Phase change storage material screening method and system based on coherent interface

Abstract

The invention provides a coherent interface-based phase change storage material screening method and system. The method comprises the following steps of: firstly, screening and constructing a storage unit initial structure comprising a phase change storage material layer and a candidate interface material layer; performing structure optimization processing on the initial structure of the storage unit to form a coherent interface structure; carrying out high-temperature stability verification on the storage unit comprising the coherent interface structure so as to judge whether the candidate interface material layer is kept in a crystal state or not at the temperature higher than the melting point of the phase-change material; performing crystallization process simulation verification on the storage unit comprising the coherent interface structure to judge whether the coherent interface promotes the phase change storage material layer to be converted from an amorphous state to a crystalline state or not; and finally, based on the results of the high-temperature stability verification and the crystallization process simulation verification, determining the candidate interface material as an effective coherent interface material suitable for accelerating crystallization of the phase change storage material so as to solve the problem of low screening efficiency of the phase change storage material.

Description

A Method and System for Screening Phase Change Memory Materials Based on Coherent Interfaces Technical Field

[0001] This application relates to the field of phase change memory technology, and in particular to a method and system for screening phase change memory materials based on coherent interfaces. Background Technology

[0002] Phase-change memory (PCM) is an important technological approach for achieving fast, non-volatile storage. It utilizes the differences in electrical or optical properties between the crystalline and amorphous states of core PCM materials to achieve storage. This technology boasts advantages such as non-volatility, high read / write speeds, and compatibility with CMOS processes, and is considered a crucial direction for next-generation storage technology, with broad application prospects in general-purpose storage, optical storage, memory-class memory, and neuromorphic computing. However, with the increasing urgency of the demands for high-bandwidth, low-latency, and low-power integrated storage and computing in the era of artificial intelligence and big data, improving the operating speed of PCM devices has become a key bottleneck in the development of this technology.

[0003] To improve the operating speed of phase change memory devices, related technologies mainly employ element doping. Specifically, this approach involves introducing additional doping elements into traditional germanium-antimony-tellurium phase change memory materials. The bonding strength of the doped elements is used to enhance the stability of the crystal nucleus precursor, thereby shortening the random nucleation incubation period and accelerating the crystallization process of the phase change memory material.

[0004] However, the aforementioned element doping schemes have significant drawbacks. By introducing additional elements into the phase change memory material, these schemes increase the material's complexity and may negatively impact its cycling performance. Furthermore, by relying solely on controlling the internal composition of the material to improve performance, these schemes may alter the crystallization kinetics of the amorphous-crystalline transition, leading to an uncontrollable phase transition process. Summary of the Invention

[0005] This application provides a method and system for screening phase change memory materials based on coherent interfaces to solve the problem of low screening efficiency for phase change memory materials.

[0006] This application provides a method for screening phase change memory materials based on coherent interfaces. The method includes: screening and constructing an initial structure of a memory cell comprising a phase change memory material layer and a candidate interface material layer, wherein the crystal structure type of the phase change memory material layer is the same as the crystal structure type of the candidate interface material layer; performing structural optimization processing on the initial structure of the memory cell to form a coherent interface structure; performing high-temperature stability verification on the memory cell comprising the coherent interface structure to determine whether the candidate interface material layer maintains a crystalline state at a temperature higher than the melting point of the phase change material; performing crystallization process simulation verification on the memory cell comprising the coherent interface structure to determine whether the coherent interface promotes the transformation of the phase change memory material layer from an amorphous state to a crystalline state; and determining the candidate interface material as an effective coherent interface material suitable for accelerating the crystallization of the phase change memory material based on the results of the high-temperature stability verification and the crystallization process simulation verification.

[0007] By constructing initial cell structures of phase change memory material layers and candidate interface material layers with the same crystal structure type, and then optimizing the structure to form a coherent interface structure, the structure is then verified through high-temperature stability verification and crystallization process simulation. Based on the verification results, effective coherent interface materials that can maintain the crystal state at high temperatures and promote the crystallization of phase change memory material layers are selected, thereby helping to improve the screening efficiency of phase change memory materials.

[0008] Optionally, the steps of screening and constructing an initial structure of a memory cell comprising a phase change storage material layer and a candidate interface material layer include: performing cell expansion processing on the phase change storage material layer and the candidate interface material layer respectively, so that the constructed interface structure satisfies periodic boundary conditions and reduces the influence of computational scale; stacking the cell-expanded phase change storage material layer and the candidate interface material layer along a specific crystal orientation, and setting an initial interlayer spacing; wherein the lattice constant mismatch rate of the phase change storage material layer and the candidate interface material layer is lower than a preset threshold.

[0009] By expanding the cell, the phase change storage material layer and the candidate interface material layer are made to meet the periodic boundary conditions and reduce the influence of the computational scale. Then, they are stacked along a specific crystal orientation and an initial interlayer spacing is set. At the same time, the lattice constant mismatch rate between the two material layers is controlled to be lower than a preset threshold. This helps to construct an initial structure that is more in line with the actual interface characteristics and is computationally reliable, laying the foundation for subsequent structure optimization and verification.

[0010] Optionally, the step of optimizing the initial structure of the storage cell includes: using the principle of energy minimization, simultaneously adjusting the lattice constant and atomic positions of the initial structure of the storage cell until the initial structure of the storage cell reaches the energy convergence criterion to form a stable coherent interface structure.

[0011] By employing the principle of energy minimization, the lattice constant and atomic positions of the initial structure of the storage cell are adjusted until the structure reaches the energy convergence criterion, thereby helping to obtain a coherent interface structure with higher lattice matching and more stable interface bonding.

[0012] Optionally, the step of verifying the high-temperature stability of the memory cell containing the coherent interface structure includes: heating the memory cell to a first temperature higher than the melting point of the phase change memory material and maintaining it for a preset time; observing and analyzing whether the atomic arrangement order of the candidate interface material layer is maintained within the preset time, and whether significant atomic interdiffusion occurs between the candidate interface material layer and the phase change memory material layer; if the candidate interface material layer maintains a crystalline state and no atomic interdiffusion occurs, then the candidate interface material is determined to meet the high-temperature stability requirements.

