JP4922381B2 - Pattern inspection apparatus and pattern inspection method - Google Patents

Description

  The present invention relates to a pattern inspection apparatus and a pattern inspection method, and relates to, for example, a pattern inspection technique for inspecting a pattern defect of an object to be a sample used in semiconductor manufacture, and is used when manufacturing a semiconductor element or a liquid crystal display (LCD). The present invention relates to an apparatus for inspecting a defect of an extremely small pattern such as a photomask, a wafer, or a liquid crystal substrate, 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 the 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. Therefore, 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, continuous light emitted from a light source such as a lamp or a continuous wave laser is introduced into an illumination optical system to illuminate a test object such as a reticle or mask. The illumination light illuminates a limited area on the object in a spot shape or a rectangular shape. Then, the light from the area illuminated in the spot shape or the rectangular shape is condensed through the imaging optical system, and an image of the illumination area of the test object is formed on the light receiving surface of the photoelectric detection element. It is known to perform an inspection by comparing the optical image obtained from this with the optical data obtained by imaging the same pattern on the design data or the sample. For example, as a pattern inspection method, a “die to die inspection” method in which optical image data obtained by imaging the same pattern at different locations on the same mask is compared, or a CAD used for drawing a mask pattern Image data (reference image data) that is used as a reference for comparison is generated based on drawing data (design data) obtained by converting the data into the inspection device input format, and this is compared with optical image data that is used as measurement data obtained by imaging the pattern. There is a “die to database inspection” method. 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 optical image (measurement image) data. In the comparison circuit, the reference image data and the optical image data are compared according to an appropriate algorithm after the images are aligned, and if they do not match, it is determined that there is a pattern defect.

  However, circuit patterns such as semiconductor manufacturing masks are becoming finer year by year, and light sources used for steppers that transfer the mask pattern onto the wafer have become shorter in wavelength. Thereby, the image resolution is also improved. Furthermore, a technique (adding auxiliary patterns (assist lines)) for correcting the pattern shape on the mask in accordance with the ideal pattern shape to be transferred onto the wafer has been developed and put into practical use. In addition, EUV-lithography aimed at high resolution using a short wavelength light source by using X-rays (EUV light) as a transfer light source has been proposed.

  With the advancement of these technologies, the defect detection performance required for the pattern inspection apparatus for inspecting defects has become more severe. In order to improve the image resolution in the pattern inspection apparatus, techniques such as shortening the wavelength of the light source and increasing the NA of the objective lens are used. The N ratio has deteriorated, and as a result, it has become difficult to acquire a high-contrast image. In addition, since the density of the pattern existing on the mask is not constant, if images are uniformly acquired for the pattern existing on the mask, for example, even if a high-contrast image is obtained with one pattern, It becomes difficult to obtain a high-contrast image. It is difficult to inspect a pattern for which a high-contrast image cannot be obtained with high accuracy. Therefore, a defect inspection apparatus having high-contrast inspection sensitivity by obtaining a high-contrast image for various patterns having different line widths and shapes is expected. As described above, in order to obtain a high-accuracy image, a technique for obtaining a high signal intensity with respect to a defect existing for each of the dense and dense patterns existing on the mask is required.

  As one of the methods to meet such a demand, the scanning relative speed of irradiation light is adjusted for a specific pattern of a sample to be inspected by adjusting the stage moving speed, and the amount of irradiation light is increased or decreased with respect to the specific pattern. Techniques for acquiring images are disclosed in literature (for example, see Patent Literature 1).

JP 2007-205828 A

  As described above, there is a need for a technique for obtaining high signal strength for each of the dense and dense patterns existing on the inspection target mask.

  Accordingly, an object of the present invention is to provide a pattern inspection apparatus and method capable of overcoming the above-described problems and obtaining a high signal intensity for each of the dense and dense patterns.

The pattern inspection apparatus according to one aspect of the present invention includes:
A first optical system for illuminating the patterned sample to be inspected;
A second optical system that optically separates a first optical image obtained from the sample to be inspected into a plurality of second optical images by illumination;
A plurality of optical image data generating units that generate a plurality of optical image data having different signal intensities for each of a coarse pattern portion and a dense pattern portion using a plurality of separated second optical images;
A reference image data generation unit for generating a corresponding respective reference image data to be compared with the plurality of optical image data,
For each pixel, a comparison unit that compares one of the plurality of optical image data corresponding to the density of the pattern and the corresponding reference image data;
A plurality of third optical systems for converting the magnifications of the plurality of separated second optical images into different magnifications;
It is provided with.
In addition, a pattern inspection apparatus according to another aspect of the present invention includes:
A first optical system for illuminating the patterned sample to be inspected;
A second optical system that optically separates a first optical image obtained from the sample to be inspected into a plurality of second optical images by illumination;
A plurality of optical image data generating units that generate a plurality of optical image data having different signal intensities for each of a coarse pattern portion and a dense pattern portion using a plurality of separated second optical images;
A reference image data generation unit that generates reference image data for comparison with one of the plurality of optical image data;
For each pixel, a comparison unit that compares one of the plurality of optical image data corresponding to the density of the pattern and the corresponding reference image data,
With
A selection unit that selects one of the plurality of optical image data according to the density of the pattern for each pixel;
The reference image data generation unit generates reference image data for comparison with one of the plurality of optical image data selected by the selection unit.

The pattern inspection apparatus according to another aspect of the present invention includes:
An optical system for illuminating the patterned sample to be inspected;
A photoelectric conversion element that photoelectrically converts an image obtained from the inspection sample by illumination; and
A plurality of optical image data generation units that respectively input photoelectrically converted signals and generate a plurality of optical image data having different signal intensities at different gains;
A reference image data generation unit that generates reference image data for comparison with one of the plurality of optical image data;
A comparison unit that compares one of the plurality of optical image data with the reference image data for each pixel;
It is provided with.

