JPH10332533A - Birefringence evaluation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To configure a high speed high accuracy birefringence evaluation system by picking up a birefringence image through an observation optical system as an analyzable image data using a sharp color plate method. SOLUTION: When a sample SP is inserted between a first polarizer 13 and a full wavelength plate 22, an optical signal is subjected to phase difference equal to the combined phase difference of the sample SP and the full wavelength plate 22. Consequently, the wavelength of the light subjected to phase difference is shifted from the reference wavelength by an amount corresponding to the birefringence of the sample SP. Consequently, the hue being observed is varied as the spectral transmittance of an optical signal LB passing through a second polarizer 23 varies and the birefringence can be estimated with higher sensitivity than the cross Nicol method. More specifically, a birefringence image representative of variation in the hue of the sample SP is picked up by means of a color image pickup element 24 and delivered to a data acquisition system 2. It is presented on a display in real time and subjected to a required processing in parallel with image observation on the monitor 40, as required.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for evaluating birefringence, and more particularly to an observation apparatus for observing the polarization of a birefringence phase difference of a sample as a birefringence image based on a sensitive color plate method which can be intuitively recognized through the eyes. The present invention relates to an optical system and a device for image processing.

[0002]

2. Description of the Related Art In recent years, with the rapid development of optical erotronics equipment equipped with optical elements such as lenses, prisms, optical disks and optical phase films, the quality of optical elements has been increased, for example, optical uniformity. There is a need to increase. Therefore, a technique for inspecting and evaluating the quality of these optical devices with high accuracy and shortening the time required for the improvement in productivity to improve productivity is particularly important in mass production sites.

For example, in recent years, polymer materials such as plastics, which are excellent in light weight, moldability, impact resistance and can be provided at a relatively low cost, are often used as optical elements such as optical disk substrates. Since many materials exhibit birefringence due to the molecular orientation formed at the time of molding, controlling the molecular orientation to prevent performance degradation is one of the important issues.

In addition, a polymer film for a wide-angle view, which is attached to a liquid crystal display substrate, is required to have birefringence for canceling birefringence caused by liquid crystal molecules. The state of orientation and the in-plane birefringence uniformity are important quality evaluation items.

[0005] In such an optical disk substrate or a polymer film, it is necessary to grasp the state of molecular orientation three-dimensionally with high accuracy in order to evaluate the quality. Therefore, as one of such quality evaluation methods, for example, a birefringence measurement method in which a three-dimensional molecular orientation of a sample is determined as a refractive index ellipsoid using an ellipsometer or the like is known. In this measurement method, light is incident not only perpendicularly to the measurement surface of the sample but also in an oblique direction, and the oblique incidence is performed from a plurality of directions to reduce the birefringence of the sample when the incident direction is changed. Measure.

[0006]

However, the above-described conventional birefringence measuring method has an advantage that the refractive index ellipsoid of the sample can be obtained, but it is a point measuring method in which measurement is performed one point at a time. To cover the whole, it is necessary to obtain a huge amount of measurement data. Therefore, this method has a limitation in shortening the measurement time, and there is a problem that it cannot be practically used especially in a mass production site where quick quality evaluation is required.

On the other hand, as a birefringence measuring method for quantitatively evaluating the amount of birefringence, for example, the Babinet compensator method, the Senarmont method and the like are conventionally known. It is a measurement method and is not conscious of the above-mentioned needs for quality evaluation.

[0008] This means that a recently proposed birefringence measurement method, for example, a method of applying a Senarmont optical system, rotating the polarizing element, receiving the light with a CCD camera, and then performing image processing (for example, Noguchi et al., "Birefringence Spatial Distribution Measurement Method", Optical Technology Contact, Vol.
5) and a method of obtaining the amount of birefringence from a phase shift algorithm using a phase modulation element and an optical rotation means (for example, Otani et al., “Measurement of two-dimensional birefringence distribution by phase shift method”, Optics, Vol. 21, No. 10) No.) and the like.

In other words, these two methods require a mechanism for rotating the optical element, and take a plurality of images into a personal computer sequentially and calculate the birefringence from the image data. A memory with a large capacity is required, and there is a natural limit to shortening the measurement time. Therefore, similar to the above, it is hardly expected to speed up the quality evaluation, and the device itself becomes complicated and relatively expensive.

The present invention has been made to solve such a conventional problem, and has as its object to relatively simply construct a system configuration for quickly evaluating the birefringence distribution of a sample with the accuracy required for quality evaluation. I do.

