JPH05288688A - Method and apparatus for inspecting foreign matter - Google Patents

Abstract

PURPOSE:To correct the sensitivity of the detected signal of scattered light by using both of the polarized-light-beam transmittance of a light transmitting member corresponding to an incident angle by scanning and the non-polarized-light-beam transmittance of the light transmitting member corresponding to the emitting angle of the detecting light path of the scattered light by the scanning. CONSTITUTION:In the detection of foreign matter on a circuit pattern, a polarized light beam is made to scan on the circuit pattern through a pellicle film 1, and the scattered light generated from the foreign matter, on which the polarized light beam is applied is detected through the pellicle film 1. The foreign matter is judged based on the size of the detected signal of the scattered light. A correcting circuit 12 accumulates the polarized-light-beam transmittance of the pellicle film 1 corresponding to the incident angle and the scattered transmittance of the pellicle film 1 corresponding to the emitting angle of the detecting light path of the scattered light for every fluctuating position X of the polarized light beam. The reciprocal of the product value of the poralized-light-beam transmittance and the non-polarized-light-beam transmittance, which are read out at the position X, is multiplied with the detected signal of the scattered light from a photoelectric detector 13, and the correcting operation is performed. A transmittance operating circuit 14 operates the polarized-light-beam transmittance from the output of a detector 34 and the non-polarized-beam transmittance from the output of a detector 35 in reference to the output of a detector 39.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects a scattered light from a foreign substance on a surface to be inspected through the light transmissive member by scanning a polarized beam on the surface to be inspected on which the light transmissive member is mounted. The present invention relates to a foreign substance inspection device for determining the foreign substance based on the detection signal of the scattered light, for example, a foreign substance inspection device for detecting a foreign substance on the circuit pattern surface of a semiconductor manufacturing mask (reticle) having a pellicle film mounted thereon.

[0002]

2. Description of the Related Art A polarizing beam is scanned on a surface to be inspected, scattered light from a foreign matter on the surface to be inspected is detected by a detection optical system, and the size of the foreign matter is discriminated by the level of a detection signal of the scattered light. The foreign material inspection method that has been put to practical use has been put to practical use for various purposes. For example, a foreign matter inspection apparatus for detecting foreign matter on the circuit pattern surface of a semiconductor manufacturing mask (reticle) is employed for the purpose of preventing defects in the circuit pattern formed on the wafer. ..

Generally, the surface to be inspected for detecting such foreign matter is required to have a high degree of cleanliness. When a light-transmissive member is attached to the surface to be inspected so that new foreign matter is not added to the surface to be inspected or unnecessary chemical reaction such as oxidation does not occur in an environment where the cleanliness is a little poor There is. For example, in the case of a semiconductor manufacturing mask, a supporting frame is arranged around the circuit pattern and a pellicle film is stretched,
A technique for cutting off a circuit pattern from the outside has already been put into practical use.

When foreign matter is detected on the surface to be inspected on which the light transmissive member is mounted, the inspection light is made incident on the surface to be inspected through the light transmissive member, and scattered light from the foreign matter on the surface to be inspected is
The light enters the detection optical system through the light transmissive member. here,
The intensity of scattered light generated by the inspection light transmitted through the light transmissive member is greater than the intensity of scattered light generated by a foreign substance of the same size attached on the surface to be inspected on which the light transmissive member is not attached, The transmittance of the light transmissive member with respect to the inspection light is reduced. Furthermore, the intensity of the scattered light that passes through the light transmissive member and enters the detection optical system is reduced to the transmittance of the light transmissive member for the scattered light when passing through the light transmissive member. Therefore, the level of the detection signal due to the foreign matter on the surface to be inspected on which the light transmissive member is mounted is the same as the level of the detection signal due to the foreign matter on the surface to be inspected on which the light transmissive member is not mounted. It is as low as the product of the transmittance of the member for the inspection light and the transmittance of the light transmissive member for the scattered light.

Therefore, in order to determine the size of a foreign matter on the surface to be inspected on which the light transmissive member is mounted and the size of a foreign material on the surface to be inspected on which the light transmissive member is not mounted to be equal, It is necessary to correct and calculate the detection signal due to the foreign matter on the surface to be inspected on which the transparent member is mounted by [1 / (transmittance of the light transmissive member with respect to inspection light x transmittance of the light transmissive member with respect to scattered light)] times. ..

However, the transmittance of the light transmissive member for the inspection light changes depending on the incident angle of the inspection light, and the transmittance of the light transmissive member for the scattered light is the emission angle of the scattered light toward the detection optical system. Change according to. The incident angle of the inspection light and the emission angle of the scattered light toward the detection optical system differ depending on the scanning position of the inspection light. Especially, the thickness of the light transmissive member is about the wavelength of the inspection light and the inspection light is a monochromatic light. In this case, the wavelength selectivity due to the thickness of the light transmissive member is added. For this reason,
If the incident angle is slightly different, the transmittance of the light transmissive member for the inspection light changes significantly, and if the output angle toward the detection optical system is slightly different, the transmittance of the light transmissive member for the scattered light changes significantly. .. In other words, the level of the detection signal is significantly different if the same foreign matter on the same surface to which the light-transmissive member is attached adheres to different scanning positions.

Therefore, at each scanning position on the surface to be inspected, the transmittance of the light transmissive member for the inspection light and the transmittance of the light transmissive member for the scattered light are set in advance and detected according to the scanning position. A foreign matter inspection method for correcting and calculating a signal has been proposed.

