Transition metal sulfide doped single-element phase change storage material and preparation method thereof

Abstract

The invention discloses a transition metal sulfide doped single-element phase change storage material and a preparation method thereof, and is characterized in that the material is a MoS2 doped Sb thin film material, the chemical structural formula of the thin film material is Sbx (MoS2) 100-x, x is greater than or equal to 65at.% and less than or equal to 85at.%, the thin film material is obtained by double-target sputtering of an Sb elementary substance target and a chalcogenide MoS2 target in a magnetron sputtering coating system, compared with a GST phase-change material, the phase-change storage material has the advantages that the crystallization temperature is higher, the melting temperature is lower, the crystallization activation energy and the ten-year data retention temperature are higher, the resistance drift is greatly reduced, and the performance of single-element phase-change Sb is successfully improved by doping the chalcogenide; and the storage stability and reliability of the phase change memory device under the conditions of long period and high cycle index are supported.

Description

Technical Field

[0001] The present invention belongs to the field of information storage phase change materials, and in particular relates to a single-element Sb-MoS2 phase change storage material doped with transition metal sulfide and a preparation method thereof. Background Art

[0002] Phase change memory (PCM) is a non-volatile memory that uses the characteristics of phase change materials for data storage. Its core lies in the fact that the phase change material can reversibly transform between the amorphous state and the crystalline state under external stimuli, corresponding to different resistance states to achieve data storage. It is compatible with the existing integrated circuit semiconductor process (CMOS), and has advantages such as a long cycle life (greater than 10 12 )), fast read / write speed (20 ns / 10 ns), and little influence from the environment, etc., which can meet the requirements of modern electronic devices for high stability, high storage density, and high-speed data access. These advantages together have promoted the phase change memory to occupy an important position in the storage field and provided strong support for the development of future storage technologies.

[0003] Among the materials currently used in the preparation of phase change memories, Ge2Sb2Te5 (GST) is recognized by the industry as the most suitable storage material for PCM applications. Its crystallization process is divided into two steps: at about 175 °C, it changes from the amorphous state to the metastable face-centered cubic structure (fcc), and then at about 280 °C, it continues to change from fcc to the hexagonal close-packed structure (hex). However, due to the ternary alloy system of GST being prone to component segregation during repeated phase change cycles, the resistance drift is relatively serious (resistance drift coefficient v = 0.11), which leads to a shortened working life and reduced reliability of the device, becoming the core bottleneck restricting the performance breakthrough of phase change memories.

[0004] In the innovation of phase change material systems, single-element phase change storage materials have shown breakthrough potential. Compared with traditional Ge-Sb-Te (GST) alloys, single-element Sb materials have achieved better physical properties by simplifying the component composition: firstly, the single-atom system avoids the complexity of interfacial bonding in multi-element materials, significantly improving the orderliness of atomic arrangement, making the phase change process have stronger controllability and repeatability; secondly, the single-atom structure endows the material with stronger size adaptability, and it still maintains stable phase change ability even at a thickness of 5 nm, providing a physical basis for the three-dimensional stacking of storage units. These characteristics enable single-element phase change memories to achieve an order-of-magnitude improvement in storage density, data retention, and durability. However, the thermal stability of elemental Sb is extremely poor, and it is prone to spontaneous crystallization at room temperature, seriously inhibiting the development of single-element phase change memories. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a single-element phase change memory material doped with transition metal sulfide, which has a relatively high crystallization temperature and phase transition temperature, and higher crystallization activation energy and ten-year data retention temperature, smaller resistance drift, and can achieve long-term stable storage, as well as a preparation method thereof.

[0006] The technical solution adopted by the present invention to solve the above technical problem is: a single-element phase change memory material doped with transition metal sulfide, which is a MoS2-doped Sb thin film material.

[0007] Preferably, the chemical structural formula of the thin film material is Sb x (MoS2) 100-x , where 65 at.% ≤ x ≤ 85 at.%.

[0008] Preferably, the chemical structural formula of the thin film material is Sb 79 (MoS2) 21 .

[0009] Preferably, the chemical structural formula of the thin film material is Sb 85 (MoS2) 15 .

[0010] Preferably, the chemical structural formula of the thin film material is Sb 70 (MoS2) 30 .

[0011] Preferably, the chemical structural formula of the thin film material is Sb 65 (MoS2) 35 .

