Nv color center measuring device, chip measuring system and measuring method

Abstract

The application discloses an NV color center measuring device, a chip measuring system and a measuring method. The NV color center measuring device comprises an NV color center magnetic probe, a microwave source, a laser source, a signal processing device and a microwave signal driving device. The NV color center magnetic probe is used for scanning the chip to be detected. The laser source and the microwave source are respectively used for providing laser and microwave signals applied to the NV color center. The signal processing device is used for collecting a fluorescence signal of the NV color center and outputting a magnetic measurement signal. The microwave source provides a microwave signal with a fixed frequency. The microwave signal driving device drives the microwave source to emit the microwave signal in a driving mode of an echo sequence. The application has the advantages that the contradiction problem that the NV color center requires a static magnetic field in scanning a micro-distribution of a magnetic field and that a magnetic field generated by a chip to be detected is an alternating magnetic field is solved, and the equipment cost is greatly reduced.

Description

Technical Field

[0001] The present invention relates to the field of magnetic measurement technology, and in particular to an NV color center measurement device, a chip measurement system and a measurement method. Background Art

[0002] The NV color center is a point defect quantum magnetic resonance structure in diamond, created by replacing two adjacent carbon atoms with a nitrogen atom and a vacancy. This structure induces a magnetic resonance effect, allowing the magnetic field strength to be determined by microwave frequency sweeps, enabling high-precision and high-spatial-resolution magnetic field measurements. The basic principle of NV color center magnetic field measurement is that the NV center's electron spin ground state has three energy levels: (ms = 0), (ms = +1), and (ms = -1), with a zero-field splitting D = 2870 MHz. In the absence of an external magnetic field, the two energy levels (ms = ±1) are degenerate. When the NV is exposed to a magnetic field, the energy levels undergo Zeeman splitting, and the magnitude of the splitting is related to the axial component of the magnetic field in the NV. Experimentally, the magnitude of the energy level splitting can be detected by optically detected magnetic resonance (ODMR) spectral lines (also known as CW spectra), thereby determining the magnitude of the magnetic field component in the NV direction. The resonance spectrum obtained by applying continuous laser light and microwaves is called CW-ODMR, or CW spectrum for short.

[0003] According to relevant theories, the NV color center should operate under the state of simultaneous driving by laser and microwave. At this time, laser irradiation will cause the NV color center to emit stimulated radiation fluorescence. When the frequency of the driving microwave and the magnetic field intensity satisfy the magnetic resonance relationship and induce magnetic resonance on the NV color center, the intensity of the stimulated radiation fluorescence will be reduced to a certain extent, generating an optical signal corresponding to the magnetic resonance state.

[0004] Existing chip inspection techniques typically measure the chip as a whole, judging chip quality based on the measured electrical parameters. However, these methods are unable to detect information such as the distribution, number, and size of defects within the chip, requiring further inspection. To address this issue, researchers are using NV color centers to detect the magnetic field distribution within the chip, thereby determining key information such as the location, size, and type of defects, achieving a higher level of chip inspection.

[0005] In recent years, the magnetic measurement function of NV centers has been gradually adopted in chip inspection services. NV centers are used to measure magnetic anomaly signals on the chip surface, thereby inverting and calculating the chip's current distribution, inspecting the chip's operating status and defect distribution, and providing a key basis for chip quality control and process parameter optimization. The principle is: when the relative position of the diamond NV center and the chip remains unchanged, and when the microwave frequency is fixed, the magnetic field changes caused by the chip current will cause changes in the NV center's fluorescence intensity. By monitoring the fluctuations in the fluorescence signal, the presence of a magnetic field induced by the chip current can be inferred. In a specific detection area, the chip's internal current pulse signal generates a pulsed magnetic field, which makes the NV center's fluorescence intensity maintain a consistent timing relationship with the signal fluctuation. In this way, dynamic capture of the current signal changes on the chip can be achieved.

[0006] At present, the magnetic sensor system based on NV color center can distinguish the magnetic field changes of 0.1uT and achieve a magnetic field spatial resolution of less than 1um, which is more in line with the requirements of chip defect detection.

[0007] In modern chip testing, AC signals are often used to check chip performance. For example, the saturation operating current parameter (a DC parameter) of a power MOSFET requires applying a rated test voltage to the drain and source pins of the MOSFET while measuring the current flowing from the drain to the source. This current amplitude represents the saturation operating current. In actual testing, current flowing through the MOSFET generates heat, causing the MOSFET parameters to vary with temperature, impacting test consistency. Therefore, the test voltage is configured as a 1kHz AC signal and the AC current is measured to reduce the heat generated during MOSFET testing. From an operational perspective, MOSFET DC parameters are often tested at a 1kHz frequency, while AC parameters are tested at a 1MHz frequency. Using a low-frequency 1kHz AC signal to measure MOSFET DC parameters avoids parameter drift caused by heating the MOSFET due to the DC test signal.

[0008] However, NV centers typically require a static magnetic field when scanning the microscopic distribution of magnetic fields. Chip testing typically uses AC current, which also generates an AC magnetic field and is difficult to measure directly. Forcing a DC current to drive the chip would generate intense heat, causing chip parameters to gradually change with rising temperature, affecting the consistency of measurement results. Summary of the Invention

[0009] The technical problem to be solved by the present invention is the contradiction between the requirement that the magnetic field to be measured is a static magnetic field when the NV color center scans the microscopic distribution of the magnetic field and the magnetic field generated by the chip to be measured is an AC magnetic field.

