JP2002074335A - Method and device for pattern inspection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To present only true defects to a user by inspecting the whole surface of the substrate of an object with uniform sensitivity so as to detect the true defects. SOLUTION: A comparing order is scheduled so as to compare the object at least twice without fail within a picture obtained by the same stage scanning in addition to a picture-detecting order. On a stage when the picture of a comparing object is confirmed, the pictures obtained by only the same stage scanning are compared with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing a substrate having a circuit pattern such as a semiconductor device or a liquid crystal, and more particularly to a technique for inspecting a pattern of a substrate being manufactured.

[0002]

2. Description of the Related Art Conventional optical or electron beam pattern inspection apparatuses are disclosed in Japanese Patent Application Laid-Open Nos. 5-258703 and 11-160.
247 etc.

FIG. 1 shows the configuration of Japanese Patent Application Laid-Open No. 5-258703 as an example of an electron beam type pattern inspection apparatus. The electron beam 2 from the electron beam source 1 is deflected in the X direction by the deflector 3 and irradiates the object substrate 5 via the objective lens 4 while simultaneously moving the stage 6 continuously in the Y direction. The secondary electron 7 from the detector 4 is detected by a detector 8, the detection signal is A / D converted by an A / D converter 9, and is converted into a digital image.
Is compared with a digital image of a place where it can be expected to be the same, a place having a difference is detected as a pattern defect candidate 11, and a defect position is determined by a real ghost determination described later.

An example of an optical inspection apparatus is disclosed in
FIG. 2 shows the configuration of 160247. The light from the light source 21 is applied to the target substrate 4 via the objective lens 22, and the reflected light at that time is detected by the image sensor 23. Stage 6
The image is detected as a detected image 24 by repeating the detection while moving at a constant speed, and stored in the memory 25. The detected image 24 is compared with a stored image 27 on the memory 25 which can be expected to have the same pattern. If the pattern is the same, a normal part is detected.
The defect position is determined by a real ghost determination described later.

As an example, the object substrate 4 is a wafer 31
FIG. 3 shows a layout in the case of. Chips 3 which are finally cut off on a wafer 31 to become individual products of the same type
2 are formed. The stage 6 is moved along the scanning line 33 to detect an image of the stripe area 34. Current,
When the detection position A is 35, the image at the detection position B on the memory 25 is extracted as the stored image 27 and compared. Thereby, a comparison is made with a pattern that can be expected to be the same pattern. Here, the memory 25 has a capacity capable of holding an image that can be expected to have the same pattern, and constitutes an actual circuit by being reused in a ring shape.

Next, a method of determining a defect location by real ghost judgment will be described with reference to FIG. Chip A42, Chip B4
3. When the wafers 31 having the chip C44 and the chip B43 having the defect 41 are sequentially inspected, the pattern defect candidate 11
Are detected at two locations, candidate A45 and candidate B46. This is the chip A42 or chip B43, respectively, and the chip
This indicates that either B43 or chip C44 has a defect. Therefore, the candidate A45 once marks the chip A42 or the chip B43, and the candidate B46 once marks the chip B43 or the chip C44. A position where two marks are counted is determined as a true defect 41.

[0007]

A method of scanning the entire surface of the object substrate 4 will be considered. Generally, as shown in FIG. 5, defects are detected by acquiring and comparing images sequentially from the end. In this case, the first chip a51 and the last chip b5
Since No. 2 has not been compared twice, a defect cannot be identified by real ghost determination, and therefore, a dummy chip 53 that can acquire an image but cannot determine a defect is used. In addition, chip c54,
Regarding the chip d55, the chip c54 is in the Y axis + direction,
The tip d55 becomes the folded tip 56 for scanning the stage 6 in the Y-axis direction to acquire an image. For this reason, it is necessary to acquire an image of a chip for which no defect is determined in the dummy chip 53, and the folded chip 56 is liable to cause various errors in the device, and the consideration regarding the defect performance is insufficient.

On the other hand, Japanese Unexamined Patent Application Publication No. 11-160247 takes measures by devising a real ghost judgment. That is,
In the case of the dummy chip 53, if the comparison partner is not defective, 2
A defect is determined even if the count is not performed. Similarly, the folded chips 56 are not compared with each other, and if the comparison partner is not a defect, it can be determined that the chip is defective even if it is not counted twice. This eliminates the need for dummy chips and eliminates the need to compare folded chips. However, the defect is determined only once, and the device is more susceptible to device errors such as noise when compared with the case where the defect is determined both times. Therefore, it cannot be said that the defect performance is sufficiently considered. Was.

[0009]

Means for Solving the Problems First problem solving means
6 is shown in FIG. Although a configuration using an electron beam is shown here, it is essentially the same as the optical type. An electron beam source 1 for generating an electron beam 2, a deflector 3 for deflecting the electron beam,
And an objective lens 4 for converging the electron beam 1 on the target substrate 4, a stage 6 for holding and scanning or positioning the target substrate 5, and detection for detecting secondary electrons 7 and the like from the target substrate 4. An A / D converter 9 for converting a detection signal into a digital image by A / D conversion, a stripe memory 61 for storing a storage image 27 for one stripe, and two stripe memories from the stripe memory 61 The comparison circuit 62 includes a comparison circuit 62 for detecting the pattern defect candidate 11 by comparing images, and a real ghost determination unit 64 for determining the true defect 41 from the pattern defect candidate 11 from the comparison circuit 62.

