Piezoelectric MEMS micromirror and preparation method thereof, and optical path switch

Abstract

The invention relates to the technical field of optical communication and optical switching, and discloses a piezoelectric MEMS micromirror, a preparation method and an optical path switch. The piezoelectric MEMS micromirror comprises a fixed frame, a micromirror structure, a first piezoelectric driver, a second piezoelectric driver, a third piezoelectric driver and a fourth piezoelectric driver. The top surface of the micro-mirror structure is provided with a first mirror layer, and the bottom surface is provided with a second mirror layer. Two opposite sides of the micro-mirror structure are respectively connected with the fixed frame through a first cantilever beam and a second cantilever beam, and the other two opposite sides of the micro-mirror structure are respectively connected with the fixed frame through a third cantilever beam and a fourth cantilever beam. And the first piezoelectric driver and the second piezoelectric driver are correspondingly arranged on the first cantilever beam and the second cantilever beam. And the third piezoelectric driver and the fourth piezoelectric driver are correspondingly arranged on the third cantilever beam and the fourth cantilever beam. According to the invention, the driving voltage can be reduced, the power consumption can be reduced, the reliability can be improved, a larger deflection angle can be realized, and the flexibility of optical path switching can be improved.

Description

Technical Field

[0001] This application belongs to the field of optical communication and optical switching technology, specifically relating to a piezoelectric MEMS micromirror and its fabrication method, and an optical path switch. Background Technology

[0002] In optical communication networks, with the rapid increase in data traffic, the number of fiber optic links and bandwidth requirements are constantly increasing. Flexible scheduling and switching of optical paths have become crucial for ensuring efficient network operation. An optical circuit switch (OCS) is a key device that enables transparent, high-speed connections between different fiber optic ports and is widely used in data center interconnects, metropolitan area networks (MANs), and long-haul backbone networks.

[0003] Existing optical path switching (OCS) technologies mostly employ free-space optical path switching based on microelectromechanical systems (MEMS) micromirror arrays. These micromirrors, with their two-dimensional tiltable design, accurately guide the input beam to the target output port. These MEMS micromirrors typically use electrostatic, thermal bimetallic, or electromagnetic actuation methods to achieve angle adjustment. Electrostatic actuation is widely used due to its mature technology and low power consumption, but it requires high driving voltages (tens to hundreds of volts), has limited driving force, and imposes certain limitations on the angle control accuracy and stability of the mirror. Thermal actuation methods have high power consumption and slow response; electromagnetic methods are structurally complex and difficult to integrate on a large scale.

[0004] With the increase in optical switching capacity and number of ports, existing driving methods can no longer fully meet the requirements in terms of low voltage, large angle, fast response and long-term stability. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems existing in the related art. Therefore, it provides a piezoelectric MEMS micromirror and its fabrication method, as well as an optical path switch.

[0006] On one hand, a piezoelectric MEMS micromirror is proposed, comprising: a fixed frame; a micromirror structure, wherein a first mirror layer is disposed on the top surface of the micromirror structure and a second mirror layer is disposed on the bottom surface; one opposite side of the micromirror structure is connected to the fixed frame via a first cantilever beam and a second cantilever beam, respectively; the other opposite side of the micromirror structure is connected to the fixed frame via a third cantilever beam and a fourth cantilever beam, respectively; a first piezoelectric drive and a second piezoelectric drive are correspondingly disposed on the first cantilever beam and the second cantilever beam, respectively, for driving the micromirror structure to deflect around a first rotation axis; a third piezoelectric drive and a fourth piezoelectric drive are correspondingly disposed on the third cantilever beam and the fourth cantilever beam, respectively, for driving the micromirror structure to deflect around a second rotation axis, wherein the second rotation axis intersects or is perpendicular to the first rotation axis.

[0007] In one optional embodiment, one end of the first cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through a first connecting structure; one end of the second cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through a second connecting structure, the extending directions of the second connecting structure and the first connecting structure forming the first rotation axis; one end of the third cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through a third connecting structure; one end of the fourth cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through a fourth connecting structure, the extending directions of the fourth connecting structure and the third connecting structure forming the second rotation axis.

[0008] In one alternative embodiment, the piezoelectric MEMS micromirror further includes at least one support post disposed on the bottom surface of the micromirror structure and located outside the second mirror layer.

[0009] On the other hand, an optical path switch is proposed, comprising: an input fiber array, the input fiber array including a plurality of input fiber collimators arranged in an array; a piezoelectric MEMS micromirror array disposed on the light-emitting side of the input fiber array, including a plurality of piezoelectric MEMS micromirrors arranged in an array as described above; and an output fiber array disposed in the reflected optical path of the piezoelectric MEMS micromirror array, the output fiber array including a plurality of output fiber collimators arranged in an array.

[0010] In one optional embodiment, the piezoelectric MEMS micromirror array is provided in two sets, including a first piezoelectric MEMS micromirror array and a second piezoelectric MEMS micromirror array respectively; the first piezoelectric MEMS micromirror array is disposed on the light-emitting side of the input fiber array; the second piezoelectric MEMS micromirror array is disposed in the reflected optical path of the first piezoelectric MEMS micromirror array; and the output fiber array is disposed in the reflected optical path of the second piezoelectric MEMS micromirror array.

[0011] Furthermore, a method for fabricating a piezoelectric MEMS micromirror is proposed, used to fabricate the aforementioned piezoelectric MEMS micromirror. The fabrication method includes the following steps: providing a silicon-on-insulator substrate, the silicon-on-insulator substrate comprising a bottom silicon layer, a buried oxide layer, and a device layer stacked sequentially; forming a driving functional layer, the driving functional layer comprising a buffer layer, a bottom electrode, a piezoelectric driving layer, and a top electrode stacked sequentially on the device layer; patterning the bottom electrode, the piezoelectric driving layer, and the top electrode to form a first piezoelectric drive, a second piezoelectric drive, a third piezoelectric drive, and a fourth piezoelectric drive, and exposing a portion of the top surface of the buffer layer; forming a first mirror layer on the top surface of the exposed portion of the buffer layer; and patterning the device layer and the buffer layer to form at least a micromirror structure, a first cantilever beam, a second cantilever beam, and a third cantilever beam. The micromirror structure includes a first cantilever beam and a fourth cantilever beam. The first mirror layer is located on the top surface of the micromirror structure. The first, second, third, and fourth piezoelectric actuators are located on the first, second, third, and fourth cantilever beams respectively. The underlying silicon and the buried oxide layer are etched to form at least a fixing frame and a back cavity. The back cavity releases at least the micromirror structure, the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam, so that one opposite side of the micromirror structure is connected to the fixing frame via the first and second cantilever beams, respectively. The other opposite side of the micromirror structure is connected to the fixing frame via the third and fourth cantilever beams, respectively. A second mirror layer is formed on the bottom surface of the micromirror structure.

[0012] In an optional embodiment, during the step of patterning the device layer and the buffer layer, a first connection structure, a second connection structure, a third connection structure, and a fourth connection structure are further formed; and the back cavity further releases the first connection structure, the second connection structure, the third connection structure, and the fourth connection structure, so that one end of the first cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the first connection structure; one end of the second cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the second connection structure; the extending directions of the second connection structure and the first connection structure form a first rotation axis; one end of the third cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the third connection structure; one end of the fourth cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the fourth connection structure; the extending directions of the fourth connection structure and the third connection structure form a second rotation axis.

[0013] In one alternative embodiment, during the step of etching the underlying silicon and the buried oxide layer, at least one support pillar is also formed, the support pillar being disposed on the bottom surface of the micromirror structure and close to the edge of the micromirror structure; and the back cavity also releases the support pillar.

[0014] In one optional embodiment, the first piezoelectric actuator includes a first driving structure formed on the piezoelectric driving layer, a first bottom electrode lead formed on the bottom electrode, and a first top electrode lead formed on the top electrode, wherein the first driving structure is electrically connected to the first bottom electrode lead and the first top electrode lead, respectively; the second piezoelectric actuator includes a second driving structure formed on the piezoelectric driving layer, a second bottom electrode lead formed on the bottom electrode, and a second top electrode lead formed on the top electrode, wherein the second driving structure is electrically connected to the second bottom electrode lead and the second top electrode lead, respectively; the third piezoelectric actuator includes a third driving structure formed on the piezoelectric driving layer, a third bottom electrode lead formed on the bottom electrode, and a third top electrode lead formed on the top electrode, wherein the third driving structure is electrically connected to the third bottom electrode lead and the third top electrode lead, respectively; the fourth piezoelectric actuator includes a fourth driving structure formed on the piezoelectric driving layer, a fourth bottom electrode lead formed on the bottom electrode, and a fourth top electrode lead formed on the top electrode, wherein the fourth driving structure is electrically connected to the fourth bottom electrode lead and the fourth top electrode lead, respectively.

[0015] In one optional embodiment, the buffer layer includes an interface adhesion layer, a lattice matching layer and a stress buffer layer stacked sequentially, wherein the stress buffer layer is formed on the top surface of the device layer.

