Piezoelectric sensor and haptic feedback device

Abstract

The embodiment of the present disclosure provides a piezoelectric sensor and a haptic feedback device, the piezoelectric sensor comprising: a substrate substrate, and a first electrode layer, a first barrier layer, a piezoelectric material layer and a second electrode layer which are sequentially stacked on the substrate substrate; wherein the first electrode layer is close to the substrate substrate, and the first barrier layer is used for blocking ion diffusion of the piezoelectric material layer to the first electrode layer.

Description

Technical Field

[0001] This disclosure relates to the field of sensor technology, and in particular to a piezoelectric sensor and a tactile feedback device. Background Technology

[0002] Haptics is a key area of ​​technological development today. Specifically, haptic feedback enables interaction between a device and the human body through touch. Haptic feedback can be divided into two categories: vibration feedback and haptic reproduction technology.

[0003] Surface tactile reproduction technology allows users to perceive object characteristics through bare-finger touchscreens, enabling efficient and natural interaction on multimedia terminals. This technology holds significant research value and has thus garnered widespread attention from researchers both domestically and internationally. Physically, surface tactile sensation involves the interaction between the roughness of an object's surface and the skin (fingertips), resulting in varying frictional forces due to differences in surface structure. Therefore, by controlling surface friction, different tactile sensations can be simulated. Summary of the Invention

[0004] This disclosure provides a piezoelectric sensor and a tactile feedback device, including: a substrate, and a first electrode layer, a first barrier layer, a piezoelectric material layer and a second electrode layer sequentially stacked on the substrate; wherein the first electrode layer is close to the substrate, and the first barrier layer is used to block ions from the piezoelectric material layer from diffusing to the first electrode layer.

[0005] In one possible implementation, in the piezoelectric sensor provided in this embodiment, the material of the first barrier layer is Ti.

[0006] In one possible implementation, in the piezoelectric sensor provided in this disclosure embodiment, the thickness of the first blocking layer is less than 10 nm.

[0007] In one possible implementation, in the piezoelectric sensor provided in the embodiments of this disclosure, the transmittance of the first blocking layer is greater than or equal to 60%.

[0008] In one possible implementation, the piezoelectric sensor provided in this embodiment further includes a second barrier layer located between the first barrier layer and the piezoelectric material layer. The material of the second barrier layer is different from that of the first barrier layer. The second barrier layer is used to prevent ions from the piezoelectric material layer from diffusing to the first electrode layer.

[0009] In one possible implementation, in the piezoelectric sensor provided in this disclosure embodiment, the material of the second barrier layer is HfO2 or LiNbO3.

[0010] In one possible implementation, in the piezoelectric sensor provided in this disclosure embodiment, the thickness of the second barrier layer is less than 50 nm.

[0011] In one possible implementation, the piezoelectric sensor provided in this embodiment further includes an insulating layer located on the side of the second electrode layer facing away from the substrate, and a wiring layer located on the side of the insulating layer facing away from the substrate; the wiring layer is electrically connected to the second electrode layer through a via penetrating the insulating layer.

[0012] The first electrode layer is grounded, and the trace layer is connected to the drive signal terminal.

[0013] In one possible implementation, in the piezoelectric sensor provided in the embodiments of this disclosure, the insulating layer is made of SiO2 or photoresist.

[0014] In one possible implementation, in the piezoelectric sensor provided in the embodiments of this disclosure, the materials of the first electrode layer and the second electrode layer are transparent conductive materials, and the material of the wiring layer is Ti / Ni / Au or Ti / Al / Ti.

[0015] In one possible implementation, the piezoelectric sensor provided in this disclosure embodiment has a piezoelectric material layer with a thickness of 500 nm to 2000 nm.

[0016] In one possible implementation, the piezoelectric sensor provided in this disclosure embodiment includes at least one of lead zirconate titanate, aluminum nitride, zinc oxide, barium titanate, lead titanate, potassium niobate, lithium niobate, lithium tantalate, and lanthanum gallium silicate.

[0017] Accordingly, this disclosure also provides a tactile feedback device, including the piezoelectric sensor described in any of the above embodiments. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a piezoelectric sensor provided in an embodiment of this disclosure;

[0019] Figure 2 The transmittance of the first barrier layer;

[0020] Figure 3 A schematic diagram showing the resistance change of the first electrode layer before and after annealing with and without a first barrier layer;

[0021] Figure 4 This is a schematic diagram of the structure of another piezoelectric sensor provided in an embodiment of the present disclosure;

[0022] Figure 5 The XRD pattern of HfO2 obtained in this disclosure and the standard XRD pattern of HfO2 are shown below.

