JP2008089428A - Substrate inspection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly detect a flaw by combining the merits of a plurality of inspection systems in a substrate inspection apparatus for inspecting a substrate for a semiconductor circuit element, a liquid crystal display element, or the like. <P>SOLUTION: The substrate inspection apparatus has an illumination means for irradiating a substrate under inspection with light of a long wavelength and light of a short wavelength, an imaging means for imaging the substrate under inspection and an inspection means for inputting the second image captured by the imaging means when the substrate under inspection is irradiated with the light of the long wavelength and the second image captured by the imaging means when the substrate under inspection is irradiated with the light of the short wavelength to inspect the flaw of the second image on the basis of the position of the flaw detected in the first image. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a substrate inspection apparatus for inspecting a substrate such as a semiconductor circuit element or a liquid crystal display element.

Conventionally, as a substrate inspection apparatus for macro-inspecting the surface of a wafer, for example, a method for detecting defects from an image captured with a short wavelength light source, a method for detecting defects from an image captured with a long wavelength light source, a dark field An apparatus using a method of detecting a defect from an image captured with illumination is known.
JP-A-11-72443 JP 9-318553 A

However, in the method of detecting defects from an image captured with a long wavelength light source, it is possible to ensure the defect detection performance in the pattern. There was a problem that it became difficult.
In addition, the method of detecting defects from an image captured with a light source with a short wavelength can avoid the influence of the underlying pattern, but the difference in appearance between the defective part and the non-defective part is reduced, and the defect identification ability is reduced. There was a problem to do.

Furthermore, in the method of detecting defects from an image picked up by dark field illumination, particles and cracks can be detected, but there is a problem that resist coating defects caused by these cannot be detected.
The present invention has been made to solve such a conventional problem, and an object of the present invention is to provide a substrate inspection apparatus capable of reliably detecting defects by combining the advantages of a plurality of inspection methods.

  A substrate inspection apparatus according to a first aspect of the present invention is an illumination unit capable of irradiating a substrate to be inspected with a long wavelength light and a short wavelength light, an imaging unit for imaging the substrate to be inspected, and irradiating the long wavelength light. The first image captured by the image capturing means and the second image captured by the image capturing means when irradiated with the light having the short wavelength are input and detected by the first image. Inspection means for inspecting the defect with the second image with reference to the position of the detected defect.

The substrate inspection apparatus according to a second aspect of the present invention is the substrate inspection apparatus according to the first aspect, wherein the inspection means inspects the detection defect and its neighboring defects with the second image with reference to the position of the detection defect. It is characterized by doing.
The substrate inspection apparatus according to a third aspect is the substrate inspection apparatus according to the first or second aspect, wherein the inspection means specifies the size of a defect in the first image and the second image. And

  A substrate inspection apparatus according to a fourth aspect of the present invention is an illumination unit capable of irradiating a substrate to be inspected with short wavelength light and long wavelength light, an imaging unit for imaging the substrate to be inspected, and irradiating with the short wavelength light. The first image captured by the image capturing means and the second image captured by the image capturing means when irradiated with the light having the long wavelength, and detected by the first image. Inspection means for inspecting the defect with the second image with reference to the position of the detected defect.

The substrate inspection apparatus according to a fifth aspect of the present invention is the substrate inspection apparatus according to the fourth aspect of the present invention, wherein the inspection unit inspects the detection defect and its neighboring defects with the second image with reference to the position of the detection defect. It is characterized by doing.
A substrate inspection apparatus according to a sixth aspect is the substrate inspection apparatus according to the fourth or fifth aspect, wherein the inspection means specifies the size of a defect in the first image and the second image. And

