JP2008139088A - Visual examination method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visual examination method which enables the detection of a local flaw with high inspection precision while permitting the size irregularity of an inspection target such as an electrode pattern or the like in the visual examination of a semiconductor emission element or the like. <P>SOLUTION: In a case that the planned shape of the inspection target subjected to quality judgment is a linear symmetric shape having at least one symmetric axis, the reference line corresponding to the symmetric axis of the inspection target is set in the image of the inspection target and one image of the inspection target based on the reference line is compared with the other image of the inspection target to judge the quality of the inspection target. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an appearance inspection method capable of imaging an inspection object such as a semiconductor chip or a wafer and performing an appearance inspection from the captured image.

An object to be inspected is imaged, the object to be inspected for the quality determination is recognized from the captured image, and the image of the object to be inspected is set in advance. An appearance inspection method for comparing the reference data and determining the quality of the inspected object is known as an appearance inspection method for semiconductor elements and the like. This is the method performed by the procedure described in FIG.
JP 2004-333144 A

  In the conventional appearance inspection method described above, the quality of each inspection object is determined based on preset quality determination reference data. However, in appearance inspection of semiconductor light emitting devices, local defects such as chips and cracks that occur in patterns such as lines and electrodes are determined to be defective, but there is some variation in pattern position and size. May not need to be determined as bad. In such a case, when the conventional appearance inspection method is used so as to allow the variation, there is a problem in that the inspection accuracy must be lowered and the local defect cannot be detected. .

  It is an object of the present invention to detect local defects with high inspection accuracy while permitting variations in the position and size of an inspection target such as an electrode pattern in an appearance inspection of an inspection target such as a semiconductor light emitting element. It is to provide an appearance inspection method.

  The invention according to claim 1 for achieving the above object is as follows: (a) an object to be inspected is imaged, and the image of the imaged object to be inspected is a line-symmetric shape with at least one reference line as a boundary (B) a reference line setting step in which a reference line is set in an image based on the image of the object to be inspected. And a determination step of determining pass / fail of the object to be inspected based on comparing one image of the object to be inspected with the reference line as a boundary with the other image. .

  In the invention according to claim 2, (a) the reference line setting step sets a plurality of reference lines in the image to be inspected, and (b) the determination step includes the plurality of reference lines. It is characterized in that pass / fail judgment is performed for each reference line.

  In the invention according to claim 3, (a) the object to be inspected is an electrode pattern fixed on the upper surface of the semiconductor light emitting element, and (b) the reference line setting step is an image of the electrode pattern of the semiconductor light emitting element. The reference line is set in the inside.

  According to the appearance inspection method of the invention according to claim 1, based on comparing one image of the object to be inspected with the reference line as a boundary with the other image, the quality determination of the object to be inspected is performed. Made. That is, the pass / fail determination of the inspection target is made based on the comparison between the one image, which is an image in the inspection target, and the other image. Therefore, it is possible to avoid the variation in the position and size of the entire inspection target from affecting the quality determination. Further, if the one image is inverted with respect to the reference line, the other image is ideally obtained. Therefore, even if a local defect is captured in either the one or the other image. The defect can be detected with high accuracy.

  According to the appearance inspection method of the invention according to claim 2, when a plurality of the reference lines are set, the pass / fail determination is performed a plurality of times for each of the inspected objects with different reference lines. Therefore, for example, when a local defect is on one of the reference lines but not on the other reference line, the local defect can be detected, so that the inspection accuracy can be improved.

  According to the appearance inspection method of the invention according to claim 3, the object to be inspected is an electrode pattern fixed on the upper surface of the semiconductor light emitting element, and the reference line is set in an image of the electrode pattern. It can be avoided that variations in the position and size of the electrode pattern affect the quality determination.

  Hereinafter, an example of an appearance inspection method according to the present invention will be described in detail with reference to the drawings in the case where a large number of semiconductor light emitting elements 10 in a wafer state are used as inspection objects.

