JPH0763689A - Rotation-type flaw inspection apparatus - Google Patents

Abstract

PURPOSE:To provide a rotation-type flaw inspection apparatus wherein flaw on the surface of a substrate on which a circuit pattern or the like has been formed is inspected by using a simple signal processing system and at a high speed. CONSTITUTION:A luminous flux from a light source 26 is cast on a point P, to be inspected, on a wafer 1. A luminous flux 32 from the point P to be inspected forms, on a rear-side focal-point face 33 via a Fourier transform lens 31, the Fourier transform spectrum of a circuit pattern on the point P to be inspected. A luminous flux which has removed a Fourier transform spectrum not containing any error from the Fourier transform spectrum by a spatial filter 34, is received by a photoelectric conversion element 41. While the wafer 1 is being turned by a turntable 21 and moved in y-direction, the spatial filter 34 is turned in synchronization with the wafer 1.

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 suitable for use in inspecting defects such as circuit patterns formed on the surface of a semiconductor element.

[0002]

2. Description of the Related Art Conventionally, a defect inspection apparatus has been used to detect the size and position of a defect in a circuit pattern formed on the surface of a semiconductor element or the like. FIG. 7 shows a conventional defect inspection apparatus. In FIG. 7, the circuit pattern 2 formed on the surface 1a of the wafer 1 is an inspection object, and the wafer 1 is placed on an XY stage 3. X
The Y stage 3 is composed of an X stage that moves the wafer 1 in the x direction parallel to the paper surface of FIG. 7 in a two-dimensional plane, and a Y stage that moves the wafer 1 in the y direction perpendicular to the paper surface of FIG. .

Above the wafer 1, a light beam 5 emitted from a light source 4 such as a halogen lamp is condensed by a collimator lens 6 and becomes a light beam 7 and enters a beam splitter 8. The light beam 9 reflected by the beam splitter 8 illuminates an illumination area having a predetermined area on the surface 1 a of the wafer 1. Of the reflected light from the surface 1 a of the wafer 1, the light flux 10 that has passed through the beam splitter 8 enters the imaging lens 11. The imaging lens 11 is arranged so that the object plane thereof coincides with the surface 1a of the wafer 1, and an image of the circuit pattern in the illumination area on the wafer 1 is formed on the image plane 12 of the imaging lens 11. .

A two-dimensional image pickup device 12 is installed on the image plane 12 so that the image pickup plane coincides with the image plane 12.
Reference numeral 2 denotes an image pickup signal S1 obtained by photoelectrically converting the image of the circuit pattern.
Is output to the signal processing unit 14. In the signal processing unit 14, the reference signal S corresponding to the design data of the circuit pattern (error-free circuit pattern) when there is no defect from the data storage unit 15
2 is supplied, and the signal processing unit 14 compares the image pickup signal S1 with the reference signal S2 to obtain the presence / absence of a defect in the circuit pattern on the surface 1a of the wafer 1, the position of the defect, the size of the defect, and the like. . The information S3 of the defect of the circuit pattern of the signal processing unit 14 is supplied to the display unit 16,
Displays the position and size of the defect of the circuit pattern on the display screen.

[0005]

In the conventional technique as described above, the signal processing unit 14 needs to perform complicated image processing at high speed in order to obtain the position and size of the defect of the circuit pattern. Therefore, a high-speed computer is required as the signal processing section 14, and the signal processing system becomes large in scale.

In this regard, conventionally, the surface 1a of the wafer 1 is conventionally used.
Instead of collectively illuminating the wide illumination area above, a laser beam as illumination light is focused on the surface of the wafer 1 in a spot shape, and an optical scanner (galvano mirror or the like) as an optical deflector is used to focus the laser beam. There is also known an apparatus for performing a defect inspection by linearly scanning the wafer 1 with a laser beam focused in a spot shape. However, since the optical scanner is a system in which the mirror is vibrated to scan the laser beam, the inspection speed is limited by the upper limit of the scan rate, and there is a disadvantage that the inspection time for inspecting the entire surface of the wafer 1 is long. there were.

