Piezoelectric drive structure, piezoelectric micromirror and method for manufacturing a piezoelectric micromirror

Abstract

The present invention discloses a piezoelectric drive structure, a piezoelectric micromirror and a method for manufacturing a piezoelectric micromirror. The piezoelectric drive structure includes a piezoelectric layer, a continuous upper electrode above the piezoelectric layer, and a continuous lower electrode below the piezoelectric layer. One end above the upper electrode is provided with an upper dielectric layer, and a lower dielectric layer is provided below the lower electrode. The lengths of the upper dielectric layer and the lower dielectric layer are less than that of the piezoelectric layer, and the upper dielectric layer and the lower dielectric layer do not completely overlap in the horizontal direction on the horizontal plane where the piezoelectric layer is located. In view of the problems existing in the piezoelectric Bimorph drive structure without lateral displacement and rotation angle, such as complex drive circuit, cumbersome leads and low drive efficiency, the present invention proposes a new simplified structure and manufacturing scheme, in which the Bimorph drive structure does not need to be provided with special leads.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectromechanical systems and their manufacturing technologies, and particularly relates to a piezoelectric driving structure, a piezoelectric micromirror, and a method for manufacturing a piezoelectric micromirror. Background Art

[0002] The micro driving structure using MEMS technology has the advantages of small size, high reliability, low power consumption, and easy mass production, and is widely used in many MEMS devices. The micromirror is a typical application of the MEMS micro driving structure, which refers to an optical MEMS device manufactured by using optical MEMS technology, integrating a micro optical mirror and an MEMS driver. Through two mechanical motions of translation and torsion, the control of the propagation direction and phase of the light beam can be realized. MEMS micromirrors generally adopt four driving methods: electrostatic, electromagnetic, electrothermal, and piezoelectric. Among them, the piezoelectric-driven micromirror has been widely studied and applied due to its advantages of large driving force, low power consumption, accurate positioning, and small size.

[0003] In the existing piezoelectric-driven micromirrors, a vertical displacement electrothermal / piezoelectric driving structure in the form of Bimorph is proposed in Patent US8148874B2 for micromirror devices. Four sections of the Bimorph structure are connected in series from beginning to end. One end of the overall structure is fixed, and the other end can achieve vertical driving without lateral displacement and rotation. This structure is mainly applied to the driving of the vertical displacement and rotation of the micromirror. In the case of piezoelectric driving, the upper and lower piezoelectric thin films of a single-section Bimorph structure adopt reverse driving (under the action of the transverse piezoelectric effect, one layer of the structure undergoes transverse contraction, and one layer of the structure undergoes transverse expansion), and adjacent Bimorph structures perform reverse displacement driving. Although the piezoelectric driving structure unit of this patent can make the most efficient use of the driving ability of Bimorph, its electrode configuration is complex, and there are also great difficulties in the process preparation.

[0004] In the literature "Development and applications of high fill-factor, small footprint mems micromirrors and micromirror arrays", "Research on the Key Technologies of Micro-Optical Scanning Devices Based on Piezoelectric Micro-Drivers", Chinese invention patents CN113759540A and CN110031966B, the aforementioned structure is simplified. The lower layer structure of the Bimorph adopts a simple structural layer without piezoelectric effect, and only the upper layer of the Bimorph is set as the piezoelectric layer. Although this structure is simplified to a certain extent, the Bimorph driving unit still uses a complex differential voltage drive (three electrode interfaces, one positive electrode, one negative electrode, and one grounded). At this time, lead wiring needs to be carried out on the Bimorph beam, occupying a certain width, wasting the width of the driving arm to a certain extent, and reducing the driving efficiency. Summary of the Invention

[0005] The object of the present invention is to provide a piezoelectric drive structure, a piezoelectric micromirror and a method for preparing a piezoelectric micromirror to overcome the defects of the prior art. Aiming at the problems of complex drive circuits, cumbersome lead wires and low drive efficiency existing in the piezoelectric Bimorph drive structure without lateral displacement and rotation, the present invention proposes a new simplified structure and preparation scheme. In this scheme, the piezoelectric Bimorph drive structure does not need to be provided with special upper and lower electrode leads for the piezoelectric layer, which simplifies the design and preparation process.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A piezoelectric drive structure, the piezoelectric drive structure includes a piezoelectric layer, a continuous upper electrode above the piezoelectric layer and a continuous lower electrode below the piezoelectric layer. One end above the upper electrode is provided with an upper dielectric layer, and a lower dielectric layer is provided below the lower electrode. The lengths of the upper dielectric layer and the lower dielectric layer are less than that of the piezoelectric layer, and the upper dielectric layer and the lower dielectric layer do not completely coincide in the horizontal direction on the horizontal plane where the piezoelectric layer is located.

