A method for improving the performance of piezoelectric materials based on ionizing irradiation

Abstract

The present invention discloses a method for improving the performance of piezoelectric materials based on ionization irradiation. The ray irradiation ionizes the piezoelectric materials to improve the ferroelectric performance of the piezoelectric materials. Before irradiation, high-vacuum coating is performed on the piezoelectric materials, which can further improve the ferroelectric performance of the piezoelectric materials. The present invention processes the piezoelectric materials by irradiation with a specific dose, realizing large-scale or ultra-large-scale batch performance improvement and controllable improvement. Compared with the traditional performance improvement methods, there is no need to change the preparation process of the piezoelectric materials. By using a specific dose to irradiate the devices, the costs of improving equipment, production lines, and processes are saved, which is conducive to large-scale promotion.

Description

Technical Field

[0001] The present invention relates to the technical field of piezoelectric material preparation, and particularly relates to a method for improving the performance of piezoelectric materials based on ionization irradiation. Background Art

[0002] With the vigorous development of science and technology, especially the semiconductor industry gradually entering a stage of rapid development, more and more semiconductor devices applicable in various directions have emerged. In recent years, the recognition of semiconductor devices made of piezoelectric materials has gradually increased. Piezoelectric materials have good dielectric, ferroelectric, piezoelectric, pyroelectric and other effects. Therefore, piezoelectric materials are gradually applied to various semiconductor devices. Among them, the piezoelectric effect is mainly found in materials with asymmetric crystal molecule arrangements. Generally speaking, if pressure is applied to a piezoelectric crystal, charges will be generated on some surfaces of the crystal, which is called the piezoelectric effect, as Figure 1 shown. Conversely, due to the displacement of the positive and negative charge centers inside it, it generates deformation vibration, and this effect is called the inverse piezoelectric effect.

[0003] Piezoelectric materials are particularly widely used in life. With the increasing demand for piezoelectric material devices by people, it is particularly important to explore how to improve the performance of piezoelectric material devices.

[0004] The traditional methods for improving the performance of piezoelectric materials mainly start from the preparation process, and the R & D cost is relatively high; there is generally an upper limit to the improvement of the performance of piezoelectric materials by the preparation process. For example, the commonly used lead zirconate titanate piezoelectric material has obtained the optimal ratio of zirconium and titanium elements, and the room for further improvement of the performance by the composition is relatively small; for large-scale preparation, changing the preparation process often affects the subsequent process steps, and it is often difficult to achieve based on reasons such as equipment and cost. Therefore, how to achieve batch processing of piezoelectric materials and further improve the piezoelectric performance without changing the existing preparation, process and other conditions remains to be solved. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for improving the performance of piezoelectric materials based on ionization irradiation. This method directly irradiates the piezoelectric materials, which can not only improve the ferroelectric performance of the piezoelectric materials, but also realize batch large-scale processing and will not change the original production line of the piezoelectric materials.

[0006] The present invention is realized through the following technical solutions:

[0007] A method for improving the performance of piezoelectric materials based on ionization irradiation, wherein the ray irradiation ionizes the piezoelectric materials.

[0008] The applicant found through experiments that:

[0009] Irradiating a piezoelectric material with special grains (preferred orientation grains) to ionize it can improve the ferroelectric properties of the piezoelectric material, including polarization intensity and the like.

[0010] The existing method for improving piezoelectric materials is to improve the production line for preparing piezoelectric materials to enhance their performance. Compared with the existing improvement methods, the present invention directly irradiates the piezoelectric material without the need to adjust the existing production line, saving the costs of equipment, production line, and process improvement. Moreover, the present invention uses irradiation to ionize the piezoelectric material to achieve performance improvement, and the amount of energy improvement can be controlled by adjusting the irradiation dose. That is, according to the performance requirements of the piezoelectric material for its application scenario, by controlling the irradiation dose, a specific irradiation dose can be used to achieve performance improvement of the piezoelectric material to meet the requirements.

[0011] Further, before irradiation, a top electrode is prepared by vacuum coating the piezoelectric material.