In view of the above problems, the present invention provides a defect inspection apparatus capable of inspecting defects on the surface of a substrate on which a circuit pattern or the like is formed at high speed using a simple signal processing system. With the goal.

[0008]

A rotary defect inspection apparatus according to the present invention is, for example, as shown in FIG. 1, an apparatus for inspecting a surface of a substrate (1) having a predetermined pattern for defects. Illumination means (26, 28, 31) for irradiating an inspection light beam onto an inspection area having a predetermined area on the surface of 1),
The Fourier transform optical element (31) for Fourier transforming the light flux from the substrate (1) and the Fourier transform surface (33) formed by this Fourier transform optical element are arranged in the vicinity of the substrate (1).
A spatial filter (34) which uses a portion corresponding to the bright portion of the Fourier transform pattern of the error-free reference pattern when there is no defect in the predetermined pattern as a light shielding portion, and the spatial filter (3
Photoelectric conversion means (4) for photoelectrically converting the light flux passing through 4).
1) and.

Further, the present invention provides a Fourier transform optical element (3
4) A turntable (21) that rotates the substrate (1) about a rotation axis parallel to the optical axis, and a spatial filter (34) that rotates about a predetermined axis in synchronization with the rotation of the turntable. Filter rotation means (35, 36)
And a moving means (24, 25) for moving the substrate (1) in a plane perpendicular to the optical axis of the Fourier transform optical element (31), the turntable (21) and the moving means (24, 2).
By rotating and moving the substrate (1) through 5), the surface of the substrate (1) is spirally scanned in the inspection area having a predetermined area, and the filter is synchronized with the rotation of the substrate (1). The spatial filter (34) is rotated through the rotating means (35, 36) to inspect for defects in a predetermined pattern on the substrate (1) from the photoelectric conversion signal output from the photoelectric conversion means (41). is there.

In this case, the filter rotating means (35, 3
6) is a spatial filter (3) centered on the position of the 0th-order light component of the Fourier transform pattern of the error-free reference pattern.
It is desirable to rotate 4). Further, as shown in FIG. 6, for example, the Fourier transform optical element has one end arranged on a spherical surface (46) centered on an inspection region having a predetermined area, and the other end has a predetermined plane (33) at the one end. ) A plurality of optical fiber bundles (47 ₁ , 47 ₂ , ..., 47 _N ) arranged at positions similar to the orthogonal projection may be bundled and formed.

[0011]

According to the present invention, the substrate (1) to be inspected is placed on the turntable (21) and rotated at a high speed without using an optical scanner, and the moving means (24, 25) are provided. By moving the substrate (1) by using, the surface of the substrate (1) is scanned at high speed with a predetermined light spot. Therefore, the inspection speed is not limited by the optical scanner or the like.

Further, in the present invention, the light flux from the substrate (1) is Fourier-transformed, and from the Fourier-transform pattern, the spatial filter (34) is used to determine the components of the Fourier-transform pattern of the error-free reference pattern. By removing the defect information, only the defect information is optically extracted. Therefore, the load on the signal processing system of the electric signal after photoelectric conversion is reduced, the configuration of the signal processing system is simplified, and the inspection speed is not limited by the processing speed of the signal processing system. At this time, when the substrate (1) rotates, the Fourier transform pattern of the pattern on the substrate (1) also rotates, so that only the defect information is always extracted by the spatial filter (34). The spatial filter (34) is rotating in synchronization.

