JPH0474916A - Defect inspecting apparatus - Google Patents

Abstract

PURPOSE:To detect a defect of a body to be inspected by applying a coherent light to the body and, processing and blocking the diffraction light by a spatial filter mechanism. CONSTITUTION:A coherent light radiated from a light source 3 is formed into a parallel light by an optical lens 5 through a half mirror 4, and applied onto the surface of a semiconductor wafer 2. Since IC chips are regularly arranged on the semiconductor wafer 2, the wafer 2 acts like a diffraction grating, and generates the diffraction light. The diffracted light is condensed by the optical lens 5, reflected by the half mirror 4 and is incident on a spatial filter mechanism 10. Rods 16, 17, 19,... 26 of the spatial filter mechanism 10 are spaced a distance corresponding to that of point images. Therefore, the point image is blocked by the rods 16, 17, 19,... 26. However, if there is a flaw on the surface of the semiconductor wafer 2, the scattering light due to the flaw is not blocked by the rods 16, 17, 19,... 26, but is allowed to pass therethrough.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a defect inspection apparatus for inspecting objects on which regular patterns are formed, such as semiconductor wafers.

(Prior Art) There are two methods of defect inspection for semiconductor wafers on which IC chips are formed: a method using a microscope and a method of irradiating laser light. Among these methods, the method using a microscope involves enlarging the semiconductor wafer through a microscope and photographing it with an ITV camera.
The enlarged image data obtained by this imaging is compared with the standard pattern image data, and defects are detected from the comparison results. Note that standard IC chip image data may be used instead of standard pattern image data.

Further, the laser beam irradiation method involves irradiating a semiconductor wafer with a laser beam, and detecting defects from an image obtained by passing the reflected light from the semiconductor wafer through a spatial filter.

In this case, the image obtained by the reflected light from the semiconductor wafer λ becomes a regular point image as shown in FIG. This is because the IC chips are arranged in a regular pattern on the semiconductor Ueno\, and due to this arrangement, the semiconductor Ueno\ performs the same function as a diffraction grating. Therefore, the spatial filter is formed with a pattern that blocks light from each of these point images. Therefore, the point image of each IC chip on the semiconductor wafer 1 is blocked by the spatial filter, and if there is a defect on the semiconductor wafer, this defect image is formed through the spatial filter.

However, in the method using a microscope, the entire apparatus becomes large and the inspection time is long.

Furthermore, in the laser beam irradiation method, if the type of semiconductor wafer 1 is changed, the size of the IC chip will differ depending on the type of semiconductor wafer. Therefore, the position of the point image obtained by the reflected light from the semiconductor wafer differs depending on the size of the IC chip. Therefore, a plurality of spatial filters with different patterns must be prepared for each type of semiconductor wafer 1, and the spatial filters must be replaced depending on the type of semiconductor wafer during inspection.

(Problems to be Solved by the Invention) As described above, the method using a microscope increases the size of the entire device and increases the inspection time, and the method that uses laser light irradiation requires replacing the spatial filter depending on the type of semiconductor wafer. Must.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a defect inspection apparatus that can easily cope with changes in pattern size and can detect defects other than patterns.

[Structure of the Invention] (Means for Solving the Problems) The present invention includes a light source that emits coherent light, and a method for irradiating the coherent light emitted from the light source onto an object to be inspected in which a regular pattern is formed. and an optical lens that focuses the diffracted light from the object to be inspected, and a light shielding position that is placed at a position where the diffracted light is focused by the optical lens and changes depending on the size of the pattern formed on the object to be inspected. and a detection means for detecting defects in the object to be inspected by forming an image of the light that has passed through the spatial filter mechanism. It is a defect inspection device that aims to achieve its purpose.

(Function) By providing such a means, the coherent light emitted from the light source is irradiated onto the object to be inspected in which a regular pattern is formed through the optical lens, and the diffracted light from the object to be inspected is collected. At this time, the spatial filter mechanism changes the light shielding position according to the size of the pattern formed on the object to be inspected, and the point image of the regular pattern is shielded from light by the spatial filter mechanism. As a result, defects in the object to be inspected are detected by imaging the light that has passed through the spatial filter mechanism.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a defect inspection device. A semiconductor wafer 2 is placed on a table 1. IC chips are regularly arranged on this semiconductor wafer 2. On the other hand, a light source 3 is arranged above the table 1. This light source 3 emits coherent light such as a laser. A half mirror 4 and an optical lens 5 are arranged between the light source 3 and the table 1. Therefore, the coherent light emitted from the light source 3 is formed into parallel light by the optical lens 5 and is irradiated onto the semiconductor wafer 2 .