[0013] The storage cell is heated to a first temperature higher than the melting point of the phase change storage material and maintained for a preset time. By observing and analyzing whether the candidate interface material layer maintains the atomic arrangement order and whether significant atomic interdiffusion occurs between it and the phase change storage material layer during this period, it can be determined whether it maintains a crystalline state. This helps to screen candidate materials with relatively stable interface structures under high-temperature operating conditions.

[0014] Optionally, the step of simulating and verifying the crystallization process of the memory cell containing the coherent interface structure includes: first heating the memory cell to make its phase change storage material layer turn into a liquid state, and then rapidly cooling it to room temperature to construct an interface structure containing an amorphous phase change storage material layer and a crystalline candidate interface material layer; heating the interface structure to a second temperature within the crystallization temperature range of the phase change storage material; observing and analyzing whether the amorphous phase change storage material layer starts from the coherent interface and epitaxially grows along the interface normal direction at the second temperature, thereby achieving rapid crystallization; if it is observed that the amorphous phase change storage material layer initiates and accelerates crystallization from the coherent interface, then it is determined that the coherent interface has the effect of promoting crystallization.

[0015] The crystallization process of memory cells containing coherent interface structures was simulated and verified. The phase change memory material layer was first transformed into an amorphous state and then rapidly cooled, and then heated to its crystallization temperature range. It was observed whether the amorphous phase change memory material layer started from the coherent interface and grew epitaxially along the normal direction. This helped to determine whether the interface could promote the transformation process of the phase change memory material from an amorphous state to a crystalline state.

[0016] Optionally, the method further includes: performing high-throughput screening on a candidate interface material library; the high-throughput screening is based on at least one of the following conditions: a first screening condition: the candidate interface material has the same crystal structure type as the phase change memory material; a second screening condition: the thermodynamic stability of the candidate interface material meets a preset standard; a third screening condition: the lattice constant mismatch rate between the candidate interface material and the phase change memory material is lower than a preset threshold; a fourth screening condition: the cohesive energy of the candidate interface material is higher than the cohesive energy of the phase change memory material, to characterize its structural stability at high temperatures.

[0017] By using high-throughput screening of candidate interface materials based on conditions such as crystal structure type matching, thermodynamic stability, lattice constant mismatch rate, and relative cohesive energy, it is possible to initially identify materials that are more likely to meet the requirements for coherent interface construction and performance from a large number of candidate materials, thereby improving the efficiency and targeting of subsequent verification steps.

[0018] Optionally, the first screening condition is: both the phase change storage material and the candidate interface material have a rock salt crystal structure.

[0019] By limiting the crystal structure type of both phase change memory materials and candidate interface materials to rock salt type, it is helpful to use the characteristics of this structure type to match and construct coherent interfaces, providing a basis for screening interface materials with specific structural compatibility.

[0020] Optionally, the effective coherent interface material selected by high-throughput screening includes at least one of the following materials: calcium selenide, cerium arsenide, cerium phosphide, cerium selenide, dysprosium arsenide, dysprosium bismuthide, dysprosium antimonide, dysprosium telluride, erbium bismuthide, erbium antimonide, erbium telluride, europium sulfide, europium selenide, gadolinium arsenide, gadolinium antimonide, gadolinium selenide, gadolinium telluride, holmium arsenide, holmium bismuthide, holmium antimonide, holmium telluride, lanthanum arsenide, lanthanum phosphide, lanthanum sulfide, lanthanum selenide, lutetium bismuthide, lutetium antimonide, lutetium telluride, neodymium arsenide, neodymium phosphide, neodymium selenide, and tellurium. Neodymium oxide, neptunium arsenide, neptunium antimonide, neptunium selenide, neptunium telluride, promethium selenide, praseodymium arsenide, praseodymium phosphide, praseodymium sulfide, praseodymium selenide, plutonium arsenide, plutonium selenide, plutonium telluride, scandium bismuthide, scandium antimonide, samarium arsenide, samarium phosphide, samarium antimonide, samarium selenide, samarium telluride, Strontium selenide, terbium arsenide, terbium bismuthide, terbium antimonyide, terbium selenide, terbium telluride, thorium arsenide, thorium germanide, thorium phosphide, thorium selenide, thulium bismuthide, thulium antimonyide, thulium telluride, uranium arsenide, uranium antimonyide, uranium selenide, yttrium arsenide, yttrium bismuthide, yttrium antimonyide, yttrium telluride.

[0021] Through high-throughput screening, at least one of calcium selenide, cerium arsenide, and cerium phosphide was identified as an effective coherent interface material, thus providing a specific and feasible range of candidate materials for the selection of interface materials in practical phase change storage devices.

[0022] Optionally, the cohesive energy of the phase change storage material is greater than 4 electron volts per atom.

[0023] Limiting the cohesive energy of phase change memory materials to greater than 4 electron volts per atom helps ensure that the materials themselves have relatively high bonding strength and structural stability, providing a basis for epitaxial growth at coherent interfaces.

[0024] A second aspect of this application provides a screening system for phase change memory materials based on coherent interfaces, applicable to the screening method for phase change memory materials based on coherent interfaces described in the first aspect. The system includes: a structure screening and construction module for screening and constructing an initial structure of a memory cell containing a phase change memory material layer and a candidate interface material layer, wherein the crystal structure type of the phase change memory material layer is the same as the crystal structure type of the candidate interface material layer; a structure optimization module for performing structural optimization processing on the initial structure of the memory cell to form a coherent interface structure; a high-temperature verification module for performing high-temperature stability verification on the memory cell containing the coherent interface structure to determine whether the candidate interface material layer maintains a crystalline state at temperatures above the melting point of the phase change material; a crystallization verification module for performing crystallization process simulation verification on the memory cell containing the coherent interface structure to determine whether the coherent interface promotes the transformation of the phase change memory material layer from an amorphous state to a crystalline state; and a material determination module for determining, based on the results of the high-temperature stability verification and the crystallization process simulation verification, the candidate interface material as an effective coherent interface material suitable for accelerating the crystallization of the phase change memory material.

