CN113072915A

CN113072915A - Sb based on oxygen doping2Te3Phase change material, phase change memory and preparation method

Info

Publication number: CN113072915A
Application number: CN202110312530.XA
Authority: CN
Inventors: 程晓敏; 曾运韬; 缪向水
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-03-24
Filing date: 2021-03-24
Publication date: 2021-07-06
Anticipated expiration: 2041-03-24
Also published as: WO2022198623A1; CN113072915B

Abstract

The invention provides Sb based on oxygen doping₂Te₃A phase change material, a phase change memory and a preparation method belong to the technical field of micro-nano electronics, and Sb is doped by adopting a simple doping process₂Te₃Method for comprehensively regulating and controlling microstructure and device characteristics and application thereof in Sb₂Te₃A shell-core microstructure is formed in the phase change layer, wherein a shell layer grain boundary of amorphous low thermal conductivity plays a role similar to a heterogeneous interface, and physically separates a crystal grain which is subjected to phase change, namely a core part, and plays a thermal resistance role, so that the electric heat utilization efficiency is improved, and the RESET power consumption is reduced. Wherein the grain boundary of the amorphous shell layer obstructs Sb₂Te₃The atomic migration of crystal grains in the phase change process improves the reliability and the cyclic erasing times of the device. Meanwhile, the doping element is bonded with the core phase-change material element, so that the phase-change material can be effectively improvedThe amorphous stability of the amorphous structure can improve the comprehensive performance of the device in all directions due to the comprehensive effect of the amorphous structure.

Description

Sb based on oxygen doping2Te3Phase change material, phase change memory and preparation method

Technical Field

The invention belongs to a micro-nano electronic technologyMore particularly, relates to a method for doping Sb based on oxygen₂Te₃The shell-core structure phase-change material and the phase-change memory.

Background

In the age of rapid development of electronic technology and information industry, along with the explosive growth of data, the performance requirements of people on nonvolatile memories are higher and higher. Phase Change Memories (PCMs) are considered by the international semiconductor industry association as the most likely future mainstream memories to replace flash and dynamic memories by virtue of their advantages of high integration, fast response speed, long cycle life, and low power consumption.

The basic principle of the phase change memory is that an electric pulse signal is applied to a memory cell to enable the phase change material to generate reversible phase change between an amorphous state and a crystalline state so as to realize the storage of '0' and '1'. An electric pulse with narrow pulse width and high amplitude is applied to the unit to carry out RESET operation on the unit, and the crystalline phase change memory material is melted and quickly cooled to be converted into an amorphous disordered state, so that quick resistance change from a low resistance state '0' to a high resistance state '1' is realized. On the contrary, an electric pulse with wide pulse width and low amplitude is applied to the phase change unit to carry out SET operation on the phase change unit, the amorphous phase change memory material is crystallized through a similar annealing process and returns to a low resistance state, and the 1 erasing and writing back 0 is realized.

The optimization of the performance of the phase-change material is the key for improving the performance of the phase-change memory, and the microstructure of the phase-change material determines the macroscopic characteristics of the phase-change memory. Researches find that the reliability and the cyclic erasing and writing characteristics of the phase change memory are mainly related to an internal atom migration mechanism of the phase change material in the repeated heating and cooling processes. The power consumption of the phase change memory is closely related to the electric heat utilization efficiency of the device in the processes of heat generation and heat dissipation, besides the melting point of the phase change material. The data retention time of a phase change memory is mainly determined by the amorphous stability of the phase change layer material.

Sb₂Te₃Is a phase change material which has attracted much attention in recent years, has a low crystallization temperature and a growth-dominated crystallization process, and has a high crystallization speed, and therefore, is based on Sb₂Te₃The phase change memory device has the characteristic of high SET speed. However, it is possible to use a single-layer,the amorphous stability is poor, and the data retention time of the device needs to be further improved.

At present, to Sb₂Te₃The main performance optimization means of phase change materials is doping. By reaction of a compound in Sb₂Te₃Other elements are introduced into the phase-change material to form different microstructures, and the local characteristics of the phase-change material are changed, so that the performance of the phase-change memory device is improved. Existing Sb₂Te₃The improvement mechanism of the doping on the performance is mainly that doping elements (such as Ti, Sc, Y and the like) are in Sb₂Te₃Form a certain local crystal structure, such as an octahedral structure, and locally regulate Sb₂Te₃By increasing Sb in the crystallization process of₂Te₃Amorphous stability of the material and data retention time of the device. The doping process is simple, but the precise regulation and control of the microstructure of the material are difficult to realize, the crystallization speed is sacrificed to a certain extent while the high-resistance stability of the device is improved, and the comprehensive improvement of the performance of the device is difficult to realize. In addition, in Sb₂Te₃A heterogeneous layer or different phase-change materials are inserted into the structure to form a similar superlattice structure, and the performance of the phase-change materials and devices can be optimized by regulating and controlling the heterogeneous interface or the superlattice interface. However, the fabrication process of the heterostructure and the superlattice-like structure is complicated, the selection condition of the other material is severe, and the device characteristics are different for the heterostructure or superlattice-like/Sb₂Te₃The structural characteristics and process parameters of the interface are particularly sensitive, which is not conducive to large-scale commercial production.

Therefore, it is required to develop a novel modified Sb₂Te₃The method realizes precise, sensitive and simple regulation and control of the microstructure of the phase change memory material, thereby enabling the phase change memory material to be applied as a commercial phase change memory material.

Disclosure of Invention

In view of the drawbacks of the prior art, the present invention provides an oxygen-doped Sb-based material₂Te₃Phase change material, phase change memory and preparation method thereof, wherein the phase change material is doped with oxygen in Sb₂Te₃A shell-Core (cs) microstructure is formed in the phase change layer, and the shell layer plays a role in thermal resistance and improves electric heating effectThe RESET power consumption is reduced by using the efficiency; the shell layer can also prevent atom migration of elements in the core, so that the reliability of the device is improved; in addition, the doping element and the element of the phase-change material at the core part form a bond, so that the amorphous stability of the phase-change material at the core part can be effectively improved, and finally, the comprehensive performance of the device is improved in an all-round manner.

