Position detection system and position detection method for storage unit in SRAM (Static Random Access Memory) chip

Abstract

The invention discloses a position detection system and a position detection method for a memory cell in an SRAM (Static Random Access Memory) chip, and relates to the technical field of semiconductors. The position detection system comprises an electric displacement table, an optical excitation module, a microwave excitation module, an avalanche photoelectric detector, a signal analysis device and a control module. The electric displacement table is used for placing an SRAM chip to be detected; the optical excitation module comprises a laser, a dichroscope, an objective lens and an optical fiber probe; a diamond particle containing an NV color center is arranged at the tip of the optical fiber probe; the optical fiber probe is used for performing point-by-point scanning on the SRAM chip to be detected; the microwave excitation module is used for applying microwave signals; the control module is used for writing a square wave signal with a preset frequency; the avalanche photoelectric detector is used for converting to obtain a voltage signal; the signal analysis device analyzes the voltage signal to determine a position of the target memory cell. The system solves the problems of intrusive detection, low position detection precision and low position detection efficiency of the storage unit in the SRAM chip in the prior art.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a position detection system and method for a storage unit in a SRAM chip. Background Art

[0002] It is very important to accurately locate the storage cells in static random-access memory (SRAM) chips, especially during design, testing and fault diagnosis.

[0003] During the design and manufacturing process, it is necessary to ensure that each memory cell can store and read data correctly. By accurately positioning the memory cell, it is possible to verify that its function is working properly, thereby ensuring the data integrity of the entire SRAM chip. Mutual interference between adjacent memory cells may cause data errors. By accurately laying out and positioning the memory cells, this interference can be minimized and the reliability of the memory can be improved. The access speed of the SRAM chip is one of the key indicators of its performance. By properly positioning the memory cells, the signal path can be optimized, the delay can be reduced, and the read and write speeds can be increased. During the production process, comprehensive testing must be carried out to ensure the quality of the SRAM chip. By positioning the memory cells, defective cells can be more easily identified and located, so that unqualified products can be quickly repaired or eliminated.

[0004] In the prior art, electrical testing technology and light emission detection technology are used to further locate the storage cells in the SRAM chip.

[0005] Electrical testing technology analyzes the state of SRAM memory cells by applying specific test voltages or signals to the cells and monitoring the current or voltage changes at the output. This method is often used in the production test phase of chips to identify faulty cells and performance anomalies. Electrical testing equipment can quickly scan the entire memory array and provide results, making it suitable for large-scale memory cell testing.

[0006] Electrical detection technology has the following defects: First, it is invasive: electrical testing often requires direct access to storage cells, which may change their contents and is not suitable for scenarios where security storage contents need to be detected or protected. Second, it is unable to provide location information: electrical testing mainly detects overall performance and fault status, and it is difficult to spatially locate a single storage cell. Third, it is not suitable for cell-level fault detection in high-density arrays: as memory density increases, electrical testing finds it difficult to identify the specific location and status of storage cells without destroying data.

[0007] The light emission detection technology obtains the working state of the storage unit or logic circuit by observing the spontaneous photon emission inside the chip. This technology usually exposes the back of the SRAM chip and uses a high-sensitivity photodetector (such as an LN2-cooled InGaAs camera) to record the emission spectrum, combined with time-resolved or differential image analysis methods to achieve storage content detection. In this technical solution, the transistors in the storage unit generate specific spontaneous emission in different logical states of the SRAM chip. By identifying these emission patterns, it can be used to analyze the state of a specific storage unit.

[0008] The optical emission detection technology has the following defects: First, in a high-density integrated SRAM storage array, the distance between units is small, and optical detection is limited by the diffraction limit, making it difficult to achieve unit-level resolution accuracy; second, this method requires the use of expensive high-sensitivity detectors and cooling devices, and usually requires operation in a low-temperature environment, which increases the cost and complexity of the equipment; third, the optical emission signal of the SRAM unit is very weak, which is greatly affected by factors such as temperature and background light, and the signal-to-noise ratio is relatively low, affecting the detection accuracy; fourth, this method requires differential imaging and spectral analysis, which increases the complexity of data processing and detection time. Summary of the invention

[0009] The object of the present invention is to provide a position detection system and a position detection method for a storage unit in an SRAM chip, which are used to realize non-intrusive positioning of the storage unit in the SRAM chip and improve the position detection accuracy and position detection efficiency.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] In a first aspect, the present invention provides a position detection system for a storage unit in an SRAM chip, comprising: an electric translation stage, an optical excitation module, a microwave excitation module, an avalanche photodetector, a signal analysis device, and a control module;

