JPH05150442A - Foreign matter inspection device - Google Patents

Abstract

PURPOSE:To efficiently set an optimum inspection region corresponding to the kind of pellicle films and pellicle frames, and to execute inspection with high accuracy without being affected by frame stray light. CONSTITUTION:Inspection light scans a rectile 1 surface in the (x) direction and the rectile 1 is moved in the (y) direction by a transfer arm 5. At this time the light generated from the rectile 1 is received by a light receiver 4 and is subjected to photoelectric conversion. A photoelectric conversion signal is sent to a signal processing part 10 and based on the signal a foreign matter inspection is carried out. A region corresponding to optical characteristics of at least one of the pellicle film 3 and the frame 2 is set as the inspection region by a discrimination part 13 by executing scanning in the (x) direction by moving the rectile 1 up to the position where the frame stray light is received.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter inspection device,
For example, the present invention relates to an apparatus suitable for inspecting foreign matter on at least one of a surface of a protective film (hereinafter referred to as a pellicle film) supported by a frame member and a photomask surface provided with the pellicle film, which is used when manufacturing a semiconductor element. is there.

[0002]

2. Description of the Related Art FIG. 4 is a perspective view schematically showing the structure of a conventional foreign matter inspection apparatus of this type. In the figure, the reticle 101 to be inspected is fixed on the transfer arm 105, and the pellicle frame 2 is placed on the pattern formation surface. A pellicle film 103 is stretched on the pellicle frame 102 so as to cover the pattern formation surface of the reticle 101. The inspection light emitted from the light source 107 obliquely enters the reticle 101 via a vibrating mirror 108 as a scanning unit. The inspection light scans the surface of the reticle 101 in a predetermined range in the x direction by the vibration of the mirror 108.

The inspection area of the reticle 101 is constant in the conventional inspection apparatus of this type, and in order to scan the entire area within the constant area, the reticle 101 is moved by the transfer arm 105 at the same time as scanning in the x direction. Is moved in the direction.
At this time, the scattered and diffracted light generated from the pattern forming surface of the reticle 101 is received by the light receiver 104 and photoelectrically converted, and the foreign matter is detected based on the output signal of the light receiver 104.

Next, the inspection area in the conventional foreign substance inspection apparatus will be described with reference to FIG. FIG. 5 shows an inspection start position 106 a on the reticle 101 to be inspected on which the pellicle film 103 is mounted by the pellicle frame 102 (the reticle 10 is not inspected by the inspection light.
1), the reticle 101 is sequentially moved in the y direction by a transfer arm (not shown) to move the inspection position to the left side of the drawing (pellicle frame 10).
2 closer to the inner wall 102a on the left side), and the inspection position 106
It shows how b is inspected. In the figure, the inspection light (incident light) incident on the reticle 101 from a light source (not shown) is indicated by a solid line, and the inspection light (received light) traveling from the surface of the reticle 101 to the light receiver 104 is indicated by a dashed line. Further, the direction of the incident light at the inspection start position 106a is I ₁ , the inspection position 1
The direction of the incident light at 06b is indicated by I ₂ .

Here, when the incident angle α (the angle formed by the normal line of the reticle 101 and the incident light) and the light receiving angle β (the angle formed by the normal line of the reticle 101 and the received light) are increased, what kind of pellicle film 103 is generally used. However, the transmittance decreases while repeating rising and falling. When the transmittance of the pellicle film 103 at at least one of the incident angle α and the light receiving angle β is not 100%,
Incident light and received light are repeatedly reflected between the pellicle film 103 and the surface of the reticle 101.

The intersection 10 of the optical paths of these incident light and received light
Inner wall 102 of pellicle frame 102 on 9a and 109b
Considering the case where there is a, the inner wall 102a of the frame is indirectly illuminated by the incident light I ₂ and generates scattered light. Then, the scattered light from the inner wall 102a is
Since it exists on the optical path of the received light, it is received by the light receiver 104 as stray light (hereinafter referred to as frame stray light).

In the conventional foreign matter inspection apparatus, the incident angle α and the light receiving angle β are set small in order to reduce the frame stray light amount, and the stray light amount can be ignored in the inspection area A (FIG. 5) in almost any pellicle film. It was configured to be reduced to a certain degree.

