Method for comprehensive measurement of large-size ultra-low expansion quartz glass

Abstract

This invention discloses a comprehensive measurement method for large-size ultra-low expansion quartz glass, belonging to the field of advanced optical material performance testing technology. The method includes establishing a first theoretical relationship between CTE and longitudinal wave velocity, and a second theoretical relationship between stress birefringence and longitudinal wave velocity; acquiring CTE calibration group samples and stress birefringence calibration group samples; establishing a CTE uniformity evaluation model based on the first theoretical relationship and the CTE calibration group samples; establishing a radial stress distribution evaluation model based on the second theoretical relationship and the stress birefringence calibration group samples; obtaining the longitudinal wave velocity distribution data of the large-size ultra-low expansion quartz glass sample to be tested; inputting this data into the CTE uniformity evaluation model and the radial stress distribution evaluation model; and outputting the results. This invention can meet the engineering requirements for rapid, non-destructive testing of CTE uniformity and stress birefringence in large-size ultra-low expansion quartz glass across all apertures.

Description

Technical Field

[0001] This invention relates to the field of advanced optical material performance testing technology, specifically to a comprehensive measurement method for large-size ultra-low expansion quartz glass. Background Technology

[0002] Ultra-low expansion quartz glass is a type of quartz glass doped with a small amount of TiO2 (7~8 wt.%). It possesses extremely strong thermal shock resistance, very high thermal stability and dimensional stability, and exhibits a near-zero coefficient of thermal expansion (CTE) in the temperature range of 5°C to 35°C (10⁻⁶ wt.%). -9 / °C level, 1×10 -9 (°C = 1 ppb / °C). Due to these properties, ultra-low expansion quartz glass is widely used in astronomical observation, laser cavities, and semiconductor manufacturing. In astronomical observation, ultra-low expansion quartz glass is a key material for manufacturing large telescope mirror blanks. In this application, the material's CTE inhomogeneity and high residual stress directly cause non-uniform deformation of the mirror body when the temperature changes, thus affecting the surface accuracy and imaging quality of the mirror. Therefore, high-precision detection of the CTE uniformity and residual stress of ultra-low expansion quartz glass is a prerequisite for ensuring its imaging performance. In laser resonant cavity structures, ultra-low expansion quartz glass, with its near-zero CTE, becomes a key material for maintaining laser frequency stability. If the material's CTE deviates from the ideal value or the residual stress is high, it will cause the cavity length to fluctuate with temperature, leading to laser frequency drift and seriously affecting the performance of equipment such as optical atomic clocks and high-precision interferometers. Therefore, rigorous detection of CTE and residual stress is the foundation for ensuring the long-term stable operation of laser systems in real working environments. In the semiconductor manufacturing field, ultra-low expansion quartz glass is the preferred substrate material for photomasks and optical components in extreme ultraviolet (EUV) lithography. EUV lithography systems employ total internal reflection optical design, imposing extreme requirements on the thermal and dimensional stability of materials. Any non-uniform CTE or residual stress can cause nanoscale deformation of optical components, affecting optical path accuracy and imaging quality, ultimately leading to chip manufacturing defects. Therefore, achieving high-precision, full-aperture detection of the CTE and residual stress of this material is crucial for ensuring the reliable operation of EUV lithography systems and the yield of next-generation chip manufacturing.

[0003] Currently, only a few companies in my country are capable of producing ultra-low expansion quartz glass. Ensuring that its CTE and residual stress meet the requirements of high-end applications has become a critical issue that urgently needs to be addressed. Common methods for CTE testing of ultra-low expansion quartz glass include the push-rod method, interferometry, photoelasticity, and ultrasonic methods. For residual stress testing, diffraction, ring-core method, photoelasticity, and ultrasonic methods are the main approaches. However, the push-rod method, interferometry, and photoelasticity have limitations in CTE measurement, such as the need for system calibration using standard samples, destructive sampling, long measurement cycles, and high labor and material costs. Similarly, diffraction, ring-core, and photoelasticity methods for residual stress measurement also have limitations such as limited measurement depth, destructive sampling, high cost, and strict environmental requirements, making it difficult to meet the need for full-diameter, rapid, and non-destructive testing of CTE uniformity and residual stress in large-size ultra-low expansion quartz glass. However, ultrasonic testing technology, due to its rapid and non-destructive characteristics, exhibits unique advantages in characterizing key material properties. Corning Incorporated abroad and the Institute of Optoelectronics, Chinese Academy of Sciences, both domestically, have used ultrasonic methods to conduct full-aperture testing of the crackle turbidity (CTE) and uniformity of large-size ultra-low expansion quartz glass, demonstrating good potential for engineering applications. However, the research of these two institutions mainly focuses on using ultrasonic methods to measure CTE and its uniformity, and has not yet simultaneously carried out comprehensive measurements of CTE and residual stress.

