a mask or a reticle, hereinafter referred to as a mask) on which a circuit pattern is formed, and the pattern is exposed and transferred onto a wafer by a reduction projection exposure apparatus called a stepper. It is manufactured by forming a circuit. Therefore, a pattern drawing apparatus capable of drawing a fine circuit pattern is used for manufacturing a mask for transferring such a fine circuit pattern onto a wafer. A pattern circuit may be directly drawn on a wafer using such a pattern drawing apparatus. For example, drawing is performed using an electron beam or a laser beam.

  In addition, improvement in yield is indispensable for manufacturing an LSI that requires a large amount of manufacturing cost. However, as represented by a 1 gigabit class DRAM (Random Access Memory), the pattern constituting an LSI is about to be in the order of submicron to nanometer. One of the major factors that reduce the yield is a pattern defect of a mask used when an ultrafine pattern is exposed and transferred onto a semiconductor wafer by a photolithography technique. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small. For this reason, it is necessary to improve the accuracy of a pattern inspection apparatus that inspects defects in a transfer mask used in LSI manufacturing.

  On the other hand, with the development of multimedia, LCDs (Liquid Crystal Display) are increasing in size of the liquid crystal substrate to 500 mm × 600 mm or more, and TFTs (Thin Film Transistors) formed on the liquid crystal substrate. : Thin film transistors) and the like are being miniaturized. Therefore, it is required to inspect a very small pattern defect over a wide range. For this reason, there is an urgent need to develop a sample inspection apparatus for efficiently inspecting defects of a photomask used in manufacturing such a large area LCD pattern and a large area LCD in a short time.

  Here, in a conventional pattern inspection apparatus, an optical image obtained by imaging a pattern formed on a sample such as a lithography mask using a magnifying optical system at a predetermined magnification and an identical pattern on the sample are captured. It is known to perform an inspection by comparing with an optical image. For example, as a pattern inspection method, “die to die inspection” for comparing optical image data obtained by imaging the same pattern at different locations on the same mask, or CAD data used for drawing a mask pattern as an inspection apparatus input format. There is a “die to database inspection” in which design image data is generated based on converted drawing data (design pattern information) and compared with optical image data that is measurement data obtained by imaging the pattern. In the inspection method in such an inspection apparatus, the sample is placed on the stage, and the stage is moved so that the light beam scans on the sample and the inspection is performed. The sample is irradiated with a light beam by a light source and an illumination optical system. The light transmitted or reflected by the sample is imaged on the sensor via the optical system. The image picked up by the sensor is sent to the comparison circuit as measurement data. The comparison circuit compares the measurement data and the reference data according to an appropriate algorithm after the images are aligned, and determines that there is a pattern defect if they do not match.

  Here, the pixel value level is adjusted so that the pixel value of the measurement image data and the pixel value of the reference image data to be compared are matched between the transmissive portions or the light shielding portions of the pattern. For example, level adjustment is performed by performing calibration before inspection. However, the pixel value level of the measurement image data may fluctuate when a comparative inspection is performed as a result due to some influence. In this case, the pixel value level of the reference image data does not match, so that there is a problem that a non-defect is erroneously determined as a defect (pseudo defect detection).

Conventionally, with respect to fluctuations in the amount of light from the light source, a technique has been disclosed in the literature in which a monitor for measuring the amount of light is provided and the output of the light receiving sensor element is corrected for the amount of fluctuation in light based on the monitor result (for example, Patent Document 1). reference). However, with this method, it is difficult to cope with a case where the pixel value level of the measurement image data fluctuates due to a cause other than the light amount fluctuation from the light source or a case where the pixel value level of the measurement image data fluctuates due to some influence after the sensor element It is.
JP 2005-241290 A

  As described above, there is a problem in that the pixel value level of the measurement image data fluctuates, and a non-defect is erroneously determined as a defect (pseudo defect detection).

  Accordingly, an object of the present invention is to provide an apparatus and method for performing pattern inspection that overcomes the above-described problems and reduces pseudo defects.

The pattern inspection apparatus according to one aspect of the present invention includes:
An optical image acquisition unit for acquiring optical image data in a patterned sample to be inspected;
The optical image data and reference image data corresponding to the optical image data are input, and the optical image data is based on a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data. A level adjustment unit that adjusts at least one of the pixel value level of the reference image data and the pixel value level of the reference image data;
A comparison unit that compares the optical image data with the pixel value level adjusted and the reference image data;
Equipped with a,
The level adjustment unit is configured to detect a pixel value level of the optical image data when a difference between a sum of a plurality of pixel values of the optical image data and a sum of a plurality of pixel values of the reference image data is equal to or less than a predetermined threshold. At least one of the pixel value level of the reference image data is adjusted .
Alternatively, the level adjustment unit may be configured such that the difference between the average value of the plurality of pixel values of the optical image data and the average value of the plurality of pixel values of the reference image data is equal to or less than a predetermined threshold value. At least one of a pixel value level and a pixel value level of the reference image data is adjusted.

The pattern inspection apparatus according to another aspect of the present invention includes:
An optical image acquisition unit for acquiring first optical image data in the patterned sample to be inspected and second optical image data corresponding to the first optical image data;
The first optical image data and the second optical image data are input, and based on the relationship between the plurality of pixel values of the first optical image data and the plurality of pixel values of the second optical image data. A level adjustment unit for adjusting at least one of a pixel value level of the first optical image data and a pixel value level of the second optical image data;
A comparison unit that compares the first optical image data and the second optical image data, each having a pixel value level adjusted;
Equipped with a,
The level adjustment unit is configured such that a difference between a sum of a plurality of pixel values of the optical image data and a sum of a plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; When the difference between the average value of the plurality of pixel values and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value, It is characterized by adjusting at least one of the pixel value level of the reference image data .

Further, the pattern inspection method of one embodiment of the present invention includes:
Obtaining optical image data in a patterned sample to be inspected;
The optical image data and reference image data corresponding to the optical image data are input, and the optical image data is based on a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data. Adjusting at least one of the pixel value level of the reference image data and the pixel value level of the reference image data;
Comparing the optical image data with the adjusted pixel value level and the reference image data, and outputting a result;
Equipped with a,
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value At least one of the levels is adjusted .

Moreover, the pattern inspection method according to another aspect of the present invention includes:
Obtaining first optical image data in a patterned sample to be inspected and second optical image data corresponding to the first optical image data;
The first optical image data and the second optical image data are input, and based on the relationship between the plurality of pixel values of the first optical image data and the plurality of pixel values of the second optical image data. And adjusting at least one of a pixel value level of the first optical image data and a pixel value level of the second optical image data;
Comparing the first optical image data with the adjusted pixel value level and the second optical image data, and outputting the result;
Equipped with a,
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value At least one of the levels is adjusted .

Further, a program for causing a computer of one embodiment of the present invention to execute is as follows.
A first storage process for storing optical image data in a patterned sample to be inspected in a first storage device;
A second storage process for storing reference image data corresponding to the optical image data in a second storage device;
The optical image data is read from the first storage device, the reference image data is read from the second storage device, and a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data is determined. A level adjustment process for adjusting at least one of a pixel value level of the optical image data and a pixel value level of the reference image data;
A comparison process for comparing the optical image data with the pixel value level adjusted with the reference image data, and outputting a result;
Equipped with a,
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value At least one of the levels is adjusted .

A program for causing a computer according to another aspect of the present invention to execute is as follows:
A first storage process for storing, in a storage device, first optical image data of the patterned sample to be inspected and second optical image data corresponding to the first optical image data;
The first optical image data and the second optical image data are read from a storage device, and a relationship between a plurality of pixel values of the first optical image data and a plurality of pixel values of the second optical image data A level adjustment process for adjusting at least one of a pixel value level of the first optical image data and a pixel value level of the second optical image data;
A comparison process of comparing the first optical image data and the second optical image data, the pixel value level of which has been adjusted, and outputting a result;
Equipped with a,
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value At least one of the levels is adjusted .

