Device and method for testing performance degradation of deep ultraviolet fused quartz material

Abstract

The invention discloses a device and method for testing performance degradation of a deep ultraviolet fused quartz material, and the method comprises the steps: employing a continuous laser beam with the wavelength of 213nm as a detection light beam, and simultaneously monitoring the transmittance change of the detection light beam after the detection light beam passes through a deep ultraviolet laser irradiation region of the deep ultraviolet fused quartz material and the instantaneous change of the light intensity of a light beam central region; the color center defect concentration change of the deep ultraviolet fused quartz material caused by deep ultraviolet laser irradiation and the absorption change of the deep ultraviolet laser irradiation wavelength are obtained, and the transmittance change of the irradiation laser beam transmitting the deep ultraviolet fused quartz material is monitored at the same time; the performance degradation data of the deep ultraviolet fused quartz material under the irradiation of the deep ultraviolet laser and the contribution of the color center defect generated by the irradiation of the deep ultraviolet laser to the performance degradation are obtained. According to the invention, the contribution of color center defects to performance degradation can be distinguished, the performance recovery mechanism of hydrogen can be measured, and the measurement sensitivity of thermal lens signals can be effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of testing performance parameters of optical materials and components, and particularly relates to a method for testing the performance degradation of deep ultraviolet fused silica materials. Background Art

[0002] Although extreme ultraviolet (EUV) lithography technology has developed rapidly and has been applied to the manufacturing process of ultra-large scale integrated circuits (ICs) with ultra-small dimensions, the mainstream process for IC manufacturing is still deep ultraviolet (DUV) excimer laser lithography with working wavelengths of 193 nm and 248 nm. In deep ultraviolet excimer laser lithography equipment, optical components based on deep ultraviolet fused silica materials are most widely used, especially in the lithography objective lens system. The deep ultraviolet fused silica materials will generate microstructural defects such as color centers (E’-center), non-bridging oxygen holes (NBOHC), and oxygen vacancies (ODC) inside the materials under long-term irradiation of deep ultraviolet lasers. These microstructural defects will cause an increase in the absorption of the fused silica materials, a decrease in the transmittance, and a change in the refractive index. The changes in the transmittance and refractive index lead to the degradation of the optical performance of the lithography machine system, limiting the service life of the lithography machine. In order to improve the performance stability of the fused silica materials, a certain concentration of hydrogen is doped during the preparation of the deep ultraviolet fused silica materials. Hydrogen reacts chemically with the microstructural defects generated by deep ultraviolet laser irradiation in the fused silica materials to generate microstructures that have no obvious absorption at 193 nm and 248 nm, alleviating or even restoring the performance degradation of the deep ultraviolet fused silica materials to a certain extent and extending the service life of the fused silica components. However, the mechanisms of performance degradation and performance recovery (defect annealing) of deep ultraviolet fused silica components under deep ultraviolet laser irradiation and their interaction with hydrogen are very complex. Among them, the interaction between color centers and hydrogen has a significant impact on the optical performance of deep ultraviolet fused silica materials at 193 nm and 248 nm. Therefore, in-depth understanding of the interaction mechanism between color centers and hydrogen and the influence of deep ultraviolet laser irradiation on this interaction is of great significance for further understanding the performance degradation process of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation.

