JP2001174418A - Appearance inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the inspection time of the appearance of a wafer. SOLUTION: A wafer having a plurality of inspection positions is placed on an electromotive XYθ stage 34. After the electromotive XYθ stage 34 is moved to the inspection position, a digital camera 31 takes the image of the inspection position. A feed sequence processing part 22 performs the transfer of the image from the digital camera 31 to a display part 19 and the movement of the electromotive XYθ stage 34 to a next inspection position in parallel after the photographing of the image is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a visual inspection apparatus, and more particularly to a semiconductor visual inspection apparatus for inspecting the appearance of a plurality of inspection points on a silicon wafer.

[0002]

2. Description of the Related Art Conventionally, the appearance inspection of a silicon wafer is performed by the naked eye using a wafer appearance inspection apparatus. The wafer appearance inspection apparatus usually includes a microscope unit for observing inspection points in a wafer (subject), a wafer loader unit for transporting a wafer in a cassette containing a plurality of wafers (subjects) to the microscope unit, a microscope unit, and the like. A transport sequence processing unit for controlling the wafer loader unit is provided. The microscope unit has an electric XYθ stage on which a wafer is mounted and which can be moved to an inspection position, and an eyepiece necessary for observing an inspection point in the wafer.

Next, the processing operation of the above-described conventional wafer appearance inspection apparatus will be described. First, when a desired wafer in the cassette is designated by the inspector, the transfer sequence processing unit gives an instruction to the wafer loader unit to extract the designated wafer from the cassette. The wafer loader unit extracts the specified wafer from the cassette according to the instruction from the transfer sequence processing unit, and drives the electric XYθ in the microscope unit.
Place on stage.

[0004] Next, the transport sequence processing section operates the electric XYθ so as to move to the inspection position pre-teached.
Give instructions to the stage. The electric XYθ stage moves to the inspection position according to an instruction from the transport sequence processing unit, and then stops. After the electric XYθ stage is stopped, the inspector observes the inspection points in the wafer with the naked eye using an eyepiece and makes a pass / fail judgment.

When the inspector completes the pass / fail judgment, the transport sequence processing section gives an instruction to the electric XYθ stage to move to the next inspection position. The electric XYθ stage moves to the next inspection position according to an instruction from the transport sequence unit, and then stops. When the electric XYθ stage is stopped, the inspector observes the inspection points with the naked eye and makes a pass / fail judgment as described above. The movement of the electric XYθ stage and the observation by the inspector are repeatedly executed until the pass / fail judgment of all the inspection points in the wafer is completed.

FIG. 4 shows an example of a timing chart when an inspector visually observes five inspection points on a wafer in the conventional wafer appearance inspection apparatus. In FIG. 4, the horizontal axis represents time t (seconds). In the example of FIG. 4, it takes 0.7 seconds for the electric XYθ stage to move from the current inspection position to the next inspection position, and it takes 1 second for the inspector to observe the inspection point and determine the quality. Therefore, in the example of FIG. 4, it takes (0.7 + 1) × 5 = 8.5 seconds until the pass / fail determination of the five inspection points is completed. In addition, 5
After the pass / fail judgment of the two inspection points is completed, it takes 0.7 seconds for the electric XYθ stage to move to the wafer transfer position, so that the total inspection time per wafer is 8.5 + 0.7 = 9. .2 seconds.

[0007]

However, in the above-mentioned conventional wafer appearance inspection apparatus, as shown in FIG. 4, while the electric XYθ stage moves from the current inspection position to the next inspection position, the inspector inspects the wafer. Since the quality of the points cannot be determined, there is a problem that the inspection time per one wafer becomes long.

Further, in the above-described conventional wafer appearance inspection apparatus, the illumination light is applied to the inspection points from when the wafer is loaded until all the inspection points are observed and unloaded. In addition, there is a problem that the wafer is damaged by short-wavelength illumination light.

In particular, in recent years, in order to improve the resolution of the microscope section, it has been desired to use shorter wavelength light instead of visible light as illumination light. For example, when observing the appearance of a wafer immediately after exposure using short-wavelength illumination light close to the wavelength of the light for pattern printing, the short-wavelength illumination light is also applied to areas that should not be exposed, causing damage to the wafer. Will be given.

SUMMARY OF THE INVENTION An object of the present invention is to provide a wafer appearance inspection apparatus capable of shortening a wafer appearance inspection time. Another object of the present invention is to provide a wafer appearance inspection apparatus capable of reducing damage to a wafer during an appearance inspection.

