CN110013999B - Tritium-polluted optical film nondestructive removal method based on inert ion beam etching - Google Patents
Tritium-polluted optical film nondestructive removal method based on inert ion beam etching Download PDFInfo
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Abstract
The invention belongs to the technical field of optical element manufacturing, and particularly relates to a tritium-polluted optical film nondestructive removal method based on inert ion beam etching. Aiming at the defect that tritium-polluted optical film is removed by acid etching in the prior art, the technical scheme of the invention is as follows: firstly, measuring the thickness of an optical film of the optical element to be stripped in the same process; then calibrating the etching rate of the ion beam to the optical film on the surface of the element; finally, the tritium-polluted optical film on the surface of the element is accurately etched and removed by adopting inert ion beams with the energy of 100 eV-1500 eV, the beam current of 100 mA-500 mA and the ion beam incidence angle of-90 DEG-90 deg. The method can effectively solve the defect that the tritium-polluted optical film is removed by the existing acid etching technology, and simultaneously ensures that the surface quality, the optical performance and the laser damage resistance of the optical substrate are not influenced.
Description
Technical Field
The invention belongs to the technical field of optical element manufacturing, and particularly relates to a tritium-polluted optical film nondestructive removal method based on inert ion beam etching.
Background
Energy sources play a vital role for economic development and social civilization progress, and the economic and social development depends on the important basis of energy sources to a great extent. The fusion energy is a new energy which is environment-friendly and renewable. Laser-driven Inertial Confinement Fusion (ICF) is one of the possible ways to realize fusion energy, and is to use intense laser to heat nuclear fuel to generate high-temperature and high-pressure plasma to realize nuclear fusion reaction and release energy. High power solid state laser devices, as drivers for ICFs, contain a large number of optical components such as gratings, windows, shields, lenses, amplifiers, polarizers, frequency conversion crystals, and the materials used include fused silica, neodymium glass, BK7, KDP, etc., and require very high output power. However, these optical elements have a reflectivity of up to 8%, and the laser energy transmitted to the target chamber is severely reduced after the laser passes through a large number of optical elements in the optical path. In order to reduce the energy loss during transmission or achieve certain optical performance, most components need to be coated with optical films, such as antireflection films, high-reflection films, polarizing films, light splitting films, wavelength separation films, and the like. In addition, the optical film in the system is required to be able to operate stably for a long period of time without significant degradation of performance.
The influence of the cleanliness of the operating environment on the load capacity of the element is a long-term cumulative effect, and various types of pollutants in the environment reach the surface of the optical element through processes of sedimentation, adsorption and the like, so that the optical film is polluted. In addition, the optical film used in the high-power laser device often contains tritium contamination and is difficult to handle. Meanwhile, the optical film can cause optical performance degradation after long-term use, and the laser damage threshold is reduced, thereby causing destructive damage. However, large-aperture optical substrates are very expensive and cannot be discarded directly, so as to avoid resource waste and environmental pollution. Therefore, the tritium-contaminated optical film on the surface of the off-shelf optical element needs to be thoroughly removed, and then the damaged point needs to be repaired, and the optical film needs to be re-plated and recycled. At present, the technology for removing the tritium-contaminated optical film is mainly an acid etching technology, and although the acid etching can quickly and effectively remove the tritium-contaminated optical film on the surface of an element, the following problems also exist: the acid etching has the characteristic of isotropy, which can cause impurities and defects to be copied downwards, increase the transverse and longitudinal dimensions, increase the roughness and deteriorate the surface quality, and the film layer in a damaged area can not be completely removed; reaction product SiF6 2-The coating is easy to deposit on the surface of an optical substrate and tends to cause large-area surface fogging; more seriously, after the tritium-polluted optical film is removed, tritium and tritium compounds are dissolved in corrosive liquid, waste liquid is not easy to recover and treat, the treatment cost is very high, the cost is high, and the damage to the environment and human bodies is very large. The defects not only seriously affect the optical transmission characteristic of the substrate after the tritium-polluted optical film is removed and reduce the laser damage resistance of the substrate, but also seriously limit the application of the acid etching technology in the removal of the tritium-polluted optical film.
