Electrostatic flat panel driver based on electret

Abstract

The present application provides an electret-based electrostatic flat panel driver, comprising a transparent substrate, an anchor point arranged on the transparent substrate, a movable flat electrode connected to the anchor point through an elastic beam, a fixed electrode arranged on the upper surface of the transparent substrate and opposite to the movable flat electrode, used to drive the movable flat electrode to make at least one of the out-of-plane translational motion and the out-of-plane torsional motion, an emission electrode arranged on the lower surface of the movable flat electrode, used to receive the excitation light irradiated from the lower surface of the transparent substrate and release electrons, and an electret film formed by the charged film arranged on the upper surface of the fixed electrode and used to capture and fix the electrons released from the emission electrode to provide a bias voltage for the fixed electrode. The present application also provides a corresponding manufacturing method of the electrostatic flat panel driver. The electrostatic flat panel driver of the present application can be compatible with the electret into the electrostatic flat panel driver to reduce the electrostatic driving voltage.

Description

Technical Field

[0001] This invention relates to electrostatic actuators, and more particularly to an electret-based electrostatic flat plate actuator. Background Technology

[0002] MEMS (Microelectromechanical Systems) refers to miniature integrated devices or systems that utilize microfabrication and integrated circuit manufacturing technologies to realize electromechanical system functions on a chip. With its advantages of small size, low cost, high integration, and mass production capability, MEMS technology has been widely applied in various fields of social production and daily life, used to fabricate various types of miniature sensors and miniature actuators. Among them, miniature actuators (also known as miniature actuators or miniature actuators), as the components that output actions and functions in MEMS devices, are one of the basic functional units in MEMS devices, and therefore have always been a research focus of MEMS technology. Successful applications include digital micromirrors (DMDs), inkjet printheads, optical switches, RF switches, micro-relays, and micro-microphones.

[0003] Electrostatic, thermoelectric, piezoelectric, and electromagnetic methods are the four most commonly used driving methods for micro actuators, each with different characteristics and applicable ranges. Among them, electrostatic actuation based on electrostatic attraction between conductors has advantages such as ease of implementation, low device power consumption, precise control, good driving repeatability, and compatibility with MEMS processes, making it the most widely used driving method. However, electrostatic actuation requires a relatively high driving voltage (typically in the range of 10–200V), which is not conducive to the integration of MEMS devices with CMOS (Complementary Metal-Oxide-Semiconductor) circuits; the required high-voltage power supply circuits suffer from high power consumption, complex design, and high hardware costs. This hinders the application of MEMS devices in fields where total system power consumption, heat dissipation, and cost are limited (e.g., mobile electronic devices, wireless sensor networks, and large displacement / angle array devices). Therefore, researching a method to reduce the electrostatic driving voltage of micro actuators (especially a low driving voltage compatible with CMOS circuits) is of great significance and value.

[0004] Therefore, electrets (also known as permanent charge materials, which are dielectric materials that can store charge or dipole charge for a long time after polarization) are introduced into micro electrostatic actuators as bias electrostatic field sources to amplify the driving effect of electrostatic driving voltage, ultimately achieving a significant reduction in electrostatic driving voltage while maintaining the same driving effect. However, the biggest challenge in introducing electrets into micro electrostatic actuators lies in process compatibility. Specifically, micro electrostatic actuators are exposed to high temperatures and various liquids and gases containing charged particles during fabrication. Therefore, completing the electret film too early increases the risk of charge dissipation or neutralization in subsequent MEMS processes. For example, when introducing electret films into micro electrostatic planar actuators, the fabrication process inevitably involves wafer-level bonding. If the electret is charged before wafer-level bonding, its fixed charge is very likely to be dissipated at the high temperature of bonding. If the electret is to be charged after wafer-level bonding, the electret film is already placed between the driving electrodes, and traditional electret charging processes (such as corona discharge) are difficult to deliver the charge to the surface of the electret material.