According to one aspect of the present invention, there is provided an oxygen-doped Sb-based composition₂Te₃A phase change material having the formula: o is_x(Sb₂Te₃)_1-xWherein O is oxygen, x represents the atomic percentage of oxygen in the whole chemical composition, 0<x<40％。

Further, oxygen atom and Sb₂Te₃The element atoms in the material are combined to form a disordered oxide, and the disordered oxide is wrapped in Sb₂Te₃Around, Sb is₂Te₃Separating into multiple islands to form a core-shell structure, wherein the shell is oxygen atom and Sb₂Te₃Wherein the element atoms are combined to form a disordered oxide, and the core part is Sb₂Te₃And (4) crystal grains.

Further, part of oxygen element enters Sb₂Te₃In the crystal grain, for increasing Sb₂Te₃Amorphous stability of (3).

Further, O_x(Sb₂Te₃)_1-xIn the material, the Sb is controlled by controlling the doping amount of O₂Te₃The property of the medium amorphous oxide grain boundary is adjusted and controlled to O-Sb₂Te₃The electrochemical properties of the phase change memory material comprise high and low resistance state resistance, crystallization temperature and O-Sb₂Te₃The phase change memory material is O_x(Sb₂Te₃)_1-xA material of which 0<x<40％。

Further, oxygen atom and Sb₂Te₃Wherein Sb atoms are combined to form a disordered oxide and are concentrated in Sb₂Te₃Amorphous grain boundaries are formed around the grains.

Further, the disordered oxide is an oxygen atom and Sb₂Te₃The disordered oxide formed by combining the Sb atoms has a melting pointHigh melting point (higher than Sb), low thermal conductivity and stable performance₂Te₃Melting point of (890K); the lower thermal conductivity means a thermal conductivity of approximately 10^-3Magnitude, almost adiabatic; the stable performance means stable structure, difficult decomposition and difficult melting.

Furthermore, the oxide crystal boundary plays the roles of improving the electrothermal efficiency and preventing atom migration in the phase change process, and is used for improving the resistance value of the amorphous state of the phase change layer and improving Sb₂Te₃Amorphous stability of the material.

In the above inventive concept, Sb can be doped by simple doping process₂Te₃Method for comprehensively regulating and controlling microstructure and device characteristics and application thereof in Sb₂Te₃A shell-core microstructure is formed in the phase change layer, wherein a shell layer grain boundary of amorphous low thermal conductivity plays a role similar to a heterogeneous interface, physically separates crystal grains (namely a core part) subjected to phase change, plays a thermal resistance role, improves the utilization efficiency of electric heat, reduces the RESET power consumption, and blocks Sb by the amorphous shell layer grain boundary₂Te₃Atom migration of crystal grains in the phase change process improves the reliability and the cyclic erasing times of the device; meanwhile, the doping element and the phase-change material element form a bond, so that the amorphous stability of the phase-change material can be effectively improved; thereby improving the comprehensive performance of the device in all directions.

According to another aspect of the present invention, there is also provided an oxygen-doped Sb-based composition₂Te₃The phase change memory of the phase change material comprises a bottom electrode, an isolation layer, a phase change memory material thin film layer and a top electrode, wherein the phase change memory material thin film layer is made of Sb based on oxygen doping₂Te₃A phase change material.

According to a third aspect of the present invention, there is also provided a method as described above, which is prepared by magnetron sputtering, chemical vapor deposition, atomic layer deposition, electroplating or electron beam evaporation.

Further, the specific magnetron sputtering method is any one of the following three methods:

(1) co-sputtering an Sb target and a Te target in an aerobic environment;

(2)Sb₂Te₃sputtering the target in an aerobic environment;

(3) sb after O doping₂Te₃And (4) sputtering an alloy target.

Generally, compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:

sb which is not regulated and controlled by oxide grain boundary amorphous structure in the prior art₂Te₃Compared with the phase change storage material, the shell-core structure O-Sb of the invention₂Te₃In the phase-change material, O atoms and Sb atoms are combined to form disordered oxide and are distributed in the phase-change material Sb₂Te₃Forming amorphous oxide grain boundary around the crystal grains to phase change material Sb₂Te₃Separated into phase change islands with small volume, the formed surface layer is heat-insulating high-resistance oxide, and the inner layer is Sb₂Te₃The "shell-core" structure of (a). The reduction of local disorder state and phase change nucleus region increases the resistance value of phase change layer in amorphous state, improves Sb₂Te₃Amorphous stability of the material. In addition, the existence of the shell-core heterostructure limits the long-range migration of atoms in the shell-core heterostructure caused by external power-on operation on a three-dimensional structure, so that the overall cycle characteristic of the memory device is improved, the resistance drift of the device is effectively inhibited, and the resistance stability of the device is improved. In addition, the heat insulation property of the shell material and the wrapping structure of the shell on the phase change crystal grains enable heat to be concentrated inside the crystal grains in the phase change process, and the dissipation of the heat is reduced, so that the electrothermal efficiency of the phase change process is improved, and the reset power consumption of the device is effectively reduced.

Drawings

FIG. 1 shows O-Sb of the shell-core structure formed after the grain boundary engineering regulation in the embodiment of the invention₂Te₃Phase change memory material film and pure Sb₂Te₃A real-time relation curve of the in-situ sheet resistance and the annealing temperature of the phase change storage material film, wherein the heating rate is 12 ℃/min, wherein ST represents pure Sb₂Te₃Phase changeStorage material, OST stands for O-Sb of "shell-core" structure₂Te₃A phase change memory material.

FIG. 2 shows O-Sb forming a "shell-core" structure after being controlled by grain boundary engineering in the embodiment of the present invention₂Te₃Phase change memory material film and pure Sb₂Te₃XRD characterization contrast diagram of phase change memory material film, wherein the corresponding temperature at each curve represents the annealing treatment temperature of the corresponding film, wherein ST represents pure Sb₂Te₃Phase change memory material, OST stands for O-Sb of 'shell-core' structure₂Te₃A phase change memory material.

FIG. 3 shows that O-Sb with a shell-core structure is formed after the regulation and control of grain boundary engineering₂Te₃in-plane-TEM microscopic analysis of the phase change memory material film, wherein the crystalline sample is annealed at 300 ℃ for 10 min. As can be seen, the sample exhibits a uniform heterostructure at the microscopic level.