FIG. 7 shows a second configuration for solving the problem. Although a configuration using an electron beam is shown here, it is essentially the same as the optical type. An electron beam source 1 for generating an electron beam 2, a deflector 3 for deflecting the electron beam, an objective lens 4 for converging the electron beam 1 on an object substrate 4, and an object substrate 5 for holding or scanning or positioning. Stage 6
And a detector 8 for detecting secondary electrons 7 from the target substrate 4, and a digital detection image 24 after A / D conversion of the detection signal.
The pattern defect candidate 11 is compared with the A / D converter 9, the memory 25 storing the detected image 24, and the stored image 26 on the memory 25 which can be expected to have the same pattern as the detected image 24. Comparison circuit 6 for detection
And a defect determining means 72 for determining the true defect 41 from the defect candidate image 71 of the pattern defect candidate 11 from the comparison circuit 62.

FIG. 8 shows a third configuration for solving the problem. Although a configuration using an electron beam is shown here, it is essentially the same as the optical type. An electron beam source 1 for generating an electron beam 2, a deflector 3 for deflecting the electron beam, an objective lens 4 for converging the electron beam 1 on an object substrate 4, and an object substrate 5 for holding or scanning or positioning. Stage 6
And a detector 8 for detecting secondary electrons 7 from the target substrate 4, and a digital detection image 24 after A / D conversion of the detection signal.
The pattern defect candidate 11 is compared with the A / D converter 9, the memory 25 storing the detected image 24, and the stored image 26 on the memory 25 which can be expected to have the same pattern as the detected image 24. Comparison circuit 6 for detection
2, a real ghost determination unit 64 that determines a temporary defect 73 from the pattern defect candidate 11 from the comparison circuit 62, and a defect that determines the true defect 41 from the defect candidate image 71 of the pattern defect candidate 11 from the comparison circuit 62. Judgment means 72
Consisting of

FIG. 9 shows a fourth configuration for solving the problem. Although a configuration using an electron beam is shown here, it is essentially the same as the optical type. An electron beam source 1 for generating an electron beam 2, a deflector 3 for deflecting the electron beam, an objective lens 4 for converging the electron beam 1 on an object substrate 4, and an object substrate 5 for holding or scanning or positioning. Stage 6
And a detector 8 for detecting secondary electrons 7 from the target substrate 4, and a digital detection image 24 after A / D conversion of the detection signal.
A / D converter 9, a memory 25 for storing a detected image 24, a reference image creating circuit 66 for creating a reference image 65 from the memory 25, and a detection that can be expected to have the same pattern as the reference image 65 Image 24 and reference image 65
And a comparison circuit 62 for detecting the true defect candidate 41 by comparing.

The operation of the first configuration for solving the problem will be described. The electron beam 2 from the electron beam source 1 is deflected in the X direction by the deflector 3 and irradiates the object substrate 5 via the objective lens 4 while simultaneously moving the stage 6 continuously in the Y direction. Secondary electrons 7 from 4 are detected by a detector 8, the detection signal is A / D converted by an A / D converter 9, converted into a digital image, and stored in a stripe memory 61. When an image of a pair described later is determined from the stripe memory 61, the image data of the pair is extracted from the stripe memory 61, and is compared with the comparison circuit 62 to extract the pattern defect candidate 11, and the pattern defect candidate 11 is The ghost judging unit 64 judges the true defect 41. FIG.
FIG. 1 shows an example of a detected target chip. The numbers are arranged in the order of detection. The paired images are selected such that the same chip is inspected at least twice. For example, a pair of 1 and 2, 1 and 3, 2 and 3, 3 and 4, 4 and 5, 5 and 6, 6 and 7, 7 and 8, 7 and 9, and 8 and 9 satisfies the condition. . In this inspection method, all the chips for which an image is detected by one stage scan can be compared and inspected twice, and the inspection can be performed with sufficient performance without including the dummy chip 53 and the folded chip 56.

The operation of the second configuration for solving the problem will be described. The electron beam 2 from the electron beam source 1 is deflected in the X direction by the deflector 3 and irradiates the object substrate 5 via the objective lens 4 while simultaneously moving the stage 6 continuously in the Y direction. The secondary electrons 7 from 4 are detected by the detector 8, the detection signal is A / D-converted by the A / D converter 9, and is stored as a digital image detection image 24 in the memory 25. The comparison circuit 62 compares the detected image 24 with the stored image 26 in the memory 25 that can be expected to have the same pattern as the detected image 24 to detect the pattern defect candidate 11. 11 defect candidate images 71
Take out. The defect candidate image 71 is a detected image 24, a stored image 26, and a comparative image 7 that can be expected to have the same pattern as the detected image detected in the memory 25 or later.
3 is assumed. When there is a difference between the detected image 24 and the comparative image 73 by the defect determining means 72, a part of the detected image is regarded as a true defect 41, and the stored image 26 and the comparative image 73 are compared by the defect determining means 72. In some cases, the portion of the stored image is regarded as a true defect 41. In this inspection method, all the defect candidate portions once detected can be compared and inspected twice, and inspection can be performed with sufficient performance.

As a deformation operation of the second configuration, the defect candidate image 71 is a detected image 24 and a stored image 26. The detected image 24 and the stored image 26 are compared to analyze in detail an image of a portion having a difference to determine which is the true defect 41. In this inspection method, a defect candidate portion once detected is analyzed in detail, and inspection can be performed with sufficient performance.

