A traceability method for sensing mass value of quartz crystal microbalance using hard film method and mass comparison method

Abstract

The traceability method of the quartz crystal microbalance (QCM) sensing mass value of the application by using the hard film method and the mass comparison method makes that as long as the metrological technology institutions and laboratories of high-precision mass comparators and high-accuracy weights can adopt the method of the application, the traceability of the QCM sensing mass value is realized; the traceability method of the QCM sensing mass value is simplified, and wider popularization is obtained; and the traceability of the QCM in the mass increment range below 16 mu g is innovatively solved, the range of the traceability method for the traceability of the small mass is expanded, the measurement range is expanded to 2 mu g to 1000 mu g; the expanded range of the traceability of the small mass can improve the mass sensitivity, and further improve the detection precision of the QCM, and further bring great changes and influences.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tracing the mass value sensed by a quartz crystal microbalance, and particularly relates to a method for tracing the mass value sensed by a quartz crystal microbalance using a hard film method and a mass comparison method. BACKGROUND

[0002] At present, in the process of transmitting a small mass value, a mass smaller than 1 kg needs to be obtained by using a component comparison method. When the mass value is transmitted by the component comparison method once, the relative uncertainty caused by various reasons will be accumulated significantly. For a mass of 1 kg, the relative uncertainty of the current mass value measurement is 2 x 10 -8 ; when the mass is transmitted to the milligram level by the component comparison method, the relative uncertainty will be 2500 times that of the relative uncertainty of 1 kg; if the component comparison method is used to transmit a smaller mass value, the relative uncertainty will be larger; and when the mass value is transmitted to the level of 1 nanogram by the component comparison method, the uncertainty may reach 10 -12 kg, that is, the uncertainty is equivalent to 1 nanogram itself. At present, the traceability capability of the existing technology for small mass is 50 μg.

[0003] A quartz crystal microbalance (QCM) is widely used in the fields of physical chemistry, life science, environmental science, aerospace, medical science and environmental science. It was developed in the late 1950s and is a highly sensitive mass detection instrument. Its measurement accuracy can reach the nanogram level, and the specific sensitivity is 1000 times higher than that of an electronic balance of the microgram level. In theory, the mass change that can be detected is equivalent to one-tenth of a monolayer or an atomic layer. The quartz crystal microbalance is constructed based on the piezoelectric effect principle of a quartz crystal. A small mass change Δm on the surface of a quartz crystal electrode is converted into a frequency change Δf of an output electrical signal of a quartz crystal oscillation circuit, and then high-precision detection data are obtained by combining a theoretical model and a computer and other auxiliary equipment. Based on the mass value measurement principle of the QCM, the quantitative analysis of the QCM mass measurement result depends largely on the theoretical model, that is, the corresponding relationship between Δm and Δf cannot be directly traced to the International System of Units.

[0004] The existing technology for tracing the mass value sensed by a quartz crystal microbalance is mainly a method for tracing the mass value sensed by a QCM proposed by Stambaugh and other researchers of the National Institute of Standards and Technology (NIST). The existing technology abroad coats a film on a QCM quartz crystal wafer, and uses a high-precision mass comparator to determine the mass difference on the quartz crystal wafer before and after coating the film to obtain the corresponding relationship between the mass increment on the wafer and the frequency shift of the QCM wafer.

[0005] The foreign prior art preliminarily realizes the linking of the corresponding relationship between the coating quality increment measured by the QCM method and the resonant frequency shift of the crystal resonator caused by the coating quality increment to the International System of Units; the foreign prior art realizes the calibration of the QCM in the mass increment range of 16.87 μg to 1044.26 μg from the results; and the E1 grade real reference mass used in the process of comparing the real reference mass is calibrated by the electrostatic force balance (EFB) which can be traced to the Planck constant h; that is, the foreign prior art can trace the relationship between the mass increment on the QCM quartz crystal resonator and the corresponding resonant frequency shift of the crystal resonator to the Planck constant through a shorter path by mass value;

[0006] The defect of the prior art is that the traditional mass comparison method relies on real mass reference weights and standard weights, but for mass values below 20 μg, the electrostatic force effect of the weight itself gradually dominates as the mass decreases; therefore, for mass values below 20 μg, it is impossible to use real standard weights and the mass comparison method for traceability;

[0007] And the foreign prior art is largely dependent on the EFB device, which is not a device that every measurement institution and laboratory can have, and the construction and maintenance cost of the equipment is high, which is inconvenient for the traceability of the QCM sensing mass value; and the mass value traced by the EFB device has not been compared with the traditional mass value traceability method;

[0008] In addition, the traceability method of the QCM sensing mass value proposed by the United States NIST only realizes the traceability of the QCM in the mass increment range of 16.87 μg to 1044.26 μg, and cannot meet the traceability of smaller QCM crystal resonator mass increments.

