JP2010016048A - Inspection device for wafer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inspect images of three surfaces of a peripheral edge of a wafer by a single camera at the same time. <P>SOLUTION: An optical system 3 having three optical paths 3a, 3b, 3c bending from a peripheral end face W1 and chamfered parts W2, W3 of the peripheral edge of a wafer toward the single camera 1 is arranged; reflected light rays guided by the optical paths 3a, 3b, 3c are imaged by the single camera 1; and the three surfaces of the peripheral end face W1 and the chamfered parts W2, W3 are formed into pictures at the same time, whereby surface defects occurring on the peripheral end face W1, the chamfered parts W2, W3 and boundaries W5, W6 thereof can be detected at the same time. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a wafer for non-destructively detecting surface defects such as pits and protrusions generated on a peripheral edge (edge) having a three-dimensional cross section of a semiconductor wafer by using optical means. It relates to an inspection device.
Specifically, the peripheral edge of the rotating wafer is irradiated with inspection light and reflected, and the reflected light is imaged by a camera, and the outer peripheral end surface of the peripheral edge of the wafer and its thickness direction The present invention relates to a wafer inspection apparatus that simultaneously detects surface defects generated in a pair of chamfered portions formed between the two.

  Conventionally, as this type of wafer inspection apparatus, as a plurality of imaging cameras for imaging different portions in the thickness direction of the peripheral edge of the wafer, the outer peripheral side surface of the wafer peripheral edge, the chamfered upper surface and the lower surface The camera has a side imaging camera, a top imaging camera, and a bottom imaging camera that are arranged with their imaging directions facing substantially at right angles, and these imaging cameras regularly reflect illumination from the C-shaped peripheral edge illumination section. A portion where the reflected light is positioned in the bright field range, and pits or protrusions are generated on the side surface, upper surface and lower surface of the peripheral edge of the wafer, and the specularly reflected light is not incident on the imaging camera. Is darkened and is extracted as a defect by image processing (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2003-243465 (pages 8-13 and FIGS. 15-16)

However, such a conventional wafer inspection apparatus requires at least three cameras corresponding to the outer peripheral end face and the chamfered portion of the peripheral edge of the wafer, so that the structure is complicated and enlarged. As a result, there is a problem that the cost becomes high.
In addition, since surface defects are detected by imaging only in the bright field, there is a problem that, for example, adhered foreign matters such as particles and dust may be erroneously determined as scratch defects such as pits.

A first aspect of the present invention is to image-inspect three surfaces of the peripheral edge of a wafer simultaneously with a single camera.
The second invention is intended to further improve the accuracy of image inspection in addition to the object of the first invention.
In addition to the objects of the first invention or the second invention, the third invention is intended to determine adhering foreign matters such as particles and dust from flaw defects such as pits.
In addition to the objects of the first invention, the second invention, or the third invention, the fourth invention is intended to prevent the occurrence of edge shadow in the plane image of the orientation flat portion.

In order to achieve the above-described object, the first invention of the present invention is provided with an optical system having three bending optical paths from the outer peripheral end surface and the chamfered portion of the wafer peripheral edge toward one camera, The reflected light guided by these optical paths is imaged by the one camera, and the three surfaces of the outer peripheral end surface and the upper and lower chamfered portions are simultaneously imaged.
According to a second invention, in the configuration of the first invention, a plurality of prisms are arranged in the optical path of the optical system, and the reflected light from the outer peripheral end surface and the chamfered surface of the peripheral edge of the wafer is refracted and synthesized. It is characterized by adding a configuration.
According to a third aspect of the present invention, in the configuration of the first aspect or the second aspect, bright field illumination and dark field illumination are provided as illumination for irradiating the inspection light, and the light sources of these bright field illumination and dark field illumination are switched. It is characterized in that a configuration for imaging is added.
According to a fourth aspect of the present invention, in the configuration of the first aspect, the second aspect or the third aspect, the moving means for moving the camera and the optical system relative to the wafer, and the orientation flat part of the wafer And detecting means for detecting delivery to the imaging position and control means for controlling operation of the moving means according to the detection result by the detecting means. It is characterized in that a configuration for moving the optical system is added.

