JPH04348050A - Material surface inspection apparatus - Google Patents

Abstract

PURPOSE:To increase a moving speed of a stage and very easily and appropriately input an image data without stopping the stage for this purpose by synchronously irradiating a light beam and fetches an image data when a test specimen placed on the stage reaches the predetermined position. CONSTITUTION:In order to fetch image data by an image processing apparatus 7, an image of specimen 1 enlarged by a microscope 4 is obtained under irradiation of light from a strobe 11. This enlarged image is input to an image processing apparatus 7 as image data via a TV camera 6. Next, the image data is processed by the image processing apparatus 7 and a computer 8 to measure (calculate) distribution, number, shape and density of crystal defects. In this case, the stage 2 is moving continuously. Therefore, defects of test specimen can be measured and evaluated at a high speed and thereby the processing capability of apparatus can be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a material surface inspection device that can quickly and reliably measure and evaluate defects on the surface of crystalline materials and other materials.

[Prior Art] Conventionally, apparatuses for measuring and observing defects on the surface of crystal materials such as semiconductor wafers and other materials are known. For example, JP-A No. 60-101942 and JP-A No. 6
Publication No. 2-33744 discloses an apparatus for measuring and observing defects such as etch pits (indentations or grooves caused by crystal defects) that occur when a wafer-shaped sample (subject) is subjected to processing such as etching. has been done.

FIG. 19 shows a schematic configuration of a conventional apparatus for measuring and observing defects in this type of crystalline material.

In the figure, numeral 1 indicates a wafer sample subjected to processing such as etching as an evaluation measurement object (subject), and numeral 2 indicates a stage on which this wafer sample 1 is placed.

This stage 2 can be moved in the vertical direction (X direction, perpendicular to the paper surface of the figure), horizontal direction (Y direction, horizontal direction of the figure), and height direction (Z direction, vertical direction of the figure). , drive mechanisms (stages in each direction) 2b, 2c, and 2d having pulse motors (stepping motors) and the like. 3 is each stage 2b, 2c, 2 in X, Y, two directions
d is a pulse motor controller that sends out a drive signal to each pulse motor; 13 is a pulse motor driver that outputs a pulse signal to the pulse motor based on a drive signal from the pulse motor controller 3;

Reference numeral 4 indicates a microscope for observing and measuring the wafer sample 1 placed on the stage 2. This microscope 4 includes an illumination lamp (halogen lamp) that is a light source for illuminating the sample 1.
5, and a TV camera 6 for taking still images of sample 1.
is installed. Reference numeral 14 indicates a microscope control unit that controls the automatic focusing mechanism of the microscope 4.

Further, 7 is an image processing device that inputs still image data from the TV camera 6 and evaluates defects such as etch pits on the sample 1 based on this image data; 8 is the stage 2;
pulse motor controller 3 and image processing device 7
A computer that sends and receives data and commands to and from computers, etc., and instructs processing of captured image data.

Reference numeral 9 denotes a monitor for displaying image data taken into the image processing device 7.

In the conventional apparatus having the above configuration, the surface of the sample is inspected as follows.

First, sample 1 is set on stage 2. The computer 8 gives commands to the pulse motor controller 3,
The stage 2 is moved so as to stop at a preset position. Then, under the illumination of the illumination lamp 5, an enlarged image of the sample 1 through the microscope 4 is obtained. This enlarged image is T
The image is input as image data to the image processing device 7 via the V camera 6. Next, the image processing device 7 and computer 8 process this image data to measure (calculate) and evaluate the distribution, number, shape, density, etc. of crystal defects.

When the above processing is completed, the stage 2 is moved to the next measurement position of the sample 1, and the same processing as described above is repeated in a stationary state. In this manner, defects in the wafer sample are measured and evaluated.

FIG. 20A shows how the entire surface of the wafer sample 1 is measured. Each rectangle 41 is an observation range where an enlarged image can be obtained through the microscope 4, in other words, an area where image data can be captured at once (for example, 0.5 mm x 0.5 m).
m or a range of about 1 mm x 1 mm). The stage 2 is moved and each rectangular area 41 serving as an observation range is sequentially measured in the order shown by the arrow 42, thereby measuring defects on the entire surface of the wafer sample 1.

