Detection system performance detection method and device, detection system and storage medium
By acquiring and modifying beam current values in SEM, the problem of difficulty in evaluating the performance of SEM detection systems is solved, enabling rapid and accurate performance evaluation and reducing detection costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-03-24
AI Technical Summary
Existing technologies make it difficult to quantify the performance of detection systems in SEM using simple and rapid methods.
The detection quantum efficiency is determined by acquiring the first grayscale data of the measurement image under blocked electron beam conditions and changing the beam current value under electron beam illumination of a reference sample. The performance of the detection system is then evaluated by combining the signal-to-noise ratio and dwell time.
It enables rapid and convenient evaluation of the performance of the detection system, improves detection accuracy, reduces detection costs, and is applicable to actual SEM products.
Smart Images
Figure CN121721069A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of detection equipment, and in particular to a detection system performance detection method and device, a detection system, and a storage medium. BACKGROUND
[0002] As an important micro-morphology analysis instrument, the imaging quality of a SEM (Scanning Electron Microscope) depends largely on the performance of a detection system. The detection system in a SEM generally includes an electron beam modulation device in a lens barrel, an electron detector, and a circuit acquisition and imaging system after the detector, and other components. Since the detection system involves multiple interrelated components, its overall performance is difficult to be quantitatively evaluated by a simple single parameter, and only through a complex test system and test method can the performance of the detection system be evaluated. Therefore, there is an urgent need for a simple and fast method for evaluating the performance of the detection system. SUMMARY
[0003] To solve the problems in the prior art, the present application provides a detection system performance detection method and device, a detection system, and a storage medium, which can evaluate the performance of the detection system by a simple and fast method. The technical solution is as follows:
[0004] In one aspect, a detection system performance detection method is provided, which includes:
[0005] In the case of blocking the electron beam, first gray scale data of a measurement image is acquired;
[0006] In the case of irradiating a reference sample with an electron beam, the electron beam current of the electron beam is controlled to change according to a plurality of beam current values in a beam current value sequence, and second gray scale data of a measurement image corresponding to each beam current value in the beam current value sequence is determined;
[0007] For each beam current value, the step of determining the detection quantum efficiency is performed, including: based on the first gray scale data, the second gray scale data corresponding to the beam current value, the beam current value, and the dwell time, determining the corresponding detection quantum efficiency;
[0008] Based on each beam current value in the beam current value sequence and the corresponding detection quantum efficiency, the performance of the detection system is determined.
[0009] Optionally, the step of determining the corresponding detection quantum efficiency based on the first gray scale data, the second gray scale data corresponding to the beam current value, the beam current value, and the dwell time includes:
[0010] determining a first signal-to-noise ratio based on the first gray scale data and the second gray scale data corresponding to the beam current value;
[0011] The second signal-to-noise ratio is determined based on the beam current value and residence time;
[0012] The corresponding detection quantum efficiency is determined based on the first signal-to-noise ratio and the second signal-to-noise ratio.
[0013] Optionally, the second signal-to-noise ratio is positively correlated with the beam current value, and the second signal-to-noise ratio is also positively correlated with the dwell time.
[0014] Optionally, the first grayscale data includes a first grayscale average value, and the second grayscale data corresponding to the electron beam includes a second grayscale value and a grayscale standard deviation; determining the first signal-to-noise ratio based on the first grayscale data and the second grayscale data corresponding to the electron beam includes:
[0015] The grayscale parameters are determined based on the second grayscale average value and the first grayscale average value;
[0016] The first signal-to-noise ratio is determined based on the grayscale parameter and the grayscale standard deviation.
[0017] Optionally, determining the first signal-to-noise ratio based on the grayscale parameter and the grayscale standard deviation includes:
[0018] The ratio of the grayscale parameter to the grayscale standard deviation is determined as the first signal-to-noise ratio.
[0019] Optionally, determining the corresponding detection quantum efficiency based on the first signal-to-noise ratio and the second signal-to-noise ratio includes:
[0020] The ratio of the square of the first signal-to-noise ratio to the square of the second signal-to-noise ratio is determined as the corresponding detection quantum efficiency.
[0021] Optionally, before acquiring the first grayscale data of the measurement image while blocking the electron beam, the method further includes:
[0022] Adjust the voltage of the photomultiplier tube until the average grayscale of the measured image reaches a preset threshold, then fix the voltage of the photomultiplier tube.
[0023] Optionally, after controlling the electron beam current to change according to multiple beam current values in the beam current value sequence, and determining the second grayscale data corresponding to each beam current value in the beam current value sequence, the method further includes:
[0024] Determine whether there is a linear relationship between multiple beam values in the beam value sequence and their corresponding second grayscale data;
[0025] If multiple beam values in the beam value sequence are linearly related to their corresponding second grayscale data, then the step of determining the detection quantum efficiency is performed.
