A method for preparing an ultra-thin wurtzite ferroelectric thin film by plasma nitriding pretreatment

Abstract

The application discloses a method for preparing an ultrathin ferroelectric wurtzite thin film through plasma nitridation pretreatment, and the method comprises the following steps: firstly, performing plasma nitridation pretreatment on the surface of a substrate to form a nitrogen-rich activated surface on the substrate; and then, performing atomic layer deposition of a ferroelectric wurtzite material on the nitrogen-rich activated surface to prepare the ultrathin ferroelectric wurtzite thin film with a thickness of not more than 10 nm; the method introduces in-situ low-temperature plasma nitridation pretreatment before atomic layer deposition, and atomically constructs a nitrogen-rich activated interface on the surface of the substrate, so that the problems of nucleation delay, island growth and interface amorphization caused by insufficient surface active sites in a conventional atomic layer deposition process are fundamentally solved, the ideal two-dimensional layer-by-layer growth mode is realized from the first cycle, and the ultrathin ferroelectric wurtzite thin film with a clear interface, complete crystallization and uniform thickness is obtained.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor manufacturing, microelectronics and information storage technology, and in particular to a method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment. Background Technology

[0002] Wurtzite ferroelectric thin films such as AlScN, AlBN, AlGaN, AlInN, AlYN, and AlGdN are considered ideal candidates for next-generation high-density, low-power ferroelectric memories due to their high remanent polarization, low coercive field, excellent fatigue resistance, and good compatibility with CMOS processes. However, when the film thickness is reduced to the nanoscale (typically ≤10nm) to meet device miniaturization requirements, maintaining excellent crystallinity and stable ferroelectric properties under ultrathin conditions becomes a core challenge in the fabrication process.

[0003] Against this backdrop, atomic layer deposition (ALD) technology, with its atomic-level thickness control, excellent uniformity, and step coverage capabilities, is considered crucial for fabricating next-generation ultrathin ferroelectric devices. However, in the initial stages of ALD growth of wurtzite ferroelectric thin films, a severe "nucleation delay" phenomenon is prevalent due to insufficient reactive sites on the substrate surface, resulting in initial growth exhibiting a random island-like structure rather than an ideal two-dimensional layer-by-layer pattern. This non-ideal growth leads to discontinuous films at ultrathin thicknesses, forming amorphous layers or high defect density layers, severely degrading the ferroelectric properties and reliability of the films, and limiting their application in cutting-edge devices such as low-power memories and nanoscale sensors. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing ultrathin (typically ≤10 nm) wurtzite ferroelectric thin films by plasma nitriding pretreatment, which mainly solves the problems of discontinuity and inhomogeneity in the initial stage of traditional atomic layer deposition growth of wurtzite ferroelectric thin films.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment includes the following steps: Step 1: Perform plasma nitriding pretreatment on the substrate surface to form a nitrogen-rich activated surface on the substrate; Step 2: Atomic layer deposition of wurtzite ferroelectric material is performed on the nitrogen-rich activated surface to prepare the ultrathin wurtzite ferroelectric thin film with a thickness of no more than 10 nm.

[0006] This invention pretreats the substrate surface by introducing plasma nitriding, creating a nitrogen-rich and activated interface that can precisely control the chemical state of the substrate surface. This provides an ideal nitriding interface for the growth of wurtzite ferroelectric thin films at the atomic level, laying the foundation for the subsequent ordered epitaxial growth of wurtzite structures.

[0007] In one embodiment, the substrate may be an elemental semiconductor such as silicon or germanium, or a compound semiconductor such as gallium nitride; or a metal electrode such as molybdenum or platinum; or a perovskite oxide such as strontium titanate; or a flexible polymer such as polyimide; or a two-dimensional material such as graphene, hexagonal boron nitride, black phosphorus, silylene, germanene, or phosphorene.