[0025] Through the collaborative work of the structure screening and construction module, the structure optimization module, the high-temperature verification module, the crystallization verification module, and the material determination module, the initial structure of the storage cell is constructed and optimized in sequence, the high-temperature stability and crystallization promotion effect of the coherent interface structure are verified, and the effective interface material is determined based on the verification results, which helps to achieve the systematic screening of accelerated crystallization interface materials in phase change storage materials.

[0026] As can be seen from the above technical solutions, this application provides a method and system for screening phase change memory materials based on coherent interfaces. First, an initial structure of a memory cell containing a phase change memory material layer and a candidate interface material layer is constructed, wherein the crystal structure type of the phase change memory material layer is the same as that of the candidate interface material layer. Then, the initial structure of the memory cell is optimized to form a coherent interface structure. The memory cell containing the coherent interface structure undergoes high-temperature stability verification to determine whether the candidate interface material layer maintains a crystalline state at temperatures above the melting point of the phase change material. Next, the memory cell containing the coherent interface structure undergoes crystallization process simulation verification to determine whether the coherent interface promotes the transformation of the phase change memory material layer from an amorphous state to a crystalline state. Finally, based on the results of the high-temperature stability verification and the crystallization process simulation verification, the candidate interface material is determined as an effective coherent interface material suitable for accelerating the crystallization of phase change memory materials, thereby solving the problem of low screening efficiency for phase change memory materials. Attached Figure Description

[0027] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 is a flowchart illustrating the method for screening phase change memory materials based on coherent interfaces provided in an embodiment of this application. Detailed Implementation

[0029] The embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described below do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application.

[0030] To address the issue of low efficiency in screening phase change memory materials, referring to Figure 1, some embodiments of this application provide a method for screening phase change memory materials based on a coherent interface. The method includes: S100: screening and constructing an initial structure of a memory cell containing a phase change memory material layer and a candidate interface material layer.

[0031] The crystal structure type of the phase change storage material layer is the same as that of the candidate interface material layer.

[0032] It should be understood that the same crystal structure type refers to a high degree of matching between the phase change memory material layer and the candidate interface material layer in core crystallographic features such as the periodic arrangement of atoms, the coordination number of atoms, and the bonding environment. Taking the typical phase change memory material Ge2Sb2Te5 (GST) as an example, it exhibits a cubic rock salt mineral structure in its crystalline state. The cubic rock salt mineral structure contains two sets of interpenetrating face-centered cubic (FCC) sublattices; in this structure, germanium (Ge) atoms / antimony (Sb) atoms randomly occupy one set of sublattices, while tellurium (Te) atoms occupy the other set. When yttrium arsenide (YAs) is selected as a candidate interface material, it is precisely because YAs also has a cubic rock salt mineral structure, and its yttrium (Y) atoms and arsenic (As) atoms each occupy a similar set of sublattices, that this "template" effect of atomic arrangement allows the atoms at the interface to naturally continue their respective lattice arrangements, thus laying the structural foundation for the formation of a coherent interface. If the two crystal structures are different, such as one being cubic and the other hexagonal, then the periodic arrangement of their atoms will be fundamentally different, and the atoms at the interface will not be able to achieve ordered alignment of lattice sites, making it unsuitable for constructing a coherent interface.

[0033] In some embodiments, the step of screening and constructing an initial structure of a memory cell comprising a phase change storage material layer and a candidate interface material layer includes: performing cell expansion processing on the phase change storage material layer and the candidate interface material layer respectively, so that the constructed interface structure satisfies periodic boundary conditions and reduces the influence of computational scale.

[0034] Specifically, regarding the cell expansion process for the GST phase change memory material layer and the YAs candidate interface material layer, it's crucial to understand that the core purpose of cell expansion is not only to meet the basic requirements of periodic boundary conditions in first-principles calculations, but more importantly, to ensure that both the upper and lower interfaces of the YAs material in the constructed interface structure can form a good coherent match with the GST material. Since the lattice constants of GST and YAs are already quite close (approximately 4% difference), this lays the foundation for the formation of a coherent interface, allowing for preliminary matching even without significant cell expansion. However, considering that the characteristics of amorphous structures typically require a certain scale range to accurately demonstrate their physicochemical behavior, appropriate cell expansion helps to more realistically simulate actual material systems. Furthermore, during cell expansion, the key is to set the number of atomic layers in both the GST and YAs materials along the z-direction (i.e., the interface normal direction) to an odd number. This special setting is because, under periodic boundary conditions, the computational system will infinitely repeat in three spatial directions. When the YAs material is placed between the GST materials to form an interface structure, its upper and lower surfaces will actually contact the adjacent GST units, forming two symmetrical interfaces. If the number of atomic layers in the z-direction is odd, the atomic arrangement (including the distribution of cation and anion sites) on the upper and lower surfaces of the YAs material can remain consistent. Thus, during periodic repetition, the GSTs at the two interfaces correspond one-to-one with the lattice sites of YAs, ensuring that both interfaces meet the requirements of coherent matching. This effectively avoids the problem of asymmetrical atomic arrangement on the upper and lower surfaces due to an even number of layers, which could lead to significant distortion of the interface structure or a substantial increase in lattice mismatch stress after periodic extension. By setting the number of atomic layers in the z-direction to an odd number, the precise matching of cation and anion sites on the two interfaces can be structurally guaranteed, minimizing structural distortion at the interface and providing a reliable model basis for subsequent accurate calculations of key properties such as the formation energy and electronic structure of the coherent interface.

[0035] The phase change storage material layer after cell expansion treatment is stacked with the candidate interface material layer along a specific crystal orientation, and an initial interlayer spacing is set.

