JPS63186132A - Foreign matter inspection device - Google Patents

Abstract

PURPOSE:To decide a surface where foreign matter sticks excellently by projecting light in different directions and comparing the quantities of scattered light from the foreign matter in respective cases. CONSTITUTION:Light sources 10 and 14 are so arranged as to project light on a thin film 1 at different angles of incidence. For example, light from the light source 10 is for oblique illumination (at a relatively small angle to the surface of the thin film 1) and light from the light source 14 is for downward illumination (at a relatively large angle to the thin film 1). The quantities of illumination light beams incident on the thin film 1 are adjusted previously by filters 12 and 16 for light quantity adjustment so that the quantities of scattered light from the foreign matter sticking on the top surface of the thin film 1, i.e. the levels of the photoelectric signals of a photoelectric detector 20 are equal between the oblique illumination and downward illumination as to the same foreign matter. Then scattered light beams from the foreign matter by the downward illumination and oblique illumination only are detected 20 and variation quantities of photoelectric signals at this time are compared to decide the surface where the foreign matter sticks.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to an apparatus for inspecting foreign matter such as minute dust, in particular,
Photomasks used in the manufacturing process of integrated circuits,
The present invention relates to an apparatus for inspecting foreign matter adhering to the surface of a reticle, semiconductor wafer, photomask, or reticle thin film (hereinafter referred to as thin film).

[Prior Art] In a photolithography process, which is one of the integrated circuit manufacturing processes, a circuit pattern is transferred onto a semiconductor wafer using a reticle, a photomask, or the like (hereinafter referred to as a "reticle or the like").

In this case, if foreign matter such as dust adheres to the reticle or the like, it will appear as a defect in the circuit pattern when it is transferred to the semiconductor square, resulting in a decrease in yield.

For this reason, a foreign matter inspection device is used to inspect whether foreign matter is attached to the surface of a reticle or the like. This foreign object inspection device illuminates the object to be inspected and detects the scattered light from the foreign object using a photoelectric detection means, thereby obtaining information regarding the position and size of the foreign object on the surface of the reticle, etc. It helps prevent inconvenience.

Recently, as a method of preventing foreign matter from adhering to the surface of a reticle, etc., a thin film called a pellicle (a foreign matter adhesion prevention film) has been attached to the surface of the reticle. By mounting the pellicle so as to cover the surface of the reticle or the like through a support frame, foreign matter is prevented from directly adhering to the reticle or the like. When using this pellicle to perform projection exposure using an exposure device, even if foreign matter adheres to the surface of the pellicle, 1. Since the image of the foreign object is not focused on the object to be projected, that is, the eight surfaces of the semiconductor sea urchin, the image of the foreign object is not transferred.

However, if the amount of foreign matter adhering to the surface of the pellicle is relatively large, there is a risk that uneven exposure will occur on the eight faces of the semiconductor. In addition, foreign matter attached to the underside of the pellicle, that is, the reticle side, may separate from the pellicle surface and attach to the reticle surface, etc., even if it is not large enough to cause uneven exposure. Then, the image is transferred to the semiconductor wafer.

Therefore, even when using a pellicle, it is necessary to inspect the position and size of foreign objects attached to the pellicle. Furthermore, it is necessary to inspect whether the foreign objects are attached to the top surface of the pellicle (the surface opposite to the reticle, etc.), and whether the foreign particles are attached to the bottom surface. It is also necessary to determine whether it is attached to the surface of the reticle, etc.

[Problems to be Solved by the Invention] As explained above, when using a pellicle, for example, it is important to know not only the position and size of the foreign matter attached to the pellicle, but also whether the foreign matter is attached to the top or bottom surface. However, with conventional foreign object inspection equipment, although it is possible to know the location and size of foreign objects on the surface of the pellicle, it is necessary to inspect whether the foreign objects are on the top surface of the pellicle (on the opposite side from the reticle, etc.). Is it attached to the bottom surface (the surface on the reticle side)?
There was a problem in that it was not possible to determine whether it was attached to the surface.