[0012] The electric translation stage is used to place the SRAM chip to be tested and adjust the position of the SRAM chip to be tested;

[0013] The optical excitation module comprises a laser, a dichroic mirror, an objective lens and an optical fiber probe; the laser light emitted by the laser is sequentially focused to the optical fiber probe through the dichroic mirror and the objective lens; the tip of the optical fiber probe is provided with diamond particles containing NV color centers; the optical fiber probe is used to scan the SRAM chip to be detected point by point;

[0014] The microwave excitation module is used to apply a microwave signal to the diamond particles containing NV color centers;

[0015] The control module is used to write a square wave signal of a preset frequency into the target storage unit on the SRAM chip to be detected;

[0016] The avalanche photodetector is used for receiving the red fluorescence fed back by the diamond particles containing the NV color center based on the dichroic mirror and converting the red fluorescence into a corresponding voltage signal;

[0017] The signal analysis device is used to receive the voltage signal and analyze the voltage signal to determine the position of the target storage unit.

[0018] Optionally, the electric translation stage adopts a zigzag scanning path when performing point-by-point scanning; the preset stepping distance of the electric translation stage in the horizontal direction is 10um, the size of a single storage unit in the SRAM chip to be detected is 25um×25um, and the minimum stepping distance of the electric translation stage is 0.4um.

[0019] Optionally, the position detection system of the storage unit in the SRAM chip also includes a bias circuit, one end of the bias circuit is connected to the control module, and the other end of the bias circuit is connected to the SRAM chip to be detected; the control module realizes the bias voltage setting of the SRAM chip to be detected through the bias circuit.

[0020] Optionally, the signal analysis device is a spectrum analyzer.

[0021] Optionally, the microwave excitation module includes a microwave source and a copper coil; the microwave source is connected to the copper coil, and the copper coil is arranged around the optical fiber probe.

[0022] Optionally, the microwave excitation module further includes a power amplifier and an isolator;

[0023] The first end of the power amplifier is connected to the microwave source; the second end of the power amplifier is connected to the first end of the isolator; and the second end of the isolator is connected to the copper coil.

[0024] Optionally, the position detection system of the storage unit in the SRAM chip further comprises an electromagnetic shielding box; the electromagnetic shielding box is used to enclose the SRAM chip to be detected, the tip of the optical fiber probe and the electric translation stage.

[0025] Optionally, the position detection system of the storage unit in the SRAM chip further includes a shockproof platform; all components in the optical excitation module are fixed on the shockproof platform.

[0026] In a second aspect, the present invention further provides a method for detecting the position of a storage unit in an SRAM chip, which is applied to a system for detecting the position of a storage unit in an SRAM chip as described in any one of the above items, wherein the position detection system comprises an electric translation stage, an optical excitation module, a microwave excitation module, an avalanche photodetector, a signal analysis device and a control module; the optical excitation module comprises a laser, a dichroic mirror, an objective lens and an optical fiber probe; the tip of the optical fiber probe is provided with diamond particles containing NV color centers;

[0027] The position detection method comprises:

[0028] Place the SRAM chip to be tested on the electric translation stage;

[0029] Adjusting the relative positions of the optical fiber probe, the microwave excitation module and the SRAM chip to be detected;

[0030] Setting the working state of the SRAM chip to be detected to a writing state and writing a square wave signal of a preset frequency to a target storage unit of the SRAM chip to be detected;

[0031] Starting the optical excitation module and the microwave excitation module to excite the diamond particles containing NV color centers to radiate red fluorescence;

[0032] Using the avalanche photodetector to generate a voltage signal from the red fluorescence and outputting the voltage signal to the signal analysis device;

[0033] Analyzing the voltage signal using the signal analysis device;

[0034] Keeping the positions of the optical fiber probe and the microwave excitation module unchanged, using the electric translation stage to adjust the position of the SRAM chip to be detected and continuing to use the signal analysis device to analyze the voltage signal continuously output by the avalanche photodetector;

[0035] When the voltage signal is consistent with the input signal period or frequency of the SRAM chip to be detected, the operation of the electric translation stage is stopped and the current coordinates are recorded;

[0036] The current coordinates are determined as the location of the target storage unit.

[0037] Optionally, the method for detecting the position of a storage unit in an SRAM chip further includes:

[0038] Using diamond particles containing NV color centers with different crystal particle diameters, the SRAM chip to be tested is tested multiple times to obtain multiple spatial resolution test results;

[0039] Based on the multiple spatial resolution detection results, the relationship between the spatial resolution of the diamond color center sensor and the crystal grain diameter is determined.