[0011]

In order to achieve this object, the present inventor has made repeated studies mainly based on literatures and the like, and as a result, aims to speed up birefringence evaluation according to the above-mentioned field needs. For this reason, it turned out that there is a natural limit in shortening the measurement time and simplifying the system configuration, although the accuracy is low in the quantitative measurement method of birefringence.

Therefore, the present inventor focused on a polarization observation method which has long been used as an observation principle of a polarization microscope or the like as a countermeasure in place of such a quantitative measurement method of birefringence. This polarization observation method is as follows: 1): Either a monochromatic light source or a white light source and a crossed Nicol in which two polarizing plates are arranged with their light transmission axes orthogonal to each other are used, and a sample is placed between the crossed Nicols. 2) A method of observing a change in birefringence as light brightness (hereinafter referred to as “crossed Nicol method”). 2) A light source and a crossed Nicol similar to 1), and two quarters between the crossed Nicols. Arrange one wave plate,
A method of inserting a sample between the quarter-wave plates and observing the change in birefringence as light brightness (hereinafter, “circular polarization method”). 3): Using only a white light source as a light source, 1) A single-wavelength plate is placed between the crossed Nicols and a sample is inserted between the polarizing plate and the one-wavelength plate placed on the light source side in the crossed Nicols, and the change in birefringence is replaced with a change in color for observation. Methods (hereinafter referred to as “sensitive color plate method”).

In any method, the two-dimensional birefringence distribution of the sample can be intuitively evaluated visually while comparing with a reference sample whose birefringence is known in advance. This has the advantage that the evaluation of birefringence can be speeded up with a relatively simple device. However,
In this method, the evaluation criterion strongly depends on the subjectivity of the operator, and may vary depending on the skill level, the familiarity with the work, the fatigue state, and the like.

Therefore, the present inventor can easily understand the birefringence distribution at the moment when he or she looks at it, especially among the above three methods, and depending on experience, it is possible to recognize even a small change of birefringence phase difference of about 1 nm. We thought that it would be desirable to basically use the "sensitive color plate method", which is expected to improve accuracy. As a result, a system configuration that can instantaneously and intuitively and accurately evaluate the birefringence distribution of the sample can be constructed relatively simply, and quantitative evaluation based on color image information unique to the sensitive color plate method, recording of the evaluation information, We have invented a new device that is also excellent in system expandability for storage and the like.

That is, the birefringence evaluation apparatus according to the present invention comprises:
Observation optical system for observing the birefringence image of the inspection part of the sample using polarized color plate method, and data acquisition for acquiring the birefringence image by this observation optical system as analyzable image data for evaluating the inspection part Means.

The data acquisition means preferably includes means for displaying the image data on a monitor together with image data relating to a preset birefringence image of a reference sample.

The data acquisition means preferably further comprises means for analyzing at least the amount of birefringence of the inspection section based on data on a preset reference sample.

The observation optical system is preferably an optical system for observing at least one of the transmitted light and the reflected light of the inspection section with polarized light.

In another aspect, the observation optical system is an optical system for observing at least one of the transmitted scattered light and the reflected scattered light of the inspection section with polarization.

Preferably, in the present invention, the observation optical system includes: a light source that emits light toward the sample; and two polarizers that form an orthogonal Nicol arrangement on an optical path sandwiching the sample on the emission side of the light source. A one-wavelength plate disposed on an optical path for receiving light from the sample between the two polarizers; and an imaging system disposed on an optical path on the emission side of the two polarizers.

The observation optical system preferably includes a quarter-wave plate on an optical path between the light source side polarizer of the two polarizers and the sample.

As one aspect of the present invention, the one-wavelength plate is formed of a birefringent element that exhibits a phase difference of one wavelength with respect to white light, and the imaging system includes a color imaging element. .

As another aspect of the present invention, the one-wavelength plate is constituted by a birefringent element showing a phase difference of one wavelength with respect to infrared light, and the imaging system sets infrared light in advance. An optical system for decomposing and extracting the image into three wavelength ranges for image synthesis, and an infrared imaging device for imaging infrared light extracted by the optical system.

For example, the optical system includes an infrared transmission filter having different transmittances according to the three wavelength ranges.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a specific embodiment of a birefringence evaluation apparatus according to the present invention will be described with reference to the drawings.

(First Embodiment) The birefringence evaluation apparatus shown in FIG. 1 uses a sensitive color for observing the state of birefringence change of the sample SP as a birefringent image showing a change in color based on a sensitive color plate method. Plate observation optical system (hereinafter simply referred to as "optical system")
1 and a data acquisition system 2 for acquiring a birefringent image of the sample SP, which is polarized and observed by the optical system 1, as image data capable of displaying the image and performing necessary image analysis.