The operation of the third configuration for solving the problem will be described. The electron beam 2 from the electron beam source 1 is deflected in the X direction by the deflector 3 and irradiates the object substrate 5 via the objective lens 4 while simultaneously moving the stage 6 continuously in the Y direction. The secondary electrons 7 from 4 are detected by the detector 8, the detection signal is A / D-converted by the A / D converter 9, and is stored as a digital image detection image 24 in the memory 25. The comparison circuit 62 compares the detected image 24 with the stored image 26 in the memory 25 which can be expected to have the same pattern as the detected image 24 to detect the pattern defect candidate 11. The real ghost determination unit 64 determines the defect candidate 11 and takes out the true defect 41. The places not compared twice are the pattern defect candidates 11 from the comparison circuit 62.
Of the defect candidate 71, and the true defect 41 is determined by the method described in the second configuration. In this inspection method, either the first or second method is applied, and inspection can be performed with sufficient performance.

The operation of the fourth configuration for solving the problem will be described. The electron beam 2 from the electron beam source 1 is deflected in the X direction by the deflector 3 and irradiates the object substrate 5 via the objective lens 4 while simultaneously moving the stage 6 continuously in the Y direction. The secondary electrons 7 from 4 are detected by the detector 8, and the detection signal is A / D converted by the A / D converter 9 to obtain a digital image detection image 24. First, a plurality of images that can be expected to have the same pattern among the detected images 24 are stored in the memory 25 as storage images 26. The stored images 26 on the memory 25 that can be expected to have the same pattern are aligned with each other, and a reference image creation unit 66 creates a reference image 65 that can be regarded as an image of an average normal part. The comparison circuit 62 compares the reference image 65 with the newly detected image 24 to detect the true defect 41. The reference image is, for example, an image of an average normal part which is not affected by variations and defects by a method such as setting an average value excluding a maximum and a minimum for each pixel among a plurality of images after alignment. And In this inspection method, it is possible to inspect with sufficient performance because it can be compared with an image of an average normal part.

[0018]

[Embodiment 1] A first embodiment of the present invention will be described. FIG. 11 shows the configuration of the first embodiment. An electron beam source 1 for generating an electron beam 2, an electron gun 102 and a virtual light source 101 which accelerate and extract an electron beam 2 from the electron beam source 1 by an electrode and form a virtual light source 101 at a certain place by an electrostatic or magnetic field superimposed lens. A condenser lens 103 for converging the electron beam 2 at a certain location and a blanking plate 104 for controlling ON / OFF of the electron beam 2 by being installed near a position converged by the electron gun 102 and the electron beam 2 in the XY directions. An electron optical system 106 comprising a deflector 105 for deflecting and an objective lens 4 for converging the electron beam 2 on the target substrate 4, a sample chamber 107 for holding a wafer 31 as a target substrate in a vacuum, and a wafer 31 are mounted. A stage 6 to which a retarding voltage 108 for enabling image detection at an arbitrary position is applied, and a detector 8 for detecting secondary electrons 7 from the target substrate 5,
And an A / D converter 9 for A / D converting a detection signal detected by the detector 8 to obtain a digital image, and a stripe memory 6 for storing a storage image 27 for one stripe.
1 and a comparison circuit 62 for detecting the pattern defect candidate 11 by comparing the two images from the stripe memory 61, and a defect list 109 is calculated from the pattern defect candidate 11 from the comparison circuit 62, and the overall control unit 110 The real ghost judging unit 64 for judging the true defect 41 from the defect list 109 in the post-processing circuit 111 to be sent to the whole control unit 110, the height of the wafer 31 is measured and the current value of the objective lens 4 is offset 112 And a Z sensor 113 for keeping the focal position of a digital image detected by controlling by adding
Loader 116 (not shown) for taking in and out of sample chamber 107,
And an orientation flat detector 117 (not shown) for positioning the wafer 31 based on the outer shape of the wafer 31, and an optical microscope 11 for observing a pattern on the wafer 31
8, a general control unit 110 for controlling the whole according to an instruction from the user (control lines from the general control unit 110 are omitted in the figure), and a standard sample piece 119 provided on the stage 6.

The operation of the first embodiment will be described. In response to a user's inspection start instruction, the overall control unit 110 performs an inspection by instructing each unit to operate in the following procedure. The loader 116 issues an instruction to the loader 116 (not shown), and the loader 116
The wafer is positioned on the basis of the external shape by the orientation flat detector 117 (not shown), the wafer 31 is mounted on the stage 6, and the inside of the sample chamber 107 is evacuated. At the same time, the conditions of the electron optical system 106 and the retarding voltage 108 are set, the voltage is applied to the blanking plate 104, and the electron beam 2 is turned off.

The stage is moved to the standard specimen 119 and Z
When the sensor 113 is enabled, the focus is maintained at a fixed value of the detection value of the Z sensor 113 + the offset 112, the deflector 105 is raster-scanned, the voltage of the blanking plate 104 is turned off in synchronization with the scan, and the electron beam 2 is required Only the wafer 31 is irradiated, the reflected electrons or secondary electrons generated from the wafer 31 at that time are detected by the detector 8, and the digital image is formed by the A / D converter 9. A plurality of digital images are detected by changing the offset 106, and the entire control unit 11
The optimum offset 120 at which the sum of the differential values of the image in the image is the highest at 0 is set as the current offset value.
After the setting, the Z sensor 113 is invalidated. The stage 6 is moved to a scanning start position of a region to be inspected on the mounted wafer 31.