[0010] The present invention solves the above-mentioned technical problems through the following technical means: an NV color center measurement device, comprising an NV color center magnetic probe, a microwave source, a laser source, and a signal processing device, wherein the NV color center magnetic probe is used to scan the chip to be detected, the laser source and the microwave source are respectively used to provide laser and microwave signals applied to the NV color center, and the signal processing device is used to collect the fluorescence signal of the NV color center and output a magnetic measurement signal. The chip to be detected is driven by an alternating current. The NV color center measurement device also includes a microwave signal driving device, the microwave source provides a microwave signal of a fixed frequency, and the microwave signal driving device drives the microwave source in an echo sequence driving mode. The waveform time interval length of the echo sequence is equal to or close to the half-cycle length of the alternating current driving signal.

[0011] As a further optimized technical solution, the microwave signal driving device adopts the driving method of Hann echo sequence to drive the microwave source to emit microwave signals.

[0012] As a further optimized technical solution, the signal processing device includes a photodetector and a signal processing circuit. The photodetector is used to detect the fluorescence signal generated by the NV color center. The signal processing circuit is used to receive the fluorescence signal and process the fluorescence signal to obtain a magnetic measurement signal.

[0013] As a further optimized technical solution, the signal processing circuit in the signal processing device includes a multiplier, a secondary filter and a reference signal source, wherein the input end of the multiplier is connected to the photodetector, the output end is connected to the secondary filter, the secondary filter outputs the magnetic measurement signal, and the reference signal source is simultaneously connected to the multiplier and the current driving circuit of the chip to be tested.

[0014] As a further optimized technical solution, the multiplier adopts any one of an analog multiplier, a digital multiplier, and a switch multiplier.

[0015] As a further optimized technical solution, the reference signal source uses a crystal oscillator + DDS chip, or a crystal oscillator + phase-locked loop, or a crystal oscillator + DAC chip to output analog signals, or uses a crystal oscillator + GPIO of a digital circuit to output digital signals.

[0016] As a further optimized technical solution, the secondary filter adopts a digital low-pass filter, or an analog RC low-pass filter or an active analog low-pass filter circuit.

[0017] As a further optimized technical solution, an anti-aliasing filter is further provided at the input end of the multiplier.

[0018] As a further optimization technical solution, the multiplier adopts an analog multiplier, the secondary filter adopts a digital low-pass filter or an analog low-pass filter, when the secondary filter adopts a digital low-pass filter, an ADC is arranged between the analog multiplier and the digital low-pass filter, when the secondary filter adopts an analog low-pass filter, the analog multiplier and the analog low-pass filter are directly connected, and the reference signal source outputs an analog signal or a digital signal.

[0019] As a further optimization technical solution, the working process of the signal processing circuit of the above-mentioned multiplier adopting an analog multiplier includes:

[0020] S11, start measurement;

[0021] S12, read the fluorescence signal for a period of time, and the time length is a pre-set window time or exposure time;

[0022] S13, read the reference signal for the same period of time, and the time length is also the window time or the exposure time;

[0023] S14, multiply the read reference signal and the fluorescence signal in the analog multiplier to obtain the output signal of the analog multiplier;

[0024] S15, low-pass filter in the secondary filter, and the filter frequency does not exceed the reference signal frequency to obtain the filtered magnetic measurement signal;

[0025] S16, judge whether to end the measurement, if yes, end the measurement, if not, return to step S12.

[0026] As a further optimization technical solution, the multiplier adopts a switch multiplier, the secondary filter adopts a digital low-pass filter or an analog low-pass filter, when the secondary filter adopts a digital low-pass filter, an ADC is arranged between the switch multiplier and the digital low-pass filter, when the secondary filter adopts an analog low-pass filter, the switch multiplier and the analog low-pass filter are directly connected, and the reference signal source outputs a digital signal.

[0027] As a further optimization technical solution, the working process of the signal processing circuit of the above-mentioned multiplier adopting a switch multiplier includes:

[0028] S21, start measurement;

[0029] S22, read the fluorescence signal for a period of time, and the time length is a pre-set window time or exposure time;

[0030] S23, judge whether the reference signal is high level, if yes, enter step S24, otherwise enter step S25,

[0031] S24, the switch multiplier is connected in forward direction, and an output signal is equal to an input signal;

[0032] S25, the switch multiplier is connected in reverse direction, and an output signal is equal to an opposite number of an input signal;

[0033] S26, the signal output by step S24 or the signal output by step S25 enters a secondary filter, and the output signal of this time is averaged with the output signal of last time in the secondary filter to obtain a magnetic measurement signal output by the secondary filter;

[0034] S27, whether to end the measurement is judged, if yes, the measurement is ended, and if no, the step S22 is returned, and a period or time required for measurement can be preset to judge whether the measurement needs to be ended.

[0035] As a further optimized technical solution, the multiplier adopts a digital multiplier, the secondary filter adopts a digital low-pass filter, the secondary filter is integrated on a digital control chip, the reference signal source comprises a preset reference signal and a crystal oscillator+GPIO, or the reference signal source comprises a built-in reference signal and a crystal oscillator+DAC chip, the preset reference signal is stored in the form of waveform data in advance and is delivered to the crystal oscillator+DAC chip or the crystal oscillator+GPIO.

