Unsteady-state excitation noise testing method for composite dielectric gate photosensitive detector

Abstract

The invention discloses an unsteady-state excitation noise testing method of a composite dielectric gate photosensitive detector, and belongs to the technical field of noise testing of imaging detection devices. In the unsteady state excitation noise test system of the composite dielectric gate photosensitive detector, the composite dielectric gate photosensitive detector to be tested is connected outwards through four ports of a wafer test probe station; three ports of the current and voltage signal sampling analyzer are connected to a drain electrode, a substrate and a source electrode of the composite dielectric gate photosensitive detector through the wafer test probe station, and a fourth port of the current and voltage signal sampling analyzer is connected to a trigger input port of the unsteady state excitation function signal generator; a signal output port of the unsteady state excitation function signal generator is connected to a control gate electrode of the photosensitive detector through the wafer test probe station; and original experimental data obtained after the hardware part is tested is stored in the current and voltage signal sampling analyzer. According to the invention, the noise data of a specific pixel device in the chip can be obtained from the level of a device level.

Description

Technical Field

[0001] The invention relates to a non-steady-state excitation noise testing method for a composite dielectric grating photosensitive detector, belonging to the technical field of noise testing of imaging detector devices, in particular to flicker noise, RTN noise, non-steady-state noise and readout noise at the detector device level. Background Art

[0002] The solid-state imaging sensor market is booming and experiencing exponential growth due to the demand in digital and video cameras, mobile imaging, surveillance and biometrics. Traditionally, CCD (Charge-coupled Device) is the dominant imaging technology. However, with the rapid development of CMOS (Complementary Metal Oxide Semiconductor) technology, CMOS image sensor (CIS) technology has been widely used in many fields, such as PC cameras, mobile phones, high-end digital cameras, etc. Moreover, with the iterative optimization of technology, it can be comparable to CCD in some performance aspects, and it has become a substitute for CCD. However, the common CMOS-APS (active pixel active sensor (APS)) consists of a photodiode and a readout gate transistor, usually with four or five transistors. As the pixel size decreases, it is difficult for CIS to maintain a large full well charge to obtain a large signal-to-noise ratio, which makes it difficult to ensure image quality.

[0003] At present, patent CN201210442007.X proposes a dual-transistor photosensitive detector based on a composite dielectric gate MOSFET, which can ensure a high full well of the pixel while reducing the pixel size.

[0004] The reported reading methods of composite dielectric grating photodetectors can only obtain the overall noise data of the pixel array in the entire chip from the chip level, but cannot obtain the noise data of a specific pixel device in the chip from the device level, and thus cannot optimize it from the perspective of a single pixel device; therefore, there is an urgent need for a device-level noise test system and characterization method suitable for the composite dielectric grating photodetector.

[0005] Moreover, considering the particularity of the readout method of the composite dielectric gate photosensitive detector, the pixel-level noise characterization method and test system usually applicable to CCD and CIS are not applicable to the new detector. CCD and CIS usually adopt the readout method of source follower level transfer, and directly transfer the voltage signal stored in the output node capacitor of the CCD and CIS sensor to the ADC (analog-to-digital converter, i.e., A / D converter) for quantitative reading. Therefore, when characterizing its noise, it is only necessary to directly read and analyze the output voltage signal of the output node under steady-state excitation. For the above-mentioned dual-transistor photosensitive detector based on composite dielectric gate MOSFET, its output signal is included in the threshold voltage change of the MOSFET transistor of the detector. When the detector is sensitive and non-sensitive, the threshold voltage of its MOSFET will change linearly with the strength of the received light signal. The quantized threshold voltage is achieved by performing a ramp voltage scan on the MOSFET, so a noise test system capable of generating non-steady-state excitation is urgently needed to test the noise of the detector. Summary of the invention

[0006] [Technical issues]

[0007] The reported reading methods of composite dielectric grating photosensitive detectors can only obtain the overall noise data of the pixel array in the entire chip from the chip level, but cannot obtain the noise data of a specific pixel device in the chip from the device level, and thus cannot optimize it from the perspective of a single pixel device.

[0008] [Technical solution]

[0009] In order to solve the above problems, the present invention adopts a non-steady-state excitation noise test system for a composite dielectric grating photosensitive detector, and proposes a working method of the noise test system in two different working modes: steady state and non-steady state.

[0010] The first object of the present invention is to provide a non-steady-state excitation noise test system for a composite dielectric grating photosensitive detector, comprising a hardware part and a software part, wherein the hardware part comprises three modules: a current and voltage signal sampling analyzer, a wafer test probe station and a non-steady-state excitation function signal generator; the software part comprises two parts: an arbitrary waveform file generation program and a current noise analysis program; the object to be tested is a composite dielectric grating photosensitive detector;

[0011] The composite dielectric grating photosensitive detector includes four independent electrodes: a control gate electrode, a source electrode, a drain electrode, and a substrate electrode;

[0012] The non-steady-state excitation signal function signal generator includes an interface for receiving an external trigger signal and an interface for transmitting a function signal outwardly;

[0013] The hardware is connected as follows:

