JP5830229B2 - Wafer defect inspection system - Google Patents

Description

  The present invention relates to a wafer defect inspection apparatus for inspecting defects such as fine pinholes and cracks existing on and inside a semiconductor silicon wafer with infrared rays.

Conventionally, as this type of wafer defect inspection apparatus, a halogen lamp of an infrared light source that irradiates a silicon substrate as an object with infrared rays, an infrared lens that collects infrared rays that have passed through the silicon substrate, and an infrared lens. An infrared camera that receives the emitted infrared light, converts it into an electrical signal, and outputs it; a monitor that inputs the electrical signal output from the infrared camera, converts it into an image signal, and displays an image based on the image signal; (For example, refer to Patent Document 1).
In this case, when an abnormal part such as a crack is included in a part of the silicon substrate, since the infrared transmission state in the abnormal part is different from other normal parts, the infrared part is abnormally transmitted in the abnormal part. A difference occurs in the transmission state, and this difference is captured as a shadow by the infrared camera. In this infrared image, the position of the abnormal part is specified by the contrast ratio between the normal transmission part and the shadow part.

JP 2006-351669 A

However, in such a conventional wafer defect inspection apparatus, since a silicon wafer is irradiated with infrared rays of a wide wavelength from a halogen lamp, the silicon wafer is innumerable on the entire surface of the wafer, particularly a wafer after chemical etching. If there are fine irregularities on the surface, the surface roughness part (rough part of the background) is displayed on the infrared image mixed with defective parts such as scratches or uneven brightness including fine pinholes and cracks, for example. Therefore, it is difficult to identify such rough portions and defective portions by image processing.
This is the biggest bottleneck in the automation of defect detection, and the yield and quality control in the automatic inspection system are serious problems.

  An object of the present invention is to cope with such a problem. Even if a silicon wafer to be inspected has a surface roughness portion, the defective portion can be reliably identified, and the surface roughness portion of the silicon wafer can be identified. Surely erase components that become stable, easily obtain stable single-wavelength near-infrared scattered light with a simple structure, uniformly irradiate a silicon wafer to be inspected with single-wavelength near-infrared scattered light, It is for the purpose.

In order to achieve such an object, a wafer defect inspection apparatus according to the present invention condenses a near-infrared light source that irradiates a silicon wafer with a single-wavelength near-infrared scattered light and a transmitted light transmitted through the silicon wafer. A camera lens, an imaging camera that receives and images the transmitted light collected by the camera lens, and an image processing unit that performs image processing on a captured image of the imaging camera. The infrared light source includes a plurality of light emitting diodes arranged so as to be close to each other and emitting near infrared rays having a single wavelength of 940 to 960 nm, and a diffusion plate arranged in an emission direction of the light emitting diodes, The near-infrared scattered light emitted from the light-emitting diode passes through the diffuser plate, and is spatially uniformly distributed and uniformly irradiated toward the surface of the silicon wafer. Processing section is characterized by erasing the ingredients and a surface roughness of the portion of the silicon wafer on the captured image of the imaging camera.

In addition to the features discussed above, characterized in that said irradiated from the near infrared light source 940~960nm the near-infrared scattered light of any single wavelength in the silicon wafer.

  Further, in addition to the above-described features, an area sensor camera is used as the imaging camera.

In the present invention having the above-described features, a silicon wafer is irradiated with a single-wavelength near-infrared scattered light from a near-infrared light source, and the transmitted light transmitted through the silicon wafer is condensed by a camera lens. Since the transmitted light is received by the imaging camera and imaged, and the image processing unit erases the component that becomes the surface roughness portion of the silicon wafer on the captured image of the imaging camera, thereby enhancing the image of the defective portion. Even if the silicon wafer to be inspected has a surface roughness portion, the defective portion can be reliably identified.
As a result, defect detection can be automated as compared with the conventional one using a halogen lamp, and the yield can be improved and quality control can be improved by the automatic inspection system.

Further, when the silicon wafer is irradiated with a near-infrared scattered light having a single wavelength of 940 to 960 nm from the near-infrared light source, the near-infrared scattered light having a single wavelength of 940 to 960 nm is converted into silicon. By passing through the wafer, the background pattern having a shape different from the shadow of the defective portion becomes gentle on the captured image of the imaging camera, so that the component that becomes the surface roughness portion of the silicon wafer can be surely erased. .
As a result, it is possible to improve the identification accuracy of the defective portion.

  In addition, when the near-infrared light source has a plurality of light-emitting diodes arranged close to each other, the difference in intensity between the near-infrared rays respectively emitted from the plurality of light-emitting diodes is reduced, so that a stable single-wavelength near-wavelength light source can be obtained. Infrared scattered light can be easily obtained with a simple structure.

In addition, when a diffusion plate is arranged in the emission direction of the light emitting diode, single-wavelength near-infrared scattered light emitted from a plurality of light emitting diodes passes through the diffusion plate, and is distributed spatially and uniformly. Therefore, it is possible to uniformly irradiate the silicon wafer to be inspected with a single-wavelength near-infrared scattered light.
As a result, it is possible to improve the identification accuracy of the defective portion.