[0036] As a further optimized technical solution, the working process of the signal processing circuit of the above-mentioned multiplier adopting a digital multiplier comprises:

[0037] S31, starting measurement;

[0038] S32, reading a fluorescent signal for a period of time, and the length of time is a preset window time or exposure time;

[0039] S33, reading a reference signal for the same period of time, and the length of time is also the window time or the exposure time;

[0040] S34, multiplying the read reference signal and the fluorescent signal in the digital multiplier to obtain an output signal of the digital multiplier;

[0041] S35, in the secondary filter, low-pass filtering is performed through a digital low-pass filter, and the filtering frequency does not exceed the reference signal frequency to obtain a filtered magnetic measurement signal;

[0042] S36, whether to end the measurement is judged, if yes, the measurement is ended, and if no, the step S32 is returned, and a period or time required for measurement can be preset to judge whether the measurement needs to be ended.

[0043] As a further optimized technical solution, in the above-mentioned solutions, there are two connecting branches between the multiplier and the filter, the input ends of the two multipliers are connected to the photodetector, the filters of the two channels output magnetic measurement signals, and the reference signals of the two multipliers differ in phase by 90°.

[0044] The present invention also discloses an NV color center measurement system, comprising the NV color center measurement device and current driving circuit described in any of the above schemes, wherein the reference signal inside the signal processing circuit of the NV color center measurement device is simultaneously output to the current driving circuit, so that the reference signal of the current driving circuit and the reference signal of the signal processing circuit maintain clock homology.

[0045] The present invention also discloses a method for measuring a chip using the NV color center measurement system described in any of the above solutions, comprising:

[0046] S1, the current driving circuit of the chip under test applies an AC current to the chip under test;

[0047] S2, applying a microwave signal and a laser signal to the NV color center magnetic probe;

[0048] S3, the photodetector detects the fluorescence signal generated by the NV color center and transmits it to the signal processing circuit;

[0049] S4. The signal processing circuit reads and calculates the fluorescence signal and then outputs a magnetic measurement signal.

[0050] As a further optimized technical solution, the specific working process of the signal processing circuit includes:

[0051] S11, start measuring;

[0052] S12, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time;

[0053] S13, reading the reference signal of the same time period, where the time length is also the window time or exposure time;

[0054] S14, multiplying the reference signal and the fluorescence signal read by the multiplier to obtain an output signal of the multiplier;

[0055] S15. In the secondary filter, low-pass filtering is performed, where the filtering frequency does not exceed the reference signal frequency, to obtain a filtered output magnetic measurement signal;

[0056] S16: Determine whether the measurement is to be ended. If yes, end the measurement. If not, return to step S12.

[0057] The advantages of the present invention are:

[0058] The echo sequence control method is used instead of the continuous wave method to drive the NV color center to measure the AC magnetic field to be measured. This solves the contradiction between the NV color center requiring the magnetic field to be measured to be a static magnetic field when scanning the microscopic distribution of the magnetic field and the magnetic field generated by the chip to be measured to be an AC magnetic field.

[0059] The signal processing circuit uses the reference signal of the circuit as a benchmark, multiplies it with the fluorescence signal through a multiplier, and then outputs it to a secondary filter for low-pass filtering, and finally outputs a magnetic measurement signal, wherein the reference signal of the current driving circuit and the reference signal of the signal processing circuit maintain clock homology.

[0060] The above-mentioned signal processing circuit can be directly implemented in a single-chip microcomputer or FPGA system without the need for additional analog circuits or microwave devices. The timing accuracy requirements are also significantly reduced (same frequency as the reference signal, about 1ms when measuring DC parameters, and about 1us when measuring AC parameters), which greatly reduces equipment costs.

[0061] The limitation of NV color center coherence time on alternating signal measurement is removed, thereby solving the problem of low-frequency signal measurement in chip DC parameter testing.

[0062] The output signal is related to the magnetic field strength at the location of the reference signal frequency, and has a good single-value response within a large magnetic field range, which is convenient for subsequent analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a timing structure diagram of the Hann echo sequence as a driving method of the microwave signal driving device compared with the traditional microwave normally open driving method;

[0064] Figure 2 1 is a block diagram of the overall structure of the NV color center measurement device according to an embodiment of the present invention;

[0065] Figure 3 is a structural block diagram of a signal processing circuit according to a first embodiment of the present invention;

[0066] Figure 4 is a structural diagram of an analog multiplier in a signal processing circuit according to a first embodiment of the present invention;

[0067] Figure 5 is a flowchart of the signal processing circuit of the first embodiment of the present invention;

[0068] Figure 6 is a structural block diagram of a signal processing circuit according to a second embodiment of the present invention;

[0069] Figure 7 is a structural diagram of a switch multiplier of a signal processing circuit according to a second embodiment of the present invention;

[0070] Figure 8is a flowchart of the signal processing circuit of the second embodiment of the present invention;

[0071] Figure 9 is a structural block diagram of a signal processing circuit according to a third embodiment of the present invention;

[0072] Figure 10 4 is a flowchart of the signal processing circuit of the third embodiment of the present invention. DETAILED DESCRIPTION

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0074] It should be noted that the following embodiments and features therein may be combined with one another unless they conflict. Furthermore, the diagrams provided in the following embodiments are merely schematic illustrations of the basic concepts of the present invention. The diagrams only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation. In actual implementation, the type, quantity, and proportion of each component may be varied arbitrarily, and the component layout may also be more complex.