[0014] The composite dielectric grating photosensitive detector to be tested is connected to the outside through the four ports SMU1, SMU2, SMU3, and SMU4 of the wafer test probe station; the three SMU ports of the current and voltage signal sampling analyzer are connected to the drain electrode, substrate electrode, and source electrode of the composite dielectric grating photosensitive detector through the wafer test probe station, and the fourth SMU port is connected to the trigger input port of the non-steady-state excitation function signal generator; the signal output port of the non-steady-state excitation function signal generator is connected to the control gate electrode of the photosensitive detector through the wafer test probe station; the experimental raw data obtained after the hardware part experimental test will be stored in the current and voltage signal sampling analyzer;

[0015] The software part operates as follows:

[0016] The arbitrary waveform file generation program will generate a specified non-steady-state excitation signal waveform file according to the test requirements, and input the waveform file into the non-steady-state excitation signal function generator;

[0017] The current noise analysis program can read the current data derived from the current and voltage signal sampling analyzer, and calculate and characterize the noise performance of the composite dielectric grating photosensitive detector to be tested according to different working modes.

[0018] In one embodiment of the present invention, the wafer test probe station is directly connected to the four independent electrodes of the composite dielectric grating photosensitive detector to form an external interface for the four independent electrodes of the composite dielectric grating photosensitive detector to achieve electrical connection with an external test instrument.

[0019] In one embodiment of the present invention, the current and voltage signal sampling analyzer includes four independent test ports SMU1, SMU2, SMU3, and SMU4. SMU1, SMU2, and SMU3 in these four independent test ports are directly connected to the source electrode, drain electrode, and substrate electrode in the outward interface of the composite dielectric grating photosensitive detector formed by the wafer test probe station, thereby realizing the electrical connection between the current and voltage signal sampling analyzer and the composite dielectric grating photosensitive detector; the fourth test port SMU4 is biased to the interface of the non-steady-state excitation signal function signal generator that receives an external trigger signal to trigger the function signal generator.

[0020] In one embodiment of the present invention, the interface of the non-steady-state excitation signal function signal generator for emitting function signals outwardly is directly connected to the fourth control gate electrode in the outward interface of four composite dielectric grating photosensitive detectors formed by a wafer test probe station, thereby realizing the electrical connection between the non-steady-state excitation signal function signal generator and the composite dielectric grating photosensitive detector to be tested.

[0021] In one embodiment of the present invention, the arbitrary waveform file generation program generates a specified non-steady-state excitation signal waveform file according to the test requirements, and inputs the waveform file into the non-steady-state excitation signal function generator.

[0022] In one embodiment of the present invention, the non-steady-state excitation signal function signal generator will output a specified function signal according to the signal waveform in an arbitrary waveform file under the control of the current and voltage signal sampling analyzer, and bias it on the control gate electrode of the composite dielectric grating photosensitive detector.

[0023] In one embodiment of the present invention, the current and voltage signal sampling analyzer controls the test process of the entire test system, and simultaneously uses the test port to collect the current data of the drain electrode of the composite dielectric grating photosensitive detector to be tested, and stores it inside the analyzer.

[0024] The second object of the present invention is to provide a working method of the non-steady-state excitation noise testing system of the composite dielectric grating photosensitive detector described in the present invention. The working method is divided into two types, the first is a working method of steady-state excitation current sampling, and the second is a working method of non-steady-state excitation current sampling.

[0025] In one embodiment of the present invention, the working method of steady-state excitation current sampling includes the following steps:

[0026] (1) Device probe connection stage:

[0027] The composite dielectric grating photosensitive detector to be tested is placed in a wafer test probe station, and the source electrode, drain electrode, substrate electrode, and control gate electrode of the photosensitive detector are connected to four external interfaces through probes on the wafer test probe station;

[0028] (2) Initialization stage of current and voltage signal sampling analyzer:

[0029] The three constant voltage signals of the current and voltage signal sampling analyzer are set to appropriate voltage values ​​(0V, 0.5V and -3V), and are biased to the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested through the test ports SMU1, SMU2 and SMU3 respectively; the fourth constant voltage signal of the current and voltage signal sampling analyzer is set to an appropriate voltage value (2.5V), and is biased to the interface of the non-steady-state excitation signal function signal generator receiving the external trigger signal through the test port SMU4;

[0030] (3) Initialization stage of the non-steady-state excitation signal function generator:

[0031] The output of the non-steady-state excitation signal function signal generator is set to a stable DC voltage (2.5V), and the signal output terminal is biased to the control gate electrode of the composite dielectric grating photosensitive detector to be tested. In this stage, the signal output of the signal generator is kept closed;

[0032] (4) Testing phase:

[0033] The operation of the whole system is controlled by the current and voltage signal sampling analyzer. When it starts to run, the signals of ports SMU1, SMU2, SMU3 and SMU4 start to output, the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested are correctly biased, and the non-steady-state excitation signal function signal generator will be triggered to generate signal output, and the output signal will be applied to the control gate electrode of the composite dielectric grating photosensitive detector to be tested; at the same time, the current and voltage signal sampling analyzer will collect the current on the drain electrode of the composite dielectric grating photosensitive detector to be tested in real time and store it in a csv format file of raw data;

[0034] (5) Data processing stage:

[0035] After the test phase, the original data of the DC current on the drain electrode of the composite dielectric grating photosensitive detector to be tested is obtained when the control gate electrode is subjected to a constant DC bias condition;

[0036] The raw data is imported into the MATLAB program on the computer, and after pre-filtering, fast Fourier analysis and power spectrum density calculation are performed to obtain the drain electrode current noise spectrum of the composite dielectric grating photosensitive detector to be tested under constant control gate bias conditions.

