KR20080028998A - Apparatus for inspecting flaw at end section - Google Patents

Abstract

A device for inspecting a flaw at an end section has an elliptic mirror having inside a mirror surface and having at its vertex a cutout into which an object to be inspected is insertable; a light emission section for applying coherent light to an end section of the object placed at a position near a first focal point of the elliptic mirror; a light detection section placed at a second focal point of the elliptic mirror; and a light shielding means for shielding regularly reflected diffraction light of low order. The light emission section can apply coherent light of different wavelengths.

Description

End flaw inspection apparatus {APPARATUS FOR INSPECTING FLAW AT END SECTION}

The present invention relates to an end scratch inspection apparatus for optically inspecting scratches at the end of an inspection object.

As an end flaw inspection apparatus which inspects flaws of an end such as narrow and long end cracks, defects, or polishing scratches formed at the end of the silicon wafer, such as the outer edge portion, an inspection apparatus using an ellipsoidal mirror has been proposed. For example, the light absorbing member is disposed on the mirror surface of the ellipsoidal mirror, and the low-dimensional diffraction light that is the specular reflection light is absorbed by the light absorbing member, so that only the high-dimensional diffraction light that is diffusely reflected from the scratches at the end is formed at the second focal position. An apparatus for detecting by a detection unit has been proposed (see Patent Document 1, for example). In addition to the first light detection unit formed at the second focus position, a second light detection unit is formed around the inspected object provided at the first focus position, so that the two light receiving units can cope with vertical and horizontal scratches. An apparatus has been proposed (see, for example, Patent Document 2). According to these end flaw inspection apparatus, it becomes possible to test over the whole periphery by rotating an inspection object, and the presence or absence of a flaw and the position of the circumferential direction can be confirmed by the intensity of the light detected by a light receiving part.

However, according to the conventional end flaw inspection apparatus, although the kind of the flaw was able to be estimated to some extent by the intensity of the light detected by the light receiving portion, it is limited to identify details such as the magnitude and type of the flaw from one measurement item of the light intensity. There was.

Patent Document 1: Japanese Unexamined Patent Publication No. 2003-287412

Patent Document 2: Japanese Patent Application Laid-Open No. 11-351850

Disclosure of the Invention

Challenges the invention seeks to solve

This invention is made | formed in view of the above-mentioned situation, and proposes the edge flaw inspection apparatus which can detect the detail, such as the magnitude | size and the kind of the flaw which arose in the edge part of a to-be-tested object.

Means to solve the problem

The present invention provides an ellipsoid mirror having a mirror surface inside, a light emitting portion for irradiating coherent light toward an end portion of the inspected object disposed near the first focal position of the ellipsoid mirror, and a second focal position of the ellipsoid mirror. And a light detection unit capable of detecting diffracted light reflected by the coherent light irradiated to the end portion and the ellipsoid of the test object and reaching the second focal point, and among the diffracted light, An end flaw inspection apparatus comprising light blocking means for shielding low-dimensional diffracted light and a holding portion for holding the inspection object and moving the end portion in the circumferential direction on the first focal position, wherein the light emitting portion has a different wavelength. The coherent light of can be irradiated.

According to the end flaw inspection apparatus according to the present invention, by detecting the intensity of diffracted light by irradiating coherent light of different wavelengths, the absorption is greatly detected in the detection of fine scratches or long coherent light. It is possible to detect scratches that were not detected or diffusely reflected only in coherent light of a specific wavelength.

Effects of the Invention

According to the present invention, coherent light of different wavelengths can detect fine scratches or scratches whose absorption is not largely detected in long coherent light, or scratches that are diffusely reflected only in coherent light of a specific wavelength. Thus, the size and the size of the scratches can be specified, and detailed end scratch inspection can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS It is a longitudinal cross-sectional view which cut | disconnected the edge flaw inspection apparatus of embodiment of this invention by the perpendicular surface.