[0023] Figure 6 This is a schematic diagram of the structure of another piezoelectric sensor provided in an embodiment of this disclosure. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. Furthermore, the embodiments and features in the embodiments of this disclosure can be combined with each other without conflict. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the scope of protection of this disclosure.

[0025] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "comprising" or "including," and similar terms as used in this disclosure, mean that an element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "inner," "outer," "upper," and "lower" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0026] It should be noted that the dimensions and shapes of the figures in the accompanying drawings do not reflect actual proportions and are intended only to illustrate the content of this disclosure. Furthermore, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0027] Thin-film piezoelectric materials possess high dielectric constants and transparency, making them ideal for use in vibrator structures integrated into screens. Lead zirconate titanate (PZT) piezoelectric ceramics are currently widely used due to their excellent piezoelectric properties. There are many methods for fabricating PZT films, including dry deposition (sputtering) and wet deposition (sol-gel method). However, to achieve good piezoelectric constant characteristics, PZT materials require a high-temperature annealing process. This process necessitates PZT grain growth in air at 550℃-650℃ to form a well-formed solid solution phase. When integrating a vibrator structure into a display device, to avoid affecting the display quality, the vibrator structure needs to use a transparent electrode (such as ITO) as the base electrode and growth layer. However, the following problems exist: Firstly, since ITO mainly conducts electricity through oxygen vacancies, but PZT is a perovskite phase and requires sufficient grain size to form piezoelectric properties, PZT requires high-temperature oxygen annealing. This annealing process leads to a significant increase in ITO resistance, increased circuit resistance, and decreased conductivity, which is detrimental to high-frequency drive of the device. Secondly, because Pb ions in PZT have a very small ionic radius, they easily diffuse between oxides. Once the PZT film is directly fabricated on ITO, under different high-temperature annealing processes, as verified by the inventors of this invention, Pb ions diffuse by about 100 nm. This diffusion not only increases the ITO resistance but also causes Pb ion deficiency in the PZT film, causing the perovskite phase to transition to the pyrochlore phase, reducing the piezoelectric properties of PZT, and thus reducing the performance of the piezoelectric device.

[0028] In view of this, embodiments of this disclosure provide a piezoelectric sensor, such as... Figure 1 As shown, it includes: a substrate 1, and a first electrode layer 2, a first barrier layer 3, a piezoelectric material layer 4, and a second electrode layer 5 sequentially stacked on the substrate 1; wherein, the first electrode layer 2 is close to the substrate 1, and the first barrier layer 3 is used to block the diffusion of ions from the piezoelectric material layer 4 to the first electrode layer 2.

[0029] The piezoelectric sensor provided in this embodiment of the invention uses a piezoelectric material layer 4 (e.g., PZT) that can be formed by dry or wet deposition. However, to achieve good piezoelectric constant characteristics, the PZT material needs to undergo a high-temperature annealing process. This process requires PZT grain growth in an air environment at 550℃-650℃ to form a good solid solution phase. Since the first electrode layer 2 (e.g., ITO) mainly conducts electricity through oxygen vacancies, during the high-temperature annealing process, oxygen in PZT diffuses to the oxygen vacancy sites in ITO, causing an increase in ITO resistance (a decrease in conductivity), which is detrimental to high-frequency drive of the device. Furthermore, due to the small radius of Pb ions, Pb ions easily diffuse between oxides. This diffusion not only increases the ITO resistance but also causes Pb ion deficiency in the PZT film, causing the phase to shift to pyrochlore, thereby reducing the piezoelectric performance of PZT. In this embodiment, a first barrier layer 3 is provided between the piezoelectric material layer 4 and the first electrode 2. The first barrier layer 3 can prevent ions (e.g., O, Pb) in the piezoelectric material layer 4 from diffusing to the first electrode layer 2. Thus, when the piezoelectric material layer 4 is subjected to a high-temperature annealing process, the conductivity of ITO can be maintained while preventing Pb from diffusing into ITO, and the PZT perovskite crystalline phase can be easily maintained, thereby improving the piezoelectric performance of the piezoelectric material layer 4.

[0030] In specific implementation, the substrate 1 can be a substrate made of glass, a substrate made of silicon or silicon dioxide (SiO2), a substrate made of sapphire, or a substrate made of metal wafers. There are no limitations here. Those skilled in the art can set the substrate 1 according to the actual application needs.