[0037] In one embodiment of the present invention, the working method of non-steady-state excitation current sampling includes the following steps:

[0038] (1) Device probe connection stage:

[0039] The composite dielectric grating photosensitive detector to be tested is placed in a wafer test probe station, and the source electrode, drain electrode, substrate electrode, and control gate electrode of the photosensitive detector are connected to four external interfaces through probes on the wafer test probe station;

[0040] (2) Initialization stage of current and voltage signal sampling analyzer:

[0041] The three constant voltage signals of the current and voltage signal sampling analyzer are set to appropriate voltage values ​​(0V, 0.5V and -3V), and are biased to the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested through the test ports SMU1, SMU2 and SMU3 respectively; the fourth constant voltage signal of the current and voltage signal sampling analyzer is set to an appropriate voltage value (2.5V), and is biased to the interface of the non-steady-state excitation signal function signal generator receiving the external trigger signal through the test port SMU4;

[0042] (3) Non-steady-state excitation arbitrary wave function signal generation stage:

[0043] The required function signal waveform is generated by using an arbitrary waveform file generation program, and is saved as a waveform file, and the waveform file is imported into the non-steady-state excitation signal function signal generator, which will be able to generate the required output signal according to the waveform file during the test process;

[0044] (4) Initialization stage of the non-steady-state excitation signal function generator:

[0045] The output of the non-steady-state excitation signal function signal generator is set to a stable DC voltage (2.5V), and the signal output terminal is biased to the control gate electrode of the composite dielectric grating photosensitive detector to be tested. In this stage, the signal output of the signal generator is kept closed;

[0046] (5) Testing phase:

[0047] The operation of the whole system is controlled by the current and voltage signal sampling analyzer. When it starts to run, the signals of ports SMU1, SMU2, SMU3 and SMU4 start to output, the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested are correctly biased, and the non-steady-state excitation signal function signal generator will be triggered to generate signal output, and the output signal will be applied to the control gate electrode of the composite dielectric grating photosensitive detector to be tested; at the same time, the current and voltage signal sampling analyzer will collect the current on the drain electrode of the composite dielectric grating photosensitive detector to be tested in real time and store it in a csv format file of raw data;

[0048] (6) Data processing stage:

[0049] After the test phase, the original data of the DC current on the drain electrode of the composite dielectric grating photosensitive detector to be tested is obtained when the control gate electrode is subjected to a constant DC bias condition;

[0050] The raw data is imported into the MATLAB program on the computer, and after pre-filtering, fast Fourier analysis and power spectral density calculation are performed to obtain the drain electrode current noise spectrum of the composite dielectric grating photosensitive detector to be tested under the condition of non-steady-state excitation signal controlled gate bias; and under specific non-steady-state excitation signal conditions, various specific noise information in the waveform can be extracted according to the actual current waveform to obtain various noise data in the raw data.

[0051] [Beneficial Effects]

[0052] (1) Compared with the existing steady-state excitation noise test system, the steady-state excitation working mode of the noise test system described in the present invention can provide a higher current signal sampling rate, thereby obtaining higher-frequency spectral information contained in the current signal, which provides more complete data analysis support for the noise analysis of the detector.

[0053] (2) The non-steady-state excitation working mode of the noise testing system described in the present invention can realize the detector noise analysis under any non-steady-state excitation signal bias, and can extract specific detector noise information based on the readout method of the composite dielectric grating photosensitive detector, which is a function that has not been realized by the existing noise testing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the overall framework diagram of the noise test system.

[0055] Figure 2 This is the signal timing diagram of each port of the noise test system during the test process.

[0056] Figure 3 This is the DC output signal waveform diagram used for testing in the non-steady-state excitation signal function signal generator when the noise test system is in the steady-state excitation current sampling working mode.

[0057] Figure 4 These are two waveform diagrams of non-steady-state arbitrary wave signals used for testing generated by the non-steady-state excitation signal function signal generator under the control of an external arbitrary wave file when the noise test system is in the non-steady-state excitation current sampling working mode. DETAILED DESCRIPTION

[0058] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0059] Example 1

[0060] A non-steady-state excitation noise test system for composite dielectric grating photosensitive detectors, such as Figure 1, including hardware and software parts. The hardware part includes three modules: current and voltage signal sampling analyzer, wafer test probe station and non-steady-state excitation function signal generator; the software part includes two parts: arbitrary waveform file generation program and current noise analysis program; the object to be tested is a composite dielectric grating photosensitive detector;

[0061] The composite dielectric grating photosensitive detector includes four independent electrodes: a control gate electrode, a source electrode, a drain electrode, and a substrate electrode;