It is a longitudinal cross-sectional view which cut | disconnected the edge scratch inspection apparatus of embodiment of this invention by the horizontal plane.

It is explanatory drawing which irradiates the edge part of a to-be-tested object by the light emission part of embodiment of this invention.

4 is a graph showing an example of a detection result by the light detection unit when the wavelength of the coherent light to be irradiated according to the embodiment of the present invention is changed.

It is a graph which shows an example of the detection result by the light detection part at the time of changing the irradiation range in the thickness direction with the coherent light of the several wavelength of embodiment of this invention.

Explanation of the sign

One … End scratch inspection device

2 … Ellipsoid

2a. Medial

2b. Mirror

3…. Light emitting part

3a. End

4 … Light emitting part

5…. Photodetector

7. Shading means

8 … Light source

9... Ultralight

10... Probe scope

? wavelength

Implement the invention  Best form for

(1st embodiment)

1-5 has shown embodiment which concerns on this invention. The longitudinal cross-sectional view which cut | disconnected the edge flaw test | inspection apparatus by the perpendicular plane in FIG. 1, and the longitudinal cross-sectional view which cut | disconnected by the horizontal plane are shown in FIG. Explanatory drawing which irradiates the edge part of a to-be-tested object by a light emitting part is shown in FIG. Moreover, the graph which shows an example of the detection result by the light detection part when the wavelength of the coherent light irradiated to FIG. 4 is changed, and FIG. 5 is a coherent light of several wavelength, and irradiation range is changed to a circumferential direction. The graph which shows an example of the detection result by a light detection part at the time of the display is shown.

As shown in FIG. 1, FIG. 2, the edge flaw inspection apparatus 1 has the notch 2d which has the mirror surface 2b in the inner side 2a, and can insert the to-be-tested object 3 in the apex part 2c. In the long axis direction of the ellipsoidal mirror 2 at the ellipsoidal mirror 2 on which the ellipsoidal mirror 2 is formed and the end portion 3a of the inspected object 3 disposed near the first focal position A of the ellipsoidal mirror 2. The light emitting part 4 which irradiates coherent light C along L), and the light detection part 5 arrange | positioned at the 2nd focal position B of the ellipsoidal mirror 2 are provided. Moreover, the edge flaw inspection apparatus 1 is equipped with the holding part 6 which hold | maintains the to-be-tested object 3 so that rotation, and the light shielding means 7 formed in the ellipsoidal mirror 2 are carried out. The inspected object 3 is a plate-shaped silicon wafer, a semiconductor wafer, etc., for example.

As shown in FIG. 3, the light emitting part 4 includes a light source 8 that emits coherent light C, and an ultralight means 9 that optically acts on the irradiated coherent light C. As shown in FIG. Equipped. The light source 8 is a laser beam, for example, and can adjust a wavelength freely. More specifically, the wavelength is freely adjusted by allowing the conversion of a plurality of lasers of various wavelengths using a He-Ne laser or a semiconductor laser. Alternatively, a tunable laser may be used. Moreover, the ultra-light means 9, when irradiating the coherent light C emitted from the light source 8 to the end part 3a of the to-be-tested object 3, the edge part 3a of the to-be-tested object 3 It is a Fresnel lens which can irradiate the whole edge part 3a in the thickness direction, and sets it as the irradiation range 10 which narrowed the width in the circumferential direction. 1 and 2, in the photodetector 5, the diffracted light D reflected by the end 3a of the inspected object 3 irradiated from the light emitting unit 4 is an elliptical mirror 2. ) Is a photodiode which detects the diffracted light D reflected on the second focal position B and is focused.

