A single-element phase change memory material doped with a rare earth element gadolinium, and a preparation method and application thereof

Abstract

The application discloses a single-element phase change memory material doped with a rare earth element gadolinium as well as a preparation method and application thereof. x Gd 100‑x 69.1 at.%≤x≤93.1 at.%, and is obtained by double-target sputtering of a Sb single-element target and a Gd single-element target in a magnetron sputtering coating system; the material successfully overcomes the inherent defect of poor thermal stability of a pure Sb thin film, has a higher crystallization temperature, a larger activation energy, a better data retention and an extremely low resistance drift compared to a traditional GST material, and provides a new material selection for realizing stable and reliable storage of a phase change memory under long-term and high-cycle working conditions.

Description

Technical Field

[0001] This invention belongs to the field of phase change materials for information storage, and in particular relates to a single-element phase change storage material doped with rare earth element gadolinium, its preparation method and application. Background Technology

[0002] Phase-change memory (PCM) is a type of non-volatile memory technology that has attracted much attention in recent years. Its core principle relies on the reversible structural transformation of phase-change materials between a crystalline (low resistance) and an amorphous (high resistance) state to achieve data storage. This technology not only has good compatibility with standard CMOS processes but also features fast read / write speeds and high cycle endurance (>10). 12 With advantages such as high speed, high density, and high reliability, it can meet the key requirements of high-performance computing, embedded storage, and other applications.

[0003] Currently, Ge2Sb2Te5 (GST) is the most widely used phase change material in the industry. During heating, it typically undergoes a two-step crystallization process: first, it transforms from an amorphous state to a metastable face-centered cubic (fcc) phase at approximately 175 °C, and then further transforms into a stable hexagonal (hex) phase at approximately 290 °C. However, as a ternary alloy, GST is prone to elemental segregation during rapid and repeated phase change cycles, causing a significant drift in the material's resistivity over time (drift coefficient v≈0.067), which in turn affects the long-term data retention and lifespan of devices. This problem has become a major bottleneck restricting the further development of PCM performance.

[0004] To fundamentally circumvent the component segregation phenomenon in multi-element alloys, single-element phase change materials (such as antimony and Sb) have been extensively studied in recent years. These materials offer advantages such as a simple atomic structure, a purer and more controllable phase transition process, avoidance of complex bonding behavior between multi-element interfaces, and improved repeatability of the phase transition process. They also exhibit good size scaling characteristics, achieving stable phase transition behavior even at nanometer-scale thicknesses, providing possibilities for future high-density three-dimensional integration. However, pure antimony films suffer from poor thermal stability at room temperature and exhibit a tendency for spontaneous crystallization, severely impacting their practical applications in devices and data retention characteristics. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a rare earth element gadolinium-doped single-element phase change memory material with high crystallization temperature and phase change temperature and extremely low resistance drift characteristics, as well as its preparation method and application, which can realize long-term stable data storage and is suitable for high-performance phase change memory.

[0006] The technical solution adopted by this invention to solve the above-mentioned technical problem is: a rare earth element gadolinium-doped single-element phase change memory material, wherein the material is a Gd-doped Sb thin film material, and the chemical structural formula of the thin film material is Sb. x Gd 100-x , of which 69.1 at.% ≤ x ≤ 93.1 at.%.

[0007] Preferably, the thin film material is obtained by dual-target sputtering using an Sb elemental target and a Gd elemental target in a magnetron sputtering coating system.

[0008] Preferably, the chemical structural formula of the thin film material is Sb 93.1 Gd 6.9 .

[0009] Preferably, the chemical structural formula of the thin film material is Sb 84.1 Gd 15.9 .

[0010] Preferably, the chemical structural formula of the thin film material is Sb 69.1 Gd 30.9 .

[0011] This invention also provides a method for preparing the above-mentioned rare earth element gadolinium-doped single-element phase change memory material, the specific steps of which are as follows: In a magnetron sputtering coating system, a single-element silicon wafer or quartz wafer is used as a substrate; an Sb single-element target is installed in a magnetron DC sputtering target; a Gd single-element target is installed in a magnetron RF sputtering target; and the sputtering chamber of the magnetron sputtering coating system is evacuated until the vacuum level inside reaches 6×10⁻⁶. -4 Pa, then high-purity argon gas at a flow rate of 45–55 mL / min is introduced into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure of 1.5 Pa. Then, the sputtering power of the Sb target is fixed at 30 W, and the sputtering power of the Gd target is adjusted to 25–40 W. Dual-target co-sputtering is performed at room temperature. After a sputtering thickness of 100 nm, a deposited Sb-Gd thin film material is obtained, with the chemical formula Sb... x Gd 100-x , of which 69.1 at.% ≤ x ≤ 93.1 at.%.