[0012] The present invention also provides a preparation method of the above MoS2-doped Sb thin film material, and the steps are as follows: obtained by co-sputtering of a Sb single-element target and a MoS2 chalcogenide target in a magnetron sputtering coating system.

[0013] Further, the specific steps are as follows: in a magnetron sputtering coating system, using a single-crystal silicon wafer or a quartz wafer as a substrate, installing the Sb single-element target in a magnetron DC sputtering target, installing the MoS2 target in a magnetron RF sputtering target, evacuating the sputtering chamber of the magnetron sputtering coating system until the indoor vacuum degree reaches 9×10 -6 Pa, then introducing high-purity argon with a volume flow rate of 50 ml / min into the sputtering chamber until the air pressure in the sputtering chamber reaches the starting glow pressure of 0.3 Pa required for sputtering, then fixing the sputtering power of the Sb single-element target at 30 - 50 W, regulating the sputtering power of the sulfide MoS2 target at 22 - 40 W, co-sputtering and coating at room temperature, and after the sputtering thickness reaches 80 nm, a deposited Sb-MoS2 thin film material is obtained, and its chemical structural formula is Sb x(MoS2) 100-x , where 65 at.% ≤ x ≤ 85 at.%.

[0014] Compared with the prior art, the advantages of the present invention are as follows: A single-element Sb-Mo-S thin film material doped with transition metal sulfide for phase change memory and its preparation method, the chemical structural formula of which is Sb x (MoS2) 100-x , where 65 at.% ≤ x ≤ 85 at.%, and MoS2, as a transition metal sulfide semiconductor material, is easy to bond with Sb element to form an amorphous structure, thereby inhibiting the crystallization of Sb, improving the amorphous thermal stability and structural order of the material, enhancing the amorphous thermal stability of the thin film and maintaining the phase change ability. The preferred phase change material Sb 79 (MoS2) 21 has a relatively high crystallization temperature ( T c ) of 232 °C, a relatively large crystallization activation energy ( E a ) of 4.16 V, a relatively strong ten-year data retention force ( T 10-year ) of 148.6 °C, and a relatively low resistance drift coefficient ν of 0.0004, successfully solving the problem of poor thermal stability of the Sb single-element phase change storage thin film. Compared with the common GST phase change material, it has a higher crystallization temperature, a higher crystallization activation energy, a ten-year data retention temperature, and an ultra-low resistance drift coefficient, and is expected to improve the stability of the phase change memory and reduce the device power consumption, and be applied to PCMs with long cycles and high cycle numbers. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is the curve of the resistance of the SSB0-SSB3 phase change thin film of the present invention varying with temperature; Figure 2 is the ten-year data retention diagram of the SSB0-SSB2 phase change thin film of the present invention; Figure 3 is the resistance drift analysis diagram of the as-deposited SSB0-SSB3 of the present invention; Figure 4 is the X-ray diffraction analysis diagram of the SSB0 thin film of the present invention in the annealing state at 150 °C - 350 °C; Figure 5 is the X-ray diffraction analysis diagram of the SSB1 thin film of the present invention in the annealing state at 150 °C - 350 °C; Figure 6 is the X-ray diffraction analysis diagram of the SSB2 thin film of the present invention in the annealing state at 150 °C - 350 °C; Figure 7X-ray diffraction analysis diagram of the SSB3 thin film of the present invention in the annealed state at 150°C - 350°C. Detailed implementation mode

[0016] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0017] I. Specific embodiment: A single-element phase change memory material doped with transition metal sulfide, which is a MoS2-doped Sb thin film material, and the chemical structural formula of the thin film material is Sb x (MoS2) 100-x , where 65 at.% ≤ x ≤ 85 at.%.

[0018] Example 1. Preparation of Sb 85 (MoS2) 15 phase change memory thin film.

[0019] In a magnetron sputtering coating system, a single-crystal silicon wafer or a quartz wafer is used as the substrate. The Sb elemental target is installed in the magnetron DC sputtering target, and the MoS2 target is installed in the magnetron RF sputtering target. The sputtering chamber of the magnetron sputtering coating system is evacuated until the indoor vacuum degree reaches 9×10 -6 Pa, and then high-purity argon gas with a volume flow rate of 50 mL / min is introduced into the sputtering chamber until the air pressure in the sputtering chamber reaches the starting glow pressure of 0.3 Pa required for sputtering. Then, the sputtering power of the Sb elemental target is fixed at 50 W, and the sputtering power of the sulfide MoS2 target is adjusted to 30 W. Co-sputtering coating is carried out at room temperature with two targets. After the sputtering thickness reaches 80 nm, a deposited Sb-MoS2 thin film material is obtained, and its chemical structural formula is Sb 85 (MoS2) 15 .

