Semiconductor wafer carrier lifetime measurement system and method

Abstract

The invention discloses a system and a method for measuring the service life of a carrier of a semiconductor wafer, which are applied to the technical field of wafer detection. The semiconductor wafer carrier lifetime measurement system comprises a signal generator, a light source and an image acquisition module. The signal generator can obtain a light source light-emitting pulse signal and an image acquisition pulse signal, and the gating opening time of the image acquisition pulse signal and the starting time of the enabling level of the light source light-emitting pulse signal have different delay durations in different light pulse periods of the light source light-emitting pulse signal. The light source can generate a pulse light beam and excite a semiconductor sample to generate carriers, and the image acquisition module can start to acquire fluorescence signals emitted by the carriers generated by the semiconductor sample in a recombination process at gating opening moments of different image acquisition periods so as to reflect a carrier recombination attenuation process. The carrier lifetime is measured through the dynamic attenuation characteristic that the intensity of the captured fluorescence signal changes along with time, and the accuracy of measuring the carrier lifetime is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of wafer detection, and particularly relates to a semiconductor wafer carrier lifetime measurement system and method. BACKGROUND

[0002] The semiconductor wafer will generate two kinds of non-equilibrium carriers, i.e. electrons and holes, under the excitation of an optical signal. The carrier lifetime is a relatively key performance index of the semiconductor wafer, which refers to the survival time of the carrier from generation to recombination. The longer the carrier lifetime is, the fewer impurities the semiconductor wafer has, and the better the crystal integrity is. Therefore, measuring the carrier lifetime of the wafer is an important means for evaluating the material performance of the semiconductor and optimizing the design of the semiconductor device.

[0003] In the prior art, a common measurement method is a time-resolved photoluminescence spectrum method (TRPL), which uses an ultrashort pulse laser to excite a sample and measures the time variation of the carrier concentration by detecting the light emission transient characteristics of the free exciton in the recombination process. However, this method needs to use a time correlation single photon counting technology (TCSPC) to record the photon arrival time, which leads to slow test speed of the above method and long time accumulation of the signal. The prior art also has a microwave photoconductance decay method, which needs to set a vibrating mirror and a displacement table and other modules to scan the semiconductor sample point by point, and measures the carrier lifetime of the semiconductor sample by detecting the variation of the carrier concentration at each detection point. However, in the case of a large area of the semiconductor sample, the point-by-point scanning using the foregoing method will increase the time consumption of measuring the semiconductor sample and reduce the efficiency of measuring the carrier lifetime of the semiconductor sample. SUMMARY

[0004] Embodiments of the application provide a semiconductor wafer carrier lifetime measurement system and method, which can solve the problems of long time consumption and low efficiency in measuring the carrier lifetime of a semiconductor sample by using related technologies.

[0005] In a first aspect, embodiments of the application provide a semiconductor wafer carrier lifetime measurement system, which comprises:

[0006] A signal generator is configured to acquire a light source light pulse signal and an image acquisition pulse signal, send the light source light pulse signal to a light source, and send the image acquisition pulse signal to an image acquisition module. The gate opening time of the image acquisition pulse signal and the starting time of the enable level of the light source light pulse signal have different delay durations in different light pulse periods of the light source light pulse signal.

[0007] A light source is electrically connected to the signal generator and configured to generate a pulsed light beam corresponding to the light source light pulse signal.

[0008] A carrier assembly for carrying a semiconductor sample in which excited carriers by a pulsed light beam can generate fluorescence;

[0009] An image acquisition module, electrically connected with the signal generator, configured to start to acquire the fluorescence signals emitted by the excited carriers in the recombination process at different positions of the semiconductor sample at the gate-on moments corresponding to different image acquisition periods, to obtain the fluorescence signal intensity corresponding to each position at different image acquisition moments respectively;

[0010] A processor, electrically connected with the image acquisition module, configured to determine the carrier lifetime at different positions of the semiconductor sample.

[0011] In a second aspect, the embodiments of the present application provide a semiconductor wafer carrier lifetime measurement method, which is applied to the semiconductor wafer carrier lifetime measurement system, and the method comprises:

[0012] The signal generator is configured to acquire the light source light pulse signal and the image acquisition pulse signal, and send the light source light pulse signal to the light source and send the image acquisition pulse signal to the image acquisition module, wherein the gate-on moment of the image acquisition pulse signal and the starting moment of the enable level of the light source light pulse signal have different delay durations in different light pulse periods of the light source light pulse signal.

[0013] A pulsed light beam corresponding to the light source light pulse signal is generated;

[0014] The image acquisition module is configured to start to acquire the fluorescence signals emitted by the excited carriers in the recombination process at different positions of the semiconductor sample at the gate-on moments corresponding to different image acquisition periods, to obtain the fluorescence signal intensity corresponding to each position at different image acquisition moments respectively.

[0015] The processor is configured to determine the carrier lifetime at different positions of the semiconductor sample.

[0016] The semiconductor wafer carrier lifetime measurement system and method provided by the embodiments of the present application, the system comprises a signal generator configured to acquire a light source light pulse signal and an image acquisition pulse signal, wherein the gate-on moment of the image acquisition pulse signal and the starting moment of the enable level of the light source light pulse signal have different delay durations in different light pulse periods of the light source light pulse signal. In this way, the image acquisition module starts to acquire the fluorescence signals emitted by the excited carriers in the recombination process at different positions of the semiconductor sample at the gate-on moments corresponding to different image acquisition periods, and the intensity of the fluorescence signals can reflect the carrier recombination decay process. In this way, the carrier lifetime at the corresponding position can be determined based on the signal intensity at different moments at the same position of the wafer. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced. Those drawings can help the ordinary skilled in the art to obtain other drawings without creative effort.

[0018] Figure 1 A structural schematic diagram of a semiconductor wafer carrier lifetime measurement system provided by an embodiment of the present application is shown.

[0019] Figure 2 A timing schematic diagram of a signal provided by an embodiment of the present application is shown.

[0020] Figure 3 A structural schematic diagram of a semiconductor wafer carrier lifetime measurement system provided by an embodiment of the present application is shown.

[0021] Figure 4 A flow schematic diagram of a semiconductor wafer carrier lifetime measurement method provided by an embodiment of the present application is shown.

[0022] Figure 5 A schematic diagram of a fluorescent image provided by an embodiment of the present application is shown.