This invention was made in order to solve such problems, and it does not only control the position and size of foreign particles attached to the thin film.
It is an object of the present invention to provide a foreign matter inspection device that can determine whether the foreign matter is attached to the upper surface or the lower surface of a thin film.

[Means for Solving the Problems] The present invention comprises: a first illumination means for irradiating light from a first incident direction onto one surface of a thin film-like object to be inspected having light transmittance; a first photoelectric detection means for detecting light scattered by a foreign object in the light of the means; a second illumination means for irradiating light from a second incident direction onto one of the surfaces of the object to be inspected; a second photoelectric detection means for detecting light scattered by a foreign object; and a judgment means for determining a foreign object adhering surface of the object to be inspected based on the detection outputs of the first and second photoelectric detection means. The technical point is to have

[Operation] When light reaches a transparent thin film-like object to be inspected, if the angle between the light and the surface of the object to be inspected is relatively large, most of the light will pass through the object to be inspected. .

On the other hand, when the angle between the light and the surface of the thin film is relatively small, most of the light is reflected by the surface of the object to be inspected and only a small amount of light is transmitted. The present invention applies this phenomenon.

Next, if foreign matter is attached to both sides of the object to be inspected,
Scattered light from a foreign object when the object is irradiated with light from different directions will be explained using figures.

Figure 1 shows a foreign object 2 on the top surface. FIG. 3 is a diagram showing the appearance of irradiated light and scattered light from foreign objects when light is irradiated from different directions onto a light-transmissive thin film 1 to which foreign objects 3 are attached to the bottom surface.

Figure 1(a) shows the irradiation light 4 and the scattered light from foreign objects when the light is irradiated from a direction with a relatively large angle with the surface of the thin film 1 (hereinafter referred to as "epi-illumination"). FIG.

In addition, the same figure (b) shows Thin II! 1 is a diagram showing the state of irradiated light 5 and scattered light from a foreign object when light is irradiated from a direction that makes a relatively small angle with the surface of FIG. 1 (hereinafter referred to as "oblique illumination").

First, a description will be given of the respective amounts of light when epi-illumination and oblique illumination are used to receive scattered light from a foreign object scattered in a certain direction, for example, the direction of arrow A in the figure.

If the amount of light scattered from the foreign matter 2 adhering to the surface of the thin film 1 is the same in epi-illumination and oblique illumination, it will be almost the same in epi-illumination and oblique illumination. , the amount of light will be the same.

- Expo 1]! Regarding foreign matter 3 attached to the back side of 1,
The amount of scattered light in the case of oblique illumination is smaller than that in the case of epi-illumination. This is because in the case of oblique illumination, most of the irradiated light 5 is reflected on the surface of the thin film 1, so the amount of light that reaches the foreign object 3 is smaller than in the case of epi-illumination, where most of the light passes through the thin film 1. It's for a reason.

Therefore, by irradiating light from different directions and comparing the amount of light scattered from the foreign object in each case, it is possible to determine whether the foreign object is attached to the top surface or the bottom surface of the thin film. Next, when light is irradiated from a certain direction, for example, when epi-illumination is used, the light scattered by foreign objects is received in different directions, for example, in directions A and B in Fig. 1(a). The amount of light when doing so will be explained.

The amount of scattered light from the foreign matter 2 attached to the upper surface of the film 1 is almost the same whether it is received from A or B.

On the other hand, in the foreign matter 3 attached to the lower surface of the thin film, the amount of scattered light when received from B is smaller than the amount of scattered light when received from A. This is because most of the scattered light from the foreign object 3 in the direction of B is reflected by the lower surface of the thin H@1.

Therefore, if light is irradiated from a certain direction, the amount of scattered light from a foreign object is received from different directions, and the amount of scattered light from the foreign object is compared on each detector, the foreign object can be detected on the top surface of the thin film. It is possible to determine whether it is attached to the surface or to the bottom surface. Furthermore, in FIG. 1(b), most of the oblique illumination light 5 is reflected by the thin film due to the foreign matter 3 attached to the lower surface of the thin film, and the scattered light is also reflected by the thin film. It goes without saying that the difference in the amount of scattered light in the directions of arrows A and B is further expanded, which is advantageous.

