A high-speed fourier spectroscopic ellipsometry device based on photoelastic modulation interferometer

Abstract

This invention belongs to the technical field of ellipsometry measurement devices, specifically relating to a high-speed Fourier spectral ellipsometry measurement device based on an elastic-optical modulation interferometer. A first polarizer is positioned along the optical path of the broadband polychromatic infrared light source, and a sample is positioned along the optical path of the first polarizer. The sample is placed on a stage, and a first rotatable compensator is positioned along the reflected optical path of the sample. A second polarizer is positioned along the optical path of the first rotatable compensator, and a high-speed elastic-optical modulation interferometer is positioned along the optical path of the second polarizer. A third polarizer is positioned along the optical path of the high-speed elastic-optical modulation interferometer, and a high-speed broadband detector is positioned along the optical path of the third polarizer. This invention solves the problem of slow broadband spectral ellipsometry measurement speed by combining high-speed elastic-optical modulation Fourier spectral spectral ellipsometry with spectral ellipsometry technology, achieving millisecond-level spectral ellipsometry measurement in the visible infrared broadband band.

Description

Technical Field

[0001] This invention belongs to the technical field of ellipticity measurement devices, specifically relating to a high-speed Fourier spectral ellipticity measurement device based on an elastic-optical modulation interferometer. Background Technology

[0002] With the development of mid-infrared technology, especially military infrared materials, which are one of the supporting technologies for military equipment, they are widely used in infrared imaging, reconnaissance, tracking, guidance, and countermeasures, and are indispensable materials for modern equipment. This has driven the need for detection in the mid-infrared band, especially high-speed detection, to improve overall efficiency. Rapid detection of the physical properties (e.g., refractive index, extinction coefficient, dielectric function) and structural properties (e.g., film thickness of surface and interface layers, alloy ratio of multi-component materials, molecular vibrations, doping concentration) of mid-infrared bulk or nanofilm materials is a fundamental requirement for materials research and application, and a key problem that must be solved in the field of infrared materials research.

[0003] Rapid mid-infrared ellipsometry is an important means to solve this problem, as it has advantages such as being non-destructive, highly sensitive, and having low environmental requirements. Currently, visible and near-infrared ellipsometry techniques are relatively mature, and the measurement speed has also improved to some extent. However, in the mid-infrared band, the measurement speed is slow due to the limitation of the moving mirror scanning time in traditional Fourier transform infrared spectroscopy systems. Summary of the Invention

[0004] To address the technical problems of slow measurement speed and slow mid-infrared ellipticity measurement speed in existing traditional Fourier infrared spectroscopy, which prevent infrared ellipticity from being used in high-speed testing, this invention provides a high-speed Fourier spectral ellipticity measurement device based on an elastic-optical modulation interferometer, which combines Fourier spectroscopy and spectral ellipticity techniques to perform real-time microsecond-level spectral ellipticity analysis.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A high-speed Fourier spectral ellipsometry measurement device based on an elastic-optical modulation interferometer includes a broadband polychromatic infrared light source, a first polarizer, a sample, a stage, a first rotatable compensator, a second polarizer, a high-speed elastic-optical modulation interferometer, a third polarizer, and a high-speed broadband detector. The first polarizer is positioned along the optical path of the broadband polychromatic infrared light source, and the sample is positioned along the optical path of the first polarizer. The sample is placed on the stage, and the first rotatable compensator is positioned along the reflected optical path of the sample. The second polarizer is positioned along the optical path of the first rotatable compensator, and the high-speed elastic-optical modulation interferometer is positioned along the optical path of the second polarizer. The third polarizer is positioned along the optical path of the high-speed elastic-optical modulation interferometer, and the high-speed broadband detector is positioned along the optical path of the third polarizer.

[0007] The first polarizer is a 0° polarizer, the second polarizer is a 0° polarizer, and the third polarizer is a 90° polarizer.

[0008] The first polarizer, the second polarizer, and the third polarizer are all made of polarizing prisms, polarizing beam splitters, or polarizing lenses.

[0009] The high-speed elastic-optical modulation interferometer is a 45° high-speed elastic-optical modulation interferometer.