[0040] Compared with the prior art, the present invention provides a position detection system and method for a storage unit in an SRAM chip. The SRAM chip to be detected is placed on an electric displacement table, a microwave excitation module and an optical excitation module are started, and a square wave signal of a preset frequency is written to the target storage unit on the SRAM chip to be detected by using a control module. After that, the diamond particles containing NV color centers on the tip of the optical fiber probe emit fluorescence under the joint action of laser and microwave. Due to the operation of the square wave signal in the SRAM chip to be detected, the change in the fluorescence intensity of the NV color center is stimulated. The changed fluorescence intensity is then fed back to the avalanche photodetector through the optical fiber probe, the objective lens and the dichroic mirror. The avalanche photodetector converts the changed fluorescence signal into a changed voltage signal and transmits it to the signal analysis device. The signal analysis device can analyze the changed voltage signal to determine the specific position of the target storage unit. In this way, the position detection system for a storage unit in an SRAM chip provided by the present invention has high spatial resolution for the position, the system components obtain the target storage unit signal accurately, the positioning method can determine the position only according to the voltage signal, and the data analysis is simple, so as to realize the non-invasive position detection of the storage unit in the SRAM chip and improve the position detection accuracy and position detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0042] Figure 1 A schematic diagram of the structure of a position detection system for a storage unit in an SRAM chip provided by an embodiment of the present invention;

[0043] Figure 2 A schematic diagram of a spectrum shift corresponding to a light-detected magnetic resonance caused by a magnetic field induced by a chip current provided in one embodiment of the present invention;

[0044] Figure 3 A schematic flow chart of a method for detecting the position of a storage unit in an SRAM chip provided by an embodiment of the present invention;

[0045] Figure 4 A schematic diagram of the circuit structure of a 6-T storage unit provided by one embodiment of the present invention;

[0046] Figure 5 A schematic diagram of the approximate location of a target storage unit on an SRAM chip provided by one embodiment of the present invention;

[0047] Figure 6 A schematic diagram of accurately positioning a target storage unit on an SRAM chip using an optical fiber probe provided by an embodiment of the present invention;

[0048] Figure 7 A pulse capture result diagram of an SRAM chip in the frequency domain provided by an embodiment of the present invention.

[0049] Figure numerals: 10 - electric translation stage; 20 - optical excitation module; 30 - microwave excitation module; 40 - avalanche photodetector; 50 - signal analysis device; 60 - SRAM chip to be detected; 70 - electromagnetic shielding box; 21 - laser; 22 - dichroic mirror; 23 - objective lens; 24 - optical fiber probe; 31 - microwave source; 32 - copper coil; 33 - power amplifier; 34 - isolator. DETAILED DESCRIPTION

[0050] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0051] It should be noted that, in the present invention, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0052] In the present invention, "at least one" means one or more, "more than one" means two or more. "And / or" describes the association relationship of the associated objects, indicating that three types of relationships may exist.

[0053] For example Figure 1 As shown, an embodiment of the present invention provides a position detection system for a storage unit in an SRAM chip, comprising: an electric translation stage 10, an optical excitation module 20, a microwave excitation module 30, an avalanche photodetector 40, a signal analysis device 50 and a control module; wherein the microwave excitation module 30 may at least include a microwave source 31 and a copper coil 32, the microwave source 31 is connected to the copper coil 32, and the copper coil is arranged around the optical fiber probe.

[0054] The electric translation stage 10 is used to place the SRAM chip 60 to be tested and adjust the position of the SRAM chip 60 to be tested;

[0055] The optical excitation module 20 includes a laser 21, a dichroic mirror 22, an objective lens 23 and an optical fiber probe 24; the laser emitted by the laser 21 is sequentially focused to the optical fiber probe 24 through the dichroic mirror 22 and the objective lens 23; the tip of the optical fiber probe 24 is provided with diamond particles 25 containing NV color centers; the optical fiber probe 24 is used to scan the SRAM chip 60 to be detected point by point; the copper coil 32 is arranged around the optical fiber probe 24;

[0056] The microwave excitation module 30 is used to apply a microwave signal to the diamond particles 25 containing NV color centers;

[0057] The control module is used to write a square wave signal of a preset frequency into a target storage unit on the SRAM chip to be detected;

[0058] The avalanche photodetector 40 is used to receive the red fluorescence fed back by the diamond particles 25 containing NV color centers based on the dichroic mirror 22 and convert the red fluorescence into a corresponding voltage signal;

[0059] The signal analysis device 50 is used to receive a voltage signal and analyze the voltage signal to determine the position of the target storage unit.

