JPH0682379A - Defect inspection device - Google Patents

Abstract

PURPOSE:To detect only a defect regardless of the condition such as the density or shape of the original pattern of an object to be inspected and to inspect a defect without blocking light by a pellicle frame. CONSTITUTION:A defect inspection device has a light source 23 continuously irradiating a reticle 4 with laser beam L9 in different directions, a light receiving lens 30 condensing the light from the reticle 4 and the shading plate 31 arranged in the vicinity of the Fourier transform surface of the light receiving lens 30 and having apertures 32A-32D formed thereto and further has a shading plate 33 selecting either one of the apertures 32A-32D, a photodetector 41 photoelectrically converting the quantity of light proportional to the light passing through the shading plate 33 and an imaging device 39 taking the conjugate image of the reticle 4.

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 example, when inspecting for foreign matters or defects on a photomask or reticle used for manufacturing a semiconductor device or the like by using a photolithography technique, particularly on a foreign matter adhesion prevention film (pellicle) attached It is suitable for application.

[0002]

2. Description of the Related Art For example, a photomask used when manufacturing a semiconductor element or the like using a photolithography technique,
A defect inspection apparatus is used when inspecting foreign matter, defects, etc. on an object to be inspected having a regular (periodic) structure such as a reticle or a wafer after exposure or a glass substrate such as an optical disk, an iron plate or a mesh. There is. Hereinafter, the photomask or reticle is generically referred to as "reticle".

FIG. 5A shows a conventional defect inspection apparatus,
In FIG. 5A, a light beam L1 emitted from a light source 1 is deflected by a vibrating mirror (galvano scanner mirror or polygon scanner mirror) 2, enters a scanning lens 3, and is emitted from the scanning lens 3. The light beam L2 scans the scanning line 5 on the reticle 4 as the inspection object. At this time, the reticle 4 is moved vertically to the scanning line 5 at a speed slower than the scanning cycle of the light beam L2.
When moved in the direction, the entire surface of the reticle 4 can be scanned by the light beam L2. In this case, reticle 4
The light beam L on the area where there are defects 6 such as foreign matter on the surface of the
When 2 is irradiated, scattered light L3 is generated. Further, when the light beam L2 is applied to a region on the reticle 4 where a periodic structure 7 (hereinafter, collectively referred to as “pattern”) different from a defect such as a foreign substance is present, the pattern 7 is formed. From which diffracted light L4 is generated.

However, the object to be detected by the defect inspection apparatus is not the pattern 7 originally existing in the reticle 4 but the defect 6 which should not exist originally. Therefore, it is necessary to distinguish between the pattern and the defect and detect only the defect. Therefore, in FIG. 5A, the light receiver 8A,
8B and 8C are arranged so as to face the scanning line 5 from different directions. The scattered light L3 generated from the defect 6 such as a foreign substance is isotropic scattered light generated in almost all directions, whereas the diffracted light L generated from the pattern 7 is generated.
Reference numeral 4 denotes light (light having a strong directivity) emitted in spatially discrete directions because it is generated by diffraction. When light is detected by all of the light receivers 8A, 8B, and 8C by using such a difference in properties, the light is scattered light from a defect, and one of the light receivers 8A, 8B, and 8C is detected. If there is any light receiver that does not detect light, it is determined that the light is diffracted light from the pattern. This gives pattern 7
Therefore, only the defect 6 can be detected.

Further, in recent years, as shown in FIG. 5B, in order to prevent the foreign matter from directly adhering to the pattern forming surface (or both surfaces) of the reticle 4, the foreign matter is interposed on the reticle 4 via a pellicle frame 9 as a support frame. Pellicle 1 as an adhesion prevention film
0 is often set up. The pellicle 10 is a light-transmissive thin film having a thickness of about 1 μm, and the pellicle frame 9 is a metal frame made of aluminum or the like.