[0004] To address the aforementioned issues, there is an urgent need for a comprehensive measurement method to rapidly assess the uniformity of thermal expansion coefficient and radial stress distribution in large-size ultra-low expansion quartz glass, thereby resolving the problems associated with traditional methods. Summary of the Invention

[0005] The purpose of this invention is to provide a comprehensive measurement method for rapidly evaluating the uniformity of thermal expansion coefficient and radial stress distribution of large-size ultra-low expansion quartz glass. This method overcomes the limitations of traditional CTE and stress measurements, such as destructive sampling, long cycle time, and high cost. It has the advantages of high efficiency and simultaneous measurement of two parameters, and can meet the engineering requirements for rapid and non-destructive testing of CTE uniformity and stress birefringence of large-size ultra-low expansion quartz glass.

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

[0007] A comprehensive measurement method for large-size ultra-low expansion quartz glass includes:

[0008] Step 1: Construct a theoretical model to establish the first theoretical relationship between CTE and P-wave velocity, and the second theoretical relationship between stress birefringence and P-wave velocity;

[0009] Step 2: Establish a sample library and prepare and screen CTE calibration group samples and stress birefringence calibration group samples from ultra-low expansion quartz glass materials produced by the same manufacturing process.

[0010] Step 3: Establish a CTE homogeneity evaluation model based on the first theoretical relationship and the CTE calibration group samples;

[0011] Step 4: Establish a radial stress distribution evaluation model based on the second theoretical relationship and the stress birefringence calibration group samples;

[0012] Step 5: Perform full-aperture longitudinal wave velocity scanning measurement on the large-size ultra-low expansion quartz glass sample to be tested to obtain its longitudinal wave velocity distribution data. Input the longitudinal wave velocity distribution data into the CTE uniformity evaluation model and the radial stress distribution evaluation model, and output the CTE uniformity distribution result and radial stress distribution result of the sample to be tested.

[0013] Furthermore, in step 1, the first theoretical relationship between CTE and P-wave velocity is established, specifically as follows:

[0014] Using the elastic modulus as an intermediate quantity, the first theoretical relationship between CTE and longitudinal wave velocity is established.

[0015] Furthermore, in step 1, a second theoretical relationship is established between stress birefringence and the longitudinal wave velocity, specifically as follows:

[0016] Based on the acoustoelastic and photoelastic effects, a second theoretical relationship between stress birefringence and longitudinal wave sound velocity is established.

[0017] Further, in step 2, a sample library is established, and CTE calibration group samples and stress birefringence calibration group samples are prepared and screened from ultra-low expansion quartz glass blanks produced by the same manufacturing process. Specifically:

[0018] Two sets of samples were designed from ultra-low expansion quartz glass blanks produced by the same manufacturing process. The first set of samples, which had significant differences in longitudinal wave velocity, was used as the CTE calibration set. The second set of samples, which had a diameter-to-thickness ratio ≥10 and a wide residual stress range, was used as the stress birefringence calibration set.

[0019] Furthermore, in step 3, a CTE homogeneity evaluation model is established based on the first theoretical relationship and the CTE calibration group samples, specifically as follows:

[0020] The ultrasonic longitudinal wave velocity of the CTE calibration group samples was measured to obtain the ultrasonic longitudinal wave velocity measurement value.

[0021] Perform CTE calibration and obtain the CTE calibration value;

[0022] By fitting the measured values ​​of ultrasonic longitudinal wave velocity with their corresponding CTE calibration values, an experimental data model for evaluating CTE uniformity is established.

[0023] Furthermore, the ultrasonic longitudinal wave velocity of the CTE calibration group samples was measured to obtain the ultrasonic longitudinal wave velocity values, specifically:

[0024] The thickness of each sample in the CTE calibration group is obtained, and samples that meet the requirements are selected based on the thickness. The ultrasonic longitudinal wave velocity is then measured using an ultrasonic water immersion echo measurement system.

[0025] Furthermore, CTE calibration was performed using an L75 laser interferometric thermal expansion meter based on the laser Michelson interferometry principle.

