JP3139665B2 - Pattern defect detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern defect detection apparatus using Fourier transform by light and phase conjugate light.
More specifically, the present invention relates to a pattern defect detection device using phase conjugate light generated by a liquid crystal spatial light modulator.

[0002]

2. Description of the Related Art Conventionally, as a pattern defect detecting apparatus using Fourier transform by light and phase conjugate light, there is a method using a hologram as a generating means for generating phase conjugate light. For example, an example in which this method is applied to a defect inspection of an IC photomask is disclosed in a known document “Holographic optical”.
processsing for submicrometer defect detection ''
(RLFusek et al., Pt. Eng., 24, P731, 1985).

FIG. 7 is a block diagram of a conventional pattern defect detecting device described in the above-mentioned known document. In the drawing, reference numeral 71 denotes an optical character system; 72, a signal light;
4 is a quarter-wave plate, 75 is a polarizing beam splitter, 76
Is a lens, 77 is a filter, 78 is a hologram, 79 is reference light, 80 is conjugate light, and 81 is output light.

A signal light 72, which is coherent light, is irradiated on a photomask 73, and a Fourier transform image of the photomask 73 is formed on a filter 77 by a lens 76. Spatial frequency filtering is performed by transmitting the light through the filter 77 to selectively remove components of the regular pattern, and the frequency components of the defect are recorded on the hologram 78 as interference fringes with the reference light 79. Next, the hologram 78 is irradiated with a conjugate light 80 with respect to the reference light 79, and the real image is reproduced and the same optical path is reversed, thereby extracting only the defect image as the output light 81. The advantage of this method is that the phase conjugate light generated by the hologram 78 can eliminate the effects of distortion of the lens 76 and other optical components of the system.

Further, as another conventional example, BaTiO ₃ or Bi ₁₂ SiO ₂₀ (BS
There is a method using a photorefractive crystal such as O). For example, Japanese Patent Application Laid-Open No. 62-54284 discloses an apparatus for performing this method in real time to suppress periodic characteristics and enhance aperiodic defects in a photomask used for manufacturing ICs. For performing the following.

An example in which a similar technique is applied to a photomask defect inspection for a liquid crystal panel is disclosed in the well-known document “Inspection of Result of Periodic Pattern Using BS—Effect of Inspection Area,” (Aoki et al. 53rd Applied Physics Proceedings of the Annual Conference of the Academic Society 17p-2,199
2, and 54th Annual Meeting of the Japan Society of Applied Physics 27p-D-1
1,1993).

FIG. 8 is a block diagram of a conventional pattern defect detecting device described in the above-mentioned known document. In the drawing, reference numeral 91 denotes an optical system, 92 denotes a mask, 93 denotes signal light, 94 denotes a beam splitter, and 95 denotes a beam splitter. Lens, 96 is BSO (Bi ₁₂
SiO ₂₀ ), 97 and 98 are pump lights, and 99 is output light.

In the optical system arrangement of degenerate four-wave mixing, the mask 9
The signal light 93 that has passed through 2 is Fourier-transformed by the lens 95. Depending on the light intensity on the Fourier transform plane (BSO 126 plane), a difference occurs in the generation efficiency of the phase conjugate light of each frequency component, and nonlinear filtering can be realized. Therefore, if the intensity ratio between the signal light 93 and the pump lights 97 and 98 is appropriately set, necessary components are emphasized.

In conventional pattern defect detection using only Fourier transform, the wavelength of coherent light used for filtering is determined in order to determine the criticality of a defect or a pseudo defect based on the positional relationship between the periodic pattern of the photomask and the defect. Incoherent light in different wavelength ranges is introduced along the same optical axis, and an image in which a defect distribution and a regular periodic pattern are superimposed is also taken in.

[0010]

Of the above-mentioned conventional examples, the former requires development of a hologram,
There is a problem that many objects cannot be inspected continuously in real time. Further, the object to be inspected, I
There is a problem that a filter suitable for the C photomask must be manufactured. Regarding the latter, although processing can be performed in real time and no filter is required,
It is difficult to set the measurement conditions, and depending on the setting conditions, it may take about 10 seconds for the response speed. In addition, there is a problem that a defect cannot be detected due to a light irradiation diameter on the object to be inspected. In addition, in the hologram type filtering, there is a problem that incoherent light cannot be used in the same optical system.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has been made in consideration of the above circumstances, and has been made in consideration of a problem that can be detected easily and at high speed in a regular synchronous pattern such as a liquid crystal thin film transistor substrate and an integrated circuit photomask. An object of the present invention is to provide a defect detection device.

