JP3709426B2 - Surface defect detection method and surface defect detection apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface defect detection method and a surface defect detection apparatus capable of detecting a minute unevenness defect on an edge portion of a silicon wafer for semiconductors and a minute unevenness defect on another mirror plate.
[0002]
[Prior art]
The inspection of the edge portion of the silicon wafer used for forming the semiconductor has not been emphasized so far compared to the inspection of the mirror surface portion. However, if there are defects such as dents, cracks, minute protrusions and adhesion of particles at the edge of a semiconductor silicon wafer, a fatal defect may occur in the silicon wafer due to this defect.
[0003]
In the case where there are dents, cracks, etc. on the edge of the silicon wafer, if the heat is applied to the silicon wafer in a process such as a heat treatment process, the mirror surface of the silicon wafer, that is, a semiconductor circuit is formed due to these defects. There is a risk of cracks occurring on the surface to be defective.
[0004]
On the other hand, in the case where particles are attached to the edge portion of the silicon wafer, there is a possibility that the particles are transferred and attached to the mirror surface portion as the process proceeds. Alternatively, a part of the dents and cracks may be peeled off and adhere to the mirror surface part.
[0005]
In recent years, as the degree of integration of LSIs has increased and the demand for fine pitches has increased, silicon wafers with such minute particles attached to the mirror surface of the silicon wafer or cracks in the mirror surface are supplied to the next process. Therefore, it is necessary to strictly inspect the presence or absence of defects such as dents, cracks, and adhesion of particles at the edge portion of the semiconductor silicon wafer.
[0006]
For inspection of micro unevenness on the mirror surface other than the edge of a silicon wafer for semiconductors, the surface of the mirror surface is irradiated with parallel light, and the intensity of the reflected brightness is generated by a collimating lens. Inspection can be performed.
[0007]
However, this inspection method cannot be used for inspection of minute irregularities on the surface of the edge portion of the silicon wafer. Because the edge portion of the silicon wafer is composed of several plane portions and R portions, only one surface can be detected by parallel light in a certain direction, and the presence or absence of defects in other plane portions and R portions can be detected. An image that can be identified cannot be captured.
[0008]
Therefore, some proposals have been made for inspection of chamfered or tapered edges of silicon wafers and the like.
[0009]
Japanese Patent No. 2999912 discloses a method for detecting uneven defects using the diffraction phenomenon of a laser, but it is difficult to detect defects of microcracks and microprojections by this method, and furthermore, it detects excessively in dirt. There is a problem of doing.
[0010]
Japanese Laid-Open Patent Publication No. 20000.46537 proposes a method of focusing on the inside of the defect on the edge surface and detecting the defect separately from the defect and the polishing scrap. However, the depth of field should be reduced. Therefore, it is difficult to detect microcracks and microprotrusions due to the eccentricity of the wafer and the alignment error of the imaging device.
[0011]
[Problems to be solved by the invention]
As described above, the inspection method used for inspecting the concave and convex defects on the mirror surface other than the edge portion of the silicon wafer for semiconductor cannot be used for inspecting the concave and convex defects on the surface other than the substantially flat surface.
[0012]
Also, the edge detection method proposed up to now is not an appropriate method for detecting microcracks and microprotrusions, as is apparent from the above explanation, and the surface contamination is not defective. There is a risk of mistakenly recognizing.
[0013]
In view of the above problems, the present invention makes it possible to detect minute irregularities on a three-dimensional surface or an irregular surface such as an edge portion of a silicon wafer or the like, and to prevent contamination on the surface to be inspected. Accordingly, it is an object of the present invention to provide a surface defect inspection method and an inspection apparatus capable of improving inspection accuracy by eliminating the recognition of a defect and setting a high inspection throughput.
[0014]
[Means for Solving the Problems]
1st invention illuminates the mirror-like surface of the test | inspection object which moves with a diffused light source, and images the image of the mirror-like surface of a test | inspection object with the several imaging means comprised by the telecentric optical system and the linear sensor array A surface defect detection method for detecting a micro uneven defect on a specular surface of an inspection object from the brightness of a signal output from the linear sensor array , wherein the diffused light source is a linear sensor on the inspection object. The imaging location of the array is illuminated in a strip shape.