[0008] In one embodiment, prior to plasma nitriding pretreatment, the substrate material may undergo necessary surface pretreatment. The purpose of this surface pretreatment is to remove organic contaminants, particulate residues, and the natural oxide layer from the substrate surface, obtaining an initial surface that is atomically clean and chemically controllable. Specifically, the substrate surface can be purged with a nitrogen gun to remove physically adsorbed dust particles; then, solvent cleaning can be used to remove organic residues and the natural oxide layer. Surface pretreatment provides a uniform and activated interface foundation for subsequent plasma nitriding pretreatment, which helps improve nitriding efficiency and suppress the formation of interface defects, thus being an important prerequisite for ensuring high-quality growth of ultrathin films.

[0009] In one embodiment, step 1 can be performed by directly performing plasma nitriding pretreatment on the substrate surface in the reaction chamber of atomic layer deposition, thereby better connecting with the deposition process in step 2.

[0010] Step 1, plasma nitriding pretreatment, is the core step of this invention. Its purpose is to perform in-situ nitriding on the substrate surface to construct an activation layer rich in nitrogen and with a high density of reaction sites. In one embodiment, the plasma nitriding pretreatment of the substrate surface is specifically implemented as follows: Nitrogen-containing process gas is introduced into the atomic layer deposition (ALD) reaction chamber, and the plasma source is activated. The radio frequency power is set between 50W and 5000W, the pretreatment temperature between 25℃ and 600℃, and the in-situ nitriding pretreatment time between 1s and 6000s, depending on the specific process requirements. The highly reactive nitrogen radicals, ions, and excited-state molecules in the plasma react chemically with the surface atoms of the substrate, forming a dense, uniform, nitrogen-rich activated surface with high-density reaction sites. This step aims to precisely control the chemical state of the substrate surface at the atomic level, significantly reducing the interfacial energy barrier for initial nucleation in ALD. This overcomes the bottleneck problems of delayed nucleation, island growth, and interfacial amorphization caused by insufficient surface active sites in traditional processes, providing an ideal nucleation template and interfacial basis for the subsequent ordered two-dimensional layered growth of wurtzite ferroelectric thin films and derived nitrides.

[0011] In one embodiment, the nitrogen-containing process gas may be: NH3, N2, N2 / H2 mixture, N2H4, or a mixture of N2H4 and an inert gas, etc.

[0012] In one embodiment, the plasma source can be a remote plasma source or a direct plasma source, specifically an inductively coupled plasma source (ICP) or a capacitively coupled plasma source (CCP), etc.

[0013] The RF power design of this invention is based on the following considerations: Different plasma source types exhibit variations in the power range required to generate high-density reactive nitrogen species: some plasma sources can achieve high-density plasma at lower power, while others require higher power to achieve comparable nitriding effects. Simultaneously, different substrate materials exhibit varying sensitivities to ion bombardment: substrates sensitive to ion bombardment require lower power to avoid surface damage; while substrates with higher bombardment tolerance can withstand higher power to improve nitriding efficiency. Furthermore, at excessively low power, the nitrogen free radical yield is insufficient, making it difficult to form a uniform and dense nitrogen-rich layer in a short time; at excessively high power, ion bombardment damage is easily introduced, leading to increased surface roughness or higher interfacial defect density.

[0014] The pretreatment temperature design of this invention is based on the following considerations: The pretreatment temperature needs to balance the thermal activation energy requirements of the nitriding reaction with the thermal tolerance of the substrate. For substrates with limited thermal budgets or where front-end devices have already been completed, a lower temperature is preferable; for substrates requiring high-quality epitaxial growth or with a high nitriding reaction rate, a higher temperature can be used. Furthermore, temperature control needs to ensure the thermal activation energy of the nitriding reaction while also being compatible with the thermal budget requirements of CMOS back-end processes.

[0015] The preprocessing time design of this invention is based on the following considerations: The in-situ nitriding time should be selected to ensure saturated coverage of nitrogen terminals on the substrate surface while avoiding over-nitriding.

[0016] Through the above parameter design, the wide range of parameter settings in this invention is based on the technical requirements of covering different plasma source types, different substrate materials, and different application scenarios.

