JP2000146857A - Pattern defect inspection method, and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce detection sensitivity for a defect having a low degree of influence as a defect to conduct inspection. SOLUTION: When an inspected pattern data provided by image-picking up a photomask 1 is compared with a design pattern data to inspect a defect on the photomask 1, the fact that a positional data for indicating a defect inspection executing position is in any area out of the plural areas set within an inspection area for executing the defect inspection is determined by a determination switching circuit provided inside a data comparing circuit 30 to select detection sensitivity in response to the determined area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention compares, for example, inspection data obtained by imaging a pattern formed on a photomask or the like with design pattern data developed from CAD data drawn on the photomask. And a device for inspecting a pattern defect for inspecting a defect on a photomask.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram of such a pattern defect inspection apparatus.

An XY table 3 is provided as an image input device 2 for picking up a pattern on a photomask 1.
The photomask 1 is placed on the Y table 3. Above the XY table 3, an exposure light source 4 is arranged, and the exposure light emitted from the light source 4 is transmitted to an illumination optical system 5.
To illuminate the photomask 1.

A sensor 7 is arranged below the XY table 3 via an image forming optical system 6, and the light transmitted through the photomask 1 is imaged on the surface of the sensor 7. This sensor 7
Captures an image of the incident photomask 1 and outputs an image signal thereof. This image signal is sent to the sensor circuit 8
And output as inspection pattern data.

On the other hand, the host CPU 10 serves as an image processing system.
A disk 11 storing CAD data of a semiconductor chip manufactured by the photomask 1 is connected to the host CPU 10. Also, the host CPU 10
Includes a design data generation circuit 12 and a data comparison circuit 13
Is connected. The design data generation circuit 12
Generates design pattern data from the CAD data stored in the disk 11 and sends the data to the data comparison circuit 13. The data comparison circuit 13 transmits the design pattern data from the design data generation circuit 12 to the image data. The defect is output by comparing with the inspection pattern data from the input device 2.

With such a configuration, when the exposure light is emitted from the light source 4, the exposure light is illuminated on the photomask 1 by the illumination optical system 5. The light transmitted through the photomask 1 forms an image on the surface of the sensor 7, and the sensor 7 captures an image of the incident photomask 1 and outputs an image signal thereof. The image signal is digitized by the sensor circuit 8 and output as inspection pattern data.

On the other hand, the design data generation circuit 12 generates design pattern data from CAD data stored on the disk 11 and sends the data to the data comparison circuit 13. The data comparison circuit 13 compares the input design pattern data with the inspection pattern data from the image input device 2 and outputs a defect.

The data comparison circuit 13 will be described in detail. As shown in FIG. 7, a differential comparison circuit 14 and a level comparison circuit 15 are provided. Among them, the differential comparison circuit 14
Inputs the design pattern data to the edge direction detection circuit 16, detects the edge direction of the pattern in the design pattern data by the edge direction detection circuit 16, and sends the edge direction to the peripheral pixel edge direction differentiation circuit 17 and the selector 18. I do.

This peripheral pixel edge direction differentiating circuit 17
The design pattern data is differentiated in the same direction as the edge direction detected by the edge direction detection circuit 16, and each differential value of pixels surrounding the differentiated pixel is obtained. These differential values are sent to the subtraction circuit 20 after the maximum value of the absolute value is detected by the maximum value detection circuit 19.

At the same time, the differentiating circuit 21 inputs the inspection pattern data, and applies XY to the inspection pattern data.
The differential processing is performed in the direction and each direction of ± 45 degrees, and the differential value of the absolute value is sent to the selector 18. This selector 18
Selects a differential value differentiated in the same direction as the edge direction detected by the edge direction detecting circuit 16 from among the differential values sent from the differentiating circuit 21 and sends it to the subtraction circuit 20.

The subtraction circuit 20 subtracts the differential value detected by the maximum value detection circuit 19 from the differential value selected by the selector 18 and sends the result to the determination circuit 22.