[0062] The non-steady-state excitation signal function signal generator includes an interface for receiving an external trigger signal and an interface for transmitting a function signal outwardly;

[0063] The hardware is connected as follows:

[0064] The composite dielectric grating photosensitive detector to be tested is connected to the outside through the four ports SMU1, SMU2, SMU3, and SMU4 of the wafer test probe station; the three SMU ports of the current and voltage signal sampling analyzer are connected to the drain electrode, substrate electrode, and source electrode of the composite dielectric grating photosensitive detector through the wafer test probe station, and the fourth SMU port is connected to the trigger input port of the non-steady-state excitation function signal generator; the signal output port of the non-steady-state excitation function signal generator is connected to the control gate electrode of the photosensitive detector through the wafer test probe station; the experimental raw data obtained after the hardware part experimental test will be stored in the current and voltage signal sampling analyzer;

[0065] The software part operates as follows:

[0066] The arbitrary waveform file generation program will generate a specified non-steady-state excitation signal waveform file according to the test requirements, and input the waveform file into the non-steady-state excitation signal function generator;

[0067] The current noise analysis program can read the current data derived from the current and voltage signal sampling analyzer, and calculate and characterize the noise performance of the composite dielectric grating photosensitive detector to be tested according to different working modes.

[0068] Furthermore, the wafer test probe station is directly connected to the four independent electrodes of the composite dielectric grating photosensitive detector, forming an external interface for the four independent electrodes of the composite dielectric grating photosensitive detector to achieve electrical connection with an external test instrument.

[0069] Furthermore, the current and voltage signal sampling analyzer includes four independent test ports SMU1, SMU2, SMU3, and SMU4. SMU1, SMU2, and SMU3 in the four independent test ports are directly connected to the source electrode, drain electrode, and substrate electrode in the outward interface of the composite dielectric grating photosensitive detector formed by the wafer test probe station, thereby realizing the electrical connection between the current and voltage signal sampling analyzer and the composite dielectric grating photosensitive detector; the fourth test port SMU4 is biased to the interface of the non-steady-state excitation signal function signal generator that receives an external trigger signal, so as to trigger the function signal generator.

[0070] Furthermore, the interface for emitting function signals outwardly of the non-steady-state excitation signal function signal generator is directly connected to the fourth control gate electrode in the outward interfaces of the four composite dielectric grating photosensitive detectors formed by the wafer test probe station, thereby realizing the electrical connection between the non-steady-state excitation signal function signal generator and the composite dielectric grating photosensitive detector to be tested.

[0071] Furthermore, the arbitrary waveform file generation program will generate a specified non-steady-state excitation signal waveform file according to the test requirements, and input the waveform file into the non-steady-state excitation signal function generator.

[0072] Furthermore, the non-steady-state excitation signal function signal generator will output a specified function signal according to the signal waveform in the arbitrary waveform file under the control of the current and voltage signal sampling analyzer, and bias it on the control gate electrode of the composite dielectric grating photosensitive detector.

[0073] Furthermore, the current and voltage signal sampling analyzer will control the test process of the entire test system, and at the same time use the test port to collect the current signal of the drain electrode of the composite dielectric grating photosensitive detector to be tested.

[0074] In the hardware part, the ports of each module do not necessarily match each other. The system described in this embodiment is used for current collection and noise analysis. It has high requirements for the transmission accuracy of the current signal, and the impedance matching between the modules of the system needs special attention. Considering two transmission lines with impedances of Z1 and Z2, the quality of impedance matching can be measured by the reflectivity of signal transmission |Z1-Z2| / (Z1+Z2). When the impedance is perfectly matched, that is, Z1=Z2, the reflectivity is 0, and there will be no overshoot in the signal; the greater the difference between Z1 and Z2, the greater the reflectivity, and the worse the impedance matching quality. When the reflectivity exceeds 10%, the overshoot phenomenon generated by this system will exceed the acceptable range; the actual system will not have a perfect match. In this system, when the reflectivity is within 1%, it can be called a good impedance match.

[0075] It is necessary to take into special consideration that: when the system works in the non-steady-state working mode, the non-steady-state excitation signal usually includes obvious mutations. When the impedance matching is poor, obvious current overshoot will occur, which will introduce unnecessary current spectrum components and additional noise, directly affecting the accuracy of the test results. In the system described in the present invention, on the one hand, the arbitrary waveform function signal is finely adjusted to avoid voltage mutations in the generated function signal, and a slowly changing ramp is used to replace the step jump. After debugging, it is determined that when the impedance matching difference is kept within 20%, the slowly changing ramp slope is controlled below 5mV / μs, which can better eliminate the current overshoot. Further, a period of voltage holding can be added after the ramp. To eliminate the impact of current overshoot on subsequent signals. Even if the impedance matching is not sufficient under the excitation of this signal, there will be no obvious current overshoot phenomenon. On the other hand, in the interconnection of various modules, it is necessary to accurately consider the impedance matching between the coaxial line, signal conversion head, and instrument port used. The impedance information of the instrument port can be obtained by querying the data sheet of the instrument (usually 50Ω). The impedance information of the coaxial line and signal conversion head can be queried in the product manual. Through the use of the signal conversion head, the three impedance values ​​of each port-coaxial line-port signal path are guaranteed to be the same. For signal paths that cannot be achieved by the above method, an additional impedance matching module can be introduced to correct the impedance value.