Further, the pattern inspection method of one embodiment of the present invention includes:
Illuminating the patterned sample to be inspected;
Optically separating a first optical image obtained from the sample to be inspected by illumination into a plurality of second optical images;
Converting the magnification of the plurality of separated second optical images into different magnifications;
Using a plurality of separated second optical images to generate a plurality of optical image data having different signal intensities for at least part of the coarse pattern portion and the dense pattern portion ;
Generating a corresponding respective reference image data to be compared with the plurality of optical image data,
For each pixel , comparing one of the plurality of optical image data corresponding to the density of the pattern with the corresponding reference image data, and outputting a result;
It is provided with.
Moreover, the pattern inspection method according to another aspect of the present invention includes:
Illuminating the patterned sample to be inspected;
Optically separating a first optical image obtained from the sample to be inspected by illumination into a plurality of second optical images;
Using the plurality of separated second optical images to generate a plurality of optical image data having different signal intensities for at least some of the coarse pattern portion and the dense pattern portion;
For each pixel, selecting one of the plurality of optical image data according to the density of the pattern;
Generating reference image data for comparison with one of the selected plurality of optical image data;
For each pixel, comparing one of the plurality of optical image data corresponding to the density of the pattern with the corresponding reference image data, and outputting the result;
It is provided with.

Moreover, the pattern inspection method according to another aspect of the present invention includes:
Illuminating the patterned sample to be inspected;
Photoelectrically converting an image obtained from the sample to be inspected by illumination;
A step of inputting each of the photoelectrically converted signals and generating a plurality of optical image data having different signal intensities at different gains;
Generating reference image data for comparison with one of the plurality of optical image data;
For each pixel, comparing one of the plurality of optical image data with the reference image data;
It is provided with.

  According to the present invention, it is possible to obtain optical image data having a high signal intensity corresponding to the pattern density from a plurality of optical image data. By inspecting with such an image, the pattern can be inspected with high accuracy.

1 is a conceptual diagram showing a configuration of a pattern inspection apparatus in Embodiment 1. FIG. FIG. 3 is a flowchart showing a flow of a main process 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 illustrating an example of signal intensity of optical image data generated under conditions in the first embodiment. FIG. 6 is a diagram for describing filter processing according to Embodiment 1. FIG. It is a conceptual diagram which shows the structure of the pattern inspection apparatus in Embodiment 2. FIG. 10 is a flowchart showing a flow of a main process 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 a flow of a main process of the pattern inspection method in the third embodiment. It is a conceptual diagram which shows the structure of the pattern inspection apparatus in Embodiment 4. FIG. 10 is a flowchart showing a main part process flow of a pattern inspection method according to a fourth embodiment. FIG. 20 is a conceptual diagram illustrating an example of the strength of reference data in the fourth embodiment. It is a conceptual diagram which shows the structure of the pattern inspection apparatus in Embodiment 5. FIG. 10 is a flowchart showing a flow of main steps of a pattern inspection method according to a fifth embodiment. It is a conceptual diagram which shows the structure of the pattern inspection apparatus in Embodiment 6. FIG. 23 is a flowchart showing a main part process flow of the pattern inspection method according to the sixth embodiment. It is a figure for demonstrating another optical image acquisition method.

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 circuit 160. The optical image acquisition unit 150 includes an XYθ table 102, a light source 103, a magnifying optical system 104, a beam splitter 131, a plurality of photodiode arrays 105 and 135 (an example of a photoelectric conversion element), a plurality of sensor circuits 106 and 136, and laser length measurement. A system 122, an autoloader 130, and an illumination optical system 170 are provided. In the control circuit 160, the control computer 110 serving as a computer transmits a position circuit 107, a comparison circuit 108 serving as an example of a comparison unit, a development circuit 111, a reference circuit 112, and an autoloader control circuit 113 via a bus 120 serving as a data transmission path. , Table control circuit 114, autofocus control circuit 140, magnetic disk device 109, magnetic tape device 115, flexible disk device (FD) 116, CRT 117, pattern monitor 118, and printer 119 as an example of a storage device. . The XYθ table 102 is driven by an X-axis motor, a Y-axis motor, and a θ-axis motor. The magnifying optical system 104 is driven by a piezoelectric transducer 142 such as a piezo element. 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.

  Prior to the start of inspection, first, the photomask 101, which is a pattern-formed inspected sample, is provided by the autoloader 130 controlled by the autoloader control circuit 113 so that it can be moved in the horizontal and rotational directions by the motors of the XYθ axes. Is loaded on the XYθ table 102 and placed on the XYθ table 102. Further, design pattern information (design data) used when forming the pattern of the photomask 101 is input to the pattern inspection apparatus 100 from the outside of the apparatus and stored in the magnetic disk device 109 which is an example of a storage device (storage unit). .

  FIG. 2 is a flowchart showing a flow of main steps of the pattern inspection method according to the first embodiment. In FIG. 2, the pattern inspection method in the first embodiment includes an illumination step (S102), an image separation step (S104), an optical image data generation step (S110 and S112), a reference data generation step (S202 and S204), and a comparison. A series of steps called step (S210) is performed.

  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. Further, the magnifying optical system 104 is driven by a piezoelectric conversion element 142 driven by an autofocus control circuit 140, and the image is focused on the photodiode arrays 105 and 135.