The offset 112 is set by adding a wafer-specific offset measured in advance to the Z sensor 1.
13, the stage 6 is sequentially scanned in the Y direction, the deflector 105 is scanned in the X direction in synchronization with the stage scanning, the voltage of the blanking plate 104 is turned off during the effective scanning, and the electron beam 2 is irradiated on the wafer 31. Scan. Wafer 31
Reflected electrons or secondary electrons generated by the detector 8 are detected,
The digital image is formed by the A / D converter 9. After the scanning of the stage 6 is completed, the Z sensor 113 is invalidated. The detected digital image has a scanning width of the deflector 3 in the X direction of 100 μm when scanning 1024 pixels with a 0.1 μm pixel size.
In the Y direction, the scanning distance of the stage 6 is 300 mm or less when a wafer having a diameter of 300 mm is inspected.

Based on a preset pattern layout on the wafer 31, a pair of chip coordinates is specified in the stripe memory 61 in a table so that comparison is always performed twice during one scan as illustrated in FIG. When the image is determined and the comparison circuit 62 is not operating, the stripe memory 61 instructs the comparison circuit 62 to operate. In the comparison circuit 62, 2
A place where there is a comparison difference between the images is extracted as a defect candidate 11, and a defect list 10 including a chip number, coordinates within a chip, a projection length, an area, a representative value, etc., compared by the post-processing circuit 111
9 is created, and the location registered in the defect list 109 two or more times by the real ghost determination unit 64 in the overall control unit 110 is determined as a true defect 41.

Next, the capacity of the stripe memory 61 will be examined. In the order of the chips shown in FIG.
Is the same speed as the detection and only one formula is used, the time chart shown in FIG. 12 is obtained. When the chip 1 is detected, it is not stored or compared. When chip 2 is detected, chip 1 is stored, and chip 1 and chip 2 are compared. The same applies hereinafter. The minimum required capacity is 3 of the chip pitch
It is twice. If the comparison method is devised as shown in FIG. 13, it becomes twice the chip pitch. If two sets of comparison circuits 62 are prepared, twice the chip pitch is sufficient even in the order of the chips in FIG. 10 as shown in FIG. If the comparison is made at twice the speed of the detection, twice the chip pitch is sufficient even in the order of the chips in FIG. 10 as shown in FIG.

According to the present embodiment, there is a feature that the entire surface of the wafer is inspected with uniform sensitivity using the SEM image, and only true defects are detected, and these are presented to the user.

That is, according to the present embodiment, it is possible to detect a defect in a chip formed in a peripheral portion of a wafer with the same sensitivity as a chip formed in a central portion of the wafer.

[Embodiment 2] A second embodiment of the present invention will be described. FIG. 16 shows the configuration of the second embodiment. An electron beam source 1 for generating an electron beam 2 and an electron gun 102 and a virtual light source 10 in which an electron beam 2 from the electron beam source 1 is accelerated by an electrode and taken out, and a virtual light source 101 is formed at a certain place by an electrostatic or magnetic field superimposed lens.
A condenser lens 103 for converging the electron beam 2 from a certain position to a certain place, and a blanking plate 104 for controlling ON / OFF of the electron beam 2 which is installed near a position converged by the electron gun 102, and the electron beam 2 in the XY directions. Optical system 106 comprising a deflector 105 for deflecting the electron beam 2 and the objective lens 4 for converging the electron beam 2 on the target substrate 4, a sample chamber 107 for holding the wafer 31 as the target substrate in a vacuum, and the wafer 3
The stage 6 on which the retarder voltage 108 is applied to enable the image detection at an arbitrary position to be mounted on the stage 1, the detector 8 for detecting secondary electrons 7 from the target substrate 5, and the detector 8. A / D converter 9 for A / D converting the detection signal to obtain detection image 24 as a digital image, and memory 25 for storing storage image 26 for one chip, and detection image 24 and memory 25 The comparison circuit 62 for detecting the pattern defect candidate 11 by comparing the two images of the stored image 26 with each other, and the defect list 109 is calculated from the pattern defect candidate 11 from the comparison circuit 62 and sent to the overall control unit 110. A post-processing circuit 111 for sending, a defect determining unit 73 for taking out the detected image 24 and the stored image 26 of the part of the pattern defect candidate 11 as a defect candidate image 71 and determining a defect;
And a real ghost determination unit 64 that determines the true defect 41 from the defect list 109 within the overall control unit 110, and measures the height of the wafer 31 and controls the current value of the objective lens 4 by adding an offset 112 thereto. Z sensor 113 that keeps the focal position of the digital image detected at
And a loader 116 (not shown) for taking the wafer 31 in the cassette 114 into and out of the sample chamber 107;
An orientation flat detector 117 (not shown) for positioning the wafer 31 based on the external shape of the optical system, an optical microscope 118 for observing a pattern on the wafer 31, and an overall control unit 110 for controlling the whole according to instructions from a user (The control line from the overall control unit 110 is omitted in the figure), and the stage 6
It consists of the standard sample piece 119 provided above.

