KR20150135431A - High-speed image capture method and high-speed image capture device - Google Patents

Abstract

The workpiece is picked up at high speed without depending on the imaging characteristics of the imaging camera.
More specifically, in the imaging process of imaging the workpiece while relatively moving the imaging unit including a plurality of imaging devices equipped with line sensors and the holding table holding the workpiece at a predetermined moving speed, The scan rate is divided equally according to the number of image pickup devices and the scan rate is sequentially assigned to the image pick-up device so that each scan The work is photographed while repeating a cycle of adjusting the exposure time of the image pickup device within each scan rate and performing image pickup of an image of the work based on the brightness value acquired from each of the image pickup devices Lt; / RTI >

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a high-speed image sensing method and a high-

The present invention relates to a high-speed image pickup method and a high-speed image pickup apparatus for picking up a work such as a glass, a semiconductor wafer and an electronic substrate.

A method has been proposed and carried out in which, while moving the area image sensor in the scanning direction, moving to a predetermined position on the moving locus and a shift to a position shifted by 1/2 pixel in the horizontal direction orthogonal to the moving direction are alternately repeated Patent Document 1).

Japanese Patent No. 3907560

However, as a work to be imaged, for example, a semiconductor device or the like is required to have a high throughput in an inspection apparatus or the like by an image analysis process in order to increase the production quantity per unit time. Therefore, in order to shorten the inspection time consumed per one substrate, there has been proposed a mode in which the movement of the holding stage for holding the work is made faster, or a plurality of imaging cameras are arranged.

It is easy to speed up the movement of the holding stage. However, when high-speed imaging is performed in excess of the scan rate of the imaging camera, an image different from the original image data to be acquired is output. That is, there is a problem that the work can not be picked up beyond the optimum moving speed determined from the resolution of the imaging camera and the scan rate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has as its main object to provide a high-speed imaging method and a high-speed imaging apparatus capable of imaging a work at high speed without being limited by the scanning rate of the imaging apparatus.

In order to achieve this object, the present invention takes the following configuration.

That is, this is one embodiment of a high-speed imaging method for picking up a work,

An image pick-up process for picking up an image of the work while relatively moving the image pick-up unit composed of a plurality of image pick-up devices provided with line sensors and the holding table holding the work relatively horizontally at a predetermined moving speed,

And an image reconstruction step of reconstructing an image of the work based on the luminance values acquired from the respective image pickup devices,

Wherein the imaging process adjusts the moving speed to a speed higher than an optimum moving speed determined from the resolution of the line sensor and the scan rate in accordance with the number of image pickup devices,

The scan rate is divided equally according to the number of the image pickup devices,

The scanning rate after division is sequentially assigned to the image pickup device to perform shuttering of the image pickup device at the start point of each scan rate and image picking up the work while repeating cycles in which the exposure time of the image pickup device is adjusted within each scan rate .

(Operation and Effect) According to this method, the scan rate is divided equally into a large number of parts of the image pickup device, and a plurality of image pickup devices are sequentially assigned to the divided scan rates, and shuttering of the image pickup device is performed at the start point of each scan rate . At this time, the exposure time of the image pickup device is adjusted every scan rate after division. The original scan rate is divided, and pickup of one cycle is repeated using a scan rate after division by a plurality of image pickup devices to pick up a work. Therefore, in the process of picking up the work at a speed exceeding the optimum moving speed of the image pickup device, an image pickup device that follows the image of the area not completely picked up by the preceding image pickup device from behind is picked up. Image data can be acquired. Since the exposure time of the line sensor of each image pickup device is not overlapped, it is possible to reconstruct the image of the work only by synthesizing the luminance values obtained from the output signals of the respective image pickup devices. In other words, it is possible to appropriately perform the exposure time by the imaging device capable of adjusting the shuttering so as to be shorter than the scan rate after the division.

According to another aspect of the present invention, there is provided an image pickup apparatus comprising: an image pickup process of picking up a workpiece while moving an image pickup unit composed of a plurality of image pickup devices provided with line sensors and a holding table holding the workpieces relatively horizontally at a predetermined moving speed;

And an image reconstruction step of reconstructing an image of the work based on the luminance values acquired from the respective image pickup devices,

Wherein the imaging process adjusts the moving speed to a speed higher than an optimum moving speed determined from the resolution of the line sensor and the scan rate in accordance with the number of image pickup devices,

The scan rate is divided equally according to the number of the image pickup devices,

The scanning rate after division is sequentially assigned to the image pickup device, shuttering of the image pickup device is performed at the start point of each scan rate, and the exposure time of the image pickup device is exceeded beyond the scan rate after the division, And a luminance value obtained by averaging the luminance values acquired over a plurality of pixels by the number of pixels for each of the image pickup devices is stored in the storage section,

The image reconstruction process includes the steps of reading the luminance value in the order obtained from the storage unit, amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging, and calculating the luminance after the amplification at the current time from the luminance value of the pixel calculated immediately before And reconstructs the image of the work based on the luminance value obtained by subtracting the value from the luminance value.

According to this method, since the exposure times of the preceding and following imaging units are overlapped with each other, the luminance values output from the respective imaging units are synthesized with each other. However, the luminance value of the pixel at the calculation time point is amplified to the luminance value before the averaging, and the luminance value obtained by subtracting the current luminance value after amplification from the luminance value of the pixel calculated immediately before is obtained. The image can be reconstructed. Therefore, an image of a work can be acquired at a high speed without being restricted by the scan rate of the image pickup device itself even if an inexpensive image pickup device whose exposure time can not be adjusted is used.

