A method for calculating the equivalence of displacements of different particles

Abstract

The present invention provides a method for calculating the displacement equivalence of different particles, and belongs to the field of space environment analysis technology. The method includes: S1, constructing a geometric model, selecting a radiation displacement damage sensitive area, setting simulation parameters, and then performing a simulated radiation experiment; S2, calling the Track function and the Step function, and calculating the non-ionizing energy deposition and the incident direction coordinates of all step particles; S3, judging whether the non-ionizing energy deposition of the output step particles is zero, if not zero, then outputting the non-ionizing energy deposition and the incident direction coordinate data of the step particles; S4, accumulating the data of the output step particles in the selected depth interval, calculating the NIEL depth distribution curve along the incident direction, and normalizing the NIEL depth distribution curve. The present invention performs a simulation test based on Geant4 software, screens the non-ionizing energy deposition and the incident direction coordinate data of the output step particles according to the judgment conditions, and then accumulates and calculates to obtain NIEL, and can quickly obtain the NIEL distribution that changes with depth.

Description

Technical Field

[0001] The present invention relates to the technical field of space environment analysis, and in particular to a method for calculating the equivalence of displacements of different particles. Background Art

[0002] The space radiation effect caused by the space radiation environment is one of the main factors that induce on-orbit failures of spacecraft. The space radiation effect refers to the phenomenon that the electronic components and materials of spacecraft experience performance degradation, functional obstruction or loss under the influence of space radiation particles. The main manifestations of space radiation effects are total dose effect, displacement damage effect and single particle effect. This requires aerospace science and technology workers to strengthen the research on the space radiation environment and effects, and incorporate space radiation environment engineering into various links such as spacecraft mission design, orbit selection, structural layout, selection of materials and electronic components, spacecraft on-orbit failure analysis and space early warning, so as to improve the on-orbit reliability and life of spacecraft.

[0003] Displacement damage effect is the main factor leading to the failure of spacecraft electronic components and materials in the space radiation environment. For silicon (Si)-based electronic devices, displacement damage effect will cause irreversible fatal damage to the silicon body. It refers to the phenomenon that a large number of radiation particles enter the interior of the silicon-based electronic device material and collide elastically with the atomic nuclei of the material, causing the displacement of the material lattice atoms, internal defects, affecting the minority carrier lifetime, and thus causing the device-related performance to gradually decline or even lose. A large number of experimental studies have shown that for most electronic components and materials, when the type of radiation particles is different, the performance change of the device caused by displacement damage and the non-ionizing energy loss (NIEL) are linearly related, that is, the distribution of NIEL has a direct relationship with the displacement damage caused by aerospace devices. The displacement damage and device performance degradation caused by the same NIEL are often the same, regardless of the type and energy of the radiation particles. Therefore, the calculation of displacement damage can be converted into the calculation of NIEL. By calculating the NIEL of specific particles with different energies in the device material, the performance change of the device under different particle irradiation can be evaluated.

[0004] At present, the NIEL calculation method for simulating space radiation particles incident on silicon-based electronic devices is mainly based on the SRIM software to simulate the energy loss and distribution of ions in the target material. However, the output data of the SRIM software is limited and the built-in physical model cannot be adjusted. There are few research reports on using Geant4 software to simulate radiation particles incident on silicon-based electronic devices to calculate NIEL. There is no reliable experimental comparison basis, which makes it difficult to understand the NIEL information caused by different radiation particles incident on silicon-based electronic devices. Therefore, if the NIEL distribution that varies with depth can be quickly obtained for different radiation particles incident on silicon-based electronic devices, it will have important engineering value and scientific significance for simplifying irradiation tests, saving scientific research resources, and equivalently evaluating damage. Summary of the invention

[0005] In view of the above problems in the prior art, the present invention provides a method for calculating the equivalence of displacements of different particles.