[0011]

According to a first aspect of the present invention, there is provided a stage in which a subject having a plurality of inspection positions is arranged, the stage being movable to the inspection positions, After the stage moves to the inspection position, an imaging unit that captures an image of the inspection position, a display unit that displays the image transferred from the imaging unit, and after the imaging of the image ends, the display unit displays the image from the imaging unit. Control means for transferring the image to the means and moving the stage to the next inspection position in parallel.

According to the first aspect of the invention, after the image capturing is completed, the transfer of the image from the image capturing unit to the display unit and the movement of the stage to the next inspection position are performed in parallel. The movement of the stage and the imaging of the image can be performed continuously, and as a result, the waste of the inspection time can be reduced and the throughput can be improved.

According to a second aspect of the present invention, there is provided a stage in which a subject having a plurality of inspection positions is arranged, the stage being movable to the inspection position, and the stage being moved to the inspection position. After the movement, an imaging unit that captures an image of the inspection position, an illumination unit that irradiates the subject with illumination light, and the illumination unit irradiates the subject with the illumination light when capturing the image, Control means for preventing the illumination light from irradiating the subject while the stage is moving.

According to the second aspect of the present invention, the illumination light is applied to the subject when the image is captured, and the illumination light is not applied to the subject while the stage is moving. The irradiation time can be reduced. Thereby, the damage which the illumination light gives to the subject can be reduced.

In a preferred embodiment of the second invention, the illumination light has a shorter wavelength than visible light.

According to the above invention, when illumination light having a wavelength shorter than that of visible light is used to increase the resolution of an image, the irradiation time of the illumination light to the subject can be reduced. Thus, it is possible to reduce damage to the subject caused by the illumination light having a wavelength shorter than the visible light.

Further, in the second aspect of the present invention, a preferable aspect further comprises a display means for displaying the image transferred from the image pickup means, and the control means further comprises: The transfer of the image from the imaging unit to the display unit and the movement of the stage to the next inspection position are performed in parallel.

According to the above invention, the inspection position can be observed even while the stage is moving, and the irradiation time of the illumination light to the subject can be reduced. This can improve throughput and
Damage caused by the illumination light to the subject can be reduced.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. However, such embodiments do not limit the technical scope of the present invention.

FIG. 1 is a block diagram showing the configuration of an embodiment of a wafer appearance inspection apparatus 1 to which the present invention is applied.
The first feature of the wafer appearance inspection apparatus 1 of FIG. 1 is that after the digital camera 31 captures an image of the inspection position, the transport sequence processing unit 22
1 is transferred to the display unit 19 and the movement of the motorized XYθ stage 34 to the next inspection position is performed in parallel. Thereby, the movement of the electric XYθ stage 34 and the image capturing of the inspection position can be continuously performed. As a result, waste of inspection time can be reduced, and throughput can be improved.

The second feature of the wafer appearance inspection apparatus 1 shown in FIG. 1 is that the transfer sequence processing section 22 opens and closes the shutter 43 in synchronization with the movement of the stage, so that the illumination light is emitted when an image is captured. The illumination light is not irradiated to the wafer while the electric XYθ stage 34 is moving. Thereby, the irradiation time of the illumination light to the wafer can be reduced. As a result, damage to the wafer caused by the illumination light can be reduced. In particular, this is effective when light having a shorter wavelength than visible light is used as illumination light to increase the resolution.

Next, the configuration of the wafer appearance inspection apparatus 1 will be described with reference to FIG. The inspector uses the input unit 1
1 to give an instruction to the wafer appearance inspection apparatus 1. The inspection position on the wafer (subject) is stored in the floppy disk 12, and the inspection position data D8 is stored in the arithmetic unit 1
3 is supplied to the transport sequence unit 22. The transfer sequence processing unit 22 controls the entire wafer appearance inspection device 1.

The wafer loader control and drive unit 14 controls the wafer loader unit 15 based on an instruction from the transfer sequence processing unit 22.
Drive. The wafer loader unit 15 extracts one designated wafer from the cassette 16 storing a plurality of wafers, and removes the wafer from the electric X at the wafer transfer position.
Stage 34 is mounted on a syringe (not shown).

The XYθ control drive section 17 moves the electric XYθ stage 34 in the microscope section 18 in accordance with the instruction D1 of the transport sequence processing section 22. The θ section 33 of the electric XYθ stage 34 is for rotating the wafer.

The alignment detecting section 35 is composed of an illuminating section (not shown) and a line sensor. The alignment is detected by using the coordinate system of the inspection position on the wafer and the coordinate system of the inspection position on the motorized XYθ stage 34. This is performed to detect a shift.