An example of a foreign matter inspection device for correcting and calculating a detection signal according to a scanning position is shown in Japanese Patent Laid-Open No. 63-208746. Here, foreign matter is detected on a circuit pattern of a semiconductor manufacturing mask (reticle) having a pellicle film mounted thereon, and a surface to be inspected (reticle) is scanned in the Y direction while scanning the laser beam in the X direction. The scattered light from the foreign matter on the surface to be inspected is detected by a plurality of photoelectric detectors arranged in a fixed positional relationship with respect to the sending and laser beam sending system. Here, since both the incident angle of the laser beam and the outgoing angle of the scattered light incident on the photoelectric detector have a one-to-one correspondence with the scanning position in the X direction, if the scanning position in the X direction is designated. , The transmittance at the time of entering the laser beam and the transmittance at the time of emitting the scattered light are both determined, and these two types of transmittance stored in the memory in advance are called to correct the scattered light detection signal. is doing. For example, the transmittance of these two types is 60% and 5
If it is 0%, the level of the detection signal is reduced to 30% (0.6 × 0.5) as compared with the case without the pellicle film, and the detection signal is automatically (1/0 . 3) It is amplified twice.

The two types of transmittance used here are stored in the memory through the actual measurement operation performed prior to the foreign matter detection. That is, the range of the incident angle of the laser beam determined by the positional relationship between the laser beam transmitting system and the surface to be inspected (reticle) during the actual foreign matter inspection, and the laser
Two angle groups are set, which correspond to the range of the emission angle of the scattered light incident on the photoelectric detector, which is determined by the positional relationship between the beam transmitting system, the surface to be inspected, and the detection optical system. Actual inspection light (laser beam) is emitted at each angle of the two angle groups, and an actual light transmitting member (pellicle film) is used.
Incident on the inspection light (ray) at two angle groups.
The transmittance of the light transmissive member with respect to the beam is measured. The transmittance may be measured in units of 1 degree within the range from the minimum value to the maximum value in the two angle groups.

[0010]

Problems to be Solved by the Invention JP-A-63-2087
According to the foreign matter inspection apparatus of Japanese Patent No. 46, the detection signal is corrected for each scanning position. Therefore, it is possible to accurately discriminate two foreign matters attached to different scanning positions by the detection signal, and the foreign matter on the surface to be inspected on which the light transmissive member is mounted and the foreign matter on the surface to be inspected on which the light transmissive member is not mounted. The foreign matter can be accurately discriminated by the detection signal. However, when foreign matter is detected using a polarized beam, it has been found that the transmittance actually measured by the method disclosed in JP-A-63-208746 cannot be accurately corrected.

In general, laser light having a specific polarization direction is often used, and a polarization beam having a specific polarization direction with respect to a surface to be inspected is a circuit pattern on the surface to be inspected. In some cases, it is used for the purpose of relatively strengthening the detection signal of the foreign matter as compared with the detection signal of the above-mentioned one, and making the presence of the foreign matter on the surface to be inspected stand out. However,
Even when irradiated with a polarized beam, the scattered light from the irregular reflection surface of the foreign matter has its polarization state collapsed, and the polarized beam transmittance and scattered light transmittance of the light transmissive member at the same incident angle are large. Different (see Figure 3).

Therefore, the transmittance measured by injecting the inspection light (polarization beam) into the light transmissive member is regarded as the scattered light transmittance, and the scattered light detection signal is corrected and calculated.
In the method disclosed in Japanese Patent No. 746, the error in the magnitude of the detection signal with respect to the size of the foreign matter on the surface to be inspected is increased, and the detection signal causes the foreign matter on the surface to be inspected on which the light transmissive member is not attached. The discrimination and the discrimination between the foreign matters attached to different scanning positions on the same surface to be inspected are not accurate.

The present invention relates to a foreign matter detection method using the transmittance of a light transmissive member, which is regarded as the transmittance of scattered light due to foreign matter, when using a polarized beam for inspection light, and the transmittance of scattered light due to foreign matter. The foreign matter inspection apparatus capable of accurately measuring the transmittance of the light transmissive member regarded as, that is, the foreign matter detection method and the foreign matter inspection apparatus capable of correcting the detection signal more accurately than the foreign matter inspection apparatus disclosed in Japanese Patent Laid-Open No. 63-208746. Is intended to provide.

[0014]

A foreign matter detecting method according to claim 1, wherein a polarization beam is scanned on a surface to be inspected on which a light transmissive member is mounted, and the foreign matter on the surface to be inspected is passed through the light transmissive member. In the foreign matter inspection method for detecting scattered light from a light source and discriminating the foreign matter by the detection signal of the scattered light, the polarization beam transmittance of the light transmissive member according to the incident angle by the scanning and the scattering by the scanning. It is a method of correcting the sensitivity of the detection signal of the scattered light by using both the non-polarized transmittance of the light transmissive member according to the emission angle of the detection light path of light.

The foreign matter detecting method according to a second aspect is the method for inspecting a foreign matter according to the first aspect, wherein the non-polarizing beam having a wavelength substantially the same as that of the polarizing beam is used as the non-polarizing beam transmittance. ..

