JPH06258233A - Defect detecting device - Google Patents

Abstract

PURPOSE:To reduce the probability of error detection, which is due to stray light, of a foreign matter and to detect a foreign matter having a small gap in high probability. CONSTITUTION:A light beam from a light source 7 is converted into a sheet light beam L2 via lens systems 8, 9 and the light beam L2 slantly irradiates an area 10 on a pellicle 1, while a light beam from a light source 11 is converted into a sheet light beam L4 via lens systems 12. 13 and the light beam L4 vertically irradiates the area 10 on the pellicle 1. Scattered light from a defect such as a foreign matter in the area 10 is condensed by a light receiving lens 14, and an image of the defect is formed on an image pickup face of a one dimensional image pickup element 15 by the condensed light. A foreign matter having a small gap is detected by scattered light of the light beam L4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reticle or a photomask used as an original plate when manufacturing a semiconductor device or the like in a photolithography process, or a foreign substance adhered to the surface of a dustproof film (pellicle) of these original plates. The present invention relates to a defect inspection apparatus suitable for application when inspecting defects such as.

[0002]

2. Description of the Related Art A reticle or photomask as an original plate (hereinafter referred to as a "reticle") when a semiconductor device, a liquid crystal display device, or the like is manufactured by a photolithography process.
There is used an exposure device that transfers the pattern formed on the photosensitive substrate through a projection optical system. If a foreign substance larger than a predetermined standard adheres to the pattern forming surface of the reticle or if there is a defect in the pattern on the pattern forming surface, the pattern formed on the photosensitive substrate becomes defective. It is necessary to inspect the presence / absence of a defect including a foreign substance, the position of the defect, the size of the defect, etc. before mounting the device on the. Also, in order to prevent foreign matter from directly adhering to the pattern forming surface of the reticle, a dustproof film called a pellicle may be stretched on both sides (or one side) of the reticle. For the reticle provided, it is necessary to inspect the surface of the pellicle for defects including foreign matter, the position of the defect, and the size of the defect.

FIG. 7 shows an example of a conventional defect inspection apparatus. In FIG. 7, a pellicle 1 made of a light-transmitting thin film is placed on a reticle 3 via a pellicle frame 2 having a rectangular frame shape. It is stretched in parallel with 3. The reticle 3 is placed on the stage 4, and the stage 4 is configured to be movable in the Y direction by the drive device 5.
The amount of movement in the Y direction is measured by a length measuring device 6 such as a linear encoder. Then, the light beam L1 emitted from the light source 7 such as a laser light source is expanded in only one direction by the cylindrical lens 8 and the condenser lens 9 to become a sheet-shaped light beam L2, which is the surface of the pellicle 1. The light is obliquely incident on the slit-shaped irradiation region 10 extending in the X direction perpendicular to the upper Y direction.

If the foreign matter 30 is present on the surface of the pellicle 1, scattered light L12 is generated from the foreign matter 30, and the scattered light L12 is collected by the light receiving lens 14, and thus collected. 1 by one-dimensional CCD etc.
An image of the foreign matter 30 in the slit-shaped irradiation region 10 is formed on the three-dimensional image pickup device 15. In this case, the one-dimensional image sensor 1
The light receiving pixels in one row 5 are arranged in a direction conjugate with the X direction on the pellicle 1, and the adhesion position in the X direction of the foreign matter 30 on the pellicle 1 is determined from the number of the light receiving pixel on the one-dimensional image sensor 15. It depends on whether the signal was obtained. Further, the position of the foreign matter 30 in the Y direction can be known from the measurement signal of the length measuring device 6 at that time. Further, the size of the foreign matter 30 can be known from the magnitude of the pixel output signal obtained from the light receiving pixel of the one-dimensional image pickup device 15. This is because the amount of scattered light generated by a large foreign substance is large and the amount of scattered light generated by a small foreign substance is small.