[0016] In one optional embodiment, the material of the interface adhesion layer includes titanium, chromium, tantalum, aluminum, nickel, titanium tungsten, titanium nitrogen, chromium nitrogen, tantalum nitrogen, nickel chromium, silane coupling agent, polyimide, epoxy resin, polyethylene terephthalate, or polytetrafluoroethylene; the material of the lattice matching layer includes strontium titanate, magnesium oxide, cerium dioxide, yttrium-stabilized zirconium oxide, or aluminum oxide; and the material of the stress buffer layer includes lanthanum nickelate, silicon nitride, silicon dioxide, or aluminum oxide.

[0017] This application provides a piezoelectric MEMS micromirror and its fabrication method, as well as an optical path switch, which can achieve at least the following technical effects: In this embodiment, the fixed frame provides anchor points for the movable micromirror structure. A first mirror layer is provided on the top surface of the micromirror structure, and a second mirror layer is provided on the bottom surface, forming a double-sided mirror structure. When applied to an optical path switch, this improves the flexibility of the optical path. One side of the micromirror structure is connected to the fixed frame via a first cantilever beam and a second cantilever beam, respectively. The other side of the micromirror structure is connected to the fixed frame via a third cantilever beam and a fourth cantilever beam, respectively. A first and second piezoelectric drive are used to drive the micromirror structure to deflect around a first rotation axis, and a third and fourth piezoelectric drive are used to drive the micromirror structure to deflect around a second rotation axis, forming a double-sided mirror dual-axis structure, achieving dual-axis deflection. When applied to an optical path switch, this enables high-precision switching of the input beam between different ports of the output fiber array. The first, second, third, and fourth piezoelectric drives correspond one-to-one with each other to drive the first, second, third, and fourth cantilever beams. Through piezoelectric actuation, the driving voltage can be reduced from hundreds of volts to tens of volts or even lower, significantly reducing power consumption and improving reliability. When applied to optical switches, the piezoelectric actuation method offers a simple structure, fast response speed, and can shorten optical path switching time to tens of microseconds, increasing the throughput of the optical switch. It also allows for larger deflection angles and improved flexibility in optical path switching.

[0018] The above general description and the description below are exemplary and illustrative only and are not intended to limit this application. Attached Figure Description

[0019] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations and drawings do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are shown as similar elements. The drawings are not to be scaled. And wherein: Figure 1 This is a schematic diagram of the structure of a piezoelectric MEMS micromirror provided in an embodiment of this disclosure; Figure 2 This is a schematic diagram of the structure of a silicon-on-insulator substrate provided in an embodiment of this disclosure; Figure 3 A schematic diagram of the structure obtained by performing the steps of forming the driving function layer according to an embodiment of this disclosure; Figure 4 A schematic diagram of a structure obtained by performing a patterning step on the bottom electrode, the piezoelectric driving layer and the top electrode, according to an embodiment of this disclosure; Figure 5 A schematic diagram of the structure obtained by performing the step of forming a first mirror layer on the top surface of the exposed portion of the buffer layer according to an embodiment of the present disclosure; Figure 6 A schematic diagram illustrating the process of graphically representing the device layer and buffer layer to obtain a structure, as provided in one embodiment of this disclosure; Figure 7 A schematic diagram of a structure obtained by performing the etching of the underlying silicon and buried oxide layer steps according to an embodiment of this disclosure; Figure 8 A schematic diagram illustrating the arrangement of the micromirror structure, the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam provided in the embodiments of this disclosure. Figure 1 ; Figure 9 A schematic diagram illustrating the arrangement of the micromirror structure, the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam provided in the embodiments of this disclosure. Figure 2 ; Figure 10 This is a schematic diagram of the structure of an optical path switch provided in one embodiment of the present disclosure; Figure 11 This is a schematic diagram of the structure of an optical path switch provided in another embodiment of the present disclosure; Figure 12 This is a schematic diagram of the structure of an optical path switch provided in yet another embodiment of the present disclosure; Figure 13 This is a schematic diagram of the structure of an optical path switch provided in another embodiment of the present disclosure; Figure 14 This is a schematic diagram of the structure of the fiber optic collimator provided in the embodiments of this disclosure; Figure 15 A flowchart illustrating the fabrication method of a piezoelectric MEMS micromirror provided in this embodiment of the disclosure; Figure 16 This is a schematic diagram of the structure of a single-axis, single-sided piezoelectric MEMS micromirror provided in an embodiment of this disclosure; Figure 17 Schematic diagram of the fabrication process of the uniaxial single-sided piezoelectric MEMS micromirror provided in the embodiments of this disclosure. Figure 1 ; Figure 18 Schematic diagram of the fabrication process of the uniaxial single-sided piezoelectric MEMS micromirror provided in the embodiments of this disclosure. Figure 2 ; Figure 19 A schematic diagram showing the arrangement of the first micromirror structure, the fifth cantilever beam, the sixth cantilever beam, the fifth connecting structure, and the sixth connecting structure provided in the embodiments of this disclosure; Figure 20 A flowchart illustrating the fabrication method of a uniaxial, single-sided piezoelectric MEMS micromirror provided in this embodiment of the disclosure.

[0020] The reference numerals in the attached figures are as follows: 100: Piezoelectric MEMS micromirror; 101: Fixing frame; 102: Micromirror structure; 103: First mirror layer; 104: Second mirror layer; 105: First cantilever beam; 106: Second cantilever beam; 107: Third cantilever beam; 108: Fourth cantilever beam; 109: First piezoelectric actuator; 110: Second piezoelectric actuator; 111: Third piezoelectric actuator; 112: Fourth piezoelectric actuator; 113: First connection structure; 114: Second connection structure; 115: Third connection structure; 116: Fourth connection structure; 117: Support pillar; 118: Silicon-on-insulator substrate; 119: Bottom silicon; 120: Buried oxide layer; 121: Device layer; 122: Actuating function layer; 123: Buffer layer; 124: Bottom electrode; 125: Piezoelectric actuator layer; 126: Top electrode; 127: Back cavity; 200: Optical path switch; 201: Input fiber array; 202: First piezoelectric MEMS micromirror array; 203: Second piezoelectric MEMS micromirror array; 204: Output fiber array; 205: Fiber collimator; 206: Fiber; 207: Microlens; 208: Piezoelectric MEMS micromirror array; 300: Single-axis single-sided piezoelectric MEMS micromirror; 301: Fixing frame one; 302: Micromirror structure one; 303: Fifth piezoelectric actuator; 304: Sixth piezoelectric actuator; 305: Fifth cantilever beam; 306: Sixth cantilever beam; 307: Third mirror layer; 308: Fifth connecting structure; 309: Sixth connecting structure; 310: Back cavity one; 311: First connecting beam; 312: Second connecting beam. Detailed Implementation

[0021] To provide a more detailed understanding of the features and technical content of the embodiments of this disclosure, the implementation of the embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. The accompanying drawings are for illustrative purposes only and are not intended to limit the embodiments of this disclosure. In the following technical description, for ease of explanation, several details are used to provide a full understanding of the disclosed embodiments. However, one or more embodiments may still be implemented without these details. In other cases, well-known structures and devices may be simplified in their depiction to simplify the drawings.

[0022] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this disclosure are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this disclosure described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0023] In this disclosure, the terms "upper," "lower," "inner," "middle," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for better description of the embodiments of this disclosure and their implementations, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to require them to be constructed and operated in a specific orientation. Furthermore, some of the aforementioned terms may be used to indicate other meanings besides orientation or positional relationship; for example, the term "upper" may in some cases indicate a dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in the embodiments of this disclosure according to the specific circumstances.

[0024] Furthermore, the terms "set up," "connect," and "fix" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this disclosure according to the specific circumstances.

[0025] Unless otherwise stated, the term "multiple" means two or more.

[0026] It should be noted that, unless otherwise specified, the embodiments and features described in the present disclosure can be combined with each other.

[0027] On the one hand, combined with Figures 1 to 7 As shown, this disclosure proposes a piezoelectric MEMS micromirror 100, including a fixing frame 101, a micromirror structure 102, a first piezoelectric actuator 109, a second piezoelectric actuator 110, a third piezoelectric actuator 111, and a fourth piezoelectric actuator 112. A first mirror layer 103 is disposed on the top surface of the micromirror structure 102, and a second mirror layer 104 is disposed on the bottom surface of the micromirror structure 102. One opposite side of the micromirror structure 102 is connected to the fixing frame 101 via a first cantilever beam 105 and a second cantilever beam 106, respectively. The other opposite side of the micromirror structure 102 is connected to the fixing frame 101 via a third cantilever beam 107 and a fourth cantilever beam 108, respectively. The first piezoelectric actuator 109 and the second piezoelectric actuator 110 are correspondingly disposed on the first cantilever beam 105 and the second cantilever beam 106, respectively, for driving the micromirror structure 102 to deflect around a first rotation axis. The third piezoelectric actuator 111 and the fourth piezoelectric actuator 112 are respectively disposed on the third cantilever beam 107 and the fourth cantilever beam 108, and are used to drive the micromirror structure 102 to deflect around the second rotation axis. The second rotation axis intersects or is perpendicular to the first rotation axis.

