A method of molecular dynamics simulation of halogen plasma etching of silicon or silicon dioxide

Abstract

The application discloses a method for simulating halogen plasma etching of silicon or silicon dioxide by molecular dynamics, which comprises the following steps: modeling of a silicon or silicon dioxide substrate material, initialization setting of LAMMPS software, plasma etching circulation, data output and analysis processing. The method can simulate the plasma-surface interaction mechanism at the atomic scale by the method of molecular dynamics, analyze the properties of the surface modification layer, and simulate the etching conditions which are independently controllable. The plasma etching of different energy, incident angle and incident dose can be simulated, and the influence of a single variable on the etching result can be accurately analyzed. The method can accurately and quickly predict the effect of halogen plasma etching of silicon or silicon dioxide under different incident conditions, avoids high cost, complexity and uncertainty caused by experiments, and greatly shortens the development process of the halogen plasma etching of silicon or silicon dioxide.

Description

Technical Field

[0001] This invention relates to a method for etching silicon or silicon dioxide using halogen plasma, and more particularly to a method for etching silicon or silicon dioxide using molecular dynamics simulation of halogen plasma. Background Technology

[0002] Plasma etching is a widely used material removal process in semiconductor manufacturing. It involves pulsed plasma streams of a suitable gas mixture directed at a sample. The plasma source (called the etchant) can be charged ions or neutral radicals, which can remove material from the surface through physical sputtering or chemical reactions to generate volatile products.

[0003] In the process of halogen plasma etching of silicon or silicon dioxide, the properties of the substrate surface modification layer have a significant impact on the final etching effect. However, the plasma-surface interaction mechanism at the atomic scale is unclear, quantitative experimental characterization of the surface etching process is difficult, and the details of the surface reaction are hard to describe accurately. Furthermore, halogen plasma etching of silicon or silicon dioxide is costly, time-consuming, and has complex experimental conditions. Ion incident conditions are uncontrollable, and the etching results (etching yield, product composition, etc.) are difficult to predict.

[0004] Molecular dynamics is a set of molecular simulation methods that primarily rely on computers to simulate the motion of molecular and atomic systems; it is a multibody simulation method. By simulating the motion of molecules and atoms over a certain period of time, it examines the behavior of the system evolving over time from a dynamic perspective. Typically, the trajectories of molecules and atoms are obtained by numerically solving Newton's equations of motion, and the potential energy (or its first partial derivative with respect to coordinates, i.e., force) can usually be given by the intermolecular interaction potential energy function. Samples are drawn from the system composed of different states of the molecular system to calculate the configuration integral of the system, and the results of the configuration integral are used to further calculate the thermodynamic quantities and other macroscopic properties of the system.

[0005] Existing molecular dynamics simulation techniques have been applied to magnetron sputtering thin film deposition, C atom bombardment of graphene, and other fields, but a molecular dynamics method for simulating halogen plasma etching of silicon or silicon dioxide is lacking. The main technical obstacle is the difficulty in extracting the key steps in the complex halogen plasma etching process of silicon or silicon dioxide and abstracting them into a molecular dynamics simulation model, while ensuring both accuracy and efficiency in the simulation results. Therefore, to address the problems of high cost, long cycle time, complex conditions, and difficulty in predicting results in actual etching experiments, it is urgent to research and develop new methods. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide an independent, controllable, and rapidly predictable method for molecular dynamics simulation of halogen plasma etching of silicon or silicon dioxide.

[0007] Technical solution: The method for etching silicon or silicon dioxide using molecular dynamics simulation of halogen plasma according to the present invention includes the following steps:

[0008] (1) Modeling of silicon or silicon dioxide substrate materials: Using the modeling software Materials Studio, an initial structural model of the substrate material is constructed according to the crystal structure of silicon or silicon dioxide. The geometric parameters are determined and saved and read into LAMMPS. The fix command is used to fix the bottom two layers of silicon or silicon dioxide atoms.

[0009] (2) LAMMPS software initialization settings: Set the LAMMPS simulation environment parameters, force field, energy minimization, initial temperature, relaxation, plasma generation region and screen output respectively, and group the silicon or silicon dioxide substrate, plasma etching material and etching products for etching process identification.

[0010] (3) Plasma etching cycle: Set the number of etching cycles, create etching ions and set the radius and density according to the type of incident ions, set the initial velocity according to the ion energy, set the incident angle, and set the atoms to keep the charge neutral; perform a single ion bombardment cycle: First, except for the bottom fixed atoms, all atoms evolve for 0.5-2 ps under the NVE ensemble so that the kinetic energy of the incident ions is fully released to the substrate material and subsequent collision cascade occurs. Then, the Langevin or Berendsen thermostat algorithm is applied to the entire system to cool the temperature to the initial temperature of 300K. Finally, the unbonded material (all sputtered or desorbed material) is removed from the system as etching products, and the remaining atoms form the input model for the next ion bombardment.

[0011] (4) Data output and analysis: Output the macroscopic measurement parameters to be measured, visualize the output using OVITO software, and analyze the properties of the modified layer on the surface of silicon or silicon dioxide substrate, as well as the silicon etching yield and product composition.

[0012] In step (1), the geometric parameters, including the number of atoms, surface area, number of stacked layers, and shape structure, are set according to the simulation requirements.