[0008] Further, there is a partial overlap between one end of the upper dielectric layer close to the midpoint of the piezoelectric layer and one end of the lower dielectric layer close to the midpoint of the piezoelectric layer, and the overlapping part forms a connection structure.

[0009] Further, the materials of the upper dielectric layer and the lower dielectric layer include any one or any combination of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT or zinc oxide.

[0010] On the other hand, the present invention also provides a piezoelectric micromirror, which includes a mirror surface and a driving unit connected to the mirror surface through a connecting portion. The driving unit includes an anchor point connected to a substrate. The driving unit includes a driving arm formed by the piezoelectric driving structure according to any one of claims 1-3. The driving arm includes a first driving member group and a second driving member group. The first driving member group is axially symmetrically connected to the anchor point with the positive sequence structure end, and the second driving member group is axially symmetrically connected to the connecting portion with the reverse sequence structure end. The positive sequence structure includes the lower dielectric layer and the lower electrode, piezoelectric layer, and upper electrode covered by the lower dielectric layer. The reverse sequence structure includes the upper dielectric layer and the upper electrode, piezoelectric layer, and lower electrode covered by the upper dielectric layer. The first driving member group and the second driving member group include an equal number of piezoelectric driving structures. The ends of the first driving member group and the second driving member group on both sides of the connecting portion away from the connecting portion or the anchor point are fixedly connected through a connecting member;

[0011] When the number of piezoelectric driving structures in the first driving member group and the second driving member group is greater than one, the piezoelectric driving structures in each driving member group are connected in series.

[0012] Furthermore, the mirror surface of the piezoelectric micromirror is axially symmetric or centrosymmetric. When the mirror surface of the piezoelectric micromirror is axially symmetric, the driving units are axially symmetrically distributed on the side of the mirror surface; when the mirror surface of the piezoelectric micromirror is centrosymmetric, the driving units are centrosymmetrically distributed on the side of the mirror surface.

[0013] Furthermore, the connecting member includes a connecting member piezoelectric layer, a continuous connecting member upper electrode above the connecting member piezoelectric layer, and a continuous connecting member lower electrode below the connecting member piezoelectric layer. One end above the connecting member upper electrode is provided with a connecting member upper dielectric layer, and a connecting member lower dielectric layer is provided below the connecting member lower electrode. The lengths of the connecting member upper dielectric layer and the connecting member lower dielectric layer are the same as that of the connecting member piezoelectric layer.

[0014] Furthermore, the connecting member is a U-shaped connecting member.

[0015] On the other hand, the present invention also provides a method for manufacturing a piezoelectric micromirror, which includes:

[0016] Prepare an SOI wafer, where the SOI wafer includes a device layer, a buried oxide layer, and a substrate layer;

[0017] Deposit a layer of dielectric on the front surface of the SOI wafer and perform patterning to prepare a lower dielectric layer;

[0018] Prepare a continuous lower electrode layer above the lower dielectric layer;

[0019] Prepare a piezoelectric layer above the lower electrode layer;

[0020] A continuous upper electrode layer is prepared above the piezoelectric layer;

[0021] A layer of dielectric is deposited above the upper electrode layer and patterned to prepare the upper dielectric layer;

[0022] A mirror surface and leads are prepared on the front side of the SOI wafer;

[0023] The back side of the SOI wafer is etched to form a back cavity;

[0024] Isotropic etching is performed from the front side of the SOI wafer to release the excess silicon and form a complete micro-mirror chip.

[0025] Furthermore, the mirror surface includes a patterned metal mirror reflection layer.

[0026] Furthermore, the etching of the back side of the SOI wafer includes photolithography and deep silicon etching.