As explained above, the thin film can be irradiated with light from different directions, and the scattered light from foreign objects can be received from a certain direction and the respective light information can be compared and processed. Alternatively, the thin film can be irradiated with light from a certain direction. By receiving scattered light from foreign objects from different directions and comparing and processing the respective optical information,
It is possible to determine whether the foreign matter is on the front or back side of the thin film.

[Examples] Examples of the present invention will be described below with reference to the accompanying drawings.

First, the configuration of the first embodiment of the present invention will be described with reference to FIG.

In FIG. 2, the thin film 1 as an object to be inspected is attached to a support frame 6.
The support frame 6 is placed on a stage 7. The stage 7 can be moved independently in the X direction and the X direction in the xyz coordinate system in the figure.

On the side and above the thin film 1, a light source 10 as an irradiation means is provided.
and 14 are arranged for epi-illumination and oblique illumination, respectively. As these light sources 10 and 14, for example, light sources used in ordinary microscopes and the like are used.

A collimating lens 11.15 and a light amount adjustment filter 12.16 are arranged on the illumination light output side of the light source 10.14. That is, the light emitted from the light sources 10.14 is turned into substantially parallel light beams by the lenses 11.15, and then the light intensity is adjusted by the filters 12.16 so that the thin film 1 is irradiated. ing.

A photoelectric detector 20 is arranged diagonally above the thin film 1, and the scattered light from the foreign matter adhering to the thin film 1 is focused by a lens 19, and the photoelectric detector 2° generates an electric current proportional to the amount of the scattered light. It is now converted into a signal. .

Next, the arrangement of the light source 10.14 and photoelectric detector 20 will be described in detail.

The light sources 10 and 14 are arranged to irradiate light onto the thin film 1 at different incident angles. The respective incident angles are set such that, for example, the light from the light source 10 is oblique illumination, and the light from the light source 14 is episcopic illumination. Specifically, light source 1
For light from 0, the angle θ between the optical axis 13 and the thin layer 11@1 is approximately 0 to 10 degrees.

On the other hand, for the light from the light source 14, the angle formed between the front axis 17 and the thin film 1 only needs to be relatively larger than the corresponding angle on the optical axis 13 from the light source 10. Specifically, the angle is about 20 degrees or more.Next, the light @18 of the photoelectric detector 20, which is a light receiving system, is aligned with the optical axis 13 of the light source 10 and the light source 14.
The angle of the light @17 and the regular reflection optical axis of these optical axes by the pellicle is shifted, and the light scattered from the foreign object is set to be received in a so-called dark field illumination state.

Next, the operation of the optical detection system as described above will be explained.

First, if the amount of scattered light from a foreign substance attached to the upper surface (irradiation surface side) of the thin film 1, that is, the magnitude of the photoelectric signal from the photoelectric detector 20, is the same in epi-illumination and in oblique irradiation, The light intensity of each irradiation light incident on the thin film 1 is adjusted in advance by the light intensity adjustment filters 12 and 1 so that the values are the same.
Adjust from 6 legs. For the irradiation, for example, only epi-illumination is performed, and the resulting scattered light from the foreign object is detected by the photoelectric detector 20. Next, only oblique illumination is performed, and the scattered light is similarly detected. For example, by repeating this operation alternately at a fixed period and comparing the amount of change in the photoelectric signal at that time, it is possible to determine whether the foreign object is on the upper surface (surface) or the lower surface ('g & surface) of the thin film 1. can do.

By the way, as a method to perform each illumination independently, for example, when one of the light sources is lit, the other light source may be turned off, or both light sources may be lit continuously, Shutters may be provided on the optical axis of each light source, and only light from one light source may be irradiated onto the thin film 1 by opening and closing these shutters.

Next, the characteristics of the photoelectric signal obtained from the photoelectric detector 20 will be explained with reference to FIG.

3 is a diagram showing the output of the photoelectric signal of the photoelectric detector 20, (A) is a diagram showing the time change of the irradiated light unit during epi-illumination by the light source 14, and (B) is a diagram showing the oblique illumination by the light source 10. (C) shows the time change of the photoelectric signal (■) in the photoelectric detector 20 of scattered light from foreign matter attached to the upper surface (irradiation surface side) of the thin film 1. FIG. 5D is a diagram showing the temporal change of the photoelectric beam V in the photoelectric detector 20 of scattered light from a foreign substance adhering to the lower surface of the thin film 1.

