Device and method for nondestructive testing of structural depth of micro-nano optical elements

Abstract

The present invention discloses a device and method for nondestructive testing of the structural depth of a micro-nano optical element, comprising a test box and a box cover for sealing the test box, wherein a light source, a monochromator, a spectrometer, a micro-nano optical element to be tested, an integrating sphere, a reflector and a photomultiplier tube are arranged in the test box, and a computer arranged outside the test box is connected to the output end of the photomultiplier tube. The method of the present invention obtains the 0th order diffraction peak intensity I according to the Fraunhofer diffraction intensity distribution formula and the diffraction grating formula. 0peak Relationship with the transmittance T of micro-nano optical elements#imgabs0#The relationship between transmittance T and structure depth h is T=80‑0.07h. Substitute the measured transmittance value into the formula to calculate the structure depth h of the micro-nano optical element. The transmittance is used to calculate the structural feature size, which has the characteristics of high test efficiency and no damage to the sample.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-nano structure detection, and in particular to a device and method for non-destructive detection of the structural depth of a micro-nano optical element. Background Art

[0002] Micro-nano structures refer to structures and feature sizes that reach the micrometer or nanometer level. Common micro-nano structures include sub-wavelength grating structures and "moth-eye" structures. With the widespread application of micro-nano structures, people have higher and higher requirements for their spectral performance. Fresnel loss occurs when light passes through media with different refractive indices during transmission, resulting in reduced light utilization. Therefore, how to increase transmittance, suppress reflectivity, and thus improve light absorption has become a research hotspot. Compared with the traditional method of using anti-reflection coatings, directly processing micro-nano structures on optical surfaces has stability, durability, and more flexible coordination capabilities, and can achieve anti-reflection functions in a wide spectral range. At present, micro-nano structures have been widely used in optoelectronics, lasers, solar energy, aerospace and other fields.

[0003] For the manufactured micro-nano structures, relevant tests are required, including structural parameters and performance. Since the characteristic size parameters of micro-nano structures are basically submicron level (≤500nm), conventional optical microscopes cannot be used for detection. Other feasible detection methods, such as laser confocal microscopes and atomic force microscopes, have problems such as high equipment configuration requirements, high testing costs, and low testing efficiency. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides a method for non-destructive testing of the structural depth of a micro-nano optical element, which has the characteristics of high cost performance, high testing efficiency and low sample damage.

[0005] The technical solution adopted by the present invention is:

[0006] A device for nondestructive testing of the structural depth of a micro-nano optical element comprises a test box and a box cover for sealing the test box. A light source, a monochromator, a spectrometer, a micro-nano optical element to be tested, an integrating sphere, a reflector and a photomultiplier tube are arranged in the test box. A computer arranged outside the test box is connected to the output end of the photomultiplier tube.

[0007] Along the optical path, a light source is installed on one side of the test box, and then a monochromator and a beam splitter are installed on the same optical axis. A reflector is installed in front of the upper part of the beam splitter, and another reflector is installed at 90° to the lower part of the reflector. A photomultiplier tube is installed behind the reflector along the optical axis extension line of the monochromator. The output end of the photomultiplier tube is connected to the computer outside the test box. An integrating sphere is installed in front of the lower part of the beam splitter, and a photomultiplier tube is installed behind the output end of the integrating sphere. The test does not require darkroom conditions.

[0008] Preferably, the light source is a halogen lamp with a wavelength of 360 to 2000 nm.

[0009] A method for nondestructive testing of the structural depth of a micro-nano optical element comprises the following steps:

[0010] Step 1: Preheat the equipment. First, turn on the power of the measurement system and computer to preheat for about 2 to 3 minutes.

[0011] Step 2: Check the optical path. Turn on the light source and the operating software to check whether the system optical path is normal. The computer will display the check completion. Open the cover of the test system to check whether the reference optical path is normal, and then close the cover.