[0008]

However, with respect to the incident angle α, the light receiving angle β and the foreign substance inspection ability described above, the scattered light intensity from the foreign substance increases as the incident angle α and the light receiving angle β increase, and the foreign substance inspection is performed. Since the capability is improved, the inspection capability is sacrificed in the conventional foreign substance inspection apparatus. That is, in the conventional apparatus, when the pellicle film or the photomask with the pellicle film is to be inspected, the arrangement of the inspection light irradiating means and the light receiving means is significantly restricted, and the inspection accuracy is improved. I couldn't.

Further, in the prior art, since the inspection area is always constant, there is a problem that the area near the inner wall of the frame is not inspected even when a pellicle film or a pellicle frame which is relatively hard to generate scattered light is used. there were.

The present invention has been made in view of the above points, and when at least one of the surface of the pellicle film and the surface of the photomask on which the pellicle film is mounted is to be inspected, depending on the type of the pellicle film or the pellicle frame. It is an object of the present invention to provide an apparatus capable of efficiently setting an optimum inspection area and capable of performing highly accurate foreign matter inspection without being affected by frame stray light.

[0011]

In order to solve the above problems, in the present invention, a protective film (pellicle film) supported by a frame member is used.
At least one of the surface and the surface of the photomask provided with the protective film is a surface to be inspected, irradiation means for irradiating the surface to be inspected with a light beam, and light receiving for photoelectrically converting light from the surface to be inspected. And a detection means for detecting a foreign matter on the surface to be inspected based on a detection signal of the light receiving means, wherein the at least one of the frame member and the protective film has an optical property according to the optical property. An inspection area setting means for setting the inspection area on the surface to be inspected so as to be changeable is provided.

A specific configuration of the inspection area setting means in the present invention corresponds to the amount of scattered light from the frame member received by the light receiving means when the surface to be inspected is irradiated with the light beam. There is one that has a measuring means for measuring the quantity and sets the inspection region based on the measurement result of the measuring means.

Further, the inspection area setting means is provided with a storage means for storing the information measured by the measuring means for at least one of the frame member and the protective film, and the information stored in the storage means. The inspection area may be set based on the above.

[0014]

The operation of the present invention will be described with reference to FIG. Figure 3
In (A), the pellicle film 3 is held by the pellicle frame 2 placed on the pattern formation surface of the reticle 1. The inspection light I illuminates the inspection point 6 on the reticle 1 from an oblique direction, is reflected by the surface of the reticle 1 and enters the light receiver 4. In the figure, the inspection light (incident light) incident on the reticle 1 from a light source (not shown) is shown by a solid line, and the inspection light (received light) traveling from the surface of the reticle 1 to the light receiver 4 is shown by a dashed line. Further, for the sake of simplicity, only the chief ray is shown for both the incident light and the received light.

Next, in order to move the inspection point on the reticle 1, when the reticle 1 is moved in the y direction in the figure, the inner wall 2a of the pellicle frame 2 relatively approaches the inspection point. This state is shown in FIG. 3 (B), and the inspection point moves to 6 '. In FIG. 3B, the inspection light I ′ is the pellicle film 3 and the reticle 1.
The inner wall 2a of the frame is repeatedly reflected multiple times on the surface.
Illuminate point i. Further, the point d on the inner wall is on the optical axis obtained by folding back the plurality of received optical axes at the angle γ formed by the light receiver 4 and the reticle. If there is a light emitting point on this optical axis, it is incident on the light receiver 4.

At this time, there are intersections a, a, c, and d of the optical path in which the incident light repeatedly reflects and travels a plurality of times and the optical axis in which the received light optical axis is refracted a plurality of times. When the reticle 1 further moves in the y direction shown in the figure, the frame inner wall 2a passes through the respective intersection positions from the intersection D to the position of the intersection A sequentially. When the frame inner wall 2a is present at each of these intersections, the frame inner wall 2a is illuminated by the incident light and produces scattered light. The scattered light is on the optical axis obtained by bending the received optical axis back a plurality of times, and thus enters the light receiver 4.