[0026] Optionally, determining the performance of the detection system based on each beam value in the beam value sequence and its corresponding detection quantum efficiency includes:
[0027] Based on each beam value in the beam value sequence and its corresponding detection quantum efficiency, a detection quantum efficiency curve is determined;
[0028] The performance of the detection system is determined based on the quantum efficiency curve.
[0029] Optionally, determining the performance of the detection system based on the detection quantum efficiency curve includes:
[0030] Determine the target line segment in the detection quantum efficiency curve, wherein the absolute value of the slope of the line connecting the start and end points of the target line segment is less than or equal to a slope threshold.
[0031] The performance of the detection system is determined based on the target line segment and its corresponding detection quantum efficiency.
[0032] On the other hand, a detection system performance testing device is provided, the device comprising:
[0033] The acquisition module is used to acquire the first grayscale data of the measurement image while blocking the electron beam;
[0034] The control module is used to control the electron beam current of the electron beam to change according to multiple beam current values in the beam current value sequence when the electron beam irradiates the reference sample, and to determine the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence.
[0035] The first determining module is used to perform the step of determining the detection quantum efficiency for each beam value, including: determining the corresponding detection quantum efficiency based on the first grayscale data, the second grayscale data corresponding to the beam value, the beam value and the dwell time;
[0036] The second determining module is used to determine the performance of the detection system based on each beam value in the beam value sequence and its corresponding detection quantum efficiency.
[0037] On the other hand, a detection system is provided, including:
[0038] A detector is used to convert optical signals into electrical signals and amplify them so that the detection system can collect the signals generated by the interaction between the electron beam and the reference sample;
[0039] Memory, used to store computer programs and / or instructions;
[0040] A processor is configured to implement the steps of the above-described detection system performance testing method when executing computer programs and / or instructions stored in the memory.
[0041] On the other hand, a computer-readable storage medium is provided, wherein a computer program is stored therein, and when the computer program is executed by a processor, it implements the steps of the above-described detection system performance testing method.
[0042] On the other hand, a computer program product containing instructions is provided, which, when run on a computer, cause the computer to perform the steps of the above-described detection system performance testing method.
[0043] The technical solution provided in this application can bring at least the following beneficial effects:
[0044] This application obtains first grayscale data of a measurement image under blocked electron beam conditions. Then, under electron beam irradiation of a reference sample, the beam current value of the electron beam is controlled to change according to multiple beam current values in a beam current value sequence, resulting in corresponding second grayscale data. For each beam current value, a step to determine the detection quantum efficiency is performed. Subsequently, the performance of the detection system is determined based on each beam current value and the detection quantum efficiency. This allows for a simple and rapid method to evaluate the performance of the detection system, simplifying detection complexity, improving detection accuracy, and quickly measuring the system's response to different signal inputs. Furthermore, compared to step-by-step testing of detector components such as scintillators, light guides, and photomultiplier tubes, or testing using a separate device that directly bombards the detector with a controllable electron beam, the method provided in this application allows for rapid and standardized testing on actual SEM products, offering greater speed, convenience, and cost-effectiveness. Attached Figure Description
[0045] Figure 1 A schematic diagram of an implementation environment provided for an embodiment of this application;
[0046] Figure 2 A schematic diagram illustrating another implementation environment provided for an embodiment of this application;
[0047] Figure 3 A flowchart illustrating a detection system performance testing method provided in this application embodiment;
[0048] Figure 4 A schematic diagram of a linear beam grayscale curve provided for an embodiment of this application;
[0049] Figure 5 A schematic diagram of a detection quantum efficiency curve provided in an embodiment of this application;
[0050] Figure 6 This is a schematic diagram of the structure of a detection system performance testing device provided in an embodiment of this application. Detailed Implementation
[0051] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.
[0052] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.
[0053] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).
[0054] Before providing a detailed explanation of the detection system performance testing method provided in the embodiments of this application, the implementation environment involved in the embodiments of this application will be introduced first.
[0055] Please refer to Figure 1 , Figure 1 This is a schematic diagram of an implementation environment according to an exemplary embodiment, the implementation environment including a detection system 1, the detection system 1 including a detector 11, a memory 12 and a processor 13.
[0056] The detector 11 converts optical signals into electrical signals and amplifies them so that the detection system can collect the signals generated by the interaction between the electron beam and the reference sample; the memory 12 is used to store computer programs and / or instructions; the processor 13 is used to implement the detection system performance detection method in this application embodiment when executing the computer programs and / or instructions stored in the memory 12. That is, the detection system 1 can perform performance evaluation autonomously through its own processor 13.