As shown to FIG. 1, FIG. 2, the holding part 6 positions the edge part 3a of the to-be-tested object 3 to the vicinity of the 1st focal position A of the ellipsoidal mirror 2, and is a rotating shaft Rotation of 6a makes it possible to move the end 3a of the inspected object 3 in the circumferential direction on the first focal position A. As shown in FIG. Moreover, the light shielding means 7 has the intersection image which the surface parallel to the thickness direction of the to-be-tested object 3 containing the 1st focus position A and the 2nd focus position B, and the ellipse mirror 2 cross | intersect. It is a masking tape bonded to a predetermined width. The diffracted light D which has reached this light shielding means 7 is reflected and absorbed by the light shielding means 7 without reaching the light detector 5. Moreover, the light shielding plate 11 is formed in the 1st focus position A side of the light detection part 5. This is because the coherent light C irradiated from the light emitting portion 4 is reflected by the end portion 3a of the inspection object 3 to become the diffracted light D. The diffracted light D is an elliptical mirror 2. This is because it does not reach the photodetector 5 directly without being reflected by the light source.

Next, the operation of this end scratch inspection apparatus 1 will be described. The light emitting part 4 irradiates arbitrary positions of the edge part 3a of the to-be-tested object 3. When a scratch is not contained in the irradiated part, the coherent light C irradiated is specularly reflected and becomes the low-dimensional diffraction light D1. As shown in FIG. 2, the low-dimensional diffraction light D1 is directed to the second focal position B with a path around the axis L of the planar ellipsoid 2 as shown in FIG. 1. Similarly, according to the shape of the end part 3a of the side to-be-tested object 3, it has a some extent in the thickness direction. For this reason, the low-dimensional diffraction light D1 is absorbed by the light shielding means 7 or the light shielding plate 11, and most of it does not reach the light detection part 5. In other words, when no scratch is present at the end 3a of the inspected object 3, the intensity R of the light detected by the light detection unit 5 is measured only at a low level. As shown in FIG. 3, when the scratch 3b is included in the irradiation range 10, the coherent light C to be irradiated is diffusely reflected to become a high-dimensional diffracted light D2. As shown in FIG. 1 and FIG. 2, the high-dimensional diffracted light D2 is widely diffused by the scratches 3b formed at the end 3a in both the planar view and the side view, and the ellipsoid 2 It reflects and reaches | attains the light detection part 5 of the 2nd focal position B. As shown in FIG. That is, when the flaw 3b exists in the edge part 3a of the to-be-tested object 3, the intensity | strength R of the light detected by the light detection part 5 is measured by a high level. Here, with respect to the wavelength λ of the coherent light C to be irradiated, the coherent light to be irradiated when the size of the scratch 3b is fine or damage that is not reflected only at a specific wavelength λ (C) is specularly reflected and becomes the low-dimensional diffracted light D1 and is not detected by the photodetector 5. That is, it is determined that the scratch 3b does not exist at the end 3a of the inspected object 3. 4 shows a wavelength? At the time of changing the wavelength? For an arbitrary position of the end 3a of the inspected object 3 and the intensity R of the light detected by the photodetector 5. Is shown as an example. As shown in FIG. 4, the flaw which was not detectable at the wavelength λ1 can be detected at the wavelength λ2 shorter than the wavelength λ1 by changing the wavelength λ. In addition, FIG. 5 shows the rotation angle θ and the light of the inspected object 3 when the end 3a of the inspected object 3 is rotated 360 degrees by the holding part 6 while changing the wavelength λ. An example of the relationship of the intensity | strength R of the light detected by the detection part 5 is shown. As shown in FIG. 2, rotation angle (theta) is an angle which made 0 degree from position O, and made the right time when it turned right. As shown in Fig. 5, each graph shows a relationship when the wavelengths (λ3, λ4, λ5, and λ6) are shown, respectively, and the size of each wavelength λ is λ3 <λ4 <λ5 < λ6. As shown in FIG. 2, FIG. 5, in this example, in the vicinity of the rotation angle (theta) p of the position P, the high-order diffraction light D2 resulting from a flaw can be remarkably detected by wavelength (lambda). In the vicinity of the rotation angle θq of the position Q, the high-dimensional diffraction light D2 resulting from the scratch can be remarkably detected at the wavelength λ. By changing and inspecting the wavelength [lambda] in this manner, even minute scratches can be detected, and in the coherent light having a long wavelength, the scratches and damages detected only at a specific wavelength can also be identified. can do.