[0075] To resolve the conflict between the static magnetic field required for NV centers to scan the microscopic distribution of magnetic fields and the AC magnetic field generated by the chip under test, a special echo sequence control method is used instead of a continuous wave method to drive the NV centers to measure the AC magnetic field. The AC magnetic field is generated by the AC current used in chip testing.

[0076] At this time, the NV color center measurement device includes an NV color center magnetic probe, a microwave source, a microwave signal driving device, a laser source, and a signal processing device.

[0077] The tip of the NV color center magnetic probe is provided with diamond particles containing NV color centers, and the NV color center magnetic probe is used to scan the chip to be detected;

[0078] The laser source is used to generate laser light for irradiating the NV color center so as to cause the NV color center to generate fluorescence;

[0079] A microwave source provides a microwave signal of a fixed frequency applied to the NV color center. The chip under test needs to be placed in a stable static magnetic field. On this basis, it is driven by an AC current to generate an alternating magnetic field. The static magnetic field can be added using various existing methods, such as electromagnets, magnetic field coils, and ordinary magnets. This is a prior art method. The magnetic field size of the static magnetic field and the frequency of the microwave satisfy the relationship of magnetic resonance. Specifically: the microwave signal frequency applied by the microwave source = 2.87GHz - 2.8MHz / Gs × static magnetic field strength (Gs);

[0080] A microwave signal driving device is used to drive the microwave source to emit a microwave signal to meet the NV color center's measurement requirements for the AC magnetic field. As an embodiment, in this application, the microwave signal driving device adopts an echo sequence driving method, and the waveform time interval length of the echo sequence is equal to or close to the half-cycle length of the AC current driving signal. When the above conditions are met, the pulse inserted in the echo sequence (such as the π pulse of the Hann sequence) will flip the state vector to the opposite direction. The phase accumulated by the DC magnetic field in the same direction during the two free evolution periods of the sequence will cancel each other, resulting in the phase accumulation of the DC magnetic field being 0. The phase of the AC magnetic field with alternating directions will be superimposed on each other, resulting in the AC magnetic field obtaining phase accumulation, which produces observable changes in the fluorescence intensity signal.

[0081] The signal processing device is used to collect the fluorescence signal of the NV color center and output the magnetic measurement signal;

[0082] The host computer is used to receive the magnetic measurement signal and process the magnetic measurement signal to obtain the magnetic field strength of the AC magnetic field to be measured.

[0083] The microwave signal driving device in the solution of the present application uses a fast switch to drive the microwave signal, and makes the switching waveform meet certain conditions. Then the NV color center fluorescence signal finally read will be related to the AC magnetic field intensity at a specific frequency of the chip to be tested.

[0084] Taking the simplest Hann echo sequence as an example of the driving method of the microwave signal driving device, compared with the traditional microwave normally open driving method, its timing structure is as follows: Figure 1 As shown, the pulse interval corresponds to the amplitude of the AC magnetic field under test. The Hann echo sequence applies a Hanning window to the echo signal to reduce spectral leakage and improve spectral resolution. The Hanning window is a commonly used window function for windowing signals in the time domain. It can be viewed as the sum of the spectra of three rectangular time windows. It uses sidelobes to cancel each other, eliminating high-frequency interference and leakage energy. It is suitable for analyzing most continuous signals, purely random signals, narrow-bandwidth signals, and signals with multiple frequency components.

[0085] Combine Figure 1 , it can be understood that the scheme of using Hann echo sequence as microwave driving mode instead of continuous wave mode to drive NV color center to measure AC magnetic field needs to meet the following conditions:

[0086] (1) The echo sequence can only measure the magnetic field strength at a specific frequency f. The microwave frequency and the static magnetic field strength of the NV color center's environment satisfy the magnetic resonance relationship. For the Hann sequence, it contains three microwave pulses with a pulse time interval of 1 / 2f.

[0087] (2) The microwave pulse width of the echo sequence needs to be carefully controlled. Of the three pulses in the Hann echo sequence, the outer two pulses have a narrower width and are called a π / 2 sequence; the inner pulse has a wider width and is called a π pulse.

[0088] (3) The width of the π / 2 pulse and the π pulse needs to be precisely controlled. Its typical value is about 300 ns, and it needs to be accurate to within 10 ns. This parameter is related to many factors such as microwave power, microwave frequency offset, microwave emission efficiency, and laser drive intensity. The influencing process is relatively complex and is generally measured on-site using the standard Rabi test method.

[0089] Laser initialization and laser readout are required before and after the echo sequence. Laser initialization requires a long period of laser irradiation to fully polarize the NV center. The laser readout part is shorter, generally not exceeding 10us, and it is required that the NV center does not undergo significant polarization during the readout process.

[0090] This solution has the function of measuring AC magnetic fields and can solve the problem of chip defect measurement to a certain extent, but it still has the following technical defects:

[0091] The output fluorescence signal of this scheme satisfies the cosine relationship with the AC magnetic field intensity, but has the problem of multi-valuedness, and it may be impossible to accurately determine the magnetic field intensity;

[0092] The total length of the microwave pulse of the Hann echo sequence is limited by the transverse delay time of the NV color center and generally cannot exceed 500us, which is not suitable for measuring the low-frequency AC magnetic field of 1kHz.

