Differential nano metal film thickness measuring system based on magnetoelectric sensor

Abstract

The invention relates to the field of differential nano-metal film thickness measurement based on a magnetoelectric sensor, in particular to a differential nano-metal film thickness measurement system based on a magnetoelectric sensor, which comprises a forward excitation coil, and a magnetic field sensor is fixedly connected in the forward excitation coil. A reverse excitation coil is arranged on the other side of the magnetic field sensor, a pre-amplification module is arranged on the side of the reverse excitation coil, a signal processing module is arranged at the end part of the pre-amplification module, a signal source module is arranged on the side of the signal processing module, and a signal acquisition module is arranged at the end part of the signal processing module; the system comprises a signal source module, an excitation coil group, a magnetoelectric sensor, a pre-amplification module, a signal processing module and a signal acquisition module. According to the structure, excitation magnetic fields at the sensor are mutually counteracted, so that the weight of an induced magnetic field in a superimposed magnetic field is enhanced to the greatest extent, and the measurement precision is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of differential nano-metal film thickness measurement based on magnetoelectric sensors, and in particular to a differential nano-metal film thickness measurement system based on magnetoelectric sensors. Background Art

[0002] The differential nano-metal film thickness measurement system based on magnetoelectric sensors utilizes the principle of eddy current testing. Compared to other technologies, eddy current testing offers advantages such as being pollution-free and contactless. An excitation coil, supplied with an AC signal, generates an alternating magnetic field in the surrounding space. This excitation field is also called the primary magnetic field. According to Faraday's law of electromagnetic induction, when the magnetic flux in a closed conductor loop changes within the magnetic field, an induced current is generated within the loop. Under the influence of the changing excitation magnetic field, an electric field is induced within the conductive material, forming a current. Because this current is vortex-shaped, it is called an eddy current. This eddy current, in turn, generates an eddy current-induced magnetic field, also known as the secondary magnetic field. The magnitude of the eddy current-induced magnetic field is affected by factors such as the conductivity, thickness, and magnetic permeability of the conductive material. The magnetic field can be detected using magnetic field sensors such as coils, magnetoresistive sensors, and Hall sensors, and information about the conductive material can be obtained based on the changes in the magnetic field.

[0003] In the fields of microelectronics, optoelectronic devices and advanced materials, precise thickness control of nanoscale metal films is a core parameter that determines device performance. Ultra-thin films are widely used in interconnect layers of semiconductor integrated circuits (such as Cu / TaN barrier layers), nano-optical coatings (such as infrared filters), flexible display electrodes (such as ITO / Ag stacks) and functional interface layers of quantum devices. A thickness deviation of only ±1nm can cause device failure problems such as abnormal conductivity, runaway quantum tunneling effect or optical transmission spectrum shift. Traditional contact measurements (such as step gauges) are prone to damage to the film layer, while optical ellipsometers have spectral decomposition ambiguities in multi-layer heterogeneous structures, making it difficult to meet the needs of nanoscale precision and online detection. Eddy current non-destructive testing technology based on magnetoelectric sensors has the advantages of non-contact, high sensitivity and nanoscale resolution, making it a key solution for nanoscale film thickness measurement.

[0004] Therefore, to address the above problems, a differential nano-metal film thickness measurement system based on magnetoelectric sensor is proposed. Summary of the Invention

[0005] To address the problems of existing nano-scale metal film thickness measurement technologies, such as large measured thickness and low probe sensitivity, this paper designs a differential nano-scale metal film thickness measurement system based on a magnetoelectric sensor. This system uses a magnetoelectric sensor with excellent performance to detect the induced magnetic field generated by the nano-scale metal film under the action of an excitation magnetic field. The output signal of the magnetoelectric sensor is processed to obtain the induced magnetic field, and the thickness of the metal film is inferred based on the changes in the induced magnetic field.

[0006] The technical solution adopted by the present invention to solve its technical problems is: a differential nano-metal film thickness measurement system based on a magnetoelectric sensor, comprising a forward excitation coil, a magnetic field sensor fixedly connected to the interior of the forward excitation coil, and a reverse excitation coil arranged on the other side of the magnetic field sensor, a preamplifier module arranged on the side of the reverse excitation coil, and a signal processing module arranged at the end of the preamplifier module, a signal source module arranged on the side of the signal processing module, and a signal acquisition module arranged at the end of the signal processing module; the signal source module, the excitation coil group, the magnetoelectric sensor, the preamplifier module, the signal processing module and the signal acquisition module, the signal source module is connected to the input end of the excitation coil group, the signal source module is also connected to the reference signal end of the signal processing module, the excitation coil group includes a forward excitation coil and a reverse excitation coil, the magnetic fields generated by the forward excitation coil and the reverse excitation coil are opposite, and the magnetoelectric sensor is connected to the input end of the preamplifier module.