[0026] Furthermore, in step 4, a radial stress distribution evaluation model is established based on the second theoretical relationship and the stress birefringence calibration group samples, specifically as follows:

[0027] The stress birefringence of the samples in the stress birefringence calibration group was calibrated to obtain the calibrated stress distribution results;

[0028] Based on the calibrated stress distribution results, several regions with the same diameter as the ultrasonic probe and uniform stress are selected as the sound velocity measurement areas. After measuring their thickness, ultrasonic longitudinal wave sound velocity is measured to obtain the ultrasonic longitudinal wave sound velocity measurement value.

[0029] A radial stress distribution evaluation model was established based on the calibrated stress distribution results and the ultrasonic longitudinal wave velocity measurement.

[0030] Furthermore, a stress birefringence meter was used to calibrate the samples in the stress birefringence calibration group.

[0031] In summary, the present invention has at least one of the following beneficial technical effects:

[0032] 1. This method possesses the capability to simultaneously detect the uniformity of thermal expansion coefficient and radial stress distribution of large-size ultra-low expansion quartz glass. By constructing experimental correlation models between CTE and longitudinal wave velocity, and stress birefringence and longitudinal wave velocity, and combining this with a highly integrated ultrasonic immersion measurement system, the probe can be positioned at any location on the surface of the glass under test to measure the sound velocity at that location, thereby calculating the corresponding CTE and stress birefringence data. The entire process does not cause any damage to the large-size sample, thus enabling the simultaneous acquisition of CTE, stress birefringence, and full-diameter uniformity information of large-size ultra-low expansion quartz glass in a completely non-destructive manner.

[0033] 2. Convenient operation and efficient detection. This method does not require temperature change treatment of the sample. It can predict the average CTE and stress birefringence of the sample in the temperature range of 5℃~35℃ based solely on the longitudinal wave velocity measured at 20℃. In the sound velocity measurement stage, a transit time estimation technique based on the correlation method is used, combined with a highly integrated water immersion sound velocity measurement system. This allows for the rapid and automatic acquisition of sound velocity data at various measuring points of large-size ultra-low expansion quartz glass. Based on the established measurement model, the corresponding CTE and stress birefringence parameters are simultaneously derived. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the method flow of the present invention;

[0035] Figure 2 A schematic diagram showing the relationship between CTE, Young's modulus, and longitudinal wave velocity;

[0036] Figure 3 This is a schematic diagram illustrating the principle of ultrasonic immersion pulse echo method.

[0037] Figure 4 This is a schematic diagram of a primary surface wave S1, a primary bottom surface echo B1, and a secondary bottom surface echo B2. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] like Figure 1 As shown, this invention provides a comprehensive measurement method for rapidly evaluating the uniformity of thermal expansion coefficient and radial stress distribution of large-size ultra-low expansion quartz glass, comprising:

[0040] Step 1: Construct a theoretical model to establish the first theoretical relationship between CTE and P-wave velocity, and the second theoretical relationship between stress birefringence and P-wave velocity;

[0041] Step 2: Establish a sample library and prepare and screen CTE calibration group samples and stress birefringence calibration group samples from ultra-low expansion quartz glass materials produced by the same manufacturing process.

[0042] Step 3: Establish a CTE homogeneity evaluation model based on the first theoretical relationship and the CTE calibration group samples;

[0043] Step 4: Establish a radial stress distribution evaluation model based on the second theoretical relationship and the stress birefringence calibration group samples;

[0044] Step 5: Perform full-aperture longitudinal wave velocity scanning measurement on the large-size ultra-low expansion quartz glass sample to be tested to obtain its longitudinal wave velocity distribution data. Input the longitudinal wave velocity distribution data into the CTE uniformity evaluation model and the radial stress distribution evaluation model, and output the CTE uniformity distribution result and radial stress distribution result of the sample to be tested.

[0045] In step 1, a theoretical model is constructed to establish the first theoretical relationship between CTE and P-wave velocity, and the second theoretical relationship between stress birefringence and P-wave velocity, specifically as follows:

[0046] First, we introduce the first theoretical relationship between CTE and longitudinal wave velocity, which uses the elastic modulus as an intermediate quantity. Specifically, the theory includes the following:

[0047] 1. The relationship between Young's modulus and CTE

[0048] From a materials science perspective, based on the principle that the increase in interatomic distance and the decrease in interatomic distance caused by atomic vibration cancel each other out with increasing temperature, materials with suitable atomic structures can be prepared using chemical methods to achieve zero expansion. Therefore, the thermal expansion and Young's modulus of a material are essentially closely related to the interatomic forces, and thus there is an inherent connection between the two.