FIG. 20B shows how a predetermined location on the wafer sample 1 is measured. Each rectangle 43 indicates an observation range in which an enlarged image can be obtained through the same microscope 4 as the rectangle 41 in FIG. 20A. The stage 2 is moved to sequentially measure each rectangular area 43 serving as an observation range, and defects in these areas of the wafer sample 1 are measured.

[Problems to be Solved by the Invention] However, in the conventional material surface inspection apparatus as described above, when acquiring image data, the stage 2 is temporarily stopped;
Since image data is processed during the stop period, the moving speed of the stage 2 cannot be increased. Furthermore, the time for moving the stage and the time for processing image data are separate. Therefore, the measurement time for one sample is long, and the throughput of the apparatus is low, especially when measuring the entire wafer as shown in FIG. 20A. For example, when measuring the entire surface of a semiconductor wafer with a diameter of 6 inches using a conventional commercially available device, it took approximately 10 hours to measure the entire surface of a semiconductor wafer.

Furthermore, if there is foreign matter such as dust on the wafer sample, or if there are scratches on the wafer sample,
It was difficult to distinguish between these and the etch pits to be inspected. Although it is conceivable that the image processing device 7 or computer 8 recognizes the shapes of etch pits and other pits in order to prevent these dusts and scratches from causing measurement errors, it is not possible to sufficiently distinguish between them.

In view of the above-mentioned circumstances, the present invention increases the moving speed of the stage and allows required image input to be performed extremely easily and appropriately without having to stop the stage for image input. The purpose is to obtain a surface inspection device. Another object of the present invention is to provide a material surface inspection device that can reliably distinguish between etch pits and other objects without error even when there are foreign objects such as dust or scratches on the surface of the object to be inspected. .

[Means for Solving the Problems] A material surface inspection device according to the present invention is a material surface inspection device that observes and inspects the surface of a flat plate-shaped object, and is movable with the object placed thereon. a stage, an illumination means for illuminating a subject on the stage, an imaging means for capturing an image of a part of the subject as image data, and an image processing means for evaluating defects in the subject based on the image data. , synchronization control means for flashing the illumination means and capturing image data by the imaging means in synchronization with the stage when the subject placed thereon reaches a predetermined position during movement of the stage; It is characterized by comprising the following.

Instead of flashing the illumination means and capturing the image data in synchronization with the position of the subject, the illumination means may be flashed and the image data captured at predetermined time intervals from the time the stage starts moving.

The present invention also provides a material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, in which illumination light of a plurality of different wavelengths is incident on the surface of the object from different predetermined directions. an illumination means for illuminating the surface of the subject;
The apparatus includes an imaging means for capturing images of the object to be inspected using illumination light of a plurality of different wavelengths as image data for each wavelength, and an image processing means for evaluating defects in the object based on the image data for each wavelength. It is characterized by

Furthermore, the present invention is a material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, which includes a stage on which the object is placed and movable, and a plurality of illumination lights of different wavelengths applied to the stage. illumination means for illuminating the surface of the subject by illuminating the surface of the subject from different predetermined directions; an imaging means for capturing the image data as image data; an image processing means for evaluating the defect of the object based on the image data for each wavelength; The present invention is characterized in that it includes synchronization control means for flashing the illumination means and capturing image data for each wavelength by the imaging means in synchronization with this.

Similarly to the above, instead of flashing the illumination means and capturing image data in synchronization with the position of the subject, the illumination means flashes at predetermined time intervals from the start of stage movement and image data is captured. Good too.

The image processing means evaluates defects in the object by calculating, for example, an exclusive OR between each wavelength-based image data.

The stage preferably includes a stage plate on which the subject is placed, and a drive mechanism that moves the stage plate at high speed. Further, as the illumination means, for example, a strobe light is used. The imaging means preferably includes a microscope having an automatic focusing mechanism and an imaging element attached to the microscope.