[0005]

In the prior art as described above, the light beam L2 is transmitted through the pellicle 1 and irradiated on the inner surface of the pellicle frame 2, and scattered light (hereinafter referred to as scattered light) unrelated to scattered light from foreign matter (hereinafter referred to as "scattered light"). , "Stray light") and the image due to this stray light is erroneously detected as a foreign matter. This will be described with reference to FIG.

FIG. 8 is a perspective view of FIG. 7 viewed from the Y direction (direction of the light receiving lens 14). In FIG. 8, a part of the sheet-shaped light beam L2 passes through the pellicle 1. Then, the light enters the area SA portion of the inner wall 2a of the pellicle frame 2. As a result, scattered light is generated from the area SA in almost all directions, and a part of the scattered light reaches a further shaded area SB of the inner wall 2a. Therefore, the scattered light from the area SA and the area SB of the inner wall 2a is condensed by the light receiving lens 14 as stray light, and the stray light is received by the one-dimensional image sensor 15 just like the scattered light from the foreign matter. The amount of such stray light depends on the pellicle 1 of the light beam L2.
The pixel output signal corresponding to stray light can be suppressed small by increasing the incident angle of the light beam L2, as will be described later.

However, the present inventor has found that at this time, there arises a disadvantage that the detection capability for a foreign substance having a low height (hereinafter referred to as "low step foreign substance") is newly reduced. That is, as shown in FIG. 9A, even if the normal high foreign matter 31 on the pellicle 1 is irradiated with the light beam L2 having a large incident angle, scattered light L13 that can be sufficiently detected is generated from the foreign matter 3. . On the other hand, as shown in FIG. 9B, the low step foreign matter 32 on the pellicle 1
When the light beam L2 having a large incident angle is irradiated onto the object, the light beam L2 is applied only to a very small portion of the foreign material because the foreign material is short, and the amount of the scattered light L14 generated becomes extremely small. It will end up.

In view of the above, the present invention can reduce the probability of erroneously detecting a foreign substance due to stray light when inspecting for defects such as a foreign substance on the surface of an object to be inspected, and can also reduce the height of a foreign substance having a low step height. An object of the present invention is to provide a defect inspection device that can reliably detect.

[0009]

A defect inspection apparatus according to the present invention is, for example, as shown in FIG. 1, an apparatus for inspecting defects on the surface of a light transmissive substrate (1).
A first light irradiation means (7-9) for obliquely irradiating the first light beam (L2), and a second light beam (L4) for substantially vertically irradiating the light transmissive substrate (1). Two light irradiation means (11 to 13), a light receiving means (14, 15) for photoelectrically converting scattered light from the defect due to the first light beam and the second light beam, and a photoelectric light from the light receiving means. From the first signal corresponding to the first light beam (L2) of the converted signal and the second signal corresponding to the second light beam (L4) of the photoelectric conversion signal, the defect And a signal processing means for discriminating the type and the size.

In this case, the first and second light irradiating means irradiate the light transmitting substrate (1) with a light beam in a time division manner, and the signal processing means thereof emits the first and second light irradiating means. The first and second signals may be extracted from the photoelectric conversion signal from the light receiving means based on the light emission timing of the irradiation means. Also, the first light beam (L2)
Is different from the wavelength of the second light beam (L4), and the light receiving means discriminates the scattered light from the defect into the first and second light beams as shown in FIG. Wavelength discriminating means (25) for obtaining the corresponding scattered light, first photoelectric conversion means (26A) for photoelectrically converting the scattered light corresponding to the first light beam separated by the wavelength discriminating means (25), It may have a second photoelectric conversion means (26B) for photoelectrically converting scattered light corresponding to the second light beam separated by the wavelength discrimination means (25).

