JPH0374854A - Surface inspection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a surface inspection apparatus that inspects the surface of an object to be inspected, such as a semiconductor wafer, by capturing an image of the object to be inspected with an imaging device.

(Prior art) Surface inspection of semiconductor wafers involves imaging the semiconductor wafer with an imaging device and detecting defects on the surface of the semiconductor wafer from the image data. A device having a small two-dimensional imaging area is sometimes used. When such an imaging device is used, the imaging device images the semiconductor wafer several times to obtain image data of the entire semiconductor wafer.

In this way, the image data of the entire semiconductor wafer is obtained by combining each image data obtained by imaging several times, but the gray level between these image data is unstable due to external disturbances, so it is necessary to The density level is made uniform.

This gray level equalization process involves equalizing the brightness level of the video signal based on the video signal of the entire semiconductor wafer output from the imaging device, or by providing a reference signal for the brightness level. I'm counting.

By the way, in the manufacture of semiconductor wafers, there are cases where various types of semiconductor wafers are manufactured in small quantities.

When the surface of the various semiconductor wafers manufactured in this way is inspected by performing each of the above-mentioned homogenization processes, the image signal level differs greatly depending on the various semiconductor wafers in the former homogenization process. The shading level of the entire image data of the semiconductor urchin changes due to the fluctuation of the shading level of parts other than the semiconductor wafer.

In particular, when an inspection is performed assuming that the amount of light reflected from the semiconductor wafer is uniform, the S/N ratio decreases. Furthermore, even if the latter equalization process attempts to equalize the luminance level using a reference signal of the same level, the video signal of the semiconductor urchin/\ portion may overflow or be buried in noise.

(Problem to be Solved by the Invention) As described above, since the level of the video signal varies greatly depending on the various semiconductor wafers, the gray level of the image data of the entire semiconductor wafer may be affected, or the gray level of the semiconductor wafer portion may overflow. Or, conversely, it gets buried in noise.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a surface inspection apparatus that can stably inspect the surface of an object to be inspected without being affected by video signals from sources other than the object to be inspected.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides an imaging device and an object other than the object to be inspected in each divided image data obtained by dividing the object to be inspected obtained by imaging with the imaging device into a plurality of regions. and a masking means for masking each of the divided image data masked by the masking means, and an average gray level of the image data of the entire inspected object created by combining each divided image data by calculating the average gray level of the unmasked part in each divided image data masked by this masking means. A conversion table creation means for creating a conversion table for making the levels uniform, and a conversion table that converts the gray level of each divided image data masked by the masking means to obtain an average gray level of the image data of the entire object to be inspected. A surface inspection device that attempts to achieve the above object by comprising a data conversion means for uniformizing data and an inspection means for inspecting the surface state of an object to be inspected from image data of the entire object to be inspected that has been made uniform by the data conversion means. It is.

(Function) By providing such means, the masking means masks the parts other than the inspected object part in each divided image data obtained by imaging with the imaging device, and the masked divided image data is received. The conversion table creation means determines the average shading level of the unmasked portion and creates a conversion table that equalizes the average shading level of the image data of the entire object to be inspected, which is a combination of each divided image data. Then, the equalization means converts the gray level of each masked divided image data using a conversion table to equalize the average gray level of the image data of the entire object to be inspected. The inspection means inspects the surface condition of the object to be inspected based on the image data.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a surface inspection device. In the same figure, 1
is an XY table, and a semiconductor wafer 2 is placed on this XY table 1.

Further, a lighting device 3 is arranged diagonally above the XY table 1, and an IT device is placed almost directly above the XY table 1.
A V camera 4 is arranged. This ITV camera 4 has an imaging area smaller than the size of the semiconductor wafer 2. Therefore, when the IVT camera 4 images the entire semiconductor wafer 2, the XY table 1 receives a movement control signal from the control circuit 5 and moves on the XY plane to capture the ITV.
The imaging areas of the camera 4 are A and B as shown in FIG.

C1..., ■ are scanned in this order.

The video signal output from the ITV camera 4 is converted into a digital video signal by an A/D converter 6 and sent to a masking section 7.