The operation of the second embodiment will be described. In response to a user's inspection start instruction, the overall control unit 110 performs an inspection by instructing each unit to operate in the following procedure. The loader 116 issues an instruction to the loader 116 (not shown), and the loader 116
The wafer is positioned on the basis of the external shape by the orientation flat detector 117 (not shown), the wafer 31 is mounted on the stage 6, and the inside of the sample chamber 107 is evacuated.

At the same time as mounting, conditions of the electron optical system 106 and the retarding voltage 108 are set, and a voltage is applied to the blanking plate 104 to turn off the electron beam 2. The stage is moved to the standard sample piece 119, and the Z sensor 113 is enabled, and the focus is set to the detection value of the Z sensor 113 + the offset 11
2, the deflector 105 is raster-scanned, the voltage of the blanking plate 104 is turned off in synchronization with the scan, and the electron beam 2 is irradiated onto the wafer 31 only when necessary, and the reflected electrons generated from the wafer 31 at that time. Alternatively, the secondary electrons are detected by the detector 8 and converted into a digital image by the A / D converter 9.

A plurality of digital images are detected by changing the offset 106, and the overall control unit 110 sets the optimum offset 12 at which the sum of the differential values of the image in the image becomes the highest for each detection.
Set 0 as the current offset value. After the setting, the Z sensor 113 is invalidated.

The stage 6 is moved and the mounted wafer 3
It moves to the scanning start position of one area to be inspected. The offset 112 is set by adding a previously measured wafer-specific offset, the Z sensor 113 is enabled, the stage 6 is sequentially scanned in the Y direction, and the deflector 105 is scanned in the X direction in synchronization with the stage scanning. At the time of effective scanning, the voltage of the blanking plate 104 is turned off and the electron beam 2 is applied to the wafer 3
Irradiate and scan 1 Reflected electrons or secondary electrons generated from the wafer 31 are detected by the detector 8 and converted into a digital image by the A / D converter 9. After completion of scanning of stage 6, Z sensor 1
13 is invalidated.

Inspection is sequentially performed based on a preset pattern layout on the wafer 31 as illustrated in FIG.
The memory 25 always stores the image of the chip immediately before the chip under inspection. A comparison circuit 62 compares the detected image 24 and the stored image 26 and extracts a location having a difference as a defect candidate 11 and includes a chip number, a coordinate in a chip, a projection length, an area, a representative value, and the like compared by the post-processing circuit 111. The defect list 109 is created, and a place registered in the defect list 109 two or more times by the real ghost determination unit 64 in the overall control unit 110 is determined as a true defect 41. The comparison between the detected image 24 and the stored image 26 is performed by closing the image obtained by the stage scan, and the comparison between the images detected by the different stage scans is not performed.

Since the first and last chips of the stage scan are detected only once, they are not determined as true defects. Therefore, the detected image 2 of the part of the pattern defect candidate 11
4 and the stored image 26 are taken out as defect candidate images 71 and sent to the defect determining means 73. The images are analyzed in detail by a plurality of CPUs capable of processing in parallel. The real ghost determination unit 64 instructs the real ghost 41 to be determined as a true defect 41 even if it is registered only once in the defect list 109.

As a first modification of the present embodiment, the defect judgment means 73 judges all the pattern defect candidates 11. Thereby, the defect can be determined with higher reliability.

As a second modification of this embodiment, Japanese Patent Application Laid-Open
A temporary defect is taken out by the method described in No. 160247,
The temporary defect is determined by the defect determining means 73. As a result, the same performance can be achieved by making a determination on a smaller number of images by the defect determination unit 73.

According to the present embodiment, it is possible to detect only true defects by inspecting the entire surface of the wafer with uniform sensitivity using the SEM image and present them to the user.

[Embodiment 3] A third embodiment of the present invention will be described. FIG. 18 shows the configuration of the third embodiment. An electron beam source 1 for generating an electron beam 2 and an electron beam 2 from the electron beam source 1
An electron gun 102 and a virtual light source 1 for accelerating the light with electrodes and taking out a virtual light source 101 at a certain place with an electrostatic or magnetic field superimposed lens
A condenser lens 103 that converges the electron beam 2 from a predetermined position to a certain location and a blanking plate 104 that is installed near the position converged by the electron gun 102 and controls ON / OFF of the electron beam 2 and the electron beam 2 in the XY directions Deflector 105 that deflects light to
And an objective lens 4 for converging the electron beam 2 on an object substrate 4
A sample chamber 107 for holding the wafer 31 as an object substrate in a vacuum, and a stage 6 on which the wafer 31 is mounted and a retarding voltage 108 for applying an image detection at an arbitrary position is applied. And a detector 8 for detecting secondary electrons 7 from the target substrate 5 and an A / D converter 9 for A / D converting the detection signal detected by the detector 8 to obtain a detection image 24 which is a digital image. And a memory 2 for storing storage images 26 for a plurality of chips.
5, a reference image creating unit 66 that aligns the stored images 26 on the memory 25 to create a reference image 65 that can be regarded as an image of an average normal part, and two of the reference image 65 and the newly detected detection image 24. A comparison circuit 62 for detecting the pattern defect candidate 11 by comparing the images, and a post-processing circuit 111 for calculating a defect list 109 of the true defect 11 from the comparison circuit 62 and sending it to the overall control unit 110; By measuring the height of the wafer 31 and controlling the current value of the objective lens 4 by adding an offset 112, the Z sensor 113 for keeping the focal position of the digital image detected constant, and the wafer 31 in the cassette 114 as a sample A loader 116 (not shown) for taking in and out of the chamber 107 and an orientation flat detector 117 (not shown) for positioning the wafer 31 based on the outer shape of the wafer 31. , And an optical microscope 118 for observing a pattern on the wafer 31, and a general control unit 110 (general control unit 11) for controlling the whole by an instruction from a user.
The control line from 0 is omitted in the drawing), and a standard sample piece 119 provided on the stage 6.