[0017] After undergoing plasma nitriding pretreatment in step 1, the substrate obtains a nitrogen-rich activated surface. Using this substrate for atomic layer deposition of wurtzite ferroelectric materials enables atomically precise growth of wurtzite ferroelectric thin films. In one embodiment, the atomic layer deposition of the wurtzite ferroelectric material is achieved as follows: Multiple atomic layer deposition cycles are performed, each cycle consisting of: a metal precursor pulse, an inert gas purging cycle one, a nitrogen-containing precursor pulse, and an inert gas purging cycle two.

[0018] Due to the activation surface formed in step 1, which is rich in nitrogen terminals and has a high density of reaction sites, the metal precursor can achieve uniform and rapid chemisorption and saturation coverage, significantly shortening the nucleation delay period and inducing the film to enter the ideal two-dimensional layer-by-layer growth mode from the first cycle. Step 2 of this invention, through self-limiting surface reaction, can precisely control the film thickness to the sub-nanometer level, while ensuring large-area uniformity and high step coverage. It is a crucial step in obtaining ultrathin wurtzite ferroelectric films with clear interfaces, complete crystal structures, and excellent ferroelectric properties.

[0019] The selection of the metal precursor pulse is related to the type of thin film to be grown. Its function is to utilize the high density of active sites on the nitrogen-rich activation surface to achieve rapid, uniform, monolayer adsorption of the metal precursor, providing a precise source of metal atoms for the subsequent nitriding reaction.

[0020] The inert gas is selected according to the specific process. Its function is to thoroughly remove the unadsorbed metal precursor molecules and reaction byproducts remaining in the gas phase of the chamber, avoid gas phase mixing reaction or non-self-limiting deposition, ensure that the subsequent nitrogen-containing precursor pulse only reacts with the already adsorbed metal monolayer, and maintain the self-limiting characteristics of atomic layer deposition.

[0021] Nitrogen-containing precursor pulses are selected according to specific processes. Their function is to cause surface chemical reactions between active nitrogen species and the metal-precursor layer adsorbed on the substrate surface, transforming the metal-organic monolayer into wurtzite-structured metal nitrides.

[0022] The inert gas purging step 2 is selected according to the specific process. Its function is to remove the remaining nitrogen-containing precursors and reaction byproducts in the chamber, restore the chamber to a clean state, and prepare for the next atomic layer deposition growth cycle.

[0023] The aforementioned "metal precursor pulse, inert gas purging one, nitrogen-containing precursor pulse, and inert gas purging two" constitute a complete atomic layer deposition growth cycle. The purging step effectively eliminates cross-reactions of the gas phase precursor, ensuring the uniformity of the film on large-area substrates. Simultaneously, thanks to the self-limiting nature of surface reactions, this method can achieve conformal coverage on three-dimensional structural surfaces with high aspect ratios, exhibiting excellent step coverage.

[0024] The contribution of this invention lies in altering the initial nucleation mode (from island-like to two-dimensional layered) through plasma nitriding pretreatment of the substrate surface, thereby enabling the acquisition of high-quality continuous films at ultrathin scales. In fact, the pretreatment method of this invention is also applicable to the preparation of thicker wurtzite films (e.g., >10 nm), and its beneficial effects on improving nucleation and crystallinity are equally present.

[0025] The number of atomic layer deposition (ALD) cycles in this invention is set during the process. Different precursor selections, temperatures, power, and other process parameters will affect the thickness. The specific quantitative relationship between the number of cycles and the film thickness is common knowledge in the field of ALD technology. After learning about the pretreatment method provided by this invention, those skilled in the art can reasonably determine the number of cycles based on the target thickness (e.g., ≤10nm) and the growth rate per cycle (which can be determined through simple experiments), without needing to elaborate on each one. For different precursor combinations or process conditions, the growth rate per cycle may vary slightly, but all of these fall within the scope of conventional optimization by those skilled in the art.

[0026] In one embodiment, the material of the ultrathin wurtzite ferroelectric thin film can be AlScN, AlBN, AlGaN, AlInN, AlYN, or AlGdN, etc.