[0006]

However, as shown in FIG.
As shown in (a), when inspecting for defects on the surface of the reticle 4 with the pellicle 10 stretched, the light beam L2 is eclipsed by the pellicle frame 9, or the light receivers 8A to 8C. Axis AX1 of the light going to
~ The AX3 may be vignetted by the pellicle frame 9. Therefore, it is difficult to inspect the inspection surface of the reticle 4 near the pellicle frame 9.

Further, in the conventional defect inspection apparatus, depending on the density and shape of the pattern 7 on the reticle 4, all the light receivers 8A, 8B even if it is the diffracted light from the pattern.
There is a disadvantage that light may be incident on 8C and 8C and may be erroneously determined as a defect. In view of such points, the present invention is
Only defects can be detected without depending on conditions such as the density and shape of the original pattern of the test object, and even if the test object has a pellicle, it is possible to perform defect inspection without being blocked by the pellicle frame. It is an object of the present invention to provide a defect inspection device that can be used.

[0008]

In the defect inspection apparatus according to the present invention, as shown in FIG. 1, for example, the inspection light is irradiated onto the inspection object (4), and the light from the inspection object (4) is used. In a device for inspecting a defect of an inspection object (4), a light irradiation means (23, 24, 27, 30) for irradiating the inspection object (4) with inspection light (L9) from different directions continuously. , Moving means (20 to 22) for changing the relative position of the object to be inspected (4) and the light irradiation means (23, 24, 27, 30), and a light collecting means for collecting light from the object to be inspected (4). The optical optical system (30) and only a partial region of the Fourier transform pattern of the light from the test object (4) arranged near the Fourier transform surface of the test object (4) by the condensing optical system (30) Diaphragm means (31) formed with openings (32A to 32D) for passing light corresponding to
Selection means (3) for selecting the region of the Fourier transform pattern of the light from the object (19) to be passed by the diaphragm means (31).
3, 35).

Further, according to the present invention, the light detecting means (41) for photoelectrically converting the light quantity proportional to the light passing through the diaphragm means (31).
And a conversion optical system (38) for forming a conjugate image of the object (4) by performing an inverse Fourier transform on the light passing through the diaphragm means (31).
And an image pickup means (39) for picking up the conjugate image thereof, and a light irradiation means (23, 24, 2) according to the illumination area of the test object (4).
7, 30) to the inspection light (L
Irradiation direction and / or irradiation angle of 9) and selection means (3
3, 35) and a control means (29) for instructing at least one of the areas of the Fourier transform pattern of the light from the test object (4).

[0010]

The optical principle underlying the present invention will be described with reference to FIG. In FIG. 6, the light beam L is applied to the surface 11 to be inspected with 11 being the surface to be inspected. However, in order to simplify the description here, it is assumed that the surface 11 to be inspected is an object that transmits light at least partially, and the light beam L is incident perpendicularly from the back surface direction of the surface 11 to be inspected.
The invention applies not only to transillumination but also to epi-illumination. Furthermore, the present invention is applicable to both bright field and dark field illumination methods.

A light receiving lens 12 is arranged in a direction in which a light beam L is emitted from the surface 11 to be inspected, and a Fourier transform image of a pattern 13 on the surface to be inspected 11 is formed on a pupil plane P1 on the image side of the light receiving lens 12. 13F is formed. The pupil plane P1 of the light receiving lens 12 is also called a Fourier transform plane. Furthermore, the pupil plane P
The lens 14 is arranged in the direction in which the light beam is emitted from the first light source 1, and the lens 14 allows the second pupil surface P2 conjugate with the pupil surface P1.
A reduced image of the Fourier transform image 13F is formed on the top.
The light receiving surface of the light receiver 15 is arranged on the second pupil plane P2, and the reduced image on the second pupil plane P2 is photoelectrically converted by the light receiver 15. Therefore, the position 11C which is conjugate with the surface 11 to be inspected by the light receiving lens 12 and the lens 14 is the second pupil plane P.
Different from 2.