[0036] It should be understood that the specific crystal orientation refers to stacking along the c-direction, i.e., the

[001] crystal orientation of the crystal; and the initial interlayer spacing is set to 3.3 Å in this embodiment. Stacking along the c-direction is chosen to ensure that the crystallographic orientation of the expanded-cell phase change storage material layer (e.g., GST) and the candidate interface material layer (e.g., YAs) remains consistent, ensuring that the atomic arrangement in the stacking direction is aligned according to the preset lattice matching relationship. Setting the initial interlayer spacing to 3.3 Å mainly considers the lattice characteristics of the two materials themselves and the small lattice mismatch. Since the lattice mismatch is small, this initial spacing is considered to be close to the stable distance when the interaction between the two material layers reaches equilibrium. This setting is beneficial for reducing the number of calculation iterations and improving optimization efficiency during subsequent structure optimization, and for faster convergence to the stable structural state with the lowest energy, laying a good foundation for subsequent accurate calculation of properties such as interface binding energy.

[0037] Among them, the lattice constant mismatch rate between the phase change storage material layer and the candidate interface material layer is lower than a preset threshold.

[0038] Specifically, the lattice constant mismatch rate is a key indicator for measuring the degree of lattice matching between two materials. In this embodiment, the preset threshold is set to 4%, meaning that only when the calculated lattice constant mismatch rate is less than 4% is the two materials considered to have the basic conditions for forming a coherent interface in that crystal direction. This is because when the lattice mismatch rate is below 4%, the stress between the material layers is small, and atoms at the interface can achieve regular arrangement through slight elastic deformation or adjustment, thereby forming a stable coherent interface structure. However, if the mismatch rate exceeds this threshold, excessive lattice differences will lead to a large number of dislocations or defects at the interface, making it difficult to maintain the coherent relationship, thus affecting the interface bonding strength and the overall performance of the phase change memory material. By strictly controlling the lattice constant mismatch rate below the preset threshold, it can be ensured that the selected candidate interface materials can form a high-quality coherent interface with the phase change memory material layer, providing an important guarantee for improving the stability and reliability of phase change memory devices.

[0039] S200: Perform structural optimization on the initial structure of the storage unit to form a coherent interface structure.

[0040] In some embodiments, the step of optimizing the initial structure of the memory cell includes: using the principle of energy minimization, simultaneously adjusting the lattice constant and atomic positions of the initial structure of the memory cell until the initial structure of the memory cell reaches the energy convergence criterion to form a stable coherent interface structure.

[0041] It should be understood that the principle of energy minimization refers to the process in atomic-scale simulations where the total energy of the initial structure of the entire memory cell gradually decreases and tends towards a minimum by continuously adjusting the geometric parameters of the system (such as lattice constant and atomic positions). This is because, under thermodynamic equilibrium, a stable structure corresponds to the lowest state of total system energy. Simultaneously adjusting the lattice constant and atomic positions of the initial structure of the memory cell means that, during the optimization process, not only are the individual atoms constituting the initial structure of the memory cell allowed to relax and move near the lattice points to find their most stable equilibrium positions, but the lattice parameters (i.e., lattice constant) of the entire system are also systematically adjusted. This adjustment of the lattice constant is crucial for ensuring that the materials on both sides of the interface can form a coherent relationship; it can effectively alleviate or eliminate stresses that may be caused by initial lattice mismatch.

[0042] Furthermore, the energy convergence criterion is a key indicator for determining whether structural optimization is complete. This typically includes two main aspects: first, the change in the total energy of the system. During iterative optimization, when the difference in the total energy of the system calculated in two adjacent iterations is less than a preset minimum threshold (e.g., it can be set to...), the energy convergence criterion is considered complete. When the energy level is at or below the lower order of magnitude, it indicates that the system's energy has essentially stopped changing significantly. Secondly, there are the forces acting on the atoms. As previously stated, the convergence criterion for these forces is set to... This means that when the maximum force experienced by all atoms in the system is less than this value, the atoms will no longer have a significant tendency to move. Only when both of these aspects (and sometimes lattice stress tensors, etc.) satisfy the preset convergence criteria are the initial structure of the memory cell considered to have reached the energy convergence standard. At this point, the optimization process stops, and the resulting structure is a stable coherent interface structure. Through such optimization, it can be ensured that the final coherent interface structure is energy stable, and that the atomic arrangement and lattice parameters are in thermodynamic equilibrium, providing a reliable structural model for subsequent performance calculations and analysis.

[0043] S300: Perform high-temperature stability verification on memory cells containing coherent interface structures to determine whether candidate interface material layers maintain a crystalline state at temperatures above the melting point of phase change materials.

[0044] In some embodiments, the step of verifying the high-temperature stability of a memory cell containing a coherent interface structure includes: heating the memory cell to a first temperature higher than the melting point of the phase change memory material and maintaining it for a preset time.

[0045] Specifically, heating the memory cell to a first temperature higher than the melting point of the phase change memory material refers to raising the temperature of the memory cell system containing a coherent interface structure of YAs / phase change material (such as germanium-antimony-tellurium) to 1500K through high-temperature molecular dynamics simulation. 1500K was chosen as the first temperature because it is significantly higher than the melting point of the phase change memory material (such as germanium-antimony-tellurium) by approximately 900K, thus simulating the extreme high-temperature environment that phase change memory devices may encounter during the RESET (amorphization) process. This stringent condition is used to test the high-temperature stability of the candidate interface material layer. The preset duration corresponds to performing a molecular dynamics simulation at 1500K for 7.5 picoseconds (ps). This duration is set to ensure sufficient time to observe the structural evolution behavior of the system at high temperatures, allowing atoms to diffuse or undergo structural transformations, thereby accurately assessing the stability of the interface.

[0046] Observe and analyze whether the atomic arrangement order of the candidate interface material layer is maintained within a preset time period, and whether significant atomic interdiffusion occurs between the candidate interface material layer and the phase change storage material layer.

