JP2007263795A - Calibration sample, pattern inspection device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to calibrate so as to obtain a proper detection sensitivity corresponding to the pattern formed on the specimen, in the calibration sample, pattern inspection device and its method. <P>SOLUTION: The pattern inspection device 50 includes the sample transfer mechanism 2 for transferring the calibration samples 1 to the inspection position, which are formed from the plurality of patterns for calibration corresponding to the patterns to be formed on the substrate 20 being the specimen, which are manufactured with the same manufacturing method as the substrate 20; the illumination optical system 3 for illuminating the inspection position; the imaging optical system 5 for imaging the calibration sample 1; and integration control means 10 which is made to regulate the image reading condition of the calibration sample 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a calibration sample, a pattern inspection apparatus, and a method for performing an image reading inspection for detecting a defect in a pattern of a test object. In particular, the present invention relates to a pattern inspection apparatus capable of self-calibration of defect detection sensitivity, for example, a pattern inspection apparatus for inspecting a circuit chip formed on a liquid crystal substrate or a wafer.

In recent years, high definition and high integration have been advanced in the fields of liquid crystal devices and semiconductor circuits. For this reason, a pattern inspection apparatus for inspecting a defect or abnormality of a pattern of a test object having a regular pattern formed on such a surface by an image reading inspection is used.
Conventionally, such a pattern inspection apparatus illuminates a test object, images the image with an imaging means, converts it into an image signal, and inspects whether the pattern is correctly formed by appropriate image processing. Yes.
In order to improve the sensitivity of the inspection, it is necessary to perform appropriate illumination and adjust the optical conditions of the imaging means, for example, variable conditions such as focus, luminance distribution, and alignment of the optical system within an appropriate fixed range. Therefore, calibration was performed using a calibration sample corresponding to each variable condition.
For example, Patent Document 1 describes an apparatus for evaluating inspection performance of a pattern inspection apparatus in which patterns for evaluating optical system characteristics, alignment characteristics, and illuminance distribution characteristics are integrally provided.
Patent Document 2 describes a calibration standard sample in which a formation position and the number of formations can be defined on a calibration standard sample, and a simulated defect having various dimensions in three dimensions is formed.
Patent Document 3 describes a standard sample for detection in which a collective pattern of an array group of pits in which the depth and width of various dimensions are combined is formed on the wafer surface.
Japanese Patent Laid-Open No. 9-87991 (page 3-5, FIGS. 1 and 3) Japanese Patent Laid-Open No. 10-325807 (pages 7-14, FIGS. 20, 21) JP 2000-58606 A (page 3-4, FIG. 3)

However, the above-described conventional calibration sample, pattern inspection apparatus and method have the following problems.
According to the technique described in Patent Document 1, calibration is performed for each characteristic, so that the detection sensitivity of the pattern inspection apparatus can be kept constant, but the pattern characteristic peculiar to the test object, for example, reflectance Changes in detection sensitivity due to changes in distribution and pattern period distribution cannot be handled. For example, even if the reflectance of the test object is high or low as a whole, the detection sensitivity is relatively inferior depending on the test object because, for example, the illumination light quantity and the aperture are calibrated to the same conditions. There is a problem of becoming a thing.
Further, according to the technique described in Patent Document 2, since a calibration standard sample is formed by a three-dimensional simulated defect, it is easy to detect a three-dimensional defect as long as it is represented by a simulated defect, but a normal pattern However, there is a problem that the detection sensitivity is relatively inferior depending on the object to be examined, including the change in the appearance of the defect when the background is used.
Further, according to the technique described in Patent Document 3, a collective pattern is formed on the wafer surface, so that calibration can be performed in a surface state close to the test object, but the collective pattern is an actual pattern of the test object. In a different point, there exists a problem similar to the technique of patent document 1,2.

  The present invention has been made in view of the above problems, and a calibration sample and pattern that can be calibrated so as to obtain appropriate detection sensitivity according to the pattern formed on the test object. An object is to provide an inspection apparatus and method.