[0013] In step (2), the LAMMPS simulation environment parameters are set as follows: the units of the simulation system are set to metal, the boundary conditions are set to ppf (x periodic boundary conditions, y periodic boundary conditions, z fixed boundary conditions), the atom type is set to sphere, the neighbor list is set to default, and the time step is set to 0.2fs when the ion energy is less than 200eV and 0.1fs when the ion energy is greater than 200eV and less than 500eV.

[0014] In step (2), the setting of the force field is the setting of the potential function. Specifically, the corresponding potential function is set according to the atom type in the simulation system. First, the force field type is set to SW potential function using the pair_style command, and then the corresponding atom type is mapped to the potential function using the pair_coeff command.

[0015] In step (2), the setting of energy minimization is specifically as follows: the min_style command is used to determine that the energy minimization algorithm is the conjugate gradient algorithm, and the minimize command is used to set the relevant parameters to minimize the system energy and eliminate unreasonable model structure;

[0016] In step (2), the initial temperature setting is specifically as follows: the temperature of the system is calculated based on the atomic velocity. The velocity command is used to apply random initial velocities to the atoms of the material substrate according to a Gaussian distribution, and the initial temperature of the system is set to 300K.

[0017] In step (2), the relaxation setting is specifically: under the NVT ensemble, the system is relaxed for 1-10 ps to obtain the substrate structure in equilibrium state;

[0018] In step (2), the plasma generation region is specifically set as follows: at a distance slightly larger than the potential function cutoff distance above the substrate surface. The plasma generation region is set up, and the substrate surface height is defined as the z-coordinate of the highest atom in the system before the start of each etching cycle.

[0019] In step (2), the screen output settings are specifically as follows: the thermo command is used to set the screen to print system information every 1000 time steps, and the thermo_style command is used to set the output physical quantities (temperature, potential energy, kinetic energy, pressure, current time step, total number of atoms in the system) so as to monitor the system information in real time during the simulation.

[0020] In step (2), the grouping setting is specifically: using the group command to group the silicon or silicon dioxide substrate, plasma etching material, etching products, etc., for etching process identification.

[0021] In step (3), the number of etching cycles is set. The plasma etching cycle consists of halogen ion cyclic bombardment of the silicon or silicon dioxide substrate surface. Before the etching cycle starts, the loop command is used to set the number of cycles. The number of cycles is preferably 800-2000 times. The number of cycles should be large enough to ensure that the system reaches a stable state and increase the statistical data of macroscopic measurement parameters.

[0022] In step (3), creating the etching ion involves: first, creating an incident ion in the etching material generation area, with its horizontal position randomized, and then setting its radius and density (F atom diameter is...) according to the type of incident ion using the set command. The density is 12.40826 g / cm³. 3 The initial velocity was set according to the ion energy (225.36 m / s for 50 eV, 318.7 m / s for 100 eV, and 390.33 m / s for 150 eV), and the incident angle (perpendicular to the substrate surface) was also set. The charge neutrality assumption was made: due to electron transfer from surface atoms, it was assumed that the incident ions were neutralized by charge before impacting the surface; therefore, all atoms remained charge neutral in the simulation. (Specifically: the diameter of an F atom is...) The density is 12.40826 g / cm³. 3 The velocity at 50 eV is 225.36 m / s, at 100 eV it is 318.7 m / s, and at 150 eV it is 390.33 m / s; the diameter of a Cl atom is... The density is 8.99186 g / cm³. 3 The energy of 50 eV corresponds to a velocity of 164.9766 m / s, the energy of 100 eV corresponds to a velocity of 233.3121 m / s, and the energy of 150 eV corresponds to a velocity of 285.7479 m / s.

[0023] In step (3), a single ion bombardment cycle can be divided into three stages: First, except for the bottom fixed atoms, all atoms evolve for 0.5-2 ps under the NVE ensemble so that the kinetic energy of the incident ions is fully released to the substrate material and subsequent collision cascade occurs. Then, the Langevin or Berendsen thermostat algorithm is applied to the entire system, with the temperature damping set to 100 times the time step, and the temperature is cooled to the initial 300K for 0.5-2.0 ps. Finally, all sputtered or desorbed materials are removed from the system as etching products using the delete_atoms command, and the remaining atoms form the input model for the next ion bombardment.

[0024] In step (3), in order to prevent the silicon or silicon dioxide substrate from being broken down during the etching process, every 200 time steps, the create_atoms command is used to add 4-8 new layers of silicon or silicon dioxide atoms to the bottom of the substrate and the fix command is used to set the forces in the x, y, and z directions to 0 to re-fix the bottom two layers of atoms.

[0025] In step (4), the dump and dump_modify commands are used to output the macroscopic measurements to be measured, including atom type, velocity, coordinates, force, diameter and other computational parameters, every certain time step (100-5000 steps). The silicon etching yield is the average number of silicon atoms removed in a single ion bombardment.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) It uses molecular dynamics to simulate the plasma-surface interaction mechanism at the atomic scale and analyzes the properties of the surface modification layer, thereby deepening the understanding of the mechanism of halogen plasma etching of silicon or silicon dioxide;

[0027] (2) The simulated etching conditions are independently controllable. Halogen plasma etching with different energies, incident angles and incident doses can be simulated, and the influence of a single variable on the etching results can be accurately analyzed.