[0047] It should be understood that the phase change memory material (germanium, antimony, and tellurium) completely transformed into a liquid state with disordered atomic arrangement after 7.5 ps at 1500 K, while the YAs material maintained its crystalline state. This indicates that, as a candidate interface material layer, YAs maintained the long-range order of its atomic arrangement under the preset high temperature and duration conditions; that is, the atomic arrangement order did not degrade, and the crystal structure was preserved. Whether significant atomic interdiffusion occurred between the candidate interface material layer and the phase change memory material layer was also determined by tracking and analyzing the atomic positions in the simulated trajectory. The observation results of this embodiment clearly show that there was no mutual atomic diffusion between the atoms on both sides of the interface. Furthermore, the statistical results of the mean square displacement of atoms along the c-axis of different layers show that the atoms farther from the interface in the phase change material have larger mean square displacements and more intense diffusion. The diffusion of the YAs material is negligible, and the diffusion of germanium, antimony, and tellurium atoms near YAs is greatly suppressed. This result further confirms from a quantitative perspective that no significant atomic interdiffusion occurred between the YAs layer and the phase change material layer, and the atomic diffusion of the YAs layer itself is also minimal.

[0048] If the candidate interface material layer remains in a crystalline state and does not undergo atomic interdiffusion, then the candidate interface material is determined to meet the high-temperature stability requirements.

[0049] Specifically, the YAs candidate interface material layer maintained its crystalline state for 7.5 ps at 1500 K, and no significant atomic interdiffusion occurred between it and the phase change material layer. Therefore, it can be clearly determined that YAs meets the high-temperature stability requirements and can fully withstand the high temperatures required for the operation of germanium-antimony-tellurium phase change memory devices, maintain its crystal structure, and form a reliable coherent interface with the phase change material.

[0050] S400: Perform crystallization process simulation verification on memory cells containing coherent interface structures to determine whether the coherent interface promotes the transformation of phase change memory material layers from amorphous to crystalline state.

[0051] In some embodiments, the step of simulating and verifying the crystallization process of a memory cell containing a coherent interface structure includes: first heating the memory cell to transform its phase change storage material layer into a liquid state, and then rapidly cooling it to room temperature to construct an interface structure containing an amorphous phase change storage material layer and a crystalline candidate interface material layer.

[0052] Specifically, the interface structure comprising crystalline YAs material and phase change memory material (such as germanium-antimony-tellurium) was heated to a high temperature of 1500K. This high temperature was sufficient to melt the phase change memory material layer (such as germanium-antimony-tellurium) into a liquid state. Subsequently, the temperature of the entire system was rapidly reduced to 300K (i.e., room temperature) through rapid cooling, thereby solidifying the originally liquid phase change memory material layer into an amorphous state. Ultimately, an interface structure in which amorphous phase change memory material (such as amorphous germanium-antimony-tellurium) and crystalline YAs material are in close contact was successfully constructed.

[0053] The interface structure is heated to a second temperature within the crystallization temperature range of the phase change storage material.

[0054] Specifically, the phase change memory material selected is germanium-antimony-tellurium. Based on the study of the crystallization behavior of this type of material in molecular dynamics simulation, the system temperature was raised to 600K, which was determined to be the second suitable temperature for the crystallization of germanium-antimony-tellurium material.

[0055] Observe and analyze whether the amorphous phase change storage material layer starts from the coherent interface and grows epitaxially along the interface normal at the second temperature, thereby achieving rapid crystallization.

[0056] Specifically, at a simulated temperature of 600K, continuous tracking of atomic trajectories and meticulous observation of structural evolution revealed that the amorphous germanium-antimony-tellurium material in the interface structure does not undergo a long period of random nucleation. Its crystallization process clearly initiates at the coherent interface and rapidly advances along the interface's normal direction (specifically, along the c-axis in this simulation system). This manifests as atoms at the interface first rearranging themselves at a relatively fast rate, forming an ordered crystal structure, and then continuously advancing towards the interior of the amorphous region based on this structure. To more accurately characterize this crystallization process, this embodiment employed methods such as correlation functions and quaternary ring statistics. Correlation functions reflect the change in the degree of order of atomic arrangement during the crystallization process, while statistics on topological structures such as quaternary rings indicate the formation and stability of the crystal nucleus precursor. Comparative analysis revealed that in pure phase-change memory cells without a coherent interface structure (i.e., systems containing only amorphous germanium-antimony-tellurium), the crystallization process is very slow. This is because the precursors of crystal nuclei in its amorphous system (such as four-membered rings and cubic structures) are few in number and have poor stability, fluctuating violently. They need to go through a long incubation period before they can finally form stable crystal nuclei and begin crystallization growth.

[0057] If it is observed that the amorphous phase change memory material layer initiates and accelerates crystallization from the coherent interface, then the coherent interface is determined to have the effect of promoting crystallization.

[0058] It should be understood that, given the above observations, that the amorphous phase change memory material layer (amorphous germanium antimony tellurium) initiates and achieves rapid crystallization from the coherent interface at a temperature of 600K, while the control group without interface structure crystallizes very slowly, this significant difference clearly indicates that the coherent interface strategy accelerates the data erase and write speed of the phase change memory cell. Therefore, it can be definitively determined that the coherent interface has the effect of promoting crystallization.

[0059] S500: Based on the results of high-temperature stability verification and crystallization process simulation verification, candidate interface materials were identified as effective coherent interface materials suitable for accelerating the crystallization of phase change memory materials.

[0060] It should be understood that the effective coherent interface material is the storage cell.

[0061] By constructing initial cell structures of phase change memory material layers and candidate interface material layers with the same crystal structure type, and then optimizing the structure to form a coherent interface structure, the structure is then verified through high-temperature stability verification and crystallization process simulation. Based on the verification results, effective coherent interface materials that can maintain the crystal state at high temperatures and promote the crystallization of phase change memory material layers are selected, thereby helping to improve the screening efficiency of phase change memory materials.