In order to solve the above-mentioned problem, the invention according to claim 1 is a calibration sample used for calibration of an image reading means for inspecting a pattern formed on a test object, and for calibration of the calibration sample. A plurality of patterns are formed by the same manufacturing method as the test object, and a plurality of patterns are provided according to the pattern to be formed on the test object.
According to this invention, since the calibration sample is provided with a plurality of patterns to be formed on the test object by the same manufacturing method as the test object, the actual pattern, material, processing state, etc. of the test object Calibration can be performed in accordance with conditions, and the detection sensitivity of defects that deviate from such conditions can be increased.

According to a second aspect of the present invention, in the calibration sample according to the first aspect, the calibration pattern is formed on a plurality of background portions having different reflectances.
According to this invention, it is possible to perform calibration suitable for inspection of patterns arranged in background portions having different reflectances.

According to a third aspect of the present invention, the calibration sample according to the first or second aspect is configured such that edge portions parallel to each other are provided between different calibration patterns within the reading visual field range.
According to the present invention, the calibration pattern can also be used for magnification calibration.

According to a fourth aspect of the present invention, in the pattern inspection apparatus, the pattern inspection apparatus includes an illuminating unit that illuminates the test object and an image capturing unit that captures an image of the test object. An image reading unit that performs reading, a reading control unit that controls image reading conditions of the image reading unit, and a calibration sample according to claim 1 provided so as to be readable by the image reading unit. The calibration pattern of the calibration sample is read by the image reading unit, and the image reading conditions during the image reading inspection are calibrated according to the read image.
According to the present invention, the calibration sample according to any one of claims 1 to 3 is read by the image reading unit, and the image reading condition of the illuminating unit and the imaging unit is controlled by the reading control unit, so that an image at the time of the image reading inspection is obtained. Reading conditions can be calibrated. Therefore, it becomes a pattern inspection apparatus provided with the same effect as the calibration sample in any one of Claims 1-3.

According to a fifth aspect of the present invention, in the pattern inspection apparatus according to the fourth aspect, the calibration of the image reading condition is performed by a plurality of calibration patterns provided in one of the calibration samples. .
According to the present invention, since the image reading conditions are calibrated by using a plurality of calibration patterns provided in one of the calibration samples, the calibration can be quickly performed without switching the calibration samples.

According to a sixth aspect of the present invention, in the pattern inspection apparatus according to the fourth or fifth aspect, the calibration sample includes a plurality of calibration patterns having different calibration patterns corresponding to a plurality of test object patterns. The calibration sample that is held in the calibration sample switching means that is selectively movably held at the image reading position of the image reading unit, and that is used for the calibration of the image reading conditions, corresponds to the pattern of the test object that performs the image reading inspection. To be switched.
According to the present invention, when configuring a test object having a different pattern, the calibration sample switching means switches the calibration sample according to the test object, thereby performing an inspection in which the test objects having different patterns are mixed. It can be done efficiently.

According to the seventh aspect of the present invention, the image reading condition of the image reading inspection is calibrated by performing the image reading inspection of the calibration pattern of the calibration sample prior to the image reading inspection of the pattern formed on the test object. A pattern inspection method, wherein a calibration pattern of a calibration sample according to any one of claims 1 to 3 is read, and an image reading condition at the time of the image reading inspection is calibrated according to the read image. .
According to the present invention, the calibration pattern of the calibration sample according to any one of claims 1 to 3 is read, and the image reading conditions during the image reading inspection are calibrated according to the read image. This is a pattern inspection method having the same function and effect as the calibration sample according to any one of 3 has.

According to the calibration sample of the present invention, since a plurality of patterns to be formed on the test object are provided by the same manufacturing method as the test object, calibration can be performed under the same conditions as the test object. Thus, it is possible to easily improve the defect detection sensitivity by the calibrated image reading conditions.
Further, according to the pattern inspection apparatus and method of the present invention for performing calibration using such a calibration sample, even when the pattern of the test object is different, it can be set to an appropriate detection sensitivity, and the pattern of the test object can be set. There is an effect that the defect can be easily detected.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Throughout all the drawings, even if the embodiments are different, the same or corresponding members will be denoted by the same reference numerals, and redundant description will be omitted.
FIG. 1 is a schematic explanatory view of a front view for explaining a schematic configuration of a pattern inspection apparatus according to an embodiment of the present invention. FIG. 2 is a partial perspective explanatory view for explaining the pattern inspection apparatus according to the embodiment of the present invention. In each figure, an xyz Cartesian coordinate system with the vertical direction as the z-axis is written to refer to the relative direction.

