JP2009150718A - Inspecting device and inspection program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce man-hours for selecting non-defective and defective articles in inspecting workpieces. <P>SOLUTION: An inspecting device includes: a first acquisition part having a first imaging part collectively imaging workpieces based on the reflection light from the workpieces and acquiring the first image of the workpiece by the imaging part; a first comparing part comparing the first workpiece image with a first reference image stored in advance; a detecting part detecting a defect candidate region in the first workpiece image based on the comparison results by the first comparing part; a second acquisition part acquiring the second workpiece image corresponding to the defect candidate region; a second comparing part comparing the second workpiece image with a second reference image corresponding to the defect candidate region in the second reference image stored in advance; and a determining part determining whether the defect candidate region is a defect region based on the comparison results by the second comparing part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inspection apparatus for inspecting an object to be inspected such as a semiconductor substrate, and an inspection program for realizing the inspection by a computer.

An apparatus for illuminating the surface of an object such as a semiconductor wafer and receiving light such as diffracted light generated from the surface of the object at this time to perform surface inspection of the object is known (for example, Patent Document 1). Such equipment automatically eliminates falsely detected defects (pseudo defects) that are not actually defects, and selects them as non-defective products, thereby eliminating wasted rework and realizing efficient production. It is required to do.
JP 2007-93330 A

  However, at present, it is up to the operator to determine whether or not the defect is a pseudo defect. In other words, the pseudo defect is eliminated by the labor and experience of the operator, such as an operator appropriately enlarging and displaying a part that is considered to be a pseudo defect and visually confirming it.

  An object of the present invention is to reduce the man-hours for sorting non-defective / defective products in the inspection of a test object.

  The inspection apparatus of the present invention includes a first imaging unit that collectively images the test object based on reflected light from the test object, and obtains a first test object image by the imaging unit. 1 acquisition unit, the first test object image, a first comparison unit that compares the first reference image stored in advance, and the first comparison unit based on the comparison result by the first comparison unit A detection unit for detecting a defect candidate area in the test object image, a second acquisition unit for acquiring a second test object image corresponding to the defect candidate area, the second test object image, and Based on the comparison result by the second comparison unit and the second comparison unit comparing the second reference image in the region corresponding to the defect candidate region among the stored second reference images, the defect And a determination unit that determines whether the candidate area is a defective area.

  Preferably, the second acquisition unit captures a region corresponding to the defect candidate region in the test object with a higher resolution than when the first test object image is captured. A second image of the test object may be acquired by the second imaging unit.

  In addition, preferably, the second acquisition unit is configured to cut out an area corresponding to the defect candidate area from the first inspection object image and electronically enlarge the second inspection object image. You may get

  Preferably, the second comparison unit sets an image obtained by electronically enlarging an area corresponding to the defect candidate area in the first reference image as the second reference image. The test object image may be compared with the second reference image.

  Preferably, the determination unit may determine whether or not the defect candidate area is a defect area in consideration of an occurrence frequency of the defect candidate area regarding a plurality of the test objects.

  Preferably, an update unit that updates at least one of the first reference image and the second reference image based on a determination result by the determination unit may be further provided.

  In addition, what expressed the structure regarding the said invention converted into the inspection program for implement | achieving the test | inspection regarding a test object with a computer is also effective as a specific aspect of this invention.

  According to the present invention, it is possible to reduce the man-hours for selecting good / defective products in the inspection of the test object.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram illustrating the configuration of the inspection apparatus 1 according to the first embodiment. The inspection apparatus 1 is an inspection apparatus that performs surface inspection of the wafer substrate T using the wafer substrate T as a test object. A repeated pattern or the like is formed at each point on the surface of the wafer substrate T (for example, a resist layer).

  As illustrated in FIG. 1, the inspection apparatus 1 includes a macro inspection unit 10, a micro inspection unit 20, and a computer 30. The macro inspection unit 10 includes a stage 11 that supports the wafer substrate T, an illumination system 12, and a light receiving system 13.

