JPH1130582A - Instrument and method for measuring polarization characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-precision polarization characteristic measuring instrument that is suppressed in measurement error due to discordance between the polarized state of incident light for measurement of the polarized state and the polarized state of incidence light for measurement of polarization characteristics. SOLUTION: After the polarized state of 1st incident light generated through a polarizer 2 positioned at a 1st position is measured without setting a sample 4 in the optical path, a 1st polarization characteristic measurement of a polarizer is taken by using the 1st incident light while the sample is set in the optical path. Then the polarizer 2 is rotated to a 2nd position to generate 2nd incident light and after a 2nd polarization characteristic measurement is taken by using the 2nd incident light while the sample 4 is held in the optical path, the polarized state of the 2nd incident light is measured while the sample 4 is taken out of the optical path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarization characteristic measuring apparatus and a polarization characteristic measuring method, and more particularly, to irradiating a sample with light having a predetermined polarization state and measuring the polarization characteristic of the sample based on the polarization state of reflected light or transmitted light. The present invention relates to an apparatus and a method for measuring.

[0002]

2. Description of the Related Art Conventionally, the analysis of the polarization characteristics of a sample has been performed by:
A polarization characteristic measuring device such as an ellipsometer is widely used. There are various types of polarization characteristic measuring devices of this type, and a generally used type of polarization characteristic measuring device is to input light of a predetermined polarization state formed through a polarizer to a sample and transmit the light. Light or reflected light is received by a detector via a rotating analyzer, and the intensity of linearly polarized light transmitted through the rotating analyzer is detected. Then, based on the rotation angle of the analyzer and the output of the detector at each rotation angle, the polarization state of the light from the sample is analyzed, and thus the polarization characteristics of the sample are measured.

In the rotation analyzer type polarization characteristic measuring apparatus as described above, the phase difference Δ between p-polarized light and s-polarized light generated upon reflection on the sample may be obtained as the polarization characteristic of the sample. In this case, even if one sample of light having a predetermined polarization state is incident on the sample and the measurement is performed, only the value of cos (Δ) is obtained, and the value of the phase difference Δ is + | Δ | | Δ | cannot be determined. Therefore, in the related art, after the light of the first polarization state is incident on the sample and the first polarization characteristic measurement of the sample is performed, the light of the second polarization state different from the first polarization state is incident on the sample. By performing the second polarization characteristic measurement of the sample, the positive / negative determination of the phase difference Δ is performed.

[0004] Specifically, the polarization state of the first incident light formed via the polarizer set at the first position is measured without setting the sample in the optical path. Thereafter, the polarization state of the incident light is changed by rotating the polarizer to the second position, and the polarization state of the formed second incident light is measured. Next, with the sample set in the optical path, the first polarization characteristic measurement of the sample is performed using the incident light formed by returning the polarizer to the first position. After that, a second polarization characteristic measurement of the sample is performed using the incident light formed by rotating the polarizer to the second position again.

[0005]

As described above, in the conventional polarization analyzer of the rotary analyzer type, in order to shorten the measurement time, first, the polarization state of two types of incident light is set without setting the sample. Was measured in advance, and then the polarization characteristics of the sample were measured for two types of incident light reproduced with the sample set. However, in this measurement operation, for example, between the measurement of the polarization state of the first incident light and the first polarization characteristic measurement, the polarizer is rotated to the second position and then returned to the first position. Because of the interposition, the polarization state of the first incident light in the polarization state measurement does not always match the polarization state of the incident light reproduced in the first polarization characteristic measurement.

Similarly, between the measurement of the polarization state of the second incident light and the second measurement of the polarization characteristic, an operation of returning the polarizer to the first position and then rotating the polarizer to the second position again. , The polarization state of the second incident light in the measurement of the polarization state does not always match the polarization state of the incident light reproduced in the second polarization characteristic measurement. The polarization characteristic measuring device performs a calculation process based on information obtained by measuring the polarization state of the incident light. Therefore, the polarization state of the incident light in the measurement of the polarization state and the polarization of the incident light reproduced in the measurement of the polarization characteristic are measured. If the state does not match, a measurement error will occur due to an error in the reproducibility of the incident light.

