JPH0727707A - Inspecting apparatus for foreign matter - Google Patents

Abstract

PURPOSE:To detect abnormality of a foreign matter inspecting apparatus itself simultaneously with the time when the abnormal point of the apparatus is specified, by branching a part of a light beam from a radiation means and directly guiding it to a photodetecting means without passing the beams through a to-be-inspected surface. CONSTITUTION:Laser beam 1A radiated from a laser light source 1 is measured by a laser power monitor 13. A shutter 14 is opened to start a self-analysis. A split light of the laser beam 1A from a beam splitter 12 is made incident on one end of a light guide 15. Accordingly, split light of the laser beam 1A is made incident on each photomultiplier 10 from the light guides 15A, 15B. At this time, if an output obtained from the photomultiplier 10 is not at a predetermined output level, the photomultiplier 10 is detected to be abnormal. Moreover, when a predetermined output is detected as a result of the self- analysis of the photomultiplier 10, the inspection is carried out by use of a scattering reference material in place of a reticle 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign substance for optically detecting a foreign substance on the surface to be inspected by scanning the surface to be inspected such as the surface of a reticle (mask) for semiconductor manufacturing with a light beam. The present invention relates to an inspection device.

[0002]

2. Description of the Related Art Generally, the components of a foreign matter inspection device are
An irradiation system for irradiating a surface to be inspected with a light beam, a light receiving system for receiving and photoelectrically converting scattered light generated from the surface to be inspected on the basis of the irradiation of the light beam, and based on an output signal of the light receiving system, It is roughly divided into a detection system that detects foreign matter on the surface to be inspected.

FIG. 3 is an explanatory view showing a schematic structure of a conventional general foreign matter inspection apparatus. As shown in FIG. 3, the conventional foreign matter inspection apparatus includes a laser light source 1, beam expanders 2 and 3, an oscillating mirror 4, and a scanning lens 5 which constitute an irradiation system.
And a reticle 6, a light receiving mirror 7 that constitutes a light receiving system, a light receiving lens 8, a slit 9, and a photomultiplier (photoelectric converter) 10.
More mainly composed. The detection system is not shown in FIG.

The laser light source 1 emits a laser beam 1A. Further, the beam expanders 2 and 3 make the emitted laser beam 1A have a desired beam diameter.

The vibrating mirror 4 is rotatable in the X-axis direction by a support device (not shown), and the laser beam 1A passing through the beam expanders 2 and 3 is passed through the scanning lens 5 to the upper surface of the reticle 6. Focus and irradiate diagonally, X
Scan in the axial direction. The reticle 6 can be moved in the Y-axis direction by a support device (not shown). Therefore, the laser beam 1A can scan the entire surface of the reticle 6 in a raster shape.

When a foreign substance is present on the upper surface of the reticle 6, the light receiving mirror 7 reflects scattered light (reflected light) of the laser beam 1A generated from the foreign substance and makes it enter the light receiving lens 8. The light receiving lens 8 collects the scattered light reflected by the light receiving mirror 7 on the slit 9. The slit 9 allows only the scattered light collected by the light receiving lens 8 to pass. The photomultiplier 10 photoelectrically converts the scattered light passing through the slit 9 and transmits the electric signal to a detection system (not shown).

Incidentally, the slit 9 has a conjugate positional relationship with the scanning line of the laser beam 1A on the reticle 6,
Light other than the scattered light generated from the foreign matter on the upper surface of the reticle 6 is prevented from entering the photomultiplier 10.

The conventional foreign matter inspection apparatus inspects the foreign matter on the upper surface of the reticle 6 by irradiating the laser beam as described above.

[0009]

However, in the above-mentioned conventional foreign matter inspection apparatus, due to some cause,
For example, when the position of the slit 9 is displaced or the photo-mal 10 has a failure, the scattered light generated from the foreign matter on the upper surface of the reticle 6 cannot be detected. There is a problem that it is not possible to distinguish whether the inspection apparatus itself has an abnormality or not, and where the abnormality is based on the irradiation system and the light receiving system.