  According to the present invention, fluctuations in the pixel value level of measured image data can be corrected by adjustment. Therefore, pseudo defects can be reduced. As a result, it is possible to effectively use the apparatus, for example, preventing re-inspection.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the first embodiment.
In FIG. 1, a pattern inspection apparatus 100 that inspects a defect of a sample using a substrate such as a mask or a wafer includes an optical image acquisition unit 150 and a control system circuit 160. The optical image acquisition unit 150 includes an XYθ table 102, a light source 103, an enlargement optical system 104, a photodiode array 105, a sensor circuit 106, a laser length measurement system 122, an autoloader 130, and an illumination optical system 170. In the control system circuit 160, a control computer 110 serving as a computer is connected via a bus 120 serving as a data transmission path to a position circuit 107, a comparison circuit 108 as an example of a comparison unit, a development circuit 111, a reference circuit 112, and an autoloader control circuit. 113, a table control circuit 114, a level adjustment circuit 140, a magnetic disk device 109 as an example of a storage device, a magnetic tape device 115, a flexible disk device (FD) 116, a CRT 117, a pattern monitor 118, and a printer 119. The XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor. In FIG. 1, constituent parts necessary for explaining the first embodiment are described. It goes without saying that the pattern inspection apparatus 100 may normally include other necessary configurations.

FIG. 2 is a flowchart showing main steps of the pattern inspection method according to the first embodiment.
In FIG. 2, the pattern inspection method performs a series of steps of a measurement data acquisition step (S102), a reference data creation step (S104), a level adjustment step (S200), and a comparison step (S300). In the level adjustment step (S200), the area extraction step (S202), the measurement data average value calculation step (S205), the reference data average value calculation step (S207), the difference calculation step (S208), and the offset step A series of steps (S220) is performed.

  Before starting the inspection, first, the photomask 101 to be inspected by the autoloader 130 controlled by the autoloader control circuit 113 is placed on the XYθ table 102 provided so as to be movable in the horizontal and rotational directions by the motors of the XYθ axes. And mounted on the XYθ table 102.

  The XYθ table 102 is driven by the table control circuit 114 under the control of the control computer 110. It can be moved by a drive system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions. For example, step motors can be used as these X motor, Y motor, and θ motor. The movement position of the XYθ table 102 is measured by the laser length measurement system 122 and supplied to the position circuit 107. The photomask 101 on the XYθ table 102 is automatically conveyed from the autoloader 130 driven by the autoloader control circuit 113, and is automatically discharged after the inspection is completed.

  After the photomask 101 is placed on the XYθ table 102, a region to be inspected is set, and level adjustment (normalization) of the brightness (pixel gradation value) of the transmission part and the light shielding part is performed. Here, the sample used for the prior level adjustment may be a dummy or a sample to be inspected. Although level adjustment before the start of inspection is not essential, it is desirable to adjust the level of pixel values in advance in this way before the start of inspection. Thereafter, there is no problem if there is no change in the pixel value level due to a change in the apparatus during the sample inspection. However, since the pixel value level actually changes, this embodiment described below is effective. It becomes.

  In step S (step) 202, as a measurement data acquisition process as an example of an optical image acquisition process, the optical image acquisition unit 150 acquires optical image data (measurement data) in the photomask 101 that is a patterned sample to be inspected. To do. Specifically, the optical image data is acquired as follows. The pattern formed on the photomask 101 is irradiated with light by an appropriate light source 103 disposed above the XYθ table 102. The light beam emitted from the light source 103 irradiates the photomask 101 serving as a sample via the illumination optical system 170. A magnifying optical system 104, a photodiode array 105, and a sensor circuit 106 are disposed below the photomask 101, and light that has passed through the photomask 101 that is a sample such as an exposure mask passes through the magnifying optical system 104. Then, an image is formed as an optical image on the photodiode array 105 and is incident thereon. The magnifying optical system 104 may be automatically focused by an unillustrated autofocus mechanism.

FIG. 3 is a diagram for explaining an optical image acquisition procedure according to the first embodiment.
As shown in FIG. 3, the inspection area is virtually divided into a plurality of strip-shaped inspection stripes 20 having a scan width W, for example, in the Y direction. Further, the operation of the XYθ table 102 is controlled so that the divided inspection stripes 20 are continuously scanned, and an optical image is acquired while moving in the X direction. In the photodiode array 105, images having a scan width W as shown in FIG. 3 are continuously input. Then, after acquiring the image of the first inspection stripe 20, the image of the scan width W is continuously input in the same manner while moving the image of the second inspection stripe 20 in the opposite direction. When an image in the third inspection stripe 20 is acquired, the image is moved in the direction opposite to the direction in which the image in the second inspection stripe 20 is acquired, that is, in the direction in which the image in the first inspection stripe 20 is acquired. While getting the image. In this way, it is possible to shorten a useless processing time by continuously acquiring images. Although the forward (FWD) -backward (BWD) method is used here, the present invention is not limited to this, and a forward (FWD) -forward (FWD) method may be used.

  The pattern image formed on the photodiode array 105 is photoelectrically converted by the photodiode array 105 and further A / D (analog-digital) converted by the sensor circuit 106. The photodiode array 105 is provided with a sensor such as a TDI (Time Delay Integrator) sensor. The TDI sensor images the pattern of the photomask 101 by continuously moving the XYθ table 102 serving as a stage in the X-axis direction. These light source 103, magnifying optical system 104, photodiode array 105, and sensor circuit 106 constitute a high-magnification inspection optical system.

  Measurement data (optical image) output from the sensor circuit 106 is sent to the level adjustment circuit 140 together with data indicating the position of the photomask 101 on the XYθ table 102 output from the position circuit 107. The measurement data is, for example, 8-bit unsigned data, and the brightness gradation of each pixel is expressed by, for example, 0 to 255.

  In S104, as a reference data creation step, the development circuit 111 and the reference circuit 112 create image data (reference data) corresponding to the measurement data as follows. Information on the design pattern used when forming the pattern of the photomask 101 is stored in a magnetic disk device 109 which is an example of a storage device (storage unit). Then, the development circuit 111 reads design pattern information from the magnetic disk device 109 through the control computer 110, and converts the design pattern to be the design graphic data of the read photomask 101 into binary or multivalued image data (design image). This image data is sent to the reference circuit 112. The reference circuit 112 performs an appropriate filtering process on the design image data which is the image data of the sent graphic.

FIG. 4 is a diagram for explaining the filter processing in the first embodiment.
The measurement data as an optical image obtained from the sensor circuit 106 is in a state in which the filter is activated by the resolution characteristics of the magnifying optical system 104, the aperture effect of the photodiode array 105, or the like, in other words, in an analog state that continuously changes. For this reason, it is possible to match the measurement data by applying the filter process to the design image data which is the image data on the design side where the image intensity (the gray value) is a digital value. In this way, a reference image (reference data) to be compared with the optical image is created. The created reference data is sent to the level adjustment circuit 140. Similarly to the measurement data, the reference data is, for example, 8-bit unsigned data, and the brightness gradation of each pixel is expressed by 0 to 255.

  In S200, as a level adjustment step, the level adjustment circuit 140 inputs measurement data and reference data corresponding to the measurement data. Then, based on the relationship between the plurality of pixel values of the measurement data and the plurality of pixel values of the reference data, at least one of the pixel value level of the measurement data and the pixel value level of the reference data is adjusted.