[0015]
A second invention is characterized in that, in the surface defect detection method of the first invention, the diffused light source is a near-infrared light source.
[0016]
According to a third aspect of the present invention, in the surface defect detection method of the first aspect, the imaging means includes a near-infrared filter, and the linear sensor array receives only near-infrared light.
[0017]
According to a fourth aspect of the present invention, there is provided a plurality of diffused light sources configured to illuminate a mirror-like surface of a moving inspection object with diffused light, a telecentric optical system that captures an image of the mirror-like surface of the inspection object, and a linear sensor array. A surface defect detection apparatus comprising: an imaging means; and an image processing means for detecting a minute unevenness defect on a mirror surface of an inspection object from the brightness of a signal output from the linear sensor array , The light source is characterized in that a light emitting portion is arranged so as to illuminate an imaging portion of the linear sensor array on the inspection object in a strip shape.
[0018]
According to a fifth invention, in the surface defect detection device according to the fourth invention, the diffuse light source is a near infrared light source.
[0019]
According to a sixth aspect of the present invention, in the surface defect detection apparatus according to the fourth aspect, the imaging means includes a near-infrared filter, and the linear sensor array receives only near-infrared light.
[0020]
7th invention is the surface defect detection apparatus of 4th invention, The said test object is the edge part of a disc, The light source part of the said diffused light source is circular arc shape, elliptical arc shape, or a gate type, A plurality of the imaging means for imaging the chamfered portion and the side surface portion of the inspection object are provided.
[0021]
[Action]
Since the surface defect inspection apparatus of the present invention illuminates the specular surface of the inspection object with the diffused light source, it illuminates so that even a three-dimensional inspection object composed of a plurality of planes can be imaged. As a result of imaging an image of the mirror-like surface of the inspection object with a plurality of imaging means composed of a telecentric optical system and a linear sensor array, it is possible to detect minute irregularities on the surface of the inspection object from the linear sensor array. It is possible to detect the intensity of the output signal.
[0022]
Further, by using a diffused light source as a near-infrared light source and using a means such as a near-infrared filter as the imaging means, the influence of the density and dirt on the inspection surface can be reduced.
[0023]
Further, by forming the diffused light source in a circular arc shape, an elliptical arc shape, or a gate shape, by simultaneously illuminating the taper portion and the end surface of the edge portion of the disk, a micro uneven defect on the surface of the three-dimensional shape can be obtained. Can be detected.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
The surface defect inspection apparatus and inspection method of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by a present Example.
[0025]
FIG. 1 shows a surface defect inspection apparatus 1 according to the present invention in a side view, and FIG. 2 is a plan view of the surface defect inspection apparatus 1. The surface defect apparatus 1 shown in FIG. 1 and FIG. 2 shows an embodiment in which an edge portion of a silicon wafer 6 for manufacturing a semiconductor is used as an inspection object. An imaging unit 3 and a lower surface imaging unit 4 are provided. Further, a C-type light source 5 is used as the illumination means.
[0026]
As shown in FIG. 3, the edge portion of the silicon wafer 6 includes two tapered portions, an upper tapered surface 61, a lower tapered surface 63 and a side surface 62. The intersection between each surface and the other surface is smoothly connected by the R surface.
[0027]
As shown in FIG. 1, the C-type light source 5 is a diffused light source in which the light emitting portion is formed in a strip shape and is formed in an arc shape or an elliptical arc shape, and the edge portion of the silicon wafer 6 is diffused from above and below and from the side. Illuminate.
[0028]
As shown in FIG. 2, the C-type light source 5 is arranged in a posture slightly inclined from the radial direction of the silicon wafer 6, and the side surface image pickup means 3 is arranged in a posture inclined from the radial direction of the silicon wafer 6 to the opposite side. Thus, the configuration is such that the regular reflection light of the light emitted from the C-type light source 5 is received most efficiently.