  In the substrate inspection apparatus of the present invention, defect detection can be reliably performed by combining the advantages of a plurality of inspection methods.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the substrate inspection apparatus according to this embodiment includes an illumination unit 11, a stage 13, an imaging unit 12, an image processing unit 17, and a display unit 19.
The illumination unit 11 includes a light source unit 21, a filter unit 23, and a lens 25. The imaging unit 12 includes a lens 34 and a camera 15. The light source unit 21 includes a halogen lamp that is a white light source. A mercury lamp may be used as the light source. The filter unit 23 limits the short wavelength filter 27 for limiting the illumination wavelength range to a predetermined short wavelength (for example, wavelength in the ultraviolet light region) and a predetermined long wavelength (for example, wavelength in the visible light region). A long wavelength filter 29 is provided. In this embodiment, the long wavelength filter 29 limits the illumination wavelength to a single wavelength of a predetermined wavelength. Then, the short wavelength filter 27 or the long wavelength filter 29 is positioned in front of the light source unit 21 by rotating the filter unit 23 by the motor 31. The lens 25 has a diameter that can illuminate the entire surface of the wafer W, and irradiates the surface (inspection surface) of the wafer W (substrate to be inspected) placed on the stage 13 with illumination light S of parallel light flux. The lens 34 collects the reflected light H regularly reflected by the wafer W and guides it to the camera 15. In the present embodiment, inspection is performed using specular reflection light, but the present invention may be applied to inspection using diffracted light.

The camera 15 is a digital camera provided with an image sensor such as a CCD, and images the reflected light H. The image processing unit 17 inputs an image captured by the camera 15 and performs predetermined image processing. Various controls associated with image processing are performed. The display unit 19 displays the detection result detected by the image processing unit 17.
FIG. 2 is a flowchart showing the operation of the substrate inspection apparatus described above.

Step S1: The wafer W is transferred onto the stage 13.
Step S2: The illumination unit 11 is turned on. That is, the light source unit 21 of the illumination unit 11 is turned on to turn on the halogen lamp.
Step S3: The filter of the illumination unit 11 is switched to a long wavelength. This switching is performed by rotating the filter unit 23 by the motor 31 and positioning the long wavelength filter 29 in front of the light source unit 21.

Step S4: The surface of the wafer W is imaged by the camera 15. The captured image is output to the image processing unit 17 as a first image G1 (shown in FIG. 3).
Step S5: The filter of the illumination unit 11 is switched to a short wavelength. This switching is performed by rotating the filter unit 23 by the motor 31 and positioning the short wavelength filter 27 in front of the light source unit 21.

Step S6: The surface of the wafer W is imaged by the camera 15. The captured image is output to the image processing unit 17 as a second image G2 (shown in FIG. 4). FIG. 5 shows the actual defect shape.
Step S7: The image processing unit 17 performs defect inspection on the first image G1.
FIG. 3 shows the first image G1 output to the image processing unit 17. Since the first image G1 is captured using long-wavelength light, the feature of the defect is relatively clear, but the photoresist transmits the long-wavelength light and the lower layer image is visible. May end up. In addition, the appearance of the lower layer becomes non-uniform due to various factors, and the influence of interference may cause shading (unevenness) in the image. Therefore, it is difficult to clearly detect the entire defects A1 and A2. Accordingly, there is a possibility that an erroneous defect location exists in the defect location detected in step S7.

Step S8: It is determined whether or not the first image G1 is uneven, and the defect is inspected.
Step S9: If the first image G1 is uneven, a normal defect inspection is performed on the second image G2. Further, the detected defect and its vicinity are inspected in detail in the second image G2 with reference to the position of the detected defect detected in the first image G1. In addition, when a defect is detected in the part of the second image G2 corresponding to the unevenness of the first image G1, the first image G1 corresponding to the unevenness position may be inspected precisely again. In this case, in order to distinguish unevenness from defects, it is necessary to perform processing in consideration of unevenness components such as applying a bias.

  FIG. 4 shows the second image G <b> 2 output to the image processing unit 17. Since the second image G2 is picked up using light of a short wavelength, only the information on the surface of the wafer W can be extracted, and the second layer image G2 will not be confused by the underlying defects. However, the image becomes thin and the entire image of the defect becomes unclear, and only the black portions in the figure can be clearly detected as the defects B1 and B2.