FIG. 5 is a conceptual diagram showing an internal configuration of the level adjustment circuit according to the first embodiment.
In FIG. 5, the level adjustment circuit 140 as an example of the level adjustment unit includes a measurement data memory 52, a reference data memory 54, an image cutout unit 56, calculation units 58, 60, 62, and a level change unit 66. Yes. The level adjustment circuit 140 inputs the acquired measurement data and stores (stores) it in the measurement data memory 52. On the other hand, the level adjustment circuit 140 inputs the created reference data and stores (stores) it in the reference data memory 54. Here, it is desirable that the comparison inspection process described later is performed in units of images obtained by cutting out data of 20 units of inspection stripes into an area of about 1024 × 1024 pixel units, for example. On the other hand, the measurement data stored in the measurement data memory 52 is acquired for each inspection stripe 20. Therefore, it is necessary to cut out into an area (area) of 1024 × 1024 pixels.

  In S202, as an area cutout process, the image cutout unit 56 reads measurement data acquired for each inspection stripe 20 from the measurement data memory 52, and reads the read measurement data into an area (area of 1024 × 1024 pixels, for example). ) Cut into units. Here, as an example, a region of 1024 × 1024 pixels is used, but the region is not limited to this, but a region of 1024 × 1024 pixels or less is desirable from the viewpoint of inspection efficiency. On the other hand, the reference data may be created from the beginning in the area corresponding to each cut out measurement data.

FIG. 6 is a diagram illustrating an example of reference data in the first embodiment.
FIG. 7 is a diagram illustrating an example of measurement data in which no level fluctuation occurs in the first embodiment.
FIG. 8 is a diagram illustrating an example of measurement data in which level fluctuation occurs in the first embodiment.
In FIGS. 6 to 8, in order to facilitate the understanding of the contents, a region of 5 × 5 pixels is shown. For example, when the pixel value is set to 200 when the entire area is a transmissive part, the pixel value of each pixel 32 of the reference data 30 is 200 as shown in FIG. Therefore, the pixel value level is 200. Here, in the measurement data 40 in which no level fluctuation occurs, if there is no defect in the pixel value of each pixel 42, the pixel value level is around 200 as shown in FIG. In FIG. 7, the pixel value of each pixel 42 is indicated by a value in the range of 197 to 202. Thus, if the difference between the pixel values of the reference data 30 is about 3 gradations, it can be ignored as an error, and it is possible to avoid detecting a false defect.

  On the other hand, in the measurement data 50 in which the level fluctuation occurs, even if there is no defect in the pixel value of each pixel 53, the pixel value level is around 180 as shown in FIG. In FIG. 8, the pixel value of each pixel 53 is indicated by a value in the range of 177 to 182. For example, if the threshold value for defect detection in the comparison circuit 108 to be described later is set to a gradation difference of 20 or more, if the difference in the pixel values of the reference data 30 is 20 gradations or more, it is ignored as an error. It cannot be detected as a pseudo defect. Here, as an example, the threshold value for defect detection is set to a gradation difference of 20 or more. However, it is preferable to set the value to 5 to 10% of the set pixel value of the transmissive portion. That is, according to this range, when the pixel value of the transmissive part is set to 200, a difference from the pixel value of the reference data 30 is determined to be a defect when the difference is 10 to 20 gradations or more.

  As described above, when the fluctuation of the pixel level as shown in FIG. 8 occurs for some reason, the conventional inspection method determines that the defect is not a defect even though it is not a defect. Therefore, in the first embodiment, the pixel value level of at least one of the reference data and the measurement data is adjusted based on the relationship between the plurality of pixel values of the measurement data and the plurality of pixel values of the reference data. Thus, the pixel value level of the measurement data is brought closer to the pixel value level of the reference data.

  In S205, as an average value calculation step of measurement data, the calculation unit 58 calculates an average value of a plurality of pixel values of the measurement data cut out into a predetermined size area. For example, the average value of the pixel values in the example of FIG.

  In S207, as a reference data average value calculation step, the calculation unit 60 reads the reference data of the corresponding area from the reference data memory 54, and calculates the average value of a plurality of pixel values of the read reference data. For example, the average pixel value in the example of FIG. Based on the average value of the plurality of pixel values of the measurement data obtained as described above and the average value of the plurality of pixel values of the reference data, the average value of the plurality of pixel values of one data approaches that of the other. The level is adjusted as follows.

  In S208, as the difference calculation step, the calculation unit 62 calculates the difference between the average value of the plurality of pixel values of the measurement data and the average value of the plurality of pixel values of the reference data. For example, in the example of FIGS. 6 and 8, the difference value is 20 gradations.

  In S220, as an offset process, the level changing unit 66 changes the pixel value level by performing an offset calculation for the entire pixel value of the measurement data by 20 gradations. Then, adjustment is made to match the pixel value level of the reference data by changing the pixel value level. Here, the offset is obtained by adding 20 gradations to each pixel value of the measurement data. Here, the entire pixel value of the measurement data is offset, but the entire pixel value of the reference data may be offset. In that case, the offset may be made by subtracting 20 gradations from each pixel value of the reference data. Alternatively, both may be offset. That is, the pixel value levels of both data need only be close.

  As described above, the measurement data and the reference data in which the pixel value level is adjusted are output to the comparison circuit 108. Then, in the comparison circuit 108, the input measurement data and reference data are aligned, and then the two are compared for each pixel according to a predetermined algorithm to determine the presence or absence of a defect. For example, as described above, a defect is determined if the pixel value differs by 10% or more.

  As described above, by performing level adjustment so that the average value of a plurality of pixel values of one data approaches that of the other, detection of pseudo defects can be reduced.

Here, it is also preferable to use the sum instead of adjusting the level based on the average value of a plurality of pixel values in the region.
FIG. 9 is a flowchart showing main steps of another pattern inspection method according to the first embodiment. 9 is the same as FIG. 2 except that a sum calculation step (S204) is provided instead of the average value calculation step (S205) and a sum calculation step (S206) is provided instead of the average value calculation step (S207). is there. Therefore, S102 to S202 are as described above.

  In S <b> 204, as a measurement data total calculation step, the calculation unit 58 calculates the sum of a plurality of pixel values of the measurement data cut out into a predetermined size area. For example, the sum of the pixel values in the example of FIG.

  In S206, as a reference data total calculation step, the calculation unit 60 calculates the sum of a plurality of pixel values of the reference data in the corresponding region. For example, the sum total of pixel values in the example of FIG. Based on the sum of the plurality of pixel values of the measurement data obtained as described above and the sum of the plurality of pixel values of the reference data, the sum of the plurality of pixel values of one data approaches that of the other Adjust the level as follows.

  In S208, as the difference calculation step, the calculation unit 62 calculates the difference between the sum of the plurality of pixel values of the measurement data and the sum of the plurality of pixel values of the reference data. For example, in the example of FIGS. 6 and 8, the difference value is 500 gradations.

  In S220, as an offset process, the level changing unit 66 changes the pixel value level by performing an offset calculation on the entire pixel value of the measurement data by 500/25 = 20 gradations. Then, adjustment is made to match the pixel value level of the reference data by changing the pixel value level. Subsequent steps are as described above.

Alternatively, even when the average value of a plurality of pixel values in the region is used, level adjustment is not performed by performing an offset calculation, but at least one of the entire pixel value of the measurement data and the entire pixel value of the reference data is uniform. It is also suitable to adjust the level by integrating.
FIG. 10 is a flowchart showing main steps of another pattern inspection method according to the first embodiment. 10 is the same as FIG. 2 except that a ratio calculation step (S209) is provided instead of the difference calculation step (S208) and an integration step (S221) is provided instead of the offset step (S220). Therefore, S102 to S207 are as described above.

  In S209, as the ratio calculation step, the calculation unit 62 calculates the ratio between the average value of the plurality of pixel values of the measurement data and the average value of the plurality of pixel values of the reference data. For example, in the example of FIGS. 6 and 8, the ratio is 200 / 180≈1.1.

