JPH11326233A - Apparatus for inspecting material surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely take an image of a wafer sample, measure a count of defects, etc., and improve a throughput, by superposing and recording a predetermined count of image data to an image pickup element, and evaluating defects of an object to be inspected on the basis of the predetermined count of image data. SOLUTION: An image process apparatus 7 takes an enlarged image of a wafer sample 1 via an optical system of a microscope 4 while a strobe light 11 emits light. The enlarged view is recorded to a CCD which is an image pickup element of a TV camera 6. The enlarged view is recorded once while the strobe light 11 emits light five times. The image data of five times of the strobe light 11 stored in the CCD is sent from the CCD and preserved in an image record part set at the TV camera 6, then input to the image process apparatus 7. The image process apparatus 7 can accordingly process the image data of five emissions of the strobe light 11 at one time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material surface inspection apparatus for measuring and evaluating defects, scratches, foreign matter and the like on the surface of a crystalline material such as a silicon wafer and other materials.

[0002]

2. Description of the Related Art A conventional example will be described with reference to FIG. This device includes a sample stage 102, a microscope 104, a strobe light 111, a TV camera 106, an image processing device 107, a trigger generation device 112, and the like.

[0003] The sample stage 102 is a stage 10
A wafer sample 101 as a test object is fixed on 2a, and X is controlled by stage driving mechanisms 102b, 102c, and 102d provided integrally with the stage 102a.
It can move at high speed in (horizontal), Y (vertical), and Z (height) directions.

A microscope 10 is provided above the wafer sample 101.
4 are provided. The microscope 104 has a TV camera 1
06, a strobe light 111, and a microscope control unit 11 for controlling an automatic focusing mechanism of the microscope 104
4 is attached.

On the right side of the microscope 104, a strobe light 1 is provided.
The light emitted from the strobe light 111 is reflected by a half mirror (not shown), and irradiates the wafer sample 101 via the optical system of the microscope 104.

[0006] Above the microscope 104, the TV camera 10
6 is provided, and light from the surface of the wafer sample 101 enters through the half mirror.

[0007] An image processing device 107 is provided above the TV camera 106 and captures image data from the TV camera 106.

[0008] The trigger generator 112 connected to the image processing device 107 is a pulse motor controller 10.
A trigger signal for strobe light emission and image capture is generated based on the signal from 3. The trigger signal for strobe emission is output to the strobe driver 110, and the strobe light 111 emits a flash in response to this signal.
The trigger signal for image capture is transmitted to the image processing device 107.
The image processing device 7 captures image data from the TV camera 106 in response to this signal.

With this configuration, it becomes possible to capture an image of the surface of the wafer sample 101 in a high-speed moving state by a microscope as a still image.

[0010]

However, in the above configuration, the observation / inspection speed of the surface of the wafer sample 101 as the object to be inspected is determined by the moving speed of the wafer sample 101, the strobe light emission interval, and the still image of the wafer surface. Of these, the speed of capturing the slowest still image, that is, the speed at which the camera captures an image, depends on the speed of capturing the still image. Since this speed is 25 to 30 frames / sec in the NTSC system used in a normal TV camera, the surface inspection speed of the wafer sample is limited by this speed. In addition, since the speed of image processing in the image processing apparatus is even lower than the speed of image capture, this speed also limits the surface inspection speed of the wafer sample.

On the other hand, in order to solve this problem, it is conceivable to use a camera having a high image capturing speed. However, such a camera is expensive, so that the cost of surface inspection increases.

Accordingly, an object of the present invention is to provide a material surface inspection for observing and inspecting the surface of a wafer sample, to more quickly and surely capture an image of the wafer sample, and to measure the number of defects, scratches, foreign matter, and the like. An object of the present invention is to provide an inexpensive material surface inspection apparatus capable of improving throughput.

[0013]

According to the present invention, a stage on which a test object is mounted and movable, illumination means for illuminating the test object on the stage, and a stage mounted on the stage during the movement of the stage. When the detected object reaches a predetermined position, in synchronization with the predetermined position, synchronization control means for flashing the illumination means, imaging means for capturing an image of a part of the object as image data, and at least one imaging means And image processing means for evaluating a defect of the test object based on the image data. To evaluate the defect of the test object.

[0014]

FIG. 1 shows an apparatus according to a first embodiment.
This apparatus includes a sample stage 2, a microscope 4, a strobe light 11, a TV camera 6, an image processing device 7, and the like.