  FIG. 1 is a configuration diagram schematically showing a main part of an inspection apparatus 12 that performs the appearance inspection method of the present embodiment. FIG. 2 is an external view of the semiconductor light emitting device 10 in a chip shape.

  As shown in FIG. 1, the inspection apparatus 12 includes a movable stage 14, a microscope camera 16, and an illuminating device 18, which are fixed in position using a fixture on a base (not shown). ing. The movable stage 14 is for placing a semiconductor wafer 22 formed from a large number of semiconductor light emitting elements 10 as inspection objects on the loading surface 20. It can be moved and positioned using a pulse motor or the like.

  The microscope camera 16 is for individually imaging the semiconductor light emitting element 10 and is arranged so that the objective lens 24 of the microscope camera 16 is opposed to the loading surface 20 of the movable stage 14 at a predetermined distance. Yes.

  The illumination device 18 is provided to provide illumination necessary for imaging the semiconductor light emitting element 10 and is installed at a position where the semiconductor light emitting element 10 imaged by the microscope camera 16 can be irradiated.

  The image capturing device 26 captures an image including the semiconductor light emitting element 10 captured by the microscope camera 16 and sequentially outputs the image to the computer 28.

  When it is determined that the focus adjustment of the microscope camera 16 is inappropriate in the input image input from the image capturing device 26, the computer 28 sends a microscope adjustment signal instructing to perform the focus adjustment of the microscope camera 16 to the microscope. Output to the controller 30. When it is determined that the brightness of the input image is inappropriate, the computer 28 outputs an illumination adjustment signal that instructs to adjust the illumination amount of the illumination device 18 to the illumination controller 32. Then, the computer 28 performs the pass / fail determination of the semiconductor light emitting element 10 that is the object to be inspected according to the appearance inspection method described in the flowchart of FIG. When the pass / fail determination for the semiconductor light emitting element 10 that is the object to be inspected is completed, a movement instruction signal for instructing to move the semiconductor wafer 22 by a predetermined distance is usually staged in order to inspect another adjacent semiconductor light emitting element 10. Output to the controller 34.

  The microscope controller 30 adjusts the focus of the microscope camera 16 according to the microscope adjustment signal output from the computer 28.

  The illumination controller 32 adjusts the amount of illumination of the illumination device 18 according to the illumination adjustment signal output from the computer 28.

  The stage controller 34 moves the semiconductor wafer 22 placed on the loading surface 20 of the movable stage 14 by a predetermined distance according to the movement instruction signal output from the computer 28.

  FIG. 3 is a flowchart for explaining a main part of the control operation of the computer 28 for visual inspection performed by the inspection device 12. It should be noted that the design shape of the inspected object whose image quality is determined by the appearance inspection method according to the present embodiment is a line-symmetric shape.

  In FIG. 3, first, in step SA <b> 1 (hereinafter, “step” is omitted), an image including the semiconductor light emitting element 10 that is the inspection object is captured from the image capturing device 26 by the microscope camera 16.

  In SA2 corresponding to the subsequent image recognition process, the outer shape of the semiconductor light emitting element 10 serving as the inspection object is recognized. Then, the electrode pattern 36 which is a part of the semiconductor light emitting element 10 shown in FIG. 2 is recognized as an object to be inspected. At that time, a binarization process is performed on the captured image to divide the image into a part having a lightness equal to or higher than the threshold value and a part having a lightness value equal to or lower than the threshold value. The electrode pattern 36 to be inspected is recognized from the contour line obtained based on the prominent contour.