[0012]

In order to solve the above-mentioned problems, the present invention provides: (1) generating means for generating coherent light; irradiating means for irradiating the coherent light to an object to be inspected; In a pattern defect detection apparatus including a conversion unit that performs a Fourier transform of a light beam irradiated on an inspection target object and a generation unit that generates a phase conjugate light of the Fourier-transformed light, a plurality of independent generation units that generate the coherent light are provided. Wherein the means for generating the phase conjugate light is a liquid crystal spatial light modulator, and (2)
A plurality of independent means for generating the coherent light,
Generating different wavelengths of light, or
(3) A plurality of independent laser devices that generate coherent light, the coherent light from the laser device is split into two light beams, and one light beam is irradiated on the object to be inspected, and the other light beam is irradiated on the reflection mirror. A liquid crystal spatial light modulator that forms a Fourier transform image by inputting signal light transmitted through the object to be inspected and a reference light from the reflecting mirror into substantially the same region as the Fourier transform image. An element and a monitor camera that separates and monitors the phase conjugate light reflected from the liquid crystal spatial light modulation element and detects a plurality of spatial frequency defects existing in the inspection target object. 4) In the above (3), the optical axes of the light from the plurality of laser devices are slightly shifted,
Preventing the Fourier transform images of the object to be inspected from overlapping on the liquid crystal spatial light modulator, or (5) a plurality of independent laser devices for generating coherent light;
Splitting the coherent light from the laser device into two light beams,
A half mirror that irradiates one light beam to the object to be inspected and the other light beam is incident on the liquid crystal spatial light modulator, and forms a Fourier transform image in which the signal light is incident upon being reflected by the object to be inspected, A liquid crystal spatial light modulator that causes the reference light from the half mirror to enter substantially the same area as the Fourier transform image; and a phase conjugate light reflected from the liquid crystal spatial light modulator, separated and monitored, and And a monitor camera for detecting a plurality of spatial frequency defects existing in (3) or (5).
In the above, the liquid crystal spatial light modulation device has two glass substrates coated with a transparent electrode, a liquid crystal layer and a photoconductive layer sandwiched between the glass substrates, and an object to be inspected is provided on the photoconductive layer. A Fourier transform image of an object is formed.

[0013]

According to the present invention, there is provided a pattern defect detecting apparatus comprising: means for generating coherent light; means for performing a Fourier transform on a light beam irradiated on the object to be inspected; and a phase conjugate light of the Fourier transformed light. In a pattern defect detection device provided with a means for generating light, a means for generating coherent light is a plurality of independent means, and a means for generating phase conjugate light is a liquid crystal spatial light modulating element, which is present in a photomask or the like. Defects at a plurality of spatial frequencies (including aperiods) can be detected simultaneously, easily and at high speed. Furthermore, the normal periodic pattern and the defect required for defect determination can be captured as the same image,
The determination as to whether or not a defect is present can be made easily and at high speed.

Further, when the plurality of independent means for generating the coherent light generate light having different wavelengths, the normal periodic pattern and the defect necessary for defect determination are taken in as the same image. It becomes easier to distinguish regular period patterns. In addition, since a plurality of independent means for generating the coherent light generate light of different wavelengths, a defect having a wavelength dependency of light can be easily detected, and the defect can be classified.

[0015]

Embodiments will be described below with reference to the drawings. FIG. 1 is a configuration diagram for explaining an embodiment (Embodiment 1) of a pattern defect detection device according to the present invention.
1 is a pattern defect detection device, 2a and 2b are He-Ne lasers, 3a and 3b are light, 4a and 4b are beam expanders, 5 is a half mirror, 6a and 6b are light beams, and 7 is TF.
T (Thin Film Transistor) substrate, 8 is a half mirror, 9 is a lens, 10a and 10b are signal lights, 11 is a liquid crystal spatial light modulator, 12a and 12b are light beams, 13 is a mirror, 14a and 14b are reference lights, and 15a. , 15b are phase conjugate lights, 16 is a monitor camera, 24 is a liquid crystal layer, and 26 is a photoconductive layer.