[0023] Figure 6 A schematic diagram of a decay curve provided by an embodiment of the present application is shown.

[0024] Figure 7 A schematic diagram of a carrier lifetime image of a semiconductor sample provided by an embodiment of the present application is shown. DETAILED DESCRIPTION

[0025] The features and exemplary embodiments of various aspects of the present application will be described in detail below, in order to make the purposes, technical solutions and advantages of the present application more clear. The following will further describe the present application in detail with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, but not to limit the present application. The present application can be implemented without some of the specific details by those skilled in the art. The following description of the embodiments is only to provide a better understanding of the present application by showing examples of the present application.

[0026] It should be noted that, in this document, the terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between such entities or operations. Moreover, the terms "comprising", "containing", or any other variant thereof are intended to cover a non-exclusive inclusion, so that a process, method, article, or apparatus that comprises a list of elements does not only include those elements, but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without more limitations, the elements defined by the statement "comprising" do not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes the elements.

[0027] It should be noted that the acquisition, storage, use and processing of data in the embodiments of the present application comply with the relevant provisions of national laws and regulations.

[0028] It should be noted that in the embodiments of the present application, some software, components, models and other existing industry solutions may be mentioned, which should be considered as exemplary, and the purpose is only to illustrate the feasibility of the implementation of the technical solutions of the present application, but it does not mean that the applicant has or will necessarily use the solution.

[0029] In the related art, the traditional microwave photoconductive decay method is usually used to scan the semiconductor sample point by point, and then the carrier lifetime of the semiconductor sample is measured by detecting the change of the wafer carrier concentration at each detection point. It can be seen that the traditional method for determining the wafer carrier lifetime is limited by the point-by-point scanning. In the case of a large area of the semiconductor sample, using this method will increase the time-consuming of measuring the carrier lifetime of the semiconductor sample and reduce the efficiency of measuring the carrier lifetime of the semiconductor sample.

[0030] In order to solve the problems in the above-mentioned related art, the image acquisition module can be used to acquire the fluorescent signal emitted by the carrier in the semiconductor sample at different times during the recombination process, and analyze the decay of the fluorescent signal intensity at different times, so as to measure the carrier lifetime of the semiconductor sample.

[0031] The embodiments of the present application provide a semiconductor wafer carrier lifetime measurement system and method. First, the semiconductor wafer carrier lifetime measurement system provided by the embodiments of the present application will be described in detail.

[0032] Figure 1 The structure schematic diagram of the semiconductor wafer carrier lifetime measurement system provided by the embodiments of the present application is shown. As Figure 1As shown, the semiconductor wafer carrier lifetime measurement system comprises a signal generator 101, a light source 102, a bearing assembly 103, an image acquisition module 104, a semiconductor sample 105 and a processor 106.

[0033] The signal generator 101 is an instrument or device with signal sending function. The signal generator 101 can obtain a light source light pulse signal and an image acquisition pulse signal, and send the light source light pulse signal to the light source 102 and the image acquisition pulse signal to the image acquisition module 104.

[0034] The light source 102 is a device capable of emitting pulsed light, which can be electrically connected with the signal generator 101 to generate a pulsed light beam corresponding to the light source light pulse signal. The pulsed light beam can excite the semiconductor sample 105 to generate carriers and emit fluorescence in the process of carrier recombination. For example, the light source 102 can be a laser emitter, such as a YAG laser, a sapphire laser, etc.

[0035] The bearing assembly 103 can be used to carry the semiconductor sample 105.

[0036] The semiconductor sample 105 can be a semiconductor wafer, such as single crystal silicon, polycrystalline silicon, silicon carbide, etc. Alternatively, the semiconductor sample 105 can be a device or material made of a semiconductor wafer, such as a diode, a perovskite, etc. For different semiconductor samples 105, the way to determine the carrier lifetime by fitting is different. For high-purity single-crystal semiconductor wafers, such as intrinsic silicon, lightly doped gallium arsenide, etc., a single-exponential fitting method can be used. For heavily doped semiconductor wafers, such as N-type doped silicon carbide, P-type doped germanium, etc., a double-exponential fitting method can be used.

[0037] The image acquisition module 104 is used to acquire the fluorescence signal emitted by the excited carriers in the semiconductor sample 105 in the process of recombination. It can be an image acquisition module in a camera, such as an enhanced camera image acquisition module. In order to improve the efficiency of image acquisition, the image acquisition range of the image acquisition module 104 at least includes the range of the semiconductor sample 105 on the bearing assembly 103. Based on this, the image acquisition module 104 can acquire the fluorescence signal emitted by the excited carriers in the semiconductor sample 105 in the process of recombination at one time, improving the efficiency of image acquisition.

[0038] The image acquisition module 104 can be electrically connected with the processor 106 to start acquiring the fluorescence signal emitted by the excited carriers in the semiconductor sample 105 at different positions in the process of recombination at the starting time of the gate opening corresponding to different image acquisition periods, to obtain the fluorescence signal intensity at each position corresponding to multiple different image acquisition times respectively.

[0039] Since the semiconductor sample 105 will first be converted from the ground state to the excited state after receiving the pulsed light beam, carriers are generated, and the fluorescence signal is generated in the recombination process of the carriers from the excited state to the ground state. In order to improve the fluorescence signal acquisition efficiency, it is necessary to start acquiring the fluorescence signal after the pulsed light beam excites the semiconductor sample 105 to the highest fluorescence signal intensity, and there is a delay time between the start time of the gate opening time of the image acquisition pulse signal and the start time of the enable level of the light source light emitting pulse signal.

[0040] In order to enable the image acquisition module 104 to acquire the fluorescence signal at different times in the carrier recombination process and capture the decay curve of the fluorescence signal intensity over time in the carrier recombination process, the signal generator 101 can control different delay times in different light pulse periods of the light source light emitting pulse signal, as shown in Figure 2 .

[0041] Figure 2 A timing diagram of a signal provided by an embodiment of the present application is shown.

[0042] As shown in Figure 2 , the delay time corresponding to the first light pulse period is the length of time from t0 to t1, t0 is the start time of the enable level of the light source light emitting pulse signal in the first light pulse period, and t1 is the start time of the enable level of the image acquisition pulse signal in the first image acquisition period. At the same time, t1 is also the gate opening time of the image acquisition pulse signal in the first image acquisition period, that is, in the first image acquisition period, the fluorescence signal is acquired from t1, and the fluorescence signal within one gate width is acquired.

