Symmetric discrete stacked piezoelectric driving structure, light splitting chip and processing method

Abstract

This invention relates to a symmetrical discrete stacked piezoelectric drive structure, a beam splitter chip, and a fabrication method. The scheme comprises an upper piezoelectric actuator formed by sequentially distributing an insulating layer, a first upper electrode, an upper piezoelectric film, and a first lower electrode on the upper surface of a substrate. The first upper and first lower electrodes provide driving voltages for the upper piezoelectric actuator. A lower piezoelectric actuator is formed by sequentially distributing an insulating layer, a second lower electrode, a lower piezoelectric film, and a second upper electrode on the lower surface of the substrate. The potentials of the first and second upper electrodes are kept consistent, as are the potentials of the first and second lower electrodes. The upper and lower piezoelectric actuators are mirror-symmetrically distributed about the substrate. This overall structure reduces the impact of residual stress on device performance, and the upper and lower piezoelectric actuators can achieve motion coupling, increasing driving displacement and driving frequency.

Description

Technical Field

[0001] This invention relates to the field of micro-opto-electro-mechanical systems technology, and more specifically, to a symmetrical discrete stacked piezoelectric drive structure, a beam splitting chip, and a fabrication method. Background Technology

[0002] Various miniature spectroscopic chips fabricated using Micro-electro-mechanical systems (MEMS) technology, namely MEMS spectroscopic chips, are core components of spectral analysis and detection systems. They not only represent a leap from static to dynamic spectroscopic elements but also offer advantages such as small size, low power consumption and cost, and strong integration and customization capabilities. Furthermore, these chips can be mass-produced using advanced semiconductor processes. The MEMS torsional spectroscopic chip, by monolithically integrating grating beam splitting and micromirror scanning, achieves a cross-scale technological leap from "mechanical movement" to "chip resonance" in spectroscopic elements. This chip, combined with the synchronous triggering mechanism and rapid acquisition capabilities of a linear array detector, makes miniaturized infrared spectral video acquisition possible.

[0003] Existing microelectromechanical systems (MEMS) torsional spectrometer chips have achieved dynamic scanning and spectral information acquisition, with driving methods covering four types: electrostatic, electromagnetic, piezoelectric, and electrothermal. Among these, electrostatic drives, limited by nonlinear force-displacement characteristics, require complex multi-level feedback control systems, significantly restricting dynamic response bandwidth. Electromagnetic drives, requiring the integration of bulk permanent magnet components, face inherent bottlenecks in miniaturization and high integration. Electrothermal drives suffer from slow response speed, high power consumption, and heat generation issues. In contrast, piezoelectric drives, leveraging the inverse piezoelectric effect, directly achieve mechanical displacement output, exhibiting high energy density and significant potential for high-frequency response.

[0004] However, piezoelectric-driven microelectromechanical systems (MEMS) torsional beam splitters still suffer from the following technical drawbacks: First, high-frequency thermal failure of lead zirconate titanate (PZT) materials: Under alternating electric fields, PZT materials experience significant dielectric losses due to ferroelectric domain flipping hysteresis, leading to local temperature rises exceeding 100°C during high-frequency driving. This thermal accumulation effect not only causes piezoelectric coefficient decay but also induces dynamic fatigue fracture, limiting its application to low-frequency, large-displacement scenarios. Furthermore, its high-temperature deposition process (>600°C) results in residual stress accumulation at the interface due to the mismatch in the thermal expansion coefficients of the material system. Second, limitations in the electromechanical coupling efficiency of aluminum nitride (AlN) materials: Aluminum nitride can achieve hysteresis-free vibrations from MHz to GHz thanks to its linear ion polarization response. However, its spontaneous polarization characteristics hinder the realization of multilayer aluminum nitride piezoelectric drive structures. In existing fabrication processes, uncontrolled grain orientation and lattice mismatch at the substrate interface lead to piezoelectric coefficient decay. Therefore, existing aluminum nitride piezoelectric drive devices struggle to achieve both high-frequency response and large-angle deflection scanning. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to overcome the technical defects of existing microelectromechanical system torsional beam splitting chips, such as large residual stress of piezoelectric actuators, low driving frequency and small displacement of single-layer aluminum nitride piezoelectric actuators. In order to overcome this technical defect, the present invention provides a symmetrical discrete stacked piezoelectric drive structure, beam splitting chip and processing method.

[0006] The first technical solution of the present invention is to provide a symmetrical discrete stacked piezoelectric driving structure, including a substrate layer, and an upper piezoelectric actuator and a lower piezoelectric actuator respectively disposed on the upper and lower surfaces of the substrate layer; the upper piezoelectric actuator includes a first insulating layer, a first lower electrode, an upper piezoelectric film and a first upper electrode sequentially disposed on the upper surface of the substrate layer; the lower piezoelectric actuator includes a second insulating layer, a second lower electrode, a lower piezoelectric film and a second upper electrode sequentially disposed on the lower surface of the substrate layer; the upper piezoelectric actuator and the lower piezoelectric actuator are mirror-symmetrically distributed about the substrate layer, and the potentials of the first upper electrode and the second upper electrode are consistent, and the potentials of the first lower electrode and the second lower electrode are consistent.

