A method for simulating a high pressure dry oxygen thermal oxidation process of single crystal silicon

Abstract

The application provides a method for simulating a high-pressure dry oxygen thermal oxidation process of monocrystalline silicon, and relates to the technical field of silicon process simulation, and comprises the following steps: step S1: a model of monocrystalline silicon is constructed, a vacuum layer is arranged on the surface of the monocrystalline silicon in the model, O2 molecules are added into the vacuum layer, and the atomic positions of the monocrystalline silicon are optimized by using a reactive force field molecular dynamics method under a state higher than atmospheric pressure; step S2: after the monocrystalline silicon is heated to a reaction temperature, the temperature and pressure are kept constant, until the monocrystalline silicon and the O2 molecules fully react, the model is annealed, the atomic positions are optimized after cooling, and an oxidation sample is obtained; the oxidation sample comprises an oxidation layer, a sub-oxidation layer and a silicon substrate layer; step S3: structural characteristic parameters of the oxidation layer and the sub-oxidation layer are obtained. The application accelerates the reaction rate by increasing the O2 molecule concentration through high pressure, and obtains the structural characteristic parameters of the oxidation layer and the sub-oxidation layer, which is beneficial to the study of the sub-oxidation state and stress distribution at the interface between the oxidation layer and the sub-oxidation layer.

Description

Technical Field

[0001] This invention relates to the field of silicon process simulation technology, and more specifically, to a method for simulating a high-pressure dry oxygen thermal oxidation process for single-crystal silicon. Background Technology

[0002] There are many methods for preparing silicon dioxide thin films by oxidizing crystalline silicon, including thermal oxidation, electrochemical anodizing, and plasma reaction. Among these, thermal oxidation is the most widely used. With the development of thermal oxidation technology, the main methods at present include the following: First, chlorine-containing oxidation, which involves adding a certain amount of chlorine-containing atmosphere (such as HCl, C2HCl3, etc.) to the oxidizing atmosphere, which greatly improves the quality of silicon dioxide and the performance of the Si-SiO2 system; Second, high-pressure oxidation, which carries out oxidation in an oxidizing atmosphere of several to tens of atmospheres, thereby reducing the oxidation temperature (commonly used temperature is 650-950 degrees Celsius, while still maintaining a high oxidation rate), and reducing the induced defects, stress, and impurity redistribution effects during the oxidation process; Third, using inert gas dilution to reduce the partial pressure of O2 and H2O and the oxidation rate, thereby precisely controlling the thickness of SiO2 and preparing ultrathin (tens of angstroms) silicon dioxide films. For silicon dioxide thin film devices prepared by high-pressure oxidation, high-precision measurement and testing methods are required when studying their device performance. However, there is usually no specific theoretical guidance for detecting the microstructure and local stress distribution of the oxidation state, especially the influence of the interfacial sub-oxidation state and stress distribution of single-crystal silicon oxidation on the electronic properties of the device. Researchers can only analyze and judge based on their experience on the basis of existing work, and then repeatedly explore and experiment under various process conditions. This results in low research efficiency and poor systematicity. Summary of the Invention

[0003] The problem addressed by this invention is how to efficiently control the interfacial sub-oxidation state and stress distribution of single-crystal silicon oxidation in order to study its influence on the electronic properties of devices.

[0004] To address the above problems, this invention provides a method for simulating a high-pressure dry oxygen thermal oxidation process for single-crystal silicon, comprising the following steps:

[0005] Step S1: Construct a model of single-crystal silicon, set a vacuum layer on the surface of the single-crystal silicon in the model, add O2 molecules in the vacuum layer, and optimize the atomic positions of the single-crystal silicon using the reactive force field molecular dynamics method under a pressure higher than atmospheric pressure;

[0006] Step S2: After heating the single crystal silicon to the reaction temperature, maintain constant temperature and pressure until the single crystal silicon and the O2 molecules react fully. Anneal the model, cool it, and optimize the atomic positions to obtain an oxide sample. The oxide sample includes an oxide layer, a sub-oxide layer, and a silicon substrate layer.