[0043] In the second light pulse period, the delay time of the first light pulse period is increased by Δt to obtain the delay time corresponding to the second light pulse period, and the delay time corresponding to the second light pulse period is the length of time from t4 to t6, wherein t4 is the start time of the enable level of the light source light emitting pulse signal in the second light pulse period, t5 is the start time of the enable level of the image acquisition pulse signal in the second image acquisition period, and t6 is the gate opening time of the image acquisition pulse signal in the second image acquisition period. That is, in the second image acquisition period, the fluorescence signal intensity is acquired from t6, and the fluorescence signal within one gate width is acquired.

[0044] In the third light pulse cycle, the delay duration of the second light pulse cycle is increased by Δt to obtain the delay duration corresponding to the third light pulse cycle, and the delay duration corresponding to the third light pulse cycle is the time length of t9 to t11, where t9 is the starting moment of the enable level of the light source light emitting pulse signal in the third light pulse cycle, t10 is the starting moment of the enable level of the image acquisition pulse signal in the third image acquisition cycle, and t11 is the gate opening moment of the image acquisition pulse signal in the third image acquisition cycle, that is, in the third image acquisition cycle, the fluorescence signal intensity is collected from t11, and the fluorescence signal in one gate width is collected.

[0045] In the fourth light pulse cycle, the delay duration of the third light pulse cycle is increased by Δt to obtain the delay duration corresponding to the fourth light pulse cycle, and the delay duration corresponding to the fourth light pulse cycle is the time length of t14 to t16, where t14 is the starting moment of the enable level of the light source light emitting pulse signal in the fourth light pulse cycle, t15 is the starting moment of the enable level of the image acquisition pulse signal in the fourth image acquisition cycle, and t16 is the gate opening moment of the image acquisition pulse signal in the fourth image acquisition cycle, that is, in the fourth image acquisition cycle, the fluorescence signal intensity is collected from t16, and the fluorescence signal in one gate width is collected.

[0046] Exemplarily, Δt is 0.1 μs, the delay duration corresponding to the first light pulse cycle is 190 μs, the delay duration corresponding to the second light pulse cycle is 190.1 μs, the delay duration corresponding to the third light pulse cycle is 190.2 μs, and the delay duration corresponding to the fourth light pulse cycle is 190.3 μs.

[0047] The above gate width refers to the gate width of the image acquisition module, and the gate width of the image acquisition module refers to the shutter width of the image acquisition pulse signal. The gate width can be set based on actual conditions, for example, the gate width can be 20 ns.

[0048] In the embodiments of the present application, the signal generator 101 and the image acquisition module 104 can be integrated in a camera. Of course, the signal generator 101 can also be a separate instrument or device, which is not specifically limited in the present application.

[0049] The processor 106 is a server or terminal device with data processing function, for example, the processor 106 can be an industrial computer. The processor 106 is electrically connected with the image acquisition module, and can determine the carrier lifetime of the semiconductor sample 105 at different positions according to the fluorescence signal intensity at different image acquisition moments of each position.

[0050] The semiconductor wafer carrier lifetime measurement system of the embodiment of the application comprises a signal generator for generating a light source light emitting pulse signal and an image acquisition pulse signal, a gate opening time of the image acquisition pulse signal and a starting time of an enable level of the light source light emitting pulse signal have different delay durations in different light pulse periods of the light source light emitting pulse signal. In this way, the fluorescence signals emitted by the excited carriers at different positions of the semiconductor sample in the compound process are collected by the image acquisition module starting at the gate opening time corresponding to different image acquisition periods, and the intensity thereof can reflect the carrier compound decay process. In this way, the carrier lifetime at the corresponding position can be determined based on the signal intensity at different time instants at the same position of the wafer. The fluorescence signal intensity collected by the image acquisition module provided in the application can accurately capture the dynamic decay characteristics of the signal of the carriers at different positions of the semiconductor sample in the compound process, and the accuracy of the carrier lifetime measured accordingly is higher. Meanwhile, the image acquisition module directly collects the fluorescence intensity of the semiconductor sample, without the need to measure the carrier lifetime by means of point-by-point scanning of the sample in the microwave photoconductance decay method, thereby improving the efficiency of measuring the carrier lifetime of the semiconductor sample.

[0051] In some embodiments of the application, the processor 106 can determine the corresponding fluorescence signal intensity decay curve at each position based on the fluorescence signal intensity at multiple different image acquisition time instants at each position, that is, each position of the semiconductor sample 105 can correspond to a fluorescence signal intensity decay curve, and the fluorescence signal intensity decay curve is the decay curve of the fluorescence signal intensity with respect to the delay duration. The processor 106 can fit each fluorescence signal intensity decay curve to determine the carrier lifetime at different positions of the semiconductor sample 105.

[0052] Therefore, the processor 106 can fit the fluorescence signal intensity decay curve to determine the carrier lifetime in the semiconductor sample 105, so that the dynamic decay characteristics of the signal of the carriers at different positions of the semiconductor sample 105 in the compound process with respect to time can be accurately captured, and the accuracy of the measured carrier lifetime is improved. It should be noted that the fluorescence signal collected above inevitably contains noise, and the noise mainly includes shot noise, Gaussian noise and impulse noise, and the noise signal intensity N(t) can be represented by the following formula:

[0053]

[0054] I0(t) is the pure fluorescence signal intensity of a standard semiconductor sample at the acquisition time t; is the shot noise, which is the quantum noise in the photoelectric detection process and is caused by the randomness of photons reaching the detector. The variance is proportional to the signal intensity. The square root of the signal intensity is used

[0055] N1 is Gaussian noise, mainly from the electronic components of the detection system, such as the thermal noise of the amplifier and the ADC converter. This kind of noise is randomly fluctuating in the time domain, and its amplitude distribution obeys the normal distribution, which is represented by a zero-mean Gaussian distribution N(0,σ 2 ), where the variance σ 2 is related to the temperature and working state of the system.

[0056] Typical σ value range: 0.5%-2% of the signal amplitude; in high-precision mode: σ = 0.005·max(I); in normal mode: σ = 0.01·max(I).