[0012] This invention also provides the application of the above-mentioned rare earth element gadolinium-doped single-element phase change memory material in the preparation of high-performance phase change memory.

[0013] Compared with existing technologies, the advantages of this invention are as follows: This invention discloses a rare-earth element gadolinium-doped single-element phase-change memory material, its preparation method, and its application. By introducing the rare-earth element Gd to dope single-element Sb, the unique electronic configuration of the 4f electron layer of rare-earth elements is utilized to stabilize the crystal structure of the material and suppress the formation of lattice defects, thereby improving thermal stability. The system has a simple composition and is easy to control, suppressing the problem of multi-element segregation from its source. Preferred Sb... 93.1 Gd 6.9 The components exhibit excellent overall performance: crystallization temperature (T) c The temperature reaches as high as 208 °C, the resistivity drift coefficient (ν) is close to 0.005, and the crystallization activation energy (E) is... a The temperature reached 3.93 eV, maintaining the temperature for ten years (T). 10-year The temperature is 141.3 °C. This material successfully overcomes the inherent defect of poor thermal stability in pure Sb thin films, and compared with traditional Ge2Sb2Te5 (GST) materials, it has a higher crystallization temperature, a larger activation energy, better data retention, and extremely low resistance drift, providing a very promising material solution for the development of high-stability, low-power phase-change memories. Attached Figure Description

[0014] Figure 1 The curves showing the relationship between the resistance of SSB0-SSB2 and pure Sb and GST phase change thin films of the present invention and temperature; Figure 2 The graphs show the resistivity drift analysis of the deposited states SSB0-SSB2 and GST in this invention. Figure 3 This is a ten-year data retention chart of SSB0-SSB2 and GST phase change thin films of the present invention; Figure 4 X-ray diffraction analysis diagrams of the SSB0 thin film of the present invention in the deposited state and the annealed state at 280°C; Figure 5 The X-ray photoelectron spectroscopy (XPS) analysis of the Sb orbitals of the SSB0-SSB1 thin film of the present invention under annealing at 280°C is shown. Figure 6 The X-ray photoelectron spectroscopy (XPS) analysis of the Gd orbitals of the SSB0-SSB1 thin film of the present invention in the annealed state at 280°C is shown. Figure 7 The images shown are transmission electron microscope (TEM) and SAED images of the SSB0 thin film of the present invention after annealing at 280°C. Figure 8 The images shown are transmission electron microscope (TEM) and SAED images of the SSB1 thin film of the present invention after annealing at 280°C. Figure 9The images shown are transmission electron microscope (TEM) and SAED images of the SSB2 thin film of the present invention after annealing at 280°C. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0016] Specific embodiment: A rare earth element gadolinium-doped single-element phase change memory material, the chemical structural formula of which is Sb x Gd 100-x , of which 69.1 at.% ≤ x ≤ 93.1 at.%.

[0017] Example 1, Sb 93.1 Gd 6.9 Preparation of phase change storage materials.

[0018] In a magnetron sputtering coating system, a single-element silicon wafer or quartz wafer is used as the substrate. An Sb target is mounted in a magnetron DC sputtering target, and a Gd target is mounted in a magnetron RF sputtering target. The sputtering chamber of the magnetron sputtering coating system is evacuated until the vacuum level reaches 6 × 10⁻⁶. -4 Pa, then high-purity argon gas at a flow rate of 50 mL / min is introduced into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure of 1.5 Pa for sputtering. Then, the sputtering power of the Sb target is fixed at 30 W, and the sputtering power of the Gd target is adjusted to 25 W. The two targets are co-sputtered at room temperature. After the sputtering thickness reaches 100 nm, the deposited Sb-Gd thin film material is obtained, and its chemical structure is Sb 93.1 Gd 6.9 .