[0007] Step S3: Obtain the structural feature parameters of the oxide layer and the sub-oxide layer.

[0008] Furthermore, in step S1, the model is in the shape of a cuboid, and the vacuum layer is disposed at both ends of the model.

[0009] Furthermore, in step S1, the thickness of the vacuum layer ranges from 2 to 5 nm.

[0010] Furthermore, in step S1, the range of pressure above atmospheric pressure is 1-100 MPa.

[0011] Further, in step S2, heating the single-crystal silicon to the reaction temperature includes:

[0012] The mixture is slowly heated from 300K to the reaction temperature, which is in the range of 1000-1400K.

[0013] Furthermore, in step S2, the time range for the single crystal silicon to fully react with the O2 molecules is 2-3 ns.

[0014] Furthermore, in step S2, the annealing method is to anneal the model to room temperature using the reactive force field molecular dynamics method, and the annealing time is 50 ps.

[0015] Furthermore, in step S2, the cooling refers to cooling to 0K, and the cooling time is 50ps.

[0016] Furthermore, in step S3, the structural feature parameters include at least bond length, bond angle, coordination number, defect type, and defect concentration.

[0017] Furthermore, in step S3, the bond length includes at least the Si-O bond length and the Si-Si bond length, and the bond angle includes at least the O-Si-O bond angle and the Si-O-Si bond angle.

[0018] The method for simulating high-pressure dry oxygen thermal oxidation of single-crystal silicon described in this invention has the advantage over existing technologies in that, by establishing a model of single-crystal silicon and increasing the distribution concentration of O2 molecules under conditions higher than atmospheric pressure, the O2 molecules in the vacuum layer react rapidly with silicon atoms on the surface of the single-crystal silicon, thereby increasing the oxidation rate of single-crystal silicon and accelerating the generation of oxidized samples using the simulated high-pressure dry oxygen thermal oxidation process. By obtaining the structural characteristic parameters of the oxide layer and sub-oxide layer in the oxidized sample, the secondary oxidation state and stress distribution at the interface between the oxide layer and sub-oxide layer can be understood at the atomic level. This is beneficial for studying the influence of the secondary oxidation state and stress distribution at the interface between the oxide layer and sub-oxide layer on the electronic properties of the device. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method for simulating high-pressure dry oxygen thermal oxidation of monocrystalline silicon in an embodiment of the present invention;

[0020] Figure 2 This is the single-crystal silicon model and the initial structural model with O2 molecules added inside the vacuum layer in the embodiments of the present invention;

[0021] Figure 3 This is a schematic diagram of the structure of the oxidation sample obtained by simulating a single-crystal silicon high-pressure dry oxygen thermal oxidation process under 1373K conditions in an embodiment of the present invention.

[0022] Figure 4 This is a statistical diagram of the bond lengths of Si-O and Si-Si bonds in the oxide layer and sub-oxide layer in the embodiments of the present invention;

[0023] Figure 5 This is a statistical diagram of the O-Si-O bond angles in the oxide layer and the sub-oxide layer in the embodiments of the present invention;

[0024] Figure 6 This is a statistical diagram of the Si-O-Si bond angles in the oxide layer and the sub-oxide layer in the embodiments of the present invention;

[0025] Figure 7 This is a statistical chart of coordination number in an embodiment of the present invention. Detailed Implementation

[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0027] It should be noted that, in the description of the embodiments of this application, the term "some specific embodiments" means that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same implementation or instance. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0028] like Figure 1 As shown, this embodiment of the invention provides a method for simulating a high-pressure dry oxygen thermal oxidation process for single-crystal silicon, comprising the following steps:

[0029] Step S1: Construct a model of single-crystal silicon, set a vacuum layer on the surface of the single-crystal silicon in the model, add O2 molecules in the vacuum layer, and optimize the atomic positions of the single-crystal silicon using the reactive force field molecular dynamics method under a pressure higher than atmospheric pressure.