[0020] The prepared thin film material is subjected to in-situ resistance and resistance drift tests and XRD analysis. It can be seen that the performance indexes of the thin film prepared in this example are as follows: crystallization temperature T c is 185 °C, the crystallization activation energy is 3.20 eV, the ten-year data retention temperature is 107.4 °C, and the resistance drift coefficient ν is 0.0024. Compared with the traditional GST material, for Sb 85 (MoS2) 15 with the same thickness, the crystallization temperature is higher, and the resistance drift coefficient is reduced by two orders of magnitude.

[0021] Example 2. Preparation of Sb 79 (MoS2) 21 phase change memory thin film.

[0022] Same as Example 1 above, the differences are as follows: During the sputtering process, the sputtering power of the Sb elemental target is controlled at 30 W, and the sputtering power of the MoS2 target is 22 W. Co-sputtering coating is carried out with the two targets at room temperature. After the sputtering thickness reaches 80 nm, a deposited preferred Sb / MoS2 phase change thin film material is obtained, and its chemical structural formula is Sb 79 (MoS2) 21 .

[0023] The prepared thin film material is subjected to in-situ resistance and resistance drift tests as well as XRD analysis. It can be seen that the performance indicators of the thin film prepared in this example are as follows: The crystallization temperature T c is 232 °C, the crystallization activation energy is 4.16 eV, the ten-year data retention temperature is 148.6 °C, and the resistance drift coefficient ν is 0.0004. Compared with the Sb 85 (MoS2) 15 material with the same thickness, the crystallization temperature increases, the crystallization activation energy increases, the ten-year data retention temperature increases, and the resistance drift coefficient decreases significantly.

[0024] Example 3, Preparation of Sb 70 (MoS2) 30 phase change storage thin film.

[0025] Same as Example 1 above, the differences are as follows: During the sputtering process, the sputtering power of the Sb elemental target is controlled at 30 W, and the sputtering power of the MoS2 target is 30 W. Co-sputtering coating is carried out with the two targets at room temperature. After the sputtering thickness reaches 80 nm, a deposited Sb-MoS2 phase change thin film material is obtained, and its chemical structural formula is Sb 70 (MoS2) 30 .

[0026] The prepared thin film material is subjected to in-situ resistance and resistance drift tests as well as XRD analysis. It can be seen that the performance indicators of the thin film prepared in this example are as follows: The crystallization temperature T c is 252 °C, the crystallization activation energy is 6.01 eV, the ten-year data retention temperature is 194.2 °C, and the resistance drift coefficient ν is 0.0021. Compared with the Sb 79 (MoS2) 21 material with the same thickness, the crystallization temperature increases, the crystallization activation energy and the ten-year data retention temperature increase, but the resistance drift coefficient increases somewhat.

[0027] Example 4, Preparation of Sb 65 (MoS2) 35 phase change storage thin film.

[0028] Same as Example 1 above, the differences are as follows: During the sputtering process, the sputtering power of the Sb elemental target is controlled at 30 W, and the sputtering power of the MoS2 target is 40 W. At room temperature, co-sputtering coating is carried out with the two targets. After the sputtering thickness reaches 80 nm, a deposited Sb-MoS2 phase change thin film material is obtained, and its chemical structural formula is Sb 65 (MoS2) 35 .

[0029] The prepared thin film material is subjected to in-situ resistance and resistance drift tests as well as XRD analysis. It can be seen that the performance indicators of the thin film prepared in this example are as follows: the crystallization temperature T c is 267 °C, and the resistance drift coefficient ν is 0.0046. Compared with the Sb 79 (MoS2) 21 material of the same thickness, the crystallization temperature increases slightly, and the resistance drift coefficient rises.

[0030] Control experiment, preparation of Ge2Sb2Te5 phase change storage thin film.