[0057] N2 is pulse noise: random outliers, analog electromagnetic interference. Pulse noise is usually caused by external electromagnetic interference or circuit transient fault, which is manifested as an outlier in the signal, and the value of N2 can be determined according to the Bernoulli-Gaussian mixed model:

[0058]

[0059] Take 0 with probability (1-p); take the value of Gaussian distribution N(0,σ 2 ) with probability p.

[0060] Alternatively, in order to quickly and accurately remove the noise signal in the collected fluorescence signal, a long short-term memory network (LSTM) network can also be used to remove or reduce the noise in the fluorescence signal. And for the time series characteristics of the fluorescence signal in the carrier recombination process, the embodiments of the present application can realize noise suppression by capturing the time sequence dependence of the signal.

[0061] The above-mentioned LSTM network can include an input layer and an LSTM layer;

[0062] The input layer is used to receive a fluorescence signal segment, and the fluorescence signal segment is obtained by overlapping segment division of the fluorescence signal intensity at multiple collection time points at the same position according to a preset sliding window to obtain multiple signal segments. Optionally, during the segment division process, there is a certain overlap between adjacent two segments, so that the LSTM network can capture the local time sequence characteristics. For example, for a signal of 1000 time points, a sliding window including 100 time points can generate 19 overlapping segments.

[0063] The LSTM layer includes 2 LSTM units (64 neurons per LSTM unit), which capture the long-term decay trend of the signal through a gating mechanism.

[0064] The first layer LSTM unit is composed of a shared parameter LSTM encoder, which is called on multiple segments in turn, thereby retaining the last hidden state of each segment as the feature vector of the input segment. The first layer LSTM encoder model output vector is then input into the second layer LSTM unit as the input of each time step of the LSTM decoder in the time sequence of the data point segmentation. The second layer LSTM unit mainly learns features and decodes to capture "inter-segment sequence information" and gradually generate segment splicing signals. The output dimension needs to be consistent with the length of the original signal.

[0065] In the embodiments of the present application, the above-mentioned LSTM network can be trained by the following training method. The training method can include the following steps:

[0066] Step A: Obtain pure fluorescence signal intensity of a plurality of standard semiconductor samples;

[0067] Step B: Superimpose each pure fluorescence signal intensity with simulated noise of different signal-to-noise ratios to obtain noisy signals at multiple different acquisition times;

[0068] Step C: Overlapping segment division is performed on the noisy signals at multiple different acquisition times according to a preset sliding window to obtain a plurality of signal segment samples;

[0069] Step C: The plurality of signal segment samples and their corresponding pure fluorescence signal intensity are paired to generate training data;

[0070] Step D: Train the LSTM network based on the training data to obtain a noise removal model.

[0071] Step D can specifically include:

[0072] Step D1: input the plurality of signal segment samples into the LSTM network to obtain a noise-removed fluorescence signal;

[0073] Step D2: Determine the function value of the loss function according to the noise-removed fluorescence signal and its corresponding pure fluorescence signal intensity;

[0074] Step D3: If the function value does not satisfy the preset condition, adjust the network parameters of the LSTM network to obtain an updated LSTM network, and return to step D1.

[0075] Step D4: If the function value satisfies the preset condition, determine the latest LSTM network as the noise removal model.

[0076] Step D2 can be specifically:

[0077] The first layer of LSTM units is used to sample features of the input signal segment sequence to obtain a feature vector. Then, the feature vector output by the first layer of LSTM units is input into the second layer of LSTM units, and the second layer of LSTM units decodes to remove noise in each signal segment, capture "inter-segment sequence information", and gradually generate a segment splicing signal to obtain a noise-removed fluorescent signal.

[0078] The process of gradually generating the segment splicing signal can specifically include: averaging the noise-removed signal segments according to the overlapping region, splicing the multiple noise-removed signal segments into a complete signal, and obtaining the noise-removed fluorescent signal.

[0079] The model training method provided in the above embodiments can significantly reduce the model parameters by dividing the segments in the sliding window overlapping manner, and further enhance the local modeling capability and model interpretability. The enhancement of the local modeling capability without losing the global features can improve the model training effect.

[0080] Based on the trained noise removal model, the processor can be used for the following operations:

[0081] The fluorescent signal intensities at each position at different image acquisition moments are normalized to obtain multiple normalized fluorescent signal intensities.

[0082] The multiple normalized fluorescent signal intensities are divided into overlapping segments according to a preset sliding window to obtain multiple signal segments.

[0083] The multiple signal segments are input into the noise removal model to obtain a noise-processed fluorescent signal.

[0084] Optionally, the embodiments of the present application can also perform smoothing processing (such as 5-point sliding average) on the noise-removed fluorescent signal to further suppress residual high-frequency noise while retaining key inflection points of the decay curve.

[0085] After the semiconductor sample 105 receives the pulsed light beam, it will first transition from the ground state to the excited state to generate carriers. The fluorescence signal is generated in the process of the carriers transitioning from the excited state back to the ground state. In some embodiments of the present application, in order to improve the fluorescence signal acquisition efficiency, the fluorescence signal needs to be collected after the semiconductor sample 105 is excited by the pulsed light beam and the fluorescence signal intensity reaches the highest. There is a delay duration between the gate-on moment of the image acquisition pulse signal and the starting moment of the enable level of the light source light emission pulse signal.

[0086] For example, the light source 102 is triggered to the duration required for the fluorescence signal intensity to reach the peak value, which is 190 μs. The delay duration corresponding to the first light pulse period can be set to 190 μs.

[0087] Thus, by setting the delay duration, the time difference between the gate opening time of the image acquisition pulse signal and the starting time of the enable level of the light source light emitting pulse signal can be accurately controlled, ensuring that the pulsed light beam has sufficient time to complete the effective excitation of the semiconductor sample 105 to enter the carrier recombination process, and ensuring the accuracy of measuring the carrier lifetime.

[0088] In some embodiments of the present application, in order to acquire the fluorescence signal at different times during the carrier recombination process and capture the decay curve of the fluorescence signal intensity during the carrier recombination process, the delay duration corresponding to the current light pulse period can be determined based on the delay duration corresponding to the previous light pulse period according to a preset duration change amount. That is, the delay duration in the time duration of the latter light pulse period in each adjacent two light pulse periods is greater than the time duration of the former light pulse period by a preset duration change amount.

[0089] For example, the delay duration change amount can be 0.1 μs, the delay duration corresponding to the first light pulse period is 190 μs, the delay duration corresponding to the second light pulse period is 190.1 μs, the delay duration corresponding to the third light pulse period is 190.2 μs, and the delay duration corresponding to the fourth light pulse period is 190.3 μs.