[0027] The beneficial effects of the present invention are as follows:

[0028] (1) The piezoelectric drive structure, piezoelectric micro-mirror and piezoelectric micro-mirror preparation method proposed by the present invention adopt a different idea from the traditional Bimorph structure that only prepares a piezoelectric layer above the dielectric layer / structural layer. The positive sequence and reverse sequence of the Bimorph structure are respectively prepared above and below the piezoelectric layer. Each drive unit has only one upper electrode and one lower electrode, and there is no need to arrange electrode leads on the Bimorph structure. The electrode arrangement is simple, the utilization rate of the Bimorph beam structure is high, and the preparation is efficient and fast.

[0029] (2) The piezoelectric micro-mirror device proposed by the present invention only requires a simple circuit to drive a single drive unit, without the need for a complex differential drive circuit, which simplifies the complexity during the subsequent development of the micro-mirror system and reduces the cost. Description of the Drawings

[0030] Figure 1 is a schematic diagram of the piezoelectric drive structure provided by an embodiment of the present invention;

[0031] Figure 2 is a top view schematic diagram of a uniaxial structure piezoelectric micro-mirror provided by an embodiment of the present invention;

[0032] Figure 3 is a top view schematic diagram of a biaxial structure piezoelectric micro-mirror provided by an embodiment of the present invention;

[0033] Figure 4 is a schematic diagram of the piezoelectric micro-mirror preparation process provided by an embodiment of the present invention; wherein, Figure 4 (a) represents a schematic diagram of wafer preparation, Figure 4 (b) represents a schematic diagram of the preparation of the lower dielectric layer, Figure 4(c) shows a schematic diagram of the preparation of the lower electrode layer, Figure 4 (d) shows a schematic diagram of the preparation of the piezoelectric layer, Figure 4 (e) shows a schematic diagram of the preparation of the upper electrode layer, Figure 4 (f) shows a schematic diagram of the preparation of the upper dielectric layer, Figure 4 (g) shows a schematic diagram of the preparation of the mirror surface, Figure 4 (h) shows a schematic diagram of the back cavity etching, Figure 4 (i) shows a schematic diagram of the complete micro-mirror chip after the release of the redundant silicon.

[0034] Description of the drawings: 1 - piezoelectric layer, 2 - upper electrode, 3 - lower electrode, 4 - upper dielectric layer, 5 - lower dielectric layer, 6 - device layer, 7 - buried oxide layer, 8 - substrate layer, 9 - lead, 10 - mirror surface, 11 - connecting part, 12 - anchor point, 13 - back cavity. Detailed implementation manners

[0035] The following uses specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0036] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0037] In the existing piezoelectric-driven micro-mirrors, a vertical displacement electrothermal / piezoelectric drive structure in the form of Bimorph is proposed in the patent US8148874B2 for micro-mirror devices. The four-segment Bimorph structure is connected in series end to end. One end of the overall structure is fixed, and the other end can achieve vertical drive without lateral displacement and rotation. This structure is mainly applied to the drive of the vertical displacement and rotation of the micro-mirror. In the case of piezoelectric drive, the upper and lower piezoelectric thin films of a single-segment Bimorph structure adopt anti-phase drive (under the action of the transverse piezoelectric effect, one layer structure undergoes transverse contraction and the other layer structure undergoes transverse expansion), and adjacent Bimorph structures perform reverse displacement drives. Although the piezoelectric drive structure unit of this patent can utilize the drive ability of Bimorph with the highest efficiency, its electrode configuration is complex and there are also great difficulties in the process preparation.

[0038] In the literature "Development and applications of high fill-factor, small footprint mems micromirrors and micromirror arrays", "Research on Key Technologies of Micro-Optical Scanning Devices Based on Piezoelectric Micro-Drivers", Chinese invention patents CN113759540A and CN110031966B, the aforementioned structure is simplified. The lower layer structure of the Bimorph adopts a simple structural layer without piezoelectric effect, and only the upper layer of the Bimorph is set as the piezoelectric layer. Although this structure is simplified to a certain extent, the Bimorph driving unit still uses a complex differential voltage drive (three electrode interfaces, one positive electrode, one negative electrode, and one grounded). At this time, wire arrangement needs to be carried out on the Bimorph beam, occupying a certain width, wasting the width of the driving arm to a certain extent, and reducing the driving efficiency.

[0039] In order to solve the above technical problems, the following various embodiments of the piezoelectric drive structure, piezoelectric micro-mirror and piezoelectric micro-mirror preparation method of the present invention are proposed.