In this case, even if the substrate (1) rotates, the position of the 0th-order light component of the Fourier transform pattern of the pattern on the substrate (1) does not change. Therefore, the spatial filter (3
It is desirable that the rotation axis of 4) be the position of the zero-order light component. In addition, the Fourier transform optical element is, for example, as shown in FIG.
As shown in, when the optical fiber bundle is formed of a plurality of optical fiber bundles, the Fourier transform optical element can be brought close to the substrate (1), and the efficiency of collecting the light flux from the substrate (1) is improved.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the rotary type defect inspection apparatus according to the present invention will be described below with reference to FIGS. FIG. 1 shows a rotary defect inspection apparatus of this example. In FIG.
The wafer 1 having a circuit pattern formed on its surface is vacuum-adsorbed on the turntable 21. The moving rotation unit 23
The turntable 21 is rotated via the rotary shaft 22. With the y-axis parallel to the plane of FIG. 1 and the x-axis perpendicular to the plane of FIG. 1, the surface 1a of the wafer 1 is always kept parallel to the xy plane defined by the x-axis and the y-axis. The turntable 21 rotates the wafer 1. Moving rotation unit 23
Is placed on the rail 25 extending in the y direction via the roller 24, and the moving rotating unit 23 rotationally drives the roller 24, whereby the moving rotating unit 23 moves in the y direction along the rail 25.

A light source 26 for generating a coherent light beam (laser beam or the like) such as a He-Ne laser light source is installed above the turntable 21, and a light beam 27 emitted from the light source 26 is cross-sectionally shaped by a beam expander 28. Is a circular parallel light beam 29. The parallel light beam 29 is reflected by the mirror 30.
Then, the light flux 29A reflected by the light is directed toward the Fourier transform lens 31, and the light flux 29A collected by the Fourier transform lens 31 is irradiated onto the inspection point P on the wafer 1 in a spot shape. Test point P
The diameter of the illumination area by the light flux 29A that is emitted in a spot-like shape is 40 μm, for example, and the illuminance of the illumination area is set to a desired value.

Further, the Fourier transform lens 31 is installed so that the effective center of the Fourier transform lens 31 is located at a position 1 times the focal length f from the surface 1a of the wafer 1.
The optical axis AX1 of the Fourier transform lens 31 is parallel to the z axis perpendicular to the xy plane. The light flux 32 generated from the test point P by the irradiation of the light flux 29A is incident on the Fourier transform lens 31, and is reflected by the light flux 32A passing through the Fourier transform lens 31 on the rear focal plane (Fourier transform surface) 33 of the Fourier transform lens 31. Then, a Fourier transform pattern (Fourier spectrum) capable of selectively filtering the circuit pattern of the test point P on the wafer 1 is formed.

Further, the light beam 29B directly reflected by the surface 1a of the wafer 1 by the irradiation of the light beam 29A again enters the Fourier transform lens 31, and the light beam 29C whose cross-sectional shape matches the parallel light beam 29 reflected by the mirror 30. Becomes
The light flux 29C forms a circular spectrum centered on the point Q on the rear focal plane 33. The point Q is also the position of the zero-order light component. A rotary spatial filter 34 is installed on the rear focal plane 33. The rotary spatial filter 34 has a disc shape, and is connected to the rotary unit 36 via a rotary shaft 35. The rotating unit 36 rotates the spatial filter 34 about the point Q in the rear focal plane 33 via the rotating shaft 35. The spatial filter 34 rotates in synchronization with the rotational movement of the wafer 1 and at the same angular velocity. The rotation directions of the wafer 1 and the spatial filter 34 may be always the same, and the relative rotation directions of the both may be the same or opposite.

The rotary type spatial filter 34 has a rear side due to a light beam generated from the error-free circuit pattern when the error-free circuit pattern is irradiated with the light beam 29A when the circuit pattern on the surface of the wafer 1 has no defect. The portion on the focal plane 33 that matches the bright portion of the Fourier transform pattern is an opaque portion, and the other portion is a transparent portion. That is, the spatial filter 34 blocks the Fourier transform pattern (Fourier spectrum) of the error-free circuit pattern.