[0019] The prepared thin film material was subjected to in-situ resistance and resistance drift tests, as well as XRD analysis. The performance indicators of the thin film prepared in this embodiment are as follows: crystallization temperature T c The crystallization activation energy is 3.93 eV, the ten-year data retention temperature is 141.3 °C, and the resistivity drift coefficient is [not specified]. ν It is 0.005. Compared to traditional GST materials, for the same thickness, Sb 93.1 Gd 6.9 The crystallization temperature is higher, and the resistance drift coefficient is reduced by an order of magnitude.

[0020] Example 2, Sb 84.1 Gd 15.9 Preparation of phase change storage materials.

[0021] Similar to Example 1 above, the difference lies in that: during the sputtering process, the sputtering power of the Sb target is controlled at 30W and the sputtering power of the Gd target is 35W. Dual-target co-sputtering deposition is performed at room temperature, and after a sputtering thickness of 100 nm, a preferred Sb / Gd phase change thin film material is obtained in the deposited state, with the chemical formula Sb... 84.1 Gd 15.9 .

[0022] The prepared thin film material was subjected to in-situ resistance and resistance drift tests, as well as a ten-year data retention test. The performance indicators of the thin film prepared in this embodiment are as follows: crystallization temperature T c The crystallization activation energy is 4.41 eV, the ten-year data retention temperature is 153.8 °C, and the resistivity drift coefficient is [not specified]. ν It is 0.026. This is comparable to Sb of the same thickness. 93.1 Gd 6.9 The material exhibits a decrease in crystallization temperature, an increase in crystallization activation energy, an increase in the ten-year data storage temperature, and an increase in the resistance drift coefficient.

[0023] Example 3, Sb 69.1 Gd 30.9 Preparation of phase change storage materials.

[0024] Similar to Example 1 above, the difference lies in that: during the sputtering process, the sputtering power of the Sb target is controlled at 30W and the sputtering power of the Gd target is 40W. Dual-target co-sputtering deposition is performed at room temperature, and after a sputtering thickness of 100 nm, a deposited Sb-Gd phase change thin film material is obtained, with the chemical formula Sb... 69.1 Gd 30.9 .

[0025] The prepared thin film material was subjected to in-situ resistance and resistance drift tests, as well as ten-year data analysis. The performance indicators of the thin film prepared in this embodiment are as follows: crystallization temperature T c The crystallization activation energy is 5.16 eV, the ten-year data retention temperature is 149.2 °C, and the resistivity drift coefficient is [not specified]. ν It is 0.055. Compared to Sb of the same thickness... 93.1 Gd 6.9 For the material, the crystallization temperature decreased slightly, while the crystallization activation energy and ten-year data showed an increase in temperature, but the resistance drift coefficient increased.

[0026] Controlled Trial The results were essentially the same as in Example 1, except that the Ge2Sb2Te5 alloy target was mounted in a magnetron sputtering target, the sputtering power was set to 30W, and a single-target sputtering deposition was performed at room temperature. After achieving a sputtering thickness of 100 nm, a pure Ge2Sb2Te5 phase change memory film was obtained. The prepared film underwent in-situ resistivity testing, and the performance indicators of the film prepared in the control experiment were as follows: crystallization temperature (… T c The temperature is 170 °C, the activation energy for crystallization is 2.98 eV, the holding temperature for ten years is 89.5 °C, and the resistance drift coefficient is 0.067.

[0027] The sputtering power, Sb and Gd content, and related thermal parameters of the target materials in the different embodiments described above are shown in Table 1.

[0028] Table 1. Composition and related thermal parameters of 100 nm Sb-Gd phase change thin film materials prepared under different conditions

[0029] II. Analysis of Experimental Results: The results of different embodiments in the specific examples are analyzed as follows.

[0030] Figure 1 The resistivity versus temperature relationship of pure Gb, GST, and SSB0-SSB2 thin films was tested at a heating rate of 30 ℃ / min. It can be seen that the resistivity of Sb at room temperature is around 10 ℃ / min. 2 The resistance is around ohms, indicating spontaneous crystallization at room temperature. The crystallization temperature of GST is 170 °C, while the crystallization temperature of Gd doped with Sb increases and is higher than that of GST. It can be observed that Sb... 93.1 Gd 6.9 The thin film exhibited a large resistivity change around 208 °C, indicating a phase transition and crystallization. With a gradual increase in Gd content, the crystallization temperature of the film decreased slightly. (Sample Sb) 84.1 Gd 15.9 and Sb 69.1 Gd 30.9 The crystallization temperatures of the thin films are ~202℃ and ~196℃, respectively, showing a slightly decreasing trend. Compared with GST material thin films and pure Sb thin films, they have better phase transition characteristics and thermal stability.