[0003] The conventional test method for the performance degradation of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation is to monitor the transmittance attenuation of the fused silica materials under laser irradiation. This method has limited test sensitivity and can only provide transmittance change data, unable to meet the need for in-depth understanding of the performance degradation mechanism of fused silica materials under deep ultraviolet laser irradiation. Chinese Patent Application No. 201010623885.2, "A Comprehensive Test Method for the Stability of Deep Ultraviolet Optical Elements", proposes to use the laser calorimetry method and the photothermal measurement method (surface thermal lens method) to monitor the absolute absorption change of deep ultraviolet elements under deep ultraviolet laser irradiation, and use the laser-induced fluorescence method to monitor the fluorescence spectrum and its real-time change of deep ultraviolet elements; Chinese Patent Application No. 201410005252.3, "A Comprehensive Test Method for the Optical Performance of Deep Ultraviolet Optical Elements", proposes to simultaneously use the laser calorimetry technology to measure the absolute value of the absorption loss of deep ultraviolet optical elements, use the laser-induced fluorescence spectroscopy technology to measure the fluorescence spectrum of deep ultraviolet optical elements under deep ultraviolet laser irradiation, and use the Raman spectroscopy technology to measure the defect energy level, doping component and impurity content of deep ultraviolet optical elements. Although the above comprehensive test methods can monitor the absorption and fluorescence spectrum changes of deep ultraviolet optical elements under deep ultraviolet laser irradiation, since the color center defects generated by deep ultraviolet laser irradiation in fused silica materials do not emit fluorescence, and the absorption characteristics at the irradiation laser wavelength are mixed with other microstructural defects (non-bridging oxygen and oxygen vacancies) and cannot be directly distinguished, the above comprehensive test methods cannot distinguish the effects of color center defects and other microstructural defects on the performance degradation of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation, restricting the in-depth understanding of the performance degradation mechanism of deep ultraviolet fused silica materials. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the object of the present invention is to provide a test method for the performance degradation of deep ultraviolet fused silica materials. By using the characteristic that the color center defects generated in deep ultraviolet fused silica elements under deep ultraviolet laser irradiation have an absorption peak at 215 nm, a 213 nm laser beam is used to directly measure the transmittance change of this absorption peak to realize the direct test of the color center defect concentration in deep ultraviolet fused silica elements; at the same time, the 213 nm laser beam is used as the probe beam in the photo-thermal absorption measurement configuration, and by using the characteristic that the sensitivity of photo-thermal absorption measurement is inversely proportional to the probe laser wavelength, the sensitivity of photo-thermal absorption measurement is effectively improved, so as to more accurately measure the absorption change characteristics of deep ultraviolet fused silica elements under deep ultraviolet laser irradiation. To achieve the above object and other advantages according to the present invention, a test method for the performance degradation of deep ultraviolet fused silica materials is provided, including:

[0005] A deep ultraviolet irradiation laser, an electronically controlled variable optical attenuator arranged on one side of the deep ultraviolet irradiation laser, and a housing communicated with the electronically controlled variable optical attenuator. Inside the housing, a beam shaping optical unit, an aperture stop, a beam splitter, an imaging lens, a deep ultraviolet fused silica element to be measured and a first energy meter are sequentially arranged along the beam direction;

[0006] A second energy meter is arranged below the spectroscope, and a 213 nm continuous laser is arranged above the spectroscope. A 213 nm partial mirror is arranged on one side of the 213 nm continuous laser, and a first photodetector is arranged on one side of the 213 nm partial mirror;

[0007] A small hole aperture is arranged below the first energy meter, and a second photodetector is arranged on one side of the small hole aperture;

[0008] A nitrogen inlet is provided on the electronically controlled variable optical attenuator, and a nitrogen outlet is provided on the outer shell.

[0009] Preferably, the transmittance of the measured deep ultraviolet fused silica component at the irradiated laser wavelength is given by the ratio of the readings of the first energy meter and the second energy meter after calibration;

[0010] And the transmittance of the measured deep ultraviolet fused silica component at the 213 nm wavelength is given by the ratio of the DC component output by the second photodetector and the output value of the first photodetector after calibration.

[0011] Preferably, the amplitude of the thermal lens signal is calculated by the ratio of the instantaneous change amount to the DC component in the signal output by the second photodetector.

[0012] Preferably, the performance degradation characteristics of the measured deep ultraviolet fused silica component are characterized by the relationship between its transmittance at the irradiated laser wavelength and the irradiation time sequence, energy density and dose.

[0013] Preferably, the change in the concentration of color center defects in the measured deep ultraviolet fused silica component caused by deep ultraviolet laser irradiation is characterized by the change in its transmittance at the 213 nm wavelength and its relationship with the irradiation time sequence, energy density and dose.