Next, FIG. 3 (C) is a drawing corresponding to FIG. 3 (B) drawn in consideration of the solid angle of each light beam of the irradiation optical system and the light receiving optical system. In the figure, the optical paths of the outermost light rays are shown for each of the incident light and the received light, and a ', a', c ',
When the frame inner wall 2a is present in the region indicated by d), the inner wall 2a is illuminated with the inspection light, and the scattered light from the inner wall 2a enters the light receiver 4.

At this time, the incident light amount of the frame stray light is 1. The rougher the surface of the inner wall 2a is The larger the reflectance at the incident angle of the pellicle film 3 (angle α in FIG. 5) is, 3. The larger the reflectance at the light receiving angle of the pellicle film 3 (angle β in FIG. 5), 4. The smaller the number of times the incident light is reflected, The smaller the number of times the received light is reflected, The smaller the angle between the optical axis of the light receiving system and the incident surface, the larger the angle.

Therefore, in FIG. 3B, the incident light amount of the scattered light from the frame inner wall 2a becomes larger in the order of D → A,
The influence on the inspection operation becomes large. The present invention has been made paying attention to that the amount of scattered light from the inner wall of the frame depends on the above 1-3, that is, the state of at least one of the pellicle film and the pellicle frame. The inspection area that is constant regardless of the change is set according to the optical properties of the pellicle film and the pellicle frame.

That is, in the present invention, for each type of pellicle film or pellicle frame, it is necessary to measure in advance how close the inspection point and the inner wall of the frame are to incident stray light to the photodetector. Then, based on this information, an optimum inspection area (an inspection area that is not affected by frame stray light and can cover the necessary inspection range most) according to the type of the pellicle film or the pellicle frame is set.

At this time, when the pellicle film or the pellicle frame is likely to generate frame stray light (when the pellicle film has a low transmittance for the inspection light and the frame has a high reflectance), an inspection requiring an inspectable area is performed. Although it may be narrower than the range, in this case, the direction of the non-inspection reticle is changed (for example, the area left uninspected is arranged in the y direction), or only the portion close to the inner wall of the frame is incident. This can be dealt with by reducing the angle α and the light receiving angle β and performing an inspection.

When the pellicle film or the pellicle frame is less likely to generate frame stray light, for example, the pellicle frame is subjected to a low reflection treatment (such as smoothing the inner wall,
This is a process of providing a diffused reflection preventing member, and is disclosed in Japanese Patent Application No. 3-
Details about No. 56935. ), It is possible to set an arbitrary inspection area that can cover the entire required inspection range.

[0023]

Embodiments of the present invention will now be described with reference to the drawings. First, FIG. 1 is a block diagram of a foreign matter inspection apparatus according to a first embodiment of the present invention. In the figure, a pellicle frame 2 is placed on a reticle 1 so as to surround a pattern formation region, and a pellicle film 3 is stretched on the pellicle frame 2.

Inspection light (incident light) I emitted from a light source (not shown) is obliquely incident on the reticle 1 via a vibrating mirror (not shown) as a scanning means. This incident angle is preferably between 80 ° and 10 ° so that the inspection light I is not blocked by the pellicle frame 2. Inspection light I
Scans the reticle 1 with a vibrating mirror within a predetermined range in the x direction (the direction perpendicular to the paper surface). At this time, since the frame stray light does not pose a problem on the inner wall of the frame in the y direction, the scanning range in the x direction is set to a predetermined range in advance.

The reticle 1 with the pellicle film 3 is fixed on the transfer arm 5, and the transfer arm 5 is driven by the drive unit 1.
5 is movable in the y-direction, preferably rotatable in the x-y plane. The amount of movement of the transfer arm 5 in the y direction is measured by a length measuring device such as a linear encoder.
The conveyance control unit 14 controls the predetermined value based on the signal from the.

