High-storage-density medium buffer layer sandwich structure phase change storage thin film material and preparation method and application thereof

Abstract

The invention relates to a high-storage-density medium buffer layer sandwich structure phase change storage thin film material and a preparation method and application thereof.The phase change storage thin film material is of a sandwich structure, and the phase change storage thin film material is prepared by alternately arranging two different phase change layer materials and medium layer materials through a magnetron sputtering method; and a similar superlattice structure is formed. The structural general formula of the multilayer film structure is [M (a nm)-A (b nm)-N (c nm)] n, M and N are two different phase change layer materials, and A is a dielectric layer material.Compared with the prior art, the multilayer film structure has the advantages that the dielectric layer with the nanoscale thickness is introduced into the multilayer film structure, the interface stress between adjacent film layers can be effectively relieved, the lattice mismatch phenomenon is reduced, and therefore the stability of the multilayer film structure is remarkably improved. In addition, the introduction of the dielectric layer can also regulate and control the electrical characteristics of the thin film in the phase change process, enhance the distinction degree of multi-stage resistance states, further improve the storage density, and solve the problem that the storage capacity of a traditional phase change memory is limited.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic technology, and in particular to a high storage density medium buffer layer sandwich structure phase change storage film material and a preparation method and application thereof. Background Art

[0002] As the performance requirements for storage devices in fields such as big data and artificial intelligence continue to increase, the explosive growth of information has posed new challenges to the density and stability of memory. Phase-Change Memory (PCM) has become a strong candidate for the next generation of information storage technology due to its high speed, non-volatility and potential multi-level storage capabilities.

[0003] Phase change memory relies on the reversible transformation of phase change materials between amorphous state (high resistance state) and crystalline state (low resistance state) to achieve data storage. Through this resistance difference, data can be written, erased and read. Traditional phase change materials (such as Ge2Sb2Te5, GST for short) are widely used due to their advantages of fast switching speed and high thermal stability. At the same time, the new superlattice-like structure can finely control the phase change behavior of the material by alternately stacking different material layers (such as GeTe, GST, etc.) with nanometer-level thickness, thereby improving the phase change speed and energy efficiency and reducing the power consumption required for write operations.

[0004] However, nowadays, in multilayer film structures, large interface stress and lattice mismatch are easily generated between adjacent film layers. These problems lead to poor stability of the multilayer structure, especially under long-term operation or high-temperature environment, which can easily cause structural instability and thus affect the reliability of the device. Secondly, traditional phase change memory materials usually only have two-level storage capabilities, and the distinction between multi-level resistance states is limited, making it difficult to effectively achieve high-density storage. In addition, due to the lack of a reasonable buffering mechanism in the thin film structure, the reset current is large and the energy consumption is high, which further limits its application in low-power storage devices.

[0005] Chinese patent CN106185800A discloses a GeTe / Ge-type superlattice nano phase change thin film material and its preparation method and application, including germanium telluride thin film material and single-element germanium thin film material, which are alternately superimposed by magnetron sputtering to form a superlattice-like structure, and have a faster phase change speed, better thermal stability and lower operating power consumption. However, this material may face the problem of interface stress and lattice mismatch between adjacent film layers in a multilayer film structure. Stress and defects may not only slow down the phase change speed, but also cause energy loss, thereby reducing the efficiency and reliability of the memory. Therefore, it is urgent to obtain a phase change memory that meets high storage density and high stability through new materials and structural design. Summary of the invention

[0006] The purpose of the present invention is to provide a high storage density medium buffer layer sandwich structure phase change storage film material and its preparation method and application, so as to improve the stability and storage density of phase change memory.

[0007] The purpose of the present invention can be achieved by the following technical solutions:

[0008] On the one hand, the present invention provides a high storage density dielectric buffer layer sandwich structure phase change storage film material, the phase change storage film material is a sandwich structure, including two phase change material layers and a dielectric layer arranged between the two phase change material layers, the phase change material layers and the dielectric layers are alternately stacked to form a superlattice-like structure.

[0009] In the present invention, the superlattice-like structure can effectively relieve interface stress, reduce lattice mismatch, stabilize the multilayer film structure, and provide multi-value storage resistance states and excellent thermal stability, thereby improving the storage density and other storage performance of the phase change storage material.

[0010] Preferably, the high storage density medium buffer layer sandwich structure phase change storage film material has three or more storage states.

[0011] Preferably, the general structural formula of the phase change memory thin film material is [M (a nm) - A (b nm) - N (c nm)] n , wherein M and N are two different phase change layer materials, A is a dielectric layer material, a and c represent the thickness of the phase change material layer, b represents the thickness of the dielectric material layer, and n represents the number of cycles of the phase change storage thin film material.