[0031] It is basically the same as Example 1, the difference is that the alloy Ge2Sb2Te5 target is installed in the magnetron radio frequency sputtering target, the set sputtering power is 30 W, and single-target sputtering coating is carried out at room temperature. After the sputtering thickness reaches 80 nm. A pure Ge2Sb2Te5 phase change storage thin film is obtained. The prepared thin film is subjected to in-situ resistance performance test. It can be seen that the performance indicators of the thin film prepared in the control experiment are as follows: the crystallization temperature ( T c ) is 176 °C, the crystallization activation energy is 2.98 eV, the ten-year data retention temperature is 89 °C, and the resistance drift coefficient is 0.11.

[0032] The sputtering powers of the targets in the above different examples, the contents of Sb and MoS2, and the relevant thermal parameters are shown in Table 1.

[0033] Table 1 Composition and relevant thermal parameters of 80nm Sb-Mo-S phase change thin film materials prepared under different conditions

[0034] II. Analysis of experimental results: The results of different examples in the specific examples are analyzed as follows.

[0035] Figure 1 shows the relationship between the resistance and temperature of the SSB0-SSB3 thin films tested at a heating rate of 30 °C / min. We can see that the resistance of all thin films gradually decreases as the temperature increases. It can be found that Sb 85 (MoS2) 15The thin film undergoes a large resistance change at around 185 °C and a phase change crystallization occurs. As the introduced MoS2 content gradually increases, the crystallization temperature of the thin film gradually rises. Sample Sb 79 (MoS2) 21 、Sb 70 (MoS2) 30 thin films and Sb 65 (MoS2) 35 The crystallization temperatures of the thin films are ~232, ~252, and ~267 °C respectively, showing a gradually increasing trend, and they have better phase change characteristics and thermal stability compared to the GST material thin film and the pure Sb thin film.

[0036] Figure 2 The ten-year data retention force diagrams of the SSB0 - SSB2 phase change thin films are given. It can be analyzed that the crystallization activation energy of the Sb 85 (MoS2) 15 thin film is 3.20 eV, and the ten-year data retention temperature is 107.4 °C. The crystallization activation energy of the Sb 79 (MoS2) 21 thin film is 4.16 eV, and the ten-year data retention temperature is 148.6 °C. The crystallization activation energy of the Sb 70 (MoS2) 30 thin film is 6.01 eV, and the ten-year data retention temperature is 194.2 °C. The crystallization activation energy and the ten-year data retention temperature of the Sb x (MoS2) 100-x thin film gradually increase with the increase of the MoS2 content, and at the same time, the stability of the thin film gradually enhances.

[0037] Figure 3 The resistance drift analysis of the SSB0 - SSB3 thin films at room temperature is given. It can be found that the resistance drift coefficient of the Sb 85 (MoS2) 15 thin film is 0.0024, the resistance drift coefficient of the Sb 79 (MoS2) 21 thin film is 0.0004, the resistance drift coefficient of the Sb 70 (MoS2) 30 thin film is 0.0021, the resistance drift coefficient of the Sb 65 (MoS2) 35 thin film is 0.0046. The resistance drift first decreases and then increases with the increase of the MoS2 content. Among them, the preferred material Sb 79 (MoS2) 21 is improved by 3 orders of magnitude compared to the GST material.

[0038] Figure 4X-ray diffraction analysis of the SSB0 thin film in the annealed state at 150 °C - 350 °C is presented. It can be found that Sb 85 (MoS2) 15 The thin film starts to precipitate the Sb(012) crystal phase and the Sb(110) crystal phase in the annealed state at 150 °C, indicating that the material begins to undergo a phase change at 150 °C. The Sb crystal phase peak rises with the increase of temperature, indicating that the crystallinity of the material gradually increases and the structure tends to be stable.

[0039] Figure 5 X-ray diffraction analysis of the SSB1 thin film in the annealed state at 150 °C - 350 °C is presented. It can be found that Sb 79 (MoS2) 21 The thin film precipitates the Sb(012) crystal phase in the annealed state at 200 °C, and starts the Sb(110) crystal phase in the annealed state at 250 °C, indicating that the material begins to undergo a phase change at 200 °C. Compared with the Sb 85 (MoS2) 15 thin film, the phase change temperature increases and the crystallization peak value at the same temperature becomes lower. At this time, the crystallization behavior of Sb is inhibited to a certain extent. The Sb crystal phase peak rises with the increase of temperature, indicating that the crystallinity of the material gradually increases and the structure tends to be stable.