[Function] According to the present invention, while moving the test object such as a wafer sample placed on the stage at high speed, when the test object placed on the stage reaches a predetermined position or at a predetermined time interval. Then, the illumination means can be flashed and at the same time image data can be taken in as a still image by the imaging means. By image processing this image data, it is possible to automatically and highly efficiently measure and evaluate defects in a wafer sample.

Furthermore, if illumination lights of a plurality of different wavelengths are made incident on the surface of the object from different predetermined directions, and defects on the object are evaluated based on the image data obtained for each wavelength, it is possible to Measurement errors due to dust or scratches on the specimen can be eliminated as much as possible.

[Example] Hereinafter, the present invention will be described in detail using an example shown in the drawings.

FIG. 1 shows a schematic configuration of a material surface inspection apparatus according to a first embodiment of the present invention. In this figure, the same or corresponding parts as in FIG. 19 described above are given the same numbers, and the explanation thereof will be omitted.

In FIG. 1, 2a is a sample stage with a vacuum chuck for fixing the wafer, 2b, 2c, 2
d shows electric stage drive mechanisms in the X, Y, and Z directions each having a pulse motor. Sample stage 2a
has a built-in rotational drive mechanism (not shown) in the θ direction (rotation direction around the Z direction). These drive mechanisms move the stage in X (vertical direction), Y (horizontal direction), Z (height direction), and θ.
(rotation direction) at high speed.

Such stage drive mechanisms 2a, 2b, 2c, 2d,
The stage 2 can be precisely moved by the pulse motor driver 13 and the pulse motor controller 3 so that any part of the wafer sample 1 is within the field of view of the microscope 4.

The microscope 4 is equipped with a TV camera 6, a strobe light 11, and a microscope control unit 14 that controls the automatic focusing mechanism of the microscope 4.

FIG. 2 is a sectional view schematically showing the strobe light 11, microscope 4, TV camera 6, and other parts of the apparatus shown in FIG. 15 indicates a half mirror.

The light emitted from the strobe light 11 passes through the half mirror 1
5 and is irradiated onto the wafer sample 1, which is the object to be inspected, through the optical system of the microscope 4. Light from the wafer sample 1 passes through the half mirror 15 and enters the TV camera 6.

Referring again to FIG. 1, 12 indicates a trigger generating device.

The trigger generator 12 is connected to the pulse motor controller 3
Trigger signals for strobe light emission and image capture are generated based on the signals extracted from the . A trigger signal for strobe light emission is output to the strobe driver 10, and in response, the strobe driver 10 causes the strobe 11 to flash.

A trigger signal for capturing an image is output to the image processing device 7, and in response to this, the image processing device 7 captures image data from the TV camera 6. Therefore, in synchronization with the strobe flash timing, an instantaneous microscope image of the wafer surface while the wafer sample 1 is moving at high speed is captured as a still image. The image processing device 7 cooperates with the computer 8 to measure and evaluate defects in the sample 1 based on this image data.

In the apparatus having the above configuration, the surface of the sample 1 is inspected as follows.

First, sample 1 is set on stage 2. The computer 8 instructs the pulse motor controller 3 to output a predetermined pulse signal.

Based on instructions from the computer 8, the pulse motor controller 3 causes the stage 2 to move continuously at high speed in a predetermined direction (for example, as shown in FIG. 20A, a rectangular area 41 that is an inspection range is A pulse signal is output to each pulse motor of stage 2 so that the measurements are sequentially performed in the following order. This results in stage 2
moves continuously (i.e. not in steps).