[0028] The fixed frame 101 can provide a fixed anchor point for the movable micromirror structure 102. Figure 1 The direction from top to bottom can also be understood as from top to bottom. A first mirror layer 103 is disposed on the top surface of the micromirror structure 102, and a second mirror layer 104 is disposed on the bottom surface of the micromirror structure 102, forming a double-sided mirror structure. When the micromirror structure 102 deflects, it will cause the first mirror layer 103 and the second mirror layer 104 to deflect as well. When applied to the optical path switch 200, this can improve the flexibility of the optical path.

[0029] The micromirror structure 102 has two opposite sides connected to the fixed frame 101 via a first cantilever beam 105 and a second cantilever beam 106, respectively. The other two opposite sides of the micromirror structure 102 are connected to the fixed frame 101 via a third cantilever beam 107 and a fourth cantilever beam 108, respectively. For example, the micromirror structure 102 is a square structure with a first side, a third side, a second side, and a fourth side connected sequentially. The first and second sides are the opposite edges of the micromirror structure 102, and the third and fourth sides are the opposite edges of the micromirror structure 102. The first side is connected to the fixed frame 101 via the first cantilever beam 105, the second side via the second cantilever beam 106, the third side via the third cantilever beam 107, and the fourth side via the fourth cantilever beam 108.

[0030] In this configuration, all or part of the first piezoelectric actuator 109 is disposed on the first cantilever beam 105 to drive the first cantilever beam 105 to deform. All or part of the second piezoelectric actuator 110 is disposed on the second cantilever beam 106 to drive the second cantilever beam 106 to deform. The first piezoelectric actuator 109 and the second piezoelectric actuator 110 drive the micromirror structure 102 to deflect around the first rotation axis. All or part of the third piezoelectric actuator 111 is disposed on the third cantilever beam 107 to drive the third cantilever beam 107 to deform. All or part of the fourth piezoelectric actuator 112 is disposed on the fourth cantilever beam 108 to drive the fourth cantilever beam 108 to deform. In this configuration, the third piezoelectric actuator 111 and the fourth piezoelectric actuator 112 drive the micromirror structure 102 to deflect around the second rotation axis, thereby forming a double-sided, double-axis structure and achieving double-axis deflection. By using piezoelectric drive, the driving voltage can be reduced from hundreds of volts to tens of volts or even lower, significantly reducing the driving voltage, reducing power consumption, and improving reliability and long-term stability. When applied to the optical path switch 200, it enables high-precision switching of input beams between different ports of the output fiber array 204. Furthermore, by replacing traditional electrostatic or electromagnetic drives with piezoelectric actuation, the piezoelectric drive method offers a simpler structure and faster response, reducing optical path switching time to tens of microseconds, thus increasing the throughput of the optical path switch 200. It also allows for larger deflection angles, enhancing the flexibility of optical path switching. In short, it enables low-voltage driving, high-speed switching, and highly reliable large-port-count optical signal switching in the optical path switch 200.

[0031] like Figure 8 As shown, Figure 8 The dashed line L1 is used to indicate the first rotation axis, and the dashed line L2 is used to indicate the second rotation axis. The first and second rotation axes can be understood as virtual rotation axes around which the micromirror structure 102 deflects. Dual-axis deflection is achieved by the intersection or perpendicularity of the first and second rotation axes.

[0032] Combination Figure 8 As shown, in some embodiments, one end of the first cantilever beam 105 is connected to the fixed frame 101, and the other end of the first cantilever beam 105 is connected to the micromirror structure 102 via a first connecting structure 113. One end of the second cantilever beam 106 is connected to the fixed frame 101, and the other end of the second cantilever beam 106 is connected to the micromirror structure 102 via a second connecting structure 114. The extending directions of the second connecting structure 114 and the first connecting structure 113 form a first rotation axis. One end of the third cantilever beam 107 is connected to the fixed frame 101, and the other end of the third cantilever beam 107 is connected to the micromirror structure 102 via a third connecting structure 115. One end of the fourth cantilever beam 108 is connected to the fixed frame 101, and the other end of the fourth cantilever beam 108 is connected to the micromirror structure 102 via a fourth connecting structure 116. The extending directions of the fourth connecting structure 116 and the third connecting structure 115 form a second rotation axis.

[0033] All or part of the first piezoelectric actuator 109 is disposed on the first cantilever beam 105. One end of the first cantilever beam 105 is connected to the fixed frame 101, and the other end of the first cantilever beam 105 is connected to the micromirror structure 102 through the first connecting structure 113. In practical applications, a periodic or step voltage drive signal can be provided to the first piezoelectric actuator 109 by a drive control circuit, causing the first piezoelectric actuator 109 to extend and retract, thereby causing the first cantilever beam 105 to bend and deform, and transmitting the result to the micromirror structure 102 through the first connecting structure 113. All or part of the second piezoelectric actuator 110 is disposed on the second cantilever beam 106. One end of the second cantilever beam 106 is connected to the fixed frame 101, and the other end of the second cantilever beam 106 is connected to the micromirror structure 102 through the second connecting structure 114. In practical applications, a periodic or step voltage drive signal can be provided to the second piezoelectric drive 110 through a drive control circuit, causing the second piezoelectric drive 110 to extend and retract, thereby causing the second cantilever beam 106 to bend and deform, and transmitting the result to the micromirror structure 102 through the second connecting structure 114. The arrangement of the second connecting structure 114 and the first connecting structure 113 allows their extension directions to form a first rotation axis. Through the cooperation of the first cantilever beam 105 and the second cantilever beam 106, the micromirror structure 102 can be deflected around the first rotation axis.

[0034] Similarly, all or part of the third piezoelectric actuator 111 is disposed on the third cantilever beam 107. One end of the third cantilever beam 107 is connected to the fixed frame 101, and the other end of the third cantilever beam 107 is connected to the micromirror structure 102 through the third connecting structure 115. All or part of the fourth piezoelectric actuator 112 is disposed on the fourth cantilever beam 108. One end of the fourth cantilever beam 108 is connected to the fixed frame 101, and the other end of the fourth cantilever beam 108 is connected to the micromirror structure 102 through the fourth connecting structure 116. The arrangement of the fourth connecting structure 116 and the third connecting structure 115 enables the extension directions of the fourth connecting structure 116 and the third connecting structure 115 to form a second rotation axis. The principle of the micromirror structure 102 deflecting around the second rotation axis is the same as the principle of the micromirror structure 102 deflecting around the first rotation axis described above, and will not be repeated here.

[0035] In this embodiment, the shapes of the first connecting structure 113, the second connecting structure 114, the third connecting structure 115, and the fourth connecting structure 116 are not limited. For example, as... Figure 8 As shown, the first connecting structure 113, the second connecting structure 114, the third connecting structure 115, and the fourth connecting structure 116 are all strip-shaped and extend along a straight line. For example, as... Figure 9 As shown, the first connecting structure 113, the second connecting structure 114, the third connecting structure 115, and the fourth connecting structure 116 are all strip-shaped and extend along a zigzag line to reduce stress and improve stability. Figure 9 By cutting the piezoelectric MEMS micromirror 100 at the position indicated by the dashed line L5, we can obtain... Figure 1 The diagram shows a piezoelectric MEMS micromirror 100.

[0036] Combination Figure 1 and Figure 7 As shown, in some embodiments, the piezoelectric MEMS micromirror 100 further includes at least one support post 117, which is disposed on the bottom surface of the micromirror structure 102 and located outside the second mirror layer 104.

[0037] Mechanical support and stability are achieved through the support column 117, which can effectively avoid or improve the situation of warping or coupled torsion in the biaxial structure.

[0038] Two support columns 117 can be provided. One support column 117 can be located in the area extending from the first rotation axis, and the other support column 117 can be located in the area extending from the second rotation axis, so that the support column 117 is equivalent to a hinge support point, thereby enabling the micromirror structure 102 to rotate independently or in combination in the first rotation axis direction and the second rotation axis direction, realizing dual-axis scanning.

[0039] Figure 7The dashed line L4 in the figure is used to indicate the bottom surface of the fixed frame 101. It can be seen that there is a distance between the bottom surface of the support column 117 and the bottom surface of the fixed frame 101. That is to say, the support column 117 is in a suspended state, so that the support column 117 can both provide support and allow the micromirror structure 102 to deflect smoothly.

[0040] On the other hand, combining Figures 1 to 13 As shown in the illustration, this disclosure also provides an optical path switch 200, including an input fiber array 201, a piezoelectric MEMS micromirror array 208, and an output fiber array 204. The input fiber array 201 includes a plurality of input fiber collimators arranged in an array. The piezoelectric MEMS micromirror array 208 is disposed on the light-emitting side of the input fiber array 201, and includes a plurality of piezoelectric MEMS micromirrors 100 arranged in an array as in any of the previous embodiments. The output fiber array 204 is disposed in the reflected optical path of the piezoelectric MEMS micromirror array 208, and includes a plurality of output fiber collimators arranged in an array.

