JP2008076827A - Method for setting illumination angle in defect inspection instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily find an illumination angle with high accuracy for detecting an image having a high contrast by diffracted light so as to detect the image of a defect in a periodical pattern of an inspection object, and to suppress variation in detection accuracy among workers. <P>SOLUTION: The method for setting an illumination angle in a defect inspection instrument includes: a step for measuring diffracted light produced by irradiating an inspection object with approximately parallel light from a light source at a plurality of angles and acquiring intensity of diffracted light at each illumination angle; a step of accumulating the data of diffracted light intensity at each illumination angle; a for calculating the evaluated value of a defect evaluating easiness of observing a defect at each illumination angle by using the data of diffracted light intensity at each illumination angle; and a step for setting an illumination angle having the maximum evaluated value of the defect. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for inspecting a defect of a periodic pattern.

  In inspection of unevenness of the periodic pattern of a photomask, a transmittance image is captured using coaxial transmission illumination or planar illumination, and the intensity (brightness) of the light in each image is compared to find an unevenness portion and a normal portion. It is visually recognized (see, for example, Patent Document 1 or 2). Therefore, in the periodic pattern of the photomask, the difference in light intensity between the uneven portion and the normal portion is originally small, i.e., by devising an intensity difference processing method for an image with low contrast, the difference is enlarged and uneven. Part is extracted and inspected.

  However, in the above-described prior art, in the imaging of the black matrix unevenness of the grid-like periodic pattern, particularly the black matrix unevenness having a large opening, the contrast between the uneven portion and the normal portion cannot be improved, and the intensity difference Even if the processing is devised, there is a problem that the inspection in the case of an image with a low contrast of the original image can only achieve a lower inspection ability than the visual sensory inspection method.

  The periodic pattern refers to a collection of slit patterns arranged at a constant period (hereinafter also referred to as pitch). For example, elongated slit patterns are arranged one-dimensionally at predetermined intervals. There are a stripe-shaped periodic pattern, a matrix-like (lattice-like) periodic pattern in which slit patterns are two-dimensionally arranged at predetermined intervals, such as a black matrix opening.

  By the way, with the increase in electronic components with fine display and bright screen, the periodic pattern tends to be miniaturized or increase the aperture ratio. In the future, a technique for inspecting the periodic pattern unevenness in a black matrix having a finer shape and having a larger opening will be required. That is, there is a limit in the conventional output with only the intensity (brightness) of the light depending on the amplitude of the light.

  Therefore, for the purpose of providing a periodic pattern unevenness inspection apparatus capable of imaging and detecting a periodic pattern, for example, a black matrix unevenness stably and with high accuracy, illumination light is irradiated to an inspection object, An inspection apparatus that inspects transmitted diffracted light caused by a periodic pattern has been proposed (see, for example, Patent Document 3). However, in this apparatus, in order to obtain an image satisfying a desired defect inspection sensitivity, it is necessary to set an optimal inspection recipe for each type of inspection object. A lot of time is required. In addition, there is a possibility that the inspection accuracy varies among workers.

On the other hand, for the purpose of providing a defect inspection device that allows easy selection of appropriate inspection conditions, the reflectance data of a part having no subject defect measured at a plurality of center wavelengths and incident angles is acquired. A defect inspection apparatus that sets a center wavelength and an incident angle at the time of capturing an image used for defect detection based on the reflectance data has been proposed (see, for example, Patent Document 4). However, even in this device, the process of determining the center wavelength and the incident angle from the reflectance data largely depends on the operator's sense, and there is a possibility of accuracy problems and the inspection accuracy may vary among operators. Still exists.
JP 2002-148210 A JP 2002-350361 A JP-A-2005-147918 JP 2005-274156 A

  The present invention solves the above-mentioned problems, and in order to detect an image of a periodic pattern defect of an inspection object, an illumination angle for detecting an image with high contrast by diffracted light is easily found with high accuracy, It is an object to suppress variation in inspection accuracy among workers.