[0005] In conclusion, researching an electret-compatible scheme for electrostatic flat plate actuators has practical significance and important value. Summary of the Invention

[0006] To address the problems in the prior art, this patent proposes an electret-based electrostatic flat panel driver, which obtains the electret by generating electrons through the photoelectric effect locally, achieving compatibility between the electrostatic flat panel driver and the electret, and ultimately reducing the driving voltage of the electrostatic flat panel driver.

[0007] To achieve the above objectives, the present invention provides an electret-based electrostatic flat plate driver, comprising:

[0008] A transparent substrate has at least one anchor point on its upper surface; a movable plate electrode is connected to the anchor point by at least one elastic beam; at least one fixed electrode is disposed on the upper surface of the transparent substrate and is positioned opposite the movable plate electrode; the fixed electrode is insulated from the movable plate electrode; the fixed electrode is configured to be subjected to a voltage different from that of the movable plate electrode to generate electrostatic force, thereby driving the movable plate electrode to perform at least one of out-of-plane translational motion and out-of-plane torsional motion; an emitting electrode is disposed on the lower surface of the movable plate electrode and is configured to receive excitation light irradiated from the lower surface of the transparent substrate, thereby releasing electrons under the photoelectric effect; an electret film is formed by a rechargeable film disposed on the upper surface of the fixed electrode to capture and fix the electrons released from the emitting electrode, and is configured to provide a bias voltage to the fixed electrode, thereby amplifying the driving effect of the electrostatic driving voltage.

[0009] Furthermore, when the number of fixed electrodes is greater than or equal to 2, the fixed electrodes are mutually insulated.

[0010] Furthermore, the excitation light comprises light with a wavelength in the range of 100nm to 400nm.

[0011] Furthermore, the transparent substrate is made of glass that can be penetrated by the excitation light.

[0012] Furthermore, the material of the emitting electrode is metal, and the work function of the emitting electrode is less than the photon energy of the shortest wavelength light in the excitation light, so that the emitting electrode can release electrons under the irradiation of the excitation light.

[0013] Furthermore, the material of the fixed electrode is at least one of doped semiconductors, metals, and alloys.

[0014] Furthermore, the movable plate electrode, the elastic beam, and the anchor point are all made of silicon, and the movable plate electrode, the elastic beam, and the anchor point are integrally formed.

[0015] Furthermore, the projection of the emitting electrode onto the transparent substrate is not entirely contained within the area where the projection of the fixed electrode onto the transparent substrate is located.

[0016] Furthermore, the material of the rechargeable film is at least one of silicon dioxide, silicon nitride, polyimide, Teflon, Parylene, PDMS, PMMA, LDPE, and CYTOP.

[0017] On the other hand, the present invention provides a method for fabricating the electret-based electrostatic flat plate actuator described above, comprising:

[0018] S10: A fixed electrode and a rechargeable thin film covering the fixed electrode are sequentially fabricated on the fabrication surface of the transparent substrate;

[0019] S20: Anchor points and emitter electrodes are sequentially fabricated on the fabrication surface of the silicon wafer, and the fabrication surface of the silicon wafer is bonded to the fabrication surface of the transparent substrate to form a bonded sheet. At this time, the fabrication surface of the silicon wafer is the lower surface of the silicon wafer, and the fabrication surface of the transparent substrate is the upper surface of the transparent substrate.

[0020] S30: Apply voltage to the emitting electrode and the fixed electrode to generate an electric field between them with the direction from the fixed electrode to the emitting electrode; at the same time, irradiate the emitting electrode with excitation light from the lower surface of the transparent substrate, so that the emitting electrode receives the excitation light and releases electrons under the photoelectric effect; the released electrons move and are fixed in the rechargeable film under the action of the electric field to form an electret film;

[0021] S40: Etch one side of the silicon wafer of the bonding wafer to obtain a movable plate electrode and an elastic beam;

[0022] The order of S30 and S40 can be interchanged.