In addition, when it is impossible to distinguish whether there is a foreign substance on the upper surface of the reticle or whether there is an abnormality in the foreign substance inspection device itself, a device for detecting these abnormalities (so-called self-diagnosis device) is provided. There are various foreign matter inspection devices, but all of them have a problem that the configuration of the diagnostic device for detecting the abnormality becomes complicated and the foreign matter inspection device itself becomes large.

The present invention has been made in view of the above problems, and does not increase the size of the foreign matter inspection apparatus itself.
An object of the present invention is to provide a foreign matter inspection device having a self-diagnosis function that can detect an abnormality of the foreign matter inspection device itself as well as the location of the occurrence.

[0012]

In order to achieve the above-mentioned object, an apparatus for inspecting foreign matter according to the present invention irradiates a surface to be inspected with a light beam, and the object to be inspected based on the irradiation of the light beam. In a foreign matter inspection device having a light receiving means for receiving and photoelectrically converting scattered light generated from a surface, and a detecting means for detecting a foreign matter on the surface to be inspected based on an output signal of the light receiving means, the foreign matter is irradiated from the irradiation means. A transmission optical system is provided, which branches a part of the light beam to directly guide it to the light receiving means without passing through the surface to be inspected.

According to a second aspect of the present invention, in the foreign matter inspection apparatus according to the first aspect, the transmission optical system includes an optical fiber serving as an optical transmission line whose end is guided to the light receiving surface of the light receiving means. And an optical branching unit for guiding a part of the light beam emitted from the irradiation unit to the optical fiber, and a blocking unit for selectively blocking the light beam transmitted through the optical fiber. is there.

[0014]

The foreign matter inspection apparatus according to the invention of claim 1 is
It is composed of an irradiation unit, a light receiving unit, a detection unit, and a transmission optical system. The irradiation means irradiates the surface to be inspected with a light beam. Then, the light receiving means receives and photoelectrically converts scattered light generated from the surface to be inspected based on the irradiation of the light beam. Further, the detection means detects foreign matter on the surface to be inspected based on the output signal of the light receiving means. here,
The transmission optical system branches a part of the light beam emitted from the irradiation means and directly guides the light beam to the light receiving means without passing through the surface to be inspected, thereby determining whether or not the light receiving means is operating normally. It becomes possible to judge whether.

According to a second aspect of the foreign matter inspection apparatus of the present invention, in the foreign matter inspection apparatus of the first aspect, the transmission optical system is composed of an optical fiber, an optical branching means, and a blocking means. Here, the optical branching means is
A part of the light beam emitted from the irradiation means is guided to the optical fiber. Further, the optical fiber is used for an optical transmission line, and its end is guided to the light receiving surface of the light receiving means. The blocking unit selectively blocks the light beam transmitted through the optical fiber, and blocks the emission of the light beam emitted from the optical fiber to the light receiving surface of the light receiving unit during the foreign matter inspection.

In the present invention, for example, when an abnormality occurs in the irradiation means and the light beam disappears, neither the light from the surface to be inspected nor the light from the transmission optical system is incident on the light receiving means. All output signals of are deleted. Also,
If there is an abnormality in the optical system from the irradiation system to the light receiving system, an output signal from only the branched light sent through the transmission optical system appears from the light receiving means. Further, for example, when three-dimensionally detecting a foreign substance by a plurality of light receiving means, etc., by checking the presence or absence of a component due to scattered light in the output signal from each light receiving means and a component due to branched light from the transmission optical system. It is possible to identify the occurrence of an abnormality in each part from the irradiation system to the light receiving system, including the quality of the photoelectric conversion element of the light receiving means.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view showing the schematic structure of a foreign matter inspection apparatus according to an embodiment of the present invention. As shown in FIG. 1, the foreign matter inspection apparatus according to the present embodiment includes a laser light source 1, beam expanders 2 and 3, an oscillating mirror 4, which constitute an irradiation system.
The scanning lens 5, the reticle 6 (surface to be inspected), the light receiving mirror 7 forming the light receiving system, the light receiving lens 8, the slit 9, the photomultiplier (photoelectric converter) 10, and the beam splitter (optical) forming the transmission optical system. (Branching means) 11, another beam splitter 12, laser power monitor 13, shutter (blocking means) 14, light guide (optical fiber) 15
It is mainly configured, and the difference from the conventional example is that a self-diagnosis system including a branch optical system is provided. Therefore, the same parts as those of the conventional example are designated by the same reference numerals and the description thereof will be omitted. Also in FIG. 1, the detection system is omitted as in the conventional example. Furthermore, in this embodiment, as shown in FIG.
As shown in FIG. 2, two light receiving systems are arranged.