[0011]

The principle of the present invention will be described with reference to FIG. FIG. 3 shows the main part of FIG. 1, and in this FIG. 3, the first light beam (L2) generated from the first light irradiation means.
Is obliquely incident on the light transmissive substrate (1) at an angle α. Further, the light receiving optical axis of the light receiving means (14, 15) (AX
1) and the surface of the light transmissive substrate (1) intersect at an angle β. For example, if the light transmissive substrate (1) is a pellicle, if the incident angle of the light beam with which the light transmissive substrate (1) is irradiated is 85 ° or more, the The light beam transmittance is considerably reduced. If the type of pellicle as the light transmissive substrate (1) is limited, the transmissivity of the light transmissive substrate (1) is several% for the first light beam (L1) having a certain specific wavelength. It is also possible to keep it below.

Therefore, for example, when the light transmissive substrate (1) is a pellicle, the light transmissive substrate (1) for the first light beam (L2) is set by setting both the angles α and β to 5 ° or less. ), The amount of the transmitted light (L2a) is suppressed to a few% of the amount of the first light beam (L2). Therefore, not only the amount of scattered light (L5) generated on the inner wall of the support frame (2) of the light transmissive substrate (1) is suppressed by the transmitted light (L2a), but also a part of the scattered light (L2a) is generated again. Even when the light-transmitting substrate (1) is transmitted to reach the light receiving means (14, 15), only a few percent of the scattered light (L2a) is transmitted corresponding to the transmittance of the light-transmitting substrate (1). Since it does not come, the scattered light (L2a) does not pose a problem as stray light.

However, in the defect inspection apparatus using only the first light beam (L2), as shown in, for example, FIGS. Foreign matter with a height (22) and foreign matter with a low step height (2
3), even if the size of the light transmissive substrate (1) viewed from above is about the same, the scattered light (L
7) and (L8) are compared, low step foreign matter (23)
The light amount of the scattered light (L8) becomes extremely small. Therefore,
In the conventional scattered light receiving type defect inspection apparatus that determines the size of a foreign substance according to the amount of scattered light, the size of the low step foreign substance (23) having a large size when viewed from above is regarded as a small foreign substance and the size is mistaken. I will judge. On the other hand, for example, as shown in FIGS. 4 (c) and 4 (d), the light beam (L4) is assumed to be from a direction substantially perpendicular to the light transmissive substrate (1).
Is irradiated, the amount of scattered light (L9, L10) does not depend much on the height of the foreign matter (22, 23).

Therefore, in the present invention, as shown in FIG. 3, the second light beam (L4) is irradiated substantially perpendicularly to the light transmissive substrate (1). For example, when the light-transmissive substrate (1) is a pellicle, the pellicle has a transmittance of about 80 to 100% when a light beam is applied almost vertically, and therefore the transmitted light (second light) of the second light beam (L4) ( L4a)
Is almost the same as that of the second light beam (L4). Then, the transmitted light (L4a) reaches, for example, the circuit pattern (21) on the substrate (3) on the back surface of the light transmissive substrate (1), and diffracted light (L6) is generated from this circuit pattern (21). . However, the diffracted light (L6) passes through the light transmissive substrate (1) before reaching the light receiving means (14, 15). Therefore, if the second light beam (L
4) and the first light beam (L2) have the same wavelength, and the angle β is set so that the transmittance of the light transmissive substrate (1) becomes small even with respect to the wavelength of the second light beam (L4). In that case,
The light quantity of the diffracted light (L6) entering the light receiving means (14, 15) becomes small, and the diffracted light (L6) does not reach the level of being a problem as stray light. However, the first light beam (L
When the foreign matter inspection is performed by irradiating only the second light beam (L4) without irradiating 2), the detection ability for small foreign matter is inferior.