[0040] Figure 6 X-ray diffraction analysis of the SSB2 thin film in the annealed state at 150 °C - 350 °C is presented. It can be found that Sb 70 (MoS2) 30 The thin film precipitates the Sb(012) crystal phase in the annealed state at 250 °C, indicating that the material begins to undergo a phase change at 250 °C. Compared with the Sb 79 (MoS2) 21 thin film, the phase change temperature increases, the Sb crystal peak at the same temperature is lower and no Sb(110) crystal phase precipitates, indicating that MoS2 inhibits the crystallization behavior of Sb. The Sb crystal phase peak rises with the increase of temperature, indicating that the crystallinity of the material gradually increases and the structure tends to be stable.

[0041] Figure 7 X-ray diffraction analysis of the SSB2 thin film in the annealed state at 150 °C - 350 °C is presented. It can be found that Sb 65 (MoS2) 35 The thin film precipitates the Sb(012) crystal phase in the annealed state at 250 °C, indicating that the material begins to undergo a phase change at 250 °C. Compared with the Sb 70 (MoS2) 30 crystal peak of the thin film at the same temperature is even lower, further indicating that MoS2 inhibits the crystallization behavior of Sb. The Sb crystal phase peak rises with the increase of temperature, indicating that the crystallinity of the material gradually increases and the structure tends to be stable.

[0042] In summary, for a single-element Sb-MoS2 phase change memory material doped with transition metal sulfide prepared by the present invention, the crystallization temperature is increased to above 232 °C, and the resistance drift coefficient reaches 0.0004, solving the problems of poor thermal stability and serious resistance drift existing in traditional phase change materials. Compared with traditional GST phase change materials, preferably Sb 79 (MoS2) 21 thin films have a higher crystallization temperature, a higher phase transition temperature, a higher activation energy and a ten-year data retention temperature, a smaller resistance drift, and improved storage stability and reliability under long cycles and high cycle numbers.

[0043] The above description is not a limitation of the present invention, nor is the present invention limited to the above examples. Changes, modifications, additions or substitutions made by those of ordinary skill in the art within the scope of the essence of the present invention shall also fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to the claims.

Claims

1. A single-element phase change memory material doped with transition metal sulfide, characterized in that: The material is a MoS2-doped Sb thin film material.

2. The single-element phase change memory material doped with transition metal sulfide according to claim 1, wherein: The chemical structural formula of the thin film material is Sb x (MoS2) 100-x , where 65 at.% ≤ x ≤ 85 at.%.

3. The single-element phase change memory material doped with transition metal sulfide according to claim 1, characterized in that: The chemical structural formula of the thin film material described is Sb 79 (MoS2) 21 .

4. The single-element phase change memory material doped with transition metal sulfide according to claim 1, wherein: The chemical structural formula of the described thin film material is Sb 85 (MoS2) 15 .

5. A single-element phase change memory material doped with transition metal sulfide according to claim 1, characterized in that: The chemical structural formula of the described thin film material is Sb 70 (MoS2) 30 .

6. The single-element phase change memory material doped with transition metal sulfide according to claim 1, wherein: The chemical structural formula of the described thin film material is Sb 65 (MoS2) 35 .

7. A method for preparing a single-element phase change memory material doped with transition metal sulfide according to any one of claims 1-6, characterized in that The steps are as follows: The MoS2-doped Sb thin film material is obtained by dual-target sputtering of an Sb elemental target and a chalcogenide MoS2 target in a magnetron sputtering coating system.

8. The preparation method of a single-element phase change memory material doped with transition metal sulfide according to claim 7, characterized in that The specific steps are as follows: In a magnetron sputtering coating system, a single-crystalline silicon wafer or a quartz wafer is used as the substrate. The Sb elemental target is installed in the magnetron DC sputtering target, and the MoS2 target is installed in the magnetron RF sputtering target. The sputtering chamber of the magnetron sputtering coating system is evacuated until the indoor vacuum degree reaches 9×10 -6 Pa. Then, high-purity argon gas with a volume flow rate of 50 ml / min is introduced into the sputtering chamber until the gas pressure in the sputtering chamber reaches the breakdown pressure of 0.3 Pa required for sputtering. Then, the sputtering power of the Sb elemental target is fixed at 30-50 W, and the sputtering power of the sulfide MoS2 target is adjusted to 22-40 W. Co-sputtering coating is carried out with two targets at room temperature. After the sputtering thickness reaches 80 nm, a deposited Sb-MoS2 thin film material is obtained, and its chemical structural formula is Sb x (MoS2) 100-x , where 65 at.% ≤ x ≤ 85 at.%.

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