[0040] Embodiment 1

[0041] This embodiment provides a piezoelectric drive structure. Aiming at the problems of complex drive circuit, cumbersome wiring and low drive efficiency existing in the piezoelectric Bimorph drive structure without lateral displacement and rotation, a new simplified structure is proposed, and no special wiring needs to be set.

[0042] Referring to Figure 1 As Figure 1 shown is a schematic diagram of the piezoelectric drive structure provided in this embodiment. The structure specifically includes:

[0043] Piezoelectric layer 1, continuous upper electrode 2 above piezoelectric layer 1 and continuous lower electrode 3 below piezoelectric layer 1. An upper dielectric layer 4 is provided at one end above the upper electrode 2, and a lower dielectric layer 5 is provided below the lower electrode 3. The lengths of the upper dielectric layer 4 and the lower dielectric layer 5 are less than that of the piezoelectric layer 1, and the upper dielectric layer 4 and the lower dielectric layer 5 do not completely overlap in the horizontal direction on the horizontal plane where the piezoelectric layer 1 is located.

[0044] It should be noted that if the lengths of the upper and lower dielectric layers are different and one of the dielectric layers is completely surrounded by the other in the horizontal direction, it also belongs to the case of complete overlap.

[0045] It should also be noted that if both endpoints of the upper dielectric layer 4 and the lower dielectric layer 5 coincide horizontally on the horizontal plane where the piezoelectric layer 1 is located, a "sandwich" structure will be formed, and no deformation can occur after power-on, so the driving effect cannot be achieved. If any one of the endpoints of the upper dielectric layer 4 and the lower dielectric layer 5 coincides horizontally on the horizontal plane where the piezoelectric layer 1 is located, then one side of the endpoint cannot generate deformation after power-on, and only the other end generates deformation, which has a greater impact on the driving effect.

[0046] As an implementation manner, a part of the end of the upper dielectric layer 4 close to the midpoint of the piezoelectric layer 1 coincides with a part of the end of the lower dielectric layer 5 close to the midpoint of the piezoelectric layer 1. Taking Figure 1 as an example, the upper part of the middle section of the piezoelectric driving structure includes the upper electrode 2 and the upper dielectric layer 4, and the lower part includes the lower electrode 3 and the lower dielectric layer 5. When the middle section of the piezoelectric driving structure includes both the upper dielectric layer 4 and the lower dielectric layer 5, a "sandwich" structure is formed. The overlapping part can be regarded as the connection structure of the positive sequence and the reverse sequence structures. After the piezoelectric driving structure generates deformation after power-on, such a structure can make the structure more firm and not easily break. If the upper dielectric layer 4 and the lower dielectric layer 5 do not coincide horizontally on the horizontal plane where the piezoelectric layer 1 is located, only the piezoelectric structure exists in the non-overlapping part, and the structural strength will be relatively poor.

[0047] As an implementation manner, the materials of the upper dielectric layer 4 and the lower dielectric layer 5 can be selected from any one or any combination of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT, or zinc oxide. When multiple materials are selected, the upper dielectric layer 4 and the lower dielectric layer 5 are composed of a composite layer of multiple materials.

[0048] The piezoelectric structure layer is located in the middle and includes the piezoelectric layer 1, the upper electrode 2, and the lower electrode 3; a pure structure layer of one section of Bimorph is located below the piezoelectric structure layer (this section of Bimorph is called the positive sequence Bimorph), and a pure structure layer of another section of Bimorph is located above the piezoelectric structure layer (this section of Bimorph is called the reverse sequence Bimorph).

[0049] The piezoelectric driving structure provided in this embodiment is improved on the driving structure of the traditional piezoelectric mirror. Different from the traditional scheme of only preparing the Bimorph structure on the dielectric layer above the piezoelectric layer, the positive sequence and the reverse sequence of the Bimorph structure are respectively prepared above and below the piezoelectric layer of the piezoelectric driving structure. The piezoelectric driving structure has only one upper electrode and one lower electrode, and there is no need to arrange electrode leads on the Bimorph structure. The electrode arrangement is simple, the utilization rate of the Bimorph beam structure is high, and the preparation is efficient and fast.