In the determination circuit 22, since the defect determination threshold value for differential comparison is set by the host CPU 10,
A defect is detected by making a determination on the differential value from the subtraction circuit 20 using a defect determination threshold for differential comparison. The detected defective portion is output as defect data through the OR gate 23.

On the other hand, the level comparison circuit 15 receives the inspection pattern data and the design pattern data, obtains a value obtained by subtracting the design pattern data from the inspection pattern data, that is, obtains a level difference between these data and sends it to the determination circuit 24.

In the determination circuit 24, since a level comparison defect determination threshold value is set by the host CPU 10, the determination is made using the level comparison defect determination threshold value for the level difference from the level comparison circuit 1. To detect a defective portion. The detected defective portion is output as defect data through the OR gate 23. FIG. 8 shows an example of the pattern of the central portion and the peripheral portion in the inspection area E of the photomask 1 and each defect G.

[0015]

The pattern of a semiconductor chip on a wafer may be formed by combining a plurality of layers by repeatedly exposing the pattern on the photomask 1 and repeating the etching process. is there. In the photomask 1 used for manufacturing such a semiconductor chip, if there is a defect G thereon, the defect G is transferred to a wafer, which causes a problem.

However, even if there is a defect G on the photomask 1 and the size of the defect G is the same, the layer where the defect G exists and the other layers among the plurality of patterns forming the photomask 1 Depending on the positional relationship with the pattern
There is a difference in the degree of influence of the defect G on the semiconductor chip.

However, despite the background of such defect inspection, the above-described apparatus inspects the entire inspection area E of one photomask 1 with the same defect detection sensitivity, and has no influence as a defect. The defect G or even the defect G having little influence as a defect is detected as a defect, and the manufacturing yield of the photomask 1 is reduced.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pattern defect inspection method and a pattern defect inspection method capable of performing defect inspection by lowering the detection sensitivity of a defect having a small influence as a defect.

[0019]

According to the present invention, a pattern for inspecting a defect on an inspection object by comparing inspection data obtained by imaging the inspection object with a preset reference pattern. The defect inspection method is a pattern defect inspection method in which a detection sensitivity is varied for each of a plurality of regions set in an inspection area where a defect inspection is performed to inspect a defect.

According to the second aspect of the present invention, there is provided a pattern defect inspection apparatus for inspecting a defect on an inspection object by comparing inspection data obtained by imaging the inspection object with a preset reference pattern. It is determined which of the plurality of regions set in the inspection area where the defect inspection is to be performed for the position data indicating the inspection position, and the detection sensitivity is selected according to the determined region. Judgment switching means,
This is a pattern defect inspection device provided with.

According to the third aspect of the present invention, the image input means for capturing an image of the object to be inspected to obtain the pattern data to be inspected, the reference pattern storing means for storing the reference patterns forming a plurality of layers, and the image input means. A determination is made as to which of the plurality of areas set in the inspection area the position data indicating the defect inspection position in the inspection area of the acquired pattern data to be inspected corresponds to. The determination switching means for selecting the detection sensitivity, and the pattern data to be inspected obtained by the image input means are compared with the respective reference patterns for each layer stored in the reference pattern storage means, respectively, and are selected by the determination switching means. And a data comparing unit for inspecting a defect on the inspection object using the detection sensitivity.

According to a fourth aspect of the present invention, in the pattern defect inspection apparatus according to the second or third aspect, the determination switching means includes a position data indicating a position at which the defect inspection is performed and a plurality of areas set in the inspection area. And a plurality of inspection area determination circuits for each area to determine whether the position where the defect inspection is being performed is within the area, and the inspection area determination circuit A selector for selecting a defect determination threshold value according to the region.

According to a fifth aspect of the present invention, in the pattern defect inspection apparatus according to the second or third aspect, the pattern data to be inspected acquired by the image input means extends over at least two areas set in the inspection area. In this case, the determination switching means has a function of selecting at least two detection sensitivities corresponding to at least two regions over which the pattern data to be inspected straddles.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The same parts as those in FIG. 6 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a block diagram of a pattern defect inspection apparatus applied to photomask inspection.

