A "sandwich" type artificial antiferroelectric film material and a method for preparing the same

Abstract

The application relates to a'sandwich' type artificial antiferroelectric film material and a preparation method thereof. The'sandwich' type artificial antiferroelectric film material comprises a substrate, a bottom electrode, a buffer layer, a'sandwich' dielectric layer and a top electrode, the substrate is a silicon single crystal substrate, the bottom electrode is an inert metal electrode, the buffer layer is a perovskite oxide, the'sandwich' dielectric layer is a ferroelectric thin film, and the top electrode is a high-conductivity metal point electrode. The'sandwich' type artificial antiferroelectric material provided by the application has a high breakdown field (>=2000 kV / cm) and excellent fatigue resistance (can withstand >=10 9 polarization cycle cycles), and the material system has a low crystallization temperature (<=500 DEG C), which is beneficial to the integrated application of microelectronic devices. The application can provide a new way for developing a novel antiferroelectric material system, and can greatly widen the research scope of performance regulation of antiferroelectric materials.

Description

Technical Field

[0001] This invention relates to the field of antiferroelectric materials technology, specifically to a "sandwich" type artificial antiferroelectric film material and its preparation method. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Antiferroelectrics, as a class of extremely important functional dielectric materials, exhibit unique double hysteresis loops and near-zero remanent polarization due to their special cellular structure. Furthermore, under external field excitation (electric field, temperature, and stress), they display rich antiferroelectric phase transitions and dramatic changes in physical parameters such as polarization intensity, cell volume, charge, and specific heat. These, coupled with significant changes in polarization intensity, deformation, current, and temperature, enable the conversion between mechanical energy, electrical energy, and thermal energy, thus exhibiting excellent antiferroelectric, dielectric, piezoelectric, pyroelectric, and electrocaloric properties. The multifaceted properties of antiferroelectric materials lead to their wide application in numerous fields, including high-density energy storage capacitors, large-displacement actuators, transducers, sensors, pyroelectric infrared detectors, and solid-state electrocaloric cooling. Because these functional devices are primarily used in important fields such as medicine, electronic information, and the military, they have sparked tremendous research interest.

[0004] Lead zirconate (PbZrO3), sodium niobate (NaNbO3), silver niobate (AgNbO3), and sodium bismuth titanate (NaNbO3) 0.5 Bi 0.5 Antiferroelectric materials, with TiO3 as a typical example, are the most representative in both academic research and industrial applications. Although these antiferroelectric materials have their unique advantages, they also have some limitations that are difficult to overcome: (1) Most antiferroelectrics rely on toxic elements (such as Pb) and some noble metal elements (such as Ag and Nb), which is not conducive to large-scale production and application; (2) A-site cations are all volatile, and impurities and defects are easily generated, resulting in high leakage loss and low withstand voltage; (3) The switching field is high, the residual polarization and hysteresis are large, and the fatigue resistance and cycle stability are poor; (4) The double hysteresis loop characteristics of lead-free antiferroelectric materials are not obvious at room temperature. These drawbacks seriously hinder their widespread application in energy storage, sensing, actuation and refrigeration. Meanwhile, the rapid development of science and technology such as electronics, information and control has made the requirements for material performance increasingly stringent, and traditional single antiferroelectric materials can no longer meet their practical application needs. Summary of the Invention

[0005] This invention aims to solve the numerous problems faced by antiferroelectric materials based on lead zirconate, silver niobate, sodium niobate, and sodium bismuth titanate. It provides a simple method for designing and preparing low crystallization temperature, breakdown resistant, and fatigue resistant "sandwich" type antiferroelectric film materials without any antiferroelectric material components, using only a large variety of low-cost elements. This opens up new avenues for the development of novel antiferroelectric material systems and enriches and broadens the scope of antiferroelectric material research.

