JP3092661B2 - Appearance inspection method and appearance inspection apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a visual inspection method and a visual inspection apparatus.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a semiconductor device, a wafer having a pattern corresponding to the photomask is formed by performing exposure after exposing through a photomask in which a fine pattern is drawn on a substrate. A process is performed. In particular, when mass production of semiconductor devices is performed, a large number of wafers are exposed using one photomask, so that if a photomask (especially a drawn pattern) has an error, it is manufactured. A large number of semiconductors are all defective. Therefore, the photomask must be formed with high precision.

[0003] Usually, when a component requiring high precision such as this photomask is manufactured, an appearance inspection for removing a defective product due to a manufacturing error or the like is performed. Specifically, as an appearance inspection, a component to be inspected is imaged, and data obtained by performing image processing on the imaged result is compared with reference image data. Is generally determined to be defective. This makes it possible to determine whether the pattern drawn on the photomask, for example, is formed according to a desired shape (reference image data stored in advance), and determine whether the pattern is good or bad.

[0004]

In recent years, semiconductor (LSI)
And the like), the pattern drawn on the photomask, which is the original, becomes finer. Then, as the pattern drawn on the photomask becomes finer (for example, when the minimum line width becomes 1 μm or less), the allowable error naturally becomes smaller, and the inspection accuracy required for the appearance inspection becomes higher. Therefore, in recent years, a visual inspection device capable of detecting an extremely small defect has been used. However, on the other hand, visual inspection equipment with extremely high inspection accuracy easily reacts to vibrations applied from the outside. There is a possibility that the imaging result of the inspection target may be shifted and determined to be defective. Recent high-precision visual inspection equipment
It is regarded as a defect in response to micro vibration of 0.1 μm or less. As described above, despite the high accuracy of the appearance inspection apparatus itself, there is a possibility that the inspection result often includes an error.

In order to determine the actual defect to be inspected and the so-called pseudo defect which is regarded as a defect due to vibration,
After the inspection by the visual inspection device, the operator must confirm each defect one by one, which is troublesome, time-consuming and inefficient. In order to suppress a pseudo defect due to vibration in the visual inspection device, the inspection resolution must be reduced, and this goes against the higher precision accompanying the miniaturization of the drawing pattern as described above.

[0006] By providing a vibration damping base as a base of the visual inspection apparatus, external vibration can be attenuated to some extent. However, vibrations caused by a person walking near the apparatus or suddenly generated from the outside can be reduced. However, the vibration cannot be completely attenuated, and the micro-vibration is transmitted to the main body of the appearance inspection apparatus, thereby causing a pseudo defect. As described above, conventionally, it has been difficult to perform a high-precision appearance inspection that can accurately inspect an object to be inspected and that is not affected by external vibration.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an appearance inspection method and an appearance inspection apparatus capable of preventing the influence of external vibration from being reflected in an inspection result and accurately inspecting the appearance of an object to be inspected.

[0008]

Means for Solving the Problems The feature of the present invention, the imaging hands
A step of imaging the object to be inspected by a step and a step of inspecting the appearance of the object to be inspected based on the imaging result, wherein the object to be inspected is scanned in the main scanning direction.
Imaging the object to be inspected while performing the main scanning
After the completion of scanning in the direction, the object to be inspected is referred to as the main scanning direction.
Scanning in the intersecting sub-scanning direction.
Thus, imaging and inspection of the inspection target are performed for each row in the main scanning direction.
Make fine appearance inspection, during said inspection object imaging by the imaging means, provided in the vicinity of the objective lens of the imaging unit
The in and vibration measurement means to measure the vibration of the objective lens, wherein when vibration measurements of the vibration measuring means is greater than the reference value, stops the visual inspection of the object to be inspected, the outer
The length of the inspection area of the visual inspection in the main scanning direction is
Shorter than the moving range of the main scanning direction査target main scanning
Acceleration period after start, deceleration period before main scanning stop,
During the inspection period, visual inspection and vibration measurement or vibration measurement
It consists in interrupting the comparison between the result and the reference value .

[0009]

[0010] When the vibration measurement result of the vibration measuring means is larger than a reference value, it is preferable to re-take an image of the column of the inspection object under measurement.