According to the experiments by the present inventor, a general foreign matter having a size of 10 μm or more can be surely detected by the inspection using the first light beam (L2), but like the plating separated from the metal, A foreign matter that is thin but large (for example, a diameter of about 100 μm and a thickness of about several μm) has a small amount of scattered light and may not be detected. On the other hand, when the second light beam (L4) is used, such a thin and large foreign matter (low step foreign matter) can be reliably detected, but conversely, a foreign matter having a size of several tens of μm cannot be detected. It turns out. Therefore,
In the present invention, two light beams are used to compliment the disadvantages of the detection methods of each other.

The first and second light irradiating means irradiate the light transmitting substrate (1) with a light beam in a time division manner, and the signal processing means irradiates the first and second light irradiating means. When the first and second signals are extracted from the photoelectric conversion signal from the light receiving means based on the light emission timing of, the first signal and the second signal can be separated with a high SN ratio.

Further, the wavelength of the first light beam (L2) and the wavelength of the second light beam (L4) are made different from each other, and the scattered light and the second light beam corresponding to the first light beam are discriminated by wavelength discrimination. When the scattered light corresponding to is separated, the inspection time can be shortened.

[0018]

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 this example, the present invention is applied to an apparatus for inspecting a defect of a pellicle stretched on a reticle via a pellicle frame.
In FIG. 7, parts corresponding to those in FIG. 7 are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a mechanical portion of the defect inspection apparatus of this embodiment. In FIG. 1, the pellicle 1 is stretched on a reticle 3 via a pellicle frame 2, and the reticle 3 is placed on a stage 4. The table 4 is placed and can be moved in the Y direction by the driving device 5, and the amount of movement in the Y direction is measured by the length measuring device 6. The light beam L1 emitted from the first light source 7 such as a laser light source is converted into a sheet-shaped light beam L2 by the negative cylindrical lens 8 and the condenser lens 9, and the light beam L2 is moved in the X direction on the pellicle 1. The extended irradiation area 10 having a slit shape is irradiated. At this time, the angle α formed by the surface of the pellicle 1 and the light beam L2 is set to be smaller than 5 ° so that the transmittance of the pellicle 1 with respect to the light beam L2 is, for example, 5% or less. In particular, it is preferable that the wavelength and polarization state of the light beam L2 be selected such that the transmittance of the pellicle 1 is low.

On the other hand, the light beam L3 emitted from the second light source 11 such as a laser light source is converted into a sheet-shaped light beam L4 by the negative cylindrical lens 12 and the positive cylindrical lens 13, and this light beam L4 is formed. The irradiation area 10 extending in the same X direction as the irradiation area of the light beam L2 is irradiated on the pellicle 1. The incident angle of the light beam L4 with respect to the pellicle 1 is set to substantially zero, and the light beam L4
Enters almost perpendicularly to the pellicle 1.

Light scattered from a defect such as a foreign substance on the pellicle 1 is condensed by the light receiving lens 14, and the light thus condensed is projected onto the one-dimensional image pickup device 15 in the slit-shaped irradiation area 10 of the pellicle 1. An image of the foreign matter inside is formed. Pellicle 1
The adhered position of the foreign matter in the X direction can be known by the number of the light receiving pixel of the one-dimensional image pickup device 17 that has received the light, and the position of the foreign matter in the Y direction can be known by the length measurement output of the length measuring device 6 at that time. . Further, the angle β formed by the optical axis AX1 of the light receiving lens 14 and the surface of the pellicle 1 (hereinafter referred to as “light receiving angle”) β is set to 5 ° or less, and the light beam L emitted from the light source 7 is set.
The transmittance of the light beam having the same wavelength as that of No. 2 when passing through the pellicle 1 at the light receiving angle β is low. At this time, it is preferable that the light beam having the wavelength of the light beam L4 emitted from the light source 11 also has a low transmittance when passing through the pellicle 1 at the light receiving angle β, which simplifies the configuration. For this purpose, the wavelength of the light beam from the light source 7 and the wavelength of the light beam from the light source 11 may be the same.