In order to achieve the above-described problems in the present invention, first, in the invention of claim 1, a method performed by a defect inspection apparatus for a periodic pattern of an inspection object,
A diffracted light intensity data acquisition step that performs measurement of diffracted light generated by irradiating light from a light source as a substantially parallel light onto an inspection object at a plurality of illumination angles, and acquires diffracted light intensity at each illumination angle;
A data accumulation step for accumulating diffracted light intensity data for each illumination angle;
Using the diffracted light intensity data for each illumination angle, a defect evaluation value calculation step for calculating a defect evaluation value for evaluating the visibility of the defect for each illumination angle,
An illumination angle determination step for setting an illumination angle at which the defect evaluation value is a maximum value;
This is an illumination angle setting method in a defect inspection apparatus including

In the invention of claim 2, the diffracted light intensity data acquisition step performs spectroscopic measurement of the diffracted light from the inspection object, acquires diffracted light intensity data for each wavelength at each illumination angle,
The data accumulation step accumulates diffracted light intensity data for each wavelength at each illumination angle,
In the defect evaluation value calculation step, as the diffracted light intensity data for each illumination angle, the data obtained by multiplying the diffracted light intensity for each wavelength at each illumination angle by multiplying by a weighting coefficient corresponding to each wavelength is used to calculate the illumination angle. Calculate the defect evaluation value to evaluate the legibility of each defect,
The illumination angle setting method in the defect inspection apparatus according to claim 1 is characterized.

  In the invention of claim 3, the defect evaluation value calculation step performs an interpolation process on the diffracted light intensity data for each illumination angle, and uses the diffracted light intensity data for each illumination angle after the interpolation process, for each illumination angle. 3. The illumination angle setting method in the defect inspection apparatus according to claim 1, wherein a defect evaluation value for evaluating the visibility of the defect is calculated.

  In the invention according to claim 4, the illumination angle determination step is obtained by detecting one or a plurality of illumination angle candidates whose defect evaluation value has a positive extreme value, and performing imaging with the illumination angle candidates. 4. The illumination angle setting method in the defect inspection apparatus according to claim 1, wherein the illumination angle is set based on a comparison of the captured images.

  According to the first aspect of the present invention, when the diffracted light generated by irradiating the inspection object having the periodic pattern with light from the light source as substantially parallel light is measured at a plurality of illumination angles, the defect inspection is automatically performed. The optimal illumination angle can be set.

In the invention of claim 2, when the spectroscopic measurement of the diffracted light generated by irradiating the inspection object having the periodic pattern with the light from the light source as substantially parallel light is performed at a plurality of illumination angles, the defect is automatically detected. The optimal illumination angle for inspection can be set. Further, in the invention of claim 2, since the diffracted light intensity data for each wavelength at each illumination angle is accumulated, the weighting coefficient for each wavelength based on the optical condition is used even when the optical condition relating to a plurality of wavelengths is inspected. By simply selecting, the optimum inspection angle can be quickly reset based on this accumulated data.

  In the invention of claim 3, by performing the interpolation process, it is possible to obtain a more detailed defect evaluation value for each illumination angle, and it is possible to set a proof angle optimal for defect inspection with high accuracy.

  In the invention of claim 4, when there are a plurality of similar maximum values in the defect evaluation value for each illumination angle, the illumination angle optimal for defect inspection can be set particularly accurately.

  Therefore, according to the present invention, when setting the inspection recipe, the inspection conditions are changed until the desired inspection sensitivity is obtained, and the conventional process of performing the inspection and observing the result is eliminated. It is possible to reduce the labor required for setting the inspection recipe. In addition, by using a quantitative method, it is possible to set an illumination angle that can detect unevenness accurately even for workpieces whose pitch and pattern are unknown to the operator, and to suppress variations in inspection accuracy among workers. Things will be possible.

  As described above, in order to detect an image of the periodic pattern defect of the inspection object, it is possible to easily find an illumination angle for detecting a high-contrast image by diffracted light with high accuracy, and to suppress variations in inspection accuracy among workers. There is an effect.

  The first embodiment of the present invention will be described below.