FIG. 4 shows that O-Sb with a shell-core structure is formed after the regulation and control of grain boundary engineering₂Te₃HRTEM microscopic analysis of the phase change memory material thin film, wherein the crystalline sample was annealed at 300 ℃ for 10 min. In the figure, the longer solid arrows indicate the "core" structure crystal portion, the shorter dashed arrows indicate the "shell" structure amorphous portion, and the rectangular boxes on the right side indicate the fourier transform of the corresponding portions. As can be seen, the grains in the sample are wrapped by the amorphous structure which is randomly distributed.

FIG. 5 shows that O-Sb with a shell-core structure is formed after the regulation and control of grain boundary engineering₂Te₃The EDX distribution diagram of the phase change memory material thin film is shown in fig. 5(a) as a bright field image of a sampling region, fig. 5(b) as an Sb element distribution image, and fig. 5(c) as a Te element distribution image. As can be seen from the figure, the Sb element and the Te element are not completely overlapped in distribution, and a wrapping phenomenon occurs.

FIG. 6 shows O-Sb forming a "shell-core" structure after grain boundary engineering control₂Te₃An X-ray photoelectron spectrum of the phase change memory material film, wherein the crystalline state sample is annealed at 300 ℃ for 10min, and Ar passes through the surface of the crystalline state sample⁺Processing to remove the surface oxidation contamination layer, FIG. 6(a)Sb element energy spectrum, and Te element energy spectrum in FIG. 6(b), wherein diffraction peaks in the spectrum correspond to corresponding chemical bonds.

Fig. 7 is a supercell model of an amorphous O-Sb-Te phase change material with 5%, 10%, and 20% O atom content in sequence, which is calculated by using a first principle, in the present invention, fig. 7(a) shows an amorphous supercell model doped with 5%, fig. 7(b) shows an amorphous supercell model doped with 10%, and fig. 7(c) shows an amorphous supercell model doped with 20%. As can be seen from the figure, the O atom tends to bond with the Sb atom. As the concentration of O atoms increases, the O — Sb bonding substance increases, and a wrapping structure to the Sb2Te3 crystal grains is formed.

FIG. 8 is a graph of the effect of simplified "shell-core" structure on the movement of atoms in the inner layer (inside the "core") at different temperatures calculated using the first principles of the invention, where the curve line1 corresponds to pure Sb₂Te₃Simulation result of atomic motion condition of conventional Phase Change Material (PCM) at high temperature (550K), curve 2 corresponds to pure Sb₂Te₃Simulation result of atomic motion condition of conventional Phase Change Material (PCM) at low temperature (300K), curve 3 corresponds to O-Sb₂Te₃The simulation result of the atomic motion condition of the represented shell-core structure phase change material (cs-PCM) at high temperature (550K) is that curve 4 corresponds to O-Sb₂Te₃The atomic motion condition simulation result of the represented shell-core structure phase change material (cs-PCM) at low temperature (300K) is obtained. As can be seen from the figure, the shell layer can effectively inhibit the movement of atoms in the core layer, and the sensitivity to temperature is obviously reduced.

Fig. 9 is a graph showing the influence of a simplified "shell-core" structure calculated by using a first principle on the atomic motion of different regions of the inner layer ("inside of core"), where

curves

1 and 3 correspond to the simulation result of the atomic motion of the region of the phase change material of the inner layer "core" close to the shell layer, and curve 2 corresponds to the simulation result of the atomic motion of the middle region of the phase change material of the inner layer "core". Wherein the inset is simplified 'shell-core' structure O-Sb₂Te₃The three-dimensional wrapping structure model comprises a region 1 and a region 3 which correspond to the atoms of a core phase-change material at the inner layer close to a shell layer region, and a region 2 which corresponds to the middle region of the core phase-change material at the inner layerAn atom. As can be seen, the atoms in the middle region move more intensely than those in the regions close to the shell.

FIG. 10 is a schematic diagram of the barrier effect of the simplified "shell-core" structure on thermal diffusion obtained by COMSOL simulation in the present invention. As can be seen, the heat is mainly concentrated in the Sb-Te phase change material area of the inner layer.

FIG. 11 is O-Sb which forms a "shell-core" structure after being controlled by grain boundary engineering₂Te₃The phase change memory material is a schematic diagram of a phase change memory unit structure with a functional layer. Wherein, 1 is a top electrode, 2 is a phase-change material with a shell-core structure, and 3 is heat-insulating SiO₂Layer 4 is the bottom electrode.

FIGS. 12 to 15 show O-Sb which forms a "shell-core" structure after being controlled by grain boundary engineering₂Te₃Phase change memory cell with phase change memory material as functional layer and undoped Sb₂Te₃Comparison graph of electrical performance test of phase change memory cell, FIG. 12 is comparison graph of I-V performance of device, FIG. 13 is comparison graph of RESET performance of device, FIG. 14 is comparison graph of drift resistance of device, FIG. 15 is comparison graph of O-Sb forming "shell-core" structure₂Te₃And (c) a phase change memory device (cs-OST) cycle performance diagram with the phase change memory material as a functional layer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a method for preparing Sb by simple doping process₂Te₃The microstructure and device characteristics of the material are comprehensively regulated and controlled, and the memory thereof relates to the method for adopting an oxygen doping process and utilizing an amorphous oxide structure to perform Sb₂Te₃The phase-change material is regulated to form a unique shell-core structure, the phase-change area is reduced, and long-range migration and thermal diffusion of atoms are blocked, so that Sb is improved₂Te₃Phase change memory performance. Specifically, in Sb₂Te₃Phase changeA shell-core microstructure is formed in the layer, wherein the amorphous 'shell layer' grain boundary with low thermal conductivity plays a role similar to a heterogeneous interface, physically separates the phase-changed crystal grains (also called 'core'), plays a role of thermal resistance, improves the utilization efficiency of electric heat, and reduces the RESET power consumption; grain boundary barrier Sb of amorphous shell layer₂Te₃Atom migration of crystal grains in the phase change process improves the reliability and the cyclic erasing times of the device; meanwhile, the doping element and the phase-change material element form a bond, so that the amorphous stability of the phase-change material can be effectively improved, and the comprehensive function is achieved, so that the comprehensive performance of the device can be improved comprehensively.