Further, when the polarization state of the light beam L4 which enters the pellicle 1 substantially vertically is linearly polarized light which is polarized in the Y direction rather than the X direction, the diffracted light from the pattern on the reticle 3 on the lower surface of the pellicle 1 It has been experimentally confirmed by the present inventor that the light intensity of the light becomes smaller. Therefore, light polarized in the Y direction may be used as the light beam L4.
With this configuration, in the present example, as shown in FIG. 3, in the obliquely incident light beam L2, the light amount of the transmitted light L2a transmitted through the pellicle 1 is small, and the transmitted light L2a is small.
The amount of scattered light L5 generated by being scattered by the inner wall of the pellicle frame 2 is also small, and the stray light due to the light beam L2 is small.

Further, in the light beam L4 incident on the pellicle 1 substantially vertically, the transmitted light L4a which passes through the pellicle 1
Of the diffracted light L from the circuit pattern 21 on the reticle 2 on the back surface of the pellicle 1 is relatively strong.
6 can occur. However, since the light receiving angle β of the light receiving lens 14 on the optical axis AX1 is small, the diffracted light L6 hardly enters the light receiving lens 14.

The advantages of using the obliquely incident light beam L2 and the substantially vertically incident light beam L4 will be described with reference to FIG. That is, when the obliquely incident light beam L2 is used, strong scattered light L7 is obtained from a normal tall foreign substance 22 as shown in FIG. 4A, whereas FIG. As shown in (4), the scattered light L8 obtained from the short, low step foreign matter 23 is weak. On the other hand, when the almost vertically incident light beam L4 is used, relatively strong scattered light L9 is obtained from the normal tall foreign matter 22 as shown in FIG. As shown in (), the scattered light L10 obtained from the low-level foreign matter 23 having a short height is also relatively strong. Therefore, by using the light beam L4 that is incident almost vertically, it is possible to increase the detection probability of the low step foreign matter.

As a first inspection method for inspecting foreign matter on the pellicle 1 in this embodiment, the light beam L2 and the light beam L4 are always irradiated onto the pellicle 1 at the same time, and the light beam L2 and the light beam L4 are irradiated. There is a method in which the scattered light generated from the foreign matter due to each of them is received by the one-dimensional imaging device 15 without distinguishing it. In this method, in order to remove signals due to stray light and electrical noise, only pixel output signals of a certain value or more among the pixel output signals obtained from the one-dimensional image pickup device 15 are detected as signals from foreign matter. Furthermore, if the detected pixel output signal is divided into, for example, three levels according to the intensity, the approximate size of the foreign matter can be determined.

The second inspection method for inspecting foreign matter on the pellicle 1 in this embodiment is the light beam L2 and the light beam L4.
Are alternately turned on, and the scattered light generated from the foreign matter due to each of the light beam L2 and the light beam L4 is time-divisionally distinguished and detected. FIG. 2 shows an example of the configuration of the signal processing unit of this example in the case of performing time division processing. In FIG. 2, the control unit 16 alternately turns on the light sources 7 and 11. Then, the pixel output signal output from the one-dimensional image sensor 15 is converted into a digital signal via the analog / digital (A / D) converter 17, and the A / D converter 17 when the light source 7 is turned on. The output signal from the first storage unit 1
8 and A / D when the light source 11 is turned on
The output signal from the converter 17 is stored in the second storage unit 19.

Then, the output signal output from the first storage unit 18, that is, the pixel output signal SH corresponding to the obliquely incident light beam L2, and the output signal output from the second storage unit 19, that is, the vertically incident light. The pixel output signal SV corresponding to the beam L4 is supplied to the calculation unit 20. The calculation unit 20
The signals SH and SV are processed to output a foreign matter detection signal S1 indicating the presence or absence of a foreign matter, a foreign matter rank signal S2 indicating the size (rank) of the foreign matter, and a low step foreign matter signal S3 indicating whether or not the foreign matter is a low step. .