[0014] Preferably, the contribution of the color center defects caused by deep ultraviolet laser irradiation in the measured deep ultraviolet fused silica component to the performance degradation of the fused silica material under deep ultraviolet laser irradiation is characterized by the difference characteristics of the measured transmittance changes at the deep ultraviolet laser irradiation wavelength and the 213 nm wavelength.

[0015] Preferably, the performance recovery of hydrogen in the measured deep ultraviolet fused silica component to the deep ultraviolet fused silica material is characterized by the recovery degree of the transmittance at the 213 nm wavelength after stopping the deep ultraviolet laser irradiation.

[0016] Preferably, the performance degradation characteristics test of the measured deep ultraviolet fused silica component is realized by designing the deep ultraviolet laser irradiation time sequence, energy density and dose according to the actual application state of the deep ultraviolet fused silica component.

[0017] A test method for the performance degradation of deep ultraviolet fused silica materials, which realizes the on-line test of the performance degradation characteristics of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation by simultaneously monitoring the transmittance change at a wavelength of 213 nm and the absorption and transmittance changes at the irradiation laser wavelength of the deep ultraviolet fused silica materials under deep ultraviolet laser irradiation; specifically:

[0018] The on-line test of the transmittance change at a wavelength of 213 nm is realized by using a photodetector to measure the change of the transmittance of the output beam of a 213 nm continuous laser passing through the deep ultraviolet laser irradiation area of the deep ultraviolet fused silica material with the irradiation time sequence, energy density and dose;

[0019] The on-line test of the absorption change at the irradiation laser wavelength is realized by using the transmission type thermal lens method, that is, using a photodetector to measure the instantaneous change amount of the light intensity in the central area after the output beam of a 213 nm continuous laser passes through the deep ultraviolet laser irradiation area of the deep ultraviolet fused silica material with the irradiation time sequence, energy density and dose;

[0020] The on-line test of the transmittance change at the irradiation laser wavelength is realized by using an energy meter to measure the change of the transmittance of the irradiation laser beam passing through the deep ultraviolet fused silica material with the irradiation time sequence, energy density and dose.

[0021] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention directly tests the change of the color center defect concentration generated in the deep ultraviolet fused silica material under deep ultraviolet laser irradiation by using the transmittance change of the 213 nm laser beam, and combines the analysis of the transmittance change of the deep ultraviolet fused silica material at the irradiation laser wavelength, so as to distinguish the contributions of the color center defects and other microstructural defects generated by deep ultraviolet laser irradiation to the performance degradation, providing a credible technical means for studying the performance degradation mechanism of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation; (2) The 213 nm laser beam is simultaneously used as the detection beam of the thermal lens signal. Compared with the prior optothermal measurement technology using a 633 nm laser beam as the detection beam, the measurement sensitivity is increased by nearly 2 times, effectively improving the resolution of the thermal lens signal for testing the absorption increase or performance degradation of deep ultraviolet fused silica materials caused by deep ultraviolet laser irradiation, and being more conducive to the study of the performance degradation mechanism of deep ultraviolet fused silica materials. Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of an on-line test device for the test method of the performance degradation of deep ultraviolet fused silica materials according to the present invention.

[0023] Figure 2 It is a relationship curve diagram of the transmittance of the deep ultraviolet fused silica material at the irradiation laser wavelength and the deep ultraviolet laser irradiation dose recorded by the test method of the performance degradation of deep ultraviolet fused silica materials according to the present invention;

[0024] Figure 3 The curve of the thermal lens signal recorded according to the test method for the performance degradation of deep ultraviolet fused silica materials of the present invention versus the irradiation dose;

[0025] Figure 4 The schematic diagram of the spectral characteristics of the 215 nm absorption peak of the color center defect according to the test method for the performance degradation of deep ultraviolet fused silica materials of the present invention;

[0026] Figure 5 The curve of the transmittance of the deep ultraviolet fused silica material at a wavelength of 213 nm versus the deep ultraviolet laser irradiation dose recorded according to the test method for the performance degradation of deep ultraviolet fused silica materials of the present invention;