[0028] (3) It can accurately and quickly predict the effect of halogen plasma etching of silicon or silicon dioxide under different incident conditions, avoiding the high cost, complexity and uncertainty of experiments, and greatly shortening the development process of halogen plasma etching of silicon or silicon dioxide. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method for molecular dynamics simulation of halogen plasma etching of silicon or silicon dioxide according to the present invention;

[0030] Figure 2 This is the front view of the initial model of fluorine plasma etching of silicon in Embodiment 1 of the present invention;

[0031] Figure 3 This is a front view of the steady-state model of silicon fluorine plasma etching in Embodiment 1 of the present invention;

[0032] Figure 4 This is a graph showing the relationship between fluorine plasma energy and the properties of the substrate surface modification layer in Embodiment 1 of the present invention;

[0033] Figure 5 This is a graph showing the relationship between chlorine plasma energy and the properties of the substrate surface modification layer in Embodiment 1 of the present invention;

[0034] Figure 6This is a graph showing the relationship between fluorine and chlorine plasma energy and silicon yield in Example 1 of the present invention;

[0035] Figure 7 This is a graph showing the relationship between fluorine plasma energy and product composition in Example 1 of the present invention;

[0036] Figure 8 This is a graph showing the relationship between chlorine plasma energy and product composition in Example 1 of the present invention;

[0037] Figure 9 This is the initial model front view of the fluorine reactive ion etching of silicon in Embodiment 2 of the present invention;

[0038] Figure 10 This is a front view of the steady-state model of fluorine reactive ion etching of silicon in Embodiment 2 of the present invention;

[0039] Figure 11 This is a graph showing the relationship between fluorine plasma energy and the properties of the substrate surface modification layer in Embodiment 2 of the present invention;

[0040] Figure 12 This is a graph showing the relationship between fluorine plasma energy and silicon yield in Embodiment 2 of the present invention;

[0041] Figure 13 This is a graph showing the relationship between fluorine plasma energy and product composition in Example 2 of the present invention;

[0042] Figure 14 This is a front view of the initial model of the silicon dioxide substrate in Embodiment 3 of the present invention;

[0043] Figure 15 This is a front view of the steady-state model of fluorine plasma etching of silicon dioxide in Embodiment 3 of the present invention;

[0044] Figure 16 This is a graph showing the relationship between fluorine plasma energy and the properties of the modified layer on the silicon dioxide substrate surface in Embodiment 3 of the present invention;

[0045] Figure 17 This is a graph showing the relationship between chlorine plasma energy and the properties of the modified layer on the silicon dioxide substrate surface in Embodiment 3 of the present invention;

[0046] Figure 18 This is a graph showing the relationship between fluorine and chlorine plasma energy and silicon yield in Example 3 of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the embodiments. The test materials used in the embodiments can all be purchased through conventional means.

[0048] Example 1

[0049] The method for etching silicon or silicon dioxide using molecular dynamics simulation of halogen plasma according to the present invention includes the following steps:

[0050] (1) Modeling of silicon or silicon dioxide substrate materials:

[0051] An initial model of the silicon substrate was constructed using Materials Studio modeling software, based on the diamond lattice structure, with a lattice constant of . The geometric parameters such as the number of atoms, surface area, number of stacked layers, and shape structure are determined according to the simulation requirements and saved as a data file that can be recognized by LAMMPS software. The read_data command is then used to read the data into LAMMPS, and the fix command is used to fix the bottom two layers of silicon atoms.

[0052] like Figure 2 As shown, in this embodiment, the initial model substrate is a substrate with a side length of A cube, with a top area of Corresponding to the silicon (100) crystal plane, there are a total of 17 silicon layers, each with 32 silicon atoms (denoted as 1ML), for a total of 544 silicon atoms.

[0053] (2) LAMMPS software initialization settings:

[0054] LAMMPS simulation environment parameter settings: The unit of the simulation system is set to metal, the boundary conditions are set to periodic boundary conditions in the X and Y directions (horizontal direction) and fixed boundary conditions in the Z direction, the atom type is set to sphere, the neighbor list is set to default, and the time step is set to 0.2fs.

[0055] Force field (potential function) settings: Use the pair_style command to set the Stillinger-Weber (SW) potential function according to the silicon and fluorine or chlorine atom system in the simulation system, and then use the pair_coeff command to set the corresponding SW potential function file and silicon, fluorine or chlorine atom mapping;

[0056] Specifically, the SW potential function takes the following form:

[0057]

[0058] Where Ф represents the total potential energy of the system, and v2 and v3 are the two-body and three-body potential terms, respectively. The total potential energy is represented by the sum of the two-body and three-body potential terms. The two-body potential term is of the Lennard-Jones type and has an exponential cutoff function to limit its range of influence; the three-body potential term provides that energy is rapidly lost when the configuration of three adjacent atoms deviates significantly from the diamond lattice, i.e., when the three-body angle ≠ 109.5°.

[0059] Energy minimization: The `min_style` command determines that the energy minimization algorithm is the conjugate gradient algorithm, and the `minimize` command sets the relevant parameters. Energy minimization eliminates unreasonable model structures.