[0006] This invention is achieved using the following technical solution:

[0007] In a first aspect, the present invention provides a low crystallization temperature, breakdown resistant, and fatigue-resistant "sandwich" type antiferroelectric film material, wherein the "sandwich" type antiferroelectric film material comprises a substrate, a bottom electrode, a buffer layer, a "sandwich" dielectric layer, and a top electrode; wherein the substrate is a single crystal of semiconductor silicon; the bottom electrode is a thin layer of inert metal platinum; the buffer layer is a perovskite-type oxide lanthanum nickelate, strontium ruthenate, lanthanum strontium manganate, or lanthanum strontium cobaltate; in the "sandwich" dielectric layer, the upper and lower layers are barium titanate, and the middle layer is selected from one of bismuth ferrite, lead zirconate titanate, and potassium sodium niobate; and the top electrode is a platinum or gold dot electrode with high conductivity.

[0008] The thicknesses of the bottom electrode layer and the buffer layer are 100-600nm and 25-300nm, respectively; the diameter of the top electrode is 50μm-1mm; the thickness of the "sandwich" dielectric layer is 60nm-3μm, wherein the thickness of the upper or lower thin film is 5nm-1.25μm, and the thickness of the middle thin film is 10nm-2.5μm; the crystallization temperature is not higher than 500℃.

[0009] Furthermore, the bottom electrode is coated with a titanium layer, which increases the adhesion between the substrate and the platinum electrode.

[0010] The low crystallization temperature, breakdown resistant, and fatigue-resistant "sandwich" type antiferroelectric film material is prepared by radio frequency magnetron sputtering technology. First, a bottom electrode is deposited on the substrate, then a sputtering buffer layer and a "sandwich" dielectric layer are deposited sequentially on the bottom electrode, and finally a top electrode is deposited.

[0011] Secondly, the present invention provides a method for preparing the above-mentioned "sandwich" type antiferroelectric film material, specifically including the following steps:

[0012] (1) Using semiconductor silicon as the substrate, in an inert argon atmosphere, and using inert metal platinum as the sputtering target, a platinum bottom electrode layer is deposited on the silicon substrate using radio frequency magnetron sputtering technology.

[0013] (2) Based on step (1), oxygen is introduced to make it a mixed gas atmosphere of argon and oxygen. Perovskite oxide lanthanum nickelate, strontium ruthenate, lanthanum strontium manganate, or lanthanum strontium cobalt oxide ceramics are used as sputtering targets. A sputtering buffer layer is deposited on the platinum electrode layer using radio frequency magnetron sputtering technology.

[0014] (3) Using barium titanate, bismuth ferrite, lead zirconate titanate, and potassium sodium niobate oxide ceramics as sputtering targets, in a mixed gas atmosphere of argon and oxygen, radio frequency magnetron sputtering technology is used to sequentially sputter and deposit the lower, middle and upper layers of the "sandwich" on the buffer layer from bottom to top.

[0015] (4) The "sandwich" membrane material obtained in step (3) is subjected to heat preservation treatment in an oxygen atmosphere; after the heat preservation is completed, it is cooled to room temperature.

[0016] (5) Using gold or platinum sheets as the target material, the top electrode is deposited on the "sandwich" film material by DC sputtering through a mask.

[0017] Furthermore, in step (1), the substrate is heated to 200-500°C under an inert argon atmosphere, wherein the gas flow rate of the inert atmosphere is 20-60 sccm and the gas pressure is 0.1-5 Pa.

[0018] Furthermore, in step (1), the sputtering pressure is 0.1-1 Pa, the sputtering power is 30-80 W, and the deposition time is controlled at 10-30 min.

[0019] Furthermore, in step (1), before depositing the platinum bottom electrode layer, titanium metal is used as the sputtering target, and a sputtered titanium layer is deposited on the silicon substrate using radio frequency magnetron sputtering technology, with a deposition time of 4-6 minutes.

[0020] Furthermore, in step (2), the argon gas flow rate is controlled at 20-100 sccm, the oxygen gas flow rate is controlled at 5-25 sccm, the gas pressure is controlled at 0.1-3 Pa, the sputtering power is 60-150 W, and the deposition time is controlled at 10-30 min.