[0062] In some embodiments, the method further includes: performing high-throughput screening on a library of candidate interface materials; the high-throughput screening is based on at least one of the following conditions: first screening condition: the candidate interface materials have the same crystal structure type as the phase change memory materials.

[0063] In some embodiments, the first screening criterion is that both the phase change storage material and the candidate interface material have a rock salt mineral-type crystal structure.

[0064] It should be understood that the core function of phase change memory materials relies on their reversible transformation between crystalline and amorphous states during operation. The crystal structure in the crystalline state (i.e., the rock salt mineral-like structure) is crucial for ensuring their specific physicochemical properties (such as high density and low resistivity) and achieving rapid and stable phase transitions. When candidate interface materials are introduced to construct coherent interfaces, if the crystal structure type of the candidate interface material differs from that of the phase change memory material, significant differences will exist in their core crystallographic characteristics, such as atomic arrangement, lattice parameters, and coordination environments of anions and cations. This difference will prevent atoms from achieving precise, atomic-level alignment and matching at the interface. Specifically, in the rock salt structure of phase change memory materials, anions and cations occupy two specific, regularly arranged sites, forming an ordered lattice. If the candidate interface material does not possess this rock salt-like structure, its atomic arrangement and site distribution will be drastically different from those of the phase change memory material, thus failing to meet the stringent requirement of a high degree of spatial matching between atoms on both sides of the coherent interface. This not only makes it difficult to form a stable coherent interface, but may also generate a large number of defects, dislocations, or lattice distortions at the interface. These interface defects will seriously affect the performance of the memory cell, such as reducing thermal stability, hindering the normal crystallization process, and increasing the risk of leakage, ultimately causing the device to fail to achieve the expected high thermal stability and accelerated crystallization effect, and may even cause the device to fail. Therefore, specifying that both the phase change memory material and the candidate interface material have a rock salt mineral-type crystal structure as the first screening criterion is the primary prerequisite and fundamental guarantee to ensure that the two can achieve alignment of anion and cation sites at the atomic scale, thereby constructing a stable coherent interface.

[0065] Second screening criterion: The thermodynamic stability of the candidate interface material meets the preset standard.

[0066] It should be understood that the preset standard specifically refers to the energy criterion for candidate interface materials, namely, the energy difference between the material and the bulge at the corresponding stoichiometric ratio must be less than 0.1 eV / atom. This numerical standard is set to ensure that the selected interface material itself possesses sufficiently high thermodynamic stability. When the bulge energy difference of the material is less than 0.1 eV / atom, it indicates that under normal conditions (including temperature cycling, electrical pulse effects, and long-term room temperature storage during phase-change memory device operation), it can maintain the integrity and stability of its crystal structure and is not prone to decomposition, phase transition, or structural collapse. This stability is crucial for maintaining the long-term effectiveness of the coherent interface, because if the interface material itself is unstable and its crystal structure changes, the originally established atomic-level coherent matching relationship will be destroyed, and interface defects may arise or increase, thus affecting the performance and reliability of the entire phase-change memory cell. Therefore, using a bulge energy difference of less than 0.1 eV / atom as the preset standard for thermodynamic stability is a key indicator for quantitatively evaluating material stability from an energy perspective and ensuring its adaptability to the operating environment of phase-change memory devices.

[0067] The third screening criterion is that the lattice constant mismatch rate between the candidate interface material and the phase change memory material is lower than a preset threshold.

[0068] It should be understood that the preset threshold can be specifically set to 4%. This threshold is primarily based on the fundamental requirement for phase change memory materials (such as germanium-antimony-tellurium) to form a coherent interface with candidate interface materials. When the lattice mismatch rate is below 4%, the crystal structures on both sides of the interface can achieve good matching at the atomic scale, maintaining the coherence of atomic arrangement, which is conducive to forming a stable coherent interface. This good lattice matching can significantly reduce the strain energy and defect density at the interface, providing a smooth transition environment for the ordered migration and crystallization of atoms during the phase transition process, thereby effectively promoting the crystallization kinetics of the phase change memory material and improving the switching speed and cycle durability of the memory cell. If the lattice mismatch rate exceeds 4%, the coherence of atomic arrangement will be difficult to maintain, and a large number of dislocations, vacancies, and other defects will easily be generated at the interface. This not only fails to promote crystallization but may also become an obstacle to the phase transition process, leading to a decrease in storage performance. Therefore, setting 4% as the preset threshold for the lattice constant mismatch rate is a key quantitative indicator to ensure that candidate interface materials can form an effective coherent interface with the phase change memory material, thereby playing a role in promoting crystallization.

[0069] The fourth screening criterion is that the cohesive energy of the candidate interface material is higher than that of the phase change memory material, in order to characterize its structural stability at high temperatures.

[0070] It should be understood that cohesive energy is an important physical quantity for measuring the strength of interatomic bonding within a crystalline material. Higher cohesive energy means stronger interatomic bonding, making the material less prone to decomposition or melting, and resulting in better high-temperature structural stability. During the operation of phase-change memory (PCM) devices, PCMs undergo frequent crystallization-amorphization transitions, a process typically accompanied by localized high temperatures, especially during the amorphization stage where the PCM is heated above its melting point. If the cohesive energy of the candidate crystalline material serving as the coherent interface is lower than that of the PCM, then when the PCM undergoes amorphization (or even melting) due to high temperatures, the candidate interface material may decompose, melt, or structurally fail before the PCM. Once the crystal structure of the interface material cannot remain stable at high temperatures, the coherent interface originally formed between it and the PCM will no longer exist. Therefore, the strategy of promoting PCM crystallization through the coherent interface becomes ineffective, and the structural collapse of the interface material may even negatively impact the performance and reliability of the entire memory device. Therefore, the requirement that the cohesive energy of the candidate interface material be higher than that of the phase change memory material is precisely to ensure that when the phase change material itself undergoes a high-temperature phase change, the interface material can maintain the integrity and stability of its crystal structure with stronger atomic bonding forces, thereby continuously and effectively playing the role of the coherent interface.