  In S220, as an integration step, the level changing unit 66 uniformly integrates the entire pixel value of the measurement data by 1.1 (or 200/180) times to change the pixel value level. Then, adjustment is made to match the pixel value level of the reference data by changing the pixel value level. Subsequent steps are as described above.

Alternatively, even when integrating, it is preferable to use the sum instead of the average value.
FIG. 11 is a flowchart showing main steps of another pattern inspection method according to the first embodiment. 11 is the same as FIG. 10 except that a sum calculation step (S204) is provided instead of the average value calculation step (S205) and a sum calculation step (S206) is provided instead of the average value calculation step (S207). is there. Therefore, S102 to S202 are as described above.

  In S <b> 204, as a measurement data total calculation step, the calculation unit 58 calculates the sum of a plurality of pixel values of the measurement data cut out into a predetermined size area. For example, the sum of the pixel values in the example of FIG.

  In S206, as a reference data total calculation step, the calculation unit 60 calculates the sum of a plurality of pixel values of the reference data in the corresponding region. For example, the sum total of pixel values in the example of FIG. Based on the sum of the plurality of pixel values of the measurement data obtained as described above and the sum of the plurality of pixel values of the reference data, the sum of the plurality of pixel values of one data approaches that of the other Adjust the level as follows.

  In S209, as the ratio calculation step, the calculation unit 62 calculates the ratio between the average value of the plurality of pixel values of the measurement data and the average value of the plurality of pixel values of the reference data. For example, in the example of FIGS. 6 and 8, the ratio is 5000 / 4500≈1.1.

  In S220, as an integrating step, the level changing unit 66 uniformly integrates the entire pixel value of the measurement data by 1.1 (or 5000/4500) times to change the pixel value level. Then, adjustment is made to match the pixel value level of the reference data by changing the pixel value level. Subsequent steps are as described above.

  As described above, it is possible to reduce or suppress pseudo defects by adjusting the pixel value level by performing offset or integration using the average value or the total sum.

  Here, in the above-described example, the case where the pixel value is set to 200 for the transmissive part and the pixel value is set to 0 for the light-shielding part has been described. However, the present invention is not limited to this. For example, the pixel value may be set to 200 for the transmissive portion and 20 for the light shielding portion. In that case, since the lower limit of the pixel value is not 0, it is desirable to change the level according to the range. For example, if the pixel value is a for the transmission part of the reference data, the pixel value is b for the light shielding part, the pixel value is c for the transmission part of the measurement data, and the pixel value is b for the light shielding part, the pixel value c is a In the case of changing the level, it is preferable to change the level to a value obtained by (x−b) × (ab) / (c−b) + b in the offset calculation, where x is the pixel value to be changed. Specifically, when the pixel value 180 is changed to 200 when the lower limit is 20, the pixel value that is the target of the level change is x, and the offset calculation is (x−20) × 18/16 + 20. It is good to change the level to the value. Thus, it is more preferable to consider the lower limit value.

Embodiment 2. FIG.
In the first embodiment, the pixel level is always adjusted if there is a difference in the pixel value level. However, if there is a defect in the entire area, the actual defect can be overlooked. Sex occurs. Therefore, in the second embodiment, a case where conditions are provided when performing level adjustment will be described.

FIG. 12 is a conceptual diagram showing an internal configuration of the level adjustment circuit according to the second embodiment.
12 is the same as FIG. 5 except that a determination unit 64 is added. Other configurations are the same as those of the first embodiment.
FIG. 13 is a flowchart showing main steps of the pattern inspection method according to the second embodiment. 13 is the same as FIG. 2 except that a determination step (S210) is added. Therefore, S102 to S208 are the same as in the first embodiment.

  In S210, as a determination step, the determination unit 64 determines whether the difference between the average value of the plurality of pixel values of the measurement data and the average value of the plurality of pixel values of the reference data is equal to or less than a predetermined threshold value. If the difference is equal to or smaller than the predetermined threshold, the process proceeds to S220. If the difference exceeds a predetermined threshold, the process proceeds to S300. That is, the process proceeds to the comparison process without adjusting the level. The subsequent steps are the same as in the first embodiment.

  In this way, when the difference between the average value of the plurality of pixel values of the measurement data and the average value of the plurality of pixel values of the reference data is equal to or less than a predetermined threshold value, the pixel value level of the measurement data and the pixel value level of the reference data And at least one of them is adjusted. For example, when the average value of the plurality of pixel values of the measurement data exceeds 15% of the average value of the plurality of pixel values of the reference data, the threshold is not adjusted. When the threshold for actual defect determination is 5 to 10%, the threshold is determined at 15%, which is obtained by adding a plus α (5%). The threshold value is not limited to 15%, and may be set as necessary.

  Here, as in the first embodiment, the pixel value level adjustment is not limited by performing the offset using the average value, but the pixel value is obtained by performing the offset or integration using the average value or the sum. Needless to say, the level should be adjusted. For example, when the level adjustment circuit 140 has a difference between the sum of the plurality of pixel values of the measurement data and the sum of the plurality of pixel values of the reference data equal to or less than a predetermined threshold, the pixel value level of the measurement data and the pixel value of the reference data A configuration in which at least one of the levels is adjusted is also preferable. Further, it is not limited to the case where the pixel value on the measurement data side is changed, and it goes without saying that at least one of the pixel value level of the measurement data and the pixel value level of the reference data may be adjusted.

  As described above, by providing a reference for performing level adjustment, when a defect exists in the entire area, it is possible to suppress missing the defect.

Embodiment 3 FIG.
In the first and second embodiments described above, the defect inspection is performed after the pixel level is adjusted. However, if the pixel value level does not fluctuate enough to cause a pseudo defect, the pixel level is not adjusted. It doesn't matter. Therefore, in the third embodiment, a configuration will be described in which defect inspection is first performed and level adjustment is performed when a defect candidate is generated as a result.

FIG. 14 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the third embodiment.
14 is the same as FIG. 1 except for the data flow order and direction. That is, each configuration is the same as that of the first embodiment.

  FIG. 15 is a flowchart showing main steps of the pattern inspection method according to the third embodiment. 15 is the same as FIG. 2 except that a comparison step (S106) is added before the level adjustment step (S200). Therefore, S102 to S104 are the same as in the first embodiment.

  In S106, as a comparison process, the comparison circuit 108 inputs measurement data and reference data. First, measurement data is cut out in an area of a predetermined size, and the measurement data and reference data are aligned. Thereafter, the two are compared for each pixel according to a predetermined algorithm to determine the presence or absence of a defect. For example, as described above, a defect is determined if the pixel value differs by 10% or more. In this way, first, defect candidates are detected. If a defect candidate exists, the process proceeds to S200. If there is no defect candidate, a result to that effect may be output. The contents of the level adjustment step (S200) and the subsequent comparison step (S300) are the same as those in the first embodiment. Here, since area extraction has already been performed in the comparison process (S106), the area extraction process (S202) in the level adjustment process (S200) is not necessary. Therefore, in FIG. 15, the area cutout process (S202) in the level adjustment process (S200) is deleted.

  Here, as in the first embodiment, the pixel value level adjustment is not limited by performing the offset using the average value, but the pixel value is obtained by performing the offset or integration using the average value or the sum. Needless to say, the level should be adjusted. Further, it is not limited to the case where the pixel value on the measurement data side is changed, and it goes without saying that at least one of the pixel value level of the measurement data and the pixel value level of the reference data may be adjusted.

  As described above, first, defect inspection is performed, and when a defect candidate is generated, the level adjustment can be performed by reducing the number of level adjustments, thereby shortening the inspection time.

Embodiment 4 FIG.
In each of the above-described embodiments, the level adjustment is performed based on the plurality of pixel values of the measurement data of the region to be inspected and the plurality of pixel values of the reference data, but the present invention is not limited to this. In the fourth embodiment, a configuration in which level adjustment is performed based on data in a region near the region to be inspected will be described. The apparatus configuration is the same as in any of the above-described embodiments.