Further, the half mirror 4 reflects the diffracted light from the semiconductor wafer 2.

A spatial filter mechanism 10 is arranged at a position where the optical lens 5 condenses the diffracted light from the semiconductor wafer 2 . This spatial filter mechanism 10 is an I formed on a semiconductor wafer 2.
The light shielding position is changed according to the size of the pattern formed by the C chip, and a point image of a regular pattern that appears due to the convergence of diffracted light from the semiconductor wafer 2 is shielded. The specific configuration is as follows. This spatial filter mechanism 10 has a configuration in which a plurality of rod moving mechanisms 11 shown in FIG. 2 are combined. This rod moving mechanism 11 is driven by a drive motor 1
2 is provided, and a screw shaft 1 is attached to the rotating shaft of this drive motor 12.
3 are connected. This screw shaft 13 has a right-hand thread 13a1 and a left-hand thread 13b from the center toward both ends.
is cut.

Nuts 14 and 15 are screwed into these right-hand threads 13a and left-hand threads 13b, respectively. These nuts 14, 15 are provided with rods 16, 17, respectively. These rods 16 and 17 are arranged in parallel. With such a configuration, if the rod 16 moves, for example, to the right due to the rotation of the drive motor 12, the rod 1
7 moves to the left, and the distance between the rods 16 and 17 becomes narrower or wider.

The entire spatial filter mechanism 10 is constructed by providing four sets of rod moving mechanisms 11. The arrangement position of each rod is as shown in FIG. 3 and FIG. 4 viewed from the direction A in the figure. The rods 19, 20 are fixedly arranged perpendicularly to each other in the shape of a cross when viewed in direction A. The rods 16, 17 are arranged parallel to the rod 19, and the rods 21, 22 are arranged outside these rods 16, 17. These rods 21 and 22 constitute a rod moving mechanism (not shown), and the distance between them is narrowed or widened by driving the drive motor. Also, rod 20
The rods 23 and 24 are arranged parallel to each other, and the rods 25 and 26 are arranged outside of these rods 23 and 24, respectively. These rods 21, 22 and 25.2
Reference numerals 6 constitute respective rod moving mechanisms (not shown), and the distance between the rods is narrowed or widened by driving the drive motor thereof. Although the arrangement positions of each rod have been explained above, the drive motor, screw shaft, and nut of each rod moving mechanism are not shown because the drawing becomes complicated.

A TV (
(television) camera 30 is arranged. This TV
The right camera 0 is placed in an imaging relationship with the surface of the semiconductor wafer 2 through the optical lens 5. Note that the image signal output from this TV right camera 0 is sent to a monitor television or the like.

Next, the operation of the apparatus configured as described above will be explained.

The coherent light emitted from the light source 3 is a half mirror 4
The light is then formed into parallel light by the optical lens 5 and irradiated onto the surface of the semiconductor wafer 2 . Since IC chips are regularly arranged on this semiconductor wafer 2, it functions similarly to a diffraction grating. Therefore, the semiconductor wafer 2 generates diffracted light of 0th order, ±1st order, ±2nd order, . . . ±nth order. This diffracted light is condensed by the optical lens 5, reflected by the half mirror 4, and enters the spatial filter mechanism 10.

The spatial filter mechanism 10 is arranged at a location where the diffracted light is focused by the optical lens 5. The image obtained by condensing this diffracted light is a regularly arranged point image as shown in FIG.

Here, each rod 16° 17 . of the spatial filter mechanism 10 .
19. ...26 are arranged at positions corresponding to the intervals between the point images. Therefore, the point images of these rods 16, 17, 1
9. ...26 blocks light. However, if there is a defect on the surface of the semiconductor wafer 2, the scattered light caused by the defect will be scattered at each rod 16°17.19. ...passes through without being blocked by 26.