[0007] The symmetrical discrete stacked piezoelectric drive structure disclosed in this invention addresses the aforementioned technical deficiencies by separately configuring piezoelectric actuators on the upper and lower surfaces of a substrate. Specifically, an insulating layer, a first upper electrode, an upper piezoelectric film, and a first lower electrode are sequentially configured on the upper surface of the substrate to form an upper piezoelectric actuator, which can be used to provide a driving voltage for the upper piezoelectric actuator. Simultaneously, an insulating layer, a second lower electrode, a lower piezoelectric film, and a second upper electrode are sequentially configured on the lower surface of the substrate to form a lower piezoelectric actuator, which can also be used to provide a driving voltage for the lower piezoelectric actuator. Furthermore, since the potentials of the first upper electrode and the second upper electrode are consistent, and the potentials of the first lower electrode and the second lower electrode are consistent, the driving voltage configuration parameters of the upper and lower piezoelectric actuators are consistent. On this basis, the upper and lower piezoelectric actuators are distributed in a mirror symmetric manner about the substrate, so the overall structure formed can effectively counteract the residual stress caused by the difference in thermal expansion coefficients between the upper and lower piezoelectric actuators due to different materials, achieve stress balance of the overall structure, significantly reduce the impact of residual stress on device performance, and at the same time, the upper and lower piezoelectric actuators can achieve motion coupling, increasing the driving displacement and driving frequency.

[0008] In one possible implementation, the first upper electrode, the first lower electrode, the second upper electrode, and the second lower electrode are made of one of gold, aluminum, molybdenum, and platinum, or a combination of two or more of the above four metal materials, in order to improve the conductivity of the electrodes and reduce energy consumption.

[0009] In one possible implementation, the upper and lower piezoelectric films are made of one of aluminum nitride, scandium aluminum nitride, lead zirconate titanate, and zinc oxide, and the materials of the upper and lower piezoelectric films are consistent to further optimize stress symmetry.

[0010] In one possible implementation, the substrate layer is made of silicon, glass, or polyimide to enhance overall robustness.

[0011] The second technical solution of the present invention is to provide a microelectromechanical system (MEMS) torsional beam splitter chip, comprising: Base; A micromirror system includes an outer layer disposed on the substrate and a micromirror located in the region enclosed by the outer layer, two torsion beams, four transmission beams, a first piezoelectric drive structure, a second piezoelectric drive structure, a third piezoelectric drive structure, and a fourth piezoelectric drive structure. Each side of the micromirror is connected to one end of a torsion beam, and the other end of all the torsion beams is connected to the outer layer. The first, second, third, and fourth piezoelectric drive structures are all connected to the outer layer. The output ends of the first and fourth piezoelectric drive structures are each connected to one of the torsion beams through a transmission beam, and the output ends of the second and third piezoelectric drive structures are each connected to the other torsion beam through a transmission beam. An integrated grating is disposed on the micromirror; in, The substrate is provided with an activity chamber for the movement of the micromirror, two torsion beams, four transmission beams, a first piezoelectric drive structure, a second piezoelectric drive structure, a third piezoelectric drive structure, and a fourth piezoelectric drive structure; The first piezoelectric drive structure, the second piezoelectric drive structure, the third piezoelectric drive structure, and the fourth piezoelectric drive structure are all symmetrical discrete stacked piezoelectric drive structures as described in this invention. The first piezoelectric drive structure and the second piezoelectric drive structure are given the same drive signal, and the third piezoelectric drive structure and the fourth piezoelectric drive structure are given the same drive signal.

[0012] The torsional beam splitter chip disclosed in this invention integrates the aforementioned symmetrical discrete stacked piezoelectric drive structures, micromirrors, and gratings to achieve integrated beam splitting and scanning. Furthermore, the integrated grating, mounted on the micromirror surface, maintains optical processing capabilities. The micromirror is fixedly connected to a pair of torsion beams to ensure rotation of the micromirror around the axis of rotation of the torsion beams. To increase the scanning angle of the micromirror, a transmission beam lever amplification mechanism is introduced between each piezoelectric driver and the torsion beam. By extending the driving arm, the torque output efficiency is improved, thereby increasing the driving displacement and driving frequency. Simultaneously, since this torsional beam splitter chip contains four discrete stacked piezoelectric drivers, the first and second piezoelectric drive structures apply the same driving signal, designated as the first group of driving signals; the third and fourth piezoelectric drive structures apply the same driving signal, designated as the second group of driving signals. The driving signals can be AC ​​signals. When the first and second group of driving signals are 180° out of phase, the micromirror will undergo torsional motion; when the first and second group of driving signals are in phase, the micromirror will undergo vertical translation. The active chamber on the substrate provides space for the aforementioned movements, thereby effectively increasing the driving displacement and driving frequency, and significantly reducing the impact of residual stress on device performance.

[0013] In one possible implementation, the transmission beam is a folded beam, a straight beam, or a trapezoidal beam to increase the torsional amplitude and further increase the driving displacement.

[0014] In one possible implementation, the integrated grating is a rectangular grating, a V-shaped grating, or a blazed grating to improve the dimming efficiency of the micromirror system.

[0015] In one possible implementation, each of the stress concentration plates on the torsion beams is equipped with a torsion angle sensing unit, which is a piezoelectric or piezoresistive sensor. The integrated torsion angle sensing unit can be used to achieve closed-loop control of the micromirror deflection angle, improving scanning accuracy and providing a stable detection signal for the closed-loop control of the micromirror deflection angle.