[0012] The applicant found through experiments that:

[0013] For a piezoelectric material with preferred orientation grains, first performing high-vacuum coating and then irradiation treatment can significantly improve the ferroelectric properties of the piezoelectric material compared with directly performing irradiation treatment.

[0014] Moreover, for a piezoelectric material with preferred orientation grains, first performing high-vacuum coating can significantly improve the performance of the piezoelectric material compared with irradiating a piezoelectric material with non-preferred orientation grains prepared by high-vacuum coating to form a top electrode and a piezoelectric material with preferred orientation grains prepared by low-vacuum coating to form a top electrode.

[0015] High-vacuum coating refers to a vacuum environment with a vacuum degree of 10 -4 ~10 -6 Pa, and low-vacuum degree refers to a vacuum environment with a vacuum degree of 10 -1 ~10 -3 Pa.

[0016] Further, specific-dose irradiation is adopted. According to the performance requirements of the piezoelectric material for its application scenario, by controlling the irradiation dose, a specific irradiation dose is used to achieve performance improvement of the piezoelectric material to meet the requirements.

[0017] Further, the method for obtaining a specific dose includes the following steps:

[0018] S1. Obtain the original ferroelectric properties of the piezoelectric material;

[0019] S2. Irradiate the piezoelectric material with rays of different doses and test the ferroelectric properties of the piezoelectric material after irradiation with the corresponding doses;

[0020] S3. Calculate the improvement in ferroelectric properties corresponding to different doses based on the original ferroelectric properties tested in step S1 and the irradiated ferroelectric properties obtained in step S2.

[0021] Further, the method also includes the following steps:

[0022] S4. Construct a relationship curve graph between the irradiation dose and the improvement in ferroelectric properties, and obtain a specific dose based on this relationship curve graph.

[0023] The irradiation doses corresponding to the improvements in ferroelectric properties of different piezoelectric materials are different. Therefore, for different piezoelectric materials, before irradiation, by obtaining the relationship between the irradiation dose and the improvement in ferroelectric properties through experiments, the required specific irradiation dose can be accurately found.

[0024] Further, the radiation source used for irradiation includes cobalt-60.

[0025] Specifically, during the decay process of cobalt-60 isotope, gamma rays are emitted. This kind of gamma ray can ionize the piezoelectric material. The irradiated rays are not limited to gamma rays. Theoretically, the energy of the rays is greater than the bandgap size of the piezoelectric material and can ionize the piezoelectric material.

[0026] Further, the piezoelectric material has preferentially oriented grains.

[0027] Further, the piezoelectric material includes lead zirconate titanate-based piezoelectric thin film or sodium potassium niobate-based piezoelectric thin film.

[0028] Further, when the piezoelectric material is a lead zirconate titanate-based piezoelectric thin film, the irradiation dose is 0.5 - 2.0 Mrad.

[0029] Further, the irradiation dose is 1.35 Mrad, and this irradiation dose can achieve the optimal performance improvement.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. The present invention directly irradiates the piezoelectric material, which can not only improve the performance of the piezoelectric material, but also can achieve batch large-scale processing, will not change the original production line of the device, and saves the costs of equipment, production line, and process improvement.

[0032] 2. The present invention first prepares a top electrode by high-vacuum coating on the piezoelectric material and then performs irradiation treatment, which can greatly improve the ferroelectric properties of the piezoelectric material.

[0033] 3. The present invention can achieve large-scale or ultra-large-scale batch performance improvement.

[0034] 4. The post - processing performance improvement achieved by the present invention is higher than that of existing traditional post - processing technologies (such as annealing), and the performance improvement can be controlled.