[0029]
On the other hand, as shown in FIG. 1, the upper surface imaging means 2 and the lower surface imaging means 4 are disposed so as to be substantially opposed to the upper tapered surface 61 and the lower tapered surface 63 of the edge portion of the silicon wafer 6, respectively. Similar to the side image pickup means 3, it is arranged at a position that receives the specularly reflected light of the light emitted from the C-type light source 5 most efficiently.
[0030]
The silicon wafer 6 has a circular shape, is placed on a rotary table (not shown), and rotates at a constant speed. The line sensor array of the upper surface imaging means 2, the side surface imaging means 3 and the lower surface imaging means 4 continuously scans the image of the edge portion of the silicon wafer 6 and sends the output to the image processing device 7 to detect defects. Perform detection.
[0031]
FIG. 4 is an explanatory diagram for explaining a telecentric optical system applied to the upper surface imaging means 2, the side surface imaging means 3, and the lower surface imaging means 4.
[0032]
A diaphragm 82 is disposed between the image side lens 81 and the linear sensor side lens 83, and the position thereof is a rear focal point of the image side lens 81 and a front focal point of the linear sensor side lens 83. Placed in. In the optical system configured as described above, the principal ray becomes a ray parallel to the optical axis of the image side lens 81, and the principal ray that has passed through the linear sensor side lens 83 is parallel to the optical axis of the linear sensor side lens 83. Become. That is, only light rays parallel to the optical axis of the telecentric optical system are incident on the linear sensor array 84.
[0033]
The linear sensor array 84 is a light receiving element that obtains a high resolution in which CCD charge elements are arranged in a line, and obtains a two-dimensional image by scanning in a direction orthogonal to the moving direction of the inspection object. The surface of the edge portion of the silicon wafer 6 that is an element and rotates is continuously imaged.
[0034]
Next, the function and inspection procedure of the surface defect inspection apparatus of this embodiment will be described.
The silicon wafer 6 placed on a turntable (not shown) is rotated at a constant speed with its central axis as the center of rotation. During this time, the line sensor array 74 provided in the upper surface imaging means 2, the side surface imaging means 3, and the lower surface imaging means 4 continuously captures images of the upper tapered surface 61, the side surface 62, and the lower tapered surface 63, respectively. To do.
[0035]
Since the imaging means used in the surface defect inspection apparatus of the present invention is a telecentric optical system imaging means, only light rays parallel to the optical axis of the optical system of the imaging means are incident on the linear sensor array 84 of the imaging device. Therefore, as shown in FIG. 5, light is scattered at a position where the surface being imaged has minute irregularities, and as a result, light rays are reduced parallel to the optical axis incident on the image pickup means, and light and dark are different from a flat area. There is a difference. The minute unevenness inspection apparatus of the present invention uses this property to detect minute unevenness on the inspection surface as a difference in brightness.
[0036]
The light source used in the defect inspection apparatus of the present invention is diffused light illumination, and since the light source has an arc shape, illumination is performed from multiple directions over the entire upper tapered surface 61, side surface 62, and lower tapered surface 63. Of these, the light whose regular reflection light is parallel to the optical axis of the imaging means is incident on the line sensor array 74.
[0037]
When illuminated with parallel rays as in the prior art, the reflected light is scattered in the R portion shown in FIG. 3 to form a dark image, so that surface defects cannot be detected. On the other hand, by using a diffused light source as the light source as in the present invention, there is a light incident on the image pickup means by the reflected light in the R portion, so that a bright image can be obtained and the presence or absence of a defect can be detected.
[0038]
As described above, even if the imaging target has a three-dimensional shape, it is possible to reliably detect minute irregularities on all inspection target surfaces by illuminating with a diffused light source and imaging with the imaging means of the telecentric optical system. it can.
[0039]
In addition, since the surface defect apparatus of the present embodiment uses a linear sensor array as an image sensor, it is possible to obtain a higher resolution than a two-dimensional area sensor, and detection of minute uneven defects. It can be carried out. Further, since the scanning speed of the linear sensor array is much faster than that of the area sensor, high throughput is ensured and inspection processing capability is high.
[0040]
Furthermore, by using near-infrared light as the light source or using a filter that allows only near-infrared light to pass through the imaging means, it is possible to configure an inspection apparatus that is not easily affected by dirt.