The operation of the third embodiment will be described. In response to a user's inspection start instruction, the overall control unit 110 performs an inspection by instructing each unit to operate in the following procedure. The loader 116 issues an instruction to the loader 116 (not shown), and the loader 116
The wafer is positioned on the basis of the external shape by the orientation flat detector 117 (not shown), the wafer 31 is mounted on the stage 6, and the inside of the sample chamber 107 is evacuated. At the same time, the conditions of the electron optical system 106 and the retarding voltage 108 are set, the voltage is applied to the blanking plate 104, and the electron beam 2 is turned off.

The stage is moved to the standard specimen 119, and Z
When the sensor 113 is enabled, the focus is maintained at a fixed value of the detection value of the Z sensor 113 + the offset 112, the deflector 105 is raster-scanned, the voltage of the blanking plate 104 is turned off in synchronization with the scan, and the electron beam 2 is required. Only the wafer 31 is irradiated, the reflected electrons or secondary electrons generated from the wafer 31 at that time are detected by the detector 8, and the digital image is formed by the A / D converter 9. A plurality of digital images are detected by changing the offset 106, and the entire control unit 11
The optimum offset 120 at which the sum of the differential values of the image in the image is the highest at 0 is set as the current offset value.
After the setting, the Z sensor 113 is invalidated.

The stage 6 is moved and the mounted wafer 3
It moves to the scanning start position of one area to be inspected. The offset 112 is set by adding a previously measured wafer-specific offset, the Z sensor 113 is enabled, the stage 6 is sequentially scanned in the Y direction, and the deflector 105 is scanned in the X direction in synchronization with the stage scanning. At the time of effective scanning, the voltage of the blanking plate 104 is turned off and the electron beam 2 is applied to the wafer 3
Irradiate and scan 1 Reflected electrons or secondary electrons generated from the wafer 31 are detected by the detector 8 and converted into a digital image by the A / D converter 9. After completion of scanning of stage 6, Z sensor 1
13 is invalidated.

Images are sequentially acquired based on the chips on the wafer 31 set in advance. The reference image creation unit 66 aligns the stored images 26 to create a reference image 65 that can be regarded as an image of an average normal part. The comparison circuit 62 compares the two types of images, the stored image 26 and the newly detected image 24, with the reference image 65, and extracts a location having a difference as a true defect 41. A defect list 109 including coordinates, a projection length, an area, a representative value, and the like is created and sent to the overall control unit 110. A reference image is created with the first N chips and inspects N + the remaining chips.

Here, the images of the second and subsequent chips are aligned with reference to the image of the first chip of the stored image 26.
The maximum and minimum values are excluded for each pixel of the aligned image, and the average of the remaining values is used as the reference image.

According to the present embodiment, since the reference image is created based on the image data of the N chips, even a defect of a type that gradually changes in the wafer can be determined as a defect.

[0043]

According to the present invention, there is a feature that the entire surface of the object substrate can be inspected with uniform sensitivity to detect only true defects and present them to the user.

[Brief description of the drawings]

FIG. 1 is a front view showing a schematic configuration of a conventional electron beam pattern inspection apparatus.

FIG. 2 is a front view showing a schematic configuration of a conventional optical pattern inspection apparatus.

FIG. 3 is a plan view showing a layout of a semiconductor wafer.

FIG. 4 is a plan view of a chip for explaining real ghost determination.

FIG. 5 is a plan view showing an inspection order of a semiconductor wafer.

FIG. 6 is a front view of an electron beam pattern inspection apparatus showing a schematic configuration of a first solution of the present invention.

FIG. 7 is a front view of an electron beam pattern inspection apparatus showing a schematic configuration of a second solving means of the present invention.

FIG. 8 is a front view of an electron beam pattern inspection apparatus showing a schematic configuration of a third solution of the present invention.

FIG. 9 is a front view of an electron beam pattern inspection apparatus showing a schematic configuration of a fourth solution means of the present invention.

FIG. 10 is a plan view of a semiconductor wafer showing chips to be compared.

FIG. 11 is a front view showing a schematic configuration of an electron beam pattern inspection apparatus according to a first embodiment of the present invention.

FIG. 12 is a diagram showing a time chart of a first study of the first embodiment of the present invention.

FIG. 13 is a diagram showing a time chart of a second study of the first embodiment of the present invention.

FIG. 14 is a diagram showing a time chart of a third study of the first example of the present invention.

FIG. 15 is a diagram showing a time chart of a fourth study of the first embodiment of the present invention.

FIG. 16 is a front view showing a schematic configuration of an electron beam pattern inspection apparatus according to a second embodiment of the present invention.

FIG. 17 is a plan view showing a scanning order on a semiconductor wafer according to a second embodiment of the present invention.