[0060] Temperature initialization: The system temperature is calculated based on the atomic velocities; therefore, temperature initialization is essentially performing velocity initialization on the atoms. The `velocity` command is used to apply random initial velocities to each atom in the substrate according to a Gaussian distribution. In this example, the initial system temperature is set to 300K.

[0061] Relaxation: Under the NVT ensemble, the system is relaxed for 5 ps with a damping time of 0.02 ps (100 times the time step) to obtain the equilibrium substrate structure.

[0062] Setting up the ion generation region: The plasma generation region is set up slightly above the substrate surface height, at a distance greater than the potential function cutoff distance. The substrate surface height is defined as the z-coordinate of the highest atom in the system before the start of each etching cycle.

[0063] Specifically, such as Figure 2 As shown, in this embodiment, above the initial model substrate An ion generation region is set at a distance of meters, and in subsequent etching cycles, the substrate surface height and the ion generation region are updated before the start of each ion incident cycle as the substrate surface height changes.

[0064] Grouping: Use the group command to group silicon substrates, plasma etching materials, etching products, etc., for identification of the etching process;

[0065] Screen output settings: Use the thermo command to set the screen to print system information every 1000 steps, and the thermo_style command to set the output physical quantities, including system temperature, potential energy, kinetic energy, and number of atoms, so as to monitor system information in real time during the simulation.

[0066] (3) Plasma etching cycle:

[0067] Setting the number of cycles: The plasma etching cycle consists of cyclically bombarding the silicon surface with halide ions. Before starting the etching cycle, use the loop command to set the number of cycles to 1000 (approximately 31 mL).

[0068] Creating an etching ion: First, create a fluoride ion in the etching material generation region using the `create_atom` command. The horizontal position is generated by a random number (using the `random` command), and the diameter is set using the `set` command. The density is 12.40826 g / cm³. 3 (If it is a chloride ion, then the diameter is) The density is 8.99186 g / cm³. 3 The ion energy was set to 50 eV, and the incident angle was set to perpendicular to the substrate surface downwards (v). z <0);

[0069] Charge neutrality assumption: Due to electron transfer of surface atoms, it is assumed that the incident ions are neutralized by charge before impacting the surface. Therefore, all atoms remain charge neutral in the simulation. This is reflected in the fact that the potential function does not consider the effect of charge and the atom type is set to sphere to exclude atomic charge information.

[0070] A single ion bombardment can be divided into three stages: First, except for the two bottom layers of fixed atoms, all atoms evolve for 1 ps under the NVE ensemble, allowing the kinetic energy of the incident ions to be fully released into the substrate material and subsequent collision cascades occur. Then, the Berendsen thermostat algorithm is applied to the entire system to cool it to the initial temperature of 300 K, with a thermal damping of 0.02 ps (100 times the time step). Finally, all atoms that do not interact with the substrate and have velocities (v) away from the surface are bombarded. z Atoms or groups of atoms with >0) are removed from the system and marked as etching products, while the remaining atoms form the input model for the next ion bombardment.

[0071] To prevent the silicon substrate from being broken down during the etching process, two silicon atomic layers are added to the bottom of the substrate after every 200 ion etching cycles and fixed with the fix command. Then the entire system is allowed to relax for 2 ps under the nvt ensemble.

[0072] (4) Data output and analysis

[0073] Etching steady state: specifically, such as Figure 3 As shown, the system reached a stable state after approximately 320 (10 mL) ion bombardments, and then the macroscopic measurement parameters of the etching system, including silicon etching yield and product composition, were statistically analyzed.

[0074] Data output: Use the dump and dump_modify commands to output the macroscopic measurement parameters to be measured every 1000 steps;

[0075] Data analysis and processing: Use OVITO software to visualize the output files, observe whether the evolution of the etching system is reasonable, and analyze the properties of the modified layer on the silicon substrate surface, as well as the silicon etching yield and product composition. The silicon etching yield is defined as the number of silicon atoms removed in a single ion bombardment.

[0076] Specifically, such as Figure 4 , Figure 5As shown, based on the data in the molecular dynamics simulation output file, the properties of the modified layer on the surface of the silicon substrate under steady-state conditions at different halogen (fluorine, chloride) ion incident energies (50-150eV) (plasma bombardment destroys the surface structure of the silicon substrate, breaking Si-Si bonds and forming Si-F bonds or Si-Cl bonds) were obtained, including the depth of the modified layer (the distance between the deepest halogen atom in the substrate and the highest atom on the substrate surface) and the proportion of halogen atoms in the substrate.

[0077] like Figure 6 As shown, based on the data in the molecular dynamics simulation output file, the relationship between the yield of silicon etched by fluorine and chlorine plasma under steady state (the average number of silicon atoms sputtered by a single ion bombardment) and the incident ion energy (50-150 eV) was obtained.

[0078] like Figure 7 , Figure 8 As shown, based on the data in the molecular dynamics simulation output file, the relationship between the composition (percentage of each product) of the products (only products containing one Si) of silicon etched by fluorine and chlorine plasma under steady state and the incident ion energy (50-150eV) was obtained.