According to another aspect of the present invention, there is provided a foreign matter inspection device which scans a polarized beam on a surface to be inspected having a light transmissive member, and detects scattered light from the foreign matter on the surface to be inspected through the light transmissive member. In the foreign matter inspecting apparatus for discriminating the foreign matter based on the detection signal of the scattered light, first measuring means for actually measuring the transmittance of the light transmissive member with respect to the polarized beam depending on the incident angle of the scanning, and the scanning. Second measuring means for actually measuring the transmittance of the light-transmissive member for the non-polarized beam having substantially the same wavelength as the polarized beam according to the outgoing angle of the detected light path of the scattered light by the above-mentioned polarized light. And a correction operation circuit for correcting the detection signal of the scattered light by using both the transmittance for the beam and the transmittance for the non-polarized beam.

A foreign matter inspection apparatus according to a fourth aspect is the foreign matter inspection apparatus according to the third aspect, wherein the second measuring means includes a depolarizing means for depolarizing the polarized beam to convert it into a non-polarized beam. , A measuring optical system for detecting the intensity of specularly reflected light by causing the non-polarizing beam to enter a light transmissive member at an angle corresponding to the exit angle of the scattered light detecting optical path by scanning, and And a non-polarization beam transmittance calculation circuit for calculating the transmittance for the polarized beam.

A foreign matter inspection apparatus according to a fifth aspect is the foreign matter inspection apparatus according to the third aspect, wherein the first measuring means is the intensity of specularly reflected light by the light transmissive member of the polarized beam scanned on the surface to be inspected. A scanning reflected light detector for detecting the light intensity, and a polarized beam transmittance calculation circuit for calculating the transmittance for the polarized beam from the intensity of the reflected light.

A foreign matter inspection apparatus according to a sixth aspect of the present invention is the foreign matter inspection apparatus according to the fourth aspect, in which a non-polarizing beam is made incident on the light transmissive member at one or more representative angles of the measurement optical system. Of the non-polarizing beam, and a non-polarizing beam transmittance calculating circuit for calculating the transmittance of all the non-polarizing beams necessary for the correction calculating circuit from the transmittance at the representative angle. It was done.

[0020]

In the foreign matter detecting method according to the present invention, instead of the transmittance of the light transmissive member for the inspection light (polarization beam), the non-polarized light having substantially the same wavelength as the polarization beam of the light transmissive member is used. The transmittance of the beam is regarded as the actual transmittance of the scattered light due to the foreign matter, and the correction calculation of the detection signal is performed. This is because the transmittance of the light transmissive member with respect to the polarized beam scattered light scattered by the irregular reflection surface of the foreign matter and collapsing the polarization state is more than that of the polarized beam with respect to the polarized beam. It is based on the recognition that it is closer to the transmittance for an unpolarized beam of approximately the same wavelength. However, in the correction calculation corresponding to the incidence of the scanning inspection light, the inspection light (polarization beam) of the light transmissive member is used as in the foreign matter inspection apparatus disclosed in Japanese Patent Laid-Open No. 63-208746.
The transmittance for is used.

Polarized beam transmittance of the light transmissive member according to the incident angle by scanning, and scattered light transmittance of the light transmissive member according to the exit angle of the detection light path of scattered light by scanning (polarized beam) Is substituted for the non-polarized beam having substantially the same wavelength) and is set for each scanning position on the surface to be inspected and used for correction calculation of the detection signal of scattered light. The input of these numerical values is the numerical value theoretically calculated based on the incident angle range of the polarized beam, the outgoing angle range of the scattered light, the thickness of the light transmitting member, the wavelength of the polarized beam, etc. Although it may be manually set in correspondence with each intersection of the matrix of XY coordinates on the inspection surface, like the foreign matter inspection apparatus disclosed in Japanese Patent Laid-Open No. 63-208746, it is possible to set an actual object prior to actual foreign matter inspection. The light transmissive member may measure and store the polarized beam transmittance and the non-polarized beam transmittance. Further, since the polarized beam transmittance and the non-polarized beam transmittance have a constant relationship according to the thickness of the light transmitting member, one of the polarized beam transmittance and the non-polarized beam transmittance is used. Only one may be measured, and the other may be calculated from this measured value or obtained by a comparison table.

In the foreign matter inspection apparatus according to the third aspect, prior to the actual foreign matter inspection, an actual light transmissive member is used to measure and store the polarized beam transmittance and the non-polarized beam transmittance. The detection signal obtained by the actual foreign matter inspection is corrected and calculated based on these numerical values. Polarized beam with real light-transmissive material
Measurement of the beam transmittance and the non-polarized beam transmittance can be performed with the polarization beam transmitting system used for the actual foreign substance inspection, while maintaining the supported state of the surface to be inspected during the actual foreign substance inspection. However, like the foreign matter inspection apparatus disclosed in Japanese Patent Laid-Open No. 63-208746, a transmittance measurement dedicated position independent of the actual foreign matter inspection location is set, and the foreign matter is located at this measured position. A dedicated light-transmitting optical system independent of the inspection light-transmitting optical system may be arranged.