[0021] Furthermore, in step (3), under a mixed gas atmosphere of argon and oxygen, radio frequency magnetron sputtering technology is used to sputter and deposit barium titanate "sandwich" lower layer, bismuth ferrite or lead zirconate titanate or potassium sodium niobate "sandwich" middle layer, and barium titanate "sandwich" upper layer from bottom to top on the buffer layer obtained in step (2). The argon flow rate is controlled at 20-100 sccm, the oxygen flow rate is controlled at 5-25 sccm, the gas pressure is controlled at 1-3 Pa, the sputtering power is 60-150 W, and the deposition temperature is 200-500℃.

[0022] Furthermore, in step (4), during heat preservation, the oxygen flow rate is controlled at 10-50 sccm, the gas pressure is controlled at 0.5-10 Pa, and the heat preservation time is 5-10 minutes; after the heat preservation is completed, the temperature is cooled to room temperature at a cooling rate of 3-10℃ / min.

[0023] Furthermore, in step (5), the discharge current is 5-10mA, the deposition time is 3-8min, and the top electrode diameter is 50μm-1mm.

[0024] To prepare a "sandwich" type antiferroelectric film material with optimal performance, a method was proposed that keeps the total sputtering deposition time constant and adjusts the thickness ratio of each layer in the "sandwich" to obtain a "sandwich" type antiferroelectric film material with optimized performance.

[0025] The "sandwich" type antiferroelectric film material of the present invention has great application potential in the fields of electrical energy storage, multi-state storage and sensing microelectronic devices due to its low crystallization temperature, breakdown resistance and fatigue resistance.

[0026] The beneficial effects of this invention are:

[0027] (1) This invention does not contain any antiferroelectric material components. It can achieve the antiferroelectric properties of materials by constructing a simple "sandwich" film structure using normal ferroelectric materials, which greatly broadens the research scope of antiferroelectric materials.

[0028] (2) The construction method of the present invention is simple, versatile and highly controllable; and the material components can be selected from a wide range.

[0029] (3) The crystallization temperature of the material system in the method provided by this invention is relatively low (350-500℃), which can effectively reduce the volatilization of elements in the system and avoid the generation of defects such as oxygen vacancies. The obtained film material has excellent performance, with a breakdown electric field strength of not less than 2000kV / cm and a polarization cycle that can withstand not less than 10 cycles. 9 Second-rate;

[0030] (4) The present invention uses radio frequency magnetron sputtering technology, and the prepared film material has good uniformity and density. The process flow and equipment operation are simple. All raw materials used are available on the market, with low cost. It is easy to integrate devices and is suitable for industrial promotion and production.

[0031] The method of the present invention will be further described in detail below with reference to the accompanying drawings and exemplary embodiments. Attached Figure Description

[0032] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0033] Figure 1 This is a schematic diagram of the structure of the "sandwich" type antiferroelectric film material system prepared in this invention; wherein, 1-substrate, 2-bottom electrode, 3-buffer layer, 4-barium titanate layer, 5-bismuth ferrite or lead zirconate titanate or potassium sodium niobate layer, 6-top electrode.

[0034] Figure 2 The diagram shows the hysteresis loop of the "sandwich" type antiferroelectric film material prepared in this invention. The upper left inset is the flip current diagram of the film material, and the lower right inset is the capacitance bias diagram of the film material.

[0035] Figure 3 The fatigue cycle diagram is shown for the "sandwich" type antiferroelectric film material prepared in this invention.

[0036] Figure 4 This is a cross-sectional scanning electron microscope image of the "sandwich" type antiferroelectric film prepared in this invention. Detailed Implementation

[0037] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] like Figure 1 As shown, the "sandwich" type antiferroelectric film material system of the present invention includes a substrate 1, a bottom electrode 2, a buffer layer 3, a "sandwich" dielectric layer, and a top electrode 6; wherein, the substrate is a semiconductor silicon single crystal, the bottom electrode is an inert metal platinum thin layer, the buffer layer is a perovskite-type oxide lanthanum nickelate or strontium ruthenate or lanthanum strontium manganate or lanthanum strontium cobaltate, the "sandwich" dielectric layer includes an upper barium titanate layer 4, an intermediate bismuth ferrite or lead zirconate titanate or potassium sodium niobate layer 5 and a lower barium titanate layer 4, and the top electrode is a platinum or gold dot electrode with high conductivity.