The light passing through this spatial filter mechanism 10 forms an image at the position of the TV right camera 0. As a result, TV right camera 0
The image captured by the camera is displayed on a monitor television. Defects are thus detected from this monitor television image.

Next, when the type of semiconductor wafer 2 is changed, each rod 16, 17, 19°, . will be placed in For example, if the size of each IC chip on a semiconductor wafer becomes smaller, each rod 16, 17, 19 . ...2
6 becomes narrower as shown in FIG. In this case, since point images appear symmetrically around each rod 19, 20, each rod 16, 17 . ...26 is each rod 19,
The interval is narrowed around 20.

Thereafter, similarly to the above, the coherent light emitted from the light source 3 passes through the half mirror 4, and then is formed into parallel light by the optical lens 5, and is irradiated onto the surface of the semiconductor wafer \2. The diffracted light from the semiconductor Ueno\2 is condensed by the optical lens 5, reflected by the No. 1-F mirror 4, and enters the spatial filter mechanism 10.

In this spatial filter mechanism 10, each rod 16.1 has a point image.
7,19. ... 26, the semiconductor wafer 2
Scattered light caused by defects on the surface of each rod 16.1
7,19. ...passes through without being blocked by 26. The light passing through this spatial filter mechanism 10 is transmitted to the TV left camera 0.
An image is formed at the location of the image and displayed on a monitor television. Defects are thus detected from this monitor television image.

In this way, in the above embodiment, the coherent light is irradiated onto the semiconductor urchin/X2 through the optical lens 5, and the diffracted light from the semiconductor wafer 2 is collected and sent to the spatial filter mechanism 10. Since the point images are blocked by moving each rod 16, 17° 19, . . . 26 according to the size of the IC chip formed on the semiconductor wafer 2, the type of the semiconductor wafer 2 can be changed. Also, the position of each rod can be immediately changed according to the size of the IC chip formed on the semiconductor wafer 2, making defect inspection easy. Further, the point image can be shielded by adjusting the position of each rod regardless of the size of any kind of semiconductor wafer, that is, the size of the IC chip. In this case, the defect inspection accuracy remains constant even if the type of semiconductor wafer is changed.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, each rod of the spatial filter mechanism may be moved by a slider or the like. Also, each rod is moved two at a time, but each rod moved in the same direction, for example 16.
17, 21.degree. 22 may be moved by the same drive motor. On the other hand, defects may be inspected using a hologram instead of the TV left camera.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a defect inspection apparatus that can easily cope with changes in pattern size and can detect defects other than patterns.

[Brief explanation of drawings]

1 to 5 are diagrams for explaining one embodiment of the defect inspection device according to the present invention, in which FIG. 1 is a configuration diagram, FIG. 2 is an external view of the rod drive mechanism, and FIG. 4 is a diagram showing the arrangement of each rod, FIG. 5 is a diagram showing the arrangement of each rod at different intervals, and FIG. 6 is a diagram showing a point image generated by the IC chip. DESCRIPTION OF SYMBOLS 1...Table, 2...Semiconductor wafer, 3...Light source, 4...Half mirror 5...Optical lens, 10...
... Spatial filter mechanism, 11... Rod movement mechanism, 1
2... Drive motor, 13... Screw shaft, 14.15.
...Natsuto, 16.17...Rod, 19-26...
・Rod, 30...TV Left Camera Applicant Representative Patent Attorney Takehiko Suzue Figure 1 Figure Figure

Claims (2)

[Claims] (1) A light source that emits coherent light; the coherent light emitted from this light source is irradiated onto an object to be inspected in which a regular pattern is formed; and the diffracted light from the object to be inspected is focused. an optical lens; and the rule, which is arranged at a position where the diffracted light is focused by the optical lens, and whose light blocking position changes depending on the size of a pattern formed on the object to be inspected, and which appears due to the focusing of the diffracted light. 1. A defect inspection apparatus comprising: a spatial filter mechanism that blocks a point image of a pattern; and a detection means that detects a defect in the object to be inspected by imaging light that has passed through the spatial filter mechanism. (2) Claim (2) wherein the spatial filter mechanism is composed of a plurality of rods arranged in a grid pattern and a moving mechanism that moves these rods according to the size of the regular pattern formed on the object to be inspected. 1) Defect inspection device as described above.