[0027] Finally, after completing the preset number of atomic layer deposition cycles and reaching the target film thickness, the sample is removed from the reaction chamber, completing the entire atomic layer deposition process. The substrate of this invention remains in a vacuum environment from cleaning and loading until the end of the process, eliminating the need for interruption and effectively avoiding risks such as film surface oxidation, contamination, or interface degradation. After sampling, the prepared ultrathin wurtzite ferroelectric thin film can be directly used for subsequent characterization or device integration, demonstrating the advantages of this invention's method: simple process, environmentally friendly, and highly compatible with semiconductor back-end processes.

[0028] Compared with the prior art, the beneficial effects of the present invention are: This invention introduces in-situ, low-temperature in-situ plasma nitriding pretreatment before atomic layer deposition (ALD) to construct a nitrogen-rich activated interface at the atomic level on the substrate surface. This fundamentally solves the problems of delayed nucleation, island growth, and interface amorphization caused by insufficient surface active sites in conventional ALD processes. It achieves an ideal two-dimensional layer-by-layer growth mode from the first cycle, resulting in ultrathin wurtzite ferroelectric films with clear interfaces, complete crystallization, and uniform thickness. It is worth noting that the "low temperature" in this invention refers to a relative low temperature compared to other processes and the temperatures compatible with CMOS processes, rather than an absolute low temperature.

[0029] Furthermore, the entire process of this invention is completed in situ continuously within the atomic layer deposition chamber, eliminating the need for high-temperature annealing, oxidation pretreatment, or pre-deposition of buffer layers. This avoids drawbacks such as interface diffusion, oxygen vacancy introduction, and increased process complexity. The processing temperature can be as low as room temperature, making it highly compatible with CMOS back-end processes and significantly reducing thermal budget and manufacturing costs.

[0030] Furthermore, this invention covers a variety of plasma source types, a variety of nitrogen-containing process gases, and a wide range of process parameters, which can be flexibly controlled for different substrate materials such as semiconductors, metals, oxides, two-dimensional materials, and flexible substrates. It has a wide process window and strong versatility, providing a key preparation path for high-quality ultrathin ferroelectric thin films for next-generation high-density non-volatile memories, in-memory computing chips, and nanopiezoelectric devices. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the initial island-like nucleation growth of atomic layer deposition on an untreated substrate.

[0032] Figure 2 This is a schematic diagram showing that the pretreated substrate surface has a high density of active sites.

[0033] Figure 3 This is a schematic diagram of achieving ideal two-dimensional growth on a pretreated substrate.

[0034] Figure 4 This is a schematic diagram of AlScN two-dimensional layered growth on a pretreated substrate.

[0035] Figure 5 This is a schematic diagram of AlScN island growth on an untreated substrate. Detailed Implementation

[0036] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and examples.

[0037] Traditional atomic layer deposition (ALD) processes for fabricating ultrathin (typically ≤10 nm) wurtzite-structured ferroelectric thin films generally suffer from severe nucleation delays due to insufficient reactive sites on the substrate surface. This leads to defects such as film discontinuities, amorphous layers, or high-defect-density interface layers at ultrathin thicknesses. These microstructural defects severely degrade the crystallinity quality, ferroelectric properties (e.g., remanent polarization, coercive field stability), and device reliability of the ultrathin films, limiting their application in next-generation high-density memories, nanosensors, and other advanced devices.

[0038] At the same time, traditional high-temperature annealing or oxidation pretreatment can introduce new problems such as interfacial reactions and oxygen vacancies, which can affect the ferroelectricity of the device.

[0039] Therefore, this invention aims to provide a novel atomic layer deposition method that addresses the aforementioned nucleation delay and interface defect problems at the atomic level by introducing a plasma nitriding pretreatment step. This enables the controllable fabrication of high-quality, ultrathin wurtzite ferroelectric thin films, providing a key technological foundation for the manufacturing of next-generation high-density ferroelectric devices. Several specific embodiments of this invention are described below.

[0040] Example 1 A method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment includes the following steps: Step 1, substrate pretreatment and loading.

[0041] The substrate material is metallic molybdenum. Its surface pretreatment is as follows: the substrate surface is purged with nitrogen to remove physically adsorbed particles; it is then sequentially cleaned with acetone, isopropanol, and ultrasonically for 5 minutes each, followed by cleaning with deionized water to remove organic residues. The substrate is then placed in the atomic layer deposition reaction chamber, and a vacuum is applied until the substrate pressure is <10. -5 Torr, heat the substrate to 350 °C and hold for 10 min to desorb surface moisture.