[0049] (1)

[0050] In the formula, k 1 and k 2 represents a constant related to material properties. α m This indicates the corresponding material in a specific temperature range ( T 1~ T 2) Average CTE within E This indicates the Young's modulus of the corresponding material at a specific temperature;

[0051] 2. The relationship between Young's modulus and the speed of sound

[0052] Since the speed of sound is determined by the elastic wave vibration characteristics and material properties, the longitudinal wave speed in a material... c L and transverse wave speed of sound c S The relationships with the material's elastic constant and density are as follows:

[0053] (2)

[0054] In the formula, E It is the Young's modulus of the material; v It is the Poisson's ratio of the material; rIt refers to the density of the material. The longitudinal wave velocity of a material is mainly related to... E , v and r Relevant. For ultra-low expansion quartz glass... E right c L Size plays a dominant role.

[0055] Based on formula (2), the following relationship can be derived between the Young's modulus of a material and the velocity of sound:

[0056] (3)

[0057] In the formula, k This represents the ratio constant between the transverse wave velocity and the longitudinal wave velocity, typically taken as 0.5 to 0.7.

[0058] 3. Relationship between CTE and P-wave velocity

[0059] Based on the inherent relationship between Young's modulus and CTE, and the intrinsic relationship between P-wave velocity and Young's modulus, a specific mapping relationship can be established between the CTE and P-wave velocity of ultra-low expansion quartz glass materials, such as... Figure 2 As shown;

[0060] Combining formulas (1) and (3), we can further derive the material's properties within a certain temperature range. α m At a specific temperature c L The relationship between them is:

[0061] (4)

[0062] According to formula (4), α m and c L The mapping relationship between them is quite complex, consisting of coefficients. k , k 1. k 2 working together, although k , k 1. k Accurately obtaining value 2 is difficult, but for the same type of ultra-low expansion quartz glass material, k , k 1. k 2 can be treated as a constant value, therefore formula (4) can be simplified to:

[0063] (5)

[0064] As can be seen from formula (5), for a relatively narrow range of sound speed variation, αm and c L They exhibit an approximately linear relationship. k 3. α 0 is a coefficient obtained by nonlinear fitting of the calibrated CTE and the longitudinal wave velocity measurement, which is fixed for the same ultra-low expansion quartz glass material.

[0065] Next, we will introduce the second theoretical relationship between stress birefringence and longitudinal wave sound velocity, which is based on the acoustoelastic and photoelastic effects. The specific theory includes:

[0066] 1. Acoustic elasticity effect

[0067] Acoustoelasticity theory is the main basis for studying the relationship between the propagation speed of ultrasonic waves and stress. It shows that the propagation speed of elastic waves in stressed solid materials depends not only on the material's second elastic constants. l , m and density r It is also related to the third elastic constant. l , m , n and stress s Relevant. When an ultrasonic longitudinal wave is incident perpendicularly onto the surface of an ultra-low expansion quartz glass, the wave propagation direction is perpendicular to the plane stress direction of the material. According to the acoustoelastic effect, this manifests specifically as follows:

[0068] (6)

[0069] In the formula, r 0 represents the density of the standard sample (in a zero-stress state). c L This represents the longitudinal wave velocity perpendicular to the stress direction. s 1 and s 2 represents the principal stress of the material. l , m It is the Lame constant. l , m It is Murnaghan's constant;

[0070] By deriving formula (6), we can obtain:

[0071] (7)

[0072] In the formula, K 1 represents the acoustoelastic constant of the material. It is mainly composed of the second-order elastic constant. l , m and density r It is also related to the third elastic constant. l , m , n constitute.

[0073] 2. Photoelastic effect

[0074] When glass is under stress, a light source of a specific wavelength passes through it, resulting in birefringence and splitting into two plane-polarized beams: one along the principal stress. s 1 direction, 1 along the principal stress s In two directions, due to the different propagation speeds of the two polarized lights, an optical path difference will be generated in the glass:

[0075] (8)

[0076] For a small region with uniform stress, according to the theory of elasticity, each stress component is a constant independent of spatial coordinates. This means that the principal stresses... s 1 and s 2 is a constant, and its ratio ( s 1+ s 2) / ( s 1- s 2) It is a constant value within this region. Therefore, combining equations (7) and (8), we can further derive the material stress birefringence. d With longitudinal wave speed c L The relationship between them is:

[0077] (9)

[0078] As can be seen from formula (9), for a relatively narrow range of sound speed variation, d and c L They exhibit an approximately linear relationship. K The coefficients are obtained by linearly fitting the calibrated stress birefringence and longitudinal wave velocity measurements, and are fixed for the same type of ultra-low expansion quartz glass.