The optical system 1 transmits an optical signal LB to the sample SP.
, And a detection optical system 20 that receives the optical signal LB via the sample SP. Between the optical systems 10 and 20, for example, an in-plane moving stage in the XY direction having a mechanism for automatically or manually tilting, rotating, or moving the sample SP in various directions automatically, θ A rotation stage of −φ−ψ and a mounting stage 9 such as a tilt stage (which can be omitted if the observer does not hinder the observation even if the sample SP is held by his own hand) are arranged.

The incident optical system 10 includes a light source (tungsten bulb, halogen bulb, fluorescent lamp, etc.) 1 that emits white light (either a continuous spectrum or an oscillation spectrum).
1. A diffuser plate (such as an opal glass, a thin paper screen, or a complex such as a lens or a mirror) 12 that keeps the brightness of the observation visual field by the detection optical system 20 uniform on the irradiation side of the light source 11, and a linear polarizer ( Hereinafter, it is referred to as a “first polarizer” for convenience) 13.

Among them, the first polarizer 13 is applied as a polarizer on the light source side in the orthogonal Nicol arrangement, and the direction of its polarization transmission axis is arbitrarily set within a plane perpendicular to the optical axis ( Hereinafter, for convenience, the azimuth of the transmission axis of the first polarizer 13 is referred to as the 0-degree azimuth of the “reference axis” of the entire system. The first polarizer 13 transmits only the polarization component that vibrates the optical signal from the diffusion plate 12 along its polarization transmission axis, and makes this incident on the sample SP. This incident light is sent to the detection optical system 20 as an optical signal reflecting the birefringence distribution of the sample SP.

The detection optical system 20 includes a quarter-wave plate 21 and its rotating mechanism (stepping motor or the like) 21a, a single-wave plate 22, and a linear polarizer (hereinafter referred to as “convenient”) on an optical path for receiving an optical signal from the sample SP. ), And a color image sensor 24. Among them, the quarter-wave plate 21 and its rotating mechanism 21a are required to compensate for the operation error of the single-wave plate 22, fine-tune the reference wavelength, and adjust the hue of the sensitive color. It is arbitrarily installed according to.

The one-wavelength plate 22 itself is positioned at exactly one wavelength with respect to white light (here, one reference wavelength preset between 530 nm and 550 nm, which is near the center of human visibility). A birefringent element showing a phase difference, for example, an optical element such as a polymer film or an optical crystal (such as quartz) having a wavelength dependence in birefringence, and the direction of the main axis of the birefringence with respect to the reference axis For example, they are arranged at 45 degrees. The one-wave plate 22 rotates the phase of the polarization state of the optical signal incident from the sample SP via the quarter-wave plate 21 according to the wavelength, and sends this to the second polarizer 23.

The second polarizer 23 is used as a polarizer on the detection side of orthogonal Nicols, and its transmission axis azimuth is the first.
The polarizer is disposed so as to have an angle of 90 degrees with respect to the polarization axis (reference axis). The optical signal that has passed through the second polarizer 23 is sent to the color image sensor 24.

The color image pickup device 24 comprises an image acquisition device such as a CCD camera and its driver.
The optical signal from the polarizer 23 is detected as an image signal projected on the imaging surface, and is sent to the data acquisition system 2.

Here, the principle of polarized light observation using the sharp color plate method by the optical system 1 will be described.

First, in the case of the crossed Nicols method in which the single-wavelength plate 22 is not used, before inserting the sample SP between the two polarizers 13 and 23 forming an orthogonal Nicol arrangement, the first polarizer 13 is turned off. Since the light signal cannot pass through the second polarizer 23, the obtained image is almost dark, but is colored by the birefringence state of the sample after the sample is inserted.

The reason is that the optical signal incident on the sample SP is elliptically polarized due to a phase shift caused by the difference in the refractive index between the two birefringent principal axes of the sample when passing through the optical signal. This is because generally the elliptically polarized light component having received the phase difference passes through the second polarizer 23, and the spectral component of the transmitted light is not uniform. Therefore, when the sample SP has a large wavelength dependence of birefringence, the optical signal is observed with coloring.

On the other hand, in the case of the sensitive color plate method using the single-wavelength plate 22, before the sample is inserted, the first
The optical signal that has passed through the polarizer 12 receives a phase difference caused by birefringence by the one-wave plate 22. For example, since the phase difference of the reference wavelength changes exactly 360 degrees, the polarization state does not change due to the periodicity of the phase.
But it is difficult to pass through other wavelength components from 0 degree to 360 degrees.
The phase difference passes through the polarizer 23 to receive a phase difference between the degrees.