FIG. 16 is a conceptual diagram for explaining a neighboring region in the fourth embodiment.
When an optical image of an inspection stripe 20 is acquired, another region 24 exists in the vicinity of the region 22 to be inspected. Here, when the pixel value level varies, the neighboring regions are expected to have the same amount of variation. However, when the brightness of the region 22 to be inspected changes abruptly compared to the neighboring region 24, it is assumed that there is a high possibility that an actual defect exists there. Therefore, in order to prevent defects from being buried by level adjustment, the level adjustment circuit 140 measures the average value of the plurality of pixel values of the measurement data in the region 24 in the vicinity of the measurement data in the target region and the measurement in the vicinity region 24. The pixel value level is adjusted based on the average value of the plurality of pixel values of the reference data corresponding to the data.

  Specifically, using the average value or sum of the plurality of pixel values of the measurement data in the vicinity region 24 of the region 22 to be inspected and the average value or sum of the plurality of pixel values of the reference data in the vicinity region 24, the offset Alternatively, an adjustment value for performing integration is calculated. The adjustment value is adjusted so that the pixel value level matches by performing offset or integration on a plurality of pixel values of the measurement data of the region 22 to be inspected. For example, the average value of the plurality of pixel values of the measurement data in the region near the measurement data of the region targeted by the level adjustment circuit 140 and the plurality of pixel values of the reference data corresponding to the measurement data in the region near this level Based on the above, it is also preferable to adjust at least one of the pixel value level of the measurement data in the target region and the pixel value level of the reference data in the target region. In addition, for example, the sum of a plurality of pixel values of measurement data in a region near the measurement data of the target region for the level adjustment circuit 140 and a sum of a plurality of pixel values of reference data corresponding to the measurement data in the region near this level Based on the above, it is also preferable to adjust at least one of the pixel value level of the measurement data in the target region and the pixel value level of the reference data in the target region.

  In addition, for the neighborhood region, one neighborhood region 24 or a plurality of neighborhood regions 24 may be used. For example, it is preferable to calculate the level adjustment value in each of the eight neighboring regions 24 surrounding the region 22 to be inspected. Furthermore, when a plurality of adjustment values are obtained, it is preferable to adjust the level with the average value.

Embodiment 5 FIG.
When the total or average of multiple pixel values of measurement data and reference data that adjust the level of pixel values is calculated, the values may differ if the position of the target measurement data and reference data is misaligned There is. In particular, it is assumed that the value varies due to the influence of the pattern of the area boundary. Therefore, in the fifth embodiment, a configuration in which alignment is first performed when performing level adjustment will be described.

FIG. 17 is a conceptual diagram showing an internal configuration of the level adjustment circuit according to the fifth embodiment.
17 is the same as FIG. 5 except that an alignment unit 57 is added. Other configurations are the same as those of the first embodiment.

  FIG. 18 is a flowchart showing main steps of the pattern inspection method according to the fifth embodiment. 18 is the same as FIG. 2 except that an alignment step (S203) is added. Therefore, S102 to S202 are the same as in the first embodiment.

  In step S203, as an alignment step, the alignment unit 57 inputs measurement data cut out into an area of a predetermined size and area reference data corresponding to the measurement data. Then, alignment is performed. The alignment is preferably performed in units of pixels. Alternatively, it is more preferable to carry out in units of subpixels. Then, using the aligned measurement data and reference data, each step after the calculation of the average value of the plurality of pixel values of the measurement data (S205) and the calculation of the average value of the plurality of pixel values of the reference data (S207) To implement. That is, the level adjustment circuit 140 aligns the measurement data and the reference data, and adjusts at least one of the pixel value level of the aligned measurement data and the pixel value level of the reference data. Each process after S205 and S207 is the same as that of the first embodiment.

  Here, as in the first embodiment, the pixel value level adjustment is not limited by performing the offset using the average value, but the pixel value is obtained by performing the offset or integration using the average value or the sum. Needless to say, the level should be adjusted. Further, it is not limited to the case where the pixel value on the measurement data side is changed, and it goes without saying that at least one of the pixel value level of the measurement data and the pixel value level of the reference data may be adjusted.

  As described above, by performing the alignment before performing the calculation for adjusting the pixel value level, in particular, the influence of the pattern of the area boundary can be eliminated. As a result, it is possible to suppress the deviation of the calculated values when calculating the above-described average value and sum.

Embodiment 6 FIG.
When performing level adjustment, the effect differs depending on the shape of the pattern. That is, there is pattern dependency. Therefore, in the sixth embodiment, a method for reducing the pattern dependency will be described. The apparatus configuration and the like may be the same as those in any of the first to fifth embodiments described above.

FIG. 19 is a conceptual diagram showing an example of a pattern for explaining pattern dependency in the sixth embodiment.
FIG. 19 shows an image of a 1: 1 line and space pattern. For example, the transmission part 26 as a line part and the light-shielding part 28 as a space part are alternately arranged in a 1: 1 pattern. If the pixel value of the transmission unit 26 is set to 200 and the pixel value of the light shielding unit 28 is set to 0 for the image in this region, the calculation result is 100 when the calculation unit 60 calculates the average value of the plurality of pixel values of the reference data. become. Regarding the measurement data, when the pixel value of the transmission unit 26 varies by 10% and the pixel value of the light shielding unit 28 does not vary, the following is obtained. That is, when the average value of a plurality of pixel values of the measurement data is calculated by the calculation unit 58, the calculation result becomes 90 due to a 10% variation. Therefore, when the difference is calculated by the calculation unit 62, the calculation result is 10 gradations. Therefore, the level changing unit 66 adds, for example, 10 gradations to all the pixels of the measurement data.

  On the other hand, in the case of all transmissive portion patterns, the calculation result is 200 when the calculation unit 60 calculates the average value of a plurality of pixel values of the reference data. Regarding the measurement data, when the pixel value of the transmissive part changes by 10% and the pixel value of the light shielding part does not change, the following is obtained. That is, when the average value of the plurality of pixel values of the measurement data is calculated by the calculation unit 58, the calculation result becomes 180 due to a 10% variation. Therefore, when the difference is calculated by the calculation unit 62, the calculation result is 20 gradations. Therefore, the level changing unit 66 adds, for example, 20 gradations to all the pixels of the measurement data.

  As described above, even if the pixel pattern level fluctuates at the same rate depending on the formed pattern, a difference occurs in the level-adjusted value. As described above, the level adjustment has pattern dependency in the method of each embodiment described above. Therefore, in the sixth embodiment, when the average value of a plurality of pixel values of measurement data is calculated by the calculation unit 58, the average value of all the pixels is not calculated, but the one having the larger gradation value (pixel value). To calculate an average value for a predetermined number of pixels. Similarly, when the calculation unit 60 calculates the average value of a plurality of pixel values of the reference data, it does not calculate the average value of all the pixels, but calculates the predetermined number of pixels from the larger gradation value. Calculate the average value. Since the fluctuation of the pixel value level is expected to occur in the larger gradation value, the pattern dependency can be suppressed by eliminating the portion where the gradation value is 0. Here, for example, there are approximately 1 million pixels in 1024 × 1024 pixels. In that case, for example, it is preferable to calculate the average value for the upper 100,000 pixels from the brighter one (the one with the larger gradation value).

  Here, as in the first embodiment, the pixel value level adjustment is not limited by performing the offset using the average value, but the pixel value is obtained by performing the offset or integration using the average value or the sum. Needless to say, the level should be adjusted. Further, it is not limited to the case where the pixel value on the measurement data side is changed, and it goes without saying that at least one of the pixel value level of the measurement data and the pixel value level of the reference data may be adjusted.

