JP2008277596A - Surface scratch defect inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method and an apparatus capable of clarifying a light intensity while the setting of a threshold is delicate since the light intensity at a scratch part is weak in a scratch inspection system of a wafer V notch using an optical method relating to a conventional technology and the lowering of a yield and the deterioration of quality management are remarkable and cause problems in an automatic inspection system in a production process. <P>SOLUTION: Simultaneously with the irradiation of an inspection surface with diffused light illumination, in order to independently constitute a dark field surface of respective surfaces on the three-dimensional configuration surface of a V notch, respective fine areas are irradiated by an optical system of optical fiber, a front surface and a back surface are imaged from an oblique direction by one camera, by the total of two cameras, and even the inspection object part of a deep focus depth can be inspected regardless of a distance. Since the light intensity of the scratch part is clear, the determination accuracy of a defect is substantially improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention is a surface flaw defect inspection apparatus and a surface flaw defect inspection apparatus for inspecting fine defects on the surface of an inspection object, particularly flaws in a V-shaped notch portion on the outer periphery of a silicon wafer.

As a method for inspecting a fine flaw defect in a mirror surface and a semi-mirror surface, a method is known in which a defect is detected by irradiating a target surface, imaging the reflected light, and performing image processing on a subtle bright and dark part.

In Patent Document 1, a fine defect detection method is proposed. In this method, the surface of each part of the notch is observed with five cameras and image processing is performed.

JP2003-243465

In Patent Document 2, the surface is observed by using a prism for each side of the V notch and imaging a large number of side regions in one image.

JP2007-10640

The inventions of Patent Document 1 and Patent Document 2 require a large number of cameras and precise special prisms, and are problematic in terms of the cost of the inspection apparatus.

On the other hand, in the conventional optical system, a threshold value is set for an image with a subtle brightness, so that even a non-defective product may be determined as a defective product, which deteriorates the yield in the manufacturing process.

As described above, in the inspection method using the optical technique according to the prior art, the setting of the light and dark threshold is delicate, and in the automatic inspection system in the production process, the yield and quality control are seriously problematic. Therefore, how to improve it is an issue.

In order to deal with such problems, the present invention provides a surface scratch inspection method and a surface scratch inspection apparatus that combine a bright field and a dark field in a well-balanced manner to sharpen a threshold and reduce costs with a minimum of optical instruments. There is to do.

In the present invention, the first problem solving means is configured to irradiate the inspection surface with diffused light illumination and irradiate the surface inspection object from the front surface, the back surface, and the wafer outer peripheral surface direction. Moreover, it is the structure which irradiates with respect to a back surface inspection object from a back surface, a surface, and a wafer outer peripheral surface direction.

The second problem solving means is dark field illumination. Although the V-notch is constituted by a three-dimensional mirror surface, since each surface forms a dark field surface independently, each minute region is irradiated with an optical system using an optical fiber.

The third means for solving the problem is that the front and back surfaces are imaged in an oblique direction by one camera each, a total of two cameras, and an inspection target part having a deep focal depth can be inspected regardless of the distance.

As described above, the surface inspection method of the present invention uses scattered light and an optical fiber light source to finely balance the bright field and dark field, and can select a wide range of contrast thresholds for bright and dark contrast, thereby improving the accuracy of scratch defect classification. . Since two cameras can be used to realize a surface scratch inspection device with the lowest cost, it can be used as an inspection device at the production site.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, this invention is not limited to a present Example.

FIG. 1 is an explanatory view of a surface flaw inspection method and a flaw inspection apparatus according to a first embodiment of the present invention.
The V-notch portion 11 of the inspection wafer 1 surrounds the upper and lower surfaces and the outer peripheral surface with the scattered light diffusing member 2 and is illuminated with the light source 7 for scattering. The scattered light diffusing member 2 has camera imaging windows 20a and 20b, and the front camera 5 and the rear camera 6 can capture images at an angle of about 45 degrees from the front and back surfaces. Further, optical fibers 3 and 4 for illuminating each field portion of the V notch with dark field illumination are installed, and a hole for optical fiber illumination (not shown) corresponding to the fiber is opened in the scattered light diffusing member 2.