According to another aspect of the present invention, there is provided an image pickup apparatus for picking up an image of a workpiece while relatively moving the image pickup unit having a plurality of image pickup devices having the same plurality of line sensors and a holding table for holding the workpiece at a predetermined moving speed, and,

And an image reconstruction step of reconstructing an image of the work based on the luminance values acquired from the respective image pickup devices,

The imaging process adjusts the moving speed to a speed higher than an optimum moving speed determined from the resolution of the line sensor and the scan rate in accordance with the line sensor of the image pickup device,

The scan rate is divided equally according to the number of line sensors of the image pickup device,

A cycle in which the scanning rate after division is sequentially assigned to the line sensor for each of the image pickup devices and shuttering is performed at the start point of each scanning rate and the exposure time for each line sensor is ended within the scanning rate after division In the process of picking up the work while repeating,

The workpiece is picked up while repeating an imaging cycle in which the same portions are overlapped alternately while shifting the imaging timings of the preceding imaging unit and the following imaging unit and the luminance values of the plurality of pixels acquired for each of the plurality of line sensors Is stored in the storage section as the luminance value for one pixel by the integral delay circuit,

The image reconstruction process includes the steps of reading the luminance value in the acquired order, amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging, subtracting the current luminance value after amplification from the luminance value of the pixel calculated immediately before, And reconstructs an image of the work based on a luminance value.

According to this method, since one imaging device has a plurality of line sensors, it is possible to expand the imaging area per one imaging device. Further, the scan rate is divided in accordance with the number of image pickup devices, and the image of the workpiece can be picked up in a state where the scan rate after division is assigned to each line sensor. Here, since the luminance values of a plurality of pixels acquired for a plurality of line sensors per image pickup device are output as the luminance values for one pixel by the integral delay circuit, the work can be picked up at a high speed by using the binning function. In addition, although a portion in which a region captured by a preceding imaging unit and an area captured by a subsequent imaging unit overlap occurs, the luminance value is read in the order of acquisition, the luminance value of the pixel at the calculation time point is amplified to the luminance value before the averaging, The image of the workpiece can be reconstructed on the basis of the luminance value obtained by subtracting the luminance value after amplification from the luminance value of the calculated pixel at the present point of time.

Further, in each of the above-described embodiments, it is also possible that a detection process of detecting a relative positional relationship with the holding table for each of a plurality of image pickup devices,

And calculating a relative displacement between the image pickup devices from the positional relationship obtained in the detection process,

The image reconstruction process preferably reconstructs the image while correcting the position of the acquired image data based on the shift amount obtained in the calculation process.

According to this method, since the positional shifts of the respective image pickup devices are offset, it is possible to easily perform accurate positional alignment while reducing the labor of performing subtle positional adjustment, and the image can be reconstructed.

In order to achieve this object, the present invention has the following configuration.

That is, this is one embodiment of a high-speed image pickup apparatus for picking up a work,

A holding table for holding the work,

An illumination unit that irradiates light toward the work loaded on the holding table;

An image pickup unit comprising a plurality of image pickup devices each having a line sensor for picking up the work,

A horizontal drive mechanism for horizontally moving the holding table and the image pickup unit at a predetermined moving speed,

The scanning speed is adjusted to a moving speed faster than the optimal moving speed determined from the resolution of the line sensor and the scanning rate in accordance with the number of the image pickup devices,

The scanning rate is divided into a plurality of image pickup units by repeating a cycle in which the scanning rate after division is sequentially assigned to the image pickup unit so that the image pickup unit is shuttered at the start point of each scan rate and the exposure time of the image pickup unit is adjusted within each scan rate, A control unit for picking up a work,

And an arithmetic processing unit for reconstructing an image of the work based on the luminance values acquired by the respective image pickup units.

According to this configuration, the control unit adjusts the moving speed faster than the optimum moving speed determined from the resolution of the line sensor and the scanning rate, and divides the scanning rate equally into a large number of parts of the image pickup device, The scan rate after division is sequentially assigned to the image pickup device so that the image pickup device is shuttered at the start point of each scan rate and the cycle of adjusting the exposure time of the image pickup device within each scan rate is repeated by a plurality of image pickup devices And picks up the work. Therefore, one embodiment of the above method can be suitably realized.

Further, in another embodiment of the high-

A holding table for holding the work,

An illumination unit that irradiates light toward the work loaded on the holding table;

An image pickup unit comprising a plurality of image pickup devices each having a line sensor for picking up the work,

A horizontal drive mechanism for horizontally moving the holding table and the image pickup unit at a predetermined moving speed,

The scanning speed is adjusted to a moving speed faster than the optimal moving speed determined from the resolution of the line sensor and the scanning rate in accordance with the number of the image pickup devices and the scanning rate is evenly divided into a large number of parts of the image pickup device, And causes the imaging device to perform shuttering at the start point of each scan rate and to terminate the exposure time of the imaging device beyond the scan rate after the division so that the exposure time of the preceding imaging device and the following imaging device are overlapped, And a luminance value obtained by averaging the luminance values acquired over a plurality of pixels by the number of pixels for each of the plurality of pixels in a storage unit,

The luminance value obtained by amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging and subtracting the luminance value after amplification at the current time from the luminance value of the pixel calculated immediately before, And an arithmetic processing unit for reconstructing an image of the work based on the calculated value.

According to this configuration, the control unit adjusts the moving speed faster than the optimum moving speed determined from the resolution of the line sensor and the scanning rate, and divides the scanning rate equally into a large number of parts of the image pickup device, The scanning rate after division is sequentially assigned to the image pickup device so that the image pickup device is shuttered at the start point of each scan rate and the exposure time of the image pickup device is exceeded beyond the scan rate after the division, The workpiece is picked up by a plurality of image pickup devices while repeating a cycle in which the exposure time of the image pickup device is overlapped and a luminance value obtained by averaging the luminance values acquired over a plurality of pixels by the number of pixels per image pickup device is stored in the storage section. Therefore, one embodiment of the above method can be suitably realized.