[0035] 5. The present invention provides a new idea for improving the performance of piezoelectric materials, enabling the performance improvement of piezoelectric materials to have a broader direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not limit the embodiments of the present invention. In the drawings:

[0037] Figure 1 is a schematic diagram of the piezoelectric effect of a piezoelectric material;

[0038] Figure 2 is a process flow chart of the present invention;

[0039] Figure 3 is a typical result diagram of the ferroelectric hysteresis loop at different irradiation doses in Example 1;

[0040] Figure 4 is a relationship curve diagram of the irradiation dose and performance improvement in Example 1;

[0041] Figure 5 is a typical result diagram of the ferroelectric hysteresis loop at different irradiation doses in Example 2;

[0042] Figure 6 is a relationship curve diagram of the irradiation dose and performance improvement in Example 2;

[0043] Figure 7 is a typical result diagram of the ferroelectric hysteresis loop at different irradiation doses in Example 3;

[0044] Figure 8 is a relationship curve diagram of the irradiation dose and performance improvement in Example 3;

[0045] Figure 9 is a typical result diagram of the ferroelectric hysteresis loop at different irradiation doses in Comparative Example 1;

[0046] Figure 10 is a relationship curve diagram of the irradiation dose and performance improvement in Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the embodiments and the drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and do not limit the present invention.

[0048] Example 1:

[0049] As Figure 2As shown in the figure, a method for improving the performance of piezoelectric materials based on ionization irradiation includes the following steps:

[0050] 1), Prepare a top electrode (Pt electrode) with a specified shape from the piezoelectric material using a high-vacuum coating equipment and a mask template;

[0051] 2), Obtain a relationship curve graph between the irradiation dose and the amount of improvement in ferroelectricity:

[0052] S1, Obtain the original ferroelectric performance of the piezoelectric material;

[0053] S2, Irradiate the piezoelectric material with rays of different doses, and test the ferroelectric performance of the piezoelectric material after irradiation with the corresponding doses;

[0054] S3, Based on the original ferroelectric performance tested in step S1 and the ferroelectric performance after irradiation obtained in step S2, calculate the amount of improvement in ferroelectric performance corresponding to different doses;

[0055] S4, Construct a relationship curve graph between the irradiation dose and the amount of improvement in ferroelectric performance, and obtain a specific dose based on this relationship curve graph;

[0056] 3), Irradiate the film coated with high vacuum in step 1) with the specific dose obtained in step S4 to obtain a product with improved performance.

[0057] In this embodiment, a lead zirconate titanate (PZT) piezoelectric film with preferentially oriented grains and an existing bottom electrode (Pt electrode) is used for illustration:

[0058] Test object: A film prepared from a lead zirconate titanate-based piezoelectric film with preferentially oriented grains (a top electrode and a bottom electrode are respectively arranged on both sides of the lead zirconate titanate-based piezoelectric film with preferentially oriented grains).

[0059] Irradiation source: Cobalt-60.

[0060] Equipment for testing electrical characterization parameters: Ferroelectric tester.

[0061] The irradiation dose parameters are shown in Table 1:

[0062] Table 1

[0063]

[0064] Perform ferroelectric performance tests on the irradiated devices, and the results are as Figure 3 、 Figure 4 shown:

[0065] The ferroelectric performance improvement of lead zirconate titanate (PZT) piezoelectric thin films with preferentially oriented grains shows a trend of first increasing and then decreasing with the increase of irradiation dose. When the irradiation dose is 0.5 - 2.0 Mrad, the ferroelectric performance improvement is 35% - 40%. When the irradiation dose is 1.35 Mrad, the ferroelectric performance improvement reaches the maximum amplitude, which is 40%.

[0066] Among them, the ferroelectric performance improvement is calculated as: (original performance value - performance value after irradiation) / original performance value.

[0067] Example 2:

[0068] This example is based on Example 1. The difference from Example 1 is that a top electrode is prepared by low-vacuum coating. That is, step 1) of this example is: using a low-vacuum coating equipment and a mask template to prepare the piezoelectric material into a top electrode with a specified shape.

[0069] In this example, a lead zirconate titanate (PZT) piezoelectric thin film with preferentially oriented grains and an existing bottom electrode (Pt electrode) is used for illustration:

[0070] Among them, the test object, irradiation source, and electrical characterization parameter testing equipment are the same as those in Example 1.