As can be seen from the same figure (C), when epi-illumination and oblique illumination are alternately repeated at a fixed period, the amount of change in the photoelectric signal (Vma
x-Vmin) becomes almost zero. On the other hand, as can be seen from the same figure (D), the amount of change in the photoelectric signal V (Vmax - V
min) is relatively larger than that in the case shown in FIG. 2C, and when the illumination angle of each light source is set to an appropriate value, the value of Vmin is approximately 50% or less of the value of Vmax.

Therefore, by comparing the difference in the amount of change in the photoelectric signal, it can be determined whether the foreign object is on the top surface or the bottom surface of the thin film. That is, for example, the normalized value (Vmax-Vmin)/(Vmax÷Vmin)
If it is smaller than a predetermined value, for example 0.33, it can be determined that foreign matter is attached to the upper surface (irradiated surface side) of the thin film 1, and if it is 0.33 or more, it can be determined that foreign matter is attached to the lower surface. Further, the approximate size of the foreign object can also be known from the magnitude of the value of Vmax.

Next, a processing device for a photoelectric signal output from the photoelectric detector 20 will be described with reference to FIGS. 4 and 5.

FIG. 4 shows an example of the configuration of the signal processing device.

In this figure, the above-mentioned stage 7 includes a drive device 60.
is provided so that the movement in the xy force direction shown in FIG. 2 is performed. Control commands to the drive device 60 are issued from a control section 62.

The light source 10.14 described above is connected to a lighting control section 64, which in turn is connected to a control section 62. The lighting control section 64 controls the lighting of the light sources 10.14 alternately, as shown in FIG.

Next, the photoelectric detector 20 described above is connected via an amplifier 66 to a level detection section 68 that detects the maximum value Vmax and minimum value Vmin of the photoelectric signal, and the detection output of this level detection section 68 is are configured to be output to the comparison section 70 and the calculation section 72, respectively.

In the comparison section 70, the data on the relationship between the size of the foreign object and the photoelectric signal, which has been statistically determined and stored in advance, is compared with the human data, and the approximate size of the foreign object is determined.

Further, the calculation unit 72 calculates the sum (Vmax+Vmin) and the difference (Vmax+Vmin) of the maximum value Vmax and minimum value Vmin of the photoelectric signal.
An operation is performed to obtain each of the values (Vmax-Vmin).

The calculation output of the calculation section 72 is connected to the determination section 74. In this determination unit 74, the standardized light amount change 4
2 (Vmax-Vmin) / (Vmax +Vm
(in) is determined, and the magnitude relationship between this standardized amount of change in light amount and a predetermined value α is determined.

The value of this reference value α is not particularly limited, but is, for example, about 0°33 as explained with reference to FIG. The standardized amount of change in light amount (V+nax −Vm
in) / (Vmax+Vmin) is smaller than the reference value α, it is determined that the foreign matter is attached to the upper surface of thin film II@1, and if it is greater than the reference value α, it is determined that the foreign matter is attached to the lower surface of thin film 1. It is judged that.

Next, the control unit 62 performs necessary button control for each of the above-mentioned parts, and also has a function of outputting the coordinate values of the illumination position of the stage 7, that is, the position of the foreign object. The operation of the photoelectric signal processing device of the detector 20 will be explained with reference to the flowchart of FIG. FIG. 5 shows the operation when a photoelectric signal is output.

First, the control unit 62 issues a control command to the lighting control unit 64, and the light sources 10.14 are controlled to be lit alternately.

Next, a control command is issued from the control unit 62 to the drive unit 60, and the movement of the stage 7, that is, the scanning of the illumination position of the illumination light on the thin l1i1 is performed at a speed slower than the lighting cycle of the light source 10.14. It will be done.

During the above operation, if a foreign object is present, scattered light from the foreign object enters the photoelectric detector 20.

