Preparation method of self-rectification tunnel junction
By preparing hafnium oxide-based ferroelectric tunnel junction on a silicon substrate and introducing cerium oxide insulator interlayer, the problems of complex preparation and insufficient performance of traditional ferroelectric materials are solved, and high switching ratio and excellent ferroelectric performance are achieved.
Patent Information
- Application Number
- CN202411574191.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-06
- Publication Date
- 2025-03-14
AI Technical Summary
Traditional ferroelectric perovskite materials have defects such as incompatible with complementary metal oxide semiconductor technology, high crystallization temperature and complex preparation process. Hafnium oxide faces low switching ratios and difficult to meet actual production needs in the field of electronic device applications.
A hafnium oxide-based ferroelectric tunnel junction was prepared by silicon substrate, and a high switching ratio ferroelectric tunnel junction was prepared by introducing cerium oxide as an insulator interlayer, and atomic layer deposition and magnetron sputtering were used to prepare.
High switching ratio, superior ferroelectricity and rectification ratio are achieved, the preparation process is simplified, and the performance and integration of tunnel junctions are improved.
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Figure CN119630270A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of ferroelectric tunnel junctions, and in particular to a method for preparing a silicon-based metal-ferroelectric-insulator-metal (MFIM) self-rectifying tunnel junction. Background Art
[0002] At present, the development trend of electronic devices is moving towards low power consumption and high performance. In this context, traditional ferroelectric perovskite materials have encountered major challenges. These materials have defects such as incompatibility with complementary metal oxide semiconductor (CMOS) technology, high crystallization temperature and complex preparation process. At the same time, hafnium oxide (HfO 2 Hafnium oxide has become an ideal candidate material for logic and memory devices due to its high dielectric constant, excellent thermal stability and good silicon process compatibility, and has attracted widespread attention from the academic community. However, hafnium oxide still faces many challenges in the application of electronic devices, such as low switching ratio and difficulty in meeting actual production needs. These factors have limited its popularity in practical applications to a certain extent.
[0003] As a potential competitor for future low-power devices, the basic concept of hafnium oxide tunnel junction was first proposed by Esaki et al. in 1971. This structure is known for its simplicity and consists of two electrodes sandwiching a layer of ferroelectric material. The most notable feature of the ferroelectric tunnel junction (FTJ) is its tunneling resistance effect, and the tunneling probability of electrons is largely affected by the height of the barrier. The two different polarization states of ferroelectric materials can make the FTJ exhibit two different resistance states, namely high resistance and low resistance. Its main characteristics include: non-volatile storage; low power consumption; high storage density. In recent years, researchers have been committed to improving the performance of tunnel junctions by regulating film structure and interface states, especially in improving the switching ratio. Significant progress has been made, which makes FTJ expected to be applied to the next generation of high-performance random access memory, logic devices, and neuromorphic computing, providing new possibilities for further miniaturization and high performance of electronic devices.
[0004] Therefore, we choose silicon substrate to prepare hafnium oxide-based ferroelectric tunnel junction, aiming to prepare a ferroelectric tunnel junction with high switching ratio by introducing an insulator intercalation layer, namely, cerium oxide, which has excellent ferroelectricity, high switching ratio and rectification ratio. Summary of the invention
[0005] The invention is aimed at the preparation technology of growing silicon-based hafnium oxide-based ferroelectric tunnel junction, and provides a preparation method of silicon-based hafnium oxide-based ferroelectric tunnel junction with simple process, compact film and good performance.
[0006] The present invention provides a method for preparing a silicon-based hafnium oxide-based ferroelectric tunnel junction, comprising the following steps:
[0007] (1) Prepare W bottom electrode on silicon wafer by electron beam evaporation;
[0008] (2) depositing on the W bottom electrode by atomic layer deposition to obtain a zirconium-doped hafnium oxide ferroelectric thin film;
[0009] (3) using the hafnium zirconium oxide ferroelectric thin film obtained in step (2) to prepare cerium oxide as an insulator intercalation layer by magnetron sputtering;
[0010] (4) preparing a W top electrode by electron beam evaporation of the thin film obtained in step (3);
[0011] (5) placing the thin film obtained in step (4) in an annealing furnace filled with an inert protective atmosphere for rapid annealing heat treatment, and taking out the sample after the annealing furnace is cooled to room temperature to obtain the target ferroelectric hafnium oxide-based ferroelectric tunnel junction.
[0012] Furthermore, the hafnium source is tetrakis(dimethylamino)hafnium (TDMAHf), the zirconium source is tetrakis(dimethylamino)zirconium (TDMAZr), and water (H2O) is used as an oxygen source.