Further, in another embodiment of the high-

A holding table for holding the work,

An illumination unit that irradiates light toward the work loaded on the holding table;

An image pickup unit comprising a plurality of image pickup devices each having a plurality of line sensors for picking up the work;

A horizontal drive mechanism for horizontally moving the holding table and the image pickup unit at a predetermined moving speed,

The moving speed of the line sensor is adjusted to a moving speed faster than the optimum moving speed determined from the resolution of the line sensor and the scanning rate and the scanning rate is divided equally according to the number of line sensors of the image sensor, And the exposure time for each line sensor is terminated within the scan rate after the division is repeated, the process is terminated while repeating the cycle in which the scan rate after the division is sequentially assigned to the line sensor and shuttering is performed at the start point of each scan rate, In the process of picking up the work,

The image pickup device picks up the work while repeating an image pickup cycle in which the same image pickup section is shifted from the image pickup timing of the preceding image pickup device and the image pickup timing of the subsequent image pickup device so as to overlap the same portions alternately and the luminance of a plurality of pixels And stores the value as a luminance value for one pixel in the storage section by an integration delay circuit;

The luminance value obtained by amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging and subtracting the luminance value after amplification at the current time from the luminance value of the pixel calculated immediately before, And an arithmetic processing unit for reconstructing an image of the work based on the calculated value.

According to this configuration, the control unit adjusts the scanning speed to a moving speed faster than the optimum moving speed determined from the resolution of the line sensor and the scanning rate, according to the line sensor of the image pickup device, And the scan rates after division are sequentially assigned to the line sensors for each image pickup device so that the shuttering is performed at the start point of each scan rate and the exposure time to each line sensor is ended within the scan rate after the division While picking up the work while repeating an imaging cycle in which overlapping portions of the same portion are alternately overlapped with each other while shifting the imaging timing of the preceding imaging unit and the following imaging unit in the process of picking up the work while repeating the adjusted cycle, The luminance values of a plurality of pixels acquired over a plurality of line sensors are integrated As a luminance value for one pixel by the open circuit and stores in the storage unit. Therefore, one embodiment of the above method can be appropriately realized.

In this configuration, the image pickup unit may include, for example, a lens barrel portion for guiding light reflected from a work irradiated from the illumination unit or light transmitted through the work,

And an optical member which partially transmits light for guiding the barrel portion and reflects a part of the light by changing the angle to guide light to a plurality of image pickup devices.

According to this configuration, the reflected light introduced from the same field of view is projected to the line sensors of a plurality of image pickup devices, so that the image of the work can be reconstructed with higher accuracy from the same condition without positional deviation.

Further, in each of the above-described embodiments, it is preferable that a detector for detecting a position relative to the holding table for each of the plurality of image pickup devices,

The control unit includes a storage unit for storing the position information detected by the detector,

It is preferable that the arithmetic processing unit reconstructs the image while correcting the position of the acquired image data based on the relative displacement between the imaging units by reading the positional information acquired for each of the imaging units from the storage.

According to this configuration, since the positional deviation of each of the image pickup devices is offset, it is possible to easily perform accurate positional alignment while reducing the labor of performing subtle positional adjustment, and the image can be reconstructed.

According to the high-speed imaging method and the high-speed imaging apparatus of the present invention, high-speed imaging of the work is possible without being limited by the scan rate of the imaging apparatus.

1 is a perspective view showing a schematic configuration of an internal inspection apparatus according to the present embodiment.
2 is a front view showing a schematic configuration of an internal testing apparatus according to the present embodiment.
3 is a flowchart for explaining the imaging operation of the high-speed imaging apparatus.
4 is a timing chart showing the switching of the imaging camera.
5 is a diagram showing an image pattern to be imaged in the embodiment.
6 is a schematic diagram showing a reconstruction process of an image.
7 is a timing chart showing the switching of the imaging camera of the modification.
8 is a diagram showing an image pattern to be imaged in the modification.
9 is a schematic diagram showing a reconstruction process of an image in the modified example.
10 is a diagram showing an image pattern to be imaged in the modification.
Fig. 11 is a schematic diagram showing the output image processing of the first imaging camera of the modification. Fig.
12 is a schematic diagram showing the output image processing of the second imaging camera of the modification.
Fig. 13 is a schematic diagram showing an image reconstruction process in a modified example. Fig.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a semiconductor wafer (hereinafter simply referred to as "wafer W") on which a circuit pattern is formed as a workpiece is used and the entire surface of the wafer is picked up for inspection of the wafer surface as an example Explain.

1 is a perspective view showing a schematic configuration of a high-speed image pickup apparatus according to an embodiment of the present invention. 2 is a front view showing a configuration of a main part of a high-speed image pickup apparatus, and a part thereof includes a sectional view.

The high-speed imaging apparatus is composed of an imaging unit 1, a test stage 2, a control unit 3, and the like.

The image pickup unit 1 includes a barrel main body 4, a first imaging camera 5, a second imaging camera 6, an illumination unit 7, objective lenses 8a, 8b and 8c and a revolver 9 .

The barrel main body 4 is divided into two at the upper side, and the first imaging camera 5 and the second imaging camera 6 are provided in each barrel. In addition, a plurality of objective lenses 8a and 8b having magnifications different from each other are provided through the revolver 9 in the lower portion of the barrel main body 4. [ That is, the imaging visual field can be changed. Further, the revolver 9 rotates about the axis P.

Further, the illumination unit 7 is provided on the side surface of the barrel main body 4. [ The light from the irradiation unit 7 is guided to the lower wafer W on the connecting portion of the irradiation unit 7 of the barrel main body 4 and the light from the irradiation unit 7 (Hereinafter referred to as " observation light ") regularly reflected from the front surface or the back surface of the wafer W through which the wafer W is transmitted. The first optical member 10 may be, for example, a half mirror or a beam splitter.