[0027] Figure 6 The curve of the transmittance of the deep ultraviolet fused silica material at a wavelength of 213 nm versus the deep ultraviolet laser irradiation timing recorded when changing the deep ultraviolet laser irradiation timing according to the test method for the performance degradation of deep ultraviolet fused silica materials of the present invention;

[0028] Figure 7 The schematic diagram of a beam splitting measurement configuration of the on-line test device according to the test method for the performance degradation of deep ultraviolet fused silica materials of the present invention;

[0029] Figure 8 The schematic diagram of another beam splitting measurement configuration of the on-line test device according to the test method for the performance degradation of deep ultraviolet fused silica materials of the present invention. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] Refer to Figure 1 , a test device for the performance degradation of deep ultraviolet fused silica materials, comprising:

[0032] A deep ultraviolet irradiation laser 1, an electrically controlled variable optical attenuator 2 arranged on one side of the deep ultraviolet irradiation laser 1, and a housing communicated with the electrically controlled variable optical attenuator 2. Inside the housing, a beam shaping optical unit 3, an aperture stop 4, a beam splitter 5, an imaging lens 6, a deep ultraviolet fused silica element to be measured 7, and a first energy meter 8 are sequentially arranged along the beam direction;

[0033] A second energy meter 9 is disposed below the beam splitter 5, and a 213 nm continuous laser 10 is disposed above the beam splitter 5. A 213 nm partial mirror 11 is disposed on one side of the 213 nm continuous laser 10, and a first photodetector 12 is disposed on one side of the 213 nm partial mirror 11;

[0034] A pinhole aperture 13 is disposed below the first energy meter 8, and a second photodetector 14 is disposed on one side of the pinhole aperture 13;

[0035] A nitrogen inlet 16 is provided on the electro - controlled variable optical attenuator 2, and a nitrogen outlet 17 is provided on the outer shell. A computer 15 is further included. The computer 15 is respectively in signal connection with the electro - controlled variable optical attenuator 2, the second energy meter 9, the second photodetector 14, the first energy meter 8, the deep ultraviolet irradiation laser 1 and the first photodetector 12. The laser beam output by the deep ultraviolet irradiation laser 1 is adjusted in laser beam energy by the electro - controlled variable optical attenuator 2, shaped in beam intensity distribution by the beam shaping optical unit 3, limited in beam size by the aperture stop 4, and then focused by the imaging lens 6 onto the measured deep ultraviolet fused silica element 7 to form deep ultraviolet laser irradiation on the fused silica element; the transmittance change of the measured deep ultraviolet fused silica element 7 at the irradiation wavelength is directly measured by the first energy meter 8; the laser beam output by the 213 nm continuous laser 10 passes through the irradiation area of the deep ultraviolet laser beam of the measured deep ultraviolet fused silica element 7 after the direction is adjusted by the 213 nm partial mirror 11, passes through the pinhole aperture 13, and is then detected by the second photodetector 14 to obtain the thermal lens signal of the measured deep ultraviolet fused silica element 7 at the irradiation laser wavelength and the transmission signal at the 213 nm wavelength; the pulse energy of the irradiation laser is monitored by the second energy meter 9, and the power of the 213 nm laser beam is monitored by the first photodetector 12; when the irradiation wavelength is less than 200 nm, the whole measurement is carried out in a nitrogen - filled environment. Nitrogen is filled from the nitrogen inlet 16 and flows out from the nitrogen outlet 17, and the nitrogen keeps flowing during the test process.