More specifically, in the shell-core structure phase change memory material (csPCM) formed by amorphous structure regulation, O is introduced into Sb₂Te₃Obtained from phase-change memory material and having a chemical composition of formula O_x(Sb₂Te₃)_1-xWherein x represents the atomic percentage of O element, and the preferable value range of x is 0<x<40 percent. By adjusting the preparation time and introducing oxygen (O)₂) The value of x can be regulated and controlled. The structure of the shell-core is O-Sb₂Te₃In the phase change memory material, the doped O atoms are combined with Sb atoms to form disordered oxide, the disordered oxide is distributed around the grain boundary of the phase change material to separate the phase change material into small phase change islands, the formed surface layer (or shell) is an oxide with high heat insulation and resistance, and the inner layer (or core part) is Sb₂Te₃The "shell-core" structure of phase change materials. Preferred "shell-core" structures O-Sb₂Te₃The thickness of the phase change storage thin film material is 50 nm-300 nm.

In the invention, the shell-core structure O-Sb is measured by adopting the real-time change curve of the sheet resistance of the in-situ film along with the annealing temperature₂Te₃The thickness of the phase change storage thin film material is about 50 nm. Said "shell-core" structure O-Sb for STEM and EDX microanalysis and characterization of X-ray photoelectron spectroscopy₂Te₃The thickness of the phase change storage thin film material is about 100nm, and a crystalline sample is obtained by annealing at 300 ℃ for 10min, wherein the shell-core structure O-Sb is used for XPS characterization₂Te₃Ar is coated on the surface of the phase change storage film material⁺And treating to remove the surface pollution oxide layer. The "shell-core" structure O-Sb₂Te₃The high resistance state of the phase change storage thin film material is 10 of the low resistance state⁴And (4) doubling. The "shell-core" structure O-Sb₂Te₃Pure Sb with relatively high phase-change temperature for phase-change storage thin film material₂Te₃Is greatly improved. The "shell-core" structure O-Sb₂Te₃The phase change memory thin film material STEM observed: sb₂Te₃The crystal grains are separated into nanometer-sized phase change islands by a random distribution of amorphous tissues, the oxide with high heat insulation resistance is formed on the surface layer (shell), and the Sb is formed on the inner layer (core part)₂Te₃The phase change material, the composition of each fraction was verified by EDX characterization. The "shell-core" structure O-Sb₂Te₃XPS characterization of the phase change storage thin film material shows that the doped O atoms are mainly bonded with Sb atoms. First-principle calculation of the "core-shell" structure O-Sb₂Te₃The formation of an O-Sb structure in the phase change memory material shows a wrapping tendency along with the increase of the concentration of O atoms. The shell-core structure is simplified, a three-dimensional wrapping structure is used for building a physical model, and the motion of atoms in the inner layer core can be inhibited by observing the outer layer shell structure through simulation calculation. Meanwhile, electrothermal simulation shows that the shell-core structure can effectively prevent thermal diffusion in the phase change process.

In one embodiment of the invention, the phase change memory unit sequentially comprises a bottom electrode, an isolation layer, a phase change memory material film layer and a top electrode. The material of the phase change storage material thin film layer is the shell-core structure O-Sb regulated and controlled by the amorphous structure₂Te₃And the phase change material is filled in small holes with the diameter of 250nm and the depth of 100 nm. The bottom electrode is made of TiN. The isolation layer is made of SiO₂. The top electrode is made of metal Pt.

The invention provides a shell-core structure O-Sb for a phase change memory₂Te₃The preparation method of the phase-change material comprises the steps of magnetron sputtering, chemical vapor deposition, atomic layer deposition and electroplatingMethods, electron beam evaporation methods, and the like. Wherein, the magnetron sputtering method is most flexible to prepare, can adopt Sb target and Te target to co-sputter in the oxygen atmosphere, and can also adopt Sb₂Te₃The target is sputtered in an aerobic environment, and O-Sb can also be used₂Te₃And (4) sputtering an alloy target. All the methods can prepare the O-Sb with the shell-core structure according to the mixture ratio of the chemical general formula₂Te₃A phase change memory material.

The shell-core structure of the invention is O-Sb₂Te₃The phase change memory material and the device are mature in preparation process and easy to realize compatibility with the existing microelectronic process technology. The formed unique 'shell-core' structure reduces the size of the phase change region, inhibits atom migration and blocks heat diffusion. The shell-core structure of the invention is O-Sb₂Te₃Phase change memory devices compared to pure Sb₂Te₃The direct current set operating current of the phase change memory device is reduced by one order of magnitude, reset power consumption is reduced by over 95%, resistance drift is obviously reduced, and cycle characteristics are greatly improved.

In order to illustrate the process of the invention in more detail, further details are given below with reference to more specific examples.

Example 1

O-Sb for phase change memory device prepared in this example₂Te₃The chemical general formula of the phase change storage thin film material is (ST)_1-xO_xWherein ST represents Sb₂Te₃In this embodiment, x is 0.1.

O-Sb₂Te₃The phase change storage film material is prepared by adopting a magnetron sputtering method; during preparation, high-purity argon is introduced as sputtering gas, a small amount of oxygen is introduced to provide an oxygen atmosphere, the sputtering pressure is 0.5Pa, and Sb is₂Te₃The target adopts an alternating current power supply, and the power supply power is 60W. The specific preparation process comprises the following steps:

1. selecting SiO with the size of 1cm multiplied by 1cm₂the/Si (100) substrate is cleaned on the surface and the back surface to remove dust particles, organic and inorganic impurities.

a) Mixing SiO₂the/Si (100) substrate is placed in an acetone solution and treated with 40W workUltrasonic vibration at a rate of 10 minutes, rinsing with deionized water.

b) Ultrasonic vibration of the substrate treated by acetone in ethanol solution at 40W power for 10 minutes, washing with deionized water and obtaining high-purity N₂And air-drying the surface and the back to obtain the substrate to be sputtered.

