JP2999712B2 - Edge defect inspection method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a defect at a required end of an inspection object such as a plate-like or linear material such as a semiconductor wafer. By irradiating the collected parallel light, only the high-dimensional diffraction light of the diffraction light generated by combining the elliptical mirror and the light shielding means is collected and detected, and the presence or absence of a defect at the end and the type of the defect are determined. The present invention relates to an edge defect inspection method and device capable of inspecting at the same time.

[0002]

2. Description of the Related Art Inspection is performed to determine whether or not an edge defect such as a crack, chip, or flaw has occurred in a narrow and long end portion such as an outer peripheral edge portion of a semiconductor wafer. And a visual inspection using a penlight or the like, only a so-called sensory test was performed.

In order to implement such an edge defect inspection apparatus, it is necessary to rely on an inspection method using image processing by a CCD camera or a computer.

[0004]

In the above-mentioned sensory test, there is a problem that the test quality lacks stability due to the experience of the inspector. In addition, in the inspection method using image processing, it takes a considerable amount of time to inspect the entire circumference or the entire length of the end of the inspection object, so that it has been difficult to put it to practical use.

SUMMARY OF THE INVENTION The present invention has been made in view of the present state of the method of inspecting a defect at a required edge of an object to be inspected such as a plate-like or linear material such as a semiconductor wafer. It is an object of the present invention to provide an edge defect inspection method and apparatus capable of easily inspecting the end face properties such as surface roughness and the like and sorting the same.

[0006]

Means for Solving the Problems The present inventors have studied various optical inspection methods with the aim of obtaining a stable inspection quality regardless of the experience of the inspector and enabling an inspection in a short time. As a result, low-dimensional diffracted light is blocked out of the diffracted light generated by irradiating the converged parallel light to the edge of the inspection object near the first focal point of the ellipsoidal mirror with the parallel light orthogonal to the end. By using an elliptical mirror that focuses high-dimensional diffracted light, a detector is placed at the second focal point of the elliptical mirror, and the components of the high-dimensional diffracted light are analyzed and classified. Nevertheless, the inventors have found that it is possible to automatically sort cracks, chips, scratches and the like, and also to automatically classify surface roughness, and have completed the present invention.

That is, the present invention provides a first focus of an elliptical mirror .
When on a plane including the second focal position, and the inspection end of the first focus or relatively movable object to be inspected an elliptical mirror in its vicinity are arranged, the inspection end and an optical system Shading hand between
Intervening steps, through which on a plane perpendicular to said plane
Irradiated with parallel light, out of the generated from the inspected end on the plane diffractive and shielding the low-dimensional diffracted light high-dimensional diffraction light condensed by the elliptical mirror, an elliptical mirror In this method, the diffraction light is detected at the second focal point, and the defect and the property of the end are specified based on the intensity and / or frequency component of the diffraction light.

Further, the present invention provides an elliptical mirror and an elliptical mirror.
On the plane containing the one focal point and the second focal point, and
Or in the vicinity of the elliptical mirror,
A holding device for holding movably pairs manner, the plane to be inspected end portion positioned in the first focal position or the vicinity thereof of the elliptical mirror
An optical system for irradiating collimated light on the vertical orthogonal plane, the front
Serial interposed between the inspected end and an optical system through which <br/> among diffracted light generated by irradiating the parallel light to be inspected end shields of low-dimensional diffracted light Light-shielding means, and a detector of the high-dimensional diffraction light arranged at the second focal position of the elliptical mirror ;
It is an edge defect inspection device having the same.

[0009]

DETAILED DESCRIPTION OF THE INVENTION end defect inspection method according to the invention, which is implemented using an optical system for irradiating the collimated light condensed on the first focal point of the ellipsoidal mirror and an elliptical mirror, an elliptical mirror
On the plane including the first focal point and the second focal point position, and put the end of the inspection object at or near the first focal point of the elliptical mirror,
With a light-shielding plate interposed , perpendicular to the plane at the end of the inspection object
The parallel light condensed on the orthogonal plane is irradiated, and of the diffraction light generated by this , low-dimensional diffraction light such as so-called specular reflection light is converted into a spatial filter by a light shielding plate arranged at the required position. And the high-dimensional diffracted light, which is the extraordinary reflected light, is collected by an elliptical mirror, and the collected diffracted light is imaged on a detector provided at the second focal point of the elliptical mirror.

The diffraction light imaged on the detector has a different frequency component depending on the type of defect and the surface roughness at the end of the inspection object. In addition, the intensity and frequency components of the diffracted light are determined in advance for each type of defect, and the detected diffracted light is classified, so that cracks, chips, scratches, and the like can be selected, and the surface roughness can also be detected. . In addition, by moving the inspection object or the apparatus, the entire circumference or the entire length of the inspection object can be continuously inspected.

The object to be inspected is a semiconductor wafer in the embodiment, but may be any object other than a plate-like material such as a wire material such as a whole wire for bonding. In addition, the size and shape of the elliptical mirror are appropriately selected according to the object to be inspected, and also appropriately determined according to the detection target such as a defect of the object to be inspected and the surface properties. As the light shielding plate, an optical filter or a polarizing filter configured to transmit parallel light and reflect the required low-dimensional diffracted light without transmitting the light is appropriately employed. The dimension setting of the diffracted light and the dimension of the diffracted light to be removed differ depending on the detection target and the surface properties, and the size, shape and installation position of the light shielding plate serving as a spatial filter are selected according to these conditions. In the present invention, although the light reflected on the normal is set to 0 dimension, the dimension is set for each required angle.
For example, if the dimension is set at ± 6 °, the horizontally incident light has one dimension at ± 6 °, seven dimensions at ± 42 °, and 15 dimensions at vertical.