As the spatial filter 34, for example, a photographic dry plate is arranged on the rear focal plane 33, and a master wafer on which an error-free circuit pattern is formed is placed on the turntable 21.
It can be produced by exposing the photographic dry plate with a Fourier transform pattern generated from the master wafer while rotating the master wafer and the photographic dry plate in synchronization.
When it is difficult to obtain an error-free circuit pattern, the following is performed.

That is, as shown in FIG. 2, there are many dies (pattern units) 37A, 37B, 37C, ... Having the same circuit on the surface of the wafer 1, but all these dies have defects. Even if they exist, the positions of the defective portions are different from each other, and the area ratio of the defective portions can be regarded to be significantly smaller than the area of the circuit portion having no defect in all the dies. Therefore, the wafer 1 is
The light pattern generated by the incident light flux 29A of
The energy of the light beam 29A is sufficiently reduced so that the photographic plate is not exposed to light, and the plurality of dies on the wafer 1 are sequentially irradiated with the light beam 29A to generate an optical pattern from a large number of error-free circuit patterns. In addition, the photographic plate may be exposed only by the light pattern from the error-free circuit pattern. According to this method, naturally, the exposure amount to the photographic dry plate can also be controlled by controlling the moving speed of the illumination area on the wafer 1. The photographic plate exposed with the light pattern generated from the error-free circuit pattern becomes the spatial filter 34 by the developing process. The fabricated spatial filter 34 is attached to the rear focal plane 33 so that the relative angular relationship with the wafer 1 is the same as during exposure (during fabrication).

The spatial filter 34 is an SLM (Spatial Light Mod) such as a liquid crystal display element (LCD) or an electrochromic element (ECD) that is already used in addition to the photographic plate.
ulator) element (spatial light modulation element). When these are used, it is desirable to measure the opaque portion corresponding to the Fourier transform pattern of the error-free circuit pattern written in the spatial filter 34 by previously disposing a two-dimensional image sensor in the rear focal plane 33. It is also possible to calculate the circuit pattern design data by a computer and to obtain it by simulation. The spatial filter 34 can be more simply manufactured by drawing a predetermined pattern on a transparent film using a well-known computer plotter. Also in this case, the drawing data can be obtained by the method described above.

In FIG. 1, the wafer 1 is moved in the y-direction while rotating about the rotating shaft 22 by the operation of the moving / rotating unit 23. By this operation, the circular illumination spot light on the point P to be inspected by the light flux 29A relatively scans and rotates on the wafer 1 in a spiral manner, and the defect inspection of the entire surface of the wafer 1 is executed at high speed. In this embodiment, when the wafer 1 is rotationally scanned, the spatial filter 34 is rotated in synchronization with the rotation of the wafer 1 about the position Q of the 0th-order light component of the Fourier spectrum formed on the rear focal plane 33. As a result, the defect inspection is performed by performing Fourier spectrum filtering while rotating the wafer 1. Therefore, the defect information carrying light flux 38, which is the light flux passing through the spatial filter 34, contains only the information relating to the defect of the circuit pattern on the inspection point P on the wafer 1. The defect information carrying light flux 38 is condensed by the condenser lens 39 on the light receiving surface of the photoelectric conversion element 41. Photoelectric conversion element 4
The defect signal S4 obtained by photoelectric conversion by 1 is supplied to the signal processing unit 42, and the signal processing unit 42 receives the position information S5 representing the two-dimensional coordinates of the test point P on the wafer 1 from the moving / rotating unit 23. Is also being supplied.

The signal processing section 42 has a threshold value of a level higher than the electrical and optical noise levels, and the defect signal S
A signal level of 4 or more that is equal to or higher than the threshold value is extracted as a defect. In this example, since the Fourier transform pattern of the error-free reference pattern is blocked by the spatial filter 34, the light flux passing through the spatial filter 34 is regarded as the light flux from the defective portion and the optical noise light, and the defect signal S4 When the signal level is equal to or higher than the threshold value, the circuit pattern of the test point P is considered to be a defective portion. At the same time, the signal processing unit 42 detects the size of the signal level of the defective portion and sets it as the size of the defect. In addition, the signal processing unit 42 detects the location of the defect on the wafer 1 based on the above-described position information S5. The signal processing unit 42 supplies the display information S6 indicating the position and size of the defect on the wafer 1 to the display unit 16, and the display unit 16 displays the location of the defect by the map display and the corresponding defect. The size of is also displayed.