FIG. 2 is a graph for explaining the above-mentioned situation, with the horizontal axis representing wavelength and the vertical axis representing transmittance. Considering the observation region (identification color) of the naked eye, the left end of the horizontal axis (wavelength 400 nm)
Blue), the right side (about 700 nm wavelength) is red, and the center near both is green. Therefore, the optical signal transmitted through the second polarizer 23 through the one-wavelength plate 22 has the minimum transmittance at the reference wavelength (green), and the observation field of view obtained is purple. This purple color is called the sensitive color.

Then, when the sample SP is inserted between the first polarizer 13 and the one-wavelength plate 22, the amount of phase difference received by the optical signal is a combined value of the sample SP and the one-wavelength plate 22,
The wavelength of the light that causes a phase difference of one wavelength moves by an amount corresponding to the amount of birefringence of the sample SP from the reference wavelength.

Therefore, a change in the spectral transmittance of the light signal LS passing through the second polarizer 23 causes a change in the observed color, and the amount of birefringence can be estimated with higher sensitivity than in the case of the cross Nicol method described above. . This is because the human eye is more responsive to color changes than simple discrimination between light and dark.

The birefringent image showing the change in the hue of the sample SP observed through the second polarizer 23 is captured by the color image sensor 24 and sent to the data acquisition system 2 therefrom.

The data acquisition system 2 includes, for example, a highly versatile personal computer equipped with a CPU 30 for executing a preset image processing algorithm and the like in its main part.
It is composed of an image capturing device, an image database, an image observation monitor 40, and the like. In addition to displaying an image signal from the color image sensor 24 on a computer display in real time, the image signal is sent to the monitor 40 as necessary. In addition, other processing is executed simultaneously with the image observation.

Here, the operation of the data acquisition system 2 will be described with reference to FIG.

First, when the system is started, the CPU 30 determines in step S1 whether data of a reference sample is registered in the image database. YES in this judgment
If (data exists), the process proceeds to step S2,
In the case of (no data), a process of registering the necessary image data of the reference sample in the image database is executed in step S1a as a process before shifting to step S2.

The reference sample to be registered in this database is not limited to one sample.
For example, a plurality of samples such as a good product sample, a limit product sample, and a defective product sample used in a normal quality control process may be used. The type of the reference sample is preferably a sample of the same quality as the sample to be measured,
The sample is not limited to this, and may be a different sample as long as the sample has been quantitatively evaluated for the amount of birefringence in advance by another method. Other samples may be used as reference samples if it is known in advance that the reference will be obtained by another evaluation method.

When the above processing is completed, it is determined in step S2 whether or not to display the image data of the reference sample in response to an instruction from the operator. NO in this judgment (not displayed)
In the case of (1), only the image of the sample to be evaluated is displayed in step S2a. On the other hand, in the case of YES (display), the image data of the sample to be evaluated is obtained by the optical system 1 in step S3. The data is displayed on the display or monitor 40 of the computer of the data acquisition system 2 simultaneously with the data.

Therefore, the operator evaluates the birefringence of the sample by observing the colors of the images of the reference sample and the sample under evaluation on the same monitor and comparing them. At this time, the magnification of the imaging lens is changed so that the evaluation part of the sample to be evaluated is enlarged and displayed, or the data of the limit sample, the non-defective sample, and the defective sample in the quality evaluation process are simultaneously displayed on the same screen as the image data of the reference sample. By displaying the information above, fluctuations in the evaluation criteria due to the skill level, familiarity, and fatigue of the operator can be suppressed beforehand, and stable evaluation can be performed without depending on the operator's memory or comparison based on photographs.

When the processing in step S2a or S3 is completed, it is determined whether or not the image information of the sample evaluated in step S4 is stored and registered in the image database in the system 2 in response to an instruction from the operator. If the determination is YES, the image information of the sample to be evaluated is stored or newly set and registered as a reference sample in step S5.
At this time, while changing the attitude of the sample, the state of the amount of birefringence that changes accordingly may be sequentially stored. The image information stored in this manner is printed by a printer or output to a recording medium such as an FD as necessary.

When the determination in step S4 is NO or when the process in step S5 is completed, an instruction from the operator is received in step S6 to determine whether or not there is a next sample to be evaluated. In this case, the above series of processing is repeated, and in the case of NO, the operation ends.

Therefore, according to this embodiment, the birefringence of the sample can be evaluated in a shorter time and more accurately than in the conventional example. As a secondary effect, the posture of the sample can be freely changed in the optical system, so not only can the intuitive determination of the optimum posture during observation be made, but also the birefringence that changes according to the tilt of the sample There is also an advantage that the state of the internal refractive index ellipsoid can be immediately understood.