[0009] Therefore, the skilled in the art is committed to developing a traceability method for the mass value of a quartz crystal microbalance using the hard film method and the mass comparison method, aiming to solve the defects in the prior art. SUMMARY

[0010] In view of the above defects of the prior art, the technical problem to be solved by the present application is that in the prior art, the traditional quality comparison method quality value measurement relies on physical quality reference weights and standard weights, and for mass values below 20 μg, physical standard weights and quality comparison methods cannot be used for traceability; the traceability method of QCM sensing mass value proposed by the United States NIST relies to a large extent on the EFB device, and the mass value traced by the EFB device has not been compared with the traditional mass value traceability method; moreover, the traceability method proposed by the United States NIST only realizes the traceability of QCM in the mass increment range of 16.87 μg to 1044.26 μg, and cannot meet the traceability of smaller QCM crystal sheet mass increments.

[0011] To achieve the above object, a traceability method of quartz crystal microbalance sensing mass value using hard film method and quality comparison method, comprising the following steps:

[0012] Step 1, establishing a traceability mechanism for rigid hard film micro-mass;

[0013] Step 2, measuring the mass on the unloaded QCM crystal sheet;

[0014] Step 3, loading micro-mass on the QCM crystal sheet;

[0015] Step 4, measuring the micro-mass loaded on the QCM crystal sheet in step 3;

[0016] The step 1, the traceability of rigid hard film micro-mass can be completed according to the classical Sauerbrey equation,

[0017] (1) In the formula, f q is the resonant frequency of the QCM crystal sheet, ρ q is the density of the crystal sheet, μ q is the shear modulus of the crystal sheet, and the minus sign means that the QCM resonant frequency is reduced;

[0018] In the step 1, if the rigid hard film attached to the crystal sheet is thin enough, the rigid hard film mass Δm and the resonant frequency shift Δf of the crystal sheet are in linear relationship;

[0019] The traceability mechanism established in the step 1 realizes the uncertainty introduced in the measurement process;

[0020] Step 2, measuring the mass on the unloaded QCM crystal sheet;

[0021] In the step 2, the mass of the unloaded QCM crystal sheet is first obtained by the quality comparison method to obtain its unloaded mass m U , and the resonant frequency f U of the unloaded QCM is obtained by using the QCM.

[0022] The step 2 needs to be placed in a stable environment for more than 48 hours before the unloaded mass measurement, so as to eliminate the instability of the crystal oscillator caused by the environment during the preparation process;

[0023] Step 3, load the micro-mass on the QCM crystal oscillator;

[0024] The method for loading the micro-mass on the QCM crystal oscillator in the step 3 is a magnetron sputtering method;

[0025] In the step 3, the micro-mass loaded on the QCM crystal oscillator is to limit the film coating area on the QCM crystal oscillator and the uniformity of the film coating, and a mask plate with different aperture sizes is designed to realize the loading area of the rigid hard film micro;

[0026] In order to obtain different micro-mass of the crystal oscillator, different thicknesses of the rigid hard film need to be deposited on the crystal oscillator in the step 3;

[0027] In the step 3, the thickness of the rigid hard film loaded on the QCM crystal oscillator is controlled by the film coating time;

[0028] In the step 3, the thickness of the rigid hard film deposited on the crystal oscillator needs to be much smaller than the thickness of the crystal oscillator, because the thickness of the deposited film has an influence on the measurement accuracy of the resonant frequency of the crystal oscillator;

[0029] The deposited film material selected in the step 3 needs to have a large density;

[0030] Step 4, measure the micro-mass loaded on the QCM crystal oscillator in step 3

[0031] After the step 3 completes the loading of the micro-mass, that is, uniformly deposits the metal hard film with different mass on the QCM crystal oscillator as the load, the measurement of the micro-mass loaded on the QCM crystal oscillator can be performed;

[0032] The step 4 measures the loaded mass m of the film coated wafer L , and then uses the QCM to obtain the resonant frequency f of the crystal oscillator under load L ;

[0033] The micro-mass measured in the step 4 can be expressed as Δm=m L -m U and Δf=f L -f U ; wherein the subscripts L and U respectively represent “loaded” and “unloaded” states;

[0034] Further, the step 3 method of loading micro-mass on the QCM crystal oscillator plate can also use pulsed laser deposition, chemical vapor deposition, sol-gel, electroplating, chemical plating;