[0006] To achieve the above objectives, the present invention is specifically implemented through the following technologies:

[0007] The present invention provides a method for calculating the displacement equivalence of different particles, comprising the following steps:

[0008] S1. Import the geometry file of the device into the Geant4 software, construct a geometry model corresponding to the device structure, select the radiation displacement damage sensitive area, set the simulation parameters, the simulation parameters include the radiation source parameters and the incident particle and material interaction model, the radiation source parameters include the incident direction, and then conduct a simulated radiation experiment;

[0009] S2, calling the Track function and the Step function to calculate the non-ionizing energy deposition and incident direction coordinates of all step particles;

[0010] S3, setting a judgment condition to judge whether the non-ionizing energy deposition of the output step particle is zero, if not zero, outputting the non-ionizing energy deposition and the incident direction coordinate data of the step particle;

[0011] S4. Accumulating the non-ionizing energy deposition data of the output step particles within the selected depth interval, calculating the non-ionizing energy loss depth distribution curve along the incident direction, and normalizing the non-ionizing energy loss depth distribution curve.

[0012] Furthermore, in step S1, the device is a MOS device, and the radiation displacement damage sensitive area is 7-9 μm away from the device interface.

[0013] Furthermore, in step S1, the incident direction is perpendicular to the device interface.

[0014] Furthermore, in step S1, the radiation source parameters also include one or more of the radiation source type, radiation source shape, radiation source position, radiation particle number and incident energy.

[0015] Furthermore, the type of radiation source includes one of hydrogen ions, carbon ions, silicon ions, germanium ions, and tin ions.

[0016] Furthermore, the shape of the radiation source includes one of a point shape and a surface shape.

[0017] Furthermore, the coordinates of the radiation source position are (0, 0, -1 mm), the number of radiation particles is 10,000, and the incident energy range is 0-10 GeV.

[0018] Furthermore, in step S1, the incident particle-matter interaction model includes an EmStandardNR model and a G4LindhardPartition model.

[0019] Further, in step S4, the non-ionizing energy deposition data of the output particles in the selected depth interval are accumulated according to a first formula, wherein the first formula includes:

[0020]

[0021] Where NIEL represents non-ionizing energy loss, x represents the depth interval, and E non -ionizing represents the non-ionizing energy deposition, x i+1 represents the upper limit of the depth interval, x i Indicates the lower limit of the depth range.

[0022] Furthermore, x is calculated by a second formula, wherein the second formula includes:

[0023]

[0024] Furthermore, in step S4, the specific operation of the normalization process includes: dividing the non-ionizing energy loss depth distribution curve by the number of radiated particles to perform the normalization process.

[0025] The present invention is based on Geant4 software, selects heavy ion standard electromagnetic model (EmStandardNR model and G4LindhardPartition model) to simulate the interaction process between heavy ions and materials, and then reads the non-ionizing energy deposition and incident direction coordinates of all step particles by calling Track function and Step function in Geant4 software package, and then accumulates the non-ionizing energy deposition data of output Step particles in the selected depth interval, and calculates the non-ionizing energy loss (NIEL), so that for any heavy ion incident on the device structure with any energy and any incident mode (including point and surface), the NIEL distribution that varies with depth can be quickly obtained. Rapidly obtaining the NIEL distribution at different depths can save scientific research resources for simplifying the device on-orbit operation life and reliability irradiation test, and provide an effective basis for displacement damage equivalence research. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 NIEL depth distribution curves after different radiation sources are incident on the device in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. In addition, the meanings of the terms "comprising", "containing", and "having" are non-restrictive, and other steps and other components that do not affect the results can be added. Unless otherwise specified, materials, equipment, and reagents are all commercially available.

[0029] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] The embodiment of the present invention provides a method for calculating the displacement equivalence of different particles, comprising the following steps:

[0031] S1. Import the device's geometry file into Geant4 software. Generally, the geometry file in CAD format is used to build a geometric model corresponding to the device structure. Select the radiation displacement damage sensitive area. The sensitive area is set according to the analysis requirements. Set the simulation parameters. The simulation parameters include the radiation source parameters and the incident particle-matter interaction model. Then conduct a simulated radiation experiment.

[0032] The radiation displacement damage sensitive area usually has the largest displacement damage. After setting the radiation displacement damage sensitive area, the method of the present invention is used to quickly simulate the NIEL distribution after irradiation with different particles. If different particles can produce the same NIEL peak distribution in the displacement damage sensitive area of ​​the same device, the displacement damage research of different radiation particles can be equivalent, and only one of the radiation sources can be studied. For example, taking MOS devices as an example, the radiation displacement damage sensitive area is 7-9μm away from the interface. If different radiation sources have the same NIEL peak at 7-9μm after irradiation, the displacement damage effects generated by these radiation sources can be equivalent or approximately equivalent. Selecting one of the typical radiation sources for research can represent other radiation sources.