The data comparing circuit 30 compares the design pattern data with the inspection pattern data and outputs a defect. As described above, the differential comparing circuit 14, the level comparing circuit 1
5, each of the determination circuits 22 and 24 and the OR gate 23. Among them, the differential comparison circuit 14 includes an edge direction detection circuit 16, an edge direction peripheral pixel edge direction differentiation circuit 17, a selector 18, a maximum value detection circuit 19, a subtraction circuit 20, and a differentiation circuit 21 as described above. .

The data comparison circuit 30 includes a judgment switching circuit 31 as shown in FIG. 2, which is used to store position data indicating the position where the defect inspection is being performed, for example, as shown in FIG. Of the plurality of areas (for example, areas A, B, and C) set in the inspection area E where the inspection is performed, the area A, B, or C is determined. Depending on the detection sensitivity, for example, the detection sensitivity of the area A is 0.2 μm and the detection sensitivity of the area B is 0.25 μm.
m, and a function of selecting any one of the detection sensitivity of the area C of 0.5 μm.

More specifically, the judgment switching circuit 31 includes a defect judgment threshold value register 32 for differential comparison and a defect judgment threshold value register 33 for level comparison. A plurality of thresholds used for the determination, that is, a plurality of differential comparison defect determination thresholds are set in the differential comparison defect determination threshold register 32, and a plurality of level comparison defect registers are stored in the level comparison defect determination threshold register 33. A defect determination threshold value is set.

The defect detection sensitivity setting coordinate register 34
Indicates that the plurality of differential comparison defect determination thresholds and level comparison defect determination thresholds set in the differential comparison defect determination threshold register 32 and the level comparison defect determination threshold register 33 are valid. 3, for example, in the case of area A as shown in FIG.
The coordinate data of the area A in which the differential comparison defect determination threshold or the level comparison defect determination threshold used for 2 μm is set.

The defect judgment threshold value switching control circuit 35
The coordinate data set in the defect detection sensitivity setting coordinate register 34 is compared with the position data under inspection sent from the host CPU 10, and the position data under inspection is compared with any one of the areas A, B, and C shown in FIG. If the area is within one of the areas, the selector 3 issues a command to select the defect determination threshold for differential comparison or the defect determination threshold for level comparison corresponding to the area.
6 is provided.

More specifically, the defect determination threshold value switching control circuit 35 includes an inspection area A determination circuit 37 as shown in FIG.
Inspection area B determination circuit 38 and inspection area C determination circuit 3
The position data (XY coordinates) under inspection from the host CPU 10 are input, and the coordinate data (XY) for each of the areas A, B, and C set in the defect detection sensitivity setting coordinate register 34 are provided. Coordinates) have been entered.

Each of the judgment circuits 37 to 39 for these inspection areas
Compares the position data during the defect inspection with the coordinate data indicating each of the areas A, B, and C set in the inspection area E, and determines the position at which the defect inspection is being performed on each of the areas A, B, It has a function of determining whether or not it is within C.

Each of the determination circuits 37 to 39 for these inspection areas
Have the same configuration. When the determination circuit 37 is described as an example, the X coordinate comparison circuit 40 and the Y coordinate comparison circuit 4
1 and an AND gate 42. The X coordinate comparison circuit 40 calculates the position data (X coordinate) and the X
It has a function of comparing with the coordinate data and transmitting a signal of the X coordinate area A to the AND gate 42 if the position data is within the X coordinate data of the area A. Further, the Y coordinate comparison circuit 41 compares the position data (Y coordinate) with the Y coordinate data of the area A, and if the position data is within the Y coordinate data of the area A, outputs the signal of the Y coordinate area A to the AND gate 42 Has the function of sending to The AND gate 42 has a function of transmitting the signal of the area A to the selector 36 when both the signal of the X coordinate area A from the X coordinate comparison circuit 40 and the signal of the Y coordinate area A from the Y coordinate comparison circuit 41 are input. Have.