[0076] In the software part, the arbitrary waveform file generation program is used to provide the non-steady-state excitation arbitrary wave function signal required by the non-steady-state excitation function signal generator. The non-steady-state excitation function signal generator itself does not support the output of arbitrary non-steady-state waveforms, and needs to be driven by an external arbitrary waveform RAF file to generate the function signal expected by the test system. In addition, for batch testing, a variety of different arbitrary wave function signals are usually required, so it is necessary to analyze the RAF file to debug a generation program that can simply and efficiently generate a variety of arbitrary waveform files, meet the system test requirements and improve test efficiency. The current noise analysis program is used to analyze the experimental test raw data obtained by the hardware part, and the noise characterization results of the device under test can be obtained after calculation and processing.

[0077] Example 2

[0078] The signal timing diagram of the non-steady-state excitation noise test system during the test process, such as Figure 2 ;

[0079] The signal timing diagram of the non-steady-state excitation noise test system during the test process includes a total of 6 definable signals, namely the output signals of the four independent SMU ports SMU1, SMU2, SMU3 and SMU4 of the current and voltage signal sampling analyzer, its internal sampling control signal and the signal of the output port of the non-steady-state excitation function signal generator.

[0080] The entire test system is controlled by the current and voltage signal sampling analyzer. When the test starts, the four independent SMU ports will be powered on. At this time, the SMU1, SMU2 and SMU3 ports will respectively provide appropriate DC bias voltage values ​​to the drain electrode, substrate electrode and source electrode of the composite dielectric grating photosensitive detector to be tested, and the SMU4 port will provide appropriate DC bias voltage value to the trigger input of the non-steady-state excitation function signal generator.

[0081] When the non-steady-state excitation function signal generator detects the rising edge of this DC bias voltage, it will generate a signal output after a certain delay (delay 1). The purpose of this delay is to wait for the DC bias voltages of SMU1, SMU2 and SMU3 to stabilize before providing a control gate electrode bias for the composite dielectric grating photosensitive detector to be tested. After a period of time after the non-steady-state excitation function signal generator generates a signal output, the sampling control signal inside the current and voltage signal sampling analyzer will be set to 1 (high level), indicating that the current and voltage signal sampling analyzer begins to perform time domain sampling of the current of the drain electrode of the composite dielectric grating photosensitive detector to be tested. The sampling rate can be pre-set before the test starts. The reason why the sampling control signal has a delay (delay 2) relative to the output signal of the function signal generator is that it is necessary to wait until all signals are stably biased on the electrodes of the photosensitive detector before accurate current signal sampling can be achieved.

[0082] The above two delays are important for the correct operation of the system and the accuracy of the test results:

[0083] If Delay 1 is not set or is set too short, the test will start before the device is biased stably, and the current data obtained will be meaningless;

[0084] If Delay 2 is not set or is set too short, the excitation signal is not yet stable and the acquired current data will be inaccurate;

[0085] Therefore, the two related parameters must be carefully set and adjusted in the instrument in the system before starting the test. For different test scenarios, the delay setting may be different. For example, for the steady-state test mode, the delay 2 is set as large as possible (more than 100μs), and waiting for the device to enter the steady state before testing can get more accurate results; for the non-steady-state test mode and the device needs a reset process, the delay 2 (100ns to 1μs) needs to be set to a smaller value to prevent the device reset process from losing its meaning.

[0086] Example 3

[0087] The working method of steady-state excitation current sampling includes the following steps:

[0088] (1) Device probe connection stage:

[0089] The composite dielectric grating photosensitive detector to be tested is placed in a wafer test probe station, and the source electrode, drain electrode, substrate electrode, and control gate electrode of the photosensitive detector are connected to four external interfaces through probes on the wafer test probe station;

[0090] (2) Initialization stage of current and voltage signal sampling analyzer:

[0091] The three constant voltage signals of the current and voltage signal sampling analyzer are set to appropriate voltage values ​​(0V, 0.5V and -3V), and are biased to the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested through the test ports SMU1, SMU2 and SMU3 respectively; the fourth constant voltage signal of the current and voltage signal sampling analyzer is set to an appropriate voltage value (2.5V), and is biased to the interface of the non-steady-state excitation signal function signal generator receiving the external trigger signal through the test port SMU4;

[0092] (3) Initialization stage of the non-steady-state excitation signal function generator:

[0093] The output of the non-steady-state excitation signal function signal generator is set to a stable DC voltage (2.5V), and the signal output terminal is biased to the control gate electrode of the composite dielectric grating photosensitive detector to be tested. In this stage, the signal output of the signal generator is kept closed;

[0094] (4) Testing phase:

[0095] The operation of the whole system is controlled by the current and voltage signal sampling analyzer. When it starts to run, the signals of ports SMU1, SMU2, SMU3 and SMU4 start to output, the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested are correctly biased, and the non-steady-state excitation signal function signal generator will be triggered to generate signal output, and the output signal will be applied to the control gate electrode of the composite dielectric grating photosensitive detector to be tested; at the same time, the current and voltage signal sampling analyzer will collect the current on the drain electrode of the composite dielectric grating photosensitive detector to be tested in real time and store it in a csv format file of raw data;

[0096] (5) Data processing stage:

[0097] After the test phase, the original data of the DC current on the drain electrode of the composite dielectric grating photosensitive detector to be tested is obtained when the control gate electrode is subjected to a constant DC bias condition;

[0098] The raw data is imported into the MATLAB program on the computer, and after pre-filtering, fast Fourier analysis and power spectrum density calculation are performed to obtain the drain electrode current noise spectrum of the composite dielectric grating photosensitive detector to be tested under constant control gate bias conditions.