[0057] In some embodiments, please refer to Figure 2 The implementation environment may also include a detection system 1 and a host computer 2, which are connected to the detection system 1. This connection may be a wired connection or a wireless connection, and this application embodiment does not limit this.
[0058] The host computer 2 can acquire the first grayscale data of the measurement image when the electron beam is blocked. Then, when the electron beam irradiates the reference sample, it controls the electron beam current to change according to multiple beam current values in the beam current value sequence, and determines the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence. For each beam current value, it performs the step of determining the detection quantum efficiency. Then, based on each beam current value in the beam current value sequence and its corresponding detection quantum efficiency, it determines the performance of the detection system 1.
[0059] The host computer 2 can be any electronic product that can interact with the user through one or more methods such as a keyboard, touchpad, touch screen, remote control, voice interaction or handwriting device, such as PC (Personal Computer), mobile phone, smartphone, PDA (Personal Digital Assistant), wearable device, PPC (Pocket PC), tablet computer, smart car system, smart TV, smart speaker, etc.
[0060] Those skilled in the art should understand that the above-described detection system 1 and host computer 2 are merely examples. Other existing or future detection systems or host computers that are applicable to the embodiments of this application should also be included within the scope of protection of the embodiments of this application, and are hereby incorporated by reference.
[0061] It should be noted that the application scenarios and implementation environments described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the emergence of new application scenarios and the evolution of implementation environments, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.
[0062] Next, a method for detecting the performance of a detection system provided in the embodiments of this application will be explained in detail.
[0063] Figure 3 This is a diagram illustrating a detection system performance testing method provided in an embodiment of this application. Please refer to it. Figure 3 The method includes the following steps:
[0064] Step 301: Acquire the first grayscale data of the measurement image while blocking the electron beam.
[0065] In some embodiments, the electron beam can be blocked by a blanking device or an internal gas valve to facilitate subsequent dark noise measurements. The blanking device, also known as an electron beam blanking device or beam blanking device, is an electro-optical component inside the SEM tube that can quickly and controllably "cut off" or "deflect" the electron beam, preventing it from reaching the sample surface for subsequent dark noise measurements.
[0066] It should be noted that the above description refers to blocking the electron beam using a blanking device or an internal gas valve in the lens barrel. Alternatively, other methods can be used to block the electron beam in practice. This application does not limit this approach.
[0067] Since noise is random, and these random noise fluctuations are amplified when the voltage of the photomultiplier tube increases and the gain increases, this manifests as fluctuations in pixel grayscale values in the measurement image. To measure a true and meaningful noise level, the photomultiplier tube voltage can be adjusted before acquiring the first grayscale data of the measurement image, with the electron beam blocked, until the average grayscale of the measurement image reaches a preset threshold, at which point the photomultiplier tube voltage is fixed. Fixing the photomultiplier tube voltage fixes the amplification factor of the noise, thus ensuring that the first grayscale data of the acquired measurement image reflects a true and meaningful noise level, enabling accurate evaluation of detector performance in subsequent processes.
[0068] In some embodiments, the voltage of the photomultiplier tube can be adjusted when the electron beam is not blocked. That is, the voltage of the photomultiplier tube can be gradually increased or decreased when the electron beam is not blocked, and the average gray level of the measured image under different voltages can be monitored. The average gray level of the measured image under the current voltage can be compared with the size of a preset threshold to determine whether the voltage of the photomultiplier tube can be fixed at the current voltage.
[0069] For example, when the voltage of the photomultiplier tube is gradually increased (decreased), if the average gray level of the measured image is less than a preset threshold at the current voltage, the voltage of the photomultiplier tube can be increased (decreased) to update the current voltage, and the average gray level of the updated measured image can be further compared with the preset threshold. If the average gray level of the measured image is greater than or equal to the preset threshold at the current voltage, the voltage of the photomultiplier tube can be fixed at the current voltage.
[0070] In some embodiments, the preset threshold may include a first preset sub-threshold and a second preset sub-threshold, where the first preset sub-threshold is less than the second preset sub-threshold. Therefore, when the average grayscale of the measured image is greater than or equal to the first preset sub-threshold and less than or equal to the second preset sub-threshold, the voltage of the photomultiplier tube is fixed. For example, if the first preset sub-threshold is 20 and the second preset sub-threshold is 30, then when the average grayscale of the measured image is greater than or equal to 20 and less than or equal to 30, the voltage of the photomultiplier tube can be fixed.
