Novel nonvolatile organic ferroelectric semiconductor storage material

Abstract

The invention relates to the field of semiconductor materials, in particular to a novel nonvolatile organic ferroelectric semiconductor storage material. In view of limitation of a traditional storage technology and existing problems of an organic ferroelectric material, the molecular structure of the material is innovatively designed, and synthesis, doping and film forming processes are optimized. The obtained material is high in polarization performance, high in stability, efficient in preparation and stable in quality, is successfully applied to the fields of flexible storage and Internet of Things storage, also has the advantages of low temperature, self-repairing and miniaturization, and powerfully promotes the innovation of a storage technology.

Description

Technical Field

[0001] The present invention relates to the field of information management systems, and particularly to a novel non-volatile organic ferroelectric semiconductor storage material. Background Art

[0002] In the current surging digital wave, data is growing explosively. As a key support for information storage and retrieval, storage technology is constantly facing severe challenges and upgrade demands. The traditional silicon-based flash memory technology has long dominated the storage field but is showing signs of fatigue. Physically, as the semiconductor process continues to shrink, silicon-based devices encounter effects such as quantum tunneling, resulting in serious leakage problems, which limit the possibility of further increasing the storage density; the read and write speed is limited by its charge transport mechanism and is difficult to meet the low-latency requirements for scenarios such as real-time big data analysis and cache, where the fleeting low latency is crucial; in terms of power consumption, continuous charge and discharge operations, especially when reading and writing large amounts of data frequently, cause significant energy consumption. For battery-powered scenarios such as mobile devices and Internet of Things sensors, the short battery life is constantly magnified. In addition, the inherent rigidity of silicon-based materials runs counter to the development trend of flexible electronics and cannot provide a suitable storage solution for emerging applications such as wearable devices and flexible displays. Organic ferroelectric semiconductor storage materials have emerged, bringing hope for breaking the deadlock. These materials cleverly combine ferroelectric properties with semiconductor performance and theoretically have many attractive advantages. The ferroelectric property of spontaneous polarization in ferroelectric materials allows data storage to be maintained without continuous power supply, greatly reducing static power consumption, which is in line with the current technological trend of green energy conservation and low power consumption; the organic component endows the material with inherent flexibility, which can perfectly fit the manufacturing process of flexible electronic devices and unlock more possibilities for wearable and portable applications. However, the actual development has not been smooth sailing, and organic ferroelectric semiconductor materials face many thorny problems.

[0003] Most organic ferroelectrics have a low ferroelectric Curie temperature, which means that with a slight increase in the ambient temperature, the ferroelectric domains will become disordered and the polarization intensity will drop sharply, resulting in a significant reduction in the performance of the material in high-temperature scenarios. For example, in high-temperature workshops in industrial production and electronic devices outdoors in summer, the data storage stability is worrying; the insufficient polarization retention ability is even more fatal. After multiple read and write cycles or long-term use, the polarization state is difficult to maintain stably, and the reliability of data storage drops sharply, leading to the risk of data loss; the carrier mobility is limited, slowing down the data transmission speed in the material and unable to meet the application standards of high-speed operation and fast storage; the immaturity of the large-area uniform film-forming process is like a pair of hands choking the throat, hindering large-scale production, driving up costs, and making it difficult to guarantee the yield rate. These pain points seriously restrict the pace of organic ferroelectric semiconductor materials towards practicality and industrialization and urgently require comprehensive and innovative solutions to overcome. Summary of the Invention

[0004] The present invention provides a novel non-volatile organic ferroelectric semiconductor storage material.

[0005] It includes a modified polymer based on poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE). The polymer backbone has nitrogen-containing heterocyclic side chains with a side chain length of 3-6 carbon chain units. One side chain is incorporated per 10-15 main chain units, and fluorine accounts for 40%-50% of the total mass of the polymer. It also includes a D-π-A type small molecule organic ferroelectric. The electron-donating group is carbazole, which is connected to the dicyanoethylene-based electron-withdrawing group through a conjugated π-bridge containing 2-3 aromatic rings.

