Online polarized light characteristic testing device

Abstract

The invention discloses an online polarized light characteristic testing device. The online polarized light characteristic testing device comprises a polarization measuring instrument and a surface to be measured, the polarization measuring instrument comprises a coupling mirror group, a polarized light phase difference adjusting element, a polarization filtering element and a detector; the coupling mirror group is used for perfecting the imaging of the to-be-detected surface on the detector; the polarized light phase difference adjusting element is an element for realizing that vibration components of light in two vertical directions generate an adjustable phase difference; the polarization filtering element is an element for realizing component transmission of light in a certain specific vibration direction and filtering in the other vibration direction; the detector is used for detecting light intensity. According to the online polarized light characteristic testing device, the coupling mirror group, the polarized light phase difference adjusting element, the polarization filtering element and the detector are arranged, online real-time monitoring of polarized light characteristics can be achieved, surface distribution for detecting the polarization characteristics of light is obtained, the length of the device is small, and the device is suitable for application and popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and particularly to an on-line polarized light characteristic testing device. Background Art

[0002] In high-precision semiconductor detection equipment, the optical path has very high requirements for the polarization of light. A polarization measuring instrument detects the polarization characteristics of a light spot through a unique optical path structure. The detected polarization characteristics may include the azimuth angle, ellipticity, polarization ratio, Stokes parameters, Mueller matrix, etc. of polarized light.

[0003] During actual equipment detection or use, it is often necessary to insert a polarization measuring device into an existing optical path, which poses strict restrictions on the size of the polarization detection device or optical path. Existing testing devices can only perform off-line testing and cannot effectively perform on-line testing due to space limitations.

[0004] Therefore, it is necessary to provide an on-line polarized light characteristic testing device to solve the above technical problems. Summary of the Invention

[0005] In view of the above situation, to overcome the defects of the prior art, the present invention provides an on-line polarized light characteristic testing device capable of realizing on-line real-time monitoring of polarized light characteristics.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An on-line polarized light characteristic testing device includes: a polarization measuring instrument and a surface to be measured; the polarization measuring instrument includes a coupling lens group, a polarized light phase difference adjustment element, a polarization filtering element, and a detector; the coupling lens group is used to complete the imaging of the surface to be measured on the detector; the polarized light phase difference adjustment element is an element that realizes an adjustable phase difference between two perpendicular vibration components of light; the polarization filtering element is an element that realizes the transmission of a component of a certain specific vibration direction of light and filters out the component of the other vibration direction; the detector is used to detect the light intensity.

[0008] Preferably, the coupling lens group includes a first lens, a second lens, and a diaphragm.

[0009] Preferably, the polarized light phase difference adjustment element is one of a variable wave plate, a photoelastic modulator, and a liquid crystal polarization modulator.

[0010] Preferably, the polarization filtering element is one of a polarizing film and a polarization beam splitting prism.

[0011] Preferably, the transmission polarization orientation of the polarization filtering element is 0 degrees.

[0012] Preferably, the polarized light phase difference adjustment element is a rotating quarter-wave plate structure or a dual photoelastic modulator structure.

[0013] Preferably, the quarter-wave plate rotation structure includes a quarter-wave plate, a mechanical transmission mechanism, and a voice coil motor.

[0014] Preferably, the dual photoelastic modulator structure includes a first photoelastic modulator, a second photoelastic modulator, and a photoelastic modulator controller.

[0015] Preferably, the fast axis orientation degrees of the first photoelastic modulator and the second photoelastic modulator are 22.5° and -22.5° respectively.

[0016] Preferably, the focal length of the first lens is 5 mm, the focal length of the second lens is 15 mm, and the aperture is 2 mm.

[0017] Preferably, the quarter-wave plate is a zero-order air-gap wave plate with a diameter of 6 mm and a wavelength of 193 nm.

[0018] Preferably, the inclination angle of the polarization filtering element is 56.5°, that is, the angle between the polarization filtering element (quartz thin plate) and the optical axis is 56.5 degrees.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] By providing a coupling lens group, a polarization light phase difference adjustment element, a polarization filtering element, and a detector, the present invention can realize on-line real-time monitoring of the polarization characteristics of polarized light, obtain the surface distribution of the polarization characteristics of the detected light, and the length of the device is small, which is suitable for popularization and use. Description of the Drawings

[0021] Figure 1 is a schematic optical path diagram of the on-line polarized light characteristic test device provided by the present invention;

[0022] Figure 2 is Figure 1 the polarization direction coordinates of the light propagation direction in the on-line polarized light characteristic test device shown;

[0023] Figure 3 is Figure 1 the schematic structural diagram of the quarter-wave plate rotation structure in the on-line polarized light characteristic test device shown;

[0024] Figure 4 is Figure 1 the schematic structural diagram of the dual photoelastic modulator structure in the on-line polarized light characteristic test device shown.