[0079] In step 2, a sample library is established. From ultra-low expansion quartz glass blanks produced using the same manufacturing process, CTE calibration group samples and stress birefringence calibration group samples are prepared and screened. Specifically:

[0080] Two sets of samples were designed from ultra-low expansion quartz glass blanks produced by the same manufacturing process. The first set of samples, which had significant differences in longitudinal wave velocity, was used as the CTE calibration set. The second set of samples, which had a diameter-to-thickness ratio ≥10 and a wide residual stress range, was used as the stress birefringence calibration set.

[0081] In step 3, a CTE homogeneity evaluation model is established based on the first theoretical relationship and the CTE calibration group samples, specifically as follows:

[0082] Step 301: Perform ultrasonic longitudinal wave velocity measurement on the CTE calibration group samples and obtain the ultrasonic longitudinal wave velocity measurement value.

[0083] Step 302: Perform CTE calibration and obtain CTE calibration values;

[0084] Step 303: Fit the measured ultrasonic longitudinal wave velocity values ​​with their corresponding CTE calibration values ​​to establish a CTE uniformity evaluation model.

[0085] In step 301, the ultrasonic longitudinal wave velocity of the CTE calibration group samples is measured to obtain the ultrasonic longitudinal wave velocity measurement value, specifically as follows:

[0086] At a temperature of 20℃, several ultra-low expansion quartz glass samples with a relatively wide range (0±100ppb / ℃) CTE were selected for ultrasonic longitudinal wave velocity measurement. The sample requirements are as follows:

[0087] (1) The sample size is Φ25mm A 50mm cylinder.

[0088] (2) In order to avoid the influence of component differences on the CTE of the sample, the sample was obtained under the same process formula but with different heat treatment regimes.

[0089] (3) The sample was subjected to fine annealing to remove the internal residual thermal stress and achieve a low stress state (all <1nm / cm). The fine annealing process included heating from room temperature to 990°C at a rate of 20°C / h; holding at 990°C for 50h; cooling from 990°C to 850°C at a rate of 3°C / h; cooling from 850°C to 100°C at a rate of 25°C / h; and naturally cooling from 100°C to room temperature.

[0090] (4) To avoid the adverse effects of ultrasonic wave scattering and attenuation at the sample interface, the sample was finely ground and polished to achieve a flatness and parallelism of 20µm and a surface roughness of [missing information]. Rq ≤1µm.

[0091] The thickness of each sample in the CTE group was obtained using a high-precision micrometer. dThen, the ultrasonic longitudinal wave velocity of the qualified samples is measured using an ultrasonic immersion echo measurement system. This system mainly consists of core components such as an ultrasonic water bath, a motion triaxial transceiver and controller, a pulse transceiver, a high-precision constant temperature chamber, and an industrial computer. The ultrasonic water bath is used to hold the coupling medium (water) and immerse the test sample to ensure effective propagation of ultrasonic waves; the motion triaxial transceiver and controller are responsible for precisely adjusting the position of the ultrasonic immersion probe to meet the measurement needs of different areas; the pulse transceiver is used to excite ultrasonic signals and receive the echo signals from the sample; the high-precision constant temperature chamber can accurately control the temperature of the test environment with a temperature control accuracy of ±0.1℃, effectively reducing the impact of temperature fluctuations on the measurement results; the industrial computer, as the control center of the system, has a built-in data acquisition card with a sampling frequency of 1.25GS / s, responsible for the coordination and control of the entire measurement process, data acquisition, and signal processing, ultimately achieving high-precision measurement of the ultrasonic longitudinal wave velocity. The principle of the ultrasonic immersion pulse echo method is as follows: Figure 3 As shown.

[0092] This principle primarily involves a pulse transceiver generating a raw ultrasonic pulse S0. The pulse first propagates in the coupling medium (water). When it reaches the water surface and the sample surface, some of the acoustic energy is reflected, forming a primary surface echo S1, while the remaining energy is transmitted into the sample. As the ultrasonic wave propagates within the sample, it is reflected between the upper and lower interfaces, forming a primary bottom echo and a secondary bottom echo, such as... Figure 4 As shown, these echoes carrying sample information are received by the same probe, and by analyzing the time intervals between echo signals that arrive sequentially and correspond to different sound paths, combined with the known thickness of the sample, the ultrasonic longitudinal wave velocity of the tested sample can be accurately calculated.