[0010] The high-speed photoelastic modulation interferometer includes a high-speed piezoelectric actuator, a broadband photoelastic crystal, a first high-reflectivity coating, and a second high-reflectivity coating. The high-speed piezoelectric actuator is connected to the broadband photoelastic crystal. The first high-reflectivity coating is disposed on one side of the broadband photoelastic crystal, and the second high-reflectivity coating is disposed on the other side of the broadband photoelastic crystal.

[0011] The broadband elastic-optical crystal is made of zinc selenide, and its spectral range is 0.5μm-25μm. The modulation frequency of the high-speed elastic-optical modulation interferometer is f=50kHz.

[0012] A second rotatable compensator is provided between the first polarizer and the sample.

[0013] The first rotatable compensator and the second rotatable compensator are respectively connected to the output shaft of the motor.

[0014] A measurement method for a high-speed Fourier spectral ellipsometry measurement device based on an elastic-optical modulation interferometer includes the following steps: the light to be measured passes through a second polarizer, a high-speed elastic-optical modulation interferometer, and a third polarizer to form a high-speed Fourier broadband infrared interferometer; the second polarizer acts as a polarizer detector for ellipsometry measurement and a polarizer for the high-speed elastic-optical modulation interferometer; and a high-speed broadband detector completes the acquisition of high-speed interference signals.

[0015] The measurement method of the high-speed broadband detector is as follows: the light being measured passes through a second polarizer, a high-speed elastic-optical modulation interferometer, and a third polarizer to form a high-speed Fourier broadband infrared interferometer. The interference signal reaching the high-speed broadband detector is:

[0016]

[0017] Where L0 is the maximum modulation optical path difference of the high-speed photoelastic modulation interferometer, ω=2πft is the modulation frequency of the high-speed photoelastic modulation interferometer, f is the modulation frequency of the high-speed photoelastic modulation interferometer, σ is the wavenumber, σ1 is the minimum wavenumber in the spectral range, and σ2 is the maximum wavenumber in the spectral range.

[0018] The Fourier transform of the interferometric signal from the high-speed broadband detector yields the measured spectrum as follows:

[0019]

[0020] Where T = 1 / f is the modulation period of the high-speed photoelastic modulation interferometer.

[0021] Compared with the prior art, the beneficial effects of this invention are:

[0022] This invention addresses the problem of slow measurement speed for wide-band spectral ellipsometrics by combining high-speed photoelastic modulation Fourier spectroscopy with spectral ellipsometric analysis, achieving millisecond-level spectral ellipsometric measurement across the visible to infrared bands. This invention is 2-3 orders of magnitude faster than traditional infrared spectral ellipsometric measurement and allows for adjustment of the photoelastic modulation frequency and compensator rotation frequency to achieve even faster spectral ellipsometric measurements. Attached Figure Description

[0023] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0024] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0025] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0026] Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention;

[0027] Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention;

[0028] Figure 4 This is a schematic diagram of the structure of Embodiment 4 of the present invention;

[0029] Figure 5 This is a schematic diagram of the structure of the high-speed elastic-optical modulation interferometer of the present invention.

[0030] Wherein: 1 is a broadband polychromatic infrared light source, 2 is the first polarizer, 3 is the sample, 4 is the stage, 5 is the first rotatable compensator, 6 is the second polarizer, 7 is a high-speed photoelectro-electro-modulated interferometer, 7-1 is a high-speed piezoelectric actuator, 7-2 is a broadband photoelectro-electro-crystalline material, 7-3 is the first high-reflectivity coating, 7-4 is the second high-reflectivity coating, 8 is the third polarizer, 9 is a high-speed broadband detector, and 10 is the second rotatable compensator. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0034] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] Example 1