Light 3 emitted from He-Ne laser 2a
The beam diameter “a” is expanded by the beam expander 4 a and split into two light beams by the half mirror 5. One of the split light beams irradiates a liquid crystal TFT substrate 7 as an object to be inspected as a light beam 6a, passes through a half mirror 8 and a lens 9, and as a signal light 10a, a liquid crystal layer of a liquid crystal spatial light modulator 11 as a signal light 10a. Light enters the photoconductor layer 26 from the side 24. When the liquid crystal spatial light modulator 11 is arranged at the focal position of the lens 9, a Fourier transform image of the TFT substrate 7 is formed on the photoconductor layer 26 of the liquid crystal spatial light modulator 11.

The other light beam 12a is reflected by the mirror 13, and is incident as the reference light 14a on the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 14a is set to be substantially perpendicularly incident on the liquid crystal spatial light modulator 11 (incident angle 0 °). The phase conjugate light 15a reflected from the liquid crystal spatial light modulator 11 is again inverse Fourier transformed by the lens 9, separated by the half mirror 8, and enters the monitor camera 16. In addition,
The imaging surface of the monitor camera 16 is set substantially at the focal plane of the lens 9.

Similarly, the beam diameter of the light 3b emitted from the He-Ne laser 2b is expanded by the beam expander 4b and split into two light beams by the half mirror 5. One of the split light beams irradiates the TFT substrate 7 as an object to be inspected as a light beam 6b, passes through a half mirror 8 and a lens 9, and as a signal light 10b, a liquid crystal layer side 24 of the liquid crystal spatial light modulator 11 From the photoconductor layer 26. When the liquid crystal spatial light modulator 11 is arranged at the focal position of the lens 9, a Fourier transform image of the TFT substrate 7 is formed on the photoconductor layer 26 of the liquid crystal spatial light modulator 11.

The other light flux 12b is reflected by the mirror 13, and is incident as the reference light 14b on the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 14 b is set to be substantially perpendicularly incident on the liquid crystal spatial light modulator 11. The phase conjugate light 15 b reflected from the liquid crystal spatial light modulator 11 is again inverse Fourier transformed by the lens 9 and separated by the half mirror 8.
The light enters the monitor camera 16.

Here, the optical axes of the light from the He-Ne lasers 2a and 2b are slightly shifted, and the Fourier transform image of the TFT substrate 7 by the light from the respective light sources is, as shown in FIG. On the modulation element 11, it does not overlap. This is because each He-Ne laser 2a, 2
b, a Fourier transform image by the liquid crystal spatial light modulator 11
This is for independent processing (spatial frequency filtering). However, the reference lights 14a and 14b irradiate substantially the same area on the liquid crystal spatial light modulator 11.

The transmittance and the reflectance of the half mirror 5 are set to unequal values. For example, a transmittance of 20%,
If the reflectance is 60%, the light amount ratio between the signal light 10a and the reference light 14a is 1: 3, and the light amount ratio between the signal light 10b and the reference light 14b is 3: 1. Therefore, the liquid crystal spatial light modulator 1
On 1, processing (spatial frequency filtering) under different conditions can be performed on each of the He-Ne lasers 2 a and 2 b.

On the monitor camera 16, the TFT substrate 7
Are filtered at different spatial frequencies. The liquid crystal layer 24 of the liquid crystal spatial light modulator 11
Uses a homogeneous (parallel) oriented nematic liquid crystal. The polarization directions of the light beams 3a and 3b emitted from the He-Ne lasers 2a and 2b are on the plane in the plane of the paper, and the liquid crystal layer 24 is homogeneously (parallel) oriented in a direction in which the polarization can be most efficiently phase-modulated. ing.

FIG. 3 is a structural view of a liquid crystal spatial light modulator according to the present invention. In the figure, reference numerals 21a and 21b denote glass substrates,
2a and 22b are transparent electrodes, 23a and 23b are alignment films, 2
Reference numerals 5a and 25b denote spacers, and other portions having the same functions as those in FIG. 1 are denoted by the same reference numerals.

