JP3085738B2 - Defect inspection apparatus and method - Google Patents

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 and method 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 such as ICs and liquid crystal displays are arranged so as to draw a repetitive and regular pattern. The pattern drawn on an IC, a liquid crystal display or the like has a periodic structure.

[0003] As an apparatus for inspecting a defect generated during such a periodic pattern, laser light is applied to an object to be inspected.
There is one that irradiates a C wafer or the like and observes scattered diffraction light. In this type of defect inspection apparatus, a spatial filter is used, and components included in the scattered diffracted light and corresponding to the periodic structure of the pattern are removed by the spatial filter. Then, a component corresponding to the defect is extracted, and the defective component is observed.

FIG. 5 shows an example of a point image formed based on the scattered diffraction light. FIG. 6 shows a spatial filter (hereinafter, referred to as a filter) for removing a 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 shape in the point image. 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 above-mentioned filter 2 has a deformed cross-shaped light-shielding pattern 4 and can remove the main components in the point image 1, but it has other features. Cannot be made to pass only the defective image while removing the small points 5. Further, the design of the light-shielding pattern 4 is constant. To remove a point image different from the point image 1 in FIG. 5, a filter having a light-shielding pattern matching the point image must be prepared separately. No.

Although not shown, as described in Japanese Patent Application No. 2-186877 filed by the present applicant, a plurality of rods can be arranged in a grid and the interval between the rods can be adjusted arbitrarily. There is a filter like this. However, this filter is relatively complicated in structure,
As the number of rods increases, the mechanism for moving the rods to adjust the distance between the rods also becomes complicated. SUMMARY OF THE INVENTION An object of the present invention is to provide a defect inspection apparatus that includes a spatial filter having a simple structure and that can inspect a defect with high accuracy.

[0007]

According to a first aspect of the present invention, an object having a periodic structure pattern is irradiated with a laser beam, and scattered and diffracted light from the object is spatially filtered. in the defect inspection apparatus and a component corresponding to the pattern from scattered diffracted light is removed by, for inspecting defects in the pattern by observing the scattered diffracted light from the object to be inspected
Placed at the focal position of the lens that collects the scattered diffraction light of
There is provided a spatial filter having a deformable frame portion and a blocking portion for deforming a portion through which light passes in conjunction with the deformation of the frame portion. According to a second aspect of the present invention, the blocking portion is formed of a band-shaped body, is connected to the frame portion, is arranged side by side, and the interval between the blocking portions is adjusted according to the deformation of the frame portion. Further
According to a third aspect of the present invention, there is provided a test apparatus having a periodic structure pattern.
A laser light irradiation step of irradiating the inspection object with laser light;
Spatial filtering of the scattered diffraction light from the inspection object
Removal of components corresponding to the pattern from the scattered diffraction light
By removing the scattered diffraction light
An observing step of inspecting for defects in the semiconductor device.
Is a lens that collects the scattered and diffracted light from the inspection object.
At the focal position, it can be deformed according to the inspection object.
It is possible to deform the part that transmits light in conjunction with the deformation of the frame.
And there. By doing so, the present invention is to simplify the structure of the spatial filter and improve the inspection accuracy.

[0008]

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

1 to 3 show one embodiment of the present invention. FIG. 1 shows the configuration 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 object to be inspected. The inspection device 12 includes a half mirror 13,
A spatial filtering unit 17 including convex lenses 14 and 15 and a spatial filter 16 (described later), and an observation unit 18
Are sequentially provided.

As shown in FIG. 2, the spatial filter (hereinafter, referred to as a filter) 16 has a frame portion 2 composed of four plate members 19a, 19b, 20a, and 20b assembled in a rectangular shape.
1 and a plurality of blocking portions 2 disposed inside the frame portion 21.
2 and so on. Of these, the frame 21
Is connected to each of the plate members 19a to 20b so as to be rotatable and displaceable, and is deformed into a parallelogram as shown in FIG.

The blocking portions 22 are made of an opaque band. Furthermore, the longitudinal ends of the blocking portions 22 are connected to the two parallel plate members 19a, 1a of the frame portion 21.
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 plate members 19a and 19b changes with the deformation of the frame portion 21.

In the above-described inspection apparatus 12, the laser light 24 passes through the half mirror 13, irradiates the element forming surface 11a of the semiconductor wafer 11, and is reflected. At this time, the pattern formed on the element forming surface 11a acts as a diffraction grating, and diffracted light is formed. The trajectory of the light transmitted through the half mirror 13 is indicated by a chain line 25 in FIG.

The scattered diffracted light from the element forming surface 11a is hard
The light returns to the mirror 13 and is reflected by the mirror surface of the half mirror 13 inclined with respect to the optical path of the laser beam 22. And ha
The scattered and diffracted light reflected by the humming light 13 reaches the spatial filtering unit 17 and is collected 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 regular 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 of 0b is oriented substantially perpendicular to the path of the scattered diffraction light, and the inside of the frame portion 21 is positioned in the path of the scattered diffraction light. Further, the filter 16 makes the longitudinal direction of the blocking portions 22... Follow the direction in which the points in the point image 1 are arranged, and makes the interval d between the blocking portions 22. The filter 16 blocks each point 3... 5 of the point image 1 by the blocking unit 22.
A component corresponding to one periodic pattern is removed.

