JPS6316964Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a surface inspection device.

Conventionally, contact measurement methods and non-contact measurement methods have been used to measure and inspect roughness such as surface irregularities. However, in the former method, the sample is brought into contact with the sample to be measured, so there is a risk that the sample surface may be deformed or damaged. In addition, in non-contact measurement methods, there are two types: one uses a laser device to shine a laser beam onto the sample surface and measures the reflected light to measure and inspect the surface condition, and the other uses a microscope to measure and inspect the surface condition. However, lasers have the disadvantage that it is difficult to simplify the equipment, and microscopes have the disadvantage that only the area within the field of view can be measured, so the measurement range is narrow.

Therefore, the purpose of this invention is to be able to simultaneously measure the entire surface of the sample without damaging the sample surface.
Moreover, it is an object of the present invention to provide a surface inspection device that can be made smaller.

This idea is aimed at measuring and inspecting fine irregularities and distortions with a large radius of curvature on the surface, and the basic configuration will be explained first. In FIG. 1, reference numeral 1 indicates a sample having a reflective surface, and a converging lens system 2 is installed on the reflective side of the sample, and a point light source 3 is installed on the same side. 4 is the focal point of the lens system 2, and the point light source 3
is installed closer to the lens system 2 than the focal point 4 of the lens system 2. The light ray 5 emitted from the point light source 3 is diffused into a light ray 6 by the lens system 2, and the light ray 6
is turned into reflected light 7 by the reflective surface of the sample 1 and re-enters the lens system 2, where it becomes a light ray 8. Figure 2 is an enlarged view of the sample 1, and there is a width on the surface of the sample 1.
There is an unevenness P in which L ₁ is several millimeters and depth L ₂ is submicron, and the radius of curvature R of the unevenness P is several meters to several tens of meters.
A center of curvature 9 is formed at that distance from the surface. When a parallel light beam a is incident on such an unevenness P at right angles to the surface of the sample 1 as shown in Fig. 3, the reflected light from the unevenness P is converged, but the reflected light from areas other than the unevenness P is reflected almost at right angles. As a result, if a screen is placed, for example, at a position that includes the region c of the convergent reflected light of the unevenness P, a difference in brightness will occur between it and the other region d. Therefore, by receiving the difference in brightness of this reflected light, the minute unevenness P can be detected. Furthermore, since the radius of curvature of the unevenness P is long, if the point light source 3 is positioned closer to the lens system 2 than the focal point 4 as shown in FIG. 1, it becomes easier to judge brightness and darkness. That is, point light source 3
When the point light source 3 is placed at the focal point 4 of the lens system 2, and when the point light source 3 is placed closer to the lens system 2 side than the focal point 4 (first
Comparing the case shown in Figure 1), the reflected light that enters the sample 1 through the lens system 2, is reflected, and passes through the lens system 2 converges at the focal point 4 in the former case, whereas in the latter case, the reflected light enters the sample 1 at the focal point 4. The light converges further away from the lens system 2 (convergence point 3'). Therefore, if we consider the case where a reflected ray is projected on position 1', the former image l' and the latter image l are related to l>
l', and the resolution of the image is increased even though sample 1 is under the same conditions.

An embodiment of this invention is shown in FIGS. 4 and 5. That is, in FIG. 4, 10 is an incident optical axis, and 11 is a reflected optical axis. A point light source 12 made of a general light source is installed on the incident optical axis 10, and the point light source 1
2 and the lens system 2, a condenser lens system 13 is installed on the incident optical axis 10. The point light source 12 and the condensing lens system 13 constitute a point light source device. The light rays emitted from the point light source 12 are focused by a condensing lens system 13 into a real image 14 of the point light source 12 . As a result, the real image 1 of the point light source 12 appears on the sample surface 1 having a reflective surface.
It becomes a ray of light that comes out from 4. A point light source 12 and a condensing lens system 13 are installed so that this real image 14 is focused at a position shorter than the focal length of the lens system 2. Then, the light beam reflected from the sample surface 1 is focused by the condenser lens system 15, and the light beam emitted from the surface of the sample 1 is projected onto the light receiving surface. Therefore, even if the size of the light-receiving surface is smaller than the surface size of the sample 1, the reflected light beam is condensed by the condenser lens system 15, so that the entire sample surface can be imaged on the light-receiving surface. As a result, the light receiving surface can be made smaller, and the device can be made more compact.