The present invention has been made in view of the above-mentioned problems, and suppresses a measurement error caused by a mismatch between the polarization state of incident light in the measurement of polarization state and the polarization state of incident light in the measurement of polarization characteristics. It is another object of the present invention to provide a highly accurate polarization characteristic measuring device and a polarization characteristic measuring method.

[0008]

According to the present invention, there is provided an illumination system for irradiating a sample with light having a predetermined polarization state via a polarizer, comprising: An analyzer for extracting linearly polarized light from light emitted from the sample with respect to the light, a detector for detecting the intensity of the linearly polarized light extracted through the analyzer, and a polarization characteristic of the sample. A control system for controlling the measurement operation of the polarization characteristic measuring apparatus for measuring the polarization characteristics of the sample based on the rotation angle of the analyzer and the intensity of the linearly polarized light at each rotation angle, wherein the control The system sets the sample in the optical path after measuring the polarization state of the first incident light formed through the polarizer positioned at the first position without setting the sample in the optical path. The polarizer with the Wherein while holding the first position the first
The first polarization characteristic measurement of the sample is performed using the incident light, and the polarizer is rotated to a second position, and a second polarization state different from the polarization state of the first incident light is obtained. After forming the incident light and performing the second polarization characteristic measurement of the sample using the second incident light in a state where the sample is held in the optical path, the sample is removed from the optical path. There is provided a polarization characteristic measuring device, wherein the polarization state of the second incident light is measured without rotating the polarizer at the second position.

According to a preferred aspect of the present invention, the irradiation system has a phase plate configured to rotate integrally with the polarizer, and rotates the polarizer and the phase plate integrally. To form a first elliptical polarized light by positioning the polarizer and the phase plate together and positioning the second polarizer to the second position by rotating the polarizer and the phase plate together. Form polarized light.

According to another aspect of the present invention, a sample is irradiated with light having a predetermined polarization state via a polarizer, and a straight line extracted from the light emitted from the sample via an analyzer. In the polarization characteristic measuring method of measuring the polarization characteristic of the sample based on the rotation angle of the analyzer and the intensity of the linearly polarized light at each rotation angle by detecting the intensity of the polarized light, the sample is set in an optical path. Without the first
The first formed through the polarizer positioned at the position of
Measuring the polarization state of the incident light of the sample, and setting the sample in the optical path, while holding the polarizer at the first position, using the first incident light, 1
Performing a second polarization property measurement, rotating the polarizer to a second position to form second incident light having a polarization state different from the polarization state of the first incident light, Performing a second polarization property measurement of the sample using the second incident light while holding the sample in the optical path, and rotating the polarizer with the sample removed from the optical path. Measuring the polarization state of the second incident light while maintaining the polarization state at the second position.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The principle of a rotating analyzer type polarization characteristic measuring apparatus and a polarization characteristic measuring method will be described in detail in "P. S. Hoge and F. H. 1973 by Dill
Research Journal of the IBM Journal of the Year (PS
Hauge and FH Dill, IBM Journal, Research, Devel
op (1973)), Kawabata's 1987 Vol. 27 No. 3 Opto-Technical Contact page 135, and Davru. Budde, Applied Optics, Vo. 1 of Vol. 1, No. 3, 1962 (W. Budde, Applied Optics, Vo
l.1, No. 3 (1962), p201).

Hereinafter, as an example of a rotating analyzer type polarization characteristic measuring device and a polarization characteristic measuring method, linear polarization is made incident on the surface of a sample and the polarization state of the reflected light is analyzed to measure the polarization characteristic of the sample surface. Will be described. In this type of polarization characteristic measuring apparatus and polarization characteristic measuring method, light from a light source is converted into linearly polarized light via a polarizer, and is incident on the surface of the sample. Here, the traveling direction of light is z
The axis, the direction of the sample p-polarized light is set as the x-axis, the direction of the sample s-polarized light is set as the y-axis, and the direction of the transmission axis of the polarizer, that is, the direction of the linearly polarized light is set at 45 ° with respect to the x-axis. In this case, the Jones vector A representing the polarization state of the linearly polarized light incident on the sample
Is given by the following equation (1).

(Equation 1)

At this time, the polarization state of the linearly polarized light in the x-axis direction (p-polarized light) and the linearly polarized light in the y-axis direction (s-polarized light) incident on the sample surface does not change even when reflected on the sample surface.
Therefore, the Jones matrix B representing the reflection action on the sample surface is given by the following equation (2).