The photoelectric signal from the photoelectric detector 20 is amplified by an amplifier 66 and then inputted to a level detection section 68, where the maximum value V
max and minimum value Vmin are determined (step 21
reference).

Among these, the maximum value Vmax is manually inputted to the comparison section 70, where it is compared with data on the relationship between the size of the foreign object and the photoelectric signal, which has been statistically determined in advance, to determine the approximate size of the foreign object. (See step 22).

Next, the maximum value Vmax and minimum value Vmin determined by the level detection unit 68 are input to the calculation unit 72, where the V
The sum (Vmax+Vmin) and difference (Vmax-Vmin) of max and Vmin are determined, respectively (see step 23).

These determined values are each input to the determination unit 74,
Here, the normalized amount of change in light amount (Vmax - Vmin
) / (Vmax + Vmin) is calculated. Then, it is determined whether this standardized amount of change in light amount is smaller than or greater than the reference value α (step 2
(see 4).

As a result, the normalized light amount change fi (VmaX
-Vmin) / (Vmax+Vmin) or smaller than the reference value α, it is determined that foreign matter is attached to the upper surface of the thin film 1 (see step 25), and if it is greater than the reference value α, it is determined that the foreign matter is attached to the lower surface of the thin film 1. (see step 26).

On the other hand, the position of the detected foreign object on the thin film 1 is output from the control section 62.

As described above, according to this embodiment, it is possible to determine not only the size and position of the foreign object attached to the thin film 1, but also whether the foreign object is attached to the upper surface or the lower surface of the thin film 1. Can be done.

Next, a second embodiment of the present invention will be described using FIG. 6.

In this second embodiment, light of different wavelengths is irradiated onto a thin film from different angles of incidence, and scattered light from a foreign object is separated by wavelength and detected.

For this reason, as shown in FIG. 6, a wavelength selection filter 31.33 is provided in place of the filter 12.16 of the first embodiment.

Further, two photoelectric detectors 37 and 38 are provided, and a wavelength discrimination filter 36 such as a dichroic filter is inserted between these and the lens 19.

To explain an example of separating light by wavelength in the above configuration, for example, the light from the light source 14 has a wavelength that passes through the wavelength discrimination filter 36, and the light from the light source 10 has a wavelength that passes through the wavelength discrimination filter 36. wavelength selection filters 31.3, respectively, so that the wavelengths are reflected by
Make adjustments in step 3.

In this way, the light scattered from the foreign object by the light from the light source 14 will be detected only by the photoelectric detector 37 and not by the photoelectric detector 38. On the other hand, the light scattered by the foreign object by the light from the light source 10 will be detected by the photoelectric detector 37 only, and not by the photoelectric detector 38. The scattered light is detected only by the photoelectric detector 38 and not by the photoelectric detector 37.

Next, the operation of the second embodiment configured as above will be explained.

The lights emitted from the light sources 10.14 are separated by wavelength selection filters 31.33 into lights having different wavelengths. Therefore, light of different wavelengths will be irradiated onto the thin film 1 at different angles of incidence.

For example, suppose that the light source 10 performs oblique illumination, the light source 14 performs epi-illumination, and scattered light from foreign matter on the thin film 1 is detected.

Scattered light from foreign objects is separated into wavelengths of each irradiation light by a wavelength discrimination filter 36, and is incident on photoelectric detectors 37 and 38 provided corresponding to each wavelength of light, respectively, and is converted into a photoelectric signal. Considering these photoelectric signals to be converted, first of all, if we focus on the scattered light from the foreign matter adhering to the upper surface of the thin film 1, the scattered light from the light source 14 is sent to the photoelectric detector 37, and the scattered light from the light source 10 is sent to the photoelectric detector 37. If each of the irradiated lights reaches the detector 38 and the amount of light is the same, then these detection signal levels will be approximately the same.

On the other hand, regarding the scattered light from the foreign matter adhering to the lower surface of the thin film 1, most of the scattered light due to epi-illumination from the light source 14 reaches the photoelectric detector 37, whereas most of the scattered light from the oblique illumination from the light source 10 reaches the photoelectric detector 37. Since most of the light is reflected by the surface of the thin film 1, the amount of scattered light that reaches the photoelectric detector 38 is reduced.