In FIG. 6, no optical element is placed at the position of the pupil plane P1, and the pupil plane P1 is a virtual plane. That is, in the configuration of FIG. 6, all the optical information on the surface 11 to be inspected is incident on the photodetector 15. Therefore, if it is left as it is, a defect is present together with the optical information of the original pattern 13 on the surface 11 to be inspected. If so, the optical information of the defect also enters the light receiver 15. Therefore, it is difficult to distinguish the defect from the pattern and detect only the defect. Similarly, even at the position 11C, which is conjugate with the surface 11 to be inspected, the original pattern and the defect are observed as a mixture, and therefore only the defect cannot be observed.

Therefore, the present invention is configured as shown in FIG. In FIG. 7 in which the same parts as those in FIG. 6 are denoted by the same reference numerals, the optical positional relationship between the surface 11 to be inspected, the light receiving lens 12, the pupil surface P1, the lens 14, the second pupil surface P2, and the light receiver 15 is shown. Same as 6. In FIG. 7, a light shielding plate 17 having an opening 16 is further provided in the pupil plane P1. At this time, when the relative position between the Fourier transform image 13F (see FIG. 6) of the pattern 13 formed on the pupil plane P1 and the aperture 16 is changed, the light spot in the Fourier transform image 13F does not exist in the aperture 16. In some cases, even if a light spot exists in the opening 16, the light amount of the light spot is weak. On the other hand, the scattered light generated from a defect such as a foreign substance existing on the surface 11 to be inspected is isotropically generated as described above, and thus the Fourier transform image 1
Even if the relative position between the 3F and the opening 16 is changed, the opening 16
The increase or decrease in the amount of scattered light that passes through is slight, or the amount of scattered light that passes through the opening 16 hardly changes. By utilizing this characteristic, only the defect is detected by distinguishing the defect from the pattern.

At this time, the light passing through the aperture 16 is detected by the light receiver 15 located at the pupil conjugate position. Fourier transform image 13F so that the photoelectric conversion signal S of the light receiver 15 becomes the smallest
If the relative position between the aperture 16 and the aperture 16 is determined, then the spot of the Fourier transform image 13F does not pass through the aperture 16 or the amount of light is small even if it passes, and thus the defect is relatively smaller than the Fourier transform image 13F. More optical information will pass through the aperture 16. At this time, if the image of the surface to be inspected 11 is observed by using the light that has passed through the opening 16 at the position 11C which is almost conjugate with the surface to be inspected 11, only the defect can be detected. An imaging means such as a charge-coupled imaging device (CCD) may be used as the observation means,
Visual observation may be used. The above is the principle of the present invention.

As described above, the relative position changing means for changing the relative position between the Fourier transform image 13F and the opening 16 is roughly classified into two means. The first means is a driving means for moving (translating and / or rotating) the light shielding plate 17 in the plane of the pupil plane P1 to change the position of the opening 16. The second means is an incident direction varying means for changing the incident vector of the light beam L, that is, the incident direction and the incident angle with respect to the surface 11 to be inspected, while the position of the opening 16 is fixed. The former will be described with reference to FIG. 8 and the latter will be described with reference to FIG.

FIG. 8A shows a state in which the pupil plane P1 shown in FIGS. 6 and 7 is viewed from a direction perpendicular to the pupil plane P1.
In (a), 13F is the Fourier transform image of the pattern 13 of FIG. 6, and the opening 16 is a part of the light shielding plate 17 of FIG. Aperture 1 for given origin PO on pupil plane P1
When the position vector representing the position of 6 is <C>, FIG.
The photoelectric conversion signal S of the light receiver 15 of the position vector <C>
Changes as shown in FIG. 8B. That is, when the light spot of the Fourier transform image 13F passes through the opening 16, the photoelectric conversion signal S becomes large, but otherwise, the defect information other than the pattern 13 passes through the opening 16, so that the photoelectric conversion signal S Is small.