(Equation 2) Here, ρ is the absolute value of the ratio between the amplitude reflectance rp of p-polarized light and the amplitude reflectance rs of s-polarized light, that is, | rp / rs |. Δ is a phase difference between p-polarized light and s-polarized light generated at the time of reflection.

From equations (1) and (2), the Jones vector C representing the polarization state of light reflected from the sample surface is:
It is given by the following equation (3).

(Equation 3) The intensity I (θ) of the linearly polarized light extracted from the reflected light having the polarization state represented by the Jones vector C in Expression (3) through the analyzer having the rotation angle θ is given by the following Expression (4).

[0015]

(Equation 4) Here, the initial state of the rotation angle θ of the analyzer is set so that θ = 0 when the transmission axis of the analyzer overlaps the x-axis.

[0016] Referring equation (4), the coefficient S _1, and the coefficient S ₂ of sin (2 [Theta]) of the coefficient of the constant term S _0, cos (2 [Theta]) is represented by the formula (5) to (7) . S ₀ = (ρ ² +1) / 2 (5) S ₁ = (ρ ² -1) / 2 (6) S ₂ = ρ · cos (Δ) (7)

Further, referring to equation (4), it can be seen that the intensity I (θ) of the linearly polarized light transmitted through the rotating analyzer changes sinusoidally with respect to the rotation angle θ of the analyzer. Therefore, by Fourier transform with respect to formulas strength (4) I (θ) θ , the coefficient S ₂ of the coefficient S ₁ and sin coefficient constant term _{S 0, cos (2θ) (} 2θ) is obtained. Then, from the obtained coefficients S _{0 to} S ₂ , the ratio ρ of the amplitude reflectance between the p-polarized light and the s-polarized light and the phase difference Δ between the p-polarized light and the s-polarized light in reflection are calculated by the following equations (8) and (9). ).

Ρ = {(S ₀ + S ₁ ) / (S ₀ −S ₁ )} ^1/2 (8) cos (Δ) = S ₂ / {(S ₀ + S ₁ ) (S ₀ −S ₁ )} ^1/2 (9) As described above, in the rotation analyzer type polarization characteristic measuring apparatus and the polarization characteristic measuring method, the polarization state of the light from the sample is determined based on the light intensity I (θ) with respect to the rotation angle θ of the analyzer. And thus the polarization characteristics of the sample, such as the amplitude reflectance ratio ρ and the phase difference Δ, can be measured.

As described above, even when one sample of light having a predetermined polarization state is incident on a sample and measurement is performed, cos
It is not possible to determine whether the value of the phase difference Δ is + | Δ | or − | Δ | just by obtaining the value of (Δ). Therefore, after the first polarization characteristic measurement is performed by irradiating the sample with the first polarization state light, the second polarization state light different from the first polarization state is incident on the sample. By measuring the characteristics, it is determined whether the phase difference Δ is positive or negative.

In the present invention, the polarization state of the first incident light formed via the polarizer positioned at the first position is measured via the analyzer and the detector without setting the sample in the optical path. . Then, with the sample set in the optical path,
The first polarization characteristic measurement of the sample is performed using the first incident light while holding the polarizer at the first position. Next, the polarizer is rotated to the second position to form second incident light having a polarization state different from that of the first incident light. Then, while the sample is held in the optical path, a second polarization characteristic measurement of the sample is performed using the second incident light. afterwards,
With the sample removed from the optical path, the polarization state of the second incident light is measured via the analyzer and the detector while the polarizer is not rotated and held at the second position.

As described above, in the present invention, there is no operation for rotating the polarizer between the measurement of the polarization state of the first incident light and the first measurement of the polarization characteristics. The polarization state of the first incident light coincides with the polarization state of the incident light in the first polarization characteristic measurement. Similarly, since the operation of rotating the polarizer does not intervene between the measurement of the polarization state of the second incident light and the second polarization characteristic measurement, the polarization state of the second incident light in the measurement of the polarization state is measured. And the polarization state of the incident light in the second polarization characteristic measurement. As described above, in the present invention, the mismatch between the polarization state of the incident light in the measurement of the polarization state and the polarization state of the incident light in the measurement of the polarization characteristics does not occur. Thus, a highly accurate polarization characteristic measurement can be performed without substantially causing a measurement error caused by the above.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram schematically illustrating a configuration of a polarization characteristic measuring apparatus according to an embodiment of the present invention. In FIG. 1, the direction in which light travels (horizontal direction in the figure) is the z-axis, the direction of sample p-polarized light (direction perpendicular to the paper surface) is the x-axis, and the direction of sample s-polarized light (vertical direction in the figure) is the y-axis. . 1 includes a light source 1 for supplying measurement light. The light from the light source 1 is converted into elliptically polarized light 10 having a predetermined polarization state via the polarizer 2 and the phase plate 3, and the sample 4
Incident on. Note that the polarizer 2 and the phase plate 3 are configured to rotate integrally about the central axis of the incident light from the light source 1.