[0093] Since the ultrasonic echo signals B1 and B2 are highly similar, a correlation coefficient is calculated between them using a correlation function. The time corresponding to the maximum correlation coefficient is the time of flight (TOF) of the ultrasonic wave in the sample. First, the original ultrasonic signal of the material is acquired and downsampled to reduce the amount of data and improve the efficiency of subsequent calculations. Then, Morlet wavelet transform is performed on the downsampled time-domain signal to obtain the wavelet coefficients corresponding to each scale. By analyzing the energy distribution of the coefficients at each scale, the time-domain location of the primary surface reflection wave S1 corresponding to the point of maximum energy is identified.

[0094] Based on the positioning results of S1, combined with the known sample thickness and reference sound velocity, the reference TOF of ultrasonic wave propagation in the sample can be calculated. According to this reference time and the time-domain information of S1, the occurrence positions of the primary bottom wave B1 and the secondary bottom wave B2 are further automatically determined. Based on this, feature points such as the peak and trough values ​​of the B1 and B2 signals are extracted, and the two signals are processed using a digital cross-correlation method. The time corresponding to the maximum correlation coefficient is used to determine the actual TOF.

[0095] Based on the thickness of the sample d And TOF, by c L =2 d / TOF yields the longitudinal wave velocity, enabling rapid measurement of the ultrasonic longitudinal wave velocity in ultra-low expansion quartz glass samples.

[0096] In step 302, CTE calibration is performed to obtain the CTE calibration value, specifically as follows:

[0097] The CTE of ultra-low expansion quartz glass samples was calibrated using an L75 laser interferometric dilatometer. This dilatometer performs high-precision CTE measurements based on the laser Michelson interferometry principle. The preparation requirements for the test samples are as follows:

[0098] (1) The specimens are subjected to the same fine annealing treatment as the longitudinal wave sound velocity measurement specimens to achieve the same stress state.

[0099] (2) The sample shape is required to be cylindrical, with dimensions of Φ6±0.5mm and a thickness of 50mm, to ensure the correspondence between the sound velocity and the CTE calibration value;

[0100] (3) The upper and lower surfaces of the sample are flat and parallel to each other, with a flatness of 0.5λ, a parallelism of 2′, and a surface roughness of 1nm~3nm;

[0101] (4) The roundness and taper of the sample are controlled according to general standards, and the perpendicularity of the end face reaches 1′.

[0102] The length change of the ultra-low expansion quartz glass sample caused by temperature change is Δ L = L 0 ( α m (( T 2- T 1) = L 0 ( α m (Δ) T The laser Michelson interferometer in the L75 laser thermal expansion meter can achieve ∆ L High-precision measurement, by recording changes in optical path difference and Δ T The sample can then be determined. αm value:

[0103] (10)

[0104] In the formula, Δ N It is a change in the number of interference fringes; l It is the wavelength of the laser. l =632.8nm. It should be noted that currently, this laser thermal dilatometer only allows for two sample lengths for CTE testing (20mm and 50mm). The formula for the length change caused by temperature variations in ultra-low expansion quartz glass samples indicates the initial sample length... L The longer the 0, the higher the uncertainty level of the CTE test. Therefore, a 50mm long ultra-low expansion quartz glass sample should be used for CTE calibration.

[0105] Based on room temperature (20℃) ultra-low expansion quartz glass samples α m The target temperature range (5~35℃) was used to set experimental parameters. The starting temperature of the CTE calibration process was set to -5℃, the ending temperature to 65℃, and the heating rate to 1℃ / min. After determining the experimental parameters, CTE calibration was performed. The specific steps included:

[0106] (1) First, the sample to be tested is dried and cleaned, and the initial length of the sample is measured at room temperature (20℃). L 0;

[0107] (2) Place the sample into the DIL and let the measuring system stand for 30 minutes;

[0108] (3) Cool the sample to the measurement start temperature (-5℃) using liquid nitrogen and keep it at that temperature for 10 min. Then heat the sample to the measurement end temperature (65℃) at a heating rate of 1℃ / min.

[0109] (4) Record the linear expansion rate data of these samples within the measurement temperature range;

[0110] (5) Expansion rate (Δ) at 5~35℃ L / L 0) - Temperature ( T The data was processed to calculate the average CTE value within the temperature range of 5~35℃. α m .