Therefore, the photoelectric conversion signal S of FIG.
Minimum value S_min It is possible to detect only defects by detecting
Wear. Specifically, a pair of thresholds S for a predetermined defect
_TH1 And S_TH2 (S_TH2 > S_TH1 > 0),
The minimum value S of the photoelectric conversion signal S _min When satisfies the expression
Determines that the defect exists. S_TH1 ≤ S_min ≤ S_TH2 At this time, the minimum value S_min The original surface 11
Pattern 13 has almost no effect, so that pattern
It is possible to detect only defects accurately regardless of
It

Next, a case where the incident vector of the light beam L changes will be described with reference to FIG. In FIG.
Let the initial incident vector of the light beam L (vector of unit length parallel to the light beam L incident on the surface 11 to be inspected) be <e
₀ >, a spot 18 of the 0th-order diffracted light of the pattern 13 is formed on the pupil plane P1. The position vector of the spot 18 with respect to the aperture 16 fixed on the pupil plane P1 is <C ₀ >.

The surface to be inspected 1 of the incident light beam L is
When the incident direction or the incident angle with respect to 1 is changed, the incident vector becomes <e '>. At this time, the spot of the 0th-order diffracted light on the pupil plane P1 becomes 18 ', and the position vector of the spot 18' with respect to the aperture 16 becomes <C '>.
₀ > ≠ <C ′>. That is, as in the case where the position of the opening 16 is changed as shown in FIG. 8, since the position vector <C ₀ > changes, only the optical information of the defect can be obtained by changing the incident vector, that is, the incident direction. Obtainable.

Further, in FIG. 6, when the inspection surface 11 is rotated, the Fourier transform image 13F of the pattern 13 of the inspection surface 11 is rotated on the pupil plane P1. Therefore, the surface to be inspected 1
By rotating 1 as well, the position vector <C> in FIG. 8 changes, and only the optical information of the defect can be obtained. Furthermore, in order to improve the defect detection capability, the above three methods may be combined, or a plurality of openings 16 may be formed in the pupil space. For example, assuming that the light receiving lens 12 is one, the light receiving lens 12 is
Needless to say, the present invention includes a configuration having a plurality of openings 16 in the pupil plane P1 of the above, a configuration having a plurality of light receiving lenses 12 instead of one, and a plurality of pupil planes and a plurality of apertures. Yes.

Now, the light beam L on the surface 11 to be inspected in FIG.
If the illumination area illuminated by the object is called a "field of view", the information obtained at the position 11C conjugate with the surface 11 to be inspected is limited to the information within that field of view. In order to inspect the entire area of the surface 11 to be inspected, a method of scanning the light beam L on the object to be inspected 11 or moving the object to be inspected 11 on a stage or the like may be used.

At this time, although omitted in FIG. 7, if a pellicle frame is mounted around the surface 11 to be inspected, the light beam that can be received by the light receiving lens 12 and the aperture 1
The movable range of 6 and the variable range of the incident vector of the light beam L are limited. Therefore, the aperture 1 is
Even if the case where the amount of light passing through 6 is minimized, the light beam L and the received light beam incident on the pellicle frame may actually be vignetting.
A normal pattern on the surface 11 to be inspected may be mistakenly determined to be a defect. Therefore, the effective range of the incident vector of the light beam L and the effective range of the position of the opening 16 are set from the beginning according to the arrangement of the pellicle frame on the surface 11 to be inspected and the field of view (illumination area). This is the principle of the invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the defect inspection apparatus according to the present invention will be described below with reference to FIGS. In the present embodiment, the present invention is applied to a case where the relative position between the aperture and the Fourier transform image of the inspection object is changed on the pupil plane by changing the incident vector of the light beam with respect to the inspection object.

FIG. 1 shows the structure of the mechanical portion of the defect inspection apparatus of this embodiment. In FIG. 1, 4 is a reticle as an object to be inspected, and the reticle 4 has a pellicle 10 via a pellicle frame 9. It is installed. The original pattern 19 is formed on the reticle 4. The reticle 4 is placed on the stage 20, and the drive units 21 and 22 can move the stage 20 and the reticle 4 in the X and Y directions, respectively, and the movement amounts of the stage 20 in the X and Y directions are not shown. It is measured by a length measuring instrument (rear encoder, etc.).

