JP2001091469A - Surface defect inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface defect inspection device obtaining a defect detecting image by the light quantity optimal for picking up the image of a sample. SOLUTION: A selection range 14 is designated on a pick-up image of a sample 2 on a stage 1, the maximum light quantity is detected in the selection range 14, and the brightness of a lamp 6 in the selection range is set to the light quantity optimal for the picking up the image of a first camera 8 and a second camera 9 from the maximum light quantity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus for inspecting a defect on a surface of an inspection object such as a semiconductor wafer or a liquid crystal glass substrate.

[0002]

2. Description of the Related Art For example, in a liquid crystal glass substrate, a layered film is formed on a substrate, and a predetermined pattern is formed thereon by a photoresist lithography process. If the film thickness of the resist is uneven or dust is attached, a defect such as a line width defect or a pinhole in the pattern may be generated at the time of pattern formation after etching.

Therefore, conventionally, defects on the surface of a substrate were prevented by visually inspecting the surface of the substrate during the process. As described above, a surface defect inspection apparatus that inspects a substrate surface while imaging the substrate surface by image processing has been considered. This apparatus irradiates a substrate surface with linear light guided from a light source at a predetermined angle, captures a regular reflection image and a diffraction / scattered image thereof, and performs image processing based on these images. Like that. The specular reflection image here is one in which light emitted from a light source is specularly reflected on a substrate and forms an image on an imaging surface. Observed, and diffraction and scattering images, if there is dust or scratches on the substrate,
The light is scattered at that portion to form an image at a position different from the above-mentioned specular reflection image, and the scattered light at this time is observed by the second image sensor.

[0004]

However, in such a surface defect inspection apparatus, since a light quantity at the time of imaging a diffraction / scattered image is small, an illumination lamp of a light source having a strong light quantity is used. ing.

For this reason, when a surface defect is detected as an object to be inspected, such as a semiconductor wafer, which has a region having a different reflectivity from a mirror surface such as a pattern or a resist, the amount of light reflected from the surface of the object to be inspected In contrast, the contrast greatly differs between the mirror surface portion and the region where the reflected light is scattered. As a result, when the optimal light amount is set for the mirror surface,
When it is desired to observe a pattern portion having a lower reflectance than a mirror portion, the pattern portion may be dark and a defective portion may not be detected. For this reason, conventionally, it is necessary to repeat several trials for each region having a different reflectance, and to set an optimal light amount for imaging in the region to be observed, and this light amount setting requires a lot of trouble. .

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a surface defect inspection apparatus capable of acquiring a defect inspection image with an optimum amount of light for imaging an inspection object.

[0007]

According to the first aspect of the present invention,
In a surface defect inspection apparatus for inspecting a defect on a surface of an inspection object, an illumination unit that irradiates illumination light to a surface of the inspection object, an imaging unit that captures an image of the inspection object, and an image captured by the imaging unit. And input means for designating an arbitrary range of the screen displayed on the display means as a selection range, light quantity detection means for detecting the light quantity in the selection range designated by the input means, and this light quantity And a dimming unit for dimming and obtaining an optimal light amount at the time of imaging by the imaging unit based on the detected light amount of the detecting unit.

According to a second aspect of the present invention, in the first aspect of the present invention, the light amount detecting means also serves as the image pickup means and detects a light amount within a selection range designated by the input means. I have.

The invention described in claim 3 is the first or second invention.
In the invention described above, the optimum light amount is a light amount at which the imaging unit does not saturate based on a maximum light amount within the selection range.

As a result, according to the present invention, it is possible to obtain a defect inspection image with an optimum light amount for a predetermined selection range of the inspection object.

Further, according to the present invention, since the imaging means can be used as the means for detecting the amount of light in the selected range, the configuration of the apparatus can be simplified.

Further, according to the present invention, since the maximum light amount in the selected range is used as the light amount for determining the optimum light amount, the optimum light amount for the image pickup by the image pickup means can be reliably obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a schematic configuration of a surface defect inspection apparatus to which the present invention is applied. In FIG. 1, reference numeral 1 denotes a stage on which an inspection object 2 such as a liquid crystal glass substrate or a semiconductor wafer is mounted. The stage 1 is connected to a stage driving unit 3. The stage driving unit 3 enables the stage 1 to move in the direction of the arrow shown in the figure according to an instruction from the control unit 10.