2. Method for preparing O-Sb by adopting alternating current power sputtering method₂Te₃Phase change storage thin film material

a) Well placed Sb₂Te₃The alloy target material with the purity of 99.99 percent (atomic percent) is vacuumized to 10 percent^-4Pa。

b) High-purity Ar gas is used as sputtering gas, and a small amount of O is introduced₂And adjusting the sputtering pressure to 0.5Pa, wherein the distance between the target and the substrate is 120 mm.

c) The power was set to 60W.

d) Rotating the empty susceptor to Sb₂Te₃Above the target, to Sb₂Te₃And (5) pre-sputtering the target for 10min, and cleaning the surface of the target.

e) After the pre-sputtering is finished, the substrate to be sputtered is rotated to Sb₂Te₃Above the target, the baffle is opened, and O-Sb with different thicknesses is sputtered according to the preset sputtering time₂Te₃And (3) phase change storage thin film material. When the sputtering time is 3min, the thickness of the prepared film is about 50nm, and the method is used for measuring the real-time change curve of the sheet resistance of the in-situ film along with the annealing temperature. When the sputtering time is 6min, the thickness of the prepared film is about 100nm and is used for XRD characterization.

Comparative example 1

Preparation of pure Sb in comparative example 1₂Te₃And (3) phase change storage thin film material.

Pure Sb₂Te₃The phase change storage film material is prepared by adopting a magnetron sputtering method; during preparation, high-purity argon is introduced as sputtering gas, the sputtering gas pressure is 0.5Pa, and Sb is₂Te₃The target adopts an alternating current power supply, and the power supply power is 60W.

The specific preparation process comprises the following steps:

1. selecting SiO with the size of 1cm multiplied by 1cm₂a/Si (100) substrate, cleaning the surfaceAnd a back side for removing dust particles, organic and inorganic impurities.

a. Mixing SiO₂the/Si (100) substrate was placed in an acetone solution and rinsed with deionized water with ultrasonic vibration at 40W power for 10 minutes.

b. Ultrasonic vibration of the substrate treated by acetone in ethanol solution at 40W power for 10 minutes, washing with deionized water and obtaining high-purity N₂And air-drying the surface and the back to obtain the substrate to be sputtered.

2. Method for preparing pure Sb by adopting alternating current power sputtering method₂Te₃Phase change storage thin film material

a. Well placed Sb₂Te₃The alloy target material with the purity of 99.99 percent (atomic percent) is vacuumized to 10 percent^-4Pa。

b. High-purity Ar gas is used as sputtering gas, the sputtering pressure is adjusted to 0.5Pa, and the distance between the target and the substrate is 120 mm.

c. The power was set to 60W.

d. Rotating the empty susceptor to Sb₂Te₃Above the target, to Sb₂Te₃And (5) pre-sputtering the target for 10min, and cleaning the surface of the target.

e. After the pre-sputtering is finished, the substrate to be sputtered is rotated to Sb₂Te₃Above the target, the shutter is opened to sputter Sb of different thicknesses according to a predetermined sputtering time₂Te₃And (3) phase change storage thin film material. When the sputtering time is 3min, the thickness of the prepared film is about 50nm, and the method is used for measuring the real-time change curve of the sheet resistance of the in-situ film along with the annealing temperature. When the sputtering time is 6min, the thickness of the prepared film is about 100nm and is used for XRD characterization.

The O-Sb in the above example 1 and comparative example 1 was added₂Te₃Pure Sb₂Te₃And testing the phase change storage thin film material. FIG. 1 shows O-Sb of the shell-core structure formed after the grain boundary engineering regulation in the embodiment of the invention₂Te₃Phase change memory material film and pure Sb₂Te₃A real-time relation curve of the in-situ sheet resistance and the annealing temperature of the phase change storage material film, wherein the heating rate is 6 ℃/min, and ST represents pure Sb₂Te₃Phase change memory material, OST stands for O-Sb of 'shell-core' structure₂Te₃A phase change memory material. The comparison shows that the formation of the shell-core structure improves the resistance value of the amorphous material, the window between the resistance value of the amorphous material and the resistance value of the crystalline material is enlarged, the phase change temperature is greatly improved to 250 ℃, and the stability of the amorphous material is obviously improved.

FIG. 2 shows that O-Sb with a shell-core structure is formed after the regulation and control of grain boundary engineering₂Te₃Phase change memory material film (abbreviated as OST in the figure) and pure Sb₂Te₃(abbreviated as ST in the figure) XRD characterization contrast diagram of the phase change memory material film. In the figure, squares correspond to diffraction peaks of Sb-Te substances, and inverted triangles correspond to diffraction peaks of Sb-O substances. After annealing at 200 ℃ the "shell-core" structure Sb₂Te₃The phase change memory material film has no diffraction peak except the base peak and is in an amorphous state. However, the pure ST film at the annealing temperature of 200 ℃ shows an obvious polycrystalline diffraction peak pattern, which shows that the formation of a shell-core structure improves the amorphous stability of a material system and is consistent with the in-situ R-T relation curve diagram of the film. At the same time, the shell-core structure Sb is in the annealing temperature of 300 DEG C₂Te₃Diffraction peaks of Sb-O substances with weak intensity appear in a phase change memory material film spectrogram, and existence of Sb-O oxides of a shell layer is verified.

Example 2

O-Sb₂Te₃The phase change storage film material is prepared by adopting a magnetron sputtering method. During preparation, high-purity argon is introduced as sputtering gas, a small amount of oxygen is introduced to provide an oxygen atmosphere, the sputtering pressure is 0.5Pa, and Sb is₂Te₃The target adopts an alternating current power supply, and the power supply power is 60W. The specific preparation process comprises the following steps:

a) Mixing SiO₂the/Si (100) substrate was placed in an acetone solution and rinsed with deionized water with ultrasonic vibration at 40W power for 10 minutes.

c) The power was set to 60W.

e) After the pre-sputtering is finished, the substrate to be sputtered is rotated to Sb₂Te₃Above the target, the baffle is opened, and O-Sb with different thicknesses is sputtered according to the preset sputtering time₂Te₃And (3) phase change storage thin film material. When the sputtering time is 6min, the thickness of the prepared film is about 100nm, and the prepared film is used for TEM, HRTEM and EDX microscopic analysis and X-ray photoelectron spectroscopy characterization.

O-Sb in the present example₂And testing the Te phase-change storage thin-film material.

FIG. 3 shows O-Sb which forms a "shell-core" structure after being controlled by grain boundary engineering in accordance with an embodiment of the present invention₂Te₃And (3) an in plane-TEM microscopic analysis image of the phase change memory material film. The as-deposited sample was annealed at 300 ℃ for 10 min. It was found that the sample microscopically exhibited a uniform heterostructure.