[0111] In step 303, the measured ultrasonic longitudinal wave velocity value is fitted with its corresponding CTE calibration value to establish a CTE uniformity evaluation model, specifically as follows:

[0112] The measured ultrasonic longitudinal wave velocity values ​​were fitted with their corresponding CTE calibration values ​​to establish a CTE uniformity evaluation model for large-size ultra-low expansion quartz glass based on ultrasonic longitudinal wave velocity. The results show... α m and c L The fitting equation between them is c L = m 1 α m + m 2, in the formula m 1. m 2 indicates that after calibration of CTE and c L The coefficients obtained by performing a least-squares linear fit; where m 1 is CTE c L The impact coefficient represents the change in CTE by one unit. c L The value will change accordingly, and its range remains at 0.4257~0.4305 (m / s) / (ppb / ℃). m A positive value of 2 indicates the value corresponding to a CTE of zero. c L Its range remains between 5745.33 and 5751.21 m / s.

[0113] In step 4, a radial stress distribution evaluation model is established based on the second theoretical relationship and the stress birefringence calibration group samples, specifically as follows:

[0114] Step 401: Perform stress birefringence calibration on the samples of the stress birefringence calibration group to obtain the calibrated stress distribution results;

[0115] Step 402: Based on the calibrated stress distribution results, select several regions with the same diameter as the ultrasonic probe and uniform stress as the sound velocity measurement area. After measuring the thickness of these regions, perform ultrasonic longitudinal wave sound velocity measurement to obtain the ultrasonic longitudinal wave sound velocity measurement value.

[0116] Step 403: Establish a radial stress distribution evaluation model based on the calibrated stress distribution results and the ultrasonic longitudinal wave velocity measurement.

[0117] In step 401, stress birefringence calibration is performed on the samples of the stress birefringence calibration group to obtain the calibrated stress distribution results, specifically as follows:

[0118] The stress birefringence of ultra-low expansion quartz glass samples was calibrated using a stress birefringence analyzer (HINDS, Exicor 300AT). This stress birefringence analyzer performs high-precision stress birefringence measurements based on the photoelastic effect. The preparation requirements for the test samples are as follows:

[0119] (1) The sample shape requirement is that the diameter-to-thickness ratio is ≥10. The sample size selected for this implementation is 120mm. 120mm 10mm;

[0120] (2) The upper and lower surfaces of the sample are flat and parallel to each other, with a flatness of 20µm, a parallelism of 2′, and a surface roughness of 1nm~3nm.

[0121] The specific calibration steps are as follows:

[0122] (1) Place the ultra-low expansion quartz glass sample in a constant temperature environment of 20°C for at least 2 hours.

[0123] (2) Turn on the testing instrument and preheat it for 30 minutes.

[0124] (3) Select and install appropriate tooling according to the shape and size of the sample.

[0125] (4) Set the detection parameters: sample thickness 10mm, measurement range 120mm 100mm, measurement step size 2mm.

[0126] (5) After calibrating and zeroing the testing instrument, start the test.

[0127] (6) Save the calibrated stress birefringence data.

[0128] In step 402, based on the calibrated stress distribution results, several regions with the same diameter as the ultrasonic probe and uniform stress are selected as the sound velocity measurement area. After measuring the thickness of these regions, the ultrasonic longitudinal wave sound velocity is measured to obtain the ultrasonic longitudinal wave sound velocity measurement value, specifically:

[0129] Based on the calibrated stress distribution results, several regions with the same diameter as the ultrasonic probe and relatively uniform stress were selected as the sound velocity measurement areas. After measuring their thickness, the ultrasonic longitudinal wave sound velocity of the stress birefringence group sample was measured at a temperature of 20°C using the sound velocity measurement steps described above.

[0130] In step 403, a radial stress distribution evaluation model is established based on the calibrated stress distribution results and the measured ultrasonic longitudinal wave velocity, specifically as follows:

[0131] The measured ultrasonic longitudinal wave velocity values ​​were fitted with their corresponding stress birefringence calibration values ​​to establish an evaluation model for the stress birefringence uniformity of large-size ultra-low expansion quartz glass based on ultrasonic longitudinal wave velocity. The results show... d and c L The fitting equation between them is c L = m 3 d + m 4, in the formula m 3. m 4 indicates that after the process of... d and c L The coefficients obtained by performing a least-squares linear fit. m 3 is the coefficient of stress on sound velocity, which represents d For every unit change, c L How much will change accordingly, and how much will it remain within the range? (m / s) / (ppb / ℃) m 4 is a positive value, indicating d When it is zero, the corresponding c L Its range remains between 5760.66 and 5767.31 m / s.