A pattern inspection apparatus according to an embodiment of the present invention will be described.
The pattern inspection apparatus 50 of the present embodiment is an apparatus for inspecting a pattern defect of a substrate 20 (test object) on which a predetermined pattern such as a liquid crystal substrate or a circuit chip formed on a wafer is formed. is there.
The substrate 20 is generally formed by laminating various patterns in the thickness direction using various materials having different reflectances. In the pattern inspection, not only the completed multilayer pattern but also the inspection is usually performed for each layer manufacturing process. Therefore, for example, even if the pattern to be inspected, such as a signal line pattern, is the same, a change occurs in that the reflectance of the surroundings changes or a different pattern is arranged in the surroundings as the manufacturing process proceeds.
The present invention is for easily optimizing each image reading condition and increasing the defect detection sensitivity when such a pattern or reflectance of the inspection object changes for each inspection.

  As shown in FIG. 1, the schematic configuration of the pattern inspection apparatus 50 includes a substrate holding / moving unit 50B that moves the substrate 20 to a predetermined inspection position and holds the substrate 20, and image reading of the substrate 20 disposed at the predetermined inspection position. It comprises an image reading unit 50A (image reading means) that performs inspection.

As shown in FIG. 2, the substrate holding / moving unit 50 </ b> B includes transport tables 12 and 12 and a sample moving mechanism 2 provided on a base 12 a.
The transport tables 12 and 12 are provided with a large number of air inlet / outlet holes 12b for floating the substrate 20 on the upper surface. The carriages 12 and 12 are arranged in parallel with a slit-like gap extending in the y-axis direction shown in the figure, and air is ejected from the empty entry exit hole 12b to float the substrate 20 on the upper surface. In the state where the substrate 20 is floated, the end portion of the substrate 20 is held by the transport means and is forcibly transported in the x-axis direction in the drawing.
The sample moving mechanism 2 includes a horizontal moving mechanism 2b movable in the y-axis direction, a vertical moving mechanism 2a provided on the horizontal moving mechanism 2b and movable in the vertical direction, and a vertical moving mechanism 2a. A rotational movement mechanism 2c is provided that can rotate around the y-axis. A calibration sample 1 (calibration sample), which will be described later, can be detachably held in the rotational movement mechanism 2c.

  As shown in FIG. 1, the image reading unit 50 </ b> A is to be tested at an inspection position set at the height of the upper surface of the substrate 20 held on the transport table 12 at a substantially central position of the gap between the transport tables 12 and 12. It is for reading an image of an object. The schematic configuration includes an illumination optical system 3 (illumination means), an illumination control means 4, an imaging optical system 5, and an integrated control means 10. The imaging optical system 5 constitutes imaging means for obtaining an image of the test object.

The illumination optical system 3 includes a line illumination light source that illuminates linear illumination light (line illumination light) on the surface of the substrate 20 that is a test object, and an optical system that condenses the illumination light at an appropriate position. Contains. The illumination optical system 3 is arranged so that its optical axis is inclined at an inclination angle θ _L with respect to the surface of the substrate 20, and is rotated around the inspection position in the zx plane in the drawing by a rotation mechanism (not shown). It is possible. Hereinafter, the rotation position is represented by an angle θ _L measured from the z axis. In FIG. 1, reference numeral 3 a is the optical axis of the illumination optical system 3.
The details of the illumination optical system 3 can be appropriately configured as necessary, but at least the amount of light can be adjusted. For example, the adjusting unit may change the amount of light emission by changing the voltage applied to the light source, or may be optically adjusted by, for example, a diaphragm or an ND filter.
If necessary, the optical elements constituting the optical system may be movable or switchable so that other optical characteristics of the illumination light can be varied. Examples of other optical characteristics include wavelength characteristics and polarization characteristics.