A lamp 6 made of, for example, a halogen lamp is arranged as illumination means for forming line illumination so that light enters the inspection object 2 on the stage 1 at a fixed angle. An illumination driving power source 7 is connected to the lamp 6 as dimming means, and controls the lamp voltage applied to the lamp 6 according to an instruction from the control unit 10 to perform dimming. When dimming with an ND filter (not shown),
It is also possible to select a desired ND filter from a plurality of ND filters having different transmittances according to an instruction from the control unit 10 and control the light amount.

On the other hand, the first camera 8 is arranged at a position where the light incident on the surface of the inspection object 2 from the lamp 6 is specularly reflected to form an image, and the first camera 8 is disposed at a position where the same scattered / diffracted light is incident. 2 cameras 9 are arranged.

The first camera 8 is a line sensor camera, and captures a regular reflection image of the inspection object 2. The second camera 9 is also a line sensor camera, and captures a diffraction / scattered image. The image processing unit 4 is connected to the first camera 8 and the second camera 9. The image processing unit 4 performs the first
In this case, respective captured images are generated from the imaging signals output from the camera 8 and the second camera 9.

The control unit 10 includes, in addition to the stage driving unit 3, the illumination driving power source 7, and the image processing unit 4, the display device 1
1, the storage device 12 and the input unit 13 are connected.

The display device 11 displays the captured image generated by the image processing section 4. The storage device 12 stores the captured image generated by the image processing unit 4.
The input unit 13 is for specifying an arbitrary selected area in the captured image displayed on the display device 11.

The control section 10 controls the entire apparatus. The control section 10 detects the maximum light amount in an arbitrary selected area specified in the captured image with respect to the illumination drive power supply 7 and determines the maximum light amount from the detected light amount data. The optimum amount of light at the time of imaging with the first camera 8 and the second camera 9 is calculated, and the lamp 6
Is set to the lamp voltage. In this case, the lamp voltage is obtained, for example, from the relationship with the light amount (illuminance) shown in FIG. 3 or FIG.

Next, the operation of the embodiment configured as described above will be described.

First, the inspection object 2 is placed on the stage 1, and the lamp 6 is turned on by the illumination driving power supply 7.

Next, the stage driving unit 3 controls the stage 1
Is moved, the specular reflection image of the inspection object 2 is captured by the first camera 8, and the captured image 2 a is displayed on the display device 11. At the time of this first imaging, the lamp 6 is dimmed so that the first camera 8 does not saturate the maximum reflectance of the inspection object 2.

In this case, it is assumed that a captured image 2a as shown in FIG. 2 is displayed on the display device 11. From this state, the input unit 13 specifies an arbitrary selection area 14 to be inspected in the captured image 2a. The designation of the selection area 14 at this time may be a line segment shown in FIG. 14A, a rectangular area shown in FIG. 14B, a circular area shown in FIG. 14C, or one line on the display screen shown in FIG. 14D. Good.

The input unit 13 designates, for example, an edge portion 14e, a process control number portion 14f, and a notch 14g of the inspection object 2 which are not related to the determination of the optimum light amount as a designation prohibited area 14h to be excluded in advance. It is also possible.

Next, the optimum light amount is set for the designated selected area. In this case, the control unit 10 executes the flowchart shown in FIG.

First, in step 501, initialization is performed. As the initial setting, the reflectance η of the two surfaces of the inspection object,
These are conditions such as the type of the optimal optical system. For example, the method of obtaining the reflectance η of the inspection object 2 includes: (1) a method of obtaining the information along with the quality and the process of the inspection object 2 via the LAN in the factory; A method in which the operator inputs the surface treatment information, and a method (3) in which the sensor is detected by a sensor attached to a transport unit (not shown) of the inspection object 2 and the like are considered.