[0031] In specific implementation, the materials of the first electrode layer 2 and the second electrode layer 5 are transparent conductive materials, such as indium tin oxide (ITO) or indium zinc oxide (IZO). Those skilled in the art can set the materials of the first electrode layer 2 and the second electrode layer 5 according to the actual application needs, and no limitation is made here.

[0032] In specific implementations, the piezoelectric material layer 4 is not limited to lead zirconate titanate (Pb(Zr,Ti)O3, PZT) mentioned above, but can also be aluminum nitride (AlN), ZnO (zinc oxide), barium titanate (BaTiO3), lead titanate (PbTiO3), potassium niobate (KNbO3), lithium niobate (LiNbO3), lithium tantalate (LiTaO3), or lanthanum gallium silicate (La3Ga5SiO3). 14At least one of the following can be used: In this way, while ensuring the transparency of the piezoelectric sensor, the vibration characteristics of the piezoelectric sensor are also guaranteed. Specifically, the material used to fabricate the piezoelectric material layer 4 can be selected according to the actual needs of those skilled in the art, and is not limited here. When using PZT to fabricate the piezoelectric material layer 4, because PZT has a high piezoelectric coefficient, the piezoelectric characteristics of the corresponding piezoelectric sensor are guaranteed, allowing the corresponding piezoelectric sensor to be applied to haptic feedback devices. Furthermore, PZT has high light transmittance, so when integrated into a display device, it does not affect the display quality of the display device.

[0033] In specific implementation, in the piezoelectric sensor provided in the embodiments of this disclosure, the material of the first barrier layer can be Ti, because Ti has stable properties, is a metal that is not easily oxidized at high temperatures, and has a relatively thin thickness after the first barrier layer is formed.

[0034] In specific implementation, in order to ensure the transparency of the piezoelectric sensor, the thickness of the first barrier layer in the piezoelectric sensor provided in the embodiments of this disclosure is less than 10nm, such as 9nm, 8nm, 7nm, 6nm, 5nm, 4nm, etc. The embodiments of this disclosure take 5nm as an example.

[0035] In specific implementations, in the piezoelectric sensor provided in the embodiments of this disclosure, such as Figure 2 As shown, the transmittance of the first blocking layer is greater than or equal to 60%, such as 60%, 70%, 80%, 90%, etc. Therefore, integrating the piezoelectric sensor of this disclosure into a display device does not affect the display quality of the display device.

[0036] The piezoelectric sensor provided in this disclosure uses Ti to create a first barrier layer between the first electrode layer and the piezoelectric material layer. After the piezoelectric material layer is subjected to a high-temperature annealing process, the inventors of this invention detect the conductivity of the first electrode layer. According to experimental measurements, as shown... Figure 3As shown, curve A represents the resistance change of the first electrode layer after film formation without the first barrier layer; curve B represents the resistance change of the first electrode layer after film formation and annealing at 250°C without the first barrier layer; and curve C represents the resistance change of the first electrode layer after film formation and annealing at 500°C without the first barrier layer. The black square, black triangle, and black circle within the small black box represent the resistance changes of the first electrode layer after film formation with the first barrier layer, after film formation and annealing at 250°C, and after film formation and annealing at 500°C, respectively. It can be seen that without the first barrier layer, the resistance change of the first electrode layer before and after annealing is more significant, while with the first barrier layer, the resistance change trend of the first electrode layer before and after annealing is very small. Therefore, after adding the first barrier layer to the surface of the first electrode layer and undergoing high-temperature annealing, the resistance value does not change significantly, and the conductivity remains unaffected.

[0037] In practical implementation, although the first barrier layer 3 made of Ti can prevent most of the ions in PZT from diffusing to the first electrode layer 2, in order to further improve the conductivity of the first electrode layer and the piezoelectric properties of the piezoelectric material layer 4, in the piezoelectric sensor provided in the embodiments of this disclosure, such as... Figure 4 As shown, it also includes a second barrier layer 6 located between the first barrier layer 3 and the piezoelectric material layer 4. The material of the second barrier layer 6 is different from that of the first barrier layer 3. The second barrier layer 6 is used to further block the diffusion of ions from the piezoelectric material layer 4 to the first electrode layer 2.

[0038] In specific implementations, in the piezoelectric sensor provided in the embodiments of this disclosure, the material of the second barrier layer can be HfO2 or LiNbO3.