[0099] Figure 3 The output signal of the non-steady-state excitation function signal generator in the steady-state excitation current sampling working mode is schematically shown. When the trigger signal is input and the function signal generator detects a rising edge, the non-steady-state excitation function signal generator will output a built-in DC signal and set it to a suitable voltage value. At this time, the composite dielectric grating photosensitive detector to be tested works under steady-state excitation. The current and voltage signal sampling analyzer will collect a steady-state current at the drain electrode of the photosensitive detector. After a sampling period, the sampling ends and the collected steady-state current data is stored inside the instrument. The steady-state current data includes the leakage current noise of the composite dielectric grating photosensitive detector under steady-state excitation, which is imported into the current noise analysis program in the external computer. The current noise analysis program will use Fourier analysis and power spectrum density analysis according to the analysis method of the steady-state excitation current sampling working mode to obtain the noise data of the composite dielectric grating photosensitive detector under steady-state excitation.

[0100] Example 4

[0101] The working method of non-steady-state excitation current sampling includes the following steps:

[0102] (1) Device probe connection stage:

[0103] The composite dielectric grating photosensitive detector to be tested is placed in a wafer test probe station, and the source electrode, drain electrode, substrate electrode, and control gate electrode of the photosensitive detector are connected to four external interfaces through probes on the wafer test probe station;

[0104] (2) Initialization stage of current and voltage signal sampling analyzer:

[0105] The three constant voltage signals of the current and voltage signal sampling analyzer are set to appropriate voltage values ​​(0V, 0.5V and -3V), and are biased to the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested through the test ports SMU1, SMU2 and SMU3 respectively; the fourth constant voltage signal of the current and voltage signal sampling analyzer is set to an appropriate voltage value (2.5V), and is biased to the interface of the non-steady-state excitation signal function signal generator receiving the external trigger signal through the test port SMU4;

[0106] (3) Non-steady-state excitation arbitrary wave function signal generation stage:

[0107] The required function signal waveform is generated by using an arbitrary waveform file generation program, and is saved as a waveform file, and the waveform file is imported into the non-steady-state excitation signal function signal generator, which will be able to generate the required output signal according to the waveform file during the test process;

[0108] (4) Initialization stage of the non-steady-state excitation signal function generator:

[0109] The output of the non-steady-state excitation signal function signal generator is set to a stable DC voltage (2.5V), and the signal output terminal is biased to the control gate electrode of the composite dielectric grating photosensitive detector to be tested. In this stage, the signal output of the signal generator is kept closed;

[0110] (5) Testing phase:

[0111] The operation of the whole system is controlled by the current and voltage signal sampling analyzer. When it starts to run, the signals of ports SMU1, SMU2, SMU3 and SMU4 start to output, the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested are correctly biased, and the non-steady-state excitation signal function signal generator will be triggered to generate signal output, and the output signal will be applied to the control gate electrode of the composite dielectric grating photosensitive detector to be tested; at the same time, the current and voltage signal sampling analyzer will collect the current on the drain electrode of the composite dielectric grating photosensitive detector to be tested in real time and store it in a csv format file of raw data;

[0112] (6) Data processing stage:

[0113] After the test phase, the original data of the DC current on the drain electrode of the composite dielectric grating photosensitive detector to be tested is obtained when the control gate electrode is subjected to a constant DC bias condition;

[0114] The raw data is imported into the MATLAB program on the computer, and after pre-filtering, fast Fourier analysis and power spectral density calculation are performed to obtain the drain electrode current noise spectrum of the composite dielectric grating photosensitive detector to be tested under the condition of non-steady-state excitation signal controlled gate bias; and under specific non-steady-state excitation signal conditions, various specific noise information in the waveform can be extracted according to the actual current waveform to obtain various noise data in the raw data.