[0035] Further, the deposition film material when loading micro-mass on the QCM crystal oscillator plate in step 3 can use gold, silver and copper as the plating film material;

[0036] Further, the thickness of the mask plate when loading micro-mass on the QCM crystal oscillator plate in step 3 is related to the uniformity of the metal hard film, and a mask plate with a thickness less than 0.1 mm or a sharp edge mask plate can be used;

[0037] Further, the loaded QCM crystal oscillator plate needs to be placed in a stable environment for more than 48 hours before quality measurement to eliminate the instability of the crystal oscillator plate itself affected by the environment during preparation;

[0038] Further, the measurement of the unloaded mass and the loaded mass in steps 2 and 4 can use a high-precision mass comparator and a high-accuracy standard weight;

[0039] With the above scheme, the traceability method for sensing the mass value of the quartz crystal microbalance using the hard film method and the mass comparison method disclosed by the present application has the following advantages:

[0040] (1) The traceability method for sensing the mass value of the quartz crystal microbalance using the hard film method and the mass comparison method of the present application realizes the simplification of the QCM sensing mass value traceability method and obtains wider popularization. The present application enables the use of the present application method by measurement technology institutions and laboratories that have a high-precision mass comparator and a high-accuracy weight with lower cost and wider popularity without relying on an EFB device, thereby realizing the traceability of the QCM sensing mass value;

[0041] (2) The traceability method for sensing the mass value of the quartz crystal microbalance using the hard film method and the mass comparison method of the present application loads micro-mass onto the QCM quartz crystal plate using a vacuum magnetron sputtering method, so that the loaded micro-mass is integrated with the quartz crystal plate through atomic interaction force, and the effect of electrostatic force is avoided in the mass range below 20 μg. The present application innovatively solves the traceability of QCM in the mass increment range below 16 μg, expands the range of traceability of micro-mass by the traceability method, and expands the measurement range to 2 μg to 1000 μg. The expanded range of traceability of micro-mass can improve the mass sensitivity, and further improve the QCM detection accuracy, thereby bringing great changes and influences;

[0042] In summary, the quartz crystal microbalance sensing mass value traceability method disclosed by the application uses the hard film method and the mass comparison method, so that the QCM sensing mass value can be traced by the measurement technology institutions and laboratories of high-precision mass comparators and high-accuracy weights, the QCM sensing mass value traceability method is simplified, and wider popularization is obtained, the traceability of QCM in the mass increment range below 16 μg is innovatively solved, the range of the traceability method for small mass is expanded, the measurement range is expanded to 2 μg to 1000 μg, the range of the expanded small mass traceability can improve the mass sensitivity, and then the QCM detection precision is further improved, and then great changes and influences are brought about.

[0043] The concept, specific technical solutions and generated technical effects of the application will be further described in combination with specific embodiments, so that the purpose, features and effects of the application can be fully understood. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a flowchart of the quartz crystal microbalance sensing mass value traceability method of the application;

[0045] Figure 2 is a structural schematic diagram of a 14mm sharp edge mask plate used in embodiment 1 when the quartz crystal microbalance sensing mass value is traced.

[0046] Figure 3 is a structural schematic diagram of a 25mm sharp edge mask plate used in embodiment 1 when the quartz crystal microbalance sensing mass value is traced. DETAILED DESCRIPTION

[0047] The multiple preferred embodiments of the application are introduced below, so that the technical content of the application is clearer and easier to understand. The application can be embodied in many different forms, and the protection scope of the application is not limited to the embodiments mentioned in the text.

[0048] Embodiment 1, the QCM sensing mass value is traced by using the method of the application

[0049] The QCM sensing mass value is traced in embodiment 1, as shown in the figure; first, step 1, the traceability mechanism of the rigid hard film small mass is established; Figure 1

[0050] The step 1, the traceability of the rigid hard film small mass can be completed according to the classical Sauerbrey equation,

[0051]

[0052] ​(1) where f is the resonance frequency of the QCM crystal, p is the density of the crystal, μ is the shear modulus of the crystal, and the negative sign indicates that the QCM resonance frequency decreases. q q q

[0053] In step 1, if the rigid hard film attached to the crystal is thin enough, then the mass of the rigid hard film Δm and the resonance frequency shift Δf of the crystal are linearly related.

[0054] The traceability mechanism established in step 1 realizes the uncertainty introduced in the measurement process.

[0055] Then, step 2 is performed, which measures the mass of the unloaded QCM crystal.

[0056] In step 2, the mass of the unloaded QCM crystal is first obtained by the mass comparison method to obtain its unloaded mass m U , and the unloaded resonance frequency f U of the QCM is obtained.