The trigger generator 12 generates a trigger signal for strobe light emission and image capture based on the pulse signal output from the pulse motor controller 3. in particular,
A pulse signal for driving a motor (for driving a stage) is extracted from a pulse motor (stepping motor) controller 3, and a trigger signal is generated by dividing the frequency of this pulse signal. The stepping motor advances one step by one pulse signal. For example, in a 10-phase stepping motor, when one predetermined pulse signal is input, the motor rotates by 1/10. Assuming that the stage advances 1 μm by inputting one pulse signal, and if a signal obtained by dividing this pulse signal by 1/1000 is used as a trigger, a trigger signal is generated from the trigger generator 12 every time the stage 2 advances 1 mm (1000 μm). is output. In response to this trigger signal, the strobe driver 10 controls the strobe 1.
1 to emit light, and the image processing device 7 captures image data. In this case, regardless of the moving speed of the stage 2, image data is captured according to the moving distance of the stage 2 (that is, the position of the stage 2).

The image processing device 7 captures image data by first obtaining an enlarged image of the sample 1 through the microscope 4 under the light emission of the strobe 11, and transmitting this enlarged image to the image processing device 7 as image data via the TV camera 6. input. Next, the image processing device 7 and computer 8 process this image data to measure (calculate) the distribution, number, shape, density, etc. of crystal defects.

The above processing is performed continuously while moving the sample 1. For example, as shown in FIG. 20A, the sample 1 is continuously moved so that each rectangular area 41, which is the observation range, is observed in the order indicated by the arrow 42, and the above measurements are performed while moving. .

In this manner, defects in the wafer sample 1 are measured.

The stage moves continuously and does not stop; the image data is captured by strobe light, and image processing (measurement) is performed while the stage is moving, so the stage moves and stops repeatedly as in conventional models. Since the image processing is performed while the stage is moving, the processing speed is increased. The moving speed of the stage can be increased up to the processing speed of image processing, and the overall processing speed almost depends on the image processing speed. If an attempt is made to increase the processing speed in the conventional example described above, the stage must repeatedly accelerate and stop suddenly, resulting in a large-scale apparatus. It is also possible to capture image data by continuously moving the stage without using a strobe as in the conventional example, but the image would flow (resembling a so-called blurred photograph) and measurement would not be possible.

It should be noted that, when measured with the conventional apparatus described above, the processing time per screen was 1 to 2 seconds, but in the apparatus of the above embodiment, it was 11/10 to 2/10 seconds per screen.

Although the movement of the sample stage 2a on which the wafer sample 1 is placed is controlled in the three axes of XYZ, the movement is not limited to the above movement (scanning the surface) in order to know the distribution of crystal defects. , various modifications are possible. for example,
As shown in FIG. 3, while rotating the sample stage 2a, the objective lens 4a of the microscope 4 is moved horizontally or vertically from the center of the wafer 1 to capture images, and crystal defects in the wafer 1 are measured and evaluated. You can. in this case,
The stage is rotated at a high speed at a constant speed, the objective lens is moved horizontally in steps by the width of the field of view, and at each position, one revolution's worth of images is sampled and captured using a strobe. The captured image looks like a collection of ring-shaped data.

Further, in the drive system of the stage 2, a pulse motor is used in this embodiment, but the present invention is not limited to this, and various drive systems such as a servo motor or an ultrasonic motor can be used.

Furthermore, the computer 8 may be substituted for the function of generating the timing signal of the trigger generator 12, and the computer 8 may generate the trigger signal.

Further, the trigger generation device may be built into the stage drive controller 3 or the drive circuit section 10 of the strobe 11. Encoder (sensor) in the stage part (motor part)
A trigger signal may be generated from that signal.

Furthermore, 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 image data may be captured and measured at predetermined time intervals from the measurement start point.

Furthermore, although image input using a strobe has been described here, a mechanism that achieves the same effect without using a strobe may be provided. For example, the exact same effect can be obtained using a shutter camera in which the image sensor has an electrical shutter function in a solid-state imaging camera such as a CCD, or a TV camera with a high-speed shutter in front of the image sensor. .

Next, a second embodiment will be described with reference to FIGS. 4 to 18.

FIG. 4 shows a schematic configuration of a material surface inspection apparatus according to a second embodiment of the present invention. In this figure, the same or corresponding parts as in FIG. 19 described above are given the same numbers, and the explanation thereof will be omitted.