At this time, depending on the circuit pattern on the wafer 1, the Fourier transform spectrum of the error-free circuit pattern may exist unevenly on the disk-shaped spatial filter 34. In this case, when the spatial filter 34 is rotated,
The light energy of the defect information carrying light flux 38 with which the photoelectric conversion element 41 is irradiated is modulated. This energy modulation affects defect detection and size discrimination. Since this energy modulation is synchronized with the rotation of the spatial filter 34, a plain wafer is placed on the turntable 21 in order to remove the influence of the energy modulation, and dust as a reference is placed on this plain wafer. A sample for calibration of defective portions such as the above is scattered, or a light source for calibration is installed at a position conjugate with the wafer 1. Then, the energy modulation of the output signal of the photoelectric conversion element 41 is measured as a function of the rotation angle of the spatial filter 34, and using the measurement result, the signal processing unit 42 uses the defect signal S4 to cancel the energy modulation.
Intensity is modulated. As a result, the entire circumference of the wafer 1 can be inspected with the same sensitivity.

Next, the relationship between the test point P on the wafer 1 and the generated Fourier spectrum will be described. In FIG. 2, when the inspection point P1 on the wafer 1 is inspected, the wafer 1
An orthogonal coordinate system (hereinafter referred to as "reference coordinate system") (x ', y'), which serves as a reference when drawing the circuit patterns of the above-mentioned many dies 37A, 37B, ..., and the coordinate system of the apparatus shown in FIG. It is assumed that an angle α ₁ is formed with (x, y). in this case,
When the wafer 1 rotates about the rotation axis 22 and the inspection point on the wafer 1 moves to the inspection points P2 and P3, the reference coordinate system (x ′, y ′) and the coordinate system of the device ( x,
y) changes so as to form an angle α ₂ and an angle α ₃ , respectively.

FIGS. 3A to 3C are respectively the rear focal planes (Fourier transform planes) of the Fourier transform lens 31 of FIG.
On 33 is shown the spectral region 33a limited by the aperture of the Fourier transform lens 31. In FIG. 3A, the reference coordinate system (x ′, x ′, of one die (pattern unit) 37 on the inspection point P on the wafer (actually located on the object plane of the Fourier transform lens 31 in FIG. 1). y ′) and the coordinate system (x, y) of the device form an angle α ₁ . At this time, the spatial frequency spectrum observed in the spectral region 33a is parallel to the reference coordinate system (x ', y') and on the coordinate system (u, v) with the position Q of the 0th-order light component as the origin. It becomes a part of the area. The angles formed by the reference coordinate system (x ′, y ′) of the die 37 and the coordinate system (x, y) of the device are α ₁ , α ₂ and α.
_When it is changed to ₃ , the observable spectral region 33a becomes
It rotates on the coordinate system (u, v) around the position Q of the 0th-order light component. When viewed from the device side (coordinate system (x, y) of the device), as shown in FIGS. 3 (a), 3 (b) and 3 (c),
The spatial frequency spectrum observed in the spectral region 33a appears to rotate about the point P to be tested in synchronization with the rotation of the die 37.

Therefore, as shown in FIG. 2, the rotation of the wafer 1 causes the points P1, P2, P to be detected on the circumferential scanning line 43.
When three, ... Are moved to inspect circuit patterns in a large number of dies (37A, 37B, etc.), as shown in FIG. 4, the spatial filter 34 that rotates in synchronization with the rotation of each die is used.
Is required. In FIG. 4, the center of rotation of the spatial filter 34 is the position Q, and the radius L of the spatial filter 34 is determined by the distance from the position Q to the farthest point 44 in the spectral region 33a.