The sample stage 2 includes a stage 2a,
The electric stage drive mechanisms 2b, 2c, and 2d are provided integrally. The wafer sample 1, which is the test object,
It is fixed on the sample stage 2a by a vacuum chuck (not shown). Stage drive mechanism 2b, 2
The pulse motor controller 3 is connected to c and 2d via a pulse motor driver 13. The pulse motor controller 3 is connected to the computer 8 and, based on signals from the computer 8, sends pulse motor drivers 13 a stage drive mechanism 2b, 2c,
A signal for controlling 2d drive timing is output.
The pulse motor driver 13 receives the signals from the pulse motor controller 3 and outputs the signals to the stage driving mechanisms 2b and 2b.
By controlling the operation of the stage 2a by driving c, 2d in the X (horizontal), Y (vertical), and Z (height) directions, the measurement point on the wafer sample 1 can be moved quickly and within the field of view of the microscope 4. The position of the stage 2a on which the wafer sample 1 is mounted is controlled so as to be precise. Further, the stage 2 a can put any place of the wafer sample 1 within the visual field of the microscope 4.

A microscope 4 is provided above the sample stage 2.
Are provided, and the surface state of the wafer sample 1 can be observed. The microscope 4 is provided with a strobe light 11, a TV camera 6, and a microscope control unit 14. The microscope control unit 14 controls an automatic focusing mechanism of the microscope 4.

The strobe light 11 is provided so as to irradiate the wafer sample 1 with the light via the optical system of the microscope 4. The pulse motor controller 3 is connected to the strobe light 11 via a strobe driver 10 and a trigger generator 12. The pulse motor controller 3 outputs a signal to the trigger generator 12 based on a signal from the computer 8. The trigger generating means 12 outputs a trigger signal to the strobe driver 10 in synchronization with the position control of the stage 2a by the stage driving mechanisms 2a, 2b, 2c based on the signal from the pulse motor controller 3. The strobe driver 10 causes the strobe light 11 to emit light at intervals set by the computer 8 based on the trigger signal. Here, referring to FIG. 2, the light emitted from the strobe light 11
Will be described. FIG. 2 is an enlarged view of a main part of a portion such as the strobe light 11, the microscope 4, and the TV camera 6 of the apparatus of FIG. Here, a half mirror 15 is provided in the optical system of the microscope 4 in the optical path of the light from the strobe light 11. Therefore, the light emitted from the strobe light 11 is incident from the horizontal direction by the half mirror 15, and is mostly reflected, and irradiates the wafer sample 1 as an object to be inspected via the optical system of the microscope 4. The light from the surface of the wafer sample 1 due to the irradiation light is
Since the light enters the half mirror 15 in the vertical direction, most of the light passes through and enters the TV camera 6.

A TV camera 6 is provided in the optical system of the microscope 4, and the TV camera 6 has a CCD (charge coupled device) as an image pickup device. The light from the strobe light 11 reflected on the surface of the wafer sample 1 is reflected by the half mirror 15
And enters the TV camera 6, whereby the surface state of the wafer sample 1 is recorded on the CCD.

An image processing device 7 is connected to the TV camera 6 to control the operation of the TV camera, while taking in image data from the TV camera 6 and cooperating with a computer 8 on the basis of the image data. The measurement and evaluation of the defect of the sample 1 are performed. The image processing apparatus is connected to the trigger generator 12 via a counter 16. Counter 1
A counter 6 counts the number of trigger signals from the trigger generator 12 and outputs a signal indicating the timing of image capture to the image processor 7 every time five trigger signals are input. Based on this signal, the image processing device 7
Causes the TV camera 6 to operate, and causes the photographing of the surface state of the wafer sample 1 to be performed once each time the strobe light 11 emits light five times.

With such a configuration, by adjusting the timing of strobe light emission and imaging, a microscope image of the surface of the wafer sample 1 in a high-speed moving state can be captured as a still image. Also, for example, if the strobe light 11 emits light five times during one image pickup, the CCD
Since five still images of strobe light are superimposed on each other, the surface state of the wafer sample at five positions can be recorded by one image capture, and the image processing can be performed only once. Therefore, in the material surface inspection for observing and inspecting defects, scratches, foreign matter, etc. on the surface of the wafer sample, the image of the wafer sample can be captured faster and more reliably, and defects, scratches,
By measuring the number of foreign substances and the like, the throughput can be improved.

The process of inspecting the wafer sample surface by the present apparatus will be described below. First, the wafer sample 1 is set on the stage 2a of the sample stage 2. The computer 8 instructs the pulse motor controller 3 to output a predetermined pulse signal. The pulse motor controller 3 sends a pulse to each of the pulse motors (not shown) for the stage driving mechanisms 2b, 2c and 2d based on a command from the computer 8 so that the stage 2a continuously moves at a high speed in a predetermined direction. Output a signal. Thus, the stage 2a moves continuously.