Reference numeral 23 denotes a light source, and the light L5 generated from the light source 23 becomes a substantially parallel light flux L6 by the lens 24.
A circular shading plate 25 in a direction symmetrical to the light source 23 of the lens 24
The light beam L6 emitted from the lens 24 is blocked by the light shielding plate 25 at the central portion thereof and is incident on the annular light shielding plate 27 having the opening 26 as the annular illumination light L7. The outer diameter of the annular illumination light L7 is slightly smaller than the outer diameter of the annular light shielding plate 27, and the inner diameter of the annular illumination light L7 is the annular light shielding plate 27.
Slightly larger than the inner diameter of. Further, the annular light-shielding plate 27 is rotatably supported by the drive unit 28 in the θ direction which is the circumferential direction, and the rotation angle is also represented by θ (0 ° ≦ θ ≦ 360 °).
The rotation angle θ means the angle between the positive direction of the Y axis and the center of the opening 26 of the annular light shielding plate 27 with the Y axis as the starting point. The main control system 29 controls the operation of the drive unit 28. Light beam L8 that has passed through the opening 26 of the annular light-shielding plate 27
Is converted into a light beam L9 by the light receiving lens 30 and obliquely enters the reticle 4.

On the other hand, light L1 consisting of diffracted light and scattered light generated from the pattern 19 of the reticle 4 and defects such as foreign matter.
0 reaches the light shielding plate 31 provided on the pupil plane of the light receiving lens 30 (that is, the Fourier transform plane of the inspection surface of the reticle 4) through the light receiving lens 30. This is because when the focal length of the light receiving lens 30 is f, the distance from the reticle 4 to the principal point of the light receiving lens 30 and the light shielding plate 3 from the principal point of the light receiving lens 30.
By setting the distance to 1 to be equal to f, the light shielding plate 3
It is equivalent to arranging 1 on the Fourier transform plane. In the light shielding plate 31, four openings 32A, 32B, 32C and 32D are formed at 90 ° intervals with the positive direction of the Y axis as a starting point. In this embodiment, the light shield plate 31 is arranged inside the ring-shaped light shield plate 27 so as to be substantially inscribed.

Further, in order from the light shield plate 31 to the circular light shield plate 25, an image is formed by a light shield plate 33 having an opening 34 formed therein, a half mirror 37, a lens 38, and a two-dimensional charge-coupled image pickup device (CCD). The device 39 is disposed, and the lens 40 and the light receiver 41 are sequentially disposed in the direction in which the light is reflected by the half mirror 37. The light-shielding plate 33 therein is arranged immediately after the light-shielding plate 31 so as to be in close contact therewith, and the light-shielding plate 33 is rotatably supported by the drive unit 35 in the φ direction which is the circumferential direction about the drive shaft 36, and is driven. The operation of the unit 35 is controlled by the main control system 29. By rotating the light blocking plate 33 in the φ direction, the light from any one of the four openings 32A to 32D of the light blocking plate 31 can be selected by the opening 34 of the light blocking plate 33.

For example, in the arrangement shown in FIG. 1, of the light passing through the four openings 32A to 32D of the light shielding plate 31, three openings 3 are provided.
Light passing through 2B, 32C and 32D is blocked by the light blocking plate 31, but only light L11 passing through the opening 32A passes through the opening 34 provided in the light blocking plate 33. In this case, since the opening 34 is configured to be equal to or larger than the four openings 32A to 32D, the opening 3
The light L11 passing through 2A is not blocked by the opening 34. That is, the light shielding plate 33 functions as a selection unit or a shutter unit that selects light that has passed through any one of the four openings 32A to 32D. Therefore,
The drive unit 35 may intermittently rotate the light shielding plate 33 so that the opening 34 is located at a position corresponding to each of the four openings 32A to 32D, and the drive unit 35 needs to rotate the light shielding plate 33 continuously. There is no.

It should be noted that instead of the light shielding plate 33, the opening 32A
Each of 32D to 32D may be provided with a liquid crystal shutter or the like capable of independently switching between transmission and blocking of light. Further, instead of the fixed light shield plate 31, a rotatable light shield plate 33 itself is arranged, and the position of the opening 34 of the light shield plate 33 is set to one of the openings 32A to 32D as required. You may do it.