(Second Embodiment) In the birefringence evaluation apparatus shown in FIG. 4, in addition to the above configuration, a quarter-wave plate 14 is provided between the first polarizer 13 and the sample SP in the incident optical system 10. The quarter-wave plate 14 is disposed at an azimuth of 45 degrees with respect to the reference axis. If this quarter wave plate 14 is added, the polarization state of the optical signal to be incident on the sample SP becomes
Instead of linearly polarized light in the above case, circularly polarized light is used.

Therefore, in the case of linearly polarized light, it is necessary to adjust the principal axis direction of the sample to 45 degrees in order to accurately evaluate the birefringence. By using, the sample orientation adjustment step can be omitted,
There is an advantage that the evaluation efficiency is further improved.

(Third Embodiment) The birefringence evaluation apparatus shown in FIG. 5 is applied to the case of a sample SP having no light transmissivity, and the detection optical system 20 is not on the transmission optical axis but on the reflection optical axis. It is arranged above. Other configurations are the same as above.

According to the configuration for detecting the reflected light as described above, not only a sample having a light transmitting property but also, for example, a sample in which a metal vapor-deposited film is provided on one side of a plastic, or a metal film between two plastic substrates. In the same manner as described above, there is an advantage that the birefringence can be effectively evaluated even for a sample having no light transmittance, such as a DVD disk sandwiching the. As shown in FIG. 6, the above-described quarter-wave plate 14 may be added to the incident optical system 10.

(Fourth Embodiment) The birefringence evaluation apparatus shown in FIG. 7 is one of the variations in the case of using reflected light.
A splitter (configured in a cube shape or a plate shape similar to a half mirror) 15 is disposed. In this case,
The optical signal from the incident optical system 10 is perpendicularly incident on the sample SP via the beam splitter 15 and the sample S
The reflected light that has been affected by the birefringence of P is made incident on the beam splitter 15 again, where the optical path is changed to the detection optical system 20 in a direction different from the normal incidence.

Therefore, according to this embodiment, there is an advantage that reflected light can be detected not only at oblique incidence but also at vertical incidence. Note that a quarter-wave plate 14 may be added to the incident optical system 10 as shown in FIG.

(Fifth Embodiment) The birefringence evaluation apparatus shown in FIG. 9 is applied to the case of a sample that diffuses and reflects light, and in addition to the above-described configuration, the detection optical system 20 is set around the sample position. And a tilting stage 9a having a mechanism for tilting the sample SP freely. The tilting stage 9a has a mechanism for tilting the sample SP freely. Polarization observation of refraction is possible. The tilt stage 9a is not always necessary when the sample is held by the operator's hand.

Therefore, according to this embodiment, the birefringence can be easily and quickly evaluated even for a sample having a light scattering property. In addition, since the incident angle of light with respect to the sample can be set arbitrarily,
It is possible to easily grasp the birefringence characteristics of the sample and the state of the refractive index ellipsoid. Note that a quarter-wave plate 13 may be added to the incident optical system 10 as shown in FIG.

In this embodiment, an optical arrangement for detecting reflected scattered light is used. However, the present invention is not limited to this, and a configuration for detecting transmitted scattered light, that is, a detection optical system may be arranged on the side opposite to the light source. . In this case, a mechanism for freely moving the detection optical system between the reflection side and the transmission side may be added.

(Sixth Embodiment) The evaluation based on the sensitive color plate method is basically based on observing a change in the hue of the birefringent image as described above. Therefore, in order to quantify the change in hue, in this embodiment, the birefringence image is separated into the three primary colors of light, red, blue, and green, and analyzed, and the birefringence amount is determined by the ratio of each color. Adopt an analysis algorithm that seeks

FIG. 11 illustrates an example of this algorithm. First, the color information of the sample whose birefringence is known,
That is, whether to register multiple light intensities in the image database,
By performing simulation calculations (in this case, also consider the wavelength dependence of birefringence in the material of the wave plate)
As shown, the relationship between the magnitude of birefringence (the amount of birefringence) and the color is registered in a color database (reference table). Hereinafter, an explanation will be given by taking an arbitrary one of the three colors as an example.

Next, the color of the sample is measured to determine the light intensity. That is, the amount of birefringence is determined by calculating which color of this sample is equal to which color registered in the color database, or which ratio is located between which color and which color. For example, if the color of the sample is located between two colors corresponding to the birefringence amounts of 40 and 50 in the figure and the ratio is 1: 4, the birefringence amount of the sample is 42.