In the high-power laser device, after the tritium-polluted optical film on the surface of the optical element is thoroughly removed, the surface of the optical substrate is required to be free of pollution, the surface quality, the optical performance and the laser damage resistance of the substrate are not affected, in addition, tritium pollutants can be conveniently and effectively treated, and the harm to the environment and human bodies is avoided. At present, the existing membrane removal technology can not meet the requirements. Therefore, there is an urgent need to find a highly efficient, uniform, safe, reliable and environmentally friendly tritium-contaminated optical film removal technique without reducing the surface quality, optical properties and laser damage threshold of the optical substrate.
The ion beam etching is to generate cascade collision by bombarding the surface of the material with energetic ions, so as to sputter out surface atoms, achieve the purpose of etching, and remove the surface of the material. The etch product of the process is often a mixture of non-volatile and volatile products, typically in the form of volatile molecules/atomic states or clusters of molecules/atoms, and the solid macromolecular clusters are typically non-volatile products. Non-volatile products will deposit on the inner walls of the vacuum chamber and volatile products can be pumped away by the continuously operating pumping system into the collector. Solid and gaseous tritium contaminants are much easier to handle than liquid tritium contaminated solutions.
The ion beam etching technology mainly has the following advantages: (1) due to the non-contact characteristic, new defects and pollution cannot be introduced in the etching process; (2) the characteristic of anisotropy, the figure outline can be controlled by changing the incident angle of an ion beam in the etching process; (3) an atomic level layer-by-layer peeling technology can obtain a smooth surface; (4) the charged particles have small energy, act on a plurality of atomic layers on the surface of the material, and almost have no damage and stress generation; (5) the parallel ion beams have good directionality and can uniformly and effectively remove the surface layer of the material; (6) the material is not selective and is not limited by materials (metals and compounds, inorganic substances and organic substances, insulators and semiconductors); (7) the etching depth can be accurately controlled; (8) the etching products are easy to handle. The ion beam etching technology is a non-contact material surface layer removing technology which is efficient, uniform, safe, reliable and environment-friendly.
However, when the ion beam bombards the surface of the material, the etching parameters have a great influence on the etching rate and surface quality of the material, the incident depth of the ions, and the damage degree of the substrate. If the parameters are not reasonable, damage may be caused to the substrate surface of the optical element, so that new defects or increased roughness may be generated on the substrate surface, which may adversely affect the surface quality, optical properties and laser damage resistance of the element substrate. At present, for ion beam etching used for surfaces of various substrate materials, ion beams with etching parameter ranges are absolutely safe and have no quantitative standard. The determination of the "quantitative standard" is not easy due to the influence of the variety of the substrate material, the etching time, the vacuum degree and other experimental conditions on the etching effect. Therefore, the current ion beam etching technology cannot be applied to the removal of the tritium-contaminated optical film.
Disclosure of Invention
Aiming at the defect of using acid etching to remove the tritium-polluted optical film in the prior art, the invention provides a tritium-polluted optical film nondestructive removal method based on inert ion beam etching, which aims to: the surface quality, the optical performance and the laser damage resistance of the optical substrate are not affected in the process of removing the optical film by inert ion beam etching.
The technical scheme adopted by the invention is as follows:
a tritium-contaminated optical film nondestructive removal method based on inert ion beam etching comprises the following steps:
[1] measuring the thickness of an optical film which has the same process with the optical element to be subjected to film removal to obtain the thickness of the film to be removed (namely the thickness of the optical film on the surface of the element to be subjected to film removal), and further determining the thickness of the film removed by ion beam etching in the calibration process;
[2] testing the optical film which has the same process with the optical element to be subjected to film removal, and calibrating the etching rate of the ion beam on the optical film of the type;
[3] calculating the time for completely removing the film to be removed according to the thickness of the film to be removed and the etching rate obtained by calibration in the steps (1) and (2); then, etching the surface of the optical element to be subjected to film removal by adopting an ion beam, wherein the etching time is set as the time for completely removing the film to be removed, which is obtained by calculation, and finally obtaining the optical element after film removal;
[4] and (4) cleaning the optical element (namely the substrate) subjected to the film removal and obtained after the treatment of the step [3 ].
After the technical scheme is adopted, the time required for completely etching the film to be removed can be estimated by calibrating the etching rate, so that the ion beam etching can be controlled to only remove the optical film on the surface of the substrate in the optical element without excessively etching the substrate, and the surface quality, the optical property and the laser damage resistance of the element substrate can not be obviously reduced.
Preferably, the method for determining the thickness of the optical film in step [1] employs one of a step meter, a scanning electron microscope cross-section or an ellipsometer. The method of measurement is selected according to the type of substrate, the film material and the thickness.
