JPH0136577B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is directed to preventing contamination, unevenness, and
The present invention relates to a specular workpiece surface inspection device that can evaluate and inspect the distribution of adhered fine particles, cleaning effectiveness, and the like.

In general, for mirror-finished products such as Si wafers whose surfaces are processed with high precision into mirror-like surfaces, dust, contaminants, and irregularities during processing that adhere to the surfaces can affect the electrical characteristics and defects of the elements formed on the wafer. Because of this, it is necessary to observe the mirror-like surface and inspect the condition of the surface, and conventionally, photography or visual inspection has been used. That is, FIG. 1 is a schematic configuration diagram showing a conventional surface inspection apparatus using photography. In the same figure, 1
is a visible light source such as a slide projector, 2
3 is a sample such as a Si wafer whose surface condition is to be inspected.
4 is a sample stage such as a rotating vacuum chuck that holds the sample 2, 4 is a camera that photographs the surface of the sample 2, and 5
is a light absorption plate for absorbing the reflected light of the sample 2.

Next, the operation of the surface inspection apparatus having the above configuration will be explained. First, a light beam from a light source 1 is irradiated onto the surface of a sample 2. If there are scratches, irregularities, contamination, or dust deposits on the surface of the sample 2, scattered light from the irradiated light will be generated from the surface of the sample 2. Therefore, this scattered light is photographed by the camera 4 located directly above, and the distribution of the scattered light, that is, the state of scratches, irregularities, dust adhesion, etc. on the surface can be observed and evaluated using photographs. Note that since this scattered light is weak, the direct reflected light from the surface of the sample becomes stray light in the photographing atmosphere, and the light reflected from the sample 2 is absorbed by the light absorption plate 5 in order to prevent the photographing sensitivity from decreasing.

However, with surface inspection equipment using conventional photography methods, (A) it is impossible to completely eliminate stray light, and the camera and attachments reflect off the surface of sample 2;
There is a so-called "imprint". (B) In the phenomenon of light scattering, the scattering intensity is weak when the side scattering (for example, right angle scattering) arrangement is used. In other words, since the shooting sensitivity is low,
It is difficult to photograph particles smaller than 1 μm. (C) It is impossible to quantitatively evaluate the surface, and it is not possible to automatically exchange samples and perform automatic evaluation. (D)
Since the light source wavelength was in the visible and infrared region, it was difficult to use a particle meter, and there were drawbacks such as heating of the sample 2.

Accordingly, an object of the present invention is to provide a mirror-like workpiece surface inspection apparatus that can increase photographic sensitivity and quantitatively evaluate a sample surface such as a workpiece surface.

In order to achieve this purpose, this invention
a light source, an optical system that irradiates a light beam from the light source almost perpendicularly to the sample surface, lenses arranged not directly facing the sample surface and parallel to each other with respect to the sample, and imaging. an imaging means for receiving scattered light, fluorescence, or polarized light from the sample surface to perform tilt-and-focus photography to obtain an image directly proportional to the sample surface; A video signal output means to output, and a data signal that processes the video signal from this video signal output means and indicates the presence or absence of scratches on the sample surface, the size of the scratches, irregularities, and the number, diameter, or distribution of attached particles. and a data signal determination device that compares and tests the data signal output from the video signal processing device with a stored reference value, and outputs a test pass signal or a test fail signal. This will be explained in detail below using examples.

FIG. 2 is a configuration diagram showing an embodiment of the specular workpiece surface inspection apparatus according to the present invention. In the same figure, reference numeral 6 indicates a powerful lens equipped with an aperture lens (not shown) so that the diameter of the light beam is slightly larger than that of sample 2, and the diameter of the light beam matches the diameter of the sample or the size of the observation area. For example, high pressure mercury lamps,
A light source such as a 200 watt xenon lamp, 7 is a filter or polarizing plate, 8 is a light intensity meter, 9a and 9b are reflectors, 10 is a filter or polarizing plate, 1
1 is a camera having a wide-angle lens (not shown) to enable tilt photography; 12 is a film; 13
is a TV camera; 14a and 14b are light absorption plates for reducing stray light in the observation area; and 15 processes the video signal output from the TV camera 13;
A TV video processing device 16 outputs data signals such as presence or absence of scratches on the surface, size of scratches, unevenness, number of particles attached to the surface, diameter, distribution, etc.; A TV video judgment device that performs a comparison test with a stored reference value, outputs a test pass signal from its output terminal 16a, and outputs a test fail signal from its output terminal 16b, 1
7 is a data signal output from the TV image processing device 15, that is, a plotter that displays the size of the scratch, the state of unevenness, the number of attached particles, diameter, distribution, etc., a TV image output device such as CRT, and 18 is an inspection device. Automatic sample supply device that sequentially sends out samples to be processed, 19
a, 19b and 19c are transport paths for sample 2, 20
21 is a passing product storage device that operates upon input of the inspection pass signal and stores samples that have passed the inspection; and 21 is a reject storage device that operates upon input of the inspection failure signal and stores samples that have failed the inspection. It is a product storage device.