The first aspect of the present invention provides an optical system having three bending optical paths from the outer peripheral end face and the chamfered portion of the peripheral edge of the wafer toward one camera, and reflects the reflected light guided by these optical paths. By imaging with one camera and simultaneously imaging the three surfaces of the outer peripheral end surface and the chamfered portion, it becomes possible to simultaneously detect surface defects generated on the outer peripheral end surface, the chamfered portion, and the boundary thereof.
Therefore, it is possible to simultaneously inspect the three surfaces of the peripheral edge of the wafer with one camera.
As a result, the structure can be simplified and made compact compared to the conventional camera that requires at least three cameras corresponding to the outer peripheral edge surface and the chamfered portion of the wafer peripheral edge, thereby reducing the cost. Reduction can be achieved.

In addition to the effects of the first invention, the second invention arranges a plurality of prisms in the middle of the optical path of the optical system to refract and synthesize the reflected light from the outer peripheral end surface and the chamfered surface of the peripheral edge of the wafer. Thereby, scattering reflection of reflected light is prevented.
Therefore, the accuracy of image inspection can be further improved.

In addition to the effects of the first invention or the second invention, the third invention includes bright field illumination and dark field illumination as illumination for irradiating inspection light, and switches between the light sources of the bright field illumination and dark field illumination. In the dark field, the adhering foreign matter such as particles and dust and the flaw defect such as the pit are identified by the difference in the reflection form, and the defect data detected in the bright field illumination is collated. Defects are removed and only scratch defects are formed.
Therefore, it is possible to determine by adhering foreign matter such as particles and dust separately from scratch defects such as pits.
As a result, it is possible to improve the determination accuracy without erroneously determining an adhering foreign matter such as a particle or dust as a defect, as compared with a conventional method in which a surface defect is detected by imaging only in a bright field.

In addition to the effects of the first invention, the second invention or the third invention, the fourth invention is a moving means for moving the camera and the optical system relative to the wafer, and the orientation flat part of the wafer is a camera. Detecting means for detecting delivery to the imaging position and control means for controlling the operation of the moving means according to the detection result by the detecting means. By moving the optical system, the position of the camera and the optical system when imaging the circumferential part where the outer peripheral end face and the chamfered part are formed, and the position of the camera when imaging the orientation flat part are changed.
Therefore, it is possible to prevent the edge shadow from occurring in the plane image of the orientation flat portion.

  In the embodiment of the wafer inspection apparatus of the present invention, the peripheral edge imaging for continuously imaging the support portion that rotatably supports the wafer W and the peripheral edge of the wafer W that is supported and rotated by the support portion. And a control unit that processes the imaging data imaged by the peripheral edge imaging unit. The peripheral edge imaging unit has a thickness of the peripheral edge of the wafer W as shown in FIGS. It consists of a single camera 1 that picks up images of parts in different directions, and an illumination 2 that irradiates the peripheral edge of the wafer W with inspection light.

  On the peripheral edge of the wafer W, there are formed an outer peripheral end surface W1 and a pair of chamfered portions W2 and W3 formed in an inclined shape with the outer peripheral end surface W1 being sandwiched in the thickness direction. , W3, the inspection light emitted from the illumination 2 is specularly reflected, and each specularly reflected light is captured and imaged by the one camera 1, thereby forming the outer peripheral end face W1 and the chamfered part W2. , W3, for example, surface defects such as pits and protrusions are simultaneously detected.

  As the illumination 2 for irradiating the peripheral edge of the wafer W with inspection light, as shown in FIGS. 2 to 4, an LED or the like is disposed so as to wrap around the peripheral edge of the wafer. It is preferable to use integrating sphere illumination composed of a hemispherical integrating sphere 2b that reflects and collects the inspection light irradiated from the spherical surface.