Therefore, the detection signal amount at the photoelectric detector 37 is set to S (3
7), the amount of detection signal at the photoelectric detector 38 is set to 5 (38)
If S (37)/S (38) is a certain value, for example, 2 or more, it is determined that the foreign object is attached to the lower surface, and if it is 2 or less, it is determined that the foreign object is attached to the upper surface.

As described above, in this second embodiment, it is possible to simultaneously perform illumination from different directions and to simultaneously detect scattered light from foreign objects caused by each illumination. Therefore, there is no need to adopt a method of alternately illuminating as in the first embodiment.

In the above-described first and second embodiments, the thin film 1 is irradiated with light at different incident angles, and the scattered light from the foreign object is transmitted to the ax illumination system at a constant acceptance angle constituting a so-called dark field illumination system. However, as described above, in principle, the same effect as in the above embodiment can be obtained by simply replacing the irradiation system and the light receiving system.

This principle has been described above, but for more details
This is clearly disclosed in Japanese Patent No. 8-62543.

Next, a third embodiment having such a configuration will be described with reference to FIG. 7.

This third embodiment differs from the first embodiment in that a photoelectric detector 46.50 is placed at the position of the light source 10.14, and a light source 40 is placed at the position of the photoelectric detector 20. There is.

The light output from the light source 40 enters the thin film 1 via the lens 41, and the scattered light from the foreign matter passes through the light amount adjustment filters 44, 48 and lenses 45, 49, and then reaches the photoelectric detector 46, 50. It is designed to be incident on .

Next, the operation of the third embodiment as described above will be explained. .

The light emitted from the light source 40 is turned into a substantially parallel light beam by the lens 41, and then is irradiated onto the thin film 1 from diagonally above. Of course, oblique illumination as shown in FIG. 1(b) is convenient.

On the other hand, scattered light from foreign matter adhering to the thin film 1 is received by two photoelectric detectors 46 and 50 placed at positions that do not directly receive the irradiated light or the specularly reflected light from the beam.

The acceptance angle of the photoelectric detector 46, that is, the optical axis 43 and the thin film 1.
The angle OA formed by the light beam is set to be approximately the same as the irradiation angle when performing oblique illumination in the first embodiment, for example, from 0° to 10°.

On the other hand, the photoelectric detector 50 similarly has a light receiving angle that is approximately the same as the irradiation angle when epi-illuminating the thin film 1 in the first embodiment, that is, approximately 20° or more.

In this third embodiment, the ratio of the values of the photoelectric signals obtained from the two photoelectric detectors 46 and 50 is determined depending on whether a foreign substance is attached to the upper surface of the thin film 1 or when it is attached to the lower surface of the thin film 1. Since they are significantly different, by comparing them, it is possible to determine the surface to which foreign matter has adhered.

That is, first, photoelectric signals S (4B
) and S (50) are adjusted in advance so that they are almost the same.

Then, when comparing the photoelectric signals S (46) and S (50) caused by scattered light from foreign matter adhering to the lower surface of the thin film 1, if the ratio S (50)/S (46) is, for example, 2 or more, If this is the case, it can be determined that foreign matter is attached to the lower surface of the thin film 1, and if not, it can be determined that the foreign matter is attached to the upper surface.

As explained above, in this third embodiment, the same effects as in the first and second practical examples can be obtained.

By the way, if polarized light, particularly S-polarized light (light polarized in a direction perpendicular to the plane of incidence) is used as the irradiation light, the determination becomes easier and the reliability increases.

In other words, when S-polarized light is obliquely incident on a thin film,
Compared to the case where normal light is incident obliquely, the proportion of light that is reflected on the thin film surface is even greater, and very little light passes through the thin film and reaches the bottom surface.As a result, foreign matter may The amount of scattered light generated by the foreign object varies greatly depending on which side of the lower surface the foreign object is attached to, so it is best to compare these.

Furthermore, for this reason, in the first and second embodiments, it is not necessary to use polarized light for all the illumination light.
This means that polarized light only needs to be used at least in the case of oblique illumination.