Embodiment 7 FIG.
FIG. 20 is a conceptual diagram showing an example of a sparse pattern in the seventh embodiment.
As shown in FIG. 19, when the pattern of the light-shielding portion 28 occupies about half of the area in the target area, the brightness (pixel value) of about 50% is obtained by calculating the sum or the average value. It is expected to be found. However, as shown in FIG. 20, in an area where the light shielding portion 29 is small and most of the region is occupied by the transmission portion 26, the influence on the sum and average value is greater when the amount of light varies. It will be.

  For example, with respect to an image in which the transmissive portions 26 and the light shielding portions 28 are alternately arranged at 1: 1 as in the example of FIG. 19, the pixel value of the transmissive portion 26 is set to 200 and the pixel value of the light shielding portion 28 is set to 0. And In that case, when the arithmetic unit 60 calculates the average value of the plurality of pixel values of the reference data, the calculation result becomes 100. When the average value of a plurality of pixel values of the measurement data is calculated by the calculation unit 58, the calculation result becomes approximately 95 due to a fluctuation of 5%. Therefore, when the difference is calculated by the calculation unit 62, the calculation result is five gradations.

  On the other hand, for an image in which the transmissive part 26 and the light shielding part 28 are formed at 99: 1 as in the example of FIG. 20, the pixel value of the transmissive part 26 is set to 200, and the pixel value of the light shielding part 28 is set to 0. To do. In this case, when the average value of a plurality of pixel values of the reference data is calculated by the calculation unit 60, the calculation result is approximately 200. When the average value of the plurality of pixel values of the measurement data is calculated by the calculation unit 58, the calculation result becomes approximately 90 due to a variation of 5%. Therefore, when the difference is calculated by the calculation unit 62, the calculation result is 10 gradations.

  The value of 5 gradations in the example of FIG. 19 is an error level value, whereas the value of 10 gradations in the example of FIG. 20 is not an error level value. In other words, in the example of FIG. 20, the level can be adjusted even with a fluctuation of 5%. Therefore, in the example of FIG. 20, the level fluctuation can be eliminated by adjustment. As a result, it is possible to determine a defect even for a minute defect. On the other hand, in the example of FIG. 19, it is difficult to adjust the level with a fluctuation of 5%. That is, as the sparse pattern is obtained, the defect can be determined even for a fine defect. In other words, the defect detection sensitivity is greatly improved. In the seventh embodiment, a configuration in which processing for detecting such a sparse pattern region is provided in the previous stage of the level adjustment circuit 140 will be described.

FIG. 21 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the seventh embodiment.
21 is the same as FIG. 1 except that the sparse pattern detection circuit 142 is added and the data flow order and direction are changed.

FIG. 22 is a conceptual diagram showing an internal configuration of the sparse pattern detection circuit according to the seventh embodiment.
In FIG. 22, the sparse pattern detection circuit 142 includes a measurement data memory 72, a reference data memory 74, an image cutout unit 76, calculation units 78 and 80, and a determination unit 82. The sparse pattern detection circuit 142 inputs the acquired measurement data and stores (stores) it in the measurement data memory 72. On the other hand, the sparse pattern detection circuit 142 inputs the created reference data and stores (stores) it in the reference data memory 74. Then, the image cutout unit 76 reads out the measurement data acquired for each inspection stripe 20 from the measurement data memory 52, and cuts out the read measurement data in units of areas (areas) of, for example, 1024 × 1024 pixels. Here, as an example, a region of 1024 × 1024 pixels is used, but the present invention is not limited to this, as described in the first embodiment.

  And the calculating part 78 calculates the average value of the several pixel value of the measurement data cut out to the area | region of predetermined size. For example, as in the example of FIG. 20, when the transmission part 26 and the light-shielding part 28 are formed at 99: 1, for example, the average value of the pixel values is approximately 200 if there is no level fluctuation. Then, the calculation unit 80 reads the reference data of the corresponding area from the reference data memory 74, and calculates the average value of the plurality of pixel values of the read reference data. For example, the average pixel value in the example of FIG.

  Then, the determination unit 82 determines whether at least one of the average value of the plurality of pixel values of the optical data and the average value of the plurality of pixel values of the reference data exceeds a predetermined threshold value. Alternatively, it may be determined whether at least one of the result of the calculation unit 78 and the result of the calculation unit 80 exceeds a predetermined ratio of the result when the same calculation is performed with the pattern of the transmission part. Since this determination determines whether the pattern is a sparse pattern, for example, it is desirable that the predetermined ratio exceeds 90%. For example, when the predetermined ratio is 90%, if the pixel value of the transmissive part is 200, 180 is desirable as the above-described predetermined threshold. For example, in the example of FIG. 20, since the average value is approximately 200, it is 90% or more. Therefore, when the transmission part 26 and the light-shielding part 28 are formed with 99: 1 as in the example of FIG. 20, the pattern is determined to be a sparse pattern. Then, the determination unit 82 outputs the determination result to the level adjustment circuit 140. Further, the measurement data and reference data cut out to a predetermined size area are output to the level adjustment circuit 140.

  Then, the level adjustment circuit 140 adjusts at least one of the pixel value level of the measurement data and the pixel value level of the reference data that exceeds a predetermined threshold value.

  Here, the sparse pattern detection circuit 142 calculates the average value of the plurality of pixel values of the optical data and the average value of the plurality of pixel values of the reference data, but only one of them may be calculated. Moreover, it is not restricted to an average value, and may be a sum. In the case of the sum, a threshold value for the sum may be set in the determination unit 82.

  Here, for example, in the case of an image pattern in which the transmissive portion (white) and the light shielding portion (black) are reversed in FIG. 20, the level adjustment is performed specifically for the light shielding portion (near 0 level). In that case, if the determination unit 82 determines that the value is below the predetermined threshold, the level adjustment circuit 140 may adjust the level. In the case of an image pattern in which the transmissive part (white) and the light-shielding part (black) are reversed in FIG. Therefore, the defect detection rate in a sparse pattern region can be further improved by applying the sparse pattern as described in the seventh embodiment.

  As described above, by detecting the sparse pattern area before input to the level adjustment circuit 140, it becomes possible to further improve the defect detection rate in the sparse pattern area, and greatly improve the defect detection sensitivity. it can.

  Here, it is practical not to detect the sparse pattern region described above, but to use the average value of pixels exceeding a threshold given in advance in the level adjustment circuit 140 as a reference.

Embodiment 8 FIG.
In the eighth embodiment, a configuration for further adjusting the level of the image corrected based on the light amount detection result will be described.

FIG. 23 is a conceptual diagram showing a configuration of a pattern inspection apparatus according to the eighth embodiment.
In FIG. 23, a point where an illumination optical system 172 is disposed instead of the illumination optical system 170, a point where a half mirror 174 is disposed within the illumination optical system 172, a point where a light amount monitor 176 is added, and a light amount correction circuit 144 Except for the added points and the change of the data flow order and direction, the operation is the same as FIG.

  Part of the light emitted from the light source 103 is branched by the half mirror 174 and enters the light amount monitor 176. The light amount monitor 176 monitors the amount of light emitted from the light source 103. The light amount measured by the light amount monitor 176 is output to the light amount correction circuit 144. The light amount correction circuit 144 receives the measurement data from the sensor circuit 106, and when the light amount emitted from the light source 103 varies, the light amount correction circuit 144 corrects the gradation value accordingly. Then, the measurement data whose gradation value is corrected is output to the level adjustment circuit 140. The steps after the measurement data is input to the level adjustment circuit 140 are the same as those in the first embodiment.

  As described above, the level adjustment circuit 140 corrects the pixel value level for the light amount fluctuation amount of the light emitted from the light source 103 in advance, so that the level adjustment circuit 140 has a pixel value generated for some reason by a mechanism after the light source 103 or the like. Level fluctuations can be adjusted. Then, if the level adjustment circuit 140 performs level adjustment, it is possible to grasp that the fluctuation of the pixel value level has occurred in the mechanism after the light source 103 or the like. Therefore, the cause can be separated from the light source 103, and the time taken to investigate the cause can be shortened.