Since the polarized beam is scanned on the surface to be inspected during the foreign matter inspection, the intensity of the polarized beam that can reach the foreign matter on the surface to be inspected is determined by the incident angle of the polarized beam (scanning position). ), The intensity of scattered light detected by the detection optical system depends on the intensity of the polarized beam reaching the foreign matter and the outgoing angle of the scattered light toward the detection optical system. It depends on the transmittance of the light transmissive member corresponding to the (scanning position). When the first measuring means actually measures the transmittance of the polarized beam, the polarized beam is incident on the light transmissive member in the incident angle range of the polarized beam covering the scanning position on the surface to be inspected. Then, the intensity of the transmitted light or the reflected light is measured, and the required polarization beam transmittance is calculated from this measured value. When the second measuring means actually measures the non-polarized beam transmittance, the non-polarized beam is incident on the light transmissive member in the emission angle range of the scattered light covering the scanning position on the surface to be inspected. The intensity of transmitted light or reflected light is measured and the required non-polarized beam is obtained from this measured value.
The system transmittance is calculated. The polarized beam transmittance and non-polarized beam transmittance thus obtained are stored so as to be extractable in correspondence with the scanning position. Then, in the actual foreign matter inspection, the correction arithmetic circuit calls the detection signal of the scattered light detected by the detection optical system corresponding to the scanning position, and transmits the polarized beam transmittance and the non-polarized beam transmittance. Both are used to perform the correction calculation.

In the foreign matter inspection device according to the fourth aspect, many members can be shared by the first measuring means and the second measuring means. The depolarizing means is means for temporally selectively using the measuring optical system as the first measuring means and the second measuring means, that is, a polarizing plate for forming detection light (polarization beam) and detection light (polarization beam).
Although a scattering plate or an optical fiber-bundle that breaks the polarization state of (1) can be inserted and withdrawn, a means for partially sharing the measurement optical system between the first measuring means and the second measuring means, that is, , The optical path of the polarized beam or the non-polarized beam emitted from the light source is divided into two, and the non-polarized beam is provided in one optical path.
In the case of a beam, a polarizing plate may be used, and in the case of a polarizing beam, a scattering plate or an optical fiber bundle may be fixedly attached. When the measurement optical system is used differently in time, there are many common points in the procedure of calculating the transmittance from the intensity of reflected light or transmitted light, and the non-polarization beam transmittance calculation circuit is used as a polarization beam transmittance calculation circuit. Can also be shared.

In the foreign matter inspection apparatus according to the fifth aspect, the light-transmitting optical system for actually performing the foreign matter inspection can be shared by the first measuring means. The scanning reflected light detector has a size and a mounting position capable of detecting the intensity of specularly reflected light by the light transmissive member of the polarized beam scanned by the light transmitting optical system on the surface to be inspected over the entire scanning width. On the other hand, the polarized beam transmittance calculation circuit calculates the transmittance for the polarized beam from the intensity of the specularly reflected light detected by the scanning reflected light detector.

In the foreign matter inspecting apparatus according to the sixth aspect, the non-polarization beam transmittance calculating circuit analogizes as the non-polarization beam transmittance of the light transmissive member according to the emission angle range of scattered light by scanning. It adopts the value. That is, the measurement optical system does not actually measure the intensity of the reflected light for all angles within the emission angle range of the scattered light due to scanning, but does not measure the non-polarized beam at one or more representative angles set within the emission angle range. The light is made incident on the light transmissive member and the intensity of the specularly reflected light is detected. Then, the non-polarization beam transmittance calculation circuit analogically calculates the transmittances for all the non-polarization beams necessary for the correction calculation circuit from the transmittance at this representative angle.

[0027]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a foreign matter inspection apparatus according to the first embodiment, FIG. 2 is a diagram showing an incident angle of a polarized beam and an outgoing angle of scattered light in the foreign matter inspection apparatus of FIG. 1, and FIG. FIG. 4 is a diagram of the transmittance of the pellicle film, and FIG. 4 is a circuit diagram of the correction calculation circuit and the transmittance calculation circuit in the foreign matter inspection apparatus of FIG.
Here, similarly to the foreign matter inspection apparatus disclosed in Japanese Patent Laid-Open No. 63-208746, the actual measurement position of the transmittance independent of the actual foreign matter inspection location is set, and the polarized beam and the non-polarized beam are set. Although the light source is shared by and, the optical system dedicated to the transmittance measurement independent of the detection optical system for inspecting foreign matter (first and second optical systems).
(Measuring means) is provided.

In FIG. 1, a pellicle film 1 stretched on a support frame 2 is provided above the circuit pattern of the reticle 3. Foreign matter on the circuit pattern is detected by the pellicle film 1
The polarized beam is scanned on the circuit pattern through the pellicle film 1 and scattered light generated by the foreign matter irradiated with the polarized beam is generated.
It is performed by detecting the foreign matter through the detector and discriminating the foreign matter based on the magnitude of the scattered light detection signal. The scanning of the polarized beam is as follows.
This is performed by oscillating the polarization beam in the X direction perpendicular to the paper surface and moving the reticle 3 in the Y direction, so that the positional relationship between the light sending optical system and the detection optical system for detecting foreign matter is fixed. Therefore, the incident angle of the polarized beam and the outgoing angle of the scattered light detecting optical path are uniquely determined by the swinging position (x) of the polarized beam.