[0030] Step S2: After heating the single crystal silicon to the reaction temperature, maintain constant temperature and pressure until the single crystal silicon reacts fully with O2 molecules. Anneal the model, cool it, and optimize the atomic positions to obtain an oxide sample. The oxide sample includes an oxide layer, a sub-oxide layer, and a silicon substrate layer.

[0031] Step S3: Obtain the structural characteristic parameters of the oxide layer and the sub-oxide layer.

[0032] The method for simulating high-pressure dry oxygen thermal oxidation of single-crystal silicon described in this invention establishes a model of single-crystal silicon and increases the distribution concentration of O2 molecules under conditions higher than atmospheric pressure. This allows O2 molecules in the vacuum layer to react rapidly with silicon atoms on the surface of the single-crystal silicon, thereby increasing the oxidation rate of the single-crystal silicon and accelerating the generation of oxidized samples using the simulated high-pressure dry oxygen thermal oxidation process. By obtaining the structural characteristic parameters of the oxide layer and sub-oxide layer in the oxidized sample, the secondary oxidation state and stress distribution at the interface between the oxide layer and sub-oxide layer can be understood at the atomic level. This is beneficial for studying the influence of the secondary oxidation state and stress distribution at the interface between the oxide layer and sub-oxide layer on the electronic properties of the device.

[0033] Specifically, such as Figure 2 As shown, the single-crystal silicon model in step S1 of this embodiment is a diamond structure. In order to avoid mutual interference, a vacuum layer can be set on one or more surfaces of the single-crystal silicon. A certain number of O2 molecules can be added to each vacuum layer, so as to realize the one-time acquisition of one or more sets of data. The acquisition of multiple sets of data can reduce the simulation time and number of simulations.

[0034] In step S2 of this embodiment, under reaction temperature and pressure above atmospheric pressure, the migration rate and concentration of O2 molecules are controlled. This improves the effective collision probability between O2 molecules and silicon atoms on the single-crystal silicon surface, greatly increasing the reaction completion rate and shortening the simulation time. After the reaction is complete, the final oxidized sample is obtained through annealing, cooling, and atomic position optimization.

[0035] In step S3 of this embodiment, the structural characteristic parameters of the oxide layer and the sub-oxide layer of the oxidized sample and their interface are statistically analyzed to obtain the structural state and stress distribution of the sub-oxide layer, which is helpful to discover the influence of the above parameters on the electronic properties of the device.

[0036] In some specific embodiments, in step S1, the model is rectangular in shape, and vacuum layers are set at both ends of the model. Therefore, by setting vacuum layers at both ends of the rectangular model, the process of generating oxidized samples using a high-pressure dry oxygen thermal oxidation process can be simulated simultaneously on both sides. This method is highly efficient, obtains structural characteristic parameters from both sides, reduces the number of simulations, and allows for comparison and correction of structural characteristic parameters, improving data accuracy and facilitating the discovery of the influence patterns on the electronic properties of the device.

[0037] In some specific embodiments, the thickness of the vacuum layer in step S1 ranges from 2 to 5 nm. This suitable thickness range provides sufficient space for O2 molecules to move and effectively collide with atoms on the single-crystal silicon surface, enabling the rapid generation of oxide samples via a high-pressure dry oxygen thermal oxidation process.

[0038] In some specific embodiments, in step S1, the pressure above atmospheric pressure ranges from 1 to 100 MPa. This effectively increases the concentration of O2 molecules within this range, raising the probability of collisions between O2 molecules and atoms on the single-crystal silicon surface, and accelerating the oxidation reaction rate.

[0039] In some specific embodiments, step S2, heating the monocrystalline silicon to the reaction temperature, includes: slowly heating from 300K to the reaction temperature, with the reaction temperature ranging from 1000-1400K.

[0040] Therefore, by slowly heating from 300K to simulate the process from actual room temperature to reaction temperature, the preparation process of the high-pressure dry oxygen thermal oxidation method can be accurately reproduced. At the same time, slow heating is conducive to the stability of the state of atoms and O2 molecules, reducing simulation errors.