In addition, in this invention, CC is used as the photoelectric detection means.
It is also possible to use a D camera, a camera using an imaging tube, or the like. If a photoelectric signal from a foreign object is processed according to the signal processing method shown in FIG. 5, the state of adhesion of the foreign object can be known.

Furthermore, if it is attempted to inspect the entire area of the thin film on which side of the thin film the foreign matter is present, it will take a lot of time. Therefore, for example, check the entire surface of the thin film in advance for the presence of foreign matter, record the xy coordinate values of the xyz coordinate system shown in FIG. If you inspect which side of the thin film the foreign matter is on after cleaning,
Efficient inspection becomes possible.

Furthermore, this foreign object inspection device can also be combined with an ordinary optical microscope capable of epi-illuminated dark field illumination. That is, a light source, a lens, a filter, etc. that emit light from the side at a low incident angle onto the thin film 1 may be added to the microscope. In this case, by alternating epi-dark field illumination and oblique illumination and visually observing changes in the amount of scattered light from the foreign object, it can be determined whether the foreign object is attached to the top or bottom of the thin film. can do.

By appropriately combining the application examples of the present invention described above, it will be possible to find a method suitable for actual inspection.

It goes without saying that the present invention can be applied not only to foreign matter inspection on a thin film for preventing foreign matter adhesion mounted on a reticle or a photomask, but also to general light-transmitting flat substrates.

[Effects of the Invention] As explained above, according to the present invention, it is possible to determine not only the position and size of the foreign object attached to the object to be inspected, but also whether the foreign object is attached to the upper surface of the object or the lower surface. This has the effect of making it possible to clearly determine whether there is a child in the room or not.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between the angle of illumination light with respect to foreign matter attached to a thin film and the angle of scattered light from the foreign matter, FIG. 2 is a configuration diagram showing the first embodiment of the present invention, and FIG. A diagram showing the output of a photoelectric signal in the photoelectric detector of the first embodiment, the fourth
The figure is a circuit block diagram showing an example of the configuration of a photoelectric signal processing device, FIG. 5 is a flowchart showing the main operations of the first embodiment, FIG. 6 is a block diagram showing the second embodiment of the present invention, and FIG. FIG. 2 is a configuration diagram showing a third embodiment of the present invention. [Explanation of symbols of main parts] 10.14.40...Light source, 11, 15, 19°45
．． 49... Lens, 12, 16, 44. 48... Light amount adjustment filter, 36... Wavelength discrimination filter, 31
．． 33...Wavelength selection filter, 20.37.38.4
6.50...Photoelectric detector.

Claims (7)

[Claims] (1) In a foreign object detection device that detects whether a foreign object is attached to either the front or back side of a thin film-like object having optical transparency, a first incident direction is applied to one of the surfaces of the object to be inspected. a first illumination means for emitting light from the illumination means; a first photoelectric detection means for detecting light scattered by the foreign object of the light from the illumination means; a second illumination means for emitting light from the illumination means; a second photoelectric detection means for detecting light scattered by the foreign object of the light of the illumination means; and based on detection outputs of the first and second photoelectric detection means. A foreign matter inspection apparatus comprising: a determining means for determining a foreign matter adhering surface of the object to be inspected. (2) The first and second illumination means alternately output light, the first and second incident directions are different, and the first and second photoelectric detection means are a single photoelectric conversion means. A foreign matter inspection device according to claim 1, which is also used as a foreign matter inspection device. (3) The foreign matter inspection device according to claim 1 or 2, wherein the determining means determines the foreign matter adhering surface based on the maximum value and minimum value of the detection output of the photoelectric detection means. (4) The foreign matter inspection apparatus according to claim 1, wherein the first and second illumination means each output light having different wavelengths. (5) The foreign matter inspection apparatus according to claim 1, wherein the first and second illumination means are a single illumination means that irradiates light onto the object to be inspected from either direction. (6) The foreign matter inspection device according to any one of claims 1 to 5, wherein the light output from the illumination means is polarized light. (7) The foreign matter inspection device according to claim 6, wherein the polarized light is S-polarized light.