[0093] The microwave pulse width of this solution has high precision requirements, requires a more complex microwave control system, and has high equipment costs.

[0094] To solve the above problems, see Figure 2 As shown, the present application also provides an NV color center measurement device, including an NV color center magnetic probe, a microwave source, a microwave signal driving device, a laser source, a single photon detector, and a signal processing circuit.

[0095] The tip of the NV color center magnetic probe is provided with diamond particles containing NV color centers, and the NV color center magnetic probe is used to scan the chip to be detected;

[0096] The laser source is used to generate laser light for irradiating the NV color center so as to cause the NV color center to generate fluorescence;

[0097] A microwave source provides a fixed-frequency microwave signal applied to the NV color center, using a normally-on continuous excitation mode to generate a DC static magnetic field. The chip under test needs to be placed in a stable static magnetic field, on this basis, it is driven by an AC current to generate an alternating magnetic field. The static magnetic field can be added using various existing methods, such as electromagnets, magnetic field coils, and ordinary magnets. This is a prior art method. The magnetic field magnitude of the static magnetic field and the frequency of the microwave satisfy the relationship of magnetic resonance. Specifically: the microwave signal frequency applied by the microwave source = 2.87 GHz - 2.8 MHz / Gs × static magnetic field strength (Gs);

[0098] A microwave signal driving device is used to drive the microwave source to emit a microwave signal to meet the NV color center's measurement requirements for the AC magnetic field. As an embodiment, in this application, the microwave signal driving device adopts an echo sequence driving method, and the waveform time interval length of the echo sequence is equal to or close to the half-cycle length of the AC current driving signal. When the above conditions are met, the pulse inserted in the echo sequence (such as the π pulse of the Hann sequence) will flip the state vector to the opposite direction. The phase accumulated by the DC magnetic field in the same direction during the two free evolution periods of the sequence will cancel each other out, resulting in the phase accumulation of the DC magnetic field being 0. The phases of the AC magnetic field that changes in alternating direction will be superimposed on each other, resulting in the AC magnetic field obtaining phase accumulation, which produces observable changes in the fluorescence intensity signal.

[0099] The single-photon detector is used to detect the fluorescence signal generated by the NV color center. Of course, as a person skilled in the art, the single-photon detector can also be other photodetectors as long as it can detect the fluorescence signal generated by the NV color center;

[0100] The signal processing circuit is used to receive the fluorescence signal, process the fluorescence signal to obtain a magnetic measurement signal, and output the magnetic measurement signal to the host computer. The host computer further processes the magnetic measurement signal to obtain the magnetic field strength of the AC magnetic field to be measured. At the same time, the reference signal inside the signal processing circuit is also used as a driving voltage for chip testing, which is used to make the chip to be tested generate an AC magnetic field. The AC magnetic field is the magnetic field that the NV color center measurement device needs to measure.

[0101] Continue reading Figure 2As shown, the signal processing circuit includes a multiplier, a secondary filter, and a reference signal source. The multiplier's input is connected to the single-photon detector, and its output is connected to the secondary filter, which outputs a magnetic measurement signal. The reference signal source is connected to both the multiplier and the current drive circuit of the chip under test. The signal processing circuit uses the multiplier to process the fluorescence signal output by the single-photon detector and cooperates with the secondary filter to generate the output magnetic measurement signal.

[0102] The NV color center measurement device using the signal processing circuit detects the chip magnetic field, including the following steps:

[0103] S1. The current driving circuit of the chip under test applies an alternating current to the chip under test to put the chip under test into a working state, wherein an NV color center magnetic probe is provided on one side of the chip under test;

[0104] S2. Applying a microwave signal and a laser signal to the NV color center magnetic probe, wherein the microwave signal is a fixed-frequency microwave signal that uses a normally-open continuous excitation mode to generate a DC static magnetic field, and a microwave signal driving device drives the microwave source to emit a microwave signal to meet the NV color center's measurement requirements for the AC magnetic field;

[0105] S3, the single-photon detector detects the fluorescence signal generated by the NV color center and transmits it to the signal processing circuit;

[0106] S4. The signal processing circuit reads the fluorescence signal, and uses the reference signal of the signal processing circuit as a reference, performs relevant multiplication calculations through the multiplier, and then outputs it to the secondary filter, and finally outputs the magnetic measurement signal. The reference signal source in the signal processing circuit is simultaneously connected to the current driving circuit of the chip to be tested and the multiplier in the signal processing circuit, so that the reference signal of the current driving circuit and the reference signal of the signal processing circuit maintain clock homology.

[0107] The multiplier can adopt three different schemes: analog multiplier, digital multiplier, and switch multiplier; the reference signal source can choose to use crystal oscillator + DDS chip (crystal oscillator connected to DDS), crystal oscillator + phase-locked loop (crystal oscillator connected to phase-locked loop), crystal oscillator + DAC chip (crystal oscillator connected to DAC chip) to output analog signals to the multiplier, or use crystal oscillator + GPIO of digital circuit (crystal oscillator connected to GPIO of digital circuit) to output digital signals to the multiplier; the secondary filter is generally implemented by digital low-pass filter at the embedded software level. Analog RC low-pass filter and active analog low-pass filter circuit can also achieve similar functions, but the performance of analog RC low-pass filter and active analog low-pass filter circuit is worse than that of digital low-pass filter.

