JP2003139523A - Surface defect detecting method and surface defect detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a microscopic irregular defect on the face of an inspection object comprising a three dimensional face or faces with a plurality of different properties such as an edge part of a silicon wafer or the like. SOLUTION: A mirror like surface of the inspection object is illuminated by a diffused light source, an image of the mirror-finished surface of the inspection object is picked up by a plurality of image pickup means composed of a telecentric optical system and a linear sensor array, and the microscopic irregular defect of the mirror-finished inspection object surface is detected from the intensity of signals outputted from the linear sensor array. Microscopic irregularity of all inspection object faces can be positively detected even in an image pickup object of a three dimensional shape, and it can be used to detect a microscopic irregular defect of a three dimensional face or an amorphous face such as the edge part of the silicon wafer or the like.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a surface defect detecting method and a surface defect detecting device capable of detecting minute unevenness defects at the edge portion of a silicon wafer for semiconductors and other minute unevenness defects on a mirror plate. Regarding

[0002]

2. Description of the Related Art The inspection of the edge portion of a silicon wafer used for forming a semiconductor has not been considered as important as the inspection of the mirror surface portion. However, if there are defects such as dents, cracks, minute projections, and adhesion of particles on the edge portion of the silicon wafer for semiconductors, fatal defects may occur in the silicon wafer due to these defects.

When there are dents, cracks, etc. at the edge of the silicon wafer, when heat is applied to the silicon wafer in the heat treatment step, etc., these defects cause the mirror surface portion of the silicon wafer, that is, the semiconductor circuit. There is a possibility that cracks may occur on the surface on which the cracks are formed, resulting in a defective product.

On the other hand, if particles adhere to the edge of the silicon wafer, there is a risk that the particles will dislocate and adhere to the mirror surface as the process proceeds. Alternatively, there is a possibility that part of the dents and cracks may peel off and adhere to the mirror surface.

In recent years, as the degree of integration of LSIs has increased and the demand for finer pitches has increased, such minute particles have adhered to the mirror surface portion of the silicon wafer, or a silicon wafer having a crack on the mirror surface is processed next. Must be completely eliminated, and for that purpose, it is necessary to strictly inspect the edge portion of the semiconductor silicon wafer for defects such as dents, cracks, and adhesion of particles.

For the inspection of microscopic unevenness defects on a mirror surface other than the edge portion of a silicon wafer for semiconductors, parallel rays are applied to the mirror-finished surface, and a collimating lens is used to generate a gradation of reflected brightness, whereby It is possible to inspect minute irregularities.

However, this inspection method cannot be used for the inspection of minute irregularities on the surface of the edge portion of a silicon wafer. Because the edge portion of the silicon wafer is composed of several flat 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 flat portions and R portions can be detected. An image that can be discriminated cannot be captured.

Therefore, some proposals have been made for the inspection of chamfered edges or tapered edge portions of silicon wafers.

[0009] Japanese Patent No. 2999712 discloses a method of detecting uneven defects by utilizing the diffraction phenomenon of laser, but it is difficult to detect defects such as fine cracks and minute protrusions by this method, and further, it becomes dirty. There is a problem of excessive detection.

Further, Japanese Laid-Open Patent Publication No. 2004.6537 proposes a method for detecting a defect by focusing on the inside of the defect on the edge surface and distinguishing the defect from the polishing waste and the like. It is necessary to make it shallow, and it is difficult to detect fine cracks and minute protrusions due to eccentricity of the wafer, alignment error of the image pickup device, and the like.

[0011]

As described above, in the inspection method used for the inspection of the irregularities on the mirror surface other than the edge portion of the silicon wafer for semiconductor, the irregularities on the surface other than the substantially flat surface are used. Cannot be used for inspection.

Further, the methods for detecting defects in the edge portion which have been proposed so far cannot be said to be suitable methods for detecting minute cracks and minute protrusions, as is apparent from the above description, and the surface You may mistakenly recognize stains as defects.

In view of the above problems, the present invention makes it possible to detect minute unevenness-like defects on a three-dimensional surface or an irregular surface such as an edge portion of a silicon wafer, and at the same time, stain the surface to be inspected. It is an object of the present invention to provide a surface defect inspection method and an inspection apparatus therefor capable of improving inspection accuracy by eliminating false recognition as a defect and further setting inspection throughput high.