A second optical member 11 for branching the observation light from the wafer W to the first imaging camera 5 and the second imaging camera 6 is disposed at the branching portion of the barrel main body 4 have. The observation light diverged by the second optical member 11 is totally reflected by the reflection mirror 12 and guided to the second imaging camera 6. [ The second optical member 11 may be, for example, a half mirror or a beam splitter.

The first imaging camera 5 and the second imaging camera 6 have the same scan rate. For example, line sensors 13a and 13b in which image pickup elements such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) are arranged one-dimensionally. The image pickup device digitally converts the luminance value to the luminance value according to the luminance of the observation light, and outputs it as luminance data.

The inspection stage 2 includes a holding table 14, a first movable table 15, a second movable table 16, and a third movable table 17.

The holding table 14 is composed of a chuck table made of a porous or metal plate larger than the wafer W and flat.

The three movable tables disposed at the lower portion of the holding table 14 are arranged in this order from the bottom to the first movable table 15, the second movable table 16 and the third movable table 17. [ The first movable base 15 is constituted by a slider 15s reciprocating in the Y axis direction along a guide rail 15r attached to the apparatus base 15b.

The second movable base 16 includes a slider 16s which reciprocates in the X axis direction along the guide rail 16r attached to the base 16b disposed on the slider 15s of the first movable base 15, .

The third movable base 17 is rotated in the? Direction by a motor 18 (for example, a direct drive motor) provided on the slider 16s of the second movable base 16. Here, in this embodiment, the movement in the X-axis direction is set as the main scanning direction.

Here, the Y-axis direction is the array direction of the image pickup elements of the line sensors 13a and 13b, and is set to the sub-scan direction. The first movable base 15 and the second movable base 16 constitute a horizontal driving mechanism of the present invention.

The control unit 3 collectively controls the operations of the image pickup unit 1 and the inspection stage 2 and includes a storage unit 20 and an arithmetic processing unit 21 therein. Details will be described with reference to the operation of the high-speed image pickup apparatus.

Next, a description will be given of the routine operation for obtaining the inspection image of the wafer W using the above-described high-speed imaging apparatus according to the flowchart of Fig.

<Step S1> Condition setting

First, the moving speed of the slider 16s of the second movable table 16, which is the main scanning direction of the inspection stage 2, is determined. Then, the optimum moving speed V1 is determined by the scanning rates of the first imaging camera 5 and the second imaging camera 6. [ That is, it is determined by the resolution of the line sensors 13a and 13b and the scan rate. In this embodiment, the exposure time to reach a predetermined resolution is determined in advance by experiment or simulation. For example, when the scan rates of the first imaging camera 5 and the second imaging camera 6 are 10 kHz, one pixel is 10 탆, and the observation magnification is 10, the first imaging camera 5 The optimum moving speed V1 of the second imaging camera 6 is 10 mm / sec.

Here, since the image pickup unit 1 includes the first imaging camera 5 and the second imaging camera 6 with two front and rear in the main scanning direction, in the case of this embodiment, The main scan speed V2 of the image pickup camera 16s is set to 20 mm / sec, which is twice the optimum movement speed V1, and the image pickup by the both image pickup cameras 5 and 6 is set alternately. Each of these conditions is stored in the storage unit 20 of the control unit 3. The exposure time of the first imaging camera 5 and the second imaging camera 6 is set to be slightly shorter than the scan rate after division but an imaging camera capable of adjusting the timing of the shutter ring is used, Change the setting appropriately within the rate. That is, the state in which the timing of the shutter ring is not adjusted is the timing indicated by the broken lines 51 and 61, but the state in which the exposure time is shortened by adjusting the timing of the shutter ring is the timing indicated by the solid lines 52 and 62.

&Lt; Step S2 >

When the condition setting is completed, the wafer W is taken out of the cassette by the carrying robot or the like, and is loaded on the holding table 14 as shown in Fig. The wafers W are aligned based on an orientation flat or a V notch formed in the peripheral region. That is to say, the first movable base 15 and the second movable base 16 are moved and aligned and the third movable base 17 is rotated around the rotation axis of the motor 18 so that the position of the wafer W Alignment is performed.

&Lt; Step S3 >

After the alignment processing of the wafer W and the movement to the initial position of the imaging start are completed, the image pickup unit 1 is moved and set to a predetermined height, and then the main scanning of the slider 16s of the second movable table 16 Imaging of the wafer W is started while scanning the speed V2 in the X-axis direction at a speed twice the optimum moving speed V1. 4, when the trigger signal 1 is transmitted from the control unit 3 to the first imaging camera 5, the shutter of the first imaging camera 5 is turned on, And the observation light is exposed to the line sensor 13a. When the trigger signal 2 is transmitted from the control unit 3 to the second imaging camera 6, the shutter of the second imaging camera 6 is turned on to start imaging, and the observation light is transmitted to the line sensor 13b . At this time, the trigger signal 1 and the trigger signal 2 are alternately outputted. The first imaging camera 5 and the second imaging camera 6 are arranged in such a manner that the half of the normal shuttering time (that is, the state indicated by the broken lines 51 and 61) 62).

It is general that the first imaging camera 5 and the second imaging camera 6 are configured so that image data is output after a lapse of a normal shuttering time even if the shuttering time is set short. The output signals from the both imaging cameras 5 and 6 are switched to the OFF state indicated by the broken lines 51 and 61 and then the luminance data 1a, 1b ... and the luminance data 2a, 2b ... Likewise, they are alternately outputted from the both imaging cameras 4 and 6. [ By doing so, the two imaging cameras 5 and 6 are used to carry out imaging at an apparently twice as high scanning rate while moving the work at a speed twice as fast.