[0060] SRAM (Static Random-Access Memory) is a common type of semiconductor memory, mainly used for temporary data storage. Unlike DRAM (Dynamic Random Access Memory), SRAM does not require a refresh circuit to maintain data integrity, so it has faster read and write speeds and lower power consumption. The basic memory cell of SRAM consists of six transistors forming two cross-coupled inverters. This structure enables the memory cell to maintain its state without external intervention, thus achieving "static" storage. Each memory cell can store one bit of binary information (0 or 1).

[0061] It is understandable that when the chip is working normally, according to the current magnetic effect, the current flowing in the chip circuit will generate a corresponding magnetic field. This magnetic field affects the electron spin in the diamond NV color center, which in turn causes the optically detected magnetic resonance (ODMR) spectrum line to shift (such as Figure 2By keeping the relative position of the diamond NV center and the chip unchanged, and when the microwave frequency is fixed, the change in the magnetic field caused by the chip current will lead to a change in the fluorescence intensity of the center. By monitoring the fluctuation of the fluorescence signal, the existence of the chip current-induced magnetic field can be inferred. In a specific detection area, the current pulse signal inside the chip will generate a pulsed magnetic field, so that the NV center fluorescence intensity and signal fluctuations maintain a consistent timing relationship. In this way, the dynamic capture of the current signal changes on the chip can be achieved.

[0062] In an embodiment of the present invention, an SRAM chip to be detected is placed on an electric translation stage, a microwave excitation module and an optical excitation module are started, and a square wave signal of a preset frequency is written to a target storage unit on the SRAM chip to be detected by using a control module. After that, diamond particles containing NV color centers on the tip of the optical fiber probe emit fluorescence under the combined action of laser and microwave. Since the square wave signal is running in the SRAM chip to be detected, the change in the fluorescence intensity of the NV color center is stimulated. The changed fluorescence intensity is then fed back to the avalanche photodetector through the optical fiber probe, the objective lens and the dichroic mirror. The avalanche photodetector converts the changed fluorescence signal into a changed voltage signal and transmits it to a signal analysis device. The signal analysis device can analyze the changed voltage signal to determine the specific position of the target storage unit.

[0063] Compared with the electrical testing technology in the prior art, first, the position detection system of the storage unit in the SRAM chip in this embodiment does not need to directly access the storage unit when positioning the SRAM chip to be tested, thereby realizing non-invasive positioning of the target storage unit in the SRAM chip; second, this embodiment adopts a microwave excitation module, an optical excitation module of diamond particles containing NV color centers, an electric translation stage and other devices for joint testing, which can accurately detect the position of the target storage unit in the SRAM chip, thereby improving the detection accuracy of the storage unit position.

[0064] Compared with the light emission detection technology in the prior art, first, the position detection system of the storage unit in the SRAM chip in this embodiment adopts an optical fiber probe containing diamond particles containing NV color centers. Since the spatial resolution of the diamond containing NV color centers is high and the electric translation stage is accurately displaced during the point-by-point scanning process, the accuracy of the position detection of the storage unit in the SRAM chip is also improved; second, the position detection system of the storage unit in the SRAM chip in this embodiment does not require expensive high-sensitivity detectors and cooling devices, and the operation in this embodiment does not need to be performed in a low-temperature environment, which reduces the operating costs of experiments and tests; third, this embodiment uses a microwave excitation module and an optical excitation module containing diamond particles containing NV color centers for detection, which can solve the defect that the light emission signal of the SRAM unit is very weak, that is, the signal intensity of the storage unit obtained by the position detection system is high and the relevant data is accurate, which can improve the position detection accuracy of the storage unit in the SRAM chip; fourth, when the position detection system in this embodiment performs position analysis on the target storage unit in the RAM chip, the position can be determined based on the voltage signal, without the need to perform differential imaging and spectrum analysis at the same time, thus avoiding the complexity of data processing and improving the position detection efficiency of the storage unit in the SRAM chip.

[0065] Optionally, the optical fiber probe 24 may be a tapered optical fiber, and the tapered design of the optical fiber tip enhances the fluorescence collection efficiency.