As described above, according to this example, the inspection point P is rotationally scanned on the wafer 1 at a relatively high speed, and the defect inspection of the entire surface of the wafer 1 is executed at a high speed. Further, since the Fourier transform pattern of the circuit pattern of the wafer 1 is also rotated by the rotation of the wafer 1, the Fourier transform spectrum from the error-free reference pattern is blocked by using the spatial filter 34 that rotates in synchronization with the rotation of the wafer 1. , Spatial filter 34
The defect information carrying light flux 38 that has passed through is detected to detect the defect. Therefore, in the signal processing system, the defect signal S4 is compared with a predetermined threshold, and the defect signal S4 is detected at the defective portion.
Since the value of 4 only needs to be held and a large computer or the like is not required, the configuration of the signal processing system is simple and the processing speed is high.

Next, a second embodiment of the present invention will be described with reference to FIG. 5, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. FIG. 5 shows the rotary type defect inspection apparatus of the second embodiment.
In FIG. 1, the wafer 1 on which the circuit pattern is formed is placed on the turntable 21, and the turntable 21 is connected to the moving and rotating unit 23 via the rotating shaft 22. By the operation of the moving / rotating unit 23, the wafer 1 moves in the y direction while rotating about the rotation shaft 22. As a result, as in the first embodiment, the spot light radiated on the test point P is
The wafer 1 is relatively spirally rotated and scanned, and defect inspection of the entire surface of the wafer 1 is executed at high speed.

Above the turntable 21, the light beam 27 emitted from the light source 26 is emitted by the beam expander 2.
8 forms a parallel light beam 29 having a circular cross section and enters the condenser lens 45. The light beam 29D focused by the condenser lens 45 is, for example, 30 μm in diameter on the test point P on the wafer 1.
It is irradiated as a spot light of about m. A Fourier transform lens 31 is arranged above the wafer 1, and the effective center of the Fourier transform lens 31 is located on the surface 1 a of the wafer 1 at a focal length f.

The light beam 32 generated by the light beam 29D from the test point P is incident on the Fourier transform lens 31, and the light beam 32A that has passed through the Fourier transform lens 31 is selectively placed on the rear focal plane 33 of the Fourier transform lens 31. Form a Fourier spectrum that can be filtered. In the Fourier transform lens 31, the relationship between the image height h due to the incident light flux and the angle θ formed by the light flux and the optical axis AX1 is such that the image height h is f.
It has a characteristic proportional to sin θ. It is assumed that the Fourier transform lens 31 has a characteristic represented by, for example, h = fsin θ. The light flux 32 from the wafer 1 makes an angle θ ₀ with the optical axis AX1 and enters the Fourier transform lens 31, and forms a light spot at a point where the image height h ₀ on the rear focal plane 33 is f sin θ ₀ . Assuming that the optical axis of the illumination system including the light source 26 and the condenser lens 45 is AX2, and the optical axis AX2 intersects the optical axis AX1 at an angle θ ₁ , it is reflected from the surface of the wafer 1 by the light beam 29D as it is. The optical axis AX3 of the light beam 29E intersects the optical axis AX1 at an angle θ ₁ .

In the present embodiment, the opening of the Fourier transform lens 31 has an angle θ with respect to the optical axis AX1 from the surface of the wafer 1.
_Since the light flux of ₁ is not large enough to be incident, the rear focal plane 3
It is not possible to measure the spatial frequency spectrum of the light beam 29E on the H.3. However, since the angle θ ₁ is known, it is obvious that the position Q of h ₁ (= f sin θ ₁ ) from the optical axis AX1 is the spectral position of the reflected light beam 29E (0th order light). Therefore, in this embodiment, as shown in FIG.
The spatial filter 34 is rotated about the position Q of the image height h ₁ on the rear focal plane 33 in the plane of FIG. The configuration and the rotating operation of the rotary spatial filter 34 are the same as those in the first embodiment.
The light-shielding portion of the spatial filter 34 blocks the Fourier transform pattern of the error-free circuit pattern, and the other light pattern generated from the defective portion on the wafer 1 passes through the light-transmitting portion of the spatial filter 34 and transmits the defect-carrying light flux. 38. Other configurations are similar to those of the first embodiment.