[0041] In some specific embodiments, in step S2, the time range for the monocrystalline silicon to fully react with O2 molecules is 2-3 ns. Therefore, under high pressure conditions of 1-100 MPa, the reaction time of a certain concentration of O2 with monocrystalline silicon is greatly improved, achieving effective control over the reaction time.

[0042] In some specific embodiments, in step S2, the annealing method involves annealing the model to room temperature using reactive force field molecular dynamics for 50 ps. This simulates the annealing process in actual manufacturing, achieving structural homogenization and eliminating defects and residual stress through reactive force field molecular dynamics.

[0043] In some specific embodiments, in step S2, cooling refers to cooling to 0K, and the cooling time is 50 ps. This simulates the actual cooling process, controls the cooling time, and improves the accuracy of simulating the actual process.

[0044] In some specific embodiments, step S3 includes at least bond length, bond angle, coordination number, defect type, and defect concentration as structural characteristic parameters. This allows for a more comprehensive understanding of the structural characteristic parameters of the interface between the oxide layer and the suboxide layer.

[0045] In some specific embodiments, in step S3, the bond lengths include at least the Si-O bond length and the Si-Si bond length, and the bond angles include at least the O-Si-O bond angle and the Si-O-Si bond angle. This allows for statistical analysis of the bond lengths and bond angles, enabling deeper structural control.

[0046] Example 1

[0047] The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon described in this embodiment includes the following steps:

[0048] In this embodiment, the interatomic interactions are described using a reactive force field. A 2.2nm × 2.2nm × 6.6nm cuboid single-crystal silicon model is constructed using the molecular dynamics simulation software LAMMPS. A vacuum layer with a thickness of 4.6nm is added to both ends of the model. A 4.6nm thick O2 molecular layer is added within each vacuum layer. O2 molecules are emitted perpendicularly to the vacuum layer along the

[100] crystal orientation. Figure 1 As shown; secondly, the atomic positions of the entire model are optimized and relaxed to maintain the silicon atoms in a low-energy equilibrium state. Under a reaction pressure of 100 MPa, the temperature is slowly increased from 300 K to 1373 K over 50 ps. Then, the reaction temperature is maintained at 1373 K for 2 ns until the reaction is complete. Finally, annealing is continued for 50 ps, ​​followed by cooling to 0 K over 50 ps. The atomic positions are optimized again, ultimately yielding the oxide sample, as shown. Figure 2 As shown, both ends of the single-crystal silicon have undergone sufficient oxidation, clearly revealing oxide and sub-oxide layer regions. Structural characteristic parameters of the oxide and sub-oxide layers were obtained, including statistical analysis of defect types and corresponding concentrations in the oxide and sub-oxide layers. The analysis results are as follows: Figure 3 As shown. Statistical results for bond angles, bond lengths, and coordination numbers of the oxide layer and sub-oxide layer are as follows. Figure 4 As shown.

[0049] Example 2

[0050] The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon described in this embodiment includes the following steps:

[0051] In this embodiment, the interatomic interactions are described using a reactive force field. A 2.2nm × 2.2nm × 6.6nm cuboid single-crystal silicon model is constructed using the molecular dynamics simulation software LAMMPS. A 2nm thick vacuum layer is added to both ends of the model, and a 2nm thick O2 molecular layer is added inside each vacuum layer. O2 molecules are emitted perpendicularly to the vacuum layer along the

[100] crystal orientation. Figure 1As shown; secondly, the atomic positions of the entire model are optimized and relaxed to keep silicon atoms in a low-energy equilibrium state. Under a reaction pressure of 100 MPa, the temperature is slowly increased from 300 K to 1000 K for 50 ps. Then, the reaction temperature is maintained at 1000 K for 3 ns. Finally, annealing is continued for 50 ps, ​​followed by cooling to 0 K for 50 ps. The atomic positions are optimized again to obtain the oxide sample. The structural characteristic parameters of the oxide layer and the sub-oxide layer are obtained, including statistical analysis of the defect types and corresponding concentrations of the oxide layer and the sub-oxide layer, as well as statistics on the bond angles, bond lengths, and coordination numbers of the oxide layer and the sub-oxide layer.