[0071] In some embodiments, the cohesive energy of the phase change storage material is greater than 4 electron volts per atom.

[0072] It should be understood that, considering that the cohesive energy of phase change materials is usually less than 3 eV / atom, the specific requirement that the cohesive energy of coherent interface materials be greater than 4 eV / atom is based on the above principle, and ensures their high-temperature structural stability through quantitative comparison of cohesive energy.

[0073] In some embodiments, the effective coherent interface materials identified by high-throughput screening include at least one of the following materials: calcium selenide, cerium arsenide, cerium phosphide, cerium selenide, dysprosium arsenide, dysprosium bismuthide, dysprosium antimonide, dysprosium telluride, erbium bismuthide, erbium antimonide, erbium telluride, europium sulfide, europium selenide, gadolinium arsenide, gadolinium antimonide, gadolinium selenide, gadolinium telluride, holmium arsenide, holmium bismuthide, holmium antimonide, holmium telluride, lanthanum arsenide, lanthanum phosphide, lanthanum sulfide, lanthanum selenide, lutetium bismuthide, lutetium antimonide, lutetium telluride, neodymium arsenide, neodymium phosphide, neodymium selenide. Neodymium telluride, neptunium arsenide, neptunium antimonide, neptunium selenide, neptunium telluride, promethium selenide, praseodymium arsenide, praseodymium phosphide, praseodymium sulfide, praseodymium selenide, plutonium arsenide, plutonium selenide, plutonium telluride, scandium bismuthide, scandium antimonide, samarium arsenide, samarium phosphide, samarium antimonide, samarium selenide, samarium telluride Strontium selenide, terbium arsenide, terbium bismuthide, terbium antimonyide, terbium selenide, terbium telluride, thorium arsenide, thorium germanide, thorium phosphide, thorium selenide, thulium bismuthide, thulium antimonyide, thulium telluride, uranium arsenide, uranium antimonyide, uranium selenide, yttrium arsenide, yttrium bismuthide, yttrium antimonyide, yttrium telluride.

[0074] Through high-throughput screening, at least one of calcium selenide, cerium arsenide, and cerium phosphide was identified as an effective coherent interface material, thus providing a specific and feasible range of candidate materials for the selection of interface materials in practical phase change storage devices.

[0075] This application also provides a phase change memory material screening system based on a coherent interface in some embodiments, which is applicable to the phase change memory material screening method based on a coherent interface provided in the above embodiments. The system includes a structure screening and construction module for screening and constructing an initial structure of a memory cell containing a phase change memory material layer and a candidate interface material layer, wherein the crystal structure type of the phase change memory material layer is the same as the crystal structure type of the candidate interface material layer.

[0076] The structure optimization module is used to optimize the initial structure of the memory cell to form a coherent interface structure; the high-temperature verification module is used to verify the high-temperature stability of the memory cell containing the coherent interface structure to determine whether the candidate interface material layer maintains a crystalline state at temperatures higher than the melting point of the phase change material.

[0077] The crystallization verification module is used to simulate and verify the crystallization process of memory cells containing coherent interface structures in order to determine whether the coherent interface promotes the transformation of the phase change memory material layer from an amorphous state to a crystalline state.

[0078] And a material determination module, which is used to determine candidate interface materials as effective coherent interface materials suitable for accelerating the crystallization of phase change memory materials based on the results of high temperature stability verification and crystallization process simulation verification.

[0079] Through the collaborative work of the structure screening and construction module, the structure optimization module, the high-temperature verification module, the crystallization verification module, and the material determination module, the initial structure of the storage cell is constructed and optimized in sequence, the high-temperature stability and crystallization promotion effect of the coherent interface structure are verified, and the effective interface material is determined based on the verification results, which helps to achieve the systematic screening of accelerated crystallization interface materials in phase change storage materials.

[0080] As can be seen from the above technical solutions, the embodiments of this application provide a method and system for screening phase change memory materials based on coherent interfaces. First, an initial structure of a memory cell containing a phase change memory material layer and a candidate interface material layer is constructed, wherein the crystal structure type of the phase change memory material layer is the same as that of the candidate interface material layer. Then, the initial structure of the memory cell is optimized to form a coherent interface structure. The high-temperature stability of the memory cell containing the coherent interface structure is verified to determine whether the candidate interface material layer maintains a crystalline state at temperatures above the melting point of the phase change material. Next, the crystallization process of the memory cell containing the coherent interface structure is simulated to determine whether the coherent interface promotes the transformation of the phase change memory material layer from an amorphous state to a crystalline state. Finally, based on the results of the high-temperature stability verification and the crystallization process simulation verification, the candidate interface material is determined as an effective coherent interface material suitable for accelerating the crystallization of phase change memory materials, thereby solving the problem of low screening efficiency for phase change memory materials.

[0081] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A method for screening phase change memory materials based on coherent interfaces, characterized in that, The method includes: screening and constructing an initial structure of a memory cell comprising a phase change storage material layer and a candidate interface material layer, wherein the crystal structure type of the phase change storage material layer is the same as the crystal structure type of the candidate interface material layer; performing structural optimization on the initial structure of the memory cell to form a coherent interface structure; performing high-temperature stability verification on the memory cell comprising the coherent interface structure to determine whether the candidate interface material layer maintains a crystalline state at temperatures above the melting point of the phase change material; performing crystallization process simulation verification on the memory cell comprising the coherent interface structure to determine whether the coherent interface promotes the transformation of the phase change storage material layer from an amorphous state to a crystalline state; and determining the candidate interface material as an effective coherent interface material suitable for accelerating the crystallization of the phase change storage material based on the results of the high-temperature stability verification and the crystallization process simulation verification.