[0042] Step 2, plasma nitriding pretreatment.

[0043] Process gas: N2 / H2 mixture (flow ratio 9:1), total gas flow rate 50 sccm.

[0044] Plasma source: Inductively coupled plasma (ICP), RF power 300 W.

[0045] Pretreatment temperature: 350 ℃.

[0046] Processing time: 120 seconds.

[0047] Procedure: Introduce process gas, start the plasma source, and perform in-situ nitriding treatment on the substrate surface. After treatment, stop the plasma and continue purging with N2 for 30 seconds.

[0048] Step 3: Atomic layer deposition of wurtzite ferroelectric material.

[0049] Target material: AlScN.

[0050] Precursor selection: Metal precursors: trimethylaluminum (TMA, Al(CH3)3) and trimethylcyclopentadienylscandium (Sc(C5H4CH3)3).

[0051] Nitrogen-containing precursor: NH3 plasma (as nitrogen source and reducing agent).

[0052] Inert purging gas: High-purity N2 (99.999% purity).

[0053] Atomic layer deposition temperature: 350 ℃.

[0054] Atomic layer deposition cycle parameters (executed sequentially in each cycle): TMA pulse: 0.1 s; N2 purging: 10 s; Sc(C5H4CH3)3 pulse: 0.2 s; N2 purging: 10 s; NH3 plasma pulse (power 200 W): 5 s; N2 purging: 10 s.

[0055] Number of loops: 20.

[0056] Finally, 1.9nm AlScN was grown.

[0057] Example 2 A method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment includes the following steps: Step 1: Substrate Pretreatment and Loading The substrate material was titanium nitride. The substrate surface was gently blown with a nitrogen gun to remove physically adsorbed particles; it was then ultrasonically cleaned in acetone and isopropanol for 3 minutes each, rinsed with deionized water, and dried with nitrogen; the substrate was then placed in the atomic layer deposition reaction chamber, and a vacuum was drawn until the substrate pressure was <10. -5 Torr, heat the substrate to 150 °C and hold for 5 min to gently desorb surface moisture.

[0058] Step 2: Plasma nitriding pretreatment Process gas: NH3 (purity 99.999%), total gas flow rate 30 sccm.

[0059] Plasma source: Remote plasma source, RF power 80 W.

[0060] Pretreatment temperature: 150 ℃.

[0061] Processing time: 90 seconds.

[0062] Procedure: Introduce process gas, start the plasma source, and perform in-situ nitriding treatment on the substrate surface. After treatment, stop the plasma and continue purging with N2 for 20 seconds.

[0063] Step 3: Atomic layer deposition of wurtzite ferroelectric materials Target material: AlScN.

[0064] Precursor selection: Metal precursors: trimethylaluminum (TMA, Al(CH3)3) and trimethylcyclopentadienylscandium (Sc(C5H4CH3)3).

[0065] Nitrogen-containing precursor: NH3 plasma.

[0066] Inert purging gas: High-purity N2.

[0067] Atomic layer deposition temperature: 200 ℃.

[0068] Atomic layer deposition cycle parameters (executed sequentially in each cycle): TMA pulse: 0.1 s; N2 purging: 15 s; Sc(C5H4CH3)3 pulse: 1.0 s; N2 purging: 15 s; NH3 plasma pulse (power 100 W): 8 s; N2 purging: 15 s.

[0069] A superloop is used, inserting one ScN loop every 10 AlN loops, for a total of 8 superloops.

[0070] An ultrathin AlScN film of approximately 8.9 nm was eventually grown.

[0071] Example 3 A method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment includes the following steps: Step 1: Substrate Pretreatment and Loading The substrate material was platinum. The substrate surface was purged with nitrogen gas to remove physically adsorbed particles; it was then ultrasonically cleaned sequentially in acetone, isopropanol, and deionized water for 5 minutes each; the substrate was then placed in the atomic layer deposition reaction chamber, and a vacuum was applied until the substrate pressure was <10. - 5 Torr, heat the substrate to 400 °C and hold for 15 min to desorb surface moisture and promote surface reconstruction.