[0039] The following examples will provide further illustration.

[0040] Example 1

[0041] A method for preparing a breakdown-resistant and fatigue-resistant "sandwich" type antiferroelectric film material includes the following steps:

[0042] (1) Matrix treatment

[0043] Substrate cleaning and mounting: Semiconductor silicon single crystal is used as the substrate. It is ultrasonically cleaned with anhydrous ethanol, rinsed with deionized water, dried with high-purity nitrogen, and then placed in the sample holder. The sample holder is then placed on the sample rack in the vacuum chamber of the magnetron sputtering instrument.

[0044] Vacuuming: Close the sputtering chamber of the magnetron sputtering system, and turn on the mechanical pump and molecular pump to evacuate the chamber until the pressure reaches 2 × 10⁻⁶. -4 Pa;

[0045] Heating and temperature rise: Before heating and temperature rise, inert argon gas is introduced into the chamber and the argon gas flow rate is adjusted to 39 sccm. At the same time, the chamber pressure is adjusted to 2.5 Pa by adjusting the plate valve, so that the substrate is heated to 300℃ in an argon atmosphere.

[0046] (2) Fabrication of the bottom electrode layer

[0047] Using titanium and platinum as sputtering targets, the chamber pressure was adjusted to 0.3 Pa and the sputtering power to 55 W. A platinum electrode layer with a titanium layer was sequentially deposited on a silicon substrate using radio frequency magnetron sputtering technology. The deposition time was controlled to be 5 min and 15 min, respectively. The titanium layer served as the attachment support layer and the platinum layer served as the bottom electrode layer.

[0048] (3) Preparation of buffer layer

[0049] Heating: Under the conditions of step (2) above, adjust the argon gas flow rate to 39 sccm, and at the same time adjust the plate valve to make the chamber pressure 2.5 Pa, and heat the substrate with the bottom electrode layer deposited in step (2) to 500℃.

[0050] Buffer layer deposition: Using lanthanum nickelate oxide ceramic as the sputtering target, the argon gas flow rate was adjusted to 60 sccm, and then oxygen was introduced into the chamber and the flow rate was adjusted to 15 sccm to make the chamber a uniform argon and oxygen mixed atmosphere. The chamber pressure was then adjusted to 0.3 Pa, and the sputtering power was set to 100 W. The lanthanum nickelate buffer layer was sputtered and deposited on the platinum base electrode layer using radio frequency magnetron sputtering technology, and the deposition time was controlled to 20 min.

[0051] (4) Preparation of the "sandwich" membrane

[0052] Barium titanate lower film preparation: Barium titanate oxide ceramic was used as sputtering target material, sputtering gas atmosphere was the same as in step (3), the chamber pressure was adjusted to 1.4 Pa, sputtering power was set to 100 W, and barium titanate film was sputtered and deposited on the buffer layer using radio frequency magnetron sputtering technology. The sputtering deposition time was 15 min.

[0053] Preparation of the intermediate film of bismuth ferrite layer: Using bismuth ferrite oxide ceramic as sputtering target, the same sputtering deposition process as in step (3) is used to sputter and deposit the intermediate bismuth ferrite layer on the above barium titanate layer. The sputtering deposition time is 30 min.

[0054] Preparation of barium titanate upper film: Using barium titanate oxide ceramic as sputtering target, barium titanate upper film was sputtered on the above bismuth ferrite intermediate film using the same sputtering deposition process as in step (3) for 15 min.

[0055] The thicknesses of the barium titanate lower film, the bismuth ferrite middle film, and the barium titanate upper film in the prepared "sandwich" structure are ~120nm, ~240nm, and ~120nm, respectively.