The selector 36 is provided with a judgment circuit 37
The threshold value of the defect judgment corresponding to the area A, B or C determined by the steps 39 to 39 is stored in the defect judgment threshold value register 32 for differential comparison and the defect judgment threshold value register 33 for level comparison.
It has a function to select from.

Next, the operation of the above-configured device will be described.

When light for exposure is emitted from the light source 4, the light for exposure is illuminated on the photomask 1 by the illumination optical system 5. The light transmitted through the photomask 1 forms an image on the surface of the sensor 7, and the sensor 7 captures an image of the incident photomask 1 and outputs an image signal thereof. The image signal is digitized by the sensor circuit 8 and sent to the data comparison circuit 30 as inspection pattern data.

On the other hand, the design data generation circuit 12 generates design pattern data from the CAD data stored in the disk 11 and sends the data to the data comparison circuit 30.

The differential comparison circuit 1 of the data comparison circuit 30
4 detects an edge direction from the design pattern data, differentiates the design pattern data in the same direction as the edge direction, obtains the maximum absolute value among the differential values of pixels around the differentiated pixel, and checks the inspection pattern. The data is differentiated in each of the XY and ± 45 degrees directions to obtain a differential value of an absolute value in the same direction as the edge direction detected from the design pattern data among the differential values, and a value obtained by subtracting these differential values is used as a determination circuit. 22.

Further, the level comparison circuit 15 receives the inspection pattern data and the design pattern data, obtains a value obtained by subtracting the design pattern data from the inspection pattern data, that is, obtains a level difference between these data and sends it to the determination circuit 24.

On the other hand, the defect judgment threshold value switching control circuit 3
5 compares the coordinate data set in the defect detection sensitivity setting coordinate register 34 with the position data under inspection sent from the host CPU 10 and compares the position data under inspection with each of the areas A, B, It is determined whether the area is in any area of C.

That is, in the inspection area A determination circuit 37, the X coordinate comparison circuit 40 compares the position data (X coordinate) with the X coordinate data of the area A. If the position data is within the X coordinate data of the area A, The signal of the X coordinate area A is sent to the AND gate 42. Also, the Y coordinate comparison circuit 41
Compares the position data (Y coordinate) with the Y coordinate data of the area A, and sends the signal of the Y coordinate area A to the AND gate 42 if the position data is within the Y coordinate data of the area A. The AND gate 42 sends the signal of the area A to the selector 36 when the signal of the X coordinate area A from the X coordinate comparison circuit 40 and the signal of the Y coordinate area A from the Y coordinate comparison circuit 41 are both input.

In the inspection area B and C determination circuits 38 and 39, similarly to the inspection area A determination circuit 37, the position data (X coordinate) is compared with the X coordinate data of the areas B and C by the X coordinate comparison circuit. If the position data is within the X coordinate data of the areas B and C, the signals of the X coordinate areas B and C are sent to the AND gate. Further, the Y coordinate comparison circuit compares the position data (Y coordinate) with the Y coordinate data of areas B and C, and if the position data is within the Y coordinate data of area A,
The signals of the coordinate areas B and C are sent to the AND gate. When the signals of the X-coordinate areas B and C from the X-coordinate comparison circuit 40 and the signals of the Y-coordinate areas B and C from the Y-coordinate comparison circuit 41 are both input, the AND gates are used.
To the selector 36.

First, if the scan position of the sensor 7 is in the area C as shown in FIG. 5, a signal of the area C is sent from the inspection area C determination circuit 39 to the selector 36.

The selector 36 receives the signal of the area C sent from the inspection area C determination circuit 39, and sets the threshold value of the differential comparison defect determination corresponding to the area C to a differential comparison defect determination threshold value register. 32, and a defect comparison threshold value for level comparison is selected from a defect comparison threshold value register 33 for level comparison, and a threshold value for defect judgment for differential comparison is sent to the decision circuit 22. The comparison defect determination threshold is sent to the determination circuit 23.

