JPH0534123A - Defect inspecting apparatus - Google Patents

Abstract

PURPOSE:To obtain a defect inspecting apparatus which has a space filter having the simple structure and can inspect a defect highly accurately. CONSTITUTION:In a defect inspecting apparatus 12, laser light 24 is applied to a semiconductor wafer (object to be inspected) 11 having the pattern of a periodic structure. The scattered and diffracted light from the semiconductor wafer 11 undergoes space filtering. The component corresponding to the pattern is removed from the scattered and diffracted light. The scattered and diffracted light is observed, and the defect in the pattern is inspected. A space filter 16, which comprises a deformable frame part 16 and cut-off parts 22..., is provided. The cut-off parts 22 are formed of strip-shaped bodies, linked to the frame part 21 and juxtaposed. The space between the cut-off parts 22 is mutually adjusted in response to the deformation of the frame part 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection apparatus for inspecting defects in a periodic pattern such as an IC and a liquid crystal display.

[0002]

2. Description of the Related Art For example, electrodes of ICs, liquid crystal displays, etc. are arranged so as to draw a regular pattern with repeatability. The patterns drawn on ICs, liquid crystal displays, etc. have a periodic structure.

As an apparatus for inspecting a defect generated during such a periodic pattern, laser light is an object to be inspected I.
There is one that irradiates a C wafer or the like to observe scattered diffracted light. In this type of defect inspection apparatus, a spatial filter is used, and a component included in the scattered diffracted light and corresponding to the periodic structure of the pattern is removed by the spatial filter. Then, the component corresponding to the defect is taken out, and this defective component is observed.

FIG. 5 shows an example of a point image formed on the basis of scattered diffracted light, and FIG. 6 shows a spatial filter (hereinafter referred to as a filter) for removing the main component of the point image 1 in FIG. ) 2
It is shown. The filter 2 has a modified cross-shaped light-shielding pattern 4 so as to remove a plurality of relatively large points 3 arranged in a cross in a point image. Then, when the point image 1 passes through the filter 2, an image obtained by removing the points 3 ... From the point image 1 is obtained.

[0005]

By the way, the filter 2 as described above has a modified cross-shaped light-shielding pattern 4, and although the main component in the point image 1 can be removed, It is impossible to pass only the defect image while removing the small points 5 ... Furthermore, the design of the light-shielding pattern 4 is constant, and when removing a point image different from the point image 1 in FIG. 5, a separate filter having a light-shielding pattern that matches the point image must be prepared. I won't.

Although not shown, as described in Japanese Patent Application No. 2-186877 filed by the present applicant, a plurality of rods are arranged in a grid and the intervals between the rods can be arbitrarily adjusted. There is a filter that does. However, this filter is relatively complex in structure,
As the number of rods increases, the mechanism for moving the rods and adjusting the distance between the rods becomes complicated. It is an object of the present invention to provide a defect inspection apparatus that includes a spatial filter having a simple structure and can inspect defects with high accuracy.

[0007]

In order to achieve the above object, the present invention irradiates an inspection object having a pattern of a periodic structure with laser light to scatter diffracted light from the inspection object. In a defect inspection apparatus for spatially filtering the scattered diffracted light to remove a component corresponding to the pattern, and observing the scattered diffracted light to inspect for defects in the pattern, a deformable frame portion and a belt-shaped body The spatial filter is composed of a blocking part that is connected to the frame part and is arranged in parallel with each other, and that has a blocking part whose distance is adjusted according to the deformation of the frame part. In this way, the present invention is able to simplify the structure of the spatial filter and improve the inspection accuracy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

1 to 3 show an embodiment of the present invention. 1 shows the structure of a defect inspection apparatus (hereinafter referred to as an inspection apparatus) 12 for inspecting a periodic pattern of defects formed on a semiconductor wafer 11 as an inspection object. The inspection device 12 includes a harf mirror 13,
A spatial filtering unit 17 including convex lenses 14 and 15 and a spatial filter 16 (described later), and an observing unit 18.
Are provided in sequence.