[0031] Figure 2 The resistivity drift analysis of GST and SSB0-SSB2 thin films at room temperature is presented. It can be found that the resistivity drift coefficient of GST is 0.067, and that of Sb... 93.1 Gd 6.9 The resistivity drift coefficient of the thin film is 0.005, Sb 84.1 Gd 15.9 The resistivity drift coefficient of the thin film is 0.026, Sb 69.1 Gd30.9 The resistivity drift coefficient of the thin film is 0.055, and the resistivity drift gradually increases with increasing Gd content, with Sb being the preferred material. 93.1 Gd 6.9 This represents an order of magnitude improvement over GST materials.

[0032] Figure 3 Ten-year data retention analysis plots for GST and SSB0-SSB2 phase change films are presented. Analysis reveals that the crystallization activation energy of the GST film is 2.98 eV, and the ten-year data retention temperature is 89.5 ℃. Sb... 93.1 Gd 6.9 The crystallization activation energy of the thin film is 3.93 eV, and the ten-year data retention temperature is 141.3℃. Sb 84.1 Gd 15.9 The crystallization activation energy of the thin film is 4.41 eV, and the ten-year data retention temperature is 153.8 ℃. (Sb) 69.1 Gd 30.9 The crystallization activation energy of the thin film is 5.16 eV, and the ten-year data retention temperature is 149.2℃. Sb x Gd 100-x The activation energy for thin film crystallization and the holding temperature over ten years gradually increased with the increase of Gd content, and the stability of the thin film gradually improved.

[0033] Figure 4 X-ray diffraction analysis of SSB0 thin films at room temperature and under annealing at 280 °C is presented. It can be found that no grains precipitate in the deposited state film, indicating that the incorporation of Gd into Sb improves its thermal stability and inhibits Sb crystallization. At 280 °C, Sb(012) and Sb(110) crystal phases precipitate.

[0034] Figure 5 The X-ray photoelectron spectroscopy (XPS) results of SSB0 and SSB1 samples after annealing at 280 °C are presented. It can be seen that for Sb... 93.1 Gd 6.9 Sample, Sb 3d 5 / 2 The binding energy of the orbital is 530.17 eV; while in Sb 84.1 Gd 15.9 In the sample, the binding energy decreased slightly to 530.16 eV. This small negative shift indicates an electronic interaction between Sb (electronegativity approximately 2.05) and the less electronegative Gd (electronegativity approximately 1.20), thus confirming the formation of the Sb–Gd chemical bond.

[0035] Figure 6 XPS spectra of the Gd 4d orbitals of SSB0 and SSB1 under the same annealing conditions are shown. In Sb 93.1 Gd 6.9 In the middle, Gd4d5 / 2 and 4D 3 / 2 The binding energies are 142.03 eV and 147.01 eV, respectively; while in Sb 84.1 Gd 15.9 In the above tests, the voltages increased to 142.23 eV and 147.30 eV, respectively. This positive shift indicates a bonding relationship between Gd and the more electronegative Sb, further supporting the formation of Sb–Gd bonds and contributing to enhanced structural stability of the thin film.

[0036] Figures 7 to 9 The system displays the transmission electron microscopy (TEM) morphology and corresponding selected area electron diffraction (SAED) patterns of Sb-Gd films with different Gd contents (6.9 at.%, 15.9 at.%, and 30.9 at.%) after annealing at 280 °C. With increasing Gd content, the microstructure and crystallization behavior of the samples show significant changes, indicating that Gd plays a crucial role in inhibiting grain growth and refining grains.

[0037] Figure 7 Corresponding to Sb 93.1 Gd 6.9 The TEM image of the sample shows an alternating contrast distribution of light and dark areas: the gray areas represent the precipitated Sb crystalline phase, while the white areas represent the amorphous matrix. The introduction of a small amount of Gd forms a capping layer on the surface of the Sb grains, effectively hindering grain boundary migration and grain growth, thus forming a composite structure where the precipitated crystalline phase is encapsulated by a matrix dominated by the amorphous phase. The SAED pattern shows sharp diffraction spots, indicating that the precipitated Sb grains are fully crystallized and their orientation is relatively random.

