JPS5848837A - Defect checking method - Google Patents

Abstract

PURPOSE:To penetrate the light reflected by a sample surface having the curvature into a microscope to convert the sample surface into the same observing status as a plane by irradiating scattered light to the sample surface. CONSTITUTION:A scattering body part 10 on which a sample 12 is held is arranged on an X-Y stage 11. The surface of the sample 12 is observed through a microscope unit 4. Directional illuminating light 7 irradiated from a reflecting and lighting device 3 is irradiated to the surface of the sample 12 through the scattering body part 10. As the result, a part of the reflected light 18 reflected by the surface of the sample 12 is penetrated into an objective lens 5. A non-defective surface 20 in an area 19 in which the light 18 reflected by the surface of the sample 12 is penetrated into the objective lens 5 has the same observing status as the positively reflected surface of a plane. A defective part 21 has the same irregular reflection as that of a plane. Consequently the clear difference of luminance levels between the non-defective part 20 and the defective part 21 appears. Thus scattered lighting can be easily realized by using an ordinary microscope.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defect inspection method for inspecting defects on a sample surface having a curvature such as a cylindrical surface.

More specifically, the present invention aims to improve an illumination method that can easily detect defects on the surface of a sample in defect inspection using a microscope.

In recent years, visual inspections (defect inspections) have been widely carried out on nine parts of each product.

Defect inspection has many benefits, such as improving quality and reducing costs.

A typical defect inspection method uses a microscope. Using a microscope makes it possible to detect minute defects. By using a deformed imaging device (such as a television camera), the presence or absence of a defect and its size can be quickly measured through video signal processing.

Therefore, defect inspection can be performed efficiently with high precision, resulting in great effects.

The first example of a defect inspection method using a conventional microscope is shown in Figure 1.
Shown below.

Defect inspection using a mirror-finished substrate 1 as a sample and scratches as defects will be described.

As shown in FIG. 1, a sample 1 is held on an XY stage 2 and illuminated by a reflective illumination device 3. A defective portion is observed by a microscope unit 4 comprising an objective lens 6, an eyepiece lens 6, etc.

Imaging device (television camera, etc.) 7 and measurement/
Defects are automatically measured using a control circuit. In this case, as shown in FIG. 2, the defect-free portions of the sample surface 8 reflect specularly, and the defective portions 9 reflect diffusely, resulting in a difference in brightness of one novel. This brightness level difference is used to detect defects using I-.

In the case of the prior art example -1- below, since the sample is flat, the defect-free surface becomes a uniform specular reflection surface, and defects can be easily detected.

In the case of a sample with a curvature, only a small portion of the specular reflection surface can be obtained.

First, normal illumination light: The light passes through a lens system and has directionality, and the specular reflection surface can only provide an i- value on a small portion of the curvature surface.

When inspecting a cylindrical surface using this method, for example, only a narrow inspection area can be obtained, and the inspection must be performed while making several rotations. This poses a major obstacle in terms of the configuration and efficiency of inspection equipment.

At the same time, the difference in brightness level between the defect-free area and the defect area is also sufficient.
Therefore, it is difficult to realize stable defect detection.

Example shown at the top - for bright field illumination. In addition to bright-field illumination, dark-field illumination is widely used for defect inspection, but even when dark-field illumination is used, good defect inspection conditions have not been obtained.

This is because it is not possible to capture only the scattered light from the defective part, which is a characteristic of dark-field illumination.

As described above, there are various problems in inspecting defects on the surface of a sample having curvature using a microscope.

The present invention aims to solve this conventional problem.

In the present invention, by irradiating a sample surface with curvature with scattered light, the reflected light from the sample surface is captured into a microscope, and the sample surface with curvature is made to be observed in the same state as a flat surface.

By splitting and irradiating the sample surface with scattered light, light incident from various directions is reflected on the sample surface and is incident at an incident angle corresponding to the curvature of the sample. It can be captured into the lens. In the area where the reflected light from the sample surface is captured by the objective lens, an observation state similar to that of the specular reflection surface described in the case of a single surface is created. As a result, the defect 5 portion existing in this area is observed in the same state as in the case of a flat surface, and a sufficient difference in brightness level between the defect-free portion and the defective portion can be obtained.

Next, we can easily measure the scattered light using an ordinary microscope device.
'1. An embodiment of the present invention capable of detecting irradiation groove defects on the F-plane will be described below.

Using a shaft as a sample, FIG. 3 shows the inspection for defects (scratches) on the shaft surface.

As shown in FIG. 3, a sample 12 (shaft) is held on a sample holding surface consisting of a scatterer portion 1o.

A scatterer section 10 is arranged on the xy stage 11. The surface of the sample 12 is observed using the microscope unit 4.

A reflective lighting device 3 is used as the lighting device.