[0036] Further, the deep ultraviolet irradiation laser 1 is a 193nm ArF excimer laser or a 248nm KrF excimer laser. After the output laser beam is adjusted in energy by the electro-controlled variable optical attenuator 2, homogenized in beam intensity distribution by the beam shaping optical unit 3, and limited in beam size by the aperture stop 4, the imaging lens 6 images the aperture stop beam onto the surface of the measured deep ultraviolet fused silica element 7, forming a uniform irradiation of the fused silica element. Laser irradiation causes the generation of microstructural defects in the measured deep ultraviolet fused silica element 7, including color centers, non-bridging oxygen, and oxygen vacancies, etc., resulting in an increase in the absorption and a decrease in the transmittance of the fused silica material at the irradiation laser wavelength, that is, performance degradation. The decrease in transmittance is determined by directly measuring the energy of the deep ultraviolet irradiation laser beam passing through the measured deep ultraviolet fused silica element 7, that is, measured by the first energy meter 8, and the transmittance is obtained by calibrating the ratio of the measured value of the energy meter 1 to the measured value of the second energy meter 9. As the irradiation dose increases, the transmittance of the fused silica element at the irradiation laser wavelength decreases, as shown in Figure 2 shown. The increase in absorption caused by the fused silica element under deep ultraviolet laser irradiation in the test method of the present invention is measured by the transmission type thermal lens technique. Its basic principle is: when the deep ultraviolet laser irradiates the fused silica element, the fused silica element absorbs the energy of the irradiation laser beam, resulting in an increase in the internal temperature, forming a refractive index gradient in the laser beam irradiation area, and generating a lens effect. When a probe laser beam passes through this refractive index gradient area, the central light intensity of its transmitted beam changes instantaneously. The small aperture stop 13 is used to select this central light intensity area and the second photodetector 14 detects its instantaneous light intensity change, that is, a photothermal signal is obtained. The thermal lens probe beam in the present invention is a 213nm laser beam. The laser beam output by the 213nm continuous laser is adjusted in direction by the 213nm partial mirror 11 and then passes through the measured deep ultraviolet fused silica element 7 in the area irradiated by the deep ultraviolet irradiation laser beam. The laser beam further passes through the small aperture stop 13 and is detected by the second photodetector 14 to obtain the thermal lens signal of the measured deep ultraviolet fused silica element 7 at the irradiation laser wavelength. Figure 3 The upper inset in Figure 3 is the typical thermal lens signal generated by a single laser pulse. The ratio of the amplitude of the thermal lens signal generated at the laser pulse irradiation moment to the DC component is the amplitude of the thermal lens signal, which is proportional to the absorption rate of the fused silica element at the irradiation laser wavelength; and its DC component is the transmission signal at the 213nm wavelength. Due to the performance degradation effect of the deep ultraviolet fused silica material, as the irradiation dose increases, the absorption of the fused silica element at the irradiation laser wavelength gradually increases, and the amplitude of the thermal lens signal also gradually increases, as shown in the main figure and the lower inset in

[0037] Under deep ultraviolet laser irradiation, the generation mechanisms of various microstructural defects inside fused silica materials are different, and their contributions to the performance degradation effect are also different. Distinguishing the contribution sizes of different defects helps to deeply understand the performance degradation mechanism of fused silica materials. Based on this technical consideration, another function of the present invention is to on-line monitor the change in the concentration of color center defects generated by deep ultraviolet laser irradiation in deep ultraviolet fused silica components, thereby distinguishing the contribution of color center defects to the performance degradation effect. The specific implementation measure is as follows: Since there is a 215 nm absorption peak in the color center defects of deep ultraviolet fused silica materials, as Figure 4 shown, a 213 nm laser beam close to the absorption peak position is used to measure the change in the 213 nm transmittance of the deep ultraviolet fused silica component under deep ultraviolet laser irradiation, and further obtain the change in the concentration of color center defects. As Figure 1 shown, the ratio of the DC component of the detection signal of the second photodetector 14 to the detection signal of the first photodetector 12 is calibrated to obtain the transmittance of the deep ultraviolet fused silica component at the 213 nm wavelength. The change in the transmittance of the deep ultraviolet fused silica component at the 213 nm wavelength caused by deep ultraviolet laser irradiation is proportional to the concentration of color center defects generated by the irradiation. Therefore, it can be used to characterize the concentration of color center defects generated by deep ultraviolet laser irradiation, as Figure 5 shown.