[0041] The optical path switch 200 is based on a piezoelectric MEMS micromirror 100. The input fiber array 201 includes multiple input fiber collimators arranged in an array, which can convert the diverging beam from the input fiber into an input collimated beam for emission. A piezoelectric MEMS micromirror array 208 is disposed on the output side of the input fiber array 201 to receive and redirect the corresponding input collimated beam. An output fiber array 204 is disposed in the reflection optical path of the piezoelectric MEMS micromirror array 208, which can focus the beam reflected by the piezoelectric MEMS micromirror array 208 and allow it to enter the corresponding output fiber.

[0042] The piezoelectric MEMS micromirror array 208 can be composed of multiple biaxial piezoelectric MEMS micromirrors 100 arranged in an array, each of which can deflect along both axes under low voltage. Alternatively, it can be composed of single-axis single-sided piezoelectric MEMS micromirrors 300 arranged in an array, each of which can deflect along a single axis under low voltage. The structure and fabrication of the single-axis single-sided piezoelectric MEMS micromirror 300 will be described later. Through piezoelectric actuation, a compact arrangement and high reliability of the piezoelectric MEMS micromirror array 100 can be achieved, as well as low-voltage, high-driving-force, and fast-response optical path switching functions.

[0043] For example, in combination Figure 10As shown, the input fiber array 201, the piezoelectric MEMS micromirror array 208, and the output fiber array 204 are all 4×4 arrays. The input fiber array 201 includes 16 input fiber collimators arranged in an array. The piezoelectric MEMS micromirror array 208 includes 16 uniaxial, single-sided piezoelectric MEMS micromirrors 300 arranged in an array. The output fiber array 204 includes 16 output fiber collimators arranged in an array.

[0044] For example, in combination Figure 11 As shown, the input fiber array 201, the piezoelectric MEMS micromirror array 208, and the output fiber array 204 are all 8×8 arrays. The input fiber array 201 includes 64 input fiber collimators arranged in an array. The piezoelectric MEMS micromirror array 208 includes 64 piezoelectric MEMS micromirrors 100. The output fiber array 204 includes 64 output fiber collimators arranged in an array.

[0045] In some embodiments, combined with Figure 12 and Figure 13 As shown, the piezoelectric MEMS micromirror array 208 comprises two sets, including a first piezoelectric MEMS micromirror array 202 and a second piezoelectric MEMS micromirror array 203. The first piezoelectric MEMS micromirror array 202 is disposed on the light-emitting side of the input fiber array 201. The second piezoelectric MEMS micromirror array 203 is disposed in the reflected optical path of the first piezoelectric MEMS micromirror array 202. The output fiber array 204 is disposed in the reflected optical path of the second piezoelectric MEMS micromirror array 203.

[0046] The optical path switch 200 is based on a piezoelectric MEMS micromirror 100. The input fiber array 201 includes multiple input fiber collimators arranged in an array, which can convert a diverging beam from the input fiber into an input collimated beam for emission. A first piezoelectric MEMS micromirror array 202 is disposed on the output side of the input fiber array 201 to receive and redirect the corresponding input collimated beam. A second piezoelectric MEMS micromirror array 203 is disposed in the reflection optical path of the first piezoelectric MEMS micromirror array 202 to receive and redirect the beam reflected by the first piezoelectric MEMS micromirror 100. The output fiber array 204 can focus the beam after secondary reflection from the second piezoelectric MEMS micromirror array 203 and direct it into the corresponding output fiber.

[0047] The first piezoelectric MEMS micromirror array 202 and the second piezoelectric MEMS micromirror array 203 can each be composed of multiple of the aforementioned biaxial piezoelectric MEMS micromirrors 100 arranged in an array, with each piezoelectric MEMS micromirror 100 capable of deflection along both axes under low voltage. Alternatively, the first piezoelectric MEMS micromirror array 202 and the second piezoelectric MEMS micromirror array 203 can each be composed of single-axis single-sided piezoelectric MEMS micromirrors 300 arranged in an array, with each single-axis single-sided piezoelectric MEMS micromirror 300 capable of deflection along a single axis under low voltage. The structure and fabrication of the single-axis single-sided piezoelectric MEMS micromirror 300 will be described later. Through piezoelectric actuation, a compact arrangement and high reliability of the piezoelectric MEMS micromirror array 100 can be achieved, along with low voltage, high driving force, and fast-response optical path switching functionality.

[0048] The piezoelectric MEMS micromirror 100 includes a silicon-based micromirror unit with a deposited piezoelectric thin film as the driving layer; that is, the material of the piezoelectric thin film, which serves as the piezoelectric actuator, includes lead zirconate titanate (PZT). By deflecting the piezoelectric MEMS micromirror 100 along a single or dual axis, high-precision switching of the input beam between different output fiber optic ports can be achieved.

[0049] In practical applications, a periodic or step voltage drive signal can be provided to the piezoelectric MEMS micromirror 100 through a drive control circuit, and then feedback control can be used to achieve closed-loop angle control. High-precision alignment and low-loss coupling of the input fiber array 201, the first piezoelectric MEMS micromirror array 202, the second piezoelectric MEMS micromirror array 203, and the output fiber array 204 can also be achieved through an encapsulated alignment module. In other words, modular packaging allows for direct docking with the fiber array, reducing insertion loss and calibration difficulty, and improving reliability and manufacturability. A strain sensor can also be integrated into the micromirror structure 102 to detect the strain generated during its deflection.

[0050] Furthermore, uniaxial deflection micromirrors can be combined with prisms or optical waveguide arrays to achieve higher port density optical path reconstruction. The optical waveguide array can be a silicon-based waveguide structure, which can be integrated and fabricated with piezoelectric MEMS micromirrors using compatible silicon-based processes. Silicon dioxide is deposited as a cladding layer on a silicon substrate using plasma-enhanced chemical vapor deposition (PECVD), followed by the fabrication of a high-refractive-index silicon-based waveguide core layer using electron beam evaporation or magnetron sputtering. The arrayed waveguide channels are then formed using a dry etching process. The waveguide core spacing can be 50 μm to 100 μm to match the size of the piezoelectric MEMS micromirror unit and the port spacing of the fiber array. The optical waveguide array can serve as a transitional transmission structure between the fiber array and the piezoelectric MEMS micromirror array. After the beam output from the input fiber array 201 is constrained and transmitted through the optical waveguide array, beam divergence loss during free-space propagation can be reduced. Simultaneously, the directional transmission characteristics of the waveguide can reduce interference from environmental vibrations and temperature fluctuations on the optical path. After being deflected by the piezoelectric MEMS micromirror 100, the light beam is then converged to the output fiber array 204 via the corresponding output waveguide array, further improving the optical signal coupling efficiency and reducing the overall insertion loss by 3dB to 5dB. Especially in high-capacity optical switching scenarios of 32×32 and above, the high-density integration of the waveguide array can effectively reduce the device size and improve port density and system stability. In practical applications, piezoelectric materials, micromirror sizes, and driving waveforms can be selected according to the specific application scenario to optimize the optical performance, response speed, and power consumption of the optical switch 200.

[0051] The optical path switch 200 in this embodiment drives the piezoelectric MEMS micromirrors 100 using piezoelectric driving technology. This significantly improves the application value of the optical path switch 200 in high-capacity optical communication systems while reducing the driving voltage, increasing the deflection angle and response speed. The piezoelectric MEMS micromirrors 100 array can be expanded to various port sizes, such as 16×16 and 32×32, to meet the needs of high-capacity optical path switches 200.

[0052] For example, in combination Figure 12 As shown, the input fiber array 201, the first piezoelectric MEMS micromirror array 202, the second piezoelectric MEMS micromirror array 203, and the output fiber array 204 are all 4×4 arrays. The input fiber array 201 includes 16 input fiber collimators arranged in an array. The first and second piezoelectric MEMS micromirror arrays 202 and 203 each include 16 uniaxial, single-sided piezoelectric MEMS micromirrors 300 arranged in an array. The output fiber array 204 includes 16 output fiber collimators arranged in an array.

[0053] For example, in combination Figure 13As shown, the input fiber array 201, the first piezoelectric MEMS micromirror array 202, the second piezoelectric MEMS micromirror array 203, and the output fiber array 204 are all 8×8 arrays. The input fiber array 201 includes 64 input fiber collimators arranged in an array. The first and second piezoelectric MEMS micromirror arrays 202 and 203 each include 64 piezoelectric MEMS micromirrors 100. The output fiber array 204 includes 64 output fiber collimators arranged in an array.

[0054] The input and output fiber optic collimators can each be fiber optic collimators 205. Fiber optic collimators 205 can be used as independent modules. For example... Figure 14 As shown, the fiber optic collimator 205 includes an optical fiber 206 and a microlens 207. The optical fiber 206 is used to transmit optical signals, and the microlens 207 can be optically coupled to the output or input end of the optical signal in the optical fiber 206. The microlens 207 is configured to convert a diverging beam from the optical fiber 206 into a parallel beam for emission, or to focus and couple an incident parallel beam into the optical fiber 206. The microlens 207 can be a gradient refractive index lens. Multiple optical fibers 206 can form an array of optical fibers 206, and multiple microlenses 207 can form an array of microlenses 207 corresponding one-to-one with multiple optical fibers 206, to achieve efficient coupling with a piezoelectric MEMS micromirror array.