Next, referring to the flowchart of FIG.
An example of the operation when performing the foreign matter inspection in a time sharing manner will be described. First, in step 101 of FIG. 5, the light source 7 for oblique incidence is turned on, and the light scattered by the foreign matter on the pellicle 1 by the irradiation of the light beam L2 is received by the one-dimensional image sensor 15 to obtain a pixel output signal. SH is stored in the first storage unit 18 (step 102). Next, the light source 11 for vertical incidence is turned on (step 103), and the light scattered by the foreign matter on the pellicle 1 by the irradiation of the light beam L4 is received by the one-dimensional image sensor 15 to obtain the pixel output signal SV. Is stored in the second storage unit 19 (step 104). The subsequent operation is the operation of the arithmetic unit 20 of FIG.

Then, in step 105, it is judged whether or not the pixel output signal SH corresponding to the obliquely incident light is larger than the detection threshold V _{1, and} if (V ₁ <SH), the foreign matter detection signal S 1 is turned on (for example, high level). After setting to "1") (step 106), the approximate size of the foreign matter is judged from the magnitude of the pixel output signal SH (step 107). In this case, the detection thresholds V ₁ , V ₂ , and V ₃ are φ10 μm,
The signal intensity is equivalent to a foreign substance having a size of φ50 μm or φ100 μm (however, a general foreign substance that is not a low step foreign substance). Therefore, if (V ₁ <SH ≦ V ₂ ), φ10 to φ
The foreign matter rank signal S2 is determined by determining that the foreign matter has a size of 50 μm.
Set the level of A to the value of A rank (step 10
8).

If (V ₂ <SH ≦ V ₃ ), it is determined that the foreign matter has a size of φ50 to φ100 μm, and the level of the foreign matter rank signal S2 is set to the value of B rank (step 109). , (V ₃ <SH), it is determined that the particle is a large particle of φ100 μm or more, and the particle rank signal S2 is set to the value of C rank (step 110). The values of the foreign matter detection signal S1 and the foreign matter rank signal S2 are set for each pixel of the one-dimensional image sensor 15 or for each predetermined length unit.
Following step 110, in step 111 in FIG.
After moving the reticle 3 by a predetermined amount in the Y direction via the mounting table 4, the operations in and after step 101 are repeated.

Further, in steps 108 and 109, the size of the foreign matter is determined to be rank A and rank B, respectively. However, there is a possibility that the foreign material having a low level difference of rank C is erroneously determined to be a small foreign matter. Therefore, step 108
And 109, the process proceeds to step 112, and it is checked whether or not the pixel output signal SV corresponding to vertical incidence is larger than a predetermined detection threshold V ₄ . The detection threshold value V ₄ is a value based on the pixel output signal SV obtained when the vertically incident light beam L 4 is irradiated on the C-rank foreign matter on the pellicle 1. Therefore, when (V ₄ <SV) is established, it means that the foreign matter of low step difference of C rank is detected, and therefore the routine proceeds to step 113, where the low step foreign matter signal S3 is detected.
Is turned on (for example, high level “1”), and the foreign matter rank signal S2 is set to a value of C rank. Thereafter, the operation shifts to step 111. On the other hand, if (V ₄ ≧ SV) in step 112, the foreign substance is not a low step foreign substance, and therefore the operation directly proceeds to step 111. The value of the low step foreign matter signal S3 is also set for each pixel of the one-dimensional image sensor 15 or for each predetermined length unit.

In step 105, (V ₁ ≧
Even in the case of SH), there is a possibility that a foreign matter with a low step difference of C rank is mistakenly missed. Therefore, the process proceeds from step 105 to step 114, and it is checked whether or not the pixel output signal SV corresponding to vertical incidence is larger than the detection threshold V ₄ . Then, when (V ₄ <SV) is satisfied, it means that a foreign matter with a low step of rank C is detected, and therefore step 1
Moving to 15, the low step foreign matter signal S3 is turned on, and the foreign matter rank signal S2 is set to the value of C rank. Thereafter, the operation shifts to step 111. On the other hand, if (V ₄ ≧ SV) in step 114, it is not a low step foreign matter, so in step 116, the foreign matter inspection signal S1 is turned off (for example, low level “0”), and then step 111 is performed. Transition.