[0071] In addition, in some embodiments, in order to prevent the signal (i.e., the electrical signal generated by the electron beam and converted by the detector) from being truncated in subsequent processing, a bias voltage can be set when the electron beam is blocked. Thus, even in the absence of an electron beam, this bias will output a small positive voltage, so that the measurement image can still show a certain grayscale.
[0072] Continuing from the above description, after setting the bias voltage and fixing the photomultiplier tube, the electron beam can be blocked by using a blanking device or an internal valve of the lens barrel, and a measurement image can be acquired. At this time, the acquired measurement image is a dark noise image, and the first grayscale data of the acquired measurement image is also dark noise data.
[0073] In some embodiments, before the detection system begins detection, the SEM's field of view needs to be moved to the surface of a reference sample (such as a featureless wafer) to set the SEM magnification. This is to avoid situations where excessive magnification leads to excessively high beam current density on the sample surface, causing carbon blackening and affecting subsequent accuracy; or to avoid situations where insufficient magnification results in differences in electron collection efficiency at different locations. For example, the SEM magnification can be controlled between 10k and 50k.
[0074] Step 302: When the reference sample is irradiated by an electron beam, the electron beam current is controlled to change according to multiple beam current values in the beam current value sequence, and the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence is determined.
[0075] In some embodiments, the electron beam can be allowed to irradiate the reference sample by closing the blanking device or opening the gas valve inside the microscope tube. That is, if the electron beam is blocked by the blanking device in step 301, then the electron beam can be allowed to irradiate the reference sample by closing the blanking device; if the electron beam is blocked by the gas valve inside the microscope tube in step 301, then the electron beam can be allowed to irradiate the reference sample by opening the gas valve inside the microscope tube.
[0076] Since the performance of a detection system is not measured by a single signal level, but rather by changing the signal quantity, the signal input can be altered by changing the electron beam current. This allows the detection system to assess its response to different signal inputs.
[0077] In some embodiments, the beam current value sequence includes multiple different beam current values, thereby allowing the electron beam current of the electron beam to be changed according to the multiple beam current values in the beam current value sequence, and obtaining a measurement image corresponding to each beam current value in the beam current value sequence. Then, the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence can be determined.
[0078] As an example, assuming the beam current values in the beam current value sequence include X1, X2, X3, and X4, then, when the electron beam irradiates the reference sample, the electron beam current can be controlled to change to X1, and the measurement image corresponding to X1 can be acquired. Based on the measurement image, the second grayscale data corresponding to the beam current value X1 can be determined. Then, the electron beam current can be controlled to change to X2, and the measurement image corresponding to X2 can be acquired. Based on the measurement image, the second grayscale data corresponding to the beam current value X2 can be determined. This process can be repeated to obtain the second grayscale data corresponding to the beam current values X3 and X4, respectively. Thus, the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence can be obtained.
[0079] It should be noted that the minimum beam current value in this beam current value sequence can be 5-10 pA, and the maximum can be the current that the detector can receive, such as 100 pA. In other words, the embodiments of this application do not limit the beam current value sequence.
[0080] As the electron beam current gradually increases, a carbonization layer may form on the surface of the reference sample (such as without a special silicon wafer). Therefore, in the process of detecting the detector performance, it is necessary to change the position of the electron beam irradiating the reference sample and move it out of the area covered by the carbonization layer.
[0081] In some embodiments, only one frame of measurement image needs to be acquired for each beam current value. This avoids additional processing of multiple frames, ensuring that subsequent results, such as the signal-to-noise ratio, accurately reflect the performance of the detection system itself.
[0082] In addition, in some embodiments, in order to ensure the accuracy of the performance evaluation of the detection system, when the electron beam irradiates the reference sample, other parameters, such as the SEM magnification and the voltage of the photomultiplier tube, need to be the same as those when the electron beam is blocked, except for the difference between whether the electron beam irradiates the reference sample or not.
[0083] In some embodiments, in order to confirm whether the detection system responds linearly to the electron beam, and to troubleshoot the components of the detection system in the case of a nonlinear response, after controlling the electron beam current to change according to multiple beam current values in the beam current value sequence and determining the second grayscale data corresponding to each beam current value in the beam current value sequence, it can also be determined whether the multiple beam current values in the beam current value sequence and their corresponding second grayscale data are linearly related. If the multiple beam current values in the beam current value sequence and their corresponding second grayscale data are linearly related, then the step of determining the detection quantum efficiency is performed.
[0084] In other words, if multiple beam values in the beam value sequence are linearly related to their corresponding second grayscale data, it indicates that no component in the detection system is faulty. Therefore, the performance of the detection system can be evaluated, and the subsequent step 303 of determining the detection quantum efficiency can be executed. If multiple beam values in the beam value sequence are not linearly related to their corresponding second grayscale data, it indicates that signal distortion may have occurred. If the performance of the detection system is tested now, an accurate performance result cannot be obtained. Therefore, it is necessary to check each component in the detection system until multiple beam values in the beam value sequence are linearly related to their corresponding second grayscale data.