[0055] In one possible implementation, the input fiber array 201 includes 4, 9, 16, 25, 36, 49, or 64 single-mode fibers, the end faces of which are collimated by microlenses. These single-mode fibers can be arranged in matrices of 2×2, 3×3, 4×4, 5×5, 6×6, 7×7, or 8×8.

[0056] In one possible implementation, the output fiber array 204 includes 4, 9, 16, 25, 36, 49, or 64 single-mode fibers. These single-mode fibers can be arranged in matrices of 2×2, 3×3, 4×4, 5×5, 6×6, 7×7, or 8×8.

[0057] On the other hand, combined with Figures 1 to 9 as well as Figure 15 As shown, a method for fabricating a piezoelectric MEMS micromirror is proposed, used to fabricate the aforementioned piezoelectric MEMS micromirror 100, specifically a biaxial, bifacial piezoelectric MEMS micromirror 100. The fabrication method includes the following steps: S121. A silicon-on-insulator substrate is provided, the silicon-on-insulator substrate comprising a bottom silicon layer, a buried oxide layer and a device layer stacked sequentially.

[0058] like Figure 2 and Figure 3As shown, the silicon-on-insulator (SOI) substrate 118 includes a bottom silicon layer 119, a buried oxide layer 120 (i.e., insulating silicon) and a device layer 121 (i.e., top silicon) stacked sequentially from bottom to top.

[0059] S122. Form a driving functional layer, which includes a buffer layer, a bottom electrode, a piezoelectric driving layer and a top electrode stacked sequentially on the device layer.

[0060] like Figure 3 As shown, a buffer layer 123, a bottom electrode 124, a piezoelectric driving layer 125 and a top electrode 126 are deposited sequentially from bottom to top on a silicon-on-insulator substrate 118 to form a driving functional layer 122.

[0061] In some embodiments, the buffer layer 123 includes an interface adhesion layer, a lattice matching layer and a stress buffer layer 123 stacked sequentially, with the stress buffer layer 123 formed on the top surface of the device layer 121.

[0062] An interface adhesion layer, a lattice matching layer, and a stress buffer layer 123 are stacked sequentially from top to bottom. The stress buffer layer 123 is formed on the top surface of the device layer 121. It is used to mitigate the difference in thermal expansion coefficients between different materials, reducing interface stress concentration under heat treatment or operating conditions, thereby lowering the risk of cracking, warping, or delamination. The lattice matching layer provides a transition layer with similar lattice parameters. Specifically, it provides a transition with similar lattice parameters between the silicon-on-insulator substrate 118 and the upper layer material, reducing lattice mismatch between the upper and lower layers and promoting the growth of the upper deposited material with high-quality crystal orientation. The interface adhesion layer provides good physicochemical adhesion, enhancing the physical and chemical bonding between the subsequent deposited layers and the silicon-on-insulator substrate 118, improving the adhesion reliability of the bottom electrode 124 during deposition, and achieving a firm bond between the bottom electrode 124 and the underlying material.

[0063] In some embodiments, the materials of the interface adhesion layer include titanium, chromium, tantalum, aluminum, nickel, titanium-tungsten, titanium-nitrogen, chromium-nitrogen, tantalum-nitrogen, nickel-chromium, silane coupling agent, polyimide, epoxy resin, polyethylene terephthalate, or polytetrafluoroethylene, etc. The materials of the lattice matching layer include strontium titanate, magnesium oxide, cerium dioxide, yttrium-stabilized zirconium oxide, or aluminum oxide, etc. The materials of the stress buffer layer 123 include lanthanum nickelate, silicon nitride, silicon dioxide, or aluminum oxide, etc.

[0064] In one possible implementation, the thickness of the interface adhesion layer is 5 nm to 500 nm.

[0065] In one possible implementation, the thickness of the interfacial adhesive layer is 5 nm, 10 nm, 30 nm, 50 nm, 60 nm, 200 nm, 500 nm, or other thickness values ​​between 5 nm and 500 nm.

[0066] In one possible implementation, the thickness of the lattice-matching layer is 20 nm to 300 nm.

[0067] In one possible implementation, the thickness of the lattice matching layer is 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 250 nm, 300 nm, or other thickness values ​​between 20 nm and 300 nm.

[0068] In one possible implementation, the thickness of the stress buffer layer 123 is 30 nm to 150 nm.

[0069] In one possible implementation, the thickness of the stress buffer layer 123 is 30 nm, 50 nm, 80 nm, 100 nm, 150 nm, or other thickness values ​​between 30 nm and 150 nm. This allows the stress buffer layer 123 to absorb and redistribute thermal stress and intrinsic stress generated during the process, and also reduces local stress peaks to below a safe threshold, maintaining the planar integrity of the device structure.

[0070] In one possible implementation, the material of the bottom electrode 124 includes platinum, copper, gold, tungsten, ruthenium, titanium, titanium nitride, tantalum nitride, or indium tin oxide. The thickness of the bottom electrode 124 is from 50 nm to 200 nm.

[0071] In one possible implementation, the top electrode 126 is made of platinum, copper, gold, tungsten, ruthenium, titanium, titanium nitride, tantalum nitride, or indium tin oxide. The thickness of the top electrode 126 is from 50 nm to 200 nm.

[0072] In one possible implementation, the material of the piezoelectric drive layer 125 includes lead zirconate titanate, aluminum nitride, scandium-doped aluminum nitride, lead magnesium niobate, barium titanate, shape memory alloy, polycrystalline silicon, or silicon nitride.

[0073] In one possible implementation, the thickness of the piezoelectric driving layer 125 is from 20 nm to 10,000 nm.

[0074] In one possible implementation, the thickness of the piezoelectric drive layer 125 is 20 nm, 100 nm, 500 nm, 1000 nm, 10000 nm, or other thickness values ​​between 20 nm and 10000 nm.

[0075] In this embodiment, the buffer layer 123, bottom electrode 124, piezoelectric driving layer 125, and top electrode 126 are formed by magnetron sputtering deposition, reactive sputtering deposition, electron beam evaporation deposition, pulsed laser deposition, low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition, atmospheric pressure chemical vapor deposition, metal-organic chemical vapor deposition, photochemical vapor deposition, thermal atomic layer deposition, plasma-enhanced atomic layer deposition, sol-gel method, spray pyrolysis method, electrochemical deposition, or molecular beam epitaxy. In practical applications, the appropriate method can be selected as needed, and there is no limitation.

[0076] S123. Pattern the bottom electrode, piezoelectric drive layer and top electrode to form a first piezoelectric drive, a second piezoelectric drive, a third piezoelectric drive and a fourth piezoelectric drive, and expose part of the top surface of the buffer layer.

[0077] Specifically, a photoresist mask with a predetermined pattern can be formed on the surface of the driving functional layer 122 using photolithography. Then, the bottom electrode 124, the piezoelectric driving layer 125, and the top electrode 126 can be selectively removed using etching to form a structure that meets the requirements of the biaxial double-sided piezoelectric MEMS micromirror 100. The exposed top surface of the buffer layer 123 is prepared for the formation of the first mirror layer 103.

[0078] Patterning can be divided into two parts: photolithography and etching. The photolithography process can use spin-coating of positive or negative photoresist to form a mask layer with the desired pattern on the surface of the driving functional layer 122 after soft baking, exposure, and development. The etching process can be dry etching or wet etching, depending on the material properties. Dry etching can be one or more of reactive ion etching, deep reactive ion etching, plasma etching, or ion beam etching. Wet etching can use acidic or alkaline solutions to selectively remove the specified material. Through the combination of the above photolithography and etching processes, fine patterns that meet the structural requirements of the biaxial, bifacial piezoelectric MEMS micromirror 100 can be formed on the buffer layer 123, bottom electrode 124, piezoelectric driving layer 125, and top electrode 126.

[0079] In some embodiments, the first piezoelectric actuator 109 includes a first actuator structure formed on a piezoelectric actuator layer, a first bottom electrode lead formed on a bottom electrode, and a first top electrode lead formed on a top electrode, wherein the first actuator structure is electrically connected to the first bottom electrode lead and the first top electrode lead, respectively. The second piezoelectric actuator 110 includes a second actuator structure formed on a piezoelectric actuator layer, a second bottom electrode lead formed on a bottom electrode, and a second top electrode lead formed on a top electrode, wherein the second actuator structure is electrically connected to the second bottom electrode lead and the second top electrode lead, respectively. The third piezoelectric actuator 111 includes a third actuator structure formed on a piezoelectric actuator layer, a third bottom electrode lead formed on a bottom electrode, and a third top electrode lead formed on a top electrode, wherein the third actuator structure is electrically connected to the third bottom electrode lead and the third top electrode lead, respectively. The fourth piezoelectric actuator 112 includes a fourth actuator structure formed on a piezoelectric actuator layer, a fourth bottom electrode lead formed on a bottom electrode, and a fourth top electrode lead formed on a top electrode, wherein the fourth actuator structure is electrically connected to the fourth bottom electrode lead and the fourth top electrode lead, respectively.