The illumination control means 4 is a control means for changing the optical characteristics of the illumination light emitted from the illumination optical system 3. According to the configuration of the illumination optical system 3, for example, appropriate control such as electrical control of the light source and movement / switching of the optical element can be performed. If necessary, it is able to perform also variable control of the rotation angle theta _L of the illumination optical system 3.

The imaging optical system 5 is an optical system including an imaging lens 6a and a line sensor camera 6b for capturing an image of the substrate 20 disposed at the inspection position.
The line sensor camera 6b is for obtaining an image signal by forming an image of the substrate 20 formed by the imaging optical system 5 on an imaging device arranged in a line.
The imaging optical system 5 is configured to be rotatable about the inspection position in the illustrated zx plane and the distance adjusting mechanism 7 for changing the distance in the optical axis direction, the focusing mechanism 8 for moving in the illustrated z direction. It is integrally held by a moving mechanism (not shown), and is arranged at a rotation position of an angle θ _C as measured from the z axis. In FIG. 1, reference numeral 5 a denotes the optical axis of the imaging optical system 5.
In this way, the imaging optical system 5 can adjust the magnification and focus the image of the substrate 20 by the distance adjusting mechanism 7 and the focusing mechanism 8. In addition, the reflected light from the board | substrate 20 imaged with the imaging optical system 5 is a diffracted light or interference light, and it adjusts the inclination angles (theta) _{L and (} theta) _C of the illumination optical system 3 or the imaging optical system 5 by line suitably. The sensor camera 6b can capture a diffraction image and an interference image. Further, both the illumination optical system 3 and the imaging optical system 5 may be provided so as to be rotatable, but one may be fixed and the other may be rotated.

The integrated control means 10 is electrically connected to the illumination control means 4, the line sensor camera 6b, the interval adjustment mechanism 7, and the focusing mechanism 8, and transmits and receives signals such as control signals and image signals to the respective parts. It is a control means for performing control. In the present embodiment, a personal computer including an appropriate input / output interface, memory, and CPU and an appropriate input / output device are configured.
As an input device, although not shown, for example, a dedicated operation panel, a keyboard, a mouse, and the like are provided as necessary.
As the output device, for example, a monitor 9 for displaying an image of a test object according to an image signal of the line sensor camera 6b, an operation screen for monitoring input information and control parameters from the input device, an inspection, and the like. An external storage device (not shown) or the like for storing the result information is provided.

Next, a calibration sample according to an embodiment of the present invention will be described.
FIG. 3 is a schematic plan view for explaining an example of the calibration sample according to the embodiment of the present invention.
As shown in FIG. 3, a calibration sample 1 which is an example of a calibration sample of the present embodiment is used for calibration on a rectangular sample substrate 1a made of the same material as a substrate 20 (see FIG. 1) as a test object. The pattern 1b is formed.
The calibration pattern 1b is a pattern extending in the longitudinal direction of the sample substrate 1a and formed in a plurality of strips in the short direction of the sample substrate 1a. For example, it is composed of three rows of a high reflectance pattern 1A, a medium reflectance pattern 1B, and a low reflectance pattern 1C.

High reflectivity pattern. 1A, the background portion B ₁ on the area 15a having a uniform reflectance in a relatively high reflectance, a plurality of patterns P3, P5 traversing respectively in the lateral direction 17a.
The background portion B ₁ is formed by forming one of the portions constituting the background of the pattern existing in the substrate 20 with the same material as that of the substrate 20 by the same manufacturing method, so that one reflecting surface forming the background in the substrate 20 is formed. Is to simulate.
Each of the patterns P ₃ and P ₅ is a pattern in which normal partial patterns existing in portions having the same reflectance as the background portion B ₁ in the substrate 20 are formed by the same manufacturing method as the substrate 20. For example, a group of parallel lines having a predetermined line width and a predetermined pitch used for signal wiring and the like can be employed. The size of each pattern is a size including the size of a defect assumed to be detected.
Note that FIG. 3 is a schematic diagram, and three strips are provided so that the patterns P ₃ and P ₅ can be easily seen. However, the present invention is not limited to this, and the pitch, width, number of strips appearing on the substrate 20 or substantially the same. The pattern should be