  FIG. 1 shows a system configuration example of a defect inspection apparatus to which the method for setting the illumination angle according to the first embodiment of the present invention is applied. The light irradiating means includes a light source 1 and a condenser lens 2 that makes the emitted light substantially parallel. As the diffracted light receiving unit, a light quantity sensor 6 that receives diffracted light generated from the object 3 to be inspected, a diffracted light intensity data accumulating unit 9 for accumulating data of the obtained diffracted light intensity, and an easier to see defect from the obtained data A diffracted light intensity data processing unit 10 that calculates a defect evaluation value for evaluating the thickness and determines an optimal illumination angle for inspection, and a data display unit 12 that displays the obtained diffracted light intensity data and the determined optimal inspection angle. Have. In applying the present invention, the image detector 7 used for the inspection is installed on the linear slider 8 together with the light quantity sensor 6, and the image detector 7 and the light quantity sensor 6 are arranged on the optical axis on the light receiving side by parallel movement. It is desirable to have a configuration in which they can be switched. With this mechanism, it is possible to search for the optimum illumination angle under the same conditions as the inspection conditions. The image detector 7 is connected to an image processing unit 11 that processes the detected image. In the defect inspection after setting the illumination angle, the inspection result is presented to the data display unit 12 using these.

  As shown in FIG. 1, the inspection object 3 has a periodic pattern 13 in which the pattern of the slits 13a is arranged with a constant width of the light shielding portion 13b. The width of one slit 13 a is also referred to as a periodic pattern interval 4. Further, the minimum interval (a value obtained by adding the width of one slit 13a and the width of one light shielding portion 13b) at which the slit 13a and the light shielding portion 13b are repeated is also referred to as a length 5 of one period of the periodic pattern. .

  The embodiment of the illumination angle setting method using the configuration of the defect inspection apparatus shown in FIG. 1 will be described with reference to FIG.

The light emitted from the light source 1 shown in FIG. 1 is made into substantially parallel light by the condenser lens 2 and illuminates the inspection object 3 having a periodic pattern. As the light source, halogen light, metal halide light, LED light, xenon light, or the like is used.

  The light irradiated on the inspection object 3 generates diffracted light depending on the dimensions of the periodic pattern interval 4 of the periodic pattern 13 and the length 5 of one period of the periodic pattern. This diffracted light is received by the light quantity sensor 6 and detected as diffracted light intensity. The measurement of the diffracted light intensity is performed each time the light illumination angle 14 is changed by a certain amount (S201), and the diffracted light intensity data for each illumination angle is accumulated in the diffracted light data storage unit 9 (S202). ).

  Using the data accumulated as described above, the diffracted light intensity data processing unit 10 calculates a defect evaluation value for each illumination angle (S203), and later uses it for inspection based on the defect evaluation value for each illumination angle. An illumination angle is selected and determined (S204).

  Here, the step (S203) of calculating the defect evaluation value will be described. FIG. 3 schematically shows the relationship between the illumination angle and the diffracted light intensity in a predetermined wavelength region. The horizontal axis represents the irradiation angle, and the vertical axis represents the diffracted light intensity. The diffracted light intensity 15 indicates the diffracted light intensity in the normal part, and the diffracted light intensity 16 indicates the diffracted light intensity in the defect part in which the defect occurs in the interval 4 of the periodic pattern and the length 5 of one period of the periodic pattern. When an image is detected at a predetermined illumination angle, the difference between the diffracted light intensity 15 indicated by the diffracted light intensity 15 from the normal portion and the diffracted light intensity 16 from the defective portion at the illumination angle is the contrast between the normal portion and the defective portion of the image. Appears as For example, when the diffracted light intensity is smaller than the peak and larger than 0 as in the illumination angle 17, the illumination angle 18, and the illumination angle 19 shown in FIG. 3, the difference in the diffracted light intensity between the normal part and the defective part is large and normal. It can be expected that the contrast between the portion and the defective portion is high.