[0014]

A first aspect of the present invention is a surface defect detection method for detecting microscopic unevenness defects on a mirror-like surface of a moving inspection object, which is a mirror-like surface of the inspection object by a diffused light source. The image of the specular surface of the inspection object is imaged by a plurality of imaging means composed of a telecentric optical system and a linear sensor array, and the specular inspection object is determined from the brightness of the signal output from the linear sensor array. It is characterized by detecting minute unevenness defects on the surface of the object.

A second invention is characterized in that, in the surface defect detecting method of the first invention, the diffused light source is a near infrared light source.

A third invention is characterized in that, in the surface defect detecting method of the first invention, the image pickup means includes a near-infrared filter, and the linear sensor array receives only near-infrared light.

A fourth aspect of the present invention is a surface defect detection apparatus for detecting microscopic unevenness defects on a mirror-like surface of a moving inspection object, and a diffused light source for illuminating the mirror-like surface of the inspection object with diffused light. , A plurality of image pickup means composed of a telecentric optical system and a linear sensor array for picking up an image of the specular surface of the inspection object, and the intensity of the signal output from the linear sensor array An image processing unit for detecting a minute unevenness defect is provided.

A fifth invention is characterized in that, in the surface defect detecting device of the fourth invention, the diffused light source is a near infrared light source.

A sixth invention is characterized in that, in the surface defect detecting apparatus of the fourth invention, the image pickup means includes a near infrared ray filter, and the linear sensor array receives only near infrared ray.

A seventh invention is the surface defect detecting apparatus according to the fourth invention, wherein the inspection object is an edge portion of a disk, and the diffused light source has a light source portion in an arc shape, an elliptic arc shape or a gate shape. It is characterized by comprising a plurality of the imaging means for imaging the chamfered portion and the side surface portion of the inspection object.

[0021]

Since the surface defect inspection apparatus of the present invention illuminates the specular surface of the inspection object by the diffused light source, it is possible to image even the inspection object having a three-dimensional shape composed of a plurality of planes. In addition to being able to illuminate, the image of the specular surface of the inspection object is picked up by a plurality of image pickup means composed of a telecentric optical system and a linear sensor array. It is possible to detect the intensity of the signal output from the sensor array.

Further, by using a near-infrared light source as the diffused light source and using a near-infrared filter as the image pickup means, it is possible to reduce the influence of density and dirt on the inspection surface.

Further, by making the shape of the diffused light source into an arc shape, an elliptic arc shape, or a gate shape, the tapered portion and the end surface of the edge portion of the disk are illuminated at the same time, so that minute irregularities on the surface of the three-dimensional shape are formed. State defects can be detected.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The surface defect inspection apparatus and inspection method of the present invention will be described in detail with reference to the drawings. The present invention is not limited to this embodiment.

FIG. 1 is a side view showing a surface defect inspection apparatus 1 according to the present invention, and FIG. 2 is a plan view of the surface defect inspection apparatus 1. The surface defect apparatus 1 shown in FIGS. 1 and 2 shows an embodiment in which an edge portion of a silicon wafer 6 for semiconductor production is used as an inspection object.
As the image pickup means, an upper surface image pickup means 2, a side surface image pickup means 3, and a lower surface image pickup means 4 are provided. Further, the C-type light source 5 is used as the illumination means.

As shown in FIG. 3, the edge portion of the silicon wafer 6 is composed of two tapered portions, an upper tapered surface 61, a lower tapered surface 63 and a side surface 62. The intersection of each surface and the other surface is smoothly connected by the R surface.

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 in an arc shape or an elliptic arc shape, and diffuses the edge portion of the silicon wafer 6 from the vertical and side surfaces. Illuminate with light.

As shown in FIG. 2, the C-type light source 5 is arranged in a posture slightly tilted from the radial direction of the silicon wafer 6,
The side surface image pickup means 3 is arranged so as to be tilted to the opposite side from the radial direction of the silicon wafer 6 so as to most efficiently receive the specular reflection light of the light emitted from the C-type light source 5.