Medium reflectance pattern 1B Similarly, regions on the background part _{B 2} of the low-reflectivity than the background portion _{B 1 13,14,15b,} 17b, are provided.
Patterns P ₁ and P ₂ are formed in the regions 13 and 14, respectively. The patterns P ₁ and P ₂ are patterns existing on the substrate 20 as in the pattern P ₁₅ or the like, or normal partial patterns substantially equivalent thereto (hereinafter referred to as the pattern P _n (n is an integer)). ).
On the other hand, patterns P ₃ and P ₅ are formed in the regions 15b and 17b. Therefore, according to the regions 15a and 15b and 17a and 17b, for example, a wiring pattern formed across a plurality of regions having different reflectivities in the substrate 20 can be simulated.

Similarly low reflectivity pattern. 1C, the background portion _B 1, regions 16, 18 on the background part _{B 3} of low reflectance than _{B 2} are provided. Patterns P ₄ and P ₆ are formed in the regions 16 and 18, respectively.

The pattern formed on the calibration sample 1 depends on the type of the substrate 20, but is not generally limited to a simple pattern such as a group of parallel lines. In order to improve the accuracy of calibration described later, it is preferable to form as many patterns as possible included in the substrate 20.
A calibration sample 30 (calibration sample) as another example will be described.
FIG. 4A is a schematic plan view of the calibration sample 30. FIG. FIG. 4B is a graph showing a histogram of luminance in the longitudinal direction of the calibration sample 30. FIG. 5 is an enlarged schematic plan view of a part of the substrate 20 for explaining a pattern formed on the substrate 20. FIG. 6 is a graph for explaining the frequency distribution of the luminance (reflectance) of the pattern formed on the substrate 20.

As shown in FIG. 4A, the calibration sample 30 has a calibration pattern 30A extending in a strip shape in the longitudinal direction on the sample substrate 1a.
The calibration pattern 30A has a pattern existing on the substrate 20 in the regions 31, 32, and 33 on the background portion 20g, or a pattern substantially equivalent to them.
In the region 31, a pattern 20a having a relatively high reflectivity having a predetermined width y ₁ y ₂ traversing in the lateral direction of the background portion 20g is formed.
In the region 32, a relatively low reflectance pattern 20d having a predetermined width y ₃ y ₄ is formed.
Similarly, patterns 20f, 20c, 20e, 20c, and 20f having predetermined widths y ₅ y ₆ , y ₆ y ₇ , y ₇ y ₈ , y ₈ y ₉ , and y ₉ y ₁₀ are formed in the region 33. The reflectance of the patterns 20f, 20c, and 20e is the reflectance that the pattern 20f has the highest reflectance and decreases in this order.
Thus, the pattern of the calibration sample 30 is an example characterized by the line width and the reflectance.

Such a calibration pattern 30A is based on the pattern of the substrate 20 as shown in FIG.
In the pattern of the substrate 20, the patterns 20a and 20b intersect in a lattice pattern on the background portion 20g. A pattern 20c having a relatively wide line width is provided in parallel to the pattern 20b, and a rectangular pattern 20e and a square pattern 20f are alternately arranged thereon. In addition, a pattern 20d that connects the pattern 20e and the pattern 20a in an L shape is provided. FIG. 5 is a partially enlarged view. In actuality, such a pattern is repeated to cover the entire substrate 20.