[0007] Preferably, the excitation magnetic fields generated by the forward excitation coil and the reverse excitation coil in the excitation coil group are equal in magnitude and opposite in direction.

[0008] Preferably, the metal film is close to the forward excitation coil and far away from the reverse excitation coil. Since the excitation magnetic field generated by the excitation coil decreases exponentially with increasing position, the metal film is mainly affected by the forward excitation coil and the excitation of the reverse excitation coil can be ignored.

[0009] Preferably, the magnetoelectric sensor is a magnetic field sensor based on the magnetoelectric effect.

[0010] Preferably, the metal film generates an induced magnetic field due to the eddy current effect under the action of the AC excitation magnetic field, and the magnetoelectric sensor simultaneously detects the superimposed magnetic field composed of the excitation magnetic field and the induced magnetic field. The magnetoelectric sensor is located between the forward excitation coil and the reverse excitation coil, and the AC excitation magnetic fields it receives are completely opposite, and the two cancel each other out. In this way, the weight of the induced magnetic field on the superimposed magnetic field can be maximized, making the thickness measurement of the metal film more accurate.

[0011] Preferably, the output signal of the magnetoelectric sensor is amplified by a preamplifier module, the amplified signal is connected to the signal processing module, and is simultaneously processed with the reference signal provided by the signal source module, and then connected to the signal acquisition module for data acquisition. The data acquisition will obtain the size of a DC quantity, and the thickness of the unknown metal film can be measured through the relationship between the calibrated DC quantity and the thickness of the metal film.

[0012] Preferably, the forward excitation coil and the reverse excitation coil are of the same size, with 10 turns, an inner radius of 10 mm, an outer radius of 10.5 mm, and a wire diameter of 0.5 mm. They are placed parallel to each other and the excitation currents passed through are equal in magnitude and opposite in direction. They are coaxially placed directly above the nano-metal film to be tested. The two excitation coils are 20 mm apart and connected in series to form an excitation coil group. The magnetic field sensor is placed at the center point of the forward excitation coil and the reverse excitation coil. When an AC excitation current is applied to the two excitation coils, the excitation magnetic fields generated are B(s)1 and B(s)2 respectively. The nano-metal film to be tested will induce eddy currents, thereby generating an induced magnetic field ΔB.

[0013] Preferably, in the dual-excitation coil model, the forward and reverse excitation coils are symmetrical about the center point of the magnetic field sensor. When excitation signals of equal magnitude and opposite directions are applied to the dual excitation coils, the excitation magnetic fields B(s)1 and B(s)2 on the magnetic field sensor are equal in magnitude and opposite in direction, and the axial component of the total excitation magnetic field B(s) is zero. At this point, the magnetic field sensor is affected only by the induced magnetic field ΔB generated by the nanofilm being measured. By adopting the dual-excitation coil model, relevant monitoring of the induced magnetic field ΔB can be achieved.

[0014] Preferably, the parameters such as the excitation coil group size and the excitation current amplitude are kept unchanged, the thickness d of the nano-gold film to be measured is set to change from 0nm to 25nm, and the distance between the bottom of the forward excitation coil and the nano-metal film to be measured is always kept at 6mm.

[0015] Preferably, the amplitude of the excitation current I is 0.1A, and the frequency is set to 20MHz, 30MHz, and 40MHz in sequence. The relationship between the induced magnetic field ΔBz and the thickness d is shown in Figure (a) below. Subsequently, the thickness d of the nano-niobium film to be measured is set to change from 0nm to 20nm, and the distance between the bottom of the forward excitation coil and the nano-metal film to be measured is always kept at 6mm. The amplitude of the excitation current I is 0.1A, and the frequency is set to 40MHz, 50MHz, and 60MHz in sequence. The relationship between the induced magnetic field ΔBz and the thickness d is shown in Figure (b) below. It can be seen that ΔBz increases with the thickness d of the nano-metal film to be measured. Therefore, we can invert the change in the thickness of the nano-metal film to be measured by detecting the change law of the induced magnetic field ΔBz and the thickness of the nano-metal film to be measured.