  In step S9, the detected defect and its vicinity are inspected in detail in the second image G2 with reference to the position of the detected defect detected in the first image G1, so that the defects A1 and A2 in FIG. It becomes clear that the thinned portions a1 and a2 are obvious defects corresponding to the defects B1 and B2 in FIG. In addition, in the defect inspection in the first image G1 in step S7, if there is an erroneous defect location (for example, indicated by a3 in FIG. 3) due to the influence of unevenness, the defect location a3 is clearly shown in FIG. Since it does not exist, it becomes clear that the defect part a3 is an erroneous defect part due to the influence of unevenness. As a result, it is possible to reliably perform defect inspection while eliminating the influence of unevenness while maintaining the detection capability of long wavelengths.

Next, in step S <b> 10, the detection result in step S <b> 9 is output to the display unit 19.
FIG. 5 shows the actual defect shape. In FIG. 3, it is difficult to see because there is a defect in the unevenness, but the defect as shown in FIG. 5 is visible.
In this embodiment, the wafer W to be inspected is after the lithography process, and a resist film is applied to the surface of the wafer W. Then, the circuit pattern of the mask (reticle) is exposed to the resist film, and further, the exposed or unexposed part of the resist film is developed, and the resist pattern is formed on the surface thereof. The coating defect C1 in FIG. 5 is caused by uneven coating of the resist film, and has a comet shape in which the tail is drawn from the center toward the outside in the image. The defocus defect C2 is caused by film thickness unevenness or cross-sectional shape abnormality due to defocus at the time of exposure, and is generated in shot units. Here, application defects and defocus defects are used as defect examples, but the same applies to other defects.

Step S11: If no defect is found in the first image G1 in step S8, the defect is inspected with the second image G2, and the inspection result is output to the display unit 19.
In the above-described substrate inspection apparatus, the detection defect and its vicinity are inspected in detail in the second image G2 with reference to the position of the detection defect detected in the first image G1, so that a single long wavelength is detected. The defects C1 and C2 can be detected even when the first image G1 picked up with the light source of the wavelength has a large unevenness and the defect cannot be reliably detected only by the first image G1. That is, defect detection can be reliably performed by combining the advantages of the inspection method using the long wavelength and the inspection method using the short wavelength. Note that the processing in step S7 may be started immediately after the first image G1 is taken in step S4.

In this embodiment, since the overall size of the coating defect C1 and the defocus defect C2 after the lithography process can be specified, the processing of the wafer W is directly performed or the resist film is peeled off. It is possible to reliably determine whether or not reworking is performed, and the yield in the semiconductor manufacturing process can be improved.
(Second Embodiment)
FIG. 6 is a flowchart showing the operation of the second embodiment of the substrate inspection apparatus of the present invention. In this embodiment, a substrate inspection apparatus having a configuration substantially similar to that in FIG. 1 is used. Therefore, the detailed description of the substrate inspection apparatus is omitted, and the same elements are denoted by the same reference numerals and the operation is described.

Step S1: The wafer W is transferred onto the stage 13.
Step S2: The illumination unit 11 is turned on. That is, the light source unit 21 of the illumination unit 11 is turned on to turn on the halogen lamp.
Step S3: The filter of the illumination unit 11 is switched to a short wavelength. This switching is performed by rotating the filter unit 23 by the motor 31 and positioning the short wavelength filter 27 in front of the light source unit 21.

Step S4: The surface of the wafer W is imaged by the camera 15. The captured image is output to the image processing unit 17 as a first image G1 ′ (shown in FIG. 7).
Step S5: The filter of the illumination unit 11 is switched to a long wavelength. This switching is performed by rotating the filter unit 23 by the motor 31 and positioning the long wavelength filter 29 in front of the light source unit 21.