[0006] Furthermore, for the novel non-volatile organic ferroelectric semiconductor storage material, the nitrogen-containing heterocyclic side chains are selected from pyridyl and pyrazolyl.

[0007] Furthermore, for the synthesis process of the novel non-volatile organic ferroelectric semiconductor storage material, the fluorine-containing organic ferroelectric polymer is synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization using a phosphorus-containing thioester chain transfer agent. The ratio of the chain transfer agent to the initiator is 1:2 - 1:3, and the polymerization reaction temperature is 60-80°C. The small molecule organic ferroelectric is synthesized by a solution condensation reaction. The solvent system is a mixture of dimethylformamide (DMF) and toluene in a ratio of 2:1 - 3:1. The reaction is initiated at 0-10°C and then heated to 40-60°C for 10-15 hours.

[0008] Furthermore, for the synthesis process

[0009] The molecular weight distribution index (PDI) of the fluorine-containing organic ferroelectric polymer synthesized by this process is 1.2 - 1.5.

[0010] Furthermore, for the doping and addition method of the novel non-volatile organic ferroelectric semiconductor storage material, it is characterized in that:

[0011] 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide salt (BMIMNTf 2 ) is doped into the fluorine-containing organic ferroelectric polymer system, and the doping amount accounts for 5%-15% of the polymer mass. Barium titanate (BaTiO 3 ) nanoparticles with a particle size of 20-50 nm are added to the small molecule organic ferroelectric, and the addition amount accounts for 1%-5% of the small molecule mass.

[0012] Furthermore, for the thin film preparation process of the novel non-volatile organic ferroelectric semiconductor storage material

[0013] The fluorine-containing organic ferroelectric polymer thin film is prepared by solvent evaporation-induced self-assembly. The polymer solution is spin-coated on a substrate, and the solvent is slowly evaporated in an environment with a saturated solvent vapor concentration of 50%-80% and a evaporation temperature of 40-60°C. The small molecule organic ferroelectric thin film is prepared by an improved Langmuir-Blodgett (LB) technique, controlling the subphase temperature at 15-25°C and the surface pressure at 20-30 mN / m, and forming a film by a multi-layer accumulation method.

[0014] Furthermore, the system for monitoring and regulating the performance of the novel non-volatile organic ferroelectric semiconductor storage material includes a combined in-situ polarization-electric field (P-E) loop and capacitance-voltage (C-V) characteristic test system, which is used to track key performance indicators such as the polarization intensity, coercive field, and capacitance of the material in real time. When the polarization intensity drops by more than 5%, or the coercive field changes by more than 8%, the subsequent process parameters are automatically adjusted. It also includes a combined device of a scanning electron microscope (SEM) and a transmission electron microscope (TEM), which is used to observe the microstructure of the material and optimize the preparation process immediately when abnormalities are found.

[0015] Furthermore, for the flexible storage chip applying the novel non-volatile organic ferroelectric semiconductor storage material, the organic ferroelectric semiconductor storage material is encapsulated with a flexible polymer, and the bendable and wearable storage function is realized by using the high polarization retention ability of the material.

[0016] Furthermore, for the Internet of Things sensor data storage module applying the novel non-volatile organic ferroelectric semiconductor storage material, by using the low power consumption and non-volatile characteristics of the material, the collected data is stored locally at the sensor node, reducing the data transmission frequency.

[0017] Furthermore, the method for improving the performance of the novel non-volatile organic ferroelectric semiconductor storage material

[0018] When synthesizing, an organic additive containing ethylene glycol accounting for 5%-10% of the total raw material mass is added to improve the low-temperature toughness of the material and ensure that the ferroelectric performance decay amplitude is <15% in a low-temperature environment of -30°C. An organic small molecule containing disulfide bonds accounting for 0.5%-1% of the material mass is incorporated. When microcracks appear in the material, under the stimulation of heat or light, the disulfide bonds break and reconnect to repair the microcracks.