The light transmitted through the sample 4 or the polarized light 11 reflected by the sample 4 is incident on the analyzer 5. Analyzer 5
It is configured to rotate about the central axis of the incident light 11 from the sample 4, and the rotation angle is monitored by measuring means (not shown) such as an encoder. Linearly polarized light 12 extracted from the polarized light 11 through the analyzer 5
Is connected to the detector 6 via a condenser lens (not shown), for example.
Reach The detector 6 detects the intensity of the linearly polarized light 12,
The detection signal is supplied to the control system 7. The control system 7 has a function of controlling the operation of measuring the polarization characteristics of the sample 4, as described later, and drives the polarizer 2, the phase plate 3, and the analyzer 5 in the measurement operation.

Thus, the control system 7 determines the rotation angle θ of the analyzer 5 based on the output of the detector 6 and the output of the encoder.
, The intensity I (θ) of the linearly polarized light 12 can be obtained. Therefore, as described in detail in the description of the operation of the present invention, the obtained light intensity I (θ) is Fourier-transformed with respect to θ, for example, the ratio ρ of the amplitude reflectance between p-polarized light and s-polarized light, and p Phase difference Δ between polarized light and s-polarized light
The polarization characteristics of the sample 4 as described above can be measured.

However, as described above, even if one sample of light having a predetermined polarization state is incident on the sample 4 and the measurement is performed, only the value of cos (Δ) is obtained, and the positive / negative judgment of the phase difference Δ is made. Can't do it. Therefore, in this embodiment, FIG.
The polarization characteristics of the sample 4 are measured using two elliptically polarized lights having different polarization states according to the flowchart shown in FIG.
Hereinafter, the operation of measuring the polarization characteristics in the polarization characteristic measuring apparatus of the present embodiment will be described with reference to FIG.

In this embodiment, the first elliptically polarized light (incident polarized light) is formed by rotating the polarizer 2 and the phase plate 3 integrally and positioning them at the first position. Then, with the sample 4 not set in the optical path, the polarization state of the first elliptically polarized light is measured via the analyzer 5 and the detector 6 (step 21). Thereafter, the sample 4 is set in the optical path (Step 22). Then, in a state where the sample 4 is set in the optical path, the first polarization characteristic measurement of the sample 4 is performed using the first elliptically polarized light while the polarizer 2 and the phase plate 3 are held at the first position. (Step 23).

Next, by rotating the polarizer 2 and the phase plate 3 integrally and positioning them at the second position, the second elliptically polarized light having a polarization state different from that of the first elliptically polarized light is obtained. (Incident polarization) is formed, and the incident polarization is switched (step 24). And sample 4
The second measurement of the polarization characteristic of the sample 4 is performed using the second elliptically polarized light while keeping the light in the optical path (step 25). Thereafter, the sample 4 is removed from the optical path (Step 26). Then, with the sample 4 removed from the optical path, the polarization state of the second elliptically polarized light is measured by the analyzer 5 and the detector while the polarizer 2 and the phase plate 3 are held at the second position without rotating. 6 (Step 2)
7).

As described above, in this embodiment, the operation of rotating the polarizer 2 and the phase plate 3 is not interposed between the measurement of the polarization state of the first elliptically polarized light and the first measurement of the polarization characteristic. The polarization state of the first elliptically polarized light in the measurement of the polarization state matches the polarization state of the incident polarized light in the first measurement of the polarization characteristics. Similarly, since the operation of rotating the polarizer 2 and the phase plate 3 does not intervene between the second measurement of the polarization characteristic and the measurement of the polarization state of the second elliptically polarized light, the second measurement of the polarization characteristic is performed. The polarization state of the incident polarized light matches the polarization state of the second elliptically polarized light in the measurement of the polarization state. As described above, in the present embodiment, since the mismatch between the polarization state of the incident light in the measurement of the polarization state and the polarization state of the incident light in the measurement of the polarization characteristics does not occur, the reproducibility of the incident light as in the related art does not occur. Highly accurate polarization characteristic measurement can be performed without substantially causing a measurement error due to the error.