The liquid crystal spatial light modulator 11 has a nematic liquid crystal layer 24 and a liquid crystal molecule homogeneously disposed between glass substrates 21a and 21b each coated with a transparent electrode 22a or 22b made of ITO (indium tin oxide) or the like. Liquid crystal alignment films 23a and 23b for (parallel) alignment and hydrogenated amorphous silicon (a-
(Si: H) film. Note that the spacer 25 is for holding a space in the liquid crystal layer. The a-Si: H film serving as the photoconductive layer 26 was formed on the glass substrate 21b on which the transparent electrode 22b was formed by a CVD method (Chemical Vapor Deposition). The characteristics of the a-Si: H film thus formed are such that the dark conductivity is 10 ⁻¹⁰ S / cm and the photoconductivity is 10 ⁻⁷ S.
/ Cm or more, and the film thickness was 1.0 μm.

Further, a nematic liquid crystal layer 24 is formed on each of the glass substrate 21b on which the transparent electrode 22b and the photoconductive layer 26 are formed and the glass substrate 21a on which the transparent electrode 22a is formed, for homogenous (parallel) alignment. Liquid crystal alignment films 23a and 23b were formed. In this example, SiO was formed by oblique evaporation at an angle of 85 ° with respect to the normal direction of the glass substrate surface as the liquid crystal alignment films 23a and 23b.

In this embodiment, the liquid crystal alignment films 23a and 23b are formed by oblique evaporation.
Although a film is used, a liquid crystal alignment film formed by applying a rubbing treatment to polyimide or polyvinyl alcohol, or a liquid crystal alignment film formed by applying another alignment agent may be used. The liquid crystal alignment film 23a and the liquid crystal alignment film 23b formed in this way are opposed to each other, a gap is formed by the spacer 25, and the gap is filled with nematic liquid crystal.
4 was formed.

In this embodiment, the nematic liquid crystal is
It is desirable to use a material exhibiting large birefringence in order to sufficiently increase the amount of phase shift, and E44 manufactured by Merck was used. In this example, the positive dielectric anisotropy in which the direction of orientation changes from a state substantially parallel to the glass substrate surface to a state perpendicular to the glass substrate surface according to the intensity of the voltage to which the nematic liquid crystal is applied. Although the nematic liquid crystal having a negative dielectric anisotropy is used in a homogeneous alignment, the nematic liquid crystal having a negative dielectric anisotropy may be used in a homeotropic alignment. In addition, since the liquid crystal spatial light modulator 11 used in the pattern defect detection device of the present invention is required to have high spatial resolution (high resolution), it is desirable that the liquid crystal layer has a small thickness. The thickness was 2 μm.

FIG. 4 is a diagram for explaining the generation of phase conjugate light by the liquid crystal spatial light modulator composed of the liquid crystal layer and the photoconductive layer in FIG. 3, and is an enlarged view of a portion A in FIG. In the figure,
28 is an interference pattern, 29 is a phase diffraction grating,
Parts having the same functions as those in FIG. 3 are denoted by the same reference numerals.

In FIG. 3, an AC voltage 27 as shown in FIG. 3 is applied in advance between the transparent electrodes 22a and 22b. The signal light 10a and the reference light 14a are
The light passes through the liquid crystal layer 24 and enters the photoconductive layer 26. Also,
At the same time, some light is reflected at the interface between the liquid crystal layer 24 and the photoconductive layer 26. In the photoconductive layer 26, the signal light 10a and the reference light 1
An interference pattern 28 of 4a is formed. Due to the interference pattern 28, a spatial impedance distribution is formed in the photoconductive layer 26.

Further, since the liquid crystal layer 24 and the photoconductive layer 26 are electrically connected in series, these changes in impedance are reflected as spatial changes in the voltage applied to the liquid crystal layer 24. In accordance with the spatial change of the voltage, the alignment direction of the liquid crystal molecules changes, and a refractive index distribution (phase diffraction grating) 29 is formed. In this way, the interference pattern 28 is
4 is transferred. As a result, the reference light 14a reflected at the interface between the liquid crystal layer 24 and the photoconductive layer 26 is modulated by the phase diffraction grating 29 formed by the interference pattern 28. Thereby, the phase conjugate light 15a of the signal light 10a
Can occur.