  An optical system 3 having three bent optical paths 3a, 3b, 3c is provided between the outer peripheral end face W1 and the chamfered portions W2, W3 of the peripheral edge of the wafer and one camera 1, and the optical paths 3a, 3b, 3c are provided. A reflector 4 such as a prism or a mirror is disposed in the middle of 3b and 3c, and the reflected light from the outer peripheral end surface W1 and the chamfered portions W2 and W3 are guided while being separated from each other and synthesized to form a single camera 1. The three images of the outer peripheral end surface W1 and the chamfered portions W2 and W3 are simultaneously imaged.

  Further, an optical path 3a for guiding the reflected light from the outer peripheral end surface W1 of the wafer peripheral edge is supported so as to be adjustable in the thickness direction of the wafer W, and an optical path 3b for guiding the reflected light from the chamfered portions W2, W3. 3c is supported so as to be adjustable in the thickness direction of the wafer W, and is provided with a focus adjustment mechanism that independently adjusts the focus of the captured image, thereby changing the diameter and thickness of the wafer W. It is preferable to adjust the focus accordingly.

  In the image processing in the control unit, it is necessary to fade the roughness of the surface white by the defect contrast and the appropriate surface diffused light to produce a contrast difference from the defect, but the coaxial incident axis is a reflector such as the prism or mirror. By rotating the axis with the optical system according to the above, regular reflected light can be released and the contrast can be adjusted to an appropriate level.

Further, as shown in FIGS. 5 to 7, the wafer W can be visually inspected even when a planar orientation flat (orientation flat) portion W4 is formed on a part of its peripheral edge. Is preferred.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  In the first embodiment, as shown in FIG. 1A, a plurality of prisms 4 are arranged in the middle of the optical paths 3a, 3b, 3c of the optical system 3, and a telecentric imaging lens 5 is arranged downstream thereof. As a result, each reflected light from the outer peripheral end surface W1 and the upper and lower chamfered portions W2 and W3 of the wafer peripheral edge is guided in parallel toward the line sensor camera 1 such as a CCD camera, and these three images are combined by relay composition. As shown in FIG. 1 (b), three images of the A portion, the B portion, and the C portion corresponding to the outer peripheral end surface W1 and the chamfered portions W2 and W3 of the peripheral edge of the wafer are displayed at the same time in one direction. I try to inspect.

As shown in FIGS. 2 to 4, the integrating sphere illumination 2 that irradiates the peripheral edge of the wafer W with inspection light passes through the spherical core (integral center) of the integrating sphere 2b. Is inserted so as to be rotatable, and the imaging centers of the chamfered portions W2 and W3 are arranged so as to match the integration center of the integrating sphere 2b.
Inside the integrating sphere 2b, flat surface light sources having a large illumination area are arranged as light sources 2a above and below the integrating sphere 2b so as to sandwich the peripheral edge of the wafer, respectively. Illumination is performed from behind the outer peripheral end surface W1 and the chamfered portions W2 and W3 toward the integrating sphere 2b.
Although not shown, it is preferable to provide a light-shielding cover 2c for limiting the influence of external light behind the light source 2a. The light-shielding cover has a slit for rotatably inserting the peripheral edge of the wafer. Is done.

  Further, a light shielding plate 2c such as a louver or a blind is disposed at the front end of the light source 2a on the wafer side so that the illumination angle with respect to the chamfered portions W2 and W3 at the peripheral edge of the wafer is limited so that direct illumination is not performed. Thus, the corner portion W5 formed between the chamfered portions W2 and W3 and the wafer surface and the corner portion W6 formed at the boundary between the chamfered portions W2 and W3 and the outer peripheral end surface W1 can be prevented from shining white. Yes.