FIG. 18 is a front view showing a schematic configuration of an electron beam pattern inspection apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron beam source 2 ... Electron beam 3 ... Deflector 4 ... Objective lens 5 ... Target substrate
6 ... Stage 8 ... Detector 9 ... A /
D converter 10 image processing circuit 11 pattern defect candidate 21 light source 22 objective lens 23 image sensor 24 detected image
25: memory 27: stored image 31:
Wafer 32: Chip 33: Scanning line
34 ... stripe region 41 ... true defect 6
1: stripe memory 62: comparison circuit
64 Real ghost determination unit 71 Defect candidate image 72 Defect determination means 73 Temporary defect 101 Virtual light source 102 Electron gun 103 Condenser lens 104・ Blanking plate 105 ・ ・ ・ Deflector 106
... Electronic optical system 109 ... Defect list 11
0: Overall control unit 111: Post-processing circuit 1
13 ··· Z sensor 118 ··· Optical microscope

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G01R 31/02 G01R 31/02 2H088 31/302 G02F 1/13 101 4M106 G02F 1/13 101 H01L 21/66 J 5B057 H01L 21/66 G01R 31/28 L (72) Inventor Masahiro Watanabe 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Hitachi, Ltd. Production Technology Research Institute (72) Inventor Chie Shishido 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Address: Hitachi, Ltd., Production Technology Laboratory (72) Inventor Maki Maki Tanaka 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Hitachi, Ltd. Production Technology Laboratory (72) Inventor: Asahiro Kuni Totsuka-ku, Yokohama, Kanagawa 292 Yoshida-cho F-term in Hitachi, Ltd. Production Research Laboratory 2G001 AA03 BA07 BA11 BA14 CA03 FA01 FA06 GA06 HA01 HA07 HA13 HA20 JA02 JA03 JA11 JA14 JA16 KA03 LA11 MA05 PA01 2G011 AA01 AD02 AE01 2G014 AA02 AA03 AB59 AC11 2G032 AE08 AF08 2G051 AA51 AA73 AB02 BA00 CA03 CA04 DA07 EA08 EA12 EA14 EB01 EB02 2H088 FA13 MA20 4M106 AA01 BA02 BA04 CA39 DB05 DB21 DB30 DJ11 DJ18 DJ21 5B057 BA01 CA02 CA03 DC03 DC03 DB03

Claims (26)