Fig. 5 shows a luminance value 90 of an image pattern to be imaged, which is an image pattern divided into a matrix shape. Here, the blank part means that the luminance value is zero. The vertical axis indicates the imaging time t0 to t16, and the horizontal axis indicates the addresses (1-16) of the line sensor used for imaging. In the figure, the timings (t1a to t8a, t1b to t8b) at which the shutters of the first imaging camera 5 and the second imaging camera 6 are turned ON are also shown on the right side of the figure. That is, at the time t2, at the addresses 8 and 9 of the line sensor, the first imaging camera 5 is used to capture the image of the brightness 90 at the timing t2a at which the shutter is turned on. Likewise, at the time t3, at the addresses 7 and 10 of the line sensor, the second imaging camera 6 is used to capture the image of the brightness 90 at the timing t2b when the shutter is turned on. The wafer W is picked up by both the imaging cameras 5 and 6 while repeating the cycle while scanning the wafer W from one end to the other end of the series of continuous imaging processing.

&Lt; Step S4 > Image reconstruction processing

A process of capturing an image by performing the series of successive image sensing processing cycles and then reconstructing an image will be described.

6A is brightness data output from the first imaging camera 5, and FIG. 6B is brightness data output from the second imaging camera 6. FIG. When the above-described continuous imaging processing cycle is repeated, the imaging timing and data output timing of the first imaging camera 5 and the second imaging camera 6 are alternately performed, as shown in Fig. 4 and Fig. As a result, as shown in Fig. 6A, the data output timings (i.e., time points d1a to d8a) corresponding to the images photographed at the timings t1a to t8a at which the shutters are turned ON are obtained from the first imaging camera 5 , Luminance data is outputted respectively. 6B, from the second imaging camera 6, at the data output timings (i.e., the time points d1b to d8b) corresponding to the images taken at the timings t1b to t8b when the shutters are turned ON, Luminance data is output.

The signals output from the both imaging cameras 5 and 6 are A / D converted and stored as the luminance values in the storage unit 20 for each of the first imaging camera 5 and the second imaging camera 6 .

The arithmetic processing unit 21 reads the luminance values of the both imaging cameras 5 and 6 from the storage unit 20 and alternately arranges the read luminance values in order from the oldest one, And the reconstruction processing of the entire image of the wafer W is performed. In addition, since the exposure time of both cameras 5 and 6 is set to half of the normal half as described above, the brightness value stored in the memory unit 20 is half of the original value 45. [ Therefore, when the image reconstruction process is performed, the process of calculating the value by multiplying the luminance value by a value (90) is also performed in consideration of this.

&Lt; Step S5 >

When imaging of the wafer W is completed, the wafer W is picked up by a carrier robot or the like, and the wafer W is carried by a cassette (not shown). Thus, the process of acquiring a series of inspection images is completed, and then the same process is repeated (step S6).

Two first imaging cameras 5 and a second imaging camera 6 arranged forward and backward in the scanning direction while using the two first imaging cameras 5 and the second imaging cameras 6 disposed in front and rear of the scanning direction It is impossible to continuously capture the entire surface of the wafer W by only one imaging camera only by setting the moving speed to twice the number of imaging cameras while using it. However, according to the above-described embodiment, the imaging of each of the imaging cameras 5 and 6 is alternately switched at the timing of dividing the scan rate into two equal parts according to the number of imaging cameras, and the exposure time is set to half, The continuous image data can be obtained without the half-image of the entire wafer being cut off while the exposure time of each of the first imaging camera 5 and the second imaging camera 6 is halved. Therefore, the entire image of the wafer W can be easily reconstructed simply by synthesizing based on the acquired image data (luminance value). That is, the image of the wafer W can be acquired easily and with high accuracy even at the speed V2 of twice the speed exceeding the optimum moving speed V1 of the imaging camera, so that the throughput of the inspection process can be increased.

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

(1) In the apparatus and method of the embodiment, the exposure times of the first imaging camera 5 and the second imaging camera 6 can not be set short. However, even when such an imaging camera is used, the object of the present invention can be achieved by means described below. That is, instead of the above-described steps S3 and S4, the following processing steps S3 'and S4' can be implemented.

&Lt; Step S3 &gt; >

After the alignment processing of the wafer W and the movement to the initial position of the imaging start are completed, the image pickup unit 1 is moved and set to a predetermined height, and then the main scanning of the slider 16s of the second movable table 16 Imaging of the wafer W is started while scanning the speed V2 in the X-axis direction at a speed twice the optimum moving speed V1. 7, when the trigger signal 1 is transmitted from the control section 3 to the first imaging camera 5, the shutter of the first imaging camera 5 is turned on and the imaging is performed And the observation light is exposed to the line sensor 13a. When the trigger signal 2 is transmitted from the control unit 3 to the second imaging camera 6, the shutter of the second imaging camera 6 is turned on to start imaging, and the observation light is transmitted to the line sensor 13b . At this time, the trigger signal 1 and the trigger signal 2 are alternately outputted. The first imaging camera 5 and the second imaging camera 6 are arranged such that the shuttering time is a normal state (that is, a state indicated by solid lines 53 and 63) I am doing. Also, as in step S3, imaging is performed at a scan rate twice as apparent in appearance, using the two imaging cameras 5 and 6 while moving the work at a speed twice as fast.

Fig. 8 shows a luminance value 90 of an image pattern to be imaged, which is an image pattern divided into a matrix shape. Here, the blank part means that the luminance value is zero. The vertical axis indicates the imaging time t0 to t16, and the horizontal axis indicates the addresses (1-16) of the line sensor used for imaging. In the figure, the timings (t1a to t8a, t1b to t8b) at which the shutters of the first imaging camera 5 and the second imaging camera 6 are turned ON are also shown on the right side of the figure. That is, over time t2 to t3, at the addresses 8 and 9 of the line sensor, the first imaging camera 5 is used to capture the image of the brightness 90 at the timing t2a when the shutter is turned on. Likewise, over time t3 to t4, at the addresses 7 and 10 of the line sensor, the second imaging camera 6 is used to capture the image of the luminance 90 at the timing t2b when the shutter is turned on. The series of image pick-up processes are performed in one cycle, and the wafer W is picked up by the two image pickup cameras 5 and 6 while the cycle is repeated while being scanned from one end to the other end of the wafer W .