[0041]
In the present embodiment, the surface defect detection apparatus has been described as detecting a surface irregularity defect on the edge of a silicon wafer. However, the present invention is not limited to this, and exists in an inspection object having a plurality of surfaces having different properties. It is possible to inspect minute irregularities.
[0042]
For example, as shown in FIG. 6, even if there are inspection target surfaces 91 </ b> A, 91 </ b> B, 91 </ b> C having steps, these inspection target surfaces 93 are illuminated with the diffused light illumination 93, and the imaging means 92 </ b> A, 92 </ b> B. , 92C, it is possible to detect a micro uneven defect present on the surface to be inspected based on a difference in brightness.
[0043]
【The invention's effect】
The surface defect detection method and the surface defect detection apparatus according to the present invention illuminate with a diffused light source and capture an image with an imaging means of a telecentric optical system, so that all inspection target surfaces can be captured even if the object is a three-dimensional shape. It is possible to reliably detect minute irregularities, and can be used to detect minute irregularities on a three-dimensional surface or an irregular surface such as an edge portion of a silicon wafer or the like.
[0044]
Further, by using near-infrared light as the light source and light reception, it is possible to prevent the dirt from being recognized as a defect and to improve the detection accuracy.
[0045]
Furthermore, by using a line sensor array for the image pickup means, there are some which can obtain high resolution and throughput and contribute to improvement of productivity.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an appearance of a surface defect apparatus of an embodiment.
FIG. 2 is a side view of the surface defect apparatus of the present embodiment.
FIG. 3 is a detailed explanatory view of an edge portion of a silicon wafer.
FIG. 4 is an explanatory diagram illustrating a telecentric optical system.
FIG. 5 is an explanatory diagram for explaining a surface with minute irregularities.
FIG. 6 is an explanatory view showing another three-dimensional inspection object.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Surface defect inspection apparatus 2 Upper surface image pickup means 3 Side surface image pickup means 4 Lower surface image pickup means 5 C-type light source 6 Silicon wafer 7 Image processing apparatus 8 Telecentric optical system image pickup means 51 Light emitting surface 61 Upper taper surface 62 Side surface 63 Lower taper Surface 81 Image side lens 82 Aperture 83 Linear sensor side lens 84 Linear sensor arrays 91A, 91B, 91C Inspection target surfaces 92A, 92B, 92C Imaging means 93 Diffused light source

Claims (7)

A mirror surface of a moving inspection object is illuminated by a diffuse light source, and an image of the mirror surface of the inspection object is picked up by a plurality of imaging means composed of a telecentric optical system and a linear sensor array. A surface defect detection method for detecting minute irregularities on a specular surface of an inspection object based on the intensity of a signal output from the diffused light source, wherein the diffused light source has a band-shaped imaging portion of a linear sensor array on the inspection object A surface defect detection method comprising illuminating . The surface defect detection method according to claim 1, wherein the diffused light source is a near-infrared light source. The surface defect detection method according to claim 1, wherein the imaging unit includes a near-infrared filter, and the linear sensor array receives only near-infrared light. A diffused light source that illuminates the mirror-like surface of the moving inspection object with diffuse light, an image of the mirror-like surface of the inspection object, a telecentric optical system that picks up an image, and a plurality of imaging means including a linear sensor array; A surface defect detection apparatus comprising: image processing means for detecting minute irregularities on a specular surface of an inspection object from the intensity of a signal output from a linear sensor array , wherein the diffused light source is on the inspection object A surface defect detection device , wherein a light emitting portion is arranged so as to illuminate an imaging portion of the linear sensor array in a strip shape. The surface defect detection device according to claim 4, wherein the diffused light source is a near infrared light source. The surface defect detection apparatus according to claim 4, wherein the imaging unit includes a near-infrared filter, and the linear sensor array receives only near-infrared light. The inspection object is an edge portion of a disk, and the diffused light source has a light source portion having an arc shape, an elliptic arc shape, or a gate shape, and a plurality of the imagings for imaging the chamfered portion and the side surface portion of the inspection object. The surface defect detection apparatus according to claim 4, further comprising a unit.

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