[0052] Example 3

[0053] The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon described in this embodiment includes the following steps:

[0054] In this embodiment, the interatomic interactions are described using a reactive force field. A 2.2nm × 2.2nm × 6.6nm cuboid single-crystal silicon model is constructed using the molecular dynamics simulation software LAMMPS. A 5nm thick vacuum layer is added to both ends of the model, and a 5nm thick O2 molecular layer is added inside each vacuum layer. O2 molecules are emitted perpendicularly to the vacuum layer along the

[100] crystal orientation. Figure 1 As shown; secondly, the atomic positions of the entire model were optimized and relaxed to maintain the silicon atoms in a low-energy equilibrium state. Under a reaction pressure of 1 MPa, the temperature was slowly increased from 300 K to 1400 K over 50 ps. Then, the reaction temperature was maintained at 1400 K for 2.8 ns. Finally, annealing was continued for 50 ps, ​​followed by cooling to 0 K over 50 ps. The atomic positions were optimized again to obtain the oxide sample. The structural characteristic parameters of the oxide layer and sub-oxide layer were obtained, including statistical analysis of the defect types and corresponding concentrations of the oxide layer and sub-oxide layer, as well as statistics on the bond angles, bond lengths, and coordination numbers of the oxide layer and sub-oxide layer.

[0055] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for simulating a high-pressure dry oxygen thermal oxidation process for single-crystal silicon, characterized in that, Includes the following steps: Step S1: Construct a model of single-crystal silicon. A vacuum layer is set on the surface of the single-crystal silicon in the model. O2 molecules are added in the vacuum layer, and the atomic positions of the single-crystal silicon are optimized using the reactive force field molecular dynamics method under a pressure higher than atmospheric pressure. The model is rectangular in shape, and the vacuum layer is set at both ends of the model. The model of single-crystal silicon is constructed using the molecular dynamics simulation software LAMMPS. Step S2: After heating the single crystal silicon to the reaction temperature, maintain constant temperature and pressure until the single crystal silicon and the O2 molecules react fully. Anneal the model, cool it, and optimize the atomic positions to obtain an oxide sample. The oxide sample includes an oxide layer, a sub-oxide layer, and a silicon substrate layer. Step S3: Obtain the structural feature parameters of the oxide layer and the sub-oxide layer; the structural feature parameters include at least bond length, bond angle, coordination number, defect type and defect concentration; the structural feature parameters of the oxide layer and the sub-oxide layer are used to understand the sub-oxidation state and stress distribution at the interface between the oxide layer and the sub-oxide layer at the atomic level.

2. The method for simulating high-pressure dry oxygen thermal oxidation of single-crystal silicon according to claim 1, characterized in that, In step S1, the thickness of the vacuum layer ranges from 2 to 5 nm.

3. The method for simulating high-pressure dry oxygen thermal oxidation of single-crystal silicon according to claim 1, characterized in that, In step S1, the range of pressure above atmospheric pressure is 1-100 MPa.

4. The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon according to claim 1, characterized in that, In step S2, heating the single-crystal silicon to the reaction temperature includes: The mixture is slowly heated from 300K to the reaction temperature, which is in the range of 1000-1400K.

5. The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon according to claim 1, characterized in that, In step S2, the time range for the single crystal silicon to fully react with the O2 molecules is 2-3 ns.

6. The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon according to claim 1, characterized in that, In step S2, the annealing method is to anneal the model to room temperature using the reactive force field molecular dynamics method, and the annealing time is 50 ps.

7. The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon according to claim 1, characterized in that, In step S2, cooling refers to cooling to 0K for 50 ps.

8. The method for simulating high-pressure dry oxygen thermal oxidation process of single-crystal silicon according to claim 7, characterized in that, In step S3, the bond length includes at least the Si-O bond length and the Si-Si bond length, and the bond angle includes at least the O-Si-O bond angle and the Si-O-Si bond angle.

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