On the other hand, the upper surface image pickup means 2 and the lower surface image pickup means 4 respectively have an upper taper surface 61 and a lower taper surface 63 at the edge portion of the silicon wafer 6, as shown in FIG.
Are arranged so as to face each other substantially, and like the side-face image pickup means 3, are arranged at a position that most efficiently receives the specularly reflected light of the light emitted from the C-type light source 5.

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 arrays of the upper surface image pickup means 2, the side surface image pickup means 3, and the lower surface image pickup means 4 continuously scan the image of the edge portion of the silicon wafer 6, and send the output to the image processing device 7 to detect defects. Detect.

FIG. 4 is an explanatory view for explaining a telecentric optical system applied to the upper surface image pickup means 2, the side surface image pickup means 3 and the lower surface image pickup means 4.

Image side lens 81 and linear sensor side lens 8
A diaphragm 82 is disposed between the diaphragm 82 and the third lens 3, and the position thereof is located at the rear focal point of the image side lens 81 and the front focal point of the linear sensor side lens 83. In the optical system configured as described above, the chief ray is the image-side lens 81.
Becomes a light ray parallel to the optical axis of the linear sensor side lens 83, and the principal ray passing through the linear sensor side lens 83 becomes parallel to the optical axis of the linear sensor side lens 83. That is, the linear sensor array 84
Will enter only the light rays parallel to the optical axis of the telecentric optical system.

The linear sensor array 84 is a light receiving element in which CCD charge elements are arranged in a row to obtain a high resolution, and the linear sensor array 84 is arranged in a direction orthogonal to the moving direction of the inspection object to perform scanning to thereby obtain a two-dimensional image. The image pickup device for obtaining the image of the surface of the edge portion of the rotating silicon wafer 6 is continuously imaged.

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 rotating at a constant speed with its central axis as the center of rotation. In the meantime, the line sensor array 74 provided in the upper surface image pickup means 2, the side surface image pickup means 3, and the lower surface image pickup means 4 continuously picks up images of the upper tapered surface 61, the side surface 62, and the lower tapered surface 63, respectively. To do.

Since the image pickup means used in the surface defect inspection apparatus of the present invention is a telecentric optical system image pickup means, only light rays parallel to the optical axis of the optical system of the image pickup means are incident on the linear sensor array 84 of the image pickup element. Therefore, as shown in FIG. 5, light is scattered at a place where the imaged surface has minute irregularities, and as a result, light rays are reduced in a direction parallel to the optical axis incident on the imaging means, and a flat place is bright and dark. There is a difference. The fine unevenness defect inspection apparatus of the present invention utilizes this property to detect the fine unevenness of the inspection surface as a difference in brightness.

The light source used in the defect inspection apparatus of the present invention is diffuse light illumination, and since the light source has an arcuate shape, the upper tapered surface 61, the side surface 62, and the lower tapered surface 63 all over the entire surface. I will illuminate from the direction,
Among them, the light whose specular reflection light is parallel to the optical axis of the image pickup means enters the line sensor array 74.

When illuminated with parallel rays as in the conventional case, FIG.
In the R portion shown in (1), the reflected light is scattered to form a dark image, so that the surface defect cannot be detected. On the other hand, by using a diffused light source as the light source as in the present invention, a bright image can be obtained because there is light reflected by the R portion and incident on the imaging means, and it is possible to detect the presence or absence of a defect.

As described above, even if an image pickup object having a three-dimensional shape is illuminated by the diffused light source and the image is picked up by the image pickup means of the telecentric optical system, the fine irregularities on all the inspection object surfaces are surely detected. can do.

Further, in the surface defect device of the present embodiment, since the linear sensor array is used as the image pickup element, it is possible to obtain a higher resolution as compared with the two-dimensional area sensor, and it is possible to obtain a fine uneven defect. Can be detected.
Further, since the scanning speed of the linear sensor array is remarkably faster than that of the area sensor, high throughput is guaranteed and inspection processing capability is high.

Furthermore, by using near infrared light as the light source or by using a filter that allows only the near infrared light to pass through the image pickup means, it is possible to construct an inspection device that is not easily affected by dirt.