The above description is based on the assumption that the signal light 10a and the reference light 14
If the light intensities a are the same, the interference occurs best and the phase conjugate light 15a can be generated. Conversely, when the signal light 10a and the reference light 14a have significantly different light intensities, the phase conjugate light 1
It becomes difficult to generate 5a.

Therefore, in FIG. 1, the fact that the light intensity pattern obtained by Fourier-transforming the TFT substrate 7 as the object to be inspected has a different light intensity depending on the magnitude of the spatial frequency component of the TFT substrate 7 is used. , Signal light 10a, 1
0b and the reference light 14a, 14b, the phase conjugate light 15
a and 15b can be reflected. That is,
On the Fourier transform plane, the light intensity of the spatial frequency component of the periodic pattern of the TFT substrate 7 increases, and the spatial frequency component of the defect relatively decreases.

Therefore, if the light intensity of the reference lights 14a and 14b is set to be equal to the light intensity from the defect,
It is possible to generate phase conjugate light of only light due to defects. Similarly, if the light intensities of the reference lights 14a and 14b are set to be equal to the light intensities from different defects, phase conjugate lights 15a and 15b of light due to different defects can be generated. That is, it is possible to take out images of various types of defects excluding the periodic pattern from the image of the TFT substrate or the like.

The light intensity of the reference lights 14a and 14b is set to T
If it is set to be equal to the light intensity of the spatial frequency component of the regular periodic pattern of the FT substrate 7, it is possible to generate the phase conjugate light of the light of the regular periodic pattern of the TFT substrate. That is, the regular periodic pattern and the defect necessary for defect determination can be captured as the same image, and the determination as to whether or not the defect exists can be performed easily and at high speed.

FIG. 5 is a block diagram for explaining another embodiment (Embodiment 2) of the pattern defect detecting apparatus according to the present invention. In the drawing, reference numeral 31 denotes a pattern defect detecting apparatus, and 32a to 32
c is a He-Ne laser, 33a to 33c are light, 34a to
34c is a beam expander, 35a and 35b are half mirrors, 36a to 36c are light beams, 37 is a TFT substrate,
38 is a half mirror, 39 is a lens, 40a to 40c are signal lights, 41a to 41c are phase conjugate lights, 42a to 42c
Is a light beam, 43 is a mirror, 44a to 44c are reference lights, 45
Denotes a monitor camera, and the other parts having the same functions as those in FIG. 1 are denoted by the same reference numerals.

In the second embodiment, processing (spatial frequency filtering) under three types of conditions can be performed using three coherent light generating means. He-N
The light 33a emitted from the e-laser 32a has its beam diameter expanded by the beam expander 34a, passes through the half mirror 35a, and is split into two light beams by the half mirror 35b. One of the split light beams irradiates the TFT substrate 37, which is an object to be inspected, as a light beam 36a, passes through a half mirror 38 and a lens 39, and outputs a signal light 40a as a signal light 40a on the liquid crystal layer side 24 of the liquid crystal spatial light modulator 11. From the photoconductor layer 26. When the liquid crystal spatial light modulator 11 is disposed at the focal position of the lens 39, the liquid crystal spatial light modulator 1
A Fourier transform image of the TFT substrate 37 is formed on one photoconductor layer 26.

The other light beam 42a is reflected by the mirror 43 and is incident as the reference light 44a on the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 44 a is set to be substantially perpendicularly incident on the liquid crystal spatial light modulator 11. The phase conjugate light 41a reflected from the liquid crystal spatial light modulator 11 is again inverse Fourier transformed by the lens 39, separated by the half mirror 38, and incident on the monitor camera 45. Note that the imaging surface of the monitor camera 45 is set substantially at the focal plane of the lens 39.

Similarly, the beam 33b emitted from the He-Ne laser 32b has its beam diameter expanded by a beam expander 34b, and is reflected by a half mirror 35a.
The light is further split into two light beams by the half mirror 35b.
One of the split light beams is irradiated as a light beam 36b on a TFT substrate 37, which is an object to be inspected, and a half mirror 38
Through the lens 39 and enters the photoconductor layer 26 from the liquid crystal layer side 24 of the liquid crystal spatial light modulator 11 as signal light 40b. When the liquid crystal spatial light modulator 11 is arranged at the focal position of the lens 39, a Fourier transform image of the TFT substrate 37 is formed on the photoconductor layer 26 of the liquid crystal spatial light modulator 11.