The light L11 which has passed through the opening 34 of the light shielding plate 33
The light that has passed through the half mirror 37
Is focused on the imaging surface of the imaging device 39. Regarding the light receiving lens 30 and the lens 38, the reticle 4 and the imaging device 39
Of the reticle 4 is formed on the image pickup surface of the image pickup device 39. However, instead of the image pickup device 39, an eyepiece lens may be arranged to visually observe the image of the reticle 4.

On the other hand, of the light L11 that has passed through the opening 34 of the light shielding plate 34, the light reflected by the half mirror 37 is focused by the lens 40 on the light receiving surface of the light receiver 41. The light-shielding plate 31 provided on the pupil plane of the light-receiving lens 30 and the light-receiving surface of the light receiver 41 are conjugated, and the light-receiver 41 photoelectrically converts an amount of light that is substantially proportional to the light passing through the opening 34 of the light-shielding plate 33. Then, the detection signal V is output. In this case, the light receiving surface 41 a of the light receiver 41 has four openings 32 provided in the light shielding plate 31.
Since the pupil conjugate plane is conjugate to all of A to 32D, the light receiving surface 41a of the light receiver 41 receives a quantity of light proportional to the light passing through any one of the openings 32A to 32D. Incident. Of course, only one of the four openings 32A to 32D is selected by the opening 34 of the light shielding plate 33.

The shape of the light shielding plate 31 will be described in detail with reference to FIG. FIG. 2 is a plan view in the XY plane when the shading plate 31 is viewed from the shading plate 33 side.
The directions correspond to the X direction and the Y direction in FIG. 1 as they are. In this embodiment, as shown in FIG.
Each of the openings 32A to 32D has a circular shape,
It can be square or rectangular. Also, four openings 32
The distances from the inner diameters of A to 32D and the center 31a (coaxial with the optical axis of the light receiving lens 30 or the drive axis 36) to the center of each opening are equal in all four openings.

Next, an example of the defect inspection operation of this example will be described with reference to FIG. 3 is a plan view of the reticle 4 of FIG. 1 in which the pellicle 10 is mounted via the pellicle frame 9 as seen from the light receiving lens 30 side. The X direction and the Y direction of FIG. 3 and the X direction of FIG. And the Y direction correspond directly. In addition, the inner surface 9a of the pellicle frame 9 of this example
Is a rectangle and connects the opposite vertices of its inner surface 9a 2
The diagonal lines 42 and 43 of the book divide the inner surface of the pellicle frame 9 of the reticle 4 into four inspection regions 44A to 44D.

In this case, the light beam L9 obliquely incident on the reticle 4 in each inspection region is reflected by the pellicle frame 9
In order to reliably irradiate the reticle 4 without being blocked by, the range in which the rotation angle θ of the opening 26 of the ring shading plate 27 of FIG. 1 can continuously change is 90 ° in the first inspection area 44A of FIG. ≦ θ ≦ 270 °, 180 in the second inspection area 44B
° ≦ θ ≦ 360 °, 0 ° ≦ θ ≦ in the third inspection region 44C
In the range of 90 ° and 270 ° ≦ θ ≦ 360 °, the fourth inspection region 44D has 0 ° ≦ θ ≦ 180 °. Further, the light L10 from the reticle 4 is reflected by the pellicle frame 9
In order not to be blocked by, the opening 32C in the first inspection area 44A, the opening 32D in the second inspection area 44B, and the second inspection area 44B are selected when selecting one opening from the four openings 32A to 32D by the opening 34. In the inspection area 44C, the opening 32A and the fourth area
In the inspection area 44D, the openings 32B may be selected respectively. The effective range of the rotation angle θ and the four openings 32A to 32
The switching of the selection method from D is performed by the main control system 29 of FIG. 1 based on the length measurement data of the length measuring device (not shown) corresponding to the position of the stage 20 in the X direction and the Y direction.