As described above, the end flaw inspection device 1 is irradiated with the coherent light C having different wavelengths λ, and thus the intensity R of the light detected by the wavelength λ and the light detection unit 5 is determined. Not only the presence or absence of a scratch, but also the magnitude of the scratch and the kind of the scratch can be specified.

As mentioned above, although embodiment of this invention was described in detail with reference to drawings, a specific structure is not limited to this embodiment, The design change etc. of the range which do not deviate from the summary of this invention are included.

In addition, although the edge part 3a of the to-be-tested object 3 was irradiated with the coherent light C along the axis L of the ellipsoidal mirror 2, it is not limited to this. Instead, the optical axis of the light source 8 may be slightly shifted (about 4 degrees) with respect to the axis L of the ellipsoidal mirror 2 so that the light source 8 and the second focal point B do not overlap. By doing in this way, since the low-dimensional diffraction light D1 reflected on the edge part 3a of the to-be-tested object 3 also deviates from the axis line L of the ellipsoidal mirror 2, since the irradiated coherent light C The light shielding plate 11 can be omitted.

In this case, the optical axis of the light source 8 may be inclined in the horizontal direction with respect to the axis L of the ellipsoidal mirror 2, but it is preferable to incline in the vertical direction. That is, when the coherent light C is irradiated to the end surface 3a of the to-be-tested object 3 supported horizontally from the direction inclined horizontally with respect to the axis line L of the ellipsoidal mirror 2, flaw detection (探傷) This is because scattered reflected light in the left and right directions including a large amount of necessary information is shifted from side to side, and there is a problem that valid information is damaged. On the other hand, when tilting in the vertical direction, since the scattered reflected light in the vertical direction does not include much of the information necessary for flaw detection, there are few problems described above. Further, even when tilted in the horizontal direction, the scattered reflected light in the left and right directions may be focused on the photodetector by a study such that the shape of the ellipsoid 2 is asymmetrically.

In addition, although the masking tape was made to adhere | attach the oval mirror 2 as the light shielding means 7, it is not limited to this. The light-shielding plate which consists of a board | plate material of predetermined width as a spatial filter between the edge part 3a of the to-be-tested object 3 and the light source 8 should just be able to shield the low-dimensional diffraction light D1 reflected at least. May be arranged to abut on the inner surface of the ellipsoidal mirror 2 in a vertical direction perpendicular to the surface of the inspected object 3. For this reason, although the low-dimensional diffraction light D1 is interrupted by the light shielding plate, the high-dimensional diffraction light D2 leaks out of the light shielding plate and is collected by the ellipsoidal mirror 2.

With coherent light of different wavelengths, it is possible to detect scratches that are not detected largely in fine scratches or long coherent light, or scratches that are diffusely reflected only by coherent light of a specific wavelength, By specifying the type, it is possible to realize detailed end scratch inspection.

Claims (1)

An ellipsoid having a mirror surface inside, a light emitting portion for irradiating coherent light toward an end portion of the inspected object disposed near the first focal position of the ellipsoid, and the irradiated portion disposed at a second focal position of the ellipsoid A light detector which detects diffracted light reflected by the coherent light to the end portion and the ellipsoid of the test object and reaches the second focal position, and among the diffracted light, a low-dimensional diffraction of specular reflection An end flaw inspection apparatus having light blocking means for shielding light and a holding portion for holding the inspection object and moving the end portion in the circumferential direction on the first focal position, The said light-emitting part can irradiate the coherent light of a different wavelength, The edge damage inspection apparatus characterized by the above-mentioned.

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