[0023] The electret-based electrostatic flat panel driver of this invention uses an electret thin film as a bias electrostatic field source and introduces it into a miniature electrostatic flat panel driver to amplify the driving effect of the electrostatic driving voltage, ultimately achieving a significant reduction in the electrostatic driving voltage while maintaining the same driving effect. Furthermore, the fabrication method of the electret-based electrostatic flat panel driver of this invention uses locally generated photoelectric electrons to charge a rechargeable thin film to fabricate the electret thin film. Therefore, the electret thin film can be fabricated after a series of high-temperature and ion-laden processes, including bonding, thus making the fabrication of the electret thin film compatible with MEMS processes and avoiding the risk of charge in the electret thin film being discharged or neutralized in subsequent processes. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of an electret-based electrostatic flat plate driver according to Embodiment 1 of the present invention.

[0025] Figure 2 For example Figure 1 The exploded view of the electret-based electrostatic plate actuator is shown.

[0026] Figure 3 For example Figure 1 The diagram shows a cross-sectional view of an electret-based electrostatic flat plate actuator.

[0027] Figure 4 This is a process flow diagram of the fabrication method of the electret-based electrostatic flat plate actuator in Example 1.

[0028] Figure 5 This is a schematic diagram of the structure of an electret-based electrostatic flat plate driver according to Embodiment 2 of the present invention.

[0029] Figure 6 For example Figure 5 The exploded view of the electret-based electrostatic plate actuator is shown.

[0030] Figure 7 For example Figure 5 The diagram shows a cross-sectional view of an electret-based electrostatic flat plate actuator. Detailed Implementation

[0031] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0032] Example 1: Electrostatic Plate Actuator Based on Electret and Its Fabrication Method

[0033] like Figures 1-3 The diagram shows a schematic diagram, exploded view, and cross-sectional view of an electret-based electrostatic flat plate actuator according to Embodiment 1 of the present invention. Figure 1 As shown, the electret-based electrostatic flat plate actuator includes a transparent substrate 10, two anchor points 13 and two fixed electrodes 14 fixed to the upper surface of the transparent substrate 10, a movable flat plate electrode 11, two elastic beams 12, two emitting electrodes 15 arranged on the lower surface of the movable flat plate electrode 11, and an electret film 16 arranged on the upper surface of the fixed electrode 14. One end of each elastic beam 12 is connected to the movable flat plate electrode 11, and the other end is connected to an anchor point 13. In this embodiment, the elastic beam 12, the movable flat plate electrode 11, and the anchor point 13 are all integrally formed.

[0034] Two fixed electrodes 14 are positioned opposite the movable plate electrode 11; the two fixed electrodes 14 and the movable plate electrode 11 are insulated from each other. The two fixed electrodes 14 are configured to be subjected to a voltage different from that applied to the movable plate electrode 11 (i.e., an electrostatic driving voltage) to generate an electrostatic force, thereby driving the movable plate electrode 11 to perform at least one of out-of-plane translational motion and out-of-plane torsional motion. That is, by applying voltage to the two fixed electrodes 14 and the movable plate electrode 11, an electrostatic force is generated between the fixed electrodes 14 and the movable plate electrode 11, thereby driving the movable plate electrode 11 to perform out-of-plane torsional motion around the axis 20 of the torsion axis, or out-of-plane translational motion along the normal direction of the transparent substrate 10, or a combination of both. This is the final driving effect of the plate actuator of the present invention. The spacing between the fixed electrodes 14 and the movable plate electrode 11 is not limited to a specific numerical range. In this embodiment, the two elastic beams 12 are located on the same axis 20 (preferably the central axis), and the two fixed electrodes 14 are symmetrically distributed on both sides of the axis 20.

[0035] The electret film 16 contains fixed electrons and is configured to provide a driving bias voltage to the fixed electrode 14, thereby amplifying the driving effect of the electrostatic driving voltage. The shape of the electret film 16 can be arbitrary; in this embodiment, the shape of the electret film 16 is consistent with the shape of the fixed electrode 14. Figure 2 and Figure 3 As shown, two emitting electrodes 15 are arranged on the lower surface of the movable plate electrode 11, opposite to the fixed electrode 14. The electret film 16 is formed by capturing and fixing electrons released from the emitting electrodes 15 through a rechargeable film arranged on the upper surface of the fixed electrode 14, and therefore carries fixed electrons.