As a result, each inspection area 44A of the reticle 4 is
.About.44D, the effective range of the rotation angle .theta. Of the opening 26 of the ring shading plate 27 and one opening selected from the four openings 32A to 32D are determined. In each of the inspection regions 44A to 44D, the drive unit 16 is operated within the effective range of the rotation angle θ to rotate the annular light-shielding plate 27, thereby rotating the rotation angle when the detection signal V of the light receiver 41 is minimized. θ ₀ is obtained. The rotation angle θ of the opening 26 of the ring shading plate 27 is fixed to the rotation angle θ _0, and the conjugate image of the reticle 4 is observed by the image pickup device 39. As described above, at this rotation angle θ ₀ , the diffracted light from the original pattern 19 of the reticle 4 is relatively small in the light passing through the opening 34 of the light shielding plate 33. It is possible to clearly detect (observe) only the defect such as the foreign matter of FIG.

The inspection area of the reticle 4 is not divided into four inspection areas as shown in FIG. 3, but the inspection surrounded by the inner surface 9a of the pellicle frame 9 on the reticle 4 as shown in FIG. The area may be divided into five areas. The example in Figure 4
A fifth inspection area is provided in the center of the four-divided inspection areas in FIG. 3, and the inspection area of the reticle 4 is four inspection areas 45A to 45D in the peripheral area and one inspection area in the central area. It is divided into areas 46 and. Then, the effective range of the rotation angle θ and the light shielding plate 31 in the inspection areas 45A to 45D of FIG.
The method of selecting the openings is the inspection areas 44A to 4A of FIG.
This is the same as the method for selecting the effective range of the rotation angle θ and the aperture for 4D. However, since the inspection area 46 at the center of FIG. 4 is separated from the pellicle frame 9, the light beam L9 incident on the reticle 4 and the light L10 from the reticle 4 are not blocked by the pellicle frame 9. Therefore, in the inspection area 46, the effective range of the rotation angle θ of the opening 26 of the annular light shielding plate 27 can be set to 0 ° ≦ θ ≦ 360 °, and a more optimal rotation angle is selected from a larger amount of optical information. θ ₀
Can be determined.

If the pellicle frame 9 is not a rectangular frame but a circular frame, the annular light-shielding plate 27 can be obtained by indicating in the polar coordinates where the light beam L9 is incident on the reticle 4. The effective range of the rotation angle θ of the opening 26 and the selection method from the four openings 32A to 32D can be easily determined.

Next, various modifications of the above-described embodiment will be described. (1) The optical axis of the light receiving lens 30 in FIG. 1 is tilted with respect to the reticle 4. In this case, since the light from the pattern 19 of the reticle 4 can be received from a direction spatially distant from the 0th-order diffracted light of the pattern 19, the intensity of the Fourier transform image of the pattern 19 becomes small and the pattern 19 is detected. The accuracy of is improved. This phenomenon is based on the optical principle of diffraction that the amount of diffracted light decreases as the distance from the 0th order light increases.

(2) Since the reticle 4 is a glass substrate having a light transmitting property, it can be used as a transillumination. (3) The light for illuminating the reticle 4 may be single wavelength light or white light. However, the light of a single wavelength is preferable because the difference in brightness between the Fourier transform images becomes clear. (4) The optical system (light receiving lens 30 etc.) of FIG.
Alternatively, a plurality of sets may be provided to obtain optical information generated in a plurality of directions from the reticle 4. In this case, there is an advantage that more optical information can be obtained.