[0090] Thus, by adjusting the size of the delay duration corresponding to the light pulse period, the fluorescence signal radiated by the semiconductor sample 105 at different times can be effectively acquired, and the dynamic decay characteristics of the fluorescence signal during the carrier recombination process can be effectively captured.

[0091] Optionally, in order to effectively acquire the fluorescence signal radiated by the semiconductor sample 105 and prevent the fluorescence signal from being missed, the preset duration change amount can be less than or equal to the gate width of the image acquisition module, where the gate width of the image acquisition module refers to the time duration of the gate opening of the image acquisition pulse signal. For example, the gate width of the image acquisition module is 20 ns, and the preset duration change amount is 10 ns.

[0092] Thus, the situation that the fluorescence signal is missed can be avoided, and the fluorescence signal radiated by the semiconductor sample 105 at different times can be acquired.

[0093] Optionally, as shown in Figure 3 , Figure 3 a structure diagram of a semiconductor wafer carrier lifetime measurement system is shown, wherein the semiconductor wafer carrier lifetime measurement system further includes an optical path adjustment assembly 301, which can be arranged on the optical path of the pulsed light beam incident on the semiconductor sample 105 and can be used to adjust the light output direction of the pulsed light beam. After adjustment by the optical path adjustment assembly, the pulsed light beam can be incident on the surface of the semiconductor sample 105.

[0094] Therefore, under the action of the optical path adjusting assembly 301, the pulsed light beam emitted by the light source 102 can be accurately and uniformly emitted onto the semiconductor sample 105, so that uniform excitation of the semiconductor sample 105 can be achieved, and local errors can be avoided.

[0095] Optionally, the optical path adjusting assembly 301 can include a mirror, a concave lens and a scattering sheet arranged in sequence along the incident direction of the pulsed light beam, the mirror is used to reflect the pulsed light emitted by the excitation light source to the concave lens, the concave lens is used to diverge the pulsed light reflected by the mirror, and the scattering sheet is used to scatter the pulsed light diverged by the concave lens into a light spot on the object table. As shown in Figure 3

[0096] As shown in Figure 3 , the optical path adjusting assembly 301 can include a mirror 3011, a concave lens 3012 and a scattering sheet 3013, the mirror 3011 can be used to reflect the pulsed light beam emitted by the light source 102 to the concave lens 3012, the concave lens 3012 can be used to diverge the pulsed light beam reflected by the mirror 3011, and the scattering sheet 3013 can be used to scatter the pulsed light beam diverged by the concave lens 3012 into a light spot on the carrier assembly 103. In addition, the semiconductor wafer carrier lifetime measurement system includes a light source 102, a processor 106, an image acquisition module 104, a semiconductor sample 105 and a signal generator 101.

[0097] Therefore, under the action of the mirror 3011, the concave lens 3012 and the scattering sheet 3013, the pulsed light emitted by the light source 102 can be accurately and uniformly emitted onto the semiconductor sample 105, so that uniform excitation of the semiconductor sample 105 can be achieved, and local errors can be avoided. Based on the semiconductor wafer carrier lifetime measurement system provided in the above embodiment, the present application further provides a semiconductor wafer carrier lifetime measurement method.

[0098] Next, a semiconductor wafer carrier lifetime measurement method provided by the present application will be described, Figure 4 A flowchart of a semiconductor wafer carrier lifetime measurement method provided by an embodiment of the present application is shown, as shown in Figure 4 , the method comprises:

[0099] S401, the signal generator acquires a light source light emitting pulse signal and an image acquisition pulse signal, and sends the light source light emitting pulse signal to the light source and the image acquisition pulse signal to the image acquisition module, the gate opening time of the image acquisition pulse signal and the starting time of the enable level of the light source light emitting pulse signal exist different delay durations in different light pulse periods of the light source light emitting pulse signal.

[0100] ​The semiconductor wafer carrier lifetime measurement system can generate a light source light pulse signal and an image acquisition pulse signal through a signal generator, send the light source light pulse signal to a light source, so that the light source emits a pulsed light beam to a semiconductor sample under the control of the signal, the semiconductor sample generates two carriers of electrons and holes under the excitation of the pulsed light beam, and emits a fluorescent signal in the process of carrier recombination. The signal generator sends the image acquisition pulse signal to the image acquisition module, so that the image acquisition module acquires the fluorescent signal emitted by the semiconductor sample under the control of the gating control of the image acquisition pulse signal. The start time of the enable level of the light source light pulse signal and the opening time of the gating of the image acquisition pulse signal have different delay durations in different light pulse periods of the light source light pulse signal. For example, the delay duration corresponding to the first light pulse period is 190 μs, the delay duration corresponding to the second pulse period is 190.1 μs, the delay duration corresponding to the third pulse period is 190.2 μs, and the delay duration corresponding to the fourth pulse period is 190.3 μs.

[0101] S402, generating a pulsed light beam corresponding to the light source light pulse signal.

[0102] S403, acquiring the fluorescent signal emitted by the excited carrier recombination process at different positions of the semiconductor sample at different image acquisition periods through the image acquisition module, and obtaining the fluorescent signal intensity corresponding to each position at multiple different image acquisition times.

[0103] The light source can generate a pulsed light beam according to the light source light pulse signal and emit the pulsed light beam to the semiconductor sample. The image acquisition module can acquire the fluorescent signal emitted by the excited carrier recombination process at different positions of the semiconductor sample at different image acquisition periods, and obtain the fluorescent signal intensity corresponding to each position at multiple different image acquisition times. The information of the fluorescent signal intensity can be represented by a fluorescent image, and the fluorescent image is specifically as shown in Figure 5 Figure 5 The fluorescent image provided by the embodiment of the present application is a schematic diagram of a fluorescent image, in which Figure 5 the horizontal and vertical coordinates are pixel values, and the fluorescent image can represent the intensity information of the fluorescent signal at different positions of the semiconductor sample, and different colors represent different fluorescent signal intensities.

[0104] S404, determining the carrier lifetime at different positions of the semiconductor sample through the processor.