[0038] The performance degradation of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation is an extremely complex process. The generation of various microstructural defects is related to many factors such as the laser energy density, pulse width, power density, continuous irradiation time, irradiation interval time, irradiation time sequence, and total irradiation dose of the irradiation laser. Moreover, in the preparation of deep ultraviolet fused silica, the annealing effect of hydrogen on various microstructural defects is utilized, and the performance degradation effect of deep ultraviolet fused silica materials is effectively inhibited by doping hydrogen, thereby prolonging the service life of the fused silica materials. Therefore, doping hydrogen makes the performance degradation effect more complicated. The present invention can design different laser irradiation time sequences, energy densities, and doses by changing parameters such as the irradiation energy density, continuous irradiation time, irradiation interval time, and total irradiation dose according to the specific application of deep ultraviolet fused silica materials, and obtain the performance degradation characteristics of fused silica components under different irradiation conditions, including the characteristics of increased absorption at the irradiation wavelength and decreased transmittance, and the characteristics of decreased transmittance at 213 nm, so as to obtain the performance degradation characteristics of deep ultraviolet fused silica components in different applications. As Figure 6 shown is a schematic diagram of the relationship curve between the 213 nm transmittance and the irradiation dose at different irradiation time sequences and irradiation doses. By analyzing the difference in the change in the transmittance at the irradiation wavelength and the 213 nm wavelength caused by deep ultraviolet laser irradiation, the contribution of color center defects caused by deep ultraviolet laser irradiation to the performance degradation of fused silica materials under deep ultraviolet laser irradiation can be distinguished and characterized.

[0039] Further, different photodetectors can be used to separately measure the 213nm transmittance change and the thermal lens signal caused by deep ultraviolet laser irradiation in the deep ultraviolet laser irradiation area passing through the deep ultraviolet fused silica material, as Figure 7 shown, a test device for the performance degradation of deep ultraviolet fused silica material, comprising:

[0040] A deep ultraviolet irradiation laser 1, an electronically controlled variable optical attenuator 2 arranged on one side of the deep ultraviolet irradiation laser 1, and a housing communicated with the electronically controlled variable optical attenuator 2. Along the beam direction in the housing, there are sequentially arranged a beam shaping optical unit 3, an aperture stop 4, a 193nm / 248nm beam splitter 5, an imaging lens 6, a deep ultraviolet fused silica element to be measured 7, and a first energy meter 8;

[0041] A second energy meter 9 is arranged below the beam splitter 5, and a 213nm continuous laser 10 is arranged above the beam splitter 5. A 213nm partial reflector 11 is arranged on one side of the 213nm continuous laser 10, and a first photodetector 12 is arranged on one side of the 213nm partial reflector 11;

[0042] A third photodetector 15, a 213nm beam splitter 13 are arranged below the first energy meter 8, and a 213nm focusing lens 14 is arranged on one side of the third photodetector 15; A 213nm beam splitter 13 is arranged on one side of the deep ultraviolet fused silica element to be measured 7, a small hole aperture 16 is arranged on one side of the 213nm beam splitter 13, and a fourth photodetector 17 is arranged on one side of the small hole aperture 16.

[0043] A nitrogen inlet 19 is opened on the electronically controlled variable optical attenuator 2, and a nitrogen outlet 20 is opened on the housing. It further includes a computer 18, and the computer 18 is respectively in signal connection with the electronically controlled variable optical attenuator 2, the second energy meter 9, the third photodetector 15, the first energy meter 8, the deep ultraviolet irradiation laser 1, and the fourth photodetector 17. That is, after the 213nm detection laser beam passes through the deep ultraviolet fused silica element, it is split into two beams of light by a beam splitter to realize the separate detection of the 213nm wavelength transmittance and the thermal lens signal. This beam splitting test configuration can eliminate the influence of the 213nm beam pointing drift on the measurement of the 213nm transmittance and improve the measurement accuracy of the 213nm wavelength transmittance change.