  In S (step) 102, as an illumination process, 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 via the illumination optical system 170 (first optical system). Illumination light emitted from the light source 103 is N (where N> 2), where the maximum amount of luminance output of the image does not exceed the measurement range of the photodiode arrays 105 and 135 is 1. Is preferable. That is, it is preferable to set the amount of illumination light so that the amount of light is N times the maximum luminance output of the measurement ranges of the photodiode arrays 105 and 135. As a result, a sufficient amount of light can be secured in both images even after image separation described later, and data can be generated with high resolution. However, the present invention is not limited to this, and the resolution is inferior, but an amount smaller than N may be used. Alternatively, the amount may not exceed the measurement range of the photodiode arrays 105 and 135. The amount of light to be supplied is adjusted so as to be within a range provided with a predetermined allowable value in consideration of the light amount variation of the illumination light source and the light amount adjustment error.

  In S <b> 104, as an image separation process, light transmitted through the photomask 101 by illumination enters a beam splitter 131, which is an example of a branching mirror or a beam splitter, via the magnifying optical system 104. Then, incident light is separated (branched) into a plurality of lights by a light beam branching element (second optical system) such as a beam splitter 131. Thereby, the transmission image (first optical image) obtained from the photomask 101 is optically separated into a plurality of images (second optical image) by the beam splitter 131. Here, the beam splitter 131 branches the incident light, for example, at a ratio of 1: N−1 using N described above. As a result, the two branched optical images of the same field of view can be converted into optical images having different amounts of light. For example, when the amount of illumination light is a light amount that is N times the maximum luminance output of the measurement ranges of the photodiode arrays 105 and 135 described above, the light amount of one of the branched lights is the maximum luminance output of the measurement range. The light quantity of the other light is (N-1) times the maximum luminance output value exceeding the maximum luminance output value of the measurement range. Then, one of the branched lights is formed as an optical image on the photodiode array 105 by the magnifying optical system 104 and is incident thereon. The other light forms an optical image on the photodiode array 135 and enters. Here, one branched light having the light amount of the maximum luminance output value of the measurement range is incident on the photodiode array 105, and the other branched light having the light amount of (N-1) times the maximum luminance output value. Light enters the photodiode array 135.

  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.

  In S110, as an optical image data generation step, one image of the pattern 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

  In S112, as the optical image data generation step, the other image of the pattern formed on the photodiode array 135 is photoelectrically converted by the photodiode array 135 and further A / D converted by the sensor circuit 136.

  In the first embodiment, the photodiode array 105 and the sensor circuit 106 are an example of an optical image data generation unit. Similarly, the photodiode array 135 and the sensor circuit 136 are an example of another optical image data generation unit. The photodiode arrays 105 and 135 are both provided with a sensor such as a TDI (Time Delay Integrator) sensor. The photodiode arrays 105 and 135 only need to be set to the same measurement range. The sensor circuits 106 and 136 may be configured by the same circuit.

  FIG. 4 is a diagram illustrating an example of signal intensity of optical image data generated under the conditions in the first embodiment. When the mask pattern image 10 in which the coarse / dense patterns as shown in FIG. 4C are mixed is collected, as shown in FIG. 4A, the amount of light incident on the photodiode array 135 is as follows. Therefore, the signal intensity output after the photoelectric conversion is also N-1 times. Similarly, if the gains of the sensor circuits 106 and 136 are the same, the signal intensity output after A / D conversion by the sensor circuit 136 is also the signal output after A / D conversion by the sensor circuit 106. N-1 times. For example, when N = 2.5, the signal intensity of the output image of the sensor circuit 136 is 1.5 times the signal intensity of the output image of the sensor circuit 106. As a result, as shown in FIG. 4B, the image output of the sensor circuit 136 obtained in the coarse pattern portion 24 having a coarse size has a portion that exceeds the maximum value of the measurement range of the photodiode array 135. For example, when the signal intensity is set with a gradation value of 0 to 255, the signal intensity values in the excess portions are all 255 and are greatly saturated. However, in the fine pattern portion 22, the contrast increases on the contrary to the increase in the signal intensity. As a result, the resolution can be improved in the fine pattern portion 22. As a result, it becomes possible to enlarge and detect the defect of the fine pattern portion 22. On the other hand, since the amount of light incident on the photodiode array 105 is the maximum value of the measurement range of the photodiode array 105, the signal intensity of the image output of the sensor circuit 106 is also the signal intensity within the measurement range. Therefore, even in the coarse pattern portion 24 having a coarse size, since the output does not exceed the maximum value, the output is not saturated and the defect inspection can be performed.

  As described above, when a target pattern image is collected with high contrast, it is effective to illuminate the pattern with a high amount of light. In general, the image contrast decreases as the pattern size becomes finer. In other words, in order to obtain an output equivalent to an image output of a coarse pitch size pattern with a fine pitch size pattern, it can be solved by irradiating a large amount of illumination light with the mask pattern. On the other hand, for the coarse pitch size pattern, the sensor is saturated with the equivalent illumination light, and therefore, by dimming the obtained image, the sensor is not saturated and a high signal output can be obtained.

  As described above, by continuously moving the XYθ table 102 serving as a stage, for example, in the X-axis direction, two TDI sensors are caused to image the same field pattern of the photomask 101 under different incident light amount conditions. Accordingly, a plurality of optical image data having different signal intensities can be generated using at least some of the optical images separated by the beam splitter 131.

  The measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 106 is sequentially compared with the data indicating the position of the photomask 101 on the XYθ table 102 output from the position circuit 107 for each inspection stripe 20. It is output to the circuit 108. Similarly, the measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 136 indicates the position of the photomask 101 on the XYθ table 102 output from the position circuit 107 in order for each inspection stripe 20. The data is output to the comparison circuit 108 together with the data. These measurement data are, for example, 8-bit unsigned data for each pixel, and the brightness gradation of each pixel is expressed by, for example, 0 to 255. The light source 103, the illumination optical system 170, the magnifying optical system 104, the beam splitter 131, the plurality of photodiode arrays 105 and 135, and the plurality of sensor circuits 106 and 136 constitute a high-magnification inspection optical system.