Also in this embodiment, as in the first embodiment, the spatial filter 34 is rotated in synchronization with the rotation of the wafer 1 while rotationally scanning the wafer 1, so that the spatial filter 34 can generate an error-free circuit pattern. The Fourier transform pattern of is blocked. Then, the defect information carrying light flux 38 passing through the spatial filter 34 is converted into the defect signal S4 by the photoelectric conversion element 41, and the position and size of the defect are detected at high speed. At this time, in this embodiment, a Fourier transform component farther from the 0th-order light component is detected on the rear focal plane 33 than in the first embodiment. Further, since the Fourier transform component from the error-free circuit pattern is generally strong around the 0th-order light component, by extracting the component apart from the 0th-order light component as in the present embodiment, the influence of the error-free circuit pattern is further improved. It is possible to reduce the number of defects and increase the defect detection capability.

Also in this embodiment, the Fourier spectrum of the error-free circuit pattern may be unevenly present on the spatial filter 34 depending on the circuit pattern on the wafer 1, and when the spatial filter 34 is rotated, the photoelectric conversion element is rotated. The light energy of the defect information carrying light flux 38 incident on 41 is modulated. This modulation can be canceled by the same method as in the first embodiment.

Next, a modification in which one set of optical fiber bundles is used instead of the Fourier transform lens 31 in the embodiment of FIG. 5 will be described with reference to FIG. FIG. 6 shows an essential part of this modified example. In FIG. 6 in which parts corresponding to those in FIG. 5 are designated by the same reference numerals, optical fiber bundles 47 ₁ , One end of each of 47 ₂ , ..., 47 _N is arranged. Then, the other ends of the optical fiber bundles 47 ₁ , 47 ₂ , ..., 47 _N are arranged on a surface 33 parallel to the surface of the wafer 1 along a normal to the surface of the wafer 1, and on this surface 33. To the spatial filter 34
To place.

The light beam 29D condensed by the condenser lens 45 is applied to the test point P on the wafer 1 through the opening 48 of a part of the spherical surface 46, and the light beam 3 generated from the test point P.
2 is guided onto the surface 33 via the optical fiber bundles 47 ₁ , 47 ₂ , ..., 47 _N. In this case, when the radius of the spherical surface 46 is R, the image height h of the light flux 32 emitted from the wafer 1 at an angle θ with respect to the normal line is Rsin θ, which is equivalent to Fourier transform. Therefore, one set of optical fiber bundles 4
7 ₁ , 47 ₂ , ..., 47 _N are the Fourier transform lens 3 of FIG.
As in the case of 1, the light flux from the circuit pattern on the wafer 1 is Fourier-transformed.

Further, the spatial filter 34 is rotated around the position (position of the 0th order light component) where the light beam 29E directly reflected from the wafer 1 by the light beam 29D passes on the surface 33. As a result, the Fourier transform component of the error-free circuit pattern from the wafer 1 and the light-shielding portion corresponding to the Fourier transform component of the error-free circuit pattern on the spatial filter 34 are not displaced. Other configurations are similar to those of the embodiment shown in FIG.

In this case, the luminous flux emitted from the inspection point P of the wafer 1 at a large angle θ with respect to the normal line is also guided to the surface 33 through the optical fiber bundle, so that the light receiving efficiency is good. Further, since the surface of the wafer 1 and the surface 33 can be brought close to each other, the device can be downsized. It should be noted that the present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0039]

According to the present invention, since the substrate to be inspected is rotationally moved using the turntable and the moving means, the defect inspection of the entire surface of the substrate can be performed at high speed.
Also, by rotating the spatial filter in synchronization with the rotation of the substrate,
Since the Fourier transform component from the error-free reference pattern is blocked, the defect inspection can be performed only by comparing the photoelectric conversion signal from the photoelectric conversion means with a predetermined threshold, and the configuration of the signal processing system is simplified. In addition, there is an advantage that the signal processing speed is high.