In the embodiment shown in FIG. 1, the opening 26 of the ring shading plate 27 is not only rotatable but also can be moved two-dimensionally in a plane parallel to the ring shading plate 27. The angle of incidence of the light beam on the reticle 4 as the test object may also be variable. in this case,
For example, the effective range of the incident angle of the light beam is set according to each inspection area 44A to 44D of the reticle 4 in FIG.
Then, depending on the inspection areas 44A to 44D of the reticle 4, the effective range of the incident direction of the light beam on the reticle 4, the effective range of the incident angle of the light beam, or the effective range of the position of the opening selected in the light shielding plate 31. To set. After that, in order to perform a good defect inspection of each inspection region 44A to 44D of the reticle 4, the incident direction of the light beam on the reticle 4, the incident angle of the light beam, or the light shielding plate 31 is selected according to the inspection region. The position of the opening to be opened may be set within a preset effective range.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0042]

According to the present invention, the irradiation direction of the inspection light from the light irradiating means to the object to be inspected is adjusted so that only the light related to the defect in the light from the object to be inspected is passed through the diaphragm means. Therefore, there is an advantage that only defects can be detected regardless of conditions such as the density and shape of the original pattern on the object to be inspected. Moreover, the shape of the defect can be observed by the imaging means.

Even if the pellicle frame or the like is attached to the object to be inspected, the irradiation direction, the irradiation angle, or the selection of the inspection light from the light irradiation means to the object to be inspected is selected according to the illumination area of the object to be inspected. By designating the area of the Fourier transform pattern of the light from the test object selected by the means, there is an advantage that the defect inspection can be performed without being blocked by the pellicle frame or the like.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a mechanical portion of an embodiment of a defect inspection apparatus according to the present invention.

FIG. 2 is a plan view showing a shape of an opening of a light shielding plate 31 of FIG.

3 is a plan view showing an example of a method of dividing an inspection area of the reticle 4 of FIG.

FIG. 4 is a plan view showing another example of a method of dividing the inspection area of the reticle 4 of FIG.

5A is a perspective view showing a configuration of a conventional defect inspection apparatus, and FIG. 5B is a sectional view showing a reticle with a pellicle.

FIG. 6 is a perspective view for explaining the detection principle of the present invention.

FIG. 7 is an explanatory diagram of a detection principle of the present invention, and is a perspective view showing a case where a light shielding plate having an opening is arranged on the pupil plane P1.

8A is a front view showing the positional relationship between the aperture 16 and the Fourier transform image 13F on the pupil plane P1, and FIG. 8B is a diagram when the positional relationship between the aperture 16 and the Fourier transform image 13F is changed. 5 is a waveform diagram showing an example of a change in photoelectric conversion signal S of the light receiver 15 of FIG.

FIG. 9 is an explanatory view of the detection principle of the present invention, and is a perspective view showing a case where the incident vector of the light beam L on the surface to be inspected changes.

[Explanation of symbols]

 4 reticle 9 pellicle frame 10 pellicle 20 stage 23 light source 24, 38, 40 lens 25, 31, 33 light-shielding plate 26, 32A to 32D, 34 aperture 27 ring-shaped light-shielding plate 28, 35 drive unit 29 main control system 30 light-receiving lens 37 Half mirror 39 Imaging device 41 Light receiver 44A to 44D, 45A to 45D, 46 Inspection area

Claims (1)

[Claims] 1. An apparatus for irradiating an inspection object with inspection light and inspecting a defect of the inspection object by the light from the inspection object, wherein the inspection object is irradiated with inspection light. Light irradiation means, moving means for changing the relative position of the object to be inspected and the light irradiation means, a condensing optical system for condensing light from the object to be inspected, and the object to be condensed by the condensing optical system. A diaphragm means arranged near the Fourier transform surface of the specimen and having an opening for passing light corresponding to only a part of the Fourier transform pattern of the light from the specimen, and the diaphragm means for passing the light. Selection means for selecting a region of the Fourier transform pattern of light from the object to be inspected, light detection means for photoelectrically converting the amount of light proportional to the light passing through the diaphragm means, and inverse Fourier transform for the light passing through the diaphragm means Converted light that is converted to form a conjugate image of the test object A system, an imaging unit that captures the conjugate image, an irradiation direction and / or an irradiation angle of the inspection light from the light irradiation unit to the test object according to an illumination area of the test object, and the selection unit 2. A defect inspection apparatus, comprising: a control unit for instructing at least one of a region of a Fourier transform pattern of light from the object to be selected selected in 1.