The determination circuit 22 sets the differential comparison defect determination threshold value selected by the selector 36, and uses the differential comparison defect value from the differential comparison circuit 14 using the differential comparison defect determination threshold value. Judge to detect a defective portion. The detected defective portion is output as defect data through the OR gate 23.

The determination circuit 24 sets the level comparison defect determination threshold value selected by the selector 36, and makes a determination on the level difference from the level comparison circuit 15 using the level comparison defect determination threshold value. To detect a defective portion. At this time, the defect detection sensitivity for the area C is 0.5 μm. Then, the detected defective portion is the OR gate 23.
Is output as defect data.

Next, if the scanning position of the sensor 7 moves and is in both areas B and C as shown in FIG.
The signals of the areas B and C are sent to the selector 36 from the inspection area B and the inspection area C determination circuits 38 and 39, respectively.

The selector 36 receives the signals of the areas B and C sent from the inspection area B and inspection area C determination circuits 38 and 39, respectively, and receives two differential comparison defect determinations corresponding to the areas B and C. A threshold is selected from the differential comparison defect determination threshold register 32, and
Two level comparison defect judgment thresholds are selected from the level comparison defect judgment threshold register 33, and two differential comparison defect judgment thresholds are sent to the judgment circuit 22, and two level comparison defect judgment thresholds are selected. The defect decision threshold is sent to the decision circuit 23.

The determination circuit 22 sets two differential comparison defect determination thresholds corresponding to the areas B and C selected by the selector 36, and sets each of the differential comparison threshold values from the differential comparison circuit 14. A defect is detected by making a determination using two defect comparison thresholds for differential comparison according to the areas B and C.
The detected defective portion is output as defect data through the OR gate 23.

The decision circuit 24 sets two defect comparison thresholds for level comparison in accordance with each of the areas B and C selected by the selector 36, and determines each area B for a level difference from the level comparison circuit 15. , C, the defect is detected by using two defect comparison thresholds for level comparison.
At this time, the defect detection sensitivity for the area B is 0.25 μm.
m and the defect detection sensitivity for area C is 0.5 μm
become. Then, the detected defective portion is output as defect data through the OR gate 23.

As described above, in one embodiment,
When inspecting a defect on the photomask 1 by comparing the inspection pattern data obtained by imaging the photomask 1 with the design pattern data, the position data indicating the position where the defect inspection is performed is the inspection area where the defect inspection is performed. Since it is determined whether any of the plurality of areas A, B, and C set in E is present, and the detection sensitivity according to the determined area A, B, or C is selected, Inspection can be performed by lowering the detection sensitivity of the defect in the inspection area where the influence of the defect is small. As a result, it is not necessary to detect even the defect having a small influence as the defect. The cost can be reduced, the time can be shortened, and the production yield of the photomask 1 does not decrease.

The present invention is not limited to the above embodiment, but may be modified as follows.

For example, it is needless to say that each of the areas A, B, and C can be set arbitrarily, and its detection sensitivity can also be changed according to the accuracy of the inspection.

The function of the decision switching circuit 31 may be processed by software.

The areas having different defect detection sensitivities may be set for each layer pattern of the semiconductor chip.

Further, when a defect is detected by the above-described apparatus, a history of the position of the detected defect or the like may be obtained and reflected in a subsequent defect inspection.

Further, it is needless to say that the present invention can be applied to not only the pattern defect inspection of the photomask 1 used for manufacturing a semiconductor chip but also the inspection of various pattern defects of a printed board or the like.

[0058]

As described above, according to the present invention, it is possible to provide a pattern defect inspection method and a pattern defect inspection method capable of performing a defect inspection by lowering the detection sensitivity of a defect having a small influence as a defect.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment in which a pattern defect inspection device according to the present invention is applied to photomask inspection.

FIG. 2 is a configuration diagram of a data comparison circuit including a determination switching circuit in the device.

FIG. 3 is a diagram showing detection sensitivity according to each area in an inspection area selected by a defect determination threshold value switching control circuit in the apparatus.

FIG. 4 is a specific configuration diagram of a defect determination threshold value switching control circuit in the device.