It is also possible to perform an appearance inspection of the object to be inspected by performing image processing on the imaging result of the object to be inspected and comparing the image processing result with reference image data.

The object to be inspected may be a photomask for manufacturing a semiconductor device.

[0013] Further, the appearance inspection apparatus of the present invention includes an imaging unit for imaging the object to be inspected, an inspection unit for inspecting the appearance of the object to be inspected based on an imaging result of the imaging unit, and a vibration measuring means for measuring the vibration in the inspection object imaging, when vibration measurements of the vibration measuring means is greater than the reference value, and a control means for stopping the visual inspection of the object to be inspected, the inspection target The main scanning direction
And and a conveying means it can be transported in the sub-scanning direction, before
The vibration measuring means is provided near the objective lens of the imaging means.
Vignetting is to measure the vibration of the objective lens, before
The conveying means is arranged so that the inspection area in the main scanning direction in the inspection area of the visual inspection is
In the range longer than the length, the inspection object is
The main scanning is started in the acceleration period.
Interval, deceleration period before main scanning is stopped, and period for performing sub-scanning
Is the appearance inspection and vibration measurement or vibration measurement result and reference value
The comparison is interrupted.

[0014]

[0015] It is preferable that the vibration measuring means is fixedly provided on the surface plate. Further, it is preferable that, when the vibration measurement result of the vibration measuring means is larger than a reference value, the control means stop the visual inspection of the inspection object and perform the imaging of the inspection object again.

The image inspection apparatus further includes image processing means for performing image processing on the imaging result, and the inspection means compares the image processing result by the image processing means with reference image data to thereby obtain the image to be processed. A visual inspection of the inspection object may be performed.

According to such a configuration, usually, a high-precision appearance inspection is performed, and when a large vibration is applied from the outside, the vibration measuring means detects the vibration and stops the appearance inspection. Not reflected in visual inspection results.
Therefore, a high-precision appearance inspection can be performed while eliminating the influence of vibration.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of an appearance inspection apparatus according to the present invention, and FIG. 2 is a block diagram thereof. The present embodiment is an apparatus for inspecting whether a desired drawing pattern is accurately formed on a photomask or a reticle used in an exposure process for manufacturing a semiconductor device. First,
The configuration of the visual inspection device will be described below.

A stone surface plate 3 is placed on an anti-vibration table 4 for attenuating external vibration. An XY table mechanism (transporting means) 2 is provided on the surface plate 3. The XY table mechanism 2 will be described. A slider 2c provided on the lower surface of the Y table 2b is fitted to a rail 3a provided on the upper surface of the surface plate 3 along the Y direction (sub-scanning direction). , Y-direction driving means 11 such as a motor and a cylinder
With reference to FIG. 2, the Y table 2b can move (sub-scan) along the rail 3a. A rail 2d is provided on the upper surface of the Y table 2b along the X direction (main scanning direction). A slider 2e provided on the lower surface of the X table 2a is fitted to the rail 2d, and the X table 2a is moved along the rail 2d by the X direction driving means 12 such as a motor or a cylinder (main scanning). It is possible.
Therefore, the X table 2a can be freely moved in the XY plane by the X-direction drive unit 12 and the Y-direction drive unit 11. An inspection target 1 such as a photomask is set on the X table 2a.

A gate-shaped frame 6 is fixedly provided on the surface plate 3. And in this frame 6,
An objective lens 5 is provided on the X table 2a at a position that can face the inspection object 1, and a vibration measuring unit 7 is provided near the objective lens 5. The frame 6, the objective lens 5, and the vibration measuring means 7 are immovably fixed on the surface plate 3 irrespective of the XY table mechanism 2.

In the present embodiment, although not shown in FIG. 1, as shown in FIG.
An imaging means 8 such as a CCD camera for imaging the image is provided. An image processing unit 9 is connected to the imaging unit 8 so that an imaging result can be transmitted from the imaging unit 8 to the image processing unit. An inspection unit 10 is connected to the image processing unit 9. Further, the imaging means 8, the image processing means 9, the inspection means 1
0, the vibration measuring means 7, the X-direction driving means 12, the Y-direction driving means 11, and the storage means 13 are connected to the control means 14, respectively. The storage unit 13 stores reference image data indicating a desired appearance of the inspection target, that is, an appearance of a photomask on which a desired pattern is accurately drawn in the present embodiment. The inspection unit 10 compares the result of the image processing by the image processing unit 9 with the reference image data stored in the storage unit 13 to determine the quality of the inspection target. The control means 14 controls all operations of the visual inspection device.

Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 3 is a flowchart of the appearance inspection, FIG. 4A is an explanatory diagram schematically showing the relative movement between the inspection object 1 and the objective lens 5 and the imaging unit 8 on the inspection object 1, and FIG. It is explanatory drawing which shows the vibration measured by 7 corresponding to FIG. 4a typically.

First, the inspection object 1 to be subjected to the appearance inspection
Is set on the X table 2a and set at the start position A (see FIG. 4) (step 101). Then, the X-direction driving means 12 operates to start the constant-speed movement (main scanning) of the X table 2a in the X direction (main scanning direction). At the same time, the imaging of the inspected object 1 by the imaging means 8 via the objective lens 5 is started (step 102). Imaging means 8
Is sent to the image processing means 9 and subjected to image processing by the image processing means 9 (step 103). As described above, the vibration measuring means 7 constantly measures the vibration while the inspection object 1 is being moved at a constant speed in the X direction and the imaging is being performed, and the predetermined reference value (the threshold value) is set. Value). If the measured vibration is equal to or smaller than the reference value (step 104), the image processing result sent from the image processing unit 9 to the inspection unit 10 is compared with reference image data stored in the storage unit 13 in advance. Then, based on whether or not the two match, the visual inspection (pass / fail judgment) of the row under inspection of the inspection target is performed (step 105).

When reaching the point B outside the inspection area 1a for one row, the main scanning by the X-direction driving means 12 and the imaging by the imaging means 8 are stopped (step 106).
Here, if there is still an untested row (step 10)
7) The Y-direction driving means 11 operates to move (sub-scan) the X table 2a and the Y table 2b by one column (to the start position C of the next column) in the Y direction (sub-scan direction) (step 108). ). Then, Steps 102 to 106 are repeated, and an appearance inspection of one line in the main scanning direction is performed by a series of operations of starting main scanning and imaging, image processing, vibration measurement, inspection, and stopping main scanning and imaging. The main scanning of the inspection target 1 (Step 102)
Is performed so as to be alternately folded left and right. In this manner, the appearance inspection is performed for each row in the main direction while repeating the main scanning and the sub-scanning. In step 107, when there are no more untested columns, the appearance inspection of the inspection target 1 is completed, and the inspection result in step 105 is integrated to determine the quality of the inspection target 1.

In the above description, in step 104,
The description will be made on the case where the vibration measured by the vibration measuring means 7 is always equal to or lower than the reference value. Next, the case where the vibration larger than the reference value is measured will be described.

Normally, during the visual inspection, slight movements always occur due to the movement and disturbance of the X stage 2a. The reference value is set as a range in which the amplitude of the fine movement is always allowed. In the present embodiment, the reference value is set to 0.1 μm. However, sudden vibration exceeding the reference value may be measured as shown at point E in FIG. 4B. That is, the case where the vibration measured by the vibration measuring means 7 exceeds the reference value in step 104. At this time, under the control of the control means 13, the visual inspection of the row F (see FIG. 4) under inspection at that time is stopped. That is, the process does not proceed to step 105. Then, the main scanning and the imaging are stopped when the scanning is performed up to the point G outside the inspection area 1a (step 109). Then, the main scanning and the imaging of the row F are started again at the point G without performing the sub-scanning (Step 102). However, at this time, the directions are opposite. In this manner, the main scanning and imaging (step 102) and the image processing (step 103) are performed again on the row F. In this retry, if the vibration measured by the vibration measuring means 7 is equal to or less than the reference value (step 10).
4) The appearance inspection of the row F is performed as usual (step 10).
5) When the main scanning is completed (Step 106), the sub-scanning is performed (Step 108).

In the flowchart of FIG. 3, for the sake of convenience, a step 104 for comparing the vibration measurement result with a reference value.
In step 103 of image processing and step 1 of visual inspection
Actually, the vibration measurement and the comparison between the vibration measurement result and the reference value are always performed during the execution of the main scanning and the imaging. As soon as a vibration exceeding the reference value is detected, the visual inspection is stopped. Step 10
4 may be inserted between steps 102 and 103, or may be inserted between steps 105 and 106.