This masking section 7 has a function of receiving a digital video signal and masking the portions other than the semiconductor wafer 2 in each divided image data of each imaging area A, B, . . . , ■, and has the following configuration. It becomes. Image memories 8 and 9 are provided, and one of the image memories 8 and 9 is connected to the A/D converter 6,
The other image memory 9 is connected to the image memory 8 via an AND circuit 10. A mask generation circuit 11 is connected to the AND circuit 10. This mask generation circuit 11 includes each imaging area A, B, . . . as shown in FIG.
Each mask pattern image data DA, D, . . .
・D is memorized. These mask pattern image data D^, D, .
The shape portions similar to the above are set to logic “1”, and the other portions are set to logic “0”.

A conversion table creation unit 12 is connected to the image memory 9, and this conversion table creation unit 12 calculates the average gray level of the unmasked portion of each divided image data masked by the masking unit 7, and calculates the average gray level of the unmasked portion of each divided image data masked by the masking unit 7. It has a function of creating a conversion table for uniformizing the average gray level of the image data of the entire semiconductor wafer 2 created together with the above. Specifically, it is composed of an average level calculation circuit 13, a conversion table generation circuit 14, and a conversion table memory 15. Among these, the average level calculation circuit 13 reads each divided image data from the image memory 9 and determines whether masking is not performed in these divided image data. The conversion table generating circuit 14 creates a conversion table for uniformizing the average gray level of the image data of the entire semiconductor wafer 2 from the average gray level of each divided image data. be. And this conversion table is converted table memory 1
5 is stored.

Reference numeral 16 denotes a data conversion circuit which converts the gray level of each divided image data masked by the masking unit 7 using a conversion table, and converts the average gray level of the image data of the entire semiconductor wafer 2 into the imaging area. It has a function of uniformizing the density according to the average density level of E.

The inspection circuit 17 has a function of inspecting the surface condition of the semiconductor wafer 2 from the image data of the entire semiconductor wafer 2 that has been made uniform by the data conversion circuit 16.

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

First, a conversion table is created.

When the semiconductor wafer 2 is illuminated by the illumination device 3 and the imaging area of the ITV camera 4 is set to A by sending a movement control signal from the control circuit 5, the ITV camera 4 images the imaging area A and outputs the video signal. Output. This video signal is converted into a digital video signal by the A/D converter 6 and temporarily stored in the image memory 8 as divided image data of the imaging area A. If this divided image data is Qa as shown in FIG.
is sent to the AND circuit 10, and at the same time, the mask generation circuit 11 sends the mask pattern image data DA of the imaging area A to the AND circuit 10.

As a result, the AND circuit 10 performs the AND of the divided image data Qa and the mask pattern image data DA to obtain masked divided image data Qa''. This divided image data Qa- is stored in the image memory 9. Ru・.

Next, a movement control signal is sent from the control circuit 5 to move the XY table 1 on the XY plane, thereby setting the imaging area of the ITV camera 4 to B.

In this state, the ITV camera 4 images the imaging area A and outputs the video signal, which is temporarily stored in the image memory 8 as divided image data of the imaging area A. Then, this divided image data is sent to the AND circuit 10, and at the same time, the mask generation circuit 11 sends the mask pattern image data D of the same imaging area B to the AND circuit 10. Divided image data of the AND of the divided image data and mask pattern image data DA is obtained and stored in the image memory 9.

Thereafter, masked divided image data of each imaging area C, D, .

Next, the average level calculating circuit 13 sequentially reads out each divided image data from the image memory 9, calculates each average gray level in each portion other than masking, and sends each of the calculated values to the conversion table generating circuit 14. This conversion table generation circuit 14 receives each average gray level of each divided image data and generates a conversion table that equalizes or normalizes the average gray level of image data of the entire semiconductor wafer 2, which is created by combining each divided image data. generate. This conversion table is then stored in the conversion table memory 15.

Next, a surface inspection of the semiconductor wafer 2 is performed. in this case,
The conditions for illuminating the semiconductor wafer 2 with the illumination device 3 and the position of the XY child table are exactly the same as when creating the conversion table.