  The inspection apparatus 1 automatically performs surface inspection of the wafer substrate T, which is an object to be tested, in the manufacturing process of semiconductor circuit elements, liquid crystal display elements, etc., and repeats pattern defects (defocus defects, scratches, etc. during exposure). To detect. After exposure / development of the surface (resist layer), the wafer substrate T is carried from the cassette or the developing device by a transport system (not shown) and is attracted to the stage 11.

  The stage 11 places the wafer substrate T on the upper surface, and fixes and holds it, for example, by vacuum suction. Further, the stage 11 can be tilted (tilted) within a predetermined angle range about an axis Ax (axis perpendicular to the paper surface) parallel to the surface of the wafer substrate T by a tilt mechanism (not shown). The stage 11 can be rotated about an axis Ay perpendicular to the surface of the wafer substrate T by a rotation mechanism (not shown). By rotating the stage 11, fine adjustment in accordance with the shot pattern of the wafer substrate T and the like can be performed.

  The illumination system 12 is a means for illuminating the wafer substrate T, and includes a lamp house 14, a wavelength selection unit 15, and a bundle fiber 16. The lamp house 14 includes a light source such as a mercury lamp inside. In addition, the wavelength selection unit 15 includes a plurality of interference filters that transmit only a single wavelength from the bright line spectrum of the lamp. For example, the filters such as g-line (436 mm) and j-line (313 nm) are selectively set. Thus, it is possible to set illumination light having only a specified single wavelength.

  The light emitted from the illumination system 12 is guided to the concave reflecting mirror 17. The concave reflecting mirror 17 is a reflecting mirror whose inner surface is a reflecting surface, and has a front focal point that is substantially conjugate with the pupil plane of the illumination system 12 and a rear focal point that substantially coincides with the surface of the wafer substrate T. The concave reflecting mirror 17 is disposed obliquely above the stage 11. The reflected light beam from the concave reflecting mirror 17 becomes a parallel light beam, and illuminates the surface of the wafer substrate T that is a test object. Then, the light beam reflected by the surface of the wafer substrate T is guided to the light receiving system 13. The light beam reflected on the surface of the wafer substrate T includes regular reflection light from the surface of the wafer substrate T and diffracted light generated from the surface of the wafer substrate T. When the incident angle of the illumination light beam with respect to the wafer substrate T and the reflection angle of the reflected light beam received by the concave reflecting mirror 18 of the light receiving system 13 are the same angle with respect to the normal line of the wafer substrate T, Only the reflected light can be received. When the stage 11 is tilted in accordance with the diffraction angle, only the diffracted light can be received.

  The light receiving system 13 is a means for receiving a light beam reflected by the surface of the wafer substrate T, and includes a concave reflecting mirror 18 and a macro imaging unit 19. The concave reflecting mirror 18 is a reflecting mirror similar to the concave reflecting mirror 17 of the illumination system 12. The macro imaging unit 19 includes an imaging lens (not shown), an imaging element, and the like. The concave reflecting mirror 18 reflects the light beam reflected by the surface of the wafer substrate T, and the reflected light beam forms an image of the wafer substrate T on the image pickup surface of the image pickup element via the imaging lens. The macro imaging unit 19 captures this image and generates a macro inspection image of the wafer substrate T.

  The micro inspection unit 20 is a microscope with an anti-vibration mount that includes a stage 21 that supports the wafer substrate T, an illumination unit 22, an objective lens unit 23, a micro imaging unit 24, and a half mirror 25. The stage 21 places the wafer substrate T on the upper surface and fixes and holds it, for example, by vacuum suction. The stage 21 can be moved in the vertical direction (Bx), the horizontal direction (By), and the front-rear direction (Bz) by a drive mechanism (not shown). The illumination unit 22 includes a light source (not shown). The objective lens unit 23 includes a plurality of objective lenses having different magnifications, and an objective lens selected by a method described later can be inserted into and removed from the optical path. The micro imaging unit 24 includes an imaging element (not shown).

  The light irradiated by the illumination unit 22 is reflected by the half mirror 25 and guided to the surface of the wafer substrate T, which is the test object, through the objective lens unit 23. The reflected light from the wafer substrate T is imaged by the objective lens unit 23 and forms an image of the wafer substrate T on the imaging surface of the imaging device of the micro imaging unit 24 via the half mirror 25. The micro imaging unit 24 captures this image and generates a micro inspection image of the wafer substrate T.