[0016] The present invention is beneficial in that:

[0017] 1. The present invention's differential nanometal film thickness measurement system based on a magnetoelectric sensor achieves high-precision and high-sensitivity measurement of nanometal film thickness through ingenious structural design and synergistic interaction between its modules. The system utilizes a differential excitation coil assembly, with the forward excitation coil and the reverse excitation coil generating magnetic fields of equal magnitude and opposite direction, symmetrically positioned about the center point of the magnetic field sensor. This structure allows the excitation magnetic fields at the sensor to cancel each other out, maximizing the weight of the induced magnetic field in the superimposed magnetic field and significantly improving measurement accuracy. Furthermore, the metal film is located near the forward excitation coil and farther from the reverse excitation coil. Because the excitation magnetic field decreases exponentially with increasing position, the metal film is primarily affected by the forward excitation coil, while the excitation from the reverse excitation coil is negligible, further optimizing measurement conditions. The magnetoelectric sensor in the system, based on the magnetoelectric effect, can sensitively detect the superimposed magnetic field formed by the excitation and induced magnetic fields. Its output signal is amplified by a preamplifier module, effectively improving the signal-to-noise ratio and anti-interference capability during transmission. The amplified signal is connected to the signal processing module, where it is processed with a reference signal provided by the signal source module. It is then connected to the signal acquisition module for data acquisition. By calibrating the relationship between the DC current and the thickness of the metal film, the thickness of the unknown metal film can be accurately measured. In addition, during the experiment, the system maintains the parameters such as the excitation coil group size and the excitation current amplitude unchanged. By changing the thickness of the nano-metal film to be measured and the frequency of the excitation current, the variation pattern of the induced magnetic field and the film thickness is studied, verifying the reliability and effectiveness of the system measurement. For example, when the thickness of the nano-gold film to be measured changes from 0nm to 25nm, and the thickness of the nano-niobium film changes from 0nm to 20nm, the induced magnetic field ΔBz increases with the increase of the film thickness d. This shows that the system can accurately reflect the change of the film thickness and provides an efficient and reliable solution for the measurement of the thickness of nano-metal films. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 It is a structural schematic diagram of the differential type nano-metal film thickness measurement of the magnetoelectric sensor of the present invention.

[0020] In the figure: 1. Forward excitation coil; 2. Magnetic field sensor; 3. Reverse excitation coil; 4. Preamplifier module; 5. Signal processing module; 6. Signal acquisition module; 7. Signal source module. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Example 1

[0023] A differential nano-metal film thickness measurement system based on a magnetoelectric sensor comprises a signal source module 1, an excitation coil group 2, a magnetoelectric sensor 3, a preamplifier module 4, a signal processing module 5, a signal acquisition module 6 and a thickness inversion module 7. The signal source module 1 utilizes the "dual-channel signal generator + frequency adjustment unit" linkage mode to generate AC signals of different frequencies, providing a stable excitation source for the excitation coil group, and deepening the integration of signal source stability and measurement accuracy; the excitation coil group 2 utilizes the "forward excitation coil + reverse excitation coil" differential structure, and the magnetic fields generated by the forward excitation coil and the reverse excitation coil are equal in magnitude and opposite in direction, and are coaxially symmetrically placed directly above the nano-metal film to be measured. Through the differential magnetic field cancellation technology, the weight of the induced magnetic field is maximized, deepening the integration of magnetic field cancellation and induced magnetic field enhancement; the magnetoelectric sensor 3 utilizes the "magnetostrictive material + piezoelectric material composite structure + permanent magnet bias" linkage mode, the magnetoelectric sensitive unit is composed of a composite of magnetostrictive material and piezoelectric material, and the permanent magnet provides the optimal DC bias magnetic field. Through the synergistic effect of the magnetoelectric effect and the bias magnetic field, the sensitivity and bandwidth of the sensor are improved, and the integration of the magnetoelectric effect and film thickness perception is deepened; the preamplifier module 4 utilizes the "charge type amplifier circuit + anti-interference filter circuit" linkage mode The signal processing module 5 adopts the linkage mode of "multiplier + filter + digital signal processor", in which the multiplier is used for signal demodulation, the filter is used for removing noise interference, and the digital signal processor is used for signal analysis and feature extraction. Through multi-level signal processing, the induced magnetic field information is accurately extracted, and the fusion of signal demodulation and thickness information extraction is deepened. The signal acquisition module 6 adopts the linkage mode of "high-speed data acquisition card + acquisition software", which can quickly and accurately collect the processed signal data, and deepen the fusion of data acquisition and analysis. The thickness inversion module 7 adopts the linkage mode of "machine learning algorithm + thickness calibration database", and analyzes the collected induced magnetic field signal through machine learning algorithm based on the calibration data of nano-metal films of different thicknesses, so as to realize fast and accurate inversion of thickness and deepen the fusion of thickness prediction and measurement accuracy improvement.