[0115] Figure 4 The output signal of the non-steady-state excitation function signal generator in the non-steady-state excitation current sampling working mode is schematically shown; the waveform of the output signal is mainly divided into Figure 4There are two types of waveforms; the first type of waveform includes a reset process and a ramp scanning process to simulate the exposure reading process of a single composite dielectric grating photosensitive detector after a single reset; the second type of waveform includes a reset process and four ramp scanning processes to simulate the sequential reading process of four columns of pixels after a single reset of a chip array composed of composite dielectric grating photosensitive detectors in the actual working process; when the trigger signal is input to the non-steady-state excitation function signal generator and it detects the rising edge of the trigger signal, it will output a periodic signal composed of one of the above two waveforms as a single cycle waveform, and the number of output cycles can be preset. At this time, the composite dielectric grating photosensitive detector to be tested works under non-steady-state ramp excitation, and the current and voltage signal sampling analyzer will collect multiple non-steady-state ramp currents at the drain electrode of the photosensitive detector, and the sampling will end after a sampling time and the collected non-steady-state ramp current data will be stored in the instrument. The non-steady-state ramp current data includes the statistical data of the readout signal noise of the composite dielectric grating photosensitive detector under non-steady-state excitation. It is imported into the current noise analysis program in the external computer. The current noise analysis program will use the analysis method of the non-steady-state excitation current sampling working mode, and use the ramp waveform analysis and statistical analysis methods to obtain the readout signal noise data of the composite dielectric grating photosensitive detector under non-steady-state excitation.

[0116] Example 5

[0117] In the hardware connection relationship of the non-steady-state noise test system, the following two points need to be considered from the perspective of impedance matching:

[0118] (1) Impedance matching between transmission line and port

[0119] In the noise test system of Example 1, the impedance of the input and output ports of all the instruments used is 50Ω, so in the connection of the system transmission line, it is necessary to give priority to the coaxial transmission line with an impedance value of 50Ω. If a 50Ω coaxial transmission line is not used, for example, a 100Ω coaxial transmission line is used in this system, a 50Ω-100Ω conversion connector is required at the input and output ports to ensure impedance matching on the entire signal transmission line.

[0120] (2) Adjustment of excitation signal

[0121] For the actual test system, due to inevitable objective factors such as instrument degradation and product errors, it is impossible to achieve perfect impedance matching in the signal transmission line. Therefore, for the steady-state excitation signal output by the current and voltage signal sampling analyzer SMU1, SMU2, SMU3, and SMU4 ports, a certain delay is required after it is applied to wait for the signal overshoot to end before the device under test can enter a stable state; for the non-steady-state excitation signal output by the non-steady-state excitation function signal generator, the sudden change signal contained in its output waveform is replaced by a 5mV / μs slow-changing ramp signal in this test system, thereby reducing or even eliminating the signal overshoot.

[0122] After the above two adjustments, the current signal sampled during the entire test process will not contain any overshoot, so no additional spectrum components will be introduced, and no subsequent processing of the signal data will be affected.

[0123] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A non-steady-state excitation noise test system for a composite dielectric grating photosensitive detector, characterized in that: It includes hardware and software parts. The hardware part includes three modules: current and voltage signal sampling analyzer, wafer test probe station and non-steady-state excitation function signal generator; the software part includes two parts: arbitrary waveform file generation program and current noise analysis program; the object to be tested is a composite dielectric grating photosensitive detector.

2. The non-steady-state excitation noise test system according to claim 1, characterized in that: The composite dielectric grating photosensitive detector comprises four independent electrodes, namely, a control gate electrode, a source electrode, a drain electrode and a substrate electrode.

3. The non-steady-state excitation noise test system according to claim 2, characterized in that: The non-steady-state excitation signal function signal generator includes an interface for receiving an external trigger signal and an interface for transmitting a function signal to the outside.

4. The non-steady-state excitation noise test system according to claim 3, characterized in that: The hardware is connected as follows: The composite dielectric grating photosensitive detector to be tested is externally connected through the four ports SMU1, SMU2, SMU3, and SMU4 of the wafer test probe station; three SMU ports of the current and voltage signal sampling analyzer are connected to the drain electrode, substrate electrode, and source electrode of the composite dielectric grating photosensitive detector through the wafer test probe station, and the fourth SMU port is connected to the trigger input port of the non-steady-state excitation function signal generator; the signal output port of the non-steady-state excitation function signal generator is connected to the control gate electrode of the photosensitive detector through the wafer test probe station; The raw experimental data obtained after the hardware part experimental test will be stored in the current and voltage signal sampling analyzer.

5. The non-steady-state excitation noise test system according to claim 4, characterized in that: The software part operates as follows: The arbitrary waveform file generation program will generate a specified non-steady-state excitation signal waveform file according to the test requirements, and input the waveform file into the non-steady-state excitation signal function generator; The current noise analysis program can read the current data derived from the current and voltage signal sampling analyzer, and calculate and characterize the noise performance of the composite dielectric grating photosensitive detector to be tested according to different working modes.

6. The non-steady-state excitation noise test system according to claim 5, characterized in that: The current and voltage signal sampling analyzer will control the test process of the entire test system, and at the same time use the test port to collect the current data of the drain electrode of the composite dielectric grating photosensitive detector to be tested, and save it inside the analyzer.

7. The non-steady-state excitation noise test system according to claim 6, characterized in that: The arbitrary waveform file generation program will generate a specified non-steady-state excitation signal waveform file according to the test requirements, and input the waveform file into the non-steady-state excitation signal function generator; the non-steady-state excitation signal function signal generator will, under the control of the current and voltage signal sampling analyzer, output the specified function signal according to the signal waveform in the arbitrary waveform file, and bias it on the control gate electrode of the composite dielectric grating photosensitive detector.

