JPH0499346A - Wafer appearance inspection device - Google Patents

Abstract

PURPOSE:To achieve accurate inspection by emitting white light onto a surface of a wafer and then allowing only light of the reflected light with higher degree of gradation to be transmitted by a color degradation filter. CONSTITUTION:A white light source 5 for emitting white light onto a surface of a wafer 7 and a color degradation filter 9 for allowing three elementary colors of the reflected light from a surface of the wafer 7 to be transmitted selectively are provided. White light is emitted onto the wafer 7 through a half mirror 4 and an objective lens 6 from the white light source 5 and the reflected light is passed through the color degradation filter 9 and is taken by an image pick-up camera 3. When only a red filter out of this color degradation filter 9 is used, a monochromic gradation image which consists of only cyanic color of the wafer 7 is taken in. The taken-in monochromic gradation image is subjected to image processing by an image processor 2 and a computer 1 and appearance inspection is performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wafer appearance inspection apparatus that inspects the shape pattern of a wafer surface by performing image processing such as pattern masochi [Prior art] Third The figure is a diagram schematically showing an example of a conventional wafer appearance inspection apparatus. Conventionally, this type of wafer appearance inspection apparatus has, for example, a stage 8 on which a wafer 7 is placed, and a half mirror 4 on the surface of the wafer 7, as shown in FIG.
and a light source 5a that projects light through an objective lens 6, an imaging camera 3a that receives light reflected from the wafer 7 and images the shape pattern formed on the wafer surface, and an imaging pattern signal from the imaging camera 3a. An image processor 2a and a computer 1 that perform image processing, compare with a reference image pattern, and inspect the pattern on the wafer.
It had a.

Further, this imaging camera 3a is usually equipped with an imaging tube or a CC camera.
I have been using one of the D cameras. Image pickup tubes are expensive, but have the advantages of high resolution and high light detection, while CCD cameras are inferior in both resolution and light detection, but are often used because they are inexpensive. It's here. Furthermore, if a color CCD camera is used, appearance inspection using color images is also possible. However, color CCD
In this case, since the pixels themselves are separated into pixels of the three primary colors of RGB, the resolution is reduced to 1/3 compared to a monotone CCD camera. Therefore, many wafer visual inspection apparatuses use monochromatic CCD cameras or image pickup tubes.

[Problem to be solved by the invention]

In the conventional wafer visual inspection apparatus described above, when an image pickup tube is used as an imaging camera, inspection is carried out by taking in white light or monochromatic light, so if the Wl tone of the captured image is small, the pattern matching ability will be reduced. However, it has the disadvantage that it cannot be tested accurately. Furthermore, since the captured image is monochrome, it has the disadvantage that it cannot be converted into color.

On the other hand, when a CCD camera is used, a color image can be obtained, but the resolution is poor.

The object of the present invention is to provide a wafer visual inspection apparatus that eliminates such drawbacks.

[Means to solve the problem]

A wafer appearance inspection apparatus of the present invention includes an imaging means for imaging a pattern on the wafer using reflected light from the wafer, and an image processor and a computer for processing an imaged pattern signal obtained by the imaging means. The device includes a white light source that generates white light that is irradiated onto the wafer surface, and a color separation filter that separates light reflected from the wafer into three primary color lights.

Further, in addition to the above-mentioned means, another wafer visual inspection apparatus is provided, in which the image processor forms a color image using a subtractive color mixing method using each of the three primary color lights with different wI tones, and reproduces this image. It is characterized by

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a diagram schematically showing a wafer visual inspection apparatus according to an embodiment of the present invention. As shown in the figure, this wafer visual inspection apparatus is equipped with a white light source 5 that irradiates the surface of the wafer 7 with white light, and a color separation filter 9 that selectively transmits the three primary colors of the light reflected from the surface of the wafer 7. It is Kato.

That is, the wafer 7 is irradiated with white light from the white light source 5 via the half mirror 4 and the objective lens 6, and the reflected light is passed through the color separation filter 9 and an image is captured by the imaging camera 3.

When the red filter is used among the color separation filters 9, the cyan color W! of the wafer 7! This will capture a monochromatic gradation image made up of light of only different tones.

Furthermore, in the case of a green filter, a magenta monochrome gradation image is captured, and in the case of a blue filter, a yellow monochrome gradation image is captured. Further, these captured monochromatic gradation images are subjected to image processing by the image processor 2 and computer 1, and an appearance inspection is performed.

2(a) to 2(d) are diagrams for explaining the operation of the wafer visual inspection apparatus shown in FIG. 19. For example, FIG. 2(a)
As shown in FIG.
1, a resist pattern 10 is formed thereon, and then the case where this resist pattern is inspected will be described.

First, the stage is moved in the inspection direction B. At this time,
Irradiates inspection light, which is white light. The Wl tone when this white light is reflected is as shown in FIG. 2(b). In this state, the contrast between the resist pattern 10 and the lens antireflection film 11 is not very large.

Next, when the reflected white light is passed through a green filter, the contrast is still small, as shown in the second [J(c)]. Next, if you pass it through a blue filter, the second
As shown in Figure (d), the contrast is clearly captured. In this way, by selecting a filter that allows for easy gradation depending on the state of the surface of the wafer to be measured, it is possible to increase the contrast and enable more accurate inspection.

Although not shown in the drawings, such white light is irradiated, the reflected light is passed through two color filters (for example, red and green), the images are captured, and an image processor and computer are used to perform subtractive color mixing. You can create a two-color image using the method, or use a three-color filter to create a two-color image.
By processing each image, extremely high-resolution visual inspection using color images becomes possible.

〔Effect of the invention〕

As explained above, the wafer visual inspection apparatus of the present invention has the following features:
By irradiating the wafer surface with white light and transmitting the reflected light through a color separation filter, only light with a higher gradation level can be transmitted, which has the effect of allowing more accurate inspection.

Additionally, by providing an image processor with a subtractive color image processing function for images of light transmitted through these filters, a color image with higher resolution can be formed.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a wafer visual inspection apparatus according to an embodiment of the present invention, and FIGS. 2(a) to 2(d) are diagrams for explaining the operation of the wafer visual inspection apparatus of FIG. FIG. 3 is a diagram schematically showing an example of a conventional wafer appearance inspection apparatus. 1.1a...Computer, 2.2a...Image processor, 3.3a...Imaging camera, 4...Half mirror 15...White light source, 5a...-Light source, 6...
1 objective lens, 7... wafer, 8... stage,
9... Color separation filter, 10... Resist pattern, 11... Resist antireflection film.

Claims (1)

[Scope of Claims] 1. A wafer appearance inspection apparatus having an imaging means for imaging a pattern on the wafer using reflected light from the wafer, and an image processor and a computer for processing an imaged pattern signal obtained by the imaging means. , a white light source that generates white light to irradiate the wafer surface;
A wafer appearance inspection apparatus comprising: a color separation filter that separates light reflected from the wafer into three primary color lights. 2. The wafer visual inspection apparatus according to claim 1, wherein the image processor forms a color image using a subtractive color mixing method, and reproduces the image, each having a different gradation using the three primary color lights.