  Here, FIG. 1 shows two sets of a set of the photodiode array 105 and the sensor circuit 106 and a set of the photodiode array 135 and the sensor circuit 136, but the present invention is not limited to this, and three or more sets are provided. It may be composed of a set of

  In S202, as a reference data generation step, first, the development circuit 111 reads design data from the magnetic disk device 109 through the control computer 110 for each predetermined area, and designs the photomask 101 that becomes the read sample to be inspected. Data is converted (development processing) into developed image data that is binary or multivalued image data. The predetermined area may be, for example, an area (area) of an image to be compared with the optical image in a comparison process described later. For example, an area (area) of 1024 × 1024 pixels is assumed.

  The figure that constitutes the pattern defined in the design data is a basic figure such as a rectangle or triangle. For example, the coordinates (x, y) at the reference position of the figure, the length of the side, and the figure type such as the rectangle or triangle Graphic data defining the shape, size, position, etc. of each pattern graphic is stored with information such as a graphic code serving as a distinguishing identifier.

When such graphic data is input to the expansion circuit 111, it expands to data for each graphic, and interprets graphic codes, graphic dimensions, etc., indicating the graphic shape of the graphic data. Then, binary or multivalued image data is developed as a pattern arranged in a grid having a grid with a predetermined quantization size as a unit. The developed image data (developed image data) is stored in a pattern memory (not shown) in the circuit or in the magnetic disk device 109. In other words, in the occupancy rate calculation unit, the design pattern data is read, and the occupancy rate of the figure in the design pattern is calculated for each cell formed by virtually dividing the inspection area as a cell with a predetermined dimension as a unit, The n-bit occupation ratio data is output to the pattern memory or the magnetic disk device 109. For example, it is preferable to set one square as one pixel. If a resolution of 1/2 ⁸ (= 1/256) is given to one pixel, 1/256 small areas are allocated by the figure area arranged in the pixel, and the occupation ratio in the pixel is set. Calculate. The developed image data is stored in the pattern memory or the magnetic disk device 109 as area-unit image data defined by 8-bit occupancy data for each pixel.

  The reference circuit 112 receives the developed image data, performs data processing (image processing) on the developed image data, and generates reference data (standard image data) for comparison with the optical image data. The reference circuit 112 is an example of a standard image data generation unit. The reference circuit 112 performs an appropriate filter process on the developed image data.

  FIG. 5 is a diagram for explaining the filter processing in the first embodiment. The optical image data (measurement data) obtained from the sensor circuits 106 and 136 is in a state in which a 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. is there. For this reason, the developed image data, which is the image data on the design side of which the image intensity (shading value) is a digital value, can also be matched to the measurement data by performing a filtering process according to a predetermined model. For example, filter processing such as resizing processing for performing enlargement or reduction processing, corner rounding processing, or blurring processing is performed. In this way, a reference image to be compared with the optical image is created. The created reference image data is sent to the comparison circuit 108. Similarly to the measurement data, the reference image data is, for example, 8-bit unsigned data in each pixel, and the brightness gradation of each pixel is expressed by 0 to 255. The generated reference data is stored in a memory (not shown) in the reference circuit 112 or the magnetic disk device 109.

  In S204, as the reference data generation step, the same operation as the reference data generation step (202) is performed to generate another reference data. For example, in the reference data generation step (202), reference data of signal intensity obtained when the amount of light that is the amount of maximum luminance output in the measurement range of the photodiode arrays 105 and 135 is generated is generated. On the other hand, in the reference data generation step (204), reference data of signal intensity obtained when a light amount that is N-1 times the maximum luminance output of the measurement range of the photodiode arrays 105 and 135 is generated is generated.

  As described above, a plurality of corresponding reference data an to n are generated in accordance with the plurality of optical image data A to N having different signal intensities obtained by changing the amount of incident light. In other words, in addition to the reference data for comparing with one of the plurality of optical image data, the reference circuit 112 further includes at least for comparing with the plurality of optical image data corresponding to the rest of the plurality of optical image data. One reference data is generated. The plurality of reference data generated for comparison with one different from the other optical image data is output to the comparison circuit 108.

  In S210, as a comparison process, the comparison circuit 108 compares each optical image data of a plurality of optical image data in a corresponding predetermined region with reference data corresponding thereto for each pixel under a predetermined determination condition. The comparison circuit 108 is an example of a comparison unit. Hereinafter, the processing in the comparison circuit 108 will be specifically described. In the comparison circuit 108, first, optical image data for one stripe is input, and the optical image data for one stripe is cut out with the same area size as the image of the reference data. In this case, it goes without saying that the area to be cut out is matched with the area when the image of the reference data is generated. The optical image data in which the region sizes are matched is stored in a memory (not shown) in the comparison circuit 108. On the other hand, the generated reference data of the predetermined area is also stored in another memory (not shown) in the comparison circuit 108. Then, the optical image data and reference data in the same region are read out and aligned. Then, the aligned optical image data and reference data are compared for each pixel according to a predetermined determination condition to determine the presence or absence of a defect. As the determination condition, for example, a threshold value for comparing the two for each pixel according to a predetermined algorithm and determining the presence or absence of a defect corresponds. Alternatively, for example, a comparison algorithm for comparing the two and determining the presence or absence of a defect is applicable.