FIG. 5 is a schematic diagram showing an operation of varying the detection sensitivity by a determination switching circuit in the same device for each area.

FIG. 6 is a configuration diagram of a conventional pattern defect inspection apparatus.

FIG. 7 is a specific configuration diagram of a data comparison circuit in the device.

FIG. 8 is a view showing an example of a pattern at a central portion and a peripheral portion in an inspection area of a photomask detected by the same device and each defect.

[Explanation of symbols]

 1: Photomask, 2: Image input device, 3: XY table, 4: Light source, 5: Illumination optical system, 6: Imaging optical system, 7: Sensor, 8: Sensor circuit, 10: Host CPU, 11: Disk , 12: design data generation circuit, 14: differential comparison circuit, 15: level comparison circuit, 22, 24: judgment circuit, 30: data comparison circuit, 31: judgment switching circuit, 32: defect judgment threshold register for differential comparison 33: Defect judgment threshold register for level comparison, 34: Defect detection sensitivity setting coordinate register, 35: Defect judgment threshold switching control circuit, 36: Selector, 37: Inspection area A judgment circuit, 38: Inspection area B Judgment circuit, 39: inspection area C judgment circuit, 40: X coordinate comparison circuit, 41: Y coordinate comparison circuit, 42: AND gate.

Continued on the front page F term (reference) 2F065 AA03 AA12 AA49 BB02 BB03 CC19 DD06 FF01 FF04 FF67 HH13 HH15 JJ03 JJ09 JJ26 NN11 PP12 QQ03 QQ07 QQ08 QQ13 QQ23 QQ25 QQ29 QQ47 RR08 CA08 EA09 AGO12A05 A02A05 EB01 EB02 ED07 4M106 AA09 BA04 CA39 DB04 DB30 DJ13 DJ14 DJ38 5B057 AA03 BA02 BA30 CA12 CA16 CB12 CB16 CC02 CH01 CH05 CH08 CH12 CH18 DA03 DA07 DA08 DA11 DB02 DC04 DC16 DC32

Claims (5)

[Claims] 1. A pattern defect inspection method for inspecting a defect on the inspection object by comparing inspection data obtained by imaging the inspection object with a preset reference pattern, wherein the defect inspection is performed. A pattern defect inspection method, wherein the defect inspection is performed by varying the detection sensitivity for each of a plurality of regions set in an inspection area. 2. A pattern defect inspection apparatus for inspecting a defect on the inspection object by comparing inspection data obtained by imaging the inspection object with a preset reference pattern, wherein the defect inspection is performed. Determining which of the plurality of areas set in the inspection area where the defect inspection is to be performed, and selecting a detection sensitivity according to the determined area. A pattern defect inspection apparatus, comprising: switching means. 3. An image input unit for capturing an image of an object to be inspected to acquire pattern data to be inspected, a reference pattern storage unit for storing each of a plurality of layers of reference patterns, A determination is made as to which of the plurality of areas set in the inspection area the position data indicating the defect inspection position in the inspection area of the pattern data to be inspected is, and a detection corresponding to the determined area is performed. Determination switching means for selecting sensitivity; comparing the pattern data to be inspected acquired by the image input means with each reference pattern stored in the reference pattern storage means for each layer; And a data comparing unit for inspecting a defect on the inspection object using the detection sensitivity selected by the following. Turn defect inspection apparatus. 4. The defect switching unit compares the position data indicating the position where the defect inspection is being performed with the coordinates indicating a plurality of areas set in the inspection area. A plurality of inspection area determination circuits for each area for determining whether or not a position where the inspection is performed is within the area; and a defect determination threshold value according to the area determined by the inspection area determination circuit. The pattern defect inspection apparatus according to claim 2, further comprising: 5. When the pattern data to be inspected acquired by the image input means extends over at least two of the areas set in the inspection area, the determination switching means determines that the pattern data to be inspected is The pattern defect inspection apparatus according to claim 2, further comprising a function of selecting at least two detection sensitivities corresponding to at least two straddling regions.