The trigger generator 12 generates a trigger signal for strobe light emission and image capture based on a pulse signal output from the pulse motor controller 3. Specifically, a trigger signal is generated by extracting a pulse signal for driving the stage 2a by the stepping motor from the pulse motor controller 3 and dividing the frequency of the pulse signal. The stepping motor is
One step is advanced by the pulse signal. When the stage 2a advances by 1 μm due to input of one pulse signal, a signal obtained by dividing the frequency of the pulse signal by 1/1000 is used as a trigger signal.
μm), the trigger signal is output from the trigger generator 12 every time the movement proceeds. In response to the trigger signal, the strobe driver 10 causes the strobe light 11 to emit light once. In the image processing device 7, the strobe light 11
A trigger signal having the same timing as the trigger signal for light emission is input to the counter 16, and every time the number of trigger signals becomes five, a trigger signal for capturing image data is issued from the counter 16, and in response to the trigger signal Image data is taken in from the TV camera 6.
The speed of capturing the image data is determined according to the desired measurement range of the wafer sample 1, and the moving speed of the sample stage 2a is determined by the speed. When the counter 16 of the present embodiment is used, the image data capturing speed is at most five times the image capturing speed of the TV camera 6.

The image data is captured by the image processing device 7 by first obtaining an enlarged image of the wafer sample 1 through the optical system of the microscope 4 under the emission of the strobe light 11, and using this enlarged image to the image sensor of the TV camera 6. The enlarged image is recorded once for five times of light emission of the strobe light 11. The image data of five flashes of the strobe light 11 stored in the CCD is stored in the CCD.
, An image recording unit (not shown) provided in the TV camera 6
And then input to the image processing device.
Since the image data can be stored in the image recording section in a time sufficiently shorter than the flash emission interval, recording of the enlarged image of the wafer sample on the CCD is not interrupted every five flashes, but is continuously performed. It is possible to perform it. Further, the image processing apparatus can process image data for five times of emission of the strobe light 11 at one time.

In this embodiment, the recording of the image data on the CCD employs an integrating method. In other words, the surface states of the five measurement positions on the wafer sample 1 are superimposed and recorded on one CCD by the five light emissions while the stage 1 is moving. In a CCD recorded by this method,
When a defect or the like overlaps at the same position among the measurement positions on the wafer sample 1, the image data is recorded as having a higher luminance than a position where the defect does not overlap.
The image data recorded on the CCD is subjected to image processing in the image processing device 7 and the computer 8, and the distribution, number, shape, density, and the like of the crystal defects are measured (calculated).

The above processing is performed continuously while moving the wafer sample 1. For example, as shown in FIG. 3, the wafer sample 1 is continuously moved so that each rectangular region 41 observed by one irradiation of the strobe light 11 is observed in the order shown by the arrow 42. The above measurement is performed in the meantime. The stage 2a moves continuously, without stopping, captures image data by emitting light from the strobe light 11, and performs image processing (measurement) while the stage is moving.・ Does not stop repeatedly. Therefore, since the image processing speed can be increased, the moving speed of the stage 2a can be increased to the image processing speed.

A modified example will be described below. Although the movement control of the sample stage is performed in three axes of XYZ, in order to know the distribution of crystal defects, the movement is not limited to the movement (scan of the surface) as shown in FIG. is there. For example, as shown in FIG. 4, while rotating the sample stage 2a, the objective lens 4a of the microscope 4 is moved in a direction away from the center of the wafer sample 1 as indicated by an arrow 20, and an image is captured. You may make it measure and evaluate. In this case, the stage 2a is rotated at a high speed at a constant speed, and the objective lens 4a is moved stepwise in the direction of arrow 20 for each width of the visual field range.
An image for one round of a is sampled and captured by the strobe light 11.

In this embodiment, a pulse motor is also used as the stage drive system. However, the present invention is not limited to this, and various drive systems such as a servo motor or an ultrasonic motor can be used.

Further, the function of the trigger generator 12 for generating the timing signal may be substituted by the computer 8 to generate the trigger signal by the computer. Also,
The trigger generator 12 may be built in a stage drive controller (not shown) or a strobe driver. An encoder or a sensor may be attached to the stage 2a or the motor, and a trigger signal may be generated from the signal.

