JPS61262607A - Visual inspection instrument - Google Patents

Abstract

PURPOSE:To enable a sharp image to be surely taken-in by taking-in the image of the whole predetermined range of an object to be inspected at the same time, dividing the image and taking-in the divided images at the same time by a plurality of two-dimensional sensors. CONSTITUTION:Light from a light source is irradiated onto the surface of a wafer 1 on a stage 2 and the image of the whole pellets of the wafer 1 is taken-in at the same time by an optical system 7. The image from the optical system 7 passes each slit 8 and is taken-in by each of CCD's 9 which are provided opposite to the slits 8. The gains of the CCD's 9 are made constant by comparing the scattered gains with that of one CCD which is made as a reference in a gain comparator 10 and feeding back the scatter of the CCD's 9 to an amplifier 11. That is, the brightness of the image taken in by each CCD 9 is made constant. Therefore, by combining the images taken-in by the respective CCD's 9, the images of the whole pellets can be taken-in at the same time and a sharp image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a visual inspection technique, and particularly to a technique that is effective when applied to visual inspection of semiconductor wafers or masks.

[Background technology]

When performing visual inspection of wafers or masks, it is conceivable to use a -dimensional line sensor.

In this case, in order to capture an image of the entire surface of each pellet of the wafer, the stage on which the wafer is placed is moved at a constant speed, and images are captured in real time accordingly.

However, since there are speed variations and vibrations in the movement of the stage, even if images are captured in real time, there is a problem that distortion will occur when all the captured images are combined to form an image of the entire pellet. The inventor discovered this.

Regarding wafer appearance inspection technology, please refer to the stock% formula% is explained in.

[Purpose of the invention]

An object of the present invention is to provide a visual inspection technique that can reliably capture a clear image.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

In other words, by capturing and dividing an image of the entire predetermined range of the object to be inspected at once, and capturing the image at once using multiple two-dimensional sensors, a clear image can be obtained without being affected by stage speed fluctuations or vibrations. This allows images to be captured reliably.

〔Example〕

FIG. 1 is an explanatory diagram of an appearance inspection apparatus which is an embodiment of the present invention.

This embodiment is an example in which the present invention is applied to the visual inspection of semiconductor wafers.

That is, a wafer 1, which is an example of an object to be inspected, is placed on and held on a movable stage 2. The stage 2 is provided on an XY table 3 and is movable in the XY directions. The wafer l is irradiated with light from a light source (not shown).

Further, above the wafer 1, an optical system 7 including an objective lens 4, a half mirror 5, a reflecting mirror 6, etc. is provided.

In this embodiment, the image captured by the optical system 7 is
and is divided into four parts by the slit 8 above it.

A charge-coupled device (COD) 9 as a two-dimensional sensor is provided above each slit 8 .

A gain comparison section 10 is located above these CCDs 9, and an amplifier section 11 is connected to the output side of the gain comparison section 10. Further, the output side of the amplifier section 11 is connected to a mixer 12 for image matching.

Next, the operation of this embodiment will be explained.

First, by irradiating the surface of the wafer 1 on the stage 2 with light from a light source (not shown), an image of the entire pellet of the wafer 1 is captured at once by the optical system 7. Since the entire pellet is divided by the slit 4, , the image from the optical system 7 passes through each of the slits 4 and is captured by a CCD 9 provided corresponding to each slit 4.

The gain of each CCD 9 is made constant by comparing mutual gain variations in a gain comparing section 10 with one CCD 9 as a reference and feeding back the gain variations of each CCD 9 to an amplifier section 11. That is,
The brightness of the image captured by each CCD 9 is constant.

Therefore, the images captured by each CCD 9 are transferred to the mixer 1.
By combining 2, the image of the entire pellet can be captured at once, and a clear image can be obtained.

As a result, the appearance of the wafer 1 can be accurately inspected, and distortion can be eliminated.

〔effect〕

(1) Consisting of an optical system that captures an image of the entire predetermined range of the object to be inspected at once, a means for dividing the image of the object to be inspected, and a plurality of two-dimensional sensors that capture the divided images at once. As a result, clear images can be captured without being affected by uneven speed of stage movement, vibration, etc.

(2) According to (11) above, a precise visual inspection can be performed.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, it is also possible to change the number of slits, the structure of the optical system, etc. other than those of the above embodiments.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to the visual inspection of wafers, which is the background field of application, but the present invention is not limited thereto. It can be widely applied to recognition technology for minute marks on parts.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of an appearance inspection apparatus which is an embodiment of the present invention. 1... Wafer (inspected object), 2... Stage, 3...
...XY table, 4...Objective lens, 5...Half mirror 16...Reflection mirror, 7...Optical system, 8...
...Slit (dividing means), 9...Two-dimensional sensor (C
OD), 10...Gain comparison section, 11...Amplifier section, 12...Mixer. Figure 1

Claims (1)

[Claims] 1. An optical system that captures an image of the entire predetermined range of the object to be inspected at once, means for dividing the image of the object to be inspected, and a plurality of two-dimensional sensors that capture the divided images at once. Appearance inspection equipment consisting of. 2. The appearance inspection apparatus according to claim 1, wherein the two-dimensional sensor is a charge coupled device. 3. The gain of each charge-coupled device is made constant by comparing the gains of each charge-coupled device using one charge-coupled device as a reference and feeding back the variation in the gain of each charge-coupled device. An appearance inspection device according to claim 1.