The light-transmitting optical system for detecting foreign matter includes a light source 4 for outputting a polarized beam of laser light and a beam splitter.
6, a reflection mirror 8, an optical scanning mirror 9 which is vibrated by the driving unit 10, and a scanning lens which covers the scanning range of the optical scanning mirror 9 to form a focal point of a polarization beam on a circuit pattern. 1
1, etc., the detection optical system for detecting a foreign matter includes a photoelectric detector 13 and the like for detecting scattered light from a foreign matter. Actually, two or more (13a, 13b) photoelectric detectors 13 are symmetrically arranged around the oscillation center of the polarization beam on the circuit pattern surface, and each includes a condenser lens and the like. (See Figure 6)

Prior to the actual foreign matter detection, the correction arithmetic circuit 12 transmits the polarization beam transmittance of the pellicle film 1 according to the incident angle and the scattering of the pellicle film 1 according to the outgoing angle of the scattered light detecting optical path. The light transmittance (substituted by the transmittance for a non-polarized beam having substantially the same wavelength as the polarized beam) is stored for each swing position (x) of the polarized beam, and is called at the swing position (x). A correction calculation is performed by multiplying the detection signal of the scattered light from the photoelectric detector 13 by the reciprocal of the product of the polarized beam transmittance and the non-polarized beam transmittance.

On the other hand, the means for measuring the polarization beam non-transmission and the non-polarization beam transmissivity using the actual pellicle film 1 uses the rotating mirror 22 to pass the non-polarization beam 23 through the optical paths 28 to 28. Two
It is displaced in the range of 9 to set various incident angles with respect to the pellicle film 1, and the intensity of the specularly reflected light 30 by the pellicle film 1 is detected. The light transmission optical system includes an optical fiber bundle 17, a field stop 19, an aperture stop 20, and a lens 2 for depolarizing the polarization beam 16 and converting it into a non-polarization beam 18.
1, a rotating mirror 22, a lens 24, a mirror 25, and a lens 26. The detection optical system includes a lens 31, a mirror 32, a lens 33, a beam splitter 36, a polarizing plate 34 for extracting the same polarization component as the polarization beam, photoelectric detectors 34, 35, and the pellicle film 1. Non-polarizing beam 2 incident on
3 including a photoelectric detector 39 for detecting the intensity of
The aperture shape of the field stop 19 is projected on the pellicle film 1 with the amount of light passing through 0. Photoelectric surfaces of the photoelectric detectors 34 and 35 are arranged at positions conjugate with the aperture stop 20 having the pellicle film 1 as a reflection surface. The transmittance calculation circuit 14 includes a photoelectric detector 39.
The polarization beam transmittance is calculated from the detection output of the photoelectric detector 34, and the non-polarization beam transmittance is calculated from the detection output of the photoelectric detector 35. To calculate the transmittance, divide the reflected light intensity by the incident light intensity to obtain the reflectance,
The difference from the total reflectance (1-reflectance) is taken as the transmittance. This is because the absorptance of the pellicle film 1 can be neglected in the wavelength range (visible light range) of light generally used as a light source.

In the foreign matter inspection device thus constructed,
First, the reticle 3 is carried into the transmittance measurement position on the right side,
The rotating mirror 22 is rotated 27 so that the non-polarizing beam 23 is incident on the pellicle film 1 within the incident angle range by scanning, and the intensity of the reflected light 30 is measured by the photoelectric detector 34. next,
Rotation mirror so that the non-polarization beam 23 is incident on the pellicle film 1 within the emission angle range of the detection of scattered light by scanning.
22 is rotated and the photoelectric detector 35 measures the intensity of the reflected light 30. Then, the rotating mirror 22 is rotated by 90 degrees so that the non-polarizing beam 18 is entirely incident on the photoelectric detector 39, and the intensity of the incident light 30 on the pellicle film 1 is measured. Based on these measured values, the "polarized beam transmittance depending on the incident angle by scanning" calculated by the transmittance calculating circuit 14 and the "non-polarized beam depending on the outgoing angle of the scattered light detection optical path by scanning". The "transmissivity" is stored in the correction arithmetic circuit 12 as an output t in a state in which it can be called in correspondence with the XY coordinate values of the circuit pattern.

After that, the reticle 3 is sent to the foreign matter detection position and the foreign matter on the circuit pattern is detected. Light source 4
The polarization beam 7 obtained by removing the incident light 16 from the polarization beam 5 output from the optical fiber bundle 17 into the optical fiber bundle 17 is an optical scanning mirror 9
Is oscillated in the X direction on the circuit pattern. on the other hand,
When the reticle 3 moves in the Y direction and a foreign matter enters the scanning line 1, scattered light is emitted from the foreign matter with which the polarized beam 7 is irradiated to the upper space, and a small part of the scattered light is detected in the detection optical path direction. Then, the light enters the photoelectric detector 13. Correction arithmetic circuit 12
Then, the polarization beam output from the drive unit 10 as the output s.
The irradiation position of the polarization beam 7 on the circuit pattern is discriminated from the swing position (x) of the beam 7 and the Y coordinate output from the Y-direction feed mechanism, and the corresponding "corresponding to the incident angle by scanning is determined. The "polarized beam transmittance" and "non-polarized beam transmittance corresponding to the outgoing angle of the detection optical path of scattered light by scanning" are called to correct the detection signal of the photoelectric detector 13.

In the foreign matter inspection apparatus of FIG. 1, while the foreign matter is being detected by the reticle 3, the next reticle is set at the transmittance measurement position on the right side, and the polarized beam transmittance by the actual pellicle film is set. And the non-polarized beam transmittance is measured. Further, since the intensity of the incident light 30 on the pellicle film 1 is measured by making the non-polarizing beam 18 incident on the photoelectric detector 39, even if the output of the light source 4 changes with time, the reflectance (final The transmittance can be accurately measured.