Step S6: The surface of the wafer W is imaged by the camera 15. The captured image is output to the image processing unit 17 as a second image G2 ′ (shown in FIG. 8).
Step S7: The image processing unit 17 performs defect inspection on the first image G1 ′.
FIG. 7 shows the first image G1 ′ output to the image processing unit 17. Since the first image G1 ′ is picked up using light having a short wavelength, only the information on the surface of the wafer W can be extracted, and the first layer image G1 ′ is not confused by defects in the lower layer. However, the image becomes thin and the entire image of the defect becomes unclear, and only the black portions in the figure can be clearly detected as the defects A1 ′ and A2 ′.

Step S8: It is determined whether or not the first image G1 ′ has a defect.
Step S9: If there is a defect in the first image G1 ′, a normal defect inspection is performed on the second image G2 ′. Further, the detected defect and its vicinity are inspected in detail in the second image G2 ′ with reference to the position of the detected defect detected in the first image G1 ′.
FIG. 8 shows the second image G2 ′ output to the image processing unit 17. Since this second image G2 ′ is captured using long-wavelength light, the feature of the defect is relatively clear, but the photoresist transmits the long-wavelength light and the underlying image is visible. May end up. In addition, the appearance of the lower layer becomes non-uniform due to various factors and may be affected by interference, resulting in the occurrence of shading (unevenness) in the image. Therefore, it is difficult to clearly detect the entire defect.

  In step S9, the detected defect and its vicinity are inspected in detail in the second image G2 ′ with reference to the position of the detected defect detected in the first image G1 ′, so that the portion of the defect A1 ′ in FIG. In addition, it becomes clear that the portion of the defect B1 ′ in FIG. In addition, in a normal defect inspection in the second image G2 ′, if there is an erroneous defect location (for example, indicated by B3 ′ in FIG. 8) due to the influence of the lower layer in the second image G2 ′, the defect location Since B3 ′ does not clearly exist in FIG. 7, it becomes clear that the defective portion B3 ′ is an erroneous defective portion due to the influence of the lower layer. As a result, it is possible to reliably perform the defect inspection that eliminates the influence of the lower layer while maintaining the long wavelength detection capability.

Next, in step S <b> 10, the detection result in step S <b> 9 is output to the display unit 19.
FIG. 9 shows an image output to the display unit 19. In this image, the coating defect C1 ′ (corresponding to A1 ′ in FIG. 7 and B1 ′ in FIG. 8) and the defocus defect C2 ′ (corresponding to A2 ′ in FIG. 7 and B2 ′ in FIG. 8) are black. It is clearly detected as a painted part. Then, the overall sizes of the coating defect C1 ′ and the defocus defect C2 ′ are specified.

  In this embodiment, the wafer W to be inspected is after the lithography process, and a resist film is applied to the surface of the wafer W. Then, the circuit pattern of the mask (reticle) is exposed to the resist film, and further, the exposed or unexposed part of the resist film is developed, and the resist pattern is formed on the surface thereof. The coating defect C1 'in FIG. 9 is caused by uneven coating of the resist film, and has a comet shape in which an image has a tail from the center toward the outside in the image. The defocus defect C2 'is caused by film thickness unevenness or cross-sectional shape abnormality due to defocus during exposure, and is generated in shot units. Here, application defects and defocus defects are used as defect examples, but the same applies to other defects.

Step S11: If no defect is found in the first image G1 ′ in Step S8, the second image G2 ′ is inspected for defects and the inspection result is output to the display unit 19.
In the substrate inspection apparatus of this embodiment, the detection defect and its vicinity are inspected in detail in the second image G2 ′ with reference to the position of the detection defect detected in the first image G1 ′. It is possible to detect the defects C1 ′ and C2 ′ even when the first image G1 ′ picked up with the light source of the wavelength becomes thin and the whole image of the defect is not clear. That is, defect detection can be reliably performed by combining the advantages of the inspection method using the long wavelength and the inspection method using the short wavelength. Note that the process of step S7 may be started immediately after the first image G1 ′ is taken in step S4.