[0050] Embodiment 2

[0051] Refer to Figure 2 As shown in Figure 2The figure shows a top view schematic diagram of a uniaxial piezoelectric micromirror provided in this embodiment. The mirror surface 10 of the piezoelectric micromirror provided in this embodiment is a square mirror surface, and each side of the driving structure is driven by a positive electrode and a negative electrode. The piezoelectric micromirror is a uniaxial structure with the straight line passing through the midpoints on the upper and lower sides of the mirror surface 10 in the figure as the axis of symmetry, including the mirror surface 10 and two driving structure units on the left and right connected to the mirror surface 10 through the connecting part 11. On the side of the two driving structure units facing away from the mirror surface 10, there are also anchor points 12, and the anchor points 12 are connected to the silicon substrate, serving as the area to support the entire micromirror. The materials of the connecting part 11 and the anchor points 12 can be selected from any one or any combination of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT, or zinc oxide. When multiple materials are selected, the upper dielectric layer 4 and the lower dielectric layer 5 are composed of a composite layer of multiple materials.

[0052] Among them, the driving structure unit is composed of a driving arm and a connecting piece. The driving arm includes a first driving component group and a second driving component group. The first driving component group is symmetrically connected to the anchor point 12 with the positive sequence structure end, and the second driving component group is symmetrically connected to the connecting part 11 with the reverse sequence structure end. The positive sequence structure includes the lower dielectric layer 5 and the lower electrode 3 and the piezoelectric layer 1 covered by the lower dielectric layer 5, and the reverse sequence structure includes the upper dielectric layer 4 and the upper electrode 2 and the piezoelectric layer 1 covered by the upper dielectric layer 4. The first driving component group and the second driving component group each contain two piezoelectric driving structures, and the two piezoelectric driving structures in each driving component group are symmetrically arranged with the connecting part 11 or the anchor point 12 as the axis of symmetry. The ends of the first driving component group on both sides of the connecting part 11 and the second driving component group on both sides of the anchor point 12 away from the connecting part 11 and the anchor point 12 are fixedly connected through the connecting piece.

[0053] As an implementation manner, the connecting piece is a U-shaped connecting piece, and the structure of the connecting piece is the aforementioned "sandwich" structure, specifically including a connecting piece piezoelectric layer, a continuous connecting piece upper electrode above the connecting piece piezoelectric layer, and a continuous connecting piece lower electrode below the connecting piece piezoelectric layer. There is a connecting piece upper dielectric layer above the connecting piece upper electrode, and a connecting piece lower dielectric layer below the connecting piece lower electrode. The lengths of the connecting piece upper dielectric layer and the connecting piece lower dielectric layer are the same as that of the connecting piece piezoelectric layer.

[0054] The piezoelectric micromirror provided in this embodiment can achieve vertical displacement and rotation around the vertical axis through driving. The specific working principle is as follows:

[0055] Apply voltage to the upper and lower electrodes of the piezoelectric structure layer of the micromirror driving arm. Under the action of the electric field, the piezoelectric layer generates lateral expansion and contraction, causing the bending of the positive sequence / reverse sequence Bimorph structure, and further resulting in the generation of non-rotating vertical translational displacement at the end point (mirror surface connection) of the driving arm. When the voltages of the two driving arms are in phase, the displacements of the driving arm end points are the same, and the micromirror mirror surface generates vertical translational displacement; when the voltages of the two driving arms are out of phase, the magnitudes of the driving arm end point displacements are the same, but the directions are opposite, and the micromirror mirror surface rotates.

[0056] For the uniaxial - structure piezoelectric micromirror provided in this embodiment, the driving - structure units are distributed symmetrically about the axis on both sides of the mirror surface. By driving the driving - structure units, the vertical displacement of the piezoelectric micromirror and the rotation about the vertical axis can be achieved. The driving unit of the piezoelectric micromirror adopts the piezoelectric driving structure provided in the foregoing embodiment, without the need to set up special leads, which can make the most of the width of the driving arm and improve the driving efficiency.