[0025] Among them, the names corresponding to the reference numerals are as follows: 1 - surface to be measured, 2 - coupling lens group, 3 - polarization light phase difference adjustment element, 4 - polarization filtering element, 5 - detector, 21 - first lens, 22 - second lens, 23 - aperture stop, 31 - quarter-wave plate, 32 - mechanical drive mechanism, 33 - voice coil motor, 34 - first photoelastic modulator, 35 - second photoelastic modulator, 36 - photoelastic modulator controller. Detailed implementation manners

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. The implementation manners of the present invention include but are not limited to the following embodiments.

[0027] Embodiment 1:

[0028] As Figures 1-3 shown, the on-line polarization light characteristic test device provided by the present invention includes: a polarization measuring instrument and a surface to be measured 1; the polarization measuring instrument includes a coupling lens group 2, a polarization light phase difference adjustment element 3, a polarization filtering element 4, and a detector 5; the coupling lens group 2 includes a first lens 21, a second lens 22, and an aperture stop 23, and is used to perfect the imaging of the surface to be measured 1 on the detector 5; the polarization light phase difference adjustment element 3 is an element that realizes an adjustable phase difference between two perpendicular vibration components of light, and is one of an adjustable wave plate, a photoelastic modulator, and a liquid crystal polarization modulator; the polarization filtering element 4 is an element that realizes the transmission of a component of a certain specific vibration direction of light and filters out the component of the other vibration direction, and is one of a polarizing plate and a polarization beam splitting prism; the detector 5 is used to detect the light intensity, and the detector 5 is a CCD area array light intensity detector 5, which is connected to a computer or other data analysis devices. Specifically, in this embodiment, the polarization light phase difference adjustment element 3 is a rotating quarter-wave plate structure, including a quarter-wave plate 31, a mechanical drive mechanism 32, and a voice coil motor 33. The transmission polarization orientation of the polarization filtering element 4 is a polarization beam splitting prism with an angle of 0 degrees. The coupling lens group 2 includes a first lens 21, a second lens 22, and an aperture stop 23. After the light beam passes through the first lens 21 and the second lens 22, the incident angle of the light beam when it enters the subsequent elements is small. When in use, the light spot of the surface to be measured 1 is conjugatedly transmitted to the surface of the detector 5 through the coupling lens group 2, and the polarization light phase difference adjustment element 3 and the polarization filtering element 4 are inserted in its optical path. Among them, the polarization light phase difference adjustment element 3 adjusts the phase difference between the vibration components of light in different directions, so that the light components in different directions and phases are transmitted to the detector 5 through the polarization filtering element 4. When the light beam passes through the rotating quarter-wave plate 31, the components of the light beam in different directions sequentially generate a delay of pi / 4 in a circular order, so as to extract the Stokes matrix of the polarization light from the second harmonic and fourth harmonic components of the detected waveform, so as to extract the polarization information of the polarization light, so as to conveniently obtain the surface distribution map of the polarization characteristics.

[0029] Embodiment 2:

[0030] like Figure 4 As shown, in this embodiment, the polarization light phase difference adjustment element 3 is a dual photoelastic modulator structure, including a first photoelastic modulator 34, a second photoelastic modulator 35 and a photoelastic modulator controller 36. The fast axis orientations of the first photoelastic modulator 34 and the second photoelastic modulator 35 are 22.5° and -22.5°, respectively. When in use, the light spot on the surface to be measured 1 is conjugately transmitted to the surface of the detector 5 through the coupling lens group 2, and the polarization light phase difference adjustment element 3 and the polarization filter element 4 are inserted into the optical path. Among them, the polarization light phase difference adjustment element 3 adjusts the phase difference of the light components in different vibration directions, so that the light components in different directions and phases are transmitted to the detector 5 through the polarization filter element 4. When the light beam passes through the dual photoelastic modulator structure, two photoelastic modulators (first photoelastic modulator 34 and second photoelastic modulator 35) with different periods and a fast axis phase difference of 45 degrees are used to make the transmitted polarized light traverse different phase modulation states, and after passing through the polarization filter element 4, it is converted into an intensity signal. The detector 5 detects the DC quantity, the first-order and second-order Basel coefficients of the light intensity signal to extract the polarization information of the polarized light. The coupling lens group 2 makes the surface to be measured 1 and the detector 5 optically conjugate, so that the polarization signals detected by different pixels of the detector 5 correspond to different positions of the surface to be measured 11, and the surface distribution diagram of the polarization characteristics is obtained.