[0057] Before performing the unloaded mass measurement in step 2, the crystal needs to be placed in a stable environment for more than 48 hours to eliminate the instability of the crystal itself caused by the environment during preparation.

[0058] After the unloaded mass measurement is completed, step 3 is performed, which loads a small mass on the QCM crystal.

[0059] The method for loading a small mass on the QCM crystal in step 3 is magnetron sputtering.

[0060] The method for loading a small mass on the QCM crystal in step 3 can also use pulsed laser deposition, chemical vapor deposition, sol-gel, electroplating, and chemical immersion plating.

[0061] In step 3, the loading of a small mass on the QCM crystal is to limit the area of the deposited film on the QCM crystal and the uniformity of the deposited film. Different aperture sizes of the mask plate are designed to realize the loading of a small area of rigid hard film.

[0062] In step 3, in order to obtain different small masses attached to the crystal, different thicknesses of rigid hard films need to be deposited on the crystal.

[0063] In step 3, the thickness of the rigid hard film loaded on the QCM crystal is controlled by the deposition time when loading a small mass.

[0064] ​​​The step 3 loads the micro-mass on the QCM crystal plate, and the thickness of the rigid hard film deposited on the crystal plate needs to be far less than the thickness of the crystal plate because the thickness of the deposited film has an influence on the measurement precision of the resonant frequency of the crystal plate;

[0065] The deposited film material selected in the step 3 needs to have a large density;

[0066] The deposited film material used in the step 2 when loading the micro-mass on the QCM crystal plate can be selected from gold, silver and copper as the plating film material;

[0067] The thickness of the mask plate in the step 2 when loading the micro-mass on the QCM crystal plate is related to the uniformity of the metal hard film, and the thickness of the mask plate can be less than 0.1 mm or a sharp edge mask plate is used;

[0068] In use, the method for loading the micro-mass of the rigid hard film on the QCM crystal plate in the embodiment 1 is implemented by using the vacuum magnetron sputtering method for plating;

[0069] In the embodiment 1, the unloaded mass and the loaded mass of the QCM crystal plate are measured by using a high-precision mass comparator and high-accuracy standard weights;

[0070] The mass comparator has a resolution of 0.1 μg, and the electric weighing range of the mass comparator is 0 to 1100 mg; the high-accuracy standard weights have a combined standard uncertainty of less than 0.4 μg;

[0071] The measuring equipment in the embodiment 1 measures in a vacuum condition, and the vacuum degree during the measurement is less than 5×10 -6 hPa, so as to avoid the influence of air buoyancy on the measurement; in an air condition, the air density measuring standard uncertainty of the air density measuring device is less than 4×10 -5 mg / cm 3 , so as to obtain accurate air buoyancy correction;

[0072] Before the unloaded and loaded QCM crystal plates are measured, the crystal plates are placed in a stable environment for more than 48 hours, so as to eliminate the instability of the crystal plates caused by the influence of the environment during the preparation process;

[0073] The deposited film material selected in the step 3 in the embodiment 1 is gold as the plating film material; and the method for loading the micro-mass of the rigid hard film on the QCM crystal plate is implemented by using the vacuum magnetron sputtering method for plating;

[0074] In the embodiment 1, the micro-mass is loaded on the QCM quartz crystal plate by using the vacuum magnetron sputtering method, so that the loaded micro-mass is combined with the electrode of the quartz crystal plate as a whole through interatomic force, and the influence of electrostatic force on the mass measurement is avoided in the mass range of 20 μg or less;

[0075] Wherein, the thickness of the mask plate is related to the uniformity of the metal hard film, in order to avoid the half-shadow effect of the mask plate, the embodiment 1 respectively adopts the mask plate with sharp edge;

[0076] The mask plate used in the embodiment 1 is as shown in the following Figure 2 、 Figure 3 , Figure 2 is a 14mm diameter sharp edge mask plate, Figure 3 is a 25mm diameter sharp edge mask plate;

[0077] The embodiment 1 uses the 14mm and 25mm diameter sharp edge mask plates in the testing process, which can be applied to the QCM crystal oscillator plate with a diameter of 14mm and 25mm;

[0078] And by adjusting the outer diameter and inner diameter of the mask plate, the embodiment 1 can match the QCM crystal oscillator plate with different diameters and the crystal oscillator plate work surface electrode with different areas respectively;

[0079] Then, step 4, measuring the micro-mass loaded on the QCM crystal oscillator plate in step 3 is completed

[0080] After the completion of the micro-mass loading in step 3, that is, the uniform deposition of the metal hard film with different mass on the QCM crystal oscillator plate as the load, the measurement of the micro-mass loaded on the QCM crystal oscillator plate can be carried out;