[0105] ​In the semiconductor wafer carrier lifetime measurement method of the embodiments of the present application, the signal generator is configured to generate a light source light emitting pulse signal and an image acquisition pulse signal, and the gate-on time of the image acquisition pulse signal and the starting time of the enable level of the light source light emitting pulse signal have different delay durations in different light pulse periods of the light source light emitting pulse signal. In this way, the fluorescence signals emitted by the excited carriers at different positions of the semiconductor sample in the recombination process are collected by the image acquisition module at the gate-on time corresponding to different image acquisition periods, and the intensity of the fluorescence signals can reflect the carrier recombination decay process. In this way, the carrier lifetime at the corresponding position can be determined based on the signal intensity at different time instants at the same position of the wafer. The fluorescence signal intensity collected by the image acquisition module provided in the present application can accurately capture the dynamic decay characteristics of the fluorescence signal of the carriers at different positions of the semiconductor sample in the recombination process, and the carrier lifetime measured based on the same has high accuracy. Meanwhile, the image acquisition module directly collects the fluorescence intensity of the semiconductor sample, and does not need to use the microwave photoconductance decay method to measure the carrier lifetime by scanning the sample point by point, thereby improving the efficiency of measuring the carrier lifetime of the semiconductor sample.

[0106] In some embodiments of the present application, S404 is involved, and S404 specifically includes that the fluorescence signal intensity decay curve at each position can be determined by the processor based on the fluorescence signal intensity at each position at different image acquisition time instants, that is, each position of the semiconductor sample can correspond to a fluorescence signal intensity decay curve, and the fluorescence signal intensity decay curve is the decay curve of the fluorescence signal intensity with the delay duration. Then, the processor is used to fit each fluorescence signal intensity decay curve to determine the carrier lifetime at different positions of the semiconductor sample.

[0107] In this way, the processor can be used to fit the fluorescence signal intensity decay curve to determine the carrier lifetime in the semiconductor sample, so that the dynamic decay characteristics of the fluorescence signal of the carriers at different positions of the semiconductor sample in the recombination process can be accurately captured, and the accuracy of the measured carrier lifetime is improved.

[0108] In some embodiments of the present application, S404 is involved, and S404 specifically includes that the fluorescence signal intensity decay curve at each position can be determined by the processor based on the fluorescence signal intensity at each position at different image acquisition time instants, that is, each position of the semiconductor sample can correspond to a fluorescence signal intensity decay curve, and the fluorescence signal intensity decay curve is the decay curve of the fluorescence signal intensity with the delay duration. Then, the processor is used to fit each fluorescence signal intensity decay curve to determine the carrier lifetime at different positions of the semiconductor sample.

[0109] I. Single exponential fitting model

[0110] As an example, for a high-purity semiconductor sample, such as an intrinsic semiconductor, a single-exponential fitting model can be employed, in which case S404 includes S4041-S4042, as follows:

[0111] S4041, a single-exponential fitting is performed on each of the fluorescence signal intensity decay curves, respectively, to obtain a first relationship.

[0112] S4042, based on the first relationship, carrier lifetimes at different locations in the semiconductor sample are determined.

[0113] The first relationship is:

[0114]

[0115] where I(t) is used to represent the fluorescence signal intensity at time t, I0 is used to represent the fluorescence signal intensity at the initial time of non-equilibrium carrier recombination, and the characteristic lifetime τ can be obtained through inverse calculation, which is taken as the carrier lifetime of the semiconductor sample.

[0116] II. Double-exponential fitting model

[0117] As an example, for a heavily doped semiconductor sample, such as an N-type silicon carbide, a double-exponential fitting model can be employed, in which case S404 includes S4043-S4044.

[0118] S4043, a double-exponential fitting is performed on each of the fluorescence signal intensity decay curves, respectively, to obtain a second relationship;

[0119] S4044, based on the second relationship, carrier lifetimes at different locations in the semiconductor sample are determined.

[0120] The second relationship is:

[0121]

[0122] where I(t) is used to represent the fluorescence signal intensity at time t, I0 is used to represent the fluorescence signal intensity at the initial time of non-equilibrium carrier recombination, and the characteristic lifetime τ can be obtained through inverse calculation, which is taken as the carrier lifetime of the semiconductor sample. bg represent background noise, I1 represents the initial contribution of the fast decay mechanism, and I2 represents the initial contribution of the slow decay mechanism. The fitting result can obtain a first characteristic lifetime τ1 of the fast recombination process and a second characteristic lifetime τ2 of the slow recombination process. Either one of τ1 and τ2 can be selected as the carrier lifetime of the semiconductor sample. Alternatively, I1 can be taken as the weight of τ1, I2 can be taken as the weight of τ2, and a weighted sum can be obtained as the carrier lifetime of the semiconductor sample.

[0123] III. Stretching exponential fitting model

[0124] As an example, for a sample with energy distribution or structural inhomogeneity, such as an amorphous semiconductor, a disordered quantum dot film, a stretched number fitting model can be used; for a sample with complex decay mechanism and cannot be described by a single exponential, such as the relaxation of carriers in a non-uniform energy level, a stretched number fitting model can be used. In this case, S404 includes S4045-S4046.

[0125] S4045, respectively, a stretched exponential fitting is performed on each fluorescence signal intensity decay curve to obtain a third relationship;

[0126] S4046, based on the third relationship, determining the carrier lifetime at different positions in the semiconductor sample;

[0127] The third relationship is:

[0128] I(t)=I0e -(t / τ)β (5)

[0129] Where I(t) is used to represent the fluorescence signal intensity at time t, τ is used to represent the characteristic lifetime, β is used to represent the stretching factor (0<β≤1), the closer β is to 1, the closer it is to single exponential decay, and the smaller β is, the more significant the inhomogeneity or energy dispersion is.

[0130] Four, three-exponential fitting model

[0131] As an example, for a semiconductor sample with multiple defect states, such as materials including shallow traps, medium-deep traps, and deep traps, a three-exponential fitting model can be used; for a sample of a multi-layer heterostructure or a composite system, such as a quantum well-quantum dot hybrid structure, a semiconductor-organic interface system, a three-exponential fitting model can be used. In this case, S404 includes S4047-S4048.