[0033] Optionally, the radiation source parameters include one or more of the type of radiation source, the shape of the radiation source, the position of the radiation source, the number of radiation particles, the incident direction and the incident energy.

[0034] The type of radiation source described above includes atomic number and atomic mass when setting, and the aforementioned parameters jointly determine the incident particles, i.e., the type of radiation source. Specifically, the type of radiation source includes one of hydrogen (H) ions, carbon (C) ions, silicon (Si) ions, germanium (Ge) ions, and tin (Sn) ions; the shape of the radiation source includes one of point and surface, wherein the surface radiation source is rectangular by default, which is defined by setting the length and width; the default position of the radiation source is (0,0,-1mm); the number of radiation particles is set according to demand, and can be greater than 1, usually 10,000; the incident direction is perpendicular to the device interface, and the default coordinates are (0,0,1); the incident energy range is 0-10GeV.

[0035] In order to simulate the interaction process between heavy ions and radiation displacement damage sensitive areas, the incident particle and matter interaction model may include the heavy ion standard electromagnetic model - EmStandardNR model and G4LindhardPartition model. non-ionizing ) is calculated using the G4LindhardPartition model according to a certain proportion in the total energy deposition. This proportion is the proportion of the displacement damage energy to the recoil atomic energy. It is obtained by G4LindhardPartition through the collision cross section. The specific process is built into the Geant4 software and is related to the atomic number and atomic mass of the atoms in the matrix material of the radiation displacement damage sensitive area and the radiation source.

[0036] S2. Call the Track function and the Step function to calculate the non-ionizing energy deposition and the incident direction coordinates of all Step particles; the NIEL distribution along the incident direction can be obtained according to the aforementioned parameters, that is, the data of the Step particles that change with depth in the incident direction are recorded to calculate the NIEL distribution.

[0037] In Geant4 software, a simulation process is established, which is called a Run. After the Run is established, the geometric structure and physical process need to be initialized; after the initialization is completed, the simulation process begins. First, a particle is emitted. The process from emitting a particle to the death of all secondary particles becomes an event, called an Event. In each Event process, the particle may generate multiple secondary particles after reacting with the device matrix material. Each particle will have a track, called a Track. The Track of each particle (including the initial particle and the secondary particle) is composed of many steps, called Steps. Step is the smallest simulation unit of the physical process reaction. It can be as small as nm or even fm in length. Information about a certain physical process of the current transmission particle can be obtained through random sampling, such as whether the photoelectric effect occurs. If so, secondary particles, i.e. free electrons with kinetic energy, will be generated, and then the physical process of sampling the electron will continue to be simulated, such as ionization, how much energy is deposited, etc.; each Step represents an interaction between the particle and the material.

[0038] S3. Set the judgment condition to judge whether the non-ionizing energy deposition of the particle of the output step is zero. If it is not zero, output the non-ionizing energy deposition and incident direction coordinate data of the particle of the step.

[0039] The judgment condition is specifically: when the non-ionizing energy deposition of the output Step is not zero, that is, greater than zero, it is determined to record the Step information, and the non-ionizing energy deposition and incident direction coordinate data of the Step particle are output.

[0040] S4. Accumulate the non-ionizing energy deposition data of the output step particles in the selected depth interval, calculate the non-ionizing energy loss (NIEL) depth distribution curve along the incident direction, and normalize the NIEL depth distribution curve to complete the displacement equivalence calculation process of different particles.

[0041] Specifically, the non-ionizing energy deposition data of the output step particles in the selected depth interval are accumulated according to the first formula, and the first formula includes:

[0042]

[0043] Where NIEL represents the non-ionizing energy loss within the depth interval x, unit: MeV cm 2 ·g -1 , x represents the depth interval, E non-ionizing represents the non-ionizing energy deposition, x i+1 Indicates the upper limit of the depth interval, x i Indicates the lower limit of the depth range.