Next, at step 502, an initial light amount is set. Here, adjustment of the lamp voltage or N (not shown)
D filter (usually provided on the front of the lamp 6,
It can also be provided on the front of the camera 9. A predetermined amount of light can be obtained in the selected area 14 of the inspected object 2 by the switching or the like. That is, the lamp voltage is adjusted so that the image sensor does not saturate when the corresponding substrate is imaged by setting the reflectivity η of the substrate and the optical system by the means described above. However, if the information of the reflectance η and the setting of the optical system includes the information of the imaging target area, the light quantity can be adjusted to the specified area only so that the imaging sensor does not saturate. If the information is reliable light amount information, the following steps 503 to 50 are performed.
5 may be omitted.

Next, in step 503, the stage 1 is moved by the stage drive unit 3, and the selected area 14 specified by the input unit 13 is imaged by the first camera 8.

Then, in step 504, the maximum light amount is detected from the image pickup output of the first camera 8, and in step 505
Then, the increment to the optimal light amount is calculated. In this case, using the relationship between the light quantity (illuminance) and the lamp voltage shown in FIG. 3 corresponding to the initially set reflectance η, the maximum light quantity of the imaging output falls in the proportional region of the relationship between the light quantity (illuminance) and the lamp voltage. Such a lamp voltage is determined, and the lamp voltage of the lamp 6 by the illumination drive power supply 7 is adjusted using the lamp voltage as an increment of the optimum light amount. Then, in step 506, the light amount of the lamp 6 based on the adjusted lamp voltage is stored in the storage device 12 as the optimum light amount at the time of imaging by the first camera 8 and the second camera 9. The storage device 12 similarly stores the optimum light amount at the time of imaging by the second camera 9.

The determination of the increment to the optimum light amount in step 505 can also be made by switching a plurality of ND filters (not shown) having different transmittances for setting the initial light amount. In this case, the ND filters DN1, DN2,.
ND having different transmittances so that the maximum light quantity of the imaging output falls within the proportional region of the relationship between the light quantity (illuminance) and the lamp voltage using the relationship between the light quantity (illuminance) and the lamp voltage shown in FIG.
The filters DN1, DN2,... May be determined, and the lamp voltage under these ND filters may be determined.

When the movement of the stage 1 is started again by the stage drive unit 3 in a state in which the light amount of the lamp 6 is optimally set, the regular reflection of the inspection object 2 by the first camera 8 is performed together with the movement of the stage 1. Image and second camera 9
, The imaging signals from the first camera 8 and the second camera 9 are sent to the image processing unit 10, and are displayed as a regular reflection image and a diffraction / scattering image on the display device 11. And at the same time, the storage device 1
2 is also stored.

In this case, from the specular reflection image of the inspection object 2 captured by the first camera 8, the film thickness unevenness is observed as interference fringes on the surface of the inspection object 2. Based on the captured diffraction / scattered image, a portion such as dust or a scratch on the surface of the inspection object 2 is observed as scattered light.

Thereafter, when the imaging of the inspection object 2 is completed,
The lamp 6 is turned off, the stage 1 is moved by the stage driving unit 3 to a position before the start of the inspection, and the inspection object 2 on the stage 1 is replaced with an uninspected one.

Accordingly, in this way, the brightness of the lamp 6 in the region of the inspected object 2 which is most desired to be detected can be set to the optimum light amount for the imaging by the first camera 8 and the second camera 9. A highly accurate specular reflection image and diffraction / scattered image of the inspection object 2 can be obtained, and a stable defect inspection image can be obtained.

Further, since the first camera 8 and the second camera 9 are used to detect the amount of light in the selection range 14, the configuration of the apparatus can be simplified and the cost can be reduced.

Further, since the maximum light quantity in the selection range 14 is adopted as the light quantity for determining the optimum light quantity in the selection range 14, the optimum light quantity for the first camera 8 and the second camera 9 Can be obtained with certainty.

Furthermore, optimal light control data for acquiring an image for defect inspection of the inspection object 2 is stored in the storage device 12.
, And by using these data in the subsequent inspection, an optimum inspection image of the inspection object 2 can be quickly obtained.

In the above description, the first camera 8 and the second camera 9 are used to detect the maximum light amount of the selection area 14 on the captured image 2a displayed on the display device 11, but the stage 1 A sensor may be arranged above or as an unillustrated light quantity taking-in means, and the sensor may be used to detect the light quantity of the whole inspection object 2 or the selected area 14 specified by the input unit 13. In this case, if a sensor having a large dynamic range is used, the optimum ND filter and lamp voltage can be obtained from the detected light amount.