Further, the wafer W is shifted by a predetermined angle in the circumferential direction of the wafer W so that the regular reflection of the integration center illumination from the light source 2a with respect to the outer peripheral end surface W1 of the peripheral edge of the wafer is efficiently incident on the imaging lens. A black streak shadow is prevented from being generated at the center of the B portion image corresponding to the end face W1.
In the case of the illustrated example, as shown in FIG. 3, the integration center line of the integrating sphere 2b coincides with the imaging axis passing through the center of the wafer W, and the circumference of the wafer W from the integration center of the integrating sphere 2b. The port 2d of the monitor optical path 3a of the outer peripheral end face W1 is opened at a position inclined by a predetermined angle (about 14 degrees) or more in the direction.
As another example, although not shown, the integrating sphere 2b is attached with its integration center line inclined at a predetermined angle (about 14 degrees) or more in the circumferential direction of the wafer W with respect to the imaging axis passing through the center of the wafer W. It is also possible to offset the imaging axis.

Further, the port 2d of the monitor optical path 3a of the outer peripheral end face W1 is opened above and below the integrating sphere 2b.

  On the other hand, the optical paths 3a, 3b, 3c of the optical system 3 are covered with a cover case 3d as shown in FIG. 5 to FIG. The wafer W is rotatably supported by the support portion.

Further, in addition to the bright field illumination of the light source 2a of the integrating sphere illumination 2, a dark field illumination using an LED or the like as a light source is provided, and the peripheral edge of the wafer W is rotated once by the bright field illumination, and the outer peripheral end surface W1. In addition, after imaging the entire outer periphery of the chamfered portions W2 and W3, imaging is performed by another rotation with dark field illumination.
As a result, adhesion defects such as particles and dust and scratch defects such as pits in the dark field are identified by the difference in their reflection form, and are compared with defect data detected by bright field illumination. Remove only scratch defects.

  Then, when the appearance inspection of the wafer W on which the orientation flat portion W4 is formed using such a wafer inspection apparatus, the outer peripheral end face W1 and the chamfered portions W2 and W3 are formed as the wafer W rotates. By changing the position of the camera 1 when imaging the circumferential portion W5 and the position of the camera 1 when imaging the orientation flat portion W4, an edge shadow (shadow of black streaks) is formed on the plane image of the orientation flat portion W4. It is trying not to occur.

  That is, when the planar orientation flat portion W4 is imaged as it is at the position of the camera 1 when imaging the circumferential portion W5, the orientation flat portion W4 is recessed as compared with the circumferential portion W5, and therefore the positional relationship with the camera 1 Changes, and a black streak shadow is generated in the plane image of the orientation flat portion W4.

  In view of this, such a wafer inspection apparatus includes a rotation drive unit that rotates the wafer W, and a moving unit that relatively moves the camera 1, the integrating sphere illumination 2, and the optical system 3 described above with respect to the wafer W. , Detecting means for automatically detecting that the orientation flat part W4 of the wafer W has been delivered to the imaging position by the camera 1, and controlling the operation of the rotation driving part, the camera 1 and the moving means according to the detection result by the detecting means. The control means stops the rotation of the wafer W when the orientation flat portion W4 of the wafer W is delivered to the camera imaging position, and the camera 1, the illumination 2 and the optical system 3 are shaded black. It has been moved to a position that does not.

  Specific examples will be described with reference to FIGS. 5A to 5F, FIGS. 6A and 6B, and FIGS. 7A and 7B. First, as shown in FIGS. Even if the imaging of the circumferential portion W5 is completed with the rotation of the wafer W, if the imaging is continued as shown in FIG. 6A, the orientation flat portion W4 of the image is obtained as shown in FIG. 6B. Black streaks appear on the side.

  In order to prevent this, as shown in FIG. 5C, the rotation of the wafer W is stopped, and the camera 1, the illumination 2 and the optical system 3 are translated in the rotation direction of the wafer W, and then FIG. As shown in d) and FIG. 7A, when the wafer W is rotated forward or backward to re-image the bent portion W6, the black stripe on the orientation flat portion W4 side is removed.