In FIG. 2, (a) is a polarization beam by scanning.
The change in the incident angle of the beam is shown in (b). The polarizing beam 7 in FIG. 1 is swung in the X direction (direction perpendicular to the paper surface) with the front side as the + back side being +, and the polarization beam 7 is swung according to the swing position x from L to R. The incident angle of 7 changes to θ _iL to θ _{iC to} θ _iR , while the emission angle of the scattered light detection optical path changes to θ _dL to θ _{dC to} θ _dR .

3, in the foreign matter inspection apparatus and reticle shown in FIG. 1, the pellicle film 1 has a thickness of 1 μm and a polarization beam.
Since the polarization beam 7 is a monochromatic light having a wavelength of about 0.6 μm of the beam 7, the wavelength selectivity of the pellicle film 1 is added, and the polarization beam 7 of the pellicle film 1 is added according to the incident angle. The transmittance i with respect to changes significantly. However, the change of the transmittance of the pellicle film 1 with respect to the scattered light from the foreign matter according to the incident angle is close to the change of the transmittance d of the pellicle film 1 with respect to the non-polarized beam, and the polarization beam is changed according to the incident angle. It changes more gently than the transmittance i for the frame 7. Therefore, in the method described in the foreign matter inspection apparatus of Japanese Patent Laid-Open No. 63-208746, the scattered light transmittance is replaced by the inspection light transmittance (polarized beam transmittance in the case of FIG. 1). An error corresponding to the difference between the transmittance d for the polarized beam and the transmittance i for the polarized beam 7 occurs. Further, in the diagram of FIG. 3, the transmittance i for the polarized beam is actually measured by the foreign matter inspection apparatus of FIG.
The range p in which is measured is the range corresponding to θ _iL to θ _{iC to} θ _iR in FIG. 2A, and the range q in which the transmittance d for the unpolarized beam is measured is shown in FIG. Only the range corresponding to θ _{dL to} θ _{dC to} θ _dR .

In FIG. 4, photoelectric detectors 13a and 13b are provided.
The output signal of is amplified by amplifiers (preamplifiers) 40 and 41 and input to variable amplifiers 42 and 43. The variable amplifiers 42 and 43 change the amplification degree according to the scanning angle output from the driving unit 10 of the scanning mirror 9, that is, the scanning position in the X direction. This is to correct that the foreign object signal at a position far from the photoelectric detector has a smaller signal amount than the foreign object signal at a position closer to the photoelectric detector even without the pellicle 1. For example, for the photoelectric detector 13a located on the back side of the reticle 3, the distance R from the photoelectric detector 13a is shorter at the point R on the back side than the point L on the front side on the scanning line 1,
Since the received foreign matter signal becomes large, the amplification factor is reduced as it approaches the point R on the far side, so that the same foreign matter signal can be obtained at any position on the scanning line 1. In this way, the signals 44 and 45 output from the variable amplifiers 42 and 43 become the signals immediately before the correction of the light amount decrease due to the transmittance of the pellicle film.

The pellicle transmittance correction value at the transmittance measurement position on the right side of FIG. 1 is determined prior to the actual foreign matter inspection. At this time, the rotating mirror 22 is rotated by the driving unit 46 of the rotating mirror 22, and in the photoelectric detector 34, the non-polarized beam is reflected on the pellicle film, and the beam splitter-3.
Only the polarization component of the light divided by 6 passes through the polarization element 37 and is converted into an electric signal. If the light quantity of the polarized beam output from the laser light source 4 is always constant, the reflectance can be obtained only by multiplying the electric signal obtained from the photoelectric detector 34 by a count. This count is given by the amplification of amplifier 47. When the rotating mirror 22 is driven by the drive unit 46 so that θ _i changes within the range of θ _iC to θ _iR ,
The reflectance R (θ _i ) can be obtained between _iC and θ _iR , but since the pellicle film does not absorb light, the incident transmittance T (θ _i )
Is calculated by T (θ _i ) = 1−R (θ _i ).

This processing is performed by the calculation unit 48. Further, as shown in FIG. 2A, the x position on the scanning line 1 and the incident angle θ _i
Since the relationship is determined as a device, the incident transmittance T according to x when θ _i and x are converted by the conversion unit 49.
_i (x) is known. Further, the photoelectric detector 35 outputs electrical information of the pellicle reflectance of the non-polarized beam, the amplifier 50 obtains the reflectance R (θ _d ), and the calculator 51 calculates T (θ _d ) = 1. -R (θ _d ), the received light transmittance T (θ
_d ) is calculated. Further, the conversion unit 52 calculates the received light transmittance T _d (x) based on FIG. In the multiplier 53, the incident transmittance T _i (x) obtained by the conversion unit 49 and the received light transmittance T _d (x) obtained by the conversion unit 52 are first multiplied to obtain T (x) and then detected. The reciprocal of T (x), T (x) ^-1, is calculated as a value for sensitivity correction.

In FIG. 1, photoelectric detectors 13a and 13b are provided.
Are symmetrically arranged (see FIG. 6), and the pellicle transmittance correction value when viewed from the photoelectric detector 13a is T (x).
^{If it is -1} , the pellicle transmittance correction value in the photoelectric detector 13b is obtained by inverting the sign of x, that is, T (-
It goes without saying that x) ⁻¹ is sufficient, and this calculation is performed in the calculation unit 54. The above two data, that is, T
(x) ⁻¹ and T (−x) ⁻¹ are stored in the memories 55 and 56, respectively.