[0044] For example, if the depth interval is 10 μm and the interval range is 2 μm, then NIEL (10μm) The E of the output Step particle in the interval [9,11] unit μm non-ionizing Add up.

[0045] Specifically, x and x i+1 and x i The relationship is described by the second formula, which includes:

[0046]

[0047] Among them, x represents the depth interval, x i+1 Indicates the upper limit of the depth interval, x i Indicates the lower limit of the depth range.

[0048] The specific operation of performing the normalization process described above includes: dividing the non-ionizing energy loss depth distribution curve by the number of radiated particles for normalization.

[0049] The present invention is based on Geant4 software, selects heavy ion standard electromagnetic model (EmStandardNR model and G4LindhardPartition model) to simulate the interaction process between heavy ions and materials, and then reads the non-ionizing energy deposition and incident direction coordinates of Step particles by calling Track function and Step function in Geant4 software package, and then accumulates the non-ionizing energy deposition data of output Step particles in the selected depth interval, and calculates the non-ionizing energy loss (NIEL), so that for any heavy ion incident on the device structure with any energy and any incident mode (including point and surface), the NIEL distribution that varies with depth can be quickly obtained. The number of radiation-induced defects in the material is approximately proportional to NIEL. It is a common practice internationally to predict the damage caused to the material by different radiation environments through NIEL, and to qualitatively estimate the displacement damage caused by heavy ion radiation approximately. NIEL is an important parameter for evaluating the displacement damage of electronic components in orbit and causing performance degradation. Rapidly obtaining NIEL distribution at different depths can save scientific research resources for simplifying the device's in-orbit operation life and reliability irradiation test. In addition, the NIEL peak value generated by the radiation particles in the displacement damage sensitive area of ​​the device will cause irreversible damage to the device. By using the method of the present invention to quickly simulate the NIEL peak value after irradiation by different particles in the displacement damage sensitive area of ​​the same device, it is possible to know in advance what type of space radiation particles will cause the greatest displacement damage to the displacement damage sensitive area of ​​the device, prevent damage to the device in the orbit environment, and save unnecessary irradiation tests. For the displacement damage research of particles from different radiation sources that can produce the same NIEL depth distribution, only one of them needs to be studied.

[0050] The present invention is based on Geant4 software, which can accurately obtain data such as the type of secondary particles, secondary particle coordinates and non-ionizing energy deposition generated by each interaction between particles and matter, and can arbitrarily adjust physical model parameters according to experimental values, and can arbitrarily adjust the minimum value range of NIEL values ​​that vary with depth. Its calculation speed is much faster than that of the SRIM software program.

[0051] It should be noted that the application objects of the method of the present invention include materials, devices, electronic systems and structures.

[0052] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually based on the conditions recommended by the manufacturer.

[0053] Example 1

[0054] A method for calculating the equivalence of displacements of different particles comprises the following steps:

[0055] S1. Import the CAD format geometry file of the MOS device (semiconductor material is silicon) into the Geant4 software, build a geometric model corresponding to the device structure, select the silicon-based device 7-9 μm away from the interface as the radiation displacement damage sensitive area, set the simulation parameters, including the radiation source parameters and the incident particle and material interaction model, and then conduct a simulated radiation experiment;

[0056] The radiation source parameters include the type of radiation source, the shape of the radiation source, the position of the radiation source, the number of radiation particles, the incident direction and the incident energy. In this embodiment, 650keV H ions, 9MeV C ions, 23MeV Si ions, 30MeVGe ions and 35MeV Sn ions are selected as radiation sources, respectively, and a point radiation source is selected to be incident vertically into the device in a single Z direction, and the number of incident particles is 10,000.