  In the defect inspection, the amount of illumination light or the setting of the image detector is adjusted so that the brightness of the inspection target portion in the image falls within the set standard value. For example, a case where a CCD camera is used as the image detector 7 and the dynamic range thereof is taken into account will be described with reference to FIGS. 4 (a), 4 (b), and 4 (c) respectively show the light intensity 21 of the normal part and the light of the defective part in the CCD dynamic range 20 at the illumination angle 17, the illumination angle 18, and the illumination angle 19 shown in FIG. It is the figure which represented intensity | strength 22 typically. When the light intensity 21 of the normal part is adjusted to a standard value at each illumination angle, the illumination angle 18 or the illumination angle 19 is different from the illumination angle 17 by the intensity ratio between the normal part and the defective part. 23 comes out greatly. That is, in the inspection image, an image in which the illumination angle 18 or the illumination angle 19 has a higher contrast between the normal part and the defective part than the illumination angle 17 having a high light amount is obtained.

  Therefore, a numerical value obtained by normalizing the absolute value of the difference between the diffracted light intensity I of the normal part and the diffracted light intensity I ′ of the defective part expressed by the following formula 1 with the diffracted light intensity I of the normal part is obtained as an inspection image. Can be used as an evaluation value of the contrast between the normal part and the defective part. Since the evaluation value of the contrast between the normal part and the defect part in this inspection image is for evaluating the visibility of the defect, this evaluation value is hereinafter referred to as a defect evaluation value.

本実施形態では図１中の光量センサー６により取得した回折光強度を正常部の回折光強度として用い、この取得した回折光強度を基に欠陥部の回折光強度の代用値を以下のように算出することで、数１による欠陥評価値を計算する。

In the present embodiment, the diffracted light intensity acquired by the light quantity sensor 6 in FIG. 1 is used as the diffracted light intensity of the normal part, and the substitute value of the diffracted light intensity of the defect part is based on the acquired diffracted light intensity as follows. By calculating, the defect evaluation value according to Equation 1 is calculated.

A method for calculating the substitute value of the diffracted light intensity of the defect portion will be described with reference to FIG. For example, considering that the defect to be inspected is very small, the difference between the diffracted light intensity of the normal part and the diffracted light intensity of the defective part is very small, and the diffracted light intensity of the defective part is the same as the diffracted light intensity of the normal part. It can be approximated by a value shifted in parallel by a minute amount in the direction of the illumination angle axis. This schematic diagram is shown in FIG. The diffracted light intensity 24 (solid line) is the diffracted light intensity in the normal part, the diffracted light intensity 25 is the diffracted light intensity in the defective part, and the diffracted light intensity 26 is a substitute for the diffracted light intensity in the defective part obtained by parallel shifting the diffracted light intensity in the normal part. Indicates the value. The diffracted light intensity 25 (broken line) of the defective portion and the substitute value 26 (one-dot chain line) of the diffracted light intensity of the defective portion are very close to each other.

That is, when the diffracted light intensity data at the m-th measured illumination angle θ _m is I _m , the diffracted light intensity data I _{m + n} at the illumination angle θ _{m + n} is used as the diffracted light of the defect portion at the illumination angle θ _m . Instead of the intensity, the defect evaluation value for each illumination angle can be calculated using Equation (1). At this time, as a shift amount for calculating the diffracted light intensity of the defect portion (that is, the difference between the illumination angles θ _{m + n} and θ _m ), a value obtained by a verification test is used.

  In calculating the defect evaluation value at this time, the diffracted light intensity data to be used may be smoothed to remove noise. Further, another calculation method may be used for calculating the substitute value of the diffracted light intensity of the defective portion.

  Next, the step of determining the illumination angle (S204) will be described with reference to FIG. The defect evaluation value 27 in FIG. 6 indicates the defect evaluation value calculated by the above method. The illumination angle at which the calculated defect evaluation value for each illumination angle shows the maximum value (illumination angle 28 in FIG. 6) is set as the optimum inspection angle.

  As described above, in the first embodiment of the present invention, the illumination angle is changed, the diffracted light intensity data at each illumination angle is accumulated, the defect evaluation value is calculated based on the diffracted light intensity data, and the defect inspection is performed. Select the optimal lighting angle.