Thereafter, as shown in FIG. 5 (e), when the wafer W is rotated in the forward direction and becomes parallel to the orientation flat portion W4, the rotation is stopped, and the camera 1, illumination 2 and optical system 3 reach the end of the orientation flat portion W4. Is moved in parallel to the rotation direction of the wafer W and moved closer to the orientation flat portion W4 for focusing, and then the camera 1, the illumination 2 and the optical system 3 are moved to the orientation flat portion as shown in FIG. The orientation flat portion W4 is imaged by parallel translation along W4.
After that, the above-described operation is repeated to remove black stripes.

In the previous embodiment, the integrating sphere illumination including the light source 2a and the integrating sphere 2b arranged so as to wrap around the wafer peripheral edge is used as the illumination 2 for irradiating the wafer peripheral edge with the inspection light. However, the present invention is not limited to this, and other illuminations may be used.
Further, reflectors such as prisms and mirrors are arranged in the middle of the optical paths 3a, 3b, and 3c, and the reflected light guided by them is guided to one camera 1. However, the present invention is not limited to this. Instead of the reflector, a fiberscope or the like may be arranged to form the three bent optical paths 3a, 3b, 3c.

An embodiment of the wafer inspection apparatus of the present invention is shown, in which (a) is an optical path diagram of an imaging optical system, and (b) is an explanatory diagram showing a positional relationship between a captured image and a wafer. It is a vertical side view which shows the positional relationship of a wafer and illumination. It is a cross-sectional top view which shows the positional relationship of a wafer and illumination. It is the front view seen from the wafer side which shows the positional relationship of a wafer and illumination. It is explanatory drawing which shows an imaging step, and is imaged according to the order of (a)-(f). (A) is explanatory drawing which shows the middle of an imaging step, (b) is the captured image. (A) is explanatory drawing which shows the middle of an imaging step, (b) is the captured image.

Explanation of symbols

W wafer W1 outer peripheral end face W2, W3 chamfered portion W4 orientation flat portion W5, W6 corner portion 1 camera 2 illumination (integrating sphere illumination) 2a light source 2b integrating sphere 2c light shielding cover 2d, 2e port 3 optical system 3a, 3b, 3c optical path 4 reflection Body (prism)
5 Telecentric imaging lens

Claims (4)

The peripheral edge of the rotating wafer (W) is irradiated with inspection light and reflected, and the reflected light is imaged and imaged by the camera (1), thereby forming an outer peripheral end surface (W1) of the peripheral edge of the wafer. In the wafer inspection apparatus for simultaneously detecting surface defects generated in a pair of chamfered portions (W2, W3) formed by sandwiching it in the thickness direction,
An optical system (3) having three bent optical paths (3a, 3b, 3c) from the outer peripheral end surface (W1) and the chamfered portions (W2, W3) of the peripheral edge of the wafer toward one camera (1). The reflected light guided by these optical paths (3a, 3b, 3c) is imaged by the one camera (1), and the outer peripheral end surface (W1) and the three surfaces of the chamfered portions (W2, W3) are simultaneously formed. An inspection apparatus for wafers characterized by being imaged. A plurality of prisms (4) are arranged in the middle of the optical path (3a, 3b, 3c) of the optical system (3) so that the peripheral edge of the wafer (W1) and the chamfered surfaces (W2, W3) The wafer inspection apparatus according to claim 1, wherein the reflected light is refracted and synthesized. 3. The wafer inspection apparatus according to claim 1, comprising bright-field illumination and dark-field illumination as illumination (2) for irradiating the inspection light, and switching between the bright-field illumination and dark-field illumination light sources for imaging. 4. A moving means for moving the camera (1) and the optical system (3) relative to the wafer (W) and an orientation flat part (W4) of the wafer (W) delivered to the imaging position by the camera (1). Detecting means for detecting this, and control means for controlling the operation of the moving means in accordance with the detection result by the detecting means. The control means detects the camera (1) and the camera when detecting the orientation flat portion (W4). 4. The wafer inspection apparatus according to claim 1, wherein the optical system is moved.