[0057] The models for the interaction between incident particles and matter are the EmStandardNR model and the G4LindhardPartition model;

[0058] S2. Call the Track function to calculate the non-ionizing energy deposition and incident direction (Z direction) coordinates of all Step particles;

[0059] S3, setting a judgment condition to judge whether the non-ionizing energy deposition of the output Step particle is zero. When the non-ionizing energy deposition of the output Step is not zero, determining the non-ionizing energy deposition and incident direction coordinate data of the output Step particle;

[0060] S4, substituting the non-ionizing energy deposition and incident direction coordinate data of the output Step particles into the first formula, accumulating the non-ionizing energy deposition data of the output Step particles in the selected depth interval, calculating the non-ionizing energy loss depth distribution curve along the incident direction, dividing the non-ionizing energy loss depth distribution curve by the number of radiated particles for normalization, and completing the normalized displacement equivalence calculation process; the first formula includes:

[0061]

[0062] Where NIEL represents the non-ionizing energy loss within the depth interval x, unit: MeV cm 2 ·g -1 , x represents the depth interval, E non-ionizing represents the non-ionizing energy deposition, x i+1 Indicates the upper limit of the depth interval, x i Indicates the lower limit of the depth range;

[0063] x is calculated according to a second formula, wherein the second formula includes:

[0064]

[0065] In this embodiment, 650keV hydrogen (H) ions, 9MeV carbon (C) ions, 23MeV silicon (Si) ions, 30MeV germanium (Ge) ions, and 35MeV tin (Sn) ions are used as radiation sources to perform simulation experiments. The output data is set to be the non-ionizing energy deposition of all Step particles in the Z direction. The first formula is used to divide the incident depth x in the Z direction into [x i+1 ,x i ] interval range, x is 100nm, data statistics are performed, and the NIEL depth distribution curve along the incident direction, i.e., the Z direction, is calculated. The results are as follows Figure 1 As shown. Figure 1 It can be seen that the normalized NIEL peaks after several different types of radiation particles enter the silicon-based device are almost at the same position, indicating that the displacement damage caused by these ions to the Si-based device at different irradiation doses is equivalent.

Claims

1. A method for calculating the equivalence of displacements of different particles, characterized in that: The following steps are involved: S1. Import the geometry file of the device into the Geant4 software, construct a geometry model corresponding to the device structure, select the radiation displacement damage sensitive area, set the simulation parameters, the simulation parameters include the radiation source parameters and the incident particle and material interaction model, the radiation source parameters include the incident direction, and then conduct a simulated radiation experiment; S2, calling the Track function and the Step function to calculate the non-ionizing energy deposition and incident direction coordinates of all step particles; S3, setting a judgment condition to judge whether the non-ionizing energy deposition of the output step particle is zero, if not zero, outputting the non-ionizing energy deposition and the incident direction coordinate data of the step particle; S4. Accumulating the non-ionizing energy deposition data of the output step particles within the selected depth interval, calculating the non-ionizing energy loss depth distribution curve along the incident direction, and normalizing the non-ionizing energy loss depth distribution curve.

2. The method according to claim 1, characterized in that In step S1, the device is a MOS device, and the radiation displacement damage sensitive area is 7-9 μm away from the device interface.

3. The method according to claim 1, characterized in that In step S1, the incident direction is perpendicular to the device interface.

4. The method according to claim 1, characterized in that: In step S1, the radiation source parameters also include one or more of the radiation source type, radiation source shape, radiation source position, radiation particle number and incident energy.

5. The method according to claim 4, characterized in that The shape of the radiation source includes one of a point shape and a surface shape, and the type of the radiation source includes one of hydrogen ions, carbon ions, silicon ions, germanium ions and tin ions.

6. The method according to claim 4, characterized in that The coordinates of the radiation source position are (0, 0, -1 mm), the number of radiation particles is 10,000, and the incident energy range is 0-10 GeV.

7. The method according to claim 1, characterized in that The incident particle and material interaction models include the EmStandardNR model and the G4LindhardPartition model.

8. The method according to claim 1, characterized in that In step S4, the non-ionizing energy deposition data of the output particles in the selected depth interval are accumulated according to a first formula, wherein the first formula includes: Where NIEL represents non-ionizing energy loss, x represents the depth interval, E non-ionizing represents the non-ionizing energy deposition, x i+1 represents the upper limit of the depth interval, x i Indicates the lower limit of the depth range.

9. The method according to claim 8, characterized in that x is calculated by a second formula, wherein the second formula includes:

10. The method according to claim 1, characterized in that In step S4, the specific operation of the normalization process includes: dividing the non-ionizing energy loss depth distribution curve by the number of radiated particles to perform the normalization process.

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