[0038] Figure 8 For Sb 84.1 Gd 15.9 TEM results of the sample. Compared with the sample with low Gd content, the white amorphous region is more uniformly distributed and its area is smaller, while the contrast of the gray crystalline region tends to be more diffuse. This indicates that with the increase of Gd content, more Gd atoms participate in the formation of the surface capping layer, further inhibiting the crystallization process of Sb and promoting grain refinement. The clear continuous diffraction rings in the SAED pattern confirm that the sample has transformed into a polycrystalline structure composed of fine grains with random grain orientation.

[0039] Figure 9 Corresponding to Sb 69.1 Gd 30.9The high Gd content sample, inset as a high-resolution transmission electron microscope (HRTEM) image. The TEM image shows uniform overall contrast with no obvious grain boundaries or phase separation contrast differences, indicating a homogeneous microstructure. The HRTEM image further reveals locally present lattice fringes, identified as Sb(012) phase, confirming the precipitation of a small amount of nanocrystals. The SAED pattern shows only typical diffuse diffraction rings, without sharp spots or segments, indicating that the Gd-formed capping layer has greatly suppressed the long-range ordered crystallization of Sb. The main body of the sample is amorphous, with only a very small amount of nanoscale crystals remaining, their size being below the specific detection limit of conventional SAED.

[0040] In summary, the rare-earth element gadolinium-doped single-element Sb-Gd phase change memory material prepared by this invention has an increased crystallization temperature of 208 °C and a resistivity drift coefficient of 0.005, solving the problems of poor thermal stability and severe resistivity drift inherent in traditional phase change materials. Compared with traditional GST phase change materials, Sb is the preferred material. 93.1 Gd 6.9 The thin film has a higher crystallization temperature and phase transition temperature, higher activation energy and ten-year data retention temperature, and smaller resistance drift, which improves storage stability and reliability under long-term and high-cycle conditions.

[0041] The foregoing description is not intended to limit the invention, nor is the invention limited to the examples given. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should also be considered within the protection scope of the invention.

Claims

1. A single-element phase change memory material doped with the rare earth element gadolinium, characterized in that: The material is a Gd-doped Sb thin film, and the chemical structural formula of the thin film material is Sb. x Gd 100-x , of which 69.1 at.% ≤ x ≤ 93.1 at.%.

2. The rare earth element gadolinium-doped single-element phase change memory material according to claim 1, characterized in that: The thin film material is obtained by dual-target sputtering using an Sb and Gd elemental target in a magnetron sputtering coating system.

3. The rare earth element gadolinium-doped single-element phase change memory material according to claim 1, characterized in that: The chemical structural formula of the thin film material is Sb 93.1 Gd 6.9 .

4. The rare earth element gadolinium-doped single-element phase change memory material according to claim 1, characterized in that: The chemical structural formula of the thin film material is Sb 84.1 Gd 15.9 .

5. The rare earth element gadolinium-doped single-element phase change memory material according to claim 1, characterized in that: The chemical structural formula of the thin film material is Sb 69.1 Gd 30.9 .

6. A method for preparing a single-element phase change memory material doped with rare earth element gadolinium according to any one of claims 1-5, characterized in that... The specific steps are as follows: In the magnetron sputtering coating system, a single-element silicon wafer or quartz wafer is used as the substrate. The Sb single-element target is installed in the magnetron DC sputtering target, and the Gd single-element target is installed in the magnetron RF sputtering target. The sputtering chamber of the magnetron sputtering coating system is evacuated until the vacuum level reaches 6 × 10⁻⁶. -4 Pa, then high-purity argon gas at a flow rate of 45–55 mL / min is introduced into the sputtering chamber until the gas pressure in the sputtering chamber reaches the required starting pressure of 1.5 Pa for sputtering. Then, the sputtering power of the Sb target is fixed at 30 W, and the sputtering power of the Gd target is adjusted to 25–40 W. Dual-target co-sputtering is performed at room temperature. After sputtering to a thickness of 100 nm, the deposited Sb-Gd thin film material is obtained, with the chemical formula Sb x Gd 100-x , of which 69.1 at.% ≤ x ≤ 93.1 at.%.

7. The application of a single-element phase change memory material doped with rare earth element gadolinium according to any one of claims 1-5 in the preparation of high-performance phase change memory.

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