[0079] Example 2

[0080] Fluorine plasma reactive ion etching (RIE) molecular dynamics simulation of silicon substrates:

[0081] The molecular dynamics simulation method of the present invention for halogen plasma etching of silicon or silicon dioxide, specifically for molecular dynamics simulation of fluorine plasma reactive ion etching of silicon substrates, includes the following steps:

[0082] (1) Modeling of silicon or silicon dioxide substrate materials:

[0083] An initial model of the silicon substrate was constructed using Materials Studio modeling software, based on the diamond lattice structure, with a lattice constant of . The geometric parameters such as the number of atoms, surface area, number of stacked layers, and shape structure are determined according to the simulation requirements and saved as a data file that can be recognized by LAMMPS software. The read_data command is then used to read the data into LAMMPS, and the fix command is used to fix the bottom two layers of silicon atoms.

[0084] like Figure 2 As shown, in this embodiment, the initial model substrate is a substrate with a side length of A cube, with a top area of Corresponding to the silicon (100) crystal plane, there are a total of 17 silicon layers, each with 32 silicon atoms (denoted as 1ML), for a total of 544 silicon atoms.

[0085] (2) LAMMPS software initialization settings:

[0086] LAMMPS simulation environment parameter settings: The unit of the simulation system is set to metal, the boundary conditions are set to periodic boundary conditions in the XY direction (horizontal direction) and fixed boundary conditions in the Z direction, the atom type is set to sphere, the neighbor list is set to default, and the time step is set to 0.2fs.

[0087] Force field (potential function) settings: Use the pair_style command to set the Stillinger-Weber (SW) potential function according to the silicon and fluorine atom system in the simulation system, and then use the pair_coeff command to set the corresponding SW potential function file and silicon and fluorine atom mapping;

[0088] Specifically, the SW potential function takes the following form:

[0089]

[0090] Where Ф represents the total potential energy of the system, and v2 and v3 are the two-body and three-body potential terms, respectively. The total potential energy is represented by the sum of the two-body and three-body potential terms. The two-body potential term is of the Lennard-Jones type and has an exponential cutoff function to limit its range of influence; the three-body potential term provides that energy is rapidly lost when the configuration of three adjacent atoms deviates significantly from the diamond lattice, i.e., when the three-body angle ≠ 109.5°.

[0091] Energy minimization: The `min_style` command determines that the energy minimization algorithm is the conjugate gradient algorithm, and the `minimize` command sets the relevant parameters. Energy minimization eliminates unreasonable model structures.

[0092] Temperature initialization: The system temperature is calculated based on the atomic velocities; therefore, temperature initialization is essentially performing velocity initialization on the atoms. The `velocity` command is used to apply random initial velocities to each atom in the substrate according to a Gaussian distribution. In this example, the initial system temperature is set to 300K.

[0093] Relaxation: Under the NVT ensemble, the system is relaxed for 5 ps with a damping time of 0.02 ps (100 times the time step) to obtain the equilibrium substrate structure.

[0094] Setting up the ion generation region: The plasma generation region is set up slightly above the substrate surface height, at a distance greater than the potential function cutoff distance. The substrate surface height is defined as the z-coordinate of the highest atom in the system before the start of each etching cycle.

[0095] Specifically, such as Figure 2 As shown, in this embodiment, above the initial model substrate An ion generation region is set at a distance of meters, and in subsequent etching cycles, the substrate surface height and the ion generation region are updated before the start of each ion incident cycle as the substrate surface height changes.

[0096] Grouping: Use the group command to group silicon substrates, plasma etching materials, fluorine radicals, etching products, etc., for identification of the etching process;

[0097] Screen output settings: Use the thermo command to set the screen to print system information every 1000 steps, and the thermo_style command to set the output physical quantities, including system temperature, potential energy, kinetic energy, and number of atoms, so as to monitor system information in real time during the simulation.

[0098] (3) Plasma etching cycle:

[0099] Setting the number of cycles: The plasma etching cycle consists of cyclically bombarding the silicon surface with halide ions. Before starting the etching cycle, use the loop command to set the number of cycles to 1000 (approximately 31 mL).

[0100] Creating the etching material: In the fluorine plasma reactive ion etching process, creating the etching material consists of two parts. The first part is the creation of fluorine radicals, which involves randomly creating 10-30 fluorine atoms of 0.1-1.0 eV on the top surface region of the substrate using the `create_atom` command, and setting the diameter using the `set` command. The density is 12.40826 g / cm³. 3 The incident angle is set to be perpendicular to the substrate surface downwards (v z <0); The second part involves creating a high-energy etched fluorine ion, specifically by using `create_atom` to create a fluorine ion in the etched material generation region. The horizontal position of this ion is generated by a random number (using the `random` command), and the diameter is set using the `set` command. The density is 12.40826 g / cm³. 3 The ion energy was set to 50 eV, and the incident angle was set to perpendicular to the substrate surface downwards (v). z <0); such as Figure 9 As shown, low-energy fluorine radicals are attached to the substrate surface, and above the substrate surface... The area contains newly generated high-energy fluoride ions.

[0101] Charge neutrality assumption: Due to electron transfer of surface atoms, it is assumed that the incident ions are neutralized by charge before impacting the surface. Therefore, all atoms remain charge neutral in the simulation. This is reflected in the fact that the potential function does not consider the effect of charge and the atom type is set to sphere to exclude atomic charge information.