[0108] Several specific embodiments are introduced below using different multipliers as examples.

[0109] Example 1

[0110] In this embodiment, the multiplier is an analog multiplier, such as Figure 3 As shown, the multiplication function of the analog multiplier is realized by the semiconductor characteristics of the transistor, a specific example of which is shown in Figure 4 As shown, the analog multiplier in this embodiment is implemented using a transistor circuit, utilizing the exponential response characteristics of the transistor to achieve a multiplication effect under small signal conditions. Of course, other existing analog multipliers can also be used.

[0111] In this signal processing circuit using an analog multiplier, a reference signal generated by a reference signal source is multiplied by the input fluorescence signal to output an analog voltage. In this embodiment, the secondary filter is a digital low-pass filter. The analog voltage output by the analog multiplier is first converted to a digital signal by an ADC (analog-to-digital converter) before being output through the digital low-pass filter, thus achieving modulation and demodulation. Alternatively, the digital low-pass filter can be replaced with an analog low-pass filter, such as an analog RC low-pass filter or an active analog low-pass filter circuit. In this case, the ADC is unnecessary.

[0112] As a preferred solution, to combat environmental noise, the signal processing circuit also includes an anti-aliasing filter positioned between the input and the analog multiplier. The input fluorescence signal first passes through the pre-filter to remove high-frequency noise, thereby improving the system's signal-to-noise ratio in field environments. This anti-aliasing filter can be implemented using a passive RC low-pass filter, an anti-interference inductor structure or magnetic ring, or an active low-pass filter.

[0113] In this embodiment, the reference signal generated by the reference signal source can be either an analog signal or a digital signal. The digital signal emitted by the reference signal source is only a square wave and can be processed as an analog square wave. Therefore, the reference signal source can employ a crystal oscillator + DAC, crystal oscillator + DDS, crystal oscillator + phase-locked loop, or crystal oscillator + digital GPIO scheme, wherein the analog multiplier connected to the reference signal source is a DAC, DDS, phase-locked loop, or digital GPIO.

[0114] Figure 3 The crystal oscillator + DAC is used as an example to illustrate the system structure. People in this field can easily understand that the crystal oscillator + DAC can be replaced with crystal oscillator + DDS, crystal oscillator + phase-locked loop, crystal oscillator + digital GPIO, etc. according to actual needs. There is no significant difference in structure and effect.

[0115] See Figure 5 , the workflow of the signal processing circuit includes:

[0116] S11, start measuring;

[0117] S12, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time;

[0118] S13, reading the reference signal of the same time period, where the time length is also the window time or exposure time;

[0119] S14, multiplying the reference signal and the fluorescence signal read by the analog multiplier to obtain an output signal of the analog multiplier;

[0120] S15. In the secondary filter, if Figure 3 The secondary filter shown first performs analog-to-digital conversion on the output signal of the analog multiplier through the ADC, and then performs low-pass filtering through a digital low-pass filter, with the filtering frequency not exceeding the reference signal frequency, to obtain a filtered output magnetic measurement signal;

[0121] S16. Determine whether to end the measurement. If yes, end the measurement. If not, return to step S12. The cycle or time required for measurement can be preset to determine whether the measurement needs to be ended.

[0122] Example 2

[0123] like Figure 6 As shown, the overall structure of the signal processing circuit is similar to that of Example 1, with the only difference being that in this embodiment, the multiplier adopts a switch multiplier, the reference signal source emits a digital signal, and the reference signal source needs to be implemented using a crystal oscillator + digital GPIO solution.

[0124] In this embodiment, the multiplier uses a transistor switch instead of a transistor with an amplifying function to avoid unstable results caused by unstable transistor properties, such as Figure 7 As shown in the figure, in this scheme, the reference signal is used as a switch control (Vctrl). When the voltage is high, the positive output of the follower is obtained, and when the voltage is low, the negative output of the inverter is obtained. This is equivalent to multiplying the input fluorescence signal by the reference signal, thus realizing the function of a multiplier. The reference signal in this scheme must be a digital signal, so the reference signal source needs to be implemented using a crystal oscillator + digital GPIO solution. This digital GPIO includes but is not limited to the high and low level timing output functions of various digital chips such as microcontrollers, DSPs, and FPGAs.

[0125] See Figure 8 , the workflow of the signal processing circuit includes:

[0126] S21, start measuring;

[0127] S22, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time;

[0128] S23, determine whether the reference signal is at a high level, if yes, proceed to step S24, otherwise proceed to step S25;

[0129] S24, the switch multiplier is connected in the forward direction, and its output signal is equal to the input signal;

[0130] S25, the switch multiplier is connected in reverse, and its output signal is equal to the opposite of the input signal;

[0131] S26: The signal output from step S24 or the signal output from step S25 enters a secondary filter. In the secondary filter, the current output signal and the previous output signal are averaged to obtain a magnetic measurement signal output by the secondary filter.

[0132] S27. Determine whether to end the measurement. If yes, end the measurement. If not, return to step S22. The cycle or time required for measurement can be preset to determine whether the measurement needs to be ended.