Preferably, the thickness of the film removed by ion beam etching in the calibration process is determined according to the measurement result of the thickness of the film to be removed.
Under the condition that the thickness of the film to be removed is greater than or equal to 100nm, the thickness of the film removed by ion beam etching in the calibration process is smaller than the thickness of the film to be removed, and the calibration method in the step [2] comprises the following specific steps: and in a fixed time, removing one layer of the optical film on the surface of the element by ion beam etching, wherein the etching depth is the thickness of the film removed by the ion beam etching in the calibration process, then measuring the etching depth or the thickness of the residual film layer to obtain the thickness of the film removed by the ion beam etching in the calibration process, and determining the etching speed of the ion beam on the optical film of the type by dividing the thickness of the film removed by the ion beam etching in the calibration process by the etching time in the calibration process.
Under the condition that the thickness of the film to be removed is less than 100nm, the thickness of the film removed by ion beam etching in the calibration process is equal to the thickness of the film to be removed, and the calibration method in the step [2] comprises the following specific steps: and (3) carrying out gradient stripping on the optical film by using ion beams, testing the transmittance of the optical element to a specific wavelength every time when etching is carried out for a period of time, obtaining a relationship curve of the transmittance and the time, wherein the transmittance inflection point approaching to the substrate of the optical element in the curve is the time point when the optical film is just completely removed, and determining the etching speed of the ion beams on the optical film of the type by dividing the thickness of the film to be removed by the etching time in the calibration process.
Further preferably, in the step [2], in the case that the thickness of the film to be removed is greater than or equal to 100nm, the etching depth is measured by using a step meter or the thickness of the remaining film layer is measured by using a scanning electron microscope cross section or by using an ellipsometer.
In the step [2], under the condition that the thickness of the film to be removed is less than 100nm, an ultraviolet-visible spectrophotometer is adopted to test the transmittance of the optical element to a specific wavelength.
Preferably, the ion beam is an inert ion beam, and the inert ion is an ion of an inert element selected from helium, neon, argon, krypton, and xenon.
More preferably, the ion beam energy is 100eV to 1500eV, the beam current is 100mA to 500mA, and the ion beam incident angle is-90 DEG to 90 deg.
Preferably, the fixed-point etching is performed on the optical element with the aperture smaller than the ion beam spot, and the scanning etching is performed on the optical element with the aperture larger than the ion beam spot.
Preferably, in the ion beam etching process in the step [2] and the step [3], a diaphragm made of the same material as a substrate of the optical element is used for shielding the optical element subjected to etching. The size of the diaphragm is adjusted according to the size of the sample so as to avoid pollution caused by sputtering deposition and maintain a clean working environment.
Preferably, in the ion beam etching process in step [2] and step [3], the treatment method of tritium-containing contaminants generated is as follows: pumping out generated gas tritium through an air pumping system, and installing a molecular sieve at an outlet of an air pumping pipeline to perform solidification treatment and collection on the gas tritium; and periodically cleaning the non-volatile tritiated deposited on the inner wall of the vacuum chamber. In this preferred scheme, gaseous tritium and small molecule granule will be taken away by air exhaust system, easily carry out solidification treatment and collection, and the tritide of large molecule group clan etc. deposits at the vacuum chamber inner wall with the form of solid, and easy clean handling finally realizes getting rid of the tritium pollution from the component surface with the form of gas and solid. Therefore, the etching product is easy to process, low in cost, environment-friendly and safe.
Preferably, the method for cleaning the optical element in the step [4] is to perform megasonic cleaning on the optical element by using deionized water, wherein the cleaning time is 10-30 min, and then blow-drying.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the invention provides a tritium-polluted optical film nondestructive removal method based on inert ion beam etching, which can effectively remove an optical film on the surface of an element, does not influence the surface quality, optical performance and laser damage resistance of a substrate and the subsequent use of the element, and has important significance for the recycling of the optical element.
2. The technical scheme successfully applies the ion beam etching to the nondestructive removal of the tritium-polluted optical film, and compared with the method adopting acid etching in the prior art, the ion beam etching has the advantages that: the method is a non-contact film removing technology, and new defects and pollution cannot be introduced in the etching process; the pattern profile can be controlled by varying the ion beam incident angle; a smooth surface can be obtained after etching, and almost no damage and stress generation can be caused; the optical film on the surface of the element can be uniformly and effectively removed, and the large-caliber optical element can be processed by scanning and etching; the coating is not limited by a film material, an element type and a coating process; the etching depth can be accurately controlled.