[0102] A single ion bombardment can be divided into three stages: First, except for the two bottom layers of fixed atoms, all atoms evolve for 1 ps under the NVE ensemble, allowing the kinetic energy of the incident ions to be fully released into the substrate material and subsequent collision cascades occur. Then, the Berendsen thermostat algorithm is applied to the entire system to cool it to the initial temperature of 300 K, with a thermal damping of 0.02 ps (100 times the time step). Finally, all atoms that do not interact with the substrate and have velocities (v) away from the surface are bombarded. z Atoms or groups of atoms with >0) are removed from the system and marked as etching products, while the remaining atoms form the input model for the next ion bombardment.

[0103] To prevent the silicon substrate from being broken down during the etching process, two silicon atomic layers are added to the bottom of the substrate after every 200 ion etching cycles and fixed with the fix command. Then the entire system is allowed to relax for 2 ps under the nvt ensemble.

[0104] (4) Data output and analysis

[0105] Etching steady state: specifically, such as Figure 10 As shown, the system reached a stable state after approximately 320 (10 mL) ion bombardments, and then the macroscopic measurement parameters of the etching system, including silicon etching yield and product composition, were statistically analyzed.

[0106] Data output: Use the dump and dump_modify commands to output the macroscopic measurement parameters to be measured every 1000 steps;

[0107] Data analysis and processing: Use OVITO software to visualize the output files, observe whether the evolution of the etching system is reasonable, and analyze the properties of the modified layer on the silicon substrate surface, as well as the silicon etching yield and product composition. The silicon etching yield is defined as the number of silicon atoms removed in a single ion bombardment.

[0108] Specifically, such as Figure 11 As shown, based on the data in the molecular dynamics simulation output file, the properties of the modified layer on the surface of the silicon substrate with a steady-state fluorine ion incident energy of (50-150eV) (the surface structure of the silicon substrate was destroyed by plasma bombardment, the Si-Si bonds were broken, and Si-F bonds were formed) were obtained, including the depth of the modified layer (the distance between the deepest fluorine atom in the substrate and the highest atom on the substrate surface) and the proportion of fluorine atoms in the substrate.

[0109] like Figure 12 As shown, based on the data in the molecular dynamics simulation output file, the relationship between the yield of silicon obtained by fluorine plasma reactive ion etching (average number of silicon atoms sputtered in a single ion bombardment) and the incident ion energy (50-150 eV) under steady state was obtained.

[0110] like Figure 13As shown, based on the data in the molecular dynamics simulation output file, the relationship between the composition (percentage of each product) of the products (only products containing one Si) of silicon reactive ion etching under steady state and the incident ion energy (50-150 eV) was obtained.

[0111] Example 3

[0112] Molecular dynamics simulation of halogen plasma etching of silicon dioxide substrate:

[0113] The molecular dynamics simulation method of halogen plasma etching of silicon or silicon dioxide of the present invention is applied to the molecular dynamics simulation of halogen plasma etched silicon dioxide substrates, and includes the following steps:

[0114] (1) Modeling of silicon or silicon dioxide substrate materials:

[0115] An initial model of the silicon dioxide substrate material was constructed using Materials Studio modeling software, based on the silicon dioxide crystal structure. The lattice constant of the ideal β-cristobalite is... The geometric parameters such as the number of atoms, surface area, number of stacked layers, and shape structure are determined according to the simulation requirements and saved as a data file that can be recognized by LAMMPS software. The read_data command is used to read the data into LAMMPS, and the fix command is used to fix the bottom two layers of atoms.

[0116] like Figure 2 As shown, in this embodiment, the top surface of the initial model substrate is a surface with a side length of... The square, the top area Depth There are 12 monolayers, each containing 32 silicon atoms and 64 oxygen atoms, for a total of 384 silicon atoms and 768 oxygen atoms. For ease of counting the dose of incident ions, we take 32 incident ions as 1 mL.

[0117] (2) LAMMPS software initialization settings:

[0118] LAMMPS simulation environment parameter settings: The unit of the simulation system is set to metal, the boundary conditions are set to periodic boundary conditions in the XY direction (horizontal direction) and fixed boundary conditions in the Z direction, the atom type is set to sphere, the neighbor list is set to default, and the time step is set to 0.2fs.

[0119] Force field (potential function) settings: Use the pair_style command to set the Stillinger-Weber (SW) potential function according to the silicon, fluorine or chlorine, oxygen atom system in the simulation system, and then use the pair_coeff command to set the corresponding SW potential function file and silicon, fluorine or chlorine, oxygen atom mapping;

[0120] Specifically, the SW potential function takes the following form:

[0121]

[0122] Where Ф represents the total potential energy of the system, and v2 and v3 are the two-body and three-body potential terms, respectively. The total potential energy is represented by the sum of the two-body and three-body potential terms. The two-body potential term is of the Lennard-Jones type and has an exponential cutoff function to limit its range of influence; the three-body potential term provides that energy is rapidly lost when the configuration of three adjacent atoms deviates significantly from the diamond lattice, i.e., when the three-body angle ≠ 109.5°.

[0123] Energy minimization: The `min_style` command determines that the energy minimization algorithm is the conjugate gradient algorithm, and the `minimize` command sets the relevant parameters. Energy minimization eliminates unreasonable model structures.

[0124] Temperature initialization: The system temperature is calculated based on the atomic velocities; therefore, temperature initialization is essentially performing velocity initialization on the atoms. The `velocity` command is used to apply random initial velocities to each atom in the substrate according to a Gaussian distribution. In this example, the initial system temperature is set to 300K.