  For example, as an internal process of the comparison process (S210), as a comparison process (S212), the comparison circuit 108 uses optical image data (for example, an optical image) with a relatively small amount of incident light when inspecting a rough pattern portion. Data A) is compared with the corresponding reference data (for example, reference data a). Conversely, in the comparison step (S214), the comparison circuit 108 checks the optical image data (for example, the optical image data N) under the condition that the amount of incident light is relatively large when inspecting the niche pattern portion and the corresponding reference. Data (for example, reference data n) is compared.

  As described above, in the first embodiment, by generating a plurality of optical image data of the same field of view with different amounts of incident light, the density of the pattern is determined for each pixel or for each region, and a rough pattern portion is determined. It is possible to use optical image data with a relatively small amount of incident light when inspecting, and use optical image data with a relatively large amount of incident light when inspecting a niche pattern portion. As a result, it is possible to inspect the optical image data having a high signal intensity corresponding to the density of the pattern from the plurality of optical image data, and the pattern can be inspected with high accuracy.

  Alternatively, it is preferable that images having the same light amount condition are compared with each other using a plurality of optical image data and a plurality of reference data obtained for each pixel regardless of the density of the pattern. As a result, for the same pixel, the first combination is OK in the comparison step (S212) and OK in the comparison step (S214), NG in the comparison step (S212), and OK in the comparison step (S214). In the comparison and comparison step (S212), NG can be obtained, and in the comparison step (S214), a third combination that becomes NG can be obtained. Therefore, it is preferable that the comparison circuit 108 determines that the first combination is not a defect and the second or third combination is a defect. Alternatively, it may be determined that the first combination and the second combination are not defects, and the third combination is a defect.

  Then, the comparison result is output. For example, it is displayed on the CRT 117. Alternatively, it is displayed on the pattern monitor 118. Alternatively, printing is performed by the printer 119. Alternatively, it is stored in the magnetic disk device 109, the magnetic tape device 115, or the FD 116.

Embodiment 2. FIG.
In the first embodiment, a plurality of optical image data having the same visual field with different signal intensities are generated by branching the light before being incident on the photodiode array by changing the light quantity ratio. The method of generating a plurality of optical image data is not limited to this. In the second embodiment, a configuration in which a plurality of optical image data of the same field of view with different signal intensities is generated by controlling a sensor circuit will be described.

  FIG. 6 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the second embodiment. 6 is the same as FIG. 1 except that the beam splitter 131 and the photodiode array 135 are deleted and the output of the photodiode array 105 is branched to the sensor circuit 106 and the sensor circuit 136.

  FIG. 7 is a flowchart showing a flow of main steps of the pattern inspection method according to the second embodiment. 7 is the same as FIG. 2 except that a photoelectric conversion step (S105) is provided instead of the image separation step (S104).

  In addition, the contents other than those specifically described in the second embodiment are the same as those in the first embodiment.

  In S <b> 102, as an illumination process, the pattern formed on the photomask 101 is irradiated with light from an appropriate light source 103 disposed above the XYθ table 102. The light beam emitted from the light source 103 irradiates the photomask 101 via the illumination optical system 170 (first optical system). The illumination light emitted from the light source 103 is preferably provided with a light quantity that maximizes the luminance output of the image within the range not exceeding the measurement range of the photodiode arrays 105 and 135. However, the present invention is not limited to this, and the resolution is inferior, but the amount may not exceed the measurement range of the photodiode arrays 105 and 135. The amount of light to be supplied is adjusted so as to be within a range provided with a predetermined allowable value in consideration of the light amount variation of the illumination light source and the light amount adjustment error. Light that has passed through the photomask 101 due to illumination enters the photodiode array 105 via the magnifying optical system 104.

  In S <b> 105, as a photoelectric conversion step, the pattern image formed on the photodiode array 105 is photoelectrically converted by the photodiode array 105. A signal output from the photodiode array 105 is electrically branched, and one is input to the sensor circuit 106 and the other is input to the sensor circuit 136.

  In S110, as an optical image data generation step, the sensor circuit 106 receives the signal output from the photodiode array 105 and performs A / D conversion.

  In S112, as an optical image data generation step, the sensor circuit 136 receives the signal output from the photodiode array 105 and performs A / D conversion.

  When the mask pattern image 10 in which the coarse / dense patterns as shown in FIG. 4C are mixed is collected in the second embodiment, the output signal of the photodiode array 105 is branched. Input to the sensor circuits 106 and 136. Therefore, in the second embodiment, when the gain value of the sensor circuit 106 at the time of A / D conversion is set to 1, the gain value of the sensor circuit 136 is set to m. However, m> 1. The gain value of the sensor circuit 106 is set so that the signal intensity of the image output does not exceed the measurement range. As a result, the signal intensity output after A / D conversion by the sensor circuit 136 can be m times the signal output after A / D conversion by the sensor circuit 106. At that time, as shown in FIG. 4B, the image output of the sensor circuit 136 obtained in the coarse pattern portion 24 having a coarse size has a portion that exceeds the maximum value of the measurement range. However, in the fine pattern portion 22, the contrast increases on the contrary to the increase in the signal intensity. As a result, the resolution can be improved in the fine pattern portion 22. As a result, it becomes possible to enlarge and detect the defect of the fine pattern portion 22. On the other hand, the signal intensity of the image output of the sensor circuit 106 is the signal intensity within the measurement range. Therefore, even in the coarse pattern portion 24 having a coarse size, since the output does not exceed the maximum value, the output is not saturated and the defect inspection can be performed.

  The contents of the subsequent steps are the same as those in the first embodiment.