[0057] Embodiment 3

[0058] Refer to Figure 3 ,as Figure 3 shown in the top - view schematic diagram of the biaxial - structure piezoelectric micromirror provided in this embodiment. The mirror surface 10 of the piezoelectric micromirror provided in this embodiment is a square mirror surface 10. Each side of the driving structure is driven by a positive electrode and a negative electrode. This piezoelectric micromirror is a biaxial - structure with the axes being the straight lines passing through the mid - points of the left - and - right sides and the up - and - down sides of the mirror surface 10 in the figure. It includes a mirror surface 10 and four driving - structure units on the up, down, left, and right sides connected to the mirror surface 10 through connecting parts 11. On the side of the four driving - structure units away from the mirror surface 10, there are also anchor points 12. The anchor points 12 are connected to the silicon substrate and are the regions that support the entire micromirror. The materials of the connecting parts 11 and the anchor points 12 can be selected from any one or any combination of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT, or zinc oxide. When multiple materials are selected, the upper dielectric layer 4 and the lower dielectric layer 5 are composed of a composite layer of multiple materials.

[0059] Among them, the driving - structure unit is composed of a driving arm and a connecting piece. The driving arm includes a first driving - piece group and a second driving - piece group. The first driving - piece group is symmetrically connected to the anchor point 12 with the positive - order - structure end, and the second driving - piece group is symmetrically connected to the connecting part 11 with the reverse - order - structure end. The positive - order structure includes a lower dielectric layer 5 and the lower electrode 3, piezoelectric layer 1, and upper electrode 2 covered by the lower dielectric layer 5. The reverse - order structure includes an upper dielectric layer 4 and the upper electrode 2, piezoelectric layer 1, and lower electrode 3 covered by the upper dielectric layer 4. The first driving - piece group and the second driving - piece group each contain two piezoelectric driving structures. The two piezoelectric driving structures in each driving - piece group are symmetrically arranged with respect to the connecting part 11 or the anchor point 12. The ends of the first driving - piece group on both sides of the connecting part 11 and the second driving - piece group on both sides of the anchor point 12 away from the connecting part 11 and the anchor point 12 are fixedly connected through a connecting piece.

[0060] As an implementation manner, the connecting piece is a U - shaped connecting piece. The structure of the connecting piece is the aforementioned "sandwich" structure, specifically including a connecting - piece piezoelectric layer, a continuous connecting - piece upper electrode above the connecting - piece piezoelectric layer, and a continuous connecting - piece lower electrode below the connecting - piece piezoelectric layer. There is a connecting - piece upper dielectric layer at one end above the connecting - piece upper electrode, and a connecting - piece lower dielectric layer is provided below the connecting - piece lower electrode. The lengths of the connecting - piece upper dielectric layer and the connecting - piece lower dielectric layer are the same as that of the connecting - piece piezoelectric layer.

[0061] The piezoelectric micromirror provided in this embodiment can achieve vertical displacement and biaxial rotation around the horizontal / vertical axes through driving. The specific working principle is as follows:

[0062] Apply a voltage across the upper and lower electrodes of the piezoelectric structure layer of the micromirror driving arm. Under the action of the electric field, the piezoelectric layer generates lateral expansion and contraction, causing the bending of the positive / negative sequence Bimorph structure, and further resulting in a non-rotational vertical translational displacement at the end point (mirror connection) of the driving arm. When the voltages of the driving arms on the four sides of up, down, left, and right are in phase, the displacements of the driving arm end points are the same, and the micromirror mirror generates a vertical translational displacement. When the voltages of the driving arms on the left and right sides are out of phase, the displacements of the driving arm end points on the left and right sides are the same in magnitude and opposite in direction, and the micromirror mirror rotates around the vertical axis. When the voltages of the driving arms on the upper and lower sides are out of phase, the displacements of the driving arm end points on the upper and lower sides are the same in magnitude and opposite in direction, and the micromirror mirror rotates around the horizontal axis.

[0063] For the biaxial structure piezoelectric micromirror provided in this embodiment, the driving structure units are distributed on the four sides of the mirror in an axisymmetric form. Through the driving of the driving structure units, the vertical displacement and biaxial rotation around the horizontal / vertical axes of the piezoelectric micromirror can be achieved. The driving unit of the piezoelectric micromirror adopts the piezoelectric driving structure provided in the foregoing embodiment, without the need to set up special leads, which can make the most of the width of the driving arm and improve the driving efficiency.

[0064] It should be noted that the mirror 10 proposed in the foregoing Embodiment 2 and Embodiment 3 being square is only an example, and other shapes of the mirror 10 such as triangular, rectangular, polygonal, etc. can also be selected. With the same setting method of the driving structure units, the vertical displacement and rotation around the axis of the mirror 10 can also be achieved.