[0125] Relaxation: Under the NVT ensemble, the system is relaxed for 5 ps with a damping time of 0.02 ps (100 times the time step) to obtain the equilibrium substrate structure.

[0126] Setting up the ion generation region: The plasma generation region is set up slightly above the substrate surface height, at a distance greater than the potential function cutoff distance. The substrate surface height is defined as the z-coordinate of the highest atom in the system before the start of each etching cycle.

[0127] Specifically, such as Figure 14 As shown, in this embodiment, above the initial model substrate An ion generation region is set at a distance of meters, and in subsequent etching cycles, the substrate surface height and the ion generation region are updated before the start of each ion incident cycle as the substrate surface height changes.

[0128] Grouping: Use the group command to group silicon dioxide substrates, plasma etching materials, etching products, etc., for identification of the etching process;

[0129] Screen output settings: Use the thermo command to set the screen to print system information every 1000 steps, and the thermo_style command to set the output physical quantities, including system temperature, potential energy, kinetic energy, and number of atoms, so as to monitor system information in real time during the simulation.

[0130] (3) Plasma etching cycle:

[0131] Setting the number of cycles: The plasma etching cycle consists of cyclically bombarding the silicon dioxide surface with halide ions. Before starting the etching cycle, use the loop command to set the number of cycles to 1000 (approximately 31 mL).

[0132] Creating an etching ion: First, create a fluoride ion in the etching material generation region using the `create_atom` command. The horizontal position is generated by a random number (using the `random` command), and the diameter is set using the `set` command. The density is 12.40826 g / cm³. 3 (If it is a chloride ion, then the diameter is) The density is 8.99186 g / cm³. 3 The ion energy was set to 50 eV, and the incident angle was set to perpendicular to the substrate surface downwards (v). z <0);

[0133] Charge neutrality assumption: Due to electron transfer of surface atoms, it is assumed that the incident ions are neutralized by charge before impacting the surface. Therefore, all atoms remain charge neutral in the simulation. This is reflected in the fact that the potential function does not consider the effect of charge and the atom type is set to sphere to exclude atomic charge information.

[0134] A single ion bombardment can be divided into three stages: First, except for the two bottom layers of fixed atoms, all atoms evolve for 1 ps under the NVE ensemble, allowing the kinetic energy of the incident ions to be fully released into the substrate material and subsequent collision cascades occur. Then, the Berendsen thermostat algorithm is applied to the entire system to cool the temperature to 300 K, with a thermal damping of 0.02 ps (100 times the time step). Finally, all atoms that do not interact with the substrate and have velocities (v) away from the surface are bombarded. z Atoms or groups of atoms with >0) are removed from the system and marked as etching products, while the remaining atoms form the input model for the next ion bombardment.

[0135] To prevent the silicon dioxide substrate from being broken down during the etching process, two silicon dioxide atomic layers are added to the bottom of the substrate after every 200 ion etching cycles and fixed with the fix command. Then the entire system is relaxed for 2 ps under the nvt ensemble.

[0136] (4) Data output and analysis

[0137] Etching steady state: specifically, such as Figure 15 As shown, the system reached a stable state after approximately 320 (10 mL) ion bombardments, and then the macroscopic measurement parameters of the etching system, including the silicon etching yield, were statistically analyzed.

[0138] Data output: Use the dump and dump_modify commands to output the macroscopic measurement parameters to be measured every 1000 steps;

[0139] Data analysis and processing: Use OVITO software to visualize the output files, observe whether the evolution of the etching system is reasonable, and analyze the properties of the modified layer on the surface of the silicon dioxide substrate and the silicon etching yield. The silicon etching yield is defined as the average number of silicon atoms removed in a single ion bombardment.

[0140] Specifically, such as Figure 16 , Figure 17 As shown, based on the data in the molecular dynamics simulation output file, the properties of the modified layer on the surface of the silicon dioxide substrate (50-150eV) under steady-state different halogen (fluorine, chloride) ion incident energies were obtained, including the depth of the modified layer (the distance between the deepest halogen atom in the substrate and the highest atom on the substrate surface) and the proportion of halogen atoms in the substrate.

[0141] like Figure 18 As shown, based on the data in the molecular dynamics simulation output file, the relationship between the silicon yield (average number of silicon atoms sputtered in a single ion bombardment) of fluorine and chlorine plasma etching of silicon dioxide substrates under steady state and the incident ion energy (50-150 eV) was obtained.

[0142] Therefore, the molecular dynamics simulation method for halogen plasma etching of silicon or silicon dioxide of the present invention simulates the plasma-surface interaction mechanism at the atomic scale using molecular dynamics methods, analyzes the properties of the surface modification layer, thereby deepening the understanding of the mechanism of halogen plasma etching of silicon or silicon dioxide, accurately and quickly predicting the effect of halogen plasma etching of silicon or silicon dioxide under different incident conditions, avoiding the high cost, complexity and uncertainty of experiments; and with the continuous development of computer hardware such as CPUs and GPUs, the computing efficiency of computer simulation is constantly improving, further significantly shortening the development process of halogen plasma etching of silicon or silicon dioxide, which has great application prospects.