[0019] Beneficial effects:

[0020] The polarization performance has achieved a qualitative leap. By combining molecular structure remodeling and precise regulation, the polarization intensity is increased by 30%-50% compared with traditional materials. The stronger polarization force provides a solid foundation for data encoding. Each storage unit is like an indestructible fortress, accurately locking the data. The stability of the coercive field is enhanced simultaneously, effectively resisting external interference, ensuring data integrity and long-term effectiveness to the greatest extent, and reducing the risks of errors and losses.

[0021] The material stability benefits from the optimized synthesis and thin film preparation processes. When exposed to a humid and hot environment (85°C, 90% RH) for 500 hours, the retention rate of ferroelectric properties exceeds 90%. Such excellent stability endows the storage device with the confidence to withstand complex environments. Whether in the sultry and humid tropical regions or the high-temperature and high-humidity workshops of industrial production, it can perform stably, reducing the costs and energy losses of frequent replacement and maintenance.

[0022] The optimization of the preparation process has achieved remarkable results. The production efficiency has increased by 30% - 50%, the yield rate of large-area preparation has jumped by 20% - 30%, and the batch consistency is good.

[0023] Precise performance regulation has become a reality. With the real-time monitoring system in place, the deviation of ferroelectric properties of each batch of materials is < 3%.

[0024] The application has been expanded in multiple areas, and two applications, namely flexible storage chips and storage for Internet of Things sensors, have taken root.

[0025] The composite system expands the performance boundaries. When compounded with two-dimensional materials, the ferroelectric properties are improved by 10% - 20% and the carrier mobility is enhanced; intelligent regulation continuously optimizes the process through machine learning, and the yield rate steadily increases; with the protection of low-temperature additives, the ferroelectric property degradation at -30°C is < 15%; the self-healing property endows the material with the ability of "self-healing", extending the device life; the MEMS process unlocks the customization of micro-devices, enabling precise embedding in special fields such as implantable medical devices and micro-sensors. Detailed implementation manners

[0026] Example 1: Preparation and performance testing of fluorinated organic ferroelectric polymers

[0027] I. Experimental preparation

[0028] Raw materials: poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) monomer, nitrogen-containing heterocyclic compound (pyridyl bromide), initiator (azobisisobutyronitrile), chain transfer agent (phosphorus and sulfur-containing ester), solvent (N,N-dimethylformamide).

[0029] Instruments: reaction kettle, rotary evaporator, vacuum drying oven, in-situ polarization - electric field (P-E) loop tester, scanning electron microscope (SEM).

[0030] II. Preparation process

[0031] The PVDF-TrFE monomer and pyridyl bromide were added to the reaction kettle at a molar ratio of 15:1, and then an appropriate amount of solvent was added to make the monomer concentration 0.5 mol / L. Then the initiator was added, and the ratio of the initiator to the chain transfer agent was 1:2.5. At 70°C, continuous stirring was carried out for 12 hours for reversible addition - fragmentation chain transfer (RAFT) polymerization reaction.

[0032] After the reaction was completed, the solvent was removed using a rotary evaporator, and the obtained product was dried in a vacuum drying oven at 80 °C for 24 hours to obtain a PVDF-TrFE derivative with a nitrogen-containing heterocyclic side chain.

[0033] III. Performance Testing and Synergy Comparison

[0034] Polarization performance: Using an in-situ P-E loop tester, the polarization intensity of this polymer was measured to reach 80 μC / cm 2 , while that of the traditional PVDF-TrFE polymer was only 50 μC / cm 2 , an increase of 60%. This is due to the nitrogen-containing heterocyclic side chain enhancing the intramolecular hydrogen bond and stabilizing the ferroelectric domain, resulting in a significantly enhanced polarization effect.