FIG. 6 shows a histogram of the luminance (reflectance) of such a pattern. The horizontal axis in FIG. 6 is luminance (reflectance), and the vertical axis is frequency.
That is, as indicated by the broken line 21, the luminance varies in a substantially Gaussian distribution from low luminance to medium luminance (the luminance range L in the drawing), and the frequency is relatively high in which the frequency decreases more slowly than the Gaussian distribution from medium luminance to high luminance. (The luminance range M shown in the drawing), and the frequency is concentrated on a predetermined value of the high luminance portion (the luminance range N shown in the drawing).
Although FIG. 6 is only an example, for example, the luminance ranges M, N, and L correspond to the luminance distribution of the pattern of the other wiring portions including the hole portion, the periphery of the hole portion, and the background portion. That is, most of the substrate 20 occupies a region where a small number of wires pass through the low-luminance background portion 20g, and a complicated pattern, for example, a functional pattern such as a hole portion, is formed and becomes the center of defect inspection. The region shows a relatively high brightness. Therefore, it is preferable that the pattern inspection apparatus 50 is also calibrated in accordance with the luminance distribution of the region that becomes the center of such pattern inspection.

  From this point of view, in the calibration sample 30, the regions 31, 32, and 33 are formed with patterns substantially the same as the illustrated horizontal direction of the regions 20 </ b> A, 20 </ b> B, and 20 </ b> C of the substrate 20 in the longitudinal direction. Therefore, the reflectance distribution of the functionally important pattern appearing on the substrate 20 is reproduced on the sample substrate 1 a having a relatively small area by the same manufacturing method as that for the substrate 20. Therefore, there is an advantage that calibration according to the characteristics of the test object can be performed efficiently.

Next, a pattern inspection method using the calibration sample and the pattern inspection apparatus 50 according to the embodiment of the present invention will be described. The calibration sample will be described using an example in which the calibration sun 30 is used.
FIG. 7 is a flowchart for explaining the pattern inspection method of the present embodiment.
Calibration of the pattern inspection apparatus 50 is performed by instructing the integrated control means 10 to start calibration automatically or manually when initializing at the time of activation, switching of the test object, or when the operator determines that it is necessary. It becomes possible.
A control signal for initializing the illumination optical system 3 is transmitted from the integrated control means 10 to the illumination control means 4. Thereby, the illumination control means 4 moves the rotation position of the illumination optical system 3 to the same angle θ _L as in the inspection, turns on the light source of the illumination optical system 3, and illuminates the inspection position with a predetermined light amount. To. If necessary, move or switch optical elements.
The rotational position of the imaging optical system 5 from the integration control means 10 to the not shown rotating mechanism control signals for the angle theta _C is transmitted. In particular, θ _C = θ _L when performing inspection with specular reflection light.
A control signal for initializing camera internal parameters such as exposure time and imaging sensitivity (gain) is transmitted to the line sensor camera 6b. A control signal for initializing the interval and position to the reference position is also transmitted to the interval adjusting mechanism 7 and the focusing mechanism 8.

Then, the calibration sample 30 is moved to the inspection position by the sample moving mechanism 2. The sample moving mechanism 2 includes position detection means (not shown), and the movement control is repeated using the vertical moving mechanism 2a, the horizontal moving mechanism 2b, and the rotational moving mechanism 2c until reaching the inspection position of the calibration sample 30.
The inspection position is a predetermined position in which the surface of the calibration sample 30 is the same height as the surface of the substrate 20 as the test object, and the longitudinal direction of the calibration sample 30 is directed in the y-axis direction of FIG.

Next, while the calibration sample 30 is imaged by the line sensor camera 6b, it is moved in the longitudinal direction by the horizontal movement mechanism 2b, the image of the calibration pattern 30A is read, and the line profile data is captured.
In this state, since the camera internal parameters and the like are in an initialized state, the focus is shifted, and the exposure time with respect to the illumination light is not appropriate, resulting in a blurred image.
For example, with respect to the calibration pattern 30A shown in FIG. 4A, a line profile like a curve 23 shown by a broken line in FIG. 4B is obtained. Here, the horizontal axis of FIG. 4B represents the arrangement of the pixels of the line sensor camera 6b, and the vertical axis represents the luminance of each pixel. Y _i (i is an integer) written on the horizontal axis is a camera pixel corresponding to a position y _i (i is an integer) on the calibration pattern 30A.
In the curve 23, the luminance corresponding to the patterns 20a and 20f having relatively high reflectivity on the calibration pattern 30A is low as the sizes a and c, respectively, and the line positions and widths thereof are shifted.
If the substrate 20 is inspected in such a state, the defect detection sensitivity is lowered because the defect cannot be distinguished from the regular pattern.
Therefore, the following calibration operation is performed continuously.