In FIG. 4, 2a is a sample stage with a vacuum chuck for fixing the wafer, and 2e is a θ stage drive mechanism that rotates the sample stage 2a in the θ direction (rotation direction around the Z direction). The θ stage drive mechanism 2e includes an electric stage drive mechanism 2b in the X, Y, and Z directions,
It is constructed on top of 2c and 2d. Such stage drive mechanisms 2b, 2c, 2d, pulse motor driver 1
3. Using the pulse motor controller 3, set any part of the wafer sample 1 within the field of view of the microscope 4.
Stage 2 can be moved precisely. Furthermore, by rotating the sample 1 and changing the angle, the direction of the irradiation light and the direction of the defect, which will be described below, can be matched.

The microscope 4 is provided with an optical system 17 for irradiating monochromatic light of different wavelengths from a specific direction. The light source 5 is a general halogen lamp, and dark field illumination (described later) using color filters and slits in the optical system 17 realizes irradiation of monochromatic light of different wavelengths from a specific direction as described above. There is. The TV camera 6 is a color TV camera, and can capture images for different wavelengths of monochromatic light of different wavelengths as irradiation light.

The image data of the color microscope image obtained by such illumination and the TV camera 6 is input to the image processing device 7, and the image processing device 7 and computer 8 process the wafer sample 1.
A measurement evaluation of defects is performed.

Before explaining the operation of the apparatus shown in FIG. 4 in detail, etch pits, which are defects appearing on the surface of a wafer sample, will be explained.

Etch pits that appear on the surface of a wafer sample often have only one specific surface. For example, silicon (Si)
The stacking fault etch pit on the surface (100) of the wafer is long in the direction parallel to the surface (110), and the surface (100) is 11
It is formed by a surface with an angle of about .

FIG. 5 shows stacking faults (OSF) caused by oxygen on the surface of the Si wafer 50. FIG. 6 shows a scanning electron microscope (SEM) image of an OSF etch pit on the surface of a Si wafer, and FIG. 7 shows a SEM image of one etch pit. FIG. 8 shows a sectional view taken along line L-L' in FIG. Note that the actual size of the etch pit is about 2 to 3 .mu.m in width and about 10-odd .mu.m in length, and is shown enlarged in FIG.

In FIGS. 5 to 8, in the case of stacking faults (OSF) caused by oxygen in the Si wafer 50, there are 5 etch pits.
Only crystal planes in four directions, 1a, 51b, 51c, and 51d, appear. Therefore, by applying irradiation light in one direction, it is possible to observe only the crystal plane in one direction.

FIG. 9 shows etch pits 51 on the surface of a Si wafer 50.
This figure shows how light of different wavelengths is irradiated from two different directions. Reference numeral 52 indicates an optical system such as an objective lens of the microscope 4 (FIG. 4), and 53 indicates an objective lens. The optical system 52 includes a mirror 56 for changing the optical path of the irradiated light near the objective lens 53;
It is equipped with 57.

In the apparatus of this embodiment, a beam 54 of red irradiation light and a beam 55 of blue irradiation light are introduced into an optical system 52 and reflected by mirrors 56 and 57, respectively, as shown in the figure. As a result, the red light beam 5 is directed to the surface of the Si wafer 50 from another direction.
4 and a blue light beam 55 are made incident. It is assumed that an etch pit 51 exists at the incident position of each of the light beams 54 and 55 on the surface of the Si wafer 50. As described above, a specific crystal plane appears as the etch pit 51. When the etch pit 51 consists of a surface 58 and a surface 59 as shown in FIG. 9, the blue light beam 55 entering from the left side of the figure is reflected by the surface 59 of the etch pit 51 and enters the surface 58. Since the surface 58 is substantially perpendicular to the surface of the Si wafer 50, this blue light will not reach the objective lens 53 thereafter. on the other hand,
A red light beam 54 entering from the right side of the figure is reflected by the surface 59 of the etch pit 51, and is directed upward toward the objective lens 59.
3. Then, it is detected as red reflected light 60.