[0065] In addition, the first driving component group and the second driving component group for determining the structure units proposed in the foregoing Embodiment 2 and Embodiment 3 only exemplarily give one piezoelectric driving structure symmetrically arranged with respect to the connecting portion 11. According to actual needs, each driving component can be composed of multiple serially connected piezoelectric driving structures, thereby increasing the driving displacement.

[0066] Embodiment 4

[0067] Refer to Figure 4 , as Figure 4 shown is a schematic diagram of the preparation process of the piezoelectric micromirror provided in this embodiment. The piezoelectric micromirror preparation method provided in this embodiment specifically includes:

[0068] Step 1: Prepare an SOI wafer, and the SOI wafer includes a device layer 6, a buried oxide layer 7, and a substrate layer 8. Figure 4 (a) shows a schematic diagram of wafer preparation. Among them, the device layer 6 is the top silicon of the SOI wafer, and the buried oxide layer 7 is thermally oxidized silicon.

[0069] Step 2: Deposit a layer of dielectric on the front side of the SOI wafer and pattern it to fabricate the lower dielectric layer 5. Figure 4 (b) shows a schematic diagram of the fabrication of the lower dielectric layer 5. The lower dielectric layer 5 is the lower layer structure of the forward Bimorph, and the materials that can be used are any one or more of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT, zinc oxide, etc.

[0070] Step 3: Fabricate a continuous lower electrode layer above the lower dielectric layer 5. Figure 4 (c) shows a schematic diagram of the fabrication of the lower electrode layer 3. The lower electrode layer 3 is the bottom electrode metal layer of the piezoelectric structure, and the materials that can be used are one or more of Ti, PT, Mo, Au, Al, AlCu, etc.

[0071] Step 4: Deposit and pattern the piezoelectric layer 1 above the lower electrode layer 3. Figure 4 (d) shows a schematic diagram of the fabrication of the piezoelectric layer 1. The materials that can be used for the piezoelectric layer 1 are PZT, AlN, AlScN, zinc oxide, etc.

[0072] Step 5: Deposit and pattern a continuous upper electrode layer above the piezoelectric layer 1. Figure 4 (e) shows a schematic diagram of the fabrication of the upper electrode layer 2. The upper electrode layer 2 is the top electrode metal layer of the piezoelectric structure, and the materials that can be used are one or more of Ti, PT, Mo, Au, Al, AlCu, etc.

[0073] Step 6: Deposit a layer of dielectric above the upper electrode layer 2 and pattern it to fabricate the upper dielectric layer 4, and at the same time form contact holes. Figure 4 (f) shows a schematic diagram of the fabrication of the upper dielectric layer 4. The upper dielectric layer 4 is the upper layer structure of the reverse Bimorph, and the materials that can be used are any one or more of silicon oxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT, zinc oxide, etc.

[0074] Step 7: Fabricate the mirror 10 and the lead 9 on the front side of the SOI wafer. Figure 4 (g) shows a schematic diagram of the fabrication of the mirror 10. As an implementation manner, the mirror 10 is a patterned metal mirror 10 reflection layer. Both the mirror 10 and the lead 9 are made of metal, and the materials that can be used are Ti, Al, AlCu, Au, Pt, etc.

[0075] Step 8: Etch the back side of the SOI wafer to form the back cavity 13. Figure 4 (h) shows a schematic diagram of the etching of the back cavity 13. As an implementation manner, in this embodiment, photolithography, deep silicon etching, and buried oxide layer etching are performed on the back side of the SOI wafer to form the back cavity 13.

[0076] Step 9: Perform isotropic etching from the front side of the SOI wafer to release the excess silicon, i.e., the silicon under the driving structure, to form a complete micro-mirror chip. Figure 4 (i) Schematic diagram of the complete micro-mirror chip after the release of the excess silicon is completed.

[0077] The piezoelectric micro-mirror preparation method provided in this embodiment can simply and efficiently prepare any one of the piezoelectric micro-mirrors provided in the foregoing embodiments.