&Lt; Step S4 &gt; Image reconstruction processing

A process of capturing an image by performing the series of successive image sensing processing cycles and then reconstructing an image will be described.

9A is luminance data output from the first imaging camera 5 and FIG. 9B is luminance data output from the second imaging camera 6. FIG.

7 and 8, the imaging timing and data output timing of the first imaging camera 5 and the second imaging camera 6 are alternately performed. As a result, as shown in Fig. 9A, the data output timings (i.e., time points d1a to d8a) corresponding to the images photographed at the timings t1a to t8a at which the shutters are turned ON from the first imaging camera 5 , Luminance data is outputted respectively. 9B, at the data output timing (i.e., the time d1b to d8b) corresponding to the image photographed at the timing t1b to t8b when the shutter is turned ON, the second image pickup camera 6 outputs, And luminance data is output, respectively (up to this point, the same as step S4). The signals output from the both imaging cameras 5 and 6 are subjected to A / D conversion and stored in the storage unit 20 as luminance values divided for each of the first imaging camera 5 and the second imaging camera 6 , The image is taken over two pixels because the shutter time is long, so that the two pixels are averaged and the brightness value is stored. Therefore, the image reconstruction processing is performed based on the following procedure, taking into consideration that the luminance values acquired from the two cameras are respectively time-averaged and obtained by overlapping with the other cameras. Which is different from the step S4).

First, under the setting conditions, when the imaging of the first imaging camera 5 and the imaging of the second imaging camera 6 are alternately repeated to acquire the image data, the imaging camera at the present time, which has received the trigger signal, And the output signal of the exposure time of the latter half of the preceding imaging camera overlap and are output. The luminance values obtained on the basis of the two output signals are stored in the storage section 20 as the combined measured luminance values of the luminance values to be obtained in advance.

The arithmetic processing unit 21 sequentially arranges the luminance values of the both imaging cameras 5 and 6 read from the storage unit 20 sequentially from the oldest one so that the read luminance value B is doubled A value (C = A-2B) obtained by subtracting the luminance value A of the immediately preceding pixel from the value (2B) is calculated and obtained. In addition, the luminance value (A) of the immediately preceding pixel to the luminance value (B) of the first column is set to 0 and processing is started.

For example, addresses 8 and 9 will be described as follows. First, the image picked up by the first image pickup camera 5 at the time t1a is outputted as the luminance value B at the time d1a. The luminance value (C) of this place is applied with the luminance value (A) of the immediately preceding pixel being zero. As a result, the portion corresponding to the addresses 8 and 9 of the time d1a is calculated as the luminance value 0. Subsequently, the image photographed at the time t1b by the second imaging camera 6 is output as the brightness value B at the time d1b. Further, the luminance value C of this place is calculated as the luminance value A of the immediately preceding pixel is zero. As a result, the portion corresponding to the addresses 8 and 9 of the time d1b is calculated as the luminance value 90. [

Subsequently, the image picked up by the first image pickup camera 5 at the time t2a is output as the luminance value B at the time d2a as 45. In addition, the luminance value C of this place is applied to the luminance value A of the immediately preceding pixel as 90. As a result, the portion corresponding to the addresses 8 and 9 of the time d2a is calculated as the luminance value 0. By performing the same processing sequentially and continuously for all the addresses, it is possible to reconstruct the whole image as a whole image showing the luminance value of the entire wafer W as shown in Fig. 9 (c).

As described above, even with an inexpensive imaging camera whose exposure time can not be adjusted, by using two imaging cameras, as in the main embodiment, the scanning rate of the imaging camera is not limited to the scanning rate, Imaging with the speed V2 can be realized.

(2) In the apparatus and method of the above embodiment, the first imaging camera 5 and the second imaging camera 6 may be configured to include a plurality of line sensors. In this case, the line sensors are arranged adjacent to the front and back in the main scanning direction, and the luminance values at the same address acquired by the respective line sensors are subjected to time delay integration processing (so-called TDI (Time Delay integration) processing) . This configuration may be implemented by a combination of a plurality of separate line sensors and a TDI circuit, or a so-called TDI camera (one integrated with the above configuration) that is generally available.

In the case of this configuration, the scan rate of the line sensor itself is subjected to time delay integration processing of the luminance values acquired by the plurality of sensors when the movement speed of the workpiece is the optimum movement speed V1, thereby realizing the high- . Therefore, when the luminance value of the work is low, it is preferable to perform inspection using such a camera. However, when the moving speed of the work does not coincide with the optimum moving speed V1, the timing of the time delay integration processing is not matched and predetermined acquired image data is not obtained. Therefore, in the modified example of the present invention, when the TDI camera is used, the following step S3 'is performed in place of the step S3' described above.

&Lt; Step S3 &gt; >

After the alignment processing of the wafer W and the movement to the initial position of the imaging start are completed, the image pickup unit 1 is moved and set to a predetermined height, and then the main scanning of the slider 16s of the second movable table 16 Imaging of the wafer W is started while the velocity V2 is set at a speed twice as fast as the optimum moving velocity V1 in the X-axis direction and scanned. At this time, the first imaging camera 5 and the second imaging camera 6 are constructed using, for example, a TDI camera equipped with a line sensor of four rows and a time delay integration processing circuit in the main scanning direction.

In the same manner as in the above-described first modification, the control unit 3 is configured to alternately transmit the trigger signal 1 and the trigger signal 2 to the first imaging camera 5 and the second imaging camera 6. In addition, the first imaging camera 5 and the second imaging camera 6 are configured to perform imaging while alternately overlapping the same part. Then, while moving the work to the main scanning speed V2, the two imaging cameras 5 and 6 are used to perform imaging.