FIG. 10 shows a partial sectional view of the optical system 17 and microscope 4 of FIG. 4. In the figure, the light source 5 has a halogen lamp 61. Optical system 17 includes a condensing lens 62 and a filter 64. The microscope 4 has a half mirror 78
, objective lens 53, mirrors 56, 5 for changing the optical path of the irradiated light.
7. It has a condensing lens 63. Instead of the filter 64, a similar filter may be installed at the position numbered 65.

FIG. 11 shows filter 64 (or 65). The filter 64 has a light-blocking region 73 in the center and a light-blocking region 74 in the periphery. 75a to 75d are four transmitted light regions that transmit light of a predetermined wavelength. In this embodiment, regions 75a and 75c transmit red light flux, and regions 75b and 75
d is designed to transmit blue light beams.

With reference to FIGS. 10 and 11, a method of making two lights, red and blue, incident on the surface of the wafer 50 from different directions will be described.

Light (white) emitted from the lamp 61 of the light source 5 becomes a parallel light beam 71 by the condenser lens 62 and enters the filter 64 . The light transmitted through the regions 75a to 75d of the filter 64 becomes light beams 76 and 77 having a ring-shaped cross section in which red and blue are alternately adjacent to each other in every quarter region, and reaches a half mirror 78. The light beams 76 and 77 are reflected by a half mirror 78,
The light is further reflected by optical path changing mirrors 56 and 57 and reaches the wafer 50. In the manner described above, light having different wavelengths (red and blue) is incident on the surface of the wafer 50 from different directions.

As described above, only the light incident from a predetermined direction is incident on the objective lens 53 as reflected light due to the form of the etch pit. This reflected light passes through the half mirror 78 and reaches the imaging surface 80 of the TV camera 6 via the condensing lens 63. This allows the TV camera 6 to acquire image data. Since the TV camera 6 is a color camera, it is possible to separately obtain image data of red reflected light and image data of blue reflected light.

In the configuration shown in Fig. 10, a filter is installed at the position numbered 64 or 65 to separate the light incident on the wafer, but a filter is installed at the position numbered 81 to separate the reflected light. You can.

The image data of the reflected light for each wavelength obtained as described above is added to the image data of FIG. 4 in the image processing device 7 and the computer 8, so that all defects can be observed.

On the other hand, when light is irradiated onto foreign matter such as dust on the wafer surface, it appears in the image no matter which direction the light is irradiated. From the above, by performing an exclusive OR (EX-OR) between the images obtained from the irradiation light in four directions, it is possible to erase only foreign matter such as dust on the wafer surface from the screen, or simply remove it from the screen. The image level of the foreign object can be lowered to the extent that it can be erased.

FIG. 12 shows how image data related to foreign objects and scratches is removed by such image processing.

Dust 91 is present on the wafer sample 50 in addition to a plurality of etch pits 51 . A blue light beam and a red light beam are incident on this wafer sample 50 from directions perpendicular to each other when viewed from a plan view, and image data for each color is obtained. 9
2 indicates image data based on a blue light flux, and 93 indicates image data based on a red light flux. Image data 92 based on the blue light beam includes an image 91a of etch pits and dust 91 along the vertical direction of the figure. Image data 93 based on the red light beam includes an image 91b of etch pits and dust 91 along the horizontal direction of the figure.

94 is the exclusive OR of image data 92 and 93 for each color (
This is image data obtained by taking EX-OR).

By calculating the exclusive OR, the garbage image data 91a
, 91b are erased, leaving only the image data of the etch pits.

Note that the portion where two etch pits overlap, as indicated by number 95, would be erased by simply calculating the exclusive OR, so processing is performed to distinguish it from dust and the like. For example, as shown in FIG. 13, the image data 101 is expanded once, the overlapping area 103 is made smaller as in the image data 102, and then the holes are filled.
Do it like 04. After that, the image data 104 is contracted (
(line thinning) to obtain appropriate image data 105.

Moreover, the overlap of etch pits can also be determined by determining the circumferential length versus area of the obtained image.