[0012] Further preferably, the two different phase change layer materials include any two different chalcogenide compound phase change storage thin film materials, and the dielectric layer material includes Ge, Si, SiO2, TiTe, SiN x , any one of Al2O3.

[0013] Further preferably, the phase change layer material includes GeTe, Ge2Sb2Te5, Ge8Sb 92 .

[0014] Further preferably, 5nm≤a≤25nm, 1nm≤b≤6nm, 5nm≤c≤25nm, n is a positive integer, 1≤n≤10, and the thickness of the phase change memory thin film material is 40-100nm.

[0015] Further preferably, the thickness of the phase change memory thin film material is 50 nm.

[0016] In the present invention, by adjusting the thickness and period number of the phase change material layer and the dielectric material layer, the stability of the multilayer film structure of the superlattice-like film is stabilized, and the storage density, thermal stability, power consumption and fatigue characteristics of the phase change storage material are improved. The thickness of the dielectric material layer is adjustable to adjust the interface stress between the phase change storage materials, optimize the phase change dynamics, and improve the storage density.

[0017] In a second aspect, the present invention provides a method for preparing the above-mentioned high storage density dielectric buffer layer sandwich structure phase change storage thin film material, wherein the phase change storage thin film material is prepared by alternatingly arranging two different phase change layer materials and dielectric layer materials by a magnetron sputtering method.

[0018] Preferably, the preparation comprises the following steps:

[0019] S1: depositing a first phase change material layer on a substrate by magnetron sputtering;

[0020] S2: depositing a dielectric layer on the first layer of phase change material by magnetron sputtering;

[0021] S3: depositing a second phase change material layer on the dielectric layer by magnetron sputtering to form an alternately stacked phase change storage thin film material;

[0022] S4: Repeat steps S1 to S3 to prepare phase change memory thin film materials with different numbers of cycles.

[0023] Preferably, the substrate includes one or more of Si / SiO2 (100), single crystal silicon, glass, polyimide, and sapphire substrates.

[0024] Further preferably, the substrate is Si / SiO2(100).

[0025] Further preferably, the Si / SiO2(100) substrate needs to be cleaned by the following steps before magnetron sputtering: the Si / SiO2(100) substrate is placed in an ethanol solution, an acetone solution, and deionized water for ultrasonic cleaning for 10 to 15 minutes in sequence, and then blown dry with Ar gas.

[0026] Preferably, the targets of the phase change material layer and the dielectric layer are both sputtered using a radio frequency power source.

[0027] Further preferably, the purity of the target material used in the magnetron sputtering is greater than 99.99%, and the background vacuum degree of the magnetron sputtering is less than 2×10 -4 Pa, the magnetron sputtering is carried out in an Ar atmosphere, the gas flow rate of the Ar atmosphere is in the range of 20-50 SCCM, the sputtering gas pressure is 0.1-1.0 Pa, and the sputtering power is 20-50 W.

[0028] Further preferably, the thickness of the phase change material layer and the dielectric layer is controlled by sputtering time.

[0029] In a third aspect, the present invention also provides an application of the above-mentioned high storage density dielectric buffer layer sandwich structure phase change storage film material, and the phase change storage film material is used to prepare high-density storage devices and neuromorphic computing devices.

[0030] Preferably, the phase change memory thin film material is used to prepare a phase change memory.

[0031] Further preferably, the phase change memory comprises a bottom electrode layer, the above-mentioned phase change memory thin film material, and a top electrode layer, wherein the bottom electrode layer is located below the phase change memory thin film material, and the top electrode layer is located above the phase change memory thin film material.

[0032] Further preferably, the electrode layer material includes aluminum or tungsten.

[0033] Further preferably, in the phase change memory, the phase change memory thin film material introduces a dielectric layer in the middle of the phase change material layer, which helps to form a clear interface, making the resistance difference in different phase change states more significant, thereby improving the distinction of resistance states in multi-level storage and helping to improve storage density.

[0034] Further preferably, the phase change memory can realize multiple reversible changes between high resistance state and low resistance state (more than 2 storage states) under the action of electric pulses, thereby realizing information storage.

[0035] The present invention adds a dielectric layer between two layers of phase change material as a buffer, which can effectively relieve the interface stress between adjacent film layers and reduce the lattice mismatch phenomenon, thereby significantly improving the stability of the multilayer film structure. In addition, the introduction of the dielectric layer can also regulate the electrical properties of the thin film phase change process, enhance the distinction between multi-level resistance states, further improve the storage density, and solve the problem of limited storage capacity of traditional phase change memory.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention provides a high storage density dielectric buffer layer "sandwich" structure phase change memory thin film material, which is composed of two phase change material layers and dielectric layers stacked alternately to form a superlattice structure. The phase change memory prepared from the phase change memory thin film material has excellent stability and storage density.