Embodiment 9 FIG.
In each of the above-described embodiments, a technique using a die-to-database inspection using design data as reference data has been described. However, the present invention is not limited to this. In the ninth embodiment, a technique using a die-to-die inspection that compares optical image data obtained by imaging the same pattern at different locations on the same photomask 101 will be described. The apparatus configuration is the same as that of any of the first to eighth embodiments described above.

FIG. 24 is a conceptual diagram showing an example of the photomask and the formed pattern in the ninth embodiment.
In FIG. 24, a plurality of pattern areas 10 and 12 (inspected areas) drawn with the same design pattern are formed on the photomask 101. The whole of the two pattern regions 10 and 12 is virtually divided into a plurality of inspection stripes 20 shown in FIG. The optical image acquisition unit 150 acquires optical image data (measurement data) for each inspection stripe 20. Therefore, the measurement data of one inspection stripe 20 includes images of both the pattern areas 10 and 12. When such measurement data is input to the level adjustment circuit 140, the image cutout unit 56 cuts out an image having a predetermined size. At this stage, the measurement data (first optical image data) of the pattern area 10 and the measurement data (second optical image data) of the pattern area 12 corresponding thereto are cut out. Then, by using one of them as reference data, the inspection can be performed in the same manner as in the first embodiment. That is, the arithmetic unit 58 may calculate an average value of a plurality of pixel values of the measurement data in the pattern region 10, and the arithmetic unit 60 may calculate an average value of the plurality of pixel values of the measurement data in the pattern region 12. Then, based on the relationship between the plurality of pixel values of the measurement data in the pattern region 10 and the plurality of pixel values of the measurement data in the pattern region 12, the pixel value level of at least one of them may be adjusted.

  As described above, even when die-to-die inspection is used, level adjustment can be similarly performed. As a result, pseudo defects can be similarly reduced even when die-to-die inspection is used.

  Here, the pattern inspection apparatus 100 does not perform only one of the die-database inspection and the die-die inspection as the inspection method, but may of course perform both.

FIG. 25 is a diagram for explaining another optical image acquisition method.
In the configuration of FIG. 1, the photodiode array 105 that simultaneously enters the number of pixels of the scan width W is used. However, the configuration is not limited to this, and as shown in FIG. 25, the XYθ table 102 is moved at a constant speed in the X direction. Each time a movement at a constant pitch is detected by the laser interferometer, the laser beam is scanned in the Y direction by a laser scanning optical device (not shown) in the Y direction, and transmitted light is detected for each area of a predetermined size. Alternatively, a method of acquiring a two-dimensional image may be used.

  Here, in each of the embodiments described above, it is preferable that the level changing unit 66 outputs information indicating that the level has been changed and the level change amount to the comparison circuit 108 for the data whose level has been changed. Alternatively, it may be stored in the magnetic disk device 109 or the magnetic tape device 115. As a result, the user can grasp which data has been level-changed and the amount of change. Therefore, the user can confirm the image whose level has been changed later. Further, it is preferable that the level changing unit 66 outputs an error when a value for level adjustment exceeds a predetermined value. The error output allows the user to check the level-changed image later.

  In the above description, what is described as “to part”, “to circuit”, or “to process” can be configured by a computer-operable program. Or you may make it implement by not only the program used as software but the combination of hardware and software. Alternatively, a combination with firmware may be used. When configured by a program, the program is recorded on a recording medium such as the magnetic disk device 109, the magnetic tape device 115, the FD 116, or a ROM (read only memory). For example, the table control circuit 114, the expansion circuit 111, the reference circuit 112, the level adjustment circuit 140, the sparse pattern detection circuit 142, or the comparison circuit 108 that constitute the arithmetic control unit may be configured by an electrical circuit. It may be realized as software that can be processed by the control computer 110. Moreover, you may implement | achieve with the combination of an electrical circuit and software.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. For example, in each embodiment, transmitted light is used, but reflected light or transmitted light and reflected light may be used simultaneously. Needless to say, when the reflected light is used, the pixel value obtained from the transmissive part and the pixel value obtained from the light-shielding part are reversed.

  In each of the above-described embodiments, the image cutout unit 56 or the image cutout unit 76 for area cutout is arranged in the level adjustment circuit 140 or the sparse pattern detection circuit 142. However, the present invention is not limited to this, and the level adjustment is not limited thereto. It is also preferable to perform area extraction of measurement data before data is input to the circuit 140 or the sparse pattern detection circuit 142.

  In addition, although descriptions are omitted for parts and the like that are not directly required for the description of the present invention, such as a device configuration and a control method, a required device configuration and a control method can be appropriately selected and used.

  In addition, all pattern inspection apparatuses or pattern inspection methods that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

1 is a conceptual diagram showing a configuration of a pattern inspection apparatus in Embodiment 1. FIG. FIG. 4 is a flowchart showing main steps of the pattern inspection method in the first embodiment. 6 is a diagram for explaining an optical image acquisition procedure according to Embodiment 1. FIG. 6 is a diagram for describing filter processing according to Embodiment 1. FIG. 3 is a conceptual diagram illustrating an internal configuration of a level adjustment circuit according to Embodiment 1. FIG. 6 is a diagram illustrating an example of reference data in Embodiment 1. FIG. It is a figure which shows an example of the measurement data in which the level fluctuation | variation has not arisen in Embodiment 1. FIG. It is a figure which shows an example of the measurement data in which the level fluctuation has arisen in Embodiment 1. FIG. FIG. 10 is a flowchart showing main steps of another pattern inspection method according to the first embodiment. FIG. 10 is a flowchart showing main steps of another pattern inspection method according to the first embodiment. FIG. 10 is a flowchart showing main steps of another pattern inspection method according to the first embodiment. FIG. 6 is a conceptual diagram showing an internal configuration of a level adjustment circuit in a second embodiment. FIG. 10 is a flowchart showing main steps of the pattern inspection method in the second embodiment. It is a conceptual diagram which shows the structure of the pattern inspection apparatus in Embodiment 3. FIG. 10 is a flowchart showing main steps of a pattern inspection method according to Embodiment 3. FIG. 10 is a conceptual diagram for explaining a neighborhood region in a fourth embodiment. FIG. 10 is a conceptual diagram illustrating an internal configuration of a level adjustment circuit according to a fifth embodiment. FIG. 10 is a flowchart showing main steps of a pattern inspection method in a fifth embodiment. FIG. 20 is a conceptual diagram showing an example of a pattern for explaining pattern dependency in the sixth embodiment. FIG. 20 is a conceptual diagram showing an example of a sparse pattern in the seventh embodiment. FIG. 10 is a conceptual diagram showing a configuration of a pattern inspection apparatus in a seventh embodiment. FIG. 20 is a conceptual diagram illustrating an internal configuration of a sparse pattern detection circuit according to a seventh embodiment. FIG. 10 is a conceptual diagram showing a configuration of a pattern inspection apparatus in an eighth embodiment. FIG. 20 is a conceptual diagram illustrating an example of a photomask and a formed pattern in the ninth embodiment. It is a figure for demonstrating another optical image acquisition method.