When the filter rotating means rotates the spatial filter around the position of the 0th-order light component of the Fourier transform pattern of the error-free reference pattern, the Fourier transform component from the error-free reference pattern is well removed. To be done. In addition, the Fourier transform optical element has a plurality of one ends arranged on a spherical surface centered on an inspection area of a predetermined area, and the other end arranged at a position similar to the orthogonal projection of the one end on a predetermined plane. When the optical fiber bundle is formed by bundling, the Fourier transform optical element can be brought close to the substrate, the apparatus can be downsized, and the light flux emitted from the substrate at a large diffraction angle can be received, so that the light receiving efficiency is improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of a rotary defect inspection apparatus according to the present invention.

2 is an enlarged plan view showing an inspection region on the wafer 1 of FIG. 1. FIG.

FIG. 3 is a reference coordinate system (x ′, y ′) in the first embodiment.
It is explanatory drawing of the state of a Fourier spectrum when the angle which the coordinate system (x, y) of an apparatus and changes.

FIG. 4 is a plan view showing a spatial filter 34 and a spectral region 33a of the first embodiment.

FIG. 5 is a configuration diagram showing a second embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a main part of a modified example in which a set of optical fiber bundles is used instead of the Fourier transform lens 31.

FIG. 7 is a configuration diagram showing a conventional defect inspection apparatus.

[Explanation of symbols]

1 Wafer 21 Turntable 23 Moving Rotating Unit 24 Roller 26 Light Source 31 Fourier Transform Lens 34 Spatial Filter 36 Rotating Unit 39 Condensing Lens 41 Photoelectric Conversion Element 42 Signal Processing Unit 47 ₁ , 47 ₂ , ..., 47 _N Optical Fiber Bundle

Claims (3)

[Claims] 1. An apparatus for inspecting defects on a surface of a substrate on which a predetermined pattern is formed, illuminating means for irradiating an inspection light beam on an inspection area having a predetermined area on the surface of the substrate, and a light beam from the substrate. A Fourier transform optical element for performing a Fourier transform of, and a bright portion of the Fourier transform pattern of the error-free reference pattern, which is arranged in the vicinity of the Fourier transform surface of the Fourier transform optical element and has no defect in the predetermined pattern on the substrate. A spatial filter having a matching portion as a light-shielding portion, a photoelectric conversion means for photoelectrically converting the light flux passing through the spatial filter, and a turn for rotating the substrate about a rotation axis parallel to the optical axis of the Fourier transform optical element. A table; filter rotating means for rotating the spatial filter about a predetermined axis in synchronization with rotation of the turntable; D) moving means for moving the substrate in a plane perpendicular to the optical axis of the conversion optical element, and by causing the substrate to rotate and move via the turntable and the moving means, The surface of the substrate is spirally scanned in the inspection area of the area, the spatial filter is rotated through the filter rotating means in synchronization with the rotation of the substrate, and a photoelectric conversion signal output from the photoelectric conversion means. A rotary defect inspection apparatus, which inspects defects of a predetermined pattern on the substrate. 2. The rotary defect inspection according to claim 1, wherein the filter rotating means rotates the spatial filter around the position of the 0th-order light component of the Fourier transform pattern of the error-free reference pattern. apparatus. 3. The Fourier transform optical element has one end disposed on a spherical surface centered on the inspection area having the predetermined area, and the other end located at a position similar to the orthogonal projection of the one end on a predetermined plane. The rotary defect inspection apparatus according to claim 1 or 2, wherein a plurality of arranged optical fiber bundles are formed by bundling.