[0056] Insulated sampling: After the "sandwich" film sputtering deposition is completed, the argon gas flow is turned off, the oxygen gas flow is adjusted to 39 sccm, and the chamber pressure is adjusted to 2.5 Pa, so that the obtained sample is kept at 500℃ for 10 min; after the insulated period, the sample is cooled to room temperature at a cooling rate of 5℃ / min, and then the sample can be taken out.

[0057] (5) Top electrode preparation

[0058] Using gold flakes as the target material and air as the sputtering atmosphere, the sputtering pressure was adjusted to ~10 Pa and the target discharge current was adjusted to ~9 mA. Gold point electrodes were deposited on the surface of the prepared "sandwich" film material by DC sputtering through a mask. The diameter of the point electrodes was 200 μm.

[0059] Example 2

[0060] The difference between this embodiment and Example 1 is that in step (3), the substrate with the deposited bottom electrode layer is heated to 300°C, 350°C, 400°C, or 450°C. Other steps and process parameters are the same as in Example 1.

[0061] Example 3

[0062] The difference between this embodiment and Example 1 is that the buffer layer deposition in step (3) uses strontium ruthenate, lanthanum strontium manganate, or lanthanum strontium cobalt oxide ceramics as sputtering targets, while the other steps and process parameters are the same as in Example 1.

[0063] Example 4

[0064] The difference between this embodiment and Example 1 is that the sputtering deposition time of the buffer layer in step (3) is controlled to be 5 min, 10 min, 15 min, 25 min, or 30 min. Other steps and process parameters are the same as in Example 1.

[0065] Example 5

[0066] The difference between this embodiment and Example 1 is that the sputtering deposition time of the lower barium titanate layer / the middle bismuth ferrite layer / the upper barium titanate layer in the "sandwich" film structure in step (4) is controlled to be 5 / 50 / 5min or 10 / 40 / 10min or 20 / 20 / 20min or 25 / 10 / 25min, respectively. Other steps and process parameters are the same as in Example 1.

[0067] Example 6

[0068] The difference between this embodiment and Example 1 is that the chamber pressure for heat preservation and cooling of the sample in step (4) is adjusted to 0.5 Pa, 5.0 Pa, or 7.5 Pa. Other steps and process parameters are the same as in Example 1.

[0069] Example 7

[0070] The difference between this embodiment and Example 1 is that in step (5), a metal platinum sheet is used as the target material for sputtering and depositing the top electrode. The other steps and process parameters are the same as in Example 1.

[0071] Example 8

[0072] The difference between this embodiment and Example 1 is that the diameter of the point electrode in step (5) is 100μm, 300μm, or 500μm, while the other steps and process parameters are the same as in Example 1.

[0073] Performance tests showed that the "sandwich" type antiferroelectric film materials obtained in Examples 1-8 possess excellent properties. For example... Figure 2 As shown, the "sandwich" type antiferroelectric film material prepared in Example 1 exhibits obvious double hysteresis loops, and the flip current curve and capacitor bias loop have four obvious flip peaks. Its breakdown electric field strength is higher than 2000kV / cm; its fatigue cycle test results are as follows: Figure 3 As shown, compared to the initial state (without polarization pulse cycles), after undergoing 10... 9 The hysteresis loop of the antiferroelectric film remained almost unchanged after the secondary polarization pulse cycle; the cross-section of the fabricated "sandwich" type antiferroelectric film material is as follows: Figure 4 As shown, the thicknesses of the lower barium titanate film, the middle bismuth ferrite film, and the upper barium titanate film in the "sandwich" structure are ~120nm, ~240nm, and ~120nm, respectively.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A "sandwich" type antiferroelectric film material, characterized in that, The "sandwich" type antiferroelectric film material includes a substrate, a bottom electrode, a buffer layer, a "sandwich" dielectric layer, and a top electrode. The substrate is a single crystal of semiconductor silicon, the bottom electrode is a thin layer of inert metal platinum, the buffer layer is a perovskite-type oxide lanthanum nickelate, strontium ruthenate, lanthanum strontium manganate, or lanthanum strontium cobaltate, the "sandwich" dielectric layer is a barium titanate "sandwich" bottom layer, a bismuth ferrite, lead zirconate titanate, or potassium sodium niobate "sandwich" middle layer, a barium titanate "sandwich" top layer, and the top electrode is a platinum or gold dot electrode with high conductivity.