3. Aiming at tritium-containing pollutants generated after etching, gaseous tritium and small molecular particles are pumped away by an air pumping system, solidification treatment and collection are easy to carry out, tritide of large molecular groups and the like are deposited on the inner wall of a vacuum chamber in a solid form, cleaning treatment is easy to carry out, and finally tritium pollution is removed from the surface of an element in the form of gas and solid. Therefore, the etching product is easy to process, low in cost, environment-friendly and safe.
Drawings
The invention will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic flow diagram of the present invention;
FIG. 2 is a microscope image of the surface of an optical member of comparative example one of the present invention;
FIG. 3 is a microscope image of the surface of an optical member of comparative example No. 2 of the present invention;
FIG. 4 is a graph showing the transmittance of an optical element at 355nm wavelength as a function of time for a given etch rate in accordance with one embodiment of the present invention;
FIG. 5 is a microscope image of the surface of an optical element after etching in accordance with one embodiment of the present invention;
FIG. 6 is a graph showing the transmittance of an optical element at 355nm wavelength as a function of time for a given etch rate in accordance with one embodiment of the present invention;
FIG. 7 is a microscope image of the surface of an optical element after etching in accordance with example two of the present invention;
FIG. 8 is a scanning electron microscope image of the surface of an optical member of comparative example three of the present invention;
FIG. 9 is a scanning electron microscope image of the surface of an optical element according to a third embodiment of the present invention;
FIG. 10 is a scanning electron microscope image of the surface of an optical element after a triple etch in accordance with an embodiment of the present invention;
FIG. 11 is a scanning electron microscope image of the surface of an optical element after four etches in accordance with an embodiment of the present invention.
Detailed Description
All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive.
The present invention will be described in detail with reference to fig. 1 to 11.
A tritium-contaminated optical film nondestructive removal method based on inert ion beam etching comprises the following steps:
(1) measurement of film thickness: measuring the thickness of the optical film which has the same process with the optical element to be stripped (specifically selecting the thickness according to the type of the substrate, the film material) by using a step instrument, a scanning electron microscope section, an ellipsometer and the like;
(2) calibrating the etching rate: aiming at the optical film on the surface of the optical element in the step (1), calibrating the etching rate of the ion beam to the optical film, wherein the calibration method comprises the following two conditions:
(a) film thickness of 100nm or more: in a fixed time, removing a layer of the optical film on the surface of the element by ion beam etching (the etching depth is required to be controlled to be smaller than the thickness of the optical film), and then measuring the etching depth by using a step instrument, or measuring the thickness of the residual film by using methods such as a scanning electron microscope section and an ellipsometer, and dividing the etching depth by time to obtain the etching rate of the ion beam on the optical film prepared by the process;
(b) case of film thickness less than 100 nm: and (3) carrying out gradient stripping on the optical film on the surface of the element by using ion beams, testing the transmittance of the optical element to a specific wavelength by using an ultraviolet-visible spectrophotometer every time when etching is carried out for a period of time, obtaining a relation curve of the transmittance and the time, wherein a transmittance inflection point approaching to the optical substrate in the relation curve is the time when the film layer is just removed, and the etching rate of the ion beams on the optical film can be obtained by dividing the thickness of the optical film by the time.
(3) Removing the film by ion beam etching: calculating the time required by the complete removal of the optical film on the surface of the element to be subjected to film removal based on the thickness of the film to be removed (namely the optical film on the surface of the element to be subjected to film removal) determined in the step (1) and the etching rate calibrated in the step (2), etching the surface of the optical element by adopting ion beams, and setting the etching time as the time obtained by the calculation, so that the tritium-polluted optical film on the surface is completely removed, and meanwhile, the surface quality, the optical property and the laser damage resistance of the element substrate are ensured.
As a preferable mode, the inert ions used in the ion beam are ions of one element of helium, neon, argon, krypton, or xenon; the energy of the ion beam is 100 eV-1500 eV; the beam current is 100 mA-500 mA; the incident angle of the ion beam is-90 to 90 degrees; the size of the beam spot of the ion beam is 600mm multiplied by 60mm, fixed-point etching is carried out on the small-caliber element, and scanning etching is carried out on the large-caliber element.