When the wafer is placed on the motorized XYθ stage 34, the motorized XYθ stage 34 moves the mounted wafer to the alignment detection position according to the instruction of the XYθ control drive unit 17, and rotates the θ unit 33. Let it. At this time, the illuminating unit irradiates the wafer with light on the line, and the line sensor detects a boundary between a dark part shielded by the wafer and a light part not shielded. Thereby, the electric XY
The external shape of the wafer placed on the θ stage 34 can be detected, and the amount of eccentricity between the rotation center of the θ unit 33 and the center of the wafer can be detected. further,
The notch direction or orientation flat direction of the wafer and the coordinate direction of the electric XYθ stage 34 can be matched.

The eccentricity D6 between the rotation center of the θ unit 33 and the center of the wafer detected by the alignment detection unit 35 is
The eccentricity data D which is supplied to the alignment operation processing unit 21
7 is supplied to the transport sequence processing unit 22. The transfer sequence processing unit 22 corrects the inspection position data D8 on the wafer which has been previously taught, based on the eccentricity data D7, and obtains the inspection position in the coordinate system of the stage.
The transport sequence processing unit 22 moves the electric XYθ stage 34 according to the corrected inspection position data.

As described above, the inspection position data D on the wafer
By converting 8 into inspection position data on the motorized XYθ stage 34, the inspection position can be accurately reproduced in the microscope section 18.

After the motorized XYθ stage 34 moves to the inspection position, the digital camera 31
The image at the inspection position is captured in accordance with the instruction of (1), and the captured image data D9 is transferred to the image storage unit 23 in the arithmetic unit 13 and stored. The image storage unit 23 stores a plurality of image data. The image data D9 stored in the image storage unit 23 is further transferred to the display unit 19,
Will be displayed on the screen. The inspector looks at the image of the inspection position displayed on the display unit 19 and determines the quality of the inspection point.
Conventionally, since the inspector directly looked at the eyepiece of the microscope to observe the inspection point, the wafer was somewhat affected by the contamination of the inspector. However, in FIG. Because unit 19 is in a separate room, the wafer is not affected by inspector contamination.

The shutter 43 is normally closed. That is, the illumination light emitted from the illumination light source 42 is blocked by the shutter 43. Shutter control drive unit 41
Causes the shutter 43 to open when capturing an image at the inspection position in accordance with an instruction from the transport sequence processing unit 22,
The illumination light is applied to the inspection position on the wafer.
On the other hand, while the electric XYθ stage 34 is moving, the shutter 4
3 is closed so that the illumination light is not irradiated on the inspection position on the wafer.

FIG. 2 is a flow chart for explaining the processing operation of the transport sequence processing section 22. FIG.
5 is a timing chart when the wafer appearance inspection apparatus 1 observes five inspection points on a wafer. FIG.
(A) to (E) show the first to fifth data in the wafer, respectively.
3 shows the timing of the inspection point. The horizontal axis in FIG. 3 represents time t (second).

Next, the processing operation of the transport sequence processing section 22 will be described below with reference to the flowchart of FIG. 2 and the timing chart of FIG. Here, a case where there are five inspection points in the wafer will be described.

First, when the appearance inspection of the wafer is started,
The transfer sequence processing unit 22 instructs the XYθ control drive unit 17 to move the electric XYθ stage 34 to the wafer transfer position (Step S1). XY
The θ control drive unit 17 moves the electric XYθ stage 34 to the wafer transfer position in accordance with an instruction from the transfer sequence processing unit 22.

Next, the transfer sequence processing section 22 instructs the wafer loader control drive section 14 to extract the wafer specified by the inspector from the cassette 16 and transfer the wafer to the wafer transfer position by the wafer loader section 15. An instruction is given (step S2). The wafer loader control drive section 14 moves the wafer loader section 15 to a wafer transfer position in accordance with an instruction from the transfer sequence processing section 22. Then, the wafer loader unit 15 places the wafer on the syringe of the electric XYθ stage 34.

Next, the transport sequence processing section 22
The θ control drive unit 17 is instructed to move the wafer placed on the electric XYθ stage 34 to the alignment detection position (step S3). The XYθ control drive unit 17 moves the wafer placed on the electric XYθ stage 34 to the alignment detection position in accordance with an instruction from the transfer sequence processing unit 22.

Next, the transport sequence processing section 22
With respect to the θ control drive unit 17,
An instruction is given to rotate the unit 33 (step S4).
The XYθ control drive unit 17 rotates the θ unit 33 at the alignment detection position in accordance with an instruction from the transport sequence processing unit 22. At this time, the alignment detecting unit 35 detects the eccentric amount D6 between the rotation center of the θ unit 33 and the center of the wafer, as described above. The detected amount of eccentricity D6 is subjected to predetermined processing in the alignment calculation processing unit 21, and is supplied to the transport sequence processing unit 22 as eccentricity data D7.