2. The "sandwich" type antiferroelectric film material according to claim 1, characterized in that, The thicknesses of the bottom electrode layer and the buffer layer are 100-600 nm and 25-300 nm, respectively; the diameter of the top electrode is 50 μm-1 mm; the thickness of the "sandwich" dielectric layer is 60 nm-3 μm, wherein the thickness of the upper or lower thin film is 5 nm-1.25 μm, and the thickness of the middle thin film is 10 nm-2.5 μm. Alternatively, the bottom electrode may have a titanium layer attached.

3. The method for preparing the "sandwich" type antiferroelectric film material according to claim 1 or 2, characterized in that, Includes the following steps: (1) Using semiconductor silicon as the substrate, in an inert argon atmosphere, and using inert metal platinum as the sputtering target, a platinum bottom electrode layer is deposited on the silicon substrate by radio frequency magnetron sputtering technology. (2) Based on step (1), oxygen is introduced to make it a mixed gas atmosphere of argon and oxygen. Perovskite oxide lanthanum nickelate, strontium ruthenate, lanthanum strontium manganate, or lanthanum strontium cobalt oxide ceramics are used as sputtering targets. A sputtering buffer layer is deposited on the platinum electrode layer using radio frequency magnetron sputtering technology. (3) Using barium titanate, bismuth ferrite, lead zirconate titanate, and potassium sodium niobate oxide ceramics as sputtering targets, in a mixed gas atmosphere of argon and oxygen, radio frequency magnetron sputtering technology is used to sequentially sputter and deposit the lower, middle and upper layers of a "sandwich" on the buffer layer from bottom to top. (4) The "sandwich" membrane material obtained in step (3) is subjected to heat preservation treatment in an oxygen atmosphere; after the heat preservation is completed, it is cooled to room temperature; (5) Using gold or platinum sheets as the target material, the top electrode is deposited on the "sandwich" film material by DC sputtering through a mask.

4. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (1), the substrate is heated to 200-500 ℃ under an inert argon atmosphere, with a gas flow rate of 20-60 sccm and a gas pressure of 0.1-5 Pa.

5. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (1), the sputtering pressure is 0.1-1 Pa, the sputtering power is 30-80 W, and the deposition time is controlled at 10-30 min; In step (1), before preparing the platinum electrode layer, titanium metal is used as the sputtering target, and a sputtered titanium metal layer is deposited on the silicon substrate using radio frequency magnetron sputtering technology. The deposition time is 4-6 min.

6. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (2), the argon gas flow rate is controlled at 20-100 sccm, the oxygen gas flow rate is controlled at 5-25 sccm, the gas pressure is controlled at 0.1-3Pa, the sputtering power is 60-150 W, and the deposition time is controlled at 10-30 min.

7. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (3), under a mixed gas atmosphere of argon and oxygen, radio frequency magnetron sputtering technology is used to sputter and deposit barium titanate "sandwich" lower layer, bismuth ferrite or lead zirconate titanate or potassium sodium niobate "sandwich" middle layer, and barium titanate "sandwich" upper layer from bottom to top on the buffer layer obtained in step (2).

8. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (3), the argon flow rate is controlled at 20-100 sccm, the oxygen flow rate is controlled at 5-25 sccm, the gas pressure is controlled at 1-3 Pa, the sputtering power is 60-150 W, and the deposition temperature is 200-500 ℃.

9. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (4), during heat preservation, the oxygen flow rate is controlled at 10-50 sccm, the gas pressure is controlled at 0.5-10 Pa, and the heat preservation time is 5-10 min; after heat preservation, the temperature is cooled to room temperature at a cooling rate of 3-10 ℃ / min.

10. The method for preparing the "sandwich" type antiferroelectric film material according to claim 3, characterized in that, In step (5), the discharge current is 5-10 mA, the deposition time is 3-8 min, and the top electrode diameter is 50 μm-1 mm.

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