  First, the maximum value of peak luminance in the line profile (for example, “a” and “c” in FIG. 4B) is evaluated to determine whether it is within the specified range. The means 4 adjusts the amount of illumination light and the exposure time among the camera internal parameters. Further, if necessary, the gain is adjusted among the internal parameters of the line sensor camera 6b. Then, evaluation of the maximum value of peak luminance is repeated.

When the maximum value of peak luminance is determined to be within the specified range, contrast evaluation is performed. For example, it is evaluated whether values such as (ab) and d in FIG. 4B are within a predetermined range.
If it is outside the specified range, the focus position is adjusted by driving the focusing mechanism 8 until it is within the specified range.

Next, the interval between the plurality of edge-shaped patterns provided in the calibration pattern 30A is measured, and the magnification is measured. For example, the distance W between y ₁ y ₁₀ is measured using the outer edge between the patterns 20a and 20f. The distance W corresponds to the pixel interval (Y ₁₀ −Y ₁ ).
When the pixel interval corresponding to y ₁ y ₁₀ on the curve 23 is w, w / W is a magnification, but when the magnification w / W does not fall within the specified range, the interval adjustment mechanism 7 is moved and adjusted. To do. At that time, the in-focus position is calculated so as not to deviate from the in-focus position adjusted in the previous step, and the in-focus mechanism 8 is corrected. However, if the imaging optical system 5 is a zoom optical system, the in-focus position can be maintained, and thus the above correction need not be performed.

  Such an evaluation of the line profile is performed by image processing that is appropriately programmed by taking the line profile as an image signal by the integrated control means 10. Then, control signals for the illumination control means 4, the focusing mechanism 8, the interval adjusting mechanism 7 and the like are automatically transmitted, and each control loop is executed. However, if necessary, the image signal may be displayed on the monitor 9 and these controls may be performed manually.

Thus, the adjustment by the calibration pattern 30A is completed, and the calibration operation is completed. At this time, the line profile of the calibration sample 30 read into the integrated control means 10 is as shown by a curve 22 in FIG.
After that, the sample moving mechanism 2 is driven to retract the calibration sample 30 below the transport table 12. Thereby, the preparation for moving the substrate 20 in the horizontal direction and performing the defect inspection at the inspection position is completed.

  When the substrate 20 is switched to another test object having a different pattern after the defect inspection is completed, the same calibration is performed by switching to a calibration sample corresponding to the substrate 20.

  When the calibration sample 1 is used instead of the calibration sample 30, the calibration pattern is divided into a high reflectance pattern 1A, a medium reflectance pattern 1B, a low reflectance pattern 1C, and the like. Can be calibrated. Since each calibration pattern corresponds to one of the inspection parts of the substrate 20, if the adjustment determined by these is changed in accordance with such an inspection part, an appropriate condition can be obtained in any inspection part. Can be inspected.

Thus, according to the pattern inspection method of the present invention, since the calibration sample manufactured by the same manufacturing method as the test object is used for the pattern existing in the test object, the image reading condition is changed to the pattern of the test object. The exposure, contrast, and magnification are adjusted appropriately. Therefore, a normal pattern can be clearly observed, and if there is a defect in the test object, it can be easily detected as an image abnormality.
Further, since different characteristic values of the image reading unit can be calibrated within one calibration sample, it is possible to calibrate efficiently and to perform quick pattern inspection.

In addition, the sample moving mechanism 2 is provided with a rotational movement mechanism 36 as shown in FIG. 8 in place of the rotational movement mechanism 2c so that the calibration sample can be replaced more quickly with the switching of the test object. Also good.
FIG. 8 is a partial perspective explanatory view showing a modification of the sample moving mechanism of the present embodiment.
The rotational movement mechanism 36 can be mounted with three different calibration samples 35a, 35b, and 35c, and the rotation angle is switched by the control signal of the integrated control means 10 to select one of the calibration samples 35a, 35b, and 35c. Can be arranged at the inspection position.
Such a configuration is advantageous in that the calibration sample can be quickly switched.