[0013] Furthermore, in step (1), the thickness of W is 20 nm.
[0014] Furthermore, in step (1), the silicon wafer is a p-type silicon wafer.
[0015] Furthermore, in step (2), the atomic layer deposition to prepare the hafnium zirconium oxide ferroelectric thin film adopts cyclic deposition, that is, one cycle is to deposit tetrakis(dimethylamino)hafnium, water once, and then deposit tetrakis(dimethylamino)zirconium, water once, and the total number of deposition cycles is 50 times (the thickness is about 10nm).
[0016] Furthermore, in step (2), the purge time of the metal source and the water source are 40 s and 60 s respectively. Sufficient purge time ensures the removal of reaction by-products during the deposition process.
[0017] Furthermore, in step (3), the electrode is a W electrode with a thickness of 20 nm.
[0018] Furthermore, in step (4), the insulator intercalation layer is cerium oxide, and the atmosphere during sputtering is Ar:O 2 =5:1, the sputtering power is 30W, the sputtering gas pressure is 0.5Pa, and the thickness is about 1nm.
[0019] Furthermore, in step (5), the inert protective atmosphere is nitrogen, and the specific annealing process is: heating from room temperature to 550°C at a heating rate of 3°C / s, keeping warm for 200s, and then cooling to room temperature before taking out. During this process, the clamping stress of the top and bottom electrodes on the hafnium zirconium oxide film promotes the emergence of the ferroelectric phase.
[0020] The structure of the prepared hafnium oxide-based ferroelectric tunnel junction is MFIM, and the electrical performance thereof is tested.
[0021] Compared with the prior art, the present invention has the following beneficial effects:
[0022] (1) The hafnium zirconium oxide ferroelectric thin film prepared by atomic layer deposition (270° C.) in the present invention is conducive to future high-level integration.
[0023] (2) The hafnium zirconium oxide ferroelectric film prepared by the present invention is dense and has a small leakage current.
[0024] (3) The hafnium zirconium oxide ferroelectric film prepared by the present invention has good ferroelectricity and rectification ratio.
[0025] (4) The preparation process of the present invention is simple, which simplifies the preparation technology.
[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 This is the PV curve of the sample in Example 1 where the ratio of hafnium to zirconium is 1:1 and the film thickness is 10 nm.
[0028] Figure 2 This is the IV curve of the sample in Example 1, where the ratio of hafnium to zirconium is 1:1 and the film thickness is 10 nm.
[0029] Figure 3 This is the IV curve of the sample in Example 2 with a hafnium-zirconium ratio of 1:1 and a film thickness of 10 nm. DETAILED DESCRIPTION
[0030] In order to make the process and purpose of the present invention clearer, we will provide a more detailed step-by-step description.
[0031] Example 1
[0032] In this embodiment, there is an insulator intercalation layer, which includes the following steps:
[0033] (1) First, a heavily doped p-type Si substrate was used as the substrate. The silicon wafer was cut into appropriate sizes (1 cm × 1 cm) and cleaned in acetone, alcohol, and deionized water in an ultrasonic cleaner for ten minutes. Finally, the wafer was placed in a culture dish and dried in an oven before sample preparation.
[0034] (2) Electron beam evaporation was used to prepare the 20 nm W bottom electrode with a vacuum degree of 10 -4 Below Pa.
[0035] (3) A hafnium zirconium oxide thin film is deposited on the W bottom electrode by atomic layer deposition. The sample obtained in step (1) is placed in a chamber, and a deposition program (hafnium source: 0.3 s, water source: 0.05 s, zirconium source: 0.3 s, water source: 0.05 s) is set. The deposition pressure is 0.005 Torr, and deposition is started to obtain a zirconium-doped hafnium oxide ferroelectric thin film.
[0036] (4) The thin film obtained in step (3) was used to prepare a CeO2 insulator intercalation layer by magnetron sputtering, with a preparation power of 30 W, a sputtering pressure of 0.5 Pa, and a sputtering time of 3 min.
[0037] (5) The thin film obtained in step (4) is subjected to electron beam evaporation to prepare metal W as a top electrode, wherein a mask plate is used for patterning. The patterned electrode is a circular electrode with a radius of 100 μm, thereby obtaining an MFIM structure.
[0038] (6) The tunnel junction structure obtained in step (5) is placed in an annealing furnace for rapid annealing heat treatment. The protective atmosphere is nitrogen. The specific annealing process is: heating from room temperature to 550°C at a heating rate of 3°C / s, keeping the temperature for 200s, cooling to room temperature and then taking it out. The ferroelectric performance is tested. The residual polarization value of the sample is measured to be 23.15μC / cm 2 , the switching ratio is 10.60, and the rectification ratio is 1.76. The hysteresis loop and IV curve of the sample are as follows: Figure 1 and Figure 2 shown.