[0071] The irradiation dose parameters are shown in Table 2:

[0072] Table 2

[0073]

[0074] The ferroelectric performance of the irradiated device is tested, and the results are as Figure 5 、 Figure 6 shown:

[0075] The ferroelectric performance improvement of lead zirconate titanate (PZT) piezoelectric thin films with preferentially oriented grains shows a trend of first increasing and then decreasing with the increase of irradiation dose, and the maximum amplitude of performance improvement is 3 - 4%.

[0076] Example 3:

[0077] The performance improvement method of this example is the same as that of Example 1, which is to first prepare the top electrode by high-vacuum coating and then perform irradiation. The difference from Example 1 is the test object:

[0078] In this example, the test object is a thin film prepared from potassium sodium niobate (KNN) with preferentially oriented grains.

[0079] In this example, a potassium sodium niobate (KNN) piezoelectric thin film with preferentially oriented grains and an existing bottom electrode (Pt electrode) is used for illustration:

[0080] Among them, the irradiation source and the electrical characterization parameter testing equipment are the same as those in Embodiment 1.

[0081] The irradiation dose parameters are shown in Table 3:

[0082] Table 3

[0083]

[0084] The ferroelectric properties of the irradiated device were tested, and the results are as Figure 7 , Figure 8 shown:

[0085] For the potassium sodium niobate KNN piezoelectric thin film with preferentially oriented grains, the improvement of ferroelectric properties shows a trend of increasing first and then decreasing with the increase of irradiation dose, and the maximum amplitude of performance improvement is about 3%.

[0086] Comparative Example 1:

[0087] The performance improvement method in this comparative example is the same as that in Embodiment 1. First, a top electrode is prepared by high-vacuum coating, and then irradiation is carried out. The difference from Embodiment 1 is that the test object is different:

[0088] In this comparative example, the test object is a thin film prepared from a non-preferentially oriented grain piezoelectric thin film PZT with an existing bottom electrode (Pt electrode).

[0089] In this comparative example, the non-preferentially oriented grain piezoelectric thin film PZT with an existing bottom electrode (Pt electrode) is used for illustration:

[0090] Among them, the irradiation source, the electrical characterization parameter testing equipment, and the irradiation dose parameters are the same as those in Embodiment 1.

[0091] The ferroelectric properties of the irradiated device were tested, and the results are as Figure 9 , Figure 10 shown:

[0092] For the non-preferentially oriented grain PZT, after preparing the top electrode by high-vacuum coating and then irradiating, the ferroelectric properties (polarization intensity) degenerate.

[0093] The specific embodiments described above have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for improving the performance of piezoelectric materials based on ionizing irradiation, characterized in that, Perform high-vacuum coating on lead zirconate titanate-based piezoelectric thin films with preferentially oriented grains. Ionize the lead zirconate titanate-based piezoelectric thin films with preferentially oriented grains by radiation irradiation, where the radiation irradiation dose is 0.5 - 2.0 Mrad.

2. The method for improving the performance of piezoelectric materials based on ionization irradiation according to claim 1, wherein, Irradiate with a specific dose.

3. The method for improving the performance of piezoelectric materials based on ionization irradiation according to claim 2, characterized in that, The method for obtaining the specific dose includes the following steps: S1. Obtain the original ferroelectric properties of the piezoelectric material; S2. Irradiate the piezoelectric material with radiation of different doses and test the ferroelectric properties of the piezoelectric material after irradiation with the corresponding doses; S3. Calculate the improvement amount of ferroelectric properties corresponding to different doses based on the original ferroelectric properties tested in step S1 and the ferroelectric properties after irradiation obtained in step S2.

4. A method for improving the performance of piezoelectric materials based on ionization irradiation according to claim 3, characterized in that It also includes the following steps: S4. Construct a relationship curve graph of irradiation dose and improvement amount of ferroelectric properties, and obtain the specific dose based on this relationship curve graph.

5. A method for improving the performance of piezoelectric materials based on ionization irradiation according to claim 1, characterized in that, The irradiation source used for irradiation includes cobalt-60.

6. A method for improving the performance of a piezoelectric material based on ionization irradiation according to claim 1, characterized in that The irradiation dose is 1.35 Mrad.

Images