[0024] Furthermore, the excitation coil group 2 includes a forward excitation coil 201 and a reverse excitation coil 202. The number of turns, inner radius, outer radius, and wire diameter of the forward excitation coil 201 and the reverse excitation coil 202 are consistent, and the excitation currents are equal in magnitude and opposite in direction. Through precise coil parameter design and current control, the magnetic field cancellation effect and the stability of the induced magnetic field are ensured.

[0025] Furthermore, the magnetoelectric sensor 3 includes a magnetoelectric sensitive unit 301 and a permanent magnet bias unit 302. The magnetoelectric sensitive unit 301 is composed of a composite of magnetostrictive material and piezoelectric material. The permanent magnet bias unit 302 provides an optimal DC bias magnetic field. Through the synergistic effect of the magnetoelectric effect and the bias magnetic field, the sensitivity and bandwidth of the sensor are improved.

[0026] Furthermore, the preamplifier module 4 adopts a charge-type amplifier circuit with high gain, low noise, and high input impedance characteristics, which can effectively amplify the weak signal output by the magnetoelectric sensor. At the same time, it is equipped with an anti-interference filter circuit to enhance the anti-interference ability of the signal.

[0027] Furthermore, the signal processing module 5 includes a multiplier 501, a filter 502 and a digital signal processor 503. The multiplier 501 is used for signal demodulation, the filter 502 is used for removing noise interference, and the digital signal processor 503 is used for signal analysis and feature extraction. Through multi-level signal processing, the induced magnetic field information is accurately extracted.

[0028] Furthermore, the thickness inversion module 7 includes a thickness feature database establishment 701 and a real-time thickness inversion signal generation 702. The thickness feature database establishment 701 is based on the calibration data of nanometal films of different thicknesses. The real-time thickness inversion signal generation 702 uses a machine learning algorithm to analyze the collected induced magnetic field signal to achieve fast and accurate thickness inversion.

[0029] Furthermore, the thickness characteristic database establishment 701 includes the collection of induced magnetic field characteristic data of different metal materials and nano-metal films of different thicknesses, the collation of data on environmental factors, and the calibration of historical measurement data. Through comprehensive data collection and analysis, the accuracy and reliability of thickness inversion are improved.

[0030] Furthermore, the signal processing module 5 also includes a signal integrity check mechanism 504 for performing integrity check on the demodulated signal to ensure the accuracy and integrity of the data during the signal processing and avoid thickness measurement errors caused by signal distortion.

[0031] Furthermore, the system also includes a temperature compensation module 8 for real-time monitoring of the measurement environment temperature and compensating and correcting the output signal of the magnetoelectric sensor according to temperature changes, eliminating the influence of temperature drift on the thickness measurement accuracy, and ensuring the stability and accuracy of the system under different environmental conditions.

[0032] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A differential nano-metal film thickness measurement system based on a magnetoelectric sensor, characterized by: The invention comprises a forward excitation coil (1), wherein a magnetic field sensor (2) is fixedly connected to the interior of the forward excitation coil (1), and a reverse excitation coil (3) is provided on the other side of the magnetic field sensor (2), a preamplifier module (4) is provided on the side of the reverse excitation coil (3), and a signal processing module (5) is provided at the end of the preamplifier module (4), a signal source module (7) is provided on the side of the signal processing module (5), and a signal acquisition module (6) is provided at the end of the signal processing module (5); The signal source module, the excitation coil group, the magnetoelectric sensor, the preamplifier module, the signal processing module and the signal acquisition module, the signal source module is connected to the input end of the excitation coil group, and the signal source module is also connected to the reference signal end of the signal processing module, the excitation coil group includes a forward excitation coil and a reverse excitation coil, the magnetic fields generated by the forward excitation coil and the reverse excitation coil are opposite, and the magnetoelectric sensor is connected to the input end of the preamplifier module.

2. The differential nano-metal film thickness measurement system based on a magnetoelectric sensor according to claim 1, characterized in that: The excitation magnetic fields generated by the forward excitation coil and the reverse excitation coil in the excitation coil group are equal in magnitude and opposite in direction.