Now, returning to the foreign matter signal processing, the correction data T (x) ^-1 is sequentially read from the memories 55 and 56 in accordance with the output signal 57 of the optical scanning position (x) of the optical scanning drive unit 10. T
(-X) ^-1 is output and is multiplied by the foreign matter signals 44 and 45 before the pellicle transmittance correction in the multipliers 57 and 58.
The signals thus obtained are converted into digital signals by A / D converters (analog / digital converters) 59 and 60, respectively, and if both signals are equal to or more than a certain value by an AND circuit 61. For example, it is detected as a foreign substance. This means that the surface of the reticle naturally has a circuit pattern in addition to foreign matter, but the diffracted light from the circuit pattern has a strong directivity, and diffracted light enters both of the two photoelectric detectors 13a and 13b. This is because the foreign matter alone is detected by distinguishing between the circuit pattern and the foreign matter by utilizing the property that nothing happens.

FIG. 5 is a schematic view of the foreign matter inspection apparatus of the second embodiment, and FIG. 6 is a perspective view of the optical system of the foreign matter inspection apparatus of FIG. Here, the transmittance of the pellicle film is measured at the same position where the foreign matter is detected prior to the foreign matter detection, and the light-transmitting optical system for detecting the foreign matter is used as it is as the light-transmitting optical system for measuring the transmittance. A photoelectric detector 100 for measuring the pellicle transmittance was provided.

In FIGS. 5 and 6, the basic light-transmitting optical system for detecting a foreign matter is the same as that of the first embodiment, but a non-polarizing beam is used here. The foreign matter inspection apparatus according to this embodiment includes a light source 4 that outputs a non-polarized beam.
The beam splitter 6, the polarizing plate 70, the reflection mirror 8, the optical scanning mirror 9 vibrated by the driving unit 10, the scanning range of the optical scanning mirror 9 is covered, and the polarization beam is polarized on the circuit pattern. −
The detection optical system for detecting a foreign matter includes a photoelectric detector 13 and the like for detecting scattered light from the foreign matter. Furthermore, in this embodiment,
Photoelectric detector 10 for measuring incident transmittance by a polarized beam
0 is set. The photoelectric detector 100 is a plurality of photoelectric detectors arranged at intervals.

Similar to the first embodiment, the correction arithmetic circuit 12 detects the polarized beam transmittance of the pellicle film 1 according to the incident angle by scanning and the scattered light by scanning prior to the actual detection of foreign matter. The scattered light transmittance of the pellicle film 1 (substituting the transmittance for a non-polarized beam having substantially the same wavelength as the polarized beam) according to the outgoing angle of the optical path is used for each swing position (x) of the polarized beam. Correction by multiplying the detection value of scattered light from the photoelectric detector 13 by the product value of the polarization beam transmittance and the non-polarization beam transmittance stored in the oscillation position (x) of the polarization beam. Carry out operations.

In the foreign matter inspection device thus constructed,
When the reticle 3 is carried into the position where the foreign matter detection is started,
The pellicle film 1 is scanned by the polarization beam via the polarizing plate 70, and the photoelectric detector array 100 measures the intensity of specularly reflected light at an incident angle corresponding to the discrete value at the scanning position x. Then, the polarization beam transmittance calculated by the transmittance calculating circuit 14 on the basis of these reflected light intensities is stored in the correction calculating circuit 12 in association with the scanning position (x) by the optical scanning mirror 9. Also in this embodiment, the polarization beam transmittance of the scanning position x which does not correspond to the discrete value of the actually measured scanning position x is calculated by analogy based on the measured values of both sides and stored. The analogy calculation is performed by an interpolation method, a method of approximating the least squares by a higher-order equation such as a quartic equation, or the like.

Thereafter, the actual foreign matter detection is performed in the same manner as in the embodiment of FIG. 1 by scanning the polarization beam through the polarizing plate 70 with the optical scanning mirror 9, and the correction arithmetic circuit 12 , The stored detected polarized beam transmittance and non-polarized beam transmittance are used to correct the detection signal by the photoelectric detector 13.

In FIG. 6, the device configuration after the field stop 19 is partly simplified, but is almost the same as that after the field stop 19 in FIG.
The length of the photoelectric detector 100 in the x direction is long so that the pellicle reflected light can be received without fail even when optical scanning is performed. In this case, the configuration after the field stop 19 in FIG. 6 is also simplified as compared with FIG. Because the non-polarizing beam is used, no fiber is needed, and the photoelectric detector 1
Since 00 plays the role of measuring incident transmittance,
Since the photoelectric detector 34, the polarization element (analyzer) 37, and the beam splitter 36 are unnecessary, the photoelectric detector 3
In addition to increasing the amount of light entering 5 and improving S / N,
The rotating mirror 22 does not need to have the incident angle θ in the range of θ _ic to θ _ir . In this embodiment, the light source 4 which emits the polarized beam may be used and the incident transmittance may be measured using the photoelectric detector 100. In this case, polarization state releasing means such as the fiber-17 is required.
Further, the polarizing plate 70 may be configured to be able to be withdrawn from the optical path 7. The non-polarizing beam transmittance of the pellicle necessary for correcting the detection signal can also be obtained by retreating the polarizing plate 70 and allowing the non-polarizing beam to enter the pellicle and repeating the same operation. ..