As a preferred approach, the beam spot uniformity and stability should be better than 95%; the background vacuum degree of the etching machine is better than 2 multiplied by 10-3Pa; adopting a diaphragm made of the same material as the optical substrate for shielding, wherein the size of the diaphragm is adjusted according to the size of the sample so as to avoid pollution caused by sputtering deposition and maintain a clean working environment; the neutralizer is used for providing negatively charged electrons to neutralize the positively charged ion beam, and the emitted electron current is 100 mA-900 mA.
As a preferable scheme, the treatment method of tritium-containing pollutants generated by etching comprises the following steps: gas tritium is pumped out through an air pumping system, and a molecular sieve and the like are arranged at the outlet of an air pumping pipeline to carry out solidification treatment and collection on the gas tritium; the non-volatile tritiated compound deposited on the inner wall of the vacuum chamber is cleaned regularly, and can be polished and combined with dry ice CO2Pellets or other methods for cleaning.
(4) Cleaning an optical substrate: and (4) carrying out megasonic cleaning on the substrate of the optical element subjected to the film removal in the step (3) by using deionized water for 10-30 min, and then drying by using nitrogen.
The technical scheme has wide application range and has no limitation on the type, the material and the coating process of the optical element.
The above scheme is further illustrated by the following specific examples:
comparative example 1
The comparative example was a fused silica element of 30 mm. times.30 mm. times.4 mm, and a surface microscopic image was obtained, and as shown in FIG. 2, the transmittance, the surface roughness, and the laser damage threshold at a wavelength of 355nm of the element were 92.69%, 1.078nm, and 6.918J/cm, respectively2Listed in table 1.
Comparative example No. two
The comparative example is a fused quartz component of 30mm × 30mm × 4mm, the surface of which is plated with triple frequency multiplication sol-gel SiO2The thickness of the antireflection film on the surface of the element is measured to be 73nm by an ellipsometer; the surface microscopic images were measured, and as shown in FIG. 3, the transmittance, surface roughness and laser damage threshold at 355nm of the device were 98.27%, 2.569nm and 8.634J/cm, respectively2Listed in table 1.
Example one
This example is an optical element to be stripped: the size of the fused quartz substrate is 30mm multiplied by 4mm, and the surface is plated with triple frequency multiplication sol-gel SiO2And (4) an anti-reflection film. Measuring the thickness of the optical film of the optical element to be stripped in the same process by using an ellipsometer to be 73 nm; then, the energy is 400eV, the beam current is 300mA, and the incident angle is 00The argon ion beam etches the optical film on the surface of the element for 1, 1.5, 2, 2.5, 3 and 6min in sequence, an ultraviolet-visible spectrophotometer is adopted to test the transmittance of the element with the wavelength of 355nm after each etching to obtain a relationship curve of the transmittance and the time, as shown in figure 4, the transmittance inflection point which approaches to the optical substrate is the time of just removing the film layer, which is 2min, and the etching rate of the ion beam to the optical film is 36.5 nm/min; by usingAnd etching the optical film on the surface of the element to be subjected to film removal at a fixed point for 2min by using the same ion beam parameters, and measuring an optical microscope image of the surface of the element after etching, wherein the optical film is completely removed and no pollution is introduced as shown in FIG. 5. The measured transmittance, surface roughness and laser damage threshold of the substrate with the wavelength of 355nm after the film is removed are listed in table 1, and the comparison with the first and second comparative examples shows that the optical performance, surface quality and laser damage performance of the substrate are not affected after the film is removed, and are even better than those of the uncoated fused quartz element.
Example two
This example is an optical element to be stripped: the size of the fused quartz substrate is 30mm multiplied by 4mm, and the surface is plated with triple frequency multiplication sol-gel SiO2And (4) an anti-reflection film. Measuring the thickness of the optical film of the optical element to be stripped in the same process by using an ellipsometer to be 73 nm; then, the energy is 1000eV, the beam current is 300mA, and the incident angle is 00The argon ion beam etches the optical film on the surface of the element for 0.5, 1, 1.5, 2 and 4min in sequence, an ultraviolet-visible spectrophotometer is adopted to test the transmittance of the element with the wavelength of 355nm after each etching to obtain a relationship curve of the transmittance and the time, as shown in figure 6, the inflection point of the transmittance approaching to the optical substrate is the time of just removing the film layer, which is 1.3min, and the etching rate of the ion beam to the optical film is 56.15 nm/min; and (3) etching the optical film on the surface of the element to be subjected to film removal at fixed points for 1.5min by using the same ion beam parameters, and measuring an optical microscope image of the surface of the element after etching, wherein the optical film is completely removed and no pollution is introduced as shown in figure 7. The measured transmittance, surface roughness and laser damage threshold of the substrate with the wavelength of 355nm after the film is removed are listed in table 1, and the comparison with the first and second comparative examples shows that the optical performance, surface quality and laser damage performance of the substrate are not affected after the film is removed.