  As described above, in the second embodiment, a plurality of optical image data having the same field of view with different signal intensities are generated by adjusting the gain, so that when a rough pattern portion is inspected, the gain is relatively small. Using optical image data, it is possible to use optical image data with a relatively large gain when inspecting a niche pattern portion. As a result, it is possible to inspect the optical image data having a high signal intensity corresponding to the density of the pattern from the plurality of optical image data, and the pattern can be inspected with high accuracy.

Embodiment 3 FIG.
In the first embodiment, a plurality of optical image data having the same visual field with different signal intensities are generated by branching the light before being incident on the photodiode array by changing the light quantity ratio. The method of generating a plurality of optical image data is not limited to this. In the third embodiment, a configuration for generating a plurality of optical image data of the same field of view with different signal intensities even when branched at the same light quantity ratio will be described.

  FIG. 8 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the third embodiment. 8 is the same as FIG. 1 except that magnification optical systems 132 and 134 are added.

  FIG. 9 is a flowchart showing a flow of main steps of the pattern inspection method according to the third embodiment. In FIG. 9, the enlargement process (S106) is performed between the image separation process (S104) and the optical image data generation process (S110), and the enlargement process (S112) is performed between the image separation process (S104) and the optical image data generation process (S112). The process is the same as that of FIG. 2 except that S108) is added.

  In addition, the contents other than those specifically described in the third embodiment are the same as those in the first embodiment.

  In S <b> 102, as an illumination process, the pattern formed on the photomask 101 is irradiated with light from an appropriate light source 103 disposed above the XYθ table 102. The light beam emitted from the light source 103 irradiates the photomask 101 via the illumination optical system 170 (first optical system). The illumination light emitted from the light source 103 is preferably provided with a light quantity that maximizes the luminance output of the image within the range not exceeding the measurement range of the photodiode arrays 105 and 135. However, the present invention is not limited to this, and the resolution is inferior, but the amount may not exceed the measurement range of the photodiode arrays 105 and 135. The amount of light to be supplied is adjusted so as to be within a range provided with a predetermined allowable value in consideration of the light amount variation of the illumination light source and the light amount adjustment error.

  In S <b> 104, as an image separation process, light transmitted through the photomask 101 by illumination enters a beam splitter 131, which is an example of a branching mirror or a beam splitter, via the magnifying optical system 104. Then, incident light is separated (branched) into a plurality of lights by a light beam branching element (second optical system) such as a beam splitter 131. Thereby, the transmission image (first optical image) obtained from the photomask 101 is optically separated into a plurality of images (second optical image) by the beam splitter 131. Here, the beam splitter 131 branches incident light at a ratio of 1: 1. Thereby, two branched optical images of the same visual field can be made into optical images having the same light quantity.

  In S106, as an enlargement step, the enlargement optical system 132 (one of the plurality of third optical systems) converts one branched image to a magnification of a. By setting a> 1, one of the branched images is enlarged to a magnification. The enlarged image enters the photodiode array 105 and forms an image.

  In S108, as an enlargement step, the enlargement optical system 134 (one of the plurality of third optical systems) converts the other branched image into a magnification of b times. By setting b> 1, the other branched image is enlarged to a magnification of b times. The enlarged image enters the photodiode array 135 and forms an image.

  Here, by setting a> b, the light amount density on the photodiode array 135 is (a × a) / (b × b) times that of the photodiode array 105, and the enlargement ratio is small with the same light amount. The image becomes brighter. On the other hand, the light amount density on the photodiode array 105 is (b × b) / (a × a) times that of the photodiode array 135, and the image becomes dark because the enlargement ratio is large with the same light amount. As a result, it can be made the same as the state in which light having a light amount substantially larger than that of the photodiode array 105 is incident on the photodiode array 135. Therefore, when a> b, the signal intensity at the output of the sensor circuit 136 is increased. As a result, the contrast in the fine pattern is increased, and the defect in the fine pattern portion can be enlarged and detected. Here, when enlarging the image by the magnifying optical systems 132 and 134, the size on the photomask 101 per element of the photodiode array may be set by switching to about 100 to 50 nm square.

  The contents of the subsequent steps are the same as those in the first embodiment.

  As described above, the third embodiment further includes a plurality of magnifying optical systems 132 and 134 for converting the magnifications of the plurality of separated optical images to different magnifications, and adjusting the magnification of each image after branching. To generate a plurality of optical image data of the same field of view with different signal intensities. Thus, when inspecting a rough pattern portion, optical image data having a relatively large enlargement ratio is used, and when inspecting a niche pattern portion, optical image data having a relatively small enlargement ratio is used. Made it possible. As a result, it is possible to inspect the optical image data having a high signal intensity corresponding to the density of the pattern from the plurality of optical image data, and the pattern can be inspected with high accuracy.

Embodiment 4 FIG.
In the first embodiment, a plurality of reference data is created for each predetermined region in accordance with a plurality of optical image data having different conditions. However, the present invention is not limited to this. In the fourth embodiment, a configuration in which one reference data is created for each predetermined area will be described.

  FIG. 10 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the fourth embodiment. 10 is the same as FIG. 1 except that a selection circuit 138 is added.

  FIG. 11 is a flowchart showing a flow of main steps of the pattern inspection method according to the fourth embodiment. In FIG. 11, a data selection step (S114) is added between the point provided with the comparison step (S216) instead of the comparison step (S210) and the optical image generation step (S110 and S112) and the comparison step (S216). 2 is the same as FIG. 2 except that a reference data generation step (S206) is provided instead of the reference data generation step (S202 and S204).

  In addition, the contents other than those specifically described in the fourth embodiment are the same as those in the first embodiment.

  The measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 106 is sequentially output to the selection circuit 138 for each inspection stripe 20. Similarly, the measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 136 is sequentially output to the selection circuit 138 for each inspection stripe 20.