[0080] The bottom electrode 124, piezoelectric driving layer 125, and top electrode 126 are patterned. Specifically, the piezoelectric driving layer 125 is patterned to form a first driving structure, a second driving structure, a third driving structure, and a fourth driving structure. The bottom electrode 124 is patterned by selectively removing material from the bottom electrode 124 to form electrode leads with clear edges and regular shapes. Specifically, a first bottom electrode lead electrically connected to the first driving structure, a second bottom electrode lead electrically connected to the second driving structure, a third bottom electrode lead electrically connected to the third driving structure, and a fourth bottom electrode lead electrically connected to the fourth driving structure are formed. The top electrode 126 is patterned by selectively removing material from the top electrode 126 to form electrode leads with clear edges and regular shapes. Specifically, a first top electrode lead electrically connected to the first driving structure, a second top electrode lead electrically connected to the second driving structure, a third top electrode lead electrically connected to the third driving structure, and a fourth top electrode lead electrically connected to the fourth driving structure are formed. This configuration forms a first piezoelectric drive 109, a second piezoelectric drive 110, a third piezoelectric drive 111, and a fourth piezoelectric drive 112, enabling independent control of each drive. These electrode leads guide the electric field to the corresponding piezoelectric drive, ensuring a uniform electric field distribution. These electrode leads can also be connected to a pre-defined electrode interface area for reliable connection to an external control circuit.

[0081] In actual processing, positive or negative photoresist can be spin-coated onto the surface to be processed first. After removing the solvent through soft baking, ultraviolet exposure is performed using a high-resolution mask, followed by development to obtain the desired patterned protective layer. Then, an appropriate etching process is selected according to different functional layers to remove the exposed areas: for the metal bottom electrode 124 and top electrode 126, wet etching or dry etching can be used. For the piezoelectric driving layer 125, ion beam etching or reactive ion etching can be used to control the etching depth and sidewalls.

[0082] S124. A first mirror layer is formed on the top surface of the exposed portion of the buffer layer.

[0083] Metal is deposited on the top surface of the exposed portion of the buffer layer 123 to form a first mirror layer 103. The metal forming the first mirror layer 103 is a high-reflectivity metal, such as aluminum, gold, silver, platinum, palladium, molybdenum, etc., so that the first mirror layer 103 is a highly reflective mirror.

[0084] In one possible implementation, the thickness of the first mirror layer 103 is 20 nm to 500 nm.

[0085] In one possible implementation, the thickness of the first mirror layer 103 is 20nm, 100nm, 200nm, 300nm, 400nm, 500nm, or other thickness values ​​between 20nm and 500nm.

[0086] The deposition methods of the first mirror layer 103 include, but are not limited to, magnetron sputtering, radio frequency, DC sputtering, electron beam evaporation, thermal evaporation, ion beam deposition, cathode arc deposition, low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition, metal-organic chemical vapor deposition, atomic layer deposition, pulsed laser deposition, electroplating or electroless plating, sol-gel, etc.

[0087] S125. Pattern the device layer and buffer layer to form at least a micromirror structure, a first cantilever beam, a second cantilever beam, a third cantilever beam, and a fourth cantilever beam, wherein the first mirror layer is located on the top surface of the micromirror structure, and the first piezoelectric drive, the second piezoelectric drive, the third piezoelectric drive, and the fourth piezoelectric drive are located on the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam respectively.

[0088] Patterning the buffer layer 123 can be achieved using a step-by-step etching method to avoid damaging the silicon substrate 118 on the insulator. After etching, residual photoresist is removed, and if necessary, ashing or O2 plasma cleaning can be performed to clean the surface.

[0089] The device layer 121 and the buffer layer 123 are patterned by first spin-coating positive or negative photoresist onto the surface to be processed, and then forming a photomask layer with a predetermined pattern through soft baking, exposure and development to define the positions of the fixing frame 101, micromirror structure 102, first cantilever beam 105, second cantilever beam 106, third cantilever beam 107, fourth cantilever beam 108, first connecting structure 113, second connecting structure 114, third connecting structure 115 and fourth connecting structure 116.

[0090] The etching method can be selected from deep reactive ion etching, reactive ion etching, anisotropic dry etching, ion beam etching, wet chemical etching, or a combination of the above methods, so as to select an appropriate process according to the material characteristics of device layer 121 and buffer layer 123, thereby forming the outline of micromirror structure 102, first cantilever beam 105, second cantilever beam 106, third cantilever beam 107, fourth cantilever beam 108, first connection structure 113, second connection structure 114, third connection structure 115 and fourth connection structure 116, and helping to achieve the integrity of subsequent release of these movable structures.

[0091] In some embodiments, during the step of patterning the device layer 121 and the buffer layer 123, a first connecting structure 113, a second connecting structure 114, a third connecting structure 115, and a fourth connecting structure 116 are also formed. Furthermore, the subsequently formed back cavity 127 can release the first connecting structure 113, the second connecting structure 114, the third connecting structure 115, and the fourth connecting structure 116. This allows one end of the first cantilever beam 105 to be connected to the fixing frame 101, and the other end to be connected to the micromirror structure 102 via the first connecting structure 113. One end of the second cantilever beam 106 is connected to the fixing frame 101, and the other end is connected to the micromirror structure 102 via the second connecting structure 114. The extending directions of the second connecting structure 114 and the first connecting structure 113 form a first rotation axis. One end of the third cantilever beam 107 is connected to the fixing frame 101, and the other end is connected to the micromirror structure 102 via the third connecting structure 115. One end of the fourth cantilever beam 108 is connected to the fixed frame 101, and the other end is connected to the micromirror structure 102 through the fourth connecting structure 116. The extending directions of the fourth connecting structure 116 and the third connecting structure 115 form the second rotation axis.

[0092] S126. Etch the underlying silicon and buried oxide layer to form at least a fixed frame and a back cavity. The back cavity releases at least the micromirror structure, the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam, so that one side of the micromirror structure is connected to the fixed frame via the first cantilever beam and the second cantilever beam, respectively; the other side of the micromirror structure is connected to the fixed frame via the third cantilever beam and the fourth cantilever beam, respectively.

[0093] The underlying silicon 119 and buried oxide layer 120 are etched to release movable structures, including a micromirror structure 102, a first cantilever beam 105, a second cantilever beam 106, a third cantilever beam 107, a fourth cantilever beam 108, a first connecting structure 113, a second connecting structure 114, a third connecting structure 115, a fourth connecting structure 116, and a support pillar 117. Specifically, a protective layer material, such as silicon dioxide, silicon nitride, or photoresist, is first deposited or spin-coated and patterned on the back side (i.e., the bottom surface) of the silicon substrate 118 on an insulator. The protective layer material is then exposed to expose the area to be etched. An etching method is selected according to design requirements, and the underlying silicon 119 is oriented to the buried oxide layer 120 or a pre-defined sacrificial layer to form a back cavity 127 and a fixing frame 101. The back cavity 127 can release the micromirror structure 102, the first cantilever beam 105, the second cantilever beam 106, the third cantilever beam 107, the fourth cantilever beam 108, the first connecting structure 113, the second connecting structure 114, the third connecting structure 115, the fourth connecting structure 116 and the support column 117, so that the micromirror structure 102 can tilt freely and realize dual-axis drive.

[0094] The etching method can be one or more of the following: deep reactive ion etching, reactive ion etching, anisotropic dry etching, plasma etching, ion beam etching, focused ion beam etching, wet chemical etching, electrochemical etching, laser-assisted etching, low-temperature plasma etching, nanosecond picosecond laser etching, etc.

[0095] In some embodiments, during the etching of the underlying silicon 119 and the buried oxide layer 120, at least one support pillar 117 is also formed. The support pillar 117 is disposed on the bottom surface of the micromirror structure 102 and near the edge of the micromirror structure 102. Furthermore, the back cavity 127 releases the support pillar 117.

[0096] The support column 117 is disposed on the bottom surface of the micromirror structure 102 and close to the edge of the micromirror structure 102, providing a position for the subsequent formation of the second mirror layer 104 on the bottom surface of the micromirror structure 102. Releasing the support column 117 from the back cavity 127 can leave the support column 117 in a suspended state, which can both support the micromirror structure 102 and allow it to deflect smoothly when the micromirror structure 102 is deflected.

[0097] S127. A second mirror layer is formed on the bottom surface of the micromirror structure.

[0098] A piezoelectric MEMS micromirror 100 was obtained.

[0099] A second mirror layer 104 is formed on the bottom surface of the micromirror structure 102 to form a biaxial, bifacial piezoelectric MEMS micromirror 100. Specifically, the bottom surface (i.e., the back surface) of the micromirror structure 102 is cleaned and dried to remove impurities and moisture so that the metal film adheres uniformly to deposit the second mirror layer 104.