[0038] (2) The introduction of the dielectric layer in the phase change memory thin film material of the present invention can effectively improve the stability of the multilayer film structure, reduce the lattice mismatch between the phase change memory material layers, thereby reducing the interface stress, which helps to improve the overall stability of the thin film structure and reduce material degradation or performance degradation caused by stress.

[0039] (3) The introduction of the dielectric layer of the present invention can provide a more stable interface structure during the phase change process, reduce material fatigue and performance degradation caused by repeated phase changes, reduce operating power consumption, and thus increase the long-term service life of the storage device.

[0040] (4) The introduction of the dielectric layer of the present invention can regulate the electrical properties of the thin film during the phase change process, enhance the distinction between the multi-level resistance states, further improve the storage density, and solve the problem of limited storage capacity of traditional phase change memory.

[0041] (5) The introduction of the dielectric layer of the present invention can optimize the phase change characteristics of the multilayer film, improve the storage density of the memory device, reduce the device operating power consumption, and make the device have a smaller resistance drift characteristic, thereby being suitable for the fields of high-density storage and neuromorphic computing. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic structural diagram of a dielectric buffer layer "sandwich" structure phase change memory film according to Example 1 of the present invention;

[0043] Figure 2 Schematic diagram of the preparation process of the dielectric buffer layer "sandwich" structure phase change memory film of Example 1 of the present invention ((a) to (d));

[0044] Figure 3 The resistance variation curves (RT curves) of the phase change memory films of Example 1 and Comparative Example 1 are as follows;

[0045] Figure 4 The resistance variation curve (RT curve) of the phase change memory film of Examples 2 and 3 is a curve showing a change in resistance with temperature.

[0046] Figure 5 The resistance variation curves (RT curves) of the phase change memory films of Example 4 and Comparative Example 2 are as a function of temperature;

[0047] Figure 6 This is a curve (RV curve) showing the change of device unit resistance with voltage pulses under different electrical pulses for the phase change memory device based on the dielectric buffer layer "sandwich" structure phase change memory thin film material in Example 1 in Example 5;

[0048] Figure 7 It is a cross-sectional structural diagram of the T-type phase change memory of Example 5. DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0050] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0051] Example 1

[0052] A high storage density medium buffer layer "sandwich" structure phase change storage film material, the structure of which is as follows Figure 2 As shown, it is obtained by alternately depositing phase change material layers GeTe, Ge2Sb2Te5 (GST) and dielectric layers Ge, and the preparation method is as follows:

[0053] Si / SiO2(100) was cleaned in ethanol, acetone and deionized water under ultrasonic wave for 15 min in turn; after cleaning, it was dried with Ar.

[0054] Preparation of [GeTe(a nm)-Ge(b nm)-Ge2Sb2Te5(c nm)] by magnetron sputtering n Thin film, in this embodiment, the purity of GeTe, Ge, Ge2Sb2Te5 target materials is better than 99.99%.

[0055] S1: Install GeTe, Ge, Ge2Sb2Te5 targets and substrates in the magnetron sputtering chamber and seal the vacuum chamber.

[0056] S2: Use the mechanical pump to pump the chamber vacuum to below 5Pa, then turn on the molecular pump to pump the chamber to a background vacuum of 2×10 -4 Below Pa.

[0057] S3: Use high-purity Ar gas as the sputtering gas, set the gas flow rate to 30 SCCM, the sputtering pressure to 0.2 Pa, the sputtering power to 20 W, and use RF power for sputtering.

[0058] S4: Switch the target position to GeTe target and turn on the RF power supply. Figure 2 As shown in b, a 24 nm thick GeTe layer (A02) is first deposited on the substrate by magnetron sputtering.

[0059] S5: Switch the target position to Ge target and turn on the RF power supply. Figure 2 As shown in c, a Ge dielectric layer (A03) with a thickness of 2 nm is deposited on the GeTe layer.

[0060] S6: Switch the target position to Ge2Sb2Te5 target and turn on the RF power supply. Figure 2 As shown in d, a Ge2Sb2Te5 layer (A04) with a thickness of 24 nm is deposited on the Ge layer.

[0061] S7: Obtain a phase change memory thin film material [GeTe(24nm)-Ge(2nm)-Ge2Sb2Te5(24nm)]1 with a period of 1.