FIG. 4 is O-Sb of the "shell-core" structure in the present example₂Te₃HRTEM microscopic analysis of the phase change memory material thin film, wherein,the as-deposited sample was annealed at 300 ℃ for 10 min. In the figure, the longer solid arrows indicate the "core" structure crystal portion, the shorter dashed arrows indicate the "shell" structure amorphous portion, and the rectangular boxes on the right side indicate the fourier transform of the corresponding portions. It is found from the figure that the crystal grains are wrapped by amorphous tissues which are randomly distributed and are separated into 'crystal islands' with nanometer sizes, the 'shell' is formed by amorphous substances with low thermal conductivity and low electric conductivity, and the 'core' in the inner layer is a 'shell-core' structure of crystals.

FIG. 5 is O-Sb of the "shell-core" structure in the present example₂Te₃The EDX distribution diagram of the phase change memory material thin film is shown in fig. 5(a) as a bright field image of a sampling region, fig. 5(b) as an Sb element distribution image, and fig. 5(c) as a Te element distribution image. As can be seen from the figure, the Sb element and the Te element are not completely overlapped in distribution, and a wrapping phenomenon occurs.

FIG. 6 is O-Sb of the "shell-core" structure in the present example₂Te₃An X-ray photoelectron spectrum of the phase change memory material film, wherein the deposited sample is annealed at 300 deg.C for 10min, and the surface is subjected to Ar⁺And (b) processing to remove the surface oxidation pollution layer, wherein an Sb element energy spectrum is shown in figure 6(a), a Te element energy spectrum is shown in figure 6(b), and diffraction peaks in the diagrams correspond to corresponding chemical bonds. The element distribution characterization results show that Sb elements are distributed on the periphery of Te elements besides Sb-Te compounds formed in the Te element distribution area, and the bonding state of Sb atoms and Te atoms is combined, so that the shell formed by introducing O atoms is Sb with low heat conductivity and low electric conductivity_iO_jThe oxide and the core in the inner layer are the shell-core structure phase change storage material of the traditional Sb-Te phase change material.

Example 3

This example used Materials Studio software to dope Sb at O element concentrations of 5%, 10% and 20%, respectively₂Te₃Modeling is carried out on the phase change storage thin film material, the three models are randomized, melted and quenched by utilizing the first principle, and the amorphous model of the OST phase change storage thin film material with the O element doping concentrations of 5%, 10% and 20% is obtained through simulation in the quenching process, and the result is shown in figure 7. Using Materials Studio software to simplifyChemical "shell-core" structure O-Sb₂Te₃And pure Sb₂Te₃Modeling is carried out, and the shell-core structure O-Sb is simulated at different temperatures by utilizing the first principle₂Te₃Model and pure Sb₂Te₃Atomic motion of and "shell-core" structure of O-Sb at the same temperature₂Te₃The movement conditions of the atoms in the middle region and the atoms in the regions close to the shell layer in the model are processed to form visual images, and FIG. 8 is the influence of the simplified shell-core structure on the movement of the atoms in the inner layer (inside the core) at different temperatures calculated by using the first principle in the invention, wherein the curve 1 corresponds to pure Sb₂Te₃Simulation result of atomic motion condition of conventional Phase Change Material (PCM) at high temperature (550K), curve 2 corresponds to pure Sb₂Te₃Simulation result of atomic motion condition of conventional Phase Change Material (PCM) at low temperature (300K), curve 3 corresponds to O-Sb₂Te₃The simulation result of the atomic motion condition of the represented shell-core structure phase change material (cs-PCM) at high temperature (550K) is that curve 4 corresponds to O-Sb₂Te₃The atomic motion condition simulation result of the represented shell-core structure phase change material (cs-PCM) at low temperature (300K) is obtained. Fig. 9 is a graph showing the influence of a simplified "shell-core" structure calculated by using a first principle on the atomic motion of different regions of the inner layer ("inside of core"), where

curves

1 and 3 correspond to the simulation result of the atomic motion of the region of the phase change material of the inner layer "core" close to the shell layer, and curve 2 corresponds to the simulation result of the atomic motion of the middle region of the phase change material of the inner layer "core". Wherein the inset is simplified 'shell-core' structure O-Sb₂Te₃The three-dimensional wrapping structure model is characterized in that the region 1 and the region 3 correspond to atoms of a region of a lining 'core' phase change material close to a 'shell' layer, and the region 2 corresponds to atoms of a middle region of the lining 'core' phase change material.

Fig. 7 is an amorphous model of the OST phase change memory thin film material with the doping concentrations of the O element of 5%, 10% and 20% respectively according to the embodiment of the present invention, and it can be found that the doped O atoms tend to bond with Sb atoms. As the concentration of O atoms increases, the O-Sb binding species increase and randomly appear at the cell boundaries. When the O atom concentration is 20%, the Sb-O binding substances at the boundary are connected to form a wrapping structure for the Sb-Te substance at the inner layer, namely, the shell is the low-thermal-conductivity low-conductivity Sb-O oxide, and the core at the inner layer is the shell-core structure of the traditional Sb-Te phase-change material.

For "shell-core" structure O-Sb₂Te₃The three-dimensional packing structure is simplified to obtain an illustration as in fig. 9, and the influence of the limitation in the three-dimensional direction on the movement of the Sb-Te atoms in the inner layer can be reflected and presumed by studying the movement of the atoms in the limited direction (Z direction). FIG. 8 shows the "shell-core" structure of O-Sb at low and high temperatures, respectively₂Te₃Model and pure Sb₂Te₃Z-direction atomic motion contrast plot. Curve 1 corresponds to pure Sb₂Te₃Simulation result of atomic motion condition of conventional Phase Change Material (PCM) at high temperature (550K), curve 2 corresponds to pure Sb₂Te₃Simulation result of atomic motion condition of conventional Phase Change Material (PCM) at low temperature (300K), curve 3 corresponds to O-Sb₂Te₃The simulation result of the atomic motion condition of the represented shell-core structure phase change material (cs-PCM) at high temperature (550K) is that curve 4 corresponds to O-Sb₂Te₃The atomic motion condition simulation result of the represented shell-core structure phase change material (cs-PCM) at low temperature (300K) is obtained. It can be seen that the shell layer can effectively inhibit the movement of atoms in the 'core' of the inner layer, and the sensitivity to temperature is obviously reduced, namely the atom movement intensity changes with higher temperature, and the Sb is purer₂Te₃There is a significant reduction. Fig. 9 is a comparison graph of the movement of atoms in the middle area and atoms near the shell area of the phase change material of the inner layer "core" at the same temperature, where