[0012] Step 3: Spectral range setting, set according to the spectral range of 400nm to 850nm that needs to be tested for micro-nano components;

[0013] Step 4: Equipment calibration, open the operating software, start the transmitted light collection, perform a spectral transmittance test once, and return the transmittance test to 100%;

[0014] Step 5: Clean the object to be tested, wipe the surface and back of the micro-nano optical element to be tested with alcohol, and then test it after cleaning;

[0015] Step 6: Load the device under test, open the test box cover of the measurement system, load the micro-nano optical element to be tested, and close the cover;

[0016] Step 7: Measure the transmittance curve, collect the transmitted light and measure the transmittance in the spectral range. At this time, the light emitted by the light source is continuously separated into monochromatic light by the monochromator, and then divided into two beams of light by the spectrometer, one for reference light and the other for measurement light. The measurement light irradiates the micro-nano optical element, and the light is refracted by the reflector. The reference light and the transmitted light of the micro-nano optical element are alternately received by the high-sensitivity photomultiplier tube, and the collected transmitted light and reference light signals are converted into electrical signals, which are output to the computer. After software processing, the transmittance curve of the micro-nano optical element is obtained.

[0017] Step 8: Calculate the structure of the micro-nano optical element according to the Fraunhofer diffraction intensity distribution formula:

[0018]

[0019] Where: I(fx) is the diffraction intensity; fx = sinθ / λ, θ is the diffraction angle, λ is the incident wavelength; L is the total width of the structure; m is the diffraction order, which can be a positive or negative integer; h is the structure depth; c is the transmittance; A is the structure period;

[0020] And the diffraction grating formula:

[0021] mλ=A(sinα±sinθ)

[0022] Where: m is the diffraction order, which can be a positive or negative integer; λ is the incident wavelength; A is the structural period; α is the incident angle; θ is the diffraction angle;

[0023] Get the 0th order diffraction peak intensity I 0peak The relationship with the transmittance T of micro-nano optical elements is:

[0024]

[0025] Where: h is the structural depth; λ is the incident wavelength;

[0026] The relationship between transmittance T and structure depth h is: T=80-0.07h. Substituting the measured transmittance value into the formula, the structure depth h of the micro-nano optical element is calculated.

[0027] Furthermore, the structure depth h is in the range of 400nm to 600nm.

[0028] The beneficial effects of the present invention are:

[0029] This method is based on optical theoretical analysis and calculates the structural feature size through transmittance. There is no need to focus on the surface. The measured depth data is reliable. It has the characteristics of high cost performance, high test efficiency and low sample damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : Schematic diagram of the structure of the micro-nano optical element under test.

[0031] Figure 2 : Schematic diagram of the composition structure of the nondestructive testing device of the present invention.

[0032] Figure 3 : Flow chart of the nondestructive testing method of the present invention.

[0033] Figure 4 : The measured transmittance curve of micro-nano optical elements using the method of the present invention.

[0034] Figure 5 : A graph showing the transmittance of micro-nano optical elements versus their structural depth.

[0035] In the figure: 1-micro-nano structure, 2-light source; 3-monochromator; 4-beam splitter; 5-micro-nano optical element to be tested; 6-integrating sphere; 7-reflector; 8-photomultiplier tube; 9-test box; 10-box cover; 11-computer. DETAILED DESCRIPTION

[0036] Reference Figure 1 Micro-nano optical elements are micro-nano structures made on transparent materials to modulate incident light. The feature size is at the sub-micron level.

[0037] Example 1

[0038] Reference Figure 2 A device for nondestructive testing of the structural depth of a micro-nano optical element comprises a test box 9 and a box cover 10 for sealing the test box. A light source 2, a monochromator 3, a spectrometer 4, a micro-nano optical element 5 to be tested, an integrating sphere 6, a reflector 7 and a photomultiplier tube 8 are arranged in the test box 9. A computer 11 arranged outside the test box 9 is connected to the output end of the photomultiplier tube 8.

[0039] A light source 2 is arranged on one side inside the test box 9, and a monochromator 3 and a beam splitter 4 are installed behind the light along the optical axis along the direction of the light path, a reflector 7 is installed just in front of the upper part of the beam splitter 4, and another reflector 7 is installed just below the reflector 7 at an angle of 90°, and a photomultiplier tube 8 is installed behind the reflector 7 along the extension line of the optical axis of the monochromator 3, and the output end of the photomultiplier tube 8 is connected to a computer 11 outside the test box 9, and an integrating sphere 6 is installed just in front of the lower part of the beam splitter 4, and the micro-nano optical element 5 to be tested is located between the beam splitter 4 and the integrating sphere 6, and a photomultiplier tube 8 is installed behind the exit end of the integrating sphere 6.

