JPS63168523A - Polarization analyzer - Google Patents

Abstract

PURPOSE:To horizontally set a specimen for the measurement of transmission, to eliminate error by making the movement of a compensator unnecessary and performing the reflection measurement of polarized light with high accuracy along with the transmission measurement thereof, by making an auxiliary polarizer accessible to the ligth path of an apparatus. CONSTITUTION:A polarizer P, a compensator C, a slide stage ST and a detector A are arranged between a light source L and a light detector D. The compensator C is fixed so that the optical axis thereof of set in an azimuth of 45 deg. with respect to the reference surface of an apparatus, and the polarizer P and the detector A are made rotatable around an optical axis. Further, the detector A and the detector D are mounted on one arm and made rotatable around the center point O of a goniometer and the stage ST is also provided in the same manner. At the time of measurement, them stage ST is detached and a specimen S is set on a turntable RT but a new auxiliary polarizer PC of which the optical axis is parallel to the reference surface is preliminarily provided on the stage ST. In this constitution, the goniometer is rotated and the polarizer PC is finely adjusted around the optical axis so as not to change the extinction position of the polarizer A.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a polarization measuring device suitable for both reflection measurement and transmission measurement.

In the prior art, ellipsometry is an effective means for measuring the refractive index of a sample and analyzing the surface layer. The polarization analyzer makes elliptically polarized light incident on the sample surface, and measures the ellipticity of the incident light so that the reflected light becomes linearly polarized light, and the relationship between the major axis direction of the incident elliptically polarized light and the direction of the reflected linearly polarized light. , to find changes in the reflectance and phase of polarized light in two directions on the sample surface. The polarization analyzer measures the azimuth angle of the polarizer, analyzer, etc. with reference to the reference plane of the apparatus (a plane that includes the optical axes of the incident light and the reflected light on the sample, and is usually a horizontal plane).

FIG. 3 shows the general configuration of a conventional polarization analyzer. L
is a light source, P is a polarizer, C is a compensator, S is a sample, A is an analyzer, and D is a photodetector. In this configuration, the paper plane of the figure is the reference plane of the apparatus. The compensator is a 1/4 wavelength plate, which converts the linearly polarized light transmitted through the polarizer P into elliptically polarized light and makes it incident on the surface of the sample S.

The compensator C is fixed so that its optical axis forms 45 degrees with the reference plane, and when the polarizer P is rotated from an azimuth angle of 45 degrees, the light transmitted through the compensator changes from linearly polarized light to elliptically polarized light.
When the polarizer is rotated by 90'', the light becomes circularly polarized, and the long axis direction of the elliptically polarized light is oriented at 45° with respect to the optical axis direction of the compensator, that is, the reference plane.

When measuring birefringence using light transmitted through a sample using an ellipsometer configured as described above, the azimuth angle of the optical axis of the sample with respect to the reference plane must be determined.

For this reason, a conventional method has been used. First, make the compensator C removable, remove the compensator, make the polarizer and analyzer orthogonal, set the sample, and rotate the sample around the optical axis. The direction of the sample optical axis is determined because the analyzer transmitted light becomes O when it becomes parallel to the direction of . Alternatively, make the compensator rotatable and set it horizontally, set the sample with the polarizer also horizontally and the analyzer vertically, and then rotate the sample to detect the direction in which the analyzer transmits light O. For example, the optical axis of the sample is set horizontally. Yet another method is to make the sample rotatable around the optical axis of the device so that the angle of rotation can be read.

C0 Problems to be Solved by the Invention In an ellipsometry device, the compensator is fixed at an azimuth angle of 45°, so if the polarizer is set at an azimuth angle of 45°, the light transmitted through the compensator will be directed at an azimuth angle of 45°. It is linearly polarized light. Therefore, if the optical axis of the sample for transmission measurement is set horizontally, polarized light with the same imaging width and the same phase will be incident on the two orthogonal axes of the sample. The birefringence of can be measured.

By the way, in the above-mentioned method of attaching and detaching the compensator, the direction of the optical axis of the sample can be set arbitrarily, but making the compensator detachable will cause errors in the set orientation of the compensator, which may cause errors in other polarization analyses. This is not a preferable method as there is a risk of this occurring.

The method for making the orientation of the second compensator horizontal is the same as above.In the case of polarimetry measurement, the orientation of the compensator tends to be distorted (in order to avoid this, it is necessary to change the orientation of the compensator). A special mechanism is required, and it is too expensive for a mechanism used only to set the optical axis of the sample horizontally in transmission measurements.The method of reading the rotation angle of the 3rd degree sample itself is This is preferable because it remains fixed, but in this case, the sample settings are
Set the orientation of the polarizer at 45°, make 45° linearly polarized light incident on the sample, rotate the sample, detect the angle at which the light transmitted through the analyzer perpendicular to the polarizer becomes O, and then from that angular position. The optical axis of the sample is set horizontally by rotating the sample by 45 degrees, which is cumbersome to operate, and requires the sample holder to be angularly readable, making the sample holder too expensive.