  In S114, as a data selection step, the selection circuit 138 selects one of the input optical image data for each pixel. The selection circuit 138 is an example of a selection unit. The selection method is selected according to the density of the pattern, for example. As described above, when inspecting a rough pattern portion, optical image data (for example, optical image data A) with a relatively small amount of incident light is desirable. Conversely, when inspecting a niche pattern portion, it is desirable to use optical image data (for example, optical image data N) with a relatively large amount of incident light. Therefore, a threshold is set for the ratio of pattern density, and it is determined for each pixel whether it is larger (rough) or smaller (dense) than the threshold, and one optical image data is selected according to the determination result. Then, the optical image data of each inspection stripe 20 is reconstructed by combining the data selected for each pixel, and the reconstructed optical image data of each inspection stripe 20 is stored on the XYθ table 102 output from the position circuit 107. The data indicating the position of the photomask 101 is output to the comparison circuit 108.

  On the other hand, reference data to be compared is generated as follows.

  In S206, as a reference data generation step, the development circuit 111 and the reference circuit 112 generate reference image data for comparison with one of a plurality of optical image data selected by the selection circuit 138 for each pixel. Here, as with the selection circuit 138, a threshold is set for the ratio of pattern density, and it is determined for each pixel whether the threshold is larger (rough) or smaller (dense). For each pixel, when generating reference data for inspecting a rough pattern portion, signal intensity reference data obtained when a light amount with a relatively small incident light amount is incident is generated. On the contrary, when generating reference data for inspecting a dense pattern portion for each pixel, reference data of signal intensity obtained when a light amount with a relatively large incident light amount is incident is generated. The generation method is the same as in the first embodiment. As described above, reference data for each predetermined area is generated. Therefore, the reference data for each predetermined area includes data with different light amounts. The plurality of generated reference data is output to the comparison circuit 108.

  In S216, as a comparison step, the comparison circuit 108 compares the optical image data of the corresponding predetermined area with the reference data of the corresponding area for each pixel under a predetermined determination condition. In the comparison circuit 108, first, optical image data for one stripe is input, and the optical image data for one stripe is cut out with the same area size as the image of the reference data. In this case, it goes without saying that the area to be cut out is matched with the area when the image of the reference data is generated. The optical image data in which the region sizes are matched is stored in a memory (not shown) in the comparison circuit 108. On the other hand, the generated reference data of the predetermined area is also stored in another memory (not shown) in the comparison circuit 108. Then, the optical image data and reference data in the same region are read out and aligned. Then, the aligned optical image data and reference data are compared for each pixel according to a predetermined determination condition to determine the presence or absence of a defect. In the fourth embodiment, since the optical image data and the reference data in the predetermined area are already distinguished from each other in accordance with the pattern density, the data value is distinguished for each pixel. There is no need to judge whether the pattern portion is rough or dense.

  Here, in the above-described example, the ratio of pattern density is used as the selection condition of the selection circuit 138. However, the present invention is not limited to this. For example, a pattern size may be used. When the width of the pattern pattern is large (thick), it may be determined as coarse, and when the width is small (thin), it may be determined as dense. The selection when generating the reference data is the same. Alternatively, the following selection is also suitable.

  FIG. 12 is a conceptual diagram illustrating an example of the strength of reference data in the fourth embodiment. For example, using the signal intensity that is planned to be obtained when the reference data is generated with the amount of light incident on the photodiode array 105 or the photodiode array 135, it is determined that pixels that have an intensity greater than the threshold value are coarse, You may judge that the pixel used as intensity | strength is dense. Then, the selection circuit 138 inputs such information from the reference circuit 112 and selects optical image data for each pixel according to the result of coarse / dense. On the other hand, when generating reference data, the reference data may be generated according to the result of the density. For example, when the threshold determination is performed using the reference data with the amount of light incident on the photodiode array 105, the reference data is generated again with the amount of light incident on the photodiode array 135 for the pixels determined to be dense. That's fine. Conversely, when the threshold determination is performed using the reference data with the amount of light incident on the photodiode array 135, the reference data is generated again with the amount of light incident on the photodiode array 105 for pixels determined to be coarse. Use it.

  As described above, it is only necessary to create one reference data for each predetermined region by selecting and using optical image data and reference data with corresponding light amounts according to the density of the pattern. For each pixel, when inspecting a rough pattern portion, optical image data and reference data having a relatively small amount of incident light are used, and when inspecting a niche pattern portion, a relatively large amount of incident light is used. Optical image data and reference data can be used. As a result, inspection can be performed with optical image data having a high signal intensity corresponding to the density of the pattern, and the pattern can be inspected with high accuracy.

Embodiment 5 FIG.
In the second embodiment, a plurality of reference data is created for each predetermined region in accordance with a plurality of optical image data having different conditions. However, the present invention is not limited to this. In the fifth embodiment, as in the fourth embodiment, a configuration in which one reference data is created for each predetermined area will be described.

  FIG. 13 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the fifth embodiment. 13 is the same as FIG. 6 except that a selection circuit 138 is added.

  FIG. 14 is a flowchart showing a flow of main processes of the pattern inspection method according to the fifth embodiment. In FIG. 14, a data selection step (S114) is added between the point provided with the comparison step (S216) instead of the comparison step (S210) and the optical image generation step (S110 and S112) and the comparison step (S216). 7 is the same as FIG. 7 except that a reference data generation step (S206) is provided instead of the reference data generation step (S202 and S204).

  In addition, the contents other than those specifically described in the fifth embodiment are the same as those in the second embodiment.

  The measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 106 is sequentially output to the selection circuit 138 for each inspection stripe 20. Similarly, the measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 136 is sequentially output to the selection circuit 138 for each inspection stripe 20. The contents of the data selection step (S114), the reference data generation step (S206), and the comparison step (S216) are the same as those in the fourth embodiment.