[0066] In the first specific embodiment, the laser emits a 532nm laser, which is focused onto a tapered optical fiber through an objective lens to continuously excite the NV color center. The refractive index of diamond is as high as n=2.4, making it easier for fluorescence to escape and be collected. When a 532nm green laser irradiates the diamond NV color center, red fluorescence is emitted, which is collected by the same optical fiber and guided to a dichroic mirror to separate it from light of other wavelengths. The separated fluorescence signal is transmitted to an avalanche photodetector and converted into an electrical signal. The electrical signal is finally transmitted to a spectrum analyzer for further observation and processing of the fluorescence response.

[0067] It should be noted that the electric translation stage adopts a zigzag scanning path when performing point-by-point scanning; the preset step distance of the electric translation stage in the horizontal direction is 10um, the size of a single storage unit in the SRAM chip to be detected is 25um×25um, and the minimum step distance of the electric translation stage is 0.4um.

[0068] From the above content, it can be seen that since the fiber optic probe needs to scan the SRAM chip to be detected point by point, if the electric translation stage is not used, but the point-by-point scanning of the SRAM chip to be detected is achieved by moving the optical excitation module, the movement of multiple system components will obviously cause the instability of the entire position detection system, thereby reducing the detection accuracy and detection efficiency. The electric translation stage is used in this embodiment to ensure that the other multiple system components remain stationary, thereby ensuring the stability of the entire position detection system, which is beneficial to detection and improving detection accuracy and detection efficiency. In addition, the minimum step distance of the electric translation stage is 0.4um, which is much smaller than the size of a single storage unit in the SRAM chip to be detected, and can achieve precise positioning of a single storage unit in the SRAM chip to be detected.

[0069] It is understandable that the position detection system of the storage unit in the SRAM chip also includes a bias circuit, one end of the bias circuit is connected to the control module, and the other end of the bias circuit is connected to the SRAM chip to be detected; the control module realizes the bias voltage setting of the SRAM chip to be detected through the bias circuit.

[0070] Since a single memory cell of an SRAM chip has multiple transistors, setting the appropriate voltage or current level for the transistors can ensure that these devices operate at specific operating points to achieve their intended functions. Reasonable circuit biasing means carefully adjusting parameters such as power supply voltage and word line voltage according to design requirements to ensure that the multiple transistors inside the SRAM cell can work stably and can accurately switch states when writing a periodic square wave signal to a specified memory cell to complete the data writing process.

[0071] Optionally, the signal analysis device is a spectrum analyzer.

[0072] The spectrum analyzer used in this embodiment is good at analyzing signals in the frequency domain and can directly display the spectrum distribution of the signal, which is particularly useful for observing the various frequency components in the signal. For example, when the spectrum analyzer displays a peak mutation of a voltage signal of a certain frequency, it indicates that the voltage signal is consistent with the input signal period or frequency of the SRAM chip to be detected and produces a frequency response. At this time, the position of the optical fiber probe is the position of the target storage unit, and the position detection accuracy is high. In addition, the spectrum analyzer can provide very high frequency resolution to help users identify weak or hidden frequency components. Finally, the spectrum analyzer has a large dynamic range and can capture strong and weak signals at the same time, which is particularly suitable for the electromagnetic environment in the embodiment of the present invention. Improve the position detection accuracy of the target storage unit of the SRAM chip.

[0073] Alternatively, see Figure 1The microwave excitation module 30 may also include a power amplifier 33 and an isolator 34; the first end of the power amplifier 33 is connected to the microwave source 31; the second end of the power amplifier 33 is connected to the first end of the isolator 34; the second end of the isolator 34 is connected to the copper coil 32.

[0074] Alternatively, see Figure 1 The position detection system of the storage unit in the SRAM chip may further include an electromagnetic shielding box 70 ; the electromagnetic shielding box 70 is used to enclose the SRAM chip 60 to be detected, the tip of the optical fiber probe and the electric translation stage 10 .

[0075] Using an electromagnetic shielding box to isolate magnetic noise can ensure measurement stability and accuracy.

[0076] Optionally, the position detection system of the storage unit in the SRAM chip may further include a shockproof platform; all components in the optical excitation module are fixed on the shockproof platform.

[0077] The anti-vibration platform can reduce the influence of noise and drift caused by environmental factors.

[0078] About the working principle of the position detection system: When the SRAM chip is working normally, the current flows through the circuit in the target storage unit and generates a corresponding magnetic field. Due to the existence of the current, the ODMR spectrum of the NV color center is shifted. By keeping the relative position of the NV color center and the chip unchanged and fixing the microwave frequency, the change in the magnetic field caused by the current in the SRAM chip will cause the change in the fluorescence intensity of the NV color center. By monitoring the fluctuation of the fluorescence signal, the change in the current signal of the storage unit can be inferred.