[0016] The third technical solution of the present invention is to provide a method for fabricating a microelectromechanical system (MEMS) torsional beam splitter chip, comprising the following steps: S1: Take a substrate as the base layer of the outer layer, deposit an insulating layer material on its surface, and perform a patterning process on the insulating layer material to form a second insulating layer with a preset pattern; S2: Electrode material is deposited on the surface of the second insulating layer, and the electrode material is patterned by a metal material patterning process to prepare the second lower electrode; S3: Deposit a piezoelectric thin film material on the surface of the second lower electrode, and perform a patterning process on the piezoelectric thin film material to complete the preparation of the lower piezoelectric thin film; S4: Deposit electrode material on the surface of the lower piezoelectric film, and pattern the electrode material using a metal material patterning process to prepare the first upper electrode; S5: Deposit bonding layer material on the surface of the base layer and perform a patterning process on this bonding layer material to prepare the first bonding layer; S6: Take another substrate as the base, deposit a bonding layer material on its surface, and perform a patterning process on the bonding layer material to prepare a second bonding layer that is compatible with the first bonding layer; S7: An axial through-hole structure is fabricated on the substrate using an etching process to obtain an active chamber for the movement of the micromirror, two torsion beams, four transmission beams, the first piezoelectric drive structure, the second piezoelectric drive structure, the third piezoelectric drive structure, and the fourth piezoelectric drive structure. S8: Using a wafer-level bonding process, the first bonding layer on the base layer is aligned and bonded to the second bonding layer of the substrate to form a bonded wafer; S9: Thin the base layer in the bonding wafer; S10: Fabricate a grating structure on the surface of the base layer after S9 thinning; S11: On the surface of the base layer after processing in S10, repeat the same process steps as S1 to S4 to sequentially complete the preparation of the first insulating layer, the first lower electrode, the upper piezoelectric film and the first upper electrode. S12: The structure at the bonding wafer of the base layer is released by etching process to form a micromirror system.

[0017] The method disclosed in this invention achieves precise alignment and integration of upper and lower double-layer substrates through wafer-level bonding technology, effectively improving the stability and integration of the device structure. By stepwise deposition of insulating layers, electrode materials, and piezoelectric thin films, combined with patterning technology, high-precision fabrication of the piezoelectric actuator is achieved, ensuring the uniformity and reliability of the driving response. Pre-fabrication of through-holes in the substrate to form moving chambers provides ample space for moving structures such as micromirrors and torsion beams, ensuring the free torsion and stable operation of the micromirror system. Thinning of the base layer after bonding and fabrication of a grating structure improves optical performance and diffraction efficiency, enhancing the sensitivity and resolution of the spectrometer chip. Simultaneously, the use of a double-sided process flow and the reuse of standardized fabrication steps improves process compatibility and repeatability. These combined steps effectively increase the driving displacement and driving frequency of the resulting chip, significantly reducing the impact of residual stress on device performance, which is conducive to large-scale, batch production. The overall process flow design is reasonable, the steps are clear, and it can effectively reduce manufacturing costs, improve device performance and yield, showing good prospects for industrial application.

[0018] In one possible implementation, the base layer in step S1 is a single-crystal silicon wafer or a silicon-on-insulator wafer; the through-hole structure in step S7 is prepared by deep reactive ion etching, surface laser ablation, or wet etching; the bonding process in step S8 is gold-tin eutectic bonding, aluminum-germanium eutectic bonding, silicon-silicon oxide-silicon direct bonding, or silicon-glass anodic bonding; the thickness of the base layer after thinning treatment in step S9 is 10μm-100μm; and the etching process in step S12 is deep reactive ion etching, surface laser ablation, or wet etching. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the working principle of a single piezoelectric actuator provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the single and dual piezoelectric actuators and the symmetrical discrete stacked piezoelectric driver in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the microelectromechanical system torsional beam splitter chip structure provided in Embodiment 1 or 2 of the present invention; Figure 4 This is a schematic diagram illustrating the working principle of the microelectromechanical system torsional beam splitter chip provided in Embodiment 1 or 2 of the present invention; Figure 5 This is a schematic diagram of the fabrication process of the microelectromechanical system torsional beam splitter chip provided in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the integrated grating fabrication process provided in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the fabrication process of the microelectromechanical system torsional beam splitter chip provided in Embodiment 2 of the present invention; Figure 8 This is a schematic diagram of the integrated grating fabrication process provided in Embodiment 2 of the present invention.

[0020] Explanation of reference numerals in the attached figures: 1.1 Upper electrode, 1.2 Piezoelectric thin film, 1.3 Lower electrode, 1.4 First piezoelectric thin film, 1.5 Intermediate electrode, 1.6 Second piezoelectric thin film, 2. Substrate, 3. Upper piezoelectric actuator, 3.1 Upper insulating layer, 3.2 First lower electrode, 3.3 Upper piezoelectric thin film, 3.4 First upper electrode, 4. Lower piezoelectric actuator, 4.1 Lower insulating layer, 4.2 Second lower electrode, 4.3 Lower... 4.4 Second upper electrode, 5. Substrate, 5.1 Active chamber, 6. Outer layer, 7. Torsion beam, 8. Transmission beam, 9. First piezoelectric driving structure, 10. Integrated grating, 11. Micromirror, 12. Second piezoelectric driving structure, 13. Torsion angle sensing unit, 14. Third piezoelectric driving structure, 15. Fourth piezoelectric driving structure, 16.1 First bonding layer, 16.2 Second bonding layer, 17. Grating structure mask. Detailed Implementation

[0021] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0022] In the description of the embodiments of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application based on the specific circumstances.

[0023] In the embodiments of this application, unless otherwise explicitly specified and limited, "above," "below," "in front of," or "behind" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature. "Before," "in front of," and "in front of" the second feature can mean that the first feature is directly in front of or diagonally in front of the second feature, or simply indicates that the first feature precedes the second feature in sequence. "After," "behind," and "behind" the second feature can mean that the first feature is directly behind or diagonally behind the second feature, or simply indicates that the first feature is after the second feature in sequence.