As shown in FIG. 4, the directional illumination light 17 emitted from the reflected illumination device 3 passes through the scatterer section 1o to the sample 1.
2 surfaces are irradiated.

The twisted and directional illumination light 17 is scattered in all directions by the scatterer section 10 and reaches the surface of the sample 12.

As a result, the reflected light 6, - reflected on the surface of the sample 12
- A part of the light beam 18 is taken into the objective lens 5.

The observed state of the sample surface in this state is shown in FIG.

A region 19 where the reflected light 18 on the surface of the sample 12 is taken into the objective lens 5 becomes as shown in FIG. The defect-free surface 20 of this region 19 is observed in the same state as a regular reflection surface in the case of a flat surface.

Furthermore, the defective portion 21 within the region 19 becomes a diffused reflection surface similar to that in the case of a flat surface. As a result, a clear brightness level difference occurs between the defect-free surface 20 and the defective portion 21. This is because by using the scatterer section 10 described above, the surface of the sample can be easily illuminated with scattered light. This is because the scatterer section 10 is used as a kind of scattered light source.

Thereby, scattered illumination can be easily realized using an ordinary microscope.

The material of the scatterer section is not limited as long as it is optically uniform and has a predetermined scattering surface (for example, resin 5 paper may be used).

In the above embodiment, a flat scatterer section 10 was shown, but another possible example is shown in FIG.

a: the scatterer part has a v-shaped cross section, b: the scatterer part has a cross-sectional shape, C
This is an example in which the test t1 is a sphere, and the scatterer portion has a conical shape.

A V-shape, a U-shape, or the like is more advantageous than a flat-plate shape because the area where the reflected light from the sample surface is captured by the objective lens is larger.

The state is shown in FIG. 7 and will be explained below. A shows the case where the flat scatterer section 10 is employed. b shows a case where a U-shaped scatterer section 10 is adopted. Compared to a, in b, the area 19 where the reflected light 18 on the surface of the sample 412 is taken into the objective lens 6 is wider. In other words, the U-shape allows irradiation of scattered light over a wider range of the sample surface than the flat-plate shape.

As a result, the shape of the scatterer part is not limited as long as it has a curvature of one angle in the direction in which the region where the light reflected from the sample surface is taken into the objective lens has a maximum value.

If you use the scatterer part as a sample holding surface, you can use it for the microscope configuration and 17 without modifying the conventional microscope.Furthermore, if you use the V-shape or U-shape, you can easily position the specimen. It's easy.

The position of the scatterer section with respect to the sample is not limited to the position of the sample holding surface as long as it is a position where the sample surface can be irradiated with scattered light.

Next, although not shown here, in order to observe the entire surface of the cylindrical sample, it has a rotation mechanism for the sample.

When the present invention is used, compared to conventional methods, a wider observation surface 19 is obtained, the number of rotations of the sample is also rapidly reduced, and inspection efficiency is improved.

Next, we will discuss defect detection and measurement methods.

The area 19 shown in FIG. 5 is selectively set as an inspection area, and an automatic defect inspection is performed using an imaging device.

The region 19' in FIG. 5 does not have a specular reflection surface state, and is a region in which it is difficult to distinguish between a defective portion and a non-defective portion.

First, if the area 19 is limited to the inspection area, good defect inspection becomes possible.

As shown in Figure 3, as is well known, defect detection using the camera 22 uses the difference in brightness between the specular reflection surface and the diffused reflection surface to extract a video signal from the camera 22 and keep it constant. Binarize using [-threshold value, determine defective part,
3.23 The opening side is the control circuit that performs ll+.

As described below, by using the present invention, defects on the surface of a sample with curvature can be inspected in the same inspection condition as on a flat surface, making it possible to perform inspection with high accuracy and high efficiency, resulting in a large effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side view showing an example of a conventional defect inspection device, FIG. 2 is a side view showing a conventional defect inspection state, and FIG. 3 is a side view showing an embodiment of the defect inspection method of the present invention. , Figure 4 is
FIG. 5 is a side view showing the principle of the present invention; FIG. 5 is a diagram showing a defect inspection state according to the present invention; FIGS. 6 a, b, and c are perspective views showing examples of the shape of the scatterer portion according to the present invention; FIGS. 7a and 7b are diagrams showing differences in the inspection area depending on the shape of the scatterer portion according to the present invention. 3...Reflected illumination device, 4...Microscope,
10...Light scatterer section, 12...Sample. Figure 1 Figure 5 Figure 6 Figure 7' /12) 7g(b)

Claims (2)

[Claims] (1) A defect inspection method in which the surface of a sample having a curvature to be inspected is irradiated with scattered light, and the sample surface irradiated with the scattered light is observed with a microscope to inspect for defects on the sample surface. (2) The defect inspection method according to claim 1, characterized in that a sample is placed on a light scattering body surface, and the sample surface is irradiated with scattered light from the light scattering body surface.