[0072] Step 2: Plasma nitriding pretreatment Process gas: N2 (purity 99.999%), total gas flow rate 60 sccm.

[0073] Plasma source: Inductively coupled plasma (ICP), RF power 500 W.

[0074] Pretreatment temperature: 400 ℃.

[0075] Processing time: 300 seconds.

[0076] Procedure: Introduce process gas, start the plasma source, and perform in-situ nitriding treatment on the substrate surface. After treatment, stop the plasma and continue purging with N2 for 45 seconds.

[0077] Step 3: Atomic layer deposition of wurtzite ferroelectric materials Target material: AlN.

[0078] Precursor selection: Metal precursor: Trimethylaluminum (TMA, Al(CH3)3).

[0079] Nitrogen-containing precursor: N2 / H2 mixed gas plasma (flow ratio 9:1).

[0080] Inert purging gas: High-purity N2 (99.999% purity).

[0081] Atomic layer deposition temperature: 400 ℃.

[0082] Atomic layer deposition cycle parameters (executed sequentially in each cycle): TMA pulse: 0.1 s; N2 purging: 8 s; N2 / H2 plasma pulse (power 250 W): 6 s; N2 purging: 8 s.

[0083] Number of cycles: 50.

[0084] An AlN film of approximately 5.2 nm was eventually grown.

[0085] Example 4 A method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment includes the following steps: Step 1: Substrate Pretreatment and Loading The substrate material was monocrystalline silicon. The substrate surface was purged with nitrogen gas to remove physically adsorbed particles; it was then ultrasonically cleaned sequentially in acetone, isopropanol, and deionized water for 5 minutes each; the substrate was then placed in the atomic layer deposition reaction chamber, and a vacuum was applied until the substrate pressure was <10. -5 Torr, heat the substrate to 300 °C and hold for 10 min to desorb surface moisture.

[0086] Step 2: Plasma nitriding pretreatment Process gas: NH3 (purity 99.999%), total gas flow rate 60 sccm.

[0087] Plasma source: Inductively coupled plasma (ICP), RF power 250 W.

[0088] Pretreatment temperature: 300 ℃.

[0089] Processing time: 150 seconds.

[0090] Procedure: Introduce process gas, start the plasma source, and perform in-situ nitriding treatment on the substrate surface. After treatment, stop the plasma and continue purging with N2 for 30 seconds.

[0091] Step 3: Atomic layer deposition of wurtzite ferroelectric materials Target material: AlGaN.

[0092] Precursor selection: Metal precursors: trimethylaluminum (TMA, Al(CH3)3) and trimethylgallium (TMG, Ga(CH3)3).

[0093] Nitrogen-containing precursor: N2 / H2 mixed gas plasma.

[0094] Inert purging gas: High-purity N2 (99.999% purity).

[0095] Atomic layer deposition temperature: 300 ℃.

[0096] Atomic layer deposition cycle parameters (executed sequentially in each cycle): TMA pulse: 0.1 s; N2 purging: 10 s; TMG pulse: 0.015 s; N2 purging: 10 s; N2 / H2 plasma pulse (power 200 W): 15 s; N2 purging: 10 s.

[0097] Number of cycles: 80 Ultimately, an AlGaN of approximately 9.2 nm was grown.

[0098] Comparative Example 1 Step 1, substrate pretreatment and loading.

[0099] Same as Example 1.

[0100] Step 2, atomic layer deposition of wurtzite ferroelectric material.

[0101] Same as step 3 in Example 1.

[0102] Finally, 1.9nm AlScN was grown.

[0103] Figure 1 The atomic layer deposition effect of Comparative Example 1 is shown. It can be seen that the substrate surface lacks active sites, and the precursor molecules are sparsely and randomly adsorbed and aggregate to form discontinuous "islands".