TABLE 1 comparison of properties of fused silica Components before and after film removal
Comparative example No. three
The comparative example is diameterThe surface roughness and the laser damage threshold of the K9 glass element with the thickness of 50mm and 5mm are respectively 1.245nm and 7.82J/cm as shown in FIG. 82Listed in Table 2.
EXAMPLE III
This example is an optical element to be stripped: the K9 substrate has a size of phi 50mm multiplied by 5mm and is coated with sol-gel SiO2And (3) a membrane. Measuring the thickness of the optical film which is processed in the same way as the optical element to be subjected to film removal by using a step profiler to be 277.6 nm; then, etching the optical film on the surface of the element for 4min by using an argon ion beam with the energy of 400eV, the beam current of 300mA and the incident angle of 30 degrees, wherein the etching depth is 141.1nm measured by using a step profiler, and the etching rate of the ion beam on the optical film is 35.27 nm/min; and etching the optical film on the surface of the element to be subjected to film removal at fixed points for 8min by adopting the same ion beam parameters, and measuring a scanning electron microscope image of the surface of the etched element, wherein the optical film is completely removed and no pollution is introduced as shown in figure 10. The measured surface roughness and the laser damage threshold of the substrate after the film is removed are listed in table 2, and as can be seen from comparison with the third comparative example, after the film is removed, the surface quality and the laser damage performance of the substrate are not affected, and even are better than those of the K9 glass element without the film.
Example four
This example is an optical element to be stripped: the K9 substrate has a size of phi 50mm multiplied by 5mm and is coated with sol-gel SiO2And (3) a membrane. Measuring the thickness of the optical film which is processed in the same way as the optical element to be subjected to film removal by using a step profiler to be 324.36 nm; then, the energy is 400eV, the beam current is 100mA, and the incident angle is 300The argon ion beam etches the optical film on the surface of the element for 9min, the etching depth measured by a step profiler is 138.64nm, and the etching rate of the ion beam on the optical film is 15.4 nm/min; and etching the optical film on the surface of the element to be subjected to film removal at fixed points for 22min by using the same ion beam parameters, and measuring a scanning electron microscope image of the surface of the etched element, wherein the optical film is completely removed and no pollution is introduced as shown in FIG. 11. The measured surface roughness and laser damage threshold of the substrate after the film removal are listed in table 2, and as can be seen from comparison with the third comparative example, the surface quality and laser damage performance of the substrate are not affected after the film layer is removed.
TABLE 2 comparison of the Properties of K9 glass elements before and after film removal
The above-mentioned embodiments only express the specific embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for those skilled in the art, without departing from the technical idea of the present application, several changes and modifications can be made, which are all within the protection scope of the present application.