[0039] Example 2
[0040] In this embodiment, there is no insulator intercalation layer, and the following steps are included:
[0041] (1) First, a heavily doped p-type Si substrate was used as the substrate. The silicon wafer was cut into appropriate sizes (1 cm × 1 cm) and cleaned in acetone, alcohol, and deionized water in an ultrasonic cleaner for ten minutes. Finally, the wafer was placed in a culture dish and dried in an oven before sample preparation.
[0042] (2) Electron beam evaporation was used to prepare the 20 nm W bottom electrode with a vacuum degree of 10 -4 Below Pa.
[0043] (3) A hafnium zirconium oxide thin film is deposited on the W bottom electrode by atomic layer deposition. The sample obtained in step (1) is placed in a chamber, and a deposition program (hafnium source: 0.3 s, water source: 0.05 s, zirconium source: 0.3 s, water source: 0.05 s) is set. The deposition pressure is 0.005 Torr, and deposition is started to obtain a zirconium-doped hafnium oxide ferroelectric thin film.
[0044] (4) The thin film obtained in step (3) is used for electron beam evaporation to prepare metal W as the top electrode, wherein a mask plate is used for patterning. The patterned electrode is a circular electrode with a radius of 100 um, thereby obtaining an MFM structure.
[0045] (5) The tunnel junction structure obtained in step (4) was placed in an annealing furnace for rapid annealing heat treatment. The protective atmosphere was nitrogen. The specific annealing process was: heating from room temperature to 550°C at a heating rate of 3°C / s, keeping the temperature for 200s, cooling to room temperature and then taking it out. The ferroelectric performance was tested. The residual polarization value of the sample was measured to be 26.43 μC / cm 2 The hysteresis loop and IV curve of the sample are as follows: Figure 1 and Figure 3 shown.
Claims
1. A method for preparing a hafnium oxide-based self-rectifying tunnel junction, characterized in that The invention has excellent ferroelectricity, high switching ratio and rectification ratio, and includes the following steps: (1) Prepare tungsten bottom electrode on flexible silicon wafer by electron beam evaporation; (2) depositing on the tungsten bottom electrode by atomic layer deposition to obtain a zirconium-doped hafnium oxide ferroelectric thin film; (3) depositing the hafnium zirconium oxide ferroelectric thin film obtained in step (2) by magnetron sputtering to obtain an insulating layer of cerium oxide; (4) using electron beam evaporation to prepare metal tungsten as a top electrode from the thin film obtained in step (3); (5) placing the thin film obtained in step (4) in an annealing furnace filled with an inert protective atmosphere for rapid annealing heat treatment, and taking out the sample after the annealing furnace is cooled to room temperature to obtain the target hafnium oxide-based ferroelectric tunnel junction.
2. The method for preparing a hafnium oxide-based self-rectifying tunnel junction according to claim 1, characterized in that: In step (1), the specific steps of preparing the tungsten electrode by electron beam evaporation include: preparing a 20nm layer of metal tungsten as a bottom electrode on a silicon wafer.
3. The method for preparing a hafnium oxide-based self-rectifying tunnel junction according to claim 1, characterized in that: In step (2), the specific steps of preparing the hafnium zirconium oxide ferroelectric film by atomic layer deposition include: placing the sample in a chamber, the deposition temperature is 270°C, changing the source time of the hafnium source and the zirconium source to change the doping ratio of hafnium and zirconium, and changing the total number of deposition cycles to change the thickness of the hafnium zirconium oxide film.
4. The method for preparing a hafnium oxide-based self-rectifying tunnel junction according to claim 1, characterized in that: In step (3), the specific steps of preparing the insulating layer cerium oxide intercalation layer by magnetron sputtering include: attaching the sample to the substrate table, controlling the sputtering power and the introduction of the atmosphere, and changing the deposition time to change the thickness of the cerium oxide intercalation layer.
5. The method for preparing a hafnium oxide-based self-rectifying tunnel junction according to claim 1, characterized in that: In step (4), the specific steps of preparing the tungsten electrode by electron beam evaporation include: using a mask plate to prepare a 20nm layer of metal tungsten as a top electrode on the hafnium zirconium oxide film.
6. The method for preparing a hafnium oxide-based self-rectifying tunnel junction according to claim 1, characterized in that: In step (5), the inert protective atmosphere is nitrogen. The specific process of rapid thermal annealing of the hafnium zirconium oxide ferroelectric film is: heating from room temperature to 550°C at a heating rate of 3°C / s, keeping the temperature for 200s, and then cooling to room temperature before taking out.