In order to determine the maximum light quantity at a desired position in the captured image 2a displayed on the display device 11, for example, a line 16 displayed on the captured image 2a as shown in FIG. The amount of light along the line is displayed on the graph 17 as shown in FIG. 3B to indicate how much the maximum light amount point 17a is in relation to the dynamic range, and the maximum light amount point 17a or an arbitrary point is indicated, thereby making the above-described operation. The optimum light amount of the lamp 6 can be set in the same manner as described above. In this case, by moving the line 16 displayed on the captured image 2a in the direction indicated by the arrow by operating the move button 16a, the maximum light amount point can be found over the entire surface of the captured image 2a.

Further, the position and size of the selected area of the captured image 2a displayed on the display device 11 can be arbitrarily changed. In this case, as shown in FIG.
1, a position setting button 18 and a zoom setting button 19 are provided. By operating the position setting button 18, the selection area 20a can be moved to 20b, and by operating the zoom setting button 19, the size of the selection area 21a can be reduced. It can be enlarged to the size of 21b.
In this case, the selection areas 20a (20b), 21a
By superimposing and displaying (21b) on the captured image 2a, these selection areas 20a (20b), 21a (21
The position of b) can be easily specified. These selection areas may specify the area of the image of the first camera 8 or the second camera 9, or the position and detection range of the light amount acquisition sensor described above may be specified on the captured image 2 a displayed on the display device 11. May be displayed so as to be arbitrarily set.

In the above description, the image acquisition by the line sensor camera for the line illumination has been described. However, if the area sensor camera is used as the illumination device for illuminating the inspection object at once, the stage can be moved without moving the stage. Operation can be realized. In addition, a plurality of lighting devices, cameras, or the like may be provided.

[0043]

As described above, according to the present invention, it is possible to provide a surface defect inspection apparatus capable of acquiring a defect inspection image with an optimal light amount for imaging an inspection object.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a selection area according to the embodiment;

FIG. 3 is a diagram illustrating a relationship between a light amount (illuminance) and a lamp voltage for describing one embodiment.

FIG. 4 is a diagram illustrating a relationship between a light amount (illuminance) and a lamp voltage for describing one embodiment.

FIG. 5 is a diagram illustrating an operation of the embodiment.

FIG. 6 is a diagram illustrating another embodiment of the present invention.

FIG. 7 is a view for explaining another different embodiment of the present invention.

[Description of Signs] 1 ... Stage 2 ... Inspection object 2a ... Captured image 3 ... Stage drive unit 4 ... Image processing unit 6 ... Lamp 7 ... Illumination drive power supply 8 ... First camera 9 ... Second camera 4 ... Image Processing unit 10 Control unit 11 Display device 12 Storage device 13 Input unit 14 Selection area 16 Line 17 Graph 18 Position setting button 19 Zoom setting button 20a, 2ob, 21a, 21b Selection area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) G01B 11/24 K F term (reference) 2F065 AA49 BB02 CC19 CC25 CC31 FF42 GG02 GG16 HH12 JJ02 JJ05 JJ08 JJ25 LL24 MM03 NN02 NN18 NN20 PP12 QQ23 QQ24 SS02 SS13 2G051 AA51 AB01 AB07 BB07 BC01 CA03 CA04 CA07 DA05

Claims (3)

[Claims] 1. A surface defect inspection apparatus for inspecting a defect on a surface of an inspection object, an illumination unit for irradiating illumination light on a surface of the inspection object, an imaging unit for imaging the inspection object, and the imaging unit Display means for displaying an image picked up by the input means, input means for designating an arbitrary range of the screen displayed on the display means as a selection range, and light quantity detection means for detecting the light quantity in the selection range designated by the input means And a dimming means for obtaining an optimal light quantity at the time of imaging by the imaging means based on the light quantity detected by the light quantity detecting means, and dimming the light. 2. The surface defect inspection apparatus according to claim 1, wherein the light amount detection unit also serves as the imaging unit and detects a light amount within a selection range designated by the input unit. 3. The surface defect inspection apparatus according to claim 1, wherein the optimum light amount is a light amount at which the imaging unit does not saturate based on a maximum light amount within the selected range.