[0079] In an SRAM chip, a specific memory cell is selected, a square wave signal with a specific frequency (such as a 4μs period) is written through the data port, and the circuit bias is set so that the current signal is stable and significant at the target cell.

[0080] Then, the fiber-coupled NV color center probe is used to scan the chip surface point by point to observe the changes in the fluorescence signal at different positions. By detecting the frequency response changes of the fluorescence signal on a spectrum analyzer, the precise position of the target storage unit can be determined.

[0081] See also Figure 3 The embodiment of the present invention further provides a method for detecting the position of a storage unit in an SRAM chip, which is applied to the system for detecting the position of a storage unit in an SRAM chip in any of the above embodiments. The method for detecting the position includes:

[0082] Step 310: placing the SRAM chip to be tested on the electric translation stage;

[0083] Step 320: adjusting the relative positions of the optical fiber probe, the microwave excitation module, and the SRAM chip to be detected;

[0084] Step 330: setting the working state of the SRAM chip to be detected to a writing state and writing a square wave signal of a preset frequency to a target storage unit of the SRAM chip to be detected;

[0085] Step 340: Start the optical excitation module and the microwave excitation module to excite the diamond particles containing NV color centers to radiate red fluorescence;

[0086] Step 350: using an avalanche photodetector to generate a voltage signal from the red fluorescence and outputting the voltage signal to a signal analysis device;

[0087] Step 360: Analyze the voltage signal using a signal analysis device;

[0088] Step 370: Keep the positions of the optical fiber probe and the microwave excitation module unchanged, use the electric translation stage to adjust the position of the SRAM chip to be detected, and continue to use the signal analysis device to analyze the voltage signal continuously output by the avalanche photodetector;

[0089] Step 380: When the voltage signal is consistent with the input signal period or frequency of the SRAM chip to be detected, the operation of the electric translation stage is stopped and the current coordinates are recorded;

[0090] Step 390: Determine the current coordinates as the location of the target storage unit.

[0091] The embodiment of the present invention realizes non-invasive SRAM chip storage unit positioning. By writing a periodic square wave signal to the target storage unit, scanning the chip surface point by point using a fiber-coupled diamond color center probe, and observing the fluorescence changes of the color center, the precise position of a single storage unit on the SRAM chip can be accurately located.

[0092] In the second embodiment, the position detection method is described. In the second embodiment, a symmetrical circuit structure of a 6-transistor (6-T) memory cell is used (see Figure 4 ). In this memory cell, M1, M3, M4 and M6 form a cross-coupled bistable latch, while M2 and M5 are transmission transistors. The input of the M1-3 inverter is connected to the output of the M4-6 inverter, and vice versa. The M2 and M5 transistors are driven by the word line (WL).

[0093] The SRAM chip used has 13-bit address input (A0-12) and 8-bit data input / output port (DQ0-7). The chip is divided into eight areas, each area corresponds to a data port. After setting the SRAM chip to the write working state, a square wave signal with a period of 4μs is written to the storage cell with address 017EH through DQ6.

[0094] See also Figure 5 The storage unit is located in the center of the chip edge to avoid the influence of leads, power and ground wires. To avoid interference from other data ports, the remaining ports are set to zero.

[0095] Since only the approximate location of the target storage unit is known ( Figure 5 The red dot pointed by the white arrow on the SRAM chip is located at the bottom of the SRAM chip, so an electric translation stage is used for precise positioning. During the detection process, the SRAM chip has been pre-opened, and the fiber probe containing NV color center diamond particles is placed above the SRAM chip. The distance between the fiber probe and the SRAM chip is about 100μm. The relative position of the fiber probe is adjusted, and the storage unit is accurately scanned using an electric translation stage. The output signal of the avalanche photodetector (APD) is monitored by a spectrum analyzer (for example, model: SAN-45, HAROGIC), and the parameters of the spectrum analyzer are set as follows: the center frequency is 250kHz, the start frequency is 249.5kHz, the end frequency is 250.5kHz, the spectrum span is 1kHz, the resolution bandwidth (RBW) is 2Hz, and the spectrum analyzer works in peak detection mode.

[0096] The SRAM chip is scanned in the x and y directions with a stepping distance of 10 μm by the horizontal movement of the electric translation stage. The scanning adopts a zigzag scanning path. After the electric translation stage moves 15 steps in the x direction, it moves one step in the y direction.