[0100] The metal forming the second mirror layer 104 is a high-reflectivity metal, such as aluminum, gold, silver, platinum, palladium, or molybdenum, to make the first mirror layer 103 a high-reflectivity mirror. A high-reflectivity mirror is formed on the bottom surface of the micromirror structure 102, and combined with a piezoelectric driving method, the biaxial, bi-sided piezoelectric MEMS micromirror 100 possesses beam deflection and efficient optical reflection functions.

[0101] In one possible implementation, the thickness of the second mirror layer 104 is 20 nm to 500 nm.

[0102] In one possible implementation, the thickness of the second mirror layer 104 is 20nm, 100nm, 200nm, 300nm, 400nm, 500nm, or other thickness values ​​between 20nm and 500nm.

[0103] The deposition methods for the second mirror layer 104 include, but are not limited to, magnetron sputtering, radio frequency, DC sputtering, electron beam evaporation, thermal evaporation, ion beam deposition, cathodic arc deposition, low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition, metal-organic chemical vapor deposition, atomic layer deposition, pulsed laser deposition, electroplating or electroless plating, sol-gel, etc.

[0104] Combination Figure 2 , Figure 3 as well as Figures 16 to 19 As shown, this disclosure also provides a uniaxial, single-sided piezoelectric MEMS micromirror 300, including a fixing frame 301, a micromirror structure 302, a fifth piezoelectric actuator 303, a sixth piezoelectric actuator 304, a fifth cantilever beam 305, a sixth cantilever beam 306, a fifth connecting structure 308, a sixth connecting structure 309, a first connecting beam 311, and a second connecting beam 312. A third mirror layer 307 is formed on one side surface of the micromirror structure 302. At least a portion of the fifth piezoelectric actuator 303 is disposed on the fifth cantilever beam 305. At least a portion of the sixth piezoelectric actuator 304 is disposed on the sixth cantilever beam 306. One end of the fifth cantilever beam 305 is connected to the fixing frame 301, and one end of the sixth cantilever beam 306 is connected to the fixing frame 301. One end of the fifth connecting structure 308 is connected to the fifth cantilever beam 305, and the other end is connected to the sixth cantilever beam 306. One end of the sixth connecting structure 309 is connected to the fifth cantilever beam 305, and the other end is connected to the sixth cantilever beam 306. One end of the first connecting beam 311 is connected to the fifth connecting structure 308, and the other end is connected to the micromirror structure 302. One end of the second connecting beam 312 is connected to the sixth connecting structure 309, and the other end is connected to the micromirror structure 302. The micromirror structure 302 can be driven to deflect around the third torsion axis by the fifth piezoelectric drive 303 and the sixth piezoelectric drive 304.

[0105] Figure 19The dashed line L3 in the diagram is used to indicate the third torsional axis. The extension directions of the first connecting beam 311 and the second connecting beam 312 form the third torsional axis. The fifth piezoelectric drive 303 is wholly or partially disposed on the fifth cantilever beam 305. The sixth piezoelectric drive 304 is wholly or partially disposed on the sixth cantilever beam 306. In practical applications, a periodic or step voltage drive signal can be provided to the fifth piezoelectric drive 303 through a drive control circuit, causing the fifth piezoelectric drive 303 to extend and retract, thereby causing the fifth cantilever beam 305 to bend and deform. This deformation is then transmitted to the first connecting beam 311 and the second connecting beam 312 through the fifth connecting structure 308 and the sixth connecting structure 309, thereby driving the micromirror structure 302 to deflect around the third torsional axis. The drive control circuit can also provide a periodic or step voltage drive signal to the sixth piezoelectric drive 304, causing the sixth piezoelectric drive 304 to extend and retract, thereby causing the sixth cantilever beam 306 to bend and deform. This deformation is transmitted to the first connecting beam 311 and the second connecting beam 312 through the fifth connecting structure 308 and the sixth connecting structure 309, thereby driving the micromirror structure 302 to deflect around the third torsion axis.

[0106] along Figure 19 By cutting a uniaxial, single-sided piezoelectric MEMS micromirror 300 at the position indicated by the dashed line L6, we can obtain... Figure 16 The diagram shows a single-axis, single-sided piezoelectric MEMS micromirror 300.

[0107] Combination Figure 2 , Figure 3 as well as Figures 16 to 20 As shown in the embodiments of this disclosure, a method for fabricating a uniaxial, single-sided piezoelectric MEMS micromirror is also provided, comprising the following steps: S171. A silicon-on-insulator substrate is provided, the silicon-on-insulator substrate comprising a bottom silicon layer, a buried oxide layer and a device layer stacked sequentially.

[0108] like Figure 2 As shown, silicon on insulator (SOI) includes a bottom silicon layer 119, a buried oxide layer 120 (i.e., insulating silicon) and a device layer 121 (i.e., top silicon) stacked sequentially from bottom to top.

[0109] S172. Form a driving functional layer, which includes a buffer layer, a bottom electrode, a piezoelectric driving layer and a top electrode stacked sequentially on the device layer.

[0110] like Figure 3 As shown, a buffer layer 123, a bottom electrode 124, a piezoelectric driving layer 125 and a top electrode 126 are deposited sequentially from bottom to top on a silicon-on-insulator substrate 118 to form a driving functional layer 122.

[0111] For details regarding the structure, materials, thickness, and formation method of each layer in the driving functional layer 122, please refer to the fabrication of the biaxial bifacial piezoelectric MEMS micromirror 100 described above; these details will not be repeated here.

[0112] S173. Pattern the bottom electrode, piezoelectric drive layer and top electrode to form the fifth piezoelectric drive and the sixth piezoelectric drive, and expose part of the top surface of the buffer layer.

[0113] like Figure 17 As shown, the piezoelectric drive layer 125 is patterned to form a fifth drive structure and a sixth drive structure. The bottom electrode 124 is patterned to form a fifth bottom electrode lead electrically connected to the fifth drive structure and a sixth bottom electrode lead electrically connected to the sixth drive structure. The top electrode 126 is patterned to form a fifth top electrode lead electrically connected to the fifth drive structure and a sixth top electrode lead electrically connected to the sixth drive structure. This results in a fifth piezoelectric drive 303 and a sixth piezoelectric drive 304.

[0114] In other words, the fifth piezoelectric actuator 303 includes a fifth actuator structure and a fifth bottom electrode lead and a fifth top electrode lead electrically connected to the fifth actuator structure. The sixth piezoelectric actuator 304 includes a sixth actuator structure and a sixth bottom electrode lead and a sixth top electrode lead electrically connected to the sixth actuator structure.

[0115] For details on the patterning of the bottom electrode 124, the piezoelectric driving layer 125 and the top electrode 126, please refer to the fabrication of the biaxial bifacial piezoelectric MEMS micromirror 100 described above, which will not be repeated here.

[0116] S174. A third mirror layer is formed on the top surface of the exposed portion of the buffer layer.

[0117] like Figure 18 As shown, a third mirror layer 307 is formed on the top surface of the exposed portion of the buffer layer 123. The deposition method of the third mirror layer 307 includes, but is not limited to, physical vapor deposition, chemical vapor deposition, atomic layer deposition, or pulsed laser deposition. Physical vapor deposition includes, for example, magnetron sputtering, radio frequency sputtering, DC sputtering, electron beam evaporation, thermal evaporation, ion beam sputtering, and cathode arc deposition. Chemical vapor deposition includes, for example, low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition, and metal-organic chemical vapor deposition.

[0118] The material and thickness of the third mirror layer 307 are described in the previous description of the first mirror layer 103, and will not be repeated here.

[0119] S175. Pattern the device layer and buffer layer to form a micromirror structure I, a fifth cantilever beam and a sixth cantilever beam, wherein the third mirror layer is located on the top surface of the micromirror structure I, and the fifth piezoelectric drive and the sixth piezoelectric drive are located on the fifth cantilever beam and the sixth cantilever beam respectively.

[0120] The device layer 121 and the buffer layer 123 can be patterned to form a fifth connection structure 308, a sixth connection structure 309, a first connection beam 311, and a second connection beam 312.

[0121] For details on how to pattern the device layer 121 and the buffer layer 123, please refer to the fabrication of the biaxial bi-sided piezoelectric MEMS micromirror 100 described above; it will not be repeated here.

[0122] S176. Etch the underlying silicon and buried oxide layer to form a fixed frame and a back cavity. The back cavity releases at least the micromirror structure, the fifth cantilever beam, and the sixth cantilever beam. The two opposite sides of the micromirror structure are connected to the fixed frame through the fifth cantilever beam and the sixth cantilever beam, respectively, to obtain a uniaxial single-sided piezoelectric MEMS micromirror.