[0062] like Figure 3 As shown, the resistance-temperature variation curve of Example 1 in which the dielectric layer Ge is introduced has an obvious intermediate resistance state, which is helpful to improve the storage density.

[0063] Example 2

[0064] A multi-period high storage density dielectric buffer layer "sandwich" structure phase change storage thin film material is obtained by alternately depositing phase change material layers GeTe, Ge2Sb2Te5 and dielectric layers Ge, and the experimental conditions are the same as those in Example 1.

[0065] The preparation method is as follows:

[0066] Steps S1 to S3 are the same as those in Example 1;

[0067] S4: Switch the target position to GeTe target and turn on the RF power supply. Figure 2 As shown in b, a 12 nm thick GeTe layer (A02) is first deposited on the substrate by magnetron sputtering.

[0068] S5: Switch the target position to Ge target and turn on the RF power supply. Figure 2 As shown in c, a Ge dielectric layer (A03) with a thickness of 1 nm is deposited on the GeTe layer.

[0069] S6: Switch the target position to Ge2Sb2Te5 target and turn on the RF power supply. Figure 2 As shown in d, a Ge2Sb2Te5 layer (A04) with a thickness of 12 nm is deposited on the Ge layer.

[0070] S7: Repeat steps S4 to S6 to obtain a phase change memory thin film material [GeTe(12nm)-Ge(1nm)-Ge2Sb2Te5(12nm)]2 with a period of 2.

[0071] Example 3

[0072] A multi-period high storage density dielectric buffer layer "sandwich" structure phase change storage thin film material is obtained by alternately depositing phase change material layers GeTe, Ge2Sb2Te5 and dielectric layers Ge, and the experimental conditions are the same as those in Example 1.

[0073] The preparation method is as follows:

[0074] Steps S1 to S3 are the same as those in Example 1;

[0075] S4: Switch the target position to GeTe target and turn on the RF power supply. Figure 2 As shown in b, a 6 nm thick GeTe layer (A02) is first deposited on the substrate by magnetron sputtering.

[0076] S5: Switch the target position to Ge target and turn on the RF power supply. Figure 2 As shown in c, a Ge dielectric layer (A03) with a thickness of 1 nm is deposited on the GeTe layer.

[0077] S6: Switch the target position to Ge2Sb2Te5 target and turn on the RF power supply. Figure 2 As shown in d, a Ge2Sb2Te5 layer (A04) with a thickness of 6 nm is deposited on the Ge layer.

[0078] S7: Repeat steps S4 to S6 to obtain a phase change memory thin film material [GeTe(6nm)-Ge(1nm)-Ge2Sb2Te5(6nm)]4 with a period number of 4.

[0079] like Figure 4 As shown, the resistance variation curve of the multi-period film with dielectric layer Ge introduced in Examples 2 and 3 also has a relatively obvious intermediate resistance state, which is helpful to improve storage density.

[0080] Comparative Example 1

[0081] A two-layer stacked film is obtained by stacking two phase change material layers GeTe and Ge2Sb2Te5. Using the same experimental conditions and preparation method as in Example 1, a 25nm thick GeTe layer is first deposited on a substrate by magnetron sputtering, and then a 25nm thick Ge2Sb2Te5 layer is deposited on the GeTe layer to obtain a phase change storage film material [GeTe(25nm)-Ge2Sb2Te5(25nm)]1 with a period of 1.

[0082] The resistance of the two-layer stacked film prepared in Comparative Example 1 was tested as a function of temperature. The test results are as follows: Figure 3 As shown, compared with the "sandwich" structure phase change memory film of Example 1 and the multi-period "sandwich" structure phase change memory films of Examples 2 and 3, this comparative example 1 does not have an intermediate resistance state and can store less information.

[0083] Example 4

[0084] A high storage density medium buffer layer "sandwich" structure phase change storage film material, consisting of a phase change material layer Ge8Sb 92Using the same experimental conditions and preparation method as in Example 1, a 24 nm thick Ge8Sb2Te5 layer is first deposited on the substrate by magnetron sputtering. 92 layer, and then on Ge8Sb 92 A 2nm thick Ge layer is deposited on the Ge layer, and then a 24nm thick Ge2Sb2Te5 layer is deposited on the Ge layer to obtain [Ge8Sb 92 (24nm)-Ge(2nm)-Ge2Sb2Te5(24nm)]1.

[0085] Comparative Example 2

[0086] A two-layer stacked film, consisting of two phase change material layers Ge8Sb 92 Using the same experimental conditions and preparation method as in Example 1, a 25 nm thick Ge8Sb layer was first deposited on the substrate by magnetron sputtering. 92 layer, and then on Ge8Sb 92 A 25 nm thick GST layer was deposited on the layer to obtain [Ge8Sb 92 (25nm)-GST(25nm)]1.