[0097] Finally, through this scanning process, the precise location of the target storage unit was successfully determined (see Figure 6 ). The output signal with a center frequency of 0.25MHz was observed on the spectrum analyzer, which was consistent with the input signal frequency and the signal peak was -110dBm (see Figure 7 ).

[0098] The successful positioning of the target memory cell of the SRAM chip verifies the application of this method to memory devices and shows that the NV probe is capable of detecting the weak magnetic field signals of the SRAM chip.

[0099] Optionally, the method for detecting the position of a storage unit in an SRAM chip may further include:

[0100] Diamond particles containing NV color centers with different crystal particle diameters are used to perform multiple tests on the SRAM chip to be tested, and multiple spatial resolution test results are obtained;

[0101] Based on multiple spatial resolution detection results, the relationship between the spatial resolution of the diamond color center sensor and the crystal particle diameter is determined.

[0102] From the above content, it can be seen that the present invention can be used for the reverse correction of the spatial resolution of the fiber-coupled diamond NV color center sensing system. In existing studies, it is assumed that the spatial resolution of the diamond color center sensor of the optical fiber system depends on the diameter of the crystal particles containing the diamond color center, but this assumption has not been verified. The present invention verifies the spatial resolution by precisely controlling the arrangement characteristics of the SRAM chip storage unit array and the electric translation stage. This verification method not only improves the position detection accuracy of the SRAM storage unit, but also provides an experimental basis for optimizing and improving the fiber-coupled NV color center detection system, making it more practical in high-density integrated circuit detection.

[0103] It can be seen from the position detection system and position detection method of the storage unit in the SRAM chip provided in the above embodiments that the present invention is based on the magnetic sensing principle and utilizes the fiber-coupled diamond NV color center sensing system to detect the weak magnetic field generated by the current in the chip, thereby achieving high-precision, non-contact positioning of the target storage unit in the SRAM chip.

[0104] Since the materials used in integrated circuits (such as silicon, copper, etc.) are all non-magnetic materials, there is no need for any pre-processing of the chip (such as thinning or back-side processing) during the detection process, which simplifies the operation process and avoids the risk of chip damage in optical detection methods. The present invention enables fast and non-destructive unit-level positioning and analysis in high-density integrated circuits.

[0105] The magnetic sensing scheme proposed in the present invention effectively solves the limitations of existing optical emission detection technology, including limited spatial resolution and weak signals, while avoiding the invasive limitations of electrical testing methods, and is very suitable for unit-level positioning and safety detection of high-density array structure chips. In addition, the scheme uses an electric translation stage to gradually scan the probe position on the SRAM chip, performing a zigzag scan in a 10um step mode, so that the probe gradually approaches each storage unit, thereby accurately detecting the weak magnetic signal of each unit, and recording the magnetic field changes at different positions one by one, verifying the spatial resolution capability of the NV color center probe in a real environment.

[0106] Since the position detection method of the present invention is based on the magnetic field response generated by the current, the technology can be extended to other storage devices based on different storage principles, such as dynamic random access memory (DRAM), resistive random access memory (RRAM), etc. These memories will also produce current changes when working, thereby generating detectable magnetic field signals. Therefore, by adjusting the adaptation parameters, the detection scheme of the present invention can perform non-invasive unit positioning and fault detection on these memories.

[0107] The present invention can be extended to the unit positioning and hardware security analysis of various array structure chips. The present invention is not only suitable for the unit positioning of memory chips such as SRAM and DRAM, but can also be extended to other array structure chips such as bus chips to achieve accurate detection of specific units. It is widely used in chip debugging, reverse engineering, and hardware and software security fields, thereby effectively improving the accuracy and security of high-density chip unit-level analysis.

[0108] The position detection method in this embodiment can also capture the pulse current signal inside the storage unit. Through the pulse capture technology, the pulse magnetic field of the current signal inside the target storage unit of the SRAM chip can be monitored, so that the NV color center fluorescence intensity and the input signal fluctuation maintain a consistent timing relationship, thereby accurately capturing the dynamic changes of the current signal inside the chip.

[0109] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0110] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the claims of the present invention and their equivalents.