[0104] In contrast, Figure 2 The active sites on the surface of the plasma nitriding pretreated substrate of Example 1 are shown. Figure 3 The atomic layer deposition effect of Example 1 is shown, from Figure 2 As can be seen, after the plasma nitriding pretreatment of this invention, a nitrogen-rich activation interface is constructed on the substrate, and the substrate surface is uniformly and densely covered with "active sites". From Figure 3 It can be seen that the precursor molecules achieved uniform, dense, monolayer adsorption on the nitrogen-rich activation interface, forming a "two-dimensional layered growth" mode.

[0105] Furthermore, according to Figure 4 As can be seen, the interface of the AlScN film obtained in Example 1 is clear, continuous, and flat, without discontinuities or voids. According to... Figure 5 It can be clearly seen that the AlScN film grown on the substrate of Comparative Example 1 without plasma nitriding pretreatment exhibits discontinuity, blurred interfaces, and a large number of gaps.

[0106] In summary, this invention pre-treats the substrate surface with plasma nitridation before atomic layer deposition growth, thereby constructing a nitrogen-rich and activated interface at the atomic level, thus precisely controlling the initial nucleation environment and ultimately preparing an ultrathin wurtzite ferroelectric thin film with a clear interface, high crystal quality, and excellent ferroelectric properties.

Claims

1. A method for preparing ultrathin wurtzite ferroelectric thin films through plasma nitriding pretreatment, characterized in that, Includes the following steps: Step 1: Perform plasma nitriding pretreatment on the substrate surface to form a nitrogen-rich activated surface on the substrate; Step 2: Atomic layer deposition of wurtzite ferroelectric material is performed on the nitrogen-rich activated surface to prepare the ultrathin wurtzite ferroelectric thin film with a thickness of no more than 10 nm.

2. The method for preparing ultrathin wurtzite ferroelectric thin films by plasma nitriding pretreatment according to claim 1, characterized in that, The substrate is made of elemental semiconductor or compound semiconductor material.

3. The method for preparing ultrathin wurtzite ferroelectric thin films according to claim 1, characterized in that, The substrate is made of a metal electrode.

4. The method for preparing ultrathin wurtzite ferroelectric thin films by plasma nitriding pretreatment according to claim 1, characterized in that, The substrate is made of perovskite oxide or a flexible polymer.

5. The method for preparing ultrathin wurtzite ferroelectric thin films by plasma nitriding pretreatment according to claim 1, characterized in that, The substrate is made of silicon, germanium, gallium nitride, platinum, molybdenum, graphene, hexagonal boron nitride, black phosphorus, silylene, germanene, phosphorene, strontium titanate, or polyimide.

6. The method for preparing ultrathin wurtzite ferroelectric thin films according to claim 1, characterized in that, In step 1, the substrate surface is subjected to plasma nitriding pretreatment in the atomic layer deposition reaction chamber.

7. The method for preparing ultrathin wurtzite ferroelectric thin films according to claim 6, characterized in that, The plasma nitriding pretreatment of the substrate surface is achieved as follows: Nitrogen-containing process gas is introduced into the atomic layer deposition reaction chamber, the plasma source is started, the radio frequency power is set to 50W~5000W, the pretreatment temperature is 25℃~600℃, and the pretreatment time is 1s~6000s.

8. The method for preparing ultrathin wurtzite ferroelectric thin films according to claim 7, characterized in that, The nitrogen-containing process gas is: NH3, N2, N2 / H2 mixture, N2H4 or N2H4 mixed with inert gases; The plasma source is: Inductively coupled plasma source or capacitively coupled plasma source.

9. The method for preparing ultrathin wurtzite ferroelectric thin films according to claim 1, characterized in that, The atomic layer deposition of the wurtzite ferroelectric material is achieved as follows: Multiple atomic layer deposition cycles are performed, each cycle consisting of: a metal precursor pulse, an inert gas purging cycle one, a nitrogen-containing precursor pulse, and an inert gas purging cycle two.

10. The method for preparing ultrathin wurtzite ferroelectric thin films according to claim 1, characterized in that, The material of the ultrathin zinc ore ferroelectric thin film is: AlScN, AlBN, AlGaN, AlInN, AlYN or AlGdN.

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