[0078] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A piezoelectric drive structure, characterized in that, the piezoelectric drive structure includes a piezoelectric layer, a continuous upper electrode above the piezoelectric layer, and a continuous lower electrode below the piezoelectric layer. One end above the upper electrode is provided with an upper dielectric layer, and a lower dielectric layer is provided below the lower electrode. The lengths of the upper dielectric layer and the lower dielectric layer are less than that of the piezoelectric layer. On the horizontal plane where the piezoelectric layer is located, the upper dielectric layer and the lower dielectric layer do not completely overlap in the horizontal direction. Among them, the piezoelectric layer generates lateral expansion and contraction under the action of an electric field, and there is partial overlap between one end of the upper dielectric layer close to the midpoint of the piezoelectric layer and one end of the lower dielectric layer close to the midpoint of the piezoelectric layer.

2. The piezoelectric drive structure according to claim 1, characterized in that, the materials of the upper dielectric and the lower dielectric layer include any one or any combination of silicon dioxide, silicon nitride, aluminum nitride, aluminum oxide, silicon carbide, PZT or zinc oxide.

3. A piezoelectric micro-mirror, characterized in that, the piezoelectric micro-mirror includes a mirror surface and a driving unit connected to the mirror surface through a connecting portion. The driving unit includes an anchor point connected to a substrate. The driving unit includes a driving arm composed of the piezoelectric drive structure according to any one of claims 1-2. The driving arm includes a first driving component group and a second driving component group. The first driving component group is axially symmetrically connected to the anchor point with a positive sequence structure end, and the second driving component group is axially symmetrically connected to the connecting portion with an inverse sequence structure end. The positive sequence structure includes the lower dielectric layer and the lower electrode, piezoelectric layer, and upper electrode covered by the lower dielectric layer. The inverse sequence structure includes the upper dielectric layer and the upper electrode, piezoelectric layer, and lower electrode covered by the upper dielectric layer. The first driving component group and the second driving component group contain an equal number of piezoelectric drive structures. One end of the first driving component group and the second driving component group on both sides of the connecting portion away from the connecting portion or the anchor point is fixedly connected through a connecting member; when the number of piezoelectric drive structures in the first driving component group and the second driving component group is greater than one, the piezoelectric drive structures in each driving component group are connected in series.

4. The piezoelectric micro-mirror according to claim 3, characterized in that, the mirror surface of the piezoelectric micro-mirror is axially symmetric or centrally symmetric. When the mirror surface of the piezoelectric micro-mirror is axially symmetric, the driving units are axially symmetrically distributed on the side of the mirror surface; when the mirror surface of the piezoelectric micro-mirror is centrally symmetric, the driving units are centrally symmetrically distributed on the side of the mirror surface.

5. The piezoelectric micro-mirror according to claim 3, characterized in that, the connecting member includes a connecting member piezoelectric layer, a continuous connecting member upper electrode above the connecting member piezoelectric layer, and a continuous connecting member lower electrode below the connecting member piezoelectric layer. One end above the connecting member upper electrode is provided with a connecting member upper dielectric layer, and a connecting member lower dielectric layer is provided below the connecting member lower electrode. The lengths of the connecting member upper dielectric layer and the connecting member lower dielectric layer are the same as that of the connecting member piezoelectric layer.

6. The piezoelectric micro-mirror according to any one of claims 3-5, characterized in that, the connecting member is a U-shaped connecting member.

7. A method for manufacturing a piezoelectric micro-mirror, characterized in that, applied to the piezoelectric micro-mirror according to claim 3, the method includes: Prepare an SOI wafer, where the SOI wafer includes a device layer, a buried oxide layer, and a substrate layer; Deposit a layer of dielectric on the front side of the SOI wafer and pattern it to prepare a lower dielectric layer; Prepare a continuous lower electrode layer above the lower dielectric layer; Prepare a piezoelectric layer above the lower electrode layer; Prepare a continuous upper electrode layer above the piezoelectric layer; Deposit a layer of dielectric on the upper electrode layer and pattern it to prepare an upper dielectric layer; Prepare a mirror surface and leads on the front side of the SOI wafer; Etch the back side of the SOI wafer to form a back cavity; Perform isotropic etching from the front side of the SOI wafer to release the excess silicon and form a complete micro-mirror chip.

8. The piezoelectric micro-mirror preparation method according to claim 7, characterized in that, the mirror surface includes a patterned metal mirror reflection layer.

9. The piezoelectric micro-mirror preparation method according to claim 7, characterized in that, the etching of the back side of the SOI wafer includes photolithography and deep silicon etching.

Images