Next, the technical meaning of this embodiment will be described in detail. When a large vibration is generated near the objective lens 5 as shown at a point E, the imaging result and the image processing result are blurred due to the vibration, and a disturbance that is not present in the original inspection object 1 is generated. When this is compared with the reference image data, they do not match, and it is considered that the inspection target 1 has a defect. Although there is actually no defect in the inspection target 1,
Inspection results can be obtained as if a defect exists due to the influence of vibration, so to say, a pseudo defect occurs. Of course, this is an inspection error. The main cause of the pseudo defect is disturbance vibration as described above. Most vibrations can be attenuated by using the vibration isolation table 4 as an active vibration isolation mechanism. However, sudden large external vibration, vibration in the resonance frequency band of the vibration isolation table 4, or high vibration The vibration of the frequency cannot be attenuated even by the vibration isolation table 4. Vibrations at a level of 1 μm or less may pass through the anti-vibration table 4, travel on the surface plate 3, and shake the vicinity of the objective lens 5 via the frame 6. Therefore, in the present embodiment, as described above, when the vibration measuring unit 7 detects a vibration exceeding the reference value, the appearance inspection is stopped and restarted. Good inspection is possible.

Since the objective lens 5 is a very precise part and the vibration measuring means 7 has a certain weight for measuring micro vibration, it is not possible to directly attach the vibration measuring means 7 to the objective lens 5. On the contrary, the inspection accuracy may be adversely affected. For this reason, in the present embodiment, the vibration measuring means 7 is attached near the objective lens 5 of the frame 6 which may transmit vibration to the objective lens 5,
The influence of external vibration during the inspection is measured. In the present embodiment, only one vibration measuring means 7 is provided in the vicinity of the objective lens 5, but it is also possible to arrange a plurality of vibration measuring means at various places for measurement.

When the XY table mechanism 2 operates,
At the scanning start point and the stop point of the X stage 2a, vibration caused by acceleration / deceleration occurs, but the scanning start point and the stop point are located outside the inspection area 1a. Then, the control unit 13 sends the inspection area 1 to the inspection unit 10.
a scanning start of the X table 2a by sending an inspection start signal so as to start the inspection after entering into the inspection area 1a, and by sending an inspection end signal to end the inspection before the departure from the inspection area 1a and the deceleration. The effect of vibration during stop and stop can also be eliminated. Although not shown, the drawing pattern is formed only in the inspection area 1a.

In this embodiment, both the main scanning and the sub-scanning are performed by moving the object 1 to be inspected by using the XY table mechanism. The vibration measuring means 7 is provided near the objective lens 5 which does not move. I have. Since the objective lens 5 has a function of enlarging the object 1 to be inspected toward the imaging means 8, a minute vibration of the objective lens 5 is reflected on the imaging result in an enlarged state. Therefore, it is effective to strictly observe the vibration of the objective lens 5 as in the present embodiment.

[0033]

The objects to be inspected are not limited to the photomasks and reticles for manufacturing semiconductor devices described above, but include wafers, liquid crystal substrates, and members without drawing patterns.
All components to be inspected for appearance can be used.

The appearance inspection is not limited to the method of pattern matching using image processing data.

[0036]

According to the present invention, since the influence of vibration applied from the outside is not reflected in the result of the appearance inspection, the occurrence of a pseudo defect due to the vibration can be prevented, and the reliability of the appearance inspection is improved. This eliminates the need for the operator to re-examine the entire surface of the object to be inspected after completion of the appearance inspection, thereby improving work efficiency. Further, even if the defect detection sensitivity is increased without considering the influence of the vibration, there is no possibility that the accuracy of the appearance inspection is deteriorated.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a visual inspection device of the present invention.

FIG. 2 is a block diagram of the embodiment shown in FIG.

FIG. 3 is a flowchart showing a visual inspection method of the present invention.