The beam splitter 11 is a laser light source 1.
A part of the laser beam 1A radiated toward the beam expander 2 is branched to separate another beam splitter 12
Incident on. The laser beam 1A that has passed through the beam splitter 12 is incident on the laser power monitor 13 and is emitted from the laser light source 1.
It is measured whether the output of A is a predetermined output. In this way, by measuring the output of the laser beam 1A, it is possible to monitor whether or not the laser light source 1 is normal.

The light beam reflected by another beam splitter 12 is incident on the light guide 15 via the shutter 14. The shutter 14 is used for the laser beam 1 to the light guide 15 which will be described later during the foreign matter inspection and the self-diagnosis.
It is provided between the beam splitter 12 and the light guide 15 in order to selectively block the incidence of A. That is, the shutter 14 blocks the laser beam 1A from entering the light guide 15 at the time of foreign matter inspection, and makes the laser beam 1A emitted through the beam splitter 12 enter the light guide 15 at the time of self-diagnosis.

When the laser beam 1A split by the beam splitter 11 is incident on one end of the light guide 15, it is divided into two and transmitted to the other end. Light guide 1
The other end of each slit 5 is near the slit 9 (preferably the slit 9
The laser beam 1A guided to the light guide 15 is directly received by the photomultiplier 10 without passing through the optical system for the surface of the reticle 6. In this embodiment, two light receiving systems are provided, so that the light guide 15 is not connected to the light guide 15 from the middle.
It branches into books (15A, 15B).

FIG. 2 is an enlarged schematic view showing the structure of the main part of the light receiving system of the foreign matter inspection apparatus according to this embodiment. As shown in FIG. 2, the other end 15A (15B) of the light guide 15
Is arranged at one end of the slit 9. A field lens 16 is provided between the slit 9 and the photomultiplier 10.
Are arranged. The field lens 16 reflects the scattered light passing through the slit 9 (the back scattered light of the laser beam 1A generated from the foreign matter on the upper surface of the reticle 6) into the photomultiplier 1.
It is a lens for irradiating 0, and the other end of the light guide 15A (or 15B) is located at one end in the field of view.

In FIG. 1, the shutter 14 is arranged between the beam splitter 12 and one end of the light guide 15. However, the arrangement is not limited to such arrangement, and the shutter 14 may be located in the middle of the light guide 15 or the light guide 15A ,. The beam splitter 11 may be disposed at the tip of 15B.
The shutter 14 may be substituted by variably adjusting the angle. That is, the light guide 1 at the time of self-diagnosis
Any laser beam may be used as long as the laser beam 1A passing through 5 is incident on the photomultiplier 10 and is not incident during the foreign matter inspection.

In the foreign matter inspection apparatus according to this embodiment constructed as described above, first, the laser power monitor 1
By measuring the output of the laser beam 1A emitted from the laser light source 1, the laser beam 1
If the output of A is a predetermined output level, the laser light source 1
The result is that there is no abnormality in.

Next, in order to start self-diagnosis, the shutter 14 is opened and the branched light of the laser beam 1A from the beam splitter 12 is made incident on one end of the light guide 15. As a result, the branched light of the laser beam 1A is incident on each photomultiplier 10 from the light guides 15A and 15B through the ends of the slits 9. At this time, if the output obtained from the Photomul 10 is not a predetermined output level, it can be seen that the Photomul 10 has an abnormality. When there are two light receiving systems (a plurality of) as in this embodiment,
By comparing the output levels of each, it is possible to identify the photomal in which the abnormality has occurred, and since it is unlikely that multiple photomals will all fail at the same time, all the photomals will output at the specified level. It is also possible to monitor the laser light source 1 depending on whether it occurs.