Claims

1. A position detection system for a storage unit in an SRAM chip, characterized in that: include: Electric translation stage, optical excitation module, microwave excitation module, avalanche photodetector, signal analysis device and control module; The electric translation stage is used to place the SRAM chip to be tested and adjust the position of the SRAM chip to be tested; The optical excitation module comprises a laser, a dichroic mirror, an objective lens and an optical fiber probe; the laser light emitted by the laser is sequentially focused to the optical fiber probe through the dichroic mirror and the objective lens; the tip of the optical fiber probe is provided with diamond particles containing NV color centers; the optical fiber probe is used to scan the SRAM chip to be detected point by point; The microwave excitation module is used to apply a microwave signal to the diamond particles containing NV color centers; The control module is used to write a square wave signal of a preset frequency into the target storage unit on the SRAM chip to be detected; The avalanche photodetector is used for receiving the red fluorescence fed back by the diamond particles containing the NV color center based on the dichroic mirror and converting the red fluorescence into a corresponding voltage signal; The signal analysis device is used to receive the voltage signal and analyze the voltage signal to determine the position of the target storage unit.

2. The position detection system of the storage unit in the SRAM chip according to claim 1, characterized in that: The electric translation stage adopts a zigzag scanning path when performing point-by-point scanning; the preset stepping distance of the electric translation stage in the horizontal direction is 10um, the size of a single storage unit in the SRAM chip to be detected is 25um×25um, and the minimum stepping distance of the electric translation stage is 0.4um.

3. The position detection system of the storage unit in the SRAM chip according to claim 1, characterized in that: It also includes a bias circuit, one end of which is connected to the control module, and the other end of which is connected to the SRAM chip to be detected; the control module sets the bias voltage of the SRAM chip to be detected through the bias circuit.

4. The position detection system of the storage unit in the SRAM chip according to claim 1, characterized in that: The signal analysis device is a spectrum analyzer.

5. The position detection system of the storage unit in the SRAM chip according to claim 1, characterized in that: The microwave excitation module comprises a microwave source and a copper coil; the microwave source is connected to the copper coil, and the copper coil is arranged around the optical fiber probe.

6. The position detection system of the storage unit in the SRAM chip according to claim 5, characterized in that: The microwave excitation module also includes a power amplifier and an isolator; The first end of the power amplifier is connected to the microwave source; the second end of the power amplifier is connected to the first end of the isolator; and the second end of the isolator is connected to the copper coil.

7. The position detection system of the storage unit in the SRAM chip according to claim 1, characterized in that: It also includes an electromagnetic shielding box; the electromagnetic shielding box is used to enclose the SRAM chip to be detected, the tip of the optical fiber probe and the electric translation stage.

8. The position detection system of the storage unit in the SRAM chip according to claim 1, characterized in that: It also includes a shockproof platform; all components in the optical excitation module are fixed on the shockproof platform.

9. A method for detecting the position of a storage unit in an SRAM chip, characterized in that: A position detection system for a storage unit in an SRAM chip according to any one of claims 1 to 8, the position detection system comprising an electric translation stage, an optical excitation module, a microwave excitation module, an avalanche photodetector, a signal analysis device and a control module; the optical excitation module comprises a laser, a dichroic mirror, an objective lens and an optical fiber probe; the tip of the optical fiber probe is provided with diamond particles containing NV color centers; The position detection method comprises: Place the SRAM chip to be tested on the electric translation stage; Adjusting the relative positions of the optical fiber probe, the microwave excitation module and the SRAM chip to be detected; Setting the working state of the SRAM chip to be detected to a writing state and writing a square wave signal of a preset frequency to a target storage unit of the SRAM chip to be detected; Starting the optical excitation module and the microwave excitation module to excite the diamond particles containing NV color centers to radiate red fluorescence; Using the avalanche photodetector to generate a voltage signal from the red fluorescence and outputting the voltage signal to the signal analysis device; Analyzing the voltage signal using the signal analysis device; Keeping the positions of the optical fiber probe and the microwave excitation module unchanged, using the electric translation stage to adjust the position of the SRAM chip to be detected and continuing to use the signal analysis device to analyze the voltage signal continuously output by the avalanche photodetector; When the voltage signal is consistent with the input signal period or frequency of the SRAM chip to be detected, the operation of the electric translation stage is stopped and the current coordinates are recorded; The current coordinates are determined as the location of the target storage unit.

10. The method for detecting the position of a storage unit in an SRAM chip according to claim 9, characterized in that: Also includes: Using diamond particles containing NV color centers with different crystal particle diameters, the SRAM chip to be tested is tested multiple times to obtain multiple spatial resolution test results; Based on the multiple spatial resolution detection results, the relationship between the spatial resolution of the diamond color center sensor and the crystal grain diameter is determined.

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