Fig. 10 shows a luminance value 20 of an image pattern to be imaged, which is an image pattern divided into a matrix shape. Here, the blank part means that the luminance value is zero. The vertical axis indicates the imaging time t0 to t16, and the horizontal axis indicates the addresses (1-16) of the line sensor used for imaging.

If an image is constructed based on the measurement luminance value divided for each of the two imaging cameras 5 and 6, the following is obtained. For example, the first imaging camera 5 is at the position shown in Fig. 11 (a) at time t3, and is at the position shown in Fig. 11 (b) at time t5. The luminance data of the front end captured and acquired using the first line sensor group from the time t2 to the time t3 is sent to the subsequent stage by the TDI process and the image data of the second line sensor group captured and acquired using the second line sensor group from time t4 to time t5 And the luminance data of the succeeding stage is integrated. Then, the integrated value of the predetermined number of stages (two stages in the above example) is output to the outside as the luminance data of the imaging time for one time at time d2a. Then, when an image is formed based on a plurality of imaging output signals, as shown in Fig. 11 (c), a portion where the brightness value overlaps occurs.

On the other hand, the second imaging camera 6 is mounted to observe the imaging position of the first imaging camera 5 and the position shifted by one pixel in the main scanning direction. Therefore, the second imaging camera 6 observes the position shown in Fig. 12 (a) at time t4, and observes the position shown in Fig. 12 (b) at time t6. The luminance data of the front end captured and acquired using the first line sensor group from the time t3 to the time t4 is sent to the subsequent stage by the TDI processing, and the second line sensor group is picked up and acquired using the second line sensor group from time t5 to t6 And the luminance data of the succeeding stage is integrated. Then, the integrated value for a predetermined number of stages (two stages in the above example) is output to the outside as the luminance data of the imaging time for one imaging at time d2b. When an image is formed based on a plurality of imaging output signals, a portion having a luminance value overlapping occurs as shown in Fig. 12 (c).

When the image of the wafer W is reconstructed from the measured brightness value, the arithmetic processing unit 21 can reconstruct the desired whole image by performing the image reconstruction process similar to that of the first modification. Further, by performing TDI processing using a plurality of line sensors, it is possible to acquire image data in which luminance values are amplified as shown in Fig.

According to this configuration, a work can be picked up with higher sensitivity than when an image pickup unit composed of an image pickup camera having one line sensor is used.

(3) In the apparatus and method of the above embodiment, the relative positional relationship with the holding table 14 for each of the first imaging camera 5 and the second imaging camera 6 is detected by the sensor or the preliminary imaging of each imaging camera The relative displacement between the imaging cameras may be obtained from the positional relationship obtained through the above-described positional relationship, and the image may be corrected according to the displacement amount.

(4) In the apparatus and method of the above embodiment, the image pickup unit 1 is provided with two first image pickup cameras 5 and a second image pickup camera 6, but the present invention is not limited thereto. That is, two or more imaging cameras may be used. In this case, the moving speed of the second movable table 16 can be made high each time the number of the imaging cameras is increased. For example, the optimum moving speed V1 is set to the number of imaging cameras, and the slider 16s of the second movable table 16 is moved. It is also possible to set the exposure time of each imaging camera such that the scan rate is divided equally into a large number of minutes and the imaging timing is switched alternately at the divided timing.

Also in the case of using a TDI camera, the number of line sensors and number of pixels (number of stages) to be paralleled in the main scanning direction are set appropriately in accordance with the main scanning speed to be set and the desired degree of increase / decrease.

1: image pickup unit
2: inspection stage
3:
4:
5: First imaging camera
6: Second imaging camera
7: Lighting unit
13a: Line sensor (for first imaging camera)
13b: line sensor (for second imaging camera)
14: Holding table
15: First movable base
16: 2nd movable base
17: Third movable base
20:
21:

Claims (9)