It is explanatory drawing which shows the wafer defect inspection apparatus which concerns on embodiment of this invention. It is the brightness profile inside the wafer surface in an Example. It is the brightness profile inside the wafer surface in a comparative example.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, a wafer defect inspection apparatus A according to an embodiment of the present invention irradiates a near-infrared scattered light R1 having a single wavelength (single wavelength or fixed wavelength) onto a silicon wafer W to be inspected. An external light source 1, a camera lens 2 that collects the transmitted light R2 that has passed through the silicon wafer W, an imaging camera 3 that receives and images the transmitted light R2 collected by the camera lens 2, and an imaging camera 3 And an image processing unit 4 that performs image processing on the captured image.

The silicon wafer W is a plate obtained by thinly slicing an ingot, and it is necessary to inspect a defective portion such as a scratch or a brightness unevenness including a fine pinhole and a crack existing on the surface and inside thereof. Examples of the inspection target include a lapped wafer, a wafer after an etching process such as chemical etching, a wafer having a mirror finish, and the like, which are created in the manufacturing process of a semiconductor silicon wafer.
Among these, the wafer after chemical etching has countless fine irregularities on the entire surface, so that the surface roughness portion (the rough portion of the background) has scratches containing fine pinholes and cracks. Or, it is displayed on an image in a mixed manner with a defective portion such as uneven brightness, and it is said that such a rough portion and a defective portion are most difficult to distinguish by image processing or the like.

The near-infrared light source 1 has a light-emitting diode (LED) 1a that emits near-infrared light having a single wavelength of about 940 to 960 nm, for example, and by arranging a plurality of the light-emitting diodes 1a, the near-infrared scattered light R1 Is preferably emitted toward the silicon wafer W.
As a specific example, it is preferable to arrange a plurality of light emitting diodes 1a so as to be close to each other so that a difference in intensity does not occur in near infrared rays respectively emitted from the plurality of light emitting diodes 1a.
Furthermore, in the emission direction of these light emitting diodes 1a, a diffuser plate 1b is arranged, and the near-infrared scattered light R1 emitted from the light emitting diode 1a passes through the diffuser plate 1b, so that it is distributed spatially and uniformly. It is preferable that the silicon wafer W is uniformly irradiated toward one of the front and back surfaces W1.

The transmitted light R2 transmitted from the other surface W2 of the silicon wafer W is collected by the camera lens 2 and forms an image of the silicon wafer W on the light receiving element provided inside the imaging camera 3.
As the imaging camera 3, an area sensor camera is preferably used.
In addition, a monitor (not shown) connected to the imaging camera 3 is provided, and an image taken by the imaging camera 3 in response to an electrical signal from the imaging camera 3 is displayed so that the inspector can detect a defective portion from the captured image. It is also possible to visually confirm the above.

  The image processing unit 4 receives image data output from the imaging camera 3 with a personal computer (not shown), and the personal computer erases, for example, a component that becomes a surface roughness portion of the silicon wafer W from the image data. Image processing is performed.

And operation | movement of the wafer defect inspection apparatus A which concerns on embodiment of this invention is demonstrated.
Near-infrared scattered light R1 having a single wavelength (about 940 to 960 nm) emitted from the plurality of light emitting diodes 1a passes through the diffusion plate 1b and is spatially uniformly distributed on one surface W1 of the silicon wafer W. Uniform irradiation.
As a result, the near-infrared scattered light R1 passes through the silicon wafer W without a fine defect portion, the fine defect portion, and the surface roughness portion existing on the surface of the silicon wafer W, respectively. The light ray R2 is imaged on the light receiving element in the imaging camera 3 by the camera lens 2, and the captured image is subjected to image processing to be described later by the image processing unit 4.

Here, since the portion without the fine defect portion is a single crystal of silicon, the image is uniform since the transmission state of the single-wavelength near-infrared scattered light R1 is always constant.
On the other hand, defects such as scratches or uneven brightness including fine pinholes and cracks cause reflection and absorption of the near-infrared scattered light R1, and thus a "shadow" of the same shape as the defect occurs. To do.
In addition, when the silicon wafer W has countless fine irregularities on the entire surface of the wafer, such as a wafer after chemical etching, the surface roughness portion (the rough portion of the background) Since reflection and absorption of the externally scattered light R1 occur, a “background pattern” having a shape different from the “shadow” of the defective portion is generated.
Based on these, the image processing unit 4 performs image processing and erases the component that becomes the surface roughness portion of the silicon wafer W on the captured image, thereby enhancing the image of the defective portion.

According to such a wafer defect inspection apparatus A, the defect portion can be reliably identified as the silicon wafer A to be inspected, for example, a wafer after chemical etching, and the defect detection can be automated.
Next, an embodiment of the present invention will be described.