  The computer 30 includes an interface unit 31 that is an interface for exchanging information with the macro inspection unit 10 and the micro inspection unit 20, an operation unit 32 such as a keyboard and a mouse that receives an operation of an operator, and a macro reference image storage unit 33. And a micro reference image storage unit 34 and a control unit 35 for controlling each unit. Details of the macro reference image storage unit 33 and the micro reference image storage unit 34 will be described later.

  Each unit of the interface unit 31, the macro reference image storage unit 33, and the micro reference image storage unit 34 is connected to the control unit 35. Further, the control unit 35 detects the state of the operation unit 32.

  The output of the control unit 35 is connected to each part of the stage 11, the lamp house 14, the wavelength selection unit 15, and the macro imaging unit 19 of the macro inspection unit 10 via the interface unit 31, and the control unit 35 Control each part. Further, the control unit 35 acquires the image data of the macro inspection image generated by the macro imaging unit 19 via the interface unit 31.

  The output of the control unit 35 is connected to each part of the stage 21, the illumination unit 22, the objective lens unit 23, and the micro imaging unit 24 of the micro inspection unit 20 via the interface unit 31, and the control unit 35 Control each part. Further, the control unit 35 acquires the image data of the micro inspection image generated by the micro imaging unit 24 via the interface unit 31.

  The inspection apparatus 1 having the configuration described above performs a macro inspection for collectively inspecting the entire surface of the wafer substrate T, which is the test object, and a part of the surface of the wafer substrate T, which is the test object, based on the result. Micro-inspection with partial scrutiny is feasible. It should be noted that whether or not to perform micro inspection is set by an operator as necessary. In addition, it is assumed that the operator also sets whether or not additional training is required in the inspection.

  FIG. 2A is a schematic diagram showing a wafer substrate T which is a test object. A defect may occur in the wafer substrate T as indicated by E1 and E2 in FIG. 2B. Such defects include what are called pseudo defects. A pseudo-defect is a defect that is not actually a defect but is erroneously detected, and is generated due to an apparatus error at the time of manufacturing and an inspection, a difference in a production process of a wafer substrate, or the like. Further, the pseudo defect tends to occur at the same position on the surface of the wafer substrate T.

  FIG. 3 is a flowchart showing the operation of the control unit 35 during the execution of the inspection.

  In step S <b> 1, the control unit 35 controls the macro inspection unit 10 to image the wafer substrate T. The control unit 35 controls the stage 11 and the macro imaging unit 19 and sets the magnification so that the entire surface of the wafer substrate T can be captured in a collective field of view. For example, when a 300-mm wafer substrate T is imaged with a 1-inch image sensor (1024 × 1024 pixels), the image resolution is about 300 μm / pixel, and the entire surface of the wafer substrate T with this resolution is obtained within the entire surface of the wafer substrate T. Can be confirmed. Then, the control unit 35 acquires a macro inspection image of the wafer substrate T generated by the macro imaging unit 19.

  In step S2, the control unit 35 detects a defect candidate region by comparing the macro inspection image acquired in step S1 with the macro reference image. The macro reference image storage unit 33 stores a good product image of the wafer substrate T in advance as a macro reference image. The control unit 35 reads out the macro reference image from the macro reference image storage unit 33 and compares the macro inspection image acquired in step S1 for each pixel to detect a defect candidate region. The detection is performed based on the luminance information of each pixel by using an overlay method or the like, but the details are the same as those of the publicly known technique, and thus description thereof is omitted. As a detection result, the control unit 35 records the coordinates, center position, area, and the like of the detected defect candidate area as defect candidate area information in a memory (not shown).

  In step S3, the control unit 35 determines whether or not micro inspection is necessary. When determining that the micro inspection is necessary, the control unit 35 proceeds to step S4. When determining that the micro inspection is not necessary, the control unit 35 determines that the wafer substrate T is a non-defective product and ends the series of processes.