If the same processing is performed for all three colors, quantitative evaluation of an arbitrary amount of birefringence becomes possible. If the same processing is performed on the sample at different incident angles, a refractive index ellipsoid can be obtained.

In each of the above embodiments, each device has been described as being individually constructed. However, it is needless to say that each device can be systematically combined.

(Seventh Embodiment) According to the above-described birefringence evaluation apparatus, in the case of a sample that transmits visible light, the state of internal stress can be observed as birefringence based on the photoelastic effect.
In the case of a sample that does not transmit visible light, such as a semiconductor wafer (silicon or compound semiconductor), it is difficult to observe the sample.

For example, as a method for measuring the internal stress of a sample that does not transmit visible light, a destructive test using an electrostrictive sensor is generally used, and in the case of a semiconductor wafer, the amount of wafer deflection (deformation) by an interferometer is used. However, in the case of an electrostrictive sensor, it is not suitable for a mass production test, and in the case of an interferometer, there are problems such as a long measurement time and relatively expensive equipment.

Thus, in this embodiment, while maximizing the advantages of the birefringence evaluation apparatus using the above-described sensitive color plate method, as an application example, a sample that does not transmit visible light, such as a semiconductor wafer, is used. In such a case, as in the case of the above-described sample that transmits visible light, a configuration was devised in which the internal stress could be easily observed in a non-contact and non-destructive manner.

Specifically, most of materials such as semiconductors that do not transmit visible light have a transmission wavelength range of an infrared range (wavelength of 1 μm).
m or more), an optical system in which the wavelength region to be detected is an infrared region instead of a visible light region and an image processing algorithm for its polarization analysis are employed. Hereinafter, this example will be described with reference to FIGS.

The birefringence evaluation apparatus shown in FIG. 12 is obtained by changing a part of the detection optical system 10 and the data acquisition system 2 in the above configuration. That is, as compared with the above configuration, the detection optical system 10 sets the reference wavelength of the one-wavelength plate 22a within the infrared region (the central wavelength region among three infrared transmission filters described later).
And an infrared extraction unit 50 for decomposing and extracting infrared light instead of the color image sensor on the side for detecting light from the one-wavelength plate 22a via the second polarizer 23, The difference is that an infrared imaging device 51 for imaging infrared light is provided.

The infrared extraction section 50 simulates the R, G, and B wavelength ranges corresponding to the colors R, G, and B in the case of the above-described color image sensor in advance in the infrared region in which the infrared image sensor 51 can image. , G, and B for three different wavelength ranges, for example, 1000 nm to 1150 nm for B, 1150 nm to 1300 nm for G, and 1300 nm to 1 for R.
Three infrared transmission filters (band-pass filters) that respectively transmit 450 nm infrared light (hereinafter referred to as “R” for infrared,
G, B filters 52, 53, and 54) and these three filters 52... 54 are arranged in a rail shape in a direction crossing the optical path between the second polarizer 23 and the infrared imaging element 51. And a rail jig 55 having a rail mechanism for holding and freely moving in the rail direction.

Of these, infrared R, G, B filters 52.
54, as shown in FIG. 13, R, G,
As in the case of the B filter, the transmittances are set in different patterns.

The infrared extraction unit 50 is provided with a rail-shaped jig 55
By moving the infrared R, G, B filters 52... 54 in the rail direction, the infrared light from the second polarizer 23 is decomposed into pseudo R, G, B image signals. These are sent to the infrared imaging element 51. The image signals for R, G, and B captured here are output to the data acquisition system 2.
For image processing.

That is, the data acquisition system 2 records the R, G, and B image signals from the infrared imaging element 51 individually in the R, G, and B areas of the frame memory 60, The color synthesis processing similar to the normal color image processing is performed in a pseudo manner from the image (1), and the synthesized image is displayed on the monitor 61 as an infrared color image.

For example, B of 1000 nm to 1150 nm
The image transmitted through the filter 52 is referred to as “blue”,
The image transmitted through the G filter 53 of 1300 nm is “green”, and the R filter 54 of 1300 nm to 1450 nm.
If the image transmitted through is set as “red” and the display wavelength on the monitor 61 is replaced and set, an infrared color image can be obtained as if a color image based on the sensitive color plate method using the visible region described above. The image is displayed on the monitor 61.

Therefore, according to this embodiment, it is possible to quickly inspect even the mass production site described above, perform quantitative evaluation with a slight change, and intuitively judge the quality of the product in a non-destructive manner. In addition to the effects, even for samples represented by semiconductor wafers, which were almost impossible to observe optically in the past,
As in the case of a sample that transmits visible light, the internal stress can be observed as birefringence using the polarization observation method based on the sensitive color plate method, and the internal stress state such as compression or tension can be easily determined. There is an advantage that it can be effectively used for analysis.