FIG. 14 is a graph of the perimeter versus area for a circular image and a rectangular image. The horizontal axis shows the circumferential length, and the vertical axis shows the area S. 111 is a graph of the circumference length versus area of a circular image, and 112 is a graph of circumference length versus area of a rectangular image. When separating these, for example, the circumferential length and area of the image to be determined are calculated, and if it falls within the hatch area 113, it can be determined that it is rectangular, and if it does not fall within the hatch area 113, it can be determined that it is circular.

Generally, the length of etch pits that appear due to stacking faults caused by oxygen varies, but by measuring the length histogram, if the circumference exceeds a certain value, the pits overlap. It can be determined that For example, in FIG. 14, if the average circumferential length is 35 μm, it is determined that two pits located at point B overlap.

The above-described processing can be realized using relatively simple software in the computer 8 and the image processing device 7, and the processing is also fast.

15A to 18B are photographs showing the crystal structure of the wafer measured in the above example.

FIG. 15A is a photograph showing etch pits, which are stacking faults caused by oxygen, on the wafer, and the oval shape on the left is dust on the wafer. FIG. 15B is a binarized image of FIG. 15A, and it can be seen that the image of dust remains as it is even after being binarized.

FIGS. 16A and 17A are images of the same location as FIG. 15A, with the present device changing the direction of light irradiation for each color. Each etch pit can be broken down into one direction. FIGS. 16B and 17B are binarized versions of FIGS. 16A and 17A, respectively.

Figures 18A and 18B are similar to Figures 16B and 1.
These are the data obtained by performing an exclusive OR (EXOR) operation on the image with FIG. 7B, and its inverted image. In FIGS. 18A and 18B, it can be seen that most of the dust has disappeared, and it has become a point that can be erased by image processing.

In the above embodiment, two colors of irradiation light (for example, red (R) and blue (B)) that can be easily separated by a color TV camera are used to illuminate the opposing crystal planes (51a, 51b and 51b in FIG. 5). 51c, 51d) By irradiating light of the same color and performing calculations between the R and B screens obtained simultaneously from a color TV camera, images of dust are erased and crystal defects are measured and evaluated.

The sample used in this example was a silicon wafer, and there were four exposed crystal planes, so two-color irradiation light was sufficient.
A case where six crystal planes are exposed as shown in s can be handled by increasing the types of irradiation light.

For the light source, a halogen lamp and filter were used, but
The light source is not limited to this, and any light source may be used as long as it can emit monochromatic light.

In the above embodiments, the object to be measured has been described as a crystal material (wafer), but the object to which the present invention is applied is not limited to this.

For example, it is not limited to crystalline materials, but can also be applied to measurement and evaluation of other substances (amorphous materials such as glass, polycrystalline materials such as ceramics, etc.).

In the second embodiment, the light source may be a strobe light, and the control described in the first embodiment may be performed. That is, the first embodiment and the second embodiment can also be combined. With this combination, it is possible to accurately measure and evaluate etch pits at a very high speed and eliminate the influence of dust and scratches.

[Effects of the Invention] As explained above, according to the material surface inspection apparatus according to the present invention, the surface image of the object to be inspected on the stage is flashed by the illumination means in synchronization with the movement of the stage, and the image data is processed at the same time. Since it is taken into the means, it is possible to measure defects in an object to be examined, such as a crystal, without having to keep the stage stationary. Therefore, it is possible to process the measurement and evaluation of defects in the object at high speed, which has the excellent effect of increasing the processing capacity of the apparatus.