[0087] The resistance variation of the "sandwich" structure phase change memory film and the two-layer stacked film prepared in Example 4 and Comparative Example 2 with temperature was tested. The test results are as follows: Figure 5 As shown, the sandwich structure phase change memory film in Example 4 has a larger intermediate state resistance platform, is more stable in information storage, and is conducive to further improving the performance of the multi-level phase change memory.

[0088] Example 5

[0089] A "sandwich" structure phase change memory thin film based memory device. On the phase change memory thin film material prepared in Example 1, a layer of top electrode material (such as aluminum or tungsten) is deposited by magnetron sputtering, and a layer of bottom electrode material is deposited at the bottom. Finally, a phase change memory with a three-layer film structure is prepared. The phase change memory is a T-type phase change memory, and its cross-sectional structure is shown in FIG. Figure 7 shown.

[0090] like Figure 6As shown, a resistance-voltage relationship diagram (RV curve) of a phase change memory with a "sandwich" structure is shown. In information storage, the high resistance state is defined as the RESET state, and the low resistance state is defined as the SET state. Under the action of a pulse, the phase change memory of this embodiment can quickly complete the SET process, and the resistance is significantly reduced. As can be seen from the figure, the phase change memory of this embodiment shows a trend of an intermediate resistance state during both the SET and RESET processes. When storing information, these three resistance states can be named "0", "1", and "2" states, respectively. Compared with the traditional "0" and "1" state storage methods, this multi-level storage logic significantly improves the storage density, can better meet the current information storage needs, and provides a more efficient solution.

[0091] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A high storage density medium buffer layer sandwich structure phase change storage film material, characterized in that: The phase change memory film material is a sandwich structure, including two different phase change material layers and a dielectric layer arranged between the two different phase change material layers. The phase change material layers and the dielectric layers are alternately stacked to form a superlattice-like structure.

2. The high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 1, characterized in that: The high storage density medium buffer layer sandwich structure phase change storage film material has three or more storage states.

3. The high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 1, characterized in that: The general structural formula of the phase change memory thin film material is [M (a nm) - A (b nm) - N (cnm)] n , where M and N are two different phase change layer materials, A is the dielectric layer material, a and c represent the thickness of the phase change material layer, b represents the thickness of the dielectric material layer, and n represents the number of cycles of the phase change storage film material.

4. The high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 3, characterized in that: The two different phase change layer materials include two different chalcogenide compound phase change storage thin film materials, and the dielectric layer material includes Ge, Si, SiO2, TiTe, SiN x , any one of Al2O3.

5. The high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 3, characterized in that: 5nm≤a≤25nm, 1nm≤b≤6nm, 5nm≤c≤25nm, n is a positive integer, 1≤n≤10, and the thickness of the phase change memory thin film material is 40-100nm.

6. A method for preparing a high storage density dielectric buffer layer sandwich structure phase change storage thin film material as claimed in any one of claims 1 to 5, characterized in that: The phase-change storage thin film material is prepared by alternately arranging two different phase-change layer materials and a dielectric layer material through a magnetron sputtering method.

7. The method for preparing a high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 6, characterized in that: The method comprises the following preparation steps: S1: depositing a first phase change material layer on a substrate by magnetron sputtering; S2: depositing a dielectric layer on the first layer of phase change material by magnetron sputtering; S3: depositing a second phase change material layer on the dielectric layer by magnetron sputtering to form an alternately stacked phase change storage thin film material; S4: Repeat steps S1 to S3 to prepare phase change memory thin film materials with different numbers of cycles.

8. The method for preparing a high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 7, characterized in that: The substrate includes one or more of Si / SiO2 (100), single crystal silicon, glass, polyimide, and sapphire substrates.

9. The method for preparing a high storage density medium buffer layer sandwich structure phase change storage thin film material according to claim 7, characterized in that: The purity of the target material used in the magnetron sputtering is greater than 99.99%, and the background vacuum degree of the magnetron sputtering is less than 2×10 -4 Pa, the magnetron sputtering is carried out in an Ar atmosphere, the gas flow rate of the Ar atmosphere is in the range of 20-50 SCCM, the sputtering gas pressure is 0.1-1.0 Pa, and the sputtering power is 20-50 W.

10. An application of a high storage density medium buffer layer sandwich structure phase change storage thin film material as claimed in any one of claims 1 to 5, characterized in that: The phase change memory thin film material is used to prepare high-density memory devices and neuromorphic computing devices.

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