[0085] In some embodiments, a beam grayscale curve can be obtained based on multiple beam values in the beam value sequence and their corresponding second grayscale data. Then, based on the beam grayscale curve, it can be more intuitively determined whether the multiple beam values and their corresponding second grayscale data are linearly related.
[0086] As an example, please refer to Figure 4 , Figure 4 This is a schematic diagram of a linear beam current grayscale curve provided in an embodiment of this application, where the horizontal axis represents the beam current value and the vertical axis represents the second grayscale data. Figure 4 As can be seen, the second grayscale data also increases linearly with the increase of the beam current value. Therefore, it can be determined that multiple beam current values in the beam current value sequence have a linear relationship with their corresponding second grayscale data, and the subsequent steps to determine the detection quantum efficiency can be performed.
[0087] Step 303: For each beam current value, perform the step of determining the detection quantum efficiency, including: determining the corresponding detection quantum efficiency based on the first grayscale data, the second grayscale data corresponding to the beam current value, the beam current value, and the residence time.
[0088] The detection quantum efficiency may vary depending on the beam current value. Therefore, for each beam current value, the detection quantum efficiency corresponding to that beam current value needs to be determined based on the first grayscale data, the beam current value and its corresponding second grayscale data, and the dwell time.
[0089] In some embodiments, the dwell time of the electron beam is set within a reasonable range according to the actual situation. If the dwell time is too short, the signal-to-noise ratio will be too poor. If the dwell time is too long, the charging effect will occur. In this application embodiment, the preferred dwell time of the electron beam is a value between 500ns and 1000ns.
[0090] In some embodiments, the corresponding detection quantum efficiency can be determined by following steps (1)-(3);
[0091] (1) Determine the first signal-to-noise ratio based on the first grayscale data and the second grayscale data corresponding to the beam current value.
[0092] In some embodiments, the first grayscale data includes a first grayscale average value, and the second grayscale data corresponding to the beam current value includes a second grayscale value and a grayscale standard deviation. The grayscale parameters can be determined first based on the second grayscale average value and the first grayscale average value, and then the first signal-to-noise ratio can be determined based on the grayscale parameters and the grayscale standard deviation.
[0093] Wherein, the first gray-scale average value is the average gray-scale value of the measurement image under the condition of blocked electron beam, the second gray-scale average value is the average gray-scale value of the measurement image under the condition of electron beam irradiation of the reference sample corresponding to the current beam current value, and the gray-scale standard deviation is the gray-scale standard deviation of the measurement image under the condition of electron beam irradiation of the reference sample corresponding to the current beam current value. Since the second gray-scale average value and the gray-scale standard deviation may change under different beam current values, the first signal-to-noise ratio obtained under different beam current values will also change.
[0094] It should be noted that the first grayscale average, the second grayscale average, and the grayscale standard deviation mentioned above can be determined using existing calculation methods. This application does not limit these methods.
[0095] In some embodiments, the reference sample is a featureless silicon wafer. Therefore, the measurement images obtained, whether with the electron beam blocked or with the reference sample irradiated by electrons, are images of the featureless silicon wafer. A featureless silicon wafer refers to a specially prepared silicon wafer with an extremely flat, smooth, and clean surface, lacking any natural or artificial microstructure. Under ideal observation conditions, it should appear as a perfectly uniform gray area. Because of its "featurelessness," any inhomogeneities (such as variations in brightness, texture, or graininess) obtained when probed by a SEM system are theoretically not from the reference sample itself, but from the probe system. Therefore, the performance of the probe system can be evaluated using the first grayscale data, second grayscale data, and grayscale standard deviation of the measurement image of the featureless silicon wafer.
[0096] As described above, the first gray-scale average value is obtained under electron beam obstruction, while the second gray-scale average value is obtained under electron beam illumination of the reference sample. Since there is no electron beam, the first gray-scale average value can be considered the average value of the background or dark signal, representing the inherent offset of the detection system itself. Because the electron beam can illuminate the surface of the reference sample, the second gray-scale average value can represent the average signal intensity measured from the reference sample, such as a featureless silicon wafer, in the presence of noise.
[0097] In some embodiments, grayscale parameters can be determined based on a second grayscale average value and a first grayscale average value. As an example, grayscale parameters can be determined by subtracting the first grayscale average value from the second grayscale average value. That is, the grayscale parameter is a parameter after deducting the system background, which is a net signal. Therefore, the grayscale parameter can be used to characterize the signal electron emission rate of silicon materials.