Next, the transport sequence processing section 22 converts the inspection position data D8 on the wafer,
The inspection position data on the electric XYθ stage 34 is corrected based on the eccentricity data D7 (step S5). As a result, the inspection position data is transferred from the coordinate system on the wafer to the electric XY
This means that the coordinate system has been converted to the coordinate system on the θ stage 34. As described above, by converting the inspection position data from the coordinate system on the wafer to the coordinate system on the electric XYθ stage 34,
In the microscope section 18, the inspection position can be accurately reproduced.

Next, the transfer sequence processing section 22 determines whether or not the pass / fail determination of all inspection points in the wafer has been completed (step S6). If it is determined in step S6 that the quality determination of all the inspection points in the wafer has not been completed, the process proceeds to step S7. Here, since the observation of the first inspection point is not performed, the process naturally proceeds to step S7.

Next, the transport sequence processing section 22
The electric XYθ stage 34 is
Is instructed to move to the first inspection position after the above-described correction (step S7). XYθ control drive unit 17
Moves the electric XYθ stage 34 to the corrected first inspection position in accordance with an instruction from the transport sequence processing unit 22. As shown in FIG. 3A, the moving time 51 of the electric XYθ stage 34 here is 0.7 seconds. While the electric XYθ stage 34 is moving, the shutter 4
Since 3 is closed, the wafer is not irradiated with illumination light.

When the movement to the first inspection position is completed, the electric XYθ stage 34 supplies a movement completion signal D2 to the transport sequence processing unit 22 via the XYθ control drive unit 17. Then, the transport sequence processing unit 22 determines whether or not the movement completion signal D2 has been received from the XYθ control driving unit 17 (Step S8). This determination is based on the electric XYθ
This is performed to check whether the movement of the stage 34 has been completed. When the movement completion signal D2 has not been received,
The transport sequence processing unit 22 continues to wait until the movement completion signal D2 is supplied.

Upon receiving the movement completion signal D2, the transport sequence processing section 22 supplies a shutter open signal D3 to the shutter control drive section 41 and supplies an imaging trigger signal D4 to the digital camera 31 (step S9). Upon receiving the shutter open signal D3, the shutter control drive unit 41 opens the shutter 43. At the same time, the digital camera 31
Upon receiving the imaging trigger signal D4, an image of the first inspection position is captured. As shown in FIG. 3A, the imaging time 52 at this time is 0.3 seconds.

After capturing the image at the first inspection position, the transport sequence processing section 22 instructs the shutter control drive section 41 to close the shutter 43 (step
S10). Then, the shutter control drive unit 41 responds to the instruction from the transport sequence processing unit 22 to
To close.

As another method, since the end point of imaging can be determined from the shutter speed of the digital camera 31, the digital camera 31 automatically receives the shutter speed after giving the imaging trigger signal D4 to the digital camera 31 for the shutter speed. The shutter 43 may be closed. In this case, the above-described step S10 becomes unnecessary.

After capturing the image of the first inspection position, the digital camera 31 transfers the captured image data of the first inspection position to the image storage unit 23 and stores it. Further, the image data at the first inspection position is transferred to the display unit 19 and displayed on the screen of the display unit 19. As shown in FIG. 3A, the transfer time 53 of the image data at this time is 2 seconds, and the time 54 required to display the image is 1
Seconds. The inspector makes a pass / fail judgment by looking at the image of the first inspection position displayed on the screen of the display unit 19.

As shown in the flowchart of FIG.
When the imaging of the image at the inspection position is completed and the shutter 43 is closed, the process returns to step S6, and the subsequent processing is repeatedly executed. That is, the processing from the remaining second inspection point to the fifth inspection point is performed as in the case of the above-described first inspection point.

If it is determined in step S6 that all the inspection points in the wafer have been inspected, step S1 is executed.
And the subsequent processing is repeatedly executed. That is,
Inspection of the second wafer is started in the same manner as the first wafer.

As described above, conventionally, the stage was moved to the inspection position, and then the observation with the naked eye was performed. Therefore, as shown in FIG. 4, it was necessary to sequentially move the stage and observe the inspection point. . Therefore, the inspection time is wasted.

On the other hand, in the present embodiment, as shown in FIG. 3, the movement of the stage with respect to a plurality of inspection positions and the imaging of the image are performed continuously, and the image transfer and display observation are performed separately. Since the movement is performed in parallel with the movement of the stage and the imaging, the total inspection time per one wafer can be reduced. The inspection time at this time is obtained by the following equation (1).