[0035] Microstructure: SEM observation showed that the surface of the polymer film prepared in this example was flat, the molecular arrangement was orderly, and there were few pores; the traditional material had a rough surface and agglomeration phenomena, proving that the new synthesis process improved the material uniformity and crystallinity.

[0036] Example 2: Synthesis and Performance Analysis of Small Molecule Organic Ferroelectrics

[0037] I. Experimental Preparation

[0038] Raw materials: carbazole, thiophene aldehyde, dicyano vinyl compound, solvent (a mixed solvent of dimethylformamide and toluene, volume ratio 2:1).

[0039] Instruments: reflux condenser, filtration device, vacuum oven, capacitance-voltage (C-V) characteristic tester, transmission electron microscope (TEM).

[0040] II. Synthesis Process

[0041] In a three-necked flask equipped with a reflux condenser, carbazole and thiophene aldehyde were added in sequence, stirred at 0 °C for 30 minutes, and then the dicyano vinyl compound was slowly added dropwise, and the temperature was raised to 50 °C and reacted for 12 hours.

[0042] After the reaction was completed, a small amount of impurities were removed by filtration, and the filtrate was placed in a vacuum oven and dried at 60 °C for 10 hours to obtain a D-π-A type small molecule organic ferroelectric.

[0043] III. Performance Testing and Synergy Comparison

[0044] Ferroelectric performance: Detected by a C-V characteristic tester, its coercive field was 100 kV / cm, a decrease of 33% compared with 150 kV / cm of the same type of traditional small molecule organic ferroelectrics, indicating that the charge transfer was smoother and the ferroelectric performance was better, due to the precise design of the conjugated bridge length.

[0045] Microstructure: The TEM image shows that the small-molecule organic ferroelectric has good crystallinity and regular molecular packing; the traditional sample has poor crystallinity and disordered molecular orientation, proving that the optimized solution condensation reaction improves the product quality.

[0046] Example 3: Study on the Effect of Ionic Liquid Doping on Fluorine-Containing Polymer

[0047] I. Experimental Preparation

[0048] Raw materials: The fluorine-containing organic ferroelectric polymer prepared in Example 1, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (BMIMNTf 2 )

[0049] Instruments: High-speed blender, hot press, dynamic mechanical analyzer, in-situ ferroelectric performance monitoring system.

[0050] II. Doping Process

[0051] Add BMIMNTf 2 to the fluorine-containing organic ferroelectric polymer at a mass ratio of 10%, and stir it at 5000 rpm for 30 minutes using a high-speed blender to make it uniformly mixed. Then, press it into a film at 120 °C and 10 MPa using a hot press.

[0052] III. Performance Testing and Synergy Comparison

[0053] Flexibility and carrier concentration: The dynamic mechanical analyzer shows that the flexibility of the doped polymer is improved and the storage modulus is reduced by 20%; at the same time, the Hall effect test shows that the carrier concentration is increased by 30%. The cations and anions of the ionic liquid interact with the polymer chains, optimizing the electrical and mechanical properties of the material.

[0054] Ferroelectric stability: The in-situ ferroelectric performance monitoring system monitors for 24 hours. The polarization intensity of the doped sample only decreases by 2%, while that of the undoped sample reaches 8%, indicating that doping significantly enhances ferroelectric stability.

[0055] Example 4: Effect of Adding Nanoceramics on Small-Molecule Ferroelectrics

[0056] I. Experimental Preparation

[0057] Raw materials: The small-molecule organic ferroelectric synthesized in Example 2, barium titanate (BaTiO 3 ) nanoparticles (particle size 30 nm).

[0058] Instruments: Ultrasonic disperser, spin coater, atomic force microscope (AFM), comprehensive ferroelectric performance test platform.