[0132] S4047, respectively, a three-exponential fitting is performed on each fluorescence signal intensity decay curve to obtain a fourth relationship;

[0133] S4048, based on the fourth relationship, determining the carrier lifetime at different positions in the semiconductor sample;

[0134] The fourth relationship is:

[0135]

[0136] Where I(t) is used to represent the fluorescence signal intensity at time t, τ is used to represent the characteristic lifetime, which can be represented by τ1, τ2, τ3 corresponding to the characteristic lifetime of three decay mechanisms, such as surface recombination, bulk defect recombination, and intrinsic radiation recombination, β is used to represent the stretching factor (0<β≤1), the closer β is to 1, the closer it is to single exponential decay, and the smaller β is, the more significant the inhomogeneity or energy dispersion is.

[0137] V. Diffusion-controlled decay model

[0138] As an example, for low-dimensional semiconductor samples in which carrier diffusion dominates the decay process, such as two-dimensional semiconductors, nanowires, quantum dot films, a diffusion-controlled decay model can be used; for scenarios in which carriers need to diffuse to the surface or interface to recombine, such as materials in which the surface recombination rate is much higher than the bulk recombination rate, a diffusion-controlled decay model can be used. The diffusion-controlled decay model is suitable for analyzing the transport and surface recombination competition mechanism of carriers in low-dimensional materials. In this case, S404 includes S4049-S40410.

[0139] S4049, respectively, for each fluorescence signal intensity decay curve, diffusion-controlled decay is performed to obtain a fifth relationship;

[0140] S40410, based on the fifth relationship, determining the carrier lifetime at different positions in the semiconductor sample;

[0141] The fifth relationship is:

[0142]

[0143] where I(t) is used to represent the fluorescence signal intensity at time t, D is used to represent the carrier diffusion coefficient, reflecting the carrier migration ability, x0 is used to represent the characteristic length of the initial distribution of carriers, and k is used to represent the bulk recombination rate constant. Taking a single exponential fitting method as an example, the decay curve of the fluorescence signal intensity is as follows Figure 6 as shown, Figure 6 A schematic diagram of the decay curve provided by an embodiment of the present application is shown. As shown in Figure 6 the horizontal axis of the decay curve is the delay time, and the vertical axis is the fluorescence signal intensity. The fluorescence signal intensity decays with increasing delay time and shows a single exponential decay trend.

[0144] Therefore, using a single exponential fitting or double exponential fitting method can accurately and quickly fit and calculate the carrier lifetime, thereby improving the efficiency of measuring the carrier lifetime of the semiconductor sample and ensuring the accuracy of measuring the carrier lifetime of the semiconductor sample.

[0145] In some embodiments of the present application, after determining the carrier lifetime of the semiconductor sample, the above method can display the information of the carrier lifetime of the semiconductor sample in a visual manner, and the processor can generate a carrier lifetime image of the semiconductor sample according to the information of the carrier lifetime of the semiconductor sample. The carrier lifetime image of the semiconductor sample is specifically as follows Figure 7 as shown, Figure 7 A schematic diagram of a carrier lifetime image of a semiconductor sample provided by an embodiment of the present application is shown. As Figure 7As shown, the horizontal axis and the vertical axis are used to represent the pixel value, the carrier lifetime image is used to characterize the length of the wafer carrier lifetime at each position of the semiconductor sample, and different colors in the carrier lifetime image represent different lengths of the wafer carrier lifetime. Thus, the carrier lifetime image of the semiconductor sample can be displayed in a visual manner, so that the user can directly view the spatial distribution of the carrier recombination characteristics in the semiconductor wafer.

[0146] In the semiconductor wafer carrier lifetime measurement method of the embodiments of the present application, through the innovative gating technology and image acquisition technology, efficient and accurate measurement of the semiconductor wafer carrier lifetime is realized. Compared with the traditional point-by-point scanning method, the system uses large-area synchronous imaging technology to significantly improve the measurement efficiency, and is especially suitable for rapid detection of large-size wafers. The accurate timing control combined with the gating acquisition technology can completely capture the dynamic decay process of the fluorescence signal, ensuring the time resolution. At the same time, the system supports single-exponential and double-exponential fitting models, and uses LSTM model machine learning to effectively suppress noise interference and greatly improve the signal-to-noise ratio of the data results. The optical path adjustment assembly disclosed in the present application can ensure uniform distribution of the excitation light and avoid local measurement errors. The carrier lifetime distribution image generated by the processor can directly display the performance differences of each region of the wafer, providing a visual basis for process optimization. The integrated deep learning algorithm of the present application further optimizes the signal processing method and promotes the development of semiconductor characterization technology towards intelligence.

[0147] It should be noted that the present application is not limited to the specific configurations and processes described above and shown in the drawings. For the sake of brevity, detailed descriptions of well-known methods are omitted here. In the above embodiments, several specific steps are described and shown as examples. However, the method process of the present application is not limited to the specific steps described and shown, and those skilled in the art can make various changes, modifications and additions, or change the order between steps, after understanding the spirit of the present application.

[0148] The functional blocks shown in the structural block diagrams above can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, and the like. When implemented in software, the elements of the present application are program or code segments that are used to perform the required tasks. The program or code segments can be stored in a machine-readable medium, or transmitted through a data signal carried in a carrier wave over a transmission medium or communication link. A "machine-readable medium" includes any medium that can store or transport information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROMs, flash memories, erasable ROMs (EROMs), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, and the like. The code segments can be downloaded via computer networks such as the Internet, intranets, and the like.

[0149] It is also important to note that the examples mentioned in the present application describe some methods or systems based on a series of steps or devices. However, the present application is not limited to the order of the above steps, that is, the steps can be performed in the order mentioned in the examples, or in an order different from the examples, or several steps can be performed simultaneously.

[0150] The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other processing device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other processing device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer program instructions can also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other processing device to operate in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks. The computer program instructions can also be loaded onto a computer, other programmable data processing apparatus, or other processing device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other processing device to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks. These computer program instructions can also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other processing device to operate in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0151] The above merely shows the specific implementation of the present application. Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described system, module and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be described herein again. It should be understood that the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application.