[0098] It should be noted that the above explanation describes determining the grayscale parameter by subtracting the first grayscale average from the second grayscale average. Alternatively, in application, the grayscale parameter can be determined in other ways. This application does not limit this method.
[0099] In some embodiments, for a measurement image of a featureless silicon wafer, any pixel brightness fluctuation is considered noise. Therefore, the grayscale standard deviation can be used to indicate the total noise level, such as shot noise and electrical noise, in the measurement image. The ratio of the grayscale parameter to the grayscale standard deviation directly reflects how many times the effective signal strength is relative to the noise level. Therefore, by determining the ratio of the grayscale parameter to the grayscale standard deviation as the first signal-to-noise ratio, the ability of the detection system to acquire reliable images can be evaluated.
[0100] (2) Determine the second signal-to-noise ratio based on the beam current value and residence time.
[0101] Because different SEMs use different types of electron beams, and the number of scattering events within the microscope tube varies, using absolute signal-to-noise ratio (SNR) to assess the performance of the detection system can introduce significant errors. Since the number of electrons falling onto the reference sample surface typically follows an ideal Poisson distribution, a theoretical SNR (containing only shot noise) can be determined based on the number of electrons falling onto the reference sample surface per unit time and used as a benchmark for comparison. The ideal Poisson distribution describes the probability distribution of the number of random events occurring within a fixed time or space; its core principle is that the events occur completely randomly and independently.
[0102] Continuing from the previous description, the theoretical signal-to-noise ratio (SNR) of the shot noise of the electron beam falling onto the surface of the reference sample, namely the second SNR, is related to the beam current and residence time of the electron beam. Therefore, the second SNR can be determined based on the beam current and residence time of the electron beam.
[0103] In some embodiments, the second signal-to-noise ratio is positively correlated with the beam current value and also positively correlated with the dwell time.
[0104] As an example, suppose there are beam current values A and B. If beam current value A is greater than beam current value B and the residence time of the electron beam remains unchanged, then the second signal-to-noise ratio (SNR) corresponding to beam current value A is greater than the second SNR corresponding to beam current value B. As another example, if beam current value A is equal to beam current value B and the residence time of beam current value A is less than the residence time of beam current value B, then the second SNR corresponding to beam current value A is less than the second SNR corresponding to beam current value B.
[0105] (3) Determine the corresponding detection quantum efficiency based on the first signal-to-noise ratio and the second signal-to-noise ratio.
[0106] In some embodiments, the ratio of the square of the first signal-to-noise ratio to the square of the second signal-to-noise ratio can be determined as the corresponding detection quantum efficiency.
[0107] It should be noted that the above explanation uses the ratio of the square of the first signal-to-noise ratio to the square of the second signal-to-noise ratio as the corresponding detection quantum efficiency. Alternatively, in applications, other methods can be used to determine the detection quantum efficiency. This application does not limit this approach.
[0108] Step 304: Determine the performance of the detection system based on each beam value in the beam value sequence and its corresponding detection quantum efficiency.
[0109] For each beam value in the beam value sequence, its corresponding detection quantum efficiency can be obtained. Therefore, the performance of the detection system can be determined based on the beam value and its corresponding detection quantum efficiency.
[0110] In some embodiments, in order to intuitively determine the performance of the detection system, a detection quantum efficiency curve can be determined based on each beam value in the beam value sequence and its corresponding detection quantum efficiency, and then the performance of the detection system can be determined based on the detection quantum efficiency curve.
[0111] As an example, the detection quantum efficiency curve can be as follows: Figure 5 As shown, the horizontal axis of the detection quantum efficiency curve represents the beam current, and the vertical axis represents the detection quantum efficiency. From... Figure 5 As can be seen, the detection quantum efficiency changes with the beam current value of the electron beam. In the first stage, when the beam current value is X1 to X5, the efficiency increases; in the second stage, when the beam current value is X5 to X7, the detection quantum efficiency curve flattens out; and in the third stage, when the beam current value is X7 to X10, the detection quantum efficiency continues to increase.
[0112] In some embodiments, a target line segment in the detection quantum efficiency curve can be determined first. The absolute value of the slope of the line connecting the start and end points of the target line segment is less than or equal to a slope threshold. Based on the target line segment and its corresponding detection quantum efficiency, the performance of the detection system is determined.
[0113] In other words, in order to determine the linear range of the detection system and to determine the performance of the detection system in subsequent processes based on the linear range and the detection quantum efficiency corresponding to that linear range, we can first determine the target curve segment in the detection efficiency curve. The absolute value of the slope of the line connecting the start and end points of the target curve segment is less than or equal to the slope threshold. Then, based on the beam current range corresponding to the target curve segment and the detection quantum efficiency, we can determine the performance of the detection system. That is, the beam current range corresponding to the target curve segment can be determined as the linear range of the detection system.