If a predetermined output is obtained as a result of self-diagnosis of the photomultiplier 10, an inspection is performed using a scattering reference material (scattering reference pattern) instead of the reticle 6. As the scattering reference material, a substrate having particles having a predetermined size (for example, 0.5 μm) attached to the surface thereof, a scattering plate roughened with a predetermined surface roughness, or the like can be applied. As a result of inspection using this scattering reference material, when the output from the Photomul 10 is smaller than a predetermined reference value, the laser beam scanned on the surface to be inspected (reticle 6, scattering reference material) and the light receiving system. It is presumed that the slit 9 is not conjugate with the slit 9. As a factor of this, there is an abnormality such as an optical axis shift or a conjugate shift in the optical system from the beam splitter 11 to the scanning lens 5 or the light receiving mirror 7 to the slit 9. The above-mentioned predetermined reference value is defined based on the output when an inspection is performed using the scattering reference material without any abnormality in the optical system.

Further, in this embodiment, as shown in FIG. 1, the light guides 15A and 15B are arranged in the vicinity of the slit 9 so that the laser light is surely incident on the photomultiplier 10. However, since the light receiving mirror 7, the light receiving lens 8 and the slit 9 are less likely to shift with respect to the photomultiplier 10, the positions of the exit ends of the light guides 15A and 15B do not have to be near the slit 9. For example, the light receiving mirror 7 may be a dielectric high-reflecting mirror, and the exit ends of the light guides 15A and 15B may be arranged on the back surface of the dielectric high-reflecting mirror. At this time, the laser light emitted from the light guides 15A and 15B is incident on the photomultiplier 10 via the light receiving lens 8 and the slit 9. As described above, the positions of the exit ends of the light guides 15A and 15B may be located in the light receiving system on the side of the photomultiplier 10 with respect to the reticle 6.

[0027]

As described above, the present invention has a self-diagnosis function for identifying and detecting an abnormality in each part of the foreign matter inspection apparatus itself, and thus has the effect of providing a reliable foreign matter inspection apparatus. . In addition, since the optical fiber is used for the configuration of the self-diagnosis function, there is no need to provide a special installation place for the self-diagnosis device, and there is an effect that it is not necessary to make the foreign matter inspection device large.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a foreign matter inspection device according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic diagram showing a configuration of a main part of a light receiving system of the foreign matter inspection apparatus shown in FIG.

FIG. 3 is an explanatory diagram showing a schematic configuration of a general conventional foreign matter inspection apparatus.

[Explanation of symbols]

 1: Laser light source 2: Beam expander 3: Beam expander 4: Vibrating mirror 5: Scanning lens 6: Reticle 7: Light receiving mirror 8: Light receiving lens 9: Slit 10: Photomal (photoelectric converter) 11: Beam splitter 12 : Beam splitter 13: Laser power monitor 14: Shutter 15: Light guide (optical fiber) 16: Field lens

Claims (2)

[Claims] 1. An irradiation unit for irradiating a light beam onto a surface to be inspected, a light receiving unit for receiving and photoelectrically converting scattered light generated from the surface to be inspected based on the irradiation of the light beam, and an output of the light receiving unit. In a foreign matter inspection device having a detection means for detecting a foreign matter on the surface to be inspected based on a signal, a part of a light beam emitted from the irradiation means is branched so that the light is received without passing through the surface to be inspected. A foreign matter inspection device comprising a transmission optical system that directly leads to a means. 2. The transmission optical system, an optical fiber as an optical transmission line whose end is guided to the light receiving surface of the light receiving means,
3. An optical branching unit for guiding a part of the light beam emitted from the irradiation unit to the optical fiber, and a blocking unit for selectively blocking the light beam transmitted through the optical fiber. The foreign matter inspection device described in.