As a silicon wafer W to be inspected, a plurality of chemically-etched wafers having different thickness dimensions are irradiated with near-infrared scattered light R1 having a single wavelength of less than 940 nm from a plurality of light-emitting diodes 1a as a near-infrared light source 1. And an experiment in which a near-infrared scattered light R1 having a single wavelength of 940 to 960 nm is irradiated, and an experiment in which a near-infrared scattered light R1 having a single wavelength longer than 960 nm is irradiated.
In addition, as a comparative example, an experiment was performed in which infrared rays were irradiated from a halogen lamp onto a wafer after chemical etching under the same conditions.

As a result of these experiments, when the near-infrared scattered light R1 having a single wavelength of less than 940 nm is irradiated onto the wafer after chemical etching, the near-infrared scattered light R1 becomes difficult to transmit, and the captured image of the imaging camera 3 is captured. Became an image where moderate brightness could not be obtained.
When the near-infrared scattered light R1 having a single wavelength of 940 to 960 nm is irradiated to the wafer after chemical etching, the near-infrared scattered light R1 is transmitted through the wafer, and the transmitted light R2 is collected by the camera lens 2. By “lighting”, “background pattern” having a shape different from the “shadow” of the same shape as the defective portion and the “shadow” of the defective portion corresponding to the surface roughness portion of the wafer on the captured image of the imaging camera 3. Was confirmed to be calm.
In addition, when the wafer after chemical etching is irradiated with a near-infrared scattered light R1 having a single wavelength longer than 960 nm, the near-infrared scattered light R1 is likely to be transmitted, and a background pattern starts to appear strongly. It was found that the defect portion and the surface roughness portion could not be imaged in a distinguishable manner.

Further, the wafer after chemical etching is irradiated with a near-infrared scattered light R1 having a single wavelength of 950 nm, and a brightness profile (luminance profile) inside the wafer surface in a part of the wafer is shown in FIG. 2 as an example.
Similarly, in a comparative example irradiated with a halogen lamp, a brightness profile inside the wafer surface in a part of the wafer is shown in FIG. 3 as a comparative example.
According to the brightness profile of the embodiment shown in FIG. 2, although there is a luminance difference due to the surface roughness portion (rough portion of the background) in the wafer after chemical etching, the luminance width is narrow and variation is small. When a luminance difference due to a portion occurs, it can be easily identified.
On the other hand, according to the brightness profile of the comparative example shown in FIG. 3, the brightness difference due to the surface roughness portion (the rough surface portion) is wide and the variation is large in the wafer after chemical etching. If a luminance difference occurs together, identification is difficult.

  According to the wafer defect inspection apparatus A according to the embodiment of the present invention, when the single-wavelength near-infrared scattered light R1 is transmitted, the shape different from the shadow of the defective portion on the captured image of the imaging camera 3 is obtained. In this case, a “background pattern” corresponding to the surface roughness portion is generated, and when the near-infrared scattered light R1 having a single wavelength of 940 to 960 nm is irradiated, the “background pattern” corresponding to the surface roughness portion is gentle. Therefore, there is an advantage that the component that becomes the surface roughness portion can be surely erased.

  Further, when the plurality of light emitting diodes 1a are arranged close to each other as the near-infrared light source 1, the difference in intensity in the near infrared rays respectively emitted from the plurality of light emitting diodes 1a is reduced. There is an advantage that the infrared scattered light R1 can be easily obtained with a simple structure.

  Further, when the diffusing plate 1b is arranged in the emission direction of the plurality of light emitting diodes 1a, the near-infrared scattered light R1 emitted from the light emitting diodes 1a passes through the diffusing plate 1b, so that it is distributed spatially and uniformly. Therefore, there is an advantage that the silicon wafer W to be inspected can be uniformly irradiated with the near-infrared scattered light R1.

  Although the case where the single-wavelength near-infrared scattered light R1 is emitted from the plurality of light-emitting diodes 1a as the near-infrared light source 1 has been described, the present invention is not limited to this, and a light source different from the light-emitting diode 1a may be used. good.

DESCRIPTION OF SYMBOLS 1 Near-infrared light source 1a Light emitting diode 1b Diffuser 2 Camera lens 3 Imaging camera 4 Image processing part R1 Near-infrared scattered light R2 Transmitted light W Silicon wafer

Claims (2)

A near-infrared light source that irradiates a silicon wafer with a single-wavelength near-infrared scattered light; and
A camera lens that collects the transmitted light transmitted through the silicon wafer;
An imaging camera that receives and images the transmitted light collected by the camera lens;
An image processing unit that performs image processing on a captured image of the imaging camera;
The near-infrared light source has a plurality of light-emitting diodes arranged so as to be close to each other and emitting near-infrared rays having a single wavelength of 940 to 960 nm, and a diffusion plate arranged in the emission direction of the light-emitting diodes The near-infrared scattered light emitted from the light-emitting diode passes through the diffusion plate, and is uniformly distributed spatially and uniformly irradiated toward the surface of the silicon wafer,
The wafer defect inspection apparatus, wherein the image processing unit erases a component that becomes a surface roughness portion of the silicon wafer on a captured image of the imaging camera. Claim 1 Symbol mounting wafer defect inspection device characterized by using the area sensor camera as the imaging camera.

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