  In SA3 corresponding to the subsequent reference line setting step, a reference line 38 is provided in the image of the electrode pattern 36 as shown in FIG. 4 according to a predetermined method according to the shape of the electrode pattern 36 to be inspected. The image of the electrode pattern 36 is divided into two parts with the reference line 38 as a boundary. One is recognized as a reference image 36a (first image) and the other is recognized as a comparative image 36b (second image). As the predetermined method, (a) when the design shape of the electrode pattern is circular as shown in FIG. 4, for example, the center of gravity 40 of the electrode pattern 36 is obtained, and one piece passing through the center of gravity 40 is obtained. (B) If the design shape of the electrode pattern is a rectangle as shown in FIG. 5, for example, two pairs of corner points 42a, 42b, 44a and 44b are extracted, and midpoints 50 and 52 of two sides 46 and 48 which are straight lines parallel to each other between the two pairs of corner points 42a, 42b, 44a and 44b are obtained. A method of obtaining one straight line passing through the points 50 and 52 as the reference line 54; and (c). If the design shape of the electrode pattern is as shown in FIG. 6, for example, the electrode pattern 6, four tip points 58, 60, 62, 64 of the outer shape projecting radially are extracted, and from the sides 66, 68, 70, 72 connecting these four tip points 58, 60, 62, 64. For example, a method is used in which the midpoints 74 and 76 of the two opposite sides 68 and 72 of the quadrangle are obtained, and one straight line passing through the two midpoints 74 and 76 is obtained as the reference line 78.

  In SA4 corresponding to the subsequent determination process, the reference images 36a, 41a and 56a on one side of the reference lines 38, 54 and 78 are compared with the comparison images 36b and 36b on the other side of the reference lines 38, 54 and 78, respectively. The images obtained by inverting 41b and 56b are compared and compared, and it is determined whether or not these images are within a preset allowable range, and the semiconductor light emitting element 10 is determined to be good or bad. For example, binarized images obtained by binarizing the two images to be compared are overlapped with the reference lines 38, 54, and 78 matched, and the logical sum of the two binarized images is used. By subtracting the area of the image obtained by the logical product of the two binarized images from the area of the obtained image, the area of the surface that does not match when the binarized images are compared and compared is obtained. When the area is within a predetermined allowable value, the electrode patterns 36, 41, and 56 are determined to be within the allowable range. When the design shape of the electrode patterns 36, 41, 56 is a line symmetrical shape having a plurality of symmetry axes as shown in FIGS. 4 to 6, for example, the reference lines 38, 54, 78 are plural. The steps SA3 to SA4 are executed a plurality of times so that the quality of the electrode patterns 36, 41, 56 is determined for each of the plurality of reference lines 38, 54, 78. The semiconductor light emitting element 10 that has never been determined to be defective is determined to be a non-defective product, and the semiconductor light emitting element 10 that has been determined to be defective even once is determined to be a defective product.

  In SA5 corresponding to the subsequent determination result storing step, mapping data is created by adding the result information of the quality determination to the position information of each semiconductor light emitting element 10 on the semiconductor wafer 22.

  In SA6 corresponding to the subsequent determination result output step, the mapping data is output on the screen or printed, or based on this, the marking for applying the mark ink to the semiconductor light emitting element 10 determined to be defective by the quality determination is performed. The semiconductor light emitting device 10 that has been performed or determined to be defective is extracted after being divided into chips.

  According to the appearance inspection method of the present embodiment, in SA3 corresponding to the reference line setting step, the predetermined method according to the shape of the electrode patterns 36, 41, and 56 to be inspected that are line-symmetrical in design. Accordingly, reference lines 38, 54, 78 are provided in the image of the electrode patterns 36, 41, 56, and the image of the electrode patterns 36, 41, 56 is divided into two parts with the reference lines 38, 54, 78 as a boundary. One side bordered on the reference lines 38, 54, 78 was recognized as the reference images 36a, 41a, 56a, and the other side bordered on the reference lines 38, 54, 78 was recognized as the comparison images 36b, 41b, 56b. Thereafter, in SA4 corresponding to the determination step, it is determined whether or not an image obtained by inverting the comparative images 36b, 41b, and 56b with respect to the reference images 36a, 41a, and 56a is within an allowable range. Quality judgment electrode pattern 36,41,56 of the optical element 10 is made. Therefore, since the reference images 36a, 41a, 56a to be compared and the comparison images 36b, 41b, 56b are all partial images in the inspection target, the electrode patterns 36, 41, It is possible to avoid the variation in the position and size of 56 from affecting the quality determination. Further, since the images obtained by inverting the comparative images 36b, 41b, and 56b with the reference lines 38, 54, and 78 as axes are ideally the reference images 36a, 41a, and 56a, local defects are compared with the comparative images. In any of the images 36b, 41b, 56b or the reference images 36a, 41a, 56a, the defect can be detected with high accuracy.