4A is an explanatory view schematically showing relative movement between an object to be inspected, an objective lens, and an imaging unit on the object to be inspected, and FIG. 4B is measured by a vibration measuring unit corresponding to FIG. 4A; It is explanatory drawing which shows the vibration which showed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object (photomask) 1a Inspection area 2 XY stage mechanism (conveying means) 2a X stage 2b Y stage 2c Slider 2d Rail 2e Slider 3 Surface plate 3a Rail 4 Anti-vibration table 5 Objective lens 6 Frame 7 Vibration measuring means 8 Imaging means 9 Image processing means 10 Inspection means 11 Y-direction drive means 12 X-direction drive means 13 Storage means 14 Control means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G01N 21/88-21/89 H01L 21/66

Claims (10)

(57) [Claims] And 1. A process for imaging an object to be inspected by the imaging means, a visual inspection method comprising the step of inspecting the appearance of the object to be inspected based on the imaging result, the direction the main scanning to be inspected Inspection while scanning
The step of imaging the target and the step after completion of scanning in the main scanning direction
The object to be inspected is set in a sub-scanning direction intersecting with the main scanning direction.
Is repeated in the main scanning direction.
Performs the imaging and visual inspection of the object to be inspected in each column, the during inspection object imaging by the imaging means, the imaging
Wherein the vibration measuring means is provided in the vicinity of the means of the objective lens to measure the vibration of the objective lens, wherein when vibration measurements of the vibration measuring means is greater than the reference value, a visual inspection of the object to be inspected Stop, and the length of the inspection area of the visual inspection in the main scanning direction is
The acceleration period after the start of the main scan and the deceleration period before the stop of the main scan , which are shorter than the movement range of the inspection target in the main scanning direction.
During the sub-scanning period, appearance inspection and vibration measurement or
An appearance inspection method that interrupts the comparison between vibration measurement results and reference values . 2. The method according to claim 1, wherein a vibration measurement result of said vibration measuring means is a reference.
If the value is greater than the value, take a picture of the
The appearance inspection method according to claim 1, wherein the image is redone . 3. The vibration measuring means is fixed to a surface plate.
The visual inspection method according to claim 1, wherein the visual inspection method is provided. 4. An image processing of an imaging result of the object to be inspected.
And compare the image processing results with the reference image data.
The visual inspection method according to any one of claims 1 to 3, wherein the visual inspection of the inspection target is performed . 5. The semiconductor device according to claim 1, wherein the object to be inspected is a semiconductor device manufacturing device.
The appearance inspection method according to claim 1, wherein the appearance inspection method is a photomask . 6. An imaging means for imaging an object to be inspected,
The appearance of the inspection object based on the imaging result of the imaging means.
Inspection means for inspecting, and said inspection target pair by said imaging means.
Vibration measuring means for measuring vibration during elephant imaging;
If the vibration measurement result of the
Control means for stopping the visual inspection of the object to be inspected;
The inspection object can be transported in the main scanning direction and sub-scanning direction.
Transport means, wherein the vibration measuring means is located near the objective lens of the imaging means.
The conveying means is provided for measuring the vibration of the objective lens, and the conveying means is provided in the main scanning direction of an inspection area for visual inspection.
Main scanning of the object to be inspected in a range longer than the length of
Direction, and the control unit controls the acceleration period after the start of the main scanning and the main scanning stop.
During the deceleration period before stopping and the period for performing sub-scanning, appearance inspection and
Interruption of vibration measurement or comparison of vibration measurement result with reference value
Appearance inspection equipment. 7. The vibration measuring means is fixed to a surface plate.
The visual inspection device according to claim 6, wherein the visual inspection device is provided. 8. The apparatus according to claim 1 , wherein said control means controls the vibration of said vibration measuring means.
If the dynamic measurement result is larger than the reference value,
Stop the visual inspection of
An appearance inspection apparatus according to claim 6 or 7, wherein 9. An image processing apparatus for performing image processing on the imaging result.
Having a step, wherein the inspection means is provided with an image by the image processing means.
By comparing the image processing result with the reference image data,
9. The method according to claim 6, wherein the visual inspection of the inspected object is performed.
Appearance inspection device according to the paragraph . 10. The semiconductor device according to claim 1, wherein the object to be inspected is a semiconductor device.
The visual inspection device according to any one of claims 6 to 9, which is a photomask .