When a defect exists in the pattern of the semiconductor wafer 11, scattered light different from the regular component in the scattered diffraction light is generated. This scattered light is transmitted to the blocking section 22 of the filter 16.
.. Pass through the convex lens 15 located at the subsequent stage of the filter 16 and enter the observation unit 18. Observation unit 18
And the semiconductor wafer 11 are in a relationship corresponding to image formation. Then, only the defect image of the pattern appears on the observation unit 18. Here, a camera, a hologram, or the like may be used as the observation unit 18. Further, the defect image can be observed with the naked eye. In the filter 16,
The distance d between the blocking parts 22 is adjusted as follows.

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

When the plate members 19a and 19b are tilted, the connecting position between the blocking portions 22 and the plate members 19a and 19b is displaced, and the blocking portions 22 also rotate while maintaining the parallel state with the pins 23 as fulcrums. Dynamically displaces. Then, the blocking portions 22... Approach in the arrangement direction while being shifted in the longitudinal direction, and reduce the distance d between each other. As the amount of deformation of the frame portion 21 increases, the blocking portion 22
Are smaller. When the four corners of the frame portion 21 are at right angles, the distance d between the blocking portions 22 is maximized.

In the inspection apparatus 12 as described above, since the filter 16 including the frame portion 21 and the band-shaped blocking portions 22 is provided, only the diffracted light on the semiconductor wafer 11 can be removed, and the point image 1 can be removed. Can be blocked by the blocking units 22. Therefore, the periodic pattern
Therefore, it is possible to reliably remove the component corresponding to the defect, and to take out only the defect image.

Further, since the blocking portions 22 are connected to the frame portion 21 and are displaced as a whole with the deformation of the frame portion 21, for example, the displacement amounts of the respective blocking portions 22 are individually adjusted. There is no need, and the structure of the filter 16 can be simplified.

Further, the distance d between the blocking portions 22 can be easily adjusted, and a plurality of types of point images having different forms can be formed, for example, by one.
Can be removed by two filters 16. Even if the inspection object and the pattern of the inspection object change, spatial filtering can be performed using the above-described filter 16.

In this embodiment, the spatial filter 16 in which the rectangular frame portions 21 are connected to the blocking portions 22 is employed, but the present invention is not limited to this. 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, a band-shaped blocking portion 36 is parallel to each other between two frame portions 34 and 35 formed by connecting plate bodies 32. It is erected. Each of the frame portions 32 and 33 deforms and expands and contracts, and changes the distance d between the blocking portions 36. When the frame portions 32, 33 extend in the direction in which the blocking portions 36 are arranged, the distance d between the blocking portions 36 increases, and the frame portions 32, 33 extend.
3 shrinks in the longitudinal direction of the blocking portions 36.
The interval d of 6 ... is reduced. In such a filter 31, when the frame parts 34 and 35 are deformed, a part (for example, a corner part) of the frame parts 34 and 35 does not protrude extremely. Further, the present invention can be variously modified without departing from the gist.

[0023]

As described above, the present invention irradiates a test object having a pattern of a periodic structure with a laser beam, spatially filters scattered diffraction light from the test object, and responds to the pattern from the scattered diffraction light. In a defect inspection apparatus for inspecting a defect in a pattern by observing scattered diffracted light by removing a component which has been removed, a lens for condensing scattered diffracted light from the inspection object
Is positioned at the focal position of the
A blocking part that deforms the part where light is transmitted in conjunction with the deformation
Provided with a spatial filter. In addition, the cut-off section
Is made of a belt-like body, connected to the frame, and juxtaposed,
The distance between them is adjusted with the deformation of the frame.
You. Further, the invention of claim 3 has a periodic structure pattern.
Laser irradiation step of irradiating the inspection object with laser light
And scattered diffraction light from the inspection object
From the scattered diffraction light to obtain a component corresponding to the pattern.
By observing the scattered and diffracted light,
And an observation step of inspecting for defects in the pattern.
The removing step focuses the scattered diffraction light from the inspection object.
At the focal position of the lens according to the inspection object,
The light transmitting part is changed according to the deformation of the deformable frame.
To shape. Therefore, the present invention has an effect that the structure of the spatial filter can be simplified and the inspection accuracy can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one 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.

FIG. 6 is a front view showing a spatial filter for blocking a point image in FIG. 5;

[Explanation of symbols]

11: semiconductor wafer (inspection object), 12: defect inspection apparatus, 16: spatial filter, 21: frame part, 22: blocking part.

Claims (3)

(57) [Claims] 1. An object having a pattern of a periodic structure is irradiated with a laser beam, and a scattered diffraction light from the object is spatially filtered to remove a component corresponding to the pattern from the scattered diffraction light. In the defect inspection apparatus for observing the scattered diffraction light and inspecting the defects in the pattern ,
The focal position of the lens that collects the scattered and diffracted light from the test object
A defect inspection apparatus, comprising: a spatial filter that is disposed at a position and has a deformable frame portion and a blocking portion that deforms a portion through which light passes in conjunction with the deformation of the frame portion. 2. The frame according to claim 2, wherein the blocking portion is formed of a belt-like body.
It is connected and juxtaposed, with the deformation of the frame
The distance between the two is adjusted.
Defect inspection equipment. 3. An object to be inspected having a pattern of a periodic structure.
A laser light irradiation step of irradiating laser light, and spatially filtering the scattered diffraction light from the inspection object.
To remove components corresponding to the pattern from the scattered diffraction light
And removing the defects in the pattern by observing the scattered diffraction light.
And an observation step of inspecting the specimen. The removing step focuses the scattered diffraction light from the inspection object.
At the focal position of the lens to be inspected
The part where light is transmitted in conjunction with the deformation of the deformable frame
A defect inspection method characterized by deforming a defect.