[0039] Specifically, when the second barrier layer is made of HfO2, HfO2 can serve as a seed layer. Thin film growth requires a seed layer for orientation. Therefore, when a piezoelectric material layer is subsequently fabricated on the second barrier layer, the crystal orientation of the piezoelectric material layer will be related to the orientation of the second barrier layer, thus benefiting the crystal orientation of the piezoelectric material layer and improving its piezoelectric properties. An XRD diagram of HfO2 deposited on the first electrode layer is shown below. Figure 5 As shown, the bottom XRD pattern is a standard XRD diagram of HfO2, and the top XRD pattern is an XRD diagram of HfO2 measured in an embodiment of this disclosure. It can be seen that the crystal phases of the two are similar.

[0040] Specifically, when the material of the second barrier layer is LiNbO3 (abbreviated as LNO), LiNbO3 can also be used as a seed layer. Since LiNbO3 itself is conductive, compared with HfO2, LiNbO3 can further improve conductivity while preventing the diffusion of Pb and O.

[0041] When fabricating piezoelectric material layers (such as PZT) using dry or wet processes, micropores will inevitably be present in the process. Once there are pores in the PZT, the first electrode layer and the second electrode layer will connect, forming a short circuit. Since LNO is a conductor, using HfO2 as a second barrier layer is more effective than using LNO as a second barrier layer in preventing short circuits between the first and second electrode layers when pores are formed in the PZT layer.

[0042] Therefore, HfO2 or LiNbO3 can be selected as the second barrier layer according to actual needs.

[0043] In specific implementations, in the piezoelectric sensor provided in the embodiments of this disclosure, the thickness of the second barrier layer is less than 50nm, for example, 40nm, 30nm, 20nm, or 10nm.

[0044] In specific implementations, in the piezoelectric sensor provided in the embodiments of this disclosure, such as Figure 6 As shown, it also includes an insulating layer 7 located on the side of the second electrode layer 5 away from the substrate 1, and a wiring layer 8 located on the side of the insulating layer 7 away from the substrate 1; the wiring layer 8 is electrically connected to the second electrode layer 5 through a via penetrating the insulating layer 7.

[0045] The first electrode layer 2 is grounded, and the trace layer 8 is connected to the drive signal terminal. In specific implementations, the inverse piezoelectric effect is utilized to ground the first electrode layer 2, and a high-frequency AC voltage signal (V) is applied to the second electrode layer 5. AC This allows for the application of a high-frequency AC voltage signal to the piezoelectric material layer 4, thereby generating high-frequency vibration. Laser can be used to measure the vibration displacement, ensuring the performance of the piezoelectric sensor. The insulating layer 7 can be made of materials such as SiO2, photoresist 9 (SOC-5004U), or silicon nitride (Si3N4), etc., without limitation. Of course, in addition to the various film layers mentioned above, other film layers can be used in this piezoelectric sensor depending on the specific application.

[0046] In specific implementations, in the piezoelectric sensor provided in the embodiments of this disclosure, the thickness of the first electrode layer and the second electrode layer can be 250nm to 500nm, and the material of the wiring layer is Ti / Ni / Au, wherein Ti can be 10nm, Ni can be 100nm, and Au can be 20nm; or the material of the wiring layer is Ti / Al / Ti, wherein Ti can be 10nm and Al can be 100nm.

[0047] In specific implementation, in the piezoelectric sensor provided in the embodiments of this disclosure, the thickness of the piezoelectric material layer can be 500nm to 2000nm. For example, the thickness of the piezoelectric material layer is 500nm, 1000nm or 2000nm. In practical applications, the thickness of the piezoelectric material layer can be set as close to zero as possible, so as to ensure good vibration characteristics of the piezoelectric material layer while taking into account the thin and light design of the piezoelectric sensor.

[0048] The piezoelectric sensor provided in this disclosure can be applied in fields such as medical, automotive electronics, and motion tracking systems. It is particularly suitable for wearable devices, external or implantable medical monitoring and treatment, or applications in fields such as artificial intelligence-based electronic skin. Specifically, the piezoelectric sensor can be applied to devices that generate vibration and mechanical properties, such as brake pads, keyboards, mobile terminals, game controllers, and automotive components.

[0049] Based on the same inventive concept, this disclosure also provides a tactile feedback device, including the piezoelectric sensor described above. Since the principle by which this tactile feedback device solves the problem is similar to that of the aforementioned piezoelectric sensor, the implementation of this tactile feedback device can refer to the implementation of the aforementioned piezoelectric sensor, and repeated details will not be elaborated further.