  The control unit 35 determines whether or not micro inspection is necessary based on the type of defect candidate area detected in step S2, the occurrence frequency in a plurality of similar objects (in the same cassette, in the same lot, etc.), and the like. . In particular, when there is a suspicion that the defect candidate area is a so-called pseudo defect, it is determined that micro inspection is necessary. Further, it is determined that micro inspection is necessary for common defects in the same process, at the same position, and of the same type. Further, it is determined that a micro inspection is necessary for a defect generated at a rotationally symmetric position on the wafer substrate T.

  In step S4, the control unit 35 determines whether or not the micro inspection is set to ON. Then, the control unit 35 proceeds to step S5 when the micro inspection is set to ON, and ends the series of processes when the micro inspection is set to OFF. However, when the micro inspection is set to OFF in step S4, the control unit 35 may notify the operator or the like that the micro inspection is necessary.

  In step S <b> 5, the control unit 35 controls the micro inspection unit 20 and images the wafer substrate T.

  The control unit 35 controls the stage 21, the objective lens unit 23, and the micro imaging unit 24 based on the defect candidate area information recorded in step S2, and views the area corresponding to the defect candidate area in the wafer substrate T. Set to a magnification that can be captured. For example, an enlarged image of an area of φ0.2 mm can be formed on the imaging element by using an objective lens having a field of view φ20 mm and about 100 times as large as the objective lens unit 23. As a result, an area of about φ0.2 to 20 mm can be covered, and defects in the chip size range of the wafer substrate T can be detected. Then, the control unit 35 acquires a micro inspection image of the wafer substrate T generated by the micro imaging unit 24.

  If a plurality of defect candidate areas are detected in step S2, the control unit 35 performs the subsequent processing for each of the plurality of defect candidate areas.

  In step S6, the control unit 35 acquires a micro reference image. In the micro reference image storage unit 34, a non-defective image of the wafer substrate T is stored in advance as a micro reference image. This micro reference image is an image (high resolution image) captured at a higher magnification than the macro reference image described in step S2. The micro reference image is composed of one or a plurality of images according to the size. The control unit 35 reads out the micro reference image from the micro reference image storage unit 34 in accordance with the position and size of the defect candidate area detected in step S2, appropriately combines and enlarges the micro reference image acquired in step S5. A micro reference image corresponding to the inspection image is acquired.

  In step S7, the control unit 35 determines whether the defect candidate area detected in step S2 is a defect area. If the control unit 35 determines that the region is a defective region, the control unit 35 proceeds to step S8. If the control unit 35 determines that the region is not a defective region, the control unit 35 determines that the wafer substrate T is a non-defective product and ends the series of processes.

  The control unit 35 determines whether the defect candidate area is a defect area by comparing the micro reference image acquired in step S7 with the micro inspection image acquired in step S5. The determination is performed by using an overlay method or the like, but the details are the same as those of the publicly known technique, and thus description thereof is omitted. The control unit 35 records the determination result in a memory (not shown).

  For example, consider a case where four wafer substrates T are inspected as samples (S = 1 to 4) as shown in FIG. In the case where a pseudo defect occurs in the region E1 of all the samples, and the original defect occurs only in one sample (S = 2), in the macro inspection described in step S1 and step S2, all the samples Is determined as a defective product. However, in the micro inspection described in steps S5 to S7, only one sample (S = 2) is determined as a defective product.

  As described above, the pseudo defects tend to occur at the same position on the surface of the wafer substrate T. Therefore, it may be determined whether or not the defect candidate area is a defect area in consideration of the occurrence frequency in a plurality of similar test objects (in the same cassette, in the same lot, etc.).

  In step S8, the control unit 35 determines whether or not to perform additional learning. And the control part 35 progresses to step S9, when additional learning is implemented, and complete | finishes a series of processes when not implementing additional learning. However, the control part 35 is good also as a structure which alert | reports to an operator etc. that additional learning is recommended.

  In step S9, the control unit 35 performs additional learning. The control unit 35 newly determines a macro inspection image or micro inspection image determined as a defective product in the macro inspection described in steps S1 and S2 and determined as a non-defective product in the micro inspection described in steps S5 to S7. The reference image is stored in the macro reference image storage unit 33 and the micro reference image storage unit 34. As a result, in the subsequent inspections, in addition to the macro reference image and the micro reference image, comparison with these reference images makes it possible to more accurately select the non-defective product / defective product.