[0024] The technical solution of this application will be further described in detail below using two embodiments, in conjunction with the accompanying drawings and specific embodiments.

[0025] Example 1: See Figure 1 and 2 (a) A traditional single-layer piezoelectric actuator mainly consists of an upper electrode 1.1, a piezoelectric film 1.2, and a lower electrode 1.3. By applying an external electric field between the upper electrode 1.1 and the lower electrode 1.3, deformation of the piezoelectric film 1.2 can be induced, thereby driving the corresponding structure to produce displacement. To amplify the deformation of the piezoelectric actuator, a multilayer piezoelectric composite structure is often used, among which the dual piezoelectric actuator is the most widely used, and its structure is as follows: Figure 2(b) shows a structure consisting of an upper electrode 1.1, a first piezoelectric film 1.4, an intermediate electrode 1.5, a second piezoelectric film 1.6, a lower electrode 1.3, and a substrate 2, with the two piezoelectric films having opposite polarization directions. By applying driving voltages of opposite polarities between the upper electrode and the intermediate electrode and between the intermediate electrode and the lower electrode, one piezoelectric film can contract while the other extends synchronously, thus achieving a more significant displacement and driving force. However, aluminum nitride piezoelectric films are inherently limited by their spontaneous polarization characteristics, requiring complex thin-film deposition processes to achieve opposite polarization directions, making the process extremely difficult. Although lead zirconate titanate piezoelectric films can have their internal domains reoriented to change their polarization direction by applying a DC electric field of sufficient intensity and duration, the piezoelectric films are concentrated on one side of the substrate, and the difference in thermal expansion coefficients between different materials causes large residual stress in the overall driving structure, thus affecting the long-term stability of the device.

[0026] See Figure 2 (c) The symmetrical discrete stacked piezoelectric structure provided in this embodiment includes a silicon substrate layer 2, and an upper piezoelectric actuator 3 and a lower piezoelectric actuator 4 respectively disposed on the surface of the silicon substrate layer 2; wherein, the upper piezoelectric actuator 3 includes a first insulating layer 3.1, a first lower electrode 3.2, an upper piezoelectric film 3.3, and a first upper electrode 3.4 sequentially disposed on the upper surface of the substrate layer 2; the lower piezoelectric actuator 4 includes a second insulating layer 4.1, a second lower electrode 4.2, a lower piezoelectric film 4.3, and a second upper electrode 4.4 sequentially disposed on the lower surface of the substrate layer 2. The second upper electrode 4.3 and the second lower electrode 4.2 are used to provide a driving voltage for the upper piezoelectric actuator 4; the first upper electrode 3.4 and the first lower electrode 3.2 are used to provide a driving voltage for the lower piezoelectric actuator 3. The driving voltage configuration parameters of the upper piezoelectric actuator 3 and the lower piezoelectric actuator 4 are the same. The two driver layers are symmetrically distributed about the substrate, which can effectively counteract the residual stress caused by the thermal expansion difference between different materials, achieve stress balance of the overall structure, and significantly reduce the impact of residual stress on device performance. It should be noted that, to further improve the overall stability of the driving structure, the materials of the first upper electrode 3.4, the first lower electrode 3.2, the second upper electrode 4.4, and the second lower electrode 4.2 are one of gold, aluminum, molybdenum, and platinum, or a combination of two or more of the above four metal materials. The materials of the upper piezoelectric film 3.3 and the lower piezoelectric film 4.3 are one of aluminum nitride, scandium aluminum nitride, lead zirconate titanate, and zinc oxide, and the materials of the upper and lower piezoelectric films are consistent. The material of the substrate layer 2 is silicon, glass, or polyimide.

[0027] See Figure 3Based on the aforementioned symmetrical discrete stacked piezoelectric drive structure, this embodiment further proposes a microelectromechanical system (MEMS) torsional beam splitter chip. This chip integrates a symmetrical piezoelectric drive structure with functional components such as micromirrors and gratings to achieve integrated beam splitting and scanning. The specific structure comprises: an outer layer 6, a substrate 5, a micromirror 11, an integrated grating 10, a torsion beam 7, a transmission beam 8, a first piezoelectric drive structure 9, a second piezoelectric drive structure 12, a third piezoelectric drive structure 14, a fourth piezoelectric drive structure 15, and a torsion angle sensing unit 13. The integrated grating 10 is integrated on the front side of the micromirror 11, and the micromirror 11 is fixedly connected to a pair of torsion beams 7. To increase the scanning angle of the micromirror 11, a lever amplification mechanism of the transmission beam 8 is introduced between the piezoelectric driver and the torsion beams 7, improving torque output efficiency by extending the driving arm. Simultaneously, a piezoelectric torsion angle sensing unit 13 is integrated on the tail end of the torsion beam 7 (i.e., the stress concentration point of the structure) to achieve closed-loop control of the micromirror deflection angle, improving scanning accuracy.

[0028] In this torsional beam splitter chip, the micromirror 11 has an aperture size of 5mm × 5mm, the transmission beam 8 adopts a folded beam structure with a width of 200μm, the torsional beam 7 has a width of 100μm, and the thickness of all the above structures is 50μm. The integrated grating 10 adopts a rectangular grating with a period of 4μm, a duty cycle of 1:1, and a groove depth of 3μm.