In addition, illumination lights of multiple different wavelengths are incident on the surface of the object from different predetermined directions, and image data for each wavelength is obtained to evaluate defects on the object. Even if there are foreign objects such as dust or scratches on the surface, it is possible to reliably distinguish between etch pits and other objects without error, enabling highly accurate measurement and evaluation.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a material surface inspection device according to a first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of parts such as a strobe light, a microscope, and a TV camera of the device in FIG. , FIG. 3 is a perspective view showing an example of the operation of a sample stage and a microscope, FIG. 4 is a block diagram showing a schematic configuration of a material surface inspection apparatus according to a second embodiment of the present invention, and FIG. , a diagram showing stacking faults (OSF) caused by oxygen on the surface of a Si wafer, FIG. 6 is a scanning electron microscope (SEM) photograph showing the crystal structure of OSF etch pits on the surface of a Si wafer, and FIG. A scanning electron micrograph showing the crystal structure of an etch pit. Figure 8 is a cross-sectional view taken along line L-L' in Figure 7. Figure 9 shows an etch pit on the surface of a Si wafer viewed from two different directions. 10 is a partial sectional view of the optical system 17 and microscope 4 in FIG. 4; FIG. 11 is a diagram showing a filter; FIG. 12 is an image A conceptual diagram showing how foreign objects and scratches are removed through processing. Figure 13 is a conceptual diagram showing how image data is expanded and contracted to determine the overlap of etch pits. Figure 14 is a diagram showing the circumference length. A graph showing the relative area between a circular image and a rectangular image. Figures 15A to 18B are photographs showing the crystal structure of the wafer measured in the above example. Figure 19 is a conventional material defect measurement method. A schematic block diagram of the configuration of the apparatus, and FIGS. 20A and 20B are plan views showing how defects in a wafer, which is an object to be inspected, are measured. 1... Wafer sample, 2a... Sample stage, 2b, 2c
, 2d... Stage drive mechanism, 3... Pulse motor controller, 4... Microscope, 6... TV camera, 7... Image processing device, 8... Computer, 9... Monitor display, 1
0... Strobe driver, 11... Strobe lamp, 12...
Trigger signal generator, 13...Pulse motor driver, 1
4...Microscope control unit. Patent applicant: Mitsui Mining & Mining Co., Ltd. Agent: Patent attorney: Tatsuo Ito Patent attorney: Tetsuya Ito

Claims (6)

[Claims] 1. A material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, comprising: a movable stage on which the object is placed; and lighting means for illuminating the object on the stage. an imaging means for capturing an image of a part of the object as image data; an image processing means for evaluating defects in the object based on the image data; A material surface inspection apparatus characterized by comprising: a synchronization control means for flashing the illumination means and capturing image data by the imaging means in synchronization with the object when the object reaches a predetermined position. 2. A material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, comprising: a movable stage on which the object is placed; and lighting means for illuminating the object on the stage. an imaging means for capturing an image of a part of the object as image data; an image processing means for evaluating defects in the object based on the image data; ,
A material surface inspection apparatus characterized by comprising synchronization control means for flashing the illumination means and capturing image data by the imaging means. 3. A material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, the apparatus comprising: illumination light of a plurality of different wavelengths being incident on the surface of the object from different predetermined directions; , an illumination means for illuminating the surface of the subject; an imaging means for capturing images of the subject by the plurality of illumination lights of different wavelengths as image data for each wavelength; 1. A material surface inspection device comprising: image processing means for evaluating defects in a specimen. 4. A material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, comprising: a stage on which the object is placed and movable; and a plurality of illumination lights of different wavelengths. illumination means for illuminating the surface of the object to be examined by illuminating the surface of the object from different predetermined directions; an imaging means for capturing image data as image data; an image processing means for evaluating defects in the object based on the image data for each wavelength; A material surface inspection apparatus characterized by comprising: a synchronization control means for flashing the illumination means and capturing image data for each wavelength by the imaging means in synchronization with this. 5. A material surface inspection device for observing and inspecting the surface of a flat plate-shaped object, comprising: a stage on which the object is placed and movable; and a plurality of illumination lights of different wavelengths emitted from the stage. illumination means for illuminating the surface of the object to be examined by illuminating the surface of the object from different predetermined directions; an image processing means for evaluating defects in the object based on the image data for each wavelength; and at predetermined time intervals from the time when the stage starts moving,
A material surface inspection apparatus characterized by comprising synchronization control means for flashing the illumination means and capturing image data for each wavelength by the imaging means. 6. The image processing means evaluates defects in the object by eliminating the influence of dust, scratches, etc. by calculating an exclusive OR between each of the image data for each wavelength, 6. The material surface inspection device according to 4 or 5.