Claims (9)
1. A tritium-contaminated optical film nondestructive removal method based on inert ion beam etching is characterized by comprising the following steps:
[1] measuring the thickness of an optical film which has the same process with the optical element to be subjected to film removal to obtain the thickness of the film to be subjected to film removal, and further determining the thickness of the film removed by ion beam etching in the calibration process;
[2] testing the optical film which has the same process with the optical element to be subjected to film removal, and calibrating the etching rate of the ion beam on the optical film of the type;
the thickness of the film removed by ion beam etching in the calibration process is determined according to the measurement result of the thickness of the film to be removed;
under the condition that the thickness of the film to be removed is greater than or equal to 100nm, the thickness of the film removed by ion beam etching in the calibration process is smaller than the thickness of the film to be removed, and the calibration method in the step [2] comprises the following specific steps: removing a layer of optical film on the surface of the element by ion beam etching within a fixed time, defining the thickness of the film removed by the ion beam etching in the calibration process as the etching depth, then measuring the etching depth or the thickness of the residual film layer, and determining the etching speed of the ion beam on the optical film of the type by dividing the etching depth in the calibration process by the etching time in the calibration process;
under the condition that the thickness of the film to be removed is less than 100nm, the thickness of the film removed by ion beam etching in the calibration process is equal to the thickness of the film to be removed, and the calibration method in the step [2] comprises the following specific steps: gradient stripping is carried out on the optical film by ion beams, the transmittance of the optical element to a specific wavelength is tested every time when the optical film is etched for a period of time, a relation curve of the transmittance and the time is obtained, a transmittance inflection point approaching to a substrate of the optical element in the curve is a time point when the optical film is just completely removed, and the etching speed of the ion beams to the optical film of the type can be determined by dividing the thickness of the film to be removed by the etching time in the calibration process;
[3] calculating the time for completely removing the film to be removed according to the thickness of the film to be removed and the etching rate obtained by calibration in the steps (1) and (2); then, etching the surface of the optical element to be subjected to film removal by adopting an ion beam, wherein the etching time is set as the time for completely removing the film to be removed, which is obtained by calculation, and finally obtaining the optical element after film removal;
[4] and (4) cleaning the optical element subjected to the film removal and obtained after the treatment in the step (3).
2. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 1, wherein: the method for measuring the thickness of the optical film in the step [1] adopts one of a step instrument, a scanning electron microscope section or an ellipsometer.
3. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 1, wherein: in the step [2], under the condition that the thickness of the film to be removed is more than or equal to 100nm, a step instrument is adopted to determine the etching depth, or a scanning electron microscope section is adopted or an ellipsometer is adopted to determine the thickness of the residual film layer;
in the step [2], under the condition that the thickness of the film to be removed is less than 100nm, an ultraviolet-visible spectrophotometer is adopted to test the transmittance of the optical element to a specific wavelength.
4. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 1, wherein: the ion beam is an inert ion beam, and the inert ion is an ion of an inert element of helium, neon, argon, krypton or xenon.
5. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 4, wherein: the ion beam energy is 100 eV-1500 eV, the beam current is 100 mA-500 mA, and the ion beam incident angle is-90 degrees.
6. A tritium-contaminated optical film nondestructive removal method based on inert ion beam etching according to any one of claims 1, 4 or 5, characterized in that: and carrying out fixed-point etching on the optical element with the caliber smaller than the ion beam spot, and carrying out scanning etching on the optical element with the caliber larger than the ion beam spot.
7. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 1, wherein: and (3) in the ion beam etching process of the step (2) and the step (3), shielding the optical element subjected to etching by adopting a diaphragm which is made of the same material as the substrate of the optical element.
8. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 1, wherein in the ion beam etching process in step [2] and step [3], the treatment method of tritium-containing contaminants generated is as follows: pumping out generated gas tritium through an air pumping system, and installing a molecular sieve at an outlet of an air pumping pipeline to perform solidification treatment and collection on the gas tritium; and periodically cleaning the non-volatile tritiated deposited on the inner wall of the vacuum chamber.
9. The method for nondestructively removing tritium-contaminated optical films based on inert ion beam etching as claimed in claim 1, wherein: and (4) the method for cleaning the optical element comprises the steps of megasonic cleaning the optical element by using deionized water for 10-30 min, and then drying.
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| CN111359996A (en) * | 2020-04-13 | 2020-07-03 | 电子科技大学 | Antireflection film cleaning and reusing device and cleaning method |
| CN112044873A (en) * | 2020-09-23 | 2020-12-08 | 夏禹纳米科技（深圳）有限公司 | Laser removal method for waterproof material on surface of electronic element |
| CN114166868B (en) * | 2021-11-25 | 2023-12-08 | 中国科学院上海硅酸盐研究所 | Preparation method of pollution-free electrode for transmission electron microscope in-situ electric field ultrathin sample |
| CN114486191A (en) * | 2022-01-18 | 2022-05-13 | 湖北航天技术研究院总体设计所 | Laser load capacity testing system and method |
| CN117930501B (en) * | 2024-03-08 | 2024-09-20 | 中国工程物理研究院激光聚变研究中心 | Dry nondestructive decontamination and film removal method for tritium-related optical element |
| CN118371494B (en) * | 2024-06-24 | 2024-09-06 | 中国工程物理研究院激光聚变研究中心 | Method for regulating and controlling chemical film surface damage in plasma in-situ cleaning |
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