[0029] See Figure 3 The torsional beam splitter chip comprises four piezoelectric driving structures: a first piezoelectric driving structure 9, a second piezoelectric driving structure 12, a third piezoelectric driving structure 14, and a fourth piezoelectric driving structure 15, all of which are symmetrically discretely stacked piezoelectric structures provided in this embodiment. The first piezoelectric driving structure 9 and the second piezoelectric driving structure 12 apply the same driving signal, designated as the first group of driving signals; the third piezoelectric driving structure 14 and the fourth piezoelectric driving structure 15 apply the same driving signal, designated as the second group of driving signals. The driving signals can be sinusoidal signals, and the first group of driving signals and the second group of driving signals are 180° out of phase, causing the micromirror 11 to undergo torsional motion. (See reference...) Figure 4 In this embodiment, the driving signal is an AC signal. When the first set of driving signals and the second set of driving signals are 180° out of phase, the micromirror will perform a torsional motion; when the first set of driving signals and the second set of driving signals are in phase, the micromirror will perform a translational motion in the vertical direction.

[0030] See Figure 5 In this embodiment, the substrate 5 is provided with an active chamber 5.1 for the movement of the micromirror 11, two torsion beams 7, four transmission beams 8, the first piezoelectric drive structure 9, the second piezoelectric drive structure 12, the third piezoelectric drive structure 14, and the fourth piezoelectric drive structure 15. The active chamber 5.1 is a through-hole structure that extends axially along the substrate 5 from the area surrounded by the outer layer 6. Figure 5 As shown in the dashed rectangle.

[0031] See Figure 5 The method for fabricating a microelectromechanical system (MEMS) torsional beam splitter chip also provided in this embodiment specifically includes the following steps: S1: See Figure 5 (a) An 8-inch high-resistivity single-crystal silicon wafer with a thickness of 500 μm is provided as the base layer of the outer layer 6. 100 nm SiO2 and 100 nm Si3N4 are sequentially deposited on its surface using plasma-enhanced chemical vapor deposition (PECVD). The pattern is defined by photolithography and the SiO2 and Si3N4 bilayer film is etched by reactive ion etching (RIE) to complete the preparation of the insulating layer 4.1. S2: See also Figure 5 (b) On the surface of the outer silicon wafer 6 after S1 treatment, i.e. the surface of the insulating layer 4.1, a photoresist pattern structure for metal stripping is first prepared by photolithography; a 200nm molybdenum (Mo) layer is deposited by magnetron sputtering as the metal material of the first lower electrode; finally, the silicon wafer is placed in the photoresist stripping solution, and excess photoresist and residual Mo on the surface are removed by ultrasonic-assisted stripping to complete the preparation of the second lower electrode 4.2. S3: See also Figure 5 (c) On the surface of the outer silicon wafer 6 of S2, i.e. the surface of the second lower electrode 4.2, a 1 μm thick lower aluminum nitride (AlN) piezoelectric film is deposited by magnetron sputtering. The film has a (002) preferred crystal orientation. Using photoresist as a mask, the AlN film is patterned by inductively coupled plasma etching (ICP) process to complete the preparation of the lower piezoelectric film 4.3.

[0032] S4: See also Figure 5 (d) On the surface of the outer silicon wafer 6 processed by S3, i.e. the surface of the lower piezoelectric film 4.3, a photoresist patterning mask for metal stripping is first prepared by photolithography, and a 200nm metal platinum (Pt) layer is deposited by magnetron sputtering. Then, the silicon wafer is placed in a special photoresist stripping solution, and excess photoresist and Pt in non-target areas on the surface are removed by ultrasonic-assisted stripping to complete the preparation of the second upper electrode 4.4.

[0033] S5: See Figure 5 (e) On the surface of the outer silicon wafer 6 of S4, i.e. the surface of the second upper electrode 4.4, 1500 nm Au and 1000 nm Sn are deposited sequentially using electron beam evaporation as bonding layer materials. Then, the first bonding layer 16.1 is fabricated by patterning it using a wet metal etching process.

[0034] S6: See also Figure 5(f) A single-crystal silicon wafer with a thickness of 500 μm is provided as substrate 5. A bonding layer material of 750 nm Au and 500 nm Sn is deposited sequentially using electron beam evaporation. An etching mask is prepared by photolithography and patterned by metal wet etching process to complete the preparation of the second bonding layer 16.2.

[0035] S7: See also Figure 5 (g) Through-hole structures are etched on the substrate silicon wafer 5 using deep reactive ion etching (DRIE) process.

[0036] S8: See Figure 5 (h) The two silicon wafers are aligned and bonded using a gold-tin eutectic bonding process. S9: See Figure 5 (i) The thickness of the silicon wafer in the area surrounded by the defined outer layer 6 was reduced from 500 μm to 50 μm by chemical mechanical polishing.

[0037] S10: See Figure 6 On the thinned outer layer 6 silicon wafer surface, a grating structure mask is fabricated using photolithography. The grating type is a rectangular grating with a period of 2-5 μm and a duty cycle of 1:1. Subsequently, a 3 μm grating groove is fabricated using DRIE etching, completing the fabrication of the integrated grating 10. Figure 6 As shown, the process consists of three sub-steps. First, as... Figure 6 (a) A grating structure mask 17 is fabricated on the silicon wafer surface. Next, as... Figure 6 (b) The grid array positions are set on the surface of the grating structure mask 17. Finally, as shown... Figure 6 (c) The grating structure is engraved at the grating array position.