  As described above, according to the first embodiment, based on the reflected light from the test object, the first test object image obtained by collectively capturing the test object is acquired, and the acquired first The test object image is compared with the first reference image stored in advance. Then, based on the comparison result, a defect candidate area in the first object image is detected. Further, the second test object image corresponding to the defect candidate area is acquired, and the area of the acquired second test object image and the second reference image stored in advance is the area corresponding to the defect candidate area. The second reference image is compared. Then, based on the comparison result, it is determined whether or not the defect candidate area is a defect area. Therefore, it is possible to reduce the number of steps for selecting good / defective products and to automate them. In particular, by automatically eliminating pseudo defects and selecting them as non-defective products, it is possible to eliminate unnecessary rework work and realize efficient production. In addition, misjudgment by the operator can be prevented.

  In addition, according to the first embodiment, since the imaging magnification is adjusted according to the size of the defect candidate area, it is possible to improve the comparison accuracy between the defect candidate area and the reference image.

  In the first embodiment, a plurality of wafer substrates T may be inspected as test objects. In this case, each process may be repeated a plurality of times. Further, more detailed determination may be performed by associating the inspection results of a plurality of objects to be examined.

  In the first embodiment, the inspection apparatus 1 including the macro inspection unit 10, the micro inspection unit 20, and the computer 30 has been described as an example. However, it is not always necessary that the casings are connected to each other. Instead, each device may be connected in a software manner by a cable or the like.

  In addition, the configurations of the macro inspection unit 10 and the micro inspection unit 20 are merely examples, and any configuration may be used as long as the macro inspection and the micro inspection can be performed.

Second Embodiment
The second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment, only different parts from the first embodiment will be described. The same configuration as that of the first embodiment will be described using the same reference numerals as those of the first embodiment.

  The inspection apparatus according to the second embodiment has a configuration in which the micro inspection unit 20 is omitted from the inspection apparatus 1 described in the first embodiment. That is, the macro inspection unit 10 and the computer 30 described in FIG. Since the configurations of the macro inspection unit 10 and the computer 30 are the same as those in the first embodiment, description thereof will be omitted.

  FIG. 5 is a flowchart showing the operation of the control unit 35 when performing inspection.

  In step S21 to step S24, the control unit 35 performs the same processing as in step S1 to step S4 of the first embodiment.

  In step S25, the control unit 35 cuts out an area corresponding to the defect candidate area information recorded in step S22 from the macro inspection image acquired in step S21 and appropriately enlarges it. The enlarged size is preferably about the size corresponding to the micro inspection image of the wafer substrate T generated by the micro imaging unit 24 described in step S5 of the first embodiment.

  In step S26, the control unit 35 performs the same process as in step S6 of the first embodiment. However, instead of the micro reference image, an image obtained by cutting out a region corresponding to the defect candidate region information recorded in step S22 from the macro reference image and appropriately enlarging it may be acquired as the micro reference image.

  In step S27, the control unit 35 compares the macro inspection image enlarged in step S25 with the micro reference image acquired in step S26. Details of the comparison are the same as in step S7 of the first embodiment, and a description thereof will be omitted.

  In step S28 to step S29, the control unit 35 performs the same processing as in step S8 to step S9 of the first embodiment.

  As described above, according to the second embodiment, the second test object image is obtained by cutting out and electronically enlarging the area corresponding to the defect candidate area from the first test object image. get. Therefore, the same effect as the first embodiment can be realized with a simple device.

  In the second embodiment, in step S25, an example is shown in which an area corresponding to the defect candidate area information recorded in step S22 is cut out and enlarged as appropriate from the image acquired in step S21. However, when the macro imaging unit 19 has a zoom optical system, an image corresponding to the image of the wafer substrate T generated by the micro imaging unit 24 described in step S5 of the first embodiment is obtained by the zoom optical system. It is good also as a structure which newly images.

  In each of the above embodiments, the wafer substrate T has been described as an example of the test object. However, the present invention can be similarly applied to the inspection of a semiconductor substrate such as a liquid crystal panel or an imaging device.