[0036] High-speed rotating single-compensator spectral ellipsometric path based on analyzer arm elastic-optical modulation interferometer, such as... Figure 1 As shown, the entire ellipsometric measurement method is the same as the single-compensator spectral ellipsometric method. The entire system consists of a broadband polychromatic infrared light source 1, a first polarizer 2, a sample 3, a stage 4, a first rotatable compensator 5, a second polarizer 6, a high-speed elastic-optical modulation interferometer 7, a third polarizer 8, and a high-speed broadband detector 9. The first rotatable compensator 5 is driven by a motor; the 0° second polarizer 6, the 45° high-speed elastic-optical modulation interferometer 7, and the 90° third polarizer 8 form a high-speed Fourier broadband infrared interferometer; the second polarizer 6 serves as an analyzer for ellipsometric measurement and as a polarizer generator for the high-speed elastic-optical modulation interferometer 7; the first polarizer 2, the second polarizer 6, and the third polarizer 8 can be polarizing prisms, polarizing beam splitters, polarizing mirrors, etc.; the high-speed broadband detector 9 mainly completes the acquisition of high-speed interference signals. The elastic-optical modulation high-speed Fourier spectral measurement method is as follows:

[0037] The light being measured passes through a second polarizer (6) at 0°, a high-speed photoelastic modulation interferometer (7) at 45°, and a third polarizer (8) at 90°, forming a high-speed Fourier broadband infrared interferometer. The interference signal reaching the high-speed broadband detector (9) is as follows:

[0038]

[0039] Where L0 is the maximum modulation optical path difference of the high-speed photoelastic modulation interferometer 7, ω=2πft is the modulation frequency of the high-speed photoelastic modulation interferometer 7, f is the modulation frequency of the high-speed photoelastic modulation interferometer 7 (typically tens to hundreds of kHz), σ is the wavenumber, σ1 is the minimum wavenumber in the spectral range, and σ2 is the maximum wavenumber in the spectral range. The Fourier transform of the interference signal from the high-speed wideband detector 9 yields the measured spectrum as follows:

[0040]

[0041] Where T = 1 / f is the modulation period of the high-speed photoelastic modulation interferometer.

[0042] The elliptic parameters can be obtained by combining equation (2) with spectral ellipticization technique.

[0043] Example 2

[0044] High-speed rotating single-compensator spectral ellipsometric path based on a polarizing arm elastic-optical modulation interferometer, such as... Figure 2 As shown, with Figure 1 Similarly, the method is similar to that in Embodiment 1. The photosensitive modulated interferometer is placed at the starting arm position. The entire ellipsometric measurement method is the same as the spectral ellipsometric method with a single rotating compensator. The entire system consists of a broadband polychromatic infrared light source 1, a third polarizer 8, a high-speed photosensitive modulated interferometer 7, a second polarizer 6, a first rotatable compensator 5, a sample 3, a stage 4, a first polarizer 2, and a high-speed broadband detector 9. The first rotatable compensator 5 is rotated by a motor; the 90° third polarizer 8, the 45° high-speed photosensitive modulated interferometer 7, and the 0° second polarizer 6 form a high-speed Fourier broadband infrared interferometer; the second polarizer 6 serves as the polarizer for ellipsometric measurement and as the polarizer detector for the high-speed photosensitive modulated interferometer 7; the first polarizer 2, the second polarizer 6, and the third polarizer 8 can be polarizing prisms, polarizing beam splitters, polarizing mirrors, etc.; the high-speed broadband detector 9 mainly completes the acquisition of high-speed interference signals. The high-speed Fourier spectrum measurement of elastic-optical modulation is the same as formulas (1) and (2) in Example 1. The ellipticity parameters can be obtained by combining the spectral ellipticity technique.

[0045] Example 3

[0046] A high-speed rotating double compensator generalized spectral ellipsometric path based on an analyzer arm elastic-optical modulation interferometer, such as... Figure 3 As shown, the entire ellipsometric measurement method is the same as the rotating double compensator spectral ellipsometric method. The entire system consists of a broadband polychromatic infrared light source 1, a first polarizer 2, a second rotatable compensator 10, a sample 3, a stage 4, a first rotatable compensator 5, a second polarizer 6, a high-speed elastic-optical modulation interferometer 7, a third polarizer 8, and a high-speed broadband detector 9. The first rotatable compensator 5 and the second rotatable compensator 10 are rotated by a motor; the 0° second polarizer 6, the 45° high-speed elastic-optical modulation interferometer 7, and the 90° third polarizer 8 form a high-speed Fourier broadband infrared interferometer; the second polarizer 6 serves as an analyzer for ellipsometric measurement and as a polarizer generator for the high-speed elastic-optical modulation interferometer 7; the first polarizer 2, the second polarizer 6, and the third polarizer 8 can be polarizing prisms, polarizing beam splitters, polarizing mirrors, etc.; the high-speed broadband detector 9 mainly completes the acquisition of high-speed interference signals. The high-speed Fourier spectrum measurement of elastic-optical modulation is the same as formulas (1) and (2) in Example 1. The generalized ellipticity parameters can be obtained by combining the generalized ellipticity technique of dual rotation compensator.