As shown in FIG. 2, the spatial filter (hereinafter referred to as a filter) 16 is a frame portion 2 composed of four plate members 19a, 19b, 20a, 20b assembled in a rectangular shape.
1 and a plurality of blocking portions 2 arranged inside the frame portion 21
2 ... and. Of these, the frame portion 21
Has its ends connected to the plate members 19a to 20b so as to be pivotally displaceable, and is transformed into a parallelogram shape as shown in FIG.

The blocking portions 22 ... Are made of an opaque strip. Further, the blocking portions 22 ... Have two longitudinal end portions of the plate portions 19a, 1a of the frame portion 21 which are parallel to each other.
9b are connected to each other via pins 23 ... The blocking portions 22 are arranged in parallel, and the intervals between the blocking portions 22 are set to be substantially equal. The angle between the blocking portions 22 ... And the plates 19a and 19b changes as the frame portion 21 deforms.

In the inspection device 12 described above, the laser light 24 passes through the half mirror 13 and is irradiated onto the element forming surface 11a of the semiconductor wafer 11 to be reflected. At this time, the pattern formed on the element forming surface 11a acts as a diffraction grating to form diffracted light. The path of the light transmitted through the half mirror 13 is shown by a chain line 25 in FIG.

The scattered diffracted light from the element forming surface 11a is hard.
Returning to the humilla-13, it is reflected by the mirror surface of the harhumira-13 inclined with respect to the optical path of the laser light 22. And har
The scattered diffracted light reflected by the Fumira-13 reaches the spatial filtering unit 17, and is condensed by the convex lens 14. Then, at the focal position of the convex lens 14, a point image 1 composed of a plurality of points regularly arranged at equal intervals as shown in FIG. 5 is formed.

The filter 16 is arranged at the focal position of the convex lens 14. The filter 16 is a plate body 19a-2.
The plate surface 0b is oriented substantially perpendicular to the path of the scattered diffracted light, and the inside of the frame portion 21 is positioned in the path of the scattered diffracted light. Further, in the filter 16, the longitudinal direction of the cutoff portions 22 is aligned with the arrangement direction of the points in the point image 1, and the distance d between the cutoff portions 22 is substantially matched with the distance between the points. Then, the filter 16 blocks each point 3, ..., 5 of the point image 1 by the blocking section 22 ,.
The component corresponding to the periodic pattern of 1 is removed.

When the pattern of the semiconductor wafer 11 has a defect, scattered light different from the regular component in the scattered diffraction light is generated. This scattered light is blocked by the blocking unit 22 of the filter 16.
It passes through a convex lens 15 located in the subsequent stage of the filter 16 and enters the observation unit 18. Observation section 18
And the semiconductor wafer 11 are in a relationship of imaging correspondence. Then, only the pattern defect image appears in the observation section 18. Here, it is conceivable to use a camera or a hologram as the observation unit 18. Furthermore, it is also possible to visually observe the defect image. In the filter 16,
The distance d between the blocking portions 22 ... Is adjusted as follows.

That is, as shown in FIG. 3, the frame portion 21 is deformed into a parallelogram shape, and the plate members 19a and 19b to which the blocking portions 22 are connected are different from the adjacent plate members 20 and 20b. , From a substantially right angle state as shown in FIG. 2 to an acute angle or an obtuse angle state. In FIG. 3, the inclination angle θ of the plate members 19a and 19b to which the blocking portions 22 are connected is shown.

When the plate members 19a and 19b are tilted, the connecting positions of the cutoff portions 22 ... And the plate members 19a and 19b are displaced, and the cutoff portions 22 ... Also rotate with the pins 23 ... It moves dynamically. Then, the blocking portions 22 approach the alignment direction while shifting in the longitudinal direction, and reduce the distance d between them. As the deformation amount of the frame portion 21 increases, the blocking portion 22
The interval d of ... becomes smaller. Further, when the four corners of the frame portion 21 are in a right angle state, the distance d between the blocking portions 22 ... Is maximized.

In the inspection device 12 as described above, since the filter 16 including the frame portion 21 and the band-shaped blocking portion 22 is provided, only the diffracted light on the semiconductor wafer 11 can be removed and the point image 1 All the points can be blocked by the blocking unit 22 ... Therefore, the periodic pattern
It is possible to surely remove the component corresponding to the defect and to extract only the defect image.

Further, the blocking portions 22 ... Are connected to the frame portion 21 and are collectively displaced as the frame portion 21 is deformed. Therefore, for example, the displacement amount of each blocking portion 22 ... Is individually adjusted. There is no need, and the structure of the filter 16 can be simplified.

Further, it is possible to easily adjust the interval d ...
It can be removed by one filter 16. Even if the pattern of the object to be inspected and the pattern of the object to be inspected are changed, it is possible to perform the spatial filtering using the filter 16 described above.

In the present embodiment, the spatial filter 16 having the rectangular frame portion 21 and the blocking portions 22 connected to each other is employed, but the present invention is not limited to this, and for example, FIG. It is also possible to employ a spatial filter (hereinafter referred to as a filter) 31 as shown in FIG.

That is, in the filter 31 shown in FIG. 4, strip-shaped blocking portions 36 ... Are parallel to each other between two frame portions 34, 35 which are formed by connecting plate bodies 32 ,. It has been installed. Each of the frame portions 32 and 33 deforms and expands and contracts to change the distance d between the blocking portions 36 ... When the frame portions 32 and 33 extend in the direction in which the blocking portions 36 are arranged, the interval d between the blocking portions 36 increases and the frame portions 32 and 3 extend.
3 is contracted in the longitudinal direction of the blocking section 36 ...
The interval d of 6 ... Is shortened. In such a filter 31, a part (for example, a corner) of the frame portions 34, 35 does not extremely project when the frame portions 34, 35 are deformed. Further, the present invention can be variously modified without departing from the scope of the invention.

[0023]

As described above, according to the present invention, the object to be inspected having the pattern of the periodic structure is irradiated with laser light, and the scattered diffracted light from the object to be inspected is spatially filtered to obtain the scattered diffracted light. In a defect inspection apparatus that removes a component corresponding to a pattern from the above, and inspects a defect in the pattern by observing scattered diffracted light, the deformable frame is connected to the frame by a band-shaped body. In addition, a spatial filter is provided which is provided in parallel with the cutoff portion and is arranged in parallel with each other in accordance with the deformation of the frame portion. Therefore, the present invention has the effects of simplifying the structure of the spatial filter and improving the inspection accuracy.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is a front view showing a spatial filter before deformation.

FIG. 3 is a front view showing a spatial filter after deformation.

FIG. 4 is a front view showing a modification of the spatial filter.

FIG. 5 is an explanatory diagram showing a general point image of a periodic pattern.

6 is a front view showing a spatial filter for blocking the point image in FIG.

[Explanation of symbols]

11 ... Semiconductor wafer (inspection object), 12 ... Defect inspection device, 16 ... Spatial filter, 21 ... Frame part, 22 ... Blocking part.

Claims (1)

Claim: What is claimed is: 1. An object to be inspected having a periodic pattern is irradiated with laser light, and the scattered diffracted light from the object to be inspected is spatially filtered to obtain the scattered diffracted light. In a defect inspection device for removing a component according to the pattern and observing the scattered diffracted light to inspect a defect in the pattern, a deformable frame part and a band-shaped body are formed on the frame part. A defect inspection apparatus comprising: a spatial filter that is connected and arranged in parallel, and that includes a blocking unit that adjusts the distance between each other according to the deformation of the frame.