Although the trigger signal is output in accordance with the position information output from the pulse motor controller 3, the present invention is not limited to this, and the image data may be captured and measured at predetermined time intervals from the measurement start time. It may be.

The counting of the trigger signal may be performed in the image processing device 7. In the present embodiment, the counter 16 counts the trigger signal. However, the computer 8 adjusts the signal output to the pulse motor controller 3 and the image processing device 7 so that the strobe light 11 is emitted every five times. May be performed once.

Alternatively, a plurality of TV cameras may be arranged, and an enlarged image of the wafer sample 1 may be recorded on all the cameras at the same time. With such a configuration, a wide range of wafer samples can be inspected at a time, and a faster material surface inspection can be performed.

Next, a second embodiment will be described with reference to FIG. In this example, five TV cameras 56 are provided, which are one in the first embodiment. When capturing the image data, the TV camera 56 that records the image data is switched every time the strobe light 11 emits light five times, and the image data is sequentially recorded on each of the five TV cameras 56. Switching of the TV camera 56 is performed by the trigger generation circuit 1
2 is performed by the TV camera controller 58 connected to the TV camera 56 in response to the trigger signal from the TV camera 2. Each TV
The image data recorded on the CCD of the camera 56 is sequentially input to the image processing device 7 simultaneously with or immediately after the switching of the camera.

In this configuration, one TV camera 56
After recording image data to the other four TV cameras 5
6, the transfer time of the image data from the TV camera 56 to the image processing apparatus can be made longer than in the case where only one TV camera is used. Therefore, it is possible to make the light emission interval of the strobe light 11 shorter than in the case of a single TV camera 56, and to capture images of defects, scratches, foreign matter, etc. on the surface of the wafer sample 1 more quickly and reliably. It is possible to provide an inexpensive material surface inspection apparatus capable of measuring the number of defects, scratches, foreign matter, and the like and improving the throughput. Other configurations and effects are the same as those of the first embodiment.

[0034]

According to the present invention, in a material surface inspection for observing and inspecting the surface of a wafer sample, an image of the wafer sample is captured more quickly and more reliably, and the number of defects, scratches, foreign matter, etc. is measured. A material surface inspection apparatus capable of improving the throughput can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a surface inspection apparatus according to a first embodiment of the present invention.

FIG. 2 shows a strobe light, a microscope and a T of the apparatus of FIG.
It is a principal part enlarged view of a part, such as a V camera.

FIG. 3 is a plan view showing a state of measuring a defect of a wafer as a test object.

FIG. 4 is a perspective view showing an example of the operation of the sample stage and the microscope.

FIG. 5 is a schematic configuration diagram of a surface inspection apparatus according to a second embodiment of the present invention.

FIG. 6 is a schematic configuration diagram of a surface inspection apparatus according to a conventional example.

[Explanation of symbols]

 Reference Signs List 1 wafer sample 2 sample stage 3 pulse motor controller 4 microscope 6 TV camera 7 image processing device 8 computer 11 strobe light 12 trigger generator 16 counter 56 TV camera

Claims (2)

[Claims] 1. A material surface inspection apparatus for observing and inspecting the surface of a test object, comprising: a movable stage mounted with the test object; and illumination means for illuminating the test object on the stage. When the test object mounted on the stage reaches a predetermined position during the movement of the stage, synchronous control means for flashing the illumination means in synchronization with the predetermined position; and a part of the test object. An imaging unit that captures an image as image data, wherein the imaging unit includes at least one image sensor, and a predetermined number of the image data are superimposed and recorded on the image sensor; A material surface inspection apparatus, comprising: image processing means for evaluating a defect of an object; and evaluating the defect of the test object based on the predetermined number of image data. 2. A material surface inspection apparatus for observing and inspecting the surface of a test object, comprising: a stage on which the test object is mounted and movable; and illumination means for illuminating the test object on the stage. When the test object mounted on the stage reaches a predetermined position during the movement of the stage, synchronous control means for flashing the illumination means in synchronization with the predetermined position; and a part of the test object. A plurality of imaging means for capturing an image as image data, an imaging means switching means for sequentially switching the plurality of imaging means, and an image processing means for evaluating a defect of the test object based on the image data, A predetermined number of the image data are superimposed and recorded on the imaging elements of the plurality of imaging units, respectively. The first imaging unit on which the predetermined number of image data is recorded is:
The image data recorded in the first image capturing means is switched to the second image capturing means by the image capturing means switching means, and the image data recorded in the first image capturing means is concurrently recorded with the image data in the second image capturing means after the switching. A material surface inspection apparatus that outputs the defect to the object to be inspected based on the image data.