[0036] In this embodiment, the fixed electrode 14 is grid-shaped, therefore, the projection of the emitting electrode 15 onto the transparent substrate 10 is not completely contained within the area of ​​the fixed electrode 14's projection onto the transparent substrate 10. Furthermore, the emitting electrode 15 is configured to receive excitation light with a specific frequency range irradiated from the lower surface of the transparent substrate 10, thereby releasing electrons under the photoelectric effect. In this embodiment, a light source for the excitation light is required to irradiate the back surface of the transparent substrate 10, and the excitation light contains light with wavelengths in the range of 100 nm to 400 nm. In this embodiment, the excitation light contains light with wavelengths less than 220 nm.

[0037] The transparent substrate 10 is made of glass that can be penetrated by the excitation light. The emitting electrode 15 is made of metal, and its work function is less than the power of the shortest wavelength light in the excitation light, allowing it to release electrons under the irradiation of the excitation light. The intensity of the excitation light has no effect on the excitation of electrons; the frequency (or wavelength) of the light is what truly matters. Under the condition of satisfying the frequency (or wavelength), the intensity of the light can increase the number of excited electrons. This invention does not require any electron density in the generated electret film 16; theoretically, even a single electron can amplify the electrostatic driving voltage to some extent. In this embodiment, the emitting electrode 15 is made of tungsten; the movable plate electrode 11, the elastic beam 12, and the anchor point 13 are made of silicon, allowing for integral molding. The fixed electrode 14 is made of gold; in other embodiments, the fixed electrode can also be at least one of a doped semiconductor, a metal, or an alloy. The material of the rechargeable film is at least one of silicon dioxide, silicon nitride, polyimide, Teflon, Parylene, PDMS, PMMA, LDPE and CYTOP, and the preferred material of the rechargeable film is silicon nitride.

[0038] like Figure 4 The diagram shows the fabrication process of the electrostatic flat panel driver based on the electret-based driver described above. The fabrication method of the electret-based electrostatic flat panel driver of the present invention includes:

[0039] Step S10: Sequentially fabricate the fixed electrode 14 and the rechargeable film covering the fixed electrode 14 on the fabrication surface of the transparent substrate 10;

[0040] Step S10 specifically includes:

[0041] Step S11: Provide a transparent substrate 10;

[0042] The material of the transparent substrate 10 is preferably glass.

[0043] Step S12: Deposit and pattern a gold thin film on the fabrication surface of the transparent substrate 10 to form a fixed electrode 14;

[0044] Step S13: Deposit and pattern a silicon nitride thin film on the surface of the fixed electrode 14 to form a rechargeable thin film.

[0045] S20: The anchor point 13 and the emission electrode 15 are sequentially fabricated on the fabrication surface of the silicon wafer, and the fabrication surface of the silicon wafer is bonded to the fabrication surface of the transparent substrate 10 to form a bonded sheet. At this time, the fabrication surface of the silicon wafer is the lower surface of the silicon wafer, and the fabrication surface of the transparent substrate 10 is the upper surface of the transparent substrate 10.

[0046] Step S20 specifically includes:

[0047] Step S21: Provide silicon wafers;

[0048] Step S22: Anchor points 13 are fabricated on the surface of the silicon wafer by dry etching of silicon.

[0049] Step S23: Deposit and pattern a tungsten thin film in the dry-etched area to form the emitter electrode 15;

[0050] Step S24: Bond the fabrication surface of the silicon wafer to the fabrication surface of the transparent substrate 10 to form a bonding sheet.