Here, the reason for creating the real image 14 of the point light source 12 as described above is that the incident optical axis 10 and the reflected optical axis 11
This is to bring the values as close as possible. For example, if you consider the sample surface as a mirror surface, and you look at the projected images when looking perpendicularly to the mirror surface and when viewing it diagonally, the image seen diagonally is better than the image seen perpendicularly. Distortion will occur more than if the For this reason, it is preferable to make the optical axis perpendicular to the sample surface. For this purpose, it is better to make the incident optical axis and the reflected optical axis coincide, but if they cannot be made to coincide, it is better to bring both optical axes as close as possible. In this case, the point light source 12
needs to be installed at a position that does not block the light beam reflected from the surface of the sample 1, and must be installed at a position shorter than the focal point of the lens system 2. For this purpose, by the condensing lens system 13,
By creating the real image 14 of the point light source 12, the incident optical axis 10 and the reflected optical axis 11 can be brought closer together.

FIG. 5 shows an example in which a television camera 16 is installed at the imaging point of the condenser lens system 15. Condensing lens system 1
5, the reflected light is condensed and the TV camera 1
6, all of the reflected light rays from the entire sample surface can be imaged, thereby making it possible to perform image processing. Furthermore, since the television camera 16 can be installed near the condenser lens system 15, the device can be made more compact. Furthermore, by making the condensing lens system 13 and the condensing lens system 15 movable in each optical axis direction, even if the size of the sample 1 having a reflective surface changes, the image captured by the television camera 16 It is also possible to keep it constant.

FIG. 6 is an image of the surface of sample 1 obtained by the apparatus shown in FIG. 5 (see attached photograph). The conditions include a focal length of lens system 2 of 1 m, a 3W miniature light bulb as point light source 12, a focal length of 50 cm of condensing lens system 13 and condensing lens system 15, and a television camera 16.
An image tube with a focal length of 35 cm as sample 1, and 3 as sample 1.
An inch silicon wafer was used. Also, point light source 12
The distance from the sample 1 to the sample 1 is 1.3 m, and the distance from the sample 1 to the television camera 16 is also about the same. When observing FIG. 6, a bright horizontal line A and a horizontal line B consisting of a bright line and a dark line can be seen. On the other hand, when the surface condition of this 3-inch silicon wafer was measured using a stylus inspection method (Talystep), the horizontal line A
As shown in Figure 7a, the depth H ₁ is 0.38 μm and the width H ₂ is 8
The brightness of the horizontal line B corresponds to the minute recesses of 0.05 μm (bright part) Q ₁ and 0.12 μm recesses (bright part) Q ₂ within the width L of 5.6 mm, as shown in Figure 7b. It was found that the convex part (dark part) Q ₃ and the convex part (dark part) between them correspond. In this way, the bright areas observed with a television camera or the like represent the depressions of the sample, and the dark areas represent the convexities, so that the irregularities can be inspected.

As described above, the surface inspection device of this invention includes a converging lens system placed in front of the reflective sample surface,
a point light source device disposed on the opposite side of the reflective sample surface of the convergent lens system and having a real image point closer to the convergent lens system than its focal length; a light-receiving surface provided on the side, and a condensing lens system disposed between the converging lens system and the light-receiving surface, the light beam of the point light source device being incident on the reflective sample surface through the converging lens system; The reflected light reflected from the sample surface,
Since the present invention is characterized in that the light passes through the converging lens system, is condensed by the condensing lens system, and is incident on the light receiving surface, the following effects can be obtained. In other words, since it is a non-contact test on the sample, it is compact and allows the entire surface of the sample to be inspected at the same time without damaging the sample.If the entire device is installed and used in a dark room, the measurement accuracy can be further improved. I can do it.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the basic configuration of this invention, Fig. 2 is an enlarged cross-sectional view of the sample surface, and Fig. 3 is a cross-sectional view of the sample showing the state of the light beam when it is applied to a recess on the sample surface. Figures 4 and 5 are schematic diagrams of an embodiment of this invention, Figure 6 is an image of the sample surface obtained with the apparatus shown in Figure 5, and Figure 7 is a sample surface obtained by actually measuring the sample surface using a Talystep. FIG. 3 is a partially enlarged sectional view. 1... Sample surface having a reflective surface, 2... Lens system, 12... Point light source, 13... Condensing lens system, 1
4... Real image of point light source, 15... Condensing lens system, 1
6...TV camera.

Claims (1)

[Claims for Utility Model Registration] (1) A convergent lens system disposed in front of the reflective sample surface, and a convergent lens disposed on the opposite side of the reflective sample surface of the convergent lens system whose focal length is shorter than the focal length of the convergent lens system. a point light source device having a real image point close to the system; a light receiving surface provided on the same side of the converging lens system as the point light source device; and a condensing lens disposed between the converging lens system and the light receiving surface. a light beam from the point light source device enters the reflective sample surface through the converging lens system, and the reflected light reflected from the sample surface passes through the converging lens system and is collected by the condensing lens system. A surface inspection device characterized in that it is configured to emit light and make it incident on the light receiving surface. (2) The point light source device has a condensing lens system that forms its real image point at a position closer to the converging lens system than the focal length of the converging lens system. Surface inspection equipment.