A high-speed imaging method for picking up a work,
An image pick-up process for picking up an image of the work while relatively moving the image pick-up unit composed of a plurality of image pick-up devices provided with line sensors and the holding table holding the work relatively horizontally at a predetermined moving speed,
And an image reconstruction step of reconstructing an image of the work based on the luminance values acquired from the respective image pickup devices,
Wherein the imaging process adjusts the moving speed to a speed higher than an optimum moving speed determined from the resolution of the line sensor and the scan rate in accordance with the number of image pickup devices,
The scan rate is divided equally according to the number of the image pickup devices,
It is possible to perform the shuttering of the image pickup device at the start point of each scan rate by sequentially assigning the scan rate after division to the image pickup device and to capture the work while repeating cycles in which the exposure time of the image pickup device is adjusted within each scan rate Speed imaging method. A high-speed imaging method for picking up a work,
An image pick-up process for picking up an image of the work while relatively moving the image pick-up unit composed of a plurality of image pick-up devices provided with line sensors and the holding table holding the work relatively horizontally at a predetermined moving speed,
And an image reconstruction step of reconstructing an image of the work based on the luminance values acquired from the respective image pickup devices,
Wherein the imaging process adjusts the moving speed to a speed higher than an optimum moving speed determined from the resolution of the line sensor and the scan rate in accordance with the number of image pickup devices,
The scan rate is divided equally according to the number of the image pickup devices,
The scanning rate after division is sequentially assigned to the image pickup device, shuttering of the image pickup device is performed at the start point of each scan rate, and the exposure time of the image pickup device is exceeded beyond the scan rate after the division, And a luminance value obtained by averaging the luminance values acquired over a plurality of pixels by the number of pixels for each of the image pickup devices is stored in the storage section,
The image reconstruction process includes the steps of reading the luminance value in the order obtained from the storage unit, amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging, and calculating the luminance after the amplification at the current time from the luminance value of the pixel calculated immediately before And reconstructs the image of the work based on the luminance value obtained by subtracting the luminance value from the luminance value. A high-speed imaging method for picking up a work,
An image capturing process of capturing an image of the work while relatively moving the image capturing unit including a plurality of image sensors having the same plurality of line sensors and the holding table holding the work relatively horizontally at a predetermined moving speed,
And an image reconstruction step of reconstructing an image of the work based on the luminance values acquired from the respective image pickup devices,
The imaging process adjusts the moving speed to a speed higher than an optimum moving speed determined from the resolution of the line sensor and the scan rate in accordance with the line sensor of the image pickup device,
The scan rate is divided equally according to the number of line sensors of the image pickup device,
A cycle in which the scanning rate after division is sequentially assigned to the line sensor for each of the image pickup devices and shuttering is performed at the start point of each scanning rate and the exposure time for each line sensor is ended within the scanning rate after division In the process of picking up the work while repeating,
The workpiece is picked up while repeating an imaging cycle in which the same portions are overlapped alternately while shifting the imaging timings of the preceding imaging unit and the following imaging unit and the luminance values of the plurality of pixels acquired for each of the plurality of line sensors Is stored in the storage section as the luminance value for one pixel by the integral delay circuit,
The image reconstruction process includes the steps of reading the luminance value in the acquired order, amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging, subtracting the current luminance value after amplification from the luminance value of the pixel calculated immediately before, And reconstructs the image of the work based on the brightness value. 4. The method according to any one of claims 1 to 3,
A detecting process of detecting a relative positional relationship with the holding table for each of the plurality of image pickup devices,
And calculating a relative displacement between the image pickup devices from the positional relationship obtained in the detecting process,
Wherein the image reconstruction process reconstructs the image while correcting the position of the acquired image data based on the shift amount obtained in the calculation process. A high-speed image pickup apparatus for picking up a work,
A holding table for holding the work,
An illumination unit that irradiates light toward the work loaded on the holding table;
An image pickup unit comprising a plurality of image pickup devices each having a line sensor for picking up the work,
A horizontal drive mechanism for horizontally moving the holding table and the image pickup unit at a predetermined moving speed,
The scanning speed is adjusted to a moving speed faster than the optimal moving speed determined from the resolution of the line sensor and the scanning rate in accordance with the number of the image pickup devices and the scanning rate is evenly divided into a large number of parts of the image pickup device, A control unit for causing the imaging unit to perform shuttering at a start point of each scan rate and for imaging the work with a plurality of imaging units while repeating cycles in which the exposure time of the imaging unit is adjusted within each scan rate,
And an arithmetic processing unit for reconstructing an image of the work based on the luminance values acquired by the respective image pickup units. A high-speed image pickup apparatus for picking up a work,
A holding table for holding the work,
An illumination unit that irradiates light toward the work loaded on the holding table;
An image pickup unit comprising a plurality of image pickup devices each having a line sensor for picking up the work,
A horizontal drive mechanism for horizontally moving the holding table and the image pickup unit at a predetermined moving speed,
The scanning speed is adjusted to a moving speed faster than the optimal moving speed determined from the resolution of the line sensor and the scanning rate in accordance with the number of the image pickup devices and the scanning rate is evenly divided into a large number of parts of the image pickup device, And causes the imaging device to perform shuttering at the start point of each scan rate and to terminate the exposure time of the imaging device beyond the scan rate after the division so that the exposure time of the preceding imaging device and the following imaging device are overlapped, And a luminance value obtained by averaging the luminance values acquired over a plurality of pixels by the number of pixels for each of the plurality of pixels in a storage unit,
The luminance value obtained by amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging and subtracting the luminance value after amplification at the current time from the luminance value of the pixel calculated immediately before, And an arithmetic processing unit for reconstructing an image of the work based on the calculated value. A high-speed image pickup apparatus for picking up a work,
A holding table for holding the work,
An illumination unit that irradiates light toward the work loaded on the holding table;
An image pickup unit comprising a plurality of image pickup devices each having a plurality of line sensors for picking up the work;
A horizontal drive mechanism for horizontally moving the holding table and the image pickup unit at a predetermined moving speed,
The moving speed of the line sensor is adjusted to a moving speed faster than the optimum moving speed determined from the resolution of the line sensor and the scanning rate and the scanning rate is divided equally according to the number of line sensors of the image sensor, And the exposure time for each line sensor is terminated within the scan rate after the division is repeated, the process is terminated while repeating the cycle in which the scan rate after the division is sequentially assigned to the line sensor and shuttering is performed at the start point of each scan rate, In the process of picking up the work,
The image pickup device picks up the work while repeating an image pickup cycle in which the same image pickup section is shifted from the image pickup timing of the preceding image pickup device and the image pickup timing of the subsequent image pickup device so as to overlap the same portions alternately and the luminance of a plurality of pixels And stores the value as a luminance value for one pixel in the storage section by an integration delay circuit;
The luminance value obtained by amplifying the luminance value of the pixel at the calculation time point to the luminance value before the averaging and subtracting the luminance value after amplification at the current time from the luminance value of the pixel calculated immediately before, And an arithmetic processing unit for reconstructing an image of the work based on the calculated value. 8. The method according to any one of claims 5 to 7,
The image pickup unit includes a lens barrel for guiding light reflected from a work irradiated from the illumination unit or light transmitted through the work,
And an optical member that partially transmits light for guiding the barrel portion and reflects a part of the light by changing the angle to guide light to a plurality of image pickup devices. 9. The method according to any one of claims 5 to 8,
And a detector for detecting a position relative to the holding table for each of the plurality of image pickup devices,
The control unit includes a storage unit for storing position information detected by the detector,
The arithmetic processing unit reads the positional information acquired for each of the imaging units from the memory, obtains a relative displacement between the imaging units, and reconstructs the image while correcting the position of the acquired image data based on the displacement amount Speed imaging device.

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