Embodiment 6 FIG.
In the third embodiment, a plurality of reference data is created for each predetermined region in accordance with a plurality of optical image data having different conditions. However, the present invention is not limited to this. In the sixth embodiment, as in the fourth embodiment, a configuration in which one reference data is created for each predetermined area will be described.

  FIG. 15 is a conceptual diagram showing the configuration of the pattern inspection apparatus according to the sixth embodiment. 15 is the same as FIG. 8 except that a selection circuit 138 is added.

  FIG. 16 is a flowchart showing a flow of main steps of the pattern inspection method according to the sixth embodiment. In FIG. 16, a data selection step (S114) is added between the point provided with the comparison step (S216) instead of the comparison step (S210) and the optical image generation step (S110 and S112) and the comparison step (S216). 8 is the same as FIG. 8 except that a reference data generation step (S206) is provided instead of the reference data generation step (S202 and S204).

  Other contents than those specifically described in the sixth embodiment are the same as those in the third embodiment.

  The measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 106 is sequentially output to the selection circuit 138 for each inspection stripe 20. Similarly, the measurement data (optical image data) of each inspection stripe 20 output from the sensor circuit 136 is sequentially output to the selection circuit 138 for each inspection stripe 20. The contents of the data selection step (S114), the reference data generation step (S206), and the comparison step (S216) are the same as those in the fourth embodiment.

  FIG. 17 is a diagram for explaining another optical image acquisition method. In the configuration of FIG. 1 and the like, the photodiode arrays 105 and 135 that simultaneously enter the number of pixels having the scan width W are used. However, the present invention is not limited to this, and the XYθ table 102 is arranged in the X direction as shown in FIG. Each time a constant pitch movement is detected by a laser interferometer while feeding at a constant speed, a laser beam is scanned in the Y direction by a laser scanning optical device (not shown) in the Y direction, and transmitted light or reflected light is detected and predetermined. Alternatively, a method of acquiring a two-dimensional image for each area of a certain size may be used.

  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 position circuit 107, the comparison circuit 108, the expansion circuit 111, the reference circuit 112, the autoloader control circuit 113, the table control circuit 114, the selection circuit 138, or the autofocus control circuit 140, which constitute the arithmetic control unit, are electrically It may be configured by a circuit or 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 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.

DESCRIPTION OF SYMBOLS 10 Mask pattern image 20 Inspection stripe 22 Fine pattern part 24 Coarse pattern part 100 Pattern inspection apparatus 101 Photomask 102 XY (theta) table 103 Light source 104,132,134 Enlargement optical system 105,135 Photodiode array 106,136 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 120 Bus 131 Beam splitter 138 Selection circuit 140 Autofocus control circuit 150 Optical image acquisition unit 160 Control circuit 170 Illumination optical system

Claims (5)

A first optical system for illuminating the patterned sample to be inspected;
A second optical system that optically separates a first optical image obtained from the sample to be inspected into a plurality of second optical images by illumination;
A plurality of optical image data generating units that generate a plurality of optical image data having different signal intensities for each of a coarse pattern portion and a dense pattern portion using a plurality of separated second optical images;
A reference image data generation unit for generating a corresponding respective reference image data to be compared with the plurality of optical image data,
For each pixel, a comparison unit that compares one of the plurality of optical image data corresponding to the density of the pattern and the corresponding reference image data;
A plurality of third optical systems for converting the magnifications of the plurality of separated second optical images into different magnifications;
A pattern inspection apparatus comprising: A first optical system for illuminating the patterned sample to be inspected;
A second optical system that optically separates a first optical image obtained from the sample to be inspected into a plurality of second optical images by illumination;
A plurality of optical image data generating units that generate a plurality of optical image data having different signal intensities for each of a coarse pattern portion and a dense pattern portion using a plurality of separated second optical images;
A reference image data generation unit that generates reference image data for comparison with one of the plurality of optical image data;
For each pixel, a comparison unit that compares one of the plurality of optical image data corresponding to the density of the pattern and the corresponding reference image data,
With
A selection unit that selects one of the plurality of optical image data according to the density of the pattern for each pixel;
The reference image data generation unit, a pattern inspection apparatus and generates the reference image data for one comparison of said plurality of optical image data selected by the selection unit. It said plurality of optical image data, pattern inspection apparatus according to claim 1 or 2, wherein the an optical image data of the same field. Illuminating the patterned sample to be inspected;
Optically separating a first optical image obtained from the sample to be inspected by illumination into a plurality of second optical images;
Converting the magnification of the plurality of separated second optical images into different magnifications;
Using a plurality of separated second optical images to generate a plurality of optical image data having different signal intensities for at least part of the coarse pattern portion and the dense pattern portion ;
Generating a corresponding respective reference image data to be compared with the plurality of optical image data,
For each pixel , comparing one of the plurality of optical image data corresponding to the density of the pattern with the corresponding reference image data, and outputting a result;
A pattern inspection method comprising: Illuminating the patterned sample to be inspected;
  Optically separating a first optical image obtained from the sample to be inspected by illumination into a plurality of second optical images;
  Using the plurality of separated second optical images to generate a plurality of optical image data having different signal intensities for at least some of the coarse pattern portion and the dense pattern portion;
  For each pixel, selecting one of the plurality of optical image data according to the density of the pattern;
  Generating reference image data for comparison with one of the selected plurality of optical image data;
  For each pixel, comparing one of the plurality of optical image data corresponding to the density of the pattern with the corresponding reference image data, and outputting a result;
  A pattern inspection method comprising:

Images