[0047] Example 4

[0048] A high-speed rotating dual-compensator generalized ellipticized optical path based on a polarizing arm elastic-optical modulation interferometer, such as... Figure 4 As shown, with Figure 1 Similarly, the method is similar to that in Embodiment 1. The photosensitive modulated interferometer is placed at the starting arm position. The entire ellipsometric measurement method is the same as the spectral ellipsometric method with a single rotating compensator. The entire system consists of a broadband polychromatic infrared light source 1, a third polarizer 8, a high-speed photosensitive modulated interferometer 7, a second polarizer 6, a first rotatable compensator 5, a sample 3, a stage 4, a second rotatable compensator 10, a first polarizer 2, and a high-speed broadband detector 9. The first rotatable compensator 5 and the second rotatable compensator 10 are rotated by a motor. The 90° third polarizer 8, the 45° high-speed photosensitive modulated interferometer 7, and the 0° second polarizer 6 form a high-speed Fourier broadband infrared interferometer. The analyzer 6 serves as the starting polarizer for ellipsometric measurement and as the analyzer for the high-speed photosensitive modulated interferometer 7. The first polarizer 2, the second polarizer 6, and the third polarizer 8 can be polarizing prisms, polarizing beam splitters, polarizing mirrors, etc. The high-speed broadband detector 9 mainly completes the acquisition of high-speed interference signals. The high-speed Fourier spectrum measurement of elastic-optical modulation is the same as formulas (1) and (2) in Example 1. The generalized ellipticity parameters can be obtained by combining the generalized ellipticity technique of dual rotation compensator.

[0049] According to Fourier spectroscopy, spectral resolution is related to the maximum optical path difference L0. To obtain a large optical path difference, a high-speed elastic-optical modulation interferometer with multiple reflections and a large optical path difference is used, such as... Figure 5 As shown, the high-speed photoelastic modulation interferometer 7 mainly consists of a high-speed piezoelectric actuator 7-1, a wide-spectrum photoelastic crystal 7-2, a first high-reflectivity coating 7-3, and a second high-reflectivity coating 7-4. If the wide-spectrum photoelastic crystal 7-2 is made of zinc selenide, the spectral range can achieve a wide-spectrum measurement of 0.5μm-25μm. The modulation frequency of the high-speed photoelastic modulation interferometer 7 is the commonly used f = 50kHz. According to equations (1) and (2), the acquisition time of one interference signal is T / 4 = 1 / 4f = 5μs. In order to have sufficient time to accurately obtain the interference signal, the frequency of the rotating compensator is three orders of magnitude smaller than the photoelastic modulation frequency. The frequency of the rotating compensator is f' = 50Hz. Therefore, the time to obtain the completed spectral ellipsoid data is 1 / f' = 0.02s, which is 2-3 orders of magnitude higher than the traditional infrared spectral ellipsoid measurement time. The photoelastic modulation frequency and the compensator rotation frequency can also be adjusted according to the measurement needs to achieve a faster spectral ellipsoid measurement.