The other light beam 42b is reflected by the mirror 43 and enters as the reference light 44b into the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 44 b is set to be substantially perpendicularly incident on the liquid crystal spatial light modulator 11. The phase conjugate light 41b reflected from the liquid crystal spatial light modulator 11 is again subjected to inverse Fourier transform by the lens 39, separated by the half mirror 38, and enters the monitor camera 45.

Similarly, the beam diameter of the light 33c emitted from the He-Ne laser 32c is expanded by the beam expander 34c and split into two light beams by the half mirror 35b. One of the split light beams irradiates the TFT substrate 37, which is an object to be inspected, as a light beam 36c, passes through a half mirror 38 and a lens 39, and as a signal light 40c, a liquid crystal layer side 24 of the liquid crystal spatial light modulator 11 From the photoconductor layer 26. When the liquid crystal spatial light modulator 11 is disposed at the focal position of the lens 39, the liquid crystal spatial light modulator 1
A Fourier transform image of the TFT substrate 37 is formed on one photoconductor layer 26.

The other light beam 42c is reflected by the mirror 43 and is incident as the reference light 44c on the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 44c is set substantially perpendicularly to the liquid crystal spatial light modulator 11. The phase conjugate light 41 c reflected from the liquid crystal spatial light modulator 11 is inversely Fourier-transformed again by the lens 39, separated by the half mirror 38, and enters the monitor camera 45.

Here, similarly to the first embodiment, the optical axes of the light from the He—Ne lasers 32a to 32c are slightly shifted,
The Fourier-transformed images of the TFT substrate 37 by the light from the respective light sources do not overlap on the liquid crystal spatial light modulator 11. However, the reference lights 44 a to 44 c irradiate substantially the same area on the liquid crystal spatial light modulator 11.
Further, similarly to the first embodiment, the half mirrors 35a and 35b
Are set to unequal values. Therefore, on the liquid crystal spatial light modulator 11, each H
Processing (spatial frequency filtering) under different conditions can be performed on the e-Ne lasers 32a to 32c.

FIG. 6 is a block diagram for explaining still another embodiment (Embodiment 3) of the pattern defect detecting device according to the present invention. In the drawing, reference numeral 51 denotes a pattern defect detecting device;
2b is a He-Ne laser, 53a and 53b are light, 54
a and 54b are beam expanders, 55 is a half mirror, 56a and 56b are light beams, 57 is a TFT substrate, 58 is a half mirror, 59 is a lens, 60a and 60b are signal lights, 61a and 61b are phase conjugate lights, 62a and 62b. 1 is a reference light, 63 is a monitor camera, and other parts having the same functions as those in FIG. 1 are denoted by the same reference numerals.

In the first and second embodiments, the defect is detected by transmitting the coherent light through the TFT substrate 57 which is the object to be inspected.
The defect is detected by reflecting the light on the FT substrate 57.
The beam diameter of the light 53a emitted from the He-Ne laser 52a is expanded by the beam expander 54a.
The light is split into two light beams by the half mirror 55. One of the split light beams irradiates a liquid crystal TFT substrate 57, which is an object to be inspected, as a light beam 56a, passes through a half mirror 58 and a lens 59, and outputs a signal light 60a as a signal light 60a. Light enters the photoconductor layer 26 from the side 24. When the liquid crystal spatial light modulator 11 is disposed at the focal position of the lens 59, the photoconductor layer 2 of the liquid crystal spatial light modulator 11
A Fourier transform image of the TFT substrate 57 is formed on 6.

The other is incident as the reference light 62a on the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 62a is the liquid crystal spatial light modulator 1
The angle is set to be substantially perpendicular to 1 (incident angle 0 °). The phase conjugate light 61 a reflected from the liquid crystal spatial light modulator 11 is inverse Fourier transformed again by the lens 59, separated by the half mirror 58, and
Incident on. The imaging surface of the monitor camera 63 is located at the focal plane of the lens 59.