curves

1 and 3 correspond to the simulation result of the movement of atoms in the area near the shell area of the phase change material of the inner layer "core", and curve 2 corresponds to the simulation result of the movement of atoms in the middle area of the phase change material of the inner layer "core". It can be seen that the atoms move more intensely in the middle region than in the regions closer to the shell. Through first-nature principle calculation simulation, the shell-core structure can effectively inhibit the movement of atoms close to an oxide interface, and the influence on the movement of atoms in the central region of the core in the inner layer is limited. I.e. "shell-core" structure can inhibit the length of material atoms in the "core" of the liningThe range shifts, but does not affect the movement of material atoms within the inner "core" of the inner layer to each other in the region within the shell.

Fig. 10 is a thermal simulation diagram of a simplified "shell-core" structure obtained by using COMSOL software, and it can be found that, during current operation, heat is mainly concentrated in the Sb-Te phase change material region of the core portion, which indicates that the shell layer of the "shell-core" structure has an obvious barrier effect on thermal diffusion, and the electrothermal utilization efficiency in the phase change process is effectively improved.

Example 4

O-Sb of the "Shell-core" Structure used in this example₂Te₃The phase change storage thin film material is used as a phase change layer material for preparing a storage device, wherein the structure of 'shell-core' is O-Sb₂Te₃The phase change layer is prepared by a magnetron sputtering method. During preparation, high-purity argon is introduced as sputtering gas, a small amount of oxygen is introduced to provide an oxygen atmosphere, the sputtering pressure is 0.5Pa, and Sb is₂Te₃The target adopts an alternating current power supply, and the power supply power is 60W. The specific preparation process comprises the following steps:

2. And preparing a 100nm TiN lower electrode by adopting a direct-current power sputtering method.

3. Depositing 100nm SiO on the TiN lower electrode in the step 2 by adopting a chemical vapor deposition method₂An insulating layer.

4. SiO in step 3 by e-beam lithography and the like₂The insulating layer formed a via hole having a depth of 100nm and a diameter of 250 nm.

5. The memory array is formed by a photolithography process.

6. Adopting an alternating current power supply sputtering method to form the through hole in the step 4Filled with O-Sb₂Te₃Phase change storage thin film material

c) The power was set to 60W.

e) After the pre-sputtering is finished, the substrate to be sputtered is rotated to Sb₂Te₃Above the target, the baffle is opened, and O-Sb with different thicknesses is sputtered according to the preset sputtering time₂Te₃And (3) phase change storage thin film material. When the sputtering time is 6min, the thickness of the prepared phase change layer is about 100 nm.

7. Preparing 100nm Pt upper electrode by using a direct-current power sputtering method to obtain complete O-Sb based on a shell-core structure₂Te₃A phase change memory device array of a phase change layer.

Comparative example 4

In this comparative example, pure Sb was used₂Te₃Pure Sb prepared by using phase change storage thin film material as phase change layer₂Te₃A memory device.

5. The memory array is formed by a photolithography process.

6. Filling pure Sb in the through hole formed in the step 4 by adopting an alternating current power sputtering method through magnetron sputtering₂Te₃Phase change storage thin film material

7. Preparing 100nm Pt upper electrode by direct-current power sputtering method to obtain complete Sb-based Pt upper electrode₂Te₃A phase change memory device array of a phase change layer.

O-Sb based on the "shell-core" structure in example 4 and comparative example 4 described above, respectively₂Te₃Phase change memory and pure Sb₂Te₃The phase change memory device is subjected to an electrical characteristic test.

FIG. 11 shows O-Sb in the form of a "shell-core" structure in this example₂Te₃The schematic diagram of the phase change memory cell structure with the phase change memory material as the functional layer can be seen from the figure, wherein 1 is the top electrode, 2 is the phase change material with the "shell-core" structure, and 3 is the thermal insulation SiO₂Layer 4 is the bottom electrode.

FIGS. 12 to 15 are O-Sb in a "shell-core" structure₂Te₃Phase change memory cell with phase change memory material as functional layer and undoped Sb₂Te₃Comparison graph of electrical performance test of phase change memory cell, FIG. 12 is comparison graph of I-V performance of device, FIG. 13 is comparison graph of RESET performance of device, FIG. 14 is comparison graph of drift resistance of device, and FIG. 15 is comparison graph of O-Sb of shell-core structure₂Te₃And (5) a device cycle performance diagram.

FIG. 12 is a graph comparing I-V characteristics of devices, both of which are evident in phase transition, operating threshold current I_th1.64. mu.A and 12. mu.A, respectively, indicating that O-Sb is a "shell-core" structure₂Te₃The operating current of the phase change memory unit with the phase change memory film material as the functional layer is reduced by one order of magnitude.

FIG. 13 is an R-V test plot of a device, reflecting the RESET performance of the device, in a "shell-core" configuration O-Sb₂Te₃The phase change memory cell using the phase change memory film material as the functional layer can be successfully reset under the pulse operation with the width of 10 ns. In addition, the high-low resistance ratio of the two devices is more than 10²The anti-interference capability of the device is improved; two devices under the same operating pulse width were compared, as shown by the dashed line in FIG. 13, with conventional Sb₂Te₃The reset voltage of the phase change memory unit taking the phase change memory film material as the functional layer reaches 2.8V under the pulse width of 10ns, compared with the phase change memory unit taking a shell-core structure O-Sb₂Te₃The phase change memory thin film material is 3 to 4 times different from 0.95V of the phase change memory unit of the functional layer. Calculation of Power consumption by ohm's Law

The results are shown in the following table:

TABLE 1 device reset Power consumption comparison

	U_RESET	R_SET	t	Energy
					ST device	2.8V	9673.322746ohm	10ns	8.105PJ
OST device	0.95V	26941.8068 ohm	10ns	0.335PJ

It is known that O-Sb is present in a "shell-core" structure₂Te₃The phase change memory unit with the phase change memory film material as the functional layer has lower power consumption, can solve the heat dissipation problem in a compact three-dimensional stacked array, and provides a possible material system for three-dimensional storage.