Since the transmission state of light due to the photoelastic effect is observed, the principle is simple and basically no mechanical drive unit is required in the measurement unit, and no complicated analysis device is required. There are also advantages such as that the entire apparatus can be constructed relatively simply and its maintenance is excellent.

According to this embodiment, the detection optical system including the infrared extraction unit using the rail mechanism is used.
The present invention is not limited to this. Hereinafter, this example will be described with reference to FIGS.

The infrared extraction section 50 shown in FIG. 14 employs a disc-shaped jig 56 for filters, and the above-mentioned three filters 52... 54 are arranged on the side surface of this jig 56 at predetermined intervals in the circumferential direction. By rotating the disc-shaped jig 56 in the configuration, infrared R, G,
The B image signals are individually extracted.

The detection optical system 10 shown in FIG. 15 employs three infrared cameras 51a, 51b, and 51c as infrared imaging elements, and the three filters 52... Is assigned to In this case, since the filter does not need to be moved, there is an advantage that an image can be captured in more real time.

The detection optical system 10 shown in FIG.
As a modified example using two infrared cameras 51a to 51c, two beam splitters 57a and 57b are arranged on the optical path on the exit side of the second polarizer 23, and the infrared light is separated using the beam splitters 57a and 57b. 54 to the respective filters 52... 54, and the images are captured by the cameras 51 a.

The detection optical system 10 shown in FIG.
As another modified example using two infrared cameras 51a to 51c, two stages of dichroic mirrors 58a and 58b are arranged on the optical path on the emission side of the second polarizer 23, and each of the mirrors 58a and 58b is The wavelengths are divided using the reflection / transmission characteristics, and the wavelengths are individually captured by the cameras 51a to 51c. In this case, the dichroic mirror 58a,
The reflection and transmission characteristics of 58b are shown in FIGS.

The mirror 58a at the front stage reflects infrared light corresponding to the transmission wavelength range of the above-described B filter, as shown in FIG. 18, and red light corresponding to the transmission wavelength range of the above-described G and R filters, as shown in FIG. Transmits external light. Also, the mirror 58b at the subsequent stage
As shown in FIG. 19, the infrared light corresponding to the transmission wavelength range of the G filter is reflected, and the infrared light corresponding to the transmission wavelength range of the R filter is transmitted.

Accordingly, the camera 51 on the mirror reflection side in the preceding stage
In a, the same image as when the B filter is used, the same image as when the G filter is used in the camera 51b on the rear mirror reflection side, and the R filter in the camera 51c on the mirror transmission side in the subsequent stage. An image similar to that used is obtained.

If it is possible to commercialize a color infrared imaging device similar to a color imaging device such as a CCD in which RGB filters are arranged in the future, the color infrared imaging device may be replaced with the infrared extraction unit and infrared imaging device described above. It may be used instead.

[0085]

As described above, according to the present invention, the in-plane birefringence distribution characteristics and the state of the refractive index ellipsoid in the birefringent sample can be intuitively grasped. By using and comparing, or performing image processing and quantitative evaluation of color change, birefringence evaluation can be performed quickly and accurately relatively easily, and quantitative analysis of birefringence and refractive index ellipsoids is also possible. .

This effect can be maximized when it is applied to an optical-related field in which a large market has been formed in recent years and the production volume of products handled there tends to greatly increase. That is, the quality of a product such as an optical disk substrate can be quickly and accurately evaluated, and for example, the state of molecular orientation in the disk substrate can be measured by a simpler process than before, thereby improving the quality stability in production and manufacturing The cost can be significantly reduced.

When an infrared region is used as a detection wavelength region, even a sample typified by a semiconductor wafer, which has been almost impossible to observe optically in the past, has a sharp color like a sample transmitting visible light. There is an excellent advantage that the internal stress can be observed as birefringence by polarized light observation based on the plate method, and that it can be effectively used for stress structure analysis such that the internal stress state such as compression or tension can be easily determined.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the overall configuration of a birefringence evaluation device according to the present invention.

FIG. 2 is a graph illustrating the principle of polarized light observation based on a sensitive color plate method.

FIG. 3 is a schematic flowchart illustrating the operation of the data acquisition system.

FIG. 4 is a conceptual diagram showing a configuration of a main part when a quarter-wave plate is added to the incident optical system.

FIG. 5 is a conceptual diagram showing a main part configuration when a detection optical system is arranged on a reflection optical axis.