[0114] Determining the linear range of the detection system ensures that the electron beam current remains within this range during actual use, minimizing signal distortion and preventing a decline in detection performance. Determining the detection quantum efficiency corresponding to the linear range allows for the evaluation of the detection system's performance; higher quantum efficiency indicates better performance, and vice versa. Furthermore, quantum efficiency detection enables the assessment of whether the detectors within the system are functioning correctly and facilitates rapid troubleshooting of issues such as abnormal noise and efficiency instability.
[0115] As an example, assuming the slope threshold is 0.1, meaning the line connecting the start and end points of the target curve segment should be roughly parallel to the horizontal axis, then in... Figure 5In the detection efficiency curves shown, the curve for the second stage, i.e., the beam current value from X5 to X7, can be defined as the target curve segment. Furthermore, the beam current value range corresponding to this target curve segment is X5 to X7, meaning the linear range of the detection system is X5 to X7. Figure 5 As can be seen, the detection quantum efficiency corresponding to the target curve segment is approximately 0.125. Therefore, the performance of the detection system can be evaluated by using the range of the linear interval and the value of the detection quantum efficiency corresponding to the linear interval.
[0116] This application embodiment obtains the first grayscale data of the measurement image under blocked electron beam conditions. Under electron beam irradiation of a reference sample, the beam current value of the electron beam is controlled to change according to multiple beam current values in a beam current value sequence, resulting in corresponding second grayscale data. Then, for each beam current value, a step to determine the detection quantum efficiency is performed. Subsequently, the performance of the detection system is determined based on each beam current value and the detection quantum efficiency. This allows for a simple and rapid method to evaluate the performance of the detection system, simplifying detection complexity, improving detection accuracy, and quickly measuring the response capability of the detection system to different signal inputs. Furthermore, compared to step-by-step testing of the efficiency of detector components in the detection system, such as scintillators, light guides, and photomultiplier tubes, or testing using a separate device that directly bombards the detector with a controllable electron beam, the method provided in this application embodiment can perform rapid and standardized testing on actual SEM products, making it faster, simpler, and lower in cost.
[0117] Figure 6 This is a schematic diagram of the structure of a detection system performance testing device provided in an embodiment of this application. See also... Figure 6 The device includes an acquisition module 601, a control module 602, a first determination module 603, and a second determination module 604.
[0118] The acquisition module 601 is used to acquire the first grayscale data of the measurement image when the electron beam is blocked;
[0119] The control module 602 is used to control the electron beam current of the electron beam to change according to multiple beam current values in the beam current value sequence when the electron beam irradiates the reference sample, and to determine the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence.
[0120] The first determining module 603 is used to perform the step of determining the detection quantum efficiency for each beam value, including: determining the corresponding detection quantum efficiency based on the first grayscale data, the second grayscale data corresponding to the beam value, the beam value and the dwell time;
[0121] The second determining module 604 is used to determine the performance of the detection system based on each beam value in the beam value sequence and its corresponding detection quantum efficiency.
[0122] The embodiments of this application enable performance evaluation of the detection system using a simple and rapid method.
[0123] It should be noted that the detection system performance testing device provided in the above embodiments is only illustrated by the division of the above functional modules when performing performance testing on the detection system. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the detection system performance testing device provided in the above embodiments and the detection system performance testing method embodiments belong to the same concept, and their specific implementation process is described above and will not be repeated here.
[0124] Those skilled in the art will understand that all or part of the functions of the various methods in the above embodiments can be implemented by hardware or by computer programs. When all or part of the functions in the above embodiments are implemented by computer programs, the program can be stored in a computer-readable storage medium, which may include: read-only memory, random access memory, disk, optical disk, hard disk, etc., and the program is executed by a computer to achieve the above functions. For example, the program can be stored in the memory of a device, and when the program in the memory is executed by the processor, all or part of the above functions can be achieved. In addition, when all or part of the functions in the above embodiments are implemented by computer programs, the program can also be stored in a server, another computer, disk, optical disk, flash drive, or external hard drive, etc., and can be downloaded or copied to the memory of a local device, or the system of the local device can be updated. When the program in the memory is executed by the processor, all or part of the functions in the above embodiments can be achieved.
[0125] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.