In the present invention, as the optical system for irradiating the parallel light condensed at the first focal position of the elliptical mirror, a known optical system in which a laser light source is configured using a mirror or a lens can be used, and it is preferable. A helium neon laser or a semiconductor laser is used. As the detector, a silicon photodiode, a solar cell, a photomultiplier, or the like can be used.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor wafer edge defect inspection apparatus according to the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic plan view of an edge defect inspection apparatus, and FIG. 2 is a schematic side view. The semiconductor wafer 1 is horizontally attracted to the turntable 2 and rotates at a predetermined speed. The elliptical mirror 3 disposed close to the rotary table 2 is a semi-elliptical sphere, and a slit is provided at the horizontal top so that the end of the rotating wafer 1 passes through a required position near the first focal point of the elliptical mirror 3. I have.

An optical system for irradiating the parallel light includes an objective lens 6 that focuses light from a parallel light source 4 outside the elliptical mirror 3 through a mirror 5 near a first focal point of the elliptical mirror 3. Is irradiated to the end of the wafer 1 through the substrate, and diffraction light is generated from the surface of the end of the wafer 1 of the inspection object by the irradiation of the parallel light. More specifically, as shown in FIG. 3, the parallel light focal point of the objective lens 6 is located at the position A within the end of the wafer 1, and the first focal point B of the elliptical mirror 3 is located at the center of the arc at the end of the wafer 1. In the present invention, a configuration that does not use an objective lens can be adopted.

On the other hand, between the end of the wafer 1 and the objective lens 6, a light shielding plate 7 is arranged as a spatial filter.
That is, the light shielding plate 7 made of a plate material having a predetermined width is attached to the wafer 1.
It is arranged so as to abut on the inner surface of the elliptical mirror 3 in the vertical direction perpendicular to the plane. Accordingly, of the diffracted light, low-dimensional diffracted light is blocked by the light shielding plate 7, but high-dimensional diffracted light, that is, diffracted light at the defect portion, leaks out of the light shielding plate and is transmitted to the elliptical mirror 3.
, And can be detected by forming an image on a detector 8 provided at the second focal point of the elliptical mirror 3.

By rotating the semiconductor wafer 1 with the turntable 2, the entire circumference of the end can be continuously inspected, and by analyzing the intensity and frequency components of the detected high-dimensional diffraction light, the end of the semiconductor wafer 1 can be analyzed. The type of the defect, or the surface roughness, etc. can be detected. For example, as shown in FIG. 4, it is possible to detect a defect by the peak value of the intensity of diffraction light.

[0017]

As is apparent from the embodiments, the edge defect inspection method and the optical edge defect inspection apparatus according to the present invention have significantly improved inspection quality compared with the conventional sensory inspection, and have a short time. The ability to carry out a full inspection at the end of the process has a significant effect on quality stabilization and process automation.

[Brief description of the drawings]

1 is a planar cross section schematic view of a semiconductor wafer for an end portion a defect inspection apparatus according to the present invention.

2 is a side cross-section schematic view of a semiconductor wafer for an end portion a defect inspection apparatus according to the present invention.

FIG. 3 is an explanatory view showing details of a first focal point in the semiconductor wafer edge defect inspection apparatus according to the present invention;

FIG. 4 is a graph showing a relationship between time and intensity of high-dimensional diffraction light.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Kazumi Komatsu 2-8-6 Takazawa Building, Nakazawa, Tama-shi, Tokyo 1st floor in Raytex Co., Ltd. (56) References JP-A-63-208747 (JP, A) 62-75306 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 21/88 G01B 11/30 H01L 21/66

Claims (3)

(57) [Claims] 1. Includes first and second focus positions of an elliptical mirror
On the plane, and the inspection end of the first focus or the <br/> relatively movable object to be inspected elliptical mirror in its vicinity are arranged, the
A light-shielding means is interposed between the inspection end and the optical system.
Irradiating collimated light on the vertical orthogonal plane to the plane through, the
Of the diffracted light generated from the end to be inspected on the plane, the low-dimensional diffracted light is shielded, and the high-dimensional diffracted light is collected by an elliptical mirror.
An end defect inspection method for detecting the diffracted light at the second focal point of the elliptical mirror and specifying a defect or property at the end based on the intensity and / or frequency component of the diffracted light. 2. An elliptical mirror, and first and second focal points of the elliptical mirror.
On the plane including the position and at or near the first focal point
The object to be inspected can be moved relative to the elliptical mirror
A holding device for holding, elliptical mirror a first focal position or vertical plane orthogonal on said plane to be inspected end portion located near the
An optical system for irradiating the parallel light, the inspection ends and the optical system
Is interposed between, which among the times generated by irradiating a collimated light diffracted light to be inspected end through, and light shielding means for shielding the low dimensional diffracted light, the second focal position of the elliptical mirror Placed
End defect inspection apparatus having a detector of the high dimensionality of the diffracted light. 3. The inspection device according to claim 2, wherein the holding device is an inspection object.
In the table that holds and rotates the semiconductor wafer is
A semiconductor wafer edge defect inspection device, wherein the light shielding means is a light shielding plate disposed between the inner surfaces of the elliptical mirrors at a required width in a direction perpendicular to the wafer surface.