[0051] Step S30: Connect the emitting electrode 15 and the fixed electrode 14 to a voltage to generate an electric field between them with the direction from the fixed electrode 14 to the emitting electrode 15; at the same time, irradiate the emitting electrode 15 with excitation light from the lower surface of the transparent substrate 10, causing it to release electrons under the photoelectric effect; the released electrons move and are fixed in the rechargeable film under the action of the electric field to form an electret film;

[0052] Specifically, grounding the silicon wafer in the bonding wafer and applying a positive voltage to the fixed electrode 14 will generate an electric field inside the bonding wafer, directed from the fixed electrode 14 to the emitter electrode 15. The emitter electrode 15 and the fixed electrode 14 are led out via wires, flying wires, or wires arranged on the silicon wafer or a transparent substrate.

[0053] S40: Etch one side of the silicon wafer of the bonding sheet to obtain the movable plate electrode 11 and the elastic beam 12.

[0054] Example 2: Electrostatic Plate Actuator Based on Electret

[0055] like Figures 5-7 The diagram shows a schematic diagram, exploded view, and cross-sectional view of an electret-based electrostatic flat plate actuator according to Embodiment 2 of the present invention. Figure 5As shown, the electret-based electrostatic flat plate actuator includes a transparent substrate 10, an anchor point 13 and a fixed electrode 14 fixed to the upper surface of the transparent substrate 10, a movable flat plate electrode 11, an elastic beam 12, an emitter electrode 15 disposed on the lower surface of the movable flat plate electrode 11, and an electret film 16 disposed on the upper surface of the fixed electrode 14. One end of the elastic beam 12 is connected to the movable flat plate electrode 11, and the other end is connected to the anchor point 13. In this embodiment, the elastic beam 12, the movable flat plate electrode 11, and the anchor point 13 are all integrally formed.

[0056] The fixed electrode 14 and the movable plate electrode 11 are positioned opposite each other and are insulated from each other. The fixed electrode 14 is configured to be subjected to a different voltage (i.e., an electrostatic driving voltage) than the movable plate electrode 11 to generate an electrostatic force, thereby driving the movable plate electrode 11 to perform an out-of-plane translational motion. In other words, by applying voltage to both the fixed electrode 14 and the movable plate electrode 11, an electrostatic force is generated between them, thereby driving the movable plate electrode 11 to perform an out-of-plane translational motion along the normal direction of the transparent substrate 10. The distance between the fixed electrode 14 and the movable plate electrode 11 is not limited to a specific numerical range.

[0057] The electret film 16 contains fixed electrons and is configured to provide a driving bias voltage to the fixed electrode 14, thereby amplifying the driving effect of the electrostatic driving voltage. The shape of the electret film 16 can be arbitrary; in this embodiment, the shape of the electret film 16 is consistent with the shape of the fixed electrode 14. Figure 6 and Figure 7 As shown, an emitter electrode 15 is disposed on the lower surface of the movable plate electrode 11, opposite to the fixed electrode 14. The electret film 16 is formed by capturing and fixing electrons released from the emitter electrode 15 through a rechargeable film disposed on the upper surface of the fixed electrode 14, and therefore carries fixed electrons.

[0058] The area of ​​the fixed electrode 14 is much smaller than the area of ​​the emitting electrode 15. The shape of the fixed electrode 14 can be arbitrary; the area ratio of the fixed electrode 14 to the emitting electrode 15 is set such that light irradiated from the lower surface of the transparent substrate 10 can reach the emitting electrode 15 above the fixed electrode 14. Therefore, the projection of the emitting electrode 15 onto the transparent substrate 10 is not completely contained within the area of ​​the projection of the fixed electrode 14 onto the transparent substrate 10. Consequently, the emitting electrode 15 can receive excitation light with a specific frequency range irradiated from the lower surface of the transparent substrate 10, ultimately releasing photoelectrons.

[0059] In this embodiment, the transparent substrate 10 is made of glass, the movable flat plate electrode 11, the elastic beam 12 and the anchor point 13 are all made of silicon, the fixed electrode 14 is made of copper, the emitting electrode 15 is made of tungsten, and the electret film 16 is made of a double-layer film of silicon dioxide and silicon nitride.