FIG. 6 is a conceptual diagram showing another embodiment in which a detection optical system is arranged on a reflection optical axis.

FIG. 7 is a conceptual diagram showing a configuration of a main part when a beam splitter is used.

FIG. 8 is a conceptual diagram showing another embodiment using a beam splitter.

FIG. 9 is a conceptual diagram showing a configuration of a main part when detecting reflected scattered light.

FIG. 10 is a conceptual diagram showing another mode for detecting reflected scattered light.

FIG. 11 is an explanatory diagram when analyzing the birefringence of a sample.

FIG. 12 is a conceptual diagram showing a configuration of a main part when light in an infrared region is used.

FIG. 13 is a graph illustrating transmission characteristics of an infrared transmission filter.

FIG. 14 is a conceptual diagram showing a main part structure when a filter is arranged on a disk-shaped jig.

FIG. 15 is a conceptual diagram showing a configuration of a main part when three infrared cameras are used.

FIG. 16 is a conceptual diagram showing a main configuration when a beam splitter is arranged.

FIG. 17 is a conceptual diagram showing a main configuration when a dichroic mirror is arranged.

FIG. 18 is a graph illustrating the reflection and transmission characteristics of the dichroic mirror in the preceding stage.

FIG. 19 is a graph illustrating the reflection and transmission characteristics of a dichroic mirror at the subsequent stage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensitive color plate observation optical system 2 Data acquisition system 9 Mounting stage 9a Tilt stage 10 Incident optical system 11 Light source 12 Diffusion plate 13 Linear polarizer (first polarizer) 14 Quarter wave plate 15 Beam splitter 20 Detection optics System 21 Quarter-wave plate 21a Rotating mechanism 22 Single-wave plate 23 Linear polarizer (second polarizer) 24 Color imaging device 30 CPU 40 Monitor for image observation 50 Infrared extractor 51, 51a, 51b, 51c Infrared Image sensor 52 Infrared R filter 53 Infrared G filter 54 Infrared B filter 55 Rail jig 56 Disk jig 57a, 57b Beam splitter 58a, 58b Dichroic mirror 60 Frame memory 61 Monitor

Claims (10)

[Claims] 1. An observation optical system for observing a birefringence image of an inspection part of a sample in a polarized state using a sensitive color plate method, and image data capable of analyzing the birefringence image by the observation optical system for evaluating the inspection part. A birefringence evaluation device, comprising: 2. The birefringence evaluation apparatus according to claim 1, wherein said data acquisition means includes means for displaying said image data on a monitor together with image data relating to a preset birefringence image of a reference sample. 3. The data acquisition means according to claim 1, further comprising means for analyzing at least a birefringence amount of the inspection section based on data on a preset reference sample.
The birefringence evaluation device described in the above. 4. The observation optical system according to claim 1, wherein the observation optical system is an optical system that performs polarization observation of a birefringent image of the inspection unit using at least one of transmitted light and reflected light of the inspection unit. The birefringence evaluation device according to claim 1. 5. The birefringence evaluation device according to claim 4, wherein the observation optical system is an optical system that observes the polarization of the inspection unit using at least one of the transmitted scattered light and the reflected scattered light of the inspection unit. . 6. The observation optical system includes: a light source that emits light toward the sample; two polarizers arranged in an orthogonal Nicols on an optical path between the light source and the sample on the emission side;
6. The apparatus according to claim 4, further comprising: a one-wavelength plate disposed on an optical path between the two polarizers for receiving light from the sample; and an imaging system disposed on an optical path on an output side of the two polarizers. Birefringence evaluation device. 7. The multiple optical system according to claim 6, wherein the observation optical system includes a quarter-wave plate on an optical path between the light source side polarizer of the two polarizers and the sample. Refraction evaluation device. 8. The one-wavelength plate according to claim 6, wherein the one-wavelength plate includes a birefringent element that exhibits a phase difference of one wavelength with respect to white light, and the imaging system includes a color imaging element. Birefringence evaluation device. 9. The one-wavelength plate is formed of a birefringent element that exhibits a phase difference of one wavelength with respect to infrared light, and the imaging system is configured to convert infrared light into a predetermined image combining signal. 7. An optical system comprising: an optical system for decomposing and extracting light into three wavelength ranges; and an infrared imaging device for imaging infrared light extracted by the optical system.
Or the birefringence evaluation apparatus according to 7. 10. The optical system according to claim 9, wherein the optical system includes an infrared transmission filter having different transmittances according to the three wavelength ranges.
The birefringence evaluation device described in the above.