FIG. 2 shows a scattering light source system necessary for the surface camera 5.
The reflected light 21b is obtained by the incident light 21a in the right tapered portion on the upper surface, and the reflected light 22b is obtained by the incident light 22a in the left tapered portion.
On the right side, the reflected light 23b is obtained with the incident light 23a, and on the left side of the side, the reflected light 24b is obtained with the incident light 24a.

FIG. 3 illustrates an incident light source of a dark field system based on FIG. In the notch portion, the main purpose is to inspect the scratch in the vertical direction. Therefore, the incident light source needs light sources in at least eight directions from the right tapered portion incident light 31 for the front camera to the left side incident light 44 for the rear camera.
Since these are required to be independent of each other, in the present invention, an illumination hole is provided at an optimum location of the scattered light diffusing member 2 and the target surface is irradiated with an optical fiber.

FIG. 4 is an explanatory view of the arrangement of optical fibers.
In the scattered light diffusing member 2, camera imaging holes 20 a and 20 b are set in a direction of an angle of 45 degrees with the V notch valley portion on the outer peripheral surface of the wafer 1 as the origin.
The optical fibers F31 to F44 correspond to the dark field incident light source system of FIG. 3, and the scattered light diffusing member 2 is provided with optical fiber illumination holes 8 corresponding to the individual fibers.
Each fiber is set to an angle at which the clearest image can be obtained while looking at the imaging camera.

FIG. 5 is a photograph taken in the first embodiment of the present invention. (A) is an image of only scattered light, and (b) is scattered light + dark field light. The inspection flaw part can be clearly copied by the dark field light.
The resolution in this image is 10 μm.

FIG. 6 is an explanatory diagram of the relationship between the vertical scratch width AB on the right side of the V-notch side surface and the visual field width FC of the surface camera. It explains that the visual field width FC depends on the notch angle β.

In the second embodiment, the optical fiber of FIG. 4 can be replaced with an LED light source. In this case, the LED light source is preferably a light source with strong directivity.

Device configuration diagram of surface defect measuring device Surface camera light source system Incident light source system for notch dark field Arrangement of dark field optical fiber Example of image processing in the present invention Relationship between camera vision and scratch width Example of cross-sectional shape of silicon wafer edge Planar shape of V-shaped notch

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inspection wafer 2 Scattered light diffusing member 3 Optical fiber 4 Optical fiber 5 Front camera 6 Back camera 7 Scattering light source 7a LED light source 8 Optical fiber hole 11 V notch

20a Front camera imaging window 20b Rear camera imaging window 21a Surface right taper portion incident light 21b Surface right taper portion reflected light 22a Surface left taper portion incident light 22b Surface left taper portion reflected light 23a Side surface right portion incident light 23b Side surface Right side reflected light 24a Side left side incident light 24b Side left side reflected light

31 Front-camera right taper incident light 32 Front-camera left taper incident light 33 Front-camera right-side incident light 34 Front-camera left-side incident light

41 Back-camera right taper incident light 42 Back-camera left taper incident light 43 Back-camera right-side incident light 44 Back-camera left-side incident light

111 Scratches on the surface right taper portion 112 Scratches on the surface left taper portion 113 Scratches on the right side surface 114 Scratches on the left side surface

F31 Optical fiber for right taper for front camera F32 Optical fiber for left taper for front camera F33 Optical fiber for right side for front camera F34 Optical fiber for left side for front camera F41 Optical fiber for rear surface right optical fiber F42 Optical fiber for rear surface F42 Optical fiber for left side taper for rear camera F43 Optical fiber for rear camera Right side optical fiber F44 Left side optical fiber for rear camera

Claims (5)

A surface inspection method that inspects microscopic defects by simultaneously irradiating the notch on the outer periphery of the wafer with scattered illumination and dark field illumination, and imaging the front and back surfaces with two cameras. The surface inspection method according to claim 1, wherein the scattered illumination is performed from a front surface, a back surface, and a wafer outer peripheral side direction of the notch portion. The surface inspection method according to claim 1, wherein the dark field illumination is performed by independently illuminating each polygonal surface of the V-shaped notch using an optical fiber optical system. 4. The surface inspection method according to claim 1, wherein the camera has a two-dimensional CCD function. 5. The surface inspection method and apparatus according to claim 1, wherein the optical fiber optical system includes a mechanism capable of finely adjusting an irradiation angle on an irradiation target surface.