[0040] Reference Figure 2 ,The light source is a halogen lamp fixed by a bracket, with a wavelength of 360 to 2000nm;

[0041] Reference Figure 2 , monochromators, beam splitters, reflectors, integrating spheres, photomultiplier tubes, and computers are all optoelectronic instruments and electronic components that meet national or industry standards.

[0042] Reference Figure 2 When using an integrating sphere, it is necessary to ensure that the transmitted light information can be collected by the photomultiplier tube, and the positions of the integrating sphere and the photomultiplier tube need to be assembled and corrected.

[0043] Example 2

[0044] Reference Figure 3, a method for nondestructively testing the structural depth of a micro-nano optical element using the device in Example 1, wherein the measurement operation flow is as follows:

[0045] Step 1: Preheat the equipment. First, turn on the power of the measurement system and computer to preheat for about 2 to 3 minutes.

[0046] Step 2: Check the system optical path. Turn on the light source and the operating software to check whether the system optical path is normal. The computer will display the completion of the check.

[0047] Step 3: Check the reference light path, open the cover of the test system, check whether the reference light path is normal, and then close the cover;

[0048] Step 4: Spectral range setting: set the spectral range of 400nm to 850nm according to the spectral range of 400nm to 850nm required for testing of micro-nano components;

[0049] Step 5: Equipment calibration, open the operating software, start the transmitted light collection, perform a spectral transmittance test once, and return the transmittance test to 100%;

[0050] Step 6: Clean the tested object, wipe the surface and back of the micro-nano optical element to be tested with alcohol, and then test it after cleaning;

[0051] Step 7: Load the device under test, open the test box cover of the measurement system, load the micro-nano optical element to be tested, and close the cover;

[0052] Step 8: Measure the transmittance curve. Collect the transmitted light and measure the transmittance in the spectral range. At this time, the light emitted by the light source is continuously separated into monochromatic light by the monochromator, and then divided into two beams by the spectrometer, one for reference light and the other for measurement light. The measurement light irradiates the micro-nano optical element, and the light is refracted by the reflector. The reference light and the transmitted light of the micro-nano optical element are alternately received by the highly sensitive photomultiplier tube, and the collected transmitted light and reference light signals are converted into electrical signals, which are output to the computer. After software processing, the transmittance curve of the micro-nano optical element is obtained.

[0053] Step 9: Calculate the structure of micro-nano optical elements. According to the Fraunhofer diffraction intensity distribution formula and the diffraction grating formula mλ=A(sinα±sinθ), when the 0th order diffraction peak intensity is positively correlated with the transmittance of the micro-nano optical element, the 0th order diffraction peak calculation formula is It can be seen that the peak intensity is determined by the structural depth and the incident wavelength. Therefore, under the premise of a fixed incident wavelength, the transmittance decreases with the increase of the micro-nano structure depth. In the range of 400nm to 600nm, the transmittance T and the structural depth h are linearly negatively correlated. Substituting the measured transmittance value into the Th relationship, the structural depth h of the micro-nano optical element can be calculated.

[0054] The data processing software of the present invention is all designed by ourselves.

[0055] Reference Figure 1 , Figure 4 ,from Figure 4 It can be seen from the transmittance curves that the transmittance curves of different micro-nano optical element samples are highly different. The reason is that the micro-nano structure depths of the two samples are different. Under the same incident wavelength conditions, according to the 0th order diffraction peak calculation formula It can be seen that the deeper the micro-nano structure is, the lower the transmittance in this band is. When the incident wavelength is 440nm, the relationship between the transmittance T and the structure depth h is: T = 80-0.07h.

[0056] Example 3

[0057] Reference Figure 4 , 5 , an example of calculating the structural depth of micro-nano optical elements:

[0058] from Figure 4 It can be read that the transmittance of sample 1 corresponding to 420nm is 47.7%, and the transmittance of sample 2 is 38.3%.

[0059] exist Figure 5 It can be seen that the structure depth corresponding to the transmittance of 47.7% is 460nm, and the structure depth corresponding to the transmittance of 38.3% is 595nm. That is, the structure depth of sample 1 is h = 460nm, and the structure depth of sample 2 is h = 595nm.