Claims

1. A method of molecular dynamics simulation of halogen plasma etching of silicon or silicon dioxide, characterized in that, The method comprises the following steps: (1) modeling of silicon or silicon dioxide substrate material: using modeling software Materials Studio to construct an initial structure model of the substrate material according to the lattice structure of silicon or silicon dioxide, determining geometric parameters and saving reading to LAMMPS, using the fix command to fix the bottom two layers of silicon or silicon dioxide atoms, wherein the geometric parameters include the number of atoms, the size of the surface area, the number of stacked layers and the shape structure, and are set according to the needs of simulation; (2) initialization setting of LAMMPS software: setting the simulation environment parameters, force field, energy minimization, initial temperature, relaxation, plasma generation area and screen output of LAMMPS respectively, and grouping the silicon or silicon dioxide substrate, plasma etching material and etching product for etching process identification; The setting of the plasma generation area is specifically: setting the plasma generation area at 5Å above the substrate surface, and the substrate surface height is defined as the z coordinate of the highest atom in the system before each etching cycle starts; The setting of the screen output is specifically: using the thermo command to set the time step interval of screen printing system information, and using the thermo_style command to set the output physical quantities including system potential energy, kinetic energy, temperature, pressure, current time step number and total number of system atoms; The setting of the grouping is specifically: using the group command to group the silicon or silicon dioxide substrate, plasma etching material and etching product for etching process identification; (3) plasma etching cycle: setting the number of etching cycles, creating etching ions and setting the radius and density according to the incident ion species, setting the initial velocity according to the ion energy, setting the incident angle, and setting the atomic charge to maintain charge neutrality; single ion bombardment cycle: first, all atoms except the bottom fixed atoms evolve in the nve ensemble for 0.5-2ps to make the kinetic energy of the incident ions fully released to the substrate material and subsequent collision cascade occurs, then the thermostat algorithm is applied to the whole system to cool the temperature to the initial temperature, and finally the materials not combined with the material are deleted from the system, and the remaining atoms form the input model for the next ion bombardment; (4) data output and analysis processing: outputting the macroscopic measurement parameters to be tested, visualizing using OVITO software, and analyzing the properties of the silicon or silicon dioxide substrate surface modification layer and the etching yield and product composition of silicon; Using the dump and dump_modify commands, the macroscopic measurement parameters to be tested including atomic type, velocity, coordinate, force, diameter and other calculated quantities are output every certain time step, and the silicon etching yield is the average number of silicon atoms removed in a single ion bombardment.

2. The method of claim 1, wherein, In step (2), the setting of the LAMMPS simulation environment parameters is as follows: the unit of the simulation system is set as metal, the boundary conditions in the x and y directions are set as periodic boundary conditions, the boundary condition in the z direction is set as a fixed boundary condition, the atom type is set as sphere, the neighbor list is defined as default, the time step is set as 0.2 fs when the ion energy is less than 200 eV, the time step is set as 0.1 fs when the ion energy is greater than 200 eV and less than 1000 eV, and the time step is set as 0.05 fs when the ion energy is greater than 1000 eV and less than 2000 eV; The setting of the force field, i.e., the setting of the potential function, is as follows: the corresponding potential function is set according to the atom type in the simulation system, the force field type is first set as the SW potential function using the pair_style command, and then the atom type to potential function mapping is set using the pair_coeff command.

3. The method of claim 1, wherein, In step (2), the setting of the energy minimization is as follows: the energy minimization algorithm is determined to be the conjugate gradient algorithm using the min_style command, and the related parameters are set using the minimize command; The setting of the initial temperature is as follows: the temperature of the system is calculated according to the velocity of the atoms, the initial velocity is applied to the atoms of the material substrate according to the Gaussian distribution using the velocity command, and the initial temperature of the system is set as 300 K; The setting of the relaxation is as follows: the system is relaxed at 300 K for 5-10 ps under the nvt ensemble to obtain the equilibrium substrate structure.

4. The method of claim 1, wherein, In step (3), the number of etching cycles is set, and the molecular dynamics etching simulation is composed of the cyclic bombardment of halogen ions on the surface of silicon or silicon dioxide; before the start of the etching cycle, the number of cycles is set using the loop command.

5. The method of claim 1, wherein, In step (3), the etching ions are created: first, an incident ion is created in the etching material generation area, and the radius and density are set according to the incident ion species using the set command, the initial velocity is set according to the ion energy, and the incident angle is set perpendicular to the substrate surface.

6. The method of claim 1, wherein, In step (3), a single ion bombardment cycle can be divided into three stages: first, all atoms except the bottom fixed atoms evolve under the nve ensemble for 0.5-2 ps to allow the kinetic energy of the incident ions to be fully released to the substrate material and subsequent collision cascades to occur, then the Langevin or Berendsen thermostat algorithm is applied to the entire system, the temperature damping is set as 100 times the time step, and the temperature is cooled to the initial temperature of 300 K for 0.5-2.0 ps, finally, all sputtered or desorbed materials are removed from the system as etching products using the delete_atoms command, and the remaining atoms form the input model for the next ion bombardment.

7. The method of claim 1, wherein, In step (3), new 4-8 layers of silicon or silicon dioxide atoms are added to the bottom of the substrate every 200 time steps during the etching process using the create_atoms command, and the x, y, and z directions are set to 0 using the fix command to re-fix the bottom two layers of atoms.

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