JPH0236893B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a surface flaw detection device for detecting flaws on a surface, such as a semiconductor pellet, on which uneven patterns that are perpendicular to each other are formed.

[Technical background of the invention and its problems]

Conventionally, as a device of this kind, there is a method in which, for example, two adjacent chips formed on a semiconductor wafer are compared at the same location and flaws are detected from the difference. With this kind of equipment, the mutual position of each chip (pellet) is accurately determined before the wafer is separated into chips, so it is possible to perform highly accurate flaw detection with simple positioning. Can be done.

However, before wafer separation,
It is not possible to detect scratches that occur during separation by dicing or when each chip is extracted after separation. For this reason, flaw inspection must be performed after separation, but with the conventional device described above, accurate flaw detection cannot be performed unless the chips are aligned accurately with each other, so alignment is complicated. Therefore, it took a lot of time and effort to detect flaws, and productivity was extremely low.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface flaw detection device that can detect surface flaws easily, accurately, and at high speed even in individually separated specimens.

[Summary of the invention]

In order to achieve the above-mentioned object, the present invention provides parallel light beams by each photoconductor arranged at a direction of 45 degrees with respect to each concavo-convex pattern and with an irradiation angle of 20 to 30 degrees with respect to the surface of the subject. Light is irradiated onto the surface of the specimen, and the scattered light from the scratches caused by this irradiation is received by a photoelectric converter placed vertically above the surface of the specimen, and the resulting image signal is subjected to level judgment, etc. to obtain surface scratch information. It was designed to ask for.

[Embodiments of the invention]

FIG. 1 is a schematic diagram of a surface flaw detection device according to an embodiment of the present invention. This device has a light source 1
The output light is converted into pseudo-parallel light by a lens system 2, and then transmitted through four photoconductors 3a, -, 3d each made of a glass fiber or the like, to the surface of a semiconductor pellet 4 as an object to be inspected. is irradiated.

By the way, each of the four photoconductors 3a, -, 3
The light output end portions d are arranged so that the optical axis is shifted by 45 degrees with respect to the directions X and Y of the pattern formed on the semiconductor pellet 4, respectively, as shown in FIG. 2a, and the irradiation angle is As shown in FIG. 2b, it is set at an angle of 20 to 30 degrees with respect to the pattern forming surface (front surface) 4a of the semiconductor pellet 4.
In addition, in FIG. 1, two photoconductors 3 are shown for convenience of illustration.
Only a and 3b are shown.

In addition, this device includes each of the photoconductors 3a, -, 3d.
The reflected optical image of the surface of the semiconductor pellet 4 illuminated by It is led to the signal processing circuit 9 via the signal processing circuit 9. Here, the binarization circuit 8 removes weak noise components by binarizing the captured image signal at a predetermined level. The signal processing circuit 9 is equipped with a computer, for example, and detects the presence or absence of scratches by pixelizing the binarized output and determining the level for each pixel. I'm looking for information on Sato.

With such a configuration, the semiconductor pellet 4
The surface 4a is simultaneously illuminated from four directions by four photoconductors 3a, . Therefore, if a pattern as shown in FIG. 3 is formed on the semiconductor pellet 4 and there are scratches, the pattern may be damaged.
Since the light is illuminated at a 45° angle, vertical upward scattering of light due to regular patterns does not occur, and even if it does occur, it will be weak, and as a result, only the scattered light from the scratches will be visible to the ITV camera. The light will be received at 7. Also, at this time, the scattered light due to the scratch ○I is illuminated from four directions simultaneously, so
The strength is higher than that in the case of only one side or the case of two sides, and the scratches are reliably generated regardless of the shape of the scratch.

Furthermore, since the surface of the semiconductor pellet 4 is illuminated at an irradiation angle of 20 to 30 degrees,
For example, compared to the case where it is set at 50 to 60 degrees,
The amount of reflected light due to the slight unevenness of the surface or the inclination of the pellet is significantly reduced, and the problem that occurs when the angle is set to 20 degrees or less, where only the edges of deep scratches shine and scattered light is not detected, does not occur.

Therefore, the ITV camera 7 receives light from only the scratches on the surface of the semiconductor pellet 4, as shown in FIG. 4, for example. The captured image signal obtained by this ITV camera 7 is further removed from noise components by a binarization circuit 8, and then subjected to signal processing by a signal processing circuit 9. As a result, the presence of the scratch ○a is detected. Furthermore, information such as its position, size, shape, etc. is identified and displayed on a display device (not shown) or the like.

As described above, in this embodiment, the surface of the semiconductor pellet 4 is illuminated with four parallel beams at an irradiation angle of 20 to 30 degrees from a direction shifted by 45 degrees with respect to the direction of the pattern. I try to do this, so
It is possible to detect flaws with an extremely high S/N ratio, and there is no need for precise positioning as in the conventional method. Therefore, flaw detection can be performed easily, accurately, and at high speed even on individually separated semiconductor pellets. Further, in this embodiment, since the illumination optical system is constructed of a photoconductor such as a glass fiber, the tip portion of the illumination section can be made smaller. This effect is
This is extremely effective when illumination is performed from four directions as in this embodiment, and when the tip of the illumination part is placed close to the surface of the semiconductor pellet at an angle of 20 to 30 degrees.

〔Effect of the invention〕

As described in detail above, according to the present invention, each of the four photoconductors is parallel to each other in a direction of 45 degrees with respect to each uneven pattern and with an irradiation angle of 20 to 30 degrees with respect to the surface of the subject. Light is irradiated, the scattered light generated by this irradiation is received by a photoelectric conversion unit placed vertically above the surface of the object to be inspected, and the resulting image signal is subjected to level judgment etc. to obtain surface flaw information. It is.

Therefore, according to the present invention, the intensity of scattered light caused by scratches can be increased regardless of the shape of the scratch, and the amount of light reflected from slight irregularities or inclinations on the surface of the object to be examined can be reduced, and moreover, only the edges of deep scratches can be detected. It is possible to provide a surface flaw detection device that can simply and accurately detect surface flaws at high speed even in individually separated objects without detecting scattered light.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a surface flaw detection device according to an embodiment of the present invention, FIGS. Fig. 4 is used to explain the operation of the apparatus shown in Fig. 1, Fig. 3 is a perspective view showing an example of the structure of the surface of the subject, and Fig. 4 is an optical image received by the photoelectric conversion section. It is a figure showing an example. 3a, -, 3d... Photoconductor, 4... Semiconductor pellet, 5... Objective optical system, 6... Eyepiece optical system, 7...
ITV camera, 8... Binarization circuit, 9... Signal processing circuit, ○I... Scratch.

Claims (1)

[Claims] 1. A light source, a lens system that converts the light from this light source into parallel light, and an optical axis that is aligned with each of the mutually orthogonal uneven patterns formed on the surface of the subject.
Four beams of light that are shifted by 45 degrees and arranged so that each has an irradiation angle of 20 to 30 degrees with respect to the surface of the object to be examined, and that irradiate the same position on the surface of the object with parallel light that has been converted by the lens system. A conductor, a photoelectric conversion unit that is arranged vertically above the surface of the subject and receives scattered light from a scratch obtained by irradiating each of the photoconductors with parallel light, and an image signal obtained by this photoelectric conversion unit. A surface flaw detection device comprising: a signal processing unit that performs level determination and the like to obtain flaw information such as the presence or absence, position, and size of flaws on the surface of the subject.