2. The method for screening phase change memory materials based on coherent interfaces according to claim 1, characterized in that, The steps for screening and constructing an initial structure of a memory cell comprising a phase change storage material layer and a candidate interface material layer include: performing cell expansion processing on the phase change storage material layer and the candidate interface material layer respectively, so that the constructed interface structure satisfies periodic boundary conditions and reduces the influence of computational scale; stacking the cell-expanded phase change storage material layer and the candidate interface material layer along a specific crystal orientation and setting an initial interlayer spacing; wherein the lattice constant mismatch rate of the phase change storage material layer and the candidate interface material layer is lower than a preset threshold.

3. The method for screening phase change memory materials based on coherent interfaces according to claim 1, characterized in that, The steps for optimizing the initial structure of the storage cell include: using the principle of energy minimization, simultaneously adjusting the lattice constant and atomic positions of the initial structure of the storage cell until the initial structure of the storage cell reaches the energy convergence criterion to form a stable coherent interface structure.

4. The method for screening phase change memory materials based on coherent interfaces according to claim 1, characterized in that, The steps for verifying the high-temperature stability of a memory cell containing the coherent interface structure include: heating the memory cell to a first temperature higher than the melting point of the phase change memory material and maintaining it for a preset time; observing and analyzing whether the atomic arrangement order of the candidate interface material layer is maintained within the preset time, and whether significant atomic interdiffusion occurs between the candidate interface material layer and the phase change memory material layer; if the candidate interface material layer maintains a crystalline state and no atomic interdiffusion occurs, then the candidate interface material is determined to meet the high-temperature stability requirements.

5. The method for screening phase change memory materials based on coherent interfaces according to claim 1, characterized in that, The steps for simulating and verifying the crystallization process of a memory cell containing the coherent interface structure include: first heating the memory cell to a liquid state for its phase change storage material layer, and then rapidly cooling it to room temperature to amorphous state for the phase change storage material layer, thereby constructing an interface structure containing an amorphous phase change storage material layer and a crystalline candidate interface material layer; heating the interface structure to a second temperature within the crystallization temperature range of the phase change storage material; observing and analyzing whether, at the second temperature, the amorphous phase change storage material layer starts epitaxial growth from the coherent interface and grows along the interface normal direction, thereby achieving rapid crystallization; if it is observed that the amorphous phase change storage material layer initiates and accelerates crystallization from the coherent interface, then it is determined that the coherent interface has the effect of promoting crystallization.

6. The method for screening phase change memory materials based on coherent interfaces according to claim 1, characterized in that, The method further includes: high-throughput screening of a candidate interface material library; the high-throughput screening is based on at least one of the following conditions: first screening condition: the candidate interface material has the same crystal structure type as the phase change memory material; second screening condition: the thermodynamic stability of the candidate interface material meets a preset standard; third screening condition: the lattice constant mismatch rate between the candidate interface material and the phase change memory material is lower than a preset threshold; fourth screening condition: the cohesive energy of the candidate interface material is higher than the cohesive energy of the phase change memory material, so as to characterize its structural stability at high temperature.

7. The method for screening phase change memory materials based on coherent interfaces according to claim 6, characterized in that, The first screening criterion is that both the phase change storage material and the candidate interface material have a rock salt crystal structure.

8. The method for screening phase change memory materials based on coherent interfaces according to claim 6, characterized in that, The effective coherent interface materials identified by the high-throughput screening include at least one of the following materials: calcium selenide, cerium arsenide, cerium phosphide, cerium selenide, dysprosium arsenide, dysprosium bismuthide, dysprosium antimonide, dysprosium telluride, erbium bismuthide, erbium antimonide, erbium telluride, europium sulfide, europium selenide, gadolinium arsenide, gadolinium antimonide, gadolinium selenide, gadolinium telluride, holmium arsenide, holmium bismuthide, holmium antimonide, holmium telluride, lanthanum arsenide, lanthanum phosphide, lanthanum sulfide, lanthanum selenide, lutetium bismuthide, lutetium antimonide, lutetium telluride, neodymium arsenide, neodymium phosphide, neodymium selenide, neodymium telluride. Neptunium arsenide, neptunium antimonide, neptunium selenide, neptunium telluride, promethium selenide, praseodymium arsenide, praseodymium phosphide, praseodymium sulfide, praseodymium selenide, plutonium arsenide, plutonium selenide, plutonium telluride, scandium bismuthide, scandium antimonide, samarium arsenide, samarium phosphide, samarium antimonide, samarium selenide, samarium telluride, strontium selenide, terbium arsenide, terbium bismuthide, terbium antimonide, terbium selenide, terbium telluride, thorium arsenide, thorium germanide, thorium phosphide, thorium selenide, thulium bismuthide, thulium antimonide, thulium telluride, uranium arsenide, uranium antimonide, uranium selenide, yttrium arsenide, yttrium antimonide, yttrium telluride.

9. The method for screening phase change memory materials based on coherent interfaces according to claim 6, characterized in that, The cohesive energy of the phase change storage material is greater than 4 electron volts per atom.

10. A screening system for phase change memory materials based on coherent interfaces, characterized in that, A method for screening phase change memory materials based on coherent interfaces, applicable to any one of claims 1-9, the system comprising: a structure screening and construction module for screening and constructing an initial structure of a memory cell containing a phase change memory material layer and a candidate interface material layer, wherein the crystal structure type of the phase change memory material layer is the same as the crystal structure type of the candidate interface material layer; a structure optimization module for performing structural optimization processing on the initial structure of the memory cell to form a coherent interface structure; a high-temperature verification module for performing high-temperature stability verification on the memory cell containing the coherent interface structure to determine whether the candidate interface material layer maintains a crystalline state at a temperature higher than the melting point of the phase change material; a crystallization verification module for performing crystallization process simulation verification on the memory cell containing the coherent interface structure to determine whether the coherent interface promotes the transformation of the phase change memory material layer from an amorphous state to a crystalline state; and a material determination module for determining the candidate interface material as an effective coherent interface material suitable for accelerating the crystallization of the phase change memory material based on the results of the high-temperature stability verification and the crystallization process simulation verification.

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