[0038] S11: See also Figure 5 (j) On the silicon wafer surface of the outer layer 6 after completing S9, repeat the process steps from S1 to S4 to sequentially complete the fabrication of the insulating layer 3.1, the first lower electrode 3.2, the upper AlN piezoelectric film 3.3 and the first upper electrode 3.4 of the upper piezoelectric actuator 3.

[0039] S12: See also Figure 5 (k) The outer silicon wafer 6 is etched using the DRIE etching process to a depth of 50μm, releasing movable structures such as micromirror 11, torsion beam 7, and transmission beam 8.

[0040] Example 2: See Figure 2(c) The dual-layer discrete piezoelectric structure provided in this embodiment includes a silicon substrate layer 2, and an upper piezoelectric actuator 3 and a lower piezoelectric actuator 4 respectively disposed on the surface of the silicon substrate layer 2; wherein, an upper insulating layer 3.1, a first lower electrode 3.2, an upper piezoelectric thin film 3.3 made of PZT material, and a first upper electrode 3.4 are sequentially disposed on the upper side of the silicon substrate layer 2, and the first upper electrode 3.4, the first lower electrode 3.2, and the upper piezoelectric thin film 3.3 together constitute the upper piezoelectric actuator 3. An upper electrode 3.4 and a first lower electrode 3.2 are used to provide driving voltage for the upper piezoelectric actuator 3. A lower insulating layer 4.1, a second lower electrode 4.1, a lower piezoelectric film 4.3 made of PZT material, and a second upper electrode 4.4 are disposed on the lower side of the silicon substrate. The second upper electrode 4.4, the second lower electrode 4.2, and the lower piezoelectric film 4.3 together constitute the lower piezoelectric actuator 4. The second upper electrode 4.4 and the second lower electrode 4.2 are used to provide driving voltage for the lower piezoelectric actuator 4. The driving voltage configuration parameters of the upper piezoelectric actuator 3 and the lower piezoelectric actuator 4 are consistent. The two actuators are symmetrically distributed about the substrate, which can effectively counteract the residual stress caused by the thermal expansion difference between different materials, achieve stress balance of the overall structure, and significantly reduce the impact of residual stress on device performance.

[0041] See Figure 3 Based on the aforementioned dual-layer discrete piezoelectric drive structure, a microelectromechanical system (MEMS) torsional beam splitter chip is further proposed. This chip integrates a symmetrical piezoelectric drive structure with functional components such as micromirrors and gratings to achieve integrated beam splitting and scanning. The specific structure comprises an outer layer 6, a substrate 5, a micromirror 11, an integrated grating 10, a torsion beam 7, a transmission beam 8, a first piezoelectric drive structure 9, a second piezoelectric drive structure 12, a third piezoelectric drive structure 14, a fourth piezoelectric drive structure 15, and a torsion angle sensing unit 13. The integrated grating 10 is integrated on the front side of the micromirror 11, and the micromirror 11 is fixedly connected to a pair of torsion beams 7. To increase the scanning angle of the micromirror 11, a lever amplification mechanism is introduced between the piezoelectric driver and the torsion beams 7, extending the driving arm to improve torque output efficiency. Simultaneously, a piezoelectric torsion angle sensing unit 13 is integrated on the tail end of the torsion beam 7 (i.e., the stress concentration point) to achieve closed-loop control of the micromirror deflection angle, improving scanning accuracy.

[0042] In this embodiment, the micromirror 11 has an aperture size of 2mm × 2mm, the transmission beam 8 adopts a straight beam structure with a width of 100μm, the torsion beam 7 has a width of 50μm, and the thickness of all the above structures is 15μm. The integrated grating adopts a V-groove grating with a period of 4μm.

[0043] Similar to Embodiment 1, this torsional beam splitter chip comprises four piezoelectric driving structures, all of which employ the dual-layer discrete piezoelectric structure described in this embodiment. The first piezoelectric driving structure 9 and the second piezoelectric driving structure 12 apply the same driving signal, designated as the first group of driving signals; the third piezoelectric driving structure 14 and the fourth piezoelectric driving structure 15 apply the same driving signal, designated as the second group of driving signals. The driving signal can be a square wave signal. The first group of driving signals and the second group of driving signals are in phase, causing the micromirror 11 to perform vertical translation.

[0044] See Figure 7 The present invention also provides a method for fabricating the torsional beam splitter chip, which specifically includes the following steps: S1: See Figure 7 (a) A 516 μm thick SOI silicon wafer is provided as the base layer of the outer layer 6, wherein the device layer is 15 μm thick, the oxide layer is 1 μm thick, and the substrate layer is 500 μm thick. A 150 nm SiO2 and a 90 nm Si3N4 are sequentially deposited on its surface using a low-pressure chemical vapor deposition (LPCVD) process. The pattern is defined by a photolithography process, and the SiO2 and Si3N4 bilayer film is etched by a BOE wet etching process to complete the preparation of the lower insulating layer 4.1. S2: See also Figure 7 (b) A 300 nm metal Al layer is deposited on the surface of the outer layer SOI silicon wafer 6 after S1 treatment, i.e. the surface of the lower insulating layer 4.1, as the metal material of the first lower electrode by electron beam evaporation. A photoresist pattern structure for metal wet etching is prepared by photolithography. Finally, the SOI silicon wafer is placed in a metal aluminum etching solution to remove excess Al and complete the preparation of the second lower electrode 4.2. S3: See also Figure 7 (c) On the surface of the outer SOI silicon wafer 6 after completing S2, i.e. the surface of the second lower electrode 4.2, a 1 μm thick lower PZT piezoelectric film is deposited using metal-organic chemical vapor deposition (MOCVD); using photoresist as a mask, the PZT film is patterned using a wet etching process with a mixed solution of hydrochloric acid, nitric acid, acetic acid and hydrofluoric acid to complete the preparation of the lower piezoelectric film 4.3.