  Further, when the design shape of the electrode pattern 36 is a line-symmetric shape having a plurality of symmetry axes, a plurality of reference lines 38 are set, and the reference image 36a and the comparison image 36b are set for each reference line 38. And a process of comparing and comparing the reference image 36a with an image obtained by inverting the comparison image 36b for each of the plurality of reference lines 38 is executed a plurality of times, for example, as shown in FIG. In the case where the local defect 80 is on the reference line 38 but not on the other reference line 82, the local defect 80 can be detected, so that the inspection accuracy can be improved.

  As mentioned above, although the Example of this invention was described in detail based on drawing, this is an embodiment to the last, and this invention is implemented in the aspect which added various change and improvement based on the knowledge of those skilled in the art. Can do.

  For example, a plurality of the above-described semiconductor light emitting elements 10 may be simultaneously imaged, and the quality determination of the plurality of semiconductor light emitting elements 10 may be performed at once by capturing an image once.

  Further, when there are a plurality of objects to be inspected in one semiconductor light emitting element 10, the processes of SA2 to SA4 after the outline of the semiconductor light emitting element 10 is recognized are executed for each of the objects to be inspected. Then, the quality of the semiconductor light emitting element 10 may be determined.

  In addition, both the conventional appearance inspection method for comparing the image to be inspected with preset acceptance / rejection determination reference data and the appearance inspection method of the above-described embodiment are performed to determine whether or not the semiconductor light emitting device 10 is acceptable. A determination may be made.

  In the above-described embodiments, the inspection target is an electrode pattern. However, a groove or a projection or the entire semiconductor light emitting element may be the inspection target.

It is the block diagram which showed typically the principal part of the inspection apparatus which enforces the external appearance inspection method which is an Example of this invention. FIG. 2 is an external view of a semiconductor light emitting element 10 in a chip shape that is inspected by the inspection apparatus of FIG. 1. It is a flowchart for demonstrating the principal part of the control action of the computer which performs the external appearance inspection method implemented with the inspection apparatus of FIG. It is a figure for demonstrating the predetermined method for calculating | requiring a reference line about the electrode pattern test | inspected with the test | inspection apparatus of FIG. It is a figure for demonstrating the predetermined method for calculating | requiring a reference line about an example of the electrode pattern test | inspected with the test | inspection apparatus of FIG. It is a figure for demonstrating the predetermined method for calculating | requiring a reference line about an example of the electrode pattern test | inspected with the test | inspection apparatus of FIG. It is the figure which showed typically an example in case there exists a local defect in the electrode pattern inspected with the inspection apparatus of FIG.

Explanation of symbols

10: Semiconductor light emitting element 38, 54, 78, 82 as inspection object: Reference line 36, 41, 56: Electrode pattern as inspection object

Claims (3)

The inspection object is imaged, and the quality of the inspection object is determined based on whether or not the captured image of the inspection object has a line-symmetric shape with at least one reference line as a boundary. An appearance inspection method,
A reference line setting step for setting a reference line in the image based on the image to be inspected;
A visual inspection, comprising: a determination step of determining pass / fail of the inspection object based on comparing one image of the inspection object with the reference line and the other image Method. The reference line setting step is to set a plurality of reference lines in the image to be inspected,
The visual inspection method according to claim 1, wherein the determining step performs a pass / fail determination for each of the plurality of reference lines. The inspection object is an electrode pattern fixed on the upper surface of the semiconductor light emitting element,
The appearance inspection method according to claim 1, wherein the reference line setting step sets the reference line in an image of an electrode pattern of the semiconductor light emitting element.

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