The present invention avoids the above-mentioned problems when trying to perform transmission measurements with an ellipsometer, and allows the optical axis of a sample to be adjusted with simple operations without moving a compensator or requiring a complicated sample holder. The aim is to make it possible to set it parallel to the reference plane.

29. Means for solving the problem: An auxiliary polarizer is provided removably between the compensator of the polarization analyzer and the sample, and the polarization direction of this polarizer is set parallel or perpendicular to the reference plane of the equipment. .

Since the emitted light from the 0-effect compensator is linearly polarized, elliptical, or circularly polarized in the direction of 45° to the device reference plane, when it passes through the auxiliary polarizer placed parallel or perpendicular to the device reference plane, the auxiliary polarizer Linearly polarized light determined by direction is obtained. Therefore, if the auxiliary polarizer and analyzer are orthogonal to each other and the sample is rotated around the optical axis of the device to find the position where the light transmitted through the analyzer becomes 0, the optical axis of the sample is parallel or perpendicular to the device reference plane. is set to

Embodiment FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is a side view of the same. In the figure, L is a light source, P is a polarizer, C is a compensator,
S is a sample, A is an analyzer, and D is a photodetector. Compensator C
is fixed so that its optical axis is oriented at 45° with respect to the reference plane of the apparatus (the plane of the drawing in FIG. 1), and the polarizer P1 and the analyzer A are rotatable around the optical axis. The zero point is the center of the goniometer, and the analyzer A and the detector are located on one arm and can rotate within the device reference plane around the zero point. ST is a sliding stage, which is also detachably set on a rotary table RT mounted on the goniometer axis G shown in FIG. 2 so that it can also rotate around the zero point.

The sliding stage ST can be moved in the device reference plane (horizontal) direction by a guide B having a sliding direction parallel to the device reference plane. In the case of measuring reflected light from the sample surface, the sliding stage ST is removed and the sample is set on the rotary table RT. In the case of transmitted light measurement, the optical axis of the incident light side consisting of a polarizer, compensator, etc. and the optical axis of the output light side consisting of an analyzer and detector are aligned as shown in the figure, and the light is aligned to the side of the goniometer. A sample S is set on the axis, and a sliding stage ST is placed on the goniometer. An auxiliary polarizer PC is attached on the sliding stage ST. The auxiliary polarizer is installed so that its optical axis is parallel to the device reference plane, but it can be finely adjusted to the optical axis in order to correct installation errors. For transmitted light measurement,
The sliding table ST is set on the goniometer, and the auxiliary polarizer PC is advanced onto the optical axis of the device. In this state, when the polarizer P is oriented horizontally, circularly polarized light is emitted from the compensator C. Since the auxiliary polarizer PC is set in the horizontal direction (device reference plane) with respect to this circularly polarized light, the transmitted light of the auxiliary polarizer PC is linearly polarized light in the horizontal direction. Therefore, the orientation of the analyzer is set perpendicular to the horizontal plane in advance, the sample S is rotated between the optical axes, the position where the photodetector output becomes O (light incidence is O) is detected, and the position is stopped. I'll keep it. At this time, the optical axis of the sample is horizontal. After setting the orientation of the sample in this way, move the sliding table to retract the auxiliary polarizer PC from the optical axis of the device, set the orientation of the polarizer P to 45°, and set the polarization direction of the sample S at 45°. input linearly polarized light.

The auxiliary polarizer PC is adjusted so that the optical axis is horizontal, but to correct this adjustment error, set the polarizer horizontally, set the analyzer vertically, find the position of the photodetection output O, and then turn the goniometer. When the auxiliary polarizer C is turned over by 180 degrees, if the optical axis of the auxiliary polarizer is not exactly horizontal, the direction of inclination of the optical axis will be opposite between the -th turn and after turning the goniometer 180 degrees. The azimuth of the analyzer at which the photodetector output becomes 0 changes slightly. Therefore, move the goniometer to 180°.
The orientation of the auxiliary polarizer PC may be finely adjusted between the optical axes so that the extinction position of the analyzer A does not change.

G. Effect: As mentioned above, with the polarization analyzer of the present invention, the optical axis of the sample for transmission measurement can be set horizontally by simply moving the auxiliary polarizer in and out of the optical path of the device, and there is no need to move the compensator. , measurement errors due to errors in the azimuthal angle of the compensator do not occur, and both reflection and transmission measurements of polarized light can be carried out with high precision. Therefore, it is cheap.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an apparatus according to an embodiment of the present invention, FIG. 2 is a side view of the same, and FIG. 3 is a plan view of a conventional polarization analyzer. L...Light source, P...Polarizer, C...Compensator, S...
...Sample, A...Analyzer, D...Photodetector, ST.
...Sliding table, RT...Rotary table, B...
Guide, PC...auxiliary polarizer, G...goniometer axis. Agent Patent Attorney Kosuke Agata 11 Figure

Claims (1)

[Claims] The device consists of a polarizer, a compensator, and an analyzer, and the sample is placed between the compensator and the analyzer.An auxiliary polarizer with a constant azimuth angle is provided between the compensator and the sample so that it can be moved in and out. A polarization analyzer characterized by: