A bismuth ferrite film material, a preparation method and application thereof

Abstract

This invention relates to electronic material development and thin film material preparation technology, specifically to a bismuth ferrite film material, its preparation method, and its applications. The preparation method includes: sequentially magnetron sputtering a bottom electrode, a bismuth ferrite film, and a top electrode onto a silicon substrate surface from bottom to top; wherein the bottom and top electrodes are made of inert metals; the gas atmosphere for magnetron sputtering the bottom electrode is a mixture of argon and oxygen, and the magnetron sputtering temperature is 200–400°C; the gas atmosphere for magnetron sputtering the bismuth ferrite film is a mixture of argon and oxygen, and the magnetron sputtering temperature is 300–500°C; the gas atmosphere for magnetron sputtering the top electrode is argon, and the magnetron sputtering temperature is 25–150°C. The bismuth ferrite film material provided by this invention, by adjusting the gas atmosphere during bottom electrode sputtering, changes the growth orientation of the bismuth ferrite material, thereby improving the overall piezoelectric properties of the bismuth ferrite film material. It eliminates the need for a buffer layer, doping with any elements, or high-temperature annealing, making the preparation method simpler.

Description

Technical Field

[0001] This invention relates to electronic material development and thin film material preparation technology, specifically to a bismuth ferrite film material and its preparation method and application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance 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] Piezoelectric materials are crystalline materials that exhibit a voltage between their two ends when subjected to pressure. Utilizing the properties of piezoelectric materials, the conversion between mechanical vibration (sound waves) and alternating current can be achieved. Therefore, piezoelectric materials are widely used in transducers, sensors, ultrasonic imaging, monitors, and collision avoidance warning functions for new energy vehicles.

[0004] Currently, the piezoelectric materials used in large-scale industrial applications are mainly lead zirconate titanate-based ferroelectric and piezoelectric materials. However, due to their high content of highly toxic lead, they pose significant challenges to the environment and human health. Therefore, the development and research of environmentally friendly lead-free piezoelectric materials has become a focus. Bismuth ferrite materials have a simple composition, contain no toxic elements, and possess high Curie temperatures and excellent magnetoelectric coupling effects, making them highly promising for applications in sensors, information storage, spintronic devices, and microelectromechanical systems (MEMS). Bismuth ferrite films are considered a strong alternative to mainstream lead zirconate titanate-based piezoelectric materials due to their high polarization intensity and excellent piezoelectric properties. However, ordinary bismuth ferrite films suffer from significant piezoelectric performance degradation due to large leakage current and high heat treatment temperatures (typically above 500°C), which also poses a significant challenge to their compatibility with large-scale integrated circuits. To improve the piezoelectric properties of bismuth ferrite films, researchers typically introduce buffer layers during film preparation, perform multi-element doping modifications, or undergo high-temperature annealing. However, these improvement methods are overly complex, making the large-scale industrial application of bismuth ferrite films a major challenge. Summary of the Invention

[0005] To overcome the above problems, this invention provides a bismuth ferrite film material, its preparation method, and its application. The bismuth ferrite film material provided by this invention improves the overall piezoelectric properties of the bismuth ferrite film material by adjusting the gas atmosphere during sputtering of the bottom electrode, thereby altering the growth orientation of the bismuth ferrite material. This eliminates the need for a buffer layer, doping with any elements, or high-temperature annealing, making the preparation method simpler.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a bismuth ferrite film material, comprising: sequentially magnetron sputtering a bottom electrode, a bismuth ferrite film, and a top electrode on a silicon substrate surface from bottom to top;

[0008] The bottom electrode and the top electrode are made of inert metal.

[0009] The gas atmosphere of the magnetron sputtering bottom electrode is a mixture of argon and oxygen, and the magnetron sputtering temperature is 200-400℃.

[0010] The gas atmosphere for magnetron sputtering of bismuth ferrite films is a mixture of argon and oxygen, and the magnetron sputtering temperature is 300–500 °C.

[0011] The gas atmosphere of the top electrode of the magnetron sputtering is argon, and the temperature of the magnetron sputtering is 25-150℃.

[0012] In a second aspect, the present invention provides a bismuth ferrite film material prepared by the above-described preparation method.

[0013] A third aspect of the present invention provides the application of the above-described bismuth ferrite piezoelectric film material in sensors, transducers, drivers, resonators, or filters.

[0014] The beneficial effects of this invention are as follows:

[0015] (1) The bismuth ferrite film material provided by the present invention changes the growth orientation of the bismuth ferrite material by adjusting the gas atmosphere when sputtering the bottom electrode, thereby improving the piezoelectric properties of the overall bismuth ferrite film material. It does not require the introduction of a buffer layer, doping with any element or high-temperature annealing, making the preparation method simpler. All the raw materials required are commercially available, and the cost is low, making it easy to promote industrialization and large-scale application.

[0016] (2) The bismuth ferrite film material provided by the present invention is prepared at a temperature not higher than 500°C and does not require high-temperature annealing treatment. This effectively suppresses the volatilization of bismuth element and the change of chemical valence state of iron element in the bismuth ferrite film caused by high-temperature heat treatment, reduces the leakage current of piezoelectric film material, and is conducive to the integration and industrial application of semiconductor devices.

[0017] (3) The radio frequency magnetron sputtering technology used in this invention is a physical vapor deposition technology. This technology is compatible with current semiconductor microelectronic integration processes and is particularly suitable for preparing large-size, high-quality, uniform and dense film materials. Attached Figure Description

[0018] 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.

[0019] Figure 1The image shown is a scanning electron microscope image after sputtering deposition of a bismuth ferrite film in step (3) of Example 1 of the present invention. The inset is an elemental energy spectrum of the silicon-based bismuth ferrite film.

[0020] Figure 2 This is a cross-sectional scanning electron microscope image of the material after sputtering and depositing a bismuth ferrite film in step (3) of Example 1 of the present invention;

[0021] Figure 3 The images show the XRD patterns of the bismuth ferrite film materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention.

[0022] Figure 4 The figure shows the tip displacement and transverse piezoelectric coefficient of the bismuth ferrite film material prepared in Example 1 of the present invention. The inset in the figure is a schematic diagram of the transverse piezoelectric testing device and a physical picture of the piezoelectric cantilever beam.

[0023] Figure 5 The figures show the hysteresis loop and polarization reversal current curves of the bismuth ferrite film material prepared in Example 1 of this invention. Detailed Implementation

[0024] 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 in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] A first typical embodiment of the present invention provides a method for preparing a bismuth ferrite film material, comprising: sequentially magnetron sputtering a bottom electrode, a bismuth ferrite film, and a top electrode on a silicon substrate surface from bottom to top;

[0027] The bottom electrode and the top electrode are made of inert metal.

[0028] The gas atmosphere of the magnetron sputtering bottom electrode is a mixture of argon and oxygen, and the magnetron sputtering temperature is 200-400℃.

[0029] The gas atmosphere for magnetron sputtering of bismuth ferrite films is a mixture of argon and oxygen, and the magnetron sputtering temperature is 300–500 °C.

[0030] The gas atmosphere of the top electrode of the magnetron sputtering is argon, and the temperature of the magnetron sputtering is 25-150℃.

[0031] In one or more embodiments, the thickness of the bottom electrode is 200–800 nm; the thickness of the top electrode is 30–150 nm; and the thickness of the bismuth ferrite film is 1.0–2.0 μm.

[0032] In one or more embodiments, the inert metal includes gold, silver, and platinum, preferably platinum.

[0033] In one or more embodiments, the gas atmosphere of the magnetron sputtering bottom electrode is a mixture of argon and oxygen, wherein the argon gas flow rate is 30-80 sccm, the oxygen gas flow rate is 5-25 sccm, and the gas pressure is 0.1-1.2 Pa.

[0034] In one or more embodiments, the magnetron sputtering power of the magnetron sputtering bottom electrode is 40–70 W, and the deposition time is 5–30 min.

[0035] In one or more embodiments, the gas atmosphere for magnetron sputtering bismuth ferrite film is a mixture of argon and oxygen, wherein the argon gas flow rate is 30-100 sccm, the oxygen gas flow rate is 5-25 sccm, and the gas pressure is 0.1-1.5 Pa.

[0036] In one or more embodiments, the magnetron sputtering power of the bismuth ferrite film is 60-150W, and the deposition time is 3-5h.

[0037] In one or more embodiments, after magnetron sputtering of the bismuth ferrite film, the film is cooled down. The cooling atmosphere is oxygen, with an oxygen flow rate controlled at 15–60 sccm and a pressure controlled at 0.5–10 Pa. The film is cooled to below 150°C at a cooling rate of 3–10°C / min.

[0038] In one or more embodiments, the gas atmosphere of the magnetron sputtering top electrode is argon, the argon flow rate is controlled at 20-60 sccm, and the sputtering pressure is controlled at 0.1-1 Pa.

[0039] In one or more embodiments, the sputtering power of the magnetron sputtering top electrode is 30–100 W, and the deposition time is 30–120 s.

[0040] A second typical embodiment of the present invention provides a bismuth ferrite film material prepared by the above preparation method.

[0041] A third typical embodiment of the present invention provides the application of the above-mentioned bismuth ferrite piezoelectric film material in sensors, transducers, drivers, resonators or filters.

[0042] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0043] Example 1: Preparation of bismuth ferrite film material

[0044] (1) Processing of silicon substrate

[0045] Semiconductor single crystal silicon wafers were used as substrates. They were ultrasonically cleaned with anhydrous ethanol, rinsed with deionized water, dried with high-purity nitrogen, and then placed in the sample tray of the magnetron sputtering chamber.

[0046] Vacuuming: Sequentially start the mechanical pump and molecular pump of the magnetron sputtering instrument to evacuate the chamber to a pressure of 2 × 10⁻⁶. -4 Pa, to ensure the uniformity and density of the bismuth ferrite film material;

[0047] Gas introduction: Introduce argon gas into the chamber at a flow rate of 40 sccm and adjust the chamber pressure to 2.5 Pa;

[0048] Heating: The silicon substrate is heated to 300°C at a rate of 5°C / min.

[0049] (2) Preparation of the bottom electrode

[0050] After the silicon substrate is heated to 300°C, a mixture of argon and oxygen gas is introduced into the chamber. The argon flow rate is adjusted to 40 sccm, the oxygen flow rate is adjusted to 10 sccm, and the chamber pressure is reduced to 0.3 Pa. Using titanium and platinum as sputtering targets, thin layers of titanium and platinum are deposited sequentially on the silicon substrate. The sputtering power is 55 W, and the deposition times are 5 min and 15 min, respectively. The platinum thin layer serves as the bottom electrode, and the titanium thin layer is used to enhance the adhesion between the silicon substrate and the platinum bottom electrode layer.

[0051] (3) Preparation of bismuth ferrite film

[0052] Bismuth ferrite oxide ceramic with 5% mol excess bismuth (chemical composition: Bi) 1.05 FeO3) was used as the sputtering target. In the sputtering atmosphere of step (2), the sputtering power was adjusted to 100W and the deposition temperature was increased to 500℃. Bismuth ferrite film was sputtered and deposited on the platinum bottom electrode. The sputtering time was controlled to be 4h. After the sputtering deposition was completed, the chamber atmosphere was adjusted to oxygen with a flow rate of 40sccm and the chamber pressure was adjusted to 2.5Pa. The temperature was then reduced to below 150℃ at a rate of 5℃ / min.

[0053] (4) Preparation of the top electrode

[0054] A thin layer of platinum was sputtered onto the surface of the bismuth ferrite film obtained in step (3) above as the top electrode. The sputtering atmosphere was argon with a flow rate of 40 sccm. The sputtering pressure was adjusted to 0.3 Pa, the sputtering power was 55 W, and the deposition time was 60 s. The sample was taken out after sputtering was completed.

[0055] The bismuth ferrite film material prepared in this embodiment was characterized. Figure 1 The images shown are scanning electron microscope images and elemental energy dispersive spectroscopy (EDS) diagrams after sputtering and depositing the bismuth ferrite film in step (3). It can be seen that the film material has a smooth surface, uniform and dense grains, and the atomic ratio of Bi:Fe:O is close to 1:1:3, which is consistent with the stoichiometric ratio of bismuth ferrite. Figure 2 The image shows a cross-sectional scanning electron microscope image of the material after sputtering and depositing the bismuth ferrite film in step (3). It can be seen that the thickness of the platinum layer on the bottom electrode is 0.71 μm and the thickness of the bismuth ferrite film is 1.2 μm.

[0056] Example 2

[0057] The difference between this embodiment and embodiment 1 is that in step (1), the silicon substrate is heated to 250°C, 350°C, or 400°C. Other steps and process parameters are the same as in embodiment 1.

[0058] Example 3

[0059] The difference between this embodiment and embodiment 1 is that the deposition time of the platinum bottom electrode layer in step (2) is controlled to be 10 min, 20 min, or 25 min. Other steps and process parameters are the same as in embodiment 1.

[0060] Example 4

[0061] The difference between this embodiment and Embodiment 1 is that the chemical composition of the bismuth ferrite oxide ceramic sputtering target in step (3) is Bi. 1.08 FeO3 or Bi 1.1 FeO3, other steps and process parameters are the same as in Example 1.

[0062] Example 5

[0063] The difference between this embodiment and embodiment 1 is that the sputtering power of the bismuth ferrite film in step (3) is 84W, while the other steps and process parameters are the same as in embodiment 1.

[0064] Example 6

[0065] The difference between this embodiment and embodiment 1 is that the sputtering deposition temperature of the bismuth ferrite film in step (3) is 400℃ or 450℃, while the other steps and process parameters are the same as in embodiment 1.

[0066] Example 7

[0067] The difference between this embodiment and embodiment 1 is that the bismuth ferrite film sputtering deposition time in step (3) is 2h or 2.5h or 3h or 3.5h or 4.5h or 5h, while the other steps and process parameters are the same as in embodiment 1.

[0068] Example 8

[0069] The difference between this embodiment and embodiment 1 is that the chamber pressure is 5 Pa or 7.5 Pa during cooling in step (3), while the other steps and process parameters are the same as in embodiment 1.

[0070] Example 9

[0071] The difference between this embodiment and Embodiment 1 is that the deposition time of the top electrode platinum thin layer in step (4) is 30s, 90s, or 120s. The other steps and process parameters are the same as in Embodiment 1.

[0072] Comparative Example 1

[0073] Compared with Example 1, in step (2), the gas atmosphere for preparing the bottom electrode is argon, and the other steps and process parameters are the same as in Example 1.

[0074] Comparative Example 2

[0075] Compared with Example 1, this comparative example adds the preparation of a buffer layer between steps (2) and (3). Lanthanum nickelate oxide ceramic is used as the sputtering target, and the buffer layer is deposited by radio frequency magnetron sputtering. The sputtering atmosphere is argon and oxygen, with the argon flow rate controlled at 60 sccm and the oxygen flow rate controlled at 15 sccm. The sputtering pressure is 1.2 Pa, the sputtering power is 100 W, and the lanthanum nickelate layer thickness is 150 nm.

[0076] Figure 3 The XRD patterns of the bismuth ferrite film materials prepared in Example 1, Comparative Example 1, and Comparative Example 2 are shown below. Figure 3 As can be seen from the XRD patterns, the bismuth ferrite film material prepared in Example 1 is well crystallized, exhibiting a randomly oriented polycrystalline state without any impurities. Compared with the XRD patterns of Comparative Examples 1 and 2, it can be seen that the grain growth orientation of the bismuth ferrite film material in Example 1 has changed. Compared with Comparative Example 1, the (110) oriented grains in Example 1 are reduced, while the (100) oriented grain content is increased; compared with Comparative Example 2, the (100) oriented grains in Example 1 are significantly reduced, while the (110) oriented grain content is significantly increased. This indicates that the (100) and (110) oriented grains in Example 1 coexist, while Comparative Examples 1 and 2 almost only exhibit one growth orientation.