  In the above description, only the calibration pattern 30A is used in the calibration sample 30, but it goes without saying that a plurality of calibration patterns may be provided as in the calibration sample 1 if necessary.

In the above description, an example in which the angles θ _L and θ _C can be varied has been described. In this way, for example, in the inspection with specular reflection light, there is an advantage that the reflection angle can be changed or the inspection with diffracted light can be performed by changing the angle θ _C to the angle θ _L. .
However, if it is not necessary to change the angle of specular reflection light or to perform inspection using diffracted light, each angle may be fixed.

It is a schematic explanatory drawing of the front view for demonstrating schematic structure of the pattern inspection apparatus which concerns on embodiment of this invention. It is a fragmentary perspective view for demonstrating the pattern inspection apparatus which concerns on embodiment of this invention. It is a plane schematic diagram for demonstrating an example of the calibration sample which concerns on embodiment of this invention. It is a graph which shows the plane schematic diagram which shows another calibration sample, and the histogram of the brightness | luminance of the longitudinal direction. It is the plane schematic diagram which expanded a part of test object for demonstrating an example of the pattern formed in a test object. It is a graph for demonstrating the frequency distribution of the brightness | luminance (reflectance) of the pattern formed in a to-be-tested object. It is a flowchart for demonstrating the pattern inspection method of this embodiment. It is a fragmentary perspective explanatory view showing the modification of the sample movement mechanism of this embodiment.

Explanation of symbols

1, 30, 35a, 35b, 35c Calibration sample (calibration sample)
1b, 30A Calibration pattern 2 Sample moving mechanism 3 Illumination optical system (illumination means)
4 Illumination control means 5 Imaging optical system (imaging means)
6b Line sensor camera (imaging means)
7 Interval adjustment mechanism 8 Focusing mechanism 10 Integrated control means (reading control means)
20 Substrate (test object)
36 Rotary movement mechanism (calibration sample switching means)
50 Pattern inspection apparatus 50A Image reading unit (image reading means)
50B substrate holding mobile unit _{B 1,} B 2, _{B 3} background section

Claims (7)

A calibration sample used for calibration of an image reading means for inspecting a pattern formed on a test object,
A calibration sample, wherein a plurality of calibration patterns of the calibration sample are formed by a manufacturing method similar to that of the test object, and a plurality of patterns are provided according to the pattern to be formed on the test object.   The calibration sample according to claim 1, wherein the calibration pattern is formed on a plurality of background portions having different reflectances.   3. The calibration sample according to claim 1, wherein edge portions parallel to each other are provided between the plurality of calibration patterns. An image reading unit that includes an illuminating unit that illuminates the test object and an imaging unit that captures an image of the test object, and performs an image reading inspection of a pattern formed on the test object;
Reading control means for controlling image reading conditions of the image reading unit;
The calibration sample according to any one of claims 1 to 3, which is provided so as to be readable by the image reading unit,
A pattern inspection apparatus, wherein the calibration pattern of the calibration sample is read by the image reading unit, and the image reading conditions at the time of the image reading inspection are calibrated according to the read image.   The pattern inspection apparatus according to claim 4, wherein the calibration of the image reading condition is performed by a plurality of calibration patterns provided in one of the calibration samples. The calibration sample is composed of a plurality of calibration patterns corresponding to a plurality of test object patterns, and is held in a calibration sample switching means that is selectively movable to the image reading position of the image reading unit. And
6. The pattern inspection apparatus according to claim 4, wherein the calibration sample used for calibration of the image reading condition is switched according to a pattern of an object to be subjected to the image reading inspection. Prior to image reading inspection of a pattern formed on a test object, a pattern inspection method for calibrating image reading conditions of the image reading inspection by performing image reading inspection of a calibration pattern of a calibration sample,
Read the calibration pattern of the calibration sample according to any one of claims 1 to 3,
A pattern inspection method comprising calibrating an image reading condition at the time of the image reading inspection according to the read image.

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