In FIG. 1, by repeating the foreign substance inspection operation of FIG. 5 while moving the reticle 3 and the pellicle 1 stepwise in the Y direction via the stage 4,
A foreign matter inspection of the entire surface of the pellicle 1 is performed. This inspection result is collated with the foreign matter management standard of the pellicle. For example, if even one foreign matter of C rank is detected, it is determined that the pellicle 1 is unusable, and if foreign matter of B rank or A rank is detected, the foreign matter is detected. The pass / fail judgment is made according to the number of detected foreign matters of rank.

Next, another embodiment of the present invention will be described with reference to FIG. Since the structure of the mechanical portion of this example is almost the same except for the light sources 7 and 11, the light receiving lens 14 and the one-dimensional image pickup device 15 of FIG. 1, only the light receiving system is shown in FIG. Further, as the light source 7 and 11 of the present embodiment 1, the light source each generating a light beam L1 and the wavelength lambda ₂ of the light beam L3 having a wavelength lambda ₁ is used, is different from the wavelength lambda ₁ and wavelength lambda ₂ . The angle α at which the light beam L2 of FIG. 1 is incident and the light receiving angle β of the light receiving system are both set so that the transmittance of the pellicle 1 becomes smaller for the light beams having the wavelength λ ₁ and the wavelength λ ₂ .

Scattered by foreign matter on the pellicle 1 in FIG. 1,
The scattered light L11 entering the light receiving lens 24 of this example in FIG. 6 includes scattered light of wavelength λ ₁ corresponding to the obliquely incident light beam and scattered light of wavelength λ ₂ corresponding to the vertically incident light beam. include. A dichroic mirror (wavelength selection mirror) 25 is provided after the light-receiving lens 24, and the scattered light of wavelength λ ₁ is transmitted through the dichroic mirror 25 to form an image of a foreign matter on the one-dimensional image pickup device 26A, and the scattered light of wavelength λ ₂ is formed. The scattered light is reflected by the dichroic mirror 25 and forms an image of the foreign matter on the one-dimensional image pickup device 26B. One-dimensional image sensor 26
From A and 26B, pixel output signals corresponding to scattered light of wavelength λ ₁ and wavelength λ ₂ , respectively are output. And
The pixel output signal corresponding to the scattered light of the wavelength λ ₁ corresponds to the pixel output signal SH corresponding to the oblique incidence of FIG. 2, and the pixel output signal corresponding to the scattered light of the wavelength λ ₂ corresponds to the vertical incidence of FIG. Since it corresponds to the pixel output signal SV, the foreign matter inspection can be performed thereafter by, for example, the processing of step 105 and subsequent steps in FIG.

As described above, in this example as well, the angle α and the light receiving angle β in FIG. 1 are set so that the transmittance of the light beam at the pellicle 1 is small, and therefore the scattered light on the inner wall of the pellicle frame 2 is set. Stray light caused by the diffracted light due to the pattern of the reticle 3 and the reticle 3 can be reduced, and the foreign matter inspection can be performed at a high SH ratio. Further, since the light sources 7 and 11 are turned on at the same time and the pixel output signals corresponding to the both are discriminated by the wavelength discrimination, the foreign matter inspection can be performed at high speed.

In the above-described embodiment, the light beam is applied to the slit-shaped illumination area on the pellicle. However, for example, the light beam is applied in a spot shape on the pellicle and the light beam is used by a vibrating mirror or the like. The present invention can be similarly applied to a system in which scanning is performed in the X direction. As described above, in the case of the method of scanning the spot-like light beam using the vibrating mirror or the like, a single light receiving element can be used instead of the one-dimensional image pickup element.