  In the first embodiment according to the present invention, when setting an inspection recipe, it has been conventionally necessary to change inspection conditions until a desired inspection sensitivity is obtained, and to repeatedly perform inspection and observation of the results. It is possible to reduce the labor required for setting the inspection recipe. In addition, by using a quantitative method, it is possible to set an illumination angle that can detect unevenness accurately even for workpieces whose pitch and pattern are unknown to the operator, and to suppress variations in inspection accuracy among workers. It becomes possible.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The outline of the system configuration of the second embodiment of the present invention is the same as that shown in FIG. However, in the second embodiment of the present invention, a spectroscope is used for the light quantity sensor 6.

  A second embodiment of the present invention will be described with reference to FIG. The light emitted from the light source 1 shown in FIG. 1 is made into substantially parallel light by the condenser lens 2 and illuminates the inspection object 3 having a periodic pattern. The light irradiated onto the inspection object 3 generates diffracted light depending on the dimension of the periodic pattern interval 4 of the periodic pattern 13 and the length 5 of one period of the periodic pattern. The light is split by a certain light quantity sensor 6 and detected as the diffracted light intensity for each wavelength. The measurement of the diffracted light intensity is performed each time the light illumination angle 14 is changed by a certain amount (S201), and the diffracted light intensity data at each wavelength for each illumination angle is stored in the diffracted light data storage unit 9. Accumulate (S202).

  Using the data accumulated as described above, the diffracted light intensity data processing unit 10 calculates a defect evaluation value for each illumination angle (S203).

The step (S203) of calculating the defect evaluation value in the second embodiment of the present invention will be described with reference to FIG. As the diffracted light intensity 31 at each illumination angle used to calculate the defect evaluation value in the second embodiment of the present invention, a series of weights corresponding to each wavelength is applied to the diffracted light intensity 29 at each wavelength at each illumination angle. Multiply by a factor of 30 and use the sum of the values. That is, as shown in 29 and 31, when the value at the wavelength λ _n at the illumination angle θ _m is P _{mn and} the weighting coefficient at the wavelength λ _n is C _n , the transmitted diffracted light intensity at the illumination angle θ _m shown at 31 The evaluation value I _m is calculated by the following formula 2.

この時の一連の重み付け係数３０には欠陥検査装置の光学機器の波長特性に基づいた値を用いても良い。光学機器の波長特性とは、具体的には欠陥検査時に使用する波長変換フィルターの透過特性や、欠陥検査に用いる画像検出機器の波長感度特性等を指す。また、用意される一連の重み付け係数は複数存在しても良く、照明角度と回折光強度の関係を計算する直前においてそれらの中から任意に選択しても良い。

The series of weighting coefficients 30 at this time may use values based on the wavelength characteristics of the optical equipment of the defect inspection apparatus. The wavelength characteristic of the optical device specifically refers to the transmission characteristic of the wavelength conversion filter used during defect inspection, the wavelength sensitivity characteristic of the image detection device used for defect inspection, and the like. Further, a plurality of prepared weighting coefficients may exist, and may be arbitrarily selected from them immediately before calculating the relationship between the illumination angle and the diffracted light intensity.

  Using the diffracted light intensity for each illumination angle obtained as described above, the defect inspection evaluation value for each illumination angle is calculated in the same manner as in the first embodiment. Note that the step of selecting the optimum illumination angle for defect inspection is also performed in the same manner as in the first embodiment.

  As described above, in the second embodiment according to the present invention, the illumination angle is changed, the diffracted light intensity data for each wavelength at each illumination angle is accumulated, the relationship between the illumination angle and the diffracted light intensity is calculated, and the illumination A defect evaluation value for each illumination angle is calculated using the diffracted light intensity data for each angle, and an optimum illumination angle for defect inspection is selected.