Similarly to the above, the semiconductor wafer 2 is illuminated by the illumination device 3, and the imaging area of the ITV camera 4 is set to A by the exit of the movement control signal of the control circuit 5, and in this state, the ITV
The camera 4 images the imaging area A and outputs the video signal. This video signal is converted into a digital video signal by the A/D converter 6 and temporarily stored in the image memory 8 as divided image data of the imaging area A. If this divided image data is Qa as shown in FIG. 4, the divided image data Qa is sent to the AND circuit 10 as shown in FIG.
is sent to the AND circuit 10, so that the AND circuit 1
0 is divided image data Qa and mask pattern image data D
Performs logical AND with A to obtain masked divided image data Qa=. This divided image data Qa'' is then stored in the image memory 9.

Hereinafter, the respective imaging areas B, C, and D are similar to the above action.

. . , each masked divided image data of ■ is obtained and stored in the image memory 9.

When each divided image data is stored in the image memory 9 in this way, the data conversion circuit 16 sequentially reads each divided image data stored in the image memory 9 and converts the gray level using the conversion table. The average gray level of image data of the entire semiconductor wafer 2 is made uniform. Then, the inspection circuit 17 inspects the surface condition of the semiconductor wafer 2 from the image data of the entire semiconductor wafer 2 that has been made uniform by the data conversion circuit 16, and detects defects, for example.

After this, if you want to perform surface inspection on a different type of semiconductor wafer,
First, a conversion table for the semiconductor wafer is created.

In this way, in the above embodiment, the image data of the entire semiconductor wafer 2 is masked by masking the parts other than the semiconductor wafer 2 in each divided image data, and calculating the average gray level of the unmasked parts of each masked divided image data. A conversion table is created to make the average gray level uniform, and the gray level of each masked divided image data is converted according to this conversion table, and the semiconductor wafer 2 is
Since the surface condition of the semiconductor wafer 2 is inspected by making the average gray level of the entire image data uniform, even if the level of the video signal differs greatly depending on the various semiconductor wafers 2, the conversion table is changed according to the gray level. The surface of the semiconductor wafer 2 can be inspected without being affected by variations in the density level of parts other than the semiconductor wafer 2. Therefore, the accuracy of the surface inspection of the semiconductor wafer 2 can be increased and the reliability can be improved.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, if the type of semiconductor wafer 2 to be manufactured is known in advance without fluctuation and is stable without disturbance, various semiconductor wafers 2
A conversion table corresponding to each type of semiconductor wafer 2 may be created in advance, and the conversion table corresponding to each type of semiconductor wafer 2 may be externally loaded into the conversion table memory at the time of inspection. Thereby, the video input from the ITV camera 4 only needs to be performed once. Furthermore, when the ITV camera 4 images each of the imaging areas A, B, . . . I, the ITV camera 4 may be moved to take the images. Further, the rules of the conversion table for uniformizing the average gray level are not limited to matching the average gray level of the imaging area E, but may be any rule that uniformizes the gray level to a level suitable for inspection.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a surface inspection apparatus that can stably inspect the surface of an object to be inspected without being affected by video signals other than the object to be inspected.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a surface inspection device according to the present invention, FIG. 2 is a diagram showing each imaging area in the same device, and FIG.
The figure is a schematic diagram of each mask pattern image data of the same device, and FIG. 4 is a diagram showing the masking action in the same device. 1...XY table, 2...semiconductor wafer, 3...
・Lighting device, 4... ITV camera, 5... Control circuit, 6... A/D converter, 7... Masking unit, 8°9... Image memory, 10... Logical product Circuit, 11...
・Mask generation circuit, 12... Conversion table creation section, 1
3... Average level calculation circuit, 14... Conversion table generation circuit, 15... Conversion table memory, 16...
Data conversion circuit, 17... inspection circuit.

Claims (1)

[Claims] an imaging device, a masking means for masking each of the divided image data obtained by dividing the object to be inspected into a plurality of regions other than the part of the object to be inspected, and each division masked by the masking means; conversion table creation means for determining an average gray level of an unmasked portion of the image data and creating a conversion table that equalizes the average gray level of the image data of the entire inspected object created by combining the respective divided image data; , an equalizing means for converting the gray level of each divided image data masked by the masking means using the conversion table to equalize the average gray level of the image data of the entire inspection object; and this equalizing means 1. A surface inspection apparatus comprising: an inspection means for inspecting the surface condition of the object to be inspected from image data of the entire object to be inspected that has been made uniform in the above.