As an application common to the above inventions, a polarization laser for inspecting a foreign substance or a combination of a laser and a polarization element and a laser for measuring pellicle transmittance are separately provided. A linear polarization He-Ne laser is used for foreign matter inspection, and a random polarization He-Ne laser is used for transmittance measurement. The pellicle transmittance is divided into a random (non-polarized) component and a polarized component. You may measure. In this case, the only difference is that no optical fiber is used as the depolarizing element.

Furthermore, the present invention does not limit the light incident angle, the light receiving angle, the light scanning, etc. of the foreign matter inspection apparatus, and, for example, microscopically inspects the foreign matter on the reticle through the pellicle by the epi-illumination dark field irradiation method. It is applied not only to the case but also to an apparatus for inspecting defects such as foreign matters through a light transmissive substrate, not limited to the pellicle.

[0051]

According to the foreign matter detecting method of claims 1 and 2,
Even if the polarized beam is used as the inspection light, the foreign matter on the surface to be inspected on which the light transmissive member is mounted can be detected without unevenness in sensitivity, and the detection accuracy is improved. Further, it is possible to accurately discriminate the foreign matter on the surface to be inspected without mounting the light transmissive member or to discriminate the foreign matter adhering to different scanning positions on the same surface to be inspected.

According to the foreign matter inspection apparatus of the third aspect, since the required transmittance is measured by using the actual light-transmitting member, the correction of the detection signal is accurate.

According to the foreign matter inspection apparatus of the fourth to fifth aspects, since the optical system can be shared, the optical system for measuring the transmittance can be simple.

According to the foreign matter inspection apparatus of the sixth aspect, the required measurement of the transmittance is simplified.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a foreign matter inspection apparatus according to a first embodiment.

FIG. 2 is a diagram showing an incident angle of a polarized beam and an outgoing angle of scattered light in the foreign matter inspection apparatus of FIG.

FIG. 3 is a diagram of the transmittance of the pellicle film of FIG.

4 is a circuit diagram of a correction calculation circuit and a transmittance calculation circuit in the foreign matter inspection apparatus of FIG.

FIG. 5 is a schematic diagram of a foreign matter inspection device according to a second embodiment.

FIG. 6 is a perspective view of an optical system of the foreign matter inspection apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pellicle film 2 Support frame 3 Reticle 4 Light source 6 Beam splitter 8 Reflection mirror 9 Optical scanning mirror 10 Drive part 11 Scanning lens 12 Correction arithmetic circuit 13 Photoelectric detector 14 Transmittance arithmetic circuit 17 Optical fiber bundle 19 Field stop 20 Aperture stop 21 Lens 22 Rotating mirror 24 Lens 25 Miller 26 Lens 31 Lens 32 Miller 33 Lens 34 Photoelectric detector 35 Photoelectric detector 36 Beam splitter 37 Polarizing element 39 Photoelectric detector

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area H01L 21/027

Claims (6)

[Claims] 1. A polarized beam is scanned on a surface to be inspected on which a light transmissive member is mounted, and scattered light from foreign matter on the surface to be inspected is detected through the light transmissive member, and the scattered light is detected. In the foreign matter inspection method for determining the foreign matter with a signal, the polarization beam transmittance of the light transmissive member according to the incident angle by the scanning,
A foreign matter inspection method, wherein the sensitivity of the scattered light detection signal is corrected by using both the non-polarized light transmittance of the light transmissive member according to the outgoing angle of the scattered light detection optical path by the scanning. 2. The foreign matter inspection method according to claim 1, wherein the non-polarized light transmittance is a transmittance for a non-polarized beam having substantially the same wavelength as the polarized beam. 3. A scattered beam from a foreign object on the surface to be inspected is detected by scanning the polarized beam on the surface to be inspected on which the light transmissive member is mounted, and the scattered light is detected. In a foreign matter inspecting apparatus for discriminating the foreign matter by a signal, first measuring means for actually measuring the transmittance of a light transmissive member with respect to a polarized beam according to an incident angle in the scanning, and a detection optical path of the scattered light in the scanning. Second measuring means for actually measuring the transmittance of the light-transmissive member for the non-polarized beam having substantially the same wavelength as the polarized beam according to the outgoing angle of the polarized beam.
A foreign matter inspecting apparatus, comprising: a correction calculation circuit that corrects the detection signal of the scattered light by using both the transmittance for the beam and the transmittance for the non-polarized beam. 4. The foreign matter inspection apparatus according to claim 3, wherein the second measuring means depolarizes the polarized beam to convert it into a non-polarized beam, and the non-polarized beam. Detection of scattered light by scanning Measurement optical system that detects the intensity of specularly reflected light by entering the light-transmissive member at an angle according to the exit angle of the optical path, and the transmittance from the intensity of the reflected light to the non-polarized beam And a non-polarization beam transmittance calculation circuit for calculating. 5. The foreign matter inspection apparatus according to claim 3, wherein the first measuring means detects the intensity of specularly reflected light by the light transmissive member of the polarized beam scanned on the surface to be inspected. And a polarization beam transmittance calculation circuit for calculating the transmittance for the polarization beam from the intensity of the reflected light. 6. The foreign matter inspection apparatus according to claim 4, wherein the measurement optical system detects the intensity of specularly reflected light by causing a non-polarizing beam to enter the light transmissive member at one or more representative angles. Further, the non-polarization beam transmittance arithmetic circuit is adapted to perform an analogy calculation of the transmittances for all the non-polarization beams necessary for the correction arithmetic circuit from the transmittances at the representative angles. Inspection equipment.