Explanation of symbols

Reference numerals 32, 42, 53 Pixels 40, 50 Measurement data 52, 72 Measurement data memories 54, 74 Reference data memories 56, 76 Image extraction unit 57 Positioning unit 58, 60, 62, 78, 80 Calculation unit 64, 82 Determination unit 66 Level change unit 100 Pattern inspection apparatus 101 Photomask 102 XYθ table 103 Light source 104 Magnifying optical system 105 Photodiode array 106 Sensor circuit 107 Position circuit 108 Comparison circuit 109 Magnetic disk device 110 Control computer 111 Expansion circuit 112 Reference circuit 115 Magnetic tape device 140 Level adjustment circuit 142 Sparse pattern detection circuit 144 Light amount correction circuit 150 Optical image acquisition unit 160 Control circuit 176 Light amount monitor

Claims (18)

An optical image acquisition unit for acquiring optical image data in a patterned sample to be inspected;
The optical image data and reference image data corresponding to the optical image data are input, and the optical image data is based on a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data. A level adjustment unit that adjusts at least one of the pixel value level of the reference image data and the pixel value level of the reference image data;
A comparison unit that compares the optical image data with the pixel value level adjusted and the reference image data;
Equipped with a,
The level adjustment unit is configured to detect a pixel value level of the optical image data when a difference between a sum of a plurality of pixel values of the optical image data and a sum of a plurality of pixel values of the reference image data is equal to or less than a predetermined threshold. A pattern inspection apparatus that adjusts at least one of the pixel value level of the reference image data .   The level adjustment unit, based on a sum of a plurality of pixel values of the optical image data and a sum of a plurality of pixel values of the reference image data, a pixel value level of the optical image data and a pixel value of the reference image data The pattern inspection apparatus according to claim 1, wherein at least one of the level and the level is adjusted. An optical image acquisition unit for acquiring optical image data in a patterned sample to be inspected;
The optical image data and reference image data corresponding to the optical image data are input, and the optical image data is based on a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data. A level adjustment unit that adjusts at least one of the pixel value level of the reference image data and the pixel value level of the reference image data;
A comparison unit that compares the optical image data with the pixel value level adjusted and the reference image data;
With
The level adjustment unit is configured to determine a pixel value of the optical image data when a difference between an average value of the plurality of pixel values of the optical image data and an average value of the plurality of pixel values of the reference image data is equal to or less than a predetermined threshold value. level features and to Rupa turn inspection device to adjust at least one of the pixel value level of the reference image data. The level adjustment unit, based on an average value of a plurality of pixel values of the optical image data and an average value of a plurality of pixel values of the reference image data, and the average value of the plurality of pixel values of the optical image data so that the average value of a plurality of pixel values of the reference image data and approaches, according to claim 3, wherein adjusting at least one of said pixel value level of the pixel value level and the reference image data of the optical image data Pattern inspection equipment.   The level adjustment unit includes a sum of a plurality of pixel values of optical image data in a region in the vicinity of the optical image data in a target region and a plurality of pixel values in reference image data corresponding to the optical image data in the region in the vicinity. The at least one of the pixel value level of the optical image data in the target area and the pixel value level of the reference image data in the target area is adjusted based on the sum of the two. Pattern inspection equipment. The level adjustment unit includes an average value of a plurality of pixel values of optical image data of a region near the optical image data of a target region and a plurality of pixels of reference image data corresponding to the optical image data of the nearby region. The at least one of a pixel value level of the optical image data in the target area and a pixel value level of the reference image data in the target area is adjusted based on the average value. 3. The pattern inspection apparatus according to 3 . The level adjustment unit aligns the optical image data and the reference image data, and adjusts at least one of the pixel value level of the aligned optical image data and the pixel value level of the reference image data the apparatus according to any one of claims 1-6, characterized in that. The level adjusting unit according to claim 1-7 The apparatus according any one characterized by offset calculating at least one of the said total pixel values of the optical image the reference image data and the general pixel data. The level adjusting unit according to claim 1-7 The apparatus according any one characterized by integrating at least one of the said total pixel values of the optical image the reference image data and the general pixel data uniformly. The pattern inspection apparatus further determines whether at least one of an average value of the plurality of pixel values of the optical image data and an average value of the plurality of pixel values of the reference image data exceeds a predetermined threshold value. It has a judgment part,
The level adjusting unit, to any one of claims 1-9, characterized by adjusting at least one of the predetermined pixel value level of the reference image data and the pixel value level of the optical image data exceeds the threshold The pattern inspection apparatus described. The pattern inspection apparatus further determines whether at least one of an average value of the plurality of pixel values of the optical image data and an average value of the plurality of pixel values of the reference image data is less than a predetermined threshold value. It has a judgment part,
The level adjusting unit, to any one of claims 1-9, characterized by adjusting at least one of the predetermined pixel value level of the reference image data and the pixel value level of the optical image data is below a threshold The pattern inspection apparatus described. Level the reference image data and the optical image data adjustment is performed, both the pattern inspection apparatus according to any one of claims 1 to 11, characterized in that the following areas data 1024 × 1024 pixels. The level adjusting unit according to claim 1 to 12 The apparatus according to any of the values for performing level adjustments and performing an error output when a exceeds a predetermined value. An optical image acquisition unit for acquiring first optical image data in the patterned sample to be inspected and second optical image data corresponding to the first optical image data;
The first optical image data and the second optical image data are input, and based on the relationship between the plurality of pixel values of the first optical image data and the plurality of pixel values of the second optical image data. A level adjustment unit for adjusting at least one of a pixel value level of the first optical image data and a pixel value level of the second optical image data;
A comparison unit that compares the first optical image data and the second optical image data, each having a pixel value level adjusted;
Equipped with a,
The level adjustment unit is configured such that a difference between a sum of a plurality of pixel values of the optical image data and a sum of a plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; When the difference between the average value of the plurality of pixel values and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value, A pattern inspection apparatus that adjusts at least one of a pixel value level of reference image data . Obtaining optical image data in a patterned sample to be inspected;
The optical image data and reference image data corresponding to the optical image data are input, and the optical image data is based on a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data. Adjusting at least one of the pixel value level of the reference image data and the pixel value level of the reference image data;
Comparing the optical image data with the adjusted pixel value level and the reference image data, and outputting a result;
Equipped with a,
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value A pattern inspection method, wherein at least one of the levels is adjusted . Obtaining first optical image data in a patterned sample to be inspected and second optical image data corresponding to the first optical image data;
The first optical image data and the second optical image data are input, and based on the relationship between the plurality of pixel values of the first optical image data and the plurality of pixel values of the second optical image data. And adjusting at least one of a pixel value level of the first optical image data and a pixel value level of the second optical image data;
Comparing the first optical image data with the adjusted pixel value level and the second optical image data, and outputting the result;
Equipped with a,
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value A pattern inspection method, wherein at least one of the levels is adjusted . A first storage process for storing optical image data in a patterned sample to be inspected in a first storage device;
A second storage process for storing reference image data corresponding to the optical image data in a second storage device;
The optical image data is read from the first storage device, the reference image data is read from the second storage device, and a relationship between a plurality of pixel values of the optical image data and a plurality of pixel values of the reference image data is determined. A level adjustment process for adjusting at least one of a pixel value level of the optical image data and a pixel value level of the reference image data;
A comparison process for comparing the optical image data with the pixel value level adjusted with the reference image data, and outputting a result;
A program for causing a computer to execute
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value A program characterized in that at least one of the levels is adjusted . A first storage process for storing, in a storage device, first optical image data of the patterned sample to be inspected and second optical image data corresponding to the first optical image data;
The first optical image data and the second optical image data are read from a storage device, and a relationship between a plurality of pixel values of the first optical image data and a plurality of pixel values of the second optical image data A level adjustment process for adjusting at least one of a pixel value level of the first optical image data and a pixel value level of the second optical image data;
A comparison process of comparing the first optical image data and the second optical image data, the pixel value level of which has been adjusted, and outputting a result;
A program for causing a computer to execute
The difference between the sum of the plurality of pixel values of the optical image data and the sum of the plurality of pixel values of the reference image data is equal to or less than a first predetermined threshold; and the average of the plurality of pixel values of the optical image data The pixel value level of the optical image data and the pixel value of the reference image data when the difference between the value and the average value of the plurality of pixel values of the reference image data is equal to or less than a second predetermined threshold value A program characterized in that at least one of the levels is adjusted .

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