[0045] S4: See also Figure 7 (d) On the surface of the SOI silicon wafer processed by S3, i.e. the surface of the lower piezoelectric film 4.3, a photoresist patterning mask for metal stripping is first prepared by photolithography, and a 200nm Pt layer is deposited by magnetron sputtering. Then, the SOI silicon wafer is placed in a special photoresist stripping solution, and excess photoresist and Pt in non-target areas on the surface are removed by ultrasonic-assisted stripping to complete the preparation of the second upper electrode 4.4.

[0046] S5: See Figure 7 (e) On the surface of the SOI silicon wafer after S4 is completed, i.e., the surface of the second upper electrode 4.4, 500 nm Al and 500 nm Ge are deposited sequentially using electron beam evaporation as bonding layer materials. Then, the first bonding layer 16.1 is fabricated by patterning it using a wet metal etching process.

[0047] S6: See also Figure 7 (f) A single-crystal silicon wafer with a thickness of 500 μm is provided as the second substrate. 500 nm Al and 500 nm Ge bonding layer materials are deposited sequentially using electron beam evaporation. An etching mask is prepared by photolithography and patterned using a wet metal etching process to complete the preparation of the second bonding layer 16.2.

[0048] S7: See also Figure 7 (g) A through-hole structure is etched on the substrate silicon wafer 5 using a wet etching process.

[0049] S8: See Figure 7 (h) The two silicon wafers are aligned and bonded using an aluminum-germanium eutectic bonding process.

[0050] S9: See Figure 7 (i) The thickness of the silicon wafer in the area surrounded by the outermost layer 6 was reduced from 500 μm to 15 μm by chemical mechanical polishing.

[0051] S10: See Figure 8 On the thinned outer layer 6 silicon wafer, a grating structure mask is prepared by photolithography. The grating type is a V-shaped grating with a period of 5 μm and a duty cycle of 1:1. Subsequently, a wet etching process is used for fabrication.

[0052] S11: See also Figure 7 (j) On the silicon wafer surface of the outer layer 6 after completing S9, repeat the process steps from S1 to S4 to sequentially complete the fabrication of the insulating layer 3.1, the second lower electrode 3.2, the upper AlN piezoelectric film 3.3, and the second upper electrode 3.4 of the upper piezoelectric actuator 3.

[0053] S12: See also Figure 7 (k) The silicon wafer is etched using the DRIE etching process to a depth of 50μm, releasing movable structures such as micromirror 11, torsion beam 7, and transmission beam 8.

[0054] The method disclosed in this embodiment achieves precise alignment and integration of the upper and lower double-layer substrates through wafer-level bonding technology, effectively improving the stability and integration of the device structure. By stepwise deposition of insulating layers, electrode materials, and piezoelectric thin films, combined with patterning technology, high-precision fabrication of the piezoelectric actuator is achieved, ensuring the uniformity and reliability of the driving response. Pre-fabrication of through-holes in the substrate to form moving chambers provides ample space for moving structures such as micromirrors and torsion beams, ensuring the free torsion and stable operation of the micromirror system. Thinning the base layer after bonding and fabricating a grating structure improves optical performance and diffraction efficiency, enhancing the sensitivity and resolution of the spectrometer chip. Simultaneously, the use of a double-sided process flow and the reuse of standardized fabrication steps improves process compatibility and repeatability. These combined steps effectively increase the driving displacement and driving frequency of the resulting chip, significantly reducing the impact of residual stress on device performance, which is conducive to large-scale, batch production. The overall process flow design is reasonable, the steps are clear, and it can effectively reduce manufacturing costs, improve device performance and yield, showing good prospects for industrial application.

[0055] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A symmetrical discrete stacked piezoelectric drive structure, characterized in that, The substrate includes a substrate (2) and an upper piezoelectric actuator (3) and a lower piezoelectric actuator (4) respectively disposed on the upper and lower surfaces of the substrate (2). The upper piezoelectric actuator (3) includes a first insulating layer (3.1), a first lower electrode (3.2), an upper piezoelectric film (3.3) and a first upper electrode (3.4) disposed sequentially on the upper surface of the substrate (2). The lower piezoelectric actuator (4) includes a second insulating layer (4.1), a second lower electrode (4.2), a lower piezoelectric film (4.3) and a second upper electrode (4.4) disposed sequentially on the lower surface of the substrate (2). The upper piezoelectric actuator (3) and the lower piezoelectric actuator (4) are mirror-symmetrically distributed about the substrate (2), and the potentials of the first upper electrode (3.4) and the second upper electrode (4.4) are consistent, and the potentials of the first lower electrode (3.2) and the second lower electrode (4.2) are consistent.

2. The symmetrical discrete stacked piezoelectric drive structure according to claim 1, characterized in that, The first upper electrode (3.4), the first lower electrode (3.2), the second upper electrode (4.4), and the second lower electrode (4.2) are made of one of gold, aluminum, molybdenum, and platinum, or a combination of two or more of the above four metal materials.

3. The symmetrical discrete stacked piezoelectric drive structure according to claim 1, characterized in that, The upper piezoelectric film (3.3) and the lower piezoelectric film (4.3) are made of one of aluminum nitride, scandium aluminum nitride, lead zirconate titanate, and zinc oxide, and the materials of the upper and lower piezoelectric films are consistent.