In the above-described embodiment, the two polarizers having different polarization states are provided via the polarizer 2 and the phase plate 3 which can be integrally rotated.
Although two elliptically polarized lights are formed, the present invention is not limited to this configuration, and it is also possible to perform measurement by generally making two polarized lights having different polarization states incident on a sample.

[0030]

As described above, according to the polarization characteristic measuring apparatus and the polarization characteristic measuring method of the present invention, the polarization state of the incident light in the polarization state measurement and the polarization state of the incident light in the polarization characteristic measurement are measured. Since no inconsistency occurs, a highly accurate polarization characteristic measurement can be performed without substantially causing a measurement error due to an error in reproducibility of incident light as in the related art.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a polarization characteristic measuring device according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating an operation of measuring a polarization characteristic in the polarization characteristic measurement apparatus according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2 Polarizer 3 Phase plate 4 Sample 5 Analyzer 6 Detector 7 Control system

Claims (4)

[Claims] 1. An irradiation system for irradiating a sample with light having a predetermined polarization state via a polarizer, and extracting linearly polarized light from the light emitted from the sample with respect to the light having the predetermined polarization state. An analyzer for detecting the intensity of linearly polarized light taken out through the analyzer, and a control system for controlling an operation of measuring the polarization characteristics of the sample, the analyzer comprising: A polarization characteristic measuring apparatus that measures the polarization characteristic of the sample based on the rotation angle of the sample and the intensity of the linearly polarized light at each rotation angle, wherein the control system is configured to set the first position in a state where the sample is not set in the optical path. After measuring the polarization state of the first incident light formed through the polarizer positioned at the first position, the first polarizer is maintained at the first position while the sample is set in the optical path. Of the sample using the incident light of A first polarization property measurement is performed, the polarizer is rotated to a second position to form second incident light having a polarization state different from the polarization state of the first incident light, and the sample is placed in an optical path. After performing a second measurement of the polarization characteristics of the sample using the second incident light while holding the sample inside, the second sample is removed from the optical path and the second polarizer is rotated without rotating the polarizer. A polarization state measuring device for measuring the polarization state of the second incident light while holding the polarization state at the position No. 2. 2. The irradiating system has a phase plate configured to rotate integrally with the polarizer, and the first position is obtained by rotating the polarizer and the phase plate integrally. Forming a first elliptically polarized light by positioning the polarizer and the phase plate together to form a second elliptically polarized light by positioning the polarizer and the phase plate at the second position. The polarization characteristic measuring device according to claim 1. 3. irradiating the sample with light having a predetermined polarization state via a polarizer, and detecting the intensity of linearly polarized light extracted from the light emitted from the sample via an analyzer, thereby detecting the intensity of the linearly polarized light. In a polarization characteristic measuring method for measuring a polarization characteristic of the sample based on a rotation angle of an analyzer and an intensity of the linearly polarized light at each rotation angle, the sample is positioned at a first position without being set in an optical path. Measuring the polarization state of the first incident light formed via the polarizer, and setting the sample in an optical path while holding the polarizer at the first position. Performing a first polarization property measurement of the sample using the first incident light; and rotating the polarizer to a second position to have a polarization state different from the polarization state of the first incident light. Forming a second incident light; Performing a second polarization characteristic measurement of the sample using the second incident light while holding the sample in the optical path; and rotating the polarizer with the sample removed from the optical path. Measuring the polarization state of the second incident light without holding the polarization state at the second position. 4. A first elliptically polarized light is formed as the first incident light by rotating the polarizer and the phase plate integrally and positioning the polarizer and the phase plate at the first position. By rotating the phase plate integrally with the phase plate and positioning the phase plate at the second position, the second incident light is converted into the second incident light.
The polarization characteristic measuring method according to claim 3, wherein the elliptically polarized light is formed.