Similarly, the beam diameter of the light 53b emitted from the He-Ne laser 52b is expanded by the beam expander 54b and split into two light beams by the half mirror 55. One of the split light beams irradiates the TFT substrate 57, which is an object to be inspected, as a light beam 56b, passes through a half mirror 58 and a lens 59, and outputs a signal light 60b as a signal light 60b on the liquid crystal layer side 24 of the liquid crystal spatial light modulator 11. From the photoconductor layer 26. When the liquid crystal spatial light modulator 11 is disposed at the focal position of the lens 59, the liquid crystal spatial light modulator 1
On the one photoconductor layer 26, a Fourier transform image of the TFT substrate 57 is formed.

The other is incident as the reference light 62b on the same area of the liquid crystal spatial light modulator 11 where the Fourier transform image is incident. The reference light 62b is the liquid crystal spatial light modulator 1
1 is set to be almost perpendicular incidence. The phase conjugate light 61b reflected from the liquid crystal spatial light modulator 11 is again subjected to inverse Fourier transform by the lens 59, and the half mirror 58
And enters the monitor camera 63.

Here, similarly to the first embodiment, the optical axes of the light from the He—Ne laser 52a and the He—Ne laser 52b are slightly shifted,
As shown in FIG. 2, the Fourier transform images of the T substrate 57 do not overlap on the liquid crystal spatial light modulator 11. This is because each He-Ne laser 52a, 52b
This is for independently processing (spatial frequency filtering) of the Fourier transform image by the liquid crystal spatial light modulator 11. However, the reference lights 62a and 62b irradiate substantially the same area on the liquid crystal spatial light modulator 11.

Further, similarly to the first embodiment, the half mirror 5
5, the transmittance and the reflectance are set to unequal values. For example, as in the first embodiment, the transmittance is 20% and the reflectance is 6
If 0%, the light quantity ratio between the signal light 60a and the reference light 62a is 1: 3, and the light quantity ratio between the signal light 60b and the reference light 62b is 3:
It becomes 1. Therefore, on the liquid crystal spatial light modulator 11, the processing under different conditions (spatial frequency filtering) is applied to each of the He-Ne lasers 52a and 52b.
It can be performed.

As described above, in the description of the first, second and third embodiments, the He-Ne lasers 2a and 2b as light sources having the same wavelength are used as means for generating coherent light. This makes it easier to distinguish the defect from the regular periodic pattern when the regular pattern and the defect necessary for defect determination are captured as the same image. In addition, it is easy to detect a defect having a wavelength dependency of light, and it is also possible to classify a defect. Further, although the description has been made using the TFT substrate as the object to be inspected, an IC or a photomask of a liquid crystal panel may be used, and the present invention is not limited thereto.

In the first embodiment shown in FIG. 1, the transmittance and the reflectance of the half mirror 5 are changed in order to change the light amount ratio between the signal light 10a and the reference light 14a and the light amount ratio between the signal light 10b and the reference light 14b. However, when the wavelength of the coherent light generating means is different, it can be adjusted by an interference filter or the like. The same applies to the second and third embodiments.

In the first embodiment, in order to perform processing (spatial frequency filtering) under different conditions, the light amount ratio between the signal light 10a and the reference light 14a and the light amount ratio between the signal light 10b and the reference light 14b are changed. Is a liquid crystal spatial light modulator 1
It can also be handled by changing the specifications and operating conditions of (1). The same applies to the second and third embodiments. Further, although a nematic liquid is used for the liquid crystal layer of the liquid crystal spatial light modulator 11, a ferroelectric liquid crystal can be used. Further, by interposing a dielectric multilayer mirror between the liquid crystal layer 24 and the photoconductive layer 26 of the liquid crystal spatial light modulator 11, light incident on the photoconductive layer 26 and reflected light can be adjusted. .

[0053]

As apparent from the above description, the present invention has the following effects. (1) generating means for generating coherent light, irradiating means for irradiating the object to be inspected with the coherent light, converting means for performing Fourier transform on a light beam irradiating the object to be inspected, It has a generating means for generating phase conjugate light, and the generating means for generating coherent light is a plurality of independent means. Since the generating means for phase conjugate light is a liquid crystal spatial light modulator, it is present on a TFT substrate or the like. Multiple spatial frequency (including aperiodic) defects,
At the same time, detection can be performed easily and at high speed. Further, the regular periodic pattern and the defect necessary for the defect determination can be captured as the same image, and the determination as to whether or not the defect exists can be performed easily and at high speed. (2) In addition, when the plurality of independent means for generating the coherent light generate light of different wavelengths to capture a regular periodic pattern and a defect necessary for defect determination as the same image, It becomes easier to distinguish regular period patterns. In addition, since a plurality of independent means for generating the coherent light generate light of different wavelengths, a defect having a wavelength dependency of light can be easily detected, and the defect can be classified.