  In addition, the second embodiment according to the present invention accumulates diffracted light intensity data of an object to be inspected, so that even when an inspection is performed for optical conditions related to a plurality of wavelengths, the optimum data can be quickly obtained based on the accumulated data. The inspection illumination angle can be reselected. This will be described with reference to FIG. Note that the case where the inspection is performed with respect to the optical conditions related to a plurality of wavelengths specifically refers to a case where the wavelength limitation of the light emitted from the light source is inspected in a plurality of ways by using a wavelength conversion function or the like. .

  Illumination is performed on a predetermined inspection object while changing the illumination angle, the diffracted light intensity for each wavelength is measured (S801), and diffracted light intensity data for each wavelength at each illumination angle is accumulated (S802). After completing these steps, the weighting coefficient based on the planned inspection optical conditions is used to calculate the diffracted light intensity for each illumination angle (S803), and the defect for each illumination angle is obtained from the obtained diffracted light intensity data. The evaluation value is calculated to determine the inspection illumination angle (S804). After these steps, it is determined whether there are other inspection optical conditions to be inspected (S805), and if there are, the weighting coefficient for each wavelength based on the second optical condition is selected (S806). Then, the diffracted light intensity for each second illumination angle is calculated using the newly selected weighting coefficient (S803), the second inspection illumination angle is determined (S804), and it is determined again whether there are other optical inspection conditions. (S805). In this way, by changing the weighting coefficient and repeating steps S803 and S804, the optimum illumination angle under each condition can be obtained for a plurality of inspection optical conditions by measuring the diffracted light intensity data once. .

  Next, a third embodiment according to the present invention will be described.

  In the third embodiment of the present invention, the acquisition of the diffracted light intensity for each illumination angle is acquired by the same method as in the first or second embodiment. Based on the diffracted light intensity data thus obtained, interpolation processing is performed to obtain diffracted light intensity data with a fine variation in illumination angle. Using the diffracted light intensity data after the interpolation processing, a defect evaluation value for each illumination angle is calculated, and an illumination angle optimum for defect inspection is obtained in the same manner as in the first or second embodiment. Select.

As described above, in the third embodiment of the present invention, the illumination angle is changed, the diffracted light intensity data at each illumination angle is accumulated, the interpolation process is performed on the diffracted light intensity data, and the diffracted light intensity data after the interpolation process is performed. Is used to calculate the defect evaluation value for each illumination angle, and the optimum illumination angle for defect inspection is selected.

  In the third embodiment according to the present invention, by performing the interpolation process, a more detailed defect evaluation value for each illumination angle can be calculated, and a proof angle optimal for defect inspection can be determined with high accuracy.

  Next, a fourth embodiment according to the present invention will be described.

  In the fourth embodiment of the present invention, the diffracted light intensity data is acquired and the defect evaluation value for each illumination angle is calculated in the same manner as in the first embodiment, the second embodiment, or the third embodiment. Do.

  In the fourth embodiment of the present invention, in the inspection illumination angle determination step (S204 in FIG. 2), a plurality of illumination angles indicating positive extreme values of defect evaluation values are detected, and these illumination angles are used as illumination angle candidates. And Next, in each illumination angle candidate, imaging is performed under the same conditions as in the inspection. The captured images obtained as described above are compared, and the illumination angle at which an image having the highest contrast between the normal part and the defective part is obtained is set as the optimum illumination angle for defect inspection. Note that the comparison of the captured images is preferably a numerical comparison based on the images.

  As described above, in the fourth embodiment of the present invention, the illumination angle is changed, the diffracted light intensity data at each illumination angle is accumulated, the defect evaluation value is calculated thereafter, and a plurality of illumination angle candidates obtained from the defect evaluation value The optimum illumination angle for the defect inspection is selected by comparing the picked-up images.

  The fourth embodiment of the present invention can determine the optimal illumination angle for defect inspection particularly accurately when there are a plurality of similar maximum values in the calculated defect evaluation values for each illumination angle. .

  According to the present invention, labor of inspection recipe setting work can be reduced in an inspection apparatus for a product having a rectangular periodic pattern such as a photomask or a wafer, and an optimal illumination angle can be set with high accuracy for defect inspection. it can. In addition, variation in inspection accuracy among workers can be suppressed.