[0077] Performance tests showed that the bismuth ferrite piezoelectric film materials prepared in Examples 1-9 have excellent properties. Figure 4The tip displacement of the bismuth ferrite film material prepared in Example 1 and the calculated transverse piezoelectric coefficient are given. The prepared bismuth ferrite film exhibits a large tip displacement that increases linearly with the applied voltage. The calculated transverse piezoelectric coefficient e 31,f It is 2.4–2.6 C / m 2 This demonstrates excellent transverse piezoelectric properties. The transverse piezoelectric coefficient e of the bismuth ferrite film prepared in Comparative Example 1 is... 31,f It is 0.65–0.72 C / m 2 The transverse piezoelectric coefficient e of the bismuth ferrite film prepared in Comparative Example 2 31,f It is 2.7–2.9 C / m 2 Therefore, compared with Comparative Example 1, the lateral piezoelectric properties of the bismuth ferrite film prepared in this embodiment are significantly improved; compared with Comparative Example 2, which has a buffer layer, the lateral piezoelectric coefficient of the bismuth ferrite film material prepared by this invention is not much different, but the preparation method of this invention is simpler.

[0078] Figure 5 The bismuth ferrite film material prepared in Example 1 exhibits a large polarization intensity (>100 C / cm). 2 It exhibits high breakdown voltage (≥150V) and its polarization current curve shows two distinct reversal current peaks. The polarization intensity (~80C / cm) of the bismuth ferrite film material prepared in Comparative Example 2 is also shown. 2 Compared to other methods, the bismuth ferrite film material prepared by this invention has a higher polarization intensity (~110 C / cm). 2 This invention enhances the content of (110) oriented grains in the bismuth ferrite film by adjusting the sputtering atmosphere of the platinum metal bottom electrode.

[0079] 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 method for preparing a bismuth ferrite film material, characterized in that, include: A bottom electrode, a bismuth ferrite film, and a top electrode are sequentially magnetron sputtered onto the surface of a silicon substrate from bottom to top. The bottom electrode and the top electrode are made of inert metal. The gas atmosphere of the magnetron sputtering bottom electrode is a mixture of argon and oxygen, and the magnetron sputtering temperature is 200~400℃; The gas atmosphere for magnetron sputtering of bismuth ferrite films is a mixture of argon and oxygen, and the magnetron sputtering temperature is 300~500℃. The gas atmosphere of the top electrode of the magnetron sputtering is argon, and the temperature of the magnetron sputtering is 25~150 ℃; When the magnetron sputtering bottom electrode is performed, the argon gas flow rate is 30~80 sccm, the oxygen gas flow rate is 5~25 sccm, and the gas pressure is 0.1~1.2 Pa. The inert metal is platinum.

2. The preparation method according to claim 1, characterized in that, The thickness of the bottom electrode is 200~800 nm; the thickness of the top electrode is 30~150 nm; and the thickness of the bismuth ferrite film is 1.0~2.0 μm.

3. The preparation method according to claim 1, characterized in that... The magnetron sputtering power of the bottom electrode is 40~70W, and the deposition time is 5~30 min.

4. The preparation method according to claim 1, characterized in that, When magnetron sputtering bismuth ferrite films, the argon gas flow rate is 30~100 sccm, the oxygen gas flow rate is 5~25 sccm, and the gas pressure is 0.1~1.5 Pa; Alternatively, the magnetron sputtering power of the bismuth ferrite film is 60~150 W, and the deposition time is 3~5 h.

5. The preparation method according to claim 1, characterized in that, After magnetron sputtering of the bismuth ferrite film, the film is cooled down. The cooling atmosphere is oxygen, with an oxygen flow rate controlled at 15~60 sccm and a gas pressure controlled at 0.5~10 Pa. The film is cooled down to below 150 ℃ at a cooling rate of 3~10 ℃ / min.

6. The preparation method according to claim 1, characterized in that, When sputtering the top electrode with magnetron sputtering, the argon gas flow rate is controlled at 20~60 sccm and the sputtering gas pressure is controlled at 0.1~1 Pa.

7. The preparation method according to claim 1, characterized in that, The sputtering power of the magnetron sputtering top electrode is 30~100W, and the deposition time is 30~120 s.

8. The bismuth ferrite film material prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the bismuth ferrite piezoelectric film material of claim 8 in sensors, transducers, drivers, resonators or filters.

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