[0050] In practical implementation, haptic feedback devices can be integrated with touchscreens. The touchscreen can determine the location of human touch, thereby generating corresponding vibration waveforms, amplitudes, and frequencies, enabling human-computer interaction. Alternatively, the haptic feedback device can be reused as a piezoelectric element. A piezoelectric sensor can determine the location of human touch, thereby generating corresponding vibration waveforms, amplitudes, and frequencies, also enabling human-computer interaction. Of course, haptic feedback devices can also be applied in fields such as medical care, automotive electronics, and motion tracking systems, depending on actual needs, which will not be detailed here.

[0051] This invention provides a piezoelectric sensor and tactile feedback device. While the piezoelectric material layer (e.g., PZT) can be formed using dry or wet deposition methods, achieving good piezoelectric constant characteristics requires a high-temperature annealing process. This process involves PZT grain growth in air at 550℃-650℃ to form a good solid solution phase. Since the first electrode layer (e.g., ITO) primarily conducts electricity through oxygen vacancies, during the high-temperature annealing process, oxygen in PZT diffuses to the oxygen vacancies in ITO, leading to an increase in ITO resistance (decreased conductivity), which is detrimental to high-frequency device operation. Furthermore, due to the small radius of Pb ions, they easily diffuse between oxides. This diffusion not only increases ITO resistance but also causes Pb ion deficiency in the PZT film, resulting in a phase transition to pyrochlore and thus reducing the piezoelectric performance of PZT. This embodiment of the present disclosure provides a first barrier layer between the piezoelectric material layer and the first electrode. The first barrier layer can prevent ions (e.g., O, Pb) from the piezoelectric material layer from diffusing into the first electrode layer. Thus, when the piezoelectric material layer is subjected to a high-temperature annealing process, the conductivity of ITO can be maintained while preventing Pb from diffusing into ITO. It is also easier to maintain the PZT perovskite crystalline phase and improve the piezoelectric performance of the piezoelectric material layer.

[0052] Although preferred embodiments of this disclosure have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this disclosure.

[0053] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this disclosure without departing from the spirit and scope of the embodiments of this disclosure. Therefore, if these modifications and variations to the embodiments of this disclosure fall within the scope of the claims of this disclosure and their equivalents, this disclosure is also intended to include these modifications and variations.

Claims

1. A piezoelectric sensor, wherein, include: A substrate, and a first electrode layer, a first barrier layer, a second barrier layer, a piezoelectric material layer and a second electrode layer sequentially stacked on the substrate; wherein the first electrode layer is close to the substrate, the first barrier layer is used to block ions from the piezoelectric material layer from diffusing to the first electrode layer, the material of the second barrier layer is different from that of the first barrier layer, the second barrier layer is used to block ions from the piezoelectric material layer from diffusing to the first electrode layer, and the material of the second barrier layer is HfO2.

2. The piezoelectric sensor as described in claim 1, wherein, The material of the first barrier layer is Ti.

3. The piezoelectric sensor as described in claim 1, wherein, The thickness of the first barrier layer is less than 10 nm.

4. The piezoelectric sensor as described in claim 1, wherein, The transmittance of the first barrier layer is greater than or equal to 60%.

5. The piezoelectric sensor as described in claim 1, wherein, The thickness of the second barrier layer is less than 50 nm.

6. The piezoelectric sensor according to any one of claims 1-5, wherein, It also includes an insulating layer located on the side of the second electrode layer away from the substrate, and a wiring layer located on the side of the insulating layer away from the substrate. The wiring layer is electrically connected to the second electrode layer through a via penetrating the insulating layer; The first electrode layer is grounded, and the trace layer is connected to the drive signal terminal.

7. The piezoelectric sensor as described in claim 6, wherein, The insulating layer is made of SiO2 or photoresist.

8. The piezoelectric sensor as claimed in claim 6, wherein, The first electrode layer and the second electrode layer are made of transparent conductive materials, and the wiring layer is made of Ti / Ni / Au or Ti / Al / Ti.

9. The piezoelectric sensor according to any one of claims 1-5, wherein, The thickness of the piezoelectric material layer is 500 nm to 2000 nm.

10. The piezoelectric sensor according to any one of claims 1-5, wherein, The piezoelectric material layer includes at least one of lead zirconate titanate, aluminum nitride, zinc oxide, barium titanate, lead titanate, potassium niobate, lithium niobate, lithium tantalate, and lanthanum gallium silicate.

11. A haptic feedback device, wherein, Including the piezoelectric sensor as described in any one of claims 1-10.

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