[0044] It is also possible to use 213nm transmittance measurement detection beams and thermal lens absorption measurement detection beams with different optical paths in the deep ultraviolet fused silica material, as Figure 8 shown, a test device for the performance degradation of deep ultraviolet fused silica material, comprising:

[0045] Deep ultraviolet irradiation laser 1, an electro-controlled variable optical attenuator 2 disposed on one side of the deep ultraviolet irradiation laser 1, and a housing communicating with the electro-controlled variable optical attenuator 2. Inside the housing, a beam shaping optical unit 3, an aperture stop 4, a 193nm / 248nm beam splitter 5, an imaging lens 6, a deep ultraviolet fused silica element 7 to be measured, and a first energy meter 8 are sequentially arranged along the beam direction;

[0046] A second energy meter 9 is disposed below the beam splitter 5, and a 213nm continuous laser 10 is disposed above the beam splitter 5. A 13nm beam splitter is disposed on one side of the 213nm continuous laser 10, a 213nm partial reflector 12 is disposed on one side of the 13nm beam splitter, and a fifth photodetector 13 is disposed on one side of the 213nm partial reflector 12;

[0047] A sixth photodetector 18 is disposed below the first energy meter 8, and a first small hole aperture 17 is disposed on one side of the sixth photodetector 18; a seventh photodetector 16 is disposed on one side of the first small hole aperture 17, a second 213nm focusing lens 15 is disposed on one side of the seventh photodetector 16, and a first 213nm focusing lens 14 is disposed at the upper left of the deep ultraviolet fused silica element 7 to be measured.

[0048] The electro-controlled variable optical attenuator 2 is provided with a nitrogen inlet 20, and the housing is provided with a nitrogen outlet 21. It further includes a computer 19, and the computer 19 is respectively connected to the electro-controlled variable optical attenuator 2, the second energy meter 9, the seventh photodetector 16, the first energy meter 8, the deep ultraviolet irradiation laser 1, and the sixth photodetector 18 by signals. That is, before the 213nm probing laser beam enters the deep ultraviolet fused silica element, it is split into two beams by a beam splitter, and passes through the irradiated area at different angles to realize the separate detection of the transmittance at the 213nm wavelength and the thermal lens signal. In this test configuration, the size of the probing beam for measuring the transmittance at the 213nm wavelength can be optimized, and the measurement sensitivity and accuracy of the change in the transmittance at the 213nm wavelength can be improved.

[0049] In the test method of the present invention, when the irradiation wavelength is lower than 200nm, the whole measurement is carried out in a nitrogen-filled environment. Nitrogen is filled from the nitrogen inlet and flows out from the nitrogen outlet, and the nitrogen remains flowing during the test process.

[0050] In summary, the present invention proposes a test method for the performance degradation of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation. Using a 213nm laser beam as the probing beam for the thermal lens signal and the measuring beam for the change in the concentration of color center defects, it can not only measure the performance degradation characteristics of deep ultraviolet fused silica materials under deep ultraviolet laser irradiation online, but also distinguish the contribution of color center defects to the performance degradation, measure the performance recovery mechanism of hydrogen, and effectively improve the measurement sensitivity of the thermal lens signal.

[0051] The number of devices and the processing scale described herein are used to simplify the description of the present invention. Applications, modifications, and variations of the present invention will be apparent to those skilled in the art. Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details and the illustrated examples described herein.

Claims

1. A test device for the performance degradation of deep ultraviolet fused silica materials, characterized in that, Including: A deep ultraviolet irradiation laser (1), an electro - controlled variable optical attenuator (2) arranged on one side of the deep ultraviolet irradiation laser (1), and a housing communicated with the electro - controlled variable optical attenuator (2). Inside the housing, a beam shaping optical unit (3), an aperture stop (4), a beam splitter (5), an imaging lens (6), a deep ultraviolet fused silica element to be measured (7), and a first energy meter (8) are sequentially arranged along the beam direction; A second energy meter (9) is arranged below the beam splitter (5), and a 213nm continuous laser (10) is arranged above the beam splitter (5). A 213nm partial reflector (11) is arranged on one side of the 213nm continuous laser (10), and a first photodetector (12) is arranged on one side of the 213nm partial reflector (11); A pinhole aperture (13) is arranged below the first energy meter (8), and a second photodetector (14) is arranged on one side of the pinhole aperture (13); A nitrogen inlet (16) is opened on the electro - controlled variable optical attenuator (2), and a nitrogen outlet (17) is opened on the housing.