It is a figure which shows the example of the system configuration | structure of the defect inspection apparatus which concerns on this invention. It is a figure which shows the flow of the illumination angle determination which concerns on this invention. It is a figure which shows typically the relationship between the illumination angle in a predetermined wavelength range, and diffracted light intensity. (A), (b), and (c) are the light intensity 21 of the normal part and the light intensity 22 of the defective part in the CCD dynamic range 20 at the illumination angle 17, the illumination angle 18, and the illumination angle 19 shown in FIG. FIG. It is a figure which shows typically that the diffracted light intensity of a defective part can be approximated by the value which shifted the diffracted light intensity of the normal part in the illumination angle axis direction by a minute amount parallel. It is a figure which shows typically the relationship between a defect evaluation value and an illumination angle. It is a figure which shows typically the calculation method of the diffracted light intensity at the time of using a spectrometer for a light quantity sensor. It is a figure which shows the flow of illumination angle determination in the some optical condition which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Condensing lens 3 ... Test object 4 ... Periodic pattern interval 5 ... Period length of one period 6 ... Light quantity sensor 7 ... Image detector 8 ... Linear slider 9 ... Diffracted light intensity data Accumulation unit 10 ... Diffraction light intensity data processing unit 11 ... Image processing unit 12 ... Data display unit 13 ... Periodic pattern 13a ... Slit 13b ... Light shielding unit 14 ... Illumination angles 15, 16 ... Diffraction light intensity 17, 18, 19 ... Illumination Angle 20 ... Dynamic range 21, 22 ... Light intensity 23 ... Light intensity difference 24, 25 ... Diffraction light intensity 26 ... Diffraction light intensity substitute value 27 ... Defect evaluation value 28 ... Illumination angle 29 ... Diffraction at each wavelength at each illumination angle Data table 30 representing light intensity ... Data table 31 representing a series of weighting coefficients corresponding to each wavelength ... Data table representing diffraction intensity at each illumination angle

Claims (4)

A method performed by a defect inspection apparatus for periodic patterns of an object to be inspected,
A diffracted light intensity data acquisition step that performs measurement of diffracted light generated by irradiating light from a light source as a substantially parallel light onto an inspection object at a plurality of illumination angles, and acquires diffracted light intensity at each illumination angle;
A data accumulation step for accumulating diffracted light intensity data for each illumination angle;
Using the diffracted light intensity data for each illumination angle, a defect evaluation value calculation step for calculating a defect evaluation value for evaluating the visibility of the defect for each illumination angle,
An illumination angle determination step for setting an illumination angle at which the defect evaluation value is a maximum value;
An illumination angle setting method in a defect inspection apparatus including: The diffracted light intensity data acquisition step performs measurement of the diffracted light from the inspection object by spectroscopic measurement, acquires diffracted light intensity data for each wavelength at each illumination angle,
The data accumulation step accumulates diffracted light intensity data for each wavelength at each illumination angle,
In the defect evaluation value calculation step, as the diffracted light intensity data for each illumination angle, the data obtained by multiplying the diffracted light intensity for each wavelength at each illumination angle by multiplying by a weighting coefficient corresponding to each wavelength is used to calculate the illumination angle. Calculate the defect evaluation value to evaluate the legibility of each defect,
The illumination angle setting method in the defect inspection apparatus according to claim 1.   The defect evaluation value calculation step performs an interpolation process on the diffracted light intensity data for each illumination angle, and evaluates the visibility of the defect for each illumination angle using the diffracted light intensity data for each illumination angle after the interpolation process. The illumination angle setting method in the defect inspection apparatus according to claim 1, wherein a defect evaluation value is calculated.   The illumination angle determination step is based on comparison of captured images obtained by detecting one or a plurality of illumination angle candidates whose defect evaluation value has a positive extreme value, and performing imaging with the illumination angle candidates. 4. An illumination angle setting method in a defect inspection apparatus according to claim 1, wherein the illumination angle is set.

Images