[0060] The process flow of the electret-based electrostatic flat plate actuator is as follows: Figure 4 As shown, it will not be elaborated upon here.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. An electret-based electrostatic flat panel driver, characterized by comprising: include: A transparent substrate, with at least one anchor point on its upper surface; A movable flat plate electrode, which is connected to the anchor point by at least one elastic beam; At least one fixed electrode is disposed on the upper surface of the transparent substrate and is positioned opposite the movable plate electrode; the fixed electrode is insulated from the movable plate electrode; the fixed electrode is configured to be subjected to a voltage different from that applied to the movable plate electrode to generate an electrostatic force, thereby driving the movable plate electrode to perform at least one of an out-of-plane translational motion and an out-of-plane torsional motion. The emitting electrode, arranged on the lower surface of the movable plate electrode, is configured to receive excitation light irradiated from the lower surface of the transparent substrate, thereby releasing electrons under the photoelectric effect. An electret film, consisting of a rechargeable film disposed on the upper surface of the fixed electrode, captures and immobilizes electrons released from the emitting electrode. It is configured to provide a bias voltage to the fixed electrode, thereby amplifying the driving effect of the electrostatic driving voltage.

2. An electret-based electrostatic flat-panel driver according to claim 1, wherein When the number of fixed electrodes is greater than or equal to 2, the fixed electrodes are mutually insulated.

3. An electret-based electrostatic flat-panel driver according to claim 1, wherein The excitation light comprises light with a wavelength in the range of 100nm to 400nm.

4. An electret-based electrostatic flat-panel driver according to claim 1 or 3, wherein The transparent substrate is made of glass that can be penetrated by the excitation light.

5. The electret-based electrostatic flat-plate actuator according to claim 1 or 3, characterized in that, The material of the emitting electrode is metal, and the work function of the emitting electrode is less than the photon energy of the shortest wavelength light in the excitation light, so that the emitting electrode can release electrons under the irradiation of the excitation light.

6. The electret-based static flat-panel driver of claim 1, wherein, The material of the fixed electrode is at least one of doped semiconductors, metals, and alloys.

7. The electret-based static flat-panel driver of claim 1, wherein, The movable plate electrode, the elastic beam, and the anchor point are all made of silicon, and the movable plate electrode, the elastic beam, and the anchor point are integrally formed.

8. The electret-based static flat-panel driver of claim 1, wherein, The projection of the emitting electrode onto the transparent substrate is not entirely contained within the area where the projection of the fixed electrode onto the transparent substrate is located.

9. The electret-based static flat-panel driver of claim 1, wherein, The material of the rechargeable film is at least one of silicon dioxide, silicon nitride, polyimide, Teflon, Parylene, PDMS, PMMA, LDPE, and CYTOP.

10. A method of manufacturing an electret-based electrostatic flat-panel driver according to any one of claims 1 to 9, characterized by, include: S10: A fixed electrode and a rechargeable thin film covering the fixed electrode are sequentially fabricated on the fabrication surface of the transparent substrate; S20: Anchor points and emitter electrodes are sequentially fabricated on the fabrication surface of the silicon wafer, and the fabrication surface of the silicon wafer is bonded to the fabrication surface of the transparent substrate to form a bonded sheet. At this time, the fabrication surface of the silicon wafer is the lower surface of the silicon wafer, and the fabrication surface of the transparent substrate is the upper surface of the transparent substrate. S30: Apply voltage to the emitting electrode and the fixed electrode to generate an electric field between them with the direction from the fixed electrode to the emitting electrode; at the same time, irradiate the emitting electrode with excitation light from the lower surface of the transparent substrate, so that the emitting electrode receives the excitation light and releases electrons under the photoelectric effect; the released electrons move and are fixed in the rechargeable film under the action of the electric field to form an electret film; S40: Etch one side of the silicon wafer of the bonding wafer to obtain a movable plate electrode and an elastic beam; The order of S30 and S40 can be interchanged.

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