[0081] The step 4 measures the loaded mass m of the plated film L , and then uses the QCM to obtain the resonant frequency f of the crystal oscillator plate under load L ;

[0082] The micro-mass measured in step 4 can be expressed as Δm=m L -m U and Δf=f L -f U ; Wherein, the subscripts L and U respectively represent “loaded (Loaded)” and “unloaded (Unloaded)” states;

[0083] The loaded QCM crystal oscillator plate needs to be placed in a stable environment for more than 48 hours before the quality measurement, in order to eliminate the instability of the crystal oscillator plate itself affected by the environment during the preparation process;

[0084] The unloaded mass and the loaded mass measured in steps 2 and 4 can use high-precision mass comparators and high-accuracy standard weights; that is, the traceability of the QCM sensing mass value is completed;

[0085] In summary, the patent technical scheme realizes the simplification of the QCM sensing mass value traceability method, and obtains wider popularization; the method makes it possible for the measurement technology institutions and laboratories with lower cost and wider popularization of high-precision mass comparators and high-accuracy weights to use the method, realizes the traceability of the QCM sensing mass value without the aid of the EFB device; and the vacuum magnetron sputtering method is used to load the small mass on the QCM quartz wafer, so that the loaded small mass is combined with the quartz wafer as a whole through interatomic force, and the action of electrostatic force is avoided in the mass range below 20 mu g; the method innovatively solves the traceability of the QCM in the mass increment range below 16 mu g, expands the traceability method to the range of small mass traceability, and expands the measurement range to 2 mu g to 1000 mu g; the expanded range of small mass traceability can improve the mass sensitivity, and further improve the QCM detection precision, thereby bringing great changes and influences.

[0086] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and changes without creative work based on the concept of the present application. Therefore, any technical solution obtained by logical analysis, reasoning or limited test based on the prior art according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A method for tracing the mass value sensed by a quartz crystal microbalance (QCM) using a hard film method and a mass comparison method, characterized in that: The steps include: Step 1: Establish a traceability mechanism for the tiny mass of rigid hard films; Step 2: Measure the mass of the unloaded QCM crystal oscillator. Step 3: Load a tiny mass onto the QCM crystal oscillator. Step 4: measuring the tiny mass loaded on the QCM crystal oscillator in step 3; the tiny mass range is as low as 2 μg; In step 2, firstly, the mass of the unloaded QCM crystal oscillator is obtained by mass comparison method to obtain its unloaded mass m U and use QCM to get its no-load resonant frequency f U ; Among them, the superscript U indicates the "unloaded" state; Before performing the no-load mass measurement in step 2, the crystal oscillator needs to be left to stand in a stable environment for more than 48 hours to eliminate the instability of the crystal oscillator itself affected by the environment during the preparation process; In step 3, the method for loading a small mass on the QCM crystal oscillator is magnetron sputtering coating. When loading the small mass, the thickness of the rigid hard film loaded on the QCM crystal oscillator is controlled by the coating time. The thickness of the rigid hard film deposited on the crystal oscillator needs to be much smaller than the thickness of the crystal oscillator. The selected deposited film material needs to have a large density, and the thickness of the mask plate should be less than 0.1 mm or a sharp-edged mask plate should be used. The step 4 measures the loaded mass m of the wafer after coating. L , and then use QCM to obtain the resonant frequency f of the crystal oscillator when it is loaded L ; The tiny mass measured in step 4 can be expressed as Δm=m L -m U and Δf=f L -f U The corresponding relationship; where the subscript L indicates the "Loaded" state; The measurements of the empty mass and loaded mass in steps 2 and 4 are performed using a high-precision mass comparator and high-accuracy standard weights.

2. The method for tracing the sensed quality value according to claim 1, wherein: In step 1, the traceability of the tiny mass of the rigid hard film is completed according to the classic Sauerbrey equation. (1) In the formula, f q is the resonant frequency of the QCM crystal, ρ q is the density of the crystal, μ q is the shear modulus of the crystal, and the negative sign means that the QCM resonant frequency is reduced; In step 1, if the rigid hard film attached to the crystal oscillator is thin enough, the mass Δm of the rigid hard film is linearly related to the resonant frequency shift Δf of the crystal oscillator.

3. The method for tracing the sensed quality value according to claim 1, wherein: The method for loading a tiny mass on the QCM crystal oscillator in step 3 also uses pulsed laser deposition, chemical vapor deposition, sol-gel, electroplating, and chemical immersion plating; the deposited film materials are selected from gold, silver, and copper as the coating materials.

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