Claims

1. A semiconductor wafer carrier lifetime measurement system, characterized by, The system comprises: a signal generator configured to obtain a light source light pulse signal and an image acquisition pulse signal, and send the light source light pulse signal to a light source and the image acquisition pulse signal to an image acquisition module, wherein a gate-on time of the image acquisition pulse signal and a start time of an enable level of the light source light pulse signal have different delay durations in different light pulse periods of the light source light pulse signal; the light source, which is electrically connected to the signal generator, is configured to generate a pulsed light beam corresponding to the light source light pulse signal; a carrier assembly configured to carry a semiconductor sample, wherein carriers excited by the pulsed light beam in the semiconductor sample can generate fluorescence; the image acquisition module, which is electrically connected to the signal generator, is configured to start to acquire fluorescence signals emitted by excited carriers at different positions of the semiconductor sample in a recombination process at a gate-on time corresponding to different image acquisition periods, to obtain fluorescence signal intensities at each position corresponding to a plurality of different image acquisition times, respectively; a processor, which is electrically connected to the image acquisition module, is configured to determine carrier lifetimes at different positions of the semiconductor sample.

2. The system of claim 1, wherein, The processor is configured to determine a fluorescence signal intensity decay curve corresponding to each position according to the fluorescence signal intensities at a plurality of different image acquisition times at each position, and to fit each fluorescence signal intensity decay curve to determine carrier lifetimes at different positions of the semiconductor sample.

3. The system of claim 1, wherein, The delay duration corresponding to a first light pulse period is determined according to a time duration required from the light source being triggered to the fluorescence signal intensity reaching a peak value.

4. The system of claim 1, wherein, The delay duration changes by a preset time duration variation amount in a time duration of a latter light pulse period than in a time duration of a former light pulse period in each adjacent two light pulse periods.

5. The system of claim 4, wherein, The preset time duration variation amount is less than or equal to a gate width of the image acquisition module.

6. The system of any one of claims 1 to 5, wherein, The system further comprises an optical path adjustment assembly arranged on an optical path of the pulsed light beam incident on the semiconductor sample, and configured to adjust an out-light direction of the pulsed light beam so that the adjusted pulsed light beam is incident on a surface of the semiconductor sample.

7. The system of claim 6, wherein, The optical path adjustment assembly comprises a mirror, a concave lens and a scattering sheet arranged in sequence along an incident direction of the pulsed light beam.

8. A method of measuring carrier lifetime in a semiconductor wafer, applied to the system of any one of claims 1-7, characterized in that, The method comprises: obtaining a light source light pulse signal and an image acquisition pulse signal by a signal generator, and sending the light source light pulse signal to a light source and the image acquisition pulse signal to an image acquisition module, wherein a gate-on time of the image acquisition pulse signal and a start time of an enable level of the light source light pulse signal have different delay durations in different light pulse periods of the light source light pulse signal; generating a pulsed light beam corresponding to the light source light pulse signal; starting to acquire fluorescence signals emitted by excited carriers at different positions of the semiconductor sample in a recombination process at a gate-on time corresponding to different image acquisition periods by the image acquisition module, to obtain fluorescence signal intensities at each position corresponding to a plurality of different image acquisition times, respectively; and determining carrier lifetimes at different positions of the semiconductor sample. Determine carrier lifetime at different positions in the semiconductor sample by the processor.

9. The method of claim 8, wherein, The determination of the carrier lifetime at different positions in the semiconductor sample by the processor according to the fluorescence signal intensity at each position at a plurality of different image acquisition time points respectively, comprises: Determine the corresponding fluorescence signal intensity decay curve at each position according to the fluorescence signal intensity at each position at a plurality of different image acquisition time points by the processor; fit each of the fluorescence signal intensity decay curves respectively to determine the carrier lifetime at different positions in the semiconductor sample.

10. The method of claim 9, wherein, In the case of a high-purity semiconductor sample, the fitting of each of the fluorescence signal intensity decay curves respectively to determine the carrier lifetime at different positions in the semiconductor sample comprises: Single exponential fitting is performed on each of the fluorescence signal intensity decay curves respectively to obtain a first relationship; Determine the carrier lifetime at different positions in the semiconductor sample based on the first relationship; The first relationship is: Where I(t) is used to represent the fluorescence signal intensity at time t, I0 is used to represent the fluorescence signal intensity of the carrier at the initial time of recombination, and τ is used to represent the characteristic lifetime; Or, in the case of a heavily doped semiconductor sample, the fitting of each of the fluorescence signal intensity decay curves respectively to determine the carrier lifetime at different positions in the semiconductor sample comprises: Double exponential fitting is performed on each of the fluorescence signal intensity decay curves respectively to obtain a second relationship; Determine the carrier lifetime at different positions in the semiconductor sample based on the second relationship; The second relationship is: where I(t) is used to represent the fluorescence signal intensity at time t, I bg to represent background noise, Ii is used to represent the initial contribution of the fast decay mechanism, I2is used to represent the initial contribution of the slow decay mechanism, ti is used to represent a first characteristic lifetime of the fast recombination process, and t2is used to represent a second characteristic lifetime of the slow recombination process; Or, in the case of a sample with non-uniform energy distribution or structure, the fitting of each of the fluorescence signal intensity decay curves respectively to determine the carrier lifetime at different positions in the semiconductor sample comprises: Stretch exponential fitting is performed on each of the fluorescence signal intensity decay curves to obtain a third relationship; Determine the carrier lifetime at different positions in the semiconductor sample based on the third relationship; The third relationship is: Where I(t) is used to represent the fluorescence signal intensity at time t, τ is used to represent the characteristic lifetime, and β is used to represent the stretching factor; Or, in the case of a multi-defect-state semiconductor sample, the fitting of each of the fluorescence signal intensity decay curves respectively to determine the carrier lifetime at different positions in the semiconductor sample comprises: Triple exponential fitting is performed on each of the fluorescence signal intensity decay curves to obtain a fourth relationship; Determine the carrier lifetime at different positions in the semiconductor sample based on the fourth relationship; The fourth relationship is: Where I(t) is used to represent the fluorescence signal intensity at time t, τ is used to represent the characteristic lifetime, and β is used to represent the stretching factor; Or, in the case of a low-dimensional semiconductor sample with carrier diffusion dominated decay process, the fitting of each of the fluorescence signal intensity decay curves respectively to determine the carrier lifetime at different positions in the semiconductor sample comprises: A diffusion-controlled decay is performed on each of the fluorescence signal intensity decay curves to obtain a fifth relationship; Based on the fifth relationship, carrier lifetimes at different positions in the semiconductor sample are determined; The fifth relationship is: where I(t) is used to represent the fluorescence signal intensity at time t, D is used to represent a carrier diffusion coefficient, reflecting a carrier migration ability, x0 is used to represent a characteristic length of an initial distribution of carriers, and k is used to represent a bulk recombination rate constant.

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