4. The symmetrical discrete stacked piezoelectric drive structure according to claim 1, characterized in that, The substrate (2) is made of silicon, glass or polyimide.

5. A microelectromechanical system (MEMS) torsional beam splitter chip, characterized in that, include: Base (5); The micromirror system includes an outer layer (6) disposed on the substrate (5) and a micromirror (11) located in the area enclosed by the outer layer (6), two torsion beams (7), four drive beams (8), a first piezoelectric drive structure (9), a second piezoelectric drive structure (12), a third piezoelectric drive structure (14), and a fourth piezoelectric drive structure (15). Each side of the micromirror (11) is connected to one end of a torsion beam (7), and the other end of all the torsion beams (7) is connected to the outer layer (6). The piezoelectric drive structure (9), the second piezoelectric drive structure (12), the third piezoelectric drive structure (14) and the fourth piezoelectric drive structure (15) are all connected to the outer layer (6). The output ends of the first piezoelectric drive structure (9) and the fourth piezoelectric drive structure (15) are each connected to one of the torsion beams (7) through a transmission beam (8). The output ends of the second piezoelectric drive structure (12) and the third piezoelectric drive structure (14) are each connected to another torsion beam (7) through a transmission beam (8). An integrated grating (10) is disposed on the micromirror (11); in, The substrate (5) is provided with an activity chamber (5.1) for the movement of the micromirror (11), two torsion beams (7), four transmission beams (8), the first piezoelectric drive structure (9), the second piezoelectric drive structure (12), the third piezoelectric drive structure (14) and the fourth piezoelectric drive structure (15). The first piezoelectric drive structure (9), the second piezoelectric drive structure (12), the third piezoelectric drive structure (14), and the fourth piezoelectric drive structure (15) are all symmetrical discrete stacked piezoelectric drive structures as described in any one of claims 1-4; The first piezoelectric drive structure (9) and the second piezoelectric drive structure (12) are given the same drive signal, and the third piezoelectric drive structure (14) and the fourth piezoelectric drive structure (15) are given the same drive signal.

6. The microelectromechanical system torsional beam splitter chip according to claim 5, characterized in that, The transmission beam (8) is a folded beam, a straight beam, or a trapezoidal beam.

7. The microelectromechanical system torsional beam splitter chip according to claim 5, characterized in that, The integrated grating (10) is a rectangular grating, a V-shaped grating, or a blazed grating.

8. The microelectromechanical system torsional beam splitter chip according to claim 5, characterized in that, Each of the torsion beams (7) has a torsion angle sensing unit (13) on its structural stress concentration plate. The torsion angle sensing unit (13) is a piezoelectric or piezoresistive sensor.

9. A method for fabricating a microelectromechanical system (MEMS) torsional beam splitter chip, characterized in that, The microelectromechanical system torsion beam splitter chip according to any one of claims 5-8 comprises the following steps: S1: Take a substrate as the base layer of the outer layer (6), deposit an insulating layer material on its surface, and perform a patterning process on the insulating layer material to form a second insulating layer (4.1) with a preset pattern. S2: Electrode material is deposited on the surface of the second insulating layer (4.1), and the electrode material is patterned by a metal material patterning process to prepare the second lower electrode (4.2). S3: Deposit a piezoelectric thin film material on the surface of the second lower electrode (4.2), and perform a patterning process on the piezoelectric thin film material to complete the preparation of the lower piezoelectric thin film (4.3); S4: Deposit electrode material on the surface of the lower piezoelectric film (4.3), and pattern the electrode material using a metal material patterning process to prepare the first upper electrode (4.4). S5: Deposit bonding layer material on the surface of the base layer and perform a patterning process on the bonding layer material to prepare the first bonding layer (16.1). S6: Take another substrate as the base (5), deposit a bonding layer material on its surface, and perform a patterning process on the bonding layer material to prepare a second bonding layer (16.2) that is compatible with the first bonding layer (16.1). S7: An axial through-hole structure is prepared on the substrate (5) using an etching process to obtain an active chamber (5.1) for the micromirror (11), two torsion beams (7), four transmission beams (8), the first piezoelectric drive structure (9), the second piezoelectric drive structure (12), the third piezoelectric drive structure (14) and the fourth piezoelectric drive structure (15). S8: Using a wafer-level bonding process, the first bonding layer (16.1) on the base layer is aligned and bonded to the second bonding layer (16.2) of the substrate (5) to form a bonded wafer; S9: Thin the base layer in the bonding wafer; S10: Fabricate a grating structure on the surface of the base layer after S9 thinning; S11: On the surface of the base layer after processing in S10, repeat the same process steps as S1 to S4 to sequentially complete the preparation of the first insulating layer (3.1), the first lower electrode (3.2), the upper piezoelectric film (3.3) and the first upper electrode (3.4); S12: The structure at the bonding wafer of the base layer is released by etching process to form a micromirror system.

10. The method for fabricating a microelectromechanical system torsional beam splitter chip according to claim 9, characterized in that, In step S1, the base layer is a single-crystal silicon wafer or a silicon-on-insulator wafer; in step S7, the through-hole structure is prepared by deep reactive ion etching, surface laser ablation, or wet etching; in step S8, the bonding process is gold-tin eutectic bonding, aluminum-germanium eutectic bonding, silicon-silicon oxide-silicon direct bonding, or silicon-glass anodic bonding; in step S9, the thickness of the base layer after thinning is 10μm-100μm; in step S12, the etching process is deep reactive ion etching, surface laser ablation, or wet etching.

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