[0123] Combination Figure 16 and Figure 19 As shown, the back cavity 310 also releases the fifth connecting structure 308, the sixth connecting structure 309, the first connecting beam 311, and the second connecting beam 312. This allows one end of the fifth cantilever beam 305 to be connected to the fixed frame 301, and one end of the sixth cantilever beam 306 to be connected to the fixed frame 301. One end of the fifth connecting structure 308 is connected to the side of the fifth cantilever beam 305 away from the fixed frame 301, and the other end is connected to the side of the sixth cantilever beam 306 away from the fixed frame 301. One end of the sixth connecting structure 309 is connected to the side of the fifth cantilever beam 305 away from the fixed frame 301, and the other end is connected to the side of the sixth cantilever beam 306 away from the fixed frame 301. One end of the first connecting beam 311 is connected to the fifth connecting structure 308, and the other end is connected to the micromirror structure 302. One end of the second connecting beam 312 is connected to the sixth connecting structure 309, and the other end is connected to the micromirror structure 302. The extension directions of the first connecting beam 311 and the second connecting beam 312 form a third torsional axis.

[0124] Specifically, a protective layer is deposited or spin-coated on the back side (i.e., the bottom surface) of the silicon substrate 118 on an insulator and patterned to expose the area to be etched. Then, an etching process is used to directionally etch the underlying silicon 119 down to the buried oxide layer 120 or a pre-defined sacrificial layer, thereby forming a through-hole or semi-through-hole back cavity 310. The back cavity 310 releases the micromirror structure 302, the fifth cantilever beam 305, the sixth cantilever beam 306, the fifth connecting structure 308, the sixth connecting structure 309, the first connecting beam 311, and the second connecting beam 312, enabling the uniaxial single-sided piezoelectric MEMS micromirror 300 to have deflectability.

[0125] The protective layer may be made of materials including but not limited to silicon dioxide, silicon nitride, silicon oxynitride, polyimide, photoresist, fluoropolymer, silicon carbide, or aluminum nitride.

[0126] The etching process can be selected from one of the following: deep reactive ion etching, reactive ion etching, anisotropic dry etching, plasma etching, ion beam etching, focused ion beam etching, sputtering etching, wet chemical etching, electrochemical etching, laser-assisted etching, low-temperature plasma etching, nanosecond picosecond laser etching, and physical bombardment etching.

[0127] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A piezoelectric MEMS micromirror, characterized in that, include: Fixed frame; A micromirror structure is provided with a first mirror layer on the top surface and a second mirror layer on the bottom surface; one opposite side of the micromirror structure is connected to the fixed frame through a first cantilever beam and a second cantilever beam, respectively; the other opposite side of the micromirror structure is connected to the fixed frame through a third cantilever beam and a fourth cantilever beam, respectively. The first piezoelectric drive and the second piezoelectric drive are respectively disposed on the first cantilever beam and the second cantilever beam, and are used to drive the micromirror structure to deflect around the first rotation axis; The third and fourth piezoelectric actuators are respectively disposed on the third and fourth cantilever beams, and are used to drive the micromirror structure to deflect around the second rotation axis, which intersects or is perpendicular to the first rotation axis.

2. The piezoelectric MEMS micromirror according to claim 1, characterized in that, One end of the first cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the first connecting structure. One end of the second cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the second connecting structure. The extension directions of the second connecting structure and the first connecting structure form the first rotation axis. One end of the third cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the third connecting structure. One end of the fourth cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the fourth connecting structure. The extension directions of the fourth connecting structure and the third connecting structure form the second rotation axis. The piezoelectric MEMS micromirror also includes at least one support pillar, which is disposed on the bottom surface of the micromirror structure and located outside the second mirror layer.

3. An optical path switch, characterized in that, include: Input fiber array, including multiple input fiber collimators arranged in the array; A piezoelectric MEMS micromirror array, disposed on the light-emitting side of the input fiber array, includes multiple piezoelectric MEMS micromirrors arranged in an array as described in claim 1 or 2. An output fiber array is disposed in the reflected optical path of the piezoelectric MEMS micromirror array, and includes multiple output fiber collimators arranged in the array.

4. The optical path switch according to claim 3, characterized in that, The piezoelectric MEMS micromirror array is provided in two sets, including a first piezoelectric MEMS micromirror array and a second piezoelectric MEMS micromirror array respectively; The first piezoelectric MEMS micromirror array is disposed on the light-emitting side of the input fiber array; The second piezoelectric MEMS micromirror array is disposed in the reflected optical path of the first piezoelectric MEMS micromirror array; The output fiber array is disposed in the reflected optical path of the second piezoelectric MEMS micromirror array.

5. A method for fabricating a piezoelectric MEMS micromirror, used to fabricate the piezoelectric MEMS micromirror as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: A silicon-on-insulator substrate is provided, the silicon-on-insulator substrate comprising a bottom silicon layer, a buried oxide layer and a device layer stacked sequentially; A driving functional layer is formed, the driving functional layer comprising a buffer layer, a bottom electrode, a piezoelectric driving layer and a top electrode sequentially stacked on the device layer; The bottom electrode, the piezoelectric driving layer, and the top electrode are patterned to form a first piezoelectric drive, a second piezoelectric drive, a third piezoelectric drive, and a fourth piezoelectric drive, and a portion of the top surface of the buffer layer is exposed. A first mirror layer is formed on the top surface of the exposed portion of the buffer layer; The device layer and the buffer layer are patterned to form at least a micromirror structure, a first cantilever beam, a second cantilever beam, a third cantilever beam, and a fourth cantilever beam, wherein the first mirror layer is located on the top surface of the micromirror structure, and the first piezoelectric drive, the second piezoelectric drive, the third piezoelectric drive, and the fourth piezoelectric drive are located on the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam respectively. The underlying silicon and the buried oxide layer are etched to form at least a fixing frame and a back cavity. The back cavity releases at least the micromirror structure, the first cantilever beam, the second cantilever beam, the third cantilever beam, and the fourth cantilever beam, so that one opposite side of the micromirror structure is connected to the fixing frame through the first cantilever beam and the second cantilever beam, respectively; the other opposite side of the micromirror structure is connected to the fixing frame through the third cantilever beam and the fourth cantilever beam, respectively. A second mirror layer is formed on the bottom surface of the micromirror structure.

6. The preparation method according to claim 5, characterized in that, In the step of patterning the device layer and the buffer layer, a first connection structure, a second connection structure, a third connection structure and a fourth connection structure are also formed. Furthermore, the back cavity also releases the first connecting structure, the second connecting structure, the third connecting structure, and the fourth connecting structure, so that one end of the first cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the first connecting structure; one end of the second cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the second connecting structure; the extending directions of the second connecting structure and the first connecting structure form a first rotation axis; One end of the third cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the third connecting structure; one end of the fourth cantilever beam is connected to the fixed frame, and the other end is connected to the micromirror structure through the fourth connecting structure; the extending directions of the fourth connecting structure and the third connecting structure form a second rotation axis.

7. The preparation method according to claim 5, characterized in that, In the step of etching the underlying silicon and the buried oxide layer, at least one support pillar is also formed. The support pillar is disposed on the bottom surface of the micromirror structure and close to the edge of the micromirror structure. Furthermore, the back cavity also releases the support column.

8. The preparation method according to claim 5, characterized in that, The first piezoelectric drive includes a first drive structure formed on the piezoelectric drive layer, a first bottom electrode lead formed on the bottom electrode, and a first top electrode lead formed on the top electrode. The first drive structure is electrically connected to the first bottom electrode lead and the first top electrode lead, respectively. The second piezoelectric drive includes a second drive structure formed on the piezoelectric drive layer, a second bottom electrode lead formed on the bottom electrode, and a second top electrode lead formed on the top electrode. The second drive structure is electrically connected to the second bottom electrode lead and the second top electrode lead, respectively. The third piezoelectric drive includes a third drive structure formed on the piezoelectric drive layer, a third bottom electrode lead formed on the bottom electrode, and a third top electrode lead formed on the top electrode. The third drive structure is electrically connected to the third bottom electrode lead and the third top electrode lead, respectively. The fourth piezoelectric drive includes a fourth drive structure formed on the piezoelectric drive layer, a fourth bottom electrode lead formed on the bottom electrode, and a fourth top electrode lead formed on the top electrode. The fourth drive structure is electrically connected to the fourth bottom electrode lead and the fourth top electrode lead, respectively.

9. The preparation method according to claim 5, characterized in that, The buffer layer includes an interface adhesion layer, a lattice matching layer and a stress buffer layer stacked sequentially, with the stress buffer layer formed on the top surface of the device layer.

10. The preparation method according to claim 9, characterized in that, The materials of the interface adhesive layer include titanium, chromium, tantalum, aluminum, nickel, titanium tungsten, titanium nitrogen, chromium nitrogen, tantalum nitrogen, nickel chromium, silane coupling agent, polyimide, epoxy resin, polyethylene terephthalate, or polytetrafluoroethylene. The lattice matching layer is made of materials including strontium titanate, magnesium oxide, cerium dioxide, yttrium-stabilized zirconium oxide, or aluminum oxide. The stress buffer layer is made of materials including lanthanum nickelate, silicon nitride, silicon dioxide, or aluminum oxide.

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