[Claims] An object substrate is irradiated with light or charged particles, and while scanning a stage, any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons is detected and A / D converted. Thus, the digital image is detected and stored, and after two predetermined images that can be expected to be identical so that one location is determined twice or more are determined, the two images are compared to determine a defect candidate. A pattern inspection method, comprising: determining a true defect if the same location is a defect candidate at least twice. 2. A target substrate is irradiated with light or charged particles, and while scanning the stage, any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons is detected and A / D converted. In this way, the digital image is detected and stored, and the defect candidate is extracted by comparing the image at least twice per location of the stored image,
A pattern inspection method comprising: determining a true defect when the same location becomes a defect candidate two or more times. 3. An object substrate is irradiated with light or charged particles, and while scanning the stage, any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons is detected and A / D converted. The digital image is detected and stored by the
A pattern inspection method characterized in that after two images that can be expected to be the same among images acquired only by scanning the stage in the direction are determined, the two images are compared to determine a defect. 4. The pattern inspection method according to claim 3, wherein the image obtained by the stage scanning in only one direction is an image obtained by one stage scanning. 5. The pattern inspection method according to claim 1, wherein the stored image has a capacity at least twice as large as a pitch at which the same pattern that is repeatedly present can be expected. 6. The pattern inspection method according to claim 1, wherein the stored image has a capacity larger than an image obtained by one-stage scanning. 7. A target substrate is irradiated with light or charged particles, and while scanning the stage, any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons is detected and A / D converted. The digital image is detected and stored in this way, and after two images that can be expected to be the same as determined in advance are determined, the two images are compared to take out a defect candidate, and the image of the defect candidate portion is stored, or A pattern inspection method characterized in that a true defect is determined by comparing two images that can be expected to be the same and that are detected in advance. 8. An object substrate is irradiated with light or charged particles, and while scanning the stage, any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons is detected and A / D converted. Thus, the digital image is detected and stored, and after two predetermined images that can be expected to be the same are determined, the two images are compared to take out a defect candidate, and the defect candidate portion is compared again. In this case, the image is determined to be a true defect when both are determined to be defect candidates twice, and when the determination is made only once, the image of the defect candidate portion is stored or is a predetermined identical value detected from this. A pattern inspection method characterized in that a true defect is determined by comparing two images that can be expected. 9. An object substrate is irradiated with light or charged particles, and while scanning the stage, any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons is detected and A / D converted. The digital image is detected and stored, and after two images that can be expected to be the same as determined in advance are determined, the two images are compared to take out a defect candidate, and the image of the defect candidate portion is further detailed. A pattern inspection method characterized in that a true defect is determined by analysis. 10. An object substrate is irradiated with light or charged particles,
A digital image is detected and stored by detecting any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and performing A / D conversion. Are determined, two images are compared, the two images are compared, and a defect candidate is extracted.
In the case where the comparison is made twice, it is determined that the defect is a true defect when both are determined to be defect candidates, and in the case that the determination is made only once, the image of the defect candidate portion is analyzed in more detail to determine the true defect. A pattern inspection method characterized by determining. 11. An object substrate is irradiated with light or charged particles,
A digital image is detected and stored by detecting any of generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and performing A / D conversion. Are determined, two images are compared, the two images are compared, and a defect candidate is extracted.
In the case where the comparison is made twice, it is determined that the defect is a true defect when both are determined to be defect candidates, and in the case that the determination is made only once, the image of the defect candidate portion is analyzed in more detail to determine the true defect. A pattern inspection method characterized by determining. 12. An object substrate is irradiated with light or charged particles,
While scanning the stage, any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons are detected and A / D converted to detect and store a digital image, and the same image in the stored image A reference image alone or a reference image and an error image are created from one or more images that can be expected to be an image, and an image at a place where the same image as the reference image can be expected is sequentially detected and compared with the reference image. And determining a defect based on a predetermined reference or a reference based on an error image. 13. An object substrate is irradiated with light or charged particles.
While scanning the stage, any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons are detected and A / D converted to detect and store a digital image, and the same image in the stored image A reference image alone or a reference image and an error image are created from one or more images that can be expected to be the same as the reference image, and are compared with a stored image in a place expected to be the same image as the reference image and sequentially detected images. And determining a defect based on a predetermined reference or a reference based on an error image. 14. An object substrate is irradiated with light or charged particles,
While scanning the stage, any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons are detected, and the digital image is detected by A / D conversion. A storage unit for storing a digital image, and 1
After two images that can be expected to be the same and are determined in advance so that the location is determined twice or more are determined, a comparison unit that compares the two images from the storage unit and extracts a defect candidate. A pattern inspection apparatus comprising: a real ghost determination unit that determines a true defect when a defect candidate has been detected more than once. 15. An object substrate is irradiated with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing the image, a comparison unit for comparing the image twice or more for each location of the stored image to extract a defect candidate, and determining that the same location is a true defect when the same location becomes a defect candidate twice or more A pattern inspection apparatus comprising a real ghost determination unit. 16. An object substrate is irradiated with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. After a storage unit for storing images and two images that can be expected to be the same among images obtained by only stage scanning in one direction in the stored images are determined,
A pattern inspection apparatus comprising: a comparison unit that determines a defect by comparing two images. 17. The pattern inspection apparatus according to claim 16, wherein the image obtained by the stage scanning in only one direction is an image obtained by one stage scanning. 18. The pattern inspection apparatus according to claim 14, wherein the stored image has a capacity at least twice as large as a pitch at which the same pattern that is repeatedly present can be expected. 19. The image storage device according to claim 14, wherein said stored image has a capacity equal to or larger than an image obtained by one-stage scanning.
17. The pattern inspection apparatus according to any one of claims 16 to 16. 20. Irradiating the object substrate with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing images, a comparison unit for extracting defect candidates by comparing the two images after a predetermined two images that can be expected to be identical, and storing an image of a defect candidate portion; Alternatively, the pattern inspection apparatus includes a defect determination unit that determines a true defect by comparing the two images that can be expected to be identical to each other and that is detected in advance. 21. Irradiating the object substrate with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing the images, a comparison unit for extracting the defect candidates by comparing the two images after the predetermined two images that can be expected to be the same, and another comparison of the defect candidate units In this case, a real ghost determination unit that determines a true defect when both are determined as defect candidates, and stores an image of a defect candidate portion when determination is made only once, A pattern inspection apparatus comprising: a defect determination unit that determines a true defect by comparing two determined images that can be expected to be the same. 22. Irradiating the object substrate with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing the images, a comparison unit for extracting the defect candidates by comparing the two images after the predetermined two images which can be expected to be the same, and an image of the defect candidate portion are further detailed. A pattern inspection apparatus, comprising: a defect determination unit that determines a true defect by performing analysis. 23. An object substrate is irradiated with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing the images, a comparison unit for extracting the defect candidates by comparing the two images after the predetermined two images that can be expected to be the same, and another comparison of the defect candidate units In this case, the real ghost determination unit determines that the defect is a true defect when both are determined to be defect candidates, and analyzes the image of the defect candidate part in more detail when the determination is performed only once. A pattern inspection apparatus comprising a defect determination unit for determining a defect of the pattern. 24. An object substrate is irradiated with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing the images, a comparison unit for extracting the defect candidates by comparing the two images after the predetermined two images that can be expected to be the same, and another comparison of the defect candidate units In this case, the real ghost determination unit determines that the defect is a true defect when both are determined to be defect candidates, and analyzes the image of the defect candidate part in more detail when the determination is performed only once. A pattern inspection apparatus comprising a defect analysis unit for determining a defect as a defect. 25. An object substrate is irradiated with light or charged particles,
While scanning the stage, any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons are detected, and the digital image is detected by A / D conversion. A storage unit for storing a digital image, and a reference image creation unit for creating only a reference image or a reference image and an error image from one or more images that can be expected to be the same image in the storage image; A pattern inspection device comprising: a comparison unit that sequentially detects images at places where the same image can be expected, compares the images with a reference image, and determines a defect based on a fixed reference or a reference according to an error image. apparatus. 26. Irradiating the object substrate with light or charged particles,
A detector that detects any of the generated light, secondary electrons, reflected electrons, transmitted electrons, and absorbed electrons while scanning the stage, and detects the digital image by A / D conversion. A storage unit for storing an image, and a reference image creation unit for creating a reference image only or a reference image and an error image from one or more images that can be expected to be the same image in the storage image, and the same as the reference image A pattern inspection apparatus, comprising: a storage image at a place where it can be expected to be an image, and a comparison unit for comparing a sequentially detected image with a predetermined reference or a reference according to an error image to determine a defect. .