3. The differential nano-metal film thickness measurement system based on a magnetoelectric sensor according to claim 2, characterized in that: The metal film is close to the forward excitation coil and far away from the reverse excitation coil. Since the excitation magnetic field generated by the excitation coil decreases exponentially with increasing position, the metal film is mainly affected by the forward excitation coil, and the excitation of the reverse excitation coil can be ignored.

4. The differential nano-metal film thickness measurement system based on a magnetoelectric sensor according to claim 2, characterized in that: The magnetoelectric sensor is a magnetic field sensor based on the magnetoelectric effect.

5. The differential nano-metal film thickness measurement system based on magnetoelectric sensor according to claim 1, characterized in that: Under the action of the AC excitation magnetic field, the metal film generates an induced magnetic field due to the eddy current effect. The magnetoelectric sensor simultaneously detects the superimposed magnetic field composed of the excitation magnetic field and the induced magnetic field. The magnetoelectric sensor is located between the forward excitation coil and the reverse excitation coil, and the AC excitation magnetic fields it receives are completely opposite. The two cancel each other out, which can maximize the weight of the induced magnetic field on the superimposed magnetic field, making the thickness measurement of the metal film more accurate.

6. The differential nano-metal film thickness measurement system based on a magnetoelectric sensor according to claim 1, characterized in that: The output signal of the magnetoelectric sensor is amplified by the preamplifier module. The amplified signal is connected to the signal processing module and processed with the reference signal provided by the signal source module at the same time. Then, it is connected to the signal acquisition module for data acquisition. The data acquisition will obtain the size of a DC quantity. The thickness of the unknown metal film can be measured through the relationship between the calibrated DC quantity and the thickness of the metal film.

7. The differential nano-metal film thickness measurement system based on magnetoelectric sensor according to claim 1, characterized in that: The forward excitation coil (1) and the reverse excitation coil (3) are of the same size, with 10 turns, an inner radius of 10 mm, an outer radius of 10.5 mm, and a wire diameter of 0.5 mm. They are placed parallel to each other and the excitation currents passed therethrough are equal in magnitude and opposite in direction. They are coaxially placed directly above the nano-metal film to be measured. The two excitation coils are 20 mm apart and connected in series to form an excitation coil group. The magnetic field sensor (2) is placed at the center point of the forward excitation coil (1) and the reverse excitation coil (3). When an AC excitation current is applied to the two excitation coils, the generated excitation magnetic fields are B(s)1 and B(s)2 respectively. The nano-metal film to be measured will induce eddy currents, thereby generating an induced magnetic field ΔB.

8. The differential nano-metal film thickness measurement system based on magnetoelectric sensor according to claim 6, characterized in that: In the dual excitation coil model, the forward excitation coil (1) and the reverse excitation coil (3) are symmetrical about the center point of the magnetic field sensor (2). When excitation signals of equal magnitude and opposite directions are applied to the dual excitation coils, the excitation magnetic fields B(s)1 and B(s)2 on the magnetic field sensor are equal in magnitude and opposite in direction, and the axial component of the total excitation magnetic field B(s) is zero. At this time, the magnetic field sensor (2) is only affected by the induced magnetic field ΔB generated by the nanofilm to be measured. By adopting the dual excitation coil model, relevant monitoring of the induced magnetic field ΔB can be achieved.

9. The differential nano-metal film thickness measurement system based on magnetoelectric sensor according to claim 7, characterized in that: The parameters such as the size of the excitation coil group and the excitation current amplitude are kept unchanged, the thickness d of the nano-gold film to be measured is set to change from 0nm to 25nm, and the distance between the bottom of the forward excitation coil (1) and the nano-metal film to be measured is always kept at 6mm.

10. The differential nano-metal film thickness measurement system based on magnetoelectric sensor according to claim 7, characterized in that: The amplitude of the excitation current I is 0.1A, and the frequency is set to 20MHz, 30MHz, and 40MHz in sequence. The relationship between the induced magnetic field ΔBz and the thickness d is shown in Figure (a) below. Subsequently, the thickness d of the nano-niobium film to be measured is set to change from 0nm to 20nm, and the distance between the bottom of the forward excitation coil (1) and the nano-metal film to be measured is always kept at 6mm. The amplitude of the excitation current I is 0.1A, and the frequency is set to 40MHz, 50MHz, and 60MHz in sequence. The relationship between the induced magnetic field ΔBz and the thickness d is shown in Figure (b) below. It can be seen that ΔBz increases with the thickness d of the nano-metal film to be measured. Therefore, we can invert the change in the thickness of the nano-metal film to be measured by detecting the change law of the induced magnetic field ΔBz and the thickness of the nano-metal film to be measured.

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