[0059] II. Adding Process

[0060] Add BaTiO 3The nanoparticles are added to the small-molecule organic ferroelectric at a mass ratio of 3%, and ultrasonically dispersed for 2 hours at a frequency of 40 kHz with an ultrasonic disperser. Subsequently, a film is spin-coated on a silicon substrate at a speed of 1000 rpm with a spin coater.

[0061] III. Performance Testing and Synergistic Comparison

[0062] Mechanical properties: The surface hardness of the film is observed to increase by AFM. The scratch test shows that after adding nano-ceramic particles, the scratch resistance of the film increases by 40%. As physical cross-linking points, they strengthen the mechanical properties of the material.

[0063] Ferroelectric properties: Tested with a comprehensive ferroelectric property testing platform, the polarization intensity increases by 25% after addition. The nano-ceramic particles optimize the growth orientation of ferroelectric domains through interfacial interactions.

[0064] Example 5: Preparation of Polymer Films by Solvent Evaporation-Induced Self-Assembly Method

[0065] I. Experimental Preparation

[0066] Raw materials: Fluorinated organic ferroelectric polymer prepared in Example 1, chloroform (as a solvent).

[0067] Instruments: Spin coater, humidity control box, profilometer, light scattering instrument, in-situ ferroelectric property monitor.

[0068] II. Film Preparation

[0069] Dissolve the fluorinated organic ferroelectric polymer in chloroform to form a 10% mass fraction solution, and spin-coat it on a silicon substrate at a speed of 2000 rpm with a spin coater. Immediately after spin-coating, put it into the humidity control box, maintain a saturated solvent vapor concentration of 60% and a temperature of 50 °C, and slowly evaporate the solvent for 1 hour.

[0070] III. Performance Testing and Synergistic Comparison

[0071] Film flatness and crystallinity: The roughness of the film measured by a profilometer is 5 nm, while that of the film prepared by the traditional spin-coating method reaches 20 nm; the light scattering instrument shows that the crystallinity of this film increases by 30%. Solvent evaporation-induced self-assembly significantly improves the film quality.

[0072] Ferroelectric properties: Tested with an in-situ ferroelectric property monitor, the polarization intensity retention rate of this film is 95% after 100 polarization reversals, while that of the traditional film is only 80%, proving that the new method stabilizes the ferroelectric properties.

[0073] Example 6: Preparation of Small-Molecule Films by Modified Langmuir-Blodgett Technique

[0074] I. Experimental Preparation

[0075] Raw materials: Small molecule organic ferroelectrics synthesized in Example 2, pure water (as the subphase).

[0076] Instruments: Langmuir trough, surface pressure sensor, ultraviolet-visible spectrometer, ferroelectric analyzer.

[0077] II. Film preparation

[0078] After dissolving the small molecule organic ferroelectrics in chloroform, it was slowly dropped onto the surface of the subphase. The temperature of the subphase was controlled at 20 °C, monitored by a surface pressure sensor, and the surface pressure was adjusted to 25 mN / m. By the method of multi-layer accumulation, one layer was deposited each time by lifting, and a total of 10 layers were deposited.

[0079] III. Performance testing and synergy comparison

[0080] Film uniformity and orientation: The absorption peak of the ultraviolet-visible spectrometer is narrow and symmetric, indicating that the film thickness is uniform; the ferroelectric analyzer shows that compared with the traditional drop-coating method, the coercive field stability of this film is increased by 20%, and the more consistent molecular orientation improves the ferroelectric performance.

[0081] Application potential: The prepared film is used for simple capacitance testing, and the capacitance value fluctuation < 5%, showing the potential for application in high-precision electronic devices, far exceeding the capacitance fluctuation range of traditional prepared films.

Claims

1. A novel non-volatile organic ferroelectric semiconductor storage material, characterized in that: It includes a modified polymer based on polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE), wherein the polymer main chain has a nitrogen-containing heterocyclic side chain, the side chain length is 3-6 carbon chain units, one side chain is connected for every 10-15 main chain units, and the fluorine element accounts for 40%-50% of the total mass of the polymer; it also includes a D-π-A type small molecule organic ferroelectric, wherein the electron donating group is carbazole, and the dicyanovinyl electron withdrawing group is connected through a conjugated π bridge containing 2-3 aromatic rings.