[0060] The present invention uses the measured transmittance curve to calculate the structural depth of the micro-nano optical element, which is consistent with the actual situation. Therefore, the measurement method and the measured depth data are reliable.

Claims

1. A method for nondestructive testing of the structural depth of a micro-nano optical element, characterized in that: The method is implemented by using a device for non-destructive detection of the structural depth of a micro-nano optical element, the device comprising: A test box (9) and a box cover (10) for sealing the test box; a light source (2), a monochromator (3), a spectrometer (4), a micro-nano optical element (5) to be tested, an integrating sphere (6), a reflector (7) and a photomultiplier tube (8) are arranged in the test box (9); a computer (11) connected to the output end of the photomultiplier tube (8) is arranged outside the test box (9); the light source (2) is arranged on one side inside the test box (9); a monochromator (3) and a spectrometer (4) are installed behind the light source (2) on the same optical axis along the direction of the light path; A reflector (7) is installed in front of the upper part of the optical device (4), another reflector (7) is installed at 90 degrees to the lower part of the reflector (7), a photomultiplier tube (8) is installed behind the reflector (7) along the optical axis extension line of the monochromator (3), the output end of the photomultiplier tube (8) is connected to a computer (11) outside the test box (9), an integrating sphere (6) is installed in front of the lower part of the spectrometer (4), the micro-nano optical element (5) to be measured is located between the spectrometer (4) and the integrating sphere (6), and a photomultiplier tube (8) is installed behind the output end of the integrating sphere (6) The method comprises the following steps: The first step is to preheat the equipment: first turn on the power of the measurement system and computer to preheat for 2 to 3 minutes; The second step is to check the optical path: turn on the light source and the operating software to check whether the system optical path is normal. The computer will display the completion of the inspection. Open the cover of the test system to check whether the reference optical path is normal, and then close the cover. The third step is to set the spectral range: set the spectral range according to the test requirements of the micro-nano components; Step 4: Equipment calibration: Open the operating software, start the transmitted light collection, perform a spectral transmittance test once, and return the transmittance test to 100%; Step 5: Clean the tested object: wipe the surface and back of the micro-nano optical element to be tested with alcohol, and then test it after cleaning; Step 6: Load the test piece: open the test box cover of the measurement system, load the micro-nano optical element to be tested, and close the cover; The seventh step is to measure the transmittance curve: collect the transmitted light and measure the transmittance in the spectral range. At this time, the light emitted by the light source is continuously separated into monochromatic light by the monochromator, and then divided into two beams of light by the spectrometer, one for reference light and the other for measurement light. The measurement light irradiates the micro-nano optical element, and the light is refracted by the reflector. The reference light and the transmitted light of the micro-nano optical element are alternately received by the high-sensitivity photomultiplier tube, and the collected transmitted light and reference light signals are converted into electrical signals, which are output to the computer. After software processing, the transmittance curve of the micro-nano optical element is obtained. Step 8: Calculate the structural depth of micro-nano optical elements: According to the Fraunhofer diffraction intensity distribution formula Where: I(fx) is the diffraction intensity, fx = sinθ / λ, θ is the diffraction angle, λ is the incident wavelength, L is the total width of the structure, m is the diffraction order, which can be a positive or negative integer, h is the structure depth, c is the transmittance, and A is the structure period; And the diffraction grating formula: mλ=A(sinα±sinθ) Where: m is the diffraction order, which can be a positive or negative integer, λ is the incident wavelength, A is the structural period, α is the incident angle, and θ is the diffraction angle; Get the 0th order diffraction peak intensity I 0peak The relationship with the transmittance T of micro-nano optical elements is: Where: h is the structural depth, λ is the incident wavelength; The relationship between transmittance T and structure depth h is: T=80-0.07h Substitute the measured transmittance T value into the formula to calculate the structural depth h of the micro-nano optical element.

2. The method according to claim 1, characterized in that In the third step: The spectrum ranges from 400nm to 850nm.

3. The method according to claim 2, characterized in that In the fourth step: The spectral transmittance is tested once, and the transmittance test is 100% and returns to zero.

4. The method according to any one of claims 1 to 3, characterized in that: The structural depth h is in the range of 400nm to 600nm.

5. The method according to any one of claims 1 to 3, characterized in that: The light source (2) is a halogen lamp with a wavelength of 360 to 2000 nm.

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