[0133] Example 3

[0134] like Figure 9 As shown, the overall structure of the signal processing circuit is similar to that of the first embodiment, with the only difference being that in this embodiment, the multiplier is a digital multiplier, the ADC is arranged between the digital multiplier and the input terminal, and the secondary filter is a digital low-pass filter. In this solution, the digital multiplier and the secondary filter are integrated on a digital control chip (such as a single-chip microcomputer, DSP, FPGA, or other digital chip). The reference signal source includes a preset reference signal and a crystal oscillator + GPIO, or the reference signal source includes a built-in reference signal and a crystal oscillator + DAC chip. The preset reference signal is stored in the digital control chip in the form of waveform data, and can also be stored in a ROM chip or Flash memory externally connected to the digital control chip, and is sent to the crystal oscillator + DAC chip or the crystal oscillator + GPIO to form an output reference signal.

[0135] When the reference signal source uses a combination of a preset reference signal and a crystal oscillator + GPIO, the preset reference signal waveform is a square wave, achieving an effect similar to switch demodulation; when the reference signal source uses a combination of a preset reference signal and a crystal oscillator + DAC chip, the preset reference signal waveform can be a sine wave or other periodic waveform.

[0136] Taking the crystal oscillator + DAC as an example, the input fluorescence signal is processed by the anti-aliasing filter and then directly collected by the ADC as a digital signal. It is then digitally multiplied with the reference signal preset in the digital control chip. The output data is filtered by a digital low-pass filter and then output as a magnetic measurement signal.

[0137] Because there is an uncontrollable phase difference between the reference signal and the input fluorescence signal, an additional digital multiplier and digital low-pass filter can be added as a preferred embodiment. Specifically, the inputs of both digital multipliers receive the input fluorescence signal, and both digital low-pass filters output the magnetic measurement signal. The reference signals of the two digital multipliers differ by 90° in phase. Multiplication and low-pass filtering are performed using the reference signal data with an additional 90° phase delay, thereby canceling out the phase effect and obtaining a more consistent output signal. This implementation scheme is also applicable to Examples 1 and 2.

[0138] The reference signal in this solution can also be implemented using digital GPIO, replacing the reference signal waveform with a square wave to achieve an effect similar to switch demodulation. Although this will reduce modulation and demodulation performance, it helps reduce system power consumption and computing power requirements, thereby helping to control equipment costs.

[0139] See Figure 10 , the workflow of the signal processing circuit includes:

[0140] The workflow of the signal processing circuit includes:

[0141] S31, start measuring;

[0142] S32, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time;

[0143] S33, reading the reference signal of the same time period, where the time length is also the window time or exposure time;

[0144] S34, multiplying the reference signal and the fluorescence signal read by the digital multiplier to obtain an output signal of the digital multiplier;

[0145] S35. In the secondary filter, low-pass filtering is performed by a digital low-pass filter, where the filtering frequency does not exceed the reference signal frequency, to obtain a filtered output magnetic measurement signal;

[0146] S36: Determine whether to end the measurement. If yes, end the measurement. If not, return to step S32. The cycle or time required for measurement can be preset to determine whether the measurement needs to be ended.

[0147] The above technical solutions of the present invention are particularly suitable for the detection of micro-scale alternating magnetic fields. The "micro-scale alternating magnetic field" in the present invention refers to the spatial magnetic field intensity distribution with a magnetic field spatial resolution not exceeding 1um.

[0148] It should be noted that the logic and / or steps represented in the flowchart or described in other ways herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer storage medium for use by an instruction execution system, device or equipment (such as a computer-based system, a system including a processor or other system that can fetch instructions from an instruction execution system, device or equipment and execute instructions), or used in combination with these instruction execution systems, devices or equipment.

[0149] It should be understood that various components of the present invention may be implemented using hardware, software, firmware, or a combination thereof. In the above-described embodiments, multiple steps or methods may be implemented using software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented using hardware, as in another embodiment, any one of the following technologies known in the art or a combination thereof may be used: a discrete logic circuit having logic gate circuits for implementing logic functions on data signals, an application-specific integrated circuit having suitable combinational logic gate circuits, a programmable gate array (PGA), a field-programmable gate array (FPGA), etc.

[0150] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A NV color center measurement device, comprising an NV color center magnetic probe, a microwave source, a laser source, and a signal processing device, wherein the NV color center magnetic probe is used to scan a chip to be detected, the laser source and the microwave source are used to provide laser and microwave signals applied to the NV color center, respectively, and the signal processing device is used to collect the fluorescence signal of the NV color center and output a magnetic measurement signal. The chip to be detected is driven by an alternating current, and is characterized by: It also includes a microwave signal driving device. The microwave source provides a microwave signal of a fixed frequency. The microwave signal driving device drives the microwave source in an echo sequence driving manner. The waveform time interval length of the echo sequence is equal to the half-cycle length of the AC current driving signal.

2. The NV color center measurement device according to claim 1, characterized in that: The microwave signal driving device adopts the driving mode of Hann echo sequence to drive the microwave source to emit microwave signals.

3. The NV color center measurement device according to claim 1, characterized in that: The signal processing device includes a photodetector and a signal processing circuit. The photodetector is used to detect the fluorescence signal generated by the NV color center. The signal processing circuit is used to receive the fluorescence signal and obtain a magnetic measurement signal after processing the fluorescence signal.

4. The NV color center measurement device according to claim 3, characterized in that: The signal processing circuit in the signal processing device includes a multiplier, a secondary filter and a reference signal source, wherein the input end of the multiplier is connected to the photodetector, the output end is connected to the secondary filter, the secondary filter outputs the magnetic measurement signal, and the reference signal source is simultaneously connected to the multiplier and the current driving circuit of the chip to be tested.