It is a functional block diagram which shows the structure of the test | inspection apparatus 1 of 1st Embodiment. It is a figure explaining the wafer substrate T which is a test object. It is a flowchart which shows operation | movement of the control part 35 at the time of test | inspection execution in the test | inspection apparatus of 1st Embodiment. It is a figure explaining a test result. It is a flowchart which shows operation | movement of the control part 35 at the time of the test | inspection execution in the test | inspection apparatus of 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inspection apparatus, 10 ... Macro inspection unit, 19 ... Macro imaging part, 20 ... Micro inspection unit, 24 ... Micro imaging part, 30 ... Computer, 33 ... Macro reference image memory | storage part, 34 ... Micro reference image memory | storage part, 35 ... Control unit

Claims (12)

A first acquisition unit that includes a first imaging unit that collectively images the test object based on reflected light from the test object, and that acquires a first test object image by the imaging unit;
A first comparison unit for comparing the first test object image with a first reference image stored in advance;
A detection unit for detecting a defect candidate region in the first test object image based on a comparison result by the first comparison unit;
A second acquisition unit for acquiring a second test object image corresponding to the defect candidate region;
A second comparison unit that compares the second test object image with the second reference image in a region corresponding to the defect candidate region among the second reference images stored in advance;
An inspection apparatus comprising: a determination unit that determines whether or not the defect candidate region is a defect region based on a comparison result by the second comparison unit. The inspection apparatus according to claim 1,
The second acquisition unit includes a second imaging unit that images a region corresponding to the defect candidate region in the test object at a higher resolution than when the first test object image is captured, The inspection apparatus, wherein the second image is acquired by the second imaging unit. The inspection apparatus according to claim 1,
The second acquisition unit acquires the second test object image by cutting out and electronically enlarging an area corresponding to the defect candidate area from the first test object image. Characteristic inspection device. The inspection apparatus according to claim 3, wherein
The second comparison unit sets an image obtained by cutting out and electronically enlarging a region corresponding to the defect candidate region from the first reference image as the second reference image, and the second test object image. And the second reference image. The inspection apparatus according to claim 1,
The said determination part determines whether the said defect candidate area | region is a defect area in consideration of the generation frequency of the said defect candidate area | region regarding the said some to-be-tested object. The inspection apparatus characterized by the above-mentioned. The inspection apparatus according to claim 1,
The inspection apparatus further comprising: an update unit that updates at least one of the first reference image and the second reference image based on a determination result by the determination unit. A first acquisition procedure for acquiring a first test object image obtained by collectively imaging the test object based on reflected light from the test object;
A first comparison procedure for comparing the first test object image with a first reference image stored in advance;
A detection procedure for detecting a defect candidate region in the first test object image based on a comparison result in the first comparison procedure;
A second acquisition procedure for acquiring a second test object image corresponding to the defect candidate region;
A second comparison procedure for comparing the second test object image and the second reference image in a region corresponding to the defect candidate region among the second reference images stored in advance;
An inspection program that realizes, by a computer, a determination procedure for determining whether or not the defect candidate region is a defect region based on a comparison result in the second comparison procedure. The inspection program according to claim 7,
In the second acquisition procedure, the second specimen image obtained by capturing an area corresponding to the defect candidate area in the specimen with a higher resolution than when the first specimen image is captured. The inspection program characterized by acquiring. The inspection program according to claim 7,
In the second acquisition procedure, the second test object image is acquired by cutting out and electronically enlarging an area corresponding to the defect candidate area from the first test object image. Characteristic inspection program. In the inspection program according to claim 9,
In the second comparison procedure, an image obtained by cutting out and electronically enlarging a region corresponding to the defect candidate region from the first reference image is used as the second reference image, and the second test object image And the second reference image. The inspection program according to claim 7,
The determination program determines whether or not the defect candidate area is a defect area in consideration of the occurrence frequency of the defect candidate area for a plurality of the test objects. The inspection program according to claim 7,
An inspection program, further comprising an update procedure for updating at least one of the first reference image and the second reference image based on a determination result obtained by the determination procedure.

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