2. The novel nonvolatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: The nitrogen-containing heterocyclic side chain is selected from pyridyl and pyrazolyl.

3. A synthesis process of the novel non-volatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: The fluorine-containing organic ferroelectric polymer is synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization, using a phosphorus-containing thioester chain transfer agent, the ratio of chain transfer agent to initiator is 1:2-1:3, and the polymerization reaction temperature is 60-80°C; the small molecule organic ferroelectric is synthesized by solution condensation reaction, the solvent system is a mixture of dimethylformamide (DMF) and toluene in a ratio of 2:1-3:1, the reaction is first initiated at 0-10°C, and then the temperature is raised to 40-60°C for reaction for 10-15 hours.

4. The synthesis process according to claim 3, characterized in that: The molecular weight distribution index (PDI) of the fluorine-containing organic ferroelectric polymer synthesized by this process is 1.2-1.

5.

5. A method for doping and adding the novel non-volatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: The imidazole ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide salt (BMIMNTf2) is doped into the fluorine-containing organic ferroelectric polymer system, and the doping amount accounts for 5%-15% of the polymer mass; barium titanate (BaTiO3) nanoparticles with a particle size of 20-50nm are added to the small molecule organic ferroelectric, and the added amount accounts for 1%-5% of the small molecule mass.

6. A thin film preparation process of the novel non-volatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: Fluorine-containing organic ferroelectric polymer films are prepared by solvent evaporation-induced self-assembly, where the polymer solution is spin-coated on a substrate and the solvent is slowly evaporated in an environment with a saturated solvent vapor concentration of 50%-80% and a evaporation temperature of 40-60°C. Small molecule organic ferroelectric films are prepared by a modified Langmuir-Blodgett (LB) technique, where the subphase temperature is controlled at 15-25°C and the surface pressure is 20-30mN / m, and the film is formed by a multilayer accumulation method.

7. A system for monitoring and controlling the performance of the novel non-volatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: It includes an in-situ polarization-electric field (PE) loop and capacitance-voltage (CV) characteristic joint test system, which is used to track the key performance indicators of the material such as polarization strength, coercive field, capacitance, etc. in real time. When the polarization strength drops by more than 5% or the coercive field changes by more than 8%, it automatically adjusts the subsequent process parameters. It also includes a scanning electron microscope (SEM) and a transmission electron microscope (TEM) combined equipment to observe the microstructure of the material and optimize the preparation process immediately when an abnormality is found.

8. A flexible memory chip using the novel non-volatile organic ferroelectric semiconductor memory material according to claim 1, characterized in that: The organic ferroelectric semiconductor storage material is encapsulated by a flexible polymer, and the high polarization retention ability of the material is utilized to realize a bendable and wearable storage function.

9. An Internet of Things sensor data storage module using the novel non-volatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: Taking advantage of the low power consumption and non-volatility of the material, the collected data is stored locally at the sensor node to reduce the frequency of data transmission.

10. A method for improving the performance of the novel non-volatile organic ferroelectric semiconductor storage material according to claim 1, characterized in that: During the synthesis, 5%-10% of organic additives containing ethylene glycol are added to the total raw material mass to improve the low-temperature toughness of the material and ensure that the ferroelectric performance degradation in a low temperature environment of -30°C is less than 15%; 0.5%-1% of organic small molecules containing disulfide bonds are incorporated into the material mass. When microcracks appear in the material, the disulfide bonds are broken and reconnected under heat or light stimulation to repair the microcracks; based on the microelectromechanical system (MEMS) process, the mold and process parameters are precisely controlled to achieve customized production of micro devices.