In this embodiment, since the entire size of the coating defect C1 ′ and the defocus defect C2 ′ after the lithography process can be specified, the processing of the wafer W is directly performed or the resist film is peeled off. Thus, it is possible to reliably determine whether or not to rework, and the yield in the semiconductor manufacturing process can be improved.
(Supplementary items of the embodiment)
As mentioned above, although this invention was demonstrated by embodiment mentioned above, the technical scope of this invention is not limited to embodiment mentioned above, For example, the following forms may be sufficient.

(1) In the above-described embodiment, the example in which the present invention is applied to the inspection of the wafer W has been described. However, the present invention can be widely applied to, for example, the case of inspecting a glass substrate for liquid crystal manufacturing in a manufacturing process of a liquid crystal display element.
(2) In the above-described embodiment, the example in which the long-wavelength and short-wavelength regular reflection images are captured by the camera 15 has been described. For example, the long-wavelength or short-wavelength is set to a single wavelength, and a single-wavelength diffraction image is obtained. You may image with the camera 15. FIG. This can be realized by rotating the stage 13 by a predetermined angle by a stage rotation mechanism (not shown) and guiding the diffracted light from the wafer W to the camera 15.

  (3) In the above-described embodiment, the example in which the detection result is output after step S9 in FIGS. 2 and 6 has been described. For example, after step S9, the defective portion found in step S9 is displayed in the first image G1. , G1 ′ may be checked again and the detection result may be output. Thereby, a defect inspection can be performed more reliably.

It is explanatory drawing which shows 1st Embodiment of the board | substrate inspection apparatus of this invention. It is explanatory drawing which shows operation | movement of the board | substrate inspection apparatus of FIG. It is explanatory drawing which shows an example of the image imaged with the long wavelength. It is explanatory drawing which shows an example of the image imaged with the short wavelength. It is explanatory drawing which shows an example of the image displayed on the display part. It is explanatory drawing which shows operation | movement of 2nd Embodiment of the board | substrate inspection apparatus of this invention. It is explanatory drawing which shows an example of the image imaged with the short wavelength. It is explanatory drawing which shows an example of the image imaged with the long wavelength. It is explanatory drawing which shows an example of the image displayed on the display part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Illuminating part, 13 ... Stage, 15 ... Camera, 17 ... Image processing part, 19 ... Display part, 27 ... Filter for short wavelength, 29 ... Filter for long wavelength, G1, G1 '... 1st image, G2, G2′—second image, W—wafer.

Claims (6)

Illumination means capable of irradiating the inspected substrate with long wavelength light and short wavelength light,
Imaging means for imaging the inspected substrate;
Input a first image captured by the imaging means when irradiated with the light of the long wavelength and a second image captured by the imaging means when irradiated with the light of the short wavelength, Inspection means for inspecting the defect in the second image with reference to the position of the detected defect detected in the first image;
A board inspection apparatus comprising: The board inspection apparatus according to claim 1,
The substrate inspection apparatus, wherein the inspection unit inspects the detection defect and a defect in the vicinity thereof with the second image on the basis of the position of the detection defect. In the board | substrate inspection apparatus of Claim 1 or Claim 2,
The substrate inspection apparatus, wherein the inspection unit specifies a size of a defect in the first image and the second image. Illumination means capable of irradiating the inspected substrate with short wavelength light and long wavelength light;
Imaging means for imaging the inspected substrate;
Input a first image captured by the imaging means when irradiated with the short wavelength light and a second image captured by the imaging means when irradiated with the long wavelength light, Inspection means for inspecting the defect in the second image with reference to the position of the detected defect detected in the first image;
A board inspection apparatus comprising: The substrate inspection apparatus according to claim 4,
The substrate inspection apparatus, wherein the inspection unit inspects the detection defect and a defect in the vicinity thereof with the second image on the basis of the position of the detection defect. In the board | substrate inspection apparatus of Claim 4 or Claim 5,
The substrate inspection apparatus, wherein the inspection unit specifies a size of a defect in the first image and the second image.

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