2. The testing device for performance degradation of deep ultraviolet fused silica material according to claim 1, wherein The transmittance of the deep ultraviolet fused silica element to be measured (7) at the irradiation laser wavelength is given after calibration by the ratio of the readings of the first energy meter (8) and the second energy meter (9); And the transmittance of the deep ultraviolet fused silica element to be measured (7) at the 213nm wavelength is given after calibration by the ratio of the DC component output by the second photodetector (14) and the output value of the first photodetector (12).

3. The testing device for the performance degradation of deep ultraviolet fused silica materials according to claim 1, characterized in that, The amplitude of the thermal lens signal is calculated by the ratio of the instantaneous change amount to the DC component in the signal output by the second photodetector (14).

4. The testing device for the performance degradation of deep ultraviolet fused silica materials according to claim 1, characterized in that, The performance degradation characteristics of the deep ultraviolet fused silica element to be measured (7) are characterized by the relationship between its transmittance at the irradiation laser wavelength and the irradiation time sequence, energy density, and dose.

5. The test device for the performance degradation of deep ultraviolet fused silica materials according to claim 1, wherein The change in the concentration of color center defects in the deep ultraviolet fused silica element to be measured (7) caused by deep ultraviolet laser irradiation is characterized by the change in its transmittance at the 213nm wavelength and its relationship with the irradiation time sequence, energy density, and dose.

6. The testing device for the performance degradation of deep ultraviolet fused silica material according to claim 1, characterized in that, The contribution of the color center defects caused by deep ultraviolet laser irradiation in the deep ultraviolet fused silica element to be measured (7) to the performance degradation of the fused silica material under deep ultraviolet laser irradiation is characterized by the difference characteristics of the measured changes in the transmittance at the deep ultraviolet laser irradiation wavelength and the 213nm wavelength.

7. The testing device for performance degradation of deep ultraviolet fused silica material according to claim 1, characterized in that, The performance recovery of hydrogen in the deep ultraviolet fused silica element to be measured (7) on the deep ultraviolet fused silica material is characterized by the recovery degree of the transmittance at the 213nm wavelength after stopping deep ultraviolet laser irradiation.

8. The test device for the performance degradation of deep ultraviolet fused silica material according to claim 1, wherein The test of the performance degradation characteristics of the deep ultraviolet fused silica element to be measured (7) is realized by designing the deep ultraviolet laser irradiation time sequence, energy density, and dose according to the actual application state of the deep ultraviolet fused silica element.

9. The testing method for performance degradation of deep ultraviolet fused silica material according to claim 1, characterized in that By simultaneously monitoring the change in the transmittance of the deep ultraviolet fused silica material at the 213nm wavelength and the absorption and transmittance changes at the irradiation laser wavelength under deep ultraviolet laser irradiation, the on - line test of the performance degradation characteristics of the deep ultraviolet fused silica material under deep ultraviolet laser irradiation is realized; specifically: The on-line measurement of the transmittance change at the wavelength of 213 nm is achieved by using a photodetector to measure the change of the transmittance of the output beam of a 213 nm continuous laser passing through the deep ultraviolet laser irradiation area of deep ultraviolet fused silica material with the irradiation time sequence, energy density and dose; The on-line measurement of the absorption change of the irradiated laser wavelength is achieved by using the transmission thermal lens method, that is, by using a photodetector to measure the instantaneous change of the light intensity in the central area after the output beam of a 213 nm continuous laser passes through the deep ultraviolet laser irradiation area of deep ultraviolet fused silica material with the irradiation time sequence, energy density and dose; The on-line measurement of the transmittance change of the irradiated laser wavelength is achieved by using an energy meter to measure the change of the transmittance of the irradiated laser beam passing through the deep ultraviolet fused silica material with the irradiation time sequence, energy density and dose.

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