FIG. 14 is a graph of measurement and comparison of device resistance drift. The resistance drift can be described by the power of the band time equation (1):

wherein R is the test resistance, R₀And τ₀Is a constant that depends on the initial state of the material. The exponential factor α is a resistance drift coefficient, which represents the rate of resistance drift. Higher values of α indicate faster drift. For disordered chalcogenide materials, the drift index α is independent of temperature and increases only with the initial resistance value. As shown in FIG. 14, O-Sb is in a "shell-core" structure₂Te₃The drift index alpha of the phase change memory unit taking the phase change memory thin film material as the functional layer is 0.005, compared with the traditional Sb₂Te₃The phase change memory unit alpha with the phase change memory film material as the functional layer is greatly improved to 0.03, and meanwhile, the data discrete bar chart in the inset also shows that the resistance of the phase change memory unit alpha is more stable and the fluctuation is smaller.

FIG. 15 is O-Sb in a "shell-core" structure₂Te₃The test result of the cycle characteristic of the phase change memory unit with the phase change memory film material as the functional layer is that the standard is that the difference of the high and low resistance values is larger than 10 timesAnd repeatedly applying set pulse (rising edge 600ns,1us, falling edge 600 ns; 2.5V) and reset pulse (rising edge 8ns,50ns, falling edge 8 ns; 2.8V), the number of cycles of the device can reach 10⁸A quantity level.

Sb which is not regulated and controlled by amorphous structure in the prior art₂Te₃Compared with the phase change storage material, the shell-core structure O-Sb of the invention₂Te₃In the phase change material, O atoms in sputtering atmosphere are combined with Sb atoms to form amorphous oxide, the amorphous oxide is distributed around SbTe crystal grains of the phase change material to form a crystal boundary, and the phase change material Sb is₂Te₃Separated into 'phase change islands' with smaller volume, wherein the 'shell' layer of the surface layer is formed by low-heat-conductivity low-electric-conductivity oxide, and the 'core' of the inner layer is formed by phase change material Sb₂Te₃The "shell-core" structure of (a). The local disorder state improves the resistance value of the amorphous state of the phase-change material, and improves Sb₂Te₃Amorphous stability of the material. In addition, the existence of the shell-core heterostructure limits the long-range migration of atoms in the inner layer of the shell-core heterostructure and the core due to external electric operation on a three-dimensional structure, so that the overall cycle characteristic and the resistance value drift characteristic of the memory device are improved. The low thermal conductivity of the "shell" layer oxide material is also effective in reducing the RESET power consumption of the device.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. Sb based on oxygen doping₂Te₃The phase-change material is characterized in that the chemical formula is as follows: o is_x(Sb₂Te₃)_1-xWherein O is oxygen, x represents the atomic percentage of oxygen in the whole chemical composition, 0<x<40％。

2. The oxygen-doped Sb-based alloy of claim 1₂Te₃Phase change materialMaterial characterized by oxygen atoms and Sb₂Te₃The element atoms in the material are combined to form a disordered oxide, and the disordered oxide is wrapped in Sb₂Te₃Around, Sb is₂Te₃Separated into multiple islands to form a shell-core structure, wherein the shell is oxygen atom and Sb₂Te₃Wherein the element atoms are combined to form a disordered oxide, and the core part is Sb₂Te₃And (4) crystal grains.

3. The oxygen-doped Sb-based alloy of claim 2₂Te₃Phase change material, characterized in that part of the oxygen element enters Sb₂Te₃In the crystal grain, for increasing Sb₂Te₃Amorphous stability of (3).

4. An oxygen-doped Sb-based alloy according to claim 3₂Te₃Phase change material, characterized in that O_x(Sb₂Te₃)_1-xIn the material, the Sb is controlled by controlling the doping amount of O₂Te₃The property of the medium amorphous oxide grain boundary is adjusted and controlled to O-Sb₂Te₃The electrochemical properties of the phase change memory material comprise high and low resistance state resistance, crystallization temperature and O-Sb₂Te₃The phase change memory material is O_x(Sb₂Te₃)_1-xA material of which 0<x<40％。

5. The oxygen-doped Sb-based alloy of claim 4₂Te₃Phase change material, characterized in that oxygen atoms and Sb₂Te₃Wherein Sb atoms are combined to form a disordered oxide and are concentrated in Sb₂Te₃Amorphous grain boundaries are formed around the grains.

6. An oxygen-doped Sb-based alloy according to claim 5₂Te₃The phase change material is characterized in that the disordered oxide is oxygen atoms and Sb₂Te₃The disordered oxide formed by combining the middle Sb atoms has higher melting point and lower thermal conductivityThe said high melting point is higher than Sb₂Te₃The melting point is high by 20-30K, and the thermal conductivity is low, namely the thermal conductivity is close to 10^-3And magnitude, approaching full insulation.

7. An oxygen-doped Sb-based alloy according to claim 6₂Te₃The phase change material is characterized in that an oxide crystal boundary plays a role in improving electrothermal efficiency and preventing atom migration in the phase change process, and is used for improving the resistance value of the amorphous state of a phase change layer and improving Sb₂Te₃Amorphous stability of the material.

8. Sb based on oxygen doping₂Te₃Phase change memory of phase change material, characterized in that the phase change memory comprises a bottom electrode, an isolation layer, a phase change memory material thin film layer and a top electrode, wherein the phase change memory material thin film layer is made of Sb based on oxygen doping according to any one of claims 1 to 4₂Te₃A phase change material.

9. Preparation of oxygen-doped Sb as claimed in any of claims 1 to 7₂Te₃The method for preparing the phase-change material is characterized by adopting a magnetron sputtering method, a chemical vapor deposition method, an atomic layer deposition method, an electroplating method or an electron beam evaporation method to prepare the phase-change material.

10. The method of claim 9, wherein the specific magnetron sputtering method is any one of the following three:

(1) co-sputtering an Sb target and a Te target in an aerobic environment;

(2)Sb₂Te₃sputtering the target in an aerobic environment;

(3) sb after O doping₂Te₃And (4) sputtering an alloy target.