[0132] In step 5, a full-aperture longitudinal wave velocity scan is performed on the large-size ultra-low expansion quartz glass sample to obtain its longitudinal wave velocity distribution data. This data is then input into the CTE uniformity evaluation model and the radial stress distribution evaluation model to output the CTE uniformity distribution results and radial stress distribution results of the sample. Specifically:

[0133] Based on the measurement principle of ultrasonic water immersion pulse echo method, the longitudinal wave velocity distribution of the large-size ultra-low expansion quartz glass sample to be tested is obtained by following the above steps. Substituting the obtained evaluation model, the CTE uniformity and radial stress distribution of the large-size ultra-low expansion quartz glass sample are calculated.

[0134] Embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0135] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure one One or more processes and / or boxes Figure one A device that provides the functions specified in one or more boxes.

[0136] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure one One or more processes and / or boxes Figure one The function specified in one or more boxes.

[0137] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure one One or more processes and / or boxes Figure one The steps of the function specified in one or more boxes.

[0138] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A comprehensive measurement method for large-size ultra-low expansion quartz glass, characterized in that, include: Step 1: Construct a theoretical model to establish the first theoretical relationship between CTE and P-wave velocity, and the second theoretical relationship between stress birefringence and P-wave velocity; Using the elastic modulus as an intermediate quantity, a first theoretical relationship between CTE and longitudinal wave velocity is established; based on the acoustoelastic effect and the photoelastic effect, a second theoretical relationship between stress birefringence and longitudinal wave velocity is established. Step 2: Establish a sample library. Prepare and screen CTE calibration group samples and stress birefringence calibration group samples from ultra-low expansion quartz glass blanks produced by the same manufacturing process. Design two groups of samples from ultra-low expansion quartz glass blanks produced by the same manufacturing process. The first group consists of samples with significant differences in longitudinal wave velocity, which are used as CTE calibration group samples. The second group consists of samples with a diameter-to-thickness ratio ≥10 and a wide residual stress range, which are used as stress birefringence calibration group samples. Step 3: Establish a CTE homogeneity evaluation model based on the first theoretical relationship and the CTE calibration group samples; Step 4: Establish a radial stress distribution evaluation model based on the second theoretical relationship and the stress birefringence calibration group samples; perform stress birefringence calibration on the samples of the stress birefringence calibration group to obtain the calibrated stress distribution results; Based on the calibrated stress distribution results, several regions with the same diameter as the ultrasonic probe and uniform stress are selected as the sound velocity measurement areas. After measuring their thickness, ultrasonic longitudinal wave sound velocity is measured to obtain the ultrasonic longitudinal wave sound velocity measurement value. A radial stress distribution evaluation model was established based on the calibrated stress distribution results and the ultrasonic longitudinal wave velocity measurement. Step 5: Perform full-aperture longitudinal wave velocity scanning measurement on the large-size ultra-low expansion quartz glass sample to be tested to obtain its longitudinal wave velocity distribution data. Input the longitudinal wave velocity distribution data into the CTE uniformity evaluation model and the radial stress distribution evaluation model, and output the CTE uniformity distribution result and radial stress distribution result of the sample to be tested.

2. The comprehensive measurement method for large-size ultra-low expansion quartz glass according to claim 1, characterized in that, In step 3, a CTE homogeneity evaluation model is established based on the first theoretical relationship and the CTE calibration group samples, specifically as follows: The ultrasonic longitudinal wave velocity of the CTE calibration group samples was measured to obtain the ultrasonic longitudinal wave velocity measurement value. Perform CTE calibration and obtain the CTE calibration value; By fitting the measured values ​​of ultrasonic longitudinal wave velocity with their corresponding CTE calibration values, an experimental data model for evaluating CTE uniformity is established.

3. The comprehensive measurement method for large-size ultra-low expansion quartz glass according to claim 2, characterized in that, The ultrasonic longitudinal wave velocity of the CTE calibration group samples was measured to obtain the ultrasonic longitudinal wave velocity values, specifically: The thickness of each sample in the CTE calibration group is obtained, and samples that meet the requirements are selected based on the thickness. The ultrasonic longitudinal wave velocity is then measured using an ultrasonic water immersion echo measurement system.

4. The comprehensive measurement method for large-size ultra-low expansion quartz glass according to claim 3, characterized in that, CTE calibration was performed using an L75 laser interferometric thermal expansion meter based on the laser Michelson interferometry principle.

5. The comprehensive measurement method for large-size ultra-low expansion quartz glass according to claim 4, characterized in that, The stress birefringence of the samples in the stress birefringence calibration group was calibrated using a stress birefringence meter.

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