[0050] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A high-speed Fourier spectroscopic ellipsometry apparatus based on a photoelastic modulator interferometer, characterized by: The application relates to a wide-band multi-color infrared light source (1), a first polarizer (2), a sample (3), a carrier (4), a first rotatable compensator (5), a second polarizer (6), a high-speed photoelastic modulation interferometer (7), a third polarizer (8) and a high-speed wide-band detector (9), wherein the light path direction of the wide-band multi-color infrared light source (1) is provided with the first polarizer (2), the light path direction of the first polarizer (2) is provided with the sample (3), the sample (3) is arranged on the carrier (4), the reflected light path of the sample (3) is provided with the first rotatable compensator (5), the light path direction of the first rotatable compensator (5) is provided with the second polarizer (6), the light path direction of the second polarizer (6) is provided with the high-speed photoelastic modulation interferometer (7), the light path direction of the high-speed photoelastic modulation interferometer (7) is provided with the third polarizer (8), and the light path direction of the third polarizer (8) is provided with the high-speed wide-band detector (9). The high-speed photoelastic modulation interferometer (7) comprises a high-speed piezoelectric driver (7-1), a wide-spectrum photoelastic crystal (7-2), a first high-reflectivity coating (7-3) and a second high-reflectivity coating (7-4), the high-speed piezoelectric driver (7-1) is connected with the wide-spectrum photoelastic crystal (7-2), the first high-reflectivity coating (7-3) is arranged on one side of the wide-spectrum photoelastic crystal (7-2), and the second high-reflectivity coating (7-4) is arranged on the other side of the wide-spectrum photoelastic crystal (7-2).

2. The high-speed Fourier spectroscopic ellipsometer based on the photoelastic modulation interferometer according to claim 1, characterized in that: The first polarizer (2) is a 0-degree polarizer, the second polarizer (6) is a 0-degree polarizer, and the third polarizer (8) is a 90-degree polarizer.

3. The high-speed Fourier spectroscopic ellipsometer based on the photoelastic modulation interferometer according to claim 1, characterized in that: The first polarizer (2), the second polarizer (6) and the third polarizer (8) are all polarizing prisms, polarizing beam splitters or polarizing lenses.

4. The high-speed Fourier spectroscopic ellipsometer based on the photoelastic modulation interferometer according to claim 1, characterized in that: The high-speed photoelastic modulation interferometer (7) is a 45-degree high-speed photoelastic modulation interferometer.

5. The high-speed Fourier spectroscopic ellipsometer based on the photoelastic modulation interferometer according to claim 1, characterized in that: The material of the wide-spectrum photoelastic crystal (7-2) is zinc selenide, the spectral range of the wide-spectrum photoelastic crystal (7-2) is 0.5-25 mu m, and the modulation frequency f of the high-speed photoelastic modulation interferometer (7) is 50 kHz.

6. The high-speed Fourier spectroscopic ellipsometer based on the photoelastic modulation interferometer according to claim 1, characterized in that: A second rotatable compensator (10) is arranged between the first polarizer (2) and the sample (3).

7. A high-speed Fourier spectroscopic ellipsometer based on a photoelastic modulator interferometer according to claim 6, characterized in that: The first rotatable compensator (5) and the second rotatable compensator (10) are respectively connected with the output shafts of motors.

8. A method of measuring a device for high-speed Fourier spectroscopic ellipsometry based on a photoelastic modulator interferometer according to any one of claims 1 to 7, characterized in that: The application further discloses a measurement method of the high-speed wide-band detector, wherein the measured light passes through the second polarizer, the high-speed photoelastic modulation interferometer and the third polarizer to form a high-speed Fourier wide-band infrared interferometer, and the interference signal of the high-speed wide-band detector is:

9. The method of measuring according to claim 8, wherein the method is characterized by: The measurement method of the high-speed wide-band detector is that the measured light passes through the second polarizer, the high-speed photoelastic modulation interferometer and the third polarizer to form a high-speed Fourier wide-band infrared interferometer, and the interference signal of the high-speed wide-band detector is: Wherein, L0 is the maximum modulation optical path difference of the high-speed photoelastic modulation interferometer, ω = 2πft is the modulation frequency of the high-speed photoelastic modulation interferometer, f is the modulation frequency of the high-speed photoelastic modulation interferometer, σ is the wave number, σ1 is the minimum wave number in the spectral range, and σ2 is the maximum wave number in the spectral range. The Fourier transform of the interference signal of the high-speed wide-band detector obtains the measured spectrum as follows: Wherein, T = 1 / f is the modulation period of the high-speed photoelastic modulation interferometer.

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