[Brief description of the drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of a pattern defect detection device according to the present invention.

FIG. 2 is an explanatory diagram of a Fourier transform image on a liquid crystal spatial light modulator according to the present invention.

FIG. 3 is a cross-sectional view illustrating a structure of a liquid crystal spatial light modulator according to the present invention.

FIG. 4 is an enlarged view of a portion A in FIG.

FIG. 5 is a configuration diagram for explaining another embodiment of the pattern defect detection device according to the present invention.

FIG. 6 is a configuration diagram for explaining still another embodiment of the pattern defect detection device according to the present invention.

FIG. 7 is a configuration diagram of a conventional pattern defect detection device.

FIG. 8 is a configuration diagram of another conventional pattern defect detection device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pattern defect detection apparatus, 2a, 2b ... He-Ne laser, 3a, 3b ... Light, 4a, 4b ... Beam expander, 5 ... Half mirror, 6a, 6b ... Light flux, 7 ... TF
T (Thin Film Transistor) substrate, 8 half mirror, 9 lens, 10a, 10b signal light, 11 liquid crystal spatial modulation element, 12a, 12b light flux, 13 mirror
14a, 14b: Reference light, 15a, 15b: Phase conjugate light, 16: Monitor camera, 24: Liquid crystal layer, 26: Photoconductive layer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-180067 (JP, A) JP-A-3-77052 (JP, A) JP-A-9-89792 (JP, A) Patent 3043962 (JP, A B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 21/84-21/958 G03H 1/00-5/00 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A generating means for generating coherent light,
A pattern comprising: irradiating means for irradiating the object to be inspected with the coherent light; transforming means for performing Fourier transform on a light beam irradiated to the object to be inspected; and generating means for generating phase conjugate light of the Fourier transformed light. In the defect detecting apparatus, the generating means for generating the coherent light is a plurality of independent means, and the generating means for the phase conjugate light is a liquid crystal spatial light modulator. 2. The pattern defect detecting apparatus according to claim 1, wherein said plurality of independent means for generating coherent light generate light having different wavelengths. 3. A plurality of independent laser devices for generating coherent light, splitting the coherent light from the laser device into two light beams, irradiating one of the light beams to an object to be inspected, and reflecting the other light beam by a reflection mirror And a liquid crystal space in which signal light transmitted through the object to be inspected is incident to form a Fourier transform image, and reference light from the reflecting mirror is incident on substantially the same region as the Fourier transform image. A light modulation element and a monitor camera that separates and monitors the phase conjugate light reflected from the liquid crystal spatial light modulation element and detects a plurality of spatial frequency defects present in the inspection target object. Pattern defect detection device. 4. An optical axis of light from the plurality of laser devices is slightly shifted so that a Fourier transform image of an object to be inspected does not overlap on the liquid crystal spatial light modulator. Item 3. The pattern defect detection device according to Item 3. 5. A plurality of independent laser devices for generating coherent light, splitting the coherent light from the laser device into two light beams, irradiating one of the light beams to an object to be inspected, and using the other light beam in a liquid crystal space. A half mirror that is incident on the light modulation element, and a signal light reflected on the object to be inspected is incident to form a Fourier transform image, and the reference light from the half mirror is incident on substantially the same area as the Fourier transform image. Liquid crystal spatial light modulator, and a monitor camera that separates and monitors the phase conjugate light reflected from the liquid crystal spatial light modulator, and detects a plurality of spatial frequency defects present in the inspection object. A pattern defect detection device characterized by the above-mentioned. 6. The liquid crystal spatial light modulator has two glass substrates provided with transparent electrodes, a liquid crystal layer and a photoconductive layer sandwiched between the glass substrates, and is provided on the photoconductive layer. 6. The pattern defect detection device according to claim 3, wherein a Fourier transform image of the inspection target object is formed.