8. The working method of the non-steady-state excitation noise test system of the composite dielectric grating photosensitive detector according to any one of claims 1 to 7, characterized in that: The working methods are divided into two types, the first is a working method of steady-state excitation current sampling, and the second is a working method of unsteady-state excitation current sampling.

9. The working method according to claim 8, characterized in that: The working method of steady-state excitation current sampling includes the following steps: (1) Device probe connection stage: The composite dielectric grating photosensitive detector to be tested is placed in a wafer test probe station, and the source electrode, drain electrode, substrate electrode, and control gate electrode of the photosensitive detector are connected to four external interfaces through probes on the wafer test probe station; (2) Initialization stage of current and voltage signal sampling analyzer: The three constant voltage signals of the current and voltage signal sampling analyzer are set to appropriate voltage values, and are biased to the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested through the test ports SMU1, SMU2 and SMU3 respectively; the fourth constant voltage signal of the current and voltage signal sampling analyzer is set to an appropriate voltage value, and is biased to the interface of the non-steady-state excitation signal function signal generator for receiving an external trigger signal through the test port SMU4; (3) Initialization stage of the non-steady-state excitation signal function generator: The output of the non-steady-state excitation signal function signal generator is set to a stable DC voltage, which is biased to the control gate electrode of the composite dielectric grating photosensitive detector to be tested through the signal output terminal. In this stage, the signal output of the signal generator is kept closed; (4) Testing phase: The operation of the whole system is controlled by the current and voltage signal sampling analyzer. When it starts to run, the signals of ports SMU1, SMU2, SMU3 and SMU4 start to output, the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested are correctly biased, and the non-steady-state excitation signal function signal generator will be triggered to generate signal output, and the output signal will be applied to the control gate electrode of the composite dielectric grating photosensitive detector to be tested; at the same time, the current and voltage signal sampling analyzer will collect the current on the drain electrode of the composite dielectric grating photosensitive detector to be tested in real time and store it in a csv format file of raw data; (5) Data processing stage: After the test phase, the original data of the DC current on the drain electrode of the composite dielectric grating photosensitive detector to be tested is obtained when the control gate electrode is subjected to a constant DC bias condition; The raw data is imported into the MATLAB program on the computer, and after pre-filtering, fast Fourier analysis and power spectrum density calculation are performed to obtain the drain electrode current noise spectrum of the composite dielectric grating photosensitive detector to be tested under constant control gate bias conditions.

10. The working method according to claim 8, characterized in that: The working method of non-steady-state excitation current sampling includes the following steps: (1) Device probe connection stage: The composite dielectric grating photosensitive detector to be tested is placed in a wafer test probe station, and the source electrode, drain electrode, substrate electrode, and control gate electrode of the photosensitive detector are connected to four external interfaces through probes on the wafer test probe station; (2) Initialization stage of current and voltage signal sampling analyzer: The three constant voltage signals of the current and voltage signal sampling analyzer are set to appropriate voltage values, and are biased to the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested through the test ports SMU1, SMU2 and SMU3 respectively; the fourth constant voltage signal of the current and voltage signal sampling analyzer is set to an appropriate voltage value, and is biased to the interface of the non-steady-state excitation signal function signal generator for receiving an external trigger signal through the test port SMU4; (3) Non-steady-state excitation arbitrary wave function signal generation stage: The required function signal waveform is generated by using an arbitrary waveform file generation program, and is saved as a waveform file, and the waveform file is imported into the non-steady-state excitation signal function signal generator, which will be able to generate the required output signal according to the waveform file during the test process; (4) Initialization stage of the non-steady-state excitation signal function generator: The output of the non-steady-state excitation signal function signal generator is set to a stable DC voltage, which is biased to the control gate electrode of the composite dielectric grating photosensitive detector to be tested through the signal output terminal. In this stage, the signal output of the signal generator is kept closed; (5) Testing phase: The operation of the whole system is controlled by the current and voltage signal sampling analyzer. When it starts to run, the signals of ports SMU1, SMU2, SMU3 and SMU4 start to output, the source electrode, drain electrode and substrate electrode of the composite dielectric grating photosensitive detector to be tested are correctly biased, and the non-steady-state excitation signal function signal generator will be triggered to generate signal output, and the output signal will be applied to the control gate electrode of the composite dielectric grating photosensitive detector to be tested; at the same time, the current and voltage signal sampling analyzer will collect the current on the drain electrode of the composite dielectric grating photosensitive detector to be tested in real time and store it in a csv format file of raw data; (6) Data processing stage: After the test phase, the original data of the DC current on the drain electrode of the composite dielectric grating photosensitive detector to be tested is obtained when the control gate electrode is subjected to a constant DC bias condition; The raw data is imported into the MATLAB program on the computer, and after pre-filtering, fast Fourier analysis and power spectral density calculation are performed to obtain the drain electrode current noise spectrum of the composite dielectric grating photosensitive detector to be tested under the condition of non-steady-state excitation signal controlled gate bias; and under specific non-steady-state excitation signal conditions, various specific noise information in the waveform can be extracted according to the actual current waveform to obtain various noise data in the raw data.

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