Note that by using a high-pressure mercury lamp or a xenon lamp of 200 watts or more as the light source 6, the irradiation light source intensity and back shadow illuminance are at least 100,000:1 or more. In addition, since the sensitivity of this device extends down to submicrons, the transport paths 19a to 19c along which the sample 2 moves
In other words, the area surrounded by the dotted line requires a clean atmosphere of at least "Class 1000" or higher.

Next, the operation of the specular workpiece surface inspection apparatus having the above configuration will be explained. First, a light beam from a light source 6 passes through a filter or a polarizing plate 7, is reflected by reflection plates 9a and 9b, and is irradiated onto the surface of the sample 2. If there are scratches, irregularities, contamination, or dust on the surface of the sample 2, scattered light (or fluorescence, which will be described later) due to the irradiated light is generated from the surface of the sample 2. At this time, forward scattering is used to make the scattered light on the surface of the sample 2 enter the camera 11 more effectively. That is, in order to bring the optical axis closer to the camera 11, the camera (optical system of the TV camera) uses tilt photography. As a result, the sample 2 and the obtained image become geometrically proportional (similar shapes). Then, the light source 6 is made stronger, while at the same time stray light is reduced, weak scattered light is made more effective, and reflections on the specular sample are eliminated. Then, this scattered light (or fluorescence) enters the camera 11 and the film 12,
Tie the statue. In this case, the position of the camera 11 is
The sample 2, the lens of the camera 11 (not shown), and the film 12
are in a parallel relationship with each other. Then, instead of a photographic image of the film 12, an image is obtained by the TV camera 13 and output to the image processing device 15. For this reason, the image processing device 15 processes the image signal and generates data signals such as the presence or absence of scratches on the surface of the sample 2, the size of the scratches, the state of irregularities, the number of particles attached to the surface, their diameter, and their distribution. It is output to the TV image determination device 16. Therefore, this TV image determination device 16 performs a comparison test with a stored reference value, and if the surface of the sample 2 is good as a result of the test, outputs a test pass signal indicating a non-defective product from the output terminal 16a. On the other hand, if the inspection results show that the surface of the sample 2 is scratched or uneven, or that a large number of particles are attached, an inspection failure signal indicating a defective product is output from the output terminal 16b. Therefore, the acceptable product storage device 20 operates in response to the inspection pass signal, and stores the sample 2 of the passed product sent from the conveyance path 19b. On the other hand, the reject storage device 21 is operated by the inspection failure signal and stores the rejected sample 2 sent through the conveyance paths 19b and 19c.

In addition, a light source with a large amount of ultraviolet light component is used as the light source 6,
Of course, by using the filters 7 and 10, it is possible to observe the fluorescent substance on the surface of the sample 2. In addition, although a Si wafer was used as the sample in the above examples, it can also be used not only for other mirror-like processed objects, but also for surface precision processing samples, photographic masks, crystal plates other than Si, mirrors, lenses, etc. Of course you can do the same. Further, the sample 2 does not necessarily have to be mirror-like, and it goes without saying that even a sample with a pattern can be photographed.

As described in detail above, the surface inspection device for a mirror-like workpiece according to the present invention is capable of quantitatively detecting the surface condition of a workpiece that has been precisely machined into a mirror-like finish with high precision (submicron). , and compared with a reference value, the reliability of the test can be greatly improved compared to conventional observation tests that rely on the human eye.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing a conventional surface inspection apparatus using a photographic method, and FIG. 2 is a configuration diagram showing an embodiment of a mirror-like workpiece surface inspection apparatus according to the present invention. 1...Light source, 2...Sample, 3...Sample stage, 4...
...Camera, 5...Light absorption plate, 6...Light source, 7...
Filter or polarizing plate, 8... Light amount measuring device, 9a
and 9b...reflector, 10...filter or polarizing plate, 11...camera, 12...film, 1
3...TV camera, 14a and 14b...light absorption plate, 15...TV image processing device, 16...TV
Video determination device, 17...TV video output device, 18
...Sample automatic supply device, 19a, 19b and 1
9c... Conveyance path, 20... Passed product storage device, 21
...Rejected product storage device. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A light source, an optical system that irradiates a light beam from the light source almost perpendicularly to the sample surface, and is arranged at a position not directly facing the sample surface and parallel to each other with respect to the sample surface. an image forming means which has a lens and an image forming surface, receives scattered light, fluorescence, or polarized light from the sample surface and performs tilt photography to obtain an image directly proportional to the sample surface; and an image formed by the image forming means. a video signal output means for outputting a video signal based on the image signal; A video signal processing device that outputs a data signal indicated by the video signal processing device and the data signal output from this video signal processing device are each compared with a stored reference value, and a test pass signal or a test fail signal is output. 1. A mirror-like workpiece surface inspection device, comprising: a signal determination device.