[0031] In addition, the device is also equipped with an adjustable attenuation plate, and uses fused quartz and XX coating technology to design and manufacture coupling mirrors, polarization beam splitters, and wave plates suitable for the ultraviolet band. A small-sized, short-focal-length macro lens is designed, and a small-sized wave plate drive structure is realized by using a voice coil motor 33. A reasonable integrated installation structure is used to reduce the size of the measuring instrument, so that the overall structure can be inserted into the optical path of existing semiconductor detection equipment.

[0032] After many rounds of experiments, the following combinations are the best experimental values:

[0033] The detection surface size is a 2mm circle;

[0034] The focal length of the first lens 21 is 5 mm, the focal length of the second lens 22 is 15 mm, and the size of the aperture 23 is 2 mm;

[0035] The quarter wave plate 31 is a zero-order air gap wave plate with a diameter of 6 mm and a wavelength of 193 nm;

[0036] The polarization filter element 4 is a coated quartz sheet, and the angle with the optical axis is 56.5 degrees. According to the experimental results of the best embodiment, the present invention can control the length dimension within 60mm, realize online real-time monitoring of polarized light characteristics, and obtain the surface distribution of the polarization characteristics of the detected light. It can realize the detection of polarization characteristics of VUV and DUV ultraviolet light. It can realize the detection of polarization characteristics of ultraviolet light, and for a narrow wavelength range, realize a total length of the detector 5 of less than 100mm.

Claims

1. An online polarization light characteristics testing device, characterized in that: include: Polarimeter and surface to be measured (1); The polarization measuring instrument comprises a coupling lens group (2), a polarized light phase difference adjustment element (3), a polarization filter element (4) and a detector (5); The coupling mirror group (2) is used to improve the imaging of the surface to be measured (1) on the detector (5); The polarized light phase difference adjusting element (3) is an element that realizes an adjustable phase difference between two vertical vibration components of light; The polarization filter element (4) is an element that allows a component of light in a certain vibration direction to pass through, while filtering out components in another vibration direction; The detector (5) is used to detect light intensity.

2. The online polarization light characteristic testing device according to claim 1, characterized in that: The coupling lens group (2) comprises a first lens (21), a second lens (22) and a diaphragm (23).

3. The online polarization light characteristic testing device according to claim 1, characterized in that: The transmission polarization orientation of the polarization filter element (4) is 0 degrees.

4. The online polarization light characteristic testing device according to claim 1, characterized in that: The polarized light phase difference adjustment element (3) is a rotating quarter-wave plate structure or a dual photoelastic modulator structure.

5. The online polarization light characteristic testing device according to claim 4, characterized in that: The rotating quarter-wave plate (31) structure comprises a quarter-wave plate (31), a mechanical transmission mechanism (32) and a voice coil motor (33).

6. The online polarization light characteristic testing device according to claim 4, characterized in that: The dual photoelastic modulator structure comprises a first photoelastic modulator (34), a second photoelastic modulator (35) and a photoelastic modulator controller (36).

7. The online polarization light characteristic testing device according to claim 6, characterized in that: The fast axis orientation degrees of the first photoelastic modulator (34) and the second photoelastic modulator (35) are 22.5° and -22.5° respectively.

8. The online polarization light characteristic testing device according to claim 2, characterized in that: The focal length of the first lens (21) is 5 mm, the focal length of the second lens (22) is 15 mm, and the size of the aperture (23) is 2 mm.

9. The online polarization light characteristic testing device according to claim 5, characterized in that: The quarter wave plate (31) is a zero-order air gap wave plate with a diameter of 6 mm and a wavelength of 193 nm.

10. The online polarization light characteristic testing device according to claim 1, characterized in that: The inclination angle of the polarization filter element (4) is 56.5°.

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