(Moving time + imaging time) × number of inspection points + last image data transfer observation time (1) In the example of FIG. 3, the motorized XYθ stage 34 moves from the current inspection position to the next inspection position. 0.7 seconds, and 0.3 seconds for the digital camera 31 to take an image of the inspection position.
Second, it takes two seconds for the digital camera 31 to transfer the image to the display unit 19, and one second for the display unit 19 to display the image. Therefore, the total inspection time per one wafer is (0.7 + 0.3) × 5 + 2 +
1 = 8 seconds. As compared with the case of FIG. 4, it can be seen that the total inspection time per one wafer is reduced by 1.2 seconds.

Further, as described above, irradiation and non-irradiation of the illumination means for the wafer are controlled in synchronization with the movement of the stage. Specifically, the illumination light is applied to the wafer when capturing an image, and the illumination light is not applied to the wafer while the electric XYθ stage 34 is moving. Therefore, the irradiation time of the illumination light to the wafer can be shortened as compared with the related art. As a result, damage to the wafer caused by the illumination light can be reduced. This is particularly effective when using illumination light having a shorter wavelength than visible light in order to increase the resolution of an image.

In the embodiment of the present invention, the shutter is used so as not to irradiate the wafer with the illumination light. However, the illumination light source is directly turned on and off without using the shutter. Is also good.

The scope of protection of the present invention is not limited to the above embodiments, but extends to the inventions described in the claims and their equivalents.

[0053]

As described above, according to the present invention, after an image is captured, the transfer of the image from the imaging means to the display means and the movement of the stage to the next inspection position are performed in parallel. Therefore, the movement of the stage and the imaging of the image can be performed continuously. As a result, the time required for the visual inspection of the subject can be reduced.

Further, according to the present invention, the illumination light is applied to the subject when the image is captured, and the illumination light is not applied to the subject while the stage is moving. Damage can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a wafer appearance inspection apparatus 1 to which the present invention is applied.

FIG. 2 is a flowchart for explaining a processing operation of a transport sequence processing unit 22 in FIG. 1;

FIG. 3 is a timing chart when observing five inspection points in the wafer appearance inspection apparatus 1 of FIG. 1;

FIG. 4 is a timing chart when observing five inspection points in a conventional wafer appearance inspection apparatus.

[Explanation of symbols]

 Reference Signs List 1 Wafer appearance inspection device 11 Input unit 13 Operation unit 14 Wafer loader control drive unit 15 Wafer loader unit 16 Cassette 17 XYθ control drive unit 18 Microscope unit 19 Display unit 21 Alignment operation processing unit 22 Transport sequence processing unit 23 Image storage unit 31 Digital camera 33 θ unit 34 Electric XYθ stage 35 Alignment detection unit 41 Shutter control drive unit 42 Illumination light source 43 Shutter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/66 G01B 11/24 K F-term (Reference) 2F065 AA03 AA12 AA17 AA20 AA49 AA51 BB01 CC19 DD06 EE00 FF02 FF42 GG08 GG21 HH05 HH15 JJ02 JJ03 JJ05 JJ09 JJ25 JJ26 LL30 NN02 NN20 PP12 PP13 PP24 QQ00 QQ23 QQ24 SS02 SS13 TT01 TT02 2G051 AA51 AB02 AB20 BA05 BA20 BC01 CA04 DA01 DA08 EA19 4M106 DB1901

Claims (4)

[Claims] A stage on which a subject having a plurality of examination positions is arranged and which can be moved to the examination position; an imaging means for taking an image of the examination position after the stage moves to the examination position; Display means for displaying the image transferred from the image pickup means; and after completion of image pickup of the image, transfer of the image from the image pickup means to the display means and movement of the stage to the next inspection position in parallel. And a control means for performing the inspection. 2. A stage on which a subject having a plurality of examination positions is arranged, the stage being movable to the examination position; an imaging means for taking an image of the examination position after the stage moves to the examination position; Illuminating means for irradiating the object with illumination light; and irradiating the object with the illumination light at the time of capturing the image, and not illuminating the object with the illumination light while the stage is moving. An appearance inspection apparatus, comprising: a control unit. 3. The visual inspection apparatus according to claim 2, wherein the illumination light has a shorter wavelength than visible light. 4. The image processing apparatus according to claim 1, further comprising a display unit configured to display the image transferred from the image capturing unit, wherein the control unit further transfers the image from the image capturing unit to the display unit after the image capturing of the image is completed. The visual inspection apparatus according to claim 2, wherein the movement of the stage to a next inspection position is performed in parallel.