5. The NV color center measurement device according to claim 4, characterized in that: The multiplier is any one of an analog multiplier, a digital multiplier and a switch multiplier.

6. The NV color center measurement device according to claim 4, characterized in that: The reference signal source uses a crystal oscillator + DDS chip, or a crystal oscillator + phase-locked loop, or a crystal oscillator + DAC chip to output an analog signal, or uses a crystal oscillator + GPIO of a digital circuit to output a digital signal.

7. The NV color center measurement device according to claim 4, characterized in that: The secondary filter adopts a digital low-pass filter, or adopts an analog RC low-pass filter or an active analog low-pass filter circuit.

8. The NV color center measurement device according to claim 4, characterized in that: The input end of the multiplier is further provided with an anti-aliasing filter.

9. The NV color center measurement device according to claim 4, characterized in that: The multiplier adopts an analog multiplier, and the secondary filter adopts a digital low-pass filter or an analog low-pass filter. When the secondary filter adopts a digital low-pass filter, an ADC is set between the analog multiplier and the digital low-pass filter. When the secondary filter adopts an analog low-pass filter, the analog multiplier and the analog low-pass filter are directly connected, and the reference signal source outputs an analog signal or a digital signal.

10. The NV color center measurement device according to claim 9, characterized in that: The workflow of the signal processing circuit includes: S11, start measurement; S12, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time; S13, reading the reference signal of the same time period, where the time length is also the window time or exposure time; S14, multiplying the reference signal and the fluorescence signal read by the analog multiplier to obtain an output signal of the analog multiplier; S15, performing low-pass filtering in a secondary filter, wherein the filtering frequency does not exceed the reference signal frequency, and obtaining a filtered output magnetic measurement signal; S16: Determine whether the measurement is to be ended. If yes, end the measurement. If not, return to step S12.

11. The NV color center measurement device according to claim 4, characterized in that: The multiplier adopts a switch multiplier, and the secondary filter adopts a digital low-pass filter or an analog low-pass filter. When the secondary filter adopts a digital low-pass filter, an ADC is set between the switch multiplier and the digital low-pass filter. When the secondary filter adopts an analog low-pass filter, the switch multiplier and the analog low-pass filter are directly connected, and the reference signal source outputs a digital signal.

12. The NV color center measurement device according to claim 11, characterized in that: The workflow of the signal processing circuit includes: S21, start measuring; S22, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time; S23, determine whether the reference signal is high level, if yes, go to step S24, otherwise go to step S25, S24, the switch multiplier is connected in the forward direction, and its output signal is equal to the input signal; S25, the switch multiplier is connected in reverse, and its output signal is equal to the opposite of the input signal; S26: The signal output from step S24 or the signal output from step S25 enters a secondary filter. In the secondary filter, the current output signal and the previous output signal are averaged to obtain a magnetic measurement signal output by the secondary filter. S27. Determine whether to end the measurement. If yes, end the measurement. If not, return to step S22. The cycle or time required for measurement can be preset to determine whether the measurement needs to be ended.

13. The NV color center measurement device according to claim 4, characterized in that: The multiplier adopts a digital multiplier, the secondary filter adopts a digital low-pass filter, the secondary filter is integrated on a digital control chip, the reference signal source includes a preset reference signal and a crystal oscillator + GPIO, or the reference signal source includes a built-in reference signal and a crystal oscillator + DAC chip, the preset reference signal is pre-stored in the form of waveform data and sent to the crystal oscillator + DAC chip or the crystal oscillator + GPIO.

14. The NV color center measurement device according to claim 13, characterized in that: The workflow of the signal processing circuit includes: S31, start measuring; S32, reading the fluorescence signal for a period of time, where the length of time is a preset window time or exposure time; S33, reading the reference signal of the same time period, where the time length is also the window time or exposure time; S34, multiplying the reference signal and the fluorescence signal read by the digital multiplier to obtain an output signal of the digital multiplier; S35. In the secondary filter, low-pass filtering is performed by a digital low-pass filter, where the filtering frequency does not exceed the reference signal frequency, to obtain a filtered output magnetic measurement signal; S36. Determine whether to end the measurement. If yes, end the measurement. If not, return to step S32. The cycle or time required for measurement can be preset to determine whether the measurement needs to be ended.

15. The NV color center measurement device according to any one of claims 4 to 14, characterized in that: There are two connecting branches between the multiplier and the filter. The input ends of the two multipliers are both connected to the photodetector. The two filters both output magnetic measurement signals. The reference signals of the two multipliers differ in phase by 90°.

16. An NV color center measurement system, characterized in that: It includes the NV color center measurement device and current driving circuit as described in any one of claims 1 to 15, wherein the reference signal inside the signal processing circuit of the NV color center measurement device is simultaneously output to the current driving circuit, so that the reference signal of the current driving circuit and the reference signal of the signal processing circuit maintain clock homology.

17. A method for measuring a chip using the NV color center measurement system according to claim 16, characterized in that: include: S1, the current driving circuit of the chip under test applies an AC current to the chip under test; S2, applying a microwave signal and a laser signal to the NV color center magnetic probe; S3, the photodetector detects the fluorescence signal generated by the NV color center and transmits it to the signal processing circuit; S4. The signal processing circuit reads and calculates the fluorescence signal and then outputs a magnetic measurement signal.

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