By scanning in the x direction by the vibrating mirror and moving the transport arm 5 in the y direction, the entire surface of a preset inspection region (described later) is uniformly scanned by the inspection light. At this time, the light emitted from the reticle 1 to be inspected is received by the light receiver 4 and is photoelectrically converted therein. The photoelectric conversion signal from the light receiver 4 is sent to the signal processing unit 10, and foreign matter is detected based on this signal. Signal processing for detecting a foreign matter is not particularly limited, but, for example, scattered and diffracted light from a pattern has relatively high directivity, and scattered and diffracted light from foreign matter is relatively omnidirectional. This can be utilized to discriminate the foreign matter from the regular pattern.

Further, when performing a surface inspection through the pellicle film 3 as shown in FIG. 1, it is desirable to perform sensitivity correction of the light receiver 4 according to the transmittance of the pellicle film 3. In this embodiment, the signal processing unit 10 can be controlled by commands from the pellicle transmittance measuring unit 12 and the sensitivity correcting unit 11 so that all inspections can be performed automatically. The transmittance of the pellicle is preferably measured by irradiating the pellicle film 3 with light having the same wavelength as the inspection light I at an incident angle and a light receiving angle at the time of actual inspection.

Next, the structure and operation for setting the inspection area in this embodiment will be described. In this embodiment, in order to always set the inspectable area with the same threshold value under the light receiving sensitivity condition equivalent to that in the actual foreign matter inspection, the light receiving system for foreign matter inspection (light receiver 4 in FIG. 1) is used and the pellicle frame 2 is used. It is configured to measure scattered light from. At this time, the light receiving sensitivity is
The loss corresponding to the pellicle transmittance is corrected in accordance with the instructions from the transmittance measuring unit 12 and the sensitivity correcting unit 11 described above. Further, in this embodiment, the y-direction stroke of the transfer arm 5 is set to be sufficiently larger than that of the conventional apparatus. This is because it is necessary to bring the inspection point close to the frame when measuring the inspectable area or when performing the foreign substance inspection of the reticle using the frame subjected to the low reflection processing.

To measure the inspectable area, first, the reticle 1 is moved by the drive unit 15 and the transfer arm 5 to a measurement position where the scattered light from the pellicle frame 2 can be received within a desired inspection area. FIG. 1 shows this state. Next, the vibrating mirror (not shown) scans the reticle 1 with the incident light I in the x direction, and the reflected light from the reticle 1 scans the frame inner wall 2a. At this time, the scattered light from the inner wall 2a of the frame is received by the light receiver 4 and photoelectrically converted. The photoelectric conversion signal from the light receiver 4 is input to the determination unit 13 via the signal processing unit 10.

In this determination unit 13, a threshold value is set in advance for the amount of frame stray light (set in consideration of whether it will interfere with the actual foreign substance inspection).
It is determined whether the signal from the light receiver 4 exceeds this threshold value. If it is less than or equal to the threshold value, the determination unit 13 sends a signal to the transport operation control unit 14 to move the transport arm 5 in the y direction by the drive unit 15 to further set the inspection point to the frame inner wall 2a.
Approach. Then, the determination unit 13 determines whether or not the frame stray light amount at that position exceeds a threshold value. By repeating the above operation, the position of the inspection point (the limit position in the y direction) when the frame stray light amount exceeds the threshold value is measured, and the inspectable area is determined by this.

Alternatively, the type of the frame 2 is determined by the signal from the light receiver 4 when the inner wall 2a of the frame is scanned by the reflected light from the reticle 1 at the measurement position (the state of FIG. 1) where the scattered light from the pellicle frame 2 can be received. Judge,
A suitable inspection area may be selected from among some preset inspection areas.

Further, when the frame stray light amount does not exceed the threshold value even when the inspection point is brought close to the frame inner wall 2a, that is, the frame 2 is appropriately subjected to the low reflection processing in the judging section 13 (or the pellicle film 3 is processed). When it is determined that the transmittance for the inspection light is almost 100%), an arbitrary inspection area is set within a range in which the inspection light I cannot fall on the frame 2.

In the actual foreign matter inspection, the determination unit 13
The information about the inspectable area is transmitted from the transfer operation control unit 14
The transport operation control unit 14 controls the drive unit 15 based on this information. Then, the inside of the inspection region set by the scanning in the x direction by the vibrating mirror and the movement in the y direction of the transport arm is scanned with the inspection light I over the entire surface to perform the foreign substance inspection. The inspection result is displayed on a display unit (not shown). When the set inspection area is insufficient with respect to the required inspection area, the orientation of the reticle 1 is changed (rotated on the x and y planes by the transporting means 5), and the area left uninspected remains. Perform an inspection.

Next, FIG. 2 shows a second embodiment of the present invention, which is different from the first embodiment in the structure for determining the inspectable area. The other structure is similar to that of the first embodiment. That is, in the embodiment of FIG. 2, an input unit 16 including a keyboard, a bar code reader and the like is provided instead of the determination unit 13 of FIG. 1, and the types of the pellicle film 3 and the pellicle frame 2 are input from the outside. It can be configured.

In this embodiment, the inspectable area is measured in advance for each type of pellicle film 3 and pellicle frame 2 mounted on the reticle 1 to be inspected (the measurement is performed in the same manner as in the first embodiment). ), The measurement results are stored in the apparatus for each type of pellicle film 3 and pellicle frame 2. At the time of actual inspection, the optimum inspection area is set by comparing the product types of the pellicle film 3 and the pellicle frame 2 input to the input unit 16 with the previously stored data regarding the above-described inspectable area. ..

Further, in this embodiment, in addition to the data regarding the inspectable area, the sensitivity correction value of the light receiver 4 according to the transmittance of the pellicle film 3 may be input from the outside.

In the above first and second embodiments, the example of inspecting the surface of the reticle on which the pellicle film is mounted has been described, but the foreign matter inspection apparatus of the present invention is also applied to the foreign matter inspection of the pellicle film itself. It goes without saying that you can do it.

[0038]

As described above, the foreign matter inspection apparatus of the present invention is provided with the means for setting the inspection area to be changeable in accordance with the optical properties of at least one of the pellicle film and the pellicle frame. The foreign substance inspection can be performed by efficiently setting the inspection region that can cover the most necessary inspection range without being affected by the frame stray light for at least one type of the film and the pellicle frame.
Further, according to the present invention, the arrangement of the inspection light irradiating means and the light receiving means is not significantly restricted, so that the inspection light irradiating means and the light receiving means are preferably arranged in order to improve the foreign matter detection capability. Therefore, the inspection accuracy can be improved.

[Brief description of drawings]

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

FIG. 2 is a schematic configuration diagram of a foreign matter inspection device according to a second embodiment of the present invention.

3 (A), (B), and (C) are explanatory views for explaining the operation of the present invention.

FIG. 4 is a perspective view showing a configuration of a conventional foreign matter inspection device.

FIG. 5 is an explanatory diagram of frame stray light in a conventional foreign matter inspection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reticle, 2 ... Pellicle frame, 2a ... Frame inner wall, 3 ... Pellicle film, 4 ... Photoreceiver, 5 ... Transport arm,
6, 6 '... Inspection point, 10 ... Signal processing section, 11 ... Sensitivity correction section, 12 ... Pellicle transmittance measurement section, 13 ... Judgment section, 14
... conveyance operation control section, 15 ... driving section, 16 ... input section.

Claims (3)

[Claims] 1. An irradiation means for irradiating a light beam onto the surface to be inspected, wherein at least one of the surface of the protective film supported by the frame member and the surface of the photomask provided with the protective film is used as the surface to be inspected. In a foreign matter inspection device having a light receiving means for receiving light from an inspection surface and photoelectrically converting it, and a detecting means for detecting foreign matter on the surface to be inspected based on a detection signal of the light receiving means, A foreign matter inspection apparatus comprising an inspection area setting means for setting an inspection area on the surface to be inspected so as to be changeable according to the optical property of at least one of the film and the film. 2. The inspection area setting means includes a measuring means for measuring an amount of scattered light from the frame member received by the light receiving means when the surface to be inspected is irradiated with the light beam. The inspection area is set based on the measurement result of the measuring means.
Foreign matter inspection device. 3. The inspection area setting means has a storage means for storing the information measured by the measuring means for each type of at least one of the frame member and the protective film, and the information stored in the storage means. The foreign matter inspection apparatus according to claim 2, wherein the inspection area is set based on