Claims
1. A method for testing the performance of a detection system, characterized in that, The method includes: Acquire the first grayscale data of the measurement image while blocking the electron beam; When an electron beam irradiates a reference sample, the electron beam current of the electron beam is controlled to change according to multiple beam current values in a beam current value sequence, and the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence is determined. For each beam current value, the step of determining the detection quantum efficiency is performed, including: determining the corresponding detection quantum efficiency based on the first grayscale data, the second grayscale data corresponding to the beam current value, the beam current value, and the dwell time; The performance of the detection system is determined based on each beam value in the beam value sequence and its corresponding detection quantum efficiency.
2. The method as described in claim 1, characterized in that, The step of determining the corresponding detection quantum efficiency based on the first grayscale data, the second grayscale data corresponding to the beam current value, the beam current value, and the residence time includes: The first signal-to-noise ratio is determined based on the first grayscale data and the second grayscale data corresponding to the beam current value; The second signal-to-noise ratio is determined based on the beam current value and residence time; The corresponding detection quantum efficiency is determined based on the first signal-to-noise ratio and the second signal-to-noise ratio.
3. The method as described in claim 2, characterized in that, The second signal-to-noise ratio is positively correlated with the beam current value, and the second signal-to-noise ratio is also positively correlated with the dwell time.
4. The method as described in claim 2, characterized in that, The first grayscale data includes a first grayscale average value, and the second grayscale data corresponding to the electron beam includes a second grayscale value and a grayscale standard deviation; determining the first signal-to-noise ratio based on the first grayscale data and the second grayscale data corresponding to the electron beam includes: The grayscale parameters are determined based on the second grayscale average value and the first grayscale average value; The first signal-to-noise ratio is determined based on the grayscale parameter and the grayscale standard deviation.
5. The method as described in claim 4, characterized in that, Determining the first signal-to-noise ratio based on the grayscale parameters and the grayscale standard deviation includes: The ratio of the grayscale parameter to the grayscale standard deviation is determined as the first signal-to-noise ratio.
6. The method as described in claim 2, characterized in that, The step of determining the corresponding detection quantum efficiency based on the first signal-to-noise ratio and the second signal-to-noise ratio includes: The ratio of the square of the first signal-to-noise ratio to the square of the second signal-to-noise ratio is determined as the corresponding detection quantum efficiency.
7. The method as described in claim 1, characterized in that, Before acquiring the first grayscale data of the measurement image while blocking the electron beam, the method further includes: Adjust the voltage of the photomultiplier tube until the average grayscale of the measured image reaches a preset threshold, then fix the voltage of the photomultiplier tube.
8. The method as described in claim 1, characterized in that, After controlling the electron beam current to change according to multiple beam current values in the beam current value sequence, and determining the second grayscale data corresponding to each beam current value in the beam current value sequence, the method further includes: Determine whether there is a linear relationship between multiple beam values in the beam value sequence and their corresponding second grayscale data; If multiple beam values in the beam value sequence are linearly related to their corresponding second grayscale data, then the step of determining the detection quantum efficiency is performed.
9. The method as described in claim 1, characterized in that, Determining the performance of the detection system based on each beam value in the beam value sequence and its corresponding detection quantum efficiency includes: Based on each beam value in the beam value sequence and its corresponding detection quantum efficiency, a detection quantum efficiency curve is determined; The performance of the detection system is determined based on the quantum efficiency curve.
10. The method as described in claim 9, characterized in that, Determining the performance of the detection system based on the detection quantum efficiency curve includes: Determine the target line segment in the detection quantum efficiency curve, wherein the absolute value of the slope of the line connecting the start and end points of the target line segment is less than or equal to a slope threshold. The performance of the detection system is determined based on the target line segment and its corresponding detection quantum efficiency.
11. A detection system performance testing device, characterized in that, The device includes: The acquisition module is used to acquire the first grayscale data of the measurement image while blocking the electron beam; The control module is used to control the electron beam current of the electron beam to change according to multiple beam current values in the beam current value sequence when the electron beam irradiates the reference sample, and to determine the second grayscale data of the measurement image corresponding to each beam current value in the beam current value sequence. The first determining module is used to perform the step of determining the detection quantum efficiency for each beam value, including: determining the corresponding detection quantum efficiency based on the first grayscale data, the second grayscale data corresponding to the beam value, the beam value and the dwell time; The second determining module is used to determine the performance of the detection system based on each beam value in the beam value sequence and its corresponding detection quantum efficiency.
12. A detection system, characterized in that, include: A detector is used to convert optical signals into electrical signals and amplify them so that the detection system can collect the signals generated by the interaction between the electron beam and the reference sample; Memory, used to store computer programs and / or instructions; A processor for implementing the method of any one of claims 1 to 10 when executing a computer program and / or instructions stored in the memory.
13. A computer-readable storage medium, characterized in that, The medium stores a computer program that can be executed by a processor to implement the method as described in any one of claims 1 to 10.