Further, in the above embodiment, the inspection object is the pellicle stretched on the reticle, but the present invention can be applied as it is to the case where the reticle itself is the inspection object. That is, even when inspecting for defects such as foreign matter adhering to the surface of the reticle itself, it is necessary to reduce stray light, etc., which passes through the surface of the reticle and is reflected by the side surfaces and enters the light receiving system. The present invention is effective because it is necessary to accurately detect As described above, the present invention is not limited to the above-described embodiments, and various configurations can be taken without departing from the gist of the present invention.

[0039]

According to the present invention, defects such as ordinary foreign matters are inspected under a small amount of stray light by using the light beam obliquely irradiated to the surface to be inspected from the first light irradiation means. can do. For low step foreign matter,
Since the scattered light of the light beam that enters the surface to be inspected substantially perpendicularly from the light irradiating means becomes strong, it can be accurately detected with a high probability.

When the signal corresponding to the first light beam from the first light irradiation means and the signal corresponding to the second light beam from the second light irradiation means are separated in a time division manner. Has the advantage that the SN ratio of both signals is high. Also, the first
A signal corresponding to the first light beam from the light irradiation means of
When the signal corresponding to the second light beam from the second light irradiation means is separated by wavelength discrimination, there is an advantage that the inspection time is short.

[Brief description of drawings]

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

FIG. 2 is a functional block diagram showing a signal processing unit when performing time division processing in the embodiment of FIG.

FIG. 3 is a perspective view showing a state of a light beam in the vicinity of a pellicle of the mechanical section of FIG.

4 (a) and 4 (b) are diagrams showing scattered light by obliquely incident light beams, and FIGS. 4 (c) and 4 (d) are diagrams showing scattered light by vertically incident light beams. is there.

5 is a flow chart showing an example of an operation when performing a foreign matter inspection in the embodiment of FIG.

FIG. 6 is a configuration diagram showing a light receiving system of another embodiment of the present invention.

FIG. 7 is a perspective view showing a conventional defect inspection apparatus.

8 is a partially cutaway perspective view showing a state of an inner wall of the pellicle frame of FIG. 7. FIG.

FIG. 9 is a diagram for explaining a problem of a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pellicle 2 Pellicle frame 3 Reticle 4 Mounting stage 5 Driving device 7,11 Light source 14,24 Light receiving lens 15, 26A, 26B One-dimensional imaging device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // H01L 21/66 J 7630-4M

Claims (3)

[Claims] 1. An apparatus for inspecting a surface defect of a light transmissive substrate, comprising: first light irradiation means for obliquely irradiating the light transmissive substrate with a first light beam; Second light irradiating means for irradiating the second light beam substantially vertically, light receiving means for photoelectrically converting scattered light from the defect due to the first light beam and the second light beam, and the light receiving means Of the defect type and the second signal of the photoelectric conversion signal corresponding to the first light beam and the second signal of the photoelectric conversion signal of the second light beam. A defect inspection apparatus comprising: a signal processing unit that determines a size. 2. The first and second light irradiating means irradiate the light-transmissive substrate with a light beam in a time division manner, and the signal processing means includes the first and second light irradiating means. 2. The defect inspection apparatus according to claim 1, wherein the first and second signals are extracted from the photoelectric conversion signal from the light receiving means based on the timing of light emission. 3. The wavelength of the first light beam is different from the wavelength of the second light beam, and the light receiving means discriminates the wavelength of scattered light from the defect to detect the first and second light beams. A wavelength discriminating means for obtaining scattered light, a first photoelectric conversion means for photoelectrically converting scattered light corresponding to the first light beam separated by the wavelength discriminating means, and a wavelength discriminating means for separating. 2. The defect inspection apparatus according to claim 1, further comprising a second photoelectric conversion unit that photoelectrically converts scattered light corresponding to the second light beam.