In the present embodiment, the surface defect detecting apparatus for detecting the minute irregularity-shaped defects existing on the edge of the silicon wafer has been described. However, the present invention is not limited to this, and the inspection object having a shape having a plurality of surfaces having different properties. It is possible to inspect micro unevenness defects existing in an object.

For example, even if an inspection object has inspection surfaces 91A, 91B and 91C with steps as shown in FIG.
By illuminating 3 and imaging with the imaging means 92A, 92B, and 92C, it is possible to detect the minute unevenness-like defects present on the surface to be inspected due to the difference in brightness.

[0043]

INDUSTRIAL APPLICABILITY The surface defect detection method and the surface defect detection device of the present invention are all illuminated by a diffused light source and imaged by the image pickup means of the telecentric optical system, so that even a three-dimensionally shaped image pickup object can be obtained. It is possible to reliably detect the minute unevenness of the surface to be inspected, and it is used to detect the minute unevenness-like defects of a three-dimensional surface or an irregular surface such as an edge part of a silicon wafer. be able to.

Further, by using near-infrared light as the light source and the received light, it is possible to prevent the stain from being mistakenly recognized as a defect and improve the detection accuracy.

Further, by using a line sensor array for the image pickup means, high resolution and throughput can be obtained, which greatly contributes to improvement in productivity.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an appearance of a surface defect device of this embodiment.

FIG. 2 is a side view of the surface defect device according to the present embodiment.

FIG. 3 is a detailed explanatory diagram 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 having minute unevenness.

FIG. 6 is an explanatory diagram showing another three-dimensional inspection object.

[Explanation of symbols]

1 Surface defect inspection equipment 2 Upper surface imaging means 3 Side image pickup means 4 Lower surface imaging means 5 C type light source 6 Silicon wafer 7 Image processing device 8 Telecentric optical system imaging means 51 Light emitting surface 61 Upper tapered surface 62 side 63 Lower taper surface 81 Image side lens 82 Aperture 83 Linear sensor side lens 84 Linear sensor array 91A, 91B, 91C Inspection surface 92A, 92B, 92C Imaging means 93 Diffuse light source

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2F065 AA49 BB01 CC19 FF04 FF42                       GG01 GG11 HH02 JJ03 JJ05                       JJ08 JJ09 JJ26 LL22 LL30                       LL59                 2G051 AA51 AB01 AB03 BA06 BB01                       CA03 CA07 CB05 CC07 CC09                       DA08 EA12

Claims (7)

[Claims] 1. A surface defect detection method for detecting microscopic irregularity defects on a mirror-like surface of a moving inspection object, which comprises illuminating the mirror-like surface of the inspection object with a diffused light source, An image of the surface is picked up by a plurality of image pickup means composed of a telecentric optical system and a linear sensor array, and minute unevenness defects on the surface of the mirror-like inspection object are detected from the brightness of the signal output from the linear sensor array. A method for detecting surface defects. 2. The surface defect detection method according to claim 1, wherein the diffused light source is a near infrared light source. 3. The surface defect detection method according to claim 1, wherein the image pickup means includes a near infrared ray filter, and the linear sensor array receives only near infrared ray light. 4. A surface defect detection device for detecting minute unevenness defects on a mirror-like surface of a moving inspection object, the diffused light source illuminating the mirror-like surface of the inspection object with diffused light, and the inspection object. A plurality of image pickup means composed of a telecentric optical system and a linear sensor array for picking up an image of the mirror-like surface of, and the minute unevenness defect of the surface of the mirror-like inspection target object from the brightness of the signal output from the linear sensor array. An image processing means for detecting the surface defect detecting device. 5. The surface defect detection device according to claim 4, wherein the diffused light source is a near infrared light source. 6. The surface defect detection device according to claim 4, wherein the image pickup means includes a near infrared ray filter, and the linear sensor array receives only near infrared ray light. 7. The inspection object is an edge portion of a disk, and the diffused light source has a light source portion in an arc shape, an elliptic arc shape, or a gate shape, and images the chamfered portion and the side surface portion of the inspection object. The surface defect detection apparatus according to claim 4, further comprising a plurality of the image pickup units that perform: